Thermal Printhead, Method for Manufacturing the Same, and Thermal Printer

Abstract

This thermal print head is provided with: a substrate having a convex part; a wiring layer on the convex part; a heat storage layer on the wiring layer; a heat generation resisting part formed on the heat storage layer and arranged along a main scanning direction; a first electrode contacting the heat generation resisting part on one side in a sub-scanning direction; a second electrode contacting the heat generation resisting part on the other side in the sub-scanning direction; and connection wiring formed in an opening part that penetrates the heat generation resisting part and the heat storage layer and reaches the wiring layer. The first electrode is electrically connected to the wiring layer via the connection wiring.

Description

Technical Field

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

Background Art

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

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

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

[0005] In order to enable a large amount of printing that is on an increasing trend, it is necessary for the thermal print head to print information on the printing medium at high speed and high definition. In order to print at high speed and high definition, it is necessary to narrow the pitch between wirings (equal to the pitch between heat generating resistor portions). However, in the wiring formation process in a high-definition thermal print head, in order to integrate the wirings at a higher density, short circuits and disconnections of the wirings frequently occur, and there is a risk that the manufacturing yield will significantly decrease.

[0006] In addition, for forming wiring layers such as common electrodes and individual electrodes, a wiring pattern is formed by screen-printing a paste containing a metal such as gold or silver.

[0007] However, the paste that forms the wiring pattern contains a solvent (dispersion medium) for dispersing metal particles, and due to this solvent, the wiring pattern may spread wider than the design, making it difficult to increase the density of the wiring pattern and impossible to form a high-definition wiring pattern. As a result, the manufacturing yield may be significantly reduced.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0009] One aspect of the present embodiment is made in view of the above in order to solve at least one of the above-described problems, and provides a thermal print head with a good yield. Another aspect of the present embodiment provides a method for manufacturing the thermal print head. Still another aspect of the present embodiment provides a thermal printer equipped with the thermal print head.

Means for Solving the Problems

[0010] In one aspect of the present embodiment, a wiring layer is provided on a substrate having a convex portion, and an electrode and the wiring layer are electrically connected via a connection wiring formed in an opening that penetrates a heat storage layer and a heat generating resistance portion on the wiring layer and reaches the wiring layer. In another aspect of the present embodiment, the heat storage layer has a laminated structure of a layer containing glass and a porous layer containing a material different from that of the layer on the layer, so that the solvent contained in the paste penetrates into the pores of the porous layer, and it becomes possible to suppress the spread of the wiring pattern. One aspect of the present embodiment is as follows.

[0011] One aspect of the present embodiment is a thermal print head including a substrate having a convex portion, a wiring layer on the convex portion, a heat storage layer on the wiring layer, a heat generating resistance portion formed on the heat storage layer and arranged along the main scanning direction, a first electrode in contact with the heat generating resistance portion on one side in the sub-scanning direction, a second electrode in contact with the heat generating resistance portion on the other side in the sub-scanning direction, and a connection wiring formed in an opening that penetrates the heat generating resistance portion and the heat storage layer and reaches the wiring layer, wherein the first electrode is electrically connected to the wiring layer via the connection wiring.

[0012] Another aspect of the present embodiment is a thermal print head including a heat storage layer having a first layer and a second layer on the first layer, a wiring formed on the heat storage layer, a heat generating resistor formed on the wiring, and a protective film covering the heat storage layer, the wiring, and the heat generating resistor, wherein the first layer contains glass and the second layer is a porous layer.

[0013] In addition, another aspect of the present embodiment is a thermal printer including the above thermal print head.

[0014] Another aspect of the present embodiment is a method for manufacturing a thermal print head, which includes forming a wiring film on a substrate surface, removing a part of the substrate and the wiring film to form a convex portion and a wiring layer on the convex portion, forming a heat storage layer on the wiring layer, forming heat generating resistance portions arranged along the main scanning direction on the heat storage layer, forming an opening that penetrates the heat generating resistance portions and the heat storage layer to reach the wiring layer, forming a connection wiring in the opening, and forming a first electrode electrically connected to the wiring layer through the connection wiring and a second electrode spaced apart from the first electrode with the heat generating resistance portions interposed therebetween along the sub-scanning direction.

[0015] Another aspect of the present embodiment is a method for manufacturing a thermal print head, which includes removing a part of a substrate to form a convex portion, forming an oxide film on the substrate, forming a wiring layer on the oxide film, forming a heat storage layer on the wiring layer, forming a plurality of heat generating resistance portions arranged along the main scanning direction on the heat storage layer, forming an opening that penetrates the heat generating resistance portions and the heat storage layer to reach the wiring layer, forming a connection wiring in the opening, and forming a first electrode electrically connected to the wiring layer through the connection wiring and a second electrode spaced apart from the first electrode with the heat generating resistance portions interposed therebetween along the sub-scanning direction.

[0016] Another aspect of the present embodiment is a method for manufacturing a thermal print head, which includes forming a first layer containing glass on a substrate, forming a second layer which is a porous layer on the first layer, thereby forming a heat storage layer including the first layer and the second layer, forming a wiring on the heat storage layer, forming a heat generating resistor on the wiring, and forming a protective film covering the heat storage layer, the wiring, and the heat generating resistor.

Advantages of the Invention

[0017] According to the present embodiment, a thermal print head with a good yield can be provided. Further, a method for manufacturing the thermal print head can be provided. Furthermore, a thermal printer including the thermal print head can be provided.

Brief Description of the Drawings

[0018]

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Mode for Carrying Out the Invention

[0019] Next, this embodiment will be described with reference to the drawings. In the description of the drawings 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 and the planar dimensions of each component is different from the actual one. Therefore, specific thicknesses and dimensions should be determined with reference to the following description. Also, it goes without saying that there are parts where the dimensional relationships and ratios are different between the drawings.

[0020] Also, the embodiments shown below are examples of devices and methods for embodying the technical idea, and do not specify the materials, shapes, structures, arrangements, etc. of each component. Various changes can be made to this embodiment within the scope of the claims.

[0021] One aspect of the specific embodiment is as follows.

[0022] <1> A thermal print head comprising a substrate having a convex portion, a wiring layer on the convex portion, a heat storage layer on the wiring layer, a heating resistance portion formed on the heat storage layer and arranged along the main scanning direction, a first electrode in contact with the heating resistance portion on one side in the sub-scanning direction, a second electrode in contact with the heating resistance portion on the other side in the sub-scanning direction, and a connection wiring formed in an opening penetrating the heating resistance portion and the heat storage layer to reach the wiring layer, wherein the first electrode is electrically connected to the wiring layer via the connection wiring.

[0023] <2> The thermal print head according to <1>, wherein the wiring layer contains a silicide.

[0024] <3> The thermal print head according to <1>, wherein the wiring layer covers the upper surface and the side surface of the convex portion.

[0025] <4> The thermal print head according to <1>, wherein the wiring layer contains a metal.

[0026] <5> The thermal print head according to any one of <1> to <4>, wherein the substrate and the convex portion are integrally formed of a single crystal semiconductor.

[0027] <6> The thermal print head according to <5>, wherein the single crystal semiconductor is made of silicon.

[0028] <7> The thermal print head according to any one of <1> to <6>, wherein the first electrode is a common electrode and the second electrode is an individual electrode.

[0029] <8> A thermal printer comprising the thermal print head according to any one of <1> to <7>.

[0030] <9> A method for manufacturing a thermal print head, comprising: forming a wiring film on a substrate surface; removing a part of the substrate and the wiring film to form a convex portion and a wiring layer on the convex portion; forming a heat storage layer on the wiring layer; forming heat generating resistance portions arranged along the main scanning direction on the heat storage layer; forming an opening that penetrates the heat generating resistance portions and the heat storage layer to reach the wiring layer; forming a connection wiring in the opening; and forming a first electrode electrically connected to the wiring layer through the connection wiring and a second electrode spaced apart from the first electrode with the heat generating resistance portions interposed therebetween along the sub-scanning direction.

[0031] <10> The method for manufacturing a thermal print head according to <9>, wherein the wiring film is formed by siliciding the substrate.

[0032] <11> A method for manufacturing a thermal print head, comprising: removing a part of a substrate to form a convex portion; forming an oxide film on the substrate; forming a wiring layer on the oxide film; forming a heat storage layer on the wiring layer; forming a plurality of heat generating resistance portions arranged along the main scanning direction on the heat storage layer; forming an opening that penetrates the heat generating resistance portions and the heat storage layer to reach the wiring layer; forming a connection wiring in the opening; and forming a first electrode electrically connected to the wiring layer through the connection wiring and a second electrode spaced apart from the first electrode with the heat generating resistance portions interposed therebetween along the sub-scanning direction.

[0033] <12> The method for manufacturing a thermal print head according to any one of <9> to <11>, wherein the convex portion is formed by performing anisotropic etching using potassium hydroxide.

[0034] <13> The method for manufacturing a thermal print head according to any one of <9> to <12>, wherein the substrate is made of a single crystal semiconductor.

[0035] <14> The method for manufacturing a thermal print head according to <13>, wherein the single crystal semiconductor is made of silicon.

[0036] <15> The first electrode is a common electrode, and the second electrode is an individual electrode. The method for manufacturing a thermal print head according to any one of <9> to <14>.

[0037] (First Embodiment) <Thermal Print Head> The thermal print head according to this embodiment will be described with reference to the drawings.

[0038] FIGS. 1 and 2 show one substrate that is a part of one thermal print head. In this embodiment, the individual piece substrate included in this one thermal print head is referred to as individual piece substrate 100. The individual piece substrate 100 includes a substrate 10 having a convex portion 11, a wiring layer 12 on the convex portion 11, an insulating layer 14 on the wiring layer 12, a heat storage layer 16 on the insulating layer 14, a resistor layer 18 on the heat storage layer 16, a first electrode 20a in contact with the resistor layer 18, a second electrode 20b on the resistor layer 18, and a protective film 22 covering the resistor layer 18, the first electrode 20a, and the second electrode 20b. Openings are provided in the heat storage layer 16 and the resistor layer 18, and the opening 19a penetrates the heat storage layer 16 and the resistor layer 18. The first electrode 20a is electrically connected to the wiring layer 12 via a connection wiring 20c formed in the opening 19a. The resistor layer 18 includes a plurality of heat generating resistor portions 18a that generate heat by an electric current flowing through the electrodes (the first electrode 20a and the second electrode 20b). The plurality of heat generating resistor portions 18a are independently formed between the opposing first electrode 20a and second electrode 20b. FIG. 1 omits the plurality of heat generating resistor portions 18a. The plurality of heat generating resistor portions 18a are linearly arranged along the main scanning direction Y, which will be described later, on the heat storage layer 16. Note that FIG. 1 omits the protective film 22 for ease of understanding.

[0039] Perspective views such as FIG. 1 may show the substrate 10 corresponding to the individual piece substrate 100 for convenience. Cross-sectional views such as FIG. 2 may show up to the outside of the substrate 10 for convenience.

[0040] In the present embodiment, the direction in which the plurality of heating resistance portions 18a extend linearly is defined as the main scanning direction Y, the direction perpendicular to the main scanning direction Y and parallel to the upper surface of the substrate 10 is defined as the sub-scanning direction X, and the direction corresponding to the thickness of the substrate 10 is defined as the thickness direction Z. In other words, the thickness direction Z is perpendicular to each of the main scanning direction Y and the sub-scanning direction X. Further, in the sub-scanning direction X, the direction in which the first electrode 20a is located when viewed from the second electrode 20b is defined as the downstream side (downstream direction) of the sub-scanning direction X, and the direction in which the second electrode 20b is located when viewed from the first electrode 20a is defined as the upstream side (upstream direction) of the sub-scanning direction X.

[0041] The substrate 10 is made of ceramic or single-crystal semiconductor. As the ceramic substrate, for example, an alumina substrate or the like can be used. As the single-crystal semiconductor substrate, for example, a silicon substrate or the like can be used. From the viewpoint of easily forming the convex portion, it is preferable to use a single-crystal semiconductor substrate as the substrate 10. From the viewpoint of heat dissipation, an alumina substrate having a relatively high thermal conductivity may be used as the substrate 10. For example, convex glass may be formed on the alumina substrate to prepare a substrate 10 having a convex portion made of glass. An insulating layer may be formed between the upper surface 10A of the substrate 10 and the wiring layer 12. As the material of the insulating layer, for example, silicon oxide, silicon nitride can be used.

[0042] The ceramic substrate has a rectangular planar shape. The silicon substrate, which is a semiconductor substrate, is also called a silicon wafer and has a substantially circular planar shape. In both the ceramic substrate and the semiconductor substrate, one substrate 10 corresponding to the individual substrate 100 is arranged in a lattice pattern when viewed along the thickness direction Z. Therefore, a plurality of individual substrates 100 are manufactured from either one ceramic substrate or one semiconductor substrate.

[0043] Hereinafter, the individual substrate 100 manufactured using a silicon substrate will be described. The wiring layer 12 is provided on the top surface 11A of the convex portion 11 in the substrate 10. The wiring layer 12 extends longitudinally along the main scanning direction Y. The wiring layer 12 is electrically connected to the first electrode 20a via the connection wiring 20c and functions as a common electrode of the individual substrate 100. The first electrode 20a electrically connects both ends of the wiring layer 12 in the main scanning direction Y to the external terminals, and a heating voltage is input from the external terminals to the first electrode 20a which is a part of the common electrode.

[0044] The wiring layer 12 can be formed using a compound obtained by performing a heat treatment on the substrate 10 and the conductive layer provided on the substrate 10 to react the materials of the substrate 10 and the conductive layer. Examples of the conductive layer include titanium, nickel, cobalt, sodium, magnesium, platinum, tungsten, molybdenum, tantalum, vanadium, zirconium, hafnium, etc. As the wiring layer 12, for example, titanium can be formed on a silicon substrate, and after performing a heat treatment, the surface of the silicon substrate and titanium react (silicidation), and a low-resistance conductive layer obtained by the reaction can be used.

[0045] The insulating layer 14 is formed on the wiring layer 12 using a high-resistance material as a base for the heat storage layer 16. The insulating layer 14 is made of an insulating material, and for example, silicon oxide, silicon nitride can be used. The dimension in the thickness direction Z of the insulating layer 14 (the thickness of the insulating layer 14) is not particularly limited. For example, one example is 5 μm to 15 μm, preferably 5 μm to 10 μm.

[0046] The heat storage layer 16 is formed on the insulating layer 14 and is sometimes also referred to as a glaze layer. The heat storage layer 16 extends longitudinally along the main scanning direction Y. The heat storage layer 16 accumulates the heat generated from the heat generating resistance portion 18a described later. The heat storage layer 16 can use an insulating material, and for example, silicon oxide which is the main component of glass, silicon nitride, etc. can be used. The dimension in the thickness direction Z of the heat storage layer 16 is not particularly limited, for example, it is 30 to 80 μm, preferably 40 to 60 μm.

[0047] An insulating layer 17 is formed on the substrate 10 of the present embodiment. The insulating layer 17 is formed on the heat storage layer 16 and on the upper surface 10A of the substrate 10. The insulating layer 17 is made of an insulating material, and for example, a silicon oxide layer or a silicon nitride layer can be used. As the silicon oxide layer, for example, silicon oxide formed by using TEOS (tetraethoxysilane) as a raw material can be used. When viewed along the main scanning direction Y, a resistor layer 18, a first electrode 20a, and a second electrode 20b, which will be described later, are formed on the insulating layer 17. When viewed along the main scanning direction Y, the insulating layer 17 is formed between the upper surface of the heat storage layer 16 and the resistor layer 18 including the heat generating resistor portion 18a. The insulating layer 17 may be formed between the upper surface of the heat storage layer 16 and the first electrode 20a and the second electrode 20b.

[0048] In the resistor layer 18, the portion where current flows from the first electrode 20a and the second electrode 20b generates heat. Specifically, the resistor layer 18 to which a heating voltage is individually applied according to a printing signal transmitted from the outside to the driving IC is selectively heated. By generating heat in this way, a printed dot is formed. The resistor layer 18 uses a material having a higher resistivity than the materials constituting the first electrode 20a and the second electrode 20b. For example, tantalum nitride or silicon oxide containing tantalum can be used. Ruthenium oxide may be used as the material of the resistor layer 18. In the present embodiment, the dimension of the resistor layer 18 in the thickness direction Z is, for example, about 0.05 to 0.2 μm. One heat generating resistor portion 18a in the resistor layer 18 corresponds to one printed dot.

[0049] The first electrode 20a is formed on one side (downstream side) in the sub-scanning direction and functions as part of the common electrode. A connection wiring 20c is formed of the same material as the first electrode 20a in an opening 19a provided so as to penetrate the heat storage layer 16, the insulating layer 17, and the resistor layer 18. The first electrode 20a is electrically connected to the wiring layer 12 via the connection wiring 20c. That is, the first electrode 20a, the connection wiring 20c, and the wiring layer 12 have a function as a common electrode. Also, in the present embodiment, the positions of both ends of the first electrode 20a are higher than the top surface 11A of the convex portion 11, but it is not limited to this. For example, the first electrode 20a may overlap with the side surface 11B of the convex portion 11 and the upper surface 10A of the substrate 10. The second electrode 20b is formed on the other side (upstream side) in the sub-scanning direction and functions as an individual electrode. The first electrode 20a and the second electrode 20b constitute a path for energizing the resistor layer 18. Specifically, current flows from the wiring layer 12, the connection wiring 20c, and the first electrode 20a, which function as a common electrode, through the resistor layer 18 in sequence to the second electrode 20b, which functions as an individual electrode.

[0050] A plurality of the above-described openings 19a are provided, and these openings 19a are also referred to as downstream openings. Further, a plurality of openings 19b are provided in the heat storage layer 16, the insulating layer 17, and the resistor layer 18 so as to penetrate, and these openings 19b are also referred to as upstream openings. The plurality of openings 19a are arranged at a ratio of one with respect to the plurality of heat generating resistor portions 18a in the vicinity of the downstream end portion of the convex portion 11. The plurality of openings 19a may be regularly arranged. In the individual substrate 100, the voltage drop at the center of the plurality of heat generating resistor portions 18a arranged along the main scanning direction Y may be a problem. In this case, it is preferable to arrange the plurality of openings 19a sparsely in the vicinity of both ends along the main scanning direction Y and densely as it approaches the center portion.

[0051] A plurality of openings 19b are arranged at least one by one at one end and the other end along the main scanning direction Y near the upstream end of the convex portion 11. When viewed along the thickness direction Z, the plurality of openings 19b are arranged so as to overlap the wiring layer 12. It is preferable that the same number of openings 19b are arranged at one end and the other end along the main scanning direction Y.

[0052] As the first electrode 20a, the second electrode 20b, and the connection wiring 20c, for example, a metal layer such as aluminum, copper, titanium, gold, etc. can be used. Further, the first electrode 20a, the second electrode 20b, and the connection wiring 20c may have a multilayer structure. For example, it may be a laminated structure of a titanium layer mainly composed of titanium and a copper layer mainly composed of copper formed on the titanium layer. Further, the dimension of the first electrode 20a, the second electrode 20b, and the connection wiring 20c in the thickness direction Z is, for example, about 0.2 to 0.8 μm.

[0053] The first electrode 20a (common electrode) is a part that has an electrically opposite polarity to a plurality of second electrodes 20b (individual electrodes) when a printer incorporating the thermal print head is used. The common electrode has a plurality of comb teeth portions that are the first electrode 20a and a wiring layer 12 that is a common portion connecting these plurality of comb teeth portions in common. The wiring layer 12 that is the common portion is formed along the main scanning direction Y on the convex portion 11 of the substrate 10, and each comb tooth portion has a strip shape extending in the sub-scanning direction X on the insulating layer 17 formed on the heat storage layer 16. When viewed along the thickness direction Z, the upstream tip of each comb tooth portion is opposed to the tip of each second electrode 20b with a predetermined interval downstream along the sub-scanning direction X.

[0054] Viewing along the thickness direction Z, at both ends of the individual substrate 100 in the main scanning direction Y, an upstream connection wiring 20d is formed on an insulating layer 17 formed on the heat storage layer 16. The wiring layer 12 formed below the heat storage layer 16 is electrically connected to the connection wiring 20d formed on the heat storage layer 16 by a connection wiring 20c at both ends of the individual substrate 100 in the main scanning direction Y when viewed along the thickness direction Z. The connection wiring 20d extends upstream in the sub-scanning direction X (the upper right side in FIG. 1). The connection wiring 20d is exposed from the protective film 22 on the upstream side in the sub-scanning direction X. A portion of the connection wiring 20d exposed from the protective film 22 constitutes a heating pad portion 20d1 to which a heating voltage is supplied. If necessary, a heating voltage is applied to each heating resistance portion 18a.

[0055] Each second electrode 20b is in a strip shape extending generally in the sub-scanning direction X, and they are not electrically connected to each other. Therefore, when a printer incorporating a thermal print head is used, different potentials can be individually applied to each second electrode 20b. An individual pad portion 20b1 is formed at the end of each second electrode 20b. The individual pad portion 20b1 and the heating pad portion 20d1 are exposed from the protective film 22 on the upstream side in the sub-scanning direction X. The upstream end of the individual pad portion 20b1 shown in FIG. 1 (in addition to FIGS. 17 and 19 referred to later) and the end of the wiring layer 12 along the main scanning direction Y are both located inside at a certain distance (for example, 0.5 mm) from the end of the substrate 10.

[0056] Conventionally, a strip-shaped electrode extending in the sub-scanning direction X has two adjacent portions including a folded-back shape. The two adjacent portions are respectively connected to two adjacent heating resistance portions. These two adjacent heating resistance portions constitute one printing dot. The center-to-center interval (dot pitch) of the formed printing dots is the center-to-center interval between two adjacent heating resistance portions and two adjacent heating resistance portions adjacent thereto. For this reason, it is difficult to form a high-definition electrode pattern by reducing the center-to-center interval, and high-definition printing cannot be performed on the printing medium.

[0057] However, in the individual substrate 100 used for the thermal print head 200 (see FIG. 39) of the present embodiment, the common electrode is formed by the first electrode 20a and the wiring layer 12, and the individual electrode is formed by the second electrode 20b. When viewed along the thickness direction Z, a part of the common electrode overlaps the individual electrode with the heat storage layer 16 sandwiched therebetween in the thickness direction Z. Therefore, it is not necessary to form the electrodes in a folded shape, and high integration of the common electrode and the individual electrode becomes possible. In addition, the center-to-center distance (electrode pitch) between adjacent electrodes is equal to the dot pitch. Therefore, by reducing the electrode pitch to form a high-definition electrode pattern, high-definition printing can be performed on the printing medium. The dot pitch can be, for example, 63.5 μm or less, and more preferably 42.3 μm or less.

[0058] The protective film 22 covers the first electrode 20a, the second electrode 20b, etc., and protects the first electrode 20a, the second electrode 20b, etc. from wear, corrosion, oxidation, etc. An insulating material can be used for the protective film 22, and for example, silicon nitride, silicon oxide, etc. can be used. The dimension of the protective film 22 in the thickness direction Z is, for example, about 3 to 8 μm. The individual pad portion 20b1 and the heat generating pad portion 20d1 on the upstream side in the sub-scanning direction X are exposed from the protective film 22.

[0059] Here, a method for manufacturing the thermal print head 200 (see FIG. 39) of the present embodiment will be described. Each figure showing the manufacturing method may show the substrate 10 corresponding to the individual substrate 100 for convenience. Actually, each step is performed on one ceramic substrate and one semiconductor substrate each including a plurality of regions corresponding to a plurality of substrates 10.

[0060] As shown in FIGS. 3 and 4, first, a semiconductor substrate (for example, a silicon substrate) including a plurality of substrates 10a is prepared. Next, after forming a conductive film 12a that becomes a wiring layer 12 on the substrate 10a, an insulating film 14a that becomes an insulating layer 14 is formed on the conductive film 12a. The substrate 10a, the conductive film 12a, and the insulating film 14a can each use the materials exemplified for the above-described substrate 10, wiring layer 12, and insulating layer 14. For the conductive film 12a, for example, titanium or the like using sputtering can be used. For the insulating film 14a, for example, silicon oxide or the like using sputtering can be used.

[0061] Next, as shown in FIGS. 5 and 6, a resist pattern 15 is formed on the insulating film 14a.

[0062] Next, as shown in FIGS. 7 and 8, using the resist pattern 15 as a mask, a part of the conductive film 12a and a part of the insulating film 14a are removed to form the wiring layer 12 and the insulating layer 14. Then, the resist pattern 15 is peeled off. For this peeling, for example, hydrofluoric acid can be used.

[0063] Next, as shown in FIGS. 9 and 10, using the wiring layer 12 and the insulating layer 14 as a mask, a part of the substrate 10a is removed to form a substrate 10 having a convex portion 11. For example, a part of the substrate 10a can be removed using anisotropic etching using potassium hydroxide. By this step, a convex portion 11 having a trapezoidal cross-sectional shape is formed along the main scanning direction Y. The convex portion 11 has a top surface 11A formed of a plane parallel to the upper surface of the substrate 10. On the top surface 11A, the wiring layer 12 and the insulating layer 14 are formed in order from the bottom. In some cases, an insulating layer (not shown) is formed between the top surface 11A and the wiring layer 12. In this case, first, before forming the conductive film 12a, a part of the substrate 10a is removed to form a substrate 10 having a convex portion 11, and then an insulating layer, a wiring layer 12, and an insulating layer 14 are formed on the substrate 10 having the convex portion 11. The insulating layer may be provided only on the top surface 11A, may be provided on the top surface 11A and the side surface 11B of the convex portion 11, or may be provided on the entire upper surface 10A of the substrate 10.

[0064] Next, as shown in FIGS. 11 and 12, a heat storage layer 16 is formed on the insulating layer 14. The heat storage layer 16 can be formed, for example, by discharging a glass paste with a dispenser and then performing a firing process. The firing process is performed, for example, at 850 to 1200° C. for 1 to 5 hours.

[0065] Next, as shown in FIGS. 13 and 14, an insulating layer 17 and a resistor layer 18 are formed on the substrate 10 and the heat storage layer 16. For the insulating layer 17, for example, silicon oxide or the like formed by depositing TEOS (tetraethoxysilane) as a raw material using CVD can be used. For the resistor layer 18, for example, tantalum nitride or the like formed by sputtering can be used.

[0066] Next, as shown in FIGS. 15 and 16, openings 19a and 19b are formed in the insulating layer 14, the heat storage layer 16, and the resistor layer 18. The openings 19a and 19b are formed so that a part of the upper surface of the wiring layer 12 is exposed. As shown in FIG. 15, the openings 19a and 19b are arranged offset when viewed along the sub-scanning direction X. Therefore, the opening 19b is not shown in FIG. 16. In the sub-scanning direction X, the opening 19b exists at the following position. The position is a position symmetric with respect to the center line of the top surface 11A of the convex portion 11 across the opening 19a shown in FIG. 16 and extended to both end sides of the substrate 10 along the main scanning direction Y.

[0067] Next, as shown in FIGS. 17 and 18, for example, by photolithography, a connection wiring 20c in the opening 19a and a first electrode 20a electrically connected to the wiring layer 12 via the connection wiring 20c are formed. The connection wiring 20c may be formed on the inner wall surface of the opening 19a, or the connection wiring 20c may be formed so as to fill the inside of the opening 19a. In the same process, when viewed along the thickness direction Z, a second electrode 20b facing the tip of the first electrode 20a with a predetermined interval along the sub-scanning direction X, a connection wiring 20c in the opening 19b, and a connection wiring 20d electrically connected to the wiring layer 12 via the connection wiring 20c are formed. When viewed along the thickness direction Z, a resistor layer 18 is exposed from the first electrode 20a and the second electrode 20b between the tips of the first electrode 20a and the second electrode 20b. After completion of this process, the wiring layer 12 formed under the insulating layer 14 is formed below the heat storage layer 16. Also, the first electrode 20a and the second electrode 20b are formed above the heat storage layer 16. Therefore, the wiring layer 12 corresponds to the lower layer wiring, and the first electrode 20a and the second electrode 20b correspond to the upper layer wiring.

[0068] The first electrode 20a functions as a part of the common electrode, and the second electrode 20b functions as an individual electrode. When viewed along the thickness direction Z, since the wiring layer 12 (lower layer wiring), which is a part of the common electrode, overlaps with the second electrode 20b (upper layer wiring), which is an individual electrode, it is not necessary to form either the common electrode or the individual electrode in a folded shape, and high integration of the common electrode (first electrode 20a) and the individual electrode (second electrode 20b) becomes possible. Therefore, a high-definition electrode pattern can be formed by reducing the electrode pitch, and high-definition printing can be performed on the printing medium.

[0069] Also, in the individual substrate 100 used for the thermal print head 200 (see FIG. 39) of the present embodiment, when viewed along the main scanning direction Y, the midpoint between the tip of the first electrode 20a and the tip of the second electrode 20b is located on the downstream side (the first electrode 20a side) in the sub-scanning direction X from the central portion of the heat storage layer 16. That is, the position of the region of the resistor layer 18 that does not overlap with the first electrode 20a and the second electrode 20b (the region where the upper surface of the resistor layer 18 is exposed from each electrode) is on the downstream side in the sub-scanning direction X from the central portion of the heat storage layer 16. By adopting such a configuration, when printing on a printing medium, the printing medium can be smoothly fed downstream in the sub-scanning direction X, so that it becomes possible to print on the printing medium at a higher speed and with higher definition. The configuration is not limited to the above, and the position of the region of the resistor layer 18 that does not overlap with the first electrode 20a and the second electrode 20b may be the central portion of the heat storage layer 16 when viewed along the main scanning direction Y.

[0070] Next, as shown in FIGS. 19 and 20, a protective film 22 is formed. For the protective film 22, for example, silicon nitride using CVD or the like can be used.

[0071] Next, for example, using a dicing saw, by cutting the semiconductor substrate, an individual substrate 100 which is an individualized single substrate is manufactured. The cutting is performed along the main scanning direction Y and the sub-scanning direction X. The position where the semiconductor substrate is cut along the main scanning direction Y is preferably slightly downstream from the point where the protective film 22 shown in FIG. 20 becomes flat on the downstream side.

[0072] Next, as shown in FIG. 39, the individual substrate 100 is fixed to the heat radiating member 8 using an adhesive (not shown) or the like. The connection substrate 5 on which the driving IC 7 and the connector 59 are mounted is fixed to the heat radiating member 8 using a screw (not shown) or the like.

[0073] Next, wiring connections are made around the driving IC7. Among the pads of the driving IC7, the pads for input / output with the outside and the pads of the connection substrate 5 are electrically connected using wires. Among the pads of the driving IC7, the pad for the heat generating resistance portion 18a and the individual pad portion 20b1 (see FIG. 1) are electrically connected using wires. The heat generating pad portion 20d1 (see FIG. 1) of the individual substrate 100 and the heat generating pad of the connection substrate 5 are electrically connected using a plurality of wires. Each of the above-described pads and each wire are not shown in FIG. 39.

[0074] Next, on the upper surface of the individual substrate 100 and the upper surface of the connection substrate 5, a sealing resin (not shown) is formed so as to include the connection portions of the respective pads and respective wires, the respective wires, and the driving IC7. As the sealing resin, for example, a thermosetting resin such as an epoxy resin is used. Through the above steps, the thermal print head 200 of the present embodiment can be manufactured.

[0075] Further, as a configuration of the individual substrate of another thermal print head according to the present embodiment, a configuration in which the wiring layer covers the upper surface and the side surface of the convex portion of the substrate 10 may be employed. A method for manufacturing the wiring layer will be described.

[0076] As shown in FIGS. 21 and 22, a substrate 10 having a convex portion 11 is prepared. The substrate 10 having the convex portion 11 can be obtained, for example, by forming a resist pattern on the above-described substrate 10a and removing a part of the substrate 10a using anisotropic etching using potassium hydroxide with the resist pattern as a mask.

[0077] Next, as shown in FIGS. 23 and 24, an insulating film 24 is formed on the substrate 10. The insulating film 24 can employ the materials and formation methods exemplified by the above-described insulating film 14a.

[0078] Next, as shown in FIGS. 25 and 26, a conductive film 26a is formed on the insulating film 24. The conductive film 26a can be formed of, for example, titanium, nickel, cobalt, sodium, magnesium, platinum, tungsten, molybdenum, tantalum, vanadium, zirconium, hafnium, etc. using sputtering.

[0079] Next, as shown in FIGS. 27 and 28, a part of the conductive film 26a is removed to form a wiring layer 26 that covers the top surface 11A and the side surface 11B of the convex portion 11 of the substrate 10. The removal can be performed, for example, by photolithography.

[0080] Subsequent formation steps of the heat storage layer, the resistor layer, the common electrode, the individual electrode, the protective film, etc. can adopt the above-described steps (the steps described with reference to FIGS. 11 to 20).

[0081] In a configuration where the wiring layer 26 covers the upper surface and the side surface of the convex portion 11 of the substrate 10, the wiring layer 26 and the first electrode 20a function as a common electrode. Also, the first electrode 20a may be in contact with the wiring layer 26 through an opening provided through the insulating layer 14, the heat storage layer 16, and the resistor layer 18 as described above. Further, an opening may be provided in a region of the resistor layer 18 that is in contact with the side surface of the convex portion 11 of the substrate 10, and the first electrode 20a and the wiring layer 26 may be in contact through the opening.

[0082] According to the present embodiment, when viewed along the thickness direction Z, since the wiring layer 12 (or the wiring layer 26), which is a part of the common electrode, overlaps with the second electrode 20b, which is an individual electrode, high integration of the common electrode and the individual electrode becomes possible. Therefore, the electrode pitch can be reduced to form a high-definition electrode pattern, and high-definition printing can be performed on the printing medium while ensuring a good yield.

[0083] (Second Embodiment) <Thermal Print Head> The thermal print head according to the present embodiment will be described with reference to the drawings.

[0084] Figs. 29 and 30 show a single substrate which is a part of a single thermal print head. In this embodiment, the individual substrate included in this single thermal print head is defined as individual substrate 100A. The individual substrate 100A includes a substrate 115, a heat storage layer 133 linearly extending on the substrate 115, individual electrodes 131 and a common electrode 132 on the heat storage layer 133, a heating resistor 140 on the individual electrode 131, on the common electrode 132, and on the heat storage layer 133, and a protective film 134 on the individual electrode 131, on the common electrode 132, on the heat storage layer 133, and on the heating resistor 140. The heat storage layer 133 has a first layer 133a and a second layer 133b on the first layer 133a. The first layer 133a contains glass, and the second layer 133b is a porous layer containing a material different from that of the first layer 133a. Also, the individual electrodes 131 and the common electrode 132 are collectively referred to as wiring. The heating resistor 140 includes a plurality of heating resistance portions 141 that generate heat by an electric current flowing through the wiring (the individual electrodes 131 and the common electrode 132). The plurality of heating resistance portions 141 are linearly arranged on the heat storage layer 133.

[0085] In this embodiment, the direction in which the plurality of heating resistance portions 141 linearly extend is defined as the main scanning direction Y, the direction perpendicular to the main scanning direction Y and parallel to the upper surface of the substrate 115 is defined as the sub-scanning direction X, and the direction corresponding to the thickness of the substrate 115 is defined as the thickness direction Z. In other words, the thickness direction Z is a direction perpendicular to each of the main scanning direction Y and the sub-scanning direction X.

[0086] The substrate 115 is made of ceramic or single crystal semiconductor. As the ceramic substrate, for example, an alumina substrate or the like can be used. As the single crystal semiconductor substrate, for example, a silicon substrate or the like can be used. From the viewpoint of heat dissipation, it is preferable to use an alumina substrate having a relatively high thermal conductivity as the substrate 115.

[0087] On a substrate 115 made of an alumina substrate or the like, a heat storage layer 133 (also referred to as a glaze layer) having a function of accumulating heat is laminated. The heat storage layer 133 accumulates heat generated from a heat generating resistance portion 141 described later. As the heat storage layer 133, an insulating material can be used. For example, silicon oxide or silicon nitride, which is a main component of glass, can be used. The dimension in the thickness direction Z of the heat storage layer 133 is not particularly limited. For example, it is 30 to 80 μm, preferably 40 to 60 μm.

[0088] The heat storage layer 133 in the present embodiment is composed of a first layer 133a and a second layer 133b. The first layer 133a is a non-porous layer containing glass. The dimension in the thickness direction Z of the first layer 133a is 20 to 60 μm, preferably 30 to 50 μm, from the viewpoint of pressure resistance.

[0089] The second layer 133b is a porous layer containing a material different from that of the first layer 133a. The second layer 133b may contain, for example, porous glass, which is a glass material different from the first layer 133a. The porous glass may be shirasu porous glass, which is CaO-Al2O3-B2O3-SiO2-based glass. A large number of holes are provided on the surface of the second layer 133b, and a solvent contained in a metal paste used for forming the individual electrodes 131 and the common electrode 132 described later penetrates into the holes on the surface of the second layer 133b. By this penetration, it becomes possible to suppress the spread of the wiring patterns of the individual electrodes 131 and the common electrode 132. The porosity of the second layer 133b is not particularly limited and may be appropriately adjusted according to the physical properties of the paste provided on the second layer 133b.

[0090] The dimension in the thickness direction Z of the second layer 133b is 10 to 30 μm, preferably 10 to 20 μm.

[0091] The second layer 133b is a porous layer and has inferior pressure resistance compared to the first layer 133a. Therefore, by using the heat storage layer 133 having a laminated structure of the first layer 133a and the second layer 133b, it is possible to ensure pressure resistance by the action of the first layer 133a and form a high-definition wiring pattern by the action of the second layer 133b. For example, by making the film thickness of the second layer 133b smaller than the film thickness of the first layer 133a or making the viscosity of the first layer 133a higher than the viscosity of the second layer 133b, it is possible to ensure pressure resistance and form a high-definition wiring pattern.

[0092] On the heat storage layer 133, wirings (individual electrodes 131 and common electrode 132) formed from a metal paste are provided. The common electrode 132 has a comb-tooth portion 132A and a common portion 132B. The individual electrode 131 has a wide portion and a narrow portion. The comb-tooth portion 132A of the common electrode 132 may also have a wide portion and a narrow portion.

[0093] The wiring is obtained by applying a metal paste by a screen printing method or the like to form a wiring pattern. Since the metal paste, which is the raw material of the wiring, is applied on the second layer 133b which is a porous layer, the solvent contained in the metal paste penetrates into the pores of the second layer 133b. By this penetration, it is possible to suppress the metal paste from spreading wet on the second layer 133b. Specifically, the actual wiring width can be made 1.5 times or less the designed value of the wiring width. By setting the viscosity of the glass paste used as the material of the second layer 133b, the porosity of the second layer 133b, etc. to appropriate values, the wiring width can be made 1.2 times or less the designed value of the wiring width. By making the ratio of the wiring width to the designed value of the wiring width close to 1, a higher-definition wiring pattern can be formed. For example, the wiring width of the wiring (individual electrode 131 and common electrode 132 (comb-tooth portion 132A)) can be made 20 μm or more and 50 μm or less. The interval between adjacent wirings (the interval between the outer edges at the wide portions of adjacent wirings (the size of the gap)) can be made 10 μm or more and 50 μm or less. The center-to-center interval between adjacent wirings (wiring pitch) can be made more than 40 μm and 70 μm or less.

[0094] As the metal paste, for example, a paste containing metal particles such as copper, silver, palladium, iridium, platinum, and gold can be used. From the viewpoints of the properties of the metal and the ionization tendency, it is preferably copper, silver, platinum, or gold, and more preferably copper or silver from the viewpoints of the properties of the metal, the ionization tendency, and cost reduction. Further, the solvent contained in the metal paste has a function of uniformly dispersing the metal particles, and examples thereof include, but are not limited to, a mixture of one or more of an ester solvent, a ketone solvent, a glycol ether solvent, an aliphatic solvent, an alicyclic solvent, an aromatic solvent, an alcohol solvent, and water.

[0095] Examples of the ester solvent include ethyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate, amyl acetate, ethyl lactate, dimethyl carbonate, and the like. Examples of the ketone solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, benzene, diisobutyl ketone, diacetone alcohol, isophorone, cyclohexanone, and the like. Examples of the glycol ether solvent include ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, and acetic acid 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 acetic acid esters of these monoethers.

[0096] Examples of the aliphatic solvent include n-heptane, n-hexane, cyclohexane, methylcyclohexane, ethylcyclohexane, and the like. Examples of the alicyclic solvent include methylcyclohexane, ethylcyclohexane, cyclohexane, and the like. Examples of the aromatic solvent include toluene, xylene, tetralin, and the like. Examples of the alcohol solvent (excluding the above-mentioned glycol ether solvent) include ethanol, propanol, butanol, and the like.

[0097] The metal paste can contain, as required, a dispersant, a surface treatment agent, an anti-friction improver, an infrared absorber, an ultraviolet absorber, a fragrance, an antioxidant, an organic pigment, an inorganic pigment, an antifoaming agent, a silane coupling agent, a titanate coupling agent, a plasticizer, a flame retardant, a moisturizing agent, an ion scavenger, etc.

[0098] Each individual electrode 131 is generally in a strip shape extending in the sub-scanning direction X, and they are not electrically connected to each other. Therefore, when a printer incorporating a thermal print head is used, different potentials can be individually applied to each individual electrode 131. An individual pad portion is formed at the end of each individual electrode 131.

[0099] The common electrode 132 is a part that has an electrically opposite polarity to a plurality of individual electrodes 131 when a printer incorporating a thermal print head is used. The common electrode 132 has a plurality of comb teeth portions 132A and a common portion 132B that commonly connects these plurality of comb teeth portions 132A. The common portion is formed in the main scanning direction Y along the upper edge of the substrate 115. Each comb tooth portion is in a strip shape extending in the sub-scanning direction X separated from the common portion. The tip of each comb tooth portion enters between the tips of two adjacent individual electrodes 131 and is opposed to them at a predetermined interval along the main scanning direction Y.

[0100] The tip of each comb tooth portion may be opposed to the tip of each individual electrode 131 at a predetermined interval along the sub-scanning direction X. In this case, it is preferable that the heat generating resistance portion 141 is formed only in the region where the tip of the comb tooth portion and the tip of the individual electrode 131 are opposed. In other words, it is preferable that the heat generating resistance portion 141 is not arranged outside the region where the tip of the comb tooth portion and the tip of the individual electrode 131 are opposed in the main scanning direction Y.

[0101] The heat - generating resistance portion 141 generates heat at the portion where current flows from the wiring (the individual electrodes 131 and the common electrode 132). Specifically, the heat - generating resistance portion 141, to which a printing signal transmitted from the outside such as a driving IC is input, is selectively energized according to the printing signal, thereby being selectively heated. By generating heat in this way, printing dots are formed. The heat - generating resistance portion 141 uses a material with a higher resistivity than the material constituting the wiring. For example, tantalum nitride or silicon oxide containing tantalum can be used. Ruthenium oxide may be used as the material of the heat - generating resistance portion 141. In the present embodiment, the dimension of the heat - generating resistance portion 141 in the thickness direction Z is, for example, about 0.05 to 0.2 μm.

[0102] The wiring and the heat - generating resistance portion 141 etc. are covered with the protective film 134, which protects the wiring and the heat - generating resistance portion 141 from wear, corrosion, oxidation, etc. The protective film 134 can use an insulating material. For example, silicon nitride, silicon oxide, etc. can be used. The dimension of the protective film 134 in the thickness direction Z is, for example, about 3 to 8 μm.

[0103] Here, the manufacturing method of the single - piece substrate 100A of the present embodiment will be described.

[0104] As shown in FIGS. 31 and 32, first, a substrate 115 is prepared, and a first glass paste (corresponding to the first layer 133a before firing) is applied onto the substrate 115 by screen printing or the like. The applied first glass paste is dried, and a first layer 133a, which becomes a part of the heat - storage layer 133, can be formed on the substrate 115 by the firing process described later. The viscosity of the first layer 133a before firing is 50 cP or more and 200 cP or less.

[0105] Next, as shown in FIGS. 33 and 34, a second glass paste (corresponding to the second layer 133b before firing) is applied onto the dried first glass paste by screen printing or the like, and the applied paste-like porous material is dried. Thereafter, the dried first glass paste and second glass paste are subjected to a firing process and a heat treatment to form a heat storage layer 133 including a first layer 133a and a second layer 133b on the substrate 115. In the present embodiment, when the second glass paste is fired and heat-treated, porous glass (porous glass) is formed from the phase-separated glass. The communication holes of the porous glass contain air. The porous glass is a material containing air. The firing process is performed, for example, at 1250° C. for 4.5 hours. The viscosity of the second layer 133b before firing is 50 cP or more and 200 cP or less.

[0106] Next, as shown in FIGS. 35 and 36, individual electrodes 131 and a common electrode 132 are formed on the heat storage layer 133. The common electrode 132 has a comb tooth portion 132A and a common portion 132B. The individual electrodes 131 and the common electrode 132 can be obtained by applying the above-described metal paste by screen printing or the like and forming a wiring pattern. Since the heat storage layer 133 in the present embodiment includes the second layer 133b which is a porous layer, the solvent contained in the metal paste penetrates into the holes of the second layer 133b. Due to this penetration, it is possible to suppress the metal paste from spreading wet on the second layer 133b, and it becomes possible to directly form the wiring patterns of the individual electrodes 131 and the common electrode 132 on the heat storage layer 133 without going through a wiring pattern forming process such as photolithography. Thereby, the wiring pattern forming process of the individual electrodes 131 and the common electrode 132 can be simplified, and furthermore, a higher-definition wiring pattern can be formed.

[0107] Next, as shown in FIGS. 37 and 38, a heating resistor 140 (heating resistance portion 141) is formed by a thick film forming technique. The heating resistor 140 (heating resistance portion 141) is formed by firing a resistor paste supplied by screen printing or a dispenser. The resistor paste contains, for example, ruthenium oxide.

[0108] Further, as shown in FIG. 30, a protective film 134 is formed by a thin film forming technique. For the protective film 134, for example, silicon nitride using CVD or the like can be used. The protective film 134 may be formed by a thick film forming technique. In this case, a protective film 134 made of glass is formed by firing a screen-printed glass paste.

[0109] Through the above steps, the thermal print head of the present embodiment can be manufactured.

[0110] According to the present embodiment, by providing the second layer 133b which is a porous layer, a high-definition wiring pattern can be obtained. Further, by providing the heat storage layer 133 in which the first layer 133a and the second layer 133b are laminated, it becomes possible to ensure the pressure resistance of the heat storage layer 133 in addition to obtaining a high-definition wiring pattern.

[0111] <Thermal Printer> The thermal print head 200 will be described with reference to FIG. 39. Here, it is described assuming that the thermal print head 200 includes the individual substrate 100 described in the first embodiment. The thermal print head 200 includes a substrate 10 (the wiring layer 12, the heat storage layer 16, etc. on the substrate 10 are not shown), a connection substrate 5, and a heat dissipation member 8. The substrate 10 and the connection substrate 5 are mounted adjacent to each other in the sub-scanning direction X on the heat dissipation member 8. A plurality of heating resistance portions 18a arranged in the main scanning direction Y are formed on the substrate 10. The heating resistance portions 18a are driven to selectively generate heat by a driving IC 7 mounted on the connection substrate 5. The heating resistance portions 18a perform printing on a printing medium 92 such as thermal paper that is pressed against the heating resistance portions 18a by a platen roller 91 according to a printing signal transmitted from the outside via a connector 59.

[0112] The connection substrate 5 can use, for example, a printed wiring board. The connection substrate 5 has a structure in which a base material layer and a wiring layer (not shown) are laminated. As the base material layer, for example, a glass epoxy resin or the like can be used. As the material of the wiring layer, for example, metals such as copper, silver, palladium, iridium, platinum, and gold can be used.

[0113] The heat dissipation member 8 has a function of dissipating heat from the substrate 10. The substrate 10 and the connection substrate 5 are attached to the heat dissipation member 8. As the heat dissipation member 8, for example, a metal such as aluminum can be used.

[0114] The thermal printer of the present embodiment can include the above-described individual substrates. The thermal printer performs printing on a printing medium. Examples of the printing medium include a barcode sheet and thermal paper for creating a receipt.

[0115] The thermal printer includes, for example, a thermal print head 200, a platen roller 91, a main power circuit, a measurement circuit, and a control unit. The platen roller 91 faces the thermal print head 200.

[0116] The main power circuit supplies power to a plurality of heat generating resistance portions 18a in the thermal print head 200. The measurement circuit measures the resistance value of each of the plurality of heat generating resistance portions 18a. The measurement circuit measures the resistance value of each of the plurality of heat generating resistance portions 18a, for example, when printing is not performed on the printing medium. Thereby, the life of the heat generating resistance portion 18a and the presence or absence of a failed heat generating resistance portion 18a can be confirmed. The control unit controls the driving states of the main power circuit and the measurement circuit. The control unit controls the energization state of each of the plurality of heat generating resistance portions 18a. The measurement circuit may be omitted.

[0117] The connector 59 is used to communicate with a device outside the thermal print head 200. Through the connector 59, the thermal print head 200 is electrically connected to the main power supply circuit and the measurement circuit. Through the connector 59, the thermal print head 200 is electrically connected to the control unit.

[0118] The drive IC 7 receives a signal from the control unit via the connector 59. Based on the signal received from the control unit, the drive IC 7 controls the energization state of each of the plurality of heat generating resistor portions 18a. Specifically, the drive IC 7 selectively energizes a plurality of individual electrodes (second electrodes 20b) to arbitrarily generate heat in any one of the plurality of heat generating resistor portions 18a.

[0119] Next, a method of using the thermal printer will be described.

[0120] When printing on a printing medium, a potential v11 is applied as a potential V1 from the main power supply circuit to the connector 59. In this case, a plurality of heat generating resistor portions 18a are selectively energized and generate heat. By transferring the heat to the printing medium, printing on the printing medium is performed. As described above, when a potential v11 is applied as a potential V1 from the main power supply circuit to the connector 59, an energization path to each of the plurality of heat generating resistor portions 18a is ensured.

[0121] When printing on the printing medium is not performed, the resistance values of the respective heating resistance portions 18a are measured. At the time of such measurement, no potential is applied to the connector 59 from the main power supply circuit. When measuring the resistance values of the respective heating resistance portions 18a, a potential v12 is applied as a potential V1 to the connector 59 from the measurement circuit. In this case, the plurality of heating resistance portions 18a are energized in order (for example, in order from the heating resistance portion 18a located at the end in the main scanning direction Y). Based on the value of the current flowing through the heating resistance portion 18a and the potential v12, the measurement circuit measures the resistance value of each heating resistance portion 18a. As described above, when the potential v11 is applied as the potential V1 to the connector 59 from the main power supply circuit, the energization paths to each of the plurality of heating resistance portions 18a are substantially blocked. Thereby, the measurement circuit can more accurately measure the resistance value of each heating resistance portion 18a, and the life of the heating resistance portion 18a and the presence or absence of a failed heating resistance portion 18a can be confirmed.

[0122] According to the present embodiment, it is possible to form a high-definition electrode pattern by reducing the electrode pitch, and it is possible to obtain a thermal printer capable of performing high-definition printing on a printing medium while ensuring a good yield.

[0123] [Other Embodiments] As described above, although some embodiments have been described, the discussions and drawings forming a part of the disclosure are exemplary and should not be understood as limiting. Various alternative embodiments, examples, and operation techniques will be apparent to those skilled in the art from this disclosure. Thus, the present embodiment includes various embodiments not described herein.

[0124] For example, in the individual substrate 100 of the first embodiment, a configuration including a heat storage layer containing two types of layers described in the second embodiment may be employed.

[0125] <Examples of Embodiments> Examples of embodiments of the present invention are given below. The embodiments of the present invention are not limited to the following examples.

[0126] [Supplementary Note 1] A thermal print head comprising a heat storage layer having a first layer and a second layer on the first layer, wiring formed on the heat storage layer, a heating resistor formed on the wiring, and a protective film covering the heat storage layer, the wiring, and the heating resistor, wherein the first layer contains glass and the second layer is a porous layer.

[0127] [Supplementary Note 2] The thermal print head according to [Supplementary Note 1], wherein the film thickness of the second layer is smaller than the film thickness of the first layer.

[0128] [Supplementary Note 3] The thermal print head according to [Supplementary Note 1] or [Supplementary Note 2], wherein the second layer contains porous glass.

[0129] [Supplementary Note 4] The thermal print head according to any one of [Supplementary Note 1] to [Supplementary Note 3], wherein the interval between adjacent wirings is 10 μm or more and 50 μm or less.

[0130] [Supplementary Note 5] The thermal print head according to any one of [Supplementary Note 1] to [Supplementary Note 3], wherein the center-to-center interval between adjacent wirings is more than 40 μm and 70 μm or less.

[0131] [Supplementary Note 6] A thermal printer comprising the thermal print head according to any one of [Supplementary Note 1] to [Supplementary Note 5].

[0132] [Supplementary Note 7] A method for manufacturing a thermal print head, comprising forming a first layer containing glass on a substrate, forming a second layer which is a porous layer on the first layer to form a heat storage layer including the first layer and the second layer, forming wiring on the heat storage layer, forming a heating resistor on the wiring, and forming a protective film covering the heat storage layer, the wiring, and the heating resistor.

[0133] [Supplementary Note 8] A method for manufacturing the thermal print head according to [Supplementary Note 7], comprising applying a first glass paste, drying the applied first glass paste, applying a second glass paste on the dried first glass paste, drying the applied second glass paste, and firing the dried first and second glass pastes to form a first layer containing glass and a second layer that is a porous layer, thereby forming the heat storage layer.

[0134] [Supplementary Note 9] A method for manufacturing the thermal print head according to [Supplementary Note 7] or [Supplementary Note 8], wherein the film thickness of the second layer is smaller than the film thickness of the first layer.

[0135] [Supplementary Note 10] A method for manufacturing the thermal print head according to any one of [Supplementary Note 7] to [Supplementary Note 9], wherein the second layer contains porous glass.

[0136] [Supplementary Note 11] A method for manufacturing the thermal print head according to any one of [Supplementary Note 7] to [Supplementary Note 10], wherein the interval between adjacent wirings is 10 μm or more and 50 μm or less.

[0137] [Supplementary Note 12] A method for manufacturing the thermal print head according to any one of [Supplementary Note 7] to [Supplementary Note 10], wherein the center-to-center interval between adjacent wirings is more than 40 μm and 70 μm or less.

[0138] The present invention relates to the subject matters of Japanese Patent Application No. 2020-133780 filed on August 6, 2020 and Japanese Patent Application No. 2020-145965 filed on August 31, 2020, and the entire disclosure contents thereof are incorporated herein by reference.

Explanation of Reference Numerals

[0139] 5 Connection substrate 7 Driving IC 8 Heat dissipation member 10, 10a, 115 Substrate 10A Upper surface 11 Protrusion 11A Top surface 11B Side surface 12 and 26 wiring layers 12a and 26a conductive films 14 and 17 insulating layers 14a and 24 insulating films 15 resist patterns 16 and 133 heat storage layers 18 resistor layer 18a and 141 heat generating resistance parts 19a and 19b openings 20a first electrode 20b second electrode 20b1 individual pad part 20c and 20d connection wirings 20d1 heat generating pad part 22 and 134 protective films 59 connector 91 platen roller 92 printing medium 100 and 100A individual substrate 131 individual electrode 132 common electrode 132A comb teeth part 132B common part 133a first layer 133b second layer 200 thermal print head

Claims

1. A substrate having a convex portion, A wiring layer on the convex portion, A heat storage layer on the wiring layer, A heating resistance portion formed on the heat storage layer and arranged along the main scanning direction, A first electrode in contact with the heating resistance portion on one side in the sub-scanning direction, A second electrode in contact with the heating resistance portion on the other side in the sub-scanning direction, A connection wiring formed in an opening that penetrates the heating resistance portion and the heat storage layer to reach the wiring layer, and comprising: The first electrode is electrically connected to the wiring layer via the connection wiring, a thermal print head.

2. The wiring layer contains silicide, the thermal print head according to claim 1.

3. The wiring layer covers the upper surface and side surfaces of the convex portion, the thermal print head according to claim 1.

4. The wiring layer contains metal, the thermal print head according to claim 1.

5. The substrate and the convex portion are integrally formed of a single crystal semiconductor, the thermal print head according to any one of claims 1 to 4.

6. The single crystal semiconductor is made of silicon, the thermal print head according to claim 5.

7. The first electrode is a common electrode, The second electrode is an individual electrode, the thermal print head according to any one of claims 1 to 6.

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

9. Form a wiring film on the substrate surface, Remove a part of the substrate and the wiring film to form a convex portion and a wiring layer on the convex portion, Form a heat storage layer on the wiring layer, Form heating resistance portions arranged along the main scanning direction on the heat storage layer, Form an opening that penetrates the heating resistance portion and the heat storage layer to reach the wiring layer, Form a connection wiring in the opening, and form a first electrode electrically connected to the wiring layer via the connection wiring and a second electrode spaced apart from the first electrode with the heating resistance portion sandwiched therebetween along the sub-scanning direction, a method of manufacturing a thermal print head.

10. The wiring film is formed by siliciding the substrate, the method of manufacturing a thermal print head according to claim 9.

11. Remove a part of the substrate to form a convex portion, Form an oxide film on the substrate, Form a wiring layer on the oxide film, Form a heat storage layer on the wiring layer, A plurality of heating resistance parts arranged along the main scanning direction are formed on the heat storage layer. An opening is formed which penetrates the heating resistance part and the heat storage layer to reach the wiring layer. A method for manufacturing a thermal print head, comprising: forming a connection wiring in the opening, and forming a first electrode electrically connected to the wiring layer through the connection wiring, and a second electrode spaced apart from the first electrode with the heating resistance part interposed therebetween along the sub-scanning direction.

12. The method for manufacturing a thermal print head according to any one of claims 9 to 11, wherein the convex portion is formed by performing anisotropic etching using potassium hydroxide.

13. The method for manufacturing a thermal print head according to any one of claims 9 to 12, wherein the substrate is made of a single crystal semiconductor.

14. The method for manufacturing a thermal print head according to claim 13, wherein the single crystal semiconductor is made of silicon.

15. The first electrode is a common electrode. The method for manufacturing a thermal print head according to any one of claims 9 to 14, wherein the second electrode is an individual electrode.

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