KR20240096346A - Method for manufacturing coating film and method for manufacturing optical film - Google Patents

Abstract

The method includes the processes of: forming an uncured coating film (8) by applying a material solution to a base material (7) having a long strip shape while continuously conveying the base material (7) from an upstream side to a downstream side in a conveying direction; and drying the uncured coating film (8) by conveying the base material (7) having the uncured coating film (8) formed thereon to a drying zone (Z3). The drying zone (Z3) includes: a wind drying zone (Z31) for wind-drying the uncured coating film (8); and a drying relaxation zone (Z32), which is a zone provided downstream of the wind drying zone (Z31), and is provided with a shielding surface part (4) disposed to face the surface of the uncured coating film (8) at a predetermined interval. The wind drying zone (Z31) sprays wind to the surface of the uncured coating film (8) along the downstream direction; and a transport speed AS of the base material (7) and a wind velocity BS of the wind satisfy a relationship of 1<=AS/BS<=50.

Description

Method for producing a coating film, and a method for producing an optical film {METHOD FOR MANUFACTURING COATING FILM AND METHOD FOR MANUFACTURING OPTICAL FILM}

The present invention relates to a method of manufacturing a coating film, etc., which continuously forms an arbitrary coating film on the surface of a substrate.

A method of forming a coating film on the surface of a long strip-shaped substrate, wherein a material solution is applied to the surface of the substrate while the substrate is being transported to form an uncured coating film, the uncured coating film is dried, and then the uncured coating film is formed. Hardening is being done.

For example, in Patent Document 1, a coating liquid having a viscosity of 0.05 Pa·s to 500 Pa·s is applied to a substrate, and then gas at a wind speed of 8 m/sec to 50 m/sec is sprayed onto the coating film along the running direction of the substrate. Drying is disclosed.

Patent Document 1 discloses that an optical film with excellent uniformity in thickness and optical function is obtained by forming a coating film using a coating liquid of the above-mentioned viscosity and spraying the above-described gas onto the coating film.

Japanese Patent Publication No. 2005-215210

However, according to the research of the present inventors, there is a risk that stripe-shaped unevenness may occur on the surface of the coating film in the method of Patent Document 1.

The purpose of the present invention is to provide a method for suppressing the unevenness of an uncured coating film and producing a coating film with excellent surface smoothness and a method for producing an optical film.

The method for producing a coating film according to the first aspect of the present invention includes the steps of forming an uncured coating film by applying a material solution to a long strip-shaped substrate while continuously conveying it from the upstream side of the conveyance direction to the downstream side of the conveyance direction, An air-drying zone comprising a step of transporting the base material on which the uncured coating film is formed to a drying zone and drying the uncured coating film, wherein the drying zone air-dries the uncured coating film, and a zone installed on the downstream side of the air-drying zone. It has a drying relief zone provided with shielding surface portions opposed to each other at a predetermined interval with respect to the surface of the uncured coating film, and the air drying zone sprays wind along the downstream side of the conveyance direction with respect to the surface of the uncured coating film, The conveyance speed AS of the substrate and the wind speed BS of the wind satisfy the relationship of 1≤AS/BS≤50.

The manufacturing method of the coating film according to the second aspect of the present invention is the manufacturing method of the first form, wherein the transport length L1 of the substrate from the application point where the material solution is applied to the substrate to the shielding surface portion is exceeds 0 m and is 3 m or less, the shielding surface portion is arranged at a distance H of 50 mm to 150 mm from the surface of the uncured coating film, and the length L2 of the shielding surface portion is 0.5 m to 2 m, and the uncured coating film The thickness D of and the length L2 of the shielding surface portion satisfy the relationship of 0.5≤D/L2≤50.

The method for producing a coating film according to the third aspect of the present invention includes the steps of forming an uncured coating film by applying a material solution to a long strip-shaped substrate while continuously conveying it from the upstream side of the conveyance direction to the downstream side of the conveyance direction, An air-drying zone comprising a step of transporting the base material on which the uncured coating film is formed to a drying zone and drying the uncured coating film, wherein the drying zone air-dries the uncured coating film, and a zone installed on the downstream side of the air-drying zone. It has a drying relief zone in which shielding surface portions are disposed facing each other at a predetermined interval with respect to the surface of the uncured coating film, and the transport length of the substrate from an application point where the material solution is applied to the substrate to the shielding surface portion. L1 exceeds 0 m and is 3 m or less, the shielding surface portion is arranged at a distance H of 50 mm or more and 150 mm or less from the surface of the uncured coating film, and the length L2 of the shielding surface portion is 0.5 m or more and 2 m or less, and the The thickness D of the cured coating film and the length L2 of the shielding surface portion satisfy the relationship of 0.5≤D/L2≤50.

The manufacturing method of the coating film according to the fourth aspect of the present invention is the manufacturing method of any one of the first to third aspects, comprising the step of curing the uncured coating film to form a coating film after the drying process. have

According to another aspect of the present invention, a method for manufacturing an optical film is provided.

In the method for producing an optical film of the present invention, at least one of the coating film and the base material of the fourth aspect has an optical function.

According to the production method of the present invention, the occurrence of unevenness in the uncured coating film can be suppressed, and therefore a coating film with excellent surface smoothness can be obtained. A film having such a coating film with excellent surface smoothness can be favorably used as an optical film.

1 is a schematic side view showing a coating film manufacturing apparatus.
Figure 2 is a schematic plan view of the device.
Figure 3 is a cross-sectional view taken along line III-III in Figure 2.
Figure 4 is a cross-sectional view taken along line IV-IV in Figure 2.

In this specification, the expression “approximately” means including the range permitted in the technical field of the present invention. In addition, in this specification, when multiple numerical ranges expressed as "lower limit Make it something that can be set.

[Overview of the method for producing the coating film of the present invention]

The manufacturing method (forming method) of a coating film of the present invention includes the steps of forming an uncured coating film by applying a material solution to a long strip-shaped substrate while continuously conveying it from the upstream side in the conveyance direction to the downstream side in the conveyance direction; An air-drying zone comprising a step of transporting the base material on which the uncured coating film is formed to a drying zone and drying the uncured coating film, wherein the drying zone air-dries the uncured coating film, and a zone installed on the downstream side of the air-drying zone. It has a dry relief zone in which shielding surface parts are disposed facing each other at a predetermined interval with respect to the surface of the uncured coating film.

The first characteristic point of the manufacturing method of the present invention is that the wind drying zone sprays wind with a predetermined wind speed along the downstream side of the conveyance direction with respect to the surface of the uncured coating film, so that the conveyance speed AS of the substrate and the wind velocity BS of the wind are It satisfies the relationship of 1≤AS/BS≤50 (hereinafter, this may be referred to as the “first feature point”).

The second characteristic point of the present invention is that the transport length L1 of the substrate from the application point at which the material solution is applied to the substrate to the shielding surface portion exceeds 0 m and is 3 m or less, and the shielding surface portion is the uncured coating film. are arranged at a distance H of 50 mm or more and 150 mm or less from the surface, and the thickness D of the uncured coating film and the length L of the shielding surface portion satisfy the relationship of 0.5≤D/L2≤50 (hereinafter referred to as “ (sometimes referred to as “second feature point”).

<Description>

The base material has a long strip shape in terms of shape when viewed in plan view. The elongated strip shape refers to a substantially rectangular shape when viewed in a plane where the length in the longitudinal direction is sufficiently longer than the width direction. Long strip-shaped substrates are usually rolled up into rolls and stored and transported. The base material wound into a roll shape is unwound in the longitudinal direction when forming a coating film thereon.

From the viewpoint of layer structure, the layer structure of the substrate may be a single layer or a multiple layer structure. When the base material is multi-layered, the number of layers is 2 or more. There is no particular upper limit, but it is generally 10 or less.

The single-layer substrate consists of a film having an optical function (hereinafter referred to as an optical function film) or a film other than the optical function film. Examples of the optical function film include a polarizing film, retardation film, anti-reflection film, light diffusion film, brightness enhancement film, and light reflection film. The polarizing film is a film that has the property of transmitting light (polarized light) vibrating in a specific direction and blocking light vibrating in other directions. The retardation film is a film that exhibits optical anisotropy, and representative examples include stretched films of acrylic resin, cycloolefin resin, and cellulose resin. Films other than optical function films include colorless and transparent resin films.

The multi-layer base material includes a laminated film in which multiple optical function films are laminated, a laminated film in which multiple films other than the optical function film are laminated, one layer or multiple layers of the optical function film, and a film other than the single or multiple layers of the optical function film. These laminated laminated films, etc. can be mentioned.

The thickness of the base material is not particularly limited, and is, for example, 50 μm or more and 300 μm or less.

<Material solution>

The material solution is the forming material of the coating film. The material solution is appropriately set depending on the type of coating film to be formed.

The material solution contains an active ingredient and a solvent that dissolves or disperses the active ingredient.

The active ingredient is an ingredient that forms a coating film, and includes various polymers and any appropriate additives. For example, when forming a coating film with an optical function, a material solution containing an active ingredient and/or an additive that expresses an optical function as an active ingredient of the material solution is used.

Depending on the type of curing, examples of the polymer include active energy ray curing type, thermosetting type, and solvent volatilization type. Reactive polymers, such as active energy ray curing type or thermosetting type, are cured by polymerizing monomers or oligomers by irradiation of active energy rays (ultraviolet rays, electron beams, etc.) or heat. In addition, the reactive polymer is generally in the state of a monomer or oligomer before curing (before reaction), but the monomer or oligomer before this curing is also called a reactive polymer for convenience. The solvent volatilization type polymer hardens by volatilization of the solvent and entanglement and orientation of the polymers.

The solvent is not particularly limited as long as it is a liquid that can dissolve or disperse the active ingredient. Solvents are roughly divided into hydrophobic solvents such as organic solvents; water; Hydrophilic solvents may be mentioned. Examples of organic solvents include tetrahydrofuran (THF); dioxane; cyclohexanone; n-hexane; Toluene, etc. can be mentioned. Hydrophilic solvents are solvents that dissolve approximately uniformly in water, and examples include alcohols such as methanol and isopropyl alcohol; Glycols such as ethylene glycol; Cellosolves such as methyl cellosolve and ethyl cellosolve; Ketones such as acetone and methyl ethyl ketone; Ester, such as ethyl acetate, etc. are mentioned. The solvent may be one type selected from these, or two or more types may be used in combination. Additionally, the solvent may be a combination of at least one type selected from the above organic solvents and at least one type selected from hydrophilic solvents.

For example, the material solution includes an active energy ray-curable polymer, a solvent that dissolves the polymer, and additives mixed in appropriate amounts as needed.

The active energy ray-curable polymer can be broadly divided into electron beam-curable type, ultraviolet ray-curable type, and visible light-curable type. In addition, active energy ray-curable polymers can be roughly divided into radically polymerizable compounds and cationically polymerizable compounds from the viewpoint of the curing mechanism.

Examples of the radically polymerizable compound include compounds having a radically polymerizable functional group of a carbon-carbon double bond, such as a (meth)acryloyl group and a vinyl group. Additionally, either a monofunctional radically polymerizable compound or a bifunctional or more polyfunctional radically polymerizable compound can be used. In addition, these radically polymerizable compounds may be used individually or in combination of two or more types. As the radically polymerizable compound, a compound having a (meth)acryloyl group is preferable, for example, a (meth)acrylamide derivative having a (meth)acrylamide group, (meth)acryloyloxy group having a (meth)acryloyloxy group. Rates, etc. can be mentioned.

When using a radically polymerizable compound, the polymerization initiator is appropriately selected depending on the active energy ray. When curing the adhesive with ultraviolet rays or visible rays, a polymerization initiator for ultraviolet ray cleavage or visible ray cleavage is used. Examples of such polymerization initiators include benzophenone-based compounds, aromatic ketone compounds, acetophenone-based compounds, aromatic ketal-based compounds, aromatic sulfonyl chloride-based compounds, and thioxanthone-based compounds.

Examples of the cationically polymerizable compound include monofunctional cationically polymerizable compounds having one cationically polymerizable functional group in the molecule, polyfunctional cationically polymerizable compounds having two or more cationically polymerizable functional groups in the molecule, and the like. Examples of the cationically polymerizable functional group include an epoxy group, oxetanyl group, and vinyl ether group. Examples of cationically polymerizable compounds having an epoxy group include aliphatic epoxy compounds, alicyclic epoxy compounds, and aromatic epoxy compounds. Examples of cationically polymerizable compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, and 3-ethyl- 3-(phenoxymethyl)oxetane, etc. can be mentioned. Examples of cationically polymerizable compounds having a vinyl ether group include 2-hydroxyethyl vinyl ether, diethylene glycol monovinyl ether, and 4-hydroxybutyl vinyl ether.

When using a cationically polymerizable compound, a cationic polymerization initiator is blended. This cationic polymerization initiator generates cationic species or Lewis acids by irradiation of active energy rays such as visible light, ultraviolet rays, and electron beams, and initiates a polymerization reaction with the epoxy group of the cationically polymerizable compound. As a cationic polymerization initiator, a photoacid generator and a photobase generator can be used.

The viscosity of the material solution is not particularly limited, but if it is too small or too large, there is a risk of uneven application when applying the material solution to the substrate. From this point of view, the viscosity of the material solution at 23°C is, for example, 0.002 Pa·s or more and 1.0 Pa·s or less, and preferably 0.01 Pa·s or more and 0.5 Pa·s or less. A material solution in the above viscosity range can be obtained mainly by adjusting the amount of solvent.

The viscosity of the material solution refers to the value measured using a commercially available E-type viscometer at 25°C.

[Coating film manufacturing device and coating film manufacturing method]

1 to 4 show an example of a coating film production apparatus 9 for carrying out the method of the present invention. FIG. 1 is a schematic side view of the coating film manufacturing apparatus 9, and FIG. 2 is a plan view thereof. In FIG. 2, only the drying zone Z3 of the coating film manufacturing apparatus 9 is shown. Figures 3 and 4 are cross-sectional views taken along lines III-III and lines IV-IV, respectively, of Figure 2. In Figure 3, only the wind dry zone (Z31) is shown, and in Figure 4, only the dryness relief zone (Z32) is shown.

In this specification, in the description of the coating film manufacturing apparatus and the coating film manufacturing method, the longitudinal direction of the substrate is referred to as the “conveyance direction”, and the side on which the substrate is transported is referred to as the “conveyance direction downstream side” or “downstream side.” The opposite side is called “conveyance direction upstream side” or “upstream side.” The width direction of the substrate refers to a direction perpendicular to the conveyance direction within the plane of the substrate.

When divided into zones, the coating film manufacturing apparatus 9 includes an unwinding zone Z1 for unwinding a base material wound into a roll shape in order from the upstream side in the conveyance direction toward the downstream side, and a material solution is applied to the surface of the base material. An application zone (Z2) for forming an uncured coating film, a drying zone (Z3) for drying the uncured coating film formed on the surface of the substrate, and a curing zone (Z4) for forming a coating film by curing the dried uncured coating film. and a winding zone Z5 for winding up the base material having the coating film (completely cured coating film).

The drying zone Z3 is an air-drying zone Z31 that air-dries the uncured coating film in order from the upstream side to the downstream side in the conveyance direction, and a drying relief zone that allows drying of the uncured coating film while preventing rapid drying thereof. (Z32) and a heat drying zone (Z33) for drying the uncured coating film by heat. The heat drying zone (Z33) is arranged as needed.

Additionally, if necessary, there may be a zone for performing arbitrary processing between each of the above zones (not shown). The above optional treatments include (a) laminating any film on the substrate, (b) peeling any film from the substrate, (c) forming any layer on the substrate, (d) stretching the substrate, etc. can be mentioned. For example, between the unwinding zone Z1 and the application zone Z2, there may be a zone for peeling any film from the substrate. Additionally, between the curing zone Z4 and the winding zone Z5, a zone for bonding an arbitrary film to the substrate may be provided.

To explain the mechanical components, the coating film manufacturing device 9 includes a conveying device 1 that conveys the base material 7 from the unwinding section 11 to the winding section 12, and an application device 2 that applies the material solution. ), a blower 3 that sprays wind on the uncured coating film 8, a shielding surface portion 4 that alleviates drying of the uncured coating film 8, and heat that heat-dries the uncured coating film 8. It has a drying device (5) and a curing device (6) that cures the uncured coating film (8).

<Unwinding zone, winding zone and conveying device>

The unwinding zone Z1 is located at the most upstream side, and the unwinding zone Z5 is located at the most downstream side. A roll-shaped base material 7 is loaded into the unwinding section 11 installed in the unwinding zone Z1. The substrate 7 loaded in the unwinding section 11 is unwound by the conveying device 1, and sequentially conveyed to the application zone (Z2), drying zone (Z3), and curing zone (Z4), and then to the unwinding zone ( It is wound on the winding unit 12 installed at Z5).

The conveying device 1 is conventionally known and has drive rolls, guide rolls, etc. The conveying device 1 continuously conveys the long strip-shaped substrate 7 from the upstream side to the downstream side at a predetermined conveying speed. The conveyance speed AS [m/min] of the base material 7 is set appropriately, for example, 5 m/min or more and 40 m/min or less, and preferably 10 m/min or more and 35 m/min or less.

<Application zone and uncured film formation process>

An application device 2 is installed in the application zone Z2. In the application zone Z2, the conveying device 1 continuously applies the material solution to the surface of the substrate 7 that is continuously conveyed from the upstream side in the conveying direction to the downstream side in the conveying direction. By applying the material solution, an uncured coating film 8 is formed on the surface of the substrate 7 (formation process).

The thin film-like material solution applied on the substrate 7 is the uncured coating film 8. The uncured coating film 8 is formed on approximately the entire surface of the substrate 7.

The coating device 2 is not particularly limited, and a conventionally known one can be used. For example, examples of the coating device 2 include a die coater, a gravure coater, a reverse coater, and a bar coater. The illustrated example illustrates a die coater.

The thickness D of the uncured coating film 8 is not particularly limited, and is, for example, 0.1 μm or more and 50 μm or less, and preferably 0.5 μm or more and 30 μm or less.

<Drying zone and drying process>

In the drying zone Z3, the excess solvent contained in the uncured coating film 8 is volatilized and the uncured coating film 8 is dried (drying process).

The drying zone Z3 in the illustrated example has an air drying zone Z31, a drying relief zone Z32, and a heat drying zone Z33.

(Wind dry zone)

A blowing device (3) is installed in the air drying zone (Z31).

The blower 3 is a device that blows wind onto the surface of the uncured coating film 8 formed on the base material 7. Here, wind refers to the flow of gas moving in a certain direction. The blower 3 forcibly generates wind and causes it to act on the surface of the uncured coating film 8. The blower 3 blows wind toward the downstream side in the conveyance direction to the surface of the uncured coating film 8.

The blower 3 is disposed in a zone between the application device 2 and the shielding surface portion 4 described later. The blower 3 is fixed to a frame (not shown) of the coating film production device 9 or the like.

The blowing device 3 includes a blower such as a blower (not shown), a nozzle part 32 having an outlet 31 for blowing out wind, and a blowing pipe 33 connecting the blower and the nozzle part 32 ( (some parts are omitted).

The jet port 31 of the nozzle portion 32 is directed toward the surface side of the uncured coating film 8 of the substrate 7 to be transported. The jet port 31 of the nozzle portion 32 may be a slit-shaped opening extending in the width direction of the substrate 7, or may be a spot-shaped opening. When the jet port is a point-shaped opening, a plurality of nozzle parts are arranged in the width direction of the base material 7 (not shown). The jet port 31 of the nozzle portion 32 in the illustrated example is slit-shaped (see Fig. 3) and extends in the width direction of the base material 7. The width of the jet port 31 (length of the jet port 31 corresponding to the width direction of the base material 7) may be smaller than the width of the base material 7 (length in the width direction of the base material 7). In order to spray wind approximately evenly over the entire surface of the uncured coating film 8, as shown in the illustration, the width of the jet nozzle 31 is larger than the width of the base material 7 or is approximately equal to the width of the base material 7. It is desirable. In the case of the jet port 31 being larger than the width of the base material 7, both ends of the jet port 31 in the width direction protrude outward from both edges in the width direction of the base material 7.

The angle of blowing wind by the blower 3 is not particularly limited, but if the angle is too large, there is a risk that wind along the downstream side of the conveyance direction cannot be blown onto the surface of the uncured coating film 8. From this point of view, the wind blowing angle θ is 45 degrees or less, and preferably 30 degrees or less. Additionally, the lower limit of the wind blowing angle θ exceeds 0 degrees, and is preferably 5 degrees or more.

The wind blowing angle θ is the internal angle formed between the direction of the wind and the uncured coating film 8 when viewed from the side shown in FIG. 1. In addition, since the wind coming out of the blower outlet 31 spreads, the direction of the wind is at a design point P2 on the surface of the uncured coating film 8 (the design point P2 is at a certain point on the surface of the uncured coating film 8). Refers to the direction where the wind direction of the air drying device is designed with the intention of hitting the center of the wind) and the outlet 31 are connected.

The location P2 in the design is located upstream in the conveyance direction from the shielding surface portion 4 described later. From the viewpoint of preventing the wind generated by the blower 3 from entering between the shielding surface portion 4 and the uncured coating film 8, the design point P2 is, for example, from the front end 4a of the shielding surface portion 4. It is a range of 20 cm to 300 cm upstream in the conveyance direction, and preferably is a range of 50 cm to 150 cm upstream in the conveyance direction from the front end 4a of the shielding surface portion 4. That is, the design point P2 facing the wind and the length L3 (see Fig. 1) of the front end 4a of the shielding surface portion 4 are within the above range.

The wind speed BS [m/sec] of the wind is set appropriately. From the viewpoint of suppressing unevenness on the surface of the uncured coating film 8 due to air drying in the air drying zone Z31, the wind speed BS [m/sec] by the blower 3 is the conveyance speed of the base material 7. It is desirable to set it considering the relationship with AS [m/min]. Specifically, the conveying speed AS [m/min] of the substrate 7 and the wind speed BS [m/sec] of the substrate 7 are adjusted to satisfy the relationship of 1≤AS/BS≤50. It is desirable to spray wind onto the surface of the cured coating film 8. In addition, the uncured coating film of the substrate 7 to be conveyed such that the conveyance speed AS [m/min] of the substrate 7 and the wind speed BS [m/sec] satisfy the relationship of 2≤AS/BS≤50. It is more preferable to spray wind on the surface of (8). The specific value of wind speed BS is, for example, 0.3 m/sec or more and 50 m/sec or less.

In addition, the wind from the blower 3 is not particularly heated, and the temperature of the wind is the ambient temperature of the place where the coating film production device 9 is installed. The gas (wind) blown out from the blower 3 is arbitrary, for example, the atmosphere of the place where the coating film production device 9 is installed.

(Dryness relief zone)

A shielding surface portion 4 is installed in the dry relief zone Z32. The shielding surface portion 4 cooperates with the base material 7 to define a space S in which the volatilized solvent resides at a high concentration between the shielding surface portion 4 and the uncured coating film 8. By forming the space S between the uncured coating film 8 and the shielding surface portion 4, it is possible to prevent rapid drying while allowing drying (volatilization of the solvent) of the uncured coating film 8. there is. Preventing rapid drying while allowing this drying is sometimes called “drying relief.” In addition, volatilization refers to the solvent in the uncured coating film 8 vaporizing and being ejected from the uncured coating film 8.

The shielding surface portion 4 is disposed opposite to the surface of the uncured coating film 8 of the substrate 7 to be transported. The shielding surface portions 4 are arranged opposite to the surface of the uncured coating film 8 at a predetermined interval.

The gap H between the surface of the shielding surface portion 4 and the uncured coating film 8 is appropriately set. This gap H affects the size of the space S where the volatilized solvent stays at a high concentration. If it is too large, there is no point in providing the shielding surface portion 4, and if it is too small, the space S ), the concentration of volatilized solvent becomes excessively high. From this viewpoint, the distance H between the shielding surface portion 4 and the surface of the uncured coating film 8 is 50 mm or more and 150 mm or less, and is preferably 70 mm or more and 120 mm or less.

The overall structure of the shielding surface portion 4 is not particularly limited as long as it has a surface covering the uncured coating film 8 with the above-mentioned gap H. In the illustrated example, a plate-shaped member 41 is used as a member constituting the shielding surface portion 4. One side of this plate-shaped member 41 constitutes the shielding surface portion 4. The material for forming the shielding surface portion 4 (for example, the plate-shaped member 41) is not particularly limited, and examples include hard resin and metal.

The shielding surface portion 4 may be formed in an uneven shape such as a wave shape, but in the illustrated example, the shielding surface portion 4 has a flat shape. In addition, when the shielding surface portion 4 is formed in an uneven shape, the standard of the shielding surface portion 4 when determining the above-mentioned interval H is based on a plane that averages the unevenness of the shielding surface portion 4. The shielding surface portion 4 is arranged in parallel with the uncured coating film 8. In addition, although not specifically shown, the shielding surface portion 4 may be disposed at a slight incline with respect to the surface of the uncured coating film 8. When the shielding surface portion 4 is inclined with respect to the surface of the uncured coating film 8, the above interval H is taken as an average value.

The shielding surface portion 4 is disposed in a zone between the blower 3 and the heat drying device 5 described later. The shielding surface portion 4 is fixed to a frame (not shown) of the coating film production device 9 or the like. The shielding surface portion 4 is not particularly heated, and the temperature of the shielding surface portion 4 itself is the ambient temperature of the location where the coating film production device 9 is installed.

The arrangement of the shielding surface portion 4 is appropriately set. The shielding surface portion 4 is preferably arranged so that its front end 4a is located 3 m or less downstream from the application point P1 of the material solution by the application device 2. With this arrangement, air drying of the uncured coating film 8 in the air drying zone Z31 can be effectively performed. The front end 4a of the shielding surface portion 4 is the end where the substrate 7 conveyed downstream first reaches the shielding surface portion 4. In addition, the application point P1 refers to a location where the material solution begins to adhere to the surface of the substrate 7. If the front end 4a of the shielding surface portion 4 is located 3 m or less downstream from the application point P1, the transport length L1 of the substrate 7 from the application point P1 to the shielding surface portion 4 and It has the same meaning. Therefore, it is preferable that the transport length L1 of the substrate 7 exceeds 0 m and is 3 m or less. Moreover, it is more preferable that the transport length L1 of the substrate 7 is 1 m or more and 2.5 m or less.

The width of the shielding surface portion 4 (the length of the shielding surface portion 4 corresponding to the width direction of the substrate 7) may be smaller than the width of the substrate 7. Since a uniform drying relief effect can be expected over the entire uncured coating film 8, the width of the shielding surface portion 4 is larger than the width of the base material 7, as shown in FIG. 2, or is smaller than the width of the base material (7). It is preferable that it is approximately the same as the width of 7). In the case of the shielding surface portion 4 that is larger than the width of the substrate 7, both ends of the shielding surface portion 4 in the width direction protrude outward from both edges in the width direction of the substrate 7.

In addition, it is preferable that the space between the uncured coating film 8 and at least one end selected from the front end 4a, the rear end 4b, and both side ends 4c, 4d of the shielding surface portion 4 is open. In the illustrated example, the space between the peripheral ends (front end 4a, rear end 4b, and both side ends 4c, 4d) of the shielding surface portion 4 and the uncured coating film 8 is open. Since the space between at least one end of the shielding surface portion 4 and the uncured coating film 8 is open, the solvent diffuses outward from the open portion. For this reason, the drying relief effect can be sufficiently exerted in the space S between the shielding surface portion 4 and the uncured coating film 8 without the solvent concentration in the space S reaching a saturation level.

The length L2 of the shielding surface portion 4 (the length of the shielding surface portion 4 corresponding to the conveyance direction of the base material 7) is appropriately set. From the viewpoint of drying relief, the length L2 of the shielding surface portion 4 is preferably set in consideration of the relationship with the thickness D of the uncured coating film 8. In detail, when the thickness D of the uncured coating film 8 is large, the volatilization amount of the solvent from the uncured coating film 8 is relatively large, and when the thickness D of the uncured coating film 8 is small, the volatilization amount of the solvent is small. When the thickness D of the uncured coating film 8 is large, an appropriate amount of solvent can be volatilized in the drying relaxation zone Z32 by increasing the length L2 of the shielding surface portion 4 correspondingly. On the other hand, when the thickness D of the uncured coating film 8 is small, the length L2 of the shielding surface portion 4 is made correspondingly small, so that an appropriate amount of solvent can be volatilized in the drying relaxation zone Z32. That is, by setting the length L2 of the shielding surface portion 4 in accordance with the thickness D of the uncured coating film 8, in the drying relief zone Z32, the thickness D of the uncured coating film 8 is not limited. , an appropriate amount of solvent can be volatilized without rapidly volatilizing the solvent. From this viewpoint, it is desirable that the thickness D [μm] of the uncured coating film 8 and the length L2 [m] of the shielding surface portion 4 satisfy the relationship of 0.5≤D/L2≤50. In addition, it is more preferable that the thickness D [μm] of the uncured coating film 8 and the length L2 [m] of the shielding surface portion 4 satisfy the relationship of 0.8≤D/L2≤30, especially 1≤D/ It is more preferable to satisfy the relationship L2≤10.

The specific value of the length L2 of the shielding surface portion 4 is preferably 0.5 m or more and 2 m or less, and more preferably 0.8 m or more and 1.7 m or less.

(heat drying zone)

In the heat drying zone Z33, a heat drying device 5 is installed to dry the uncured coating film 8 by heat.

The heat drying device 5 is not particularly limited, and an oven, a heater that sprays warm air, etc. can be used.

By passing the substrate 7 through the heat drying zone Z33, the solvent in the uncured coating film 8 can be sufficiently volatilized.

<Curing zone and curing process>

In the curing zone Z4, the uncured coating film 8 is cured (curing process). As a result, the coating film 81 (coating film 81 after curing) is formed on the surface of the substrate 7.

A curing device 6 is installed in the curing zone Z4. As the curing device 6, an appropriate one according to the curing form of the material solution is used. For example, when the material solution is a curing type of active energy rays such as ultraviolet rays, an active energy ray irradiation device such as ultraviolet rays is used as the curing device 6. Additionally, when the material solution is of a thermosetting type, a heating device is used as the curing device 6. In addition, when a thermosetting type material is cured by the heat of the heat drying zone Z33, the curing device 6 may be omitted. In addition, when the material solution is a solvent volatilization type, the uncured coating film 8 is cured in the heat drying zone Z33, so the curing device 6 is omitted.

The base material 7 on which the coating film is formed is wound around the winding unit 12 after any appropriate treatment is performed as necessary.

According to the method of the present invention, a coating film 81 with excellent surface smoothness can be obtained. This is because, in the drying process of drying the uncured coating film 8, the occurrence of stripe-shaped unevenness (stripe-shaped convexity or depression) on the surface of the uncured coating film 8 can be suppressed. Although the reason is not clear, the present inventors estimate as follows.

That is, when the base material 7 is transported from the upstream side to the downstream side, the surface of the uncured coating film 8 receives wind directed opposite to it. This wind is a gas flow from the downstream side to the upstream side that is generated on the surface of the substrate 7 (surface of the uncured coating film 8) as the substrate 7 is conveyed (hereinafter referred to as “conveyance air flow”). do). In Fig. 1, the direction of the conveying air flow is indicated by a white arrow. The intensity of this conveying air flow is proportional to the conveying speed AS of the base material 7. In addition, due to factors such as vibration of the conveyance device 1 and the atmosphere of the installation location of the coating film production device 9 (e.g., air conditioning equipment at the installation location), the conveyance air current acting on the surface of the substrate 7 may , it is presumed that the gas does not flow uniformly from the downstream side to the upstream side, but is disrupted, such as by creating strengths and weaknesses here and there or by subtly changing the direction. This disturbance of the conveying air flow causes unevenness to occur on the surface of the uncured coating film 8. The air dry zone (Z31) of the present invention has the first characteristic point. In the wind drying zone Z31, the relationship of 1≤AS/BS≤50 is satisfied and wind is sprayed onto the uncured coating film 8 along the conveyance direction downstream with respect to the surface of the uncured coating film 8, thereby conveying the uncured coating film 8. Disturbances in airflow can be removed. For this reason, it is possible to suppress the occurrence of unevenness on the surface of the uncured coating film 8, and by spraying wind, volatilization of the solvent in the uncured coating film 8 can be promoted.

Next, even if drying is promoted while suppressing the occurrence of unevenness by the air drying, the uncured coating film 8 is not sufficiently dried. Therefore, after the air drying (Z31), the uncured coating film 8 is dried by the conveying air stream. There is a risk of unevenness in the surface. In particular, immediately after drying is promoted by blowing wind, the solvent is likely to volatilize even without actively blowing wind. In this regard, in the present invention, immediately after conveying the air drying zone Z31, the substrate 7 is conveyed to the drying relief zone Z32 having the second characteristic point. Due to the second characteristic point, a space S is formed between the shielding surface portion 4 and the surface of the uncured coating film 8 in the dry relaxation zone Z32. In this space S, the solvent volatilizes from the uncured coating film 8 of the base material 7, but since the solvent concentration increases in the space S partitioned by the shielding surface portion 4, the solvent rapidly evaporates. Volatilization can be prevented. By providing a drying relief zone Z32 to prevent rapid drying, the uncured coating film 8, which is still unstable, is dried slowly after air drying, thereby suppressing the occurrence of unevenness on the surface of the uncured coating film 8.

[etc]

In the coating film manufacturing apparatus and coating film manufacturing method, both a wind drying zone Z31 having a first characteristic point and a drying relaxation zone Z32 having a second characteristic point are provided, but only one of the first characteristic point or the second characteristic point is provided. You may have it (not shown). For example, the base material 7 on which the uncured coating film 8 is formed may be transported to an air-drying zone without the first characteristic point and a drying relaxation zone Z32 with the second characteristic point. For example, after transporting the base material 7 in the air dry zone without forcibly spraying wind with a blower (in this air dry zone, the transport airflow accompanying the transfer of the base material 7 causes the uncured coating film 8 ), the base material 7 may be conveyed to the drying relaxation zone Z32 having the second characteristic point. Alternatively, in the air dry zone, after blowing wind that does not satisfy the conditions of the first characteristic point from the blower 3 to the uncured coating film 8, it is described as a drying relief zone Z32 having the second characteristic point (7). You may return it. Alternatively, after conveying the substrate 7 to the air drying zone Z31 having the first characteristic point, the substrate 7 may be conveyed to the drying relaxation zone having the shielding surface portion that does not satisfy the conditions of the second characteristic point.

Example

Hereinafter, examples and comparative examples will be shown to describe the present invention in more detail. However, the present invention is not limited to the following examples.

[write]

As the substrate, a 60-μm-thick triacetylcellulose film (trade name “TG60UL” manufactured by Fuji Film Co., Ltd.) was used.

[Material solution]

The material solution was a solution in which an ultraviolet curable polymer (pentaerythritol triacrylate) was dissolved in an organic solvent (methyl isobutyl ketone) (trade name “Viscott #300” manufactured by Osaka Yuki Kagaku Kogyo Co., Ltd.). . The viscosity of this material solution was 0.007 Pa·s at 25°C. The viscosity was measured using an E-type viscometer at 25 degrees.

[Example 1]

A coating film manufacturing apparatus 9 as shown in FIGS. 1 to 4 was used. Each setting of the manufacturing device was as follows.

Applicator (2): Die coater.

Thickness D of the uncured coating film 8: 15 μm.

Wind blowing angle θ of the blower 3: 15 degrees.

Point facing the wind P2 (length L3): 100cm.

Transport speed AS of base material (7): 30 m/min.

Wind speed BS: 1m/sec.

Transport length L1: 2m.

Spacing H between the shielding surface portion (4) and the uncured coating film (8): 100 mm.

Length L2 of the shielding surface (4): 1.5 m.

Heat drying device (5): Oven at 60°C to 80°C.

Curing device (6): Ultraviolet irradiation device.

The base material 7 is transported at the above speed AS, an uncured coating film 8 of thickness D is continuously formed on the surface of the base material 7 using the coating device 2, and the base material 7 is subjected to air drying (Z31). ), sequentially conveyed to the drying relaxation zone (Z32) and the heat drying zone (Z33), and curing the uncured coating film (8) with the curing device (6), thereby obtaining the coating film of Example 1.

The state of the surface of the coating film (coating film after curing) was observed with the naked eye. The results are shown in Table 1.

"○" in the column for the state of the coating film surface in Table 1 indicates that it was at a level where the haze of the non-uniform shape could not be recognized, and "△" indicates that the haze of the non-uniform shape was slightly visible, but it did not affect the display quality of the display. It indicates that it was a level that did not provide a level, and “×” indicates that it was a level that caused the non-uniform pattern to be strongly visible and significantly lowered the display quality of the display. Here, the above-mentioned “haze” refers to a state in which transparent portions and portions where cloudiness can be visually observed occur randomly in a transparent film.

Additionally, the numbers with decimal points in the AS/BS column of Table 1 are rounded off to 2 decimal places.

[Examples 2 to 11 and Comparative Examples 1 to 11]

Some of the conveyance speed AS, wind speed BS, conveyance length L1, gap H, length L2 of the shielding surface portion 4, and thickness D of the uncured coating film 8 of the base material 7 were changed as shown in Table 1. Except for this, a coating film was formed in the same manner as in Example 1. Additionally, Comparative Example 11 did not provide a shielding surface.

Table 1 shows the observation results of the surface conditions of these coating films.

4: Shielding face part
7: Listing
8: Uncured film
9: Paint film manufacturing device
P1: Application point of material solution
L1: Transport length of substrate
L2: Length of shielding surface
Z2: Application zone
Z3: Drying zone
Z31: Wind dry zone
Z32: Dry relief zone

Claims (5)

A process of forming an uncured coating film by applying a material solution to a long strip-shaped substrate while continuously conveying it from the upstream side of the conveyance direction to the downstream side of the conveyance direction,
A step of transporting the substrate on which the uncured coating film is formed to a drying zone and drying the uncured coating film,
The drying zone includes an air-drying zone for air-drying the uncured coating film, and a drying relief zone installed on the downstream side of the air-drying zone and equipped with a shielding surface portion facing the surface of the uncured coating film at a predetermined distance. With
The air drying zone sprays wind along the downstream side of the conveyance direction with respect to the surface of the uncured coating film,
A method for producing a coating film, wherein the conveyance speed AS of the substrate and the wind speed BS of the wind satisfy the relationship of 1≤AS/BS≤50. According to claim 1,
The conveyance length L1 of the substrate from the application point where the material solution is applied to the substrate to the shielding surface portion exceeds 0 m and is 3 m or less,
The shielding surface portion is arranged at a distance H of 50 mm or more and 150 mm or less from the surface of the uncured coating film,
The length L2 of the shielding surface is 0.5 m or more and 2 m or less,
A method for producing a coating film, wherein the thickness D of the uncured coating film and the length L2 of the shielding surface portion satisfy the relationship of 0.5≤D/L2≤50. A process of forming an uncured coating film by applying a material solution to a long strip-shaped substrate while continuously conveying it from the upstream side of the conveyance direction to the downstream side of the conveyance direction,
A step of transporting the substrate on which the uncured coating film is formed to a drying zone and drying the uncured coating film,
The drying zone includes an air-drying zone for air-drying the uncured coating film, and a drying relief zone installed on the downstream side of the air-drying zone and equipped with a shielding surface portion facing the surface of the uncured coating film at a predetermined distance. With
The conveyance length L1 of the substrate from the application point where the material solution is applied to the substrate to the shielding surface portion exceeds 0 m and is 3 m or less,
The shielding surface portion is arranged at a distance H of 50 mm or more and 150 mm or less from the surface of the uncured coating film,
The length L2 of the shielding surface is 0.5 m or more and 2 m or less,
A method for producing a coating film, wherein the thickness D of the uncured coating film and the length L2 of the shielding surface portion satisfy the relationship of 0.5≤D/L2≤50. The method according to any one of claims 1 to 3,
A method for producing a coating film, comprising a step of curing the uncured coating film to form a coating film after the drying process. A method for producing an optical film, wherein at least one of the coating film and the substrate according to claim 4 has an optical function.