JPH07125290A - Density gradation control type thermal printer - Google Patents

Abstract

PURPOSE:To accurately regenerate desired density gradation on a record sheet by providing means for calculating a coefficient for representing thermal influence at a recording time by linear approximation and calculating thermal influence of a near heat generating resistance element for a heat generating resistance element during recording from a supply heat quantity to the near element and the coefficient of the influence. CONSTITUTION:Correction means 1 for correcting application energy to a heat generating resistance element during recording at each area based on an approximate coefficient value obtained by a coefficient for representing thermal influence degree as linear approximation at dividing points of start and end of each area by dividing a conducting time of each pixel to the elements R1-R512 during recording into one or two divided regions is provided as calculating means for calculating a coefficient for representing thermal influence from the near element at the element during recording. As a result, no variation in the density gradation due to the thermal influence from the near element of the element during recording occurs, and desired temperature gradation can be accurately reproduced on a record sheet.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a density gradation control type thermal printer.

[0002]

2. Description of the Related Art Generally, the energy applied to each heating resistor element corresponding to the density of a recording pixel printed by a thermal printer determines the heat generation amount of each heating resistor element to determine the density of a desired recording pixel. It is an important parameter as it occurs. This important applied energy is obtained by controlling the applied energy to each heat generating resistance element in accordance with the input density gradation.

Conventionally, as shown in FIG. 4, the structure of a thermal printer of this type is such that a thermal head 10 has a heating resistor 12 in which heating resistors R1 to R512 are arranged in a line.
And a shift register 14 and a latch circuit 16 having a capacity for supplying the same number of bit signals corresponding to the respective heating resistance elements. On the other hand, the data Din is input to the line buffer 22 of the input unit and the density gradation data of each pixel of one printing line is stored. Where Di
a1j to a512j of n are pixels of one line, for example, 51
When two lines are arranged and a plurality of such lines are arranged, a1 to a512 represent the density gradation of each pixel, and j represents the current input line number. The density gradation data of each pixel of the line buffer 22 is converted into energization timing data 36A by a density / energization timing conversion circuit 36 and is multiplied by a coefficient Ck described later, and stored in the energization timing buffer 20. The energization timing buffer 20 keeps the heat generation resistance elements R1 to R51 during the printing time of each printing line.
The serial energization timing data corresponding to 2 is sequentially given to the shift register 14. This application period is a constant period and is given according to the count value of the plural times energization counter 38.

When the gradation data of each time is loaded into the shift register 14 in synchronization with the clock signal CK from the clock circuit 30, the timing of the latch signal LA from the latch signal generating circuit 32 is next passed through the latch circuit 16. And sent to the heating resistor 12. A voltage VR applied to the heating resistor elements R1 to R512 is applied to the heating resistor 12 from the power supply device 50. These applied voltages VR generate heat by selectively energizing for a unit energizing cycle ΔT time according to the information content of the corresponding gradation bit. C
The PU 40 controls the operation procedure of these circuit systems.

Here, the operation of the density / energization timing conversion circuit 36 and the thermal head 10 will be described with reference to FIGS. First, FIG. 6 is a characteristic diagram showing the relationship between the density gradation G to be recorded and the heating resistor element temperature, FIG. 7 is an explanatory diagram showing the steps of the heating resistor element temperature with respect to the recording time of one line and the energization time, and FIG. FIG. 5 is an explanatory diagram showing the presence / absence of energization and the number of times of energization for each pixel to the heating resistance element, and FIG. 5 is a timing chart showing the energization timing data 20, the energization cycle ΔT for each pixel, and the energization time te.

In FIG. 6, recording density gradation G (gradation) input as density data 22A on the vertical axis.
On the other hand, the horizontal axis shows the stage T of the heating resistance element temperature required for each pixel. Here, a case of recording density gradation G of 64 steps is shown. In order to obtain the heating resistance element temperature described in FIG. 6 for each pixel, one line is composed of 512 pixels, and as shown in FIG.
The heating resistance element temperature determined for every four gradations is required. As shown in FIG. 8, this temperature is divided into 512 heating elements, 512 in this example, the number of times of energization. When the temperature is “1”, energization is performed, and when the temperature is “0”, no temperature is applied. Energization is controlled to secure the temperature of the heating resistor element in FIG. 7 for a total of 512 times. The unit time of one energization is set to the unit energization cycle ΔT. The number of times of energization is counted by the number of energization counter 38. The energization timing buffer 20 outputs the energization timing data 20A that is turned on and off for each unit energization cycle ΔT shown in FIG. 5 via the concentration / energization timing conversion circuit 36.

The unit energization cycle ΔT is defined by the latch signal LA. The strobe signal ST from the strobe signal generation circuit 34 is determined by the energization enable time that actually flows through the heating resistance element for each unit energization cycle ΔT.
Is controlled by. 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 designed to rise to the temperature of the heating resistor element to which gradation is applied.

In this conventional example, a normal density gradation can be obtained when the temperature of the heating resistor element is controlled only by the energizing power during the energization enable time of the heating resistor element itself. However, in reality, an unnecessary temperature rise occurs due to the influence of the heat of the adjacent heat generating resistor element. FIG. 9 shows this state diagram. That is, the temperature when the self-heating resistor is not energized is (e), and the temperature when the neighboring heating resistor is energized and the temperature is rising within the energizing time is (c). Here, the self-heating resistor is affected by the temperature of the adjacent thermal resistance element shown in (c) and rises from the temperature (e) to the temperature (d). Therefore, not the normal gradation density but the abnormal density occurs due to the temperature (d). As another conventional example for solving the problem of this abnormal concentration, Japanese Patent Application No. 3-241567 is available.
A "density gradation control type thermal printer" is known.
This conventional example is provided with means for canceling the thermal influence of the neighboring heating resistance element on the heating resistance element during recording in the self-heating resistance element during recording in the printing line which is currently being recorded. That is, 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. Specifically, the calculation means of the thermal effect from the neighboring heating resistance element to the heating resistance element during recording, and the applied energy in the printing line currently being recorded from each neighboring heating resistance element to the printing line being recorded And a means for multiplying by a coefficient indicating the magnitude of the thermal effect exerted, so that the energy applied to the heating resistance element during recording is corrected. That is, as shown in FIG. 10, the temperature (f) to be corrected limits the energy applied to the self-heating resistor so that the temperature (f) should be corrected at a constant temperature from time 0 to tl. In the state corrected by this applied energy, as shown in the corrected self-heating resistor temperature (g), the temperature is corrected close to the temperature (e), but the left side is overcorrected and the right side is corrected with time t1 as a boundary. There was a shortage.

[0009]

This conventional density gradation control type thermal printer is provided with means for obtaining the degree of thermal influence of the adjacent heating resistance element on the self-heating resistance element and correcting this influence degree. However, the correction means maintains a constant correction amount of the energy applied to the heating resistor element during recording against the thermal influence from the neighboring heating resistor element over the entire energization time from the start time to the end time of the energization time of the nearby heating resistor. Therefore, there is a drawback that it is not possible to accurately correct the thermal influence from the neighboring heating resistance element that changes momentarily during the energization time.

An object of the present invention is to provide a thermal printer capable of obtaining a printed image of high print quality without fluctuations in density gradation due to thermal influences from neighboring heating resistance elements with respect to each heating resistance element. .

[0011]

A density gradation control type thermal printer of the present invention controls the energy applied to a heating resistor element formed in a thermal head to control the color density of a thermal paper or an ink sheet on a recording paper. It is a thermal printer that controls the transfer density of the ink to the printer.
The heating resistance element during recording is adjusted so that the pixels to be recorded have a desired density gradation in accordance with the thermal influence on the heating resistance element during recording from a plurality of heating resistance elements in the vicinity that are simultaneously recorded. In the density gradation control type thermal printer that corrects the energy applied to the heating resistor element, one or a period of energization time to the heating resistor element is calculated as a calculation means of the thermal influence from the neighboring heating resistor element on the heating resistor element during recording. Each area is divided into a plurality of areas, each of which has a coefficient representing the degree of thermal influence of each heating resistance element in the vicinity at the start point and the end point of each area on the heating resistance element during recording, and each divided area. In the middle time, from the coefficient indicating the thermal influence from each neighboring heating resistance element at the start point and the end point of the area, the coefficient indicating the thermal influence at the recording time is calculated by linear approximation. Near Characterized in that it comprises means for calculating the thermal influence from the neighboring heating resistance element and a coefficient of heat supplied thermal influence of the heating elements for heating resistance elements in the recording. Further, the energization time to the heating resistance element is divided into two or more, and one coefficient representing the degree of thermal influence of each heating resistance element in the vicinity in each divided area on the heating resistance element during recording. And the heat from the neighboring heating resistor element to the heating resistor element being recorded is multiplied by a coefficient representing the degree of thermal influence from each neighboring heating resistor element in the divided area and the amount of heat supplied to each neighboring heating resistor element. It is characterized by comprising means for calculating a physical influence.

[0012]

The present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of a first embodiment of the present invention.

In FIG. 1, the same reference numerals as those in the conventional example of FIG. 4 have the same configuration and function. That is, in the first embodiment, the heat influence degree calculation circuit 1 is added. The heat influence degree calculation circuit 1 performs the calculation for correcting the heat influence degree from the neighboring heating resistor 12 to the self-heating resistor, but the difference from the conventional correction means is shown in the state diagram of FIG. Shows. That is, in the conventional example of FIG. 10, the temperature (f) to be corrected is constant over the entire energization time region, but in the embodiment of FIG. 2, as shown by the approximate value (a), the correction amount is approximated by the divided regions ( It is adjusted according to a). That is, in the case where there is a temperature increase (c) due to heating of one of the adjacent adjacent left and right heat generating resistance elements shown in FIG. 2 and a temperature increase (d) due to the thermal effect of the self-heating resistance element to be corrected accompanying this. In addition, the calculation of the degree of thermal influence of each heat generating element on the adjacent heat generating resistor element is performed, for example, if correction is made for one adjacent left and right element, the heat generating resistor element R1 of the heat generating resistor 12 is used.
-Each left and right one element Rn of the element Rn of R51-
1. Determine the thermal impact from 1 and Rn + 1. The heat influence degree calculation circuit 45 determines that the heat generation resistance element Rn− adjacent to the elapsed time Δt from the energization start time in the printing line during recording is adjacent to the heat generation resistance element Rn−.
1. Energy applied to Rn + 1, Qn-1, Qn + 1
For example, if the energization time t1 is divided into two by the elapsed time tk after the start of energization, the adjacent left and right one element Rn-1
Of the applied energies Qn-1 and Qn + 1 to Rn + 1 and Rn + 1, the division points A1, A2, B1 are transmitted to the heat generating element to be corrected at the boundaries between the division areas A and B.
Coefficient a indicating the ratio of the amount of heat of each of 1, A2 and B1
When (0), a (tk), and a (tl) are obtained, the thermal influence degree ΔQn (Δt) can be obtained from Equation 1 and Equation 2. Equations 1 and 2 are the elapsed time Δt from the energization start time (time 0).
Selected by.

(0 ≦ Δt <tk) ΔQn (Δt) = a (0) · (Qn−1 + Qn + 1) + a (tk) − (a (0) / Δt) · (Qn−1 + Qn + 1) (Formula 1) ( tk ≦ Δ ≦ tl) ΔQn (Δt) = a (tk) · (Qn−1 + Qn + 1) + {a (tl) −a (tk)} / {(Δt−tk)} · (Qn−1 + Qn + 1) (Formula 2) ) In each energization cycle, the thermal influence degree ΔQn (Δt) to be corrected by the current energization cycle and the thermal influence degree ΔQni (Δti) corrected by the previous energization cycle
The difference Δqnji with the difference Δqnji is compared with the heat quantity Δqnj of the difference supplied in this energization cycle. If Δqnji is equal to or greater than Δqnj, the gradation data of the nth dot in the energization cycle is not energized “0”. To correct the thermal influence from the adjacent left and right elements. By performing the same process for all the energization cycles of all the heating resistance elements, the energization timing data [Ck P1j to Ck P5 of each heating resistance element is obtained.
12j] is corrected to obtain corrected energization timing data [Cak P1j to Cak P512j] 45A.

Corrected energization timing data [Cak
P1j to Cak P512j] 45A is stored in the energization timing buffer 20.

As described above, the density gradation data is corrected according to the energization timing data 20B by correcting the thermal influence from the heat generating resistance elements near the heat generating resistance elements, and each heat generating resistance element (R1 to R512). ) To electricity. As a result, each of the heating resistance elements R1 to R512 records a density gradation that matches the density gradation data on the recording paper in the applied energy.

Next, a second embodiment of the present invention will be described with reference to the state diagram of FIG. In FIG. 3, if the temperature rise due to the degree of thermal influence from the nearby heating resistor to the self-heating resistor is (i) and (d), and the energization time is tl, this energization time tl
Is divided into a divided region (c) corresponding to a temperature rise (i) with a small temperature rise and a divided region (d) corresponding to a temperature rise (d) with a large temperature rise. Here, the divided area (c) is applied energy (area of hatch in the figure) corresponding to temperature rise (i).
The area PQRS equivalent to is calculated, and a constant coefficient corresponding to PQ is corrected as an approximate value (h). Also in the divided area (d), the area STUV equivalent to the applied energy (dotted line hatch in the figure) corresponding to the temperature rise (d) is calculated, and a constant coefficient corresponding to ST is corrected as the correction value (b). The calculation of this correction is performed by the heat influence degree calculation circuit 1 in FIG. 1, but since the coefficient a (tk) of (Equation 1) and (Equation 2) has a constant value in each region, the calculated ΔQn The calculation of (Δt) is also simplified. The second embodiment is applied when there is little thermal influence from the nearby heating resistor. Specifically, it is suitable when the gradation of the density gradation data is entirely low.

[0019]

As described above, the present invention has the following effects by including the heat influence degree calculation circuit. The coefficient of influence is calculated for each dividing point in the area where the thermal effect from the adjacent heating resistance element to the self-heating resistance element during recording changes, and the applied energy is corrected for each area to obtain the desired density gradation. Can be reproduced with high accuracy on recording paper. Further, when the thermal influence is small, it is possible to easily realize a desired density gradation by correcting the constant applied energy in each of the regions having a large thermal influence and the regions having a small thermal influence in the energization cycle time. There is also an effect.

[Brief description of drawings]

FIG. 1 is a block diagram common to the first and second embodiments of the present invention.

FIG. 2 is a state explanatory view of the first embodiment.

FIG. 3 is a state explanatory view of the second embodiment.

FIG. 4 is a block diagram of a conventional density gradation control type thermal printer.

FIG. 5 is a timing chart of a general energization cycle time.

FIG. 6 is an explanatory diagram of a recording density of temperature of a general heating resistance element.

FIG. 7 is an explanatory diagram of general energization time and heating resistor element temperature.

FIG. 8 is an explanatory diagram of a general energization counter.

FIG. 9 is a state explanatory view of a conventional example.

FIG. 10 is a state explanatory view of another conventional example.

[Explanation of symbols]

 1 Thermal Impact Calculation Circuit 10 Thermal Head 12 Heating Resistor 14 Shift Register 16 Latch Circuit 20 Energization Timing Buffer 22 Line Buffer 30 Clock Circuit 32 Latch Signal Generation Circuit 34 Strobe Signal Generation Circuit 36 Density / Energization Timing Conversion Circuit 38 Energization Counter 40 CPU 50 Power supply circuit

Claims (2)

[Claims] 1. A thermal printer which controls the color density of thermal paper or the transfer density of ink from an ink sheet to a recording paper by controlling the energy applied to a heating resistance element formed in a thermal head. Regarding the heating resistance element during recording of the printing line inside, the pixel to be recorded has a desired density level in accordance with the thermal influence from a plurality of heating resistance elements in the vicinity that are simultaneously recorded to the heating resistance element during recording. In a density gradation control type thermal printer that corrects the energy applied to the heating resistance element during recording so as to obtain the same gradation, the calculation of the thermal influence from the neighboring heating resistance element on the heating resistance element during recording. As a means, the energization time to the heating resistance element is divided into one or a plurality of regions, and the heating resistors in the vicinity of the start point and the end point of each region are divided. Each of the anti-elements has a coefficient representing the degree of thermal influence on the heating resistance element during the recording, and at the time in each divided area, the thermal resistance from each neighboring heating resistance element at the start point and the end point of the area is set. From the coefficient indicating the degree of influence, the coefficient indicating the degree of thermal influence at the recording time is calculated by linear approximation, and the heat generation resistance during the recording is calculated from the amount of heat supplied to each neighboring heating resistance element and the coefficient of thermal influence. A density gradation control type thermal printer comprising means for calculating a thermal influence of a neighborhood heating resistance element on the element. 2. A thermal printer for controlling the color density of thermal paper or the transfer density of ink from a recording sheet to a recording sheet by controlling the energy applied to a heating resistance element formed on a thermal head. Regarding the heating resistance element during recording of the printing line inside, the pixel to be recorded has a desired density level in accordance with the thermal influence from a plurality of heating resistance elements in the vicinity that are simultaneously recorded to the heating resistance element during recording. In a density gradation control type thermal printer that corrects the energy applied to the heating resistance element during recording so as to obtain the same gradation, the calculation of the thermal influence from the neighboring heating resistance element on the heating resistance element during recording. As a means, the energization time to the heating resistance element is divided into two or more, and each heating resistance element in the vicinity of each divided area is in the recording state. It has one coefficient representing the degree of thermal influence on the heating resistance element, and is multiplied by the coefficient representing the degree of thermal influence from each neighboring heating resistance element in the divided area and the amount of heat supplied to each neighboring heating resistance element. A density gradation control type thermal printer comprising means for calculating a thermal influence from a neighboring heating resistance element on a heating resistance element during recording.