JP7454937B2 - Optical film manufacturing method and optical film manufacturing device - Google Patents

Description

The present invention relates to an optical film manufacturing method and an optical film manufacturing apparatus.

Optical films are usually manufactured by subjecting the film to at least one treatment to impart desired optical properties while being transported. For example, when the optical film is a polarizing film, at least one treatment is performed to impart linear polarization properties to the film as an optical property. As described above, when manufacturing an optical film, the width of the film changes during the process of manufacturing the optical film from the film. When the film is being transported, the rate of change between the film width on the upstream side and the width of the film on the downstream side is known as the neck-in rate (see Patent Document 1). During the manufacturing process of optical films, if the neck-in rate of the film deviates from the preset tolerance range (control range), the film may break or the film thickness may deviate from the desired thickness. . Therefore, in order to appropriately manufacture optical films, it is important to manage the neck-in rate.

Japanese Patent Application Publication No. 8-226811

In the technique described in Patent Document 1, in order to calculate the neck-in rate, the width of the film is measured at an upstream measurement point and a downstream measurement point. However, in Patent Document 1, at the upstream measurement point and the downstream measurement point, the same part of the film (web in Patent Document 1), that is, the part of the film measured at the upstream measurement point, is the same at the downstream measurement point. As it passes, the width of the film is measured at a downstream measurement point. Therefore, while the film is moving from the upstream measurement point to the downstream measurement point, it cannot be confirmed whether the neck-in rate deviates from the allowable range.

Therefore, an object of the present invention is to provide an optical film manufacturing method and an optical film manufacturing apparatus that can efficiently measure the neck-in rate, have stable quality, and further reduce material costs. do.

A method for manufacturing an optical film according to one aspect of the present invention is a method for manufacturing an optical film by subjecting a long film to N treatments (N is an integer of 1 or more), the method comprising: is carried out while conveying the film, and during the conveyance, the width of the film is continuously measured at each of multiple locations, and the measurement results at the upstream location and downstream of the two locations selected from the multiple locations are measured. The rate of change in the width of the film is calculated based on the measurement results obtained at the same timing among the measurement results at the location.

An optical film manufacturing apparatus according to another aspect of the present invention includes N processing units (N is an integer of 1 or more) for performing a process of imparting at least optical properties to the film, and transporting the film. a conveyance mechanism; a plurality of width measuring devices disposed at a plurality of locations on the conveyance mechanism, each of which continuously measures the width of the film being conveyed by the conveyance mechanism at each of the plurality of locations; The width of the film is determined based on the measurement result of the upstream width measurement device and the measurement result of the downstream width measurement device obtained at the same timing among the two width measurement devices selected from the width measurement devices. and a calculation unit that calculates the rate of change.

In the above manufacturing method and the above manufacturing apparatus, the width of the film is measured at multiple locations. This allows the width of the film to be continuously measured while the film is being transported. Furthermore, the rate of change in the width of the film is calculated based on the measurement results of the width of the film measured at the same timing at the upstream and downstream locations among the widths of the film that are continuously measured at a plurality of locations. Therefore, the neck-in rate can be measured efficiently, the quality is stable, and the material cost of the optical film can be reduced.

In the manufacturing method, the upstream location may be a location before one of the N treatments is performed, and the downstream location may be a location after the one treatment is performed. good.
In the manufacturing apparatus, the upstream width measuring device is arranged in front of one of the N processing sections, and the downstream width measuring device is arranged after the one processing section. You can leave it there.

The width of the film is likely to change as each of the N treatments is applied. Therefore, with the above configuration, the rate of change in the width of the film can be calculated at locations where the width of the film is likely to change.

In the manufacturing method, the N processes include an i-1st process, an i-th process, and an i+1-th process (i is an integer of 2 or more), and the upstream location is the i-1st process. and the i-th processing position, and the downstream location may be between the i-th processing position and the i+1-th processing position.
In the manufacturing apparatus, the N processing units include an i-1th processing unit, an i-th processing unit, and an i+1-th processing unit (i is an integer of 2 or more), and the upstream width measuring device is , disposed between the i-1st processing section and the i-th processing section, and the downstream width measuring device is disposed between the i-th processing section and the i+1th processing section. You can leave it there.

The width of the film is subject to change when processing is applied to the film. Therefore, with the above configuration, the rate of change in the width of the film can be calculated at locations where the width of the film is likely to change. Furthermore, in the above configuration, if the rate of change in the width of the film exceeds the allowable range, the rate of change in width is due to the i-th treatment, or the state of the film before the i-th treatment has changed. Therefore, by adjusting the rate of change in the width of the film within an allowable range, problems can be avoided.

In the above manufacturing method, the N processes include an i-1th process and an i-th process (i is an integer of 2 or more), the upstream location is at a position during the i-1 process, and The downstream location may be between the i-1st processing position and the i-th processing location, and the upstream location and the downstream location may each be between the i-1th processing location and the i-1st processing location. It may be between the positions of the i-th processing, or the upstream location is a position before the i-1 processing and the downstream location is the location during the i-1 processing. It may be.
In the manufacturing apparatus, the N processing sections include an i-1th processing section and an i-th processing section (i is an integer of 2 or more), and the upstream width measuring device is the i-1th processing section. The downstream width measuring device may be arranged at the position of the processing section, and the downstream width measuring device may be arranged between the i-1th processing section and the i-th processing section, and the upstream width measuring device and the downstream width measuring device may be arranged between the i-1th processing section and the i-th processing section, respectively, or the upstream width measuring device may be arranged between the i-1th processing section and the i-1th processing section, respectively. The downstream width measuring device may be placed in front of the i-1th processing section, and the downstream width measuring device may be placed in front of the i-1th processing section.

With the above configuration, it is possible to calculate the rate of change in the width of the film while the film is being processed, or the rate of change in the width of the film from the end of one process to the next process.

In the manufacturing method, the width of the film may be measured by capturing an image of at least an end portion of the film using an imaging unit during the transport.
In the manufacturing apparatus, at least one of the plurality of width measuring devices may include an imaging unit that images at least an end portion of the film.

In this case, the width of the film can be calculated using the image acquired by the imaging section.

In the manufacturing method, the width of the film may be measured based on the brightness of at least one of reflected light and transmitted light from the film caused by light incident on the film during the transport.
In the manufacturing apparatus, at least one of the plurality of width measuring devices may include a light detection section for detecting at least one of reflected light and transmitted light from the film caused by light incident on the film. .

In the manufacturing apparatus, at least one width measuring device among the plurality of width measuring devices may include a light irradiation section that irradiates the film with light. For example, when detecting the transmitted light from the film, if the difference in the brightness of the light with the surrounding environment is small, the brightness of the surrounding environment can be increased with the light from the light irradiation section. As a result, it is easy to measure the width of the film.

In the above manufacturing method, the film is transported by a transport roll, the film on the transport roll is irradiated with the light, and based on the difference in brightness between the reflected light of the film and the transport roll caused by the irradiation of the light, , the width in the film may be measured by detecting an edge of the film.
In the manufacturing apparatus, the transport mechanism includes a transport roll, the light irradiation unit irradiates the film on the transport roll with light, and at least one width measuring device among the plurality of width measuring devices The width of the film may be measured based on the difference in brightness between reflected light of the film and the transport roll, which is generated by light from the light irradiation section onto the film on the transport roll.

In this case, it is easy to identify the edge of the film based on the difference in brightness between the light reflected from the film and the light reflected from the transport roll. As a result, the width of the film can be calculated more accurately based on the position of the edge. If the reflected light from the film is specular and has sufficient brightness, the measurement is not limited to the transport roll.

In the above manufacturing method, the transmitted light may be transmitted light from the film caused by light that is incident on the film via a polarizing filter. Alternatively, in the manufacturing method, the width of the film may be measured based on the brightness of light obtained by passing the transmitted light through a polarizing film.
One embodiment of the above-mentioned manufacturing device may have a polarizing filter between the above-mentioned light irradiation part and the above-mentioned film. Alternatively, an embodiment of the manufacturing apparatus may include a polarizing filter between the photodetector and the film.

For example, when the film has linear polarization characteristics, the width of the film can be easily measured by arranging the polarizing filter and the film in a crossed nicol state.

In the manufacturing method, the N treatments may include at least one of a swelling treatment, a dyeing treatment, a crosslinking treatment, a stretching treatment, and a drying treatment.
In the manufacturing apparatus, the N processing sections may include at least one of a swelling processing section, a dyeing processing section, a crosslinking processing section, a stretching processing section, and a drying processing section.

An example of the optical film is a polarizing film.

According to the present invention, it is possible to provide an optical film manufacturing method and an optical film manufacturing apparatus that can efficiently measure the neck-in rate, have stable quality, and further reduce material costs.

FIG. 1 is a schematic diagram for explaining a method for manufacturing an optical film according to one embodiment. FIG. 2 is a drawing for explaining changes in film width in the optical film manufacturing method. FIG. 3 is a diagram for explaining a width measuring device and a calculating section. FIG. 4 is a diagram for explaining an example of a width detector included in the width measuring device. FIG. 5 is a diagram for explaining another example of the width detector included in the width measuring device.

Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and redundant explanation will be omitted. The dimensional proportions in the drawings do not necessarily correspond to those in the description.

FIG. 1 is a schematic diagram for explaining one embodiment of the present invention. Hereinafter, the case where a polarizing film is manufactured as an optical film will be described as an example.

In this embodiment, the polarizing film (optical film) 4 is manufactured by sequentially performing N treatments (N is an integer of 1 or more) on the film 2 being transported while transporting the long film 2. . The N treatments are treatments that give the film 2 at least linear polarization characteristics as optical characteristics. The upper limit of N is not particularly limited, but N is usually an integer of 30 or less, may be an integer of 25 or less, may be an integer of 20 or less, or is an integer of 10 or less. Good too.

When the film 2 is given linear polarization characteristics, the film 2 functions as a polarizing film 4. Since the linear polarization property is substantially imparted before all N processes are completed, in the method for manufacturing polarizing film 4 using film 2, film 2 does not function as polarizing film 4 during the manufacturing process. have However, for convenience of explanation, unless otherwise specified, the film 2 after all the N processes have been completed will be referred to as the polarizing film 4, and all the films before the N processes have been completed will be referred to as the film 2. When manufacturing the polarizing film 4, the film 2 is usually subjected to swelling treatment, dyeing treatment, crosslinking treatment, stretching treatment, and drying treatment. The stretching treatment may be applied to the film 2 during any one treatment (for example, crosslinking treatment) or in parallel while performing a plurality of treatments.

Film 2 is a polyvinyl alcohol resin film. An example of the length of the film 2 in the longitudinal direction is 1000 m or more and 30000 m or less, preferably 1000 m or more and 20000 m or less. An example of the length of the film 2 in the width direction (direction perpendicular to the longitudinal direction) is 1300 mm to 5000 mm. An example of the thickness of the film 2 before N treatments is 10 μm to 100 μm. The film 2 can be manufactured by a known method such as a melt extrusion method or a solvent casting method. The film 2 may be a purchased film or a film that has been subjected to treatments such as stretching and lamination in advance. In FIG. 1, a case is illustrated in which the film 2 is prepared as a raw roll 6, and the film 2 fed out from the raw roll 6 is subjected to N treatments to obtain a polarizing film 4. When the film 2 is manufactured by the above method (melt extrusion method, solvent casting method, etc.), for example, the film 2 manufactured by the above method (melt extrusion method, solvent casting method, etc.) is continuously conveyed, The above N processes may be performed during transportation.

The manufacturing apparatus 10 for the polarizing film 4 includes a plurality of nip rolls 11, a plurality of guide rolls 12, a swelling processing section ₁₃₁ , a dyeing processing section ₁₃₂ , a crosslinking processing section ₁₃₃ , a cleaning processing section ₁₃₄ , A drying processing section ₁₃₅ is provided.

The plurality of nip rolls 11 and the plurality of guide rolls 12 are included in the film 2 transport mechanism and are transport rolls for transporting the film 2. A transport path for the film 2 is configured by appropriately arranging a plurality of nip rolls 11 and a plurality of guide rolls 12.

The nip roll 11 has a function of applying the rotational force of the nip roll 11 to the film 2 by sandwiching and pressing the film 2. The nip roll 11 also has the function of changing the transport direction of the film 2. In the transport direction of the film 2, for example, by applying a peripheral speed difference between the two adjacent nip rolls 11, the film 2 transported between the two adjacent nip rolls 11 is subjected to a stretching process (for example, a uniaxial stretching process). Ru. FIG. 1 illustrates a case where the manufacturing apparatus 10 has eight nip rolls 11. When separately explaining the six nip rolls 11, the six nip rolls 11 are referred to as nip rolls 11 ₁ to 11 ₆ , as shown in FIG.

The guide roll 12 has the function of supporting the film 2 and changing the conveying direction of the film 2. FIG. 1 illustrates a case where the manufacturing apparatus 10 has 12 guide rolls 12. When explaining the 12 guide rolls 12 separately, the 12 guide rolls 12 are referred to as guide rolls 12 ₁ to 12 ₁₂ , as shown in FIG.

The swelling processing section ₁₃₁ is a section that performs swelling processing on the film 2. The swelling processing section ₁₃₁ has a processing tank in which a processing liquid for swelling processing is stored. By immersing the film 2 in the treatment liquid possessed by the swelling treatment section ₁₃₁ , the film 2 is subjected to a swelling treatment. In this embodiment, the nip roll 11 ₁ and the guide rolls 12 ₁ to 12 ₃ form a film transport path for immersing the film 2 in the processing liquid. In this configuration, the nip roll 11 ₁ and the guide roll 12 ₃ are arranged before and after the film 2 is subjected to the swelling treatment by the swelling treatment section 13 ₁ (in other words, before and after the swelling treatment section 13 ₁ ). ing.

The above-mentioned swelling treatment is performed for the purpose of removing foreign matter from the surface of the film 2, removing a plasticizer in the film 2, imparting dyeability in a subsequent process, plasticizing the film 2, and the like. The conditions for the swelling treatment can be determined within a range that can achieve these objectives and within a range that does not cause problems such as extreme dissolution or devitrification of the film 2. In the swelling treatment section ₁₃₁ , swelling treatment is performed by immersing the film 2 in a treatment liquid at a temperature of, for example, 10 to 50°C, preferably 20 to 50°C. The swelling treatment time is about 5 to 300 seconds, preferably about 20 to 240 seconds. An example of the treatment liquid in the swelling treatment section ₁₃₁ is water. Therefore, the swelling treatment can also serve as a water washing treatment for the film 2.

The dyeing processing section ₁₃₂ is a section that performs dyeing processing on the film 2. The dyeing processing section ₁₃₂ has a processing tank in which a processing solution for dyeing processing is stored. A dyeing process is performed on the film 2 by immersing the film in a processing liquid possessed by the dyeing process section ₁₃₂ . In this embodiment, the nip roll 11 ₂ and the guide rolls 12 ₄ to 12 ₆ form a film transport path for immersing the film 2 in the processing liquid. In this configuration, the nip roll 11 ₂ and the guide roll 12 ₆ are arranged before and after the dyeing process is performed on the film 2 by the dyeing process unit 13 ₂ (in other words, before and after the dye process unit 13 ₂ ). ing.

The processing liquid possessed by the dyeing processing section ₁₃₂ in this embodiment is an aqueous solution of a dichroic dye, and in the dyeing process, the film 2 is dyed with the dichroic dye. The usual dyeing process using a dichroic dye is carried out for the purpose of adsorbing the dichroic dye onto the film 2. The processing conditions are determined according to the desired optical properties within a range that can achieve the above objectives and that do not cause problems such as extreme dissolution or devitrification of the film 2. Examples of dichroic dyes used for dyeing are iodine and dichroic dyes.

When using iodine as a dichroic dye, add 0.003 to 0.2 parts by weight of iodine to 100 parts by weight of water at a temperature of, for example, 10 to 50°C, preferably 15 to 40°C. The dyeing treatment is carried out by immersing the film 2 in an aqueous solution containing 0.1 to 10 parts by weight of potassium chloride for 10 to 600 seconds, preferably 30 to 300 seconds. Other iodides such as zinc iodide may be used in place of potassium iodide. Other iodides may be used in combination with potassium iodide. Furthermore, compounds other than iodide, such as boric acid, zinc chloride, cobalt chloride, etc., may be present. Any treatment liquid containing 0.003 parts by weight or more of iodine per 100 parts by weight of water can be regarded as a treatment liquid for dyeing.

When using a water-soluble dichroic dye as the dichroic dye, the dichroic dye is mixed at a temperature of, for example, 20 to 80°C, preferably 30 to 60°C, and 0.001 to 100% of the dichroic dye is added to 100 parts by weight of water. The dyeing treatment is carried out by immersing the film 2 in an aqueous solution containing 0.1 part by weight for 10 to 600 seconds, preferably 20 to 300 seconds. The dichroic dye aqueous solution used may contain a dyeing aid, an inorganic salt such as sodium sulfate, a surfactant, and the like. Only one type of dichroic dye may be used, or two or more types of dichroic dyes may be used in combination depending on the desired hue.

The crosslinking processing section ₁₃₃ is a section that performs crosslinking processing on the film 2. The crosslinking processing section ₁₃₃ has a processing tank in which a processing liquid for crosslinking processing is stored. The film 2 is cross-linked by immersing the film in a treatment liquid possessed by the cross-linking section ₁₃₃ . In this embodiment, the nip roll 11 ₃ and the guide rolls 12 ₇ to 12 ₉ form a film transport path for immersing the film 2 in the processing liquid. In this configuration, the nip roll 11 ₃ and the guide roll 12 ₉ are arranged before and after the crosslinking process is performed on the film 2 by the crosslinking process unit 13 ₃ (in other words, before and after the crosslinking process unit 13 ₃ ). ing.

The crosslinking process is a process performed for the purpose of making the film resistant to water and adjusting the hue (preventing the film 2 from becoming bluish, etc.).

The treatment liquid used in the crosslinking treatment section ₁₃₃ is, for example, an aqueous solution containing, for example, about 1 to 10 parts by weight of boric acid per 100 parts by weight of water. When the dichroic dye used in the dyeing treatment is iodine, it is preferable that the treatment liquid used in the crosslinking treatment section ₁₃₃ contains iodide in addition to boric acid, and the amount thereof is 100 parts by weight of water. For example, the amount is 1 to 30 parts by weight. Examples of iodides include potassium iodide and zinc iodide. Compounds other than iodide, such as zinc chloride, cobalt chloride, zirconium chloride, sodium thiosulfate, potassium sulfite, and sodium sulfate, may be present.

In the crosslinking treatment in the crosslinking treatment section ₁₃₃ , the concentrations of boric acid and iodide and the temperature of the treatment liquid can be changed as appropriate depending on the purpose.

For example, if the purpose of the crosslinking treatment is to make the polyvinyl alcohol resin film water resistant by crosslinking, and a polyvinyl alcohol resin film is subjected to swelling treatment, dyeing treatment, and crosslinking treatment in this order, the crosslinking agent-containing liquid in the treatment liquid may have a concentration of It is an aqueous solution with a ratio of boric acid/iodide/water = 3 to 10/1 to 20/100. If necessary, other crosslinking agents such as glyoxal or glutaraldehyde may be used in place of boric acid, or boric acid and other crosslinking agents may be used in combination. The temperature of the treatment liquid when immersing the film 2 is usually about 50°C to 70°C, preferably 53°C to 65°C, and the immersion time of the film 2 is usually about 10 to 600 seconds, preferably 20°C. -300 seconds, more preferably 20-200 seconds. When dyeing treatment and crosslinking treatment are performed in this order on the pre-stretched film 2 before the swelling treatment, the temperature of the treatment liquid is usually about 50 to 85°C, preferably 55 to 80°C.

When the purpose of the crosslinking treatment is hue adjustment, for example, when iodine is used as a dichroic dye, a crosslinking agent-containing solution with a concentration of boric acid/iodide/water in a weight ratio of 1 to 5/3 to 30/100 is used. can be used as a processing liquid. The temperature of the treatment liquid when immersing the film 2 is usually about 10 to 45°C, and the immersion time of the film 2 is usually about 1 to 300 seconds, preferably 2 to 100 seconds.

The cleaning processing section _{134 is} a section that performs a cleaning treatment on the film 2 after the crosslinking treatment. The cleaning processing section ₁₃₄ has a processing tank in which processing liquid for cleaning processing is stored. A cleaning process is performed on the film 2 by immersing the film 2 in a treatment liquid possessed by the cleaning process section ₁₃₄ . In this embodiment, the nip roll 11 ₄ and the guide rolls 12 ₁₀ to 12 ₁₂ form a film transport path for immersing the film 2 in the processing liquid. In this configuration, the nip rolls 11 ₄ and the guide rolls 12 ₁₂ are arranged before and after the cleaning process is performed on the film 2 by the cleaning process unit 13 ₄ (in other words, before and after the cleaning process unit 13 ₄ ). ing. Examples of the treatment liquid in the cleaning treatment include water, an aqueous solution containing potassium iodide, and an aqueous solution containing boric acid. The temperature of the treatment liquid is usually about 2°C to 40°C, and the treatment time is usually about 2 seconds to 120 seconds.

In the cleaning process in the cleaning processing section ₁₃₄ , the film 2 may be cleaned by spraying the treatment liquid as a shower, or by using a combination of dipping and spraying.

The drying processing section ₁₃₅ is a section that performs drying processing on the film 2. In this embodiment, the drying processing section ₁₃₅ is a drying device. The film 2 that has been washed in the cleaning processing section ₁₃₄ is carried into the drying processing section ₁₃₅ , and is dried while the film 2 passes through the drying processing section ₁₃₅ . In this embodiment, the nip rolls 11 ₅ and 11 ₆ form a film transport path for immersing the film 2 in the processing liquid. Guide rolls 12 may be appropriately disposed within the drying processing section ₁₃₅ to support and convey the film 2. Drying in the drying section ₁₃₅ is carried out for about 30 seconds to about 600 seconds in the drying section ₁₃₅ maintained at a temperature of about 40.degree. C. to 100.degree. In FIG. 1, the drying processing section ₁₃₅ is schematically shown. The drying section ₁₃₅ is not particularly limited as long as it can dry moisture adhering to the film 2, and may be any known device that is commonly used in the manufacture of polarizing films.

In the manufacturing apparatus 10, a stretching process is performed in which the film 2 is uniaxially stretched using the peripheral speed difference between at least two nip rolls 11 (upstream nip roll 11 and downstream nip roll 11) among the plurality of nip rolls 11. In this case, the two nip rolls 11 that contribute to the uniaxial stretching process function as a stretching section.

For example, a stretching process may be performed in which uniaxial stretching is performed using the difference in circumferential speed between the nip roll 11 ₃ placed in front of the cross-linking part 13 ₃ and the nip roll 11 ₄ placed after the cross-linking part 13 ₃ . . In this case, since the stretching process is performed in parallel with the crosslinking process, the crosslinking process section ₁₃₃ also functions as a stretching process section. Stretching treatment is also effective for suppressing the occurrence of wrinkles.

While the two nip rolls 11 placed before and after one processing section (for example, the above-mentioned crosslinking processing section 13 ₃ ) are used to mainly carry out the stretching process, the other nip rolls 11 are used to gradually further carry out the stretching process. It may be applied.

The manufacturing apparatus 10 may have a separate stretching processing section for performing stretching processing. In this case, the stretching section is arranged, for example, after the crosslinking section ₁₃₃ (for example, between the crosslinking section ₁₃₃ and the cleaning section ₁₃₄ ).

The manufacturing apparatus 10 may have a plurality of at least one processing section among a swelling processing section 13 ₁ , a dyeing processing section 13 ₂ , a crosslinking processing section 13 ₃ , a washing processing section 13 ₄ , and a drying processing section 13 ₅ . For example, the manufacturing apparatus 10 may include a plurality of crosslinking processing units ₁₃₃ . The same applies when the manufacturing apparatus 10 includes a stretching processing section, and the manufacturing apparatus 10 may include, for example, a plurality of stretching processing sections.

When manufacturing the polarizing film 4 using the manufacturing apparatus 10 described above, first, the film 2 is unrolled from the original fabric roll 6, and the film 2 is moved along a conveyance path formed by a plurality of nip rolls 11 and a plurality of guide rolls 12. Convey in its longitudinal direction. Examples of transport speeds may be from 1 m/min to 60 m/min, and from 1.5 m/min to 50 m/min. The conveyance path of the film 2 is provided with a swelling processing section 13 ₁ , a dyeing processing section 13 ₂ , a crosslinking processing section 13 ₃ , a washing processing section 13 ₄ and a drying processing section 13 ₅ from the raw roll 6 side. Furthermore, as described above, at least two nip rolls 11 also function as a stretching section. Therefore, the film 2 being transported is subjected to swelling treatment, dyeing treatment, crosslinking treatment, washing treatment, drying treatment, and stretching treatment. As a result, linear polarization characteristics (optical characteristics) are imparted to the film 2, and a polarizing film 4 is obtained.

The polarizing film 4 obtained through the drying processing section _13.5 is used, for example, for the manufacture of a polarizing plate including the polarizing film 4. For example, the polarizing plate can be manufactured by carrying out a lamination process or the like in which a protective film is laminated to one or both sides of the polarizing film 4. The polarizing film 4 obtained through the drying processing section _13.5 may be transported continuously for the manufacture of the polarizing plate, or may be wound up once into a roll.

As shown in FIG. 2, the length of the film 2 in the width direction changes during the process of manufacturing the polarizing film 4 by performing N treatments while transporting the film 2. The width of the film 2 at a location located on the upstream side (hereinafter referred to as "upstream location") among any two locations during transport of the film 2 is defined as W1, and the width of the film 2 at a location located on the downstream side of the upstream location (hereinafter referred to as "upstream location") is W1. In this embodiment, when the width of the film 2 at the "downstream location" is referred to as W2, and the rate of change in the width of the film 2 between the upstream location and the downstream location is referred to as the neck-in rate (%), in this embodiment, , the neck-in rate is defined by the following formula.
Neck-in rate = ((W1-W2)/W1) x 100

An embodiment of the present invention further includes a monitoring step of monitoring the neck-in rate. In the monitoring process, as shown in FIG. 1, the width of the film 2 is continuously measured at a plurality of measurement points 20 (multiple locations) on the film 2 being transported. In FIG. 1, a plurality of measurement points 20 of the width of the film 2 are indicated by arrows. When the plurality of measurement points 20 are to be distinguished and explained, the plurality of measurement points 20 will be referred to as measurement points 20 ₁ to 20 ₁₂ .

The measurement point 20 may be a point for measuring the width of the film 2 wound around the nip roll 11 or the guide roll 12, or a point for measuring the width of the film 2 that is not wound around the nip roll 11 or the guide roll 12. It may also be a point to be measured. The measurement point 20 shown in FIG. 1 is an example; for example, the measurement point 20 ₁ may be a position for measuring the width of the film 2 fed out from the nip roll 11 _{1, and the measurement point 20 4 may be a position for measuring the width of the film 2 fed out from the nip roll 11 1} , and the measurement point 20 ₄ may be a It may also be a position for measuring the width of the film 2 wound around the roll ₁₂₆ (the film 2 on the guide roll ₁₂₆ ).

The measurement points 20 ₁ to 20 ₃ before the dyeing treatment is applied to the film 2 are preferably points for measuring the width of the film 2 wound around the nip roll 11 or the guide roll 12. On the other hand, after the measurement point ₂₀₄ , the relationship between the nip roll 11 or the guide roll 12 and the film 2 is usually not limited.

The measurement points 20 can be placed, for example, before and after one of the N treatments is applied to the film 2. For example, _the measurement point ₂₀₁ is a point at which the width of the film 2 is measured while being wound around the nip roll ₁₁₁ in FIG. This is the measurement point. The measurement point ₂₀₂ is a point at which the width of the film 2 is measured on the guide roll ₁₂₃ or immediately after being sent out from the guide roll ₁₂₃ .

Therefore, the measurement points 20 ₁ and 20 ₂ are points for measuring the width of the film 2 before and after the swelling treatment is applied to the film 2. In this way, the measurement points before and after one treatment is performed (before and after the film is immersed in the treatment liquid of a certain treatment section) are also the measurement points before and after the treatment section where that treatment is performed.

Other examples of such measurement points 20 are measurement points 20 ₃ , 20 ₄ , measurement points 20 ₅ , 20 ₇ , measurement points 20 ₈ , 20 ₁₀ , and measurement points 20 ₁₁ , 20 ₁₂ . Measurement points 20 ₃ , 20 ₄ , measurement points 20 ₅ , 20 ₇ and measurement points 20 ₈ , 20 ₁₀ are measurement points for the width of the film 2 before and after the swelling treatment, dyeing treatment, crosslinking treatment and washing treatment. be. Measurement points 20 ₁₁ and 20 ₁₂ are points for measuring the width of the film 2 before and after the drying process.

The measurement point 20 may be a point at which the width of the film 2 is measured during a process in which the film 2 is being subjected to a single treatment. Examples of such measurement points 20 are measurement points 20 ₆ , 20 ₉ . The measurement point ₂₀₆ is a measurement point while the film 2 is being conveyed between the guide rolls ₁₂₇ and ₁₂₈ . Similarly, the measurement point ₂₀₉ is a measurement point while the film 2 is being conveyed between the guide rolls ₁₂₁₀ and ₁₂₁₁ . At measurement points 20 ₆ and 20 ₉ , the width of the film 2 in the processing liquid is measured.

In the monitoring process, among the measurement results obtained by continuously measuring the width of the film 2 at two locations (upstream location and downstream location) selected in advance from the plurality of measurement points 20, the width of the film 2 is measured at the same timing at the two locations (i.e., At the same time, the neck-in rate is calculated based on the measured measurement results. The above-mentioned "same timing (that is, at the same time)" may be slightly different from each other without departing from the spirit of the present invention. The time difference between the time of measurement at the upstream location and the time of measurement at the downstream location is not particularly limited, but may be within about 1 minute, within 30 seconds, or within 20 seconds. , may be within 10 seconds. Preferably, the monitoring process is automated.

In the example of the above-described upstream location and downstream location, the upstream location is before one of the N processes (hereinafter referred to as "predetermined processing"), and the downstream location is after the above-mentioned predetermined processing. For example, when the predetermined process is a dyeing process, the upstream location is before the dyeing process, and the downstream location is after the dyeing process. "Before the predetermined process" and "after the predetermined process" include cases where other processes are performed between the upstream location, the downstream location, and the "predetermined process".

Any two adjacent processes among the N processes are referred to as the i-1st process and the i-th process (i is an integer of 2 or more), and the corresponding processing units are referred to as the i-1th process and When referred to as the i-th processing section, the upstream location and downstream location may be any of the following arrangement examples 1 to 3.
[Layout example 1]
The upstream location is at the position where the i-1th process is being performed (the position of the i-1st processing section), and the downstream location is at the location where the i-1st processing is being performed (the i-1st processing section) and the i-th location. It is between the positions of the processing (i-th processing section). For example, when the i-1th treatment is a crosslinking treatment, examples of the upstream location and the downstream location are the measurement point 20 ₆ and the measurement point 20 ₇ among the plurality of measurement points 20 shown in FIG.
[Layout example 2]
The upstream location and the downstream location are between the position of the i-1th process (i-1th processing unit) and the position of the i-th process (i-th processing unit), respectively. For example, when the i-1th treatment is a crosslinking treatment, examples of the upstream location and the downstream location are the measurement point 20 ₇ and the measurement point 20 ₈ among the plurality of measurement points 20 shown in FIG.
[Layout example 3]
The upstream location is the position before the i-1th processing (i-1st processing section), and the downstream location is the location during the i-1st processing (position of the i-1st processing section). . For example, when the i-1th treatment is a crosslinking treatment, examples of the upstream location and the downstream location are the measurement point 20 ₅ and the measurement point 20 ₆ among the plurality of measurement points 20 shown in FIG.

When i is an integer of 2 or more, the process following the i-th process is called the i+1-th process, and the corresponding processing section is called the i+1-th processing section, examples of upstream locations and downstream locations are as follows. Arrangement example 4 may be used.
[Layout example 4]
The upstream location is between the position of the i-1st process (i-1st processing unit) and the position of the i-th process (i-th processing unit), and the downstream location is between the i-th process (i-1st processing unit) and the position of the i-th process (i-th processing unit). It is between the position of the i-th processing unit) and the position of the i+1-th processing unit (i-th processing unit). For example, when the i-1th treatment is a crosslinking treatment, examples of the upstream location and the downstream location are the measurement point 20 ₇ and the measurement point 20 ₁₀ among the plurality of measurement points 20 shown in FIG.

As a set of an upstream location and a downstream location, for example, a set of two measurement points 20 that are not adjacent to each other may be adopted, such as the upstream location being the measurement point ₂₀₁ and the downstream location being the measurement point ₂₀₈ .

When the manufacturing apparatus 10 has a plurality of at least one of the swelling processing section 13 ₁ , the dyeing processing section 13 ₂ , the crosslinking processing section 13 ₃ , the washing processing section 13 ₄ , and the drying processing section 13 ₅ , the upstream location and the downstream location are , may be locations that perform processing for the same purpose, or may be locations that perform processing for different purposes. For example, if the manufacturing apparatus 10 has two or more swelling processing units 13 ₁ and the two swelling processing units 13 ₁ are referred to as swelling processing units 13 ₁ -a and 13 ₁ -b, the upstream location is the swelling processing unit 13 ₁ -a position (or before or after it), the downstream location may be the swelling processing section 13 ₁ -b location (or before or after it), or the upstream location may be the swelling processing section 13 ₁ -b position (or before or after it). -a or the position of the swelling processing section 13 ₁ -b (or before or after it), and the downstream location may be the position of the dyeing processing section 13 ₂ (or before or after it). The same applies when there are multiple stretching processing sections.

The neck-in rate may be calculated using a plurality of pairs of upstream locations and downstream locations selected from the plurality of measurement points 20. For example, the neck-in rate is calculated based on the measurement results at measurement point ₂₀₁ and measurement point ₂₀₂ , and the neck-in rate is calculated based on the measurement result at measurement point ₂₀₅ and measurement point ₂₀₇ . The neck-in rate may also be calculated by Among the plurality of sets of upstream locations and downstream locations, there may be a set in which the upstream location or the downstream location is common. For example, the neck-in rate is calculated based on the measurement results of measurement point _20-1 and measurement point _20-2 , and the neck-in rate is calculated based on the measurement results of measurement point _20-1 and measurement point _20-4 . It may be calculated. Similarly, the neck-in rate is calculated based on the measurement results of the measurement point _20-5 and the measurement result of the measurement point _20-7 , and the neck-in rate is calculated based on the measurement result of the measurement point _20-6 and the measurement result of the measurement point _20-7 . may be calculated.

In order to calculate the neck-in rate, the optical film manufacturing apparatus 10 includes a plurality of width measuring instruments 30 and a calculating section 40, as shown in FIG.

Each width measuring device 30 is a device that continuously measures the width of the film 2. The plurality of width measuring instruments 30 are arranged one-to-one at the plurality of measurement points 20. That is, one width measuring device 30 is placed at one measurement point 20. In FIG. 3, two width measuring devices 30 selected to calculate the neck-in rate among the plurality of width measuring devices 30 (i.e., an upstream width measuring device 30 UP disposed at an upstream location, and an upstream width measuring device 30 _{UP disposed} at a downstream location The downstream side width measuring device 30 ( _DOWN ) disposed at , and the calculating section 40 are schematically shown.

The width measuring device 30 has two edge detectors 31. One of the two edge detectors 31 is a detector that detects one edge 2a in the width direction of the film 2, and the other is a detector that detects the other edge 2b (opposite to the edge 2a) in the width direction of the film. This is a detector that detects the side edges). The width measuring device 30 is configured to detect the ends 2 a and 2 b of the film 2 depending on the state of the film 2 at the measurement point 20 . Therefore, the configuration of the width measuring device 30 may be different for each measurement point 20. However, the configurations of the two edge detectors 31 (two edge detectors 31 disposed at one measurement point 20) of one width measuring device 30 are the same.

FIG. 4 is a schematic diagram for explaining the schematic configuration of an edge detector 31A, which is an example of the edge detector 31. The edge detector 31A is a detector used when measuring the width of the film 2 on the transport roll R. The conveyance roll R is the nip roll 11 or the guide roll 12 shown in FIG.

Two edge detectors 31A are arranged on the film 2 so as to detect the edges 2a and 2b, respectively. Since the configuration of the edge detector 31A is the same as described above, the case where the edge detector 31A detects the edge 2a will be described.

The edge detector 31A includes a light irradiation section 32 and a light detection section 33. In FIG. 4, the case where the film 2 is placed on the transport roll R is illustrated.

The light irradiation section 32 irradiates light toward the film 2. The light irradiation unit 32 is configured to irradiate light to the end 2a of the film 2 and to the outside of the end 2a. Therefore, as shown in FIG. 4, when the film 2 is placed on the transport roll R, the light from the light irradiation section 32 is also irradiated to the part of the transport roll R that does not overlap with the film 2. . The light irradiation section 32 may be a linear light source extending in the width direction of the film 2. The light irradiation unit 32 may include, for example, an LED.

The light irradiation unit 32 may be placed inside the housing 34. The housing 34 has a window 34a for irradiating the film 2 with the light output from the light irradiation section 32. The window portion 34a may be made of a material that transmits the light output from the light irradiation portion 32. For example, examples of the material for the window portion 34a include polycarbonate resin, acrylic resin, vinyl chloride resin, polypropylene resin, polyethylene terephthalate resin, and glass.

The light detection section 33 detects the brightness of the light (reflected light) that is reflected by the film 2 from the light irradiated onto the film 2 from the light irradiation section 32 . The light detection unit 33 may be an imaging unit such as a camera (for example, a CCD camera) that captures an image of at least the end portion 2a of the film 2. As shown in FIG. 4, when the film 2 is placed on the transport roll R, the light detection unit 33 detects, for example, the light reflected by the transport roll R out of the light irradiated onto the film 2 from the light irradiation unit 32. It also detects the brightness of

The photodetector 33 may be placed inside the housing 35. The housing 35 has a window 35a for the light detection section 33 to detect the reflected light. The window portion 35a may be made of a material that transmits the reflected light. The example of the material for the window portion 35a is the same as that for the window portion 34a.

The measurement points 20 ₁ , 20 ₂ , 20 ₃ before the dyeing treatment is applied to the film 2 are usually points at which the width of the film 2 on the transport roll R is measured. Therefore, the edge detector 31A is preferably applied at the measurement points 20 ₁ , 20 ₂ , 20 ₃ .

FIG. 5 is a schematic diagram for explaining the schematic configuration of an edge detector 31B, which is another example of the edge detector (width measuring device) 31. The edge detector 31B is a detector that is applied when the film 2 has linear polarization characteristics (when an absorption axis is formed). Normally, the edge detector 31B can be applied to the film 2 after being subjected to the dyeing process in the dyeing process section ₁₃₂ .

Two edge detectors 31B are arranged with respect to the film 2 so as to detect the edge 2a and the edge 2b, respectively. However, since the configuration of the edge detector 31B is the same as described above, a case will be described in which the edge detector 31B detects the edge 2a.

The edge detector 31B includes a photodetector 36 and a polarizing filter 37.

The light detection unit 36 detects the brightness of light in the surrounding environment of the film 2 that is incident on the film 2 and transmitted through the film 2 (hereinafter referred to as "light from the film 2"). The light detection unit 36 may be an imaging unit such as a camera (for example, a CCD camera) that images at least the end portion 2a of the film 2.

The above-mentioned "light from the surrounding environment of the film 2" refers to illumination light from a lighting fixture installed in a factory that manufactures the polarizing film 4, and the illumination light from elements constituting the manufacturing apparatus 10 (for example, the nip roll 11 and the guide roll 12). This includes light reflected on the transport roll R, at least one of the side wall and bottom wall of the processing tank included in each processing section shown in FIG. 1, the floor of the above-mentioned factory, etc.). In FIG. 5, light in the surrounding environment of the film 2 is schematically indicated by white arrows.

The polarizing filter 37 is a filter having linear polarization characteristics. The polarizing filter 37 is arranged between the photodetector 36 and the film 2 so that the absorption axis of the film 2 and the absorption axis of the polarizing filter 37 are in a crossed nicol state. The above-mentioned crossed Nicol state is not limited to the case where the angle between the absorption axis of the film 2 and the absorption axis of the polarizing filter 37 is 90°, but for example, an error of about ±5°, ±10°, or 15° with respect to 90°. It is a meaning that includes.

The photodetector 36 and the polarizing filter 37 may be arranged in the casing 35 having the window 35a, similarly to the photodetector 33. The window portion 35a may be made of any material that allows light from the film 2 to pass therethrough.

When only the light from the surrounding environment of the film 2 is used, if the difference in brightness between the light from the surrounding environment detected by the light detection unit 36 and the light transmitted through the film 2 is small, the edge detector 31B detects the auxiliary illumination. (light irradiation part). The configuration of the auxiliary illumination section may be the same as that of the light irradiation section 32. The auxiliary illumination unit may be smaller than the light irradiation unit 32 or may be configured to output light with a power smaller than the power of the light output from the light irradiation unit 32. Similar to the case of the light irradiation section 32, the auxiliary illumination section may be arranged within the casing 34 having the window section 34a. The auxiliary illumination unit illuminates at least one of the detection area (or imaging area) of the light detection unit 33 and its surroundings, and is arranged so that the light from the auxiliary illumination unit enters the film 2 as light from the surrounding environment. .

The edge detector 31B may be used when measuring the width of the film 2 on the transport roll R. The edge detector 31B can be used, for example, to measure at the measurement points 20 ₅ , 20 ₈ , 20 ₁₀ . In this case, the transport roll R is preferably a white roll in order to make the difference in brightness clear.

The edge detector 31B may be used to measure the width of the film 2 between the transport rolls R. The edge detector 31B can be used, for example, to measure the width of the film 2 at the measurement points 20 ₄ , 20 ₆ , 20 ₇ , 20 ₉ , 20 ₁₁ , 20 ₁₂ . In this case, in order to clarify the difference in brightness, a white plate-shaped member or the like may be installed in the background of the detection area of the photodetector 33 (or the background of the imaging area). When using an auxiliary illumination unit in measuring the width of the film 2 between the two transport rolls R, the auxiliary illumination unit may be placed on the same side of the film 2 as the edge detector 31B, or It may be arranged on the opposite side of the film 2 to the edge detector 31B.

In the case of measuring the width of the film 2 at the measurement points 20 ₆ , 20 ₉ , the edge detector 31B measures the width of the film 2 in the processing liquid. In this case, for example, as shown in FIG. 5, the edge detector 31B has a housing 35 having a window 35a, and the housing 35 is arranged such that the window 35a is located in the processing liquid. may be placed. When the window portion 35a is disposed in the processing liquid, the outer surface of the window portion 35a may be subjected to at least one of hydrophilic treatment, uneven processing, and slope processing. This makes it difficult for air bubbles to accumulate on the outer surface of the window portion 35a, making it easy to accurately detect the end portion 2a of the film 2. When using an auxiliary illumination unit to measure the width of the film 2 in the processing liquid, the auxiliary illumination unit may illuminate the bottom wall of the processing tank in which the film 2 is processed, for example. In this case, the brightness of transmitted light emitted from the auxiliary illumination section, reflected on the bottom wall of the processing tank, and transmitted through the film 2 is detected by the light detection section 36 via the polarizing filter 37.

The polarizing filter 37 included in the end detector 31B may be placed, for example, on the light incident side of the film 2. For example, when the edge detector 31B has an auxiliary illumination section (light irradiation section), the polarization filter 37 is arranged between the auxiliary illumination section and the film 2 instead of the light detection section 33. You can. Also in this case, the polarizing filter 37 is arranged in a crossed nicol state with the film 2.

The calculation unit 40 shown in FIGS. 3 to 5 is connected by wire or wirelessly to a plurality of width measuring instruments 30 (width measuring instruments 30 disposed at upstream locations and downstream locations). The neck-in rate is calculated based on the measurement results obtained from the above.

Specifically, the calculation unit 40 determines the end portion 2 a and the end portion 2 b of the film 2 at the location where each width measuring device 30 is arranged based on the measurement results of the plurality of width measuring devices 30 . The end portion 2a and the end portion 2b can be determined by a change in brightness data that is a measurement result of the width measuring device 30.

For example, as shown in FIG. 4, when measuring the width of the film 2 placed on the transport roll R using the width measuring device 30 including the edge detector 31A, the photodetector 33 The brightness of the reflected light from the film 2 and the reflected light from the transport roll R is detected. Since there is a difference in the brightness of the reflected light from the film 2 and the brightness of the reflected light from the transport roll R, the calculation unit 40 determines that the areas where the difference occurs are the ends 2a and 2b of the film 2. good.

For example, as shown in FIG. 5, when measuring the width of the film 2 using the width measuring device 30 including the edge detector 31B, the polarizing filter 37 and the film 2 are in a crossed nicol state. 2 is substantially blocked, while light from other than the film 2 is detected. Therefore, in the image formed by the brightness data detected by the photodetector 36, there is a difference in brightness between the film 2 and the parts other than the film 2 (the film 2 side is dark and the parts other than the film 2 are bright). The location where the difference occurs may be determined to be the ends 2a and 2b of the film 2.

When the edges 2a and 2b of the film 2 are specified, the calculation unit 40 calculates, for example, the arrangement position of the edge detector 31A (or edge detector 31B) and the edges 2a and 2b in the detected luminance data. The width of the film 2 is calculated from the relationship with the position of . For example, if the end of the transport roll R can be identified from the brightness data obtained by the end detector 31A (or end detector 31B), the end of the transport roll R and the end 2a of the film 2 in the brightness data , 2b and the actual position of the end of the transport roll R.

Next, the calculation unit 40 calculates two width measuring instruments 30 (upstream width measuring instrument 30 UP and downstream width measuring instrument 30 _UP and downstream width measuring instrument 30 UP and The neck-in rate is calculated using the width of the film 2 calculated based on the measurement results of the device 30 ( _DOWN ). Examples of the upstream location and downstream location are as described above.

In the method for manufacturing the polarizing film 4 and the apparatus 10 for manufacturing the polarizing film 4, the width of the film 2 is measured by the width measuring device 30 disposed at each of the plurality of measurement points 20 (multiple locations). Thereby, the width of the film 2 can be continuously measured while the film 2 is being transported. Furthermore, the neck-in rate is calculated based on the measurement results of the width of the film 2 measured at the same timing at the upstream and downstream locations among the widths of the film 2 that are continuously measured at the plurality of measurement points 20. . Therefore, the neck-in rate of the film 2 can be obtained in real time while the film 2 is being transported. That is, the neck-in rate can be measured efficiently. In other words, the neck-in rate can be monitored in real time.

The neck-in rate represents the rate of change in the width of the film 2. Therefore, for example, if the allowable range of neck-in rate (control range of neck-in rate) obtained in advance through experiments or simulations is exceeded at the location where the width is measured, for example, the film 2 may break in the subsequent process, or the film 2 may The thickness of the film may deviate from the desired thickness (designed thickness), or a defective film may be produced that is inferior in desired optical properties or appearance such as streaks or unevenness.

Therefore, in the method for manufacturing polarizing film (optical film) 4 and the manufacturing apparatus 10 for polarizing film 4 that can monitor the neck-in rate in real time, for example, when the neck-in rate exceeds the allowable range, can be interrupted. If the production is interrupted, the production conditions for the polarizing film 4 may be adjusted (for example, the treatment liquid, the stretching treatment conditions, etc.) so that the neck-in rate falls within an allowable range. Further, for example, manufacturing can be continued while adjusting the neck-in rate to be within an allowable range. Thereby, it is possible to prevent the film 2 from breaking in the post-process described above, and to suppress the production of the polarizing film 4 that becomes a defective product. Therefore, the polarizing film 4 can be manufactured through a stable process. Furthermore, the polarizing film 4 with stable quality can be uniformly manufactured. Furthermore, the material cost of the polarizing film 4 can be reduced. Furthermore, since the polarizing film (optical film) 4 of good quality can be efficiently manufactured, the manufacturing yield of the polarizing film 4 is improved.

The width of the film 2 is likely to change by subjecting the film 2 to at least one of the N treatments. Therefore, as described above, if the upstream location is before a predetermined process among the N processes, and the downstream location is after the predetermined process, there may be a problem in the production of the polarizing film 4 (for example, a problem in the post-process). It is easy to monitor the neck-in rate that contributes to breakage of the film 2, deviation of the film 2 from the desired thickness, etc.).
For the same reason, in the case of the above-described arrangement examples 1 to 4, it is easy to monitor the neck-in rate that contributes to defects in the production of the polarizing film 4. For example, in the placement state, identify that changes in the state before or after a certain process, changes in the state due to that process, or changes in the state during the process are affecting the neck-in rate. can. Therefore, it is easy to adjust the manufacturing conditions when the neck-in rate is outside the allowable range.
As a result, the material cost of the polarizing film 4 can be further reduced, and the manufacturing yield of the polarizing film 4 can be further improved. Moreover, the polarizing film 4 of even more stable quality can be uniformly manufactured in a more stable process.

When measuring the width of the film 2 at the measurement point ₂₀₁ (before N treatments are applied), the film 2 does not have linear polarization characteristics, for example. Therefore, the film 2 is usually a transparent film that does not have an absorption axis. In this case, by detecting the ends 2a, 2b of the film 2 on the transport roll R using the width measuring device 30 having the end detector 31A shown in FIG. can be reliably detected. As a result, the width of the film 2 can be measured more accurately. Here, the case of the measurement point 20 ₁ has been explained as an example, but the measurement points 20 ₂ and 20 ₃ can also be similarly measured using the width measuring device 30 having the edge detector 31A shown in FIG. The ends 2a, 2b of can be reliably detected.

When the film 2 is dyed and stretched, the film 2 is given linear polarization characteristics. When the film 2 is transported, tension is applied to the film 2 along the transport direction of the film 2. Therefore, when the film 2 is gradually subjected to stretching treatment by any one of swelling treatment, dyeing treatment, crosslinking treatment, and drying treatment while conveying the film 2, linear polarization characteristics are gradually imparted to the film 2 after the dyeing treatment. . Furthermore, as shown in FIG. 1, the drying process is usually performed at the end of the N processes. Therefore, when measuring the width of the film 2 after the dyeing process and the stretching process, the width of the film 2 can be measured by using the width measuring device 30 having the edge detector 31B shown in FIG. Can be detected reliably. As a result, the width of the film 2 can be measured more accurately.

As shown in FIGS. 4 and 5, when the width measuring device 30 includes the housings 34 and 35, corrosion of the light irradiation section 32 and the light detection sections 33 and 36 due to iodine can be prevented. Since a processing liquid containing iodine is used to manufacture the polarizing film 4, iodine is present in the manufacturing environment and corrodes, for example, the photodetectors 33, 36 and the like. On the other hand, as shown in FIGS. 4 and 5, by arranging the light irradiation section 32 and the light detection sections 33, 36 within the housings 34, 35, the corrosion caused by the iodine can be prevented. It is preferable to maintain a positive pressure inside the casings 34 and 35 by supplying air or the like.

In addition to the embodiment described above, various modifications have been described. However, the present invention is not limited to the above embodiments and various modifications, but is indicated by the claims, and includes all changes within the meaning and range equivalent to the claims. is intended.

The case where a polarizing film is manufactured as an optical film is illustrated. However, the present invention can be applied to optical film manufacturing methods and manufacturing apparatuses that require monitoring of the neck-in rate in the process of manufacturing optical films from films. Other examples of optical films include protective films, retardation films, surface treatment films, antireflection films, and diffusion films.

The width measuring device having the edge detector 31B shown in FIG. 5 measures the width of the film that has been subjected to the dyeing process and the stretching process when the N processes include the dyeing process and the stretching process. It can be suitably applied in cases where This is because in this case, when measuring the width of the film at an upstream location, the film tends to have linear polarization characteristics. When the film is subjected to N treatments while being transported, as described above, the film is gradually subjected to the stretching treatment. Therefore, the width measuring device having the edge detector 31B can be suitably applied even when the upstream location is a location where the width of a dyed film is measured.

The method for measuring the width of the film 2 is not particularly limited to the exemplified method. For example, the width may be measured using a measuring device such as a laser displacement meter or an LED displacement meter. The entire film 2 may be photographed with a camera or the like, and the width may be calculated from the obtained image. As shown in FIG. 3, in the method of obtaining the positions of the ends 2a and 2b of the film 2, devices for measuring the positions of the ends 2a and 2b may be placed at the ends 2a and 2b of the film 2, respectively. Therefore, it is preferable from the viewpoint of installation space and equipment management (maintenance inspection, etc.).

The stretching process in the stretching section is not limited to a wet stretching method, and a dry stretching method may be adopted. In the embodiments described above, the order of the processes illustrated for manufacturing the polarizing film may be changed or combined as appropriate without departing from the spirit of the present invention. The number of processing tanks that each processing section has may be one or more. The N processes are not limited to the number of illustrated processes.

The definition of the rate of change in the width of the film (neck-in rate) is not limited to the exemplified definition as long as the rate of change in the width of the film between the upstream location and the downstream location is expressed.

The above embodiments and various modified examples may be combined as appropriate without departing from the spirit of the present invention.

2... Film, 4... Polarizing film (optical film), 10... Manufacturing device, 11... Nip roll (conveyance mechanism), 12... Guide roll (conveyance mechanism), 20... Measurement point (multiple locations), 30... Width measuring device, 30 _UP ... Upstream width measuring device, 30 _DOWN ... Downstream width measuring device, 32... Light irradiation section, 33... Photo detection section (imaging section), 36... Photo detection section (imaging section).

Claims (32)

A method of manufacturing an optical film by subjecting a long film to N treatments (N is an integer of 2 or more), the method comprising:
The N processes are performed while transporting the film,
The N treatments include a dyeing process and a stretching process,
During the conveyance, the width of the film is continuously measured at each of a plurality of locations, and among the two selected from the plurality of locations, the measurement results at the upstream location and the measurement results at the downstream location are obtained at the same timing. calculating a rate of change in the width of the film based on the measurement results;
Method for manufacturing optical film. The film is a film unwound from a raw roll,
A method for producing an optical film according to claim 1 . The stretching process is a wet stretching process,
The method for producing an optical film according to claim 1 or 2. The upstream location is a position before one of the N processes is performed,
The downstream location is a position after the one process has been performed,
The method for producing an optical film according to any one of claims 1 to 3 . The N processes include an i-1st process, an i-th process, and an i+1th process (i is an integer of 2 or more),
The upstream location is between the i-1th processing position and the i-th processing location, and the downstream location is between the i-th processing location and the i+1th processing location. be,
The method for producing an optical film according to any one of claims 1 to 3 . The N processes include an i-1th process and an i-th process (i is an integer of 2 or more),
whether the upstream location is at the position where the i-1 processing is being performed, and the downstream location is between the i-1 processing location and the i-th processing location;
The upstream location and the downstream location are between the i-1th processing position and the i-th processing location, respectively, or
The upstream location is a position before the i-1th process, and the downstream location is a location during the i-1th process,
The method for producing an optical film according to any one of claims 1 to 3 . measuring the width of the film by acquiring an image of at least an edge of the film with an imaging unit during the transport;
A method for producing an optical film according to any one of claims 1 to 6 . The imaging unit is housed in a housing,
The inside of the housing is under positive pressure,
The method for producing an optical film according to claim 7. Measuring the width of the film based on the brightness of at least one of reflected light and transmitted light from the film due to light incident on the film during the conveyance;
A method for producing an optical film according to any one of claims 1 to 6 . The film is transported by a transport roll,
By irradiating the film on the transport roll with light and detecting the edge of the film based on the difference in brightness between the reflected light of the film and the transport roll caused by the irradiation of the light, measure the width,
A method for producing an optical film according to any one of claims 1 to 9 . The transmitted light is transmitted light from the film due to light incident on the film via a polarizing filter.
The method for producing an optical film according to claim 9 . Measuring the width of the film based on the brightness of the light obtained by passing the transmitted light through a polarizing filter .
The method for producing an optical film according to claim 9 . At least one of the plurality of locations for measuring the width of the film is a location for measuring the width of the film located in a processing solution for performing at least one of the N treatments,
A method for producing an optical film according to any one of claims 1 to 3 . measuring the width of the film by acquiring an image of at least an end of the film with an imaging unit housed in a housing during the transport;
The method for producing an optical film according to claim 13. The N treatments further include at least one of a swelling treatment , a crosslinking treatment , and a drying treatment.
A method for producing an optical film according to any one of claims 1 to 14 . The optical film is a polarizing film,
A method for producing an optical film according to any one of claims 1 to 15 . N processing sections (N is an integer of 2 or more) including a dyeing processing section and a stretching processing section for carrying out processing to impart at least optical properties to the film;
a conveyance mechanism that conveys the film;
a plurality of width measuring instruments disposed at a plurality of locations on the transport mechanism, each of which continuously measures the width of the film being transported by the transport mechanism at each of the plurality of locations;
Based on the measurement results obtained at the same timing among the measurement results of the upstream width measurement device and the measurement results of the downstream width measurement device among the two width measurement devices selected from the plurality of width measurement devices, a calculation unit that calculates the rate of change in the width of the film;
Equipped with
Optical film manufacturing equipment. The film is a film unwound from a raw roll,
The optical film manufacturing apparatus according to claim 17 . The stretching process carried out in the stretching processing section is a wet stretching process,
The optical film manufacturing apparatus according to claim 17 or 18. The upstream width measuring device is placed in front of one of the N processing units,
The downstream width measuring device is arranged after the one processing section,
The optical film manufacturing apparatus according to any one of claims 17 to 19 . The N processing units include an i-1th processing unit, an i-th processing unit, and an i+1-th processing unit (i is an integer of 2 or more),
The upstream width measuring device is disposed between the i-1th processing section and the i-th processing section,
The downstream width measuring device is arranged between the i-th processing section and the i+1-th processing section,
The optical film manufacturing apparatus according to any one of claims 17 to 20 . The N processing units include an i-1th processing unit and an i-th processing unit (i is an integer of 2 or more),
The upstream width measuring device is disposed at a position of the i-1th processing section, and the downstream width measuring device is disposed between the i-1th processing section and the i-th processing section. Is it done?
The upstream width measuring device and the downstream width measuring device are respectively arranged between the i-1th processing section and the i-th processing section, or
The upstream width measuring device is disposed in front of the i-1th processing section, and the downstream width measuring device is disposed at a position of the i-1th processing section,
The optical film manufacturing apparatus according to any one of claims 17 to 20 . At least one of the plurality of width measuring devices has an imaging unit that images at least an edge of the film.
The optical film manufacturing apparatus according to any one of claims 17 to 22 . The imaging unit is housed in a housing,
The inside of the housing is under positive pressure,
The optical film manufacturing apparatus according to claim 23. At least one of the plurality of width measuring devices has a light detection unit for detecting at least one of reflected light and transmitted light from the film due to light incident on the film.
The optical film manufacturing apparatus according to any one of claims 17 to 22 . At least one width measuring device among the plurality of width measuring devices has a light irradiation part that irradiates the film with light.
The optical film manufacturing apparatus according to any one of claims 17 to 25 . The conveyance mechanism has a conveyance roll,
The light irradiation unit irradiates the film on the transport roll with light,
At least one width measuring device among the plurality of width measuring devices is based on a difference in brightness between reflected light of the film and the conveying roll caused by light from the light irradiation section to the film on the conveying roll, measuring the width of the film;
The optical film manufacturing apparatus according to claim 26 . a polarizing filter is provided between the light irradiation section and the film;
The optical film manufacturing apparatus according to claim 26 . a polarizing filter is provided between the photodetector and the film;
The optical film manufacturing apparatus according to claim 25 . At least one of the plurality of width measuring devices is arranged to measure the width of the film located in the processing liquid contained in at least one processing section of the N processing sections,
The optical film manufacturing apparatus according to any one of claims 17 to 19 . At least one of the plurality of width measuring devices has an imaging section that is housed in a housing and that captures an image of at least an end portion of the film.
The optical film manufacturing apparatus according to claim 30. The N processing sections include at least one of a swelling processing section , a crosslinking processing section , and a drying processing section.
The optical film manufacturing apparatus according to any one of claims 17 to 31 .

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