JPS6294359A - Thermal recording apparatus - Google Patents

Abstract

PURPOSE:To enable the control of gradation recording by a simple constitution, by providing a means performing the control of a pulse width to obtain a gradation printing pulse and a means adding a pulse within a range generating no color forming recording of a thermal recording material to a gradation printing pulse to obtain the printing pulse of a thermal head. CONSTITUTION:When the cycle of the output (b) of a clock signal generating circuit 3 is set to T, the output (a) of a gradation recording signal generation part 2 is inputted to a recording signal adding part 6 where a pulse having a width within a range allowing a recording material to form no color is added to obtain output (d). When a pulse width is 18T, a power source 5 is regulated to lower the voltage thereof so that recording density comes to saturated density Dmax. Whereupon, in the relation between a recording signal pulse width and recording density, is gradations are taken between Do-Dmax with respect to the 16-stage change in the pulse width of 3T-18T. That is, by adding a pulse with a definite width to the recording signal having received the modulation of a pulse width, recording having a number of gradations corresponding to the number of stages in the modulation of the pulse width for gradation recording is enabled.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a thermal recording device that has a thermal head and performs gradation recording printing.

2. Description of the Related Art A conventional thermosensitive recording apparatus of this type was constructed as shown in FIG. That is, in the figure, 1 is a thermal head, 2 is a thermal head, and 2 is a thermal head.
4 is a memory for storing gradation print data; 3 is a clock generation circuit having a cycle corresponding to the minimum resolution; and 5 is a power source for the thermal head 1.

The operation of the thermal storage device configured as described above will be described below assuming that the memory 4 contains gradation print data in advance. - For example, when printing with 16 steps of pulse width modulation, the output C of the memory 4 that stores gradation print data requires 4 bits, and the clock that determines the time unit of minimum resolution for gradation storage. Assuming that the period of the output l) of the generating circuit 5 is T, the gradation recording signal generating section 2 inputs the gradation printing data C output from the memory 4 in synchronization with the output of the clock generating section 3, and generates a clock. The pulse width is controlled so that the period T of the output of the circuit 3 is a time unit of minimum resolution, and a recording signal a corresponding to the gradation print data is output. Since the gradation print data is a 4-bit digital signal, the recording signal a is 0. T, 2T, 3T,
---It becomes a pulse signal with a width of 15T. FIG. 5 is a timing chart showing the above operation.

The recording signal a is input to the thermal head 1, and the heating element of the thermal head 1 generates heat by being supplied with power from the power supply 5 according to the pulse width of the storage signal a, and develops color by heating the thermosensitive recording material. Make a record.

Further, the relationship between the recording signal pulse width and the recording density at this time generally has characteristics as shown in FIG. Note that D wax is the saturation density, and Do is the density of the recording base paper.

FIG. 6 shows that there are 13 gradations between no-r)max for the 16-step change in pulse width from 0 to 15T.

Problems to be Solved by the Invention In gradation recording with such a conventional configuration, the relationship between the recording signal pulse width and the recording density is as shown in Fig. 6. The signal does not color the recording material. Therefore, the number of stages of pulse width modulation for gradation recording does not directly correspond to the number of gradations, and the number of gradations becomes smaller than the number of stages of pulse width modulation. Furthermore, in order to increase the number of gradations, it is necessary to increase the number of stages of pulse width modulation, which has the problem of complicating the process of increasing the clock frequency.

The present invention has been made in view of these points, and an object of the present invention is to provide a heat-sensitive recording device that can perform gradation recording control with a simple configuration and without the above-mentioned drawbacks.

Means for Solving the Problems In order to solve the above problems, the present invention provides a thermal head having an element that generates heat in accordance with printing pulses, and a means for controlling pulse width for gradation recording printing to obtain gradation printing pulses. and a means for adding a pulse within a range in which color recording does not occur in the heat-sensitive recording material to the gradation printing pulse to form a printing pulse for the thermal head.

Effects According to the present invention, according to the configuration described in -F, a pulse within a range that does not cause color development in the heat-sensitive recording material is added to the gradation printing pulse, and the number of stages of pulse width modulation can be effectively utilized for gradation recording.

Embodiment FIG. 1 is a block diagram of a thermal recording apparatus according to an embodiment of the present invention. In the figure, numerals 1 to 5 are the same as those indicated by the same symbols in FIG. 4, and their explanation will be omitted. Reference numeral 6 denotes a recording signal adding section that adds a pulse having a predetermined width to the output a of the gradation recording signal generating section.

The operation of this device will be explained below. It is assumed that the memory 4 contains gradation print data in advance, and that the data is 4 bits in order to apply 16 steps of pulse width modulation. Further, assuming that the period of the output of the clock signal generation circuit 3 is T, the gradation recording signal generation section 2 operates similarly to the conventional example.
The output a is as shown in FIG. This output a is inputted to the recording signal adding section 6, and a pulse having a width within a range in which the recording material does not develop color is added to it, resulting in an output d. FIG. 2 is a timing chart when the added pulse width is 3T. The recording signal d is input to the thermal head 1, and the heating element of the thermal head 1 is powered by the power source 5 according to the pulse width of the recording signal d.
A voltage is applied to generate heat, and color recording is performed by heating the heat-sensitive recording material. Further, the relationship between the recording signal pulse width and the recording density at this time has the characteristics shown in FIG. 6 (portion 3T-18T). DIIla× is the saturation density, and Do is the density of the recording base paper.

Here, when the pulse width is 18T, the recording density is the saturation density D w
Adjust the voltage of the power supply 5 so that , indicates that there are 16 gradations between Do and Dmax.

In other words, by adding pulses of a constant width to the pulse width modulated recording signal, it is possible to develop color even in areas where the recording material would not develop color in the conventional configuration. It becomes possible to record as many gradations as there are stages.

In the configuration of the embodiment, the printing pulses are placed in the front, but it goes without saying that the printing pulses may be placed in the back and added at the end of recording in a range where the recording material does not develop color.

Effects of the Invention As described below, according to the present invention, the number of pulse width modulation steps for tone recording can be effectively used with an extremely simple configuration, and even with the same number of pulse width modulation steps, the number of tone levels can be increased. can do. In addition, the power supply voltage applied to the thermal head can be lowered, making it possible to use less power and make the device more compact.The gradation can be effectively secured without increasing the memory capacity, and the cost of the device can be reduced. realizable. Further, the basic clock can be left as is, which is advantageous for high-speed recording without increasing the number of data processes and transfers.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a thermal recording device according to an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the device, FIG. 3 is a recording characteristic diagram of the same, and FIG. 4 is a diagram of a conventional thermal recording device. A block diagram, FIG. 5 is a timing chart showing its operation, and FIG. 6 is a recording characteristic diagram. 1... Thermal head 2... Gradation recording signal generation section 3... Clock signal generation circuit 4... Memory 5... Power supply 6...
・Name of the agent of the recording signal addition department: Patent attorney Toshio Nakao and one other person Figure 3: 1,18 tongues, 8,000 yen (×T) Circle 4, E, Tomomoma” Figure 5, Figure 6

Claims (1)

[Claims] A thermal head having an element that generates heat in accordance with the printing pulse, a means for controlling the pulse width for gradation recording printing to obtain the gradation printing pulse, and a printing pulse having a pulse width within a range that does not cause color recording on the heat-sensitive recording material. In addition to the gradation printing pulse, a thermal recording device further comprises means for generating a printing pulse for the thermal head.