JPS5830839B2 - How to apply energizing pulses to thermal printers - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of applying an energizing pulse to a thermal printer that attempts to print on thermal paper that cooperates with a heating element by applying an electrical signal.

It has been several years since thermal printers appeared, but the reality is that they have not become widespread.

One reason for this is the unreliability of the thermal head, which is the heart of a thermal printer.

Thermal heads can be roughly divided into those using semiconductor IC technology, those using thin film resistors, and those using thick film resistors, but those using semiconductor IC technology are difficult to mass produce.
Moreover, it has the disadvantage of being expensive because it requires advanced electronic technology.

However, those using thin film resistors also have the drawback of being difficult to mass produce and being expensive.

On the other hand, those using thick film resistors are easy to mass produce and are inexpensive, but are said to be vulnerable to repeated thermal shocks.

However, thermal heads using thick film resistors have also been put into practical use, but the firing temperature of the thick film resistor, which is the heating element, is high, and the base material of the thermal head is restricted, such as ceramics or alumina that can withstand high temperatures. will be limited to.

Therefore, improvements in the reliability of conventional thermal heads have been pursued only from the aspect of thermal head manufacturing technology, but the present invention improves the reliability of thermal heads by using a method of applying energizing pulses of thermal printers. This provides an inexpensive thermal printer.

FIGS. 1 and 2 are enlarged views showing the arrangement of heat generating elements and electric conductors of the thermal head.

Figure 1. In Figure 2, 11.21 is a common electrical conductor, 1
2.22 is a signal supply electric conductor, and 13.23 is a heating element.

A configuration diagram when printing is performed by dot-sial drive using the thermal head shown in FIGS. 1 and 2 is shown in FIG. 3.

In FIG. 3, 31 is a heat generating element, and 13 in FIG.
This corresponds to 23 in FIG.

32 is a wraparound prevention element.

A group of heating elements, ASBMC, which are grouped together via a wrap-around prevention element, are connected to a large current driver 33, and the base of the driver 33 is connected to a decoder 34.

35 is a driver for digits, and if there are n digits, n drivers are required.

Base HROM (READ) of driver 35 for digits
ON MEMORY) 36, and the digit driver 35 is turned on or off depending on the character to be printed.

The conventional energization method using dot serial drive is shown in Fig. 4, and the enlarged view of the applied pulse and the temperature rise waveform of the heating element are shown in Figs. 5-a, 5-b, 6-a, and 6-a. 6th-
Shown in Figure b.

Fig. 5-a shows a pulse of applied voltage 1 and tp1 during energization, and Fig. 5-b shows a temperature rise waveform when the pulse of Fig. 5a is applied to the heating element.

In FIG. 5-b, Ts indicates a certain coloring temperature of the thermal paper.

As can be seen from Figures 5-a and 5-b, if the duration of energization is shortened and the applied voltage is increased, it is necessary to increase the instantaneous temperature rise of the heat generating element.

In other words, the reliability of the rethermal head, in which the thermal shock of the heat generating element is large, deteriorates.

On the other hand, as shown in Figure 6-a, if the applied voltage of the pulse is lowered and the energization period is extended, a gentle temperature rise waveform will be obtained as shown in Figure 6-b.

Fig. 6a shows a pulse of applied voltage 2 and tp2 during energization, and Fig. 6-b shows a temperature rise waveform when the pulse of Fig. 6-b is applied to the heating element.

In FIG. 6-b, T8 indicates a certain coloring temperature of the thermal paper.

As shown in Figures 6-a and 6-b, as the current is turned on for a longer time and the applied voltage is lowered, the temperature rise of the heat generating element becomes gentler and the thermal shock becomes smaller. Improved reliability.

However, since the current is being energized for a longer time, the applied power must be increased due to the thermal conductivity of the base material of the thermal head.

The base material of the thermal head is glass, and the energization time is t1.
The applied voltage is ■, and the resistance value of the heating element of the thermal head is R.
Then, the applied power is P=V2t...(1-
1) It is expressed as the formula.

When the power supply time is increased based on the equation (1-1), the power required to obtain the optimum uniform density printing is calculated, and the ratio thereof is determined, resulting in the characteristic line shown in FIG.

First, the optimum print density cannot be obtained unless the power is applied in excess of the amount of heat that escapes to the substrate due to the longer time the current is being applied.

As described above, if the applied voltage is increased by shortening the period during which the current is being energized, the thermal shock in the heat generating element increases, resulting in a decrease in reliability.

On the other hand, if the duration of energization is prolonged and the applied voltage is lowered, the thermal shock of the heating element is reduced and reliability is improved, but there is a drawback that the applied power must be increased.

The present invention solves the above drawbacks.

An embodiment of the present invention is shown in FIG.

For ease of understanding, an enlarged view of FIG. 8 and a temperature rise waveform of the heat generating element are shown in FIGS. 9-a and 9-b.

In Figure 9-a, S is the applied voltage v4 and tp3 during energization.
Here, an example of four pulsers with a duty of 1/2 is used.

U is a pulse sufficient to color the thermal paper, and the applied voltage is 4 and Tp4 during energization.

Naturally, T p4 > j p3. 9th
FIG. 9-b shows a temperature rise waveform of the heat generating element when the pulse shown in FIG. 9-a is applied to the heat generating element.

In FIG. 9-b, Ts indicates a certain coloring temperature of the thermal paper.

As can be seen from Figure 9-b, the heating element is preheated by the S preheating pulse and its temperature rises to a certain extent, and then by applying the U pulse, the heating element is heated to a temperature sufficient to color the thermal paper. It makes it rise.

Therefore, according to the embodiment of the present invention, the thermal shock of the heat generating element of the thermal head is reduced and reliability is improved.

Further, since it is not necessary to keep the current flowing for a long time, there is no need to increase the applied power, and there is an advantage that the applied power can be reduced.

In FIG. 9-a, the number of preheating pulses is four for the sake of clarity, but it may be one or more.

As described above, according to the embodiments of the present invention, it is possible to provide a reliable method for energizing a thermal head without applying sudden thermal shock to the heat generating element of the thermal head.

According to the present invention, the voltage values of the applied preliminary (preheating) pulse and the heating energization pulse are the same, and only the pulse width needs to be changed, so there is no need to prepare multiple voltage values in the power supply. , control is possible with a simple circuit configuration.

Furthermore, the present invention can improve the reliability of a thermal head using a thick film resistor that can be mass-produced and is said to be vulnerable to repeated thermal shocks, and has the advantage of providing an inexpensive thermal printer, which is extremely useful. It is something.

[Brief explanation of drawings]

FIGS. 1 and 2 are enlarged views showing the arrangement of heat generating elements and electric conductors of the thermal head. Figure 3 is the same as Figure 1. FIG. 3 is a configuration diagram when the thermal head having the heating element and electric conductor shown in FIG. 2 is driven by dot serial drive. FIG. 4 shows a conventional energizing pulse application method, and FIGS. 5-a and 6-a are enlarged views of the energizing pulse in FIG. 4. Figure 5-a shows a pulse with a short conduction width and a high applied voltage, and Figure 6-a shows a pulse with a long conduction width and a low applied voltage. 5-b and 6-b. FIG. 7 is a characteristic line diagram showing the power ratio when the energization time to the thermal head is increased. Fig. 8 shows an embodiment of the present invention, Fig. 9-a is an enlarged view of Fig. 8, and Fig. 9-b shows the state when the energizing pulse as shown in Fig. 9-a is applied to the heating element. This is a temperature rise waveform.

Claims (1)

[Claims] 1. energize the heat-generating element and record on the thermal paper that comes into contact with it; A method of applying current pulses to a thermal printer, characterized in that a plurality of pulses having a short pulse width and not causing coloring of the thermal paper are preliminarily applied to the heating element.