JP6890115B2 - Processing tank for polarizing film manufacturing and polarizing film manufacturing equipment - Google Patents

Description

The present invention relates to a processing tank and a polarizing film manufacturing apparatus used when a polarizing film is manufactured by immersing a raw film in a treatment liquid.

Conventionally, a polarizing film has been used as a constituent material for a liquid crystal display device, polarized sunglasses, and the like. As the polarizing film, for example, a film dyed with a dichroic substance such as iodine is known.
Such a polarizing film can be obtained, for example, by immersing a polyvinyl alcohol-based film, which is a raw film, in a swelling treatment tank, a dyeing treatment tank, a cross-linking treatment tank, a stretching treatment tank, and a cleaning treatment tank in this order (Patent Document). 1).

Japanese Unexamined Patent Publication No. 2013-210520

By the way, each treatment liquid such as the cross-linking treatment liquid is housed in each treatment tank such as the cross-linking treatment tank. The treatment tank comprises a metal tank body and a coating layer coated on the inner surface of the tank body. The coating layer is for preventing the metal tank body from being eroded by a treatment liquid such as a cross-linking treatment liquid, and is formed of FRP such as a fiber-reinforced epoxy resin.
However, after long-term use, the coating layer may crack or the coating layer may be partially peeled off from the tank body. When the coating layer is cracked or peeled off, the treatment liquid comes into contact with the tank body from that portion, so that the tank body is eroded by the treatment liquid, and the treatment tank must be repaired or replaced.

An object of the present invention is to provide a processing tank for producing a polarizing film and an apparatus for producing a polarizing film, which are less likely to be eroded by the contained processing liquid.

The processing tank for producing a polarizing film of the present invention is a processing tank for accommodating a processing liquid used when producing a polarizing film from a raw film, and the processing tank is a metal tank body and the tank. It has a coating layer that covers the inner surface of the main body, and the coating layer is formed of a coating material having an elongation rate of 150% or more.

In the treatment tank for producing a preferred polarizing film of the present invention, the coating layer is formed of a coating material having an elongation rate of 350% to 450%.
In the treatment tank for producing a preferred polarizing film of the present invention, the coefficient of thermal expansion of the tank body is 10 × 10 ^-6 / ° C to 24 × 10 ^-6 / ° C.
In the treatment tank for producing a preferable polarizing film of the present invention, the coating material contains a polyurea resin having an elongation rate of 150% or more.
In the treatment tank for producing a preferable polarizing film of the present invention, the coating material contains a polyurea resin having an elongation rate of 350% or more.
In the treatment tank for producing a preferable polarizing film of the present invention, the coating material contains a rubber or an elastomer having an elongation rate of 350% or more.
In the treatment tank for producing a preferable polarizing film of the present invention, the thickness of the coating layer is 1.0 mm or more.
In the treatment tank for producing a preferable polarizing film of the present invention, the tank body is made of stainless steel.
The preferred treatment tank for producing a polarizing film of the present invention is used for at least one of a cross-linking treatment tank for cross-linking the raw film and a stretching treatment tank for stretching the raw film.

According to another aspect of the present invention, there is provided an apparatus for producing a polarizing film.
The manufacturing apparatus for producing a polarizing film of the present invention includes any of the above-mentioned processing tanks, a processing liquid contained in the processing tank, and a transport device for transporting the raw film and immersing it in the processing liquid in the processing tank. Has.

In the preferred polarizing film production apparatus of the present invention, the treatment liquid contains at least one of an iodine compound and a boron compound.
In the preferred polarizing film manufacturing apparatus of the present invention, the temperature of the treatment liquid is 40 ° C. or higher.

The processing tank for producing a polarizing film of the present invention is not easily eroded by the processing liquid, and can be used for producing a polarizing film for a long period of time without repair or replacement.
Further, the manufacturing apparatus having the processing tank can reduce the frequency of maintenance of the processing tank and can produce a polarizing film for a long period of time.

FIG. 3 is a cross-sectional view of a processing tank for producing a polarizing film according to one embodiment of the present invention. The schematic which shows the manufacturing apparatus of the polarizing film of this invention.

In the present specification, the numerical range represented by "lower limit value X to upper limit value Y" means a lower limit value X or more and an upper limit value Y or less. When a plurality of the numerical values are described separately, it is possible to select an arbitrary lower limit value and an arbitrary upper limit value and set "arbitrary lower limit value to arbitrary upper limit value".
It should be noted that each figure is shown for reference only, and the dimensions, scale and shape of the members etc. shown in each figure may differ from the actual ones.

The processing tank for producing a polarizing film of the present invention is a container for accommodating a processing liquid used when producing a polarizing film from a raw film.
As a method for producing a polarizing film from a film raw fabric, for example, a step of swelling the film raw fabric with a swelling treatment liquid, a step of dyeing the swollen film raw fabric with a dyeing treatment liquid, and a dyed film raw fabric are used. It has a step of cross-linking with a cross-linking treatment liquid, and preferably further has a step of washing the original film with a washing treatment liquid. Further, in the production method, after the cross-linking step, the film raw fabric is stretched in a stretching treatment liquid, or at least one step selected from the swelling step, the dyeing step and the cross-linking step. The process of stretching the film raw fabric in at least one step selected from the swelling step, the dyeing step, and the cross-linking step, and after the cross-linking step, further includes a step of stretching the film raw fabric in the stretching treatment liquid. ..
The treatment tank of the present invention is installed in a polarizing film production line in a state of accommodating a treatment liquid such as the swelling treatment liquid.

[Processing tank for manufacturing polarizing film]
FIG. 1 is a cross-sectional view of a processing tank 1 for manufacturing a polarizing film.
With reference to FIG. 1, the processing tank 1 has a metal tank body 11 and a coating layer 12 covering the inner surface of the tank body 11. In the present invention, the coating layer 12 is formed of a coating material having an elongation rate of 150% or more.
Specifically, the shape of the tank body 11 is not particularly limited as long as it has a shape that can accommodate the treatment liquid and has an entrance / exit that allows the film raw material to be carried in and out. In the illustrated example, the tank body 11 is formed in a concave shape having an open top surface having a bottom surface portion 111 and a peripheral wall surface portion 112 raised from the periphery of the bottom surface portion 111. The top opening of the top opening type tank body 11 serves as an entrance / exit for the original film. A lid material (not shown) on which the entrance and exit of the original film is formed may cover the upper surface opening of the tank body 11. Further, the entrance / exit of the original film may be formed above the peripheral wall surface portion 112 of the tank body 11 (not shown).

The coefficient of thermal expansion of the tank body 11 is preferably 10 × ^10-6 / ° C to 24 × ^10-6 / ° C, and further is 10 × ^10-6 / ° C to 18 × ^10-6 / ° C. More preferably, it is more preferably 15 × 10 ^-6 / ° C to 18 × 10 ^-6 / ° C. By providing the coating layer 12 having an elongation rate of 150% or more with respect to the tank body 11 having the coefficient of thermal expansion in the above range, cracks or peeling of the coating layer 12 can be prevented even if the treatment tank 1 is used for a long period of time. ..
The coefficient of thermal expansion refers to a value indicating a change in the length and volume of an object caused by an increase in temperature as a rate of change per 1 ° C.
The coefficient of thermal expansion of the tank body 11 is the coefficient of thermal expansion of the tank body 11 itself, which does not include the coating layer 12 and the like. Usually, the coefficient of thermal expansion of the tank body 11 is equal to the coefficient of thermal expansion of the metal forming the tank body 11.
The coefficient of thermal expansion is an average value between 0 ° C. and 100 ° C. The coefficient of thermal expansion is measured in accordance with JIS Z 2285: 2003 (method for measuring the coefficient of linear thermal expansion of a metal material).

The metal forming the tank body 11 is not particularly limited, but it is preferable to use a metal having a coefficient of thermal expansion of ^{10 × 10 -6} / ° C. to 24 × 10 ^{-6 / ° C.} For example, examples of the metal forming the tank body 11 include stainless steel, iron, aluminum, and alloys, and stainless steel is preferably used. Various materials such as SUS304, SUS305, SUS316, SUS410, and SUS430 are specified for the stainless steel rope in the JIS standard. In the present invention, SUS316L or SUS304 is preferably used, although it can be appropriately selected and used from these stainless steels. The coefficient of thermal expansion of SUS304 is 17.3 × 10 ^-6 / ° C, and the coefficient of thermal expansion of SUS316L is 16.0 × 10 ^-6 / ° C.
The wall thickness of the tank body 11 is not particularly limited as long as it has mechanical strength capable of accommodating the treatment liquid, but if the wall thickness is too large, the material cost will rise. From this point of view, the wall thickness of the tank body 11 is, for example, 0.5 mm to 10 mm, preferably 2 mm to 6 mm, and more preferably 2.5 mm to 5 mm.

The coating layer 12 is a coating provided on the inner surface of the tank body 11 so that the treatment liquid does not come into contact with the inner surface of the tank body 11.
In the illustrated example, the coating layer 12 is continuously provided from the inner surface of the bottom surface portion 111 of the tank body 11 to the inner surface of the peripheral wall surface portion 112 without any gap.
In the illustrated example, the coating layer 12 is provided on the entire inner surface of the tank body 11 without a gap, but there may be a portion of the inner surface of the tank body 11 where the coating layer 12 is not provided. As described above, since the coating layer 12 is provided to prevent the treatment liquid from coming into contact with the tank body 11, the coating layer 12 is provided on the inner surface of the tank body 11 where the treatment liquid does not clearly come into contact. It does not have to be. Examples of the portion where the treatment liquid does not clearly contact include the upper end portion of the peripheral wall surface portion 112 on the inner surface of the tank body 11.

The coating layer 12 is formed of a coating material having an elongation rate of 150% or more. Preferably, the coating layer 12 is formed from a coating material having an elongation rate of 350% or more, and more preferably from a coating material having an elongation rate of 375% or more. The upper limit of the elongation rate of the material forming the coating layer 12 is not particularly limited, but for example, the elongation rate of the coating material is 500% or less, preferably 450% or less.
Here, the elongation rate is measured by measuring the length before pulling and the length at break by a tension test, and the elongation rate (%) = (length at break-length before pulling) / length before pulling, Is required by.
A specific method for measuring the elongation of the coating material can be measured under standard conditions (23 ° C., 1 atm, 50% RH) by a tensile test based on ASTM-D412.

Further, as the material for forming the coating layer 12, a material that is not easily eroded by the treatment liquid is used. Hereinafter, the property of being hard to be eroded by the treatment liquid is referred to as corrosion resistance. In particular, the coating material preferably has corrosion resistance to a treatment liquid containing at least one of an iodine compound such as potassium iodide and sodium iodide and a boron compound, and a treatment containing at least one of potassium iodide and boric acid. It is more preferable to have corrosion resistance to the liquid.
The coating material is not particularly limited as long as it has an elongation rate of 150% or more and corrosion resistance. Specifically, examples of the coating material include polyurea resin, rubber, and elastomer, and a material containing a polyurea resin is particularly preferable.

The polyurea resin is a resin having a urea bond formed by a chemical reaction between an isocyanate group and an amino group. Examples of the polyurea resin include a polymer obtained by reacting polyisocyanate with polyamine.
The method of forming the coating layer 12 on the inner surface of the tank body 11 is not particularly limited, and an appropriate method can be appropriately adopted depending on the coating material. For example, when a polyurea resin is used as the coating material, the coating layer 12 can be formed by spraying the polyurea resin onto the tank body 11 using a coating machine. Further, the present invention is not limited to the coating machine, and the polyurea resin may be applied to the tank body 11 by hand coating. In the case of a two-component type polyurea resin, the two-component type (isocyanate and amine) is reacted and coated. The polyurea resin can be applied by spraying or hand-painting as described above. Therefore, even if the coating layer is cracked or peeled off, the polyurea resin can be partially coated or recoated on the cracked portion without replacing the treatment tank. Therefore, the treatment tank can be easily repaired.

The thickness of the coating layer 12 is not particularly limited, but if it is too small, the thickness of the coating layer 12 may be partially reduced due to the expansion of the coating layer 12 following the deformation of the tank body 11. From this point of view, the thickness of the coating layer 12 is preferably 1 mm or more, more preferably 1.5 mm or more, still more preferably 2 mm or more. The upper limit of the thickness of the coating layer 12 is not particularly limited, but is 10 mm or less, preferably 4 mm or less in consideration of cost effectiveness.
Hereinafter, the processing tank 1 described in the column of [Processing tank for producing a polarizing film] may be referred to as “specific processing tank 1”.

[Polarizing film manufacturing equipment]
The polarizing film manufacturing apparatus of the present invention is an apparatus for carrying out a step of immersing a film raw fabric in a processing tank containing a processing liquid to obtain a polarizing film from the film raw fabric. That is, the original film after performing a predetermined process by the manufacturing apparatus is a polarizing film.
The polarizing film manufacturing apparatus of the present invention conveys one or more treatment tanks containing a treatment liquid for treating a film raw fabric, the treatment liquid contained in the treatment tank, and the film raw fabric. It has a transport device for immersing in the treatment liquid in the treatment tank.
The specific processing tank 1 is used as at least one processing tank of the processing tanks of the manufacturing apparatus.

FIG. 2 is a reference diagram showing a polarizing film manufacturing apparatus 2. The arrows in the figure indicate the traveling direction (conveying direction) of the film raw fabric 3.
The manufacturing apparatus 2 has a front roll portion 28 around which the original film 3 to be processed is wound, and a rear roll portion 29 around which the polarizing film is wound. The manufacturing apparatus 2 manufactures a polarizing film by a so-called roll-to-roll method.
Various treatment tanks are arranged between the front roll portion 28 and the rear roll portion 29. The treatment tank includes a swelling treatment tank containing a swelling treatment liquid, a dyeing treatment tank containing a dyeing treatment liquid, a cross-linking treatment tank containing a cross-linking treatment liquid, a stretching treatment tank containing a stretching treatment liquid, and a cleaning treatment liquid. Examples include a cleaning treatment tank.
The manufacturing apparatus 2 of the illustrated example has a swelling treatment tank 1A, a dyeing treatment tank 1B, a cross-linking treatment tank 1C, a stretching treatment tank 1D, and a cleaning treatment tank 1E in this order from the front roll portion 28 to the rear roll portion 29.

The specific treatment tank 1 is used for at least one selected from the swelling treatment tank 1A, the dyeing treatment tank 1B, the cross-linking treatment tank 1C, the stretching treatment tank 1D, and the cleaning treatment tank 1E, preferably two or more. Used. The specific processing tank 1 may be used for all the processing tanks included in the manufacturing apparatus 2.
The specific treatment tank 1 is preferably used at least in a treatment tank containing a treatment liquid containing at least one of an iodine compound and a boron compound. Iodine compounds such as potassium iodide and boron compounds such as boric acid easily erode the metal tank body 11, and therefore, by using the specific treatment tank 1, even when such a treatment liquid is contained, the tank body The erosion of 11 can be effectively prevented.
As a treatment tank containing at least one of potassium iodide (iodine compound) and boric acid (boric acid compound), as described later, a swelling treatment tank 1A, a dyeing treatment tank 1B, a cross-linking treatment tank 1C, and a stretching treatment tank are used. Examples thereof include a treatment tank 1D and an adjustment treatment tank.
From the viewpoint of the components of the treatment liquid, the specific treatment tank 1 is preferably used at least in the stretching treatment tank 1D, and more preferably at least in the crosslinking treatment tank 1C and the stretching treatment tank 1D. For example, from the viewpoint of the components of the treatment liquid, the specific treatment tank 1 may be used in the swelling treatment tank 1A, the dyeing treatment tank 1B, the crosslinking treatment tank 1C, the stretching treatment tank 1D, and the adjustment treatment tank, respectively.

Further, the specific treatment tank 1 is preferably used at least in a treatment tank containing a treatment liquid having a treatment liquid temperature of 40 ° C. or higher (preferably 60 ° C. or higher). When the temperature of the treatment liquid is relatively high, the metal tank body 11 may thermally expand to cause cracks in the coating layer 12 or partial peeling of the coating layer 12, but the specific treatment tank 1 has a coating layer. Since the 12 follows the thermal expansion of the tank body 11, cracks or peeling of the coating layer 12 can be effectively prevented even when such a treatment liquid is contained.
Examples of the treatment liquid for raising the liquid temperature to 40 ° C. or higher when producing the polarizing film include a dyeing treatment liquid, a cross-linking treatment liquid, a stretching treatment liquid, and the like, as will be described later.
From the viewpoint of the temperature of the treatment liquid, the specific treatment tank 1 is preferably used at least in the stretching treatment tank 1D, and more preferably at least in the crosslinking treatment tank 1C and the stretching treatment tank 1D. For example, from the viewpoint of the temperature of the treatment liquid, the specific treatment tank 1 may be used for the dyeing treatment tank 1B, the crosslinking treatment tank 1C, and the stretching treatment tank 1D, respectively.
In the illustrated example, the cross-linking treatment tank 1C and the stretching treatment tank 1D are all composed of the specific treatment tank 1, and the swelling treatment tank 1A, the dyeing treatment tank 1B and the cleaning treatment tank 1E are all other than the specific treatment tank. It consists of a treatment tank. However, this is just an example, and the specific treatment tank 1 can be used at an appropriate place.

Further, in order to transport the film raw fabric 3 from the front roll portion 28 through the processing tank to the rear roll portion 29, a transport device for the film raw fabric 3 is transported between the front roll portion 28 and the rear roll portion 29. Is provided.
The transport device is a drive device (motor, etc.) that drives at least one roller selected from the nip roller 24 and the guide roller 25 in order to transport the plurality of nip rollers 24, the plurality of guide rollers 25, and the film raw fabric 3. Not shown) and.
Some guide rollers 25 are arranged in each processing tank. The film raw fabric 3 is conveyed from the front roll portion 28 to the rear roll portion 29 by the nip roller 24 and the guide roller 25 while passing through each treatment tank and being immersed in the treatment liquid.

<Film original fabric>
The untreated film raw fabric 3 is wound around the front roll portion 28.
The original film 3 has a long strip shape. The long strip shape is a rectangular shape whose length in the longitudinal direction is sufficiently larger than the length in the lateral direction (direction orthogonal to the longitudinal direction). The length of the long strip-shaped film raw fabric 3 in the longitudinal direction is, for example, 10 m or more, preferably 50 m or more.
The original film 3 is not particularly limited, but is excellent in dyeability with a bicolor substance. Therefore, a film containing a hydrophilic polymer film (for example, a polyvinyl alcohol-based film) is preferably used, and more preferably. A hydrophilic polymer film is used. Examples of the film containing the hydrophilic polymer film include a film in which a hydrophilic polymer film and a non-hydrophilic polymer film are laminated. In this case, it is preferable that the hydrophilic polymer film is laminated on the front surface and / or the back surface of the non-hydrophilic polymer film. In this case, the hydrophilic polymer film laminated on the front surface and / or the back surface of the non-hydrophilic polymer film may be in the form of a thin film having a thickness of about several μm.

The hydrophilic polymer film is not particularly limited, and conventionally known films can be used. Specifically, examples of the hydrophilic polymer film include polyvinyl alcohol (PVA) -based film, partially formalized PVA-based film, polyethylene terephthalate (PET) film, ethylene / vinyl acetate copolymer film, and partial saponification of these. Examples include films. In addition to these, polyene-oriented films such as a dehydrated product of PVA and a dehydrochlorinated product of polyvinyl chloride, a stretch-oriented polyvinylene-based film, and the like can also be used. Among these, a PVA-based polymer film is particularly preferable because it is excellent in dyeability with a dichroic substance.
As the raw material polymer of the PVA-based polymer film, for example, a polymer obtained by polymerizing vinyl acetate and then saponified, or a copolymerizable monomer such as a small amount of unsaturated carboxylic acid or unsaturated sulfonic acid is copolymerized with vinyl acetate. Polymers, etc. The degree of polymerization of the PVA-based polymer is not particularly limited, but is preferably 500 to 10000, more preferably 1000 to 6000, from the viewpoint of solubility in water and the like. The saponification degree of the PVA-based polymer is preferably 75 mol% or more, more preferably 98 mol% to 100 mol%.
The thickness of the original film 3 before the treatment is not particularly limited, but is, for example, 15 μm to 110 μm. A film raw fabric 3 having a thickness of 38 μm to 110 μm or 50 μm to 100 μm before treatment may be used.

<Swelling treatment tank>
The swelling treatment tank 1A is a treatment tank containing the swelling treatment liquid 41. The swelling treatment tank 1A swells the film raw fabric 3.
In the illustrated example, only one swelling treatment tank 1A is installed, but two or more swelling treatment tanks 1A may be arranged side by side in the traveling direction of the film raw fabric 3 (not shown).
The swelling treatment liquid 41 contained in the swelling treatment tank 1A is a treatment liquid for swelling the film raw fabric 3 before treatment.
As the swelling treatment liquid 41, for example, water can be used. Further, water obtained by adding an appropriate amount of an iodine compound such as glycerin or potassium iodide to water may be used as the swelling treatment liquid. When glycerin is added, the concentration is preferably 5% by weight or less, and when an iodine compound such as potassium iodide is added, the concentration is preferably 10% by weight or less.

<Dyeing tank>
The dyeing treatment tank 1B is a treatment tank containing the dyeing treatment liquid 42. The dyeing treatment tank 1B dyes the film raw fabric 3.

In the illustrated example, only one dyeing treatment tank 1B is installed, but two or more dyeing treatment tanks 1B may be arranged side by side in the traveling direction of the film raw fabric 3 (not shown).
The dyeing treatment liquid 42 is a treatment liquid for dyeing the film raw fabric 3.
Examples of the dyeing solution 42 include a solution containing a dichroic substance as an active ingredient. Examples of the dichroic substance include iodine and organic dyes.
Preferably, as the dyeing treatment liquid 42, a solution in which iodine is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. The concentration of iodine in the dyeing solution is not particularly limited, but is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and 0.025% by weight. It is more preferably% to 5% by weight.
Further, in order to further improve the dyeing efficiency, it is preferable to add an iodine compound to the dyeing treatment liquid. An iodine compound is a compound containing iodine and an element other than iodine in the molecule. Examples of the iodine compound include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. When an iodine compound is added, its concentration is preferably 0.01% by weight to 10% by weight, more preferably 0.1% by weight to 5% by weight. Among the iodine compounds, it is preferable to add potassium iodide.
When the dyeing solution 42 contains iodine and an iodine compound, iodine may be the main component of the dyeing solution (the main component means a component having a large content (weight basis)), or the iodine compound is the dyeing solution. It may be the main component of. Usually, a dyeing solution containing more iodine compounds than iodine is used.

<Crosslink processing tank>
The cross-linking treatment tank 1C is a treatment tank containing the cross-linking treatment liquid 43. The cross-linking treatment tank 1C cross-links the dyed film raw fabric 3.
In the illustrated example, only one cross-linking treatment tank 1C is installed, but two or more cross-linking treatment tanks 1C may be arranged side by side in the traveling direction of the film raw fabric 3 (not shown).
The cross-linking treatment liquid 43 is a treatment liquid for cross-linking the film raw fabric 3 on which the dichroic substance is adsorbed.
As the cross-linking treatment liquid 43, a solution containing a boron compound as an active ingredient can be used. For example, as the cross-linking treatment liquid 43, a solution in which a boron compound is dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax. Above all, it is preferable to use boric acid. The concentration of the boron compound in the cross-linking treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight, and 2% by weight to 6% by weight. Is even more preferable. Further, if necessary, glyoxal, glutaraldehyde, or the like may be added to the cross-linking treatment liquid.
Further, since a polarizing film having uniform optical characteristics can be obtained, it is preferable to add an iodine compound to the cross-linking treatment liquid. The iodine compound is not particularly limited, and examples thereof include those exemplified in the above dyeing treatment liquid. Of these, potassium iodide is preferable. The concentration of the iodine compound is not particularly limited, but is preferably 0.05% by weight to 15% by weight, more preferably 0.5% by weight to 8% by weight. When an iodine compound is added, the ratio of the boron compound (preferably boric acid) to the iodine compound (preferably potassium iodide) is preferably in the range of 1: 0.1 to 1: 6 in terms of weight ratio. , 1: 0.5 to 1: 3.5, more preferably 1: 1 to 1: 2.5.
When the cross-linking treatment liquid 43 contains a boron compound and an iodine compound, the boron compound may be the main component of the solution, or the iodine compound may be the main component of the solution.

<Stretching tank>
The stretching treatment tank 1D is a treatment tank containing the stretching treatment liquid 44. The stretching treatment tank 1D stretches the film raw fabric 3.
In the illustrated example, only one stretching treatment tank 1D is installed, but two or more stretching treatment tanks 1D may be arranged side by side in the traveling direction of the film raw fabric 3 (not shown).
The stretching treatment liquid 44 is not particularly limited, but for example, a solution containing a boron compound as an active ingredient can be used. As the stretching treatment liquid 44, for example, a solution in which a boron compound and, if necessary, various metal salts, zinc compounds and the like are dissolved in a solvent can be used. Water is generally used as the solvent, but an organic solvent compatible with water may be further added. Examples of the boron compound include boric acid and borax, and among them, boric acid is preferably used. The concentration of the boron compound in the stretching treatment liquid is not particularly limited, but is preferably 1% by weight to 10% by weight, more preferably 2% by weight to 7% by weight.
Further, from the viewpoint of suppressing the elution of iodine adsorbed on the film, it is preferable that the stretching treatment liquid contains an iodine compound in addition to the boron compound. The iodine compound is not particularly limited, and examples thereof include those exemplified in the above dyeing treatment liquid. Of these, potassium iodide is preferable. The concentration of the iodine compound in the stretching treatment liquid is not particularly limited, but is preferably 0.05% by weight to 15% by weight, more preferably 0.5% by weight to 8% by weight.
When the stretching treatment liquid 44 contains a boron compound and an iodine compound, the boron compound may be the main component of the solution, or the iodine compound may be the main component of the solution. Usually, a stretching treatment liquid containing more iodine compounds than boron compounds is used.
For example, as the stretching treatment liquid 44, a solution containing about 5% by weight of potassium iodide and about 4% by weight of boric acid can be used.

<Washing tank>
The cleaning treatment tank 1E is a treatment tank containing the cleaning treatment liquid 45. The cleaning treatment tank 1E cleans the stretched film raw fabric 3.
In the illustrated example, only one cleaning treatment tank 1E is installed, but two or more cleaning treatment tanks 1E may be arranged side by side in the traveling direction of the film raw fabric 3 (not shown).
The cleaning treatment liquid 45 is a treatment liquid for cleaning the treatment liquid such as the dyeing treatment liquid and the cross-linking treatment liquid adhering to the original film 3.
As the cleaning treatment liquid, water such as ion-exchanged water, distilled water, and pure water is typically used.

<Others>
A drying device 21 is provided between the cleaning treatment tank 1E and the rear roll portion 29. The drying device 21 is provided for drying the film raw fabric 3.
In the illustrated example, the manufacturing apparatus 2 has a swelling treatment tank 1A, a dyeing treatment tank 1B, a cross-linking treatment tank 1C, a stretching treatment tank 1D, and a cleaning treatment tank 1E. You do not have to have it. For example, the manufacturing apparatus 2 may have a swelling treatment tank 1A, a dyeing treatment tank 1B, a cross-linking treatment tank 1C, and a cleaning treatment tank 1E as the treatment tank, or the swelling treatment tank 1A and the dyeing treatment as the treatment tank. It may have a tank 1B and a cross-linking treatment tank 1C.
Further, the manufacturing apparatus 2 may further have an adjustment processing tank (not shown).
The adjustment treatment tank is a treatment tank in which the adjustment treatment liquid is stored. Although not shown in FIG. 2, this adjustment treatment tank is provided between the cross-linking treatment tank 1C and the stretching treatment tank 1D, or between the stretching treatment tank 1D and the cleaning treatment tank 1E.
The adjusting treatment liquid is a solution for adjusting the hue of a film, and a solution containing an iodine compound as an active ingredient can be used. For example, as the adjustment treatment liquid, a solution in which an iodine compound is dissolved in a solvent can be used. The concentration of the iodine compound in the adjusting treatment liquid is not particularly limited, but is preferably 0.5% by weight to 20% by weight, more preferably 1% by weight to 15% by weight.

<Manufacturing method of polarizing film>
With reference to FIG. 2, the untreated film raw fabric 3 is unwound from the front roll portion 28, and the film raw fabric 3 is conveyed to the swelling treatment tank 1A by a conveying device.
The film raw fabric 3 is swelled by immersing the film raw fabric 3 in the swelling treatment liquid 41 while transporting the film raw fabric 3 by the guide roller 25 in the swelling treatment tank 1A.
The temperature of the swelling treatment liquid 41 is not particularly limited, but is, for example, 20 ° C to 45 ° C, preferably 25 ° C to 40 ° C. The time for immersing the film raw fabric 3 in the swelling treatment liquid 41 is not particularly limited, but is, for example, 5 seconds to 300 seconds, preferably 8 seconds to 240 seconds.

The film raw fabric 3 after the swelling step is pulled out from the swelling treatment tank 1A, and the film raw fabric 3 is conveyed to the dyeing treatment tank 1B.
By immersing the film raw fabric 3 in the dyeing treatment liquid 42 while transporting the film raw fabric 3 by the guide roller 25 in the dyeing treatment tank 1B, the film raw fabric 3 is dyed with a dichroic substance.
The temperature of the dyeing solution 42 is not particularly limited, but is, for example, 20 ° C to 50 ° C, preferably 25 ° C to 40 ° C. The time for immersing the film raw fabric 3 in the dyeing treatment liquid 42 is not particularly limited, but is, for example, 5 seconds to 300 seconds, preferably 8 seconds to 240 seconds.

The film raw fabric 3 after the dyeing step is pulled out from the dyeing treatment tank 1B, and the film raw fabric 3 is conveyed to the cross-linking treatment tank 1C.
The dichroic substance of the film raw fabric 3 is crosslinked by immersing the film raw fabric 3 in the cross-linking treatment liquid 43 while transporting the film raw fabric 3 by the guide roller 25 of the cross-linking treatment tank 1C.
The temperature of the cross-linking treatment liquid 43 is not particularly limited, but is, for example, 25 ° C. or higher, preferably 30 ° C. to 85 ° C., and more preferably 40 ° C. to 70 ° C. The time for immersing the film raw fabric 3 in the cross-linking treatment liquid 43 is not particularly limited, but is, for example, 5 seconds to 800 seconds, preferably 6 seconds to 500 seconds.

The film raw fabric 3 after the cross-linking step is pulled out from the cross-linking treatment tank 1C, and the film raw fabric 3 is conveyed to the stretching treatment tank 1D.
In the stretching treatment liquid 44 of the stretching treatment tank 1D, the film raw fabric 3 is stretched while being conveyed by the guide roller 25. The temperature of the stretching treatment liquid 44 is not particularly limited, but is, for example, 40 ° C. to 90 ° C., preferably 60 ° C. to 90 ° C. or 60 ° C. to 85 ° C. The draw ratio can be appropriately set depending on the intended purpose, but the total draw ratio is, for example, 2 to 7 times, preferably 4.5 to 6.8 times. The total draw ratio means the final draw ratio of the film raw fabric 3. The film raw fabric 3 may be stretched in at least one of the swelling treatment tank 1A, the dyeing treatment tank 1B and the cross-linking treatment tank 1C, or the film raw fabric 3 may be stretched only in the stretching treatment tank 1D. It may have been done. The total stretching ratio means the ratio when it is stretched only in the stretching treatment tank 1D, and means the total of those stretching ratios when it is also stretched in the swelling treatment tank 1A or the like.

The film raw fabric 3 after the stretching step is conveyed to the adjusting treatment tank and immersed in the adjusting treatment liquid, if necessary. The temperature of the adjusting treatment liquid is not particularly limited, but is, for example, 15 ° C to 40 ° C. The time for immersing the film raw fabric 3 in the adjusting treatment liquid is not particularly limited, but is, for example, 2 seconds to 20 seconds.

The film raw fabric 3 after the stretching step or the adjusting step is conveyed to the cleaning treatment tank 1E and immersed in the cleaning treatment liquid 45 to clean the film raw fabric 3.
The temperature of the cleaning treatment liquid 45 is, for example, 5 ° C. to 50 ° C., preferably 10 ° C. to 45 ° C. The cleaning time is, for example, 1 second to 300 seconds, preferably 3 seconds to 240 seconds.
The polarizing film 5 is obtained by drying the original film 3 after the washing step with a drying device 21 as needed. The produced polarizing film 5 is wound around the rear roll portion 29.

In the processing tank 1 for producing a polarizing film of the present invention, since the coating layer 12 having an elongation rate of 150% or more is provided on the inner surface of the metal tank body 11, the tank body 11 is eroded by the treatment liquid. Can be prevented. Specifically, since the corrosion-resistant coating layer 12 is provided on the inner surface of the tank body 11, the treatment liquid does not come into contact with the tank body 11, and erosion of the tank body 11 can be prevented. Further, when the treatment tank 1 is used for a long period of time, the metal tank main body 11 is deformed, and when a treatment liquid having a relatively high temperature (for example, 40 ° C. or higher) is housed in the treatment tank, the tank main body 11 is formed. The metal is thermally expanded and easily deformed. In this respect, in the present invention, since the inner surface of the tank body 11 is covered with the coating layer 12 having a ^{coefficient of thermal expansion of 10 × 10 -6} / ° C. to 24 × 10 ^{-6 / ° C., the tank body 11 is thermally expanded.} The coating layer 12 flexibly extends in accordance with the above. Therefore, the coating layer 12 is less likely to be cracked or peeled due to the deformation of the tank body 11, and the tank body 11 can be prevented from being eroded by the treatment liquid.
Conventionally, when a crack or peeling occurs in a processing tank for producing a polarizing film, the processing tank is repaired or replaced, considering that it is caused by aged deterioration. In this regard, the present inventors have investigated the cause of cracks or peeling in the conventional coating layer, and found that it is the thermal expansion of the metal tank body and the followability of the coating layer to the expansion. .. Then, the present inventors provide a treatment tank capable of effectively suppressing the occurrence of cracks in the coating layer by combining a coating material that easily follows the expansion (deformation) of the tank body and the tank body. Is.

[Use of polarizing film, etc.]
The polarizing film of the present invention can be used, for example, in lenses such as sunglasses, dimming windows, image display devices such as liquid crystal displays, and the like.
The polarizing film of the present invention can also be used as a polarizing plate by laminating a protective film on one side or both sides thereof. When used as a polarizing plate, a retardation film may be further laminated.

Hereinafter, Examples and Comparative Examples will be described, and the present invention will be described in more detail. However, the present invention is not limited to the following examples.

[Material for forming the tank body]
-Stainless steel plate Vertical x horizontal x thickness = 100 mm x 50 mm x 5 mm SUS304 stainless steel plate. This SUS304 is a JIS standard product, and its coefficient of linear expansion is 17.3 × 10 ^-6 / ° C.

[Coating material]
・ Polyurea resin (1)
Product name "Nukote ST" (Manufacturer: NUKOTE Co., Ltd., Distributor: Kanamori Tohei Shoji Co., Ltd.). The growth rate is 400%.
・ Polyurea resin (2)
Product name "Nukote HT" (Manufacturer: NUKOTE Co., Ltd., Distributor: Kanamori Tohei Shoji Co., Ltd.). The growth rate is 375%.
・ Polyurea resin (3)
Product name "Nukote CG" (Manufacturer: NUKOTE Co., Ltd., Distributor: Kanamori Tohei Shoji Co., Ltd.). The growth rate is 175%.
・ Polyurea resin (4)
Product name "Nukote XT-Plus" (manufacturer: NUKOTE, manufacturer, distributor: Kanamori Tohei Shoji Co., Ltd.). The growth rate is 50%.
The polyurea resins (1) to (3) are two-component curable types of an agent A containing an isocyanate as a main component and an agent B containing an amine compound as a main component.

-Butyl rubber Product name "Butyl rubber" (manufacturer: Meiwa Rubber Industry Co., Ltd.). The growth rate is 360%.
-Vinyl chloride resin Product name "Vinyl chloride" (manufacturer: Shin-Etsu Chemical Co., Ltd.). The growth rate is 60%.
・ FRP (fiber reinforced plastic)
Product name "Neopole 8411LH" (Manufacturer: Japan U-Pica Co., Ltd.). The growth rate is 2%.
-Ceramic / metal composite polymer Product name "Nukote Chemishield" (Manufacturer: NUKOTE, manufacturer, distributor: Tohei Kanamori Shoji Co., Ltd.). The growth rate is 5%.
The elongation rates of the polyurea resins (1) to (4) were measured by a tensile test based on ASTM-D412. The elongation of butyl rubber was measured by a tensile test in accordance with JIS K6251: 2017. The elongation rate of the vinyl chloride resin was measured by a tensile test according to ASTM-D638. The elongation rate of FRP (fiber reinforced plastic) is measured by a tensile test based on JIS K7161-1: 2014. The elongation of the ceramic-metal composite polymer was measured by a tensile test according to ASTM-D638.

[Example 1]
A polyurea resin (1) was applied so as to cover the entire surface of the stainless steel plate, and the polyurea resin (1) was cured. In this way, a sample piece in which the entire surface of the stainless steel plate was covered with a coating layer having a thickness of 3 mm made of the polyurea resin (1) was prepared.

[Example 2]
A sample piece of Example 2 was prepared in the same manner as in Example 1 except that the polyurea resin (2) was used instead of the polyurea resin (1).

[Example 3]
A sample piece of Example 3 was prepared in the same manner as in Example 1 except that the polyurea resin (3) was used instead of the polyurea resin (1).

[Example 4]
A sample piece of Example 4 was prepared in the same manner as in Example 1 except that butyl rubber was used instead of the polyurea resin (1).

[Comparative Examples 1 to 4]
Sample pieces of Comparative Examples 1 to 4 were prepared in the same manner as in Example 1 except that the coating material shown in Table 1 was used instead of the polyurea resin (1).

[Durability test]
An aqueous solution containing boric acid and potassium iodide (boric acid concentration of about 7% by weight, potassium iodide concentration of about 8%) containing each of the sample pieces of Examples 1 to 4 and Comparative Examples 1 to 4 at a liquid temperature of 70 ° C. ) Was immersed for 1 month.
After soaking for 1 month, each sample piece was taken out from the solution, and the state of the coating layer was visually observed. The results are shown in Table 1.
In the test results in Table 1, "AAA" indicates that the coating layer was not cracked or peeled, and the coating layer was not eroded, and "AA" was that the coating layer was cracked or peeled. Although it did not occur, it indicates that the surface of the coating layer was slightly eroded, and "B" indicates that cracks or peeling occurred at at least one position of the coating layer.
The coating layers of Examples 1 to 4 formed of a coating material having an elongation rate of 175% or more are not cracked or peeled off, and are formed of a coating material having an elongation rate of 60% or less. The coating layer of was cracked and peeled off. From this, it can be said that by using a coating material having an elongation rate of about 150% or more, a coating layer in which cracks and peeling are unlikely to occur can be formed. Further, from the comparison between Examples 1 and 2 and Examples 3 and 4, by using a polyurea resin having an elongation rate of 350% or more, a coating layer that is less likely to cause cracks or coating and is less likely to be eroded by the treatment liquid for a long period of time can be obtained. It turns out that it can be formed.

1 Treatment tank 1A Swelling treatment tank 1B Dyeing treatment tank 1C Cross-linking treatment tank 1D Stretching treatment tank 1E Cleaning treatment tank 11 Tank body 12 Coating layer 2 Polarizing film manufacturing equipment 3 Original film

Claims (12)

In a treatment tank for accommodating a treatment liquid used when producing a polarizing film from a raw film.
The treatment tank has a metal tank body and a coating layer covering the inner surface of the tank body.
The coating layer is formed of a coating material having an elongation rate of 150% or more.
A processing tank for manufacturing polarizing films. The processing tank for producing a polarizing film according to claim 1, wherein the coating layer is formed of a coating material having an elongation rate of 350% to 450%. The processing tank for producing a polarizing film according to claim 1 or 2, wherein the coefficient of thermal expansion of the tank body is 10 × 10 ^-6 / ° C to 24 × 10 ^{-6 / ° C.} The processing tank for producing a polarizing film according to any one of claims 1 to 3, wherein the coating material contains a polyurea resin having an elongation rate of 150% or more. The processing tank for producing a polarizing film according to any one of claims 1 to 3, wherein the coating material contains a polyurea resin having an elongation rate of 350% or more. The processing tank for producing a polarizing film according to any one of claims 1 to 3, wherein the coating material contains a rubber or an elastomer having an elongation rate of 350% or more. The processing tank for producing a polarizing film according to any one of claims 1 to 6, wherein the coating layer has a thickness of 1.0 mm or more. The processing tank for producing a polarizing film according to any one of claims 1 to 7, wherein the tank body is made of stainless steel. The processing tank for producing a polarizing film according to any one of claims 1 to 8, which is used for at least one of a cross-linking treatment tank for cross-linking the raw film and a stretching treatment tank for stretching the raw film. The processing tank according to any one of claims 1 to 9 and
The treatment liquid contained in the treatment tank and
An apparatus for producing a polarizing film, comprising a transport device for transporting the raw film and immersing it in the treatment liquid in the treatment tank. The apparatus for producing a polarizing film according to claim 10, wherein the treatment liquid contains at least one of an iodine compound and a boron compound. The polarizing film manufacturing apparatus according to claim 10 or 11, wherein the temperature of the treatment liquid is 40 ° C. or higher.

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