JPH0241262A - Thermal transfer printer - Google Patents

Abstract

PURPOSE:To always maintain an optimum heat generating temperature by providing a profile correcting circuit for increasing or decreasing power to be supplied to individual heat generating elements by a level difference compared to the mean value of power to be supplied to adjacent heat generating element and setting the corresponding relationship on the basis of the density of a printed image. CONSTITUTION:A profile compensator 15 corrects input digital picture information 24 to a predetermined value by using a delay circuit 30 and an arithmetic circuit 23 contained therein, and inputs the correction digital picture information 23 to a density data comparator 16. On the other hand, a data counter 14 outputs density comparison gradation data 26 to the comparator 16 while a heat generating element 2 prints one dot. The information 25 is compared by the comparator 16 with the data 26. As a result, the comparator 16 outputs an open selection signal 27 of the element 2 to a shift register 3. A printing power is supplied to the element 2. The compensator 15 connects the circuit 30 and an adder 31 to an input terminal in, and outputs a correction value from a calculator 33 to an output terminal out.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a printing apparatus equipped with a line-type thermal head.

[Prior Art] Various configurations of printing devices are known for printing images and the like. Among them, there is a thermal transfer printing device that has a relatively simple structure and is easy to handle.

This thermal transfer printing device is a device that uses a thermal head to develop color in ink applied to thermal paper or to transfer ink applied to thermal transfer paper onto recording paper for printing.

Some thermal transfer printing devices include a line-type thermal head that can print one line on recording paper at a time.

FIG. 6 shows a block diagram of a line-type thermal head of a conventional thermal transfer printing device.

The figure is a block diagram showing a line-type thermal head 1 and its peripheral circuits.

In the figure, a large number of heating elements 2 are mounted on a line-type thermal head 1. These heating elements 2 include
An NPN transistor 6, an AND gate 5, a latch circuit 4, and a shift register 3 are connected. These components are normally mounted integrally on the substrate of a line type thermal head. Further, the heating element 2 is connected to a power source 7 that supplies printing power.

In the line type thermal head 1 having the above configuration, when digital image information is input to the shift register 3, the latch circuit 4 latches this digital image information by inputting a latch signal. When the drive signal is input to the AND gate 5, the gate opens and the NPN)-ranji star is turned on. Thereby, the heating element 2 is supplied with printing power from the power source 7. Thereby, the heating element 2 generates a predetermined amount of heat, and printing can be performed.

FIG. 7 shows a front view of the main parts of the conventional line type thermal head 1. As shown in FIG.

The figure is an enlarged view of the part where the heating elements 2 of the line-type thermal head 1 shown in FIG. 5 are arranged.

In the figure, a large number of heating elements 2 are arranged on the surface of a substrate 1a of a line-type thermal head 1 along its longitudinal direction.

Each heating element 2 in the figure is in a state in which it is receiving a supply of printing power and is respectively generating a predetermined amount of heat. The heating element 2 (heating element 2a) that performs high-density printing generates heat at a high temperature, and the heating element 2 (heating element 2b) that performs low-density printing generates heat at a low temperature.

The temperature distribution of the heat generation temperature of the above-mentioned line type thermal head 1 will be explained using FIG. 8.

FIG. 8 is a graph showing the heat generation temperature of the heating element 2 of the line type thermal head 1 shown in FIG.

The figure can be roughly divided into a high temperature section H and a low temperature section. The high temperature section H indicates the heat generation temperature of the heat generating element 2a (FIG. 7), and the low temperature section indicates the heat generation temperature of the heat generating element 2b (FIG. 7).

In the figure, when paying attention to both ends of the high temperature section H, the heat generation temperature at both ends is lower than that at the center. Also, if we pay attention to the low temperature area adjacent to this high temperature area H,
Its exothermic temperature is higher than other low temperature parts.

This is the heating element 2a of the heating elements 2 shown in FIG.
In the part where and the heating element 2b are adjacent, the heating element 2a is
This is because the temperature of the heat generated by the heating element 2b has decreased due to the influence of the heating element 2b. Furthermore, regarding the heating element 2b, the heating element 2a
This is because the heat generation temperature rose due to the influence of If variations occur in the heating elements 2a and 2b as described above, density unevenness will occur during printing.

Therefore, in order to reduce such variations in the heat generation temperatures of adjacent heating elements 2, it is possible to apply a contour compensation circuit used in television receivers and the like.

FIG. 9 shows a block diagram of a conventional contour compensation circuit.

As shown in the figure, the contour compensation circuit 15 includes two delay circuits 40.
41, a multiplier 42, and an adder 43.

Delay circuits 40 and 41 are circuits that delay data by a predetermined time (τH). Furthermore, the multiplier 42 is a circuit that performs multiplication by (-2) times.

In the contour compensation circuit 15 having the above configuration, the heating element 2 of the line type thermal head 1 explained in FIGS. 7 and 8 is added.
A case will be described in which print information similar to the information that causes heat generation in a and 2b is input.

FIG. 10 shows a graph showing the input/output characteristics of the conventional contour compensation circuit 15.

As shown in FIG. 10(a), the contour compensation circuit 15 (ninth
The print information is input manually to the input input shown in the figure. In this printed information, level N indicates information that causes the heat generating element 2a (FIG. 7) to generate heat, and level M indicates information that causes the heat generating element 2b to generate heat. When this print information is input, the output from the contour compensation circuit 15 is outputted from the output as shown in FIG.
A compensation signal as shown in b) is output. When this compensation signal is set at a predetermined level and added to the print information shown in FIG. 10(a), compensation print information as shown in FIG. 10(C) is obtained.

By using this compensation printing information, the heat generation temperature of the heating elements 2a and 2b shown in FIG. 7 can be corrected as indicated by the broken line (FIG. 8), and a predetermined heat generation temperature can be obtained.

[Problems to be Solved by the Invention] Here, a case where the heat generation temperature of the heating element 2 shown in FIG. 7 is at a high level as a whole and a case where it is at a low level will be described.

FIG. 11 shows a temperature distribution diagram of the conventional line type thermal head 1.

The figure shows a waveform (a) with an overall high heat generation temperature and a waveform (b) with a similarly low heat generation temperature. Further, both waveforms can be roughly divided into two parts: a high temperature part H and a low temperature part.

The high temperature section H indicates the heat generation temperature of the heat generating element 2a shown in FIG. 7, and the low temperature section similarly indicates the heat generation temperature of the heat generating element 2b.

In the case of waveform (a), when paying attention to the heat generation temperature by the heat generation element 2b, the heat generation temperature of the heat generation element 2b in the portion adjacent to the heat generation element 2a is high. This is because the temperature of the heating element 2b rose under the influence of the adjacent heating element 2a. In the case of waveform (b), when paying attention to the heat generation temperature by the heating element 2a, the heat generation temperature is lower in the portion where the heating element 2b is adjacent, that is, at the end of the series of heating elements 2a. This is influenced by the adjacent heating element 2b,
This is because the heat generation temperature of the heating element 2a has decreased.

In this way, the state of interference between the heating elements 2a and 2b differs depending on whether the overall level of the heat generation temperature of the heating element 2 (FIG. 7) is high or low. Therefore, even if the contour compensation circuit 15 shown in FIG.
In the case of the waveform (a) shown in the figure, the temperature at both ends of the series of heating elements 2a (FIG. 7) rises too much. Furthermore, in the case of waveform (b), the heating element 2 adjacent to the heating element 2a
The exothermic temperature of b becomes too low. For this reason, the 8th
Even if the contour compensation circuit 15 shown in the figure is used, it is not possible to appropriately correct the print information.

The present invention has been made with attention to the above points, and is a thermal transfer printing method that can always maintain an optimal heat generation temperature without being affected by the overall level of heat generation temperature of a series of heat generation elements or adjacent heat generation elements. The purpose is to provide a device.

[Means to solve the problem]

The thermal transfer printing device of the present invention selectively supplies printing power to a large number of heating elements mounted on a line-type thermal head at a level corresponding to the density of a printed image. The power supplied to the element is
A contour that increases or decreases from a predetermined amount depending on the level difference compared to the average value of the power supplied to the heating elements adjacent on both sides, and sets the correspondence relationship between the increase or decrease and the level difference based on the density of the input print image. It has a correction circuit, and this contour correction circuit is composed of two delay sections, an addition section, and a compensation calculation section.

[Effect]

In the above device, the power supplied to each heating element of the line type thermal head is increased or decreased from a predetermined amount depending on the level difference compared to the average value of the power supplied to the heating elements adjacent on both sides. The correspondence relationship between the level difference and the level difference is set based on the density of the input print image.

This increases the difference in heat generation between adjacent pixels, and the level is determined by the density of the input image, so
Image boundaries can be optimally emphasized at any density.

[Embodiment] FIG. 1 is a block diagram showing an embodiment of a thermal transfer printing apparatus of the present invention.

In FIG. 1, a line-type thermal head 1 is equipped with a large number of heating elements 2. As shown in FIG. In order to selectively energize these heating elements 2, a shift register 3 is used.
, a latch circuit 4, an AND gate 5, and an NPN transistor 6 are connected in series. These blocks are normally mounted integrally on the head substrate of the line type thermal head 1.

On the other hand, in order to process print data, an A/
A D conversion circuit 11, a data memory 12 for storing one screen worth of this digital image information, an address counter 13, a data counter 14, a contour compensation circuit 15, and a shading circuit for processing the digital image information and sending it to the shift register 3. A data comparison circuit 16 and an AND gate 17 are provided.

In these circuits, when digital image information for one screen is stored in the data memory 12, the address counter 1
3 accepts the reference clock 21 and sequentially data memory 1
The read address 23 is output to 2. Digital image information 24 corresponding to this address 23 is read from the data memory and input to the contour compensation circuit 15. The contour compensation circuit 15 corrects the input digital image information 24 to a predetermined value using a built-in delay circuit and arithmetic circuit (not shown), and inputs the corrected digital image information 25 to the gradation data comparison circuit 16.

On the other hand, the address counter 13 and data counter 14 are
Both are reset by the line synchronization signal 22. The data counter 14 outputs gradation data 26 for density comparison, for example, 64 times, to the gradation data comparison circuit 16 while the heating element 2 prints one dot. This gradation data 26 is output while being counted in units of 1 from 0 to 64 at a constant cycle.

The corrected digital image information 25 and this gradation data 26 are compared in the gradation data comparison circuit 16, and as a result, the gradation data comparison circuit 16 outputs an opening signal for determining whether or not each heating element 2 should be opened. A selection signal 27 is output to the shift register 3. The corrected digital image information 25 is composed of a several-bit digital signal corresponding to the density of a predetermined dot to be printed. That is, in the case of gradation 64, "111
111” (binary notation), if the tone is 0, “ooo
ooo'' (binary notation).The gradation data 26 is also composed of several bits of digital signals corresponding to the threshold level corresponding to the density at each gradation.

Further, the data counter 14 sends a strobe signal 28 to an AND gate 5 which controls the timing of energization for printing.
While this strobe signal 28 is being output, the AND gate 17 is open, and as a result, the reference clock 21 is input to the shift register 3. During this time, the opening selection signal 27 for one line is sent to the shift register 3.
Enter.

The latch circuit 4 receives the open selection signal 27 stored in the shift register 3 in parallel, and
The signal is latched for a predetermined period of time by a latch pulse 29 outputted from the latching pulse 29 .

The AND gate 5 opens its gate in response to the strobe signal 28 output from the data counter 14, and the NPN
This circuit performs the operation of turning on the transistor 6. N
When the PN transistor 6 is turned on, printing power is supplied from the power source 7 to the heating element 2 via the resistor 2.

Now, a detailed explanation of the contour compensation circuit 15 will be given here.

FIG. 2 shows a block diagram of the contour compensation circuit 15 according to the present invention.

In the figure, the contour compensation circuit 15 has a delay circuit 30 and an adder 31 connected to an input terminal in. Delay circuit 3
The output of 0 is connected to the delay circuit 32 and the arithmetic unit 33. The output of the delay circuit 32 is connected to the adder 31. The output of the adder 31 is connected to the arithmetic unit 33. The output of the arithmetic unit 33 is connected to the output terminal out.

The delay circuits 30 and 32 are circuits that are structured to delay by a predetermined time (TeH). The adder 31 is a circuit that adds two input values. The arithmetic unit 33 is a circuit that performs a predetermined arithmetic operation based on the outputs of the delay circuit 30 and the adder 31. This arithmetic unit 33 is composed of a ROM (not shown), etc., and a predetermined correction constant α is stored in this ROM.

If the value input to the input terminal in is a, the value output from the delay circuit 30 is s, and the value output from the adder 31 is C, then the correction value d output from the arithmetic unit 33 to the output terminal out is , d=b+α(2b-c).

FIG. 3 shows a time chart showing the operation of the contour compensation circuit 15 according to the present invention.

FIG. 3(a) shows the waveform input to the input terminal in (FIG. 2). FIG. 3(b) shows the waveform output from the adder 31 (FIG. 2). Figure 3 (C) is
The waveform output from the delay circuit 32 (FIG. 2) is shown. FIG. 3(d) shows the waveform output from the arithmetic unit 33 (FIG. 2).

When the waveform shown in FIG. 3(a) is input to the input terminal in, the delay circuit 30 (FIG. 1) as shown in FIG. 3(b)
A waveform delayed by H from the waveform shown in FIG. 3(a) is output. As shown in FIG. 3(C), the waveform shown in FIG. 3(a) and the delay circuit 30.
The waveform delayed by H is added and outputted from the adder 31.

The arithmetic unit 33 performs a predetermined calculation based on the outputs of the delay circuit 30 and the adder 31, and outputs a waveform as shown in FIG. 3(d) to the output terminal out (FIG. 2).

Here, the contour compensation circuit 15 according to the present invention will be explained in detail using FIGS. 4 and 5.

FIG. 4 is a graph showing the operating characteristics of the contour compensation circuit 15 according to the present invention. Further, FIG. 5 is a waveform diagram showing the input/output characteristics of the contour compensation circuit 15 according to the present invention.

First, the operation of the arithmetic unit 33 will be explained using FIG.

In the arithmetic unit 33 shown in FIG. 2, d=b+α(2b−c
) is performed. d is the output of the arithmetic unit 33,
b is the output of the delay circuit 30, and C is the output of the adder 31. Further, the correction constant α is determined by the RO provided in the arithmetic unit 33.
With a predetermined value stored in M etc., the value of b and (2b-c)
It changes appropriately depending on the sign of .

Now, as shown in FIG. 4, the correction amount A, that is, a(2b
-c) becomes positive if the result of (2b-c) is positive, and becomes negative if the result of (2b-c) is negative. Furthermore, the greater the level difference between adjacent waveforms, the greater the amount of correction.

Now, according to the arithmetic unit 33 having the above characteristics, as shown in FIG. 4, the amount of correction can be adjusted depending on the overall level of print information input to the input terminal in (FIG. 1).

First, as shown in ■ in Figure 5, if the value of the waveform input to the input terminal in (Figure 2) is large overall, the correction amount will be applied to the position where the density level is high, as shown by the broken line. In this case, the presser foot is increased at positions where the density level is low. If the printing information of this density level is used to energize the heating element 2 shown in FIG. 1, it is possible to prevent waveform rounding as shown in FIG. 11 (2) and (2).

In addition, in the case of ■ in Figure 5, if the value of the waveform input to the input terminal in (Figure 2) is small overall, the correction amount will increase at positions where the density level is high, as shown by the broken line. and hold down at low concentration levels. If the printing information of this density level is used to energize the heating element 2 shown in FIG. 1, it is possible to prevent waveform rounding as shown in FIG. 11 (2) and (2).

If the information a input to the input terminal in (FIG. 2) is 8 bits, the output of the delay circuit 30 is 8 bits, and the output C of the adder 31 is 9 bits, the compensation calculator 33 calculates a
2 Cb” = I M bit capacity is sufficient.
Practically speaking, a=8 bits, b=7 bits, c=8 bits, and aX 2 (bee)=256 bits.

〔Effect of the invention〕

The thermal transfer printing apparatus of the present invention having the above configuration increases or decreases the correction of the high density level and the correction of the low density level of the waveform depending on the density level of the data to be printed, so that the entire data has a high density. Optimal correction can always be performed regardless of whether the density level is high or the low density level.

This makes it possible to print data with clear outlines between high-density parts and low-density parts.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a thermal transfer printing apparatus of the present invention. FIG. 2 is a block diagram of the contour compensation circuit according to the present invention, FIG. 3 is a time chart showing the operation of the contour compensation circuit according to the present invention, and FIG. 4 is a graph showing the operating characteristics of the contour compensation circuit according to the present invention. , FIG. 5 is a waveform diagram showing the input/output characteristics of the contour compensation circuit according to the present invention, FIG. 6 is a block diagram of a line-type thermal head of a conventional thermal transfer printing device, and FIG. 7 is a diagram showing the main points of a conventional line-type thermal head. 8 is a graph showing the heat generation temperature of the heating element of a conventional line-type thermal head, and FIG. 9 is a block diagram of a conventional contour compensation circuit.
FIG. 10 is a waveform diagram showing input/output characteristics of a conventional contour compensation circuit, and FIG. 11 is a temperature distribution diagram of a conventional line type thermal head. 1... line type thermal head, 2... heating element,
15...Contour compensation circuit, 30.32...Delay circuit,
31...Adder, 33...Compensation calculator. Patent Applicant: Victor Japan Co., Ltd. Representative: Kunio Kakiki Figure 2 Figure 3 -m-Nicho] - τH % Figure 4 Figure 5 Western Time Figure 7 Figure 8 Figure 9 Figure 6 Figure 10 Figure Ju1 Illustrated scroll element

Claims (1)

[Claims] In a printing device that selectively supplies printing power to a large number of heating elements mounted on a line-type thermal head at a level corresponding to the density of the printed image, the power supplied to each heating element is controlled on both sides. Contour correction that increases or decreases from a predetermined amount depending on the level difference compared to the average value of the power supplied to heating elements adjacent to the heater element, and sets the correspondence between the increase or decrease and the level difference based on the density of the input printed image. 1. A thermal transfer printing device comprising: a contour correction circuit comprising two delay sections, an addition section, and a compensation calculation section.