JPS60162663A - Thermal head - Google Patents

Abstract

PURPOSE:To print characters positively extending over the whole range of the arrangement of heating elements by setting the calorific value of the heating elements positioned at both ends in a large number of a rectilinearly disposed heating elements to values larger than that of other heating elements. CONSTITUTION:A substrate to which a large number of heating elements 5 are arranged rectilinearly is mounted to a carriage 23, and attached or detached to or from recording paper 11 wound on a platen 17. The heating elements 5a positioned at both ends are set so that their areas are made larger than other heating elements 5 in the direction of arrangement. A common electrode 26 and several electrode 27 are brought to the state in which they are connected extending over the whole width of the heating elements 5, and currents flowing through the heating elements 5a at both ends are made larger than currents flowing through other heating elements 5, power consumption is increased and calorific value is augmented when all the heating elements 5 are conducted. Accordingly, printing capability at both end sections is improved, and no white line is generated among lines even through a strip of contact prints extending over a large number of lines. Even when longitudinal lines are printed, there is no broken character, and the lines are continued.

Description

Detailed Description of the Invention Technical Field of the Invention The present invention involves forming a large number of heat generating elements in a linear array on a substrate, and moving the substrate in a direction perpendicular to the arrangement direction of the heat generating elements. The present invention relates to a thermal head used in a thermal printer that forms characters and figures as a collection of dots when energized.

TECHNICAL BACKGROUND AND PROBLEMS The structure and printing examples of a conventional thermal head of this type will be explained with reference to FIGS. 1 to 5. First, the substrate 1 is made up of an aluminum plate 2 that serves as both a heat sink and a support plate, and a ceramic substrate 3 that is laminated and fixed in a rectangular shape on the aluminum plate 2. A positionable mounting portion 4 is formed on the aluminum plate 2. 6 Further, the ceramic substrate 3 is provided with 24 heating elements 5 arranged in a straight line and a drive circuit member 6. , these ends are connected by an electrode (not shown). For example, one of the heating elements 5 has a size of 150×150μ! It forms a summer 1 square, and the interval between each is set to be 10 to 15μIfl. A flexible cable 7 is connected to the drive circuit member 6. The drive circuit includes heating elements 5 labeled R1 to R24 as shown in FIG.
Transistor 8 labeled T r t~T1' 24
These transistors 8 are connected to a print control circuit IO.

During printing, the transistors 9 are selectively made conductive by commands from the printing control circuit 10 while the substrate l is moved relative to the recording paper in a direction perpendicular to the arrangement direction of the heating elements 5. , thereby energizing the heating element 5 to generate heat. When the recording paper is thermal paper, the color develops directly, and when the recording paper is plain paper, the ink is transferred and printed via a printing ribbon coated with heat-melting ink. When the printing of the - line is completed in this way, the recording paper is fed in the direction in which the heating elements 5 are arranged, and the second line is printed.

Although the printing conditions are extremely diverse, there is one problem, for example, when all the heating elements 5 are energized at the same time, such as "1", or when solid printing is performed. Now, Fig. 4 shows a part of an example of a colored state (the shaded area is colored), but the gap between each heating element 5 is visually observed due to thermal interference of the heating elements 5 from both sides. Color develops and solid black printing occurs even though it does not cause any problems.

However, the heating element 5 located at the end lacks the amount of heat on the edge side, resulting in areas where the coloring is weak or no coloring occurs. This is a phenomenon that occurs because there is no thermal interference, but if the platen is roll-shaped, the contact pressure against the recording paper 11 is weak at the edges, making it even more difficult to develop color at both ends. be done.

When one line of solid printing is completed in this way and it is printed over many lines, white lines will appear between each line as shown in FIG. 5, making it impossible to print as desired.

This phenomenon also occurs when forming vertical lines. That is, the long vertical line is a continuation of short vertical lines generated by the 24 heating elements 5 generating heat at the same time, and white spots occur at the connected portions, making it impossible to form a continuous vertical line.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a thermal head that can reliably print over the entire array range of heating elements.

Summary of the Invention The present invention provides that among a large number of linearly arranged heating elements,
The heat generation amount of the heating elements located at both ends is set to be larger than that of the other heating elements, so that when all the heating elements are energized at the same time, the area where the heating elements are arranged can be printed faithfully. This is so that white spots do not occur when printing solid images or printing long vertical lines.

Embodiment of the Invention An embodiment of the present invention will be described with reference to FIGS. 6 to 10. The same parts as those described in FIGS. 1 to 5 are designated by the same reference numerals, and description thereof will be omitted. First, the main body case 13 of the thermal printer 12 consists of a lower case 14 and an upper case 15.

This upper case 15 has a cover 16. is removably provided. A knob 18 connected to the platen 17 is formed protruding from the side surface of the main body case 13. Next, the one shown in FIG. 7 is one in which the first case 15 is removed, and a paper guide 21 having a paper pail 20 is fixed between the opposing frames 19, and the above-mentioned paper pail 20 is fixed to the first part of this paper guide 21. A platen 17 is detachably attached. On the front side of such a platen 17, there is a key V that is supported by a guide part 22 and reciprocates left and right.
A ridge 23 is provided, and this carriage 23 is driven by a wire 24. Such a carriage 23 has a substrate l on which a large number of heating elements 5 are linearly arranged.
is attached, and this substrate 1 is provided so as to come into contact with and separate from the recording paper 11 wound around the platen 17.

Next, the heating elements 5 are, for example, 24 elements arranged in a straight line, and the heating elements 5a located at both ends have a larger area than the other heating elements 5. That is, the size of 1 normal heating element 5 is 150×150μ
Il+, but the heating elements 5a at both ends are 150X180
It is μm. Furthermore, since the purpose of increasing the area of the heating elements 5a at both ends is to decrease the resistance value and increase the current, the area is set to increase in the direction in which the heating elements 5 are arranged. Moreover, the common electrode 26 and the individual electrodes 27 are in a connected state over the entire width of the heating element 5.

In such a configuration, when all the heating elements 5 are energized, the current flowing through the heating elements 5a at both ends is larger than the current flowing through the other heating elements 5, increasing the power consumption, so that heat is generated. The amount is increasing. Therefore, the printing ability at both ends is high, and the heating element 5
Printing is performed faithfully over the entire array range. Therefore, even if solid printing is performed over many lines, white lines will not appear between the lines, and even if vertical lines are printed, they will be continuous without any blanks.

Next, what is shown in FIGS. 11 to 13.

This is a modification of this invention. In other words, if we look at the temperature distribution of each heating element 5, the temperature at the center will naturally be the highest. and.

As mentioned above, one side of the heating element 5a at both ends is 180 μIf.
If the temperature is increased to 1, the temperature at the center of the heating element 5a may become too high. In order to avoid this, a non-current-carrying part 28 is formed in the center of the heating element 5 at both ends along the current-carrying direction by a minute gap.

Therefore, although the non-current-carrying portion 28 does not generate heat, the temperature at the center of the heating element 5a does not become too high.

In the above embodiment, the area of the heating elements 5a at both ends is increased in order to lower the resistance. You can also make it larger.

Further, the voltage applied to the heating element 5a at both ends of one heating element 5a is higher than the voltage applied to the other heating element 5, so that the heating element 5a at both ends is
The amount of heat generated may be increased.

Furthermore, any number of heating elements 5 can be adopted as required, and the head type is also a so-called line thermal head, in which a very large number of heating elements are arranged in a straight line. It also applies to those who have been

Effects of the Invention The present invention provides a substrate in which a large number of heating elements are linearly arranged on a substrate as described above, and the amount of heat generated by the heating elements located at both ends of these heating elements is calculated by comparing the amount of heat generated by the heating elements located at both ends of the heating elements. Since the heat output is set to be larger than that of the heat generating element, when printing by energizing all the heat generating elements at the same time, the heat generated by the heat generating elements at both ends will be large, so printing will be performed faithfully in the area where the heat generating elements are arranged. As a result, when performing solid printing or printing vertical lines, even if multiple lines are repeated, there will be no gaps between lines, and printing that is faithful to the printing command can be performed. It is.

[Brief explanation of the drawing]

Fig. 1 is a perspective view of the thermal head, Fig. 2 is a plan view showing the arrangement of conventional heating elements, Fig. 3 is a partially enlarged plan view showing an example of printing, Fig. 4 is a circuit diagram, FIG. 5 is a plan view showing an example of multi-line printing. Fig. 6 is a perspective view of the thermal printer, Fig. 7 is an exploded perspective view of a part thereof, Fig. 8 is a plan view showing the arrangement of heating elements according to an embodiment of the present invention, and Fig. 9 is a perspective view of the thermal printer. A plan view showing the relationship, FIG. 10 is a plan view showing an enlarged example of printing, and FIG. 11 is a plan view showing the relationship.
The figure is a plan view showing the arrangement state of heating elements in a modified example.
The figure is a plan view showing the relationship with the electrodes, and FIG. 13 is a plan view showing an enlarged example of printing. l...Substrate, 5...Heating element 5a...Heating element

Claims (1)

[Claims] 1. A large number of heating elements that generate heat when selectively energized are formed in a linear array on a substrate, and the amount of heat generated by the heating elements located at both ends of these heating elements is calculated. A thermal head characterized by being set so that the amount of heat generated is greater than that of other heating elements. 2. The thermal head according to claim 1, wherein the thickness of the heating elements located at both ends is set larger than the thickness of the other heating elements. 3. The thermal head according to claim 1, wherein the voltage applied to the heating elements located at both ends is higher than the voltage applied to the other heating elements. 4. Claim 1, characterized in that the area of the heating elements located at both ends is larger than the area of the other heating elements.
Thermal head described in section. 5. The thermal head according to claim 4, characterized in that a non-current-carrying portion is formed in the center of the heating elements located at both ends along the current-carrying direction. 6. The thermal head according to claim 4, wherein the heating elements located at both ends are rectangular in shape, elongated in the direction in which they are arranged.