JPH03205162A - Thermal head - Google Patents

Abstract

PURPOSE:To obtain a thermal head with adequate heat release capability without a radiator plate and excellent compatibility with sheets by using a heat resistant insulating resin substrate and a multilayer copper-plate heat-resistant insulating resin substrate. CONSTITUTION:A multilayer copper-plate heat-resistant insulating resin substrate 1 is a multilayer copper-plated plate consisting of sandwich-like laminated metal layers, for example, copper foils 3a to 3d between layers 2a to 2c of heat-resistant cloth impregnated with heat-resistant resin and on the both lateral surfaces. To manufacture the substrate 1, the same processing technique as applied to a hard printed circuit board such as an ordinary glass epoxy substrate can be easily used. Furthermore, multilayer wired boards with through-holes can be easily manufactured using the same processing technique as applied to the substrate 1. A thermal head is completed by mounting necessary parts such as ICs for drive control 9 which controls the drive of a thermal resistor 5 and parts of a drive control circuit and connector parts on the heat-resistant resin substrate 1 on which the thermal resistor 5 is formed. The thermal head 1 has a significantly increased heat release capability as its substrate 1 is composed of copper foils 3a to 3d, and does not require a radiator plate within a certain printing condition range.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application This invention relates to a thermal head used in thermal printing and recording devices such as facsimiles and printers.

(b) Prior Art FIG. 4 is a cross-sectional view showing the structure around the heating resistor portion of a conventional thermal head using a ceramic substrate. In the figure, 4-1 is a ceramic substrate made of alumina, etc.;
2 is a glaze layer made of high melting point glass formed on the surface thereof. On the glaze layer 4-2, TaSi
Oz. A heating resistor 4-3 such as Rust, a common electrode 4-4 and individual electrodes 4-5 made of AI, Au, etc., SiAI
Protective films 4-6 made of ON, SiON, amorphous glass, etc. are sequentially laminated. These are formed by vapor deposition or sputtering in the case of a thin film method, and by printing and baking in the case of a thick film method, but they basically have the same structure.

FIGS. 5 to 7 show the overall structure of a conventional thermal head using a ceramic substrate. Figure 5 shows the heating resistor 5-
2 and a hard printed wiring board 5
-3 in combination, the electrical connection between both bases 5-1 and 5-3 uses an Au wire to wire-bond the drive control IC 54 that drives the low-pressure antibody 5-2. are doing.

6 and 7 show a ceramic substrate 6-1.7-1 on which a heating resistor 6-2.7-2 is formed and a reinforcing plate 6-5.7-
FPC attached with 5 (Flexible group 1i) 6-4
．． In this example, both boards 6-1 and 6-4.7-4 are combined.
For the electrical connection between 7-1 and 7-4, pressure bonding with rubber 6-6 is used in FIG. 6, and thermocompression bonding with solder is used in FIG. 7.

(c) Problems to be Solved by the Invention Incidentally, in such a conventional thermal head, it is necessary to apply heat of at least several hundred degrees in the manufacturing process to form the heating resistor part, so an insulating substrate that can withstand this temperature is required. However, because ceramic substrates have poor processability, they are combined with hard printed wiring boards and FPCs, which increases material costs and increases the material cost. The number of steps in the assembly process also increases, and the number of defects tends to increase.

In order to solve this problem, the applicant of the present application (Sat) proposed a material with heat resistance of 300 to 400°C or more and a general hard material. We proposed a thermal head that electrically consists of a single board using a heat-resistant insulating material that has processability similar to that of printed wiring. Its structure is shown in FIG. In Fig. 8, a copper clad board covered with copper foil is used as the heat-resistant insulating 1tlif board 8-3, similar to a normal hard printed wiring board, and the copper foil is left solid near the heating resistor as a heat dissipation layer 8. -2. Thereon, an insulating film 8-4 is formed as a heat storage layer, for example, from polyimide, and further a heating resistor 8-5 and a common electrode 8-4 are formed.
6. It has a structure in which individual electrodes 8-7 and protective films 8-8 are sequentially laminated. In the thermal head with this configuration, the ninth
As shown in the figure, along with the heating resistor 9-2, its drive control circuit components (the drive control IC therein is shown as 9-3)
, connector parts (not shown) for connection with external circuits can also be mounted on a single heat-resistant 1# resin base Ifjc9-1, and the connection lines between them are copper-clad. Since Saka's copper foil can be used, a certain thermal head can be electrically connected to a single board.

However, a heat sink is essential in both the thermal head shown in FIG. 8 and the thermal head shown in FIG. 4 which uses a conventional ceramic substrate. When printing pulses are applied continuously without a heat sink to generate heat,
Due to insufficient heat dissipation, the temperature of the substrate rises, making it impossible to print normally, and in some cases, the heating resistor may be destroyed. Heat sinks are used to prevent these problems, but heat sinks usually have a thickness of 5 to 6 mm.
An aluminum plate of RM or higher is used, and its material cost and assembly cost account for a large proportion of the overall cost of the thermal head. In addition, in the thermal head shown in FIG. 8, a metal layer (Cu foil layer) 8-2 is provided below the heating resistor through an insulating layer 8-4, so heat dissipation is improved, and the printing pulse 1 Although the difference between the peak temperature after continuous printing and the printing pulse is smaller than when there is no metal layer, bleeding during continuous black printing and trailing after continuous black printing still occur. If the printing energy is lowered in an attempt to eliminate this problem, a smudge will occur at the start of printing, and good printing quality will not be achieved. In addition, since the heating resistor has a recessed structure, it has poor contact with the paper, and the efficiency of heat transfer to the paper is poor.

The present invention has been made in consideration of these circumstances, and aims to provide a thermal head that has sufficient heat dissipation even without a heat sink and has good paper contact properties.

(2) Means for Solving the Problem This invention includes a plurality of heating resistors on a substrate, a common electrode commonly connected to one end of each heating resistor, and a common electrode connected to the other end of each heating resistor individually. lTL! from the drive circuit to each heating resistor via the common electrode and the individual electrodes.
In a thermal head configured to
It consists of a heat-resistant resin substrate and several metal layers laminated on its front and back surfaces through insulating layers, and the metal layers are further patterned to connect the common electrode and the individual TIX electrodes to the drive circuit, respectively. and a connecting capacitor formed by
an insulating layer made of heat-resistant resin; a common electrode and individual electrodes formed on the insulating layer; and a common electrode formed on the insulating layer;
a heating resistor extending from one end of the E pole to one end of the individual electrode;
The thermal head is characterized in that it includes a protective film that covers the heating resistor, and that the other ends of the common electrode and the individual electrodes are connected to a connection electrode.

Further, the present invention includes a plurality of heat generating resistors on a substrate, a common electrode commonly connected to one end of each heat generating resistor, and an individual electrode individually connected to the other end of each heat generating resistor, In a thermal head configured to conduct electricity to each heating resistor through a common electrode and individual electrodes, the substrate is made of a heat-resistant resin substrate and multiple metal layers laminated on its front and back surfaces with insulating layers interposed therebetween. Furthermore, a common electrode and individual electrodes are formed by patterning the uppermost metal layer, a heat storage layer made of a heat-resistant resin is formed near the common electrode and individual electrodes, and a common electrode is formed on the heat storage layer. This thermal head is characterized by comprising a heating resistor formed over individual electrodes and a protective layer covering the heating resistor.

It is preferable that the above-mentioned dovetail layer is thicker than the common electrode and the wiring conductor, so that the heating layer of the heating resistor protrudes from the surface of the substrate.

(E) Effect By using a multilayer steel-clad heat-resistant insulating resin board as the heat-resistant insulating resin board, not only the surface copper layer but also the interior copper foil layer contributes to heat dissipation, so heat dissipation is improved. Significantly improved. Even when printing pulses are continuously applied to a thermal head with this configuration without a heat dissipation temporary to generate heat, the rise in the surface temperature of the heating resistor is very small, and the temperature on the back surface of the substrate also rises only slightly. Therefore, it is possible to realize a printable thermal head without a heat sink.

In addition, by protruding the heating portion of the heating resistor, the paper contact property is improved, the heat conduction efficiency to the paper is improved, and printing is possible with less printing energy. The smaller the application energy is, the smaller the difference in peak temperature between the first printing pulse and the peak temperature after continuous printing pulses is applied, so the printing quality is improved due to the synergistic effect with the improvement in heat dissipation.

(F) EXAMPLES The present invention will now be described in detail based on practical examples shown in the drawings.

Figures 1 and 2 are a cross-sectional view of the main parts around the heating resistor part and an overall configuration diagram of the thermal head in an embodiment of the present invention, and Figure 3 is a multilayer steel plate used in this embodiment. FIG. 2 is a cross-sectional view of a stretched heat-resistant insulating resin substrate. First, in FIG. 3, a multilayer copper-clad heat-resistant insulating resin board 1 has metal layers (
For example, it is a multilayer copper clad board in which copper foils 3a to 3d are laminated in a sandwich shape, and the same processing method as that for hard printed wiring boards such as ordinary glass epoxy boards can be applied, and through holes are formed to create a multilayer copper clad board. It can also be easily made into a wiring board. Moreover, since the substrate 1 uses heat-resistant cloth and heat-resistant resin, it has heat resistance that can withstand temperatures of 300 to 400° C. or more.

In FIG. 1, the multilayer steel-clad heat-resistant insulating resin substrate + a metal layer 3b is etched into a desired pattern using the usual hard printed wiring pattern and the same three-way wiring pattern method.
A wiring pattern is formed to mount drive control circuit components for a firing resistor, external circuit connection connectors, etc., which will be described later. The metal layer 3b is patterned to leave as wide an area as possible in order to improve heat dissipation. Next, Nl plating and Au plating are applied to necessary portions of the etched wiring pattern. Please note that these platings are not necessarily required.

Next, a polyimide varnish is applied to the entire surface by spin coating, roll coating, screen printing, etc., temporarily cured, etched, and further fully cured to form the polyimide insulating layer 4 covering the metal layer 3b. When a polyimide-based face is used, the etched end face has a gentle taper, so that the electrical connection between the AI%K pole described below and the wiring pattern can be made without any problem. A heating resistor 5 made of Ta-Sift is placed on the insulating layer 4 thus formed, and a common electrode 6 and individual electrodes 7 made of AI are deposited by vapor deposition or sputtering. , etching and patterning.

Then, the common electrode 6 and the individual electrodes 7 (connected to the wiring pattern of the earth metal layer 3b) are formed.Furthermore, SiAION is formed thereon as a protection@8 by the vapor deposition method or the Subanota method.Finally, heat treatment is applied. Note that examples of the polyimide varnish used for forming the insulating layer 4 include Toray's Toray Co., Ltd.'s Tolenice or Senmico Fine, Chisso Corporation's PS I-G series, and the like.

The thermal head thus formed has significantly improved heat dissipation performance because the substrate has the metal layers 3a to 3d.

In addition, as shown in FIG. 2, the overall structure of the thermal head includes a drive control IC 9 for driving and controlling the heat generating resistor 5 on a heat-resistant insulating resin substrate l on which the heat generating resistor 5 is formed. The thermal head is completed by mounting necessary components such as drive control circuit components and connector components (not shown) for connection with external circuits. The substrate 1 of this embodiment has internal copper foil layers 3h and 3c, and furthermore, the internal copper foil layers are well arranged and the number of layers can be optimally adjusted to improve heat dissipation within a certain range of printing conditions. It is possible to create a thermal head that does not require temporary storage.

In actual use, a reinforcement plate is required to maintain the mechanical strength of the thermal head, but since there is no need to consider release properties, the reinforcement As! t
Costs can be reduced by using a finger or by using the case of the printing and recording device instead of mounting a thermal head.

FIG. 10 shows the change over time in the temperature of the back surface of the substrate when printing pulses were continuously applied to this thermal head.

Further, FIGS. 11 and 12 show changes in substrate back surface temperature in a conventional thermal head using a ceramic substrate shown in FIG. 4 and in a thermal head shown in FIG. 8, respectively. From these figures, it can be seen that the temperature of the back surface of the substrate of the thermal head of this example hardly rises after the printing pulse is applied, and the thermal head of this example has extremely excellent heat dissipation performance compared to others.

FIG. 13 is a sectional view of the periphery of the attracting resistor portion of a thermal head showing another example of the present invention. In the same figure,
Let's have a multilayer copper-clad insulation resin base, its structure:
This is the same as shown in Figure 3.

The copper of the multilayer copper-clad heat-resistant insulating resin substrate l is etched into a desired pattern by using the same wiring pattern forming method as for ordinary hard printed wiring boards to form the common electrode 3b-1 and the individual electrodes 3b-2. form. Ni plating and Au plating are usually applied on the electrodes. The insulating film 10 is formed into a convex shape using polyimide, for example. When forming the insulating film 10 using polyimide, first, a polyimide varnish is applied to the entire surface by spin coating, roll coating, screen printing, etc., and after temporary curing, it is etched into a desired shape, and then it is fully cured. When polyimide varnish is used, the etched end face has a gentle taper as shown in FIG. On the insulating film 10 thus formed, Ta-Sin as the heating resistor l1 and SiAION as the protective film l2 are laminated by sputtering or vapor deposition. Finally, heat treatment is added. Note that since the end face of the insulating layer 10 has a tapered surface, the insulating layer above it is also a resistor! Step 1: If it's a problem, don't worry. As the polyimide varnish used for forming the insulating film 10, for example, Toray (l
ti) Trenice: Yo Semico Fine, Chisso (
There are PSI-G series manufactured by Ajinomoto Co., Ltd.

The thermal head formed in this way has significantly improved heat dissipation performance since the substrate l has internal copper (3a and 3c), and the heat dissipation performance is reduced after the first printing pulse and after continuous printing pulses are applied. The difference in surface peak temperature is shown in (A) in Figure 14.
The characteristics of the comparative example having the structure shown in Figure 8 (B
), it can be seen that it is sufficiently small compared to Therefore, even with the same applied power, the surface peak temperature of the heating resistor remains low, which means that there is little difference between the printing conditions at the start of printing and during continuous black printing. In addition, according to this embodiment, by protruding the heat generating portion of the heat generating resistor, the paper contact property is improved, the transmission efficiency of the islands to the paper is improved t5, and the printing density with respect to the printing energy is 15th. It can be seen that sufficient printing degree a can be obtained with a smaller applied energy than in the comparative example shown in FIG. 8(B) (the configuration shown in FIG. 8). In this way, when the application energy is small, the difference between the peak temperature after the first printing pulse and the continuous application of printing pulses becomes even smaller.Secondly, due to the synergistic effect with the effect of improving heat dissipation mentioned above, , a thermal head with high printing quality.

Furthermore, by using multiple copper foil layers, heat dissipation performance is significantly improved, so when printing pulses are continuously applied without a heat sink to generate heat, the surface temperature of the heating resistor increases. The change is sufficiently small, and as shown in FIG. 16, the temperature on the back surface of the substrate increases only slightly compared to FIG. 12 (comparative example). Therefore, in this example, an example is given in which the interior copper foil layer is two layers, but by optimally adjusting the thickness, position, and number of layers of the interior copper foil layer,
Within a certain range of printing conditions, it is possible to realize a thermal head that does not use a heat sink, similar to the above embodiment.
It is configured as shown in FIG.

Each of the above embodiments has described the thin film method, but even in the case of the thick film method, the firing temperature and the heat resistance are the same or the same temperature. The same applies to 11 Rararon.

(G) Effects of the Invention According to this invention, by using a multilayer copper-clad heat-resistant resin substrate, the inner copper foil improves heat dissipation.
The difference between the printing conditions at the start of printing and during continuous black printing is reduced. In addition, by making the heating part of the heating resistor protrude,
Since the printing efficiency is improved, a thermal head with high printing quality can be provided by a synergistic effect with the above-mentioned effect of improved heat dissipation. Furthermore, the internal copper foil significantly improves heat dissipation performance, making it possible to create a thermal head that does not require a heat sink. Moreover, since it uses a heat-resistant insulated resin substrate that can be processed using the same processing methods as ordinary hard printed wiring boards, it can be used not only for heating resistors but also for drive control circuit components and connections with external circuits. Since the connector parts and the connection wiring between them are integrally formed and mounted on a single board, and the shape can be made compact, a low-cost and highly versatile thermal hemotor is available.

[Brief explanation of drawings]

Fig. t is a sectional view of the vicinity of the heating resistor of a thermal head showing one practical example of the present invention, Fig. 2 is an overall configuration diagram of the thermal head of the present invention, and Fig. 3 is a multilayer steel-clad heat-resistant insulating resin substrate. 4 is a sectional view of the area around the heating resistor of a conventional thermal head using a ceramic substrate. FIGS. 5 to 7 are overall configuration diagrams of a conventional thermal head using a ceramic substrate. Figure 8 is a cross-sectional view of the area around the heating resistor of the thermal head of the comparative example, Figure 9 is the overall configuration diagram of the thermal head of the comparative example shown in Figure 8, and Figure lo shows the temperature on the back side of the substrate of the thermal head of the present invention. Graphs showing changes,
FIG. 11 is a graph showing temperature changes on the back surface of a conventional thermal head using a ceramic substrate, FIG. 12 is a graph showing temperature changes on the back surface of a thermal head according to a comparative example, and FIG. 13 is a graph showing temperature changes on the back surface of a thermal head according to a comparative example. 14 is a graph showing the transition of the surface peak temperature of the heating resistor, and FIG. 15 is a graph showing the relationship between printed #mark and applied energy. FIG. 16 is a rough graph showing the change in temperature on the back side of the substrate. 1...Multilayer copper-clad heat-resistant insulating resin substrate, 2a to 2c
... Layer of heat-resistant cloth impregnated with heat-resistant resin, 3a to 3d ... Metal layer, 4 ... Insulating layer,
5...Heating resistor, 6...Common electrode,
7...Individual electrode, 8...Protective film. Baku 5 Maro 6 Sen 7 Ma 9 Fig. 13 Kazu 10m}'1 Iji 12 Fig. 15

Claims (1)

[Claims] 1. A plurality of heating resistors on a substrate, a common electrode commonly connected to one end of each heating resistor, and individual electrodes individually connected to the other end of each heating resistor. In a thermal head configured to supply electricity from a drive circuit to each heating resistor through a common electrode and individual electrodes, the substrate is laminated with a heat-resistant resin substrate and an insulating layer on the front and back surfaces of the substrate. furthermore, a connection electrode formed by patterning the metal layer to connect the common electrode and the individual electrodes to the drive circuit, an insulating layer made of a heat-resistant resin, and an insulating layer on the insulating layer. A heating resistor formed on the insulating layer and extending from one end of the common electrode to one end of the individual electrode, and a protective film covering the heating resistor, each of the common electrode and the individual electrodes. A thermal head characterized in that an end is connected to a connecting electrode. 2. A plurality of heat generating resistors are provided on the substrate, a common electrode commonly connected to one end of each heat generating resistor, and an individual electrode individually connected to the other end of each heat generating resistor. In a thermal head configured to conduct electricity to each heating resistor through individual electrodes, the substrate is made up of a heat-resistant resin substrate and multiple metal layers laminated on the front and back surfaces of the same with insulating layers interposed therebetween. , a common electrode and individual electrodes formed by patterning the uppermost metal layer, a heat storage layer made of heat-resistant resin formed near the common electrode and individual electrodes, and a heat storage layer extending from the common electrode to the individual electrodes on the heat storage layer. A thermal head comprising a heating resistor and a protective layer covering the heating resistor. 3. The thermal head according to claim 2, wherein the heat storage layer is formed thicker than the common electrode and the individual electrodes, so that the heat generating portion of the heat generating resistor protrudes from the surface of the substrate.