Stacked runner type coating machine

Abstract

The utility model relates to the technical field of coating, in particular to a stacked runner type coating machine, which comprises a coating die head and a first gasket, the coating die head comprises an upper die and a lower die, the first gasket is arranged between the upper die and the lower die and is provided with a first runner, the coating machine further comprises a second gasket, and the second gasket is arranged between the upper die and the lower die and is provided with a second runner. The second gasket and the first gasket are arranged in a stacked mode, the second gasket is provided with a second flow channel, and the second flow channel and the first flow channel form a stacked flow channel, so that the flow resistance borne by fluid is the same. According to the utility model, the coating transverse consistency can be simply and effectively improved at low cost.

Description

Technical Field

[0001] The utility model relates to the technical field of coating, in particular to a stacked flow channel type coater. Background Art

[0002] The slot die extrusion coating die head is widely used in the production of optical films, plastic films, lithium battery electrodes, hydrogen fuel cells, and photovoltaic perovskite thin film products. In the coating industry, the dry film thickness or the coefficient of variation (COV) value of the surface density is often used as an important indicator to measure the quality of coating. The dry film uniformity in the coating width direction is mainly affected by factors such as the rheological properties of the coating slurry, the die head flow channel design, die head processing, installation and debugging. The quality of the coating during the commissioning and acceptance stage can directly or indirectly indicate the application ability of the coating die head manufacturer for the extrusion coating die head.

[0003] In the scenario of lithium battery coating, the target value of the coating lateral uniformity is generally COV ≤ ±0.5% - ±1%. Due to the high viscosity of the coating slurry, thick coating, and high coating speed, in order to reduce the coating pressure and achieve stable and good coating, gaskets with a thickness of about 0.5 - 1.5 mm are mostly used. Most of them use adjustable slot die extrusion coating die heads, such as micrometer adjustment coating die heads, closed-loop motor adjustment coating die heads, push-pull rod adjustment coating die heads, mother-screw adjustment coating die heads, and clamping bolt adjustment coating die heads. In most cases, good adjustment effects can be obtained, but there are also cases where adjustment is impossible due to mechanical structure interference.

[0004] In the ultra-thin coating scenario where the dry film thickness of photovoltaic perovskite thin films is between 0.5 - 1 μm, the target value of the coating lateral uniformity is generally COV ≤ ±2% - ±5%. Due to the low viscosity of the coating slurry, thin coating, and slow coating speed, gaskets with a thickness of 0.05 - 0.15 mm are mostly used. Most of them use slot die extrusion coating die heads without an adjustment mechanism. Generally, the lateral distribution trend of the dry film thickness after stable film formation is thick in the middle and thin on both sides, or thick on both sides and thin in the middle. Since the gasket is too thin to use an adjustment mechanism, generally speaking, for the case of thick in the middle and thin on both sides, the coating uniformity can be improved by replacing the thin gasket, and for the case of thick on both sides and thin in the middle, a thick gasket can be used for improvement. However, when the coating lateral uniformity exceeds ±5%, the coating uniformity does not meet the standard, and continuing to thicken the gasket still cannot achieve the expected coating lateral uniformity, resulting in poor final coating quality, and ultimately affecting the production progress due to the inability to adjust.

[0005] In the existing technical solutions, such as CN216727951U, a sub-gasket is arranged in the middle of the flow channel of the gasket to improve the coating lateral uniformity by restricting the flow rate in the middle part. This structure has the following problems: (1) The sub-gasket can only adjust the problem of thick in the middle and thin on both sides, and cannot solve the problem of thin in the middle and thick on both sides; (2) When the mother gasket is very thin, it is difficult to machine the protrusions or grooves on the sub-gasket. Summary of the Utility Model

[0006] The purpose of the present utility model is to provide a stacked flow channel type coater, so that the flow resistance suffered by the fluid when flowing through the middle route and the two side routes is the same, so that the lateral distribution consistency of the fluid flow rate is better, and the coating lateral consistency is improved.

[0007] To achieve the above purpose, the present utility model provides the following technical solutions:

[0008] A stacked flow channel type coater includes a coating die head and a first gasket. The coating die head includes an upper die head and a lower die head. The first gasket is arranged between the upper die head and the lower die head. The first gasket is provided with a first flow channel. A second gasket is further included. The second gasket is stacked with the first gasket. The second gasket is provided with a second flow channel. The second flow channel and the first flow channel form a stacked flow channel, so that the flow resistance suffered by the fluid is the same.

[0009] Further, the bottom wall of the second flow channel is successively provided with point A, point B and point C. Among them, point A and point C are respectively located at both ends of the bottom wall, point B is located in the middle of the bottom wall, the straight line AC is parallel to the long side of the die head, and point B is located on the perpendicular bisector of the straight line AC; the angles of ∠BAC and ∠BCA are both θ. If point B protrudes from the front end of the connection line of point A and point C, then θ < 0. If point B is recessed from the rear end of the connection line of point A and point C, then θ > 0; when only using the first gasket, if the distribution trend of several film thicknesses or surface densities is that the middle is greater than the two sides, then θ < 0 is adopted, and vice versa, θ > 0 is adopted.

[0010] Further, the value of the θ angle is determined by the following formula:

[0011] θ = [57.29578·arctan(2·COV·L c / L b )]°;

[0012] Wherein, COV is the coating lateral consistency value; L b is the length of the slit choke flow channel, and this length is equal to the length of the straight line AC, that is, L b = L AC ; L c is the width of the slit choke flow channel.

[0013] Further, the vertical length of point B from the die head lip is L m , and the value range of L m is as follows:

[0014] When θ > 0, 0.5·L b ·tanθ ≤ L m ≤ L c ;

[0015] When θ < 0, 0 ≤ Lm ≤L c -0.5·L b ·tanθ。

[0016] Furthermore, the bottom wall of the second flow channel coincides with the hypotenuse AB and the hypotenuse BC.

[0017] Furthermore, the bottom wall of the second flow channel is arc-shaped, and points A, B, and C are three points on the arc.

[0018] Furthermore, arcs AB and BC are made respectively from points A, B and points B, C, and points A, B, C are not collinear. The bottom wall of the second flow channel coincides with arcs AB and BC.

[0019] Furthermore, arcs AB and BC are symmetrically arranged, and the radii R of arcs AB and BC are the same. The radius R is determined by the following formula:

[0020] R≥0.5·L b / sin(2θ / 57.29578°).

[0021] Compared with the prior art, the beneficial effects of the present utility model are as follows:

[0022] 1. After the slurry enters the distribution cavity through the feed port, it then flows through the stacked flow channel formed by the first gasket and the second gasket. By means of the stacked flow channel formed by 1 or more second gaskets and the first gasket, the flow resistance suffered by the fluid when flowing through the middle route and the two side routes is the same, so that the lateral distribution consistency of the fluid flow rate is better, and the coating lateral consistency is improved.

[0023] 2. Compared with the existing adjustment methods or existing designs, the use of a cumbersome adjustment mechanism is avoided, and the structural design of the existing coating die head is greatly simplified, realizing flexible adjustment of the lateral distribution trend of the dry film thickness of the coating. The structure is simple, and the processing difficulty is low. The cost and usage threshold of the second gasket are much lower than those of the conventional micrometer adjustment and die head deformation adjustment, while the use effects are the same, achieving cost reduction and efficiency improvement.

[0024] 3. Solve the industry pain points and difficulties such as the dry film thickness distribution being thick at both sides and thin in the middle and being unable to be adjusted when using a thin gasket for coating in scenarios such as ultra-thin coating of lithium batteries or perovskite ultra-thin coating. On the original first gasket, a second gasket is superimposed. By changing the number, geometric shape, and parameters of the second gasket, the dry film thickness distribution trend of being thick at both sides and thin in the middle can be corrected. In the ultra-thin coating scenario where the gasket thickness is less than 0.15 mm, by using the second gasket adjustment method proposed by the present utility model, the dry film thickness distribution trend of being thick at both sides and thin in the middle can be effectively solved.

[0025] 4. The method proposed by the present utility model can be adapted to the slot die extrusion coating dies of all coating die manufacturers, and can be applied to the application scenarios of slot die extrusion coating dies including but not limited to lithium batteries, fuel cells, photovoltaic perovskite batteries, optical films, water treatment films, etc. The method proposed by the present utility model only needs to calculate simply according to the distribution trend of the dry film thickness on site, and then stack or replace the corresponding second gasket to meet the requirements.

[0026] In summary, the method proposed by the present utility model can simply, low-cost and effectively improve the coating consistency, providing a new idea for the coating consistency adjustment method in the slot die extrusion coating die industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 FIG. is a schematic diagram of the overall structure when the second gasket proposed by the embodiment of the present utility model is used in combination with a conventional slot die extrusion coating die;

[0028] Figure 2 is Figure 1 a schematic diagram of the cross-sectional structure at the midpoint of the die length of

[0029] Figure 3 is Figure 1 a schematic diagram of the structure when the conventional gasket of

[0030] Figure 4 FIG. is a schematic diagram of the second gasket structure when θ>0 in Scheme 1 is adopted when the on-site dry film thickness or surface density distribution trend is greater on both sides than in the middle;

[0031] Figure 5 FIG. is a schematic diagram of the second gasket structure when θ>0 in Scheme 2 is adopted when the on-site dry film thickness distribution trend is greater on both sides than in the middle;

[0032] Figure 6 FIG. is a schematic diagram of the second gasket structure when θ<0 in Scheme 1 is adopted when the on-site dry film thickness distribution trend is less on both sides than in the middle;

[0033] Figure 7 FIG. is a comparison of the effects before and after using the second gasket for the slot die extrusion coating die at the photovoltaic perovskite battery coating production site;

[0034] Figure 8 FIG. is a comparison of the effects before and after using the second gasket for the slot die extrusion coating die at the lithium battery coating production site;

[0035] Figure 9 FIG. is a comparison of the effects before and after using the second gasket for the slot die extrusion coating die at the optical film coating production site.

[0036] Among them, 100 - upper die; 101 - mold clamping hole position; 200 - lower die; 201 - feed port; 202 - distribution cavity; 203 - slit choke flow channel; 204 - exhaust return port; 300 - first gasket; 400 - second gasket; L b - length of the slit choke flow channel; Lc - width of the slit choke flow channel; L m - vertical length from point B to the die lip; θ - θ angle. Specific embodiments

[0037] To make the objectives, technical solutions and advantages of the embodiments of the present utility model clearer, the technical solutions in the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model. Therefore, the following detailed description of the embodiments of the present utility model provided in the drawings is not intended to limit the scope of the present utility model to be protected, but merely represents selected embodiments of the present utility model. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the scope of protection of the present utility model.

[0038] Embodiment 1

[0039] Please refer to Figures 1 to 4 , the embodiments of the present utility model provide a stacked flow channel type coater. The stacked flow channel type coater proposed by the present utility model is not limited by the application scenarios of the coating die head and can be applied to slit extrusion coating scenarios such as lithium battery coating, optical film coating, photovoltaic perovskite battery coating, and water treatment membrane coating; it is not affected by the number of coating layers and can be applied to single-layer coating, double-layer coating, and multi-layer coating; it is not limited by the number and cross-sectional shape of the distribution cavities 202 of the coating die head. The distribution cavity 202 can be designed with a single cavity, a double cavity, or multiple cavities, and the cross-section of the distribution cavity 202 is a simple or complex geometric shape such as a rectangle, a square, a trapezoid, a triangle, a rhombus, a semi-circle, a semi-drop shape, a circle, a drop shape, or a hanger shape. The stacked flow channel type coater proposed by the present utility model is applicable to all slit extrusion coating die heads with a sandwich structure mainly composed of an upper die 100, a lower die 200, and a conventional gasket 300.

[0040] The stacked flow channel type coater includes a coating die head and a first gasket 300. The coating die head includes an upper die 100 and a lower die 200, and the first gasket 300 is disposed between the upper die 100 and the lower die 200.

[0041] The lower die 200 is provided with a feed port 201, a distribution cavity 202, a slit choke flow channel 203, and an exhaust return port 204. After the coating slurry is injected through the feed port 201, it enters the distribution cavity 202 and flows out through the slit choke flow channel 203.

[0042] Please refer toFigure 3 The first gasket 300 is provided with a first flow channel. The first flow channel communicates with the distribution cavity 202 and the slit flow blocking channel 203, thereby restricting the flow rate of the coating slurry passing through the slit flow blocking channel 203.

[0043] It can be understood that the upper die 100, the lower die 200 and the first gasket 300 can adopt conventional design structures commonly used in the industry.

[0044] The stacked flow channel type coater further includes a second gasket 400. The second gasket 400 is stacked with the first gasket 300. The second gasket 400 is provided with a second flow channel, and the second flow channel and the first flow channel form a stacked flow channel, so that the flow resistance of the fluid is the same. That is, the flow resistance of the fluid when flowing through the middle route and the two side routes is the same, so that the lateral distribution consistency of the fluid flow rate is better, and the coating lateral consistency is improved.

[0045] It can be understood that the number of the second gaskets 400 can be set to one or more according to needs. Specifically, the user can add the second gaskets 400 according to the distribution of the dry film thickness of the coating until the final coating lateral consistency value COV meets the design requirements.

[0046] In addition, in the illustrated embodiment, the first gasket 300 is closer to the lower die 200. In other embodiments, the second gasket 400 can also be closer to the lower die 200. There is no need to distinguish the stacking order between multiple second gaskets 400, and the geometric shapes of multiple second gaskets 400 can be the same or different, as long as the flow channels after stacking meet the desired lateral distribution of flow resistance.

[0047] By adjusting the geometric shape and dimensional parameters of the second gasket 400, it is possible to suppress the middle flow or suppress the two-side flow on the whole trend, thereby regulating the overall trend of the dry film thickness distribution on site and improving the coating lateral consistency.

[0048] In Embodiment 1, the geometric shape of the second gasket 400 is as Figure 4 shown. The bottom of the second flow channel of the second gasket 400 is symmetrically provided with equal-length hypotenuses AB and BC. ABC forms an isosceles triangle, and both base angles ∠BAC and ∠BCA are θ angles. The straight line AC is parallel to the long side of the die head. Because the hypotenuses AB and BC are of equal length, ∠BAC = ∠BCA, that is, point B is located on the perpendicular bisector of the straight line AC.

[0049] If point B protrudes from the front end of the line connecting points A and C (point B is closer to the outlet of the slit flow blocking channel 203 on the straight line AC), then θ < 0. If point B is recessed from the rear end of the line connecting points A and C (point B is farther from the outlet of the slit flow blocking channel 203 on the straight line AC), then θ > 0.

[0050] By controlling the positive or negative value of the θ angle, it is possible to suppress the flow in the middle or suppress the flow on both sides. That is, the positive or negative value of the θ angle is determined according to the effect of only using the first gasket 300. If the on-site dry film thickness or surface density distribution trend is thick in the middle and thin on both sides, then θ < 0 is adopted; otherwise, θ > 0 is adopted.

[0051] By controlling the magnitude of the θ angle, the degree of suppressing the flow is controlled.

[0052] Specifically, the magnitude of the θ angle is determined according to the coating lateral uniformity COV value of different coating dies, the length L b of the slit choke flow channel, and the width L c of the slit choke flow channel. For the slit choke flow channel L c of the coating die, the larger it is, the larger θ is; the higher the coating lateral uniformity COV value is, the larger θ is; for the length L b of the slit choke flow channel, the larger it is, the smaller the θ angle is.

[0053] The value of the θ angle is determined by the following formula:

[0054] θ = [57.29578 · arctan(2 · COV · L c / L b )]°;

[0055] where 57.29578 is the conversion between radians and degrees, 1 radian ≈ 57.29578°; arctan is the arctangent function operator; COV is the coating lateral uniformity value; L b is the length of the slit choke flow channel, and this length is equal to the length of the straight line AC, that is, L b = L AC ; L c is the width of the slit choke flow channel.

[0056] The vertical length of point B from the die lip is L m , and the value range of L m is as follows:

[0057] When θ > 0, 0.5 · L b · tanθ ≤ L m ≤ L c ;

[0058] When θ < 0, 0 ≤ L m ≤ L c - 0.5 · L b · tanθ;

[0059] where tan is the tangent function operator.

[0060] Example 2

[0061] In Example 2, the geometric shape of the second gasket 400 is asFigure 5 As shown, the shape of the bottom of the second flow channel is: a three-point arc is formed by passing through the left endpoint A, the center endpoint B, and the right endpoint C of the bottom of the second flow channel.

[0062] Similar to Embodiment 1, in Embodiment 2, the angles ∠BAC and ∠BCA can still be made, and their values are both θ. The requirements for the value of the θ angle are the same as those in Embodiment 1. That is:

[0063] If point B protrudes from the front end of the line connecting point A and point C (point B is closer to the outlet of the narrower slit blocking flow channel 203 than the AC line), then θ < 0. If point B is recessed from the rear end of the line connecting point A and point C (point B is farther from the outlet of the narrower slit blocking flow channel 203 than the AC line), then θ > 0.

[0064] By controlling the positive and negative of the θ angle, the flow in the middle or on both sides can be inhibited. That is, the positive and negative values of the θ angle are determined according to the effect of only using the first gasket 300. If the on-site dry film thickness or surface density distribution trend is thick in the middle and thin on both sides, then θ < 0 is adopted; otherwise, θ > 0 is adopted.

[0065] By controlling the magnitude of the θ angle, the degree of flow inhibition is controlled.

[0066] Specifically, the magnitude of the θ angle depends on the coating lateral uniformity COV value of different coating dies, the length L b of the slit blocking flow channel, and the width L c of the slit blocking flow channel. The larger the length L c of the slit blocking flow channel of the coating die, the larger θ; the higher the coating lateral uniformity COV value, the larger θ; the larger the length L b of the slit blocking flow channel, the smaller the θ angle.

[0067] The value of the θ angle is determined by the following formula:

[0068] θ = [57.29578 · arctan(2 · COV · L c / L b )]°;

[0069] where 57.29578 is the conversion between radians and degrees, 1 radian ≈ 57.29578°; arctan is the arctangent function operator; COV is the coating lateral uniformity value; L b is the length of the slit blocking flow channel, and this length is equal to the length of the straight line AC, that is, L b = L AC ; L c is the width of the slit blocking flow channel.

[0070] The vertical length of point B from the die lip is L m , and the value range of L m is as follows:

[0071] When θ > 0, 0.5·L b ·tanθ ≤ L m ≤ L c ;

[0072] When θ < 0, 0 ≤ L m ≤ L c -0.5·L b ·tanθ;

[0073] Wherein, tan is the tangent function operator.

[0074] Embodiment 3

[0075] In Embodiment 3, the shape of the bottom of the second flow channel is: an arc AB is made through the left end point A and the center end point B of the bottom of the second flow channel, and an arc BC is made through the center end point B and the right end point C of the bottom of the second flow channel.

[0076] The arc AB and the arc BC are symmetrically arranged, and the arc AB and the arc BC have the same radius, and the radius R is determined by the following formula:

[0077] R ≥ 0.5·L b / sin(2θ / 57.29578°).

[0078] Wherein, when R = 0.5·L b sin(2θ / 57.29578°), the three points A, B, and C are collinear on a circle, and at this time, Embodiment 3 is equivalent to Embodiment 2.

[0079] Similarly, in Embodiment 3, the angles ∠BAC and ∠BCA can still be made, and their values are both θ. The value requirements of the θ angle are the same as those in Embodiment 1.

[0080] Embodiment 4

[0081] In Embodiment 4, the geometric shape of the second gasket 400 is as Figure 6 shown, and Embodiment 4 is a schematic diagram of θ < 0 in Embodiment 1.

[0082] Embodiment 5

[0083] This embodiment provides a method for using a stacked flow channel type coater, including the steps:

[0084] S1: Install the first gasket 300 between the upper die 100 and the lower die 200;

[0085] S2: Detect the dry film consistency value COV in the coating width direction. If it is higher than the target value, install the second gasket 400 between the upper die 100 and the lower die 200 and stack it on the first gasket 300;

[0086] S3: Re-detect the dry film consistency value COV in the coating width direction. If it is higher than the target value, install another second spacer 400 between the upper die 100 and the lower die 200 and stack it on top of the previous second spacer 400;

[0087] S4: Repeat S3 until the COV is lower than the target value and perform the coating operation.

[0088] The structure of the second spacer 400 is as described in Embodiments 1-4, and its θ angle meets the requirements of the above embodiments.

[0089] The following uses some specific embodiments to illustrate the design of the present invention.

[0090] Embodiment 6

[0091] At the slot die head in the production site of photovoltaic perovskite battery coating, the method of the first spacer + single second spacer proposed by the present invention is adopted, and the second spacer design of Embodiment 1 is used. As Figure 7 , when only the first spacer is used, the lateral distribution trend of the on-site dry film thickness is thick on both sides and thin in the middle, and the COV is as high as ±10.87%, which does not meet the coating consistency requirement that the COV is less than ±2.5%. Since the die head does not have any adjustment mechanism and cannot be adjusted, it is considered to use the superimposed second spacer proposed by the present invention. The second spacer adopts the geometric shape of Embodiment 1, L c = 25, L b = 600, COV = 10.87%. From the formula θ = [57.29578 · arctan(2 · COV · L c / L b )]°, the θ of the second spacer is calculated to be 0.52°. After superimposing the second spacer, the lateral distribution trend of the on-site dry film thickness is slightly thick in the middle and thin on both sides, and the COV reaches ±0.40%, meeting the requirements.

[0092] Embodiment 7

[0093] At the slot die head in the production site of lithium battery negative electrode coating, the method of the first spacer + single second spacer proposed by the present invention is adopted, and the second spacer design of Scheme 2 is used. As Figure 8 , when only the first spacer is used, the lateral distribution trend of the on-site dry film surface density is heavy on both sides and light in the middle, and the COV is as high as ±2.20%, which does not meet the coating consistency requirement that the COV is less than ±1.00%. After the micrometer is pressed down, the effect is still not good, and the micrometer is mechanically interfered, and the pressing down has reached the limit and cannot be debugged further. It is considered to add a second spacer, and Embodiment 1 is adopted. At this time, L c = 55, L b = 1500, COV = 2.20%. From the formula θ = [57.29578 · arctan(2 · COV · Lc / L b )]° calculates that θ of the second gasket is 0.09°. After stacking the second gasket, the on-site dry film surface density trend becomes slightly heavier in the middle and lighter on both sides, and the COV reaches ±0.32%, meeting the requirements.

[0094] Example 8

[0095] At the slot die coater on the optical film coating production site, the method of the first gasket + a single second gasket proposed by the present utility model is adopted, and the second gasket design of Example 3 is used. As Figure 9 , when only the first gasket is used, the transverse distribution trend of the on-site dry film surface density is heavier on both sides and lighter in the middle, and the COV is as high as ±3.83%, not meeting the coating uniformity requirement that the COV is less than ±2.00%. Due to cost reasons, the slot die coater on site is not equipped with an adjustment mechanism, so it cannot be adjusted. Therefore, it is considered to add a second gasket and adopt Example 3. At this time, L c = 30, L b = 1200, COV = 2.20%. From the formula θ = [57.29578·arctan(2·COV·L c / L b )]° calculates that θ of the second gasket is 0.11°. After stacking the second gasket, the on-site dry film thickness trend becomes slightly thicker in the middle and thinner on both sides, and the COV reaches ±0.33%, meeting the requirements.

[0096] Although the embodiments of the present utility model have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principle and spirit of the present utility model. The scope of the present utility model is defined by the appended claims and their equivalents.

Claims

1. A stacked flow channel coater, comprising a coating die head and a first gasket, wherein the coating die head comprises an upper die and a lower die, the first gasket is arranged between the upper die and the lower die, and the first gasket is provided with a first flow channel, characterized in that: It also includes a second gasket, which is stacked with the first gasket. The second gasket is provided with a second flow channel, and the second flow channel and the first flow channel form a stacked flow channel so that the flow resistance of the fluid is the same.

2. The stacked flow channel coater according to claim 1, characterized in that: The bottom wall of the second flow channel is provided with point A, point B and point C in sequence, wherein point A and point C are respectively located at the two ends of the bottom wall, point B is located in the middle of the bottom wall, straight line AC is parallel to the long side of the die head, and point B is located on the perpendicular bisector of straight line AC; the angles of ∠BAC and ∠BCA are both θ, if point B protrudes from the front end of the line connecting point A and point C, then θ<0, if point B is recessed from the rear end of the line connecting point A and point C, then θ>0; when only the first gasket is used, if the distribution trend of some film thickness or surface density is thick in the middle and thin on both sides, then θ<0 is adopted, otherwise θ>0 is adopted.

3. The stacked flow channel coater according to claim 2, characterized in that: The value of the angle θ is determined by the following formula: θ=[57.29578·arctan(2·COV·L c / L b )]°; Among them, COV is the coating transverse consistency value; L b is the length of the slit flow path, which is equal to the length of the straight line AC, that is, L b =L AC ; L c is the width of the slit choke flow channel.

4. The stacked flow channel coater according to claim 3, characterized in that: The vertical distance from point B to the die lip is L m , L m The value range of is as follows: When θ>0, 0.5·L b tanθ≤L m ≤L c ; When θ<0, 0≤L m ≤L c -0.5·L b ·tanθ.

5. The stacked flow channel coater according to claim 4, characterized in that: The bottom wall of the second flow channel coincides with the hypotenuse AB and the hypotenuse BC.

6. The stacked flow channel coater according to claim 4, characterized in that: The bottom wall of the second flow channel is arc-shaped, and point A, point B and point C are three points on the arc.

7. The stacked flow channel coater according to claim 4, characterized in that: Points A and B and points B and C form arcs AB and BC respectively, and the three points ABC are not cocircular. The bottom wall of the second flow channel coincides with the arcs AB and BC.

8. The stacked flow channel coater according to claim 7, characterized in that: The arc AB and the arc BC are set symmetrically, and the radius R of the arc AB and the arc BC are the same. The radius R is determined by the following formula: R≥0.5·L b / sin(2θ / 57.29578°)。

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