JP2014189016A - Thermal print head and thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit damages to a printed medium while securing proper print density even if the printing is performed at a high speed.SOLUTION: A thermal print head comprises: a rectangular ceramic substrate 22; a glaze layer 25 formed on a surface of the ceramic substrate 22; heating resistors; an electrode; and a protection film layer 29. Two projections 71 extending along a long side of the ceramic substrate 22 are formed on the glaze layer 25. The heating resistors are formed on a resistor layer 26. The heating resistors are arranged in a main scanning direction spaced away from each other and extend lying astride the two projections 71. The electrode is formed on an electrode layer 28. The electrode is connected with the heating resistors at both ends in a sub-scanning direction. The protection film layer 29 covers the resistor layer 26 and the electrode layer 28.

Description

  The present invention relates to a thermal print head and a thermal printer.

  Thermal print heads are attracting attention as output devices such as video printers, imagers, and seal printers. The thermal print head has heating resistors arranged on a substrate. When these heating resistors are heated in a predetermined pattern, recording on a medium such as thermal paper or plate-making film photographic paper is performed using a thermal print head. Various developments have been made to provide advantages such as low noise and low running costs.

  The thermal print head has a support base in which a glaze layer is formed as a heat retaining layer on the surface of a ceramic substrate such as alumina. A heating resistor layer and a conductive layer serving as an electrode such as aluminum are laminated on the support substrate by a thin film forming method such as sputtering, and then the heating resistor and individual electrodes are patterned by a photoengraving process. Thereafter, an insulating protective film layer covering the heating resistor layer and a predetermined portion of the electrode is formed by a thin film forming method such as sputtering.

  The heat generating plate manufactured in this way and the separately manufactured circuit board are fixed to the surface of the heat radiating plate. Further, the electrodes of the heating plate and the driving IC mounted on the circuit board are connected by bonding wires or the like, and the driving IC or the like is sealed with resin to manufacture a thermal print head.

JP 2011-140138 A

  A temperature distribution having a peak at the center of the heating resistor is generated in the heating resistor of the thermal print head. For this reason, when high-power printing is performed as printing speed increases, the heat generation peak temperature may become excessively high. Also, when the length of the heating resistor is shortened with emphasis on image quality, the peak heat generation temperature may become excessively high. Thus, when the exothermic peak temperature is too high compared to the color development temperature, the printing medium is damaged or energy efficiency is deteriorated.

  Therefore, for example, there is a method in which the heating resistor is divided in the sub-scanning direction to lower the heat generation peak temperature, thereby suppressing damage to the printing medium and suppressing deterioration of energy efficiency. In order to divide the heating resistor in the sub-scanning direction, an intermediate electrode made of a material having high heat resistance is laminated on the heating resistor. In this case, since the intermediate electrode portion that does not generate heat protrudes more than the heating resistor, the contact pressure of the platen roller on the surface of the heat generating portion where heat transfer is to be performed most efficiently becomes weak, and heat transfer Efficiency will decrease.

  Therefore, an object of the present invention is to suppress damage to a printing medium while ensuring an appropriate printing density even when printing with a thermal print head is accelerated.

  In order to solve the above-described problems, the present invention is a thermal printer, wherein a rectangular insulating substrate and two protrusions extending along a long side of the insulating substrate are formed on the surface of the insulating substrate. A glaze layer, a heating resistor arranged at intervals along the long side and extending over the two protrusions, and electrodes connected to the heating resistor at both ends in the sub-scanning direction; A thermal print head having the heating resistor and a protective film covering the electrode, and a cylindrical shape having an axis parallel to the direction in which the heating resistors are arranged, and the two protrusions on the side surface are formed. And a platen roller pressed against the thermal print head at a position.

  In addition, the present invention provides a thermal printhead having a rectangular insulating substrate, and a glaze formed on a surface of the insulating substrate having a first protrusion and a second protrusion extending along a long side of the insulating substrate. Layers, heating resistors arranged at intervals along the long side and extending over the two protrusions, electrodes connected to the heating resistors at both ends in the sub-scanning direction, And a protective film that covers the heating resistor and the electrode.

  According to the present invention, it is possible to suppress damage to a printing medium while securing an appropriate printing density even when printing with a thermal print head is accelerated.

1 is a partially enlarged cross-sectional view of an embodiment of a thermal print head according to the present invention. 1 is a partially cutaway top view of an embodiment of a thermal print head according to the present invention. It is sectional drawing of the thermal printer using the thermal print head concerning this invention. It is a partial expanded sectional view of the modification of one embodiment of the thermal print head concerning the present invention. It is a partially expanded sectional view of the other modification of one Embodiment of the thermal print head concerning this invention.

  An embodiment of a thermal print 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.

  FIG. 1 is a partially enlarged 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. FIG. 3 is a cross-sectional view of a thermal printer using the thermal print head of the present embodiment.

  The thermal print head 10 according to the present embodiment includes a heat radiating plate 30, a heat generating plate 20, and a circuit board 40. The heat sink 30 is a rectangular flat plate made of a metal such as aluminum.

The heating element plate 20 has an insulating substrate composed of a ceramic substrate 22 and a glaze layer 25. The ceramic substrate 22 is a rectangular flat plate made of alumina (Al ₂ O ₃ ), for example. One surface of the ceramic substrate 22 faces the heat sink 30, and the glaze layer 25 is fused to the other surface. The glaze layer 25 is made of glass.

  Two protrusions 71 are formed on the glaze layer 25. These protrusions 71 protrude from the surface of the ceramic substrate 22 and extend in the longitudinal direction of the ceramic substrate 22, that is, in the main scanning direction. The cross section of these protrusions 71 is trapezoidal. The width of the two ridges 71 is, for example, about 10 to 20 μm, and the distance between the two ridges 71 is, for example, about 10 to 20 μm. The protrusion height of the protrusion 71 is, for example, about 1 to 3 μm.

  A resistor layer 26 is formed on the surface of the glaze layer 25. An electrode layer 28 is formed on the surface of the resistor layer 26. A notch portion is formed in the electrode layer 28, and a portion of the resistor layer 26 that does not overlap the electrode layer 28 is a heating resistor. The heating resistor is disposed across the two protrusions 71 of the glaze layer 25. The length of the heating resistor in the sub-scanning direction is, for example, 100 μm. In this manner, a plurality of heating resistors are arranged on the entire surface of the glaze layer 25 at intervals, and a belt-like heating region 24 extending in the longitudinal direction (main scanning direction) of the ceramic substrate 22 is formed. The thickness of the resistor layer 26 is, for example, about 0.1 μm, and the thickness of the electrode layer 28 is, for example, about 0.8 μm.

  A protective coating layer 29 is formed on the surfaces of the electrode layer 28 and the heating resistor. The protective coating layer 29 is made of, for example, SiON. The surface of the protective coating layer 29 is formed flat, for example, by polishing.

  The thermal print head 10 has a drive circuit that generates heat in the heat generating region 24. The drive circuit is formed on a circuit board 40 mounted on the heat dissipation plate 30 on the same surface as the heating element plate 20, for example. 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. The drive circuit has electrical components such as a drive element 42 provided on the circuit board 40, for example. The heat generating plate 20 and the drive circuit are electrically connected by, for example, a bonding wire 44 spanned between the heat generating plate 20 and the circuit board 40. Further, the wiring pattern formed on the surface of the circuit board 40 and the drive element 42 are also electrically connected by the bonding wire 44. The drive element 42 and the bonding wire 44 are sealed with a resin 48, for example.

  The printer using the thermal print head 10 has a cylindrical platen roller 50 centering on an axis 52 located on the normal line of the surface of the heat generating area 24. The printing medium 60 is pressed against the thermal print head 10 by the platen roller 50. In this state, the heat generating resistor in the heat generating region 24 generates heat, and the image is printed on the printing medium 60. While the printing medium 60 is conveyed in the sub-scanning direction, the heat generation area 24 extending in the main scanning direction generates heat in a predetermined pattern, so that a desired image is formed on the printing medium 60.

  Next, the manufacturing method of this Embodiment is demonstrated.

  First, a glass paste is printed on the main surface of the ceramic substrate 22. The thickness of the glass paste is, for example, 30 to 120 μm. Thereafter, the glass paste attached to the ceramic substrate 22 is fired at 1200 ° C., for example. Thereafter, protrusions corresponding to the two protrusions 71 are formed by polishing or etching. Further, it is then heated to about 900 ° C. and cooled to room temperature. As a result, the glaze layer 25 having the two ridges 71 that are trapezoidal and have a curved surface with a certain degree of smoothness is formed.

  Next, a resistance film layer and a metal layer are formed on the surface of the glaze layer 25. The resistor layer 26 and the electrode layer 28 having a predetermined pattern are formed by etching the resistance film layer and the metal layer into a predetermined shape. Thereafter, a protective coating layer 29 that covers the resistor layer 26 and the electrode layer 28 is formed. The protective coating layer 29 is formed by sputtering, for example. Thereby, the heat generating body plate 20 is obtained. A plurality of heating element plates 20 may be obtained by forming a portion to be a plurality of heating element plates 20 on a single ceramic plate and dividing it in the middle or at the end of the manufacturing process.

  The circuit board 40 on which the heating element plate 20 and the driving element 42 manufactured in this manner are mounted is placed on the heat dissipation plate 30, and the bonding wire 44 is bridged between the driving element 42 and the heating element plate 20 to drive the circuit board 40. The thermal print head 10 is completed by sealing the element 42 and the bonding wire 44.

  In such a thermal print head 10, the heating resistor is formed on the surface of the thermal print head 10, that is, in the central portion in the sub-scanning direction of the heat generation region 24, that is, in the recess 72 between the two protrusions 71. It is located relatively far from the surface of the protective coating layer 29. That is, the heat from the heating resistor at the top of the two ridges 71 is easily transmitted to the surface of the thermal print head 10, and the heat from the heating resistor in the recess 72 between the two ridges 71 is thermal. It is difficult to be transmitted to the surface of the print head 10. As a result, the temperature of the surface of the thermal print head 10 is flattened in the sub-scanning direction.

  When the temperature of the surface of the thermal print head 10 is flattened in the sub-scanning direction, it is not necessary to excessively increase the peak temperature even if the temperature is higher than the color development temperature of the printing medium 60 in a wide area. Therefore, the possibility of damage to the printing medium 60 is reduced. In addition, energy efficiency is improved. Further, the heat transfer distribution can be adjusted by changing the length and position of the protrusion 71 in the sub-scanning direction.

  As described above, according to the present embodiment, it is possible to suppress damage to the printing medium while securing an appropriate printing density even when printing with the thermal print head is accelerated.

  FIG. 4 is a partially enlarged cross-sectional view of a thermal print head in a modification of the present embodiment.

  In this modification, the two ridges 81 are formed so that the cross section draws an arc. Further, the surface shape of the protective coating layer 29 is made substantially the same as the shape of the glaze layer 25 without polishing the protective coating layer 29. That is, the depression 83 is also formed on the surface of the protective coating layer 29 in correspondence with the depression 82 formed in the glaze layer 25.

  Thus, even in the thermal print head 10 in which the cross-sectional shape of the protrusion 81 is not a trapezoidal shape but an arc, the contact pressure of the platen roller 50 is reduced at the center of the heat generating region 24 in the sub-scanning direction. The platen roller 50 does not contact the bottom of the recess 82. Therefore, the heat from the heating resistor at the top of the two ridges 81 is easily transmitted to the surface of the thermal print head 10, and the heat from the heating resistor in the recess 82 between the two ridges 81 is the thermal print. It is difficult to be transmitted to the surface of the head 10. As a result, the temperature of the surface of the thermal print head 10 is flattened in the sub-scanning direction.

  Further, an intermediate electrode may be provided with titanium or the like at the position of the depression 82 of the glaze layer 25, and the heating resistor may be divided in the sub-scanning direction. Even if the intermediate electrode is provided in this way, the depression 83 on the surface of the protective coating 29 only becomes shallow, and does not become higher than the protrusions on both sides, and the pressing pressure of the platen roller 50 remains small.

  FIG. 5 is a partially enlarged cross-sectional view of a thermal print head in another modification of the present embodiment.

  In the present embodiment, the height of the surface of the glaze layer 25 on the upstream side and the downstream side of the heat generating region 24 is the same as the height of the top portions of the two protrusions 71. Therefore, the depressions 74 on the surface of the protective coating layer 29 are also formed at both ends of the heat generating region 24 in the sub-scanning direction.

  Even in such a thermal print head 10, the contact pressure of the platen roller 50 becomes small at the center of the heat generating region 24 in the sub-scanning direction, and in some cases, the platen roller 50 has a protective coating layer 29 between the two protrusions 71. No contact with the bottom of the depression 73 on the surface. Therefore, the heat from the heating resistor at the top of the two ridges 71 is easily transmitted to the surface of the thermal print head 10, and the heat from the heating resistor in the recess 72 between the two ridges 71 is thermal. It is difficult to be transmitted to the surface of the print head 10. As a result, the temperature of the surface of the thermal print head 10 is flattened in the sub-scanning direction.

  Further, since the depression 74 is formed on the downstream side of the heat generating area 24, when foreign matter such as residue of the printing medium 60 is generated, it stays in the depression 74 and hardly affects the printing. .

DESCRIPTION OF SYMBOLS 10 ... Thermal print head, 20 ... Heat generating body board, 22 ... Ceramic substrate, 24 ... Heat generating area, 25 ... Glaze layer, 26 ... Resistor layer, 28 ... Electrode layer, 29 ... Protective coating layer, 30 ... Heat sink, 40 ... Circuit board, 42 ... Drive element, 44 ... Bonding wire, 48 ... Resin, 50 ... Platen roller, 52 ... Shaft, 60 ... Medium to be printed, 71 ... Projection, 72 ... Indentation, 73 ... Indentation, 74 ... Recessed part, 81 ... ridge, 82 ... Recessed part, 83 ... Recessed part

Claims (3)

A rectangular insulating substrate, a glaze layer formed on the surface of the insulating substrate having two protrusions extending along the long side of the insulating substrate, and arranged at intervals along the long side A thermal element having a heating resistor extending over the two protrusions, electrodes connected to the heating resistor at both ends in the sub-scanning direction, and a protective film covering the heating resistor and the electrode A printhead;
A platen roller having a cylindrical shape with an axis parallel to the direction in which the heating resistors are arranged, and a side surface pressed against the thermal print head at a position where the two protrusions are formed;
A thermal printer comprising:   The thermal printer according to claim 1, wherein a groove is formed on the surface of the protective film between the two protrusions. A rectangular insulating substrate;
A glaze layer formed on a surface of the insulating substrate having a first protrusion and a second protrusion extending along a long side of the insulating substrate;
Heating resistors arranged at intervals along the long side and extending over the two ridges,
Electrodes connected to the heating resistor at both ends in the sub-scanning direction;
A protective film covering the heating resistor and the electrode;
A thermal print head comprising:

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