JP2007230206A - Printer, heat storage correction control method, and print control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer having a large tone level difference between a high density and a low density and capable of reducing a trailing phenomena in a case of rapid printing. <P>SOLUTION: When a density (tone level) to print is varied from a high tone level (e.g. 255 tone level) to a low tone level (e.g. 64 tone level), correction is started from the N<SP>th</SP>line prior to variation of the tone level, that is, the heat applied to an ink ribbon is gradually decreased from the fore by N lines so as to diminish the heat to be accumulated on a thermal head. Since the accumulated heat is already small when the tone level changes high to low, a result of enough correction can be obtained by a small amount of correction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a printer, a heat storage correction control method, and a print control method, and in particular, a gradation difference from a high density to a low density is large at the time of printing by thermal transfer. The present invention relates to a printer, a heat storage correction control method, and a print control method that can reduce the tailing phenomenon due to heat accumulation and can achieve both “rising density deficiency correction” and “tailing correction” of an image to be printed.

  A dye sublimation printer presses a thermal head against an ink ribbon coated with a dye or pigment and heats the thermal head to transfer the ink ribbon dye or pigment onto a recording medium such as paper to form an image. It is used for printing purposes.

  FIG. 7 is a diagram illustrating a configuration example of the printing unit of the sublimation printer. As shown in FIG. 7A, an ink ribbon roll 33 (unused portion) wound around a supply core 34 on the unwinding side is provided on the upper surface side of the print paper 32 unwound from the roll paper 31 (supply side). ), The ink ribbon guide roll 36, the thermal head 18, the ink ribbon guide roll 37, and the winding core 38 on the winding side are arranged in this order. The ink ribbon 35 unwound from the ink ribbon roll 33 is superposed on the print paper 32 unwound from the roll paper 31 by being guided by the guide roll 36, and conveyed between the thermal head 18 and the platen roll 39. After that, it is wound around the winding core 38 via the guide roll 37.

  On the lower surface side of the print paper 32, a platen roll 39 is disposed at a position facing the thermal head 18. The platen roll 39 causes the print paper 32 to be heated by the heating resistor 19 of the thermal head 18 (see FIG. 7B). Is moderately pressed. A feed roll 41 is disposed at a position facing the pinch roll 40. The print paper 32 is conveyed by sandwiching the print paper 32 between the pinch roll 40 and the feed roll 41 and rotating the feed roll 41.

  Further, the thermal head 18 includes a heating resistor 19 provided corresponding to each dot for one line of an image to be formed as shown in FIG. 7B (when a plurality of heating resistors are arranged). The dye or pigment of the ink ribbon 35 is transferred to the print paper 32 by applying a pulse current to these heating resistors 19.

  FIG. 8 is a view showing an example of an ink ribbon. As shown in FIG. 8, the ink ribbon includes three ink layers of Y (yellow), M (magenta), and C (cyan), and OP (overcoat layer) is periodically arranged. Then, a region indicated by a dotted line in the ink layer of the ink ribbon is printed on the printing paper.

  In the sublimation printer having the above configuration, the print density (gradation) is changed by the intensity of heat applied from the thermal head 18 to the ink ribbon 35. When a strong heat is applied to the ink ribbon, printing is performed at a high density, and when a weak heat is applied, printing is performed at a low density.

  By the way, when the ink ribbon ink is transferred to the printing paper, the beginning of the low density area becomes dark where the print density (gradation) changes from high density to low density. This is because during high density printing, heat accumulates inside the thermal head, and when changing from a high density area to a low density area, the temperature of the thermal head cannot be instantaneously lowered from a high state, resulting in excessive heat. It is a phenomenon that arises from This phenomenon is called a tailing phenomenon.

  FIG. 9 is a diagram illustrating an example of the tailing phenomenon. As shown in FIG. 9, in the print result shown in FIG. 9B with respect to the original image shown in FIG. 9A, “bleeding” occurs when the high density area changes to the low density area. This “smear” is the tailing phenomenon.

  FIG. 10 is a diagram showing an example of conventional heat storage correction control (tailing correction control), and the tailing phenomenon occurs where the concentration changes from high to low. In such a case, the attribute phenomenon can be reduced by correcting the heat applied from the thermal head to the ink ribbon to be small.

  As shown in FIG. 10A, in the case of no correction, the heat given to the ink ribbon in the low gradation area (128 gradations) is constant. On the other hand, as shown in FIG. 10B, when the correction is made, the heat applied to the ink ribbon is reduced when the high gradation (255 gradation) is changed to the low gradation (128 gradation). (Part surrounded by dotted line G). This reduces the tailing phenomenon.

  However, with the conventional tailing correction method. The tailing cannot be corrected sufficiently where the gradation difference from the high density to the low density is large and the density in the low density area is small. The tailing correction control is realized by correcting the heat applied to the ink ribbon so as to be small. The heat applied to the ink ribbon is the smallest when no heat generation command is issued to the thermal head (hereinafter referred to as “non-energization”). At this time, the strongest correction can be performed. The limit of correction is when the power is turned off, and a stronger correction cannot be performed.

  FIG. 11 is a diagram illustrating an example of a case where the correction cannot be sufficiently performed by the tailing correction control. This is an example in which the gradation is changed from 255 gradations (highest density) to 64 gradations. In the case of no correction as shown in FIG.

  FIG. 11B shows an example when tail correction is performed, and correction (negative thermal correction) as indicated by a portion surrounded by a dotted line G in the graph is necessary to obtain a sufficient correction result. . However, since the correction stronger than the non-energization cannot be performed, the correction indicated by the thick line H is performed. As described above, since the correction amount is insufficient, a sufficient correction result cannot be obtained and the tail remains.

  The effect of this problem is further increased by high-speed printing. Since the heat storage amount of the thermal head increases because printing is performed with stronger heat, and the paper travels a long distance while the correction amount is insufficient because the paper conveyance speed is fast, the length of the tail is increased.

  FIG. 12 is a diagram illustrating an example of insufficient tailing correction. FIG. 12A shows an example in which characters are printed. Since a lot of heat is accumulated in the thermal head by the vertical line, the vertical line becomes long. Further, when the barcode shown in FIG. 12B is printed, the space between the bars is not clear.

  By the way, in the sublimation type printer, in addition to the above-described correction of the tailing phenomenon (see the portion surrounded by the dotted line G in FIG. 10), when printing 0 gradation data (especially 0 gradation data continuously). In the case of printing), as the bias energy applied to the thermal head, the first 0 gradation data printing system that gives preheating within a range where the ink ribbon does not develop color, and the second that makes the thermal head completely unenergized. There is a zero gradation data printing method.

  In the first 0 gradation data printing method (method of applying bias energy), the thermal head is preheated even when 0 gradation data continues, so that 1 When printing data of gradation or higher, the thermal head is warmed to some extent, so the “rise of density of print gradation data” is good, and data of 0 gradation and 1 gradation or more are included in one line. When present, the energy level difference is small, and there is an advantage that “wrinkles” due to the difference in expansion and contraction of the ink ribbon during printing are less likely to occur.

  In the second 0 gradation data printing method (non-energization method), the thermal head becomes non-energized when printing 0 gradation data after high gradation data continues. This has the maximum effect for reducing the “tailing phenomenon”.

  For this reason, in order to improve the quality of the printed image, it has been required to simultaneously realize the advantages of the first 0 gradation data printing method and the second 0 gradation data printing method. Also, due to the speeding up of the printer, in the first 0 gradation data printing method, “the effect of improving the rise in print density” and “the effect of reducing ink ribbon wrinkles” are reduced, and the second 0 gradation is printed. In the data printing method, the effect of “correcting the tailing phenomenon” is reduced, and if only one of the two methods is effective, satisfactory print quality tends to be not obtained.

  There is a conventional thermal recording apparatus (see, for example, Patent Document 1). The prior art thermal recording apparatus is intended to provide a thermal recording apparatus that can always record pixels of the same density and can perform high-quality printing. For this purpose, a plurality of heating elements are constituted by a plurality of blocks with at least two heating elements adjacent in the main scanning direction as a unit block, a block to which the heating elements to be heated belong, and the main scanning direction of the block The amount of energy applied to the heat generating element to be heated is set based on the heat generation data of the heat generating elements belonging to a pair of blocks adjacent to. As a result, the amount of energy applied to the heating element to be heated is set in consideration of the heating state of the heating element located in the vicinity of the heating element to be heated. There is provided a thermal recording apparatus that can always record pixels with the same density without causing problems such as an increase in dot diameter due to the influence of the ink, printing bleeding, and blurring, and capable of high-quality printing. be able to.

However, in the conventional thermal recording apparatus, the print quality is improved by setting the amount of energy applied to the heating element that should generate heat in consideration of the heating state of the heating element located in the vicinity of the heating element. The object and configuration of the present invention are different from those of the present invention in which the tailing phenomenon caused by the change in print density (gradation) is reduced.
Japanese Patent Laid-Open No. 11-235839

  As described above, in the conventional tail correction method, the tailing cannot be corrected sufficiently where the gradation difference from the high density to the low density is large and the density in the low density area is small. In particular, when printing at high speed, the thermal head prints with a greater amount of heat, and the amount of heat stored in the thermal head increases. There was a problem that the length became long.

  In addition, when printing 0 gradation data (especially when printing 0 gradation data continuously), as a bias energy applied to the thermal head, a first heating that gives preheating within a range where the ink ribbon does not develop color is applied. There is a zero gradation data printing method and a second zero gradation data printing method in which the thermal head is completely de-energized. In order to improve the quality of the printed image, the first zero gradation data printing method is used. It has been demanded to simultaneously realize the advantages of the method and the second 0 gradation data printing method.

  The present invention has been made to solve such a problem. The first object of the present invention is that a gradation difference from a high density to a low density is large, and the tailing phenomenon is also observed in high-speed printing. An object of the present invention is to provide a printer and a tail correction control method that can be reduced.

  The second object of the present invention is to provide bias energy when “preheating” is required when printing 0 gradation data, and to correct “tailing phenomenon”. Is to provide a printer and a print control method that can be turned off.

The present invention has been made to solve the above-described problems. The printer of the present invention presses an ink ribbon against a print sheet by a thermal head provided with a heating resistor for each dot in the line direction of an image to be formed. A printer that performs printing by transferring the ink of the ink ribbon onto a sheet of paper by applying a heat amount corresponding to the gradation of the image density to the ink ribbon by the thermal head. For the dots, a gradation value change detecting means for detecting in advance a gradation value change up to N (an arbitrary number set in advance) line destination in the print direction, and the N line destination by the gradation value change detecting means A thermal head heating correction unit that corrects the amount of heating to the ink ribbon at the dot of interest when it is detected that there is a change in tone value between Characterized in that it comprises and.
With such a configuration, a change in gradation value between the target dot and the N line ahead in the print direction is detected in advance. Then, when it is detected that there is a change in gradation value up to N lines ahead, the amount of heat applied to the ink ribbon at the target dot is corrected. For example, when changing from a high gradation to a low gradation, the correction is started from the Nth line before the gradation value changes. That is, the heat applied to the ink ribbon is gradually reduced from the N line before the gradation value changes, and the heat storage amount of the thermal head is reduced. In this way, when changing from a high gradation to a low gradation, the amount of heat stored in the thermal head is already small, so that a sufficient correction result can be obtained with a small correction amount.
Thereby, in the sublimation type printer, it is possible to reduce the tailing phenomenon when the print density (gradation) changes.

In the printer according to the aspect of the invention, the thermal head heating correction by the thermal head heating correction unit is performed when the gradation value change detection unit determines that the gradation value falls below a predetermined range. Features.
With such a configuration, the correction is performed when it is determined that the gradation to be printed changes from a high gradation to a low gradation and the gradation value falls below a predetermined range. That is, when the change in gradation value is large, the heat applied to the ink ribbon is gradually reduced from before the N line before the gradation value changes, thereby reducing the heat storage amount of the thermal head. In this way, when changing from a high gradation to a low gradation, the amount of heat stored in the thermal head is already small, so that a sufficient correction result can be obtained with a small correction amount.
Thereby, in the sublimation printer, the tailing phenomenon that occurs when the gradation difference from the high density to the low density is large can be reduced. Further, the tailing phenomenon can be reduced even in the case of high-speed printing.

In the printer according to the present invention, when the gradation value detecting unit detects a change in the gradation value up to the N line destination, an average gradation value that is an average value of the gradation values up to the N line destination. And a change in gradation value is detected based on the average gradation value.
With such a configuration, when detecting a change in gradation value, an average gradation value that is an average value of gradation values up to N lines ahead is obtained for the target dot, and the average gradation value is determined based on the average gradation value. A change in gradation value is detected.
Thereby, the correction of the gradation value can be performed smoothly.

In the printer of the present invention, the correction by the thermal head heating correction unit is performed by a calculation formula of “target dot tone value after correction = target dot tone value before correction−correction value”, where N is The correction value when the number of dots to be referenced under the target dot is used, Lv is the average gradation value of the N dots below the target dot, and Ii is the gradation value that can be printed with the current heat storage amount of the thermal head. Is obtained by a predetermined function having (Ii−Lv) as a variable.
With such a configuration, “corrected dot tone value after correction = target dot tone value before correction−correction value”. Then, the correction value is obtained by a function having (Ii−Lv) as a variable. For example, the correction value is obtained by a primary expression or a secondary expression of (Ii−Lv).
As a result, the correction value can be calculated in an optimum form according to the characteristics of the thermal head and the ink ribbon, so that the tailing phenomenon can be effectively reduced.

In the printer of the present invention, the correction by the thermal head heating correction unit is performed by a calculation formula of “target dot tone value after correction = target dot tone value before correction−correction value”, where N is The number of dots to be referenced under the target dot, Lv is the average gradation value of the N dots below the target dot, Ii is the gradation value that can be printed with the current heat storage amount of the thermal head, and W is the correction value When S is a predetermined threshold (positive number) that determines whether to correct or not, and “(Li−Lv)> S” and “(Ii−Lv)> 0” , “Correction value = (Ii−Lv) ² × W”; otherwise, “correction value = 0”.
With such a configuration, “corrected dot tone value after correction = target dot tone value before correction−correction value”. When “(Li−Lv)> S (threshold)” and “(Ii−Lv)> 0”, “correction value = (Ii−Lv) ² × W” is obtained. Value = 0 ”. For “(Li−Lv)> S”, the gradation difference between dots becomes small and the boundary becomes unclear when correction is performed, so only for the case where the gradation difference from high density to low density is somewhat large. Make corrections. For “(Ii−Lv)> 0”, correction is performed when the thermal head has a high heat storage amount and the average gradation value Lv or higher is printed (Ii> Lv). When the heat storage amount is low and the average gradation value Lv or higher is not printed, no correction is performed. As for “correction value = (Ii−Lv) ² × W”, a quadratic expression is used so that weighting can be performed for correction and smooth correction can be realized.
Thereby, in the sublimation printer, the tailing phenomenon that occurs when the gradation difference from the high density to the low density is large can be reduced. Further, the tailing phenomenon can be reduced even in the case of high-speed printing. Furthermore, the weighting coefficient W according to the characteristics of the thermal head and the ink ribbon can be selected, and smooth correction can be realized.

Also, the tail correction control method of the present invention is such that an ink ribbon is pressed against a print sheet by a thermal head provided with a heating resistor for each dot in the line direction of the image to be formed, and the image is applied to the ink ribbon by the thermal head. A tailing correction control method in a printer that performs printing by transferring an ink ribbon ink onto paper by applying an amount of heat according to the gradation of the density of the image, and printing a current image by the control unit in the printer A gradation value change detection procedure for detecting a change in gradation value in advance in a print direction up to N (an arbitrary number set in advance) line destination in the print direction, and the gradation value change detection procedure When it is detected that there is a change in the gradation value up to N lines ahead, the sensor for correcting the heating amount of the ink of interest at the dot of interest is corrected. And heads or others heated correction procedure is equal to or Okonawaru.
By such a procedure, a change in gradation value between the target dot and N (an arbitrary number set in advance) in the print direction is detected in advance. Then, when it is detected that there is a change in gradation value up to N lines ahead, the amount of heat applied to the ink ribbon at the target dot is corrected. For example, when changing from a high gradation to a low gradation, correction is started from the Nth line before the gradation value changes. That is, the heat applied to the ink ribbon is gradually reduced from the N line before the gradation value changes, and the heat storage amount of the thermal head is reduced. In this way, when changing from a high gradation to a low gradation, the amount of heat stored in the thermal head is already small, so that a sufficient correction result can be obtained with a small correction amount.
Thereby, in the sublimation type printer, it is possible to reduce the tailing phenomenon when the print density (gradation) changes.

In addition, the printer of the present invention presses the ink ribbon against the print paper with a thermal head provided with a heating resistor for each dot in the line direction of the image to be formed, and the thermal head presses the ink ribbon against the ink ribbon. A printer that prints by transferring the ink of the ink ribbon onto the paper by applying a heat amount according to the tone, and when the thermal storage amount of the thermal head is below a predetermined value when printing 0 gradation data The bias energy application means for printing by applying bias energy for preheating the thermal head, and when the thermal storage amount of the thermal head exceeds a predetermined value, the bias energy is not applied to the thermal head. And a non-energized printing unit that performs non-energized printing.
With such a configuration, printing of 0 gradation data or low gradation data is continuous, and when the thermal storage amount of the thermal head is small, bias energy (ink ribbon does not develop color) when printing 0 gradation data. Apply energy that gives preheating within the range. Further, when printing of high gradation data is continued and the thermal storage amount of the thermal head is high, printing is performed without energization without applying bias energy when printing 0 gradation data. That is, when “preheating” is necessary, bias energy is applied, and when “tail correction” is necessary, no energization is performed.
As a result, it is possible to realize a high-quality print in which “rising density deficiency correction” and “tail correction” are compatible.

The printer according to the present invention is characterized in that the heat storage amount of the thermal head is calculated based on thermal history data obtained by adding printed gradation data.
Thereby, the heat storage amount of the thermal head can be easily calculated, and when printing 0 gradation data, it can be determined whether to print by applying bias energy or without printing.

Further, the print control method of the present invention uses an ink ribbon pressed against a print sheet by a thermal head provided with a heating resistor for each dot in the line direction of the image to be formed, and the density of the image against the ink ribbon by the thermal head. Is a print control method in a printer that performs printing by transferring the ink of the ink ribbon onto a sheet by applying an amount of heat according to the gradation of the image, when printing 0 gradation data by the control unit in the printer In addition, when the thermal storage amount of the thermal head is less than or equal to a predetermined value, the bias energy application procedure for printing by applying bias energy for preheating the thermal head, and when the thermal storage amount of the thermal head is greater than or equal to the predetermined value Is a non-energized printing procedure for printing without energizing without applying bias energy to the thermal head. And wherein the Rukoto.
According to such a procedure, when 0 gradation data or low gradation data is continuously printed and the thermal head has a small amount of heat accumulation, when the 0 gradation data is printed, the bias energy (the ink ribbon does not develop color) is printed. Apply energy that gives preheating within the range. Further, when printing of high gradation data is continued and the thermal storage amount of the thermal head is high, printing is performed without energization without applying bias energy when printing 0 gradation data. That is, when “preheating” is necessary, bias energy is applied, and when “tail correction” is necessary, no energization is performed.
As a result, it is possible to realize a high-quality print in which “rising density deficiency correction” and “tail correction” are compatible.

  In the printer and the tailing correction control method of the present invention, the tailing phenomenon that occurs when the gradation difference from high density to low density is large in a sublimation printer can be reduced. Further, the tailing phenomenon can be reduced even in the case of high-speed printing.

  In the printer and the print control method of the present invention, it is possible to realize high-quality printing in which “rising density deficiency correction” and “tailing correction” are compatible.

[First Embodiment]
First, as a first embodiment of the present invention, an embodiment for reducing the tailing phenomenon when the print density shifts from a high gradation to a low gradation will be described with reference to the drawings.

  FIG. 1 is a diagram for explaining a tail correction control method in the printer of the present invention. As shown in FIG. 1, in the present invention, the gradation changes when the print density (gradation) changes from a high gradation to a low gradation (255 gradations to 64 gradations in the example of FIG. 1). Correction starts from the Nth line. That is, the heat applied to the ink ribbon is gradually reduced from before the N line, and the heat storage amount of the thermal head is reduced. When changing from a high gradation to a low gradation, the thermal storage amount of the thermal head is already small, so that a sufficient correction result can be obtained with a small correction amount.

  In FIG. 1, the portion indicated by the solid line in the graph represents the tailing correction control according to the present invention, and since the heat applied to the ink ribbon is reduced in the N line section, the target density cannot be obtained (becomes small). ). However, a certain level of density is obtained by the residual heat, and the influence on the print is smaller than the “smear” caused by the tailing.

Next, a method for realizing the tailing correction control of the present invention will be described.
FIG. 2 is a diagram showing the arrangement of the target dot and the dots of the lower N lines. As shown in FIG. 2, the target dot 3 is a dot to be corrected from now on. When correcting, the lower N dots of the target dot 3 are referred to. The lower N dot of the target dot 3 indicates a dot to be printed after the target dot 3. It is checked whether or not the gradation changes from a high gradation to a lower gradation during the next N line, and if it changes, correction is performed. This is performed for all dots in each line. By referring to the dots below the N line, correction can be started from the front of the N line.

Next, a correction value calculation method will be described. First, the values used in the calculation are defined as follows.
N: The number of dots to be referenced below the target dot.
Li: The gradation value of the target dot.
Lv: an average gradation value of N dots below the target dot.
Vi :: Thermal storage amount of the thermal head at the time of dot printing of interest, and a value obtained according to the characteristics of the thermal head.
Ii: A gradation value that can be printed with the thermal storage amount Vi of the thermal head, and an optimum thermal head thermal storage amount that provides a target density for each gradation value is defined in advance, and the value obtained from this definition For example, as shown in FIG. 3, a gradation value Ii that can be printed is derived from the heat storage amount Vi by a method indicated by a dotted arrow.
W: correction weight, a coefficient for adjusting the magnitude of the correction value.
S: A threshold value (positive number) to be corrected / not corrected, and correction is performed when (Li−Lv)> S. Further, correction is made only when there is a certain level of gradation change from high density to low density.

The calculation formula is as follows.
“Li after correction = Li correction value before correction”,
Here, when “(Li−Lv)> S” and “(Li−Lv)> 0”,
Correction value = (Ii−Lv) ² × W,
In other cases, the correction value = 0.

Next, the above equation will be described.
As for “(Li−Lv)> S”, when this correction is performed, the gradation difference between dots becomes small when the density changes from high density to low density, and the boundary becomes unclear. If correction is performed at all locations where the density changes from high density to low density, the overall print result is blurred. In order to prevent this, the correction is performed only for the portion where the gradation difference from the high density to the low density is large to some extent.
For “(Ii−Lv)> 0”, when the heat storage amount Vi is high and the average gradation value Lv or higher is printed (when Ii> Lv), the gradation value Li of the target dot is corrected. When the heat storage amount Vi is low and the average gradation value Lv or higher is not printed, no correction is performed.
For “correction value = (Ii−Lv) ² × W”, the strength of correction is determined by the gradation value Ii that can be printed with the heat storage amount and the average gradation value Lv. The correction is stronger as Ii-Lv is larger. W is a coefficient multiplied by this and acts as a weight.

  A quadratic equation is used to realize smooth correction. As shown in FIG. 4 (a), linear correction is performed when the linear expression is used, whereas smooth correction is performed when a quadratic expression is used as shown in FIG. 4 (b). Can be realized. In this correction section, the density gradually decreases, but if a quadratic equation is used, a rapid density decrease can be suppressed. Smoothness appears in the print result, and a good correction result is obtained.

  FIG. 5 is a diagram showing an example of correction. In the example, the dot surrounded by the solid line is the target dot 3, the dot surrounded by the dotted line is the lower N dot, and N = 5. As shown in FIG. 5, the average gradation value of the lower N dots becomes smaller and the correction value becomes larger as the target dot 3 approaches the place where the density changes from high density to low density. A smooth correction result can be obtained by gradually increasing the correction value.

FIG. 6 is a diagram showing a system configuration example of the printer according to the present invention.
In the printer 1 illustrated in FIG. 6, reference numeral 11 denotes a main control unit that includes a CPU and the like and controls each unit of the printer. An image buffer 12 receives an image to be printed from an external host (host computer) 2 as image data such as YMC (yellow (Y), magenta (M), cyan (C)) and temporarily stores the image.

  A print control unit 13 performs processing necessary for printing the image data transmitted from the host 2. The print image data generation unit 14 in the print control unit 13 is a processing unit for converting the YMC input image data received from the host 2 into print image data corresponding to the ink color of the ink ribbon. Further, the ink ribbon winding / rewinding processing unit 15 transmits a command signal to the motor drive control unit 20 so that the ink surface of the ink ribbon is at an appropriate position at the time of printing, so that the winding of the ink ribbon is performed. A processing unit for performing take-up / rewind control. The roll paper drive processing unit 16 is a processing unit that transmits a command signal to the motor drive control unit 20 to perform print paper feed control, and performs print paper cut processing and the like.

  Reference numeral 17 denotes an energization pulse generator that energizes the heating resistor 19 in the thermal head 18 by energizing pulse patterns according to the gradation (density). Reference numeral 18 denotes a thermal head in which heating resistors are arranged for each dot to be printed. Reference numeral 19 denotes a heating resistor corresponding to each dot. A motor drive control unit 20 controls the drive of an ink ribbon take-up motor that transports the ink ribbon, an ink ribbon rewind motor that rewinds the ink ribbon, a roll paper drive motor that transports print paper, and the like.

  The printer 1 of the present invention is characterized by the thermal head heating correction processing unit 21 in the print control unit 13.

  The gradation value change detection processing unit 22 in the thermal head heating correction processing unit 21 examines the image data generated by the print image data generation unit 14 and determines N in the print direction for the target dot on which the current image is to be printed. (Predetermined arbitrary number) Processing for detecting in advance whether there is a change in gradation value between the line destinations is performed. When detecting a gradation value, an average gradation value that is an average value of gradation values up to N lines ahead is obtained, and a change in gradation value may be detected based on the average gradation value. is there.

  When the gradation value change detection processing unit 22 detects that there is a change in the gradation value, the correction value calculation processing unit 23 changes the gradation value by the correction value calculation method described above. The correction value of the amount of heat applied to the ink ribbon by the thermal head is calculated from before the line.

  As described above, in the printer of the present invention, the tailing phenomenon can be reduced by controlling the heat applied from the thermal head to the ink ribbon. Also, the printing speed is fast, and after the previous line is printed, the time until the next line is printed before the heat accumulated inside the thermal head is released to the outside, the accumulated heat is transferred to the ink ribbon. Even when the ink is transferred to the paper and the next line cannot be printed at the original density and the tail is generated, this tailing phenomenon can be reduced.

[Second Embodiment]
In the conventional print control, the energization time to the thermal head in one line (for example, the time width of the energization pulse) is increased or decreased by calculation of thermal history correction of the thermal head as shown by the portion surrounded by the dotted line G in FIG. The correction processing to be performed and the processing to determine the length of the bias energization time (the preheating energy application time to be applied to the thermal head in a range where the ink ribbon does not develop color) when printing 0 gradation data are performed independently. It was. (The thermal history of the thermal head is calculated based on, for example, thermal history data obtained by adding gradation data applied to the thermal head. Also, based on this added data, the heat dissipation amount to the heat sink of the thermal head. And may be calculated in consideration of factors of ambient temperature (measured by a thermistor, etc.))

  In the second embodiment of the present invention, the above two processes are associated with each other, the bias energization time when printing 0 gradation data is controlled based on the thermal history data, and the length is increased or decreased. To do.

  For example, as shown in FIG. 13A, when the 0 gradation data is continuous (when the area 1 portion is printed), the 0 gradation data continues and the thermal head has a small amount of heat storage. Do not decrease the energization time, and continue to preheat the thermal head. For example, as shown in the diagram showing the relationship between the heat storage amount (Vi) and the print tone (Ii) in FIG. 14, the heat storage amount (Vi) of the thermal head is less than or equal to Vimin (the limit heat storage amount at which the ink ribbon does not develop color). In the case of, continue to preheat the thermal head. However, the heat storage amount (Vi) should not exceed Vimin. By doing so, when starting to print the portion of the region 2, the thermal head is warmed to some extent, so that “rise of print density” is improved.

  Further, as shown in FIG. 13B, when printing with high gradation density (printing in the area 3) is continued, and thereafter 0 gradation data is printed (printing in the area 4), the heat The bias energization time is reduced to 0 (no energization) by calculating the history correction. For example, as shown in FIG. 14, when the heat storage amount (Vi) of the thermal head is Vin (Vin> Vimin), the bias energization time is reduced to 0 (no energization). As a result, the maximum countermeasure effect can be provided for the “tailing phenomenon”.

  FIG. 15 is a diagram illustrating a system configuration example of a printer according to the second embodiment. The configuration of the printer 1A shown in FIG. 15 is different from the printer 1 shown in FIG. 6 in the configuration of the thermal head heating correction processing unit 21 in the print control unit 13, and other parts are shown in FIG. It is the same as that.

  The vice energy application processing unit 24 in the thermal head heating correction processing unit 21 determines the current heat storage amount of the thermal head when printing 0 gradation data, and prints 0 gradation data or low gradation data. When the heat storage amount is continuously less than or equal to a predetermined value, processing for printing zero gradation data by applying bias energy to preheat the thermal head is performed.

  The non-energized print processing unit 25 determines the current heat storage amount of the thermal head when printing 0 gradation data, and if the high and low gradation data is continuously printed and the heat storage amount is a predetermined value or more, there is no Processing to print 0 gradation data by energization is performed.

  Note that when printing 0 gradation data after printing high gradation data in the second embodiment, the dot of interest (dots for printing high gradation data) is printed in the print direction as in the first embodiment. If it is detected in advance that the gradation value changes up to N lines ahead and 0 gradation data is printed before N lines, the Nth line before printing 0 gradation data is detected. Correction may be started from. That is, the heat applied to the ink ribbon is gradually reduced from the N line before printing 0 gradation data, and the heat storage amount of the thermal head is reduced. In this way, when the 0 gradation data is printed, the thermal storage amount of the thermal head is already small, so that the tail correction can be performed more effectively.

  The embodiment of the present invention has been described above. However, the printer of the present invention is not limited to the illustrated example described above, and various modifications can be made without departing from the scope of the present invention. It is.

  In the present invention, the gradation difference from high density to low density is large at the time of printing, and the trailing phenomenon can be reduced even in the case of high-speed printing. The present invention is useful for printers and the like because high-quality printing that achieves both “shortage correction” and “tail correction” can be realized.

It is a figure for demonstrating the tailing correction | amendment control by this invention. It is a figure which shows arrangement | positioning of the attention dot and the dot of a lower N line. It is a figure which shows the relationship between the thermal storage amount Vi of a thermal head, and the gradation value Ii which can be printed. It is a figure which shows the example at the time of using the case where a primary expression is used for a correction value, and a quadratic expression. It is a figure showing an example of amendment. 1 is a diagram illustrating a system configuration example of a printer according to the present invention. FIG. 2 is a diagram illustrating a configuration example of a print unit of a printer. FIG. It is a figure which shows the example of an ink ribbon. It is a figure for demonstrating a tailing phenomenon. It is a figure for demonstrating the conventional tailing correction | amendment control. It is a figure for demonstrating the problem of the conventional tailing correction control. It is a figure which shows the example of the tailing phenomenon at the time of high-speed printing. It is a figure for demonstrating the printing method in 2nd Embodiment. It is a figure which shows the relationship between the thermal storage amount Vi and printing tone Ii in 2nd Embodiment. It is a figure which shows the system configuration example of the printer in 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1A ... Printer 2 ... Host 3 ... Target dot 11 ... Main control part 12 ... Image buffer 13 ... Print control part 14 ... Print image data generation part 15 ... Ink ribbon winding / rewinding processing part 16 ... Roll paper drive Processing unit 17: Energization pulse generation unit 18 ... Thermal head 19 ... Heating resistor 20 ... Motor drive control unit 21 ... Thermal head heating correction processing unit 22 ... Tone value change detection processing unit 23 ... Correction value calculation processing unit 24 ... Vise Energy application processing unit 25 ... Non-energized printing processing unit 31 ... Roll paper 32 ... Print paper 33 ... Ink ribbon roll 34 ... Supply core 35 ... Ink ribbon 36, 37 ... Ink ribbon guide roll 38 ... Take-up core 39 ... Platen Roll 40 ... Pinch roll 41 ... Feed roll

Claims (9)

A thermal head provided with a heating resistor for each dot in the line direction of the image to be formed presses the ink ribbon against the print paper, and the thermal head applies a heat amount corresponding to the gradation of the image density to the ink ribbon. A printer that performs printing by transferring the ink of the ink ribbon onto the paper,
Gradation value change detecting means for detecting in advance a gradation value change between N (predetermined arbitrary number) line destinations in the print direction for a target dot to be printed on the current image;
A thermal head heating correction unit that corrects the heating amount of the ink dot at the dot of interest when it is detected by the gradation value change detection unit that there is a change in gradation value up to N lines ahead; A printer comprising: Thermal head heating correction by the thermal head heating correction means,
The printer according to claim 1, which is performed when the gradation value change detection unit determines that the gradation value falls below a predetermined range. When detecting a change in gradation value between N lines ahead by the gradation value detecting means,
The average gradation value which is an average value of gradation values up to N lines ahead is obtained, and a change in gradation value is detected based on the average gradation value. Printer. Correction by the thermal head heating correction means,
“Fixed dot tone value after correction = Target dot tone value before correction−correction value”,
The calculation formula
N is the number of dots to be referenced below the target dot,
Let Lv be the average tone value of the bottom N dots of the dot of interest,
When Ii is a gradation value that can be printed with the current heat storage amount of the thermal head,
The printer according to claim 1, wherein the correction value is obtained by a predetermined function having (Ii−Lv) as a variable. Correction by the thermal head heating correction means,
“Focus dot gradation value after correction = Focus dot gradation value before correction−Correction value”
The calculation formula
N is the number of dots to be referenced below the target dot,
Let Lv be the average tone value of the bottom N dots of the dot of interest,
Let Ii be the gradation value that can be printed with the current heat storage amount of the thermal head,
Let W be a correction coefficient for adjusting the magnitude of the correction value,
S is a predetermined threshold value (positive number) that determines whether to correct or not,
When “(Li−Lv)> S” and “(Ii−Lv)> 0”, “correction value = (Ii−Lv) ² × W” is obtained. Otherwise, “correction value = 0”. The printer according to any one of claims 1 to 4, wherein: A thermal head provided with a heating resistor for each dot in the line direction of the image to be formed presses the ink ribbon against the print paper, and the thermal head applies a heat amount corresponding to the gradation of the image density to the ink ribbon. A heat storage correction control method in a printer that performs printing by transferring the ink of the ink ribbon onto the paper,
By the control unit in the printer,
A gradation value change detection procedure for detecting in advance a change in gradation value up to N (an arbitrary number set in advance) line destination in the print direction for the target dot to be printed on the current image;
A thermal head heating correction procedure for correcting the heating amount of the ink of the target dot when the gradation value change is detected by the gradation value change detection procedure up to N lines ahead; A heat storage correction control method that is performed. A thermal head provided with a heating resistor for each dot in the line direction of the image to be formed presses the ink ribbon against the print paper, and the thermal head applies a heat amount corresponding to the gradation of the image density to the ink ribbon. A printer that performs printing by transferring the ink of the ink ribbon onto the paper,
When printing 0 gradation data,
When the thermal storage amount of the thermal head is less than or equal to a predetermined value, bias energy application means for applying and printing bias energy for preheating the thermal head;
A non-energized printing unit that performs non-energized printing without applying bias energy to the thermal head when the thermal storage amount of the thermal head is equal to or greater than a predetermined value. The printer according to claim 7, wherein the thermal storage amount of the thermal head is calculated based on thermal history data obtained by adding printed gradation data. A thermal head provided with a heating resistor for each dot in the line direction of the image to be formed presses the ink ribbon against the print paper, and the thermal head applies a heat amount corresponding to the gradation of the image density to the ink ribbon. A print control method in a printer that performs printing by transferring the ink of the ink ribbon onto the paper,
By the control unit in the printer,
When printing 0 gradation data, if the thermal storage amount of the thermal head is less than or equal to a predetermined value, a bias energy application procedure for printing by applying bias energy for preheating the thermal head;
And a non-energized printing procedure for performing non-energized printing without applying bias energy to the thermal head when the thermal storage amount of the thermal head is greater than or equal to a predetermined value.

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