Method for manufacturing optical films

Abstract

To provide a method capable of completing subjecting a film roll including a polarizer to humidification in a relatively short time.SOLUTION: A method for manufacturing an optical film capable of controlling humidity by humidifying a film roll 1 including a polarizer comprises spraying water vapor having a temperature of 35°C or more and a humidity of 80% RH or more at a pressure of 0.5 kPa or more on the film roll 1 including the polarizer, for example, competing the tension of the film roll 1 and the spray pressure of the water vapor by spraying the water vapor on the film roll 1 from the arc surface part 711 of a spray part 7 to convey the film roll 1 along the arc surface part 711 while separating from the arc surface part 711.SELECTED DRAWING: Figure 8

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing an optical film containing a polarizer. [Background technology]

[0002] Conventionally, optical films containing polarizers have been used as constituent materials for liquid crystal displays and polarized sunglasses. Examples of such optical films include laminated films in which a protective film is laminated onto a polarizer, and laminated films in which a phase difference film is laminated onto a polarizer. The aforementioned optical film is manufactured by applying any treatment to a film roll containing a polarizer, and one of these treatments is known to be humidification of the film roll. For example, Patent Document 1 discloses a method for adjusting the moisture content of a film roll (raw material film) by guiding the film roll into a humidity control furnace and transporting the film roll in a humidified atmosphere inside the humidity control furnace. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-28285 [Overview of the project]

[0004] As described above, by applying a humidification treatment to the film roll, it is possible to manufacture an optical film that is less prone to warping over time. However, the humidification method described in Patent Document 1 requires a relatively long time to incorporate a predetermined amount of moisture into the film roll. Prolonged humidification not only reduces the efficiency of optical film production but also leads to larger equipment. Furthermore, if condensation occurs on the film roll containing the polarizer during the humidification process, there is a risk of obtaining an optical film with a defective appearance. Patent Document 1 discloses a method for preventing condensation on the outer wall surface of a humidity control furnace. However, Patent Document 1 does not disclose or suggest any method for preventing condensation on film raw materials inside the humidity control furnace. [Problems that the invention aims to solve]

[0005] The first object of the present invention is to provide a method for humidifying a film roll containing a polarizer in a relatively short time. A second objective of the present invention is to prevent condensation on the film roll during humidification treatment and to produce an optical film with excellent optical properties. [Means for solving the problem]

[0006] A method for manufacturing an optical film according to a first aspect of the present invention is: The polarizer comprises a polarizer and a first film and a second film laminated on one side and the opposite side of the polarizer, respectively. A method for producing a humidity-controlled optical film by humidifying a film roll, The moisture permeability of the first film is 100 g / m². 2 ·900g / m for 24 hours or more 2 • Less than 24 hours , The aforementioned For film rolls From the first film side , 35℃ or higher Below 80℃ Furthermore, water vapor at 80% RH or higher, at 0.5 kPa or higher Below 4.0 kPa under pressure For a time of 10 seconds or more but less than 90 seconds Spray it on. However, the aforementioned moisture permeability is measured under conditions of 65°C and a relative humidity difference of 90% using the JIS Z 0208-1976 (aluminum cup method). .

[0007] A method for manufacturing an optical film according to a second aspect of the present invention is the manufacturing method according to the first aspect, wherein the polarizer is a dyed and stretched hydrophilic polymer film. 。

[0008] This invention Third The method for manufacturing an optical film according to the above-mentioned aspect is the first or 2In the production method according to the aspect, the original film web is introduced into a chamber adjusted to a predetermined atmospheric temperature, and while the original film web is being conveyed inside the chamber, water vapor at the aforementioned pressure is sprayed onto the original film web.

[0009] The present invention's 4th The method for producing an optical film according to the aspect, in the above Third In the production method according to the aspect, the atmospheric temperature inside the chamber is in a range of not less than the temperature of the water vapor minus 5°C and not more than the temperature of the water vapor plus 20°C. The present invention's Fifth The method for producing an optical film according to the aspect, in the above 4th In the production method according to the aspect, the original film web is conveyed inside the chamber for 3 seconds or more before the water vapor is sprayed onto the original film web.

[0010] The present invention's 6th The method for producing an optical film according to the aspect, in the above Third In the production method according to the aspect, a spraying part having an arc-shaped surface portion in which a plurality of discharge holes are formed is disposed inside the chamber, and while the original film web is conveyed along the arc-shaped surface portion in a tensioned state, the water vapor is sprayed from the discharge holes onto the original film web, so that the tension of the original film web and the spraying pressure of the water vapor counteract each other, and the original film web is conveyed along the arc-shaped surface portion while being separated from the arc-shaped surface portion.

[0011] The present invention's 7th The method for producing an optical film according to the aspect, in the above Third In the production method according to the aspect, a spraying part having a flat surface portion in which a plurality of dot-shaped discharge holes are formed is disposed inside the chamber, and while the original film web is conveyed along the spraying part in a tensioned state, the water vapor is sprayed from the discharge holes in a vertical direction against one surface of the original film web.

[0012] The present invention's 8th The method for producing an optical film according to the aspect, in the above first to 7thIn the manufacturing method according to the aspect of before The water vapor transmission rate of the first film is higher than that of the second film expensive . [Effects of the Invention]

[0013] According to the method for producing an optical film of the present invention, the humidification treatment can be completed in a relatively short time for the original film web including a polarizer. The obtained optical film contains an appropriate amount of moisture and is less prone to bending deformation over time. Further, according to the preferred production method of the present invention, it is possible to prevent dew condensation from occurring on the original film web during the humidification treatment. Therefore, the obtained optical film has appropriate optical properties. [Brief Description of the Drawings]

[0014] [Figure 1] A partially omitted plan view of the original film web of the present invention. [Figure 2] A diagram showing one example of the layer configuration of the original film web. [Figure 3] A diagram showing another example of the layer configuration of the original film web. [Figure 4] A diagram showing still another example of the layer configuration of the original film web. [Figure 5] A schematic side view of the optical film production system. [Figure 6] A side view of the humidifying device of the first embodiment, including a cross-section of the chamber and the like cut along the conveyance direction of the original film web. [Figure 7] A plan view of the same humidifying device. [Figure 8] An enlarged cross-sectional view of the original film web and the spraying part cut along the line VIII-VIII in Figure 7. [Figure 9] A reference perspective view showing the original film web and the spraying part inside the chamber of the first embodiment. [Figure 10] (a) and (b) are respectively reference plan views showing the arrangement of the discharge holes of the spraying part. [Figure 11] A side view of the humidifying device of the second embodiment, including a cross-section of the chamber and the like cut along the conveyance direction of the original film web. [Figure 12] Enlarged cross-sectional view of the film roll and spraying section of the humidifier. [Figure 13] A reference perspective view showing the film raw material and spraying section inside the chamber of the second embodiment. [Figure 14] A reference perspective view showing the spraying section of one modified example of the second embodiment. [Figure 15] An enlarged cross-sectional view of the spraying section of a humidifier in another modified example of the second embodiment. [Figure 16] A reference plan view showing the film raw material and spraying section inside the chamber of the third embodiment. [Modes for carrying out the invention]

[0015] In this specification, if multiple numerical ranges such as "greater than or equal to a lower limit" or "less than or equal to an upper limit" are described separately, any lower limit or upper limit can be selected to set a numerical range of "greater than or equal to any lower limit" or "less than or equal to any upper limit." In this specification, "abbreviated" means a range that is permissible in the art to which the present invention belongs. In this specification, terms may be preceded by "first," "second," etc., but these prefixes are added solely to distinguish terms and do not have any special meaning such as order or superiority.

[0016] [Film raw materials and optical films] Figure 1 is a partially abbreviated plan view of the film raw material 1 of the present invention. The optical film of the present invention is obtained by performing at least a humidification treatment on the film roll 1. Therefore, the optical film is a film containing a polarizer that has been subjected to at least a humidification treatment. If necessary, the optical film may be manufactured by performing any appropriate treatment other than humidification on the film roll 1 before or after the humidification treatment. The film roll 1 to be processed is generally in the form of a long strip, as shown in Figure 1. A long strip is defined as a roughly rectangular shape in plan view, where the length in the longitudinal direction is sufficiently longer than the width direction.

[0017] Film roll 1 contains a polarizer. A polarizer is an optical element that transmits light that vibrates in only one specific direction (polarized light) and blocks light that vibrates in other directions (this property is called polarization property). Examples of polarizers include hydrophilic polymer films dyed with a dichroic substance and stretched. Such hydrophilic polymer films possess polarization properties. Examples of the hydrophilic polymer film include a film on which a hydrophilic polymer has been deposited; and a film obtained by applying a coating solution containing a hydrophilic polymer to one side of a support film and drying the coating solution. The support film can be a colorless and transparent resin film, such as an ester-based resin film such as polyethylene terephthalate resin. Examples of the hydrophilic polymer include polyvinyl alcohol (PVA) resin and ethylene-vinyl alcohol copolymer. Preferably, a film on which a hydrophilic polymer has been deposited is used as the hydrophilic polymer film.

[0018] Figures 2 to 4 show several layer configurations of film roll 1. Figure 2 is a view of film roll 11 relating to one layer configuration example, seen from the direction of arrow II in Figure 1. Similarly, Figures 3 and 4 are views of film rolls 12 and 13 relating to other layer configuration examples, also seen from the direction of arrow II in Figure 1. Referring to Figure 2, a film roll 11 of one layer configuration example comprises a polarizer 2 and a first film 31 and a second film 32 laminated on one side and the opposite side of the polarizer 2, respectively. A first adhesive layer 41 is interposed between the polarizer 2 and the first film 31 for bonding them together, and a second adhesive layer 42 is interposed between the polarizer 2 and the second film 32 for bonding them together. Referring to Figure 3, the film roll 1 of another layer configuration example has a polarizer 2 and a first film 31 laminated on one side of the polarizer 2. A first adhesive layer 41 is interposed between the polarizer 2 and the first film 31 to bond them together. Referring to Figure 4, the film base 1 of another layer configuration example consists only of polarizers 2.

[0019] The first film 31 may be a single-layer film, or a laminated film formed by laminating two or more films. The second film 32 may be a single-layer film, or a laminated film formed by laminating two or more films. The laminated film may be formed by laminating two or more films having the same function, or by laminating two or more films having different functions. Furthermore, the laminated film may be formed by directly joining two or more films, or by joining two or more films via an adhesive layer.

[0020] In the film roll 1 provided with first and second films 31 and 32 on both sides of the polarizer 2 as shown in Figure 2, the moisture permeability of the first film 31 and the second film 32 are not particularly limited. However, if the moisture permeability is too low, the water vapor may be blocked by the first film 31 and the second film 32, and the polarizer 2 may not be sufficiently humidified. From this viewpoint, the moisture permeability of the first and second films 31 and 32 are independently set to 50 g / m². 2 • 24 hours or more, preferably 100 g / m² 2 • It must be 24 hours or longer. There are no specific upper limits on the moisture permeability of the first and second films 31 and 32, but a realistic value would be 900 g / m² each. 2 • Less than 24 hours

[0021] Furthermore, the moisture permeability of the first film 31 and the moisture permeability of the second film 32 may be the same or different. In one example, the moisture permeability of the first film 31 is higher than that of the second film 32. When the moisture permeability of the first film 31 is higher than that of the second film 32, the difference in moisture permeability between the two is not particularly limited, but it is preferable that it be relatively large in order to effectively absorb moisture into the polarizer 2. When the moisture permeability of the first film 31 is higher than that of the second film 32, the difference in moisture permeability between the two (moisture permeability of the first film 31 - moisture permeability of the second film 32) is, for example, 50 g / m 2 ·700g / m for 24 hours or more 2·24 h or less, preferably 100 g / m 2 ·24 h or more and 600 g / m 2 ·24 h or less. However, the water vapor transmission rate can be measured according to JIS Z 0208-1976 (aluminum cup method) under the conditions of 65°C and a relative humidity difference of 90%.

[0022] As the first film 31, for example, a protective film, an optical functional film, a release liner, or the like can be used. For example, when the first film 31 is a single-layer film, a protective film, an optical functional film, or the like can be used as the first film 31. For example, when the first film 31 is a laminated film, a laminated film in which a protective film and an optical functional film are laminated, a laminated film in which a release liner and a protective film are laminated, a laminated film in which a release liner, an optical functional film and a protective film are laminated, or the like can be used as the first film 31.

[0023] As the second film 32, for example, a protective film, an optical functional film, a release liner, or the like can be used. For example, when the second film 32 is a single-layer film, a protective film, an optical functional film, a release liner, or the like can be used as the second film 32. For example, when the second film 32 is a laminated film, a laminated film in which a release liner and a protective film are laminated, a laminated film in which a release liner, an optical functional film and a protective film are laminated, a laminated film in which a protective film and an optical functional film are laminated, or the like can be used as the second film 32.

[0024] The protective film is a film used to protect the polarizer 2 and the like. As the protective film, a colorless and transparent film is typically used. The aforementioned optical functional film is a film used to impart optical functions. Examples of the aforementioned optical functional film include phase difference films, light diffusion films, brightness enhancement films, anti-glare films, and light reflection films. Phase difference films are films that exhibit optical anisotropy, and typical examples include stretched films of acrylic resins, cycloolefin resins, cellulose resins, etc. A release liner is a film that protects the adhesive layer and is usually peeled off when using an optical film. Examples of release liners include resin films such as polyethylene, polypropylene, polyethylene terephthalate, and polyester films; paper; porous films such as woven fabrics, nonwoven fabrics, and mesh fabrics; and foamed resin films.

[0025] As the adhesives constituting the first adhesive layer 41 and the second adhesive layer 42, for example, solvent-type adhesives, non-aqueous emulsion-type adhesives, aqueous adhesives, hot-melt adhesives, etc., can be used. Adhesives based on acrylic polymers are preferably used because they have excellent transparency and heat resistance. In this specification, "adhesive" generally includes what is called a bonding agent. In terms of moisture permeability, the first adhesive layer 41 is formed using an adhesive having a moisture permeability equal to or higher than that of the first film 31. Similarly, the second adhesive layer 42 is formed using an adhesive having a moisture permeability equal to or higher than that of the second film 32. In Figures 2 and 3, the first film 31 is bonded to the polarizer 2 via the first adhesive layer 41, but the first film 31 may also be directly bonded to the polarizer 2 (without the adhesive layer) (not shown). In Figure 2, the second film 32 is bonded to the polarizer 2 via the second adhesive layer 42, but the second film 32 may also be directly bonded to the polarizer 2 (without the adhesive layer) (not shown).

[0026] [First Embodiment of a Method for Manufacturing an Optical Film Including a Method for Humidifying a Film Roll] The present invention provides a manufacturing method for producing a humidity-controlled optical film by humidifying a film roll containing a polarizer. One feature of the present invention is that water vapor at 35°C or higher and 80% RH or higher is blown onto the film roll at a pressure of 0.5 kPa or higher.

[0027] Figure 5 is a schematic diagram of the optical film manufacturing system. The optical film manufacturing system A has a humidification zone for humidifying the film roll 1. The optical film manufacturing system A may further have, if necessary, a roll manufacturing zone for manufacturing the film roll 1 including the polarizer 2, and a recovery zone for winding and recovering the obtained optical film. However, the method of the present invention is not limited to being carried out using the manufacturing system A.

[0028] In the illustrated example of manufacturing system A, the raw material manufacturing zone is equipped with a polarizer manufacturing apparatus B for manufacturing polarizers 2, and, if necessary, a lamination apparatus C for bonding the first film 31 and / or the second film 32 to the polarizers 2. A humidification apparatus D is provided in the humidification zone. A winding apparatus E for winding up the optical film 1a is provided in the recovery zone.

[0029] <Manufacturing of polarizers> Polarizer manufacturing apparatus B imparts polarization properties to a hydrophilic polymer film 2a, such as a polyvinyl alcohol-based resin, by a known method, for example. The hydrophilic polymer film 2a to which polarization properties have been imparted is a polarizer. For example, polarizer manufacturing apparatus B produces a polarizer by dyeing and stretching the hydrophilic polymer film 2a using a wet processing method.

[0030] Apparatus for manufacturing polarizers by such wet processing method is conventionally known. the law of nature, To explain simply 。The polarizer manufacturing apparatus B comprises, in order from upstream, a film loading section 51, a swelling treatment bath 52, a dyeing treatment bath 53, a crosslinking treatment bath 54, a stretching treatment bath 55, a washing treatment bath 56, and a drying section 57. The polarizer manufacturing apparatus B is not limited to the above configuration; for example, it may not have a swelling treatment bath 52, or it may not have a stretching treatment bath 55. If there is no stretching treatment bath 55, the hydrophilic polymer film 2a is stretched in the dyeing treatment bath 53 or the like. The polarizer manufacturing apparatus B may also have other treatment baths, such as an adjustment treatment bath. In this specification, the downstream side refers to the side in the direction of transport of the film roll 1 (the direction in which the film roll 1 travels), and the upstream side refers to the opposite side. The white arrows in each figure indicate the direction of film transport.

[0031] Next, the polarizer manufacturing process will be briefly explained. Referring to Figure 5, the hydrophilic polymer film 2a wound on a roll and loaded into the film loading section 51 is unwound. The hydrophilic polymer film 2a is transported to the swelling treatment bath 52 and swelled with a swelling solution such as water or potassium iodide aqueous solution (swelling process). The swollen hydrophilic polymer film 2a is transported to the dyeing treatment bath 53 and dyed with a dyeing solution containing a dichroic substance such as iodine (dyeing process). The dyed hydrophilic polymer film 2a is transported to the crosslinking treatment bath 54 and crosslinked with a crosslinking solution such as a boron compound aqueous solution (crosslinking process). The hydrophilic polymer film 2a is transported to the stretching treatment bath 55 and stretched (stretching process). The dyed and stretched hydrophilic polymer film 2a is transported to the washing treatment bath 56 and washed with a washing solution such as water (washing process). The washed hydrophilic polymer film 2a is dried in the drying section 57 (drying process). By applying each step to the hydrophilic polymer film 2a in this way, the hydrophilic polymer film 2a acquires polarization properties (i.e., a polarizer 2 is obtained).

[0032] In Figure 5, the polarizer 2 is transported to the lamination device C immediately after its manufacture (i.e., the film is laminated immediately after the manufacture of the polarizer 2), but this is not the only option. For example, the obtained polarizer 2 may be wound onto a roll, stored and transported as needed, and then unwound from the roll and laminated with the first film 31 or the like in the lamination device C (not shown).

[0033] <Manufacturing of film raw materials> The lamination apparatus C laminates the first film 31 and / or the second film 32 onto the polarizer 2. Such a lamination apparatus C is conventionally known. Briefly, the lamination apparatus C includes film loading sections 611, 612, a coating section (not shown) for coating the first and second films 31, 32 with adhesive, and a bonding section 613 for bonding the first and second films 31, 32 to the polarizer 2. Note that if the first film 31 and second film 32 have adhesive pre-coated, the coating section is omitted. Referring to Figure 5, the first film 31, wound on a roll and loaded into the film loading section 611, and the second film 32, loaded into the film loading section 612, are unwound. They are then guided to the bonding section 613, and the first and second films 31 and 32 are bonded to the polarizer 2. If the first film 31 consists of two or more laminated films, multiple bonding sections may be provided, and after bonding one film to the polarizer 2, other films may be bonded to that film on top to form a first film 31 made of laminated films. The same applies if the second film 32 consists of two or more laminated films. In this way, a film base 11 can be obtained in which the first film 31 is bonded to one side of the polarizer 2 and the second film 32 is bonded to the opposite side of the polarizer 2 (the opposite side being the side opposite to the one side), as shown in Figure 2.

[0034] In Figure 5, the film roll 1 is transported to the humidifier D immediately after its manufacture (i.e., humidification is performed immediately after the manufacture of the film roll 1), but this is not the only option. For example, the obtained film roll 1 may be wound onto a roll, stored and transported as needed, and then unwound from the roll and subjected to humidification in the humidifier D (not shown). When producing a film roll 12 with the layer configuration shown in Figure 3, only the first film 31 is laminated to the polarizer 2. Also, when producing a film roll 13 consisting only of the polarizer 2 as shown in Figure 4, the lamination apparatus C is omitted.

[0035] <Humidifying film rolls> The manufactured film roll 1 is transported to a humidifier D and humidified to contain an appropriate amount of moisture. Because heating and drying are performed during the manufacturing of the polarizers 2, the polarizers 2 contained in the film roll 1 immediately after manufacturing have a low moisture content. Polarizers 2 with a relatively low moisture content tend to bend and deform easily over time. By humidifying the film roll 1 containing such polarizers 2 to increase the moisture content of the polarizers 2, it is possible to manufacture an optical film 1a that is less prone to bending and deforming over time.

[0036] Figure 6 is a detailed side view of the humidifier D of the first embodiment shown in Figure 5. However, in Figure 6, the chamber 62 is shown as a cross-section cut along the conveying direction of the film roll 1, and further, in order to make the communication state between each pipe and the chamber 62 easier to understand, the part of the pipe connected to the chamber 62 is shown as a cross-section. Figure 7 is a plan view of the humidifier D (viewed from above looking downwards). Figure 8 is a cross-section of the spraying section 7 and the film roll 1 cut along the conveying direction, and is a cross-sectional view that clearly shows the state in which the film roll 1, to which water vapor is being sprayed, is being conveyed along the spraying section 7. Figure 9 is a reference perspective view showing the state in which the film roll 1 is being conveyed along the spraying section 7. In Figure 9, the film roll 1 is shown as a dashed line (two-dot line).

[0037] Referring to Figures 5 to 9, the humidifier D blows water vapor at 35°C or higher and 80% RH or higher, at a pressure of 0.5 kPa or higher, onto the long strip of film raw material 1 (film raw material including a polarizer) that is being transported. In the first embodiment, the humidifier D has an arc-shaped surface portion 711 in the blowing section 7 that blows water vapor onto the film raw material 1. Specifically, the humidifier D comprises a chamber 62 and a spraying section 7 located within the chamber 62 and having an arc-shaped surface portion 711 with a plurality of discharge holes 721 formed therein. The chamber 62 surrounds the spraying section 7 and is a chamber with sufficient space for transporting the film roll 1. An inlet 621 for introducing the film roll 1 into the chamber 62 is opened on the upstream side of the chamber 62, and an outlet 622 for transporting the film roll 1 out of the chamber 62 is opened on the downstream side of the chamber 62. Guide rollers 623 for guiding the transport of the film roll 1 are positioned appropriately within the chamber 62. The chamber 62 is also provided with a pressure adjustment means 64 for adjusting the atmospheric pressure (air pressure inside the chamber 62) and a temperature adjustment means 65 for adjusting the atmospheric temperature (temperature inside the chamber 62).

[0038] The pressure adjustment means 64 measures the atmospheric pressure inside the chamber 62 and adjusts the atmospheric pressure inside the chamber 62 based on the measured value.

[0039] The temperature adjustment means 65 measures the temperature inside the chamber 62 and adjusts the temperature inside the chamber 62 based on the measured value.

[0040] The spraying section 7 includes a hollow case body 731 having an arc-shaped surface portion 711 with a plurality of discharge holes 721 formed therein, and a supply port 741 for supplying water vapor into the case body 731. The arc-shaped surface portion 711 is arc-shaped when viewed from the side, and this arc shape extends continuously in the width direction of the film roll 1 to form an arc-shaped surface. In the illustrated example, the arc-shaped surface portion 711 is a substantially semi-circular arc-shaped surface, but is not limited to this, and may be a substantially quarter-circular arc-shaped surface, etc.

[0041] The dot-shaped discharge holes 721 formed on the arc-shaped surface portion 711 are, for example, openings that are approximately circular in plan view. However, the dot-shaped discharge holes 721 are not limited to openings that are approximately circular, but may be openings that are approximately square in plan view, etc. The size of the discharge holes 721 is not particularly limited, but if they are too small, clogging may occur, and if they are too large, variations in steam pressure may occur. From this viewpoint, the size of the discharge holes 721 is, based on the case where the discharge holes 721 are approximately circular, a diameter of 0.8 mm or more and 4.0 mm or less, preferably a diameter of 1.0 mm or more and 3.0 mm or less. If the discharge holes 721 are not approximately circular in plan view, the size of the discharge holes 721 is the equivalent diameter of a circle.

[0042] As shown in Figures 8 and 9, the multiple discharge holes 721 are formed at intervals in the circumferential direction (the direction in which the film roll 1 is transported) of the arc-shaped surface portion 711. Furthermore, as shown in Figure 9, the multiple discharge holes 721 are formed at intervals in the width direction of the film roll 1. Therefore, the multiple point-shaped discharge holes 721 are formed along the curved surface of the arc-shaped surface portion 711, and the multiple discharge holes 721 formed along that curved surface are also formed in the width direction. Each discharge hole 721 may be formed at equal intervals, or at random intervals. It is preferable that the multiple discharge holes 721 are formed at equal intervals in order to blow water vapor onto the film roll 1 in a substantially uniform manner. Furthermore, the specific arrangement of each discharge port 721 is not particularly limited and can be set as appropriate. Figure 10 is a plan view illustrating some examples of the arrangement of the discharge holes 721. When multiple discharge holes 721 arranged along the width direction of the film roll 1 are referred to as "rows," the rows of discharge holes 721 are arranged in multiple rows in the transport direction of the film roll 1 (circumferential direction of the arc-shaped surface portion 711). Figure 10(a) shows the case where discharge holes 721 in adjacent rows in the transport direction are arranged without shift in the width direction (hereinafter, this arrangement of point-like discharge holes 721 will be called a grid arrangement). Figure 10(b) shows the case where the discharge holes 721 in odd-numbered rows are arranged to the left (or right) in the width direction relative to the discharge holes 721 in even-numbered rows (hereinafter, this arrangement of point-like discharge holes 721 will be called a staggered arrangement).

[0043] The number of discharge holes 721 formed per unit area is not particularly limited and is set appropriately considering the size of the discharge holes 721. For example, the size and number of discharge holes 721 are set so that the opening ratio is in the range of 0.2% to 5.0%, preferably in the range of 0.5% to 3.0%. Here, the opening ratio is the ratio of the total opening area of ​​discharge holes 721 per unit area of ​​the arc-shaped surface portion 711 facing the film roll 1, and is calculated by the formula: (total opening area of ​​discharge holes 721 / unit area of ​​the arc-shaped surface portion 711 of the spraying section 7) × 100. For example, any 100 mm of the arc-shaped surface portion 711 facing the film roll 1 2 If 10 discharge holes 721 with a diameter of 2 mm are formed within this range, the opening ratio (%) = (1 mm × 1 mm × π × 10 / 100 mm 2 ) × 100, which is the result.

[0044] Each of the discharge holes 721 is drilled in the arc-shaped surface 711 so that water vapor is blown out radially from the arc-shaped surface 711 (see Figure 8). As water vapor is blown out radially from each discharge hole 721 from the arc-shaped surface 711, the water vapor can be blown in a substantially vertical direction (in the substantially thickness direction of the film roll 1) to one side of the film roll 1 being conveyed along the arc-shaped surface 711.

[0045] The supply port 741 of the spraying unit 7 is provided with a supply means for supplying steam into the case body 731 of the spraying unit 7. The supply means includes a steam generator 81, a heating unit 82 for heating the steam, a blower 83 for sending out the steam at a predetermined pressure, a pipe, and a supply control unit 84. Furthermore, it is preferable that the supply means includes a steam trap. The supply means may also include a temperature sensor, a humidity sensor, a speed sensor, etc., as needed.

[0046] In this embodiment, the supply means generally recovers the steam in the chamber 62, adds new steam as needed, heats this steam to a predetermined temperature, and supplies it to the spraying unit 7. For example, the supply means includes a pipe, a first steam trap 861, a steam generator 81, a heating unit 82 such as an electric heater, a blower 83, a temperature sensor 87 and a humidity sensor 88, a second steam trap 862, and a supply control unit 84. The supply means is usually provided outside the chamber 62, but part or all of it may be provided inside the chamber 62.

[0047] Referring to Figures 5 to 7, the pipe has a first pipe 851 connected to any point in the chamber 62 (a steam outlet in the chamber 62), a second pipe 852 connected to the supply port 741 of the spraying unit 7, and a third pipe 853 connected between the first pipe 851 and the second pipe 852. A steam generator 81, a heating unit 82, a blower 83, a temperature sensor 87, a humidity sensor 88, a second steam trap 862, etc. are provided along the path of the third pipe 853. The first steam trap 861 is positioned, for example, near the first pipe 851. The first steam trap 861 allows the steam from the chamber 62, which is taken out through the first pipe 851, to pass into the third pipe 853 without including any condensed water. Here, a steam trap (also called a drain trap) is a device that discharges drain (condensed water) from the steam atmosphere while minimizing the leakage of steam, and allows the steam to pass through. The steam generator 81 replenishes steam when the amount of steam taken from the chamber 62 and passing through the first steam trap 861 is insufficient. The heating unit 82 heats the steam (steam taken from the chamber 62 and steam from the steam generator 81 replenished as needed) to a predetermined temperature. The blower 83 sends the heated steam through the third pipe 853 and the second pipe 852 to the supply port 741 of the spraying unit 7. The second steam trap 862 is located, for example, at the outlet of the blower 83. The second steam trap 862 allows the steam sent from the blower 83 to pass through the second pipe 852 without containing any condensation. The temperature sensor 87 and humidity sensor 88 are located, for example, in the pipes along the path of the third pipe 853 between the blower 83 and the spraying unit 7. The supply control unit 84 controls the amount of steam supplied by the steam generator 81, the heating temperature of the steam by the heating unit 82, and the steam blowing pressure by the blower 83, according to the measurement information from the temperature sensor 87 and the humidity sensor 88.

[0048] A method for humidifying the film roll 1 using the humidifier D described above will be explained. However, the present invention is not limited to the case in which the film roll 1 is humidified using the humidifier D described above. The atmospheric pressure inside the chamber 62 is adjusted to be approximately the same as or slightly higher than the pressure outside the chamber 62. By adjusting the atmospheric pressure inside the chamber 62 to be equal to or slightly higher than the pressure outside the chamber 62, it is possible to prevent air from outside the chamber 62 from entering the chamber 62 through the inlet 621 or the like. The atmospheric pressure inside the chamber 62 can be adjusted by the pressure adjustment means 64. Specifically, the pressure adjustment means 64 measures the atmospheric pressure inside the chamber 62, determines the difference between the atmospheric pressure inside the chamber 62 and the set pressure (the set pressure is equal to or higher than the outside pressure), and adjusts the intake and exhaust volume to the desired atmospheric pressure.

[0049] Furthermore, the ambient temperature inside the chamber 62 is adjusted to a range of -5°C or higher and +20°C or lower than the water vapor temperature. -5°C means that the water vapor temperature is 5°C lower than the temperature of the water vapor blown onto the film roll 1, and +20°C means that the water vapor temperature is 20°C higher than the temperature of the water vapor blown onto the film roll 1. Preferably, the ambient temperature inside the chamber 62 is adjusted to a range of -10°C or higher and +10°C or lower than the water vapor temperature. By adjusting the ambient temperature inside the chamber 62 to -5°C or higher, condensation on the film roll 1 can be prevented. By adjusting the ambient temperature inside the chamber 62 to +20°C or lower, a decrease in optical properties can be suppressed, and moisture absorbed by the film roll 1 can be prevented from escaping from the film roll 1.

[0050] The ambient temperature inside the chamber 62 can be adjusted by the temperature adjustment means 65. Specifically, the temperature adjustment means 65 measures the ambient temperature inside the chamber 62 and controls the heat source heater by a temperature controller to achieve the desired ambient temperature.

[0051] Water vapor is sprayed onto the film roll 1 from the discharge hole 721 of the spraying unit 7. The water vapor is a gas containing water vapor, and may be, for example, a gas consisting only of water vapor, or a gas containing water vapor and air, etc.

[0052] The temperature of the water vapor blown onto the film roll 1 is 35°C or higher, preferably 37°C or higher, and more preferably 40°C or higher. By using water vapor at 35°C or higher, moisture can be quickly absorbed by the polarizer of the film roll 1. There is no particular upper limit to the temperature of the water vapor, but if it is too high, the film roll 1 may suffer thermal damage, so for example, it should be 80°C or lower, preferably 70°C or lower.

[0053] Furthermore, the humidity (relative humidity %RH) of the water vapor blown onto the film base is 80%RH or higher, preferably 95%RH or higher, and more preferably 98%RH or higher. By using water vapor of 80%RH or higher, moisture can be quickly absorbed by the polarizer of the film base 1. The upper limit of the humidity of the water vapor is 100%RH or lower, preferably 95%RH or lower.

[0054] Furthermore, the pressure of the water vapor blown onto the film roll is 0.5 kPa or higher, preferably 1.0 kPa or higher, and more preferably 1.5 kPa or higher. By blowing water vapor with a blowing pressure of 0.5 kPa or higher onto the film roll 1, moisture can be quickly absorbed by the polarizer of the film roll 1. There is no particular upper limit to the water vapor pressure, but if it is too high, the film roll 1 may break. From this viewpoint, the water vapor pressure is, for example, 4.0 kPa or lower, and preferably 3.0 kPa or lower. However, the temperature and humidity of the water vapor mentioned above refer to values ​​measured on one side of the film roll 1 (the one side of the film roll 1 being the portion where the water vapor emitted from the discharge hole 721 comes into contact with the film roll 1). Furthermore, the water vapor pressure refers to the value determined by the difference between the pressure measured near one side of the film roll 1 and the pressure outside the chamber (atmospheric pressure).

[0055] The aforementioned water vapor with temperature, humidity, and pressure can be supplied to the spraying section 7 by the supply means. More specifically, the supply control unit 84 operates the blower 83. When the blower 83 is operated, the water vapor in the chamber 62 enters the first steam trap 861 through the first pipe 851, and the condensed water is removed in the trap 861. In particular, when the ambient temperature inside the chamber 62 is higher than the temperature of the water vapor blown onto the film roll 1, some of the water vapor taken out from the chamber 62 tends to condense. By placing the first steam trap 861 near the water vapor outlet of the chamber 62, only the water vapor can be sent to the blowing unit 7 via the blower 83.

[0056] The steam that has passed through the first steam trap 861 is drawn into the blower 83 through the third pipe 853. If the humidity is low with only the steam taken out from the chamber 62, the supply control unit 84 operates the steam generator 81 to replenish the steam in the third pipe 853. The replenished steam merges with the steam taken out from the chamber 62 in the third pipe 853. By taking out the steam from the chamber 62 and reusing it, the steam can be used effectively, and the humidifier D can be operated stably.

[0057] The supply control unit 84 operates the heating unit 82 to heat the steam flowing through the third pipe 853 to a predetermined temperature. The heated steam is sent by the blower 83 through the second pipe 852 and the supply port 741 into the case body 731 of the spraying unit 7 and blown out from the discharge hole 721 of the arc-shaped surface 711. The supply control unit 84 controls the heating by the heating unit 82 according to the temperature measurement information from the temperature sensor 87, adjusting so that the steam coming out of the discharge hole 721 reaches the above temperature. The supply control unit 84 also controls the amount of steam replenished by the steam generator 81 according to the humidity measurement information from the humidity sensor 88, adjusting so that the steam coming out of the discharge hole 721 reaches the above humidity. Note that the pressure of the steam does not fluctuate much while the humidifier D is in operation, so the blower 83 can be set so that the pressure of the steam is the above pressure from the beginning. However, sensors such as flow meters may be installed in the third pipe 853 or elsewhere. The supply control unit 84 may control the strength of the blower 83 according to the measurement information from the sensor, adjusting it so that the water vapor coming out of the discharge port 721 reaches the above pressure.

[0058] Furthermore, data on the temperature, humidity, and / or pressure changes of the water vapor during operation of the humidifier D may be obtained by trial running the humidifier D. Based on this data, the programmed supply control unit 84 can control the heating unit 82 and other components to adjust the temperature and pressure of the water vapor. In this case, the temperature sensor 87 and humidity sensor 88 may be omitted.

[0059] A long, strip-shaped roll of film material 1 is introduced into the chamber 62. The film material 1 introduced into the chamber 62 from the inlet 621 is transported along the arc-shaped surface 711 of the spraying section 7 that blows water vapor, and exits the chamber 62 from the outlet 622. The transport speed of the film material 1 is not particularly limited, but for example, it is between 2 m / min and 35 m / min.

[0060] It is preferable to transport the film roll 1 in the chamber 62 for 3 seconds or more before spraying the water vapor onto the film roll 1. In other words, it is preferable that the time it takes for the film roll 1 that has entered the chamber 62 to reach the point X where the water vapor is to be sprayed (hereinafter referred to as the "spraying start point X") (hereinafter referred to as the "curing time") is 3 seconds or more. It is more preferable that the curing time be 5 seconds or more, and even more preferable that it be 10 seconds or more. The curing time can be measured, for example, by marking a portion of the film roll 1 being transported and measuring the time from when the mark passes the entrance 621 until it passes the spraying start point X. By transporting the film roll 1 for the curing time in a chamber 62 adjusted to a temperature of -5°C or higher for the sprayed water vapor, condensation on the film roll 1 can be effectively prevented. The path length of the film roll 1 from the loading entrance 621 to the spraying start point X can be determined from the curing time and the transport speed of the film roll 1. In this specification, the path length refers to the transport length of the film roll from one point to another.

[0061] As shown in Figures 6 and 8, while the film roll 1 is being transported along the arc-shaped surface portion 711, water vapor is blown onto one side of the film roll 1 from the discharge holes 721 of the arc-shaped surface portion 711. The thin arrows in Figures 6 and 8 indicate the direction of water vapor discharge (the same applies to the thin arrows shown in other figures below). By blowing water vapor onto the film roll 1, moisture can be absorbed by the polarizer. Figure 8 illustrates a case where the film roll 1 is a laminate having a first film 31 / polarizer 2 / second film 32 as shown in Figure 2. If the moisture permeability of the first film 31 is higher than that of the second film 32, it is preferable to blow the water vapor from the first film 31 side, as shown in Figure 8. By blowing water vapor from the first film 31 side, which has higher moisture permeability, moisture can be effectively absorbed by the polarizer. Furthermore, when humidifying a film roll 1 with the layer configuration shown in Figure 3 or Figure 4, the polarizer 2 can directly absorb moisture by blowing water vapor onto the polarizer 2 side of the film roll 1.

[0062] The film roll 1 is transported in the chamber 62 under a predetermined tension. The tension applied to the film roll 1 is not particularly limited, and is, for example, 50 N / m or more and 300 N / m or less, preferably 100 N / m or more and 200 N / m or less. The film roll 1, under tension, is transported along the arc-shaped surface portion 711, curving in an arc shape when viewed from the side. While the film roll 1 is being transported along the arc-shaped surface portion 711 of the spraying section 7, the tension of the film roll 1 and the spraying pressure of the water vapor are in equilibrium, and the film roll 1 is transported along the arc-shaped surface portion 711 while moving away from it. In this way, the tension and spraying pressure are in equilibrium, causing the film roll 1 to curve in an arc shape, and the film roll 1 is transported along the arc-shaped surface at a distance L (the symbol L representing distance is shown in Figure 8) from the arc-shaped surface portion 711. Therefore, water vapor from the discharge holes 721 of the arc-shaped surface portion 711 can be blown almost evenly onto one side of the film roll 1, allowing the polarizer to effectively absorb moisture.

[0063] According to the present invention, since moisture can be effectively absorbed by the polarizer, the humidification process can be completed on the film roll 1 in a relatively short time. For example, the time for which water vapor is sprayed onto the film roll 1 (hereinafter referred to as "spraying time") is 10 seconds or more and 90 seconds or less, preferably 30 seconds or more and 60 seconds or less. The spraying time refers to the transport time of the film roll 1 from the spraying start point X to the point Y where the spraying of water vapor ends (spraying end point Y). The spraying time can be measured, for example, by marking a portion of the transported film roll 1 and measuring the time from when the mark passes the spraying start point X to when it passes the spraying end point Y. The path length of the film roll 1 from the spraying start point X to the spraying end point Y can be determined from the spraying time and the transport speed of the film roll 1.

[0064] By performing the above-described humidification treatment on the film roll 1, a humidified optical film 1a is obtained. The film roll 1 (optical film 1a) that has passed the spraying end point Y is transported out of the chamber 62 from the discharge port 622. The obtained optical film 1a is wound onto the winding device E. If necessary, any appropriate treatment may be performed on the optical film 1a after the humidification treatment and before winding it onto the winding device E.

[0065] Other embodiments of the present invention will be described below, but in this description, the configurations and effects that differ from those of the embodiments described above will be explained, and similar configurations will be retained by using the same terms or reference numerals, and their descriptions may be omitted.

[0066] [Second Embodiment] The humidifier D of the first embodiment described above has a spraying section 7 having an arc-shaped surface portion 711, but the spraying section 7 is not limited to this and can be modified in various ways. Figure 11 is a detailed side view of the humidifier D of the second embodiment, and, similar to Figure 6, shows a cross-section of the chamber 62 and a part of the pipe. Figure 12 is a cross-section of the spraying section 7 and the film roll 1 of the humidifier D of the second embodiment, cut along the transport direction. Figure 13 is a reference perspective view showing the state in which the film roll 1 is being transported along the spraying section 7 in the humidifier D of the second embodiment. In Figure 13, the film roll 1 is represented by dashed lines.

[0067] In Figures 11 to 13, the spraying section 7 of the humidifier D of this embodiment has slit-shaped discharge holes 722. Specifically, the spraying section 7 has a hollow case body 732 having a flat surface portion 712 on which a plurality of discharge holes 722 are formed, and a supply port 742 for supplying water vapor into the case body 732. The flat surface portion 712 is linear in side view. The discharge hole 722 formed in the flat surface portion 712 is, for example, an elongated slit-shaped opening in plan view. In the illustrated example, the discharge hole 722 is an elongated slit shape extending in the width direction of the film roll 1 (see Figure 13).

[0068] The size of the discharge holes 722 is not particularly limited, but if they are too small, clogging may occur, and if they are too large, variations in water vapor pressure may occur. From this viewpoint, the width of the discharge holes 722 is, for example, 0.8 mm or more and 5.0 mm or less, preferably 2 mm or more and 4 mm or less. The number of discharge holes 722 formed per unit area is not particularly limited and is set appropriately considering the size of the discharge holes 722. For example, the size and number of discharge holes 722 are set so as to be in the range of 0.2% or more and 5.0%, preferably in the range of 0.5% or more and 3.0% or less. Here, the opening ratio is the ratio of the total opening area of ​​discharge holes 722 per unit area of ​​the flat surface portion 712 facing the film roll 1, and is calculated by the formula: (total opening area of ​​discharge holes 722 / unit area of ​​the flat surface portion 712 of the spraying section 7) × 100.

[0069] Each of the discharge holes 722 is drilled in the flat surface portion 712 so that water vapor is blown out in the vertical direction of the flat surface portion 712. As water vapor is blown out from each discharge hole 722 in the vertical direction of the flat surface portion 712, the water vapor can be blown onto one side of the film roll 1 in a substantially vertical direction (the water vapor is blown in the substantially thickness direction of the film roll 1). Furthermore, transport nip rollers 624 are positioned on the upstream and downstream sides of the spraying section 7 to prevent the film roll from flapping due to the water vapor being sprayed onto it. Other components of the humidifier D in the second embodiment can be the same as those in the first embodiment.

[0070] In this embodiment, as in the first embodiment, the humidifier D transports the film roll 1 into a chamber 62 adjusted to a predetermined ambient temperature, and the spraying section 7 sprays water vapor at 35°C or higher, 80% RH or higher, and a spraying pressure of 0.5 kPa or higher onto the film roll 1. In this embodiment as well, the humidification process for the polarizer is completed in a relatively short time, and a humidified optical film 1a containing an appropriate amount of moisture can be obtained.

[0071] [Modified version of the second embodiment] The discharge hole 722 in the second embodiment described above is an elongated slit shape extending in the width direction of the film roll 1, but is not limited to this. For example, as shown in Figure 14, the discharge hole 722 may be an elongated slit shape extending in the transport direction of the film roll 1. Also, although not specifically shown, the slit-shaped discharge hole 722 may be formed to extend in a direction inclined with respect to the transport direction of the film roll 1.

[0072] Furthermore, in the above embodiment, water vapor is blown from only one side of the film roll 1, but water vapor may also be blown from both one side and the opposite side of the film roll 1. For example, as shown in Figure 15, by arranging the spraying unit 7 on one side of the film roll 1 being transported into the chamber 62, and arranging the spraying unit 7 on the opposite side of the film roll 1, water vapor can be blown from both sides of the film roll 1.

[0073] [Third Embodiment] Figure 16 is a reference plan view showing the state in which the film roll 1 is being transported along the spraying section 7 in the humidifier D of the third embodiment. In Figure 16, the film roll 1 is represented by dashed lines (two-dot lines).

[0074] In Figure 16, the spraying section 7 of the humidifier D in this embodiment has a flat surface section 713 on which dot-shaped discharge holes 723 are formed. Specifically, the spraying section 7 has a hollow case body 733 having a flat surface section 713 on which a plurality of dot-shaped discharge holes 723 are formed, and a supply port 743 for supplying water vapor into the case body 733. The flat surface section 713 is linear in side view, similar to the flat surface section 712 in the second embodiment. Furthermore, the spraying section 7 in the third embodiment is substantially the same as that of the second embodiment, except for the discharge holes 723. The discharge holes 723 formed in the flat surface portion 713 are, for example, substantially circular openings in plan view. The dot-shaped discharge holes 723 are not limited to substantially circular openings, but may also be substantially square openings in plan view, etc. Also, in Figure 16, the arrangement of the multiple dot-shaped discharge holes 723 is staggered. The arrangement of the discharge holes 723 is not limited to staggered arrangement, but may be a grid arrangement, or other arrangements. The shape, size, number and opening ratio of the discharge holes 723 in the third embodiment can be adapted from the shape of the discharge holes 721 in the first embodiment.

[0075] Each of the discharge holes 723 is drilled in the flat surface portion 713 so that water vapor is blown out in the vertical direction of the flat surface portion 713. As water vapor is blown out from each discharge hole 723 in the vertical direction of the flat surface portion 713, the water vapor can be blown in a substantially vertical direction to one side of the film roll 1. Furthermore, in order to prevent the film roll from flapping, transport nip rollers are arranged on the upstream and downstream sides of the spraying section 7 in the third embodiment, similar to the second embodiment (not shown). Other components of the humidifier D in the third embodiment can be the same as those in the first embodiment.

[0076] In the third embodiment of the humidifier D, similar to the first embodiment, the film roll 1 is transported into a chamber 62 adjusted to a predetermined ambient temperature, and water vapor at 35°C or higher, 80% RH or higher, and a spraying pressure of 0.5 kPa or higher is sprayed onto the film roll 1 in the spraying section 7. In this embodiment as well, the humidification treatment of the polarizer is completed in a relatively short time, and a humidified optical film 1a containing an appropriate amount of moisture can be obtained.

[0077] [Fourth Embodiment] In the embodiments described above, the film roll was humidified after the first film and / or second film were laminated onto the polarizer. However, the polarizer itself may be used as the film roll for humidification, and the first film and / or second film may be laminated onto the humidified film roll (polarizer) (not shown).

[0078] [Applications of optical films, etc.] The applications of the optical film containing the polarizer of the present invention are not particularly limited. Since the optical film of the present invention is resistant to bending and deformation over time, it can be suitably used as an optical film for displays such as liquid crystal displays and organic displays. Furthermore, the optical film of the present invention is not limited to use in the aforementioned displays, but can also be used for applications other than displays. Examples of applications other than displays include optical equipment, buildings, and the medical and food industries. When the optical film is used in optical equipment, it is processed into, for example, a polarizing lens or a transparent radio wave shielding film. When the optical film is used in electronic devices, it is processed into, for example, a dimmable window film. When the optical film is used in the medical or food industries, it is processed into, for example, a light degradation prevention film. [Examples]

[0079] The present invention will be further described below with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

[0080] [Film rolls used] A long strip of film material was used, in which a 40 μm thick triacetylcellulose (TAC) film (Konica Minolta, Inc., product name "KC4CT") was laminated to one side of an 18 μm thick polarizer (Kuraray Co., Ltd., product name "VF-PE#4500") via an adhesive, and a 40 μm thick cyclic olefin (COP) film (Zeonor Film ZF-16), manufactured by Zeon Corporation, was laminated to the opposite side of the polarizer via an adhesive. The moisture permeability of this TAC film is 620 g / m². 2 • After 24 hours, the moisture permeability of the COP film is 1.2 g / m². 2 The result was 24 hours. Moisture permeability was measured according to JIS Z 0208-1976 (aluminum cup method) under conditions of 65°C and a relative humidity difference of 90%.

[0081] [humidifier] A humidifier D was prepared, which had a spraying section 7 having an arc-shaped surface section 711 with multiple discharge holes 721 formed therein, as shown in Figures 6 to 9. The discharge port 721 was circular with a diameter of 400 mm, and its opening ratio was 1.0%.

[0082] [Method for measuring water vapor temperature, humidity, and pressure] The temperature and humidity of the water vapor were measured near the outlet of the discharge hole in the spraying unit. The temperature and humidity of the water vapor were measured using a VAISALA product called "HM70 Humidity and Temperature Meter". The pressure measured near the outlet of the discharge hole in the spraying section (approximately the same as the area near one side of the film roll) and the pressure outside the chamber (atmospheric pressure) were defined as the water vapor pressure. The pressure near the discharge hole in the spraying section was measured using a product called "Manostar Gauge" manufactured by Yamamoto Electric Works Co., Ltd. However, the temperature, humidity, and pressure of the water vapor were measured approximately 30 minutes after the start of operation (after the operation had stabilized). [Method for measuring ambient temperature and humidity inside a chamber] Measurements were taken using temperature and humidity sensors placed inside the chamber. However, the temperature and humidity inside the chamber were measured approximately 30 minutes after the start of operation (after the operation had stabilized).

[0083] [Method for measuring the increase in absorbance] Absorbance was measured using the "RX200" product manufactured by Kurabo Industries Ltd. The absorbance of the film roll before humidification treatment was measured, and then the absorbance after humidification treatment was measured again. The increase in absorbance was calculated using the following formula. Formula: Increase in absorbance = Absorbance after humidification - Absorbance before humidification.

[0084] [Example 1] Under the humidification conditions shown below, the film roll was transported into the chamber of the humidifier and humidified. The film roll was transported in such a way that water vapor was directly blown onto the TAC film side. <Humidification conditions> Temperature of water vapor emitted from the discharge holes of the spraying unit: 35°C. Humidity of water vapor emitted from the discharge holes of the spraying unit: 80 %RH. Pressure of water vapor emitted from the discharge port of the spraying unit: 0.8 kPa. Ambient temperature inside the chamber: 32℃. Ambient humidity inside the chamber: 70 %RH. Curing time: Approximately 10 seconds. Spraying time: Approximately 15 seconds. Film roll transport speed: 3m / min.

[0085] To confirm the degree of increase in moisture content of the film roll obtained in Example 1 after humidification, the increase in absorbance was measured. The results are shown in Table 1. Furthermore, the appearance of the film roll after humidification treatment was visually observed. The results are shown in Table 1. However, in the "Appearance" column of Table 1, "A" indicates that no condensation water was present on the film roll, "B" indicates that condensation water was present on a portion of the film roll, and "C" indicates that condensation water was present on almost the entire film roll.

[0086] [Table 1]

[0087] [Examples 2 to 7, Comparative Examples 1 and 2] The film roll was humidified in the same manner as in Example 1, except that the humidification conditions were changed as shown in Table 1. In Examples 2 to 7 and Comparative Examples 1 and 2, the increase in absorbance of the film base material was measured and the appearance after humidification treatment was observed, in the same manner as in Example 1. The results are shown in Table 1.

[0088] [Comparative Example 3] The film roll was humidified in the same manner as in Example 1, except that the film roll was transported into a chamber without a steam spraying section for humidification. In other words, the film roll was humidified by transporting it into a chamber with the temperature and humidity shown in Table 1, without blowing steam from a spraying section. In Comparative Example 3, as in Example 1, the increase in absorbance of the film roll was measured and the appearance after humidification treatment was observed. The results are shown in Table 1.

[0089] [evaluation] Examples 1 to 7 demonstrate that, while using the same spraying time as Comparative Examples 1 and 2, a sufficient amount of moisture could be incorporated into the film roll. In Comparative Example 1, where the water vapor pressure was 0.45 kPa, it was found that the spraying time had to be increased to incorporate a sufficient amount of moisture. Similarly, in Comparative Example 2, where the water vapor temperature was 30°C and the humidity was 70% RH, it was also found that the spraying time had to be increased to incorporate a sufficient amount of moisture. Furthermore, it can be seen that Examples 4 to 7, in which the water vapor humidity is 95%RH, are more effective at imparting moisture to the film base compared to Examples 1 to 3, in which the water vapor humidity is 80%RH. [Explanation of Symbols]

[0090] 1 film roll 1a Optical film 2 polarizers 31 Film No. 1 32 Film No. 2 62 Chambers 7. Spraying section 711 Arc-shaped surface part 721, 722, 723 Steam discharge holes A optical film manufacturing apparatus B Polarizer manufacturing equipment C Laminating device D Humidifier

Claims

1. A method for producing a humidity-controlled optical film by humidifying a film base having a polarizer and a first film and a second film laminated on one side and the opposite side of the polarizer, respectively, The moisture permeability of the first film is 100 g / m²·24h or more and 900 g / m²·24h or less. A method for manufacturing an optical film, comprising spraying water vapor at 35°C to 80°C and with a RH of 80% or higher onto the film raw material from the first film side at a pressure of 0.5 kPa to 4.0 kPa for a period of 10 seconds to 90 seconds. However, the aforementioned moisture permeability is measured under conditions of 65°C and a relative humidity difference of 90% by JIS Z 0208-1976 (aluminum cup method).

2. The method for producing an optical film according to claim 1, wherein the polarizer is a dyed and stretched hydrophilic polymer film.

3. The aforementioned film raw material is guided into a chamber adjusted to a predetermined ambient temperature. A method for manufacturing an optical film according to claim 1 or 2, wherein while the film roll is being transported in the chamber, steam at the pressure described above is blown onto the film roll.

4. The method for manufacturing an optical film according to claim 3, wherein the ambient temperature inside the chamber is in the range of -5°C or higher and +20°C or lower than the temperature of the water vapor.

5. The method for manufacturing an optical film according to claim 4, wherein the film roll is transported in the chamber for 3 seconds or more before the water vapor is blown onto the film roll.

6. A spraying section having an arc-shaped surface portion with multiple discharge holes is arranged inside the chamber. The method for manufacturing an optical film according to claim 3, wherein, while the film roll is being conveyed along the arc-shaped surface in a taut state, water vapor is blown onto the film roll from the discharge hole, so that the tension of the film roll and the pressure of the blown water vapor are in equilibrium, causing the film roll to move away from the arc-shaped surface while being conveyed along the arc-shaped surface.

7. A spraying section having a flat surface portion with a plurality of dot-shaped discharge holes is arranged inside the chamber. The method for manufacturing an optical film according to claim 3, wherein while the film roll is being transported along the spraying section in a taut state, the water vapor is sprayed vertically from the discharge hole onto one side of the film roll.

8. The method for manufacturing an optical film according to claim 1 or 2, wherein the moisture permeability of the first film is higher than that of the second film.

Images