JPS6387259A - Thermal head driving method for thermal printer - Google Patents

Abstract

PURPOSE:To contrive a shorter printing time, by driving all thermal heads for gradations of at least (k+1) for the same driving time at the time of driving a thermal head corresponding to a gradation (k), and regulating respective driving times. CONSTITUTION:At the time of printing a first gradation, not only a thermal head corresponding to the first gradation (k=1) is driven for a driving time T1 but also thermal heads corresponding to gradations (2, 3,...n) not lower than the second gradation (k=2) are also driven (driving time: T1) for printing. At the time of printing the second gradation, the thermal heads corresponding to gradations (3, 4,...n) not lower than the third gradation are driven for the second superimposing printing (driving time: t2). Since heat generating resistors of the thermal heads and a printing paper is heated to predetermined temperatures by the first printing (driving time: T1), a predetermined printed density can be obtained even when t2 is shorter than T1. Similarly, the third, the fourth...the n-th gradations are printed. Therefore, printing time can be shortened. Further,by regulating the driving times for the thermal heads driven for superimposing printing (n) times, printed densities of the entire part of a print image are controlled. Accordingly, the driving times can be shortened.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for driving a thermal head of a thermal printer.

[Prior Art] When printing with a density of n gradations from the first gradation to the nth gradation (n is an integer of 2 or more) using a thermal printer, the time ( There is a method of obtaining printing with density of n gradations by controlling the driving time of the thermal head (hereinafter simply referred to as the driving time of the thermal head) and shifting the timing of the driving time for each gradation.

Conventionally, such a method of driving a thermal head first involves a first
Select only the thermal head for gradation printing and
Print the gradation, then select only the thermal head for printing the second gradation and print the second gradation, then increase the gradation one by one and print each gradation, and finally For example, as shown in Figure 2, thermal heads arranged in a horizontal line (for example, 256 The dot) (1) is divided into four blocks A, B, C, and D (64 dots in each block), and the timing of the drive time of the thermal head (1) is shifted for each block to suppress the drive current capacity. In a thermal printer designed to
As shown in the figure, a case will be described in which printing is performed by dividing one horizontal scanning period (LH) into 16 gradation densities from the first gradation (white level) to the 16th gradation (black level).

First, in order to print the first gradation, only the corresponding thermal head (1) is selected, and as shown in FIG. 4, the driving time T1 is shifted in the order of blocks A, B, C, and D. By driving, printing of the first gradation is performed. Then, only the corresponding thermal head (1) is selected for printing the second gradation, and its driving time Tz("rz
> rt) in the order of blocks A, B, C, and D as shown in FIG.
Gradation printing is performed. Thereafter, the corresponding thermal heads (1) are sequentially selected for printing in the third, fourth, and so on gradations, and their driving times T3, T... (T z <T
s < T 4 <...) as shown in Figure 4.
, C, and D blocks at different timings to print the 3rd, 4th, and so on gradations, and finally, the thermal head selected for printing the 16th gradation ( 1) is driven for a driving time Txs (Tyu, <T15), and printing of the 16th gradation is performed.

[Problems to be Solved by the Invention] As mentioned above, in the conventional method of driving a thermal head, 16
When performing gradation printing, at least Tj ("Tz◆T ÷...÷T1.) (Tj)16 for one block.
Since a driving time of T1) is required, a driving time of at least 4Tj is required for four blocks, which increases the printing time, and there is a problem that the printing time becomes longer as the number of gradations of printing density increases. Ta.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a method for driving a thermal head of a thermal printer that can shorten printing time.

[Means for Solving the Problems] The method for driving a thermal bed according to the present invention controls the driving time of the thermal head and shifts the timing of this driving time for each gradation, thereby improving printing density. In a thermal printer that prints in n gradations from the 1st gradation to the nth gradation (n is an integer of 2 or more) with high print density, the printer corresponds to each of the first to nth gradations. The thermal heads are sequentially driven to perform printing, and when the thermal head corresponding to the first gradation (k is an integer from 1 to n-1) is driven, all thermal heads of +IPJ tone or higher are simultaneously driven. The thermal head is driven for the same driving time and prints n gradations by n times of overlapping printing, and the shading of the entire printing screen is controlled by expanding or contracting the driving time of each of the thermal heads that perform the n times of overlapping printing. It is characterized by the fact that

[Operation] First, when printing the first gradation, the first gradation (k=1)
The thermal head corresponding to the drive time T,! Not only does it move, but it also moves at the second gradation (k÷1=2) or higher (2, 3) at the same time.
,...n) also prints (driving time T
, ). Next, when printing the second gradation (k = 2), at the same time print the gradation (3,
4°...n) performs second overlapping printing (driving time ta). At this time, the driving time t2 required for the second printing of the thermal head corresponding to the second gradation is T1. becomes smaller (t2<Tl)++ because the first
Since the heating resistor of the thermal head and the photographic paper have risen to a predetermined temperature by the second printing (driving time T1),
This is because even if t3 is shorter than T1, a predetermined print density can be obtained. Thereafter, printing of the third, fourth, . . . , nth gradation is performed in the same manner. At this time, for the thermal head corresponding to the nth gradation, n times of overlapping printing <yjA moving time t 1
"t 2" t 3◆...tn), but for the same reason as mentioned above, at least t, <T1, t, <T
... Since tn<T1, the total driving time of the thermal head required for printing n gradations is Tt (=T1+t, +t,
+...÷tn<nT1) is the total drive time of the conventional thermal head Tj (:TL''Tz÷-+Tn>
nTL), and as a result, the printing time can be made shorter than before.

Further, by expanding or contracting the drive time of each of the thermal heads that perform n-times overlapping printing, the density of the printing on the entire printing screen is controlled. For this reason, compared to the conventional method, the corresponding gradation was printed by only one printing of each selected thermal head, and the shading of the print density on the entire printing screen was controlled by expanding and contracting the driving time of each thermal head. In comparison, the driving time of the thermal head is shortened when controlling the print density of the second gradation or higher.

[Embodiment] FIG. 1 shows an embodiment of the present invention, in which thermal heads (1) (for example, 256
The dots) are divided into four blocks A, B, C, and D (64 dots in each block), and the timing of the drive time of the thermal head (1) is shifted for each block to suppress the drive current capacity. The third thermal printer
As shown in the figure, the present invention was utilized when printing was performed by dividing one horizontal scanning period (IH) into 16 gradations of density from the 1st gradation (white level) to the 16th gradation (black level). This figure shows a timing chart of the time. For convenience of explanation, the length of the time axis (horizontal axis) for the same time interval is approximately twice that in FIG. 1 as in FIG. 4.

(b) First, when printing the first gradation, the first gradation (k
=1) The thermal head (1) corresponding to A, B, C, and D blocks prints at different timings (driving time T1
), at the same time, the second gradation (k÷1=2)
The thermal head (1) corresponding to the above floor $1 (2, 3, . . . ) also performs the first printing (driving time T,) with the timing shifted for each block.

(b) Next, printing of the second gradation is performed, but the second gradation (k
The thermal head (1) corresponding to =2) prints at different timings for each block of A, B, C, and D.

At this time, as shown in FIG. 1, the second driving time of the thermal head (1) of each block of A, B, C, and D is
Assuming that avtzbvt*ctt2d, the cooling times just before that are ttzavt and *bvtsxC1t1zd, respectively, and the time from the end of the first printing to the beginning of the second printing as T1□, from Fig. 1, t, a= 3T, +T1. −(1)jlzl)=
= 2T, +T, 1+t2a...(2)tB
c= T, +T, , +t, a+t, b - (3)
tl, d= T, , +t, a+t, b+t, c
-(4).

On the other hand, the driving time for the second printing is tza@t2bytz
cytzd is shorter than T□ because the heating resistor of the thermal head (1) and the photographic paper have reached a predetermined temperature during the first printing (driving time T1). For this reason, the above (
1) (2) (3) From equation (4), t2. a>t,,
b > t12c > t,, d ''・(S). The above equation (5) shows that the cooling time immediately before the second printing becomes shorter as it goes to blocks A, B, C, and D. This cooling time t1mal
timbttiICttl! Second printing driving time t@a * tz b t tx Cv corresponding to d
ts d into blocks A and B.

By sequentially controlling C and D in short order, A and B
There is no difference in printing density between the , C, and D bronzes 9, and the same printing density of the same gradation can be obtained.

Also, at the same time as printing the second gradation, the third additional gradation (k+1=3
) The thermal head (1) corresponding to the above gradations (3, 4, . . . ) also has driving times t, a, t, b, t, c, for each block of A, B, C, D, respectively. Perform the second overlapping printing of t and d.

(c) Thereafter, the third and fourth gradations are printed in the same manner as in (b) above, and finally the thermal head (1) corresponding to the 16th gradation prints A, B, C:, D. The drive time tzsaet1*b*t1actt>r for each block of
The 16th overlapping printing of d is performed and the printing is completed. Therefore, the driving time of the thermal head required for printing in 16 gradations is Tta==T, +t2a+t, a+-+t1. a(16
T, -(6). Similarly, for B, C, and D blocks, Ttb='r, +t2b+t, b
+...+t, sb<16T, ...(7
)Ttc=T,+t,c+t,c◆−+t,,c<1
6T, -(8)Ttd=T, +t, d+t,
d÷・ +t1sd<16T1 - (9), so the total driving time Tt of the thermal head (1) for all blocks A, B, C, and D is Tt=:Tta+
Ttb+Ttc+Ttd<64T, ...(to
), which is sufficiently smaller (Tt
<Tj).

Therefore, even if a time period (T1□, T13, etc.) in which the thermal head (1) is not driven during overprinting is provided as shown in FIG. 1, the printing time can be made shorter than in the past.

(d) When controlling the shading of the entire printing screen, this is done by expanding or contracting the driving time of each of the thermal heads (1) that perform n-times overlapping printing. That is, as shown by the dotted line in FIG. 1, the driving time of the thermal head (1) for each block of A, B, C, and D is T, e (=T, ÷ΔT, ), and for the second printing, t, ae (= t, a+Δtza), t,
be (= t , b + Δt, b), t, ce (= t
2c + Δt , c), t 2da (= t , d + Δt
, d)..., t for the 16th printing
,,ae(=t,sa+Δttaa),j,,be
(= ttab÷Δtxsb), t, ee("j
xsc+Δj xsc), txsde(”txsd+Δ
t zsd), it is possible to increase the print density of the entire print screen. Furthermore, as shown by the dashed line in FIG. ), and for the second printing, t 2ar (= t 2a - Δt2a), t , b
r (= t , b - Δt, b), t zcr (= t
, C-Δt, c), t, dr(= t, d-Δt2
d)...For the 16th printing, t1.
ar(=t 1.a-Δj xsa), txsbr(
= t , @b-Δtz@b), t , , cr (= t
1. c-Δt tse), tlsdr(= txi(1
-Δj tsd), the print density of the entire print screen can be made lighter. Note that when controlling the print density of the entire print screen to be darker or lighter than the standard density, the time during which the thermal head (1) is not driven (for example, T1□, T13, etc.) is the same as when controlling the standard density. )
is appropriately selected, taking into consideration that if the length is too long, the heating resistor of the thermal head and the photographic paper will not cool down to a predetermined temperature or below, and if it is too short, the print quality will not deteriorate.

In the above embodiment, a thermal printer that prints in 16 gradations from the 1st gradation to the 16th gradation has been described. However, the present invention is not limited to 16 gradations, and prints in n gradations (n
Of course, the present invention can be used for a thermal printer that prints an integer of 2 or more).

In the above embodiment, a thermal printer was described in which thermal heads arranged in a horizontal line are divided into a plurality of blocks, and the timing of the driving time of the thermal heads is shifted for each block to suppress the driving current capacity. However, the present invention is not limited to this, and if there is no need to suppress the drive current capacity (for example, when the number of thermal heads is small), the driving time of the thermal heads is controlled and the timing of this driving time is changed for each gradation. The present invention can be applied to any thermal printer that performs n-gradation printing by shifting control.

[Effects of the Invention] As described above, the method for driving a thermal head of a thermal printer according to the present invention sequentially drives the thermal heads corresponding to each of the first to nth gradations to perform printing, and When driving a thermal head corresponding to a gradation (k is an integer from 1 to n-1), simultaneously driving a thermal head corresponding to all gradations of +1 gradation or higher for the same driving time; Since printing is performed in n tones by n times of overprinting, the driving time of the thermal head for printing in gradations higher than the second gradation can be made shorter than in the past.

The overall printing time can be made shorter than before.

Furthermore, the shading of the printing density on the entire printing screen is controlled by controlling the drive time of each of the thermal heads that perform n times of overlapping printing. The driving time of the thermal head that controls this can be made shorter than in the past, and as a result, the overall printing time can be made shorter than in the past.

[Brief explanation of the drawing]

FIG. 1 is a timing chart showing an embodiment of the thermal head driving method for a thermal printer according to the present invention, FIG. 2 is an explanatory diagram of the thermal head, FIG. 3 is a diagram showing the gradation of print density, and FIG. 3 is a timing chart showing a conventional example. (1)...Thermal head of a thermal printer.

Claims (2)

[Claims] (1) By controlling the driving time of the thermal head and by shifting the timing of this driving time for each gradation, from the first gradation with light print density to the nth gradation with high print density (n is 2 In a thermal printer that prints at n gradations up to an integer of (k is an integer from 1 to n-1) When driving the thermal head corresponding to the kth gradation (k is an integer from 1 to n-1), all the thermal heads for the k+1st gradation or higher are simultaneously driven for the same driving time, and n gradation printing is performed by repeating printing n times. A method for driving a thermal head for a thermal printer, characterized in that the shading of the entire printing screen is controlled by expanding or contracting the drive time of each of the thermal heads that perform the n-times overlapping printing. (2) The thermal printer is constructed by dividing thermal heads arranged in a horizontal line into a plurality of blocks, and shifting the driving time timing of the thermal heads for each block to suppress the driving current capacity. A method for driving a thermal head of a thermal printer described in Section 1.