JPS61189954A - Thermal head - Google Patents

Abstract

PURPOSE:To prevent the generation of printing inferiority and the irregularity in printing density even when the center of a heat generating element line is shifted from that of glaze, by forming the shape of the cross-section of glaze into a trapezoidal shape and forming a flat surface to the top part of the glaze. CONSTITUTION:Heat generating elements 24, 25 each having a width (l) are respectively formed to the flat surfaces 36, 37 each having a width L provided to the top parts of glazes in the direction vertical to the surface of paper. The width L of each of the flat surfaces 36, 37 of the top parts of the glazes 32, 33 is made long so as to prevent the heat generating element lines 24, 25 from protruding from the flat surfaces 36, 37 even when the centers of the heat generating element lines 24, 25 are shifted from the centers of the glazes 32, 33 by the limit of accuracy from a manufacturing aspect. Therefore, the contact state of the surfaces of the heat generating element lines 24, 25 with a platen 18 becomes uniform and, therefore, it is prevented that the shape of a printed dot pattern becomes imperfect and density irregularity is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION - [Field of Application of the Invention] The present invention relates to a thermal head, and particularly to a thermal head suitable for use in a thermal serial printer.

[Background of the invention]

Figure f42 is an external view of the thermal serial printer. In FIG. 2, a carriage 5 is slidably attached to a shaft 4 fixed between side plates 1 and 2. The carriage 5 is adapted to move in the left-right direction in FIG. 2 via a timing pel 10 pivoted by a carriage motor 8. The ribbon cassette 7 containing the ink ribbon 16 and the thermal head 15 are placed on the carriage 5.

The platen 18 is rotated by the line feed motor 11 via the gear 12, but can also be rotated by manually rotating the platen knob 13e. Nine paper pressing rows 217 rotatably fitted on the shaft 3 are pressed against the platen 18 or moved away from the platen 18 by moving the release lever 20 in the front and back direction. Then, the paper 14 is held between the platen 18 and the paper pressing roller 17, and is moved upward in FIG.

The line feed motor 11, carriage motor 8, home position sensor 6, thermal head 15, etc. are controlled by a controller 21, and the thermal head 15, etc. are energized by a flat cable 9. Note that some thermal serial printers print when the carriage 5 moves in both left and right directions, but for the sake of explanation,
This is a thermal serial printer of a unidirectional printing type that prints when a carriage 5 moves rightward.

FIG. 3 is an external view of the thermal head. In FIG. 3, a thermal head 15r1 has two heating element rows 24 and 25 on a ceramic substrate 26 to increase printing speed. Each of the heating element rows 24 and 25 includes a plurality of heating elements 34 each having a rectangular planar shape.
are arranged vertically in a straight line or in a staggered manner, and the heating element row 24 is arranged on the glaze 22, and the heating element row 25 is arranged on the glaze 22.
are formed on the glaze 23, respectively. Then, the plurality of heating elements 34 in the heating element rows 24 and 25 are controlled by dot pattern signals input to the plugs 28, respectively.
It is heated by electricity through a driver 27.

Figure 4 is an enlarged cross-sectional view of the contact area between the thermal head and the platen when the conventional thermal head is pressed against the platen.

In FIG. 4, two glazes 2 having a semicircular cross section are placed on the ceramic substrate 26 of the thermal head 15.
2 and 23 are formed at a pitch P in the direction perpendicular to the paper surface. The heating element array 24 is placed on the top of the arcuate surface of the glaze 22, along the arcuate surface in a direction perpendicular to the plane of the paper, and the heating element row 25 is placed on the top of the arcuate surface of the glaze 23, in the arcuate surface. They are formed in a direction perpendicular to the plane of the paper. In the heating element rows 24 and 25, there are already steep,
A plurality of heating elements 34 having a rectangular planar shape as shown in FIG.

Of the two sides perpendicular to the plane of the paper of a plurality of heating elements (not shown) arranged in the heating element row 24, on the side opposite to the heating element row 25, the same number of individual electrodes 30 as the number of the plurality of heating elements are arranged.
They are connected to the common voltage 29 on the side of the heating element array 25. Similarly, heating element row 2
Of the two sides perpendicular to the plane of the paper of a plurality of heat generating elements (not shown) arranged in 5, the side opposite to the iA element row 24 is connected to the individual electrodes 35 of the same number as the number of the plurality of heat generating elements. The heating element array 24 is connected to the common electrode 29 all at once on the side of the heating element row 24 .

Therefore, a common electrode is connected to a plurality of heating elements (not shown) arranged in the heating element rows 24 and 25 from a plurality of individual electrodes 30 and 35 connected to each of the plurality of heating elements, respectively. Heat is generated by the current flowing through 29. Then, the platen 18 and the thermal head 1
heating element rows 24 and 2 of the recording paper (not shown) between
The part that is in contact with 5 will be printed.

The ceramic substrate 26 has a function of cooling the thermal head 15 by dissipating heat generated from plugs, wiring, heating elements, etc. (not shown), which are connected to the thermal head 15, into the surrounding air.

Therefore, the heat necessary for thermal printing generated from the glazes 22 and 23 frames and the heating element arrays 24 and 250 (not shown) disposed on the ceramic substrate 26 is prevented from being conducted to the ceramic substrate 26. In addition to having the function of a sashimi material that is intended to be used as a safety precaution, it also has the function of a companion pedestal on which a plurality of very thin heating elements (not shown) are arranged to form heating element rows 24 and 25. There is. Therefore, the glazes 22 and 23 are made of glass and have smooth and flat surfaces.

When printing on recording paper that is similar to the cross-sectional shape of the glazes 22 and 23, the surfaces of the glaze element rows 24 and 25 are arranged so that the surfaces of the glaze element rows 24 and 25 can be used for recording. It has a cylindrical shape to ensure sufficient contact with the paper. As already explained, on the arc-shaped surfaces of the glazes 22 and 23, which have semicircular cross-sections, that is, on the tops of the arc surfaces, a plurality of extremely thin heating elements (not shown) are arranged along the arc surfaces. Heat generating element rows 24 and 25 are arranged vertically in a straight line or staggered in a direction perpendicular to the plane of the paper.

Thermal head 15 configured as explained above
When the platen 18 is pressed against the platen 18, which is made of a resilient material such as rubber, the surface of the platen 18 conforms to the shape of the arcuate surfaces of the gongs 22 and 23, which have semicylindrical cross sections. Then, in this state, the surfaces of the heating element arrays 24 and 25 move while rubbing against the surface of the recording paper (not shown) between the thermal head 15 and the platen 18, thereby creating a dot ζ on the surface of the recording paper. The turn is printed.

- In this case, if the centers of the glazes 22 and 23 and the centers of the heating element rows 24 and 25 match or are slightly shifted, a well-shaped dot pattern can be printed. However, due to manufacturing limitations,
If the centers of the glazes 22 and 23 and the centers of the heat generating element rows 24 and 25 are greatly misaligned, a well-shaped dot pattern cannot be printed. That is, the shape of the dot pattern may be incomplete or a flame may be formed in the density of the dot pattern.

Figures 5 and 6 are enlarged cross-sectional views of the contact area between the thermal head and the platen when a conventional thermal head in which the center of the heating element row and the center of the glaze are largely misaligned is pressed against the platen. In the case where the center of the heating element array in Figure 5a is shifted from the center of the glaze in the printing direction, and in Figure 6, the center of the heating element array is shifted from the center of the glaze in the opposite direction to the printing direction. FIG.

In Fig. 5 and Fig. 6, the fourth
The parts with the same numbers as those in the diagram are the same parts with the same configuration and the same function, and in order to make the diagram easier to understand,
It is not shown on the recording paper or the like between the thermal head and the platen.

In FIG. 5, as already explained in FIG. 4, the thermal head 15 is pressed against the platen 18, and the surface of the platen 18, which is made of an elastic material such as rubber, is
The glazes 22 and 23, each having a semicircular cross-sectional shape, are recessed in the shape of an arcuate surface. In this case, glaze 22
surface 1 of platen 18 located between and glaze 23
The elasticity of the glazes 22 and 23, which are stretched from side to side by the glazes 22 and 23, is reduced and the restoring force is weak.

Therefore, a non-contact portion occurs between the arcuate surface of the glaze 22 in the direction opposite to the printing direction indicated by the arrow, the arcuate surface of the glaze 23 in the printing direction indicated by the arrow, and the surface 18C of the platen 18. Therefore, among the surfaces of the heating element array 25 formed on the arcuate surface of the glaze 23, the surface 25' of the side in the printing direction indicated by the arrow A does not come into contact with the recording paper (not shown). The dot pattern in this area is not printed, or the dot pattern in this area is printed too thin.

On the other hand, since the surface 18Ri of the platen 18 in the printing direction shown by the arrow is not stretched, the elasticity is not impaired and the restoring force is strong. Therefore, the entire surface a1 of the heating element row 24 formed on the arcuate surface of the glaze 22 comes into sufficient contact with the surface 18R of the platen 18, so that the dot pattern is printed well on the recording paper (not shown).

As shown in FIG. 6, when the centers of the heating element rows 24 and 25 are shifted from the centers of the glazes 22 and 23 in the direction opposite to the printing direction indicated by arrow A, the reason is the same as that already explained in FIG. For some reason, the surface 24' of the heating element array 24 formed on the arcuate surface of the glaze 22, on the side opposite to the printing direction indicated by the arrow, does not contact the recording paper (not shown). , the dot pattern in this part is not printed, or the dot pattern in this part is printed with a low density. Also, Glaze 23
On the entire surface of the heating element row 25 formed on the circular arc surface,
Surface 18L of platen 18 in the opposite direction to the direction indicated by arrow A
Since the dots are in sufficient contact with the dots, the dot pattern is well printed on recording paper (not shown).

In order to eliminate printing defects caused by the thermal head 15 having a plurality of heating element rows 24 and 25 as described above, the glazes 22 and 2 in FIG.
By increasing the pitch P of 3, the heating element array 24
This prevents the surface 18C of the platen 18 located between the thermal head 15 and the heating element array 25 from being pulled left and right, reducing its elasticity and weakening its restoring force.
This has been a problem for some time because it is difficult for dogs to hear and is expensive.
o Figure 7 (a) i. When pressing a conventional thermal head with one row of heating elements and the center of the heating element row and the center of the glaze being slightly offset from the center of the glaze, the thermal This is an enlarged cross-sectional view of the contact portion between the head and the platen. f47 Figures (b) and (C) t-f, Figure 7 (a
) is a vector diagram showing the direction of the force applied to the platen by the heating element array when performing bidirectional printing using the thermal head shown in FIG.

In FIGS. 7(a), (b), and (C), the thermal head 15 is pressed against the platen 18, and the surface of the platen 1B made of elastic material such as rubber has a cross-sectional shape. It is recessed in the shape of the arcuate surface of the glaze 22, which is shaped like a semi-cylindrical fish paste. In this case, thermal head 1
The center of the heating element row 31 of No. 5 is an arrow from the center of the glaze 22! Although there is a large deviation in the printing direction indicated by l: lIA,
Since there is only one heating element row 31, the entire surface of the heating element row 31 formed on the arcuate surface of the glaze 22 is in sufficient contact with the surface of the platen 18.

In this state, the thermal head 1
5, the direction of the force with which the heating element array 31 presses against the surface of the platen 18 is the force FW that presses the thermal head 15 against the platen 18 and the force F' that moves the thermal head 15 in the direction of arrow A. It becomes the direction of the force F1 of the vector sum with CF. Therefore, the direction of the force Fi in which the heating element row 31 presses against the surface of the platen 18 matches the direction in which the center of the heating element row 31 is shifted from the center of the glaze 22, so that there is a gap between the thermal head 15 and the platen 18. The dot pattern is printed well on a recording paper (not shown).

On the other hand, when the thermal head 15 is moved in the printing direction indicated by arrow B, which is opposite to the printing direction indicated by arrow A, the direction of the force with which the heating element row 31 presses against the surface of the platen 18 is The force F2 is the vector sum of the force FH that presses the thermal head 15 against the platen 18 and the force F'CR that moves the thermal head 15 in the printing direction shown by arrow B.
Therefore, the direction of the force F2 in which the heating element row 31 presses against the surface of the platen 18 is opposite to the direction in which the center of the heating element row 31 is deviated from the center of the glaze 22. The density of the dot pattern printed on the recording paper becomes lighter.

If the center of the heating element row 31 of the thermal head 15 is largely shifted from the center of the glaze 22 in the printing direction indicated by arrow A or in the printing direction indicated by arrow B, the above will be opposite.

That is, when the thermal head 15 is moved in the printing direction shown by arrow B, the dot pattern is printed well, and when the thermal head 15 is moved in the printing direction shown by arrow A, the density of the printed dot pattern becomes thinner. .

In this way, even if there is only one row of heating elements 31, if the center of the heating element row 31 and the center of the glaze 22 are misaligned due to the limit of manufacturing precision, the density of the printed dot pattern will be affected. This has been a problem for some time because shading occurs.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and it is possible to prevent printing defects and print density when printing in one direction or both directions using a plurality or a single heating element row in a thermal serial printer. The object of the present invention is to provide a thermal head that does not cause shading or the like.

[Summary of the invention]

In this invention, by making the cross-sectional shape of the glaze that forms the heating element row into a trapezoid and forming a flat surface on the top of the glaze, even when the center of the heating element row and the center of the glaze are misaligned, It is characterized by preventing printing defects and print density shading from occurring.

[Embodiments of the invention]

Embodiments of the invention will be described based on the drawings.

FIG. 1 is an enlarged cross-sectional view of the contact portion between the thermal head and the platen, just in case the thermal head of the present invention is pressed against the platen. In addition, in FIG. 1, the parts with the same numbers as those in FIG. The membrane, recording paper, ink ribbon, etc. between the thermal head and the platen are not shown.

In FIG. 1, two glazes 32 having a trapezoidal cross section are placed on the ceramic substrate 26 of the thermal head 15.
and 33 are formed in a direction perpendicular to the paper surface. Then, a heating element row 24 with a width t is placed on a flat surface 36 of the width of the top of the glaze 32 in a direction perpendicular to the plane of the paper, and a heating element row 25 of a width t is placed on a flat surface 36 of the top width of the glaze 33 with a width of @L. Face 37
They are formed on the top in a direction perpendicular to the plane of the paper. Furthermore, flat surfaces 36 and 37 on top of glazes 32 and 33
Even if the centers of the heating element rows 24 and 25 are shifted from the centers of the groups 32 and 33 due to manufacturing precision limits, the width of the heating element rows 24 and 25 of width t is The flat surfaces 36 and 37 are also long so that they do not protrude.

Therefore, whether in the case of unidirectional printing or bidirectional printing, the state of contact between the surfaces of the heating element rows 24 and 25 and the platen 18 is uniform over the entire surface of the heating element rows 24 and 25. The shape of the printed dot pattern becomes incomplete and the density of the dot pattern becomes uneven.

〔Effect of the invention〕

As explained above, the present invention has a trapezoidal cross-sectional shape of the glaze, which is a pedestal for forming a row of heat-generating elements, and forms a flat surface with a width wider than the width of the row of heat-generating elements at the top of the trapezoid. are doing.

Therefore, even if the center of the heating element row and the center of the glaze are misaligned due to manufacturing precision limits, the thermal head can be pressed against the platen and the state of contact between the surface of the heating element row and the platen can be maintained. Since it is uniform over the entire surface of the heating element array, the shape of the printed dot pattern will not be incomplete, and the density of the dot pattern will not be shaded, resulting in high quality printing. .

[Brief explanation of the drawing]

Fig. 1 is an enlarged cross-sectional view of the contact area between the thermal head and the platen when the thermal head of the present invention is pressed against the platen, Fig. 2 is an external view of the thermal serial printer, and Fig. 3 is the thermal head of the present invention. External view of the head, Figure 4a1: Enlarged cross-sectional view of the contact area between the thermal head and the platen when a conventional thermal head is pressed against the platen;
Figures 5 and 6 show the cross section of the contact area between the thermal head and the platen when a conventional thermal head in which the center of the heating element row and one center of the glaze are shifted from each other is pressed against the platen. Enlarged view, Fig. 7(a) t-1, Thermal when a conventional thermal head with one row of heating elements and the center of the heating element row and the center of the glaze is shifted against the platen. Cross-sectional views of the contact portion between the head and the platen, FIGS. 7(b) and (C) id, and FIG. 87(
FIG. 6 is a vector diagram showing the direction of the force applied to the platen by the heating element array when performing bidirectional printing using the thermal head shown in a). 1.2... Side plate, 3.4... Axis, 5... Carriage, 6... Home position sensor, 7... Ribbon cassette, 8... Carriage motor, 9... Flat cable , 10...timing belt, 11...
Line feed motor, 12... Gear, 13... Platen knob, 14... Paper, 15... Thermal head, 16... Ink ribbon, 17... Paper holding roller, 18... Platen, 20... Lily lever, 21
...Controller, 22,23°32.33...Glaze, 24,25.31...Heating element row, 26...Ceramic board, 27...Driver, 28...Connection, 2
9... Common electrode, 30.35... Individual electrode, 34.
...heating element, 36.37...flat surface.

Claims (1)

[Claims] 1. In a thermal serial printer having a heating element row in which a plurality of heating elements are arranged in a linear or staggered manner on a glaze formed on a substrate, a width wider than the width of the heating element row is provided on the glaze. A thermal head characterized in that it is provided with a flat surface.