JPH06105946B2 - Printer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printing apparatus that prints a still image signal using a thermal head or the like to obtain a hard copy.

[Outline of Invention]

The present invention relates to a printer for printing a still image signal by using a thermal head to obtain a hard copy, and in particular, a plurality of thermal head elements are divided, and each gradation is
By driving the divided thermal head elements alternately and moving the recording paper and the ink ribbon in synchronization with the first print start timing, the current consumption of the thermal head element is reduced and the deterioration of the image quality is prevented. It was made possible.

[Conventional technology]

The thermal printer is constructed as shown in FIG.

In the figure, reference numeral 1 denotes a cylindrical platen, a recording paper 2 for hard copy is attached to the peripheral surface of the platen, and a thermal head H is pressed against the recording paper 2 while being pressed against the recording paper 2. A sublimable ink ribbon 4 is arranged between the recording paper 2 and the ink ribbon 4 is transferred in the arrow direction in synchronization with the rotation of the platen 1.

The thermal head H is supplied with a still image signal (such as a reproduction of a still image signal recorded on a magnetic disk) that is PWM-modulated according to its gradation, and is printed with light and shade corresponding to that gradation. The still image is printed on the recording paper 2.

When printing a color hard copy, for example, cyan, magenta, yellow, and black color signals are prepared as image signals, while the ink ribbon 4 is
Sublimation type cyan, magenta, yellow, and black ink ribbons are prepared. Then, by transferring this ink ribbon in synchronization with the color signal, the printing of one color described above is executed with an arbitrary color signal, and then the platen 1 is returned to the original print start position, Printing of the next color signal is executed. By repeating this printing operation, a predetermined color image is printed (transferred) on the recording paper 2.

The image data printed on the recording paper 2 is formed as follows.

In FIG. 6, assuming that there are n horizontal scanning lines and m vertical scanning lines, the intersections of these lines are picture elements P _{11 to} Pmn, and the picture element data corresponding to these intersections are Sampled. Therefore, the thermal head H is
As shown in the figure, it is composed of n thermal head elements A _{1 to} Bn arranged in the vertical scanning line direction. n is usually set to about 480.

The relationship between the rotation of the platen 1 and the timing of printing can be the relationship shown in FIG. 8 or 9.

The one shown in FIG. 8 is of a batch printing type, and at the timing when the driving pulse P _D for printing is supplied to the thermal head H,
This is the case where the platen 1 is also supplied with the rotation drive pulse D _H having a predetermined pitch.

The maximum length of the drive period T ₂ of the drive pulse D _H is determined by the gradation. For example, in the case of 64 gradations, the pulse width T ₂ corresponds to 64 gradations. On the other hand, the drive pulse P _{D of the} platen 1
Has a constant pulse width T ₁ .

FIG. 9 shows a case of a divided printing type in which the thermal head H is divided into two and each of them is driven in a time division manner. Of the plurality of thermal head elements constituting the thermal head H, one of the first half is used. After the drive pulse D _A for the thermal head element having the number of / 2 (the same figure B) is completed, the drive pulse D _B for the thermal head element having the number of half of the latter half (the same figure C)
Is obtained. Then, the drive pulse P _D for rotation (A in the figure) for the platen 1 is generated at a predetermined timing after the end of the drive pulse D _B.

The rotation drive pulse PD for the platen 1 is set at a predetermined timing after the drive pulse DB is finished because the thermal head H must be cooled once for the next printing process.

[Problems to be solved by the invention]

By the way, in the printing apparatus 10 in which the printing operation as shown in FIG. 8 is performed, the driving pulse D _H for printing is simultaneously supplied to the thermal head H composed of a plurality of thermal head elements for batch printing. Therefore, there is a drawback that the printing current supplied to the thermal head H becomes large and the current consumption increases. When the current consumption increases, the configuration of the power supply circuit becomes complicated.

Further, when the current supplied to the thermal head H is large in this way, the voltage drop due to the head resistance of the thermal head H becomes large, and in order to perform light and shade printing matching the gradation,
There are also drawbacks such as the need for some voltage correction.

On the other hand, as shown in FIG. 9, a plurality of thermal head elements constituting the thermal head H are divided into upper and lower halves, and the upper thermal head element and the lower thermal head element are separately driven. The print method can reduce power consumption compared to the batch print method.

However, as described above, after the driving of the thermal head element by the drive pulse DB is finished, the platen 1 has to be rotated after cooling the thermal head element, so that the image quality is greatly deteriorated by the sticking. I will end up.

Here, a process in which the image quality is deteriorated by this sticking will be described. The ink ribbon 4 has a heat-resistant active layer on one side of which a head abuts, and a dye layer formed by mixing powdery dye and glue (resin or the like) on the other side of the base film. In addition, the recording paper 2 is configured by forming a receiving layer (resin or the like) made of a material to which the sublimated dye is easily attached on the base material. Then, the recording paper 2 and the ink ribbon 4 are
Since it is pressed against the platen 1 by the thermal head element, heat is generated in the thermal element by the drive pulse DB given to the thermal head element during printing, and the dye on the ink ribbon 4 is sublimated by this heat. Chart paper 2
The information to be printed is transferred to the recording paper 2 as a result. At this time, since the glue of the dye layer on the base film of the ink ribbon 4 is made of resin, it is slightly melted by the heat of the heat sensitive element.

Therefore, when printing is completed, that is, when the driving of the thermal head element by the drive pulse DB is finished, the recording paper 2 and the ink ribbon 4 are pressed against the platen 1 by the thermal head element for a predetermined time (the thermal head element is Since it is left for a while, the heat of the thermal head element does not immediately drop even if the driving of the thermal head element is terminated by the drive pulse DB. Even after the above, the glue of the dye layer of the ink ribbon 4 remains in a molten state due to the heat of the thermal head element.

Therefore, when the thermal head element radiates heat and is cooled in this state, the ink ribbon 4 and the recording paper 2 are pressed against the platen roller 1 by the thermal head element. Since the heat received from the thermal head element is also reduced, the ink ribbon 4 and the recording paper 2 are fixed in a state of being in contact with each other by the glue of the ink ribbon 4 and the receiving layer of the recording paper 2. This is substantially the same as the case where, for example, when the molten resin and the molten resin are pressed against each other, both resins cool and harden into a bonded state.

As described above, when the ink ribbon 4 and the recording paper 2 are in the adhered state, when the platen 1 is rotated as described above, this rotational force causes the platen 1 to rotate and the recording paper from the ink ribbon 4 to rotate. Acts as if peeling 2. Therefore, the force for peeling the recording paper 2 from the ink ribbon 4 is
The platen 1 is rotated, the ink ribbon 4 and the recording paper 2 are partially loaded, respectively. As a result, the ink ribbon 4 and the recording paper 2 are loosened, damaged, misaligned, and misaligned due to the load applied to the platen 1. As a result, streak-like noise is printed on this portion of the recording paper 2 or a portion adjacent to this portion, which significantly deteriorates the quality of both still images printed on the recording paper 2. There was an inconvenience.

Even if the platen 1 is rotated before cooling the thermal head element, the thermal head element may be moved up and down (for example, on the upper side).
(50 thermal head elements and 50 thermal head elements on the lower side)
Since each of them is driven separately, if the gradation of the upper half of the image to be printed is the minimum and the gradation of the lower half is the maximum (in the case of the subtractive color method), the upper thermal sensitivity corresponding to the upper half of the image Since the head element is driven for a long time, the lower thermal head element corresponding to the lower half of the image is cooled by heat radiation during that time, which causes sticking as in the above case.

Therefore, the present invention is intended to propose a printing apparatus that can reduce power consumption and prevent deterioration of image quality.

[Means for solving problems]

According to the present invention, a plurality of image data sampled in one direction is compared with each gradation data to form a comparison output for each gradation, and the comparison force corresponding to the odd-numbered image data among these comparison outputs is reduced. It is supplied to the first thermal head element group HA which is arranged in an odd number of the plurality of thermal head elements H which are arranged so as to correspond to the direction, and the comparison output corresponding to the even number image data is arranged in the even number. It is supplied to the second thermal head element group HB, and the first and second thermal head element groups HA and HB are alternately driven for each gradation so that a print result can be obtained at a density according to the comparison output. It was made to be done.

[Action]

According to the present invention described above, a plurality of image data sampled in one direction is compared with each gradation data to form a comparison output for each gradation, and the comparison output corresponding to the odd-numbered image data is output. The comparative output is supplied to the first thermal head element group HA arranged in an odd number of the plurality of thermal head elements H arranged so as to correspond to one direction, and the comparative output corresponding to the even-numbered image data is even numbered. It is supplied to the second thermal head element group HB arranged in the second order, so that the print results can be obtained at the densities according to the comparison output in the first and second thermal head element groups HA and HB, in each gradation. Drive them alternately. Thereby, the first and second thermal head element groups
Since HA and HB print a predetermined image alternately for each gradation, the drive current supplied to these thermal head element groups HA and HB can be reduced, thereby reducing the current consumption during printing. be able to.

Further, the first and second thermal head element groups HA and HB are divided by not simply dividing the upper and lower sides of the thermal head element H but, for example, as shown in FIG. Since they are alternately divided as the thermal head elements of the first or second thermal head element group HA or HB, for example, because the gradation of the upper half and the lower half of the image to be printed is significantly different, Even if only the upper thermal head element is driven much, the thermal head elements are not uniformly driven over the upper thermal head element and the lower thermal head element, but are arranged uniformly over the entire thermal head element H. A first thermal head element group HA, a thermal head element adjacent to each thermal head element of the first thermal head element group HA, and a first thermal head element group HA.
Similarly to the above, the driving is performed by the second head element group HB evenly arranged over the entire thermal head element H, so that only a group (for example, a plurality of consecutive) thermal head elements in the thermal head element H are driven. It is possible to avoid a state where the sticking is not performed, and thus it is possible to suppress the occurrence of sticking.

〔Example〕

FIG. 1 is a system diagram showing an example of a heat-sensitive printing apparatus 10 according to the present invention, and FIG. 2 and subsequent figures are waveform charts for explaining the operation thereof. As shown in FIG. 7, the thermal head H used in the present invention has an odd-numbered thermal head element A _{1 to} An _-1 among a plurality of thermal head elements arranged in the vertical direction. The element group H _A is used as the element group H _A , and the even-numbered thermal head elements B _{2 to} Bn are used as the second thermal head element group H _B.

For convenience of description, first, referring to the waveform diagrams of FIG.
A schematic printing operation of this printer will be described.

Printing is P gradation (P is an integer and can be 16, 32, 64, etc.)
Image data on a certain vertical scanning line are compared for each gradation, the comparison output obtained for each gradation is printed for each gradation, and when the printing of P gradation is completed, the vertical The print operation on the scan line is completed. Similarly, for the next vertical scanning line, the image data on the vertical scanning line is compared with the P gradation data, and the printing operation is repeated.

Therefore, in FIG. 2, the drive pulses D _A and D _B shown in FIG. 2 are supplied to the first and second thermal head element groups H _A and H _B each time each gradation data is obtained.

The printing operation for each gradation is specifically shown in FIG.

In this embodiment, all the printing operations of one vertical scanning line are completed in four frames, and as shown in FIGS. 3A and 3B, a period T _W close to one frame in the first one frame period T _W in one image data in the vertical scanning line is stored in the memory (RAM) to be described later, in a period T _R close to 1 frame of the next one frame period, based on the stored image data in the memory, one vertical scanning The line printing operation is executed. In this example, assuming that a printing time of 27 msec is required for P gradations, the printing time 2T _{3 for} one gradation is 2 if the gradation is set to represent 64 gradations.
It becomes 7 / 64msec.

The printing at each gradation shown in C in FIG.
If the first thermal head element group H _A is driven and printed in the first half as shown in FIG. 2, printing is performed by the second thermal head element group H _B in the latter half. As described above, the driving of the first and second thermal sensitive Heno element groups H _A and H _B is time-divisional driving (hence, pulse driving).

FIG. 1 is a system diagram showing an example of a printing apparatus according to the present invention.

The printing apparatus 10 comprises a head drive system 20 and a control circuit 25 for the head drive system 20, and the head drive system 20 includes a first thermal head element group H _A.
Further, it has a vertical shift register 21 and a buffer 22 for supplying a predetermined comparison output X, and similarly has a vertical shift register 23 and a buffer 24 corresponding to the second thermal head element group H _B.

The control circuit 25 is configured as follows.

Digital image data D _IN of a predetermined bit sampled for each picture element is supplied to the terminal 26A. In order to realize 64 gradations, 6-bit image data is input. The image data D _IN is once stored in the ROM 26, and the γ-corrected image data D (FIG. 4A) is read out by this.
This is stored in the memory (RAM) 27. Therefore, the address counter 27 is provided, and the data writing clock WCK (B in the figure) supplied to the terminal 29 is supplied to the address counter 30 via the switching circuit 30 so that all the image data of one vertical scanning line is supplied. Is stored.

To read the image data D, a read clock RCK (B in the figure) is used. Reference numeral 31 is a generator of this clock, which is also supplied to the address counter 28 via the switching circuit 30, and the image data for one vertical scanning line is serially read from the memory 27 and supplied to the comparator 33. .
The gradation data G (G _{1 to} G _P ) corresponding to each gradation is output from the gradation counter 34 to the comparator 33, and the level comparison with the image data D of each picture element is executed. In this example, when the P input (image data D) is equal to or larger than the Q input (gradation data G), the comparison output X is “1”, and when the P input (image data D) is the opposite, it is “0”. The data.

The comparison output X is directly supplied to the second vertical shift register 23 and is also supplied to the first vertical shift register 21 via the D-type flip-flop 36.

Here, of the plurality of comparison outputs X, only the odd-numbered comparison outputs X _{11 to} X ₁ n ₋₁ are supplied to the first vertical shift register 21, and the even-numbered comparison outputs X _{11 to} X ₁ n ₋₁ are supplied to the second vertical shift register 23. A flip-flop 36 is provided so that only the comparison outputs X _{12 to} X ₁ n are supplied. Therefore, the flip-flop 36 is supplied with the clock CK _F (G in the figure) which is the counter 37 counting down the read clock RCK and the data is taken in at the rising edge of the flip-flop 36. The comparison outputs X _{11 to} X ₁ n _{-1 of} are output.

A clock CK _S (H in the figure) obtained by inverting the phase of the clock CK _F by the inverter 38 is supplied to the first and second vertical shift registers 21 and 23 as a shift clock. As a result, the first vertical shift register 21 receives the comparison output shown in FIG. 11E and the second vertical shift register 23 receives the comparison output shown in FIG.

When the comparison between the image data D ₁ n stored at the final address and the grayscale data G _P is completed, all the comparison outputs X have been fetched into the shift registers 21 and 23. When the address counter 28 reaches the final address, a carry pulse P _C (I in the same figure) is obtained from this, and this is supplied to the monomulti 39 and the latch pulse P _L shown in L in the same figure is formed. 24, and the comparison output X of one vertical scanning line is simultaneously latched.

Carry pulse P _C is further supplied to the second monostable multivibrator 40, a 50% duty cycle of the drive pulse D _A (FIG. J) is formed, the driving pulse D _A is first through the first and 42A The drive pulse D _B (K in the figure) supplied to the first thermal head element group H _A and phase-inverted by the inverter 41 is the second pulse.
Is supplied to the second thermal head element group H _B via the gate 42 _B of the.

Therefore, the first and second moving head element groups H _A and H _B are time-divisionally driven based on the comparison data X compared with the _first gradation data G ₁ to generate one vertical scanning line. Image is printed. However, since this printing is for one gradation, this printing operation is sequentially repeated for 64 gradations.

The drive pulse D _A is also supplied as a clock to the gradation counter 34, and the gradation counter is supplied at the timing of supply of this clock.
The data contents of 34 are sequentially incremented. The carry pulse P _C is also supplied as a reset pulse to the address counter 28 via the OR circuit 43, and when the carry pulse P _C is obtained as a result, the address counter 28 is returned to the first address, and eventually the memory 27 does not receive the address. Similar to the first gradation,
The image data D for one vertical scanning line used previously is output.

For this reason, in comparison with the gray scale data G ₂ of the previous image data D and the second gray level of is performed, the printing operation is performed in a manner similar to above timing. 64th gradation data Gp
When the comparison with (p = 64) is completed and printing is executed, the writing period T _W is reached, and the enable pulse p _E from the terminal 47 to the first and second ANDs 42A and 42B (N in the figure). Is supplied and the printing operation is prohibited.

In the writing period T _W , the image data D (D _{21 to} D ₂ n) for the next vertical scanning line is stored in the memory 28, and the same printing operation is executed thereafter, and such printing operation is performed for one screen. It is sequentially executed to form one hard copy.

In FIG. 1, the switching pulse supplied to the terminal 45, the reset pulse supplied to the terminal 46, the enable pulse P _E supplied to the terminal 47, and the reset pulse supplied to the terminal 48 are all system controllers. The pulse generated by (not shown) is used.

Further, when the reading and printing period T _R is reached, a pulse P _D for rotation drive shown in FIG.
Is supplied, and the recording paper 2 is fed by a predetermined pitch regardless of the printing period. The pulse width of the drive pulse P _D is
When 3msec is selected, the paper is fed up to the 8th gradation, but the image is printed by the subtractive color method, so it is not printed in the high gradation part. Therefore, even if the paper is fed during the printing as described above, the image quality of the copy image is hardly affected.

When making a hard copy for color, the image data D is image data corresponding to a plurality of color signals as described above, and the above-described printing operation is executed for each color.

〔The invention's effect〕

According to the present invention described above, a plurality of image data sampled in one direction is compared with each gradation data to form a comparison output for each gradation, and the comparison output corresponding to the odd-numbered image data is output. The comparative output is supplied to the first thermal head element group HA arranged in an odd number of the plurality of thermal head elements H arranged so as to correspond to one direction, and the comparative output corresponding to the even-numbered image data is even numbered. It is supplied to the second thermal head element group HB arranged in the second order, so that the print results can be obtained at the densities according to the comparison output in the first and second thermal head element groups HA and HB, in each gradation. Since they are driven alternately, the first and second thermal head element groups HA and HB can print a predetermined image alternately for each gradation.
The drive current supplied to these thermal head element groups HA and HB can be reduced, and the current consumption during printing can be reduced, which allows the power supply circuit to be downsized and the thermal head resistance loss. There is an advantage that the voltage correction for gradation can be eliminated.

Further, the first and second thermal head element groups HA and HB are divided by not simply dividing the upper and lower sides of the thermal head element H but, for example, as shown in FIG. Since they are alternately divided as the thermal head elements of the first or second thermal head element group HA or HB, for example, because the gradation of the upper half and the lower half of the image to be printed is significantly different, Even if only the upper thermal head element is driven much, the thermal head elements are not uniformly driven over the upper thermal head element and the lower thermal head element, but are arranged uniformly over the entire thermal head element H. A first thermal head element group HA, a thermal head element adjacent to each thermal head element of the first thermal head element group HA, and a first thermal head element group HA.
Similarly to the above, the driving is performed by the second head element group HB evenly arranged over the entire thermal head element H, so that only a group (for example, a plurality of consecutive) thermal head elements in the thermal head element H are driven. Since it is possible to avoid such a state that sticking is not performed, it is possible to suppress the occurrence of sticking, thereby preventing streak noise from being printed and improving the image quality of hard copy.

Therefore, the present invention is extremely suitable when applied to a heat-sensitive printing device.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a printing apparatus according to the present invention,
2 to 4 are waveform charts for explaining the printing operation, and FIG.
FIG. 6 is a block diagram of the printer, FIG. 6 is a diagram for explaining the sampling position of the image data, FIG. 7 is a diagram showing an example of the configuration of the thermal head, and FIGS. 8 and 9 are for explaining the operation thereof. It is a waveform diagram to be provided. 1 is a platen, 2 is a recording paper, 4 is an ink ribbon, H is a thermal head, H _A and H _B are the first and second thermal head element groups, and 2
0 is a head drive system, 25 is a control circuit, 27 is an image data memory, 34 is a gradation counter, X is a comparison output, D _A and D _B are drive pulses, P _L is a latch pulse, and CK _S is a shift clock. is there.

Claims (1)

[Claims] 1. A plurality of image data sampled in one direction are compared with each gradation data to form a comparison output for each gradation, and a comparison output corresponding to an odd-numbered image data among these comparison outputs is the above-mentioned. It is supplied to the first thermal head element group which is arranged in an odd number of the plurality of thermal head elements which are arranged so as to correspond to one direction, and the comparison output corresponding to the even number image data is arranged in the even number. It is supplied to the second thermal head element group, and the first and second thermal head element groups are alternately driven for each gradation so that a print result can be obtained at a density according to the comparative output. A printing device characterized in that