JPH02289363A - Recorder - Google Patents

Abstract

PURPOSE:To obtain a recorder improving an image quality and obviating the need for increasing the temperature of recording elements by mounting a pulse dispersion means for dispersing pulses to be applied to the recording elements within a 1-line image recording time. CONSTITUTION:In a pulse width timer, the frequency of an output signal of a level synchronous pulse generator 18 is divided into halves by a half dividing circuit 20 to be ORed with an output signal of a head strobe signal generator 19 by an OR circuit 22 through a buffer 21. On the other hand, an output signal of the half dividing circuit 20 is inverted by an inverter 23 and ORed with an output signal of the head strobe signal generator 19. The output signals of the OR circuits 22, 24 are transmitted to a thermal head as a strobe pulse SB1 selecting heating resistor pairs R1, R3,..., R2559 of a first group and a strobe pulse SB2 selecting heating resistor pairs R2, R4,..., R2560 of a second group. Because comparison data from a comparison data generation counter 16 is changed, a plurality of pulses per dot applied to the heating resistor pairs R1 - R2560 are dispersed at approximately uniform intervals in accordance with image data within an image recording time. Thus, a dense pulse application performed in a prior art can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a recording apparatus that records one pixel by applying at least one or more pulses to the eight elements of a recording head.

[Conventional technology]

Normally, a dye-sublimation thermal printer using a thermal head records an image on recording paper by applying a pulse to the heating resistor in the thermal head, which has a recording element consisting of a plurality of heating resistors arranged in a line to generate heat. When performing multi-gradation image recording, the dot density is controlled by changing the pulse width applied to the heating resistor. A plurality of heating resistors in the thermal head are provided in a number corresponding to the number of dots (pixels) for one line, and as the recording paper is moved, image recording is performed line by line.

In a sublimation thermal printer, variations in the resistance value of each heating resistor in the thermal head cause variations in the amount of heat generated. Therefore, in order to correct this variation in the amount of heat generated by each heating resistor, each heating resistor is classified into multiple groups based on its resistance value, and the pulse application time to each heating resistor is changed for each group. Such a device is known from Japanese Patent Laid-Open No. 59-45176.

Further, in general, in an electric transfer type printer, a recording element consisting of a recording electrode of a recording head and a common electrode is brought into contact with an ink sheet consisting of a resistive layer, a conductive layer, and an ink layer.
Electricity is applied to the ink sheet from an electrode or a common electrode, and Joule heat generated in the resistance layer selectively transfers ink from the melting type or sublimation type ink layer to the recording paper.

As shown in FIG. 21, the recording electrode 31 is generally formed by plating on a ceramic substrate 32, so its maximum thickness is about 70 μm. As shown in FIG. 22, the recording head 33 actually uses the ink sheet 3.
4, the contact width of the recording electrode 31 with respect to the ink sheet 34 is approximately 100 μm. If the recording electrodes 31 are made thicker, the positional accuracy between the recording electrodes will deteriorate or the recording electrodes will easily peel off, so the practical thickness of the recording electrodes is about 10 μm to 30 μm.

For these reasons, the recording pixel density is, for example, 6 dots/m.
In the case of m, the contact area of the recording electrode 31 with the ink sheet 34 is ideally desired to be 167 μm x 1.57 μm, but in reality it is 140 μra x 30 μm.
It is small, about m. Therefore, in order to increase the area of a recording pixel, there is a continuous drive method in which the recording electrode and the ink sheet are moved while the recording electrode and the ink sheet are being energized from the recording electrode and the common electrode. In addition, when performing multi-gradation image recording, the width of the pulse applied to the ink sheet from each recording electrode and the common electrode may be changed as shown in FIG. 23(a) depending on the J degree of the pixel, or The number of pulses is varied as shown in FIG. 23(b).

[To be solved by the invention: sM] In the above dye-sublimation thermal printer, when printing a multi-tone image, the dot density is controlled by changing the pulse width applied to the heating resistor. As shown in Figure 1I, a pulse Pm1n with a short pulse width is applied to the heating resistor of the thermal head while moving the head, and a pulse Pm1n with a short pulse width is applied for dot recording with a high concentration, and a pulse Pmax with a long pulse width is applied for high density dot recording. Therefore, as shown in FIG. 12, each dot D is recorded from the same starting line St+Sz+ . . . every line, and the center position changes between the low-density dot and the high-density dot.

The quality of recorded images deteriorates. Further, since there are many white areas where the dots D have a low density, the interaction between this and the high density dots results in a recorded image having a high frequency and a rough image, which deteriorates the image quality.

Furthermore, in order to correct for variations in the amount of heat generated by each heating resistor, each heating resistor is classified into multiple groups based on its resistance value, and the pulse application time to each heating resistor is changed for each group. As shown in FIGS. 13 and 14, the heating resistor with a low resistance value has a pulse width P2 of the pulse applied to the heating resistor with a high resistance value.
A pulse with a shorter pulse width P□ will be applied compared to , and the dot Ds recorded with a heating resistor with a low resistance value will be recorded with a heating resistor with a high resistance value, as the pulse application time will be shortened. The size is smaller than that of the dot DI. Therefore, dot D can be achieved with a heating resistor with a low resistance value.
When recording dots DS, there will be more white areas than when recording dots Dl using a heating resistor with a high resistance value. The concentration must be higher than that of the dot D1, and the pulse application must be performed so that the temperature of the heating resistor with a lower resistance value is higher than that of the heating resistor with a higher resistance value. For this reason, the heat generating resistor with a low resistance value becomes high temperature and its life is shortened, and the influence of heat accumulation on the next line of dot recording changes, causing density unevenness. Furthermore, when synthetic paper or OHP paper is used as the recording paper, the recording paper may be deformed or the surface gloss of the recording paper may be reduced due to heating due to the high temperature of the heating resistor having a low resistance value. Furthermore, since the temperature of the heating resistor having a low resistance value is increased, special treatment such as making the base material of the ink sheet heat resistant is required. Furthermore, as the recording speed increases, the time for the heat to diffuse from the heating resistor affects the coloring of the recording paper, so if a heating resistor with a low resistance value is heated to a high temperature in a short period of time by pulse application, the printing paper will not develop color. There will be cases.

In addition, in the case of recording an image with multiple gradations in the above-mentioned current transfer type printer, three recording pixels are required for each gradation as shown in FIG.
5 have different sizes and the white background stands out in areas with low density levels, giving the recorded image a rough appearance.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printing apparatus that can improve the above-mentioned drawbacks, improve image quality, and eliminate the need to raise the temperature of the printing element.

[Means to solve the problem]

In order to achieve the above object, the present invention provides a recording apparatus that records one pixel by applying at least one pulse to a recording element of a recording head, in which the pulse to be applied to the recording element is applied for one line of image recording time. The device is equipped with a pulse dispersion means for dispersing pulses within the pulse.

[For production]

The pulse to be applied to the recording element is divided into 1 pulse by the pulse dispersion means.
It is distributed within the image recording time of the line.

〔Example〕

FIG. 5 shows a circuit configuration of a thermal head in an embodiment of the present invention.

This embodiment is an embodiment of a sublimation type thermal printer, in which the thermal head has recording elements R1 to R2, 6° each consisting of a plurality of heating resistors corresponding to the number of dots for one line. R1~R.

are arranged in a line in the main scanning direction, and image recording is performed line by line as the recording paper moves in the sub-scanning direction.

D flip-flop FF L F Fzss. The shift register consisting of
Capture line by line, latch circuit LH1~LH2,,
. latches one line of image data from the shift register using a latch signal LD. Heat generating resistor R1~
RyusGa is divided into two groups, odd numbered ones and even numbered ones, and the first strobe pulse SDI
Accordingly, the odd numbered gate G, G1. ..., G2
5s9 is turned on and the odd-numbered latch circuits LH□, LH,
,...L H25s 9 is passed through the odd-numbered gates 611G+II...+azss, to the odd-numbered transistors Tr, l Tri,"
``'tTrzsss, and the second strobe pulse SB2 causes the even-numbered gates G, , G4 .
..., G25. . turns on and the even numbered latch circuits LH2, LH, . . . , LH26,. The image data from the even-numbered gate G2. G4...
, G2□. through the even-numbered transistors T r, ,
Tr,...,Tr2□. added to the base of.

The heating resistors R~R21° are transistors Tr.
, ~Tr, sGo and transistor T rl, ~Tr,
, 6° is gate G ~ G1. . When turned on according to the image data from the DC power supply, a constant voltage is applied from the DC power supply, which generates heat, heats the thermal paper or ink sheet, and records one line of image on the recording paper such as thermal paper as it moves. Have them do it one minute at a time. In addition, the above-mentioned D flip-flop FF, ~
F F25G. , latch circuits LH to LH, □. , gate G~G26GO9h transistor Tr,~Tr256.
．． The driver consisting of Tr, , ~Tr, , , is the sixth driver.
40 driver chips DR,~DR as shown in the figure
These driver chips DR1~D
R4, each has a 64-bit configuration.

FIG. 1 shows the line buffer, data converter, and comparison data generation counter of this embodiment.

Line buffer 11 includes line memory 12 and counter 1
3 and 14 are used, and the line memory 12 is divided into two areas 12A and 12B of 4 bytes each and switched by a line synchronization signal. The counters 13 and 14 are a write counter 13 and a read counter 14, and have an initial value of 2559, and count down each time multi-gradation image data is written or read from the memory 12. After that.

Image data is not written to the memory 12. counter 1
The output value of 3.14 is switched by the Read/Write mode signal, and the output values of counters 13 and 14 are output alternately. As shown in FIG. 2, multi-tone image data is written to the memory 12 at 2559.2558. ...
, O, and so on, the image data is written to the lower memory addresses one by one in the memory 12, and the image data is read out at 2559.2495. ..., 63,2558
, 2494. . . 62° . . . , 0, the image data is read from every 64th memory address in the memory 12. This is the thermal head driver chip ~DR. This is because it has a 64-bit configuration. The image data written to the memory 12 is written to each of the heating resistors R1 to R2s, in order to correct variations in the amount of heat generated by each of the heating resistors R1 to R256e. It is possible to input the heat to the memory 12 after correction by a correction circuit so as to eliminate variation in the amount of heat generated due to variation in the resistance value.

The data converter 15 includes first-stage latch circuits Lll to Ll4.
0. PNM (Puls
e Nusber Module) circuit PNMI-PN
M40, head memories old to M5 are used, and the first stage latch circuit Lll-L140 first reads addresses 2559, 2495, . . . , 40 image data sequentially read from 63 are latched. When the 40 image data are latched, the contents of the first stage latch circuits LL1 to L140 are simultaneously latched to the second stage latch circuits L21 to L240. ■The data of the second stage latch circuits L21-L240 is transferred to the next stage PNM circuit PN.
In M1 to PNM40, it is compared with 0' of the comparison data from the comparison data generation counter 16, and if it is larger than the comparison data, it is binarized to ``1'', and if it is less than the comparison data, it is binarized to 0'.
It is written to the next stage head memory old to M5.

Next, the data in the second stage latch circuits L21 to L240 are compared with the comparison data 1' from the comparison data generation counter 16 in the next stage PNM circuits PNold to PNM40, and if it is larger than the comparison data, the data is 1';0' if less than data
The data is binarized and written to the next stage head memos υM1 to M5.

Next, the data of the latch circuits ML21 to 1,2/I□ of the second stage are transferred to the 128 of the comparison data from the comparison data generation counter I6 in the next stage PNM@paths PNM 1 to PNM40.
If it is larger than the comparison data, it is binarized to 1', and if it is less than the comparison data, it is binarized to 0' and written to the next stage head memory old to M5. In this embodiment, as shown in FIG. 3, the bit arrangement of the comparison data from the comparison data generation counter I6 is changed so that the least significant bit (LSB) and the most significant bit (MSB) are reversed.
As shown in FIG. 4, the comparison data for the PNM circuits PNMI to PNM40 are 1', '2', 3', 4', '5', 6', and '7 in the conventional device.
', .
29', '64', '65', 192', '193'
' ..., '255' are discontinuous threshold levels. FIG. 7 shows changes in this comparative data. Similarly, the second stage latch circuit LSI~L24
The data of 0 is the next stage PNM@ro pN, Wi-pNM40
Each comparison data ゛1 from the comparison data generation counter 16
29','64',"65',"192
', '193'..., 255' are compared one after another and binarized, and each binary data is stored in the head memory s.
1 to M5. Through such an operation, the data in the second stage latch circuits L21 to L240 is converted into 256-gradation data and written into the head memory υMl-MS.

In the address of head memory old to M5, the upper 6 bits indicate the dot number, and the lower 8 bits indicate the level number (gradation level number). In the above cases ① to ②, the dot number of the addresses of the head memories Ml-M5 is 0', and the level number is `o' to `255' in accordance with the comparison data (gradation level) of the comparison data generation counter 16.

During the work in steps 1 to 2 above, the following 40 image data are stored at addresses 2558, 249/I, . . . in the line memory 12.
, 62 are read out and the first stage latch circuits Lll to L
140 and is on standby.

When the above steps ■ to ■ are completed, the first stage latch circuit L
The contents of ll to L 140 are simultaneously stored in the second stage latch circuit L.
21~L 240 is latched and the dot number is l'
As a result, the second
The data in the stage latch circuits L21-L240 is converted into 256-gradation data and written into the head memories M1-M5.

Similarly, 40 pieces of WJ image data are read out from line memo month 2 and converted into 256-gradation data.

Written to head memory old to M5. In this case, the dot number is switched from 2' to 63' in response to reading out image data of 40 pieces at a time.

Next, the head latch signal L is sent from the head memories M1 to M5.
In synchronization with D, data is read out with level number ``0'' and dot numbers ``O'' to ``63'' and sent to the thermal head as image data DI, and then with level number ``1'' and dot number ``o''. '~'63', the data is read out and sent to the thermal head as image data DI, and in the same way, each level number '2'~'255'
The data is read out as dot numbers 0 to 63' and sent to the thermal head as image data DI. FIG. 8 shows the timing of the above operation. The six head memories old to M5 are each divided into two areas of 64.times.256 bytes like the line memory 12, and these two areas are switched by a line synchronization signal.

FIG. 9 shows the pulse width timer of this embodiment.

The line synchronization pulse generator 17 generates a line synchronization signal, and the level synchronization pulse generator 18 generates a level synchronization pulse with a period of time t for applying a pulse to each block of heating resistors R4 to R25GQ in the thermal head. do. The head strobe signal generator 19 generates pulse application enable signals for each gradation level '1' to '255', and uses the line synchronization signal from the line synchronization pulse generator 17 to activate the level synchronization pulse generator 18 and the head strobe signal generator. 19 is reset. The output signal of the level synchronization pulse generator 18 is divided by two in a frequency divider 20, passed through a buffer 21, and ORed with the output signal of the head strobe signal generator 19 in an OR circuit 22.
The output signal of the frequency dividing circuit 20 is inverted by an inverter 23 and ORed with the output signal of the head strobe signal generator 19 by an OR circuit 24. The output signals of the OR circuits 22, 24 are the heating resistors R1, R, . . . of the first group.
...Strobe pulse SBI for selecting +Lsss, second group heating resistor R,, R4, ...tRz
sa. is sent to the thermal head as a strobe pulse SB2 that selects. A NAND circuit 25 performs a NAND operation on the output signal of the level synchronization pulse generator 18 and the output signal of the divide-by-2 circuit 20, and the output signal of this NAND circuit 25 is sent to the thermal head as a head latch signal LD.

In this embodiment, since the comparison data from the comparison data generation counter 16 changes as shown in FIG.
As shown in Fig. 10, the multiple pulses per dot applied to R2 and R6 are distributed at almost uniform intervals within the image recording time of one line, so that the pulses applied to R2 and R6 are distributed at almost uniform intervals according to the image data, and the pulses are not as dense as in the conventional method. It ceases to be something. As a result, the center position of each dot does not change, the image frequency also decreases, and the image quality improves.

Moreover, there is no need to raise the temperature of the single heating resistor.

The aforementioned problems caused by the high temperature of the heating resistor are eliminated.

FIG. 15 shows a comparison data generation counter in another embodiment of the present invention.

This embodiment is an example in which the comparison data generation counter 16 shown in FIG. 15 is used in the above embodiment.
is composed of a comparison data counter 161 and a level conversion read-only memory (ROM) 162.

The comparison data counter 161 counts clocks, and the count value changes sequentially from 0 to 254. The level conversion ROMI (i2 has an address specified by the count value of the counter 161, and by reading data from there, the count value of the counter 161 is output as is from 0 to 30 as shown in FIG. 17, and from 31 to 254. Until then, the PNM circuit PNMI-PNM is converted into data that is dispersed at almost uniform intervals.
By outputting the data to 40 as comparison data, the gradation level is sequentially increased up to 30 as shown in FIG. 17, and from 31 onwards, the gradation level is set to values that are approximately uniformly spaced. This PN
The comparison data for the M circuit PNMI-PNM40 is that the threshold level increases sequentially from '1' to 30', but the threshold level is discontinuous from 31' to 255', and the operation timing of this embodiment is the first. It will look like Figure 16.

FIGS. 19(a) and 19(b) show the temperature characteristics of this embodiment and the conventional apparatus, and FIG. 20 shows the glossiness with respect to printing density of this embodiment and the conventional apparatus. In the conventional device, since a plurality of pulses are continuously applied per dot to the heating resistor of the thermal head, the temperature of one heating resistor rises rapidly as shown in FIG. exceeded the
Moreover, as shown in the characteristic curves A and B in FIG. 16, the gloss becomes worse at high concentrations. However, in the above embodiment, a plurality of pulses per dot to be applied to the heating resistor are densely applied to the front side and dispersed at the rear side within the printing time of one line, so that the temperature of the heating resistor is as shown in FIG. 19(b). As shown in , the deterioration temperature T of the recording paper
a, and does not deteriorate even when the gloss level is high, as shown by characteristic curve C in FIG. 20.

In this embodiment, the comparison data from the comparison data generation counter 16 increases sequentially from 0 to 30 and from 31 to 25.
Up to 4, the data is scattered at almost uniform intervals, so the 1 applied to each heating resistor R~R56°
The plurality of pulses per dot 1 to 1 are distributed such that the front side up to 30 increases sequentially and the rear side from 31 to 254 fills approximately evenly within the image recording time of one line, as shown in FIG. It is no longer continuous like before. Therefore, the center position of each dot does not change, and the frequency of one image is also lowered, improving the image quality. Furthermore, there is no need to raise the temperature of the heating resistor, and the above-described problems caused by the high temperature of the heating resistor are eliminated.

FIG. 26 shows another embodiment of the present invention, and FIG. 27 is its timing chart.

This embodiment is an example of a current transfer type printer, and one current transfer head is used. This current transfer head has a recording element consisting of a plurality of recording B electrodes and a common electrode arranged in a line for recording an image for one line as in the conventional case, and the recording electrode and the common electrode are connected to a resistive layer and a conductive layer. ′? It is brought into contact with an ink sheet consisting of an ri layer and an ink layer. Image data is 1
The image data A for one line is sequentially written to the memory 37 line by line, and the image data A for one line from the memory 37 is compared with each gradation data B from the gradation counter 39 in the comparator 38, and when A>B, the gradation is A pulse signal is output from the counter 39 to the energized transfer head. Like the comparison data generation counter 16, the gradation counter 39 is connected to the comparator 38 so that the most significant bit and the least significant bit are reversed, and outputs gradation data that changes as shown in FIG. 7 to the comparator 38. However, the output pulses of the comparator 38 include one or more pulses for the same pixel and are distributed at approximately uniform intervals within the image recording time of one line. In the current transfer head, a pulse from the comparator 38 is applied between each of the plurality of recording electrodes and the common electrode, and current is applied to the ink sheet from between each recording electrode and the common electrode to generate Joule heat in the resistance layer. This Joule heat causes the ink to be transferred from the F ink layer to the recording sheet, thereby recording an image on the recording paper. The ink sheet and the recording paper are driven to run by a drive mechanism, and images are recorded on the recording paper one line at a time. In the low-density portion of the image, conventional electrical transfer printers record small pixels 35 as shown in FIG. 25(a), but in this embodiment, one pixel is recorded between the recording electrode and the common electrode. Since one or more pulses are applied between the recording electrode and the common electrode in a distributed manner within the image recording time of one line, a large pixel 36 will be recorded. This pixel 36 is approximately the same size as the pixel in the high density area.

The concentration is low. Therefore, even in low-density areas of the recorded image, the white background does not stand out, and the image quality is improved.

In this embodiment, the gradation counter 39 may be constructed of a counter whose output data increases sequentially and a level conversion ROM which converts the data into predetermined data as described above.

〔Effect of the invention〕

As described above, according to the present invention, in a recording apparatus that records one pixel by applying at least one pulse to a recording element of a recording head, the pulse to be applied to the recording element is applied within the image recording time of one line. Since a pulse dispersion means for dispersing the pulses is provided, the image quality can be improved and there is no need to raise the temperature of the recording element.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a line buffer, a data converter, and a comparison data generation counter in one embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the line buffer in the same embodiment, and FIG. 3 is a block diagram showing the operation of the line buffer in the same embodiment. A block diagram showing the relationship between the comparison data generation counter and the PNM circuit in the example, FIG. 4 is a diagram showing comparison data between the same example and the conventional device, and FIG. 5 is a block diagram showing the circuit nitric acid of the thermal head in the same example. 6 is a block diagram showing the driver of the thermal head, FIG. 7 is a diagram showing changes in comparison data in the same embodiment, FIG. 8 is a timing chart showing the operation of the same embodiment, and FIG. FIG. 10 is a block diagram showing the pulse width timer in the same embodiment. FIG. 10 is a waveform diagram showing each pulse applied to the heating resistor in the same embodiment.
The figure is a waveform diagram showing each pulse applied to the heat generating resistor in the conventional device, Figure 12 is a characteristic diagram showing the relationship between the heat generating resistor and the applied pulse in the conventional device, and Figure 13 is the waveform diagram showing the relationship between the heat generating resistor and the applied pulse in the conventional device. A characteristic diagram showing the relationship between pulse width and temperature, Fig. 14 is a diagram showing recording dots of the conventional device, Fig. 1
FIG. 5 is a block diagram showing the configuration of a comparison data generation counter in another embodiment of the present invention, FIG. 16 is a timing chart showing the operation of the same embodiment, and FIG. 17 shows changes in comparison data in the same embodiment. 18 is a waveform diagram showing the applied pulse to the heat generating resistor in the same embodiment, FIG. 19 (a) (b") is a diagram showing the temperature characteristics of the conventional device and the above embodiment, and FIG. FIG. 21 is a schematic diagram showing a part of the current transfer head; FIG. 22 is a diagram showing the state of contact between the current transfer head and the ink sheet; 23 and 24 are diagrams for explaining the conventional device, and FIGS. 25(a) and 25(b) are diagrams showing the recording state of the conventional device and another embodiment of the present invention. A block diagram showing a part of the example, and FIG. 27 is a timing chart of the same example. 11... line buffer, 15... data converter,
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Claims (1)

[Claims] A recording apparatus that records one pixel by applying at least one pulse to a recording element of a recording head, comprising a pulse dispersion means for dispersing the pulses to be applied to the recording element within an image recording time of one line. A recording device characterized by: