JP2000127474A - Thermal recording apparatus and method for controlling thermal head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form high-quality images by analyzing a print pattern every time one line or a plurality of lines are printed by a plurality of heating elements, determining divide positions of the plurality of heating elements corresponding to record dots of a low print density, dividing the plurality of heating elements at the divide positions and driving the heating elements. SOLUTION: A total number of heating elements 102 formed on a thermal line head 101 is generally 500-5000. The heating bodies are divided to several blocks, so that each block includes 100-1000 heating elements. These heating element blocks 102a-102d are connected to a heating element separate conducting means 108. A command is sent from a control part 107a of a CPU 197 to the conducting means. A divide position-determining part 107b of the CPU 107 determines a divide position among boundary positions 109X-109Z of the heating element blocks 102a-102d on the basis of input image data of every line. At this time, between the heating elements 102 corresponding to a record dot of a low density, preferably, the lowest density in the image is determined as the divide position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal recording apparatus for printing on recording paper using a thermal line head and a method for controlling the thermal head.

[0002]

2. Description of the Related Art Thermal line printers include a thermal transfer method in which the back of an ink ribbon superimposed on recording paper is heated by a thermal head to transfer ink to the recording paper, and a thermal recording paper is directly heated by a thermal head. There is known a thermosensitive recording system in which the color is developed. In any of these methods, the thermal head has a plurality of heating elements arranged in a line.

When a plurality of heating elements are heated, generally,
The heating elements arranged in a line are divided and energized. That is, instead of energizing all of the heating elements all at once,
It is divided into several blocks and energized. This allows
It avoids the need for large amounts of power in a short time and reduces the load on the power supply.

FIG. 3 is a schematic configuration diagram of a conventional thermal line printer. As shown in the drawing, the conventional thermal line printer device has a plurality of heating elements 302 in a thermal head 301, and these heating elements 302
Is divided into, for example, four blocks. Then, of the four heating element blocks 302a to 302d, the first heating element block 3 that heats the left portion on the thermal recording paper 303.
02a and the second heating element block 302b are connected to the left heating element energizing means 304. Further, a third heating element block 302c for heating a right portion on the thermal recording paper 303 and a fourth heating element block 302c are provided.
The heating element block 302d has a heating element energizing means 305 on the right side.
Connect. These heating element energizing means 304 and 30
By making the energizing timings of 5 different, it is possible to avoid energizing all the heating elements 302 in the thermal head 301 all at once.

The operation from the n-th line to the (n + 1) -th line when printing an image pattern as shown in FIG. 4 in the above-described conventional thermal line printer will be described.

First, the heating elements 302 of the first heating element block 302a and the second heating element block 302b are simultaneously energized by the left heating element energizing means 304. As a result, of the heat generating elements 302 of the first heat generating element block 302a and the second heat generating element block 302b, those for which printing is instructed generate heat. For this reason, a portion of the heat-sensitive recording paper 303 that is in contact with the heat-generating body 302 is colored. As a result, recording dots indicated by oblique lines in FIG. 3 are printed in the left half on the n-th line.

Next, the heating elements 302 of the third heating block 302c and the fourth heating block 302d are simultaneously energized by the right heating element energizing means 305. As a result, of the heat generating elements 302 of the third heat generating element block 302c and the fourth heat generating element block 302d, the one for which printing is instructed generates heat. For this reason, a portion of the heat-sensitive recording paper 303 that is in contact with the heat-generating body 302 is colored. As a result, recording dots indicated by black dots in FIG. 3 are printed in the right half on the n-th line. Next, the thermal recording paper 303 is moved by one line. Then, printing on the (n + 1) th line is performed according to the above procedure.

[0008]

However, in the conventional thermal line printer, a heating element block that is energized at the same time when energization is switched is fixed. Therefore, the heating element 302 located at the block boundary position
e and 302f are one of the heating elements 302g and 30f.
It receives heat conduction only from 2h. As a result, the heating elements 302e and 302f located at the block boundary position have a smaller amount of temperature rise than the heating elements 302 located at positions other than the block boundary position. According to this, the thermal recording paper 30 corresponding to the heating elements 302e and 302f located at the block boundary position is used.
The print density of No. 3 decreases. In this state, the thermal recording paper 3
Since the transport of 03 is performed, the image having the reduced print density is continuous in the transport direction. As a result, there is a problem that a white line 306 is generated on the thermal recording paper 303 as shown in FIG. In FIG. 3, dots printed at a normal density because the heating element 302 is not at the block boundary position are printed at a normal density dot 307, and printed at a low density because the heating element 302 is at the block boundary position. The dots are represented by reduced density dots 308.

The heating element 30 located at the block boundary position
In the image formation, 2e and 302f always have lower heat conduction than the heating element 302 located at a position other than the block boundary position. Therefore, as the image is formed, the difference in the heat storage temperature between these heating elements 302 becomes larger. The difference in the amount of heat stored in the heating element 302 is also one of the causes that the white line 306 becomes apparent.

As a means for making the above-mentioned white line 306 less noticeable, there is a method disclosed in Japanese Patent Application Laid-Open No. Hei 7-329335. This method is a method of printing by changing the division boundary position every time one line is moved.
FIG. 5 is an image forming diagram when this method is used.
According to this method, the reduced density dots 308 are recorded at different positions on the line for each line. As a result, generation of the white line 306 on the thermal recording paper 303 can be prevented. However, with this method, the density-reduced dots 308 are only slightly less noticeable than when the white line 306 is generated. Therefore, the specific heating element 30
2 does not provide a complete solution to the thinning of the image due to the occurrence of the reduced density dots 308.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a thermal recording apparatus and a thermal head control method capable of forming a high-quality image without generating a white line. I do.

[0012]

According to the present invention, each time one or more lines are printed by a plurality of heating elements arranged substantially linearly, a print pattern is analyzed to correspond to a recording dot having a low print density. Determine the division position of the multiple heating elements,
A plurality of heating elements are divided and driven at the division position.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A thermal recording apparatus according to a first aspect of the present invention comprises a thermal head having a plurality of heating elements arranged in a substantially straight line, and a thermal head capable of driving the plurality of heating elements in a divided manner. A print pattern is analyzed each time one line or a plurality of lines are printed by a head control unit, and a division position of the plurality of heat generating units by the thermal head control unit is determined between the heat generating units corresponding to the recording dots having a low print density. And a division position determination unit that determines the position between the two.

According to this configuration, the division position determination unit determines a division position between the heating elements corresponding to the recording dots having a low print density among the plurality of heating elements. Then, the thermal head controller divides and drives the plurality of heating elements at the determined division position. As a result, since the division positions of the plurality of heating elements overlap portions where the density of the print image itself is low on each line, it is possible to make a white line due to a decrease in print density less noticeable to a level that cannot be visually recognized.

Further, according to this configuration, the white line on the recording paper can be made inconspicuous to a level at which the white line cannot be visually recognized without changing the energizing energy and the number of times of energizing the heating element. As a result, there is no need to increase power consumption or shorten the life of the thermal line head.

According to a second aspect of the present invention, there is provided a thermal recording apparatus comprising:
In the aspect, the thermal head control unit can divide the plurality of heating elements into a plurality of blocks and drive each block, and the division position determination unit sets the division position adjacent to a boundary between the blocks. A configuration is adopted in which heating elements are determined between those corresponding to recording dots with low print density.

According to this configuration, the division position determination unit determines the division position between the heating elements adjacent to the boundary between the predetermined plurality of heating element blocks corresponding to the recording dots with low print density. decide. For this reason, it is not necessary to examine the heating element other than the boundary of the heating element block. Therefore, the division position determination unit does not determine whether a division position can be set between all the heating elements. Thereby, the division position can be determined in a short time.

According to a third aspect of the present invention, there is provided a thermal recording apparatus having a plurality of heating elements arranged substantially linearly, and a thermal head control unit capable of driving the plurality of heating elements in a divided manner. A dividing position determining unit for determining a dividing position of the plurality of heating elements by the thermal head control unit between heating elements having a small amount of generated heat every time one line or a plurality of lines are printed. take.

According to this configuration, the division position determination unit determines a division position between heating elements having a small amount of generated heat among a plurality of heating elements. Then, the thermal head controller divides and drives the plurality of heating elements at the determined division position. As a result, the divided positions of the plurality of heating elements overlap the portions where the density of the print image itself is low on each line, so that a white line due to a shortage of heat generation can be made inconspicuous to a level that cannot be visually recognized.

Further, according to this configuration, it is possible to make the white line on the recording paper inconspicuous to a level at which the white line on the recording paper cannot be visually recognized without changing the energizing energy and the number of energizing operations to the heating element. As a result, there is no need to increase power consumption or shorten the life of the thermal line head.

The thermal recording apparatus according to the fourth aspect of the present invention has a third aspect.
In the aspect, the thermal head control unit can divide the plurality of heating elements into a plurality of blocks and drive each block, and the division position determination unit sets the division position adjacent to a boundary between the blocks. A configuration is adopted in which a heating element having a small heat value is determined.

According to this configuration, the division position determination unit determines the division position between the heating elements having a small amount of heat among the heating elements adjacent to the predetermined boundary between the plurality of heating element blocks. For this reason, it is not necessary to examine the heating element other than the boundary of the heating element block. Therefore, the division position determination unit does not determine whether a division position can be set between all the heating elements. Thereby, the division position can be determined in a short time.

In a thermal head control method according to a fifth aspect of the present invention, each time the thermal head prints one line or a plurality of lines, the print pattern is analyzed and the print density of the plurality of heating elements of the thermal head is reduced. The method includes a step of determining a division position between the heating elements corresponding to the low recording dots, and a step of dividing and driving the plurality of heating elements at the determined division position.

According to this method, of the plurality of heating elements,
The space between the heating elements corresponding to the recording dots having a low print density is determined as the division position. As a result, since the division positions of the plurality of heating elements overlap portions where the density of the print image itself is low on each line, it is possible to make a white line due to a decrease in print density less noticeable to a level that cannot be visually recognized.

A thermal head control method according to a sixth aspect of the present invention is the method of controlling a thermal head according to claim 6, wherein each time the thermal head prints one line or a plurality of lines, a plurality of heating elements of the thermal head have a small heating value. And the step of dividing and driving the plurality of heating elements at the determined division position.

According to this method, of the plurality of heating elements,
The division position is determined between the heating elements having a small amount of generated heat. As a result, the divided positions of the plurality of heating elements overlap the portions where the density of the print image itself is low on each line, so that a white line due to a shortage of heat generation can be made inconspicuous to a level that cannot be visually recognized.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 1 is a schematic diagram showing the configuration of a thermal line printer according to an embodiment of the present invention. In FIG. 1, a thermal line head 101 has a plurality of heating elements 102 arranged in a line along a scanning direction. Below the thermal line head 101, a platen roller 103 is arranged substantially parallel to the direction in which the heating elements 102 are arranged. The platen roller 103 applies heat-sensitive recording paper 104 to the thermal line head 101 with a constant load.
Is pressed or separated. Also, the platen roller 103
Is connected to a sheet transport means 105 for the thermal recording paper 104. The paper transport means 105 is connected to a drive motor 106. The drive motor 106 drives the sheet conveying means 105 in accordance with an instruction from a control unit 107a (hereinafter, referred to as a control unit) of the CPU 107. Thereby, the thermal recording paper 104 is conveyed. At this time, the platen roller 103 rotates in conjunction with the sheet conveying means 105.

The plurality of heating elements 102 in the thermal line head 101 are divided into several blocks.
Generally, the total number of the heating elements 102 formed on the thermal line head 101 is 500 to 5000, which are divided into several blocks, and 100 to 10
There are 00 pieces. FIG. 1 shows an example in which the total number is 20 and the number of blocks per block is 5, and the first block 102a is divided into the fourth block 102d to simplify the drawing.

These heating element blocks 102a-102
d is connected to the heating element dividing and energizing means 108, respectively. The heating element dividing and energizing means 108 can simultaneously energize a single heating element block or a plurality of adjacent heating element blocks. The heating element dividing and energizing means 108 includes a CPU 107
It is connected to the.

The CPU 107 has a control unit 107a and a division position determination unit 107b. The control unit 107a controls the boundary positions 109X of the heating element blocks 102a to 102d.
Among the 109Z, a command is given to the heating element division energizing means 108 so as to energize the heating element blocks 102a to 102d with a timing shifted with respect to an arbitrary boundary position (hereinafter referred to as a division position). The division position determination unit 107b (hereinafter, referred to as a division position determination unit) of the CPU 107 determines the boundary positions 109X to 109Z of the heating element blocks 102a to 102d based on the input image data for each line.
The division position is determined from.

More specifically, the division position determination unit 107b
An image to be printed by the thermal line printer device according to the present embodiment based on image data for each line (hereinafter, an image to be printed)
A division position is determined between the heating elements 102 corresponding to recording dots having a low density, preferably the lowest density, in a printing pattern (referred to as a printing pattern). In other words, a division position is determined between the heating elements 102 that generate a small amount of heat during printing, preferably the smallest. In this example, the case of monochrome printing of a binary image is described. Therefore, when the pixel data indicates a white pixel, the recording dot corresponding thereto is not colored, and the heating element 102 does not generate heat. Therefore, the image data is analyzed, and the division position is determined between the heating elements 102 corresponding to the pixels whose pixel data is a white pixel.

In this example, the division positions are the boundary positions 109X-109 of the heating element blocks 102a-102d.
Since Z is selected from among Z, the density of the corresponding recording dot is low from the pair of heating elements (hereinafter referred to as adjacent heating elements) 102e and 102f, 102g and 102h, 102i and 102j adjacent to the boundary positions 109X to 109Z. , That is, one with a small calorific value is selected. Therefore, by analyzing the image data, the adjacent heating elements 102e and 102f, 102g and 102h, 102i and 1
From the pair of 02j, when both correspond to a pixel whose pixel data is a white pixel, the division position can be determined.

The division position determination unit 107b determines an energization pattern according to the determined division position and sends it to the control unit 107a. The control unit 107a controls energization of the heating blocks 102a to 102d according to the energization pattern.

Next, the operation of the thermal line printer having the above configuration will be described. FIG. 2 is a flowchart showing the operation of the thermal line printer according to the embodiment.

First, in step (hereinafter referred to as ST) 201, the control unit 107a initializes a line counter (not shown). Next, the division position determination 107b is performed in ST2
At 02, the input image data of the first line is read. Then, in order to select the boundary position of the energization switching of the first line, the image data is analyzed. The analysis of the image data is performed in the following procedure.

First, in ST203, the division position determination unit 107b determines whether the pixel data of the pixels corresponding to the adjacent heating elements 102e and 102f adjacent to the first boundary position 109X (hereinafter, referred to as adjacent pixel data) indicates a white pixel. It determines whether or not. Here, when both adjacent pixel data are white pixels, in ST204, the division position determining unit 107b determines the first boundary position 109X as a division position.

Next, in ST205, the division position determination unit 107b determines the energization switching pattern when the first boundary position 109X is determined as the division position. Then
In ST206, control section 107a gives a command to heating element split energizing means 108 to perform energization in accordance with the energization switching pattern determined in ST205. In response to this, the heat-dividing energizing means 108 causes the heat-sensitive recording paper 104
Above, the first heating element block 102a on the left side with respect to the first boundary position 109X is energized. afterwards,
The second heating element block 102b to the fourth heating element block 102d on the right side with respect to the first boundary position 109X are simultaneously energized. As a result, of the heat generating elements 102, those for which a print instruction is issued generate heat. As a result, recording dots are printed on the first line of the thermal recording paper 104.

On the other hand, in ST203, when any one of the adjacent pixel data is a black pixel, in ST207, the division position determining unit 107b determines the second boundary position 109
It is determined whether or not the adjacent pixel data of Y indicates a white pixel. Here, when both adjacent pixel data are white pixels, in ST208, the division position determination unit 107b
The second boundary position 109Y is determined as a division position.

Next, in ST209, the division position determining section 107b determines an energization switching pattern when the second boundary position 109Y is determined as a division position. Then
In ST206, control section 107a gives a command to heating element split energizing means 108 to energize according to the energization switching pattern determined in ST209. In response to this, the heat-dividing energizing means 108 causes the heat-sensitive recording paper 104
Above, the first heating element block 102a and the second heating element block 102b on the left side with respect to the second boundary position 109Y are simultaneously energized. Then, the third heating element block 1 on the right side with respect to the second boundary position 109Y.
02c and the fourth heating element block 102d are simultaneously energized. As a result, of the heat generating elements 102, those for which a print instruction is issued generate heat. As a result, recording dots are printed on the first line of the thermal recording paper 104.

In ST207, if any one of the adjacent pixel data is a black pixel, in ST210, the division position determining unit 107b sets the third boundary position 109
It is determined whether or not both adjacent pixel data of Z indicate white pixels. Here, if both are white pixels, ST2
In 11, the division position determination unit 107b determines the third boundary position 109Z as the division position.

Next, in ST212, the division position determining unit 107b determines the energization switching pattern when the third boundary position 109Z is determined as the division position. Then
In ST206, an instruction is given to the heating element split energizing means 108 to energize in accordance with the energization switching pattern determined in ST212. In response to this, the heating division energizing means 108 simultaneously energizes the first heating element block 102a to the third heating element block 102c on the left side with respect to the third boundary position 109Z on the thermal recording paper 104. Thereafter, power is supplied to the fourth heating element block 102d on the right side with respect to the third boundary position 109Z. As a result, of the heat generating elements 102, those for which a print instruction is issued generate heat. As a result, recording dots are printed on the first line of the thermal recording paper 104.

On the other hand, in ST210, when any one of the adjacent pixel data indicates a black pixel, division position determination section 107b determines second boundary position 108Y as a division position in consideration of a reduction in load on the power supply. . Then, processing is performed when the second boundary position is determined to be the division position. That is,
The processing of ST208, ST209 and ST206 is performed.

Next, in ST213, the division position determination unit 107b determines whether or not printing of all lines has been completed. Here, if printing of all lines has been completed,
End the entire printing process. On the other hand, if the printing of all the lines has not been completed, the line data is counted up by one line in the line counter in ST214. Thereafter, the process returns to ST202, and the next line ST202
To ST213 are repeated.

In accordance with the above-described procedure, the division position serving as a reference for the energization switching is determined for each line, and the thermal recording paper 104
Form the image above. A dotted line A shown in FIG. 1 indicates a locus of a division position when an image pattern as shown in FIG. 5 is printed.

As described above, according to the thermal line printer of the present embodiment, the thermal line head 101
The plurality of heating elements 102 arranged inside are divided into several heating element blocks 102a to 102d so as to be energized. Then, among the boundary positions 109X to 109Z between the heating element blocks 102a to 102d, the adjacent heating element 102
e and 102f, 102g and 102h, 102i
And the neighboring pixel data corresponding to 102j indicating white pixels are determined as the division positions. Power is applied to the heating element blocks located on the left and right opposite sides at different timings based on the determined division position. As a result, similarly to the conventional thermal line printer, the amount of heat generated by the adjacent heating element 102 adjacent to the division position is reduced. However, since the adjacent pixel data at the division position indicates a white pixel, the recording dots corresponding to these need not be colored. As a result, it is possible to make a white line generated due to a decrease in print density inconspicuous to a level that cannot be visually recognized. In addition, since the density of the recording dots that should originally be colored does not decrease, the image quality can be maintained at a high level.

Further, according to the thermal line printer of the present embodiment, the division position is determined for each line. For this reason, it is possible to prevent the energization switching positions from always being the same, thereby preventing a decrease in print density due to a difference in heat storage temperature between the heating elements 102.

Further, according to the thermal line printer of the present embodiment, the thermal recording paper 104 is not changed without changing the energizing energy and the number of energizing times for the heating element 102.
The upper white line can be made inconspicuous to a level that cannot be visually recognized. As a result, there is no concern that power consumption will increase or the life of the thermal line head 101 will be shortened.

In this embodiment, a case has been described where the division position is determined based on whether or not both adjacent pixel data indicate white pixels. However, when the print image has multiple gradations, among the boundary positions 109X to 109Z,
The boundary position where the density of the recording dot based on the corresponding adjacent pixel data becomes the lowest may be determined as the division position.

Further, in the present embodiment, the mode in which the thermal recording paper is pressed and conveyed by rotating the platen roller with the thermal head fixed is described. However, the platen roller may be changed to flat rubber, and the thermal head may be conveyed horizontally with the flat rubber surface while the thermal recording paper is fixed.

Further, in this embodiment, the thermal line printer of the thermal type using the thermal recording paper of the monochrome printing has been described. However, without using the thermal recording paper of the present invention, a thermal transfer type thermal line printer using an ink sheet, a multi-tone printing type thermal line printer, and a thermosensitive printer having yellow, magenta, and cyan self-coloring layers The present invention can be applied to various thermal recording apparatuses such as a direct thermal printing (Temo-Autochrom) type thermal line printer using a recording sheet. .

[0052]

As described above, according to the present invention,
A high-quality image without a white line at a specific position can be formed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a thermal line printer device according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the thermal printer according to the embodiment.

FIG. 3 is a schematic configuration diagram of a conventional thermal printer device.

FIG. 4 is an image pattern diagram for explaining a printing operation.

FIG. 5 is an image forming diagram when a method of changing a division boundary position for each line is used.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 Thermal line head 102 Heating element 103 Platen roller 104 Thermal recording paper 107 CPU 108 Heating element division energizing means 109 Block boundary position

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Taichi Ito 2-3-8 Shimomeguro, Meguro-ku, Tokyo Matsushita Electric Transmission System Co., Ltd. F-term (reference) 2C066 AA05 AB02 AC01 CC03 CC07

Claims (6)

[Claims] 1. A thermal head including a plurality of heating elements arranged in a substantially straight line, a thermal head control unit capable of driving the plurality of heating elements in a divided manner, and each time one or more lines are printed And a division position determination unit that analyzes a print pattern and determines a division position of the plurality of heating elements by the thermal head control unit between heating elements corresponding to recording dots with low print density. A thermal recording device characterized by the above-mentioned. 2. The thermal head control section can divide a plurality of heating elements into a plurality of blocks and drive each block, and the division position determination section determines a division position adjacent to a boundary between the blocks. 2. The thermal recording apparatus according to claim 1, wherein the determination is made between heating elements corresponding to recording dots having a low print density. 3. A thermal head having a plurality of heating elements arranged substantially linearly, a thermal head control unit capable of driving the plurality of heating elements in a divided manner, and each time one or more lines are printed. And a dividing position determining unit for determining a dividing position of the plurality of heating elements by the thermal head control unit between the heating elements having a small amount of generated heat. 4. A thermal head control unit can divide a plurality of heating elements into a plurality of blocks and drive each block, and the division position determination unit sets a division position adjacent to a boundary between the blocks. 4. The thermal recording apparatus according to claim 3, wherein the determination is made during a heating element having a small calorific value. 5. A printing pattern is analyzed each time the thermal head prints one line or a plurality of lines, and a heating element corresponding to a recording dot having a low print density among a plurality of heating elements of the thermal head is analyzed. A method of controlling a thermal head, comprising: a step of determining a division position; and a step of dividing and driving the plurality of heating elements at the determined division position. 6. A step of determining a division position between heating elements having a small amount of heat among a plurality of heating elements of the thermal head each time the thermal head prints one line or a plurality of lines; And driving the plurality of heating elements by dividing the heating elements at positions.