JPH09314882A - Thermal head, thermal head driving circuit, and thermal printer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize the printing quality in high speed printing by controlling the heat history of printing in a thermal head, a thermal head driving circuit and a thermal printer. SOLUTION: A thermal head is produced by providing a printing heat generating member a1 for printing on a paper, and a heat generation compensating member a2 for heating the heat generating member al on the same head adjacent to each other. In particular, the heat generation compensating member a2 is placed at the rear side of the printing heat generating member when viewed from the printing surface of the printing heat generating member. Furthermore, a thermal head driving circuit where data with the logic of the previously printed data inverted are transferred to a data latch circuit for driving the heat generation compensating member a2 of the thermal head, and a thermal printer using the thermal head and the thermal head driving circuit are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head, a thermal head drive circuit, and a thermal printer, in which thermal quality control of printing is performed to stabilize printing quality during high-speed printing.

In a thermal printer, as the printing speed increases, the heat storage effect of the heating element of the thermal head greatly affects the previous driving state of the heating element. For example, when a large number of heating elements are arranged in a line on the thermal head and the paper is fed in a direction perpendicular to the line,
Let us focus on one specific point on the line.

When printing is performed on the line immediately before, the heat of the heating element remains and the temperature is not lowered sufficiently. The temperature is appropriately lowered. Therefore, the temperature of the heating element during printing varies depending on the driving state of the heating element in the past (mainly immediately before), and the printing result is not uniform.

Therefore, in order to obtain stable printing quality, it is necessary to take measures to keep the temperature of the heating element constant during printing. In other words, it is necessary to control the driving of the heating element for each heating element according to the driving state up to now.

[0005]

2. Description of the Related Art Next, the energization time is calculated based on the previous and previous driving states of the heating element to be printed and the driving states of the adjacent heating elements, and the individual heating elements are driven in accordance with this. At this time, it is necessary to control the energization time for each heating element.

Therefore, (1) the maximum energization time required for printing is divided, and the heating element is energized a number of times corresponding to the calculated energization time required for the target heating element, (2) heating element A measure such as providing an energization control circuit for each and controlling energization of the heating element according to the calculated time has been taken.

[0007]

According to the above-mentioned conventional measures, (1) when printing is performed by dividing the maximum energization time required for printing, the data is serially transferred to the thermal head by the divided number for each heating element. Since it is necessary to transfer data at a very high speed (several MHz or more), the number of data that can be transferred is limited depending on the printing speed and the printing width is limited. (2) Heating element There is a problem that the circuit becomes complicated to provide an energization control circuit for each.

The present invention provides a thermal head, a thermal head drive circuit and a thermal printer which do not cause the above problems.

[0009]

FIG. 1 is a structural diagram of a thermal head heating element portion according to the present invention. In the figure, a1 indicates a heating element for printing, and a2 indicates a heating element according to the present invention. b
Is an electrical insulator layer, which electrically insulates between a1 and a2, but conducts heat between them.

FIG. 2 is a block diagram of the drive circuit of the thermal head according to the present invention shown in FIG. In the figure,
A1 is a heating element array, and A2 is a heating correction element array. B1 is a drive circuit for controlling energization of each heating element which is a constituent element of the heating element array A1. B2 is a drive circuit for controlling energization of each heat generation correction body which is a constituent element of the heat generation correction body array A2.

C1 is a data latch circuit for selecting each heating element which is a constituent element of the heating element array A1. C2 is a data latch circuit for selecting each heat generation correction body which is a constituent element of the heat generation correction body array A2. D1 is a shift register for setting data in the latch circuit C1. D2 is a shift register that is connected in series to the shift register D1 and is used for setting data in the latch circuit C2.

E is an inverter for inverting the logic of the transfer data from the shift register D1. Further, S1 represents an energization control signal of the drive circuit B1, and S2 represents an energization control signal of the drive circuit B2.

Printing by the thermal head according to the present invention is performed as follows. That is, the data in the shift register D1 is cleared in the initial state, and the print data is transferred to the shift register D1 when the printing of the first line is executed next. When the transfer of the data for one line is completed, the data of the inversion of the clear data (that is, the energization of all the heating elements) is automatically transferred to the shift register D2, and at the same time, the heating element array A1 is energized by the energization control signal S1. The heating element array A2 is simultaneously energized by the signal S2.

Next, when printing the second line, the data of the second line is transferred to the shift register D1 and at the same time, the inverted data of the data of the first line is transferred to the shift register D2. In this case, focusing on one dot,
One heating correction element a2 paired with the heating element for printing a1 not energized in the first line is heated at the same time as the heating element for printing a1, and the heating element a1 for printing is energized in the first line. One heating correction body a2 forming a pair is not heated,
Printing is performed by the heat generated only by the printing heating element a1.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 3 is a diagram for explaining the operation of the present invention, showing the heat generation state of a particular printing heating element a1.

Since A1 is cleared at the initial stage, the heating element a1 for printing, which is an element thereof, is not heated, and the heating correction element a2 is energized during the first line printing, and the heating element for printing is also heated. A1 is also energized for printing. Therefore, the temperature of the heating element reaches the coloring temperature.

At the printing timing of the second line, the heating element does not completely radiate heat. In this case, the heating correction element a2 is turned off according to the data of the first line, and since the printing heating element a1 is not turned on, the temperature of the heating element is lowered.

In the third line, the heating element is in a low temperature state, but like the first line, the printing heating element a1 and the heating correction element a are used.
Since the two are simultaneously energized, the heating element reaches the heating temperature.
In the fourth line, the heating element temperature is at a high level because printing is performed in the third line.

In this case, the heating correction element a2 is not energized, and only the printing heating element a1 is energized so that the heating element rise is suppressed and the temperature is controlled to a predetermined temperature. Similarly, the temperature of the heating element is controlled according to the printing condition of the previous line to perform printing.

In the above example, the energization control signal S1 and the energization control signal S2 are controlled at the same timing to correct the print density at a constant cycle (speed). However, since the color development temperature varies depending on the type of paper, It is effective to set the heating time of the heat generation correction body of the thermal head independently of the heating time of the heat generation body of the thermal head according to the color development characteristics of the paper. That is, the energization time by the energization control signal S2 is designated independently of the energization time by the energization control signal S1.

Further, in the thermal printer, heat radiation conditions differ depending on the printing cycle. That is, as the printing speed increases, the heat storage effect of the heating element of the thermal head greatly affects the previous driving state of the heating element. The energization time for correction is controlled by the energization control signal S2 according to this time, and the density can be corrected according to the printing cycle (printing speed). For example, the slower the printing speed, the longer the energization time by the energization control signal S2 and the more the auxiliary heating is desired.

If a thermal printer is constructed by using the above-mentioned thermal head and the thermal head drive circuit, the driving condition of the heating correction body is determined by the presence or absence of printing of the immediately preceding printing line, and each line is uniform. Although it is expected that the print will be performed at a density, further improvement in quality can be expected by considering the accumulation effect (heat history) of whether or not the previous line is printed. Such a thermal printer can be realized by a configuration in which the energization time is adjusted by the energization control signal S2 in consideration of the heat history.

Both the heating element and the heating correction element described above can be most simply constituted by resistors, but the same effect can be obtained by combining the heating element and the heating correction element based on another heating principle. You can For example, it is conceivable that the heat generation correction body is a specific solid and is heated by a laser beam. Further, a modification is conceivable in which the heating element and the heating correction element are integrally formed of a resistor, the heating is performed by a normal electric signal, and the heating correction is performed by irradiating a laser beam.

[0024]

As described above, according to the present invention,
It is possible to perform heat history control without performing complicated calculations and without performing data transfer a plurality of times, to control the heating element temperature at a constant level, and to stabilize print quality. Further, since the data processing is simplified, the load on the CPU and the like can be reduced, and the printer can be speeded up easily.

[Brief description of drawings]

FIG. 1 is a structural diagram of a thermal head heating element portion.

FIG. 2 is a configuration diagram of a drive circuit.

FIG. 3 is an operation explanatory diagram.

[Explanation of symbols]

 a1 is a heating element for printing, a2 is a heating correction element, b is an electrical insulator layer, A1 is a heating element row, A2 is a heating correction element row, B1 is a driving circuit, B2 is a driving circuit, C1 is a latch circuit, C2 Is a latch circuit, D1 is a shift register, D2 is a shift register, E is an inverter, S1 is an energization control signal, and S2 is an energization control signal.

Claims (6)

[Claims] 1. A heating element for locally heating a printing portion for printing on a sheet and a heating correction element for adjusting a temperature of the heating element after heating are provided adjacent to each other on the same head. The thermal head that is characterized. 2. The thermal head according to claim 1, wherein the heat generation correction body is located at the back of the heat generation body when viewed from the printing surface of the heat generation body. 3. A data latch circuit for controlling electric power for heating a heat generation correction body of the thermal head, wherein the data latch circuit stores data obtained by inverting the logic of the data used in the previous printing. A thermal head drive circuit characterized by transfer. 4. The thermal head, wherein the heating time of the heating element of the thermal head can be set independently of the heating time of the heating element of the thermal head according to the color development characteristics of the paper. Head drive circuit. 5. A thermal head drive circuit, wherein the heat-correction body of the thermal head is controlled in accordance with an energization time in accordance with a drive cycle of the heat-generating body. 6. A thermal printer comprising the thermal head and the thermal head drive circuit.