Method for producing coating film

Abstract

Provided is a method for producing a coating film, the method comprising: step A for continuously conveying a long support and applying a coating liquid in multiple strips onto the continuously conveyed support; and step B for drying the coating liquid film obtained in step A. In step B, for a laminate composed of the support and the coating liquid film, curl control is started while the solid concentration of the coating liquid film is 90 mass% or less, and the temperature of the laminate is maintained at 40-100°C during the curl control.

Description

Coating film manufacturing method

[0001] The present disclosure relates to a method for producing a coating film.

[0002]

[0003] Methods for producing a desired coating film on a support by a continuous roll-to-roll process are known. For example, one method for producing a coating film involves applying a coating liquid to a support to obtain the desired coating film, and then drying the resulting coating liquid film. In this method, a curl control device may be used to suppress curling (also known as warping) of the coating film.

[0003] For example, WO 2021 / 210542 describes a method for producing a coating film, which includes step A of continuously transporting a long support and applying an aqueous coating liquid onto the continuously transported support, and step B of drying the coating liquid film obtained in step A on the continuously transported support, and in the constant-rate drying stage of step B, while the solids concentration of the coating liquid film is between 70% by mass and 95% by mass, non-contact curl regulation of the coating liquid film is initiated for a laminate consisting of the support and the coating liquid film.

[0004] When a coating film is produced by applying a coating liquid in multiple stripes onto a continuously transported support, such as in a continuous process using a roll-to-roll method, folds and wrinkles may occur in areas where the coating liquid is not applied (hereinafter simply referred to as "uncoated areas").

[0005] Therefore, the problem that one embodiment of the present disclosure aims to solve has been made in consideration of the above circumstances, and is to provide a method for producing a coating film that can suppress the occurrence of folds and wrinkles in uncoated parts in a method for producing a coating film by applying a coating liquid in multiple stripes onto a continuously transported support (for example, a method using a continuous process using a roll-to-roll system).

[0006] The present disclosure includes the following aspects. <1> A method for producing a coating film, comprising: Step A: continuously transporting a long support and applying a coating liquid in multiple stripes onto the continuously transported support; and Step B: drying the coating liquid film obtained in Step A, wherein in Step B, curl regulation is initiated for a laminate comprising the support and the coating liquid film while the solid content of the coating liquid film is 90% by mass or less, and the temperature of the laminate is maintained at 40°C to 100°C during curl regulation. <2> The method for producing a coating film according to <1>, wherein curl regulation is initiated in Step B while the solid content of the coating liquid film is 50% by mass to 70% by mass. <3> The method for producing a coating film according to <1> or <2>, wherein both surfaces of the laminate are heated in Step B. <4> The method for producing a coating film according to any one of <1> to <3>, wherein the curl regulation is non-contact. <5> The method for producing a coated film according to <4>, wherein the non-contact curl control is performed by blowing gas onto both sides of the laminate and continuously conveying the laminate while curving it in the thickness direction by the gas pressure. <6> The method for producing a coated film according to any one of <1> to <5>, wherein the coating liquid is applied in multiple stripes onto the support so that uncoated portions are formed in the longitudinal direction of the support. <7> The method for producing a coated film according to <6>, wherein the uncoated portions have a width of 10 mm to 100 mm. <8> The method for producing a coated film according to any one of <1> to <7>, wherein the coating liquid contains particles. <9> The method for producing a coated film according to any one of <1> to <8>, wherein the support is a metal support. <10> The method for producing a coated film according to any one of <1> to <9>, wherein the support has a thickness of 10 μm to 30 μm.

[0007] According to one embodiment of the present disclosure, a method for producing a coating film by applying a coating liquid in multiple stripes onto a continuously transported support is provided, which is capable of suppressing the occurrence of folds and wrinkles in uncoated areas.

[0008] Fig. 1 is a schematic diagram showing each step of a method for producing a coating film according to one embodiment. Fig. 2 is a schematic side view illustrating an example of a curl suppression means in step B. Fig. 3 is a schematic side view illustrating another example of a curl suppression means in step B.

[0009] Hereinafter, embodiments of the method for producing a coating film will be described. However, the present disclosure is not limited to the following embodiments and can be implemented with appropriate modifications within the scope of the object of the present disclosure.

[0010] In the present disclosure, a numerical range indicated using "to" means a range that includes the numerical values ​​before and after "to" as the minimum and maximum values, respectively. In the numerical ranges described in stages in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Furthermore, in the numerical ranges described in the present disclosure, the upper or lower limit value described in a certain numerical range may be replaced with a value shown in the Examples. The elements in the drawings shown in the present disclosure are not necessarily to scale, and the focus is on clearly illustrating the principles of the present disclosure, with some emphasis placed on certain points. Furthermore, in the drawings, components having the same function are denoted by the same reference numerals, and redundant explanations are omitted. In the present disclosure, the "width direction" refers to the direction perpendicular to the longitudinal direction of the long support, coating liquid film, and coating film. In the present disclosure, a combination of two or more preferred embodiments or aspects is a more preferred embodiment or aspect.

[0011] <<Method for Producing a Coating Film>> The method for producing a coating film according to the present disclosure includes step A of continuously transporting a long support and applying a coating liquid in multiple stripes onto the continuously transported support, and step B of drying the coating liquid film obtained in step A, wherein in step B, curl regulation is initiated for a laminate comprising the support and the coating liquid film while the solid content concentration of the coating liquid film is 90 mass % or less, and the temperature of the laminate is maintained at 40°C to 100°C during curl regulation.

[0012] According to the method for producing a coating film of the present disclosure, the occurrence of folds and wrinkles in uncoated areas is suppressed. The reason for this is not clear, but is presumed to be as follows.

[0013] In the past, when a coating liquid was applied in multiple stripes onto a continuously conveyed support, the coating liquid film shrunk as it dried, resulting in creases and wrinkles in the uncoated areas. This phenomenon does not occur when the coating liquid is applied to the entire surface of the support. That is, this phenomenon occurs when uncoated areas exist between multiple coating liquid films formed in a longitudinal direction, particularly when uncoated areas exist between coated areas. The present inventors investigated a method for producing a coating film by applying a coating liquid in multiple stripes onto a support, and found that the occurrence of creases and wrinkles in the uncoated areas can be suppressed by initiating curl regulation of a laminate consisting of a support and a coating liquid film while the solids concentration of the coating liquid film is 90% by mass or less during the drying process of the coating liquid film, and maintaining the temperature of the laminate at 40°C to 100°C during curl regulation.

[0014] On the other hand, the method for producing a coating film described in WO 2021 / 210542 does not mention multi-line coating of the coating liquid, and problems caused by the presence of uncoated areas are not anticipated.

[0015] Each step of the coating film manufacturing method of the present disclosure will be described below.

[0016] First, an example of a method for producing a coating film will be described with reference to Figure 1. As shown in Figure 1, when the leading end of a wound long support 10 is fed out and continuous transport begins, an aqueous coating liquid is applied by a coating means 20 (step A). ​​In step A, a coating liquid film (not shown) made of the aqueous coating liquid is formed on the long support. Subsequently, a laminate 12 of the coating liquid film formed in step A and the support 10 is continuously transported through a drying means 30, whereby the coating liquid film is dried on the support 10 (step B). In step B, the coating liquid film on the long support is dried, forming a coating film (not shown).

[0017] [Step A] In step A, a long support is continuously transported, and the coating liquid is applied in multiple stripes onto the continuously transported support.

[0018] - Support - The long support used in this step is not particularly limited as long as it is a long support that can be used in roll-to-roll printing. On the other hand, supports with high thermal conductivity, such as metal supports, are prone to creases and wrinkles in the uncoated areas. The coating film manufacturing method according to the present disclosure can obtain a coating film in which creases and wrinkles are suppressed, even when a support with high thermal conductivity is used.

[0019] Examples of supports with high thermal conductivity include supports with a thermal conductivity of 200 W / (m K) or more. In addition, when the support used in this process is, for example, a multilayer support containing a metal foil and a resin film, if the thermal conductivity of the entire support is 200 W / (m K) or more, the support is considered to have a thermal conductivity of 200 W / (m K) or more. The upper limit of the thermal conductivity of the support is not particularly limited, and is, for example, 500 W / (m K).

[0020] Examples of supports exhibiting the above thermal conductivity include metal supports. More specifically, examples of supports exhibiting the above thermal conductivity include metal supports made of copper, aluminum, silver, gold, and alloys thereof. Other metal supports may also be made of stainless steel, nickel, titanium, or an invar alloy. Among these, copper supports and aluminum supports are preferably used in terms of shape stability as a support, proven use, etc.

[0021] The thermal conductivity of the support is measured using a laser flash method. Specifically, it is measured, for example, by the following method. First, the support is cut into pieces with a size of φ5 mm to 10 mm at three locations along the width direction of the support to obtain three measurement samples. The thermal conductivity of the obtained three measurement samples is measured using a thermal property measurement device (Kyoto Electronics Manufacturing Co., Ltd., Model LFA-502) that applies the laser flash method. Specifically, the three locations along the width direction of the support are positions 5 mm from both edges in the width direction of the support and the center of the support in the width direction. The arithmetic mean value of the measured values ​​obtained at the three locations is taken as the thermal conductivity of the support.

[0022] The thickness of the support may be appropriately set from the viewpoint of application to the roll-to-roll system. The thickness of the support is, for example, preferably 3 μm to 50 μm, and more preferably 10 μm to 30 μm. The width and length of the support may be appropriately set from the viewpoint of application to the roll-to-roll system and the width and length of the intended coating film.

[0023] The thickness of the support is measured as follows. That is, the thickness of the support is measured at three locations along the width direction of the support using a contact-type thickness measuring device, for example, S-2270 manufactured by Fujiwork Co., Ltd. Specifically, the three locations along the width direction of the support are positions 5 mm from both edges in the width direction of the support and the center of the support in the width direction. The arithmetic mean value of the measurements obtained at the three locations is taken as the thickness of the support.

[0024] - Coating Liquid - The coating liquid used in this step is not particularly limited as long as it is a liquid containing a solvent (or dispersion medium) and solids. The solids contained in the coating liquid include components for obtaining the desired coating film as well as components for improving coatability. The solids refer to components excluding the solvent (or dispersion medium).

[0025] The solvent may be water, an organic solvent, or a mixed solvent of water and an organic solvent.

[0026] That is, the coating liquid may be a water-based coating liquid or a solvent-based coating liquid. Here, the water-based coating liquid refers to a coating liquid in which the solvent (or dispersion medium) contained in the coating liquid is substantially water. The phrase "the solvent (or dispersion medium) is substantially water" means that the inclusion of a solvent other than water that is introduced when using a solid content is permitted, and refers to the proportion of water in all solvents (or all dispersion mediums) being 90% by mass or more, preferably the proportion of water in all solvents (or all dispersion mediums) being 95% by mass or more, and particularly preferably all solvents (or all dispersion mediums) being water.

[0027] Examples of water contained in the aqueous coating liquid include natural water, purified water, distilled water, ion-exchanged water, pure water, and ultrapure water (e.g., Milli-Q water). Milli-Q water is ultrapure water obtained using a Milli-Q water production system manufactured by Merck Millipore, a company owned by Merck Ltd.

[0028] The water content in the aqueous coating liquid is not particularly limited, and is preferably 40% by mass or more, more preferably 50% by mass or more, based on the total mass of the aqueous coating liquid. The upper limit of the water content is sufficient as long as it is less than 100% by mass, but from the viewpoint of coatability, it is, for example, 80% by mass based on the total mass of the aqueous coating liquid.

[0029] The coating liquid may contain particles as one of the solid components. That is, the coating liquid may be a coating liquid containing particles. When a coating liquid containing particles is used, the particles also aggregate during the drying stage, which tends to cause creases and wrinkles in the uncoated portions. However, by applying the method for producing a coating film according to the present disclosure, creases and wrinkles in the uncoated portions can be suppressed even when a coating liquid containing particles is used.

[0030] The particles are not particularly limited as long as they are granular, and may be inorganic particles, organic particles, or composite particles of inorganic and organic substances.

[0031] As inorganic particles, can be used known inorganic particles that can be applied to the intended coating film.As inorganic particles, for example, can be listed metal particles (alkali metal, alkaline earth metal, transition metal etc. and the alloy of these metals), semimetal particles (silicon etc.), metal or semimetal compound particles (oxide, hydroxide, nitride etc.), pigment particles containing carbon black etc., etc. As inorganic particles, can also be listed mineral particles such as mica, inorganic pigment particles, polycrystalline diamond etc.

[0032] As the organic particles, known organic particles that can be applied to the target coating film can be used, and the organic particles are not particularly limited as long as they are particles of solid organic substances, including resin particles and organic pigment particles.

[0033] Examples of composite particles of an inorganic substance and an organic substance include composite particles in which inorganic particles are dispersed in a matrix of an organic substance, composite particles in which organic particles are coated with an inorganic substance, and composite particles in which inorganic particles are coated with an organic substance.

[0034] The particles may be surface-treated for the purpose of imparting dispersibility, etc. The particles may be surface-treated to form the above composite particles.

[0035] There are no particular limitations on the particle size, specific gravity, or form of use (e.g., whether or not to use in combination), and these may be selected appropriately depending on the desired coating film or the conditions suitable for producing the coating film.

[0036] The content of particles in the coating liquid is not particularly limited and may be determined appropriately depending on the desired coating film, the conditions suitable for producing the coating film, or the purpose of adding the particles.

[0037] The solid content contained in the coating liquid is not particularly limited, and may include various components used to obtain the desired coating film. Specific examples of the solid content contained in the coating liquid include, in addition to the above-mentioned particles, binder components, components that contribute to particle dispersibility, reactive components such as polymerizable compounds and polymerization initiators, components for improving coating performance such as surfactants, and other additives.

[0038] The solid content of the coating liquid used in this step is not particularly limited, but is preferably less than 70% by mass, and more preferably 30% to 60% by mass.

[0039] - Thickness of coating liquid film - The thickness of the coating liquid film formed in this step is not particularly limited and may be determined appropriately depending on the desired coating film. The thickness of the coating liquid film can be selected, for example, from 10 μm to 200 μm, and can be selected from 20 μm to 100 μm.

[0040] The thickness of the coating liquid film is measured as follows. That is, the coating liquid film is measured at three locations along the width direction of the coating liquid film using an optical interference thickness measuring device, for example, an infrared spectroscopic interference film thickness meter SI-T80 manufactured by Keyence Corporation. The three locations along the width direction of the coating liquid film are specifically positions 5 mm from both edges in the width direction of the coating liquid film and the center in the width direction of the coating liquid film. The arithmetic mean of the measurements obtained at the three locations is calculated and this is defined as the thickness of the coating liquid film.

[0041] -Multiple Strip Coating- In this process, the coating liquid is applied in multiple stripes onto the support. Multi-stripe coating means that the coating liquid is applied in multiple stripes (stripes). Multi-stripe coating results in the presence of areas on the support where the coating liquid is not applied (uncoated areas) between areas where the coating liquid is applied (coated areas).

[0042] The coating direction is not particularly limited, but from the viewpoint of obtaining a long coating film, it is preferable to apply the coating liquid in multiple stripes on the support so that uncoated portions are formed in the longitudinal direction of the support.

[0043] The number of threads when applying the coating liquid is 2 or more, preferably 3 to 5.

[0044] The width of the uncoated portion is preferably 10 mm to 100 mm. When the width of the uncoated portion between coated portions is 10 mm or more, wrinkles are less likely to occur. On the other hand, when the width of the uncoated portion is 100 mm or less, unnecessary uncoated portions are less likely to occur, resulting in good use efficiency of the support.

[0045] From the viewpoint of ease of manufacturing the battery cell, the width of the coated portion is preferably 100 mm to 500 mm.

[0046] The widths of the uncoated and coated portions are measured as follows: The width is measured from the upper surface of the coating liquid film using a FALCIO-APEX776 made by Mitutoyo Corporation.

[0047] - Coating - The coating liquid in this step is applied by a known coating means. Specific examples of the coating means (for example, coating means 20 in FIG. 1 ) include coating devices that use a curtain coating method, a dip coating method, a spin coating method, a print coating method, a spray coating method, a slot coating method, a roll coating method, a slide coating method, a blade coating method, a gravure coating method, or a wire bar method.

[0048] [Step B] In step B, the coating liquid film obtained in step A is dried on the support being continuously conveyed. Then, in step B, while the solid content concentration of the coating liquid film is 90 mass % or less, curl regulation is initiated for the laminate consisting of the support and the coating liquid film, and the temperature of the laminate is maintained at 40°C to 100°C during curl regulation.

[0049] - Curl Control - In this step, curl control is started for the laminate consisting of the support and the coating liquid film while the solid content concentration of the coating liquid film is 90 mass % or less.

[0050] Here, the solids concentration of the coating liquid film can be determined by measuring the non-contact thickness from the time the coating liquid is applied to the support until it becomes a dry film using a Keyence infrared spectroscopic interference film thickness meter SI-T80. Specifically, the non-contact thickness is first measured from the time the coating liquid is applied to the support until it becomes a dry film. Next, the thickness of the film (dry film) after drying is measured using a contact thickness meter. The measured dry film thickness is subtracted from the previously measured non-contact thickness to calculate the thickness of the solvent (or dispersion medium) in the coating liquid film at each measurement point. The obtained dry film thickness and solvent (or dispersion medium) thickness are multiplied by their respective densities (dry film density and solvent density), which converts them into the dry film mass and solvent mass per unit area of ​​the coating liquid film at the measurement point, thereby determining the solids concentration value.

[0051] When the solid content concentration of the coating liquid film is 90% by mass or less, the components contained in the coating liquid film are fluid in the coating liquid film, and the residual stress is low. By starting curl regulation in a state where the residual stress is low and maintaining the temperature of the laminate at 40°C to 100°C during curl regulation, it is possible to suppress the occurrence of folds and wrinkles in the uncoated parts.

[0052] From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, the solids concentration of the coating liquid film at the start of curl control is preferably 70% by mass or less, and from the viewpoint of improving drying efficiency, the solids concentration of the coating liquid film at the start of curl control is preferably 50% by mass or more.

[0053] The curl control method used in this step is not particularly limited as long as it is a means that can prevent the width direction end of the laminate of the coating liquid film and the support from curling (i.e., warping) toward the coating liquid film.

[0054] The curling may be controlled by a means that comes into contact with the coating liquid film, or by a means that does not come into contact with the coating liquid film.

[0055] The method for restricting curl due to contact is not particularly limited as long as it is a method that can restrict the width direction edge of the laminate of the coating liquid film and the support from curling (i.e., warping) toward the coating liquid film by bringing a restricting member into contact with the coating liquid film. The restriction of curl due to contact is preferably carried out, for example, by holding the support with a roller or by holding the edge of the support with a clip.

[0056] From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, the curl control is preferably a non-contact curl control.

[0057] The non-contact curl control is not particularly limited as long as it is a means that can prevent the width direction edges of a laminate of a coating liquid film and a support from curling toward the coating liquid film (i.e., warping) without coming into contact with the coating liquid film. From the viewpoint of excellent curl control ability, non-contact curl control is preferably performed by a means that blows gas onto one or both sides of the laminate and continuously conveys the laminate while curving it in the thickness direction by the gas pressure (hereinafter also referred to as a curl control means). The curl control means also functions as part of the drying means, as it blows gas onto the laminate to promote drying (i.e., an increase in solids concentration).

[0058] Curl Control Means The curl control means will be described using FIGS. 2 and 3. FIGS. 2 and 3 are schematic side views illustrating the curl control means in step B. In FIGS. 2 and 3, 32 indicates a pre-curl control region, and 34 indicates a curl control region. In the drying means 30A shown in FIG. 2, the curl control region 34 employs a curl control means that ejects gas onto one side of the laminate 12 (i.e., the surface on which the coating liquid film is formed) and continuously conveys the laminate while curving it in the thickness direction due to the gas's air pressure. In the drying means 30B shown in FIG. 3, the curl control region 34 employs a curl control means that ejects gas onto both sides of the laminate 12 (i.e., the surface on which the coating liquid film is formed and the exposed surface of the support) and continuously conveys the laminate while curving it in the thickness direction due to the gas's air pressure. With such a curl control means, the laminate 12 can be conveyed while undulating in a wave-like manner, as shown in the schematic side views of FIGS. 2 and 3. By conveying the laminate 12 while undulating it in this manner, curl regulation is effectively achieved, and the curl suppression effect can be enhanced. The drying speed of the coating liquid film can also be controlled by adjusting the type of gas ejected from the curl regulation means, the air pressure, temperature, humidity, etc.

[0059] From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, the non-contact curl control is preferably the curl control means shown in Fig. 3. That is, the non-contact curl control is preferably performed by a means for blowing gas onto both sides of the laminate and continuously conveying the laminate while curving it in the thickness direction by the gas pressure.

[0060] The drying means 30A shown in Fig. 2 will be described. As shown in Fig. 2, the laminate 12 of the coating liquid film and the support is transported through the drying means 30A to dry the coating liquid film. In Fig. 2, the solids concentration of the coating liquid film in the laminate 12 is increased in a pre-curl control region 32, and curl control is initiated in a curl control region 34 while the solids concentration of the coating liquid film on the support 10 is 90 mass % or less.

[0061] In the pre-curl control region 32 in FIG. 2, a drying means (for example, a hot air blower) as described later is used to increase the solid content concentration of the coating liquid film in the laminate 12 .

[0062] 2, a plurality of transport rolls 36 are arranged side by side on the same plane on the support side, and a plurality of gas-spouting units 38 are arranged side by side on the same plane on the coating liquid film side between the installation positions of the transport rolls 36. Gas (e.g., air) is sprayed from the spray units 38 toward the laminate 12, and the transport rolls 36 rotate, whereby the laminate 12 is curved in its thickness direction by the wind pressure of the gas while being transported.

[0063] The drying means 30B shown in Fig. 3 will be described. As shown in Fig. 3, the laminate 12 of the coating liquid film and the support is transported through the drying means 30B to dry the coating liquid film. In Fig. 3, the solids concentration of the coating liquid film in the laminate 12 is increased in a pre-curl control region 32, and curl control is initiated in a curl control region 34 while the solids concentration of the coating liquid film on the support 10 is 90 mass % or less.

[0064] In the pre-curl control region 32 in FIG. 3, a drying means (for example, a hot air blower) as described later is used to increase the solid content concentration of the coating liquid film in the laminate 12 .

[0065] 3, a plurality of ejection portions 38a for ejecting gas are arranged side by side on the same plane on the support side, and a plurality of ejection portions 38b for ejecting gas are arranged side by side on the same plane on the coating liquid film side between the positions of the ejection portions 38a. Gas (e.g., air) is ejected from the ejection portions 38a toward the laminate 12, and gas (e.g., air) is also ejected from the ejection portions 38b toward the laminate 12, so that the laminate 12 is conveyed while being curved in its thickness direction by the wind pressure of the gas.

[0066] 2 and 3 may be located at a position where curl regulation begins while the solids concentration of the coating liquid film on the transported laminate 12 is 90% by mass or less. The location of the curl regulation region 34 can be determined based on the results of a prior investigation into the transition of the solids concentration of the coating liquid film. Alternatively, the location of the curl regulation region 34 may be determined in advance, and the drying state of the coating liquid film may be controlled so that the solids concentration of the coating liquid film reaches 90% by mass or less by appropriately adjusting the transport speed of the laminate 12, the drying conditions of the pre-curl regulation region 32, and the like. Furthermore, the end point of the curl regulation region 34 is preferably, for example, at the exit of the drying means 30A or 30B.

[0067] In the curl control region 34 in FIGS. 2 and 3 , the gas ejected toward the laminate 12 may be, for example, air. The temperature of the ejected gas is preferably, for example, 60°C to 140°C, and more preferably 90°C to 130°C. The velocity of the ejected gas is preferably, for example, 1.5 m / s to 50 m / s. The amount of deformation of the laminate 12 in the curl control region 34 may be adjusted. As shown in FIGS. 2 and 3 , the amount of deformation of the laminate 12 includes the distance p between adjacent peaks in the undulating laminate 12 and the height difference h between the peaks and valleys in the laminate 12 when viewed from the side. The distance p is equal to the distance between the transport rolls 36 or the distance between the ejection portions 38b. The distance p is, for example, preferably 100 mm to 1500 mm, and more preferably 200 mm to 1000 mm. The height difference h is preferably 10 mm to 500 mm, and more preferably 20 mm to 200 mm. Furthermore, the smaller the value of distance p / height difference h, the stronger the curl-regulating force, so it is preferably 10 or less, and more preferably 5 or less. Since a smaller value of distance p / height difference h increases the number of components in the curl-regulating region 34 or increases its size, it is preferable to optimally design the lower limit of distance p / height difference h taking into account factors such as equipment installation space, air intake capacity, and cost. An example of the lower limit of distance p / height difference h is 2.

[0068] In this step, the laminate is dried using a known drying means. Specific examples of the drying means (for example, a part of the drying means 30 in FIG. 1 , or drying in the pre-curl control region 32 in FIGS. 2 and 3 ) include an oven, a hot air blower, an infrared (IR) heater, etc.

[0069] From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, it is preferable to heat both sides of the laminate in this step. Both sides of the laminate mean both the side on which the coating liquid is applied and the side on the support side. Conventionally, only the side on which the coating liquid is applied has been heated in order to dry the coating liquid applied to the support. In this step, it is preferable to heat both sides of the laminate in order to maintain the temperature of the laminate at 40°C to 100°C during curl regulation.

[0070] - Temperature of Laminate - In this process, the temperature of the laminate is maintained at 40°C to 100°C during curl regulation. The temperature of the laminate is measured as the surface temperature of the coating liquid film (film surface temperature). The film surface temperature is measured with an infrared thermometer.

[0071] During curl control, the temperature of the laminate is maintained at 40°C to 100°C, causing the support to stretch. After drying is complete, the laminate returns to room temperature, causing the support to shrink, thereby preventing folds and wrinkles from occurring in the uncoated areas.

[0072] From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, the temperature of the laminate is preferably 60°C to 80°C during curl regulation.

[0073] By going through step B in this manner, a coating film is formed on the support.

[0074] The thickness of the coating film obtained through step B is not particularly limited, and may be any thickness depending on the purpose, application, etc. In the coating film manufacturing method of the present disclosure, the thickness of the coating film is preferably 40 μm or more, more preferably 50 μm or more, and even more preferably 60 μm or more. The upper limit of the thickness of the coating film is not particularly limited, and may be determined depending on the application, but is, for example, 65 μm. The thickness of the coating film is measured in the same manner as the thickness of the coating liquid film.

[0075] [Other Steps] Other steps may be included, if necessary, at least either before step A or after step B. The other steps are not particularly limited and include a pretreatment step carried out before applying a coating liquid film, and a post-treatment step carried out on the formed coating film depending on the application of the coating film. Specific examples of the other steps include a step of surface treating the support, a step of curing the coating film, a step of compressing the coating film, a step of cutting the coating film, and a step of peeling the support from the coating film.

[0076] The method for producing a coating film according to the present disclosure is a method for producing a coating film on a continuously transported support, and is therefore suitable for producing coating films for applications requiring high productivity.

[0077] The present invention will be explained in more detail below with reference to examples. The materials, amounts used, ratios, details of each step, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below. Note that "parts" are all based on mass.

[0078] <Preparation of Support> Aluminum foil: 1000 mm wide, 12 μm thick, and 1000 m long aluminum foil (product name "1N30", manufactured by UACJ Foil Co., Ltd.) Copper foil: 1000 mm wide, 10 μm thick, and 1000 m long copper foil (product name "NC-WS", manufactured by Furukawa Electric Co., Ltd.)

[0079] <Preparation of Coating Liquid> [Preparation of Water-Based Coating Liquid A] The following components were mixed and then diluted with pure water to prepare Water-Based Coating Liquid A with a solids concentration of 60% by mass.

[0080] Polyvinyl alcohol: 58 parts (CKS-50: saponification degree 99 mol%, polymerization degree 300, Nippon Synthetic Chemical Industry Co., Ltd.) Cellogen PR, Daiichi Kogyo Seiyaku Co., Ltd.: 24 parts Surfactant (Emalex 710, Nippon Emulsion Co., Ltd.): 5 parts Water dispersion of Art Pearl J-7P prepared by the following method: 913 parts

[0081] (Art Pearl J-7P Aqueous Dispersion) 3 parts of Emalex 710 (Nippon Emulsion Co., Ltd., nonionic surfactant) and 3 parts of sodium carboxymethylcellulose (Dai-ichi Kogyo Seiyaku Co., Ltd.) were dissolved in 74 parts of pure water. 20 parts of Art Pearl (registered trademark) J-7P (Negami Chemical Industrial Co., Ltd., silica composite crosslinked acrylic resin microparticles) were added to the resulting aqueous solution, and the mixture was dispersed for 15 minutes at 10,000 rpm (revolutions per minute; the same applies hereinafter) using an Ace Homogenizer (Nippon Seiki Mfg. Co., Ltd.) to obtain an Art Pearl J-7P aqueous dispersion (particle concentration: 20% by mass). The true specific gravity of the silica composite crosslinked acrylic resin microparticles in the resulting aqueous dispersion was 1.20, and the average particle size was 6.5 μm.

[0082] [Preparation of Solvent-Based Coating Solution B] LiNi ０．５ Co ０．２ Mn ０．３ O２ 95 parts by mass of (NCM523) and 2.5 parts by mass of acetylene black were mixed, and 2.5 parts by mass of polyvinylidene fluoride powder (product name "PVDF5130", manufactured by Solvay) was gradually added thereto, followed by kneading with a planetary mixer. 54 parts by mass of N-methylpyrrolidone was added thereto, yielding a solvent-based coating solution B with a solids concentration of 65% by mass.

[0083] Example 1 Using an apparatus configured as shown in FIG. 1, a water-based coating solution A was applied to a support to form a coating film, and the formed coating film was dried to obtain a coating film. Specifically, the water-based coating solution A was applied in two lines onto a continuously conveyed support, with each coated area having a width of 450 mm, an uncoated area between the edge of the support and the coated area having a width of 30 mm, and an uncoated area between adjacent coated areas having a width of 40 mm (Step A). ​​This resulted in an uncoated area being formed on the support in the longitudinal direction of the support. Next, while conveying the laminate 12 of the coating solution film and support obtained in Step A through the drying means 30B shown in FIG. 3, the coating solution film was dried using the curl control method (non-contact) listed in Table 1 (Step B). In the pre-curl control region 32 of the drying means 30B shown in FIG. 3, the gas temperature and air velocity were adjusted so that the solids concentration of the coating solution film at the start of curl control would be the value listed in Table 1. The solid content concentration of the coating liquid film was measured using an infrared spectroscopic interference film thickness meter SI-T80 manufactured by Keyence Corporation. In the curl control region 34 in the drying means 30B shown in Figure 3, gas was sprayed onto both sides of the laminate 12, and the laminate was continuously conveyed while being curved in the thickness direction by the gas wind pressure. The conditions for curl control in the curl control region 34 were as follows: Type of gas: air Gas temperature: 120°C Wind pressure of gas sprayed onto the coating liquid film formation surface: 1.3 kPa Wind volume of gas sprayed onto the coating liquid film formation surface: 5 m ３ / min Deformation amount of laminate: Distance p in FIG. 3: 300 mm, height difference h in FIG. 3: 60 mm, distance p / height difference h: 5

[0084] The solids concentration of the coating liquid film when curl regulation started was as shown in Table 1, and the solids concentration of the coating liquid film when curl regulation was completed was 99% by mass. The conveying speed of the support in steps A and B was 3.0 m / min. A coating film was formed through steps A and B as described above.

[0085] [Examples 2 to 9, Comparative Example 1] A coating film was formed in the same manner as in Example 1, except that the type of support, the type of coating liquid, the number of threads, the solids concentration of the coating liquid film at the start of curl control, the film surface temperature, and the curl control method were appropriately changed as shown in Table 1.

[0086] The contact curl control used in Example 9 was carried out by holding the support with a roller.

[0087] [Evaluation of folds and wrinkles in uncoated areas] The coating film obtained in each example was visually inspected for the condition of the uncoated areas between coated areas. The evaluation criteria are as follows: A: No folds or wrinkles. B: Wrinkles, but no folds. C: Folds and wrinkles.

[0088] The evaluation results are shown in Table 1.

[0089]

[0090] As shown in Table 1, the manufacturing methods of Examples 1 to 9 include a step A of continuously conveying a long support and applying a coating liquid in multiple stripes onto the continuously conveyed support, and a step B of drying the coating liquid film obtained in step A. In step B, curl regulation was started for a laminate consisting of the support and the coating liquid film while the solid content concentration of the coating liquid film was 90 mass % or less, and the temperature of the laminate was maintained at 40°C to 100°C during curl regulation, thereby suppressing the occurrence of folds and wrinkles in uncoated parts.

[0091] In the manufacturing method of Comparative Example 1, the temperature of the laminate was below 40° C. during curl regulation, and folds and wrinkles occurred in the uncoated portions.

[0092] In Example 1, the curling was regulated by non-contact curling regulation, and it was found that, compared to Example 9, the occurrence of folds and wrinkles in the uncoated portions was suppressed.

[0093] (Explanation of symbols) 10 Support 12 Laminate of coating liquid film and support 14 Laminate of coating film and support 20 Coating means 30, 30A, 30B Drying means 32 Pre-curl regulation area 34 Curl regulation area 36 Transport rolls 38, 38a, 38b Spouting section 40 Unit C Curl amount h Height difference between peak and valley (height difference of undulation) p Distance between peak and adjacent peak (spacing of undulation)

[0094] The disclosure of Japanese Patent Application No. 2023-141763, filed on August 31, 2023, is incorporated herein by reference in its entirety. In addition, 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 was specifically and individually indicated to be incorporated by reference.

Claims

1. A method for producing a coating film comprising: step A of continuously transporting a long support and applying a coating liquid in multiple stripes onto the continuously transported support; and step B of drying the coating liquid film obtained in step A, wherein in step B, curl regulation of a laminate including the support and the coating liquid film is initiated while the solid content concentration of the coating liquid film is 90 mass % or less, and the temperature of the laminate is maintained at 40°C to 100°C during the curl regulation.

2. The method for producing a coating film according to claim 1, wherein in step B, curl regulation is started when the solid content of the coating liquid film is between 50% by mass and 70% by mass.

3. A method for producing a coating film as described in claim 1 or claim 2, wherein in step B, both sides of the laminate are heated.

4. The method for producing a coating film according to claim 1 or 2, wherein the curl control is a non-contact curl control.

5. A method for producing a coating film as described in claim 4, wherein the non-contact curl control is performed by blowing gas onto both sides of the laminate and continuously transporting the laminate while curving it in the thickness direction by the air pressure of the gas.

6. A method for producing a coating film as described in claim 1 or claim 2, in which the coating liquid is applied in multiple stripes onto the support in the longitudinal direction of the support so that uncoated areas are formed between the coating liquid films.

7. The method for producing a coating film according to claim 6, wherein the width of the uncoated portion is 10 mm to 100 mm.

8. A method for producing a coating film according to claim 1 or 2, wherein the coating liquid contains particles.

9. A method for producing a coating film according to claim 1 or claim 2, wherein the support is a metal support.

10. The method for producing a coating film according to claim 1 or 2, wherein the thickness of the support is 10 μm to 30 μm.

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