Patent Publication Number: US-8525860-B2

Title: Printer

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2010-293606, filed on Dec. 28, 2010, the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a printer. 
     BACKGROUND 
     Conventionally, printers having a plurality of print heads as an image forming unit for forming an image on a medium are known. In this type of printer, a plurality of image forming units are used in forming ink images on a medium. Further, for forming the ink images, the printer may use a temperature-sensitive ink that changes its color according to the ambient temperature. 
     In the printer above, when forming an image with a temperature-sensitive ink on a medium, it is desirable to prevent any problems caused by the color change of the temperature-sensitive ink. Unfortunately, the conventional printer does not provide any suitable mechanism to control the color change of the temperature-sensitive ink. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating a schematic configuration of a printer according to a first embodiment. 
         FIGS. 2A and 2B  are explanatory views illustrating one example of the temperature-sensitive properties of a temperature-sensitive ink,  FIG. 2A  depicting the discoloring property of a temperature-sensitive ink having one threshold temperature and  FIG. 2B  depicting the discoloring property of a temperature-sensitive ink having two threshold temperatures. 
         FIG. 3  is a front view showing a cooling mechanism included in the printer. 
         FIGS. 4A and 4B  are section views showing a spouting portion included in the cooling mechanism shown in  FIG. 3 ,  FIG. 4A  illustrating a state in which a gas is spouted at a right angle with respect to a medium and  FIG. 4B  illustrating a state in which the gas is obliquely spouted with respect to the medium. 
         FIG. 5  is a plan view of a portion of the spouting portion of the cooling mechanism shown in  FIG. 3 , when seen from a front surface of a backing paper. 
         FIG. 6  is a perspective view of a blocking unit. 
         FIG. 7  is a side view illustrating a side surface of a blocking unit. 
         FIG. 8  is a block diagram showing one example of a control circuit included in the printer. 
         FIG. 9  is a block diagram showing one example of a CPU included in the printer. 
         FIGS. 10A and 10B  are views showing one example of a product label as a medium obtained in the printer,  FIG. 10A  illustrating a state in which images with a temperature-sensitive ink are hard to see (invisible) and  FIG. 10B  illustrating a state in which images with a temperature-sensitive ink are easy to see (visible). 
         FIGS. 11A and 11B  are side views schematically showing portions of ink ribbon cartridges included in the printer,  FIG. 11A  illustrating an ink ribbon cartridge having a long contact section over which an ink ribbon makes contact with a medium and  FIG. 11B  illustrating an ink ribbon cartridge having a short contact section over which an ink ribbon makes contact with a medium. 
         FIG. 12  is a plan view showing a movable plate included in a printer according to a modified example of the first embodiment. 
         FIG. 13  is a view showing one example of a product label as a medium obtained in the printer according to the modified example of the first embodiment. 
         FIG. 14  is a side view showing a schematic configuration of a printer according to a second embodiment. 
         FIG. 15  is a block diagram illustrating an exemplary control circuit included in a printer. 
     
    
    
     DETAILED DESCRIPTION 
     According to one embodiment of the present disclosure, a printer includes a conveying unit configured to convey a medium. The printer further includes an image forming unit provided in a conveyance path of the medium, the image forming unit being configured to form an image with a temperature-sensitive ink, whose color is changed depending on a temperature, on the medium. A cutter for cutting the medium is provided in the conveyance path downstream of a medium conveyance direction of the image forming unit. Further, a coloring conversion unit is provided in the conveyance path downstream of a medium conveyance direction of the cutter. The coloring conversion unit is configured to change a coloring state of the image of the temperature-sensitive ink by heating or cooling the image of the temperature-sensitive ink formed on the cut medium. 
     Certain embodiments will now be described in detail with reference to the drawings. The embodiments described below include like components. In the following description, like components will be designated by common reference symbols and will not be described repeatedly. 
       FIG. 1  is a side view illustrating a schematic configuration of a printer according to a first embodiment. In the present embodiment, a printer  1  is made up of, e.g., a thermal printer configured to heat an ink ribbon and transfer an ink to a medium M such as a paper. The medium M may be, e.g., a label like the one shown in  FIGS. 10A and 10B . A plurality of media M is attached to a surface of a strip-shaped backing paper  2  at a specified interval (pitch). Notches may be formed on the backing paper  2  so that the media M can be cut away from the backing paper  2 . 
     As shown in  FIG. 1 , in the printer  1 , a conveyance path P is formed with a conveying unit  50  at the inside of a body unit  1   a  to guide a roll  2   a  of the backing paper  2  to a discharge outlet  40 . Further, in the printer  1 , a print block  30 , a cutter  60 , and a cooling mechanism  10  are sequentially arranged from upstream toward downstream of a conveyance direction of the medium along the conveyance path P. 
     The printer  1  includes a body unit  1   a  to which a plurality of (four, in the present embodiment) ink ribbon cartridges  3  ( 3 A through  3 D) can be attached in a removable manner. The ink ribbon cartridges  3  are arranged side by side along a conveyance path P of the strip-shaped backing paper  2  defined inside the printer  1 . Each of the ink ribbon cartridges  3  includes a head (thermal head)  3   a  and an ink ribbon  3   d  (see  FIGS. 11A and 11B ). By causing the head  3   a  to heat the ink of the ink ribbon  3   d , each of the ink ribbon cartridges  3  forms ink images (not shown in  FIG. 1 ) on the medium M conveyed along the conveyance path P. In other words, the head (thermal head)  3   a  of each of the ink ribbon cartridges  3  corresponds to an image forming unit. The number of the ink ribbon cartridges  3  is not limited to four but may be set differently. 
     A roll  2   a  of the backing paper  2  is removably and rotatably mounted to the body unit  1   a  at the most upstream side of the conveyance path P. Upon rotation of conveying rollers  4 , the backing paper  2  is drawn away from the roll  2   a  and conveyed through the conveyance path P. 
     The conveyance path P is defined not only by the arrangement of the ink ribbon cartridges  3  but also by the arrangement of the conveying rollers  4  and auxiliary rollers  5 . The printer  1  includes a plurality of conveying rollers  4  rotationally driven by a motor  6 . Rotation of the motor  6  is transmitted to the respective conveying rollers  4  through a rotation-transmitting mechanism (or a speed-reducing mechanism)  7 . The printer  1  includes auxiliary rollers  5  arranged in such positions that the auxiliary rollers  5  pinch the backing paper  2  in cooperation with the conveying rollers  4  or in such positions that the backing paper  2  is stretched between the conveying rollers  4  or between the auxiliary rollers  5 . The printer  1  further includes a sensor  8  for detecting the medium M and a tension detecting mechanism  9  for detecting the tension of the backing paper  2 . In the present embodiment, the motor  6 , the rotation-transmitting mechanism  7 , the conveying rollers  4  and the auxiliary rollers  5  make up the conveying unit  50  for conveying the backing paper  2  (the medium M). 
     The print block  30  that forms a portion of the conveyance path P is installed downstream of the conveying unit  50  in the conveyance direction of the medium M. The print block  30  may include an ink ribbon cartridge  3  having an ink ribbon of non-temperature-sensitive ink whose color is not changed depending on a temperature. Further, the print block  30  may include an ink ribbon cartridge  3  having an ink ribbon of temperature-sensitive ink whose color is changed depending on a temperature. Additionally or alternatively, the print block  30  may include an ink ribbon cartridge  3  having a differently-colored ink ribbon (with a non-temperature-sensitive ink or a temperature-sensitive ink). Each of the ink ribbon cartridges  3  can be removably mounted in one of the mounting positions of the ink ribbon cartridges  3  ( 3 A through  3 D) provided in the print block  30  of the body unit  1   a.    
     Further, the conveying roller  4 , which is installed adjacent to the ink ribbon cartridge  3  and opposite to the head (thermal head)  3   a  with the ink ribbon  3   d  interposed therebetween, functions as a so-called platen roller. The conveying roller  4  functioning as a platen roller is disposed at a position below the conveyance path P, and the head (thermal head)  3   a  is provided above the conveyance path P, such that the head  3   a  detachably contacts with the conveying roller  4  through the conveyance path P. In this configuration, the conveying roller  4  is rotationally driven to convey the backing paper  2  (medium M) toward the discharge outlet  40 . 
     Among the temperature-sensitive inks is an ink whose coloring state varies above and below a threshold temperature Th as depicted in  FIG. 2A . For example, the temperature-sensitive ink depicted in  FIG. 2A  becomes white (S 2 ) if the temperature T exceeds the threshold temperature Th but is colored (S 1 ) if the temperature T is equal to or lower than the threshold temperature Th. If the medium M is a white color and the temperature-sensitive ink remains white (S 2 ), the temperature-sensitive ink images formed on the medium M are hard to see or invisible. The temperature-dependent change of the coloring state of the temperature-sensitive ink is reversible. 
     Among the temperature-sensitive inks, there is also an ink whose coloring state varies above and below two different threshold temperatures Th 1  and Th 2  when the temperature T goes up and down as depicted in  FIG. 2B . For example, the temperature-sensitive ink depicted in  FIG. 2B  remains white (S 2 ) if the temperature T, when going down, is higher than a first threshold temperature Th 1  but is colored (S 1 ) if the temperature T, when going down, becomes equal to or lower than the first threshold temperature Th 1 . If the medium M is a white color and the temperature-sensitive ink remains white (S 2 ), the temperature-sensitive ink images formed on the medium M are hard to see or invisible. The temperature-sensitive ink depicted in  FIG. 2B  remains colored (S 1 ) if the temperature T, when going up, is equal to or lower than a second threshold temperature Th 2  but becomes white (S 2 ) if the temperature T, when going up, grows higher than the second threshold temperature Th 2 . In this regard, the second threshold temperature Th 2  is higher than the first threshold temperature Th 1  as can be seen in  FIG. 2B . Therefore, as long as the temperature T remains between the first threshold temperature Th 1  and the second threshold temperature Th 2 , the coloring state of the temperature-sensitive ink in the falling process of the temperature T (i.e., changing from a temperature T exceeding the second threshold temperature Th 2  to a temperature T equal to or lower than the second threshold temperature Th 2 ) differs from the coloring state of the temperature-sensitive ink in the rising process of the temperature T (i.e., changing from a temperature T equal to or lower than the first threshold temperature Th 1  to a temperature T greater than the first threshold temperature Th 1 ). Since many different kinds of temperature-sensitive inks are available, it is possible to appropriately change the threshold temperatures Th, Th 1  and Th 2  and the coloring states. 
     In addition, the cutter  60  for cutting the backing paper  2  (medium M) being conveyed along the conveyance path P is installed downstream in the medium conveyance direction of the print block  30 . The cutter  60  forms a portion of the conveyance path P. 
     In the case of a thermal printer, the temperature T goes up during an image forming process (heat transfer process). Therefore, if images with a temperature-sensitive ink whose color is changed to the same color as the medium M at a temperature higher that the threshold temperatures Th, Th 1  and Th 2  mentioned above are formed on the medium M through the use of the printer  1 , it is often impossible or difficult to determine whether the temperature-sensitive ink images are successfully formed on the medium M. Depending on the kinds of temperature-sensitive inks, it is sometimes the case that the temperature-sensitive ink images formed on the medium M are hardly visible at a normal temperature. Therefore, in the present embodiment, the printer  1  includes a cooling mechanism  10  provided as a portion of the conveyance path P downstream in the medium conveyance direction of the cutter  60 , which serves as a coloring conversion mechanism for converting the coloring state of temperature-sensitive ink images formed on the medium M. The cooling mechanism  10  is disposed at a lower part of the conveyance path P and in the vicinity of the discharge outlet  40  in the printer  1 . In the present embodiment, the temperature T is reduced by, e.g., cooling the temperature-sensitive ink images with the cooling mechanism  10 . Thus, the temperature-sensitive ink images get visualized and become readily visible, thereby making it easy to check the formation situation of the temperature-sensitive ink images on the medium M. In other words, the cooling mechanism  10  may be referred to as a coloring conversion mechanism or a visualizing mechanism of temperature-sensitive ink images. 
     In the present embodiment, the cooling mechanism  10  is configured to spout, e.g., a gas, and reduce the temperature of the medium M, namely the temperature of the temperature-sensitive ink images, using the adiabatic expansion or the latent heat of the gas. More specifically, the cooling mechanism  10  includes a mounting portion  10   a  configured to hold a gas cartridge  11  of a gas cylinder, a spouting portion  10   b , a tube  10   c , a valve  10   d  and a cooling fin  10   e.    
     The gas cartridge  11  is removably mounted to the mounting portion  10   a . The mounting portion  10   a  serves as a connector for receiving a connector  11   a  of the gas cartridge  11 . The mounting portion  10   a  may include a movable lever (not shown) used in removing the gas cartridge  11  and a lock mechanism (not shown) for fixing the gas cartridge  11  in a mounting position. 
     The gas cartridge  11  may be made up of, e.g., a gas cylinder (gas bomb) filled with a liquefied gas. As the gas (coolant), it is possible to use, e.g., tetrafluoroethane. 
     As shown in  FIGS. 1 and 3 , the spouting portion  10   b  is arranged to extend in the width direction of the backing paper  2  along the rear surface of the backing paper  2 . The spouting portion  10   b  is a gas pipe having a gas flow path formed therein. Referring to  FIG. 5 , the spouting portion  10   b  has an upper wall  10   f  and a plurality of nozzle holes  10   g  formed side by side in the upper wall  10   f  at a regular interval (pitch). The gas is spouted from the nozzle holes  10   g  toward the rear surface of the backing paper  2 . The nozzle holes  10   g  may be arranged in plural rows. 
     The spouting portion  10   b  is supported by brackets  10   h  to rotate about a rotation axis Ax extending in the width direction of the backing paper  2  and is capable of changing the spouting angle (spouting direction) of the gas G as illustrated in  FIGS. 4A and 4B . More specifically, as shown in  FIG. 3 , the spouting portion  10   b  can be fixed at an arbitrary angle by arranging the spouting portion  10   b  at a specified spouting angle and then tightening nuts  10   j  to the male screw portions  10   i  of the spouting portion  10   b  inserted into the through-holes (not shown) of the brackets  10   h . The cooling degree of the backing paper  2  cooled by the gas G can be variably set by variably setting the spouting angle. For instance, cooling is more heavily performed in the arrangement shown in  FIG. 4A  than in the arrangement shown in  FIG. 4B . Thus, the temperature-sensitive ink images formed on the medium M have a lower temperature in the arrangement shown in  FIG. 4A  than in the arrangement shown in  FIG. 4B . In the present embodiment, the spouting portion  10   b  includes a spouting condition adjusting mechanism as set forth above. 
     The tube  10   c  has pressure resistance and flexibility required for the tube  10   c  to serve as a gas conduit between the mounting portion  10   a  and the spouting portion  10   b  regardless of the change of the angle of the spouting portion  10   b.    
     The valve  10   d  can switch the spouting of the gas from the spouting portion  10   b  and the blocking of the gas by opening or closing a gas flow path extending from the gas cartridge  11  to the spouting portion  10 . The valve  10   d  may be made up of, e.g., a solenoid valve which is opened in response to an electric signal supplied from a CPU  20   a  (see  FIG. 8 ). The valve  10   d  can be attached to the mounting portion  10   a . The spouting condition of the gas can be variably set by controlling the opening and closing of the valve  10   d  (e.g., the length of opening time, the number of repetition of opening and closing, and the period of repetition of opening and closing). 
     The cooling fin  10   e  includes a base portion  10   k  close to or adjoining the outer circumferential surface  11   b  of the gas cartridge  11  and a plurality of plate-shaped portions  10   m  extending in the conveying direction and protruding from the base portion  10   k  toward positions near the rear surface of the backing paper  2 . When the temperature of the gas cartridge  11  is reduced by spouting the gas, the cooling fin  10   e  can enhance the cooling performance for the medium M. The cooling mechanism  10  can be removably mounted to the body unit  1   a.    
     Further, a blocking unit  70  is provided between the cooling mechanism  10  and the print block  30  and blocks air cooled by the cooling mechanism  10  from staying at a predetermined point while preventing at least a portion of the air cooled by the cooling mechanism  10  from flowing into the print block  30 . The blocking unit  70  has a blower  71  configured to blow air cooled by the cooling mechanism  10  and a guide  72  configured to guide the air blown by the blower  71  such that the air does not reach the print block  30 . In one embodiment, the blocking unit  70  may further include a conveying roller  4  (see  FIG. 7 ) configured to convey the medium M. The conveying roller  4  may control the conveyance speed such that the medium M can stay in the blocking unit  70  for a predetermined period of time, thereby adjusting the cooling/heating duration of the medium M in the blocking unit  70 . 
       FIG. 6  is a perspective view illustrating the blocking unit  70  according to one embodiment. As shown in  FIG. 6 , the guide  72  of the blocking unit  70  is a member formed as a portion of the conveyance path P, the member configured to guide air blown by the blower  71  toward downstream of the medium conveyance direction of the medium M. The guide  72  may be formed with, for example, a metal material or a resin material. The guide  72  includes a front wall portion  72 A disposed in the downstream side of the medium conveyance direction of the conveyance path P, a rear wall portion  72 B disposed opposite the front wall portion  72 A, and a ceiling surface portion  72 C disposed in parallel to the conveyance path P, the ceiling surface portion  72 C connecting the front wall portion  72 A and the rear wall portion  72 B above the conveyance path P. 
       FIG. 7  is a side view of the blocking unit  70 . As shown in  FIG. 7 , a side cross-section of the guide  72  of the blocking unit  70  has an approximately concave shape. Further, a length of the guide  72  in its width direction Z is approximately equal to a width of the conveyance path P, and the guide  72  is disposed adjacent the upper surface side of the conveyance path P and aligned with the width of the conveyance path P. 
     The guide  72  having the above configuration guides air (wind) blown from the blower  71  toward the cooling mechanism  10  disposed below the blower  71  and discharges the air Y cooled in the cooling mechanism  10  through a discharge outlet O formed in a lower part of the front wall portion  72 A. 
     Further, the conveying roller  4  is installed in the blocking unit  70 . The conveying roller  4  is disposed above or in contact with the conveyance path P, and additionally in contact with the cooling mechanism  10  through the conveyance path P. By such a structure, as the conveying roller  4  is rotationally driven to apply a conveyance force to the backing paper  2  (medium M), the backing paper  2  (medium M) is conveyed toward the discharge outlet  40 . 
     Further, as shown in  FIG. 1 , the printer  1  includes a dew condensation removing member  16  in the body unit  1   a  at the periphery of the discharge outlet  40 . The dew condensation removing member  16  may be formed of, for example, a sponge material or a rubber scoop. As the dew condensation removing member  16  is provided in the body unit  1   a  at the periphery of the discharge outlet  40 , while the backing paper  2  is discharged from the discharge outlet  40  and the medium M attached on the backing paper  2  is colored, small amounts of moisture generated by dew condensation on the backing paper  2  can be removed. The removal of such moisture facilitates treatment of a printed and cut label (because the printed label may become easily detached from a cutting unit). 
     Further, as shown in  FIG. 8 , the control circuit  20  of the printer  1  includes a CPU (Central Processing Unit)  20   a  as a control unit, a ROM (Read Only Memory)  20   b , a RAM (Random Access Memory)  20   c , an NVRAM (Non-Volatile Random Access Memory)  20   d , a communication interface (I/F)  20   e , a conveying motor controller  20   f , a head controller  20   g , a ribbon motor controller  20   h , a valve controller  20   i , an input unit controller  20   j , an output unit controller  20   k  a sensor controller  20   m , a cutter motor controller  20   q , and a blower controller  20   r , all of which are connected to one another through a bus  20   n  such as an address bus or a data bus. 
     The CPU  20   a  controls each unit of the printer  1  by executing various kinds of computer-readable programs stored in the ROM  20   b  or other places. The ROM  20   b  stores, e.g., various kinds of data processed by the CPU  20   a  and various kinds of programs (such as a basic input/output system abbreviated as BIOS, an application program and a device driver program) executed by the CPU  20   a . The RAM  20   c  temporarily stores data and programs while the CPU  20   a  executes various kinds of programs. The NVRAM  20   d  stores, e.g., an OS (Operating System), an application program, a device driver program and various kinds of data which are to be kept intact even when the power is turned off. 
     Further, the communication interface (I/F)  20   e  controls data communication with other devices connected through telecommunication lines. 
     The conveying motor controller  20   f  controls the motor  6  pursuant to an instruction supplied from the CPU  20   a . The head controller  20   g  controls the head  3   a  (see  FIG. 11 ) in response to an instruction supplied from the CPU  20   a . The ribbon motor controller  20   h  controls a ribbon motor  3   b  built in each of the ink ribbon cartridges  3  according to an instruction supplied from the CPU  20   a . The valve controller  20   i  controls the valve  10   d  (the solenoid of the valve  10   d ) of the cooling mechanism  10  based on an instruction supplied from the CPU  20   a.    
     The cutter motor controller  20   q  controls driving of a cutter motor  61 , which in turn drives the cutter  60 , based on an instruction from the CPU  20   a . Further, the blower controller  20   r  controls driving of the blower  71  of the blocking unit  70  based on an instruction from the CPU  20   a.    
     The input unit controller  20   j  transmits to the CPU  20   a  signals inputted through an input unit  12  (e.g., push buttons, a touch panel, a keyboard, a microphone, knobs or DIP switches) for inputting manual operations or voices of a user. The output unit controller  20   k  controls an output unit  13  (e.g., a display, a light-emitting unit, a speaker or a buzzer) for outputting images or voices pursuant to an instruction supplied from the CPU  20   a . The sensor controller  20   m  transmits to the CPU  20   a  a signal indicative of the detection result of a sensor  8 . 
     Referring back to  FIG. 9 , the CPU  20   a  as a control unit works as a print control unit  21   a , a coloring conversion setting unit  21   b , a counter unit  21   c , a determination unit  21   d  and a coloring conversion control unit  21   e  according to the programs executed. The programs contain modules corresponding to at least the print control unit  21   a , the coloring conversion setting unit  21   b , the counter unit  21   c , the determination unit  21   d  and the coloring conversion control unit  21   e.    
     The print control unit  21   a  controls the motor  6 , the head  3   a , the ribbon motor  3   b , and the cutter motor  61  through the conveying motor controller  20   f , the head controller  20   g , the ribbon motor controller  20   h  and the cutter motor controller  20   q . Images such as letters or pictures are formed on the medium M under the control of the print control unit  21   a . A character or an image is formed on the medium M by operation of the print control unit  21   a . Further, by operation of the print control unit  21   a , the backing paper  2  (medium M) on which an image is formed is cut by the cutter  60  positioned downstream of the medium conveyance direction of the print block  30  on the conveyance path P and is conveyed to the cooling mechanism  10 . 
     The coloring conversion setting unit  21   b  performs various kinds of setting operations associated with the coloring conversion of the temperature-sensitive ink images printed on the medium M (the cooling performed by the cooling mechanism  10  in the present embodiment). More specifically, the coloring conversion setting unit  21   b  can cause the storage unit such as the NVRAM  20   d  to store a pitch (frequency) at which coloring conversion (cooling) is performed with respect to the medium M and a parameter for setting the opening or closing conditions of the valve  10   d  (e.g., the opening/closing timing, the opening/closing duration, the number of opening/closing times and the opening/closing time period), which are inputted through the input unit  12 . 
     The counter unit  21   c  counts the number of the media M (or the number of image formation areas) detected by the sensor  8 . The determination unit  21   d  compares the count value counted by the counter unit  21   c  with the pitch (frequency) stored in the storage unit and determines whether to perform coloring conversion (cooling in the present embodiment). The coloring conversion control unit  21   e  controls each part or unit (the respective parts of the cooling mechanism  10  in the present embodiment) in order to perform coloring conversion (cooling in the present embodiment) with respect to the medium M (the temperature-sensitive ink images formed on the medium M) that is determined to be subjected to coloring conversion. In the present embodiment, the coloring conversion control unit  21   e  performs the coloring conversion of the medium M by controlling the opening/closing state of the valve  10   d  and consequently controlling the spouting state of the gas. The coloring conversion control unit  21   e  also corresponds to the spouting condition adjusting mechanism. In the present embodiment, pursuant to the setting of the pitch (frequency), the coloring conversion can be performed with respect to the temperature-sensitive ink images formed on all the media M or some of the media M. 
     The printer  1  configured as above can produce, e.g., a medium M as illustrated in  FIG. 10A  or  10 B.  FIG. 10A  illustrates a product label as a medium M outputted from the printer  1  with no cooling performed by the cooling mechanism  10 .  FIG. 10B  illustrates a product label as a medium M outputted from the printer  1  with the cooling performed by the cooling mechanism  10 . The temperature-sensitive ink images Im 1  and Im 2  are visualized when the cooling is performed by the cooling mechanism  10 . Accordingly, a user or an operator of the printer  1  is easily able to visually recognize the formation of the temperature-sensitive ink images Im 1  and Im 2  on the medium M.  FIGS. 10A and 10B  illustrate a case where images Im 1  and Im 2  of two kinds of temperature-sensitive inks differing in threshold temperature Th are formed on the medium M. Moreover, an image Im 3  (e.g., a barcode) formed by a typical ink whose coloring state is not changed by the temperature is also formed on the medium M. 
     As one example, the medium M illustrated in  FIGS. 10A and 10B  can be used for temperature management in refrigerating or freezing a product. More specifically, the medium M on which the images Im 1  and Im 2  of the temperature-sensitive ink having the temperature-sensitive property depicted in  FIG. 2A  formed by the printer  1  is used as a product label. The printer  1  utilizes a temperature-sensitive ink having a threshold temperature Th as a management temperature (e.g., 5 degrees Celsius) that a product to be refrigerated or frozen is not allowed to exceed. As a result, if a product temperature exceeds the threshold temperature Th, the medium M comes into the state as illustrated in  FIG. 10A . Thus, the temperature-sensitive ink images Im 1  and Im 2  become hard to see or invisible (S 2  in  FIG. 2A ). On the other hand, if the product temperature is equal to or lower than the threshold temperature Th as the management temperature, the medium M is kept in the state illustrated in  FIG. 10B  (S 1  in  FIG. 2A ). This enables a worker or other persons to determine whether the product temperature is higher than or lower than the management temperature, based on whether the temperature-sensitive ink images Im 1  and Im 2  are easy to see (visible) or hard to see (invisible). In the example illustrated in  FIGS. 10A and 10B , the images Im 1  and Im 2  of two kinds of temperature-sensitive inks differing in the threshold temperature Th are formed on the medium M to thereby indicate the product management results in respect of two kinds of management temperatures (first and second management temperatures). In this example, the formation condition of the temperature-sensitive ink images Im 1  and Im 2  on the medium M can be visually confirmed by cooling the medium M with the cooling mechanism  10 . 
     As another example, images Im 1  and Im 2  of a temperature-sensitive ink with a temperature-sensitive property showing a hysteresis in temperature rising and falling processes as depicted in  FIG. 2B  can be formed by the printer  1  on a product label as a medium M illustrated in  FIGS. 10A and 10B . In this case, the printer  1  forms the images Im 1  and Im 2  on the medium M through the use of a temperature-sensitive ink having a threshold temperature Th 2  as a management temperature (e.g., −5 degrees Celsius) that a product to be refrigerated or frozen is not allowed to exceed and a threshold temperature Th 1  as a temperature (e.g., −30 degrees Celsius) that cannot be realized in a specified refrigerating or freezing state. In the printer  1 , the cooling mechanism  10  cools the images Im 1  and Im 2  to the threshold temperature Th 1  or lower (e.g., −40 degrees Celsius) so that the images Im 1  and Im 2  formed by the printer  1  can be visualized on the medium M. In the case of this example, all of the media M are cooled by the cooling mechanism  10  to first reduce the temperature of the media M to the threshold temperature Th 1  or lower. As a result, if a product temperature exceeds the threshold temperature Th 2  as the management temperature even for a single time, the medium M comes into the state illustrated in  FIG. 10A . Thus, the temperature-sensitive ink images Im 1  and Im 2  become hard to see or invisible (S 2  in  FIG. 2B ) and continue to remain in this state (S 2 ). On the other hand, if the product temperature is equal to or lower than the threshold temperature Th 2  as the management temperature, the medium M is kept in the state illustrated in  FIG. 10B  (S 1  in  FIG. 2B ). This enables a worker or other persons to determine whether the product temperature has ever exceeded the management temperature before, based on whether the temperature-sensitive ink images Im 1  and Im 2  are easy to see (visible) or hard to see (invisible). In this example, the images Im 1  and Im 2  of two kinds of temperature-sensitive inks differing in the threshold temperature Th 2  are formed on the medium M to thereby indicate the product management results in respect of two kinds of management temperatures (first and second management temperatures). 
     In the printer  1  of the present embodiment, as shown in  FIGS. 11A and 11B , it is possible to use ink ribbon cartridges  3  that differ from each other in the positions of the ribbon rollers  3   c  with respect to the head  3   a . In the configuration shown in  FIG. 11A , the ink ribbon  3   d  and the medium M make contact with each other for a long period of time. In the configuration shown in  FIG. 11B , the ink ribbon  3   d  and the medium M make contact with each other for a short period of time. One of these configurations can be selected depending on the properties of the temperature-sensitive ink or the non-temperature-sensitive ink. In the present embodiment, the ink ribbon cartridge  3  corresponds to an ink ribbon holding unit. The ribbon motor  3   b  and the ribbon rollers  3   c  make up a ribbon conveying unit. 
     In the printer  1  of the present embodiment described above, the head  3   a  of the ink ribbon cartridge  3  as an image forming unit forms temperature-sensitive ink images on the medium M and the cooling mechanism  10  as a coloring conversion mechanism converts the coloring of the images. According to the present embodiment, it is therefore possible to impart desired coloring states to the temperature-sensitive ink images formed on the medium M outputted from the printer  1 . It is also easy to confirm whether desired temperature-sensitive ink images are successfully formed on the medium M. 
     In the present embodiment, the cooling mechanism  10  as a coloring conversion mechanism reduces the temperature of the images by spouting a gas. This makes it possible to obtain the cooling mechanism  10  with a relatively simple structure. 
     In the present embodiment, the printer  1  includes, as the spouting condition adjusting mechanism for adjusting the spouting condition of the gas, a mechanism for adjusting the posture of the spouting portion  10   b  (e.g., the spouting direction of the gas G spouted from the nozzle holes  10   g ) and a mechanism for variably setting the gas spouting timing or the gas spouting time period (e.g., the opening/closing time period of the valve  10   d ). This makes it possible to suitably adjust the condition of the cooling performed by the gas. 
     As the spouting condition adjusting mechanism, it is possible to employ, e.g., a movable plate  14  for changing the number of effective nozzle holes  10   g  as shown in  FIG. 12 . The movable plate  14  is supported on the upper wall  10   f  of the spouting portion  10   b  to movably slide along the upper wall  10   f . The movable plate  14  has through-holes  14   a  overlapping with all of the nozzle holes  10   g  when the movable plate  14  is in one position and through-holes  14   b  overlapping with some of the nozzle holes  10   g  when the movable plate  14  is in another position. By sliding the movable plate  14 , it is possible to switch a state in which the gas is spouted from all of the nozzle holes  10   g  through the through-holes  14   a  and a state in which the gas is spouted from some of the nozzle holes  10   g  through the through-holes  14   b . This makes it possible to variably set the amount of the spouting gas, thereby variably setting the cooling degree of the temperature-sensitive ink images. 
     In the present embodiment, the printer  1  includes the heads  3   a  of the ink ribbon cartridges  3  as a plurality of image forming units for forming images with different temperature-sensitive inks on the medium M. Accordingly, a plurality of ink images differing in temperature-sensitive property can be formed on the medium M, which makes it possible to perform temperature management in multiple stages. 
     In the present embodiment, the cooling mechanism  10  cools the temperature-sensitive ink image extracted (selected or designated) and converts the coloring state thereof. This configuration can reduce energy consumption as compared with a case where all the temperature-sensitive ink images are cooled. 
     In the printer  1 , it is also possible to use a temperature-sensitive ink having a property opposite to the property of the temperature-sensitive ink stated above, namely a temperature-sensitive ink having such property that the temperature-sensitive ink is visualized when the temperature thereof exceeds a management temperature. For example, as shown in  FIG. 13 , if the ink temperature is higher than the threshold temperature, a message of “caution” or “warning” indicating that the temperature of the temperature-sensitive ink image Im 4  or Im 5  has exceeded the management temperature appears on the medium M as a product label. In this example, images Im 4  and Im 5  of temperature-sensitive inks differing in the threshold temperature are formed on the medium M, which makes it possible to manage a product at different temperatures. In the printer  1  corresponding to the example shown in  FIG. 13 , a heating mechanism instead of the cooling mechanism  10  can be provided as the coloring conversion mechanism. In this example, it is equally possible to form the temperature-sensitive ink images Im 4  and Im 5  over a non-temperature-sensitive ink image Imb formed on the medium M. In this example, the temperature-sensitive ink images Im 4  and Im 5  are visualized to issue a caution notice or a warning notice when a specified temperature condition is not satisfied. 
     The present embodiment may resolve the problem that it cannot be determined whether a desired image of temperature-sensitive ink is formed on the medium M after the medium M is cut by the cutter. This problem occurs when an image of temperature-sensitive ink formed on the medium M, whose coloring state is changed by the cooling mechanism  10  as a coloring conversion unit, disappears due to a factor such as a temperature increase until the medium M is cut by the cutter  60 . However, according to the present embodiment, the cutter  60  is provided upstream of the cooling mechanism  10  as a coloring conversion unit. This makes it possible to determine the coloring state of the image of temperature-sensitive ink immediately after the medium M having an image of temperature-sensitive ink formed thereon, whose coloring state has been changed by the coloring conversion unit, is discharged from a discharge outlet. Thus, in forming an image of temperature-sensitive ink on the medium M in a printer, the above problem caused by a change in the coloring of the temperature-sensitive ink can be resolved. 
     The following is a description of a second embodiment of the present disclosure. Further, the same elements as those of the first embodiment are denoted by the same reference numerals and a description thereof will be omitted. 
       FIG. 14  is a side view illustrating a schematic configuration of a printer according to a second embodiment. As shown in  FIG. 14 , a printer  101  according to the present embodiment disposes a cooling element  90  as a coloring conversion unit, instead of the cooling mechanism  10  of the printer  1  of the first embodiment, below the conveyance path P. The cooling element  90  may be implemented using, for example, a Peltier element. The Peltier element is cooled by air blown by the blower  71  of a blocking unit  70 . The blocking unit  70  includes the conveying roller  4  (see  FIG. 7 ), which controls the cooling/heating duration of the medium M by controlling the conveyance speed of the medium M. 
     The operation of the cooling element  90  is controlled by a cooling element controller  20   s  based on an instruction from a CPU  20   a , as shown in  FIG. 15 . 
     According to the present embodiment, the cooling element  90  (provided instead of the cooling mechanism  10  in the printer  1  of the first embodiment) can be implemented at a smaller size, compared with the cooling mechanism  10  of the printer  1  of the first embodiment. This results in a decrease in the size of the printer. Also, in performing the cooling process, a change in humidity decreases, and noise and vibration can be suppressed. 
     While certain preferred embodiments have been described above, the present disclosure is not limited thereto but may be modified in many different forms. For example, the printer may include three or more image forming units for forming images with different temperature-sensitive inks. The printer may include both the cooling mechanism and the heating mechanism as the coloring conversion mechanism. In this case, one of the cooling mechanism and the heating mechanism may be caused to act on the temperature-sensitive ink images to first bring the images into an easy-to-see (visible) state. Thereafter, the other may be caused to act on the temperature-sensitive ink images to bring the images into a hard-to-see (invisible) state (namely, to return the images to the original state). This enables a worker or other persons to confirm the temperature-sensitive ink images in the easy-to-see (visible) state. The number of the cooling mechanism and the heating mechanism may be changed to many other numbers. 
     The printer may include a spouting portion for spouting a cold gas or a hot gas as the cooling mechanism or the heating mechanism. A cold gas or a hot gas can be fed from the outside to the spouting portion through a connector and a pipe. In this configuration, it is possible to omit the gas cartridge, which makes it possible to reduce the size of the printer proportionate to the omission of the gas cartridge. 
     The printer may be configured from a printer of another type using ink (e.g., an inkjet printer). In case of an inkjet printer, an ink head corresponds to the image forming unit. 
     The specifications (type, structure, shape, size, arrangement, position, number, constituent or temperature-sensitive property) of the respective components (the print system, the printer, the medium, the ink ribbon cartridge, the image forming unit, the coloring conversion mechanism, the cooling mechanism, the heating mechanism, the spouting condition adjusting mechanism, the coloring conversion device, the image or the temperature-sensitive ink) may be appropriately modified and embodied. 
     According to the above embodiments and modified examples, in forming an image of temperature-sensitive ink on the medium M in a printer, the problems caused by the change in the coloring of the temperature-sensitive ink can be resolved. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the disclosures. Indeed, the novel apparatuses described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the disclosures. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the disclosures.