JP2015178220A - thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal head, in which functionality thereof is enhanced and printing quality is maintained.SOLUTION: A thermal head 10 is provided with: a circuit board 40; an insulation plate 22a, placed on an upper face of a radiator plate 30 adjacently in a sub-scanning direction ds to the circuit board 40, in which a lower floor part 64, which is thinner than a higher floor part 62 closer to the circuit board 40 in at least a part of a side away from the circuit board 40, is formed; a heat insulation layer 22b formed on an upper face of an insulation plate 22a; heating resistors 23a that are formed on the upper face of the heat insulation layer 22b and arrayed in plural numbers at intervals in a main-scanning direction dm; individual electrodes 28a that are arrayed at intervals in the main-scanning direction dm and formed on the upper faces of the heating resistors 23a in the high floor part 62; and a common electrode 28b that is formed, along the main-scanning direction dm at an interval from the individual electrodes 28a at a position further away from the circuit board 40 than the individual electrodes 28, on the upper faces of the heating resistors 23a in the high floor part 62 and above the low floor part 64.

Description

  The present invention relates to a thermal head used in a thermal printer or the like.

  The thermal head generates heat on the heating portions of a plurality of heating resistors arranged in a direction (main scanning direction) orthogonal to the direction in which the printing medium such as thermal recording paper is conveyed, and the heat causes characters on the printing medium. This is an output device for forming images such as images and figures. This thermal head is widely used in recording devices such as a barcode printer, a digital plate making machine, a video printer, an imager, and a seal printer.

  A general thermal head includes a heat radiating plate, a heat generating plate attached to the heat radiating plate, and a circuit board attached to the heat radiating plate on the same side as the heat generating plate. Heat generating resistors are linearly arranged at predetermined intervals in a heat generating region extending in a band shape on the surface opposite to the surface of the heat generating plate opposite to the heat radiating plate. Also, a drive IC (Integrated Circuit) that is a part of a drive circuit that drives the heating resistor is mounted on, for example, a circuit board (see, for example, Patent Document 1).

JP 2012-66476 A

  A thermal printer using such a thermal head has a platen roller formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller is arranged and rotated so that the peripheral side surface is in contact with the heat generating area, and forms a desired image on the printing medium inserted between the platen roller and the heat generating area.

  In such a thermal printer, there is a case where it is required to use a platen roller having a larger diameter than before and to enhance the functionality.

  SUMMARY An advantage of some aspects of the invention is to maintain print quality while enhancing the functionality of a thermal head.

  In order to solve the above-described problems, the present invention provides a thermal head, a heat sink, a circuit board placed on the upper surface of the heat sink, and a direction in which a printing medium is conveyed with respect to the circuit board. A low floor portion that is placed on the upper surface of the heat sink adjacent to the sub-scanning direction and that is thinner than the high floor portion that is the side close to the circuit board is formed on at least a part of the side away from the circuit board. An insulating substrate, a heat insulating layer formed on the upper surface of the insulating substrate, a heating resistor formed on the upper surface of the heat insulating layer and arranged in a plurality in the main scanning direction perpendicular to the sub-scanning direction; A first electrode arranged on the upper surface of the heating resistor in the high floor portion and arranged at intervals in the main scanning direction, and the first electrode on the upper surface of the heating resistor in the high floor portion and above the low floor portion. The circuit than the electrode A second electrode formed along the main scanning direction by providing a gap with the first electrode at a position separated from the plate, a protective layer formed on an upper surface of the heat retaining layer, and the heating resistor mounted on the circuit board A driving IC for driving the body; and a bonding wire for connecting the first electrode and the driving IC.

  According to the present invention, it is possible to maintain the print quality while enhancing the functionality of the thermal head.

1 is a cross-sectional view of a part of a thermal printer using an embodiment of a thermal head according to the present invention. It is sectional drawing in one Embodiment of the thermal head which concerns on this invention. It is a top view in one embodiment of a thermal head concerning the present invention. A conventional thermal head is shown, (A) is a sectional view, and (B) is a plan view.

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

  1 to 4, the direction of the arrow ds represents the direction in which the printing medium is conveyed (sub-scanning direction), and the direction of the arrow dm is the direction orthogonal to the direction in which the printing medium is conveyed (main scanning). Direction).

  As shown in FIGS. 1 to 3, the thermal head 10 of the present embodiment includes, for example, a heating plate 20, a circuit board 40, and a radiator plate 30. The heat generating plate 20 and the circuit board 40 are placed on the same surface of the heat radiating plate 30. The heat sink 30 is a plate formed of a metal such as aluminum.

  The heat generating plate 20 is fixed to the heat radiating plate 30 with an adhesive such as a double-sided tape along one end side of the circuit board 40 in the sub-scanning direction ds. The heat generating plate 20 is formed with a heat generating region 24 extending in a strip shape. A control signal and driving power for forming a predetermined heat generation pattern in the heat generation region 24 are input to the circuit board 40 and further input to the heating element plate 20 electrically connected to the circuit board 40.

  A thermal printer using the thermal head 10 has a platen roller 50 formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller 50 has a shaft 52 on a straight line parallel to the main scanning direction dm. Further, the peripheral side surface of the platen roller 50 is disposed so as to be in contact with the heat generating region 24, and is provided to be rotatable about the shaft 52.

  As the platen roller 50 rotates, the thermal recording medium 60 inserted between the platen roller 50 and the heat generating area 24 moves in the sub-scanning direction ds. The heat-sensitive recording medium 60 is, for example, heat-sensitive recording paper that develops color when heated to a color development temperature or higher.

  The thermal printer presses the thermal head 10 against the platen roller 50 by a head pressing portion (not shown) constituted by a drive motor, thereby pressing the heat generating area 24 against the thermal recording medium 60 and applying a nip pressure.

  At the same time, the thermal printer moves the thermal recording medium 60 in the sub-scanning direction ds and changes the heat generation pattern of the heat generating area 24 with the movement of the thermal recording medium 60, thereby forming a desired image on the thermal recording medium 60. To do.

  The heating element plate 20 includes a support substrate 22, a heating resistor layer 23, an electrode layer 28, and a protective layer 29.

The support substrate 22 is formed in a rectangular plate shape, for example, ceramic such as alumina (Al ₂ O ₃ ), and the thickest portion is an insulating plate 22a having a thickness of about 1 mm, and silicon oxide ( It has a heat insulating layer 22b called a glaze layer made of SiO ₂ ) and having a thickness of about 50 μm. A protrusion 21 extending in the main scanning direction dm is formed on the heat retaining layer 22b.

  The insulating plate 22a includes a high floor portion 62 having a thickness of, for example, about 1 mm between the end of the heating element plate 20 spaced from the circuit substrate 40 and the protrusion 21, and a thickness of about 1 mm, for example. A lower floor portion 64 having a thickness smaller than that of the portion 62, for example, about 0.5 mm, and a step at the boundary between the high floor portion 62 and the lower floor portion 64 is a straight line along the main scanning direction dm. It extends to the shape. That is, in order to form the flat high floor 62 and the flat low floor 64, the insulating plate 22 a is thick at the high floor 62 and thin at the low floor 64. The back surface bonded to the heat sink 30 has a planar shape. The low floor portion 64 has a uniform thickness from one end to the other end in the sub-scanning direction ds, and has a length of about 5 mm in the sub-scanning direction ds. As a result, the insulating plate 22a has a shape in which the lower floor portion 64 has its upper surface cut away from the higher floor portion 62.

  The heat insulating layer 22b is formed on the upper surface of the high floor portion 62 of the insulating plate 22a, but is not formed on the upper surface of the low floor portion 64.

The heating resistor layer 23 is formed in layers on the upper surface of the heat insulating layer 22b and a part of the upper surface of the low floor portion 64 of the insulating plate 22a, for example, with cermet such as TaSiO ₂ . In the heating resistor layer 23, the heating resistors 23a are arranged in a row continuously from one end to the other end in the main scanning direction dm of the one heating plate 20 at intervals in the main scanning direction dm. It extends in the direction ds.

  The electrode layer 28 is formed in a layer on a part of the upper surface of the heating resistor layer 23. The electrode layer 28 includes a common electrode 28b and individual electrodes 28a made of, for example, aluminum (Al).

  The common electrode 28 b is formed to extend in the main scanning direction dm on the upper surface of the low floor portion 64 and the upper surface of the end portion of the high floor portion 62 adjacent to the low floor portion 64. The individual electrodes 28 a are arranged in a row continuously from one end to the other end in the main scanning direction dm of the single heating element plate 20 with an interval in the main scanning direction dm, and the circuit board 40 with respect to the top of the protrusion 21. A gap 46 provided at a position slightly separated from the common electrode 28b is disposed opposite to the gap 46 from the sub-scanning direction ds.

  Since the current flowing through the common electrode 28b passes through the heating resistor 23a in the gap 46 portion located between the individual electrode 28a and the common electrode 28b, the heating resistor 23a in the gap 46 portion becomes the heating portion 23b. Function as. The heat generating portions 23b are arranged at intervals in the main scanning direction dm and form heat generating regions 24 extending in the sub scanning direction ds.

  One end of the bonding wire 44 is connected to the bonding pad 26 of the individual electrode 28a, and the other end is connected to the drive IC 42 on the circuit board 40, and a control signal for forming a predetermined heat generation pattern is supplied to the heat generation region 24. Is done. One end of a bonding wire 45 is connected to the drive IC 42, and the other end is connected to a circuit pattern on the circuit board 40.

  The individual electrode 28 a, the common electrode 28 b, and the heating resistor layer 23 are covered with a protective layer 29. The protective layer 29 is not provided on a part of the surface of the individual electrode 28a, and a bonding wire 44 is connected to this part. The drive IC 42 and the bonding wire 44 are sealed with a resin 48.

  In addition, the low floor portion 64 of the insulating plate 22a is formed to be lower than the high floor portion 62, and the heat retaining layer 22b is not formed on the upper surface of the low floor portion 64. The surface of the protective layer 29 is formed lower than the surface of the protective layer 29 above the high floor portion 62.

  Here, a manufacturing method of the thermal head 10 in the present embodiment will be described.

In the method of manufacturing the thermal head 10 in the present embodiment, first, an insulating plate 22a such as alumina (Al ₂ O ₃ ) is formed. Next, a glass paste made of silicon oxide (SiO ₂ ) is applied to the upper surface of the insulating plate 22a by screen printing or the like. Next, the insulating plate 22a on which the glass paste is printed is baked, so that the glass paste is dissolved and fixed to the insulating plate 22a, and the heat insulating layer 22b is formed.

  Next, in the insulating plate 22a on which the heat insulating layer 22b is formed, the insulating plate 22a and the heat insulating layer 22b are scraped off by, for example, sand blasting, to form the low floor portion 64.

  Next, a resistance material such as cermet is fixed to the surface of the low floor portion 64 of the insulating plate 22a and the surface of the heat insulating layer 22b above the high floor portion 62 by sputtering or the like, whereby the low floor portion 64 of the insulating plate 22a. The heating resistor layer 23 is formed on the surface and the surface of the heat insulating layer 22b above the raised floor 62.

  Thereafter, the heating resistor layer 23, the individual electrode 28a, and the common electrode 28b are formed on the surface of the heat insulating layer 22b. Specifically, first, a resistance material such as cermet is fixed to the surface of the heat retaining layer 22b by sputtering or the like, and a conductive material such as aluminum is fixed thereon by sputtering or the like. Thereafter, the heating resistor layer 23 and the electrode layer 28 are patterned by etching, thereby forming the heating resistors 23a arranged at intervals in the main scanning direction dm and the gap 46 corresponding to the heating portion 23b.

  Next, the protective layer 29 is fixed to the entire surface by sputtering or the like to protect the heat insulating layer 22b, the heating resistor layer 23, the individual electrode 28a, and the common electrode 28b so as to exclude the portion that becomes the bonding pad 26 in the individual electrode 28a. Layer 29 is deposited.

  The heating plate 20 thus formed is placed on the heat sink 30 together with the circuit board 40. Further, the thermal head 10 is manufactured by connecting the heating element plate 20 and the circuit board 40 with the bonding wires 44, and further sealing the connection portion with the bonding wires 44 with the resin 48.

  In the above configuration, the thermal head 10 is mounted on the upper surface of the heat sink 30 adjacent to the circuit board 40 placed on the upper surface of the heat sink 30 and the sub-scanning direction ds with respect to the circuit board 40. An insulating plate 22a having a lower floor portion 64 that is thinner than the high floor portion 62 that is close to the circuit board 40 on at least a part of the side that is separated from 40, and a heat insulating layer 22b that is formed on the upper surface of the insulating plate 22a And a plurality of heating resistors 23a formed on the upper surface of the heat retaining layer 22b and arranged in the main scanning direction dm at intervals, and the heating resistors 23a in the high floor portion 62 arranged in the main scanning direction dm at intervals. The individual electrode 28a as the first electrode formed on the upper surface, and the upper surface of the heating resistor 23a in the high floor portion 62 and the upper portion of the lower floor portion 64 are separated from the circuit board 40 than the individual electrode 28a. Mounted on the circuit board 40, the common electrode 28b as the second electrode formed along the main scanning direction dm, the individual electrode 28a and the gap 46 at the positions, the protective layer 29 formed on the upper surface of the heat insulating layer 22b, and A driving IC 42 for driving the heating resistor 23a and a bonding wire 44 for connecting the individual electrode 28a and the driving IC 42 are provided.

  By the way, as shown in FIG. 4, it is also conceivable that a large-diameter platen roller is brought into contact with the heating plate 220 having the insulating plate 22a having a substantially uniform thickness from one end to the other end in the sub-scanning direction ds. . In the heat generating plate 220, a pair of adjacent heat generating resistors 23 a are conductively connected by a folded electrode 268 at the end of the heat generating plate 220 that is separated from the circuit board 40.

  Furthermore, the folded electrode 268 adjacent in the main scanning direction dm is connected to be a common electrode (not shown), and the surface area of the common electrode is made larger than the surface area of the folded electrode 268, thereby improving the heat dissipation in the common electrode. It is also possible.

  However, in such a case, since the width of the folded electrode 268 or the common electrode (not shown) in the sub-scanning direction ds is long, when a large-diameter platen roller is used, the platen roller and the thermal recording medium are turned into the folded electrode 268 or the common electrode. There is a possibility of physical interference (not shown).

  On the other hand, in the thermal head 10 of the present embodiment, the insulating plate 22a is a heating element plate adjacent to the circuit board 40 between the end of the heating element plate 20 spaced from the circuit board 40 and the protrusion 21. The common electrode 28b having the low floor portion 64 formed lower than the height of the end portion 20 and having a long width in the sub-scanning direction ds is formed on the upper surface of the low floor portion 64.

  As described above, since the thermal printer according to the present embodiment can use the large-diameter platen roller 50, the nip pressure is increased and the bending of the platen roller 50 is suppressed as compared with the case where the small-diameter platen roller is used. The thermal head 10 can be stably pressed against the platen roller 50, and the reliability can be improved.

  Moreover, since the thermal head 10 does not form the heat insulating layer 22b above the low floor portion 64 of the insulating plate 22a, the heat dissipation can be further improved as compared with the case where the heat insulating layer 22b is formed.

  Furthermore, since the thermal floor 10 has the lower floor portion 64 of the insulating plate 22a thinner than the insulating plate 22a of the heat generating plate 220 (FIG. 4), heat is efficiently transferred from the common electrode 28b to the heat radiating plate 30 and the heat radiating performance. Can be increased.

  Thus, the thermal printer of this embodiment can suppress heat storage while using the large-diameter platen roller 50. As a result, the thermal printer of the present embodiment can maintain the print quality while improving the functionality. Here, the large-diameter platen roller is, for example, a platen roller having a diameter longer than the length of the heating plate 20 in the sub-scanning direction ds.

  In the thermal head 10 described above, the low floor portion 64 is formed to have a uniform thickness from one end to the other end in the sub-scanning direction ds. However, the thickness is not limited to this, and for example, the thickness decreases as the distance from the circuit board 40 increases. May be formed to be thin. In this case, it is necessary to cut the insulating plate 22a so that the thickness gradually decreases in the manufacturing process of the thermal head 10, but the contact between the low floor portion 64 and the platen roller 50 can be further prevented.

  In the thermal head 10 described above, the heating resistor layer 23 is formed above the low floor portion 64. However, the present invention is not limited to this, and the heating resistor layer 23 may not be formed above the low floor portion 64. .

  Furthermore, in the thermal head 10 described above, the heat insulating layer 22b is not formed above the low floor portion 64, but the heat insulating layer 22b may be formed above the low floor portion 64 without being limited thereto.

  Furthermore, in the thermal head 10 described above, the thickness of the high floor portion 62 is about 1 mm, and the thickness of the low floor portion 64 is about 0.5 mm, which is almost half of the high floor portion 62. As long as the part 64 is lower than the high floor part 62, various thickness may be sufficient.

  Further, in the thermal head 10 described above, the entire surface between the end of the heating element plate 20 spaced from the circuit board 40 and the protrusion 21 is formed thinner than the protrusion 21 closer to the circuit board 40. However, the present invention is not limited thereto, and only a part of the portion that may come into contact with the platen roller 50 between the end of the heating element plate 20 that is separated from the circuit board 40 and the ridge 21 is a circuit rather than the ridge 21. It may be formed thinner than the side close to the substrate 40.

  Further, in the thermal head 10 described above, the common electrode 28b is provided on the side separated from the circuit board 40 with the gap 46 between the individual electrode 28a. However, the present invention is not limited to this, and the portion separated from the heating element plate 20 rather than the gap. A folded electrode may be used as a second electrode for conductively connecting a pair of adjacent heating resistors.

DESCRIPTION OF SYMBOLS 10 ... Thermal head, 20, 120, 220 ... Heat generating body plate, 21 ... Projection, 22 ... Support substrate, 22a ... Insulating plate, 22b ... Thermal insulation layer, 23 ... Heating resistor layer, 23a ... Exothermic resistor, 23 b .. exothermic part, 24 .. exothermic region, 26... Bonding pad, 28 .. electrode layer, 28 a .. individual electrode, 28 b .. common electrode, 29 ... protective layer, 30. ...... Heat sink, 40 ... Circuit board, 42 ... Drive IC, 44,45 ... Bonding wire, 46 ... Gap, 48 ... Resin, 50 ... Platen roller, 52 ... Shaft, 60 ... Heat sensitive Recording medium 62... High floor portion 64. Low floor portion 268 .. Folded electrode dm... Main scanning direction ds.

Claims (5)

A heat sink,
A circuit board placed on the upper surface of the heat sink;
Mounted on the upper surface of the heat radiating plate adjacent to the circuit board in the sub-scanning direction, which is the direction in which the substrate is transported, and close to the circuit board on at least part of the side away from the circuit board An insulating substrate in which a low floor portion thinner than a high floor portion which is a side to be formed is formed;
A heat insulating layer formed on the upper surface of the insulating substrate;
A plurality of heating resistors formed on an upper surface of the heat retaining layer and arranged at intervals in a main scanning direction orthogonal to the sub-scanning direction;
A first electrode arranged on the upper surface of the heating resistor in the high floor portion and arranged at intervals in the main scanning direction;
A first gap is formed along the main scanning direction by providing a gap with the first electrode at a position farther from the circuit board than the first electrode on the upper surface of the heating resistor in the high floor portion and above the low floor portion. Two electrodes,
A protective layer formed on an upper surface of the heat retaining layer;
A driving IC mounted on the circuit board for driving the heating resistor;
A bonding wire connecting the first electrode and the driving IC;
A thermal head comprising: The thermal head according to claim 1, wherein the heat retaining layer is not formed on an upper surface of the low floor portion. The thermal head according to claim 1, wherein the second electrode is a common electrode formed over the main scanning direction. The thermal head according to claim 1, wherein the second electrode is a folded electrode that connects a pair of adjacent heating resistors. The thermal head according to claim 1, wherein the low floor portion has a substantially uniform thickness over the entire surface.

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