WO2025047198A1 - Method for producing coating film - Google Patents

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

This disclosure relates to a method for producing a coating film.

2. Description of the Related Art A method for producing a desired coating film on a support by a continuous process using a roll-to-roll system is known.
As a method for producing a coating film, for example, a coating liquid for obtaining a desired coating film is applied onto a support, and the obtained coating liquid film is dried. In this method, a curl control means may be used to suppress curling (also called warping) of the coating film.

For example, WO 2021/210542 describes a method for producing a coating film, which includes a process A in which a long support is continuously transported and an aqueous coating liquid is applied onto the continuously transported support, and a process B in which the coating liquid film obtained in process A is dried on the continuously transported support, and in the constant rate drying stage of process B, curl regulation without contacting the coating liquid film is started for a laminate consisting of the support and the coating liquid film while the solid content concentration of the coating liquid film is between 70% by mass and 95% by mass.

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

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 areas in a method for producing a coating film by applying multiple stripes of a coating liquid onto a continuously transported support (e.g., a method using a continuous process using a roll-to-roll method).

The present disclosure includes the following aspects.
＜1＞
A process A of continuously conveying a long support and applying a coating liquid in multiple stripes onto the continuously conveyed support;
A process B for drying the coating liquid film obtained in the process A;
Including,
In step B, while the solid content concentration of the coating liquid film is 90% by mass or less, curl regulation is started for the laminate consisting of the support and the coating liquid film;
A method for producing a coating film, wherein 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 in step B, curl regulation is started when the solid content concentration 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 in step B, both sides of the laminate are heated.
＜4＞
The method for producing a coating film according to any one of <1> to <3>, wherein the curl control is a non-contact curl control.
＜5＞
The method for producing a coating 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 air pressure of the gas. <6>
The method for producing a coating film according to any one of <1> to <5>, wherein the coating liquid is applied in multiple stripes onto the support so that an uncoated portion is formed in the longitudinal direction of the support.
＜７＞
The method for producing a coating film according to <6>, wherein the width of the uncoated portion is 10 mm to 100 mm.
The method for producing a coating film according to any one of <1> to <7>, wherein the coating liquid contains particles.
＜9＞
The method for producing a coating film according to any one of <1> to <8>, wherein the support is a metal support.
＜10＞
The method for producing a coating film according to any one of <1> to <9>, wherein the support has a thickness of 10 μm to 30 μm.

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.

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 for explaining an example of the curl regulating means in the step B. As shown in FIG. FIG. 3 is a schematic side view for explaining another example of the curl regulating means in the step B. As shown in FIG.

Below, an embodiment of the method for producing a coating film is described. However, this disclosure is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope of the purpose of this disclosure.

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 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 the present disclosure. In addition, 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 illustrated in this disclosure are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present disclosure.
In addition, in each drawing, components having the same function are given the same reference numerals, and duplicated explanations are omitted.
In the present disclosure, the "width direction" refers to a direction perpendicular to the longitudinal direction of a long support, a coating liquid film, and a coating film.
In the present disclosure, a combination of two or more preferred aspects or embodiments is a more preferred aspect or embodiment.

<Coating film manufacturing method>
The method for producing a coating film of the present disclosure includes a step A of continuously transporting a long support and applying a coating liquid in multiple stripes onto the continuously transported support, and a step B of drying the coating liquid film obtained in the step A, wherein in the step B, while the solid content concentration of the coating liquid film is 90 mass % or less, curl regulation is initiated for a 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.

The coating film manufacturing method disclosed herein prevents creases and wrinkles from occurring in uncoated areas. The reason for this is unclear, but is presumed to be as follows.

Conventionally, when a coating liquid is applied in multiple stripes onto a continuously transported support, a phenomenon has been observed in which the coating liquid film shrinks as the coating liquid film dries, causing folds 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, it occurs when there are uncoated areas between multiple coating liquid films formed in a long shape in the longitudinal direction, and in particular when there are uncoated areas between coated areas.
The present inventors have investigated a method for producing a coating film by applying a coating liquid onto a support in multiple stripes, and have found that, in the process of drying the coating liquid film, curl regulation of a laminate consisting of a support and a coating liquid film is started 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, thereby suppressing the occurrence of folds and wrinkles in uncoated parts.

On the other hand, the coating film manufacturing method described in WO 2021/210542 does not mention applying the coating liquid in multiple stripes, and issues due to the presence of uncoated areas are not anticipated.

The following describes each step of the coating film manufacturing method disclosed herein.

First, an example of a method for producing a coating film will be described with reference to FIG.
As shown in Fig. 1, when the leading end of a wound long support 10 is fed and continuous transport is started, an aqueous coating liquid is applied by a coating means 20 (step A). By step A, a coating liquid film (not shown) made of the aqueous coating liquid is formed on the long support.
Next, the laminate 12 of the coating liquid film and the support 10 formed in step A is continuously transported through the drying means 30, whereby the coating liquid film is dried on the support 10 (step B). By step B, the coating liquid film on the long support is dried, and a coating film (not shown) is formed.

[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.

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

Examples of the support having high thermal conductivity include a support having a thermal conductivity of 200 W/(m·K) or more. In the case where the support used in this step is, for example, a multi-layered support including a metal foil and a resin film, if the support as a whole has a thermal conductivity of 200 W/(m·K) or more, the support has 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).

Examples of the support exhibiting the above-mentioned thermal conductivity include metal supports. More specifically, examples of the support exhibiting the above-mentioned thermal conductivity include metal supports made of copper, aluminum, silver, gold, and alloys thereof.
In addition, the metal support may be a support 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 and past usage records.

The thermal conductivity of the support is measured using a laser flash method.
Specifically, for example, the measurement is performed by the following method.
First, the support is cut into three pieces with a diameter of 5 mm to 10 mm at three locations along the width direction of the support to obtain three measurement samples. The thermal conductivity of the three measurement samples obtained is measured using a thermal property measuring 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 average value of the measured values obtained at the three locations is taken as the thermal conductivity of the support.

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 from 3 μm to 50 μm, and more preferably from 10 μm to 30 μm.
The width and length of the support may be appropriately determined from the viewpoint of application to a roll-to-roll system and the width and length of the intended coating film.

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

- Coating fluid -
The coating liquid used in this step is not particularly limited as long as it is a liquid containing a solvent (or a dispersion medium) and a solid content.
The solid content of the coating solution includes components for obtaining the desired coating film, as well as components for improving coating suitability.
The solid content refers to components excluding the solvent (or dispersion medium).

The solvent may be water, an organic solvent, or a mixture of water and an organic solvent.

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 therein 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 the total solvent (or total dispersion medium) being 90% by mass or more, preferably the proportion of water in the total solvent (or total dispersion medium) being 95% by mass or more, and particularly preferably the total solvent (or total dispersion medium) being water.

Examples of water contained in the aqueous coating liquid include natural water, purified water, distilled water, ion-exchanged water, pure water, ultrapure water (e.g., Milli-Q water), etc. Milli-Q water is ultrapure water obtained by a Milli-Q water production device manufactured by Merck Millipore Co., Ltd.

The water content in the aqueous coating liquid is not particularly limited, and is, for example, preferably 40% by mass or more, and more preferably 50% by mass or more, based on the total mass of the aqueous coating liquid.
The upper limit of the water content may be less than 100% by mass, but from the viewpoint of coatability, it is, for example, 80% by mass relative to the total mass of the water-based coating liquid.

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 folding and wrinkling in the uncoated parts. However, by applying the coating film manufacturing method according to the present disclosure, folding and wrinkling in the uncoated parts can be suppressed even when a coating liquid containing particles is used.

There are no particular limitations on the particles as long as they are granular, and they may be inorganic particles, organic particles, or composite particles of inorganic and organic substances.

As the inorganic particles, known inorganic particles that can be applied to the desired coating film can be used.
Examples of inorganic particles include particles of metals (alkali metals, alkaline earth metals, transition metals, etc., and alloys of these metals), particles of semi-metals (silicon, etc.), particles of metal or semi-metal compounds (oxides, hydroxides, nitrides, etc.), and particles of pigments including carbon black, etc.
Other examples of inorganic particles include particles of minerals such as mica, inorganic pigment particles, and polycrystalline diamond.

As the organic particles, known organic particles that can be applied to the desired coating film can be used.
The organic particles are not particularly limited as long as they are particles of solid organic matter, including resin particles and organic pigment particles.

Examples of composite particles of inorganic and organic substances include composite particles in which inorganic particles are dispersed in a matrix of organic substances, composite particles in which organic particles are coated with inorganic substances, and composite particles in which inorganic particles are coated with organic substances.

The particles may be surface-treated for the purpose of imparting dispersibility, etc.
The composite particles may be formed by subjecting the particles to a surface treatment.

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 according to the desired coating film or the conditions suitable for producing the coating film.

The amount of particles contained in the coating liquid is not particularly limited, and may be determined as appropriate depending on the desired coating film, the conditions suitable for producing the coating film, or the purpose of adding the particles.

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

The solids concentration of the coating liquid used in this process is not particularly limited, but is preferably less than 70% by mass, and more preferably 30% to 60% by mass.

- Coating liquid film thickness -
The thickness of the coating liquid film formed in this step is not particularly limited, and may be appropriately determined 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.

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 type thickness measuring device, for example, an infrared spectroscopic interference film thickness meter SI-T80 manufactured by Keyence Corporation. Specifically, the three locations along the width direction of the coating liquid film are 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 value of the measurements obtained at the three locations is calculated and this is regarded as the thickness of the coating liquid film.

-Multiple strip coating-
In this process, the coating liquid is applied in multiple stripes on the support. Multiple stripe coating means that the coating liquid is applied in multiple stripes (stripes). By multiple stripe coating, there are areas on the support where the coating liquid is not applied (uncoated areas) between the areas where the coating liquid is applied (coated areas).

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

The number of threads when applying the coating liquid should be 2 or more, preferably 3 to 5.

The width of the uncoated portion is preferably 10 mm to 100 mm.
When the width of the uncoated portion between the coated portions is 10 mm or more, wrinkles are less likely to occur, whereas 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.

From the perspective of ease of manufacturing the battery cell, it is preferable that the width of the coated portion is between 100 mm and 500 mm.

The width of the uncoated and coated areas is measured as follows.
The width is measured from the upper surface of the coating liquid film using a FALCIO-APEX776 manufactured by Mitutoyo Corporation.

- Coating -
In this step, the coating liquid is applied by a known coating means.
Specific examples of the coating means (e.g., coating means 20 in FIG. 1) include coating devices that utilize 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, a wire bar method, etc.

[Step B]
In step B, the coating liquid film obtained in step A is dried on the support which is being continuously transported.
Then, in step B, while the solid content concentration of the coating liquid film is 90 mass % or less, curl regulation is started 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.

- Curl regulation -
In this step, curl regulation 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% by mass or less.

Here, the solid content concentration of the coating liquid film can be determined by measuring the non-contact thickness from the time when the coating liquid is applied onto the support until the coating liquid becomes a dry film, using an infrared spectroscopic interference film thickness meter SI-T80 manufactured by Keyence Corporation.
Specifically, first, the non-contact thickness is measured from the time when the coating liquid is applied onto the support until the coating liquid becomes a dry film.
Next, the thickness of the film after drying (dry film) is measured with 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 thickness of the dry film and the thickness of the solvent (or dispersion medium) are multiplied by their respective densities (density of the dry film and density of the solvent) to convert them into dry film mass and solvent mass per unit area of the coating liquid film at the measurement point, thereby determining the solid concentration value.

When the solids concentration of the coating liquid film is 90% by mass or less, the components contained in the coating liquid film are fluid and the residual stress is low. By starting curl control when the residual stress is low and maintaining the temperature of the laminate at 40°C to 100°C during curl control, it is possible to prevent folds and wrinkles from occurring in the uncoated parts.

From the viewpoint of further suppressing the occurrence of folds and wrinkles in uncoated parts, it is preferable that the solids concentration of the coating liquid film when curl regulation starts is 70 mass % or less. Also, from the viewpoint of improving drying efficiency, it is preferable that the solids concentration of the coating liquid film when curl regulation starts is 50 mass % or more.

The curl control used in this process is not particularly limited as long as it is a means that can prevent the widthwise ends of the laminate of the coating liquid film and the support from curling (i.e., warping) toward the coating liquid film.

Curl control may be achieved 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.

The method for regulating curl due to contact is not particularly limited as long as it is a means that can bring a regulating member into contact with the coating liquid film and regulate the widthwise end of the laminate of the coating liquid film and the support from curling (i.e., warping) toward the coating liquid film.
The curl control due to contact is preferably carried out, for example, by holding the support on a roller or by holding the edges of the support with clips.

In order to further prevent the occurrence of folds and wrinkles in uncoated areas, it is preferable that the curl control be non-contact curl control.

The non-contact curl control is not particularly limited as long as it is a means that can control the widthwise end portion of the laminate of the coating liquid film and the support from curling (i.e., warping) toward the coating liquid film 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 for blowing gas onto one or both sides of the laminate and continuously transporting the laminate while curving it in the thickness direction by the gas pressure (hereinafter also referred to as a curl control means).
The curl regulating means expels gas onto the laminate to promote drying (i.e., an increase in the solid content concentration), and therefore also functions as a part of the drying means.

Curl Restricting Means The curl restricting means will be described with reference to Figures 2 and 3. Figures 2 and 3 are schematic side views for explaining the curl restricting means in step B.
2 and 3, reference numeral 32 denotes a pre-curl regulation area, and 34 denotes a curl regulation area.
In the drying means 30A shown in FIG. 2, a curl control area 34 uses a curl control means that blows gas onto one side of the laminate 12 (i.e., the side on which the coating liquid film is formed) and continuously transports the laminate while curving it in the thickness direction by the air pressure of the gas.
In the drying means 30B shown in FIG. 3, a curl control area 34 employs a curl control means that blows 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 transports the laminate while curving it in the thickness direction by the air pressure of the gas.
According to such curl regulating means, the laminate 12 can be conveyed while undulating in a wave-like manner, as shown in the schematic side views of Figures 2 and 3. By conveying the laminate 12 while undulating in this manner, curl regulation is effectively exerted, 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 control means, the air pressure, the temperature, the humidity, and the like.

From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated portions, the non-contact curl regulation is preferably the curl regulation means shown in FIG.
That is, non-contact curl regulation is preferably 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.

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 a drying means 30A, whereby the coating liquid film is dried.
In FIG. 2 , in pre-curl control region 32, the solids concentration of the coating liquid film in laminate 12 is increased, and in curl control region 34, curl control is initiated while the solids concentration of the coating liquid film on support 10 is 90 mass % or less.

In the pre-curl control region 32 in FIG. 2, a drying means (e.g., a hot air blower) as described below is used to increase the solids concentration of the coating liquid film in the laminate 12.

In the curl control area 34 in Figure 2, multiple transport rolls 36 are arranged side by side on the same plane on the support side, and multiple gas ejection sections 38 are arranged side by side on the same plane between the installation positions of the transport rolls 36 on the coating liquid film side.
Gas (for example, air) is blown out from the blowing section 38 toward the laminate 12 and the transport roll 36 rotates, so that the laminate 12 is transported while being curved in its thickness direction by the wind pressure of the gas.

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 a drying means 30B, whereby the coating liquid film is dried.
In FIG. 3 , in pre-curl control region 32, the solids concentration of the coating liquid film in laminate 12 is increased, and in curl control region 34, curl control is initiated while the solids concentration of the coating liquid film on support 10 is 90 mass % or less.

In the pre-curl control region 32 in FIG. 3, a drying means (e.g., a hot air blower) as described below is used to increase the solids concentration of the coating liquid film in the laminate 12.

In the curl control area 34 in Figure 3, multiple ejection sections 38a that eject gas on the support side are arranged side by side on the same plane, and multiple ejection sections 38b that eject gas are arranged side by side on the same plane on the coating liquid film side between the installation positions of the ejection sections 38a.
Gas (e.g., air) is sprayed from spray portion 38a toward stack 12, and gas (e.g., air) is sprayed from spray portion 38b toward stack 12, so that stack 12 is curved in its thickness direction by the wind pressure of the gas while being transported.

The curl control region 34 in FIG. 2 and FIG. 3 may be provided at a position where curl control starts while the solid content of the coating liquid film of the transported laminate 12 is 90% by mass or less.
The position of the curl control region 34 can be determined in advance based on the results of a study of the transition of the solids concentration of the coating liquid film.
In addition, by determining the installation position of the curl control area 34 and appropriately adjusting the conveying speed of the laminate 12 and the drying conditions of the pre-curl control area 32, etc., the drying state of the coating liquid film can be controlled so that the solid content concentration of the coating liquid film is in the range of 90 mass% or less when it reaches the curl control area 34.
Furthermore, the end point of the curl control region 34 is preferably, for example, at the exit of the drying means 30A or 30B.

In the curl control region 34 in FIG. 2 and FIG. 3, the gas ejected toward the laminate 12 may be, for example, air.
The temperature of the gas to be ejected is, for example, preferably 60°C to 140°C, and more preferably 90°C to 130°C.
Furthermore, the wind speed of the gas to be ejected is preferably, for example, 1.5 m/sec to 50 m/sec.
Furthermore, the amount of deformation of the laminate 12 in the curl control region 34 may be adjusted.
2 and 3, when the laminate 12 is viewed from the side, the deformation amount of the laminate 12 includes a distance p between adjacent peaks in the wavy laminate 12 and a height difference h between peaks and valleys in the laminate 12. The distance p is equivalent 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, since the smaller the value of distance p/height difference h, the stronger the curl regulating power, it is preferable that the value is 10 or less, and more preferably 5 or less. Since a smaller value of distance p/height difference h increases the number of members or increases the size of the curl regulating region 34, it is preferable that the lower limit value of distance p/height difference h is optimally designed taking into account the equipment installation space, suction capacity, cost, etc. An example of the lower limit value of distance p/height difference h is 2.

- Drying -
In this step, a known drying means is used to dry the laminate.
Specific examples of the drying means (for example, part of the drying means 30 in FIG. 1, drying in the pre-curl control area 32 in FIGS. 2 and 3) include an oven, a hot air blower, an infrared (IR) heater, and the like.

From the viewpoint of further suppressing the occurrence of folds and wrinkles in the uncoated parts, 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, in order to dry the coating liquid applied to the support, only the side on which the coating liquid is applied is heated. 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.

- Temperature of laminate -
In this step, 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.

During curl control, the temperature of the laminate is kept between 40°C and 100°C, causing the support to stretch. After drying is complete, the laminate returns to room temperature and the support shrinks, preventing folds and wrinkles from occurring in uncoated areas.

In order to further prevent the occurrence of folds and wrinkles in uncoated areas, it is preferable that the temperature of the laminate be 60°C to 80°C during curl control.

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

The thickness of the coating film obtained through step B is not particularly limited, and may be any thickness appropriate for 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.
There is no particular upper limit to the thickness of the coating film, and it may be determined depending on the application, but it 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.

[Other steps]
At least one of before step A and after step B may include other steps, if necessary.
The other steps are not particularly limited, and examples thereof 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.

The coating film manufacturing method disclosed herein is a method for manufacturing a coating film on a continuously transported support, and is therefore suitable for manufacturing coating films for applications requiring high productivity.

The present invention will be described 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.
In addition, all "parts" are based on mass.

<Preparation of support>
Aluminum foil: Aluminum foil with a width of 1000 mm, a thickness of 12 μm, and a length of 1000 m (product name "1N30", manufactured by UACJ Foil Co., Ltd.)
Copper foil: Copper foil with a width of 1000 mm, a thickness of 10 μm, and a length of 1000 m (product name "NC-WS", manufactured by Furukawa Electric Co., Ltd.)

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

Polyvinyl alcohol: 58 parts (CKS-50: saponification degree 99 mol%, polymerization degree 300, Nippon Synthetic Chemical Industry Co., Ltd.)
Cellogen PR (Dai-ichi 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

(Water dispersion of Art Pearl J-7P)
3 parts of Emalex 710 (Nihon Emulsion Co., Ltd., nonionic surfactant) and 3 parts of sodium carboxymethylcellulose (Dai-ichi Kogyo Seiyaku Co., Ltd.) were added and dissolved in 74 parts of pure water. 20 parts of Art Pearl (registered trademark) J-7P (Negami Chemical Industries Co., Ltd., silica composite cross-linked acrylic resin fine particles) were added to the obtained aqueous solution, and the mixture was dispersed for 15 minutes at 10,000 rpm (revolutions per minute; the same applies below) using an Ace Homogenizer (Nihon Seiki Seisakusho Co., Ltd.) to obtain an aqueous dispersion of Art Pearl J-7P (particle concentration: 20% by mass).
The silica composite crosslinked acrylic resin fine particles in the resulting aqueous dispersion had a true specific gravity of 1.20 and an average particle size of 6.5 μm.

[Preparation of Solvent-Based Coating Solution B]
95 parts by mass of _{LiNi0.5Co0.2Mn0.3O2} ( _{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, to obtain a solvent-based coating solution B having a solid content concentration of 65% by mass.

[Example 1]
Using an apparatus configured as shown in FIG. 1, the water-based coating liquid A was applied onto a support to form a coating liquid film, and the formed coating liquid film was dried to obtain a coating film.
Specifically, the aqueous coating solution A was applied in two stripes onto a continuously transported support such that the width of each coated portion was 450 mm, the width of the uncoated portion between the edge of the support and the coated portion was 30 mm, and the width of the uncoated portion between adjacent coated portions was 40 mm (Step A). As a result, an uncoated portion was formed on the support in the longitudinal direction of the support.
Next, while transporting the laminate 12 of the coating liquid film and the support obtained in step A through the drying means 30B shown in FIG. 3, the coating liquid film was dried using the curl control method (non-contact) described in Table 1 (step B).
3, the gas temperature and air velocity were adjusted so that the solids concentration of the coating liquid film when curl regulation started was the value shown in Table 1. The solids concentration of the coating liquid film was measured using an infrared spectroscopic interference film thickness meter SI-T80 manufactured by Keyence Corporation.
3, gas was blown onto both sides of the laminate 12, and the laminate was continuously conveyed while being curved in the thickness direction by the air pressure of the gas. The conditions for curl regulation in the curl regulation area 34 were as follows.
Gas type: air Gas temperature: 120°C
Wind pressure of gas ejected onto the coating liquid film surface: 1.3 kPa
Volume of gas sprayed onto the coating liquid film surface: 5 ^m3 /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

The solid content concentration of the coating liquid film when curl regulation was started was as shown in Table 1, and the solid content concentration of the coating liquid film when curl regulation was completed was 99% by mass.
The transport speed of the support in steps A and B was 3.0 m/min.
Through steps A and B as described above, a coating film was formed.

[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 regulation, the film surface temperature, and the curl regulation method were appropriately changed as shown in Table 1.

In addition, the contact curl control used in Example 9 was performed by holding the support on a roller.

[Evaluation of folds and wrinkles in uncoated parts]
For the coating film obtained in each example, the state of the uncoated areas between the coated areas was visually observed. The evaluation criteria were as follows:
A: No creases or folds.
B: There are wrinkles but no folds.
C: There are folds and wrinkles.

The evaluation results are shown in Table 1.

As shown in Table 1, the manufacturing method of Examples 1 to 9 includes a process A in which a long support is continuously transported and a coating liquid is applied in multiple stripes onto the continuously transported support, and a process B in which the coating liquid film obtained in process A is dried. In process B, curl control is started on 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, and the temperature of the laminate is maintained at 40°C to 100°C during curl control, thereby suppressing the occurrence of folds and wrinkles in the uncoated parts.

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 areas.

In Example 1, the curl control was non-contact, and it was found that the occurrence of folds and wrinkles in the uncoated parts was suppressed compared to Example 9.

(Explanation of symbols)
REFERENCE SIGNS LIST 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 peaks and valleys (height difference of undulation)
p Distance between adjacent peaks (spacing between swells)

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 (10)

A process A of continuously transporting a long support and applying a coating liquid in multiple stripes onto the continuously transported support;
A process B for drying the coating liquid film obtained in the process A;
Including,
In the step B, while the solid content concentration of the coating liquid film is 90% by mass or less, curl regulation is started for the laminate including the support and the coating liquid film,
The method for producing a coating film, wherein the temperature of the laminate is maintained at 40°C to 100°C during the curl regulation. The method for producing a coating film according to claim 1, wherein in step B, curl regulation is started while the solid content of the coating liquid film is between 50% by mass and 70% by mass. The method for producing a coating film according to claim 1 or 2, wherein both sides of the laminate are heated in step B. The method for producing a coating film according to claim 1 or claim 2, wherein the curl control is non-contact curl control. The method for producing a coating film according to claim 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 wind pressure of the gas. The method for producing a coating film according to 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. The method for producing a coating film according to claim 6, wherein the width of the uncoated portion is 10 mm to 100 mm. The method for producing a coating film according to claim 1 or 2, wherein the coating liquid is a coating liquid containing particles. The method for producing a coating film according to claim 1 or claim 2, wherein the support is a metal support. 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.