JP3389419B2 - Thermal head - Google Patents

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 such as a word processor and a facsimile.

[0002]

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

In such a conventional thermal head, Joule heat is selectively generated in the heating resistor 12 as the driver IC 13 is driven, and the generated heat is conducted to the heat-sensitive recording medium to perform predetermined printing on the heat-sensitive recording medium. It functions as a thermal head by forming an image.

In the conventional thermal head described above, the temperature detecting element 1 such as a thermistor is provided on the flexible wiring board 14 in order to monitor the temperature of the thermal head.
6 is attached, and the electric 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 used.
Since 6 is arranged 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 transferred to the temperature detecting element 16. There is a large difference between the temperature detected by the element 6 and the actual temperature in the vicinity of the heat-generating resistor due to heat generation or heat being dissipated into the atmosphere during the process. For this reason,
When performing halftone printing or high-speed printing in which the power applied to the heating resistor 12 must be controlled with high accuracy, it is not possible to apply appropriate power to the heating resistor 12 and the print quality is high. It was extremely difficult to achieve.

Therefore, in order to solve the above-mentioned drawback, it may be considered 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 projects from the upper surface of the insulating substrate 11 in the vicinity of the heat generating resistor 12, so that a thermal recording medium is formed during printing. Temperature detecting element 16
However, when printing is performed on a medium that is difficult to bend, such as a plastic card, there is a risk that the medium cannot run stably.

[0008]

SUMMARY OF THE INVENTION The present invention has been devised in view of the above-mentioned drawbacks, and an insulating substrate having a plurality of heating resistors and a plurality of conductive layers on its upper surface, and a plurality of heat generating members. A thermal head having a driver IC for selectively causing Joule heating of a resistor and a chip-shaped temperature detecting element for detecting the temperature of the insulating substrate, the insulating being located in the vicinity of the heating resistor. A recess is formed on the upper surface of the substrate, and a temperature detecting element is provided in the recess.
The element is embedded so that the upper surface of the element is arranged substantially in the same plane as the upper surface of the insulating substrate, and further, a part of the conductive layer on the insulating substrate is extended to a terminal electrode provided on the upper surface of the temperature detecting element. It is characterized by being present and electrically connected.

Further, in the thermal head of the present invention, the temperature detecting element is arranged in a range of 0.6 mm to 12.0 mm from the heating resistor.
It is characterized in that it is arranged at a distant position. Further, the thermal head of the present invention is characterized in that the opening of the recess is chamfered. Further, the thermal head of the present invention is characterized in that a recess in which the plurality of driver ICs are embedded is provided on the upper surface of the insulating substrate.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a plan view showing an embodiment of the thermal head of the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, and FIG. 3 is FIG.
2 is a sectional view taken along the line Y-Y of FIG. 1, 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, 3a and 3b are power supply to the heating resistor 2. Conductive layer, 3c is a conductive layer for supplying a signal to the driver IC 4,
3d and 3e are conductive layers for the temperature detecting element, and 7 is a flexible wiring board.

The insulating substrate 1 has a thermal conductivity of 0.9 to 26 W.
/ M · k and a thickness of about 1 mm are formed of an electrically insulating material such as glass or alumina ceramics,
When formed from alumina ceramics, alumina,
Silica, a suitable organic solvent to the ceramic raw material powder such as magnesia, to form a slurry by adding and mixing a solvent to form a ceramic green sheet by adopting a conventionally known doctor blade method or calender roll method, Then, the ceramic green sheet is punched into a predetermined shape and fired at a high temperature.

On the upper surface of the insulating substrate 1, a plurality of heating resistors 2 arranged linearly and the heating resistors 2 are arranged.
A pair of conductive layers 3a and 3b connected to both ends of the driver, and a conductive layer 3c connected to the input terminal electrode of the driver IC 4
And the conductive layer 3 connected to the terminal electrode of the temperature detecting element 5.
d and 3e are respectively applied.

Since the heating resistor 2 is made of tantalum nitride or the like and has a predetermined electric resistivity, electric power from an external power source is applied through the pair of conductive layers 3a and 3b. Then, Joule heat is generated and a predetermined temperature necessary to form a printed image on the thermosensitive recording medium, for example, 2
It exotherms to 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 have the function of applying a predetermined electric power to each of the heating resistors 2 described above.
The conductive layer 3c has a function of supplying a print control signal or the like to the driver IC 4, and the conductive layers 3d and 3e have a function of transmitting the temperature information from the temperature detecting element 5 to an external electric circuit (control circuit of the printer main body or the like). Do

These heating resistors 2 and conductive layers 3a to 3e
Is deposited on the upper surface of the insulating substrate 1 with a predetermined pattern and a predetermined thickness, for example, by adopting the conventionally known sputtering method and photolithography technique.

On the upper surface of the insulating substrate 1 on which the heat generating resistor 2 and the like are adhered, a position apart from the heat generating resistor 2 by a predetermined distance (for example, when the thickness of the insulating substrate 11 is 1 mm, the heat generating resistor 2 is used). The recess 1 at a position apart from 2 by about 1.5 mm)
a and 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 comprises a pair of conductive layers 3
It is for controlling ON / OFF of the electric power applied to the heating resistor 2 via a and 3b, and has a built-in logic circuit such as a switching transistor connected to each conductive layer 3a, and the upper surface thereof. 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 a print control signal from the outside. Through the conductive layer 3c, etc.
And an input terminal electrode for supplying to.
The ground terminal electrode of the driver IC 4 is for applying power from an external power source to each heating resistor 2 through the conductive layer 3a and the switching transistor of the driver IC 4, and the like is held at a reference potential. As a result, 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.
When the temperature information detected by is transmitted to an external electric circuit (control circuit of the printer body, etc.), the amount of Joule heat generated by the heating 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 recess 1b is formed on the upper surface of the insulating substrate 1 on which the plurality of heating resistors 2 are adhered, and the temperature detecting element 5 is embedded in the recess 1b.
The temperature detecting element 5 can be arranged close to the heating resistor 2, and the temperature in the vicinity of the heating resistor 2 can be accurately detected in a short time. As a result, even when performing halftone printing or high-speed printing, it is possible to always apply appropriate power to the heating resistor 2 and improve printing quality.

Moreover, since the temperature detecting element 5 and the driver IC 4 are embedded in the recesses 1a and 1b of the insulating substrate 1, and none of them protrudes from the upper surface of the insulating substrate 1, there is no need for printing. The temperature detection element 5 and the driver IC 4 do not hinder the running of a thermal recording medium or the like, and the medium is allowed to run stably even when printing is performed on a medium such as a plastic card that is difficult to bend. be able to.

In this case, if the temperature detecting element 5 is arranged at a position separated by 0.6 mm to 12.0 mm from the heating resistor 2, for example, halftone printing of 256 gradations or more is performed. Even if there is, 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 heat storage unevenness and the like due to the provision of the recess 1b. Therefore, it is preferable to dispose the temperature detecting element 5 at a position separated from the heating resistor 2 by 0.6 mm to 12.0 mm.

Incidentally, the concave portions 1a, 1 of the insulating substrate 1 as described above.
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 recesses 1a and 1b, the driver IC 4 and the temperature detecting element 5 can be easily embedded in the recesses 1a and 1b. Driver IC
It is also possible to effectively prevent the resin material 6 filled between the concave portion 4 and the concave portion 1a from rising above the upper surface of the insulating substrate 1 due to surface tension or the like. Therefore, the recesses 1a, 1 of the insulating substrate 1
It is preferable that a predetermined chamfer is applied to the opening of b.

The electrical connection between the conductive layers 3a-3e and the terminal electrodes of the driver IC 4 and the temperature detecting element 5 is as follows.
It is performed at the same time when the conductive layers 3a to 3e are patterned. Specifically, first, the driver IC 4 and the temperature detecting element 5 are arranged such that the surface on which the terminal electrode is provided is in the same plane as the upper surface of the insulating substrate 1 and the recess 1 of the insulating substrate 1 is formed.
a, 1b, and then the conductive layers 3a to 3e
Is formed by the above-mentioned pattern forming method (sputtering method and photolithography technology) so 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, 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 for forming the resin material 6,
It is preferable that the coefficient of thermal expansion be between the alumina ceramics forming the insulating substrate 1 and the silicon forming the driver IC 4, etc. By using such a material, the conductive layer caused by the volume change of the resin material 6 or the like. 3a ~
It is possible to effectively prevent damage to 3e.

The short side of the insulating substrate 1 described above (the side along the direction orthogonal to the arrangement direction of the heating resistors 2).
In addition, the 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 board 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 the connecting structure is provided for stable running of the medium.

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

Furthermore, the insulating substrate 1, the flexible wiring substrate 7 and the like are placed on a radiator plate (not shown) made of a material having good thermal conductivity such as aluminum via an adhesive such as a double-sided tape. The heat in the insulating substrate 1 is sequentially dissipated to the atmosphere by such a heat dissipation plate.

Thus, the above-described thermal head applies a predetermined electric power between the conductive layers 3a and 3b in accordance with the driving of the driver IC 4 to selectively cause the heating resistor 2 to generate Joule heat on the basis of the print control signal. Heating resistor 2
The thermal recording medium is brought into sliding contact with the above to form a predetermined print image on the thermal recording medium, thereby functioning as a thermal head.

The present invention is not limited to the above-described embodiment, and various modifications and improvements can be made without departing from the gist of the present invention. For example, a concave portion is formed on the upper surface of the insulating substrate. It is also possible to form only one and to embed the temperature detecting element and the driver IC together in it, or to use a thermistor with leads instead of the chip thermistor as the temperature detecting element. The same effect as that of the above embodiment is obtained.

[0031]

[0032]

According to the thermal head of the present invention, since the concave portion is formed on the upper surface of the insulating substrate located near the heating resistor and the temperature detecting element is embedded in the concave portion, the temperature detecting element is provided. Can be arranged in the vicinity of the heating resistor, and the temperature in the vicinity of the heating resistor can be accurately detected in a short time. As a result, even when performing halftone printing or high-speed printing, it is 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, by chamfering the opening of the recess, the opening of the recess is widened and the temperature detecting element is easily embedded, and the workability in embedding the temperature detecting element is improved. Therefore, the productivity of the thermal head can be further improved.

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

[Brief description of drawings]

FIG. 1 is a plan view showing an embodiment of a thermal head of 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.

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

[Explanation of symbols]

1 ... Insulating substrate 1a, 1b ... Recess 2 ・ ・ ・ ・ ・ ・ Heating resistor 3a to 3e ... Conductive layer 4 ... Driver IC 5 ... Temperature detection element 6 ... ・ ・ ・ Resin material 7 --- Flexible wiring board

─────────────────────────────────────────────────── --Continued from the front page (56) References JP-A 5-221004 (JP, A) JP-A 2-217261 (JP, A) JP-A 60-19561 (JP, A) JP-A 60- 168947 (JP, A) JP 62-255163 (JP, A) JP 1-196132 (JP, A) Actual flat 5-85640 (JP, U) JP 58-50947 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) B41J 2/335 B41J 2/345 B41J 3/365

Claims (4)

(57) [Claims] 1. A plurality of heating resistors and a plurality of conductors on the upper surface.
An insulating substrate provided with an electric layer and a driver IC for selectively causing Joule heat generation of the plurality of heating resistors
And a chip-shaped temperature sensor for detecting the temperature of the insulating substrate.
A thermal head having a degree detecting element, to form a recess on the upper surface of the insulating substrate located in the vicinity of the heating resistor, the temperature sensing element in the recess, the plain
Make sure that the upper surface of the child is approximately flush with the upper surface of the insulating substrate.
And a part of the conductive layer on the insulating substrate.
Extends over the terminal electrode provided on the upper surface of the temperature detection element
The thermal head is characterized by being electrically connected
De. 2. The temperature detecting element is formed from a heating resistor to 0.6.
The thermal head according to claim 1, wherein the thermal heads are arranged at positions separated by mm to 12.0 mm . 3. The chamfer is applied to the opening of the recess.
The server according to claim 1 or 2, characterized in that
Maruhead. 4. A top surface of the insulating substrate, the thermal head according to any one of claims 1 to 3, wherein the plurality of driver IC are provided with a recess to be buried.