TWI736787B - Manufacturing method of multilayer film - Google Patents

Abstract

The manufacturing method of the multilayer film of the present invention includes the step of removing the porous forming material from the original film (22); using the original film under the first roller (27, 28) and the second roller (26) The second roller is the step of applying the coating liquid containing fine particles; the step of extending the original film in the width direction according to the fluidity of the coating liquid; and the step of drying the coating liquid to form a multilayer with a fixed fine particle layer Film steps. When coating, the angle between the line connecting at least one of the rotation axis position of the first roller and the rotation axis position of the second roller and the direction in which the second roller presses the original film is 0° or more and 150° or less.

Description

Manufacturing method of multilayer film

The present invention relates to a method of manufacturing a multilayer film.

Conventionally, stretch films have been used in various products. For example, as a separator for a lithium ion battery (hereinafter referred to as "LIB"), a stretched film made of a polyolefin-based material is used. In addition, in order to improve the heat resistance of such a separator, there are cases where organic materials or inorganic materials are arranged on the surface of the stretched film.

As an example, it has been used to apply a coating solution that mixes ceramic particles such as alumina or silica, which are inorganic materials, and a solvent on the surface of the stretched film, and then dry the solvent to provide the surface of the stretched film. The technique of a film composed of such fine particles (refer to Patent Document 1 and Patent Document 2). In addition, there is also a method of applying a resin material such as polyamide or polyimide, which is an organic material, on the surface of the stretched film, and then dispose a film made of the resin material on the surface of the stretched film. Furthermore, there are cases where these organic materials and inorganic materials are mixed and used (refer to Patent Document 3 and Patent Document 4).

[Prior Technical Literature] [Patent Literature]

Patent Document 1: Japanese Patent Laid-Open No. 2013-114751

Patent Document 2: Japanese Patent Laid-Open No. 2014-203680

Patent Document 3: Japanese Patent Laid-Open No. 2009-21265

Patent Document 4: Japanese Patent No. 4460028

The stretched film used as a separator for LIB is generally microporous for the movement of lithium ions and the like. The microporosity can be formed, for example, by a method (so-called wet method) in which a resin used as a stretched film material is mixed with a solvent or the like to form a film, and then the solvent or the like is drawn out. However, when using this method, since the shrinkage of the stretched film may cause the microporosity to be clogged during the process of extracting the solvent, etc., it is generally used to reopen the clogged microporosity. After drawing out, stretch the stretched film again. Moreover, when it is extended again, the microporous size is also adjusted.

However, in the above-mentioned case where a film composed of various fine particles (hereinafter also referred to as a "fine particle layer") is arranged on the stretched film in order to improve the heat resistance, from the viewpoint of miniaturization of the manufacturing system or rationalization of the manufacturing steps, etc., Sometimes it is better to provide a fine particle layer on the stretched film at a time point before the above-mentioned re-stretching. However, in general, since the fine particle layer is more difficult to deform than the material constituting the stretched film, cracks of the fine particle layer or peeling of the fine particle layer from the stretched film may occur during the re-stretching process. In other words, if a fine particle layer is provided on the stretched film before various stretching steps including re-stretching, the fine particle layer may not be able to maintain a proper fixed state on the stretched film.

One of the objectives of the present invention is to provide a method for manufacturing a multilayer film, which can appropriately fix a fine particle layer on the surface of the stretched film.

[1] The first aspect of the present invention is a method for manufacturing a multilayer film, which is a method for manufacturing a multilayer film in which a microparticle layer composed of microparticles is provided on the surface of a porous film, which includes: a removal step, which is composed of: The original film containing the resin material and the porous forming material constituting the film is removed from the porous forming material; the coating step is performed at two different positions in the conveying direction of the original film after the removal step. One surface of the film abuts against a pair of first rollers, and is held by the pair of first rollers in the conveying direction, and the other surface of the original film abuts against the second roller, in this state The coating liquid containing the above-mentioned fine particles is applied to the above-mentioned original film using the above-mentioned second roll; the horizontal stretching step is to maintain the fluidity of the above-mentioned coating liquid that has been applied to the above-mentioned original film. The film is stretched in the width direction; and the fixing step is to dry the coating liquid to fix the fine particle layer on the film to form the multilayer film; in the coating step, the second roller is pressed along the predetermined When the original film is pressed in the direction and viewed from the direction along the rotation axis of the second roller, the line connecting at least one of the rotation axis position of the first roller and the rotation axis position of the second roller is connected to the pressing The angle between the rolls of the angle between the directions is 0° or more and 150° or less.

In the first aspect described above, in the coating step, the coating liquid is applied to the original film under the pressure of the second roller to the original film. In particular, according to the experiments and investigations conducted by the inventor of the present case, it is clarified that the coating liquid is applied to the original film by arranging the first roller and the second roller such that the angle between the rollers becomes 0° or more and 150° or less. , The adhesion between the particles contained in the coating liquid and the original film is significantly improved. Furthermore, in the horizontal stretching step, the original film is stretched in the width direction according to the state in which the coating liquid has fluidity (in other words, the state in which the coating liquid is not completely dried). As a result, since the coating fluid flows following the extension of the original film, compared to the case where the coating fluid is completely dried to form a fine particle layer and stretched horizontally, it is ultimately possible to suppress the tortoises placed on the fine particle layer of the multilayer film. Cracking or peeling, etc. Thereby, according to the manufacturing method of the first aspect, the fine particles can be appropriately fixed on the surface of the stretched film.

[2] The second aspect of the present invention is in the first aspect, and the horizontal stretching step includes: a preliminary step of preheating; and a formal step of extending in the width direction under heating; in the preliminary step , The drying amount equivalent to the reduction of the coating liquid before and after the preliminary step, that is, the preliminary drying amount is less than 20wt%; in the formal step, it belongs to the drying amount equivalent to the reduction of the coating liquid before and after the formal step, That is, the formal drying amount is 20wt% or less.

Regarding the above-mentioned second aspect, experiments and investigations conducted by the inventors of the present case clarified that in the preliminary steps and formal steps included in the horizontal stretching step, the reduction of the coating liquid can be reduced to 20wt% or less. Improve the followability of the coating liquid to the extension of the original film. Therefore, according to the manufacturing method of the second aspect, it is possible to more appropriately fix the fine particles on the surface of the stretched film.

[3] The third aspect of the present invention is in the second aspect, and the above-mentioned preliminary step includes: performing the above-mentioned original film in such a way that the heat per unit area given to the above-mentioned original film is less than 1.5kW/h Heating treatment; the above-mentioned formal steps include: heating the above-mentioned original film in such a way that the amount of heat per unit area given to the above-mentioned original film is less than 1.2kW/h.

Regarding the third aspect, the experiments and investigations conducted by the inventor of the present case clarified that the heat per unit area given to the original film is set to 1.5 kW/h or less in the preliminary step, and in the formal step In this case, the amount of heat per unit area given to the original film is set to 1.2 kW/h or less, and the reduction of the coating liquid can be set to the second aspect described above. Therefore, according to the manufacturing method of the third aspect, it is possible to more appropriately fix the fine particles on the surface of the stretched film.

[4] The fourth aspect of the present invention is in any one of the first to third aspects, and the coating step includes: the rotation speed G of the second roller is relative to the conveying speed L of the original film A process where the ratio G/L is greater than 0 and 10 or less.

Regarding the above-mentioned fourth aspect, according to experiments and investigations conducted by the inventor of the present case, it is clarified that the ratio G/L of the rotation speed G of the second roller to the conveying speed L of the original film is set to be greater than 0 and 10 With the following values, the coating liquid can be applied to have a predetermined thickness. Therefore, according to the manufacturing method of the fourth aspect, it is possible to more appropriately fix the fine particles on the surface of the stretched film.

[5] The fifth aspect of the present invention is in any one of the first to fourth aspects, and the fixing step includes: extending the original film in the conveying direction while making the coating liquid Slowly drying under heating, thereby fixing the fine particle layer on the surface of the original film.

According to the above-mentioned fifth aspect, after the microporous openings of the original film are opened by the horizontal stretching step (that is, the above-mentioned re-extending), a fine particle layer can be formed on the surface of the original film. Therefore, since the fine particle layer has not been formed at the time of the horizontal stretching step, the cracking or peeling of the fine particle layer provided in the multilayer film is finally suppressed. Furthermore, by extending the original film in the conveying direction, the degree of opening of the microporous can be adjusted. Therefore, by the manufacturing method of the fifth aspect, it is possible to appropriately fix the fine particles on the surface of the microporous stretched film having a desired degree of opening.

[6] The sixth aspect of the present invention is in any one of the first to fifth aspects, and the multilayer film is a separator for lithium ion batteries.

According to the sixth aspect described above, the manufacturing method of the multilayer film of any one of the first to fifth aspects described above can be applied to a manufacturing method of a lithium ion battery separator with high industrial value.

According to the present invention, fine particles can be appropriately fixed on the surface of the stretched film.

1‧‧‧Wet diaphragm manufacturing system

2‧‧‧Extruder

2A‧‧‧Compression mold

3‧‧‧Casting roll

4‧‧‧Vertical Stretching Machine

5‧‧‧The first horizontal stretch machine

6‧‧‧Extractor

7‧‧‧The second horizontal stretch machine

8‧‧‧Off-line applicator

8A‧‧‧Production line coater (gravure coater)

9‧‧‧Upstream side

10‧‧‧Downstream

22‧‧‧Film

22A‧‧‧Diaphragm

23‧‧‧Take-up mechanism

24‧‧‧Guide roller

25‧‧‧Scraper room

26‧‧‧Gravure roll (2nd roll)

26a‧‧‧Rotation axis

26A‧‧‧Gravure pattern

26B‧‧‧Vertical line

27‧‧‧Inlet side approach roller (1st roller)

28‧‧‧Out-side approach roller (1st roller)

28a‧‧‧Rotation axis

30‧‧‧Preheating zone

31‧‧‧Extension Area

40‧‧‧di

50‧‧‧Taiwan

51‧‧‧Coated film

52‧‧‧Low Adhesive Tape

53‧‧‧Load Yuan

54‧‧‧Fixture

120‧‧‧Coating head

121‧‧‧Unwinding Department

122‧‧‧Film

122A‧‧‧diaphragm

123‧‧‧The first dryer

124‧‧‧The second dryer

125‧‧‧The third dryer

126‧‧‧ Coiling section

R‧‧‧Rotation direction

H‧‧‧Height

Fig. 1 is a schematic configuration diagram showing the LIB diaphragm manufacturing system of the present invention.

Fig. 2(a) is a specific configuration diagram of the production line coater of Fig. 1; Fig. 2(b) and Fig. 2(c) are schematic diagrams showing the roll angle specified by the gravure roll and the approach roll.

Fig. 3 is a form other than Fig. 1 and shows a schematic configuration diagram of a method of applying a bonding agent for a production line for BOPET.

Fig. 4 is a form other than Fig. 1 and shows a schematic configuration diagram of a production line ceramic coating method for a diaphragm.

Fig. 5 is a configuration diagram of a demonstration device of the LIB diaphragm manufacturing system of the present invention.

Fig. 6 is a schematic configuration diagram showing the main parts of the demonstration device shown in Fig. 5.

Fig. 7 is an explanatory diagram showing the coating thickness adjustment conditions of the production line coater of Fig. 1.

Fig. 8 is an explanatory diagram showing the horizontal stretching and drying conditions for the production line coater of Fig. 1.

Fig. 9 is an explanatory diagram of the peel strength measurement test of the separator of the present invention.

Fig. 10 is a schematic configuration diagram showing a conventional off-line LIB diaphragm manufacturing system.

Fig. 11 is a schematic configuration diagram showing a conventional off-line off-line coater.

The following describes an embodiment of the system when the manufacturing method of the multilayer film of the present invention is applied to the LIB diaphragm manufacturing system (hereinafter also referred to as "system"). In this system, from the viewpoint of miniaturization of the system or rationalization of manufacturing steps, the production line coater is installed between the draw-out machine and the horizontal stretching machine.

First, before describing the system of the present invention, a brief description of the conventional system will be made with reference to FIGS. 10 and 11. The conventional system has the wet membrane manufacturing system 1 of FIG. 10 and the offline coater 8 of FIG. 11. In FIG. 10, the wet membrane manufacturing system 1 starts from the upstream side 9 toward the downstream side 10, and has an extruder 2, a casting roll 3, a longitudinal stretcher 4, a first horizontal stretcher 5, and an extruder 6 in this order. , The second horizontal stretching machine 7. On the downstream side 10 of the second horizontal stretching machine 7 or elsewhere, an offline coater 8 is provided. The offline coater 8 is not a production line configuration included in the production line of the wet diaphragm manufacturing system 1, but is an offline configuration independently.

FIG. 11 shows the specific structure of the offline coater 8. The film 122 for the diaphragm sent from the unwinding part 121 is dried by the first, second, and third dryers 123, 124, 125 after the solution containing ceramic particles is applied by the coating head 120. After that, the separator 122A is wound up by the winding part 126.

In contrast, in the embodiment of the system to which the manufacturing method of the multilayer film of the present invention shown in FIG. 1 is applied, the wet diaphragm manufacturing system 1 has an extruder 2 on the upstream side 9. The film 22 extruded from the die 2A of the extruder 2 toward the downstream side 10 is an original film containing a resin material constituting the film 22 and a porous forming material (e.g., a solvent, etc.). After the film 22 is stretched by the longitudinal stretcher 4 and the first lateral stretcher 5, it is supplied to the draw-out machine 6. Furthermore, for the parts that are substantially the same as the above-mentioned conventional system, the same symbols as those shown in FIG. 10 are used. In addition, the film 22 from the time when the resin extruded by the extruder 2 passes through the casting roll 3 to become the film 22 and before the LIB separator (multilayer film) is finally obtained through various treatments is called the "raw film" .

In the extraction machine 6, washing and extraction (removal) of the solvent are performed. With the downstream coater 8A, a slurry coating liquid in which ceramic particles are mixed with an aqueous solvent or an organic solvent is applied to the film 22 to form a diaphragm 22A. The sheet-like diaphragm 22A transferred from the production line coater 8A to the downstream side 10 is stretched in the width direction by the second horizontal stretcher 7 arranged after the production line coater 8A, and is wound by The mechanism is taken up by 23. In addition, the average particle size of the ceramic fine particles used in this example is greater than 10 μm and 400 μm or less.

Here, the "average particle size" in this embodiment is obtained by the laser diffraction scattering method. Specifically, the measurement was performed using MT3300 manufactured by MicrotracBEL Co., Ltd. in accordance with the method of JIS Z8825. Then, the particle size distribution measured and calculated by the device is analyzed by the automatic calculation processing device to specify the average particle size.

The production line coater 8A is configured as shown in Fig. 2(a). The film 22 subjected to the extraction process by the extraction machine 6 is conveyed to the gravure roller 26 (second roller) of the doctor chamber 25 through a plurality of guide rollers 24. The film 22 is applied as a sheet after the above-mentioned coating process is carried out in a state of being nipped in the thickness direction by the gravure roller 26, a pair of entrance side approaching rollers 27, and exit side approaching rollers 28 (a pair of first rollers). The shaped diaphragm 22A is sent to the second horizontal stretching machine. The entrance side approach roller 27 and the exit side approach roller 28 abut on one surface of the film 22 at two different positions in the transport direction of the film 22. The gravure roller 26 is at a position pinched by the entrance side approach roller 27 and the exit side approach roller 28 in the conveying direction, and abuts against the other surface of the film 22. Furthermore, the gravure roller 26 has a mechanism (not shown) for rotating the gravure roller 26.

The positional relationship between the gravure roller 26 and the respective approach rollers 27 and 28 can be adjusted by a variable mechanism not shown. Specifically, as shown in FIG. 2(b) and FIG. 2(c), it is arranged such that the film 22 is pressed along the predetermined pressing direction (refer to the arrow in the figure) on the gravure roller 26, and at the same time, the film 22 is pressed along the recessed portion roller 26. When viewed in the direction of the rotation axis, the line connecting the rotation axis 28a of at least one of the entry side approach roller 27 and the exit side approach roller 28 and the rotation axis 26a of the gravure roller 26 forms an angle θ (hereinafter also referred to as (Referred to as "angle between rolls") becomes 0° or more and 150° or less. The angle θ between the rollers can be adjusted by moving the position of the gravure roller 26 back and forth (that is, left and right in the figure). Moreover, when the angle θ between the rollers is 0°, at least one of the entrance side approach roller 27 and the exit side approach roller 28 is in a positional relationship adjacent to the gravure roller 26 left and right in the figure.

The gravure roller 26 is shown in FIG. 2(a), and the gravure roller 26 has a regular arrangement on its surface and an intaglio pattern 26A engraved with a square bank 40 including a rhombus. The bank 40 has a recessed portion formed on the inner side thereof, and when the coating liquid is applied to the film 22 as described later, the coating liquid can be stored on the inner side and the coating liquid can be transported toward the film 22. The intaglio pattern 26A is configured such that the angle θ of the longitudinal line 26B with respect to the rotation direction R of the intaglio roll 26 (θ=45° in FIG. 2) is 0°≦θ≦90°. In addition, the ratio of the short side to the long side of the quadrangular bank 40 is 0<L≦1. The wall height of the bank 40 is 0μm<H≦1mm. The gravure roller 26 has 0<N≦500 banks 40 in a 1-inch square. In addition, the production line coater (gravure coater) 8A does not have the drying function (dryer) of the conventional off-line coater 8 only for drying, but also has the drying function of the second horizontal stretcher 7 function.

In the production line coater system shown in Fig. 1, the drying furnace necessary for the off-line coater shown in Fig. 10 is combined with the drying function of the second horizontal stretcher 7 in the diaphragm manufacturing system. That is, the conventional drying furnace is omitted. In addition, since the winding and winding mechanism 23 is also included in the system, only the production line coater 8A can be placed after the draw-out machine 6 in the wet membrane manufacturing system 1 and before the second horizontal stretching machine 7 .

Next, the coating method of the coating liquid in the system shown in FIG. 1 will be described. First, as a comparison target, FIG. 3 shows an example of a coating method used in the well-known BOPET (Bioxially-Oriented Polyethylene terephthalate, biaxially stretched polyethylene terephthalate). In this example, an adhesive layer is finally formed on the surface of the film 22. First, prepare a coating solution in which approximately 10% by weight of polyurethane resin, which will eventually become the adhesive layer, dissolved in approximately 90% by weight of water. This coating liquid is applied to the film 22 in a thickness of about 4 μm before horizontal stretching in a water-containing state. In the preheating step in the second horizontal stretching machine 7, the coating liquid evaporates the water, and then the film 22 is stretched about 4 times in the width direction. As a result, a layer of polyurethane resin or the like (that is, an adhesive layer) having a thickness of about 1 μm is finally laminated on the film 22. When the film 22 is stretched in the width direction, the polyurethane resin or the like is in a fluid state (for example, a paste-like state) even after the moisture in the coating liquid evaporates, so even if the film 22 is stretched, The state of being attached to the film 22 can still follow the deformation of the film 22.

On the other hand, different from the example in FIG. 3, when the coating liquid containing ceramic particles is coated by the production line coater system shown in FIG. In the stretching machine 7, the horizontal stretching is performed in accordance with the state in which the coating liquid is applied to the film 22. In addition, in the manufacture of the LIB separator, the micropores in the film 22 blocked during the extraction (removal) process are opened due to this horizontal extension, and a porous film 22 (multilayer film) is formed. Here, if the method of forming the adhesive layer shown in FIG. 3 is directly used, there is a risk of peeling or cracking of the fine particle layer during the stretching of the film 22. Therefore, the manufacturing method of the multilayer film of the present invention is used.

Specifically, as shown in FIG. 4, unlike the BOPET used in FIG. 3, the moisture of the coating liquid is first retained in the preheating zone 30 without drying, and the liquidity of the coating liquid is maintained. , The film 22 (not shown) passes through the extension area 31. Then, the coating solution is dried and the film is heat-fixed after stretching, thereby preventing the peeling or cracking of the fine particle layer. In addition, various parameters related to the stretching and drying steps can be set according to the type of film 22 or the requirements of the coating thickness.

For example, the coating liquid containing ceramic particles can be configured to contain ceramic particles about 30-40% by weight, solvents, etc., 60-70% by weight. Especially when used as a heat-resistant separator, the coating liquid can be constituted to contain about 40% by weight of alumina as ceramic fine particles and about 60% by weight of aqueous solvent.

In the drying step of the diaphragm 22A, the diaphragm 22A adjusts the temperature and air volume in such a way that the heat per unit area given to the film in the preheating step (preparatory step) is 1.5 kW/h or less. Thereby, the amount of drying (preliminary drying amount) that belongs to the reduction of the coating liquid before and after the treatment can be suppressed to 20 wt% or less. In addition, in the subsequent horizontal stretching step (formal step), the temperature and air volume are adjusted so that the heat per unit area given to the film is 1.2kW/h or less, so that the coating before and after this treatment The amount of dryness (official dry amount) of the liquid reduction is suppressed to 20 wt% or less. In addition, the unit area is, for example, 1 m ² .

The following describes the evaluation of the multilayer film manufactured using the system of the present invention. The physical property values described in the following evaluation are the values obtained by the methods shown below.

Surface observation: The produced sheet was vapor-deposited with a thickness of 0.3 nm using a vacuum vapor deposition device (E-1045 manufactured by Hitachi High-Technologies). The surface of this sheet was observed using FE-SEM (SUPRA55VP manufactured by Carl Zeiss).

Peel strength: Use a precision universal testing machine (Autograph, manufactured by Shimadzu Corporation AG‧20kNG), implemented in accordance with JIS6854-1. Specifically, FIG. 9 shows an outline of a test for measuring the peel strength of the separator 22A. A low-adhesion tape 52 is attached to the coated film 51 on the diaphragm 22A on the stage 50, and the coated film 51 is connected to the jig 54 provided with a load cell 53 through the low-adhesive tape 52, and the maximum of the jig 54 is measured The load is used as the peel strength.

(Example 1)

Using the device shown in Fig. 5 and Fig. 6, the coating and extension of the coating liquid can be easily carried out. As the film 22, a commercially available polyethylene film (LL-XMTM) manufactured by Futamura Chemical Co., Ltd. was used. As the ceramic fine particles contained in the coating liquid, BM-2000M manufactured by ZEON, Japan was used. In order to fix the coating thickness condition of the coating liquid, as shown in Figure 7, the rotation speed G (m/min) of the gravure roll 26 of the production line coater 8A and the film transport speed (= production line speed, m /min) L ratio G/L is controlled to 0<G/L≦10. Specifically, as conditions for uniformly coating the coating liquid on the film 22 particularly stably, the conveying speed was set to 6 m/min and G/L=2. The film 22 coated with the coating liquid under this condition is processed through the 10th zone of the horizontal stretching machine shown in FIG. 8. With the first zone of the entrance shown in Fig. 8 as the preheating part, the second zone as the extension part, and the remaining 8 zones as the heat fixing part, the conditions shown in Example 1 of Table 1 below were set. In addition, the film 22 is stretched 1.2 times in the stretched part.

(Example 2)

Under the same conditions as in Example 1, the film transport speed was set to 12 m/min, and the experiment was performed under the conditions shown in Example 2 in Table 1.

(Example 3)

Under the same conditions as in Example 1, the film transport speed was set to 16 m/min and the experiment was performed under the conditions shown in Example 3 in Table 1.

(Example 4)

Under the same conditions as in Example 1, the film transport speed was set to 20 m/min and the experiment was performed under the conditions shown in Example 4 in Table 1.

(Example 5)

Under the same conditions as in Example 1, the film transport speed was set to 24 m/min and the experiment was performed under the conditions shown in Example 5 in Table 1.

(Comparative example 1)

In the 10 zone of the horizontal stretching machine shown in Fig. 8, the second zone of the entrance is used as the preheating part, the third zone is used as the extension part, and the remaining 4 zones are used as the heat fixing part. The conditions are shown, and the other experiments are carried out under the same conditions as in Example 1.

(Comparative example 2)

In the 10 zone of the horizontal stretching machine shown in Figure 8, the second zone of the entrance is used as the preheating part, the third zone is used as the extension part, and the remaining 4 zones are used as the heat fixing part, and follow the example in Table 1 above. 2 Perform the experiment under the same conditions.

(Evaluation)

Table 2 below shows the evaluation results. In the SEM photographs under the conditions of Examples 1 to 2 and 3, it was observed that the fine particle layer composed of ceramic fine particles was partially cracked due to the extension of the film. The same applies to Comparative Examples 1 and 2. It is considered that the reason is that the preheating part and the extension part are given a large amount of heat, and the extension is carried out in a state where the water content of the coating liquid is reduced.

Comparing Examples 1 to 3, as the amount of heat applied to the preheating portion and the extension portion decreases, the state of cracks is improved and the peel strength tends to increase. Furthermore, in Examples 4 and 5, the microparticle layer did not appear to be cracked, and the peel strength was more improved than that in Examples 1-3.

In Table 2, as a reference example, the observation results of the microparticle layer of the multilayer thin film manufactured under the optimal conditions using the offline LIB separator manufacturing system shown in FIG. 10 are shown. With respect to this reference example, the surface properties of the fine particle layer shown in the SEM images of Examples 4 and 5 produced by using the system of the present invention are almost the same, and the peel strength shows a value equal to or higher than the same. In this way, if the heat of the preheating part and the extension part and the extension conditions are optimized, the system of the present invention can produce a multilayer film having mechanical properties equal to or higher than the offline LIB diaphragm manufacturing system.

As described above, in the step of applying the coating liquid to the film 22, the coating liquid is applied to the film 22 under the pressing of the film 22 by the gravure roll 26. In particular, based on the above experiments and investigations, it is clarified that by applying the coating liquid to the film 22 in a state where the rollers 27, 28 and the gravure roller 26 are arranged so that the angle between the rollers becomes 0° or more and 150° or less, the coating liquid is applied to the film 22. The adhesion between the fine particles contained in the liquid and the film 22 is significantly improved. Furthermore, in the horizontal stretching step, the film 22 is stretched in the width direction according to the state in which the coating liquid has fluidity (in other words, the state in which the coating liquid is not completely dried). As a result, since the coating liquid flows following the elongation of the film 22, compared to the case where the coating liquid is completely dried to form a fine particle layer and stretched horizontally, it is possible to suppress the tortoise that is finally placed on the fine particle layer of the multilayer film. Cracking or peeling, etc. Therefore, according to the manufacturing method of this embodiment, fine particles can be appropriately fixed to the surface of the stretched film.

Furthermore, based on the above-mentioned experiments and investigations, it is clarified that the reduction of the coating liquid to 20wt% or less in the preheating step and the formal step included in the horizontal stretching step can improve the follow-up of the coating liquid to the stretching of the film 22. sex.

Furthermore, based on the above-mentioned experiments and investigations, it is clarified that the amount of heat per unit area given to the film 22 is set to 1.5 kW/h or less in the preliminary step, and the amount of heat given to the film 22 is set to be less than 1.5 kW/h in the formal step. The heat per unit area is set to 1.2kW/h or less, and the reduction of the coating liquid can be adjusted to be fixed within the above range.

Furthermore, based on the above experiments and investigations, it is clarified that by setting the ratio G/L of the rotation speed G of the gravure roller 26 to the transport speed L of the film 22 to a value greater than 0 and less than 10, the coating liquid Coated to have the required thickness.

Furthermore, by arranging a production line coater between the draw-out machine and the horizontal stretching machine and manufacturing the multilayer film under the above conditions, it is possible to achieve a stretched film that can only be manufactured by an off-line manufacturing system so far. The production line for the production of high heat resistance separators obtained by coating. Thereby, the manufacturing cost of the high heat resistance separator can be suppressed, and the productivity of the high heat resistance separator can be improved drastically.

Furthermore, as another feature of the manufacturing method of the multilayer film used in this system, since the ceramic particles have the above-mentioned average particle size, the adhesion of the ceramic particles to the film 22 becomes good. In addition, the production line coater 8A is composed of the gravure roller 26, the doctor blade chamber 25, the entrance side approaching roller 27, the exit side approaching roller 28, and a plurality of guide rollers 24, so that the production line coater 8A can be made compact. change. Therefore, it is easy to arrange a production line coater between the drawing machine 6 and the second horizontal stretching machine 7. In addition, since the line coater 8A (gravure coater) does not have a drying function, and the dryer of the second horizontal stretching machine 7 is used as a drying machine, it can greatly contribute to the production line coater 8A. miniaturization. In addition, by setting the angle, height, and number of the banks 40 provided on the surface of the gravure roller 26 according to the type of material to be coated, etc., optimal coating can be performed.

The present invention is not limited to the above-mentioned embodiments, and various modifications can be adopted within the scope of the present invention. For example, the present invention is not limited to the above-mentioned embodiment, and may be modified, improved, etc. as appropriate. In addition, the material, shape, size, number, arrangement, etc. of the constituent elements in the above-mentioned embodiment are arbitrary and not limited as long as they can be used as the invention.

This application is based on a Japanese patent application (Japanese Patent Application 2017-149893) filed on August 2, 2017, and the content is incorporated herein by reference.

(Industrial availability)

The manufacturing method of the multilayer film of the present invention can appropriately fix the fine particles on the surface of the stretched film. The present invention having this effect can be used, for example, in the production of separators for lithium ion batteries.

1‧‧‧Wet diaphragm manufacturing system

2‧‧‧Extruder

2A‧‧‧Compression mold

3‧‧‧Casting roll

4‧‧‧Vertical Stretching Machine

5‧‧‧The first horizontal stretch machine

6‧‧‧Extractor

7‧‧‧The second horizontal stretch machine

8A‧‧‧Production line coater (gravure coater)

9‧‧‧Upstream side

10‧‧‧Downstream

22‧‧‧Film

22A‧‧‧Diaphragm

23‧‧‧Take-up mechanism

Claims (10)

A method for manufacturing a multilayer film is a method for manufacturing a multilayer film in which a microparticle layer composed of microparticles is provided on the surface of a porous film. The original film of the porous forming material removes the two different positions in the conveying direction of the original film of the extractor of the porous forming material, abuts a pair of first rollers on one surface of the original film, and conveys it In the position held by the pair of the first rollers in the direction, the other surface of the original film abuts against the second roller, and in this state, the coating liquid containing the fine particles is applied to the second roller using the second roller The original film; the horizontal stretching step is to extend the original film in the width direction while maintaining the fluidity of the coating liquid applied to the original film; and the fixing step is to make the coating liquid Drying to fix the fine particle layer on the film to form the multilayer film; in the coating step, the second roller presses the original film along a predetermined pressing direction while being driven along the axis of rotation of the second roller When viewed from the direction, the line connecting at least one of the rotation axis position of the first roller and the rotation axis position of the second roller, the angle between the rollers forming an angle between the pressing direction is 0° or more and 150° the following. The method for manufacturing a multilayer film according to claim 1, wherein the horizontal stretching step includes: a preliminary step of preheating; and a formal step of extending in the width direction under heating; in the preliminary step, the preliminary step The reduction amount of the coating liquid before and after the equivalent drying amount, that is, the preliminary drying amount is less than 20wt%; in the formal step, the reduction amount of the coating liquid before and after the formal step is equivalent The dry amount, that is, the formal dry amount, is 20wt% or less. The method for manufacturing a multilayer film of claim 2, wherein the preliminary step includes: heating the original film in such a way that the amount of heat per unit area given to the original film is less than 1.5 kW/h; The formal step includes: heating the original film in such a way that the amount of heat per unit area given to the original film is 1.2 kW/h or less. The method for manufacturing a multilayer film according to any one of claims 1 to 3, wherein the coating step includes: the ratio G/L of the rotation speed G of the second roller to the conveying speed L of the original film is greater than 0 and 10 or less processing. The method for manufacturing a multilayer film according to any one of claims 1 to 3, wherein the fixing step includes: extending the original film in the conveying direction while slowly drying the coating liquid under heating, by This is the process of fixing the fine particle layer on the surface of the original film. The method for manufacturing a multilayer film according to any one of claims 1 to 3, wherein the multilayer film is a separator for lithium ion batteries. The method for manufacturing a multilayer film according to claim 4, wherein the fixing step includes: while extending the original film in the conveying direction, while slowly drying the coating liquid under heating, the original film The process of fixing the above-mentioned fine particle layer on the surface. The method for manufacturing a multilayer film according to claim 4, wherein the multilayer film is a separator for lithium ion batteries. The method for manufacturing a multilayer film according to claim 5, wherein the multilayer film is a separator for lithium ion batteries. The method for manufacturing a multilayer film according to claim 7, wherein the multilayer film is a separator for lithium ion batteries.

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