JPH03143643A - Driving of thermal head - Google Patents

Abstract

PURPOSE:To realize high thickness without reducing resolution by a method wherein a thermal head is heated for unsaturable time of density, same data is printed at second position separated by a specified pitch from a first position, and the second position is set between a third position wherein the density of printing at the first position becomes almost zero and a fourth position where positions having approximately one half the maximum value overlaps with each other. CONSTITUTION:A current is made to flow for specified time so that the density in the central part of a heating element 3 has a maximum value Dmax i.e. the density is not saturated and besides, printing is performed on a line C by shifting the printing position by a pitch P2 so that positions having density one half the maximum value overlap with each other. Consequently, dencities on the lines A and C are not decreased but rather increased. Consequently, suitable thickness as a whole can be realized. Where printing is performed so that positions where the density becomes almost zero overlap with each other, the maximum resolution can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a thermal head suitable for printing characters, symbols, etc. on transparent media such as base paper for 0IIP, X-ray film, and slides. Regarding the driving method.

[Prior Art] For example, transparent media such as base paper for 0IIP, X-ray film, and slides have high thermal conductivity and allow heat to escape easily.

Therefore, it is relatively difficult to perform high-density printing on these media using a thermal head.

Therefore, for example, Japanese Patent Application Laid-open No. 63-233855, TV
87'-24r Prototype production of color video printer for A4 size HDTV'' discloses that high density can be achieved by making the heating resistor of the thermal head smaller and printing one pixel multiple times.

[Problems to be Solved by the Invention] However, in the conventional method, printing is simply performed a plurality of times, and although high density can be achieved, there is a drawback that resolution is reduced.

The present invention was made in view of this situation, and aims to achieve high density without reducing resolution.

[Means for Solving the Problems] The thermal head driving method of the present invention heats the thermal head and prints characters, symbols, etc. on a predetermined print medium. The same data is printed in at least two positions, the first position and a second position spaced apart by a predetermined pitch from the second position, and the density of the printing at the first position is approximately zero. and a fourth position where the positions where the density is approximately 1/2 of the maximum value overlap with each other.

[Operation] In the thermal head driving method configured as described above, printing using the same data is performed at at least two positions, the first position and the second position, which are separated by a predetermined pitch. At this time, the thermal head is heated at each position for a period of time that does not saturate the density. Further, the second position is between a third position where the printing density at the first position is approximately zero and a fourth position where the positions where the density is approximately 1/2 of the maximum value overlap each other. is set to .

Therefore, high density can be achieved while ensuring appropriate resolution.

[Embodiment 1] FIG. 1 is a plan view showing the configuration of an embodiment of the thermal head of the present invention.

In the figure, 1 and 2 are electrodes, and 3 is a heating resistor supported between the electrodes 1 and 2.

A predetermined number of these elements are arranged, and a predetermined element is driven in accordance with print data.

FIG. 2 is a sectional view showing the structure of an embodiment of the print medium of the present invention.

In the figure, reference numeral 11 is a receiving paper, and has a receiving layer 12 on the upper surface of which printing is performed. A transfer paper 16 on which ink 13, film 14, and barcodes 1 and 15 are sequentially formed is placed on the receiver N12. A thermal head 17 configured as shown in FIG. 1 is pressed from above the back coat 15.

Electrode 1. When a current is passed through the heat generating resistor 3 through the heat generating resistor 3, the heat generating resistor 3 generates heat. This heat is transferred to the ink 13 via the balloon coat 15 and the film 14, and the ink 13
is heated and sublimated and transferred to the receiving layer 12 of the receiving paper 11.

Next, the density of the transferred ink will be explained.

When printing is performed by aligning the center line A of the heating resistor 3 in FIG. 1 with the line A in FIG. ) is the maximum value D max
The concentration decreases as the distance from line A increases. If the next printing is performed on line B by shifting the position of the thermal head 17 by the pitch P so that the positions where the density is approximately zero overlap, the density will similarly increase as you move away from line B with line B as the center. The print quality deteriorates.

When printing in this manner, an area where ink is not transferred is formed between lines A and B. Therefore, high concentration cannot be achieved.

Therefore, as shown in FIG. 4(a), the time for which the current is passed through the heat generating resistor 3 is increased, and the peripheral area of the heat generating resistor 3 (electrode 1
．． It is conceivable to increase the concentration of the portion (close to 2). However, in this case, when a predetermined period of time has elapsed after the start of heating and time LI has come, the heating resistor 3
The concentration at the center of the heating resistor 3 reaches the maximum value D max ', but if the heating is continued further, the concentration at the center becomes saturated at a predetermined time L2 when the concentration at the periphery of the heating resistor 3 reaches the maximum value D max. However, it further decreases below the value D max '. One of the reasons for this is that the temperature becomes too high and the ink escapes.

Therefore, as shown in FIG. 3(b), the concentration in the middle part between lines A and B (the peripheral area of the heating resistor 3) is improved compared to the case in FIG. 3(a), but the concentration on line A The concentration in the vicinity of and B (the central part of the heating resistor 3) warps and decreases.

On the other hand, as shown in FIG. 3(c), for example, the heating resistor 3
Current is applied for a predetermined time so that the density at the center of the area becomes the maximum value D max, that is, so that the density does not become saturated, and the printing position (main scanning printing pitch) is adjusted to a density that is 1/2 of the maximum value. (0,5D max) If you print on line C by shifting it by bit P2 so that the positions of The density is also improved over that in FIG. 3(a). As a result, an appropriate concentration can be achieved as a whole.

That is, in this case, as shown in FIG. 4(b), the same data is printed at multiple locations until a predetermined time (the density at the center of the heating resistor 3 is the maximum value). 1) When the max is reached, the same printing is performed at a position shifted by a predetermined bit.
The overall density increases to approximately the maximum value Dmax.

Of course, if the pitch P2 is further shortened, an even higher density can be achieved, but if the pitch P2 is made longer, the density decreases.

Next, considering the resolution, the maximum resolution can be obtained when printing is performed so that the positions where the density is approximately zero overlap each other, as shown by the hatched area in FIG. An example of printing in this case is shown in FIG. 6(a), for example.

On the other hand, if the printing pitch is brought closer to the position where the density is approximately zero, that is, a line separated by pitch P3 from line A, as shown by the broken line in FIG.
b). In this case, a suitable resolution can still be obtained, but if the distance is moved any closer, the resolution will drop sharply.

From the above, in order to achieve high density and appropriate resolution, the main scanning print bit P of the thermal head 17 should be set to a value of 23.
It can be seen that it is preferable to set the value above and below the value P2.

As shown in FIG. 7, electrode 1. 2 (the length of the heating resistor 3) is 85.0 um, the pitch of the heating resistor 3 is 85.4 μm, and the thickness of the film 14 in FIG. 2 is 6 μm1. When a printing experiment was conducted with the added thickness of 13 being 3 μm, the results shown in FIG. 8 were obtained.

In this case, the width of 0, 5 D max, which is the optimal concentration,
That is, the value Pz was 87 μm. Further, the value P3 was approximately 77 μm. In this case, if the main scanning print bit P is, for example, 85.4 μm, a one-to-one pixel configuration can be achieved.

Figure 9 shows the thermal head with the configuration shown in Figure 7.
It shows the density measurement results when printed on 11P base paper.

In this case, the width of 0.5Dmax, which is the optimum density, ie, the value P2, was 63 μm1, and the value P3 was 55 μm.

This is because in the case of OHP, heat escapes quickly, so the pitch width cannot be widened very much. Therefore, the main scanning pitch is P
A value of 59 μm, which is between P2 and P3, is appropriate.

In this way, the print density distribution differs depending on the shape of the thermal and y-axis heating resistors, the thickness of the transfer paper, the receiving paper, etc., so the main scanning printing pitch is determined according to these values. .

[Effects of the Invention] As described above, according to the thermal head driving method of the present invention, the thermal head is heated for a period of time such that the density does not become saturated, and the printing pitch is adjusted so that the printing density at the first position is approximately Since the setting is made between the third position where the density is zero and the fourth position where the density is approximately 1/2 of the maximum value, which overlap each other, it is possible to maintain high density while ensuring appropriate resolution. It can be realized.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of an embodiment of the thermal head of the present invention, FIG. 2 is a sectional view showing the configuration of an embodiment of the print medium of the present invention, and FIGS. Figure 4 is a diagram explaining the print density of the embodiment shown in the figure, Figure 4 is a characteristic diagram of heating time of the thermal head and print density, Figure 6 is a diagram explaining the printing state when the print pitch is changed, Figure 7 8 is a plan view showing the structure of another embodiment of the thermal head of the present invention, and FIGS. 8 and 9 are measurement diagrams of the density distribution of printing according to the embodiment of FIG. 7. 1.2... Electrode, 3... Heating resistor, 11... Receiving paper, 12... Receiving layer, 13... Ink, 14...
...Film, 15...Back coat, 16...Transfer paper, 17...S°-maru head.

Claims (1)

[Claims] In a thermal head driving method in which characters, symbols, etc. are printed on a predetermined print medium by heating a thermal head, the thermal head is heated for a time that does not saturate the density, and a first position and a second position separated by a predetermined pitch from the first position are heated. The same data is printed in at least two positions of the second position, and the second position is a third position where the printing density at the first position is approximately 0, and the density is approximately 1, which is the maximum value. A method of driving a thermal head in which a position where the angle becomes /2 is set between a fourth position that overlaps with each other.