Patent Publication Number: US-2016236482-A1

Title: Method for printing surface of battery cell

Description:
TECHNICAL FIELD 
     The present invention relates to a method of printing the surface of a battery cell and, more particularly, to a method of printing information on the surface of a battery cell using a heat transfer machine, the method including unwinding a heat transfer film having an adhesion layer for indicating the information stacked on a release paper from a heat transfer roller, on which the heat transfer film is wound, locating the heat transfer film on one major surface of the battery cell, applying heat and pressure to the heat transfer film to attach the adhesion layer of the heat transfer film to one major surface of the battery cell, and winding the release paper of the heat transfer film on a release paper roller. 
     BACKGROUND ART 
     As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased. Among such secondary batteries is a lithium secondary battery having high energy density and operating voltage and excellent charge retention and service-life characteristics, which has been widely used as an energy source for various electronic products as well as for the mobile devices. 
     Depending upon the kind of an external device in which a secondary battery is used, the secondary battery may be configured to have a detachable type structure in which the secondary battery can be easily inserted into and removed from the external device or to have an embedded type structure in which the secondary battery is embedded in the external device. For example, the secondary battery can be inserted into or removed from devices, such as laptop computers, as needed. On the other hand, devices, such as some kinds of mobile phones and MPEG Audio Layer-3 (MP3) players, require an embedded type battery pack due to the structure or capacity thereof. 
     Product information of the secondary battery is indicated on the surface of the secondary battery such that a user may recognize characteristics, performance, and use of the secondary battery. That is, product information, such as type, voltage, and capacity, of the secondary battery is printed on the surface of the secondary battery such that the user can easily recognize product information of the secondary battery so as to prevent improper use of the secondary battery and to estimate performance of the secondary battery. 
     The product information may be indicated on the secondary battery using various methods. For example, a label having product information printed thereon may be attached to the surface of the secondary battery. In this case, however, air bubbles may be formed at the surface of the secondary battery when the label is attached to the surface of the secondary battery or the label, which has already been attached to the surface of the secondary battery, may be separated from the surface of the secondary battery. 
     In recent years, on the other hand, a PAD printing method has been used to print the product information on the secondary battery. In the PAD printing method, however, it takes too much time to set various conditions for PAD printing due to various factors. In addition, it may be difficult to maintain a printing machine for PAD printing. Furthermore, it is necessary to perform ultraviolet (UV) irradiation after the PAD printing, which leads to incurrence of cost related to equipment and processes necessary to perform the UV irradiation. 
     Consequently, there is a high necessity for a technology that is capable of fundamentally solving the above problems. 
     DISCLOSURE 
     Technical Problem 
     Therefore, the present invention has been made to solve the above problems and other technical problems that have yet to be resolved. 
     Specifically, it is an object of the present invention to provide a method of printing the surface of a battery cell that is capable of printing product information on the surface of the battery cell through a simplified process. 
     It is another object of the present invention to provide a battery cell having battery cell information printed thereon using the method of printing information on the surface of the battery cell. 
     Technical Solution 
     In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a method of printing information on the surface of a battery cell using a heat transfer machine, the method including unwinding a heat transfer film having an adhesion layer for indicating the information stacked on a release paper from a heat transfer roller, on which the heat transfer film is wound, locating the heat transfer film on one major surface of the battery cell, applying heat and pressure to the heat transfer film to attach the adhesion layer of the heat transfer film to one major surface of the battery cell, and winding the release paper of the heat transfer film on a release paper roller. 
     In the method of printing the surface of the battery cell according to the present invention as described above, therefore, it is possible to solve problems, such as generation of air bubbles or separation, caused during a conventional process of printing battery cell information on a battery cell using a label attachment method or a PAD printing method or problems, such as high expense necessary to acquire equipment, thereby providing an effect of printing battery cell information on the surface of the battery cell through a simplified process and with low expense. 
     The heat transfer machine, which prints information on the surface of the battery cell, may be configured to have a structure including the heat transfer roller, on which the heat transfer film is wound, a heat stamp for applying heat and pressure to the heat transfer film unwound from the heat transfer roller on the battery cell, the release paper roller, on which the release paper is wound after heat is transferred to the battery cell, and a battery cell feeder for feeding a plurality of battery cells such that heat is sequentially transferred to the battery cells. 
     The heat stamp may perform heat transfer at a temperature which does not cause chemical change of the battery cell. Specifically, the heat stamp may perform heat transfer at a temperature of 30 to 60° C. In a case in which heat transfer is carried out at a temperature of less than 30° C., a portion of the adhesion layer of the heat transfer film may not be attached to the surface of the battery cell, which is not preferable. In a case in which heat transfer is carried out at a temperature of more than 60° C., on the other hand, the battery cell may be deteriorated with the result that reaction between electrode active materials and an electrolyte of the battery cell may be accelerated to generate gas and the battery cell may expand due to the gas generated in the battery cell, which is also not preferable. 
     In addition, the heat stamp may apply a pressure of 0.5 to 1.5 bar to the heat transfer film and the battery cell. In a case in which the pressure is less than 0.5 bar, it may be difficult to attach the adhesion layer of the heat transfer film to the surface of the battery cell, which is not preferable. In a case in which the pressure is more than 1.5 bar, on the other hand, electrodes of the battery cell may be twisted or damaged, which is also not preferable. 
     Meanwhile, a concrete process of printing information on the surface of the battery cell using the heat transfer machine with the above-stated construction is as follows. 
     First, the heat transfer film is unwound form the heat transfer roller and then the heat transfer film is located on one major surface of the battery cell. Subsequently, the heat stamp applies heat and pressure to the heat transfer film such that the heat transfer film is attached to one major surface of the battery cell. The adhesion layer of the heat transfer film is attached to the battery cell and the release paper, from which the adhesion layer is separated, is wound on the release paper roller. 
     In the present invention, adhesion layers of the heat transfer film are arranged on the release paper at predetermined intervals and battery cells are fed by the battery cell feeder such that heat is sequentially transferred to the respective battery cells. Consequently, it is possible to continuously transfer heat to the surfaces of the battery cells through rotation of the heat transfer roller and the release paper roller and operation of the battery cell feeder. 
     The heat transfer film may be configured to have a structure in which the adhesion layer is stacked on the release paper. The adhesion layer may be configured to have a structure in which a print layer and an adhesive layer are stacked. Battery cell information may be printed on the print layer and the adhesive layer may attach the print layer to the surface of the battery cell when heat and pressure are applied to the heat transfer film. 
     The material for the print layer is not particularly restricted . For example, the print layer may be formed of paper, polymer resin, or metal. 
     In addition, the battery cell information of the print layer may include any one or a combination of two or more selected from among a manufacturing company, logo, manufacturing date, type, voltage, and capacity of the battery cell. Some or all of the battery cell information may be formed as a code that can be recognized by an additional recognition device. For example, some or all of the battery cell information may be formed as a barcode or a quick response (QR) code. 
     Type of the battery cell is not particularly restricted. For example, the battery cell may be configured to have a structure in which an electrode assembly impregnated with an electrolyte and having a cathode, an anode, and a separator disposed between the cathode and the anode, is mounted in a prismatic can or a pouch-shaped case made of a laminate sheet. 
     That is, the battery cell may be a prismatic battery cell having an electrode assembly received in a prismatic can or a pouch-shaped battery cell configured to have a structure in which an electrode assembly is received in a pouch-shaped case made of a laminate sheet. 
     The prismatic can may be configured to have a rectangular parallelepiped structure open at the upper end thereof. The prismatic battery cell may be manufactured by receiving an electrode assembly in the prismatic can and coupling an insulative plate to the upper end of the prismatic can. 
     The laminate sheet may include a resin layer exhibiting high durability, a metal blocking layer, and a resin sealant layer exhibiting a high thermal bonding property. The resin layer may be thermally bonded. 
     It is required for the resin layer to exhibit high resistance against external environment. That is, it is required for the resin layer to exhibit more than a predetermined tensile strength and weather resistance. For this reason, the resin layer may be made of a polymer resin, such as polyethylene terephthalate (PET) or oriented nylon film; however, the present invention is not limited thereto. 
     The metal blocking layer may function to prevent introduction or leakage of foreign matter, such as gas and moisture and, in addition, to enhance strength of the battery case. To this end, the metal blocking layer may be formed of aluminum. 
     The resin sealant layer may be made of a polyolefin-based resin which exhibits a high thermal bonding property (a high thermal adhesive property) and a low hygroscopic property, which is necessary to restrain permeation of an electrolyte, and is not expanded or is not corroded by the electrolyte. In a concrete example, the resin sealant layer may be made of a cast polypropylene (CPP) resin. 
     In the present invention, the battery cell may be a lithium secondary battery exhibiting high energy density and discharge voltage. Examples of the lithium secondary battery may include a lithium ion secondary battery and a lithium polymer secondary battery. In addition, the lithium secondary battery may further include a nickel metal hydride secondary battery. 
     In accordance with another aspect of the present invention, there is provided a battery cell having battery cell information printed thereon using the method of printing the surface of the battery cell as described above. 
     In accordance with a further aspect of the present invention, there is provided a device including the battery cell with the above-stated construction as a power source. 
     Concrete examples of the device, in which the battery cell may be used, may include, a mobile phone, a portable computer, a smart phone, a smart pad, a netbook computer, a light electronic vehicle (LEV), an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, and a power storage device. 
     The structure and manufacturing method of the device are well known in the art to which the present invention pertains and, therefore, a detailed description thereof will be omitted. 
    
    
     
       DESCRIPTION OF DRAWINGS 
       The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a typical view showing a process of printing the surface of a battery cell according to an embodiment of the present invention; 
         FIG. 2  is a flowchart showing a method of printing the surface of a battery cell according to an embodiment of the present invention; and 
         FIG. 3  is a typical view showing a prismatic battery cell having battery cell information printed thereon. 
     
    
    
     BEST MODE 
     Now, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted, however, that the scope of the present invention is not limited by the illustrated embodiments. 
       FIG. 1  is a typical view showing a process of printing the surface of a battery cell according to an embodiment of the present invention and  FIG. 2  is a flowchart showing a method of printing the surface of a battery cell according to an embodiment of the present invention. 
     Referring to  FIGS. 1 and 2 , a heat transfer machine  100  is configured to have a structure including a heat transfer roller  110 , on which a heat transfer film  200  is wound, a heat stamp  130  for applying heat and pressure to the heat transfer film  200  unwound from the heat transfer roller  110  on a battery cell  304 , a release paper roller  120 , on which a release paper  210  is wound after heat is transferred to the battery cell  304 , and a battery cell feeder (not shown) for feeding a plurality of battery cells  302 ,  304 , and  306  such that heat is sequentially transferred to the battery cells  302 ,  304 , and  306 . 
     A process of printing the surfaces of the battery cells  302 ,  304 , and  306  using the heat transfer machine  100  with the above-stated construction is as follows. 
     First, a heat transfer film  200  having adhesion layers  220  stacked on a release paper  210  is prepared. Each of the adhesion layers  220  includes a print layer having battery cell information printed thereon and an adhesive layer configured to be attached to a battery cell during a heat transfer process. The adhesion layers  220  are arranged on the release paper  210  at predetermined intervals. In this way, the heat transfer film  200  is manufactured. 
     The manufactured heat transfer film  200  is wound on the heat transfer roller  110  of the heat transfer machine  100 . Subsequently, the manufactured heat transfer film  200  wound on the heat transfer roller  110  is unwound such that one of the adhesion layers  220  of the heat transfer film  200  is located on one major surface of the battery cell  304 . Subsequently, the heat stamp  130  applies heat having a temperature of 40 to 50° C. and a pressure of 1 bar to the heat transfer film  200  such that one of the adhesion layers  220  of the heat transfer film  200  is attached to one major surface of the battery cell  304 . The release paper  210 , from which one of the adhesion layers  220  is separated, is wound on the release paper roller  120 . 
     The battery cell feeder sequentially feeds the battery cells  302 ,  304 , and  306  such that the surfaces of the battery cells  302 ,  304 , and  306  are printed through the heat transfer process. Consequently, it is possible to continuously transfer heat to the surfaces of the battery cells  302 ,  304 , and  306  through rotation of the heat transfer roller  110  and the release paper roller  120  and operation of the battery cell feeder. 
       FIG. 3  is a typical view showing a battery cell having battery cell information printed thereon using a process of printing the surface of a battery cell according to an embodiment of the present invention. 
     Referring to  FIG. 3 , a battery cell  300  is configured to have a structure in which an electrode assembly is mounted in a prismatic battery cell case  310  configured to have a rectangular parallelepiped structure open at one side thereof and a cap plate  320  is coupled to the open side of the battery cell case  310 . Battery cell information  330  is printed on one major surface of the battery cell case  310 . The battery cell information  330  is printed on the surface of the battery cell case  310  through the process described with reference to  FIGS. 1 and 2 . 
     The battery cell information  330  includes a manufacturing company, logo, manufacturing date, type, voltage, and capacity of a battery cell or caution during use of the battery cell. Some of the battery cell information is indicated as a barcode  332 . 
     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. 
     INDUSTRIAL APPLICABILITY 
     As is apparent from the above description, in the method of printing the surface of the battery cell according to the present invention, it is possible to solve problems, such as generation of air bubbles or separation, caused during a conventional process of printing battery cell information on a battery cell using a label attachment method or a PAD printing method or problems, such as high expense necessary to acquire equipment, thereby providing an effect of printing battery cell information on the surface of the battery cell through a simplified process and with low expense.