JP6422281B2 - Thermal head - Google Patents

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 driver 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

  In such a thermal head, it is required to make the printing width wider by making the length in the main scanning direction longer than that in the past.

  Accordingly, an object of the present invention is to maintain print quality while elongating a thermal head in the main scanning direction.

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. An insulating substrate placed on the upper surface of the heat sink adjacent to the sub-scanning direction, a heat insulating layer formed on the upper surface of the insulating substrate, a main layer formed on the upper surface of the heat insulating layer and orthogonal to the sub-scanning direction. A plurality of heating resistors arranged at intervals in the scanning direction, individual electrodes formed on the upper surface of the heating resistors arranged at intervals in the main scanning direction, and the individual electrodes on the upper surface of the heating resistors And n electrode blocks arranged along the main scanning direction, with the individual electrodes and a common electrode formed along the main scanning direction at a position farther away from the circuit board, and the electrode block Variation in resistance value To adjust the formed on the circuit board electrically independent of each other, and each of said supplying power to said common electrode in the electrode block the n power supply unit, the heating resistor, the individual electrodes and the A protective layer formed on the upper surface of the common electrode, a driving IC mounted on the circuit board for driving the heating resistor in each of the electrode blocks, a bonding wire for connecting the individual electrode and the driving IC, It is characterized by comprising.

  According to the present invention, it is possible to maintain the print quality while elongating the thermal head in the main scanning direction.

It is a perspective view in one embodiment of a thermal head concerning the present invention. 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. One Embodiment of the thermal head which concerns on this invention is shown, (A) is a top view, (B) is a side view of a heat generating body board. It is a top view in one embodiment of a thermal head concerning the present invention. It is sectional drawing in one Embodiment of the thermal head which concerns on this invention. FIG. 3 is a schematic circuit diagram of a heating element plate according to the present invention. It is a top view which shows other embodiment of the thermal head based on this invention. It is a typical circuit diagram of the conventional heat generating body board.

  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 5, 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 5, the thermal head 10 of the present embodiment includes, for example, a heating plate 20, a circuit board 40 (40 a and 40 b), and a heat radiating 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 circuit boards 40a and 40b are each formed in a rectangular plate shape and are arranged along the main scanning direction dm. The circuit board 40a and the circuit board 40b are physically and electrically independent from each other, and power is supplied from the outside through the connector 46a and the connector 46b.

  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 boards 40 a and 40 b 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.

  This thermal printer is used to create a stencil printing original for printing a wide range of printed materials such as newspapers and posters.

  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, an insulating plate 22a made of a ceramic such as alumina (Al ₂ O ₃ ), and a silicon oxide (SiO ₂ ) layer on the upper surface of the insulating plate 22a. And a heat insulating layer 22b called a glaze layer. A protrusion 21 extending in the main scanning direction is formed on the heat retaining layer 22b.

The heating resistor layer 23 is formed in a layer on a part of the upper surface of the heat insulating layer 22b, for example, with a 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 28b is divided at the center of the main scanning direction at the end of the heating element plate 20 that is separated from the circuit board 40, and is formed to extend in the main scanning direction. The individual electrodes 28a 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. They are arranged to face the common electrode 28b from the scanning direction ds.

  Since the current flowing through the common electrode 28b passes through the heating resistor 23a in the gap portion located between the individual electrode 28a and the common electrode 28b, the heating resistor 23a in the gap portion functions as the heating portion 23b. To do. 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.

  The electrode layer 28 includes a first electrode block 62a and a second electrode block 62b configured by a common electrode 28b and a plurality of individual electrodes 28a connected to the common electrode 28b. The common electrode 28b in the first electrode block 62a and the common electrode 28b in the second electrode block 62b are electrically independent from each other.

  Since the first electrode block 62a and the second electrode block 62b are formed with lengths L1 and L2 of about 14 inches in the main scanning direction, respectively, the heat generating portion 23b has a length of about 28 inches in the main scanning direction. It has a length. For this reason, the thermal head 10 can perform printing for about 28 inches in the main scanning direction, and has a wider printing width than a conventional thermal head. Incidentally, the first electrode block 62a and the second electrode block 62b can each perform printing of 16100 dots.

The first electrode block 62a is separated from the connector 46a in the main scanning direction (that is, the portion adjacent to the second electrode block 62b), and the second electrode block 62b is separated from the connector 46b in the main scanning direction (that is, the first electrode block 62b). In the connection portions 64a and 64b, for example, jumper wires 66a and 66b in which a conductor made of tin-plated copper wire is covered with an insulator made of semi-rigid vinyl are connected to the common electrode 28b. Connected.

  One end of the conductive foil 70 in a flexible printed circuit (FPC) 74 in which the conductive foil 70 is sandwiched between insulators 72 is connected to the common electrode 28b by an anisotropic conductive film (ACF) 68. The other end of the conductor foil 70 is connected to one end of a jumper wire 66 (66a and 66b).

  The jumper wires 66a and 66b wrap around the end of the heat generating plate 20 that is separated from the circuit board 40 and the lower side of the heat radiating plate 30, and the other ends are connected to the connectors 46a and 46b, respectively.

  As a result, the common electrode 28b of the first electrode block 62a and the common electrode 28b of the second electrode block 62b are supplied with driving power from the circuit board 40 to the connecting portions 64a and 64b via the jumper lines 66a and 66b, respectively. Is done.

  The circuit boards 40a and 40b are configured to be adjustable so that the driving power supplied via the jumper lines 66a and 66b can be individually varied for the connecting portion 64a and the connecting portion 64b.

  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 common electrode 28b has one end of a bonding wire 44 connected to a bonding pad (not shown) provided at one end close to the connector 46a in the main scanning direction in the first electrode block 62a, and the other end connected to the connector 46a of the circuit board 40. Connected.

The common electrode 28b has one end of the bonding wire 44 connected to a bonding pad (not shown) provided at the other end adjacent to the connector 46b in the main scanning direction in the second electrode block 62b, and the other end of the circuit board 40. Connected to the connector 46b.

  Thus, the common electrode 28b is supplied with driving power from the connector 46a at both ends in the main scanning direction in the first electrode block 62a, and is supplied with driving power from the connector 46b at both ends in the main scanning direction in the second electrode block 62b. .

  Part of the individual electrode 28 a and 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 the common electrode 28b, 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.

  By the way, in the case of the thermal head using the common electrode 28b formed so as to extend in the main scanning direction at the end of the heating plate 20 that is separated from the circuit board 40, as shown in FIG. 8, the heating resistor 23a (not shown). Since the individual electrodes 28a and the like exist, driving power can be supplied only to the connection points Pa1 and Pb1 at both ends of the common electrode 28b in the main scanning direction via wire bonding.

  For this reason, when the conventional thermal head is simply elongated in the main scanning direction, the voltage applied to the connection points Pa1 and Pb1 increases toward the center of the common electrode 28b in the main scanning direction. The current drops due to R, and the current flowing through the heating resistor 23a decreases. Therefore, in the conventional thermal head, the print density at the center in the main scanning direction is thinner than at both ends, and the print density may not be uniform.

  As described above, in the conventional thermal head, a voltage drop occurs in the main scanning direction, and the printing density is not uniform. Therefore, the printing density is made uniform from one end to the other end of the heat generating portion 23b in the main scanning direction. It was difficult to make.

On the other hand, the thermal head 10 is bonded to the bonding wire 44 that is connected to both ends of the common electrode 28b in the main scanning direction in the first electrode block 62a and the second electrode block 62b formed along the main scanning direction. In addition, jumper wires 66a and 66b are connected to the connecting portions 64a and 64b (connection points Pa2 and Pb2 in FIG. 6 ) to supply driving power.

  For this reason, the thermal head 10 can stabilize the potential in the main scanning direction of the common electrode 28b by reinforcing the power source and preventing the voltage drop along the main scanning direction, and the current flowing through all the heating resistors 23a. Can be made uniform.

  Thereby, the thermal head 10 can make the print density uniform from one end to the other end of the heat generating portion 23b in the main scanning direction, and improve the print quality.

  Here, when the resistance value varies between the first electrode block 62a and the second electrode block 62b, the density printed in the first electrode block 62a and the density printed in the second electrode block 62b vary. There is a possibility that.

  On the other hand, the circuit board 40 is configured to be adjustable so that the driving power supplied via the jumper lines 66a and 66b can be individually varied for the connecting portion 64a and the connecting portion 64b.

  For this reason, the thermal head 10 adjusts the potential applied to the connection portion 64a and the connection portion 64b even when the resistance value varies between the first electrode block 62a and the second electrode block 62b. In addition, it is possible to suppress the influence of variations in resistance values on the print density.

  Thereby, the thermal head 10 can make the print density uniform from one end to the other end of the heat generating portion 23b in the main scanning direction, and improve the print quality.

  As described above, in the thermal head 10 of the present embodiment, power is supplied from the circuit board 40a as the first power supply unit to the common electrode 28b of the first electrode block 62a, and is electrically independent from the circuit board 40a. Power is supplied from the circuit board 40b as the second power supply unit to the common electrode 28b of the second electrode block 62b that is electrically independent of the common electrode 28b of the first electrode block 62a.

  By the way, when making a heat generating body plate longer than before, it is also conceivable that heat generating body plates having a shorter length in the main scanning direction (for example, 14 inches) are arranged side by side in the main scanning direction. However, in that case, a step is likely to occur at the joint between the heat generating plates, and the respective heat generating plates are individually warped, so that the print quality is deteriorated, the print scratches, the thermal recording medium 60 is broken. Abnormal conveyance is likely to occur. Moreover, in order not to generate such a level | step difference, a high positional accuracy will be calculated | required by the joint of a heat generating body board.

  On the other hand, in the present embodiment, only one heating element plate 20 is used and the length is longer than that of the conventional heating element plate. For this reason, the thermal head 10 does not need to connect the heating element plates to each other, can eliminate the step, and can suppress the warping of the heating element plate to only one flat warp. As a result, the thermal head 10 can improve the printing quality and prevent the occurrence of printing flaws, tearing of the thermal recording medium 60, abnormal conveyance, and the like.

  In the thermal head 10 described above, the connectors 46a and 46b and the common electrode 28b are connected by the jumper wires 66a and 66b. However, the present invention is not limited to this, and may be connected by other conductive cables or FPCs. good.

  In the thermal head 10 described above, the driving power is supplied from the circuit board 40 to the two connection portions 64a and 64b. However, the present invention is not limited to this, and a predetermined number of connection portions are provided at one location or three or more locations. The driving power may be supplied to the connection portion.

  In the thermal head 10 described above, the driving power is supplied from the two circuit boards 40a and 40b to the first electrode block 62a and the second electrode block 62b in one heating element plate 20, but this is not limitative. Instead, as shown in FIG. 7, three electrode blocks may be provided on one heating element plate 120 to supply driving power from the three circuit boards 140a, 140b, and 140c. In this case, the drive power may be supplied by connecting the connector 46c attached to the circuit board 140c and the central electrode block with jumper wires 66c and 66d.

  Further, in the thermal head 10 described above, the circuit board 40a and the circuit board 40b, which are two physically independent plates, are provided, but not limited thereto, a circuit board as a single board is provided, A drive circuit for driving the first electrode block 62a and the second electrode block 62b may be provided on the circuit board so that the circuit configurations are electrically independent from each other.

  In that case, considering the difference in thermal expansion coefficient among the heat sink 30, the circuit boards 40a and 40b, and the heating element board 20, for example, when the thermal expansion coefficient of the circuit board is large, the circuit board is divided into two circuit boards. Thus, the deformation of the circuit board due to heat may be suppressed.

  In the above-described thermal head 10, the length of the heat generating portion 23b in the main scanning direction is about 28 inches. However, the length is not limited to this, and various lengths of 28 inches or less or 28 inches or more may be set. . In particular, when the length is set to 28 inches or more, the potential can be stabilized by supplying driving power to three or more connecting portions.

  Further, in the thermal head 10 described above, the connection portions 64a and 64b are provided in the first electrode block 62a at a location away from the connector 46a and at the location away from the connector 46b in the second electrode block 62b, respectively. However, the connecting portions 64a and 64b may be provided at various locations in the common electrode 28b.

  In general, the platen roller 50 has a tendency that the central portion along the main scanning direction dm tends to make a strong contact with the heat generation region 24 as compared with both end portions, and the print density tends to be dark. The positions of the connecting portions 64a and 64b may be set so that the print density is constant along the main scanning direction dm.

  In the thermal head 10 described above, a current is supplied from the common electrode 28b toward the individual electrode 28a. However, the present invention is not limited thereto, and a current may be supplied from the individual electrode 28a toward the common electrode 28b.

  10, 120 ... Thermal head, 20, 110 ... Heating element plate, 21 ... Projection, 22 ... Support substrate, 22a ... Insulating plate, 22b ... Insulation layer, 23 ... Heating resistor layer, 23a ... Exothermic resistor, 23 b .. exothermic part, 24... Exothermic region, 28... Electrode layer, 28 a .. individual electrode, 28 b .. common electrode, 26 ... bonding pad, 29. DESCRIPTION OF SYMBOLS 130 ... Radiating plate, 40a, 40b, 140a, 140b ... Circuit board, 42 ... Driver IC, 44, 45 ... Bonding wire, 46a, 46b, 46c ... Connector, 48 ... Resin, 50 ... Platen roller, 52 ... Shaft, 60 ...... thermosensitive recording medium, 62a ... first electrode block, 62b ... second electrode block, 64a, 64b, 64c, 64d ... connection, 66a, 66b, 66c, 66d ... jumper wire, 68 ... anisotropic conductive film, 70 ...... conductive foil, 72 ...... insulator, 74 ... flexible substrate, dm ...... main scanning direction, ds ...... subscanning direction

Claims (6)

A heat sink,
A circuit board placed on the upper surface of the heat sink;
An insulating substrate placed on the upper surface of the heat radiating plate adjacent to the circuit board and adjacent to the sub-scanning direction, which is the direction in which the printing medium is conveyed,
A heat insulating layer formed on the upper surface of the insulating substrate;
A plurality of heating resistors formed on the heat retaining layer and arranged in the main scanning direction perpendicular to the sub-scanning direction, and formed on the upper surface of the heating resistor arranged in the main scanning direction at intervals. And a common electrode formed along the main scanning direction by providing a gap between the individual electrode and the circuit board at a position farther from the circuit board than the individual electrode on the upper surface of the heating resistor. N electrode blocks arranged along the direction;
N power supply units that are formed on the circuit board and are electrically independent from each other and configured to supply power to the common electrode in each of the electrode blocks, in order to adjust a variation in resistance value for each of the electrode blocks ;
A protective layer formed on the upper surface of the heating resistor, the individual electrode and the common electrode;
A driving IC mounted on the circuit board for driving the heating resistor in each of the electrode blocks ;
A bonding wire connecting the individual electrode and the driving IC;
A thermal head comprising: 2. The thermal head according to claim 1, further comprising a plurality of jumper lines that connect the n power supply units and the common electrode of the electrode block corresponding to the power supply unit . The thermal head according to claim 1 , wherein each of the n power supply units variably supplies driving power .   Three or more electrode blocks are arranged along the main scanning direction, and are formed on the circuit board and are electrically independent from each other, and a plurality of power supply units that supply power to the electrode blocks, and the electrode blocks The thermal head according to claim 1, further comprising a plurality of driving ICs for driving the heat generating resistor in the head. The common electrode is supplied with power from a wire connected to one end side in the main scanning direction,
The jumper line is connected to the other end side in the main scanning direction of the common electrode and the wire.
The thermal head according to claim 2. 2. The thermal head according to claim 1, wherein a plurality of the circuit boards are arranged along the main scanning direction so as to come into contact with the upper surface of the heat radiating plate.

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