Slot die coater

Abstract

The slot die coater of the present invention is a slot die coater having a slot for discharging a coating liquid in a direction opposite to gravity onto a substrate surface that is continuously driven and transported by a coating roll, comprising: a first die block installed at a base; a second die block forming the slot between itself and the first die block; and a bending unit connected to the lower end of the base, and is configured such that when the center of the rotation axis of the coating roll is changed relative to the slot die coater, the bending center by the bending unit is also changed.

Description

Technology Field

[0001] The present invention relates to a slot die coater, and more specifically, to a vertical die type slot die coater in which the direction of discharge of the coating liquid is opposite to the direction of gravity. Background Technology

[0002] Secondary batteries, which possess electrical characteristics such as high energy density and high applicability across product groups, are widely applied not only to portable devices but also to electric vehicles (EVs) or hybrid electric vehicles (HEVs) powered by electric sources. These secondary batteries are attracting attention as a new energy source for enhancing eco-friendliness and energy efficiency, not only for the primary advantage of drastically reducing the use of fossil fuels but also because they generate no by-products from energy use.

[0003] These secondary batteries essentially include an electrode assembly, which is a power generation element. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are stacked at least once, and the positive electrode and the negative electrode are manufactured by coating and drying a positive active material slurry and a negative active material slurry, respectively, onto a current collector made of aluminum foil and copper foil. In order to make the charge and discharge characteristics of the secondary battery uniform, these positive active material slurries and negative active material slurries must be evenly coated onto the current collector, and a slot die coater has been used conventionally.

[0004] Figure 1 is a cross-sectional view showing a conventional slot die coater.

[0005] Referring to FIG. 1, in a conventional method for manufacturing electrodes using a slot die coater (1), an electrode active material slurry discharged from the slot die coater (1) is applied onto a current collector (3) that is transported by a coating roll (2). The electrode active material slurry discharged from the slot die coater (1) is widely applied to one surface of the current collector (3) to form an active material layer. The slot die coater (1) includes two die blocks (4, 5) and has a slot (6) formed between the two die blocks (4, 5). A single layer of active material can be formed by discharging one type of electrode active material slurry through a discharge port (7) connected to the slot (6). The slot die coater (1) has the advantage of enabling high-speed application compared to bar coating or comma coating, and is widely applied from the perspective of high productivity. The slot die coater (1) exemplified in FIG. 1 is a vertical die type in which the electrode active material slurry is discharged in a direction opposite to gravity.

[0006] In order to manufacture high-energy-density secondary batteries, the thickness of the active material layer, which was about 130 μm, is gradually increasing to reach 300 μm. When a thick active material layer is formed using a conventional slot die coater (1), migration of binders and conductive materials within the electrode active material slurry intensifies during drying, resulting in an unevenly manufactured final electrode. To solve this problem, if the active material layer is coated in two stages—such as by applying a thin layer, drying it, and then applying it again and drying it—there is a disadvantage that it takes a long time. To simultaneously improve electrode performance and productivity, a dual slot die coater equipped with two slots is required to simultaneously apply two types of electrode active material slurries to form a double layer of upper and lower layers.

[0007] Since slot die coaters form slots on the bonding surfaces of die blocks, three die blocks are basically required to have two slots, as in a dual slot die coater. In a process using such a dual slot die coater, forming each active material layer to a desired thickness is quite challenging because electrode active material slurries must be discharged simultaneously from different discharge ports connected to each of the two slots.

[0008] In addition, the distance from the discharge port (7) to the surface of the current collector (3) is a coating gap, which is a very important variable in determining the coating quality of the active material layer. Generally, the thickness of the active material layer is affected by the discharge amount of electrode active material slurry through the discharge port (7), the type of electrode active material slurry, and this coating gap. In addition, stable coating is possible only if the coating gap is uniform in the width direction (TD direction) of the current collector, and if there is a deviation in the coating gap in the width direction, it has a significant effect on the coating width and the shape of the boundary of the uncoated area. Since even a change of only a few micrometers in the thickness of the active material layer can seriously affect the coating quality, it must be managed very strictly, and in order to stably perform uniform coating in the width direction of the current collector, it is necessary to manage it very strictly to exhibit uniform dimensional accuracy in the width direction.

[0009] However, when the width of the slot die coater (1) increases in order to use a wide current collector to increase production volume, it becomes more difficult to apply uniform coating in the width direction, and thus more precise control of the coating gap becomes necessary. In addition, as shown in FIG. 1, the coating roll (2) has curvature, and the current collector (3) placed on it also has curvature, so the coating gap changes depending on the position. Specifically, when the center of the coating roll (2) and the discharge port (7) are aligned in a line, the coating gap is minimal at the aligned position, and the coating gap increases as it deviates from the aligned position.

[0010] In particular, coating processes utilizing dual-slot die coaters require the simultaneous discharge and application of electrode active material slurries from different discharge ports, making coating gap management even more critical. Furthermore, issues such as leakage and side rings become more severe and problematic compared to when forming a single layer. Among these, leakage refers to the instability where a portion of the coating solution is lost upstream from outside the die lip, which forms the leading edge of the die block. This implies a loss of pre-measured coating solution, making it impossible to predict the final coating thickness. Such leakage can cause the coating solution to remain stagnant for extended periods and solidify, or lead to variations in coating thickness along the width direction. Leakage can be exacerbated, especially when the coating gap is lowered to several hundred micrometers and the coating solution is discharged under high pressure to achieve thin film coating or to reduce variations in the width direction of the coating layer. As such, the coating gap is linked to leakage and must be managed precisely. The problem to be solved

[0011] The present invention was conceived in consideration of the aforementioned problems, and the problem that the present invention aims to solve is to provide a slot die coater capable of precise control of the coating gap and suppression of leakage.

[0012] However, the technical problems that the present invention aims to solve are not limited to those described above, and other unmentioned problems will be clearly understood by those skilled in the art from the description of the invention below. means of solving the problem

[0013] The slot die coater of the present invention for solving the above-mentioned problem is a slot die coater having a slot for discharging a coating liquid in a direction opposite to gravity onto a substrate surface that is continuously driven and transported by a coating roll, comprising: a first die block installed at a base; a second die block forming the slot between itself and the first die block; and a bending unit connected to the lower end of the base, and is configured such that when the center of the rotation axis of the coating roll is changed relative to the slot die coater, the bending center by the bending unit is also changed.

[0014] The center of the rotation axis of the coating roll may be positioned toward the second die block direction rather than the upper part of the first die rib forming the leading edge of the first die block with respect to the substrate.

[0015] The hole formed in the base to connect the bending unit and the base can be formed as a front-rear elongated hole, thereby enabling the position of the bending unit to be changed.

[0016] It may further include a third die block disposed on the front of the second die block and forming an additional slot between it and the second die block.

[0017] The cross-section of the second die block above may be a right triangle.

[0018] The first die block, the second die block, and the third die block each have a first die lip, a second die lip, and a third die lip forming the leading edge of each die, and the center of the rotation axis of the coating roll is located toward the second die block rather than the upper part of the first die lip with respect to the substrate, and the first die lip, the second die lip, and the third die lip may be located on the same straight line, or the third die lip may be recessed from the first die lip or the second die lip.

[0019] The first die block, the second die block, and the third die block each have a first die lip, a second die lip, and a third die lip forming the leading edge of each die, and the center of the rotation axis of the coating roll is positioned toward the second die block rather than the upper part of the first die lip with respect to the substrate, and the first die lip may be retracted from the second die lip or the third die lip, or the second die lip may be retracted from the first die lip or the third die lip, or the third die lip may be advanced from the first die lip or the second die lip.

[0020] The thickness of the third die rib may be greater than the thickness of the first die rib and the thickness of the second die rib.

[0021] The thickness of the third die rib may be equal to the thickness of the first die rib and greater than the thickness of the second die rib.

[0022] The first die block may be vertically installed integrally with the base at the rear part of the upper surface of the base, and the second die block may be positioned at the front of the first die block.

[0023] The second die block above may not come into contact with the base, or even if it does, it may form a bending space between itself and the base.

[0024] The position of the bending unit may be adjustable so that the center of the rotation axis of the coating roll is aligned with the bending center of the bending unit.

[0025] A hole formed in the base to connect the bending unit and the base may be formed as a front-rear elongated hole, so that the center of the rotation axis of the coating roll is aligned with the bending center of the bending unit.

[0026] The above elongated hole may be in a shape that extends from behind the upper part of the first die lip to in front of the lower part of the third die lip forming the tip of the third die block.

[0027] The coating roll rotates clockwise, and the substrate is transported from upstream to downstream, and the first die block may be on the downstream side and the second die block may be on the upstream side. Effects of the invention

[0028] According to the present invention, it is easy to adjust and maintain the distance between the die lip and the substrate, that is, the coating gap, to a desired degree.

[0029] According to the present invention, the center of rotation of the coating roll and the center of bending can be aligned at any part of the die rib of a vertical die-type slot die coater.

[0030] According to the present invention, by forming a hole for connecting the bending unit and the base as an elongated hole, the bending center can move together when the vertical die alignment position is changed. According to the present invention, the position change and alignment of the rotation axis center of the coating roll and the bending center are easy, and since the coating gap is maintained without significant change during the process, the occurrence of coating gap deviation in the width direction perpendicular to the travel direction of the substrate can be suppressed.

[0031] According to the present invention, the coating gap can be precisely maintained by taking into account the curvature of the coating roll. According to the present invention, by maintaining a uniform (±2%) coating gap, the coating amount and the resulting coating quality can be uniformly controlled. Therefore, by using a slot die coater with a uniform coating gap, a coated product of uniform quality, particularly an electrode for a secondary battery, can be obtained.

[0032] According to the present invention, a space for bending may be secured in a slot die coater. Bending deforms the area that needs to be aligned, and according to the present invention, even when using a bending unit for controlling coating uniformity in the width direction, the deformation is performed with high uniformity. As such, according to the present invention, the deformation of the die blocks can be controlled very uniformly, thereby providing excellent coating uniformity, and a major advantage is that this can be easily achieved.

[0033] When using the slot die coater of the present invention to manufacture electrodes for secondary batteries by applying an electrode active material slurry onto a current collector while driving the current collector, there is an advantage that uniform coating is possible even under high-speed driving or wide-width coating conditions.

[0034] In particular, according to the present invention, by moving the center of the rotation axis of the coating roll toward the second die block rather than the upper part of the first die lip, the effect of preventing back leak during coating is excellent. In particular, when applied to a dual slot die coater, the coating gap between the upper and lower layers is made uniform, thereby ensuring individual loading quality of the upper and lower layers.

[0035] In addition, according to the present invention, the bending center is also easily moved together, so by moving the center of the rotation axis of the coating roll and the bending center toward the second die block rather than the upper part of the first die lip, the pressure part where the bending force by the bending unit is applied can be made to have the smallest coating gap, thereby maintaining the bending effect (sensitivity).

[0036] As such, using the slot die coater according to the present invention allows for the uniform formation of a coating layer, particularly an active material layer, with a desired thickness, and preferably enables the simultaneous coating of two types of electrode active material slurries, thereby providing excellent effects in both performance and productivity. Brief explanation of the drawing

[0037] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further enhance understanding of the technical concept of the present invention together with the detailed description of the invention provided below; therefore, the present invention should not be interpreted as being limited only to the matters described in such drawings. FIG. 1 is a schematic cross-sectional view of a slot die coater according to the prior art. FIG. 2 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention. Figure 3 is a schematic perspective view of the slot die coater of Figure 2. Fig. 4 is an exploded perspective view of Fig. 3. FIG. 5 illustrates another embodiment of a core that can be included in the slot die coater of FIG. 2. Fig. 6 is a variation of Fig. 3. FIG. 7 illustrates a hole for connecting a bending unit included in the slot die coater of FIG. 2 and a base. FIG. 8 is a schematic cross-sectional view of a dual slot die coater according to another embodiment of the present invention. Figures 9 and 10 are enlarged views of section A of Figure 8. FIG. 11 is a schematic cross-sectional view of a dual slot die coater according to a comparative example. Figure 12 is a graph simulating the coating gap at different positions when the center of the rotation axis of the coating roll is aligned with the upper part of the first die lip, as in the comparative example. FIG. 13 is a graph simulating the coating gap at each position when the center of the rotation axis of the coating roll is aligned with the lower part of the first die lip according to one embodiment of the present invention. FIG. 14 is a graph simulating the coating gap at different positions when the center of the rotation axis of the coating roll is aligned with the upper part of the second die lip according to another embodiment of the present invention. FIG. 15 illustrates the results of a center and side loading test according to the bending level, while changing only the center alignment of the rotation axis of the coating roll from the bottom of the first die lip to the top of the third die lip without moving the bending center. Fig. 16 is a variation of Fig. 8. Specific details for implementing the invention

[0038] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. Prior to this, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention. Accordingly, the embodiments described in this specification and the configurations illustrated in the drawings are merely some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention; therefore, it should be understood that various equivalents and modifications capable of replacing them may exist at the time of filing this application.

[0039] The slot die coater of the present invention is a device equipped with one or two slots for discharging a coating liquid in a direction opposite to gravity, and for coating a coating liquid onto a substrate in a single layer or a double layer. The "substrate" described below is a current collector, and the "coating liquid" is an electrode active material slurry. In the case of double-layer coating, both the first coating liquid and the second coating liquid are electrode active material slurries, and may refer to electrode active material slurries that are identical or different in composition (type of active material, conductive material, binder), content (amount of active material, conductive material, binder), or physical properties. The slot die coater or dual slot die coater of the present invention is optimized for forming electrodes of secondary batteries. In particular, the dual slot die coater is optimized for pattern coating by simultaneously applying two types of electrode active material slurries or by alternately applying two types of electrode active material slurries. However, the scope of the rights of the present invention is not necessarily limited thereto. For example, the above-mentioned substrate may be a porous support constituting a separator, and the first coating solution and the second coating solution may be organic materials with different compositions or physical properties. That is, if thin film coating is required, the above-mentioned substrate, the first coating solution, and the second coating solution may be any of them.

[0040] FIG. 2 is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention. FIG. 3 is a schematic perspective view of the slot die coater of FIG. 2, and FIG. 4 is an exploded perspective view of FIG. 3. FIG. 5 illustrates another embodiment of a core that may be included in the slot die coater of FIG. 2. FIG. 6 is a variation of FIG. 3. FIG. 2 may be a cross-sectional view taken along line II-II' of FIG. 3.

[0041] First, referring to FIGS. 2 and FIGS. 3, the slot die coater (100) is provided with one slot (115) and can discharge an electrode active material slurry through a discharge port (116) connected to the slot (115) to coat the electrode active material slurry on the surface of a substrate (60).

[0042] A slot die coater (100) is provided with a slot (115) for discharging a coating liquid, such as an electrode active material slurry, in a direction opposite to gravity onto the surface of a substrate (60) that is continuously driven and transported by a coating roll (50). To this end, the slot die coater (100) includes a first die block (110) and a second die block (120). The second die block (120) forms a slot (115) between it and the first die block (110).

[0043] The slot die coater (100) is installed with the direction of discharge of the coating liquid (X direction) nearly perpendicular (nearly ± 5 degrees). In an embodiment of the present invention, the X-axis direction shown in the drawing is the direction of discharge of the coating liquid, the Z-axis is the width direction or TD direction of the slot die coater (100), and the Y-axis direction is a horizontal direction perpendicular to both the X-axis direction and the Z-axis direction. In addition, the Y-axis direction refers to the front-back direction in relation to the die blocks. In particular, the Y-axis direction refers to the direction from the first die block (110) toward the second die block (120). In this specification, the direction from the first die block (110) toward the second die block (120) is defined as the front, and conversely, the direction from the second die block (120) toward the first die block (110) is defined as the back.

[0044] The first die block (110) and the second die block (120) each have a first die lip (112) and a second die lip (122) that form the leading edge of the substrate (60). The Y-axis direction may also refer to the up-and-down direction with respect to the die lip. The direction from the first die lip (112) toward the second die lip (122) is defined as downward, and conversely, the direction from the second die lip (122) toward the first die lip (112) is defined as upward.

[0045] The substrate (60) is transported by a coating roll (50), and the coating roll (50) can be positioned in the direction of discharging the coating liquid from the slot die coater (100). The slot die coater (100) can discharge the coating liquid in the direction opposite to gravity (X-axis direction), and can continuously or discontinuously coat the substrate (60) by discharging the coating liquid through the slot (115).

[0046] The coating roll (50) rotates around the center of the rotation axis (50_C). At this time, the center of the rotation axis (50_C) of the coating roll (50) is positioned toward the second die block (120) rather than the upper part (112a) of the first die lip (112) with respect to the substrate (60). Here, the upper part (112a) of the first die lip (112) refers to the left side of the first die lip (112) in the drawing. For reference, the lower part (112b) of the first die lip (112) refers to the right side of the first die lip (112) in the drawing. Here, the fact that the center of the rotation axis (50_C) of the coating roll (50) is positioned toward the second die block (120) rather than the upper part (112a) of the first die lip (112) with respect to the substrate (60) indicates that the center of the rotation axis (50_C) of the coating roll (50) is actively positioned toward the second die block (120) away from the upper part (112a) of the first die lip (112) to further avoid the error range that inevitably occurs when the center of the rotation axis (50_C) of the coating roll (50) is aligned straight with the upper part (112a) of the first die lip (112).

[0047] For example, even if the center of the rotation axis (50_C) of the coating roll (50) is aligned straight with the upper part (112a) of the first die lip (112), it may be aligned within a position approximately 50 μm apart from the front and back. In the present invention, the center of the rotation axis (50_C) of the coating roll (50) may be located further toward the second die block (120) from a position approximately 100 μm apart from the upper part (112a) of the first die lip (112) toward the lower part (112b) of the first die lip (112).

[0048] Preferably, the first die block (110) is vertically installed integrally with the base (105) at the rear portion of the upper surface (105a) of the base (105). Although the lower surface (110a), which is opposite to the direction in which the coating liquid is discharged from the first die block (110), is shown in FIG. 2, this lower surface (110a) may not be distinguishable when the first die block (110) and the base (105) are installed integrally. The upper cross-section of the first die block (110) may be formed in a triangular shape. The first die block (110) is a plate-like structure that extends along the width direction. The first die block (110) is placed and assembled with respect to the base (105). When the base (105) and the first die block (110) are integrally formed in this way, alignment with respect to the base (105) is not required, and they can be handled as a single unit, making handling convenient. The first die block (110), which is integral with the base (105), may also be called a body block. The XY cross-section of the first die block (110) can be seen as approximately L-shaped.

[0049] At this time, the slot (115) can be perpendicular to the donation (105).

[0050] The second die block (120) is positioned on the front of the first die block (110). The second die block (120) is also a plate-like structure that extends along the width direction. The upper cross-section of the second die block (120) may also be formed in a triangular shape.

[0051] The surface opposite to the direction in which the coating liquid is discharged from the first die block (110) and the second die block (120), that is, the lower surface (110a, 120a), is positioned nearly horizontally (YZ plane). Since these die blocks (110, 120) have parts where the corners formed by the surfaces are formed at right angles, there are right angles in the cross-section, and since a vertical or horizontal plane can be used as a reference plane, manufacturing and handling are easy and precision is guaranteed. In addition, when combining the first die block (110) and the second die block (120), the facing parts can be supported by each other with a high degree of surface contact, so fastening, fixing, and maintenance are excellent. Furthermore, the combined state of the first die block (110) and the second die block (120) has an overall shape of a rectangular prism, and only the upper part where the coating liquid is discharged has an oblique shape toward the substrate (60). The first die block (110) and the second die block (120) are made of, for example, SUS material. Easy-to-process materials such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L can be used. SUS has the advantages of being easy to process, inexpensive, having high corrosion resistance, and being able to be manufactured into a desired shape at a low cost.

[0052] A shim (117) forming a slot (115) may be provided between the first die block (110) and the second die block (120). By creating a gap between the first die block (110) and the second die block (120) through the shim (117), a slot (115) corresponding to a passage through which a coating liquid can flow may be formed. In this case, the thickness of the shim (117) determines the upper and lower width (slot gap) of the slot (115).

[0053] As can be seen in FIG. 4, the core (117) may have an opening (117a) formed by cutting at least one region. At this time, as shown in FIG. 5, the core (117) may have a plurality of openings (117a) formed by intermittently cutting the one region.

[0054] It is preferable that the shim (117) be made of a material having sealing properties, which also functions as a gasket to prevent the coating liquid from leaking through the gap between the first die block (110) and the second die block (120), except for the area where the discharge port (116) is formed.

[0055] Referring to FIG. 2, the first die block (110) may include a manifold (118) that receives a coating liquid and communicates with a slot (115). The manifold (118) may also be provided in the second die block (120). The manifold (118) may have a predetermined shape and depth. Although not shown in the drawing, this manifold (118) is connected to a coating liquid supply chamber (not shown) installed externally via a supply pipe to receive the coating liquid. When the manifold (118) is filled with coating liquid, the coating liquid is induced to flow along the slot (115) and discharged to the outside through the discharge port (116).

[0056] A shim (117) is provided between the first die block (110) and the second die block (120) to define the shape of the slot (115). The slot die coater (100) applies a coating liquid onto a substrate (60) by discharging it through an outlet (116) that is in communication with the slot (115). The coating width of the coating layer coated on the substrate (60) is determined by the width of the slot (115). If a change in the coating width is required, various coating widths can be achieved by changing the internal space of the manifold (118) and the shim (117) that determines the width of the slot (115).

[0057] The core (117) is interposed in the remaining portion of the edge area of ​​the opposing surfaces of the first die block (110) and the second die block (120), excluding one side. For example, as shown in FIG. 4, the width of the opening (117a) of the core (117) can be designed to be a so that an active material layer with a coating width of a is formed on the substrate (60) and a blank area is formed on both sides of the active material layer. The core (117) of FIG. 5 shows an example in which the width of the opening (117a) of the core (117) is designed to be b so that multiple active material layers with a coating width of b are formed on the substrate (60) and a blank area is formed on both sides of each active material layer. When such a core (117) is applied, a stripe pattern-shaped coating layer is formed on the substrate (60).

[0058] As illustrated in FIG. 2, the coating roll (50) can rotate clockwise around a horizontal rotation axis center (50_C). The substrate (60) can travel along its lower surface in the forward and backward direction (from right to left, i.e., from upstream to downstream).

[0059] As shown in FIGS. 2 to 4, the second die block (120) may not come into contact with the base (105) and thus may have a bending space (S) between the lower surface of the second die block (120) and the upper surface of the base (105). Alternatively, as shown in FIG. 6, even if the second die block (120) comes into contact with the base (105), a bending space (S) may be formed between it and the base (105).

[0060] In the example illustrated in FIGS. 2 to 4, the second die block (120) is formed to have a shorter length than the first die block (110), so that the second die block (120) does not come into contact with the base (105), and a bending space (S) is formed between the lower surface (120a) of the second die block (120) and the upper surface (105a) of the base (105). If the length of the first die block (110) is L and the length of the second die block (120) is L', then there is a relationship where L > L'. In this bending space (S), the front is open and the rear is formed as the front of the first die block (110), and both left and right sides are open in the width direction.

[0061] In the example illustrated in FIG. 6, the length L of the first die block (110) and the length L' of the second die block (120) are equal. Instead, the lower surface (120a) of the second die block (120) is formed with an uneven structure so that it intermittently contacts the upper surface (105a) of the base (105). The length of the second die block (120) in the contacting portion may be L', and the length of the second die block (120) in the non-contacting portion may be L' (L'=L>L'). In the example illustrated in FIG. 6, the lower surface (120a) of the second die block (120) contacts the upper surface (105a) of the base (105), thereby increasing the force with which the base (105) supports the second die block (120). The lower surface (120a) of the second die block (120) A bending space (S) is provided in the portion that is not in contact with the upper surface (105a) of the donation (105). A stress relief effect can be expected through this bending space (S).

[0062] As shown in FIG. 4, the first die block (110) and the second die block (120) can be fastened together by a connecting bolt (B). When the internal pressure of the die blocks (110, 120) increases due to the discharge of the coating liquid, torque due to the internal pressure may be generated starting from the connecting bolt (B), and as a result, the part furthest from the connecting bolt (B) receives the greatest force, causing the first die lip (112) and the second die lip (122) to separate. As shown in FIG. 6, if the lower surface (120a) of the second die block (120) is made to come into contact with the upper surface (105a) of the base (105), the contacting surfaces of the first die block (110) and the second die block (120) can be supported even if torque due to the internal pressure of the slot die coater (100) is generated.

[0063] In addition, regarding the assembly process of the die blocks, the lower surface (120a) of the second die block (120) is placed on the base (105) so as to be in contact with the upper surface (105a) of the base (105), and bolts (not shown) can be fastened from the underside of the base (105) to the second die block (120) at each contacting position. In this way, by fastening bolts at the contacting positions in advance and simultaneously grinding the first die rib (112) and the second die rib (122), it is possible to align each die rib on the same straight line solely by fastening bolts at the contacting positions.

[0064] Referring to FIG. 2, a bending unit (140) can be connected to the bottom of the base (105). The bending unit (140) can be fastened to a hole (H) formed at the bottom of the base (105). The bending unit (140) can deform the bending space (S) by pressing the lower surface (105b) of the base (105).

[0065] The bending unit (140) may be provided with a die connecting part (142) that is fastened to the lower surface (105b) of the base (105) and presses the base (105). The die connecting part (142) may include a die connecting part (142a) and a main body connecting part (142b). If the hole (H) formed in the base (105) to fasten the bending unit (140) and the base (105) is formed as a front-rear elongated hole, the position of the bending unit (140) can be changed in the front-rear direction (see bidirectional arrow) by changing the position of the die connecting part (142) connected thereto.

[0066] Since the bending effect changes depending on the change in the forward and backward direction of the rotation axis center (50_C) of the coating roll (50), it is desirable for the position of the bending center (142_C) to also change along with the rotation axis center (50_C) of the coating roll (50). The bending center (142_C) may point to the center of the die connection part (142). The bending center (142_C) may be located in the center portion in the width direction of the slot die coater (100).

[0067] As shown in FIG. 2, it is preferable that the center of the rotation axis (50_C) of the coating roll (50) and the bending center (142_C) be aligned with each other. Accordingly, the bending center (142_C) can coincide with the center of the rotation axis (50_C) of the coating roll (50) in the forward and backward directions of the slot die coater (100).

[0068] The bending unit (140) may include a servo motor (146) inside the main body (144). The servo motor (146) may be connected to a moving part (148) of the bending unit (140). The moving part (148) of the bending unit (140) is connected to a die connecting part (142). By the rotation of the servo motor (146), the moving part (148) can move in the X-axis direction and the -X-axis direction, and the die connecting part (142) connected thereto can press or pull the base (105) accordingly.

[0069] The pressure side where the bending force by the bending unit (140) is applied can be made to have the smallest coating gap. The pressure side is the bending center (142_C), and if this coincides with the rotation axis center (50_C) of the coating roll (50), the bending effect (sensitivity) can be maintained.

[0070] In FIG. 2, the center of the rotation axis (50_C) of the coating roll (50) is shown to be aligned with, for example, the lower part (112b) of the first die rib (112) so as to be moved toward the second die block (120) rather than the upper part (112a) of the first die rib (112).

[0071] When the center of the rotation axis (50_C) of the coating roll (50) and the lower part (112b) of the first die rib (112) are aligned in a line, the coating gap is minimized at the alignment position, and as it moves away from the alignment position, that is, as the coating gap increases in the forward and backward direction of the slot die coater (100).

[0072] The position of the bending unit (140) can be set so that when the vertical line (Lc) passes through the lower part (112b) of the first die rib (112) from the center of the rotation axis (50_C) of the coating roll (50), the bending center (142_C) also passes through. To this end, in the present invention, a hole (H) for connecting the bending unit (140) and the base (105) is formed as an elongated hole as shown in detail in FIG. 7 so that the bending center (142_C) can also move together when the vertical die alignment position is changed.

[0073] FIG. 7 illustrates a hole for connecting a bending unit included in the slot die coater of FIG. 2 and a base.

[0074] In an embodiment of the present invention, it is proposed that a hole (H) connecting the bending unit (140) and the base (105) be formed as an elongated hole. The elongated hole is formed in a shape that extends along the front-rear direction. A die connecting part (142a) is connected to the hole (H) of the elongated hole, and a main body connecting part (142b) is connected thereto so that the die connecting part (142) is connected to the base (105). Since the position of the die connecting part (142a) can be changed according to the front-rear direction when connecting the die connecting part (142a) to the hole (H) of the elongated hole, the die connecting part (142) connected thereto can be connected to a different position along the front-rear direction.

[0075] That is, since the hole (H) connecting the bending unit (140) and the base (105) is made into an elongated hole, the position of the bending unit (140) connected thereto can be moved. The position of the bending unit (140) may be located in the center part of the base (105) in the front-rear direction, or, if necessary, may be placed closer to the second die block (120) than to the first die block (120). The closer the part is to the bending unit (140), the greater the force it receives and the greater the bending effect. The bending unit (140) can push the base (105) toward the discharge direction or pull the base (105) toward the opposite direction of the discharge direction. The bending unit (140) can bend the base (105) by pushing or pulling it. The bending space (S) can be deformed. When the base (105) is bent, not only the first die block (110) formed integrally with the base (105) but also the second die block (120) connected to the first die block (110) by fastening it with a bolt (B) can be bent at the same time.

[0076] Preferably, the center of rotation (50_C) of the coating roll (50) is shifted toward the second die block (120) rather than the upper part (112a) of the first die lip (112). For example, the center of rotation (50_C) of the coating roll (50) is changed so that it is not aligned with the upper part (112a) of the first die lip (112), but rather to a lower part, such as the middle part of the first die lip (112), or the lower part (112b) of the first die block (110), or to another place, such as the second die block (120). Additionally, the bending center (142_C) is also changed to a position aligned with it. Through this, a stable coating bead can be formed.

[0077] If the center of the rotation axis (50_C) of the coating roll (50) is aligned with the upper part (112a) of the first die lip (112), the problem of the coating gap varying in the forward and backward directions of the slot die coater (100) due to the curvature of the coating roll (50) is severe, which can have an adverse effect on the coating quality. This will be explained in detail later in the comparative example below.

[0078] FIG. 8 is a schematic cross-sectional view of a dual slot die coater according to another embodiment of the present invention. FIG. 9 and FIG. 10 are enlarged views of section A of FIG. 8.

[0079] First, referring to FIG. 8, the dual slot die coater (200) has one more slot compared to the slot die coater (100) of FIG. 2.

[0080] To this end, the dual slot die coater (200) further includes a third die block (130) positioned on the front of the second die block (120) to form an additional slot (125) between it and the second die block (120). For convenience, the slot (115) between the first die block (110) and the second die block (120) will be referred to as the first slot (115), and the additional slot (125) between the second die block (120) and the third die block (130) will be referred to as the second slot (125).

[0081] A dual slot die coater (200) can coat a coating liquid, such as an electrode active material slurry, by extruding it through at least one of a first slot (115) and a second slot (125) onto the surface of a substrate (60) that is continuously moving. The dual slot die coater (200) can discharge the coating liquid in a direction opposite to gravity, and can simultaneously or alternately coat two types of coating liquids, which are the same or different from each other, by discharging them through the first slot (115) and the second slot (125) onto the substrate (60).

[0082] In a dual slot die coater (200), the first die block (110) may be called the top plate, the second die block (120) may be called the middle plate or inner die, and the third die block (130) may be called the bottom plate or outer die.

[0083] The second die block (120) of the present embodiment illustrated in FIG. 8 has a cross-section of a right triangle, but it is not necessarily limited to this shape and, for example, may have a cross-section of an isosceles triangle. When the cross-section is a right triangle, the first slot (115) is aligned almost perpendicularly with respect to the substrate (60), making it easy to control the discharge of the coating liquid through the first slot (115).

[0084] The third die block (130) may have an upper cross-section formed in a triangular shape. The third die block (130) is also a plate-like structure extending along the width direction. The third die block (130) is provided with a third die rib (132) that forms its tip portion with respect to the substrate (60).

[0085] A core (127) may also be provided between the second die block (120) and the third die block (130). The core (117) provided between the first die block (110) and the second die block (120) may be called the upper core (117), and the core (127) provided between the second die block (120) and the third die block (130) may be called the lower core (127). The upper core (117) and the lower core (127) may be the same.

[0086] Here, the lower surface of the second die block (120) and the lower surface of the third die block (130) do not come into contact with the base (105), so a bending space (S) can be provided between them and the upper surface of the base (105). Alternatively, the lower surface of the second die block (120) and the lower surface of the third die block (130) may have a configuration as described with reference to FIG. 6, so even if they come into contact with the base (105), a bending space (S) can be formed between them and the base (105). It has been explained that the first die block (110) contains a coating liquid and includes a manifold (118) that communicates with the first slot (115). The third die block (130) may contain a coating liquid that is the same as or different from the coating liquid and includes a manifold (138) that communicates with the second slot (125). For convenience, the manifold (118) formed in the first die block (110) may be called the upper manifold (118), and the manifold (138) formed in the third die block (130) may be called the lower manifold (138). The coating liquid contained in the upper manifold (118) may be called the first coating liquid (150), and the coating liquid contained in the lower manifold (138) may be called the second coating liquid (160). In this way, the manifolds (118, 138) are formed in the first die block (110) and the third die block (130), respectively. By doing so, the deformation of the second die block (120), which is structurally the weakest, can be reduced. Furthermore, by dividing the second die block (120) into a left die (rear) and a right die (front), and configuring the left die to move integrally with the first die block (110) and the right die to move integrally with the third die block (130), a structure can be implemented in which the left die block and the right die block can slide at the interface between the left die and the right die, thereby making it easier to implement a structure in which the position of the first slot (115) and the second slot (125) can be varied.

[0087] Referring to FIGS. 9 and 10, a first discharge port (116) communicating with a first slot (115) is formed between the first die lip (112) and the second die lip (122), and a second discharge port (126) communicating with a second slot (125) is formed between the second die lip (122) and the third die lip (132). The second discharge port (126) discharges a second coating liquid (160) contained in the lower manifold (138) shown in FIG. 8 onto a substrate (60). The first discharge port (116) is positioned spaced downstream from the second discharge port (126) in the coating direction and discharges a first coating liquid (150) contained in the upper manifold (118) shown in FIG. 8 onto a substrate (60). That is, the upper layer can be formed using the first discharge port (116) and the lower layer can be formed using the second discharge port (126) to form a double layer coating.

[0088] In this way, a coating roll (50) that is rotatably arranged is positioned on the discharge direction side of a dual slot die coater (200), and by rotating the coating roll (50) to drive the substrate (60) to be coated, the first coating liquid (150), which is a first electrode active material slurry, and the second coating liquid (160), which is a second electrode active material slurry, are continuously brought into contact with the surface of the substrate (60), thereby allowing a two-layer structure to be simultaneously coated on the substrate (60). The second coating liquid (160) is coated on the substrate (60) first to form a lower slurry layer, and almost simultaneously, the first coating liquid is coated on the lower slurry layer to form an upper slurry layer.

[0089] In this embodiment as well, the center of the rotation axis (50_C) of the coating roll (50) is moved toward the second die block (120) rather than the upper part (112a) of the first die rib (112).

[0090] In FIGS. 8 and 9, as a first reference line (L1), a vertical line from the center of the rotation axis (50_C) of the coating roll (50) is shown to be aligned with the upper part (112a) of the first die lip (112). In this embodiment, a vertical line (Lc) from the center of the rotation axis (50_C) of the coating roll (50) can be aligned to the right, that is, forward, of this first reference line (L1).

[0091] In FIGS. 8 and 9, as a second reference line (L2), a vertical line from the center of the rotation axis (50_C) of the coating roll (50) is shown aligned with the lower part (132b) of the third die lip (132). In this embodiment, a vertical line (Lc) from the center of the rotation axis (50_C) of the coating roll (50) can be aligned to the left, i.e., rear, of this second reference line (L2).

[0092] For example, the center of the rotation axis (50_C) of the coating roll (50) may be aligned with the middle of the first die rib (112) (between reference numerals 112a and 112b) and be in the LA position. A vertical line (Lc) passes through the middle of the first die rib (112) from the center of the rotation axis (50_C) of the coating roll (50).

[0093] As another example, the center of the rotation axis (50_C) of the coating roll (50) may be aligned with the upper part (122a) of the second die rib (122) and be in the LB position. A vertical line (Lc) passes through the upper part (122a) of the second die rib (122) from the center of the rotation axis (50_C) of the coating roll (50).

[0094] As another example, the center of the rotation axis (50_C) of the coating roll (50) may be aligned with the lower part (112b) of the first die rib (122). A vertical line (Lc) passes through the lower part (112b) of the first die rib (112) from the center of the rotation axis (50_C) of the coating roll (50).

[0095] As another example, the center of the rotation axis (50_C) of the coating roll (50) can be aligned at a point 1 mm away from the lower part (112b) of the first die rib (122) toward the second die rib (122). The position of the second die rib (122) can change depending on the thickness of the upper layer core (117). The point 1 mm away from the lower part (112b) of the first die rib (122) toward the second die rib (122) can be the upper part (122a) of the second die rib (122), i.e., the LB position, when the thickness of the upper layer core (117) is 1 mm.

[0096] As another example, the center of the rotation axis (50_C) of the coating roll (50) may be located in the middle of the second die rib (122) (between reference numerals 122a and 122b), in the lower part (122b) of the second die rib (122), or in the upper part (132a) of the third die rib (132).

[0097] At this time, since the bending effect changes depending on the change in the rotation axis center (50_C) of the coating roll (50), it is desirable for the position of the bending center (142_C) to change together. Therefore, preferably, the rotation axis center (50_C) of the coating roll (50) and the bending center (142_C) are aligned with each other.

[0098] For example, the position of the bending unit (140) is determined such that when the vertical line (Lc) passes through the middle of the first die rib (112) from the center of the rotation axis (50_C) of the coating roll (50), the bending center (142_C) also passes through. That is, when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the middle of the first die rib (112) and is in the LA position, the position of the bending unit (140) is changed so that the bending center (142_C) is also placed in the LA position.

[0099] Likewise, the position of the bending unit (140) is determined such that when the vertical line (Lc) passes from the center of the rotation axis (50_C) of the coating roll (50) through the upper part (122a) of the second die rib (122), the bending center (142_C) also passes through. That is, when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the upper part (122a) of the second die rib (122) and is in the LB position, the position of the bending unit (140) is changed so that the bending center (142_C) is also placed in the LB position.

[0100] To this end, the present invention explains that the hole (H) connecting the bending unit (140) and the base (105) is formed as an elongated hole, as shown in FIG. 7, so that the bending center (142_C) can also move together when the vertical die alignment position is changed.

[0101] Since the hole (H) connecting the bending unit (140) and the base (105) is made into an elongated hole, the position of the bending unit (140) connected thereto can be moved in the forward and backward directions (see double-direction arrow). The position of the bending unit (140) may be located in the center part of the base (105), or, if necessary, it may be placed closer to the second die block (120) or closer to the third die block (130). The closer the part is to the bending unit (140), the greater the force it receives and the greater the bending effect. The bending unit (140) may push the base (105) toward the discharge direction or pull the base (105) toward the opposite direction of the discharge direction.

[0102] Preferably, in the dual slot die coater (200), the center of rotational axis (50_C) of the coating roll (50) is aligned so as to be moved toward the second die block (120) rather than the upper part (112a) of the first die lip (112). For example, the center of rotational axis (50_C) of the coating roll (50) is changed to the lower part of the first die block (110) or another location, rather than being aligned to the upper part (112a) of the first die lip (112), that is, the upper part of the first die block (110). And, the bending center (142_C) is also changed to a position aligned with it. Through this, a stable coating bead can be formed.

[0103] Comparative example

[0104] FIG. 11 is a schematic cross-sectional view of a dual slot die coater according to a comparative example.

[0105] Referring to FIG. 11, the comparative example aligns the center of the rotation axis (50_C) of the coating roll (50) and the center of the bending (142_C) with the upper part (112a) of the first die rib (112), which is a ‘first die block upper part’ alignment method. In this way, the coating gap at the back bead (BB) becomes excessively large, so the coating bead is not formed stably, and a problem may arise where the coating bead is unstable and a back leak occurs, causing it to burst out backward.

[0106] FIG. 12 is a graph simulating the coating gap at different positions when the center of the rotation axis (50_C) of the coating roll is aligned with the upper part (112a) of the first die lip (112), as in the comparative example. It was assumed that the thickness of the shim (117, 127) is 1 mm and the diameter of the coating roll (50) is 350 mm.

[0107] In FIG. 12, the vertical axis represents the physical thickness and spacing of the die ribs (indicated as upper plate LIP, middle plate LIP, and lower plate LIP), with the unit being mm. The left side of the upper plate LIP is positioned at vertical axis 0, indicating alignment with the upper part (112a) of the first die rib (112). In FIG. 12, the horizontal axis represents the spacing between the die rib and the coating roll (indicated as C-Roll), with the unit being mm. The end of the die rib is at position 1 on the horizontal axis, and the outer edge of the coating roll at the center of the rotation axis (50_C) of the coating roll is at position 2.5. Therefore, the coating gap set for calculation is 1.5 mm. The additional gap for each die rib position is shown in FIG. 12. The additional gap is an increased value compared to the set coating gap of 1.5 mm.

[0108] The upper plate / upper refers to the upper part (112a) of the first die rib (112). Since the center of the rotation axis (50_C) of the coating roll is located at that position, the additional gap relative to the set coating gap is 0.0. The upper plate / lower is the additional gap at the lower part (112b) of the first die rib (112) and was calculated as 2.9 μm. The middle plate / upper is the additional gap at the upper part (122a) of the second die rib (122) and was calculated as 11.4 μm. The middle plate / middle is the additional gap at the midpoint between the upper part (122a) and the lower part (122b) of the second die rib (122) and was calculated as 17.9 μm. The middle plate / lower is the additional gap at the lower part (122b) of the second die rib (122) and was calculated as 25.7 μm. The lower plate / upper is an additional gap at the upper (132a) of the third die rib (132), calculated to be 44.4 μm. The lower plate / lower is an additional gap at the lower (132b) of the third die rib (132), calculated to be 137.7 μm. As such, the additional gap increases as it moves further away from where the center of the rotation axis (50_C) of the coating roll is located.

[0109] The additional gap in the upper layer was calculated as 7.1 μm by averaging the additional gap of 2.9 μm in the upper / lower plate and 11.4 μm in the middle / upper plate, and the additional gap in the lower layer was calculated as 35.0 μm by averaging the additional gap of 25.7 μm in the middle / lower plate and 44.4 μm in the lower / upper plate. Since the center of the rotation axis (50_C) of the coating roll is offset from the first die block (110) by aligning with the upper part (112a) of the first die rib (112), it can be seen that an additional coating gap of 27.9 μm (relative value of the lower additional gap) occurs in the lower layer due to the curvature of the coating roll (50).

[0110] In this way, when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the upper part (112a) of the first die rib (112), a problem arises in which the coating gap in the forward and backward directions of the slot die coater (100) varies significantly due to the curvature of the coating roll (50), and in particular, it can be confirmed that the coating gap increase is more severe in the lower part compared to the upper part.

[0111] In particular, in the case of a dual slot die coater (200), the upper and rear bead (BB) positions of the first die block (110), which are aligned positions, are farther apart than in a single-layer slot die coater (100), so the coating gap at the rear bead (BB) position becomes larger, making it particularly vulnerable to back leakage in the case of a double-layer coating aligned with the upper part of the first die block (110).

[0112] Examples

[0113] In the present invention, the center of the rotation axis (50_C) of the coating roll (50) is moved toward the second die block (120) rather than the upper part (112a) of the first die lip (112) to prevent back leakage.

[0114] FIG. 13 is a graph simulating the coating gap at different positions when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die lip (112) according to one embodiment of the present invention. As in the comparative example, conditions were assumed where the thickness of the shim (117, 127) is 1 mm and the diameter of the coating roll (50) is 350 mm.

[0115] As shown in FIG. 13, the additional gap for each die-lip position is compared with the comparative example as follows. Since the center of the rotation axis (50_C) of the coating roll is located at the top / bottom, the additional gap relative to the set coating gap is 0.0. Since the top / top is off from the center of the rotation axis (50_C) of the coating roll, the additional gap was calculated to be 2.9 μm. The additional gap at the middle / top is 2.9 μm, the additional gap at the middle / middle is 6.4 μm, the additional gap at the middle / bottom is 11.4 μm, the additional gap at the bottom / top is 24.7 μm, and the additional gap at the bottom / bottom is 100.8 μm. Although the additional gap increases as it deviates from the location of the center of the rotation axis (50_C) of the coating roll, in the case of this embodiment, the additional gap for each die-lip position is significantly smaller compared to the comparative example. Therefore, the back bead does not move much further away compared to the comparative example, so back leakage is improved.

[0116] Additionally, the additional gap in the upper layer was calculated to be 1.4 μm, and the additional gap in the lower layer was calculated to be 18.1 μm. It can be seen that even if a coating gap occurs in the lower layer due to the curvature of the coating roll (50) because the center of the rotation axis (50_C) of the coating roll is not aligned with the upper part (112a) of the first die rib (112) and is slightly closer to the second die block (120), a coating gap of 16.6 μm, which is much smaller than in the comparative example, occurs. Therefore, the coating conditions of the upper and lower layers become more similar, making the control of coating layer quality more reliable. By reducing the difference in coating gap between the upper and lower layers, individual loading quality of the upper and lower layers can be secured.

[0117] FIG. 14 is a graph simulating the coating gap at different positions when the center of the rotation axis (50_C) of the coating roll is aligned with the upper part (122a) of the second die lip (122) according to another embodiment of the present invention.

[0118] Referring to FIG. 14, the additional gap for each die-lip position is compared with the comparative example as follows. Since the center of the rotation axis (50_C) of the coating roll is located at the middle plate / upper, the additional gap relative to the set coating gap is 0.0. The upper plate / upper and upper plate / lower are offset from the center of the rotation axis (50_C) of the coating roll, so the additional gaps were calculated as 11.4 μm and 2.9 μm, respectively. The additional gap at the middle plate / middle is calculated as 0.7 μm, the additional gap at the middle plate / lower is calculated as 2.9 μm, the additional gap at the lower plate / upper is calculated as 10.8 μm, and the additional gap at the lower plate / lower is calculated as 69.7 μm. Although the additional gap increases as it deviates from where the center of the rotation axis (50_C) of the coating roll is located, the additional gap for each die-lip position in this embodiment is also significantly smaller than that of the comparative example. Therefore, the back bead does not move much further away compared to the comparative example, so back leakage is significantly improved.

[0119] Additionally, according to FIG. 14, the additional gap in the upper layer was calculated to be 1.4 μm, and the additional gap in the lower layer was calculated to be 6.8 μm. Even if a coating gap occurs in the lower layer due to the curvature of the coating roll (50) as the center of the rotation axis (50_C) of the coating roll is not aligned with the upper part (112a) of the first die rib (112) and moves closer to the second die block (120), it can be seen that a coating gap of 5.4 μm occurs, which is much reduced compared to the comparative example or one embodiment of the present invention, and this amount is practically equivalent to having no difference in coating gap. Therefore, by making the coating gaps of the upper and lower layers uniform, the individual loading quality of the upper layer and lower layer can be secured.

[0120] As previously mentioned, since the bending effect changes depending on the change in the center of the rotation axis (50_C) of the coating roll (50), it is desirable to change the position of the bending center (142_C) as well. If the hole (H) connecting the bending unit (140) and the base (105) is formed in a circular shape, the position of the bending unit (140) is fixed. However, if the hole (H) connecting the bending unit (140) and the base (105) is formed as an elongated hole as proposed in the present invention, the bending unit (140) can change its position along the front-rear direction and can be aligned with the center of the rotation axis (50_C) of the coating roll (50).

[0121] FIG. 15 illustrates the results of a center and side loading test according to the bending level (-40㎛ to 40㎛) while changing only the alignment of the rotation axis center (50_C) of the coating roll (50) from the lower part (112b) of the first die rib (112) to the upper part (132a) of the third die rib (132) without moving the bending center (142_C). The bending center (142_C) was aligned and fixed at the lower part (112b) of the first die rib (112) and was not moved.

[0122] In FIG. 15, the horizontal axis represents the center of rotation (50_C) of the coating roll (50), and the unit is an arbitrary unit. The value of the horizontal axis is 0 when the center of rotation (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die rib (112). As the center of rotation (50_C) of the coating roll (50) moves toward the upper part (132a) of the third die rib (132), the horizontal axis has a negative value.

[0123] In Fig. 15, the vertical axis represents the difference in loading between the center and side portions of the coating layer, and the unit is arbitrary. The greater the loading in the center portion, the more positive the value becomes.

[0124] A bending level of -40㎛ is a condition when the base (105) is pushed that much to press the bending space (S), a bending level of 0 is a condition when no bending occurs, and a bending level of 40㎛ is a condition when the base (105) is pulled that much to increase the bending space (S).

[0125] When the center of the rotation axis (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die lip (112), the bending level is 40 μm, and the loading difference between the center part and the side part is about 10, and as the center of the rotation axis (50_C) of the coating roll (50) moves toward the upper part (132a) of the third die lip (132), the loading difference between the center part and the side part gradually decreases. When the center of the rotation axis (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die lip (112), the bending level is 0 μm, and the loading difference between the center part and the side part is almost zero, and as the center of the rotation axis (50_C) of the coating roll (50) moves toward the upper part (132a) of the third die lip (132), the loading difference between the center part and the side part gradually becomes a negative value. When the center of the rotation axis (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die rib (112), the bending level is -40 μm, and the loading difference between the center part and the side part is about -10, and as the center of the rotation axis (50_C) of the coating roll (50) moves toward the upper part (132a) of the third die rib (132), the loading difference between the center part and the side part becomes increasingly negative.

[0126] However, the loading difference (△BL1) at each bending level when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the lower part (112b) of the first die rib (112) is different from the loading difference (△BL2) at each bending level when the center of the rotation axis (50_C) of the coating roll (50) is aligned with the upper part (132a) of the third die rib (132).

[0127] As shown in FIG. 15, it is analyzed that the bending effect varies slightly depending on the position of the center of the rotation axis (50_C) of the coating roll (50). Attention must be paid to the interaction. Since the bending effect varies depending on the position of the center of the rotation axis (50_C) of the coating roll (50), it is desirable to change the position of the bending center (142_C) as well. The pressure part where the bending force by the bending unit (140) is applied can be made to have the smallest coating gap, thereby maintaining the bending effect (sensitivity).

[0128] According to the present invention, by forming a hole (H) that connects the bending unit (140) and the base (105) as an elongated hole, the bending center (142_C) can also move together when the vertical die alignment position is changed. The elongated hole (H) may be in a shape that extends from behind the upper part (112a) of the first die rib (112) to in front of the lower part (132b) of the third die rib (132).

[0129] In this way, in the present invention, when the rotation axis center (50_C) of the coating roll (50) is changed relative to the slot die coater (100, 200), the bending center (142_C) by the bending unit (140) can also move together.

[0130] Accordingly, the center of rotation axis (50_C) of the coating roll (50) and the bending center (142_C) may be aligned with each other and moved toward the second die block (120) rather than the upper part (112a) of the first die lip (112). This becomes the location where the coating gap is smallest at the bending pressure part position pressed by the bending unit (140). According to the present invention, the center of rotation axis (50_C) of the coating roll (50) and the bending center (142_C) can be aligned at any part of the die lip of a vertical die type slot die coater (100, 200).

[0131] In particular, since the injection direction of the coating liquid in the dual slot die coater (200) is the center of the die blocks (110, 130), the amount of liquid applied in the center is greater than in the side portions, and as a result, it may have an uneven coating profile in the width direction (perpendicular to the MD direction) of the substrate (60). In other words, the loading of the coating liquid may be concentrated at the center of the width direction of the first slot (115) and the second slot (125). In such a case, the coating gap can be adjusted and the loading dispersion can be adjusted accordingly by changing the position of the second die lip (122) and the third die lip (132) by pushing or pulling the portion of the base (105) corresponding to the second die block (120) or the third die block (130) with the bending unit (140). By pushing each die block (110, 120, 130) toward the discharge direction with the bending unit (140), the coating gap in the center portion can be reduced. Conversely, by pulling each die block (110, 120, 130) with the bending unit (140) in the opposite direction of the discharge direction, the coating gap in the center portion can be increased.

[0132] As previously explained, according to a comparative example in which the center alignment differs from that of the present invention, the coating gap widens at the rear bead, and the coating bead becomes unstable, causing back leakage. According to the present invention, a stable coating bead can be formed by changing the alignment position of the coating roll (50) and the bending unit (140). Furthermore, the bending center (142_C) can also be moved together to have a uniform coating profile.

[0133] Meanwhile, the first die rib (112), the second die rib (122), and the third die rib (132) may be located on the same straight line. Also, the thickness of the third die rib (132) may be greater than the thickness of the first die rib (112) and the thickness of the second die rib (122).

[0134] The appropriate coating area (window margin) exists between the leaking area and the side ring area. The wider this appropriate process area, the better the productivity. The coating gap has a significant influence on the size and shape of the coating bead formed between the substrate (60) and the die lip (112, 122, 132) during coating, as well as the position of the dynamic contact line. According to the present invention, there is an advantage that the coating gap can be maintained at a constant level by aligning the die lip (112, 122, 132), and by adjusting the size of the die lip (112, 122, 132), the area can be expanded to the appropriate process area, allowing for more flexibility in setting initial conditions to minimize leaking by adjusting initial conditions such as the physical properties of the coating liquid, the flow rate and speed of the coating liquid.

[0135] Preferably, referring again to FIG. 9, the thickness (D3) of the third die lip (132) is made larger than the thickness (D2) of the second die lip (122) and the thickness (D1) of the first die lip (112). Thus, the thickness (D3) of the third die lip (132) is greater than the average thickness of the thickness (D1) of the first die lip (112) and the thickness (D2) of the second die lip (122). In this way, the thickness (D3) of the third die lip (132) is the largest (D3 > D2, D3 > D1, D3 > (D1 + D2) / 2). Also, the thickness (D2) of the second die lip (122) and the thickness (D1) of the first die lip (112) can be made equal to each other. The thickness (D1) of the first die lip (112) can also be made larger than the thickness (D2) of the second die lip (122).

[0136] The thickness (D3) of the third die lip (132) and the thickness (D1) of the first die lip (112) may be 1.2:1 or greater. That is, the thickness (D3) of the third die lip (132) may be 1.2 times or more than the thickness (D1) of the first die lip (112). If the thickness (D3) of the third die lip (132) is greater than the thickness (D1) of the first die lip (112), an increase in the appropriate process area can be achieved, but if the thickness (D3) of the third die lip (132) is 1.2 times or more than the thickness (D1) of the first die lip (112), there is an effect of reliably suppressing the occurrence of leaking. If the thickness (D1) of the first die lip (112) is greater than the thickness (D3) of the third die lip (132), leaking occurs.

[0137] The thickness (D3) of the third die lip (132) and the thickness (D2) of the second die lip (122) may be 1.2:1 or greater. That is, the thickness (D3) of the third die lip (132) may be 1.2 times or more the thickness (D2) of the second die lip (122). If the thickness (D3) of the third die lip (132) is greater than the thickness (D2) of the second die lip (122), an increase in the appropriate process area can be achieved, but if the thickness (D3) of the third die lip (132) is 1.2 times or more the thickness (D2) of the second die lip (122), there is an effect of reliably suppressing the occurrence of leaking. If the thickness (D3) of the third die lip (132) and the thickness (D2) of the second die lip (122) are the same, leaking occurs. If the thickness (D2) of the second die rib (122) is greater than the thickness (D3) of the third die rib (132), it causes other pattern defects even if leaking does not occur.

[0138] According to the above example, the thickness (D3) of the third die lip (132) is the largest, being greater than the thickness (D2) of the second die lip (122) and the thickness (D1) of the first die lip (112). As the thickness (D3) of the third die lip (132) increases, the appropriate process area becomes wider. Therefore, there is more room for control of the coating gap or setting of initial conditions. Thus, according to this configuration, productivity is excellent, and during coating, the dynamic contact line can be used in various positions depending on the target coating product and quality. According to the present invention, as a result of the widening of the appropriate process area, the leakage limit can be improved, that is, raised. And the area where side rings occur can be reduced. As the coating gap decreases, if the dynamic contact line moves in the opposite direction of the coating, leakage occurs above a certain level; however, according to the present configuration, leakage can be improved by increasing the thickness (D3) of the third die lip (132). This is because the second coating liquid (160) can be retained in the third die lip (132) without leaking out. According to the present invention, leakage is reduced even when the coating gap is insufficient or when the amount of coating liquid supplied is large compared to the travel speed of the substrate (60).

[0139] In a preferred example, the thickness (D3) of the third die rib (132): the thickness (D2) of the second die rib (122): the thickness (D1) of the first die rib (112) is 1.5:0.5:1.

[0140] As another example, the thickness (D3) of the third die rib (132) and the thickness (D1) of the first die rib (112) are equal to each other and may be greater than the thickness (D2) of the second die rib (122) (D3=D1>D2).

[0141] The thickness (D3) of the third die lip (132) and the thickness (D2) of the second die lip (122) may be 1.2:1 or greater. That is, the thickness (D3) of the third die lip (132) may be 1.2 times or more the thickness (D2) of the second die lip (122). If the thickness (D3) of the third die lip (132) is greater than the thickness (D2) of the second die lip (122), an increase in the appropriate process area can be achieved, but if the thickness (D3) of the third die lip (132) is 1.2 times or more the thickness (D2) of the second die lip (122), there is an effect of reliably suppressing the occurrence of leaking. If the thickness (D3) of the third die lip (132) and the thickness (D2) of the second die lip (122) are the same, leaking occurs. If the thickness (D2) of the second die rib (122) is greater than the thickness (D3) of the third die rib (132), it causes other pattern defects even if leaking does not occur.

[0142] The thickness (D1) of the first die lip (112) can be made equal to the thickness (D3) of the third die lip (132) and thus larger than the thickness (D2) of the second die lip (112). The thickness (D1) of the first die lip (112) is not made larger than the thickness (D3) of the third die lip (132) to suppress the occurrence of leaking.

[0143] According to the above example, the thickness (D3) of the third die lip (132) is large, so the appropriate process area is widened. Therefore, there is more room for control of the coating gap or setting of initial conditions.

[0144] For example, the electrode active material slurry coating method using the slot die coater of the present invention is applied to the manufacture of a positive electrode for a secondary battery. The positive electrode has a structure in which a lower active material layer formed by a lower slurry layer and an upper active material layer formed by an upper slurry layer are sequentially stacked on a current collector. The lower active material layer contains a high content of conductive material, and the upper active material layer contains a relatively low content of conductive material. In this case, the content of the conductive material in the lower active material layer can be controlled within the range of 0.5 to 5 weight%. By reducing the content of the conductive material in the upper active material layer, the content of the active material on the electrode surface can be increased and the electrical conductivity can be lowered to a certain level. In particular, if the content of the conductive material in the upper active material layer is controlled to a very low level of 0.02 weight% or less, the exothermic reaction during an internal short circuit of the cell can be reduced.

[0145] In another example, the average particle size (P1) of the active material forming the lower active material layer is in the range of 50 to 95% of the average particle size (P2) of the active material forming the upper active material layer. In this case, an active material with a relatively small particle size is applied to the lower active material layer. By applying an active material with a relatively large particle size to the upper active material layer, electrolyte impregnation can be facilitated and the smooth movement of ions or holes can be induced.

[0146] Here, the flow rate ratio of the first coating solution and the second coating solution (160) may be 1:1. The viscosity of the first coating solution and the second coating solution (160) may be 1000 cps or higher. Since it must be possible to coat a coating solution with a viscosity of 1000 cps or higher, the dual slot die coater (200) of the present invention differs from the device structure for applying ordinary resin solutions with lower viscosity than this, such as photographic emulsions, magnetic solutions, solutions that impart anti-reflection or anti-glare properties, solutions that impart a viewing angle expansion effect, or pigment solutions for color filters, and is not a device that can be achieved by modifying it. The first coating solution and the second coating solution (160) may include graphite, a conductive material, CMC, and a binder.

[0147] Under the above coating conditions, most preferably, the thickness (D3) of the third die lip (132): the thickness (D2) of the second die lip (122): the thickness (D1) of the first die lip (112) is 3:1:1. With this dual slot die coater (200), process efficiency can be increased and the defect rate reduced when forming a two-layer active material layer on a current collector.

[0148] As a specific example, the present invention can be applied to the manufacture of a positive electrode active material slurry by coating it using a dual slot die coater (200) of the present invention. The positive electrode comprises a current collector and a positive electrode active material layer formed on the surface of the current collector. The current collector may be one that exhibits electrical conductivity, such as Al or Cu, and may be appropriate depending on the polarity of the current collector electrode known in the field of secondary batteries. The positive electrode active material layer may further include one or more of a plurality of positive electrode active material particles, a conductive material, and a binder. In addition, the positive electrode may further include various additives for the purpose of supplementing or improving electrochemical properties.

[0149] The active material is not limited to specific components as long as it can be used as a positive electrode active material for a lithium-ion secondary battery. Non-limiting examples include layered compounds such as lithium manganese complex oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2), or compounds substituted with one or more transition metals; chemical formula Li 1+x Mn 2-x Lithium manganese oxides such as O4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-x M xNi-site type lithium nickel oxide represented by O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 ~ 0.3); chemical formula LiMn 2-x M x It may include a lithium manganese composite oxide represented by O2 (where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li2Mn3MO8 (where M = Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of the Li in the chemical formula is substituted with alkaline earth metal ions; a disulfide compound; and a mixture of two or more of Fe2(MoO4)3. In the present invention, the anode may include one or more of a polymer-based solid electrolyte, an oxide-based solid electrolyte, and a sulfide-based solid electrolyte as a solid electrolyte material.

[0150] The conductive material may typically be added in an amount of 1 wt% to 20 wt% based on the total weight of the mixture containing the active material. Such conductive material is not particularly limited as long as it is conductive without causing chemical changes in the battery, and may include, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; metal powders such as carbon fluoride, aluminum, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; or one or more mixtures selected from conductive materials such as polyphenylene derivatives.

[0151] The above binder is not particularly limited as long as it is a component that assists in the bonding of the active material and the conductive material, and the bonding to the current collector, and examples include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber, fluororubber, and various copolymers. The above binder may typically be included in a range of 1 wt% to 30 wt% or 1 wt% to 10 wt% relative to 100 wt% of the electrode layer.

[0152] The present invention may be applied to the manufacture of a negative electrode of a secondary battery by coating a negative electrode active material slurry using a dual slot die coater (200). The negative electrode comprises a current collector and a negative electrode active material layer formed on the surface of the current collector. The negative electrode active material layer may further include one or more of a plurality of negative electrode active material particles, a conductive material, and a binder. Additionally, the negative electrode may further include various additives for the purpose of supplementing or improving electrochemical properties.

[0153] The above-mentioned negative electrode active material is a carbon material such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotubes, carbon nanohorns, etc., a lithium metal material, an alloy-based material such as silicon or tin, Nb2O5, Li5Ti4O. 12 Oxide-based materials such as TiO2, or composites thereof, may be used. For the cathode, the conductive material, binder, and current collector may be described in the section on the anode.

[0154] The electrode active material slurry containing such positive or negative active materials has a very high viscosity. For example, the viscosity may be 1000 cps or higher. The viscosity of the electrode active material slurry intended for forming a secondary battery electrode may be 2000 cps to 30000 cps. For example, the viscosity of the negative electrode active material slurry may be 2000 cps to 4000 cps. The viscosity of the positive electrode active material slurry may be 8000 cps to 30000 cps. Since it must be possible to coat a coating liquid with a viscosity of 1200 cps or higher, the dual slot die coater (200) of the present invention differs from the device structure for applying ordinary resin liquids with lower viscosity than this, such as photographic emulsions, magnetic liquids, liquids that impart anti-reflection or anti-glare properties, liquids that impart a viewing angle expansion effect, pigment liquids for color filters, etc., and is not a device that can be achieved by modifying it. The dual slot die coater (200) of the present invention is intended to apply an electrode active material slurry that may include, for example, an active material having an average particle size of about 10 μm, and is therefore different from the structure of a device that applies other coating liquids that do not include particles of this size, and is not a device that can be achieved by changing it.

[0155] Fig. 16 is a variation of Fig. 8.

[0156] Referring to FIG. 16, the third die rib (132) is retracted from the first die rib (112) or the second die rib (122).

[0157] The distance (H1) between the substrate (60) and the first die lip (112) and the distance (H2) between the substrate (60) and the second die lip (122) is greater than the distance (H3) between the substrate (60) and the third die lip (132). By positioning the third die lip (132) further away from the substrate (60) in the opposite direction of the discharge direction compared to the first die lip (112) and the second die lip (122), this difference in distance can be created to form a step between the die lip. The distance (H1) between the substrate (60) and the first die lip (112) and the distance (H2) between the substrate (60) and the second die lip (122) may be equal to each other.

[0158] Thus, a predetermined step (D') is formed between the second discharge port (126) and the first discharge port (116). This step (D') is equal to the distance (H3) between the substrate (60) and the third die lip (132) minus the distance (H1) between the substrate (60) and the first die lip (112). As the second discharge port (126) and the first discharge port (116) are positioned at a mutually spaced position along the horizontal direction by this step (D'), there is no risk that the first coating liquid (150) discharged from the first discharge port (116) will flow into the second discharge port (126), or that the second coating liquid (160) discharged from the second discharge port (126) will flow into the first discharge port (116). As described above, the configuration of the present embodiment is also characterized by the fact that the second die block (120) and the third die block (130) forming the second discharge port (126) are spaced apart from each other.

[0159] As described above, with the positions of the die lip (112, 122, 132) set, the first discharge port (116) is positioned so as to be spaced apart from the second discharge port (126) in the downstream direction of the coating direction. By driving the substrate (60) from the third die lip (132) toward the first die lip (112) and simultaneously discharging the coating liquid through the second discharge port (126) and the first discharge port (116), a two-layer active material layer can be formed on the substrate (60).

[0160] The present invention separates only the lower upstream from the substrate (60) in a direction further away from the lower slurry, that is, the second coating liquid (160) discharged from the second discharge port (126). In other words, by creating a height difference between the second die block (120) and the third die block (130), which are the two plates forming the second discharge port (126), the third die block (130) is moved further away from the substrate (60). This differs from the case where only the movement of the discharge port itself is utilized without distinguishing between upstream and downstream.

[0161] The ratio of the average thickness (T1) of the lower slurry layer formed by the second coating liquid (160) discharged through the second discharge port (126) to the average thickness (T2) of the upper slurry layer formed by the first coating liquid discharged through the first discharge port (116) may be in the range of 1:3 to 3:1 (T1 : T2). The thickness ratio represents the average value of the thickness direction length of each layer relatively. Additionally, the average thickness (T1, T2) of the lower slurry layer and the upper slurry layer may be 40 to 200 μm.

[0162] The thickness of the slurry layer as described above can be seen as the pressure of the supplied coating liquid. If the pressure of the first coating liquid (150) is supplied at a level exceeding three times the pressure of the second coating liquid (160) so that the thickness ratio of the lower slurry layer to the upper slurry layer is 1:3 or greater, the upper layer has a stronger pressure than the lower layer, so the second coating liquid (160) is pushed backward in the opposite direction of the coating process, increasing the likelihood of leakage, and the second coating liquid (160) may not be properly supplied due to the strong pressure of the first coating liquid (150). In addition, because the supply of the second coating liquid (160) is not uniform due to the high pressure of the first coating liquid (150), there is a problem in that the lower slurry layer is difficult to form uniformly.

[0163] Meanwhile, if the pressure of the second coating liquid (160) is supplied at more than three times the pressure of the first coating liquid (150) so that the thickness ratio of the lower slurry layer and the upper slurry layer is 3:1 or more, there is a problem that the first coating liquid (150) supply becomes difficult or the coating of the first coating liquid (150) is pushed in the direction of coating progress, and the surface of the coating liquid may become uneven.

[0164] The above step (D') is preferably in the range of 20 to 70% of the combined thickness of the average thickness (T1) of the lower slurry layer and the average thickness (T2) of the upper slurry layer. If the above range is less than 20%, the effect of shortening the loading exit length when the coating liquid supply is stopped is minimal. If the above range exceeds 70%, the total area of ​​the space where the coating liquid stays to be coated relative to the amount of coating liquid, that is, the space between the die lip (122, 132) and the lower slurry layer, is insufficient, so the supplied second coating liquid (160) cannot be coated and leakage occurs.

[0165] For intermittent coating, if the supply of coating liquid is stopped during pattern formation, the loading is cut off gradually, and a loading drop phenomenon occurs. This loading drop phenomenon occurs when the supply of coating liquid is stopped to form an end, and the residual coating liquid that remains forming a meniscus or bead between the dual slot die coater (200) and the substrate (60) is coated onto the substrate (60). In this embodiment, as shown in FIG. 16, the third die block (130) is in a retracted state, so the amount of residual coating liquid remaining forming a meniscus or bead between the dual slot die coater (200) and the substrate (60) is reduced. The length (S') from the upper die lip (112) to the meniscus of the second coating liquid (160) is shortened. Accordingly, when the coating liquid is stopped, the loading is not cut off gradually, and the length of the loading drop is short. Accordingly, the pattern end can be ideally formed almost perpendicularly to the substrate (60), and the length of the loading off section can be reduced. The loading off section acts as a wasteful excess portion, which leads to a decrease in process efficiency and an increase in manufacturing costs. According to the present configuration, since the loading off section is shortened, the wasteful excess portion is reduced, and the effect of increasing process efficiency and reducing manufacturing costs is achieved.

[0166] As another example, the first die-lip (112) may be recessed from the second die-lip (122) or the third die-lip (132).

[0167] In this case, although not separately illustrated, there is a relationship between the distance (H1) between the substrate (60) and the first die lip (112) shown in FIG. 16, the distance (H2) between the substrate (60) and the second die lip (122), and the distance (H3) between the substrate (60) and the third die lip (132) such that H1 > H2 and H1 > H3. At this time, H2 may be equal to H3. By positioning the first die lip (112) further away from the substrate (60) in the opposite direction of the discharge direction compared to the second die lip (122) and the third die lip (132), such a difference in distance can be created to form a step between the die lips. In this case, the upper coating gap and the lower coating gap can be individually controlled depending on the degree to which the first die lip (112) is retracted.

[0168] As another example, the second die-lip (122) may be recessed from the first die-lip (112) or the third die-lip (132).

[0169] In this case, although not separately illustrated, the distance (H1) between the substrate (60) and the first die lip (112) shown in FIG. 16, the distance (H2) between the substrate (60) and the second die lip (122), and the distance (H3) between the substrate (60) and the third die lip (132) are in a relationship where H2 > H1 and H2 > H3. At this time, H1 may be equal to H3. By positioning the second die lip (122) in the opposite direction of the discharge direction to the first die lip (112) and the third die lip (132) and positioning it far from the substrate (60), such a difference in distance can be created to form a step between the die lips. In this case, when the supply of coating liquid is stopped for intermittent coating, the residual coating liquid attached to the second die lip (122) falls messily onto the substrate (60), which has the effect of preventing pattern defects such as drag lines.

[0170] As another example, the third die-lip (132) may be advanced beyond the first die-lip (112) or the second die-lip (122).

[0171] In this case, although not separately illustrated, the distance (H1) between the substrate (60) and the first die lip (112) shown in FIG. 16, the distance (H2) between the substrate (60) and the second die lip (122), and the distance (H3) between the substrate (60) and the third die lip (132) have a relationship such that H1 > H3 and H2 > H3. At this time, H1 may be equal to H2. By pushing the position of the third die lip (132) toward the discharge direction closer to the substrate (60) than the first die lip (112) and the second die lip (122), such a difference in distance can be created to form a step between the die lips. In the case where back leakage occurs due to an excessive additional gap in the lower layer, back leakage can be further reduced by positioning the center of the rotation axis (50_C) of the coating roll (50) toward the second die block (120) rather than the upper part (112a) of the first die lip (112) as proposed in the present invention, thereby reducing back leakage, and by advancing only the third die lip (132) to reduce the lower layer coating gap. Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs. Explanation of the symbols

[0172] 50: Coating Roll 60: Substrate 100: Slot Die Coater 105: Donation 110: 1st Die Block 112: 1st Die Rip 115: Slot, 1st slot 116: Discharge port 117: Sim 118: Manifold 120: 2nd Die Block 122: 2nd Die Rip 125: 2nd slot 126: 2nd discharge port 127: Sim 130: 3rd Die Block 132: 3rd Dirip 138: Manifold 140: Bending unit 142: Die connector 144: Main body 150: First coating liquid 160: Second coating solution 200: Dual slot die coater B: Bolt H: Hole S: Bending space

Claims

Claim 1 A slot die coater having a slot for discharging a coating liquid in a direction opposite to gravity onto a substrate surface that is continuously driven and transported by a coating roll, comprising: a first die block installed at a base; a second die block forming the slot between the first die block and the second die block; and a bending unit connected to the lower end of the base, wherein the bending center by the bending unit is also changed when the center of the rotation axis of the coating roll is changed relative to the slot die coater, and wherein a hole formed in the base to connect the bending unit and the base is formed as an elongated hole in the front-rear direction so as to enable the position of the bending unit to be changed. Claim 2 A slot die coater according to claim 1, characterized in that the center of the rotation axis of the coating roll is positioned toward the second die block direction rather than the upper part of the first die lip forming the leading edge of the first die block with respect to the substrate. Claim 3 delete Claim 4 A slot die coater according to claim 1, further comprising a third die block disposed on the front of the second die block and forming an additional slot between it and the second die block. Claim 5 A slot die coater characterized in that, in paragraph 4, the cross-section of the second die block is a right triangle. Claim 6 A slot die coater according to claim 4, wherein the first die block, the second die block, and the third die block each have a first die lip, a second die lip, and a third die lip forming the leading edge of each die, and the center of the rotation axis of the coating roll is positioned toward the second die block rather than the upper part of the first die lip with respect to the substrate, and the first die lip, the second die lip, and the third die lip are positioned on the same straight line, or the third die lip is recessed from the first die lip or the second die lip. Claim 7 A slot die coater according to claim 4, wherein the first die block, the second die block, and the third die block each have a first die lip, a second die lip, and a third die lip forming the leading edge of each die, and the center of the rotation axis of the coating roll is positioned toward the second die block rather than the upper part of the first die lip with respect to the substrate, and the first die lip is retracted from the second die lip or the third die lip, or the second die lip is retracted from the first die lip or the third die lip, or the third die lip is advanced from the first die lip or the second die lip. Claim 8 A slot die coater according to claim 6, characterized in that the thickness of the third die rib is greater than the thickness of the first die rib and the thickness of the second die rib. Claim 9 A slot die coater according to claim 6, characterized in that the thickness of the third die rib is equal to the thickness of the first die rib and greater than the thickness of the second die rib. Claim 10 A slot die coater according to claim 1, characterized in that the first die block is vertically installed integrally with the base at the rear portion of the upper surface of the base, and the second die block is positioned at the front of the first die block. Claim 11 A slot die coater according to claim 10, characterized in that the second die block does not come into contact with the base, or even if it does come into contact, forms a bending space between it and the base. Claim 12 A slot die coater according to claim 1, characterized in that the position of the bending unit can be changed so that the center of the rotation axis of the coating roll is aligned with the bending center of the bending unit. Claim 13 delete Claim 14 A slot die coater according to claim 7, characterized in that the above-mentioned elongated hole extends from behind the upper portion of the first die lip to in front of the lower portion of the third die lip forming the leading edge of the third die block. Claim 15 A slot die coater according to paragraph 2, wherein the coating roll rotates clockwise, the substrate is transported from upstream to downstream, and the first die block is on the downstream side and the second die block is on the upstream side.

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