JPH07214823A - Printing method of serial printer - Google Patents

Abstract

PURPOSE:To reduce the unevenness of printing density caused by white streaks, etc., by a method wherein, when printing dots are formed at an overlapping part, recording elements are driven by the printing energy corresponding to the gradation value lower than that indicated by a gradation printing data. CONSTITUTION:Gradation printing data is retained in a line buffer 15 or 16, a portion thereof corresponding to dots n-m is read and retained in a latch circuit 17 and another portion of the gradation printing data corresponding to the dot (m) at the lower part of the same main scanning position in the aforesaid line is output from a memory 18. In this way the gradation printing data of the dot (n) necessary for printing the aforesaid line is obtained from the gradation printing data output from the latch circuit 17 and the memory 18. The gradation printing data of the dot (n) is then processed through a mask circuit 19 and is replaced with the gradation printing data lower in gradation than a gradation printing data of the dot (m) at each of the upper and lower end parts of recording element columns of a thermal head.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a serial printer for recording a desired image or character on a recording sheet by repeating a series of operations of scanning the recording head in the main scanning direction and line feed in the sub scanning direction. Is.

[0002]

2. Description of the Related Art In recent years, serial printers have come into widespread use as personal printers, word processor printers, etc. because of their relatively simple construction, small size, and low price. Recording heads include dot impact heads, thermal heads, inkjet heads, etc.
It is used in a form that can take advantage of the characteristics of each head.

FIG. 5 is a block diagram of a serial printer using a thermal head as a recording head, which comprises a thermal head 1, an ink ribbon cartridge 2, a carriage 3, a guide 4 and a platen 5. The printing operation is as follows.

First, the carriage 3 holding the thermal head 1 and the ink ribbon cartridge 2 is moved in the direction of arrow x along the guide 4 to perform scanning in the main scanning direction. At this time, a recording signal corresponding to a desired recording image is applied to the thermal head 1, and the ink ribbon 2A is heated according to the recording signal to print one line on the recording paper 6. Next, the platen 5 is rotationally driven to feed the recording paper 6 to perform line feed for one line in the sub-scanning direction, return the carriage 3 to the original position, and scan the next line. In this way, by repeating the scanning in the main scanning direction and the line feed in the sub scanning direction, it is possible to print one page of the recording paper 6.

It should be noted that, when printing is performed by the above printing operation, the recording paper 6 may expand or contract, slip, or have uneven feeding.
As shown in (3), a gap may be formed in the seam portion between the lines, and white lines may appear in the recorded image, resulting in deterioration of print quality. For this reason, the conventional serial printer employs a printing method capable of preventing the occurrence of white streaks as described below.

An example of the printing method of the conventional serial printer will be described below with reference to FIGS. 6 and 8. As shown in FIG. 6, the thermal head 1 has a recording element array composed of recording elements (heating elements) 1A of n dots in the sub-scanning direction. One row is printed with the width h of the printing element column. Next, when the recording paper 6 is sent and a line feed is performed, the line feed is performed not in the width of h but in a width shorter than h. Therefore, as shown in FIG. 8, since the line to be scanned next is overlapped by the width d, a white line can be prevented from occurring without forming a gap in the seam portion between the lines (for example, Japanese Patent Laid-Open Publication No. Sho. 6
3-69657).

[0007]

However, in the above-mentioned structure, the print density of the overlap-printed portion is increased, and conversely, it is recognized as a black streak. In particular, when multi-gradation recording is performed by taking gradations in units of 1 dot, as shown in FIG. 9b), the portion with overlapping printing has been printed twice with the same print density, and compared with the portion without overlapping printing. As a result, the printing density becomes extremely high, which causes a problem in that the printed image becomes shaded and the printing quality is deteriorated.

In view of the above-mentioned problems, the present invention reduces the recording density unevenness due to white lines and black lines at the seam portion between lines even when performing multi-gradation recording with a serial printer, and enables high-quality printing. The printing method of a printer is provided.

[0009]

In order to solve the above problems, in the printing method of the serial printer of the present invention, the line feed width in the sub-scanning direction is made shorter than the scanning width in the main scanning direction so that the scanning in the main scanning direction is performed. A predetermined number of print dots are overlapped with the preceding and following scans, and when forming print dots in the overlapping portion, the recording element is driven with print energy corresponding to a value that is lower than the gradation value indicated by the gradation print data. It is a method of doing.

Further, when the print dots are formed in the portion overlapping the next line, the gradation value indicated by the gradation print data is periodically set in the main scanning direction or in both the main scanning direction and the sub-scanning direction in units of a predetermined number of print dots. The recording element is driven with the printing energy corresponding to the changed gradation value, and when the print dots of the portion overlapping the previous row during the scanning of the next row in the main scanning direction are formed, the floor indicated by the gradation print data is displayed. This is a method in which the recording element is driven by the printing energy corresponding to the gradation value in which the gradation value is changed in the opposite phase to the preceding row.

When forming print dots in the overlapping portion,
This is a method in which the recording element is driven with print energy corresponding to a value that becomes lower than the gradation value indicated by the gradation print data as the distance from the non-overlapping portion increases.

[0012]

According to the present invention, since the scanning in the main scanning direction overlaps the scanning before and after the scanning, there is no gap between the rows and it is possible to prevent the generation of white lines. Further, since the recording element is driven with the printing energy such that the overlapping portion has a lower density than the original printing density, the printing density does not become extremely high even if the printing is performed by scanning twice. Also, by changing the print density of the overlapping part periodically, or by driving the recording element with the print energy so that the print density of the overlapping part becomes lower as it goes away from the non-overlapping part, It is also possible to blur the boundaries of the to make them inconspicuous.
By printing with the above printing method,
Even when performing multi-gradation recording with a serial printer, it is possible to reduce the density of the recording density that occurs at the joint portion of the print line and obtain a recorded image of high print quality.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A printing method of a serial printer according to a first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration for realizing a printing method of a serial printer according to an embodiment of the present invention. In FIG. 1, 1 is a thermal head, 10 is a CPU for executing a printing sequence of a printer, and 11
Is a motor drive circuit for driving the carriage motor 12 and the paper feed motor 13, 14 is a print control circuit for controlling the drive timing of the thermal head 1, and 15 and 16 are equivalent to one line from a host such as a computer (not shown). It is a row buffer that receives gradation print data, and has a toggle structure in which one is in a read state and the other is in a write state, and the state is switched every time one line is printed. The gradation print data is composed of, for example, 8 bits / print dot, and 256 gradations can be expressed per print dot. Further, 17 is a latch circuit for temporarily holding gradation print data for driving the recording element 1A, and 18 is 1 m gradation print data of m dots at the lower end of the previous row.
A memory for holding lines, and a mask circuit 19 for adjusting the print density. The structures of the mechanical section of the serial printer and the thermal head 1 are the same as those of the conventional one, and are as shown in FIGS. 5 and 6, respectively. However, ink ribbon 2
As A, a sublimation type thermal transfer type ribbon capable of gradation recording is used.

The operation of the printing method of the serial printer having the circuit configured as described above will be described below with reference to FIGS. 1, 2, and 5.

In FIG. 1, the CPU 10 drives the carriage motor 12 by means of the motor drive circuit 11 so that the CPU 10 shown in FIG.
The carriage 3 is moved in the direction of arrow x to perform scanning in the main scanning direction.

When scanning in the main scanning direction is started, a print dot having a desired print density is formed on each recording element 1A of the thermal head 1 every time the carriage 3 is moved by one print dot in the main scanning direction. Printing energy is applied to print one line on the recording paper 6 with the width h of the recording element 1A column. The printing energy is controlled by changing the voltage or pulse width applied to each recording element 1A according to the gradation print data, and the processing of the gradation print data is performed as follows.

First, the gradation print data held in the row buffer 15 or 16 is read out by n−m dots and held in the latch circuit 17. Also, the gradation print data for m dots at the lower end at the same main scanning position in the preceding line is stored in the memory 18
Output more. As a result, the latch circuit 17 and the memory 18
It is possible to obtain the gradation print data for n dots necessary for the printing of this line from the gradation print data output by the above. Next, the gradation printing data for n dots is supplied to the mask circuit 19
To process. In other words, the gradation print data for m dots at each of the upper end and the lower end of the recording element 1A row of the thermal head 1 has a lower gradation (e.g., corresponds to a light gradation of about 1/2 of the original gradation). Replace with gradation print data. The original n-2m dots in the central portion of the printing element 1A row remain unchanged from the original gradation print data and are not replaced. Therefore, the printing energy is applied to the printing element 1A of the thermal head 1 in accordance with the gradation printing data that is replaced so that the upper and lower end portions of the printing element 1A row have low gradation for m dots. In addition, after the printing energy is applied to the recording element 1A, the recording element 1 is included in the gradation print data for nm dots held in the latch circuit 17.
Gradation print data for m dots at the lower end of column A is stored in the memory 18
It is stored in and used when printing the next line.

When the printing of one line is completed, the CPU 10 causes the motor drive circuit 11 to rotate the carriage motor 12 in the reverse direction to return the carriage 3 to the original position, and at the same time, drives the paper feed motor 13 to rotate the platen 5 in FIG. Then, the recording paper 6 is fed to break the line in the sub-scanning direction. The line feed amount at this time is shorter than the print width h for one line, and n-
The width is equivalent to m dots. Therefore, when scanning the next row, m dots of the previous row are printed in duplicate. After that, by repeating the scanning in the main scanning direction and the line feed in the sub-scanning direction in the same manner, the printing for one page of the recording paper 6 is performed while performing the overlapping printing for the preceding and succeeding lines by m dots. The relationship between the print density a) in each line and the composite print density b) when they are combined in the case of printing by this printing method is as shown in FIG.

FIG. 2 shows the print result when the gradation print data from the host has a constant value. In FIG. 2, each line is printed so that its upper and lower ends have a density of 1/2 of the original width, except for the first line (and the last line not shown), as shown in a). ing. It is assumed here that the composite print densities of the overlap printed portions are simply added. Therefore nm
If a line break is exactly made with a width corresponding to dots,
The width of overlapping printing between lines is m dots (= d1),
With the combined print density, a recorded image having no density variation between lines can be obtained. On the other hand, if a line feed is not performed with a width corresponding to nm dots due to uneven feeding of the recording paper 6 or the like, the overlap printing widths between the lines are d2 and d3.
The composite print density slightly fluctuates between lines as shown in b), but the extreme density fluctuation such as the composite print density b) shown in FIG. 9 does not occur.

Further, the gradation print data of the portion to be overlapped and printed is not uniformly set to a value corresponding to half the gradation of the original gradation print data, and is lowered as the distance to the line end is increased as shown in FIG. 3a). By changing the processing content in the mask circuit 19 so as to obtain the print density, the composite print density as shown in FIG. 3B) can be obtained. In this case, in particular, the density fluctuation at the overlap start portion becomes gentle as compared with FIG.

As described above, according to the present embodiment, the occurrence of white lines or black lines at the seam portion can be reduced by adjusting the print density of the overlapped print portion even if an accurate line feed is not performed. It is possible to obtain a multi-tone recorded image with high print quality.

A second embodiment of the present invention will be described below with reference to the drawings. The configuration and operation of the serial printer mechanism unit for realizing the printing method of the serial printer of this embodiment are the same as those of the first embodiment. Further, the circuit configuration is the same as that of FIG. 1 shown in the first embodiment, and by changing the processing contents in the mask circuit 19, printing by the printing method of the serial printer of this embodiment becomes possible.

FIG. 4 is a diagram showing the printing result by the printing method of the serial printer in the second embodiment of the present invention, and shows the case where the gradation printing data from the host has a constant value.

In FIG. 4, a) is an enlarged view of the lower part of the preceding row, where 3 dots at the lower end are provided as an overlapping portion with the next row when m = 3. In addition, b) is an enlarged view of the upper part of the next line, and line feed is performed in the sub-scanning direction with a width of n−3 dots so that the 3 dots at the upper end are overlapped with the previous line a). Here, the feature of this embodiment is that the mask circuit 19 is configured so that the print density of the overlapping print dots periodically changes in the main scanning direction.
Is to be processed in. That is, in the preceding row a), the shading of the print density is repeated every other dot in the main scanning direction, and in the next row b), the shading is repeated in the opposite phase to the preceding row a). In both the preceding row and the next row, the mask circuit 19 adjusts the densities of the overlapping print portions so that when the dark portions and the light portions of the overlapping portions are overlapped and recorded, the densities of the overlapping printing portions become equal. Therefore, when the line feed in the sub-scanning direction is accurately performed with a width of n-3 dots, a recorded image having no density fluctuation between lines can be obtained, but when the line feed in the sub-scanning direction is not accurately performed. Becomes like FIG. 4c) d).

C) is a print result when the previous line a) and the next line b) are line-printed with a line feed error of n-2.5 dots and overlapped and printed. A part with low print density occurs before and after the overlapped print part, but since the low density part is not a constant density and the density is repeated periodically, the line spacing is blurred and it becomes inconspicuous, and it is recognized as a white line. It gets harder.

Further, d) is a printing result when line-feeding is performed with a width of n-3.5 dots and overlapping printing is performed. Contrary to the case of c), a portion having a high printing density is formed before and after the overlapping printing portion. . However, in this case as well, as in c), the density of the high density portion is periodically changed, so that the space between lines becomes inconspicuous, and it is difficult to recognize as black streaks.

As described above, according to the present embodiment, even if a line feed error occurs, the line spacing is blurred by the periodic density of the print density so that the white or black lines at the seam portion are inconspicuous and the print quality is improved. It is possible to obtain a multi-tone recorded image with high print quality without deterioration.

Although the thermal head 1 and the ink ribbon cartridge 2 are used as the printing means in the first and second embodiments, other printing means capable of multi-gradation recording (for example, an ink jet head) may be used. .

Further, in the first embodiment, it is assumed that the print densities of the overlap-printed portions are simply added, and the gradation print data of the overlap-printed portion is 1 of the original gradation print data as shown in FIG. Although the print density is adjusted to a value corresponding to / 2, the print density of the overlapped print portion may not be simply added depending on the printing conditions of the printing means, the recording paper 6 and the like. Therefore, in accordance with each printing condition, if the gradation print data of the overlap printed part is adjusted so that the print density of the overlap printed part becomes the print density corresponding to the original gradation print data, a good result can be obtained. be able to.

Further, in the first embodiment, the print density of the portion to be overprinted is linearly changed as shown in FIG. 3. However, depending on the printing condition, it is better to change it in a curved line to obtain a better result. You may be able to.

Further, in the second embodiment, the number of print dots to be overlapped is set to m = 3, but the value of m may be determined according to the line feed accuracy of the serial printer.

Further, in the second embodiment, the print density of the portion to be overprinted is periodically changed every other dot in the main scanning direction, but it may be changed every predetermined dot. It may be changed periodically in the scanning direction. In addition, it is more effective to make the gradation lower as the distance from the non-overlapping portion increases.

[0034]

As described above, according to the present invention, by setting the line feed width in the sub-scanning direction to be mn dots and shorter than the scanning width of n dots in the main scanning direction, the scanning in the main scanning direction is before and after that. By overlapping m scans with each scanning, and driving the recording element with the printing energy corresponding to the value lower than the gradation value indicated by the gradation printing data when forming the printing dot in the overlapping portion. It is possible to obtain a multi-tone recorded image with high print quality by adjusting the print density of the overlapping print portion and reducing the density of print density generated between the lines.

Further, when forming print dots in a portion overlapping the next row, the recording element is driven with print energy corresponding to the gradation value obtained by periodically changing the gradation value indicated by the gradation print data in the main scanning direction. In addition, when forming the print dots in the portion that overlaps with the preceding row when scanning the next row in the main scanning direction, the gradation value indicated by the gradation print data is changed in the phase opposite to that of the preceding row. By driving the recording element with the printing energy corresponding to the value, the line spacing is blurred by the periodic density of the printing density, and the white and black lines generated at the seam part are inconspicuous, and the printing quality is not deteriorated and high printing quality is achieved. It is possible to obtain a multi-gradation recorded image.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention.

FIG. 2 is a diagram showing a printing result in the example.

FIG. 3 is a diagram showing another printing result in the example.

FIG. 4 is a diagram showing a printing result in the second embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional serial printer.

FIG. 6 is a configuration diagram of a thermal head

FIG. 7 is a diagram showing a printing method of a conventional serial printer.

FIG. 8 is a diagram showing a printing method in overlapping printing of a conventional serial printer.

FIG. 9 is a diagram showing a print result in duplicate printing of a conventional serial printer.

[Explanation of symbols]

 1 Thermal Head 2 Ink Ribbon Cartridge 3 Carriage 5 Platen 6 Recording Paper 15 and 16 Row Buffer 14 17 Latch Circuit 18 Memory 19 Mask Circuit

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Claims (3)

[Claims] 1. Printing with a desired recording density by scanning a recording head having a plurality of recording elements in the main scanning direction and driving the recording elements with a printing energy corresponding to a gradation value indicated by gradation printing data. In a serial printer for recording by forming a dot and repeating a series of operations for line feed in the sub-scanning direction, a line feed width in the sub-scanning direction is made shorter than a scan width in the main scanning direction and A predetermined number of print dots are overlapped with the scan before and after the scan, and at the time of forming print dots in the overlapping portion, the print energy corresponding to a value lower than the gradation value indicated by the gradation print data is used. A printing method for a serial printer, characterized in that the recording element is driven. 2. When forming print dots in a portion overlapping with the next row, the gradation value indicated by gradation print data is cycled in the main scanning direction or in both the main scanning direction and the sub scanning direction in units of a predetermined number of print dots. The recording element is driven by the printing energy corresponding to the gradation value that has been changed dynamically, and the gradation print data is formed when the print dot is formed in the portion overlapping the preceding row in the scanning of the next row in the main scanning direction. 2. The printing method for a serial printer according to claim 1, wherein the recording element is driven by the printing energy corresponding to the gradation value obtained by changing the gradation value indicated by <1> in the opposite phase to the preceding row. 3. When the print dots are formed in the overlapping portion, the recording element is driven with a printing energy corresponding to a value lower than the gradation value indicated by the gradation print data as the distance from the non-overlapping portion is increased. The printing method of a serial printer according to claim 1 or 2, wherein.