Manufacturing method for light control film, and light control film

Abstract

To suppresses appearance deterioration caused by curling.SOLUTION: A laminate 11 of a light control film comprises, as constituent members: a film base material 12 formed from a thermoplastic resin; and two types of polarizing films 15A and 15B each formed from a different type of thermoplastic resin other than the film base material 12. A process of manufacturing a light control film includes a laminate forming process and a straightening process. In the laminate forming process, the two types of polarizing films 15A and 15B are arranged alternately in a first direction and bonded to a surface 13 to be laminated of the film base material 12, thereby forming the laminate 11. In the straightening process, the laminate 11 curled in a thickness direction due to heating and cooling during bonding is heated from both sides while being pressed from at least one side in the same direction by a pair of rollers 41 and 42. Curling is corrected by heating the roller 41 on a non-curled side at a higher temperature than the heating using the roller 42 on the curled side.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] The present invention relates to a method for producing a light control film used in a light control device, and to a light control film. [Background technology]

[0002] A light control device is known that includes a pair of light control films arranged facing each other in the thickness direction. In this light control device, the light transmittance of both light control films is adjusted by displacing the two light control films relatively in a first direction perpendicular to the thickness direction (see, for example, Patent Document 1).

[0003] The laminate of each light control film includes a film substrate and two types of polarizing films each laminated on the film substrate. The film substrate has one surface in the thickness direction as a surface to be laminated. Each polarizing film is in the shape of a strip whose dimension in a second direction perpendicular to both the thickness direction and the first direction is longer than the dimension in the first direction. The two types of polarizing films have polarization axes extending in different directions.

[0004] When manufacturing the light control film, for example, a film substrate having an adhesive layer formed on the surface to be laminated is used. Two types of polarizing films are arranged alternately in the first direction and are bonded to the surface to be laminated via the adhesive layer. The film substrate to which all the polarizing films are bonded is heated and cooled, whereby the adhesive layer is cured to form a laminate. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 9-310567 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the conventional manufacturing method of the light control film, a laminate is formed that curls due to heating and cooling. This is because the film substrate and the polarizing film are made of thermoplastic resins with different thermal shrinkage rates. In the laminate, the film substrate and two types of polarizing films are laminated in the thickness direction as components, and the light control film curls toward the component with the larger thermal shrinkage rate in the thickness direction. When curling occurs, the appearance of the laminate and, ultimately, the light control film is impaired.

[0007] Even when two types of polarizing films are bonded to a film substrate by a method other than adhesion, if the bonding involves heating and cooling, the same problems as described above can occur. [Means for solving the problem]

[0008] A method for producing a light control film and various aspects of the light control film to solve the above problems will be described below. [Aspect 1] In a light control device having a pair of light control elements arranged opposite to each other in a thickness direction, and adjusting the amount of light transmitted through both light control elements by relatively displacing the two light control elements in a first direction perpendicular to the thickness direction, a method for manufacturing a light control film used as the light control elements, wherein a laminate of the light control film comprises, as components, a film base material formed from a thermoplastic resin and two types of polarizing films each formed from a type of thermoplastic resin different from that of the film base material, the film base material has one surface in the thickness direction as a surface to be laminated, and the two types of polarizing films are arranged in the thickness direction and the first direction. a second direction perpendicular to both directions, the second direction being longer than the first direction, and the film has a polarization axis extending in different directions; and the process for producing the light-controlling film includes a laminate formation process for forming the laminate by arranging two types of the polarizing films alternately in the first direction and bonding them to the laminated surface; and a straightening process for straightening the curl by heating the laminate from both sides while applying pressure to at least one side in the same direction, the laminate having curled in the thickness direction due to the heating and cooling during the bonding, and heating the uncurled side at a higher temperature than the heating from the curled side.

[0009] According to the above method, in the laminate formation step, two types of rectangular polarizing films, each having a dimension in the second direction longer than the dimension in the first direction, are arranged alternately in the first direction. All of the polarizing films are bonded to the surface to be laminated of the film substrate to form a laminate.

[0010] Here, the film substrate, which is a constituent member of the laminate, and the polarizing film, which is also a constituent member of the laminate, are formed from different types of thermoplastic resins. Therefore, when heating and cooling are performed during the above-mentioned bonding of the polarizing film, a curled laminate is formed in the thickness direction on the side of the constituent member with a larger heat shrinkage rate due to the difference in the heat shrinkage rate between the above-mentioned constituent members. The appearance of the formed laminate is inferior to that of a laminate that is not curled.

[0011] In the straightening process, the curled laminate as described above is heated from both sides while being pressurized from at least one side in the thickness direction. Heating from the non-curled side is performed at a higher temperature than heating from the curled side. More heat is applied to the components on the non-curled side than to the components on the curled side. Due to this difference in the amount of heat applied, the components on the non-curled side attempt to deform more than the curled components, and the laminate deforms toward the non-curled side. As a result, it is believed that the curl is straightened and the amount of curl is reduced. As the amount of curl is reduced, the degree to which the curl degrades the appearance of the laminate and therefore the light control film is reduced.

[0012] [Aspect 2] A method for producing a light control film according to [Aspect 1], wherein in the laminate formation process, the two types of polarizing films are each bonded to the laminated surface by adhesion. According to the above method, in the laminate formation step, two types of polarizing films are arranged alternately in the first direction and adhered to the surface of the film substrate to be laminated. This adhesion bonds each polarizing film to the surface to be laminated via an adhesive layer. When heating and cooling are performed to harden the adhesive layer, a curled laminate is formed in the thickness direction on the side of the component with the smaller thermal shrinkage rate due to the difference in thermal shrinkage rate between the above-mentioned components. However, the curl is straightened by performing the above-mentioned curl straightening step on the curled laminate.

[0013] [Aspect 3] The straightening process uses a pair of rollers that are arranged opposite each other in the thickness direction and rotate in opposite directions while being heated so that at least their outer circumferential surfaces are at different temperatures, and in the straightening process, the laminate is passed between the pair of rollers with the component that is curled in the thickness direction positioned on the side of the roller with a lower temperature and the component that is not curled positioned on the side of the roller with a higher temperature, thereby sending the laminate while being pressurized and heated. This is a method for manufacturing a light-controlling film as described in [Aspect 1] or [Aspect 2].

[0014] According to the above method, in the straightening step, the component of the laminate on the side that is curled in the thickness direction is positioned on the side of the roller with a lower temperature, and the component of the uncurled side is positioned on the side of the roller with a higher temperature. The laminate in this state is then passed between a pair of rollers. The laminate is fed by a pair of rollers that rotate in opposite directions. Furthermore, the laminate is pressed by at least one of the rollers as it passes between the pair of rollers. Furthermore, the laminate is heated by both rollers as it passes. Heating by the roller on the uncurled side is performed at a higher temperature than heating by the roller on the curled side.

[0015] In this manner, by using a pair of rollers, the laminate is fed while being pressurized and heated, and therefore, it is possible to perform pressurization and heating of the laminate continuously and efficiently perform curl correction.

[0016] [Aspect 4] A method for manufacturing a light-controlling film as described in [Aspect 3], wherein the outer periphery of one of the rollers used in the straightening process is formed from a material having a higher elasticity than the outer periphery of the other roller, and in the straightening process, the laminate is passed between the pair of rollers with the component member having lower strength among the components of the laminate positioned on the side of the roller whose outer periphery is formed from the material having higher elasticity, and the component member having higher strength positioned on the side of the roller whose outer periphery is formed from the material having lower elasticity.

[0017] According to the above method, in the straightening step, among the constituent members of the laminate, the constituent member having low strength is positioned on the side of the roller whose outer periphery is formed of a material with high elasticity. The constituent member having high strength is positioned on the side of the roller whose outer periphery is formed of a material with low elasticity. Then, the laminate in the above state is passed between a pair of rollers. The laminate is sent by a pair of rollers rotating in opposite directions. At this time, the constituent member having low strength is contacted by the outer periphery of the roller whose outer periphery is formed of a material with high elasticity. The constituent member having high strength is contacted by the outer periphery of the roller whose outer periphery is formed of a material with low elasticity. Therefore, the constituent member having low strength is less likely to be damaged, such as scratched, than when the constituent member has a contact with the outer periphery of the roller whose outer periphery is formed of a material with low elasticity.

[0018] [Aspect 5] The outer periphery of one of the rollers is formed using rubber as the highly elastic material, and the outer periphery of the other roller is formed using metal as the less elastic material, and in the correction process, the laminate is passed between the pair of rollers with each polarizing film being the component with lower strength and the outer periphery positioned on the roller side formed from the rubber, and the film substrate being the component with higher strength and the outer periphery positioned on the roller side formed from the metal. This is a method for manufacturing a light-controlling film as described in [Aspect 4].

[0019] According to the above method, of the constituent members of the laminate, the polarizing film is the constituent member having low strength, and the film substrate is the constituent member having high strength. In the straightening process, the polarizing film is positioned on the side of the roller whose outer periphery is made of rubber. The film substrate is positioned on the side of the roller whose outer periphery is made of metal. The laminate in the above state is then fed by the pair of rollers. At this time, the outer periphery of the roller whose outer periphery is made of rubber contacts the polarizing film having low strength. The outer periphery of the roller whose outer periphery is made of metal contacts the film substrate having high strength. Therefore, when the laminate is fed by the pair of rollers, the polarizing film having low strength is less likely to be damaged, such as scratched.

[0020] [Aspect 6] In a light control device having a pair of light control elements arranged opposite to each other in a thickness direction, and adjusting the amount of light transmitted through both light control elements by relatively displacing both light control elements in a first direction perpendicular to the thickness direction, a light control film used as the light control element has a laminate having, as components, a film base material formed from a thermoplastic resin and two types of polarizing films each formed from a type of thermoplastic resin different from that of the film base material, and the film base material has one surface in the thickness direction as a laminated surface, and the two types of polarizing films have a dimension in a second direction perpendicular to both the thickness direction and the first direction that is equal to or larger than the above. A light-controlling film having a rectangular shape longer than one dimension and having polarization axes extending in different directions, the laminate being formed by arranging two types of the polarizing films alternately in the first direction and bonding them to the laminated surface, and further having been subjected to a process for straightening curl in the thickness direction, a square portion of the laminate with one side measuring 100 mm is used as a test piece, the test piece is placed on a horizontal surface with the thickness direction aligned in the up-down direction, and further, when the curl amount is the distance between the horizontal surface and the point of the test piece that is farthest from the horizontal surface due to the curl, the average curl amount of the curled portion of the test piece is 1 mm or less.

[0021] Here, the film substrate and the polarizing film, which are the constituent members of the laminate, are made of different types of thermoplastic resins. Therefore, when the polarizing film is heated and cooled during the above-mentioned bonding, the laminate is curled in the thickness direction toward the constituent member with the larger thermal shrinkage rate due to the difference in thermal shrinkage rate between the constituent members. This curling deteriorates the appearance of the laminate, and therefore the light control film.

[0022] In this regard, according to the above configuration, the laminate is subjected to a treatment for straightening the curl. Of the laminate that has been subjected to this treatment, a square portion with one side measuring 100 mm is used as the test piece. The test piece is placed on a horizontal surface with the thickness direction aligned vertically. Furthermore, the distance between the horizontal surface and the point of the test piece that is farthest from the horizontal surface due to curling is determined as the curl amount. The average curl amount of the curled portion of the test piece is set to 1 mm or less. The appearance of the laminate is close to that of an uncurled one. Effect of the Invention

[0023] According to the present invention, deterioration in appearance caused by curling can be suppressed. [Brief description of the drawings]

[0024] [Figure 1] FIG. 1 is a perspective view of a light control device according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing a pair of light control films in FIG. 1 in a separated state. [Diagram 3] FIG. 2 is a perspective view showing a laminate and a frame that constitute one of the light control films (the lower side in FIG. 2) in the embodiment, in which the laminate and the frame are separated. [Figure 4] FIG. 4 is a perspective view showing components of the laminate in FIG. 3 separated from one another. [Diagram 5] FIG. 5 is a partial cross-sectional view showing the layer structure of the polarizing film in FIG. [Figure 6] FIG. 2 is a perspective view showing the function-added laminate and the frame that constitute the other light control film (upper side in FIG. 2) in the embodiment, in a separated state. [Figure 7]FIG. 7 is a perspective view showing components of the function-added laminate in FIG. 6 in a separated state. [Figure 8] FIG. 8 is a partial cross-sectional view showing the layer structure of the polarizing film in FIG. [Figure 9] FIG. 2 is a perspective view illustrating how a first polarizing film and a second polarizing film are attached to a surface to be laminated of a film substrate in the embodiment. [Figure 10] FIG. 2 is a perspective view showing the relationship between a test piece of a curled laminate and the amount of curl in the embodiment. [Figure 11] FIG. 2 is a perspective view illustrating how curls in a laminate are corrected by a pair of rollers in the embodiment. [Figure 12] FIG. 2 is a perspective view showing the relationship between a test piece of a laminate whose curl has been straightened and the amount of curl in the embodiment. [Figure 13] FIG. 13 is a perspective view showing a modified example, illustrating how a first polarizing film and a second polarizing film are attached to a surface to be laminated while a raw material film is being pulled out. [Figure 14] FIG. 13 is a partial perspective view showing a modified example, illustrating how curls in a laminate are continuously corrected. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, a light control film used in a light control device and a method for manufacturing the light control film will be described with reference to FIGS. 1 to 12 with regard to one embodiment. 1 and 2, the light control device A includes a pair of light control elements, that is, a pair of light control films 10 and 30. The pair of light control films 10 and 30 are arranged facing each other in their thickness directions (the vertical directions in each of FIGS. 1 and 2), more specifically, overlapping each other.

[0026] Here, a direction perpendicular to the thickness direction of each of the light control films 10 and 30 is defined as a first direction, and a direction perpendicular to both the thickness direction and the first direction is defined as a second direction. The light control device A adjusts the amount of light transmission by displacing the two light control films 10 and 30 relatively in a first direction. In this embodiment, the relative displacement is achieved by sliding only one of the light control films 10 in the first direction.

[0027] <Light Control Film 10> As shown in FIG. 2 and FIG. 3, one of the light control films 10 (lower side of FIG. 2) includes a laminate 11 and a frame 27. The laminate 11 includes a film substrate 12 and two types of polarizing films bonded to the film substrate 12 as components. Here, when it is necessary to distinguish between the two types of polarizing films, one is referred to as a first polarizing film 15A and the other is referred to as a second polarizing film 15B. In addition, in each figure, in order to distinguish between the first polarizing film 15A and the second polarizing film 15B and to make them easier to see, only the former is dotted. The laminate 11 uses a plurality of the first polarizing films 15A and the second polarizing films 15B. When it is not necessary to distinguish between the two types of polarizing films, they are simply referred to as the polarizing films 15A and 15B.

[0028] [Film base material 12] 3 and 4, the film substrate 12 is made of a transparent thermoplastic resin and has flexibility. Examples of the resin include PET (polyethylene terephthalate) resin, PE (polyethylene) resin, PP (polypropylene) resin, ABS (acrylonitrile-butadiene-styrene copolymer) resin, PVA (polyvinyl alcohol) resin, and TAC (triacetyl cellulose) resin.

[0029] The film substrate 12 has a rectangular shape. One surface of the film substrate 12 in the thickness direction, which is the upper surface in Figs. [First polarizing film 15A and second polarizing film 15B] Each of the first polarizing films 15A and each of the second polarizing films 15B is made of a thermoplastic resin different from that of the film substrate 12, and has flexibility. As shown in Fig. 5, each of the first polarizing films 15A and the second polarizing films 15B includes a film body 16 and a pair of transparent protective films 17 that sandwich the film body 16 from both sides in the thickness direction. The film body 16 is made of, for example, a PVA resin dyed with an iodine solution.

[0030] The film body 16 is produced, for example, as follows: A PVA resin film is dyed with iodine. The PVA resin molecules that make up the film are bonded together and stabilized by boric acid. The film is pulled in one direction while still wet. The PVA resin molecules and iodine molecules are oriented in the direction in which they are pulled. When this film is dried, the film body 16 having a polarization axis and polarizing properties is obtained.

[0031] Each protective film 17 is intended to protect the film body 16 from external impact, heat, humidity, etc. Each protective film 17 is made of an optically isotropic material, such as TAC resin. Each protective film 17 is attached to the film body 16.

[0032] As shown in Fig. 4, each of the first polarizing films 15A and each of the second polarizing films 15B is in the form of a strip whose dimension in the second direction is longer than its dimension in the first direction. The dimension in the second direction is set to be the same for the first polarizing film 15A and the second polarizing film 15B. Each of the first polarizing films 15A and each of the second polarizing films 15B has a polarization axis extending in a different direction. In this embodiment, the polarization axis of each of the second polarizing films 15B extends in a direction perpendicular to the polarization axis of each of the first polarizing films 15A.

[0033] 3 to 5, each first polarizing film 15A has one surface in the thickness direction as a front surface 21A and the other surface as a back surface 22A. Each first polarizing film 15A has side surfaces 23A on both sides in the first direction.

[0034] Each second polarizing film 15B has one surface in the thickness direction as a front surface 21B and the other surface as a back surface 22B. Each second polarizing film 15B has side surfaces 23B on both sides in the first direction.

[0035] As shown in Fig. 3 and Fig. 4, the first polarizing films 15A and the second polarizing films 15B are arranged alternately in the first direction. The first polarizing films 15A and the second polarizing films 15B adjacent to each other are in contact with each other at the side surfaces 23A and 23B adjacent to each other. The back surface 22A of each of the first polarizing films 15A and the back surface 22B of each of the second polarizing films 15B shown in Fig. 5 are joined to the laminated surface 13 by adhesion. In other words, the back surfaces 22A and 22B of each of the polarizing films 15A and 15B are attached to the laminated surface 13.

[0036] In Fig. 4, the layer of adhesive that adheres each of the polarizing films 15A and 15B to the laminated surface 13 is illustrated as an adhesive layer 25. Note that the adhesive layer 25 is illustrated only in Fig. 4 and Fig. 7 which corresponds to Fig. 4. In the other figures, the adhesive layer 25 is omitted.

[0037] [Frame 27] 3 and 4, the frame 27 is made of a resin material and has a thin rectangular frame shape, and is flexible. The frame 27 has a strength higher than that of the laminate 11. The frame 27 is disposed on the opposite side of the laminate 11 to the polarizing films 15A and 15B across the film substrate 12, that is, on the lower side in FIG. 3. The laminate 11 is attached to the frame 27 from the upper side in FIG. 3.

[0038] <Light Control Film 30> 2 and 6, the other light control film 30 (upper side in FIG. 2) has a similar configuration to the above-mentioned light control film 10. Therefore, in the light control film 30, components common to the light control film 10 are given the same reference numerals, and duplicated explanations are omitted. The light control film 30 will be described focusing on the differences from the light control film 10.

[0039] The light control film 30 has a function-added laminate 31 shown in Figures 6 and 7 as a component corresponding to the laminate 11. The function-added laminate 31 includes the laminate 11, and further includes a low friction layer 32 and a hard coat layer 33. The light control film 30 includes this function-added laminate 31 and a frame 27.

[0040] As shown in Figs. 7 and 8, the rectangular film substrate 12 has one surface in the thickness direction, which is the lower surface in Fig. 8, as a surface 13 to be laminated. The polarizing films 15A and 15B each have one surface in the thickness direction, which is the lower surface in FIG. 8, as the front surface 21A or 21B, and the other surface, which is the upper surface in FIG. 8, as the back surface 22A or 22B. In the first polarizing films 15A and the second polarizing films 15B arranged alternately in the first direction, the adjacent side surfaces 23A or 23B are in contact with each other. In this state, the back surfaces 22A or 22B of the polarizing films 15A or 15B are bonded (joined) to the laminated surface 13. In other words, the back surfaces 22A or 22B of the polarizing films 15A or 15B are bonded to the laminated surface 13.

[0041] In FIG. 7, the layer of adhesive that bonds each of the polarizing films 15A and 15B to the lamination surface 13 of the film substrate 12 is illustrated as an adhesive layer 25. [Low friction layer 32] As shown in Fig. 7 and Fig. 8, the low friction layer 32 is formed on the surface 21A, surface 21B of the polarizing film 15A, 15B. The low friction layer 32 is provided for the purpose of increasing the slipperiness, for example, increasing the sliding property of the light control film 10 relative to the light control film 30, increasing the water repellency, etc. The low friction layer 32 is formed by subjecting the surfaces 21A, 21B to a lubricant treatment, for example, a water repellent coating treatment, a silicone coating treatment, etc. The low friction layer 32 is only shown in Fig. 7 and Fig. 4 (see the two-dot chain line) corresponding to Fig. 7. In other figures, the low friction layer 32 is omitted from the illustration.

[0042] [Hard coat layer 33] 7, the hard coat layer 33 is formed by applying a known surface treatment agent to the surface 14 opposite the laminated surface 13, among both surfaces of the film substrate 12 in the thickness direction. The hard coat layer 33 provides useful effects to the film substrate 12 on which it is formed, such as an effect of suppressing scratches, an effect of making it difficult for dirt to adhere, an effect of improving light resistance and weather resistance by blocking ultraviolet rays, and a water repellent effect.

[0043] 6 and 7, the frame 27 formed of a resin material in a thin rectangular frame shape is disposed on the opposite side of the polarizing films 15A and 15B, or on the upper side in Fig. 6, of the function-added laminate 31, with the film substrate 12 sandwiched therebetween. The function-added laminate 31 is assembled to the frame 27 from the lower side in Fig. 6.

[0044] 2, in the light control device A, the pair of light control films 10 and 30 described above are arranged so that their frames 27 are located at both ends in the thickness direction. The light control film 10 is assembled to the light control film 30 so as to be slidable in the first direction.

[0045] Next, the operation of this embodiment will be described together with a manufacturing method for the light control films 10 and 30. The pair of light control films 10 and 30 are manufactured through similar processes. Therefore, the light control film 10 will be mainly described here. The light control film 30 will be described with a focus on the differences from the light control film 10.

[0046] In manufacturing the light control film 10, a laminate formation step and a correction step are performed. <Laminate formation process> 9, in the laminate formation step, for example, a film substrate 12 having an adhesive layer 25 (not shown in FIG. 9) formed on a surface 13 to be laminated is used as the film substrate 12. A liquid such as a surfactant or water is applied to the adhesive layer 25.

[0047] A plurality of first polarizing films 15A and a plurality of second polarizing films 15B are attached to the laminated surface 13 in a state where they are arranged alternately in a first direction. For example, when the second polarizing film 15B is to be bonded adjacent to the first polarizing film 15A that has already been bonded to the lamination surface 13, the following operations are carried out.

[0048] The second polarizing film 15B is placed while being positioned on the lamination surface 13 at a predetermined location adjacent to the first polarizing film 15A in the first direction, as indicated by the two-dot chain line in Fig. 9. This positioning is performed by sliding the second polarizing film 15B on the liquid.

[0049] Then, the positioned second polarizing film 15B is bonded to the lamination surface 13 via the adhesive layer 25 and the liquid. During this bonding, the side surface 23A of the already bonded first polarizing film 15A comes into contact with the side surface 23B of the second polarizing film 15B to be bonded.

[0050] Incidentally, when the first polarizing film 15A is to be bonded adjacent to the second polarizing film 15B that has already been bonded to the lamination surface 13, the same operations as those described above are carried out. Then, all of the first polarizing films 15A and all of the second polarizing films 15B are bonded to the film substrate 12, and then the laminated surface 13 of the film substrate 12 is heated and cooled. This heating causes the liquid to evaporate and hardens the adhesive layer 25. Then, the first polarizing films 15A and the second polarizing films 15B are bonded (joined) to the laminated surface 13 of the film substrate 12 via the adhesive layer 25.

[0051] Here, the film substrate 12, which is a component of the laminate 11, and the polarizing films 15A and 15B, which are also components of the laminate 11, are formed from different types of thermoplastic resins. Here, the heat shrinkage rate of the polarizing films 15A and 15B is greater than that of the film substrate 12. Therefore, during the heating and cooling, due to the difference in the heat shrinkage rate between the components, the laminate 11 is formed curled toward the polarizing films 15A and 15B, which are components with a greater heat shrinkage rate, in the thickness direction.

[0052] In this example, the laminate 11 is formed by curling the polarizing films 15A and 15B in the longitudinal direction (see FIG. 11). <Correcting process> 11, in the straightening step, the curl of the laminate 11 is straightened by a straightening device 40. In the straightening device 40, the curled laminate 11 is heated from both sides while being pressed from at least one side in the thickness direction. Heating from the non-curled side is performed at a higher temperature than heating from the curled side.

[0053] The straightening device 40 includes a pair of rollers 41, 42 arranged facing each other and parallel to each other in the thickness direction. The pair of rollers 41, 42 are rotated in opposite directions while applying pressure to the laminate 11 from at least one side in the thickness direction, in a state where at least the outer circumferential surfaces of the pair of rollers 41, 42 are heated to different temperatures.

[0054] The outer periphery of roller 42 is formed of a material having higher elasticity than the outer periphery of roller 41. In this embodiment, the outer periphery of roller 42 is formed of rubber as a material having higher elasticity. The outer periphery of roller 41 is formed of metal (iron) as a material having lower elasticity than rubber. Roller 42 is heated so that the temperature of the outer periphery becomes, for example, about 50°C. In contrast, roller 41 is heated so that the temperature of the outer periphery becomes, for example, about 90°C.

[0055] Furthermore, in this embodiment, the pair of rollers 41, 42 rotate at a constant speed while applying approximately the same pressure to the laminate 11 from both sides in the thickness direction. In the straightening step, among the components of the laminate 11, the polarizing films 15A and 15B, which are the components curled in the thickness direction, are positioned on the side of the roller 42 having a lower temperature. The film substrate 12, which is the component on the side that is not curled, is positioned on the side of the roller 41 having a higher temperature.

[0056] Further, here, the laminate 11 is disposed so that the longitudinal direction of the polarizing films 15A and 15B extends in a direction perpendicular to the axis of the rollers 41 and . The positional relationship between the laminate 11 and the pair of rollers 41, 42 is such that, among the constituent members of the laminate 11, the polarizing films 15A and 15B, which are low-strength constituent members, are located on the side of the roller 42, the outer periphery of which is made of rubber, a material with high elasticity, and the film substrate 12, which is a high-strength constituent member, is located on the side of the roller 41, the outer periphery of which is made of metal (iron), a material with low elasticity.

[0057] In this state, the curled laminate 11 is passed between a pair of rollers 41, 42. The laminate 11 is sent in the direction indicated by the outline arrow in Fig. 11 by the pair of rollers 41, 42 which rotate in opposite directions. Furthermore, when the laminate 11 passes between the pair of rollers 41, 42, it is heated while being pressed by both rollers 41, 42. Heating by roller 41 on the uncurled side is performed at a higher temperature than heating by roller 42 on the curled side.

[0058] In this manner, by using the pair of rollers 41 and 42, the laminate 11 is fed while being pressurized and heated. More heat is applied to the component on the non-curled side (film substrate 12) than to the component on the curled side (polarizing films 15A, 15B). Due to this difference in the amount of heat applied, the component on the non-curled side (film substrate 12) attempts to deform more than the curled component (polarizing films 15A, 15B), and the laminate 11 deforms toward the non-curled side. As a result, the curl is corrected and the amount of curl is reduced. As the amount of curl decreases, the degree to which the curl degrades the appearance of the laminate 11 and, ultimately, the light control film 10 becomes less.

[0059] Furthermore, when the laminate 11 is fed by the pair of rollers 41, 42, the outer periphery of the roller 42, whose outer periphery is made of a highly elastic material (rubber), comes into contact with the low-strength component member (polarizing films 15A, 15B). The outer periphery of the roller 41, whose outer periphery is made of a low-elasticity material (iron), comes into contact with the high-strength component member (film substrate 12). Therefore, the low-strength component member (polarizing films 15A, 15B) is less likely to be scratched than when it comes into contact with the outer periphery of the roller 41, whose outer periphery is made of a low-elasticity material.

[0060] Here, the curl amount C1 of the laminate 11 was measured before and after the straightening process as follows. A square portion with a side length of 100 mm was cut out of the laminate 11 as shown in FIG. 10, and this was used as a test piece 45. The test piece 45 was placed on a horizontal surface 46 with the thickness direction aligned with the up-down direction. The distance between the horizontal surface 46 and the point of the test piece 45 that was farthest from the horizontal surface 46 due to the curl was measured, and this was used as the curl amount C1. Then, the average value of the curl amounts C1 of the curled portions of the test piece 45 was calculated.

[0061] The average curl amount C1 of the test pieces 45 (see FIG. 10) before the straightening process was 9 mm. In contrast, the average curl amount C1 of the test pieces 45 (see FIG. 12) after the straightening process was 1 mm or less. The appearance of the laminate 11 that had undergone the straightening process was close to the appearance of a flat laminate that had not curled.

[0062] After the straightening process, the excess portion is cut and removed from the laminate 11. Then, as shown in Fig. 3, the remaining portion of the laminate 11 is assembled to a frame 27, thereby obtaining a light control film 10 that is entirely flexible, as shown in Fig. 2. In this light control film 10, the frame 27 has a higher strength than the laminate 11.

[0063] In addition, when manufacturing the light control film 30, a laminate formation process and a straightening process are performed in the same manner as the light control film 10. A low friction layer 32 and a hard coat layer 33 shown in FIG. 7 are formed on the laminate 11 whose curl has been straightened, to form a function-added laminate 31. The excess portion of the function-added laminate 31 is also cut and removed in the same manner as the laminate 11. Then, as shown in FIG. 6, the remaining portion of the function-added laminate 31 is assembled to a frame 27, to obtain a light control film 30 that is entirely flexible, as shown in FIG. 2. In this light control film 30, the frame 27 has a higher strength than the function-added laminate 31.

[0064] Incidentally, when light is incident on one of the light control films 10 and 30, for example, the light control film 30, from the outside of the light control device A shown in Fig. 1, the light becomes linearly polarized in a direction along the polarization axis of the first polarizing film 15A when it passes through the first polarizing film 15A. In addition, the light incident on the light control film 30 becomes linearly polarized in a direction along the polarization axis of the second polarizing film 15B when it passes through the second polarizing film 15B.

[0065] The degree of light transmission in both light control films 10, 30 is determined by which of the polarizing films 15A, 15B in the light control film 10 overlaps with the polarizing films 15A, 15B in the light control film 30. The combination of the first polarizing film 15A and the second polarizing film 15B that overlap in the thickness direction is changed by sliding the light control film 10 in a first direction, or in other words, by relatively displacing both light control films 10, 30 in the first direction.

[0066] The first polarizing film 15A in the light control film 30 and the first polarizing film 15A in the light control film 10 overlap. Then, the direction in which the polarization axis of the first polarizing film 15A of the former and the direction in which the polarization axis of the first polarizing film 15A of the latter become parallel. At this time, the second polarizing film 15B in the light control film 30 and the second polarizing film 15B in the light control film 10 overlap. The direction in which the polarization axis of the second polarizing film 15B of the former and the direction in which the polarization axis of the second polarizing film 15B of the latter become parallel. Therefore, all of the light that enters the light control film 30 and then passes through the light control film 30 passes through the light control film 10.

[0067] On the other hand, the first polarizing film 15A in the light control film 30 and the second polarizing film 15B in the light control film 10 overlap. Then, the direction in which the polarization axis of the first polarizing film 15A of the former and the direction in which the polarization axis of the second polarizing film 15B of the latter are perpendicular to each other. At this time, the second polarizing film 15B in the light control film 30 and the first polarizing film 15A in the light control film 10 overlap each other. The direction in which the polarization axis of the second polarizing film 15B of the former and the direction in which the polarization axis of the first polarizing film 15A of the latter are perpendicular to each other. Therefore, all of the light that enters the light control film 30 and then transmits through the light control film 30 is blocked (shielded) by the light control film 10.

[0068] Next, the effects of this embodiment will be described. (1) In manufacturing the light control films 10 and 30, a laminate formation process and a straightening process are performed. As shown in Fig. 9, in the laminate formation process, a plurality of first polarizing films 15A and a plurality of second polarizing films 15B are arranged alternately in a first direction and joined to a surface 13 to be laminated to form a laminate 11. As shown in Fig. 11, in the straightening process, the laminate 11 curled in the thickness direction due to heating and cooling during the above-mentioned joining is heated from both sides while being pressurized from at least one side in the same direction. Heating from the non-curled side is performed at a higher temperature than heating from the curled side.

[0069] Therefore, the component on the non-curled side of the laminate 11 is deformed more than the component on the curled side, and the laminate 11 is deformed toward the non-curled side. The amount of curl in the laminate 11 is reduced, and the appearance of the laminate 11 can be made closer to that of a flat laminate that is not curled. Therefore, deterioration in the appearance of the laminate 11 and, ultimately, the light control films 10 and 30 caused by curling can be suppressed.

[0070] (2) As shown in Fig. 9, in the laminate formation step, a plurality of first polarizing films 15A and a plurality of second polarizing films 15B are bonded to the lamination surface 13 by adhesion. When heating and cooling are performed to harden the adhesive layer 25, the laminate 11 is formed in such a way that the laminate 11 curls toward the component having the larger thermal shrinkage rate in the thickness direction due to the difference in thermal shrinkage rate between the above-mentioned components. However, by performing the straightening step (see Fig. 11), the curl of the laminate 11 can be straightened, and the effect of (1) above can be obtained.

[0071] (3) As shown in Fig. 11, a pair of rollers 41, 42 are disposed opposite to each other in the thickness direction and rotate in opposite directions while being heated so that at least the outer circumferential surfaces are at different temperatures, as the straightening device 40. In the straightening process, the component that is curled in the thickness direction is positioned on the side of the roller 42 with a lower temperature, and the component that is not curled is positioned on the side of the roller 41 with a higher temperature. In this state, the laminate 11 is passed between the pair of rollers 41, 42, so that the laminate 11 is fed while being pressurized and heated. Therefore, the laminate 11 is pressurized and heated, and the curl can be straightened.

[0072] (4) The outer periphery of roller 42 is formed from a material having a higher elasticity than the outer periphery of roller 41. Then, in the straightening process, the components of laminate 11 having a lower strength are positioned on the roller 42 side, whose outer periphery is formed from a material having a higher elasticity. The components with a higher strength are positioned on the roller 41 side, whose outer periphery is formed from a material having a lower elasticity. In this state, laminate 11 is passed between the pair of rollers 41, 42. This makes it possible to prevent the components with a lower strength from being damaged by scratches, etc. The components with a lower strength can be protected from being scratched.

[0073] (5) The outer periphery of the roller 42 is made of rubber, which is a highly elastic material. The outer periphery of the roller 41 is made of metal (iron in this embodiment), which is a less elastic material. In the straightening process, the polarizing films 15A and 15B are positioned on the roller 42 side, the outer periphery of which is made of rubber, as a component with low strength. The film substrate 12 is positioned on the roller 41 side, the outer periphery of which is made of metal (iron), as a component with high strength. In this state, the laminate 11 is passed between the pair of rollers 41 and 42. Therefore, when the laminate 11 is fed by the pair of rollers 41 and 42, the effect of (4) above, which suppresses damage such as scratches to the polarizing films 15A and 15B, is easily obtained.

[0074] (6) In the light control film 10, the laminate 11 is assembled to the frame 27. In the light control film 30, the function-added laminate 31 is assembled to the frame 27. The frame 27 has a strength higher than that of the laminate 11 and the function-added laminate 31. Therefore, even if heat is applied to the light control films 10 and 30 when the light control device A is used at high temperatures after manufacture, the curling phenomenon can be suppressed.

[0075] (7) Since the light control films 10 and 30 are flexible, they can be bent into a curved shape. Therefore, even if the area where the light control device A is applied has a curved surface, the light control films 10 and 30 can be curved to follow the curved surface. This effect cannot be obtained or is difficult to obtain when the object to which the polarizing films 15A and 15B are attached is a plate-like object instead of the film substrate 12.

[0076] The above embodiment can also be implemented as modified examples as follows: The above embodiment and the following modified examples can be implemented in combination with each other within a range that does not cause technical contradiction.

[0077] <Matters regarding the structure of the light control films 10 and 30> The side surfaces 23A, 23B of the adjacent polarizing films 15A, 15B may be spaced apart in the first direction.

[0078] The size in the first direction may be the same or different between first polarizing film 15A and second polarizing film 15B. The size in the second direction is also the same as the size in the first direction.

[0079] The low friction layer 32 may be formed on the surfaces 21A and 21B of the polarizing films 15A and 15B in the light control film 10, instead of the light control film 30, as shown by the two-dot chain line in Fig. 4. The low friction layer 32 may also be formed on the surfaces 21A and 21B of the polarizing films 15A and 15B in both light control films 10 and 30.

[0080] The hard coat layer 33 may be provided on the light control film 10 instead of or in addition to the light control film 30. One or both of the low friction layer 32 and the hard coat layer 33 in FIG. 7 may be omitted as appropriate.

[0081] The polarization axis of each second polarizing film 15B may extend in a direction that intersects obliquely (is tilted) with the direction in which the polarization axis of each first polarizing film 15A extends, instead of in a direction that is perpendicular to the direction in which the polarization axis of each first polarizing film 15A extends.

[0082] The polarization axes of the polarizing films 15A and 15B may be formed by metal wires in a wire grid. A wire grid is a structure in which metal wires are arranged in parallel at regular intervals.

[0083] The polarizing films 15A and 15B may be joined to the lamination surface 13 of the film substrate 12 by a method other than adhesion. For example, when the film substrate 12 is made of TAC resin, which is the same material as the outermost layer portion (protective film 17) of the polarizing films 15A and 15B, the films can be joined by welding.

[0084] In this case, the film body 16 forming the framework of the polarizing films 15A and 15B is made of PVA resin. The film base 12 and the film body 16 are made of different types of materials. Since the thermal shrinkage rates of the film base 12 and the film body 16 are different, if welding involves heating and cooling in the laminate formation process, a curled laminate 11 is formed.

[0085] In this case, the curl can be corrected by carrying out the straightening step. <Matters regarding the manufacture of light control films 10 and 30> In the laminate formation step, for example, instead of or in addition to the laminated surface 13 of the film substrate 12, the polarizing films 15A and 15B may have adhesive layers 25 formed on their rear surfaces 22A and 22B.

[0086] In the laminate formation process, depending on the combination of the type of material of the film substrate 12 and the type of material of the polarizing films 15A and 15B, it is expected that the laminate 11 formed may be curled in the short direction instead of or in addition to the long direction of the polarizing films 15A and 15B. Even in this case, the curl of the laminate 11 can be straightened by carrying out the straightening process.

[0087] Depending on the combination of the material type of the film substrate 12 and the material types of the polarizing films 15A and 15B, the laminate 11 will curl to different sides in the thickness direction. In other words, among the film substrate 12 and the polarizing films 15A and 15B that are the components of the laminate 11, the component that curls in the thickness direction will be different from the component that does not curl.

[0088] Even in this case, the curl can be corrected by heating the laminate from both sides while applying pressure from at least one side in the thickness direction, and heating the uncurled side at a higher temperature than heating the curled side.

[0089] When the rollers 41 and 42 are used for straightening, the component member curled in the thickness direction is positioned on the side of the roller 42, which has a lower temperature, and the component member not curled is positioned on the side of the roller 41, which has a higher temperature. In this state, the laminate is passed between the pair of rollers 41 and 42, whereby the laminate is fed while being pressurized and heated.

[0090] In the laminate formation step, as shown in Fig. 13, a raw material film 50 in which the raw material of the film substrate 12 is wound in a roll shape may be used. The raw material film 50 can be considered as a plurality of film substrates 12 arranged in a row and connected. In this case, the raw material film 50 is pulled out, and one surface of the raw material film 50 becomes the surface 13 to be laminated. As in the above embodiment, a plurality of first polarizing films 15A and a plurality of second polarizing films 15B may be bonded to the surface 13 to be laminated in a state where they are alternately arranged in the first direction.

[0091] Then, after the raw material film 50 with the polarizing films 15A and 15B bonded together is heated and cooled, a straightening step may be performed as shown in Fig. 14. The raw material film 50 with the polarizing films 15A and 15B bonded together is passed between a pair of rollers 41 and 42 rotating in opposite directions, whereby the raw material film 50 is sent in the direction of the white arrow while the curl is straightened, and is then cut at an appropriate location. In this case, it is possible to continuously form laminates with the curl straightened.

[0092] 14, in the straightening step, the laminate 11 may be disposed so that the longitudinal direction of the polarizing films 15A, 15B extends in a direction parallel to the axes of the rollers 41, 42, and in this state, the laminate 11 may be passed between the pair of rollers 41, 42. In this case as well, curls can be straightened, as in the above embodiment.

[0093] In the straightening step, the laminate curled in the thickness direction may be pressed only from one side in the thickness direction. <Matters regarding orthodontic appliance 40> The pair of rollers 41, 42 may be heated so that at least the outer circumferential surfaces are heated to different temperatures. Therefore, the temperature of only the outer circumferential portion of roller 41 may be different from the temperature of only the outer circumferential portion of roller 42. Also, the temperature of the entire roller 41 may be different from the temperature of the entire roller 42.

[0094] In the straightening step, the curl of the laminate 11 may be straightened by a straightening device different from the straightening device 40 using the rollers 41, 42 described in the above embodiment. This straightening device may be any device capable of heating the curled laminate 11 from both sides while applying pressure from at least one side in the thickness direction. For example, a press machine that applies pressure to the laminate 11 from both sides in the thickness direction may be used as the straightening device. In this case, the laminate 11 is heated from both sides in the thickness direction. In this case, the heating from the non-curled side is performed at a higher temperature than the heating from the curled side.

[0095] The highly elastic outer circumferential parts of the rollers 41, 42 may be made of a material other than rubber. Also, the less elastic outer circumferential parts of the rollers 41, 42 may be made of a metal material other than iron. Also, the less elastic outer circumferential parts of the rollers 41, 42 may be made of a material other than metal.

[0096] The outer periphery of the roller 41 and the outer periphery of the roller 42 may be formed from the same material. <Matters regarding dimming device A> The relative displacement of the pair of light control films 10, 30 in the first direction may be achieved by sliding at least one of the light control films 10, 30 in the first direction. Therefore, as in the above embodiment, only the light control film 10 may be subject to sliding, or only the light control film 30 may be subject to sliding. Also, both light control films 10, 30 may be subject to sliding. [Explanation of symbols]

[0097] 10,30...Light-adjusting film (light-adjusting element) 11...Laminate 12...Film substrate (constituent member of laminate) 13…Surface to be laminated 15A…First polarizing film (constituent member of laminate) 15B: Second polarizing film (constituent member of laminate) 41,42…Laura 45...Test piece 46…Horizontal plane A…Dimmer device C1: Curl amount

Claims

1. A method for manufacturing a light control film to be used as a light control element in a light control device that includes a pair of light control elements arranged opposite to each other in a thickness direction, and that adjusts the amount of light transmitted through the light control elements by relatively displacing the light control elements in a first direction perpendicular to the thickness direction, comprising: The laminate of the light control film includes, as components, a film substrate made of a thermoplastic resin and two types of polarizing films each made of a thermoplastic resin different from the film substrate; The film substrate has one surface in the thickness direction as a surface to be laminated, The two types of polarizing films have a rectangular shape whose dimension in a second direction perpendicular to both the thickness direction and the first direction is longer than the dimension in the first direction, and have polarization axes extending in directions different from each other, The process for producing the light control film includes: a laminate forming step of forming the laminate by arranging the two types of polarizing films alternately in the first direction and bonding them to the laminated surface; a straightening step of straightening the curl of the laminate curled in the thickness direction due to the heating and cooling during the joining by heating from both sides while applying pressure from at least one side in the same direction, and heating from the non-curled side at a higher temperature than heating from the curled side; A method for manufacturing a light control film comprising the steps of:

2. The method for producing a light control film according to claim 1 , wherein in the laminate formation step, the two types of polarizing films are bonded to the laminated surfaces by adhesion.

3. In the straightening step, a pair of rollers are used that are arranged opposite to each other in the thickness direction and rotate in opposite directions while being heated such that at least the outer circumferential surfaces are at different temperatures, 2. The method for manufacturing a light-controlling film according to claim 1, wherein in the straightening process, the laminate is passed between a pair of rollers with the component that is curled in the thickness direction positioned on the side of the roller with a lower temperature and the component that is not curled positioned on the side of the roller with a higher temperature, thereby feeding the laminate while being pressurized and heated.

4. an outer circumferential portion of one of the rollers used in the straightening step is formed of a material having higher elasticity than an outer circumferential portion of the other of the rollers; 4. The method for manufacturing a light-controlling film according to claim 3, wherein in the correction process, the laminate is passed between a pair of rollers in a state in which the component members of the laminate having a lower strength are positioned on the side of the roller whose outer periphery is formed from the material with high elasticity, and the component members having a higher strength are positioned on the side of the roller whose outer periphery is formed from the material with low elasticity.

5. the outer circumferential portion of the one roller is formed using rubber as the highly elastic material, the outer circumferential portion of the other roller is formed using a metal as the low elastic material, 5. The method for manufacturing a light-controlling film according to claim 4, wherein in the correction process, the laminate is passed between a pair of rollers with each polarizing film being the component with low strength and the outer periphery being positioned on the side of the roller formed of the rubber, and the film substrate being the component with high strength and the outer periphery being positioned on the side of the roller formed of the metal.

6. A light control device includes a pair of light control elements arranged opposite to each other in a thickness direction, and the light control elements are relatively displaced in a first direction perpendicular to the thickness direction to adjust the amount of light transmitted through the light control elements. The light control film is used as the light control elements, The present invention has a laminate including, as constituent members, a film substrate made of a thermoplastic resin and two types of polarizing films each made of a thermoplastic resin different from the film substrate, The film substrate has one surface in the thickness direction as a surface to be laminated, The two types of polarizing films have a rectangular shape whose dimension in a second direction perpendicular to both the thickness direction and the first direction is longer than the dimension in the first direction, and have polarization axes extending in directions different from each other, the laminate is formed by arranging two types of polarizing films alternately in the first direction and bonding them to the laminated surface, and further by performing a treatment to correct curl in the thickness direction; A light-controlling film in which a square portion of the laminate with sides of 100 mm is used as a test piece, the test piece is placed on a horizontal surface with the thickness direction aligned in the up-down direction, and the distance between the horizontal surface and the point of the test piece that is farthest from the horizontal surface due to curling is defined as the curl amount, and the average curl amount of the curled portion of the test piece is 1 mm or less.

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