JPH0439432B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a printing method in a thermal printer that can print barcodes as well as regular characters or figures, and particularly relates to a method for driving a thermal head heating element of a thermal printer. .

B. Prior Art When printing a barcode using a thermal printer, the shape of each printed dot is close to a circle, so the outline L of the barcode
As shown in Figure 6a, the barcode has severe irregularities, and the thick line of the barcode has a color missing part B inside the bar, which is compared to a barcode printed by a barcode-specific printer. However, there was a problem in that the accuracy of bar detection by the barcode reader was extremely low.

C. Problems to be Solved by the Invention The present invention solves the above-mentioned problems, and aims to provide a printing method for a thermal printer that is as linear as possible and can print a barcode with high detection accuracy by a barcode reader. That is.

D. Means for Solving Problems In order to achieve the above object, the thermal printer according to the present invention normally applies a heating element driving pulse signal once during one data cycle when printing characters or figures, and prints a bar code. 1 when printing
The heating element driving pulse signal is applied twice during a data cycle.

Function When printing barcodes, the heating element becomes hotter than when printing normal characters or figures, and each dot is printed with a larger diameter.
The unevenness of the contour of the barcode can be reduced to make it closer to a straight line, and the color missing portion within the contour can be made as small as possible to make it less noticeable or completely eliminated.

Embodiment FIG. 1 shows an embodiment of the heating element drive circuit when the present invention is applied to a line head thermal printer, in which dot pattern data sent to the shift register 1 is controlled by a latch signal. It is held in a latch circuit 2, and the output of the latch circuit 2 is applied to each heating element 5 through a gate 3 and an amplifier 4. In addition, the pulse signal for driving the heating element at this time is used in order to downsize the power supply for driving the heating element.
In order to prevent mutual interference between adjacent heating elements 5,
As shown in Fig. 2, multiple phases φa, φb, φc,
It is added to each gate 3 divided into φd.

Figure 2 shows the operation of each part during normal character or figure printing. During one data cycle τ, one pulse Pa, Pb, Pd of each phase is applied to each heating element 5, and the temperature of the heating element 5 increases. T rises rapidly during the pulse period and falls relatively slowly after the pulse period passes. Each of the dots printed at this time is composed of independent circles that do not overlap each other, as shown in FIG. 6b.

Next, FIG. 3 shows the operation during barcode printing, in which two heating element driving pulse signals Pa ₁ are applied to each heating element during one data cycle τ,
Pa ₂ , Pb ₁ , Pb ₂ , ... are applied. Paper feeding is performed at the end of one data cycle. In this way, the second pulse is applied so that the temperature caused by the first pulse does not drop completely, so that it rises to a temperature T ₂ higher than the temperature T ₁ caused by the first pulse. Note that this temperature T ₂ corresponds to two pulses Pa ₁ and Pa ₂
It can be adjusted by appropriately setting the interval between them.

As shown in FIG. 4a, the thus printed barcode has a contour line L with smaller irregularities than the conventional example shown in FIG. 6a. Figure b shows this enlarged, and as an example, the radius D ₂
is approximately 1.4 times as large as D ₁ , indicating that the diamond-shaped discolored portion B has just disappeared.

FIG. 5 shows a circuit configuration for switching whether to apply the heating element driving pulse once or twice within one data cycle. A control circuit (not shown) generates heating element driving pulses φa ₁ , φb ₁ , φc ₁ , and φd ₁ as well as heating element driving pulses φa ₂ , φb ₂ , and the same period after a certain period of time from each of these pulses. φc ₂ , φd ₂
is outputting. Although FIG. 5 shows only the φa phase, the same applies to other phases.
Gate G is normally closed when printing characters or figures, and only φa ₁ is applied to gate 3, but when printing barcodes, the control circuit (not shown) is closed.
A signal is applied to the terminal a to open it, and both pulses φa ₁ and φa ₂ are applied to the gate 3 during one data cycle.

In the above embodiment, when printing a document in which normal characters or graphics are mixed with barcodes, the entire line in which the barcodes are mixed is printed with pulses of 1 data cycle 2, but only the dots are printed. If the column is divided into several blocks and each block is energized in turn, it is sufficient to print two pulses per data cycle only for the block containing the bar code.

Effects of the Invention As described above, the present invention applies two driving pulses to the heating element during the same data cycle when printing a bar code, and increases the radius of each dot. By doing so, it is possible to reduce the unevenness of the outline of the barcode, and also to reduce or eliminate the missing color part within the outline. It has the advantage of being able to print barcodes that are close to straight lines and have high detection accuracy.

Note that it is also possible to uniformly drive the heating element with two pulses per data cycle without distinguishing between normal characters or graphics and barcodes, but this would make the circuit configuration and printer control program somewhat simpler, but on the other hand, This is accompanied by a new problem in that the temperature of the thermal head increases significantly and the life of the head is significantly shortened.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the heat generating element driving section of a thermal printer according to the present invention, Fig. 2 is an explanatory diagram of the operation when printing regular characters or figures as above, and Fig. 3 is an illustration of the operation when printing a bar code as above. Fig. 4a is a printed pattern of the same barcode as above, b is a partially enlarged view thereof, Fig. 5 is a circuit diagram of an example of a pulse switching circuit for driving a heating element, and Fig. 6a is a conventional circuit diagram. Example barcode print pattern diagram,
b is an enlarged view thereof. 1...Shift register, 2...Latch circuit, 3
...Gate, 4...Amplifier, 5...Heating element.

Claims (1)

[Claims] 1 When printing normal characters or figures, the pulse signal for driving the heating element is applied once during one data cycle, and when printing a bar code, the pulse signal for driving the heating element is applied twice during one data cycle. A printing method in a thermal printer characterized by: