JPS602386A - Thermal printing head - Google Patents

Abstract

PURPOSE:To enable to print efficiently and with high quality even at a place where temperature is low, by impressing a preheating voltage on a heating element to previously maintain the temperature of the element at least at a predetermined temperature at which a thermal recording paper does not form a color. CONSTITUTION:A plurality of diodes D1-Dn+1 and a plurality of transistors Tr1-Trn are connected to the heating element 3 of the thermal printing head. When printing, the heating element 3 is supplied with printind voltages for each part thereof sectioned by the diodes and the transistors. In the head, before starting printing or at blank parts in printing, voltages such as not to cause the pirnting paper to form a color are impressed on the element 3 by utilizing the diodes D1-Dn+1 and the transistors Tr1-Trn, thereby maintaining the element 3 at, for example, about normal temperature. Accordingly, it is made possible to print efficiently and with high quality when printing by impressing printing voltages.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to thermal printheads, and more particularly to preheating heating elements.

Conventionally, when using a thermal print head in a place where the ambient temperature is extremely low, such as in a cold region, it is necessary to widen the pulse width of the printing voltage applied to the heating element of the thermal print head, or to use a preheater for the heating element. We are also setting up By the way, in the former case, unless the nominal width of the printing voltage is accurately controlled in accordance with each ambient temperature, the heat generation temperature will be too high or too low. However, it is not always easy to control the pulse width for each surrounding arrangement, and it is desirable to be able to control the heat generation temperature by minimizing the number of pulse width control operations hk as much as possible. In addition, in the latter case, not only the parts cost of the preheating heater itself is high, but also the assembly cost is high, and it is extremely difficult to uniformly preheat the entire heating element.
This uneven heat generation tends to deteriorate printing quality. Furthermore, since the preheating efficiency is poor, it is not preferable from the viewpoint of power saving.

An object of the present invention is to provide a thermal print head that solves the above-mentioned technical problems and that can efficiently obtain the temperature necessary for printing and perform high-quality printing even in low-temperature locations such as cold regions. It is.

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a plan view of one embodiment of the present invention. A band-shaped heating element 3 is formed on the head base 2 of the thermal printing head 1 . Driving circuits for controlling the current flowing through the heating element 3 are formed on the head base 2 on both sides of the heating element 30 (vertical direction in FIG. 1), and are connected to the protective cover 4, respectively.
4b. The protective covers 4a+4b are screwed onto the heat sink 12 by a plurality of screws 5.

7a and 13b are circuit boards for connecting an external circuit and a drive circuit, and a plurality of lead wires 7. a, 9; 10° 11 connects the external circuit and the drive circuit.

FIG. 2 is a simplified circuit diagram of the vicinity of the heating element 3. The heating element 3 includes a plurality of diodes D1. ...Dn+ 1 and a plurality of transistors T,...'rrn are connected, so that during printing, the part separated by the diodes D, ~Dn+ r, and transistors Tr1 to Trn of the heating element 3 The voltage of the printing reservoir is applied every time.

That is, by applying a voltage for printing/writing to a predetermined portion of the heating element 3 to be printed, the coloring necessary for coloring printing paper such as thermal paper is obtained.

In the thermal printhead according to the invention, these diodes D
, ,D2. D3-Dn+, and transistor 'rr,
, 'rr2°Tr3...Trn, a voltage is applied to the extent that the printing paper does not develop color, and a predetermined temperature is maintained.

This voltage need not be applied all the time, but may be applied, for example, before the print head 1 starts printing or to blank areas during printing.

Therefore, according to this embodiment, even in a cold region, the heating element 3 can be kept at about room temperature by applying voltage using the above-mentioned printing drive circuit, thereby reducing costs. There is no need to provide a heater, which is expensive and causes an increase in size, and the entire heating element 3 can be preheated uniformly, so when printing by applying a printing voltage, it is possible to print efficiently and with high quality. It becomes possible to do so.

In the above-mentioned embodiment, the preheating voltage was applied to the entire heating element 3, but in another embodiment of the present invention, the heating element 3 is divided into several sections and the preheating voltage is applied to each section. It may be maintained at a predetermined temperature that does not cause the printing paper to develop color. In this way, heating element 3
Rather than applying preheating voltage to the entire head, it is possible to apply preheating voltage only to the parts that actually require preheating, which helps reduce power consumption during preheating, especially for large heads. , it is possible to eliminate local temperature unevenness,
You can get beautiful printing.

As described above, according to the present invention, in order to maintain the temperature of the heating element in advance at a predetermined temperature at least to the extent that the printing paper does not develop color, a preheating voltage is applied to the heating element using a printing dry circuit. Since the voltage is applied, the heating element can be maintained at a predetermined temperature even in cold regions. Therefore, there is no need to provide a preheating heater which is costly and causes an increase in size, and the heating element can be preheated with a simple and inexpensive configuration. Furthermore, since the preheating voltage is directly applied to the heating element, it is possible to efficiently preheat the heating element, and the temperature of the heating element can be controlled uniformly, so that high quality printing of i% can be performed.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an embodiment of the present invention, and FIG. 2 is a heating element 3.
It is a simplified circuit diagram of the vicinity. 1. Thermal printing head, 2. Head base, 3. Heating element, 4a, 4b. Protective cover, 12. Heat sink. Applicant: ROHM Co., Ltd. Agent: Kazuhide Okada, patent attorney Figure 1 Figure 2

Claims (1)

[Claims] (1) A thermal print head characterized in that a preheating voltage is applied to the heating element in advance to maintain the temperature of the heating element at a predetermined temperature at least to the extent that printing paper such as thermal paper does not develop color. .