JPH1086429A - Thermal transfer printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To print with high image quality by eliminating change in a periodical frictional resistance between an ink sheet and a print sheet generated by conducting and non-conducting band period of a heating resistor by dispersively conducting a strobe pulse to a thermal head to print, and suppressing occurrence of vibration of the head during printing. SOLUTION: The thermal transfer printer comprises a thermal head 4 for thermally transferring ink from an ink sheet 3 to a print sheet 2 to print an image, a pulse array RAM 20 for storing addresses by dispersing generating order of strobe pulses for conducting the head generated in one line printing time corresponding to number of gradations of printed image and repeatedly reading and outputting the generating orders at each one line printing time, a comparator 21 for comparing output generating order with the number of gradations of the image, and a pulse generator 22 for generating the pulse to the head 4 when the read and output generating order is smaller than the number of gradations of the image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer printing apparatus for performing gradation recording by thermally transferring ink on an ink sheet to printing paper.

[0002]

2. Description of the Related Art FIG.
FIG. 2 is a waveform diagram of a print pulse that energizes a thermal head of a conventional gradation printer disclosed in Japanese Patent Application Laid-Open Publication No. H11-209,873. FIG. 6 is a configuration diagram of a thermal transfer printing apparatus including a thermal head to which a printing pulse having such a waveform is supplied. In FIG.
1 is a platen roller, 2 is a printing paper on which an image is printed,
Reference numeral 3 denotes an ink sheet coated with the printing ink, and 4 denotes a plurality of heating resistors for transferring the image to the printing paper 2 in the dot configuration by thermally melting the printing ink applied to the ink sheet 3 in the main scanning direction. Thermal heads arranged side by side. The ink sheet 3 and the printing paper 2 are overlapped and sandwiched between the thermal head 3 and the platen roller 1.

[0003] Reference numeral 11 denotes a microprocessor (CPU) for controlling the entire thermal transfer printing apparatus; 12, an image data input terminal for inputting image data to be printed; and 13, temporary storage of image data input from the image data input terminal 12. A buffer circuit for generating the number of gradations of the image data from the clock signal output from the CPU 11 and a counter for generating an address number which is an arrangement position of the heating resistor in the thermal head 4; and 15, a number corresponding to the number of gradations of the image data. Gradation data control circuit for generating printed gradation data
Reference numeral 6 denotes an energization width control circuit for setting the energization time width of the print pulse from the print gradation data. Reference numeral 18 denotes a head control circuit including a shift register and a latch circuit. The head control circuit 18 is set by an address control circuit 17. In the heating resistor of the thermal head 4 at the position corresponding to the address,
A print pulse having a power-on time width set by the power-on width control circuit 16 is supplied to generate heat.

In the thermal transfer printing apparatus, a head control circuit 18 applies a printing pulse to each heating resistor of the thermal head 4 at a power-on time width controlled by a power-on width control circuit 16 in accordance with the number of gradations of a corresponding printing dot of image data. Add to body. As a result, when the amount of heat generated by the heating resistor is controlled according to the number of gradations, the amount of ink to be thermally transferred from the ink sheet 2 to the printing paper 2 is determined according to the number of gradations, and gradation printing by thermal transfer is realized.

[0005] In FIG. 4, Tp is a feed time per line in the sub-scanning direction determined by the dot density of pixels and the feed speed of the printing paper 2. Tw is the conduction width control circuit 1
6, the energizing time to the heating resistor of the thermal head 4 controlled by the thermal sheet 4. When the number of gradations is small, the energizing time is short.
Energy, ie, the amount of thermal transfer, is increased.

Tf is a non-energizing time, and the non-energizing time Tf stops energizing the heating resistor. The feed time Tp = Tw + Tf. Depending on the value of the number of gradations, there may be a case where Tw = Tf where the energizing time and the non-energizing time are equal as shown in FIG.

[0007]

In the conventional thermal transfer printing apparatus configured as described above, when the base material of the ink sheet 2 is formed of a PET film or the like, the heat is applied to the heating resistor during the printing operation. When the temperature rises due to energization, the base material itself becomes soft, and the coefficient of friction between the ink sheet base material and the heating resistor increases.

Conversely, during the power supply OFF time, the temperature of the heating resistor decreases and the temperature of the ink sheet also decreases, so that the coefficient of friction between the ink sheet and the heating resistor decreases. Therefore,
During the printing operation, the coefficient of friction between the ink sheet and the heating resistor repeatedly increases and decreases.

For this reason, as shown in FIG. 4 (c), in the case of printing near the entire solid printing at the number of gradations in which the energizing time Tw and the non-energizing time Tf are substantially equal, a vibration with a period Tp occurs. This vibration easily causes the thermal head 4 pressing the platen roller 1 to float slightly from the platen roller 1 to generate horizontal stripes due to uneven feeding on the printing screen of the printing paper, thereby deteriorating the printing quality. Further, there is a problem that the vibration of the period Tp resonates the driving mechanism components connected to the platen roller 1 and the support member of the thermal head 4 to generate unpleasant noise.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a high image quality that suppresses unpleasant noise and does not generate horizontal stripes on a print screen even when a solid print of any number of gradations is executed. It is an object of the present invention to obtain a thermal transfer printing device capable of realizing printing.

[0011]

SUMMARY OF THE INVENTION A thermal transfer printing apparatus according to the present invention is a thermal transfer printing apparatus which thermally transfers ink from an ink sheet to printing paper to print an image.
A head control means is provided for setting and outputting the generation timing of the energizing strobe pulse generated within the line printing time according to the gradation of the image.

A thermal transfer printing apparatus according to the present invention is characterized in that a thermal head for thermally transferring ink from an ink sheet to a printing paper to print an image, and the thermal head generated within one line printing time in accordance with the gradation of the image to be printed. Strobe pulse setting means for setting the generation timing of the strobe pulse for energizing the thermal head; and inputting image data for printing, and determining the generation timing of the strobe pulse according to the gradation of the image data by the strobe pulse setting means. And a pulse generating means for generating a strobe pulse in the thermal head at a time interval based on the generation timing.

A thermal transfer printing apparatus according to the present invention includes a thermal head for thermally transferring ink from an ink sheet to printing paper to print an image, and a thermal head generated within one line printing time corresponding to each gradation number of the image to be printed. Storage means for dispersing the order of generation of the strobe pulse for energizing the thermal head for each address, repeatedly reading and outputting each generation order, and storing the read-out generation order and the number of gradations of the image. And a pulse generating means for generating a strobe pulse to the thermal head when the order of the read-out and output is smaller than the number of gradations of the image.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram of the thermal transfer printing apparatus according to the first embodiment. In the drawing, the same reference numerals as those in FIG. 6 indicate the same or corresponding parts. In the figure, reference numeral 20 denotes a pulse array RAM that stores a pulse train output order n of a strobe pulse having a fixed time width for generating heat by energizing a heating resistor;
Reference numeral 21 denotes a comparator for comparing the pulse train output order n read from the pulse array RAM 20 in accordance with the address signal output from the counter 14 with the number of gradations N of the image data stored in the buffer circuit 13, and 22 denotes a comparison result. A pulse generating circuit 23 outputs a strobe pulse to the head control circuit 18 based on the pulse signal. A pulse width generating circuit 23 determines a time width of the strobe pulse for the head control circuit 18.

Here, the comparator 21 is a pulse array RAM 2
The pulse train output order n starting from 0 is compared with the number of gradations N of the image data of the buffer circuit 13, and from the pulse array RAM 20, the pulse train output order that satisfies the condition of “pulse train output order n” ≦ “image data gradation number N” Each time n is read, a trigger signal is output to the pulse generation circuit 22. The pulse generation circuit 22 receives the trigger signal and the head control circuit 18
Outputs a strobe pulse. The pulse array RAM
Reference numeral 20 denotes a strobe pulse setting unit or a storage unit, and the comparator 21 and the pulse generation circuit 22 constitute a pulse generation unit.

FIG. 2 is a diagram showing an arrangement of the pulse train output order stored in the pulse arrangement RAM 20. The pulse array RAM 20 distributes and stores the pulse train output order n of the strobe pulse corresponding to the number of gradations in each memory address. This allocation is set so that the strobe pulse for gradation control is not biased within the feed time Tp per dot. The allocation determines the strobe pulse generation timing within the feed time Tp.

Next, the operation of this embodiment will be described with reference to the timing chart of FIG. Now, the count values sequentially output from the counter 14 are the address signals (1 to N).
Is input to the pulse array RAM 20, the pulse array RAM 20 sequentially reads the pulse output order 0 to n−1 from the memory addresses 1 to N and inputs the pulse output order to one input terminal of the comparator 21.

At this time, for example, if the gradation number 3 is input from the buffer circuit 13 to the other input terminal of the comparator 21, the pulse train output order 1 read out from the memory addresses 2, N / 2, N-2 , 3 and 2 are “pulse train output order n” ≦
The condition of “the number N of image data tones” is satisfied.

As a result, the comparator 21 outputs a trigger signal to the pulse generating circuit 22 every time the pulse train output order 1, 3, 2 is read out at intervals, and the head control circuit 1
In step 8, the thermal head 4 outputs a strobe pulse. In this case, it is not necessary to select a specific heating resistor of the thermal head 4 and energize it because solid printing is performed.

If the number of gradations is 0, the pulse arrangement R
Since the pulse train output order n sequentially read from the AM 20 is always larger than the gradation number 0, the condition of “pulse train output order n” ≦ “image data gradation number N” is not satisfied, and no strobe pulse is generated. However, when the gradation number N is the full gradation, the gradation number N always satisfies the condition of “pulse train output order n” ≦ “image data gradation number N”.
Each time the pulse train output order n is read from 20, a strobe pulse is output to the head control circuit 18. As a result, the energizing time of the thermal head is longer than the energizing time in the case of the number of gradations 3, and the thermal transfer amount of the ink from the ink sheet 3 to the printing paper 2 is increased, resulting in a high quality image.

In this way, the energizing time Tw and the non-energizing time Tf of the thermal headon, which are determined by the generation of the strobe pulse, are alternately and evenly distributed within the feeding time Tp. Energizing time T
The deviation of f is eliminated, and the coefficient of friction between the ink sheet and the heating resistor is not repeatedly increased or decreased.

Therefore, even in the case of solid printing in the vicinity of an intermediate gradation number, the thermal head 4 is floated minutely from the platen roller 1 to generate horizontal stripes due to uneven feeding, thereby deteriorating the image quality. The driving mechanism components connected to the roller 1 and the supporting member of the thermal head 4 resonate, thereby eliminating the pleasant sound generated.

[0023]

According to the present invention, a thermal head for printing an image by thermally transferring ink from an ink sheet to a printing paper, and the thermal head generated within one line printing time in accordance with the gradation of the image to be printed. Strobe pulse setting means for setting the generation timing of the strobe pulse for energizing the head, and inputting image data for printing, and determining the generation timing of the strobe pulse according to the gradation of the image data by the strobe pulse setting means. Pulse generating means for generating a strobe pulse to the thermal head at a time interval based on the occurrence timing, and performing printing by distributing the strobe pulse to the thermal head in a distributed manner. There is no periodic change in frictional resistance between the ink sheet and the printing paper due to It, there is an effect that it is possible to perform the printing of high quality since it is possible to suppress the occurrence of vibration during the printing of the thermal head.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a thermal transfer printing apparatus according to an embodiment of the present invention.

FIG. 2 shows a pulse array RAM 20 according to the present embodiment.
FIG. 3 is a diagram showing an arrangement configuration of a pulse train output order.

FIG. 3 is a timing chart showing the relationship between the number of gradations and the output position of a strobe pulse in the present embodiment.

FIG. 4 is a waveform diagram of an energizing pulse to a thermal head of a conventional thermal transfer printing apparatus.

FIG. 5 is a configuration diagram of a conventional thermal transfer printing apparatus.

[Explanation of symbols]

1 platen roller, 2 printing paper, 3 ink sheet, 4 thermal head, 11 microprocessor (CPU), 12 image data input terminal, 13 buffer circuit, 14 counter, 15 gradation data control circuit, 1
6. Current width control circuit, 18 head control circuit, 20 pulse array RAM, 21 comparator, 22 pulse generation circuit.

Claims (3)

[Claims] 1. A thermal head for printing an image by thermally transferring ink from an ink sheet to printing paper.
A thermal transfer printing apparatus, comprising: a head control means for setting and outputting a generation timing of an energizing strobe pulse generated within a line printing time in accordance with the gradation of the image. 2. A thermal head for printing an image by thermally transferring ink from an ink sheet to printing paper, and a strobe pulse for energizing the thermal head generated within one line printing time according to the gradation of the image to be printed. A strobe pulse setting means for setting the generation timing of the image data, and inputting image data for printing, and determining the generation timing of the strobe pulse by the strobe pulse setting means in accordance with the gradation of the image data. And a pulse generating means for generating a strobe pulse to the thermal head at time intervals. 3. A thermal head for printing an image by thermally transferring ink from an ink sheet to printing paper, and a power supply for energizing the thermal head generated within one line printing time corresponding to each gradation number of the image to be printed. A storage unit for dispersing and storing the generation order of strobe pulses at each address, and repeatedly reading and outputting each generation order for each line printing time, and comparing the output generation order with the number of gradations of the image. And a pulse generating means for generating a strobe pulse to the thermal head when the read-out generation order is smaller than the gradation number of the image.