Slot die coater

Abstract

The slot die coater of the present invention is a slot die coater equipped with slots for discharging a coating liquid in the opposite direction to gravity onto the surface of a substrate that is continuously transported by a coating roll, and comprises a first die block and a second die block that forms the slots between the first die block and the second die block, wherein the center of the rotation axis of the coating roll is located further toward the second die block than the upper part of the first die lip that forms the tip of the first die block relative to the substrate.

Description

[[Technical Field]]

[0001] The present invention relates to a slot die coater, and more particularly, to a vertical die type slot die coater in which a coating liquid is discharged in a direction opposite to gravity.

[0002] This application claims priority based on Korean Patent Application No. 10-2024-0004388 filed on January 10, 2024 and Korean Patent Application No. 10-2024-0079909 filed on June 19, 2024, and all contents disclosed in the specification and drawings of the said applications are incorporated into this application. [[Background Art]]

[0003] Secondary batteries, which have high applicability depending on product groups and electrical characteristics such as high energy density, are generally applied not only to portable devices but also to electric vehicles (EV) driven by electric drive sources or hybrid electric vehicles (HEV). Such secondary batteries have not only the advantage of being able to drastically reduce the use of fossil fuels, but also the advantage that no by-products are generated at all along with energy use, so they are attracting attention as a new energy source for achieving environmental friendliness and improving energy efficiency.

[0004] Such a secondary battery essentially includes an electrode assembly as a power generating element. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are laminated at least once or more, and the positive electrode and the negative electrode are manufactured by applying and drying a positive electrode active material slurry and a negative electrode active material slurry onto current collectors made of aluminum foil and copper foil, respectively.

[0005] In order to uniformize the charge-discharge characteristics of a secondary battery, such a positive electrode active material slurry and a negative electrode active material slurry must be uniformly coated on a current collector, and slot die coaters have been conventionally used for this purpose.

[0006] Figure 1 is a cross-sectional view showing a conventional slot die coater.

[0007] Referring to Figure 1, in a conventional electrode manufacturing method using a slot die coater 1, electrode active material slurry discharged from the slot die coater 1 is applied onto a current collector 3 conveyed by a coating roll 2. The electrode active material slurry discharged from the slot die coater 1 is broadly applied to one side of the current collector 3 to form an active material layer. The slot die coater 1 includes two die blocks 4 and 5, with a slot 6 formed between the two die blocks 4 and 5. One type of electrode active material slurry can be discharged through a discharge port 7 communicating with the slot 6 to form a single layer of active material. The slot die coater 1 has the advantage of being able to coat at high speed compared to bar coating or comma coating, and is therefore widely adopted due to its high productivity. The slot die coater 1 shown as an example in Figure 1 is a vertical die type in which the electrode active material slurry is discharged in the opposite direction to gravity.

[0008] To manufacture high-energy-density secondary batteries, the thickness of the active material layer, which was approximately 130 μm, has gradually increased to 300 μm. After forming a thick active material layer using a conventional slot die coater 1, migration of the binder and conductive material in the electrode active material slurry becomes severe during drying, resulting in the production of non-uniform electrodes. To solve this problem, coating the active material layer in two stages—applying a thin layer, drying it, and then applying another layer and drying it—has the disadvantage of taking a long time. To improve both electrode performance and productivity simultaneously, a dual-slot die coater with two slots is necessary to coat two types of electrode active material slurries simultaneously as an upper / lower double layer.

[0009] A slot die coater forms slots on the bonding surface between die blocks, so to have two slots like a dual slot die coater, basically three die blocks are required. A drawback of using such a dual slot die coater is that it is necessary to use electrode active material slurries that are discharged simultaneously from different discharge ports that communicate with each of the two slots, making it very complicated to form each active material layer to the desired thickness.

[0010] Furthermore, the distance from the discharge port 7 to the surface of the current collector 3 is the coating gap, which is an extremely important variable in determining the quality of the active material layer coating. 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 the coating gap. In addition, uniformity of the coating gap in the width direction (TD direction) of the current collector is essential for stable coating, and variations in the coating gap in the width direction have a significant impact on the width of the coating and the shape of the boundary of the plain area. Even a change of just a few μm in the thickness of the active material layer can have a serious impact on the quality of the coating, so very strict control is required. Moreover, in order to stably achieve uniform coating in the width direction of the current collector, it is necessary to strictly control the dimensional accuracy to be maintained at a high level uniformly across the width direction. In addition, as shown in Figure 1, since the coating roll 2 has curvature, the current collector 3 placed on it also has curvature, and 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 straight line, the coating gap is minimized at that alignment point, and the further away from the alignment point they are, the greater the coating gap becomes.

[0011] In particular, in coating processes using dual-slot die coaters, it is necessary to simultaneously discharge and coat electrode active material slurry from different discharge ports, making coating gap management even more crucial. Moreover, problems such as leaking and side ringing tend to be more severe than when forming a single layer. Leaking refers to an unstable phenomenon in which a portion of the coating liquid flows out from the outside of the die lip that forms the tip of the die block to the upstream side. This means a loss of pre-measured coating liquid, which makes it impossible to predict the final coating thickness. When leaking occurs, the coating liquid may remain stagnant for a long time and solidify, or variations in the coating thickness in the width direction may occur. In particular, when aiming for thin film coating or to reduce variations in the layer thickness in the width direction of the coating layer, if the coating gap is narrowed to several hundred μm and the coating liquid is discharged under high pressure, the above-mentioned leaking may become even more severe. Thus, since the coating gap is closely related to leaking, high-precision management is required. [Overview of the Initiative] [Problems that the invention aims to solve]

[0012] This invention was created in view of the above circumstances, and the problem that this invention aims to solve is to provide a slot die coater that can accurately control the coating gap and suppress the occurrence of leakage.

[0013] However, the technical problems that the present invention aims to solve are not limited in any way to those described above, and other problems not mentioned should be clearly understood by those skilled in the art from the description of the invention below. [Means for solving the problem]

[0014] The present invention, which solves the above-mentioned problems, is a slot die coater equipped with slots for discharging a coating liquid in the opposite direction to gravity onto the surface of a substrate that is continuously transported by a coating roll, and comprises a first die block and a second die block that forms the slots between the first die block and the second die block, wherein the center of the rotation axis of the coating roll is located further toward the second die block than the upper part of the first die lip that forms the tip of the first die block relative to the substrate.

[0015] The first die block is disposed vertically and integrally with the base at the rear of the upper surface of the base, and the second die block may be positioned in front of the first die block.

[0016] The second die block may not be in surface contact with the base, or even if it is in surface contact, it may form a bending space between itself and the base.

[0017] A bending unit can be connected to the lower end of the base so as to deform the bending space.

[0018] The position of the bending unit can be changed by forming a hole in the base, which fastens the bending unit to the base, as an elongated hole in the front-to-back direction.

[0019] The center of the rotation axis of the coating roll can be aligned with the bending center of the bending unit.

[0020] The slot die coater of the present invention can be realized not only as a device for coating a single layer, but also as a dual slot die coater, which is a device for coating a double layer. For this purpose, the dual slot die coater of the present invention may further include a third die block positioned in front of the second die block and forming an additional slot between it and the second die block.

[0021] In this case, the center of the rotation shaft of the coating roll may be located midway along the first die lip, located at a lower portion of the first die lip, located above the second die lip that forms the tip end of the second die block, located midway along the second die lip, located at a lower portion of the second die lip, or alternatively located above the third die lip that forms the tip end of the third die block.

[0022] Particularly, in a dual slot die coater, the second die block does not come into surface contact with the base, or even if it comes into surface contact with the base, a bending space is formed between the second die block and the base, a bending unit is connected to the lower end of the base so as to deform the bending space, and a hole formed in the base for fastening the bending unit and the base is formed as an elongated hole extending in the front-rear direction, so that the center of the rotation shaft of the coating roll can be aligned with the bending center provided by the bending unit.

[0023] In this case, the elongated hole may have a shape that extends from a position rearward of an upper portion of the first die lip to a position forward of a lower portion of the third die lip.

[0024] Another slot die coater of the present invention for solving the above problems is a slot die coater comprising a slot for discharging a coating liquid in a direction opposite to gravity onto the surface of a substrate that is continuously run and conveyed by a coating roll, the slot die coater comprising: a first die block that is integrally and vertically disposed at a rear portion of the upper surface of a base; a second die block that forms the slot between the same and the first die block; and a bending unit connected to the lower end of the base, wherein when the position of the center of the rotation shaft of the coating roll is changed relative to the slot die coater, the bending center of the bending unit is configured to move accordingly.

[0025] The center of the rotation shaft of the coating roll may be positioned further toward the second die block side than the upper portion of the first die lip, which forms the tip end of the first die block, relative to the substrate.

[0026] A hole formed in said base for fastening said bending unit and said base may be formed as a longitudinally elongated hole in the front-rear direction, enabling the position of said bending unit to be changed.

[0027] Said slot die coater may further comprise a third die block disposed on a front face of said second die block and forming an additional slot between the third die block and said second die block.

[0028] A cross-section of said second die block may be a right triangle.

[0029] Said first die block, said second die block and said third die block respectively comprise a first die lip, a second die lip and a third die lip that each form a tip portion of the corresponding die; a center of a rotation shaft of said coating roll is located on a side closer to said second die block than an upper portion of said first die lip relative to said base material; said first die lip, said second die lip and said third die lip may be located on the same straight line, or said third die lip may be retracted further than said first die lip and said second die lip.

[0030] As another example, said first die lip may be retracted further than said second die lip and said third die lip, or said second die lip may be retracted further than said first die lip and said third die lip, or said third die lip may protrude further than said first die lip and said second die lip.

[0031] A thickness of said third die lip may be larger than a thickness of said first die lip and a thickness of said second die lip.

[0032] As another example, a thickness of said third die lip may be equal to a thickness of said first die lip, and larger than a thickness of said second die lip. Effects of the Invention

[0033] According to the present invention, the distance between the die lip and the substrate, i.e., the coating gap, can be easily adjusted to a desired gap and maintained.

[0034] According to the present invention, the center of the rotation axis of the coating roll and the bending center can be aligned at any part of the die lip of a vertical die-type slot die coater.

[0035] According to the present invention, by forming the holes for fastening the bending unit and the base as elongated holes, the bending center moves in conjunction with the positioning of the vertical die when the alignment point is changed. According to the present invention, it is easy to change and align the position of the center of the rotation axis of the coating roll and the bending center, and changes in the coating gap are less likely to occur during the process, thus making it possible to suppress variations in the coating gap in the width direction perpendicular to the running direction of the substrate.

[0036] According to the present invention, the coating gap can be accurately maintained by taking into account the curvature of the coating roll. The present invention has the effect of maintaining a uniform (±2%) coating gap, thereby uniformly controlling the coating amount and the resulting coating quality. Therefore, a slot die coater with a uniform coating gap can be used to obtain coated products of uniform quality, particularly electrodes for secondary batteries.

[0037] According to the present invention, space for bending can be secured in the slot die coater. Bending deforms areas that require alignment, but according to the present invention, deformation is achieved with high uniformity even when using a bending unit to control the uniformity of the coating in the width direction. Thus, according to the present invention, the deformation of the die block can be controlled very uniformly, resulting in excellent coating uniformity, and moreover, this can be easily achieved, which is a great advantage.

[0038] The slot die coater of the present invention has the advantage of being able to uniformly coat an electrode active material slurry even under high-speed travel or wide coating conditions when manufacturing electrodes for secondary batteries and the like by coating an electrode active material slurry onto a current collector while the current collector is in motion.

[0039] In particular, according to the present invention, by moving the center of the rotation axis of the coating roll further back toward the second die block than the upper part of the first die lip, the effect of preventing back leaks during coating can be outstandingly achieved. Especially when applied to a dual-slot die coater, the coating gap between the upper and lower layers can be made uniform, and loading quality can be ensured separately for the upper and lower layers.

[0040] Furthermore, according to the present invention, since the bending center is also easily moved, by moving the center of the rotation axis of the coating roll and the bending center further back toward the second die block direction than the upper part of the first die lip, the pressing portion on which the bending force is applied by the bending unit can be made to the point where the coating gap is minimized, and the bending effect (sensitivity) is maintained.

[0041] Thus, by using the slot die coater according to the present invention, a coating layer, particularly an active material layer, can be uniformly formed to a desired thickness, and preferably, two types of electrode active material slurries can be coated simultaneously, resulting in excellent performance and productivity.

[0042] The drawings accompanying this specification illustrate preferred embodiments of the present invention and are intended to further illustrate the technical idea of ​​the invention along with the content of the invention; therefore, the present invention shall not be construed as being limited solely to what is shown in the drawings. [Brief explanation of the drawing]

[0043] [Figure 1] This is a schematic cross-sectional view of a slot die coater using conventional technology. [Figure 2]This is a schematic cross-sectional view of a slot die coater according to one embodiment of the present invention. [Figure 3] Figure 2 is a schematic perspective view of the slot die coater. [Figure 4] Figure 3 is an exploded perspective view. [Figure 5] Figure 2 shows another embodiment of the shim that may be included in the slot die coater. [Figure 6] This is a modified example of Figure 3. [Figure 7] Figure 2 shows the holes that fasten the bending unit and the base included in the slot die coater. [Figure 8] This is a schematic cross-sectional view of a dual-slot die coater according to another embodiment of the present invention. [Figure 9] This is an enlarged view of section A in Figure 8. [Figure 10] This is an enlarged view of section A in Figure 8. [Figure 11] This is a schematic cross-sectional view of a dual-slot die coater as an example. [Figure 12] This graph simulates the coating gap at different positions when the center of the rotation axis of the coating roll is aligned with the top of the first die lip, as in the comparative example. [Figure 13] This graph, according to one embodiment of the present invention, simulates 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. [Figure 14] This graph, according to another embodiment of the present invention, simulates the coating gap at different positions when the center of the rotation axis of the coating roll is aligned with the top of the second die lip. [Figure 15] This figure shows the results of testing loading to the center and side sections according to the bending level, while changing only the alignment of the center of 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. [Figure 16] This is a modified version of Figure 8. [Modes for carrying out the invention]

[0044] Preferred embodiments of the present invention will now be described in detail based on the accompanying drawings. Prior to this, terms and words used in this specification and in the claims are not to be interpreted in their ordinary or dictionary sense, but rather in accordance with the principle that the inventor may appropriately define the concepts of terms in order to best describe the invention, and are to be interpreted in the sense and concepts corresponding to the technical idea of ​​the present invention. Therefore, the embodiments described herein and the configurations shown in the drawings are merely preferred embodiments of the present invention and do not represent the entire technical idea of ​​the present invention; it should be understood that there may be a variety of equivalent and modified embodiments that can be substituted for these at the time of this application.

[0045] The slot die coater of the present invention is a device that has one or two slots for discharging the coating liquid in the opposite direction to gravity, and coats a substrate with the coating liquid in a single or double layer. In the following description, the "substrate" is a current collector, and the "coating liquid" is an electrode active material slurry. When coating in a double layer, the first coating liquid and the second coating liquid are both electrode active material slurrys, and may mean electrode active material slurrys that are identical or different in composition (type of active material, conductive material, and binder), content (amount of active material, conductive material, and binder), and 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 manufacturing electrodes that are pattern-coated by simultaneously applying two types of electrode active material slurry or by alternately applying two types of electrode active material slurry. However, the scope of the present invention is not necessarily limited thereto. For example, the substrate is a porous support constituting a separator, and the first coating liquid and the second coating liquid may be organic substances with different compositions and physical properties. In other words, if a thin film coating is required, the substrate, the first coating liquid and the second coating liquid can be anything.

[0046] Figure 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 in Figure 2, and Figure 4 is an exploded perspective view of Figure 3. Figure 5 shows another embodiment of a shim that may be included in the slot die coater in Figure 2. Figure 6 is a modification of Figure 3. Figure 2 may be a cross-sectional view taken along the line II-II' in Figure 3.

[0047] First, referring to Figures 2 and 3, the slot die coater 100 is equipped with one slot 115 and can coat the surface of the substrate 60 by discharging electrode active material slurry through a discharge port 116 that communicates with the slot 115.

[0048] The slot die coater 100 is equipped with slots 115 for discharging a coating liquid, such as an electrode active material slurry, in the opposite direction to gravity onto the surface of a substrate 60 that is continuously transported by a coating roll 50. For this purpose, 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 itself and the first die block 110.

[0049] The slot die coater 100 is positioned so that the direction in which the coating liquid is discharged (X direction) is approximately perpendicular (approximately ±5°). In the embodiment of the present invention, the X-axis direction shown in the figure is the direction in which the coating liquid is discharged, the Z-axis is the width direction or TD direction of the slot die coater 100, and the Y-axis direction is the horizontal direction which is perpendicular to both the X-axis direction and the Z-axis direction. Furthermore, the Y-axis direction means the front-to-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 toward the second die block 120 toward the first die block 110 is defined as the front, and conversely, the direction toward the first die block 110 toward the second die block 110 is defined as the back.

[0050] The first die block 110 and the second die block 120 are each provided with a first die lip 112 and a second die lip 122 that form their respective leading edges relative to the substrate 60. The Y-axis direction may also mean 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 down, and conversely, the direction from the second die lip 122 toward the first die lip 112 is defined as up.

[0051] The substrate 60 is conveyed by the coating roll 50, which may be positioned to discharge the coating liquid from the slot die coater 100. The slot die coater 100 can discharge the coating liquid in the opposite direction to gravity (X-axis direction), discharging the coating liquid through the slots 115 to coat the substrate 60 continuously or discontinuously.

[0052] The coating roll 50 rotates with 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 further toward the second die block 120 than the upper part 112a of the first die lip 112 relative 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 figure. 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 figure. Here, the fact that the center 50_C of the rotation axis of the coating roll 50 is located further toward the second die block 120 than the upper part 112a of the first die lip 112 relative to the substrate 60 means that the center 50_C of the rotation axis of the coating roll 50 is actively positioned further toward the second die block 120 than the upper part 112a of the first die lip 112, so as to move beyond the range of error that inevitably occurs when the center 50_C of the rotation axis of the coating roll 50 is aligned straight with the upper part 112a of the first die lip 112.

[0053] For example, even if the center 50_C of the rotation axis of the coating roll 50 is aligned straight with the upper part 112a of the first die lip 112, the alignment may be performed within a position approximately 50 μm away in the front and back directions. In the present invention, the center 50_C of the rotation axis of the coating roll 50 may be located further towards the second die block 120 from a position approximately 100 μm away from the lower part 112b of the first die lip 112, rather than the upper part 112a of the first die lip 112.

[0054] Preferably, the first die block 110 is disposed vertically and integrally with the base 105 at the rear of the upper surface 105a of the base 105. Figure 2 shows the side opposite to the direction in which the coating liquid is discharged from the first die block 110, i.e., the lower surface 110a, but when the first die block 110 and the base 105 are disposed integrally, it may become impossible to distinguish the lower surface 110a. The upper cross-section of the first die block 110 may also be triangular. The first die block 110 is a plate-like structure that extends along the width direction. Assembly is performed by placing the first die block 110 on the base 105, but if the base 105 and the first die block 110 are integrated in this way, alignment with the base 105 becomes unnecessary, and they can be handled as a single unit, thus improving handling efficiency. The first die block 110, which is integrated with the base 105, is sometimes called the body block. The XY cross-section of the first die block 110 is generally considered to be L-shaped.

[0055] In this case, the slot 115 may be perpendicular to the base 105.

[0056] The second die block 120 is positioned in 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 triangular.

[0057] The surfaces of the first die block 110 and the second die block 120 opposite to the direction from which the coating liquid is discharged, i.e., the lower surfaces 110a and 120a, can be placed approximately horizontally (YZ plane). In these die blocks 110 and 120, there are parts where the corners formed by the surfaces are right angles, so a right angle exists in cross-sectional view, and a vertical or horizontal plane can be used as the reference plane, making them easy to manufacture and handle, and guaranteeing high precision. Furthermore, when the first die block 110 and the second die block 120 are combined, the opposing parts can support each other with a high degree of surface contact, resulting in excellent clamping and holding performance. Moreover, when the first die block 110 and the second die block 120 are combined, the overall shape is generally that of a rectangular parallelepiped, and only the upper part from which the coating liquid is discharged has a diagonal shape toward the base material 60. The first die block 110 and the second die block 120 are made of, for example, SUS material. Easily machinable materials such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L can be used. SUS has the advantages of being easy to process, inexpensive, highly corrosion-resistant, and able to be manufactured into desired shapes at low cost.

[0058] A shim 117 may be provided between the first die block 110 and the second die block 120 to form a slot 115. By providing a gap between the first die block 110 and the second die block 120 with the shim 117, it becomes possible to form a slot 115 which corresponds to a passage through which the coating liquid can flow. In this case, the thickness of the shim 117 determines the vertical width (slot gap) of the slot 115.

[0059] As is clear from Figure 4, the shim 117 may have an opening 117a by cutting out at least one region. In this case, as shown in Figure 5, the shim 117 may also have multiple openings 117a by intermittently cutting out the aforementioned region.

[0060] It is preferable that the shim 117 is made of a sealing material that also functions as a gasket to prevent the coating liquid from leaking into the gap between the first die block 110 and the second die block 120, except in the area where the discharge port 116 is formed.

[0061] Referring to Figure 2, the first die block 110 may include a manifold 118 that contains the coating liquid and communicates with the slots 115. The manifold 118 may also be provided on the second die block 120. The manifold 118 may have a predetermined shape and depth. Although not shown, such a manifold 118 is connected to an external coating liquid supply chamber (not shown) and a supply pipe to supply the coating liquid. When the manifold 118 is full of coating liquid, the flow of the coating liquid is guided along the slots 115 and discharged to the outside through the outlet 116.

[0062] 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 discharges and applies the coating liquid onto the substrate 60 through a discharge port 116 that communicates with the slot 115. The coating width of the coating layer applied to the substrate 60 is determined by the width of the slot 115. If it is necessary to change the coating width, 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.

[0063] The shim 117 can be interposed in the remaining portion of the peripheral region of the opposing surfaces of the first die block 110 and the second die block 120, excluding one side. For example, as shown in Figure 4, the width of the opening 117a of the shim 117 can be designed to be a, so that an active material layer with a coating width a is formed on the substrate 60, and plain areas are formed on both sides of the active material layer. Figure 5 shows an example where the width of the opening 117a of the shim 117 is designed to be b, so that multiple active material layers with a coating width b are formed on the substrate 60, and plain areas are formed on both sides of each active material layer. When such a shim 117 is applied, a striped pattern coating layer is formed on the substrate 60.

[0064] As shown in Figure 2, the coating roll 50 can rotate clockwise around the center 50_C of its horizontal axis of rotation. The substrate 60 can travel along its lower surface in a front-to-back direction (from right to left, i.e., from upstream to downstream).

[0065] As shown in Figures 2 to 4, the second die block 120 does not make surface contact with the base 105, and therefore a bending space S may be provided between the lower surface of the second die block 120 and the upper surface of the base 105. Alternatively, as shown in Figure 6, even if the second die block 120 makes surface contact with the base 105, a bending space S may be formed between it and the base 105.

[0066] In the examples shown in Figures 2 to 4, the second die block 120 is formed to be even shorter in length than the first die block 110. Therefore, the second die block 120 does not make surface 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. When the length of the first die block 110 is L and the length of the second die block 120 is L', the relationship L > L' holds. In such a bending space S, the front is open, the back is formed on the front surface of the first die block 110, and both the left and right sides are open in the width direction.

[0067] In the example shown in Figure 6, the length L of the first die block 110 and the length L'' of the second die block 120 are the same. Instead, the lower surface 120a of the second die block 120 has an uneven structure so that it intermittently contacts the upper surface 105a of the base 105 with a surface. The length of the second die block 120 in the parts that are in surface contact is L'', and the length of the second die block 120 in the parts that are not in surface contact can be L' (L''=L>L'). In the example shown in Figure 6, because the lower surface 120a of the second die block 120 is in surface contact with the upper surface 105a of the base 105, the force with which the base 105 supports the second die block 120 becomes larger. In the parts where the lower surface 120a of the second die block 120 is not in surface contact with the upper surface 105a of the base 105, a bending space S is provided. This bending space S can be expected to relieve stress.

[0068] As shown in Figure 4, the first die block 110 and the second die block 120 can be fastened together by mounting bolts B. When the internal pressure of the die blocks 110 and 120 increases due to the discharge of the coating liquid, there is a risk that torque will be generated due to the internal pressure starting from the mounting bolts B, and as a result, the part furthest from the mounting bolts B will receive the greatest force, potentially causing the first die lip 112 and the second die lip 122 to separate. As shown in Figure 6, if the lower surface 120a of the second die block 120 is in surface contact with the upper surface 105a of the base 105, the contact surfaces of the first die block 110 and the second die block 120 can support the torque generated due to the internal pressure of the slot die coater 100.

[0069] Referring to the die block assembly process, the lower surface 120a of the second die block 120 is placed on the base 105 so as to be in surface contact with the upper surface 105a of the base 105, and bolts (not shown) can be tightened from the underside of the base 105 to the second die block 120 at each position where surface contact occurs. In this way, by tightening bolts at the positions where surface contact occurs in advance and simultaneously polishing the first die lip 112 and the second die lip 122, it is possible to align each die lip on the same straight line simply by tightening bolts at the positions where surface contact occurs.

[0070] Referring to Figure 2, a bending unit 140 can be connected to the lower end of the base 105. The bending unit 140 can be fastened to a hole H formed in the lower end of the base 105. The bending unit 140 can deform the bending space S by pressing against the lower surface 105b of the base 105.

[0071] The bending unit 140 may include a die connecting portion 142 that is fastened to the lower surface 105b of the base portion 105 and presses against the base portion 105. The die connecting portion 142 may include a die fastening portion 142a and a main body fastening portion 142b. If the hole H formed in the base portion 105 to fasten the bending unit 140 to the base portion 105 is formed as an elongated hole in the front-rear direction, the position of the bending unit 140 can be changed in the front-rear direction (see the arrows in both directions) by changing the position of the die connecting portion 142 connected thereto.

[0072] Since the bending effect changes with the front-to-back change of the center 50_C of the rotation axis of the coating roll 50, it is preferable that the position of the bending center 142_C also changes in accordance with the center 50_C of the rotation axis of the coating roll 50. The bending center 142_C may refer to the center of the die connecting portion 142. The bending center 142_C may be located in the center portion in the width direction of the slot die coater 100.

[0073] As shown in Figure 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. Therefore, the bending center 142_C can coincide with the center of the rotation axis 50_C of the coating roll 50 in the front-rear direction of the slot die coater 100.

[0074] The bending unit 140 may include a servo motor 146 inside the main body 144. The servo motor 146 may be connected to a movable part 148 of the bending unit 140. The movable part 148 of the bending unit 140 is connected to a die coupling part 142. The rotation of the servo motor 146 allows the movable part 148 to move in the X-axis direction and the -X-axis direction, and the die coupling part 142 connected thereto can push or pull the base 105 accordingly.

[0075] The pressing portion where the bending force from the bending unit 140 is applied can be positioned so that the coating gap is minimized. When the pressing portion is the bending center 142_C, and this coincides with the center 50_C of the rotation axis of the coating roll 50, the bending effect (sensitivity) can be maintained.

[0076] In Figure 2, the center 50_C of the rotation axis of the coating roll 50 is aligned with, for example, the lower part 112b of the first die lip 112 so that it moves further toward the second die block 120 than the upper part 112a of the first die lip 112.

[0077] When the center 50_C of the rotation axis of the coating roll 50 and the lower part 112b of the first die lip 112 are aligned in a straight line, the coating gap is minimized at the alignment point, and as the alignment point moves away, that is, the coating gap increases in the front-to-back direction of the slot die coater 100.

[0078] The position of the bending unit 140 can be determined such that when the vertical line Lc passes the lower part 112b of the first die lip 112 at the center 50_C of the rotation axis of the coating roll 50, the bending center 142_C also passes through it. For this purpose, in the present invention, the hole H that fastens the bending unit 140 and the base 105 is formed as an elongated hole, as shown in detail in Figure 7, so that the bending center 142_C also moves when the position of the vertical die is changed.

[0079] Figure 7 shows the holes that fasten the bending unit and the base included in the slot die coater in Figure 2.

[0080] In an embodiment of the present invention, it is proposed that the hole H for fastening 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. The die fastening portion 142a is fastened to the hole H of such an elongated hole, and the main body fastening portion 142b is connected to it, thereby connecting the die connecting portion 142 to the base 105. When fastening the die fastening portion 142a to the hole H of the elongated hole, the position can be changed along the front-rear direction, so it becomes possible to fasten the die connecting portion 142 connected thereto to other positions along the front-rear direction.

[0081] In other words, since the hole H for fastening the bending unit 140 and the base 105 is formed as an elongated hole, the position of the bending unit 140 fastened thereto can be made movable. The position of the bending unit 140 can be the position of the center portion of the base 105 in the front-rear direction, and if necessary, it may be positioned even closer to the second die block 120 than the first die block 120. As the bending unit 140 approaches, it receives an even greater force, resulting in the effect of bending even more. The bending unit 140 can push the base 105 toward the discharge direction or pull the base 105 toward the opposite direction of discharge. The bending unit 140 can bend the base 105 by pushing or pulling it. It can also deform the bending space S. When the base portion 105 is bent, not only the first die block 110, which is integrally formed with the base portion 105, but also the second die block 120, which is fastened and connected to the first die block 110 by bolts B, can be bent simultaneously.

[0082] Preferably, the center 50_C of the rotation axis of the coating roll 50 is moved further toward the second die block 120 than the upper part 112a of the first die lip 112. For example, instead of aligning the center 50_C of the rotation axis of the coating roll 50 with the upper part 112a of the first die lip 112, it is moved further down, to the so-called middle part of the first die lip 112, or to the lower part 112b of the first die block 110, or to another location, so-called toward the second die block 120. The bending center 142_C is also moved to a location that aligns with it. This makes it possible to form stable coated beads.

[0083] If the center 50_C of the rotation axis of the coating roll 50 is aligned with the upper part 112a of the first die lip 112, the curvature of the coating roll 50 causes a significant problem in which the coating gap differs in the front-to-back direction of the slot die coater 100, potentially negatively affecting the quality of the coating. This will be explained in more detail in the comparative example section below.

[0084] Figure 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 portion A in Figure 8.

[0085] First, referring to Figure 8, the dual-slot die coater 200 has one more slot compared to the slot die coater 100 in Figure 2.

[0086] For this purpose, the dual-slot die coater 200 further includes a third die block 130 positioned in front of the second die block 120, forming an additional slot 125 between the second die block 120 and the third die block 130. For ease of explanation, 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.

[0087] The dual-slot die coater 200 can coat the surface of a continuously moving substrate 60 by extruding a coating liquid, such as an electrode active material slurry, through at least one of the first slot 115 and the second slot 125. The dual-slot die coater 200 can discharge the coating liquid in the opposite direction to gravity and can discharge two types of coating liquids, identical or different, through the first slot 115 and the second slot 125 to coat the substrate 60 simultaneously or alternately.

[0088] In the dual-slot die coater 200, the first die block 110 may also be called the top die, the second die block 120 the middle die or inner die, and the third die block 130 the bottom die or outer die.

[0089] The second die block 120 of this embodiment, shown in Figure 8, has a right-angled triangular cross-section, but is not necessarily limited to this shape; for example, the cross-section may be formed as an isosceles triangle. When the cross-section is a right-angled triangle, the first slot 115 is positioned approximately perpendicular to the substrate 60, making it easier to control the discharge of the coating liquid through the first slot 115.

[0090] The third die block 130 may also have a triangular cross-section at its upper part. The third die block 130 is also a plate-like structure that extends along the width direction. The third die block 130 includes a third die lip 132 that forms its tip relative to the base material 60.

[0091] A shim 127 may also be provided between the second die block 120 and the third die block 130. The shim 117 provided between the first die block 110 and the second die block 120 may be called the upper shim 117, and the shim 127 provided between the second die block 120 and the third die block 130 may be called the lower shim 127. The upper shim 117 and the lower shim 127 may be the same.

[0092] Here, since the lower surface of the second die block 120 and the lower surface of the third die block 130 do not make surface contact with the base 105, a bending space S may be provided between them and the upper surface of the base 105. Alternatively, even if the lower surfaces of the second die block 120 and the lower surface of the third die block 130 make surface contact with the base 105 due to the configuration described with reference to Figure 6, a bending space S may be formed between them and the base 105. It has already 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 include a manifold 138 that contains the same or a different coating liquid as the above and communicates with the second slot 125. For ease of explanation, the manifold 118 formed on the first die block 110 may be referred to as the upper manifold 118, and the manifold 138 formed on the third die block 130 may be referred to as the lower manifold 138. The coating liquid contained in the upper manifold 118 may be referred to as the first coating liquid 150, and the coating liquid contained in the lower manifold 138 may be referred to as the second coating liquid 160. In this way, the manifolds 118 and 138 are formed in the first die block 110 and the third die block 130, respectively. This makes it possible to minimize the impact on the deformation of the structurally weakest second die block 120. Moreover, if the second die block 120 is divided into a left die (rear side) and a right die (front side), and the left die is configured to move integrally with the first die block 110, and the right die is configured to move integrally with the third die block 130, a mechanism can be realized 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 realizing a structure in which the positions of the first slot 115 and the second slot 125 can change even more easily.

[0093] Referring to Figures 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 the second coating liquid 160, which is contained in the lower manifold 138 shown in Figure 8, onto the substrate 60. The first discharge port 116 is located downstream of the second discharge port 126 in the coating direction and discharges the first coating liquid 150, which is contained in the upper manifold 118 shown in Figure 8, onto the substrate 60. In other words, the upper layer can be formed using the first discharge port 116 and the lower layer using the second discharge port 126 to form a double-layer coating.

[0094] In this way, the rotatable coating roll 50 is positioned on the discharge direction side of the dual-slot die coater 200, and by rotating the coating roll 50, the substrate 60 to be coated is moved along the substrate 60, and the first coating liquid 150, which is the first electrode active material slurry, and the second coating liquid 160, which is the second electrode active material slurry, are continuously brought into contact with the surface of the substrate 60, thereby simultaneously coating the substrate 60 with a two-layer structure. The second coating liquid 160 is coated onto the substrate 60 first to form a lower slurry layer, and almost simultaneously, the first coating liquid 150 is coated onto the lower slurry layer to form an upper slurry layer.

[0095] In this embodiment as well, the center 50_C of the rotation axis of the coating roll 50 is further moved toward the second die block 120 than the upper part 112a of the first die lip 112.

[0096] In Figures 8 and 9, the first reference line L1 is shown to be a vertical line aligned with the upper part 112a of the first die lip 112 at the center 50_C of the rotation axis of the coating roll 50. In this embodiment, the vertical line Lc can be aligned to the right of, i.e., forward of, such a first reference line L1 at the center 50_C of the rotation axis of the coating roll 50.

[0097] In Figures 8 and 9, the second reference line L2 is shown to be a vertical line aligned with the lower part 132b of the third die lip 132 at the center 50_C of the rotation axis of the coating roll 50. In this embodiment, the vertical line Lc may be aligned to the left, i.e., behind, such a second reference line L2 at the center 50_C of the rotation axis of the coating roll 50.

[0098] For example, the center 50_C of the rotation axis of the coating roll 50 may be located at position LA, aligned with the middle of the first die lip 112 (between reference numerals 112a and 112b). At the center 50_C of the rotation axis of the coating roll 50, the vertical line Lc passes through the middle of the first die lip 112.

[0099] To give another example, the center 50_C of the rotation axis of the coating roll 50 may be aligned with the upper part 122a of the second die lip 122 and be located at position LB. At the center 50_C of the rotation axis of the coating roll 50, the vertical line Lc passes through the upper part 122a of the second die lip 122.

[0100] In yet another example, the center 50_C of the rotation axis of the coating roll 50 may be aligned with the lower part 112b of the first die lip 122. At the center 50_C of the rotation axis of the coating roll 50, the vertical line Lc passes through the lower part 112b of the first die lip 112.

[0101] To give yet another example, the center 50_C of the rotation axis of the coating roll 50 may be aligned to a point 1 mm away from the lower part 112b of the first die lip 122 toward the second die lip 122. Depending on the thickness of the upper shim 117, the position of the second die lip 122 may change. If the thickness of the upper shim 117 is 1 mm, the point 1 mm away from the lower part 112b of the first die lip 122 toward the second die lip 122 may be the upper part 122a of the second die lip 122, i.e., the position of LB.

[0102] To give yet another example, the center 50_C of the rotation axis of the coating roll 50 may be located in the middle of the second die lip 122 (between reference numerals 122a and 122b), or at the lower part 122b of the second die lip 122, or at the upper part 132a of the third die lip 132.

[0103] In this case, since the bending effect changes as the center 50_C of the rotation axis of the coating roll 50 changes, it is preferable that the position of the bending center 142_C also changes accordingly. Therefore, it is preferable that the center 50_C of the rotation axis of the coating roll 50 and the bending center 142_C are aligned with each other.

[0104] 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 lip 112 at the center 50_C of the rotation axis of the coating roll 50, the bending center 142_C also passes through. That is, when the center 50_C of the rotation axis of the coating roll 50 is aligned with the middle of the first die lip 112 and is at position LA, the position of the bending unit 140 is changed so that the bending center 142_C is also at position LA.

[0105] Similarly, the position of the bending unit 140 is determined such that when the vertical line Lc passes over the upper part 122a of the second die lip 122 at the center 50_C of the rotation axis of the coating roll 50, the bending center 142_C also passes over it. That is, when the center 50_C of the rotation axis of the coating roll 50 is aligned with the upper part 122a of the second die lip 122 and is at position LB, the position of the bending unit 140 is changed so that the bending center 142_C is also at position LB.

[0106] For this reason, in the present invention, the hole H for fastening the bending unit 140 and the base 105 is formed as an elongated hole, as shown in Figure 7 above, so that the bending center 142_C also moves when the position of the vertical die is changed.

[0107] Since the hole H for fastening the bending unit 140 and the base 105 is formed as an elongated hole, the position of the bending unit 140 fastened thereto can be made movable in the front-rear direction (see the arrows in both directions). The position of the bending unit 140 can be the center position of the base 105, and may be set to a position closer to the second die block 120 or closer to the third die block 130, as needed. As the bending unit 140 approaches, it receives a greater force and the effect of bending it more. The bending unit 140 may also push the base 105 in the discharge direction or pull the base 105 in the direction opposite to the discharge direction.

[0108] Preferably, even in the dual-slot die coater 200, the center 50_C of the rotation axis of the coating roll 50 is positioned further toward the second die block 120 than the upper part 112a of the first die lip 112. For example, instead of aligning the center 50_C of the rotation axis of the coating roll 50 with the upper part 112a of the first die lip 112, i.e., the upper part of the first die block 110, it is changed to the lower part of the first die block 110 or another location. The bending center 142_C is also changed to a location that is aligned with it. This makes it possible to form stable coated beads.

[0109] Comparative Example Figure 11 is a schematic cross-sectional view of a dual-slot die coater according to a comparative example.

[0110] Referring to Figure 11, the comparative example aligns the center 50_C of the rotation axis of the coating roll 50 with the bending center 142_C of the upper part 112a of the first die lip 112, which is the alignment method of the "upper part of the first die block". In this case, the coating gap in the rear beads BB becomes excessively large, the coating beads are not formed stably, the coating beads become unstable, and there is a risk of so-called back leak occurring, where they rupture and flow out to the rear.

[0111] Figure 12 is a graph simulating the coating gap at each position when the center 50_C of the rotation axis of the coating roll is aligned with the upper part 112a of the first die lip 112, as in the comparative example. Here, it is assumed that the thickness of the shims 117 and 127 is 1 mm and the diameter of the coating roll 50 is 350 mm.

[0112] In Figure 12, the vertical axis shows the physical thickness and spacing of the die lips (labeled as upper plate LIP, middle plate LIP, and lower plate LIP), in units of 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 lip 112. In Figure 12, the horizontal axis shows the spacing between the die lip and the coating roll (labeled as C-roll), in units of mm. The end of the die lip is at position 1 on the horizontal axis, and the outer circumference of the coating roll at the center of the rotation axis 50_C is at position 2.5. Therefore, the coating gap, which was set for calculation purposes, is 1.5 mm. Inside Figure 12, the additional gaps for each die lip position are shown. The additional gaps are values ​​increased compared to the set coating gap of 1.5 mm.

[0113] The top plate / upper section refers to the upper section 112a of the first die lip 112. Since the center 50_C of the rotation axis of the coating roll is located at this position, the additional gap is 0.0 compared to the set coating gap. The top plate / lower section is the additional gap at the lower section 112b of the first die lip 112, and is calculated as 2.9 μm. The middle plate / upper section is the additional gap at the upper section 122a of the second die lip 122, and is calculated as 11.4 μm. The middle plate / middle section is the additional gap at the midpoint between the upper section 122a and the lower section 122b of the second die lip 122, and is calculated as 17.9 μm. The middle plate / lower section is the additional gap at the lower section 122b of the second die lip 122, and is calculated as 25.7 μm. The bottom plate / upper section is the additional gap at the upper section 132a of the third die lip 132, and is calculated as 44.4 μm. The lower plate / bottom is an additional gap at the bottom 132b of the third die lip 132, calculated as 137.7 μm. Thus, the additional gap increases as it moves away from the center 50_C of the rotation axis of the coating roll.

[0114] The additional gap in the upper layer is calculated as 7.1 μm, which is the average of the additional gap of 2.9 μm in the upper / lower part of the top plate and the additional gap of 11.4 μm in the middle / upper part of the middle plate. The additional gap in the lower layer is calculated as 35.0 μm, which is the average of the additional gap of 25.7 μm in the middle / lower part of the top plate and the additional gap of 44.4 μm in the lower / upper part of the bottom plate. Because the center 50_C of the rotation axis of the coating roll is aligned with the upper part 112a of the first die lip 112, it is biased toward the first die block 110, and it is observed that an additional coating gap of 27.9 μm (relative value of the additional gap in the lower layer) is generated in the lower part due to the curvature of the coating roll 50.

[0115] Thus, when the center 50_C of the rotation axis of the coating roll 50 is aligned with the upper part 112a of the first die lip 112, a problem arises in which the coating gap changes significantly in the front-rear direction of the slot die coater 100 due to the curvature of the coating roll 50. In particular, it can be confirmed that the increase in the coating gap in the lower layer is even more pronounced than that in the upper layer.

[0116] In particular, in the case of a dual-slot die coater 200, the position of the upper part of the first die block 110, which is the alignment point, and the position of the rear bead BB are further apart than in a single-layer slot die coater 100, and the coating gap at the position of the rear bead BB becomes even larger, making it particularly vulnerable to back leaks in the case of an upper alignment double-layer coating of the first die block 110.

[0117] Examples In the present invention, back leaks can be prevented by moving the center 50_C of the rotation axis of the coating roll 50 further toward the second die block 120 than the upper part 112a of the first die lip 112.

[0118] Figure 13 is a graph simulating the coating gap at different positions when the center 50_C of the rotation axis 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. Similar to the comparative example, it is assumed that the thickness of the shims 117 and 127 is 1 mm and the diameter of the coating roll 50 is 350 mm.

[0119] As shown in Figure 13, the additional gaps for each die lip position are compared with the comparative example as follows: Since the center of the coating roll's rotation axis 50_C is located at the top / bottom of the plate, the additional gap is 0.0 compared to the set coating gap. The top / top is off-center from the center of the coating roll's rotation axis 50_C, so the additional gap is calculated as 2.9 μm. The additional gap at the middle / top is calculated as 2.9 μm, the middle / middle is 6.4 μm, the middle / bottom is 11.4 μm, the bottom / top is 24.7 μm, and the bottom / bottom is 100.8 μm. The additional gap increases as the distance from the center of the coating roll's rotation axis 50_C increases, but in this embodiment, the additional gap for each die lip position is significantly smaller than in the comparative example. Therefore, the rear beads do not move as far away as in the comparative example, and back leak is improved.

[0120] Furthermore, the additional gap in the upper layer is calculated as 1.4 μm, and the additional gap in the lower layer is calculated as 18.1 μm. Even if the center 50_C of the rotation axis of the coating roll is not aligned with the upper part 112a of the first die lip 112, and a coating gap occurs in the lower layer due to the curvature of the coating roll 50 as it approaches the second die block 120, it is observed that a coating gap of 16.6 μm is generated, which is much narrower than in the comparative example. Therefore, the coating conditions of the upper and lower layers become even more identical, and as a result, the quality of the coating layer can be controlled even more firmly. By reducing the difference in the coating gap between the upper and lower layers, the quality of individual loading of the upper / lower layers can be ensured.

[0121] Figure 14 is a graph illustrating the positional coating gap when the center 50_C of the rotation axis 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.

[0122] Based on Figure 14, the additional gaps for each die lip position are compared with the comparative example as follows: Since the center of the coating roll's rotation axis 50_C is located at the middle plate / upper section, the additional gap is 0.0 compared to the set coating gap. At the upper plate / upper section and upper plate / lower section, since they are off-center from the center of the coating roll's rotation axis 50_C, the additional gaps are calculated to be 11.4 μm and 2.9 μm, respectively. The additional gap at the middle plate / middle section is calculated to be 0.7 μm, at the middle plate / lower section it is 2.9 μm, at the lower plate / upper section it is 10.8 μm, and at the lower plate / lower section it is 69.7 μm. As before, the additional gap increases as the distance from the center of the coating roll's rotation axis 50_C increases, but in this embodiment as well, the additional gaps for each die lip position are significantly smaller than those at the comparative example. Therefore, the rear beads do not move as far away as in the comparative example, and back leaks are greatly improved.

[0123] Furthermore, according to Figure 14, the additional gap in the upper layer is calculated as 1.4 μm, and the additional gap in the lower layer is calculated as 6.8 μm. Even if the center 50_C of the rotation axis of the coating roll is not aligned with the upper part 112a of the first die lip 112, and even if a coating gap occurs in the lower layer due to the curvature of the coating roll 50 as it approaches the second die block 120, it is observed that a coating gap of 5.4 μm is generated, which is much narrower than in the comparative example and the embodiment of the present invention. This value is considered to have no significant difference in the coating gap. Therefore, the coating gaps of the upper and lower layers can be made uniform, and the individual loading quality of the upper and lower layers can be ensured.

[0124] As described above, the bending effect changes as the center 50_C of the rotation axis of the coating roll 50 is changed, so the position of the bending center 142_C should also be changed accordingly. If the hole H for fastening the bending unit 140 and the base 105 is formed in a circular shape, the position of the bending unit 140 will be fixed. However, if the hole H for fastening 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 made to coincide with the center 50_C of the rotation axis of the coating roll 50.

[0125] Figure 15 shows the results of testing the loading of the center and side sections according to the bending level (-40 μm to 40 μm) while changing only the position of the center 50_C of the rotation axis of the coating roll 50 from the lower part 112b of the first die lip 112 to the upper part 132a of the third die lip 132, without moving the bending center 142_C. The bending center 142_C was fixed in position by aligning it with the lower part 112b of the first die lip 112 and was not moved.

[0126] In Figure 15, the horizontal axis represents the center 50_C of the rotation axis of the coating roll 50, and the units are arbitrary. The value on the horizontal axis is 0 when the center 50_C of the rotation axis of the coating roll 50 is aligned with the lower part 112b of the first die lip 112. As the center 50_C of the rotation axis of the coating roll 50 moves toward the upper part 132a of the third die lip 132, the horizontal axis takes on negative values.

[0127] In Figure 15, the vertical axis shows the loading difference between the center and side portions of the coating layer, and the units are arbitrary. The values ​​are positive as the loading in the center portion increases.

[0128] A bending level of -40 μm is the condition when the base 105 is pressed down by that amount, compressing the bending space S; a bending level of 0 is the condition when it is not bent; and a bending level of 40 μm is the condition when the base 105 is pulled up by that amount, increasing the bending space S.

[0129] When the center 50_C of the rotation axis of the coating roll 50 is aligned with the lower part 112b of the first die lip 112, if the bending level is 40 μm, the loading difference between the center and the side is approximately 10, and as the center 50_C of the rotation axis of the coating roll 50 moves toward the upper part 132a of the third die lip 132, the loading difference between the center and the side gradually decreases. When the center 50_C of the rotation axis of the coating roll 50 is aligned with the lower part 112b of the first die lip 112, if the bending level is 0 μm, the loading difference between the center and the side is approximately 0, or almost zero, and as the center 50_C of the rotation axis of the coating roll 50 moves toward the upper part 132a of the third die lip 132, the loading difference between the center and the side gradually becomes a negative value. When the center 50_C of the rotation axis of the coating roll 50 is aligned with the lower part 112b of the first die lip 112, if the bending level is -40 μm, the loading difference between the center and the side is approximately -10. As the center 50_C of the rotation axis of the coating roll 50 moves toward the upper part 132a of the third die lip 132, the loading difference between the center and the side gradually becomes negative.

[0130] However, the loading difference (ΔBL1) for each bending level when the center 50_C of the rotation axis of the coating roll 50 is aligned with the lower part 112b of the first die lip 112 is different from the loading difference (ΔBL2) for each bending level when the center 50_C of the rotation axis of the coating roll 50 is aligned with the upper part 132a of the third die lip 132.

[0131] As shown in Figure 15, it can be analyzed that the bending effect differs slightly depending on the position of the center 50_C of the rotation axis of the coating roll 50. Please note the interaction. As the bending effect differs depending on the position of the center 50_C of the rotation axis of the coating roll 50, it is preferable to change the position of the bending center 142_C accordingly. The pressing portion where the bending force from the bending unit 140 is applied can be made to the point where the coating gap is minimized, thereby maintaining the bending effect (sensitivity).

[0132] According to the present invention, by forming the hole H for fastening the bending unit 140 and the base 105 as an elongated hole, the bending center 142_C is made to move along with the position of the vertical die when the alignment point is changed. The elongated hole H may have a shape that extends from behind the upper part 112a of the first die lip 112 to in front of the lower part 132b of the third die lip 132.

[0133] Thus, in the present invention, when the center 50_C of the rotation axis of the coating roll 50 is changed relative to the slot die coaters 100 and 200, the bending center 142_C of the bending unit 140 can also move in conjunction.

[0134] Therefore, the center of rotation axis 50_C of the coating roll 50 and the bending center 142_C can be aligned with each other and moved further toward the second die block 120 than the upper part 112a of the first die lip 112. The coating gap is minimized at the position of the bending press 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 with any part of the die lip of a vertical die type slot die coater 100, 200.

[0135] In particular, the dual-slot die coater 200 has a coating liquid injection direction that is towards the center of the die blocks 110 and 130, resulting in a larger amount of liquid coating in the center than on the sides. This allows for a non-uniform coating profile in the width direction (perpendicular to the MD direction) of the substrate 60. In other words, the loading of the coating liquid can be concentrated at the widthwise center of the first slot 115 and the second slot 125. In this case, the coating gap can be adjusted by pushing or pulling the base portion 105 corresponding to the second die block 120 and the third die block 130 using the bending unit 140, thereby changing the position of the second die lip 122 and the third die lip 132, and thus adjusting the loading distribution. By pushing each die block 110, 120, and 130 toward the discharge direction using the bending unit 140, the coating gap in the center portion can be narrowed. Conversely, by using the bending unit 140 to pull each die block 110, 120, and 130 in the opposite direction to the discharge direction, the coating gap in the center portion can be widened.

[0136] As described above, in comparative examples where the center alignment differs from that of the present invention, the coating gap widens in the rear beads, causing the coated beads to become unstable and resulting in back leaks. According to the present invention, stable coated beads can be formed by changing the alignment point between the coating roll 50 and the bending unit 140. Furthermore, the bending center 142_C can also be moved to achieve a uniform coating profile.

[0137] On the other hand, the first die lip 112, the second die lip 122, and the third die lip 132 may be located on the same straight line. Furthermore, the thickness of the third die lip 132 may be greater than the thickness of the first die lip 112 and the second die lip 122.

[0138] The appropriate coating area (window margin) lies between the leakage occurrence area and the side ring occurrence area. Productivity improves as this appropriate process area widens. The coating gap greatly affects the size and shape of the coating beads formed between the substrate 60 and the die lips 112, 122, and 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 kept constant to some extent by aligning the die lips 112, 122, and 132. By adjusting the size of the die lips 112, 122, and 132, the appropriate process area can be expanded, and initial conditions such as the physical properties of the coating liquid, the flow rate and speed of the coating liquid can be adjusted, giving more leeway to set initial conditions that minimize the occurrence of leakage.

[0139] Preferably, returning to Figure 9, the thickness D3 of the third die lip 132 is greater 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). The thickness D2 of the second die lip 122 and the thickness D1 of the first die lip 112 can be equal to each other. The thickness D1 of the first die lip 112 may be even larger than the thickness D2 of the second die lip 122.

[0140] The ratio of the thickness D3 of the third die lip 132 to the thickness D1 of the first die lip 112 can be 1.2:1 or greater. That is, the thickness D3 of the third die lip 132 can be 1.2 times or more the thickness D1 of the first die lip 112. If the thickness D3 of the third die lip 132 is even greater than the thickness D1 of the first die lip 112, it is possible to increase the appropriate process area, but when the thickness D3 of the third die lip 132 is 1.2 times or more the thickness D1 of the first die lip 112, there is an effect in that the occurrence of leakage is firmly suppressed. If the thickness D1 of the first die lip 112 is even greater than the thickness D3 of the third die lip 132, leakage will occur.

[0141] The ratio of the thickness D3 of the third die lip 132 to the thickness D2 of the second die lip 122 can be 1.2:1 or greater. That is, the thickness D3 of the third die lip 132 can 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 even greater than the thickness D2 of the second die lip 122, it is possible to increase the appropriate process area, but when 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 effectively suppressing the occurrence of leaking. When the thickness D3 of the third die lip 132 and the thickness D2 of the second die lip 122 are equal, leaking occurs. If the thickness D2 of the second die lip 122 is even greater than the thickness D3 of the third die lip 132, even if leaking does not occur, other pattern defects will be caused.

[0142] As shown in the above example, the thickness D3 of the third die lip 132 is the maximum, being even 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 widens. This allows for more leeway in controlling the coating gap and setting initial conditions. Therefore, this configuration offers excellent productivity, and during coating, the dynamic contact line can be used at various positions depending on the target coated product and quality. According to the present invention, as a result of widening the appropriate process area, the leaking limit can be improved, i.e., the leaking limit can be raised. Furthermore, the area in which side rings occur can be narrowed. As the coating gap narrows, if the dynamic contact line moves in the direction opposite to the coating, leaking occurs above a certain level, but according to the configuration of the present invention, the leakage can be improved by increasing the thickness D3 of the third die lip 132. This is because the second coating liquid 160 is not allowed to flow out to the rear, and a larger amount of the second coating liquid 160 can be retained in the third die lip 132. According to the present invention, leakage is reduced even when the coating gap is insufficient, or when the amount of coating liquid supplied is even greater than the running speed of the substrate 60.

[0143] A preferred example is when the thickness D3 of the third die lip 132, the thickness D2 of the second die lip 122, and the thickness D1 of the first die lip 112 are in a ratio of 1.5:0.5:1.

[0144] To give another example, the thickness D3 of the third die lip 132 and the thickness D1 of the first die lip 112 are equal to each other and may be even greater than the thickness D2 of the second die lip 122 (D3 = D1 > D2).

[0145] The ratio of the thickness D3 of the third die lip 132 to the thickness D2 of the second die lip 122 can be 1.2:1 or greater. That is, the thickness D3 of the third die lip 132 can 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 even greater than the thickness D2 of the second die lip 122, it is possible to increase the appropriate process area, but when 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 a clear effect of suppressing the occurrence of leaking. When the thickness D3 of the third die lip 132 and the thickness D2 of the second die lip 122 are equal, leaking occurs. If the thickness D2 of the second die lip 122 is even greater than the thickness D3 of the third die lip 132, even if leaking does not occur, other pattern defects will be caused.

[0146] The thickness D1 of the first die lip 112 may be equal to the thickness D3 of the third die lip 132 and even greater than the thickness D2 of the second die lip 122. Alternatively, the thickness D1 of the first die lip 112 may not be greater than the thickness D3 of the third die lip 132, thereby suppressing the occurrence of leakage.

[0147] As shown in the above example, the large thickness D3 of the third die lip 132 results in a wider optimal process area. Therefore, more leeway is available for controlling the coating gap and setting initial conditions.

[0148] For example, the method for coating an electrode active material slurry using the slot die coater of the present invention is applicable to the manufacture of a positive electrode for a secondary battery. The positive electrode has a structure in which a lower active material layer made of a lower slurry layer and an upper active material layer made of an upper slurry layer are stacked in this order 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 adjusted within the range of 0.5% to 5% by 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, when the content of the conductive material in the upper active material layer is controlled to a very low level of 0.02% by weight or less, the heat generation reaction when a short circuit occurs inside the cell can be reduced.

[0149] 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 smaller particle size is applied to the lower active material layer. By applying an active material with a relatively larger particle size to the upper active material layer, it is possible to facilitate impregnation with the electrolyte and induce the smooth movement of ions or holes.

[0150] Here, the flow rate ratio of the first coating liquid 150 to the second coating liquid 160 may be 1:1. The viscosity of the first coating liquid 150 and the second coating liquid 160 may be 1000 cps or more. Because it is necessary that the device is capable of coating with a coating liquid having a viscosity of 1000 cps or more, the dual-slot die coater 200 of the present invention differs in structure from devices that coat ordinary resin liquids, such as photographic photosensitive emulsions, magnetic liquids, liquids that provide anti-reflective or anti-glare properties, liquids that provide a viewing angle expansion effect, and pigment liquids for color filters, and is not a device that can be conceived by modifying such devices. The first coating liquid 150 and the second coating liquid 160 may contain graphite, a conductive material, carboxymethylcellulose (CMC), and a binder.

[0151] 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, and the thickness D1 of the first die lip 112 are in a ratio of 3:1:1. With such a dual-slot die coater 200, process efficiency can be increased and the defect rate can be reduced when forming a two-layer active material layer on the current collector.

[0152] To give a specific example, the present invention can be applied to the manufacture of a positive electrode for a secondary battery by coating a positive electrode active material slurry using the dual-slot die coater 200 of the present invention. The positive electrode includes a current collector and a positive electrode active material layer formed on the surface of the current collector. The current collector is made of an electrically conductive material such as Al or Cu, and an appropriate one can be used 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, conductive materials, and binders. The positive electrode may also further include various additives aimed at complementing or improving its electrochemical properties.

[0153] The active material is not limited to any specific component, as long as it can be used as the positive electrode active material for lithium-ion secondary batteries. Examples of this non-limiting nature include layered compounds such as lithium manganese composite oxides (LiMn2O4, LiMnO2, etc.), lithium cobalt oxide (LiCoO2), and lithium nickel oxide (LiNiO2), as well as 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; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiV3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-x M x Ni-site type lithium nickel oxide represented as O2 (where M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3); chemical formula LiMn 2-x M xLithium manganese composite oxides represented as 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 part of the Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3 may be included, or a mixture of two or more of these. In the present invention, the positive electrode may include one or more of polymer-based solid electrolytes, oxide-based solid electrolytes, and sulfide-based solid electrolytes as the solid electrolyte material.

[0154] Conductive materials can typically be added in an amount of 1% to 20% by weight relative to the total weight of the mixture containing the active material. Such conductive materials can be used without particular limitations as long as they do not cause chemical changes in the battery and are conductive. For example, they may include one or more of the following conductive materials selected from: graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Zinnel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fiber and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0155] The binder is not particularly limited as long as it is a component that assists in the bonding of the active material to the conductive material and 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, or various copolymers. The binder is usually included in an amount of about 1% to 30% by weight, or 1% to 10% by weight, relative to the total weight of the electrode layer.

[0156] The present invention can also be applied to the manufacture of a negative electrode for a secondary battery by coating a negative electrode active material slurry using the dual-slot die coater 200. The negative electrode includes 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 a plurality of negative electrode active material particles and one or more of a conductive material and a binder. The negative electrode may also further include various additives aimed at complementing or improving its electrochemical properties.

[0157] The negative electrode active material may include carbon materials such as graphite, amorphous carbon, diamond-like carbon, fullerene, carbon nanotubes, and carbon nanohorns, as well as lithium metal materials, alloy materials such as silicon and tin, Nb2O5, and Li5Ti4O 12 Oxide-based materials such as TiO2, or composites thereof, can be used. For the negative electrode, please refer to the description regarding conductive materials, and for the binder and current collector, please refer to the description regarding the positive electrode.

[0158] Electrode active material slurries containing such positive and negative electrode active materials have very high viscosity. For example, the viscosity can be 1000 cps or more. The viscosity of electrode active material slurries used for forming secondary battery electrodes may be 2000 cps to 30000 cps. For example, the viscosity of negative electrode active material slurry may be 2000 cps to 4000 cps. The viscosity of positive electrode active material slurry may be 8000 cps to 30000 cps. Because it is necessary to be able to coat with coating liquids with a viscosity of 1200 cps or more, the dual-slot die coater 200 of the present invention differs in structure from devices that coat ordinary resin liquids, such as photographic photosensitive emulsions, magnetic liquids, liquids that provide anti-reflective or anti-glare properties, liquids that provide a widening of the viewing angle, and pigment liquids for color filters, and it is not a device that can be conceived by modifying such devices. The dual-slot die coater 200 of the present invention is for coating an electrode active material slurry that may contain an active material having an average particle size of approximately 10 μm. Therefore, it differs in structure from other coating devices that do not contain particles of such size, and it is not a device that can be conceived by simply modifying the existing device.

[0159] Figure 16 is a modified version of Figure 8.

[0160] Referring to Figure 16, the third die lip 132 is set back even further than the first die lip 112 and the second die lip 122.

[0161] The distance H3 between the base material 60 and the third die lip 132 is greater than the distance H1 between the base material 60 and the first die lip 112 and the distance H2 between the base material 60 and the second die lip 122. By moving the third die lip 132 further away from the base material 60 in the opposite direction to the discharge direction than the first die lip 112 and the second die lip 122, such a distance difference can be generated to form a step between the die lip and the base material 60. The distance H1 between the base material 60 and the first die lip 112 and the distance H2 between the base material 60 and the second die lip 122 may be equal to each other.

[0162] As a result, a predetermined step D' is formed between the second discharge port 126 and the first discharge port 116. This step D' is 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. By positioning the second discharge port 126 and the first discharge port 116 so that they are separated from each other horizontally by an amount corresponding to this step D', there is no concern 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, a characteristic of the configuration of this embodiment is that the second die block 120 and the third die block 130 that form the second discharge port 126 are separated from each other.

[0163] As shown in the figure, with the positions of the die lips 112, 122, and 132 set, the first discharge port 116 is located downstream in the coating direction and separated from the second discharge port 126. By simultaneously discharging the coating liquid through the second discharge port 126 and the first discharge port 116 while running the substrate 60 from the third die lip 132 toward the first die lip 112, a two-layer active material layer can be formed on the substrate 60.

[0164] The present invention separates only the upstream portion of the lower layer from the substrate 60, using the lower layer slurry, i.e., the second coating liquid 160 discharged from the second discharge port 126, as a reference. In other words, a height difference is created between the second die block 120 and the third die block 130, which are the two plates forming the second discharge port 126, so that the third die block 130 moves further away from the substrate 60. This differs from cases where only the movement of the discharge port itself is utilized without distinguishing between upstream and downstream.

[0165] 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 150 discharged through the first discharge port 116 can be in the range of 1:3 to 3:1 (T1:T2). The ratio of thicknesses represents the relative average values ​​of the lengths in the thickness direction of each layer. The average thicknesses T1 and T2 of the lower slurry layer and the upper slurry layer, respectively, can be 40 μm to 200 μm.

[0166] The thickness of the slurry layer as described above is considered to be the pressure of the supplied coating liquid. If the pressure of the first coating liquid 150 is supplied at more than 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 more, the pressure of the upper layer is even stronger than that of the lower layer, which pushes the second coating liquid 160 backward in the opposite direction to the direction of coating progress, increasing the likelihood of leakage, and there is a risk that the second coating liquid 160 will not be supplied properly due to the strong pressure of the first coating liquid 150. In addition, because the supply of the second coating liquid 160 is uniform due to the high pressure of the first coating liquid 150, there is a problem that the lower slurry layer will not be formed uniformly.

[0167] On the other hand, 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 to the upper slurry layer is 3:1 or more, problems arise such as difficulty in supplying the first coating liquid 150, or unevenness of the coating surface due to the coating of the first coating liquid 150 being pushed in the direction of coating progression.

[0168] The step D' is preferably in the range of 20% to 70% of the sum of the average layer thickness T1 of the lower slurry layer and the average layer thickness T2 of the upper slurry layer. If the range is less than 20%, the effect of shortening the loading gap length when the supply of the coating liquid is interrupted is not significant. If the range exceeds 70%, the total area of ​​the space where the coating liquid remains for coating, i.e., the space between the die lips 122, 132 and the lower slurry layer, is insufficient compared to the amount of coating liquid, and as a result, leakage occurs where the supplied second coating liquid 160 leaks out to the rear without being able to coat.

[0169] Due to intermittent coating, interrupting the supply of coating liquid during pattern formation causes a gradual interruption in loading, resulting in a so-called loading disappearance phenomenon. This loading disappearance phenomenon occurs when the supply of coating liquid is interrupted to form the edges, causing a meniscus to form between the dual-slot die coater 200 and the substrate 60, or when residual coating liquid remaining in bead form is coated onto the substrate 60. In this embodiment, as shown in Figure 16, the third die block 130 is retracted, so a meniscus is not formed between the dual-slot die coater 200 and the substrate 60, and the amount of residual coating liquid remaining in bead form is reduced. The length S' from the first die lip 112 to the meniscus of the second coating liquid 160 is shortened. As a result, when the supply of coating liquid is interrupted, loading does not gradually interrupt, and the length over which loading gradually disappears is shortened. Therefore, it becomes possible to ideally form the edges of the pattern approximately perpendicular to the substrate 60, and the length of the loading disappearance section can be shortened. The loading loss section acts as a waste portion, which leads to decreased process efficiency and increased manufacturing costs. According to the configuration of the present invention, the loading loss section is shortened, reducing the waste portion and resulting in increased process efficiency and reduced manufacturing costs.

[0170] In another example, the first die lip 112 may be further recessed than the second die lip 122 or the third die lip 132.

[0171] In this case, although not shown separately in the illustration, the relationship H1 > H2 and H1 > H3 holds between the distance H1 between the substrate 60 and the first die lip 112, 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, as shown in Figure 16. In this case, H2 may be equal to H3. By moving the first die lip 112 further away from the substrate 60 in the direction opposite to the discharge direction than the second die lip 122 and the third die lip 132, such a distance difference can be generated to form a step between the die lip and the substrate. In this case, the upper layer coating gap and the lower layer coating gap can be controlled separately depending on the degree to which the first die lip 112 is moved back.

[0172] To give yet another example, the second die lip 122 may be even further recessed than the first die lip 112 or the third die lip 132.

[0173] In this case, although not shown separately in the illustration, the relationship H2 > H1 and H2 > H3 holds between the distance H1 between the substrate 60 and the first die lip 112, 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, as shown in Figure 16. In this case, H1 may be equal to H3. By moving the second die lip 122 further away from the substrate 60 in the direction opposite to the discharge direction than the first die lip 112 and the third die lip 132, such a distance difference can be generated to form a step between the die lip and the substrate. In this case, when the supply of the coating liquid is interrupted for intermittent coating, it is possible to prevent residual coating liquid adhering to the second die lip 122 from falling haphazardly onto the substrate 60 and causing pattern defects such as drag lines.

[0174] To give yet another example, the third die lip 132 may be even further advanced than the first die lip 112 or the second die lip 122.

[0175] In this case, although not shown separately in the illustration, the relationship H1 > H3 and H2 > H3 holds between the distance H1 between the base material 60 and the first die lip 112, the distance H2 between the base material 60 and the second die lip 122, and the distance H3 between the base material 60 and the third die lip 132, as shown in Figure 16. In this case, H1 may be equal to H2. By pressing the third die lip 132 further toward the discharge direction than the first die lip 112 and the second die lip 122 and positioning it near the base material 60, such a distance difference can be generated, forming a step between the die lip and the base material 60. If an excessive additional gap occurs in the lower layer, causing back leakage, as proposed in the present invention, in addition to further displacing the center 50_C of the rotation axis of the coating roll 50 toward the second die block 120 beyond the upper part 112a of the first die lip 112 to reduce back leakage, the back leakage can be further reduced by advancing only the third die lip 132 to narrow the lower layer coating gap.

[0176] Although the present invention has been described above with limited embodiments and drawings, the technical idea of ​​the present invention is not limited in any way to these, and it goes without saying that it is possible for a person with ordinary skill in the art to which the present invention belongs to to implement the invention with various modifications and variations within the equivalent scope of the technical idea and claims of the present invention. [Explanation of Symbols]

[0177] 50 coating rolls 60 Base material 100 Slot Die Coater 105 Base 110 First Die Block 112 First Dilip 115 slots, 1st slot 116 Discharge port 117 Sims 118 Manifold 120 Second Die Block 122 Second Dilip 125 Second slot 126 Second discharge port 127 Sims 130 Third Die Block 132 Third Dilip 138 Manifold 140 Bending Unit 142 Die connection section 144 Main unit 150 First coating liquid 160 Second coating liquid 200 Dual Slot Die Coater B bolt H hole S-shaped bending space

Claims

1. A slot die coater having slots for discharging a coating liquid in the opposite direction to gravity onto the surface of a substrate that is continuously transported by a coating roll, The first die block and A second die block that forms the slot between itself and the first die block, Includes, A slot die coater in which the center of the rotation axis of the coating roll is located further toward the second die block than the upper part of the first die lip that forms the tip of the first die block relative to the substrate.

2. The slot die coater according to claim 1, wherein the first die block is disposed vertically and integrally with the base at the rear of the upper surface of the base, and the second die block is disposed in front of the first die block.

3. The slot die coater according to claim 2, wherein the second die block is not in surface contact with the base, or if it is in surface contact, a bending space is formed between it and the base.

4. The slot die coater according to claim 3, wherein a bending unit is connected to the lower end of the base so as to deform the bending space.

5. The slot die coater according to claim 4, wherein the hole formed in the base for fastening the bending unit to the base is formed as an elongated hole in the front-rear direction, thereby allowing the position of the bending unit to be changed.

6. The slot die coater according to claim 4, wherein the center of the rotation axis of the coating roll is aligned with the bending center of the bending unit.

7. The slot die coater according to claim 2, further comprising a third die block positioned in front of the second die block and forming an additional slot between itself and the second die block.

8. The slot die coater according to claim 7, wherein the center of the rotation axis of the coating roll is located in the middle of the first die lip, located below the first die lip, located above the second die lip that forms the tip of the second die block, located in the middle of the second die lip, located below the second die lip, or located above the third die lip that forms the tip of the third die block.

9. The slot die coater according to claim 7, wherein the second die block is not in surface contact with the base, or even if it is in surface contact, a bending space is formed between it and the base, a bending unit is connected to the lower end of the base so as to deform the bending space, and a hole is formed in the base as a long hole in the front-rear direction to fasten the bending unit and the base, so that the center of the rotation axis of the coating roll is aligned with the center of bending by the bending unit.

10. The slot die coater according to claim 9, wherein the elongated hole extends from behind the upper part of the first die lip to in front of the lower part of the third die lip that forms the tip of the third die block.

11. A slot die coater having slots for discharging a coating liquid in the opposite direction to gravity onto the surface of a substrate that is continuously transported by a coating roll, A first die block is disposed vertically and integrally with the base at the rear of the upper surface of the base, A second die block that forms the slot between itself and the first die block, A bending unit connected to the lower end of the base, Includes, A slot die coater configured such that when the center of rotation axis of the coating roll is changed relative to the slot die coater, the bending center of the bending unit also moves in conjunction with it.

12. The slot die coater according to claim 11, wherein the center of the rotation axis of the coating roll is located further toward the second die block than the upper part of the first die lip that forms the tip of the first die block relative to the substrate.

13. The slot die coater according to claim 12, wherein the hole formed in the base for fastening the bending unit to the base is formed as an elongated hole in the front-rear direction, thereby allowing the position of the bending unit to be changed.

14. The slot die coater according to claim 11, further comprising a third die block positioned in front of the second die block and forming an additional slot between itself and the second die block.

15. The slot die coater according to claim 14, wherein the cross-section of the second die block is a right triangle.

16. The slot die coater according to claim 14, wherein the first die block, the second die block and the third die block each comprises a first die lip, a second die lip and a third die lip that form the tip of the die, the center of the rotation axis of the coating roll is located further toward the second die block 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 located on the same line, or the third die lip is set further back than the first die lip and the second die lip.

17. The slot die coater according to claim 14, wherein the first die block, the second die block and the third die block each comprises a first die lip forming the tip of the die, a second die lip and a third die lip, the center of the rotation axis of the coating roll is located further toward the second die block than the upper part of the first die lip with respect to the substrate, the first die lip is further retracted than the second die lip and the third die lip, the second die lip is further retracted than the first die lip and the third die lip, or the third die lip is further forward than the first die lip and the second die lip.

18. The slot die coater according to claim 16, wherein the thickness of the third die lip is greater than the thickness of the first die lip and the thickness of the second die lip.

19. The slot die coater according to claim 16, wherein the thickness of the third die lip is equal to the thickness of the first die lip and greater than the thickness of the second die lip.

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