JP2932661B2 - Manufacturing method of thermal head - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a printer as an output device such as a word processor or a personal computer, and a method of manufacturing a thermal head used in a facsimile recording unit or the like.

[Conventional technology]

Recently, a thermal head has been widely used for a printer as an output device of a word processor, a personal computer or the like, or a head constituting a recording unit of a facsimile.

The thermal head forms a heat-generating portion with at least one pair of electrodes and a heat-generating resistor provided so as to bridge the electrode pair, and heats the heat-generating resistor by applying a current to the electrode pair, This is to form characters or figures on the recording medium by coloring the heat-sensitive recording paper or sublimating the ink donor film.

This type of thermal head, due to differences in manufacturing method,
It is roughly classified into a thick film type and a thin film type.

Thick-film thermal heads are easier to manufacture and have better mass productivity than thin-film thermal heads, which require large-scale deposition equipment. There is a disadvantage that the printing quality is inferior to that of the thermal head.

To solve this, for example, lift-off method or MO
The D method is known.

The prior art relating to the heating resistor of this type of thermal head and its manufacturing method is disclosed in, for example, JP-A-63-164301.

[Problems to be solved by the invention]

However, both the thick-film type thermal head and the thin-film type thermal head have a resistance value variation inherent to the heating resistor.

This resistance value variation causes uneven heating temperature on the printing surface of the resistor, and appears as uneven printing density.

In a conventional thermal head, in a thick-film type, a resistance value variation between adjacent heating resistors is adjusted by pulse trimming.

On the other hand, in the thin film type, the resistance value variation between adjacent heating resistors is small, but the distribution of the resistance value has a large undulation, so that pulse trimming for locally adjusting the resistance value like the thick film type cannot be applied. Can not.

In addition, since the heating temperature distribution of the heating resistor is a mountain-shaped temperature distribution having a peak at the center of the heating resistor, there is a disadvantage that the shape of the printed dot becomes round.

As a countermeasure, it is possible to drive the large current to increase the peak heating temperature so that the print dot shape can accurately reproduce the heating resistor shape.However, if the temperature is increased, the deterioration of the heating resistor is accelerated. In addition, there is a problem that the heating resistor is destroyed.

Deterioration and destruction of the heating resistor occur due to the heating temperature of the heating resistor itself.

Therefore, the conventional thermal head, the maximum rated energy (approximately 100,000 sheets of A4-size) at 10 ⁸ pulses (about 0.43MJ) defines a specification of life is common.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art. (1) Self-controlling the heating temperature of a heating resistor to generate heat at a constant temperature. (2) Making the heating temperature distribution of the heating resistor uniform and improving dot reproducibility. (3) An object of the present invention is to provide a thermal head and a method of manufacturing the same, which can prevent the thermal destruction of the heating resistor by itself.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a common electrode on an insulating substrate, a plurality of drive electrodes arranged opposite to the common electrode, and a heating resistor for connecting the common electrode and the plurality of drive electrodes. Is formed, and in the method of manufacturing a thermal head using a BaTiO ₃ -based valence control semiconductor as the heating resistor, the application and firing of a mixed solution of a metal organic material containing at least Ba and Ti on an insulating substrate is performed a plurality of times. Repeat thickness 4
After forming a multilayer resistive film having a thickness of about 8 μm, annealing is performed to grow grains to form a polycrystal of a BaTiO ₃ -based valence control semiconductor, and this is used as a heating resistor.

[Action]

BaTiO ₃ based valence controlled semiconductor porcelain is generally PTC (Posit
ive Temperature Coefficient) Thermistor (positive characteristic thermistor) is widely used as a heater with a self-temperature control function, and applied products such as electronic appliances, electronic jars, and hot air heaters are known.

A part of Ba ²⁺ of BaTiO _3, the ion radius is close to Ba ^2+, and large metal valence than ^{Ba 2+ (Y 3+, La 3+} , Ce 3+, Sd
³⁺ , Sb ³⁺ , Th ^4+, etc.) or replace part of Ti ⁴⁺ with Ti
^A valence control semiconductor is formed by substituting so-called impurities of a metal (Nb ⁵⁺ , Ta ⁵⁺ , W ^6+, etc.) whose ionic radius is close to ⁴⁺ and whose valence is higher than that of Ti ⁴⁺ .

Addition amount of the above impurities necessary for semiconductor conversion is 0.1-0.5at%
It is about.

FIG. 8 is a temperature characteristic diagram of a PTC thermistor in which a part of Ba is replaced by Pb.

BaTiO ₃ has a Curie temperature (Tc) at around 120 ° C., and the resistivity rapidly increases from this Tc.

As shown in the figure, the Curie temperature can be shifted to a higher temperature side by replacing Ba with Pb. The temperature ratio is 4 ° C / at% Pb.

When a voltage is applied to the BaTiO ₃ -based valence controlling semiconductor, the temperature starts to rise due to self-heating, but when the Curie temperature is reached, the resistance value sharply increases, the current is suppressed, and the temperature rise stops.

On the other hand, when the temperature of the heating element drops due to heat flowing out to the surroundings of the heating resistor, the resistance value decreases, the current increases, and an attempt is made to increase the temperature again.

When this operation is repeated to reach an equilibrium state, the heating element continues to maintain a constant temperature.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a main part of a thermal head manufactured by a first embodiment of a method of manufacturing a thermal head according to the present invention, wherein 1 is a heating resistor, 2 is a common electrode, 3 is a drive electrode, Is an abrasion-resistant layer, 5 is an underglaze layer, and 6 is an insulating substrate such as a ceramic substrate.

 FIG. 2 is a sectional view taken along line AA of FIG.

1 and 2, an underglaze layer 5 is applied to the surface of a ceramic substrate 6 and the heating resistor 1 is formed thereon.

The heating resistor 1 is formed discontinuously in the main scanning direction X, and the common electrode 2 and the drive electrode 3 are spaced apart in the sub-scanning direction on the heating resistor 1 so as to form individual heating portions. They are arranged facing each other.

Then, a heating portion corresponding to one dot is formed by the common electrode 2, the drive electrode 3, and the portion of the heating resistor 1 that bridges each electrode.

An abrasion-resistant layer 4 is formed to cover the electrodes 3, 3 and the exposed portions of the heating resistor 1, to smooth the sliding contact with the recording medium, to protect the heating resistor 1 and each electrode, 1 is prevented from being oxidized.

In this embodiment, a BaTiO ₃ -based valence controlling semiconductor ceramic is used as the heating resistor 1.

In a conventional thermal head, if it is a thick-film type, there is a large variation in the resistance value between adjacent layers, and the resistance value is adjusted by pulse trimming. The thin-film type has a small variation in the resistance value between adjacent layers, but has a large undulation in the distribution of the resistance values, and cannot perform pulse trimming like the thick-film type.

In the case of the heating resistor according to the present invention, since the heating temperature is a constant-temperature heating of the Curie temperature of the BaTiO ₃ based valence control semiconductor, if the dispersion state of the additive element inside the polycrystal of BaTiO ₃ is uniform, each Even if there is variation in the resistance value due to the shape and thickness of the resistor, it does not affect the heating temperature of the resistance value, so there is no variation in print density.

FIG. 3 is an explanatory diagram of the transient response of the heat generation temperature of the thermal head and the heat storage characteristics. The transient response of the heat generation temperature is, as shown in FIG.
As shown in (a-2), the temperature of the heating resistor of this embodiment increases as time elapses.
It becomes flat in c).

Then, a square wave voltage (b−b) as shown in FIG.
When (1) is given, the conventional heating resistor has a high heat generation peak temperature as shown in (b-2), so that the heat is not completely reduced until the next cycle, and the heat is stored as shown in Pt. The peak temperature increases, which will increase the next exothermic temperature.

In addition, since the heat generation of the adjacent dots also has the effect of increasing the peak temperature, it is necessary to control the heat storage by some means.

On the other hand, since the heating resistor according to the present embodiment generates heat at a constant temperature, it becomes flat at the Curie temperature Tc, there is no influence of the heat storage layer heat due to continuous printing nor the influence of the adjacent bit, and heat storage control is unnecessary. As shown in (b-3), the transient response of heat generation can be made to have a heat generation characteristic closer to a square wave by increasing the applied voltage.

4A and 4B are explanatory diagrams of the heat generation temperature distribution of the thermal head and the shape of the printed dots, wherein FIG. 4A shows the heat generation temperature distribution of the conventional thermal head, FIG. 4B shows the heat generation temperature distribution of the thermal head of the present invention, and FIG. (D) shows the print dot shape by the conventional thermal head, and (d) shows the print dot shape by the thermal head of the present invention.

If the shape of the heating resistor is rectangular as in the thermal head having the configuration described in FIGS. 1 and 2, the heating temperature distribution of the conventional heating resistor is as shown in FIG. Further, the distribution has a mountain shape having a peak at the center of the heating resistor.

Actually, there is a temperature difference of 25 to 30% with respect to the heat generation peak between the central part and the peripheral part of the resistor.

Therefore, the heating resistor of the conventional thermal head has a round print dot shape as shown in FIG.

For this reason, conventionally, the printing dot shape was made rectangular by giving sufficient printing power and increasing the heat generation temperature, but this meant that excessive thermal stress was applied to the center of the resistor compared to the periphery of the resistor. And the central portion of the resistor was easily deteriorated.

On the other hand, the heating resistor of the thermal head according to the present embodiment has a function of suppressing the temperature rise by rapidly increasing the resistance value when the Curie temperature is reached, so that heat concentration hardly occurs locally.

For example, when a peak at which heat generation starts from the central portion of the resistor is reached, the resistance value at the central portion of the resistor increases, and current flows on both sides of the resistor having a low resistance value.

Although both sides of the resistor release more heat than the central portion, this heating resistor tends to supply a large amount of current to compensate for the temperature drop due to the release of heat. Then, current is preferentially continued to flow until the heat generation temperature on both sides of the resistor becomes equal to that of the center of the resistor.

When the transient state is reached in this way, the heating resistor has a uniform temperature distribution (b).

Therefore, the print dot shape faithfully reproduces the resistor shape rectangle as shown in FIG.

However, it is necessary to apply a voltage sufficiently so that the heat generation temperature reaches the Curie temperature.

Since the BaTiO ₃ -based valence controlling semiconductor does not reach the Curie temperature or higher, it does not cause thermal breakdown even if a large voltage is applied by mistake.

 Therefore, it has a function to prevent thermal destruction by itself.

Next, a method for manufacturing the thermal head of the present invention will be described.

FIG. 5 is an explanatory view of a method of manufacturing a thermal head according to the present invention, which is manufactured in the order of steps (a) to (f).

BaTiO ₃ -based valence controlling semiconductors, which are heating resistors, are manufactured by printing and firing a mixture of metal organic materials to obtain a metal oxide thin film, the so-called MOD method (Meiallo Oreganic Deposition).
After a metal oxide film having a predetermined thickness is formed by repeatedly performing position), BaTiO ₃ crystal grains can be grown by annealing.

The MOD method is characterized in that a uniform metal oxide compound having an arbitrary composition can be easily formed by mixing a metal organic substance, and the film thickness can be freely controlled by repeating this process.

Hereinafter, a method of forming a heating resistor according to the present invention will be described in detail.

In the present embodiment, as described below, organic materials of Ba and Ti as main materials and organic materials of Pb and Ta as additive materials are used.

First, the specification of the heating temperature of the heating resistor is determined, and the mixing ratio of Ba and Pb is determined based on the specification. Ta is used as an additional element.

For example, assuming that the heating temperature of the heating resistor is 200 ° C., the mixing ratio of Ba and Pb is 0.8: 0.2, and part of Ti is 0.3 at Ta.
% (Atomic%) and make it semi-moving,
The chemical formula is (Ba _0.8 Pb _0.2 ) (Ti _0.997 Ta _0.003 ) O ₃ .

As the metal organic material for the MOD heating resistor, for example, a mixture of the following solutions of metal resinate (trade name) of NE Chemcat Co. is used.

# 137-C (Ba organic material) # 207A (Pb organic material) # 9428 (Ti organic material) # 7522 (Ta organic material) In other words, the atomic ratio after firing each of the above solutions is Ba: Pb: Yi: Mix at a ratio such that Ta = 0.8: 0.2: 0.997: 0.003, and further adjust to an appropriate viscosity using a solvent such as α-terpineol and butyl carbitol acetate.

As shown in FIG. 5A, the MOD heating resistor paste is deposited on the glazed ceramic substrate 6 having an underglaze layer formed on its surface by screen printing or spin coating.

After drying the substrate on which the MOD heating resistor paste has been deposited, raise the temperature to 600 ° C at a heating rate of 10 to 200 ° C / min in an infrared belt firing furnace, etc., hold at 600 ° C for 1 hour, and then cool. I do.

A MOD film of about 350 nm can be obtained by this one deposition process. This process is repeated to form a laminated resistance film having a thickness of 4 to 8 μm.

Finally, the temperature is raised to 1200 ° C at a heating rate of 5 ° C / min.
Anneal for 1 hour and cool, average particle size is about 0.2μ
As a result, a heating resistor layer 10 of BaTiO ₃ -based valence controlling semiconductor of m is obtained.

Next, as shown in (b), for example, D27 manufactured by Noritake Co., Ltd.
Metallo organic gold paste such as (trade name) is solid printed and fired to form a gold electrode film 20 '.

Then, as shown in (c), a resist layer is applied to the surface of the gold electrode film 2 and dried, and a photomask for exposure is superposed thereon to perform an exposure and a phenomenon. Photolitho etching for removing the resist by etching using a potassium solution is performed to obtain an Au electrode film 20.

Next, as shown in (d), using the Au electrode film 20 as a mask, the MOD heating resistor layer 10 is etched using fluorinated nitric acid.

When the exposed portion of the heating resistor is removed from the Au electrode film 20 again by photolithographic etching, the heating resistor 1 divided in the main scanning direction can be obtained as shown in FIG.

Finally, as shown in (f), when a wear-resistant layer 4 is formed on the surface of the substrate subjected to the above-described processing, a thermal head as shown in FIG. 1 is completed.

The thermal head manufactured in this manner has, for example, a length of 120 μm in the sub-scanning direction and a length of 100 μm in the main scanning direction.
When a resistor of m is formed, the resistivity becomes at least about 10 Ω · cm, so that the average resistance becomes 15 to 30 kΩ.

Therefore, the driving voltage of the thermal head becomes high.

FIG. 6 is a block diagram of a second embodiment of the thermal head according to the present invention, and the same reference numerals as those in FIG. 1 correspond to the same parts.

The thermal head shown in FIG. 1 is a thermal head having an alternating electrode wiring structure in which a common electrode 2 and a drive electrode 3 are meshed in a sub-scanning direction, and a heating resistor 1 is formed so as to traverse the meshed portion in a main scanning direction. If the width of the heating resistor 1 in the sub-scanning direction is 130 μm and the width of the alternating electrodes is 20 μm,
When the resistivity is 10 Ω · cm, the average resistance value is 2 to 4 kΩ, and the driving voltage can be reduced.

FIG. 7 is a block diagram of a third embodiment of the thermal head according to the present invention, and the same reference numerals as those in FIGS. 1 and 6 correspond to the same parts.

The thermal head shown in FIG. 1 has a structure in which a heating resistor 1 is sandwiched between a rectangular patch-shaped common electrode 2 and a drive electrode 3 from above and below. With such a structure, the shape of the upper electrode (drive electrode 3) is changed. By setting the size to 100 μm × 100 μm, the average resistance value can be reduced to 40 to 80 Ω when the resistivity of the heating resistor 1 is 10 Ω · cm.

If it is desired to further increase the resistance value, the resistivity can be increased by 10 to 100 times by reducing the amount of impurities added.

[Effects of the Invention] As described above, according to the present invention, the heating resistor is
By using a polycrystalline BaTiO ₃ based valence control semiconductor, its Curie temperature can be shifted to higher temperatures,
It is possible to provide a thermal head in which the heating temperature is self-controlled to generate a constant temperature, the temperature distribution of the heating section is made uniform, the reproducibility of print dots is improved, and the self-destruction of the heating resistor is prevented.

[Brief description of the drawings]

FIG. 1 shows a first method of manufacturing a thermal head according to the present invention.
FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is a description of a transient response of heat generation temperature and heat storage characteristics of the thermal head manufactured according to the embodiment. FIG. 4, FIG. 4 is an explanatory diagram of the heat generation temperature distribution of the thermal head and the shape of the printed dots, FIG. 5 is an explanatory diagram of the method of manufacturing the thermal head according to the present invention, and FIG. 6 is a second embodiment of the thermal head according to the present invention. FIG. 7 is a block diagram of a third embodiment of the thermal head according to the present invention, and FIG.
FIG. 4 is a temperature characteristic diagram of a PTC thermistor in which a part of Ba is substituted with Pb. DESCRIPTION OF SYMBOLS 1 ... Heating resistor, 2 ... Common electrode, 3 ... Drive electrode, 4 ... Wear-resistant layer, 5 ... Underglaze layer, 6 ...
... Insulating substrate such as ceramic.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-27962 (JP, A) JP-A-2-34361 (JP, A) JP-A-62-181162 (JP, A) JP-A-61-181 254358 (JP, A) JP-A-60-244563 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41J 2/335

Claims (1)

(57) [Claims] A first electrode formed on the insulating substrate; a plurality of drive electrodes disposed opposite to the common electrode; and a heating resistor connecting the common electrode and the plurality of drive electrodes. In a method of manufacturing a thermal head using a BaTiO ₃ -based valence controlling semiconductor as a body, a method of coating and firing a mixed solution of a metal organic material containing at least Ba and Ti on an insulating substrate by repeating a plurality of times a film thickness of 4 to
A thermal head comprising a step of forming a BaTiO ₃ -based valence control semiconductor polycrystal by forming an 8 μm multilayer resistive film, and then performing an annealing treatment to grow a grain, and using this as a heating resistor. Manufacturing method.