Heating device and manufacturing method for coated sheet

Abstract

To provide a heating apparatus which, upon heating a coated film of a sheet in a production process for the sheet with a coated film, can prevent both end portions thereof in a sheet width direction from being excessively heated and can uniformly heat the coated film.SOLUTION: The present invention is directed to a heating apparatus for irradiating a coating liquid of a sheet under conveyance, which is coated with the coating liquid except on one or both end portions in a sheet width direction, with radiant light. The heating apparatus has a heating mechanism for irradiating the sheet with radiant light, and a shield member provided between the sheet and the heating mechanism, for covering a portion not coated with coating liquid of a sheet. The shield member is formed such that a surface opposed to the heating mechanism is inclined at a portion starting from an end closer to a center in the sheet width direction so as to get closer to the heating mechanism in an outward direction and that a surface opposed to the sheet is inclined at the portion starting from the end closer to the center in the sheet width direction so as to be departed from the sheet in the outward direction.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a heating device and a method for producing a coated sheet. [Background technology]

[0002] A simple hot air nozzle is generally used as a device for drying a coating liquid applied to a sheet. An infrared heater may also be used as a means for accelerating the heating of the coating liquid. Patent Document 1 discloses a heating device for efficiently drying a coating liquid, in which hot air nozzles and hot air outlets are alternately arranged in the sheet conveyance direction, with an infrared heater installed at the hot air outlet. This device uses radiant heat from the infrared heater to quickly raise the temperature of the sheet and coating liquid, and also blows hot air onto the sheet from the hot air nozzle, peeling off the evaporation layer near the surface of the sheet and venting it to the outside. This quickly heats the sheet and maintains a low vapor concentration near the coating liquid, thereby quickly drying the coating liquid.

[0003] The heating device disclosed in Patent Document 1 will be described below when applied to a production apparatus for sheets such as resin films. FIG. 2 is a schematic diagram of a resin film production apparatus incorporating a heating device, which includes an extruder 7, a die 8, a cooling drum 9, a longitudinal stretching machine 10, a coating liquid applicator 11, a heating device 12, a transverse stretching machine 13, and a take-up device 14. First, a polymer is extruded by the extruder 7, and the polymer is formed into a sheet through the die 8 and the cooling drum 9. The sheet is then stretched in the conveying direction by the longitudinal stretching machine 10, and a coating liquid is applied to one or both sides of the sheet by the coating liquid applicator 11. After the coating liquid is dried by the heating device 12, the sheet is stretched in the width direction by the transverse stretching machine 13 and continuously taken up by the take-up device 14. The transverse stretching machine 13 stretches the sheet in the width direction by gripping both widthwise ends of the sheet with a gripping mechanism called a clip or the like.

[0004] In this way, the sheet is stretched in a certain direction during the manufacturing process, aligning the molecules in the deformation direction and increasing its strength. However, after transverse stretching, both widthwise ends of the sheet have marks from gripping with clips or the like, making them unusable as a product. Therefore, both widthwise ends of the sheet with gripping marks are cut off at the exit of the transverse stretching machine 13. Both widthwise ends of the cut sheet are recovered, melted, and reused as polymer. However, if the recovered sheet has been coated with a coating liquid, it will become an impurity when melted, so both widthwise ends of the sheet are left uncoated in the coating liquid applicator 11 and are not coated with the coating liquid.

[0005] When the coating liquid is dried in the heating device 12, the uncoated portions at both widthwise ends of the sheet are prone to high temperatures because heat is not consumed by the latent heat of evaporation of the coating liquid, as in the coated portions. This leads to thermal deformation of the uncoated portions at both widthwise ends of the sheet, causing problems such as the inability of the gripping mechanism to grip the uncoated portions at both widthwise ends of the sheet at the entrance of the subsequent transverse stretching machine 13. Other problems include selective stretching of only the hot uncoated portions during stretching, resulting in uneven thickness and poor stretching. Furthermore, the coated portions that will become the final product may not be stretched the required amount, resulting in insufficient strength for the finished sheet or sheet tearing originating from the uncoated portions. In particular, the thicker the coating liquid in the coated portions, the greater the amount of heat that must be applied to complete drying, leading to increased overheating of the uncoated portions. Therefore, overheating of the uncoated portions is necessary. One solution is to install shielding members between the infrared heaters and hot air nozzles and the sheet at both widthwise ends of the sheet. In particular, since the main heating source is radiant heat from an infrared heater rather than a hot air nozzle, it is important to block infrared rays.

[0006] As a technique for blocking infrared rays, Patent Document 2 discloses a technique for reducing radiant light incident on both widthwise ends of a sheet using a porous shielding plate. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP2010-101595 Public Relations [Patent Document 2] Patent Publication No. 2012-198012 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the technology of Patent Document 2 poses a problem of uneven heating across the width of the sheet. This will be explained using Figures 3, 4, and 5. Figures 3, 4, and 5 are schematic cross-sectional views of a sheet heating device according to one embodiment of the prior art, taken along the direction perpendicular to the paper surface, in which the sheet travels. Reference numeral 1 denotes a sheet, and a coating film 2 applied in a previous process is formed in the central portion of the width of the sheet 1. Reference numeral 3 denotes a heating mechanism, such as a heater, that heats the coating film 2 with radiant light such as infrared rays. Reference numeral 4 denotes a shielding member that reduces the radiant light from reaching uncoated portions at both ends of the sheet 1 across the width. In Figure 3, radiant light incident on an arbitrary point X near the center of the coating film 2 is indicated by hatching and arrows. Similarly, in Figure 4, radiant light incident on an arbitrary point Y near both ends of the coating film 2 is indicated by hatching and arrows. In this way, near both ends of the coating film 2, part of the incident radiant light is blocked by the shielding member 4, so when the shielding member 4 is installed, the amount of heat received by the coating film 2 decreases, resulting in the problem that it is not heated uniformly.

[0009] On the other hand, Figure 5 shows the case where the shielding member 4 is placed close to the sheet 1. When the shielding member 4 is placed close to the sheet 1, the radiant light incident on any point Y near both ends of the coating film 2 is not blocked, allowing the coating film 2 to be heated uniformly. Placing the shielding member 4 close to the sheet 1 is one possible way to uniformly heat the coating film 2. However, since the shielding member 4 is constantly exposed to radiant light and reaches a very high temperature, using the shielding member 4 close to the sheet can result in heating of the uncoated areas at both ends of the sheet 1 in the width direction due to radiant heat or heat transfer from the shielding member 4. Patent Document 2 discloses a method of using a porous shielding plate and cooling the plate with gas flowing through the holes. However, when the shielding plate is placed close to the sheet 1, it becomes difficult for gas to flow through the holes, which can result in the shielding plate not fully achieving its cooling effect.

[0010] The present invention provides a method and heating device for producing a coated sheet that can prevent the above-mentioned problems from occurring when an applied coating liquid is heated in a heating device in the production of a coated sheet, can suppress overheating in uncoated areas, and can uniformly irradiate the coating with radiant light. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a heating device that irradiates radiant light toward a coating liquid on a sheet being conveyed, the coating liquid having been applied to the entire sheet except for one or both ends in the sheet width direction, the heating device comprising: a heating mechanism that irradiates radiant light toward a travel position of the sheet; a shielding member that is provided between a traveling position of the sheet and the heating mechanism, and that observes the sheet from the heating mechanism side while the sheet is being conveyed and covers the portion of the sheet that is not coated with the coating liquid; The shielding member has a width direction from the center toward the edge of the sheet defined as an outward direction. The surface facing the heating mechanism is inclined at a portion starting from an end closer to the center in the sheet width direction and approaching the heating mechanism as it moves outward, The surface facing the travel position of the sheet is inclined so as to move away from the travel position of the sheet as it moves toward the outside, at a portion starting from the end closer to the center in the width direction of the sheet. A heating device is provided.

[0012] According to a preferred embodiment of the present invention, there is provided a heating device, wherein the shielding member is a plate-like body having a main surface facing the heating mechanism and a main surface facing the sheet travel position.

[0013] Furthermore, according to a preferred embodiment of the present invention, there is provided a heating device in which the shielding member has a mechanism that can adjust the inclination angle of the inclined portion of the surface facing the heating mechanism and the inclined portion of the surface facing the running position of the sheet relative to the running position of the sheet.

[0014] According to a preferred embodiment of the present invention, there is provided a heating device in which the shielding member has a flow path therein for allowing a fluid to flow.

[0015] According to a preferred embodiment of the present invention, there is provided a heating device in which the flow path is disposed inside the shielding member at a portion closer to the center in the sheet width direction.

[0016] According to a preferred embodiment of the present invention, there is provided a heating device having an air supply mechanism that blows gas toward the running position of the sheet, and an exhaust mechanism that exhausts the gas blown by the air supply mechanism.

[0017] Furthermore, according to a preferred embodiment of the present invention, there is provided a heating device in which the surface of the shielding member facing the heating mechanism is covered with a coating material, and the material of the coating material is a material that has a higher reflectivity with respect to the radiant light irradiated from the heating mechanism than the material of the shielding member, and according to an even more preferred embodiment, there is provided a heating device in which the material of the coating material is a material containing gold.

[0018] In order to solve the above problems, the present invention provides a method for producing a coated sheet, which includes a step of applying a coating liquid to a sheet being transported, excluding one or both ends in the sheet width direction, and a heating step of drying the coating liquid applied to the sheet using the heating device of the present invention to form a coating film.

[0019] In the present invention, the "traveling position of the sheet" means the position through which the sheet travels when passing through the heating device while the sheet is actually being transported. [Effects of the Invention]

[0020] The heating device according to the present invention can suppress radiant light from entering both widthwise ends of the sheet where no coating liquid is applied when heating a coating film applied to the sheet in a continuous sheet production process. Furthermore, since a distance is maintained between the shielding member and the uncoated portion, heat transfer from the heated shielding member to the sheet can be prevented. Furthermore, radiant light can be uniformly irradiated onto the coating film. Therefore, uneven heating of the coating film can be prevented while suppressing overheating of both widthwise ends of the sheet where no coating liquid is applied. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a schematic cross-sectional view showing a seat heating device according to one embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a manufacturing process of a resin film according to one embodiment of the present invention. [Figure 3] FIG. 1 is a schematic cross-sectional view showing a seat heating device according to an embodiment of the prior art. [Figure 4] FIG. 1 is a schematic cross-sectional view showing a seat heating device according to an embodiment of the prior art. [Figure 5] FIG. 1 is a schematic cross-sectional view showing a seat heating device according to an embodiment of the prior art. [Figure 6] 1 is a schematic cross-sectional view showing a seat heating device according to one embodiment of the present invention. [Figure 7] 1 is a schematic cross-sectional view showing a seat heating device according to one embodiment of the present invention. [Figure 8] 1 is a schematic cross-sectional view showing a seat heating device according to one embodiment of the present invention. [Figure 9] 1 is a schematic cross-sectional view showing a seat heating device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, examples of the best mode of the present invention will be described with reference to the drawings, but the present invention is not limited to the following mode.

[0023] 1 and 6 to 9 are schematic cross-sectional views of a sheet heating device according to one embodiment of the present invention, in the direction in which the sheet travels in the direction perpendicular to the paper surface.

[0024] First, the configuration of the heating device of the present invention will be described using Figure 1. Reference numeral 1 denotes a sheet, and a coating film 2 applied in a previous process is formed in the central portion of the width direction of the sheet 1. Reference numeral 3 denotes a heating mechanism, which heats the coating film 2 with radiant light. In the best mode of the present invention, an infrared heater is used for this heating mechanism 3. However, the heating mechanism 3 is not limited to an infrared heater; any heater can be used that is optimal, taking into account the absorption wavelengths of the sheet 1 and coating film 2, the heater's maximum output, and lifespan. Furthermore, the distance between the sheet 1 and the heating mechanism 3 is preferably small for efficient heating, but is also preferably large enough to prevent contact even if the sheet 1 is thermally deformed or shaken vertically. Specifically, the distance is preferably in the range of 10 to 100 mm. Furthermore, the heating mechanism 3 preferably has a width length sufficiently larger than the width length of the coating film 2 so that the coating film 2 can be heated uniformly across the sheet width. Specifically, the heating mechanism 3 is preferably 10 to 100 mm longer on both sides than the width of the coating film 2.

[0025] Reference numeral 4 denotes a shielding member that prevents radiant light from the heating mechanism 3 from reaching both widthwise ends of the sheet 1 where the coating film 2 is not formed. The shielding member 4 has an inclined surface 5 facing the heating mechanism 3 and an inclined surface 6 facing the sheet 1. If the direction from the center of the width of the sheet 1 toward the edges is defined as the outward direction, the inclined surface 5 is inclined from the edge closer to the center of the width of the sheet 1, approaches the sheet 1 on the side closer to the center of the width of the sheet 1, and approaches the heating mechanism 3 as it moves outward. Similarly, the inclined surface 6 is inclined from the edge closer to the center of the width of the sheet 1, approaches the sheet 1 on the side closer to the center of the width of the sheet 1, and moves away from the sheet 1 as it moves outward. Here, the inclination angle of the inclined surface 5 relative to the sheet 1 is defined as inclination angle a, and the inclination angle of the inclined surface 6 relative to the sheet 1 is defined as inclination angle b. Point Y is an arbitrary point near both ends of the coating film 2. The radiant light irradiated from the heating mechanism 3 and incident at point Y is indicated by an arrow and hatching.

[0026] Because the shielding member 4 has an inclined surface 5 facing the heating mechanism 3, the radiant light can be irradiated up to near both ends of the coating film 2 without being blocked, as shown at point Y in Figure 1, thereby enabling the coating film 2 to be heated uniformly across the width. The inclination angle a of the inclined surface 5 will be explained in detail using Figures 1 and 6. Figure 6 shows a diagram in which the inclination angle a is larger than that shown in Figure 1, but when considering the radiant light incident on point Y, which is near both ends of the coating film 2 as in Figure 1, some of the radiant light is cut off. As such, the smaller the inclination angle a, the wider the area that can be heated uniformly, so a smaller inclination angle a is preferable.

[0027] Furthermore, because the shielding member 4 has an inclined surface 6 on the sheet 1 side, a distance is secured between the sheet 1 and the shielding member 4. This allows for a reduction in heat transferred from the shielding member 4 to both widthwise ends of the sheet 1 by thermal radiation or conduction, even if the shielding member 4 is constantly irradiated with radiant light from the heating mechanism 3 and becomes hot, and also makes it difficult for the sheet 1 to come into contact with the shielding member 4 even if it deforms. Therefore, the inclination angle b of the inclined surface 6 is preferably as large as possible in order to further secure a distance between the sheet 1 and the shielding member 4.

[0028] From the above, it is preferable that the inclination angle a is smaller, and the inclination angle b is larger. However, since the inclination angles a and b are the angles of the inclined surfaces on the front and back of the same member, it is difficult to make the inclination angle a extremely small and the inclination angle b extremely large, but it is preferable that both the inclination angles a and b are 10 to 60°. It is more preferable that both the inclination angles a and b are 30 to 60°.

[0029] The shielding member 4 does not need to be configured as a flat surface, but may have a curved surface. Similarly, the inclined surface 5 and the inclined surface 6 may also be curved surfaces.

[0030] Furthermore, the shielding member 4 is preferably a thin plate-like body. This will be explained using FIGS. 1 and 9. FIG. 9 shows a case where the thickness of the shielding member 4 is thicker than that of FIG. 1. However, when considering the radiant light incident at point Y near both ends of the coating film 2, as in FIG. 1, a portion of the radiant light is cut off. As described above, if the shielding member 4 is thick, the area that cannot be uniformly heated becomes wider. Therefore, the shielding member 4 is preferably a plate-like body, and the thinner the thickness, the better. However, if the strength is reduced by making the shielding member 4 thinner, there is a risk that the shielding member 4 will come into contact with the sheet 1 due to thermal deformation. Therefore, although depending on the material, the thickness of the plate-like body is preferably 0.05 to 10 mm. More preferably, the plate-like thickness is 0.05 to 2 mm.

[0031] The position of the shielding member 4 perpendicular to the sheet 1 is preferably close to the sheet 1 to prevent radiant light from obliquely entering the uncoated portions of the sheet 1 at both ends in the width direction. This will be explained using FIG. 7. The radiant light entering the uncoated portions is indicated by hatching in FIG. 7. As described above, radiant light enters the uncoated portions of the sheet 1 through the gap between the shielding member 4 and the sheet 1, heating the uncoated portions. Therefore, it is preferable to reduce this as much as possible. The smaller the distance between the shielding member 4 and the sheet 1, the less likely this radiant light is to enter. Therefore, it is preferable to position the shielding member 4 close to the sheet 1. However, if the distance between the shielding member 4 and the sheet 1 is too close, the shielding member 4 may come into contact with the sheet 1 if the sheet 1 vibrates in a direction perpendicular to the conveying direction. Therefore, it is desirable to set the distance between the sheet 1 and the shielding member 4 to 3 to 20 mm at the closest point.

[0032] The position of the shielding member 4 in the width direction of the sheet will be explained using Figure 8. Point P is the end of the shielding member 4 closest to the center of the sheet 1 in the width direction. The closer Point P is to the center of the sheet 1 in the width direction, the more radiant light can be suppressed from entering the uncoated areas, but the area of the coating film 2 that is uniformly irradiated with radiant light will be narrower. Conversely, the closer Point P is to both ends of the sheet 1 in the width direction, the more radiant light will enter the uncoated areas, but the area of the coating film 2 that is uniformly irradiated with radiant light can be widened. Therefore, the position of the shielding member 4 in the width direction can be determined taking into account the area of the coating film 2 that is desired to be uniformly heated and the degree of temperature rise in the uncoated areas at both ends of the sheet 1 in the width direction. However, when the positions of both ends of the coating film 2 in the width direction are indicated by the dashed dotted line, it is preferable that Point P be within a range of ±15 mm of the dashed dotted line. It is preferable that the shielding member 4 has a mechanism that can adjust the inclination angle using a feed screw, etc. It is also preferable that the shielding member 4 has a mechanism that can adjust not only the inclination angle but also the width direction of the sheet 1 and the vertical direction of the sheet 1.

[0033] It is preferable that the shielding member 4 has a flow path inside for flowing a fluid. By having the inclined surface 6, heat is less likely to be transferred to the sheet 1 even when the shielding member 4 becomes hot, but by flowing a fluid through the shielding member 4 to cool it, it is possible to further reduce the heat transferred to the uncoated parts of the sheet 1. While it is possible to flow cooling air or cooling water, it is more preferable to flow cooling water, which has a high thermal conductivity. Furthermore, instead of cooling the entire surface of the shielding member 4, the internal flow path may be configured to cool only the portion of the shielding member 4 that is close to the sheet 1. By limiting the cooling to a certain portion, energy can be saved.

[0034] The material for the shielding member 4 may be any metal such as aluminum, stainless steel, silver, or copper, or ceramic or glass, but it is preferable to use a material that has a high infrared reflectance, thermal conductivity, and heat resistance temperature, and a low thermal expansion coefficient. This makes it difficult for the temperature of the shielding member 4 to rise due to infrared rays, increases the cooling effect of a fluid such as cooling water, and makes it less likely for the shielding member 4 to burn or thermally deform.

[0035] The higher the reflectivity of the shielding member 4 with respect to the radiant light irradiated from the heating mechanism 3, the more the heat absorption of the shielding member 4 can be reduced. Therefore, it is preferable to cover the surface of the shielding member 4 facing the heating mechanism 3 with a coating material, and to use a material that has a higher reflectivity with respect to the radiant light irradiated from the heating mechanism 3 than the material of the shielding member 4. Even if a material with high reflectivity is expensive, by using a material with high reflectivity only for the coating material in this way, the reflectivity of the shielding member 4 can be improved more inexpensively than if the shielding member 4 itself were made of a material with high reflectivity. It is not necessary to cover the entire surface of the shielding member 4 facing the heating mechanism 3 with a coating material; it is also effective to cover only the portion that is frequently hit by radiant light, but it is more preferable to cover the entire surface with a coating material.

[0036] The specific coating material can be selected based on the wavelength of the radiant light emitted from the heating mechanism 3 and the operating environment, but a material containing gold, which has high reflectivity in the near-infrared range, is preferred. A material containing 90% or more by mass of gold is more preferred.

[0037] In addition to the heating mechanism 3, the heating device preferably has an air supply mechanism that blows gas toward the sheet 1, and an exhaust mechanism that exhausts the gas blown by the air supply mechanism. The air supply mechanism and exhaust mechanism heat the coating film 2, removing evaporated components and enabling efficient drying. In the best mode of the present invention, a metal nozzle is used for the air supply mechanism. Examples of the nozzle include a slit nozzle, a hole nozzle, and a stripe nozzle. Furthermore, by arranging the air supply nozzle and the exhaust outlet of the exhaust mechanism alternately in the conveyance direction of the sheet 1 and arranging the heating mechanism 3 at the exhaust outlet, it is possible to achieve both highly efficient heating of the coating film 2 and removal of evaporated components.

[0038] In the best mode of the present invention, air is used as the gas to be supplied, but steam or inert gas may also be used when used in explosion-proof equipment. The temperature of the gas depends on the sheet 1 and the coating film 2, but is preferably 30 to 150°C, more preferably 60 to 120°C. If the hot air temperature is within this range, the drying efficiency is higher and the shielding member 4 is less likely to be overheated.

[0039] Examples of the sheet 1 to be heated by the heating device of the present invention include films made of polyester, polyolefin, polyamide, polyphenylene sulfide, acetate, polycarbonate, acrylic resin, etc. The resin film may be a single-layer film or a composite film having a laminated structure of two or more layers. In the composite film, the resins constituting the inner layer and the surface layer may be chemically different resins or the same resin. The thickness of the sheet 1 is not particularly limited, but from the viewpoints of mechanical strength and handleability, the thickness is preferably 10 to 500 μm, and more preferably 20 to 300 μm.

[0040] The tension applied per unit width when conveying the sheet 1 is preferably 100 to 3000 N / m. When the tension is in this range, the sheet 1 is less likely to meander or vibrate up and down perpendicular to the conveying direction, reducing the possibility of scratches on the surface of the sheet 1 due to friction with the rolls or contact with the heating device. Furthermore, the sheet 1 is less likely to deform even when heated, reducing the possibility of scratches occurring in areas where high contact pressure is locally generated between the rolls and the sheet 1.

[0041] Examples of the coating liquid to be applied to the surface of the sheet 1 include acrylic resins, urethane resins, melamine resins, epoxy resins, and polyester resins, and the film thickness is preferably 1 to 15 μm. The coating liquid may be applied to only one side of the sheet 1 or to both sides.

[0042] Coating methods using a coating device include rod coating, gravure coating, and reverse roll coating. These methods can be used alone or in combination. These coating methods are suitable for obtaining a uniformly coated surface with little coating unevenness. In the present invention, it is more preferable to use rod coating, which allows for easy adjustment of the coating amount. [Example]

[0043] Next, the above embodiment will be specifically described based on examples, but the above embodiment is not necessarily limited to the following examples.

[0044] [Example 1] Chips of polyethylene terephthalate (PET) with an intrinsic viscosity (also known as inherent viscosity) of 0.62 dl / g (measured in o-chlorophenol at 25°C according to JIS K7367, 1996) were thoroughly vacuum-dried at 180°C, fed into extruder 7 (Fig. 2), melted at 285°C, extruded into a sheet through T-shaped die 8, and then wrapped around mirror-finished cooling drum 9 (surface temperature 23°C) using an electrostatic casting method, where it was cooled and solidified to form an unstretched film. Subsequently, in longitudinal stretching machine 10, this unstretched film was heated between rolls heated to 80°C, stretched 3.2 times in the conveying direction while being heated by an infrared heater, and cooled between cooling rolls adjusted to 50°C to form uniaxially stretched sheet 1. Sheet 1 had a width of 900 mm and a thickness of 200 μm.

[0045] Next, a coating liquid was applied to the upper surface of this sheet 1, which was traveling at a speed of 50 m / min, using a coating liquid applicator 11. The width of the coating film 2 was 700 mm, and 100 mm of uncoated area was provided at each end of the sheet 1. The coating liquid applicator 11 was a rod coating type, and the coating rod was a stainless steel round bar with a diameter of 12.7 mm and a length of 1400 mm. The groove specifications of the coating rod were a groove depth of 17 μm and a groove pitch of 100 μm. The thickness of the coating liquid in the coating film 2 was measured at the outlet of the coating liquid applicator 11 using a moisture meter (RX-200, manufactured by Kurabo Industries Co., Ltd.) and was found to be 6 μm.

[0046] Next, as the heating device 12, a heating device in which air supply mechanisms and exhaust mechanisms are alternately arranged in the conveying direction of the sheet 1 and a heating mechanism 3 is provided at the exhaust outlet of the exhaust mechanism was used to heat the coating film 2 from the top surface of the sheet 1, thereby completing the drying of the coating film 2.

[0047] The coated sheet was then introduced into a 90°C oven (preheating section) in the transverse stretching machine 13, where it was heated, and subsequently stretched 3.5 times in the width direction in the 100°C oven (stretching section). The coated sheet was then heat-set in the 220°C oven (heat-setting section) while being relaxed by 5% in the width direction, to obtain a biaxially stretched film with a coating on one side. The tension between the longitudinal stretching machine 10 and the transverse stretching machine 13 was controlled by a dancer roll so that the tension per unit width applied in the running direction of the sheet 1 was 8000 N / m.

[0048] The coating liquid was a mixture of 100 parts by mass of a polyester copolymer emulsion (components: 90 mol% terephthalic acid, 10 mol% 5-sodium sulfoisophthalic acid, 96 mol% ethylene glycol, 3 mol% neopentyl glycol, and 1 mol% diethylene glycol), 5 parts by mass of a melamine-based crosslinking agent (a solution prepared by diluting imino-methylated melamine with a mixed solvent of 10% isopropyl alcohol and 90% water), and 1 part by mass of colloidal silica particles with an average particle size of 0.1 μm. The viscosity of this coating liquid was 2 mPa·s at 25°C. Furthermore, when the temperature of the sheet 1 at the outlet of the coating liquid applicator 11 was measured using a thermograph (CPA-E6, manufactured by FLIR), the temperature was 25–26°C for the coating film 2 and 28–29°C for the uncoated area.

[0049] The heating device 12 had four air intake units and five exhaust units, arranged alternately in the conveyance direction of the sheet 1, and three heating units 3 were arranged at the exhaust outlets of the exhaust units, for a total of 15 units. The air intake and exhaust units were made of stainless steel (SUS304), and were 100 mm long in the conveyance direction of the sheet 1 and 1200 mm long in the width direction, with a gap of 30 mm between them and the sheet 1. The heating unit 3 was a short-wavelength infrared heater (ZKC6000 / 1000G, manufactured by Heraeus Inc.) 23 mm long in the conveyance direction of the sheet 1, 1150 mm long in the width direction, and 11 mm long in the vertical direction, and was installed so that the distance between the sheet 1 and the surface of the short-wavelength infrared heater was 40 mm.

[0050] The hot air blowing section of the air supply mechanism was a hole nozzle with 8mm diameter holes evenly distributed in a staggered pattern with an aperture ratio of 9.5%, and air heated to 100°C was blown out from the holes at a wind speed of 12m / s. The output of the short-wave infrared heater was set to 6.5kW per heater. This resulted in the filament temperature of the infrared heater being approximately 2100°C (Heraeus Inc. catalog value). The suction flow rate from the exhaust mechanism was set to the same as the total flow rate of the hot air blown out of the air supply mechanism.

[0051] Shielding members 4, made by bending a 4 mm thick stainless steel plate (SUS304), were attached between both widthwise ends of the sheet 1 and the heating device 12. The inclination angles a and b of the shielding members 4 were both 26°. The shielding members 4 were positioned so that point P, at the end of the sheet center side of the shielding member 4 shown in Figure 8, was located 10 mm vertically from the sheet 1 toward the heating device 12, and in the width direction, point P was aligned with both widthwise ends of the coating film 2. The shielding members 4 were also positioned so that the distance between the horizontal surface of the shielding member 4 on the sheet 1 side and the sheet 1 was 20 mm.

[0052] To evaluate whether the uncoated area was overheated, the temperature of the uncoated area was measured at the outlet of the heating device 12 using a thermograph (CPA-E6, manufactured by FLIR) and it was confirmed whether the temperature of the highest point was below the allowable temperature of 70°C. This allowable temperature was determined by repeating the experiment.

[0053] The method for evaluating the uniformity of heating of the coated area was to measure the residual moisture in the coating film 2 at the exit of the heating device 12 using a moisture meter (RX-200, manufactured by Kurabo Industries, Ltd.). If residual moisture was detected in the central area of the sheet excluding 20 mm from both ends of the width direction of the coating film 2, which will become the product, the sheet was evaluated as having uneven drying and being poor; if no residual moisture was detected, the sheet was evaluated as having no uneven drying and being good.

[0054] When coated sheets were manufactured using this equipment, no residual moisture was found in the product, and it was evaluated as having no uneven drying. In addition, the temperature of the uncoated part was 67°C, which was within the allowable range, and stable production was possible.

[0055] [Example 2] The coating was dried under the same conditions as in Example 1, except that the shielding member 4 was replaced with a shielding member having an internal flow path and cooling water was passed through. Since no residual moisture was found in the product, it was evaluated as having no uneven drying. Furthermore, the temperature of the uncoated portion was 58°C, which was within the allowable range, allowing stable production. It was confirmed that this was more preferable than Example 1, as there was a margin of error up to the allowable temperature of 70°C.

[0056] [Example 3] The coating was dried under the same conditions as in Example 1, except that the shielding member 4 was changed to a shielding member in which the entire surface facing the heating mechanism 3 was coated with a coating material containing 99.6% by mass of gold. Since no residual moisture was found in the product, it was evaluated as having no uneven drying. In addition, the temperature of the uncoated part was 63°C, which was within the allowable range, and stable production was possible. It was confirmed that there was a margin up to the allowable temperature of 70°C, which was more preferable than in Example 1.

[0057] [Comparative Example 1] The coating was dried under the same conditions as in Example 1, except that the shielding member 4 was changed to a 4 mm thick plate with no inclined surface that was horizontal to the sheet 1 and the distance from the sheet 1 was changed to 20 mm. The temperature of the uncoated area was 69°C, which was within the allowable range, but residual moisture was found in the 10 mm edge of the product, so it was evaluated as having uneven drying.

[0058] Comparative Example 2 The coating was dried under the same conditions as in Example 1, except that the shielding member 4 was changed to a 4 mm thick plate with no inclined surface that was horizontal to the sheet 1, and the distance from the sheet 1 was changed to 10 mm. No residual moisture was found in the product, so it was evaluated as having no uneven drying, but the temperature of the uncoated part was 71°C, which exceeded the allowable range.

[0059] [summary] The results of the examples and comparative examples are summarized in Table 1. In Examples 1 to 3, a plate material with an inclined surface was used as the shielding member, which prevented overheating of the uncoated area while also suppressing uneven drying. Furthermore, since the temperature of the uncoated area in Examples 2 and 3 was lower than in Example 1, it can be said that it is more preferable to run cooling water inside the shielding member or to cover the shielding member with a covering material.

[0060] Comparative Examples 1 and 2 show the results when a horizontal plate material without an inclined surface was used as the shielding member. In Comparative Example 1, the shielding member was separated from the sheet, while in Comparative Example 2, the shielding member was placed close to the sheet. In Comparative Example 1, the temperature of the uncoated area did not exceed the allowable temperature, but uneven drying occurred. Conversely, in Comparative Example 2, the temperature of the uncoated area exceeded the allowable temperature, but uneven drying did not occur. It can be said that the use of a shielding member with an inclined surface is important.

[0061] [Table 1] [Industrial Applicability]

[0062] The present invention is not limited to heating of coating films, but can also be applied to heating of resin films, etc., but the scope of application is not limited to these. [Explanation of symbols]

[0063] 1 sheet 2 Coating 3 Heating mechanism 4 Shielding material 5 Inclined surface on the heating mechanism side 6. Inclined surface on the seat side 12 Heating device

Claims

1. A heating device that irradiates radiant light toward a coating liquid on a sheet being conveyed, the coating liquid having been applied to the sheet except for one or both ends in the sheet width direction, the heating device comprising: a heating mechanism that irradiates radiant light toward a travel position of the sheet; a shielding member that is provided between a travel position of the sheet and the heating mechanism, and that observes the sheet from the heating mechanism side while the sheet is being conveyed and covers a portion of the sheet that is not coated with the coating liquid; The shielding member has a width direction from the center toward the edge of the sheet defined as an outward direction. The surface facing the heating mechanism is inclined at a portion starting from an end closer to the center in the sheet width direction and approaching the heating mechanism as it extends outward, The surface facing the sheet travel position is inclined so as to move away from the sheet travel position as it extends outward from the end closer to the center in the sheet width direction, a mechanism for adjusting the inclination angle of the inclined portion of the surface facing the heating mechanism and the inclined portion of the surface facing the sheet travel position relative to the sheet travel position; heating device.

2. A heating device that irradiates radiant light toward a coating liquid on a sheet being conveyed, the coating liquid having been applied to the sheet except for one or both ends in the sheet width direction, the heating device comprising: a heating mechanism that irradiates radiant light toward a travel position of the sheet; a shielding member that is provided between a travel position of the sheet and the heating mechanism, and that observes the sheet from the heating mechanism side while the sheet is being conveyed and covers a portion of the sheet that is not coated with the coating liquid; The shielding member has a width direction from the center toward the edge of the sheet defined as an outward direction. The surface facing the heating mechanism is inclined at a portion starting from an end closer to the center in the sheet width direction and approaching the heating mechanism as it extends outward, The surface facing the sheet travel position is inclined so as to move away from the sheet travel position as it extends outward from the end closer to the center in the sheet width direction, a flow path for allowing a fluid to flow inside the shielding member, the flow path being arranged in a portion of the shielding member closer to the center in the sheet width direction; heating device.

3. 3. A method for producing a coated sheet, comprising: a step of applying a coating liquid to a sheet being conveyed, except for one or both ends in the sheet width direction; and a heating step of drying the coating liquid applied to the sheet using the heating device of claim 1 or 2 to form a coating film.

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