Abstract:
A coating apparatus to apply a coating solution onto a base material, including a first body portion, a second body portion spaced-apart by a gap from the first body portion, a coating solution inlet arranged in one region of the second body portion, a coating solution passage connecting the coating solution inlet to said gap, a coating solution outlet arranged at one end of the gap to discharge the coating solution supplied to the coating solution inlet and a gap adjusting arrangement including a plurality of gap adjusting portions arranged on the first body portion to adjust a size of the coating solution outlet, the plurality of gap adjusting portions being arranged in a width direction of the base material.

Description:
CLAIM OF PRIORITY 
     This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for COATING APPARATUS AND METHOD FOR COATING USING THE SAME earlier filed in the Korean Intellectual Priority Office on 13 Dec. 2010 and there duly assigned Serial No. 10-2010-0126938. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     An aspect of the present invention relates to a coating apparatus and a method for coating using the same, which can maintain a coating thickness with equal quality. 
     2. Description of the Related Art 
     In general, a coating apparatus is assembled with a gap of a predetermined thickness, formed in the middle thereof. Here, the gap is a space through which a coating solution emerges from the coating apparatus. When coating is performed on a coating object by using the coating apparatus, the gap is adjusted to control the thickness of the coating. 
     First, there is a method for adjusting a gap in a coating apparatus using a bolt and a nut. In this method, the gap is adjusted according to the pitch of the bolt, but it is difficult to perform minute adjustments. Further, since the bolt itself receives a reaction force applied thereto, the gap is not adjusted as necessary when the bolt is rotated. In addition, when a forward mode is changed into a backward mode or when the backward mode is changed into the forward mode, a backlash phenomenon occurs. 
     Since it is difficult to adjust the gap at ordinary times in the coating apparatus using the bolt and the nut, the method is practically used to perform initial setting. If the gap is continuously adjusted by using the bolt and the nut, damage occurs due to the friction between the bolt and the nut. 
     Next, there is a method for adjusting a gap in a coating apparatus using expansion and contraction of metal due to temperature changes. However, this method is complicated and has low response speed. Further, the expansion and contraction of metal due to temperature changes are influenced by the limited range of temperature. As a result, there is a need for a practical design for a coating apparatus that allows for adjustments to the gap while the coating apparatus is in use to provide a coating having uniform characteristics. 
     SUMMARY OF THE INVENTION 
     Embodiments provide a coating apparatus and a method for coating using the same, which can automatically/manually control the thickness of coating by using an air pressure controller when the coating is performed on a coating object. 
     According to an aspect of the present invention, there is provided a coating apparatus including a first body portion, a second body portion spaced-apart by a gap from the first body portion, a coating solution inlet arranged in one region of the second body portion, a coating solution passage connecting the coating solution inlet to said gap, a coating solution outlet arranged at one end of the gap to discharge the coating solution supplied to the coating solution inlet and a gap adjusting arrangement including a plurality of gap adjusting portions arranged on the first body portion to adjust a size of the coating solution outlet, the plurality of gap adjusting portions being arranged in a width direction of the base material. 
     Each of the first and second body portions may include an inclined surface that narrows toward the coating solution outlet. The first body portion may further include a concave portion extending in the width direction of the base material from one region of the inclined surface of the first body portion to the coating solution outlet. The coating apparatus may also include a protruding portion arranged at the concave portion along the width direction of the base material and a plurality of grooves arranged at intervals at an end portion of the protruding portion. The gap adjusting portion may include an air pressure cylinder that includes a moving member having one end inserted into one of the grooves of the protruding portion, the moving member may move in accordance to an air pressure supplied to the air pressure cylinder. The air pressure cylinder may also include a forward air pressure controller and a backward air pressure controller. The coating apparatus may also include an air pressure controller and a switching valve to control forward and backward movements of the moving member of the air pressure cylinder. 
     A side of the coating solution outlet in the first body portion may include a material having elasticity. The coating apparatus may also include a coating thickness sensing portion arranged on a side of the coating apparatus opposite from that of the gap adjusting arrangement. The coating apparatus may also include a coating solution supply portion arranged at an outside of the coating solution inlet to supply the coating solution to the coating solution inlet. The coating apparatus may also include a spacer arranged within a portion of the gap between the first and second body portions opposite the coating solution outlet. 
     According to another aspect of the present invention, there is provided a method of coating a coating solution to a base material using a coating apparatus, the method including supplying the coating solution to a coating solution inlet of the coating apparatus, coating the coating solution onto the base material by discharging the coating solution from a coating solution outlet of the coating apparatus, determining whether a coating thickness of the coating solution on the base material is uniform by measuring the coating thickness using a coating thickness sensing portion of the coating apparatus and controlling a rate of discharge of the coating solution ejected from the coating solution outlet by changing a size of the coating solution outlet via a gap adjusting portion of the coating apparatus upon the coating thickness being determined to be non-uniform. 
     The controlling the rate of the coating solution discharged from the coating apparatus may include narrowing a size of the coating solution outlet in a region of the coating apparatus by moving a moving member of the gap adjusting portion forward upon determination that said coating thickness on a corresponding region of said base material is thicker than that of other regions. The controlling the rate of discharge of the coating solution ejected may instead include widening a size of the coating solution outlet in a region of the coating apparatus by moving a moving member of the gap adjusting portion backward upon determination that said coating thickness on a corresponding region of said base material is thinner than that of other regions. In the controlling of the rate of discharge of the coating solution ejected from the coating apparatus, a moving member of the gap adjusting portion may be moved forward or backward by forward and backward by a plurality of air pressure controllers respectively. In the controlling of the rate of discharge of the coating solution ejected from the coating apparatus, a moving member of the gap adjusting portion may be moved forward or backward by an air pressure controller and a switching valve. The gap adjusting portion may include an oil pressure cylinder that may include a moving member that may vary a size of an opening of the coating solution outlet by moving either forward or backward a moving member which pushes on or releases a force to or from an elastic sidewall of the coating solution outlet by varying an amount of pressure applied to the oil pressure cylinder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the invention, and many of the attendant advantages thereof, will be readily apparent as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein: 
         FIG. 1  is a schematic view illustrating a process for preparing a base material by using a coating apparatus according to the present invention; 
         FIG. 2  is a perspective view of a coating apparatus according to an embodiment of the present invention; 
         FIG. 3  is a graph showing variations of a coating gap with respect to pressures applied to an air cylinder; 
         FIG. 4  is a sectional view showing a forward state of an air cylinder mounted to the coating apparatus according to the embodiment of the present invention; 
         FIG. 5  is a sectional view showing a backward state of the air cylinder mounted to the coating apparatus according to the embodiment of the present invention; and 
         FIG. 6  is a sectional view showing a state that coating is performed on a coating object by using a coating apparatus according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. In addition, when an element is referred to as being “on” another element, it can be directly on the another element or be indirectly on the another element with one or more intervening elements interposed therebetween. Also, when an element is referred to as being “connected to” another element, it can be directly connected to the another element or be indirectly connected to the another element with one or more intervening elements interposed therebetween. Hereinafter, like reference numerals refer to like elements. In the drawings, the thickness or size of layers are exaggerated for clarity and not necessarily drawn to scale. 
     Turning now to  FIG. 1 ,  FIG. 1  is a schematic view illustrating a process for preparing a base material by using a coating apparatus according to the present invention. Referring to  FIG. 1 , a base material wound around rolls  20  at both sides is provided to be continuously transferred, and a coating apparatus  30 , a drying apparatus  40  and a slitting apparatus  50  are sequentially provided at the top side of the base material. The coating apparatus  30  according to the present invention may be used in a variety of fields, however a coating apparatus to coat an active material slurry on a metallic material of a secondary battery will be described in the following embodiments. 
     First, a binder solution is made by mixing a binder and a solvent together. An active material and a conducting agent or additive is then mixed with the binder solution, thereby preparing an active material slurry. Subsequently, the active material slurry is coated on a metallic material that is a collector by using the coating apparatus  30 , and then dried using the drying apparatus  40 . Subsequently, rolling is performed to increase the capacity density of the active material, and slitting is then performed using the slitting apparatus  50 , thereby obtaining an electrode plate with a constant width. 
     Here, the active material slurry is in a state that it contains the solvent, and the active material is in a state that the solvent is removed by drying the active material slurry. 
     Turning now to  FIG. 2 ,  FIG. 2  is a perspective view of a coating apparatus according to an embodiment of the present invention. Referring to  FIG. 2 , the coating apparatus  30  according to this embodiment includes a first body portion  30   a , a second body portion  30   b , a coating solution inlet  31 , a coating solution outlet  32  and a gap adjusting portion  80 . 
     The first and second body portions  30   a  and  30   b  are assembled with a predetermined gap A interposed therebetween. The gap A may be formed by a spacer  60  positioned between the first and second body portions  30   a  and  30   b . That is, the gap A between the first and second body portions  30   a  and  30   b  is primarily determined by the spacer  60 , and may be adjusted by the gap adjusting portion  80  which will be described later. Here, the spacer  60  may be positioned at the top side of the gap A between the first and second body portions  30   a  and  30   b.    
     One side of the gap A between the first and second body portions  30   a  and  30   b  may be used as the coating solution outlet  32 . The coating solution inlet  31  is formed in one region of the second body portion  30   b . The coating solution inlet  31  may be extended to a coating solution passage  36  passed though up to the gap A. A coating solution supply portion  70  to supply a coating solution may be further formed at an outside of the coating solution inlet  31 . 
     Accordingly, if the coating solution supplied from the coating solution supply portion  70  is injected through the coating solution inlet  31 , the injected coating solution moves along the coating solution passage  36  passed through up to the gap A. Then, the coating solution is jetted through the one side of the gap A between the first and second body portions  30   a  and  30   b , i.e., through the coating solution outlet  32 . Since the size of the gap A is identical to that of the coating solution outlet  32 , the thickness of the coating solution coated on a base material (not shown) is also determined accordingly. 
     In this instance, an inclined surface  37  narrowed toward the gap A may be formed at the side of the coating solution outlet  32  in each of the first and second body portions  30   a  and  30   b . A concave portion  33  is formed along the width direction of the base material (not shown) from one region of the inclined surface  37  to the coating solution outlet  32 . 
     The side of the coating solution outlet  32  in the first body portion  30   a  is narrowed by the concave portion  33 , and may be made out of a material with elasticity, such as rubber or urethane rubber. A protruding portion  35  is formed along the width direction of the base material at the concave portion  33 , and grooves  34  may be formed at a predetermined interval at an end portion of the protruding portion  35 . 
     The gap adjusting portion  80  may have a plurality of gap adjusting portions provided in the width direction of the base material on the inclined surface  37  of the first body portion  30   a . Here, the gap adjusting portion  80  may be an air pressure cylinder that includes a forward air pressure cylinder  80   a  and a backward air pressure cylinder  80   b . Accordingly, the forward and backward movements of a moving member  81  in the air pressure cylinder  80  can be selectively controlled according to the control of air pressure. 
     In this instance, one side of the moving member  81  in the air pressure cylinder  80  is inserted into the groove  34  of the protruding portion  35 , so that the protruding portion  35  moves according to the forward/backward movement of the air pressure cylinder  80 , and thus the size of the coating solution outlet  32  can be adjusted. 
     Here, the air pressure controllers  80   a  and  80   b  are apparatuses that regulate the pressure of air supplied to air pressure cylinder  80 . The air pressure controllers  80   a  and  80   b  are supplied with a high air pressure and output a desired and lower air pressure and supply the lower and desired air pressure to the air pressure cylinder  80 . Accordingly, the air pressure controllers  80   a  and  80   b  control the operational force of the air pressure cylinder  80 , and thus the size of the coating solution outlet  32  can be adjusted by the operational force. 
     The forward and backward air pressure controllers  80   a  and  80   b  may be operated in an automatic or manual mode. In a case where the forward and backward air pressure controllers  80   a  and  80   b  are operated in the automatic mode, they measure the thickness of the coating solution and then automatically adjust the coating thickness when it is unequal, so that coating can be more rapidly performed. 
     As described above, the size of the coating solution outlet  32  is changed to adjust the thickness of the coating solution coated on the base material by controlling the amount of the jetted coating solution. In the coating apparatus  30  of the present invention, a coating thickness sensing portion  90  may be further formed at the rear of the coating solution outlet  32  formed in the movement direction of the base material. In a case where the thickness of the coating solution is unequal, the coating thickness sensing portion  90  allows the air pressure cylinder  80  at a corresponding position to be operated, so that the thickness of the coating solution can be equally maintained. 
     Turning now to  FIG. 3 ,  FIG. 3  is a graph showing variations of a coating gap A with respect to pressures applied to an air cylinder. Referring to  FIGS. 2 and 3 , the gap A of the coating apparatus  30  may be adjusted by controlling the side of the coating solution outlet  32  in the first body portion  30   a  of the coating apparatus  30 , made out of a metallic material, using the air pressure cylinder  80  within the elastic limit range of the coating apparatus  30 . In this instance, the size of the gap A of the coating apparatus  30  is essentially linear with respect to pressure and is thus in proportion to the pressure of the air pressure cylinder  80 . Thus, the size of the gap A of the coating apparatus  30  can be determined from the pressure applied to the air pressure cylinder  80  by using the proportion relation. 
     Hereinafter, a measuring method of a variation in the gap A of the coating apparatus  30  using the internal pressure of the air pressure cylinder  80  will now be described. 
     σ=E×ε[σ: stress, E: elastic modulus, ε: deformation ratio] 
     F=K×x [F: force, K: spring modulus, x: extended length of spring] 
     ∵F=σ[since the force and the stress have the same system unit, a variation in the gap of the coating apparatus may be expressed using an extended length] 
     ∵F=P×A [F: operational force of air pressure cylinder, P: internal pressure of air pressure cylinder, A: internal area of air pressure cylinder] 
     ∵K×x=P×A→x=(P×A)/K 
     As can be seen through the measuring method described above, the size of the gap A of the coating apparatus  30  is in proportion to the internal pressure of the air pressure cylinder  80 . That is, it can be seen that as the internal pressure of the air pressure cylinder  80  is increased, the size of the gap A is also increased within the elastic limit range of the coating apparatus  30 . 
     Turning now to  FIGS. 4 and 5 ,  FIG. 4  is a sectional view showing a forward state of the air cylinder mounted to the coating apparatus according to the embodiment of the present invention and  FIG. 5  is a sectional view showing a backward state of the air cylinder mounted to the coating apparatus according to the embodiment of the present invention. 
     Referring to  FIGS. 4 and 5 , the coating apparatus is used when a coating solution  100  is coated on a base material  10 . The coating solution  100  is supplied to the coating solution inlet  31  by using the coating solution supply portion  70 , preferably a coating solution pump. The supplied coating solution  100  is jetted through the coating solution outlet  32  by passing through the coating solution passage  36  and moving to one side of the gap A between the first and second body portions  30   a  and  30   b . In this instance, the initial gap A of the coating apparatus  30  is determined by the spacer  60 . The thickness B of the coating solution  100  coated on the base material  10  is determined depending on the size of the gap A. Accordingly, the coating solution  100  with the equal thickness B is coated on the base material  10 . 
     However, the equal thickness B of the coating solution  100  cannot be maintained due to the limit of processing accuracy and the change in material properties of the coating solution  100 . Therefore, the thickness B of the coating solution B is controlled by adjusting the size of the gap A. In this instance, the size of the gap A may be adjusted using the air pressure cylinder  80  provided in the first body portion  30   a  of the coating apparatus  30 . The forward air pressure controller  80   a  and the backward air pressure controller  80   b  may be individually formed in the air pressure cylinder  80 . Accordingly, the thickness B of the coating solution  100  can be controlled by adjusting the size of the gap A to be wide or narrow. 
     A plurality of air pressure cylinders  80  may be provided in a direction perpendicular to the coating direction, i.e., in the width direction of the base material  10  to adjust the size of gap A at various points along the coating apparatus  30 . In this instance, a plurality of grooves  34  are formed at the end portion of the protruding portion  35  of the first body portion  30   a , and therefore, the location of the air pressure cylinders  80  may be changed. Accordingly, the thickness of the coating solution  100  in the coating width direction can be controlled by partially adjusting the gap A of the coating apparatus  30  in the width direction of the base material  10 . 
     Here, the coating apparatus  30  is further provided with the coating thickness sensing portion  90 , so that when a non-uniform thickness B of the coating solution  100  is sensed, one or more of the air pressure cylinders  80  can be operated. In a case where it is determined that the thickness B is thicker than those of other regions, the moving member  81  of the air pressure cylinder  80  moves forward so that the size of gap A and thus the size of coating solution outlet  32  is narrowed. Thus, the amount of the jetted coating solution  100  can be decreased. 
     In a case where it is determined that the thickness B is thinner than those of other regions, the moving member  81  of the air pressure cylinder  80  of the thin region moves backward so that the size of the coating solution outlet  32  is widened. Thus, the amount of the jetted coating solution  100  can be increased. Accordingly, it is possible to form the coating having a thickness B equal to those of other regions. 
     That is, in the forward movement, the moving member  81  inserted in the groove  34  of the protruding portion  35  moves forward, so that the size of the coating solution outlet  32  is narrowed. In the backward movement, the moving member  81  moves backward and pulls the first body portion  30   a  at the side of the coating solution outlet  32 , so that the size of the coating solution outlet  32  is widened. Here, the forward and backward movements of the air pressure cylinder  80  are performed by the forward and backward air pressure controllers  80   a  and  80   b , respectively. The forward and backward air pressure controllers  80   a  and  80   b  may be operated in an automatic or manual mode. 
     Turning now to  FIG. 6 ,  FIG. 6  is a sectional view showing a state that coating is performed on a coating object by using a coating apparatus  39  according to a second embodiment of the present invention. As in the first embodiment, coating apparatus  39  according to the second embodiment has a first body portion  39   a  and a second body portion  39   b . However, instead of using air pressure controllers  80   a  and  80   b  to control the air pressure cylinder  80  as in the first embodiment, the first body portion  39   a  of coating apparatus  39  of the second embodiment of  FIG. 6  includes one air pressure controller  82  and an air pressure valve  83  to control air pressure cylinder  80 . The air pressure switching valve  83  may be a 3-way air pressure switching valve, and can control an operational direction of the air pressure cylinder  80 . That is, the air pressure switching valve  83  can control a forward/backward direction of the air pressure cylinder  80 . Here, the air pressure controller  82  and the air pressure switching valve  83  may be operated in an automatic or manual mode. 
     Hereinafter, a method for adjusting a coating thickness using the coating apparatus according to the present invention will be described. 
     In the method for adjusting the coating thickness B using the coating apparatus  30  according to the present invention, the coating solution  100  is first supplied to the coating solution inlet  31 . Then, the coating solution  100  is jetted through the coating solution outlet  32  by passing through the coating solution passage  36 . The coating solution  100  jetted through the coating solution outlet  32  is coated on the transferred base material  10 . In this instance, the coating thickness sensing portion  90  determines whether the coating thickness B is uniform or non-uniform by measuring the coating thickness B. Here, if it is determined that the coating thickness B is not uniform, the coating solution outlet  32  is narrowed or widened to vary the coating solution outlet so that the coating thickness becomes uniform. 
     In a case where it is determined that the coating thickness B is thicker than those of other regions, the moving member  81  of the air pressure cylinder  80  moves forward, so that the size of the coating solution outlet  32  can be reduced. In a case where it is determined that the coating thickness B is thinner than those of other regions, the moving member  81  of the air pressure cylinder  80  moves backward, so that the size of the coating solution outlet  32  can be increased. 
     In this instance, the forward and backward movements of the air pressure cylinder  80  may be controlled by the forward and backward air pressure controllers  80   a  and  80   b , respectively. Alternatively, the forward and backward movements of the air pressure cylinder  80  may be controlled by the air pressure controller  82  and the air pressure switching valve  83  to control the forward/backward movement of the air pressure cylinder  80 . 
     As described above, according to embodiments of the present invention, in a case where the thickness of the coating solution is unequal due to the limit of processing accuracy in the coating apparatus and the change in material properties of the coating solution, the gap at a portion of the coating apparatus can be adjusted using the air pressure cylinder. Accordingly, it is possible to maintain the uniform thickness of the coating solution. 
     Although an apparatus for coating an active material layer on an electrode plate of a secondary battery has been described in the aforementioned embodiments, the present invention may be applied to apparatuses for coating any coating solution on other base materials. In addition, the present invention is not limited to the use of an air pressure cylinder to vary the size of the gap through which a solution passes, as an oil pressure cylinder may instead be used to vary the gap size and still be within the scope of the present invention. 
     While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.