JP2020095132A - Processing tank for polarizing film manufacturing, and manufacturing method of polarizing film - Google Patents

Abstract

To provide a processing tank for polarizing film manufacturing that is hardly corroded by a stored process liquid.SOLUTION: A processing tank for storing a process liquid used when a polarizing film is manufactured from an original film 3 comprises a metal tank body 11 and a coating layer 12 for coating an inner surface of the tank body 11. The coating layer 12 is formed by a coating material whose elongation percentage is 150% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a treatment tank used when a raw film is immersed in a treatment liquid to produce a polarizing film, and a polarizing film producing apparatus.

Conventionally, polarizing films have been used as constituent materials for liquid crystal display devices, 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 by, for example, immersing a polyvinyl alcohol-based film, which is a raw material film, in a swelling treatment tank, a dyeing treatment tank, a crosslinking treatment tank, a stretching treatment tank, and a washing treatment tank in that order (Patent Document 1).

JP, 2013-210520, A

By the way, in each processing tank such as the above-mentioned crosslinking processing tank, each processing liquid such as a crosslinking processing solution is stored. The treatment tank includes 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 main body from being eroded by a treatment liquid such as a crosslinking treatment liquid, and is formed of FRP such as fiber reinforced epoxy resin.
However, during long-term use, the coating layer may crack or the coating layer may partly peel off from the tank body. When the coating layer is cracked or peeled off, the treatment liquid comes into contact with the bath main body from that portion, so the bath main body is eroded by the treatment liquid, and the treatment bath must be repaired or replaced.

An object of the present invention is to provide a processing tank for manufacturing a polarizing film and an apparatus for manufacturing a polarizing film, which are difficult 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 containing a processing solution used in producing a polarizing film from a film original film, wherein the processing tank is a metal tank body and the tank. 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 of 150% or more.

In a preferred processing tank for producing a polarizing film of the present invention, the coating layer is formed of a coating material having an elongation of 350% to 450%.
In a preferred processing tank for producing a polarizing film of the present invention, the thermal expansion coefficient of the tank body is 10×10 ⁻⁶ /° C. to 24×10 ⁻⁶ /° C.
In a preferred treatment tank for producing a polarizing film of the present invention, the coating material contains a polyurea resin.
In a preferred processing tank for producing a polarizing film of the present invention, the thickness of the coating layer is 1.0 mm or more.
In a preferred processing tank for producing a 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 crosslinking treatment tank for crosslinking a raw film and a stretching treatment tank for stretching a raw film.

According to another aspect of the present invention, an apparatus for manufacturing a polarizing film is provided.
The manufacturing apparatus for manufacturing the polarizing film of the present invention includes any one of the above-mentioned processing tanks, a processing liquid contained in the processing tanks, and a transporting device that transports the film original fabric and immerses the processing liquid in the processing baths. , With.

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

The treatment tank for producing a polarizing film of the present invention is unlikely to be eroded by a treating solution 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 treatment tank can reduce the frequency of maintenance of the treatment tank and can manufacture the polarizing film for a long period of time.

Sectional drawing of the processing tank for polarizing film manufacture which concerns on one Embodiment of this invention. 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 ranges 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 the drawings are for reference only, and the dimensions, scales, and shapes of the members shown in the drawings may be different from the actual ones.

The processing tank for producing a polarizing film of the present invention is a container for containing a processing solution used when a polarizing film is produced 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 The method further comprises the step of crosslinking with a crosslinking treatment solution, and preferably further comprises the step of washing the raw film film with a washing treatment solution. Further, in the manufacturing method, after the cross-linking step, a step of stretching the raw material film in a stretching treatment liquid, or a stretching of the raw material film in at least one step selected from the swelling step, the dyeing step and the cross-linking step. Or a step of stretching the raw material film in at least one step selected from the swelling step, the dyeing step and the crosslinking step and stretching the raw material film in a stretching treatment liquid after the crosslinking step. ..
The treatment tank of the present invention is installed in a polarizing film production line in a state of containing a treatment liquid such as the swelling treatment liquid.

[Treatment tank for polarizing film production]
FIG. 1 is a cross-sectional view of a processing tank 1 for manufacturing a polarizing film.
Referring to FIG. 1, the processing bath 1 has a bath main body 11 made of metal, and a coating layer 12 that covers the inner surface of the bath main 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 the processing liquid can be accommodated therein and has an inlet/outlet through which the raw material film can be loaded and unloaded. In the illustrated example, the tank main body 11 is formed in a top-opening concave shape having a bottom surface portion 111 and a peripheral wall surface portion 112 that is raised from the periphery of the bottom surface portion 111. The top opening type tank main body 11 has an opening on the top surface that serves as an entrance/exit for the original film. Note that a lid member (not shown) provided with an entrance/exit for the original film may cover the upper opening of the tank body 11. Further, the inlet/outlet of the original film may be formed above the peripheral wall surface portion 112 of the tank body 11 (not shown).

The thermal expansion coefficient of the tank body 11 is preferably 10×10 ⁻⁶ /° C. to 24×10 ⁻⁶ /° C., and more preferably 10×10 ⁻⁶ /° C. to 18×10 ⁻⁶ /° C. It is more preferable that it is 15×10 ⁻⁶ /° C. to 18×10 ⁻⁶ /° C. By providing the coating layer 12 having an elongation of 150% or more with respect to the tank body 11 having a thermal expansion coefficient in the above range, cracks or peeling of the coating layer 12 can be prevented even when 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 length/volume of an object caused by an increase in temperature as a change rate per 1°C.
The thermal expansion coefficient of the tank body 11 is the thermal expansion coefficient 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.
Moreover, the said thermal expansion coefficient is an average value in 0 degreeC-100 degreeC. The coefficient of thermal expansion is measured according to JIS Z 2285:2003 (a method for measuring the coefficient of linear thermal expansion of metallic materials).

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, alloys, and the like, and preferably stainless steel is used. Various materials such as SUS304, SUS305, SUS316, SUS410, and SUS430 are specified for stainless steel according to the JIS standard. In the present invention, these stainless steels can be appropriately selected and used, but SUS316L or SUS304 is preferably used. 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 main body 11 is not particularly limited as long as it has a mechanical strength capable of containing the processing liquid, but if the wall thickness is too large, the material cost rises. From this viewpoint, 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 in order to prevent the treatment liquid from coming into contact with the inner surface of the tank body 11.
In the illustrated example, the coating layer 12 is continuously provided without a gap 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.
In the illustrated example, the coating layer 12 is provided on the entire inner surface of the tank body 11 without a gap, but a portion of the inner surface of the tank body 11 where the coating layer 12 is not provided may be provided. As described above, since the coating layer 12 is provided to prevent the treatment liquid from contacting 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 obviously contact. It does not have to be. Examples of locations where the treatment liquid does not obviously contact include the upper end of the peripheral wall surface portion 112 of the inner surface of the tank body 11.

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

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

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 polymers obtained by reacting polyisocyanate and polyamine.
The method for forming the coating layer 12 on the inner surface of the tank body 11 is not particularly limited, and an appropriate method can be 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 on the tank body 11 using a coating machine. In addition to the coating machine, polyurea resin may be applied to the tank body 11 by hand coating. For a two-pack type polyurea resin, coating is performed while reacting two packs (isocyanate and amine). The polyurea resin can be applied by spraying or hand coating as described above. Therefore, even if the coating layer is cracked or peeled off, the polyurea resin can be partially coated or overcoated on the cracked portion without replacing the treatment tank. Therefore, the processing 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 partially become too small due to the extension of the coating layer 12 following the deformation of the tank body 11. From this viewpoint, the thickness of the coating layer 12 is preferably 1 mm or more, more preferably 1.5 mm or more, and further 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 section of "Processing tank for manufacturing polarizing film" may be referred to as "specific processing tank 1".

[Polarizing film manufacturing equipment]
The apparatus for producing a polarizing film of the present invention is an apparatus that performs a predetermined process of immersing a raw film film in a treatment tank containing a treatment liquid to obtain a polarizing film from the raw film film. In other words, the original film after being subjected to the predetermined processing by the manufacturing apparatus is the polarizing film.
The polarizing film manufacturing apparatus of the present invention conveys one or more processing tanks for containing a processing solution for processing a film original sheet, a processing solution contained in the processing tank, and a film original sheet. And a transfer device that is immersed in the processing liquid in the processing tank.
The specific processing tank 1 is used as at least one of the processing tanks of the manufacturing apparatus.

FIG. 2 is a reference diagram showing a polarizing film manufacturing apparatus 2. The arrow in the figure indicates the traveling direction (conveying direction) of the original film 3.
The manufacturing apparatus 2 includes a front roll unit 28 around which the raw film 3 to be processed is wound, and a rear roll unit 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 processing tanks are arranged between the front roll unit 28 and the rear roll unit 29. As the treatment tank, a swelling treatment tank containing a swelling treatment liquid, a dyeing treatment tank containing a dyeing treatment liquid, a crosslinking treatment tank containing a crosslinking treatment liquid, a stretching treatment bath containing a stretching treatment liquid, and a washing treatment liquid are contained. And a cleaning treatment tank for cleaning.
The manufacturing apparatus 2 of the illustrated example has a swelling treatment tank 1A, a dyeing treatment tank 1B, a crosslinking treatment tank 1C, a stretching treatment tank 1D, and a cleaning treatment tank 1E in this order from the front roll unit 28 to the rear roll unit 29.

The specific treatment tank 1 is used in at least one selected from the swelling treatment tank 1A, the dyeing treatment tank 1B, the crosslinking treatment tank 1C, the stretching treatment tank 1D, and the cleaning treatment tank 1E, and preferably two or more. Used. The specific treatment tank 1 may be used for all the treatment tanks included in the manufacturing apparatus 2.
The specific treatment tank 1 is preferably used at least in a treatment tank that stores 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 corrode the metal bath main body 11, and therefore, by using the specific treatment bath 1, even when such a treatment liquid is stored, the bath main body Erosion of 11 can be effectively prevented.
As the treatment tank for containing the treatment liquid containing at least one of potassium iodide (iodine compound) and boric acid (boron compound), as described later, a swelling treatment tank 1A, a dyeing treatment tank 1B, a crosslinking treatment tank 1C, and a stretching treatment tank. A treatment tank 1D, an adjustment treatment tank, and the like are included.
From the viewpoint of the components of the treatment liquid, the specific treatment tank 1 is preferably used in at least the stretching treatment tank 1D, and more preferably used in at least 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 as 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 that stores 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 bath body 11 may thermally expand to cause cracks in the coating layer 12 or partial peeling of the coating layer 12. Since 12 follows the thermal expansion of the tank main body 11, even when containing such a treatment liquid, cracking or peeling of the coating layer 12 can be effectively prevented.
Examples of the treatment liquid for controlling the liquid temperature to 40° C. or more when producing the polarizing film include a dyeing treatment liquid, a crosslinking treatment liquid, and a stretching treatment liquid as described below.
From the viewpoint of the temperature of the treatment liquid, the specific treatment tank 1 is preferably used in at least the stretching treatment tank 1D, and more preferably used in at least 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 as 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 both composed of a 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 is composed of a processing tank. However, this is merely an example, and the specific treatment tank 1 can be used at an appropriate place.

Further, in order to convey the raw film film 3 from the front roll unit 28 to the rear roll unit 29 after passing through the processing tank, a transport device for the raw film film 3 is provided between the front roll unit 28 and the rear roll unit 29. Is provided.
The transport device drives a plurality of nip rollers 24, a plurality of guide rollers 25, and at least one roller selected from the nip rollers 24 and the guide rollers 25 in order to transport the film original fabric 3, such as a motor. (Not shown).
Several guide rollers 25 are arranged in each processing tank. The original film film 3 is conveyed from the front roll part 28 to the rear roll part 29 by the nip roller 24 and the guide roller 25 while passing through each processing tank and being immersed in the processing liquid.

<Film source>
The unprocessed film original 3 is wound around the front roll portion 28.
The film original fabric 3 has a long strip shape. The long strip shape means 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 in the longitudinal direction of the long film raw film 3 is, for example, 10 m or more, preferably 50 m or more.
The raw film 3 is not particularly limited, but a film containing a hydrophilic polymer film (for example, a polyvinyl alcohol-based film) is preferably used because it is excellent in dyeability with a dichroic substance, and more preferably For, 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 a thin film having a thickness of about several μm.

The hydrophilic polymer film is not particularly limited, and a conventionally known film can be used. Specifically, as the hydrophilic polymer film, for example, polyvinyl alcohol (PVA)-based film, partially formalized PVA-based film, polyethylene terephthalate (PET) film, ethylene/vinyl acetate copolymer-based film, and partial saponification thereof Examples include films. In addition to these, a polyene oriented film such as a dehydrated product of PVA or a dehydrochlorinated product of polyvinyl chloride, a stretch-oriented polyvinylene-based film, or the like can also be used. Among these, the PVA-based polymer film is preferable because it is particularly excellent in dyeability with a dichroic substance.
Examples of the raw material polymer for the PVA-based polymer film include a polymer obtained by saponifying vinyl acetate after polymerization, and a small amount of a copolymerizable monomer such as unsaturated carboxylic acid or unsaturated sulfonic acid with vinyl acetate. Polymers, and the like. The degree of polymerization of the PVA-based polymer is not particularly limited, but is preferably 500 to 10000, more preferably 1000 to 6000 in view of solubility in water. 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 raw material film 3 before processing is not particularly limited, but is, for example, 15 μm to 110 μm. In addition, you may use the film original fabric 3 which has the thickness before a process of 38 micrometers-110 micrometers or 50 micrometers-100 micrometers.

<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 original 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 in parallel in the traveling direction of the original film 3 (not shown).
The swelling treatment liquid 41 contained in the swelling treatment tank 1A is a treatment liquid for swelling the unprocessed film original fabric 3.
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, its concentration is preferably 5% by weight or less, and when an iodine compound such as potassium iodide is added, its 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 processing tank 1B dyes the film original 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 in parallel in the traveling direction of the original film 3 (not shown).
The dyeing treatment liquid 42 is a treatment liquid for dyeing the original film 3.
Examples of the dyeing treatment liquid 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 obtained by dissolving iodine 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 treatment liquid 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. % To 5% by weight is more preferable.
Furthermore, in order to further improve the dyeing efficiency, it is preferable to add an iodine compound to the dyeing treatment liquid. The 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 the 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 treatment liquid 42 contains iodine and an iodine compound, iodine may be the main component of the dyeing treatment liquid (the main component is a component with a large content (weight basis)), or the iodine compound is the dyeing treatment liquid. May be the main component of. Usually, a dyeing treatment liquid containing an iodine compound in a larger amount than iodine is used.

<Cross-linking treatment tank>
The cross-linking treatment tank 1C is a treatment tank containing the cross-linking treatment liquid 43. The crosslinking treatment tank 1C crosslinks the dyed film original 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 juxtaposed in the traveling direction of the original film 3 (not shown).
The cross-linking treatment liquid 43 is a treatment liquid for cross-linking the raw film 3 on which the dichroic substance is adsorbed.
As the crosslinking 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. Of these, boric acid is preferably used. The concentration of the boron compound in the crosslinking treatment solution 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 more preferable. If necessary, glyoxal, glutaraldehyde, or the like may be added to the crosslinking treatment liquid.
Furthermore, it is preferable to add an iodine compound to the crosslinking treatment liquid because a polarizing film having uniform optical properties can be obtained. 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 weight 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. , 1:0.5 to 1:3.5, more preferably 1:1 to 1:2.5.
When the crosslinking 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 original film 3.
In the illustrated example, only one stretching treatment tank 1D is installed, but two or more stretching treatment tanks 1D may be arranged in parallel in the traveling direction of the raw film 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 an iodine compound in a larger amount than the boron compound is used.
For example, the stretching treatment liquid 44 may be a solution containing about 5% by weight potassium iodide and about 4% by weight boric acid.

<Cleaning tank>
The cleaning processing tank 1E is a processing tank in which the cleaning processing liquid 45 is stored. The cleaning treatment tank 1E cleans the stretched film original 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 in parallel in the moving direction of the original film 3 (not shown).
The cleaning treatment liquid 45 is a treatment liquid for cleaning the treatment liquid such as the dyeing treatment liquid or the cross-linking treatment liquid attached to the original film 3.
As the cleaning treatment liquid, typically, water such as ion-exchanged water, distilled water, and pure water is used.

<Other>
A drying device 21 is provided between the cleaning treatment tank 1E and the rear roll unit 29. The drying device 21 is provided to dry the film original fabric 3.
In the illustrated example, the manufacturing apparatus 2 has a swelling treatment tank 1A, a dyeing treatment tank 1B, a crosslinking treatment tank 1C, a stretching treatment tank 1D, and a cleaning treatment tank 1E, but one or two of these treatment tanks are used. It does not have to have. For example, the manufacturing apparatus 2 may have a swelling treatment tank 1A, a dyeing treatment tank 1B, a crosslinking treatment tank 1C, and a cleaning treatment tank 1E as the treatment tanks, or as the treatment tanks, the swelling treatment tank 1A, the dyeing treatment tank. It may have a tank 1B and a crosslinking treatment tank 1C.
Moreover, the manufacturing apparatus 2 may further include an adjustment processing tank (not shown).
The adjustment processing tank is a processing tank in which the adjustment processing liquid is stored. Although not shown in FIG. 2, this adjustment processing tank is provided between the crosslinking processing tank 1C and the stretching processing tank 1D, or between the stretching processing tank 1D and the cleaning processing tank 1E.
The adjustment treatment liquid is a solution for adjusting the hue of the film, and a solution containing an iodine compound as an active ingredient can be used. For example, a solution prepared by dissolving an iodine compound in a solvent can be used as the adjustment treatment liquid. The concentration of the iodine compound in the conditioning 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.

<Production method of polarizing film>
With reference to FIG. 2, the unprocessed film original fabric 3 is fed from the front roll unit 28, and the original film film 3 is conveyed to the swelling treatment tank 1A by a conveying device.
The original film film 3 is swollen by immersing the original film film 3 in the swelling treatment liquid 41 while the original film film 3 is being conveyed 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 original film 3 in the swelling treatment liquid 41 is not particularly limited, but is, for example, 5 seconds to 300 seconds, and preferably 8 seconds to 240 seconds.

The film raw fabric 3 after the swelling step is pulled out from the swelling treatment bath 1A, and the film raw fabric 3 is conveyed to the dyeing treatment bath 1B.
By dipping the film original fabric 3 in the dyeing treatment liquid 42 while conveying the film original fabric 3 by the guide roller 25 in the dyeing treatment tank 1B, the film original fabric 3 is dyed with the dichroic substance.
The temperature of the dyeing treatment liquid 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 original film 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 process is pulled out from the dyeing treatment tank 1B, and the film raw fabric 3 is conveyed to the crosslinking treatment tank 1C.
By dipping the original film 3 in the crosslinking treatment liquid 43 while the original film 3 is conveyed by the guide roller 25 of the crosslinking tank 1C, the dichroic substance of the original film 3 is crosslinked.
The temperature of the crosslinking 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 original film 3 in the crosslinking 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 crosslinking step is pulled out from the crosslinking treatment tank 1C, and the film raw fabric 3 is conveyed to the stretching treatment tank 1D.
In the stretching treatment liquid 44 in the stretching treatment tank 1D, the film roll 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 stretching ratio can be appropriately set according to the purpose, but the total stretching ratio is, for example, 2 times to 7 times, preferably 4.5 times to 6.8 times. The total draw ratio means the final draw ratio of the original film 3. The original film film 3 may be stretched in at least one tank selected from the swelling tank 1A, the dyeing tank 1B and the crosslinking tank 1C, or may be stretched only in the drawing tank 1D. It may have been done. The total draw ratio means the draw ratio when it is drawn only in the draw treatment tank 1D, and the total draw ratio when it is drawn also in the swelling treatment tank 1A and the like.

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

The film raw fabric 3 after the stretching process or the adjusting process is conveyed to the cleaning treatment tank 1E and immersed in the cleaning treatment liquid 45, whereby the film raw fabric 3 is cleaned.
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 film original fabric 3 after the said washing process with the drying device 21 as needed. The manufactured polarizing film 5 is wound around the rear roll portion 29.

In the treatment tank 1 for producing a polarizing film of the present invention, the coating layer 12 having an elongation of 150% or more is provided on the inner surface of the metal tank body 11, so that the tank body 11 is eroded by the treatment liquid. Can be prevented. More 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 the tank body 11 can be prevented from eroding. Further, when the processing tank 1 is used for a long period of time, the tank body 11 made of metal is deformed, and in particular, when a processing liquid having a relatively high temperature (for example, 40° C. or higher) is contained in the processing tank, the tank body 11 is configured The metal that undergoes thermal expansion easily deforms. 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. Following this, the coating layer 12 can be stretched flexibly. Therefore, the coating layer 12 is less likely to be cracked or peeled off due to the deformation of the tank body 11, and the tank body 11 can be prevented from being eroded by the processing liquid.
Conventionally, when cracks or peeling occur in a treatment tank for producing a polarizing film, it is considered that the deterioration is due to aged deterioration, and the treatment tank is repaired or replaced. In this respect, the present inventors searched for the cause of cracking or peeling of the conventional coating layer, and found that it was due to 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 that can effectively suppress the occurrence of cracks in the coating layer by combining the tank material with the tank material that easily follows expansion (deformation) of the tank body. Is.

[Uses of polarizing film, etc.]
The polarizing film of the present invention can be used, for example, in lenses such as sunglasses, light control windows, and image display devices such as liquid crystal displays.
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, the present invention will be described in more detail by describing Examples and Comparative Examples. However, the present invention is not limited to the following examples.

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

[Coating material]
・Polyurea resin (1)
Product name “Nukote ST” (manufacturer: manufactured by NUKOTE company, sold by: Kanamori Tohei Trading Co., Ltd.). The growth rate is 400%.
・Polyurea resin (2)
Product name "Nukote HT" (manufacturer: manufactured by NUKOTE Co., Ltd., distributor: Kanamori Tohei Co., Ltd.). The growth rate is 375%.
・Polyurea resin (3)
Product name "Nukote CG" (manufacturer: manufactured by NUKOTE Co., Ltd., distributor: Tohei Kanemori Corporation). The growth rate is 175%.
・Polyurea resin (4)
Product name "Nukote XT-Plus" (manufacturer: manufactured by NUKOTE Co., Ltd., sold by: Kanamori Tohei Co., Ltd.). The growth rate is 50%.
The polyurea resins (1) to (3) are a two-component curing type of agent A containing isocyanate as a main component and agent B containing an amine compound as a main component.

-Butyl rubber Trade 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 resin)
Product name "Neopol 8411LH" (Manufacturer: Nippon Yupica Co., Ltd.). The growth rate is 2%.
・Ceramic/metal composite polymer Product name “Nukote ChemiShield” (Manufacturer: NUKOTE Co., Ltd., Distributor: Kanemori Tohei Co., Ltd.). The growth rate is 5%.
The elongation percentages of the polyurea resins (1) to (4) are measured by a tensile test according to ASTM-D412. The elongation percentage of butyl rubber is measured by a tensile test according to JIS K6251:2017. The elongation of the vinyl chloride resin is measured by a tensile test according to ASTM-D638. The elongation percentage of FRP (fiber reinforced resin) is measured by a tensile test according to JIS K7161-1:2014. The elongation percentage of the ceramic-metal composite polymer is measured by a tensile test according to ASTM-D638.

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

[Example 2]
A sample piece of Example 2 was produced 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 produced 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 materials shown in Table 1 were used instead of the polyurea resin (1).

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

1 Treatment Tank 1A Swelling Treatment Tank 1B Dyeing Treatment Tank 1C Crosslinking Treatment Tank 1D Stretching Treatment Tank 1E Cleaning Treatment Tank 11 Tank Body 12 Coating Layer 2 Polarizing Film Manufacturing Equipment 3 Film Raw Fabric

Claims (10)

In a processing tank for containing a processing liquid used in producing a polarizing film from a film original film,
The processing tank has a tank body made of metal, and a coating layer that covers 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 manufacturing a polarizing film according to claim 1, wherein the coating layer is formed of a coating material having an elongation of 350% to 450%. The processing bath for producing a polarizing film according to claim 1, wherein the thermal expansion coefficient of the bath main body is 10×10 ⁻⁶ /° C. to 24×10 ⁻⁶ /° C. 4. The processing tank for manufacturing a polarizing film according to claim 1, wherein the coating material contains a polyurea resin. The processing tank for manufacturing a polarizing film according to claim 1, wherein the coating layer has a thickness of 1.0 mm or more. The processing tank for manufacturing a polarizing film according to claim 1, wherein the tank body is made of stainless steel. The treatment tank for producing a polarizing film according to any one of claims 1 to 6, which is used in at least one of a cross-linking treatment tank for crosslinking a raw film and a stretching treatment tank for stretching a raw film. A processing tank according to any one of claims 1 to 7,
A treatment liquid contained in the treatment tank,
An apparatus for producing a polarizing film, comprising: a transporting device that transports a raw film and immerses it in the treatment liquid in the treatment tank. The polarizing film manufacturing apparatus according to claim 8, wherein the treatment liquid contains at least one of an iodine compound and a boron compound. The polarizing film manufacturing apparatus according to claim 8 or 9, wherein the temperature of the treatment liquid is 40°C or higher.

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