WO2021205920A1

WO2021205920A1 - Method for producing coating film

Info

Publication number: WO2021205920A1
Application number: PCT/JP2021/013082
Authority: WO
Inventors: 諭司國安; 貴之佐野; 一孝知花
Original assignee: 富士フイルム株式会社
Priority date: 2020-04-06
Filing date: 2021-03-26
Publication date: 2021-10-14
Also published as: CN115443195A; JP7358631B2; JPWO2021205920A1; KR20220145907A; CN115443195B

Abstract

The present disclosure provides a method for producing a coating film, comprising a step A of continuously conveying a long support which has a thermal conductivity of 200 W/(m∙K) or more and applying a water-based coating liquid on the support being continuously conveyed, and a step B of drying a coating liquid film obtained in the step A, wherein the step B includes a constant-rate drying stage for the coating liquid film which satisfies conditions (1) and (2) (condition (1) : ∆T[°C] obtained from formula (A) is -10°C<∆T<0°C, where A_(T0%) is the film surface temperature of a widthwise end part of the coating liquid film, and B_(T0%) is the film surface temperature of a widthwise center part thereof at a T0% point at which the constant-rate drying starts, and A_(T90%) is the film surface temperature of the widthwise end part of the coating liquid film, and B_(T90%) is the film surface temperature of the widthwise center part thereof at a T90% point after 90% of the constant-rate drying time has passed, and condition (2): an average value of the film surface temperatures A_(T0%), B_(T0%), A_(T90%), and B_(T90%) is 35°C or higher).

Description

Manufacturing method of coating film

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

A method of producing a target coating film on a support by a continuous process of a roll-to-roll method is known.
As a method for producing a coating film, for example, there is a method of applying a coating liquid for obtaining a target coating film on a support and drying the obtained coating liquid film.

As an example of a method for producing a coating film, Patent Document 1 includes a drying step of applying an ink absorbing layer coating solution containing inorganic fine particles and a water-soluble resin to a continuously running web and then drying the ink absorbing layer. In the method for producing an inkjet recording sheet, a method for producing an inkjet recording sheet is disclosed in which the drying rate distribution of the ink absorbing layer in the web width direction is within 20% in the drying step.

Further, in Patent Document 2, inorganic fine particles are dispersed in the presence of a water-soluble polyvalent metal compound to obtain a dispersion (1), and separately, inorganic fine particles are dispersed in the presence of an organic cationic polymer to obtain a dispersion (2). ), The obtained dispersions (1) and (2) are mixed, coated on a support, and dried.
Further, Patent Document 3 describes a step of applying a negative electrode paste containing a negative electrode active material, a thickener and a binder to the surface of a negative electrode current collector, and a step of applying the negative electrode paste to the surface of the negative electrode current collector. A method for manufacturing a negative electrode including a drying step of drying the formed negative electrode paste layer so as to satisfy Equation 1: (surface temperature of the negative electrode paste layer)-(temperature of the negative electrode current collector) ≤ 1 ° C. is disclosed. There is.

Japanese Unexamined Patent Publication No. 2004-268392 Japanese Unexamined Patent Publication No. 2006-187883 Japanese Unexamined Patent Publication No. 2016-66460

For example, it is a method of manufacturing a coating film on a support that is continuously conveyed, such as a continuous process in a roll-to-roll method, in which a water-based coating liquid is applied onto a support having high thermal conductivity. In the method for producing a coating film in which the step of forming the coating liquid film and the step of drying the formed coating liquid film are performed, cracks occur at the widthwise end of the obtained coating film. There is.

Therefore, the problem to be solved by one embodiment of the present disclosure has been made in view of the above circumstances, and is a method of manufacturing a coating film on a support that is continuously conveyed (for example, by a roll-to-roll method). In the method using the continuous process of the above), it is an object of the present invention to provide a method for producing a coating film capable of suppressing cracks generated at the widthwise end portion of the coating film.

Means for solving the above problems include the following embodiments.
<1> A step A in which a long support having a thermal conductivity of 200 W / (m · K) or more is continuously transported and a water-based coating liquid is applied onto the continuously transported support, and the continuous transport is performed. Including step B of drying the coating liquid film obtained in step A on the support.
Step B includes a constant drying step of the coating liquid film satisfying the following conditions (1) and (2).
Manufacturing method of coating film.
Condition (1): The film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T0% when the constant drying is started is set to A _(T0%) , and the center in the width direction of the coating liquid film. The film surface temperature of the part is B _(T0%) , and the film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T90% after 90% of the constant drying time is A _{(T90). %)} _{, And the film surface temperature B (T90%) at the} center of the coating liquid film in the width direction, ΔT [° C.] obtained from the following formula (A) is −10 ° C. <ΔT <0 ° C. ..
Formula (A) ΔT [° C.] = (A _(T0%) -B _(T0%) )-(A _(T90%) -B _(90%) )
Condition (2): _{The average value of the film surface temperature A (T0%)} , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) is 35 ° C. or higher. ..

<2> When the thickness at a position 5 mm from the widthwise edge of the coating liquid film is At and the thickness at the center of the coating liquid film in the width direction is Bt, 0.9 ≦ At / Bt ≦ 1.1. The method for producing a coating film according to <1>, which satisfies the above relationship.
<3> The method for producing a coating film according to <1> or <2>, wherein the water-based coating liquid is a coating liquid containing particles.
<4> The method for producing a coating film according to any one of <1> to <3>, wherein the thickness of the coating film after step B is 40 μm or more.

According to one embodiment of the present disclosure, in a method of manufacturing a coating film on a support that is continuously conveyed, there is provided a method of manufacturing a coating film that can suppress cracks that occur at the widthwise end of the coating film. Will be done.

FIG. 1 is a schematic view showing each step of the method for producing a coating film of one embodiment. FIG. 2 is a schematic top view for explaining the film surface temperature of the coating liquid film formed on the support. FIG. 3 is a graph for explaining the film surface temperature in the constant rate drying stage.

Hereinafter, embodiments of a method for manufacturing a coating film will be described. However, the present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the scope of the object of the present invention.

The numerical range indicated by using "-" in the present disclosure means a range including the numerical values before and after "-" as the minimum value and the maximum value, respectively.
In the numerical range described stepwise in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the upper limit value or the lower limit value of another numerical range described stepwise. Further, in the numerical range described in the present disclosure, the upper limit value or the lower limit value described in a certain numerical range may be replaced with the value shown in the examples.
Each element in each of the drawings presented in this disclosure is not necessarily on an exact scale, with an emphasis on clearly showing the principles of this disclosure and some emphasis.
Further, in each drawing, components having the same function are designated by the same reference numerals, and duplicate description will be omitted.
In the present disclosure, the "width direction" refers to a direction orthogonal to the longitudinal direction of any of a long support, a coating liquid film, and a coating film.
In the present disclosure, the "width direction edge portion" refers to the coating liquid film or the edge portion in the width direction of the coating film, and when the film surface of the coating liquid film or the coating film is viewed from above, the coating area. It is visually recognized as a boundary line between (that is, the coating liquid film or the forming portion of the coating film) and the non-coated area (that is, the exposed portion of the support).
In the present disclosure, the "width direction end portion" refers to the coating liquid film or the width direction end portion of the coating film, and the width direction edge portion (specifically, the above-mentioned coated area and non-coated area). (Boundary line with) to 20 mm toward the center in the width direction.
In the present disclosure, a combination of two or more preferred forms or embodiments is a more preferred embodiment or embodiment.

≪Manufacturing method of coating film≫
As described above, this is a method of manufacturing a coating film on a support that is continuously conveyed, and is a step of applying a water-based coating liquid onto a support having high thermal conductivity to form a coating liquid film. In the method for producing a coating film, which comprises a step of drying the formed coating liquid film, cracks may occur at the widthwise end portion of the obtained coating film.
As described above, for cracking at the widthwise end of the coating film, a support having excellent thermal conductivity such as metal is used as the support for forming the coating film, and the coating liquid is used. This is a phenomenon that occurs when a water-based coating liquid in which the solvent or dispersion medium is substantially water is used.
When the present inventors examined the above-mentioned method for producing a coating film, they focused on the amount of change in the temperature difference between the center in the width direction and the end in the width direction of the coating liquid film in the constant rate drying stage. It has been found that by controlling this amount of change (ΔT in (1) of the above condition), cracks generated at the widthwise end of the coating film can be suppressed, and the present invention has been made.

In the method for producing a coating film according to the present embodiment, a long support having a thermal conductivity of 200 W / (m · K) or more is continuously conveyed, and a water-based coating liquid is applied onto the continuously conveyed support. The step A includes the step A of coating and the step B of drying the coating liquid film obtained in the step A on the support that is continuously conveyed, and the step B includes the following conditions (1) and (2). ) Is a method for producing a coating film, which includes a constant drying step of the coating film.
Condition (1): The film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T0% when the constant drying is started is set to A _(T0%) , and the center in the width direction of the coating liquid film. The film surface temperature of the part is B _(T0%) , and the film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T90% after 90% of the constant drying time is A _{(T90). %)} _{, And the film surface temperature B (T90%) at the} center of the coating liquid film in the width direction, ΔT [° C.] obtained from the following formula (A) is −10 ° C. <ΔT <0 ° C. ..
Formula (A) ΔT [° C.] = (A _(T0%) -B _(T0%) )-(A _(T90%) -B _(90%) )
Condition (2): _{The average value of the film surface temperature A (T0%)} , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) is 35 ° C. or higher. ..

According to the coating film manufacturing method according to the present embodiment, cracks generated at the widthwise end of the coating film can be suppressed.

On the other hand, in the coating film manufacturing methods described in Patent Documents 1 to 3, attention is not paid to the amount of change in the temperature difference between the center in the width direction and the end in the width direction of the coating liquid film in the constant rate drying stage. , There is no mention of cracks at the widthwise edges of the coating film.

Hereinafter, each step of the coating film manufacturing method of the present embodiment will be described.

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 tip of the wound long support 10 is sent out and continuous transportation is started, the water-based coating liquid is applied by the coating means 20 (step A). In step A, a coating liquid film of the water-based coating liquid is formed on the long support.
Subsequently, the coating liquid film is dried on the support 10 by continuously transporting the support 10 having the coating liquid film formed in the step A through the drying means 30a and 30b (step). B). In step B, the coating liquid film on the long support is dried and the coating film is formed.

[Step A]
In step A, a long support having a thermal conductivity of 200 W / (m · K) or more is continuously conveyed, and a water-based coating liquid is applied onto the continuously conveyed support.
Here, the water-based coating liquid refers to a coating liquid in which the solvent (or dispersion medium) contained in the coating liquid is substantially water. "The solvent (or dispersion medium) is substantially water" means that the inclusion of a solvent other than water introduced when the solid content is used is allowed, and the total solvent (or total dispersion medium) contains. The ratio of water in the total solvent (or total dispersion medium) is preferably 95% by mass or more, and the total solvent (or total dispersion medium) is water. Is particularly preferred.
Further, the solid content refers to a component excluding a solvent (or a dispersion medium).

-Support-
The long support used in this step is a support having a thermal conductivity of 200 W / (m · K) or more. When the support used in this step is, for example, a support having a multi-layer structure including a metal foil and a resin film, the support as a whole has a thermal conductivity of 200 W / (m · K) or more. Just do it.
The upper limit of the thermal conductivity of the support is not particularly limited, and is, for example, 500 W / (m · K).

Specific examples of the support exhibiting the thermal conductivity include copper, aluminum, silver, gold, and a metal support made of an alloy thereof.
Among them, a copper support and an aluminum support are preferably used from the viewpoints of shape stability as a support, a track record of use, and the like.

The thermal conductivity of the support is measured as follows.
First, the support is cut out to a size suitable for the device described later to obtain a sample for measurement. With respect to the obtained measurement sample, the thermal diffusivity in the thickness direction is measured by a laser flash method using "LFA467" manufactured by NETZSCH. Next, the specific gravity of the measurement sample is measured using the balance "XS204" (using the "solid density measurement kit") of METTLER TOLEDO Co., Ltd. Further, using "DSC320 / 6200" of Seiko Instruments Inc., the specific heat of the measurement sample at 25 ° C. is determined using the software of DSC7 under the heating condition of 10 ° C./min. The thermal conductivity of the measurement sample (that is, the support) is calculated by multiplying the obtained thermal diffusivity by the specific gravity and the specific heat.

The thickness of the support may be appropriately set from the viewpoint of applying to the roll-to-roll method.
The thickness of the support is, for example, preferably 5 μm to 100 μm, and more preferably 10 μm to 30 μm.
The width and length of the support may be appropriately set from the viewpoint of applying to the roll-to-roll method and the width and length of the target coating film.

The thickness of the support is measured as follows.
That is, using a contact-type thickness measuring machine, the thickness of the support at three points in the width direction (that is, the position 5 mm from both edges in the width direction and the center part in the width direction) is separated by 500 mm in the longitudinal direction. Measure 3 points.
The arithmetic mean value of a total of nine measured values is obtained, and this is used as the thickness of the support.
As the contact type thickness measuring machine, for example, S-2270 of Fujiwork Co., Ltd. is used.

-Water-based coating liquid-
As described above, the water-based coating liquid used in this step is not particularly limited as long as it is a liquid material containing water as a solvent (or dispersion medium) and a solid content.
The solid content contained in the water-based coating liquid includes a component for obtaining a target coating film, a component for improving coating suitability, and the like.

Examples of the water contained in the water-based coating liquid include natural water, purified water, distilled water, ion-exchanged water, pure water, ultra-pure water (for example, Milli-Q water) and the like. The Milli-Q water is ultrapure water obtained by the Milli-Q water production apparatus of Merck Millipore Co., Ltd.

The content of water in the water-based coating liquid is not particularly limited, and is preferably 40% by mass or more, more preferably 50% by mass or more, based on the total mass of the water-based coating liquid, for example.
The upper limit of the water content may be less than 100% by mass, but for example, from the viewpoint of coating suitability, it is 90% by mass with respect to the total mass of the water-based coating liquid.

The water-based coating liquid may contain particles as one of the solid contents. That is, the water-based coating liquid may be a coating liquid containing particles.
When a water-based coating liquid containing particles is used, agglutination of particles is also added at the constant rate drying stage, so that the widthwise end portion of the coating film tends to be cracked. However, by applying the coating film manufacturing method according to the present embodiment, it is possible to suppress cracking at the widthwise end portion of the coating film even when a water-based coating liquid containing particles is used. can.

The particles are not particularly limited as long as they are granular particles, and may be inorganic particles, organic particles, or composite particles of an inorganic substance and an organic substance.

As the inorganic particles, known inorganic particles that can be applied to the target coating film can be used.
Examples of the inorganic particles include metal (alkali metal, alkaline earth metal, transition metal, etc. and alloys of these metals) particles, metalloid (silicon, etc.) particles, or metal or metalloid compounds (oxides). , Hydroxide, nitride, etc.) particles, pigment particles containing carbon black and the like, and the like.
Other examples of the inorganic particles include mineral particles such as mica and inorganic pigment particles.

As the organic particles, known organic particles applicable to the target coating film can be used.
The organic particles are not particularly limited as long as they are solid organic particles such as resin particles and organic pigment particles.

As the composite particles of the inorganic substance and the organic substance, the composite particles in which the inorganic particles are dispersed in the matrix of the organic substance, the composite particles in which the periphery of the organic particles is coated with the inorganic substance, and the periphery of the inorganic particles are coated with the organic substance. Examples include composite particles.

The particles may be surface-treated for the purpose of imparting dispersibility and the like.
The composite particles may be formed as described above by being subjected to surface treatment.

There are no particular restrictions on the particle size, specific gravity, usage pattern (for example, the presence or absence of combined use, etc.) of the particles, depending on the target coating film or the conditions suitable for producing the coating film. , It may be selected as appropriate.

The content of the particles in the water-based coating liquid is not particularly limited, and is appropriately determined according to the target coating film, the conditions suitable for producing the coating film, or the purpose of adding the particles. , Should be decided.
The more particles are contained in the water-based coating film, the more conspicuous (that is, visually recognizable) the cracks at the widthwise end of the coating film tend to be. By applying the method for producing a coating film according to the present embodiment, cracking of the widthwise end portion of the coating film is suppressed even if the content of particles in the water-based coating liquid is, for example, 50% by mass or more. can do.

The solid content contained in the water-based coating liquid is not particularly limited, and examples thereof include various components used to obtain the desired coating film.
Specifically, as the solid content contained in the water-based coating liquid, in addition to the above-mentioned particles, a binder component, a component contributing to the dispersibility of the particles, a polymerizable compound, a reactive component such as a polymerization initiator, a surfactant, etc. Ingredients for enhancing the coating performance of the above, other additives and the like can be mentioned.

-Thickness of coating liquid film-
The thickness of the coating liquid film formed in this step is not particularly limited, and may be appropriately determined according to the target coating film.
For example, the thickness of the coating liquid film formed in this step is At at a position 5 mm from the widthwise edge of the coating liquid film, and Bt is the thickness at the center of the coating liquid film in the width direction. When, the relationship of 0.8 ≦ At / Bt ≦ 2.5 (preferably 0.9 ≦ At / Bt ≦ 1.5, more preferably 0.9 ≦ At / Bt ≦ 1.1) is satisfied. preferable.
As described above, when the difference in thickness between the thickness At and the thickness Bt is small, that is, when a coating liquid film having a thickness close to uniform in the plane is formed, the coating according to the present embodiment. By applying the film manufacturing method, cracking at the widthwise end portion of the coating film can be effectively suppressed.

In addition, although it is common to form a coating liquid film having a uniform thickness in the plane, in the method for producing a coating film according to the present embodiment, the thickness At and the thickness Bt of the coating liquid film are different. May be.
When the thickness At and the thickness Bt of the coating liquid film are different, the film surface temperature and the amount of change thereof in the step B described later also change due to the difference in the thickness. Therefore, in step B, ΔT may be controlled according to the change in the film surface temperature.

The thickness At and the thickness Bt are measured as follows.
First, as the thickness At, an optical interferometry type thickness measuring machine is used to select one from the widthwise edges of the two coating liquid films, and from the selected edges to the center of the coating liquid film in the width direction. The thickness of the coating liquid film at a position of 5 mm is measured at three points with an interval of 500 mm in the longitudinal direction.
The arithmetic mean value of the measured values of the three measured points is obtained, and this is defined as the thickness At.
Further, as the thickness Bt, a light interference type thickness measuring machine is used to measure the thickness of the central portion of the coating liquid film in the width direction at three points with an interval of 500 mm in the longitudinal direction.
The arithmetic mean value of the measured values of the three measured points is obtained, and this is defined as the thickness Bt.
As the optical interferometry type thickness measuring device, for example, an infrared spectroscopic interferometry film thickness meter SI-T80 manufactured by KEYENCE Corporation can be used.

-Coating width-
The coating width (that is, the width of the coating liquid film) in this step is not particularly limited, and a coating width in which cracks are likely to occur may be applied to the end portion of the manufactured coating film in the width direction. From the viewpoint of suppressing cracking at the widthwise end portion of the coating film, the coating width is, for example, preferably 30 mm or more, more preferably 50 mm or more, and further preferably 100 mm or more.
The upper limit of the coating width is the width of the support.

When the coating liquid film on the support is formed, the width of the non-coated area (that is, the width of the exposed portion of the support), which is the distance from the widthwise edge of the support to the coating liquid film, is From the viewpoint that the effect of the coating film manufacturing method according to the present embodiment can be easily obtained, it is preferably 2 mm or more, and more preferably 5 mm or more, respectively, at both ends in the width direction.

The coating width is measured as follows.
That is, the film surface of the coating liquid film is viewed from above, and the width of the coating liquid film is measured at three points with a ruler at intervals of 500 mm in the longitudinal direction.
Obtain the arithmetic mean value of the measured values of the three measured points, and use this as the coating width.

-Application-
A known coating means is applied to the coating of the coating liquid in this step.
Specific examples of the coating means (for example, the coating means 20 in FIG. 1) include 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, and a slide coating method. Examples thereof include a coating device using a method, a blade coating method, a gravure coating method, a wire bar method, or the like.

[Step B]
In step B, the coating liquid film obtained in step A is dried on the support that is continuously conveyed.
Then, the step B includes a constant rate drying step of the coating liquid film satisfying the conditions (1) and (2) described later.

Drying in this step refers to the process until the coating liquid film formed in step A reaches the target solid content concentration through the constant rate drying step and the reduced rate drying step.
Here, "constant drying" is a form of drying in which the content of the solvent (or dispersion medium) in the coating liquid film decreases with time.
In general, the coating liquid film exhibits constant rate drying from immediately after formation until a certain period of time elapses, and then exhibits rate reduction drying. The time indicating constant drying is described in, for example, the Chemical Engineering Handbook (pages 707 to 712, published by Maruzen Co., Ltd., October 25, 1980).
In the present disclosure, the change over time in the film surface temperature (film surface temperature B described later) at the center of the formed coating liquid film in the width direction is measured, and the film surface temperature immediately after coating (immediately after the formation of the coating liquid film). In the measurement of, the period during which the film surface temperature shows a constant value (specifically, the period during which the temperature change of the film surface temperature is within ± 5 ° C.) is regarded as the “constant drying stage”.
Then, after the period in which the film surface temperature shows a constant value, the period in which the film surface temperature rises is regarded as the "declining rate drying stage".
The film surface temperature is measured with a non-contact radiation thermometer.

In step B, the drying temperature may be changed stepwise or continuously toward the transport direction of the coating liquid film. In this case, it is considered that the film surface temperature of the coating liquid film is also affected and changes. Therefore, in step B, the period in which the film surface temperature of the coating liquid film changes to the same extent as the amount of change in the drying temperature is included in the "period in which the film surface temperature shows a constant value".
That is, until the film surface temperature of the coating liquid film rises beyond the amount of change in the drying temperature, it is regarded as a constant rate drying stage.

The drying in this step includes a constant drying step that satisfies the conditions (1) and (2).
Hereinafter, the conditions (1) and (2) will be described.

-Condition (1)-
In the constant drying stage of this step, the following condition (1) is satisfied.
Condition (1): The film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T0% when the constant drying is started is set to A _(T0%) , and the center in the width direction of the coating liquid film. The film surface temperature of the part is B _(T0%) , and the film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T90% after 90% of the constant drying time is A _{(T90). %)} _{, And the film surface temperature B (T90%) at the} center of the coating liquid film in the width direction, ΔT [° C.] obtained from the following formula (A) is −10 ° C. <ΔT <0 ° C. ..
Formula (A) ΔT [° C.] = (A _(T0%) -B _(T0%) )-(A _(T90%) -B _(90%) )

2 and 3 show the film surface temperature A _(T0%) , the film surface temperature B _{(T0%), the} film surface temperature A _(T90%) , and the film surface temperature B _{(90%) in the formula (A).} Will be described with reference to. Here, FIG. 2 is a schematic top view for explaining the film surface temperature of the coating liquid film formed on the support. Further, FIG. 3 is a graph for explaining the film surface temperature in the constant rate drying stage. Here, FIGS. 2 and 3 show a case where the drying temperature is constant during the step B.
As shown in FIG. 2, in the coating liquid film 40 formed on the support 10, the film surface temperature A at a position 5 mm from the widthwise edge indicated by LA and the widthwise central portion indicated by LB. The time-dependent changes in the film surface temperature B and the film surface temperature B are measured, and the relationship between the film surface temperatures A and B and the elapsed time is graphed as shown in FIG. The film surface temperature A is selected from the widthwise edges of the two coating liquid films 40, and is located at a position of 5 mm from the selected edges toward the center of the coating liquid film 40 in the width direction. The film surface temperature.
As shown in FIG. 3, in the graph, in the measurement of the film surface temperature B immediately after coating (immediately after the formation of the coating liquid film), the period during which the film surface temperature B shows a constant value (specifically, The period during which the temperature change of the film surface temperature is within ± 5 ° C.) is regarded as the constant drying stage. The change point of the film surface temperature B at which the film surface temperature B starts to rise is set as the end point of the constant rate drying step (T100% in FIG. 3). The change points are a straight line (dotted line x in FIG. 3) extending the film surface temperature B during the period showing a constant value to the elapsed time side (right side in FIG. 3) and a gradient of the film surface temperature B. It is obtained from the intersection with the tangent line (dotted line y in FIG. 3) drawn at the point where is maximum.
Then, the period from the start point of the period in which the film surface temperature B shows a constant value to the change point of the film surface temperature B is defined as the constant rate drying time.
Next, the start point of the period in which the film surface temperature B shows a constant value is set as "the time at T0% when the constant rate drying is started", and from the start point to the end point (T100% in FIG. 3) of this period. The point where 90% has passed with respect to the entire period (that is, the constant drying time) is defined as "the time at T90% when 90% of the constant drying time has passed".
Next, from the graph shown in FIG. 3, the film surface temperature A _(T0%) and the film surface temperature B _(T0%) at the time of T0% when the constant rate drying was started were obtained, and further, the constant rate drying time of 90. _{The film surface temperatures A (T90%)} and B _(T90%) at the time of T90% after% has passed are determined.
The values of the film surface temperature A _(T0%) , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) obtained in this manner are set as described above. By substituting into the equation (A), ΔT is obtained.

The ΔT obtained as described above needs to be more than −10 ° C. and lower than 0 ° C.
Since the film surface temperature B at the central portion in the width direction of the coating liquid film 40 as shown in FIG. 2 is not easily affected by the thermal conductivity of the support, it is unlikely to increase with time. On the other hand, the film surface temperature A at a position 5 mm from the widthwise edge of the coating liquid film 40 is easily affected by the support exposed in the non-coated area, and even in the constant drying stage. , There may be an increase over time.
When the film surface temperature A rises remarkably with time in the constant rate drying step, ΔT [° C.] obtained from the formula (A) does not satisfy −10 ° C. <ΔT <0 ° C.
As described above, if the film surface temperature A is significantly increased with time in the constant rate drying step, the drying proceeds only at the widthwise end portion of the coating liquid film 40. It is presumed that cracks occur at the widthwise end of the obtained coating film.
On the other hand, the fact that ΔT [° C.] satisfies −10 ° C. <ΔT <0 ° C. means that a significant increase in the film surface temperature A in the coating liquid film 40 with time is suppressed.
That is, if the significant increase in the film surface temperature A with time is suppressed, it is considered that the drying progresses only at the widthwise end portion of the coating liquid film 40, and thus it is obtained through this step. Cracks that occur at the widthwise ends of the coating film are suppressed.
ΔT [° C.] may be −8 ° C. <ΔT <0 ° C. ΔT [° C.] may be −6 ° C. <ΔT <0 ° C. ΔT [° C.] may be -4 ° C. <ΔT <0 ° C.

-Condition (2)-
In the constant drying stage of this step, the following condition (2) is satisfied.
Condition (2): _{The average value of the film surface temperature A (T0%)} , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) is 35 ° C. or higher. ..

The values of the film surface temperature A _(T0%) , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) are shown in the graph as shown in FIG. Just ask. Here, the average values of the film surface temperature A _(T0%) , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , and the film surface temperature B _(T90%) were obtained from the graph 4 The arithmetic mean of the two values.

When the average value of the film surface temperature in the constant rate drying stage is 35 ° C. or higher, it is easily affected by the thermal conductivity of the support exposed in the uncoated area, and in the constant rate drying stage, The film surface temperature A tends to increase with time.
That is, the condition (2) indicates a condition in which the end portion in the width direction of the coating film is likely to be cracked.
In the method for producing a coating film according to the present embodiment, even if the condition (2) is satisfied, the above-mentioned condition (1) is also satisfied. Therefore, the width direction of the coating film obtained through this step is satisfied. Cracks that occur at the edges are suppressed.
As long as it does not deviate from the gist of the present disclosure, the upper limit of the average value of the above-mentioned film surface temperature in the constant rate drying stage is not limited. The upper limit of the average value of the film surface temperature in the constant rate drying step may be, for example, 90 ° C., 80 ° C., 70 ° C., 60 ° C., 50 ° C. or 40 ° C.

-Drying-
In this step, a known drying means is applied to the drying of the coating liquid film.
Specific examples of the drying means (for example, the drying means 30a and 30b in FIG. 1) include an oven, a hot air blower, an infrared (IR) heater, and the like.

In particular, in this step, as the drying means for satisfying the conditions (1) and (2), particularly the drying means for controlling ΔT, the following means can be mentioned.
-Using a warm air blower, change the wind speed of the warm air blown to the coating liquid film and the wind speed of the warm air blown to the non-coating area (exposed part of the support) of the coating liquid film (for example, the coating liquid). Compared to the wind speed of the warm air blown to the membrane, the wind speed of the warm air blown to the uncoated area (exposed part of the support) is made smaller).
-Using a warm air blower, change the temperature of the hot air blown on the coating liquid film and the temperature of the hot air blown on the non-coated area (exposed part of the support) (for example, the hot air blown on the coating liquid film). The temperature of the hot air blown to the uncoated area (exposed part of the support) is lower than the temperature of (or the hot air blown to the uncoated area (exposed part of the support) is cold air below room temperature. ).

The drying means for satisfying the above conditions (1) and (2), particularly the drying means for controlling ΔT, may be applied immediately after the coating liquid film is formed in the step A, or may be constantly applied. It may be applied from the rate drying stage.
Further, the drying means for satisfying the above conditions (1) and (2), particularly the drying means for controlling ΔT, continues during the constant rate drying stage (that is, from the time T0% to the time T100%). Is preferable.

Further, as another means for satisfying the conditions (1) and (2), particularly for controlling ΔT, the following means can be mentioned.
-Apply water of the same thickness as the coating liquid film to the non-coated area of the coating liquid film (that is, the support is not exposed to the non-coated area of the coating liquid film).
-The non-coated area of the coating liquid film is not formed or reduced (for example, the shortest distance from both ends of the support in the width direction to both ends of the coating liquid film is 2 mm or less).
When these means are adopted, it is preferable to use a means for blowing warm air with a warm air blower to the coating liquid film from the viewpoint of satisfying the condition (2) and controlling the drying speed.

The above-mentioned drying means and various means for satisfying the above-mentioned conditions (1) and (2) may be used alone or in combination of two or more.
Further, the drying means, drying conditions, etc. in the constant rate drying step and the reduced rate drying step may be the same or different. If the constant rate drying step satisfying the above conditions (1) and (2) is passed, even if the drying means, drying conditions, etc. in the rate reduction drying step are changed, the cracks generated at the end in the width direction are affected. Hard to exert.

As described above, a coating film is formed on the support through step B.

The thickness of the coating film obtained through the step B is not particularly limited, and may be any thickness according to the purpose, application, and the like.
In the method for producing a coating film according to the present embodiment, the thickness of the coating film is preferably 40 μm or more, more preferably 50 μm or more, and further preferably 60 μm or more. Compared with the conventional method for producing a coating film, in the method for producing a coating film according to the present embodiment, cracks at the widthwise end portion of the coating film are less likely to occur even if the thickness of the coating film is increased.
The upper limit of the thickness of the coating film is not particularly limited and may be determined according to the intended use, but is, for example, 300 μm.
The measurement of the thickness of the coating film is the same as the measurement of the thickness of the coating liquid film.

[Other processes]
If necessary, other steps may be provided before step A and at least one after step B.
The other steps are not particularly limited, and include a pretreatment step performed before applying the coating liquid film, a posttreatment step performed on the formed coating film depending on the use of the coating film, and the like. Be done.
As other steps, specifically, 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 removing the support from the coating film. Examples thereof include a peeling step.

Since the method for producing a coating film according to the present embodiment is a method for producing a coating film on a support that is continuously conveyed, it is suitable for producing a coating film for applications requiring high productivity.

Hereinafter, the present invention will be described in more detail with reference to examples. The materials, amounts used, ratios, details of each step, etc. shown in the following examples can be appropriately changed as long as they do not deviate from the gist 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 support>
An aluminum support 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 support 2 (thermal conductivity: 230 W / (m · K)) having a width of 203 mm, a thickness of 20 μm, and a length of 300 m was prepared (abbreviated as AL2).

<Preparation of water-based coating liquid>
[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: 99 mol% saponification degree, degree of polymerization 300, Nippon Synthetic Chemical Industry Co., Ltd.)
・ Serogen PR of Dai-ichi Kogyo Seiyaku Co., Ltd .: 24 parts ・ Surfactant (Nippon Emulsion Co., Ltd., Emarex 710): 5 parts ・ Aqueous dispersion of Artpearl J-7P prepared by the following method: 913 parts

(Aqueous dispersion of Art Pearl J-7P)
To 74 parts of pure water, 3 parts of Emarex 710 (Nippon Emulsion Co., Ltd., nonionic surfactant) and 3 parts of sodium carboxymethyl cellulose are added and dissolved. To the obtained aqueous solution, 20 parts of Art Pearl (registered trademark) J-7P (Negami Kogyo Co., Ltd., silica composite crosslinked acrylic resin fine particles) was added, and an ace homogenizer (Nissei Tokyo Office Co., Ltd.) was used at 10,000 rpm (1). The mixture was dispersed for 15 minutes with revolutions per minute; the same applies hereinafter) to obtain an aqueous dispersion of Artpearl J-7P (particle concentration: 20% by mass).
The true specific gravity of the silica composite crosslinked acrylic resin fine particles in the obtained aqueous dispersion is 1.20, and the average particle size is 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 liquid B (dispersion A: dispersion B = 25: 75). The viscosity of the water-based coating liquid B was 20 mPa · s, and the average particle size of the particles 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 mass) % Aqueous solution): 230.7 parts (Kuraray Co., Ltd., PVA 235, saponification degree 88%, polymerization degree 3500)
-Diethylene glycol monobutyl ether: 2.7 parts (Buchisenol 20-P, KH Neochem Co., Ltd.)
-Ion-exchanged water: 93.5 parts-Polyoxyethylene lauryl ether (surfactant): 0.49 parts (10% by mass 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 ultrasonically dispersed, and then the dispersion was heated to 30 ° C. and held for 8 hours to prepare a dispersion A.
・ Gas phase method silica fine particles (inorganic fine particles): 299.6 parts (AEROSIL 300SF75, Nippon Aerosil Co., Ltd.)
-Ion-exchanged water: 1400 parts-Alpha Inn 83 (40.0% by mass aqueous solution): 300 parts (dispersant, Taimei Chemicals Co., Ltd.)

(Preparation of dispersion B)
The following components were mixed and ultrasonically dispersed, and then the dispersion was heated to 30 ° C. and held for 8 hours to prepare a dispersion B.
・ Gas phase method silica fine particles (inorganic fine particles): 225.2 parts (AEROSIL 300SF75, Nippon Aerosil Co., Ltd.)
-Ion-exchanged water: 1185 parts-Cationic polymer A (25% by mass aqueous solution) having the following structure: 90 parts

[Example 1]
In the apparatus configured as shown in FIG. 1, a water-based coating liquid A is applied onto the aluminum support 1 to form a coating liquid film, and the formed coating liquid film is dried for coating. A membrane was obtained.
Specifically, the water-based coating liquid A was applied onto the support that was continuously conveyed (step A). The coating width and thickness of the formed coating liquid film are as shown in Table 1.
Subsequently, warm air was blown using a warm air blower, and the coating liquid film was dried using the ΔT control means shown in Table 1 (step B).
The blowing of warm air using a warm air blower and the drying by the ΔT control means continued during the constant rate drying stage (that is, from the time of T0% to the time of T100%). Even in the subsequent lapse rate drying stage, the blowing of warm air and drying by the ΔT control means were continued.
The transport speed of the support in step A and step B was 20 m / min.
As described above, the coating film was formed through the steps A and B.

[Examples 2 to 6]
A coating film was formed in the same manner as in Example 1 except that the specific means for drying the coating liquid film in step B was changed as shown in Table 1.
In Example 4, the aluminum support 2 was used instead of the aluminum support 1.

[Examples 7 to 13]
The coating film was prepared in the same manner as in Example 1 except that the coating width of the coating liquid film formed in the step A and the thickness of the coating liquid film were appropriately changed as shown in Table 1. Formed.

[Examples 14 to 19]
A coating film was formed in the same manner as in each of Examples 1 to 6 except that the water-based coating liquid A was changed to the water-based coating liquid B.

[Comparative Examples 1 to 4]
In step B, in addition to the coating liquid film, the non-coating area of the coating liquid film was also blown with the same warm air as the coating liquid film, except that the ΔT control means was not adopted. A coating film was formed in the same manner as in each of 5, 6 and 14.

[Reference example]
Instead of the aluminum support, a polyethylene terephthalate (PET) support (thermal conductivity: 0.3 W / (m · K)) having a width of 220 mm, a thickness of 38 μm, and a length of 300 m was used, and further coated in step B. In addition to the coating liquid film, the non-coated area of the coating liquid film is also coated in the same manner as in Example 1 except that the same warm air as that of the coating liquid film is applied and the ΔT control means is not adopted. A film was formed.

[Measurement of film surface temperature, calculation of ΔT]
With respect to the coating liquid film formed in the above Examples and Comparative Examples, the film surface temperature A _(T0%) , the film surface temperature B _(T0%) , the film surface temperature A _(T90%) , And the film surface temperature B _(T90%) was determined, and ΔT was calculated.
The obtained values are shown in Table 1.

[Evaluation of cracks at the widthwise edge of the coating film]
With respect to the coating film formed in the above Examples and Comparative Examples, an arbitrary portion was cut out by 1 m in the longitudinal direction to obtain a measurement sample.
Visually observe the presence or absence of cracks occurring at the widthwise end of the obtained measurement sample (that is, the region from the widthwise edge of the coating film to 20 mm toward the widthwise center of the coating film). confirmed.
The results are shown in Table 1.

As is clear from Table 1, it can be seen that according to the coating film manufacturing method of the example, a coating film in which cracking at the end in the width direction is suppressed is formed.

The disclosure of Japanese Patent Application No. 2020-068517, filed on April 6, 2020, is incorporated herein by reference in its entirety. All documents, patent applications, and technical standards described herein are to the same extent as if the individual documents, patent applications, and technical standards were specifically and individually stated to be incorporated by reference. Incorporated herein by reference.

10 Long support 20 Coating means 30a Drying means 30b Drying means 40 Coating liquid film LA 5mm position from the widthwise edge of the coating liquid film LB Width central part of the coating liquid film A Coating liquid film Membrane surface temperature 5 mm from the width direction edge B Membrane surface temperature at the center of the coating liquid film in the width direction T0% When constant rate drying starts T100% When constant rate drying ends x constant value A straight line extending the film surface temperature B during the period shown by y to the elapsed time side y A tangent line drawn at the point where the gradient of the film surface temperature B becomes maximum

Claims

Step A in which a long support having a thermal conductivity of 200 W / (m · K) or more is continuously conveyed, and a water-based coating liquid is applied onto the continuously conveyed support.
Step B of drying the coating liquid film obtained in step A on the support that is continuously conveyed, and step B.
Including
Step B includes a constant drying step of the coating liquid film satisfying the following conditions (1) and (2).
Manufacturing method of coating film.
Condition (1): The film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T0% when the constant drying is started is set to A (T0%) , and the center in the width direction of the coating liquid film. The film surface temperature of the part is B (T0%) , and the film surface temperature at a position 5 mm from the widthwise edge of the coating liquid film at T90% after 90% of the constant drying time is A (T90). %) , And the film surface temperature B (T90%) at the center of the coating liquid film in the width direction, ΔT obtained from the following formula (A) is −10 ° C. <ΔT <0 ° C.
Formula (A) ΔT [° C.] = (A (T0%) -B (T0%) )-(A (T90%) -B (90%) )
Condition (2): The average value of the film surface temperature A (T0%) , the film surface temperature B (T0%) , the film surface temperature A (T90%) , and the film surface temperature B (T90%) is 35 ° C. or higher. ..
When the thickness at a position 5 mm from the widthwise edge of the coating liquid film is At and the thickness at the center of the coating liquid film in the width direction is Bt, the relationship of 0.9 ≦ At / Bt ≦ 1.1 is established. The method for producing a coating film according to claim 1, wherein the coating film is satisfied.
The method for producing a coating film according to claim 1 or 2, wherein the water-based coating liquid is a coating liquid containing particles.
The method for producing a coating film according to any one of claims 1 to 3, wherein the thickness of the coating film after step B is 40 μm or more.