JPH03263A - Thermal transfer recording device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

BACKGROUND OF THE INVENTION In recent years, thermal transfer 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 transfer recording apparatus has a configuration as shown in FIG.

That is, 1 is a thermal head, and heating elements IR are arranged in a line in a direction perpendicular to the plane of the drawing. 3
is a heat-sensitive transfer ink sheet, in which a heat-melting ink 3a is coated on a base film 3b. A recording paper 4 is inserted between the thermal head 1 and the platen 2 together with the thermal transfer ink sheet 3. Note that the platen 2 is sufficiently pressed toward the thermal head 1 so that the recording paper 4 and the thermal transfer ink sheet 3 and the thermal transfer ink sheet 3 and the heating element are brought into sufficient contact with each other.

Next, the heating element IR of the thermal head 1 has a configuration as shown in FIG. 6a.

That is, 1a is a heating element, and a negative pair of electrodes 1b are connected to both ends thereof. The heating element 1a is formed to have a wider width near the electrodes 1b, and a narrower width closer to the center between the electrodes 1b. As a result, as shown in FIG. 6, the resistance value of the heating element 1a becomes smaller in the vicinity of the electrode 1b, and becomes larger in the central part between the electrodes 1b.

Therefore, when a constant voltage is applied to the heating element IR for a certain period of time, the portion with a higher resistance value generates more heat (therefore, the calorific value density at the center of the heating element IR becomes higher.Using this, the heating element By changing the voltage application time of the voltage applied to the IR, the heating element IR generates a heat amount in accordance with the voltage application time in a form concentrated in the center of the heating element IR, and 1 The recording area per dot can be changed freely.In other words, multi-tone recording is possible (Japanese Patent Application Laid-open No. 58877/1983).

The operation of the thermal transfer recording apparatus configured as described above will be explained below.

FIG. 7 is a block diagram of a thermal transfer recording apparatus using a conventional signal generating circuit, which is divided into a thermal radar section IA and a signal generating circuit section 5.

The thermal head section IA is arranged in parallel on an insulating substrate, and is electrically divided into N groups of M elements to ensure heat dissipation time of the heating elements. A heating element JR, N driver circuits 6 provided for each group of the heating element IR, N latch circuits 7 provided corresponding to each of the driver circuits 6, and each of the latch circuits 7. It is constituted by N shift registers 8 provided correspondingly.

In this thermal head section IA, one electrode of the heating element IR is connected in common to a power supply for printing, and the other electrode is connected to an output terminal of the driver circuit 6. Further, the input terminal of the driver 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 is configured so that an enable signal for controlling the operation of the driver circuit 6 is applied independently and in parallel to each driver circuit.

Next, in the signal generation circuit section 5, 9 is a RAM (random access memory) in which one line of image information consisting of a plurality of bits (having gradations) is stored. 10 is a counter, which stores position information indicating the address of RAM 9 where image information for each heating element is stored.
9, and also outputs threshold information to be compared with the image information to the comparator 11. A comparator 11 compares the image information in the RAM 9 with the threshold information from the counter 10, and sequentially outputs whether it is larger or smaller as a print data signal to the shift register 8.

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 print data signal sent from the latch circuit 7 drives the driver circuit 6, and the print data signal is sent to the corresponding latch circuit 7 as a parallel signal. The heating element IR corresponding to the data signal is energized, and thermal transfer recording is performed.

The above operation will be further explained using FIG. 8.

To make the explanation easier to understand, it is assumed that the image information stored in the RAM 9 is 2 bits, and that M=256.
．． 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.

FIG. 8a is a circuit diagram of the signal generation circuit section, and the RAM 9 stores image information corresponding to 1024 lines of heating elements.
The information is stored in order starting from the address, and 256 pieces of information from address O to address 256 correspond to heating element group 1a, and information for each 256 pieces corresponds to heating element group Ib,
Corresponds to lc and ld. The counter 10 has a 10-bit output, and the output from the least significant bit to the 8th bit is sequentially output to the terminal from the least significant bit to the 8th bit of the address terminal of the RAM 9. Specify one of the heating elements. The outputs of the 9th and 10th bits from the bottom of the counter 10 are output to the terminals of the 9th and 1st bits of the address of the RAM 9, and designate one of the four heating element groups. Image information is RAM
The signals are sequentially output from 9 to the comparator 11 in series. Note that the numbers in parentheses ( ) in the figure are numbers representing the contents of each storage unit in decimal notation. In the comparator 11, each element IR
The image information corresponding to the 7th and 8th bits from the lowest output (threshold information) of the counter 10 are compared, and the results are sequentially sent to the shift register 8.

For example, if the output (threshold information) of the counter 10 to the comparator 11 is 0, a comparison is made to see if the gradation is 0 or more for each image information shown in FIG. If "1" is less than 0, "O" is output. When the output (threshold information) of the counter 1o to the comparator 11 is incremented by 1 from O to 2 every time 256 of these are completed, the signal shown in C in Figure 8 is output from the comparator 11. is output. Next, when a signal as shown in FIG. The driver circuit is driven, and the waveform output shown in D in Figure 8 is the element IR.
is applied to Then, by an enable signal that is applied independently and in parallel to each driver circuit 6, only each element of a desired heating element group (256 pieces) generates heat. At this time, a pulse is generated in each element IR as shown in Fig. 8D, and the recording surface precision per dot varies depending on the width of this pulse. As shown in the figure, the gradation changes in four stages and the gradation is controlled in four stages.

Then, by performing the above series of operations in the order of 1a → 1b → 1c → 1d for the four heating element groups 18 to 1d corresponding to the outputs of the 9th and 10th bits from the bottom of the counter 10, recording of one line is completed. Then, by repeating the recording of one line while feeding the recording paper, an image consisting of a plurality of lines is formed as shown in FIG. 9.

Problems to be Solved by the Invention However, the above configuration has the advantage that since the heat generating elements of the thermal head are divided into a plurality of groups and driven separately, sufficient time can be secured for the heat generating elements to cool down after generating heat. However, in the heating elements at both ends of the heating element group that generate heat at the same time, the heat interference between adjacent heating elements is only on one side, that is, the heat dissipation to the outside of the group is large. The recording area is reduced compared to when recording the same gradation using heating elements other than the group ends, and a printing gap (in the printing direction) as shown in Figure 9 is created at a position on the recording surface corresponding to the boundary between heating element groups. However, there was a problem in that image quality deteriorated due to the occurrence of white streaks (observed as white streaks). SUMMARY OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to eliminate printing gaps that occur at boundaries between heating element groups.

Means for Solving the Problems In order to achieve this object, the thermal transfer recording apparatus of the present invention has a plurality of heating element groups each consisting of a plurality of consecutive heating elements, and a plurality of heating elements arranged in a line. a thermal head arranged in a row, and a current discharging time of the heating element is made different for each heating element according to image information having a gradation for each pixel, and heating elements at both ends of the heating element group, or a plurality of heating elements from both ends. and a signal generating circuit section that changes the gradation of image information corresponding to the heating element.

Effect: With the above-described configuration, the present invention reduces the amount of heat corresponding to the shortage of heat generated in the heating elements at both ends of the heating element group, with regard to the print gap that has occurred at the position of the recording surface corresponding to the boundary between the heating element groups. In order to compensate for this, the gradation of image information corresponding to multiple heating elements from both ends or both ends of the heating element group is increased in advance. A recording area per dot equivalent to that of the heating element can be obtained, and the printing gap can be eliminated.

EXAMPLE An example of the present invention will be described below with reference to the drawings. Note that the thermal head 1, platen 2, thermal transfer ink sheet 3, and recording paper 4 are the same as in the conventional example, and a description of their structure and characteristics will be omitted.

FIG. 1 is a block diagram of a thermal transfer recording apparatus according to the present invention, which is divided into a thermal head section IA and a signal generating circuit section 12. Of these, the thermal head section IA is the same as the conventional example, so a description of its configuration will be omitted. Next, in the signal generation circuit section 12, 9 is a RAM, in which one line of image information consisting of a plurality of bits is stored. A counter 10 counts up in response to a clock signal, outputs position information indicating the address of the RAM where image information for each heating element is stored to the RAM 9, simultaneously outputs the same position information to the selector 13, and outputs the same position information to the selector 13. 11 outputs threshold information to be compared with image information. 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 14 denotes 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 13. A comparator 11 compares the image information in the ROM 14 with the threshold information output from the counter 10, and outputs the result to the shift register 8 as a print data signal indicating whether the image information is larger or smaller.

The operation of the thermal transfer recording apparatus configured as described above will be explained using FIG. 2. As with the conventional example, in order to make the explanation easier to understand, the image information stored in the RAM 9 is assumed to be 2 bits, and furthermore, M=256. As N-work 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 RA
The address of M9 is specified by the position information output from the counter 10 in the same configuration as the conventional example, and the output of RAM9 is specified by the RO.
It is output to the lower two bits of address M14. counter 1
The position information outputted by 0 is also output to the selector 13, and the selector 13 outputs 1 to the third bit from the bottom of the address of the ROM 14 when the position information is a value (0 and 255) indicating the end of the heating element group. , outputs 0 in cases other than the above. ROM14 is an image information change table, and R
The address is designated by the image information from AM9 (2 bits from the lowest) and the information indicating the end of the heating element group from the selector 13 (hereinafter abbreviated as group end information) (3rd bit from the lowest), and the 3rd bit from the lowest is O. The same information as the lower two bits of the address is stored at an address, and the information different from the lower two bits of the address is stored at an address where the third lowest bit of the address is 1. As a result, when the group end information from the selector 13 is O 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 RAM 14, and the group end information is 1 indicating the heating element at the group end. In this case, the ROM 14 outputs information that is different from the image information output from the RAM 9, for example, the number of gradations has been increased. Furthermore, these R.O.
The output information of M14 is compared with the threshold information from the counter 10 by the comparator 11 in the same manner as in the conventional example as shown in FIG.
1 is output as print data to the shift register 8 of the thermal head section 1, and printing is performed.

As described above, according to this embodiment, by increasing the gradation of image information corresponding to the heating elements at the ends of the heating element group, due to the lack of heat due to heat dissipation 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, which could not record the recording area per dot that should have been recorded, in advance to compensate for the shortage. It is possible to record in the same recording area as other heat generating elements, and as shown in FIG. 3, the printing gaps that have occurred on the recording surface corresponding to the boundaries between the heat generating element groups are eliminated.

In Figure 2, image information is
We used a simple configuration in which the image information is increased by 1 only when the image information is "01" and "10" for the group end heating element in the ROM 14, but by increasing the number of image information bits, the phenomenon becomes more It is possible to perform corrections that are faithful to and accurate. 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 best to set the key increase amount to be thick (as shown in Figure 4).

Further, in this embodiment, the gradation of image information is changed only for the group end heating elements, but by increasing the number of output bits of the selector 13 and enlarging the area used by the ROM 14, 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.

Furthermore, in this embodiment, the shape of the heating element 1a of the thermal head 1 is configured such that the width is wider near the electrodes and narrower towards the center, but the shape of the heating element may be any shape below the above. .

Effects of the Invention As described above, the present invention makes the energization time of the heating element different for each heating element according to image information having a gradation for each pixel, and the heating element is connected to both ends of a group or a plurality of heating elements from both ends. By providing a signal generation circuit unit that changes the gradation of image information corresponding to the heating elements, it is possible to eliminate printing gaps that occur at positions corresponding to boundaries between the heating element groups on the recording surface, A thermal transfer recording device capable of multi-gradation recording with excellent image quality can be realized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a thermal transfer recording apparatus according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a signal generation circuit section in the embodiment, FIG. 3 is an explanatory diagram of the operation of the embodiment, and FIG. 4 7 is a block diagram of the conventional example, and FIGS. 8 a and 8 b are circuit diagrams and principle explanatory diagrams of the signal generating circuit section of the conventional example. FIG. 9 is an explanatory diagram of the operation of the conventional example. IA...Thermal head section, IR...
Heat generating element, 9...RAM, 10...Counter, 11...Comparator, 12...
...Signal generation circuit section, 13...Selector, 14
...ROM. Name of agent: Patent attorney Shigetaka Awano and one other person Figure 1 Y 10 II /Z /J /4 /S Image 1
Houkai kan (change ¥ front small □

Claims (2)

[Claims] (1) A thermal head having a plurality of heating element groups each consisting of a plurality of consecutive heating elements and arranging the plurality of heating elements in a line; and a signal generating circuit section that varies the energization time of the heating elements 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. A thermal transfer recording device characterized by: (2) The thermal transfer recording apparatus according to claim 1, wherein the heating element has a resistance value that is higher in the center and lower in the vicinity of the electrode.