JPH06198939A - Driver for thermal printing head - Google Patents

Abstract

PURPOSE:To provide a driver solved for thermal printing head, which realizes very fine and high speed printing, by a method wherein the battering of image developing between the picture elements on one line and in the previous line or adjacent to each other is soled through simple driving circuit structure with out complicating the driving circuit structure. CONSTITUTION:Timing controlling circuit 9 performs time-division driving by bit unit such as on alternate picture elements or on every three picture elements so as to prevent heating elements 1 adjacent to each other from generating heat simultaneously. In addition, since the above-mentioned timing control is performed on the basis of one strobe signal input with one timing controlling circuit 9, the battering of image can be solved under the condition that the structure of a driver 13 is easily obtained at low cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal print head driver, and more particularly to a thermal print head driver having a high recording density and a high printing speed.

[0002]

2. Description of the Related Art Generally, a thermal print head has a structure shown in FIG.
As shown in FIG. 5, an insulating substrate 903 in which a plurality of heating elements 901 that generate heat by applying a voltage and perform printing are arranged, and print data (DI) input as serial data based on a clock pulse (CLK). And a shift register 905 that transfers the print data transferred by the shift register 905 and the latch circuit 907 that temporarily holds the print data based on the latch signal (LP) and converts the print data to parallel data (Dp) and the print data (Dp) and strobe. Based on the strobe signal (STB) as a timing control signal input through the input line 909, the heating element 90
The main part is composed of a drive circuit 913 having a switching element 911 for controlling the voltage application to No. 1.

A plurality of heating elements 901 arranged in a row are usually
For example, 1st to 64th, 65th to 128th, etc. are grouped into 1 block for each strobe, and each strobe is connected to one strobe input line 909 to input one strobe signal (STB). The voltage application timing is controlled based on Then, within the time selected based on the strobe signal (STB), the heating element 901 prints based on the print data (Dp).

The number of the plurality of heating elements 901 arranged in a row is not limited to 64 pixels as shown in FIG. 9, but various types may be selected depending on the purpose as a thermal print head and manufacturing restrictions. It is used, for example, there is one that has a total of 2048 dots or 4096 dots of heating elements in one thermal print head.

[0005]

[Problems to be Solved by the Invention] By the way, in recent years, there has been an increasing demand for higher-definition and higher-speed printing for facsimiles, plate-making machines, plotters, ticket vending machines, etc. using the above-mentioned thermal print heads. There is.

However, in the conventional thermal print head as described above, the heating element and the insulating substrate have characteristics such as isotropicity of heat storage and heat diffusion due to the recording method utilizing the heat generation of the heating element. However, depending on the image to be printed, the amount of heat input during printing is too large, and the image is crushed between the pixels on the previous line or the line before the previous line, or between adjacent pixels. However, there is a problem in that it lacks fineness and is extremely difficult to see. In addition, due to such a problem, for example, 3 ms / lin at 400 dpi or more.
It is not easy to realize high-definition and high-speed printing such as e or less.

As a measure for solving such a problem, it is stored in the drive circuit 913 whether or not a voltage is applied to the previous line, the previous line, or an adjacent heating element, and the voltage is applied to the heating element at the next timing based on the stored information. By adding a means for controlling the voltage to be applied, in other words, by adding a means for controlling the voltage applied to the heating element by checking the presence or absence of recording on the previous line, the previous two lines and the adjacent element in the driver, The present inventor has examined a method intended to prevent an excessive amount of heat input per pixel.

However, according to this method, the presence or absence of voltage application to the previous line, the previous line, or the adjacent heating element is stored in the drive circuit, and the voltage to be applied to the heating element at the next timing is stored based on this. Although an arithmetic / control circuit for performing arithmetic processing and control must be built in, the structure of a drive circuit in which such an arithmetic / control circuit is built becomes complicated. That is, the driver becomes large, which is inconvenient for miniaturization. In addition, such a complicated circuit becomes expensive. For example, according to the conventional example of FIG.
Since the complicated calculation / control circuits as described above must be arranged so as to be connected to each of the individual switching elements 911, the structure of the drive circuit becomes extremely complicated and the thermal print head There is a problem that it is inconvenient for downsizing and cost reduction.

Therefore, as another solution to the above problem, it is checked from the input print data whether or not a voltage is applied to the preceding line, the preceding line or the adjacent heating element, and the next heating element is selected. The inventors of the present invention have studied a method of adding a control circuit 914 designed to prevent the excessive amount of heat input per pixel as described above by controlling the voltage application time to the outside of the thermal print head. .

According to this method, one control circuit 914 is formed and this is used as a drive circuit 91 for the thermal print head.
Since there is no need to connect the control circuit 3 to the thermal print head, the thermal print head can be downsized, and the cost can be reduced as compared with the case where the control circuit as described above is provided in the driver for the thermal print head.

However, in this method, the input print data is further time-divided so that the voltage application to the previous line, the previous two lines and the adjacent heating elements is not continuous, so that the print data can be printed at a higher speed. However, there is a problem that it is difficult to deal with high-speed processing of print data. In addition, such a control circuit 914
However, since it is necessary to store and process the print data of the front line and the left and right pixels for each pixel for several pixels, there is a problem that the circuit becomes complicated.

The present invention has been made to solve such a problem, and an object thereof is to provide a pixel on a front line or on a line before the line without making the structure of a drive circuit complicated and expensive. Another object of the present invention is to provide a driver for a thermal print head having a simple structure that solves the problem of image crushing that occurs between adjacent pixels, and realizes high definition and high speed printing.

[0013]

In order to solve the above problems, a thermal print head according to the present invention is a thermal print head driver for driving a thermal print head in which a plurality of heating elements are arranged in a line. A shift register for transferring image information that is continuously input, a driving element for driving the heating element, a latch circuit for recording the same number of image information as the number of driving elements, and a supply element for the heating element. In a driver for a thermal printhead having a strobe circuit that controls the current-carrying time of the current and a power element that controls the current supplied to the heating element, the one-system strobe signal input from the strobe circuit causes the adjacent The heating element is divided into two or more systems so that the heating elements are not simultaneously energized at the same time. The power device is electrically connected.

[0014]

When the thermal print head driver of the present invention is used by incorporating it into a thermal print head unit, it is possible to avoid heat generation due to simultaneous application of voltage to adjacent heat generating elements, and to generate heat at different timings. It can be displaced to generate heat. This avoids excessive heat input due to heat diffusion or heat storage between adjacent pixels, and eliminates the problem of image blurring between pixels on the previous line or the line before the previous line, or between adjacent pixels. It can be resolved. In order to prevent the adjacent heating elements from generating heat at the same time as described above, it suffices to perform time-divisional driving on a bit-by-bit basis such as every other pixel or every three pixels. In the present invention, such timing control is performed. One strobe circuit and its strobe signal are used.

Since the timing control circuit forms a plurality of strobe signals from one strobe signal input from the outside, it is not necessary to increase the number of strobe signal input systems. Moreover, the print data (DI) that is input
In addition, since an expensive arithmetic control circuit or the like having a complicated structure for performing more complicated print data processing can be omitted, it is possible to eliminate the inconvenience of complicating the driving circuit and supporting high-speed processing.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a diagram showing an outline of a circuit structure of a driver for a thermal print head according to the present invention. See also FIG.
Is a latch pulse (LP) used for it, a strobe signal (STB) of one system, a first timing control signal (STB1), a second timing control signal (STB2)
It is a waveform diagram showing.

A thermal print head using the driver of the present invention has an insulating substrate 3 on which a plurality of heating elements 1 for printing by applying a voltage to generate heat, a shift register 5, a latch circuit 7, and timing control. The circuit 9, the power element 11, and the driver 13 form a main part. A control circuit 14 having a strobe circuit therein is connected to the driver 13. The driver 13 will be described in detail below.

The shift register 5 transfers the print data (DI) input as serial data based on the clock pulse (CLK). The latch circuit 7 temporarily holds the print data transferred by the shift register 5 based on the latch signal (LP) and converts it into parallel print data (Dp).

As shown in FIG. 2, the timing control circuit 9 receives an input signal from the strobe circuit in the control circuit 14.
The strobe signal (STB) of the system is used as the timing control signal, and the timing control signals (STB1, STB2) of the two systems are formed based on this, and the adjacent heating elements 1
The timing control signals of different systems are input to the power elements 11 connected to each other. Ie 1,
The first timing control signal STB1 is input to the odd-numbered heating elements 1 such as 3, 5, 7 ..., and the second timing is input to the even-numbered heating elements 1 such as 2, 4, 6 ... Input the control signal STB2. Such a timing control circuit 9 can be built in one IC. The timing control circuit 9 is formed of a standard shift register.

As described above, the power element 11 receives the timing control signal from the timing control circuit 9 and the parallel print data (Dp) from the latch circuit 7.
Is entered. The power element 11 controls the time division selection timing of the heating element 1 based on the timing control signals (STB1, STB2) described above, and
The voltage application to the heating element 1 is controlled based on the print data (Dp) input within the selection timing (selection time). This power element 11 has a timing control signal (ST
B1, STB2) and the print data (Dp) are calculated,
When the timing control signal is the selection timing and the print data is on, the voltage application to the heating element 1 is turned on.

The heating element 1 is controlled by the power element 11 and each print data (D) input within the time selected by the timing control signals (STB1, STB2).
Based on p), a voltage is applied and heat is generated to perform a printing operation. At this time, the odd-numbered heat-generating elements 1 and the even-numbered heat-generating elements 1 adjacent to each other are different in the selection timing of the switching elements connected to each other, as shown in FIG. Even if the print data (DI) is input, it is possible to avoid a state in which the adjacent heating elements 1 are selected at the same time and a voltage is applied.

As for the image crushing caused by the heat accumulation between the previous line and the two lines before the line, as shown in FIG.
Since it is good to prepare a pattern having a recording pulse width of about the pattern, the processing of print data (DI) becomes simple.

As described above, in the thermal print head driver according to the present invention, heat is generated so that adjacent heat generating elements 1 of the thermal print head generate heat at different timings while avoiding heat generation due to simultaneous voltage application. The timing can be appropriately time-divided and shifted to two systems to generate heat. This avoids excessive heat input due to heat diffusion or heat storage between adjacent pixels, and eliminates the problem of image blurring between pixels on the previous line, the pixel on the previous line, and between adjacent pixels. can do.

Further, in order to prevent the adjacent heating elements 1 from generating heat at the same time as described above, time-divisional driving is performed in bit units such as every other pixel or every three pixels. Moreover, in the present invention, such timing control is performed by one timing control circuit 9 based on one strobe signal input.

As described above, by adding one timing control circuit 9 having a simple structure to the driver 13 and performing the timing control as described above, an operation control circuit having a complicated structure and expensive is used. Without the driver 13, the structure of the driver 13 can be made simple and inexpensive, and the problem of image crushing can be solved.

Further, the timing control circuit 9 forms a plurality of (two systems in this embodiment) timing control signals (STB1, STB2) from one system of strobe signals input from the strobe circuit in the control circuit 14. Therefore, it is not necessary to increase the number of systems of the strobe signal (STB) or add a circuit for performing time division processing to the print data (DI) from the outside. This allows the driver 13
It is possible to solve the inconvenience and the inconvenience for high-speed processing.

In the thermal print head driver 13 of this embodiment, 64 heating elements 1 are connected to each driver, and 64 segments formed by such drivers 13 and heating elements 1 are connected. The individual heating elements 1 having a total of 4096 dots are formed in one thermal print head. Heater resolution
It is 400 dpi. The total number of strobes for one thermal print head was 4.

FIG. 3 is a diagram showing a second embodiment of the thermal print head according to the present invention, and FIG. 4 is a latch pulse (LP), strobe signal (STB), and first timing control signal (STB1) used for the same. ), Second timing control signal (STB2), third timing control signal (STB3), fourth timing control signal (STB4)
It is a waveform diagram showing. In order to simplify the explanation, the first
The same parts as those of the embodiment are given the same reference numerals.

In this second embodiment, the timing control circuit 209 receives four timing control signals (STB) having different timings from one strobe signal (STB) input.
1, STB2, STB3, STB4) are formed, and only one heating element 1 is selected at a time for every four continuous heating elements 1 so that heat is generated at a different timing from the other three heating elements 1. The heating element 1 is heated by time-divisionally shifting the heating timing to 4 systems. As a result, the adverse effect of heat storage and heat diffusion between the four adjacent heating elements 1 is suppressed to be smaller than that in the first embodiment, and the problem of image crushing is solved.

The number of systems of the timing control signal is the second
There are cases where there are four systems as in the first embodiment, or there are cases where there are two systems as in the first embodiment. Regarding the number of systems of such timing control signals, the insulating substrate 3
It is desirable to appropriately change the heat storage element 1 according to the conditions such as the heat storage capacity and the heat diffusion area that are unique to each thermal print head, which are determined by the material of the heating element 1, the pixel density, and the like. That is, as the heat storage capacity is higher and the heat diffusion area is wider, the number of systems is increased to increase the interval between the heating elements 1 that generate heat at one time, and prevent an excessive amount of heat input between neighboring pixels. You can do it like this.

FIG. 6 shows three points (points 5, 1, 6) in the preceding line and one point in the preceding line for a specific pixel to be recorded as indicated by black circles in the conventional thermal print head. (Point 4), 2 adjacent left and right pixels (Points 2 and 3)
FIG. 6 is a diagram showing each pixel arrangement when the presence or absence of recording (heat generation) of a total of 6 points is confirmed and the voltage application to a specific one pixel is controlled based on this.

As shown in FIG. 6, in this thermal print head, recording (heating) of a total of 6 points was confirmed for one specific pixel to be recorded, and in each case, one specific pixel was recorded. The pattern of the recording pulse width applied to each of the 6 points surrounding the must be converted. There are 64 possible combinations of patterns of the recording pulse width applied to each of the 6 points. However, for example, when the points 4, 5 and 2 and the points 4, 6 and 3 of FIG. If the symmetry and other factors are considered together in this way, the effect on pixels to be recorded can be summarized in about 7 patterns. FIG. 7 is a diagram showing an example of a pattern of the recording pulse width applied to each point in that case. In this way, the recording pulse width can be controlled in a total of 7 steps.

However, although this method seems to be effective, the inventor of the present invention made a trial of such a circuit and examined it. It is not easy to perform time-division conversion as data corresponding to each point of (3), and the driver 13 becomes complicated and processing time is delayed.
As a result, it has been difficult to increase the printing speed and definition.

On the other hand, if the thermal print head driver according to the present invention is used, as shown in FIG.
Since it is good to prepare patterns of three recording pulse widths as shown in, it is possible to realize high-speed and high-definition printing with a simple circuit structure.

Further, as shown in FIG. 8, the strobe input is simply connected to the two strobe signal input lines 801 and 803.
In the case of the second comparative example in which two heating elements 1 are connected to different strobe signal input lines 801 and 803 respectively, the two adjacent heating elements 1 are adjacent to each other similarly to the thermal print head driver of the present invention. Since the heat generating elements 1 that match each other are driven in a time-division manner, they may be driven in a pattern of three recording pulse widths as shown in FIG. However, when we actually prototyped and examined such a circuit, it was necessary to input strobe signals from two systems with different timings from the outside. 2) Strobe signal input circuits 801 and 803 for connecting 2 external strobe input lines to each switching element are added to the circuit by patterning. Because of the necessity and the like, actually, such a circuit change was extremely complicated.

In comparison with this, in the thermal print head using the driver according to the present invention, as described above, the input is made from the strobe circuit in the control circuit 14.
Since the timing control circuit 9 forms a plurality of timing control signals based on the strobe signal of one system, the strobe signal (STB) of the strobe circuit in the control circuit 14
There is no need to increase the number of lines. This allows the driver 13
It is possible to eliminate the inconvenience and the inconvenience for high-speed processing.

As described above, by using the thermal print head driver of the present invention, it is possible to avoid making the driving circuit configuration complicated and expensive and to make the thermal print head unit a simple configuration. Therefore, it is possible to solve the problem of image crushing that occurs between the pixels on the previous line and the pixels on the previous line, between adjacent pixels, and the like, and it is possible to realize high definition and high speed printing.

The thermal print head driver of the present invention can be used for a thermal print head having a strobe number of 1 for controlling all heating elements by one strobe signal input (STB), or in the present embodiment. It can also be used for a thermal print head divided into a plurality of strobes.

The circuit forming the timing control circuit is not limited to the above IC. Other than this, it is also possible to form a combination of logic circuits having a simple structure. Needless to say, various modifications can be made without departing from the scope of the present invention.

[0041]

As described in detail above, the driver for a thermal print head according to the present invention does not have a complicated and expensive structure and can be driven by a simple drive circuit.
It is possible to solve the problem of image crushing that occurs between pixels on the previous line and the pixel on the previous line, between adjacent pixels, and the like, and it is possible to realize high definition and high speed printing.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a circuit configuration of a driver for a thermal print head according to a first embodiment of the invention.

FIG. 2 is a latch pulse (LP) used in the thermal print head driver of the first embodiment according to the present invention;
Strobe signal (STB), first timing control signal (STB1), second timing control signal (STB2)
FIG.

FIG. 3 is a diagram showing an outline of a circuit configuration of a thermal print head driver of a second embodiment according to the present invention.

FIG. 4 is a latch pulse (LP) used in a thermal print head driver according to a second embodiment of the present invention;
Strobe signal (STB), first timing control signal (STB1), second timing control signal (STB2)
), A third timing control signal (STB3) and a fourth timing control signal (STB4).

FIG. 5 is a diagram showing an example of a combination of recording pulse width patterns of the thermal print head drivers of the first and second embodiments according to the present invention.

FIG. 6 shows a total of 6 recording (heating) points to be confirmed for one pixel in a thermal print head using a thermal print head driver of a comparative example to the thermal print head driver according to the present invention. Fig.

FIG. 7 is a diagram showing an example of a combination of patterns of recording pulse widths in a thermal print head using the thermal print head driver of the first comparative example for the thermal print head driver according to the present invention.

FIG. 8 is a diagram showing an outline of a circuit configuration of a thermal print head driver of a second comparative example with respect to the thermal print head driver according to the present invention.

FIG. 9 is a diagram showing an outline of a circuit configuration of a conventional thermal print head.

[Explanation of symbols]

1 ... Heating element, 3 ... Insulating substrate, 5 ... Shift register, 7
... latch circuit, 9 ... timing control circuit, 11 ... switching element, 13 ... driver, 14 ... control circuit

Claims (1)

[Claims] 1. A thermal print head driver for driving a thermal print head in which a plurality of heating elements are arranged in a line, a shift register for transferring image information continuously input, and the heating element. A driving element for driving the heating element, a latch circuit for recording the same number of image information as the driving elements, a strobe circuit for controlling a conduction time of a current supplied to the heating element, and a current supplied to the heating element In a driver for a thermal print head having a power element that operates, the heating elements are provided in two or more systems by avoiding that currents are simultaneously applied to the adjacent heating elements by the one-system strobe signal input from the strobe circuit. A driver for a thermal print head, characterized in that the power elements are divided and electrically connected.