JPS62278058A - Thermal head - Google Patents

Abstract

PURPOSE:To improve the thermal response property and the pulse duration of a thermal head by power saving and further to improve the insulating property of a heating element and a metal base material, by establishing a projected heat storage layer between the surface formed by coating a metal base material with a glass ceramics layer and the heating element. CONSTITUTION:A heat storage layer 4 is established between the insulating substrate formed by coating a metal base material 1 with a glass ceramics layer 2 and a heating element 5. SUS 430 is used as the metal base material 1 and the glass ceramics layer 2 is so formed that the thickness of a film becomes 100mum. Thereby, an insulating substrate is obtained. The glass ceramics layer 2 cosists of the composition having 15 weight % at least of any one of alkaline earth metals(BaO, MgO, CaO, and ZnO) and 2 weight % max. of one valency alkaline metal oxide (K2O, Na2O, and Li2O). Then, the linear heat storage layer of 1 mm in width and 20mum in thickness is formed by screen printing. By this construction, the thermal head efficient in the insulation of the heating element to the metal base material, high in the heating temperature of the heating element, and capable of printing by power saving is obtained.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention Field of Industrial Application The present invention relates to a thermal head that can be used in various printers, facsimile machines, and the like.

2. Description of the Related Art A conventional thermal head used in a 77 mm printer or the like has a typical configuration as shown in FIG. In FIG. 4, 21 is an insulating ceramic substrate, 22 is a heat storage glass layer, 23 is an etching prevention layer, 24 is a resistor, 26 is a pair of electrodes and conductor wiring, 26 is a wear-resistant layer,
Reference numeral 27 denotes a driving IC 128, which is a cooling substrate, and is bonded to a bonding layer 29 using an adhesive.

On the other hand, there is a thermal head that does not use a ceramic substrate but uses a substrate whose surface is a metal plate coated with an insulating glass layer.

This has the configuration shown in FIG. 5, and has high heat dissipation properties, so it is said to be effective for use in high-density, high-speed thermal heads.

Problems to be Solved by the Invention The present invention uses a metal base material to serve as both a heat sink and a substrate for forming a heating element. However, in the configuration shown in FIG. 5, the heat storage property of the insulating glass layer is is not good, so when printing,
The energy radiated from the metal plate is greater than the thermal energy applied to the paper, so printing in actual use requires high power.

In addition, the surface of the metal plate is covered with an insulating glass layer,
The composition of this insulating glass layer has a great effect on the lifespan of the SUMARU head, so the current situation is that the characteristics of using a metal plate are not fully utilized.

Means for Solving the Problems The present invention provides a convex heat storage layer between a heating element and an insulating substrate formed by coating a metal base material with a glass ceramic layer, and the glass ceramic layer is made of at least alkaline earth. Oxides of similar metals (BaO, MgO.

Contains at least 15% by weight of any of Cab, Zn○) and monovalent alkali metal oxides (K2O, Na2o, Li
2o) in a composition of 2% by weight or less.

Effects of the Invention The present invention provides a thermal head that has excellent insulation between a heating element and a metal base material, has a high heat generation temperature of the heating element, and can print with low power consumption.

Examples Examples of the present invention will be described below. FIG. 1 is a diagram showing an embodiment of the present invention. 1 is a metal base material, 2 is a glass ceramic layer, 3 is an electrode layer, 4 is a heat storage layer, 5 is a heating element layer, and 6 is a wear-resistant layer. Although FIG. 1 shows the configuration of a thick film thermal head, the present invention is not limited to this, and also includes a thin film thermal head and a mixed thin film/thick film thermal head.

The metal base material is steel plate for hollow holes and stainless steel plate.

Fe-Ni alloy and clad steel plate can be used. In addition, the thermal expansion coefficient of the metal base material is 60 to 140 x 1o-
A steel plate within the range of 7/°C is preferable.

The glass-ceramic layer insulates the metal base material, and the insulating layer must have heat resistance, high heat storage properties, and excellent adhesion to the metal base material. Glass ceramic layer monovalent alkali metal oxide (
Na20. It consists of 2% by weight or less of Li2o, Li2o), and its thermal expansion coefficient is 6o to 16o x 10-7/℃
must consist of a range of

Alkaline earth metal oxides (BaO, MgO, Cab
.

ZnQ ) containing 16% by weight or more reacts with S 102 and B2O3, which are the main components of glass, to form a highly insulating crystalline phase. This crystal phase is basically Bao・2MO・2Si02 (M is Mg
, Ca.

Zn), 2M0-B20 (M is Mg, Ca,
In addition, the composition ratio is CaO-
MgO-2S i○2゜2ZnO"3i02sMqo-
8i02 fx Tomo formation Sarel.

Also, alkaline earth metal oxides (BaO, MgO.

If the amount of any one of Cab, ZnO) is less than 166% by weight, the above-mentioned crystal phase is difficult to form, and even if it is formed, the proportion is small, so it cannot be used as an insulating substrate for a thermal head.

Furthermore, monovalent alkali metal oxide (Na2C) + L
t20. If the weight of K, O) is 2 or more, it becomes difficult to form a crystal phase of the alkaline earth metal oxide and S102 and B2O3, resulting in poor insulation and low heat resistance. Therefore, a material containing 2% by weight or more of a monovalent alkali metal oxide cannot be used as an insulating substrate for a thermal head.

6.＼-7゛On the other hand, the thermal expansion of the glass-ceramic layer is determined by the type of metal base material used, and preferably has a slightly lower coefficient of thermal expansion than the metal base material.

Therefore, it is necessary to select the composition ratio of the glass ceramic that suits the metal base material.

Next, a method for forming the glass ceramic layer will be described. A process diagram of the method for forming the glass ceramic layer is shown in FIG. The glass raw material is first melted at 1200-1600'C, and a glass ceramic cullet is obtained in a roll cooler.

Grind this and make a slip with ethyl alcohol and kaisoprobil alcohol.

On the other hand, if the metal base material must be cut into a predetermined shape, degreased, and partially electrodeposited, it is masked and placed in an electrophoretic layer, with a distance between electrodes of 2 to 5 cm and a sliding voltage of 200 to 200 cm. Electrophoretic electrodeposition of glass ceramic powder particles dispersed in alcohol at 6oov and 76oV after drying.
Firing is performed at 0 to 950°C to obtain an insulating substrate having a glass ceramic layer.

Here, the glass-ceramic layer was coated by electrophoretic electrodeposition, but compared to immersion or spraying methods, this method provides a more uniform coating and is more densely formed. Resistors and electrodes can be formed accurately and easily.

The optimum glass ceramic powder for this electrophoretic electrodeposition is one with an average particle size in the range of 2 to 7 μm; if the particle size is larger than this, the surface of the glass ceramic layer will become rough, and the electrophoretic electrodeposition will During deposition, the adhesion strength between the electrodeposited particles and the metal is weak, and this occurs in the glass ceramic particles when the metal substrate is pulled up from the electrolytic bath. On the other hand, particles with a small average particle size have the advantage of being able to be electrodeposited at low voltage and in an extremely dense manner, but when the metal base material on which the glass ceramic particles have been electrodeposited is pulled out of the electrolytic bath. , the electrodeposited layer dries rapidly, causing problems such as peeling of the electrodeposited layer from the metal base material.

The heat storage layer is made of Pb0.8102. B2O3, Bad,
Cab.

A glass layer whose basic composition is three or more of ZnO, AI, 03, and also Zr, Ti, Bi, Sr, Cd,
Mg.

Oxides such as p and sb are included as additives.

Li, Na, monovalent alkali metal oxides are 1.
Must be less than 0 weight. The thermal expansion of this heat storage layer is about 10 degrees smaller than that of the glass ceramic layer. As a result, even when the heating element is subjected to a thermal cycle test, it does not peel off or crack from the glass ceramic layer, and can withstand a long period of time.

The heat storage layer is formed by making a paste of glass powder having the composition shown above, printing it on the surface of the glass ceramic coating layer by screen printing, and then firing it.

Furthermore, the method for forming the heating element, electrode, and #4 wear layer will be described. The structure of the thermal head of the present invention is such that a heating element, an electrode, and an abrasion resistant layer are formed on the above-mentioned insulating substrate, and the formation methods thereof include a method of forming a thin film and a method of forming a thick film. be.

A process diagram of the formation method is shown in FIGS. 3a and 3b. These methods are conventionally used methods, and the present invention is not limited thereto.

[Example 1] In the configuration of the thermal head shown in FIG. 1, 5US430 (thickness 0, 8+mn) was used as the metal base material 1,
A glass ceramic layer having a thickness of 100 μm was formed using the glass ceramic composition shown in Table 1 using the manufacturing method shown in FIG. 2 to obtain an insulating substrate. Next, the glass composition shown in Table 2 was made into a paste using terpineol and ethyl cellulose, and a linear heat storage layer having a width of 1 mm and a thickness of 20 μm was formed by screen printing.

Furthermore, a thermal head was experimentally manufactured using the thin film manufacturing method shown in FIG. 3a. As a comparative example, in the above process,
The insulating board is made of a hollow board (ELPOR manufactured by Nippon Ferro).
-[) and glazed alumina substrate (Narumi Seito Co., Ltd. NCG-s
o1) was used. The manufacturing conditions and characteristic evaluation are shown in Table 3.

The recording density test shown in Table 3 shows that the reflection density (0, D) was 1.0 when current was applied for a period of 1 ms and a recording period of 5 ms. In addition, the pulse life is 4 m8 for energizing time.
．． This is the lifespan when the recording cycle is 16m5.

Table 1 S 102 22.6 Wt Chi B 20315
-3 # MqO39,27 BaO20,0/I Z r O24, On AZ 20 s 0.7 rtP2o6
0.3 ll 5i02 5.3 wt% B2o3 6.4 〃 PbO66,0# ZnO12,6# CaO4,0# At203 es, sp From Table 3, Example 1 is a hollow substrate of a comparative example.

It can be seen that the recording density requires approximately % to % less power than the glazed alumina substrate. Furthermore, the pulse life is about four times longer than that of the hollow substrate of the comparative example.

[Example 2] The low alkaline insulating hollow coating layer for the thermal head used in the present invention has a surface roughness Ra (center line average roughness) of 0.06 in order to form the functional part of the thermal head.
~0.6 μm is required. For this reason, it is necessary to electrodeposit a low alkaline glass frit using an electrophoretic electrodeposition method to glaze the glass frit. Further, the thermal head is a type of heater, and requires a dielectric strength of 5 KV or more because it locally passes a large current.

However, normally, when the monovalent alkali metal component (Li20, Na2O, K2O) increases in the glass component, the insulating properties of the glass and the electrophoretic electrodeposition properties of the powdered glass deteriorate approximately in proportion to the increased amount. Therefore, from A to T shown in Table 4.
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The glass composition is a monovalent alkali metal oxide (L 120
The table shows that the various properties of the glass and the properties of the thermal head differ significantly depending on the amount of addition of divalent alkaline earth metal oxides (BaO, MgO, CaO, ZnO) and divalent alkaline earth metal oxides (BaO, MgO, CaO, ZnO). ing. The thermal head had the configuration shown in FIG. 1 and was manufactured according to the thick film process shown in FIG. 3. The heat storage layer is the same as in Example 1, and the electrodes include Au,
RuO2 is used for the resistor, and a glass layer is used for the wear-resistant layer.

Thermal response of the thermal head was tested with a pulse width of 1 ms and a pulse period of 5 ms. The dot part was heated using an In-8b infrared microscope manufactured by Nippon Burns Co., Ltd. by applying current at 0.5 W/ims. Measures the condition and indicates the maximum temperature.

The results of the various characteristics in Table 4 are summarized as follows.

(1) The monovalent alkali metal oxide (Li20.Na2O, Ni20) is 0.2-2% by weight in the glass composition.
A range of is preferred. 0.2% by weight or less is impurity 15
.

Due to the limit of contamination, it is difficult to synthesize glass of less than this, and conversely, when the weight ratio exceeds 2, electrophoretic electrodeposition of glass frit becomes difficult, and the dielectric strength deteriorates rapidly (E, F, G,
L, M, N, ○, S.

T).

(2) Amount of divalent alkaline earth metal oxide (Mqo.

It is preferable that the amount of oxides of CaO, BaO, Zn0) is at least 16% by weight, and particularly preferably the total amount of oxides of divalent alkaline earth metals is 55% by weight or more.

These relationships require a balance between the amount of monovalent alkali and the amount of divalent alkali (A, B, C, D).

L, M, N, O, P, Q, R).

(3) With the low alkali glass composition shown in Table 1, if the amount of monovalent alkali is 2% by weight or less, the sliding voltage will be 250 to 350.
(2) enables electrophoretic electrodeposition in an alcohol solvent containing a small amount of moisture, and the thermal head has excellent properties such as dielectric strength and thermal response (A, B, C, D, 1
．． K.

S, T).

(4) As the amount of monovalent alkali in the glass increases, a high sliding voltage of 350 to 650 V is required during electrophoretic electrodeposition, and as a result, the dielectric strength voltage becomes lower than 0.5 KV (G,
L, M, N, ○, R).

(6) General hollow glasses (L, M, N) have a relatively large amount of monovalent alkali and a small amount of divalent alkali, require high pressure for electrophoretic electrodeposition, have a large bubble structure in the hollow layer, and are thermally It has poor characteristics as a head substrate.

(6) The coefficient of thermal expansion of the glass of the insulating hollow layer is as understood from the diagram (it is difficult to synthesize glass with a diameter of 60 x 10 /'c or less. Also, the coefficient of thermal expansion of the metal base material is 60 to 14
The majority are in the range of 5×10°C. Therefore, the coefficient of thermal expansion of glass is 6o to 145X10-n°C.
Low alkali glass (A, B, C, D, E,
F.H.

I, 1. (P, Q, S, T) are preferable, and the combination can be determined by selecting the metal base material and the glass to match the thermal expansion coefficients.

Effects of the Invention As detailed above, according to the present invention, a convex heat storage layer is provided between the surface of a metal base material coated with a glass ceramic layer and the heating element, thereby saving power and generating heat. Responsiveness and pulse life can be improved, and the insulation between the heating element and the metal base material can also be improved. Furthermore, since the thermal head of the present invention can also be equipped with a heat sink, it can be miniaturized and
It can also significantly contribute to high reliability, long life, and cost reduction.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the basic configuration of a thermal head according to an embodiment of the present invention, FIG. 2 is a manufacturing process diagram of an insulating substrate of the thermal head, and FIG. 3 is a manufacturing process diagram of the thermal head.
Figure 4 is a cross-sectional configuration diagram of a conventional thin film type thermal head.
FIG. 5 is a cross-sectional configuration diagram of a conventional thermal head using a hollow substrate. 1...metal base material, 2...glass ceramic layer, 3...electrode, 4...heat storage layer,
5... Heating element, 6... Wear-resistant layer. Figure 2 Figure 3 (Kyu) (b)

Claims (2)

[Claims] (1) A thermal head characterized in that a heat storage layer is provided between an insulating substrate formed by covering a metal base material with a glass ceramic layer and the heating element. (2) The glass ceramic layer contains at least 15% by weight of any one of alkaline earth metal oxides (BaO, MgO, CaO, ZnO), and monovalent alkali metal oxides (Na_2O, K_2O, Li_2O) 2% by weight
The thermal head according to claim 1, characterized in that it has the following composition.