JPH0449060A - Driving method for thermal head of heat transfer recorder - Google Patents

Abstract

PURPOSE:To obtain an accurate density printing even if the number of heat generating resistors is increased by deciding an application signal every value to be applied to the resistor according to a coefficient value of an area ratio to be printed and an application signal energy value before correction, and applying the energy to the resistor. CONSTITUTION:The number of heat generating resistors is counted by a first calculator 1, a transfer efficiency, a transfer efficiency coefficient and an applying pulse width after correct are obtained by a second calculator 2 based on it, and applied to a heat generating resistor 3. Here, the transfer efficiency Y(X) is an area ratio occupied by dots due to the heat generated from the resistor in an arbitrary zone on a recording medium. The efficiency W(X) of this case is represented by W(X) = Y(X)/Tmax, where the Tmax is the maximum transfer efficiency, and represented by an area ratio occupied at the maximum by dots in an arbitrary zone on the medium. The width P(X) after correction is obtained by P(X) = P0 X c/W(X), where P0 is an applying pulse width before correction, and c is a correction coefficient to be decided according to the relationship between a thermal head, a recording sheet and an ink sheet or thermal head and a heat sensitive recording sheet.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for driving a thermal head in a thermal transfer recording apparatus that performs printing by a thermal head.

(b) Conventional technology A plurality of heating resistors are provided in parallel on the thermal head of a thermal transfer recording device, and dot-shaped printing is performed on the recording medium by energizing the heating resistors and generating heat. It is now possible to do so.

A circuit diagram of the thermal head of the thermal transfer recording apparatus is shown in FIG. Further, R (i=0-1279) represents a heating resistor, r represents a common resistance, and r represents an FPC electrode resistance. From this circuit diagram, the voltage V applied to the heating resistor is
It is shown in the first equation that it is a function of the number n of heating resistors printed simultaneously, the common resistance value r, and the FPC 1 pole resistance value r.

■Two ~ 'FIXR/' (R+n r) =
(1) However, ~': Voltage applied to the heating resistor v8: Voltage applied to the thermal head R2 Resistance value of the heating resistor n: Number of heating resistors printed at the same time r: Difference between the common resistance value and the FPC electrode resistance value It is Japanese.

From the first equation, when the number n of heating resistors that generate heat at the same time increases, the sum r of the common resistance value and the FPCi polar resistance
If you do not make it as small as possible, a so-called voltage drop phenomenon will occur in which the voltage applied to the thermal head (8) will become small, the thermal head will no longer generate the desired heat, and the printed density on the recording medium will be low. turn into.

Using this thermal head, printing is performed while making the heat generating resistors print at a constant density while sequentially increasing the number of heat generating resistors that generate heat.

Figure 5 shows that the heating resistor has a temperature of 2
The actual printing density value by the heating resistor (shown on the vertical axis on the left side of the figure) and the number of heating resistors that generate heat (total heating resistors) when printing at a constant density at every 0 degrees (number).

The value in the figure, for example 20 degrees, is the 20th density from the thinnest side, and the value on the vertical axis on the left side of the figure is,
The density values on the recording medium for those density prints are expressed as OD values.

From the same figure, even if the heating resistor prints at a constant density,
It can be seen that as the number of heating resistors that generate heat increases, the printing density value of the heating resistor linearly decreases from the desired printing density value.

A method for correcting such a decrease in print density due to a voltage drop occurring in a heating resistor is disclosed in Chapter 4 of Dye Sublimation Thermal Transfer Recording Technology, Trikebbs (1988). However, in order to solve this problem, it is necessary to reduce the sum r of the common resistance value and the FPC electrode resistance value. To do this, the size of the ceramic substrate must be increased, etc., resulting in an increase in costs. .

Therefore, unless the sum r of the common resistance value and the FPC electrode resistance value is made small, as the number n of heating resistors that generate heat at the same time increases, the reduction in the printing density value due to the voltage drop phenomenon will continue to occur, and the thermal Accurate printing by the head will be hindered.

(c) Problems to be Solved by the Invention The present invention has been made in view of the above-mentioned problems, and provides a novel thermal printer that can obtain accurate density printing even if the number of heating resistors that generate heat is increased. The present invention provides a method for driving a head.

(d) Means for solving problems The present invention provides a means for solving the problem of heat generation on a recording medium due to the heat generated by the heat generating resistors when the number of heat generating resistors that generate heat is changed among the plurality of heat generating resistors on the thermal head. A printed area ratio coefficient is determined based on the printed area ratio within a given section, and the applied signal energy value applied to the heating resistor is determined from this coefficient value and the applied signal energy value before correction. It is characterized in that the energy is applied to the heating resistor.

(E) Operation While causing the heat generating resistors to perform constant density printing, the constant density printing is continued while simultaneously increasing the number of heat generating resistors that generate heat.

From this printing result, the area ratio of dots in any section on the recording medium, that is, the transfer efficiency, is determined, and from this transfer efficiency, the transfer efficiency coefficient is determined, and the pulse width of the applied signal applied to the heating resistor is determined. This applied signal is then applied to the heating resistor.

(f) Embodiment Figure 3 shows that while the heating resistor is printing at a constant density,
This is the relationship between the transfer efficiency and the total number of heat generating resistors when the number of heat generating resistors that generate heat is increased. Here, the transfer efficiency is the area ratio occupied by the heat generated by the heating resistor in an arbitrary section on the recording medium.

From the figure, it can be seen that the transfer efficiency decreases linearly as the number of heating resistors that generate heat increases.

This is reflected in the fact that the printed density value on the recording medium shown in FIG. 5 becomes thinner.

The transfer efficiency 'r'(X) in Figure 3 is expressed as Y(X)=a-X+b-N) However, if X・Total number of heating resistors generating heat a, b: If it can be expressed as a coefficient, When the transfer efficiency coefficient is W(X)
Then, w(X) is W(X)=Y(X)/T□8・
・Represented by (2).

However, T□yo is the maximum transfer efficiency, which is expressed as the area ratio that can be occupied by dots in an arbitrary section on the recording medium.

Then, based on the transfer efficiency coefficient W(X) determined by the second equation, the corrected applied pulse width P(X) is determined.

That is, the applied pulse width p(x) after correction is P (X )
= P aX c / Vv (X)...
・(3) However, Po: Applied pulse width before correction C: Can be determined by a correction coefficient determined by the mutual relationship between the thermal head, recording paper and ink sheet, or thermal head and thermal recording paper, and this correction Later applied pulse width P(X
) is applied to the heating resistor.

In the present invention, the applied signal pulse width P(X) to be applied to the heating resistor is determined based on the transfer efficiency coefficient W(X).

The method for determining the applied signal pulse width will be explained with reference to the flowchart in FIG. 1 and the block diagram in FIG. 2.

In step S1, the first calculation circuit 1 counts the number X1 of heating resistors that generate heat on the same line, and transfers this value to the second calculation circuit 2. Based on this number of heating resistors Xi, in step S2, the second calculation circuit 2 calculates the transfer efficiency Y1 from the approximation of the first equation. In step S3, the second calculation circuit 2 calculates the transfer efficiency coefficient W1 from the second equation.
Find it with In step S4, the second calculation circuit 2 calculates the corrected applied pulse width P1 from the third equation. In step s5, the applied pulse width P1 obtained in step S4 is
is applied to the heating resistor 3. In step S6, when printing the next line, return to step Sl again,
If you do not want to print anything, end recording.

In the embodiment, only the pulse width of the applied signal is corrected, but it goes without saying that the voltage may also be corrected.

(G) Effects of the Invention According to the present invention, it is possible to prevent a decrease in transfer efficiency due to a voltage drop, so that stable printing quality can always be obtained regardless of the number of heating resistors that generate heat.

[Brief explanation of the drawing]

FIG. 1 is a flowchart in the present invention, and FIG. 2 is a flow chart of the present invention.
Figure 3 is a diagram of the relationship between the conventional transfer efficiency and the total number of heating resistors, Figure 4 is a circuit diagram of the thermal gate, and Figure 5 is an actual diagram of the conventional heating resistor. FIG. 3 is a relationship diagram between the concentration value of and the number of heating resistors that generate heat. Figure 2

Claims (1)

[Claims] (1) Among multiple heating resistors on one thermal head,
When the number of heating resistors that generate heat is changed, a printing area ratio coefficient is calculated based on the printing area ratio within an arbitrary section on the recording medium due to the heat generated by the heating resistors, and this coefficient value and correction are made. A method for driving a thermal head in a thermal transfer recording apparatus, comprising: determining an applied signal energy value to be applied to the heating resistor based on a previous applied signal energy value, and applying the determined energy to the heating resistor.