JP7812804B2 - Manufacturing method of laminate - Google Patents

Description

This disclosure relates to a method for manufacturing a laminate.

A method is known in which a target film is formed on each of both surfaces (i.e., a first surface and a second surface opposite to the first surface) of a strip-shaped substrate in a continuous roll-to-roll process, thereby producing a laminate in which the film, substrate, and film are arranged in this order.
The laminate can be produced, for example, by applying a coating liquid for obtaining a desired film onto a substrate and then drying the resulting coating liquid film.

As an example of a method for manufacturing a laminate, Japanese Patent Application Laid-Open No. 2004-344693 discloses a sequential coating method in which a coating liquid is applied to the surface of a moving, strip-shaped plastic support, and the applied coating film is dried at a temperature approximately equal to or higher than the glass transition temperature of the support, a coating and drying process being performed on both sides of the support.

In addition, Japanese Patent Application Laid-Open No. 2-119968 discloses a method in which a coating liquid is applied to a first surface of a substrate, the coating liquid applied to the first surface is cooled to promote gelation, and then the first surface (i.e., the coating surface) is continuously moved while being supported and floated by a gas ejection device, and the coating liquid is applied to a second surface (the surface opposite the first surface).

For example, as described in Japanese Patent Laid-Open No. 2004-344693, there is a method for manufacturing a laminate in which a coating liquid is applied to a first surface of a substrate that is being continuously conveyed, the formed coating liquid film is dried, and then application of the coating liquid to a second surface of the substrate opposite the first surface is started, and the formed coating liquid film is dried. In this case, curling may occur at the width direction edge of the substrate during the drying stage of the coating liquid film formed on the first surface.
Furthermore, as described in Japanese Patent Laid-Open No. 2-119968, even in the case of a laminate manufacturing method in which a coating liquid is applied to a first surface of a substrate, the formed coating liquid film is allowed to gel, and then application of the coating liquid to a second surface of the substrate opposite the first surface is started, curling may occur at the widthwise ends of the substrate during the gelation process inside the coating liquid film formed on the first surface.
The curling caused as described above can impair the flatness of the substrate, which can cause problems when the substrate is transported or when a coating liquid is applied to the second surface.

Therefore, the problem that one embodiment of the present disclosure aims to solve is to provide a method for manufacturing a laminate in which a film is formed on both sides of a continuously transported substrate to manufacture a laminate, which can reduce curling at the widthwise ends of the substrate that occurs during the process of forming a film on both sides of the substrate.

Means for solving the above problems include the following embodiments.
<1>
a step of starting application of a first coating liquid to a first surface of a substrate being continuously transported, and starting application of a second coating liquid to a second surface of the substrate opposite to the first surface before displacement occurs at an end portion of the substrate in the width direction on which a first coating liquid film formed by the first coating liquid is formed;
A method for manufacturing a laminate, wherein the amount of positional misalignment between the width of a first coating liquid film on the first surface and the width of a second coating liquid film formed by the second coating liquid on the second surface is within 1 mm.

<2>
The method for producing a laminate according to <1>, wherein the thickness of the substrate is 5 μm or more and 80 μm or less.
<3>
The method for producing a laminate according to <1> or <2>, wherein the first coating liquid film and the second coating liquid film have a thickness of 40 μm or more.
＜4＞
<3> The method for producing a laminate according to any one of <1> to <3>, wherein coating of the second coating liquid is started on a second surface opposite to the first surface of the substrate before the solid content concentration of the first coating liquid film reaches 70 mass %.
<5>
<4> The method for producing a laminate according to any one of <1> to <4>, wherein coating of the second coating liquid is started on a second surface opposite to the first surface of the substrate while the solid content concentration of the first coating liquid film is 55% by mass or more and 70% by mass or less.
<6>
<5> The method for producing a laminate according to any one of <1> to <5>, wherein the second coating liquid is applied using an extrusion die coater.

According to one embodiment of the present disclosure, in a method for forming a film on both sides of a continuously transported substrate to produce a laminate, a method for producing a laminate is provided that can reduce curling at the widthwise ends of the substrate that occurs during the process of forming a film on both sides of the substrate.

1A to 1C are schematic diagrams illustrating steps of a method for producing a laminate according to an embodiment. 10A and 10B are cross-sectional schematic views for explaining displacement at the width direction end portions of the substrate.

The following describes an embodiment of a method for manufacturing a laminate. However, the present invention is not limited to the following embodiment, and can be implemented with appropriate modifications within the scope of the present invention.

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 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 functions are given the same reference numerals, and duplicated explanations will be omitted.
In the present disclosure, a "substrate" refers to a substrate that is continuously transported and has a belt-like shape.
In the present disclosure, the "width direction" refers to a direction perpendicular to the longitudinal direction (i.e., the transport direction) of any of the continuously transported substrate (i.e., the belt-shaped substrate), the coating liquid film, and the film.
In the present disclosure, the "first surface" of a substrate refers to one surface of a strip-shaped substrate, and unless otherwise specified, refers to the surface on which a coating liquid is applied first. Furthermore, the "second surface" of a substrate refers to the other surface of the strip-shaped substrate, i.e., the surface opposite to the first surface, and unless otherwise specified, refers to the surface on which a coating liquid is applied second.
In the present disclosure, a combination of two or more preferred aspects or embodiments is a more preferred aspect or embodiment.

<<Laminate manufacturing method>>
As described above, in a laminate manufacturing method in which a coating liquid is applied to a first surface of a substrate being continuously transported, the formed coating liquid film is dried (specifically, after the constant-rate drying and decreasing-rate drying of the coating liquid film are completed), and then application of the coating liquid to a second surface of the substrate opposite the first surface is initiated and the formed coating liquid film is dried, curling may occur at the widthwise edge of the substrate during the drying stage of the coating liquid film formed on the first surface. If curling occurs at the widthwise edge of the substrate at this stage, the substrate may wrinkle or bend, causing a loss of flatness of the substrate or being cut, which may cause problems in transporting the substrate. Furthermore, if curling occurs at the widthwise edge of the substrate at the above stage, it becomes difficult to apply the coating liquid to a uniform thickness in the width direction when applying the coating liquid to the second surface.
Therefore, the inventors discovered that by controlling the timing at which application of the coating liquid to the second surface of a substrate begins after application of the coating liquid to the first surface of the substrate is started, it is possible to reduce curl that occurs during the drying stage of the coating liquid film formed on the first surface, and thus developed a method for manufacturing a laminate according to this embodiment.

The method for manufacturing a laminate according to this embodiment includes a step in which application of a first coating liquid to a first surface of a substrate being continuously transported is initiated, and before displacement occurs at the widthwise end of the substrate on which a first coating liquid film formed by the first coating liquid is formed, application of a second coating liquid to a second surface of the substrate opposite the first surface, and the amount of positional misalignment between the width of the first coating liquid film on the first surface and the width of the second coating liquid film formed by the second coating liquid on the second surface is within 1 mm.
According to the method for manufacturing a laminate of this embodiment, a laminate is obtained in which a film formed on the first surface side of a substrate, the substrate, and a film formed on the second surface side of the substrate are arranged in this order.

According to the method for manufacturing a laminate according to this embodiment, it is believed that curling at the width direction edges of the substrate that occurs in the process of forming films on both sides of the substrate can be reduced by the mechanism described below.
That is, in the laminate manufacturing method according to this embodiment, application of the second coating liquid to the second surface of the substrate is initiated before displacement occurs at the widthwise end of the substrate on which the first coating liquid film is formed by the first coating liquid. This allows the substrate to be transported stably, and the second coating liquid can be applied to the second surface without damaging the flatness of the substrate. As a result, in the laminate manufacturing method according to this embodiment, when applying the second coating liquid to the second surface, it is possible to apply the coating liquid to a set area of the second surface with a uniform thickness in the width direction. In this way, the application accuracy of the second coating liquid to the second surface is improved, making it possible to reduce the positional misalignment between the width of the coating liquid film formed on the first surface and the width of the coating liquid film formed on the second surface (i.e., within 1 mm).
By keeping the misalignment within 1 mm, the force of curling toward the first surface due to shrinkage caused by drying of the first coating liquid film and the force of curling toward the second surface due to shrinkage caused by drying of the second coating liquid film can be counterbalanced with the substrate as the center, As a result, curling is less likely to occur at the width direction ends of the substrate during the process of applying coating liquids to both surfaces of the substrate and drying them to form films.

On the other hand, in the method described in JP 2004-344693 A, the coating of the second surface of the substrate is started after the coating liquid film formed on the first surface of the substrate has dried, and therefore, it is thought that curling has occurred at the widthwise end of the substrate at the stage when coating of the second surface is started.
Furthermore, in the method described in JP-A-2-119968, coating of the second surface of the substrate is initiated after the coating liquid film formed on the first surface of the substrate has gelled. This method has problems such as the tendency for curling to occur due to gelling within the coating liquid film during the gelling process, and the length of the gelling process being so long that there is a large amount of misalignment between the width of the first coating liquid film on the first surface and the width of the second coating liquid film on the second surface.

Below, each step of the method for manufacturing the laminate of this embodiment is described.

First, an example of a method for producing a laminate will be described with reference to Fig. 1. Here, Fig. 1 is a schematic diagram of an apparatus to which the method for producing a laminate of one embodiment is applied, and is used to explain each step.
As shown in FIG. 1, the conveyance of a strip-shaped substrate 10 wound into a roll is started by feeding out its leading end in the direction of the arrow, and the substrate is conveyed continuously until it is wound into a roll.
1 , in a region where the substrate 10 is wound around the backup roll 20, the coating means 30 starts coating the first surface of the substrate 10 with the first coating liquid (hereinafter also referred to as step A). By step A, a first coating liquid film (not shown) made of the first coating liquid is formed on the first surface of the belt-shaped substrate 10.
Next, the belt-shaped substrate 10 having a first coating liquid film (not shown) formed on its first surface is transported along the outer peripheral surface of the roll-shaped floating transport means 40 in a state of non-contact with the surface on the first surface side (i.e., a state of non-contact with the first coating liquid film). Then, in the region where the belt-shaped substrate 10 is transported by the floating transport means 40, the coating means 50 begins applying the second coating liquid to the second surface of the substrate 10 (hereinafter also referred to as step B). By step B, a second coating liquid film (not shown) made of the second coating liquid is formed on the second surface of the belt-shaped substrate 10.
Subsequently, after the second coating liquid film is formed on the second surface, the belt-shaped substrate 10 passes through drying means 60 (hereinafter also referred to as step C). In step C, the first coating liquid film on the first surface of the belt-shaped substrate 10 and the second coating liquid film on the second surface thereof are dried, and films are formed on both surfaces of the substrate 10, respectively.
Subsequently, the substrate 10 after passing through the drying means 60 is wound into a roll after undergoing any step not shown, as required.

[Step A]
In step A, application of the first coating liquid to a first surface of a substrate that is being continuously transported is started.

The substrate used in this step is not particularly limited as long as it can be continuously transported, and a substrate may be selected depending on the application of the laminate to be formed.
The substrate may be made of resin or metal, and may have a multi-layer structure including a resin layer and a metal layer.

Furthermore, the substrate may be one having a thermal conductivity of 200 W/m K or more. For example, in the case of a substrate having a multilayer structure including a metal layer and a resin layer, the substrate as a whole may have a thermal conductivity of 200 W/m K or more.
The upper limit of the thermal conductivity of the substrate is not particularly limited, and is, for example, 500 W/m·K.

Specific examples of substrates exhibiting the above thermal conductivity include metal substrates made of copper, aluminum, silver, gold, and alloys thereof.
Among these, copper substrates and aluminum substrates are preferably used from the viewpoint of shape stability as a substrate, usage track record, and the like.

The thermal conductivity of the substrate is measured as follows.
First, the substrate is cut to a size suitable for the apparatus described below to obtain a measurement sample. The thermal diffusivity of the obtained measurement sample in the thickness direction is measured using a laser flash method. Next, the specific gravity of the measurement sample is measured using a balance equipped with a specific gravity measurement kit. Furthermore, using a differential scanning calorimeter (DSC), the specific heat of the measurement sample at 25°C is measured under a temperature increase condition of 10°C/min. The thermal conductivity of the measurement sample (i.e., the substrate) is calculated by multiplying the obtained thermal diffusivity by the specific gravity and specific heat.
Here, for example, the "LFA467" manufactured by NETZSCH is used to measure the thermal diffusivity. Furthermore, for example, the "XS204" balance manufactured by Mettler-Toledo K.K. using a solid specific gravity measurement kit is used to measure the specific gravity. Furthermore, for example, the "DSC320/6200" manufactured by Seiko Instruments Inc. is used to measure the specific heat.

The thickness of the substrate may be appropriately set from the viewpoint of application to the roll-to-roll method.
The thickness of the substrate is, for example, preferably 5 μm to 100 μm, more preferably 5 μm to 80 μm, and even more preferably 10 μm to 30 μm.
Even in a case where the thickness of the substrate is thin as described above and displacement is likely to occur at the widthwise ends of the substrate when the coating liquid film dries, the method for manufacturing a laminate according to this embodiment can reduce curling.
The width and length of the substrate may be appropriately set in consideration of application to the roll-to-roll method and the width and length of the desired film.

The thickness of the substrate is measured as follows.
That is, using a contact-type thickness measuring device, the thickness of the substrate is measured at three points in the width direction (specifically, at positions 5 mm from both edges in the width direction and at the center in the width direction) at three points spaced 500 mm apart in the longitudinal direction.
The arithmetic mean value of the nine measured values is calculated and used as the thickness of the substrate.
As a contact type thickness measuring instrument, for example, S-2270 manufactured by Fuji Work Co., Ltd. is used.

-First coating liquid-
The first coating liquid used in this step is not particularly limited as long as it is a liquid that contains a solvent (or a dispersion medium) and has fluidity, and is capable of forming the desired film.
The first coating liquid may use an organic solvent or water as a solvent (or dispersion medium).

The first coating liquid may be, for example, an aqueous coating liquid in which the solvent (or dispersion medium) contained in the coating liquid is substantially water. "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 component in preparing the coating liquid is permitted. Specifically, "the solvent (or dispersion medium) is substantially water" means that the proportion of water in all solvents (or all dispersion media) is 90% by mass or more, preferably the proportion of water in all solvents (or all dispersion media) is 95% by mass or more, and it is particularly preferred that all solvents (or all dispersion media) are water.
The solid content refers to components excluding the solvent (or dispersion medium).

The water-based coating liquid is not particularly limited as long as it is a liquid containing water as a solvent (or dispersion medium) and solids.
The solid content contained in the aqueous coating liquid includes components for obtaining the desired film as well as components for improving coating suitability.

Examples of water contained in aqueous coating solutions 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 Ltd.

The water content in the water-based coating liquid is not particularly limited, and is preferably 40% by mass or more, and more preferably 50% by mass or more, based on the total mass of the water-based 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 coating suitability, it is, for example, 90% by mass relative to the total mass of the water-based coating liquid.

The water-based coating liquid may contain particles as one of the solid components, that is, the water-based coating liquid may be a coating liquid containing particles.
When a water-based coating liquid containing particles is used, the particles also aggregate during the drying stage, which tends to cause displacement of the width direction edge of the substrate. In the method for producing a laminate according to this embodiment, even when a water-based coating liquid containing particles is used as the first coating liquid, curling of the width direction edge of the substrate can be reduced.

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

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

As the organic particles, known organic particles that can be applied to the target 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 pigments.

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

The particles may be surface-treated for the purpose of imparting dispersibility or the like.
The particles may be subjected to a surface treatment to become the above-mentioned composite particles.

There are no particular restrictions on the particle size, shape, specific gravity, or usage form (e.g., whether or not to use in combination), and these may be selected appropriately depending on the desired membrane or the conditions suitable for producing the membrane.

There are no particular restrictions on the particle content in the aqueous coating liquid, and it may be determined appropriately depending on the desired film, the conditions suitable for producing the film, or the purpose of adding the particles.

The solid content contained in the aqueous coating liquid is not particularly limited, and includes various components used to obtain the desired film.
Specific examples of the solid components contained in the aqueous 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.

-Thickness of the first coating liquid film-
There are no particular limitations on the thickness of the first coating liquid film formed in this step, and it may be determined appropriately depending on the desired film.
The thickness of the first coating liquid film is, for example, preferably 40 μm or more, more preferably 40 μm to 200 μm, and even more preferably 40 μm to 100 μm.
The thicker the first coating liquid film, the more likely it is that displacement will occur at the width direction edge of the substrate when the first coating liquid film is dried. In the method for manufacturing a laminate according to this embodiment, curling at the width direction edge of the substrate can be reduced even when the first coating liquid film is thick.

The thickness of the coating liquid film is measured as follows.
That is, the thickness of the first coating liquid film is measured at three locations along the width direction (specifically, at positions 5 mm from both edges in the width direction and at the center in the width direction) using an optical interference thickness measuring device. The arithmetic mean value of the measurements at the three locations is calculated and used as the thickness of the coating liquid film.
As an optical interference type thickness measuring device, for example, Keyence Corporation's infrared spectroscopic interference type film thickness meter SI-T80 is used.

-Width of coating liquid film-
The width of the first coating liquid film (i.e., coating width) in this step is not particularly limited, and may be determined depending on the width of the substrate, the use of the film, and the like.
The width of the first coating liquid film can be selected to be, for example, 100 mm or more, or 1000 mm or more.
The upper limit of the width of the first coating liquid film is the width of the substrate.

-Width of uncoated area-
When the first coating liquid film is formed on the first surface of the substrate, the width of the non-coated area (i.e., the width of the exposed portion of the substrate) is preferably, for example, 2 mm or more, and more preferably 5 mm or more, at both widthwise ends of the substrate, from the viewpoint of easily achieving the effects of the laminate manufacturing method of this embodiment.
The upper limit of the width of the non-coated region on the first surface is preferably 30 mm, for example, although it depends on the width of the substrate.

The width of the coating liquid film is measured as follows.
That is, the width of the coating liquid film is measured at three points with a ruler at intervals of 500 mm in the longitudinal direction when viewed from above from the film surface side of the coating liquid film.
The arithmetic mean value of the measured values at the three points is calculated and is regarded as the width of the coating liquid film.
The width of the coated area is measured as follows.
That is, when viewed from above from the film surface side of the coating liquid film, the shortest distance from the end of the substrate in the width direction to the end of the coating liquid film is measured with a ruler at three points spaced 500 mm apart in the longitudinal direction. This measurement is performed at each end of the substrate in the width direction.
The arithmetic mean value of the measured values at the six points is calculated and is defined as the width of the coated area.

--Application of first coating liquid--
In this step, the first coating liquid is applied by a known coating means.
Specific examples of the coating means (for example, coating means 30 in FIG. 1) include coating devices that use a curtain coating method, a dip 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.
Among these, as the coating means in this step, a coating device using a slot coating method, more specifically an extrusion type die coater, is preferably used from the viewpoint of enabling high-definition coating.

-Backup role-
In this step, when applying the first coating liquid, the substrate can be transported in a tensioned state, and from the viewpoint of improving coating accuracy, it is preferable that the application be performed in an area where the substrate is wound around a backup roll, as shown in FIG. 1 .

The backup roll is a rotatable member. By rotating the backup roll, the substrate can be transported in a tensioned state along the outer surface of the backup roll.

The backup roll may be heated to control the drying process of the coating liquid film and to prevent blushing of the coating film (i.e., whitening of the coating film due to the formation of fine condensation) caused by a decrease in the surface temperature of the coating liquid film.

The surface temperature of the backup roll is preferably controlled by a temperature control means. It is more preferable that the surface temperature of the backup roll is controlled by a temperature control means based on the detected surface temperature.

Temperature control means include, for example, heating means and cooling means. Heating means may use, for example, induction heating, water heating, or oil heating. Cooling means may use, for example, cooling with cooling water.

The diameter of the backup roll is preferably 100 mm to 1,000 mm, more preferably 100 mm to 800 mm, and particularly preferably 200 mm to 700 mm, from the viewpoints of ease of wrapping the substrate, ease of application using the die head, and manufacturing costs of the backup roll.

From the standpoint of productivity and coating performance, it is preferable that the transport speed of the substrate by the backup roll be, for example, 10 m/min to 100 m/min.

The wrap angle of the substrate relative to the backup roll is preferably 60° or greater, and more preferably 90° or greater, from the viewpoint of stabilizing substrate transport during application of the first coating liquid and suppressing uneven thickness of the coating liquid film. The upper limit of the wrap angle can be set to, for example, 180°. The wrap angle refers to the angle formed by the substrate transport direction when the substrate contacts the backup roll and the substrate transport direction when the substrate separates from the backup roll.

[Step B]
In step B, before displacement occurs at the widthwise end of the substrate on which the first coating liquid film is formed by the first coating liquid, application of the second coating liquid is started to a second surface opposite to the first surface of the substrate.

- Displacement of the width direction end of the substrate -
In this step, "displacement occurs at the widthwise end of the substrate on which the first coating liquid film is formed by the first coating liquid" means that the displacement F of the widthwise end of the substrate measured by the method described below exceeds 5 mm.
In other words, in this step, application of the second coating liquid to the second surface opposite the first surface of the substrate begins before the displacement amount F of the widthwise end of the substrate on which the first coating liquid film is formed by the first coating liquid reaches 5 mm.
Hereinafter, the "amount of displacement F of the width direction end of the substrate on which the first coating liquid film of the first coating liquid is formed" will also be simply referred to as the "amount of displacement F."

The measurement of the displacement F at the end of the substrate in the width direction will be described with reference to FIG.
FIG. 2 is a schematic diagram of a cross section of the substrate cut along the width direction.
As shown in FIG. 2, the amount of lift at the end of the substrate in the width direction when the center of the substrate 10 on which the first coating liquid film is formed is used as a reference is measured with a ruler, and this is defined as the displacement F at the end of the substrate in the width direction.
The environmental conditions when measuring the floating amount are the same as those when this step is performed.

When this step is performed using existing equipment, the pre-drying conditions, the coating speed of the first coating liquid (i.e., the transport speed of the substrate), and the solids concentration when preparing (or applying) the first coating liquid may be adjusted as appropriate so that the displacement F of the widthwise end of the substrate on which the first coating liquid film has been formed by the first coating liquid is 5 mm or less at the coating position of the second coating liquid on the second surface.
Here, pre-drying means drying of the first coating liquid film at a stage before the second coating liquid film is formed.

In addition, the timing to start applying the second coating liquid to the second surface of the substrate may be determined based on a position on the transport path at which the displacement F reaches 5 mm during the drying process of the first coating liquid film formed on the first surface, which is determined in advance.
Specifically, using the above method, the displacement F is measured intermittently as the drying of the first coating liquid film formed on the first surface progresses, and a position on the transport path where the displacement F reaches 5 mm during the drying process of the first coating liquid film formed on the first surface (for example, position P in FIG. 1) is identified. Then, application of the second coating liquid to the second surface can be started at the identified position on the transport path or upstream of that position in the transport direction of the substrate. For example, in FIG. 1, the installation position of the coating unit 50 can be set so that application of the second coating liquid to the second surface can be started at the identified position P on the transport path or upstream of position P in the transport direction of the substrate 10.
Alternatively, the application position of the second coating liquid to the second surface (for example, the installation position of coating means 50 in Figure 1) may be fixed, and the application position of the first coating liquid to the first surface (for example, the installation position of coating means 30 in Figure 1) may be changed to move the position on the transport path where the displacement F reaches 5 mm, so that application of the second coating liquid to the second surface may begin at a position on the transport path (for example, position P in Figure 1) or upstream of that position in the transport direction of the substrate.

-Solid content concentration-
The second coating liquid is preferably applied to the second surface of the substrate before the solid content concentration of the first coating liquid film on the first surface of the substrate, which is the back surface, reaches 75% by mass, more preferably 70% by mass, and even more preferably 65% by mass.
When the solid content concentration of the first coating liquid film formed on the first surface of the substrate is 75 mass % or less, the flatness of the substrate is not impaired, the substrate is stably transported, and the second coating liquid can be easily applied to a set region on the second surface with a uniform thickness in the width direction, thereby making it possible to further reduce the amount of positional misalignment between the width of the first coating liquid film formed on the first surface and the second coating liquid film formed on the second surface.

The timing for starting application of the second coating liquid to the second surface of the substrate is preferably when the fluidity of the first coating liquid film formed on the first surface has decreased to a certain extent, for example, from the viewpoint of minimizing the impact on the first coating liquid film during transport by the floating transport means described below.
Therefore, the application of the second coating liquid to the second surface of the substrate is preferably carried out while the solid content concentration of the first coating liquid film on the first surface of the substrate, which is the back surface, is 50% by mass to 75% by mass, more preferably started while it is 55% by mass to 75% by mass, even more preferably started while it is 55% by mass to 70% by mass, and particularly preferably started while it is 55% by mass to 65% by mass.

The solid content concentration of the coating liquid film can be determined by measuring the optical thickness from the time of coating to the time of forming a dry film using an optical interference type thickness measuring device (for example, Keyence Corporation's infrared spectroscopic interference film thickness meter SI-T80).
Specifically, first, the optical thickness is measured from the time of application until the film becomes dry. Next, the thickness of the film after drying (i.e., dry film) is measured using a contact thickness meter. The measured thickness of the dry film is divided by the optical thickness, and the thickness of the wet film (i.e., coated liquid film) is calculated from the optical thickness. Then, the amount of solvent (or dispersion medium) at the measurement point is obtained. The mass of the solvent (or dispersion medium) is calculated from the obtained amount of solvent (or dispersion medium), and the solid concentration value at the measurement point is calculated.

In order to start applying the second coating liquid to the second surface of the substrate before the displacement amount F reaches 5 mm and while the solid content concentration of the first coating liquid film formed on the first surface is within the above-mentioned range, for example, the following may be done.
That is, first, the relationship between the solid content concentration of the first coating liquid film formed on the first surface of the substrate and the displacement amount F is experimentally determined. Then, based on the obtained relationship between the solid content concentration of the first coating liquid film and the displacement amount F, the following (1) to (4) may be appropriately adjusted so that the solid content concentration of the first coating liquid film formed on the first surface falls within the above-mentioned range until the displacement amount F reaches 5 mm at the position in the apparatus where application of the second coating liquid begins (for example, the installation position of the coating means 50 in FIG. 1). From the viewpoint of minimizing constraints on equipment, it is preferable to adjust, for example, at least one of the following (1) and (2), and when there is a high degree of freedom in the formulation of the first coating liquid, it is preferable to adjust the following (3).
(1) Coating speed of the first coating liquid (i.e., conveying speed of the substrate)
(2) Pre-drying and its conditions; (3) Solid content concentration of the first coating liquid when it is prepared (or when it is applied); (4) Distance from the position where application of the first coating liquid to the first surface of the substrate starts (for example, the installation position of the coating unit 30 in FIG. 1) to the position where application of the second coating liquid to the second surface of the substrate starts (for example, the installation position of the coating unit 50 in FIG. 1).

- Second coating liquid -
The second coating liquid used in this step is not particularly limited as long as it is a fluid liquid containing a solvent (or dispersion medium) and capable of forming the desired film, similar to the first coating liquid.
The second coating liquid may be a coating liquid similar to the first coating liquid (for example, an aqueous coating liquid exemplified as the first coating liquid), or may be a coating liquid different from the first coating liquid.

From the viewpoint of efficiently reducing curl at the widthwise ends of the substrate that occurs during the process of forming a film on both sides of the substrate, it is preferable that the second coating liquid be a coating liquid similar to the first coating liquid (for example, an aqueous coating liquid exemplified as the first coating liquid).

-Thickness of the second coating liquid film-
There are no particular limitations on the thickness of the second coating liquid film formed in this step, and it may be determined appropriately depending on the desired film.
The thickness of the second coating liquid film is, for example, preferably 40 μm or more, more preferably 40 μm to 200 μm, and even more preferably 40 μm to 100 μm.
The second coating liquid film has a thickness equal to that of the first coating liquid film, and the curl at the width direction edge of the substrate is more easily reduced. Therefore, it is preferable that the difference in thickness between the first coating liquid film and the second coating liquid film is small, for example, preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 0.

-Width of the coating liquid film and width of the non-coated area-
The width of the second coating liquid film in this step (i.e., coating width) is preferably set to be equal to the width of the first coating liquid film, from the viewpoint of satisfying the range of the positional misalignment amount described below.
Furthermore, it is preferable that the width of the non-coated area when the second coating liquid film is formed on the second surface of the substrate (i.e., the width of the exposed portion of the substrate) be equal to the width of the non-coated area on the first surface side, in order to satisfy the range of positional misalignment amount described below.

--Application of second coating liquid--
In this step, the second coating liquid is applied by a known coating means.
Examples of the coating means (for example, the coating means 50 in FIG. 1) include various coating devices similar to those used to coat the first coating liquid.
Among these, as the coating means in this step, a coating device using a slot coating method, more specifically an extrusion type die coater, is preferably used from the viewpoint of enabling high-definition coating.

- Floating transport means -
In this step, when the second coating liquid is applied to the second surface of the substrate, the substrate is transported while the first coating liquid film formed on the first surface is kept out of contact with the transport means.
As a means for transporting the substrate in a non-contact state, known means can be used. For example, from the viewpoint of minimizing the impact on the coating liquid film, a floating transport means is preferably used, which ejects gas onto the first surface side of the substrate (i.e., the film surface of the first coating liquid film) to float the substrate from the transport means while transporting it.

As shown in Figure 1, an example of the floating transport means is a roll-shaped floating transport means 40 that transports the substrate 10 along the outer peripheral surface of the floating transport means 40 in a non-contact state with the first surface (i.e., in a non-contact state with the first coating liquid film). The floating transport means may be a means that transports the substrate while curving it, as in the case of using a roll-shaped floating transport means 40, or a means that transports the substrate without curving it (e.g., a means that transports the substrate horizontally).

In this step, the application of the second coating liquid is preferably carried out in an area where the substrate 10 is transported along the outer surface of the roll-shaped floating transport means 40, as shown in Figure 1, from the viewpoint that the substrate can be transported in a tensioned state and coating accuracy is improved.

A gas outlet is provided on the outer surface of the roll-shaped floating and conveying means, and by directing the gas (preferably air) ejected from this outlet onto the first surface of the substrate, the substrate can be conveyed along the outer surface of the roll-shaped floating and conveying means 40 while being floated from said outer surface.

For example, a roll-shaped floating transport means having a radius of curvature of 100 mm to 1000 mm is used. It is preferable that the radius of curvature of the roll-shaped floating transport means be 150 mm to 500 mm.

The wrap angle of the substrate relative to the roll-shaped floating conveying means is preferably 60° or more, more preferably 90° or more, and even more preferably 120° or more. The upper limit of the wrap angle can be set to, for example, 180°. The wrap angle is the angle formed by the conveying direction of the substrate at the start point of the bending of the substrate by the floating conveying means and the conveying direction of the substrate at the end point of the bending.

The floating amount of the substrate relative to the floating transport means used in this step is, for example, preferably 500 μm or less, more preferably 300 μm or less, from the viewpoint of stabilizing the transport of the substrate. The lower limit of the floating amount of the substrate may be determined depending on the thickness of the first coating liquid film, and may be, for example, the thickness of the first coating liquid film + 50 μm, and preferably the thickness of the first coating liquid film + 100 μm.
The floating amount of the substrate relative to the floating transport means refers to the shortest distance between the substrate on which the first coating liquid film is not formed and the outer circumferential surface of the floating transport means.
Here, the flying height can be measured by a laser displacement meter.

The roll-shaped floating transport means is preferably, for example, a roll member equipped with a gas ejection mechanism capable of ejecting gas from the ejection ports on the outer peripheral surface, as described above.
As the roll-shaped floating transport means, a device such as a backup roll (backup body) 11 described in JP-A-2001-310148 can also be applied. Note that the various conditions relating to the floating transport of the substrate described in JP-A-2001-310148 can also be applied to the present disclosure.
Instead of a roll-shaped floating conveying means, a floating conveying means having an arc-shaped outer peripheral surface may be used. The floating conveying means having an arc-shaped outer peripheral surface may be any member having an outer peripheral surface with an outlet for ejecting gas that is arc-shaped in side view. Even in the case of a floating conveying means having an arc-shaped outer peripheral surface, the radius of curvature, wrap angle, floating amount, etc., can be selected to be the same as those described above. Examples of floating conveying means having an arc-shaped outer peripheral surface include the non-contact conveying device described in JP 2004-256264 A (see, for example, FIG. 2 ), the web support device described in JP 2020-050455 A (see, for example, FIG. 6 ), and the conveying device described in JP 2020-152570 A (see, for example, FIG. 9 ).

- Positional deviation amount -
In the method for producing a laminate according to this embodiment, the amount of misalignment between the width of the first coating liquid film on the first surface and the width of the second coating liquid film formed by the second coating liquid on the second surface is set to within 1 mm. From the viewpoint of effectively suppressing curling at the width direction ends of the substrate, the amount of misalignment is more preferably within 0.5 mm.
When the misalignment amount is small as described above, the coating liquid film is formed in approximately the same range (i.e., the same region) on both sides of the substrate, which makes it possible to suppress curling of the width direction edges of the substrate that occurs during the process of forming the film on both sides of the substrate.
That is, if the amount of misalignment exceeds 1 mm, it may become impossible to suppress curling at the widthwise ends of the substrate that occurs in the process of forming films on both sides of the substrate.

The amount of misalignment can be determined by the same method as that for measuring the width of the non-coated area described above.
The amount of misalignment can be controlled by adjusting the widthwise positions of the coating unit that coats the first coating liquid on the first surface and the coating unit that coats the second coating liquid on the second surface. The amount of misalignment can also be controlled by adjusting the alignment of the roll member that contacts the substrate between coating the first coating liquid on the first surface and coating the second coating liquid on the second surface, thereby changing the widthwise position of the substrate.

[Step C]
In step C, the substrate on which the first and second coating liquid films are formed is dried. That is, in this step, the first and second coating liquid films are dried.

- Drying -
In this step, a known drying method is used to dry the coating liquid film.
Specific examples of the drying means (for example, the drying means 60 in FIG. 1) include an oven, a hot air blower, an infrared (IR) heater, and the like.

The drying conditions in this step may be determined appropriately depending on the material of the substrate, the type of coating liquid film, etc.

In this way, films are formed on both sides of the substrate, resulting in a laminate in which the film, substrate, and film are arranged in this order.

The thickness of the film obtained through step C is not particularly limited, and may be any thickness depending on the purpose, application, etc.
In the method for manufacturing a laminate according to this embodiment, the thickness of each of the films formed on both sides of the substrate 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 film formed on both sides of the substrate, and it may be determined depending on the application, but it is, for example, 300 μm.
The thickness of the film obtained through step C is measured in the same manner as in measuring the thickness of the coating liquid film.

[Other processes]
Before step A and/or after step C, other steps may be included as necessary.
The other processes are not particularly limited, and examples thereof include a pretreatment process carried out before forming a coating liquid film, and a posttreatment process carried out on the film formed on the first and second surfaces or on the laminate depending on the application of the laminate.
Specific examples of the other steps include a step of surface treating the substrate, a step of curing the formed film, a step of compressing the laminate, and a step of cutting the laminate.

The laminate manufacturing method of this embodiment involves forming a film on both sides of a substrate that is being continuously transported, making it suitable for manufacturing laminates 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.
All "parts" are based on mass.

<Preparation of substrate>
An aluminum substrate 1 (thermal conductivity: 230 W/m·K) having a width of 220 mm, a thickness of 20 μm and a length of 300 m was prepared (abbreviated as AL1).
An aluminum substrate 2 (thermal conductivity: 230 W/m·K) having a width of 220 mm, a thickness of 40 μm and a length of 300 m was prepared (abbreviated as AL2).
A PET (polyethylene terephthalate) substrate 1 (thermal conductivity: 0.23 W/m·K) having a width of 220 mm, a thickness of 75 μm and a length of 300 m was prepared (abbreviated as P1).

<Preparation of water-based coating solution>
[Preparation of Water-Based Coating Liquid A]
The following components were mixed to prepare a water-based coating liquid A.
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 (registered trademark) J-7P prepared by the following method: 913 parts

(Art Pearl J-7P water dispersion)
Three parts of Emalex 710 (a nonionic surfactant manufactured by Nippon Emulsion Co., Ltd.) and three parts of sodium carboxymethylcellulose were dissolved in 74 parts of pure water. 20 parts of Art Pearl J-7P (silica composite cross-linked acrylic resin fine particles manufactured by Negami Chemical Industrial Co., Ltd.) 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 (manufactured by Nippon 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 Water-Based Coating Liquid B]
The following components were mixed and stirred with a dissolver (2000 rpm, 30 minutes) to prepare a water-based coating solution B (dispersion A:dispersion B=25:75). The viscosity of water-based coating solution B was 20 mPa s, and the average particle size was 0.108 μm.
Dispersion A prepared by the following method: 132.1 parts Dispersion B prepared by the following method: 396.2 parts Boric acid (crosslinking agent): 2.94 parts Polyvinyl alcohol (7.3% by weight aqueous solution): 230.7 parts (Kuraray Co., Ltd., PVA 235, saponification degree 88%, polymerization degree 3500)
Diethylene glycol monobutyl ether: 2.7 parts (Butycenol 20-P, KH Neochem Co., Ltd.)
Ion-exchanged water: 93.5 parts Polyoxyethylene lauryl ether (surfactant): 0.49 parts (10% by weight aqueous solution of Emulgen 109P, HLB value 13.6, Kao Corporation)
Ethanol: 41.4 parts

(Preparation of Dispersion A)
The following components were mixed and dispersed ultrasonically, and then the dispersion was heated to 30° C. and maintained for 8 hours to prepare Dispersion A.
Fumed silica fine particles (inorganic fine particles): 299.6 parts (AEROSIL 300SF75, Nippon Aerosil Co., Ltd.)
Ion-exchanged water: 1,400 parts Alphaine 83 (40.0% by mass aqueous solution): 300 parts (dispersant, Taimei Chemical Industry Co., Ltd.)

(Preparation of Dispersion B)
The following components were mixed and dispersed ultrasonically, and then the dispersion was heated to 30° C. and maintained for 8 hours to prepare Dispersion B.
Fumed silica fine particles (inorganic fine particles): 225.2 parts (AEROSIL 300SF75, Nippon Aerosil Co., Ltd.)
Ion-exchanged water: 1,185 parts Cationic polymer A (25% by weight aqueous solution) having the following structure: 90 parts

[Example 1]
In an apparatus configured as shown in Figure 1, application of aqueous coating liquid A to a first side of an aluminum substrate (AL1) being continuously conveyed was started, and then application of aqueous coating liquid A to a second side was started when the displacement F of the aluminum substrate was a value shown in Table 1 below and the solids concentration of the coating liquid film of aqueous coating liquid A formed on the first side was a value shown in Table 1 below, thereby forming coating liquid films of aqueous coating liquid A on both sides of the substrate. Thereafter, the aluminum substrate with coating liquid films of aqueous coating liquid A formed on both sides thereof was passed through drying means 60 adjusted to 60°C, whereby the coating liquid films were dried.
In this manner, films were formed on both sides of the aluminum substrate to obtain a laminate.
Here, the water-based coating liquid A was applied to the first surface using a first coating means (specifically, an extrusion-type die coater) 30 in a region where the aluminum substrate was wrapped around a backup roll 20. The water-based coating liquid A was applied to the second surface using a second coating means (specifically, an extrusion-type die coater) 50 in a region where the aluminum substrate was curved along the outer peripheral surface of a roll-shaped floating transport means 40. The transport speed of the substrate was 20 m/min.
The radius of curvature of the outer peripheral surface of the floating transport means 40 was 150 mm, the wrap angle of the substrate 10 with respect to the floating transport means 40 was 150°, and the floating transport distance of the substrate 10 was 785 mm. The floating amount of the substrate 10 from the outer peripheral surface of the floating transport means 40 was 200 μm.
In this example, the positional deviation between the width of the first coating liquid film on the first surface (i.e., the coating liquid film made of water-based coating liquid A formed on the first surface) and the width of the second coating liquid film made of the second coating liquid on the second surface (i.e., the coating liquid film made of water-based coating liquid A formed on the second surface) was 0.2 mm.

[Examples 2 to 6]
Films were formed on both sides of the aluminum substrate to obtain a laminate in the same manner as in Example 1, except that the timing at which the application of the water-based coating liquid A to the second surface of the aluminum substrate was started was changed.
In Examples 2 to 6, the displacement F of the aluminum substrate when the application of the water-based coating liquid A to the second surface was started, and the solids concentration of the coating liquid film of the water-based coating liquid A formed on the first surface are shown in Table 1 below.
In Examples 2 to 6, the amount of positional misalignment between the width of the first coating liquid film on the first surface (i.e., the coating liquid film of water-based Coating Liquid A formed on the first surface) and the width of the second coating liquid film formed from the second coating liquid on the second surface (i.e., the coating liquid film of water-based Coating Liquid A formed on the second surface) is shown in Table 1 below.
In Example 6, the solids concentration of the coating liquid film formed on the first surface by the water-based coating liquid A was relatively low, and gas was ejected onto the surface of this coating liquid film by the floating and conveying means 40, which caused the surface condition of the coating liquid film to become slightly disturbed. Also, in the case of Example 6, the drying process took a long time.

[Examples 7 and 8]
Films were formed on both sides of an aluminum substrate to obtain laminates in the same manner as in Examples 1 and 2, except that the water-based coating liquid A was changed to the water-based coating liquid B.
In Examples 7 and 8, the displacement F of the aluminum substrate when the application of the water-based coating liquid A to the second surface was started, and the solids concentration of the coating liquid film of the water-based coating liquid A formed on the first surface are shown in Table 1 below.
In Examples 7 and 8, the amount of positional misalignment between the width of the first coating liquid film on the first surface (i.e., the coating liquid film of water-based coating liquid A formed on the first surface) and the width of the second coating liquid film formed from the second coating liquid on the second surface (i.e., the coating liquid film of water-based coating liquid A formed on the second surface) is shown in Table 1 below.

[Example 9]
Films were formed on both surfaces of the aluminum substrate to obtain a laminate in the same manner as in Example 1, except that the application of the water-based coating liquid A to the second surface of the aluminum substrate was carried out on the aluminum substrate being transported horizontally by a floating transport means.
The distance the substrate was horizontally transported by the floating transport means was 785 mm, and the amount of floating of the substrate from the outer peripheral surface (flat surface) of the floating transport means was 200 μm.

[Comparative Example 1]
After starting to apply the water-based coating liquid A to the first surface, the coating liquid film of the water-based coating liquid A formed on the first surface was dried (specifically, after the constant-rate drying and falling-rate drying were completed and the solids concentration of the coating liquid film reached 100 mass %), and then the water-based coating liquid A was applied to the second surface of the curved aluminum substrate by the floating conveying means, and films were formed on both surfaces of the aluminum substrate to obtain a laminate in the same manner as in Example 1.
In this Comparative Example 1, the displacement F of the aluminum substrate when the application of the water-based coating liquid A to the second surface was started, and the solids concentration of the coating liquid film of the water-based coating liquid A formed on the first surface are shown in Table 1 below.

[Examples 10 and 11]
Films were formed on both sides of the substrate to obtain laminates in the same manner as in Example 1, except that the type of substrate was changed as shown in Table 2 below.
In Examples 10 and 11, the displacement F of the substrate when the application of the water-based coating liquid A to the second surface was started, and the solids concentration of the coating liquid film of the water-based coating liquid A formed on the first surface are shown in Table 2 below.
In Examples 10 and 11, the amount of positional misalignment between the width of the first coating liquid film on the first surface (i.e., the coating liquid film made of water-based coating liquid A formed on the first surface) and the width of the second coating liquid film made of the second coating liquid on the second surface (i.e., the coating liquid film made of water-based coating liquid A formed on the second surface) is shown in Table 2 below.

[Examples 12 to 14]
Films were formed on both sides of the aluminum substrate in the same manner as in Example 1, to obtain a laminate, except that the thickness of the first coating liquid film formed on the first side and the thickness of the second coating liquid film formed on the second side were appropriately changed as shown in Table 2 below.
In Examples 12 to 14, the displacement F of the aluminum substrate when the application of the water-based coating liquid A to the second surface was started, and the solids concentration of the coating liquid film of the water-based coating liquid A formed on the first surface are shown in Table 2 below.
In Examples 12 to 14, the amount of positional misalignment between the width of the first coating liquid film on the first surface (i.e., the coating liquid film of water-based Coating Liquid A formed on the first surface) and the width of the second coating liquid film formed from the second coating liquid on the second surface (i.e., the coating liquid film of water-based Coating Liquid A formed on the second surface) is shown in Table 2 below.

[Various measurements]
The thickness of the substrate, the thickness of the first coating liquid film, and the thickness of the second coating liquid film were measured by the methods already described.
The displacement F of the end portion in the width direction of the aluminum substrate at the time when application of the second coating liquid to the second surface of the aluminum substrate was started was measured by the method already described.
At the time when the application of the second coating liquid to the second surface of the aluminum substrate was started, the solid content concentration of the coating liquid film formed on the first surface of the aluminum substrate was measured by the method already described.

[Evaluation of positional misalignment amount]
In the examples, the amount of positional misalignment between the width of the first coating liquid film on the first surface and the width of the second coating liquid film formed by the second coating liquid on the second surface was also measured by the method already described.
Note that the amount of misalignment between the width of the dry film of the first coating liquid film on the first surface (i.e., the dry film of the coating liquid film of water-based Coating Liquid A formed on the first surface) and the width of the dry film of the second coating liquid film formed from the second coating liquid on the second surface (i.e., the dry film of the coating liquid film of water-based Coating Liquid A formed on the second surface) was measured only for Comparative Example 1. This measurement was performed in the same manner as for the amount of misalignment between the width of the first coating liquid film on the first surface and the width of the second coating liquid film on the second surface.
The results are shown in Tables 1 and 2.

[Evaluation of curl at the end of the substrate in the width direction]
The aluminum substrates obtained in each example, each having a film on both sides thereof, were evaluated for curl at the edges in the width direction of the substrate.
The curl amount C was measured in the same manner as in the measurement of the lift amount when determining the displacement amount F, and was evaluated according to the following criteria.
-Evaluation criteria-
G1: The curl amount C was 2 mm or less. G2: The curl amount C was more than 2 mm and 5 mm or less. G3: The curl amount C was more than 5 mm. The results are shown in Tables 1 and 2.

As is clear from Tables 1 and 2, the laminates obtained by the laminate manufacturing methods of the Examples show less curling of the coating liquid films formed on both sides of the substrate after drying.
Furthermore, in the laminates obtained in the examples, the positional deviation between the width of the dry film of the first coating liquid film and the width of the dry film of the second coating liquid film was measured by the method described above and confirmed to be within 1 mm. Thus, it is presumed that the laminates obtained in the examples have reduced curling because the dry films are formed in approximately the same region on the first and second surfaces of the substrate.
On the other hand, as is clear from Table 1, when the amount of misalignment is large, as in Comparative Example 1, the curl becomes large.

[Explanation of symbols]
10: belt-shaped substrate 20: backup roll 30: first coating means 40: floating transport means 50: second coating means 60: drying means P: position on the transport path where the displacement F reaches 5 mm during the drying process of the first coating liquid film formed on the first surface

The disclosure of Japanese Patent Application No. 2020-210735, filed on December 18, 2020, is incorporated herein by reference in its entirety. 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 (6)

a step of starting application of a first coating liquid to a first surface of a substrate being continuously transported, and starting application of a second coating liquid to a second surface of the substrate opposite to the first surface until a displacement F of an end portion of the substrate in the width direction on which a first coating liquid film of the first coating liquid has been formed reaches 5 mm and a solid content concentration of the first coating liquid film reaches 81 mass % ,
A method for manufacturing a laminate, wherein the amount of positional misalignment between the width of a first coating liquid film on the first surface and the width of a second coating liquid film formed by the second coating liquid on the second surface is within 1 mm.
The displacement F indicates the amount of lift at the end portions in the width direction of the substrate when the center of the substrate on which the first coating liquid film is formed is used as a reference. The method for manufacturing a laminate according to claim 1, wherein the thickness of the substrate is 5 μm or more and 80 μm or less. The method for producing a laminate described in claim 1 or claim 2, wherein the film thickness of the first coating liquid film and the second coating liquid film is 40 μm or more. The method for manufacturing a laminate described in any one of claims 1 to 3, wherein application of the second coating liquid to the second surface opposite the first surface of the substrate is initiated before the solids concentration of the first coating liquid film reaches 70% by mass. The method for manufacturing a laminate described in any one of claims 1 to 4, wherein application of the second coating liquid to the second surface opposite the first surface of the substrate is initiated while the solids concentration of the first coating liquid film is 55% by mass or more and 70% by mass or less. The method for manufacturing a laminate described in any one of claims 1 to 5, wherein the application of the second coating liquid is carried out using an extrusion-type die coater.