Thermal Print Head, Method for Manufacturing the Same, and Thermal Printer

Abstract

To provide a thermal print head which secures good printing performance, and to provide a manufacturing method of the thermal print head and a thermal printer including the thermal print head.SOLUTION: A thermal print head 100 includes: an insulator; a heat accumulation layer 33 disposed on the insulator; a protection film 34A disposed on the heat accumulation layer 33 and having a groove part 38; a heating resistance element 40 disposed on the heat accumulation layer 33 and embedded in the groove part 38; an individual electrode 31 electrically connected to the heating resistance element 40; a common electrode 32 having a comb teeth part 32A electrically connected with the heating resistance element 40; and a protection film 34B which covers the heating resistance element 40 and the protection film 34A. The individual electrode 31 is spaced apart from the comb teeth part 32A of the common electrode 32 and faces the comb teeth part 32A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present embodiment relates to a thermal print head, a method for manufacturing the same, and a thermal printer.

Background Art

[0002] A thermal print head includes, for example, a large number of heat generating portions arranged in the main scanning direction on a head substrate. Each heat generating portion is formed by laminating a common electrode and an individual electrode with their ends facing each other on a resistor layer formed on the head substrate via a glaze layer so that a part thereof is exposed. By passing an electric current between the common electrode and the individual electrode, the exposed portion (heat generating portion) of the resistor layer generates heat due to Joule heat. By transferring the heat to a printing medium (such as a barcode sheet or thermal paper for creating a receipt), printing on the printing medium is performed.

[0003] For example, in a logistics center or the like, sorting of articles, details, and invoice numbers are printed on a label, and by using the label, the inspection work is simplified and made more efficient.

[0004] However, in recent years, traceability has been emphasized, and all kinds of information such as a manufacturer-specific symbol, manufacturing date, expiration date, etc. are being described on printing media such as labels and receipts. Furthermore, in food products, etc., due to the obligation of nutritional component labeling and changes in allergy labeling, etc., the amount of printed information and the label printing volume in the logistics field have a tendency to increase.

[0005] In order to enable a large amount of printing that is on an increasing trend, it is necessary for the thermal print head to print information on the printing medium at high speed and with high definition. In order to print at high speed and with high definition (to improve printing performance), it is necessary to narrow the pitch of the heat generating portions.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] The heat generating portion is formed in a portion of the glaze layer that bulges upward, and a protective film is disposed so as to cover the heat generating portion. However, in order to completely cover the end portion of the heat generating portion with the protective film, it is necessary to form the protective film thickly in consideration of the covering property of the end portion of the heat generating portion. Since heat generated from the heat generating portion is transmitted to the printing medium through the protective film, if the protective film is too thick, heat cannot be efficiently transmitted to the printing medium, and there is a risk that the printing performance may deteriorate. One aspect of the present embodiment provides a thermal print head that ensures good printing performance. Another aspect of the present embodiment provides a method for manufacturing the thermal print head. Still another aspect of the present embodiment provides a thermal printer including the thermal print head.

MEANS FOR SOLVING THE PROBLEMS

[0008] In the present embodiment, by using a first protective film having a groove portion, a heating resistor electrically connected to an individual electrode and a common electrode is formed in the groove portion, and a second protective film covering the heating resistor is thinly formed, the printing performance of the thermal print head can be improved. One aspect of the present embodiment is as follows.

[0009] One aspect of the present embodiment includes an insulator, a heat storage layer disposed on the insulator, a first protective film disposed on the heat storage layer and having a groove portion, a heating resistor disposed on the heat storage layer and embedded in the groove portion, an individual electrode electrically connected to the heating resistor, a common electrode having a comb-shaped portion electrically connected to the heating resistor, and a second protective film covering the heating resistor and the first protective film, wherein the individual electrode is spaced apart from the comb-shaped portion of the common electrode and faces the comb-shaped portion. The interface between the heating resistor and the second protective film is on the insulator side of the interface between the first protective film and the second protective film. A thermal print head.

[0010] Another aspect of the present embodiment is a thermal printer including the thermal print head.

[0011] Another aspect of the present embodiment is a method for manufacturing a thermal print head, including forming a heat storage layer on an insulator, forming a common electrode having comb teeth and individual electrodes on the heat storage layer, forming a resist on the heat storage layer, on the individual electrodes, and on the comb teeth, forming a first protective film having a groove portion using the resist, forming a heating resistor electrically connected to the individual electrodes and the common electrode in the groove portion, forming a second protective film covering the heating resistor and the first protective film, and the individual electrodes being spaced apart from and facing the comb teeth of the common electrode. The interface between the heating resistor and the second protective film is formed to be on the insulator side of the interface between the first protective film and the second protective film. It is a method for manufacturing a thermal print head.

[0012] Another aspect of the present embodiment is a method for manufacturing a thermal print head, including forming a heat storage layer on an insulator, forming a resist on the heat storage layer, forming a first protective film having a groove portion using the resist, forming a heating resistor in the groove portion, forming a common electrode having comb teeth and individual electrodes on the heating resistor and on the first protective film, forming a second protective film covering the heating resistor, the first protective film, the common electrode, and the individual electrodes, and the individual electrodes being spaced apart from and facing the comb teeth of the common electrode. The interface between the heating resistor and the second protective film is formed to be on the insulator side of the interface between the first protective film and the second protective film. It is a method for manufacturing a thermal print head.

Advantages of the Invention

[0013] According to the present embodiment, it is possible to provide a thermal print head ensuring good printing performance. Further, it is possible to provide a method for manufacturing the thermal print head. Furthermore, it is possible to provide a thermal printer including the thermal print head.

Brief Description of the Drawings

[0014]

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DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, this embodiment will be described with reference to the drawings. In the following description of the drawings, the same 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 the planar dimensions of each component is different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Also, it goes without saying that there are portions where the dimensional relationships and ratios are different between the drawings.

[0016] Also, the following embodiments exemplify devices and methods for embodying the technical idea, and do not specify the materials, shapes, structures, arrangements, etc. of each component. Various changes can be made to this embodiment within the scope of the claims.

[0017] One aspect of the specific embodiment is as follows.

[0018] <1> An insulator, a heat storage layer disposed on the insulator, a first protective film disposed on the heat storage layer and having a groove portion, a heating resistor disposed on the heat storage layer and embedded in the groove portion, an individual electrode electrically connected to the heating resistor, a common electrode having a comb-shaped portion electrically connected to the heating resistor, and a second protective film covering the heating resistor and the first protective film, wherein the individual electrode is spaced apart from the comb-shaped portion of the common electrode and faces the comb-shaped portion, a thermal print head.

[0019] <2> The heating resistor is disposed on the individual electrode and on the comb-shaped portion, the thermal print head according to <1>.

[0020] <3> The individual electrode and the common electrode are disposed on the heating resistor and on the first protective film, the thermal print head according to <1>.

[0021] <4> The heating resistor, the second protective film, the first protective film, and the second protective film are on the insulator side from the boundary surface, the thermal print head according to any one of <1> to <3>.

[0022] <5> Among the main surfaces on the opposite side of the side where the first protective film is located of the second protective film, the portion overlapping the heating resistor when viewed from the normal direction of the main surface is a flat surface, the thermal print head according to any one of <1> to <4>.

[0023] <6> The main surface of the heating resistor on the side where the second protective film is located has a concave curved surface, the thermal print head according to any one of <1> to <5>.

[0024] <7> The insulator is a substrate, the thermal print head according to any one of <1> to <6>.

[0025] <8> The substrate is made of ceramic, the thermal print head according to <7>.

[0026] <9> A thermal printer comprising the thermal print head according to any one of <1> to <8>.

[0027] <10> A method of manufacturing a thermal print head, comprising: forming a heat storage layer on an insulator; forming a common electrode having a comb-shaped portion and an individual electrode on the heat storage layer; forming a resist on the heat storage layer, on the individual electrode, and on the comb-shaped portion; using the resist to form a first protective film having a groove portion; forming a heating resistor in the groove portion that is electrically connected to the individual electrode and the common electrode; forming a second protective film that covers the heating resistor and the first protective film; and the individual electrode being spaced apart from and facing the comb-shaped portion of the common electrode.

[0028] <11> A method of manufacturing a thermal print head, comprising: forming a heat storage layer on an insulator; forming a resist on the heat storage layer; using the resist to form a first protective film having a groove portion; forming a heating resistor in the groove portion; forming a common electrode having a comb-shaped portion and an individual electrode on the heating resistor and on the first protective film; forming a second protective film that covers the heating resistor, the first protective film, the common electrode, and the individual electrode; and the individual electrode being spaced apart from and facing the comb-shaped portion of the common electrode.

[0029] <12> The method of manufacturing a thermal print head according to <10> or <11>, wherein the first protective film is formed by firing a material paste to be the first protective film.

[0030] <13> The method of manufacturing a thermal print head according to any one of <10> to <12>, wherein the heating resistor is formed by embedding a resistor paste in the groove portion of the first protective film and firing the resistor paste.

[0031] <14> The method of manufacturing a thermal print head according to any one of <10> to <13>, wherein the heating resistor is formed by screen printing.

[0032] <15> The method for manufacturing a thermal print head according to any one of <10> to <13>, wherein the heating resistor is formed using a mask.

[0033] <16> The method for manufacturing a thermal print head according to <15>, wherein the mask is a stencil mask.

[0034] <17> The method for manufacturing a thermal print head according to any one of <10> to <16>, wherein the first protective film is formed through a firing process, and the resist is removed by one or more processes selected from the group consisting of the firing process and the organic peeling process.

[0035] <18> The method for manufacturing a thermal print head according to any one of <10> to <17>, wherein the main surface of the heating resistor on the side where the second protective film is located has a concave curved surface.

[0036] <Thermal print head> (First Embodiment) The thermal print head according to the present embodiment will be described with reference to the drawings.

[0037] FIG. 1 is a partial perspective view showing a thermal print head. FIG. 2 is a partial cross-sectional view taken along line A-A of FIG. 1 in the main scanning direction X. FIG. 3 is a partial cross-sectional view taken along line B-B of FIG. 1 in the sub-scanning direction Y. FIGS. 1 to 3 show a part of the thermal print head (corresponding to one thermal print head). In the present embodiment, this one thermal print head is taken as an individual-piece thermal print head 100. The thermal print head 100 includes a substrate 15 which is an insulator, a heat storage layer 33 on the substrate 15, a plurality of individual electrodes 31 on the heat storage layer 33, a common electrode 32 on the heat storage layer 33, a protective film 34A having a groove portion 38 on the heat storage layer 33, on the plurality of individual electrodes 31, and on the common electrode 32, a plurality of heating resistors 40 disposed on the heat storage layer 33, on the individual electrodes 31, and on the common electrode 32 and embedded in the groove portion 38, and a protective film 34B covering the plurality of heating resistors 40 and the protective film 34A. The heating resistor 40 is electrically connected to the individual electrode 31 and the common electrode 32. Each of the individual electrodes 31 is spaced apart from the comb-tooth portion 32A of the common electrode 32 so as to sandwich each of the heating resistors 40 and faces the comb-tooth portion 32A. Further, the heating resistor 40 includes a heating resistance portion 41 that generates heat by an electric current flowing through the individual electrode 31 and the common electrode 32. The plurality of heating resistance portions 41 are independently formed between the individual electrode 31 and the common electrode 32. FIG. 1 omits the illustration of the plurality of heating resistance portions 41. The plurality of heating resistance portions 41 are linearly arranged on the heat storage layer 33.

[0038] In the present embodiment, the direction in which the plurality of heating resistance portions 41 extend 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 a direction perpendicular to each of the main scanning direction X and the sub-scanning direction Y. Further, the direction in which the heat storage layer 33 is located as viewed from the substrate 15 is defined as the upward direction, and the direction in which the substrate 15 is located as viewed from the heat storage layer 33 is defined as the downward direction.

[0039] The substrate 15 is an insulator and is made of, for example, ceramic. As the ceramic, for example, alumina or the like can be used. From the viewpoint of heat dissipation, it is preferable to use alumina, which has a relatively high thermal conductivity, for the substrate 15.

[0040] On the substrate 15, a heat storage layer 33 (also referred to as a glaze layer) having a function of storing heat is laminated. The heat storage layer 33 stores the heat generated from the heat generating resistance portion 41 described later. As the heat storage layer 33, an insulating material can be used. For example, silicon oxide or silicon nitride, which is the main component of glass, can be used. The dimension of the heat storage layer 33 in the thickness direction Z is not particularly limited and is, for example, 5 to 100 μm, preferably 10 to 30 μm.

[0041] On the heat storage layer 33, an individual electrode 31 and a common electrode 32 formed from a metal paste are provided. The individual electrode 31 and the common electrode 32 are obtained by applying a metal paste by screen printing or the like and then firing to form an electrode pattern.

[0042] As the metal paste, for example, a paste containing metal particles such as copper, silver, palladium, iridium, platinum, and gold can be used. From the viewpoints of the properties and ionization tendency of the metal, copper, silver, platinum, and gold are preferable, and silver is more preferable from the viewpoints of the properties, ionization tendency, and cost reduction of the metal. Further, the solvent contained in the metal paste has a function of uniformly dispersing the metal particles, and examples thereof include, but are not limited to, a mixture of one or more of an ester-based solvent, a ketone-based solvent, a glycol ether-based solvent, an aliphatic-based solvent, an alicyclic-based solvent, an aromatic-based solvent, an alcohol-based solvent, and water.

[0043] Examples of ester solvents include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, dimethyl carbonate, etc. Examples of ketone solvents include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, diisobutyl ketone, diacetone alcohol, isophorone, cyclohexanone, etc. Examples of glycol ether solvents include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, etc., acetates 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, etc., and acetates of these monoethers, etc.

[0044] Examples of aliphatic solvents include n-heptane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, etc. Examples of alicyclic solvents include methylcyclohexane, ethylcyclohexane, cyclohexane, etc. Examples of aromatic solvents include toluene, xylene, tetralin, etc. Examples of alcohol solvents (excluding the above-mentioned glycol ether solvents) include ethanol, propanol, butanol, etc.

[0045] The metal paste can contain, if necessary, a dispersant, a surface treatment agent, an anti-friction improver, an infrared absorber, an ultraviolet absorber, a fragrance, an antioxidant, an organic pigment, an inorganic pigment, an antifoaming agent, a silane coupling agent, a titanate coupling agent, a plasticizer, a flame retardant, a moisturizing agent, an ion scavenger, etc.

[0046] Each individual electrode 31 is generally in a strip shape extending in the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when a printer incorporating a thermal print head is used, different potentials can be individually applied to each individual electrode 31. An individual pad portion (not shown) is connected to the end of each individual electrode 31.

[0047] The common electrode 32 is a part that has an opposite electrical polarity to a plurality of 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 that commonly connects the comb tooth portions 32A. The common portion 32B is formed in the main scanning direction X along the upper edge of the substrate 15. In the sub-scanning direction Y, the direction in which the common electrode 32 is located when viewed from the individual electrode 31 is defined as the upper side in the sub-scanning direction Y. Each comb tooth portion 32A has a strip shape extending in the sub-scanning direction Y. The tip of each comb tooth portion 32A is opposed to the tip of each individual electrode 31 with a predetermined interval therebetween along the sub-scanning direction Y. By adopting such a configuration, the pitch of the heating resistors 40 can be narrowed, enabling high-definition printing.

[0048] The protective film 34A has a groove portion 38. The individual electrodes 31, the common electrode 32, etc. are covered with the protective film 34A to protect the individual electrodes 31, the common electrode 32, etc. from wear, corrosion, oxidation, etc. An insulating material can be used for the protective film 34A, for example, it can be made of amorphous glass. The protective film 34A is formed by thick-film printing a glass paste and then firing it. The dimension of the protective film 34A in the thickness direction Z is, for example, about 1 to 10 μm.

[0049] The heating resistor 40 is electrically connected to the individual electrode 31 and the common electrode 32, and the portion where the current from the individual electrode 31 and the common electrode 32 flows generates heat. Specifically, the heating resistor 40 (heating resistance portion 41) to which a heating voltage is individually applied according to a printing signal transmitted from the outside to a driving IC or the like is selectively heated. The heating resistance portion 41 is selectively heated by being individually energized according to the printing signal. By generating heat in this way, printing dots are formed. The heating resistor 40 can use a material having a higher resistivity than the materials constituting the individual electrode 31 and the common electrode 32, for example, ruthenium oxide can be used.

[0050] The heating resistor 40 can be formed by embedding a resistor paste in the groove portion 38 of the protective film 34A and firing it. In the present embodiment, the dimension of the heating resistor 40 in the thickness direction Z is, for example, about 1 to 10 μm.

[0051] The resistor paste that becomes the heating resistor 40 shrinks when fired. For example, even if the resistor paste is supplied so as to completely fill the groove portion 38, when viewed microscopically as shown in FIG. 4 after firing, the surface of the heating resistor 40 that is in contact with the protective film 34B is on the substrate 15 side with respect to the surface of the protective film 34A that is in contact with the protective film 34B. In other words, the boundary surface between the heating resistor 40 and the protective film 34B is on the substrate 15 side (lower side) with respect to the boundary surface between the protective film 34A and the protective film 34B. When it is difficult to distinguish the boundary between the protective film 34A and the protective film 34B because they are made of the same material or the like, the boundary surface between the protective film 34A and the protective film 34B is defined as the portion separated by the thickness of the protective film 34B from the main surface of the protective film 34B (the main surface of the protective film 34B on the side opposite to the side where the protective film 34A is located). Since the boundary surface between the heating resistor 40 and the protective film 34B is on the substrate 15 side with respect to the boundary surface between the protective film 34A and the protective film 34B, the end portion of the heating resistor 40 is on the substrate 15 side with respect to the boundary surface between the protective film 34A and the protective film 34B, so it is preferable because the end portion of the heating resistor 40 can be completely covered by the protective film 34B.

[0052] Also, among the main surfaces of the protective film 34B on the side opposite to the side where the protective film 34A is located, the portion that overlaps with the heating resistor 40 when viewed from the normal direction of the main surface may be a flat surface. In this specification and the like, the "flat surface" includes a surface with an average surface roughness of 0.5 μm or less. The average surface roughness can be obtained, for example, in accordance with JIS B 0601:2013 or ISO 25178. It is preferable that the portion overlapping with the heating resistor 40 is a flat surface because it becomes easier to contact the platen roller of the thermal print head.

[0053] As shown in FIG. 5, the heating resistor 40 may have a concave curved surface 40A on its main surface (the surface opposite to the surface on which the heat storage layer 33 is located). In the process of forming the heating resistor 40, since the resistor paste is embedded in the groove portion 38 of the protective film 34A and fired, the main surface of the resistor paste may have a concave curved surface 40A due to the surface tension with the protective film 34A. It is preferable that the main surface of the heating resistor 40 has a concave curved surface 40A because the protective film 34B and the like can be formed well.

[0054] The heating resistor 40, the protective film 34A, etc. are covered with the protective film 34B, and the protective film 34B protects the heating resistor 40, the protective film 34A, etc. from wear, corrosion, oxidation, etc. The protective film 34B can be made of an insulating material, for example, amorphous glass. The protective film 34B is formed by thick-film printing a glass paste and then firing it. The dimension of the protective film 34B in the thickness direction Z is, for example, about 2 to 8 μm. It is preferable that the thickness is in this range because it is possible to suppress breakdown voltage failure and obtain a thermal print head 100 capable of maintaining good printing quality. Even if the protective film 34B is made thinner, the end portion of the heating resistor 40 can be completely covered, and the printing performance of the thermal print head 100 can be improved.

[0055] Here, the manufacturing method of the thermal print head 100 of the present embodiment will be described.

[0056] As shown in FIGS. 6 to 8, first, the substrate 15 is prepared, and the heat storage layer 33 is formed on the substrate 15. Next, the wiring layer 30 is formed on the heat storage layer 33.

[0057] The heat storage layer 33 can be formed, for example, by applying a glass paste 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.

[0058] The wiring layer 30 will become the individual electrodes 31 and the common electrode 32 to be formed later. The wiring layer 30 is obtained by applying the above-mentioned metal paste that will become the individual electrodes 31 and the common electrode 32 by screen printing or the like, and then baking it.

[0059] Next, as shown in FIGS. 9 to 11, the wiring layer 30 is etched to form the individual electrodes 31 and the common electrode 32.

[0060] Next, as shown in FIGS. 12 to 14, a resist 36 is formed on the heat storage layer 33, on the individual electrodes 31, and on the common electrode 32. The heat generating resistor 40 will be formed later in the region where the resist 36 exists. Since defects in the shape pattern of the resist 36 are related to defects in the shape pattern of the heat generating resistor 40 to be formed later, it is preferable to appropriately adjust the etching conditions to accurately form the resist 36. By shaping the resist 36 into a desired shape, a groove 38 having a desired shape can be formed, and a desired heat generating resistor 40 can be obtained by the groove 38. Therefore, by accurately processing the shape pattern of the resist 36, defects in the shape pattern of the heat generating resistor 40 can be reduced.

[0061] Next, as shown in FIGS. 15 to 17, a protective film 34A is formed on the heat storage layer 33, on the individual electrodes 31, and on the common electrode 32 where the resist 36 is not provided. The protective film 34A is made of, for example, amorphous glass. The protective film 34A is formed by thick film printing a material paste (for example, a glass paste) that will become the protective film 34A and then baking it.

[0062] Next, as shown in FIGS. 18 to 20, the resist 36 is removed by the baking process when forming the protective film 34A, and the groove 38 is formed in the protective film 34A. The resist 36 may be removed by an organic stripping process. Solvents that can be used in the organic stripping process include, for example, the stripping liquid 10 manufactured by Tokyo Ohka Kogyo Co., Ltd.

[0063] Thus, by forming the protective film 34A using the resist 36, the groove 38 can be easily formed in the protective film 34A without using an etchant that requires great care in handling, such as hydrofluoric acid.

[0064] Next, as shown in FIGS. 21 to 23, a resistor paste that becomes the heating resistor 40 (heating resistance portion 41) is formed so as to fill the groove 38. The resistor paste is supplied to the groove 38 using a mask such as screen printing or a stencil mask. For example, supplying the resistor paste using a stencil mask is preferable because the printing accuracy is improved. The resistor paste contains, for example, ruthenium oxide.

[0065] Next, the heating resistor 40 (heating resistance portion 41) is formed by baking the above-described resistor paste.

[0066] In the step of forming the heating resistor 40, since the resistor paste is embedded in the groove 38 of the protective film 34A and baked, the main surface of the heating resistor 40 may have a concave curved surface 40A due to the surface tension with the protective film 34A. It is preferable that the main surface of the heating resistor 40 has a concave curved surface 40A because the protective film 34B and the like can be formed well.

[0067] Next, as shown in FIGS. 1 to 3, the protective film 34B is formed. The protective film 34B is made of, for example, amorphous glass. The protective film 34B is formed by thick-film printing a glass paste and then baking it.

[0068] Through the above steps, the thermal print head 100 of the present embodiment can be manufactured.

[0069] According to the present embodiment, since the heating resistor 40 is formed so as to be embedded in the groove portion 38, even if the protective film 34B is made thin, the end portion of the heating resistor 40 can be completely covered, and the printing performance of the thermal print head 100 can be improved. Further, since the heating resistor 40 is formed in the groove portion 38 of the protective film 34A without forming a plurality of heating resistors by wet etching or the like based on one heating resistor, defects in the pattern shape of individual heating resistors can be reduced.

[0070] (Second Embodiment) The thermal print head according to the present embodiment will be described with reference to the drawings.

[0071] FIG. 24 is a partial perspective view showing a thermal print head. FIG. 25 is a partial cross-sectional view taken along line A-A of FIG. 24 in the main scanning direction X. FIG. 26 is a partial cross-sectional view taken along line B-B of FIG. 24 in the sub-scanning direction Y. FIGS. 24 to 26 show a part of the thermal print head (corresponding to one thermal print head), and in the present embodiment, this one thermal print head is referred to as an individual-piece thermal print head 100A. The thermal print head 100A includes a substrate 15 that is an insulator, a heat storage layer 33 on the substrate 15, a protective film 34A having a groove portion 38 on the heat storage layer 33, a plurality of heating resistors 40 disposed on the heat storage layer 33 and embedded in the groove portion 38, a common electrode 32 and a plurality of individual electrodes 31 on the heating resistor 40 and on the protective film 34A, and a protective film 34B covering the plurality of heating resistors 40, the protective film 34A, the common electrode 32, and the plurality of individual electrodes 31.

[0072] The difference between the thermal print head 100A according to the present embodiment and the thermal print head 100 according to the first embodiment is that the individual electrodes 31 and the common electrode 32 are disposed on the heating resistor 40 and on the protective film 34A. In the present embodiment, the points common to the first embodiment are applied to the description of the first embodiment, and hereinafter, the different points will be described.

[0073] When the individual electrodes 31 and the common electrode 32 are arranged on the heating resistor 40 and the protective film 34A, the individual electrodes 31 and the common electrode 32 generate heat on the main surface side of the heating resistor 40 (the surface opposite to the side where the heat storage layer 33 is located). Therefore, the generated heat can be efficiently transmitted to the printing medium, and the printing performance of the thermal print head 100A can be improved more favorably.

[0074] Here, a method for manufacturing the thermal print head 100A of the present embodiment will be described.

[0075] As shown in FIGS. 27 to 29, first, a substrate 15 is prepared, and a heat storage layer 33 is formed on the substrate 15. Next, a resist 36 is formed on the heat storage layer 33. In the region where the resist 36 exists, a heating resistor 40 will be formed later.

[0076] Next, as shown in FIGS. 30 to 32, a protective film 34A is formed on the heat storage layer 33 where the resist 36 is not provided.

[0077] Next, as shown in FIGS. 33 to 35, the resist 36 is removed by the firing process when forming the protective film 34A, and a groove portion 38 is formed in the protective film 34A. The resist 36 may be removed by performing an organic peeling process.

[0078] In this way, by forming the protective film 34A using the resist 36, the groove portion 38 can be easily formed in the protective film 34A without using an etchant that requires sufficient attention in handling hydrofluoric acid or the like.

[0079] Next, as shown in FIGS. 36 to 38, a resistor paste that will become the heating resistor 40 (heating resistance portion 41) is formed so as to fill the groove portion 38. Next, the heating resistor 40 (heating resistance portion 41) is formed by firing the above-described resistor paste.

[0080] Next, as shown in FIGS. 24 to 26, a protective film 34B is formed. The protective film 34B is made of, for example, amorphous glass. The protective film 34B is formed by thick-film printing a glass paste and then firing it.

[0081] Through the above steps, the thermal print head 100A of the present embodiment can be manufactured.

[0082] According to the present embodiment, since the heating resistor 40 is formed so as to be embedded in the groove portion 38, even if the protective film 34B is made thin, the end portion of the heating resistor 40 can be completely covered, and the printing performance of the thermal print head 100A can be improved. Further, since the heating resistor 40 is formed in the groove portion 38 of the protective film 34A without forming a plurality of heating resistors by wet etching or the like based on one heating resistor, defects in the pattern shape of each heating resistor can be reduced.

[0083] (Other Embodiments) As described above, one embodiment has been described. However, the discussions and drawings that form a part of the disclosure are exemplary and should not be construed as limiting. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure. Thus, this embodiment includes various embodiments and the like not described herein.

[0084] <Thermal Printer> A thermal print head (for example, thermal print head 100) further includes a substrate 15 (the heat storage layer 33 etc. on the substrate 15 are not shown), a connection substrate 5, a heat dissipation member 8, a driving IC 7, a plurality of wires 81, a resin part 82, and a connector 59 as shown in FIG. 39. The substrate 15 and the connection substrate 5 are mounted adjacent to each other in the sub-scanning direction Y on the heat dissipation member 8. A plurality of heat generating resistor parts 41 arranged in the main scanning direction X are formed on the substrate 15. The heat generating resistor parts 41 are driven to selectively generate heat by the driving IC 7 mounted on the connection substrate 5. The heat generating resistor parts 41 perform printing on a printing medium 92 such as thermal paper that is pressed against the heat generating resistor parts 41 by a platen roller 91 according to a printing signal transmitted from the outside via the connector 59.

[0085] For the connection substrate 5, for example, a printed wiring board can be used. The connection substrate 5 has a structure in which a base material layer and a wiring layer (not shown) are laminated. For the base material layer, for example, a glass epoxy resin or the like can be used. For the wiring layer, for example, metals such as copper, silver, palladium, iridium, platinum, and gold can be used.

[0086] The heat dissipation member 8 has a function of dissipating heat from the substrate 15. The substrate 15 and the connection substrate 5 are attached to the heat dissipation member 8. For the heat dissipation member 8, for example, a metal such as aluminum can be used.

[0087] For the wires 81, for example, a conductor such as gold can be used. There are a plurality of wires 81, and a part of them is electrically connected between the driving IC 7 and each individual electrode by bonding. Also, a part of the other wires 81 is electrically connected between the driving IC 7 and the connector 59 through the wiring layer in the connection substrate 5 by bonding.

[0088] The resin part 82 can use, for example, a black resin. As the resin part 82, for example, an epoxy resin, a silicone resin, etc. can be used. The resin part 82 covers the drive IC 7 and the plurality of wires 81, etc., and protects the drive IC 7 and the plurality of wires 81. The connector 59 is fixed to the connection substrate 5. Wires for supplying power from the outside of the thermal print head to the thermal print head and for controlling the drive IC 7 are connected to the connector 59.

[0089] The thermal printer can include the above-described thermal print head. The thermal printer performs printing on a print medium conveyed along the sub-scanning direction Y. Usually, the print medium is conveyed from the connector 59 side toward the heat generating resistance part 41 side. Examples of the print medium include a barcode sheet and thermal paper for creating a receipt.

[0090] The thermal printer includes, for example, a thermal print head 100, a platen roller 91, a main power circuit, a measurement circuit, and a control unit. The platen roller 91 faces the thermal print head 100.

[0091] The main power circuit supplies power to the plurality of heat generating resistance parts 41 in the thermal print head 100. The measurement circuit measures the resistance value of each of the plurality of heat generating resistance parts 41. The measurement circuit measures the resistance value of each of the plurality of heat generating resistance parts 41, for example, when printing is not performed on the print medium. Thereby, the life of the heat generating resistance part 41 and the presence or absence of a failed heat generating resistance part 41 can be confirmed. The control unit controls the driving states of the main power circuit and the measurement circuit. The control unit controls the energization state of each of the plurality of heat generating resistance parts 41. The measurement circuit may be omitted.

[0092] The connector 59 is used for communicating with a device outside the thermal print head 100. Through the connector 59, the thermal print head 100 is electrically connected to the main power circuit and the measurement circuit. Through the connector 59, the thermal print head 100 is electrically connected to the control unit.

[0093] 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 energization state of each of the plurality of heat generating resistance portions 41. Specifically, the drive IC 7 selectively energizes a plurality of individual electrodes to arbitrarily generate heat in any one of the plurality of heat generating resistance portions 41.

[0094] Further, the thermal print head is not limited to the above-described configuration. For example, the drive IC 7 may be directly mounted on the substrate 15 without providing the connection substrate 5, or the wire 81 may not be provided by flip chip mounting, or the heat dissipation member 8 may not be provided.

[0095] Next, a method of using the thermal printer will be described.

[0096] When printing on the printing medium, a potential v11 is applied as the potential V1 from the main power supply circuit to the connector 59. In this case, a plurality of heat generating resistance portions 41 are selectively energized and generate heat. By transferring the heat to the printing medium, printing on the printing medium is performed. As described above, when the potential v11 is applied as the potential V1 from the main power supply circuit to the connector 59, an energization path to each of the plurality of heat generating resistance portions 41 is ensured.

[0097] When printing on a printing medium is not performed, the resistance values of the respective heating resistor portions 41 are measured. At the time of such measurement, no potential is applied to the connector 59 from the main power supply circuit. At the time of measuring the resistance values of the respective heating resistor portions 41, a potential v12 is applied as a potential V1 to the connector 59 from the measurement circuit. In this case, a plurality of heating resistor portions 41 are energized in order (for example, in order from the heating resistor portion 41 located at the end in the main scanning direction X). Based on the value of the current flowing through the heating resistor portion 41 and the potential v12, the measurement circuit measures the resistance value of each heating resistor portion 41. As described above, when the potential v11 is applied as the potential V1 to the connector 59 from the main power supply circuit, the energization paths to each of the plurality of heating resistor portions 41 are substantially blocked. Thereby, the measurement circuit can more accurately measure the resistance values of the respective heating resistor portions 41, and the life of the heating resistor portion 41 and the presence or absence of a failed heating resistor portion 41 can be confirmed.

[0098] According to the above, a thermal printer with good printing performance can be obtained.

Explanation of Reference Numerals

[0099] 5 Connection substrate 7 Driving IC 8 Heat dissipation member 15 Substrate 30 Wiring layer 31 Individual electrode 32 Common electrode 33 Heat storage layer 34A, 34B Protective film 36 Resist 38 Groove portion 40 Heating resistor 40A Curved surface 41 Heating resistor portion 59 Connector 81 Wire 82 Resin portion 91 Platen roller 92 Printing medium 100, 100A Thermal print head

Claims

1. An insulator, a heat storage layer disposed on the insulator, a first protective film disposed on the heat storage layer and having a groove portion, a heating resistor disposed on the heat storage layer and embedded in the groove portion, an individual electrode electrically connected to the heating resistor, a common electrode having a comb-tooth portion and electrically connected to the heating resistor, and a second protective film covering the heating resistor and the first protective film, wherein the individual electrode is spaced apart from and faces the comb-tooth portion of the common electrode, and a boundary surface between the heating resistor and the second protective film is on the insulator side of a boundary surface between the first protective film and the second protective film, a thermal print head.

2. The thermal print head according to claim 1, wherein the heating resistor is disposed on the individual electrode and on the comb-tooth portion.

3. The thermal print head according to claim 1, wherein the individual electrode and the common electrode are disposed on the heating resistor and on the first protective film.

4. The thermal print head according to any one of claims 1 to 3, wherein a portion of a main surface of the second protective film on a side opposite to a side where the first protective film is located and overlapping the heating resistor as viewed from a normal direction of the main surface is a flat surface.

5. The thermal print head according to any one of claims 1 to 4, wherein a main surface of the heating resistor on a side where the second protective film is located has a concave curved surface.

6. The thermal print head according to any one of claims 1 to 5, wherein the insulator is a substrate.

7. The thermal print head according to claim 6, wherein the substrate is made of ceramic.

8. A thermal printer including the thermal print head according to any one of claims 1 to 7.

9. Form a heat storage layer on an insulator, form a common electrode having a comb-tooth portion and an individual electrode on the heat storage layer, form a resist on the heat storage layer, on the individual electrode, and on the comb-tooth portion, use the resist to form a first protective film having a groove portion, form a heating resistor electrically connected to the individual electrode and the common electrode in the groove portion, form a second protective film covering the heating resistor and the first protective film, wherein the individual electrode is spaced apart from and faces the comb-tooth portion of the common electrode, The interface between the heating resistor and the second protective film is formed so as to be on the insulator side with respect to the interface between the first protective film and the second protective film. Method for manufacturing a thermal print head.

10. A heat storage layer is formed on an insulator. A resist is formed on the heat storage layer. Using the resist, a first protective film having a groove portion is formed. A heating resistor is formed in the groove portion. A common electrode having comb teeth portions and individual electrodes are formed on the heating resistor and on the first protective film. A second protective film is formed to cover the heating resistor, the first protective film, the common electrode, and the individual electrodes. The individual electrodes are spaced apart from the comb teeth portions of the common electrode and face the comb teeth portions. The interface between the heating resistor and the second protective film is formed so as to be on the insulator side with respect to the interface between the first protective film and the second protective film. Method for manufacturing a thermal print head.

11. The first protective film is formed by baking a material paste that becomes the first protective film. The method for manufacturing a thermal print head according to claim 9 or 10.

12. The heating resistor is formed by embedding a resistor paste in the groove portion of the first protective film and baking the resistor paste. The method for manufacturing a thermal print head according to any one of claims 9 to 11.

13. The heating resistor is formed by screen printing. The method for manufacturing a thermal print head according to any one of claims 9 to 12.

14. The heating resistor is formed using a mask. The method for manufacturing a thermal print head according to any one of claims 9 to 12.

15. The mask is a stencil mask. The method for manufacturing a thermal print head according to claim 14.

16. The first protective film is formed through a baking process. The resist is removed by one or more processes selected from the group consisting of the baking process and the organic peeling process. The method for manufacturing a thermal print head according to any one of claims 9 to 15.

17. The main surface of the heating resistor on the side where the second protective film is located has a concave curved surface. The method for manufacturing a thermal print head according to any one of claims 9 to 16.

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