JPH0632935B2 - Thermal head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head, more specifically, a plurality of quadrilateral heating resistors arranged at a predetermined interval in a direction orthogonal to the transfer direction of a thermal recording medium. The present invention relates to a thermal head having a pair of electrodes connected to both ends of the heating resistor.

2. Description of the Related Art As a thermal head in which a plurality of heating resistors are arranged, for example, a thin model thermal head is formed by arranging a plurality of heating resistors 11 ... In a row at a minute interval on an insulating substrate 10 as shown in FIG. At the same time, the common electrode 12 and the individual electrode 18 are connected to the front and rear ends of the thermal recording medium in the transport direction P. The other end of the individual electrode is connected to a driving IC (not shown), and each heating resistor 11 is connected by the IC.
... are selectively energized. Each of the heating resistors 11 ... Generates Jewel heat when energized, and causes the heat-sensitive recording paper as a heat-sensitive recording medium to develop a color, thereby forming dots. In this case, since the thermal recording paper is being transferred, dots are also formed in the direction in which the heating resistors are arranged and in the transfer direction of the thermal recording paper. Therefore, the dot matrix records desired patterns such as characters and symbols. You can do it.

By the way, in such a thermal head, a heating resistor having a rectangular shape as shown in FIG. 4 was initially used. Therefore, there are the following drawbacks.

Problems to be Solved by the Invention That is, when a wide heating resistor is energized to generate heat,
Since the central portion has the property of easily retaining heat, the heating resistor has a temperature distribution when the central portion has a high temperature and the ambient temperature has a low temperature. In this case, if the high temperature in the center is adjusted to the reaction temperature of the thermosensitive recording paper, the thermosensitive recording paper does not develop color in the surrounding low temperature area, and therefore the size of the dots becomes small, as shown by the solid line in FIG. Dot 14, 14
The white portions 15 between them become large, the image becomes a grid pattern, and uneven density occurs. This appears to be a problem when the image quality deteriorates, especially when the input energy of the heating resistor is reduced to reduce the density in gradation printing. In this case, if a slightly longer energizing pulse is applied to the heating resistors, the cross-cut shape can be eliminated while the dots in the thermal recording paper transfer direction continue, but the gap between the heating resistors remains as a white part, A pattern is formed and uneven density cannot be eliminated.

On the other hand, when the input energy to the heat-generating resistor is increased to raise the temperature of the surrounding area of the heat-generating resistor to the reaction temperature of the thermal recording paper, the temperature of the central part becomes too high. It takes a long time to cool to the temperature below, so that dots are formed in places where printing is not required, and there is a drawback that a beautiful image cannot be obtained.

At present, in order to improve such a defect, it is currently used in Japanese Utility Model Publication No. 55-739.
The technique disclosed in Japanese Patent No. 6 has been proposed. In this technique, as shown in FIG. 6, the heat generating resistors 21 are formed so as to be inclined with respect to the thermal recording paper transport direction P. When the heating resistors 21 are formed so as to be inclined in this manner, it is possible to overlap the regions occupied by the heating resistors with respect to the direction orthogonal to the transfer direction P, so that the heating resistors are energized. By appropriately lengthening the pulse, it is possible to eliminate the gap between the dots in the direction orthogonal to the transfer direction P. Therefore, the image of the grid pattern or the draft pattern is eliminated, and the image of uniform density can be obtained. Has returned to the principle. In the figure, 22 and 23 are electrodes.

However, the above technique cannot fully eliminate the drawbacks of the heating resistor shown in FIG. 4 for the following reasons. That is, since the current generally has the property of flowing through the shortest distance, in the diamond-shaped heating resistor shown in FIG. 6, the current flows intensively along the diagonal side on the short side indicated by the arrow Q, and both sides thereof are at the ends. The current density decreases as it goes to the part. The portion 21a having a small current density is a dead space that does not contribute to color development of the thermosensitive recording paper and thus remains as a white portion on the recording paper. Therefore, the dots are recorded on the thermosensitive recording paper in the shape shown by the solid line in FIG.

Although this dot has a different direction as compared with the dot shown in FIG. 5, there is no significant difference in shape and size. Therefore, even if the energizing pulse is lengthened, the gap between adjacent heating resistors is not sensitive to heat. Since it remains as a white portion on the recording paper, there is a problem that the image of the draft pattern cannot be eliminated.

The present invention is proposed in view of the above problems, and an object thereof is to devise a pattern of the heating resistor so that the above-described technique of inclining the heating resistor can exert the effect in accordance with its principle. It is to achieve power saving so that printing can be performed with low energy.

Means for Solving the Problems According to the present invention, in order to achieve the above object, a plurality of quadrilateral heating resistors are arranged at a predetermined interval in a direction orthogonal to a transfer direction of a thermal recording medium, and each heating resistor is arranged. In a thermal head having a pair of electrodes connected to both ends of each of the heating resistors, a pair of opposite sides of each heating resistor is substantially parallel to the arrangement direction of the heating resistors, and an electrode including a connection portion with the heating resistors is provided. A slit having a width substantially the same as the gap width between adjacent heating resistors over the inclined connecting portion of the electrodes from the heating resistor. It is characterized by being formed. In this case, it is preferable that the heating resistors divided by the slit have substantially the same width, and the width of the slit is within a maximum of twice the total width of the dividing heating resistors. Is desirable.

Action According to the above configuration, the heating resistor is completely divided by the slit, the density of the current flowing through the heating resistor is equalized, and the dead space that does not contribute to the color development of the thermal recording medium is narrowed. A sharp-angled electrode end is formed near the slit and on both sides of the heating resistor, and the energy when power is applied between a pair of electrodes concentrates on the heating resistor near the slit and on both sides of the heating resistor. Therefore, although the slit portion that does not generate heat and the adjacent heating resistor do not generate heat by themselves, the heat is transmitted from the surroundings to a high temperature, which causes almost the entire heating resistor to contribute to color development and uneven density on the thermal recording medium. It is possible to form a good print which is not present.

Further, since the slit is formed to have a width substantially the same as the gap width between the adjacent heating resistors, when the adjacent heating resistors are simultaneously heated, the color development efficiency between the slit portion and the adjacent heating resistors is high. Even if the difference is slightly different from other portions, the different printing color development efficiencies are substantially equal between the slit portion and the adjacent heating resistors, and even when gradation printing is performed, the above-described difference in printing color development efficiency is caused. The resulting uneven density does not occur.

Embodiment FIG. 1 shows an embodiment of the present invention, 1 ...
Reference numeral 2 is a common electrode, 3 is an individual electrode, each of which is formed as a thin film on an insulating substrate by using a semiconductor manufacturing technique. Although not shown, an antioxidation film (SiO ₂ ) and a wear resistant film (Ta ₂ O ₅ ) are formed on the heating resistors 1 ... The heating resistors 1 ... Are arranged with a degree of integration of about 8 in 1 mm, and are arranged at a minute interval in the direction orthogonal to the transfer direction of the thermal recording paper. Ti, CrSiO, TaSiO or Ta ₂ N is used as the material of the heating resistors 1, ... And Al or Au is used as the material of the electrodes 2 and 3. As the insulating substrate, for example, an alumina plate coated with a glass layer is used. The glass layer is coated over the alumina substrate,
Alternatively, the heating resistor may be partially coated only on the portion where the heating resistor is to be formed.

Thus, in this structure, the portions 2a and 3a of the electrodes including the heating resistors 1 ... And the connection portions 4 with the heating resistors are substantially parallel to the arrangement direction of the heating resistors 1, and The slits 5 are formed so as to be inclined with respect to the transfer direction P and extend over the inclined portions of the heating resistor 1 and the portions 2a and 3a of the electrodes.

With this configuration, when the heating resistors 1 ... Are energized, the entire divided portions 1a and 1b divided by the slit 5 generate heat substantially uniformly. Acute angled parts 6 at the ends of electrodes 2 and 3
Since the energy flows intensively to the divided parts through ..., The divided parts can generate heat to the required temperature with low energy, and power saving can be achieved. The slit is also divided into parts 1 on both sides.
The thermal recording paper can be colored by the heat that is fused from a and 1b. Therefore, large dots with few white parts can be formed on the thermal recording paper as shown by the solid line in FIG. Further, since the heating resistor forming the slit is inclined, it is possible to achieve the effect and advantage when the image of a grid pattern or a vertical draft can be eliminated. In addition, in FIG. 2, broken lines indicate respective divided portions of the heating resistor.

Although the inclination angle of the heating resistor 1 and the portions 2a and 3a of the electrodes is set to 45 ° in the illustrated example, the inclination angle may be set to an appropriate angle.

The number of slits 5 is not limited to one as in the illustrated example, but two
You may form more than one piece. Rather, the greater the number of slits, the greater the effect of eliminating density unevenness, so it can be said that it is desirable to increase the number of slits. However, the upper limit is naturally limited from the viewpoint of manufacturing technology, and it is usually preferable to set it within 2 to 3.

The method for forming the slit may be etching or laser cutting. Also, by masking the portion where the slit is to be formed, the heating resistor is vapor-deposited, and after the vapor deposition, the mask is removed, and any known method can be carried out. . It is desirable inclination angle of the slit to match the heating resistor 1 ... inclination angle of, in which case the heating resistors 1 ... formed substantially the center in the width direction of the both sides of the divided portion 1a, the width d ₁ = 1b, It is preferable that d ₂ be substantially the same (d ₁ = d ₂ ). By doing so, since the divided portions 1a and 1b have the same shape and size, the divided portions 1a and 1b generate heat in the same pattern to eliminate density unevenness, which improves image quality. Also,
In that case, each divided portion has a length c along the slit longitudinal direction.
It was confirmed by experiments that a uniform image without density unevenness can be obtained by setting the ratio of the widths d ₁ and d ₂ to 2: 1 or more.

The width W _{1 of the} slit 5 depends on the divided portions 1a, 1 of the heating resistor.
It is preferable that the maximum width of the widths d ₁ and d ₂ of b is (d ₁ −d ₂ ) or less. This is because if it is within this range, the heat-sensitive recording paper located above the slit can also change the color due to the fusion of heat from the divided portions 1a and 1b on both sides.

Further, in order to make the print density uniform, the width W of the slit 5 is
₁ is preferably equal to the gaps W ₂ , W ₃ ... Between adjacent heating resistors 1. Since it is difficult to form the two completely equal in terms of manufacturing accuracy, it is permissible that the slit is wider than the gap between the heating resistors in the range of 20 μm. The main reason for allowing the slits to be wider than the gap is that the heat from the divided parts on both sides is fused to the slits, so that the thermal recording paper can be colored even if it is a little wider. That is the reason.

As described above, the thermal head of the present invention has a plurality of quadrilateral heating resistors, the pair of opposing pieces being substantially parallel to the arranging direction of the heating resistors, and And a gap width between the heating resistors which are arranged with a part of the electrode including the connecting portion inclined with respect to the transfer direction of the thermosensitive recording medium and which are adjacent to the inclined connecting portion of the electrode from the heating resistor. By providing the slits having substantially the same width, the following effects can be obtained.

Since a slit is formed on the heating resistor and the slit divides the heating resistor into two or more pieces, uniform heating with a small dead space is possible.
Since the heating resistors having such slits are formed to be inclined, the heating area occupied by each heating resistor overlaps along the arranging direction of the heating resistors, resulting in a grid-shaped or draft image. This makes it possible to create beautiful prints without uneven density. As a result, there is an advantage when a good image quality can be obtained especially at low density printing of gradation printing.

Since it is possible to eliminate an image of a grid pattern or a vertical draft pattern, it is possible to further increase the upper limit of the image density as a whole. Therefore, it is possible to perform gradation printing having a wider density range than ever before.

Since the slits are formed in the heating resistor, the width of the heating resistor is narrowed by the width of the slit, and the power consumption is reduced accordingly, and in addition, the electrode including the connection part with the heating resistor is reduced. Since the part is inclined, an acute angled part where energy is concentrated is formed at the electrode end part, and the presence of this acute angled part allows the desired printing to be performed without lowering the performance even if the supplied energy is lowered. Therefore, it is possible to significantly reduce power consumption from these two reasons. According to the experiment, the electric power could be reduced by about 20% compared with the conventional one.

[Brief description of drawings]

FIG. 1 is a diagram showing a main part of the thermal head of the present invention, and FIG.
The figure shows the shape of dots printed on a thermal recording medium.
FIG. 3 is an overall schematic plan view of the thermal head, FIG. 4 is a view showing a pattern of a heating resistor in the initial thermal head, and FIG. 5 is a thermal recording medium by heat generation of the heating resistor of FIG. FIG. 6 is a view showing the shape of dots printed, FIG. 6 is a view showing a pattern of a heating resistor in a conventional thermal head, and FIG. 7 is printed on a heat-sensitive recording medium by heat generation of the heating resistor shown in FIG. It is a figure which shows the shape of the dot. 1 ... Heating resistor, 1a, 1b ... Divided part, 2, 3 ...
… Electrodes, 4 …… The connection between the electrodes and the heating resistor, 5 ……
Slit, P ... Transfer direction.

Claims (3)

[Claims] 1. A plurality of quadrilateral heat generating resistors are arranged at a predetermined interval in a direction orthogonal to the transfer direction of a thermosensitive recording medium, and a pair of electrodes are connected to both ends of each heat generating resistor. A thermal head, wherein each of the heating resistors has a pair of opposing sides substantially parallel to the arrangement direction of the heating resistors, and a part of an electrode including a connecting portion with the heating resistors together with a part of the thermal recording medium. A thermal head characterized in that the slits are arranged to be inclined with respect to the transfer direction, and a slit having a width substantially the same as the gap width between adjacent heating resistors is formed from the heating resistor over the inclined connection portion of the electrode. . 2. The thermal head according to claim 1, wherein the heating resistors divided by the slit have substantially the same width. 3. The width of the slit is within a maximum of twice the total width of the divided heating resistors, and the width of the slit is within a maximum of two times. The thermal head described in.