JP2006027153A - Electric power supply control method for thermal head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power supply control method for a thermal head which can impart recording energy (power supply amount) sufficient for transferring ink having a necessary dot size to a heating element corresponding to each dot constituting the pixels of a recording image. <P>SOLUTION: In the electric power supply control method for a thermal head, the dots, which are located at the position, on the upstream side of the scanning direction of the thermal head, adjacent to the recording dots which correspond to the heating elements of the thermal head to which electric power is imparted for transferring the ink of an ink ribbon on a sheet, are made to be target dots. When the electric power is not imparted to the heating elements corresponding to the target dots for the purpose of transferring the ink on the sheet, according to the record information with reference to the target dots, the electric power is controlled to be imparted to the heating elements corresponding to the target dots, to the extent melting no ink of the ink ribbon. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  According to the present invention, the thermal head of the thermal head in which a plurality of heat generating elements are arranged in a line to control the energization amount to each of the heat generating elements to express the gradation of each dot constituting a pixel of a recorded image. The present invention relates to an energization control method for a heating element.

  A thermal printer (hereinafter referred to as a thermal transfer printer) that performs thermal transfer recording using a thermal head in which a plurality of heating elements are arranged in a line form a desired ink on a base film between a platen and the thermal head. By sandwiching the applied ink film and paper, feeding out the ink film and transporting the paper, selectively applying recording energy to the plurality of heating elements of the thermal head based on the recording information, and generating heat, The ink of the ink film is partially transferred onto the paper to record an image such as a desired character. This type of thermal transfer printer is widely used as an output device for computers, word processors, and the like for reasons such as high recording quality, low noise, low cost, and ease of maintenance.

  As one of thermal transfer printers, a thermal transfer printer (hereinafter referred to as a thermal transfer printer) that records on paper using an ink ribbon (hereinafter referred to as a thermal meltable ink ribbon) in which a hot melt ink is applied to a base film such as a plastic film. (Referred to as a thermal melting type printer).

  This hot-melt type printer is capable of recording on a wide variety of paper such as plain paper, cardboard, and postcards, and is excellent in usability, but in order to perform gradation recording using the hot-melt ink film, Since the density gradation cannot be expressed in dot units constituting each pixel of the recorded image, for example, a dither matrix method (hereinafter referred to as a dither method) is used.

  Here, the dither method as a density gradation recording method is a method in which one pixel of recording information is composed of a plurality of dots, and when the plurality of heating elements of the thermal head are selectively energized, the energization patterns of the respective colors. Is a method of recording a multi-tone image while controlling the number of energized dots in one pixel. In the case of recording a color image, a multi-tone color image is recorded by controlling the number of energized dots in one pixel and the growth order according to the tone data for each color of cyan, magenta, and yellow. It becomes.

  Needless to say, the basis of image recording using the dither method is the printing accuracy of each dot. In other words, when forming a recorded image using a hot-melt printer, the recording energy (energization amount) applied to the heating element corresponding to each dot constituting the pixels of the recorded image is controlled to provide necessary and sufficient dots. Transferring the hot-melt ink to the size is a requirement for obtaining a good recorded image.

JP 2003-182132 A

  However, when recording an image in the thermal melting type printer, there is a power limitation in relation to the heat resistance specifications of the heat generating elements of the thermal head, so that the thermal melting is performed to such an extent that a necessary and sufficient dot size can be secured for each dot. In some cases, the photosensitive ink cannot be melted and transferred onto the paper.

  For example, FIG. 2 (A) shows that one pixel of ink of a certain color is obtained by dithering three pixels arranged in the scanning direction of the thermal head in the print image area, nine dots constituting each pixel, and each dot. It is a schematic diagram which shows the electricity supply order at the time of transcription | transfer. 2A is also used as a dot number representing each dot.

  In this conventional example, the dither method uses the 9th floor in which all nine dots are energized from the 0 gradation (0% in duty) indicating that none of the nine dots constituting each pixel is energized. Control is performed so that the density gradation of each pixel is processed (hereinafter referred to as dither processing) with 10 gradations (0 to 100% for Duty) up to the tone (about 89 to 100% for Duty). In this conventional example, the pixel located at the most upstream in the scanning direction of the thermal head (first pixel) is 0 gradation (0% in duty) in which no power is applied to any dot, and the thermal head The middle pixel (second pixel) and the most downstream pixel (third pixel) in the scanning direction of each of the three gray levels (duty 22 to 33 in a state where power is applied to only three dots, respectively) % Dithering).

  FIG. 2B shows the thermal head heating element corresponding to the dots arranged in the row indicated by the white arrow in FIG. 2A (the scanning direction of the thermal head) by the conventional thermal head energization control method. The schematic diagram of ON / OFF of electricity supply and the dot formed by the electricity supply is shown.

  As shown in FIG. 2B, in the conventional energization control method for the thermal head, before the recording of the first dot of the second pixel with respect to the heating element of the thermal head corresponding to the dots arranged in the row. As shown in FIG. 2B, there is no energization history for the heating elements corresponding to the dots for at least four dots. That is, since the heating element is in a temperature state substantially the same as the ambient temperature, even when the highest power in the allowable range of the heat resistance specification of the heating element is applied during the recording of the first dot of the second pixel, In some cases, the heat-meltable ink cannot be melted to such an extent that the temperature of the heat generating element can ensure the required dot size for the dots. In that case, as shown in FIG. 2B, it goes without saying that the dot size of the first dot of the second pixel is reduced or not formed, and a good recording result cannot be obtained.

  The present invention has been made in view of the above-described points, and provides recording energy (energization amount) sufficient for transferring ink of a necessary dot size to a heating element corresponding to each dot constituting a pixel of a recorded image. It is an object of the present invention to provide a method for controlling energization of a thermal head.

  In order to achieve the above-described object, the energization control method of the thermal head of the present invention performs energization control of the heating element of the thermal head based on the recording information composed of a large number of recording dots for constituting a recording image, and the ink ribbon The thermal head energization control method for transferring the ink on the paper to the recording dots corresponding to the heating elements of the thermal head to which electric power is applied for the purpose of transferring the ink on the ink ribbon to the paper. A dot located adjacent to the upstream side in the scanning direction of the thermal head is set as a target dot, and the recording information relating to the target dot is applied with power for the purpose of transferring the ink to the heat generation element corresponding to the target dot. If the ink ribbon does not melt, the ink on the ink ribbon does not melt to the heating element corresponding to the target dot. And performing control to grant the power.

  In addition, when control is performed to apply power to the heating element corresponding to the target dot so that the ink of the ink ribbon does not melt, the thermal head is further upstream in the scanning direction of the thermal head. In the case where the dot located in the adjacent position is a target dot, and the recording information regarding the target dot does not apply power for the purpose of transferring the ink to the paper to the heating element corresponding to the target dot, It is characterized in that the control for applying the electric power that does not melt the ink of the ink ribbon to the heat generating element corresponding to the target dot is repeated a plurality of times (reverse pre-energization).

  Further, for the recording dots, when there are a plurality of target dots that are to be controlled to apply power to the corresponding heating element so that the ink of the ink ribbon does not melt, the targets arranged near the recording dots Stepwise setting the power to be applied to the heating element so that the power applied to the heating element corresponding to the dot is equal to or higher than the power to be applied to the heating element corresponding to the target dot arranged far from the recording dot. (Stepwise preliminary energization).

  Furthermore, in consideration of the head temperature detected by the thermistor arranged for detecting the temperature of the thermal head, when the head temperature is equal to or higher than the set temperature, the ink of the ink ribbon melts in the heating element corresponding to the target dot. It is characterized in that control for canceling the control for applying electric power to such an extent is performed.

  According to the energization control method for a thermal head of the present invention, preliminary energization is performed on each heating element corresponding to the target dot, and the heating element is preheated in advance. By conducting the main energization within the range of the heat resistance specification of the heat generating element, the heat generating element can be sufficiently heated, and the ink of the hot-melt ink ribbon can be transferred satisfactorily.

  Further, when there are a plurality of non-energized dots on the upstream side of the recording dot thermal head in the scanning direction, by performing retroactive pre-energization and stepwise pre-energization, the heat generation is performed during ink transfer of the recording dots. The temperature of the element can be reliably preheated.

  Further, in consideration of the head temperature detected by the thermistor arranged for detecting the temperature of the thermal head, the control to apply the power to the extent that the ink of the ink ribbon does not melt to the heating element corresponding to the target dot is canceled. This prevents the heating element from overheating in the dots without ink transfer, and in the recording dots, the heat storage of the heating element in the thermal head is used as usual, and the heat resistance specifications of the heating elements are as usual. By conducting the main energization in the category, the heating element can be sufficiently heated, and the ink of the hot-melt ink ribbon can be transferred satisfactorily.

  The thermal transfer printer used in this embodiment is a thermal melting type printer that records a color image using a thermal melting ink ribbon, and is a line in which a large number of heating elements corresponding to pixels in the scanning direction of the head are arranged in a line. It has a thermal head (hereinafter simply referred to as a thermal head). Then, based on the image information input from the host computer, image reader, or the like, the image information is separated into recording information for each color of cyan, magenta, and yellow in the control unit of the hot melt printer, Based on the recording information, the energization control of each heating element of the line thermal head is performed, so that the inks of each color of cyan, magenta, and yellow are sequentially superimposed and transferred to obtain a color recording image. At this time, in the present embodiment, control is performed so as to perform multi-tone recording of a color recording image using a dither method. Further, the control unit performs the following energization correction control in consideration of the result of dither processing.

  That is, the dots (hereinafter referred to as recording dots) to which electric power (hereinafter referred to as recording power) is applied in order to transfer the ink of the hot-melt ink ribbon to the corresponding heating elements, are described above. Similarly, as to the dot positioned adjacent to the upstream side in the scanning direction of the thermal head (hereinafter referred to as a target dot), is the recording power applied to the heating element of the corresponding thermal head as a result of the dither processing? Judge whether or not.

  That is, in the control unit, the recording information regarding the target dot is examined, and when the recording power is applied to the heating element corresponding to the target dot, the heating element is put in a preheated state when the recording dot is recorded. It is determined that there is, and control is performed to apply normal power to the heat generating element corresponding to the target dot.

  When recording power is not applied to the heating element corresponding to the target dot, it is determined that there is a possibility that the heating element is not in a preheated state when recording dots are recorded, and the heating element corresponding to the target dot Is controlled to apply power (hereinafter referred to as “preliminary power”) that does not melt the heat-meltable ribbon ink to the heating element (hereinafter referred to as “preliminary power supply”).

  This pre-energization process is not limited to only one dot positioned immediately before the recording dot upstream of the thermal head in the scanning direction. That is, when control for applying reserve power to the heating element corresponding to the target dot is performed, a dot positioned adjacently on the upstream side in the scanning direction of the thermal head from the target dot is further targeted. When the recording power is not applied to the heating element corresponding to the target dot, and the recording power is applied to the heating element corresponding to the target dot, the recording is performed by repeating the control a plurality of times. A plurality of dots on the upstream side in the scanning direction of the thermal head of the dots can be a plurality of correction dots to which preliminary power is applied (hereinafter referred to as retroactive preliminary energization).

  Further, when a plurality of dots are used as correction dots, the same power is not applied to all the correction dots. For example, the ink of the heat-meltable ribbon is not melted to the correction dots that are separated from the recording dots. A relatively low power is applied, and a relatively high power is applied to the correction dots positioned immediately before the recording dots so that the ink of the hot-melt ribbon is not melted. May be set automatically (hereinafter referred to as stepwise preliminary energization).

  Further, a thermistor may be provided in the thermal head for detecting the temperature of the thermal head, and control may be performed so as to determine the necessity of energization power for the correction dot in consideration of the head temperature detected by the thermistor.

  By performing energization control on the heating element of such a thermal head, recording energy (energization amount) sufficient for transferring the ink of the required dot size to the heating element corresponding to each dot constituting the pixel of the recorded image. Can be granted.

  This will be specifically described below.

  FIG. 1A is a diagram corresponding to FIG. 2A in the above-described conventional example, and in the area of the recorded image in the present embodiment, three pixels arranged in the scanning direction of the thermal head and each pixel are configured. It is a schematic diagram which shows the energization order of a certain color by the dither method for each of the nine dots to be performed and each dot. 2A is also used as a dot number representing each dot.

  In FIG. 1B, the energization of the heating elements of the thermal head corresponding to the dots arranged in the rows indicated by white arrows in FIG. 1A is turned on by the above-described thermal head energization control method of the present embodiment. A schematic diagram of dots formed by turning off and energizing is shown.

  Also in the present embodiment, the 9 gradations (89 for Duty) that energize all nine dots from the 0 gradation (0% for Duty) indicating a state in which no current is supplied to any of the nine dots constituting each pixel. Control is performed so that the density gradation of each pixel is processed (hereinafter referred to as dither processing) with 10 gradations (about 0 to 100%) (up to about 100%). In this embodiment, the pixel (first pixel) located at the uppermost stream in the scanning direction of the thermal head has 0 gradation (0% in duty) in a state where no power is applied to any dot, and the thermal head. The middle pixel (second pixel) and the most downstream pixel (third pixel) in the scanning direction of each of the three gray levels (duty 22 to 33 in a state where power is applied to only three dots, respectively) % Dithering).

  Then, after the dither process, when the ink of each dot is transferred, the above-described energization correction control for the heating element of the thermal head is performed.

  In the present embodiment, at the time of transferring the ink of the recording dots, whether power is applied to the corresponding heating element in the result of the dithering process for the target dots located adjacent to the upstream side in the scanning direction of the thermal head. Judge whether or not.

  When power is applied to the corresponding heat generating element for the target dot, it is determined that the heat generating element is in a preheated state at the time of recording the recording dot, and normal recording power is applied to the target dot. It controls to give (henceforth this energization).

  For example, the first pixel of the second pixel as the target dot when the second dot of the second pixel is the recording dot, or the third pixel as the target dot when the second dot of the third pixel is the recording dot This corresponds to the control for each heating element corresponding to the first dot. In this case, each energization element corresponding to the first dot of the second pixel and the first dot of the third pixel is energized and heated. Therefore, during the transfer (recording) of the second dot of the second pixel or the second dot of the third pixel as a recording dot, the first dot of the second pixel or the first dot of the third pixel By using the heat storage during recording as preheating and carrying out the main energization in the category of the heat resistance specification of the heating element as usual, the heating element can be sufficiently heated, and the ink of the hot-melt ink ribbon can be used. It can be transferred well.

  Further, when power is not applied to the corresponding heat generating element for the target dot, it is determined that the heat generating element may not be in a preheated state during recording of the recording dot, and the target dot is set as a target for current correction. Then, control is performed to apply reserve power to the corresponding heating element (hereinafter referred to as reserve energization).

  In the present embodiment, the retroactive preliminary energization is performed.

  That is, when the target dot is a correction target, the dot positioned next to the upstream side in the scanning direction of the thermal head is set as the target dot, and whether or not power is applied as a result of the dither processing is determined. If the power is not applied to the heat generating element, the determination that the control is performed to apply the reserve power to the corresponding heat generating element is also performed with the target dot as the target of the energization correction.

  In the present embodiment, the number of retroactive pre-energizations is determined as 3 times, and the dots up to the third upstream side of the recording dot in the scanning direction of the thermal head are sequentially treated as the target dots, It is determined whether or not preliminary energization processing is necessary for each corresponding heating element. Note that it is possible to set all the dots to which power is not applied as a result of the dithering process as the target dots for energization correction without setting the number of retroactive energizations of the target dots.

  In the present embodiment, the stepwise preliminary energization is performed.

  That is, a relatively low power is applied to the correction dots that are separated from the recording dots so that the ink of the heat-meltable ribbon does not melt, and the correction dots that are positioned immediately before the recording dots are heat-meltable. Control is performed to set the applied power in a stepwise manner, such as applying relatively high power that does not melt the ribbon ink.

  For example, in FIG. 1B, when the first dot of the second pixel is the recording dot, the ink is transferred in the result of the dither process for the fourth dot of the second pixel that is the first target dot. In addition, since no power is applied to the heating element, the heating element is not in a preheated state when the recording dots are recorded. Accordingly, preliminary energization with relatively high power is performed on the heat generating element so that the ink of the heat-meltable ribbon does not melt.

  Subsequently, the second dot of the first pixel on the upstream side in the scanning direction of the thermal head from the fourth dot of the second pixel is set as the next target dot, and whether or not preliminary energization processing is necessary for the target dot Make a decision. As for the second dot of the first pixel, in the result of the dithering process, the ink is not transferred and no power is applied to the heating element, so that the heating element is not in a preheated state when recording the recording dots. Therefore, preliminary energization with relatively low power is performed to the heat generating element so that the ink of the heat-meltable ribbon does not melt.

  Further, the first dot of the first pixel on the upstream side in the scanning direction of the thermal head from the second dot of the first pixel is set as the third target dot, and the target dot needs to be pre-energized. Judge whether or not. As for the first dot of the first pixel, since the ink is not transferred and no power is applied to the heat generating element in the result of the dithering process, the heat generating element is not in a preheated state when recording the recording dots. Therefore, as in the case of the second dot of the first pixel, the heating element is pre-energized with a relatively low power so that the ink of the hot-melt ribbon is not melted.

  In this way, by preliminarily energizing each heat generating element corresponding to the target dot and preheating the heat generating element in advance, the heat resistant specification of the heat generating element is transferred as usual at the time of ink transfer of the recording dots. If the energization is performed in the category, the heating element can be sufficiently heated, and the ink of the hot-melt ink ribbon can be transferred satisfactorily.

  In addition, when there are a plurality of non-energized dots on the upstream side of the thermal head in the scanning direction of the recording head as in this embodiment, the recording dot is obtained by performing retroactive preliminary energization and stepwise preliminary energization. When the ink is transferred, the temperature of the heating element can be reliably increased without any load.

  Further, in the present embodiment, a thermistor is provided in the thermal head for temperature detection of the thermal head, and control is performed to determine whether or not energization power is required for the correction dot in consideration of the head temperature detected by the thermistor. Do.

  For example, the fourth dot of the third pixel shown in FIG. 1B is a target dot when the first dot of the third pixel is a recording dot. In the fourth dot of the third pixel, no ink is transferred and no power is applied to the heating element in the result of the dithering process. Therefore, according to the energization control described above, the fourth dot of the third pixel is also preliminarily energized as a correction dot, but the main energization is performed on the two dots immediately before that, and the ink transfer is performed. Therefore, when the first dot of the third pixel as the recording dot is recorded, the heat generating element of the thermal head may still be in the heat storage state. Therefore, in consideration of the detected temperature of the thermistor, when a temperature equal to or higher than a temperature set as a constant preheating temperature is detected, control for canceling normal energization correction control is performed.

  In this way, the heating element is prevented from overheating in the dots without ink transfer, and in the recording dot, the heat storage of the heating element of the thermal head is used as usual, and in the category of the heat resistance specification of the heating element. By performing this energization, the heating element can be sufficiently heated, and the ink of the hot-melt ink ribbon can be transferred satisfactorily.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible as needed.

  For example, the thermal printer using the energization control method for the thermal head of the present invention is not limited to the above-described line thermal printer.

  Further, for each dot, it is also possible to use a gradation expression for adjusting the diameter size of a dot to which ink is transferred in combination with the above-described dither method. The present invention is not only applicable to hot melt printers, but can also be applied to thermal sublimation printers that transfer ink onto paper using a heat sublimable ink ribbon.

FIG. 4A is a schematic diagram illustrating pixels, dots, and energization orders of dots within a recorded image area. (B) is a schematic diagram of dots formed by energization on and off of the heating elements corresponding to the dots arranged in the row indicated by the arrows in (A) by the energization control method of the thermal head of the present embodiment. Figure FIG. 4A is a schematic diagram illustrating pixels, dots, and energization orders of dots within a recorded image area. (B) is a schematic diagram of dots formed by energization on and off of the heating elements corresponding to the dots arranged in the row indicated by the arrows in (A), and the energization control method of the conventional thermal head.

Claims (4)

A thermal head energization control method for performing energization control of a heating element of a thermal head based on recording information consisting of a large number of recording dots for forming a recording image, and transferring ink of an ink ribbon onto a sheet,
For the recording dot corresponding to the heating element of the thermal head to which electric power is applied for the purpose of transferring the ink of the ink ribbon onto the paper, the dot positioned adjacent to the upstream side in the scanning direction of the thermal head is the target dot. And when the recording information relating to the target dot does not apply power to the heater element corresponding to the target dot to transfer ink to the paper, the ink ribbon is applied to the heater element corresponding to the target dot. A method for controlling energization of a thermal head, wherein control is performed so as to apply electric power that does not melt the ink.   When control is performed to apply power to the heat generating element corresponding to the target dot so that the ink of the ink ribbon does not melt, it is further adjacent to the target dot on the upstream side in the scanning direction of the thermal head. If the dot located at the position is the target dot and the recording information relating to the target dot does not apply power for the purpose of transferring the ink to the paper on the heating element corresponding to the target dot, the target dot 2. The energization control method for a thermal head according to claim 1, wherein the control for applying the electric power to the extent that the ink of the ink ribbon is not melted to the heating element corresponding to is repeated a plurality of times.   For the recording dots, when there are a plurality of target dots that have been subjected to control to apply power to the corresponding heat generating elements so that the ink of the ink ribbon does not melt, the target dots arranged near the recording dots The power to be applied to the heating element is set stepwise so that the power to be applied to the corresponding heating element is equal to or higher than the power to be applied to the heating element corresponding to the target dot arranged far from the recording dot. The energization control method for a thermal head according to claim 2. Taking into account the head temperature detected by the thermistor disposed for detecting the temperature of the thermal head, when the thermal head temperature is equal to or higher than the set temperature, the ink ribbon ink does not melt in the heating element corresponding to the target dot 4. The method for controlling energization of a thermal head according to claim 1, wherein control for canceling the control for applying the electric power is performed.