JPH0486268A - Thermal recording device - Google Patents

Abstract

PURPOSE:To enable multi-gradation recording which eliminates a print gap by increasing previously a specified amount of image information gradation corresponding to heat generating elements at both ends of or from both ends of a heat generating element group in accordance with image information in order to compensate for a thermal calorie corresponding to a heat shortage generated at the heat generating elements on both ends of the heat generating element group. CONSTITUTION:A pair of electrodes 1f are connected to both ends of a heat generating element 1e, and 4m pieces of heat generating element are divided into groups 1a to 1d, each group consisting of (m) pieces of heat generating element. Then the groups are sequentially driven with each (m) pieces of the element in the order of 1a, 1b, 1c and 1d. The heating pieces of the first and the (m)th heat generating elements of the group consisting of the (m) pieces of heat generating element are constituted so that the (m)-second and following heat generating pieces are shorter than the (m)-first heat generating piece. The first and mth heat generating pieces have a lower resistance than the other heat generating pieces. Therefore, if the same voltage is applied, the thermal calories of the first and (m)-first heat generating elements are higher than those of other heat generating pieces. Subsequently, the thermal calorie runs short due to heat dissipation to an area outside the heat generating element group. Print dots equal to an image-receiving sheet in size are recorded by adding the thermal calorie of the heat generating piece to those of the first and (m)th heat generating pieces using a signal generation circuit part 12.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a thermal recording device capable of highly accurate multi-gradation recording.

BACKGROUND OF THE INVENTION In recent years, thermal recording devices have become full-color and faster, and highly accurate multi-tone recording is required in order to obtain good half-tone recorded images.

Generally, this type of thermal recording device has a configuration as shown in FIG.

That is, 1 is the thermal Rad, and the heating element IR
They are arranged in a line in a direction perpendicular to the plane of the figure.

3 is a heat-sensitive transfer ink-1, which is a heat-melting ink 3.
a or base film 31) It is covered with soil. A recording paper 4 is inserted between the thermal head 1 and the platen 2 together with the thermal transfer ink cartridge 3. The platen 2 is arranged so that the thermal head 1. There is sufficient pressure towards the

Next, the heating element IR of the thermal head 1 is shown in FIG.
It has a configuration as shown in t.

That is, 1e is a heating element, and a pair of electrodes 1f are connected to both ends thereof. And heating element]e is electrode 1
The diameter is made wider near the electrode 1f, and the width becomes narrower at the center between the electrodes 1f.

As a result, as shown in FIG. 7(1), the resistance value of the heating element 1e becomes smaller in the vicinity of the electrodes 1f, and becomes larger in the central part between the electrodes 1f. Therefore, when a constant voltage is applied to the heating element IR for a certain period of time, the higher the resistance value of the part, the greater the amount of heat generated, and therefore the density of the amount of heat generated at the center of the heating element R becomes higher. Utilizing this, each time the voltage application time of the voltage applied to the heating element IR is changed, a heat amount corresponding to the voltage application time is generated in the heating element IR in a form concentrated in the center of the heating element IR, The recording area per dot can be freely changed depending on the amount of heat generated. In other words, multi-tone recording is possible (Japanese Patent Laid-Open No. 6058877).

The operation of the thermal recording device configured as described above will be described below.

FIG. 8 is a block diagram of a thermal recording device using a conventional signal generating circuit, which is divided into a thermal head section IA and a signal generating circuit section 5.

The thermal head section IA is made of an insulating substrate, which is arranged in a line in two rows, and is electrically divided into N groups of M elements to ensure heat dissipation time for the heating elements. The heating element IR and the − of the heating element IR
N driver circuits 6 provided for each group, N latch circuits 7 provided corresponding to each of the driver circuits 6, and N latch circuits 7 provided corresponding to each of the latch circuits 7. It is composed of a shift register 8.

In this thermal head section IA, one electrode of the heating element 1R is connected in common to a printing power source, and the other electrode is connected to an output terminal of the driver circuit 6. Further, the input terminal of the dry noise circuit 6 is connected to the output terminal of the latch circuit 7, and the input terminal of the latch circuit 7 is connected to the output terminal of the shift register 8. Further, each of the driver circuits 6 includes a driver circuit 6.
The circuit is configured such that an enable signal for controlling the operation of each is applied independently and in parallel to each individual.

Next, in the signal generation circuit unit 5, 9 is a RAM (random access memory) in which image information consisting of a plurality of nobits (having gradation) for one line is stored. ]-〇 is a counter, and the position information indicating the address of RAM9 where image information for each heating element is stored is R.
At the same time, it outputs threshold information to the comparator 11 for comparison with the image information. ] 1 is the Konnoku letter, and the image information in RAM 9 is stored in the counter 10.
Is it sequentially larger compared to the threshold information from
The smaller value is output to the shift register 8 as a print data signal.

As a result, the print data signal input to each shift register 8 is sent as a parallel signal to the corresponding latch circuit 7, and the driver circuit 6 is driven by the print data signal sent from the latch circuit 7, and the print data signal is sent to the corresponding latch circuit 7 as a parallel signal. The heating element IR corresponding to the theta signal is energized and thermal recording is performed.

The second operation will be further explained using FIG. 9.

In order to make the explanation easier to understand, it is assumed that the image information stored in RAM 9 is 2 bits, and that M=2.
56. Assuming N=4, 1 line has 1024 heating elements JR
, and four heating element groups each consisting of 256 heating elements are designated 1a to 1d.

Figure 9 (al is a circuit diagram of the signal generation circuit section, RAM
9 stores image information corresponding to 1024 line heating elements in order starting from address 0, and from address 0 to 256
The 256 pieces of information up to the address correspond to heating element group 1a, and the information of each 256 pieces sequentially corresponds to heating element group l.
Corresponds to b, lc, and ld. The counter 10 has a 10-bit output, and the output from the lowest pin to the 8th bit is sequentially output to the address terminal of the RAM 9 from the lowest bit to the 8th bit.
Specify one of the 56 heating elements. counter 10
The outputs of the 9th and 10th bits from the lowest are output to the terminals of the 9th and ]0th bits of the lowest address of the RAM 9, and designate one of the four heating elements. Image information is R
The signals are sequentially output from A M 9 to the comparator 11 in series. Note that the numbers in parentheses in the same figure are numbers representing the contents of each storage unit in decimal notation. The comparator 11 compares the image information corresponding to each element IR with the outputs (threshold information) of the 7th and 8th bits from the bottom of the counter 10, and the results are sequentially sent to the transfer register 8.

For example, if the output (threshold information) of the counter 10 to the comparator 11 is 0, the gradation of each piece of image information shown in FIG. If 1°゛ is less than 0 then′
0" is output. Every time 256 of these are completed,
When the output (threshold information) of the counter 10 to the comparator 11 is repeated one by one from 0 to 2, a signal as shown in C in Fig. 9 fbl is output from the comparator. Next, register 8
When a signal such as that shown in C in FIG. 9(b) is input to the circuit, this signal is sent in parallel to the corresponding latch circuit 7, and the signal sent to the latch circuit 7 causes the dry nozzle circuit. Figure 9(b)
The waveform output shown in D is applied to the element 1R. and,
By means of an enable signal applied independently and in parallel to the circuit 6, only each element of a desired heating element group (256 elements) generates heat. At this time, each element I
In R, a pulse is generated as a result, as shown in D in Fig. 9 (bl), and the recording area per one dosoto is determined according to the width of this pulse, as shown in E in Fig. 9 (bl). The gradation changes in 4 steps, and the gradation is controlled in 4 steps.

Then, each time the above series of operations is performed for the four heating element groups 1a to 1d corresponding to the outputs of the 9th and 10th bits from the bottom of the counter 10 in the order of 1a → 1b → 1C → 1d, recording of one line is completed. Then, each time the recording of one line is repeated while feeding the recording paper, an image consisting of a plurality of lines is formed as shown in FIG. 10.

Problems to be Solved by the Invention However, in the above configuration, since the heating elements of the thermal head are divided into a plurality of groups and driven separately, there is an advantage that sufficient time can be secured for the heating elements to cool down after generating heat. However, in the heating elements at both ends of a group of heating elements that generate heat simultaneously, the interference of heat between adjacent heating elements is only on one side, that is, the heat dissipates to the outside of the group. When recording the same gradation with heating elements other than the edges of the group, the recording area decreases to This has the problem that the image quality deteriorates due to the occurrence of white streaks (observed as white stripes in different directions).

Conventionally, as a technique used to prevent deterioration of image quality due to printing gaps, a method was proposed in which immediately after driving a heating element group, only the elements at both ends were driven again for a certain period of time (Japanese Patent Laid-Open No. 6
]--224772), which is 2
Although it is effective as a means of correcting printing gaps in value recording, in multi-gradation recording, the drive time differs for each element depending on the recording gradation (low gradation, short to high gradation, long), so the fixed time In re-driving, it was difficult to perform good correction without excess or deficiency in all gradation ranges. Furthermore, a method of making the shapes of the elements at both ends of a group of heating elements driven simultaneously in a thermal head different from that of other elements (Japanese Patent Application Laid-open No. 61-144.
No. 367 and JP-A No. 6,118,5462) have been proposed, but in this method, the heat amount of the group end element is always corrected to be a constant ratio with respect to the elements other than the group end, regardless of the recording gradation. Therefore, as in the previous example, it is difficult to make a good correction without excess or deficiency in all gradation ranges, and in order to determine the shape of the group end element so that the printing gap is eliminated without excess or deficiency even in binary recording. It was necessary to make several prototypes of the thermal head.

In view of the above-mentioned problems, the present invention provides a thermal recording device for multi-gradation recording that eliminates printing gaps that occur at boundaries between heating element groups.

] 0 Means for Solving the Problem In order to achieve this object, the thermal recording device of the present invention has a plurality of heat generating elements arranged in a line, and a heat generating device consisting of a plurality of successive heat generating elements driven simultaneously. In response to a thermal head having a plurality of element groups and image information having a gradation for each pixel.

the heat generating element group, the energization time of the heating element is made different for each heating element, and the gradation of image information corresponding to the heating elements at both ends of the heating element group or a plurality of heating elements from both ends is changed according to the image information. 43 generating portion, and the shape and dimensions of the heating element at the end of the heating element group or the plurality of heating elements or electrodes from the end are different from those of the other heating elements or electrodes.

Effect of the Invention The present invention solves the problem of the printing gap occurring at the position of the recording surface corresponding to the boundary between the heating element groups due to the configuration described in 2. In order to compensate for the amount of heat equivalent to Even with heating elements of It becomes.

EXAMPLE A first example of the present invention will be described below with reference to the drawings. In addition, thermal head 1. Waraten 2. Thermal transfer ink-1/3. The same recording paper 4 as in the conventional example is used, and the explanation of its structure and characteristics will be omitted.

FIG. 1 is a block diagram of a thermal recording apparatus according to the present invention, which is divided into a thermal head section A and a signal generating circuit section 12. Of these, the thermal head section 1A is shown in FIG.
(The configuration is as shown in bl, and will be described later.

Next, in the signal generating circuit section 12, numeral 9 is a RAM, which stores one line of image information consisting of a plurality of bits. 10 is a counter which counts up in response to a clock signal and outputs position information indicating the address of the RAM where image information of the heating element is stored to the RAM 9, and at the same time outputs the same position information to the selector 13; Threshold information for comparison with image information is output to the comparator 11. 13 is a selector which outputs 1- to the ROM (read only memory) 14 only when the position information from the counter 10 is a value indicating the heating elements at both ends of the heating element group.

Reference numeral 1-4 is a ROM, which stores changed image information when the image information output from the RAM 9 is changed in accordance with the output from the selector 1.3. ] 1 is a comparator which compares the image information in the ROM 1.4 with the threshold information output from the counter 10 and outputs it to the shift register 8 as a print data signal indicating whether it is larger or smaller.

The operation of the thermal recording device configured as described above will be explained using FIG. 2. As with the prior art example, to make the explanation easier to understand, the image information stored in RAM 9 is assumed to be 2 bits, and furthermore, the image information stored in RAM 9 is assumed to be 2 bits, and the image information stored in RAM 9 is assumed to be 2 bits. Assuming that N=4, one line is composed of 1024 heating elements IR, and four heating element groups 1a to 1d, each consisting of 256 heating elements, are designated as 1a to 1d.

Image information corresponding to 1024 lines of heating elements is stored in the RAM 9 in the same configuration as the conventional example, and the RAM
The address of M9 is specified by the position information output from counter]0 in the same configuration as the conventional example, and the output of RA and M9 is specified by the position information output from counter 0.
It is output to the lower two bits of the address of OM14. The position information output by the counter 10 is also output to the selector 13,
The selector 13 outputs 1 to the third bit from the bottom of the address of ROM 1.4 when the position information is a value indicating the end of the heating element group (0 and 255), and outputs O when the position information is other than "-". do. ROM 1.4 is an image information change table, which includes image information from the RAM 9 (lower two bits) and information indicating the end of the heating element group from the selector 13 (hereinafter abbreviated as group end information) (third bit from the lower). )
An address where the third bit from the bottom is 0 stores the same information as the two bottom bits of the address, and an address where the third bit from the bottom is 1 stores the same information as the bottom two bits of the address. Information is stored. As a result, if the group end information from the first node 13 is 0 indicating a heating element other than the group end, the same information as the image information output of the RAM 9 is output from the ROM 14, and the group end information or the heating element at the group end is output from the ROM 14. RA if not indicated and 1
The ROM 14 outputs information different from the image information output from the M9, for example, information in which the number of gradations is increased. Furthermore, the output information of these ROMI 4 is sent to the comparator 11.
The comparison result is compared with the Threnjord information from the counter 10 using the same method as in the conventional example as shown in FIG. It will be done.

As described above, according to this embodiment, each time the gradation of the image information corresponding to the heating element at the end of the heating element group is increased, the amount of heat is insufficient due to the dissipation of heat to the outside of the heating element group. It is possible to supply an extra amount of heat in advance to the heating elements at the end of the heating element group, where it was not possible to record the recording area per dot. It is possible to record the same recording area as the heating elements on the edge, and as shown in FIG. 3, the printing gap that was created on the recording surface corresponding to the boundary between the heating element groups is eliminated.

In Figure 2, image information is
In ROM 1.4, the image information is increased by 1 only when it is "01" and "10" for the heating element at the end of the group. Therefore, it is possible to perform accurate correction that is more faithful to the phenomenon. When the number of bits of image information is increased, the relationship between the image information before and after the change in the heating element at the group end is that the print gap becomes most noticeable at the intermediate gradation, so the image information is most noticeable at the intermediate gradation. It is preferable to have a relationship as shown in FIG. 4, in which the amount of key increase is increased.

Further, in this embodiment, the gradation of image information is changed only for the group end heating element, but each time the number of output bits of the selector 13 is increased and the area used by the ROM 14 is expanded, The gradation may be independently changed for each of the heat generating elements and a plurality of heat generating elements to perform more accurate correction.

FIG. 5 shows the thermal head section of this embodiment, and in FIG. There are four heating element groups (each consisting of m heating elements).Next, the heating element 1R of the thermal head has a configuration as shown in FIG. 5(b).

That is, 1e is a heating element, and a pair of electrodes 1f are connected to both ends of the heating element. The heating element consisting of 4m pieces is
The motors are divided into four groups 1a to 1d, and the m motors are simultaneously driven in the order of 1a→1b-c-→1, d. and 1 of a group consisting of m heating elements.
The body length of heat generation in the th and mth heating elements is l, or 2
It is configured to be shorter than the heating elements from the m-th to the m-]th heating elements.

In a thermal recording device using a thermal head configured as described below, the length l of the heating element is proportional to the length of the second to m-1 heating element for the first and m-th heating elements. small. Since the resistance value of a heating element is generally proportional to (length 7 width), the resistance value of the 1st and mth heating elements is smaller than the other heating elements, and therefore the amount of heat generated when the same voltage is applied. is larger than the 1st and m-1th heating elements or other heating elements. When printing is performed using such m heating elements, the amount of heat generated by the 1st and mth heating elements, which conventionally was insufficient due to heat escaping to the outside of the heating element group, can be reduced by the configuration described in 1. By increasing the amount of heat corresponding to the shortage, the amount of heat generated by the second to m-1th heating element is approximated, and further, by the signal generation circuit section]2 in Fig. 1, the amount of heat generated from the second to Every time the correction is made to the calorific value of the th heating element, the difference between the calorific value of the 1st and mth heating elements and the 2nd to m-1th heating element becomes negligible.

Therefore, each time the first to mth print dots of the same size are recorded on the image receiving paper 4, the print gaps between the heat generating element groups that have conventionally occurred are eliminated.

Therefore, by configuring the thermal head section 1A as shown in FIG. 5, the absolute value of the amount of correction by the signal generation circuit section 12 can be reduced, resulting in more accurate correction than when the same signal generation circuit is used. It becomes possible.

In addition, in this embodiment, the heating element shape and image information gradation were changed only for the heating element at the end of the group, but the heating element shape and the gradation of the image information were changed independently for the second, third, and multiple heating elements from the group end. Furthermore, in this embodiment, the shape of the heating element 1e of the thermal head 1 is configured such that the diameter width near the electrode is wide and narrow in the center part. The shape may be any shape other than those shown in ``2''.

Finally, although the thermal transfer ink sheet 3 and the recording paper 4 were used in this embodiment, they may be a combination of a heat-sublimable dye sheet and an image receiving paper, or a thermal paper.

Effects of the Invention As described above, the present invention provides a thermal head having a plurality of consecutive heat generating element groups in which a plurality of heat generating elements are arranged in a line and driven at the same time, and The energization time of the heating element is varied for each heating element according to image information having a gradation, and the gradation of image information corresponding to both ends of the heating element group or a plurality of heating elements from both ends is adjusted according to the image information. By providing a signal generating circuit section to be changed, and making the shape and dimensions of the heating element at the end of the heating element group or the heating element or electrode of the plurality of heating elements from the end different from the other heating elements or electrodes, the recording surface "2" It is possible to eliminate printing gaps occurring at positions corresponding to boundaries between the heating element groups, and to realize a thermal recording device capable of multi-gradation recording with excellent image quality.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a thermal recording device according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a signal generation circuit section in the same embodiment, FIG. 3 is an explanatory diagram of the operation of the same embodiment, and FIG. Relationship diagram showing control details regarding image information in the same embodiment, No. 5
Figures (al and fbl are a perspective view of a thermal head section and a configuration diagram of a heating element of the second embodiment of the present invention, Figure 6 is a configuration diagram of a conventional thermal transfer recording device, and Figures 7 (at, (
b) is the configuration diagram and characteristic diagram of the heating element of the conventional example, No. 8
The figure is a block diagram of a conventional example, FIG.
FIG. 0 is an explanatory diagram of the operation of the conventional example. IA...Thermal head section, 1-R...
・Heating element, 9---- RAM, 10 ・-
- Counter, 11... Comparator, 12...
... Signal generation circuit section, 13 ... Selector, 14
...ROM 0 I'm sorry ± Hata@Kenfuyuugamo (輛 shouting thing) く [F] Mouth. Ward C Ka

Claims (1)

[Claims] A thermal head that has a plurality of heating element groups arranged in a line and driven simultaneously, each consisting of a plurality of successive heating elements, and a thermal head that has a plurality of heating element groups each consisting of a plurality of successive heating elements that are arranged in a line, and a thermal head that has a plurality of heating element groups that are arranged in a line and that are driven at the same time. A signal generation circuit that varies the energization time of the heating element for each heating element and changes the gradation of image information corresponding to the heating elements at both ends of the heating element group or a plurality of heating elements from both ends according to the image information. 1. A thermal recording device comprising: a heat generating element at an end of the heat generating element group or a plurality of heat generating elements or electrodes starting from the end of the heat generating element group having different shapes and dimensions from other heat generating elements or electrodes.