JP3004093B2 - Thermal head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a thermal head incorporated in a printer mechanism such as a word processor, a facsimile or an electronic typewriter.

[0002]

2. Description of the Related Art The principle of a thermal head is to convert an electric signal read from a subject into a voltage, apply the voltage to an electric resistance material to generate Joule heat, and make the thermosensitive recording paper or ribbon sensitive by the Joule heat. The gist is to print and print.

As shown in FIG. 2, such a conventional thermal head has a heating resistor layer 12 made of tantalum nitride (Ta ₂ N) on a substrate 11 made of an electrically insulating material such as alumina.
And a pair of conductive layers 13a and 13b made of aluminum (Al), copper (Cu) or the like are sequentially laminated, and a constant power is applied to the heating resistor layer 12 via the pair of conductive layers 13a and 13b. By applying the voltage and causing the heating resistor layer 12 to generate Joule heat, it functions as a thermal head.

In this conventional thermal head, the heating resistor layer 12 and the pair of conductive layers 13a and 13b are usually used for contact abrasion by a thermal recording paper or a thermal transfer ribbon and moisture contained in the atmosphere and chlorine contained in the thermal recording paper. Sialon (S) is provided on the upper surfaces of the heating resistor layer 12 and the pair of conductive layers 13a and 13b in order to protect against corrosion caused by contact with sodium or sodium.
A protective film 14 made of (i-Al-ON) is deposited by sputtering to a thickness of about 4 μm.

[0005]

However, in this conventional thermal head, when a protective film 14 made of sialon is deposited on the upper surfaces of the heating resistor layer 12 and the pair of conductive layers 13a and 13b by a sputtering method, the protective film is protected. The film 14, in particular, the heating resistor layer 12 and the pair of conductive layers 13
a, protection film 1 located at the step formed by 13b
4 has a large internal stress, which is increased by the pressing force of pressing the thermal recording paper or the like against the thermal head and pressing the thermal recording paper or the like when a print image is formed on the thermal recording paper or the like. As a result, the protective film 14 cracks due to the large stress, or peels off from the upper surfaces of the heating resistor layer 12 and the pair of conductive layers 13a and 13b, thereby causing the heating resistor layer 12 and the pair of conductive layers 13a and 13b to be separated. Wear caused by contact with thermal recording paper or thermal transfer ribbon,
There is a drawback that corrosion occurs due to contact with chlorine or sodium contained in moisture in the air or in thermosensitive recording paper.

[0006]

According to the thermal head of the present invention, a heating resistor layer, a pair of conductive layers and a protective layer are sequentially deposited on an electrically insulating substrate, and the protective layer is made of aluminum nitride, A first member made of at least one of silicon carbide, carbon, boron nitride, aluminum oxide, silicon nitride, and sialon, and a mixed material of a second member made of at least one of silicon oxide, selenium oxide, and tantalum oxide, In addition, the mixing ratio is in the following order of A, B, and C from the electrically insulating substrate side.

A first member / second member = 1.5 to 4.0 B first member / second member = 1.0 or less C first member / second member = 2.3 or more

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a sectional view showing one embodiment of the present invention, wherein 1 is a substrate, 2 is a heat storage layer, 3 is a heating resistor layer, 4a,
4b is a conductive layer.

The substrate 1 is made of, for example, an electrically insulating material having excellent heat resistance such as alumina ceramics. A ceramic material powder such as alumina, silica, magnesia or the like is mixed with an appropriate organic solvent or solvent to form a slurry. A ceramic green sheet is formed by employing a well-known doctor blade method, and then the ceramic green sheet is punched into a predetermined shape and fired at a high temperature (about 1600 ° C.). .

On the upper surface of the substrate 1, a heat storage layer 2 is adhered. The heat storage layer 2 stores and dissipates heat generated by a heating resistor layer 3, which will be described later, to improve the thermal response characteristics of the thermal head. Works to keep

The heat storage layer 2 is made of glass, and a glass paste obtained by adding and mixing an appropriate organic solvent and a solvent to the glass powder is formed on the substrate 1 by a conventionally known thick film method such as screen printing. It is applied to the upper surface of the substrate 1 by printing and coating, and then firing at a high temperature (about 700 ° C.).

When the heat storage layer 2 made of glass has a thickness of 50 to 80 μm, the heat generated by the heating resistor layer 3 can be efficiently stored and dissipated, and the thermal response characteristics of the thermal head can be extremely improved. It can be made excellent. Therefore, the thickness of the heat storage layer 2 made of glass is preferably set to 50 to 80 μm.

On the upper surface of the heat storage layer 2, a heating resistor layer 3 is adhered, and on the heating resistor layer 3, a pair of conductive layers 4a, 4b with a fixed interval are covered. Is being worn.

The heating resistor layer 3 is made of, for example, tantalum nitride and has a predetermined electric resistance. Therefore, when electric power is applied through a pair of conductive layers 4a and 4b, Joule heat is generated. And generates heat at a temperature required to form a printed image, for example, at a temperature of 250 to 400 ° C.

A pair of conductive layers 4a and 4b provided on the heating resistor layer 3 are made of metal such as aluminum or silver, and the conductive layers 4a and 4b And acts to apply a predetermined electric power required to cause the above.

The heating resistor layer 3 and the pair of conductive layers 4a and 4b are sequentially deposited on the heat storage layer 3 by employing a conventionally known sputtering method and photolithography technique.

On the upper surfaces of the heating resistor layer 3 and the pair of conductive layers 4a and 4b, a protective layer 5 is adhered. The protective layer 5 is composed of an adhesive layer 5a, an ion blocking layer 5b and a wear-resistant layer 5a.
c has a three-layer structure.

The adhesive layer 5a, the ion blocking layer 5b, and the wear-resistant layer 5c constituting the protective layer 5 are all made of aluminum nitride (AlN), silicon carbide (SiC), carbon (C), boron nitride (BN), and oxide. Aluminum (Al ₂ O ₃ ),
Silicon nitride (Si ₃ N _4), sialon (Si-Al-O
-N) and a _second member made of at least one of silicon oxide (SiO ₂ ), selenium oxide (CeO), and tantalum oxide (Ta ₂ O ₅ ). By changing the mixing ratio of the first member and the second member, the adhesive layer 5a, the ion blocking layer 5b, and the wear-resistant layer 5c are formed.

The adhesive layer 5a of the protective layer 5 has a mixing ratio of a first member such as aluminum nitride or silicon carbide and a second member such as silicon oxide or selenium oxide, such that first member / second member = 1.
The bonding layer 5a is formed on the upper surface of the heating resistor layer 3 and the pair of conductive layers 4a and 4b by employing a conventionally well-known sputtering method. It functions to firmly join the heating resistor layer 3 and the pair of conductive layers 4a and 4b.

In this case, since the adhesive layer 5a has a small amount of oxide that is weakly bonded to oxygen, the oxygen in the adhesive layer 5a is dissociated by the heat generated by the heating resistor layer 3, and this is separated from the heating resistor. There is no change in the electrical resistance value of the heating resistor layer 3 by reacting with the layer 3.

The adhesive layer 5a is made of aluminum nitride,
A first member such as silicon carbide and a second member such as silicon oxide and selenium oxide
When the mixing ratio with the member exceeds the first member / second member = 4.0, the protective layer 5 is formed into the heating resistor layer 3 and the pair of conductive layers 4a,
4b, the first member / second member = less than 1.5, the amount of the second member increases, and the weakly-bonded oxygen contained in the second member loses the heat-generating resistor. It reacts with the layer 3 and causes a variation in the heat generation temperature of the heating resistor layer 3. Therefore, the adhesive layer 5a has a mixing ratio of the first member and the second member of the first member / the second member = 1.5 to
It is specified in the range of 4.0.

Further, the adhesive layer 5a has a thickness of 0.5
When the thickness is set to 1.0 μm, the protective layer 5 can be firmly joined to the heating resistor layer 3 and the pair of conductive layers 4a and 4b. Therefore, the adhesive layer 5a has a thickness of 0.5 to
It is preferable to set it to 1.0 μm.

The ion blocking layer 5b of the protective layer 5 has a mixing ratio of a first member such as aluminum nitride or silicon carbide and a second member such as silicon oxide or selenium oxide of the first member / second member = 1. 0, and the ion blocking layer 5
b is adhered to the upper surface of the adhesive layer 5a by employing the bias sputtering method.

The ion-shielding layer 5b formed by the bias sputtering method has no film-forming defects, and completely blocks permeation of moisture contained in the atmosphere and chlorine and sodium contained in the thermosensitive recording paper. It is possible to effectively prevent corrosion of the heating resistor layer 3 and the like due to contact of the moisture contained in the atmosphere and the chlorine and sodium contained in the thermosensitive recording paper with the heating resistor layer 3 and the like.

The mixing ratio of the first member such as aluminum nitride or silicon carbide to the second member such as silicon oxide or selenium oxide is 1.0 / 1.0.
Is exceeded, when forming the ion blocking layer 5b on the adhesive layer 5a by the bias sputtering method,
b, a large stress is inherent therein, which becomes large in combination with a pressing force for pressing the thermal recording paper or the like when a printed image is formed on the thermal recording paper or the like. The conductive layers 13a and 13b are separated from the upper surfaces. Therefore, in the ion-blocking layer 5b, the mixing ratio of the first member and the second member is specified to be equal to or less than the first member / the second member = 1.0.

When the ion blocking layer 5b has a thickness of 3.0 to 4.0 .mu.m, it effectively blocks moisture and the like contained in the atmosphere, and oxygen and the like prevent the heat generating resistor layer 3 and the pair of conductive layers. 4a, 4b, etc., can be completely prevented. Therefore, it is preferable that the ion blocking layer 5b has a thickness in the range of 3.0 to 4.0 μm.

Further, the wear-resistant layer 5c of the protective layer 5 has a mixing ratio of a first member such as aluminum nitride or silicon carbide and a second member such as silicon oxide or selenium oxide, ie, first member / second member =
2.3 or more, and is formed on the upper surface of the ion-blocking layer 5b by employing a conventionally known sputtering method. The wear-resistant layer 5c is composed of the heating resistor layer 3 and the pair of conductive layers 4a, 4b. Has the effect of preventing wear due to contact with the thermal recording paper or thermal transfer ribbon.

The wear-resistant layer 5c is made of a mixture of a first member such as aluminum nitride and silicon carbide and a second member such as silicon oxide and selenium oxide, and is large when the wear-resistant layer 5c is applied. Since the second member has no internal stress, the wear-resistant layer 5c does not have a large stress even if it is applied to the upper surface of the ion-blocking layer 5b by a sputtering method. When a printed image is formed on a recording paper or the like, even if a pressing force for pressing the thermal recording paper or the like is applied to the wear-resistant layer 5c, the wear-resistant layer 5c does not peel off from the ion-blocking layer 5b.

In the wear-resistant layer 5c, the mixing ratio of the first member such as aluminum nitride or silicon carbide and the second member such as silicon oxide or selenium oxide is less than 2.3 (first member / second member). If this happens, the hardness of the wear-resistant layer 5c decreases, and it is not possible to effectively prevent wear due to contact with thermal recording paper or the like. Therefore, in the wear-resistant layer 5c, the mixing ratio of the first member and the second member is specified to be equal to or more than 2.3 (first member / second member).

Further, the wear-resistant layer 5c has a thickness of 1.
When the thickness is set to 0 to 2.0 μm, even if the thermal recording paper slides, the abrasion of the protective layer 5 can be minimized, and the heating resistor layer 3 and the pair of conductive layers 4a, 4b are protected for a long time. be able to. Therefore, it is preferable that the thickness of the wear-resistant layer 5c be in the range of 1.0 to 2.0 μm.

The adhesive layer 5a, the ion-blocking layer 5b and the wear-resistant layer 5c constituting the protective layer 5 are all deposited on the heating resistor layer 3 and the pair of conductive layers 4a and 4b by a sputtering method or the like. Since each layer has the same basic material, each layer can be firmly joined.

Thus, the above-described thermal head applies electric power between the pair of conductive layers 4a and 4b in response to an external electric signal to cause the heating resistor layer 3 to generate Joule heat to a predetermined temperature and to generate the heat. Is transferred to a thermosensitive recording paper or the like, and a predetermined printed image is formed on the thermosensitive recording paper or the like to function as a thermal head.

[0034]

According to the thermal head of the present invention, a protective layer having a three-layer structure of an adhesive layer, an ion-blocking layer and a wear-resistant layer is applied to the upper surfaces of the heating resistor layer and the pair of conductive layers. Therefore, the moisture contained in the air and the chlorine and sodium contained in the heat-sensitive recording paper are completely blocked by the ion-blocking layer, and as a result, the heating temperature of the heating resistor layer is reduced without any corrosion of the heating resistor layer. Can always be constant,
High quality printed images can be formed on thermal recording paper or the like.

Further, since the protective layer is made of a wear-resistant layer having a high hardness and a small intrinsic stress, it hardly wears even when the thermal recording paper or the like slides in contact, and the wear-resistant layer is peeled off. The thermal head can be operated stably and satisfactorily for a long period of time.

Further, since the protective layer is firmly joined to the heating resistor layer and the pair of conductive layers by an adhesive layer therebelow, the protective layer cannot be separated from the heating resistor layer and the pair of conductive layers by application of an external force. Therefore, the thermal head can be operated stably and satisfactorily for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal head according to the present invention.

FIG. 2 is a sectional view of a conventional thermal head.

[Explanation of symbols]

 1... Substrate 2... Thermal storage layer 3... Heating resistor layer 4a, 4b Conductive layer 5.・ Ion blocking layer 5c ・ ・ ・ ・ Abrasion resistant layer

Claims (1)

(57) [Claims] 1. A thermal head in which a heating resistor layer, a pair of conductive layers and a protective layer are sequentially deposited on an electrically insulating substrate, wherein the protective layer is made of aluminum nitride, silicon carbide,
A mixture of a first member made of at least one of carbon, boron nitride, aluminum oxide, silicon nitride, and sialon and a second member made of at least one of silicon oxide, selenium oxide, and tantalum oxide, and a mixture thereof A thermal head, wherein the ratio is in the following order of A, B, and C from the electrically insulating substrate side. A first member / second member = 1.5 to 4.0 B first member / second member = 1.0 or less C first member / second member = 2.3 or more