JPH0289660A - Method of driving recording head - Google Patents

Abstract

PURPOSE:To prevent the occurrence of excess heat accumulation in a recording head even when black continues by making No.2 dot conduction energy smaller than No.3 dot conduction energy when a picture signal is changed into a heat- generating signal from a non-heat-generating signal and three dots or more continue. CONSTITUTION:When conduction to a heating element D5 is observed in the order of the processing of a line, L from L4 to L7 and L from L19 to L23 are acquired as the line, on which there is black in the travelling direction of a recording head 6, but the quantity of heat accumulated in the recording head 6 is reduced extremely because black starts after white continues for a while in L4 and L19. Consequently, since conduction energy is increased in L4 and L19, pulse width is brought to t1 and lengthened in the dot of L4 and the dot of L19, and a picture edge section is made distinct. Dots corresponding to L5 and L20 represent No.2 dots changed into black from white in the travelling direction of the recording head 6, and comparatively high conduction energy is applied to No.1 dots before the dots, thus decreasing pulse width to t2 and conducting electricity in L5 and L20 corresponding to No.2 dots.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a recording method that controls the energy applied to each heating element when performing thermal recording by selectively generating heat from a plurality of heating elements according to an image signal. This relates to a method of driving a henod.

<Background Art> In recent years, with the rapid development of the information industry, various information processing systems have been developed, and recording methods suitable for each information processing system have been developed. Among such recording methods, there is a thermal recording method, which has recently been widely used because the apparatus used is lightweight, small, generates little noise, and has excellent operability and maintainability.

The thermal recording method includes a thermal recording method and a thermal transfer recording method. The thermal recording type uses a color-forming thermal recording paper containing a coloring agent and a color developer as a recording medium, and a recording head consisting of a plurality of heating elements that generate heat when energized is arranged on five Hen Door plates. A recorded image is obtained by applying a thermal signal.

The thermal transfer recording method uses a thermal transfer material made by coating a film-like support with a thermal transfer ink made by dispersing a coloring agent in a heat-melting binder. The heat-transferable ink is transferred onto the recording medium by superimposing the heat-transferable ink stones so as to be in contact with a recording medium such as plain paper, and applying a heat signal from the support side of the heat-sensitive transfer material by the recording head. .

<Problems to be Solved by the Invention> The above-mentioned thermal recording method has the following problems in both the thermal recording type and the thermal transfer recording type.

That is, when selectively driving a heating element according to a recorded image signal, if the amount of energy applied to the heating element is constant when the image signal generates heat no matter what the image signal is, then the state of the image signal will be changed. As a result, the degree of cooling and heat storage in the substrate of the recording head and the inside of the glaze differs, so that the recorded image may become unclear.

For example, along the direction of movement of the recording head relative to the recording medium, where there was no image signal (hereinafter simply referred to as "black J") that causes heat generation for a while, black begins at a certain point and the heat generating element is energized. The temperature and residual heat inside the recording head are different between when the heating element is started and when the heating element is energized while a certain level of black continues, and the state of residual heat is different before the heating element is energized. The temperature reached by the heat generated from the element differs.

In order to solve this problem, for each heating element, a dot of a non-heating signal (hereinafter referred to as "white j") is traced along the direction of movement of the recording head relative to the recording medium, and a dot of a heating signal (the above-mentioned "black") is ), a higher energizing energy is applied to only the first black dot, and a constant energizing energy lower than that of the first black dot is applied to the second black dot. . When this kind of correction is performed, high energy is applied to the first dot (the beginning of the image) where there is less heat accumulation in the hand along the direction of movement of the print head relative to the print medium, so the image edges are Be sharp.

Further, the second dot and subsequent dots can be recorded with relatively less energizing energy due to heat accumulation in the first dot and subsequent dots.

However, when attempting to perform high-speed recording using the drive control described above, the influence of the high energizing energy of the first black dot remains on the third and fourth black dots, or the subsequent dots. may lead to deterioration of image quality. This is not limited to high-speed recording, but also applies when the energizing energy for the first black dot is higher than the energizing energy for the second and subsequent black dots.

Furthermore, the influence of heat accumulation occurs even when a recorded image is formed in the form of a film that does not permeate the recording medium by thermal transfer recording, and the recorded image is erroneously erased by so-called lift-off. That is, excessive melting of the ink occurs due to the influence of the heat accumulation, resulting in the formation of areas where the ink penetrates into the recording medium, resulting in non-uniform erasing due to lift-off.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for driving a recording head that solves the above-mentioned conventional problems and does not cause excessive heat accumulation in the recording head even when black continues.

<Means for Solving the Problem> A means for solving the problem is a recording head which performs thermal recording on a recording medium by selectively applying energizing energy to a heating element according to an image signal in units of dots. In the driving method, when energizing the heating element according to the image signal, an image signal within a predetermined range centered around the image signal to be energized is detected, and the heating element is energized according to the detection result. In controlling the energy applied to the heating element, the image signal changes from a non-heating signal to a heating signal along the direction of movement of the recording head relative to the recording medium, and the heating signal continues for three or more dots. In some cases, the energization energy of the second dot of the heat generation signal is made smaller than the energization energy of the third dot of the heat generation signal.

According to the above means, when there is a continuous negative movement in the direction of relative movement of the recording head to the recording medium, in order to sharpen the image edge, the first dot is moved more than the second dot. Even if a high energizing power is applied, the energizing energy applied to the second dot is small, so the influence of heat accumulation due to energization to the first dot will not be excessively exerted on the third dot and beyond. . Therefore, it is possible to record an overall clear image.

<Embodiment> Next, an embodiment in which the above means is applied to a thermal transfer recording system will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective explanatory diagram of a thermal transfer recording apparatus, and FIG. 2 is a schematic explanatory diagram showing the arrangement of heating elements of a recording head.

First, to explain the general structure of the entire recording device, (2) is an ink ribbon in which a long base film is coated with ink that melts when heated and transfers to a recording sheet. 2, and the cassette 2 is configured to be removably loaded into the carriage 3. A bell 4c is connected to the carriage 3, and is configured to be able to reciprocate along a guide shaft 5 by driving a carriage motor 4d connected to the pulley 4a. There is.

Further, the carriage 3 is equipped with a recording head 6 in which a large number of heat generating elements are arranged in a line, and when the head 6 is lowered for recording during recording, the ink ribbon 1 is placed on the recording sheet 8 whose back side is supported by a platen 7. When the carriage 3 is pressed and moves in the direction of the arrow (main scanning direction) in this state, the ink ribbon 1 is sequentially fed out in the direction of the arrow B from the supply reel 9a. Furthermore, in synchronization with the movement of the carriage 3 in the direction of arrow A, the recording head 6
When the ink is heated in response to the image signal, the ink melted by this heat is transferred to the recording sheet 8.

The ink ribbon 1 after the ink transfer is transferred to the recording sheet 8.
It is configured such that it is peeled off from the film and wound onto the winding wheel 9b.

Furthermore, when one line of transcription is completed as described above,
The recording pad 6 performs a heft assist to return the carriage 3 to the home position, and at the same time, the conveyance roller IO is rotated by a predetermined amount by the conveyance motor 11 to convey the recording sheet 8 by - lines in the direction of arrow C (sub-scanning direction). The configuration is such that recording from the next line onwards is repeated in the same manner as above.

Now, to explain the recording head 6 used in this embodiment, as shown in FIG. It will be done. The heating elements 6b individually generate heat when energized, and are driven by a heating signal from the control system. As shown in the block diagram of FIG. 3, in this control system, the data to be recorded is transferred to the recording head 6 via the image signal buffer 12a in synchronization with the clock signal output from the sequence controller +2b, and after the transfer is completed. Data is sent by providing a latch signal. on the other hand,
Heat generating element drive power source 12d via drive current controller 12c
While supplying the common current from the pulse width: i? R.H.
A strobe signal is given to the recording head 6 in accordance with the drive pulse width calculated by 2e. While the strobe signal is being output, the supplied common current flows through the heating element 6b and generates heat.

Next, a method for driving the recording head 6 when recording an image will be explained.

The heating element 6b of the recording head 6 generates heat by being energized in response to a heat generation signal from the control system as described above, but the energizing energy at this time is distributed over several dots within a predetermined range around the energized heating element 6b. It detects whether or not there is a problem, and is controlled according to the detection result.

In this embodiment, the range of dots to be detected centered on the dot to be recorded by energizing the heating element 6b is set as shown in FIG.

In other words, the dot DI L that is one spot behind the dots D and L to be energized in the running direction of the recording head.
, , , Detect whether the two dots Di L, , □2, and one 11th edition) Di L, , are black or white, and apply the pass through to the dots D and L. Determine the appropriate energizing energy.

Here, based on the detection result, "PJ" as shown in FIG.
Taking the case of recording a pattern image as an example, an example of the manner in which the 24 heating elements 6b of the recording pen are energized is shown in the waveform of the energizing pulse of the strobe signal as shown in FIG.

In addition, in FIG. 5, each heating element 6b is placed in order from the top to
, D2. ...Dl:1. Dl4 (see FIG. 2), and each line in the scanning direction of the recording hand is sequentially La, Lz, . . . L23+L12 from the left. FIGS. 6A and 6B show pulse waveforms when energizing the backs of the heating elements 6b, D, , D, etc., according to the scanning direction of the recording head 6.

Further, in FIGS. 6(^) and (B), ▪ represents the voltage applied to the heating element 6b, and T represents the pulse period.

Then, the pulse width for determining the energization energy to the heating element 6b is determined according to the image signal in the range to be detected.
Select three types: tf+L3. In this embodiment, the pulse period is T=2.0+m5ec, and the three types of pulse widths are t+=1.3m5ec, L,
=0.5m5ec, tt=0. lll++sec
It is set to .

In recording the "P" pattern, for example, the energization state of the heating elements Ds and D+1 will be specifically explained.

First, looking at the energization of the heat generating elements in the order in which the lines advance, as shown in FIG. ,. However, 1. ．． 4 and I-1, the color starts after a while of white, so the amount of heat stored in the recording hexagon is very small. Therefore, in 11) L4 and L19, in order to increase the energization energy, the dots of L and L
The pulse width of dot 19 is set to be long as t, and the edge portion of the image is made clear.

Next, the 1-゛ dot corresponding to L2゜ is the second dot that changes from white to black in the direction of travel of the recording nozzle 6, and relatively high energizing energy is applied to the previous 1-dot. This prevents the influence of the heat accumulation from reaching subsequent dots in the recording direction of the gutter 6. Therefore, it corresponds to the second dot, and I7□. Now, the pulse width is reduced to t2 and the current is applied.

Then, from La, Lt, and L2□ J-22, Lt3, that is, the third dot that changes from white to black in the running direction of the recording head 6, appropriate energizing energy is applied to record continuous dots. In order to generate uniform heat, the pulse width should be set as (,).

By reducing the energizing energy of the second dot as described above, the excess heat accumulated due to the large energizing energy of the first dot, which changes from white to black in the direction of travel of the recording nozzle 6, is absorbed by the second dot. , the influence of the heat accumulation does not extend to the third dot and beyond. Therefore, a rapid temperature drop can be achieved even at the falling edge of heat, and a clear image faithful to the image signal can be obtained.

Similarly, in the line of the heating element D13, as shown in FIGS. 5 and 6(B), the first dot changes from white to male, and the pulse width is 1. ．． The pulse width of the second dot LS [I7. FromLll+
In this case, electricity is applied with a pulse width to generate heat.

The above-mentioned energization control is the same for other heating element lines.

As mentioned above, the heating element of the recording throat 6 is connected to -D.

The energization control is performed using the pulse width calculator +2e in Fig. 3.
The calculation procedure at this time is shown in the flowchart of FIG.

First, in step S1, it is determined whether or not the recording head 6 is down. If it is not down, the pulse width is not calculated because it is not in a recording state. When the head is down in step 31, it is in a recording state, so the process moves to step S2 to calculate the pulse width.

Next, in step S2, the value of counter j is set to 1 without indicating the order of each line L, and in step S3, the value of counter i is set to 1 without indicating the order of dots on the corresponding line. .

Next, in step S4, it is determined whether the second dot DILj (that is, D, L, which refers to the upper left dot in FIG. 5) of the image determined by the values of i and J is black or not. do.

When the dot DI LJ is not black, there is no need to energize the heating element corresponding to this dot, so step S
7, the pulse width, which is the energization time within one pulse cycle, is set to 0, and the process proceeds to step Sll.

Further, when the dots D and L are determined to be black in the step S4, the process moves to step S5 to record the dots i on the line Lj-1 that is one line behind in the running direction of the rad 6.
It is determined whether or not the th dot, ie, L, is black. When this discrimination is not black, that is, Tono)-D, L,
When is the first village or is black immediately after the man is interrupted, the process advances to step S8, where the pulse width t within one pulse period of the current dot DtL; is set to tl, and the process advances to step Sll. .

On the other hand, if the dot Di Lj- is black in step S5, that is, if the dot D+J is the second or subsequent black dot, the process moves to step S6 and the recording is started in the direction of travel of the rad 6. Yet another line L
, -□, it is determined whether the i-th dot D+L, +-z is black or not.

If the dots D+LJ- are not black in this step S6, the dots D and L correspond to the second dot after black starts in the running direction of the recording head 6, and therefore, in step S9
The process proceeds to step Sll, where the pulse width within one pulse period is set to t2, and then the process proceeds to step Sll.

Also, when Dora [) and Lj-2 are black in step S6,
Since the corresponding dot DILj corresponds to the third dot or later after black starts in the running direction of the recording head 6, the process advances to step SIO, where the pulse width t within one pulse period is also set to Proceed to SIL.

Then, in step Sll, it is determined whether or not i is equal to or less than 24, and when i is determined to be less than 24, that is, the line L,
If the process has not been completed, the process advances to step S13, where the value of the counter i is incremented by 1, and the process returns to step S4. If it is determined in step S11 that i is not less than 24, it means that all dot processing for the line concerned has been completed, and the process moves to step SI2 to proceed to dot processing for the next line.

In step S12, it is determined whether the recording head 6 is a head amplifier or not, and when it is determined that it is not a head amplifier, that is, the processing line is not the final line and there is data on the next line Lj+1. If so, the process advances to step S14, where the value of the counter J is incremented by 1, and the process returns to step S3.

Also, when it is determined in step S12 that it is a hend attachment,
That is, when the processing line LJ is the last line, it means that all dot processing has been completed, and the processing is ended.

[Other Examples]

The functions of the flowchart of FIG. 7 described above can be easily realized not only by software but also by hardware using constituent elements such as registers and counter comparators.

In addition, in the control according to the flowchart of FIG. 7 mentioned above,
The energization pulse width was determined for the energy application dot DI Lj according to the white and black detection results of the previous dots D, L, and DtJ-z, but the energy application pulse width was
For Di Lj, the next recorded 1' cut DiLJ,
When , is white (when there is no heat generation No. 13), by making the energizing energy of the current dot D+LJ slightly smaller than t, the heat can be lowered more quickly.

Furthermore, in the above recording, in order to improve the rise of heat at the first black dot, the energy mark m at the lth black dot was added.
Preheating may be added beforehand. Even in this case, the heat accumulated in the recording helix can be effectively absorbed by applying energy to the second dot.

Further, in the above-described embodiment, the amount of energizing energy is controlled by the energizing pulse width, but the same effect can be obtained by controlling the value of the applied voltage (2) while keeping the pulse width constant. When changing the applied voltage, replace the pulse width in FIG. 3 with a voltage value and send a voltage control signal to the drive current controller +2c instead of a strobe signal to modulate the voltage value. good.

Further, in the above-described embodiment, an example of so-called serial type recording in which the recording head 6 runs is shown, but it can be similarly applied to so-called in-type recording in which recording is performed by conveying a recording sheet to the recording head. It is.

Furthermore, in the above-mentioned embodiment, an example of a thermal transfer recording type was shown, but
It goes without saying that the present invention can be similarly applied to a heat-sensitive recording type.

[Experimental Results] When actual recording was performed as in the above example,
The edges of the image appeared clearly, and a high-quality image with uniform density was obtained even in areas with a lot of black in the image. In addition, materials that have film properties during transfer (ethylene/acrylic copolymers, ethylene/vinyl acetate copolymers, acrylic resins, polyamide resins, etc.) are used as thermal transfer inks, and the transferred recorded images are transferred to adhesive tapes or thermosensitive When removed and erased using lift-off tape with an adhesive layer:
There was no residue after erasing, indicating good erasability.

On the other hand, the image signal was detected along the running direction of the recording head, and the pulse width of the first black dot was 1.3 m5e.
c, but after 2 dots, the pulse width is set to 0.8m5.
Similar to the example described above as ec, when the image of the Pj pattern was recorded, a clear image was seen in the edge part of the image on the left, but the beginning of a black signal was observed in the edge part of the right image. Due to the influence of heat accumulation from the first and second dots, the image lacked sharpness, and the density was uneven, especially in areas with large black areas.Furthermore, during lift-off, partial penetration caused Due to over-erasing, erasing residues were left behind, resulting in poor erasability.

<Effects of the Invention> As described above, in the present invention, when there is continuous black in the direction of movement of the recording head relative to the recording medium,
Since the energizing energy for the first dot is lower than the energizing energy for the third dot, excess heat is not accumulated in the recording head, and image density and non-uniformity are reduced.
Alternatively, the effect of preventing unerased data at the time of lift-off can be obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a thermal transfer recording apparatus, FIG. 2 is an explanatory diagram showing the arrangement of heating elements of a recording head according to an embodiment of the present invention, FIG. 3 is a block diagram of a control system, and FIG. FIG. 5 is an explanatory diagram of the heat generation signal detection range, FIG. 5 is an explanatory diagram of the recording pattern, FIGS. 6(A) and (B) are timing charts showing the energization pulse width, and FIG. 7 is a flowchart for determining the pulse width. 1 is the ink ribbon, 2 is the drawer, 3 is the carriage, 4
a, 4b are pulleys, 4c is a heald, 4d is a carriage motor, 5 is a guide shaft, 6 is a recording head, 6a is a head substrate, 6b is a heating element, 7 is a platen, 8 is a recording sheet, 9a is a supply reel, 9b is a take-up reel, IO is a transport roller, 11 is a transport motor, 12a is an image signal buffer,
12b is a sequence controller, 12c is a drive current controller,
12d is a heating element driving power source, and 12e is a pulse width calculator.

Claims (1)

[Scope of Claims] A method for driving a recording head for performing thermal recording on a recording medium by selectively applying energizing energy to a heating element according to an image signal in dot units, the method comprising: When energizing the heating element, detecting an image signal within a predetermined range around the image signal to be energized, and controlling the energy energized to the heating element according to the detection result, When the image signal changes from a non-heating signal to a heating signal along the direction of movement of the recording head relative to the medium, and when the heating signal continues for three or more dots, the energization energy of the second dot of the heating signal A method for driving a recording head, characterized in that: is made smaller than the energization energy of the third dot of the heat generation signal.