JPH03281261A - Thermal head - Google Patents

Abstract

PURPOSE:To improve heat dissipation of a heat producing part by providing a thermal head pattern consisting of a metal base plate having a projecting part formed thereon, a glaze glass layer formed on the upper surface of the metal base plate and a heating resisting body formed on the glaze glass layer covering the projecting part. CONSTITUTION:A metal base plate 1 on which a glaze layer 2 is to be formed in later process is partly subjected to deformation processings such as pressing, rolling, extruding and drawing to form a projecting part 11 on its surface or to processings such as spraying, vapor deposition, plating and cutting to form thereon a curved surface having an arcuate cross section or a ridged projecting part 11 defined by two straight lines. On the surface formed as aforesaid, is laid a glaze glass layer 2 having a sufficient thickness to completely cover the projecting part 11 and make its surface flat and smooth or a curved surface with a large radius of curvature. In this way the thickness of the glaze glass layer 2 formed over the projecting part 11 can be reduced to at most 50mum to form a metal base plate 4 excellent in heat dissipating ability.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates generally to printers, and more particularly to a thermal head for a thermal transfer printer having an improved metal substrate.

[Prior art 1] A metal substrate (indicated by reference numeral 4 in Figs. 11-13 below) generally used for a thermal head is (a) as shown in Fig. 11, a glaze is coated on one side of a flat metal plate 1. (b) As shown in FIG. 12, a glaze glass layer 2 is formed on both sides of a flat metal plate l. (c) As shown in FIG. There are three types in which a flat glazed glass layer 2 is formed on one side of a flat metal plate 1, and a partial glazed glass layer 3 is further formed on a part of the flat glazed glass layer 2.

In the case of (a), patterns such as the heating resistor of the thermal head are formed on the glaze glass layer 2. The glaze glass layer 2 is fired at around 1000°C, and when it is cooled from the firing temperature to room temperature, distortion occurs due to the difference in thermal expansion coefficients between glass and metal, causing the entire board to warp and cause functional problems. It often causes problems.

Therefore, in (b), glaze glass layers are formed on both sides of the substrate to balance the strain and prevent warping.

In the case of (c), the heating resistor of the thermal head is formed on the partially glazed glass layer 3 to improve the contact state between the thermal head and the blinking paper.

2) The metal substrate thermal head of Japanese Patent Application No. 1-128920, which is the applicant's earlier application, is a metal substrate thermal head in which a glaze glass layer 2 is laminated on a metal substrate l.
As shown in FIGS. 15 and 16, a glaze glass layer 2 is laminated on a metal substrate 1, and a plurality of heating resistors 3a are placed on top of the glaze glass layer 2.
+~3an are arranged in parallel, and furthermore, a common electrode 4a and IC electrodes 4b, ~4b, which face the common electrode 4a with a predetermined interval therebetween, are formed.
n is connected to one pole of a power supply 7 via a common control IC 5 and a power supply electrode 8, the electrode of the power supply 7 is directly connected to the metal substrate 1, and the metal substrate 1 and the common electrode 4a are connected to each other by a solder 10. electrically connected.

The reason why the peripheral edge of the metal substrate 1 and the common electrode 4a are electrically connected by solder lO is as follows.

As shown in FIG. 14, if the common electrode 4a is simply connected to the electrode of the power source 7 by a lead wire or the like at one point A at its end, each heating resistor 3a+ The distance up to 3 a n is the shortest when it is 38, and it becomes longer in the following order.

Since the common electrode 4a has a relatively small cross-sectional area, the resistance value that the current flowing through the common electrode 4a receives depending on the distance is not negligible, and the amount of heat generated by the heating resistor that is far from the end A of the common electrode 4a is small. It becomes smaller and causes uneven printing on Bunonta.

As shown in FIG. 15, the metal substrate 1 is
If the common electrode 4a is connected to the metal substrate 1 itself, the metal substrate 1 itself forms the common electrode, and
Since the distances to ++ are equal and the cross-sectional area is extremely large compared to the common electrode 4a, the resistance value can be ignored and the heat generation amount of each heating resistor is the same, so that printing unevenness due to the difference in heat generation amount can be solved for the time being.

[Problems to be Solved by the Invention] In the case of 1) B), Fig. 11, the board often warps as described above, causing problems in the printing function, and in the case of (C), Fig. 13, It is difficult to control the shape of the partial glazed glass layer 3, it is difficult to form a stable shape, and the thickness of the partial glazed glass layer 3 is 60 μm or less compared to the full-surface glazed glass layer of (a). Since this is not possible, the thermal insulation effect of this part is excessive, resulting in poor heat dissipation and significant deterioration of the thermal characteristics of the thermal head, resulting in poor print clarity and a disadvantage that printing speed cannot be increased.

2) According to the metal substrate thermal head of the aforementioned Japanese Patent Application No. 1-128920, which is the applicant's earlier application, the distance from the end A of the common electrode 4a to each heating resistor 3a+ to 3ar+ is 3.
This solves the problem of uneven printing in the printer due to the decreasing length of the heating resistor located away from the end A of the common electrode 4a, which becomes longer in order from a+, but as shown in FIG. 16. Since the metal substrate 1 and the common electrode 4a are electrically connected together, the glaze glass layer 2, which is an insulator, is sandwiched between the lead electrode and the metal substrate 1 to form a capacitor, and when the capacitance becomes large, , a problem arises in that a delay occurs in the signal on the thermal head.

[Means for Solving the Problems] l) A protrusion is formed on a part of the metal substrate on which the glaze glass layer is to be formed by plastic working such as pressing, rolling, extrusion, or drawing, or by thermal spraying, A chevron-shaped protrusion whose cross section is defined by a curved surface such as an arc or two straight lines is formed on the surface by processing other than plastic processing such as vapor deposition, plating, and cutting, and the protrusion is completely buried and the upper surface is By forming a glazed glass layer thick enough to flatten the surface, or by covering with a glazed glass layer having a curved surface with a large radius of curvature, the thickness of the covering glazed glass layer formed on the top of the protrusion is 50 μm. Below, a thin metal substrate with excellent heat dissipation properties is used.62) Furthermore, when the common electrode 4a described above is adopted, the lead electrode, the metal substrate 1, and the glazed glass layer 3 between them form a capacitor. We will discuss how to solve the problems associated with this.

The capacitance C of the capacitor is calculated using the following formula.

C=ε・S/d where, C: capacitance, ε: permittivity,
S: surface area, d: thickness of capacitor.

It is.

Since the thickness d of the capacitor is T1 in Fig. 10,
By keeping the overall thickness of the glaze glass layer 2 large, the capacitance of the capacitor can be reduced, and this is combined with the fact that the thickness T2 of the glaze glass layer formed at the top of the protrusion is made thinner than 50 μm. The problem was solved by maintaining good heat dissipation in the heat generating part.

[Function] Unlike conventional flat metal substrates, the glazed glass layer can be made thinner at the top of the deformation, providing excellent heat dissipation, and can be made thicker at parts other than the top of the deformed protrusion.
Since the capacitor capacity can be reduced, when this metal substrate is applied to a thermal head of a quib that uses a common electrode, it is possible to reduce the signal delay on the thermal head due to the glaze glass layer forming a capacitor. can.

[Example] Fig. 1 shows a metal plate 1 having a curved surface such as an arc shape with a radius of curvature r at the top, and Fig. 2 shows a curved surface defined by two straight lines,
A substrate 4 is shown in which a chevron-shaped protrusion 11 having a width of 2 and an obtuse-angled apex A is formed by press working or the like.

In these examples, a recess 12 is formed on the opposite side of the metal plate from the protrusion 11, but both are functionally glazed using the same technology as the conventional full-surface glazed glass layer (see Figure 11.12). A glass layer can be formed.

1 and 2, the glaze glass layer 2 is formed on one side (the upper surface in the figure) of the metal plate l, but it may be formed on either one side or both sides, and the glaze glass layer 2 shown in FIG. A double-sided glaze glass layer 2 is formed on a metal plate l having the structure shown in the figure, and FIG. Furthermore, FIG. 5 shows a modified embodiment in which a protrusion 21 is formed on the metal plate 1 so as to correspond to the partially glazed glass layer 3 in FIG. 13. Such a shaped material can be formed by processing methods such as rolling using upper and lower contour rolls corresponding to such a cross section, extrusion using a die, drawing, or embossing. In this case, 1st to 4th
Unlike the processing that involves bending deformation as shown in the figure, no recesses are formed on the back side of the metal plate 1.

The formation of a glazed glass layer on a metal substrate is usually done by applying a glass paste onto the metal plate using thick film technology.
A method of firing at a high temperature of around °C is used.

At this time, the glass paste on the protrusion shown in FIG. 5 becomes almost flat due to the leveling effect, and if the surface is further polished after firing, the flatness of the surface can be ensured.

The thickness T2 of the glazed glass layer 2 at the top A of the raised portion 21 is the thickness T2 of the flat portion other than the raised portion.
1, and it goes without saying that this can also be applied to the embodiments shown in FIGS. 1 and 2.

In addition, when forming the glazed glass layer on both sides, it is also effective to cut out a part of the glazed glass layer 2 on the side opposite to the protrusion of the metal plate, that is, on the back side, as shown in Fig. 3. be.

2 In addition, as shown in FIG. 6, the metal plate 1 is located at the positions of the protrusions 11 on the metal plate 1 from FIGS. 1 to 4 and the raised protrusions 21 in FIG. Separate projections 31 may be brought into close contact.

If the protrusion 31 is made of a material different from the glaze glass 2, it can be made of metal, ceramics, etc. with appropriate properties, and methods for making it in good contact include Al pressure welding, b) thermal spraying, C
) vapor deposition, d) plating, etc.

FIG. 7 shows that a protrusion II having an arcuate cross section is formed on the top surface of the substrate 1, and a recess 12 of approximately the same shape is formed on the back surface.
This embodiment shows a case where the glaze glass layer is cut out in this recess.

A flat glazed glass layer is formed on the protrusion ll. Further, a glazed glass layer 22 on the top of the protrusion 11
At this portion, the heat generating portion 24 of the heat generating resistor 25 and a pair of lid electrodes 23 connected thereto and facing each other are disposed so as to extend substantially to this protruding portion.

The thickness 3 T2 of the glaze glass layer 22 at the top A of the protrusion 11 is the thickness T of the flat part other than the raised part, and as already mentioned with reference to FIG. 5, it can be made thinner more easily. .

Claims (1)

[Scope of Claims] 1. A thermal head for a printer, comprising: a protrusion which is a metal substrate, and whose longitudinal cross-sectional shape is defined by an arc or two straight lines, and which has an obtuse, acute, or right-angled chevron-shaped apex; A glazed glass layer formed on the upper surface of the metal substrate, and a thermal head pattern such as a heating resistor formed on the glazed glass layer on the protrusion. A thermal head featuring 2. The thermal head according to claim 1, wherein the surface of the glaze glass layer formed on the upper surface of the metal substrate is flattened by embedding the protrusion. 3. In the thermal head according to claim 1, the surface of the glazed glass layer formed on the upper surface of the metal substrate has a portion covering the protrusion that is a curved surface with a radius of curvature larger than the radius of curvature of the protrusion, or A thermal head characterized by the top angle being formed as a large chevron-shaped protrusion, and the remaining portion being flat. 4. The thermal head according to any one of claims 1 to 3, wherein the protrusion on the metal substrate is formed by plastic working involving bending deformation such as press working or rolling;
A thermal head characterized in that a recess is formed on a surface opposite to the surface on which the protrusion is formed. 5. In the thermal head according to any one of claims 1 to 3, a glazed glass layer is formed on the surface of the metal substrate on which the protrusion is formed and on the opposite surface thereof, including the recess. A thermal head characterized by: 6. The thermal head according to claim 2, wherein the glaze glass layer is formed on a surface of the metal substrate on which the protrusion is formed and a portion of the opposite surface excluding the recess. thermal head. 7. The thermal head according to claim 1, wherein the protrusion is formed by rolling, extrusion, drawing, etc. without bending deformation of the metal substrate, and the back surface of the metal substrate is flat. thermal head. 8. The thermal head according to claim 1, wherein the protruding portion of the metal substrate is made of a material different from the glaze glass and is tightly adhered to the metal plate by pressure welding, thermal spraying, vapor deposition, plating, etc. thermal head. 9. The thermal head according to any one of claims 1 to 8, wherein the thermal head pattern such as the heating resistor includes a heating resistor formed on the protrusion of the glazed glass layer; and a lead electrode connected to the heating resistor, the heating portion of the heating resistor, the tip of the lead electrode, and a portion near the end substantially extending over the glazed glass layer on the protrusion. A thermal head characterized by being arranged with 10. The thermal head according to any one of claims 1 to 9, wherein the metal substrate is connected to one pole of a power source, and the thermal head pattern such as the heating resistor is connected to the thermal head of the glazed glass layer. The heating resistor includes a heating resistor formed on the protrusion, a lead electrode connected to the heating resistor and the other pole of the power source, and a common electrode facing the heating resistor and electrically connected to the metal substrate. The capacitance of the capacitor formed by the glazed glass layer sandwiched between the metal substrate and the lead electrode is reduced by the thick portion of the glazed glass layer other than the protrusion, and signal delay due to the capacitor is prevented. A thermal head characterized by: