JPS59220382A - Thermal head for thermal recording - Google Patents

Abstract

PURPOSE:To reduce the amount of heat accumulated in a thermal head, by using a substrate material consisting of SiC or comprising SiC as a main constituent for a substrate of a heating element. CONSTITUTION:An SiC-Si substrate material obtained by incorporating Si into an SiC powder followed by reactive sintering is used as a material for the substrate 1 of the heating element. A glass glaze layer is provided on the substrate material as an electrically and thermally insulating layer 2. In providing the glass glaze layer, a glass material having a coefficient of thermal expansion of smaller than that of the SiC-Si substrate material is used. Materials for the heati ng element 3 and electrodes 4a, 4b can be selected without any restriction from those materials which are conventionally used. When a material having a coefficient of thermal expansion of smaller than that of the glass material is used for an abrasion-resistant layer 5, a heating element having favorable resistance to thermal pulse can be obtained.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a thermal head for heat-sensitive recording.

Conventional Structures and Problems Thermal recording methods are applied to various fields such as facsimiles, printers, and recorders as a recording method that is easy to maintain.

As these various applications progress, countermeasures against heat buildup in the thermal recording head during use have become important.

That is, heat accumulation in the thermal head is a very important problem in both the improvement of recording speed, which is an important technical issue in the current thermal recording system, and the color recording by the thermal transfer recording system.

The heat buildup in the thermal head is as follows. FIG. 1 is a sectional view of the heating element portion of the thermal head. On a heating element substrate 1 made of A12O3, a thermal/electrical insulating layer (usually glass) 2, a heating resistance layer 3, an electrode 4a,
4b and wear-resistant layers 6 are sequentially laminated to form a heating element part, and the heating element substrate 1 is adhered to the head base 6 to constitute the entire thermal head.

In a thermal head such as a facsimile thermal head in which a large number of heating elements are arranged in a line, for example, a diode or an I for driving the heating element is installed on the electrode 4b side.
C etc. are connected.

In such a heating element structure, when a heating element heating pulse is applied as shown in Fig. 2 (,), the application part becomes as shown in Fig. 2 (■)
Heat is generated as shown by the solid line, but when the heating element pulse is repeatedly applied, for example, the temperature at point 7 directly below the heating element rises as shown by the broken line, and the maximum temperature on the heating element surface when the heating pulse is applied gradually increases as shown in the figure. Rise.

A temperature rise (heat buildup in the head) as shown by the broken line in FIG. 2(b) becomes a major hindrance to obtaining constant recording conditions under constant heating pulse conditions. That is, in order to increase the recording speed, increasing the applied power to obtain a predetermined recording density with a short pulse width and shortening the applied pulse period both cause a sudden increase in heat in the thermal head. .

However, even if the heat source is the same, the degree of interference is significant when gradation is expressed by applying electric power with various pulse widths to the same heating element, for example, in the case of color recording using a transfer thermosensitive recording method.

A thermal head having a heating element portion as shown in FIG. 1 is configured into a thermal head as shown in FIG. 3, for example. In FIG. 3, a heating element substrate 1 and a printed circuit board 8 are bonded onto a head base 6. As shown in FIG. A heating element array 9 in which a large number of heating elements are arranged in a row is formed on the heating element substrate 1, and a diode or an IC (integrated circuit) for driving this heating element array is formed using, for example, film carrier technology. Electrical connection is made between the heating element board 1 and the printed circuit board 8, and drive terminals for the entire head are collected in the connector 1o. 11 and 12 are elements such as electrodes, diodes, or ICs.

The head shown in FIG. 3 can be called a planar thermal head because the heating element is formed on one main plane of the heating element substrate.

When configuring a recording apparatus using a thermal head, an end-face type head in which a heating element is formed on one side of a heating element substrate is also known.

FIG. 4 shows a sectional view of the heating element portion of the end face type thermal head.

In FIG. 4, the heating resistance layer 3 is the thermally and electrically insulating layer 2.
are formed on one side of the substrate 1 via electrodes aa,
4b is formed on the surface on which the heating element resistance layer is formed and on two surfaces in contact with this surface, and a wear-resistant layer 5 is formed on the heating resistance layer 3 to complete the heating element section.

An example of the configuration of an end face type thermal head having such a heating element portion is shown in FIG.

The thermal head shown in FIG. 6 is constructed by fixing a substrate 1, on which a heating element row 9 (shown by a dashed line) is formed, between a head base 13 and a cover 14 with screws 15. The electrodes of each heating element, the connection between the IC and the connector 10 are made in the same manner as in the thermal head shown in FIG.

FIG. 6 shows the arrangement of the ICs 16 when the ICs are connected using film carrier technology.

Straight leads and L-shaped leads are formed on the IC 16, and each of these leads is connected to the heating element board 1 and the printed circuit board 8, but the electrode patterns of the heating element board 1 and the printed circuit board 8 are complicated in the diagram. This is omitted because it is.

On the other hand, in both the heads shown in Fig. 3 and Fig. 5, in order to solve problems caused by heat build-up during use of the head, for example, the recording density increases over time, conventionally, the heat generation of the head The power (usually pulse width) applied to the next heating element to be recorded is adjusted in consideration of, for example, the temperature of the base near the body and the heating history of each heating element.

However, even with these methods, if the rise of the broken line portion shown in FIG. 2 is too rapid, it becomes difficult to control the recording state.

OBJECTS OF THE INVENTION The main object of the present invention is to provide a thermal head that can reduce such heat buildup.

Another object of the present invention is to improve the heat pulse resistance of the heating element.

Structure of the Invention In the present invention, in order to achieve the above-mentioned two objects, a substrate material made of SiC or having SiC as a main component is used as a heating element substrate. By using this substrate material, (1) it has a lower thermal conductivity than Al2O3, which is commonly used in the past, so it is possible to reduce heat buildup in the thermal head;

(2) Since the thermal expansion coefficient is smaller than that of conventional Al2O3 substrates, heat pulse resistance can be improved.

DESCRIPTION OF THE EMBODIMENTS In this embodiment, the heating element portion is formed as shown in FIG. The material of the heating element substrate 1 is SiC powder and S.
A 5iC-3i substrate material containing 10% i and sintered by reaction is used. The thermal conductivity of this material is 0.4ca at room temperature.
l-cm ・Wt ・℃, thermal expansion coefficient is 4 × 10 ℃
It is.

On top of this substrate material is an electrically and thermally insulating layer 2 with a thickness of 6
Form a glass glaze layer of 0 to 80 μm.

In forming this glass glaze layer, it is important to select a glass material with a coefficient of thermal expansion smaller than that of the 5iC-8L substrate material, otherwise cracks will occur in the glaze layer after glazing.

In order to satisfy such conditions, a borosilicate glass having a thermal expansion coefficient of 3×10 to 3.5×IC)C is used as the glass.

For the heating element 3 and the electrodes aa and 4b, conventionally used materials can be selected without any restriction, but in this embodiment, a 5L-Ta heating element and a Cr-Cu electrode were selected.

On the other hand, if a material with a coefficient of thermal expansion smaller than that of the glass material is selected for the wear-resistant layer 6, a heating element with good heat pulse resistance can be obtained.

For this purpose, in this embodiment, a wear-resistant film is formed by sputtering using a 5iC-8t3N4 target.

The thermal expansion coefficient of this target material is 3×10℃
However, by further adjusting the sputtering conditions, 5
When compressive strain is introduced into the iC-8i3N4 wear-resistant film,
Heat pulse resistance can be further improved.

In order to evaluate the characteristics of the thermal head assembled as shown in Figure 3 using the heat generating substrate formed through the above steps, the heat generating element, electrodes, and abrasion resistant layer were placed on a conventional glass glazed Al2O3 substrate. A comparative test with the formed thermal head yielded the following results.

(1) Effect on heat buildup in the head The thermal head is used under certain recording conditions (constant pulse width of the heating element) to stop recording every time a checkered pattern is recorded on one A4 size sheet, and then to start recording again. , and if the thermal head is kept in contact with the heat-generating thermal paper in the non-recording area between each recording screen (A4 checkered pattern) for a certain period of time, the non-recording area will become colored due to the accumulation of heat from the head. .

As a result of comparing the number of recording screens until this non-recording area reaches color development with the above two types of thermal heads, the configuration of this actual case has a slightly different number depending on each recording condition, but on average it is about 3
Color development occurred in the non-recorded area on the double recorded screen.

(2) Effect of Improving Heat Pulse Resistance In the step stress heat pulse test for the above two types of heating elements, the heating element of this example broke down at about 1.4 times the power.

As can be seen from the above description, the present invention has the effect of preventing heat build-up in the thermal head and improving the heat pulse resistance of the heating element.

Furthermore, the present invention does not cause problems such as melting of the substrate material itself, even if the manufacturing process for a conventional 1 m thin thermal head is used almost as is, for example, even if the heating element is etched with a strong acid and 9 strong alkali. This is an effect of using the heating element substrate material as being made of SiC or having SiC as its main component. Another great effect of the present invention is that the conventional glass glaze technology can be used as is to form a thermal insulating layer, which is essential for transmitting heat to the recording paper side as much as possible when the heating element is heated.

On the other hand, the present invention can be applied to the heads having the structures shown in FIGS. 1 and 4, and various improvements can be made without being limited to the embodiments. These improvements mainly relate to the substrate material and the method of forming the composition of the thermal insulating layer, and to further reduce the coefficient of thermal expansion of the wear-resistant layer of the heating element. Furthermore, thermal transfer color printer recording devices, which are expected to become widely popular in the future, are often easier to design with the thermal head shown in FIG. 5 than the thermal head shown in FIG. According to this paper, this end-face type thermal head has a great effect on the low-frequency range of heat buildup.

As described in detail, the present invention has great industrial value in manufacturing high-performance thermal heads using conventional thermal head manufacturing techniques.

[Brief explanation of the drawing]

Figures 1 and 4 are diagrams for explaining the configuration of the heating element of the thin-film thermal head, Figure 2 is a diagram for explaining the accumulation of heat in the thermal head, Figures 3 and 5, respectively. 1 and 4 are external views of thermal heads constructed using the heating element substrates shown in FIGS. 1 and 4, respectively. 1...Heating element substrate, 2...Electrical/thermal insulating layer, 3...Heating resistance layer, 4a, 4b...
・Electrode, 5...--Resistance, wear layer, 6, 13...
・Head base, 9... Heating element row. Name of agent: Patent attorney Toshio Nakao and one other person
A2 figure 1 hour 1 figure 4

Claims (1)

[Claims] A heat-sensitive recording device comprising a substrate made of SiC or having SiC as a main component, and a heating element formed on the surface of the substrate via an electrical insulating layer having a coefficient of thermal expansion smaller than that of the substrate. thermal head.