Method and apparatus for manufacturing laminated film

Abstract

To reduce the occurrence of MD threading in a laminate film with a coating layer.SOLUTION: A manufacturing method for a laminate film in which a coating layer is formed on a substrate film while continuously conveying the substrate film in a longitudinal direction, includes a coating process for forming a coating film, and a surface treatment process for treating the surface of the coating film in a surface treatment part. The surface treatment part comprises a circular cross-sectional rotor having a groove on its surface, and the rotor is positioned to contact the coating film, is configured to provide specific conditions, and rotates in the opposite direction to a substrate film conveying direction.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method and apparatus for manufacturing laminated films. [Background technology]

[0002] The development of transparent films with a coating layer is being considered as a glass substitute for flexible displays. Such transparent films require high quality in terms of physical properties such as flexibility and hardness, as well as a high level of film appearance, as they are intended to be glass substitutes.

[0003] As a method for forming a coating layer, a technique has been disclosed in which a wire bar is rotated in the forward or reverse direction relative to the transport direction of the substrate film to adjust the film thickness of the film coated by the coating means, thereby forming the coating film (Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-47677 [Overview of the project] [Problems that the invention aims to solve]

[0005] When forming a coating layer on a transparent film, the resulting laminated film may exhibit appearance defects such as streaks (MD streaks) along the longitudinal direction of the film, unevenness (steps) along the transverse direction, dot-like defects, and thickness variations. Therefore, in order for a transparent film with a coating layer to satisfy a high-quality level as an optical film, technology is needed to improve these appearance defects.

[0006] However, our investigations have revealed that, in the technology described in Patent Document 1, even when using a low-viscosity coating liquid, sufficient effect in eliminating appearance defects cannot be obtained for thick coating layers, or the appearance quality of the coating layer may actually deteriorate due to worsening thickness unevenness or the inclusion of air bubbles. Among appearance defects, reducing dark MD streaks is often a particular challenge.

[0007] One aspect of the present invention aims to realize a method for manufacturing a laminated film and a manufacturing apparatus that can reduce the occurrence of MD streaks, in particular, among surface defects. [Means for solving the problem]

[0008] As a result of diligent research, the inventors have discovered that the occurrence of MD streaks can be reduced in the process of forming a coating film on a base film by treating the surface of the coating film while rotating a rotating body having a specific groove structure in the opposite direction to the film transport direction, and have completed the present invention. That is, one embodiment of the present invention includes the following configuration.

[0009] [1] A method for manufacturing a laminated film in which a coating layer is formed on a base film while the base film is continuously conveyed in the longitudinal direction, A coating step of applying a coating liquid onto the base film to form a coating film, and This includes a surface treatment step of treating the surface of the coating film with a surface treatment unit, The surface treatment unit comprises a rotating body with a circular cross-section having grooves on its surface, The rotating body is positioned to contact the coating film, The rotating body is configured such that 0.1w ≤ A ≤ 1.5w, (In the formula, w(mm) is the thickness of the coating film, and A(mm) 2 A' / mm) is the unit cross-sectional area of ​​the groove in the rotating body, and is calculated using the formula A = A' / P, where A'(mm) 2 (where ) is the cross-sectional area of ​​the groove, and P(mm) is the groove pitch.) In the surface treatment step, the rotating body rotates in a direction opposite to the conveyance direction of the base film, a method for manufacturing a laminated film.

[0010] 〔2〕The rotating body is rotated so that 1≦Vr≦50A + 1.3 (where Vr is the rotation speed ratio of the rotating body with respect to the conveyance speed of the base film, and A (mm 2 / mm) is the unit cross-sectional area of the groove of the rotating body), the method for manufacturing a laminated film according to 〔1〕.

[0011] 〔3〕The groove of the rotating body is a concavo-convex groove inclined with respect to the conveyance direction of the base film, the method for manufacturing a laminated film according to 〔1〕 or 〔2〕.

[0012] 〔4〕When the conveyance direction of the base film is 0°, the direction of the concavo-convex groove of the rotating body is inclined by 10 to 45°, the method for manufacturing a laminated film according to 〔3〕.

[0013] 〔5〕The coating liquid has a viscosity of 1 cp to 100 cp, the method for manufacturing a laminated film according to any one of 〔1〕 to 〔4〕.

[0014] 〔6〕The coating film has a film thickness of 20 μm or more, the method for manufacturing a film according to any one of 〔1〕 to 〔5〕.

[0015] 〔7〕A manufacturing apparatus for a laminated film that forms a coating layer on the base film while continuously conveying the base film in the longitudinal direction, a coating section that applies a coating liquid onto the base film to form a coating film, and a surface treatment section that treats the surface of the coating film, the surface treatment section includes a rotating body having a groove on the surface and having a circular cross-section, the rotating body is disposed so as to contact the coating film, the rotating body is configured so that 0.1w≦A≦l.5w, (where w (mm) is the film thickness of the coating film, and A (mm 2(mm) is the unit cross-sectional area of the groove of the rotating body, obtained by A = A’ / P, where A’ (mm 2 ) is the cross-sectional area of the groove, and P (mm) is the groove pitch) The rotating body rotates in a direction opposite to the conveyance direction of the base film, and is a manufacturing apparatus for a laminated film. [Effect of the Invention]

[0016] According to one aspect of the present invention, a laminated film with reduced occurrence of MD streaks can be manufactured. [Brief Description of the Drawings]

[0017] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a manufacturing apparatus for manufacturing a laminated film according to an embodiment of the present invention. [Figure 2] FIG. 2 is a schematic view showing the conveyance direction of the base film and the rotation direction of the rotating body in a manufacturing method for manufacturing a laminated film according to an embodiment of the present invention. [Figure 3] FIG. 3 is a schematic view showing the cross-sectional area A’ and the groove pitch P of the groove of the rotating body in a manufacturing method for manufacturing a laminated film according to an embodiment of the present invention. [Figure 4] FIG. 4 is a schematic view showing that the direction of the groove of the rotating body is inclined with respect to the conveyance direction of the base film in a manufacturing method for manufacturing a laminated film according to an embodiment of the present invention. [Embodiments for Carrying Out the Invention]

[0018] One embodiment of the present invention is described below, but the present invention is not limited thereto. The present invention is not limited to the configurations described below, and various modifications are possible within the scope of the claims. Furthermore, embodiments or examples obtained by combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Moreover, new technical features can be formed by combining the technical means disclosed in each embodiment. All patent documents mentioned herein are incorporated herein by reference. Furthermore, unless otherwise specified herein, "A to B" representing a numerical range means "A or greater (including A and greater than A) and B or less (including B and less than B)."

[0019] [The technological philosophy behind Armbum] As a result of our investigations, we found that the technology described in Patent Document 1, as mentioned above, has the problem that, even when using a low-viscosity coating liquid, it is not possible to obtain sufficient effect in eliminating appearance defects in thick coating layers, or the appearance quality of the coating layer may actually deteriorate due to worsening thickness unevenness or the inclusion of air bubbles. For example, if MD streaks occur densely in the coating film, it is difficult to eliminate the MD streaks, and if the wire bar described in Patent Document 1 is used, the quality of the coating layer may actually deteriorate due to appearance defects caused by the rotation of the wire bar.

[0020] One embodiment of the present invention aims to solve the above-mentioned problems.

[0021] More specifically, the present inventors have found that, as a method to enhance the effect of improving appearance defects, (i) it is effective to use a rotating body (bar) in which the surface grooves are inclined with respect to the conveying direction of the base film, and the volume of one groove is relatively small compared to the coating film, and to rotate the rotating body in the opposite direction to the conveying direction of the base film; and (ii) the optimal condition for the ratio of the rotation speed of the rotating body to the conveying speed of the base film is determined by the groove specifications (groove unit area) of the rotating body, and have arrived at one embodiment of the present invention. According to one embodiment of the present invention, the above problems can be solved.

[0022] [Damn David] A method for manufacturing a laminated film according to one embodiment of the present invention (hereinafter sometimes referred to as "this manufacturing method") is a method for manufacturing a laminated film in which a coating layer is formed on a base film while the base film is continuously conveyed in the longitudinal direction, and includes a coating step of applying a coating liquid to the base film to form a coating film, and a surface treatment step of treating the surface of the coating film with a surface treatment unit, wherein the surface treatment unit comprises a rotating body with a circular cross-section having grooves on its surface, the rotating body is arranged to be in contact with the coating film, and the rotating body is 0.1w ≤ A ≤ 1.5w (wherein w (mm) is the thickness of the coating film and A (mm) 2 A' / mm) is the unit cross-sectional area of ​​the groove in the rotating body, and is calculated using the formula A = A' / P, where A'(mm) 2 The configuration is such that (where ) is the cross-sectional area of ​​the groove and P(mm) is the groove pitch, and in the surface treatment process, the rotating body rotates in the opposite direction to the conveying direction of the base film.

[0023] According to this manufacturing method, the occurrence of MD streaks can be reduced in laminated films with a coating layer. Therefore, the appearance quality of laminated films with a coating layer can be improved.

[0024] A manufacturing method and apparatus for producing a laminated film according to one embodiment of the present invention will be described below with reference to Figure 1. Figure 1 is a schematic diagram showing an example of a manufacturing apparatus for producing a laminated film according to an embodiment of the present invention.

[0025] (1. Coating process) The coating process in this manufacturing method can be any process that involves applying a coating liquid onto a base film to form a coating film. More specifically, in the coating process, the base film is continuously conveyed by a conveyor roll, and the coating liquid is continuously applied to the surface of the base film using a coating means.

[0026] As shown in Figure 1, the laminated film manufacturing apparatus 10 comprises a coating unit 2, a surface treatment unit 3, a dryer 4 as a drying means, and a UV irradiation unit. The coating step in this manufacturing method is, for example, a step in which a coating liquid is applied to a base film 1 in the coating unit 2 to form a coating film 5.

[0027] The manufacturing apparatus 10 is configured to continuously transport the base film 1 using a plurality of transport rollers. The die 2a is provided in the coating section 2, which uniformly applies a coating liquid to the surface of the continuously transported base film 1. The die 2a discharges the coating liquid supplied from the tank onto the base film 1. In the configuration shown in Figure 1, the coating section 2 is a die coater having a die 2a. The coating section 2 is not limited to a die coater, but is not particularly limited as long as it is configured to uniformly apply a coating liquid to the surface of the base film 1. Examples of coating sections 2 include gravure coaters, bar coaters, spray coaters, etc.

[0028] Furthermore, the manufacturing apparatus 10 includes a surface treatment section 3 for treating the surface of the coating film 5. The rotating body 3a is provided in the surface treatment section 3 and is positioned between the die 2a and the dryer 4 in the transport direction of the base film 1. The coating film 5 formed by the coating section 2 is prone to appearance defects (especially MD streaks). This problem tends to occur particularly when the thickness of the coating film 5 is relatively large and the viscosity of the coating liquid is relatively low. The rotating body 3a of the surface treatment section 3 treats the surface of the coating film 5 in order to reduce the occurrence of MD streaks.

[0029] The dryer 4 is a device that dries the coating film 5 to form a laminated film in which the coating layer 6 is laminated onto the base film 1. The coating layer 6 dried by the dryer 4 is further cured by a UV irradiation machine.

[0030] (1-1. Base film 1) The base film 1 is preferably formed in the form of a long strip of a flexible film or sheet with a uniform thickness. The material of the base film 1 is not particularly limited, but examples include resin, paper, cloth, metal, etc., and can be appropriately selected depending on the application. As for the material of the base film 1, any transparent plastic film can be used without particular limitations. When the material constituting the base film 1 is a resin, specific examples of such materials include polyolefin resins such as polyethylene, polypropylene, and polycyclic olefins; acrylic resins; cellulose resins; polyamide resins such as nylon 6 and nylon 6,6; polyester resins such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polycarbonate; polyimide; and mixtures of these resins. When the laminated film is used for displays such as smartphones, among these resins, the material of the base film 1 is preferably a polyimide resin.

[0031] The thickness of the base film 1 is preferably 10 μm to 300 μm, and more preferably 20 μm to 200 μm. If the thickness of the base film 1 is less than 10 μm, the strength of the base film 1 decreases, resulting in poor processability. If it exceeds 300 μm, problems arise such as decreased transparency or an increase in the weight of the base film 1.

[0032] The shape of the base film 1 can be any strip that can be continuously transported, and its width (short direction) and length (long direction) are not limited. The width of the base film is preferably 1 cm to 200 cm, more preferably 10 cm to 100 cm, in terms of stabilizing transportability. The length of the base film is preferably 100 cm to 100,000 cm, in terms of handlingability after winding.

[0033] The base film 1 may be formed from a single layer or multiple layers including other layers. When formed from multiple layers, other layers may include an adhesive layer, a tack layer, etc. A similar coating layer may also be formed on the back surface.

[0034] (1-2. Coating liquid) The coating liquid is the raw material for the coating film 5, and in addition to the curable resin, curing agent, and solvent, it may further contain additives. The coating film 5 refers to the state of the coating layer contained in the laminated film before drying. The curable resin used in the coating liquid may be either a photocurable resin or a thermosetting resin. The curing agent used in the coating liquid may be either a photopolymerization initiator or a thermal polymerization initiator.

[0035] The curable resins (photocurable resins, thermosetting resins) used in coating solutions are polyfunctional compounds having two or more polymerizable (photopolymerizable, thermopolymerizable) functional groups. These polyfunctional compounds may be monomers or oligomers. Examples of polymerizable functional groups include vinyl groups, (meth)acryloyl groups, and other functional groups having ethylenically unsaturated double bonds, as well as cyclic ether groups such as epoxy groups and oxetane groups.

[0036] Specific examples of curable resins used in coating liquids include acrylic urethane resins, polyester acrylate resins, epoxy acrylate resins, polyol acrylate resins, and epoxy resins. As a photocurable resin, polysiloxane resins having epoxy groups as photopolymerizable functional groups, as disclosed in WO2018 / 096729, WO2014 / 204010, and Japanese Patent Application Publication No. 2017-8142, may also be used.

[0037] When the curing agent is a thermal polymerization initiator, the curable resin becomes a thermosetting resin when combined with the thermal polymerization initiator. Similarly, when the curing agent is a photopolymerization initiator, the curable resin becomes a photocurable resin when combined with the photopolymerization initiator.

[0038] Depending on the polymerizability of the curable resin, photoradical polymerization initiators, photocationic polymerization initiators (photoacid generators), etc., may be used as photopolymerization initiators. Examples of photoradical polymerization initiators include acetophenones, benzophenones, Michler-benzoylbenzoates, α-aminooxime esters, thioxanthones, propiophenones, benzyls, benzoins, and acylphosphine oxides. Examples of photocationic polymerization initiators include strong acids such as toluenesulfonic acid or boron tetrafluoride; onium salts such as sulfonium salts, ammonium salts, phosphonium salts, iodonium salts, and selenium salts; iron-allene complexes; silanol-metal chelate complexes; sulfonic acid derivatives such as disulfones, disulfonyldiazomethanes, disulfonylmethanes, sulfonylbenzoylmethanes, imidosulfonates, and benzoin sulfonates; and organic halogen compounds.

[0039] The amount of photopolymerization initiator is approximately 0.05 to 10 parts by weight per 100 parts by weight of curable resin, and may be 0.1 to 5 parts by weight, or 0.2 to 2 parts by weight.

[0040] In addition to photopolymerization initiators, photosensitizers may be included for purposes such as improving photosensitivity. Examples of photosensitizers include anthracene derivatives, benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives, and benzoin derivatives. Among these, anthracene derivatives, thioxanthone derivatives, and benzophenone derivatives are preferred from the viewpoint of photo-induced electron-donating properties.

[0041] The coating liquid may contain additives such as fine particles, colorants, plasticizers, dispersants, wetting agents, thickeners, leveling agents, defoamers, flame retardants, antistatic agents, antioxidants, UV absorbers, and polymerization inhibitors. In addition, the hard coat composition may contain thermoplastic or thermosetting resin materials in addition to the above-mentioned photocurable resin.

[0042] The coating solution may be solvent-free or may contain a solvent. Preferably, the solvent does not dissolve the film substrate. On the other hand, using a solvent with sufficient solubility to swell the polyimide film may improve the adhesion between the substrate film and the coating layer.

[0043] Suitable solvents include ketones such as acetone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; alcohols such as ethanol, isopropyl alcohol, butanol, and cyclohexanol; esters such as methyl acetate, ethyl acetate, butyl acetate, and isopropyl acetate; ethers such as dioxane, tetrahydrofuran, diethylene glycol methyl ether, and propylene glycol methyl ether; aliphatic hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as toluene and xylene; amides such as N,N-dimethylacetamide, N,N-dimethylformamide, and N-methyl-2-pyrrolidone; alkyl halides such as chloroform, dichloromethane, and dichloroethane; sulfoxides such as dimethyl sulfoxide; and cellosolves such as methyl cellosolve and ethyl cellosolve.

[0044] The solvent may be present in an amount of 5 to 90% by weight, preferably 10 to 85% by weight, when the coating solution is considered to be 100% by weight. If the solvent content is less than 5% by weight, the viscosity will be high, reducing the leveling effect on the surface of the coating film and making coating defects more likely. If it exceeds 90% by weight, it will be difficult to adjust the thickness of the coating film, resulting in defects in appearance.

[0045] (Preparation of coating solution) The method for preparing the coating solution is not particularly limited. For example, the above components may be combined and mixed using a hand mixer or static mixer, or kneaded using a planetary mixer, disperser, roller, kneader, etc.

[0046] The coating liquid is effective in eliminating appearance defects in the coating film when a relatively low viscosity coating liquid is used, so it is preferable to have a viscosity of 1 cp to 100 cp, more preferably 5 cp to 80 cp, and even more preferably 10 cp to 70 cp.

[0047] (1-3. Coating Method) The coating method used in the coating process can be any known industrially available method and is not particularly limited. For example, the coating liquid can be applied to the substrate film using methods such as wire bar coating, roll coating, die coating, or screen printing. Among these, the die coating method is preferred in terms of uniform coating in the width direction.

[0048] (1-4. Coating film 5) The coating film 5 is formed by applying a coating liquid to the base film 1 using the coating unit 2. The coating film 5 preferably has a thickness of 20 μm or more. According to the manufacturing method of this embodiment, when a coating film 5 with a thickness of 20 μm or more, i.e., a relatively thick film, is dried to form a coating layer 6, it is possible to manufacture a laminated film in which MD streaks are reduced and appearance defects are eliminated. The coating film 5 is more preferably 30 μm or more thick, and even more preferably 40 μm or more thick. In order to allow it to pass through the surface treatment unit 3 in the surface treatment process, the total thickness of the base film 1 and the coating film 5 is preferably 500 μm or less, more preferably 400 μm or less, and even more preferably 300 μm or less.

[0049] (2. Surface treatment process) The surface treatment process is a process in which the surface treatment unit 3 treats the surface of the coating film 5. In Figure 1, the surface treatment process is the process up to the point before the upper layer coating film 5 (lower layer: base film 1) formed in the coating process comes into contact with the rotating body 3a of the surface treatment unit 3 and is dried by the dryer 4.

[0050] (2-1. Solids of revolution) The surface treatment unit 3 comprises a rotating body 3a with a circular cross-section and grooves. As shown in Figure 2, the rotating body 3a has uneven grooves 3b on its surface, and is positioned to be in contact with the coating film 5. During the surface treatment process, the rotating body 3a rotates in the opposite direction to the transport direction of the base film 1.

[0051] The shape of the rotating body 3a is not particularly limited as long as the cross-section is circular, but a cylindrical shape as shown in Figure 2 is preferred in order to reduce the occurrence of thickness variations in the resulting laminated film.

[0052] The uneven groove 3b on the surface of the rotating body 3a is preferably an uneven groove inclined with respect to the conveyance direction of the base material film 1. By having the rotating body 3a have such an inclined uneven groove, the generation of MD streaks in the obtained laminated film is reduced, and the effect of eliminating appearance defects is enhanced. When the conveyance direction of the base material film 1 is 0°, the direction of the uneven groove 3b of the rotating body 3a is preferably inclined at 10° to 45°. In other words, as shown in FIG. 4, if the inclination angle of the uneven groove 3b with respect to the conveyance direction of the base material film 1 is θ, the inclination angle θ is preferably 10° to 45° with respect to the conveyance direction of the base material film 1. Further, the inclination angle θ is more preferably 20° to 40°, and even more preferably 25° to 35°. By setting the inclination angle θ within the above range, the generation of MD streaks can be further reduced, and the effect of eliminating appearance defects can be improved.

[0053] The smaller the unit cross-sectional area A of the uneven groove 3b of the rotating body 3a is with respect to the film thickness of the coating film 5, the higher the effect of eliminating appearance defects. That is, the rotating body 3a is configured such that 0.1w ≦ A ≦ 1.5w (where w (mm) is the film thickness of the coating film 5, A (mm 2 / mm) is the unit cross-sectional area of the uneven groove 3b of the rotating body 3a, and is obtained by A = A’ / P, where A’ (mm 2 ) is the cross-sectional area of the uneven groove 3b, and P (mm) is the groove pitch) (see FIG. 3). As shown in FIG. 3, A’ is the cross-sectional area of the uneven groove 3b per groove pitch. When A is 0.1w or more, it is possible to prevent the uneven groove 3b from being blocked, and the rotating body 3a can obtain the effect of reducing MD streaks without clogging the coating liquid and reducing the coating thickness. When A is 1.5w or less, the unevenness difference of the uneven groove 3b can be made an appropriate size, so that the generation of MD streaks due to rotation can be reduced. Also, the occurrence of thickness unevenness can be suppressed.

[0054] The rotating body 3a is preferably configured such that 0.1w ≦ A ≦ 1.3w, and more preferably configured such that 0.1w ≦ A ≦ 1.0w. The cross-sectional area A’ of the groove can be arbitrarily set as long as it satisfies the above range, but 0.0005mm2 ~0.1mm 2 Preferably, 0.001 mm 2 ~0.05mm 2 This is more preferable. Furthermore, the groove pitch P can be set arbitrarily as long as it satisfies the above range, but 0.1 mm to 1.0 mm is preferred, and 0.2 mm to 0.8 mm is more preferred.

[0055] The material of the rotating body 3a is not particularly limited as long as it satisfies the above conditions. Examples include metal, resin, and ceramic. From the viewpoint of durability of the rotating body, the material of the rotating body 3a is preferably metal and ceramic, and more preferably metal.

[0056] The method for manufacturing the uneven grooves 3b on the surface of the rotating body 3a is not particularly limited, as long as grooves that satisfy the above conditions can be produced. Examples of methods for shaping the grooves include a method of creating grooves by applying a strong force while rotating the material to deform it (rolling), a method of creating grooves by cutting the material, and a method of creating grooves by shaping the material and then setting it. In terms of dimensional accuracy of the grooves, rolling is preferred.

[0057] The rotating body 3a rotates in the opposite direction to the transport direction of the base film 1. If the rotating body 3a is rotated in the forward direction of transport, or if it is used without rotation, the rotating body 3a will block the coating liquid, which will worsen the appearance defects of the resulting laminated film or reduce the thickness of the coating film 5.

[0058] By controlling the ratio of the rotational speed of the rotating body 3a to the transport speed of the base film 1, according to the unit cross-sectional area A of the uneven grooves 3b of the rotating body 3a used, it is possible to obtain a high-quality coating film 5 while reducing the occurrence of appearance defects originating from the rotating body 3a. For example, the rotational speed of the rotating body 3a is 1 ≤ Vr ≤ 50A + 1.3 (wherein Vr is the ratio of the rotational speed of the rotating body 3a to the transport speed of the base film 1, and A (mm) 2It is preferable to rotate the rotating body such that Vr (where A is the unit cross-sectional area of ​​the grooves of the rotating body) is equal to 1. When Vr is 1 or greater, the speed of the rotating body 3a becomes faster than the transport speed of the base film 1, and the occurrence of MD streaks can be effectively suppressed. Also, when Vr is 50A + 1.3 or less, the speed of the rotating body 3a becomes moderately fast, which avoids a state in which the uneven grooves 3b of the rotating body 3a are filled with the coating liquid and the uneven grooves 3b tend to become blocked, thereby reducing the occurrence of MD streaks. By adjusting the rotation speed of the rotating body 3a so that Vr satisfies the above range according to the unit cross-sectional area A of the uneven grooves 3b of the rotating body 3a, the occurrence of MD streaks in the resulting laminated film can be greatly reduced, and other appearance defects such as unevenness (unevenness occurring in a direction perpendicular to the transport direction) can also be prevented, thus providing an excellent effect in eliminating appearance defects.

[0059] (Coating layer 6) The coating layer 6 refers to the coating film 5 that has been dried using a drying method such as a dryer. After applying the coating liquid to the base film 1, the coating layer 6 is formed by evaporating volatile substances such as solvents using a drying method at a temperature of 50°C to 150°C for 10 seconds to 1 hour, more specifically 30 seconds to 10 minutes. Then, as shown in Figure 1, the coating layer 6 is cured by irradiating it with UV light using a UV irradiation machine. The amount of UV light irradiated is specifically about 50 mJ / cm². 2 ~10000 mJ / cm 2 That would be fine, or more specifically, 100 mJ / cm² 2 ~5000 mJ / cm 2 That would be fine.

[0060] The thickness of the formed coating layer 6 is preferably 5 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more, in order to obtain an excellent MD streak reduction effect.

[0061] (Laminated film) The laminated film is a film in which a coating layer 6 is formed on a base film 1. The laminated film obtained by the manufacturing method of the present invention only needs to have a coating layer 6 formed on the base film 1, and may be a laminated film in which the coating layer 6 is formed on one or both sides of the base film 1. Other layers, such as an adhesive layer, may be included between the base film 1 and the coating layer 6.

[0062] (Laminated film manufacturing equipment) The laminated film manufacturing apparatus 10 according to the above embodiment (hereinafter sometimes referred to as "the manufacturing apparatus") may also be included as one embodiment of the present invention. The manufacturing apparatus will be described in accordance with the manufacturing method described above as appropriate. According to the manufacturing apparatus 10, the occurrence of MD streaks can be reduced and the appearance can be improved in the laminated film on which the coating layer 6 is formed.

[0063] A laminated film according to one embodiment of the present invention can be used in various image display devices such as plasma displays, field emission displays, organic EL displays, inorganic EL displays, and electronic paper. [Examples]

[0064] The present invention will be described in more detail below with reference to examples and comparative examples. These examples and comparative examples are merely for illustrative purposes, and it will be obvious to those skilled in the art that the scope of the present invention is not limited thereto. One embodiment of the present invention will be described in detail below.

[0065] (1) Preparation of polyamic acid solution 383 parts by weight of N,N-dimethylformamide (DMF) was added to a reaction vessel and stirred under a nitrogen atmosphere. 31.8 parts by weight of 2,2'-bis(trifluoromethyl)benzidine and 10.5 parts by weight of 3,3'-diaminodiphenylsulfone were added, and the mixture was stirred under a nitrogen atmosphere to obtain a diamine solution. To this diamine solution, 15.9 parts by weight of p-phenylenebis(trimellitic anhydride), 37.4 parts by weight of 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropanoic acid anhydride, and 10.4 parts by weight of 3,3',4,4'-biphenyltetracarboxylic acid dianhydride were added, and the mixture was stirred under a nitrogen atmosphere to obtain a polyamic acid solution.

[0066] (2) Imidization and extraction of polyimide resins To the polyamic acid solution obtained in (1) (100 parts by weight of polyamic acid solids), 38.4 parts by weight of pyridine was added as an imidation catalyst and the mixture was stirred. Then, 49.5 parts by weight of acetic anhydride was added and the mixture was stirred at 120°C for 2 hours, after which it was cooled to room temperature to obtain a polyimide solution. While stirring the polyimide solution, 1 L of isopropyl alcohol was added dropwise to precipitate the polyimide resin. The filtered polyimide resin was then washed three times with isopropyl alcohol and dried at 120°C for 12 hours to obtain a polyimide resin powder.

[0067] (3) Preparation of polyimide film (base film) The polyimide resin obtained in (2) was dissolved in methylene chloride to obtain a polyimide solution with a solid content of 10%. The polyimide solution was applied to the substrate using a comma coater and dried under atmospheric pressure at 40°C for 10 minutes, 80°C for 10 minutes, 150°C for 10 minutes, and 180°C for 10 minutes in that order. After drying, it was peeled off the substrate to obtain a transparent polyimide film (substrate film) with a thickness of 50 μm.

[0068] (4) Preparation of hard coat composition (coating liquid) In a reaction vessel, 100 parts by weight of β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 0.12 parts by weight of magnesium chloride, 11 parts by weight of water, and 11 parts by weight of propylene glycol monomethyl ether were charged. After stirring at 130°C for 3 hours, the mixture was degassed under reduced pressure at 60°C to obtain a siloxane resin. Then, 100 parts by weight of the obtained siloxane resin, 2 parts by weight of a propylene carbonate solution of triarylsulfonium·SbF6 salt, 0.2 parts by weight of a xylene / isobutanol solution of polyether-modified polydimethylsiloxane, and 150 parts by weight of propylene glycol monomethyl ether were combined to obtain a hard coat composition. The viscosity of this hard coat composition was 30 cp.

[0069] (Fabrication of a rotating body) Rotating bodies A-D and F were fabricated by forming grooves in stainless steel using a rolling die, according to the conditions described in Table 1, for use in the surface treatment process. For rotating body E, a wire rotating body (wire bar) according to the conditions shown in Table 1 was used.

[0070] (Example 1) As described above, the base film was continuously conveyed in the longitudinal direction at a conveying speed of 2 m / min, and the prepared coating liquid was applied to the base film using a die to form a coating film with a thickness of 0.05 mm (coating process).

[0071] The substrate film with the coating film formed on it was continuously conveyed in the surface treatment area while the coating film was in contact with a set rotating body A (surface treatment process). Rotating body A was rotated in the opposite direction to the conveying direction of the substrate film. The rotation speed of rotating body A was adjusted so that the speed ratio Vr (rotation speed relative to the conveying speed of the substrate film) = 1, as shown in Table 1.

[0072] The substrate film on which the coating film was formed was dried with a dryer to obtain a substrate film with a coating layer formed on it. Next, a UV irradiation machine (H03M-L21, manufactured by Iwasaki Electric Co., Ltd.) was used to irradiate the substrate film with a UV light of 1000 mJ to 2000 mJ / cm². 2The coating layer formed on the continuously transported substrate film was cured by irradiating it with UV light to obtain a laminated film. The appearance of the laminated film was evaluated using the evaluation method described below. The results are shown in Table 1.

[0073] (Examples 2-16) As shown in Table 1, a laminated film was obtained using the same manufacturing method as in Example 1, except that the rotation speed of the rotating bodies was adjusted to achieve the speed ratio Vr listed in Table 1, using rotating bodies A to D with different unit cross-sectional areas A and inclination angles of the grooves, and the bodies were rotated in the opposite direction to the conveying direction of the base film. The appearance of the laminated film was evaluated using the evaluation method described below. The results are shown in Table 1.

[0074] (Comparative Examples 1-4) Using the rotating body D used in Examples 13 to 16, the rotation speed of the rotating body was adjusted to achieve the speed ratio Vr shown in Table 1, and the rotation direction of the rotating body was set to the direction shown in Table 2 (forward direction with respect to the conveying direction of the base film or no rotation), otherwise a laminated film was obtained by the same manufacturing method as in Example 1. The appearance of the laminated film was evaluated using the evaluation method described below. The results are shown in Table 2.

[0075] (Comparative Examples 5-11) As shown in Table 2, rotating bodies E (wire rotating body) and F were used, with different unit cross-sectional areas A and inclination angles of the grooves. The rotation speed of the rotating bodies was adjusted to achieve the speed ratio Vr listed in Table 1, and the rotation direction of the rotating bodies was set to the forward direction relative to the conveying direction of the base film. Laminated films were obtained using the same manufacturing method as in Example 1. The appearance of the laminated films was evaluated using the evaluation method described below. The results are shown in Table 2.

[0076] (Method for evaluating the appearance of laminated films) In a darkroom, an inspection light (S-light SA, manufactured by Japan Technical Center) was placed 140 cm away from a white screen, and a hard coat film was placed at an equidistant distance (70 cm from both) from the light and the white screen. The light from the light source was shone onto the hard coat film, and the projected light was displayed on the white screen to check for the presence of streaky shadows (streaks) extending in the transport direction and stepped irregularities (step irregularities) extending in the width direction. The appearance of the laminated film was evaluated visually according to the following criteria.

[0077] <Appearance Evaluation Criteria> 1: There are no MD slits, and no other cosmetic defects. 2: There are MD streaks, but they are very faint or few in number, and there are no other cosmetic defects. 3: There are MD lines, but they are faint, and there are almost no other cosmetic defects. 4: There are dark MD streaks and / or many other cosmetic defects and / or the coating film thickness is reduced.

[0078] [Table 1]

[0079] [Table 2]

[0080] Examples 1 to 16 demonstrate that the laminated films obtained by the manufacturing method according to the present invention exhibited reduced occurrence of MD streaks and other appearance defects, resulting in an excellent reduction in appearance defects. In particular, Examples 1, 2, 5, 6, 9, 10, 11, and 13 to 16 showed a significant reduction in the occurrence of MD streaks in the resulting laminated films, and also prevented other appearance defects such as unevenness (unevenness occurring in a direction perpendicular to the conveying direction), demonstrating an excellent reduction in appearance defects. In particular, Examples 6 and 11 yielded laminated films with extremely excellent appearance, free from MD streaks and other appearance defects. In contrast, the laminated films obtained in Comparative Example 1, where A was small and the rotating body was in forward rotation, and in Comparative Example 2, where A was small and the rotating body was not rotating, had a relatively good appearance, but the coating film thickness was significantly reduced to 0.004 mm, and the desired film thickness (0.05 mm) could not be obtained. The laminated films obtained by the manufacturing methods of Comparative Examples 3 to 11 failed to reduce the occurrence of MD streaks and other appearance defects occurred.

[0081] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Industrial applicability]

[0082] One embodiment of the present invention can provide a laminated film with excellent appearance and transparency. Therefore, the laminated film obtained by one embodiment of the present invention can be suitably used as a glass substitute film for, for example, the front panels of personal computers, smartphones and tablets, and the windows of automobiles. [Explanation of symbols]

[0083] 1. Base film 2. Coating section 2a Die 3. Surface treatment 3a Solid of revolution 3b Uneven groove 4 Hair dryer 5. Coating film 6. Coating layer 10. Laminated film manufacturing equipment

Claims

1. A method for manufacturing a laminated film, in which a coating layer is formed on a base film while the base film is continuously conveyed in the longitudinal direction, A coating step of applying a coating liquid onto the base film to form a coating film, and This includes a surface treatment step of treating the surface of the coating film with a surface treatment unit, The surface treatment unit comprises a groove-forming rotating body with a circular cross-section having grooves on its surface, The groove-shaping rotating body is positioned to contact the coating film, The groove-forming rotating body is configured such that 0.1w ≤ A ≤ 1.5w, (In the formula, w (mm) is the thickness of the coating film, and A (mm) ２ A' / mm) is the unit cross-sectional area of ​​the groove in a groove-shaped rotating body, and is calculated using the formula A = A' / P, where A'(mm) ２ (where ) is the cross-sectional area of ​​the groove, and P (mm) is the groove pitch.) The aforementioned surface treatment step is a step for reducing MD streaks without reducing the coating thickness. A method for manufacturing a laminated film, wherein in the surface treatment step, the groove-forming rotating body rotates in the opposite direction to the conveying direction of the base film.

2. The method for manufacturing a laminated film according to claim 1, wherein the groove-forming rotating body is rotated such that 1 ≤ Vr ≤ 50A + 1.

3. (In the formula, Vr is the ratio of the rotational speed of the groove-forming rotating body to the transport speed of the base film, and A (mm) ２ ( / mm) is the unit cross-sectional area of ​​the groove in the groove-forming rotating body.

3. The method for manufacturing a laminated film according to claim 1 or 2, wherein the grooves of the groove-forming rotating body are uneven grooves inclined with respect to the conveying direction of the base film.

4. The method for manufacturing a laminated film according to claim 3, wherein, when the conveying direction of the base film is set to 0°, the direction of the grooves of the groove-forming rotating body is inclined at 10° to 45°.

5. The method for manufacturing a laminated film according to any one of claims 1 to 4, wherein the coating liquid has a viscosity of 1 cp to 100 cp.

6. The method for manufacturing a laminated film according to any one of claims 1 to 5, wherein the coating film has a thickness of 20 μm or more.

7. A manufacturing apparatus for laminated films, which forms a coating layer on a base film while continuously conveying the base film in the longitudinal direction, The system comprises a coating section for applying a coating liquid onto the base film to form a coating film, and a surface treatment section for treating the surface of the coating film. The surface treatment unit comprises a groove-forming rotating body with a circular cross-section having grooves on its surface, The groove-shaping rotating body is positioned to contact the coating film, The groove-forming rotating body is configured such that 0.1w ≤ A ≤ 1.5w, (In the formula, w (mm) is the thickness of the coating film, and A (mm) ２ A' / mm) is the unit cross-sectional area of ​​the groove in a groove-shaped rotating body, and is calculated using the formula A = A' / P, where A'(mm) ２ (where ) is the cross-sectional area of ​​the groove, and P (mm) is the groove pitch.) The surface treatment section is for reducing MD streaks without reducing the coating thickness, and the groove-forming rotating body rotates in the opposite direction to the conveying direction of the base film, in a laminated film manufacturing apparatus.

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