JPH04185358A - Thermal head - Google Patents

Abstract

PURPOSE:To ensure electric consumption savings, speed acceleration and cost reduction by bonding and laminating polyimide film as a heat accumulation layer on a heat resistant resin substrate. CONSTITUTION:Polyimide film as a heat accumulation layer 12 has a thermal conductivity of about 1/10 of a glass glaze layer, so that the heat accumulation layer 12 can be thinned to a film thickness of 6mum to 20mum. For this reason, the thermal capacity of the heat accumulation layer 12 is reduced to realize electric consumption saving. Therefore, the thermal diffusion of the heat accumulation layer 12 to a heat resistant resin substrate 11 is insignificant, and in image does not come out cleary even if an applied pulse is of a low power level. On the other hand, if the application of a pulse is discontinued, heat is diffused by a heat release layer of the heat resistant resin substrate 1 and the substrate 1 is cooled off rapidly because of the adequately low heat accumulation capacity of the heat accumulation layer 12. Also a tailing phenomenon does not occur, and rapid printing is possible. In addition, it is possible to save many manhours and reduce labor cost by bonding and laminating polyimide film on the heat resistant resin substrate 11.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure of a thermal head used in thermal printers, facsimile machines, and the like.

<Prior art> In recent years, printing devices such as facsimiles and thermal printers have
The market demands lower power consumption, faster speeds, lower prices, etc.

Therefore, in a conventional thermal head, as shown in FIG. 4, a glaze layer 2 made of high melting point glass and a plurality of heating resistors 3 arranged in the main scanning direction are provided on a ceramic substrate l made of alumina or the like. A common electrode 4 and individual electrodes 5 are provided for applying and supplying voltage to the heat generating resistor 3, and the heat generating resistor 3 is further protected by a protective film 6.

FIG. 5 shows a diagram of the entire configuration of a thermal head using a ceramic substrate.

As shown in the figure, a ceramic substrate I on which a heating resistor 3 and the like are formed is combined with a double-sided copper-clad printed wiring board 7, and the electrical connection wiring between both substrates 1.7 is connected to the double-sided copper-clad printed wiring board. Drive element (driver IC) 8 on top of 7
is mounted, and connections are made using bonding wires 88 such as gold wires.

In the figure, 9 is a head cover that protects the driver IC 8, and 10 is a connector for connecting an external circuit.

In the above configuration, when driving with an applied voltage of 24 V, pulse application time of 0.8 m5 ec, and pulse application period of 5 m5 ec in order to supply power to the heating resistor 3 and print on thermal paper, the power output is 0.3 W/dot. A higher applied voltage is required.

Furthermore, the process of forming the heat generating resistor 3 requires a manufacturing process of several hundred degrees or more, and the heat generation temperature required for printing instantaneously exceeds several hundred degrees.

For this reason, an expensive ceramic substrate 1 is used as a heat-resistant insulating substrate. However, ceramic substrates have poor workability and require the formation of through holes, etc. 1 In this case, they become expensive, so as mentioned above, the structure is divided into a ceramic substrate 1 and a double-sided copper-clad printed wiring board 7. is taking.

〉 Problems to be Solved by the Invention 〉 However, in the conventional thermal head in which a heating resistor 3, a current-carrying electrode 4.5, and a protective film 6 are formed on a ceramic substrate l on which a glaze layer 2, which is a heat storage layer, is formed, Since the thermal conductivity of the ceramic substrate l is high, the heat storage effect of the glaze layer 2 is not sufficiently exhibited.

Therefore, in order to fully utilize the heat storage effect of the glaze layer 2 and save power in the thermal head, the glaze layer 2, which is a heat storage layer, must be made thicker. If the glaze layer 2 is thickened, the amount of heat stored in the glaze layer 2 will increase, or even if the application pulse is stopped, printing will continue on the thermal paper, resulting in a so-called trailing phenomenon.

In order to eliminate this tailing phenomenon, it can be improved by forming the glaze layer 2 thinner to reduce the amount of heat storage, or by increasing the period of the applied pulse to release the heat of the glaze layer 2 to the ceramic substrate l.

However, in the former method, at the beginning of writing, heat diffusion into the ceramic substrate 1 is large, causing a blurring phenomenon due to insufficient applied power, and it is only possible to cope with power saving. Furthermore, the latter method cannot cope with higher speeds. That is,
No matter which method you use,
It is difficult to simultaneously reduce power consumption and increase speed.

Therefore, in order to achieve power saving and speed-up of the thermal head, we developed a thermal head that uses a heat-resistant resin substrate as the substrate, laminates polyimide resin as a heat storage layer, and provides a heating resistor on this heat storage layer. Proposed.

This heat-resistant resin board is preliminarily coated with copper foil on both sides, similar to conventional hard printed wiring boards.

Then, this copper foil is processed by photolithography etc.
A circuit pattern is formed for the arrangement of wiring electrodes, connectors, etc., including through holes.

Moreover, it is a circuit board that can be integrated with a heating resistor.

However, in this thermal head, the method for forming the polyimide resin that is the heat storage layer is to apply a polyimide face and temporarily cure it, then apply renost by photolithography, exposure, development, etching, resist peeling, and polyimide conversion. There are many steps such as curing, which increases production costs.

In view of the above, an object of the present invention is to provide a thermal head that can achieve power saving, high speed, and low cost at the same time.

Means for Solving the Problems> As shown in FIG. A driving element 14 for controlling current supply to the body 13, a connector 22 for connection with an external circuit, and a wiring pattern 18° 19 for connecting between the driving element I4 and the connector 22 are integrally formed and mounted. In the thermal head, as the heat storage layer 12, a polyimide film is adhesively laminated on a heat-resistant resin substrate 11.

In the above means for solving the problem, the polyimide film as the heat storage layer 12 has a thermal conductivity of about 1/10 of that of a conventional glass glaze layer, so the thickness of the heat storage layer I2 is reduced to 6.
It can be formed as thin as μIll to 20 μm. Therefore, the heat capacity of the heat storage layer 12 is reduced, and power saving can be achieved.

In this first step, at the beginning of printing, since the heat-resistant resin substrate 11 is used as the heat-resistant substrate, the heat diffusion of the heat storage layer 12 to the heat-resistant resin substrate II is small, and the blurring phenomenon occurs even with a small power applied pulse. Does not occur.

On the other hand, when the applied pulse is stopped, the heat capacity of the heat storage layer 12 is sufficiently small, so the heat is diffused by the heat dissipation layer of the heat-resistant resin substrate II and is quickly cooled down, allowing high-speed printing without causing the trailing phenomenon. becomes.

Furthermore, by adhesively laminating a polyimide film on the heat-resistant resin substrate 11, many of the processes such as polyimide face coating, temporary curing, lenost coating, exposure, development, etching, and resist peeling that are required when using a conventional polyimide varnish can be avoided. This process can be omitted and labor costs can be reduced.

Furthermore, the heating resistor 13 and the wiring patterns 18 and 19 that connect between the driving element 14 and the connector 22 can be integrated on the heat-resistant resin substrate II, reducing material costs and assembly costs. I can figure it out.

From the above, it is possible to achieve power saving, high speed, and low cost of the thermal head at the same time.

<Example> Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a cross-sectional view of a main part of a thermal head showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing its overall structure, and FIG. This is a surface that shows print density characteristics.

As shown in FIG. 1.2, the thermal head of this embodiment has a polyimide film (for example, manufactured by Upilex S Co., Ltd., Ube Industries) as a heat storage layer I2 on a heat-resistant resin substrate 11.
are laminated with adhesive, and are provided on the heat storage layer 12 with a plurality of heating resistors 13 and a driving element (driver IC) 14 for controlling energization of the heating resistor I3.

A common electrode 15 and individual electrodes 16 are provided for energizing the heating resistor 13.
The driver IC 14 is connected and fixed by face-down bonding or wire hop ink at the human electrode 19 and the wiring electrode I8 including the through hole 17 on the heat-resistant resin substrate 11, and the connection with an external circuit. A connector 22 for use is mounted.

Then, the wiring electrode 18 and the polyimide film I
The input electrodes 19 of the driver TCI 4 on the top 2 are connected and fixed by solder or the like, and are integrated on the heat-resistant resin substrate 11.

The heat-resistant resin substrate 11 is a double-sided copper-clad laminate in which copper foil is laminated on both sides of a layer of heat-resistant floss (eg, glass fiber) impregnated with heat-resistant resin (eg, EBOKINO).

Then, this heat-resistant resin board II is formed by drilling holes for through-holes 17 and copper plating, and then forming wiring electrodes 18 including through-holes I7 by photolithography, as in the case of commercially available double-sided through-hole printed wiring boards.
, a circuit pattern such as a heat dissipation layer 23 is formed, and then a solder resist 24 is applied to a predetermined portion by printing,
It is formed by curing this.

The heat storage layer 12 is formed by laminating and fixing a polyimide film of 6 μm to 20 μm on the heat dissipating layer 23 of the heat-resistant resin substrate 11 with an adhesive.

The heating resistors I3 are arranged at predetermined intervals in the main scanning direction, and are formed by photolithography by depositing TatN, Ta-5i-0, Ni-Cr, or the like by vapor deposition or sputtering.

The common electrode 15 and individual electrodes I6 are led out on the heating resistor 13, and the input electrode 19 of the driver IC 14 is formed on the individual electrode 16 side. These electrodes 15, 16, 19 are made of ALTi, CuNi,
It is made of Au and is formed into a predetermined pattern by photolithography after being sequentially formed into films by vapor deposition or sputtering.

Moreover, 5iAf! The protective film 21 is formed by coating ON or the like by vapor deposition, sputtering, or the like.

The common electrode 15 has a small current capacity because it is formed as a thin film, and the voltage drops at the center of the thermal head during printing, so that the density of the print becomes lighter as it approaches the center. In order to prevent this, a solder layer 25 is laminated with a constant thickness on the common electrode I5 by printing and reflowing a solder paste.

In addition, the input electrode 19 on the heat storage layer 12 and the heat-resistant resin substrate 1
．． Also for connection with the wiring electrode 18 on the top 1, a solder base 20 is printed and a solder layer 20 is laminated to a constant thickness by reflow.

Note that the solder layer 25 on the common electrode 15 and the wiring electrode I8
Reflow of the solder bumps of the upper solder layer 20 and the driver JC 14 by the face-down bonding method is performed in the same process to reduce production costs.

A method of manufacturing the above thermal head will be briefly explained.

First, a polyimide film is adhesively laminated as the heat storage layer 12 on the heat-resistant resin substrate 11 .

Then, on the heat storage layer 12, a heating resistor 13 and a common electrode 1 are disposed.
5 and individual electrodes 16 are formed, and the heating resistor 13, the common electrode 15, and the individual electrodes 16 are covered with a protective layer 21.

Thereafter, the driver IC 14 is connected and fixed to the individual electrode 16 and the manual electrode I9 by face-down bonding or wire bonding.

Then, wiring electrodes 18 including through-poles 17, connectors 22 for connection with external circuits, etc. are mounted on the heat-resistant resin substrate 11, and wiring electrodes 18 on the heat-resistant resin substrate 11 are mounted.
8 and the input electrode 19 on the heat storage layer I2 are connected and fixed by solder 20, and these are integrated on the heat-resistant resin substrate 11 to complete the process.

In the past, in order to provide a heat storage layer, a polyimide film was applied and temporarily cured, and then a number of steps were required, including resist application using photolithography, exposure, development and etching, resist peeling, and curing for polyimidation. However, by using a polyimide film as the heat storage layer 12, the step of forming the heat storage layer is only adhesive fixing of the polyimide film, and the production cost can be reduced.

In addition, by etching the copper foil on the heat-resistant resin substrate Il using photolithography or the like, dry/<-I
The input electrodes 19 of the CI4 and the wiring electrodes 18 for installing connectors etc. can be patterned and integrated with the heating resistor 13 on the heat-resistant resin substrate 11, reducing the material cost of the polyimide heat storage layer. reduction and assembly cost can be achieved.

Furthermore, since the polyimide film as the heat storage layer 12 has a thermal conductivity of about /lO of a conventional glaze layer, the thickness of a conventional glaze layer on a ceramic substrate is 60 μm to 80 μm. In contrast, the heat storage layer 12
The film thickness can be formed as thin as 6 μm to 20 μm. Therefore, the heat capacity of the heat storage layer 12 is reduced, and power saving can be achieved.

Therefore, at the beginning of printing, since the heat-resistant resin substrate 11 is used as the base substrate, the heat diffusion from the heat storage layer 12 to the heat-resistant resin substrate 11 is reduced, and even with a small power applied pulse, the blurring phenomenon is prevented. No occurrence 1 - On the other hand, when the applied pulse is stopped, the heat capacity of the heat storage layer 12 is sufficiently small, so the heat is diffused and quickly cooled by the heat dissipation layer 23 made of copper of the heat-resistant resin substrate 11, causing tailing. This phenomenon no longer occurs, and high-speed printing becomes possible.

As a result of the above, it is possible to simultaneously reduce the power consumption, speed, and cost of the thermal head.

In addition, FIG. 3 shows the print density characteristics with respect to the applied power. In the figure, (a) is for the thermal head of this embodiment, and (b) is for the conventional thermal head.

As is clear from the figure, it can be seen that the thermal head of this embodiment is improved by saving power in applied power compared to the conventional thermal head.

It should be noted that the present invention is not limited to the above embodiments, and it goes without saying that many modifications and changes can be made to the above embodiments within the scope of the present invention.

<Effects of the Invention> As is clear from the above description, according to the present invention, by adhesively laminating a polyimide film as a heat storage layer on a heat-resistant resin substrate, a polyimide film, which was conventionally required when forming a heat storage layer, can be removed. It is possible to eliminate many steps such as coating and temporarily curing Lennost coating by photolithography, exposure, development etching, and Lennost peeling.
It is possible to reduce production costs.

Furthermore, by etching the copper foil on the heat-resistant resin substrate using photolithography, it is possible to form a pattern for the wiring that connects the drive element and the connector, and to integrate these with the heating resistor on the heat-resistant resin substrate. Because I can,
Material costs and assembly costs can be reduced.

In addition, since the polyimide film used as the heat storage layer has a thermal conductivity of about 1/1O of that of a conventional glaze layer,
The thickness of the heat storage layer can be formed thin, the heat capacity of the heat storage layer is reduced, and power saving can be achieved.

Therefore, when the applied pulse is stopped, the heat is diffused by the heat dissipation layer made of copper on the heat-resistant resin substrate, and the heat is quickly cooled, and no trailing phenomenon occurs. High-speed printing is possible.

From the above, there is an excellent effect that the thermal head can simultaneously achieve power saving, high speed, and low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a main part of a thermal head showing one embodiment of the present invention, FIG. FIG. 4 is a sectional view of a main part of a conventional thermal head, and FIG. 5 is a sectional view showing the overall structure thereof. 11: Heat-resistant resin substrate, 12. Heat storage layer, 13: Heat generating resistor, 14: Drive element, I 8.19: Wiring pattern, 22
．． connector. Applicant: Nyab Co., Ltd.

Claims (1)

[Claims] On a heat-resistant resin substrate, a heat storage layer, a plurality of heat generating resistors,
In the thermal head, a driving element for controlling current flow to the heat generating resistor, a connector for connecting to an external circuit, and a wiring pattern for connecting between the driving element and the connector are integrally formed and mounted. A thermal head characterized in that a polyimide film is adhesively laminated on a heat-resistant resin substrate as a heat storage layer.