JP3325359B2 - 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 as a printer mechanism of a word processor, a facsimile or the like.

[0002]

2. Description of the Related Art Conventionally, as an example of a thermal head incorporated as a printer mechanism such as a word processor, an end face type thermal head in which a heating resistor is disposed on an end face of a head substrate is shown in FIG. A plurality of heating resistors 12 made of tantalum nitride or the like, an individual conductive layer 13a individually connected to each heating resistor 12, on an end surface of an electrically insulating substrate 11 made of
Common conductive layer 1 commonly connected to each of the heating resistors 12
3b and a part of the common conductive layer 13b is led out to the lower surface of the electrically insulating substrate 11, and a head substrate J is mounted on a metal plate 15 made of aluminum or the like. A predetermined power is applied between the individual conductive layer 13a and the common conductive layer 13b in accordance with an external electric signal to selectively cause the heating resistor 12 to generate Joule heat and to use the generated heat as a heat-sensitive element. Conducted on paper etc.
By forming a predetermined print image on thermal paper or the like, it functions as a thermal head.

In such a conventional thermal head, when the head substrate J is placed on the metal plate 15 as it is, the common conductive layer 13b attached to the lower surface of the head substrate J and the metal plate 15 When a short circuit occurs and the thermal head is incorporated in the printer device, the metal plate 15 comes into contact with other electronic components in the printer device, and a large current flows into the other electronic components via the common conductive layer 13b. Therefore, an insulating film 14 (thickness: about 75 μm) made of polyester or the like is interposed between the head substrate J and the metal plate 15 so that the lower surface of the head substrate J is interposed between the head substrate J and the metal plate 15. The attached common conductive layer 13b and the metal plate 15 are electrically insulated.

[0004]

However, in this conventional thermal head, the thick insulating film 14 having a thickness of about 75 μm is provided between the head substrate J and the metal plate 15.
And the insulating film 14 is made of polyester or the like having poor thermal conductivity (thermal conductivity: 5.7 × 10 ^−5).
cal / mm · sec · ° C.), when the heating resistor 12 is repeatedly heated in a short time to generate Joule heat and high-speed printing is performed, the heat generated by the heating resistor 13 is generated by the head substrate J. The insulating film 14 blocks the escape from the metal plate 15 to the metal plate 15 side, and as a result, the temperature of the head substrate J becomes excessively high, so that unnecessary printing is formed on thermal paper or the like. are doing.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thermal head capable of always forming a head substrate at a temperature suitable for printing and forming a good and clear printed image on thermal paper or the like.

[0006]

According to the present invention, there is provided a thermal head comprising: a plurality of heating resistors; an individual conductive layer individually connected to each of the heating resistors; A head substrate formed by applying a common conductive layer commonly connected to each heating resistor and leading a part of the common conductive layer to the lower surface of the electrically insulating substrate is moved up to a predetermined depth region. A thermal head mounted on an anodized metal plate, wherein a potential difference (V) generated between the common conductive layer and the metal plate during use, a depth (d) of the anodized portion, It is characterized in that the withstand voltage (E) of the metal oxide forming the anodized portion is set so as to satisfy the following expression “V / d ≦ E”.

The thermal head according to the present invention is characterized in that the metal oxide forming the anodized portion is made of aluminum oxide, and the depth (d) is set to 5 μm to 10 μm. .

Further, in the thermal head according to the present invention, the metal oxide forming the anodized portion is magnesium oxide.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view showing an embodiment of a thermal head according to the present invention, FIG. 2 is a sectional view taken along line XX of FIG. 1, FIG. 3 is an enlarged sectional view of a portion A in FIG. Insulating substrate, 2 a heating resistor, 3a an individual conductive layer, 3b a common conductive layer, 5
Is a metal plate.

The electrically insulating substrate 1 is made of an electrically insulating material such as alumina ceramics. A ceramic material powder such as alumina, silica, magnesia or the like is mixed with an appropriate organic solvent and solvent to form a slurry. The ceramic green sheet is formed by employing a conventionally known doctor blade method, calender roll method, or the like, and then the ceramic green sheet is punched into a predetermined shape and fired at a high temperature.

A glaze layer 1a made of glass or the like is deposited on the end surface of the electrically insulating substrate 1 so as to have a thickness of 10 μm to 80 μm, and the glaze layer 1a is formed on the upper surface of the heating resistor 2. Accumulates the heat generated by the thermal head to bring the thermal head to a temperature required for forming a print image on thermal paper or the like in a short time.

The glaze layer 1a is formed by applying a glass paste obtained by adding a suitable organic solvent to a glass powder and applying the glass paste to the end face of the electrically insulating substrate 1 by a spray method. By baking at a temperature of ° C., it is adhered to the end surface of the electrically insulating substrate 1.

A plurality of heating resistors 2 are attached to an end surface of the electrically insulating substrate 1 on which the glaze layer 1a is attached, and the heating resistors 2 are made of tantalum nitride or the like.
Since it itself has a predetermined electric resistivity, when a predetermined power is applied between the individual conductive layer 3a and the common conductive layer 3b described later, it is necessary to form a printed image on thermal paper or the like. It acts to generate Joule heat at a certain temperature.

The heating resistor 2 is attached to the end surface of the electrically insulating substrate 1 on which the glaze layer 1a is attached by employing a conventionally known sputtering method and photolithography technique.

Each of the heating resistors 2 is individually connected at one end thereof to an individual conductive layer 3a extending to the upper surface of the electrically insulating substrate 1, and at the other end thereof. Are connected in common to a common conductive layer 3b led out to the lower surface of the substrate.

The individual conductive layer 3a and the common conductive layer 3b
Is made of a metal material such as aluminum, copper, or the like, acts to apply a predetermined electric power necessary for causing the heating resistor 2 to generate Joule heat, and performs a thin film forming technique such as a sputtering method, or a screen printing technique. It is attached so as to be led out from the end surface of the electrically insulating substrate 1 to the upper surface and the lower surface, respectively, by a thick film technique.

As described above, the head substrate K having the heating resistor 2 or the like attached to the end surface of the electrically insulating substrate 1 and the common conductive layer 3b extending out from the lower surface is made of aluminum, magnesium, titanium, tantalum or the like. Is mounted on a metal plate 5 composed of:

The metal plate 5 has a function of supporting the head substrate K on the upper surface thereof, absorbing the heat of the head substrate K, and maintaining the temperature of the head substrate K at a temperature suitable for printing.

Since the upper surface of the metal plate 5 is anodically oxidized, the common conductive layer 3b partially led out to the lower surface side of the head substrate K is formed by the anodized portion on the upper surface of the metal plate 5. Is electrically isolated from the common conductive layer 3b and the metal plate 5 can be effectively prevented from being short-circuited. Therefore, when the thermal head is incorporated in a printer, even if the metal plate 5 contacts another electronic component in the printer, a large current does not flow into the other electronic component via the common conductive layer 3b. No other electronic components will be damaged.

Further, the upper surface of the metal plate 5 is anodized, and the common conductive layer 3b, part of which is led out to the lower surface side of the head substrate K, and the metal plate 5 are electrically insulated by the anodized portion. Therefore, the step of interposing an insulating film or the like between the head substrate K and the metal plate 5 can be omitted, and the number of components of the thermal head can be reduced by eliminating the need for the insulating film or the like, thereby improving the workability of assembling the thermal head. Can be made.

Further, the upper surface of the metal plate 5 is anodically oxidized so that a metal oxide having a high thermal conductivity (aluminum oxide:
About 7.2 × 10 ⁻³ cal / mm · sec · ° C., magnesium oxide: 8.7 × 10 ⁻³ cal / mm · sec · ° C.
Titanium oxide: 1.6 × 10 ⁻³ cal / mm · sec ·
° C) and the metal oxide is polyethylene or the like forming an insulating film (thermal conductivity: 5.7 × 10 ^-5 cal)
/Mm.sec..degree. C.). Therefore, when high-speed printing is performed by causing the heating resistor 2 to repeatedly generate Joule heat in a short time, the heat generated by the heating resistor 2 is transferred from the lower surface of the head substrate K to the metal plate 5 on which the metal oxide is formed. Metal plate 5 through the upper surface of
Side, it is possible to keep the head substrate K in a good temperature state at all times, and it is possible to prevent unnecessary printing from being formed on thermal paper or the like, and to print good and clear on thermal paper or the like. An image can be formed.

The metal plate 5 is anodized by first forming an ingot (a lump) made of aluminum or the like into a predetermined shape by using a conventionally known metal working method.
It is immersed in an electrolyte containing about 5 to 30% of an inorganic acid such as sulfuric acid or phosphoric acid, or an organic acid such as oxalic acid or acetic acid, and is applied with a positive voltage of about 30 V for about 2 minutes via an external power supply. to 20mA / cm ² ~50mA / cm flowed ² current of about negative ions OH in the electrolyte solution ^- was attached to the upper surface of the metal plate 5, the top surface of a predetermined depth d of the metal plate 5, for example 5 This is done by oxidizing to a depth of 10 μm. The depth d of the anodized portion is determined by the potential difference V between the common conductive layer 3b and the metal plate 5 when the thermal head is incorporated in a printer. What is necessary is to set so that V / d divided by d is equal to or smaller than the dielectric strength (critical electric field) E of the metal oxide formed by anodic oxidation.

Thus, according to the thermal head of the present invention, the individual conductive layer 3a and the common conductive layer 3b correspond to the external electric signal.
A predetermined power is applied between the thermal head and the thermal head by selectively causing the heating resistor 2 to generate Joule heat and transmitting the generated heat to a thermal paper or the like to form a predetermined print image on the thermal paper or the like. Function as

It should be noted that the present invention is not limited to the above embodiment, and various changes and improvements can be made without departing from the scope of the present invention. If the resistor 2 is covered with a protective layer made of silicon nitride or the like, the protective layer protects the heat generating resistor 2 and the like from oxidative corrosion due to contact with moisture or the like contained in the air and abrasion due to sliding contact with thermal paper or the like. Can be protected well. Therefore, it is preferable to cover the heating resistor 2 with a protective layer.

In the above embodiment, an end-face type thermal head in which the heating resistor 2 is disposed on the end face of the head substrate K has been described. However, as shown in FIG. A C end face type thermal head in which a heating surface is formed and the heating resistor 22 is adhered to the C surface, a heating resistor is adhered to the upper surface of the electrically insulating substrate, and a common conductive layer is formed on the heating resistor. Connected, a part of the common conductive layer may be applied to a flat-type thermal head led out to the lower surface of the electrically insulating substrate, and when applied to any of the thermal heads, the same effect as in the above embodiment can be obtained. Obtainable.

[0027]

According to the thermal head of the present invention, a plurality of heating resistors, an individual conductive layer individually connected to each of the heating resistors, and each of the heating resistors are provided on the upper surface or the end surface of the electrically insulating substrate. A head substrate formed by applying a common conductive layer commonly connected to the substrate and leading a part of the common conductive layer to the lower surface of the electrically insulating substrate has an upper surface anodized to a predetermined depth region. It is placed on a metal plate and the potential difference (V) generated between the common conductive layer and the metal plate at the time of use, the depth (d) of the anodized portion, and the withstand voltage of the metal oxide forming the anodized portion (E) is set so as to satisfy the expression “V / d ≦ E”, the common conductive layer partially led out on the lower surface side of the head substrate is connected to the metal plate by the anodized portion on the upper surface of the metal plate. Electrically isolated, short circuit between common conductive layer and metal plate Can be effectively prevented. Therefore, the thermal head can always be normally operated, and when the thermal head is incorporated into the printer, even if the metal plate contacts another electronic component in the printer, the thermal head is commonly used by the other electronic components. A large current does not flow through the conductive layer, and no other electronic components are damaged.

According to the thermal head of the present invention, the upper surface of the metal plate is anodically oxidized, and the common conductive layer and the metal plate partially exposed on the lower surface side of the head substrate are electrically connected by the anodic oxidation portion. Since it is insulated, the step of interposing an insulating film or the like between the head substrate and the metal plate can be omitted, and the number of parts of the thermal head can be reduced by eliminating the need for the insulating film or the like. Can be made favorable.

Further, according to the thermal head of the present invention, since the metal oxide forming the anodized portion has a high thermal conductivity, heat can be conducted more quickly than polyethylene or the like forming the insulating film. . Therefore, when high-speed printing is performed by repeatedly causing the heating resistor to generate Joule heat in a short time, the heat generated by the heating resistor is transmitted from the lower surface of the head substrate to the upper surface of the metal plate on which the metal oxide is formed. Escapes very well to the metal plate side, so that the head substrate can always be kept in a good temperature state, and no unnecessary printing is formed on thermal paper etc. It is possible to form a perfect printed image.

Further, according to the thermal head of the present invention, by using magnesium oxide having a high thermal conductivity as the metal oxide forming the anodized portion, a part of the heat in the head substrate is transferred to the metal plate side. It is possible to transmit the image more satisfactorily, and thereby, it is possible to record a clear image with less density unevenness on thermal paper or the like, even in high-speed printing for a long time.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment applied to an end face type thermal head of the present invention.

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

FIG. 3 is an enlarged sectional view of a portion A in FIG. 2;

FIG. 4 is a sectional view showing an embodiment in which the present invention is applied to a C-plane type thermal head.

FIG. 5 is a sectional view of a conventional thermal head.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electric insulating board, 2 ... Heating resistor, 3a.
..Individual conductive layers, 3b ... common conductive layers, 5 ... metal plates, K ... head substrates

Claims (3)

(57) [Claims] 1. A plurality of heating resistors, an individual conductive layer individually connected to each heating resistor, and a common connection commonly connected to each heating resistor on an upper surface or an end surface of an electrically insulating substrate. the head substrate made by deriving a portion of the common conductive layer to the lower surface of the electrically insulating substrate with depositing a conductive layer, so the upper surface placed on the anodized metal plate on to a predetermined depth region Thermal head
A potential difference (V) generated between the common conductive layer and the metal plate;
The depth of the anodized portion (d) and the formation of the anodized portion
Withstand voltage (E) of the metal oxide satisfying the following equation:
A thermal head characterized in that it is set so that: V / d ≦ E ... 2. The method according to claim 2, wherein the metal oxide forming the anodized portion is
Made of aluminum oxide, having a depth (d) of 5 μm or more
2. The method according to claim 1, wherein the distance is set to 10 μm.
The described thermal head. 3. The method according to claim 1, wherein the metal oxide forming the anodized portion is
2. The method according to claim 1, wherein the material is magnesium oxide.
On-board thermal head.