JP7680828B2 - 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.

To form the common electrode and individual electrodes, electrode patterns are formed by screen printing a paste using metals such as gold and silver.

In recent years, there has been an emphasis on traceability, and 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 display of nutritional information and changes to allergy labeling.

To enable the increasing trend of large-volume printing, thermal printheads need to print information on print media at high speed and with high resolution. To print at high speed and with high resolution, it is important to evenly distribute the heat generated by current flow or to narrow the pitch between electrodes (equal to the pitch between heating resistors). However, in the electrode formation process for thermal printheads capable of high-speed, high-resolution printing, the electrodes are packed even more densely, which can lead to frequent short circuits and breaks in the electrodes, raising concerns about a decline in printing characteristics such as the efficiency of printing on the print medium.

JP 2000-141729 A

One aspect of this embodiment provides a thermal printhead that improves printing characteristics on a print medium. Another aspect of this embodiment provides a method for manufacturing the thermal printhead. Still another aspect of this embodiment provides a thermal printer that includes the thermal printhead.

In this embodiment, by providing electrodes above and below the heat storage layer, it is possible to evenly distribute the generated heat or narrow the pitch between the electrodes, thereby improving the printing characteristics on the print medium. One aspect of this embodiment is as follows.

One aspect of this embodiment is a thermal print head comprising: a heat storage layer; a first electrode portion on the heat storage layer; a heating resistor on the first electrode portion; a second electrode portion on the heating resistor; and a protective film covering the second electrode portion and the heating resistor. The first electrode portion has a plurality of first electrodes. The second electrode portion has a plurality of second electrodes. One of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes. In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.
Another aspect of this embodiment is a thermal print head including a heat storage layer, a first electrode portion on the heat storage layer, a heating resistor on the first electrode portion, a second electrode portion on the heating resistor, and a protective film covering the second electrode portion and the heating resistor. The first electrode portion has a plurality of first electrodes. The second electrode portion has a plurality of second electrodes and a plurality of third electrodes different from the second electrodes. The second electrodes and the third electrodes are arranged alternately. One of the second electrodes and the third electrodes is an individual electrode. The other of the second electrodes and the third electrodes is a common electrode. Each of the plurality of second electrodes or the plurality of third electrodes, which is the common electrode, is a comb tooth portion and is connected to a common portion of the common electrode.

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; forming a plurality of first electrodes on the heat storage layer; forming an insulating layer that covers a portion of each of the plurality of first electrodes; forming a heating resistor that covers an area of the plurality of first electrodes that is not covered by the insulating layer; forming a plurality of second electrodes on the heating resistor and the insulating layer; and forming a protective film that covers the plurality of second electrodes, the heating resistor, and the insulating layer . One of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes. In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.

Another aspect of this embodiment is a method for manufacturing a thermal printhead, comprising forming a heat storage layer, forming a plurality of first electrodes on the heat storage layer, forming a heating resistor covering the plurality of first electrodes, forming a plurality of second electrodes and a plurality of third electrodes different from the second electrodes on the heating resistor and on the heat storage layer, forming a protective film covering the plurality of second electrodes, the plurality of third electrodes, and the heating resistor, the second electrodes and the third electrodes being arranged alternately. One of the second electrodes and the third electrodes is an individual electrode. The other of the second electrodes and the third electrodes is a common electrode. Each of the plurality of second electrodes or the plurality of third electrodes, which is the common electrode, is a comb tooth portion and is connected to a common portion of the common electrode.

According to this embodiment, it is possible to provide a thermal printhead that improves the printing characteristics on a print medium. It is also possible to provide a method for manufacturing the thermal printhead. Furthermore, it is possible to provide a thermal printer equipped with 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 A-A' in FIG. 1 in the main scanning direction X. FIG. 3 is a partial cross-sectional view taken along line B-B' in FIG. FIG. 4 is a partial perspective view (part 1) illustrating a method for manufacturing the thermal printhead according to the first embodiment. FIG. 5 is a partial cross-sectional view taken along line A-A' in FIG. 4 in the main scanning direction X. FIG. 6 is a partial cross-sectional view taken along line B-B' in FIG. FIG. 7 is a partial perspective view (part 2) illustrating the method for manufacturing the thermal printhead according to the first embodiment. FIG. 8 is a partial cross-sectional view taken along line A-A' in FIG. 7 in the main scanning direction X. FIG. 9 is a partial cross-sectional view taken along line B-B' in FIG. FIG. 10 is a partial perspective view (part 3) illustrating the method for manufacturing the thermal printhead according to the first embodiment. FIG. 11 is a partial cross-sectional view taken along line A-A' in FIG. 10 in the main scanning direction X. FIG. 12 is a partial cross-sectional view taken along line B-B' in FIG. 10 in the sub-scanning direction Y. FIG. 13 is a partial perspective view (part 4) illustrating the method for manufacturing the thermal printhead according to the first embodiment. 14 is a partial cross-sectional view taken along line A-A' in FIG. 13 in the main scanning direction X. 15 is a partial cross-sectional view taken along line B-B' in FIG. 13 in the sub-scanning direction Y. FIG. 16 is a partial perspective view (part 5) illustrating the method for manufacturing the thermal printhead according to the first embodiment. 17 is a partial cross-sectional view taken along line A-A' in FIG. 16 in the main scanning direction X. 18 is a partial cross-sectional view taken along line B-B' in FIG. 16 in the sub-scanning direction Y. FIG. 19 is a partial perspective view illustrating a thermal printhead according to the second embodiment. 20 is a partial cross-sectional view taken along line A-A' in FIG. 19 in the main scanning direction X. 21 is a partial cross-sectional view taken along line B-B' in FIG. 19 in the sub-scanning direction Y. FIG. 22 is a partial perspective view (part 1) illustrating a method for manufacturing a thermal printhead according to the second embodiment. 23 is a partial cross-sectional view taken along line A-A' in FIG. 22 in the main scanning direction X. 24 is a partial cross-sectional view taken along line B-B' in FIG. 22 in the sub-scanning direction Y. FIG. 25 is a partial perspective view (part 2) illustrating a method for manufacturing a thermal printhead according to the second embodiment. 26 is a partial cross-sectional view taken along line A-A' in FIG. 25 in the main scanning direction X. 27 is a partial cross-sectional view taken along line B-B' in FIG. 25 in the sub-scanning direction Y. FIG. 28 is a partial perspective view (part 3) illustrating a method for manufacturing a thermal printhead according to the second embodiment. 29 is a partial cross-sectional view taken along line A-A' in FIG. 28 in the main scanning direction X. 30 is a partial cross-sectional view taken along line B-B' in FIG. 28 in the sub-scanning direction Y. FIG. 31 is a partial perspective view (part 4) illustrating a method for manufacturing a thermal printhead according to the second embodiment. 32 is a partial cross-sectional view taken along line A-A' in FIG. 31 in the main scanning direction X. 33 is a partial cross-sectional view taken along line B-B' in FIG. 31 in the sub-scanning direction Y. FIG. 34 is a partial cross-sectional view of a first modified example of the thermal printhead according to the first embodiment taken along the main scanning direction X. FIG. 35 is a partial cross-sectional view of the thermal printhead according to the second modification of the first embodiment taken along the main scanning direction X. FIG. 36 is a partial cross-sectional view of the thermal printhead according to the third modification of the first embodiment taken along the main scanning direction X. FIG. 37 is a partial cross-sectional view of a first modified example of the thermal printhead according to the second embodiment taken along the main scanning direction X. FIG. 38 is a partial cross-sectional view of a second modified example of the thermal printhead according to the second embodiment taken along the main scanning direction X. FIG. 39 is a partial cross-sectional view of a third modified example of the thermal printhead according to the second embodiment taken along the main scanning direction X. FIG. 40 is a cross-sectional view illustrating a thermal printhead according to the present embodiment.

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.

In addition, the ordinal numbers "first," "second," and "third" used in this specification are used to avoid confusion between components and are not intended to limit the number.

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 print head comprising a heat storage layer, a first electrode portion on the heat storage layer, a heating resistor on the first electrode portion, a second electrode portion on the heating resistor, and a protective film covering the second electrode portion and the heating resistor.

<2> The thermal printhead described in <1>, in which the first electrode portion has a plurality of first electrodes, the second electrode portion has a plurality of second electrodes, and one of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes.

<3> The thermal printhead described in <2>, in which the width of the first electrode is smaller than the width of the second electrode in the main scanning direction.

<4> A thermal printhead according to <2> or <3>, in which the width of the area in which one of the plurality of first electrodes and one of the plurality of second electrodes overlap in the main scanning direction is the same as the width of the area in which one of the plurality of first electrodes and another of the plurality of second electrodes overlap.

<5> A thermal printhead according to any one of <2> to <4>, in which one of the first electrode and the second electrode is an individual electrode, and the other of the first electrode and the second electrode is a common electrode, and each of the plurality of first electrodes or the plurality of second electrodes that is the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.

<6> The thermal printhead described in any one of <2> to <5> further includes an insulating layer located between a portion of the first electrode portion and a portion of the second electrode portion, and at least one of the insulating layer and the heating resistor is provided between the first electrode portion and the second electrode portion.

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

<8> The thermal printhead described in <7>, in which one of the plurality of first electrodes overlaps one of the plurality of second electrodes and also overlaps one of the plurality of third electrodes.

<9> A thermal printhead according to <7> or <8>, in which the width of the first electrode is greater than the width of the second electrode and the width of the third electrode in the main scanning direction.

<10> A thermal printhead according to any one of <7> to <9>, in which one of the second electrode and the third electrode is an individual electrode, and the other of the second electrode and the third electrode is a common electrode, and each of the plurality of second electrodes or the plurality of third electrodes that is the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.

<11> A thermal printer having a thermal printhead according to any one of <1> to <10>.

<12> A method for manufacturing a thermal printhead, comprising forming a heat storage layer, forming a plurality of first electrodes on the heat storage layer, forming an insulating layer that covers a portion of each of the plurality of first electrodes, forming a heating resistor that covers an area of the plurality of first electrodes that is not covered by the insulating layer, forming a plurality of second electrodes on the heating resistor and on the insulating layer, and forming a protective film that covers the plurality of second electrodes, the heating resistor, and the insulating layer.

<13> The method for manufacturing a thermal printhead described in <12>, in which one of the first electrode and the second electrode is an individual electrode, and the other of the first electrode and the second electrode is a common electrode, and each of the plurality of first electrodes or the plurality of second electrodes that is the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.

<14> A method for manufacturing a thermal printhead, comprising forming a heat storage layer, forming a plurality of first electrodes on the heat storage layer, forming a heating resistor covering the plurality of first electrodes, forming a plurality of second electrodes and a plurality of third electrodes different from the second electrodes on the heating resistor and on the heat storage layer, forming a protective film covering the plurality of second electrodes, the plurality of third electrodes, and the heating resistor, and arranging the second electrodes and the third electrodes alternately.

<15> The method for manufacturing a thermal printhead described in <14>, in which one of the second electrode and the third electrode is an individual electrode, and the other of the second electrode and the third electrode is a common electrode, and each of the plurality of second electrodes or the plurality of third electrodes that is the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.

<16> The method for manufacturing a thermal printhead according to <12> or <13>, wherein one of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes.

<17> The method for manufacturing a thermal printhead according to any one of <12>, <13>, and <16>, wherein the width of the first electrode is smaller than the width of the second electrode in the main scanning direction.

<18> The method for manufacturing a thermal printhead according to any one of <12>, <13>, <16>, and <17>, wherein the width of the area where one of the plurality of first electrodes and one of the plurality of second electrodes overlap in the main scanning direction is the same as the width of the area where one of the plurality of first electrodes and another of the plurality of second electrodes overlap.

<19> The method for manufacturing a thermal printhead according to <14> or <15>, wherein one of the plurality of first electrodes overlaps one of the plurality of second electrodes and also overlaps one of the plurality of third electrodes.

<20> The method for manufacturing a thermal printhead according to any one of <14>, <15>, and <19>, wherein the width of the first electrode is greater than the width of the second electrode and the width of the third electrode in the main scanning direction.

<Thermal print head>
(Embodiment 1)
The thermal printhead according to this embodiment will be described with reference to the drawings.

Figure 1 is a partial perspective 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 an individual thermal printhead 100A. Thermal printhead 100A at least comprises a heat storage layer 33, a first electrode portion on heat storage layer 33, a heating resistor 40 on the first electrode portion, a second electrode portion on heating resistor 40, and a protective film 34 covering the second electrode portion and heating resistor 40. Specifically, the thermal printhead 100A includes a substrate 15, a heat storage layer 33 on the substrate 15, a plurality of first electrodes 31 included in a first electrode portion on the heat storage layer 33, an insulating layer 35 covering a portion of each of the plurality of first electrodes 31, a heating resistor 40 covering an area of the plurality of first electrodes 31 that is not covered by the insulating layer 35, a plurality of second electrodes 32 included in a second electrode portion on the heating resistor 40 and the insulating layer 35, and a protective film 34 covering the plurality of second electrodes 32, the heating resistor 40, and the insulating layer 35. One of the first electrode 31 and the second electrode 32 is an individual electrode, and the other of the first electrode 31 and the second electrode 32 is a common electrode. For example, in this embodiment, the first electrode 31 is an individual electrode, and the other of the second electrode 32 is a common electrode. The heating resistor 40 includes a plurality of heating resistor parts 41 that generate heat due to current flowing through the individual electrodes and the common electrode. The plurality of heating resistor parts 41 are formed independently between the first electrode 31 and the second electrode 32. The plurality of heating resistor parts 41 are omitted in FIG. 1. The plurality of heating resistor parts 41 are arranged in a straight line on the heat storage layer 33. Also, in FIG. 1, the protective film 34 is omitted for ease of understanding.

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 a direction perpendicular to both the main scanning direction X and the sub-scanning direction Y.

The substrate 15 is made of ceramic or a single crystal semiconductor. As the ceramic, for example, alumina can be used. As the single crystal semiconductor, for example, silicon 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 a substrate 15 made of an alumina substrate or the like. The heat storage layer 33 stores heat generated from a 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, 30 to 80 μm, and preferably 40 to 60 μm.

On the heat storage layer 33, a plurality of first electrodes 31, which are individual electrodes formed from a metal paste, are provided. The first electrodes 31 are obtained by applying the metal paste by a screen printing method or the like and forming 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, copper and silver are 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-based solvents, alicyclic-based solvents, aromatic-based 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 first electrode 31 is generally strip-shaped extending in the sub-scanning direction Y, and they are not electrically connected to each other. Therefore, when a printer incorporating a thermal printhead is used, each first electrode 31 can be individually applied with a different potential. An individual pad portion (not shown) is connected to the end of each first electrode 31. The individual pad portion is provided away from the heating resistor 40, and is not covered with the insulating layer 35.

The insulating layer 35 is provided so that the first electrode 31 and the second electrode 32 are not in direct contact with each other. The insulating layer 35 does not completely cover each of the first electrodes 31, and each of the first electrodes 31 has a part of an area that is not covered by the insulating layer 35, and each of the first electrodes 31 contacts the heating resistor 40 through the area that is not covered by the insulating layer 35. The insulating layer 35 is made of, for example, amorphous glass. The insulating layer 35 is formed by printing a thick film of glass paste and then firing it.

The heating resistor 40 generates heat in the portions through which current flows from the individual electrodes and the common electrode. Specifically, the heating resistors 40 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 heated. The heating resistor sections 41 are selectively heated by being individually energized in accordance with the print signal. Print dots are formed by generating heat in this manner. The heating resistor 40 is made of a material with a higher resistivity than the material constituting the wiring, such as ruthenium oxide. The heating resistor 40 can be formed by firing resistor paste supplied by screen printing or a dispenser. In this embodiment, the dimension of the heating resistor 40 in the thickness direction Z is, for example, about 1 to 10 μm.

On the heating resistor 41 and the insulating layer 35, a plurality of second electrodes 32 are provided as common electrodes formed from a metal paste. The second electrodes 32 are obtained by applying the metal paste by a screen printing method or the like and forming an electrode pattern. The second electrodes 32 can be made of the same material as that described for the first electrodes 31, or a different material. For example, the first electrodes 31 and the second electrodes 32 may each be copper, or the first electrodes 31 may be copper and the second electrodes 32 may be gold.

The second electrode 32, which is a common electrode, is a portion that has an electrically opposite polarity to the first electrodes 31 when a printer incorporating the thermal printhead is used. The common electrode has the second electrode 32, which is a comb tooth portion 32A, and a common portion 32B that connects the comb tooth portions 32A together. In this embodiment, the comb tooth portion 32A and the common portion 32B may be collectively referred to as the second electrode 32. 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 second electrode 32 is located as viewed from the first electrode 31 is 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 is located in the area between the tips of two adjacent first electrodes 31 and faces the two first electrodes 31 at a predetermined interval along the main scanning direction X.

The tip of each comb tooth portion 32A may be opposed to the tip of each first electrode 31 at a predetermined interval along the sub-scanning direction Y. In this case, it is preferable that the heat generating resistor portion 41 is formed only in the region where the tip of the comb tooth portion 32A and the tip of the first electrode 31 face each other. In other words, it is preferable that the heat generating resistor portion 41 is not disposed in any region other than the region where the tip of the comb tooth portion 32A and the tip of the first electrode 31 face each other in the main scanning direction X.

In this embodiment, one end of the first electrode 31 in the main scanning direction X overlaps one of the two adjacent second electrodes 32, and the other end of the first electrode 31 overlaps the other of the two adjacent second electrodes 32. This configuration makes it possible to narrow the pitch between the electrodes (equal to the pitch between the heating resistors), thereby improving the printing characteristics on the print medium.

In addition, in the main scanning direction X, it is preferable that the width of the region where the first electrode 31 overlaps with one of the two adjacent second electrodes 32 is the same as the width of the region where the first electrode 31 overlaps with the other of the two adjacent second electrodes 32, since this allows the generated heat to be evenly distributed. Here, "having the same width" also includes a difference between the two widths of 5% or less based on the larger of the two widths.

The multiple second electrodes 32, the heating resistor 40, the insulating layer 35, etc. are covered with a protective film 34, which protects the multiple second electrodes 32, the heating resistor 40, the insulating layer 35, etc. from wear, corrosion, oxidation, etc. The protective film 34 can be made of an insulating material, for example, amorphous glass. The protective film 34 is formed by printing a thick film of glass paste and then firing it. The dimension of the protective film 34 in the thickness direction Z is, for example, about 3 to 8 μm.

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

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

Next, as shown in Figures 7 to 9, a plurality of first electrodes 31 are formed on the heat storage layer 33. The plurality of first electrodes 31 can be obtained by applying the above-mentioned metal paste by screen printing or the like and forming an electrode pattern.

Next, as shown in Figures 10 to 12, an insulating layer 35 is formed to cover a portion of each of the first electrodes 31. The insulating layer 35 does not completely cover each of the first electrodes 31, and each of the first electrodes 31 has a portion that is not covered by the insulating layer 35. In this embodiment, the insulating layer 35 is generally strip-shaped extending in the main scanning direction X, and the central portion of each of the first electrodes 31 is not covered by the insulating layer 35 because it is the region that contacts the heating resistor 40 described later.

Next, as shown in Figures 13 to 15, a heating resistor 40 (heating resistor portion 41) that covers the areas of the multiple first electrodes 31 that are not covered by the insulating layer 35 is formed by thick film formation technology. The heating resistor 40 is formed by firing a resistor paste that is applied by screen printing or a dispenser. The resistor paste contains, for example, ruthenium oxide.

By forming the insulating layer 35 and the heating resistor 40, the first electrodes 31 are completely covered. In addition, the individual pads (not shown) connected to the ends of the first electrodes 31 are provided away from the heating resistor 40 and are not covered by the insulating layer 35. In this embodiment, the insulating layer 35 is formed, and then the heating resistor 40 is formed to cover the area not covered by the insulating layer 35. However, this is not limited to this, and the heating resistor 40 may be formed in the center of each of the first electrodes 31, and then the insulating layer 35 may be formed to cover the area not covered by the heating resistor 40.

Next, as shown in Figures 16 to 18, a plurality of second electrodes 32 are formed on the heating resistor 40 and the insulating layer 35. The second electrodes 32 are part of a common electrode, and the common electrode has second electrodes 32 that are comb-tooth portions 32A and a common portion 32B that commonly connects the comb-tooth portions 32A. The second electrodes 32 can be obtained by applying the above-mentioned metal paste by screen printing or the like and forming an electrode pattern.

In this embodiment, one end of the first electrode 31 in the main scanning direction X overlaps one of the two adjacent second electrodes 32, and the other end of the first electrode 31 overlaps the other of the two adjacent second electrodes 32. This configuration makes it possible to narrow the pitch between the electrodes (equal to the pitch between the heating resistors), thereby improving the printing characteristics on the print medium.

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

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

According to this embodiment, by overlapping one end of the first electrode 31 with one of the two adjacent second electrodes 32 and overlapping the other end of the first electrode 31 with the other of the two adjacent second electrodes 32, the pitch between the electrodes can be narrowed and the printing characteristics on the print medium can be improved.

(Embodiment 2)
The thermal printhead according to this embodiment will be described with reference to the drawings.

Figure 19 is a partial perspective view showing a thermal printhead. Figure 20 is a partial cross-sectional view taken along line A-A' in Figure 19 in the main scanning direction X. Figure 21 is a partial cross-sectional view taken along line B-B' in Figure 19 in the sub-scanning direction Y. Figures 19 to 21 show a portion of a thermal printhead (corresponding to one thermal printhead), and in this embodiment, this one thermal printhead is an individual thermal printhead 100B. Thermal printhead 100B at least comprises a heat storage layer 33, a first electrode portion on heat storage layer 33, a heating resistor 40 on the first electrode portion, a second electrode portion on heating resistor 40, and a protective film 34 covering the second electrode portion and heating resistor 40. Specifically, the thermal printhead 100B includes a substrate 15, a heat storage layer 33 on the substrate 15, a plurality of third electrodes 30 included in a first electrode portion on the heat storage layer 33, a heating resistor 40 covering each of the plurality of third electrodes 30, a plurality of first electrodes 31 and a plurality of second electrodes 32 included in a second electrode portion on the heating resistor 40 and the heat storage layer 33, and a protective film 34 covering the plurality of first electrodes 31, the plurality of second electrodes 32, and the heating resistor 40. The first electrodes 31 and the second electrodes 32 are arranged alternately. In this embodiment, the ordinal numbers "first", "second", and "third" are used to avoid confusion between components, and may differ from the ordinal numbers in the claims.

Furthermore, one of the first electrode 31 and the second electrode 32 is an individual electrode, and the other of the first electrode 31 and the second electrode 32 is a common electrode. In this embodiment, the first electrode 31 is an individual electrode, and the other of the second electrode 32 is a common electrode. For example, in this embodiment, the first electrode 31 is an individual electrode, and the other of the second electrode 32 is a common electrode. The heating resistor 40 includes a plurality of heating resistance parts 41 that generate heat by a current flowing through the individual electrode and the common electrode. The plurality of heating resistance parts 41 are formed independently between the first electrode 31 and the second electrode 32. In FIG. 1, the plurality of heating resistance parts 41 are omitted. The plurality of heating resistance parts 41 are arranged in a straight line on the heat storage layer 33. In addition, in FIG. 19, the protective film 34 is omitted for ease of understanding.

The description of embodiment 1 can be applied to the substrate 15, the heating resistor 40 (heating resistor portion 41), and the protective film 34.

On the heat storage layer 33, a plurality of third electrodes 30 formed from a metal paste are provided. The third electrodes 30 are obtained by applying the metal paste by a screen printing method or the like and forming an electrode pattern. The third electrodes 30 may also be formed by a lithography process. The third electrodes 30 may be made of the same material as the first electrodes 31 described in embodiment 1, or a different material.

Current flows from the common electrode to the third electrode 30 via the heating resistor 40, and current also flows from the third electrode 30 to the individual electrode via the heating resistor 40. By forming such a current path, it becomes possible to evenly distribute the generated heat, improving the printing characteristics on the print medium.

A plurality of first electrodes 31 and a plurality of second electrodes 32 are provided on the heating resistor 40 and the heat storage layer 33. The description of embodiment 1 can be applied to the positions other than where the plurality of first electrodes 31 and the plurality of second electrodes 32 are provided.

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

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

Next, as shown in Figures 25 to 27, a plurality of third electrodes 30 are formed on the heat storage layer 33. The plurality of third electrodes 30 can be obtained, for example, by forming an electrode pattern using a lithography process.

Next, as shown in Figs. 28 to 30, a heating resistor 40 (heating resistor portion 41) that covers each of the multiple third electrodes 30 is formed by thick film formation technology. By forming the heating resistor 40, the multiple third electrodes 30 are completely covered. The heating resistor 40 is formed by firing a resistor paste that is applied by screen printing or a dispenser. The resistor paste contains, for example, ruthenium oxide.

Next, as shown in Figures 31 to 33, a plurality of first electrodes 31 and a plurality of second electrodes 32 are formed on the heating resistor 40 and the heat storage layer 33. The second electrode 32 is a part of a common electrode, and the common electrode has a second electrode 32 that is a comb tooth portion 32A and a common portion 32B that commonly connects the comb tooth portions 32A. The first electrodes 31 and the second electrodes 32 are arranged alternately. Furthermore, the third electrode 30 is arranged in the region between the first electrodes 31 and the second electrodes 32. The plurality of first electrodes 31 and the plurality of second electrodes 32 can be obtained by applying the above-mentioned metal paste by screen printing or the like to form an electrode pattern.

In this embodiment, a current path is formed in which a current flows from the common electrode through the heating resistor 40 to the third electrode 30, and further from the third electrode 30 through the heating resistor 40 to the individual electrode, making it possible to evenly distribute the generated heat and improving the printing characteristics on the print medium.

Next, as shown in Figs. 19 to 21, a protective film 34 is formed. The protective film 34 is made of, for example, amorphous glass. The protective film is formed by printing a thick film of glass paste and then firing it.

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

According to this embodiment, by interposing the third electrode 30 in part of the current path through which current flows from the common electrode to the individual electrode, it is possible to evenly distribute the generated heat, thereby improving the printing characteristics on the print medium.

Other Embodiments
As described above, several embodiments have been described, but the descriptions and drawings forming 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.

For example, in thermal printhead 100C, which is a first modification of thermal printhead 100A of embodiment 1, the width of the first electrode 31 is smaller than the width of the second electrode 32 in the main scanning direction X, as shown in FIG. 34. With this configuration, when the first electrode 31 is an individual electrode, the width of the individual electrode is small, so that the current path through which the current flows from the common electrode to the individual electrode can be concentrated. This makes it possible to control the distribution of the generated heat, and further improves the printing characteristics on the print medium.

In addition, the thermal printhead 100D, which is a second modification of the thermal printhead 100A of the first embodiment, may be configured such that the first electrode 31 and the second electrode 32 do not overlap each other, as shown in FIG. 35.

Thermal printhead 100E, which is variant 3 of thermal printhead 100A of embodiment 1, may have a configuration in which second electrode 32 completely overlaps first electrode 31, as shown in FIG. 36.

As shown in FIG. 37, in thermal printhead 100F, which is a first modification of thermal printhead 100B of embodiment 2, one end of third electrode 30 overlaps with one of adjacent first electrode 31 and second electrode 32 in the main scanning direction X, and the other end of third electrode 30 overlaps with the other of adjacent first electrode 31 and second electrode 32. With this configuration, the distance between third electrode 30 and first electrode 31 and the distance between third electrode 30 and second electrode 32 can be shortened, so that the current path in heating resistor 40 is shortened and the spread of the distribution of generated heat can be controlled. This control can further improve the printing characteristics on the print medium.

As shown in FIG. 38, the thermal printhead 100G, which is a second modification of the thermal printhead 100B of the second embodiment, has a configuration in which the third electrode 30 is divided into smaller parts compared to FIG. 37. This configuration forms a current path in which a current flows from the common electrode to the third electrode 30 via the heating resistor 40, then from the third electrode 30 to another adjacent third electrode 30 via the heating resistor 40, and further from the other adjacent third electrode 30 to an individual electrode via the heating resistor 40. Current flows from a certain third electrode 30 to the other adjacent third electrode 30 via the heating resistor 40, and heat is also generated along this path, so that the generated heat can be distributed more evenly, and the printing characteristics on the print medium can be further improved.

In addition, in thermal printhead 100H, which is variant 3 of thermal printhead 100B of embodiment 2, as shown in FIG. 39, when the width of third electrode 30 is greater than the width of first electrode 31 and the width of second electrode 32 in the main scanning direction, the distance between both ends of third electrode 30 becomes larger, so that it is possible to more evenly distribute heat near both ends of third electrode 30, thereby further improving the printing characteristics on the print medium.

<Thermal printer>
40 , the thermal printhead of this embodiment (for example, thermal printhead 100A) further includes a substrate 15 (the heat storage layer 33, the first electrode layer, and the second electrode layer on the substrate 15 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. The substrate 15 has a plurality of heat generating resistor portions 41 formed thereon 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.

The thermal printer of this embodiment can be equipped with the thermal printhead described above. The thermal printer prints on a print medium transported along 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 printhead 100A, a platen roller 91, a main power supply circuit, a measurement circuit, and a control unit. The platen roller 91 faces the thermal printhead 100A.

The main power supply circuit supplies power to the multiple heating resistors 41 in the thermal print head 100A. 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 100A. Through the connector 59, the thermal printhead 100A is electrically connected to the main power supply circuit and the measurement circuit. Through the connector 59, the thermal printhead 100A 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.

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.

According to this embodiment, a thermal printer that improves the printing characteristics on the print medium can be obtained.

5 Connection board 7 Drive IC
8 Heat dissipation member 15 Substrate 30 Third electrode 31 First electrode 32 Second electrode 32A Comb tooth portion 32B Common portion 33 Heat storage layer 34 Protective film 35 Insulating layer 40 Heating resistor 41 Heating resistor portion 59 Connector 81 Wire 82 Resin portion 91 Platen roller 92 Printing medium 100A, 100B, 100C, 100D, 100E, 100F, 100G, 100H Thermal print head

Claims (11)

A heat storage layer;
A first electrode portion on the heat storage layer;
a heating resistor on the first electrode portion;
a second electrode portion on the heating resistor;
a protective film covering the second electrode portion and the heating resistor ,
The first electrode portion has a plurality of first electrodes,
the second electrode portion has a plurality of second electrodes,
one of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes;
In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.
Thermal print head. 2. A thermal printhead as described in claim 1, wherein the width of an area in which one of the plurality of first electrodes and one of the plurality of second electrodes overlap in the main scanning direction is the same as the width of an area in which one of the plurality of first electrodes and another of the plurality of second electrodes overlap. one of the first electrode and the second electrode is an individual electrode;
the other of the first electrode and the second electrode is a common electrode,
3. The thermal printhead according to claim 1 , wherein each of the plurality of first electrodes or the plurality of second electrodes that are the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode. further comprising an insulating layer located between a portion of the first electrode portion and a portion of the second electrode portion;
4. The thermal printhead according to claim 1 , wherein at least one of the insulating layer and the heating resistor is provided between the first electrode portion and the second electrode portion. A heat storage layer;
A first electrode portion on the heat storage layer;
a heating resistor on the first electrode portion;
a second electrode portion on the heating resistor;
a protective film covering the second electrode portion and the heating resistor.
The first electrode portion has a plurality of first electrodes,
the second electrode portion includes a plurality of second electrodes and a plurality of third electrodes different from the second electrodes,
the second electrodes and the third electrodes are arranged alternately;
one of the second electrode and the third electrode is an individual electrode;
the other of the second electrode and the third electrode is a common electrode,
Each of the plurality of second electrodes or the plurality of third electrodes which are the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.
Thermal print head. 6. The thermal printhead of claim 5, wherein one of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps one of the plurality of third electrodes. 7. The thermal printhead according to claim 5, wherein the width of the first electrodes is greater than the width of the second electrodes and the width of the third electrodes in the main scanning direction. A thermal printer comprising the thermal printhead according to any one of claims 1 to 7 . Forming a heat storage layer,
forming a plurality of first electrodes on the heat storage layer;
forming an insulating layer covering a portion of each of the plurality of first electrodes;
forming a heating resistor covering an area of the plurality of first electrodes that is not covered with the insulating layer;
forming a plurality of second electrodes on the heating resistor and the insulating layer;
forming a protective film covering the second electrodes, the heating resistor, and the insulating layer;
one of the plurality of first electrodes overlaps one of the plurality of second electrodes and overlaps another of the plurality of second electrodes;
In the main scanning direction, the width of the first electrode is smaller than the width of the second electrode.
A method for manufacturing a thermal printhead. one of the first electrode and the second electrode is an individual electrode;
the other of the first electrode and the second electrode is a common electrode,
The method for manufacturing a thermal printhead according to claim 9 , wherein each of the plurality of first electrodes or the plurality of second electrodes that is the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode. Forming a heat storage layer,
forming a plurality of first electrodes on the heat storage layer;
forming a heating resistor covering the plurality of first electrodes;
forming a plurality of second electrodes and a plurality of third electrodes different from the second electrodes on the heating resistor and the heat storage layer;
forming a protective film covering the second electrodes, the third electrodes, and the heating resistor;
the second electrodes and the third electrodes are arranged alternately;
one of the second electrode and the third electrode is an individual electrode;
the other of the second electrode and the third electrode is a common electrode,
Each of the plurality of second electrodes or the plurality of third electrodes which are the common electrode is a comb-tooth portion and is connected to a common portion of the common electrode.
A method for manufacturing a thermal printhead.

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