Method for manufacturing multilayer film and coating apparatus

Abstract

The present disclosure provides a method for producing a multilayer film, said method comprising: conveyance of a base material, which comprises a first surface and a second surface that is on the reverse side of the first surface, toward a coating device that comprises an ejection part which ejects a coating liquid; and application of the coating liquid to the first surface of the base material with use of the coating device, while floating and conveying the base material, in such a manner that the first surface of the base material faces the coating device, along a conveyance path that is curved above the coating device so as to protrude in the direction away from the coating device. The present disclosure also provides a coating device.

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing a multilayer film and a coating apparatus.

Background Art

[0002] Patent Document 1 below discloses a coating apparatus including an extrusion type coater head and a pair of gas ejection means for floating and guiding a web-like support on the upstream side and the downstream side of the coater head, and characterized in that it applies a coating to the support running between the coater head and the pair of gas ejection means.

[0003] Patent Document 2 below discloses a coating apparatus including a backup body for supporting a running web and a die head for applying a coating liquid to the web on the backup body, wherein a plurality of air ejection ports for ejecting air against the web along the width direction of the web are provided on the surface of the backup body, blowers are connected to each air ejection port of the backup body via air flow paths, and control valves are provided in the air flow paths on the inlet side of each air ejection port.

[0004] Patent Document 3 below discloses a method for manufacturing a magnetic recording medium in which a magnetic coating liquid with a coating thickness of 4 μm or less is sequentially and repeatedly coated on a previously applied wet lower layer coating liquid by an extrusion type coating apparatus that continuously extrudes a coating liquid from a slot tip onto the surface of a flexible support continuously running along a back edge surface and a doctor edge surface.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

[0006] In the above-mentioned Patent Document 1, the support is levitated by a pair of gas ejection means provided upstream and downstream of the coater head, and the coater head applies the coating liquid to the support as it travels between the coater head and the pair of gas ejection means. However, at the coating point, the support is not directly supported by the pressure of the gas discharged from the gas ejection means, and the coating liquid is applied to the support as it travels in a flat state. As a result, the support is easily affected by the discharge pressure of the coating liquid, and wrinkles are likely to occur in the traveling film. Therefore, the uniformity of the film thickness distribution of the coating film formed on the support may decrease.

[0007] In the above-mentioned Patent Document 2, the web is supported at a predetermined distance from the backup body by air discharged from the air outlet of the backup body, and the die head applies a coating liquid to the web as it travels between the die head and the backup body. However, the direction of the pressure exerted on the web by the air discharged from the air outlet at the application point is opposite to the direction of the pressure exerted on the web by the coating liquid discharged from the die head, and the web traveling between the die head and the backup body is susceptible to the effects of the air pressure and the coating liquid pressure acting in opposite directions as described above. As a result, the uniformity of the film thickness distribution of the coating film formed on the web may decrease.

[0008] In the above-mentioned Patent Document 3, the support runs in a manner that it is pressed against the back edge surface and the doctor edge surface, and the discharge pressure of the coating liquid increases in order to apply the coating liquid to the support running along the back edge surface and the doctor edge surface. When the discharge pressure of the coating liquid increases, the uniformity of the film thickness distribution of the coating film formed on the support may decrease.

[0009] One aspect of this disclosure aims to provide a method for manufacturing a multilayer film that can form a coating film having a uniform film thickness distribution. Another aspect of this disclosure aims to provide a coating apparatus capable of forming a coating film having a uniform film thickness distribution. [Means for solving the problem]

[0010] This disclosure includes the following aspects: <1> A method for manufacturing a multilayer film, comprising: transporting a substrate having a first surface and a second surface on the opposite side of the first surface toward a coating apparatus having a dispensing section for dispensing a coating liquid; and applying the coating liquid to the first surface of the substrate using the coating apparatus, while levitating and transporting the substrate along a transport path that is curved convexly above the coating apparatus toward the coating apparatus with the first surface of the substrate toward the coating apparatus. <2> The levitation transport of the substrate includes blowing gas from a blowing nozzle located upstream and downstream of the discharge nozzle in the transport direction of the substrate toward the first surface of the substrate. <1> A method for manufacturing a multilayer film as described above. <3> This includes controlling the amount of the substrate floating by controlling the pressure of the gas blown out from the above-mentioned outlet, <2> A method for manufacturing a multilayer film as described above. <4> The levitation transport of the substrate includes blowing gas toward the first surface of the substrate from a first discharge section located upstream of the discharge section and a second discharge section located downstream of the discharge section in the transport direction of the substrate, and independently controlling the pressure of the gas blown from the first discharge section and the pressure of the gas blown from the second discharge section. <1> A method for manufacturing a multilayer film as described above. <5> The pressure of the gas present in the space between the substrate and the first outlet is lower than the pressure of the gas present in the space between the substrate and the second outlet. <4> A method for manufacturing a multilayer film as described above. <6> A coating apparatus for applying a coating liquid to a substrate having a first surface being transported and a second surface on the opposite side of the first surface, comprising: a discharge unit for discharging the coating liquid toward the first surface of the substrate; and at least one blowing unit disposed upstream and downstream of the discharge unit in the transport direction of the substrate, for blowing gas toward the first surface of the substrate in order to levitate the substrate. [Effects of the Invention]

[0011] According to one aspect of this disclosure, a method for manufacturing a multilayer film is provided that can form a coating film having a uniform film thickness distribution. According to another aspect of the present disclosure, a coating apparatus capable of forming a coating film having a uniform film thickness distribution is provided. [Brief explanation of the drawing]

[0012] [Figure 1] Figure 1 is a schematic side view illustrating a method for manufacturing a multilayer film according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a schematic side view showing a magnified view of the tip of the coating apparatus shown in Figure 1. [Modes for carrying out the invention]

[0013] The embodiments of this disclosure are described in detail below. This disclosure is not limited to the embodiments described below. The embodiments described below may be modified as appropriate within the scope of the purposes of this disclosure.

[0014] When describing embodiments of this disclosure with reference to the drawings, explanations of redundant components and reference numerals in the drawings may be omitted. Components indicated by the same reference numeral in the drawings are considered to be the same component. Dimensional ratios in the drawings do not necessarily represent actual dimensional ratios.

[0015] In the present disclosure, a numerical range indicated using “~” represents a range that includes the numerical values described before and after “~” as the lower limit value and the upper limit value, respectively. In the numerical ranges described step by step in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of the numerical range described in other step-by-step descriptions. Further, in the numerical ranges described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.

[0016] In the present disclosure, the amount of each component in the composition means the total amount of a plurality of substances present in the composition when there are a plurality of substances corresponding to each component in the composition, unless otherwise specified.

[0017] In the present disclosure, the term “step” includes not only an independent step but also a step that cannot be clearly distinguished from other steps, provided that the intended purpose of the step is achieved.

[0018] In the present disclosure, “mass %” and “weight %” are synonymous, and “parts by mass” and “parts by weight” are synonymous.

[0019] In the present disclosure, a combination of two or more preferred embodiments is a more preferred embodiment.

[0020] In the present disclosure, “solid content” means components other than the solvent.

[0021] <Method for manufacturing a multilayer film> A method for manufacturing a multilayer film according to one embodiment of the present disclosure includes: transporting a substrate having a first surface and a second surface on the opposite side of the first surface toward a coating apparatus that includes a dispensing unit for dispensing a coating liquid (hereinafter sometimes referred to as the "transportation step"); and applying the coating liquid to the first surface of the substrate using the coating apparatus, while levitating and transporting the substrate along a transport path that is convexly curved above the coating apparatus and away from the coating apparatus, with the first surface of the substrate toward the coating apparatus (hereinafter sometimes referred to as the "coating step"). According to the above embodiment, a method for manufacturing a multilayer film capable of forming a coating film having a uniform film thickness distribution is provided. In the present disclosure, the phrase "above the coating apparatus" used when describing the relationship between an object and a coating apparatus refers to the relative position of an object with respect to the coating apparatus.

[0022] The reason why a coating film with a uniform film thickness distribution is formed is presumed to be as follows. Compared to the methods disclosed in Patent Document 1, Patent Document 2, and Patent Document 3, the method for manufacturing a multilayer film according to one embodiment of this disclosure includes applying a coating liquid to the first surface of a substrate using a coating device, while the substrate is levitated and conveyed along a transport path that is convexly curved away from the coating device above the coating device, with the substrate facing the coating device. In other words, the coating liquid discharged from the discharge section of the coating device is applied to the first surface of the substrate facing the discharge section of the coating device, which is convexly curved away from the coating device by levitation transport. During the coating process, the substrate is curved convexly away from the coating device and levitated, allowing the coating liquid to be applied to the substrate at a low discharge pressure, and the substrate is less affected by the discharge pressure of the coating liquid. As a result, it is presumed that a coating film with a uniform film thickness distribution is formed.

[0023] The following describes each step in the manufacturing method of multilayer films in detail.

[0024] <<Conveying Process>> In the conveying process, the substrate, which includes a first surface and a second surface on the opposite side of the first surface, is conveyed toward a coating apparatus which includes a dispensing section for dispensing the coating liquid.

[0025] (base material) Examples of components of the base material include polymers and metals. Examples of polymers include polyethylene terephthalate, polyethylene naphthalate, and triacetylcellulose. The base material may contain one or more polymers. Examples of metals include iron, chromium, nickel, titanium, copper, aluminum, silver, and gold. The metal may be an alloy. Examples of alloys include stainless steel and Invar. The base material may contain one or more metals. In some embodiments, the base material preferably contains polymers, and more preferably contains at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, and triacetylcellulose. In some embodiments, the base material preferably contains metals, more preferably contains at least one selected from the group consisting of nickel, titanium, copper, aluminum, silver, and gold, even more preferably contains at least one selected from the group consisting of copper and aluminum, and particularly preferably contains aluminum.

[0026] The substrate is preferably a film. Examples of films include films containing the polymers described above and films containing the metals described above. Specific examples of films containing polymers include polyethylene terephthalate films, polyethylene naphthalate films, and triacetylcellulose films. Specific examples of films containing metals include copper films and aluminum films.

[0027] The substrate may have high thermal conductivity. Examples of substrates with high thermal conductivity include those with a thermal conductivity of 200 W / (m·K) or higher. There is no upper limit to the thermal conductivity of the substrate. The thermal conductivity of the substrate may be 500 W / (m·K) or less. The thermal conductivity of the substrate is measured using the laser flash method. First, the substrate is cut at three locations along its width (specifically, 5 mm from both ends in the width direction and in the center in the width direction), with diameters of φ5 mm to 10 mm, to obtain three measurement samples. The thermal conductivity of each measurement sample is measured using a thermophysical property measuring device that applies the laser flash method (e.g., LFA-502, Kyoto Electronics Manufacturing Co., Ltd.). The arithmetic mean of the three measured values ​​is taken as the thermal conductivity of the substrate.

[0028] The layer structure of the substrate is not limited. The substrate may have a single-layer structure or a multi-layer structure.

[0029] From the viewpoint of improving productivity, the base material is preferably a long base material. The length of the base material is preferably 10m or more, more preferably 100m or more, and particularly preferably 200m or more. There is no upper limit to the length of the base material. The upper limit of the length of the base material may be 1,000m or 500m. The length of the base material is usually in the range of 10m to 1,000m. "Length of the base material" means the distance from end to end of the base material in the direction of conveying the base material.

[0030] The width of the substrate is not limited. From the viewpoint of productivity and wrinkle suppression, the width of the substrate is preferably in the range of 100 mm to 1,800 mm, more preferably in the range of 300 mm to 1,600 mm, and particularly preferably in the range of 500 mm to 1,400 mm.

[0031] The thickness of the substrate is not limited. From the viewpoint of handling, the thickness of the substrate is preferably in the range of 3 μm to 50 μm, and more preferably in the range of 10 μm to 30 μm.

[0032] (Transportation) The substrate is transported, for example, using a known transport device. The transport device may include a tension control mechanism for controlling the tension of the substrate. Examples of transport devices include transport rollers and transport belts. Other examples of transport devices include a feeder for feeding out the substrate and a winder for winding up the substrate. The feeder and winder can also be used, for example, as a roll-to-roll transport device. A roll-to-roll transport device is preferably used as a device for transporting long lengths of substrate.

[0033] The conveying speed of the substrate is preferably in the range of 1 m / min to 100 m / min.

[0034] The tension of the substrate is preferably in the range of 30 N / m to 300 N / m, and more preferably in the range of 50 N / m to 200 N / m. Tension control is performed, for example, using a known tension control device. Tension control may also be performed using a known conveying device that includes a tension control mechanism. An example of a conveying device that includes a tension control mechanism is a conveying device that includes a tension drive roller. The tension drive roller rotates, for example, by friction or magnetic force acting between a rotating shaft that supports the tension drive roller and the tension drive roller. The rotating shaft is rotated, for example, by a motor. In other words, the force that rotates the rotating shaft is transmitted to the tension drive roller, and the tension drive roller rotates. A conveying device that includes a tension drive roller can control the tension of the film according to the rotation speed of the rotating shaft, for example. Technology relating to a tension drive roller is described, for example, in Japanese Patent Publication No. 4066904. The contents of the above-mentioned documents are incorporated herein by reference. Tension control may be performed using a dancer roller. Tension control may be performed using a rotary draw control system.

[0035] (Coating device) The coating apparatus includes a dispensing section for dispensing the coating liquid. The coating apparatus may include a plurality of dispensing sections. Examples of materials for the dispensing section include metal. Examples of metals include stainless steel. The structure of the dispensing section is not limited as long as it has the function of dispensing the coating liquid. The dispensing section may include one or more dispensing ports. Examples of the shape of the dispensing port in a plan view include circular, elliptical, polygonal, linear, and irregular shapes. From the viewpoint of uniformizing the film thickness distribution of the coating film, it is preferable that the dispensing section includes a dispensing port that extends in the width direction of the substrate.

[0036] The coating apparatus preferably includes a gas outlet. The coating apparatus may include one or more gas outlets. The gas outlet supplies gas between the substrate and the coating apparatus. The gas supplied between the substrate and the coating apparatus supports the substrate in the coating process described later and lifts the substrate away from the coating apparatus. Examples of components of the discharge section include metal. Examples of metals include stainless steel. The structure of the gas outlet is not limited as long as it has the function of blowing gas. The gas outlet may include one or more outlets. Examples of outlet shapes in plan view include circular, elliptical, polygonal, linear, and irregular shapes. The gas outlet may include a space (i.e., a flow path) that communicates with the discharge port and through which gas flows. The gas outlet may be a nozzle. The gas outlet may be a porous material.

[0037] As described below, the coating apparatus applies a coating liquid to a substrate being transported. The coating apparatus for applying a coating liquid to a substrate being transported preferably includes a discharge unit that discharges the coating liquid toward a first surface of the substrate, and at least one blowing unit located upstream and downstream of the discharge unit in the transport direction of the substrate, which blows gas toward the first surface of the substrate in order to levitate the substrate. According to the above embodiment, a coating apparatus capable of forming a coating film having a uniform film thickness distribution is provided. The blowing units are preferably located upstream and downstream of the discharge unit in the transport direction of the substrate. The blowing unit located upstream of the discharge unit in the transport direction of the substrate (hereinafter sometimes referred to as the "first blowing unit") and the blowing unit located downstream of the discharge unit in the transport direction of the substrate (hereinafter sometimes referred to as the "second blowing unit") stabilize the levitation transport of the substrate and improve the uniformity of the film thickness distribution of the coating film. The first blowing unit may or may not be adjacent to the discharge unit. The second discharge section may be adjacent to the discharge section, or it may not be adjacent to the discharge section. Preferably, the first discharge section is adjacent to the discharge section, and the second discharge section is adjacent to the discharge section.

[0038] <<Coating process>> In the coating process, the substrate is levitated and transported along a transport path that curves convexly above the coating apparatus and away from the coating apparatus, with the substrate's first surface facing the coating apparatus. The coating liquid is then applied to the first surface of the substrate using the coating apparatus. According to the above coating process, a coating film with a uniform film thickness distribution is formed.

[0039] (Floating transport) In the coating process, the substrate is transported by floating above the coating apparatus. That is, the substrate is transported without contacting the coating apparatus. The amount of substrate floating is determined, for example, according to the coating conditions (e.g., the type of coating liquid). From the viewpoint of stabilizing the floating transport and ensuring uniformity of the coating film thickness distribution, the amount of substrate floating is preferably 10 μm or more, and more preferably 20 μm or more. The lower limit of the amount of substrate floating may be 50 μm or 100 μm. From the viewpoint of preventing the coating bead from becoming unstable due to the influence of gravity, the amount of substrate floating is preferably 1,000 μm or less, more preferably 500 μm or less, and particularly preferably 400 μm or less. The amount of substrate floating is preferably in the range of 10 μm to 1,000 μm, more preferably in the range of 20 μm to 500 μm, and particularly preferably in the range of 50 μm to 400 μm. "Substrate levitation" refers to the shortest distance between the first surface of the substrate and the surface of the discharge section facing the first surface of the substrate. The substrate levitation is measured using a laser displacement meter according to the following procedure (1) to (3). Note that the substrate levitation is measured under conditions that exclude the influence of the coating liquid, i.e., under conditions where no coating liquid is applied to the substrate. (1) Using a laser displacement meter positioned opposite the discharge section of the coating device, the position of the surface of the discharge section is detected, and then, while the substrate is being levitated and transported, the position of a second surface of the substrate traveling between the discharge section of the coating device and the laser displacement meter is detected. (2) Based on the measurement results obtained in (1) above, measure the distance D from the surface of the discharge section to the second surface of the floating substrate. (3) The value obtained according to the following formula shall be considered as the amount of the substrate floating. Formula: Amount of substrate levitation = [Distance D] - [Thickness of substrate]

[0040] The degree of curvature of the substrate during the coating process is expressed, for example, by the radius of curvature. The greater the degree of curvature, the smaller the radius of curvature, and the smaller the degree of curvature, the larger the radius of curvature. From the viewpoint of uniformizing the film thickness distribution of the coating film, the radius of curvature of the substrate at the contact point between the substrate and the coating liquid is preferably in the range of 50 mm to 1,000 mm, more preferably in the range of 70 mm to 600 mm, and particularly preferably in the range of 100 mm to 300 mm. The radius of curvature of the substrate is measured under conditions that exclude the influence of the coating liquid, that is, under conditions where the coating liquid is not applied to the substrate.

[0041] The method for levitating the substrate is not limited. One example of a method for levitating the substrate is to supply gas between the substrate and the coating device. The gas supplied between the substrate and the coating device supports the substrate and causes it to levitate from the coating device. When the substrate is supported by gas, the coating liquid can be applied to the substrate at a lower discharge pressure, further improving the uniformity of the coating film thickness distribution.

[0042] The type of gas is not limited. Examples of gases include nitrogen and air. Air is preferred.

[0043] The gas may be supplied, for example, by a known method. The gas may be supplied using a blower, a compressor, or a gas storage container (e.g., a cylinder).

[0044] The gas pressure is not limited. The gas pressure affects, for example, the amount of substrate levitation and the degree of substrate curvature. The greater the gas pressure, the greater the amount of substrate levitation, and the less the gas pressure, the less the amount of substrate levitation. Also, the greater the gas pressure, the greater the degree of substrate curvature, and the less the gas pressure, the smaller the degree of substrate curvature. From the viewpoint of stabilizing levitation transport and curvature of the substrate, the gas pressure present in the space between the substrate and the coating device (hereinafter sometimes referred to as "P0") is preferably 10 Pa or more, more preferably 50 Pa or more, and particularly preferably 100 Pa or more. "Gas present in the space between the substrate and the coating device" includes not only gas intentionally supplied between the substrate and the coating device, but also gas present in the space between the substrate and the coating device due to unintentional factors (e.g., air). Furthermore, P0 is preferably 150 Pa or more, and more preferably 200 Pa or more. The smaller the gas pressure fluctuation, the better the uniformity of the coating film thickness distribution. From the viewpoint of reducing gas pressure fluctuations, P0 is preferably 2,000 Pa or less, more preferably 1,600 Pa or less, and particularly preferably 1,300 Pa or less. The upper limit of P0 may be 1,000 Pa, 800 Pa, or 500 Pa. P0 is preferably in the range of 10 Pa to 2,000 Pa, more preferably in the range of 100 Pa to 1,600 Pa, and particularly preferably in the range of 150 Pa to 1,300 Pa. P0 is measured by inserting a metal tube connected to a manometer gauge into the space between the substrate and the coating device.

[0045] The levitation transport of the substrate preferably includes blowing gas toward the first surface of the substrate from a blowing outlet that is located upstream and downstream of the discharge outlet in the transport direction of the substrate. The gas blown toward the first surface of the substrate from the blowing outlet supports the substrate and causes the substrate to levitate from the coating apparatus. The above method stabilizes the levitation transport of the substrate and improves the uniformity of the coating film thickness distribution. From the viewpoint of stabilizing the levitation transport, it is preferable that the blowing outlets are located upstream and downstream of the discharge outlet in the transport direction of the substrate. The blowing outlets may be part of the coating apparatus or an element independent of the coating apparatus. It is preferable that the blowing outlets are part of the coating apparatus. The configuration of the blowing outlets is described in the "Transportation Process" section above.

[0046] A method for manufacturing a multilayer film according to one embodiment of the present disclosure preferably includes controlling the amount of substrate floating by controlling the pressure of the gas blown out from the blowing section. The pressure of the gas blown out from the blowing section is controlled, for example, within the range of the aforementioned pressure (i.e., P0). The amount of substrate floating is controlled, for example, within the range of the aforementioned floating amounts.

[0047] The levitation transport of the substrate preferably includes blowing gas toward the first surface of the substrate from a first discharge section located upstream of the discharge section and a second discharge section located downstream of the discharge section in the transport direction of the substrate, and independently controlling the pressure of the gas blown from the first discharge section and the pressure of the gas blown from the second discharge section. The above method stabilizes the levitation transport of the substrate and also improves the controllability of the degree of curvature of the substrate. As a result, the uniformity of the film thickness distribution of the coating film is improved. The pressure of the gas present in the space between the substrate and the first discharge section (hereinafter sometimes referred to as "P1") may be the same as or different from the pressure of the gas present in the space between the substrate and the second discharge section (hereinafter sometimes referred to as "P2"). "Gas present in the space between the substrate and the discharge section" includes not only gas intentionally supplied between the substrate and the discharge section, but also gas present in the space between the substrate and the discharge section due to unintentional factors (e.g., air). P1 and P2 are controlled, for example, within the range of the previously described pressure (i.e., P0). From the viewpoint of homogenizing the film thickness distribution of the coating film, the ratio of P1 to P2 (i.e., P1 / P2) is preferably 0.1 to 1.5, and more preferably 0.3 to 1. It is preferable that P1 is lower than P2. When P1 is lower than P2, the influence of tension fluctuations of the substrate on the film thickness distribution of the coating film is reduced, and the uniformity of the film thickness distribution of the coating film is also improved. From the above viewpoint, the ratio of P1 to P2 (i.e., P1 / P2) is preferably 0.1 or more and less than 1, more preferably 0.3 to 0.9, and particularly preferably 0.4 to 0.8. It is preferable that P1 is 50 Pa or more lower than P2, and more preferably 100 Pa or more lower than P2. For example, it is preferable that P1 is in the range of 10 Pa to 250 Pa, and P2 is in the range of 300 Pa to 500 Pa. P1 is measured by inserting a metal tube connected to a manometer into the space between the substrate and the first outlet. P2 is measured by inserting a metal tube connected to a manometer into the space between the substrate and the second outlet.

[0048] (Application) Examples of coating methods include curtain coating, dip coating, spin coating, print coating, spray coating, slot coating, roll coating, slide coating, blade coating, gravure coating, and wire bar coating. In the coating process, it is preferable to apply the coating liquid by the slot coating method. In the slot coating method, for example, the coating liquid is discharged from a discharge section that includes a discharge port extending in the width direction of the substrate.

[0049] The thickness of the coating solution applied to the substrate (hereinafter sometimes referred to as "liquid film thickness") is not limited. The liquid film thickness may be in the range of 10 μm to 200 μm. The liquid film thickness may be in the range of 20 μm to 100 μm.

[0050] (Application liquid) The type of coating solution is not limited. The type of coating solution is determined, for example, according to the application of the multilayer film. The coating solution is preferably an aqueous coating solution. "Aqueous coating solution" means a coating solution in which the solvent contained in the coating solution is substantially water. "The solvent contained in the coating solution is substantially water" means that water accounts for the majority of the solvent contained in the coating solution. The proportion of water in the solvent contained in the aqueous coating solution is preferably 90% by mass or more, more preferably 95% by mass or more, and particularly preferably 100% by mass.

[0051] Examples of water contained in aqueous coating solutions include natural water, purified water, distilled water, ion-exchanged water, pure water, and ultrapure water.

[0052] The water content in the aqueous coating solution is preferably 40% by mass or more, and more preferably 50% by mass or more, relative to the total mass of the aqueous coating solution. The water content in the aqueous coating solution is preferably less than 100% by mass, and more preferably 80% by mass or less, relative to the total mass of the aqueous coating solution.

[0053] The aqueous coating solution may contain particles. Examples of particles include inorganic particles, organic particles, and composite particles of inorganic and organic substances.

[0054] Examples of inorganic particles include metal particles, metalloid particles, metal compound particles, metalloid compound particles, inorganic pigment particles, mineral particles, and polycrystalline diamond particles. Examples of metals include alkali metals, alkaline earth metals, transition metals, and their alloys. Examples of metalloids include silicon. Examples of metal compounds and metalloid compounds include oxides, hydroxides, and nitrides. Examples of inorganic pigments include carbon black. Examples of minerals include mica.

[0055] Examples of organic particles include resin particles and organic pigment particles.

[0056] Examples of composite particles of inorganic and organic materials include composite particles in which inorganic particles are dispersed in a matrix of organic material, composite particles in which organic particles are coated with inorganic material, and composite particles in which inorganic particles are coated with organic material.

[0057] To impart dispersibility, the particles may be surface-treated. Composite particles may be formed by the surface treatment.

[0058] The particle size, specific gravity, and usage are not limited. The particle size, specific gravity, and usage are determined, for example, according to the coating film formed by the coating solution and the manufacturing conditions of the coating film.

[0059] The aqueous coating solution may contain one or more types of particles.

[0060] The particle content in the aqueous coating solution is not limited. The particle content in the aqueous coating solution is determined, for example, according to the purpose of particle addition, the coating film formed by the coating solution, and the manufacturing conditions of the coating film.

[0061] Components of an aqueous coating solution include, for example, binder components, components that contribute to particle dispersibility, polymerizable compounds, polymerization initiators, and components that enhance coating performance (e.g., surfactants).

[0062] The solid content concentration of the coating solution is preferably less than 70% by mass, and more preferably between 30% and 60% by mass.

[0063] <<Other processes>> A method for manufacturing a multilayer film according to one embodiment of the present disclosure may include steps other than those described above, if necessary.

[0064] (drying process) A method for manufacturing a multilayer film according to one embodiment of the present disclosure may include drying the coating solution after the coating step. That is, the coating solution applied to the substrate may be dried. Examples of drying methods include heating and blowing air. The temperature of the gas used in blowing air is preferably in the range of 25°C to 200°C, and more preferably in the range of 30°C to 150°C. The air velocity used in blowing air is preferably in the range of 1.5 m / sec to 50 m / sec. Examples of drying equipment used to dry the coating solution include ovens, hot air blowers, and infrared heaters.

[0065] (Cutting process of multilayer film) A method for manufacturing a multilayer film according to one embodiment of this disclosure may include a step of cutting the multilayer film. By cutting the multilayer film, the width of the multilayer film can be adjusted. Examples of methods for cutting the multilayer film include using a cutting tool.

[0066] <<Production Method>> From the viewpoint of improving productivity, the method for manufacturing a multilayer film according to one embodiment of this disclosure is preferably carried out by a roll-to-roll method. In the method for manufacturing a multilayer film carried out by a roll-to-roll method, at least a conveying step and a coating step are carried out between the supply of the rolled film and the winding of the film.

[0067] Next, an example of a method for manufacturing a multilayer film will be described with reference to Figures 1 and 2. Figure 1 is a schematic side view illustrating a method for manufacturing a multilayer film according to one embodiment of the present disclosure. Figure 2 is a schematic cross-sectional view showing an enlarged view of the tip of the coating apparatus shown in Figure 1. In Figure 2, direction X is perpendicular to direction Y.

[0068] The manufacturing apparatus 100 shown in Figure 1 includes a conveyor roller 10, a conveyor roller 11, a conveyor roller 12, a conveyor roller 13, a conveyor roller 14, a conveyor roller 15, a conveyor roller 16, a conveyor roller 17, a conveyor roller 18, a coating device 20, a drying device 30, a dispensing device (not shown), and a winding device (not shown).

[0069] The conveying rollers 10, 11, 12, 13, 14, 15, 16, 17, and 18 convey the film F while supporting it. Each roller is rotatable. The film F is a substrate having a first surface F1 and a second surface F2 on the opposite side of the first surface F1.

[0070] The coating device 20 applies a coating liquid to the film F being transported. The coating device 20 includes a discharge unit 21, a first blowing unit 22, and a second blowing unit 23.

[0071] The discharge unit 21 discharges the coating liquid L toward the first surface F1 of the film F. The discharge unit 21 includes a discharge port 21a. The discharge port 21a extends in the width direction of the film F, i.e., in a direction perpendicular to directions X and Y. The coating liquid L is supplied from a liquid delivery device (not shown) connected to the coating apparatus 20 and discharged through the discharge port 21a.

[0072] The first blowing section 22 blows gas toward the first surface F1 of the film F. The first blowing section 22 is located upstream of the discharge section 21 in the transport direction of the film F. The first blowing section 22 is adjacent to the discharge section 21. The first blowing section 22 includes a plurality of outlets 22a. The gas is supplied from a compressor (not shown) connected to the coating device 20 and blown out through the outlets 22a.

[0073] The second discharge section 23 blows gas toward the first surface F1 of the film F. The second discharge section 23 is located downstream of the discharge section 21 in the conveying direction of the substrate F. The second discharge section 23 is adjacent to the discharge section 21. The second discharge section 23 includes a plurality of outlets 23a. The gas is supplied from a compressor (not shown) connected to the coating device 20 and blown out through the outlets 23a.

[0074] The drying apparatus 30 dries the coating liquid L applied to the film F.

[0075] The feeding device (not shown) supplies film F from roll film RF1. The feeding device has roll film RF1 mounted along a rotating shaft that extends from the front to the back in Figure 1.

[0076] The winding device (not shown) forms a roll film RF2 by winding a multilayer film containing film F into a roll. The winding device loads the roll film RF2 along a rotating shaft that extends from the front to the back in Figure 1.

[0077] The manufacturing method for the multilayer film shown in Figure 1 is carried out by a roll-to-roll method. The film F, fed out from the roll film RF1, passes through the transport rollers 10, 11, 12, 13, 14, coating device 20, 15, drying device 30, 16, 17, and 18, and is wound into a roll.

[0078] As shown in Figure 1, the film F fed from the roll film RF1 is conveyed toward the coating device 20. As shown in Figure 2, upon reaching the coating device 20, the film F is levitated and conveyed along a conveying path that curves convexly in the direction Y away from the coating device 20 above the coating device 20. The levitated film F is supported by gas blown from the first blowing section 22 and the second blowing section 23. The first surface F1 of the levitated film F faces the coating device 20. The coating device 20 applies the coating liquid L to the first surface F1 of the levitated film F as described above. The coating liquid L is applied to the first surface F1 of the film F, which is curved convexly in the direction Y away from the coating device 20 by the levitation conveying. As shown in Figure 2, the film F is lifted and transported by the gas blown from the first discharge section 22 and the second discharge section 23, curving in a convex shape in the direction Y away from the coating device 20, thereby allowing the coating liquid L to be applied to the film F at a low discharge pressure. As a result, it is presumed that the uniformity of the distribution of the coating liquid L applied to the film F is improved, and a coating film with a uniform film thickness distribution is formed.

[0079] The coating liquid applied to film F is dried in drying apparatus 30. A multilayer film is formed by the drying of the coating liquid. The multilayer film is wound into a roll using a winding device (not shown). The rolled multilayer film forms a roll film RF2. [Examples]

[0080] The present disclosure will be described in detail below with reference to examples. However, the present disclosure is not limited to the following examples.

[0081] <Example 1> (Preparation of base material AL1) As the base material AL1, an aluminum film with a width of 220 mm, a thickness of 10 μm, a length of 300 m, and a thermal conductivity of 230 W / (m·K) was prepared. The base material AL1 was wound into a roll to form a roll film.

[0082] (Preparation of coating solution A) The following components were mixed to prepare coating solution A. Polyvinyl alcohol (CKS-50, degree of saponification: 99 mol%, degree of polymerization: 300, Nippon Synthetic Chemical Industry Co., Ltd.): 58 parts by mass • Selogen PR (Daiichi Kogyo Seiyaku Co., Ltd.): 24 parts by mass • Surfactant (Nippon Emulsion Co., Ltd., Emarex 710): 5 parts by mass • Artpearl (registered trademark) J-7P aqueous dispersion: 913 parts by mass

[0083] An aqueous dispersion of Artpearl J-7P was prepared by the following method: 74 parts by mass of pure water was mixed with 3 parts by mass of Emarex 710 (Nippon Emulsion Co., Ltd., nonionic surfactant) and 3 parts by mass of sodium carboxymethylcellulose (Daiichi Kogyo Seiyaku Co., Ltd.). 20 parts by mass of Artpearl J-7P (Negami Kogyo Co., Ltd., silica composite crosslinked acrylic resin fine particles) were added to the resulting aqueous solution and dispersed at 10,000 rpm (revolutions per minute, hereafter the same) for 15 minutes using an Ace homogenizer (Nippon Seiki Seisakusho Co., Ltd.) to obtain an aqueous dispersion of Artpearl J-7P (particle concentration: 20% by mass). The true specific gravity of the silica composite crosslinked acrylic resin fine particles in the obtained aqueous dispersion was 1.20, and the average particle size of the fine particles was 6.5 μm.

[0084] (Manufacturing of multilayer films) Using a manufacturing apparatus containing the components shown in Figure 1, coating solution A was applied to the substrate AL1, and then the coating solution was dried. A multilayer film was obtained by this procedure. The film transport speed was 20 m / min. The specific manufacturing conditions are shown in Table 1.

[0085] <Examples 2-7> A multilayer film was obtained using the same procedure as in Example 1, except that the manufacturing conditions were changed according to the information in Table 1.

[0086] <Comparative Example 1> A coating solution A was applied to a substrate AL1 using a coating apparatus as shown in Figure 1 of Japanese Patent Publication No. 5-208165, and then the coating solution was dried. A multilayer film was obtained by the above procedure. The film transport speed was 20 m / min. The specific manufacturing conditions are shown in Table 1.

[0087] <Comparative Example 2> As shown in Figure 1 of Japanese Patent Publication No. 2001-310148, coating liquid A was applied to a substrate AL1 that traveled between a backup roller, which was used as an air-blowing outlet, and a coating device, and then the coating liquid was dried. A multilayer film was obtained by the above procedure. The film transport speed was 20 m / min. The specific manufacturing conditions are shown in Table 1.

[0088] <Rating> (Film thickness distribution) Using a film thickness measuring instrument (SI-T90, Keyence Corporation), the thickness of the coating film along the longitudinal direction of a multilayer film was measured at 10 locations at 5 mm intervals. The coating film thickness distribution T was calculated and evaluated according to the following criteria. The evaluation results are shown in Table 1. A: T ≤ 1% B:1% <T<2% C: 2% ≤ T < 5% D: 5% ≤ T

[0089] [Table 1]

[0090] The following is a description of the items listed in Table 1. The "dispensing section" refers to the dispensing section that dispenses the coating liquid. The "discharge section" refers to the section from which gas (specifically air) is blown out. In Comparative Example 2, the discharge section is a backup roller that blows out gas. The "shortest distance between the dispensing unit and the substrate" refers to the shortest distance between the dispensing unit and the transported substrate, measured under conditions where no coating liquid is applied to the substrate. Furthermore, the "shortest distance between the dispensing unit and the substrate" for Examples 1 to 7 corresponds to the amount of substrate levitation described above. "Shortest distance between the discharge point and the substrate" refers to the shortest distance between the discharge point and the transported substrate, measured under conditions where no coating liquid is applied to the substrate. "P0" indicates the pressure of the gas present in the space between the substrate and the outlet. "P1" indicates the pressure of the gas present in the space between the substrate and the first outlet. "P2" indicates the pressure of the gas present in the space between the substrate and the second outlet.

[0091] Table 1 shows that the uniformity of the film thickness distribution in Examples 1 to 7 is superior to that in Comparative Examples 1 to 2. Compared to Examples 1 to 7, in Comparative Example 1, the uniformity of the film thickness distribution is thought to have decreased because the substrate was not levitated and conveyed by gas. Compared to Examples 1 to 7, in Comparative Example 2, the uniformity of the film thickness distribution is thought to have decreased because the substrate, which is levitated and conveyed between the backup roller that blows out gas and the coating device, is curved in a convex shape in the direction from the backup roller towards the coating device.

[0092] The disclosure of Japanese Patent Application No. 2020-209440, filed on 17 December 2020, is incorporated herein by reference. All documents, patent applications and technical standards described herein are incorporated herein by reference to the same extent as if each individual document, patent application and technical standard were specifically and individually described as being incorporated by reference. [Explanation of Symbols]

[0093] 10, 11, 12, 13, 14, 15, 16, 17, 18: Conveyor rollers 20: Coating device 21:Discharge part 21a: Discharge port 22: First outlet 23: Second outlet 22a, 23a: Air outlet 30:Drying equipment 100: Manufacturing equipment F: Film F1: First side F2: Second side RF1, RF2: Roll film

Claims

1. A substrate including a first surface and a second surface on the opposite side of the first surface is conveyed toward a coating apparatus including a dispensing unit that dispenses a coating liquid. The process includes: applying the coating liquid to the first surface of the substrate using the coating apparatus, while levitating and conveying the substrate along a conveying path that is curved convexly in a direction away from the coating apparatus above the coating apparatus, with the first surface of the substrate facing the coating apparatus; The floating transport of the substrate includes blowing gas toward the first surface of the substrate from a first discharge section located upstream of the discharge section and a second discharge section located downstream of the discharge section in the transport direction of the substrate, and independently controlling the pressure of the gas blown from the first discharge section and the pressure of the gas blown from the second discharge section. The ratio (P1 / P2) of the pressure of the gas in the space between the substrate and the first outlet (P1) to the pressure of the gas in the space between the substrate and the second outlet (P2) is 0.1 to 1.

5. The shortest distance between the first surface of the substrate and the surface of the discharge portion facing the first surface of the substrate is 10 μm or more. A method for manufacturing multilayer films.

2. A method for manufacturing a multilayer film according to claim 1, comprising controlling the amount of the substrate floating by controlling the pressure of the gas blown out from the blowing section.

3. A method for manufacturing a multilayer film according to claim 1, wherein the pressure of the gas present in the space between the substrate and the first outlet is lower than the pressure of the gas present in the space between the substrate and the second outlet.

4. A coating apparatus for applying a coating liquid to a substrate that includes a first surface being transported and a second surface on the opposite side of the first surface, A dispensing unit for dispensing the coating liquid toward the first surface of the substrate, In the conveying direction of the substrate, a first blowing section is located upstream of the discharge section and blows gas toward the first surface of the substrate in order to levitate the substrate, The transport direction of the substrate includes a second blowing section, which is located downstream of the discharge section and blows gas toward the first surface of the substrate in order to levitate the substrate, The pressure of the gas blown out from the first outlet and the pressure of the gas blown out from the second outlet are controlled independently of each other. The ratio (P1 / P2) of the pressure of the gas in the space between the substrate and the first outlet (P1) to the pressure of the gas in the space between the substrate and the second outlet (P2) is 0.1 to 1.

5. The shortest distance between the first surface of the substrate and the surface of the discharge portion facing the first surface of the substrate is 10 μm or more. Coating device.

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