JP2013202862A - Thermal print head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the durability of ends of a head substrate where heating resistors are arrayed.SOLUTION: A thermal print head is equipped with a ceramic substrate 22, a glaze layer 25, heating resistors 26, an electrode layer 28 making electric currents flow to the heating resistors 26, and a protection film 29. The glaze layer 25 has ridges 21 differently inclining formed with a first border line 71 as a boundary. The heating resistors 26 are arrayed along the ridges 21 with spaces interposed between. The protection film 29 covers the glaze layer 25, the heating resistors 26 and the electrode layer 28, and the surface is folded at a guiding edge 74 formed at a portion of the first border line 71.

Description

  The present invention relates to a thermal print head.

  Thermal print heads are used in fax machines and plate-making machines. In recent years, thermal print heads are increasingly used in applications that require low cost, small size, and high image quality, such as photo printers and labels / cards.

  A thermal print head is generally configured by placing a head substrate having a heating resistor arranged on the surface of an insulating substrate on a heat sink together with a circuit board constituting a drive circuit for driving the heating resistor. . There are cases where the heating resistor is composed of one element per pixel and one where one pixel is composed of a plurality of elements. In the one-pixel-one-element type, a predetermined voltage is normally applied to the heating resistor via a common electrode extending in the main scanning direction (the arrangement direction of the heating resistors) on the downstream side in the medium transport direction. The heating resistor is connected to a lead electrode extending upstream in the transport direction, and is connected to a ground potential (GND level) via a driving element (driving IC) having a switching function.

  In the type in which one pixel is composed of a plurality of heat generating resistors, at least two heat generating resistors are arranged in the main scanning direction and electrically connected in series so as to be in series. One of the two lead electrodes drawn out from the plurality of heating resistors constituting one pixel is connected to a common electrode extending in the main scanning direction on the upstream side in the transport direction, and a predetermined potential is applied thereto. The other lead electrode is connected to the ground potential via the drive element.

  A protective film is formed on the upper layer of the heating resistor and the electrode by an electrically insulating material having wear resistance, and the resistance against abrasion accompanying conveyance while the medium is in contact is ensured. At the time of printing, every time the medium is transported in the sub-scanning direction, the arranged heating resistors are selectively heated by the control of the driving element to obtain a desired image.

  As a printing method, there is a method of transferring to a photographic paper or a card by thermal paper, a sublimation ribbon or a melting ribbon. In the melting ribbon method, ribbon ink is melted in a heat generating area in which heating resistors are arranged and transferred to a recording medium such as photographic paper. In the fused ribbon method, it is required to shorten the time until the ribbon is peeled off from the recording medium after the transfer. For this reason, there is a need for a thermal printhead having a structure in which the end of the substrate is close to the heating resistor.

JP 2010-23296 A

  In the thermal print head used in the melt transfer system, the heating resistor and the end of the head substrate are close to each other. For this reason, the end portion of the head substrate is also subjected to the pressing pressure by the platen roller via the recording medium, the ink ribbon, and the like. The edge of the head substrate may be damaged depending on the printing speed, the structure of the printer, the pressure of the platen roller, and the like. For this reason, it is necessary to give priority to a printer mechanism and transfer conditions that do not damage the substrate edge, and as a result, the quality of the melt transfer and the printing speed may be sacrificed.

  Accordingly, an object of the present invention is to improve the durability of the end portion of the head substrate on which the heating resistors of the thermal print head are arranged.

  In order to solve the above-described problems, the present invention provides a thermal printhead comprising: an insulating substrate having at least one edge; and a surface on the surface of the insulating substrate that extends away from the edge and extends along the edge. A first slope that rises from one boundary line and is inclined with respect to the surface; and a second boundary line that is substantially parallel to the first boundary line and is connected to the first slope. A second slope having a gentler inclination with respect to the surface and a ridge line substantially parallel to the second boundary line and connected to the second slope and descending from the ridge line toward the insulating substrate. 3, a glaze layer covering the surface, a heating resistor arranged at intervals along the ridgeline and at least a part of which is located on the second slope, and the heating resistor Connected to both ends in the direction across the edge An electrode for energizing the serial heating resistor, characterized by comprising a protective film covering at least the heat-generating resistor and the second boundary line, the.

  Further, the present invention provides a method for manufacturing a thermal printhead, wherein an application step of applying a glass paste to a surface of an insulating substrate so as to have a flat portion and a protruding portion extending linearly projecting from the flat portion; After the step, the glass paste is baked to form a glass layer having a ridge formed with two slopes with a ridge line sandwiched between the protrusions, and the ridge line of the glass layer after the baking step On the other hand, the insulating substrate side of one inclined surface is removed to form a first inclined surface extending to a first boundary line on the surface extending substantially parallel to the ridge line, and the insulation on the opposite side of the ridge line A step of exposing the substrate, wherein an inclination of the first inclined surface with respect to the surface is connected to the first inclined surface at the second boundary line substantially parallel to the first boundary line and the ridge line; From the second slope A gentle slope removal step, a wiring step for forming a heating resistor and an electrode on the surface of the glaze layer after the removal step, and a protective film covering at least the heating resistor and the boundary line after the wiring step And a protective process.

  According to the present invention, it is possible to improve the durability of the end portion of the head substrate on which the heating resistors of the thermal print head are arranged.

It is sectional drawing of the head board | substrate in one Embodiment of the thermal print head which concerns on this invention. It is a partially cutaway plan view of the thermal print head in the present embodiment. It is a side view of the thermal printer using the thermal print head in this Embodiment. It is sectional drawing after baking a glass paste in the manufacture process of the head substrate in this Embodiment. It is sectional drawing after removing a part of glass layer in the manufacture process of the head substrate in this Embodiment. It is sectional drawing after laminating | stacking a resistor layer and an electrode layer in the manufacture process of the head substrate in this Embodiment. It is sectional drawing after forming a protective film in the manufacture process of the head substrate in this Embodiment.

  An embodiment of a thermal print head according to the present invention will be described with reference to the drawings. Note that this embodiment is merely an example, and the present invention is not limited thereto.

  FIG. 1 is a cross-sectional view of a head substrate in an embodiment of a thermal print head according to the present invention. FIG. 2 is a partially cutaway plan view of the thermal print head in the present embodiment. FIG. 3 is a side view of a thermal printer using the thermal print head in the present embodiment.

The thermal print head 11 of the present embodiment has a head substrate 20, a heat sink 30, and a circuit board 40. The head substrate 20 has a wiring layer composed of a ceramic substrate 22, a glaze layer 25, a resistor layer 27 and an electrode layer 28, and a protective film 29. The ceramic substrate 22 which is an electrically insulating substrate is a ceramic rectangular plate such as alumina (Al ₂ O ₃ ).

  The glaze layer 25 is a glass layer fused to the surface of the ceramic substrate 22. A portion along one long side of the surface of the ceramic substrate 22 is exposed without being covered with the glaze layer 25. In a part of the glaze layer 25, a protrusion 21 having a thickness greater than that of the other part extends in the longitudinal direction of the ceramic substrate 22. The ridge 21 is formed in the vicinity of the long side of the portion where the ceramic substrate 22 is exposed.

  A first slope 81 rises from a first boundary line 71 that is a boundary between the exposed portion of the ceramic substrate 22 and the glaze layer 25. The first inclined surface 81 is substantially flat and is inclined with respect to the surface of the ceramic substrate 22.

  The tangent plane at the ridge line 84 portion that is the portion farthest from the ceramic substrate 22 of the ridge 21 is parallel to the bottom surface of the ceramic substrate 22. On both sides of the ridge line 84, a second slope 82 and a third slope 83 that form a smooth curved surface are formed. The first slope 81 and the second slope 82 are connected by a second boundary line 72. The second inclined surface 82 has a gentler inclination with respect to the surface of the ceramic substrate 22 than the first inclined surface 81. A tangential plane of the second slope 82 at the second boundary line 72 intersects the first slope 81. That is, a corner portion is formed on the surface of the glaze layer 25 at the second boundary line 72 portion.

  The resistor layer 27 and the electrode layer 28 are laminated on the surface of the glaze layer 25 in a predetermined pattern. The resistor layer 27 is formed with heating resistors 26 arranged at intervals in the longitudinal direction (main scanning direction) of the ceramic substrate 22. On the electrode layer 28, electrodes connected to both ends of the heat generating resistor 26 in the short direction (sub-scanning direction) of the ceramic substrate 22 are formed. The heating resistor 26 generates heat when a current flows through the electrodes formed on the electrode layer 28, and forms a belt-like heating region 24 extending in the main scanning direction. The heating resistor 26 extends in the sub-scanning direction across the ridge line 84 of the glaze layer 25.

  Most of the resistor layer 27 and the electrode layer 28 and the glaze layer 25 where the resistor layer 27 and the electrode layer 28 are not stacked are covered with a protective film 29. A guide edge 74 extending in the main scanning direction is formed on the surface of the protective film 29 at a position corresponding to the second boundary line 72 of the glaze layer 25. In the vicinity of the long side of the ceramic substrate 22 far from the heat generating region 24, the protective film 29 is not formed, and the electrode layer 28 is exposed.

  On the first slope 81 of the glaze layer 25, a portion 99 that is not electrically connected to the heating resistor 26 may be left on the resistor layer 27 and the electrode layer 28. The remaining portion 99 can increase the adhesive force of the protective film 29.

  The head substrate 20 is placed on one surface of the heat sink 30. The head substrate 20 and the heat sink 30 are fixed with an adhesive, for example. The circuit board 40 is, for example, a flexible board, and is placed and fixed on the side of the heat sink 30 on which the head board 20 is placed via a hard board 41. On the circuit board 40, at least a part of a drive circuit for driving the heating resistor 26 is formed. The circuit board 40 is disposed adjacent to an edge opposite to the guide edge 74 formed on the protective film 29 on the surface of the head substrate 20.

  A driving element 42 which is an IC (Integrated Circuit) is placed on the surface of the circuit board 40. The driving element 42 and the electrode layer 28 exposed without being covered with the protective film 29 are electrically connected by a bonding wire 44. A bonding wire is also bridged between the wiring of the circuit board 40 and the driving element 42. The exposed electrode layer 28, bonding wire 44, drive element 42, and the like are sealed with a sealing resin body 48.

  A connector 49 is attached to the circuit board 40. A drive circuit including the circuit board 40 and the drive element 42 is supplied with a control signal and electric power from the outside via the connector 49 to drive the head board 20 and heat the heat generating area 24 in a predetermined pattern.

  The thermal printer includes a thermal print head 11, a platen roller 60, a sending side ribbon roller 64, a winding side ribbon roller 63, and a ribbon guide 65. The platen roller 60 is formed in a cylindrical shape having an axis in the normal direction of the heat generating region 24 of the thermal print head 11. The side surface of the platen roller 60 has a certain degree of elasticity.

  The feeding-side ribbon roller 64, the winding-side ribbon roller 63, and the ribbon guide 65 are disposed closer to the heat radiating plate 30 than the heat generating region 24 of the thermal print head 11. The delivery-side ribbon roller 64 and the ribbon guide 65 are arranged on the upstream side of the heat generating area 24 of the thermal print head 11, that is, on the circuit board 40 side. The winding-side ribbon roller 63 is disposed on the downstream side with respect to the heat generating area 24 of the thermal print head 11, that is, on the guide edge 74 side.

  The delivery-side ribbon roller 64 is obtained by winding an unused ink ribbon 62. The take-up side ribbon roller 63 rotates the used ink ribbon 62 by being rotated by a rotation mechanism (not shown). The ribbon guide 65 changes the transport direction of the unused ink ribbon 62.

  The direction of the ink ribbon 62 delivered from the delivery-side ribbon roller 64 is changed by the ribbon guide 65 and heads toward the heat generating area 24 of the thermal print head 11. The ink ribbon 62 whose direction is changed on the arc-shaped surface near the heat generating area 24 of the thermal print head 11 is further changed in direction by the guide edge 74 of the thermal print head 11 and heads toward the take-up ribbon roller 63.

  Next, a method for manufacturing such a thermal print head will be described.

First, for example, a glass paste is applied to the main surface of a ceramic plate having a thickness of about 0.8 mm by screen printing or the like. The ceramic plate is formed of, for example, alumina (Al ₂ O ₃ ), silica (SiO ₂ ), magnesia (MgO), or the like. The thickness of the glass paste is, for example, 30 to 120 μm. Next, a photosensitive resist is applied to the surface of the glass paste.

  After applying a glass paste and a photosensitive resist on the surface of the ceramic plate, a part of the photosensitive resist is exposed using a mask. In the mask, a light shielding portion is formed at a portion of the glaze layer 25 where the protrusion 21 is formed. After exposing the photosensitive resist, the etched portion of the photosensitive resist is removed. After etching the photosensitive resist, the glass paste is etched using the remaining portion of the photosensitive resist as an etching mask.

  By etching the glass paste using the remaining portion of the photosensitive resist as an etching mask, a protrusion having a thick glass paste is formed on the portion of the glaze layer 25 where the protrusion 21 is formed. The etching depth is, for example, 30 μm. This protrusion has a shape with an angular ridgeline. Thereafter, the remaining photosensitive resist is removed.

  Thereafter, the glass paste applied to the ceramic plate is fired. At this time, the temperature of the glass paste is set to, for example, about 900 ° C. which is equal to or higher than the softening point temperature of the glass, held for a predetermined time, and then cooled to room temperature.

  FIG. 4 is a cross-sectional view after baking the glass paste in the manufacturing process of the head substrate in the present embodiment.

  In the present embodiment, two head substrates 20 are manufactured from one ceramic plate 90. In the firing step, the glass paste becomes a temperature higher than the softening point and becomes more fluid, becomes rounded by the action of surface tension and gravity, and the glass layer 91 is formed. The glass layer 91 is fused to the entire main surface of the ceramic plate 90. Two protrusions 21 parallel to each other are formed on one ceramic plate 90. The thickness of the protrusion 21 at the ridge line 84 is 40 μm, for example. On both sides of the ridge line 84, a second slope 82 and a third slope 83 that form a smooth curved surface are formed.

  Next, the glass layer 91 is irradiated with laser light to remove a part thereof.

  FIG. 5 is a cross-sectional view after removing a part of the glass layer in the manufacturing process of the head substrate in the present embodiment.

  A laser beam is irradiated between the two ridges 21, and a part of the glass layer 91 is heated and sublimated to be removed. Thereby, the first inclined surface 81 is formed on each of the two protrusions 21. Since the application of energy by the laser beam is local, the thermal influence on the glass layer 91 other than the portion to be removed is small. Accordingly, the second slope 82 adjacent to the first slope 81 has a small thermal influence, and the glass layer 91 is softened at a wide portion sandwiching the second boundary line 72 as a boundary between them, so that the cross section is smooth. It is not a curved surface.

  In addition, the ceramic plate 90 between the first boundary lines 71 that are the opposite sides of the first inclined surface 81 to the second inclined surface 82 is exposed. In this way, two glaze layers 25 are formed on one ceramic plate 90.

  A scribe line 92 that is a linear groove is formed in a portion where the ceramic plate 90 between the two glaze layers 25 is exposed. The scribe line 92 is also formed by laser light irradiation.

  Here, laser light is used to remove the glass layer 91, but water jet processing may be used. In any case, after the glass layer 91 is baked, the first slope 81 is formed without being heated to a temperature above the wide range softening temperature of the glass layer 91 on the second slope 72 side. As a result, a wide range of the connection portion between the first slope 81 and the second slope 82 does not become a smooth curve due to surface tension, and the bent second boundary line 72 can be formed.

  In particular, when the glass layer 91 is removed using laser light, the possibility of cracks and chipping occurring in the glass layer 91 can be suppressed as compared with the case of mechanical polishing. In addition, also when using water jet processing, generation | occurrence | production of a crack and chipping can be suppressed by making small the magnitude | size of the abrasive grain to contain.

  FIG. 6 is a cross-sectional view after the resistor layer and the electrode layer are laminated in the manufacturing process of the head substrate in the present embodiment.

  After the glaze layer 25 is formed on the surface of the ceramic plate 90 in this way, the resistor layer 27 and the electrode layer 28 are formed on the surface of the glaze layer 25. The resistor layer 27 and the electrode layer 28 may be formed on the exposed surface of the ceramic plate 90.

The resistor layer 27 is formed, for example, by depositing SiO ₂ doped with tantalum (Ta) or the like on the surface of the glaze layer 25 by sputtering. The electrode layer 28 is made of aluminum (Al), gold (Au), silver (Ag), copper (Cu), nickel (Ni), chromium (Cr), titanium (Ti), tungsten (W), or a main component thereof. Or a laminated body of these metals or alloys is laminated on the surface of the resistor layer 27 by sputtering or the like. The laminated thickness of the resistor layer 27 and the electrode layer 28 is, for example, about 1 μm.

  Thereafter, the resistor layer 27 and the electrode layer 28 are etched into a predetermined shape, whereby the heating resistor 26 and the electrode are formed. The width of the heating resistor 26 and the electrode is, for example, about 10 μm. The distance between the electrodes is, for example, about 10 μm.

  FIG. 7 is a cross-sectional view after forming a protective film in the manufacturing process of the head substrate in the present embodiment.

After patterning the resistor layer 27 and the electrode layer 28, a protective film 29 is coated. The protective film 29 is made of, for example, SiO ₂ or SiON. The thickness of the protective film 29 is, for example, about 10 μm. A bent guide edge 74 is formed on the surface of the protective film 29 at a portion of the second boundary line 82 that is the boundary between the first inclined surface 81 and the second inclined surface 82 of the glaze layer 25.

  Thereafter, the ceramic plate 90 is divided by applying bending stress around the scribe line 92 formed on the ceramic plate 90. Thereby, the two head substrates 20 are formed.

  The circuit board 40 on which the head substrate 20 and the driving element 42 thus manufactured are mounted is placed on the heat sink 30, and a bonding wire 44 is bridged between the driving element 42 and the head substrate 20. The thermal print head 11 is completed by sealing the bonding wire 44 with the sealing resin body 48.

  The print medium 61 moves in the sub-scanning direction while being pressed against the heat generating area 24 of the thermal print head 11 by the platen roller 60. At this time, the ink ribbon 62 is interposed between the printing medium 61 and the heat generating region 24. At the time of printing on the printing medium 61, current is supplied from the driving circuit such as the driving element 42 to the heating resistor 26 by a signal supplied from the outside and the like, and heat is generated. A desired image is printed on the printing medium 61 by moving the printing medium 61 in the sub-scanning direction while changing the heating pattern of the heating area 24 of the thermal print head 11.

  The used portion used for printing the ink ribbon 62 is sequentially sent to the take-up side ribbon roller 63. The ink ribbon 62 is conveyed while being in contact with the second inclined surface 82 of the thermal print head 11 by an ink ribbon feeding mechanism including a feeding side ribbon roller 64, a winding side ribbon roller 63, a ribbon guide 65, and the like.

  The ink on the ink ribbon 62 is melted by the heat generated in the heat generating area 24 and transferred to the printing medium 61. The ink ribbon 62 and the printing medium 61 are in contact with each other in the heat generating area 24, but are separated from the heat generating area 24 as well. Due to the adhesive force of the ink melted in the vicinity of the heat generating area 24, the ink ribbon 62 moves to the downstream side to some extent while sticking to the printing medium 61. Thereafter, the adhesive force is reduced by solidification of the melted ink, and the ink ribbon 62 moving in a direction different from the printing medium 61 is peeled from the printing medium 61 at the guide edge 74 portion.

  By making the glass layer 91 by firing, the surface of the glaze layer 25 draws a smooth curved surface. Thereafter, a part of the glass layer 91 is removed to form the first slope 81, so that the second boundary line 72, which is the boundary between the first slope 81 and the second slope 82, is interposed 2 Two slopes are bent. That is, the first slope at the second boundary line 72 and the tangential plane of the second slope 82 at the second boundary line 72 intersect at the second boundary line 72. Therefore, the curved surface and the flat surface are also bent and connected at the guide edge 74 which is the surface of the protective film 29 in the second boundary line 72 portion. As a result, the guide edge 74 can be used as a peeling portion of the ink ribbon 62.

  The distance from the heat generating region 24 until the ink ribbon 62 and the printing medium 61 are peeled depends on the angle between the conveyance direction of the ink ribbon 62 and the conveyance direction of the printing medium 61. If the angle between the conveyance direction of the ink ribbon 62 and the conveyance direction of the printing medium 61 is large, the force for separating the ink ribbon 62 from the printing medium 61 becomes large. The distance from the heat generating area 24 is reduced.

  If the distance from the heat generating region 24 until the ink ribbon 62 and the printing medium 61 are peeled off is too long, the ink ribbon 62 is peeled from the printing medium 61 after the melted ink is completely solidified. As a result, there may be a problem that the solidified ink is peeled off from the printing medium 61 while remaining on the ink ribbon 62.

  In the present embodiment, since the bent guide edge 74 is formed in the protrusion 21 of the thermal print head 11, the ink ribbon 62 can be peeled from the printing medium 61 in the very vicinity of the heat generating region 24. .

  On the other hand, the glaze layer 25 is covered with the protective film 29 in the vicinity of the guide edge 74. For this reason, even if the pressing pressure by the platen roller 60 is increased, the possibility of breakage of the end portion of the glaze layer 25 of the head substrate 20 is reduced. Thus, according to the present embodiment, the durability of the end portion of the head substrate 20 in the vicinity of the end portion of the head substrate 20 on which the heating resistors 26 are arranged is improved. As a result, the pressing pressure of the platen roller 60 can be increased and the heat transfer coefficient from the heating resistor 26 can be increased.

  In the present embodiment, the transport direction of the ink ribbon 62 on the downstream side of the heat generating area 24 is determined by the relative positional relationship between the heat generating area 24 and the guide edge 74. The conveyance direction of the printing medium 61 is uniquely determined if it is determined to be parallel to the bottom surface of the heat dissipation plate 30, for example. Therefore, in the present embodiment, the angle between the transport direction of the ink ribbon 62 and the transport direction of the printing medium on the downstream side of the heat generating region 24 is determined by the shape of the thermal print head 11.

  When the conveyance direction of the ink ribbon 62 on the downstream side of the heat generating area 24 is determined by a ribbon guide or the like, detailed position adjustment of the thermal print head 11 and the ribbon guide is required when the thermal print head 11 is assembled to the thermal printer. However, in the present embodiment, the angle between the transport direction of the ink ribbon 62 and the transport direction of the printing medium 61 on the downstream side of the thermal region 24 is determined by the shape of the thermal print head 11, so Position adjustment becomes easy.

  Further, by adjusting the relative positional relationship between the ridge 21 and the second boundary line 72 when the glaze layer 25 is formed, the surface of the protective film 29 corresponding to the ridge 21 and the second boundary line 72 is adjusted. The relative positional relationship of the guide edge 74 can be adjusted. Cutting and polishing in forming the glaze layer 25 can be easily performed with relatively high accuracy. Therefore, the heat generating region 24 and the guide edge 74 can be manufactured with high accuracy so that they have a predetermined relative positional relationship. As a result, the transport direction of the ink ribbon 62 on the downstream side of the heat generating area 24 can be controlled with high accuracy, and the print quality is improved.

DESCRIPTION OF SYMBOLS 11 ... Thermal print head, 20 ... Head substrate, 21 ... Projection, 22 ... Ceramic substrate, 24 ... Heat generation area, 25 ... Glaze layer, 26 ... Heat generation resistor, 27 ... Resistance layer, 28 ... Electrode layer, 29 ... Protective film, 30 ... Radiation plate, 40 ... Circuit board, 41 ... Hard substrate, 42 ... Drive element, 44 ... Bonding wire, 48 ... Sealing resin body, 49 ... Connector, 60 ... Platen roller, 61 ... Printing medium, 62 ... Ink ribbon, 63 ... Winding side ribbon roller, 64 ... Delivery side ribbon roller, 65 ... Ribbon guide, 71 ... First boundary line, 72 ... Second boundary line, 74 ... Guide edge, 81 ... First 1 slope, 82 ... second slope, 83 ... third slope, 84 ... ridge line, 90 ... ceramic plate, 91 ... glass layer, 92 ... scribe line

Claims (7)

An insulating substrate having at least one edge;
A first inclined surface rising from a first boundary line on the surface of the insulating substrate extending along the edge edge apart from the edge, and substantially inclined to the first boundary line; A second slope connected to the first slope at a second boundary line parallel to the first slope and having a gentler inclination relative to the surface than the first slope, and a ridge line substantially parallel to the second boundary line A glaze layer having a third slope that is connected to the second slope and descends from the ridge line toward the insulating substrate and covers the surface;
A heating resistor arranged at intervals along the ridgeline and at least partly located on the second slope;
Electrodes connected to both ends of the heating resistor in a direction crossing the edge and energizing the heating resistor;
A protective film covering at least the heating resistor and the second boundary line;
A thermal print head comprising:   2. The first slope according to claim 1, wherein the first slope is planar, the second slope is curved, and a tangential plane at the second boundary line intersects the first slope. Thermal print head.   The thermal print head according to claim 1, wherein the heating resistor extends across the ridge line. A coating step of applying a glass paste on the surface of the insulating substrate so as to have a flat portion and a protruding portion extending linearly from the flat portion;
A baking step of baking the glass paste after the coating step to form a glass layer having a protrusion on which two slopes are formed with a ridge line sandwiched between the protrusions;
After the firing step, a first slope that extends to the first boundary line on the surface that extends substantially parallel to the ridgeline by removing one side of the slope of the glass layer with respect to the ridgeline of the glass layer And exposing the insulating substrate on the opposite side of the ridge line, wherein the inclination of the first inclined surface with respect to the surface is substantially parallel to the first boundary line and the ridge line. A slope removing step that is gentler than the second slope connected to the first slope at a boundary line of
A wiring step of forming a heating resistor and an electrode on the surface of the glaze layer after the removing step;
A protective step of forming a protective film covering at least the heating resistor and the boundary line after the wiring step;
A method of manufacturing a thermal print head, comprising:   The method for manufacturing a thermal print head according to claim 4, wherein the removing step includes a step of irradiating a part of the glass layer with laser light to sublimate and removing the glass layer.   The method of manufacturing a thermal print head according to claim 4, wherein the removing step includes a step of removing a part of the glass layer by water jet processing. The removing step includes forming a scribe line;
A dividing step of dividing the insulating substrate along the scribe line;
The method for manufacturing a thermal print head according to claim 4, comprising:

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