JPH0679903A - Density gradation control type thermal printer - Google Patents

Abstract

PURPOSE:To obtain an image recorded in high image printing quality without variations in density gradation due to thermal influences to be caused by heating resistance elements in a vicinity by correcting applied energy in accordance with thermal influences to be exerted on heating resistance elements during recording operation. CONSTITUTION:A thermal head 10 is provided with a heating resistor 12 consisting of, for example, 512 pieces of heating resistance elements R1 to R512 arranged in a row, a shift register 14 having the same number (512) of bit capacities, and a latch circuit 16. During a period of image printing time for each image printing line, a power supply timing buffer 20 gives serial correction power supply timing data c'KP 1j to c'KP 512j on 512 bits with respect to 512 pieces of the heating resistance elements R1 to R512, respectively, to the shift register 14 in a predetermined period and in the number of plural times, for example, 256 times in succession, according to a value K counted by a counter 38 for the number of times of power supply.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal printer capable of obtaining a desired density gradation by controlling the energy applied to a heating resistance element.

[0002]

2. Description of the Related Art In a thermal printer, the energy applied to each heating resistance element is an important parameter that determines the amount of heat generated by each heating resistance element, and thus determines the density of a recording pixel.

Therefore, conventionally, the applied energy during the unit energization time is controlled in accordance with the density gradation of the input to control the temperature of the heat generating resistance element.
The density gradation was controlled.

FIG. 6 shows a main structure of a conventional density gradation control type thermal printer.

The thermal head 110 includes a heating resistor 112 having heating resistors arranged in a line, and a shift register 11 having the same number of bit capacities as the heating resistors.
4 and a latch circuit 116 are provided.

In the line buffer 122, the density gradation data of each pixel of one printing line is input from the data input Din and stored. The density gradation data of each pixel of the line buffer 122 is the density-energization timing conversion circuit 136.
Thus, it is converted into energization timing data and stored in the energization timing buffer 120.

The energization timing buffer 120 continuously shifts the serial energization timing data corresponding to the heating resistance element a plurality of times in a constant cycle during the printing time of each printing line according to the count value of the energization number counter 138. Give to.

The gray scale data for each time is synchronized with the clock signal CK from the clock circuit 130, and the shift register 114
Then, it is sent to the heating resistor 112 via the latch circuit 116 at the timing of the latch signal LA from the latch signal generating circuit 132. This heating resistor 11
A power supply device 150 supplies a recording power supply voltage VR to the heating resistor element 2. Then,
These heating resistance elements selectively output the unit energization cycle ΔT according to the information content of the corresponding gradation bit.
Generates heat by energizing inside.

The unit energization cycle ΔT is defined by the latch signal LA. The strobe signal ST from the strobe signal generating circuit 134 in the unit energization cycle ΔT controls the energization enable time during which the current actually flows through the heating resistance element. The energization enable time can have different values for each unit energization cycle. The energization enable time of each unit energization cycle is the highest level of density for each pixel on one printing line, because energization is instructed in all unit energization cycles during the energization time of one printing line. It is set so as to rise to the temperature of the heating resistor element to which gradation is applied.

With the above structure, according to the density gradation data of each pixel on one printing line, the current is converted into the energization timing data which becomes the temperature of the heating resistor element for obtaining the target density gradation, and the current is energized to record. Done.

[0011]

However, in the density gradation control type thermal printer which controls the temperature of the heat generating resistance element in accordance with the density gradation of the input as described above, the heat of the heat generating resistance element during recording causes heat generation. The heat is transferred to the periphery of the resistance element, and the temperature of the periphery of the heat generation resistance element during recording rises including the temperature of the adjacent heat generation resistance element.

As described above, each heating resistor element has a thermal effect on the amount of heat generated by the heating resistor elements adjacent to each other.

Therefore, even if the heating resistance element temperature of each heating resistance element is controlled in accordance with the input density gradation, the heating resistance element temperature fluctuates due to the thermal effect from the heating resistance element in the vicinity thereof. There is a problem that a desired density gradation cannot be accurately reproduced on the recording paper.

The present invention has been made in view of the above problems, and in each heat generating resistance element, there is no variation in the density gradation due to the thermal influence from the heat generating resistance elements in the vicinity, and a printed image of high print quality can be obtained. An object is to provide a density gradation control type thermal printer.

[0015]

In order to achieve the above-mentioned object, the first density gradation control type thermal printer of the present invention has a heating resistor element in the vicinity of the heating resistor element in the printing in the printing line in the recording. The energy applied to the heating resistor element during recording is adjusted so that the pixels recorded by the heating resistor element during recording have a desired density gradation in accordance with the thermal effect of the resistor element on the heating resistor element during recording. It is configured to include means for correcting

In the second density gradation control type thermal printer of the present invention, the target heating resistance element temperature is changed against the fluctuation of the heating resistance element temperature of the heating resistance element during recording due to the thermal influence of the neighboring heating resistance element. It is configured to include a means for correcting the above.

In the third density gradation control type thermal printer of the present invention, the density gradation fluctuation due to the fluctuation of the heating resistance element temperature of the heating resistance element during recording due to the thermal influence of the neighborhood heating resistance element is In order to obtain a desired density gradation, the constitution is provided with a means for correcting the energization time for applying energy to the heating resistance element during recording.

In the fourth density gradation control type thermal printer of the present invention, as a means for calculating the thermal influence of the neighboring heating resistor element on the heating resistor element during recording, the neighboring heating resistor elements are currently recording. The applied energy in the printing line is multiplied by a coefficient that indicates the magnitude of the thermal effect on the printing line during recording to obtain the thermal effect degree of each neighborhood heating resistor element, and the thermal influence degree is calculated as the neighborhood heating resistance. A configuration is provided in which a unit is added to calculate the thermal influence from the neighboring heating resistance element on the heating resistance element during recording.

[0019]

The first density gradation control type thermal printer of the present invention is adapted to the thermal influence from the heat generating resistor element in the vicinity of the heat generating resistor element during recording on the print line during recording to the heat generating resistor element during recording. Then, the energy applied to the heating resistor element during recording is corrected so that the pixel recorded by the heating resistor element during recording has a desired density gradation.

In the second density gradation control type thermal printer of the present invention, the target heating resistance element temperature is changed against the fluctuation of the heating resistance element temperature of the heating resistance element during recording due to the thermal influence of the neighboring heating resistance element. Correct the error between and.

In the third density gradation control type thermal printer of the present invention, the density gradation fluctuation due to the fluctuation of the heating resistance element temperature of the heating resistance element during recording due to the thermal influence of the neighborhood heating resistance element, In order to obtain a desired density gradation, the energization time is corrected so that a target density gradation can be obtained with the heating resistor element temperature including an error.

In the fourth density gradation control type thermal printer of the present invention, as a means for calculating the thermal influence of the neighboring heating resistor element on the heating resistor element being recorded, the neighboring heating resistor elements are currently recording. The applied energy in the printing line is multiplied by a coefficient that indicates the magnitude of the thermal effect on the printing line during recording to obtain the thermal influence degree of each heating element in the vicinity, and the thermal influence degree is further calculated in the neighborhood heat generation. From the first aspect of the present invention based on the degree of thermal influence from the plurality of neighboring heating resistance elements, the thermal influence from the neighboring heating resistance elements on the heating resistance element during recording is calculated by adding for the resistance elements. Correction is performed by the third density gradation control type thermal printer.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the main structure of a density gradation control type thermal printer according to an embodiment of the present invention.

The thermal head 10 includes, for example, a heating resistor 12 formed by arranging 512 heating resistor elements R1 to R512 in a line, a shift register 14 having the same number (512) of bit capacities as those heating resistor elements, and And a latch circuit 16.

The energization timing buffer 20 has 512 heating resistance elements R1 to R51 during the printing time of each printing line.
The 512-bit serial correction energization timing data [C'K P1j to C'K P512j] corresponding to 2 is counted a plurality of times in a constant cycle, for example, 256 times (K = 1 to 256) continuously in the energization number counter 38. It is given to the shift register 14 according to the value (K).

Here, the nth bit CK Pnj has information as to whether or not the nth heating resistor element Rn should be energized during the unit energization cycle ΔT. That is, if "1", the energization is instructed, and if "0", the non-energization is instructed.

When the grayscale data of each time is loaded into the shift register 14 in synchronization with the clock signal CK from the clock circuit 30, each grayscale bit C'at the timing of the latch signal LA from the latch signal generating circuit 32. K P1j ~
C′K P512j is sent to the heating resistor 12 as an electric pulse via the latch circuit 16. A recording power supply voltage VR to be applied to the heating resistance elements R1 to R512 is applied to the heating resistor 12 from the power supply device 50. Then, the heating resistance elements R1 to R512 selectively generate electricity during the unit energization cycle ΔT according to the information content of the corresponding grayscale bits C′K P1j to C′K P512j to generate heat.

This unit energization cycle ΔT is defined by the latch signal LA. Unit energization cycle ΔT
As shown in FIG. 2, the strobe signal ST from the strobe signal generating circuit 34 is composed of an energization enable time tE and a time tC during which the current actually flows through the heating resistance element. The energization enable time tE can have different values for each unit energization cycle. The energization enable time tE of each unit energization cycle is, for example, 64 steps (e.g., 64 steps) for each pixel on one printing line when energization is instructed in all the unit energization cycles during the energization time of one printing line. As shown in FIG. 4, up to the heating resistor element temperature (T = 63) that gives the highest level (G = 63) as shown in FIG. 3 among the density gradations at equal intervals (G = 0 to 63), In addition, the heating resistor element temperature is set to rise. The strobe signal ST is input to the thermal head 10.

In the line buffer 22, density gradation data (a1j to a512j) of each pixel of one printing line is input from the data input Din and stored. Line buffer 22
The density gradation data (a1j to a512j) of each pixel of
It is transferred to the energization timing conversion circuit 36, and is converted into energization timing data [CK P1j to CK P512j] in the density-energization timing conversion circuit 36.

Energization timing data [CK P1j to CK P
512j] gives density gradation (G = 0 to 63) suitable for density gradation data (a1j to a512j) to each heating resistance element when each heating resistance element generates heat independently. In order to reach the heating resistance element temperature (T = 0 to 63), it is determined whether to energize ("1") or de-energize ("0") in each unit energization cycle as shown in FIG. The energization timing data [CK P1j to CK P512j] is transferred to the heat influence degree calculation circuit 45.

The thermal influence degree calculation circuit 45 records from the energization timing data [CK P1j to CK P512j] input from the concentration-energization timing conversion circuit 36 and the energization enable time tE input from the strobe signal generation circuit 34. The energy applied to each heating resistance element in the printing line inside is calculated, and the thermal effect that each heating element during recording exerts on the neighboring heating resistance element from the energy applied to each heating resistance element in the printing line during recording. Ask for degrees.

Here, the calculation of the degree of thermal influence of each heat generating element on the heat generating resistance element in the vicinity is performed by, for example, calculating the left and right sides of adjacent ones.
If the element is to be corrected, for example, the energy applied to each adjacent heating resistance element is multiplied by a coefficient indicating the ratio of the amount of heat transferred to the adjacent heating resistance element.

Next, from the degree of thermal influence of each heating element on the neighboring heating resistor elements, the degree of thermal influence on each heating resistor element from the neighboring heating resistor elements is calculated, and based on this, each heat generation is calculated. In order to correct the energy applied to the resistance elements, the energization timing data [CK P1j to CK of each heating resistance element is used.
P512j] and correct energization timing data [C'K
P1j to C'K P512j].

Here, the calculation of the thermal influence degree and the correction energization timing data [C'K P1j to C'K P512j] that each heating resistance element receives from the neighboring heating resistance elements is performed for, for example, one adjacent left and right element. If the correction is performed by the correction, for example, the thermal influences of the left and right heating elements on the adjacent heating resistance elements are added, and the thermal influences of the left and right heating resistance elements are obtained. Corrected energization timing data [C'K P1j to C'that gives the required energy during the energization time by subtracting the thermal effect from the left and right heating resistors from the applied energy of the heating resistor to be corrected to obtain the required applied energy. K P51
2j].

Corrected energization timing data [C'K P1j ~
C′K P512j] is stored in the energization timing buffer 20.

As described above, the density gradation data (a1j to a1
512j) to correct the thermal effect from the heat generating resistance elements near each heat generating resistance element and to correct the energization timing data [C'K
P1j to C'K P512j], and each heating resistor element (R1 to R512) is energized according to the corrected energization timing data [C'K P1j to C'K P512j]. As a result, each of the heating resistance elements (R1 to R512) has a density gradation (G = 0 to 6) that matches the density gradation data (a1j to a512j) during the energization time.
3) The heating resistor element temperature (T = 0 to 63) is obtained, and recording is performed on the recording paper with the desired density gradation.

[0037]

The present invention has the following effects by having the above-mentioned structure.

According to the thermal printer of the first aspect, the heat generating resistance element being recorded in the printing line being recorded is recorded in accordance with the thermal influence from the neighboring heat generating resistance element to the heat generating resistance element being recorded. By correcting the energy applied to the heating resistance element during recording so that the pixel has the desired density gradation, there is no fluctuation in the density gradation due to the thermal effect from the neighboring heating resistance element, and the desired density It becomes possible to reproduce the gradation on the recording paper with high accuracy, and a recorded image of high print quality can be obtained.

According to the thermal printer of the second aspect, an error from the target heating resistance element temperature is corrected with respect to the fluctuation of the heating resistance element temperature of the heating resistance element during recording due to the thermal influence of the neighboring heating resistance element. By doing so, it is possible to reproduce the desired density gradation on the recording paper with high accuracy without changing the temperature of the heating resistor element due to the thermal effect from the neighboring heating resistor element, and to obtain a printed image of high print quality. Is obtained.

According to the thermal printer of the third aspect, a desired density gradation can be obtained against the fluctuation of the density gradation due to the fluctuation of the temperature of the heating resistance element of the heating resistance element during recording due to the thermal influence of the neighboring heating resistance element. Therefore, even if the heating resistor element temperature is different from the target heating resistor element temperature by correcting the energization time so that the target density gradation is obtained with the heating resistor element temperature including an error, It is possible to reproduce the density gradation of No. 2 on the recording paper with high accuracy, and a recorded image with high printing quality can be obtained.

According to the thermal printer of the fourth aspect, as a calculation means of the thermal influence from the neighboring heating resistor element on the heating resistor element during recording, the energy applied to each neighboring heating resistor element at the printing line currently being recorded is used. In contrast, the coefficient indicating the magnitude of the thermal effect on the printing line during recording is multiplied to obtain the thermal effect degree of each neighboring heating resistor element, and the thermal influence degree is added for each neighboring heating resistor element. hand,
The thermal influence from the neighboring heating resistor elements on the heating resistor element during recording is calculated, and the first to third density gradation control of the present invention is performed based on the thermal influence degree from the plurality of neighboring heating resistor elements. By correcting with a thermal printer, it is possible to reproduce desired density gradations on recording paper with high accuracy without fluctuations in density gradations due to thermal effects from nearby heating resistance elements. A print image of print quality can be obtained. .

[Brief description of drawings]

FIG. 1 is a block diagram showing a main circuit configuration of a density gradation control type thermal printer according to an embodiment of the present invention.

FIG. 2 is a diagram showing the timing of a unit energization cycle according to the embodiment.

FIG. 3 is a diagram showing a heating resistance element temperature-recording density characteristic by density gradation control.

FIG. 4 is a diagram showing a change in temperature of a heating resistance element during recording of one printing line.

FIG. 5 is a diagram showing the contents of an energization timing buffer according to the embodiment.

FIG. 6 is a block diagram showing a main circuit configuration of a density gradation control type thermal printer according to a conventional example.

[Explanation of symbols]

 10 Thermal Head 12 Heating Resistor 20 Energization Timing Buffer 36 Density-Energization Timing Conversion Circuit 38 Energization Counter 40 CPU

Claims (4)

[Claims] 1. A thermal printer for controlling the color density of a thermal paper or the transfer density of ink from an ink sheet onto a recording paper by controlling the energy applied to a plurality of heating resistance elements formed on a thermal head, In a density gradation control type thermal printer for controlling the temperature of the heating resistance element in accordance with the density gradation of an input, the heating resistance element corresponding to the printing line currently being recorded is constant. In accordance with the thermal effect from the heat generating resistor element in the vicinity, so that the pixel recorded by the heat generating resistor element during recording has a desired density gradation,
A density gradation control type thermal printer comprising means for correcting the energy applied to the heating resistance element during recording. 2. A means for correcting a variation in temperature of the heating resistance element of the heating resistance element during the recording due to a thermal effect of the neighboring heating resistance element to a target heating resistance element temperature. The density gradation control type thermal printer according to claim 1. 3. A desired density gradation is obtained in response to a change in density gradation due to a change in temperature of the heating resistance element of the heating resistance element during recording due to a thermal effect of the neighboring heating resistance element. 2. The density gradation control type thermal printer according to claim 1, further comprising means for correcting an energization time for applying energy to the heating resistance element during the recording. 4. As a means for calculating the thermal influence of the neighboring heating resistor element on the heating resistor element during recording, the recording energy for the applied energy in the printing line of each neighboring heating resistor element is being recorded. During the recording, the coefficient of thermal influence on the printing line is multiplied to obtain the degree of thermal effect of each neighboring heating resistor element, and the degree of thermal influence is added for each neighboring heating resistor element. 2. The density gradation control type thermal printer according to claim 1, further comprising means for calculating a thermal influence of the neighboring heating resistance element on the heating resistance element.