JPH04232763A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent a heating region from becoming a wedge shape and to reduce the size of a cuff printing dot. CONSTITUTION:A thermal head consists of an insulating substrate, the comb- tooth shape common electrode 4 formed on the insulating substrate, the individual electrodes 3 arranged in opposed relation to the comb-tooth shape lead-out parts 4a of the common electrode 4 in a staggered state, the heat diffusion parts 3a, 4b respectively independently formed on the extension lines of the lead-out parts 4a of the common electrode 4 and the extension lines on the leading end sides of the individual electrodes 3, the strip like heating resistor 5 with definite width formed to the common electrode 4, the individual electrodes 3 and a part of the heat diffusion parts 3a, 4b in a contact state and the protective layer formed so as to cover the common electrode, the individual electrodes and the strip like heating resistor.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in thermal recording devices such as printers and facsimiles.

0002

2. Description of the Related Art FIG. 6 is a sectional view of a main part of a conventional thick film thermal head. This thick film type thermal head is
A heat storage layer 2 is formed on an insulating substrate 1, and individual electrodes 3 and a common electrode 4 are formed on this heat storage layer 2 to face each other. As shown in FIG. 7, the common electrode 4 has a comb-shaped lead-out part 4a projecting therefrom, and each individual electrode 3 is arranged opposite to the lead-out part 4a in a staggered manner. A heating resistor 5 having a constant width and a semicircular cross section is formed on the tip of the individual electrode 3 and the lead-out portion 4a. Further, a protective layer 6 is formed on the insulating substrate 1, and covers the heating resistor 5, the individual electrodes 3, and the common electrode 4.

In a thermal printer having this structure, a voltage is applied to the common electrode and the individual electrodes are selectively turned on and off to generate heat in the heating resistor, and the heat-sensitive resistor is transferred while being pressed by the platen roller B. Print information on recording paper A.

0004

[Problems to be Solved by the Invention] In the conventional thermal head described above, as shown in FIG. It corresponds to one of the printing dots that develop color. In this thick film type thermal head, when a voltage is applied to both electrodes (common electrode and individual electrodes) 3 and 4, the overlapping part of the combs of the common electrode and individual electrodes (the lead-out part 4a and the individual electrode 3
The current is concentrated at the opposing tip portions of the heating resistor 5, and the central portion of the heating resistor 5 generates heat. The generated heat diffuses inside the resistor 5 by thermal conduction, and at the same time escapes from the lead electrode to the outside of the resistor 5. For this reason, the heat generation shape (heat generation area C) on the surface becomes a wavy and meandering shape as shown in FIG. Therefore, when one line in the main scanning direction (longitudinal direction of the heating resistor) is printed on thermal paper, the printing results in a meandering pattern, resulting in poor printing quality. Further, since the heat generation temperature distribution spreads in the sub-scanning direction (width direction of the heat generating resistor), there is a drawback that it is not possible to reduce the print dot size.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thermal head in which the heat generating area is substantially linear and strip-shaped, and the print dot size can be reduced.

[0006]

Means and Effects for Solving the Problems In order to achieve this object, a thermal head according to claim 1 of the present invention has the following configuration. The thermal head includes an insulating substrate, a comb-tooth-shaped common electrode formed on the insulating substrate, individual electrodes arranged opposite to the comb-tooth-shaped lead-out portion of the common electrode, and the above-mentioned electrodes. A thermal diffusion section formed independently on an extension line of the lead-out portion of the common electrode and an extension line on the tip side of the individual electrode, and a thermal diffusion section formed in contact with a part of the common electrode, the individual electrodes, and each heat diffusion section. It is characterized by comprising a band-shaped heating resistor having a constant width, a common electrode, an individual electrode, and a protective layer formed to cover the heating resistor.

[0007] In the thermal head having such a configuration, independent heat diffusion portions (thermal diffusion layers) are provided on extension lines of the common electrode and the individual electrodes, respectively. Therefore, when a voltage is applied between the common electrode and the individual electrodes,
Heat diffusion becomes almost uniform between the common electrode side and the individual electrode side. Therefore, the heat generating area becomes a belt shape with almost straight sides,
Good printing without meandering (wavy) can be obtained. Furthermore, for example, if the overlap width of the comb between the common electrode and the individual electrodes (the portion where the extraction part and the tip of the individual electrode face each other) is made smaller, the thermal diffusion part can also be used in this case.
Excessive heat (heat whose heat generation temperature distribution spreads in the sub-scanning direction) can be quickly diffused to the outside of the resistor. Therefore, the print dot size can be easily reduced.

The thermal head according to the second aspect of the present invention has the following configuration. The thermal head includes an insulating substrate, a comb-tooth-shaped common electrode formed on the insulating substrate, individual electrodes arranged opposite to the comb-tooth-shaped lead-out portion of the common electrode, and the above-mentioned electrodes. A heat diffusion section formed independently on an extension line of the extension part of the common electrode and an extension line on the tip side of the individual electrode, and a part of the heat diffusion part on the tip part of the extension part of the common electrode and the individual electrode side. Except for the first insulating layer with a constant width and thickness formed on the common electrode, and the tip of the individual electrode and a part of the heat diffusion part on the common electrode side, A second insulating layer with a constant width and thickness, a heating resistor that spans the first insulating layer and the second insulating layer and is formed on the protruding electrode portion between both the insulating layers, a common electrode, and individual electrodes. and a protective layer formed to cover the heating resistor.

[0009] In the thermal head having such a configuration, independent thermal diffusion portions are formed in the common electrode and the individual electrodes, respectively, as in the thermal head according to claim 1 of the present invention. Therefore, the shape of the heat generating region (heat generating shape) does not become a meandering band shape, and the print dot size can also be reduced. Furthermore, with this thermal head,
A line-shaped insulating layer having a certain width and thickness is arranged at a certain interval between the common electrode and the individual electrodes arranged opposite each other, and the line-shaped insulating layer is placed between the two insulating layers and within the interval between the two insulating layers. A heating resistor is formed on both exposed electrodes. Therefore, both ends of the heating resistor ride on the insulating layer, and the central portion becomes concave. This concave portion is a portion that functions in contact with the electrode, and is a relatively flat portion. As a result, the central portion of the protective layer formed on the insulating substrate and covering the electrode, the insulating layer, and the heating resistor corresponding to the heating resistor also has a concave shape. Therefore, when the thermal recording paper is pressed and moved by the platen roller, an upward force is generated on the thermal recording paper by the recessed portion. In other words, the pressure acting on the portions of the thermal recording paper corresponding to the recessed portions is smaller than on the raised portions at both ends of the heating resistor. Therefore, even if heat is concentrated in the center of the heating resistor, the thermal recording paper is easily separated from the protective layer, and sticking is prevented.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of a main part of a specific embodiment of a thermal head according to claim 1. As is well known, the thermal head includes an insulating substrate 1,
A heat storage layer 2 formed on this insulating substrate, and a heat storage layer 2 formed on this insulating substrate.
A comb-tooth-shaped common electrode 4 formed above, individual electrodes 3 arranged in a staggered manner to face the comb-tooth-shaped extraction portion 4a of the common electrode 4, and the extraction portion 4a of the common electrode and the individual It consists of a band-shaped heating resistor 5 of a constant width formed on the upper surface of an electrode 3 (see FIG. 6).

In the embodiment, the insulating substrate 1 is a flat plate made of a material such as alumina ceramic, and an amorphous glass paste is printed and fired on this substrate to form a heat storage layer (underglaze layer) 2. There is. The individual electrodes 3 and the common electrode 4 are formed on this heat storage layer 2. Individual electrode 3
The common electrode 4 is made of gold (Au) on the surface of the heat storage layer 2, for example.
A paste is printed, baked to form a conductor layer, and then this conductor layer is etched to form a pattern. As shown in FIG. 1, the lead portion 4a of the comb-shaped common electrode 4 and the individual electrodes 3 are arranged opposite to each other in a staggered manner. In addition, in the embodiment, the common electrode (lead portion 4a) 4
The pattern is formed such that the overlapping width of the combs of the individual electrodes 3 (the opposing portion of the drawn-out portion 4a and the tip of the individual electrode 3) is smaller than the line width of the heating resistor 5.

A feature of the present invention is that the lead-out portion 4a of the common electrode 4 and the individual electrodes 3 are provided with thermal diffusion portions 4b and 3, respectively.
It is at the point where a is set. That is, as shown in FIG. 1, a conductor pattern section (thermal diffusion layer) 4b for heat diffusion independent of the common electrode 4 is formed on the extension line of the tip of the lead-out section 4a of the common electrode 4, and the tip of the individual electrode 3 Also on the extension line, individual electrode 3
and an independent conductor pattern section (thermal diffusion layer) 3a for heat diffusion.
is formed.

In the thermal head having such a configuration, independent heat diffusion portions (thermal diffusion layers) 4b and 3a are provided on extension lines of the common electrode 4 and the individual electrodes 3, respectively. Therefore, when a voltage is applied between the common electrode 4 and the individual electrodes 3, heat diffusion becomes approximately uniform between the common electrode side and the individual electrode side. Therefore, the heat generating area D has a band shape with substantially straight sides, and good printing without meandering (wavy) can be obtained. Further, since there is no meandering (no unevenness on both sides of the heat generating region D), the width of the band-shaped heat generating region D is also reduced. Furthermore, the overlapping width of the combs between the common electrode 4 and the individual electrodes 3 (the length of the opposing portion between the extended portion 4a and the tip of the individual electrode 3) is made small. Therefore, even in this case, by using the heat diffusion parts 4b and 3a, the extra heat (
The heat whose temperature distribution expands in the sub-scanning direction can be quickly diffused to the outside of the resistor 5, and the print dot size can be easily reduced. Figure 2 shows an electrode pattern (P
FIG. 3 is an explanatory diagram showing print dot sizes in the sub-scanning direction of the electrode pattern (Q pattern) provided with the thermal diffusion portions 4b and 3a of the example. In this explanatory diagram, the vertical axis represents the print dot size in the sub-scanning direction, and the horizontal axis represents the overlapping width of the combs between the common electrode 4 and the individual electrodes 3. Here, the line width of the heating resistor 5 is 120 μm, and the common electrode 4
The overlapping width of the combs of the individual electrodes 3 is 40, 60, and 100 μm.
The case is shown below. The electrode pattern (Q pattern) of the embodiment including the thermal diffusion parts 4b and 3a has a smaller print dot size in the sub-scanning direction than the electrode pattern (P pattern) without the thermal diffusion part, regardless of the size of the overlap width of the combs. is getting smaller.

FIG. 3 is a cross-sectional view of a main part of a specific embodiment of the thermal head according to claim 2 of the present invention. This thermal head has substantially the same structure as the previous embodiment (the embodiment shown in FIG. 1 of the thermal head recited in claim 1). In other words, the insulating substrate 1, the heat storage layer 2, the comb-shaped common electrode 4 formed on the heat storage layer 2, and the comb-shaped lead-out portion 4a of the common electrode 4 are arranged opposite to each other in a staggered manner. the individual electrodes 3 and
It consists of thermal diffusion pattern parts 4b and 3a formed independently on the extension line of the tip of the lead-out part 4a of the common electrode 4 and on the extension line of the tip of the individual electrode 3, respectively.

A feature of the present invention is that a first insulating film having a constant width and thickness is provided on the common electrode 4, except for the tip of the lead-out portion 4a of the common electrode 4 and a part of the heat diffusion portion 3a on the individual electrode 3 side. At the same time as forming the layer 7, a second insulating layer 8 having a constant width and thickness is formed on the individual electrode 3, except for the tip of the individual electrode 3 and a part of the heat diffusion part 4b on the common electrode side. The heating resistor 5 is formed across the first insulating layer 7 and the second insulating layer 8 and on the exposed electrode portion between both the insulating layers 7 and 8.

The first insulating layer 7 and the second insulating layer 8 are formed using an insulating material such as glass paste or SiO2. First insulating layer 7 and second insulating layer 8
is formed in a line shape having a constant width and thickness. That is, as shown in FIG. 4, the individual electrodes 3 and the common electrode (the lead-out portion 4a) 4 are arranged in parallel with each other orthogonally with a certain interval between them. As shown in FIG.
A part of the thermal diffusion part 3a on the side, the tip of the individual electrode 3, and a part of the thermal diffusion part 4b on the common electrode 4 side are exposed.

The heating resistor 5 is formed, for example, by screen printing a paste containing ruthenium oxide and firing the paste. This heating resistor 5 is connected to the first insulating layer 7
and the second insulating layer 8, and is formed on both the electrodes 3, 4 with an interval between the first and second insulating layers 7, 8. As a result,
A recessed portion 5a is formed on the surface of the heating resistor 5 (see FIG. 3).

Furthermore, a protective layer 6 is formed on the insulating substrate 1, and covers the electrodes 3, 4, insulating layers 7, 8, and heating resistor 5. This protective layer 6 is formed, for example, by printing an amorphous glass paste and firing it. As a result,
A recess 6a is formed on the surface of the protective layer 6 at a portion corresponding to the recess 5a of the heating resistor 5 (see FIG. 3). In the thermal head having such a configuration, both ends of the heating resistor 5 ride on the insulating layers 7 and 8, respectively, and the central portion forms a concave shape 5a. This recessed portion 5a is a portion that functions in contact with the electrode, and is a relatively flat portion. As a result, the portion of the protective layer 6 corresponding to the heating resistor 5 also becomes a recessed portion 6a. Therefore, when the thermal recording paper A is pressed and moved by the platen roller B, an upward force is generated on the thermal recording paper A by the recessed portion 6a. In other words, the pressure acting on the portion of the thermal recording paper A corresponding to the recessed portion 5a is smaller than that on the raised portions at both ends of the heating resistor 5. As a result, even if heat is concentrated in the center of the heating resistor 5, the thermal recording paper A is easily separated from the protective layer 6, and sticking is prevented.

It should be noted that if the height difference x between the recessed part 6a of the protective layer 6 and the protruding part 6b of the protective layer 6 of the embodiment thermal head shown in FIG. The contact pressure between the part and the thermal paper becomes weak, the heat transfer state becomes insufficient, and the print density decreases. For this reason, extra printing energy is inevitably required, so it is desirable that the amount of depression be x≦1.5 μm if possible. x≦1.5μm
If it is below, there will be no printing energy loss (see FIG. 5). The conditions that make this condition possible include the insulating layers 7 and 8.
The distance between the two is 150 μm or less, and the thickness of the insulating layers 7 and 8 is 10 μm.
This is a thermal head that satisfies the requirement that the width of the upper resistor 5 be 400 μm or more, which is sufficiently large.

[0020]

Effects of the Invention As described above, in the thermal head according to claim 1, since the common electrode and the individual electrodes are provided with independent heat diffusion sections, heat diffusion is improved. As a result of the common electrode side and the individual electrode side being almost uniform, the heat generating area does not meander and good printing can be obtained, and the printing dot size can be reduced.

Further, in the thermal head according to claim 2, two insulating layers are arranged at a constant interval on the common electrode side and the individual electrode side, and these two insulating layers Since the heating resistor is formed on both electrodes that are exposed between the two insulating layers, it is possible to reduce the print dot size and obtain good print quality. Both ends ride on the insulating layer, and the central portion becomes recessed, so that the portion of the protective layer corresponding to the heating resistor also becomes recessed. Therefore, when the thermal recording paper is pressed and moved by the platen roller, an upward force is generated on the thermal recording paper by this concave portion, and even if heat is concentrated in the center of the heating resistor, this heat concentration can be accommodated. Since the pressing force on the heat-sensitive recording paper portion is small, it is easily separated from the protective layer and sticking is prevented, which has excellent effects that achieve the purpose of the invention.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a main part of an embodiment of a thermal head according to claim 1;

FIG. 2 is an explanatory diagram showing print dot sizes of the example thermal head.

FIG. 3 is a cross-sectional view of a main part showing an embodiment of a thermal head according to claim 2 of the present invention.

FIG. 4 is a plan view of a main part showing an embodiment of a thermal head according to claim 2 of the present invention.

FIG. 5 is a diagram showing the relationship between the depth of the protective layer and energy loss of the thermal head shown in FIG. 3;

FIG. 6 is a sectional view of a main part of a conventional thermal head.

FIG. 7 is a plan view showing a heat generating area of a conventional thermal head.

[Explanation of symbols] 1 Insulating substrate 3. Individual electrodes 4 Common electrode 5 Heating resistor 7 First insulating layer 8 Second insulating layer 3a/4b Heat diffusion part 4a Drawer part

Claims (3)

[Claims] 1. An insulating substrate, a comb-tooth-shaped common electrode formed on the insulating substrate, and individual electrodes arranged opposite to the comb-tooth-shaped lead-out portions of the common electrode in a staggered manner. A thermal diffusion section formed independently on an extension line of the lead-out portion of the common electrode and an extension line of the tip end side of the individual electrode, and a thermal diffusion section formed in contact with a part of the common electrode, the individual electrode, and each heat diffusion section. A thermal head comprising: a band-shaped heating resistor having a constant width; and a protective layer formed to cover the common electrode, the individual electrodes, and the band-shaped heating resistor. 2. An insulating substrate, a comb-tooth-shaped common electrode formed on the insulating substrate, and individual electrodes arranged opposite to the comb-tooth-shaped lead-out portions of the common electrode in a staggered manner. A thermal diffusion section is formed independently on an extension line of the extension part of the common electrode and an extension line on the tip side of the individual electrode, and a heat diffusion part is formed on the tip part of the extension part of the common electrode and on the individual electrode side. A first insulating layer having a constant width and thickness formed on the common electrode except for a part, and a part of a heat diffusion part on the tip part of the individual electrode and the common electrode side. a second insulating layer having a constant width and thickness; a heat generating resistor formed on the protruding electrode portion between the first insulating layer and the second insulating layer; and the common electrode; A thermal head consisting of an electrode and a protective layer formed to cover a heating resistor. [Claim 3] The depth of the concave part of the heat generating part of the protective layer is 1.5 μm.
The thermal head according to claim 2, characterized in that the following settings are made.