JP3744142B2 - Thermal printer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  According to the present invention, a thermal head in which a plurality of heating dots are arranged is moved relative to a recording medium, and the heating dots are selectively driven to generate heat based on image information including gradation information. The present invention relates to a thermal printer for recording with gradation expression, and in particular, a part of the recording medium is2The present invention relates to a thermal printer capable of performing beautiful gradation recording even in an overlap region where recording is performed once.
[0002]
[Prior art]
  A general serial thermal printer records a thermal head in which a plurality of heat generating dots are arranged from the recording start position in the main scanning direction of the recording medium while the heat generating dots are selectively driven to generate heat based on image information. After moving to the end position and recording for one line, the recording medium is transported in the sub-scanning direction by a predetermined amount (the length for which the heating dots are arranged), and the thermal head is recorded in the main scanning direction. From the position to the recording start position, the thermal head is moved again from the recording start position in the main scanning direction to the recording end position to repeat the recording of the next line. The thermal printer capable of recording control corresponding to the gradation information while the image information includes gradation information can perform beautiful recording by gradation expression on the recording medium.
[0003]
  However, when the recording medium is transported in the sub-scanning direction by a predetermined amount, if the transport control is inappropriate, a gap is generated between the lines, and white streaks appear on characters and other images recorded on the recording medium. Appears. Therefore, the conveyance amount of the recording medium in the sub-scanning direction is made smaller than the predetermined amount (the length for which the heat generation dots are arranged), and a part of the recording medium is recorded as an overlap area. However, if the recording control of the overlap area is inappropriate, black streaks appear on the recorded characters on the recording medium.
[0004]
[Problems to be solved by the invention]
  In order to solve such a problem, for example, the image forming apparatus described in Japanese Patent Publication No. 6-38628 uses an overlap during the first recording of the overlap area with respect to the image information recorded in the overlap area. The image information is weighted with a coefficient that gradually decreases from the beginning to the end of the overlap area, and weighting is performed on the image information. During the second recording of the overlap area, a coefficient that gradually increases from the start to the end of the overlap area is obtained. A recording control method is employed in which weighting is applied to image information. However, with weighted recording control in which a uniform coefficient is applied to image information, sufficient gradation expression cannot be achieved, and it may be difficult to perform beautiful recording. Further, in the recording control in which the coefficient is applied to the image information every time the overlap area is recorded, the recording speed may be slow.
  The present invention has been made to solve the above problems, and an object of the present invention is to provide a thermal printer capable of performing beautiful recording at a high speed and by gradation expression.
[0005]
[Means for Solving the Problems]
  In order to achieve the above object, according to the thermal printer of the first aspect of the present invention, the thermal head in which a plurality of heating dots are arranged is moved relative to the recording medium, and image information including gradation information is obtained. Based on theBy controlling the size of the dots to be recorded, the gradation corresponding to the gradation information on the recording mediumIn a thermal printer that performs recording,In the image information,The thermal head is moved relative to the recording medium, and a part of the recording medium is moved.2Area to be recorded in one timeOrA non-overlapping area for recording a part of the recording medium at a timeWhether existsDiscriminating means for discriminating;Density data indicating the density on the recording medium,The first density data for the overlap area and the second density data for the non-overlap areaAs for each gradation,Associate and storeFirstStorage means;Second storage means for storing the density data and application time data for applying energy to each of the heat generation dots in correspondence;Said discrimination meansWhen it is determined that there is an overlap area in the image information, the first density data stored in the first storage means is read corresponding to the heat generation dots of the thermal head located in the overlap area After that, the heating dots are heated based on the application time data read from the second storage means corresponding to the first density data, and there is a non-overlapping area in the image information via the discrimination means. If it is determined, the second density data stored in the first storage means corresponding to the heat generation dots of the thermal head located in the non-overlapping area is read out, and the second density data is read out. Based on the application time data read from the second storage means, the heat generation of the heat generation dots is performed.And a control means.
  As a result, the discrimination meansThroughNon-overlapping areaExistThe control meansFirstThe second density data for the gradation information stored in the storage means is read out, whereas the determination meansThroughOverlap areaExistThe control meansSecondReading out first density data stored in association with second density data for non-overlapping areas corresponding to gradation information stored in the storage meansAfter that, the application time data corresponding to the density data is read from the second storage means, and as a result, the energy applied to each heating dot is also determined,The heating dots of the thermal head are selectively driven to generate heat.
[0006]
  According to a second aspect of the present invention, in the thermal printer according to the first aspect, the density data for the overlap area is half of the density data for the non-overlap area for the same gradation information. It is set to be larger than 1. Thereby, CoveredThe thermal head records the overlap area of the recording medium twice.Hits theSince the density data for the overlap area corresponding to the same gradation information is larger than half the density data for the non-overlap area, clear and dark recording can be performed.
[0007]
[0008]
[0009]
[0010]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, the thermal printer of the present invention is, for example, a tape printer with a keyboard that prints a large number of characters or marks such as hiragana, kanji and symbols on a recording medium such as a tape, or a recording paper via an ink ribbon. This is done with a printer that prints.
  FIG. 1 is a front view showing main parts such as a carriage and a thermal head provided in the thermal printer of this embodiment, and FIG. 2 is a block diagram showing an electrical configuration of the thermal printer.
[0011]
  As shown in FIG. 1, the thermal printer 1 according to this embodiment includes a carriage CA for moving the thermal head HD relative to the recording medium P1. The carriage CA can be mounted with a color ribbon cassette RC, and is supported by two guide shafts GD for carriage conveyance, and includes a carriage conveyance mechanism (not shown) including a drive motor 7a (see FIG. 2). ) In the longitudinal direction (arrow Y1 direction) of the ribbon cassette RC.
  In addition, a flat platen PA that supports a recording medium P1 such as a recording sheet is disposed below the carriage CA in FIG. 1, and a direction intersecting the arrow Y1 direction on the flat platen PA (see FIG. 1). A pair of left and right transport rollers R1 and R2 are provided so as to transport the recording medium P1 in the direction of arrow Z1). These transport rollers R1 and R2 are configured to rotate in a state where the recording medium P1 is sandwiched by a recording medium transport mechanism (not shown) including a driving motor 7b (see FIG. 2). . A thermal head HD is attached to the lower side of the carriage CA. On the recording surface HD1 side of the thermal head HD, a heating dot HD2 (see FIG. 8) capable of generating heat in units of one dot is recorded on the recording medium P1. They are arranged in a line along the transport direction (arrow Z1 direction). Since the ribbon cassette RC is detachably mounted on the carriage CA, the thermal head HD is installed in the opening RC3 of the ribbon cassette RC with the ribbon cassette RC mounted on the carriage CA. It is supposed to get stuck.
[0012]
  As shown in FIG. 1, the ribbon cassette RC includes an ink ribbon IR having a plurality of color ink regions such as cyan, magenta, and yellow ink regions in order in a substantially rectangular cassette case. Store. Specifically, both end portions of the ink ribbon IR are wound and stored on a reel RC1 for winding an unused ribbon and a reel RC2 for winding a used ribbon, respectively, and the reel RC2 is stored in the drive motor 7c. By rotating clockwise in response to the driving force (see FIG. 2), the ink ribbon IR drawn from the reel RC1 passes through the ribbon end detection and color detection sensor SE, and then the guide member RB1 and the ribbon. It passes through the opening RC3 of the cassette RC and is further wound around the reel RC2 via the guide member RB2. As a result, the ink ribbon IR is sequentially fed to the recording surface HD1 of the thermal head HD as the thermal head HD is conveyed in the main scanning direction.
[0013]
  As shown in FIG. 1, the thermal head HD is configured to be separated from the recording medium P1 (solid line) or abutted (two-dot chain line), and performs a recording operation on the recording medium P1. When the recording operation is not performed, the recording medium P1 is separated from the recording medium P1. With the thermal head HD in contact with the recording medium P1, the carriage CA conveys the thermal head HD for one line from the recording start position in the main scanning direction (arrow Y1 direction) to the recording end position. When the heat generating dot HD2 (heat generating element) generates heat in units of one dot, the ink on the ink ribbon IR melts in units of one dot and adheres to the recording medium P1, so Recording is sequentially performed in the intersecting direction (arrow Y1 direction).
[0014]
  After the recording for one line in the direction of the arrow Y1, the recording medium P1 is transported by a predetermined amount (the amount corresponding to the array of the heating dots HD2 or an amount smaller than the amount) in the transport direction (the direction of the arrow Z1), By returning the thermal head HD from the recording end position in the main scanning direction to the recording start position and transporting the carriage CA again from the recording start position in the main scanning direction to the recording end position, the thermal head HD is similar to the recording medium P1. The recording operation is performed. Hereinafter, the above-described aspect is repeated, and the thermal head HD in which a plurality of heat generating dots HD2 are arranged is relatively moved with respect to the recording medium P1, and the heat generating dots HD2 are selectively driven to generate heat based on the image information. Images such as characters and symbols are formed on the recording medium P1.
  Here, the operation of the thermal head HD and the transport amount of the recording medium P1 are schematically shown on the recording medium P1 in FIG. 8 as follows. That is, after the thermal head HD is moved from the recording start position K1 in the main scanning direction of the recording medium P1 to the recording end position K2, the first line H1 for one line is recorded, and then the recording medium P1 is moved to the sub recording medium P1. While transporting a predetermined amount in the scanning direction (a transport amount S2 that is slightly shorter than the length S1 in which the heating dots HD2 are arranged), the thermal head HD is returned from the recording end position K2 in the main scanning direction to the recording start position K1, and again. The mode in which the thermal head HD is moved from the recording start position K1 in the main scanning direction to the recording end position K2 to perform recording of the next line (second line H2) is repeated.
[0015]
  The sensor SE includes a light emitting element SE1 that emits light toward the ink ribbon IR and a light receiving element SE2 that receives light transmitted through the ink ribbon IR. The sensor SE protrudes toward the front side in FIG. 1 on the carriage CA. It is arranged like this. In this case, when the ribbon cassette RC is mounted on the carriage CA, the light emitting element SE1 and the light receiving element SE2 fit into the pair of through holes RC5 of the ribbon cassette RC, and ribbon end detection and color detection are performed. Can do.
[0016]
  In addition, as shown in FIG. 1, a plurality of marker portions RC6 are provided on the upper right side of the ribbon cassette RC. Whether these marker portions RC6 are recessed or not recessed. For example, the type of ribbon cassette RC is shown. The control device CP can identify the type of the ink ribbon IR in the ribbon cassette RC by detecting the presence / absence of the concave portion of the label portion RC6 by the detection sensor SQ disposed opposite to the label portion RC6. it can.
[0017]
  As shown in FIG. 2, the control device CP of the thermal printer 1 includes a central control device (hereinafter referred to as CPU) as a core, a keyboard 3 as an input device, and a character generator used for displaying characters or printing. Memory (CG-ROM) 4, display (LCD) 5 as a display device, drive motor 7a for carriage conveyance, drive motor 7b for conveyance of recording medium, drive motor 7c for conveyance of ink ribbon IR, etc. Are connected to a motor drive circuit 6 for driving a drive motor group 7 including the thermal head HD, sensors 8 including the sensor SE, and a power source 9 for driving the thermal printer 1. The control device CP includes the CPU, a read-only memory (hereinafter referred to as ROM), and a readable / writable memory (hereinafter referred to as RAM).
  On the keyboard 3, in addition to a plurality of keys 3a indicating characters for inputting hiragana, katakana, etc., for example, editing keys 3b such as an execution key and a cancel key are disposed. The keyboard 3 can transmit and receive signals such as data input through various keys to and from the control device CP.
[0018]
  The motor drive circuit 6 is a circuit for driving the drive motors 7a, 7b, 7c of the drive motor group 7, and is controlled by the control device CP. When the control device CP drives the drive motors 7a, 7b, and 7c by a predetermined amount via the motor drive circuit 6, the carriage CA transports the carriage CA in the arrow Y1 direction, and the transport rollers R1 and R2 The recording medium P1 is rotated by a predetermined amount to convey the recording medium P1 in the direction of the arrow Z1, or the reel RC2 is rotated by a predetermined amount to convey the ink ribbon IR by a predetermined amount.
[0019]
  When the control device CP appropriately controls the drive amount of the drive motor 7b for transporting the recording medium via the motor drive circuit 6, the array portion S1 (see FIG. 8) of the heat generation dots HD2 or the array thereof Only a length S2 (see FIG. 8) smaller than the minute S1 can be conveyed. Therefore, after one line of recording is performed on the recording medium P1 by the heating dots HD2 of the thermal head HD, the recording medium P1 is transported by an amount S2 (see FIG. 8) smaller than the arrangement amount S1 of the heating dots HD2. Then, when the recording is first performed by the lower heating dot HD2 in FIG. 8, the upper heating dot HD2 in FIG. 8 is positioned, and when recording is performed by the heating dot HD2 in this state, Part of the recording medium P12The overlap area W1 is recorded once. On the other hand, if the recording medium P1 is transported by the amount S1 of the heating dots HD2 after recording is performed on the recording medium P1, the heating dots HD2 are not positioned at the place where the recording was performed first. When recording is performed in this state, a non-overlap area W2 in which a part of the recording medium P1 is recorded at one time is obtained.
[0020]
  Therefore, when the control device CP controls the transport amount of the recording medium P1, it becomes the overlap area W1 or the non-overlap area W2. Thereby, the control device CP transfers a part of the recording medium P1.2It can be divided into an overlap area W1 to be recorded once and a non-overlap area W2 to record a part of the recording medium P1 at one time.
[0021]
  The sensors 8 including the sensor SE and the like detect the presence or absence of the cassette RC, the type of the recording medium P1, and the like in addition to the color detection and end detection of the ink ribbon IR, and control the detection signals. Send to device CP.
  The CG-ROM is a character generator for generating image data when characters are displayed or printed. The CG-ROM converts data indicating characters or the like into image data and sends the image data to the control device CP. The display 5 displays characters, marks and the like input from the keyboard 3 as image data on the screen over a plurality of lines.
[0022]
  The RAM is provided with various data storage areas such as a display buffer and a print buffer. For example, the storage area temporarily stores the image data and the like, but the print buffer can store at least image information for one line of the recording medium P1. The ROM has a drive control program for the drive motor 7, a display program for displaying characters and the like input via the keys of the keyboard 3 on the display 5, and other various programs necessary for operating the thermal printer 1. In addition, a control program necessary for recording with pseudo gradation using a dither method or the like is stored.
[0023]
  Further, the ROM as the storage means, as shown in FIG. 3, has first density data D1 for the overlap area W1 and second density data D2 for the non-overlap area W2 for gradation information. 4 is stored, and the table DT is stored that associates the density data D2 as shown in FIG. 4 with the application time data T1 for applying energy to each of the heating dots HD2. . However, the storage means is not necessarily limited to the ROM, and may be an external storage device, for example.
[0024]
  Next, the tables DD and DT will be described.
  In the upper part of the table DD shown in FIG. 3, the second density data D2 for basic dot gradation (for non-overlapping area W2) is listed in order from “0” to “63”. The lower row lists the first density data D1 for divided dot gradation (for the overlap region W1) from “0” to “32” corresponding to the second density data D2 “0” to “63”. Has been. In this case, the smaller the density data D1 and D2 is, the lighter the image on the recording medium is. However, the numerical value (for example, the numerical value “7” indicated by D3) indicated by the first density data D1 in the lower stage is low. When the numerical value is the same as the second density data D2 in the upper stage (for example, the numerical value “7” indicated by D3), the image on the recording medium P1 has the same density.
[0025]
  Also, the upper second density data D2 in the table DT shown in FIG. 4 corresponds to the lower application time data T1, and this application time data T1 is the actual image recorded on the recording medium P1. Is set on the basis of the density. In this case, in the upper part of the table DT, the second density data D2 for basic dot gradation (for the non-overlapping area W2) is listed in order from “0” to “63”, and in the lower part of the table DT. In addition, “time data t1” to “time data t63” are listed in order corresponding to “0” to “63” of the second density data D2 in the upper stage.
[0026]
  Specifically, in the case of the time Q1 during which energy as shown in FIG. 6A is applied to the heat generating dots HD2, dots (pixels) shown in FIG. 6B are formed on the recording medium P1. Recorded with diameter d1. In the case of the application time Q2, recording is performed with a dot diameter d2 on the recording medium P1. Thus, it can be seen that the longer the application time, the larger the pixel (dot) diameter on the recording medium P1 and the higher the image density.
[0027]
  Then, the larger the second density data D2 is, the darker the image on the recording medium P1, so that the numbers also increase from “time data t1” to “time data t63” corresponding to the density. Accordingly, the pulse application time Q1 (see FIG. 6) is set to be longer. Therefore, by confirming the application time Q1 of the energy applied to the heat generating dot HD2 and the required pixel size on the recording medium P1, the “time data t1” to the “time data” for the second density data D2 are confirmed. t63 "can be set. Accordingly, the application time data T1 for the density data D1 and D2 can be appropriately corrected according to the actual density of the image recorded on the recording medium P1.
[0028]
  Therefore, when the control device CP reads the density data D1 and D2 from the ROM based on the image information, and reads the application time data T1 for the density data D1 and D2 and outputs it to the thermal head HD, the control device CP obtains the application time data T1. Accordingly, the heat generating dot HD2 is driven to generate heat, and the size of the dot (pixel) recorded on the recording medium P1 is controlled. When the density data D1 and D2 read by the control device CP are dark, the size of the dots (pixels) recorded on the recording medium P1 increases, but is read by the control device CP. When the density data D1 and D2 are thin, the size of the dots (pixels) recorded on the recording medium P1 is reduced, and recording is performed according to the density data D1 and D2.
[0029]
  The reason why the first density data D1 is smaller than the second density data is that the thermal head HD is moved relative to the recording medium P1, and a part of the recording medium P1 is moved once. This is because recording is different from recording a part of the recording medium P1 by overlapping twice.
  If the same density data is used in the case of recording with overlapping when recording without overlapping, the image of characters or the like recorded on the recording medium P1 is darkened or black lines appear. However, since the first density data D1 is set smaller than the second density data D2 as described above, such inappropriate recording is not performed. In addition, clear recording is performed.
[0030]
  However, as shown in FIG. 5, the density data D1 for the overlap area is set to be larger than half of the density data D2 for the non-overlap area W2 for the same gradation information. FIG. 5 is a graph showing a correspondence relationship between the first density data, the second density data, and half of the second density data. 2 of the density data D2 of “0” to “63” (the straight line L1 in FIG. 5) and the size of the first density data D1 of the lower stage from “0” to “32” ( Comparison with the graph L2) in FIG. 5 shows that the graph L2 in FIG. 5 is larger than the straight line L1.
[0031]
  This is when the thermal head HD is set to record the overlap area W1 of the recording medium P1 twice, and the density data D1 for the same gradation information is smaller than half of the density data D2. When the numerical value of the density data D1 is small, the image on the recording medium P1 tends to become thin, and a clear image cannot be recorded. On the other hand, when the density data D1 is larger than half of the density data D2, the pixels become large, and a dark and clear image can be recorded.
[0032]
  Next, the operation of the control device CP will be described according to the flowchart shown in FIG. The steps in the flowchart are abbreviated as S.
  As shown in FIG. 7, the control device CP reads the image information for one line (S1), and then determines whether or not there is an overlap area for each heating dot HD2 in the image information for one line. (S2). In the case of NO in S2, that is, for the heat generation dot HD2 that is not located in the overlap area, the control device CP reads out the second density data D2 for the non-overlap area and uses the second density data D2 as the second density data D2. The corresponding application time data T1 is read (S3) and output to the thermal head HD to drive the corresponding heat generating dot HD2 to generate heat (S4).
  In the case of YES in S2, that is, for the heat generating dot HD2 located in the overlap region, the control device CP reads out the first density data D1 stored in association with the second density data, and the first density data D1 is stored. The application time data T1 corresponding to the density data D1 is read out (S5) and output to the thermal head HD to drive the heat generation dot HD2 to generate heat (S6).
[0033]
  Specifically, when it is determined as the non-overlapping area W2, the numerical value indicated by D3 of the second density data D2, for example, the second density data D2, with respect to the gradation information stored in the ROM. “7” is read, and application time data t7 corresponding to the second density data D2 is read and output to the thermal head HD. On the other hand, when the control device CP determines that it is the overlap region W1, the first density data D1 (the second density data) stored in association with the second density data corresponding to the gradation information stored in the ROM. The numerical value “6” on the lower side of the numerical value “7” indicated by the density data D3 is read, and the application time data t6 corresponding to the first density data D1 is read and output to the thermal head HD.
  As a result, in the case of the normal non-overlapping region W2, the control device CP selectively drives the heat generating dots HD2 to generate heat based on the second density data D2. However, only in the overlapping region W1, the control device CP Instead of the density data D2, the heat generation dots HD2 are selectively driven to generate heat based on the first density data D1, and recording is performed on the recording medium P1 as shown in FIG. 8, for example.
[0034]
  Here, FIG. 9 shows an enlarged view of the vicinity of the boundary between the overlap region W1 and the non-overlap region W2 in FIG. 8 (the portion surrounded by the one-dot chain line in FIG. 8).
  The pixel D4 (shown by hatching) of the overlap region W1 recorded earlier and the pixel D5 (shown by black circles) of the overlap region W1 recorded later are both recorded with a small diameter, whereas both are small in diameter. The non-overlapping area W2 pixel D6 (shown by diagonal lines) and the non-overlapping area W2 pixel D7 (shown by black circles) recorded later both have a large diameter. This is because the pixels of the overlap area W1 of the recording medium P1 are small.2When the recording is performed once, the small pixels as a whole become large to the same extent as the pixels of the non-overlapping area W2. Accordingly, when the image is greatly enlarged as shown in FIG. 9, the pixel D4, D5 overlapped with the pixel D6, D7 is slightly different from the pixel D6, D7, but the entire image of the recording medium P1 is clearly recorded by gradation expression. .
[0035]
  Thereafter, the control device CP determines whether or not the image information recording operation for one line has been completed (S7). If NO is determined in S7, that is, if the recording operation is not completed, S2 to S6 are repeated.
  If YES in S7, the control device CP conveys the recording medium P1 by a predetermined amount (S8). In this case, the transport amount of the recording medium P1 is set in advance in order to obtain a clear image in consideration of whether recording is performed on the recording medium P1 with or without overlap.
  Next, the control device CP determines whether or not the recording operation for all image information has been completed (S9). If NO is determined in S9, that is, if the recording operation is not completed, S1 to S8 are repeated. If YES in S9, the recording operation is terminated.
[0036]
  As described above, according to this embodiment, the thermal head HD in which a plurality of heating dots HD2 are arranged is moved relative to the recording medium P1, and the heating dots HD2 are set based on the image information including gradation information. In the thermal printer 1 that selectively drives to generate heat and records on the recording medium P1, the thermal head HD is moved relative to the recording medium P1, and a part of the recording medium P1 is moved.2A control device CP (discriminating means) for discriminating between an overlap area W1 to be recorded once and a non-overlap area W2 to record a part of the recording medium P1 at one time, and the overlap area for gradation information Discrimination results of the ROM (storage means) for storing the first density data D1 for W1 and the second density data D2 for the non-overlapping area W2 in association with each other and the control device CP (discrimination means) And a control device CP (control means) for selectively reading out the first density data D1 or the second density data D2 in the ROM (storage means).
  As a result, when the control device CP (discriminating means) discriminates the non-overlap region W2, the control device CP (control means) determines the second density data for the gradation information stored in the ROM (storage means). When the control device CP (discriminating means) discriminates the overlap area W1 while reading out D2, the first density data D1 corresponding to the second density data D2 corresponding to the gradation information is read out, and the thermal head HD is read out. And output to the heating dot HD2.
[0037]
  In addition, this Embodiment is only a mere illustration and does not limit this invention at all. Therefore, the present invention can be variously improved and modified without departing from the scope of the invention..
  MaThe thermal printer of the present invention does not need to be a tape printer, for example, and may be a thermal printer such as a line thermal printer. Further, the method for expressing the gradation on the image on the recording medium P1 does not necessarily adopt the dither method, and other pseudo-halftone expression methods may be used.
[0038]
【The invention's effect】
  As described in detail above, according to the thermal printer of the invention according to claim 1,In a thermal printer that performs gradation recording according to gradation information on a recording medium by controlling the size of dots to be recorded, in the image information,Move the thermal head relative to the recording medium to move a part of the recording medium.2Area to be recorded in one timeOrA non-overlapping area for recording a part of the recording medium at a timeWhether existsDiscriminating means for discriminating, first density data for the overlap area with respect to gradation information, and second density data for the non-overlap areaEach other for each gradationStore in associationFirstStorage means;Corresponds between the density data and application time data for applying energy to each heating dot Second storage means for storingSaid discrimination meansWhen it is determined that there is an overlap area in the image information, the first density data stored in the first storage means is read corresponding to the heat generation dots of the thermal head located in the overlap area After that, the heating dots are heated based on the application time data read from the second storage means corresponding to the first density data, and there is a non-overlapping area in the image information via the discrimination means. If it is determined, the second density data stored in the first storage means corresponding to the heat generation dots of the thermal head located in the non-overlapping area is read out, and the second density data is read out. Based on the application time data read from the second storage means, the heat generation of the heat generation dots is performed.And control means, so that the discrimination meansThroughPerformed overlap area or non-overlap areaWhether there isBased on the determination result, the control means selectively reads out the second density data corresponding to the gradation information in the recording means or the first density data corresponding to the second density data.After that, the application time data corresponding to the density data is read from the second storage means, and as a result, the energy applied to each heating dot is also determined,The heating dots of the thermal head are selectively driven to generate heat.
  As a result, for example, the control of multiplying the image information by the coefficient from the start to the end of the overlap area as shown in Japanese Patent Publication No. 6-38628 becomes unnecessary. A beautiful record can be made.
[0039]
  According to the thermal printer of the present invention, the density data for the overlap area is set to be larger than half of the density data for the non-overlap area for the same gradation information. Because, CoveredThe thermal head records the overlap area of the recording medium twice.Hits theThe density data for the overlap area corresponding to the same gradation information is larger than half the density data for the non-overlap area. Therefore, when the density data for the overlap area is thin, an image that tends to be thin on the recording medium can be made particularly dark, and as with the density data for the non-overlap area, the image is clear and dark. It can be performed.
[0040]
[0041]
[0042]
[Brief description of the drawings]
FIG. 1 is a front view showing main parts of a carriage, a thermal head, and the like provided in an embodiment embodying a thermal printer according to the present invention.
FIG. 2 is a block diagram showing an electrical configuration of this embodiment.
FIG. 3 is a diagram showing a correspondence relationship between first density data for an overlap region and second density data for a non-overlap region with respect to gradation information according to this embodiment.
FIG. 4 is a diagram showing a relationship between second density data of this embodiment and application time data for applying energy to a heating dot.
FIG. 5 is a graph showing a correspondence relationship between the first density data, the second density data, and a half of the second density data according to this embodiment.
FIG. 6 shows the relationship between the application time data for applying energy to the heat generating dots of this embodiment and the actual density recorded on the recording medium, and (a) is a waveform diagram of the applied pulse. (B) is a figure which shows the actual dot diameter recorded.
FIG. 7 is a flowchart showing the operation of this embodiment.
FIG. 8 is a diagram showing the relationship between the heat generation dots of the thermal head of this embodiment and the actual image recorded on the recording medium.
FIG. 9 is an enlarged view showing an actual image recorded on the recording medium of this embodiment.
[Explanation of symbols]
  1 Thermal printer
  HD thermal head
  HD2 fever dot
  CA carriage
  IR ink ribbon
  SE sensor
  W1 overlap area
  W2 non-overlapping area
  D1 First concentration data
  D2 Second concentration data
  T1 application time data
  P1 Recording medium
  CP control device (discriminating means)
  CP control device (control means)

Claims (2)

A thermal head in which a plurality of heating dots are arranged is moved relative to the recording medium, and the heating dots are selectively driven to generate heat based on image information including gradation information, and the size of the dots to be recorded is set. In a thermal printer that performs gradation recording according to gradation information on a recording medium by controlling ,
In said image information, said thermal head are moved relative with respect to the recording medium, the overlapping region or recorded in the two part of the recording medium, a portion of the recording medium in one Discriminating means for discriminating whether or not there is a non-overlapping area to be recorded;
Density data indicating the density on the recording medium is stored as first density data for the overlap area and second density data for the non-overlap area in association with each other for each gradation. First storage means to
Second storage means for storing the density data and application time data for applying energy to each of the heat generation dots in correspondence;
If it is determined through the determination means that an overlap area exists in the image information, the first density stored in the first storage means corresponding to the heat generation dots of the thermal head located in the overlap area. After the data is read, the heating dots are heated based on the application time data read from the second storage means corresponding to the first density data, and non-overlapping is included in the image information via the discrimination means. If it is determined that the area exists, the second density data is read after reading the second density data stored in the first storage means corresponding to the heat generation dots of the thermal head located in the non-overlapping area. corresponds characterized in that it comprises a control means for heating the driving of the heat generating dots on the basis of the application time data read from the second storage means in Thermal Printer. The thermal printer according to claim 1,
The thermal printer according to claim 1, wherein the density data for the overlap area is set to be larger than half of the density data for the non-overlap area for the same gradation information.

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