Patent Publication Number: US-9889676-B2

Title: Printing device

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a printing device, and particularly relates to a thermal transfer type of printing device. 
     Description of the Related Art 
     A technique is known for providing a protective layer (also referred to as an overcoat layer) on the outermost surface of printing paper for the purpose of protecting the printing surface or adjusting the glossiness of the printing surface. For example, Japanese Patent Laid-Open No. 2005-271321 proposes that in a thermal printer that uses printing paper provided with a transparent protective layer over a thermal color-forming layer, heat is applied to the protective layer using a thermal head after recording an image so as to change the glossiness of the protective layer in a regular manner, thereby giving a visual effect. 
     Japanese Patent Laid-Open No. 2005-271321 is based on the presumption that printing paper provided with a protective layer in advance is used, but there are apparatuses constituted to add a protective layer at the time of printing. Examples of such apparatuses include sublimation printers constituted to transfer a protective layer after printing with colors, inkjet printers for printing with transparent ink for smoothing the surface of paper, and the like. 
     In particular, in thermal transfer-type printers such as a sublimation printer, the surface texture of a protective layer after being transferred can be controlled by the heating pattern of the head when transferring the protective layer. For example, it is conceivable to improve the visual recognizability of a printed article by making the surface texture of the protective layer rough and suppressing reflection. However, depending on the heating pattern and the heat amount implemented in order to make the surface texture of the protective layer rough, the fusion strength between the protective layer and the resin film that supports the protective layer increases, and insufficient separation occurs, which prevents the protective layer from being transferred to printing paper. 
     SUMMARY OF THE INVENTION 
     The present invention has been made in light of such an issue in conventional techniques. The present invention provides a thermal transfer type of printing device that can improve the visual recognizability of printed articles while suppressing insufficient separation of a protective layer. 
     According to an aspect of the present invention, there is provided a printing device comprising: a thermal head that transfers overcoat ink provided on an ink sheet onto a surface of printing paper; and a controller that causes the thermal head to perform the transfer based on pattern data, wherein the pattern data is data in which a first pattern and a second pattern are arranged alternately in a primary scanning direction and a secondary scanning direction, the first pattern includes a rectangular block of high tonal value pixels, a frame-like group of low tonal value pixels surrounding the rectangular block, and a group of high tonal pixels surrounding the group of low tonal value pixels, and the second pattern includes a rectangular block of low tonal value pixels, a group of high tonal value pixels surrounding the rectangular block, and a frame-like group of low tonal pixels surrounding the group of high tonal value pixels. 
     According to another aspect of the present invention, there is provided a printing device comprising: a thermal head that transfers overcoat ink provided on an ink sheet onto a surface of printing paper; and a controller that causes the thermal head to perform the transfer based on pattern data, wherein the pattern data is data in which a first pattern and a second pattern are arranged alternately in a primary scanning direction and a secondary scanning direction, the first pattern includes a rectangular block of high tonal value pixels and a frame-like group of low tonal value pixels surrounding the rectangular block, and the second pattern includes a rectangular block of low tonal value pixels, and a group of high tonal value pixels surrounding the rectangular block. 
     According to a further aspect of the present invention, there is provided a printing device that transfers overcoat ink provided on an ink sheet onto a surface of printing paper by printing the overcoat ink using pattern image data, wherein the pattern image data is constituted by first pixels having a tonal value that causes the overcoat ink to be fused with the printing paper, and second pixels having a tonal value that is lower than that of the first pixels and causes the overcoat ink to be fused with the printing paper, within the total of pixels constituting the pattern image data, a percentage of the first pixels and a percentage of the second pixel are each 40% or more, each pixel line in a primary scanning direction of the pattern image data includes at least one area in which two or more first pixels are consecutive, and a percentage of an area in which the first pixels are consecutive in a secondary scanning direction within the pattern image data is less than 50%. 
     Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an appearance example of a sublimation printer according to an embodiment. 
         FIG. 2  is an exploded perspective view showing a configuration example of an ink cassette. 
         FIGS. 3A and 3B  are diagrams showing a configuration example of an ink sheet and a configuration example of a printer. 
         FIG. 4  is a block diagram showing an example of a functional configuration of a printer. 
         FIG. 5  is a flowchart of printing processing. 
         FIGS. 6A and 6B  are diagrams showing an example of a pattern image. 
         FIGS. 7A and 7B  are diagrams showing another example of a pattern image. 
         FIGS. 8A to 8E  are diagrams each showing an example of the relationship between a pattern image and a heating value of a resistor. 
         FIG. 9  is a diagram showing an example of a conventional pattern image. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Exemplary embodiments of the present invention will now be described in detail in accordance with the accompanying drawings. Here, an example is described in which the present invention is applied to a sublimation printer as an example of a printing device, but the present invention can be applied to any printer that can form a protective layer by a thermal transfer method. 
       FIG. 1  is a perspective view showing an appearance example of a sublimation printer according to this embodiment. 
       FIG. 1  shows a state in which a printing paper tray  300  and an ink cassette  400  have been removed from a printer  100 . The ink cassette  400  is detachable from a compartment  101  provided on the side of the printer  100  casing, in a direction indicated by an arrow A. The printing paper tray  300  is detachable from a compartment  104  provided on the front side of the printer  100 , in the direction of an arrow B. 
     A display unit  102  and an operation unit  103  are provided on the top surface of the printer  100  casing. The display unit  102  is an LCD, for example, and displays a screen for selecting an image to be printed and setting a printing condition, a screen for displaying printer information, and the like. The operation unit  103  (including a touch panel in the case where the display unit  102  is a touch display) is constituted by switches and buttons for a user to give instructions to and set settings of the printer  100 , and the like. 
       FIG. 2  is an exploded perspective view showing a configuration example of the ink cassette  400 . 
     The ink cassette  400  has an upper holder  401 , a lower holder  402 , an ink sheet  404 , a supplying bobbin  405 , and a winding bobbin  407 . One end of the ink sheet  404  is fixed to the supplying bobbin  405 , and the other end is fixed to the winding bobbin  407 . The supplying bobbin  405  and the winding bobbin  407  are rotatably held by a bearing structure formed by the upper holder  401  and the lower holder  402 . When the ink cassette  400  is mounted to the compartment  101 , the shafts of the supplying bobbin  405  and the winding bobbin  407  are fitted into a driving mechanism of the printer  100 . 
       FIG. 3A  is a top view and a side view showing a configuration example of the ink sheet  404 , and approximately one unit of repetition in ink arrangement is shown here. The ink sheet  404  has a configuration in which a plurality of color ink layers and a protective ink (also referred to as an overcoat ink) layer are repeatedly arranged on a continuous sheet-like base material in a predetermined order in the length direction. Markers for detection are also arranged in boundary portions between colors of ink and boundary portions between the units of repetition. 
     A base material  404   i  is formed of a resin sheet. A start position marker a  404   a  is a marker indicating the boundary portion between the units of repetition, and a start position marker b  404   b  is a marker indicating the boundary portion between colors of ink. Yellow ink (Y)  404   c , magenta ink (M)  404   d , cyan ink (C)  404   e , and a protective ink or overcoat ink (OC) layer  404   f  constitute one unit of repetition. The protective ink layer  404   f  is comprised of a heat bonding layer  404   g  that is heat-bonded to printing paper, which is an example of a recording medium, and a protective sheet  404   h . The ink layers including the protective ink layer, and the markers are formed by coating the base material  404   i  with a material for each of the layers in a sheet-like manner. 
       FIG. 4  is a block diagram showing an example of the functional configuration of the printer  100 . 
     A main controller  201  is provided with a programmable processor (ex. a CPU or an MPU), a ROM, and a RAM, for example. The main controller  201  controls the operations of the units of the printer  100  by deploying a program stored in the ROM to the RAM and executing the program using the programmable processor, thereby realizing various functions of the printer  100 . 
     A paper feed driving motor  213  drives a paper feeding roller  133 , a conveyance motor  212  drives a conveyance roller  131 , and a winding motor  217  drives the winding bobbin  407 . A head motor  219  causes a thermal head  120  to move between a position at which the thermal head  120  comes into contact with a platen roller  130  (printing position) and a position at which the thermal head  120  is separated from the platen roller  130  (standby position). 
     A paper start position sensor  206  detects that the edge of printing paper  301  has reached a predetermined position. In addition, an ink sheet start position sensor  207  detects that the start position marker a  404   a  and the start position marker b  404   b  of the ink sheet  404  have reached predetermined positions. The paper start position sensor  206  and the ink sheet start position sensor  207  may be optical sensors, for example. 
     An image data input unit  229  is a memory card slot, for example, and can read image data recorded in a memory card mounted thereto and the like. Note that alternately or additionally, the image data input unit  229  may have a configuration in which image data is obtained from an external device through wireless communication, wired communication or the like. 
     A ROM  202  stores a temperature correction table used for driving pulse correction that depends on the temperature of the thermal head  120 , data of screens to be displayed on the display unit  102 , and various types of data used by the main controller  201  such as print settings. Note that the ROM  202  may be included in the main controller  201 . 
     A tone-pulse conversion unit  242  converts image data to be printed into pulse data for driving the thermal head  120 . In this embodiment, it is assumed that the tone-pulse conversion unit  242  generates 256-tone (8 bit) pulse data for each color component. Transfer energy is smallest at a tonal value of 0 that is the lowest tone, and transfer energy is largest at a tonal value of 255 that is the highest tone. 
     A temperature detection unit  208  detects the environmental temperature of the vicinity of the thermal head  120 , for example. A temperature correction unit  243  corrects the pulse data generated by the tone-pulse conversion unit  242  using the temperature correction table stored in the ROM  202 . A gamma correction unit  244  applies correction that depends on a predetermined gamma property to the pulse data after the temperature correction. The main controller  201  controls a head driving circuit  226  using the pulse data after the gamma correction so as to heat the thermal head  120 . 
     A pattern data recording unit  240  is a non-volatile memory, and stores the data of a pattern image for forming a protective layer, which will be described later. Note that the pattern image stored in the pattern data recording unit  240  may be partial image data corresponding to a unit of repetition, or may be image data corresponding to the entire surface of printing paper. In this embodiment, assume that the data of a pattern image is 256-tone (8 bit) data similarly to the pulse data. As will be described later, the pattern data recording unit  240  stores at least the data of a pattern image for matte finish that suppresses glossiness. The data of a pattern image for gloss finish may or may not be stored. 
     In this embodiment, the data of the pattern image for gloss finish is data made up of a low tonal value (L), and the data of the pattern image for matte finish is data made up of one high tonal value (H) and one low tonal value (L). The low tonal value (L) used for matte finish and the low tonal value (L) used for gloss finish may be the same or may be different. Assume that specific tonal values for the low tonal value (L) and the high tonal value (H) are determined in advance in accordance with the materials of the base material and the protective sheet of the ink sheet, which will be described later, the heating value of the thermal head, and the like. For example, the low tonal value (L) can be determined within the range of tonal values that are sufficient for heat bonding between the adhesive layer and the printing paper but do not cause fusion of the base material and the protective sheet. The high tonal value (H) can be determined within the range of tonal values that can realize the fusion of the base material and the protective sheet. Note that the high tonal value (H) is not limited to a value that can realize fusion of the base material and the protective sheet by driving a single pixel, and may be a value that can realize fusion of the base material and the protective sheet when driving a plurality of pixels consecutively in a primary scanning direction. In the case of 256-tone data (tonal values 0 to 255), the high tonal value (H) can be determined from the range of 200 to 255, for example, and the low tonal value (L) can be determined from the range of 80 to 120, for example. 
     The internal configuration of the printer  100  and the operations of the same at the time of printing will be described with reference to  FIG. 4  and  FIG. 3B  that is a side cross-sectional view of the printer  100 . In  FIG. 3B , the same reference numerals are given to the configurations described with reference to  FIGS. 1 and 2 .  FIG. 3B  shows a state in which the ink cassette  400  has been mounted. 
     The thermal head  120  has a configuration in which a plurality of resistors are arranged in a line in the primary scanning direction, which is a direction orthogonal to the conveyance direction (secondary scanning direction) of printing paper. Note that in this embodiment, it is assumed that the thermal head  120  is a line head, and has a length that covers the maximum size in the primary scanning direction of the printing paper that is printable with the printer  100 . Therefore, in this embodiment, the thermal head  120  does not move in the primary scanning direction, but the thermal head  120  may be configured as a serial head. The main controller  201  controls the driving of the resistors (heating bodies) of the thermal head  120  through the head driving circuit  226 . Note that in this embodiment, the thermal head  120  is assumed to have one line worth of resistors, but may have a plurality of lines worth of resistors. 
     A separation plate  125  is provided for changing the conveyance direction of the ink sheet  404  to a direction that deviates from the conveyance direction of the printing paper. The platen roller  130 , the conveyance roller  131 , a driven roller  132 , the paper feeding roller  133 , and a paper discharge roller  134  are rollers for conveying the printing paper along a conveyance route. Note that F indicates a paper feeding direction and G indicates a paper discharge direction in the drawings. 
     The main controller  201  drives the paper feed driving motor  213 , pulls out the printing paper  301  from the printing paper tray  300  using the paper feeding roller  133 , and conveys the printing paper  301  in the paper feeding direction F. The main controller  201  also drives the conveyance motor  212 , causes the conveyance roller  131  and the driven roller  132  to sandwich the printing paper  301 , and conveys the printing paper  301  in the paper feeding direction F to a position at which the leading edge is detected by the paper start position sensor  206  (not illustrated in  FIG. 3B ). When the leading edge of the printing paper  301  is detected by the paper start position sensor  206 , the main controller  201  starts the driving of the winding bobbin  407  using the winding motor  217 . 
     When the ink sheet start position sensor  207  (not illustrated in  FIG. 3B ) detects the start position marker a  404   a , the main controller  201  drives the head motor  219  so as to move the thermal head  120  to the printing position at which the thermal head  120  comes in contact with the platen roller  130 . When the thermal head  120  has moved to the printing position, the upper surface of the ink sheet  404  and the lower surface of the printing paper  301  are pressed against each other by the thermal head  120  and the platen roller  130 . In this state, the main controller  201  heats resistors of the thermal head  120  in the primary scanning direction based on pulse data for yellow data, and transfers the yellow ink layer  404   c  onto the printing paper  301 . When one head driving operation in the primary scanning direction ends, the main controller  201  drives the conveyance motor  212  and the winding motor  217 , and moves the printing paper  301  and the ink sheet  404  in the secondary scanning direction (the paper discharge direction G) by a predetermined amount. Note that the movement amount in the secondary scanning direction is defined in accordance with how many lines of resistors the thermal head  120  has. 
     When the printing in the primary scanning direction and the conveyance of the ink sheet  404  and the printing paper  301  in the secondary scanning direction are performed repeatedly, the leading edge of the yellow ink layer  404   c  reaches the separation plate  125 . Downstream of the separation plate  125 , the conveyance route of the ink sheet  404  and the conveyance route of the printing paper  301  deviate from each other. More specifically, the direction of the conveyance route of the ink sheet  404  changes to upward such that the ink sheet  404  is stripped from the printing paper  301 . In particular, at the time of forming (at the time of transferring) the protective layer, the protective sheet  404   h  is separated from the base material  404   i  at the position of the separation plate  125  and is transferred onto the printing paper  301  due to the adhesive force between the adhesive layer  404   g  and the printing paper  301  exceeding the binding force between the protective sheet  404   h  and the base material  404   i.    
     When the amount of conveyance in the secondary scanning direction (the paper discharge direction G) reaches the predetermined amount, the main controller  201  drives the head motor  219  so as to move the thermal head  120  to a standby position. The main controller  201  also reverses the driving direction of the conveyance motor  212 , and conveys the printing paper  301  back in the paper feeding direction F until the leading edge is detected by the paper start position sensor  206 . 
     The above operations are repeatedly performed for the magenta ink layer  404   d , the cyan ink layer  404   e  and the protective ink layer  404   f  in this order. Each time the type of ink used for printing changes, the printing paper  301  is conveyed in the paper feeding direction F, and is then conveyed in the paper discharge direction G while being printed on, and thus the color components are sequentially printed on the printing paper  301 , and the protective layer is lastly formed. At the time of forming the protective layer, the printing operation is performed using pulse data that is based on the data of a pattern image stored in the pattern data recording unit  240 , instead of image data for printing. After forming the protective layer, the main controller  201  drives the paper feed driving motor  213  so as to discharge the printing paper  301  from between the paper feeding roller  133  and the paper discharge roller  134  to the upper portion of the paper tray  300 . 
     Next, the operations of the printer  100  at the time of printing will be further described with reference to a flowchart in  FIG. 5 . Assume that in the printer  100  of this embodiment, gloss finish or matte (deglossing) finish can be selected as a print option. The main controller  201  forms the protective layer using data of different pattern images when gloss finish is selected and when matte finish is selected. 
     In step S 101 , the main controller  201  accepts a finish mode setting as a setting value for a finish mode setting item included in a print setting screen displayed on the display unit  102 , for example. Here, assume that either “gloss finish” or “matte finish” has been set. 
     In step S 102 , the main controller  201  accepts an instruction to select an image to be printed. For example, the main controller  201  displays, on the display unit  102 , a list display screen of image data that exists in, for example, a storage medium mounted to the image data input unit  229 . The list display screen may include thumbnails of a plurality of images selectably arranged along with the number of print sets, for example. 
     In step S 103 , the main controller  201  determines whether or not a printing instruction has been input through the operation unit  103 , and if input of a printing instruction is not detected, returns the procedure to step S 102  so as to continue the display of the list display screen. However, if input of a printing instruction is detected, the main controller  201  obtains a selected result in the list display screen and a designated result of the number of print sets, and advances the procedure to step S 104 . 
     In step S 104 , the main controller  201  performs color printing processing. Specifically, the main controller  201  reads out the data of the image selected in step S 102  from the storage medium mounted to the image data input unit  229 , for example, then applies decoding processing or the like, subsequently converts the data into CMY data, and write the CMY data to an internal memory (RAM). The main controller  201  then generates temperature-corrected and gamma-corrected pulse data from the CMY data using the tone-pulse conversion unit  242 , the temperature correction unit  243  and the gamma correction unit  244 , as described above. Subsequently, the main controller  201  sequentially performs printing processing for yellow ink layer  404   c , magenta ink layer  404   d , and cyan ink layer  404   e , as described with reference to  FIG. 3A . 
     Steps S 105  to S 107  are protective layer forming operations. 
     In step S 105 , the main controller  201  obtains the environmental temperature from the temperature detection unit  208 . 
     In step S 106 , the main controller  201  branches the processing so as to advance the procedure to step S 111  if gloss finish was set in step S 101 , and advance the procedure to step S 121  if matte finish was set. 
     In step S 111 , for example, the main controller  201  converts the data of the pattern image for gloss finish (or the low tonal value (L)) stored in the pattern data recording unit  240  into CMY data, and writes the CMY data to the internal memory. In step S 112 , the main controller  201  converts the CMY data into pulse data using the tone-pulse conversion unit  242 , and then applies temperature correction that is based on temperature correction data for color ink stored in the ROM  202  using the temperature correction unit  243 . The main controller  201  further applies gamma correction to the pulse data using the gamma correction unit  244 . 
     In step S 113 , the main controller  201  performs printing processing for the protective ink layer  404   f  with the same operation as the color printing processing performed in step S 104 . The printing processing performed in step S 113  is the first protective layer heat bonding process. As described above, printing processing with the low tonal value of the pixels constituting the pattern image for gloss finish does not cause fusion of the protective sheet and the base material, and therefore, the surface of the protective sheet separated from the base material (the surface that was in contact with the base material) is not made rough by the printing processing. Therefore, the protective layer having glossiness is formed on the surface of the printing paper, thereby realizing gloss finish. 
     On the other hand, in the case of matte finish as well, basically the same processing may be performed, except that the type of pattern image to be used for the printing is different. Specifically, in step S 121 , the main controller  201  converts the data of the pattern image for matte finish stored in the pattern data recording unit  240  into CMY data, and writes the CMY data to the internal memory. In step S 122 , the main controller  201  converts the CMY data into pulse data using the tone-pulse conversion unit  242 , and then applies temperature correction that is based on the temperature correction data for the color inks stored in the ROM  202  to the pulse data using the temperature correction unit  243 . As necessary, the main controller  201  may further apply temperature correction that is based on temperature correction data for the protective ink stored in the ROM  202  to the pulse data, using the temperature correction unit  243 . Furthermore, the main controller  201  applies gamma correction to the pulse data using the gamma correction unit  244 . 
     The printing processing performed in step S 123  is the second protective layer heat bonding step. The printing speed of the printer  100  is lowered below the printing speed at the time of transferring color ink so as to allow heat bonding of the protective layer. Step S 107  is a printing ending determination step. Normally, the procedure returns to step S 101  so as to wait for the next printing instruction. 
     In step S 123 , the main controller  201  performs printing processing for the protective ink layer  404   f  with the same operation as the color printing processing performed in step S 104 . As described above, the high tonal value (H) of the pixels constituting the data of the pattern image has been determined so as to cause fusion of the protective sheet  404   h  and the base material  404   i . Therefore, the printing processing brings the base material and the surface of the protective sheet into a fused state in the portion of pixels corresponding to the high tonal value (H). When the protective sheet  404   h  is separated from the base material  404   i  at the position of the separation plate, the fused portion is stripped away, and the surface of the protective sheet  404   h  (the surface that was in contact with the base material  404   i ) is made rough. Therefore, the protective layer  404   h  having rough surface portions is formed on the surface of the printing paper, thereby realizing matte finish. Note that as in the case where fusion of the base material  404   i  and the protective sheet  404   h  cannot be caused by the high tonal value (H) at a normal printing speed, the printing speed at the time of forming the protective layer may be lowered below the speed for the color printing as necessary. 
     The following describes an event that can be a problem in the case of making the surface of the protective sheet  404   h  rough by heating the heat bonding layer so as to adhere the protective ink layer  404   f  to the surface of the printing paper, and simultaneously fusing the base material  404   i  and the protective sheet  404   h  of the ink sheet  404  by the printing processing. 
       FIGS. 8A to 8E  are diagrams schematically showing the relationship between the arrangement of pixels with a high tonal value (H) in the data of a pattern image and the temperature of a resistor of the thermal head  120 . These examples show the resistor (heating body) corresponding to a pixel  6012  that is second from the left in a pixel block  600  constituted by four pixels  6011  to  6014  that are consecutive in the primary scanning direction, and how the temperature of this resistor changes in accordance with the arrangement pattern of the high tonal value (H). 
     In  FIGS. 8A to 8E , the arrangement pattern of the high tonal value (H) is shown on the left, and change in the temperature of the resistor of the thermal head at the position of the pixel  6012  is shown on the right. Reference numeral  605  denotes the temperature at which the protective sheet and the base material are fused (fusing temperature). 
       FIGS. 8A to 8C  show the case in which there is no influence from driving the thermal head for one or more other pixels with the high tonal value (H) in the secondary scanning direction, or the case where there is no necessity to consider such influence, and  FIGS. 8D and 8E  show the case in which there is influence from driving the thermal head for one or more other pixels with the high tonal value (H) in the secondary scanning direction. 
       FIG. 8A  shows the case of driving the thermal head  120  with the high tonal value (H) for the pixel  6012  among the pixels  6011  to  6014 , and driving the thermal head  120  with a low tonal value (L) for the other pixels  6011 ,  6013 , and  6014 . In this example, even if the resistor corresponding to the pixel  6012  is driven with a pulse that corresponds to the high tonal value (H), the fusing temperature  605  is not reached. This is because surrounding resistors are not heated, and therefore the heat generated in the resistor corresponding to the pixel  6012  easily escapes by being conducted to the surrounding resistors. Note that, in order to describe the influence of heat accumulation, assume here that a high tonal value (H) and a printing speed at which fusion does not occur with the pattern in  FIG. 8A  have been set. However, it should be noted that in actuality, a high tonal value (H) (and additionally a printing speed as necessary) at which fusion occurs with the pattern in  FIG. 8A  as well can be set. 
     However, in the case where the pixel  6013  adjacent in the primary scanning direction also has the high tonal value (H) as shown in  FIG. 8B , two adjacent resistors are heated at the same time, and therefore the heating efficiency increases. In addition, the amount of heat escaping to the periphery also decreases, and therefore the temperature of the resistor corresponding to the pixel  6012  exceeds the fusing temperature  605 . 
     Even if the number of pixels adjacent or close in the primary scanning direction and having the high tonal value (H) increases as in the case where all of the pixels  6011  to  6014  have the high tonal value (H) as shown in  FIG. 8C , the temperature of the resistor corresponding to the pixel  6012  hardly changes from the case in  FIG. 8B . 
     On the other hand,  FIG. 8D  shows the case where the pattern in  FIG. 8A  is repeated in two lines in the secondary scanning direction, and the change in the temperature of the resistor in the first line is the same as in  FIG. 8A . After the thermal head is driven for the first line and subsequently the printing paper is conveyed in the secondary scanning direction, the thermal head is driven for the second line. The same resistor is heated for a pixel  6022  in the second line and the pixel  6012  in the first line, but the temperature of the resistor sufficiently decreases by the time of driving the thermal head for the second line, and therefore driving the thermal head for the first line does not influence the temperature of the resistor at the time of the driving the thermal head for the second line. Therefore, the temperature of the resistor does not reach the fusing temperature  605  at the time of driving the thermal head for the second line either. 
       FIG. 8E  shows the case in which the pattern in  FIG. 8B  is repeated in two lines in the secondary scanning direction, and the changes in the temperature of the resistors for the first line is the same as in  FIG. 8B . In this case, even if driving the thermal head for the first line does not influence the temperature of the resistors at the time of driving the thermal head for the second line, the temperature of the resistor  6022  in the second line also exceeds the fusing temperature  605  since the changes in the temperature of the second line is the same as in  FIG. 8B . Furthermore, the temperature of the resistor  6012  that rose above the fusing temperature  605  when driving the thermal head for the first line has not sufficiently decreased by the time of driving the thermal head for the second line. Therefore, when driving the thermal head for the second line, the degree of the fusion of the protective sheet  404   h  and the base material  404   i  increases above that for the first line. Note that in  FIG. 8E , the highest temperature in the second line is substantially the same as in the first line, because the pulse data has been underwent temperature correction. 
     For example, it is also theoretically possible to use the data of a pattern image constituted only by pixels of a high tonal value (H) in the case of performing matte finish. However, it is highly possible that the degree of the fusion of the protective sheet  404   h  and the base material  404   i  excessively increases, the binding force between the protective sheet  404   h  and the base material  404   i  exceeds the adhesive force between the adhesive layer  404   g  and the printing paper, and a phenomenon in which the protective sheet  404   h  is not completely separated (insufficient separation) occurs. 
     On the other hand, a better deglossing effect is obtained when variation in the surface state is larger, for example, as in the case where both glossy surface portions and rough surface portions exist, compared to when making the surface of the protective sheet  404   h  uniformly rough. This is because, when the variation in the surface state is large, light reflected on the surface of the protective sheet  404   h  scatters. Therefore, in this embodiment, the data of the pattern image constituted by pixels of a high tonal value (H) and a low tonal value (L) is used. 
     For example, consider the use of data of a pattern image in which pixels with a high tonal value (H) and pixels with a low tonal value (L) form a checkered pattern as shown in  FIG. 9 . In a pattern image  1000  shown in  FIG. 9 , rectangular blocks each constituted by 2×2 pixels with a high tonal value (H) (first pixels or high tonal pixels) in the primary scanning direction and in the secondary scanning direction, and rectangular blocks each constituted by 2×2 pixels with a low tonal value (L) (second pixels or low tonal pixels) in the primary scanning direction and in the secondary scanning direction are alternately arranged. Here, assume that white pixels correspond to the high tonal pixels and that black pixels correspond to the low tonal pixels, and a rectangular block  1001  is constituted by the high tonal pixels, and a rectangular block  1002  is constituted by the low tonal pixels. Note that a pattern image serving as a unit of repetition is shown in  FIG. 9 , but the data of a pattern image corresponding to the entire surface of the printing paper may be stored. 
     In the case where the protective layer is formed using such a pattern image, the temperature of the resistors in the thermal head at the positions corresponding to the rectangular block  1001  change as shown in  FIG. 8E . As was described, regarding the pattern shown in  FIG. 8E , the degree of the fusion of the protective sheet  404   h  and the base material  404   i  is larger in the second line than in the first line. This means that the binding force between the protective sheet  404   h  and the base material  404   i  in the secondary scanning direction increases, causing a rise in the probability of occurrence of insufficient separation of the protective sheet  404   h . According to the inventors&#39; examination, in the case of using the pattern image having a checkered pattern shown in  FIG. 9 , insufficient separation between the protective sheet  404   h  and the base material  404   i , and paper jam accompanying the insufficient separation occurred. Therefore, the inventors repeated examinations, and as a result of that, the following was found. 
     In the case of making the surface of the protective sheet rough by fusing the protective sheet and the base material: 
     (A) a certain size of a fusion area makes reflection light easily scatter, and therefore realizes a better matte effect; and 
     (B) on the other hand, the larger the fusion area in the secondary scanning direction is, the more force is required when separating the protective sheet  404   h  from the base material  404   i , and therefore if a large number of fusion areas that are large in the secondary scanning direction exist on the same line in the primary scanning direction, insufficient separation easily occurs. 
     Moreover, as a result of earnest examination in light of such properties, it was found that both a high deglossing effect and suppression of insufficient separation can be realized by using a pattern image constituted by high tonal pixels and low tonal pixels, the pattern image satisfying the following conditions: 
     (1) the percentage of pixels having a high tonal value (high tonal pixels) and the percentage of pixels having a low value (low tonal pixels) within the total of the pixels constituting the pattern image are each 40% or more; 
     (2) each pixel line in the pattern image in the primary scanning direction includes at least one area in which two or more high tonal pixels are consecutive; and 
     (3) the percentage of high tonal pixel areas in which two pixels of high tonal data are consecutive in the secondary scanning direction within the total of the pixels constituting the pattern image is less than 50%. 
     It was also found that it is preferred that one or more of the following conditions are further satisfied: 
     (3-1) the percentage of pixels that are included in each pixel line in the primary scanning direction and belong to a high tonal pixel block in which two or more high tonal pixels are consecutive in the primary scanning direction and the secondary scanning direction is preferably 30% or less, and more preferably, 20% or less,
 
(3-2) the percentage of pixels that belong to a high tonal pixel area in which two or more high tonal pixels are consecutive in the secondary scanning direction within the total of the pixels constituting the pattern image is 40% or less, and the percentage of pixels that are included in each pixel line in the primary scanning direction and belong to a high tonal pixel area is 50% or less, and
 
(4) the length of one side of an area in which high tonal pixels are consecutive both in the primary scanning direction and the secondary scanning direction is 500 μm or less and 100 μm or more, and preferably 300 μm or less and 100 μm or more.
 
     Note that rough areas and gloss areas are arranged in a balanced manner with the condition 1 among the above-described conditions, and thus large variation in the surface state can be maintained over the entity of the surface, making it possible to obtain a good deglossing effect. The condition 2 is a condition considering mainly A, the condition 3 is a condition considering mainly B, and the conditions 3-1, 3-2 and 4 are conditions considering both A and B. 
     An example of a specific pattern image that satisfies the above-described conditions will be described below with reference to  FIGS. 6A to 7B . Note that in the following description, assume that one pixel is a rectangle that is 80 to 90 μm on each side (300 dpi), and that the pattern image is constituted by high tonal pixels having a tonal value of 220 and low tonal pixels having a tonal value of 100. 
       FIG. 6A  is a diagram showing two types of unit patterns constituting a pattern image according to this embodiment, and pixels corresponding to a high tonal value (high tonal pixels) are indicated in white, and pixels corresponding to a low tonal value (low tonal pixels) are indicated in black. A first pattern  2000  shown on the left and a second pattern  3000  shown on the right have a relationship in which the low tonal pixels and the high tonal pixels are reversed. 
     The first pattern  2000  is constituted by a rectangular block H  1001  having high tonal pixels, a frame-like group of low tonal pixels (a frame L  2003 ) surrounding the rectangular block H  1001 , and a group of high tonal pixels (a frame H  2004 ) surrounding the frame L  2003 . 
     The second pattern  3000  is constituted by a rectangular block L  1002  having low tonal pixels, a frame-like group of high tonal pixels (a frame H  3003 ) surrounding the rectangular block L  1002 , and a group of low tonal pixels (a frame L  3004 ) surrounding the frame H  3003 . 
     The first pattern  2000  and the second pattern  3000  are constituted by 6×6=36 pixels, and the size of each side of the patterns in the primary scanning direction and the secondary scanning direction is 480 to 540 μm. Also, the frame L  2003 , the frame H  2004 , the frame H  3003  and the frame L  3004  are each formed with a one-pixel width, and thus the width is 80 to 90 μm. 
     Both the first pattern  2000  and the second pattern  3000  are constituted by 6×6=36 pixels, but the first pattern  2000  includes 24 high tonal pixels, and the second pattern  3000  includes 24 low tonal pixels. In the case where the first pattern  2000  and the second pattern  3000  that are adjacent to each other form one unit of repetition, the percentage of high tonal pixels and the percentage of low tonal pixels within the unit of repetition (72 pixels) are both 50% (36 pixels). 
       FIG. 6B  shows a portion of a pattern image  4000  constituted by the first pattern  2000  and the second pattern  3000  in  FIG. 6A . As shown in the figure, the first pattern  2000  and the second pattern  3000  are arranged alternately both in the primary scanning direction (the right-left direction in the drawing) and the secondary scanning direction (the up-down direction in the drawing), and are arranged in a checkered pattern or in a checker-board manner such that the same pattern is not repeated adjacently. At least one unit of repetition including the first pattern  2000  and the second pattern  3000  is stored as a pattern image in the pattern data recording unit  240 . 
     In the case of forming the protective layer using the pattern image  4000 , the protective sheet is made rough in the rectangular block H  1001 , the frame H  2004  and the frame H  3003  that have consecutive high tonal pixels. In addition, the protective sheet is not made rough in the rectangular block L  1002 , the frame L  2003 , and the frame L  3004  that have consecutive low tonal pixels, thus maintaining a glossy surface. Because rough surface areas and glossy surface areas exist alternatively at a short cycle, change in the surface state of the protective sheet is large, and a good deglossing effect can be obtained, making it possible to improve the visual recognizability of the printed image. 
     In the pattern image  4000 , the percentage of high tonal pixels and the percentage of low tonal pixels are 50%, and thus the condition 1 is satisfied. In addition, each pixel line in the primary scanning direction includes at least one area that has two or more consecutive high tonal pixels, and thus the condition 2 is satisfied. Furthermore, the percentage of a high tonal pixel area in which two pixels of high tonal data are consecutive in the secondary scanning direction within the total of the pixels constituting the pattern image is 30%, and thus the condition 3 is satisfied. 
     In addition, the percentage of pixels that are included in each of the pixel lines in the primary scanning direction and belong to a high tonal pixel block in which two or more high tonal pixels are consecutive in the primary scanning direction and the secondary scanning direction is 0 to 17%, and thus the condition (3-1) is also satisfied. 
     The percentage of pixels that belong to a high tonal pixel area in which two or more high tonal pixels are consecutive in the secondary scanning direction within the total of the pixels constituting the pattern image is 30%, and the percentage of pixels that are included in each of the pixel lines in the primary scanning direction and belong to a high tonal pixel area is 17 to 50%. Therefore, the condition (3-2) is also satisfied. 
     Furthermore, the length of one side of an area in which high tonal pixels are consecutive both in the primary scanning direction and the secondary scanning direction (here, the rectangular block H  1001 ) is 160 to 180 μm, and thus the condition (4) is also satisfied. 
     High tonal pixels that belong to the rectangular block H  1001  make up only about 17% of one line in the primary scanning direction, and thus insufficient separation can be sufficiently suppressed. In addition, a pattern in which two, four, and six high tonal pixels are consecutive in the primary scanning direction and the secondary scanning direction is included, thus making it possible to effectively realizing a rough surface. 
       FIGS. 7A and 7B  show a modified example of the pattern image shown in  FIGS. 6A and 6B . As shown in  FIG. 7A , in the modified example, the frame L  2003  and the rectangular block L  1002  are modified, and a frame L  2003   a  and a rectangular block L  1002   a  in which the number of low tonal pixels consecutive in the primary scanning direction is increased are used. Specifically, the modification is made such that out of two sides (pixel lines) making up the frame L  2003  and the rectangular block L  1002  and having low tonal pixels consecutive in the primary scanning direction, one to be used lastly (last in the secondary scanning direction) is extended on two sides. Due to this extension, some pixels of the two sides in the secondary scanning direction of the frame H  2004  and the frame H  3003  become low tonal pixels, thereby separating the high tonal pixels. In  FIG. 7A , reference signs G 1  and G 2  respectively indicate a printing-starting pixel line and a printing-ending pixel line of the frame L  2003   a.    
       FIG. 7B  shows a pattern image  4000 ′ in which a first pattern  2000 ′ and a second pattern  3000 ′ that are modified are used.  FIG. 7B  is the same as  FIG. 6B  except that the frame L  2003   a  and the rectangular block L  1002   a  are used. 
     The reason for increasing the number of low tonal pixels included in the printing-ending line in the primary scanning direction of the frame L  2003   a  and the rectangular block L  1002   a  in this modified example will be described below. In the case of actually driving the thermal head with the pattern image in  FIG. 6B , the degree of fusion to be obtained is different between a line for which the thermal head is driven earlier and a line for which the thermal head is driven later even though the number of high tonal pixels consecutive in the primary scanning direction is the same. Specifically, in the frame H  3003  and the frame H  2004  in  FIG. 6A , the degree of fusion due to high tonal pixels consecutive in the primary scanning direction is different between a line for which the thermal head is driven first (L 1  and L 3 ) and a line for which the thermal head is driven last (L 2  and L 4 ). 
     This is because the influence of the driving of the thermal head on high tonal pixels included in the lines for which the thermal head has been driven so far is different between the lines L 1  and L 3  and the lines L 2  and L 4 . In the case where high tonal pixels not consecutive in the primary scanning direction are simply consecutive in the secondary scanning direction as shown in  FIG. 8D , heating for the line for which the thermal head is driven earlier does not influence the heating value for pixels in the line for which the thermal head is driven later. However, in the case where high tonal pixels are consecutive in the primary scanning direction in the line for which the thermal head is driven later, pixels near the location in which the direction in which high tonal pixels are consecutive changes from the secondary scanning direction to the primary scanning direction are affected by the influence of the heat accumulation. For example, in the case where in  FIG. 8E , the pixels  6012 ,  6022 , and  6023  are high tonal pixels, the pixels  6022  and  6023  are influenced by the heat accumulation, and the degree of fusion increases. In the modified example, in the area in which high tonal pixels included in the line in the primary scanning direction for which the thermal head is driven later are consecutive, high tonal pixels included in a line in the primary scanning direction for which the thermal head is driven immediately before are not adjacent, thereby reducing the difference in the degree of the fusion. Accordingly, the sound at the time of the separation can be reduced more than in the case of using the pattern image in  FIGS. 6A and 6B . 
     Note that the case in which the pitch of the thermal head (dpi) is 300 dpi was described with reference to  FIGS. 6A to 7B , but in the case of another pitch, it is sufficient to convert the number of pixels in accordance with the pitch so as to have the same size as with 300 dpi. For example, in the case of a 600 dpi head, it is sufficient to double the number of pixels. 
     In  FIGS. 6A and 6B , the first pattern  2000  and the second pattern  3000  are each a pattern having 6×6 pixels, but may be a pattern having 4×4 pixels. In the case of the 4×4 pixel pattern, preferably, a first pattern is constituted by the rectangular block  1001  of high tonal pixels and a low tonal pixel frame  2003  surrounding the rectangular block  1001 , and a second pattern is constituted by the rectangular block  1002  of low tonal pixels and a high tonal pixel frame  3003  surrounding the rectangular block  1002 . Similarly, a modified pattern of the pattern in  FIGS. 7A and 7B  may be a pattern of 4×4 pixels. 
     Working Examples 
     Evaluation 1 
     Protective sheets  404   h  (i.e., protective ink layers  404   f ) were printed (heat-transferred) under the same conditions except for the image data that was used, and glossiness, visual recognizability, and insufficient separation were compared and evaluated. 
     Specifically, as image data used for printing the protective sheet  404   h , (1) a pattern image having high tonal pixels for the entire image, (2) the pattern image  1000 , and (3) the pattern image  4000  were used. Subsequently, the tonal value of the low tonal pixels was fixed at 89, the tonal value of the high tonal pixels was changed in 13 ways, that is to say was set to 100, every 10 tones from 150 to 250, and 255, the protective sheets  404   h  were printed, and the glossiness of the surface of the printing paper onto which the protective sheets had been transferred was measured. Note that in the case of using a pattern image having high tonal pixels for the entire image, a low tonal value is not used. 
     In a state in which a new ink cassette (RP-54 manufactured by Cannon Inc.) was mounted to a sublimation printer (SELPHY CP820 manufactured by Cannon Inc.), printing was performed at the room temperature of 25 degrees, with the electric power supplied to the head being 89 mW, and at a protective sheet transferring speed of 0.3 ips, while changing the pattern images. Glossiness is a numeral value measured using a gloss meter (micro-haze plus manufactured by BYK) by a method conforming to Method 5 of JISZ 8741 (20° specular gloss), and is a relative value when the glossiness of a glass surface (the refractive index is 1.567 over the total visible wavelength range) is 100(%). 
     Difference in gloss can be sufficiently recognized when glossiness differs by 10 or more. In addition, from the viewpoint of the visual recognizability of a printed image, the smaller the glossiness is, the better the visual recognizability is. The average value of glossiness when gloss finish is applied is 50, and thus if the glossiness after applying matte finish is 40 or less, improvement of visual recognizability over gloss finish can be sufficiently recognized. The more the glossiness further decreases, the more the visual recognizability improves. Therefore, glossiness when matte finish is applied (in the case of using the pattern image  1000  or  4000 ) needs to be 40 or less, preferably 30 or less, and more preferably 25 or less. 
     Moreover, insufficient separation was evaluated by visually checking whether or not a trace different from a pattern image used for printing or the like existed on the surface of the protective sheet  404   h.    
     Measurement and evaluation results are shown in Table 1 below. 
     
       
         
           
               
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Tonal 
                 High tonal pixels 
                 Pattern image 1000 
                 Pattern image 4000 
               
               
                 value 
                 for entire image 
                 (FIG. 9) 
                 (FIG. 6) 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 of high 
                   
                 Visual 
                   
                 visual 
                   
                 Visual 
               
               
                 tonal 
                 Glossi- 
                 recogniz- 
                 Glossi- 
                 recogniz- 
                 Glossi- 
                 recogniz- 
               
               
                 pixels 
                 ness 
                 ability 
                 ness 
                 ability 
                 ness 
                 ability 
               
               
                   
               
               
                 100 
                 50 
                 Poor 
                 50 
                 Poor 
                 50 
                 Poor 
               
               
                 150 
                 50 
                 Poor 
                 49 
                 Poor 
                 50 
                 Poor 
               
               
                 160 
                 49 
                 Poor 
                 49 
                 Poor 
                 50 
                 Poor 
               
               
                 170 
                 49 
                 Poor 
                 49 
                 Poor 
                 49 
                 Poor 
               
               
                 180 
                 48 
                 Poor 
                 48 
                 Poor 
                 49 
                 Poor 
               
               
                 190 
                 46 
                 Poor 
                 45 
                 Poor 
                 48 
                 Poor 
               
               
                 200 
                 36 
                 Good 
                 40 
                 Good 
                 45 
                 Poor 
               
               
                 210 
                 25 
                 Very 
                 35 
                 Good 
                 40 
                 Good 
               
               
                   
                   
                 good 
                   
                   
                   
                   
               
               
                 220 
                 11 
                 Very 
                 27 
                 Very 
                 37 
                 Good 
               
               
                   
                   
                 good 
                   
                 good 
                   
                   
               
               
                 230 
                 Insuf- 
                 — 
                 18 
                 Very 
                 33 
                 Good 
               
               
                   
                 ficient 
                   
                   
                 good 
                   
                   
               
               
                   
                 separa- 
                   
                   
                   
                   
                   
               
               
                   
                 tion 
                   
                   
                   
                   
                   
               
               
                 240 
                 Insuf- 
                 — 
                 Insuf- 
                 — 
                 27 
                 Very 
               
               
                   
                 ficient 
                   
                 ficient 
                   
                   
                 good 
               
               
                   
                 separa- 
                   
                 separa- 
                   
                   
                   
               
               
                   
                 tion 
                   
                 tion 
                   
                   
                   
               
               
                 250 
                 Insuf- 
                 — 
                 Insuf- 
                 — 
                 22 
                 Very 
               
               
                   
                 ficient 
                   
                 ficient 
                   
                   
                 good 
               
               
                   
                 separa- 
                   
                 separa- 
                   
                   
                   
               
               
                   
                 tion 
                   
                 tion 
                   
                   
                   
               
               
                 255 
                 Insuf- 
                 — 
                 Insuf- 
                 — 
                 18 
                 Very 
               
               
                   
                 ficient 
                   
                 ficient 
                   
                   
                 good 
               
               
                   
                 separa- 
                   
                 separa- 
                   
                   
                   
               
               
                   
                 tion 
                   
                 tion 
               
               
                   
               
            
           
         
       
     
     As seen from Table 1, insufficient separation occurred when the tonal value of high tonal pixels was 230 or more in the case of using a pattern image having high tonal pixels for the entire image, and when the tonal value of high tonal pixels was 240 or more in the case of using the pattern image  1000 . However, insufficient separation did not occur even when the tonal value of high tonal pixels was 255 in the case of using the pattern image  4000 . 
     In addition, good visual recognizability is obtained when the tonal value of the high tonal pixels is in the range of 200 to 220 in the case of the pattern image having high tonal pixels for the entire image, and when the tonal value of the high tonal pixels is in the range of 200 to 230 in the case of the pattern image  1000 . On the other hand, in the case of the pattern image  4000 , good visual recognizability was obtained when the tonal value of the high tonal pixels was in the range of 210 or more (210 to 255). In other words, the pattern image  4000  has a broad range of tonal values of the high tonal pixels at which good visual recognizability is obtained. Moreover, it is seen that visual recognizability equivalent to that for the pattern image  1000  can be realized. 
     Evaluation 2 
     Next, the rate of occurrence of insufficient separation during continuous printing was evaluated. In the case of performing continuous printing, insufficient separation easily occurs due to the rise in the temperatures of thermal head and the environment. In addition, when the diameter of the winding bobbin  407  increases as the printing procedure proceeds, the winding torque of the ink sheet decreases and the separation timing becomes delayed, still allowing insufficient separation to easily occur. Therefore, as the ink cassette becomes used up due to continuous printing, insufficient separation easily occurs synergistically. 
     In view of this, glossiness and insufficient separation were evaluated in the case where continuous printing of 54 sheets was performed. Here, the tonal value of high tonal pixels was set to 220 at which a good value was obtained with each of the pattern images in Evaluation 1, and 248 at which only the pattern image  4000  did not cause insufficient separation to occur. The pattern image  4000 ′ shown in  FIGS. 7A and 7B  was also evaluated. The other conditions are same as in Evaluation 1. 
     Measurement and evaluation results are shown in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                   
                   
                 Number of occurrences of 
               
               
                   
                 Tonal value 
                 Tonal value 
                 insufficient separation 
               
               
                   
                 of high tonal 
                 of low tonal 
                 during continuous 
               
               
                   
                 pixels 
                 pixels 
                 printing of 54 sheets 
               
               
                   
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 High tonal 
                 220 
                 — 
                 35 
               
               
                 pixels for 
               
               
                 entire image 
               
               
                 Pattern image 
                 220 
                 89 
                 7 
               
               
                 1000 (FIG. 9) 
               
               
                 Pattern image 
                 220 
                 89 
                 0 
               
               
                 4000 (FIG. 6) 
               
               
                 Pattern image 
                 220 
                 89 
                 0 
               
               
                 4000′ (FIG. 7) 
               
               
                 Pattern image 
                 248 
                 89 
                 23 
               
               
                 4000 (FIG. 6) 
               
               
                 Pattern image 
                 248 
                 89 
                 3 
               
               
                 4000′ (FIG. 7) 
               
               
                   
               
            
           
         
       
     
     In the case where the tonal value of high tonal pixels was set to 220 and the tonal value of low tonal pixels was set to 89, insufficient separation occurred in 35 sheets out of 54 sheets in the case of using high tonal pixels for the entire image, and 7 sheets out of 54 sheets in the case of using the pattern image  1000 . In contrast, in the case of using the pattern images  4000  and  4000 ′, insufficient separation did not occur in any sheet. In this manner, by printing the protective sheet using the pattern image of this embodiment, suppression of insufficient separation in the protective sheet and improvement of the visual recognizability of the printed article can be realized. 
     In addition, in order to compare the pattern images  4000  and  4000 ′, similar evaluation was performed with the tonal value of the high tonal pixels being set to 248 at which insufficient separation more easily occurs. As shown in Table 2, insufficient separation occurred in 23 sheets out of 54 sheets in the case where the pattern image  4000  was used, and insufficient separation occurred in 3 sheets out of 54 sheets in the case where the pattern image  4000 ′ was used. In addition, the average glossiness was 18 in the case of using the pattern image  4000 , and 20 in the case of using the pattern image  4000 ′. Therefore, it was found that the pattern image  4000 ′ was a pattern image with which insufficient separation was unlikely to occur regardless of the fact that glossiness did not change very much compared to the pattern image  4000 . 
     In this manner, in this embodiment, in the printing device for fusing the protective sheet and the base material of the ink sheet using the thermal head so as to make the surface of the protective sheet rough, the thermal head is driven with a pattern image that satisfies specific conditions. In particular, a pattern image is used in which (1) there is no large difference between the percentage of high tonal pixels and the percentage of low tonal pixels, (2) each line in the primary scanning direction has an area having consecutive high tonal pixels, and (3) the percentage of an area in which high tonal pixels included in the same line in the primary scanning direction are consecutive in the primary scanning and secondary scanning directions is less than 50%. By using such a pattern image, suppression of insufficient separation of the protective sheet and improvement of the visual recognizability of a printed article can be realized. 
     OTHER EMBODIMENTS 
     Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as a ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. 
     This application claims the benefit of Japanese Patent Application No. 2015-83705, filed on Apr. 15, 2015, which is hereby incorporated by reference herein in its entirety.