JPH08118703A - Heat transfer recording method and recording apparatus - Google Patents

Abstract

PURPOSE: To obtain well intermediate tone reproducibility for a tassel etc., and reproducibility of letters etc., by a method wherein when a pixel on a specified line is two value data for black, one refers to each image data and when the each-th image date is all two value data for white, recording is performed by decreasing the number of pulses of the two value data for black. CONSTITUTION: When the m-th recording pixel a of the 1 line to be aimed at in the case when an image data is a letter and a fine line is two value data for black, one refers to (m-1)-th, m-th and (m+1)-th image data of the (1+1) line. In addition, when each of the each image data of the (1+1) line is all two value data for white, recording is performed by decreasing the number of pulses of the two value data for black of the m-th recording image a of the l line. It is possible thereby to make intermediate tone reproducibility in printing on a tassel etc., and reproducibility in printing of a letter, a fine line etc., well and to improve the quality of printing.

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 for printing image data using a thermal head in which a plurality of heating resistors are arranged in parallel in the main scanning direction, and more particularly to the width of the heating resistors in the sub scanning direction. The present invention relates to a thermal transfer recording apparatus capable of recording image information such as a picture in halftone by making the width of the recording pixel shorter than one recording pixel.

[0002]

2. Description of the Related Art Conventionally, sublimation type thermal transfer recording and melting type thermal transfer recording have been known as color halftone recording systems of thermal transfer recording apparatuses for printing image data using a thermal head. Sublimation type thermal transfer recording has a problem that a large amount of energy is required and thus it takes a long time for printing and a special paper is used, resulting in a high cost. On the other hand, the fusion type thermal transfer recording can print with a small amount of energy, but the cost is low,
Since the ink donor film itself cannot obtain gradation even if the applied energy is changed, multi-gradation recording is difficult. Therefore, in fusion type thermal transfer recording, a matrix method such as a dither method and a method of taking gradation by reducing a heat generation area such as sub-scanning division and heat concentration have been proposed.

For example, in JP-A-60-248074 and JP-A-3-219969, a heating element having a width in the sub-scanning direction shorter than that in the main-scanning direction is used.
A method for recording halftones (hereinafter referred to as a sub-scanning division method) is described. FIG. 10 is a plan view of a heat generating portion of a thermal head used in the sub-scanning division method, in which a common electrode 100 having a plurality of comb-shaped portions 101 and comb-shaped selections arranged between the comb-shaped portions 101 are formed. It has an alternating lead type electrode structure including electrodes 102 and strip resistors 103 arranged in a line in the main scanning direction on the comb-shaped portion 101 and the selection electrodes 102.

In the printing by the thermal head, a resistor portion (in the sub-scanning direction) sandwiched between the selected selection electrode 102 and the comb-shaped portions 101 of the common electrode 100 on both sides thereof by selecting and energizing the selection electrode 102. Is performed by the heat generated by the heating element having a short width. That is, the thermal head is continuously moved relative to the recording paper arranged on the thermal head, and the ink of the thermal transfer ink donor film provided on the thermal head side of the recording paper is heated by the heat generated by each heating element. It is melted and transferred to a recording paper to record one recording pixel X corresponding to image data. Therefore, the energy (driving time, applied voltage, etc.) applied to each heat generating element according to the density of the pixel to be recorded while the thermal head moves a distance of one recording pixel (sub scanning direction) with respect to the recording paper. By controlling
Halftone recording is now possible.

[0005]

11 and 12 show examples of print recording when halftone recording is performed by using the thermal head having the above structure. When the energy applied to the heating element is increased to increase the number of gradations, as shown in FIGS. 11 and 12, the printing area is increased mainly in the sub-scanning direction to enable halftone recording. FIG. 11 shows the print dots 105 of one recording pixel when the energy applied to the heating element is increased, and FIG. 12 compares the print dots 105 of one recording pixel. As can be seen from each figure, the print area also increases in the main scanning direction due to the heat distribution due to diffusion as the number of gradations increases, and the print dot shape becomes a trapezoid. When the print dot shape is trapezoidal, when printing an image formed by continuously forming square dots such as characters and thin lines, there is a problem that the connection of adjacent dots is deteriorated and print quality is degraded. Further, since almost no heat is generated on the comb-shaped electrodes, there arises a problem that the thickness of the vertical line using one heating element is less than the pixel size.

In order to solve the above problem, it is conceivable to increase the printing energy until the main scanning width of the printing dots is sufficiently secured, but the dot size at the initial stage of printing becomes large and halftone printing is performed. As the highlight characteristic deteriorates, the density change on the high density side also saturates with respect to the number of pulses, making it difficult to obtain many gradation levels.
Further, there arises a problem that the thickness of the horizontal line defined by the number of pulses per pixel becomes larger than the pixel size.

The present invention has been made in view of the above circumstances, and a thermal transfer recording method capable of improving both the halftone reproducibility in the printing of pictures and the reproducibility in the printing of characters and fine lines. It is also an object to provide a device.

[0008]

In order to solve the above-mentioned problems, the method of the present invention according to claim 1 uses a plurality of heating resistors whose width in the sub-scanning direction is shorter than the width of one recording pixel. The thermal transfer recording method for printing image data using the thermal heads arranged in parallel in the main scanning direction is performed in the following procedure. First, it is determined whether the image data is a picture, a character, or a thin line. When the image data is a picture, it is converted into binary data for the thermal head, which is composed of a plurality of pulses according to the gradation of the halftone. Image data is text,
In the case of a thin line, the binary data for black for the thermal head or the binary data for white with the number of pulses of 0 is composed of twice the number of pulses corresponding to the maximum density of the halftone. Convert. Then, the thermal head is driven by the binary data. At this time, when the image data is a character or a thin line and the mth recording pixel of the l line is binary data for black, the (m + 1) th, mth, ((l + 1) th line Referring to the (m + 1) th image data, when all the respective first image data of the (l + 1) line are binary data for white, the pulse of the binary data for black of the mth print dot of the l line Record with a reduced number.

According to a second aspect of the present invention, in the first aspect, when the image data is a picture, recording is performed by recording pixels whose width in the sub-scanning direction is twice the width in the main scanning direction. When the line is a thin line, printing is performed by printing pixels having the same width in the sub-scanning direction and width in the main scanning direction.

According to a third aspect of the present invention, in the thermal head, a plurality of heating resistors, each of which has a heating resistor whose width in the sub-scanning direction is shorter than the width of one recording pixel, are arranged in parallel in the main scanning direction. A thermal transfer recording apparatus that prints image data by using is characterized by the following configuration. A picture / character determination means for determining whether the image data is a picture, a character, or a thin line is provided. Data conversion means for converting the image data into binary data for a thermal head composed of a plurality of pulses is provided. When the image data of interest is the mth recording pixel on the l line, the (m−1) th, mth, (m
Data detection means for referencing each +1) th image data is provided. Then, the binary data of the data conversion means is
The printing energy is controlled based on the signals from the picture / character determining means and the data detecting means.

[0011]

According to the present invention, the image data is composed of a plurality of pulses by the data converting means.
The data is converted into value data, and the binary heating data causes the heating resistor to generate heat for printing. At this time, the picture / character determining means determines whether the image data is a picture, a character, or a thin line. If it is determined that the image data is a picture, the pulse density is changed and the gradation of the halftone is changed. Printing is performed by causing the heating resistor to generate heat with a plurality of pulse trains corresponding to. Since the width of the heating resistor in the sub-scanning direction is shorter than the width of one recording pixel, the printing area within one recording pixel can be adjusted by controlling the printing energy by changing the number of pulses.
Halftone recording is possible. When it is determined that the image data is a picture, good halftone reproducibility can be obtained by recording with the recording pixels whose width in the sub-scanning direction is twice the width in the main-scanning direction.

Further, when it is determined that the image data is a character or a thin line, the number of pulses corresponding to the maximum density of the halftone is doubled by the recording pixels having the same width in the sub-scanning direction and the width in the main scanning direction. The vertical dots and the printed dots can be printed by making the heating resistor generate heat with the binary data for black for the thermal head or the binary data for white with 0 pulses It is possible to secure a sufficient line width when printing diagonal lines. At this time, when the m-th recording pixel of the 1-line of interest is the binary data for black, the (m-1) -th line of the (l + 1) -th line,
Referring to the m-th and (m + 1) -th image data, all the respective image data of the (l + 1) -th line are for white 2
In the case of the value data, the number of pulses of the binary data for black of the m-th recording pixel on the l-line is reduced and recording is performed to correct the width of the recording pixel in the sub-scanning direction, and the horizontal line of the print dot is thus corrected. Can be adjusted to the pixel size, and the deterioration of the print quality, which is a problem with the connection between adjacent print dots and the print dot width, can be eliminated.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the thermal transfer recording apparatus according to the present invention will be described with reference to FIGS. FIG.
Is a block diagram of a thermal transfer recording apparatus according to an embodiment,
An image input unit 1 such as a scanner, an A / D converter 2 for converting data from the image input unit 1 into image data of a digital signal, an image data memory 3 for storing image data,
An image data processing circuit 4 having a judging circuit for judging whether the image data is a picture, a character or a thin line, and a gradation converting circuit.
And a binary conversion circuit 5 for converting image data into binary data.
And a buffer memory 6 for storing the binary data as print data for a thermal head, and a plurality of heating resistors in which a width of the heating resistor in the sub-scanning direction is shorter than a width of one recording pixel. A head 7, a driver 8 that outputs a drive signal (printing pulse) for causing each heating resistor of the thermal head to generate heat, and a pulse generation circuit that outputs a strobe signal for controlling the drive of each heating resistor to the driver 8. 9 and a control circuit 10 which is connected to each circuit and a memory and operates while synchronizing a series of processes. Further, in the image data processing circuit 4, when the image data of interest is the mth recording pixel on the l line, the (m-1) th, mth, and
Data detection means for referencing each (m + 1) th image data is provided.

The thermal head is an alternating lead type as shown in FIG. 10, and has a resolution of 300 DPI in the main scanning direction.
Then, the width of the heating resistor in the sub-scanning direction is set to about 43 μm, and recording is performed on the synthetic paper using a high resolution ink donor film (PET substrate thickness 4.5 μm, ink application amount 2.0 g / m ² ). Has become. The recording paper which moves relatively on the thermal head is set to be sent at a constant speed, and the speed is set so that the width of one recording pixel X in the sub-scanning direction (170 μm) is sent in a print cycle T = 25 ms. It is set. The size of one recording pixel recorded on the recording paper with one heating resistor is 170 μm in width in the sub-scanning direction (about 4 times the width of the heating resistor) and 84.7 μm in width in the main scanning direction.
The width in the sub-scanning direction is doubled with respect to the width in the main scanning direction, and a printing method that makes it easy to obtain halftone recording is adopted to obtain halftone recording of about 64 gradations. That is, according to the thermal head of the present embodiment, 1 in the sub-scanning direction.
It is configured so that it can be printed at a resolution of 50 DPI, and as will be described later, the print density is 150 DPI or 300 DPI depending on the type of print image (whether it is a picture, a character, or a thin line).
Can be printed with.

Next, the principle of halftone expression by the thermal transfer recording apparatus of the above embodiment will be described with reference to FIGS. Each heating resistor that constitutes the thermal head is shown in FIG.
As shown in (b), it is driven by a print pulse that periodically applies pulses of the same width, and is driven by a maximum of 88 short pulses per print cycle T. As shown in FIG. 2B, the short pulse has a period of about 284 μsec, and the heating resistor generates heat at 1/4 of the period, and the applied power is about 0.0.
It is 56W. The print dot shape corresponding to the short pulse number when driving the heating resistor has a print density of 150D in which the width in the sub-scanning direction is twice the width in the main-scanning direction as shown in FIG.
As PI, printing is not started for 0 to 10 pulses and printing is started for about 10 or more pulses. For 15 pulses, it is an alternating lead electrode (the common electrode 1 on both sides with respect to the selection electrode 102).
(Because the comb-shaped portion 101 of 00 is arranged), one recording pixel in the main scanning direction is divided into two, and the width of the heating resistor in the main scanning direction and the width of the print dot in the main scanning direction are close to 20 pulses. Matched print records are possible. Furthermore, if the number of short pulses of the print pulse that is sequentially added is increased, the print dots are expanded in the sub-scanning direction, and halftone recording can be performed. Therefore, the area gradation of the halftone expression is almost performed only in the sub-scanning direction, but actually, as shown in FIG. 11, the print dots are expanded in the main scanning direction due to thermal diffusion. However, such printing conditions can improve the halftone characteristics, especially the highlight characteristics.

FIG. 3 shows the result of actual measurement of the relationship between the short pulse number and the concentration. Concentration measurement is X-Rit
A 2 cm square halftone patch was measured using a densitometer (Model No. 938) manufactured by e. As can be seen from FIG. 3, according to the above printing conditions, smooth halftone characteristics are obtained from highlights, and gradation representation can be 64 gradations or more.

Next, the case of recording characters / thin lines will be described. In order to satisfactorily record characters / thin lines, it is necessary to obtain rectangular print dots that fill one recording pixel X with a heating resistor. Since the printing energy is small under the halftone recording condition (printing density 150 DPI) described above, the highlight characteristic is good, but conversely, the area filling degree of the printing dot of one recording pixel in the main scanning direction at the beginning of printing is poor. Therefore, in order to record a rectangular print dot, a recording pixel (300D having the same width in the sub-scanning direction and the width in the main scanning direction) is used.
PI) and the binary data for black for the thermal head (pulse density is doubled) or the number of pulses is 0, which is composed of twice the number of pulses corresponding to the maximum density of the halftone. By using the binary data for white, a large printing energy is applied to the heating resistor. In order to increase the printing energy, it is possible to increase the density of the pulse and also to change the applied voltage and the pulse width.

On the other hand, by increasing the printing energy, the width of the recording pixel in the main scanning direction can be ensured to correspond to the pixel, but as a result, a new problem arises that the width of the recording pixel in the sub scanning direction increases. . As will be described later, this is corrected by the data detecting means of the image data processing circuit 4.

Next, the image data processing circuit 4 in FIG.
The image data processing in the binary conversion circuit 5 will be described. The image data is data having a resolution corresponding to a print density of 300 DPI in both the main scanning direction and the sub scanning direction in order to express both pictures and characters. This image data is input to the image data processing circuit 4, and an internal determination circuit first determines whether the image is a character, a thin line, or a picture composed of a halftone image. This determination is made based on the number of gradations of the image data of the print pixel and the image data of the peripheral pixels. That is, for example, if the gradation number of the image data of the print pixel is an intermediate value, it is determined to be a halftone.

When the image data of the print pixel is determined to be halftone, the print density of the print image in the sub-scanning direction is set to 150.
Since printing is performed by DPI, the printing density of the image data of 300 DPI in the sub-scanning direction is converted. That is, two pixels in the sub-scanning direction are averaged to form 150 DPI image data. In this example, the print density conversion is 2 for image data.
Although the average of the pixels is used, it is also possible to add pixels in the vicinity of the average and average them, or 150D by thinning without averaging.
Image data of PI may be obtained.

Next, the averaged image data (1 to 256 gradations) is .gamma.-corrected by a gradation conversion circuit in the image processing circuit so as to match the gradation characteristic corresponding to the print density. Obtain halftone recording pulse data. The halftone recording pulse data is input to the binary conversion circuit and converted into halftone recording print data composed of a plurality of binary data suitable for printing by the thermal head.

When the image data of the print pixel is determined to be a character or a thin line, it is 30 in both the main scanning direction and the sub scanning direction.
Since it is designed to record at a print density of 0 DPI,
This image data (characters, pulse data for recording thin lines)
Input to the value conversion circuit to obtain characters and fine line recording print data (white binary data (0 pulse) or black binary data (plural pulses)). The print density in the sub-scanning direction is set to 150 DPI in the halftone recording, and the print density is set to 300 DPI in the character / thin line recording because the print density in the main scanning and the sub-scanning is not the same in the character / thin line recording. This is because fine line reproducibility cannot be obtained. Further, when the image data of interest is the binary data for black for the m-th recording pixel of the l line, the data detecting means in the image data processing circuit 4 makes the (m + 1) th and mth of the (l + 1) th line. , (M
If each of the (+1) th image data is referred to and all the image data of the (l + 1) line is binary data for white,
The correction is performed to reduce the number of pulses of the black binary data of the m-th recording pixel on the line.

The print data output from the binary conversion circuit is guided to the driver 8 via the buffer memory 6,
Further, the strobe signal from the pulse generating circuit 7 is guided to the driver 8. In a thermal head equipped with a commercially available general-purpose driver, a print pulse is generated by the logical product of the strobe signal and the print data. Therefore, as shown in FIG. The pulse density of the print pulse can be changed to 1/2 and 1/4 by changing the ratio of "1" and "0" of the print data to 1/2. That is, by changing the print data by using the same strobe signal, a print pulse having a pulse density of 1/4 is printed for halftone printing and a pulse density of 1/2 is printed for printing characters and thin lines. Each print pulse can be obtained. As a result, the highlight characteristic is good for halftone printing, and for printing characters and fine lines, printing energy is increased by increasing the pulse density so that rectangular dots can be obtained at the same time. I have to.

FIG. 5 shows a print pulse for halftone recording and a print pulse for recording characters and fine lines, which are obtained by a logical product of the strobe signal and the print data. In this embodiment, the print pulse for halftone recording has a pulse density of 1/4 over the entire area (print pulse for halftone recording in FIG. 5). 88 print pulses for halftone recording correspond to one recording pixel (150 DPI). The print pulse for recording characters and fine lines has a pulse density of 1/2 over the entire area (print pulse for recording characters and fine lines in FIG. 5). Print pulse for recording characters and fine lines is 8
Eight pixels correspond to one recording pixel (300 DPI).

Further, the print data input to the driver 8 has a pulse density of the strobe signal of 1 /
2 and is "1" or "0" for each pulse of the strobe signal (88 in total) at a cycle of 12.5 ms.
Therefore, the number of print data is 88
It becomes an individual.

Next, the operation of the thermal transfer recording apparatus will be described with reference to FIG. That is, the image data sent from a computer or a scanner is a digital signal having 256 gradations, and the resolution of the image data is 300 DPI in both the main scanning direction and the sub scanning direction for expressing pictures and characters. (Step 60). In the halftone printing in this embodiment, the resolution in the sub-scanning direction is 150D.
Since it is PI, processing is performed in units of two pixels connected in the sub-scanning direction.

This image data is sent to the image data processing circuit 4, and it is determined whether the image data is a picture, a character or a thin line based on the gradation number of the print pixel and its peripheral pixels (step 61). If it is determined to be a picture (halftone), the resolution of the image data in the sub-scanning direction is 300 DPI, and in actual printing it is 150 DPI. Therefore, the averaging process is performed on two pixels in the sub-scanning direction. The sub-scanning resolution of the image data is converted in the same manner (step 6).
2).

Next, the averaged image data (0 to 255 gradations) is obtained by the gradation conversion circuit in the image data processing circuit 4.
Γ-corrected to match the gradation characteristics of this system
Halftone recording pulse number data consisting of 8 pulse number data
(Step 63). Subsequently, the halftone recording pulse number data is converted into halftone recording print data (176 "0""1" data) which is binary data corresponding to the strobe signal (step 64). .

When the image data processing circuit determines that the image data is a character or a thin line, it suffices to record 300 DPI pixels having the same width in the main scanning direction and the width in the sub scanning direction. Two pixels of data are allocated to 88 pulses or 0 pulses corresponding to twice the pulse density of the halftone (step 65).

Next, the data detection means detects the (m-1) th, mth, (m + 1) th image data of the (l + 1) th line with respect to the mth recording pixel of the lth line of interest. (Step 66). And the above (l + 1)
It is determined whether or not all the image data of each line are binary data for white (0 pulse) (step 6).
7). When all the image data are binary data for white, the m-th recording pixel of the l line is binary data for black (8
If it is 8 pulses), the number of pulses is reduced and the pulse data is corrected to 60 pulses (step 68).

That is, as shown in FIG. 7, when the pixel p of interest is the m-th line of the l line, (l +
1) The (m-1) th, mth, and (m + 1) th image data of the line is detected. When the reference pixel a in the drawing is binary data for black, the width in the sub-scanning direction of the pixel of interest p does not matter, so no correction is performed. Further, when the reference pixel b is binary data for black, rather than reproducing a dot faithful to the pixel size, a larger dot width in the sub-scanning direction results in better connection of diagonal lines of 1 dot and good character reproducibility. Since it was confirmed, no correction is made in this case as well. Therefore, when the reference pixels a, b, a in the figure are all binary data for white, the pixel of interest p is corrected.

The number of pulses for correction is set to 88.
The number of 60 pieces was set based on the following measurement results. That is, FIG. 8 is a measurement result showing the width of one dot in the main scanning direction with respect to the applied pulse number. Since the printing energy is larger than that in the halftone printing condition, the rise of the line width is large, but when the temperature distribution is saturated, the pulse number is The line width increases in accordance with the paper feed distance (inclination A in the figure) with respect to. From this result, since the line width corresponds to the size of one pixel of 300 DPI (84.7 μm) with about 60 pulses, the number of pulses was set to 60.

Then, it is judged whether or not all the pulse data for characters and thin lines (in this embodiment, two pixels to be processed simultaneously) have been completed (step 69), and if so, the binary conversion circuit displays the characters and thin lines. The recording pulse data is transferred and converted into binary data print data for characters and fine lines (step 7).
0).

The halftone recording pulse data and the character and fine line recording pulse data are collectively transferred to the thermal head 71, and the strobe signal generated by the pulse generating circuit is used to output the halftone recording print data as described above. -Ta and letters,
Fine line recording print data is created for every two pixels in the sub-scanning direction, which enables simultaneous printing of pictures (halftones), characters, and fine lines. These series of processes are performed by a look-up table using a microprocessor or ROM for controlling the thermal head.

In the above embodiment, the pictogram determination process and the reference image data determination are separately configured, but the reference image data may be referred to in the pictogram determination process. Further, in the present embodiment, the processing is performed every two pixels according to the resolution of the halftone, but it is also possible to perform the processing for each larger area or each pixel.

Next, a printing example using the thermal transfer recording apparatus of the above embodiment will be described with reference to FIG. The halftone print dot 105a shown in FIG. 9 is a print dot recorded by using a print pulse for halftone recording.
Reference numeral 05b is a print dot recorded using a print pulse for recording characters and fine lines. The halftone print dot 105a recorded by the print pulse for halftone recording has one recording pixel X
(Width in the main scanning direction 84.7 μm, width in the sub scanning direction 170 μm
In m), the printing area is increased mainly in the sub-scanning direction, and halftone recording is possible. Since the width in the sub-scanning direction is doubled with respect to the width in the main scanning direction, the area of the white portion can be increased when the pulse train of the printing pulse is small, and the halftone can be easily obtained. Further, the character print dots 105b recorded by the print pulse for characters and fine lines have a rectangular dot shape so that almost one entire recording pixel is recorded with two dots, so that the connection with the adjacent dots is good and the quality is high. Good characters and fine lines can be printed. Also,
In this case, two rectangular dots having the same width in the main scanning direction and the width in the sub scanning direction are printed within one recording pixel X, so that the printing quality can be maintained even when printing characters or fine lines. Therefore, in the recording in which pictures and characters are mixed, good print recording can be realized.

According to the thermal transfer recording apparatus of the above embodiment, the following effects can be obtained. Whether the image data is a picture or a character or a thin line is judged by the picture / character judgment means,
When it is determined that the image data is a picture, the heating resistor is heated by a plurality of pulses of a certain density to perform printing, and the width in the sub-scanning direction is recorded in one recording pixel that is longer than the width in the main scanning direction. By doing so, it is possible to improve the highlight characteristic during printing, and it is possible to obtain a halftone print record with excellent print quality.

When the image data is determined to be a character or a thin line, the energy can be increased by making the pulse density of a plurality of pulses dense, and a rectangular dot that fills all one recording pixel can be used. It becomes possible to record, and it is possible to improve the print quality by improving the connection with adjacent dots. Further, in this case, since the width of the print pixels in the main scanning direction is the same as the width in the sub scanning direction, it is possible to prevent deterioration of print quality.

When the dots in the sub-scanning direction, such as a horizontal line of one dot, are to be reproduced exactly, the correction is made to reduce the number of black binary data pulses from 88 to 60. It is possible to prevent the width in the sub-scanning direction from increasing due to the increase in energy, and to obtain good character and fine line reproducibility.

Further, the energy applied to the thermal head is controlled by changing the print pulse density by changing the print data, so that only one type of strobe signal is required, and a special driver is mounted. Ser
It doesn't have to be Mullhead. Therefore, an inexpensive thermal head equipped with a commercially available general-purpose driver can simultaneously perform halftone recording and character / thin line recording.

[0041]

According to the present invention, since the image data is judged by the picture / character judging means and the print recording suitable for each is carried out, when the image data is a character or a thin line, the dot shape is almost rectangular. Since one pixel as a whole is printed and recorded, and the reference pixel is detected and corrected, the connection with adjacent dots is good, the reproducibility of characters and thin lines is improved, and the printing quality can be improved. Further, when performing halftone recording, since the printing area can be modulated mainly in the sub-scanning direction to perform area gradation, good halftone reproducibility can be obtained. Then, these printings can be performed at the same time, and recording can be performed with good printing quality even if pictures and characters are mixed.

The present invention can be applied to any thermal recording system, but by applying it to melt transfer recording, particularly color-halftone recording, which has not been able to express multi-gradation in the past, in these recordings. A print record of good quality can be obtained.

[Brief description of drawings]

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

FIGS. 2A and 2B are for explaining the principle of halftone recording. FIG. 2A shows print dots when a print pulse is changed, and FIG. 2B corresponds to FIG. Indicates the print pulse to perform.

FIG. 3 is a graph showing a halftone recording characteristic in the example.

FIG. 4 is a timing chart showing a method of creating a print pulse in the embodiment.

FIG. 5 is a timing chart for explaining the relationship between a print pulse for driving the thermal head and a strobe signal in the embodiment.

FIG. 6 is a flow chart for explaining the operation of the thermal transfer recording apparatus according to the embodiment.

FIG. 7 is an explanatory plan view of a recording pixel for explaining correction of a target pixel by a reference pixel.

FIG. 8 is a graph showing the relationship between the number of black binary data pulses and the width of recording pixels in the sub-scanning direction.

FIG. 9 is an explanatory plan view showing print recording when printing is performed by the thermal transfer recording apparatus of the embodiment.

FIG. 10 is an explanatory plan view showing the structure of a thermal head.

FIG. 11 is a print recording diagram showing a print example when the energy for driving the thermal head is changed.

12 is an explanatory diagram of print recording in which the print dots of FIG. 11 are overlapped.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Image input part, 2 ... A / D converter, 3 ... Image data memory, 4 ... Image data processing circuit, 5 ... Binary conversion circuit, 7 ... Thermal head, 8 ... Driver, 9
... pulse generator, 10 ... control circuit, 100 ... common electrode, 101 ... comb-shaped portion, 102 ... comb-shaped selection electrode, 1
03 ... band-shaped resistor, 105 ... printing dot, 105a
... Halftone print dots, 105b ... Character print dots,
X ... One recording pixel, p ... Pixel of interest, a, b ... Reference pixel

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H04N 1/405 H04N 1/40 B

Claims (3)

[Claims] 1. A thermal transfer recording in which image data is printed using a thermal head in which a plurality of heating resistors each having a width in the sub-scanning direction shorter than the width of one recording pixel are arranged in parallel in the main scanning direction. In the method, it is determined whether the image data is a picture, a character, or a thin line, and when the image data is a picture, binary data for a thermal head composed of a plurality of pulses corresponding to gray scale of a halftone is used. If the converted image data is a character or a thin line, the binary data for black for the thermal head or the number of pulses is 0, which is composed of twice the number of pulses corresponding to the maximum density of the halftone. In the recording method of converting into certain binary data for white and driving the thermal head by the binary data, when the image data is a character or a thin line, the m-th recording pixel of the l line is for black 2 When it is value data (L
When the (m-1) th, mth, and (m + 1) th image data on the (+1) th line are referred to, and each of the respective image data on the (l + 1) th line is binary data for white, A thermal transfer recording method, wherein recording is performed by reducing the number of pulses of binary data for black of an m-th recording pixel on a line. 2. When the image data is a picture, recording is performed by recording pixels whose width in the sub-scanning direction is twice the width in the main scanning direction, and when the image data is characters or fine lines, the sub-scanning is performed. The thermal transfer recording method according to claim 1, wherein recording is performed by recording pixels having a width in the direction and a width in the main scanning direction that are equal to each other. 3. A thermal transfer recording in which image data is printed using a thermal head in which a plurality of heating resistors each having a width in the sub-scanning direction shorter than the width of one recording pixel are arranged in parallel in the main scanning direction. In the apparatus, a picture / character determination unit that determines whether the image data is a picture, a character, or a thin line, and a data conversion unit that converts the image data into binary data for a thermal head composed of a plurality of pulses, When the image data of interest is the mth recording pixel on the l line, the (m−1) th, mth, (m
Data detecting means for referencing each +1) th image data, and the binary energy of the data converting means is controlled in printing energy based on signals from the picture / character determining means and the data detecting means. A thermal transfer recording device characterized by the above.