JP5615658B2 - Thermal printer and thermal print head used therefor - Google Patents

Description

  The present invention relates to a thermal printer that prints on a print medium and overcoats a print screen, and a thermal print head used therefor.

  Thermal print heads are attracting attention as output devices such as video printers, imagers, and seal printers. The thermal print head records on thermal paper, plate-making film photographic paper, media, etc. by generating heat from a heating resistor disposed on a support substrate having a heat insulating layer. Since thermal print heads have advantages such as low noise and low running cost, various developments have been made.

  A general thermal print 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. A plurality of heating resistors are linearly arranged at predetermined intervals in a heating region extending in a band shape on the surface opposite to the surface of the heating plate opposite to the heat sink. The circuit board is mounted with electrical components such as a drive IC that is a part of a drive circuit that drives the heating resistor.

  A printer using such a thermal print head generally includes a platen roller formed in a cylindrical shape with a material having a predetermined elasticity. The platen roller is disposed so that its side surface is in contact with the heat generating area on the support substrate with the main scanning direction in which the heat generating resistors are arranged as an axis, and is provided rotatably about the axis. Due to the rotation of the platen roller, the medium inserted between the platen roller and the heat generating area moves in the sub-scanning direction perpendicular to the main scanning direction. While pressing the medium against the heat generation area by the platen roller, the medium is moved in the sub-scanning direction, and the heat generation pattern of the heat generation resistance is changed with the movement of the medium, thereby forming a desired image on the medium.

  In a thermal printer, for example, a single type that is electrically connected to one end of all the heating resistors and each heating resistor draws one pixel, and two heating resistors that are connected by folded electrodes There is a folding type (see, for example, Patent Document 1) in which one pixel is drawn.

JP 2008-168485 A

  In the folded-type thermal print head, a gap is required between two heat generating resistors that draw one pixel, so that heat is diffused as compared with the single type, and the peak temperature in the heat generating portion is lowered. For this reason, a melt-type thermal printer may have poor efficiency and response.

  In order to improve the efficiency and response to the level of a single type, it is effective to bring the heating resistor that draws the same pixel toward the center of the pixel. However, this method increases the distance between adjacent pixels, and it is difficult to ensure uniformity during overcoating.

  Therefore, an object of the present invention is to improve the uniformity of the overcoat while increasing the peak temperature of the heat generating portion with a folded-type thermal print head.

  In order to solve the above-described problems, the present invention relates to an insulating substrate and a surface of the insulating substrate arranged at intervals in a thermal print head used in a thermal printer that prints on a printing medium and overcoats a printing screen. The plurality of heating resistors and the plurality of heating resistors are repeatedly arranged in the arrangement direction with the first heating resistor, the second heating resistor, the third heating resistor, and the fourth heating resistor. A first folded electrode that connects the second heating resistor and the third heating resistor, and one of the second heating resistor and the third heating resistor opposite to the first folded electrode. A first electrode connected on the side, a second folded electrode connecting the first heating resistor and the fourth heating resistor, and any one of the first heating resistor and the fourth heating resistor Second fold A second electrode connected on the opposite side of the first electrode, and connected to the first electrode and the second electrode to heat the second heating resistor and the third heating resistor during printing, And a drive element that generates heat from all of the heating resistors.

The present invention also relates to a thermal printer that prints on a print medium and overcoats a print screen, and includes an insulating substrate, a plurality of heating resistors arranged at intervals on the surface of the insulating substrate, and the plurality of the heating resistors. wherein a heating resistor that has a first heating resistor and the second heating resistor and the third heating resistor and the fourth heating resistor is repeatedly arranged in the array direction and Kino the second heating resistor first A first folded electrode connecting three heating resistors, a first electrode connected to one of the second heating resistor and the third heating resistor on the opposite side of the first folded electrode, and the first A second folded electrode that extends along one folded electrode and connects the first heating resistor and the fourth heating resistor; and the first heating resistor and the fourth heating resistor are connected to the first heating resistor. 2 Connected on the opposite side of the folded electrode The second heating resistor is connected to the first electrode and the second electrode to cause the second heating resistor and the third heating resistor to generate heat during printing, and when overcoating , all of the heating resistors are A drive element for generating heat, and a transport unit for transporting the print medium are provided.

  According to the present invention, it is possible to improve the uniformity of the overcoat while increasing the peak temperature of the heat generating portion with the folded-type thermal print head.

FIG. 2 is a partially cutaway top view of an embodiment of a thermal print head according to the present invention. 1 is a partially enlarged cross-sectional view of an embodiment of a thermal print head according to the present invention. 1 is a perspective view of an embodiment of a thermal print head according to the present invention. 1 is a cross-sectional view of a thermal printer using an embodiment of a thermal print head according to the present invention. It is a graph which shows the temperature distribution in the surface of the protective layer of the position corresponding to the heating resistor in one embodiment of the thermal print head concerning the present invention.

  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 partially cutaway top view of an embodiment of a thermal print head according to the present invention. FIG. 2 is a partially enlarged sectional view of the thermal print head according to the present embodiment. FIG. 3 is a perspective view of the thermal print head according to the present embodiment.

  The thermal print head 10 according to the present embodiment includes a heat dissipation board 20, a heating element plate 30, a circuit board 41, and a drive element 42. The heat dissipation substrate 20 is a plate formed of a material having a high thermal conductivity such as aluminum.

  The heating element plate 30 has an insulating substrate 31. The insulating substrate 31 has a heat insulating layer 39 formed of glass on the surface of a ceramic plate 38 or the like.

  A resistor and electrodes are stacked on the surface of the insulating substrate 31. Of these resistors, portions where the electrodes are not stacked are heating resistors 91, 92, 93, 94. The length of the heating resistors 91, 92, 93, 94 is, for example, 100 μm.

  The heating resistors 91, 92, 93, 94 are arranged in the longitudinal direction (main scanning direction) of the insulating substrate 31 with an interval on the surface of the insulating substrate 31, and form a belt-like heating region 32 extending substantially linearly. doing. Each of the heating resistors 91, 92, 93, 94 extends in the sub-scanning direction perpendicular to the main scanning direction. A protrusion may be provided on the heat retaining layer 39, and the heating resistors 91, 92, 93, 94 may be formed on the protrusion.

  These heating resistors 91, 92, 93, 94 are arranged such that the first heating resistor 91, the second heating resistor 92, the third heating resistor 93, and the fourth heating resistor 94 are sequentially repeated in the arrangement direction. Yes. The second heating resistor 92 and the third heating resistor 93 are connected by a first folded electrode 81. The first heating resistor 91 and the fourth heating resistor 94 are connected by a second folded electrode 82. The second folded electrode 82 extends along the first folded electrode 81.

  In the heating resistors 91, 92, 93, 94, electrodes 71, 72, 73, 74 extend from the opposite ends of the folded electrodes 81, 82, respectively. The first electrode 71 connected to the first heating resistor 91 and the third electrode 73 connected to the third heating resistor 93 extend to the bonding pad 33, respectively. The second electrode 72 connected to the second heating resistor 92 and the fourth electrode 74 connected to the fourth heating resistor 94 are connected to the reference potential electrode 75. A predetermined reference potential is applied to the reference potential electrode 75.

  A part of the surface of the heating plate 30 is covered with a protective layer 36. The region where the bonding pad 33 of the heating plate 30 is formed is not covered with the protective layer 36 and is exposed.

  The circuit board 41 is a printed board using, for example, glass epoxy resin as an insulator base material. A wiring pattern is formed on the surface of the circuit board 41, and the wiring pattern is covered with an insulating film except for a connection portion with the outside.

  A drive element 42 is mounted on the circuit board 41. The drive element 42 is a semiconductor integrated circuit (IC).

  The heating plate 30 and the circuit board 41 are placed on the surface of the heat dissipation board 20. The heat generating plate 30 and the circuit board 41 are bonded to the surface of the heat dissipation board 20 with, for example, a double-sided tape. The heating element plate 30 and the circuit board 41 are arranged so that the long side of the heating element plate 30 near the bonding pad 33 and the long side of the circuit board 41 on the side where the driving element 42 is arranged are closely opposed to each other. Has been.

  A bonding wire 51 formed of a metal such as gold, for example, is bridged between the driving element 42 mounted on the circuit board 41 and the bonding pad 33 of the heating plate 30 and is electrically connected.

  The bonding wire 51 is sealed with a sealing resin 52. The sealing resin 52 covers the region exposed without being covered with the protective layer 36 of the heating plate 30, the bonding wire 51, and the driving element 42. The sealing resin 52 is a thermosetting epoxy resin. This sealing is performed by applying an epoxy resin and curing it by heating at about 100 ° C. for several hours.

  FIG. 4 is a cross-sectional view of a thermal printer using the thermal print head of the present embodiment.

  The thermal printer using the thermal print head 10 according to the present embodiment has a conveying means for a printing medium 64 such as paper. The conveying means for the printing medium 64 is, for example, a platen roller 60. The platen roller 60 is an elastic cylinder having a shaft 61 as a straight line parallel to a linear heat generating region in which the heat generating resistors 91, 92, 93, 94 are arranged.

  The thermal printer also includes a thermal ribbon 63 that is a thermal recording medium. The thermal ribbon 63 is wound around a shaft 65 parallel to the shaft 61 of the platen roller 60 in a roll shape. The heat-sensitive ribbon 63 wound in a roll shape is wound around an axis 66 parallel to the axis 65. The winding-side shaft 66 is driven by a motor or the like.

  The thermal ribbon 63 is conveyed so as to pass between the side surface of the platen roller 60 and the thermal print head. The print medium 64 is conveyed so as to pass between the thermal ribbon 63 and the platen roller 60.

  The thermal ribbon 63 has a plurality of types of color areas and an overcoat area in the winding direction. Each color area of the thermal ribbon 63 is colored when a predetermined temperature or higher is reached, and the color is transferred to the printing medium 64 in contact therewith. The overcoat region of the thermal ribbon 63 is partially melted when heated, and an overcoat is formed on the surface of the printing medium 64 that is in contact therewith.

  The drive element 42 has the second heating resistor 92 and the third heating resistor at predetermined positions when printing, that is, when the respective color regions of the thermal ribbon 63 are positioned on the heating resistors 91, 92, 93, 94. A current is passed through the body 93 to generate heat. As a result, one line of a predetermined image is drawn on the print medium 64. Further, the drive element 42 has all of the heating resistors 91, 92, 93, when overcoating, that is, when the overcoat region of the thermal ribbon is located on the heating resistors 91, 92, 93, 94. A current is passed through 94 to generate heat. As a result, an overcoat is formed over the entire printing area of the printing medium 64.

  In the present embodiment, for example, when printing at 300 dpi, the four heating resistors 91, 92, 93, 94 are taken as one group, and the distance (pitch) between the centers of adjacent groups is 84.5 μm. . At this time, the width of the heating resistors 91, 92, 93, 94 in the main scanning direction is, for example, 8 μm. In this case, when two heating resistors are considered as a set like a conventional folded thermal print head, the heating resistors are arranged at an equivalent of 600 dpi. The width may be changed between the heating resistors 92 and 93 for printing and the heating resistors 91 and 94 used only for the overcoat.

  In the folded electrode type thermal print head, it is not necessary to provide a common electrode at a position away from the heating resistor downstream in the sub-scanning direction. Therefore, the size can be reduced as compared with the common electrode type thermal print head. In particular, the length on the downstream side in the sub-scanning direction with respect to the heating resistors 91, 92, 93, and 94, which tends to hinder the conveyance of the printing medium, can be shortened. On the other hand, in the folded electrode type thermal print head, since the heating resistor that draws the same pixel is divided into two, the surface temperature of the protective layer 36 increases due to the heat generation of the heating resistor, that is, a thermal ribbon or the like. The amount of heat transferred to the thermal recording medium tends to be small.

  However, in the present embodiment, the four heating resistors 91, 92, 93, 94 form a set. At the time of printing, printing is performed using the two heating resistors 92 and 93 at the center among these four heating resistors 91, 92, 93 and 94. That is, the heating resistors 92 and 93 for printing are arranged close to each other at the center position of each pixel. For this reason, the temperature peak by the heating resistors 92 and 93 that draw the same pixel can be increased.

  FIG. 5 is a graph showing a temperature distribution on the surface of the protective layer at a position corresponding to the heating resistor in the present embodiment. FIG. 5 shows the case of the common electrode type, that is, the case where the same pixel is printed by the heat generated from one heating resistor, and the case of the folded electrode type where the heating resistors are evenly arranged in the main scanning direction. The case where the distance between the two heating resistors that print the same pixel is larger than that of the embodiment is also shown. FIG. 5 shows a comparison calculation result when the resistance value and the electric power input thereto are constant and only the shape of the heating resistor is different.

  From FIG. 5, it can be seen that the temperature peak is lowered when the heating resistor is arranged in the main scanning direction evenly in the folded electrode type as compared with the common electrode type. However, when the interval between two heating resistors that print the same pixel is reduced as in the present embodiment, the heating resistors are arranged in the folded direction and are evenly arranged in the main scanning direction. It can be seen that the temperature peak increases compared to the case.

  However, when the overcoat is formed on the printing medium 64, the overcoat is uneven if the temperature distribution in the main scanning direction is not uniform. Therefore, when the interval between two heating resistors for printing the same pixel in the folded electrode type is reduced, if the overcoat is formed only by the heating resistors 92 and 93 for printing, the overcoat becomes uneven and the print quality deteriorates. there's a possibility that.

  Therefore, in the present embodiment, not only the heat generating resistors 92 and 93 for printing but also the heat generating resistors 91 and 94 for overcoat provided between the heat generating resistors 92 and 93 during overcoating are provided. Also generate heat. For this reason, the temperature distribution in the main scanning direction can be made uniform, and the possibility of unevenness in the overcoat is reduced.

  In addition, a pair of heat generation for printing connected by a folded electrode between a set of the first heating resistor 91, the second heating resistor 92, the third heating resistor 93, and the fourth heating resistor 94. Resistors may be arranged. That is, a set composed of the first heat generating resistor 91, the second heat generating resistor 92, the third heat generating resistor 93, and the fourth heat generating resistor 94 is arranged with the pair of heat generating resistors for printing interposed therebetween. Also good. As a result, the resolution of the print can be increased.

  As described above, in this embodiment, it is possible to improve the uniformity of the overcoat while increasing the peak temperature of the heat generating portion with the folded-type thermal print head.

DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 20 ... Radiation board, 23 ... Double-sided tape, 30 ... Heat generating body board, 31 ... Insulating board, 32 ... Heat generation area, 33 ... Bonding pad, 36 ... Protective layer, 38 ... Ceramic board, 39 ... Thermal insulation Layers 41... Circuit board 42. Driving element 51. Bonding wire 52. Sealing resin 60. Platen roller 63 .. Thermal ribbon 64 .. Print medium 71. 72. 73. 74. Electrode 75. ... reference potential electrode, 81, 82 ... folded electrode, 91, 92, 93, 94 ... heating resistor

Claims (4)

In a thermal print head used for a thermal printer that prints on a printing medium and overcoats a printing screen,
An insulating substrate;
A plurality of heating resistors arranged at intervals on the surface of the insulating substrate;
The plurality of heating resistors are the second heating resistors when the first heating resistor, the second heating resistor, the third heating resistor, and the fourth heating resistor are repeatedly arranged in the arrangement direction. And a first folded electrode connecting the third heating resistor,
A first electrode connected to one of the second heating resistor and the third heating resistor on the opposite side of the first folded electrode;
A second folded electrode connecting the first heating resistor and the fourth heating resistor;
A second electrode connected to one of the first heating resistor and the fourth heating resistor on the opposite side of the second folded electrode;
A driving element connected to the first electrode and the second electrode to cause the second heating resistor and the third heating resistor to generate heat during printing, and to generate heat to all of the heating resistors during overcoating;
A thermal print head comprising:   The thermal print head according to claim 1, wherein the second folded electrode extends along the first folded electrode.   The thermal print head according to claim 1, wherein the plurality of heating resistors are arranged at equal intervals. In a thermal printer that prints on a printing medium and overcoats the printing screen,
An insulating substrate;
A plurality of heating resistors arranged at intervals on the surface of the insulating substrate;
Wherein the plurality of heat generating resistor and the first heating resistor and the second heating resistor and the third heat generating resistor and the fourth heating resistor and is that are repeatedly arranged Kino said second heating resistor in the array direction A first folded electrode connecting the third heating resistor;
A first electrode connected to one of the second heating resistor and the third heating resistor on the opposite side of the first folded electrode;
A second folded electrode extending along the first folded electrode and connecting the first heating resistor and the fourth heating resistor;
A second electrode connected to one of the first heating resistor and the fourth heating resistor on the opposite side of the second folded electrode;
A driving element connected to the first electrode and the second electrode to generate heat at the second heating resistor and the third heating resistor at the time of printing, and to generate heat at all of the heating resistors at the time of overcoating ;
Conveying means for conveying the printing medium;
A thermal printer comprising:

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