JP2514566Y2 - Thermal printer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a thermal printer that prints line by line with a thermal head.

[Conventional technology]

When printing is performed with a thermal head, the print density changes depending on the temperature. Therefore, for example, JP-A-60-1
Japanese Patent No. 1374 proposes heating a substrate of a thermal head with a heater.

Further, Japanese Patent Laid-Open No. 61-49867 proposes to supply a driving pulse to the thermal head to preheat the thermal head before printing.

Further, JP-A-60-72757 proposes to provide a line counter for counting the number of lines to be printed and to correct the width of the drive pulse for driving the thermal head in accordance with the output of this line counter. Has been done.

[Problems to be solved by the device]

However, the former two methods can heat the thermal head to a predetermined temperature, but the first method has a drawback that the desired density cannot be obtained at the start of printing because the reaction speed of heating is slow. is there.

On the other hand, the second method avoids the delay of the reaction speed, but has a drawback that heat is accumulated in the latter half of printing and the density increases to a desired value or more. This also applies to the first method.

Furthermore, even the third method may not be able to prevent an increase in density due to heat storage, and good color printing cannot be performed when the characteristics of the print density due to heat storage are different for each ink color. There was a problem.

The present invention has been made in view of such a situation, and it is possible to reliably prevent an increase in density due to heat storage, and even if the characteristics of the print density due to heat storage are different for each ink color, it is possible to obtain a favorable result. An object of the present invention is to provide a thermal printer capable of color printing.

[Means for solving the problem]

The thermal printer of the present invention is a thermal printer that performs predetermined printing with a thermal head using a plurality of colors of ink, and prints with a drive pulse generating means that generates a drive pulse for driving the thermal head in correspondence with recording data. A line counter that counts the number of lines, a temperature data creation unit that creates temperature data by detecting the temperature of the thermal head, a color code representing each of a plurality of colors of ink, the number of lines output from the line counter, and temperature data And a correction unit that corrects the width of the drive pulse according to the temperature data output from the creation unit.

[Action]

In the thermal printer configured as described above, the width of the drive pulse for driving the thermal head is adjusted for each color of ink in accordance with the number of lines and the temperature data. Therefore, it is possible to reliably prevent an increase in density due to heat storage for each ink color.

〔Example〕

FIG. 1 is a block diagram showing the principle of the thermal printer of the present invention.

In the figure, 1 is an address counter, which counts an input clock (CK) and parallelly generates an address of a thermal head to be driven. Reference numeral 2 denotes a gradation counter, which outputs data concerning gradation within a predetermined range to the pulse length correction table 3 and the data comparison circuit 5 each time a carry signal is inputted from the address counter 1. The data comparison circuit 5 compares the print data input from the data storage unit 4 with the output of the gradation counter 2, and serially outputs the comparison result to the shift register 8.

The output of the shift register 8 is once latched by the latch circuit 9, and the output of the latch circuit 9 is supplied as a driving pulse to the bases of the NPN transistors T _{1 to} Tn via the gates G _{1 to} Gn. Heating resistors R _{1 to} Rn forming a thermal head are connected to the collectors of NPN transistors T _{1 to} Tn whose emitters are grounded.

A line counter 6 counts the input line pulse (LP) and outputs the count value to the pulse length correction table 3. Reference numeral 7 denotes a gate pulse generation circuit, which outputs a gate pulse for controlling the width of the drive pulse supplied to the NPN transistors T _{1 to} Tn corresponding to the output of the pulse length correction table 3 to the gates G _{1 to} Gn. Has become.

The gradation counter 2, the pulse length correction table 3, the gate pulse generation circuit 7, the gates G _{1 to} Gn, etc. constitute a correction means.

 Next, the operation will be described.

The address counter 1 counts an input clock and generates addresses of the driving heating resistors R _{1 to} Rn,
Output to the data storage unit 4. The data storage unit 4 supplies the data stored in advance to the data comparison circuit 5 in correspondence with this address.

On the other hand, the address counter 1 outputs a carry signal to the gradation counter 2 each time n addresses corresponding to the heating resistors R _{1 to} Rn are generated. The gradation counter 2 outputs data in a predetermined range regarding gradation of density each time a carry signal is input. For example, when the density has 256 gradations, the gradation counter 2 sequentially outputs the values from 0 to 255 to the data comparison circuit 5.

The data comparison circuit 5 compares the value input from the gradation counter 2 with the value related to the density input from the data storage unit 4. For example, when the density value input from the data storage unit 4 is 30, the data comparison circuit 5 determines that the value input from the gradation counter 2 is 0 to 30 (the value of the gradation counter 2 is When the value is less than or equal to the value of the storage unit 4), a logical 1 is output, and when the value is from 31 to 255 (when the value of the gradation counter 2 is greater than the value of the data storage unit 4), the logical 0 is output.

In this way, the value of logic 1 or 0 generated for each address is serially output to the shift register 8. When n pieces of data corresponding to the heating resistors R _{1 to} Rn are input to the shift register 8, the data is latched in synchronization with the carry signal output from the address counter 1.
Transferred to. The data transferred to the latch circuit 9 is supplied to the bases of the NPN transistors T _{1 to} Tn via the gates G 1 to Gn. The NPN transistors T _{1 to} Tn turn on when a logic 1 is input and turn off when a logic 0 is input. One of the heating resistors R _{1 to} Rn connected to the turned-on NPN transistor is energized to generate heat.

The heating resistor connected to the NPN transistor that is off does not conduct current and does not generate heat.

The above operation is repeated 256 times. The heating resistor corresponding to the dot set to the lightest density does not generate heat even once, and the heating resistor corresponding to the dot set to the darkest density generates 255 times.

Such an operation is performed corresponding to the data stored in the data storage unit 4, and predetermined printing is executed.

When printing is performed without adding any correction processing in this way, the temperature of the heating resistors R _{1 to} Rn rises due to the heat storage effect as the number of printing lines increases. As a result, the second
As shown in FIG. 7A, the print density increases as the number of print lines increases.

Therefore, the operation for adjusting the print density will be described next.

The value from 0 to 255 indicating the gradation output by the gradation counter 2 is also input to the pulse length correction table 3. The line counter 6 counts the number of lines to be printed and outputs the count value to the pulse length correction table 3. Pulse length data corresponding to the number of lines is stored in advance in the pulse length correction table 3, and the pulse length correction table 3 reads out pulse length data corresponding to the number of lines input from the line counter 6 to obtain a gate pulse. Output to the generation circuit 7. The gate pulse generation circuit 7 outputs a gate pulse having a length corresponding to the input pulse length data to the gates G _{1 to} Gn.

The pulse length data stored in advance in the pulse length correction table 3 is set so that the width of the drive pulse becomes shorter as the number of lines increases, as shown in FIG. 2 (b). Therefore, as described above, when the number of lines increases, the concentration tends to increase due to the heat storage effect, but since the heat generation (energization) time of the heating resistors R _{1 to} Rn decreases as the number of lines increases, Overall, as shown in FIG. 2 (c), a constant density can be realized regardless of the number of lines.

In the case of FIG. ₁ , since the gates G _{1 to} Gn are composed of AND circuits, the width of the drive pulse output from the latch circuit 9 is set to a value for obtaining the maximum density. The length is limited to the length corresponding to the gate pulse input from the gate pulse generating circuit 7.

FIG. 3 is a block diagram showing the configuration of an embodiment of the thermal printer of the present invention to which the principle of FIG. 1 is applied, and the portions corresponding to those in FIG. 1 are designated by the same reference numerals.

In FIG. 3, reference numeral 22 is a temperature sensor having a thermistor 21, and heat generating resistors R _{1 to} R ₁ which constitute a thermal head.
It is located near Rn and detects its temperature. A temperature data creation circuit 23 creates data relating to the temperature of the thermal head from the output of the temperature sensor 22 and outputs it to the pulse length correction addition data table 24. The pulse length correction addition data table 24 is also supplied with the color code (CC) and the output of the line counter 6.
The adding circuit 25 adds the outputs of the pulse length correction addition data table 24 and the pulse length correction reference table 26 and outputs the result to the gate pulse generating circuit 7.

 Other configurations are the same as those in FIG.

 Next, the operation will be described.

The pulse length correction reference table 26 basically functions in the same manner as the pulse length correction table 3 in FIG.

On the other hand, in the pulse length correction addition data table 24, an addition value for setting the pulse width corresponding to the number of lines is prepared for each color and for each temperature.

That is, as shown in FIG. 4, a predetermined addition value is set for each color of yellow, magenta, cyan, and black, and the addition value decreases as the number of lines increases. Further, this added value is adapted to change with temperature. As shown in FIG. 5, the change due to the temperature is set so that the added value for the same number of lines becomes smaller as the temperature becomes higher.

As described above, the pulse length correction reference table 26 outputs pulse length data corresponding to the number of lines output by the line counter 6. Then, the pulse length correction addition data table 24 outputs the temperature data output by the temperature data creating circuit 23 and the addition value corresponding to the number of lines output by the line counter 6. This added value also differs for each color signal.

The outputs of the pulse length correction reference table 26 and the pulse length correction addition data table 24 are added in the adding circuit 25.
The gate pulse generation circuit 7 outputs a gate pulse so that the width of the drive pulse output from the gates G _{1 to} Gn corresponds to the output of the adder circuit 25.

[Effect of device]

As described above, according to the thermal printer of the present invention, the drive pulse for driving the thermal head is corrected according to the color code representing each of the inks of a plurality of colors, the number of lines to be printed, and the temperature data of the thermal head. Therefore, the width of the drive pulse is corrected for each color of a plurality of colors of ink, and even if the characteristics of the print density due to heat storage are different for each color of ink, the correction can be performed according to each characteristic. Further, since the width of the drive pulse is corrected in consideration of not only the number of lines but also the temperature data, it is possible to more accurately prevent the density increase due to heat storage of the thermal head.

[Brief description of drawings]

1 is a block diagram showing the principle of the thermal printer of the present invention, FIGS. 2 (a) to 2 (c) are characteristic diagrams for explaining the operation of the principle of FIG. 1, and FIG. 3 is a diagram of the thermal printer of the present invention. A block diagram showing the configuration of the embodiment, FIGS. 4 and 5 are characteristic diagrams for explaining the operation of the embodiment of FIG. 1 ... Address counter, 2 ... Gradation counter, 3 ...
Pulse length correction table, 4 ... Data storage unit, 5 ... Data comparison circuit, 6 ... Line counter, 7 ... Gate pulse generation circuit, 8 ... Shift register, 9 ... Latch circuit, 21 ... Thermistor, 22 …… Temperature sensor, 23 …… Temperature data creation circuit, 24 …… Pulse length correction addition data table, 25 …… Addition circuit, 26 …… Pulse length correction reference table.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Creator Toru Nibe 3-12 Moriya-cho, Kanagawa-ku, Yokohama, Kanagawa Pref., Victor Company of Japan, Ltd. (56) Reference JP-A-2-155755 (JP, A) JP JP-A-60-72757 (JP, A) JP-A-62-101468 (JP, A) JP-A-49-15322 (JP, A)

Claims (1)

(57) [Scope of utility model registration request] 1. A thermal printer for performing predetermined printing with a thermal head using a plurality of colors of ink, a drive pulse generating means for generating a drive pulse for driving the thermal head corresponding to recording data, and a line for printing. A line counter for counting the number, a temperature data creating unit for creating temperature data by detecting the temperature of the thermal head, a color code representing each of the plurality of colors of ink, the number of lines output from the line counter,
A thermal printer, comprising: a correction unit that corrects the width of the drive pulse according to the temperature data output from the temperature data creation unit.