JP2006347041A - Thermal print head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a thermal print head structure which can obtain an enough electricity eliminating effect to static electricity. <P>SOLUTION: The thermal print head is equipped with a heat dissipating substrate 10, a head substrate 20 provided on one main face of this heat dissipating substrate and a driving circuit substrate 30. The head substrate 20 has a heating resistor 22 formed on one main face of this heat dissipating substrate, an electrode 24 exposing a part of this heating resistor to make it to be a heating part 23, and a covering layer 25 at least covering the heating part. The driving circuit substrate 30 has a driving circuit wiring 31. In a thermal head wherein a driving IC 26 for controlling electric current passing through the heating part is mounted on either the head substrate or the driving circuit substrate and is covered by a protective body 33 (34), an electricity eliminating brush 40 electrically connected to the heat dissipating substrate or the driving circuit wiring of the driving circuit substrate is arranged at least one position on a tangent (a) of the protective bodies 33 and 34 passing through the heating part 23. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a thermal print head mounted on a recording device such as a printer, and more particularly to a thermal print head of a printer applied to a non-conductive thermal medium.

  In a recording device such as a printer equipped with a thermal print head, a medium travels inside the device and contacts or approaches each part, so that static electricity due to friction is induced and discharge occurs. For this reason, measures are taken to eliminate static electricity by making the periphery of the head conductive, but the media is paper, plate-making sheets, and ink ribbons. In particular, the ink ribbons used in word processors, facsimiles, etc. are very easily charged polyethylene.・ The main thing is made of terephthalate (PET) resin, and there is a considerable amount of static electricity inside most recording devices. For this reason, if the platen roller presses the medium against the heating resistor of the thermal print head, or the recording device has a structure in which the medium contacts the thermal print head heating resistor, it is charged if there is insufficient static elimination measures. The electric charge breaks through the heat generating part of the thermal print head and the insulating coating layer covering the electrode, and discharges (lightning strike) toward the electrode. For this reason, the head substrate and the drive circuit substrate of the thermal head are seriously damaged, causing electrode disconnection and drive IC malfunction. Alternatively, there is a risk of damage to the thermal print head drive circuit of the device or the connected recording device circuit portion through the thermal print head due to discharge.

  When taking measures against static electricity with a thermal print head, as a measure against static electricity, a head substrate provided with a conductive coating layer having a charge eliminating effect has been put into practical use.

  Lamination of the conductive coating layer is performed by adding a step of depositing or printing the layer on the upper layer of the insulating coating layer by a vacuum deposition apparatus, a sputtering apparatus or a printing apparatus. In addition, since it is necessary to connect the conductive coating layer to an electrode that holds a potential, it is necessary to devise such an insulating coating layer that allows charges to escape. For this reason, this measure has become a major obstacle in reducing the product manufacturing cost because the manufacturing process becomes complicated. On the other hand, a metal cover or conductive resin cover is placed on the upper surface side of the encap protection layer of the drive IC, and is locked to the heat dissipation board with screws and electrically connected at the same time to eliminate static electricity during discharge (lightning strike). Although a structure for achieving the effect has been put into practical use, a sufficient effect has not been obtained because the metal cover cannot be actively brought into contact with the medium.

  An object of the present invention is to provide a thermal printhead structure that can solve the above-described problems and that can obtain a sufficient static elimination effect against static electricity with an inexpensive and simple structure that cannot be achieved by conventional techniques.

  The present invention includes a heat dissipation substrate, a head substrate and a drive circuit substrate provided on one main surface of the heat dissipation substrate, and the head substrate has a heating resistor formed on the main surface of the head substrate and the heat generation. It has an electrode that exposes a part of the resistor and serves as a heat generating part, and a coating layer that covers at least the heat generating part, and has the same circuit wiring as the drive circuit board, and controls the current flowing through the heat generating part. In the thermal head in which the driving IC is mounted on the head substrate or the driving circuit substrate and covered with a protective body, the neutralizing brush electrically connected to the heat dissipation substrate or the driving circuit of the driving circuit substrate A thermal print head is provided, wherein the thermal print head is disposed at at least one location on a tangent line of the protective body passing through the heat generating portion.

  In the recording device, the static electricity that is most likely to be damaged by static electricity is placed on the thermal print head that is most likely to fail. It supplies strong and highly reliable thermal print heads.

If the thermal print head structure according to the present invention is used, it is possible to sufficiently eliminate static electricity even when used in a recording device that has not been adequately protected against static electricity, thereby reducing the occurrence of problems such as disconnection of the thermal print head and abnormal signals due to static electricity. I can do it.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a thermal print head according to a first embodiment of the present invention. A head substrate 20 and a drive circuit substrate 30 are disposed on one main surface of a heat radiating substrate 10 with long sides contacting each other. It is bonded and arranged using an adhesive tape.

  The heat dissipation substrate 10 is a long substrate formed of stainless steel or aluminum metal, and has a function of supporting the head substrate 20 and the drive circuit substrate 30 and radiating heat generated by the active thermal resistor.

  The head substrate 20 is an insulating long substrate made of ceramic, and includes a glaze layer 21 formed on one main surface of the head substrate, a plurality of heating resistors 22 arranged on the glaze layer, and a heating resistor. The electrode 24 is laminated on the heating resistor so that a part of the opening is exposed and the exposed portion becomes the heat generating portion 23, and an insulating coating layer 25 that covers at least the heat generating portion. A plurality of heat generating portions 23 are arranged in the same number as the required number of recording dots along the longitudinal direction, and they are arranged thermally independently. The electrode 24 supplies driving power to each heat generating portion, and is formed in an electrode pattern in which an electrode connected to one end of the heat generating portion is an individual electrode 24a and an electrode connected to the other end is a common electrode 24b. .

  A coating layer 25 of an inorganic insulator is provided on the electrode including the heat generating portion 23 and in the vicinity of the heat generating portion, and a plurality of driving ICs 26 are mounted on the side close to the driving circuit substrate, and bonded to the pads of the individual electrodes. A coating layer 27 of a photosensitive insulating film is applied on the exposed electrode between the coating layer 25 and the driving IC 26, and the coating layer of this embodiment is formed by the inorganic insulating protective layer and the photosensitive protective layer.

  The drive circuit board 30 includes a substrate made of resin such as glass epoxy and constitutes a printed circuit board. A driving circuit wiring layer 31 is provided on one surface, and a wire 32 is bonded between the driving IC 26 and the wiring layer 31. An encap layer 33 made of a resin such as epoxy is coated on the drive IC and the bonding connection portion as a protective body across the head substrate 20 and the drive circuit substrate 30.

  A metal cover 34 is fixed by screwing with a screw 35 at the position of the drive circuit board so as to cover the drive IC 26. The screw 35 reaches the heat dissipation board 10 and electrically connects the metal cover to the heat dissipation board. In the present embodiment, the metal cover 34 constitutes a part of the protector. A neutralizing brush 40 is disposed between the metal cover 34 and the screw 35. The neutralizing brush is a brush-like contact portion 42 formed by planting a thin conductive wire bundle of amorphous fibers or the like at a side edge of a plate-like support 1 of a conductive material such as stainless steel to a length of about 1 to 3 mm. The support 41 is fixed to the metal cover 34 with a conductive adhesive, and the contact portion is electrically connected to the heat dissipation substrate 10 via the support and the metal cover.

  FIG. 2 shows a state in which the platen roller 50 is pressed against the thermal print head in this embodiment. For example, a PET resin sublimation ink ribbon and a recording paper are combined so that the ribbon is on the head side. In this case, the travel path in the sub-scanning direction of the ribbon is shown. Assuming that the ribbon a is in a position close to the cover so as not to contact the metal cover 34, the travel path of the ribbon is substantially along the tangent line (a) in contact with the upper surface of the metal cover. become.

  The brush-like contact portion 42 of the static eliminating brush is always in contact with the traveling ribbon a by arranging it so as to protrude beyond the tangent line (a). The ribbon that travels in the direction of the arrow as the platen roller rotates is in contact with the static elimination brush 40 to discharge the charged electric charge, and then reaches the heat generating portion 23 that is pressed against the platen roller 50. And damage that can occur due to discharge is avoided.

  The metal cover 34 may be a conductive resin cover, and instead of the conductive adhesive, a conductive double-sided tape, welding connection, or solder connection can be used. Moreover, screwing, welding, etc. may be sufficient as long as it is electrically and mechanically connected.

  According to the present embodiment, for example, a sublimation ribbon made of PET is charged on a sublimation ribbon path in a conventional head structure without a charge-removing brush with respect to the charging amount inside a printing device that performs color printing on a J-SX6301 compliant plastic card. In the present embodiment, it was confirmed that the amount was about 5 kv to 20 kv (by a handy type static electricity meter), but it was 0.5 kv or less in the vicinity of the head.

  FIG. 3 illustrates a second embodiment of the present invention. Here, the same reference numerals as those in FIG. 2 indicate the same parts. In the structure without a metal cover, the static elimination brush 40a is attached on the drive circuit board 30. Suitable for small thermal print heads where it is difficult to attach a metal cover. In this case, an epoxy type thermosetting resin having a sufficient strength against mechanical pressure from the upper surface is used for the encap protector 33 in order to protect the drive IC.

  The neutralizing brush 40a is easily attached to the drive circuit board 30 without the metal cover with respect to the tangent (a) extending from the heat generating portion 23 and in contact with the upper surface of the protector 33. The brush-like contact portion 42a is positioned beyond the tangent line (a) by adjusting the angle of the static eliminating brush. The ribbon traveling along the tangent line is contacted with the charge removal brush and discharged, and then comes into contact with the platen roller 50 and is pressed against the heat generating portion 23 of the head substrate 20 and is brought into sliding contact. Ribbon ink is printed on the recording paper by sliding contact, but malfunction due to discharge does not occur. In addition, since no discharge current is generated in the head electrode, it is possible to prevent damage to the head and damage to the drive circuit and peripheral circuits.

  As a modification of the static elimination brush, a sponge-like conductive elastic body can be used instead of a brush-like one. Other structures can be used as long as they have similar functions.

  Further, the static elimination brush may be arranged in a long shape along the heating resistor row or may be partially arranged.

  In addition, the static elimination brush of this invention can be attached together with the head structure which formed the electroconductive film in the coating layer on a head board | substrate, and took the countermeasure against static elimination, and can further improve the effect of static elimination.

Sectional drawing explaining the 1st Embodiment of this invention. BRIEF DESCRIPTION OF THE DRAWINGS Sectional schematic drawing explaining the 1st Embodiment of this invention. The cross-sectional schematic diagram explaining the 2nd Embodiment of this invention.

Explanation of symbols

10: heat dissipation substrate 20: head substrate 21: glaze layer 22: heating resistor 23: heating element 24: electrode 25: coating layer 26: drive IC
30: Drive circuit board 31: Drive circuit wiring 33: Encap protector 34: Metal cover (protector)
35: Screw 40: Static elimination brush 41: Support body 42: Brush-like contact part a: Ribbon (a): Tangent

Claims (3)

A heat dissipating substrate, and a head substrate and a drive circuit substrate provided on one main surface of the heat dissipating substrate, and the head substrate includes a heating resistor formed on one main surface of the head substrate and one of the heating resistors. An electrode that exposes the heat generating portion and a coating layer that covers at least the heat generating portion, the drive circuit board includes drive circuit wiring, and a drive IC that controls a current flowing through the heat generating portion includes the driving IC. In a thermal head mounted on a head substrate or the drive circuit substrate and covered with a protective body, a static elimination brush electrically connected to the heat dissipation substrate or the drive circuit wiring of the drive circuit substrate passes through the heat generating portion. A thermal print head, wherein the thermal print head is disposed at at least one location on a tangent line of the protector. 2. The thermal print head according to claim 1, wherein the protector has a metal cover attached to the drive circuit board, and the static elimination brush is fixed to the metal cover. The thermal print head according to claim 1, wherein the static eliminating brush has a conductive elastic body disposed on a support.

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