JP2006116952A - Thermal printer and the thermal print method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress density unevenness due to transportation load fluctuation of recording paper by a thermal head. <P>SOLUTION: Printing thermal energy Epi for one line in a recording area is subtracted from recording area maximum printing thermal energy Epmax for one line when printing a recording area by an unrecording area printing thermal energy calculating unit 23, and the difference ESi thereof serves as unrecording area printing thermal energy. Common printing thermal energy is obtained by dividing the unrecording area printing heat energy ESi by the number of the heating elements positioned in the unrecording area. Virtual image data for generating the common printing thermal energy is obtained. A recording sheet 2 is printed based on the virtual image data and image data of the recording area. Total printing thermal energy of each line is kept constant, and printing thermal energy fluctuation upon line printing is eliminated. Transport load fluctuation due to the printing thermal energy fluctuation is suppressed to prevent uneven in density. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermal printer and a thermal printing method for thermally recording an image on a recording paper using a thermal head.

  2. Description of the Related Art There is known a thermal printer that heats a thermal recording paper provided with a thermal coloring layer with a thermal head to color and record an image. In the thermal head, a large number of heating elements are arranged in a line along the main scanning direction. The thermal printer records an image line by line while relatively moving the thermal head and the thermal recording paper in the sub-scanning direction. Each heating element is driven based on image data for one line, and gives printing thermal energy to the thermal recording paper.

  The coefficient of friction between the thermal recording paper and the thermal head varies depending on the printing heat energy. That is, if the printing heat energy is large, the temperature of the heating element increases and the friction coefficient decreases, while if the printing heat energy is small, the temperature of the heating element decreases and the friction coefficient increases. Therefore, in the portion where the density of the original image changes suddenly, the fluctuation of the printing thermal energy is large, so that the fluctuation of the friction coefficient also becomes large. When the friction coefficient varies, the conveyance load of the thermal recording paper varies, so the conveyance pitch of the thermal recording paper changes. As a result, there is a problem in that the printing thermal energy given per unit area changes and density unevenness occurs.

For example, as shown in Patent Document 1, there is described a thermal printer that does not generate density unevenness even when a load fluctuation caused by the density change occurs. In this thermal printer, the load amount of the thermal head is obtained for each line, the load fluctuation amount is obtained from the difference between the load amount of the line to be recorded and the load amount of the adjacent line, and recording is performed based on the load fluctuation amount. The printing thermal energy of the line to be corrected is corrected. For this reason, even if the conveyance pitch of the thermal recording paper changes due to fluctuations in the conveyance load, the printing thermal energy is also corrected in accordance with the change, so that density unevenness is prevented.
JP 2002-67370 A

  By the way, when the printing thermal energy is corrected based on the conveyance load variation as described above, the relationship between the dynamic friction coefficient of each heating element with respect to the thermal recording paper and the printing thermal energy, and the pressure distribution of each heating element against the thermal recording paper. It is necessary to grasp the state accurately. For this reason, it is necessary to actually operate each printer to acquire various data, and there is a problem that it takes time to acquire the data. Moreover, even if the print heat energy is corrected using the data acquired in this way, it does not act directly on the recording paper, and the conveyance load fluctuation is suppressed in the form of correction of the print heat energy. There is a problem that sufficient correction cannot be performed.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thermal printer and a thermal printing method that suppress the occurrence of density unevenness that occurs due to fluctuations in the recording paper conveyance load. To do.

  In order to achieve the above object, according to the present invention, each heating element is heated according to image data using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, and intersects the main scanning direction. In a thermal printing method in which recording paper is fed in the sub-scanning direction and an image is recorded line by line on the recording paper, the recording paper is divided into a recording area and a surplus area in the main scanning direction, and a heating element corresponding to the recording area Is driven to record an image, and a heating element corresponding to the surplus area is driven to make the total print thermal energy of each line constant. The print heat energy for each line for the recording area is obtained, and the print heat energy for each line is subtracted from the reference print heat energy for one line, and this value is used as the print heat energy for the surplus area. preferable. The reference print heat energy is preferably the maximum total print heat energy for one line with respect to the recording area. Further, according to the present invention, each heating element is heated according to image data using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, and recording is performed in the sub-scanning direction intersecting the main scanning direction. In a thermal printer that feeds paper and records an image on a recording paper line by line, the recording paper is divided into a recording area and a surplus area in the main scanning direction, and print thermal energy for each line with respect to the recording area is obtained. A thermal head drive unit for recording an image by subtracting the print thermal energy for each line from the reference print thermal energy for the line and using this value as the print thermal energy for the surplus area, and a cutter for separating the surplus area from the recording area It is characterized by providing.

In the thermal printing method of the present invention, the heating elements are divided into a first group facing a recording area where an image is recorded and a second group facing a surplus area where the image is not recorded. Based on the data, the first group is driven to record one line in the recording area, and is the sum of the first printing thermal energy generated by the first group and the second printing thermal energy generated by the second group. The second group is driven so that the total print heat energy is substantially the same in each line. The total print heat energy is preferably equal to or greater than the maximum value of the first print heat energy. Further, the second printing thermal energy is divided by the number of heating elements of the second group to obtain common printing thermal energy, virtual image data for generating the common printing thermal energy is obtained, and according to the virtual image data It is preferable to drive the second group of heating elements. The surplus area is preferably located on both sides of the recording area. Furthermore, it is preferable to separate the surplus area from the recording area.
Further, the thermal printer of the present invention includes a first calculation unit that calculates the first printing thermal energy generated by the first group of heating elements facing the recording area where the image is recorded, for each line;
A total print in which the second print heat energy generated by the second group of heating elements facing the surplus area where the image is not recorded is calculated for each line and the first print heat energy and the second print heat energy are summed. A second calculation unit that makes thermal energy substantially the same in each line, and the second group so as to generate the second print thermal energy by driving the first group with image data for the first line. And a thermal head driving unit for driving the group. The total print heat energy is preferably equal to or greater than the maximum value of the first print heat energy. And a third calculation unit for determining virtual print data from the common print thermal energy by dividing the second print thermal energy by the number of heating elements of the second group, and driving the thermal head. Preferably, the unit drives the second group according to the virtual image data.

  According to the present invention, the recording paper is divided into a recording area and a surplus area in the main scanning direction, and an image is recorded by driving a heating element corresponding to the recording area, and a heating element corresponding to the surplus area is driven. Since the total printing thermal energy of each line is made constant, the total printing thermal energy is always kept constant at the time of recording each line, so that there is almost no fluctuation in the conveyance load between the recording paper and the thermal head. Therefore, fluctuations in the transport load can be suppressed with a simple configuration, and the occurrence of density unevenness and color unevenness due to this can be suppressed. Similarly, the heating elements are divided into a first group facing a recording area where an image is recorded and a second group facing a surplus area where the image is not recorded, based on one line of image data. The first group is driven to record one line in the recording area. The total print heat energy, which is the sum of the first print heat energy generated by the first group and the second print heat energy generated by the second group, is By driving the second group so that the lines are almost the same, fluctuations in the conveyance load between the recording paper and the thermal head can be almost eliminated, and uneven density and color unevenness due to fluctuations in the conveyance load can occur. It can be suppressed.

  FIG. 1 is a schematic view showing a main part of a color thermal printer embodying the present invention. In this color thermal printer, a long color thermal recording paper (hereinafter simply referred to as recording paper) 2 fed from a recording paper roll (not shown) is used. The recording paper 2 is fed by the conveying roller pair 3 in a paper feeding direction and a printing direction opposite to the paper feeding direction. The conveyance roller pair 3 is composed of a capstan roller 3a driven by a conveyance motor 4 composed of a pulse motor, and a pinch roller 3b that is movable between a position where it is in pressure contact with the capstan roller 3a and a position where it is separated. Has been. The transport motor 4 is controlled by the controller 10 via the driver 4a.

  As is well known, the recording paper 2 has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, a yellow thermosensitive coloring layer, and a protective layer sequentially formed on a support. The yellow thermosensitive coloring layer, which is the uppermost layer as the thermosensitive layer, has the highest thermal sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large heat energy. The yellow thermosensitive coloring layer loses its coloring ability when irradiated with 420 nm blue-violet light. The magenta thermosensitive coloring layer develops magenta with a thermal energy intermediate between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer, and loses the coloring ability when irradiated with near ultraviolet rays of 365 nm.

  A thermal head 6 is disposed on the downstream side in the paper feeding direction of the pair of conveying rollers 3. The thermal head 6 includes a heating element array 6a in which a large number of heating elements are arranged in a line, and is fixed in the printer.

  A platen roller 7 is arranged at a position facing the thermal head 6 so as to sandwich the recording paper 2. The platen roller 7 is movable in the vertical direction, and is biased in a direction in which it is pressed against the thermal head 6 by a spring (not shown).

  When the recording paper 2 is conveyed in the printing direction by the conveying roller pair 3, the thermal head 6 causes each heating element of the heating element array 6 a to generate heat to a predetermined temperature, and develops each thermosensitive coloring layer of the recording paper 2. . The platen roller 7 is lowered by a shift mechanism (not shown) using a cam, a solenoid or the like at the time of paper supply and paper discharge, thereby forming a clearance for passing the recording paper 2 between the thermal head 6.

  On the downstream side of the thermal head 6 in the paper feeding direction, an optical fixing device 11 is arranged facing the recording paper 2. The optical fixing device 11 includes a yellow fixing lamp 12, a magenta fixing lamp 13, and a reflector 14. The yellow fixing lamp 12 emits blue-violet light having an emission peak of 420 nm, and the magenta fixing lamp 13 emits ultraviolet light having an emission peak of 365 nm. By irradiating the fixing light from these fixing lamps 12 and 13, the yellow thermosensitive coloring layer and the magenta thermosensitive coloring layer of the recording paper 2 are fixed so as not to develop color even when heated.

  A cutter 16, a slitter 17, and a discharge roller pair 18 are provided on the downstream side in the paper feeding direction of the optical fixing device 11. The cutter 16 separates the full color image from the unrecorded area. Further, the slitter 17 cuts off the surplus areas on both sides of the recording paper 2 cut by the cutter 16. As a result, the sheet-like recording paper 2 from which the excess area has been cut off is discharged from the discharge port (not shown) to the outside of the printer by the discharge roller pair 18.

  The controller 10 controls each part and records the yellow, magenta, and cyan color heat-sensitive coloring layers in the surface sequential manner. Further, the printing thermal energy of each line is obtained at the time of recording each color, and the heating elements facing the surplus area are driven based on the printing thermal energy to keep the printing thermal energy of each line substantially uniform.

  Therefore, the controller 10 is provided with a frame memory 21, a first line memory 22, a surplus area printing thermal energy calculation unit 23, a second line memory 24, and an energization time calculation control unit 25.

  The image data written in the frame memory 21 is sent to the first line memory 22 line by line. The first line memory 22 stores image data for a plurality of lines, for example, five lines. The image data input to the line memory 22 is sent line by line to the surplus area printing thermal energy calculation unit 23.

  The surplus area printing thermal energy calculation unit 23 includes a first calculation unit 23a, a second calculation unit 23b, and a third calculation unit 23c. The first calculation unit 23a calculates the first printing heat energy Epi generated by the first group of heating elements facing the recording area for each line. The second computing unit 23b subtracts the first printing thermal energy Epi for the i-th line from the recording area maximum printing thermal energy Epmax (reference printing thermal energy) for one line when printing the recording area PA. The difference Esi is set as the surplus area printing thermal energy (second printing thermal energy) of this line. The third computing unit 23c divides the second printing thermal energy by the number of heating elements located in the surplus area, and obtains virtual image data based on this value using, for example, a lookup table memory. Then, the virtual image data and the image data of the original recording area are written into the second line memory 24.

  Next, the image data of the second line memory 24 is read and sent to the energization time calculation control unit 25, where the energization time of each heating element is calculated according to the number of gradations of the image data. This energization time data is sent to the head drive unit of the thermal head 6. The head drive unit causes each heating element to generate heat with the energization time control data. In synchronization with the driving of the heat generating elements, the rotation of the conveying roller pair 3 is controlled via the driver 4a and the conveying motor 4, and an image is recorded on the recording paper 2 line by line. Therefore, based on the image data of one line, the total heat of print, which is the sum of the first print heat energy generated by the first group and the second print heat energy generated by the second group, by the second calculation unit 23b. Since the second printing heat energy is obtained so that the energy is almost the same in each line, fluctuations in the conveyance load can be suppressed with a simple configuration, and the occurrence of density unevenness and color unevenness due to this can be suppressed.

  Next, the operation of the above embodiment will be described. As shown in FIG. 1, at the time of printing, the recording paper 2 is fed in the printing direction by the conveying roller pair 3. When it is detected that the leading edge of the recording area of the recording paper 2 has reached the thermal head 6, the heating element array 6a generates heat, and one line of yellow image is recorded on the yellow thermosensitive coloring layer. Thereafter, the yellow image is recorded line by line in synchronization with the feeding of the recording paper 2.

  In this line recording, the surplus area printing thermal energy calculation unit 23 subtracts the printing thermal energy Epi for the i-th line in the recording area from the recording area maximum printing thermal energy Epmax when printing the recording area PA line by line. The difference Esi is obtained as surplus area printing thermal energy for the i-th line. Next, the surplus area printing thermal energy is divided by the number of heating elements located in the surplus area to obtain common printing thermal energy, and virtual image data for generating the common printing thermal energy is obtained. Then, the virtual image data and the image data of the original recording area are written into the second line memory 24. Next, the image data of the second line memory 24 is read and sent to the energization time calculation control unit 25, where the energization time of each heating element is calculated according to the number of gradations of the image data. The energization time data is sent to the head drive unit of the thermal head 6, and each heating element is heated by the head drive unit according to the energization time control data. Then, in synchronization with the driving of the heat generating elements, the conveyance roller pair 3 is rotationally controlled via the driver 4 a and the conveyance motor 4, and an image is recorded line by line on the recording paper 2. Thus, since the total printing thermal energy by the thermal head 6 when recording each line is always a constant value, there is no fluctuation of the dynamic friction coefficient or fluctuation of the conveyance load due to the printing thermal energy fluctuation, Recording paper is always fed at a constant pitch, and density unevenness due to fluctuations in the conveyance speed does not occur.

  When the recording of all the lines of the yellow image is completed, the feeding of the recording paper 2 in the printing direction is stopped, and then the recording paper 2 is fed in the paper feeding direction. When the recording paper is fed in the paper feeding direction, the platen roller 7 is retreated to a retreat position away from the thermal head 6 by a shift mechanism (not shown). Simultaneously with the conveyance in the paper feeding direction, the yellow fixing lamp 12 of the optical fixing device 11 is turned on to fix the yellow thermosensitive coloring layer in the recording area of the recording paper 2. When the optical fixing for the recording area is completed, the conveyance motor 4 stops. Thereafter, the recording paper 2 is fed in the printing direction, and magenta recording and fixing of the magenta thermosensitive coloring layer are performed in the same manner as yellow recording, and further cyan recording is performed. Also in this magenta recording and cyan recording, surplus area printing thermal energy is obtained in the same manner as yellow printing, and each heating element corresponding to the surplus area is driven based on this printing thermal energy. Therefore, the total printing heat energy at the time of recording each line is always constant, and when printing each line, each color is recorded without causing a variation in transport load and without uneven density.

  When the three-color surface sequential recording is completed, as shown in FIG. 3A, the recording paper 2 is cut at the first cutting line C1 by the cutter 16 (see FIG. 1), and the leading margin 2a is separated from the recording paper 2. It is. Next, as shown in (B), the recording paper 2 is cut by the slitter 17 along the second cutting line C2, and the surplus portions 2b and 2c on both side edges composed of the surplus area SA are separated from the recording paper 2. In the middle of separation by the slitter 17, as shown in (C), the recording paper 2 is cut at the third cutting line C3 by the cutter 16 shown in FIG. 1, and the print P1 having the recording area PA is obtained. Thereafter, separation along the second cutting line C2 is continued by the slitter 17, and as shown in (D), the surplus portions 2b and 2c on both sides of the recording paper 2 are separated from the portion of the print P1 having the recording area PA. It is. In this color print P1, the printing heat energy of each line is always made the same, and printing is performed. Therefore, there is no occurrence of fluctuations in conveyance load during printing, and density unevenness due to fluctuations in conveyance load is eliminated. Further, since the recording position of each line is the same for each color, the occurrence of color unevenness is eliminated.

  The recording paper 2 is cut by the cutter 16 along the cutting lines C1 and C2 in the width direction, and the recording paper 2 is cut by the cutting line C3 in the recording paper feed direction by the slitter 17. As long as 2b and 2c can be cut off, the type of the cutter 16 and the slitter 17 and the cutting order thereof do not matter. Further, the cutter 16 may be built in the printer, or the surplus portions 2b and 2c made of the surplus area SA may be cut out by the cutter 16 provided separately from the printer.

  In the above embodiment, a 1-head 3-pass color thermal printer has been described as an example. However, the present invention may be applied to a 3-head 1-pass color thermal printer as shown in FIG. In addition, the same code | symbol is attached | subjected to the same structural member as the said embodiment. Reference numeral 44 denotes a yellow fixing device, and 45 denotes a magenta fixing device. Also in this case, in the print stages 41 to 43 of the respective colors, the print thermal energy Epi for one line in the recording area is subtracted from the maximum recording area thermal energy Epmax when the recording area PA is printed, and this difference Esi is calculated. The surplus area printing heat energy is divided by the number of heating elements located in the surplus area SA, and the divided value is used as a common printing heat energy. The surplus area SA is exposed to the surplus area SA based on the common printing heat energy. Virtual image data of each heating element to be obtained is obtained. Then, an image is recorded in the recording area PA and the surplus area SA based on the image data for each of the heating elements. In this case as well, the total print energy can be made substantially constant during the recording of each line of each color, and there is no fluctuation in the transport load, and density unevenness due to this can be eliminated.

  Further, in the above-described embodiment, the print area energy for one line when the print area PA is printed is subtracted from the print heat energy Epi for one line in the print area, and this difference Esi is used as the surplus area print. The thermal energy is not limited to the maximum printing thermal energy Epmax as long as it is equal to or greater than the maximum value of the recording area printing thermal energy. However, the total print heat energy amount for one line can be efficiently defined by using the maximum print area print heat energy.

  In the above embodiment, the surplus area SA of the recording paper 2 is separated by the slitter 17, but instead of this, the surplus area SA does not have a color developing layer and does not develop color even when heat is applied. May be. Further, instead of not providing the color developing layer, the yellow fixing lamp 12 and the magenta fixing lamp 13 are used to lightly fix the surplus area SA so that yellow and magenta do not develop color, and cyan develops color. Heat may be applied to the surplus area with no thermal energy. In these cases, the slitter 17 becomes unnecessary, and the configuration becomes simple.

  In the above embodiment, the color thermal printer has been described. However, other printers in which the conveyance load fluctuates due to the fluctuation amount of the printing thermal energy of each line, for example, a sublimation type using yellow, magenta, and cyan color ink sheets, The present invention may be implemented in a thermal melting type thermal transfer printer.

1 is a schematic view showing a color thermal printer of the present invention. It is explanatory drawing which shows the relationship between the heating element array of a thermal head, the recording area of a recording paper, and a surplus area. It is explanatory drawing which shows an example of the procedure which cut | disconnects the leading edge margin part and the excess part of a both-sides edge from a recording paper. It is the schematic of another embodiment which shows the color thermal printer of a 1 pass 3 head system.

Explanation of symbols

2 Recording Paper 3 Conveying Roller Pair 4 Conveying Motor 6 Thermal Head 6a Heating Element Array 7 Platen Roller 10 Controller 11 Light Fixer 23 Surplus Area Printing Thermal Energy Calculation Units 30 to 32 Platen Rollers 36 to 38 Conveying Roller Pair

Claims (15)

Using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, each heating element is heated according to the image data, and the recording paper is sent in the sub-scanning direction intersecting the main scanning direction. In the thermal printing method that records one line at a time on recording paper,
The recording paper is divided into a recording area and a surplus area in the main scanning direction, and an image is recorded by driving a heating element corresponding to the recording area, and each line is driven by driving a heating element corresponding to the surplus area. A thermal printing method characterized in that the total printing thermal energy of the ink is constant.   The printing thermal energy for each line with respect to the recording area is obtained, the printing thermal energy for each line is subtracted from the reference printing thermal energy for one line, and this difference is used as the printing thermal energy for the surplus area. The thermal printing method according to claim 1.   3. The thermal printing method according to claim 2, wherein the reference printing thermal energy is equal to or greater than a maximum value of total printing thermal energy for one line with respect to a recording area. Using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, each heating element is heated according to the image data, and the recording paper is sent in the sub-scanning direction intersecting the main scanning direction. In a thermal printer that records one line at a time on recording paper,
The recording paper is divided into a recording area and a surplus area in the main scanning direction, print heat energy for each line for the print area is obtained, and the print heat energy for each line is subtracted from the reference print heat energy for one line. The thermal head drive unit that records an image using the difference between the levers as the print thermal energy for the surplus area,
A thermal printer comprising: a cutter for separating the surplus area from the recording area.   5. The thermal printer according to claim 4, wherein the reference printing thermal energy is equal to or greater than a maximum value of total printing thermal energy for one line with respect to a recording area. Using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, each heating element is heated according to the image data, and the recording paper is sent in the sub-scanning direction intersecting the main scanning direction. In the thermal printing method that records one line at a time on recording paper,
The heating element is divided into a first group facing a recording area where the image is recorded and a second group facing a surplus area where the image is not recorded,
Based on the image data of one line, the first group is driven to record one line in the recording area, and the first print heat energy generated by the first group and the second print heat energy generated by the second group. The second group is driven so that the total print thermal energy, which is the sum of the two, is substantially the same in each line.   The thermal printing method according to claim 6, wherein the total print thermal energy is equal to or greater than a maximum value of the first print thermal energy.   The second print thermal energy is divided by the number of heating elements of the second group to obtain common print thermal energy, virtual image data for generating the common print thermal energy is obtained, and the second image thermal energy is determined according to the virtual image data. 8. The thermal printing method according to claim 6, wherein two groups of heating elements are driven.   9. The thermal printing method according to claim 6, wherein the surplus area is located on both sides of the recording area.   10. The thermal printing method according to claim 6, wherein the surplus area is separated from the recording area. Using a thermal head in which a plurality of heating elements are arranged along the main scanning direction, each heating element is heated according to the image data, and the recording paper is sent in the sub-scanning direction intersecting the main scanning direction. In a thermal printer that records one line at a time on recording paper,
A first calculation unit that calculates, for each line, first print heat energy generated by a first group of heating elements facing a recording area in which the image is recorded;
A total print in which the second print heat energy generated by the second group of heating elements facing the surplus area where the image is not recorded is calculated for each line, and the first print heat energy and the second print heat energy are summed. A second computing unit that causes the thermal energy to be substantially the same in each line;
A thermal printer, comprising: a thermal head driving unit that drives the second group so as to generate the second print thermal energy by driving the first group with image data for the first line.   The thermal printer according to claim 11, wherein the total print thermal energy is equal to or greater than a maximum value of the first print thermal energy.   The second print heat energy is divided by the number of heating elements of the second group to obtain common print heat energy, and a third calculation unit that obtains virtual image data from the common print heat energy is provided. The thermal printer according to claim 11 or 12, wherein the second group is driven in accordance with the virtual image data.   The thermal printer according to claim 11, wherein the surplus area is located on both sides of the recording area. 15. The thermal printer according to claim 11, wherein the surplus area is separated from the recording area.

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