JPH10202931A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase density of dots in a thermal head and maintain a contact pressure between the thermal head and a printing medium at an appropriate level. SOLUTION: Two arrays of thermal resistors are arranged, in a subscan direction, on one of the faces of a heat sink 4. The two arrays of thermal resistors are bonded to each of the peaks of an insulating substrate 5 of chevron cross-section having two peaks, and the heating parts of the arrays of thermal resistors are arranged, at an equal interval L, in a main scan direction. Further, the two arrays of thermal resistors have the heating parts deviated by L/2 from each other in the main scan direction. In addition, the two arrays of thermal resistors can be formed by arranging plural independent thermal resistors at an equal interval in the maim scan direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head for thermal recording or thermal transfer recording, and more particularly to a card printer, a bar code printer, a video printer, and the like.
The present invention relates to a thermal head suitable for high-density recording when applied to a ticket vending machine or the like.

[0002]

2. Description of the Related Art An example of a conventionally known thermal head is shown in FIGS. FIG. 6 is a plan view of a main part of a conventional thermal head, FIG. 7 is a sectional view taken along the line XX 'in FIG. 6, and FIG. 8 is a sectional view taken along the line YY'. In these figures, individual electrodes 105 are placed on a flat insulating substrate 100.
And the common electrode 106 are formed. The common electrode 1
A large number of projections 107 are formed at regular intervals in 06, and the common electrode 106 as a whole has a comb shape.

The tip portion of the individual electrode 105 is formed so as to be located in the middle of two adjacent projections 107 of the common electrode 106, and the individual electrodes 105 and the projections 107 of the common electrode 106 are alternately arranged at equal intervals. Lined up. Two strip-shaped heating resistors 101a, 101 arranged in parallel with each other
b so that the projection 107 and the individual electrode 10 are electrically connected to the projection 107 and the individual electrode 105.
5 are formed on top of each other. The individual electrodes 105 are electrically connected by wire bonding or the like to a driving IC (not shown) mounted on the side opposite to the side on which the common electrode 106 is disposed. An example of a thermal head having such a high-density arrangement is disclosed in JP-A-4-2907.
No. 56 discloses this.

[0004]

The above-mentioned conventional thermal head has the following problems. In the conventional high-density type thermal head, as shown in FIG.
A portion which is disposed so as to cross in a direction perpendicular to a and 101b and is sandwiched between the individual electrode 105 and the projection 107 of the common electrode 106 on both sides becomes a heat generation region. So, for example,
When a current is supplied to energize the heat-generating region 108a, the heat-generating region 108a also has a thermal effect on the adjacent heat-generating regions 108b and 108c.
b, 108c are easily affected by heat due to energization. As described above, the heating region affected by the adjacent portion is finally overlapped with the heating region of the other strip-shaped heating resistor, and when a desired print is obtained, only the desired heating region is reliably heated. As a result, the outline of each heat generating area becomes unclear, and as a result, a clear print cannot be obtained.

[0005] The two strip-shaped heating resistors 101
a and 101b are not only disposed on the flat insulating substrate 100, but also because the wear-resistant layer 104 is formed on the strip-shaped heating resistors 101a and 101b as shown in FIGS. The portions directly above the strip-shaped heating resistors 101a and 101b are relatively flat. For this reason, the printing medium comes into contact with almost the entire surface of the wear-resistant layer 104, and the force for pressing the printing medium against the belt-shaped heating resistors 101a and 101b is dispersed. Therefore, the printing medium can be
Further, in order to uniformly press the belt-shaped heating elements 101a and 101b, the pressing force must be increased, and as a result, there is a problem that the resistance when the print medium passes through the thermal head increases. Was.

Further, in the transport of a hard print medium,
There is also a problem that the protruding portion of the individual electrode 105 and a driving IC (not shown) connected to the individual electrode 105 becomes an obstacle, and the printing between the printing medium and the strip-shaped heating resistor is incomplete and printing becomes unclear. there were.

The present invention solves the above-mentioned problems, and in various printers, it is possible to increase the quality of printing and printing by increasing the density, and to improve the adaptability to a rigid printing medium such as a plastic card. It is another object of the present invention to provide a thermal head capable of increasing a degree of freedom regarding a printing medium traveling method.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve the object, the present invention provides a thermal head in which heating resistors are arranged in two rows in the sub-scanning line direction on one surface of a heat sink. The two heating resistor rows are formed at respective peaks on an insulating substrate having a mountain-shaped cross section having two peaks, and the heating portions of the heating resistor rows are arranged at equal intervals L in the main scanning direction. Between the two heating resistor rows,
The first feature is that the heat generating portions are shifted from each other by L / 2 in the main scanning direction. In addition, the second electrode is arranged in the middle of the two heating resistor arrays, and the individual electrodes are arranged on the side of the two heating resistor arrays opposite to the side on which the common electrode is arranged. There are two features.

Further, the present invention has a third feature in that the two heating resistor rows are arranged with a plurality of independent heating resistors at regular intervals in the main scanning direction. Further, the present invention provides
A fourth feature is that the interval between the two heating resistor arrays in the sub-scanning line direction is set to an integral multiple of 1/2 of the interval L between the heating portions.

According to the first to fourth features, since the heating resistor array is formed at the peak of the chevron shape of the insulating substrate, the pressing force of the printing medium pressed by the heating resistor array is uniform. And stabilize. Further, since the heating resistor array is at the peak, that is, at the top, there is no protruding portion that hinders the printing medium from moving relative to the heating resistor array.

In particular, according to the third feature, since the adjacent heat-generating portions are not close to each other, it is possible to reduce the influence of heat on the adjacent heat-generating resistors in the energized state. According to the fourth feature, when the aspect ratio of the dot distribution is set to 1: 1, the energization timing for one heating resistor row and the other heating resistor row can be simplified.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a plan view of a thermal head according to the present invention, and FIG. 2 is a cross-sectional view taken along line CC 'of FIG. Also, FIG.
FIG. 5 is a diagram showing the heat generating portion main body in detail. In particular, FIG. 3 is a plan view of a main part of the thermal head 1, and FIG.
FIG. 5 is a cross-sectional view of FIG.

In FIG. 1 and FIG.
Is composed of a heating unit main body 2, a wiring board 3 for supplying power to the heating unit main body 2, and a heat sink 4 supporting the heating unit main body 2 and the wiring board 3. The heat sink 4 is made of a metal having good heat conductivity, such as aluminum having a rectangular parallelepiped shape.

The heat generating portion main body 2 provided on one surface of the heat sink 4 is provided near the center of the surface of the heat sink 4 and along the longitudinal direction of the heat sink 4, that is, in the main scanning direction at the time of printing. And a plurality of (in this example, eight on each side) driving ICs 6 disposed on both sides of the insulating substrate 5. The insulating substrate 5 is made of, for example, alumina. The wiring board 3 includes a wiring body and a base such as glass epoxy for supporting or protecting the wiring body. The wiring board 3 includes a portion 3a on which the driving IC 6 is mounted, and an extension portion 3
b, each of which is closely attached to the heat sink 4 and joined to the heat sink 4 with an adhesive or the like. Thus, the width of the thermal head 1 in the sub-scanning direction can be reduced by dividing the wiring board 3 into two parts 3a and 3b and bending the wiring board 3 while making the wiring board 3 hard using glass epoxy. .

The insulating substrate 5 forms a mountain shape having two peaks as understood from the cross-sectional shape of FIG. 2, and as shown in FIGS. 3 to 5, each of the two peaks is formed. The heating resistor 10 is formed in a stepping stone shape at predetermined intervals. Individual electrodes 12 individually connected to the heating resistor 10
Is connected to the driving IC 6 by wire bonding. Further, the driving IC 6 is connected to a power supply terminal (not shown) included in the portion 3a of the wiring board 3 by wire bonding.

On the other hand, the heating resistor 10 has a common electrode 1
1, and the common electrode 11 is connected to the power supply terminal 7 (see FIG. 1). Power supply terminal 7 and power supply drive IC
6 is entirely covered with a protective resin 9, and the driving IC 6 can be further covered with a protective cover 8 if necessary. In FIG. 1, the protective cover 8 is not shown. Next, the heating unit main body 2 will be described in detail. 3 to 5, a plurality of heating resistors 10 are formed on the insulating substrate 5 by, for example, a CVD method. The plurality of heating resistors 10 are positioned at the respective peaks of the two peaks of the insulating substrate 5 and are arranged in a straight line in the main scanning direction to form two heating resistor arrays 10a and 10b. Two heating resistor arrays 1
The peaks are formed in a straight line in the main scanning direction so that 0a and 10b are parallel to each other. Each heating resistor row 1
In 0a and 10b, the individual heating resistors 10 are arranged at equal intervals L in the main scanning direction, but the two heating resistor arrays 10a and 10b are shifted from each other by L / 2 in the main scanning direction. That is, the heating resistor arrays 10a and 10b are arranged in a staggered manner. By shifting the two heating resistor arrays 10a and 10b by L / 2 in this manner, the interval L between the heating resistor arrays 10a and 10b becomes
That is, it is sufficient to double the dot interval required as a product specification. That is, when a dot density of 600 DPI is required as a product specification, the interval L is 1 of 600 DPI.
The interval may correspond to a dot density of 300 DPI of / 2.

The interval between the heating resistor arrays 10a and 10b, that is, the interval D in the sub-scanning direction orthogonal to the main scanning direction is defined as the interval L between the heating resistors 10 for the reason described later.
Is preferably set to an integral multiple of 1/2 of the above. That is, [D =
(L / 2) × n, where n is an integer]. For example, when the dot density required for printing is 600 DPI, n is appropriately set to 64 in consideration of digital processing in energization control and current capacity of the common electrode.

Further, a common electrode 11 for supplying power to the heating resistor 10 and a plurality of individual electrodes 12 arranged on both sides of the common electrode 11 are provided. These electrodes 11,
12 can be formed by thin film technology such as photolithography. The common electrode 11 is connected to the power supply terminal 7 and the individual electrode 12 is electrically connected to the driving IC 6 by wire bonding. The heating resistor 10, the common electrode 11, and the individual electrodes 12 are covered with a wear-resistant layer 13 so as to withstand contact with a print medium.

Subsequently, the heating resistor arrays 10a, 10b
The reason why the interval D in the sub-scanning direction is set as described above will be described. In thermal recording or thermal transfer recording, a desired one of the plurality of heating resistors 10 is energized to generate heat, and a portion of the thermal paper or ink ribbon facing the heating resistor 10 is connected to the heating resistor 10. The color is generated in the size of the dot corresponding to the size of the dot, or the color is transferred to the print medium, and a character, an image, and the like are obtained by the aggregate of the dots.

Feeding of print medium (feed in the sub-scanning line direction)
Is usually performed so that the dot arrangement is square, in other words, the ratio of the dot intervals in the main scanning direction and the sub-scanning direction (vertical and horizontal ratio) is 1: 1. That is, the dot interval in the main scanning line direction is determined by １ ／ of the arrangement interval L of the heating resistors, and the dot interval in the sub-scanning direction is determined so that the feed amount of the print medium is L / 2. Therefore, when odd-numbered dots in the main scanning direction are printed by the heating resistor 10a and even-numbered dots are printed by the heating resistor 10b, the odd-numbered dot and the even-numbered dot are aligned so that the aspect ratio is square. For this purpose, the interval D is preferably set to an integer multiple of the dot interval, that is, L / 2.

The interval D is preferably set as described above in order to simplify the timing of energizing the heating resistor arrays 10a and 10b and simplify the energizing control. That is, after energizing the preceding heating resistor (for example, 10a), energizing the subsequent heating resistor (for example, 10b) may be performed at the timing when the print medium is fed n times.
In this manner, printing without deviation between print dots is performed by simple energization control. As an example, the dot spacing or L
/ 2 can be set in the range of 42.5 to 43 μm, and the interval D can be set in the range of 2 to 2.5 mm.

Since the driving ICs 6 are distributed to the respective heating resistor arrays 10a and 10b, the mounting density can be reduced, the connection by wire bonding does not become too dense, and the manufacturing is convenient.

As described above, according to the present embodiment, since the heating resistors 10 are arranged in a staggered arrangement, the arrangement interval of the heating resistors 10 can be approximately double the interval corresponding to the required dot density. As a result, the mounting interval of the driving ICs 6 can be doubled as compared with the one in which the driving ICs 6 are arranged in one row, and it is possible to meet the demand (specification) for the high density of the thermal head 1.

Further, since the heating resistor 10 is arranged at the peak of the two peaks of the insulating substrate 5, the contact surface with the print medium becomes small and the pressing force increases, so that the pressing force is stabilized. Further, since the common electrode 11 is formed along the ridges of the insulating substrate 5, the creepage length of the common electrode 11 between the heating resistor arrays 10a and 10b is smaller than that in the case where a flat insulating substrate is used. Can be long. As a result, since the electric resistance can be reduced, there is an advantage that a loss at the time of energization is reduced and an electric capacity can be increased.

In the present embodiment, a plurality of heating resistors 10 are arranged. However, for example, in the thermal head shown in FIG. 6, the insulating substrate 100 is modified to have two peaks like the insulating substrate 5. However, if the strip-shaped heating resistors 101a and 101b are arranged at the peak, a certain effect can be expected in that the contact surface with the print medium becomes small and the pressing force is stabilized.

[0026]

As is apparent from the above description, according to the first to fourth aspects of the present invention, since the heating resistor array is formed at the peak of the mountain shape of the insulating substrate, the heating resistor is formed. The pressing force of the printing medium pressed in the rows is made uniform and stable. As a result, it is possible to reduce design restrictions such as the shape and arrangement of the platen roller for pressing the print medium and the heat generating portion against each other.

Further, since the heat-generating portion becomes the most protruding portion, the running surface of the print medium does not have any other obstacles, so that printing can be easily performed even on a hard print medium which is hardly deformed. Further, since the printing medium can be easily moved in both directions, a highly versatile high-density thermal head can be provided.

In particular, according to the third aspect of the present invention, since the thermal head is formed by a plurality of independent heating resistors, the thermal effect due to the current supply from adjacent heating resistors can be reduced.

Further, according to the fourth aspect of the present invention, the timing of energizing the two heating resistor arrays can be simplified with respect to the heating resistor of high density, so that alignment in printing is easy. High quality can be achieved in printing or printing by various printers.

[Brief description of the drawings]

FIG. 1 is a plan view of a thermal head according to an embodiment of the present invention.

FIG. 2 is a sectional view of a thermal head according to an embodiment of the present invention.

FIG. 3 is a plan view of a main part of a thermal head according to an embodiment of the present invention.

FIG. 4 is a sectional view of a main part of a thermal head according to an embodiment of the present invention.

FIG. 5 is a sectional view of a main part of a thermal head according to an embodiment of the present invention.

FIG. 6 is a plan view of a main part of a conventional thermal head.

FIG. 7 is a sectional view of a main part of a conventional thermal head.

FIG. 8 is a sectional view of a main part of a conventional thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Thermal head, 3 ... Wiring board, 4 ... Heat sink, 5 ... Insulating board, 6 ... Driving IC, 8 ... IC protection cover, 10 ... Heating resistor, 10a, 10b ...
Heating resistor array, 11: common electrode, 12: individual electrode,
13: Wear-resistant layer

Claims (4)

[Claims] 1. A heat sink, an insulating substrate mounted on the heat sink and having a mountain-shaped cross section in a sub-scanning direction having two peaks, formed at each peak of the insulating substrate, and formed along the peaks. It comprises two heating resistor arrays extending in the main scanning direction, and a common electrode and an individual electrode for supplying power to each of the heating resistor arrays. The sandwiched heat-generating portions are arranged at equal intervals L in the main scanning direction.
The thermal head according to claim 1, wherein the heating portions are shifted from each other by L / 2 in the main scanning direction. 2. The common electrode is arranged in the middle of the two heating resistor arrays, and the individual electrode is arranged on the side of the two heating resistor arrays opposite to the side on which the common electrode is arranged. The thermal head according to claim 1, wherein: 3. The two heating resistor arrays are each formed by arranging a plurality of independent heating resistors at equal intervals.
The described thermal head. 4. The apparatus according to claim 1, wherein an interval between the two heating resistor arrays in the sub-scanning line direction is set to an integral multiple of 1/2 of an interval L between the heating portions. A thermal head according to any of the above.