JPH06143651A - Thermo-history correction method for thermal printer - Google Patents

Abstract

PURPOSE:To embody a high print quality easily by reducing the number of conduction timing of heating element. CONSTITUTION:A plurality of equal number of mutually adjacent heating elements constitues one block. Conduction time during each pulse cycle is set variably by means of a conduction start timer and a conduction end timer such that one of start-of-conduction or end-of-conduction is controlled for individual heating element whereas the other is controlled for individual block. This method simplifies the control through reduction of the number of timing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention corrects the energization signals to a plurality of heat generating elements of a thermal printer according to the heat history of the heat generating elements so as to perform printing with a uniform print density. The present invention relates to a thermal history correction method for a printer.

[0002]

2. Description of the Related Art Generally, in a thermal printer,
A thermal head in which a plurality of heating elements are arranged in a line is provided, and the thermal transfer medium such as an ink ribbon or the thermal recording paper and the thermal head are moved relative to each other in a direction orthogonal to the alignment direction of the heating elements. The printing is performed by energizing while controlling the energizing time for each movement (1 pulse cycle) of the width of each heating element.

Thin film resistors, which generate heat by using jule heat, are often used for such heating elements, but conventionally, uneven printing density due to the influence of past heating of each heating element is prevented. Therefore, in each cycle, the non-energization time during which the heating element is not energized is increased to sufficiently cool each heating element, and then the heating element is energized for a predetermined time to generate heat to perform printing.

However, providing a large non-energization time for each pulse cycle is an obstacle to increasing the printing speed. Also, if the non-energization time is shortened to increase the printing speed, each heat generating element takes a longer heat radiation time than the heating time, so that the thermal head gradually accumulates heat and its temperature rises. As it rose, the print density eventually became uneven. Such a phenomenon causes print density unevenness particularly when the dot density is increased by using a large number of heating elements and the printing speed is increased.

This is because the pulse cycle to each heating element becomes shorter than the heat radiation time constant of each heating element as the printing speed increases and the dot density of the thermal head increases.

For this reason, conventionally, the energization start timing is set according to the heat history of each heating element, and the energization end timing is set according to the heat history of the entire heating element, so that the energization pulse for the heating element is set. The width was controlled.

FIG. 2 shows such a conventional thermal history correction method for a thermal printer. The correction for each heating element in FIG. 2 is a control for setting the energization start timing according to the thermal history of each heating element. Therefore, by setting the energization start timing according to the heat history of each heating element, the pulse width (pulse cycle Tc) T _{11 to} T ₁₅ according to the heat history of each heating element is set.

Further, the overall correction is a control for setting the energization end timing according to the heat history of the entire heating element, and the heat history of the entire heating element for setting the energization end timing according to the heat history of the entire heating element. One pulse width T according to
₂ is set.

Then, each heating element is energized with a pulse width obtained by adding the pulse widths T _{11 to} T ₁₅ according to the thermal history of each heating element and one pulse width T ₂ according to the thermal history of the entire heating element. It is supposed to be done. That is, the pulse widths for energizing each heating element are (T ₁₁ + T ₂ ), (T ₁₂ +
T ₂ ), (T ₁₃ + T ₂ ), (T ₁₄ + T ₂ ), (T ₁₅ + T
Only the 5 types of ₂ ) are required. Moreover, in such control, since the individual correction and the overall correction are used together, either the energization start timing or the energization end timing of the energization pulse can be fixed, and the pulse width can be controlled only by the other timing. did it.

[0010]

However, when the number of heat generating elements increases, a single pulse width setting according to the heat history of the entire heat generating elements causes a difference in the heat history of each heat generating element. The generated heat gradient in the alignment direction of the heating elements cannot be absorbed any more, and it is necessary to set the energization pulse width to the heating elements for each block as one block for every equal number of adjacent heating elements. . On the other hand, since it is naturally necessary to set the pulse width according to the heat history of each heating element, the number of timings for controlling the energization pulse width in each heating element is (number of timings for each heating element) x (timing for each block However, the number of timings has become very large, and control has become very complicated.

The present invention provides a thermal history correction method for a thermal printer which overcomes the problems of the prior art and can control the number of timings so as to easily and obtain good print quality. The purpose is to provide.

[0012]

In order to achieve the above-mentioned object, a thermal history correction method for a thermal printer according to the present invention determines the energization time during each pulse cycle to a plurality of heating elements provided in a thermal head. In a thermal history correction method for a thermal printer that corrects according to the thermal history of the heating elements, a plurality of heating elements adjacent to each other are set as one block for each equal number, and the energization time during each pulse cycle is set. The energization start timer and the energization end timer control one of the energization start and the energization end individually for each heating element, and the other one for each block, which is variably set. I am trying.

[0013]

According to the present invention, the number of timings for controlling the energizing pulse width in each heating element is the sum of the number of heating element-specific timings and the number of block-specific timings. can do.

[0014]

The present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 shows an embodiment of a method for correcting heat history supplementary heat history of a thermal printer according to the present invention. The thermal head of this embodiment has a total of 160 heating elements arranged in an array as an example. have. In addition, a plurality (two in this embodiment, but not limited to this number) of the heating elements adjacent to each other are set as one block, and each heating element is composed of two heating elements. A block (block 1 to block 80) is formed. Further, in order to set the energization time to each of the heating elements during the pulse cycle, two timers are provided: an energization start timer for forming a pulse and an energization end timer. In the present embodiment, the energization start timer sets the energization start timing to the heating element according to the heat history of each heating element, and the energization end timer sets the heat in the block of the heating element. According to the history, the timing for ending the energization of the heating element of the block is set.

That is, in this embodiment, five energization start timings (T _{11 to} T ₁₅ ) to the heating elements are set by the energization start timer according to the heat history of each heating element. In addition, nine energization end timings (T _{21 to} T ₂₉ : in FIG. 1) to the two heating elements included in the block according to the total thermal history of the two heating elements included in the specific block. Shown is T ₂₃ ,
It is possible to control the pulse width (pulse cycle Tc) to each heating element by setting the energization termination timer (T ₂₅ , T ₂₉ only).

The number of timings for controlling the energization pulse width in each of the heating elements thus formed is only 14 in total, which is the sum of the five energization start timings and nine energization end timings. 1 including the heating element that does not energize in the pulse cycle
It is possible to control with five timing numbers, and the control can be simplified.

As described above, according to the present embodiment, it is possible to control the energization of each heating element with 15 timing numbers, and it is possible to obtain good quality due to the thermal history of absorbing the thermal gradient in the alignment direction of the heating elements. Printing can be performed. Also,
Since the number of power-on timings is small, the hardware or software can be simplified.

The present invention is not limited to the above-described embodiments, but various modifications can be made as necessary.

For example, in the above-described embodiment, the energization start timing is controlled according to the thermal history of each heating element, and the energization end timing is controlled according to the thermal history of the two heating elements in each block. However, on the contrary, the energization end timing may be controlled according to the thermal history of each heating element, and the energization start timing may be controlled according to the thermal history of the heating elements in each block. Good.

[0021]

As described above, according to the present invention, it is possible to reduce the number of energization timings to the thermal head and to easily control the thermal head so as to obtain good print quality.

[Brief description of drawings]

FIG. 1 is a timing chart showing an embodiment of a thermal history correction method for a thermal printer of the present invention.

FIG. 2 is a timing chart showing an embodiment of a conventional thermal history correction method for a thermal printer.

Claims (1)

[Claims] 1. A thermal history correction method for a thermal printer, which corrects an energization time during each pulse cycle to a plurality of heat generating elements provided in a thermal head according to a heat history of the heat generating elements, A plurality of heating elements adjacent to each other are set as one block for each equal number, and the energization time during each pulse cycle is determined by a timer for starting energization and a timer for ending energization. The heat history correction method for the thermal printer is characterized in that the heating history is controlled for each heating element, and the other is controlled for each individual block, so as to be variably set.