JPS6213192B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for driving a thermal recording head that performs recording by applying thermal energy to thermal paper.

A thermal recording head has one heating element arranged in a line with a recording width of one scanning line at a predetermined pitch, and utilizes the Joule heat generated in the heating element by selectively energizing the heating element according to the image signal. to record an image on thermal paper.

FIG. 1 is a block diagram of a conventionally used thermal recording head. In the figure, reference numeral 101 denotes the heating elements 1 arranged on a substrate (not shown) such as ceramic.
02 is one diode for blocking reverse current.
One end of each heating element 101 is connected to the cathode side of a diode 102, and these diodes 102
The anode side of is connected to the external connection terminals 103 ₁ to 103k by connecting n adjacent ones. On the other hand, the other ends of the heating elements 101 are connected every (n-1), and are connected to external connection terminals 104 ₁ to 104 respectively.
104n. And these connection terminals 103 ₁ to 103k, 104 ₁ to 104n
are each externally connected to a driving transistor (not shown).

With this configuration, the l heating elements 101 are n
Each group is divided into k groups (k=l/n). Hereinafter, each of the above groups will be named (G1), (G2)... (Gk). Also,
In order to distinguish between the two types of external connection terminals, 103
₁ to 103k (totally denoted as 103) are called group selection signal input terminals, and ₁₀₄₁ to 104n (totally denoted as 104) are called parallel image signal input terminals.

Next, a method of driving a conventional thermal recording head having the configuration shown in FIG. 1 will be explained using the image signal shown in FIG. 2 as an example. Note that in this example, l=18, n=6, k
= 3. Among the image signals shown in Figure 2, white circles indicate white signals, black circles indicate black signals, and the group name of the corresponding heating element is indicated in curly brackets. It is tied up and shown.

Figure 3 is a diagram showing the timing of applying the selection signal and the image signal to the group selection signal input terminal and the parallel image signal input terminal, respectively. High when the transistor is OFF. It shows that it is in an impedance state, and the period without diagonal lines shows that it is in an ON state.

As can be seen from this figure, during the first recording, the G1 group selection signal input terminal 103 ₁
The transistors connected to the 4th, 5th, and 6th parallel image signal input terminals ₁₀₄₄ to ₁₀₄₆ are turned on and set to the "L" level (the others are set to the "L" level). (all high impedance), current flows through the 4th, 5th, and 6th heating elements of the G1 group. Then, during the second recording, the group selection signal input terminal ₁₀₃₂ of G2 is set to the "H" level, the first and second parallel image signal input terminals ₁₀₄₁ , ₁₀₄₂ are set to the "L" level, and the G2 Current is passed through the first and second heating elements of the group (ie, the seventh and eighth from the left end of the scanning line). During the third recording, the group selection signal input terminal ₁₀₃₃ of G3 is set to "H" level, but the parallel image signal input terminals ₁₀₄₁ to 104
₆ are all high impedance, so no current flows through any of the heating elements in this case.
Thermal paper (not shown) pressed onto the heating element 101 in this manner develops color only in the portions corresponding to the fourth to eighth energized heating elements, and a recorded image as shown in FIG. 2 is obtained.

By the way, the heating element 101 is manufactured using thick film or thin film technology, and the one using thick film technology has a pitch of 165 μm, a recording width of 200 mm, and a resistance value of 200 mm.
Ohm type has been put into practical use, and a predetermined recording density can be obtained by passing a current of 100 mA per heating element for about 4 msec. Since the energization time required for each heating element is large, the conventional driving method requires a very long recording time per scanning line. In other words, in order to record hand-drawn circuit diagrams on A4 size paper with a resolution of 8 dots/mm, the group configuration of heating elements is set to n=
128, k=14 (l=1792), and if the time required for one recording is 4 msec, the recording time per scanning line is 4 msec x 14 = 56 msec.

Here, a method can be considered to reduce the recording time per scanning line by reducing the number of groups k, but in this method, the parallel image signal input terminal 1
As the number n of 4 increases, manufacturing of the thermal recording head becomes more complicated, and the number of heating elements (maximum n) to be energized at the same time increases, making the power supply for the drive circuit expensive.

This invention was made for the purpose of shortening the recording time per scanning line without increasing the number of parallel image signal terminals n, by increasing the number of groups k and dividing into a plurality of series. Only the groups containing heating elements corresponding to the black signal to be recorded are discriminated one by one and energized at the same time. Hereinafter, this will be explained in detail using examples.

FIG. 4 is a configuration diagram showing an example of a thermal recording head to which the present invention is applied.
The number l of heating elements 101 is 18, and heating element 1
01 is G ₁ to _{G 6} connected in parallel in 8 pieces in the order of arrangement.
The signals are divided into six groups, and are connected to group selection signal input terminals 103 ₁ to 103 ₆ , respectively. Furthermore, the six groups are G ₁ , G ₃ , G ₅
The heating elements in each group in the same series are connected in parallel in the order of arrangement, and _are respectively connected to parallel image signal input terminals _{104 1 to} 104 _{6 .} It is connected. The difference between this configuration example and the conventional one explained using FIGS. 2 and 3 is that the number of groups k increases from 3 to 6, and the number of heating elements in each group increases from 6 to 3. However, the feature of this invention lies in the difference in the driving method. This will be explained in detail below with reference to FIGS. 5 and 6.

FIG. 5 shows the same image signals as shown in FIG. 2, and the corresponding group names are shown in curly brackets. When organized by each series, the first series (G ₁ , G ₃ ,
G ₅ ) signal train is [(white, white, white), (black, black,
white), (white, white, white)], and that of the second series is [(black, black, black) (white, white, white) (white, white,
white)].

In the driving method to which this invention is applied, it is determined for each series whether each group belonging to that series contains a black signal or not, and groups that do not contain a black signal are skipped, and only groups containing a black signal are sequentially selected. It is equipped with a selection device for selection. Therefore, during the first recording, in the first series, the G ₁ group is removed and the G ₃ group is selected first. On the other hand, in the second series, group G ₂ is selected,
Here, the group selection signal input terminals 103 ₃ , 103 ₂ connected to the two groups G ₃ and G ₂ are driven to “H” level, and at the same time the parallel image signal signal terminals 104 ₁ , 104 ₂ , 104 ₄ , 104 ₅ ,
₁₀₄₆ is driven to the "L" level, and as a result, five heating elements 101 from the fourth to the eighth from the left end of the scanning line are energized at the same time.

In this example, since there are no groups remaining that include black signals in either of the two series, the recording of one scanning line ends in one recording.

As described above, in the driving method according to the present invention, the number of heating elements whose terminals are connected in parallel to one group selection signal input terminal 103 is decreased to increase the number of groups, and each group is divided into a plurality of series. The heating elements in each group belonging to the same series are configured such that the other terminal is connected in parallel to one parallel image signal input terminal in the order of arrangement, and when driving, each series generates heat corresponding to the black signal. This system distinguishes only the groups containing elements and sequentially selects them to energize them.Since the number of heating elements in one group is relatively small, the probability that the group does not contain a black signal increases, and it is different from the conventional method. As in the driving method described above, even when only a white signal is used, a certain recording time is not wasted, so the time required to record one scanning line can be significantly shortened.

As explained earlier, in the conventional drive method, it takes 4 scans to record one scanning line of a hand-drawn circuit diagram on A4 size paper.
Although it required a time of msec x 14 = 56 msec, by applying this invention, the number of parallel image signal input terminals n = 128,
Number of heating elements in one group i = 32, number of groups k
= 1792/32 = (1792/128) x 4 = 56, number of series cases J =
4, the time required to record one scanning line was only 8.73 msec on average, reducing the time to about 1/6.4.

In addition, in the driving method according to the present invention, the discrimination and selection means discriminates whether or not each group includes a black signal, selects only the group containing the black signal by skipping the group containing no black signal, and energizes the group. However, such a function requires one for each series.
A shift register that temporarily stores the group's image signal, a clock generation circuit for rotating the image signal in this shift register, a black signal counting circuit (0
It is sufficient to be able to identify whether the ), the explanation will be omitted here.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a conventional thermal recording head;
The figure shows an example of an image signal, FIG. 3 is a timing diagram of a conventional thermal recording head driving method, FIG. 4 is a configuration diagram showing an example of a thermal recording head used in the present invention, and FIG. 5 is an image signal. A diagram showing an example, FIG. 6, is a timing diagram of a method of driving a thermal recording head according to the present invention. In the figure, 101 is a heating element, 102 is a reverse current blocking diode, 103 is a group selection signal input terminal, and 104 is a parallel image signal input terminal. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Claims] 1. Using a thermal recording head having the following configurations (a) to (c), an image signal is recorded one scanning line at a time as shown in (d) to (e) below. A method for driving a thermal recording head, characterized in that: (b) It has l heating elements each configured to correspond to a pixel signal for one scanning line of the image signal, and these l heating elements are divided into i heating elements and k heating elements each in the scanning order of the image signal. divided into groups. (b) One input terminal of the l heating elements is connected to one group selection signal input terminal for each group via connected diodes,
It has a total of l/i=K group selection signal input terminals. (c) The other input terminal of the l heating elements is connected to the J
For each series, the other input terminals of the heating elements in each group belonging to the series are connected in parallel to one common image signal input terminal one by one in the order of arrangement, so that the total number of i× It has J common image signal input terminals. (d) Divide the pixel signals for one scanning line of the image signal into k groups of i pieces according to the above (a), and further divide them into k groups.
These groups are divided into J series according to (c) above. (e) For each series of group J, determine whether there is a pixel signal to be recorded one group at a time, select only the group containing the pixel signal to be recorded, and input the corresponding group selection input terminal in (b) above. , a selection signal is simultaneously input for each series one group at a time, and at the same time, the common image signal input terminal (c) corresponding to the pixel signal to be recorded is selected and the image signal is input.