Patent Description:
As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and such secondary batteries essentially include an electrode assembly which is a power generation element. The electrode assembly has a form in which a positive electrode, a separator, and a negative electrode are stacked at least once, and the positive electrode and the negative electrode are prepared by coating and drying a positive electrode active material slurry and a negative electrode active material slurry on current collectors made of aluminum foil and copper foil, respectively. In order to equalize charging/discharging features of secondary batteries, the positive electrode active material slurry and the negative electrode active material slurry should be uniformly coated on the current collectors, and a slot die coater is conventionally used therefor.

<FIG> is a cross-sectional view of a conventional slot die coater.

Referring to <FIG>, in an electrode manufacturing method using the slot die coater, an active material slurry discharged from a slot die coater <NUM> is coated on an current collector <NUM> transferred by a coating roll <NUM>. The active material slurry discharged from the slot die coater <NUM> is widely coated on one surface of the current collector <NUM> to form an active material layer. The slot die coater <NUM> includes two die blocks <NUM> and <NUM> and forms a single slot <NUM> between the two die blocks <NUM> and <NUM>, and may form the active material layer of one layer by discharging one type of active material slurry through a discharge port <NUM> communicatively connected to the single slot <NUM>. A slot die coater enables fast coating as compared with bar coating or comma coating, and thus has been widely applied in terms of high productivity. The slot die coater exemplified in <FIG> is a vertical die type in which an active material slurry is discharged in a direction opposite to gravity.

In order to manufacture a secondary battery of high energy density, the thickness of the active material layer which was about <NUM> gradually increased to reach <NUM>. When the thick active material layer is formed with the conventional slot die coater <NUM>, since migration of a binder and a conductive material in the active material slurry deepens during drying, a final electrode is manufactured non-uniformly. In order to solve this problem, when coating is performed two times such as coating thinly and drying the active material layer and then coating and drying the active material layer, it takes a long time. In order to simultaneously improve electrode performance and productivity, a dual slot die coater capable of simultaneously coating two types of electrode active material slurries is required.

Since a slot die coater constitutes a slot on a coupling surface of die blocks, basically three die blocks are required to include two slots like the dual slot die coater. Since a process using the dual slot die coater should use active material slurries simultaneously discharged from different discharge ports, it is quite difficult to form each active material layer to a desired thickness.

A separation distance from a discharge port to the surface of a current collector is a coating gap, which is a very important variable in determining the coating quality of an active material layer. In general, the thickness of each active material layer is affected by the discharge amount of each of the active material slurries through the discharge ports, the types of the active material slurries, and the coating gap. When the coating gap is uniform in a width direction (transverse direction (TD)) of the current collector, stable coating is possible, and, when there is a coating gap deviation in the width direction, a coating width and the shape of a non-coated portion boundary have a lot of influence. The thickness of an active material layer is a very small value of several tens to several hundreds of µm, and should be very strictly controlled because even a change of only several µm in the thickness seriously affects the coating quality. The thickness of the active material layer needs to be very strictly controlled so as to exhibit uniform dimensional accuracy in the width direction in order to stably perform uniform coating in the width direction of the current collector. However, when the width of the dual-slot die coater increases in order to use a long-width current collector to increase production, it becomes more difficult to perform uniform coating in the width direction, and precise control of the coating gap becomes more necessary.

In addition, an appropriate coating gap range is determined according to the type of active material slurry. In a production process, it is necessary to manufacture various products using several types of active material slurries instead of using one type of active material slurry. In order to use various active material slurries, it is difficult to individually provide a dual-slot die coater dedicated to each active material slurry. Therefore, it is necessary to coat a certain type of active material slurry by using one dual-slot die coater and then coat another type of active material slurry by using the dual-slot die coater. In this case, a previously set coating gap needs to be changed. In addition, since it is difficult to always uniformly manufacture the same type of active material slurries, there is dispersion in physical properties of the active material slurries depending on a manufacturing time point, so it is necessary to respond to such dispersion. Moreover, coating gap control becomes more important because fast coating reveals great coating quality variations due to dispersion in the physical properties of active material slurries.

In the conventional art, in order to produce a desired coating gap, it is necessary to repeat a task of disassembling and reassembling each die block while experimentally performing a coating process several times to adjust and check the coating gap. However, this coating gap is not only a variable that is adjusted sensitively enough to change even according to the fastening strength of bolts used for assembling between the die blocks, but also may be changed even by the force through which the active material slurry is discharged.

In order to configure a device having a foot print and volume similar to the conventional slot die coater <NUM> including one slot, the thickness of each of the die blocks must be thin, and for this reason, there is a problem of being structurally vulnerable to deformation and torsion inevitably. When deformation or torsion occurs, the painstakingly adjusted coating gap is twisted, which is a serious problem of causing defects in an electrode process. <CIT> discloses a dual-slot die coater.

The present disclosure is designed to solve the problems of the related art, and therefore the present disclosure is directed to providing a dual-slot die coater capable of easy coating gap adjustment and control of a width direction deviation of a coating gap.

In the present invention, there is provided a dual-slot die coater as defined in the appended set of claims, the dual-slot die coater includes a first slot and a second slot for discharging a coating solution in a direction opposite to gravity, the dual-slot die coater including a first die block vertically installed on a rear portion of an upper surface of a base, a second die block arranged on a front surface of the first die block to form the first slot between the second die block and the first die block, and a third die block arranged on a front surface of the second die block to form the second slot between the third die block and the second die block, and further including an alignment block provided between a front portion of the upper surface of the base and a lower surface of the second die block and fastened and coupled to the lower surface of the second die block and a lower surface of the first die block by bolts.

According to an embodiment of the present disclosure, the base and the first die block are integrated with each other.

The first slot may be perpendicular to the base.

A cross-section of the second die block may be a right triangle.

A vertical length of each of the second die block and the third die block may be less than a vertical length of the first die block.

The alignment block includes a stepped portion seated on the front portion of the upper surface of the base and a front surface of the base.

The bolts include a bolt fastened to the alignment block and the second die block by penetrating through a lower surface of the base, and a bolt fastened to the third die block by penetrating through the alignment block.

The bolts may further include a bolt fastened to the base by penetrating through a front surface of the alignment block.

The lower surface of the second die block and a lower surface of the third die block may closely contact an upper surface of the alignment block and may be arranged with each other.

The first die block, the second die block, and the third die block may include a first die lip, a second die lip, and a third die lip as respective front end portions, respectively, and the first die lip, the second die lip, and the third die lip may be located on a same straight line.

A first discharge port communicatively connected to the first slot may be formed between the first die lip and the second die lip, and a second discharge port communicatively connected to the second slot may be formed between the second die lip and the third die lip,the dual-slot die coater may extrude and coat an active material slurry through at least one of the first slot and the second slot on a surface of a continuously running substrate, and a step may be formed between the first discharge port and the second discharge port.

The alignment block may be provided in plural in a width direction of the dual-slot die coater.

A vertical cross-section of the alignment block may include a first cross-section portion and a second cross-section portion extending vertically from the first cross-section portion. In other words, the vertical cross-section may have a '¬' or 'L' shape.

The alignment block may be a single monolithic component rather than being divided into several components.

According to the present disclosure, respective lower surfaces of die blocks are aligned with each other through an alignment block. The respective lower surfaces of the die blocks may be naturally aligned with each other by a combination of the die blocks with respect to the alignment block. Then, misalignment between the die blocks may be prevented, and a distance between respective front end portions of the die blocks and a substrate, that is, a coating gap, may be always maintained at a desired degree. Since the die blocks are fixed through the alignment block, a once-determined coating gap is not easily changed during a process and is maintained, thereby suppressing occurrence of a variation in the coating gap in a width direction.

Therefore, according to the present disclosure, there is no need to adjust the coating gap while disassembling and reassembling the die blocks which are structurally weak because of their small thicknesses, and a constant coating gap may be maintained all the time by a simple operation of coupling the die blocks to the alignment block. The alignment block securely controls a uniform width direction gap through a large surface contact of a block.

According to the present disclosure, even considering that a die block is deformed by the pressure of a discharged active material slurry, there is an effect of uniformly controlling the coating amount and a coating quality by maintaining a uniform (±<NUM>%) coating gap. Thus, a coating product of uniform quality, in particular, an electrode for a secondary battery, may be obtained using a dual-slot die coater with a uniform coating gap.

As described above, according to the present disclosure, even when the discharge pressure of the active material slurry increases and thin die blocks are used, the effect of maintaining the once adjusted coating gap is excellent. This has the effect of securing coating process ability and securing reproducibility.

Using such a dual-slot die coater, it is possible to uniformly form a coating layer, in particular, an active material layer, to a desired thickness, and preferably, simultaneous coating of two types of active material slurries is possible, and thus there are effects that both performance and productivity are excellent.

According to the present disclosure, a plurality of alignment blocks may be arranged in the width direction of a dual-slot die coater. Then, precise control is possible without deviation of the coating gap in the width direction. Therefore, control may be made to exhibit uniform dimensional accuracy in order to stably perform uniform coating in the width direction even on a large-width current collector.

An appropriate coating gap range may be determined according to the type of active material slurry. In the present disclosure, several types of alignment blocks having appropriate thicknesses are prepared, and a process is performed by replacing alignment blocks necessary for production processes, and thus, in order to use various active material slurries, a dual-slot die coater may be used universally even when a dual-slot die coater dedicated to each active material slurry is not individually provided. Moreover, even when dispersion exists in an active material slurry, a quick response may be made to such dispersion by adjusting the coating gap by immediately replacing only the alignment block.

As described above, when the dual-slot die coater of the present disclosure is used to manufacture an electrode of a secondary battery by applying the active material slurry on a current collector while allowing the current collector to travel, there is an advantage that uniform coating is possible even under high-speed traveling or wide-width coating conditions.

A dual-slot die coater according to an embodiment of the present disclosure is an apparatus that includes a first slot and a second slot for discharging a coating solution in a direction opposite to gravity and coats a coating solution in a double layer on a substrate. The 'substrate' described below is a current collector and the coating solution is an 'active material slurry'. Both a first coating solution and a second coating solution are active material slurries, and may refer to active material slurries that have the same or different composition (types of an active material, a conductive material, and a binder), content (an amount of each of the active material, the conductive material, and the binder), or physical properties. The dual-slot die coater according to an embodiment of the present disclosure is optimized for electrodes manufactured by applying at least two types of electrode active material slurries at the same time, or by applying at least two types of electrode active material slurries in an alternating manner to perform pattern coating. However, the scope of the present disclosure is not limited thereto. For example, the substrate may be a porous support constituting a separator, and the first coating solution and the second coating solution may be organic materials having different compositions or physical properties. In other words, when thin film coating is required, any substrate, any first coating solution, and any second coating solution may be good.

<FIG> is a schematic cross-sectional view of a dual-slot die coater according to an embodiment of the present disclosure, and <FIG> is a perspective view of an alignment block included in the dual-slot die coater of <FIG>. <FIG> is a plan view of a lower surface of a dual-slot die coater according to an embodiment of the present disclosure.

A dual-slot die coater <NUM> according to an embodiment of the present disclosure is an apparatus including a first slot <NUM> and a second slot <NUM> and capable of simultaneously or alternately coating two types of same or different coating solutions on a substrate <NUM> through the first slot <NUM> and the second slot <NUM>. Referring to <FIG>, the dual-slot die coater <NUM> includes a base A, a first die block <NUM>, a second die block <NUM>, and a third die block <NUM>.

In <FIG>, the dual-slot die coater <NUM> is installed in a substantially vertical direction (X direction) in which an active material slurry which is a coating solution is discharged (approximately: ± <NUM> degrees).

The base A may be viewed as a rectangular parallelepiped having a predetermined length in the left and right directions and extending in a direction (Z direction) perpendicular to the paper as shown in the drawings. The first die block <NUM> is vertically installed in a rear portion of an upper surface of the base A. Preferably, the base A and the first die block <NUM> are integrally formed with each other. The first die block <NUM> has a plate-shaped structure in which the direction (Z direction) perpendicular to the paper is a width direction and the first die block <NUM> extends along this direction. The first die block <NUM> is put on the base A and assembled therewith. When the base A and the first die block <NUM> are integrally formed with each other in this way, alignment with respect to the base A is not necessary, and the base A and the first die block <NUM> may be integrally handled, and thus handling is convenient.

The second die block <NUM> is a block located in the middle of blocks constituting the dual-slot die coater <NUM>, and is a block disposed between the first die block <NUM> and the second die block <NUM> to form a dual slot. A cross-section of the second die block <NUM> of the present embodiment is a right triangle, but is not necessarily limited to this shape. For example, the cross section may be provided as an isosceles triangle.

The second die block <NUM> is disposed on a front surface of the first die block <NUM>. The second die block <NUM> has a plate-shaped structure in which the direction (Z direction) perpendicular to the paper is a width direction and the second die block <NUM> extends along this direction. A first surface 120a of the second die block <NUM> facing the first die block <NUM> lies almost perpendicular to the base A. In other words, the first surface 120a of the second die block <NUM> is a vertical surface. A second surface 110b of the first die block <NUM> facing the first surface 120a of the second die block <NUM>, and the first surface 120a (that is, a surface forming a rear surface of an outer circumferential surface of the dual-slot die coater <NUM>) opposite to the second surface 110b also lie almost perpendicular to the base A. In other words, the first and second surfaces 120a and 120b of the first die block <NUM> are vertical surfaces. In this way, the first surface 120a of the second die block <NUM> and a first surface 110a of the first die block <NUM>, and the second surface 110b are almost parallel to each other. In the first die block <NUM>, a forwardly-inclined inclined surface 110a' is formed above the first surface 110a, and accordingly a cross section of an upper portion of the first die block <NUM> is substantially triangular.

The third die block <NUM> is disposed on a front surface of the second die block <NUM>. The third die block <NUM> also has a plate-shaped structure in which the direction (Z direction) perpendicular to the paper is a width direction and the second die block <NUM> extends along this direction. The second surface 120b of the second die block <NUM> facing the third die block <NUM>, the first surface 130a of the third die block <NUM> facing the second surface 120b of the second die block <NUM>, and the second surface 130b (i.e., a surface that forms a front surface of the outer circumferential surface of the dual-slot die coater <NUM>), which is opposite to the first surface 130a, are almost parallel to one another. In the third die block <NUM>, a rearwardly inclined inclined surface 130b' is formed above the second surface 130b. A cross section of an upper portion of the third die block <NUM> is also substantially triangular. A surface 130b" below the second surface 130b of the third die block <NUM> lies almost perpendicular to the base A. In other words, the surface 130b" is also a vertical surface.

Surfaces of the first die block <NUM>, the second die block <NUM>, and the third die block <NUM> which are opposite to a direction in which the active material slurry is discharged, namely, lower surfaces 110c, 120c, and 130c, lie almost horizontally (Y direction). In such die blocks <NUM>, <NUM>, and <NUM>, since corners formed by surfaces have portions formed at right angles, there is a right angle portion in the cross section, and since a vertical or horizontal surface is used as a reference surface, manufacturing or handling of the die blocks <NUM>, <NUM>, and <NUM> is easy and the precision thereof is guaranteed.

The first die block <NUM>, the second die block <NUM>, and the third die block <NUM> are not necessarily limited to shapes taken as the above examples, and may be configured, for example, as horizontal dies with the direction in which the active material slurry is discharged as a horizontal direction and the lower surfaces 110c, 120c, and 130c as rear surfaces.

The die blocks <NUM>, <NUM>, and <NUM> are made of, for example, a SUS material. Materials that are easy to process, such as SUS420J2, SUS630, SUS440C, SUS304, and SUS316L, may be used. SUS has advantages in that it is easy to process, inexpensive, has high corrosion resistance, and may be manufactured in a desired shape at low cost.

The first die block <NUM> is a block located behind and on the right side in <FIG>, from among the blocks constituting the dual-slot die coater <NUM>, and, because the second surface 110b facing the second die block <NUM> is perpendicular to the base A, the first slot <NUM> may be perpendicular to the base A. The first slot <NUM> may be formed where the first die block <NUM> and the second die block <NUM> face each other. The first slot <NUM> is formed by a combination of the first die block <NUM> and the second die block <NUM>. For example, a first spacer <NUM> is interposed between the first die block <NUM> and the second die block <NUM> to provide a gap therebetween, so that the first slot <NUM> corresponding to a passage through which a first coating solution <NUM> may flow may be formed. In this case, a thickness of the first spacer <NUM> determines a vertical width (slot gap) of the first slot <NUM>.

The first spacer <NUM> includes an opening portion in which one area is cut, and may be interposed in a remaining portion except for one side of a border area of an opposite surface of each of the first die block <NUM> and the second die block <NUM>. Accordingly, a first discharge port 101a through which the first coating solution <NUM> may be discharged to the outside is formed only between a front end portion of the first die block <NUM> and a front end portion of the second die block <NUM>. The front end portion of the first die block <NUM> and the front end portion of the second die block <NUM> are defined as a first die lip <NUM> and a second die lip <NUM>, respectively. In other words, the first discharge port 101a may be formed by making the first die lip <NUM> and the second die lip <NUM> spaced apart from each other. Each of the first die lip <NUM> and the second die lip <NUM> extends in the width direction, and may be a rectangular parallelepiped having a flat upper surface.

For reference, the first spacer <NUM> functions as a gasket to prevent the first coating solution <NUM> from leaking into a gap between the first die block <NUM> and the second die block <NUM> except for the area where the first discharge port 101a is formed, and thus the first spacer <NUM> is preferably made of a material having sealing properties.

The first die block <NUM> includes a first manifold <NUM> having a predetermined depth on the second surface 110b facing the second die block <NUM> and communicatively connected to the first slot <NUM>. The first manifold <NUM> is a space provided from the second surface 110b of the first die block <NUM> facing the second die block <NUM> toward the first surface 110a opposite to the second surface 110b. The first manifold <NUM> is connected to a first coating solution supply chamber (not shown) installed outside through a supply pipe to receive the first coating solution <NUM>. When the first coating solution <NUM> is filled in the first manifold <NUM>, the flow of the first coating solution <NUM> is induced along the first slot <NUM> and discharged to the outside through the first discharge port 101a.

The third die block <NUM> is arranged in front of the second die block <NUM> and forms the second slot <NUM> between the third die block <NUM> and the second die block <NUM>. The second slot <NUM> is thus formed where the second die block <NUM> and the third die block <NUM> face to each other. In other words, the second slot <NUM> is formed by a combination of the third die block <NUM> and the second die block <NUM>.

Like the first slot <NUM> described above, a second spacer <NUM> may be interposed between the second die block <NUM> and the third die block <NUM> to provide a gap therebetween. Accordingly, the second slot <NUM> corresponding to a passage through which a second coating solution <NUM> may flow is formed. In this case, a vertical width (slot gap) of the second slot <NUM> is determined by the second spacer <NUM>.

In addition, the second spacer <NUM>, which also has a structure similar to that of the above-described first spacer <NUM>, includes an opening portion in which one area is cut, and may be interposed in the remaining portion except for one side of a border area of an opposite surface of each of the second die block <NUM> and the third die block <NUM>. Similarly, a circumferential direction of the second spacer <NUM> except for the front of the second slot <NUM> is blocked, and the second discharge port 102a is formed only between the front end portion of the second die block <NUM> and a front end portion of the third die block <NUM>. The front end portion of the third die block <NUM> is defined as a third die lip <NUM>. In other words, the second discharge port 102a may be formed by making the second die lip <NUM> and the third die lip <NUM> spaced apart from each other. The third die lip <NUM> also extends in the width direction, and may be a rectangular parallelepiped having a flat upper surface.

The third die block <NUM> includes a second manifold <NUM> having a predetermined depth on the first surface 130a facing the second die block <NUM> and communicatively connected to the second slot <NUM>. The second manifold <NUM> is a space provided from the first surface 130a toward the second surface 130b opposite to the first surface 130a. Although not shown in the drawings, the second manifold <NUM> is connected to a supply chamber of the second coating solution <NUM> installed outside through a supply pipe to receive the second coating solution <NUM>. When the second coating solution <NUM> is supplied from the outside along the supply pipe in the shape of a pipe and filled in the second manifold <NUM>, the flow of the second coating solution <NUM> is induced along the second slot <NUM> communicatively connected to the second manifold <NUM> and discharged to the outside through the second discharge port 102a.

The second slot <NUM> and the first slot <NUM> form a certain angle, and the angle may be approximately <NUM> degrees to <NUM> degrees. The second slot <NUM> and the first slot <NUM> may intersect each other at one point, and the second discharge port 102a and the first discharge port 101a may be provided near the intersection. Accordingly, discharge points of the first coating solution <NUM> and the second coating solution <NUM> may be concentrated approximately at one point.

The first and second manifolds <NUM> and <NUM> form the first die block <NUM> and the third die block <NUM>, respectively. This may less affect deformation of the second die block <NUM>, which is structurally weakest. In addition, when the second die block <NUM> is divided into a left die and a right die, the left die is configured to move integrally with the third die block <NUM>, and the right die is configured to move integrally with the first die block <NUM>, the second die block <NUM> may be implemented as a structure in which a left die block and a right die block are slidable at an interface between a left die and a right die, and thus may be implemented as a structure facilitating location changes in the first slot <NUM> and the second slot <NUM>.

An angle θ between the second surface 120b of the second die block <NUM> facing the third die block <NUM> and the first surface 120a of the second die block <NUM> facing the first die block <NUM> may be preferably determined within a range in which an active material slurry discharged from the second discharge port 102a and an active material slurry discharged from the first discharge port 101a do not form a vortex immediately after being simultaneously discharged. When the angle θ is too small, the second die block <NUM> is too thin to be very vulnerable to deformation and torsion.

According to the dual-slot die coater <NUM> having such a configuration, a rotatably provided coating roll <NUM> is disposed over the dual-slot die coater <NUM>, and, while the substrate <NUM> to be coated by rotating the coating roll <NUM> is being driven, the first coating solution <NUM> and the second coating solution <NUM> are continuously contacted with the surface of the substrate <NUM> so that the substrate <NUM> may be coated in a double layer. Alternatively, supply and interruption of the first coating solution <NUM> and supply and interruption of the second coating solution <NUM> are alternately performed so that pattern-coating may be intermittently performed on the substrate <NUM>.

The dual-slot die coater <NUM> further includes an alignment block <NUM> that is fastened to the lower surfaces 120c and 130c of the die blocks <NUM> and <NUM>, which are opposite to the front end portions of the die blocks <NUM> and <NUM>, by bolts <NUM> and <NUM> to bond the two die blocks <NUM> and <NUM> together. The alignment block <NUM> is included between a front portion of the upper surface of the base A and the lower surface 120c of the second die block <NUM>.

Here, an example in which a vertical length h1 of each of the second die block <NUM> and the third die block <NUM> is less than a vertical length h2 of the first die block <NUM> is taken. A vertical length indicates a vertical distance from the lower surface of each die block to a die lip. In this state, when the front end portion of the second die block <NUM> is aligned with that of the first die block <NUM>, a space may be formed between the lower surface 120c of the second die block <NUM> and the upper surface of the base A. This space may be a space in which an upper surface is formed on the lower surface 120c of the second die block <NUM>, an upper portion is formed by the upper surface of the base A, a front surface is open, a rear surface is formed by the front surface of the first die block <NUM>, and left and right side portions are open.

The alignment block <NUM> is installed in this space. In particular, the alignment block <NUM> includes a stepped portion <NUM>' seated on the front portion of the upper surface of the base A and the front surface of the base A. For example, the thickness D of the stepped portion <NUM>' may correspond to a difference between the vertical length h1 of each of the second die block <NUM> and the third die block <NUM> and the vertical length h2 of the first die block <NUM>.

The bolt <NUM> penetrates through the lower surface of the base A and is fastened to the alignment block <NUM> and the second die block <NUM> in a vertical direction. The bolt <NUM> penetrates through the alignment block <NUM> and is fastened to the third die block <NUM> in a vertical direction. A bolt <NUM> penetrates through the front surface of the alignment block <NUM> and is fastened to the base A in a horizontal direction. The bolts <NUM>, <NUM>, and <NUM> may be fastened at locations where they do not interfere with one another. Through this structure, the lower surface 120c of the second die block <NUM> and the lower surface 130c of the third die block <NUM> may be in contact with the upper surface of the alignment block <NUM> and aligned with each other, and the lower surface 120c of the second die block <NUM> and the lower surface 130c of the third die block <NUM> may have a step with the lower surface 110c of the first die block <NUM>.

As shown in <FIG>, the alignment block <NUM> has an upper surface 140a that is in contact with the lower surface 120c of the second die block <NUM> and the lower surface 130c of the third die block <NUM>. In contrast with the upper surface 140a, the lower surface 140b includes the stepped portion <NUM>' having the thickness D, which is less than a thickness of the other portion. The stepped portion <NUM>' has a structure capable of being seated on the front portion of the upper surface of the base A and the front surface of the base A. In the alignment block <NUM>, holes H through which the bolts <NUM>, <NUM>, and <NUM> penetrate may be further formed to fasten the bolts <NUM>, <NUM>, and <NUM>. The number of holes H and the locations of the holes H may be changed from those shown in the drawings. A vertical cross-section of the alignment block <NUM> that passes through all of the upper surface 140a, the lower surface 140b, and the stepped portion <NUM>' includes a first cross-section portion and a second cross-section portion extending vertically from the first cross-section portion. In other words, the vertical cross-section has a '¬' or 'L' shape. In this way, processing of a simple block shape is not cumbersome, and precise processing is possible. By doing this, similar to the die blocks <NUM>, <NUM>, and <NUM>, since corners formed by surfaces of the alignment block <NUM> are at right angles, there is a right angle portion in the cross section, and since a vertical or horizontal surface is used as a reference surface, manufacturing or handling of the alignment block <NUM> is easy and the precision thereof is guaranteed. When the first die block <NUM>, the second die block <NUM>, and the third die block <NUM> are combined and the alignment block <NUM> is fastened to the combination, facing portions thereof may be supported by one another with a high degree of surface contact, and thus may be fastened and fixed and may be maintained very well.

The dual-slot die coater may be generally formed of an SUS material. In general, since liquid leakage easily occurs on a bonding surface of an SUS assembly, a rubber ring or other soft material is placed between components and sealed to suppress leakage. However, this sealing method is not suitable for controlling a uniform assembly shape (e.g., an assembly deviation of less than <NUM>), and thus is difficult to apply to a dual-slot die coater.

For this reason, in the dual slot die coater, a die block processed with a very high precision (straightness, flatness ±<NUM>) needs to be assembled by bolting. To prevent liquid leakage, bolting is at a high pressure of about <NUM> to 350N. However, this high-pressure bolting cause a minute stress imbalance, block die deformation may be accordingly induced, and deformation or twisting of die blocks occur due to the pressure of a coating solution supplied during coating. The alignment block <NUM> having a cross section of a '¬' or 'L' shape is a structure that may withstand such high-pressure bolting.

The alignment block <NUM> may be a single monolithic component rather than being divided into several components. In other words, the alignment block <NUM> is an integral, seamless component. Accordingly, not only accuracy of the alignment block <NUM> is improved during assembly, but also the structure of the alignment block <NUM> is robust, so the alignment block <NUM> has excellent stability against external shocks during handling and use.

According to the present embodiment, the alignment block <NUM> bonds the third die block <NUM> and the second die block <NUM> together. Because the lower surface 130c of the third die block <NUM> and the lower surface 120c of the second die block <NUM> are bonded in parallel, when the respective vertical lengths h1 of the second die block <NUM> and the third die block <NUM> are identical to each other, the third die lip <NUM> and the second die lip <NUM>, which are respectively the front end portions of the die blocks <NUM> and <NUM>, may be located on the same straight line. In other words, the third die lip <NUM> and the second die lip <NUM> may be at the same height from the base A, and a lower circumferential surface of the coating roll <NUM> is located with a coating gap over the third die lip <NUM> and the second die lip <NUM>. In this way, the alignment block <NUM> determines locations of the third die lip <NUM> and the second die lip <NUM>, thereby affecting the coating gap.

As shown in <FIG>, several alignment blocks <NUM> may be arranged in the width direction of the dual-slot die coater <NUM>. The alignment block <NUM> securely controls a uniform width direction gap through a large surface contact of a block.

According to this structure of the alignment block <NUM>, the third die block <NUM> and the second die block <NUM> are combined to move integrally, and relative locations of the second discharge port 102a and the first discharge port 101a may be adjusted. The degree of location adjustment varies according to the thickness D of the stepped portion <NUM>' of the alignment block <NUM>, and the coating gap is determined accordingly. In addition, location misalignment between the die blocks <NUM>, <NUM>, and <NUM> may be prevented. In contrast with the conventional art, the coating gap is easily determined through a combination of the die blocks <NUM> and <NUM> with the alignment block <NUM>. Therefore, inconvenience of adjusting the coating gap while dismantling the die blocks <NUM>, <NUM>, and <NUM> and adjusting the positions thereof may be greatly addressed, and assembly precision may be improved.

The present embodiment illustrates an example in which the vertical length h1 of the third die block <NUM> (vertical distance from the lower surface 130c to the third die lip <NUM>) and the vertical length of the second die block <NUM> (vertical distance from the lower surface 120c to the second die lip <NUM>) is less than the vertical length h2 of the first die block <NUM> (vertical distance from the lower surface 110c to the first die lip <NUM>). In this state, when the alignment block <NUM> including the stepped portion <NUM>' having the thickness D corresponding to a difference between the vertical lengths h1 and h2 is fastened to the third die block <NUM> and the second die block <NUM>, the first die lip <NUM>, the second die lip <NUM>, and the third die lip <NUM> may be located on the same straight line. In this case, the entirety of the dual-slot die coater <NUM> may be coated with various layers while moving forwards or backwards with respect to the substrate <NUM>.

If the vertical length of each of the third die block <NUM> and the second die block <NUM> is equal to the vertical length of the first die block <NUM>, fastening of the alignment block <NUM> may make the second die lip <NUM> and the third die lip <NUM> protrude toward the substrate <NUM> farther than the first die lip <NUM>. Then, a step is formed between the first discharge port 101a and the second discharge port 102a. When a step is formed between the first discharge port 101a and the second discharge port 102a as such and the first discharge port 101a and the second discharge port 102a are arranged apart from each other in a vertical direction, the second coating solution <NUM> discharged from the second discharge port 102a is not transferred to the first discharge port 101a, and the first coating solution <NUM> discharged from the first discharge port 101a is neither transferred to the second discharge port 102a. In other words, a coating solution discharged through the first discharge port 101a or the second discharge port 102a is blocked by a surface forming the step formed between the first discharge port 101a and the second discharge port 102a so that the coating solution has no fear of flowing into other discharge ports. Thus, a smoother multi-layer active material coating process may be conducted.

Through this fastening with the alignment block <NUM>, a distance between the third die lip <NUM>, the second die lip <NUM>, and the first die lip <NUM>, which are the respective front end portions of the die blocks <NUM>, <NUM>, and <NUM>, and the substrate <NUM>, namely, the coating gap, may be always maintained at a desired level, and the die blocks <NUM> and <NUM> are fixed to each other, and accordingly a once-determined coating gap is maintained without changing during a process.

Therefore, there is no need to adjust the coating gap while disassembling and reassembling the die blocks <NUM>, <NUM>, and <NUM> which are structurally weak because of their small thicknesses, and a constant coating gap may be maintained all the time by a simple operation of coupling the die blocks <NUM> and <NUM> to the alignment block <NUM>.

As described above, according to the present disclosure, even when the discharge pressure of the active material slurry increases, the effect of maintaining the once adjusted coating gap is excellent. This has the effect of securing coating process ability and securing reproducibility.

In particular, inclusion of a plurality of alignment blocks <NUM> in the width direction of the dual-slot die coater <NUM> enables precise control without a deviation of the coating gap even in the width direction.

An appropriate coating gap range is determined according to the type of active material slurry. In the present disclosure, several types of alignment blocks having stepped portions with appropriate thicknesses are prepared, and a process is performed by replacing an alignment block necessary for each production process, and thus, in order to use various active material slurries, a dual-slot die coater may be used universally even when a dual-slot die coater dedicated to each active material slurry is not individually provided. Moreover, even when dispersion exists in an active material slurry, a quick response may be made to such dispersion by immediately replacing only the alignment block.

As described above, when the dual-slot die coater of the present disclosure is used to manufacture an electrode of a secondary battery by applying the active material slurry on a current collector while allowing the current collector to travel, there is an advantage that uniform coating is possible even under high-speed traveling or wide-width application conditions.

In the present embodiment, a case of coating a coating solution in two layers or a case of pattern-coating by alternately supplying a coating solution has been described as an example. However, the present disclosure is applicable to a case where three or more layers are simultaneously coated by providing three or more slots.

Claim 1:
A dual-slot die coater (<NUM>) including a first slot (<NUM>) and a second slot (<NUM>) for discharging a coating solution in a direction opposite to gravity, the dual-slot die coater comprising:
a first die block (<NUM>) vertically installed on a rear portion of an upper surface of a base (A), a second die block (<NUM>) arranged on a front surface of the first die block (<NUM>) to form the first slot (<NUM>) between the second die block (<NUM>) and the first die block (<NUM>), and a third die block (<NUM>) arranged on a front surface of the second die block (<NUM>) to form the second slot (<NUM>) between the third die block (<NUM>) and the second die block (<NUM>); and
an alignment block (<NUM>) provided between a front portion of the upper surface of the base (A) and a lower surface of the second die block (<NUM>) and fastened and coupled to the lower surface of the second die block (<NUM>) and a lower surface of the first die block (<NUM>) by bolts (<NUM>, <NUM>),
wherein the alignment block (<NUM>) comprises a stepped portion (<NUM>') seated on the front portion of the upper surface of the base (A) and a front surface of the base (A), and
characterized in that the bolts (<NUM>, <NUM>) comprise a bolt (<NUM>) fastened to the alignment block (<NUM>) and the second die block (<NUM>) by penetrating through a lower surface of the base (A), and a bolt (<NUM>) fastened to the third die block (<NUM>) by penetrating through the alignment block (<NUM>).