JPH106543A - Thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To apply proper power by detecting accuragte temp. to enhance the quality of a printing image by embedding a temp. detection element in the recessed part formed on the upper surface of an insulating substrate and controlling the Jule heat value of a heating resistor corresponding to the detected temp. SOLUTION: Conductive layers 3a, 3b; 3c; 3d, 3e are provided on the upper surface of an insulating substrate 1 and apply predetermined power to heating resistors 2 to generate Jule heat and the conductive layer 3c supplies a printing control signal to a driver IC4 and the conductive layers 3d, 3e transmit the signal of a temp. detection element to an external electric circuit. The driver IC4 is provided in a recessed part 1a provided at a predetermined distance from the heating resistors 2 and the temp. detection element 5 is provided in a recessed part 1b and the temp. of the heating resistors 2 is controlled by this signal. Therefore, the temp. in the vicinity of the heating resistors is accurately detected within a short time and, even if medium contrast printing or high speed printing is performed, proper power is applied to the heating resistors 2 to enhance printing quality.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated as a printer mechanism of a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, a thermal head incorporated as a printer mechanism of a word processor or the like is, for example, as shown in FIG. 4, an alumina ceramic having a plurality of heating resistors 12, a driver IC 13, a conductive layer 14 and the like attached to an upper surface thereof. Wiring board (not shown) and a flexible wiring board 15 to which a connector 16 is attached.
And a structure in which the conductive layer 14 on the insulating substrate 11 is electrically connected to the wiring conductor of the flexible wiring substrate 15 by soldering or the like.

Such a conventional thermal head selectively causes the heating resistor 12 to generate Joule heat in accordance with the driving of the driver IC 13 and conducts the generated heat to a heat-sensitive recording medium, thereby performing predetermined printing on the heat-sensitive recording medium. It functions as a thermal head by forming an image.

In the above-described conventional thermal head, a temperature detecting element such as a thermistor is provided on the flexible wiring board 14 in order to monitor the temperature state of the thermal head.
6, the power applied to the heating resistor 12 is adjusted based on the temperature information from the temperature detecting element 16.

[0005]

However, in such a conventional thermal head, the temperature detecting element 1 is required.
6 is disposed at a position relatively far from the heating resistor 12 (such as on the flexible wiring board 14), it takes a little time for the heat generated by the heating resistor 12 to be transmitted to the temperature detecting element 16. Or a heat is dissipated into the air during the process, and a large difference is generated between the temperature detected by the element 6 and the temperature near the actual heating resistor. For this reason,
When performing halftone printing, high-speed printing, or the like in which the applied power to the heating resistor 12 needs to be controlled with high precision, appropriate power cannot be applied to the heating resistor 12 and high-quality printing is performed. It was extremely difficult to do.

In order to solve the above-mentioned disadvantage, it is conceivable to dispose the temperature detecting element 16 on the insulating substrate 11.

However, when the temperature detecting element 16 is arranged on the insulating substrate 11, the temperature detecting element 16 protrudes from the upper surface of the insulating substrate 11 in the vicinity of the heating resistor 12, so that the heat-sensitive recording medium is not printed during printing. Temperature detection element 16
In particular, when printing is performed on a medium that is difficult to bend such as a plastic card, a drawback that the medium cannot be stably run is induced.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and comprises an insulating substrate having a plurality of heating resistors arranged on an upper surface thereof, and a plurality of the heating resistors selectively. A thermal head for performing printing by making a thermal recording medium slidably contact the heating resistor, wherein a concave portion is formed on an upper surface of the insulating substrate, and a temperature is detected in the concave portion. The temperature of the insulating substrate is detected by burying the element, and the amount of Joule heat generated by the heating resistor is controlled according to the temperature of the insulating substrate.

The thermal head according to the present invention is characterized in that a concave portion is formed on the upper surface of the insulating substrate and the driver IC is embedded in the concave portion.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing one embodiment of the thermal head of the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG.
1 is an insulating substrate, 1a and 1b are concave portions, 2 is a heating resistor, 4 is a driver IC, 5 is a temperature detecting element, and 3a and 3b are power supply to the heating resistor 2. A conductive layer for supplying a signal to the driver IC 4;
Reference numerals 3d and 3e denote conductive layers for temperature detecting elements, and 7 denotes a flexible wiring board.

The insulating substrate 1 has a thermal conductivity of 0.9 to 26 W.
/ M · k, about 1 mm thick, made of an electrically insulating material such as glass or alumina ceramics.
When formed of alumina ceramics, alumina,
A ceramic green sheet is formed by adding a suitable organic solvent to a ceramic raw material powder such as silica and magnesia, and adding a solvent to form a slurry and adopting a conventionally known doctor blade method or a calender roll method. Thereafter, the ceramic green sheet is manufactured by stamping into a predetermined shape and firing at a high temperature.

On the upper surface of the insulating substrate 1, a plurality of heating resistors 2 arranged linearly,
And a conductive layer 3c connected to the input terminal electrode of the driver IC4.
And a conductive layer 3 connected to a terminal electrode of the temperature detecting element 5
d and 3e are respectively attached.

Since the heating resistor 2 is made of tantalum nitride or the like and has a predetermined electric resistivity, power from an external power supply is applied through a pair of conductive layers 3a and 3b. Then, Joule heat is generated, and a predetermined temperature required to form a print image on the thermal recording medium, for example, 2
It generates heat at a temperature of 00 to 350 ° C.

On the other hand, the conductive layers 3a to 3e are made of a metal such as aluminum or copper, and the conductive layers 3a and 3b function to apply a predetermined power to each of the heating resistors 2 described above.
The conductive layer 3c has a function of supplying a print control signal and the like to the driver IC 4, and the conductive layers 3d and 3e have a function of transmitting temperature information from the temperature detecting element 5 to an external electric circuit (a control circuit of the printer main body). Do

The heating resistor 2 and the conductive layers 3a to 3e
For example, by adopting a conventionally known sputtering method and photolithography technique, they are respectively attached to the upper surface of the insulating substrate 1 with a predetermined pattern and a predetermined thickness.

On the upper surface of the insulating substrate 1 on which the heating resistor 2 and the like are attached, a position separated by a predetermined distance from the heating resistor 2 (for example, when the thickness of the insulating substrate 11 is 1 mm, the heating resistor At a position 1.5 mm away from 2)
a, 1b are formed, a plurality of driver ICs 4 are provided in the recess 1a, and a temperature detecting element 5 such as a chip thermistor is provided in the recess 1b. It is embedded so as to be arranged in the same plane as the upper surface.

The driver IC 4 includes a pair of conductive layers 3.
a, 3b for controlling the on / off of the power applied to the heating resistor 2 via the heating resistor 2, and includes a logic circuit such as a switching transistor connected to each conductive layer 3a. A plurality of output terminal electrodes for connecting the output side of the switching transistor to the conductive layer 3a, a ground terminal electrode (not shown) for connecting the switching transistor to a reference potential, and an external print control signal Through a conductive layer 3c or the like.
And an input terminal electrode for supplying the power to the input terminal.
The ground terminal electrode of the driver IC 4 is for applying power from an external power supply to the respective heating resistors 2 via the conductive layer 3a, the switching transistor of the driver IC 4, and the like, and this is maintained at a reference potential. Thus, a predetermined potential difference is provided between the conductive layer 3b and the conductive layer 3b.

On the other hand, the temperature detecting element 5 is for detecting the temperature of the insulating substrate 1.
Is transmitted to an external electric circuit (such as a control circuit of the printer body), the Joule heat amount of the heat generating resistor 2 is controlled according to the temperature state of the insulating substrate 1 by a command from the external electric circuit. Will be done.

As described above, the concave portion 1b is formed on the upper surface of the insulating substrate 1 on which the plurality of heating resistors 2 are attached, and the temperature detecting element 5 is embedded in the concave portion 1b.
The temperature detecting element 5 can be arranged close to the heating resistor 2, and the temperature near the heating resistor 2 can be accurately detected in a short time. As a result, even when performing halftone printing or high-speed printing, appropriate power can always be applied to the heating resistor 2 and printing quality is improved.

In addition, since the temperature detecting element 5 and the driver IC 4 are embedded in the concave portions 1a and 1b of the insulating substrate 1 and there is nothing protruding from the upper surface of the insulating substrate 1, the printing is not performed. The temperature detecting element 5 and the driver IC 4 do not hinder the running of the thermosensitive recording medium or the like, and the medium can run stably even when printing is performed on a hard-to-bend medium such as a plastic card. be able to.

In this case, if the temperature detecting element 5 is disposed at a position 0.6 mm to 12.0 mm away from the heating resistor 2, for example, when performing halftone printing of 256 gradations or more. Even if it does, it is possible to finely control the electric power applied to the heating resistor 2, and it is possible to effectively prevent the occurrence of uneven heat storage or the like due to the provision of the concave portion 1b. Therefore, it is preferable that the temperature detecting element 5 is disposed at a position 0.6 mm to 12.0 mm away from the heating resistor 2.

The recesses 1a, 1a, 1b,
b is formed by processing the upper surface of the insulating substrate 1 using a laser or the like. At this time, if chamfering such as R-surface processing or C-surface processing is performed on the openings of the concave portions 1a and 1b, the driver IC 4 and the temperature detecting element 5 can be easily embedded in the concave portions 1a and 1b. Driver IC
It is also possible to effectively prevent the resin material 6 filled between the substrate 4 and the recess 1a from rising from the upper surface of the insulating substrate 1 due to surface tension or the like. Therefore, the concave portions 1a, 1
It is preferable that a predetermined chamfer is applied to the opening b.

The electrical connection between the conductive layers 3a to 3e, the driver IC 4, and the terminal electrodes of the temperature detecting element 5 is as follows.
This is performed at the same time as pattern formation of the conductive layers 3a to 3e. Specifically, first, the driver IC 4 and the temperature detecting element 5 are arranged such that the surface on which the terminal electrodes are provided is arranged in the same plane as the upper surface of the insulating substrate 1.
a, 1b, and then the conductive layers 3a to 3e
Is formed by the above-described pattern forming method (sputtering method and photolithography technique) such that one end thereof extends over each terminal electrode of the driver IC 4 and the temperature detecting element 5. A resin material 6 made of polyimide resin or the like is filled between the concave grooves 1a and 1b and the driver IC 4 and the temperature detecting element 5,
By appropriately adjusting the filling amount of the resin material 6, the upper surface of the driver IC 4 is set to the same height as the upper surface of the insulating substrate 1. At this time, as a material forming the resin material 6,
It is preferable that the coefficient of thermal expansion be between alumina ceramics forming the insulating substrate 1 and silicon forming the driver IC 4. By using such a material, the conductive layer caused by a change in volume of the resin material 6 or the like is preferable. 3a ~
3e can be effectively prevented from being damaged.

The above-mentioned insulating substrate 1 has a short side (a side along a direction orthogonal to the arrangement direction of the heating resistors 2).
In addition, a flexible wiring board 7 is connected to a position outside the passage area of the thermal recording medium.

As described above, the flexible wiring board 7 is for connecting the thermal head to an external electric circuit (printer main body), and is connected to the insulating substrate 1 at a position outside the passage area of the thermal recording medium. Therefore, such a connecting portion does not hinder the running of the thermal recording medium, and has a connecting structure for stably running the medium.

The flexible wiring board 7 has a plurality of wiring conductors connected to the conductive layers 3a to 3e on the insulating substrate 1, for example, sandwiched between two films made of polyimide resin. It has a structure in which a connector (not shown) or the like is attached to one end.

Further, the insulating substrate 1 and the flexible wiring substrate 7 are mounted on a heat radiating plate (not shown) made of a good heat conductive material such as aluminum via an adhesive such as a double-sided tape. The heat in the insulating substrate 1 is sequentially radiated to the atmosphere by such a heat sink.

Thus, in the above-described thermal head, a predetermined power is applied between the conductive layers 3a and 3b as the driver IC 4 is driven, and the heating resistor 2 selectively generates Joule heat based on a print control signal. Heating resistor 2
The thermal recording medium functions as a thermal head by sliding the thermal recording medium into contact with the recording medium and forming a predetermined printed image on the thermal recording medium.

It should be noted that the present invention is not limited to the above-described embodiment, and various changes and improvements can be made without departing from the scope of the present invention. Only one is formed, and the temperature detecting element and the driver IC are both buried in it. Alternatively, as the temperature detecting element, a thermistor with a lead may be used instead of the chip-type thermistor. The same effects as in the above embodiment can be obtained.

In the above-described embodiment, a thermistor having a pair of terminal electrodes provided on one principal surface of the chip is used as the temperature detecting element. A thermistor provided on each of the surfaces may be used. In this case, at least one of the terminal electrodes is buried in the concave portion. Therefore, in order to electrically connect the terminal electrode to the conductive layer or the like on the insulating substrate, a conductor or the like for lead-out is separately provided on the wall surface or the like of the concave portion. You only have to wear it.

[0032]

According to the thermal head of the present invention, a plurality of heating resistors and concave portions are provided on the upper surface of the insulating substrate, and the temperature detecting element is embedded in the concave portions.
The temperature detection element can be arranged near the heating resistor, and the temperature near the heating resistor can be accurately detected in a short time. As a result, even in the case of performing halftone printing, high-speed printing, or the like, it becomes possible to apply appropriate power to the heating resistor, and the printing quality is improved.

Further, according to the thermal head of the present invention, since the temperature detecting element is embedded in the concave portion of the insulating substrate,
The temperature detecting element does not hinder the running of the thermal recording medium or the like during printing, and the medium can run stably even when printing is performed on a hard-to-bend medium such as a plastic card. It is possible.

[Brief description of the drawings]

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

FIG. 2 is a sectional view taken along line XX of FIG.

FIG. 3 is a sectional view taken along line YY of FIG. 1;

FIG. 4 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 1 ... Insulating substrate 1a, 1b ... Recess 2 ... Heat generating resistor 3a-3e ... Conductive layer 4 ... ····· Driver IC 5 ········································ Resin material 7 ····················· Flexible wiring board

Claims (2)

[Claims] An insulating substrate having a plurality of heating resistors arranged on an upper surface thereof, and a driver IC for selectively generating Joule heat from the plurality of heating resistors, wherein thermal recording is performed on the heating resistor. A thermal head for performing printing by sliding a medium, wherein a concave portion is formed on an upper surface of the insulating substrate, and a temperature detecting element is buried in the concave portion to detect a temperature of the insulating substrate. A thermal head characterized in that the amount of Joule heat generated by a heating resistor is controlled in accordance with the value. 2. The thermal head according to claim 1, wherein a concave portion is formed on an upper surface of the insulating substrate, and the driver IC is embedded in the concave portion.