JPH04140152A - Thermal head - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a thermal printer head for facsimiles, word processors, etc.

[Prior art]

Conventionally, one form of a thermal head is to form a protective film on a ceramic substrate such as alumina.

There is a hybrid configuration in which a heating element is provided on the heating element and the driving circuit is connected to the heating element by wire bonding.

However, such thermal heads as described above are subject to mounting restrictions such as wire bonding in response to higher resolution and an increase in the number of dots, making it difficult to reduce the size and cost of thermal heads. Additionally, the thermal conductivity of the ceramic substrate used in this thermal head is 20w-m.
-'·k-1, and plays the role of dissipating the heat generated by the heating element, but it cannot be said that malfunctions due to heat accumulation do not occur at all.

Another aspect of the thermal head is one that enables miniaturization, which was difficult with the hybrid thermal head described above, namely, an integrated thermal head using rCMoS ultra-thin film transistors (Sony, Sony Magne Products), Institute of Electrical Communication Engineers. There is also a report VLD 88-66. This thermal head directly attaches to the quartz substrate.
Polycrystalline silicon is formed as a heating element, and a driving circuit is integrally formed on the substrate. The thermal conductivity of the quartz substrate or glass substrate is 0.5 to 1.5 w・m−′・k−”
There are problems with heat storage, as the heat generated by the heating element may accumulate and cause malfunctions.

Incidentally, substrates forming thin film semiconductor devices include glass substrates, quartz substrates, and the like as transparent insulating substrates. If a transparent insulating substrate such as a glass substrate that does not require this protective film is used for a thermal head, the thermal conductivity of the substrate will be 0.5 to 1.5.
w-m-1・k-", so the heat generated by the heating element is stored, which means that even if the thermal head is turned off, the temperature will be high due to heat storage, resulting in black printing, which is sufficient in terms of print quality. It wasn't.

〔the purpose〕

SUMMARY OF THE INVENTION An object of the present invention is to provide an excellent thermal head that eliminates the influence of heat accumulation, that is, improves heat radiation efficiency.

〔composition〕

A first aspect of the present invention relates to a thermal head having a heating element formed on an insulating substrate, characterized in that a heat radiating element is provided around the heating element.

A second aspect of the present invention provides a thermal head in which a polysilicon thin film formed on a transparent insulating substrate is used as a heat generating element, in which a second polysilicon heat sink is arranged to surround the first polysilicon heat sink of each bit. The present invention relates to a thermal head characterized in that a pattern is formed.

A third aspect of the present invention relates to a thermal head formed on a transparent insulating substrate, characterized in that a heat sink, an insulating film, and a heat generating body are sequentially laminated on the substrate.

A fourth aspect of the present invention provides, in the thermal head, an active layer and/or an active layer of a drive circuit provided on a substrate of the thermal head.
Alternatively, the present invention relates to a thermal head characterized in that the gate and the heat sink are made of the same material.

Substrates that can be used in the present invention include quartz glass, Corning-7059 (manufactured by Corning Corporation), Asahi Glass A
There are glass substrates such as N series (manufactured by M Glass Co., Ltd.), and high melting point glass is particularly preferred.

Examples of materials that can be used as heat radiators include those having a thermal conductivity of 10 to 430 wm-1.k-1, such as metals such as Au, Cu, and Ag, and Ta.

Examples include high melting point metals such as MO, alloys such as nichrome and Ta:5in2, thin films such as Si, Ge, and C (graphite), and semiconductor thin films such as polycrystalline silicon and amorphous silicon.

When a quartz substrate is used as a substrate, silicon has a much higher thermal conductivity than quartz (silicon; 168
w-m-1・k-”, quartz; 1.4w・m-1・k-1
) Therefore, it is better to use silicon as the heat sink. In this case, a pattern of polysilicon is formed as a heat sink around the heating element portion, and the polysilicon serves as a heat sink, thereby solving the problem of heat accumulation. That is, the heat of the heating element can be radiated using a material with good thermal conductivity.

Among the heat sinks, those that can be used as an active layer and/or a gate, that is, those that can be used as an active layer and/or a gate and heat sink in the fourth aspect of the present invention, include polycrystalline silicon, amorphous silicon, There are silicon-based semiconductor thin films such as high quality silicon.

In addition, as the insulating film, SiOx film, SiNx film, Si
An OxNy film or the like can be used.

As a specific example of the thermal head of the present invention, a polysilicon thin film transistor is fabricated on a quartz or glass substrate, and during the manufacturing process, a polysilicon thin film is simultaneously formed as a heating element, and the polysilicon heating element portion of each bit is For example, a polysilicon pattern may be formed as a heat sink so as to surround the radiator.

Hereinafter, a thermal head of the present invention will be explained with reference to the drawings.

Fig. 1 is a cross-sectional view of a conventional thermal head without a heat sink, Fig. 2 is a cross-sectional view showing an example of the thermal head of the present invention, Fig. 3 is a plan view thereof, and Fig. 4 is another embodiment. FIG. 5 is a cross-sectional view of a thermal head according to still another embodiment of the present invention, and FIG. 6 is a cross-sectional view of a thermal head of the present invention in which a drive circuit portion and a heating element portion are formed on the same substrate. It is a diagram.

First, FIGS. 2 to 4 will be explained.

Polysilicon is deposited on a substrate 1 made of quartz or glass by the LPCVD method, and portions that will become the active region 2 and heating element 3 of the thin film transistor are patterned by photolithography and etching. Next, after forming a gate insulating film 4 by thermal oxidation, polysilicon is deposited again. The portion 5 that will become the gate electrode of the thin film transistor and the heat sink 6 are patterned by photolithography and etching. Next, phosphorus and boron are sequentially implanted by ion implantation to lower the resistance of the source and drain of the drive circuit and the heating element 3. that time.

The heat sink 6 does not need to be made low in resistance.

After that, an interlayer insulating film 7 of SiO□ was deposited using the LPCVD method, and a contact hole was opened.
The wiring 8 is deposited and patterned, and finally the wear-resistant layer 9 of Si is deposited and patterned.
, N4 is deposited to complete the thermal head.

In the manufacturing method, the polysilicon of the active layer of the thin film transistor is used as the heat generating body 3, and the polysilicon of the gate 5 is used as the heat dissipating body 6.
However, the reverse is also possible, and both the heating element 3 and the heat radiating element 6 may be formed of polysilicon of the active layer 2 or polysilicon of the gate 5.

Further, there is no problem even if the heating element and the heat radiating element are made of different materials.

Next, FIGS. 5 and 6 will be explained.

The thermal head of the present invention shown in FIG. 5 has II! II A thin film of metal such as Au, alloy such as nichrome, silicon, etc. with a thermal conductivity of 10 is deposited on the II substrate 1.
A heat sink 6 of ~430 wm-1·k-1 is formed, and an insulating film 10 such as SiOx is formed thereon. Hereinafter, like a normal thermal head, Ta: Sin,
, T a 2N, nichrome film, etc.3. A thermal head is formed by forming wiring 8 such as Au, a protective film 9 such as SiOx, SiNx, etc., and performing patterning. Note that the heating element 6 or the wiring 8 may be made of the same material as the heat radiating element 6.

The thermal head of the present invention shown in FIG. 3 has a drive circuit portion and a heating element portion formed on the same substrate. When manufacturing this thermal head, the heat sink 6 and the active layer 2 of the drive circuit can be made of the same material, for example polycrystalline silicon. Further, the insulating film 10 and the gate insulating film 4 can be formed of the same material, for example, SiOx, and the heating element 3 and the gate electrode 5 can be formed of the same material, for example, polycrystalline silicon. Therefore, in the case of Fig. 5, the heating element is formed by laminating the heat sink and the insulating film on the substrate, but when manufacturing it as shown in Fig. 6, it can be formed without increasing the number of steps. can do.

In the case of FIG. 6, after forming the gate electrode 5 and heating element 3, ion implantation is performed to lower the resistance of the gate electrode 5, heating element 3, and active layer 2. It is not necessary to lower the resistance. Further, the gate insulating film 4 can be made into a Si film by thermal oxidation, but
CVD method Sun, membrane, P-CVD method SiOx, Si
It may also be formed using an OxNy or SiNx film.

〔Example〕

Example 1 (see Figures 2 to 4) 1000 ml of polysilicon was deposited on a quartz substrate 1 using the LPCVD method.
After deposition, the parts that would become the active region 2 and heating element 3 of the thin film transistor were patterned by photolithography and etching. Next, after forming 750 gate insulating films 4 by thermal oxidation,
Polysilicon was deposited again by 3,000 people. A portion 5 that will become the gate electrode of the thin film transistor and a portion 6 that will serve as a heat sink were patterned by photolithography and etching. Next, four people implanted phosphorus and boron in sequence to reduce the resistance of the source and drain of the C-MO5 thin film transistor in the drive circuit and the heat generating resistor. After that, 6000 layers of SiO□ were deposited as the interlayer insulating film 7 using the LPCVD method, and 5 contact holes were opened.
After μ-deposition and patterning, finally the wear-resistant layer 9 of Si,
A thermal head was fabricated by depositing N.

This thermal head was able to maintain good print quality without accumulating heat.

Example 2 (see FIG. 5) A nichrome film was formed as a heat dissipation film 6 on a glass substrate 1,
Next, an insulating film 10 was formed. Insulating film 1 (SiOx film formed by P-CVD method was used. Next, heating element 3
A nichrome film is formed and patterned into a predetermined shape to form an Au film with a pattern of tIA8, and then a protective film 9 is formed.
(SiOx film or SiNx film) was formed to produce a thermal head (the heat dissipation film may be an Au film for wiring, and the heating element may be Ta:Sin, etc.).

Example 3 (See FIG. 6) A polycrystalline silicon film was formed on a quartz substrate 1 and patterned to form an active layer 2 and a heat dissipation film 6 of a thin film transistor. Next, an insulating film 10 was formed on the gate insulating film 4 and the heat dissipating film 6. This gate insulating film was formed by a thermal oxidation method (LP-
CVD method Sin, film, P-CVD method SiOx, S
An iOxNy or SiNx film may also be used. ).

Next, the gate 5 and the heating element 3 were formed using a polycrystalline silicon film, and ions were implanted to lower the resistance of the gate electrode 5, the heating element 3, and the active layer 2.

Next, a PSG film was formed as an insulating film 7 between the eyebrows, a contact hole was formed, an AΩ wiring section 8 was formed, a protective film 9 (SiOxM or SiNx film) was formed, and a thermal head was manufactured.

〔effect〕

According to the present invention, even in a thermal head formed on a transparent insulating substrate such as a glass substrate, heat is not retained more than necessary, so malfunctions can be extremely reduced and printing quality can be maintained.

In addition, in a thermal head in which a drive circuit is integrally formed on a transparent insulating substrate such as a glass substrate, the heat sink and the active layer can be formed of the same material, so it can be manufactured without increasing the number of steps. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional thermal head without a heat sink, Fig. 2 is a sectional view showing an example of the thermal head of the present invention, Fig. 3 is a plan view thereof, and Fig. 4 is a sectional view of another embodiment of the thermal head. Plan view,
FIG. 5 is a cross-sectional view of a thermal head according to still another embodiment of the present invention, and FIG. 6 is a cross-sectional view of a thermal head of the present invention in which a drive circuit portion and a heating element portion are formed on the same substrate. 1...Substrate 2...Active region 3...Heating element 4...Gate insulating film 5...Gate electrode 6...Heat sink 7...Interlayer insulating film 8...Al2-5i wiring 9... Wear-resistant layer 10/ Insulating film

Claims (1)

[Scope of Claims] 1. A thermal head in which a heating element is formed on an insulating substrate, characterized in that a heat radiating element is provided around the heating element. 2. In a thermal head configured with a polysilicon thin film formed on a transparent insulating substrate as a heating element, a pattern of a second polysilicon heat sink is formed to surround the first polysilicon heat sink of each bit. A thermal head characterized by: 3. A thermal head formed on a transparent insulating substrate, characterized in that a heat sink, an insulating film, and a heat generating body are sequentially laminated on the substrate. 4. The thermal head according to claims 1, 2 and 3, wherein the active layer and/or gate of the drive circuit provided on the substrate of the thermal head and the heat sink are formed of the same material. head.