JPS60143979A - Driving method for thermal head in thermal printer - Google Patents

Abstract

PURPOSE:To enable an optimum printng quality to be secured over the range from a character pattern with a high black/white ratio to one dot line, by varying an impressed voltage in accordance with the quantity of impressed power. CONSTITUTION:When a printing power source 15 is connected to a terminal 4 of a common electrode, a voltage drop is generated between the terminals 4, 5 of the common electrode due to a resistance element 6 and an operating current, whereby a voltage proportional to the number of heating elements in a heating element group 2 which are simultaneously supplied with an electric current to generate heat. A controlling voltage amplified by a comparing operational amplifier 11 is received by a voltage-controlling part 14, the black/white ratio of the pattern being printed is discriminated, and the value of a voltage to be impressed is determined. This information is transmitted to the power source 15, which generates an optimum impressed voltage based on the information. Accordingly, since the impressed voltage is controlled in accordance with the black/ white ratio of the pattern to be printed, the optimum printing quality can be obtained over the range from a character pattern with a high black/white ratio to one dot line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a thermal head in a thermal printer such as a thermal coloring type or a thermal transfer type.

[Description of prior art]

Conventionally, in this type of thermal printer, the driving voltage when energizing and generating heat according to the character pattern information to be recorded is fixed, and the applied pulse width is also fixed, so that it depends on the black/white ratio of the character pattern to be recorded. First, the applied energy was always constant.

Therefore, in the case of so-called complex characters with a large black/white ratio, the line elements that make up the character pattern become thicker than necessary due to thermal interference between the fired heating elements, making the character as a whole 1
A phenomenon called "collapse" occurred.

In addition, in order to eliminate this "collapse", when the applied energy is set to a low value of 7, it becomes difficult to reproduce a line element whose width is equal to the number of heating elements.

As described above, the conventional configuration has the drawback that it is difficult to record with optimum print quality from a character pattern with a large black/white ratio to a one-dot line.

[Detailed description of the invention]

The present invention solves the above-mentioned drawbacks by changing the applied voltage depending on the magnitude of the applied power when energizing and generating heat according to the character pattern information to be printed. The present invention provides a method that can guarantee optimal print quality.

[Structure of the invention]

The present invention is equipped with a thermal head having a linear group of heat generating elements, and a voltage driver that simultaneously drives the heat generating elements with pulse voltage according to character pattern information. A method for driving a thermal head in a thermal printer is characterized in that the pulse drive voltage is sequentially decreased each time the threshold value is recovered, and the pulse drive voltage is sequentially increased each time the threshold value is restored.

[Explanation of Examples]

Next, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, linear heating element groups 2 are arranged in multiple rows parallel to each other at a pitch that is an integral multiple of the dot pitch of the characters to be printed on the thermal head substrate 1, and the heating elements of each group are A pattern is formed between the lead wires 7, . . . , the common electrode 3, the first common electrode terminal 4, the second common electrode terminal 5, and the two common electrodes 3°5. A thermal head 10 is constituted by the formed resistance element 6. Note that the heating element group may be arranged in one row. Note that the thermal head 10 is moved in a direction perpendicular to the direction in which a row of heating elements are arranged by a head moving mechanism (not shown).

FIG. 2 is a block diagram using the thermal head 10. A comparative operational amplifier 11 is connected to the common electrode terminal 4°5 of the thermal head IO, and the common electrode terminal 5 is connected to the resistor 12.
is grounded through. The comparison amplification calculator 11 is connected to the voltage control section 14, and the printing power supply 15 is connected from the voltage control section 14 to the voltage control section 14.
A voltage control signal is sent to. A printing power source 15 serving as a voltage driver for simultaneously driving the heating elements with pulse voltage in accordance with character pattern information is connected to the common electrode terminal 4 to drive all the heating elements of the thermal head 10 to generate heat.

The thermal head drive section 13 is connected to the electrode group 8 of the thermal head 10.

Below is a step-by-step explanation of the movements.

When the printing power supply 15 is connected to the common electrode terminal 4, a voltage drop occurs between the common electrode terminals 4 and 5 due to the resistance element 6 and the operating current, and a voltage proportional to the number of heat generated by simultaneous energization of the heating element group 2 is generated. The voltage controller 14 receives the control voltage amplified by the comparison operational amplifier 11, determines the black/white ratio of the pattern being printed, determines the voltage value to be applied, and transmits this information to the printing power source 15. As a result, the printing power supply 15 generates the optimum applied voltage.

[Detailed description of the invention]

As described above, the present invention has the following features:
Since the applied voltage is controlled by the white ratio, it has the effect of realizing optimal print quality from large black/white print patterns to one-dot lines.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing the configuration of a thermal print head according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a partial block diagram of an embodiment of the present invention. 1... Thermal head board, 2... Heat generating element group, 3
...Common electrode, 4, 5...Common electrode terminal, 6...Resistance element 7...Lead wire, 10...Thermal head, 1
DESCRIPTION OF SYMBOLS 1... Comparison operational amplifier, 13... Thermal head drive section, 14... Voltage control section, 15... Printing power supply patent applicant NEC Corporation 1'+1

Claims (1)

[Claims] (1) A thermal head having a linear heating element group,
It is equipped with a voltage driver that simultaneously drives the heating elements with pulse voltage according to the character pattern information, and the pulse drive voltage is sequentially lowered each time the power consumed per unit time exceeds a threshold value, and conversely, each time the threshold value is restored. A method for driving a thermal head in a thermal printer characterized by sequentially increasing pulse drive voltage.