JPH0872284A - Thermal transfer color recorder - Google Patents

Abstract

PURPOSE: To realize accurate and stable recording characteristics without impairing ink superposing characteristics in a melt type multi-gradation thermal transfer color recording. CONSTITUTION: Fig. (A) is the state that yellow ink 37 is transferred by 50% of printing area ratio (5 pulses). Magenta ink 38 is printed thereon by 70% of printing area ratio (7 pulses). When a print pulse is applied by normal energy, as shown in Fig. (B), transfer failure occurs at the part where the inks are superposed. As shown in Fig. (C), when printed with high energy, the superposition of the inks can be improved, but the printing area to the sheet 22 to be transferred is increased. As shown in Fig. (D), even if the pulse number is increased, the superposing characteristics are not altered. As shown in Fig. (E), magenta printing pulse 25 is the energy higher by five pulses to be printed on the yellow ink, and the residual two pluses to be printed on the sheet is printed by normal energy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal transfer color recording apparatus capable of recording in a color halftone by using a thermal transfer thermal head.

[0002]

2. Description of the Related Art Conventionally, a melting type is known as a color halftone recording method using a thermal head. Compared to sublimation type, fusion type can print with less energy,
Although there is an advantage that the cost is low, the density of the ink donor film itself cannot be changed even when the applied energy is changed. Therefore, it is not possible to perform gradation expression by the density difference, and it is difficult to perform multi-gradation recording. . Therefore, it is described in a matrix method such as a dither method, a sub-scanning division method as described in JP-A-60-248074, JP-A-3-219969 and the like, JP-A-59-76264 and the like. The gradation is expressed in a pseudo manner by using an area gradation method or the like in which the gradation is changed by changing the heat generation area by the heat concentration method as described above.

FIG. 4 is a partial sectional view showing an example of a fusion type thermal transfer recording apparatus. In the figure, 31 is a platen, 32 is a transfer paper, 33 is an IDF, 34 is a base film, 35 is ink, and 36 is a thermal head. The fusion type thermal transfer recording apparatus shown in FIG. 4 shows an example in which a thermal head having the same size as the paper width is used. The IDF (ink donor film) 33 is configured by coating a base film 34 with a heat-meltable ink 35. The IDF 33 and the transfer target paper 32 are overlapped and passed between the thermal head 36 and the platen 31. The ink 35 on the IDF 33 is melted by energizing the thermal head 36, and the pressure applied to the platen 31 increases the adhesiveness between the transfer paper 32 and the ink, so that the ink 35 is separated from the base film 34 and the transfer paper 32 is transferred. Is transferred to and recorded.

FIG. 5 is a cross-sectional view of a transfer paper on which recording is performed by a fusion type thermal transfer recording device. Ink 35 is transferred onto the surface of the transfer-receiving paper 32 on which recording is performed as shown in FIG. When the surface of the transfer paper 32 is flat, good recording is performed as shown in FIG. However, if the surface smoothness of the transferred paper 32 is poor, as shown in FIG. 5 (B), a portion where the adhesiveness between the transferred paper 32 and the ink is not sufficiently obtained occurs, and transfer failure occurs. Therefore, a synthetic paper having a good surface smoothness is used as the transfer paper 32, or a plain smooth paper having a poor smoothness is used by applying a transparent smoothing layer on the surface in advance.

As described above, when performing color halftone recording, for example, three colors of cyan, magenta, and yellow are used.
Various colors are expressed by superimposing colors or four colors with black added thereto at an arbitrary ratio. Therefore,
The overlapping ink may be directly transferred onto the transfer paper or may be transferred onto another color.

FIG. 6 is a sectional view of a transfer paper showing an example when color recording is performed by the fusion type thermal transfer recording apparatus. In the figure, 37 to 39 are inks of different colors. For example, consider a case where recording is performed using the three colors of cyan, magenta, and yellow described above. The ratio of the printed area within one pixel will be called the printed area ratio. 10% yellow printing area, 5 magenta printing area
It is assumed that there is a color that expresses 0% and the printing area ratio of cyan as 100%. Printing is performed for the three colors in the same position in the pixel so that the area increases with the same pattern. FIG. 6 shows a state in which ideal printing is performed in the order of yellow, magenta, and cyan at this time. In FIG. 6, the ink 37 is yellow, the ink 38 is magenta, and the ink 39 is cyan. Although all the yellow ink 37 is transferred onto the transfer paper, 10% of the magenta ink 38 is transferred onto the yellow ink, and the remaining 40% is transferred onto the transfer paper. And 50 of the cyan ink 39
% Is transferred onto the magenta ink, and the remaining 50% is transferred onto the transfer paper.

FIG. 7 is a sectional view of a transfer paper showing another example when color recording is performed by the fusion type thermal transfer recording apparatus. In the fusion type thermal transfer recording apparatus, as shown in FIG. 6, inks of a plurality of colors are overlaid and recorded. At this time,
If each color is printed in a good overlap, for example, as shown in FIG.
Recording is performed in the state as shown in FIG. But,
The ink on the transfer paper 32 should ideally be completely transferred from the IDF, but when the transfer paper 32 and the IDF 33 are peeled off, a part of the ink is transferred to the IDF 33 due to the adhesiveness between the base film 34 and the ink. It may remain. In such a portion, in the process in which the once melted ink is solidified again and peeled off, a crack occurs between the transferred ink and the remaining ink, and the transferred ink surface is not smooth.

Further, even if the surface condition of the ink can be improved, there is no difference in the surface condition between the transfer paper and the ink. In order to express a stable color, the transfer characteristics of the inks of each color are important. Even if a transfer paper having good surface smoothness is used, depending on the state of the surface of the ink already transferred, it is possible that the transfer state of FIG. As shown in (B), the ink 3 that is superposed on the ink 37 whose surface is not smooth
In the case of No. 8, as in the case where the surface of the recording paper 32 is not smooth, a transfer failure occurs in part. If three or four color inks are superposed, this problem occurs at the overlapping surfaces of the respective inks.

In order to solve such a problem, for example, as described in JP-A-5-270038, a method of increasing the printing energy for the second and subsequent colors, and JP-A-5-38838. As described in (1), a method of correcting the data for each pixel according to the printing state of the previous color has been proposed. However, unlike the dither method in which one pixel is apparently formed by using a plurality of pixels, the actual heating resistor is changed by changing the printing energy like in the sub-scanning division method or the heat concentration method. In the method of modulating the print area within one pixel determined by the size, when the print area ratio of the color to be printed is larger than that of the ink of the base, a portion to be transferred onto the transfer paper is generated. Then, when printing is performed with higher energy than usual as in the former case, there is a problem that the transfer amount of ink increases in the portion transferred onto the transfer paper. Further, in the latter method, there is a problem that a desired ink mixture ratio cannot be obtained by the correction.

The above problem will be described with reference to FIG. FIG. 8 is an explanatory diagram of a transfer state by superimposing inks, a left side is a cross-sectional view of the recording paper on which recording is performed, and a right side shows a printing pulse. Here, as an example, the width of one pixel in the sub-scanning direction is modulated by using a thermal head in which a plurality of heating resistors whose width in the sub-scanning direction of the heating resistor is shorter than the width of one pixel are arranged in parallel in the main-scanning direction. Then, consider a sub-running division method in which the printing area of one pixel is changed while increasing the area, and halftone expression is performed. A method of changing the area by modulating the width of one pixel in the sub-scanning direction is disclosed in Japanese Patent Laid-Open No. 60-248074, Japanese Patent Laid-Open No. 3-219969, and the like. This method will be called a sub-scanning division method.

Now, the sub-scanning division method will be described with reference to FIG. In the figure, 21 is a print area corresponding to one pixel,
22 is a printed portion, and 23 is a pulse. In this sub-scanning division method, the printing area 21 corresponding to one pixel is divided in the sub-scanning direction, and the divided small areas are sequentially filled to change the printing area and perform gradation printing. . For example, if one pixel has 16 gradations,
3A shows the first gradation, FIG. 3B shows the eighth gradation with half the area filled, and FIG. 3C shows the 16th gradation with the entire area filled. Represents the state of.

An example of control of a thermal head that realizes this is to divide the printing time of one line by a number corresponding to the number of divisions in the sub-scanning direction, and input energy for a time corresponding to the number of gradations. That is, when the number of divisions is n, FIG.
In (A), energy is applied to the thermal head for 1 / n time, and in FIG. 3 (B), energy is applied for 1/2 time.

Returning to FIG. 8, the transfer state by the sub-scanning division method will be described. In the figure, 24 is a yellow print pulse,
Reference numeral 25 is a magenta print pulse, 32 is a transfer target paper, 37 is a yellow ink, and 38 is a magenta ink. FIG. 8A shows a state in which, for example, the yellow ink 37 is transferred at a print area ratio of 50%. For convenience of explanation, the number of divisions is set to 10 and the printing time is given by the number of pulses. Therefore, when the printing area ratio is 10% (1 gradation), printing is performed with 1 pulse, and when the printing area ratio is 50% (5 gradations), printing is performed with 5 pulses. When the yellow print area ratio shown in FIG. 8A is 50%, five print pulses 24 are applied, and the ink is transferred to the transfer target paper 32 at the print area ratio of 50%.

A magenta ink 38 is transferred onto the yellow ink 37 at a printing area ratio of 70%. Seven magenta print pulses 25 are applied. When the energy of this print pulse is applied with normal energy, transfer failure occurs at the portion where the inks overlap, as shown in FIG. 8B. Therefore, as shown in FIG. 8C, when the printing energy for magenta ink is increased by changing the height of the printing pulse to perform similar printing with high energy, the ink overlap can be improved. However, in the area where the yellow ink is not on the base, the printing characteristics on the transfer paper 32 change due to the effect of heat accumulation and the like due to the increase in energy, so there is a problem that the printing area increases.

Instead of increasing the energy of the print pulse, data correction is performed as shown in FIG.
If you increase the number of pulses and increase the printing area ratio of magenta,
Although the amount of transferred ink is increased, the overlapping characteristic does not change, and there is a problem that the desired color cannot be obtained.

[0016]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and in melt-type multi-gradation thermal transfer recording, in order to obtain a desired printing area ratio even in color recording, ink of The purpose is to realize stable recording characteristics without damaging the overlapping characteristics.

[0017]

SUMMARY OF THE INVENTION According to the present invention, in a thermal transfer color recording apparatus, a plurality of color inks are overprinted in the same area and the printing energy is changed stepwise to change the printing area in one pixel and to print the intermediate area. In a thermal transfer color recording apparatus for expressing tones, a printing energy generation unit that generates a plurality of printing energies, a printing history storage unit that stores a printing history of a previous color, and past printing stored in the printing history storage unit. It is characterized by further comprising a comparing means for comparing the information with the printing information to be printed at present, and a selecting means for selecting the printing energy generated by the printing energy generating means based on the comparison result of the comparing means. .

[0018]

According to the present invention, in an area modulation type thermal transfer color recording apparatus, the printing energy is changed depending on the presence or absence of the base ink when transferring each color, so that the occurrence of transfer failure can be prevented and the presence or absence of the base ink can be prevented. Regardless, the printing area ratio can be made accurate and stable color reproduction is possible.

[0019]

1 is a block diagram showing the outline of an embodiment of a thermal transfer color recording apparatus of the present invention. In the figure, 1 is a photo sensor, 2 is an A / D conversion unit, 3 is a color conversion unit, 4 is a UCR / black plate generation unit, 5 is a print data storage unit, 6 is a print control unit, and 7 is a pulse data generation unit. , 8 is a thermal head driving IC, 9 is a printing energy generating unit, and 10 is a thermal head.

FIG. 1A is a block diagram for obtaining print data. In this example, a photo sensor was used to read an image. Photo sensor 1
Reads an image by converting it into an electric signal for each color of red, green and blue. The A / D conversion unit 2 has analog signals R1, G1, B of the image read by the photo sensor 1.
1 is converted into a multilevel digital signal. The color conversion unit 3
Red, green and blue signals R2, G2 and B
Signals C from 2 to cyan, magenta, and yellow
1, M1, Y1. The UCR / black plate generator 4
The background color is removed, the black portion is extracted from the signals of cyan, magenta, and yellow, and the print data C2 and M of four colors of cyan, magenta, yellow, and black are extracted.
Create 2, Y2 and K2. The print data storage unit 5 stores print data C2, M2, Y2 and K2 of four colors of cyan, magenta, yellow and black, respectively.

The print data stored in the print data storage unit 5 is printed out by the print unit shown in FIG. 1 (B). The print data D1 of each color read from the print data storage unit 5 by the control signals S1, S2, S3 from the print control unit 6.
Is converted into pulse data P1 for driving the thermal head drive IC 8 in the pulse data generator 7 and sent to the thermal head 10. Thermal head drive IC8
When the print start enable signal S3 is input from the print control unit 6, the print energy generation unit 9 sends the print signal S5 to the bit for which the pulse data is 1, and the print energy E3 is thermally transferred according to the print signal S5. It is put into the head 10. In the printing energy generation unit 9, area gradation is performed by the sub-scanning division method, and the time for printing one pixel is equally divided into, for example, 127, and printing is performed according to the number of gradations within each divided time. While outputting the pulse, the printing energy E3 of the printing pulse is determined. Therefore, the number of pulses applied to the thermal head 10 for printing one pixel is any value from 0 to 127. In each pixel, the number of pulses is set according to the gradation data, and the pulses enter the thermal head 10 from the first to the set number of pulses. Here, the set number of pulses will be referred to as the number of gradations. Again 127
The time divided into equal parts is called a pulse timing, and from the start to 127 pulse timing, the printing of one pixel is completed.

FIG. 2 is a block diagram of an embodiment of the printing energy generator. In the figure, the same parts as those in FIG. Reference numeral 11 is a print history storage unit, 12 is a data comparison unit, 13 is a print energy selection unit, 14 is a high print energy generation unit, and 15 is a low print energy generation unit. The print history storage unit 11 stores the print data D2 of the previous color from the print data storage unit 5 as a print history according to the control signal S8 from the print control unit 6.
The data comparison unit 12 receives the control signal S4 from the print control unit 6.
Controlled by, the storage information S6 from the print history storage unit 11 is compared with the print data S6 of the current print status.

In the present invention, the pulse energy given by the thermal head 10 is made different when the transfer is performed on the ink that has already been transferred to the transfer paper and when it is transferred on the transfer paper. Therefore, in this embodiment, the high printing energy generating unit 14 that generates the printing energy E1 when transferring onto the ink and the low printing energy generating unit 15 that generates the printing energy E2 when transferring onto the transfer paper are used. To be The printing energy selection unit 13 determines that the comparison result S7 from the data comparison unit 12
Printing energy E1 from the high printing energy generation unit 14
And the printing energy E2 from the low printing energy generating unit 15 to select the selected printing energy E2.
3 is applied to the thermal head 10.

The printing operation will be described with a specific example. It is assumed that the print of the first color is yellow and the print of the second color is magenta. In printing the first color yellow, first, the print control unit 6
Sends a yellow print start signal to the print data storage unit 5 to read the print data and erase the stored information in the print history storage unit 11. The print data is sent to the pulse data generator 7, and the pulse data corresponding to the gradation is sent to the thermal head drive IC in order from the beginning.
Since the first color is all transferred onto the transfer paper, that is, there is no print history, when the print signal S5 is sent, the print energy selection unit 13 selects the low print energy E2 for all the pixels. In this way, all the yellow ink is transferred onto the transfer paper. Then, the print history storage unit 11 stores the number of gradations of yellow in each pixel after the printing of yellow is completed. Next, also in the case of the magenta printing of the second color, the print data is converted into pulse data and sent to the thermal head drive IC 8 as in the case of yellow. This time, the printing energy selection unit 13 uses the printing history storage unit 11
The number of gradations stored in (1) is compared with the current pulse timing. If the pulse timing is smaller, the high printing energy E1 is selected, and conversely, if the pulse timing is larger, the lower printing energy E2 is selected. In this way, the printing energy is switched midway according to the printing history, and proper printing energy can be obtained. The state is shown in FIG.

In FIG. 8 (E), the magenta print pulse 2
5 is the 5 pulses printed on the yellow ink,
The energy is high as described with reference to FIG. 8C, and the remaining two pulses printed on the transfer paper are normal energy as described with reference to FIG. 8B. When it is transferred over the ink, it is possible to improve the overlap of the ink by printing with high energy, and when it is transferred onto the transfer paper, the printing is performed with normal energy. It is possible to obtain an accurate print area ratio.

In the above embodiment, the printing energy is changed by changing the height of the printing pulse, but it is also possible by changing the width of the pulse. Both the height and the width of the pulse may be changed. When the printing of magenta is completed, the number of magenta gradations of each pixel is compared with the number of yellow gradations, and the larger one is stored in the printing history storage unit 11 as a printing history. The third and fourth colors are printed in the same manner as the second color.

In this embodiment, the thermal head is driven by the number of pulses in order to perform the halftone recording. However, the present invention is not limited to this, and one pulse is driven by one pulse, Halftone recording may be performed by changing the pulse width. Further, although two types of printing energy are used, three or more types of printing energy may be selected in consideration of matching with the color of the ink of the base. Furthermore, although the example of the sub-scanning division method is shown in the embodiment, it is obvious that the present invention can be applied to a method of changing the transfer area of ink by the energy applied to the thermal head, such as a heat concentration method.

[0028]

As is apparent from the above description, according to the present invention, the instability of the transfer caused by the deterioration of the surface smoothness caused by the defective transfer of the ink is eliminated without increasing the printing area ratio. be able to. As a result, since stable recording characteristics can be guaranteed, there is an effect that high-quality color halftone recording can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing the outline of an embodiment of a thermal transfer color recording apparatus of the present invention.

FIG. 2 is a block configuration diagram of an embodiment of a printing energy generation unit.

FIG. 3 is an explanatory diagram of a sub-scanning division method.

FIG. 4 is a partial cross-sectional view showing an example of a fusion type thermal transfer recording device.

FIG. 5 is a cross-sectional view of a transfer paper on which recording is performed by a fusion type thermal transfer recording device.

FIG. 6 is a cross-sectional view of a transfer paper showing an example when color recording is performed by a fusion type thermal transfer recording device.

FIG. 7 is a cross-sectional view of a transfer paper showing another example when color recording is performed by a fusion type thermal transfer recording device.

FIG. 8 is an explanatory diagram of a transfer state by superposing ink.

[Explanation of symbols]

1 ... Photo sensor, 2 ... A / D converter, 3 ... Color converter,
4 ... UCR / black plate generation unit, 5 ... Print data storage unit, 6 ...
Print control unit, 7 ... Pulse data generation unit, 8 ... Thermal head drive IC, 9 ... Printing energy generation unit, 10 ... Thermal head, 11 ... Print history storage unit, 12 ... Data comparison unit, 13 ... Printing energy selection unit, 14 ... High printing energy generation part, 15 ... Low printing energy generation part.

Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI Technical display area H04N 1/40 B

Claims (1)

[Claims] 1. A thermal transfer color recording apparatus that prints a plurality of colors of ink in the same area in an overlapping manner and changes the printing energy stepwise to change the printing area within one pixel to express halftone. And a print history storing means for storing the print history of the previous color, and a comparing means for comparing the past print information stored in the print history storing means with the print information to be printed now. And a selection unit for selecting the printing energy generated by the printing energy generation unit based on the comparison result of the comparison unit.