Coating device and coating method

Abstract

An object of the present invention is to provide a coating device and the like that can easily thin a coating film using a highly viscous coating liquid. [Solution] A coating device comprising a conveying section for conveying an object to be coated and a coating section for forming a coating film on the surface of the object being conveyed, wherein the coating section includes a die for ejecting a coating liquid onto the surface of the object to be coated, the die including a lip that forms a slot, and is capable of ejecting a coating liquid from the slot having a viscosity of 0.1 Pa·s or more and an elongation of 2 mm or more, the lip having a downstream lip arranged downstream in the direction of travel of the object to be coated, the gap between the slot and the surface of the object to be coated being 0.1 to 2 mm, the slot width, which is the length of the slot in the direction of travel, being 38 μm or more and less than 300 μm, and the lip width, which is the length of the tip surface of the downstream lip in the direction of travel, being 0.1 mm or more and 2 mm or less.

Description

[Technical Field]

[0001] The present invention relates to a coating device and a coating method. [Background technology]

[0002] Coating devices and coating methods are used in the production of films such as optical films. In the production of films, for example, a coating film is formed on the surface of an object to be coated, such as a substrate, using a coating device, and the coating film is then cured.

[0003] A conventional coating method known as slot die coating is known. In slot die coating, a coating solution is ejected from an outlet called a slot onto the surface of a moving object to form a coating film on the surface of the object. In slot die coating, the coating solution contained in a sealed tank is supplied to the die using a pump or compressor, ensuring the stability of the coating solution. Furthermore, using a metering pump has the advantage of making it easier to control the thickness of the coating film.

[0004] Patent Document 1 describes a coating method for forming a distinctive bead that can improve the quality of the coating film by increasing the gap between the slot and the surface of the workpiece. Specifically, the method describes forming a bead that has a bulging portion that bulges out from the slot toward the workpiece at the tip of the downstream lip, and an extended portion of the coating fluid extending from the bulging portion onto the surface of the workpiece located further downstream of the downstream lip. The examples in Patent Document 1 show that using a coating device with a wide slot and a wide downstream lip effectively forms a bead with a large bulging portion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-202250 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to realize the miniaturization of various products, it is desirable to provide a thinner film. One possible method for producing such a film is to use a coating liquid diluted with a solvent. On the other hand, from the viewpoint of reducing the environmental load, it is desirable to reduce the amount of solvent used in preparing the coating liquid. However, a coating liquid with a reduced amount of solvent has a high viscosity and is difficult to handle, which can make it difficult to thin the coating film.

[0007] In view of the above circumstances, an object of the present invention is to provide a coating device and a coating method that can easily thin a coating film using a highly viscous coating liquid. [Means for solving the problem]

[0008] The coating device according to the present invention is as follows. [1] A coating device comprising a conveying section that conveys an object to be coated and a coating section that forms a coating film on the surface of the object to be coated being conveyed, The coating unit includes a die that ejects a coating liquid onto a surface of the object to be coated, the die includes a lip that forms a slot, and is capable of discharging a coating liquid having a viscosity of 0.1 Pa s or more and an elongation of 2 mm or more from the slot; The lip has a downstream lip arranged downstream in the direction of travel of the workpiece, The gap between the slot and the surface of the object to be coated is 0.1 to 2 mm, The slot width, which is the length of the slot in the traveling direction, is 38 μm or more and less than 300 μm, A coating device, wherein a lip width, which is the length of the tip end surface of the downstream lip in the traveling direction, is 0.1 mm or more and 2 mm or less.

[0009] [2] The coating device according to [1] above, wherein the die is configured to eject the coating liquid onto the surface of the workpiece traveling at a speed of 5 m / min or more and 100 m / min or less.

[0010] The coating method according to the present invention is as follows. [3] A coating film is formed on the surface of the moving object using a die, the die includes a lip that forms a slot; The lip has a downstream lip arranged downstream in the direction of travel of the workpiece, The gap between the slot and the surface of the object to be coated is 0.1 to 2 mm; The slot width, which is the length of the slot in the traveling direction, is 38 μm or more and less than 300 μm, A lip width, which is the length of the tip surface of the downstream lip in the traveling direction, is 0.1 mm or more and 2 mm or less, A coating method in which a coating liquid having a viscosity of 0.1 Pa·s or more and an elongation of 2 mm or more is discharged from the slot.

[0011] [4] The coating method according to [3] above, wherein the coating solution is ejected from the die onto the surface of the workpiece traveling at a speed of 5 m / min or more and 100 m / min or less. [Effects of the Invention]

[0012] As described above, the present invention can provide a coating device and a coating method that can easily thin a coating film using a highly viscous coating liquid. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic enlarged view of a coating section of a coating device according to an embodiment, showing a coating object traveling while being supported by a die lip and a backup roller. [Figure 2] FIG. 2 is a diagram illustrating a method for measuring the elongation of a coating liquid. [Figure 3]1 is a table and graph showing the evaluation results of Test 2. [Figure 4] 10 is a table and graph showing the evaluation results of Test 3. [Figure 5] 10 is a table and graph showing the evaluation results of Test 4. [Figure 6] 10 is a table and graph showing the evaluation results of Test 5. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a coating device according to an embodiment of the present invention will be described with reference to the drawings.

[0015] As shown in Figure 1, the coating device of this embodiment includes a backup roller 1 that supports the back surface of a traveling belt-shaped workpiece W, and a die 2 that ejects a coating liquid toward the surface of the workpiece W. In the coating device of this embodiment, the coating liquid is continuously ejected from the die 2 to form a belt-shaped coating film on the surface of the workpiece W.

[0016] The coating liquid of this embodiment has a reduced solvent content, and therefore exhibits a viscosity of 0.1 Pa·s or more at a shear rate of 0.1 [1 / s] and a temperature of 20°C. The coating liquid may be a solvent-free coating liquid. In this case, the viscosity of the coating liquid may be 1 Pa·s or more. 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. The viscosity of the coating liquid is measured using a rheometer (manufactured by HAAKE).

[0017] The coating device of this embodiment is intended to form a thin coating film with a thickness of 10 μm or less, even using a coating liquid with the above-mentioned viscosity. The thickness of the coating film is determined by measuring the thickness at the center and both ends in the width direction at 10 arbitrary points in the direction of travel of the coated object W, and averaging these 30 thicknesses to obtain an average thickness.

[0018] The coating liquid exhibits an elongation of 2 mm or more as measured by the measurement method described below. The elongation is, for example, 100 mm or less, 50 mm or less, or 25 mm or less. To measure the elongation, a cylindrical member C with an inner diameter of 2 mm and a roller R are prepared, as shown in FIG. 2. A metering pump for delivering the coating liquid is connected to one end of the cylindrical member C, and the opening at the other end serves as the coating liquid outlet. The cylindrical member C is positioned so that its length is parallel to the horizontal. The roller R is positioned so that its rotation axis is parallel to the horizontal. The peripheral surface of the roller R faces the outlet of the cylindrical member C, and the peripheral surface moves from bottom to top at the position opposite the outlet. The rotation axis of the roller R is positioned on an extension of the central axis extending in the length direction of the cylindrical member C. During measurement, the coating liquid is discharged from the cylindrical member C toward the peripheral surface of the roller R at a rate of 5 g / min. The roller R is rotated at a speed of 30 m / min. The starting point is a position where the gap D between the circumferential surface of the roller R and the opening of the cylindrical member C is 1 mm, and the cylindrical member C is moved horizontally so as to increase the gap D. The gap D (mm) between the cylindrical member C and the roller R when the coating fluid connecting the cylindrical member C and the roller R is severed is defined as the elongation. The temperature of the measurement environment is 23°C, the relative humidity is 50% RH, and the temperature of the coating fluid is 23±2°C.

[0019] An example of a coating liquid exhibiting the above-described elongation degree is a pressure-sensitive adhesive composition. An example of the pressure-sensitive adhesive composition is an active energy ray-curable pressure-sensitive adhesive composition. Such a pressure-sensitive adhesive composition contains a base polymer, a monomer and an oligomer that react with the base polymer upon irradiation with active energy rays, and a photopolymerization initiator. Examples of methods for improving the elongation degree include increasing the blending ratio of the base polymer or increasing the molecular weight (degree of polymerization) of the base polymer.

[0020] Examples of the base polymer include rubber-based polymers such as natural rubber, polyisobutylene rubber, styrene-butadiene rubber, styrene-isoprene-styrene block copolymer rubber, reclaimed rubber, butyl rubber, polyisobutylene rubber, and nitrile rubber (NBR); silicone-based polymers; and acrylic-based polymers. These polymers may be used alone or in combination.

[0021] The coating device of this embodiment is configured to form the coating film into a film. Specifically, the coating device of this embodiment includes a payout section including a payout roller for forming a web from a rolled substrate, a coating section including a backup roller 1 and a die 2, a curing section for curing the coating film to form a film, and a winding section including a winding roller for forming the substrate carrying the film into a roll. As described above, the coating device of this embodiment includes a conveying section including the payout section and the winding section. The payout section and the winding section may each include a motor for rotating the payout roller and the winding roller. These motors are configured to control the rotational speed of the payout roller and the winding roller to determine the speed of the workpiece W.

[0022] The film may be composed of one functional layer or a laminate of two or more functional layers.

[0023] As described above, the workpiece W in this embodiment is a web unwound from a rolled substrate. In this embodiment, the surface of the substrate is the surface to be coated on which a coating film is formed by die 2. In another aspect, a first coating film may be formed on the surface of the substrate in a separate coating section located upstream of die 2, or the first coating film may be converted into a first functional layer in a separate curing section located upstream of die 2. That is, in another aspect, the surface of the first coating film or the surface of the first functional layer is the surface to be coated on which a coating film is formed by die 2.

[0024] The substrate is, for example, a substrate made of resin. Examples of the resin include polyester resin, polyolefin resin, cellulose resin, acrylic resin, polycarbonate resin, polyethersulfone resin, polyarylate resin, melamine resin, polyamide resin, polyimide resin, and polystyrene resin. Examples of polyester resin include polyethylene terephthalate (PET), polybutylene terephthalate, and polyethylene naphthalate. Examples of polyolefin resin include polyethylene, polypropylene, and cycloolefin polymer (COP). Examples of cellulose resin include triacetyl cellulose (TAC).

[0025] As shown in Fig. 1, the workpiece W is wound around the backup roller 1 so as to be in surface contact with the peripheral surface of the backup roller 1. Specifically, the workpiece W is wound around the backup roller 1 so that the direction of travel of the workpiece W immediately after it is released from support by the backup roller 1 changes by 90° to 180° relative to the direction of travel immediately before it was supported by the backup roller 1. The angle range here may be 120° to 180°, or 150° to 180°.

[0026] The backup roller 1 in this embodiment is disposed so that its peripheral surface moves upward at a position opposite the die 2. The workpiece W supported by the backup roller 1 moves upward at a position opposite the die 2.

[0027] The die 2 is configured to eject a coating fluid having the above-described viscosity and elongation from the slot S. Specifically, the die 2 includes a first block having an upstream lip 2a and a second block having a downstream lip 2b. A manifold is formed between the first and second blocks. A flow path extending from the manifold to the lip tip is formed between the upstream lip 2a and the downstream lip 2b. The upstream lip 2a has a tip surface facing the surface of the workpiece W. Similarly, the downstream lip 2b has a tip surface facing the surface of the workpiece W. The tip surfaces of the upstream lip 2a and the downstream lip 2b form a slot S that opens toward the surface of the workpiece W. In this specification, the length of the slot S in the direction of travel of the workpiece W is defined as the slot width. The die 2 typically includes a shim plate for adjusting the slot width.

[0028] The die 2 is configured to discharge the coating liquid from the slot S at a constant flow rate. For example, the coating unit may be equipped with a metering pump that supplies the coating liquid to the die 2. Here, a constant flow rate means that during steady operation, the value calculated by [maximum flow rate - minimum flow rate] / average flow rate is 0.2 or less, preferably 0.1 or less. Here, the flow rate means the mass flow rate.

[0029] The slot S is arranged to face the surface of the workpiece W supported by the backup roller 1. The slot S is also arranged so that the slot width is along a vertical plane. Accordingly, the tip surfaces of the upstream lip 2a and the downstream lip 2b are also arranged so as to be along a vertical plane. In this specification, the lip width is defined as the length of the tip surfaces of the upstream lip 2a and the downstream lip 2b in the traveling direction of the workpiece W.

[0030] A gap G is formed between the slot S and the surface of the workpiece W. The gap G is 0.1 to 2 mm. This allows the coating device of this embodiment to form a bead B having a bulging portion B1 that bulges from the slot S toward the workpiece W at the tip surface of the downstream lip 2b, and an extending portion B2 that extends between the bulging portion B1 and the surface of the workpiece W located downstream of the downstream lip 2b. The bulging portion B1 is formed so as not to come into contact with the surface of the workpiece W. In other words, the extending portion B2 is a bridge formed by the coating liquid extending from the bulging portion B1 onto the surface of the workpiece W. By retaining the coating liquid on the tip surface of the downstream lip 2b to form the bulging portion B1, discontinuity of the coating film at the gap G can be prevented. Furthermore, the coating liquid is stretched from the bulging portion B1 to form the extending portion B2, thereby reducing the thickness of the coating film. More specifically, the coating device of this embodiment has a slot width that is large relative to the target coating thickness of 10 μm or less, but the coating film can be made thinner by stretching the coating liquid as described above.

[0031] The slot width in this embodiment is 38 μm or more. This allows even highly viscous coating fluids to be ejected. The slot 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 a thinner coating film. Note that the slot width refers to the average width of nine points dividing the slot S into ten equal parts in the longitudinal direction. The coating fluid in this embodiment may exhibit a decrease in viscosity in a shear region greater than the viscosity at a shear rate of 0.1 [1 / s] (at a temperature of 20°C). Furthermore, by setting the slot width to less than 300 μm, a shear force capable of reducing the viscosity is applied to the coating fluid as it passes through the slot S, allowing the coating fluid to be ejected from the slot S.

[0032] The lip width of the downstream lip 2b is 0.1 mm or more and 2 mm or less. The lip width of the downstream lip 2b is preferably 0.1 mm or more and 1 mm or less. This reduces the bulging portion of the bead, thereby making it possible to thin the extended portion (bridge portion). In other words, such a lip width makes it easier to further thin the coating film.

[0033] The speed of the workpiece W is preferably 5 m / min or greater. This not only improves productivity, but also allows the coating fluid, forcefully ejected from a narrow slot S with a slot width of less than 300 μm, to spread without excessive retention on the tip surface of the downstream lip 2b. In other words, a speed of 5 m / min or greater for the workpiece W facilitates the formation of a thinner coating film. The speed of the workpiece W is preferably 10 m / min or greater to 100 m / min or less, more preferably 10 m / min or greater to 50 m / min or less, even more preferably 10 m / min or greater to 40 m / min or less, and even more preferably 10 m / min or greater to 35 m / min or less. This allows the bead extension (bridged portion) to be formed normally.

[0034] The amount of coating liquid discharged from the slot S is adjusted to an amount that will form the above-mentioned bead, taking into consideration the speed of the workpiece W.

[0035] Next, a coating method as an embodiment of the present invention will be described.

[0036] The coating method of this embodiment uses the coating device described above. The coating method of this embodiment uses the die 2 to form a coating film on the surface of the workpiece W 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 a bead B having the bulging portion B1 and the extending portion B2 (bridged portion) as described above.

[0037] The coating device and coating method according to the present invention are not limited to the above-described embodiments. Furthermore, the coating device and coating method according to the present invention are not limited to the above-described effects. The coating device and coating method according to the present invention can be modified in various ways without departing from the spirit and scope of the present invention. [Example]

[0038] The present invention will now be further described with reference to examples.

[0039] [Materials used] Coating liquid: the following UV-curable adhesive composition (viscosity: 10 Pa·s (shear rate 1 (1 / s), 20°C), elongation: 2 mm) Substrate: PET film [Preparation of UV-curable adhesive composition] A monomer mixture was prepared by adding 61 parts by weight of 2-ethylhexyl acrylate (2EHA), 14 parts by weight of N-vinylpyrrolidone (NVP), 22 parts by weight of 4-hydroxybutyl acrylate (4HBA), 3 parts by weight of hydroxyethyl acrylate (HEA), and 0.05 parts by weight of two photopolymerization initiators (trade name: Irgacure 184, manufactured by BASF) and 0.05 parts by weight of a photopolymerization initiator (trade name: Irgacure 651, manufactured by BASF) to a four-neck flask. The monomer mixture was then partially photopolymerized by exposure to ultraviolet light under a nitrogen atmosphere to obtain a partially polymerized product (acrylic polymer syrup) with a polymerization rate of approximately 10% by weight. To 100 parts by mass of the acrylic polymer syrup, 0.035 parts by mass of trimethylolpropane triacrylate (TMPTA) and 0.3 parts by mass of a silane coupling agent (trade name: KBM-403, manufactured by Shin-Etsu Chemical Co., Ltd.) were added, and then these were uniformly mixed to prepare a UV-curable pressure-sensitive adhesive composition.

[0040] [Test 1] As shown in Table 1 below, the downstream lip width was 2 mm, the slot width was 700 μm, and the speed of the workpiece was varied to form a coating film on the surface of the workpiece. The gap in Test 1 was adjusted to 0.5 to 2 mm so that the bulging part of the bead did not come into contact with the surface of the workpiece. The thickness of the coating film obtained in each test was measured. The results are shown in Table 1. It can be seen that a large slot width limits the range of workpiece speeds at which a thin coating can be formed.

[0041] [Table 1]

[0042] [Test 2: Slot width comparison 1] As shown in Table 2 in Figure 3, the downstream lip width was set to 1 mm, and the slot width and speed of the workpiece were varied to form a coating film on the surface of the workpiece. In Test 2, the gap was adjusted to 0.1 to 1 mm so that the bulging part of the bead did not come into contact with the surface of the workpiece. The thickness of the coating film obtained in each test was measured. The results are shown in Table 2 and Figure 3.

[0043] [Test 3: Slot width comparison 2] As shown in Table 3 in Figure 4, the downstream lip width was set to 0.18 mm, and the slot width and speed of the workpiece were varied to form a coating film on the surface of the workpiece. The gap in Test 3 was adjusted to 0.1 to 1 mm so that the bulging part of the bead did not come into contact with the surface of the workpiece. The thickness of the coating film obtained in each test was measured. The results are shown in Table 3 and Figure 4.

[0044] [Test 4: Comparison of downstream lip width 1] As shown in Table 4 in Figure 5, the slot width was set to 100 μm, and the downstream lip width and the speed of the workpiece were varied to form a coating film on the surface of the workpiece. In Test 4, the gap was adjusted to 0.1 to 1 mm so that the bulging part of the bead did not come into contact with the surface of the workpiece. The thickness of the coating film obtained in each test was measured. The results are shown in Table 4 and Figure 5.

[0045] [Test 5: Comparison of downstream lip width and slot width] As shown in Table 5 in Figure 6, the downstream lip widths were set to 1 mm, 0.5 mm, and 0.18 mm, and the slot widths were set to 100 μm and 75 μm. The speed of the workpiece was varied to form a coating film on the surface of the workpiece. In Test 5, the gap was adjusted to 0.1 to 1 mm so that the bulging part of the bead did not contact the surface of the workpiece. The thickness of the coating film obtained in each test was measured. The results are shown in Table 5 and Figure 6. [Explanation of symbols]

[0046] 1: backup roller, 2: die, 2a: upstream lip, 2b: downstream lip, S: slot, G: gap, B: bead, B1: bulge, B2: extension

Claims

1. A coating device comprising a conveying section that conveys an object to be coated and a coating section that forms a coating film on the surface of the object to be coated being conveyed, The coating unit includes a die that ejects a coating liquid onto a surface of the object to be coated, the die includes a lip that forms a slot, and is capable of discharging a coating liquid having a viscosity of 0.1 Pa s or more and an elongation of 2 mm or more from the slot; The lip has a downstream lip arranged downstream in the direction of travel of the workpiece, a gap between the slot and the surface of the workpiece is 0.1 to 2 mm; A slot width, which is the length of the slot in the traveling direction, is 38 μm or more and less than 300 μm, a lip width, which is the length of the tip end surface of the downstream lip in the traveling direction, is 0.1 mm or more and 2 mm or less.

2. 2. The coating device according to claim 1, wherein the die is configured to eject the coating liquid onto the surface of the workpiece traveling at a speed of 5 m / min or more and 100 m / min or less.

3. A coating film is formed on the surface of the moving object using a die, the die includes a lip that forms a slot; The lip has a downstream lip arranged downstream in the direction of travel of the workpiece, a gap between the slot and the surface of the workpiece is 0.1 to 2 mm; A slot width, which is the length of the slot in the traveling direction, is 38 μm or more and less than 300 μm, a lip width, which is the length of the tip surface of the downstream lip in the traveling direction, is 0.1 mm or more and 2 mm or less; A coating method in which a coating liquid having a viscosity of 0.1 Pa·s or more and an elongation of 2 mm or more is discharged from the slot.

4. The coating method according to claim 3, wherein the coating solution is ejected from the die onto the surface of the workpiece traveling at a speed of 5 m / min or more and 100 m / min or less.

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