JPS60139464A - Thermal head driving apparatus - Google Patents

Abstract

PURPOSE:To make the security of clear picture possible even when recorded at a high speed, by controlling present applied energy while estimating a future heat storage state. CONSTITUTION:An applied pulse width determining circuit 33 inputs an applied pulse width T1 by each unit picture element level being synchronized with a clock signal 34 and outputs gate control signals 35-1-35-3 corresponding to applied pulse widths from its output terminals 01-03. The applied pulse width determination circuit 33 divides the printing pulse width into 3 stages and regulates the heating value of unit heating element. Until the printing operation at the third stage ends, a back roller 39 stands still and the ink donor sheet 41 and the recording paper 41 as a thermal recording medium stop motion in the sub scanning directions thereof. At that time, optimum heat energy is generated from each unit heating element by regulating applied pulses at 3 stages. Thereby, when a future information discrimination means 17 detects, for example, the end of solid portion, it reduces applied energy by a fixed amount in printing at this portion and secures the definition of the recording or display of edge portion.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a recording device that performs thermal recording using a thermal head, or a recording device that uses a thermal head to form a magnetized latent image and uses this to display a display. The present invention relates to a thermal head drive device used in a display device.

[Prior Art 1] A thermal head consisting of a large number of unit heating elements usually arranged in a row can selectively cause these unit heating elements to generate heat in accordance with image data. The heat pulses thus generated are used to record images in thermal recording devices or thermal transfer recording devices, and are used to form latent magnetized images in some types of display devices.

By the way, recording devices and display devices using thermal heads use thermal energy to record or display (hereinafter simply referred to as recording), so if there is an excess or deficiency in this energy, it will affect the shading of the image. , it also results in a reduction in image quality. The risk of such image quality deterioration is due to the unit process of printing (repetition period of mark ';') for example] Q
It becomes larger as the speed increases, such as ITIS or lower, or as the recording density increases.

Therefore, it is necessary to devise ways to maintain good image quality at all times. For this reason, a thermal head driving device has been proposed that calculates the heat storage state of the thermal head and adjusts the energy applied thereto.

The outline of this proposal is explained below.

FIG. 1 shows the arrangement of image data for calculating the heat storage state of the thermal head.

The data row L1 located at the bottom in this figure represents the data on the line to be recorded from now on. Further, the column L2 that is one line above this represents data that is one line past this in terms of time. Similarly, the topmost data string L5 represents data from the past four lines.

Now, in the data string L1, arbitrary data D is shaded in the figure. Focus on. This data (hereinafter referred to as data of interest D).

That's what it means. ) corresponds to one unit heating element for which printing processing, that is, calculation of applied energy, is to be performed. In this case, reference data D1 to if 10 are hatched in the figure.
DIG is a reference data group used to calculate the heat storage state. Data of interest D among these reference data groups. Data of interest D does not have a relatively large thermal effect during printing. Reference data D adjacent to the unit heating element to which belongs,
, D. Also, the reference data D regarding the same unit heating element in the data string L2 one line before (past) has the least significant thermal influence.

It is. As shown in 2, the focused data D. The importance of each reference data that affects heat storage when printing differs depending on the distance between unit heating elements and the printing interval of each line.

Therefore, each of the reference data D1 to DIG is given a weight in advance, and only the data in the printed state is added to calculate the heat storage state from the sum. Weighty
For example,

(Left space below) Table 1: Data of interest D is determined according to the value of the heat storage data added in this manner. The thermal energy for printing is set. That is, the time width and voltage of the application pulse applied to the nine unit heating elements of the thermal head are adjusted, and thermal energy is applied.

FIG. 2 shows an example of how heat storage data and applied pulse width are converted in this proposed device. In the figure, the horizontal axis represents each data D1 to D based on Table 1. This is the value obtained by adding up the data of interest I). Corresponds to the heat storage data of the unit heating element to which it belongs.

This added value becomes O luck when all of the reference data D1 to Dto are non-print data (white data), and reaches a maximum value of 620 when the opposite is true. In addition, the vertical axis in the figure is the applied pulse width (mS
> is expressed.

In FIG. 2, for example, the data of interest I). If the added value at a certain point in time is 620, the heat storage state is the most severe, so the applied pulse width is the shortest, 0.3 mS. Also, if the added value is 0, there is no heat accumulation, so the applied pulse width is the longest 0.
It becomes 5mS. In this way, the applied pulse width is not necessarily determined only by the added value, but in reality, it is set by referring to the applied pulse width of one line in the past. However, in such a conventional thermal head drive device, the past image data is referred to and the heat storage state is calculated.
This is to set the applied pulse width short.

<Problems with the prior art> In a multi-head drive device such as
Edges of solid pattern and solid black to white (ground)
There was a drawback that the sharpness of the print could not be ensured in the élan part where the color changes. This will be explained using FIG. The shaded area in this figure is the solid black printing area 11.
It is. As a result of the heat storage correction being performed for each print line 12, the applied energy is optimally controlled for solid black printing within the print area 11. Of course, consider the effect of heat storage.
In M L, although the applied pulse width is set relatively narrow, sufficient thermal energy is applied by 1J so that adjacent printed dots are continuous with each other.

Such control of the applied pulse width is achieved by applying four pulses to the edge portion 13.
5) Even if you stay, you will get 1j. This is reference data D
This is natural since 1 to DIO are current and past image data. As a result, "line drawing" as an edge part
In order to print ', excessive thermal energy would be generated, making it impossible to achieve sharp edges.

[Purpose of the invention]

In view of these circumstances, it is an object of the present invention to provide a thermal head driving device that can predict the future printing state and adjust the energy applied to the unit heating element in the current printing unit process. purpose.

[Structure of the invention]

The present invention provides a recording or display device that records or displays both data by repeatedly and selectively driving a plurality of unit heating elements of a thermal head for each printing unit process, as shown in principle in FIG. A storage means 16 sequentially distributes image data 15 for a plurality of printing unit processes, and stores the printing state of the thermal head in a future printing unit process in the storage means 16 with a time delay. The energy applied to each unit heating element in the unit process of the current printing to be determined is determined based on the image data stored temporally in the upper row of the memory J. Future information determination means 1
An applied energy setting means 18 that takes into account the future printing state determined by 7 and a thermal head driving means 19 that drives each unit heating element with the set applied energy 11 to a thermal drive 71 and a driving device. Make the ingredients 1iii. Here, the "printing state" that is taken into consideration is not only the two-dimensional arrangement of image data during printing, but also the state of information obtained by processing these image data, such as thermal energy. It also includes the state of pulse width information for adjustment.

In this way, in the present invention, when the future information determining means 17 detects the end of a solid portion, for example, when printing is performed in this portion, the applied energy is reduced by a predetermined amount, so that the edge portion is clearly recorded or displayed. ensure the degree of

The energy applied to the thermal head may be adjusted by the time width of the applied pulse, or may be adjusted by the voltage value.

In addition, in the case of a thermal head in which many unit heating elements are arranged in a row, the printing unit process is a printing process for each rusk, and in the case of a thermal head in which unit heating elements are arranged in a matrix, , the process is to print line by line.

〔Example〕

The present invention will now be explained in detail with reference to Examples.

[First Embodiment] FIG. 5 shows a main part of a thermal head driving device and a part of the recording g+< connected to this device in a first embodiment. The thermal head driving device of this embodiment includes a buffer memory (storage means) 23 that stores image data 15 for three lines (three rasters). Hereinafter, in this specification, the lines 41 and 11'P are currently being printed, the next line to be printed is the ill line, and the line to be printed one after this is 1''-2.
I'll call it the line. Buffer memory 23 (Mai
-i +2 Store both data of line.

From this buffer memory 23, the image data of the first line is sequentially supplied bit by bit as address information to a ROM (read only memory) 25 in synchronization with a clock signal (not shown). This image data corresponds to the unit heating element used to calculate the thermal energy for printing.
This will be called data D1.

From the storage area 111 of the buffer memory 2:3 and the second line of 1'', image data regarding the same unit heating element is read out in synchronization with the readout of the data of interest D. These are reference data DI+l and DI, respectively.

I'll call it 2. Reference data D ill , Di
+2 is also supplied to 1st cell 0M25 as address information. These reference data D,+1, D,+2 are future data for two lines.

The ROM 25 includes a conversion table for determining the applied pulse width T1 for the data of interest D1. The applied pulse width ゛F1 is determined by the following formula.

T+ = f (tt, Dr, D, ++, I)
++2)...(1) Here, Ll is the expected applied pulse width on the i+1 line determined when printing the data of interest D1, The address information is manually entered into the ROM 25 (memory) 26, delayed by one line, and then entered again into the ROM 25 as address information.

The principle of the conversion table written in the ROM 25 will be explained next.

No. 61z1 represents certain image data in one column for 11 bits in the sub-scanning direction. In this thermal head driving device, the applied pulse width when heat storage has not progressed is set to 0.0mS, when the heat storage has progressed slightly, it is 0.9mS, and when the heat storage has progressed further, it is 0.8mS.

First of all, in Figure 6, 2 to 3 bits of image data 27
1 to 273 are output from the buffer memory 23, and 120
It is manually operated by M25 (Fig. 7 (Δ)).

At this time, it is printing on the first line, and there is no heat accumulation. Therefore, -C1C1 application pulse 1 is initially set to 1.1] mS. Since both the 1+1 line and the 1st 2nd line are non-print data (white bits), it is expected that the heat storage will not be as high as the first 11th line. Therefore, both data 27. of the l line. The applied pulse width ′1゛1 is set to 1, (]lη8,
The expected applied pulse width of the image data 272 of the i+1 line is also set to 1.01r18.

Figure 7 (■3) shows 1 to 0 when printing the next line.
This represents image data 272 to 27 degrees manually inputted to M25. In this case, heat storage does not proceed and the image data 2
Since 72 is non-print data, no pulse is applied. Therefore, the applied pulse width '1'1 is OmS, and the applied pulse width ti is 1. It remains OmS.

FIG. 7(C) shows the state when printing the next line. Since printing is performed from the next i+1 line, heat accumulation is expected. However, printing is not performed on line 1, and line i+1 is the line where heat storage starts, so there is no need to suppress thermal energy yet. Therefore, the applied pulse width is '1'.

is OmS, and the applied pulse width t1 is 1. It remains OmS.

FIG. 3(D) shows the state when the next line is printed. Since both the data 275 and 276 on the i+1 line and the l+2 line are print data, it is expected that heat storage will progress. On the other hand, the applied pulse width t+ =1. Om
It can be seen from S that image data 27° is the first print data. Therefore, the applied pulse width]゛1 is 1. OmS,
Also, the applied pulse width t1 is one step shorter, 0.9 mS.

The same figure (li> represents the state when printing the next line) is similar to that shown in FIG. i+' 1 line and l+2
Based on the line image data 276 and 277, it is predicted that heat storage will further progress. However, since the applied IJ width L i is O19m S , the corresponding unit heating element of the thermal head has not yet stored that much heat. Therefore, the applied pulse width '1'1 and the applied pulse width t.

are 0', 9 mS and 0.8 mS, both of which are one step shorter.

Figure (F) shows the state when printing the next line. The progress of heat accumulation is predicted from the 1+1 line image data 276, and the 1+2 line image data 27. It is expected that the edge portion will arrive. Therefore, in order to suppress thermal energy, two types of applied pulse widths '1''l, t
, are both set to 0.8 mS.

FIG. 6G shows the state when the next line is printed. Since 1 line of image data 277 is print data and 1+1 line of image data 278 is non-print data, it can be seen that the dots currently being printed are edges. Due to continuous printing data, heat storage is progressing slightly in this state.

The applied pulse width 'F1 and the applied pulse width t1 are both 0.
It is set to 8'mS.

FIG. 1 (1-1) shows the state when printing the next line. Although the l-line image data 278 is non-print data, heat accumulation is progressing due to the influence of past line printing. Therefore, the applied pulse width T.

is Q m S, but the applied pulse width [1 is 0.9 mS, which is just one step longer.

Figure (1) shows the state when the next line is printed. Since heat storage has progressed somewhat, the applied pulse width T+ and the applied pulse width [1 are both 0.9 mS.

The following Tables 2 and 3 are the contents of the conversion table of the ROM 25 created based on the principle explained below.

(Leaving space below) Table 2 Table 3 The second table shows the applied pulse width '1'1, and the third table shows the expected applied pulse width t1.

Both positions m are mS.

The applied pulse width 'x' determined for each unit heating element for each line is supplied to a thermal head drive circuit 31 shown in FIG.

FIG. 8 shows the main part of the thermal head drive circuit. The applied pulse width determination circuit 33 of this circuit manually inputs the applied pulse width '■' for each pixel in synchronization with the tarok signal 34, and outputs a gate control signal corresponding to the applied pulse width from its output terminals 0 and -03. 35-1 to 35-3 are output. The applied pulse width determining circuit 33 is
The pulse width for printing is set in three stages (Q, 8, 0.9 and 1.
0m5) and adjust the calorific value of each unit heating element. When the applied pulse width is 0.8 mS, only the first gate control signal 35-1 becomes H (high) level.

When the time is 0.9 mS, the first and second gate control signals 35-■ and 35-2 are at the level of 35-2.

When the time is 1.0 mS, the first to third gate control signals 35
-1 to 35-3 Rikizuki Lebel.

These gate control signals 35-1 to 35-3 are transmitted to three corresponding buffer memories IJ 36-1 to 36-3, respectively.
3 will be done manually. ■When all the life image data is input to the three buffer memories 36-1 to 36-3 as applied pulse width information, first the first buffer memory IJ3
The contents of 6-1 are read out, and the contents of
It is set in the shift register (not shown in the figure). Then, as shown in FIG. 9a, an applied pulse with a time width of 0.8 TllS is generated, and the first stage printing operation is performed. Next, the contents of the second buffer memory IJ 36-2 are read out and set in the shift register described above. In this case, as shown in FIG. 9, an applied pulse of 0.1 ms is generated, and the second stage printing operation is performed.

Finally, the contents of the third buffer memory IJ 36-3 are read out and set in the same shift register as described above, and an applied pulse of 0.1 mS is generated as shown in FIG. 1j, C.

, - until the third stage printing operation is completed, the back T-1-ra 39 is stationary, and the ink toner sheet 41 as a thermal recording medium and the recording paper (plain paper) 42 are Movement in the sub-scanning direction has stopped. At this time, by adjusting the applied pulse width in three stages, optimal thermal energy is generated from each unit heating element, and the thermal transferable ink 43 is clearly transferred.

When the three-stage printing operation is completed, the back roller 39
The ink donor sheet 41 and the recording paper 42 are sub-scanned by one line and moved to the next printing position. In this way, the printing operation is repeated and image data is recorded.

[Second Example] In the first example described below, the heat storage state of the unit heating element corresponding to the data of interest is calculated only from future data directly related to the heat generation of this unit heating element. Of course, it is also possible to determine the heat storage state of the unit heating element of interest from the surrounding pattern.

FIG. 10 shows the main points 1 of the thermal head driving device according to the second embodiment of the present invention.

The thermal head drive device of this embodiment also converts image data into three
The buffer memory 23 that stores lines (3 rasters) is (
+it is getting better. Three lines of data are read out in parallel pixel by pixel from the buffer memory 23 and supplied to the latch circuit 51.

In the latch circuit 51, there are three
Two latches 52-54 are arranged.

Image data 551 of the first line that is currently being printed 1j
is supplied to a circuit 52 consisting of a three-stage shift register. ■ Line future 14-1st line image information 5
514. is supplied to a latch 53 consisting of another three stages of shift registers. The image data 55++2 of the 1st+2nd line two lines in the future is delayed by 2 bits by a delay element (not shown) and then supplied to the latch 54.

The image data held in the latch 52 is serial-parallel converted, and the 1# old image data is supplied to the address terminal ΔO of the first ROM 57. The newest image data is supplied to address terminal Δ1 of this ROM 57. Image data corresponding to the data of interest is supplied to the seamal head drive circuit 58 for printing. The image data held in the latch 53 is also serial-parallel converted, and the address terminal Δ2 of the first ROM 57 is sequentially converted from lf+fortune-telling image data.
~Δ4. The image data held in the latch 54 is supplied to the address terminal Δ5 of the first ROM 57.

FIG. 11 shows the relationship between each print position of the image data output from the latch circuit 51 and the address terminal of the first ROM 57. The image data indicated by the X mark in the figure is the target data for calculating the applied energy.

The first ROM 57 uses such surrounding image data as address information to calculate the heat storage state of the unit heating element corresponding to the data of interest. The following table 4 shows the OM for the first I.
57 shows the contents of the conversion table written in 57.

(Leaving space below) Table 4 In this table, the number "1" shown in the address terminal column represents the image data to be printed (black image data), and the number "1" indicates the image data to be printed (black image data).
o'' represents image data (white image data) for which printing is not performed.

The second ROM 61 calculates applied pulse width information from applied energy information 59 according to Table 5 below.

(The following is a margin) As is clear from the relationship with Table 4, the less image data to be printed, the longer the applied pulse width becomes, and the more image data to be printed, the shorter it becomes.

The thermal head drive circuit 58 manually inputs the applied pulse width information 62 determined in this way, and when the image data corresponding to the data of interest is Pa1''' (printing state), the thermal head drive circuit 58 generates the corresponding unit heat generation of the thermal head 38. The body is energized with this applied pulse width to generate heat.Of course, this image data is "0"
”- (non-printing state), no electricity is applied.

FIG. 12 corresponds to FIG. 9 of the first embodiment, and shows how each unit heating element of the thermal head 38 is driven. The applied pulses are generated in the order of a to d in the figure, and by combining these pulses, the pulses range from 0.7 mS to 1.0 mS.
Four stages of heat generation control up to OmS are performed for each unit heating element.

In the first and second embodiments described above, heat accumulation was predicted by referring to image data two lines (raster) ahead, but it was also possible to use image data from an even further line to perform detailed heat generation control. It is also possible to do so.

Further, in the embodiment, the applied energy was adjusted by changing the time width of the applied pulse, but the same energy control may be performed by changing the voltage value.

In the above embodiments, the recording unit δ that prints one raster at a time has been described, but the present invention can also be applied to a recording device that prints in units of raster using a thermal head arranged in the shape of an IJ hook. The same can be applied.

〔Effect of the invention〕

As explained below-1-, according to the present invention, the current applied energy is controlled while predicting the future heat storage state.
Is the applied energy narrowly controlled even during high-speed recording?
+J function, which ensures the clarity of the image.

[Brief explanation of drawings]

Fig. 1 is an explanatory layout diagram showing the arrangement of image data for calculating the heat storage state of the thermal head in a conventionally proposed thermal head drive device, and Fig. 2 shows the relationship between the calculated heat storage state and the applied pulse width. The characteristic diagram shown in Figure 3 is an explanatory diagram for explaining the printing condition at the edge portion, and Figure 4 is an explanatory diagram to explain the printing condition at the edge part.
The figure is a block diagram showing the principle configuration of the present invention, and Figures 5 to 9 are for explaining the first embodiment of the present invention. Fig. 6 is a data array diagram showing an example of image data in the sub-scanning direction, and Fig. 7 (Δ) to (1) show the predicted heat accumulation in each line. An explanatory diagram showing the case of the image data shown in FIG. 6,
FIG. 8 is a block diagram showing the main parts of the thermal head drive circuit, FIG. 9 is a timing diagram showing the timing of generation of applied pulses, and FIGS. 10 to 12 show a second embodiment of the present invention. For the sake of explanation, Fig. 10 is a block diagram schematically showing the thermal head driving device.
FIG. 1 is an explanatory layout diagram showing the layout of image data for calculating the heat storage state, and FIG. 12 is a timing chart showing the timing of generation of applied pulses. 15... Both data, 16... Storage means, 17... Future information determination means, 18... Applied energy setting means, 19...
・→Normal head drive means, 23...Buffer memory, 25...ROM. 26...■2ΔM1 31.58...Thermal throat drive circuit, 38
...Zama/l/hel+', 51...
Latch circuit, 57...first IMAOM, 61...second R01VI. Applicant Fujiguchi Tsukusu Co., Ltd. Representative Umeo Yamauchi Figure 1 O Figure 2 0 100200300400500620, Karo 1
Figure 3 Figure 5 Figure 6 Figure 7 T, = 1.0+nS T・0.9mS T1=0.8m
Sti=09mStr=08mS t;=0.8mS Fig. 7 (H) (1) Fig. 8

Claims (1)

[Scope of Claims] (1) In a recording or display device that records or displays image data by repeatedly and selectively driving a plurality of unit heating elements of a thermal head for each printing unit process, a storage means for sequentially storing a plurality of units of unit processes; and a future information determining means for determining a printing state of the thermal head in a future printing unit process from image data stored in the storage means with a time delay; 01j The energy applied to each unit heating element in the unit process of the current printing to be determined based on the image data stored temporally earlier in the storage means is determined by the future printing determined by the future information determining means. A thermal head drive characterized in that it is equipped with an applied energy setting means that takes into account the state and sets an applied energy, and a thermal head driving means that drives each unit heat generating element listed in I) with the set applied energy. Device. 2. The thermal head driving device according to claim 1, wherein the energy applied to the thermal head is increased or decreased depending on the time width of the applied pulse. 3. The thermal head driving device according to claim 1, wherein the energy applied to the thermal head is increased or decreased depending on the voltage value of the applied pulse. 4. The thermal head driving device according to claim 1, wherein a thermal head having a large number of unit heating elements arranged in a line is used, and the unit printing process is a printing process for each rusk. 5. The thermal head drive device according to claim 1, wherein the thermal head drive device uses a multi-head head in which unit heating elements are arranged in a matrix, and the unit printing process is a printing process line by line.