Coating device and coating method

Abstract

The present invention relates to a coating device provided with a transport unit for transporting an object to be coated, and a coating unit for forming a coating film on the surface of the transported object to be coated, the coating unit including a die head for discharging a coating liquid onto the surface of the object to be coated, the die head including a die lip for forming a slit, a coating liquid having a viscosity of 0.1 Pa * s or more and an elongation of 2 mm or more can be discharged from the slit, the die lip has a downstream-side die lip disposed on the downstream side in the traveling direction of the object to be coated, and the gap between the slit and the surface of the object to be coated is 0.1-2 mm. The slit width, which is the length of the slit in the travel direction, is 38 [mu] m or more and less than 300 [mu] m, and the lip width, which is the length of the tip surface of the downstream side lip in the travel direction, is 0.1 mm or more and 2 mm or less.

Description

Technical Field

[0001] This invention relates to a coating apparatus and a coating method. Background Technology

[0002] Coating apparatus and coating methods are used in the manufacture of films such as optical films. In the manufacture of films, a coating film is formed on the surface of a substrate or other object to be coated using a coating apparatus, and then the coating film is cured.

[0003] Previously, a coating method known as slot die coating was employed. In slot die coating, a coating liquid is sprayed from a nozzle called a slot onto the surface of a moving object, forming a coating film on the object's surface. In slot die coating, a pump or compressor is used to supply the coating liquid, which is stored in a sealed container, to the die head, thus ensuring the stability of the coating liquid. Furthermore, when using a metering pump, it is advantageous to easily control the coating thickness.

[0004] Patent Document 1 discloses a coating method that forms characteristic droplets that improve the quality of the coating film by increasing the gap between the slit and the surface of the object being coated. Specifically, it describes forming droplets with a bulging portion and an extended portion. The bulging portion bulges from the leading edge of the downstream die lip of the slit toward the object being coated, and the extended portion is formed by the coating liquid extending from the bulging portion toward the surface of the object being coated, located further downstream than the downstream die lip. In the embodiment of Patent Document 1, it is shown that by using a coating apparatus with a large slit width and a large die lip width on the downstream side, droplets with large bulging portions can be advantageously formed.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent Application Publication No. 2019-202250 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] To achieve miniaturization of various products, it is desirable to provide thin-film coatings. One method for manufacturing such coatings is to use a coating solution diluted with a solvent. However, from the perspective of reducing environmental impact, it is desirable to reduce the amount of solvent used in the coating solution. However, coating solutions with reduced solvent content are difficult to process due to their high viscosity, which may hinder the achievement of thin-film coatings.

[0010] In view of the above, the objective of the present invention is to provide a coating apparatus and coating method that can easily form a thin film using a high-viscosity coating liquid.

[0011] Problem Solving Methods

[0012] The coating apparatus of the present invention is described below. [1]

[0014] A coating apparatus includes a transport section for transporting a workpiece to be coated and a coating section for forming a coating film on the surface of the transported workpiece.

[0015] The coating section includes a die that sprays coating liquid onto the surface of the object to be coated.

[0016] The aforementioned die head includes a die lip forming a slit, from which a coating liquid having a viscosity of 0.1 Pa·s or more and an elongation of 2 mm or more is ejected.

[0017] The aforementioned die lip has a downstream die lip disposed on the downstream side of the traveling direction of the object to be coated.

[0018] The gap between the aforementioned slit and the surface of the object to be coated is 0.1~2mm.

[0019] The length of the aforementioned slit in the aforementioned direction of travel, i.e., the slit width, is 38 μm or more and less than 300 μm.

[0020] The length of the front end face of the downstream mold lip in the aforementioned travel direction, i.e., the mold lip width, is 0.1 mm or more and 2 mm or less. [2]

[0022] According to the coating apparatus described above [1], wherein,

[0023] The aforementioned die head is configured to spray the aforementioned coating liquid onto the surface of the object to be coated, which is traveling at a speed of 5 m / min or more and 100 m / min or less.

[0024] The application method of the present invention is as follows. [3]

[0026] A method of application, comprising:

[0027] The die is used to form a coating film on the surface of the object being coated while it is moving.

[0028] The aforementioned die head includes a die lip that forms a slit.

[0029] The aforementioned die lip has a downstream die lip disposed on the downstream side of the traveling direction of the object to be coated.

[0030] The gap between the aforementioned slit and the surface of the object to be coated is 0.1~2mm.

[0031] The length of the aforementioned slit in the aforementioned direction of travel, i.e., the slit width, is 38 μm or more and less than 300 μm.

[0032] The length of the front end face of the downstream die lip in the aforementioned travel direction, i.e., the die lip width, is 0.1 mm or more and 2 mm or less.

[0033] A coating liquid with a viscosity of 0.1 Pa·s or higher and an elongation of 2 mm or higher is sprayed out from the aforementioned slit. [4]

[0035] According to the application method described above [3], wherein,

[0036] The coating liquid is sprayed from the aforementioned die head onto the surface of the object to be coated, which is traveling at a speed of 5 m / min or more and 100 m / min or less.

[0037] The effects of the invention

[0038] According to the present invention, a coating apparatus and coating method are provided that can easily form a thin film using a high-viscosity coating liquid. Attached Figure Description

[0039] Figure 1 This is a simplified enlarged view of the coating section of a coating apparatus according to one embodiment, showing the object to be coated moving while being supported by the die lip of the die head and the support roller.

[0040] Figure 2 This is a diagram illustrating the method for determining the elongation of an application solution.

[0041] Figure 3 The table and graph show the evaluation results of Experiment 2.

[0042] Figure 4 The table and graph show the evaluation results of Experiment 3.

[0043] Figure 5 The table and graph show the evaluation results of Experiment 4.

[0044] Figure 6 The table and graph show the evaluation results of Experiment 5.

[0045] Symbol Explanation

[0046] 1: Support roller

[0047] 2: Mold head

[0048] 2a: Upstream side mold lip

[0049] 2b: Downstream side mold lip

[0050] S: Slit

[0051] G: Gap

[0052] B: Liquid droplets

[0053] B1: The bulging part

[0054] B2: Extension Section Detailed Implementation

[0055] Hereinafter, the coating apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0056] like Figure 1 As shown, the coating apparatus of this embodiment includes: a support roller 1 supporting the back side of a traveling strip-shaped object to be coated W; and a die 2 spraying coating liquid toward the surface of the object to be coated W. In the coating apparatus of this embodiment, coating liquid is continuously sprayed from the die 2 to form a strip-shaped coating film on the surface of the object to be coated W.

[0057] The coating liquid of this embodiment achieves a viscosity of 0.1 Pa·s or higher at a shear rate of 0.1 [1 / s] and a temperature of 20°C by reducing the solvent content. The coating liquid can be a solvent-free type. In this case, the viscosity of the coating liquid can reach 1 Pa·s or higher. The viscosity of the coating liquid is, for example, 100 Pa·s or less, 50 Pa·s or less, or 25 Pa·s or less. It should be noted that the viscosity of the coating liquid is the viscosity measured using a rheometer (manufactured by HAAKE Corporation).

[0058] Furthermore, the purpose of the coating apparatus in this embodiment is to form a coating film with a thickness of 10 μm or less, even when using a coating liquid exhibiting the viscosity described above. It should be noted that the thickness of the coating film is defined as the average thickness obtained by measuring the thickness at the center and both ends in the width direction at any 10 locations along the travel direction of the object being coated W, and then averaging these 30 thicknesses.

[0059] The elongation of the above-mentioned coating liquid, obtained by the measurement method described below, is 2 mm or more. The elongation is, for example, 100 mm or less, 50 mm or less, or 25 mm or less. In the above-described method for measuring elongation, if... Figure 2As shown, a cylindrical component C with an inner diameter of 2 mm and a roller R are prepared. A metering pump for dispensing coating liquid is connected to one end of the cylindrical component C, and the opening at the other end serves as the spray outlet for the coating liquid. The cylindrical component C is configured such that its length direction is parallel to the horizontal direction. The roller R is configured such that its rotation axis is parallel to the horizontal direction. Furthermore, the circumferential surface of the roller R is positioned opposite the spray outlet of the cylindrical component C, and the circumferential surface moves upward from below at this opposite position. The rotation axis of the roller R is located on the extension line of the central axis extending along the length direction of the cylindrical component C. During measurement, the coating liquid is sprayed from the cylindrical component C toward the circumferential surface of the roller R at a speed of 5 g / min. The roller R is rotated at a speed of 30 m / min. Starting from a position where the distance D between the circumferential surface of the roller R and the opening of the cylindrical component C is 1 mm, the cylindrical component C is moved horizontally by increasing the distance D. The distance D (mm) between the cylindrical component C and the roller R when the coating liquid connecting them is cut off is defined as the elongation length. It should be noted that the ambient temperature is set to 23℃, the relative humidity to 50%RH, and the coating liquid temperature to 23±2℃.

[0060] Examples of coating liquids exhibiting the elongation described above include adhesive compositions. Examples of such adhesive compositions include, for example, active energy ray-curable adhesive compositions. This adhesive composition comprises: a base polymer, at least one monomer and oligomer that reacts with the base polymer upon irradiation by active energy rays, and a photopolymerization initiator. Methods for increasing the elongation include, for example, increasing the proportion of the base polymer or increasing the molecular weight (degree of polymerization) of the base polymer.

[0061] Examples of the aforementioned basic polymers include: natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, reclaimed rubber, butyl rubber, polyisobutylene rubber, nitrile rubber (NBR), and other rubber-based polymers; organosilicon polymers; and acrylic polymers. These polymers can be used alone or in combination of two or more.

[0062] The coating apparatus of this embodiment is configured to form the aforementioned coating film. Specifically, the coating apparatus of this embodiment includes: a continuous feeding section comprising a continuous feeding roller for forming a mesh from a substrate to be rolled; a coating section comprising a support roller 1 and a die head 2; a curing section for curing the aforementioned coating film to form a film; and a winding section comprising a winding roller for rolling the film-bearing substrate into a roll. Thus, the coating apparatus of this embodiment includes a transport section comprising the aforementioned continuous feeding section and the aforementioned winding section. The aforementioned continuous feeding section and the aforementioned winding section may each include a motor for rotating the aforementioned continuous feeding roller and the aforementioned winding roller. These motors are configured to control the rotational speed of the aforementioned continuous feeding roller and the aforementioned winding roller to determine the speed of the workpiece W to be coated.

[0063] The membrane described above can be composed of a single functional layer or a stack of two or more functional layers.

[0064] As described above, the coating material W in this embodiment is a mesh continuously released from a substrate that has been rolled into a roll. In this embodiment, the surface of the substrate is the coating surface to be coated by the die 2. It should be noted that, in another embodiment, the first coating film may be formed on the surface of the substrate in another coating section disposed upstream of the die 2, or the first coating film may be converted into a first functional layer in another curing section disposed upstream of the die 2. That is, in another embodiment, the surface of the first coating film or the surface of the first functional layer is the coating surface to be coated by the die 2.

[0065] The substrate described above may be a resin-based substrate. Examples of resins include: polyester resins, polyolefin resins, cellulose resins, acrylic resins, polycarbonate resins, polyethersulfone resins, polyarylate resins, melamine resins, polyamide resins, polyimide resins, and polystyrene resins. Examples of polyester resins include: polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resins include: polyethylene, polypropylene, and cyclic olefin polymers (COP). Examples of cellulose resins include: cellulose triacetate (TAC).

[0066] like Figure 1 As shown, the object to be coated, W, is wound in a manner that brings it into surface contact with the circumferential surface of the support roller 1. Specifically, the object to be coated, W, is wound around the support roller 1 such that its direction of travel immediately after being released from the support of the support roller 1 changes by 90° to 180° relative to its direction of travel before being supported by the support roller 1. This angle range can be 120° to 180° or 150° to 180°.

[0067] In this embodiment, the support roller 1 is configured such that its circumferential surface travels upward from below in the position opposite to the die head 2. The workpiece W supported by such a support roller 1 travels upward from below in the position opposite to the die head 2.

[0068] The die head 2 is configured to eject a coating liquid with the viscosity and elongation described above from the slit S. Specifically, the die head 2 includes a first piece having an upstream die lip 2a and a second piece having a downstream die lip 2b. A manifold is formed between the first and second pieces. A flow path extending from the manifold to the front end of the die lip is formed between the upstream die lip 2a and the downstream die lip 2b. The upstream die lip 2a has a front end face facing the surface of the object to be coated, W. Similarly, the downstream die lip 2b has a front end face facing the surface of the object to be coated, W. Furthermore, each front end face of the upstream die lip 2a and the downstream die lip 2b forms a slit S opening toward the surface of the object to be coated, W. In this specification, the length of the slit S in the direction of travel of the object to be coated, W, is defined as the slit width. The die head 2 typically includes a shim for adjusting the slit width.

[0069] The die head 2 is configured to spray coating liquid from the slit S at a constant flow rate. For example, the coating section described above may include a metering pump that supplies coating liquid to the die head 2. It should be noted that "constant flow rate" here means that, during stable operation, the value calculated as [maximum flow rate - minimum flow rate] / average flow rate is 0.2 or less, preferably 0.1 or less. In addition, the flow rate here refers to the mass flow rate.

[0070] The slit S is configured to face the surface of the workpiece W supported by the support roller 1. Furthermore, the slit S is configured such that its width is along a vertical plane. Correspondingly, the leading edges of the upstream die lip 2a and the downstream die lip 2b are also configured along a vertical plane. In this specification, the length of the leading edges of the upstream die lip 2a and the downstream die lip 2b in the direction of travel of the workpiece W is defined as the die lip width.

[0071] A gap G is formed between the slit S and the surface of the object to be coated W. The gap G is 0.1 to 2 mm. Therefore, the coating apparatus of this embodiment can form a droplet B, which has a bulging portion B1 extending from the leading edge of the downstream die lip 2b of the slit S toward the object to be coated W, and an extension portion B2 between the bulging portion B1 and the surface of the object to be coated W located further downstream than the downstream die lip 2b. The bulging portion B1 is formed in a manner that it does not contact the surface of the object to be coated W. In other words, the extension portion B2 is a bridging portion formed by the coating liquid extending from the bulging portion B1 to the surface of the object to be coated W. By retaining the coating liquid at the leading edge of the downstream die lip 2b in such a way as forming the bulging portion B1, interruption of the coating film at the gap G can be suppressed. Furthermore, since the extension portion B2 is formed by stretching the coating liquid out of the bulging portion B1, a thin film coating can be achieved. More specifically, the coating apparatus of this embodiment has a large slit width relative to the target coating thickness of less than 10 μm, and the coating can be made into a thin film by stretching the coating liquid as described above.

[0072] In this embodiment, the slit width is 38 μm or more. Therefore, even coating liquids with high viscosity can be sprayed out. The slit width is preferably 38 μm or more and 250 μm or less, more preferably 38 μm or more and 200 μm or less, and even more preferably 38 μm or more and 100 μm or less. This allows for the formation of a thin film. It should be noted that the slit width refers to the average width of the 9 points where the slit S is divided into 10 equal parts along its length. The coating liquid of this embodiment exhibits a decrease in viscosity in a larger shear region relative to the viscosity described above at a shear rate of 0.1 [1 / s] (temperature 20°C). Furthermore, by making the slit width less than 300 μm, a shear force capable of reducing viscosity is applied to the coating liquid passing through the slit S, thus allowing the coating liquid to be sprayed out from the slit S.

[0073] The width of the downstream die lip 2b is 0.1 mm or more and 2 mm or less. Preferably, the width of the downstream die lip 2b is 0.1 mm or more and 1 mm or less. This reduces the size of the bulging portion of the liquid droplet, thereby allowing the extended portion (bridging portion) to become thinner. In other words, with the die lip width described above, it is easier to further thin the coating film.

[0074] The velocity of the object to be coated, W, is preferably 5 m / min or more. This not only improves productivity but also allows the coating liquid, violently ejected from a narrow slit S with a slit width of less than 300 μm, to elongate without excessive retention on the leading edge of the downstream die lip 2b. In other words, by setting the velocity of the object to be coated, W, to 5 m / min or more, it is easier to further thin the coating film. The velocity of the object to be coated, W, is preferably 10 m / min or more and 100 m / min or less, more preferably 10 m / min or more and 50 m / min or less, even more preferably 10 m / min or more and 40 m / min or less, and even more preferably 10 m / min or more and 35 m / min or less. This allows for the proper formation of extended portions (bridging portions) of the liquid droplets.

[0075] The amount of coating liquid ejected from the slit S can be adjusted to form droplets as described above, while taking into account the velocity of the object being coated, W.

[0076] Next, an application method as an embodiment of the present invention will be described.

[0077] In the coating method of this embodiment, the coating apparatus described above is used. In this coating method, a die 2 is used to form a coating film on the surface of the object to be coated, W, which is traveling at a speed of 5 m / min or more and 50 m / min or less. In the coating method of this embodiment, it is preferable to form liquid droplets B having the raised portion B1 and the extended portion B2 (bridging portion) as described above.

[0078] It should be noted that the coating apparatus and coating method of the present invention are not limited to the embodiments described above. Furthermore, the coating apparatus and coating method of the present invention are not limited to the effects described above. Various modifications can be made to the coating apparatus and coating method of the present invention without departing from the spirit of the present invention.

[0079] Example

[0080] The present invention will be further described below by way of examples.

[0081] [Materials Used]

[0082] • Coating liquid: The following UV-curable adhesive composition (viscosity: 10 Pa·s (shear rate 1 (1 / s), 20°C), elongation: 2 mm)

[0083] • Coated material: PET film

[0084] [Preparation of UV-curable adhesive compositions]

[0085] As monomer components, 61 parts by mass of 2-ethylhexyl acrylate (2EHA), 14 parts by mass of N-vinylpyrrolidone (NVP), 22 parts by mass of 4-hydroxybutyl acrylate (4HBA), 3 parts by mass of hydroxyethyl acrylate (HEA), and 0.05 parts by mass of two photopolymerization initiators (trade name: IRGACURE 184, manufactured by BASF) and 0.05 parts by mass of a photopolymerization initiator (trade name: IRGACURE 651, manufactured by BASF) were added to a four-necked flask to prepare a monomer mixture. Then, the monomer mixture was exposed to ultraviolet light under a nitrogen atmosphere to partially induce photopolymerization, thereby obtaining a partial polymer (acrylic polymer slurry) with a polymerization rate of approximately 10% by mass.

[0086] A UV-curable adhesive composition was prepared by adding 0.035 parts by weight of trimethylolpropane triacrylate (TMPTA) and 0.3 parts by weight of silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) to 100 parts by weight of the above acrylic polymer slurry and mixing them until homogeneous.

[0087] [Experiment 1]

[0088] As shown in Table 1 below, the downstream die lip width was set to 2 mm, the slit width to 700 μm, and the speed of the workpiece was varied, resulting in a coating film forming on the surface of the workpiece. It should be noted that the gap in Experiment 1 was adjusted to 0.5–2 mm to prevent the bulging portion of the liquid droplets from contacting the surface of the workpiece. The thickness of the coating film obtained in each experiment was measured. The results are shown in Table 1. It can be seen that when the slit width is large, the speed range of the workpiece that can achieve a thin coating film is limited.

[0089]

[0090] [Experiment 2: Comparison of Slit Widths 1]

[0091] like Figure 3 As shown in Table 2, by setting the lip width of the downstream die lip to 1 mm, the slit width and the speed of the coated object were altered, resulting in a coating film forming on the surface of the object. It should be noted that the gap in Experiment 2 was adjusted to 0.1–1 mm to prevent the bulging portion of the liquid droplets from contacting the surface of the coated object. The thickness of the coating film obtained in each experiment was measured. The results are shown in Table 2 and... Figure 3 As shown.

[0092] [Experiment 3: Comparison of Slit Widths 2]

[0093] like Figure 4As shown in Table 3, the lip width of the downstream die lip was set to 0.18 mm, which changed the slit width and the speed of the workpiece, thus forming a coating on the surface of the workpiece. It should be noted that the gap in Experiment 3 was adjusted to 0.1~1 mm to prevent the bulging part of the liquid droplets from contacting the surface of the workpiece. The thickness of the coating obtained in each experiment was measured. The results are shown in Table 3 and... Figure 4 As shown.

[0094] [Experiment 4: Comparison of die lip widths on the downstream side]

[0095] like Figure 5 As shown in Table 4, by setting the slit width to 100 μm, the lip width of the downstream die lip and the speed of the workpiece were altered, resulting in a coating film forming on the surface of the workpiece. It should be noted that the gap in Experiment 4 was adjusted to 0.1–1 mm to prevent the bulging portion of the liquid droplets from contacting the surface of the workpiece. The thickness of the coating film obtained in each experiment was measured. The results are shown in Table 4 and… Figure 5 As shown.

[0096] [Experiment 5: Comparison of die lip width and slit width on the downstream die lip]

[0097] like Figure 6 As shown in Table 5, combinations of downstream die lip widths of 1 mm, 0.5 mm, and 0.18 mm with slit widths of 100 μm and 75 μm altered the velocity of the substrate, resulting in a coating film on its surface. It should be noted that the gap in Experiment 5 was adjusted to 0.1–1 mm to prevent the bulging portion of the liquid droplets from contacting the substrate surface. The thickness of the coating film obtained in each experiment was measured. The results are shown in Table 5 and... Figure 6 As shown.

Claims

1. A coating apparatus comprising: a conveyance section that conveys a coated object; and a coating section that forms a coating film on a surface of the conveyed coated object, the coating section including a die that ejects a coating liquid toward the surface of the coated object, the die including a die lip that forms a slit, the die being capable of ejecting a coating liquid having a viscosity of 0.1 Pa-s or more and an elongation of 2 mm or more from the slit, the die lip having a downstream die lip disposed on a downstream side in a traveling direction of the coated object, a gap between the slit and the surface of the coated object being 0.1 to 2 mm, a length of the slit in the traveling direction, that is, a slit width, being 38 μm or more and less than 300 μm, and a length of a tip surface of the downstream die lip in the traveling direction, that is, a die lip width, being 0.1 mm or more and 2 mm or less.

2. The coating apparatus according to claim 1, wherein the die is configured to eject the coating liquid toward the surface of the coated object traveling at 5 m / min or more and 100 m / min or less.

3. A coating method comprising: forming a coating film on a surface of a coated object traveling using a die, the die including a die lip that forms a slit, the die lip having a downstream die lip disposed on a downstream side in a traveling direction of the coated object, a gap between the slit and the surface of the coated object being 0.1 to 2 mm, a length of the slit in the traveling direction, that is, a slit width, being 38 μm or more and less than 300 μm, and a length of a tip surface of the downstream die lip in the traveling direction, that is, a die lip width, being 0.1 mm or more and 2 mm or less, and ejecting a coating liquid having a viscosity of 0.1 Pa-s or more and an elongation of 2 mm or more from the slit.

4. The coating method according to claim 3, wherein the coating liquid is ejected from the die toward the surface of the coated object traveling at 5 m / min or more and 100 m / min or less. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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