JP2023057696A - Thermal print head, manufacturing method of the same, and thermal printer - Google Patents

Abstract

To provide a thermal print head which secures the excellent printing performance while reducing a manufacturing cost, a manufacturing method of the thermal print head, and a thermal printer having the thermal print head.SOLUTION: A thermal print head 100 comprises: an insulating body; a heat accumulation layer 33 on the insulating body; a heating resistor 40 on the heat accumulation layer 33; an individual electrode 31 which is electrically connected to the heating resistor 40; a common electrode 32 which is electrically connected to the heating resistor 40; a protection film 34A which covers the heat accumulation layer 33, the heating resistor 40, the individual electrode 31 and the common electrode 32; and a protection film 34B which covers at least a region of the protection film 34A overlapping the heating resistor 40 when viewed from the thickness direction of the insulating body. The protection film 34A is made of amorphous glass. The protection film 34B is made of crystallized glass. The individual electrode 31 is apart from/opposed to the common electrode 32.SELECTED DRAWING: Figure 1

Description

The present embodiment relates to a thermal printhead, a method for manufacturing the same, and a thermal printer.

A thermal print head includes, for example, a large number of heat generating portions (also referred to as heat generating resistors) arranged in the main scanning direction on a head substrate. Each heat-generating portion has a common electrode and an individual electrode facing each other with their ends facing each other so that a portion of the heat-generating portion is exposed on a resistor layer formed on the head substrate via a glaze layer (also called a heat storage layer). It is formed by stacking By energizing between the common electrode and the individual electrodes, the exposed portion (heat generating portion) of the resistor layer generates heat due to Joule heat. By transferring the heat to a print medium (a bar code sheet, thermal paper for creating a receipt, etc.), printing is performed on the print medium.

The heating resistor is covered and protected by a protective layer. The protective layer includes, for example, a first inner layer made of amorphous glass covering the heating resistor, a second inner layer containing silicon carbide (SiC) or the like formed on the first inner layer by sputtering, and a metal nitride. or an outer layer made of a metal nitride-containing compound.

WO 2008/015958 International Publication No. 2008/105307 WO 2008/111575

Depending on the type of print medium, there are hard ones, and depending on the usage environment, foreign substances may enter the interior of the printer and damage the protective layer of the thermal print head. If the protective layer is scratched, the protective layer becomes thin due to the scratches, exposing the heating resistor, and there is a possibility that the printing performance of the thermal print head may be greatly deteriorated. For this reason, as described above, two layers of protective films are used to improve the abrasion resistance of the thermal print head. , which is disadvantageous in terms of manufacturing cost. Furthermore, when printing on a print medium, a sticking phenomenon may occur in which the print medium sticks to the thermal print head. When the sticking phenomenon occurs, the print medium is not conveyed smoothly, and printing is not performed on the print medium. An object of one aspect of the present embodiment is to provide a thermal printhead that ensures good printing performance while reducing manufacturing costs, a method for manufacturing the thermal printhead, and a thermal printer including the thermal printhead. and

The present embodiment covers the heating resistor and covers at least a first protective film made of amorphous glass and a region of the first protective film overlapping the heating resistor, and , and a second protective film made of crystallized glass. By forming the protective layer in this manner, the printing performance of the thermal print head can be improved while reducing the manufacturing cost. One aspect of this embodiment is as follows.

One aspect of the present embodiment includes an insulator, a heat storage layer on the insulator, a heating resistor on the heat storage layer, individual electrodes electrically connected to the heating resistor, and the heating resistor. a common electrode electrically connected to a body; a first protective film covering the heat storage layer, the heating resistor, the individual electrodes, and the common electrode; and a second protective film covering at least a region of the first protective film overlapping with the heating resistor, wherein the first protective film is made of amorphous glass, and the second protective film is made of amorphous glass. In the thermal print head, the protective film 2 is made of crystallized glass, and the individual electrodes are separated from and face the common electrode.

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

In another aspect of the present embodiment, a heat storage layer is formed on an insulator, a common electrode having a comb tooth portion and individual electrodes are formed on the heat storage layer, and the individual electrode and the common electrode are formed on the heat storage layer. forming a heating resistor electrically connected to, forming a first protective film covering the heat storage layer, the heating resistor, the individual electrode, and the common electrode, and viewing from the thickness direction of the insulator forming a second protective film covering at least a region of the first protective film overlapping with the heating resistor, the first protective film being made of amorphous glass, and the second protective film In the method of manufacturing a thermal printhead, the film is made of crystallized glass, and the individual electrodes are separated from the comb teeth of the common electrode and face the comb teeth.

According to this embodiment, it is possible to provide a thermal print head that ensures good printing performance while reducing manufacturing costs. Also, a method for manufacturing the thermal print head can be provided. Also, a thermal printer having the thermal print head can be provided.

FIG. 1 is a partial perspective view illustrating a thermal print head according to this embodiment. 2 is a partial cross-sectional view along line AA in FIG. 1 in the main scanning direction X. FIG. 3 is a partial cross-sectional view along the line BB in FIG. 1 in the sub-scanning direction Y. FIG. FIG. 4 is a partial perspective view (No. 1) explaining the method of manufacturing the thermal print head according to the present embodiment. 5 is a partial cross-sectional view along line AA in FIG. 4 in the main scanning direction X. FIG. 6 is a partial cross-sectional view along the line BB in FIG. 4 in the sub-scanning direction Y. FIG. FIG. 7 is a partial perspective view illustrating the method of manufacturing the thermal print head according to this embodiment (No. 2). 8 is a partial cross-sectional view along line AA in FIG. 7 in the main scanning direction X. FIG. 9 is a partial cross-sectional view along line BB in FIG. 7 in the sub-scanning direction Y. FIG. FIG. 10 is a partial perspective view explaining the method of manufacturing the thermal print head according to this embodiment (No. 3). 11 is a partial cross-sectional view along line AA in FIG. 10 in the main scanning direction X. FIG. 12 is a partial cross-sectional view along the line BB in FIG. 10 in the sub-scanning direction Y. FIG. FIG. 13 is a partial perspective view for explaining the method of manufacturing the thermal print head according to this embodiment (No. 4). 14 is a partial cross-sectional view along line AA in FIG. 13 in the main scanning direction X. FIG. 15 is a partial cross-sectional view along the line BB in FIG. 13 in the sub-scanning direction Y. FIG. FIG. 16 is a partial perspective view explaining a thermal print head according to a modification. 17 is a partial cross-sectional view along line AA in FIG. 16 in the main scanning direction X. FIG. 18 is a partial cross-sectional view along line BB in FIG. 16 in the sub-scanning direction Y. FIG. FIG. 19 is a cross-sectional view illustrating a thermal printhead.

Next, this embodiment will be described with reference to the drawings. In the description of the drawings described below, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic, and the relationship between the thickness of each component and the planar dimensions, etc., differs from the actual one. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. In addition, it goes without saying that there are portions with different dimensional relationships and ratios between the drawings.

Further, the embodiments shown below are examples of apparatuses and methods for embodying technical ideas, and do not specify the material, shape, structure, arrangement, etc. of each component. Various modifications can be made to this embodiment within the scope of the claims.

One specific aspect of this embodiment is as follows.

<1> An insulator, a heat storage layer on the insulator, a heating resistor on the heat storage layer, an individual electrode electrically connected to the heating resistor, and electrically connected to the heating resistor A first protective film covering the connected common electrode, the heat storage layer, the heating resistor, the individual electrodes, and the common electrode, and the heating resistor viewed from the thickness direction of the insulator and a second protective film covering at least a region of the first protective film overlapping with the first protective film, wherein the first protective film is made of amorphous glass, and the second protective film is , a thermal printhead made of crystallized glass, wherein the individual electrodes are spaced apart from and face the common electrode.

<2> The thermal print head according to <1>, wherein the crystallized glass contains a conductive material.

<3> The coefficient of linear expansion of the second protective film is greater than the coefficient of linear expansion of the first protective film, and the coefficient of linear expansion of the first protective film is greater than the coefficient of linear expansion of the heat storage layer. The thermal print head according to <1> or <2>.

<4> The thermal printhead according to any one of <1> to <3>, wherein the hardness of the second protective film is higher than the hardness of the first protective film.

<5> The thermal print according to any one of <1> to <4>, wherein the arithmetic mean roughness of the surface of the second protective film is greater than the arithmetic mean roughness of the surface of the first protective film. head.

<6> The thermal printhead according to any one of <1> to <5>, wherein the insulator is a substrate.

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

<8> A thermal printer comprising the thermal print head according to any one of <1> to <7>.

<9> A heat storage layer is formed on an insulator, a common electrode having a comb tooth portion and an individual electrode are formed on the heat storage layer, and the heating resistor is electrically connected to the individual electrode and the common electrode. forming a first protective film covering the heat storage layer, the heat generating resistor, the individual electrode, and the common electrode, and overlapping the heat generating resistor when viewed from the thickness direction of the insulator forming a second protective film covering at least a region of the first protective film where the The method of manufacturing a thermal print head, wherein the individual electrodes are spaced apart from the comb teeth of the common electrode and face the comb teeth.

<10> In <9>, the first protective film is formed by firing a first material paste, and the second protective film is formed by firing a second material paste A method of manufacturing the described thermal printhead.

<11> The second protective film is formed by applying and firing the second material paste on the first protective film after firing the first material paste, <10> A method of manufacturing the described thermal printhead.

<12> The method of manufacturing a thermal print head according to any one of <9> to <11>, wherein the second material paste contains a conductive material.

<13> The coefficient of linear expansion of the second protective film is greater than the coefficient of linear expansion of the first protective film, and the coefficient of linear expansion of the first protective film is greater than the coefficient of linear expansion of the heat storage layer. The method for manufacturing a thermal print head according to any one of <9> to <12>.

<14> The method of manufacturing a thermal print head according to any one of <9> to <13>, wherein hardness of the second protective film is higher than hardness of the first protective film.

<15> The thermal print according to any one of <9> to <14>, wherein the arithmetic mean roughness of the surface of the second protective film is greater than the arithmetic mean roughness of the surface of the first protective film. How the head is made.

<Thermal print head>
A thermal print head according to this embodiment will be described with reference to the drawings.

FIG. 1 is a partial perspective view showing a thermal printhead. 2 is a partial cross-sectional view along line AA in FIG. 1 in the main scanning direction X. FIG. 3 is a partial cross-sectional view along the line BB in FIG. 1 in the sub-scanning direction Y. FIG. 1 to 3 show a portion of a thermal print head (corresponding to one thermal print head), and in this embodiment, this one thermal print head is assumed to be an individual thermal print head 100. . The thermal print head 100 includes a substrate 15 that 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, on the heat storage layer 33, The heating resistors 40 on the plurality of individual electrodes 31 and the common electrode 32, the protective film 34A covering the heat storage layer 33, the individual electrodes 31, the common electrode 32, and the heating resistors 40, and the protective film 34A. and a protective film 34B. The protection film 34A and the protection film 34B are also collectively referred to as a protection layer 34 . The heating resistor 40 includes a plurality of heating resistors 41 that generate heat by current flowing through the individual electrodes 31 and the common electrode 32 . The plurality of heat generating resistors 41 are formed independently between the individual electrodes 31 and the common electrode 32 . FIG. 1 omits the plurality of heating resistors 41 . The plurality of heat generating resistors 41 are linearly arranged on the heat storage layer 33 .

In this embodiment, the main scanning direction X is the direction in which the plurality of heating resistors 41 extend linearly, and the sub-scanning direction Y is the direction perpendicular to the main scanning direction X and parallel to the upper surface of the substrate 15 . , the direction corresponding to the thickness of the substrate 15 is defined as a thickness direction Z. As shown in FIG. In other words, the thickness direction Z is a direction perpendicular to the main scanning direction X and the sub-scanning direction Y, respectively. Also, the direction in which the heat storage layer 33 is located when viewed from the substrate 15 is defined as the upward direction, and the direction in which the substrate 15 is located when viewed from the heat storage layer 33 is defined as the downward direction.

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

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

An individual electrode 31 and a common electrode 32 made of metal paste are provided on the heat storage layer 33 . The individual electrodes 31 and the common electrode 32 are obtained by applying a metal paste by screen printing or the like and then baking 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. Copper, silver, platinum, and gold are preferred from the viewpoint of metal properties and ionization tendency, and silver is more preferred from the viewpoint of metal properties, ionization tendency, and cost reduction. In addition, the solvent contained in the metal paste has a function of uniformly dispersing the metal particles, and examples thereof include ester solvents, ketone solvents, glycol ether solvents, aliphatic solvents, alicyclic solvents, and aromatic solvents. Examples include, but are not limited to, one or a mixture of two or more of solvent, alcohol, water, and the like.

Examples of ester solvents include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate and dimethyl carbonate. Ketone solvents include, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone benzene, diisobutyl ketone, diacetone alcohol, isophorone, cyclohexanone and the like. Glycol ether-based solvents include, for example, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether and the like, acetic acid esters of these monoethers, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol monoethyl ether and diethylene glycol monobutyl ether. , propylene glycol monomethyl ether, propylene glycol monoethyl ether, acetic acid esters of these monoethers, and the like.

Examples of aliphatic solvents include n-heptane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane and the like. Examples of alicyclic solvents include methylcyclohexane, ethylcyclohexane, cyclohexane and the like. Examples of aromatic solvents include toluene, xylene, tetralin, and the like. Alcohol-based solvents (excluding the above-mentioned glycol ether-based solvents) include ethanol, propanol, butanol, and the like.

The metal paste may contain dispersants, surface treatment agents, anti-friction agents, infrared absorbers, ultraviolet absorbers, fragrances, antioxidants, organic pigments, inorganic pigments, antifoaming agents, silane coupling agents, if necessary. , a titanate-based coupling agent, a plasticizer, a flame retardant, a humectant, an ion scavenger, and the like.

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

The common electrode 32 is a portion electrically opposite in polarity to the plurality of individual electrodes 31 when a printer incorporating a thermal print head is used. The common electrode 32 has a comb tooth portion 32A and a common portion 32B that commonly connects the comb tooth portions 32A. The common portion 32B is formed in the main scanning direction X along the edge of the substrate 15 on the upper side. In the sub-scanning direction Y, the direction in which the common electrode 32 is located when viewed from the individual electrodes 31 is defined as the upper side in the sub-scanning direction Y. As shown in FIG. Each comb tooth portion 32A has a strip shape extending in the sub-scanning direction Y. As shown in FIG. The tip of each comb tooth portion 32A faces the tip of each individual electrode 31 along the sub-scanning direction Y with a predetermined gap therebetween. With such a configuration, the pitch of the heating resistor portions 41 can be narrowed, so that high-definition printing is possible.

The heating resistor 40 is electrically connected to the individual electrode 31 and the common electrode 32, and heat is generated in the portion to which the current from the individual electrode 31 and the common electrode 32 flows. Specifically, the heating resistors 40 (heating resistor portions 41) to which a heating voltage is individually applied in accordance with a print signal sent from the outside to the driving IC or the like are selectively caused to generate heat. The heating resistors 41 are selectively heated by being individually energized according to the print signal. Print dots are formed by such heat generation. The heating resistor 40 is made of a material having a higher resistivity than the material of the individual electrodes 31 and the common electrode 32, such as ruthenium oxide.

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

The heating resistor 40 and the like are covered with a protective layer 34, and the protective layer 34 protects the heating resistor 40 and the like from wear, corrosion, oxidation and the like. The protective layer 34 has a protective film 34A and a protective film 34B covering the protective film 34A.

An insulating material can be used for the protective film 34A, which is made of amorphous glass. The protective film 34A is formed by applying glass paste, which is a material paste, and then baking the paste. The dimension in the thickness direction Z of the protective film 34A is, for example, about 7 to 10 μm. A thickness within this range is preferable because it is possible to obtain the thermal print head 100 capable of suppressing defective pressure resistance and maintaining good print quality.

An insulating material can be used for the protective film 34B, which is made of crystallized glass. Crystallized glass is obtained by melting glass by heat treatment and depositing crystals uniformly inside the glass. By controlling the glass composition and heat treatment conditions, the crystallized glass can be adjusted in terms of the crystals that precipitate, the grain size of the crystals, and the amount of crystals. ) can be obtained. The protective film 34B is formed by applying glass paste, which is a material paste, and then baking the paste. Since crystallized glass is more expensive than amorphous glass, it only needs to have a minimum thickness that can withstand wear, corrosion, oxidation, etc., and the dimension in the thickness direction Z of the protective film 34B is, for example, 2. ~6 μm. Thus, the manufacturing cost can be reduced by using the protective layer 34 including the protective films 34A and 34B.

Since the protective film 34B has precipitated crystals, it has a high hardness (Vickers hardness), which is higher than the hardness of the protective film 34A. The hardness of the protective film 34B is, for example, 800-1400 HV, more preferably 1000-1200 HV. By using the protective film 34B having hardness within such a range, wear, corrosion, oxidation, etc. of the protective film 34B can be suppressed.

In addition, the protective film 34B may have a rough surface due to the meltability of the glass and the precipitated crystals during the formation of the crystallized glass, and the arithmetic mean roughness of the surface of the protective film 34B is Greater than the arithmetic mean roughness. The arithmetic average roughness of the surface of the protective film 34B is, for example, 0.3 to 0.7 μm, more preferably 0.4 to 0.6 μm. By using the protective film 34B having a surface arithmetic mean roughness within such a range, the surface area of the print medium that contacts the protective film 34B of the thermal print head 100 is reduced, so that the sticking phenomenon can be suppressed.

Furthermore, the coefficient of linear expansion of the protective film 34B is preferably larger than the coefficient of linear expansion of the protective film 34A, and the coefficient of linear expansion of the protective film 34A is preferably larger than the coefficient of linear expansion of the heat storage layer 33 . The coefficient of linear expansion can be adjusted by the composition of the protective film 34A, the protective film 34B, and the heat storage layer 33. If the protective film 34B is provided directly on the heat storage layer 33, the protective film 34B will peel off from the surface of the heat storage layer 33 due to thermal stress or the like due to the large difference in coefficient of linear expansion. By providing a protective film 34A having a larger coefficient of linear expansion than the heat storage layer 33 on the layer 33, and providing a protective film 34B having a larger coefficient of linear expansion than the protective film 34A on the protective film 34A, the above-mentioned peeling due to thermal stress or the like can be prevented. can be suppressed.

Examples of the protective film 34B include Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass, fresnoite-type Ba ₂ TiSi ₂ O ₈ -based crystallized glass, tellurite-based crystallized glass containing TeO ₂ as a main component, Ln ₂ O ₃ —BaO—TeO ₂ system (Ln: rare earth element) crystallized glass, SiO ₂ —BaO—Al ₂ O ₃ —ZnO system crystallized glass, and the like. Li ₂ O—Al ₂ O ₃ —SiO ₂ -based crystallized glass contains β-quartz solid solution or β-spodumene solid solution as main crystals.

Furthermore, the crystallized glass forming the protective film 34B may contain a conductive material. The conductive material is, for example, 15-25% by weight, preferably 17-23%, relative to the crystallized glass. 2. Description of the Related Art Generally, in a printer having a thermal print head, a print medium moves inside the printer and comes into contact with or close to a protective film. Thermal paper and other printing media are very easily charged, and static electricity is generated and charged inside the printer. Discharge towards the electrode. As a result, electrode disconnection, malfunction and damage of the driving IC, and the like may occur. In the present embodiment, static electricity generated in the protective film 34B can be suppressed by the crystallized glass containing a conductive material having a static elimination effect.

As the conductive material, it is preferable to use the same material as the heating resistor 40, for example, it is preferable to use ruthenium oxide. By using the same material as the heat-generating resistor 40 as the conductive material, it is possible to suppress the generation of gas when forming the crystallized glass, and to suppress foaming due to the gas. Since foaming can be suppressed, it is possible to suppress a decrease in the hardness of the protective film 34B made of crystallized glass due to foaming.

Here, a method for manufacturing the thermal print head 100 of this embodiment will be described.

As shown in FIGS. 4 to 6, first, the substrate 15 is prepared, and the heat storage layer 33 is formed on the substrate 15. As shown in FIGS.
The heat storage layer 33 can be formed, for example, by applying a glass paste, which is a material paste, by screen printing or the like, drying the applied glass paste, and then performing a firing treatment. The baking treatment is performed, for example, at 800 to 1200° C. for 10 minutes to 1 hour. The dimension in the thickness direction Z of the heat storage layer 33 is, for example, 25 μm.

Next, the individual electrodes 31 and the common electrode 32 are formed on the heat storage layer 33, as shown in FIGS. The individual electrodes 31 and the common electrode 32 are obtained by applying the above-described metal paste by screen printing or the like and then firing the paste.

Next, as shown in FIGS. 10 to 12, resistor paste is formed to form the heating resistor 40 (heating resistor portion 41). The resistor paste contains, for example, ruthenium oxide. Next, the heating resistor 40 (heating resistor portion 41) is formed by firing the resistor paste described above.

Next, as shown in FIGS. 13 to 15, a protective film 34A is formed. The protective film 34A is made of amorphous glass, for example. The protective film 34A is formed by applying glass paste, which is a material paste, and then baking the paste.

Next, as shown in FIGS. 1 to 3, a protective film 34B is formed to cover the protective film 34A. The protective film 34A is made of, for example, crystallized glass. The protective film 34B is formed by applying glass paste, which is a material paste, on the protective film 34A formed by baking glass paste, and then baking the paste. In this embodiment, the glass paste that becomes the crystallized glass contains the same conductive material as the heating resistor 40 .

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

According to the present embodiment, by using the protective layer 34 including the protective film 34A made of amorphous glass and the protective film 34B made of crystallized glass, the manufacturing cost can be reduced, and the thermal printer can ensure good printing performance. A printhead can be provided.

<Modification>
A configuration of a thermal print head 100A according to this modification will be described. FIG. 16 is a partial perspective view showing the thermal print head 100A. 17 is a partial cross-sectional view along line AA in FIG. 16 in the main scanning direction X. FIG. 18 is a partial cross-sectional view along line BB in FIG. 16 in the sub-scanning direction Y. FIG. The thermal print head 100A includes a substrate 15 that 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, on the heat storage layer 33, Thicknesses of the heating resistors 40 on the plurality of individual electrodes 31 and the common electrode 32, the protective film 34A covering the heat storage layer 33, the individual electrodes 31, the common electrode 32, and the heating resistors 40, and the substrate 15 and a protective film 34B covering at least a region of the protective film 34A overlapping the heating resistor 40 when viewed from the direction. The thermal print head 100A according to this modification is different from the thermal print head 100 shown in FIGS. , and covers the periphery of the protective film 34A. In this modified example, the points common to the thermal print head 100 shown in FIGS. 1 to 3 refer to the above description, and different points will be described below.

The protective film 34B only needs to cover at least the region of the protective film 34A that overlaps with the heating resistor 40 when viewed from the thickness direction of the substrate 15 . By adopting such a configuration, the amount of the glass paste that becomes the expensive crystallized glass that constitutes the protective film 34B can be reduced, and the manufacturing cost can be further reduced.

According to this modification, the protective film 34A made of amorphous glass and the crystallized glass covering at least the region of the protective film 34A overlapping the heating resistor 40 when viewed from the thickness direction of the substrate 15 By using the protective layer 34 including the protective film 34B, it is possible to provide a thermal print head that secures good printing performance while further reducing the manufacturing cost.

(Other embodiments)
As noted above, although one embodiment has been described, the discussion and drawings forming part of the disclosure are to be understood as illustrative and not limiting. Various alternative embodiments, implementations and operational techniques will become apparent to those skilled in the art from this disclosure. Thus, this embodiment includes various embodiments and the like that are not described here.

<Thermal printer>
Further, as shown in FIG. 19, the thermal print head (for example, the thermal print head 100) includes a substrate 15 (the heat storage layer 33 and the like on the substrate 15 are not shown), a connection substrate 5, a heat dissipation member 8, a driving IC 7, A plurality of wires 81 , a resin portion 82 and a connector 59 are provided. 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 heating resistors 41 arranged in the main scanning direction X are formed on the substrate 15 . The heat generating resistor portion 41 is driven to selectively generate heat by the drive IC 7 mounted on the connection substrate 5 . The heating resistor section 41 prints on a printing medium 92 such as thermal paper that is pressed against the heating resistor section 41 by the platen roller 91 according to a print signal transmitted from the outside through the connector 59 .

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

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

A conductor such as gold can be used for the wire 81, for example. There are a plurality of wires 81, some of which are bonded to electrically connect the driving IC 7 and each individual electrode. Some of the other wires 81 are bonded to connect the drive IC 7 and the connector 59 through the wiring layer of the connection board 5 .

For example, black resin can be used for the resin portion 82 . As the resin portion 82, for example, epoxy resin, silicone resin, or the like can be used. The resin portion 82 covers the driving IC 7 and the plurality of wires 81 and protects the driving IC 7 and the plurality of wires 81 . The connector 59 is fixed to the connection board 5 . The connector 59 is connected with wiring for supplying electric power to the thermal print head from outside the thermal print head and for controlling the drive IC 7 .

A thermal printer can comprise a thermal printhead as described above. A thermal printer prints on a print medium conveyed along the sub-scanning direction Y. As shown in FIG. Normally, the print medium is conveyed from the connector 59 side toward the heating resistor section 41 side. Print media include, for example, 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 section. A platen roller 91 faces the thermal print head 100 .

The main power supply circuit supplies power to the plurality of heating resistors 41 in the thermal print head 100 . The measuring circuit measures the resistance value of each of the plurality of heating resistors 41 . The measuring circuit measures the resistance value of each of the plurality of heating resistors 41, for example, when printing on a print medium is not performed. As a result, it is possible to check the life of the heat generating resistor 41 and the presence or absence of a malfunctioning heat generating resistor 41 . The control unit controls driving states of the main power supply circuit and the measurement circuit. The controller controls the energized state of each of the plurality of heating resistors 41 . The measuring circuit may be omitted.

Connector 59 is used to communicate with devices outside thermal printhead 100 . Through connector 59, thermal print head 100 is electrically connected to the main power supply circuit and the measurement circuit. The thermal printhead 100 is electrically connected to the controller via the connector 59 .

The drive IC 7 receives signals from the control section via the connector 59 . The driving IC 7 controls the energization state of each of the plurality of heating resistors 41 based on the signal received from the control section. Specifically, the drive IC 7 selectively energizes a plurality of individual electrodes to arbitrarily generate heat in any one of the plurality of heating resistor portions 41 .

Moreover, the thermal print head is not limited to the above-described configuration. For example, the configuration may be one in which the drive IC 7 is directly mounted on the substrate 15 without providing the connection substrate 5, or a configuration in which the wires 81 are not provided by flip-chip mounting. or a configuration in which the heat radiating member 8 is not provided.

Next, how to use the thermal printer will be described.

When printing onto a print medium, the connector 59 is supplied with a first potential, which is an input signal, from the main power supply circuit. In this case, the plurality of heating resistors 41 are selectively energized to generate heat. By transferring the heat to the print medium, printing is performed on the print medium. As described above, when the first potential is applied to the connector 59 from the main power supply circuit, the energization path to each of the plurality of heating resistors 41 is secured.

When printing on the print medium is not performed, the resistance value of each heating resistor portion 41 is measured. During the measurement, no potential is applied to the connector 59 from the main power supply circuit. When measuring the resistance value of each heating resistor portion 41, the second potential is applied to the connector 59 from the measuring circuit. In this case, the plurality of heating resistors 41 are energized in order (for example, in order from the heating resistor 41 positioned at the end in the main scanning direction X). The measuring circuit measures the resistance value of each heating resistor 41 based on the value of the current flowing through the heating resistor 41 and the second potential. As described above, when the second potential is applied to the connector 59 from the measurement circuit, the current-carrying paths other than those for which the resistance value is to be measured to each of the plurality of heating resistors 41 are substantially cut off. . As a result, the resistance value of each heating resistor 41 can be measured more accurately by the measurement circuit, and the life of the heating resistor 41 and the presence or absence of a failed heating resistor 41 can be confirmed.

According to the above, it is possible to obtain a thermal printer that ensures good printing performance while reducing manufacturing costs.

5 connection board 7 drive IC
8 Heat dissipation member 15 Substrate 31 Individual electrode 32 Common electrode 32A Comb tooth portion 32B Common portion 33 Heat storage layer 34 Protective layer 34A Protective film 34B Protective film 40 Heating resistor 41 Heating resistor 59 Connector 81 Wire 82 Resin portion 91 Platen roller 92 Printing Media 100, 100A Thermal print head

Claims (15)

an insulator;
a heat storage layer on the insulator;
a heating resistor on the heat storage layer;
an individual electrode electrically connected to the heating resistor;
a common electrode electrically connected to the heating resistor;
a first protective film covering the heat storage layer, the heating resistor, the individual electrodes, and the common electrode;
a second protective film covering at least a region of the first protective film overlapping with the heating resistor when viewed from the thickness direction of the insulator,
The first protective film is made of amorphous glass,
The second protective film is made of crystallized glass,
The thermal print head, wherein the individual electrodes are spaced apart from and face the common electrode. 2. The thermal printhead of claim 1, wherein the crystallized glass comprises a conductive material. The coefficient of linear expansion of the second protective film is greater than the coefficient of linear expansion of the first protective film,
3. The thermal printhead according to claim 1, wherein the coefficient of linear expansion of said first protective film is greater than the coefficient of linear expansion of said heat storage layer. 4. The thermal printhead according to claim 1, wherein hardness of said second protective film is higher than hardness of said first protective film. 5. The thermal printhead according to claim 1, wherein the arithmetic mean roughness of the surface of said second protective film is greater than the arithmetic mean roughness of the surface of said first protective film. A thermal printhead according to any one of claims 1 to 5, wherein said insulator is a substrate. 7. The thermal printhead of claim 6, wherein said substrate is made of ceramic. A thermal printer comprising the thermal print head according to any one of claims 1 to 7. forming a heat storage layer on the insulator,
forming a common electrode having a comb tooth portion and an individual electrode on the heat storage layer;
forming a heating resistor electrically connected to the individual electrode and the common electrode;
forming a first protective film covering the heat storage layer, the heating resistor, the individual electrode, and the common electrode;
forming a second protective film that covers at least a region of the first protective film that overlaps with the heating resistor when viewed from the thickness direction of the insulator;
The first protective film is made of amorphous glass,
The second protective film is made of crystallized glass,
The method of manufacturing a thermal print head, wherein the individual electrodes are spaced apart from the comb teeth of the common electrode and face the comb teeth. The first protective film is formed by firing a first material paste,
10. The method of manufacturing a thermal printhead according to claim 9, wherein said second protective film is formed by firing a second material paste. 11. The thermal device according to claim 10, wherein the second protective film is formed by applying and baking the second material paste on the first protective film after baking the first material paste. A method of manufacturing a printhead. The method of manufacturing a thermal printhead according to any one of claims 9 to 11, wherein the second material paste contains a conductive material. The coefficient of linear expansion of the second protective film is greater than the coefficient of linear expansion of the first protective film,
13. The method of manufacturing a thermal printhead according to claim 9, wherein the coefficient of linear expansion of said first protective film is greater than the coefficient of linear expansion of said heat storage layer. 14. The method of manufacturing a thermal print head according to claim 9, wherein hardness of said second protective film is higher than hardness of said first protective film. 15. The method of manufacturing a thermal printhead according to claim 9, wherein the arithmetic mean roughness of the surface of said second protective film is greater than the arithmetic mean roughness of the surface of said first protective film.

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