JPH0577472A - Thermal printer - Google Patents

Abstract

PURPOSE:To enhance printing quality by preventing the tailing of a dot by reducing the driving energy of a heating element wherein the driving or non- driving is stored with the past line of the x-th surface from a present line as a border when the max. number of dots expressing the thickness of the side of a character is (x). CONSTITUTION:An ROM 14 storing fixed data, an RAM 15 storing variable data and a clock signal oscillator 16 are connected to a CPU 13 to constitute a printing control part 17. A pulse motor 18 driving a platen or a taking-up shaft is connected to the CPU 13 to constitute a feed part 19 of pasteboard with labels and a thermal head 10 is also connected to the CPU 13. A heating state memory part 21 storing driving or non-driving in the past line of the heating elements constituting the thermal head 10 is formed in the CPU 13. The driving energy of the heating element wherein driving on non-driving is stored with the past line of the x-th surface from a present line as a border when the max. number of dots expressing the thickness of the side of a character is (x) is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer which prints in a thermal recording system by selectively heating a plurality of heating elements while controlling thermal history.

[0002]

2. Description of the Related Art Conventionally, as a kind of non-impact type printer, there is a type called a thermal printer for printing by a thermal recording type. This thermal printer has a structure in which a heating element is heated to form dots on a recording medium by a method of direct color development or thermal transfer, and predetermined printing is performed by selectively collecting the dots.

In such a thermal printer, preheating remains in the heating element after heating because of the structure in which the heating element is heated to form dots. Therefore, the temperature of the heating element on the current line, which is about to heat the heating element, changes depending on the heating state of the heating element on the previous line before that, and there is a disadvantage that the dot density is not constant. .. Therefore, conventionally, in order to improve the print quality by keeping the dot density constant, thermal history control may be performed when the heating element is heated. The heat history control is control in which the heat generation state of the heat generation element in the past line is stored and the drive energy applied to the heat generation element for driving the heat generation element is increased or decreased according to the heat generation state. As a means for increasing or decreasing the driving energy applied to the heating element, a means for varying the magnitude of the applied voltage applied to the heating element and a means for varying the pulse width of the applied voltage can be considered. For this, means for varying the pulse width of the applied voltage is used.

Here, a conventional example of heat history control will be specifically described with reference to FIG. The thermal printer in which the thermal history control illustrated here is performed stores the past lines of two dots as viewed from the current line, that is, the presence or absence of driving of the heating elements of the one-dot past line and the two-dot past line,
The pulse width of the voltage applied to the heating element can be varied in three steps according to the stored contents. Here, in FIG. 5, the pulse width T of the applied voltage is T ₁ > T ₂ > T
There is a relationship of ₃ . In FIG. 5, a pattern is shown when the heating element is not driven in both the 2-dot past line and the 1-dot past line, and a pattern is shown when the heating element is driven in the 2-dot past line but not in the 1-dot past line. The pattern shows the case where the heating element is not driven in the 2-dot past line but is driven in the 1-dot past line, and the pattern is the case where the heating element is driven in both the 2-dot past line and the 1-dot past line.

The thermal history control in the thermal printer having such a structure is performed as follows. First, in the case of the pattern, since the number of driving the heating elements in the past line is 0, it is assumed that the heating elements in the current line do not have preheating, and the heating elements are caused to generate heat with large driving energy.
Therefore, the pulse width of the voltage applied to the heating element is set to T ₁ which is the widest. Then, in the case of pattern or
Since the number of driving the heating elements in the past line is one, it is assumed that some preheating remains in the heating elements in the current line, and the heating elements are caused to generate heat with medium driving energy.
Therefore, the pulse width of the voltage applied to the heating element is set to T ₂ . In the case of the pattern, since the number of driving the heating elements in the past line is two, it is assumed that a large amount of preheating remains in the heating elements in the current line, and the heating elements are caused to generate heat with a small driving energy. Therefore, the pulse width of the applied voltage to the heating element is narrowest T _3. Thus, according to the heat history control, the pulse width of the applied voltage to the heating element is changed according to the degree of preheating remaining in the heating element on the current line, and the temperature of the heating element on the current line is made uniform. Therefore, the density of the dots formed becomes constant, and the printing quality is improved.

[0006]

Here, the number of dots forming one character is 24 × 24 dots, the maximum number of dots expressing the thickness of a character side is 2 dots, and the minimum number of dots between character sides is 1 dot. An example of a line type thermal printer that performs certain printing will be described. "Den" illustrated in FIG.
The characters are examples of characters printed by such a thermal printer, and the main scanning direction of this thermal printer is indicated by an arrow in FIG.

However, as is clear from FIG. 6, the minimum number of dots between the character sides is 1 dot, and the interval is narrow. On the other hand, when the thermal history control is performed at the time of printing, the pulse width of the applied voltage is T ₂ in the pattern of FIG. 5, so when the future line next to the present line is blank, the current line is There is a drawback that ink tends to adhere to the blank area due to the trailing of the dots.
For this reason, when two character sides in the main scanning direction are printed at intervals of 1 dot, there is a disadvantage that the blank portion for the interval of 1 dot is crushed by ink and the print quality is degraded.

In the conventional thermal history control, such dot trailing or blurring occurs due to the adjustment of the pulse width of the voltage applied to the heating element of the present line from the number of driving heating elements in the past line. This is because the dot density is merely made uniform and the dot configuration of characters to be printed is not considered at all.

[0009]

The invention according to claim 1 is
When the maximum number of dots expressing the thickness of the character side is x,
The heat history control means reduces the drive energy for the heating element stored in the heat generation state storage unit that the past line closer to the current line is not driven than the x-th past line when viewed from the current line and is driven. A pulling prevention means is provided.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, when the maximum number of dots expressing the thickness of a character side is x, all x past points when viewed from the present line. A dot dropout prevention unit is provided for increasing the drive energy for the heating element stored in the heating state storage unit when driven by the line, by the thermal history control unit.

[0011]

According to the first aspect of the invention, the print control section drives the transport section to relatively move the thermal head and the recording medium. In the process, the heating element of the thermal head is selectively driven by the print control unit to generate heat, and predetermined printing is performed on the recording medium. At this time, the heat generation state storage unit stores the heat generation state of each heating element in the past line. Therefore, when the maximum number of dots expressing the thickness of the character side is x, it is determined that the past line on the x-th surface viewed from the current line is not driven and the past line closer to the current line is driven than the current line. The drive energy for the heating element stored in is reduced by the tailing prevention means. As a result, the tailing of the xth dot that is continuously formed is prevented, and even if the space between the character sides is narrow, the space is reliably maintained in the blank state.

According to the second aspect of the present invention, when the maximum number of dots forming the thickness of the character side is x, it is stored in the heat generation state storage unit that it has been driven in all x past lines viewed from the current line. The driving energy for the generated heating element is increased by the dot dropout prevention unit. As a result, dot omission, dot blurring, etc., which are likely to occur in long lines such as a key line and a parallel bar code, are prevented. That is, in the future line next to the present line where the driving energy for the heating element is reduced by the tailing prevention means, a large amount of preheating does not remain in the heating element. If the applied drive energy is weak, dot dropout or dot blurring is likely to occur. Therefore, in the invention according to the second aspect, the drive energy applied to the heating element in the future line is increased by the dot dropout prevention means, and dot dropout or the like is prevented. Therefore, long lines such as key lines and parallel bar codes are clearly printed.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. This embodiment is an example of a thermal printer configured as a label printer, and its structure is shown in FIG. That is, a label mount 3 in which a plurality of labels 1 as recording media are attached to a long mount 2 at equal intervals is provided, and the label mount 3 is wound in a roll shape on the holding shaft 4. Is held. A guide path 5 for guiding the labeled mount 3 drawn out from the holding shaft 4 to a predetermined path is formed. In the guide path 5, a printing section 6 for printing the label 1 and a printed section 6 for printing A peeling plate 7 for peeling the label 1 from the mount 2 is provided in order,
A winding shaft 8 for winding only the mount 2 is arranged at the end of the guide path 5. Here, the printing unit 6 includes a platen 9, a thermal head 10 that abuts the platen 9 with a plurality of heating elements 10 a arranged in a line with the labeled mount 3 interposed therebetween, and the thermal head 10.
And a ribbon feeding mechanism 12 for feeding an ink ribbon 11 between the label 1 and the label 1.

Next, the electrical connection of each part is shown in FIG. First, a CPU 13 that intensively performs various processes is provided, and the CPU 13 has a ROM 14 for storing fixed data such as operation programs and a RAM 15 for storing variable data.
And an oscillator 16 for generating a clock signal are connected to each other, and a print control unit 17 is configured here. A pulse motor 18 serving as a drive source for the platen 9 and the winding shaft 8 is provided, and the pulse motor 18 is used for the CPU 1
By being connected to the label mount 3, a transport unit 19 that transports the label-mounted backing sheet 3 is configured. The pulse motor 18 also serves as a drive source for the ribbon feeding mechanism 12. Further, the thermal head 10 is connected to the CPU 13, and an interface 20 that connects the CPU 13 and an external device is connected. further,
Inside the CPU 13, a heat generation state storage unit 21 is formed. The heat generation state storage unit 21 stores whether or not the heating element 10a has been driven by a past line of two dots as viewed from the current line being printed, that is, a past dot line of two dots and a past line of one dot. It has a structure that

In such a configuration, the print controller 17
When the heating element 10a of the thermal head 10 is selectively driven to generate heat, the ink of the ink ribbon 11 is melted and transferred to the label 1, and one line of dots is selectively formed on the label 1. At this time, the pulse motor 18 is driven by the print control unit 17 and the platen 9
The label mount 3 is transported by the transport unit 19 such as. Therefore, the dot formation on the label 1 and the transport of the labeled mount 3 are performed by the print control unit 17 in synchronization with each other, whereby predetermined printing is performed on the label 1.
Then, the label 1 after the image formation is peeled from the mount 2 by the peeling plate 7 in accordance with the winding operation of the mount 2 by the winding shaft 8 and is issued from a label issuing port (not shown). here,
In the present embodiment, when Chinese characters are printed on the label 1, the number of dots forming one character is 24 × 24 dots, the maximum number of dots expressing the thickness of the character side is 2 dots, and the minimum dot between the character sides. The number is 1 dot.

The thermal head 10 and the pulse motor 18 are driven by a voltage applied from the print controller 17 in a constant cycle. That is, the CPU 13 generates a drive signal having a constant cycle based on the clock signal of the oscillator 16, and the pulse voltage is applied to the pulse motor 18 and the heating element 10a of the thermal head 10 in accordance with the drive signal. At this time, which heating element 10a generates heat depends on C
It is selected by a control signal given from the PU 13 to the thermal head 10.

On the other hand, the pulse voltage applied to the heating element 10a has three different pulse widths T, and the width of the pulse voltage applied to the heating element 10a depends on the past line of the heating element 10a. Is selected according to the heat generation pattern in the above, and the heat history control means is configured here.
That is, as illustrated in FIG. 3, the printing cycle for one line is formed by four strobe signals, and the pulse width T of the pulse voltage is T ₁ (set to a width of 2.5 strobe signal intervals)> T ₂ (set to width of 2 strobe signal intervals)> T ₃ (set to width of 1 strobe signal interval). Then, as the heat generation pattern in the past line of the heat generating element 10a, as illustrated in FIG.
A pattern in which the heating element 10a is not driven in both the 2-dot past line and the 1-dot past line, a pattern in which the heating element 10a is driven only in the 2-dot past line, and a pattern in which the heating element 10a is driven only in the 1-dot past line There are four patterns in which the heating element 10a is driven in both the 2-dot past line and the 1-dot past line, and the heating pattern of each heating element 10a is temporarily stored in the heating state storage unit 21.

However, in the pattern in which it is assumed that preheating does not remain in the heating element 10a in the current line, the pulse width T of the applied voltage is set to T ₁ which is the widest, and the heating element 10
The driving energy for a is increased. Further, in the pattern preheating remains due to heating of the heating elements 10a in two-dot past the line to the heating element 10a in the current line, the pulse width T of the applied voltage is narrow T ₂ than T _1. Therefore, the amount of heat generated by the heating element 10a is substantially the same when the past line is a pattern and when the pattern is a pattern, and the dot density formed is uniform.

Next, when the space between the character sides printed on the label 1 is one dot, the space between the character sides is easily collapsed by the trailing of dots. Therefore, in this embodiment,
In the case of the pattern, that the pulse width T of the voltage applied at the current line is the narrowest T _3, the drive energy to the heating element 10a is weakened. The trailing prevention means is configured here. That is, in the present embodiment, in which the maximum number of dots expressing the thickness of the character side is 2 dots, in the case of a pattern, dots expressing the thickness of the character side may be formed in the current line. The drive energy for the heating element 10a is weakened, and the occurrence of dot tailing is prevented. Therefore, in the pattern, when the future line next to the current line is blank and dots are formed in the next future line, the trailing of the dots on the current line is prevented, so that the space between the character sides becomes white. It is maintained in the removed state. As a result, even a character having a large number of strokes can be prevented from being crushed in the white part, and the printing quality can be improved.

Further, in the pattern, the pulse width T of the applied voltage in the current line is T ₂ wider than T _3, and the drive energy applied to the heating element 10a is increased to some extent. Here, a dot dropout prevention unit is configured. That is, in the pattern, when dots are formed on the future line next to the current line, the future line corresponds to the current line of the pattern. In contrast,
In the pattern, the heating element 10a is formed by the tailing prevention means.
Since the driving energy for the heating element is reduced, the heating element
There is not much preheating in a. So in the pattern,
If the driving energy applied to the heating element 10a is weak, the density of dots becomes low, and when printing a long line such as a key line or a parallel bar code, it is easy to cause missing dots or faint dots. Therefore, in the pattern, the heating element 10
The drive energy for a is increased by the dot omission prevention means, and dot omission and the like can be prevented. As a result, long lines such as key lines and parallel bar codes are clearly printed.

It should be noted that the heating element 10 is stored in the heating state storage section 21.
The past lines in which the presence / absence of driving a is stored are the one-dot past line and the two-dot past line because the maximum number of dots expressing the thickness of the character side is two in this embodiment. That is, in the implementation, when the maximum number of dots forming a character side is x, the heat generation state storage unit 21 stores the presence / absence of driving of the heat generating elements 10a in all x past lines as viewed from the current line. It Then, a pulse voltage having a pulse width T ₃ is applied to the heating element 10a in which all the past lines closer to the current line are driven without driving the x-th past line as viewed from the current line. It

[0022]

According to the first aspect of the present invention, when the maximum number of dots expressing the thickness of a character side is x, driving is not performed on the x-th past line from the current line, and the current line is more than that. In the past line close to, the driving energy for the heating element stored in the heating state storage unit as being driven is reduced by the tailing prevention unit, so that tailing of dots expressing the thickness of the character side can be prevented. Therefore, even if the space between the character sides is narrow, the space can be surely maintained in the white state,
This has the effect of improving the printing quality.

According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, when the maximum number of dots expressing the thickness of a character side is x, all x past points as seen from the present line. Since the driving energy for the heating element stored in the heat generation state storage section when driven by the line is configured to be increased by the dot omission prevention means, preheating in the next line of the heating element for reducing the driving energy by the tailing prevention means The temperature of the heating element in this line can be increased even when the number of lines is reduced, and this prevents dot dropouts and dot blurring when printing long lines such as key lines and parallel bar codes. And thus can clearly print such lines,
This has the effect of improving the printing quality.

[Brief description of drawings]

FIG. 1 is a block diagram of electrical connection of each part showing an embodiment of the present invention.

FIG. 2 is a side view showing the overall structure.

FIG. 3 is a timing chart of a 1-line cycle of a print signal and an applied pulse width.

FIG. 4 is a plan view of dots showing, for each pattern, the relationship between the presence or absence of driving of the heating elements in the past line and the pulse width of the applied voltage to the heating elements in the current line.

FIG. 5 is a plan view of dots showing, for each pattern, a relationship between the presence or absence of driving of a heating element in a past line and a pulse width of a voltage applied to the heating element in a current line, as a conventional example.

FIG. 6 is a plan view of a set of dots illustrating a character “Den” as an example of a printed character.

[Explanation of symbols]

 1 Recording Medium 9 Platen 10 Thermal Head 10a Heating Element 17 Printing Control Section 19 Conveying Section 21 Heating State Storage Section

Claims (2)

[Claims] 1. A thermal head having a plurality of heating elements arranged in a straight line, a transport unit for relatively moving the thermal head and a recording medium, and the heat generation in synchronization with driving of the transport unit. A print control unit that drives elements to generate heat, a heat generation state storage unit that stores whether or not the heat generation elements have been driven in the past line, and drive energy for the heat generation elements according to the stored contents of the heat generation state storage unit. In the thermal printer provided with the thermal history control means for increasing / decreasing, when the maximum number of dots expressing the thickness of the character side is x, it is not driven on the x-th surface past line as viewed from the current line, and In the past line close to the present line, a tailing prevention means for reducing the driving energy for the heating element stored in the heating state storage section as being driven is provided. Thermal printer to collect. 2. The heating element stored in the heating state storage unit as being driven in all x past lines when viewed from the current line when the maximum number of dots expressing the thickness of a character side is x. 2. The thermal printer according to claim 1, further comprising dot dropout prevention means for increasing drive energy for the printer.