JP5425564B2 - Thermal print head and thermal printer - Google Patents

Description

  The present invention relates to a thermal print head and a thermal printer using the same.

  A conventional thermal print head will be described with reference to FIGS. FIG. 8 is a diagram for explaining a conventional thermal print head, and is a schematic diagram showing a temperature distribution in the sub-scanning direction on the surface of the protective film, together with a schematic top view of the heating element plate. FIG. 9 is a diagram for explaining a conventional thermal print head, and is a schematic view showing a temperature distribution in the main scanning direction on the surface of the protective film, together with a schematic top view of the heating element plate. The top view of the heating element plate shown in FIGS. 8 and 9 is a view in which the protective film disposed on the outermost surface is removed.

  A thermal print head is an output device that heats a plurality of resistors arranged in a heat generating area and forms images such as characters and figures on a heat-sensitive recording medium such as heat-sensitive recording paper by the heat (for example, Patent Documents). 1). This thermal print head is widely used in recording devices such as barcode printers, digital plate-making machines, video printers, imagers, and seal printers.

  The thermal print head includes a heat radiating plate, and a heat generating plate and a circuit board disposed on the same surface of the heat radiating plate.

  The heating element plate has an insulating substrate having a glaze layer formed on a support substrate. A plurality of resistor layers 140 are formed on the insulating substrate. Each resistor layer 140 is formed in a substantially U-shaped pattern. The plurality of resistor layers 140 are arranged side by side in the main scanning direction 91 at intervals. Each resistor layer 140 serves as one heating element and outputs one dot to the recording medium.

  The substantially U-shaped resistor layer 140 includes a series of a first resistance portion 141, a folding resistance portion, and a second resistance portion 142 (hereinafter referred to as “one-diffractive structure”). The first resistance portion 141 and the second resistance portion 142 are portions that extend in the sub-scanning direction 92 and are arranged with an interval in the main scanning direction 91. The folding resistance portion is a portion connecting one end of the first resistance portion 141 and one end of the second resistance portion 142. Individual electrodes 151 and 153 are connected to the other end of the first resistor 141 and the other end of the second resistor 142, respectively.

  The folded conductive portions 146 are laminated on the surface of the folded resistance portion, and the folded conductive portion 146 electrically connects one end of the first resistance portion 141 and one end of the second resistance portion 142. When a voltage is applied between the individual electrodes 151, 153, the first resistance portion 141 and the second resistance portion 142 arranged in the main scanning direction 91 generate heat, and a heat generation region 132 extending in a strip shape in the main scanning direction 91 is formed. To do. A protective film that covers the insulating substrate, the resistor layer 140, the electrodes 151, 153, and the like is formed on the heating element plate.

The reason for adopting such a “one diffraction return structure” is as follows:
(1) As shown in FIG. 9, since a slit (a portion that does not generate heat) 150 is formed between the first resistor portion 141 and the second resistor portion 142, the center of the protective film surface in the main scanning direction is formed. Because the temperature peak is lowered and damage to the recording medium is reduced,
(2) If “1 diffraction return structure” is not adopted, it is necessary to adopt a common electrode for one of the electrodes for structural reasons. As a result, image quality deterioration due to common drop occurs.
Etc.

  The solid line shown in FIG. 9 shows the temperature distribution 186 on the surface of the protective layer in the conventional thermal print head. Also, the dotted lines shown in FIG. 9 indicate temperature distributions 187 and 188 on the virtual protective layer surface when the first resistance part 141 and the second resistance part 142 generate heat independently.

  On the other hand, an electrical component such as a driving IC that is a driving circuit for supplying power to the resistor layer 140 is mounted on the circuit board.

  A thermal printer using such a thermal print head generally includes a platen roller. The platen roller is arranged so that its side surface is in contact with the heat generating region 132 with the main scanning direction 91 as an axis, and is provided to be rotatable around the axis. The thermal printer rotates the platen roller to move the thermal recording medium in the sub-scanning direction 92 while pressing the thermal recording medium inserted between the platen roller and the heat generating area 132 against the heat generating area 132. In addition, a desired image is formed on the thermal recording medium by changing the heat generation pattern of the heat generating area 132 as the thermal recording medium moves.

JP 2006-205520 A

  In the above-described “one diffraction return structure”, the individual electrodes 151 and 153 and the folded conductive portion 146 are arranged to face each other with the heat generating region 132 interposed therebetween. The individual electrodes 151 and 153 and the folded conductive portion 146 are made of a conductor having a relatively high thermal conductivity such as aluminum. Therefore, part of the heat generated from the first resistance part 141 and the second resistance part 142 is radiated through the individual electrodes 151 and 153 and the folded conductive part 146.

  Here, since the individual electrodes 151 and 153 extend on the heating element plate to the vicinity of the circuit board, the heat dissipation is high. Therefore, the temperature on the surface of the protective film near the individual electrodes 151 and 153 tends to decrease. On the other hand, the folded conductive portion 146 has a smaller surface area than the individual electrodes 151 and 153, and therefore has a low heat dissipation and becomes a heat reservoir. Therefore, the temperature on the surface of the protective film near the folded conductive portion 146 is unlikely to decrease. As a result, as shown in FIG. 8, the temperature peak in the sub-scanning direction 92 on the surface of the protective film deviates from the center 183 of the heat generating region 132 in the sub-scanning direction 92, and the temperature distribution in the sub-scanning direction 92 on the surface of the protective film. 181 is biased toward the folded conductive portion 146 (positive direction in the sub-scanning direction 92).

  As described above, when the temperature distribution 181 in the sub-scanning direction 92 on the surface of the protective film is biased, the density distribution of each dot forming the image recorded on the recording medium is also biased, and the image quality is deteriorated.

  Therefore, the present invention has been made to solve the above-described problem, and an object thereof is to correct a temperature distribution bias in the sub-scanning direction.

In order to achieve the above object, a thermal print head according to the present invention extends in the sub-scanning direction in which a recording medium travels on the surface of the insulating substrate and the surface of the insulating substrate, and is arranged in order at intervals in the main scanning direction. A first folded conductive portion that connects the first resistance portion, the second resistance portion, and the third resistance portion arranged in a row, and one end of the second resistance portion and one end of the first resistance portion adjacent to the one end; A second folded conductive portion connecting the other end of the second resistance portion and one end of the third resistance portion proximate to the other end, the first resistance portion, the first folded conductive portion, and the second Including an individual electrode connected to the other end of the first resistor unit and a common electrode connected to the other end side of the third resistor unit in the order of the resistor unit, the second folded conductive unit, and the third resistor unit. comprising an electrode, the surface area of the second folded conductive portions of the first It returns smaller than the surface area of the conductive part and said.

In order to achieve the above object, a thermal printer according to the present invention includes an insulating substrate and a surface extending from the surface of the insulating substrate in the sub-scanning direction in which the recording medium travels and spaced apart from each other in the main scanning direction. A first folded conductive portion that connects the first resistor portion, the second resistor portion, and the third resistor portion arranged side by side, and one end of the second resistor portion and one end of the first resistor portion adjacent to the one end. A second folded conductive portion connecting the other end of the second resistance portion and one end of the third resistance portion proximate to the other end, the first resistance portion, the first folded conductive portion, the first 2 resistance portion, the second folded conductive portion and possess an electrode energizing the order of the third resistance portion, upstream of the traveling direction of the recording medium and the second folded conductive parts with respect to the first folded conductive portion Disposed on the side, the surface area of the second folded conductive portion is And characterized by including a small thermal printhead as compared to the surface area of the first folded conductive portion.

  According to the present invention, the uneven temperature distribution in the sub-scanning direction can be corrected.

1 is a perspective view of a thermal print head according to a first embodiment of the present invention. 1 is a partial cross-sectional view of a thermal printer according to a first embodiment of the present invention. It is a figure for demonstrating the thermal print head concerning the 1st Embodiment of this invention, Comprising: It is the upper side figure which expanded a part of heat generating body board | substrate except the protective layer. FIG. 4 is a cross-sectional view taken along arrow IV-IV in FIG. 3. It is a figure for demonstrating the thermal print head which concerns on the 1st Embodiment of this invention, Comprising: It is the schematic diagram which showed the temperature distribution of the subscanning direction in the protective film surface with the schematic top view of a heat generating body board. It is a figure for demonstrating the thermal print head which concerns on the 1st Embodiment of this invention, Comprising: It is the schematic diagram which showed the temperature distribution of the main scanning direction in the protective film surface with the schematic top view of a heat generating body board. It is a figure for demonstrating the thermal print head which concerns on the 2nd Embodiment of this invention, Comprising: It is the upper side figure which expanded a part of heat generating body board except the protective layer. It is a figure for demonstrating the conventional thermal print head, Comprising: It is the schematic diagram which showed the temperature distribution of the subscanning direction in the protective film surface with the schematic top view of a heat generating body board. It is a figure for demonstrating the conventional thermal print head, Comprising: It is the schematic diagram which showed the temperature distribution of the main scanning direction in the surface of a protective film with the schematic top view of a heat generating body board.

[First Embodiment]
A thermal print head and a thermal printer according to a first embodiment of the present invention will be described.

  First, an outline of the thermal print head 10 and the thermal printer according to the first embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a perspective view of a thermal print head according to the first embodiment of the present invention. FIG. 2 is a partial cross-sectional view of the thermal printer according to the first embodiment of the present invention.

  The thermal print head 10 includes a heat radiating plate 20, a heating element plate 30, and a circuit board 60. The heat generating plate 30 and the circuit board 60 are placed on the same surface of the heat radiating plate 20.

  The heat sink 20 is made of a metal such as aluminum and extends in the main scanning direction 91.

  The heat generating plate 30 is placed on the heat radiating plate 20 and extends in the main scanning direction 91. A heat generating region 32 extending in the main scanning direction 91 is formed on the heat generating plate 30.

  The circuit board 60 is placed on the heat radiating plate 20 and extends in the main scanning direction 91 in parallel with the heating element plate 30. A driving IC 62 and connectors 64 and 65 are mounted on the circuit board 60. The driving IC 62 serves as a driving circuit that generates heat in the heat generating region 32. Further, a control signal and driving power for forming a predetermined heat generation pattern in the heat generation region 32 are input via the connectors 64 and 65.

  The heating element plate 30 and the driving IC 62 are electrically connected by, for example, a bonding wire 66. Further, the driving IC 62 and the wiring pattern formed on the circuit board 60 are electrically connected by, for example, bonding wires 67. The driving IC 62 and the bonding wires 66 and 67 are sealed with a resin 68, for example.

  The thermal printer has a platen roller 70 made of a material having a predetermined elasticity and formed in a cylindrical shape. The platen roller 70 is provided so as to be rotatable about the shaft 72 with the main scanning direction 91 as a shaft 72. The platen roller 70 is disposed such that the side surface 74 is in contact with the heat generating region 32.

  When the thermal printer is used, a thermal recording medium 76 is inserted between the platen roller 70 and the heat generating area 32. The thermal recording medium 76 is, for example, thermal paper, and develops color when heated to a temperature higher than the thermal printing temperature. The thermal printer rotates the platen roller 70 to move the thermal recording medium 76 in the sub-scanning direction 92 perpendicular to the main scanning direction 91 while pressing the thermal recording medium 76 against the heat generating area 32. In addition, the thermal printer changes the heat generation pattern of the heat generating area 32 as the heat sensitive recording medium 76 moves, thereby forming a desired image on the heat sensitive recording medium 76.

  Next, details of the heating element plate 30 of the thermal print head 10 according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a view for explaining the thermal print head according to the first embodiment of the present invention, and is an enlarged top view of a part of the heating plate excluding the protective layer. 4 is a cross-sectional view taken along arrow IV-IV in FIG.

  The heating element plate 30 has an insulating substrate in which a glaze layer 36 is formed on one surface of a support substrate 34 made of an insulator such as alumina.

  On the surface of the glaze layer 36 of the insulating substrate, a plurality of resistor layers 40 are formed. Each resistor layer 40 is formed in a substantially S-shaped pattern. The plurality of resistor layers 40 are arranged side by side in the main scanning direction 91 at intervals.

  An individual electrode 51 is formed at one end of each resistor layer 40, and a common electrode 52 is formed at the other end of each resistor layer 40. The electrodes 51 and 52 are made of, for example, aluminum. The electrodes 51 and 52 are connected to the driving IC 62 through, for example, bonding wires 66. Each resistor layer 40 serves as a heating element and outputs one dot to the thermal recording medium 76.

  The substantially S-shaped resistor layer 40 includes a first resistor 41, a first folded resistor, a second resistor 42, a second folded resistor, and a third resistor 43. Yes.

  The first resistor portion 41, the second resistor portion 42, and the third resistor portion 43 are portions that extend in the sub-scanning direction 92 and are arranged side by side in the main scanning direction 91 with an interval therebetween. . A slit 50 that does not generate heat is formed between the first resistor portion 41 and the second resistor portion 42 and between the second resistor portion 42 and the third resistor portion 43. Note that when the dot density of the thermal print head 10 is 300 dpi, the width of each of the resistance portions 41 to 44 is, for example, 20 μm, and the width of the slit 50 is, for example, 8 μm.

  The first folding resistance portion is a portion connecting one end 42a of the second resistance portion 42 and one end 41a of the first resistance portion 41 adjacent to the one end 42a. The second folding resistance portion is a portion connecting the other end 42b of the second resistance portion 42 and one end 43b of the third resistance portion 43 adjacent to the other end 42b.

  The individual electrode 51 is connected to the other end 41 b of the first resistor portion 41, and the common electrode 52 is connected to the other end 43 a of the third resistor portion 43.

  A first folded conductive portion 46 and a second folded conductive portion 47 are laminated on the surfaces of the first folded resistance portion and the second folded resistance portion of the resistor layer 40, respectively. The resistance part and the second folded resistance part are not visible.) That is, the first folded conductive portion 46 electrically connects one end 42a of the second resistance portion 42 and one end 41a of the first resistance portion 41 adjacent to the one end 42a. Further, the second folded conductive portion 47 electrically connects the other end 42b of the second resistor portion 42 and one end 43b of the third resistor portion 43 adjacent to the other end 42b.

  Here, in the thermal printer according to the present embodiment, the thermal recording medium 76 travels from the individual electrode 51 side through the heat generation region 32 toward the common electrode 52 side (that is, in the positive direction of the sub-scanning direction 92). Drive). In this thermal printer, the thermal print head 10 is designed such that the surface area A2 of the second folded conductive portion 47 is smaller than the surface area A1 of the first folded conductive portion 46.

  The first folded conductive portion 46 and the second folded conductive portion 47 are each formed of a conductor such as aluminum. Therefore, when a voltage is applied between the electrodes 51 and 52, the first resistance portion 41, the first folded conductive portion 46, the second resistance portion 42, the second folded conductive portion 47, and the third resistance portion 43 are sequentially arranged. , Energized in the reverse order.

  When a voltage is applied between the electrodes 51 and 52, the first resistor 41, the second resistor 42, and the third resistor 43 of the plurality of resistor layers 40 arranged in the main scanning direction 91 generate heat. The heat generating region 32 refers to a band-shaped region in which the first resistor 41, the second resistor 42, and the third resistor 43 are arranged.

  Here, the heating element plate 30 is formed as follows, for example. First, a support substrate 34 made of ceramic is formed, and a glaze layer 36 made of glass is fused to the surface thereof. Next, a resistor and a conductor are sequentially laminated on the entire surface of the glaze layer 36 by a thin film forming apparatus such as a sputtering apparatus.

  Thereafter, the resistor layer 40, the first folded conductive portion 46, the second folded conductive portion, and the electrodes 51 and 52 are formed in a predetermined shape by a photoengraving process. Thereafter, a protective film 58 covering the resistor layer 40, the first folded conductive portion 46, the second folded conductive portion, and the electrodes 51 and 52 is formed, and is formed on the surfaces of the electrodes 51 and 52 connected to the bonding wires 66. Openings are formed by a photo-engraving process.

  The effects of the thermal print head 10 and the thermal printer according to the present embodiment will be described with reference to FIGS. FIG. 5 is a diagram for explaining the thermal print head according to the first embodiment of the present invention, and is a schematic diagram showing the temperature distribution in the sub-scanning direction on the surface of the protective film. FIG. 6 is a diagram for explaining the thermal print head according to the first embodiment of the present invention, and is a schematic diagram showing the temperature distribution in the main scanning direction on the surface of the protective film. The top view of the heating element plate 30 shown in FIGS. 5 and 6 is a view in which the protective film 58 is removed.

  As described above, when the “one diffraction return structure” is employed as in the conventional thermal print head, the electrodes 151 and 153 have high heat dissipation, whereas the folded conductive portion 146 becomes a heat reservoir, and FIG. As shown, the temperature distribution 181 in the sub-scanning direction 92 on the surface of the protective film is biased toward the folded conductive portion 146 (positive direction in the sub-scanning direction 92).

  On the other hand, in the present embodiment, the first folded conductive portion 46 and the second folded conductive portion 47 serving as heat pools are formed on both sides of the heat generating region 32 in the sub-scanning direction 92, respectively. Therefore, in the thermal print head 10 according to the present embodiment, the temperature peak 82 in the sub-scanning direction 92 on the surface of the protective film 58 is on the individual electrode 51 side (negative direction of the sub-scanning direction 92) as compared with the conventional thermal print head. The deviation of the temperature distribution 81 in the sub-scanning direction 92 on the surface of the protective film 58 is corrected.

  Here, as described above, the thermal recording medium 76 travels from the individual electrode 51 side through the heat generation region 32 toward the common electrode 52 side. Considering that the protective film 58 in the vicinity of the individual electrodes 51 is cooled by the thermal recording medium 76 when the thermal recording medium 76 approaches the heat generating area 32, the temperature distribution 81 in the sub-scanning direction 92 on the surface of the protective film 58 is It is desirable to be biased toward the individual electrode 51 side (the negative direction of the sub-scanning direction 92).

  In the present embodiment, the surface area A2 of the second folded conductive portion 47 is designed to be smaller than the surface area A1 of the first folded conductive portion 46. Therefore, heat is more likely to accumulate in the second folded conductive portion 47 than in the first folded conductive portion 46. Therefore, the temperature distribution 81 in the sub-scanning direction 92 of the heat generating region 32 is biased toward the individual electrode 51 side.

  In addition, according to the present embodiment, the second folded conductive portion 47 warms the heat-sensitive recording medium 76 before being inserted into the heat generating area 32, so that the image quality is improved.

  In the present embodiment, electrodes 51 and 52 having high heat dissipation are formed on both sides of the heat generating region 32 in the sub-scanning direction 92, respectively. Therefore, the influence of the electrodes 51 and 52 on the deviation of the temperature distribution 81 is small.

  By the way, as described above, when a “one diffraction return structure” is employed as in a conventional thermal print head, one slit (a portion that does not generate heat) 150 is formed between the first resistor portion 141 and the second resistor portion 142. Therefore, the temperature peak in the main scanning direction on the surface of the protective film is lowered, and the damage to the recording medium is reduced.

  In the present embodiment, three resistance portions 41 to 43 are formed, between the first resistance portion 41 and the second resistance portion 42, and between the second resistance portion 42 and the third resistance portion 43, Two slits 50 are formed.

  The dotted lines 87 to 89 in the graph of FIG. 6 indicate the temperature distributions 87 to 89 on the surface of the virtual protective film 58 when the three resistance portions 41 to 43 generate heat independently. When the three resistance portions 41 to 43 generate heat at the same time, the temperature distribution 86 in the main scanning direction on the surface of the protective film is flattened as indicated by the solid line 86 in the graph of FIG. By flattening the temperature distribution 86, damage to the thermal recording medium can be reduced and energy efficiency can be improved.

  Since the thermal print head according to the present embodiment has a larger number of resistance portions and slits per dot than the conventional thermal print head, the temperature distribution 86 in the main scanning direction 91 on the surface of the protective film 58 is easily flattened. .

  Further, this flattening is determined by the width and thickness of the three resistance portions 41 to 43 or the width of the two slits 50, but according to the present embodiment, it is 1 as compared with the conventional thermal print head. This adjustment is easy because the number of resistance portions and slits per dot is large.

[Second Embodiment]
A thermal print head according to a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is a view for explaining a thermal print head according to the second embodiment of the present invention, and is an enlarged top view of a part of the heating plate excluding the protective layer. In addition, since this embodiment is a modification of 1st Embodiment, duplication description is abbreviate | omitted.

  In the present embodiment, each resistor layer 40 is formed in a substantially M-shaped pattern. The substantially M-shaped resistor layer 40 includes a first resistance portion 41, a first folding resistance portion, a second resistance portion 42, a second folding resistance portion, a third resistance portion 43, a third folding resistance portion 48, and The fourth resistance unit 44 is configured in series.

  The four resistance portions 41 to 44 are portions that extend in the sub-scanning direction 92 and are arranged side by side in the main scanning direction 91 with an interval therebetween. In addition, when the dot density of the thermal print head 10 is 300 dpi, the width of each of the resistance portions 41 to 44 is, for example, 15 μm, and the interval between the adjacent resistance portions 41 to 44 is, for example, 8 μm. Is formed.

  The first folding resistance portion is a portion connecting one end 42 a of the second resistance portion 42 and one end 41 a of the first resistance portion 41. The second folding resistance portion is a portion connecting the other end 42 b of the second resistance portion 42 and one end 43 b of the third resistance portion 43. The third folding resistor portion is a portion connecting the other end 43a of the third resistor portion 43 and one end 44a of the fourth resistor portion 44 adjacent to the other end 43a.

  On the surfaces of the first folding resistance part, the second folding resistance part, and the third folding resistance part of the resistor layer 40, a first folding conductive part 46, a second folding conductive part 47, and a third folding conductive part, respectively. Portions 48 are stacked. That is, the first folded conductive portion 46 electrically connects one end 42 a of the second resistor portion 42 and one end 41 a of the first resistor portion 41, and the second folded conductive portion 47 is connected to the second resistor portion 42. The end 42b and the one end 43b of the third resistance portion 43 are electrically connected. Further, the third folded conductive portion 48 electrically connects the other end 43a of the third resistor portion 43 and one end 44a of the fourth resistor portion 44 adjacent to the other end 43a.

  The individual electrode 51 is connected to the other end 41 b of the first resistor portion 41, and the individual electrode 53 is connected to the other end 44 a of the fourth resistor portion 44.

  When a voltage is applied between the electrodes 51 and 53, the first resistance portion 41, the first folded conductive portion 46, the second resistance portion 42, the second folded conductive portion 47, the third resistance portion 43, the third folded conductive portion 48, Energization is performed in the order of the fourth resistance unit 44 or in the reverse order.

  Also in this embodiment, the temperature distribution in the sub-scanning direction 92 can be corrected as in the first embodiment.

  In the present embodiment, the individual electrodes 51 and 53 with high heat dissipation are both disposed on one side of the heat generating region 32. On the other hand, the first folded conductive portion 46 and the third folded conductive portion 48 serving as a heat reservoir are both disposed on the opposite side of the heat generating region 32 from the individual electrodes 51 and 53. Therefore, it is desirable that the surface area A2 of the second folded conductive portion 47 be smaller than the surface area A1 of the first folded conductive portion 46 and the surface area A3 of the third folded conductive portion 48. Thus, the temperature distribution in the sub-scanning direction 92 on the surface of the protective layer 58 can be adjusted by changing the surface areas of the folded conductive portions 46 to 48.

  In the present embodiment, unlike the first embodiment, the common electrode 52 is not employed. Therefore, the image quality is not deteriorated due to the common drop, and the space for the common electrode 52 is not necessary, which contributes to the miniaturization of the thermal print head 10.

[Other Embodiments]
The first and second embodiments are merely examples, and the present invention is not limited to these. For example, one resistor layer 40 may be formed of five or more resistance portions and four or more folding resistance portions.

  Further, in the first and second embodiments, the flat glaze layer 36 is employed, but a convex glaze layer that rises along the heat generating region 32 may be employed.

DESCRIPTION OF SYMBOLS 1 ... Thermal printer, 10 ... Thermal print head, 20 ... Heat sink, 30 ... Heat generating body plate, 32 ... Heat generating area, 34 ... Support substrate, 36 ... Glaze layer, 40 ... Resistor layer, 41 ... 1st resistance part, 42 ... 2nd resistance part, 43 ... 3rd resistance part, 44 ... 4th resistance part, 46 ... 1st folding conductive part, 47 ... 2nd folding conductive part, 48 ... 3rd folding conductive part, 50 ... slit, 51 ... individual electrode, 52 ... common electrode, 53 ... individual electrode, 58 ... protective film, 60 ... circuit board, 62 ... driving IC, 64, 65 ... connector, 66, 67 ... bonding wire, 68 ... resin, 70 ... platen Roller, 72 ... Platen roller shaft, 74 ... Side surface of platen roller, 76 ... Thermal recording medium, 81 ... Temperature distribution in the sub-scanning direction on the protective film surface, 82 ... Temperature peak in the sub-scanning direction on the protective film surface, 83 ... Sub-scanning direction center position of the hot zone, 91 ... main scanning direction, 92 ... sub scanning direction

Claims (5)

An insulating substrate;
A first resistance portion, a second resistance portion, and a third resistance portion, which extend in the sub-scanning direction in which the recording medium travels on the surface of the insulating substrate and are arranged side by side in order in the main scanning direction;
A first folded conductive portion connecting one end of the second resistance portion and one end of the first resistance portion proximate to the one end;
A second folded conductive portion connecting the other end of the second resistance portion and one end of the third resistance portion proximate to the other end;
The first resistor, the first folded conductive portion, the second resistor, the second folded conductive portion, and the individual resistor connected to the other end of the first resistor in the order of the third resistor, An electrode including a common electrode connected to the other end of the third resistance portion ;
And a surface area of the second folded conductive portion is smaller than a surface area of the first folded conductive portion .   A fourth resistor portion arranged on the opposite side of the third resistor portion from the second resistor portion at a distance from the third resistor portion on the surface of the insulating substrate and extending in the sub-scanning direction;
  A third folded conductive portion connecting the other end of the third resistance portion and one end of the fourth resistance portion proximate to the other end;
A thermal print head comprising:
  The thermal print head according to claim 1, wherein the common electrode is connected to the other end of the fourth resistance unit.   An insulating substrate, and a first resistor portion, a second resistor portion, and a third resistor portion, which extend in the sub-scanning direction in which the recording medium travels on the surface of the insulating substrate and are arranged side by side at intervals in the main scanning direction A first folded conductive portion connecting one end of the second resistance portion and one end of the first resistance portion proximate to the one end, the other end of the second resistance portion, and the first close to the other end. A second folded conductive portion that connects one end of the three resistance portion, and the first resistance portion, the first folded conductive portion, the second resistance portion, the second folded conductive portion, and the third resistance portion in this order. The second folded conductive portion is disposed upstream of the first folded conductive portion in the running direction of the recording medium, and the surface area of the second folded conductive portion is the first folded conductive portion. Has a thermal print head that is smaller than the surface area Thermal printer characterized in that the.   The thermal printer according to claim 3, wherein the electrode includes a first electrode connected to the other end of the first resistance portion and a second electrode connected to the other end of the third resistance portion. .   The thermal print head is arranged on the surface of the insulating substrate at a distance from the third resistance portion and arranged on the opposite side of the third resistance portion from the second resistance portion, and extends in the sub-scanning direction. And a third folded conductive portion that connects the other end of the third resistance portion and one end of the fourth resistance portion adjacent to the other end, and the electrode includes the first resistance portion and the third resistance portion. The thermal printer according to claim 4, further comprising a first electrode connected to an end and a third electrode connected to the other end of the fourth resistance portion.

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