JP7701181B2 - Thermal printhead, its manufacturing method, and thermal printer - Google Patents

Description

This embodiment relates to a thermal printhead, a manufacturing method thereof, and a thermal printer.

A thermal printhead, for example, has many heating elements arranged in the main scanning direction on a head substrate. Each heating element is formed by laminating a common electrode and an individual electrode with their ends facing each other, with a portion of the heating element exposed on a resistor layer formed on the head substrate via a glaze layer. By passing current between the common electrode and the individual electrodes, the exposed portion (heating element) of the resistor layer generates heat due to Joule heat. The heat is transferred to a print medium (such as thermal paper for creating barcode sheets or receipts), and printing is performed on the print medium.

For example, at logistics centers, the classification of goods, details of contents, and shipping slip number are printed on labels, and the labels are used to simplify and streamline inspection work.

However, in recent years, with the emphasis on traceability, various information such as the manufacturer's unique code, production date, and expiration date are now printed on printed media such as labels and receipts. Furthermore, in the case of food products, the amount of printed information and the amount of label printing are on the rise, with the mandatory labeling of nutritional content and changes to allergy labeling.

To enable the increasing volume of printing, thermal print heads need to print information on print media at high speed and with high resolution. To print at high speed and with high resolution (to improve printing performance), the pitch of the heating elements needs to be narrow.

JP 2006-159866 A

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 of the heat generating portion with the protective film, it is necessary to form the protective film thick in consideration of the coverage of the end of the heat generating portion. Since heat generated from the heat generating portion is transferred to the print medium via the protective film, if the protective film is too thick, the heat cannot be transferred to the print medium efficiently, and there is a risk of degraded printing performance. One aspect of this embodiment provides a thermal printhead that ensures good printing performance. Another aspect of this embodiment provides a method for manufacturing the thermal printhead. Another aspect of this embodiment provides a thermal printer equipped with the thermal printhead.

In this embodiment, a first protective film having a groove is used, a heating resistor electrically connected to the individual electrode and the common electrode is formed in the groove, and a second protective film is formed thinly to cover the heating resistor, thereby improving the printing performance of the thermal printhead. One aspect of this embodiment is as follows.

One aspect of this embodiment is a thermal print head comprising an insulator, a heat storage layer arranged on the insulator, a first protective film arranged on the heat storage layer and having a groove portion, a heating resistor arranged on the heat storage layer and embedded in the groove portion, individual electrodes electrically connected to the heating resistor, a common electrode having a comb tooth portion electrically connected to the heating resistor, and a second protective film covering the heating resistor and the first protective film, wherein the individual electrodes are spaced apart from the comb tooth portion of the common electrode and face the comb tooth portion , and the boundary surface between the heating resistor and the second protective film is on the insulator side of the boundary surface between the first protective film and the second protective film .

Another aspect of this embodiment is a thermal printer equipped with the above-mentioned thermal printhead.

Another aspect of this embodiment is a method for manufacturing a thermal printhead, comprising the steps of forming a heat storage layer on an insulator, forming a common electrode having a comb tooth portion and individual electrodes on the heat storage layer, forming a resist on the heat storage layer, the individual electrodes, and the comb tooth portion, forming a first protective film having a groove portion using the resist, forming a heating resistor in the groove portion that is electrically connected to the individual electrodes and the common electrode, forming a second protective film that covers the heating resistor and the first protective film, forming the individual electrodes to be spaced apart from the comb tooth portion of the common electrode and opposed to the comb tooth portion, and forming the boundary surface between the heating resistor and the second protective film on the insulator side relative to the boundary surface between the first protective film and the second protective film .

Another aspect of this embodiment is a method for manufacturing a thermal printhead, comprising the steps of 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 a comb tooth portion 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, the individual electrodes being spaced apart from the comb tooth portion of the common electrode and facing the comb tooth portion, and the boundary surface between the heating resistor and the second protective film being on the insulator side relative to the boundary surface between the first protective film and the second protective film .

According to this embodiment, it is possible to provide a thermal printhead that ensures good printing performance. It is also possible to provide a method for manufacturing the thermal printhead. Furthermore, it is possible to provide a thermal printer that includes the thermal printhead.

FIG. 1 is a partial perspective view illustrating a thermal printhead according to a first embodiment. FIG. 2 is a partial cross-sectional view taken along line AA of FIG. FIG. 3 is a partial cross-sectional view taken along the line BB in the sub-scanning direction Y of FIG. FIG. 4 is an enlarged cross-sectional view of the heating resistor and its surroundings. FIG. 5 is an enlarged perspective view of the heating resistor. FIG. 6 is a partial perspective view (part 1) illustrating the method for manufacturing the thermal printhead according to the first embodiment. FIG. 7 is a partial cross-sectional view taken along line AA of FIG. FIG. 8 is a partial cross-sectional view taken along line BB in FIG. FIG. 9 is a partial perspective view (part 2) illustrating the method for manufacturing the thermal printhead according to the first embodiment. FIG. 10 is a partial cross-sectional view taken along line AA of FIG. FIG. 11 is a partial cross-sectional view taken along line BB of FIG. FIG. 12 is a partial perspective view (part 3) illustrating the method for manufacturing the thermal printhead according to the first embodiment. 13 is a partial cross-sectional view taken along line AA of FIG. 12 in the main scanning direction X. FIG. 14 is a partial cross-sectional view taken along line BB of FIG. 12 in the sub-scanning direction Y. FIG. FIG. 15 is a partial perspective view (part 4) illustrating the method for manufacturing the thermal printhead according to the first embodiment. 16 is a partial cross-sectional view taken along line AA of FIG. 15 in the main scanning direction X. FIG. FIG. 17 is a partial cross-sectional view taken along the line BB in FIG. FIG. 18 is a partial perspective view (part 5) illustrating the method for manufacturing the thermal printhead according to the first embodiment. FIG. 19 is a partial cross-sectional view taken along line AA of FIG. FIG. 20 is a partial cross-sectional view taken along line BB of FIG. 18 in the sub-scanning direction Y. FIG. 21 is a partial perspective view (part 6) illustrating the method for manufacturing the thermal printhead according to the first embodiment. 22 is a partial cross-sectional view taken along line AA of FIG. 21 in the main scanning direction X. FIG. 23 is a partial cross-sectional view taken along line BB of FIG. 21 in the sub-scanning direction Y. FIG. FIG. 24 is a cross-sectional view illustrating a thermal printhead according to the second embodiment. 25 is a partial cross-sectional view taken along line AA of FIG. 24 in the main scanning direction X. FIG. 26 is a partial cross-sectional view taken along line BB of FIG. 24 in the sub-scanning direction Y. FIG. FIG. 27 is a partial perspective view (part 1) illustrating a method for manufacturing a thermal printhead according to the second embodiment. 28 is a partial cross-sectional view taken along line AA of FIG. 27 in the main scanning direction X. FIG. 29 is a partial cross-sectional view taken along line BB of FIG. 27 in the sub-scanning direction Y. FIG. FIG. 30 is a partial perspective view (part 2) illustrating the method for manufacturing the thermal printhead according to the second embodiment. 31 is a partial cross-sectional view taken along line AA of FIG. 30 in the main scanning direction X. FIG. 32 is a partial cross-sectional view taken along line BB of FIG. 30 in the sub-scanning direction Y. FIG. FIG. 33 is a partial perspective view (part 3) illustrating the method for manufacturing the thermal printhead according to the second embodiment. 34 is a partial cross-sectional view taken along line AA of FIG. 33 in the main scanning direction X. FIG. 35 is a partial cross-sectional view taken along line BB of FIG. 33 in the sub-scanning direction Y. FIG. FIG. 36 is a partial perspective view (part 4) illustrating the method for manufacturing the thermal printhead according to the second embodiment. 37 is a partial cross-sectional view taken along line AA of FIG. 36 in the main scanning direction X. FIG. 38 is a partial cross-sectional view taken along line BB of FIG. 36 in the sub-scanning direction Y. FIG. FIG. 39 is a cross-sectional view illustrating a thermal printhead.

Next, this embodiment will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are given 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 the actual relationship. Therefore, the specific thickness and dimensions should be determined with reference to the following description. In addition, the drawings naturally include parts with different dimensional relationships and ratios.

The embodiments shown below are merely examples of devices and methods for embodying the technical ideas, and do not specify the materials, shapes, structures, arrangements, etc. of each component. Various modifications can be made to the present embodiments within the scope of the claims.

A specific aspect of this embodiment is as follows:

<1> A thermal printhead comprising an insulator, a heat storage layer disposed on the insulator, a first protective film disposed on the heat storage layer and having a groove, a heating resistor disposed on the heat storage layer and embedded in the groove, individual electrodes electrically connected to the heating resistor, a common electrode having a comb-tooth portion electrically connected to the heating resistor, and a second protective film covering the heating resistor and the first protective film, the individual electrodes being spaced apart from the comb-tooth portion of the common electrode and facing the comb-tooth portion.

<2> The thermal printhead described in <1>, in which the heating resistor is disposed on the individual electrodes and on the comb teeth portion.

<3> The thermal printhead described in <1>, in which the individual electrodes and the common electrode are disposed on the heating resistor and on the first protective film.

<4> A thermal printhead according to any one of <1> to <3>, in which the heating resistor is located on the insulator side of the boundary surface between the heating resistor and the second protective film, the first protective film, and the second protective film.

<5> A thermal printhead according to any one of <1> to <4>, in which the portion of the main surface of the second protective film opposite the side where the first protective film is located that overlaps with the heating resistor when viewed from the normal direction of the main surface is a flat surface.

<6> A thermal printhead described in any one of <1> to <5>, in which the main surface of the heating resistor on the side where the second protective film is located has a concave curved surface.

<7> A thermal printhead according to any one of <1> to <6>, wherein the insulator is a substrate.

<8> The thermal printhead described in <7>, wherein the substrate is made of ceramic.

<9> A thermal printer equipped with a thermal printhead according to any one of <1> to <8>.

<10> A method for manufacturing a thermal printhead, comprising forming a heat storage layer on an insulator, forming a common electrode having a comb-tooth portion and individual electrodes on the heat storage layer, forming a resist on the heat storage layer, the individual electrodes, and the comb-tooth portion, forming a first protective film having a groove portion using the resist, forming a heating resistor in the groove portion and electrically connecting with the individual electrodes and the common electrode, forming a second protective film covering the heating resistor and the first protective film, and the individual electrodes being spaced apart from the comb-tooth portion of the common electrode and facing the comb-tooth portion.

<11> A method for manufacturing a thermal printhead, comprising forming a heat storage layer on an insulator, forming a resist on the heat storage layer, forming a first protective film having a groove using the resist, forming a heating resistor in the groove, forming a common electrode having a comb-tooth portion and individual electrodes on the heating resistor and the first protective film, forming a second protective film covering the heating resistor, the first protective film, the common electrode, and the individual electrodes, the individual electrodes being spaced apart from the comb-tooth portion of the common electrode and facing the comb-tooth portion.

<12> The method for manufacturing a thermal printhead described in <10> or <11>, in which the first protective film is formed by firing a material paste that will become the first protective film.

<13> The method for manufacturing a thermal printhead described in any one of <10> to <12>, wherein the heating resistor is formed by filling the groove of the first protective film with resistor paste and firing the resistor paste.

<14> The method for manufacturing a thermal printhead described in any one of <10> to <13>, wherein the heating resistor is formed by screen printing.

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

<16> The method for manufacturing a thermal printhead according to <15>, wherein the mask is a stencil mask.

<17> The method for manufacturing a thermal printhead according to any one of <10> to <16>, wherein the first protective film is formed through a baking process, and the resist is removed through one or more processes selected from the group consisting of the baking process and an organic peeling process.

<18> The method for manufacturing a thermal printhead 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.

<Thermal print head>
(First embodiment)
The thermal printhead according to this embodiment will be described with reference to the drawings.

Figure 1 is a partial oblique view showing a thermal printhead. Figure 2 is a partial cross-sectional view taken along line A-A in Figure 1 in the main scanning direction X. Figure 3 is a partial cross-sectional view taken along line B-B in Figure 1 in the sub-scanning direction Y. Figures 1 to 3 show a portion of a thermal printhead (corresponding to one thermal printhead), and in this embodiment, this one thermal printhead is referred to as an individual thermal printhead 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 grooves 38 on the heat storage layer 33, the plurality of individual electrodes 31, and the common electrode 32, a plurality of heating resistors 40 disposed on the heat storage layer 33, the individual electrodes 31, and the common electrode 32 and embedded in the grooves 38, and a protective film 34B which covers the plurality of heating resistors 40 and the protective film 34A. The heating resistors 40 are electrically connected to the individual electrodes 31 and the common electrode 32. Each of the individual electrodes 31 is spaced apart from the comb-tooth portions 32A of the common electrode 32 so as to sandwich each of the heating resistors 40, and faces the comb-tooth portions 32A. The heating resistor 40 also includes a heating resistor portion 41 that generates heat due to a current flowing through the individual electrode 31 and the common electrode 32. The heating resistor portions 41 are formed independently between the individual electrodes 31 and the common electrode 32. The heating resistor portions 41 are not shown in FIG. 1. The heating resistor portions 41 are arranged in a straight line on the heat storage layer 33.

In this embodiment, the direction in which the multiple heat generating resistors 41 extend linearly is the main scanning direction X, the direction perpendicular to the main scanning direction X and parallel to the top surface of the substrate 15 is the sub-scanning direction Y, and the direction corresponding to the thickness of the substrate 15 is 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 as viewed from the substrate 15 is the upward direction, and the direction in which the substrate 15 is located as viewed from the heat storage layer 33 is the downward direction.

The substrate 15 is an insulator, and is made of, for example, ceramic. As the ceramic, for example, alumina 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.

A heat storage layer 33 (also called a glaze layer) having the function of storing heat is laminated on the substrate 15. The heat storage layer 33 stores heat generated from the heating resistor portion 41 described below. The heat storage layer 33 can be made of an insulating material, such as silicon oxide or silicon nitride, which are the main components of glass. The dimension of the heat storage layer 33 in the thickness direction Z is not particularly limited, and is, for example, 5 to 100 μm, and preferably 10 to 30 μm.

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 the metal paste by screen printing or the like, and then firing it to form an electrode pattern.

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 viewpoint of the metal properties and ionization tendency, copper, silver, platinum, and gold are preferable, and from the viewpoint of the metal properties, ionization tendency, and cost reduction, silver is more preferable. In addition, 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, one or a mixture of two or more of ester-based solvents, ketone-based solvents, glycol ether-based solvents, aliphatic solvents, alicyclic solvents, aromatic solvents, alcohol-based solvents, water, etc.

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

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.

The metal paste may contain dispersants, surface treatment agents, anti-friction improvers, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, defoamers, silane coupling agents, titanate coupling agents, plasticizers, flame retardants, moisturizers, ion traps, etc., as necessary.

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 incorporating a thermal print head is used, each individual electrode 31 can be individually applied with a different potential. An individual pad portion (not shown) is connected to the end of each individual electrode 31.

The common electrode 32 is a portion that has an electrically opposite polarity to the individual electrodes 31 when a printer incorporating a thermal printhead is used. The common electrode 32 has a comb tooth portion 32A and a common portion 32B that connects the comb tooth portions 32A together. 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 as viewed from the individual electrodes 31 is defined as the upper side of the sub-scanning direction Y. Each comb tooth portion 32A has a strip shape that extends in the sub-scanning direction Y. The tip of each comb tooth portion 32A faces the tip of each individual electrode 31 at a predetermined interval along the sub-scanning direction Y. This configuration allows the pitch of the heating resistors 40 to be narrowed, enabling high-definition printing.

The protective film 34A has a groove 38. The individual electrodes 31 and the common electrode 32 are covered with the protective film 34A, which protects the individual electrodes 31 and the common electrode 32 from wear, corrosion, oxidation, and the like. The protective film 34A can be made of an insulating material, for example, amorphous glass. The protective film 34A is formed by printing a thick film of 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.

The heating resistor 40 is electrically connected to the individual electrodes 31 and the common electrode 32, and heat is generated in the portions through which current flows from the individual electrodes 31 and the common electrode 32. Specifically, the heating resistors 40 (heating resistor sections 41), to which a heating voltage is individually applied in accordance with a print signal sent from the outside to a drive IC or the like, are selectively made to generate heat. The heating resistor sections 41 are selectively made to generate heat by being individually energized in accordance with the print signal. Print dots are formed by generating heat in this manner. The heating resistors 40 are made of a material with a higher resistivity than the material constituting the individual electrodes 31 and the common electrode 32, and for example, ruthenium oxide can be used.

The heating resistor 40 can be formed by filling the grooves 38 of the protective film 34A with resistor paste and firing it. In this embodiment, the dimension of the heating resistor 40 in the thickness direction Z is, for example, about 1 to 10 μm.

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 38, when viewed microscopically as shown in FIG. 4, the surface of the heating resistor 40 that contacts the protective film 34B is closer to the substrate 15 than the surface of the protective film 34A that contacts the protective film 34B. In other words, the boundary surface between the heating resistor 40 and the protective film 34B is closer to the substrate 15 (lower) than the boundary surface between the protective film 34A and the protective film 34B. In addition, if the protective film 34A and the protective film 34B are made of the same material, etc., and it is difficult to distinguish the boundary, the part that is 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 opposite the side where the protective film 34A is located) is regarded as the boundary surface between the protective film 34A and the protective film 34B. If the boundary surface between the heating resistor 40 and the protective film 34B is closer to the substrate 15 than the boundary surface between the protective film 34A and the protective film 34B, the end of the heating resistor 40 is closer to the substrate 15 than the boundary surface between the protective film 34A and the protective film 34B, so that the end of the heating resistor 40 can be completely covered by the protective film 34B, which is preferable.

In addition, the portion of the principal surface of the protective film 34B opposite the side where the protective film 34A is located that overlaps with the heating resistor 40 when viewed from the normal direction of the principal surface may be a flat surface. In this specification, etc., the term "flat surface" includes a surface having an average surface roughness of 0.5 μm or less. The average surface roughness can be determined, 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, since this facilitates contact with the platen roller of the thermal print head.

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, the resistor paste is embedded in the grooves 38 of the protective film 34A and fired, so the resistor paste may have a concave curved surface 40A on its main surface due to the surface tension between the resistor paste and the protective film 34A. It is preferable for the heating resistor 40 to have a concave curved surface 40A on its main surface, since this allows for good coverage when forming the protective film 34B, etc.

The heating resistor 40 and the protective film 34A are covered with the protective film 34B, which protects the heating resistor 40 and the protective film 34A from wear, corrosion, oxidation, and the like. The protective film 34B can be made of an insulating material, for example, amorphous glass. The protective film 34B is formed by printing a thick film of 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. A thickness in this range is preferable because it is possible to obtain a thermal printhead 100 that can suppress pressure resistance defects and maintain good print quality. Even if the protective film 34B is made thin, it is possible to completely cover the end of the heating resistor 40, and the printing performance of the thermal printhead 100 can be improved.

Here, we will explain the manufacturing method of the thermal printhead 100 of this embodiment.

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

The heat storage layer 33 can be formed, for example, by applying 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.

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

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

Next, as shown in Figures 12 to 14, a resist 36 is formed on the heat storage layer 33, the individual electrodes 31, and the common electrode 32. The heating resistors 40 will be formed later in the areas where the resist 36 is present. Since defects in the shape pattern of the resist 36 are related to defects in the shape pattern of the heating resistors 40 that will be formed later, it is preferable to form the resist 36 with precision by appropriately adjusting the etching conditions. By forming the resist 36 into the desired shape, it is possible to form grooves 38 of the desired shape, and the grooves 38 make it possible to obtain the desired heating resistors 40. Therefore, by precisely processing the shape pattern of the resist 36, it is possible to reduce defects in the shape pattern of the heating resistors 40.

Next, as shown in Figs. 15 to 17, a protective film 34A is formed on the heat storage layer 33, the individual electrodes 31, and 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 of a material paste (for example, glass paste) that will become the protective film 34A, followed by firing.

Next, as shown in Figures 18 to 20, the resist 36 is removed by a baking 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 carrying out an organic peeling process. An example of a solvent that can be used in the organic peeling process is Stripping Solution 10 manufactured by Tokyo Ohka Kogyo Co., Ltd.

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 such as hydrofluoric acid, which must be handled with great care.

Next, as shown in Figs. 21 to 23, resistor paste that will become the heating resistor 40 (heating resistor portion 41) is formed so as to fill the groove portion 38. The resistor paste is supplied to the groove portion 38 by screen printing or using a mask such as a stencil mask. For example, supplying the resistor paste using a stencil mask is preferable because it improves printing accuracy. The resistor paste contains, for example, ruthenium oxide.

Next, the resistor paste is fired to form the heating resistor 40 (heating resistor portion 41).

In the process of forming the heating resistor 40, the resistor paste is embedded in the grooves 38 of the protective film 34A and fired, so the main surface of the heating resistor 40 may have a concave curved surface 40A due to the surface tension between the resistor paste and the protective film 34A. If the main surface of the heating resistor 40 has a concave curved surface 40A, it is preferable because it allows for good coverage and allows the protective film 34B and the like to be formed.

Next, as shown in Figs. 1 to 3, protective film 34B is formed. Protective film 34B is made of, for example, amorphous glass. Protective film 34B is formed by printing a thick film of glass paste and then firing it.

The above steps allow the thermal printhead 100 of this embodiment to be manufactured.

According to this embodiment, the heating resistor 40 is formed so as to be embedded in the groove 38, so that even if the protective film 34B is made thin, the end of the heating resistor 40 can be completely covered, improving the printing performance of the thermal printhead 100. In addition, since the heating resistor 40 is formed in the groove 38 of the protective film 34A without forming multiple heating resistors based on one heating resistor by wet etching or the like, defects in the pattern shape of each heating resistor can be reduced.

Second Embodiment
The thermal printhead according to this embodiment will be described with reference to the drawings.

Figure 24 is a partial oblique view showing a thermal printhead. Figure 25 is a partial cross-sectional view taken along line A-A of Figure 24 in the main scanning direction X. Figure 26 is a partial cross-sectional view taken along line B-B of Figure 24 in the sub-scanning direction Y. Figures 24 to 26 show a portion of a thermal printhead (corresponding to one thermal printhead), and in this embodiment, this one thermal printhead is referred to as an individual thermal printhead 100A. The thermal printhead 100A includes a substrate 15 that is an insulator, a heat storage layer 33 on the substrate 15, a protective film 34A having grooves 38 on the heat storage layer 33, a plurality of heating resistors 40 that are disposed on the heat storage layer 33 and embedded in the grooves 38, a common electrode 32 and a plurality of individual electrodes 31 on the heating resistors 40 and the protective film 34A, and a protective film 34B that covers the plurality of heating resistors 40, the protective film 34A, the common electrode 32, and the plurality of individual electrodes 31.

The thermal printhead 100A according to this embodiment differs from the thermal printhead 100 according to the first embodiment in that the individual electrodes 31 and the common electrode 32 are disposed on the heating resistor 40 and the protective film 34A. In this embodiment, the points in common with the first embodiment are explained by referring to the explanation of the first embodiment, and the points of difference will be explained below.

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 of the heating resistor 40 (the surface opposite to the surface on which the heat storage layer 33 is located), and the generated heat can be efficiently transmitted to the printing medium, thereby improving the printing performance of the thermal printhead 100A.

Here, we will explain the manufacturing method of the thermal printhead 100A of this embodiment.

As shown in Figures 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. A heating resistor 40 will later be formed in the area where the resist 36 exists.

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

Next, as shown in Figures 33 to 35, the resist 36 is removed by a baking process when forming the protective film 34A, and a groove 38 is formed in the protective film 34A. The resist 36 may be removed by carrying out an organic peeling process.

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 such as hydrofluoric acid, which must be handled with great care.

Next, as shown in Figures 36 to 38, a resistor paste that will become the heating resistor 40 (heating resistor portion 41) is formed so as to fill the groove portion 38. Next, the resistor paste is fired to form the heating resistor 40 (heating resistor portion 41).

Next, as shown in Figures 24 to 26, protective film 34B is formed. Protective film 34B is made of, for example, amorphous glass. Protective film 34B is formed by printing a thick film of glass paste and then firing it.

The above steps allow the thermal printhead 100A of this embodiment to be manufactured.

According to this embodiment, the heating resistor 40 is formed so as to be embedded in the groove 38, so that even if the protective film 34B is thin, the end of the heating resistor 40 can be completely covered, improving the printing performance of the thermal print head 100A. In addition, since the heating resistor 40 is formed in the groove 38 of the protective film 34A without forming multiple heating resistors based on one heating resistor by wet etching or the like, defects in the pattern shape of each heating resistor can be reduced.

Other Embodiments
As described above, one embodiment has been described, but the descriptions and drawings forming a part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples, and operating techniques will become apparent to those skilled in the art. Thus, the present embodiment includes various embodiments not described herein.

<Thermal printer>
39, a thermal printhead (e.g., thermal printhead 100) further includes a substrate 15 (heat storage layer 33 on substrate 15 and the like are not shown), a connection substrate 5, a heat dissipation member 8, a drive IC 7, a plurality of wires 81, a resin portion 82, and a connector 59. 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 portions 41 are formed on the substrate 15 and arranged in the main scanning direction X. The heat generating resistor portions 41 are driven to selectively generate heat by the drive IC 7 mounted on the connection substrate 5. The heat generating resistor portions 41 print on a print medium 92, such as thermal paper, pressed against the heat generating resistor portions 41 by a platen roller 91 in accordance with a print signal transmitted from the outside via the connector 59.

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

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

The wires 81 may be made of a conductor such as gold. There are multiple wires 81, some of which are bonded to connect the driving IC 7 to each individual electrode. Some of the other wires 81 are bonded to connect the driving IC 7 to the connector 59 via the wiring layer in the connection board 5.

The resin portion 82 may be, for example, a black resin. For example, epoxy resin, silicone resin, or the like may be used as the resin portion 82. The resin portion 82 covers the driving IC 7 and the multiple wires 81, etc., and protects the driving IC 7 and the multiple wires 81. The connector 59 is fixed to the connection board 5. Wiring is connected to the connector 59 to supply power from outside the thermal print head to the thermal print head and to control the driving IC 7.

Thermal printers can be equipped with the thermal printhead described above. Thermal printers print on a print medium transported in the sub-scanning direction Y. Typically, the print medium is transported from the connector 59 side toward the heating resistor section 41 side. Examples of print media include thermal paper for creating barcode sheets and receipts.

The 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 the thermal print head 100.

The main power supply circuit supplies power to the multiple heating resistors 41 in the thermal print head 100. The measurement circuit measures the resistance value of each of the multiple heating resistors 41. The measurement circuit measures the resistance value of each of the multiple heating resistors 41, for example, when no printing is being performed on a print medium. This makes it possible to confirm the life of the heating resistors 41 and whether or not there are any faulty heating resistors 41. The control unit controls the drive state of the main power supply circuit and the measurement circuit. The control unit controls the power supply state of each of the multiple heating resistors 41. The measurement circuit may be omitted.

The connector 59 is used to communicate with devices outside the thermal printhead 100. Through the connector 59, the thermal printhead 100 is electrically connected to the main power supply circuit and the measurement circuit. Through the connector 59, the thermal printhead 100 is electrically connected to the control unit.

The driving IC 7 receives a signal from the control unit via the connector 59. Based on the signal received from the control unit, the driving IC 7 controls the current-carrying state of each of the multiple heating resistors 41. Specifically, the driving IC 7 selectively causes multiple individual electrodes to be electrified, thereby selectively causing any of the multiple heating resistors 41 to generate heat.

The thermal print head is not limited to the above-mentioned configuration, and may be configured, for example, such that the drive IC 7 is mounted directly on the substrate 15 without providing a connection substrate 5, or such that the wires 81 are not provided by flip-chip mounting, or such that the heat dissipation member 8 is not provided.

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

When printing on the print medium, a potential v11 is applied to the connector 59 from the main power supply circuit as potential V1. In this case, the multiple heat generating resistors 41 are selectively energized and generate heat. Printing on the print medium is performed by transferring the heat to the print medium. As described above, when a potential v11 is applied to the connector 59 from the main power supply circuit as potential V1, a current path to each of the multiple heat generating resistors 41 is ensured.

When printing is not performed on the print medium, the resistance value of each heating resistor 41 is measured. During this measurement, no potential is applied from the main power supply circuit to the connector 59. When measuring the resistance value of each heating resistor 41, a potential v12 is applied from the measurement circuit to the connector 59 as the potential V1. In this case, the multiple heating resistors 41 are energized in sequence (for example, in sequence from the heating resistor 41 located at the end of the main scanning direction X). Based on the value of the current flowing through the heating resistor 41 and the potential v12, the measurement circuit measures the resistance value of each heating resistor 41. As described above, when the potential v11 is applied from the main power supply circuit to the connector 59 as the potential V1, the current path to each of the multiple heating resistors 41 is substantially cut off. This allows the measurement circuit to more accurately measure the resistance value of each heating resistor 41, and the life of the heating resistor 41 and the presence or absence of a broken heating resistor 41 can be confirmed.

As a result of the above, a thermal printer with good printing performance can be obtained.

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

Claims (17)

An insulator;
A heat storage layer disposed on the insulator;
a first protective film disposed on the heat storage layer and having a groove;
a heating resistor disposed on the heat storage layer and embedded in the groove;
an individual electrode electrically connected to the heating resistor;
a common electrode having a comb-tooth portion electrically connected to the heating resistor;
a second protective film covering the heating resistor and the first protective film,
the individual electrodes are spaced apart from and face the comb-tooth portion of the common electrode,
an interface between the heating resistor and the second protective film is located closer to the insulator than an interface between the first protective film and the second protective film;
Thermal print head. The thermal printhead according to claim 1, wherein the heating resistor is disposed on the individual electrodes and on the comb teeth. The thermal printhead according to claim 1, wherein the individual electrodes and the common electrode are disposed on the heating resistor and on the first protective film. 4. The thermal printhead according to claim 1, wherein a portion of a main surface of the second protective film opposite to a side on which the first protective film is located that overlaps with the heating resistor when viewed from a normal direction of the main surface is a flat surface. 5. The thermal printhead according to claim 1 , wherein the main surface of the heating resistor on the side where the second protective film is located has a concave curved surface. The thermal printhead according to any one of claims 1 to 5 , wherein the insulator is a substrate. The thermal printhead of claim 6 , wherein the substrate is made of ceramic. A thermal printer comprising the thermal printhead according to any one of claims 1 to 7 . A heat storage layer is formed on the insulator,
A common electrode having a comb-tooth portion and individual electrodes are formed on the heat storage layer;
forming a resist on the heat storage layer, the individual electrodes, and the comb tooth portion;
forming a first protective film having a groove portion using the resist;
a heating resistor electrically connected to the individual electrode and the common electrode is formed in the groove;
forming a second protective film covering the heating resistor and the first protective film;
the individual electrodes are spaced apart from and face the comb-tooth portion of the common electrode,
an interface between the heating resistor and the second protective film is formed to be closer to the insulator than an interface between the first protective film and the second protective film;
A method for manufacturing a thermal printhead. A heat storage layer is formed on the insulator,
A resist is formed on the heat storage layer,
forming a first protective film having a groove portion using the resist;
A heating resistor is formed in the groove portion,
forming a common electrode having a comb-tooth portion and an individual electrode on the heating resistor and the first protective film;
forming a second protective film covering the heating resistor, the first protective film, the common electrode, and the individual electrodes;
the individual electrodes are spaced apart from and face the comb-tooth portion of the common electrode,
an interface between the heating resistor and the second protective film is formed to be closer to the insulator than an interface between the first protective film and the second protective film;
A method for manufacturing a thermal printhead. The method for manufacturing a thermal printhead according to claim 9 or 10 , wherein the first protective film is formed by firing a material paste that becomes the first protective film. The method for manufacturing a thermal printhead according to any one of claims 9 to 11, wherein the heating resistor is formed by filling the grooves of the first protective film with a resistor paste and firing the resistor paste. The method for manufacturing a thermal printhead according to any one of claims 9 to 12 , wherein the heating resistor is formed by screen printing. The method for manufacturing a thermal printhead according to any one of claims 9 to 12 , wherein the heating resistor is formed using a mask. The method of claim 14 , wherein the mask is a stencil mask. The first protective film is formed through a baking process,
The method for manufacturing a thermal printhead according to any one of claims 9 to 15 , wherein the resist is removed by one or more steps selected from the group consisting of the baking step and an organic peeling step. The method for manufacturing a thermal printhead according to any one of claims 9 to 16 , wherein the main surface of the heating resistor on the side where the second protective film is located has a concave curved surface.

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