KR100780918B1 - Print control device and method of printing using the device - Google Patents

Abstract

A thermal head having a set of fine heating elements each of which serves as a heating element and a temperature detector, and a drive circuit for supplying current to drive the heating element; A control circuit for switching the current flowing to each heating member between the heating driving state and the temperature detecting state; A circuit for converting a temperature value from each heating member into a voltage value using the current flowing during the temperature detection state and detecting the voltage value; An analog / digital conversion circuit for converting the voltage value into a digital value; An adder for accumulating and adding digital values obtained by digital conversion from the start of heating; A comparator for determining which value is larger by comparing a cumulative value obtained by the adder against a target print density value preset for a certain time point at which printing should be executed and transmitted from an upper device; And a circuit for stopping the heating operation of the heating member when the comparator detects that the target print density value has been reached, and a method of using the apparatus is disclosed.

Thermal head, print density, color density, heating element, temperature, digital

Description

Print control device and printing method using this device {PRINT CONTROL DEVICE AND METHOD OF PRINTING USING THE DEVICE}

1 is a characteristic diagram showing a relationship between heat energy and color development concentration applied to a general thermal recording paper;

Fig. 2 illustrates the difference in applied energy when thermal color development starts at different initial temperatures, if heating operation control is done for a predetermined time interval.

3 is a view for explaining a method of measuring the magnitude of the applied thermal energy by the cumulative addition by repeatedly measuring the temperature of the heating member.

4 illustrates the increased energy conservation and increased printing speed realized by the present invention.

5 is a circuit diagram illustrating an embodiment of the present invention.

6 is a timing flow diagram in accordance with an embodiment of the present invention.

Brief description of part numbers for major parts of drawings

100; Fine heating member 112; Analog / digital converter

101; Data register 113; adder

102; Input terminal 117; Size comparison circuit

109; Inverter 120; Driving transistor                 

111; Linear amplifier circuit

The present invention provides a thermal head of a printing apparatus which gives a variation of contrast according to the amount of thermal energy applied, which is colored on a medium, and which performs printing by image transfer using a fusion transfer of a coherent thermal transfer film or a sublimation transfer thereof. A printing control apparatus and method for controlling the generated thermal energy.

Conventionally, as a method for controlling the thermal energy to be applied to the thermal recording medium, the temperature of the fixed-resistance element on the thermal head has to be calculated based on past print history information to be generated by the fixed-resistance element on the thermal head. A method called "heat history control" was used to control the amount of thermal energy.

This method is carried out by making an estimation, so that different heating radiating conditions are applied between the printing executed in the cooling zone and in the tropical zone, and the temperature on the surface of the paper medium also fluctuates so that control errors easily occur. There was a problem. Therefore, since the control was performed in accordance with the calculation based on the estimation, it was difficult to achieve high precision and stable printing control.

Alloys such as Cr, Al, etc., whose resistance values change with temperature, are used as heating elements to fabricate this thermal head, and the temperature is measured so that the print history is not dependent upon printing to perform print control. There is a way. However, even in this method, the purpose of the control is not the value of the thermal energy generated by the heating member. Rather, the control is performed using the detected temperature data, and thus there is a problem that the color density to be realized on the thermal recording medium cannot be accurately controlled.

Moreover, as indicated by the fact that the color development characteristic of the thermal recording medium is called a property, there is no linear relationship between the supplied thermal energy and the color development characteristic, so it is required to deal with an error in the resulting print density.

In addition, there was a problem that it was impossible to detect overheating of the thermal head even when damage could occur as a result of affecting the reliability of print control. For example, if heating control is performed when the thermal head is not in contact with the surface of the paper medium, the temperature of the overheating member of the thermal head is raised to an abnormally high level and thus the heating member is burned or damaged.

It is an object of the present invention to provide a printing control apparatus and method which solves the above problems inherent in the prior art methods and apparatus and enables high precision and stable printing control.

According to the invention, there is provided a thermal head having a set of fine heating elements each of which serves as a heating element and a temperature detector, and a driving circuit for supplying current to drive the heating element; A control circuit which enables switching of a current flowing to each heating member between a heating driving state and a temperature detecting state; A circuit for converting a temperature value from each heating member into a voltage value using the current flowing during the temperature detection state and detecting the voltage value; An analog / digital conversion circuit for converting the voltage value into a digital value; An adder for cumulatively adding digital values obtained by digital conversion from the start of heating; A comparator that compares the accumulated value obtained by the adder with the value transmitted from the host device to a preset target print density value for a certain point where printing should be performed, and thus determines which is large; And a circuit for stopping the heating operation of the heating member when the comparator detects that the target print density value has been reached.

In addition, according to the present invention, in order to perform a proper heating control on the color development medium to obtain a printed image with excellent image quality, the temperature of the heat generated by each heating element of the heated thermal head is measured and the generated thermal The energy is calculated repeatedly at regular time intervals, yielding a result in which the intended color concentration is achieved at each of the color spots of the color medium.

Another aspect of the invention provides a printing control apparatus comprising a set of fine heating elements each of which serves as a heating element and a temperature detector and a thermal head having a drive circuit; Supplying a current to drive the heating member; Switching a current supplied to each heating member between a heating driving state and a temperature detecting state; Converting the temperature value from each heating member into a voltage value; Determining a voltage value based on a current flowing during the temperature detection state; Converting the voltage value into a digital value; Adding a digital value to obtain a cumulative value; Comparing the cumulative value and the target print density value to determine which value is the largest; And blocking supply of current to the heating member when the target print density value is reached.

Now, a detailed description of the present invention will be described. Apparatus to which the present invention can be applied include a fusion thermal transfer type printer and a sublimation type thermal transfer printer. However, a thermal printer using a so-called thermal recording medium can be used in addition to these apparatuses.

An example of the use of a thermal printer using a thermal recording medium is described below.

Also described is the use of a thermal head having a structure in which fine heating elements are arranged in an array having a concentration of 200 or 300 dots per inch.

When the density of dots is 200 dots / inch, when printing is performed by the thermal head, the head moves across the medium at a pitch of 1/200 of an inch while performing printing.

In the following, when the printing operation is performed for one pitch each at a time, a heating control operation for one pitch is performed. The present invention, in the print control for one print pitch, has no need at all with regard to the heating control for the pitch where printing has already been made and only the thermal head as measured at each time when printing has been done for each individual pitch. It differs from the conventional print control method called the hysteresis control method in that only the temperature of is used for print control.

That is, in the present invention, control is always performed independently for each pitch regardless of past history.

As the thermal recording medium of this embodiment, for example, a coloring medium such as a thermoautochrome recording paper, a two-color thermal recording paper, or a monochrome thermal recording paper called a TA medium manufactured by a FUJI film is used.

Regarding the color development characteristics of each color in these arbitrary thermal recording media, as shown in FIG. 1, for example, the color development density D in printing is a thermal energy E applied by a heating element on the thermal head. Determined by Properties for that have been published by each thermal recording paper manufacturer for each type of thermal recording paper.

It should be noted that in the characteristic diagram the horizontal axis represents the value of heat generated in the thermal head, which is the value of the thermal energy supplied to the medium. As such, it does not represent a temperature value. Therefore, in order to achieve the desired color development concentration "d1" at a constant fine color development point on the medium of FIG. 1, only performing control so that the thermal energy generated by the corresponding fine heating element on the thermal head is "e1". Is enough. However, in the case where the thermal head is the thermal head mentioned in the paragraph of the prior art using a fixed-resistance heating element, the amount of heat energy generated is ultimately determined by calculation based on print history obtained based on past printing results. Presumed ". Therefore, when several sheets of media were printed in succession, the thermal head accumulated heat and the temperature rose. Thus, as the number of printed sheets increased, the color development density on the paper surface also undesirably increased. This problem is based on the determination of the thermal energy (e1) that is required to be generated to obtain the concentration (d1), in that an error occurs because the estimation calculation is used to determine the current temperature of the thermal head itself. Its roots. In other words, in the conventional method, the temperature of the heating member before the heating member was heated was not clear, and therefore, when determining the heating amount of the heating member based on the estimation, the error was that the estimated temperature did not accurately reflect the actual temperature. The case occurred.

Moreover, as explained in the paragraph of the prior art, the printing value is dependent on the print history by employing as the heating element a substance whose resistance value varies with the temperature of generated heat and the temperature whose temperature is measured while printing is performed. Recently, a method of using a thermal head, which is performed without using, has been shown.

In this method in which the control is performed by measuring the temperature, the heating member generates heat and the temperature rises as in the result of the temperature t1 being measured, so that the control of the color development density is the print density d1. This is made possible by the assumption that it is proportional to). However, an error occurs in this method because the temperature fluctuates repeatedly over time and thus differs from the initial temperature when actual printing occurs.

In other words, in FIG. 2, the vertical axis represents temperature and the horizontal axis represents time, and the relationship between the temperature increase of the minute heating element of the thermal head during heating and the passage of time is examined, and the initial temperature "ta" increases and the target control temperature is increased. When the "to" is reached and the drive is stopped at time "Td" and the comparison is made between the case where the temperature "tb" increases to the target control temperature "to" and the drive is stopped at "Td", The amount becomes larger when the heating starts from the temperature "tb" by an amount proportional to the hatched portion, which causes an error.

That is, the total temperature change ta-tb corresponding to each time variation Td is an error E. In other words, the amount of energy represented by E = KΣ (ta-tb) · Td is an error. Where K is a proportionality constant comprising a specific heat capacity q as described later.

The above is confirmed in actual printing and it is confirmed that there is a difference in the degree of print density between the two cases.

Here, the inventor performed the measurement as shown in Fig. 3, wherein the temperature measurement of the heating element was repeatedly performed at regular time intervals after the start of heating of the fine heating member on the medium. The value "tx" of this temperature was obtained and accumulated in each measurement, and heating continued until the value "s0" which was set as the target value was reached. Thereafter, control was performed such that the heating drive was stopped at the point when the accumulated value reached s0. At this point, it was confirmed that the color concentration was always the same regardless of the initial temperature.

This is also evident in the fact that the total generated heat energy s0 accompanying the temperature change can be calculated as described below.

That is, if the specific heat capacity of the fine heating member is q and the temperature at a certain point in time is tx, the thermal energy Ex generated at that time is obtained as Ex = q X tx.

Therefore, when the cycle to be measured is determined at a very short time duration Td, the total column value s0 becomes the total cumulative value for the entire time length, where s0 = ΣEx · Td = q X Σtx · Becomes Td.

Here, Td is a constant, and therefore s0 = q · Td X Σtx, so if K = q · Td, the total column value s0 is ultimately s0 = K X Σtx.

The total heat value (s0) of the heat applied to the medium from this formula is proportional to the cumulative value of the temperature measured repeatedly at regular time intervals.

Therefore, the measured temperature values at each time must be added together until s0 = KX Σtx, and heating must be continued until the product of the cumulative value and the multiplication of the proportional constant (K) reaches the target concentration value s0. do.

In other words, this means that the area under the temperature fluctuation curve of FIG. 3 is proportional to the print density.

Here, the proportional constant K is a constant determined according to the conversion range by the analog / digital converter of the print control circuit described below and the voltage amplification factor of the temperature measurement result signal.

According to the invention, it is possible to calculate the thermal energy generated using the above formula, and high precision control of the color development concentration can be done according to the energy / color concentration characteristic as shown in FIG. 1 published by the paper manufacturer. .

In the case of conventional monochrome thermal color generation, when printing should be performed in black and white, for example as shown in FIG. 4, white printing is done without heating, and as indicated by point " A " No heat energy is applied. On the other hand, black develops to the maximum color development concentration, and heat increases until the energy value e1 is reached, which is deep in the saturated color development concentration region S, as indicated by point "B". It belongs. This is set in the vicinity of the central region S, and therefore, a shift from the saturated color development concentration region does not occur even if the control error exceeds or insufficient the amount of thermal energy for developing the black color.

In contrast, in the control according to the present invention, since there is almost no such variation, for example, stopping the heating operation at the energy value e2 at the edge of the saturated color development concentration region S with a high level of precision is possible. It is possible. As a result, the difference of the energy values, i.e., e1-e2, becomes unnecessary, thus enabling energy conservation. In the case of a printer using a battery as the power source, there is an advantage that the length of the interval at which the battery needs to be replaced becomes longer, and in the printing operation, printing is completed early by the same amount as a part of the hatched line. Therefore, high speed printing becomes possible.

Example

In the following, embodiments of the present invention are described in more detail. 5 is a diagram illustrating an embodiment of the present invention.

First, there is a heating element arranged in an array on the thermal head, which varies its resistance value according to the temperature of the generated heat, and printing is performed when the heating is started at the same time on each line. If the thermal head has a 300 dot pitch or 300 dpi, it is normal that the line pitch for sub scanning or simultaneous printing should also be performed at 300 dpi. Thermal printing on the surface of the sheet by the head is cyclically repeated at this pitch.                     

For the fine heating member 100 shown in FIG. 5, a resistive member, generally called a thermistor, is used, which varies its resistance value in accordance with the temperature of the generated heat. The metal composition of the thermistor must be selected from those compositions that have a linear relationship between variation in resistance and variation in heating temperature. One example of a composition that can be used may be an alloy of aluminum, chromium, boron, and the like. The operation of the circuit is described below. The piece "1" of data from the device higher than the data register 101 corresponding to a certain element in the minute heating member is written to the input terminal 102 in accordance with the timing signal 105.

Then, when the signal "0" is input to the input terminal 102 from the upper device, the inverter 109 inverts the signal and the signal is input as "1" to the AND gate 110.

To the other input terminal of the gate 110, the above-described output signal 106 of the data register 101 is input as "1", so that the logical product of the gate 110 is calculated, which causes the driving transistor 120 to be turned on. Let it be. Note that the transistor 121 is in the OFF state because the control signal 108 is "0" during the heating drive. As a result, current flows to the heating member 100 and the driving transistor 120. As described above, when the heating member 100 receives the flow of electric current, it starts to generate thermal energy and its resistance value fluctuates. According to this embodiment, an element whose resistance value decreases when the temperature rises is used. As a result, the value of the current flowing through the driving transistor 120 increases as the temperature increases.

Means for detecting a state in which the temperature of the heating member 100 rises will be described. The drive transistor 120 is ON while the temperature is rising, but this allows current to flow through. However, upon detection of the temperature, the control signal 108 becomes " 1 ", so that the drive transistor 120 is turned off, and another transistor 121 is turned from off to on. As a result, current flows into the current detection resistor, and in this embodiment, the fixed resistor 122 has a fixed resistance value of about 70 Ohm.

As the heating member 100 generates heat and its temperature rises, the resistance value drops and the current value increases. As a result, the current flowing into the fixed resistor 122 increases and the voltage between the terminals of the fixed resistor 122 rises. The output voltage of the fixed resistor 122 is amplified by the linear amplifier circuit 111 and the amplified signal then flows to the analog / digital converter 112 of the next stage. As a result, the output value of the analog / digital converter 112 is converted into a digital value represented by the number of bits of about 8 bits as the temperature value of the heating member 100 of the head.

According to an embodiment, the detected data is continuously and continuously input to the adder 113 periodically at intervals of about 20 μm, and thus each time the measurement is accumulated, the measurement is performed after the heating starts. As a result, by the digital output of the adder 113, it is possible to detect the thermal energy value generated after the heating is started. In the following, the generated thermal energy values are abbreviated as detected energy values "A". This " A " is proportional to s0 = K Σtx described in the operation paragraph above. The detected energy value "A" may be input to the magnitude comparison circuit 117 and compared. The adder 113 is cleared to zero by the setting signal 103 before print control is started for each line, and at each time the control signal 108 is " 0 " during the print control for each line. Is switched to " 1 ", and the digital output of the analog-to-digital converter 112 is added to the adder 113 by a signal 128 that is approximately delayed by the delay circuit 127. In FIG.

On the other hand, at this point, the designated value data regarding the print density for the fine heating member being controlled is transmitted from the upper device to the input terminal 116 in the form of 8-bit data for 256-gradation representation. This data is calculated in advance based on the relationship between the concentration and the energy as shown in FIG. 1, and the concentration data value is converted into the energy value by the generated data conversion table 114.

The conversion table for this purpose is a structural diagram of a chart for establishing a correspondence between concentration data values and energy values. For example, if a gradation indication of which the numerical value is 128 is transmitted from the upper device to the signal line 116, this numerical value will be converted into an energy value of 2.56.

In other words, the conversion table is calculated in consideration of the color development characteristics of the paper as shown, for example, in FIG. In this table, the print density is input data and the detected energy target value is output data.

A conversion value of 2.56 in this data conversion table is stored in the register 115 during print control of the fine color generator in printing, which is input to the size comparison circuit 117 as the target energy control value " B " Is compared with A ".

As long as the detected value "A" is smaller than the target energy control value "B", heating continues because the control line 118 is "0". However, gradually, the cumulative energy value increases and the detection value "A" becomes larger than the target value "B", and at this point the control line 118 for the output of the comparing circuit 117 is "0" to " Changes to 1 ". As a result, the output of the logical addition gates 125 and 126 becomes "1". Thus, register 101 is reset and the output of logical product 110 is " 0 ". Therefore, the driving transistor 120 is turned off, the current is stopped flowing to the thermistor heating member 109, and the heating is stopped. In other words, energy is applied up to a predetermined concentration, whereby the heat generation drive is stopped. This kind of heating operation is carried out on all the fine heating elements arranged in one array on the thermal head, which operation is carried out with the same control as is carried out independently and in a similar manner. However, the heating element designated to develop the color at a low color development density is set to a small target value "B", so that the heating operation naturally ends earlier than the heating operation for the heating member designated for darker color development.

Thereafter, even when the temperature detection signal 108 is input from the host device, the signal 106 becomes "0" because the register 101 is reset. Therefore, the logical product gate 129 remains as in " 0 ", which results in the transistor 121 being also turned OFF, so the thermistor 100 is no longer driven to generate heat.

As a protective means to prevent the thermal head from being damaged and overheated as a result when an operation failure occurs during a printing operation, at the next operation, that is, at the start of printing, the highest possible temperature value is determined by the input terminal ( 200, set in the register 123 according to the set timing 201, and compared by the comparator 124 to the output from the analog / digital converter 112. Then, when the output value of the analog / digital converter 112 is larger than the value set in the register 123, the output changes from " 0 " to " 1 " and the logical addition gate (as a reset signal for the register 10) 125, 126 and the printing operation is stopped as described above, which results in preventing overheating and improving the reliability of the device.

When the heating of all the heating members is finished and the head position is moved by one pitch interval on the surface of the paper, subsequent color development operations are started at the same time, and the above operations are repeatedly performed sequentially on the medium. A timing diagram based on this description is shown in FIG.

In the case of monochrome thermal recording paper, for example, the above operation should be performed for one color per sheet of media. However, in the case of three-color thermal recording paper, heating control according to three different types of color characteristics is performed three times in total for each different energy region.

In either case, the cumulative value of the thermal energy applied to each line of the surface is obtained repeatedly while detecting the surface temperature, so that very high precision color-deployment management can be performed for the thermal recording medium.

For example, 256-gradation multi-color-density printing on monochrome thermal recording paper has become possible, which was very difficult to control in the prior art. Therefore, printing with images that do not differ at all from photographic image quality can be performed at high speed. It is also possible to use hologram printing, a printing technique using a mold called a hot stamp only in the prior art, which requires heating in a high temperature region and a very low temperature region. The printing method also employs a free print pattern that does not require the use of a fixed mold.

Claims (6)

A thermal head having a set of fine heating elements each of which serves as a heating element and a temperature detector, and a drive circuit for supplying current to drive the heating element; A control circuit for switching the current flowing to each heating member between the heating driving state and the temperature detecting state; A circuit for converting a temperature value from each heating member into a voltage value using the current flowing during the temperature detection state and detecting the voltage value; An analog / digital conversion circuit for converting the voltage value into a digital value; An adder for accumulating and adding digital values obtained by digital conversion from the start of heating; A comparator for determining which value is larger by comparing a cumulative value obtained by the adder against a target print density value preset for a certain point at which printing should be performed and transmitted from an upper device; And a circuit for stopping the heating drive of the heating member when the comparator detects that a target print density value has been reached. The method of claim 1, further comprising a circuit for temporarily stopping the heating operation when it is detected that the detected temperature exceeds the pre-set value before the cumulative value reaches the target print density value. Print control device characterized in that. The printing control apparatus according to claim 2, further comprising means for correcting the target print density value according to the color development characteristics of the medium used. Providing a thermal head having a set of fine heating elements each of which serves as a heating element and a temperature detector; Supplying a current to drive the heating member; Switching a current supplied to the heating member between the heating driving state and the temperature detecting state; Converting the temperature value from each heating member into a voltage value; Measuring a voltage value based on a current flowing during the temperature detection state; Converting the voltage value into a digital value; Adding the digital value to obtain a cumulative value; Comparing the cumulative value with a target print density value to determine which value is the largest; And Cutting off the supply of current to the heating member when a target print density value is reached. 5. The printing by the print control apparatus according to claim 4, further comprising: temporarily blocking a current driving the heating member when the detected value exceeds a pre-set value smaller than the target print density value. Way. 6. The printing method according to claim 5, further comprising the step of correcting the target print density value according to the color development characteristics of the medium used.

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