JP5852387B2 - Thermal print head - Google Patents

Description

  The present invention relates to a thermal print head.

  A thermal print head is an output device that generates heat from a plurality of heating elements arranged in a heat generating portion and forms images such as characters and figures on a medium such as thermal recording paper by the heat. This thermal print head is widely used in recording devices such as barcode printers, digital plate-making machines, video printers, imagers, and seal printers.

  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. The electrode connected to the heating resistor and the drive IC are connected by wire bonding. The bonding wire brought into the connection is sealed with resin.

  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 the thermal print head, the heating plate and the circuit board are combined on the heat sink. In order to combine the heat generating plate and the heat radiating plate, either an adhesive or a double-sided tape is often used. When the heat generating plate and the heat radiating plate are combined using an adhesive, distortion may occur with hardening during fixation, and the linearity of the heat generating region may be impaired. Therefore, it is difficult to apply to a thermal print head having a print width of 150 mm or more. When a double-sided tape is used, the heat dissipation from the back side of the heat-generating region that affects the thermal history of the thermal print head is poor, and heat storage tends to be large.

  Therefore, there is also a hybrid structure in which the back surface of the heating plate close to the circuit board is fixed with double-sided tape, and the back surface of the heat generating area is fixed using a resin material such as silicone resin. In this hybrid structure, the heat generating plate is supported away from the heat radiating plate by the thickness of the double-sided tape, and the resin material fills the thickness of the double-sided tape to enhance the adhesion between the heat generating plate and the heat radiating plate.

JP 2004-351800 A

  In a thermal printer using a thermal print head, a heating resistor in a heating area formed on a heating plate is heated and printed on a medium pressed against the thermal print head by a platen roller. Therefore, it is important that the heat generating plate combined with the heat radiating plate is not peeled off from the heat radiating plate due to the pressure from the platen roller. However, in the hybrid structure in which the heat generating plate is combined with a resin such as silicone resin and double-sided tape, if the combined strength is not sufficient, the heat generating plate is peeled off from the heat radiating plate, resulting in a gap in the resin adhesive layer, and printing quality. It has a big influence on.

  Therefore, an object of the present invention is to increase the bonding strength in a thermal print head in which a heat radiating plate and a heating element plate are bonded with a double-sided tape and a resin material.

In order to solve the above-described problems, the present invention provides a thermal printhead in which a heat sink having a rectangular mounting surface formed with a resin-filled groove extending in the longitudinal direction and a separation groove extending in parallel with the resin-filled groove; The heating resistor arranged at intervals in the longitudinal direction is provided on the surface opposite to the surface facing the mounting surface, and the rear side of the heating resistor is disposed so as to face the resin filling groove. A heat- radiating plate formed on the side wall of the resin-filled groove with a plurality of side-wall grooves, and the mounting surface on the opposite side of the separation groove with respect to the resin-filled groove A double-sided tape for bonding the heat generating plate, and a resin filled in a region including the resin filling groove between the heat radiating plate and the heat generating plate.

  ADVANTAGE OF THE INVENTION According to this invention, in the thermal print head which joins a heat sink and a heat generating body board with a double-sided tape and a resin material, joining strength can be raised.

It is sectional drawing in one Embodiment of the thermal print head which concerns on this invention. 1 is a partially cutaway plan 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 table | surface which shows the test result of the soundness of one Embodiment of the thermal print head which concerns on this invention. It is a table | surface which shows the test result of the thermal radiation characteristic of one Embodiment of the thermal print head which concerns on this 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 sectional view of an embodiment of a thermal print head according to the present invention. FIG. 2 is a partially cut-out top view of the thermal print head according to the present embodiment.

  The thermal print head 10 according to the present embodiment includes a heat radiating plate 20, a heat generating plate 30, and a circuit board 41. The heating element plate 30 includes an insulating substrate 31 and a heating resistor 32 formed on the surface of the insulating substrate. The insulating substrate 31 has a heat insulating layer 39 formed of glass on the surface of a ceramic plate 38 or the like.

  The heating resistors 32 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 heat generating region extending substantially linearly. Each heating resistor 32 extends in the sub-scanning direction perpendicular to the main scanning direction. A protrusion extending in the main scanning direction may be provided on the heat retaining layer 39, and the heating resistor 32 may be arranged on the protrusion.

  An electrode 34 extending to the bonding pad 33 is connected to each heating resistor 32. The end of the heating resistor 32 opposite to the side connected to the bonding pad 33 is connected to the folded electrode 35. The heating resistor 32 and the electrodes 34 and 35 are provided by being laminated on the surface of the insulating substrate 31. The electrodes 34 and 35 are made of, for example, aluminum. The length of the heating resistor 32 not covered with the electrodes 34 and 35 is, for example, 100 μm.

  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 rigid printed board using, for example, a 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 driving element 42 is a semiconductor integrated circuit (IC), and causes each heating resistor 32 to generate heat by flowing a predetermined current at a predetermined timing.

  The heat dissipation substrate 20 is a plate formed of a material having a high thermal conductivity such as aluminum. The heat generating plate 30 and the circuit board 41 are placed on the same surface of the heat radiating plate 20. 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. A bonding wire is also bridged between the drive element 42 and the terminal on the circuit board 41.

  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.

  The heat generating plate 30 and the circuit board 41 are bonded to the surface of the heat radiating plate 20 with a double-sided tape 23. The double-sided tape 23 is not present on the back side of the heating resistor 32 of the heating plate 30. The thickness of the double-sided tape 23, that is, the distance between the heating element plate 30 and the circuit board 41 and the surface of the heat dissipation board is, for example, 150 μm.

  A resin-filled groove 21 extending linearly in the arrangement direction of the heating resistors 32, that is, in the main scanning direction is formed on the surface of the heat radiating plate 20. The resin filling groove 21 is filled with a silicone resin 22. The silicone resin 22 embedded in the resin filling groove 21 is bonded to the vicinity of the back side of the heating resistor 32 of the heating plate 30. Since the resin embedded in the resin filling groove 21 joins the ceramic plate 38 and the metal heat sink 20 having different thermal expansion coefficients, a silicone resin having some elasticity is preferable.

  The resin filling groove 21 is formed below the heating resistor 32 so that heat from the heating plate 30 is efficiently transmitted to the silicone resin 22. The resin filling groove 21 has a bottom portion and a side wall between the bottom portion and the uppermost surface of the heat dissipation substrate 20. A plurality of side wall grooves 61 are formed on opposite side walls of the resin filling groove 21. These side wall grooves 61 have, for example, a V-shaped cross section, and extend in parallel with the resin filling grooves 21, that is, in the arrangement direction of the heating resistors 32.

  The width of the resin filling groove 21 is, for example, 1.5 mm to 4 mm, and the depth is, for example, 1 mm to 3 mm. Side wall groove 61 has a width of, for example, 100 μm to 500 μm, and a depth of, for example, 100 μm to 500 μm.

  A separation groove 24 is formed between the resin filling groove 21 and the long side of the double-sided tape 23 on the heating element plate 30 side. By forming the separation groove 24, the possibility of the silicone resin 22 flowing out to the region where the double-sided tape 23 is disposed can be reduced.

  When manufacturing the thermal print head 10, first, the heat radiating plate 20, the heating plate 30 and the circuit board 41 are manufactured. Thereafter, the resin filling groove 21 of the heat sink 20 is filled with the silicone resin 22. A double-sided tape 23 is attached to the heat sink 20. Thereafter, the heating plate 30 and the circuit board 41 are placed on the heat dissipation board 20.

  In this way, after the heating element plate 30 is placed on the heat dissipation substrate 20, the silicone resin 22 is cured by performing a heat treatment at 120 ° C. for 3 hours, for example. Thereafter, the drive element 42 is mounted on the circuit board 41 and connected by wire bonding, and the bonding wire 51 and the like are sealed with a sealing resin 52.

  In the present embodiment, the mounting surface on which the heat generating plate 30 and the circuit board 41 of the heat radiating plate 20 are placed is a flat surface having no step, but the step is formed to make the circuit board 41 the heat generating plate 30. You may fix to the heat sink 20 in a lower position. In this case, the double-sided tape 23 uses two types for fixing the heat generating plate 30 and the heat sink 20 and fixing the circuit board 41 and the heat sink 20. Thus, by fixing the circuit board 41 to the heat radiating plate 20 at a position lower than the heat generating plate 30, the height from the heat generating plate 30 to the uppermost portion of the sealing resin 52 can be reduced. As a result, the possibility that the sealing resin 52 hinders the conveyance of the thermal recording medium can be reduced.

  FIG. 3 is a cross-sectional view of a thermal printer using the thermal print head of the present embodiment.

  This thermal printer has a thermal print head 10 and a platen roller 60. The platen roller 60 is a cylinder formed of a material having a predetermined elasticity having an axis parallel to a line in which the heating resistors 32 are arranged. A side surface of the platen roller 60 is pressed against a portion of the heating plate 30 where the heating resistors 32 are arranged. A thermal recording medium 62 is sandwiched between the platen roller 60 and the heating plate 30.

  When the heating resistor 32 is heated in a predetermined pattern by the driving element 42, the thermal recording medium 62 is colored according to the predetermined pattern. Further, after the thermal recording medium 62 has developed a color corresponding to a predetermined pattern, it is sent out in the sub-scanning direction by the platen roller 60. By sequentially performing these operations, a predetermined image is formed on the thermal recording medium.

  In the thermal print head 10 of the present embodiment, the heating element plate 30 is bonded to the heat dissipation plate 20 with a silicone resin 22 filled in the resin filling groove 21. In the absence of such a resin-filled groove 21, the cross-sectional shape such as the thickness and width of the silicone resin between the heat radiating plate 20 and the heat generating plate 30 may vary greatly due to fluctuations in the amount of application. .

  However, in the present embodiment, the thickness and width of the silicone resin 22 on the back side of the portion where the heating resistors 32 are arranged are substantially determined by the thickness and width of the resin filling groove 21. Therefore, since a resin layer having a stable thickness is formed along the resin filling groove 21, heat dissipation from the heating element plate 30 can be made uniform in the main scanning direction, and each manufactured product can be made uniform. Variations can also be reduced.

  In the thermal print head 10, it is important that the heat generating plate 30 combined with the heat radiating plate is not peeled off from the heat radiating plate 20 due to the pressure from the platen roller. However, in a hybrid structure in which the heat generating plate is combined with a resin such as silicone resin and a double-sided tape, the heat generating plate 30 is peeled off from the heat radiating plate 20 if the combined strength is not sufficient. In this case, a gap occurs in the resin adhesive layer, and the print quality deteriorates.

  However, in this embodiment, the resin filling groove 21 is filled with the silicone resin 22 used for joining the heat generating plate 30 and the heat radiating plate 20. The contact area between the silicone resin 22 and the heat sink 20 is increased by the presence of the resin filling groove 21 and the side wall groove 61 formed on the side surface thereof. For this reason, the adhesive strength by the silicone resin 22 increases.

  If the resin-filled groove 21 has a planar side wall that simply descends vertically from the top surface, that is, if the width of the resin-filled groove 21 does not change in the depth direction, the silicone filled without deformation is filled in the silicone. The resin 22 can move in the depth direction of the groove. For this reason, in this case, the silicone resin 22 is easily removed from the resin filling groove 21.

  On the other hand, in the present embodiment, a side wall groove 61 is formed on the side wall of the resin filling groove 21. In addition, the width of the resin filling groove 21 is not constant in the depth direction, and narrow and wide portions are alternately formed in the depth direction. For this reason, the silicone resin 22 cannot move inside the resin filling groove 21 unless it is deformed. As a result, the heat generating plate 30 is not easily peeled off from the heat sink 20.

  In addition, heat dissipation characteristics are improved by increasing the contact area. As a result, high print quality can be maintained.

  Further, in the present embodiment, the side wall groove 61 formed on the side surface of the resin filling groove 21 extends in the same direction as the resin filling groove 21. That is, the cross-sectional shape of the heat sink 20 is the same at any position in the main scanning direction. Therefore, the heat sink 20 of the present embodiment is easy to mold.

  FIG. 4 is a table showing the soundness test results after the operation of the thermal print head in the present embodiment. This test summarizes the presence or absence of peeling between the heat sink 20 and the heat generating plate 30 after printing a predetermined number of times using thermal print heads with different widths and depths of the resin-filled grooves 21. It is.

  From this table, when the width of the resin-filled groove 21 is 1 mm, peeling occurs even when the depth changes in the range of 1 mm to 4 mm, whereas the width of the resin-filled groove 21 is from 1.5 mm. It can be seen that in the range of 4 mm, no peeling occurs if the depth is between 1 mm and 4 mm. Therefore, it can be seen that the resin filling groove 21 is preferably a predetermined width or more in order to appropriately fix the heating element plate 30 to the heat radiating plate 20. This predetermined width is 1.5 mm or more when the silicone resin 22 is used as an adhesive.

  FIG. 5 is a table showing the test results of the heat radiation characteristics during the operation of the thermal print head of the present embodiment. This test is a summary of the presence or absence of tailing when continuous printing is performed for a predetermined time using thermal print heads in which the width and depth of the resin-filled grooves 21 are changed. The tailing is an event in which a black portion is generated in a portion that should be white when black is printed on a surface for a certain period and then is not printed, that is, white.

  From this table, when the depth of the resin filling groove 21 is 3.5 mm or more, tailing occurs even when the depth changes in the range of 1 mm to 4 mm, whereas the depth of the resin filling groove 21 is It can be seen that tailing does not occur when the depth is between 1 mm and 3 mm when the depth is between 1 mm and 4 mm. Therefore, it can be seen that the resin-filled groove 21 is preferably a predetermined depth or less in order to obtain sufficient heat dissipation characteristics. This predetermined depth is 3 mm or less when the silicone resin 22 is used as an adhesive.

  Thus, when the silicone resin 22 is used as the adhesive, the width of the resin filling groove is preferably 1.5 mm or more and 4 mm or less, and the depth is preferably 1 mm or more and 3 mm or less.

DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 20 ... Heat sink, 21 ... Resin filling groove, 22 ... Silicone resin, 23 ... Double-sided tape, 24 ... Separation groove, 30 ... Heat generating board, 31 ... Insulating substrate, 32 ... Heat generating resistor, 33 DESCRIPTION OF SYMBOLS Bonding pad 34 ... Electrode 35 ... Folded electrode 36 ... Protection layer 38 ... Ceramic board 39 ... Heat insulation layer 41 ... Circuit board 42 ... Drive element 51 ... Bonding wire 52 ... Sealing resin 60 ... Platen roller, 61 ... Side wall groove, 62 ... Thermal recording medium

Claims (4)

A heat radiating plate in which a resin loading groove extending in the longitudinal direction and a separation groove extending in parallel with the resin filling groove are formed on a rectangular mounting surface, and a plurality of side wall grooves are formed on the side wall of the resin filling groove A heat sink ,
A heating resistor arranged at intervals in the longitudinal direction is provided on the surface opposite to the surface facing the mounting surface, and the back side of the heating resistor is disposed so as to face the resin filling groove. Heating plate,
A double-sided tape that bonds the mounting surface and the heating element plate on the opposite side of the separation groove with respect to the resin filling groove;
A resin filled in a region including the resin filling groove between the heat dissipation plate and the heating element plate;
A thermal print head comprising: The thermal print head according to claim 1, wherein the side wall groove extends parallel to the resin filling groove. 3. The thermal print head according to claim 1, wherein the resin-filled groove has a width of 1.5 mm to 4 mm and a depth of 1 mm to 3 mm. The thermal print head according to any one of claims 1 to 3, wherein the resin is a silicone resin.

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