CN115397568B

CN115397568B - Method for producing coating film

Info

Publication number: CN115397568B
Application number: CN202180027275.2A
Authority: CN
Inventors: 内海京久; 国安谕司; 落合昭纪
Original assignee: Fujifilm Corp
Current assignee: Fujifilm Corp
Priority date: 2020-04-16
Filing date: 2021-04-12
Publication date: 2023-08-01
Anticipated expiration: 2041-04-12
Also published as: JPWO2021210542A1; CN115397568A; WO2021210542A1; KR20220146650A; JP7446412B2

Abstract

The present invention provides a method for producing a coating film, comprising: step A, continuously conveying a long support, and coating an aqueous coating liquid on the continuously conveyed support; and a step (B) of drying the coating liquid film obtained in the step (A) on a continuously conveyed support, wherein the coating liquid film starts to be curled in a non-contact manner with respect to a laminate composed of the support and the coating liquid film during a period in which the solid content concentration of the coating liquid film is 70 to 95 mass% in the constant-speed drying stage of the coating liquid film in the step (B).

Description

Method for producing coating film

Technical Field

The present invention relates to a method for producing a coating film.

Background

A method of producing a target coating film on a support in a continuous process in a roll-to-roll manner is known.

As a method for producing a coating film, 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, for example. In this method, in order to suppress curling (also referred to as warping) of the coating film, a curl restricting mechanism is sometimes used.

As an example of a method of applying the curl restricting mechanism in the drying step, patent document 1 discloses a method of using a film developing apparatus including: a developing unit for performing a developing process on the undeveloped film; and a drying processing section for drying the film developed by the developing processing section, wherein the film developing device includes: a hot air blowing mechanism for drying the developed film by blowing hot air; a conveying mechanism for conveying the film while drying the film; and a curl restricting mechanism for restricting curl in the film width direction caused by the drying process of the film, wherein the curl restricting mechanism uses a film developing device provided downstream in the conveying direction from a position where the film is in a decelerated dry state.

Patent documents 2 to 5 disclose various curl restricting mechanisms.

Technical literature of the prior art

Patent literature

Patent document 1: japanese patent laid-open No. 2006-154375

Patent document 2: japanese patent laid-open No. 2014-166900

Patent document 3: japanese patent laid-open publication No. 2014-005085

Patent document 4: japanese patent application laid-open No. 2012-125973

Patent document 5: japanese patent laid-open No. 10-337848

Disclosure of Invention

Technical problem to be solved by the invention

For example, in a method for producing a coating film on a continuously conveyed support by a continuous process such as a roll-to-roll method, a step of forming a coating liquid film by applying an aqueous coating liquid to the support and a step of drying the formed coating liquid film are performed, and in this method for producing a coating film, cracks and curls may occur in the obtained coating film.

Accordingly, an object of an embodiment of the present invention is to provide a method for producing a coated film, in which a coated film with suppressed cracks and curling is obtained in a method for producing a coated film on a continuously conveyed support (for example, a method using a continuous process in a roll-to-roll manner).

Means for solving the technical problems

The means for solving the above problems include the following embodiments.

< 1 > a method for producing a coating film, comprising: step A, continuously conveying a long support, and coating an aqueous coating liquid on the continuously conveyed support; and

A step B of drying the coating liquid film obtained in the step A on the continuously conveyed support,

in the constant-speed drying stage of the coating liquid film in the step B, the coating liquid film starts to be curled in a non-contact manner with respect to the laminate composed of the support and the coating liquid film while the solid content concentration of the coating liquid film is 70 to 95 mass%.

The method for producing a coating film according to < 2 > and < 1 >, wherein the solid content concentration of the coating liquid in the step A is 30 to 60% by mass.

The method for producing a coating film according to < 1 > or < 2 >, wherein the aqueous 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 non-contact curl restriction is performed by a method of jetting a gas to one or both surfaces of the laminate and continuously transferring the laminate while bending the laminate in the thickness direction by using the wind pressure of the gas.

< 5 > the method for producing a coating film according to any one of < 1 > to < 4 >, wherein the support is a metal support.

< 6 > the method for producing a coating film according to any one of < 1 > to < 5 >, wherein the thickness of the support is 10 μm to 30 μm.

Effects of the invention

According to an embodiment of the present invention, there is provided a method for producing a coated film, in which a coated film having suppressed cracks and curling is obtained in a method for producing a coated film on a continuously conveyed support.

Drawings

Fig. 1 is a schematic diagram showing steps of a method for producing a coating film according to an embodiment.

Fig. 2 is a schematic side view for explaining an example of the curl restricting mechanism in step B.

Fig. 3 is a schematic side view for explaining another example of the curl restricting mechanism in step B.

Fig. 4 is a schematic diagram illustrating a method of measuring the curl amount.

Detailed Description

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

In the present invention, the numerical range indicated by the term "to" refers to a range in which numerical values before and after the term "to" are included as a minimum value and a maximum value, respectively.

In the numerical ranges described in stages in the present invention, the upper limit or the lower limit described in one numerical range may be replaced with the upper limit or the lower limit of the numerical range described in other stages. In the numerical ranges described in the present invention, the upper limit value or the lower limit value described in any numerical range may be replaced with the values described in the examples.

The elements in the drawings illustrated in the present invention are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention, and the emphasis instead being placed upon clearly illustrating the principles of the present invention.

In the drawings, constituent elements having the same function are denoted by the same reference numerals, and redundant description thereof is omitted.

In the present invention, the "width direction" means a direction orthogonal to the longitudinal direction of the long support, the coating liquid film, and the coating film.

In the present invention, a combination of 2 or more preferred forms or modes is a more preferred form or mode.

Method for producing coated film

As described above, in the method for producing a coating film on a continuously conveyed support, there are cases where a step of forming a coating liquid film by applying an aqueous coating liquid to the support and a step of drying the formed coating liquid film are performed, and in the method for producing a coating film, cracks and curls are generated in the obtained coating film.

The occurrence of cracks and curling in the coating film is a remarkable phenomenon occurring when an aqueous coating liquid in which a solvent or a dispersion medium is actually water is used as the coating liquid.

As a result of the study of the above-described method for producing a coating film, the inventors have found that a coating film having suppressed cracking and curling can be produced by restricting the curl of the coating liquid film at a certain timing in the constant-speed drying stage.

The method for producing a coating film according to the present embodiment includes: step A, continuously conveying a long support, and coating an aqueous coating liquid on the continuously conveyed support; and a step (B) of drying the coating liquid film obtained in the step (A) on a continuously conveyed support, wherein the coating liquid film starts to be curled in a non-contact manner with respect to a laminate composed of the support and the coating liquid film during a period in which the solid content concentration of the coating liquid film is 70 to 95 mass% in the constant-speed drying stage of the coating liquid film in the step (B).

According to the method for producing a coated film of the present embodiment, a coated film in which cracks and curling are suppressed is obtained.

On the other hand, in any of patent documents 1 to 5, curl restriction in the step of drying the coating liquid film is not described. That is, in any of patent documents 1 to 5, the relation between the solid content concentration of the coating liquid film and the timing of starting curl restriction is not described.

Hereinafter, each step of the method for producing a coating film according to the present embodiment will be described.

First, an example of a method for producing a coating film will be described with reference to fig. 1.

As shown in fig. 1, when the wound long support body 10 is fed out at the tip end thereof and continuous conveyance is started, an aqueous coating liquid is applied by the coating mechanism 20 (step a). In step a, a coating liquid film is formed on the long support from the aqueous coating liquid.

Next, the coating liquid film formed in step a and the laminate 12 of the support 10 are continuously transferred to the drying mechanism 30, whereby the coating liquid film is dried on the support 10 (step B). In step B, the coating liquid film on the long support is dried to form a coating film.

(Process A)

In step a, the long support is continuously conveyed, and the aqueous coating liquid is applied to the continuously conveyed support.

The aqueous coating liquid is a coating liquid in which a solvent (or a dispersion medium) contained in the coating liquid is actually water. The "solvent (or dispersion medium) is actually water" means that a solvent other than water introduced when a solid component is used is allowed to be contained, and means that the proportion of water in the total solvent (or total dispersion medium) is 90% by mass or more, preferably 95% by mass or more, and particularly preferably the total solvent (or total dispersion medium) is water.

The solid component refers to a component other than the solvent (or dispersion medium).

Support body-

The long support used in this step is not particularly limited as long as it can be applied to a roll-to-roll long support.

On the other hand, a support having high thermal conductivity such as a metal support is likely to cause cracks and curling in the coating film. In the method for producing a coating film according to the present embodiment, a coating film in which cracks and curling are suppressed can be obtained even when a support having high thermal conductivity is used.

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

The upper limit of the thermal conductivity of the support is not particularly limited, and is, for example, 500W/(mK).

Examples of the support exhibiting the thermal conductivity include metal supports. More specifically, as the support exhibiting the above thermal conductivity, a metal support composed of copper, aluminum, silver, gold, and alloys thereof can be mentioned.

The metal support may be a support made of stainless steel, nickel, titanium, or invar.

Among them, copper supports and aluminum supports are preferably used in view of shape stability, practical performance, and the like as supports.

The thermal conductivity of the support was measured using a laser flash method.

Specifically, for example, measurement is performed by the following method.

First, the support was sheared at 3 places in the width direction (specifically, a position 5mm apart from both side portions in the width direction and a widthwise central portion) by phi 5mm to 10mm to obtain 3 measurement samples. The thermal conductivity of the 3 measurement samples obtained was measured by a thermophysical property measuring device (KYOTO ELECTRONICS MANUFACTURING co., ltd., model LFA-502) to which a laser flash method was applied. The arithmetic average of the 3 measurements was taken as the thermal conductivity of the support.

The thickness of the support may be appropriately set from the viewpoint of being applied to the roll-to-roll system.

The thickness of the support is, for example, preferably 3 μm to 50 μm, more preferably 10 μm to 30 μm.

The width and length of the support are appropriately set from the viewpoint of being applied to the roll-to-roll system, and the width and length of the target coating film.

The thickness of the support is measured as follows.

That is, regarding the thickness of the support body, it is measured at 3 in the width direction (specifically, a position 5mm away from both side portions in the width direction and a widthwise central portion) using a contact thickness measuring machine such as Fujiwork co. The arithmetic average of the 3 measurements was taken as the thickness of the support.

Aqueous coating liquid

The aqueous coating liquid used in the present step is not particularly limited as long as it is a liquid containing water and a solid component as a solvent (or dispersion medium), as described above.

The solid component contained in the aqueous coating liquid contains a component for improving coating suitability, in addition to the component for the target coating film.

Examples of the water contained in the aqueous coating liquid include natural water, purified water, ion-exchanged water, pure water, ultrapure water (for example, milli-Q water), and the like. In addition, milli-Q water was ultrapure water obtained by a Milli-Q water production apparatus of Merck Millipore Corporation.

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

The upper limit of the water content may be less than 100 mass%, for example, 80 mass% relative to the total mass of the aqueous coating liquid from the viewpoint of coating suitability.

The aqueous coating liquid may contain particles as one of the solid components. That is, the aqueous coating liquid may be a coating liquid containing particles.

When an aqueous coating liquid containing particles is used, aggregation of the particles is also increased in the constant-speed drying stage, and thus cracks and curling tend to be easily generated. However, by applying the method for producing a coating film according to the present embodiment, even when an aqueous coating liquid containing particles is used, the occurrence of cracks and curling in the coating film can be suppressed.

The particles are not particularly limited as long as they are 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, and alloys of these metals), semimetal (silicon, and the like) particles, metal or semimetal compound (oxide, hydroxide, nitride, and the like) particles, and pigment particles including carbon black, and the like.

Examples of the inorganic particles include mineral particles such as mica, inorganic pigment particles, and polycrystalline diamond.

As the organic particles, known organic particles that can be applied to the target coating film can be used.

The organic particles are not particularly limited as long as they are solid organic particles, and are represented by resin particles and organic pigment particles.

Examples of the composite particles of an inorganic substance and an organic substance include composite particles in which inorganic particles are dispersed in a matrix made of an organic substance, composite particles in which the periphery of the organic particles is covered with an inorganic substance, and composite particles in which the periphery of the inorganic particles is covered with an organic substance.

The particles may be subjected to a surface treatment for the purpose of imparting dispersibility or the like.

The composite particles can be obtained by performing a surface treatment.

The particle diameter, specific gravity, use mode (for example, presence or absence of use) and the like of the particles are not particularly limited, and may be appropriately selected according to the intended coating film or according to conditions suitable for producing the coating film.

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

The solid component contained in the aqueous coating liquid is not particularly limited, and various components used for obtaining a target coating film may be mentioned.

The solid component contained in the aqueous coating liquid includes, specifically, a binder component, a component contributing to dispersibility of the particles, a reactive component such as a polymerizable compound and a polymerization initiator, a component for improving coating performance such as a surfactant, and other additives, in addition to the above particles.

The solid content concentration of the aqueous coating liquid used in the present step is not particularly limited, but is preferably less than 70% by mass, more preferably 30% by mass to 60% by mass.

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.

The thickness of the coating liquid film may be, for example, 10 to 200 μm and 20 to 100 μm from the viewpoint of easiness of occurrence of cracks and curling.

The thickness of the coating liquid film was measured as follows.

That is, the coating liquid film was measured at 3 points in the width direction (specifically, a position 5mm away from both sides in the width direction and a center part in the width direction) by an optical interferometry thickness measuring machine such as an infrared spectroscopic interferometry thickness meter SI-T80 of KEYENCE CORPORATION. An arithmetic average of the measured values at 3 points was obtained and used as the thickness of the coating liquid film.

Coating width-

The application width (i.e., the width of the coating liquid film) in this step is not particularly limited, but may be selected to be 100mm or more and 1000mm or more from the viewpoint of easy occurrence of curling.

The upper limit of the coating width is the width of the support.

The coating width was measured as follows.

The width of the coating liquid film was measured from the upper surface of the film surface of the coating liquid film by FALCIO-APEX776 of MITUTOYO CORPORATION, and this was used as the coating width.

Coating-

The application of the coating liquid in this step is performed by a known application mechanism.

Specific examples of the coating means (for example, the coating means 20 in fig. 1) include coating apparatuses using a curtain coating method, a dip coating method, a spin coating method, a print coating method, a spray coating method, a slit coating method, a roll coating method, a slide coating method, a doctor blade coating method, a gravure coating method, a bar coating method, and the like.

[ procedure B ]

In step B, the coating liquid film obtained in step a is dried on the continuously conveyed support.

Then, in the constant-speed drying stage of the coating liquid film in the step B, the coating liquid film starts to be curled in a non-contact manner with respect to the laminate composed of the support and the coating liquid film while the solid content concentration of the coating liquid film is 70 to 95 mass%.

The drying in this step means that the coating liquid film formed in step a is subjected to a constant-speed drying stage and a deceleration drying stage until the target solid content concentration is reached.

Here, "constant-speed drying" is a drying method in which the content of the solvent (or dispersion medium) in the coating liquid film decreases with time.

In general, the coating liquid film is dried at a constant speed immediately after formation until a predetermined time elapses, and then dried at a reduced speed. The time for which the film exhibits constant-rate drying is described, for example, in chemical engineering toilet paper (pages 707 to 712, MARUZEN GROUP hairstyle, sho 55 (1980)) for 10 months and 25 days.

In the present invention, the change with time of the film surface temperature in the widthwise central portion of the formed coating liquid film is measured, and the period in which the film surface temperature shows a predetermined value (specifically, the period in which the temperature change of the film surface temperature is kept within ±5 ℃ C.) is regarded as a "constant-speed drying stage" in the measurement of the film surface temperature immediately after coating (immediately after forming the coating liquid film).

Then, after a period in which the film surface temperature shows a predetermined value, a period in which the film surface temperature rises is regarded as a "deceleration drying stage".

The film surface temperature was measured by a noncontact radiation thermometer.

In step B, the drying temperature may be changed stepwise or continuously in the direction of conveyance of the coating liquid film. In this case, it is considered that the surface temperature of the coating liquid film is also affected and changed. 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 predetermined value".

That is, the constant-speed drying stage is considered until the film surface temperature of the coating liquid film rises to a level equal to or higher than the variation of the drying temperature.

The constant-speed drying stage when the drying temperature in step B is constant will be described in detail.

First, the change with time of the film surface temperature in the widthwise central portion is measured with respect to the coating liquid film formed on the support, and the relationship between the measured film surface temperature and the elapsed time is plotted by, for example, setting the film surface temperature on the vertical axis and setting the elapsed time on the horizontal axis.

In the obtained graph, a period in which the film surface temperature shows a predetermined value (specifically, a period in which the temperature change of the film surface temperature is kept within ±5 ℃) is regarded as a constant-speed drying stage in the measurement of the film surface temperature immediately after coating (immediately after forming a coating liquid film).

The change point of the film surface temperature, which changes when the film surface temperature increases, is set as the end point of the constant-speed drying stage. The change point is obtained from the intersection point of a straight line extending the film surface temperature during a predetermined period to the elapsed time side and a tangential line drawn at a point where the gradient of the film surface temperature is maximum.

Crimping restraint

In the step, in the constant-speed drying stage of the coating liquid film, the coating liquid film is restrained from coming into non-contact with the laminate composed of the support and the coating liquid film during the period in which the solid content concentration of the coating liquid film is 70 to 95 mass%.

That is, in this step, in the constant-speed drying stage (i.e., in a period in which the film surface temperature shows a predetermined value), the solid content concentration of the coating liquid film increases, and the non-contact curl of the coating liquid film is restricted from 70 mass% to 95 mass% with respect to the laminate composed of the support and the coating liquid film.

When the solid content concentration of the coating liquid film reaches 70 mass%, the solid content concentration is sufficiently high, and therefore, even if stress is applied to the coating liquid film due to curl limitation (for example, even if gas is blown out), occurrence of cracks can be suppressed.

On the other hand, in the constant-speed drying stage, by performing curl restriction until the solid content concentration of the coating liquid film reaches 95 mass%, the curl restricting effect can be improved as compared with the case where curl restriction is performed after reaching the deceleration drying stage.

Further, since the curl restriction performed in this step is not in contact with the coating liquid film, the curl restriction does not come into contact with the surface of the coating liquid film having residual fluidity in the constant-speed drying stage. As a result, the curl restriction can suppress the influence on the surface morphology, the property, and the like of the surface of the coating liquid film.

Therefore, by restricting curl at the above timing, a coating film with suppressed cracks and curl is formed.

The measurement of the solid content concentration of the coating liquid film can be obtained by measuring the non-contact thickness from the time of coating the aqueous coating liquid on the support until the aqueous coating liquid becomes a dry film using an infrared spectroscopic interferometer SI-T80 of KEYENCE CORPORATION.

Specifically, first, the non-contact thickness from the time of applying the aqueous coating liquid on the support until the aqueous coating liquid becomes a dry film is measured.

Then, the thickness of the dried film (dry film) was measured by a contact thickness gauge. The thickness of the solvent (or dispersion medium) in the coating liquid film at each measurement point is calculated by subtracting the thickness of the measured dry film from the non-contact thickness measured previously.

The solid content concentration value was obtained by multiplying the thickness of the obtained dry film and the thickness of the solvent (or dispersion medium) by the respective densities (dry film density and solvent density), and converting the obtained product into dry film weight and solvent weight per unit area of the coating liquid film at the measurement point.

The non-contact curl restriction used in this step is not particularly limited as long as it is a mechanism that can restrict the curling (i.e., warping) of the coating liquid film on the coating liquid film side at the widthwise end of the laminate of the coating liquid film and the support without contacting the coating liquid film.

From the viewpoint of excellent curl restricting ability, the noncontact curl restriction is preferably performed by a mechanism (hereinafter, also referred to as curl restricting mechanism) that ejects gas to one or both surfaces of the laminate and continuously conveys the laminate while bending the laminate in the thickness direction by the wind pressure of the gas.

The curl restricting mechanism promotes drying (i.e., increases the solid content concentration) by ejecting gas to the laminate, and therefore also functions as a part of the drying mechanism.

Curl limiting mechanism

The curl restricting mechanism will be described with reference to fig. 2 and 3. Fig. 2 and 3 are schematic side views for explaining the curl restricting mechanism in step B.

In fig. 2 and 3, 32 denotes a region before curl restriction, and 34 denotes a curl restriction region.

In the drying mechanism 30A shown in fig. 2, a curl restricting mechanism that ejects a gas onto one surface of the laminate 12 (i.e., the surface on which the coating liquid film is formed) and continuously conveys the laminate while bending the laminate in the thickness direction by the wind pressure of the gas is used in the curl restricting region 34.

In the drying mechanism 30B shown in fig. 3, a curl restricting mechanism is used in which gas is ejected to both sides of the laminate 12 (i.e., the formation surface of the coating liquid film and the exposed surface of the support) and the laminate is continuously conveyed while being bent in the thickness direction by the wind pressure of the gas.

As shown in the schematic side views of fig. 2 and 3, according to this curl restricting mechanism, the laminated body 12 can be conveyed while undulating in a wave shape. As described above, by conveying the laminate 12 while waving, curl restriction can be effectively found, and the curl suppression effect can be improved.

In addition, the drying speed of the coating liquid film can be controlled by adjusting the type, wind pressure, temperature, humidity, and the like of the gas ejected from the curl restricting mechanism.

The curl restricting mechanism shown in fig. 2 and 3 has the same curl restricting capability.

The drying mechanism 30A shown in fig. 2 will be described.

As shown in fig. 2, the laminate 12 of the coating liquid film and the support is transferred to the drying mechanism 30A, whereby the coating liquid film is dried.

In fig. 2, in the pre-curl set region 32, the solid content concentration of the coating liquid film in the laminate 12 is increased, and in the curl set region 34, curl set is started while the solid content concentration of the coating liquid film on the support 10 is 70 mass% to 95 mass%.

In the region 32 before curl restriction in fig. 2, a drying mechanism (for example, a fan heater) as described later is used to increase the solid content concentration of the coating liquid film in the laminate 12.

In the curl restricting region 34 in fig. 2, a plurality of transfer rollers 36 are arranged in parallel on the same plane on the support body side, and a plurality of discharge portions 38 for discharging gas are arranged in parallel on the same plane between the positions where the transfer rollers 36 are arranged on the coating liquid film side.

The gas (for example, air at 40 ℃) is ejected from the ejection section 38 toward the laminate 12, and the transfer roller 36 rotates, whereby the laminate 12 is transferred while being bent in the thickness direction thereof by the wind pressure of the gas.

The drying mechanism 30B shown in fig. 3 will be described.

As shown in fig. 3, the laminate 12 of the coating liquid film and the support is transferred to the drying mechanism 30B, whereby the coating liquid film is dried.

In fig. 3, in the pre-curl set region 32, the solid content concentration of the coating liquid film in the laminate 12 is increased, and in the curl set region 34, curl set is started while the solid content concentration of the coating liquid film on the support 10 is 70 mass% to 95 mass%.

In the region 32 before curl restriction in fig. 3, a drying mechanism (for example, a fan heater) as described later is used to increase the solid content concentration of the coating liquid film in the laminate 12.

In the curl restricting region 34 in fig. 3, a plurality of gas-discharge portions 38a are provided in parallel on the same plane on the support side, and a plurality of gas-discharge portions 38b are provided in parallel on the same plane between the positions where the gas-discharge portions 38a are provided on the application liquid film side.

The gas (for example, air at 40 ℃) is ejected from the ejection portion 38a toward the laminated body 12, and the gas (for example, air at 40 ℃) is ejected from the ejection portion 38b toward the laminated body 12, whereby the laminated body 12 is conveyed while being bent in the thickness direction thereof by the wind pressure of the gas.

The curl restricting region 34 in fig. 2 and 3 may be provided at a position where curl restriction is started during a period in which the solid content concentration of the coating liquid film of the transferred laminate 12 is 70 mass% to 95 mass%.

The change in the solid content concentration of the coating liquid film can be investigated in advance, and the installation position of the curl limit region 34 can be set based on the difference adjustment result.

Further, by determining the installation position of the curl restricting region 34 and appropriately adjusting the conveyance speed of the laminate 12, the drying conditions of the region 32 before curl restricting, and the like, the drying state of the coating liquid film can be controlled so that the solid content concentration of the coating liquid film becomes in the range of 70 mass% to 95 mass% when reaching the curl restricting region 34.

In addition, the end point of the curl restricting region 34 is preferably, for example, up to between the outlets of the drying mechanism 30A or 30B. That is, curl limit region 34 preferably continues from a constant speed drying stage to a retarded drying stage.

In the curl restricting region 34 in fig. 2 and 3, air or the like is used as a gas to be ejected toward the laminate 12.

The temperature of the gas to be discharged is, for example, preferably 25 to 200 ℃, more preferably 30 to 150 ℃.

The wind speed of the gas to be discharged is preferably, for example, 1.5 m/sec to 50 m/sec.

In addition, the deformation amount of the laminated body 12 in the curl restricting region 34 can be adjusted.

As shown in fig. 2 and 3, when the laminated body 12 is viewed from the side, there are a distance p between the mountain and the adjacent mountain in the laminated body 12, and a height difference h between the mountain and the valley in the laminated body 12, as the deformation amount of the laminated body 12. The distance p is equal to the distance between the conveying rollers 36 or the distance between the ejection portions 38b.

The distance p is, for example, preferably 100mm to 1500mm, more preferably 200mm to 1000mm.

The height difference h is preferably 10 to 500mm, more preferably 20 to 200mm.

Further, since the curl restricting force increases as the value of the distance p/height difference h is smaller, it is preferably 10 or less, more preferably 5 or less. If the value of the distance p/step h is reduced, the number of components in the curl limit area 34 increases or the size thereof increases, and therefore, the lower limit value of the distance p/step h is preferably set optimally in consideration of the installation space, the air suction capability, the cost, and the like. The lower limit value of the distance p/height difference h is, for example, 2.

Membrane surface temperature-

The film surface temperature in the constant-speed drying stage is not particularly limited, and may be, for example, 35 ℃ or higher.

Drying-

In this step, a known drying mechanism is applied to dry the coating liquid film.

As the drying means (for example, a part of the drying means 30 in fig. 1, and drying in the region before the curl restriction in fig. 2 and 3), specifically, an oven, a fan heater, an Infrared (IR) heater, and the like are given.

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

The thickness of the coating film obtained in the step B is not particularly limited as long as it is a 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 even more preferably 60 μm or more, from the viewpoint of easiness of occurrence of cracks and curling.

The upper limit of the thickness of the coating film is not particularly limited as long as it is determined according to the application, and is, for example, 65 μm.

The thickness of the coating film was measured as same as that of the coating liquid film.

[ other procedures ]

At least one of the steps a and B may have other steps as needed.

The other steps are not particularly limited, and examples thereof include a pretreatment step performed before applying a coating liquid film, a post-treatment step performed on a formed coating film according to the application of the coating film, and the like.

The other steps include, specifically, a step of surface-treating the support, a step of hardening the coating film, a step of compressing the coating film, a step of cutting the coating film, a step of peeling the support from the coating film, and the like.

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, and is therefore suitable for producing a coating film for applications requiring high productivity.

Examples

The present invention will be described in more detail with reference to the following examples. The materials, amounts used, proportions, details of the steps and the like shown in the following examples can be appropriately changed without departing from the spirit of the present invention. Accordingly, the scope of the present invention is not limited to the specific examples shown below.

In addition, "parts" are mass references.

Preparation of support body

An aluminum support 1 (thermal conductivity: 230W/(mK)) having a width of 220mm, a thickness of 10 μm and a length of 300m (abbreviated as AL 1) was prepared.

An aluminum support 2 (thermal conductivity: 230W/(mK)) having a width of 220mm, a thickness of 30 μm and a length of 300m (abbreviated as AL 2) was prepared.

Preparation of aqueous coating liquid

[ preparation of aqueous coating solution A1 and A2 ]

The following components were mixed to prepare an aqueous coating liquid a. Then, the aqueous coating liquid a was diluted with pure water to prepare an aqueous coating liquid A1 having a solid content of 60 mass% and an aqueous coating liquid A2 having a solid content of 30 mass%, respectively.

Polyvinyl alcohol: 58 parts of

( CKS-50: saponification degree 99 mol%, polymerization degree 300, nippon Synthetic Chemical Industry co., ltd. )

DKS co.ltd.cellogenpr:24 parts of

Surfactant NIHON EMULSION co., ltd., EMALEX 710): 5 parts of

An aqueous dispersion of ART PEARL J-7P prepared by the method of: 913 parts of

(Water-dispersible product of ART PEARL J-7P)

To 74 parts of pure water, 3 parts of dissolved EMALEX 710NIHON EMULSION Co, ltd, nonionic surfactant) and 3 parts of carboxymethyl cellulose (DKS co.ltd.) were added. To the obtained aqueous solution, 20 parts of ART PEARL (registered trademark) J-7P (Negami Chemical Industrial Co., ltd., silica composite crosslinked acrylic resin fine particles) was added, and dispersed at 10,000 rpm (revolutions per minute; the same applies hereinafter) for 15 minutes by an ACE homogenizer (NIHONSEIKI KAISHA LTD.) to obtain an aqueous dispersion (particle concentration: 20 mass%) of ART PEARL J-7P.

The silica composite crosslinked acrylic resin fine particles in the obtained water dispersion had a true specific gravity of 1.20 and an average particle diameter of 6.5. Mu.m.

[ preparation of aqueous coating liquid B1 ]

The following ingredients were mixed and stirred by a dissolver (2000 rpm, 30 minutes), to prepare an aqueous coating liquid B (dispersion a: dispersion b=25:75). The viscosity of the aqueous coating liquid B was 20 mPas, and the average particle diameter of the particles was 0.108. Mu.m. Then, the aqueous coating liquid B was diluted with ion-exchanged water (or pure water) to adjust the solid content concentration to 30 mass%, and this was used as the aqueous coating liquid B1.

Dispersion a prepared by the following method: 132.1 parts

Dispersion B prepared by the following method: 396.2 parts

Boric acid (crosslinker): 2.94 parts

Polyvinyl alcohol (7.3 mass% aqueous solution): 230.7 parts of

(KURARAY co., ltd., PVA 235, saponification degree 88%, polymerization degree 3500)

Diethylene glycol monobutyl ether: 2.7 parts of

(butisenol 20-P、KH Neochem Co.,Ltd.)

Ion-exchanged water: 93.5 parts

Polyoxyethylene lauryl ether (surfactant): 0.49 part

(10 mass% aqueous solution of EMULGEN 109P, HLB value 13.6, kao Corporation)

Ethanol: 41.4 parts

(preparation of Dispersion A)

After the following ingredients were mixed and ultrasonically dispersed, the dispersion was heated to 30 ℃ and held for 8 hours to prepare a dispersion a.

Fumed silica particles (inorganic particles): 299.6 parts

(AEROSIL 300SF75、NIPPON AEROSIL CO.,LTD.)

Ion-exchanged water: 1400 parts

Alphain83 (40.0 mass% aqueous solution): 300 parts of

(dispersant, TAIMEI CHEMICALS co., ltd.)

(preparation of Dispersion B)

After the following ingredients were mixed and ultrasonically dispersed, the dispersion was heated to 30 ℃ and held for 8 hours to prepare a dispersion B.

Fumed silica particles (inorganic particles): 225.2 parts

(AEROSIL 300SF75、NIPPON AEROSIL CO.,LTD.)

Ion-exchanged water: 1185 parts

Cationic polymer a (25 mass% aqueous solution) of the following structure: 90 parts of

[ chemical formula 1]

Example 1

With the apparatus configured as shown in fig. 1, a coating film is formed by applying an aqueous coating liquid A1 onto an aluminum support 1 (i.e., AL 1), and the formed coating film is dried to obtain a coating film.

Specifically, the aqueous coating liquid A1 is applied to the continuously conveyed support AL1 at a coating width of 200mm (step a). The thickness of the formed coating liquid film is shown in table 1.

Next, the coating liquid film obtained in step a was dried using the curl restricting mechanism described in table 1 while transferring the laminate 12 of the coating liquid film and the support to the drying mechanism 30A shown in fig. 2 (step B).

In the curl restricting region 34 in the drying mechanism 30A shown in fig. 2, gas is ejected to one surface of the laminated body 12 (i.e., the surface on which the coating liquid film is formed), and the laminated body is continuously conveyed while being bent in the thickness direction by the wind pressure of the gas (one surface floats in table 1). The conditions of curl restriction in the curl restricting area 34 are as follows.

Type of gas: air-conditioner

Temperature of gas: 40 DEG C

Wind pressure of gas sprayed to the forming surface of the coating liquid film: 1.3kPa

Air volume of gas ejected to the formation surface of the coating liquid film: 5m ³ /min

Deformation amount of the laminate: distance p in fig. 2: 300mm, height difference h in fig. 2: 60mm, distance p/height difference h:5

The solid content concentration of the coating liquid film at the start of curl restriction is shown in table 1, and the solid content concentration of the coating liquid film at the end of curl restriction is 99 mass%.

The conveyance speed of the support in the steps a and B was 3.0 m/min.

The coating film is formed as described above through the steps a and B.

Examples 2 to 15 and comparative examples 1 to 10

A coating film was formed in the same manner as in example 1, except that the type of support, the type and solid concentration of the coating liquid, the thickness of the coating liquid film, and the solid concentration of the coating liquid film at the start of curl restriction were appropriately changed as shown in table 1.

[ evaluation of cracking of coating film ]

With respect to the coating films obtained in each example, the measurement samples were sheared from the central portions in the width direction and the long side direction. The size of the sheared measurement sample was a square of 50mm by 50 mm.

The surface of the sample was observed with a 50-fold microscope to confirm the presence or absence of cracks having a diameter of 0.5mm to 2mm, and the cracks were evaluated according to the following criteria.

Evaluation index-

A: without cracks (i.e. no cracks)

B: check (i.e., crack) of 1mm or less

C: check (i.e. crack) exceeding 1mm

The results are shown in Table 1.

[ evaluation of curl of coating film ]

With respect to the coating films obtained in each example, a measurement sample including the width-direction side portions of the coating film was cut from the center portion in the long-side direction. The size of the sheared measurement sample was a rectangle of 3.5mm by 35 mm.

As shown in fig. 4, a measurement sample (i.e., the laminate 14 of the coating film and the support) was left standing on a flat table 40, the floating (i.e., the curl amount C) of the portion corresponding to the widthwise side portion of the coating film was measured at 3, the arithmetic average of the values at 3 was obtained, and the curl was evaluated according to the following index.

In addition, the measurement is carried out in an environment with the temperature of 23-25 ℃ and the relative humidity of 45-55%.

Evaluation index-

A: floating to less than 1mm

B: the floating is more than 1mm and less than 2mm

C: floating to more than 2mm

TABLE 1

As is clear from table 1, according to the method for producing a coating film of the example, a coating film having no cracks and little curl was formed.

The entire disclosure of japanese patent application 2020-073689 filed on 4 months and 16 days 2020 is incorporated herein by reference. All documents, patent applications and technical standards described in this specification are incorporated by reference into this specification to the same extent as if each document, patent application and technical standard was specifically and individually described to be incorporated by reference.

Symbol description

10-support, 12-coating liquid film and support laminate, 14-coating film and support laminate, 20-coating mechanism, 30A, 30B-drying mechanism, 32-curl pre-limit area, 34-curl limit area, 36-conveying roller, 38a, 38B-ejection section, 40-bench, C-curl amount, h-height difference of mountain and valley (height difference of the waves), p-mountain distance of adjacent mountain (interval of the waves).

Claims

1. A method for producing a coating film, comprising:

step A, continuously conveying a long support, and coating an aqueous coating liquid on the continuously conveyed support; and

in the constant-speed drying stage of the coating liquid film in the step B, the coating liquid film is restrained from starting to be curled in a non-contact manner relative to the laminate composed of the support and the coating liquid film during the period when the solid content concentration of the coating liquid film is 70 to 95 mass%,

the term "non-contact curl control" means that the coating liquid film is not in contact with the coating liquid film, and the widthwise end of the laminate of the coating liquid film and the support can be controlled to curl on the coating liquid film side,

the "aqueous coating liquid" refers to a coating liquid in which the ratio of water in the total solvent or the total dispersion medium contained in the coating liquid is 90 mass% or more,

the "drying" in the step B means that the coating liquid film formed in the step a is subjected to a constant-speed drying stage and a deceleration drying stage until the target solid content concentration is reached.

2. The method for producing a coated film according to claim 1, wherein,

the solid content concentration of the coating liquid in the step A is 30 to 60 mass%.

3. The method for producing a coated film according to claim 1 or 2, wherein,

the aqueous coating liquid is a coating liquid containing particles.

4. The method for producing a coated film according to claim 1 or 2, wherein,

the non-contact curl limitation is performed by the following means:

the laminate is continuously conveyed while being bent in the thickness direction by the air pressure of the air by blowing the air toward one or both surfaces of the laminate.

5. The method for producing a coated film according to claim 1 or 2, wherein,

the support body is a metal support body.

6. The method for producing a coated film according to claim 1 or 2, wherein,

the thickness of the support is 10-30 μm.