JPS6218278A - Multi-value thermal printer - Google Patents

Abstract

PURPOSE:To enable multi-value recording by using a recording material for binary recording, by controlling the peak value and applying time of the recording signal applied to a heat generating element from a recording power source part in relation approx. in inverse proportion corresponding to recording gradation. CONSTITUTION:Gradation data GD is latched by a latch circuit 5. The gradation data GD being latch output is decoder 6 and either one of gate circuits G1-Gn is selected by a decoding output signal. A line start signal LST comes to a trigger signal and monomultivibrators MM1-MMn respectively output signals each having a set pulse width. When the output voltages V1-Vn of a recording power source part 8 are set to V1>V2>...>Vn, the pulse widths W1-Wn of the outputs of the monomultivibrators MM1-MMn are set to the relation of W1<W2<...<Wn. When it is assumed that the gate circuit G1 was selected, a recording signal with voltage V1 is applied to the heat generating element of a thermal head from an output terminal 9 during the pulse width W1.

Description

[Detailed Description of the Invention] [Summary] The peak value of the recording signal applied to the heating element and the application time are almost inversely proportional to each other, and the recording signal has a high peak value and a short application time, so that the recording dots are small. On the other hand, by recording the signal with a low peak value and a long application time,
Since the recording dots are large, a recording signal with a relationship between the peak value and the application time corresponding to the gradation data is applied to the heating element of the thermal head, and multi-level recording is performed using the recording material for binary recording. It is something.

[Industrial application field]

The present invention relates to a multivalued thermal printer capable of performing multivalued recording using a recording material for binary recording.

[Conventional technology]

Thermal printers that use heat to record information such as characters include a thermal recording method and a thermal transfer recording method. In the former method, the thermal head is brought into direct contact with the recording paper, which changes color due to heat, and the heating element of the thermal head is heated.
In this method, recording is performed by changing the color of the recording paper, and in the latter case, the ink sheet is heated by a thermal head to melt or sublimate the ink sheet, thereby transferring the ink sheet to the recording paper and recording. Also, in terms of the scanning method of the heating element, it can be broadly classified into a line recording method and a serial recording method.The line recording method is used for high speed recording, and the serial recording method is used for low speed recording.

FIG. 9 shows the main parts of the above-mentioned line recording type thermal printer, in which the thermal head 21, the ink sheet 22. It faces a platen 24 with a recording paper 23 in between. This ink sheet 22 is heat-meltable, and by heating the ink sheet 22 with the thermal head 21, the ink on the ink sheet 22 is melted and transferred to the recording paper 23, and recording is performed.

The thermal head 21 has one line of heating elements arranged in a direction perpendicular to the plane of the paper.
Recording for one line is performed almost simultaneously. When this one line of recording is completed, the recording paper 23 and the ink sheet 2
2 is transported in the direction of the arrow.

The thermal head 21 has a multilayer structure, as shown in the schematic cross-sectional view of main parts in FIG. A protective layer 25 is formed on the substrate 29, and heat dissipation fins 30 are provided on the back surface of the substrate 29.

When a recording material such as a thermal paper for binary recording or a melt-type thermal transfer ink sheet is used, recording is performed in a binary manner. That is, if the thermal energy applied within the recording period of one line is less than the darkness value of the recording material, recording is not performed, and if it is more than that, recording is performed. Actually, as shown in the explanatory diagram of the relationship between applied heating energy and recording density in Fig. 11,
When the applied thermal energy is in the range of EF to E, intermediate density recording is performed, but within this range, the density is unstable, the density varies widely, and the reproducibility is poor. Therefore, when recording, the recording period should be adjusted so that thermal energy equal to or higher than EN is applied to the recording material, and when not recording, the recording cycle should be adjusted so that thermal energy sufficiently smaller than EF is applied to the recording material. heat dissipation characteristics,
Conditions such as the driving energy of the thermal head will be determined.

The heating element of the thermal head has been put into practical use in various shapes, but a typical one is square, and the temperature distribution of the heating element is as shown in FIG. That is, when the temperature is 200° C. at the center and 100° C. at the periphery, the temperature distribution is almost concentric. Recording is performed at a portion where the thermal energy applied to the recording material is equal to or higher than E shown in FIG. It has a shape similar to , and there are some intermediate density regions around it.

[Problem that the invention seeks to solve]

The area gradation recording method in which one pixel is composed of multiple dots and pseudo gradation recording is performed by selecting the number of recording dots is (1).
As the number of dots constituting one pixel increases and the number of gradations increases, the resolution decreases.

(2) There are drawbacks such as significant deterioration of image quality at low density levels.

Additionally, special thermal paper, sublimation ink sheets, and the like are known as recording materials for multi-level recording, but (1) they are expensive. (2) Generally, the resolution of the recording material itself is low. (3) Since the sensitivity of the recording material itself is generally low, there are drawbacks such as the inability to perform high-speed recording.

An object of the present invention is to enable multilevel recording with good reproducibility even when using a recording material for binary recording that is capable of high-speed recording.

[Means for solving problems]

The multivalued thermal printer of the present invention will be explained with reference to FIG. 1. The multivalued thermal printer of the present invention includes a recording power source section 2 that can control the peak value directly or equivalently, and a heating element 1 from the recording power source section 2 according to the recording gradation. A recording control circuit 3 is provided which controls the peak value of the recording signal to be applied and the application time so that the relationship is almost inversely proportional.

[Effect]

If the application time of the recording signal is shortened, the recording dots become smaller, and conversely, when the application time of the recording signal is lengthened, the recording dots become larger.

However, as the application time of the recording signal is shortened, the recording energy becomes smaller, and no recording is performed at all below the application time. That is, in order to stably record small dots, it is necessary to increase the peak value of the recording signal so that the recording energy is sufficiently large even if the application time is shortened.

Conversely, if the application time is increased, the recording energy increases, and if the application time is longer than that, the power resistance and heat dissipation conditions of the thermal head will be exceeded, and stable recording will no longer be possible. That is, in order to stably record large dots, it is necessary to reduce the peak value of the recording signal so that the application time is long and the recording energy does not become excessive.

Therefore, when gradation data with low recording density is added,
A voltage with a high peak value from the recording power supply section 2 is transmitted to the recording control circuit 3.
On the other hand, when gradation data with high recording density is added, the recording control circuit 3 selects a voltage with a low peak value from the recording power source 2 and lengthens the application time. It performs multivalue recording with good reproducibility.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a block diagram of an embodiment of the present invention, in which 5 is a latch circuit that latches grayscale data GD using line start signal LST as a latch signal, 6 is a decoder that decodes grayscale data CD, and 7 is a latch circuit that latches grayscale data GD using line start signal LST as a latch signal. Line start signal LST
8 is a delay circuit that delays different peak values (voltages) Vl
~ Recording power supply section that outputs Vn, 9 is an output terminal connected to the heating element of the thermal head, MMI ~ MMn are mono-multi-bi brakes each having a different output time, 01
~Gn is a gate circuit, and Q1~Qn are drive transistors.

The gradation data CD applied to the latch circuit 5 is latched by the latch circuit 5 with the line start signal LST serving as a launch signal. The gradation data GD of the latch output is decoded by the decoder 6, and one of the gate circuits G1 to Gn is selected according to the decoded output signal. Also, the line start signal L is delayed for a predetermined time by the delay circuit 7.
ST becomes a trigger signal for mono multi-by break MMI~M Mn, and each mono multi-by break MMI~
MMn each outputs a signal with a set pulse width.

The output voltages V1 to Vn of the recording power supply unit 8 are set as vi>V2>V.
3...>Vn, mono multivibrator MM
The pulse widths W1 to Wn of the outputs of I to MMn are Wl<W2
The relationship is set as W3...Wn. Therefore, if the gate circuit G1 is selected by the decode output signal of the decoder 6, the recording signal of the voltage v1 is applied to the heating element of the thermal head during the pulse width W1 of the output of the mono-multi-bi-break MMI via the drive transistor Q1. Output terminal 9
It will be applied from

FIG. 3 is an explanatory diagram of the operation, where fa) is the line start signal LST, (bl is the input gradation data CD, and (C)
is the grayscale data GD of the latch output, (d) is the line start signal LST delayed by the time Td in the delay circuit 7, (8
1, (f), (g) are mono multi-vibrake MM1
, MM 2 , MM n pulse width Wl, W2
．． The output signal of Wn is shown. Delay time Td of delay circuit 7
is selected so that it is slightly longer than the time required for the decoder 6 to decode the gradation data CD latched by the latch circuit 5 and for the decoded output signal to be determined. Moreover, the mono-multi-bi-breaks MMI to MMn are triggered by the rising edge of the line start signal LST delayed by the delay circuit 7.
Signals having respective set pulse widths W1 to Wn are outputted and applied to the gate circuits G1 to Gn.

FIG. 4 is an explanatory diagram of the relationship between the recording signal and the temperature at the center of the heating element, and shows the recording signal S1 with a voltage of 1 and a pulse width of W1.
When is applied to the heating element, the temperature of the heating element rises rapidly as shown by curve a, and the peak temperature becomes T1. When a recording signal 3n with a voltage Vn (<Vl) and a pulse width Wn (>Wl) is applied to the heating element, the temperature of the heating element rises gradually as shown by curve C, and the peak temperature is T3 (
(Tl). Also, when the recording signal S2 with a voltage v2 of 1>V2>Vn and a pulse width W2 of W1<W2<Wn is applied to the heating element, the temperature of the heating element rises as shown in the curve vAb, The peak temperature will be T2.

FIGS. 5(a) to dl are explanatory diagrams of the temperature distribution of the heating element, and when a recording signal S1 with a high peak value and a short application time is applied, as shown in (al):'r"l>T2>T
The temperature distribution becomes 3>T4, and the difference between the temperature T1 at the center and the temperature T4 at the periphery becomes large. Further, when a recording signal Sn having a low peak value and a long application time is applied, the temperature T3 at the center becomes low and the difference from the temperature T4 at the periphery becomes small, as shown in (d). Also (kll, (C) is
(al) shows the temperature distribution of the heating element in an intermediate case between the recording signal conditions shown in (d).

FIG. 6 (al to Fdl is an explanatory diagram of recording dots, and shows an example of dots recorded by a heating element with a temperature distribution of fat to (dl) in FIG. When the short recording signal S1 is applied to the heating element, the center temperature TI increases as shown by curve a in FIG.
As shown in FIG. 5(a), the range of temperature T1 is only at the center of the heating element and the duration is short, so the thermal energy given to the thermal paper or ink sheet will not exceed the dark value. Only the center part will be crossed. As a result, the recorded dots become smaller, as shown in FIG. 6(a).

Furthermore, when a recording signal Sn with a low peak value and a long application time is applied to the heating element, the difference between the temperature T3 at the center and the temperature T4 at the periphery is small, as shown by curve C in FIG. Since the temperature is the same over a wide range, and the duration is long even though the temperature is low, the thermal energy given to the thermal paper or ink sheet exceeds the dark value, which corresponds to the wide range of the heat generating element, and the temperature is low but the duration is long. As shown in d), the recording dot becomes larger.

Similarly, when the temperature distribution of the heating element shown in (bl, (C) in FIG. 5) is obtained, the recorded dots are shown in (b), (C1) in FIG. 6.

Therefore, in FIG. 2, when the gradation data CD with the highest recording density is launched into the launch circuit 5, the decoder 6
The gate circuit Gn is selected by the output of the gate circuit Gn. Therefore,
A signal with a pulse width Wn from the mono-multivibrator MMn is applied from the gate circuit Gn to the gate of the drive transistor Qn, and a recording signal Sn with a voltage Vn from the recording power supply section 8 is applied to the heating element via the drive transistor Qn. Become. This results in a large recording dot as shown in FIG. 6 (dl).Therefore, the area of the recording dot within a minute unit area is large, and the density becomes pseudo-high.

Furthermore, when tone data GD with low recording density is latched in the latch circuit 5, the gate circuit G1 is selected by the decoded output of the decoder 6, and the mono multivibrator MM is selected.
A signal with a pulse width W1 from I is applied to the gate of the drive transistor Q1 via the gate circuit G1, and the recording power supply section 8
From this, a recording signal S1 of voltage 1 is applied to the heating element via the drive transistor Q1, thereby forming a recording dot as shown in FIG. 6(a). Therefore, the recording dot area within a minute unit area is small, and the density is pseudo-low. Therefore, multi-value recording is possible by combining them.

FIG. 7 is a block diagram of another embodiment of the present invention, which is an embodiment in which the pulse height values are made isometrically different by varying the pulse duty, and the same reference numerals as in FIG. 2 indicate the same parts. 10 indicates read-only memory (ROM
), 11 to 13 are timers, 14 is OR circuit, 15.1
6 is an inverter, and 17 and 18 are AND circuits. The line start signal a is applied to the latch circuit 5 as a launch signal for the gradation data b, and is delayed by the delay circuit 7 for a time slightly longer than the time when the output signal d of the read-only memory 10 becomes valid, and the delayed signal e is timer 11.
Added to 12. The latch output signal C of the launch circuit 5 is applied to the read-only memory 1o, and the timers 11 to 13
The setting signal d of is read out.

The output pulse width of the timer 11 is set by the setting signal d, the timer 11 is triggered by the delay signal e, the output signal f is applied to the AND circuit 17 and 18, and the output signal i of the AND circuit 17 is used to trigger the timer 13. It becomes a signal,
The output signal j of the timer 13 is inverted by an inverter 16 and applied to an AND circuit 18. The output signal of the AND circuit 18 is passed through the OR circuit 14 and becomes a trigger signal for the timer 12. The output signal of the timer 12 is outputted from the output terminal 9, inverted by the inverter 15, and applied to the AND circuit 17.

FIG. 8 is an explanatory diagram of the operation, and (a) to (k) show examples of waveforms of the signal a- in each part of FIG. In addition, the gradation data GD shown in (bl) is latched. (C)
indicates the latch output signal C, which serves as the address input of the read-only memory 10. A setting signal d shown in (d) corresponding to the gradation data GD is read out from the read-only memory 10 and applied to the timers 11-13. The setting signal d sets the pulse width Wm in the timer 11,
A pulse width WS1 is set in the timer 12, and a pulse width WS1 is set in the timer 13.
A pulse width WS2 is set in .

The line start signal a is delayed for a time Td by the delay circuit 7, resulting in a delayed signal e shown in (Q). This delayed signal e is transmitted to the timer 12 via the timer 11 and the OR circuit 14.
When the delayed signal e rises, the timer 11 outputs a signal r with a pulse width Wm shown in fl. triggered, (
A pulse signal with a pulse width Wsl is output as shown by hl.

Further, the timer 13 is triggered by the output signal i of the AND circuit 17, and outputs a pulse signal j having a pulse width WS2 as shown in (Jl).

The “1” output signal f of the timer 11 is output to the AND circuit 17.1
8 and the output signal of timer 12.13 is applied to AND circuit 17.18 via inverter 15.16. and are alternately triggered by the falling edge of their respective output signals, j. Therefore, a pulse signal having a pulse width WsI and a pulse interval WS2 is output from the output terminal 9.

The pulse width WsI, the pulse interval WS2, and the pulse width Wm have different values stored in the read-only memory 10 in correspondence with the gradation data CD, and the pulse width Wsl is wide and the pulse interval WS2 is wide. If it is narrow, the recording signal will equivalently have a high peak value, and in that case, the pulse width Wm will be narrow. When the timers 11 to 13 are set by this setting signal d, the recording dots will be recorded small. On the other hand, if the pulse width Wsl is narrow (and the pulse interval W S 2 is wide), the recording signal will equivalently have a low peak value, and in that case, the pulse width Wm will be widened.

When the timers 11 to 13 are set by this setting signal d, the recording dot becomes larger. Therefore, multi-level recording is possible as in the first embodiment.

The present invention is not limited only to the above-mentioned embodiments,
For example, in combination with a dither method, it is possible to increase the number of gradations without reducing resolution.

〔Effect of the invention〕

As explained above, the present invention makes the peak value of the recording signal applied to the heating element and the application time almost inversely proportional to each other,
A recording signal according to the gradation data GD is applied to the heating element, and multilevel recording is possible using a recording material for binary recording.

Therefore, there are advantages in that high-speed and high-resolution recording is possible, and multi-level recording is possible at low cost.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the principle of the present invention, Fig. 2 is a block diagram of an embodiment of the invention, Fig. 3 is an explanatory diagram of its operation, and Fig. 4 is an explanation of the relationship between the recording signal and the center temperature of the heating element. Figure, 5th
The figure is an explanatory diagram of the temperature distribution of the heating element, Fig. 6 is an explanatory diagram of recording dots, Fig. 7 is a block diagram of another embodiment of the present invention, Fig. 8 is an explanatory diagram of its operation, and Fig. 9 is a thermal printer. 10 is a schematic sectional view of the main part of the thermal head, FIG. 11 is a diagram illustrating the relationship between applied heating energy and recording density, and FIG. 12 is a diagram illustrating the temperature distribution of the heating element. 1 is a heating element, 2, 8.10 is a recording power supply section, 3 is a recording control section, 5 is a latch circuit, 6 is a decoder, 7 is a delay circuit,
MMI~MMn are mono multivibrators, G1~Gn
is a gate circuit, Q1 to Qn are drive transistors, 10 is a read-only memory (ROM), 11 to 13 are timers, 14 is an OR circuit, 15.16 is an inverter, 17.1
8 is an AND circuit.

Claims (1)

[Claims] In a thermal printer that applies a recording signal to a heating element (1) to record on a recording medium, a recording power supply section (2) that can directly or equivalently control the peak value.
and a recording control circuit (3) that controls the peak value and application time of the recording signal applied from the recording power supply unit (2) to the heating element (1) according to the recording gradation. Multilevel thermal printer.