JPS63202468A - Drive of thermal recording head - Google Patents

Abstract

PURPOSE:To enable prevention of generation of white streaks or density variation of vertical and horizontal lines by causing adjoining heat generating elements to generate heat with time delay. CONSTITUTION:CPU 4, RAM 5 and ROM 6 are connected to a host computer 7 via a signal line Sa. In addition, CPU 4 controls a 144-bit shift register 8, LATCH 9 and a driver 10 through a signal Sb, signals STB, LATCH, TX and CLK. To this driver 10, each heat generating element of a recording head 1 is connected. Each heat generating element and each phase of a pulse motor 12 are excited under the control of CPU 4. For drive of the recording head 1, heat generating elements of odd number are first used for printing a single line starting with a heat generating element at left end, and after termination of printing with these elements, those of even number are used for printing. For this reason, the adjoining heat generating elements do not generate heat simultaneously but with time delay. Subsequently, printing dots are not closed together by the heating of the adjoining heat generating elements, and recording is performed in superior quality print.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for driving a thermal recording head used in thermal recording, thermal transfer recording, etc.

<Prior Art> Today, facsimile machines, printers, and the like are widely used, and there are many recording methods for these recording devices, such as a wire dot type, an inkjet type, and a thermal recording type.

Among them, the thermal recording type presses a thermal recording head consisting of a plurality of heating elements arranged against the recording sheet, and generates heat in the heating elements according to the image signal to form an image pattern on the recording sheet. This thermal recording type is a typical non-impact recording device, and has features such as low noise and miniaturization.

In particular, line-type thermal recording devices use a thermal recording head in which a plurality of heating elements are arranged horizontally in a row over the same length as the recording width on a head substrate made of ceramic or the like, and records row by row as the recording sheet is conveyed. The recording speed is much faster than that of a serial type thermal recording device, and since there is no head movement, the recording accuracy is good. For this reason, a line-type thermal recording type is often used in ordinary facsimiles and the like.

However, the line-type thermal recording device has a large number of heating elements, and if it is attempted to generate heat from all of them at the same time, a large amount of electric power is required, the power supply becomes large, and the efficiency of the circuit deteriorates. Therefore, in general, the heating elements of one line are divided into several groups, and control is performed such that recording is performed with a time difference for each group.

<Problems sought to be solved by the invention> In the line-type thermal recording device, when observing dots recorded by simultaneous heating of successive heating elements, as shown in Fig. The dots are assisted by the heat generated by the adjacent heating elements, and the adjacent dots, which should normally be blank, develop color, so that the dots appear connected. Conversely, the dots do not connect at the boundaries between the divided heating element groups, and blank areas appear.

For example, when full solid printing (solid black printing performed by generating heat from all heating elements) is performed as shown in FIG. 9, the boundary 14 between the divided heating element groups is such that the blank area is connected to the conveyance direction of the recording sheet. Then, white streaks appear. These white stripes look bad and have become a problem because they impair print quality.

Also, as mentioned above, dots in the horizontal direction (digit direction) can be connected if adjacent heating elements are made to generate heat at the same time, but dots in the vertical direction (direction of conveyance of the recording sheet) are always connected during printing. Since the paper feed operation is involved, no heat is generated at the same time, so the dots do not connect.

Therefore, when looking at the recorded characters, as shown in FIG. 10, connected dots in the horizontal direction appear to have a high print density when viewed as lines, and dots in the contraction direction that are not connected appear to be thin. Therefore, it has been a problem that characters are formed in which the horizontal and vertical lines have different print densities or line thicknesses.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for driving a thermal recording head that can solve the above-mentioned conventional problems and effectively prevent white lines in solid printing and differences in density between horizontal lines and 11 lines. be.

<Means for Solving the Problems> The means of the present invention for solving the above-mentioned problems includes a method for driving a thermal recording head in which a plurality of heating elements that generate heat according to image signals are arranged in a line. , is characterized in that adjacent heating elements are driven with a time difference.

<Example> Next, an embodiment of the present invention to which the above means is applied will be described.

First, to explain the outline of a line-type thermal recording apparatus to which the above-mentioned means is applied, a plurality of heating elements 1a are provided on the recording sheet 2 side of a line-type thermal recording head 1 shown in FIG.
are arranged in a horizontal row, and the recording head 1 presses the platen roller 3 through the recording sheet 2 by a biasing means (not shown).

The platen roller 3 is connected to each heating element 1a of the recording head 1.
The recording sheet 2 is rotated in pitch in synchronization with both driving signals, and the recording sheet 2 is conveyed in the direction of the arrow. At the same time as this conveyance, the heating element 1
A generates heat in response to both signals and performs predetermined recording on a recording sheet 2 made of a heat-sensitive sheet.

Next, a method of driving the recording disk 1 in the above-mentioned apparatus will be explained.

First, the configuration of the drive circuit of the device is as shown in FIG.
The PU4, RAM5, and ROM6 are connected to the host computer 7 via the signal line Sa, and the CPU4 also receives the signals sb, STB, LATCII, and TX.

144-bit shift register 8, LAT via CLK
CH9 controls the driver 10. This driver 1
The heating elements DT, -DT144 of the recording head l are connected to the driver 11, and the excitation phases Sφ1 to Sφ of the pulse motor 12 are connected to the driver 11.
Under the control of U4, each heating element DT to DT+44 and each phase of the pulse motor 12 are excited to perform predetermined recording. In addition, 13 is a power switch of the recording device,
When the switch 13 is turned on, the CPU 4 and the driver l
O, driver 11. Recording head 1, pulse motor 1
2 is in the operating state.

In the above device, when driving the recording head L, printing of the L line is first performed from the leftmost heating element to the odd-numbered heating element (hereinafter referred to as r-odd number J),
After this is completed, the even-numbered heating elements from the left end (hereinafter referred to as r-even ton J) are printed.

An example of printing the driving process according to the data shown in FIG. 3 will be described with reference to the flowchart in FIG. 4. In FIG. 3, rla is heat-generating dot data, and r□j is non-heat-generating dot data.

First, the received data is input to the print buffer, and after this buffer becomes full (MAX) and preparations for starting recording are completed, rlJ4J is input to the bit counter stored in RAM5, and rlJ4J is input to the dot counter. 16" respectively to make initial settings (step S1). This sets the total number of bits of the recording head 1 of this embodiment to 144 bits, and the number of heating elements la that generate heat at the same time to 6 dots (6 bits). It means that.

Next, in step S2, data is read, and in step S3, it is determined whether the data is r13 or rQJ.

When the data is rlJ, shift r14 to the shift register 8 at the timing shown in FIG.
Shift rol immediately after that (step 34.S5)
, the value of the bit counter initialized in step S6 is decremented by 2, and the value of the dot counter is decremented by 1 in step S7.

Furthermore, in step S8, the value of the dot counter becomes "01".
In other words, it is determined whether the number of dots that generate heat at the same time, which was initially set in step S1, has reached "6". And if the number of heating dots is not r5J,
That is, if the value of the dot counter is not rol, the process advances to step S9, and if it is OJ, the process goes to step S1.
Proceed to step 3.

If the data is rQJ in step S3, the process advances to step SIO, where rQ' is shifted into the shift register 8, and immediately after that, the same < roJ is shifted (step SIO).
311), and the bit counter is decremented by 12 in step S12, and the process proceeds to step S9.

In step S9, it is determined whether the value of the bit counter is rQ4 or not, and if it is not rQJ, the process returns to step S2 and rQJ
If so, jump to step 317.

As shown in steps 31-312, even-numbered dots in the read data are unconditionally set to rQ3.

In step S8, the value of the dot counter is 10.
When it reaches 1, it means that the number of dots to be divided and generated to generate heat is equal. In the example of FIG. 3, when the data from DA1 to DA13 are transferred, the value of the dot counter becomes rOj in step S8.

At this time, the value of the bit counter is 144-14=130.

Therefore, in step S13, the value of the dot counter is set to r5.
The process returns to J and proceeds to step S14, where it is determined whether or not the odd number end flag is set. If the odd number end flag is not set, the process proceeds to step S15, and if it is set, the process proceeds to step S316. In the example of FIG. 3, printing of odd numbered dots has not yet been completed, so the flag is not set.Therefore, in step S15, the bit counter is shifted rQJ by the value of the bit counter to mask the dots other than the 6 dots that are simultaneously heated. That is, 144-14=130 tart' OJ shift All recorded information from L70A15 to DA144 is masked. This means that all the 144-bit data that you want to print with heat cycle 1 is complete.
The data is latched in step S17, and step 318
- In S21, a prescribed heating pulse determined by a timer is applied to the heating element 1a at the timing shown in FIG. 5 using the signal STB shown in FIG. This completes the heat cycle 1.

Next, in step S22, the value of the bit counter is rO
If it is not rQJ, the process goes to step S23, and if it is rQl, the process goes to step 326. This determination is to determine whether or not one line of printing cycle has been completed in the heat cycle l. be. In the example of FIG. 3, since r130J is input as the bit counter value, the process proceeds to step S23, and it is determined whether or not the odd number end flag is set. If it is not set, the process proceeds to step 524, and if it is not set. If so, the process advances to step S25. In the above example, the odd number end flag is not set, so the process proceeds to step S24, and from r144 J, the value of the bit counter, ie, ri 144-130-14, is ri! (shift) and return to subtub S2. That is, OAI printed with heat cycle l
- Shift rQJ to DA14 and set the leading point for manually inputting data in heat cycle 2 shown in FIG.

When the heat cycle is repeated several times by repeating steps 32 to S24, the heat treatment of the odd numbered dots in one line is completed.

After the odd numbered dots have been processed as described above, even numbered dots are then processed.

That is, when the heat cycle of the odd numbered dots in the l line is completed as described above, the value of the bit counter becomes rol in step S22. Then, step S2
6, it is determined whether or not the odd number end flag is set. If it is not set, the process goes to step S27, and if it is set, the process goes to step S31.

The odd number end flag is not set when the processing of the odd numbered dots is completed, so the odd number end flag is set in step 327, the value of the bit counter is returned to l'144J in step S2B, and the buffer is cleared in step 329. Reload the first data stored in .

When reading the data, the first data is unconditionally set to rQJ in step S30, and after this is shifted, the process returns to step S2 and the same operation as described above is performed.

That is, in the example of FIG. 3 through the process of step S30, rQJ is entered in DAI, so rQl is unconditionally shifted for odd numbered dots, data for only even numbered dots is read, and 6 dots are read as described above. heat treated each time.

When heating even numbered dots, the bit counter is decremented based on D^2 in Figure 3, so the data for the 6 dots that are simultaneously heated are complete, and the 1'' that is shifted when masking the other dots is The number of 01s is one less than in odd number processing.

For example, when performing heat cycle a in Figure 3, 0A20
It is necessary to mask ~D^144, but step S1
6, the bit counter value is 144-18-126
It becomes. So, subtract 1 from the bit counter value by 1
125, [) A20 to 08 144 are masked and heat cycle a is processed.

In addition, when performing heat cycle a or below, the process of masking already printed data is such that even number processing is one more than odd number processing. For example, when heat cycle b is performed in FIG. 3, DAI to DA19 must be masked, but the value of the bit counter in step S22 is 126 as before.Therefore, in step S25, (bit counter value + 1) is subtracted from 144, i.e. 144-126 + 1 = 19, masking 081 to DA19 and processing heat cycle b.

As described above, by executing steps S2 to S30, odd numbered dots are printed first of the print data in one line, and then even numbered dots are printed, thereby completing one line printing. After that, in step S31, the recording sheet 2 is
Performs transport processing for the line.

When the recording head 1 is driven as described above, the heating elements 1a adjacent to each other do not generate heat at the same time, but generate heat with a time difference. Therefore, the printing dots are not connected to each other due to the heat generated by the adjacent heating elements, and it is possible to record with good printing quality.

Other Embodiments In the above-described embodiments, odd-numbered dot processing is performed before even-numbered dot processing, but it goes without saying that this order may be reversed.

Further, it is not necessary to divide the dots into odd-numbered dots and even-numbered dots, as long as adjacent heating elements do not generate heat at the same time. For example, when heating adjacent dots as shown in FIG. 6, it may be possible to thin out the dots, store the thinned out dots, and heat them later.

Further, to explain an example in which solid recording is performed, heat may be generated every two dots or every three dots by sequentially performing heat cycles 1, 2, and 3 as shown in FIG.

<Effects of the Invention> As described above, the present invention prevents adjacent heating elements from generating heat at the same time, thereby effectively preventing the generation of white lines and the shading of vertical and horizontal lines, which have been problems in the past, and is extremely effective. This has effects such as being able to perform high-quality recording.

[Brief explanation of the drawing]

FIG. 1 is a diagram schematically illustrating the configuration of the thermal recording device, FIG. 2 is a diagram illustrating the drive circuit configuration of the thermal recording device, FIG. 3 is a diagram illustrating heat generation data, and FIG. 4 is a flowchart showing the driving state of the recording head. , FIG. 5 is a timing chart of the driving circuit, FIGS. 6 and 7 are explanatory diagrams of a driving method according to another embodiment, and FIG.
Figures 1 through 10 are explanatory diagrams of the prior art. 1 is a recording head, 1a is a heating element, 2 is a recording sheet, 3
is the platen roller, 4 is the CPU, 5 is the RAM, 6 is the RO
M, 7 is a host computer, 8 is a shift register, 9
is LATC)I, 10.11 is a driver, 12 is a pulse motor, and 113 is a switch. Figure 1 Figure 5 Ca 44bit Figure 6 ■ (2n (2n (l2) (?n, ::l) (expand) ≧)
■Convex■;:2) Guhi,,:l::@C knee'; @L,:
:r ■@ (Tetsuki 11 embrace,,
, g) Figure 7 ()○○■○○■○○ Heat cycle 10
■○○■○○■O Heat Cycle 2 00■○0000■ Heat Cycle 3 8th
Figure 9 Figure 10

Claims (2)

[Claims] (1) In a method of driving a thermal recording head in which a plurality of heating elements that generate heat according to image signals are arranged in a line, the thermal recording head is characterized in that adjacent heating elements are driven with a time difference. Driving method. (2) Driving the thermal recording head according to claim 1, wherein even-numbered heating elements and odd-numbered heating elements are driven with a time difference based on any one of the heating elements. Method.