JPH0752437A - Thermal transfer recording device - Google Patents

Abstract

(57) [Summary] [Objective] In a thermal transfer recording device using a multi-ink sheet, the same voltage as that applied to the thermal head can be applied to the thermal head, but the same print density can be obtained. A recording device is provided. In a thermal transfer recording apparatus for controlling multi-gradation recording by controlling energization time to a thermal head, a print dot density in the sub-scanning direction is set higher than a print dot density in the main-scanning direction, and dots in the sub-scanning direction are set. A control unit is provided to control printing so that a part of the sheets overlap.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer recording apparatus, and in particular, in a printing method using a multi-ink sheet that can be used many times, the image density is increased and the image quality is improved without increasing the energy supplied to the thermal head. The present invention relates to a thermal transfer recording device that can be used.

[0002]

2. Description of the Related Art A thermal transfer recording apparatus is one in which a dye or ink on an ink sheet is selectively sublimated or melted by a recording head such as a thermal head or an energization recording head to transfer the dye or ink onto an image receiving sheet. A recording image is formed on the image receiving sheet. Ink sheets used in the thermal transfer recording apparatus include one-time ink sheets and multi-ink sheets. The ink sheet length required to print one sheet with the multi-ink sheet is 1 / n as compared with the one-time ink sheet, but the ink layer is thicker than the one-time ink sheet. Therefore, if the same voltage is applied to the thermal head when the one-time ink sheet and the multi-ink sheet are used, the energy density becomes insufficient and the print density becomes lighter when the multi-ink sheet is used. Increasing the voltage applied to the thermal head when using the multi-ink sheet to increase the density brings about the disadvantages of increasing the size of the power supply and increasing the heat generation cost.

JP-A-58-55261 and JP-A-6-56261
No. 0-253565 discloses that one-time ink sheets have different sensitivities depending on the manufacturers, lots, etc., and the sensitivity (ink melting point information, energizing time to the head, etc.). It is disclosed that the index indicating the value is written on the ink cassette itself, and the recording device reads the index to control the heat generation amount according to the difference in sensitivity. Since the voltage applied to the head is increased, there are problems that the size of the power source is increased and the heat generation cost is increased. In addition, JP-A-6
Japanese Laid-Open Patent Publication No. 1-24370 describes an area gradation recording method, and in an area gradation recording method in which gradation recording is performed in an area of a colored portion according to density in a matrix composed of n × m elements, There is disclosed a configuration in which the printing position is shifted (overlapped) by 1/2 pitch in the direction to form the colored portion and the number of gradation levels is increased. It is different from the recording method that is designed to obtain the key. That is, the area gradation method has a drawback that the resolution is low because a color is represented by a plurality of dots, but the dot density modulation method has a good resolution and a good color because a color is represented by one dot. However, in the dot density modulation method, when trying to obtain a sufficient density using a multi-ink sheet, energy is required as described above,
There was a strong demand for a solution to this point.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and in a thermal transfer recording apparatus using a multi-ink sheet, the same voltage is applied to the thermal head as in the case of the one-tam ink sheet, but the same It is an object of the present invention to provide a thermal transfer recording device capable of obtaining a print density.

[0005]

In order to achieve the above object, the present invention is a thermal transfer recording apparatus for controlling the energization time to the thermal head to perform multi-gradation recording, in which the print dot density in the sub-scanning direction is changed to that in the main scanning direction. The controller has a control unit that controls the printing so that the dots are higher than the print dot density so that some of the dots in the sub-scanning direction overlap, and the control unit uses a multi-ink sheet for printing and a one-time ink sheet. Controlling to switch the print dot density in the sub-scanning direction depending on the printing used, and setting the overlapping range of the print dots in the sub-scanning direction to 1/2 or less of one dot diameter,
In order to switch the print dot density in the sub-scanning direction,
By changing the conveyance speed of the image receiving paper, the control unit controls so that the magnification in the main scanning direction is different in each case of printing using a multi-ink sheet and printing using a one-time ink sheet. It is characterized by that.

The present invention will be described in detail below with reference to the embodiments shown in the accompanying drawings. FIG. 1 is a circuit block diagram when the present invention is applied to a video printer, which is a type that can use both a one-time ink sheet and a multi-ink sheet. NTSC input from host device such as VTR
By subjecting the signal to predetermined processing by the video printer 2, a print signal for the thermal head is generated, and the heating element of the thermal head is caused to generate heat to transfer the dye and ink on the ink sheet onto the recording medium. The image corresponding to the image displayed on the CRT of the television is printed. In the signal processing circuit 3 constituting the video printer 2,
The NTSC composite signal input from the VTR is separated into a luminance signal and a chrominance signal, and then converted into a digital signal by the A / D conversion circuit 4. The digitized image data is
It is stored as a luminance signal Y and a color signal UV (RGB is obtained by combining both signals Y and UV). Next, the image processing circuit 6 performs color conversion of the luminance and color signal YUV into RGB, γ correction, color conversion from RGB to YMC,
Processing such as scaling and edge enhancement is performed. As for the contents of the scaling processing, in the case of a one-time ink sheet, only the vertical is 6/5 times, and in the case of multiple, the same size processing is performed. The thermal control circuit 8 performs thermal head temperature correction, rising / falling correction, adjacency history correction, element number correction, and the like. The image processing circuit 6, the heat control circuit 7, the driver 10 and the like are controlled by a control signal from the CPU 9. When the print start switch 15 is turned on, the print start signal is sent to the CPU.
When input to 9, the CPU 9 outputs a control signal to the driver 10 or the like to shift the mechanical printing mechanism unit to the printable state. Specifically, the ink sheet winding motor 1
1, ink sheet supply motor 12, image receiving paper transport motor 1
After 3 is made operable, the ink sheet and the image receiving paper are started to be conveyed, and the thermal head 8 is supplied with an image signal and power to print out. Reference numeral 14 is a multi / one-time selection changeover switch.
In the present invention, the driving pulse frequency of the pulse motor 13 is changed so that the conveyance speed of the image receiving paper when using the multi-ink sheet is 5/6 that when using the one-time ink sheet. It is characteristic.

FIGS. 2 (a) and 2 (b) are diagrams showing the printed states of pixels when multi-printing is performed and when one-time printing is performed by the apparatus of the present invention. N input from VTR
The TSC image signal has 480 effective scanning lines out of 525 scanning lines, and the video printer prints out 768 pixels per scanning line, but the original TV screen has an aspect ratio of 3: 4. Therefore, if the image information of the television screen is printed out by the printer with 480 dots in the vertical direction and 768 dots in the horizontal direction, there is a disadvantage that it becomes a horizontally long image. Therefore, if a one-time ink sheet is used to solve this problem, the vertical direction should be 6 /
It is magnified 5 times to 576 dots (Fig. 2 (b)). By the way, even when a multi-ink sheet is used, printing may be performed with the same pixel density, but since the ink thickness of the multi-ink sheet is thicker than that of the one-time ink sheet as described above, application to the thermal head is performed. When the energy is the same, the printout image density of the multi becomes lighter than in one time.

Therefore, in the present invention, in order to make the printout image density the same as that of the one-time ink sheet, the energy applied when using the multi-ink sheet is the same as that of the one-time ink sheet. As shown in FIG. 2 (a), while maintaining 480 dots in a column, when printing 768 dots forming a row, each dot is printed so as to partially overlap in the horizontal direction. The degree of this overlap is such that the aspect ratio is 3: 4, in other words, when the height is 480 dots, the width is 6
The printout is executed so that the length becomes 40 dots, in other words, the overlap becomes ½ or less of the dot diameter. As a result, a non-horizontally long image can be obtained as in the case of one-time printing. The degree of overlap of dots in the horizontal direction can be variously changed within a range not exceeding 1/2. In order to set the horizontal length to 640 dots while performing printing of 768 dots, the carrying speed of the image receiving paper carrying motor 13 in the case of multi is 5/6 as compared with the case of one time. It may be controlled by the CPU.

As described above, according to the present invention, in the case of multi-printing, the dot density in the sub-scanning direction is set higher than the dot density in the main-scanning direction, so that the energy supplied to the thermal head is the same as in the case of one-time printing. Even if it is the same, the image density of the printout can be increased, and the deterioration of the image quality can be prevented. In addition, since the print dot density in the sub-scanning direction is switched for each of the multi-printing and the one-time printing, the printed image does not have a distorted shape, and the one-time printing The image can be made larger. In other words, even if the images are the same, the image becomes more compact in the case of multiple images.

Since the dot overlap in the sub-scanning direction is suppressed to 1/2 or less, it is possible to obtain a sufficient image density while reducing the deterioration of the image quality of the printout. Further, since the dot density switching in the sub-scanning direction is performed by switching the speed of the image receiving paper transport motor, it is possible to set an arbitrary dot overlap at low cost. Since the magnification in the main scanning direction is switched between one-time printing and multi-printing, the printed image does not become distorted, and the one-time printing can be larger than multi-printing. Furthermore, the number of effective pixels obtained from the NTSC image signal is 480.
Since the image information of x758 dots can be fully utilized even at the time of printing out, the image quality does not deteriorate. Although the video printer has been illustrated in the above embodiments, this is only an example, and the present invention is applicable to general thermal transfer recording apparatuses that perform multi-gradation recording by controlling the energization time to the thermal head. .

[0011]

As described above, according to the present invention, in the thermal transfer recording apparatus using the multi-ink sheet, the same voltage is applied to the thermal head as in the case of the one-tam ink sheet, but the same print density is obtained. It becomes possible to obtain.

[Brief description of drawings]

FIG. 1 is a circuit block diagram when the present invention is applied to a video printer.

FIGS. 2A and 2B are diagrams showing pixel printing states when multi-printing and one-time printing are performed by the apparatus of the present invention.

[Explanation of symbols]

2 video printer, 3 signal processing circuit, 4 A / D conversion circuit, 5 image memory, 6 image processing circuit, 7 thermal control circuit, 8 thermal head, 9 CPU, 10 driver, 11 ink sheet winding motor, 12 ink sheet Supply motor, 13 Image receiving paper transport motor.

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Claims (5)

[Claims] 1. A thermal transfer recording apparatus for controlling multi-gradation recording by controlling energization time to a thermal head, wherein a print dot density in the sub-scanning direction is set higher than a print dot density in the main-scanning direction. The thermal transfer recording apparatus is provided with a control unit that controls the printing so that some of the dots are overlapped. 2. The control unit controls to switch the print dot density in the sub-scanning direction between printing using a multi-ink sheet and printing using a one-time ink sheet. Thermal transfer recording device. 3. The thermal transfer recording apparatus according to claim 1, wherein the overlapping range of the print dots in the sub-scanning direction is ½ or less of one dot diameter. 4. The thermal transfer recording apparatus according to claim 2, wherein a transfer speed of the image receiving paper is switched in order to switch the print dot density in the sub-scanning direction. 5. The control unit controls the magnification in the main scanning direction to be different in each case of printing using a multi-ink sheet and printing using a one-time ink sheet. The thermal transfer recording apparatus according to any one of 1 to 4.