JP2023148288A - Polarizer and polarizer manufacturing method - Google Patents

Abstract

An object of the present invention is to provide a polarizer in which decolorization is suppressed. A polarizer according to an embodiment of the present invention includes iodine, is composed of a resin film having a first principal surface and a second principal surface facing each other, and includes a phenolic compound. The phenolic compound may be present on at least the first main surface of the resin film. [Selection diagram] Figure 1

Description

The present invention relates to a polarizer and a method for manufacturing a polarizer.

Image display devices represented by liquid crystal display devices and electroluminescent (EL) display devices (eg, organic EL display devices, inorganic EL display devices) are rapidly becoming popular. A polarizing plate is typically used in an image display panel mounted on an image display device. Practically, a polarizing plate with a retardation layer that integrates a polarizing plate and a retardation plate is widely used (for example, Patent Document 1). However, the polarizing performance of the polarizer included in the polarizing plate may deteriorate when the image display device is used for a long time or placed in a harsh environment (for example, a high temperature, high humidity environment). For example, decolorization (color loss) is one of the causes of deterioration in polarization performance.

Patent No. 3325560

The present invention was made to solve the above problems, and its main purpose is to provide a polarizer in which decolorization is suppressed.

A polarizer according to an embodiment of the present invention includes iodine, is composed of a resin film having a first principal surface and a second principal surface facing each other, and includes a phenolic compound.
In one embodiment, the phenolic compound includes catechol.
In one embodiment, the phenolic compound is present on at least the first main surface of the resin film.
In one embodiment, the contact angle of the first principal surface is 85° or less.
In one embodiment, the thickness of the polarizer is 8 μm or less.
According to another aspect of the present invention, a method for manufacturing the above polarizer is provided. The method for manufacturing a polarizer according to the first embodiment includes immersing a resin film containing iodine in a liquid containing a phenolic compound.
The method for manufacturing a polarizer according to the second embodiment includes coating a liquid containing a phenolic compound on at least the first main surface of a resin film containing iodine and having a first main surface and a second main surface facing each other. including doing.
In one embodiment, the manufacturing method includes surface-modifying the surface to be coated before the coating.
In one embodiment, the surface modification is performed by at least one of corona treatment or plasma treatment.
A polarizing plate according to another embodiment of the present invention includes the above polarizer and at least one of a protective layer and a retardation layer.

According to the embodiments of the present invention, a polarizer in which decolorization is suppressed can be obtained.

FIG. 1 is a schematic cross-sectional view of a polarizer according to one embodiment of the invention. 1 is a schematic cross-sectional view showing the general structure of a laminate used for manufacturing a polarizer in one embodiment of the present invention. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. It is a graph showing the evaluation results of decolorization.

Embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
Definitions of terms and symbols used herein are as follows.
(1) Refractive index (nx, ny, nz)
"nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., slow axis direction), and "ny" is the direction perpendicular to the slow axis in the plane (i.e., fast axis direction) "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is an in-plane retardation measured with light having a wavelength of λnm at 23°C. For example, "Re(550)" is an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is determined by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Phase difference in thickness direction (Rth)
"Rth (λ)" is a retardation in the thickness direction measured with light having a wavelength of λ nm at 23°C. For example, "Rth (550)" is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is determined by the formula: Rth(λ)=(nx−nz)×d, where d (nm) is the thickness of the layer (film).
(4) Nz coefficient The Nz coefficient is determined by Nz=Rth/Re.
(5) Angle When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Therefore, for example, "45°" means ±45°.

A. Polarizer FIG. 1 is a schematic cross-sectional view of a polarizer according to one embodiment of the invention. Note that in FIG. 1, the cross section of the polarizer is not hatched to make the diagram easier to read. The polarizer 10 is composed of a resin film having a first principal surface 10a and a second principal surface 10b facing each other. The polarizers 10 are connected via end faces 10c.

The polarizer 10 is made of a resin film containing iodine. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or a partially saponified ethylene/vinyl acetate copolymer film is used.

The thickness of the polarizer 10 is preferably 15 μm or less, may be 12 μm or less, may be 10 μm or less, or may be 8 μm or less. On the other hand, the thickness of the polarizer is preferably 1 μm or more.

The polarizer 10 preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance (Ts) of the polarizer 10 is preferably 35% or more, may be 37% or more, may be 40% or more, or may be 42% or more. On the other hand, the single transmittance of the polarizer 10 is, for example, 45% or less. The degree of polarization (P) of the polarizer 10 is preferably 98% or more, may be 99% or more, or may be 99.99% or more. On the other hand, the degree of polarization of the polarizer 10 is, for example, 99.996% or less.

The above-mentioned single transmittance is typically a Y value measured using an ultraviolet-visible spectrophotometer and subjected to visibility correction. The degree of polarization is typically determined by the following formula based on parallel transmittance Tp and cross transmittance Tc measured using an ultraviolet-visible spectrophotometer and corrected for visibility.
Degree of polarization (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 ×100

Polarizer 10 contains a phenolic compound. Examples of the phenolic compound include phenols such as phenol and polyhydric phenol, naphthols such as naphthol and dihydroxynaphthalene, and anthrols such as anthrol. Examples of polyhydric phenols include catechol, resorcinol, hydroquinone, pyrogallol, 1,2,4-benzenetriol, and phloroglucinol. These may be used alone or in combination. By including a phenolic compound, a polarizer with suppressed decolorization can be obtained. Specifically, it is possible to obtain a polarizer in which decolorization of the entire polarizer and decolorization of the ends of the polarizer are suppressed.

The phenolic compound may exist uniformly throughout the polarizer 10, or may be unevenly distributed in the polarizer 10. In the latter case, the phenolic compound may be present on at least one main surface (the first main surface 10a), and may be present on each of the first main surface 10a and the second main surface 10b, for example. In one embodiment, a phenolic compound is selectively present on one main surface, for example, from the viewpoint of simplifying the manufacturing process. In another embodiment, a phenolic compound is present on either main surface from the viewpoint of effectively suppressing decolorization. The phenolic compound may also exist on the end surface 10c.

The area where the phenolic compound exists on the first principal surface 10a is not particularly limited. Specifically, it is sufficient that it exists in at least a portion of the first main surface 10a, but it is preferable that it exists over the entire first main surface 10a.

The contact angle of the first main surface 10a (the main surface where the phenolic compound is present) is preferably 85° or less, more preferably 75° or less, still more preferably 70° or less, and particularly preferably 65° or less. ° or less. On the other hand, the contact angle of the first main surface 10a (the main surface where the phenolic compound is present) is, for example, 60° or more. When the phenolic compound is selectively present on the first main surface 10a, the contact angle on the second main surface 10b may be, for example, more than 85°, 87° or more, or 90° or more. . The difference between the contact angle of the second main surface 10b and the contact angle of the first main surface 10a is, for example, 5° or more, may be 10° or more, may be 15° or more, and may be 20° or more. It may be more than °.

B-1. Manufacturing method 1
The above polarizer can be obtained, for example, by immersing a resin film containing iodine in a liquid containing a phenolic compound. Specifically, it can be obtained by immersing a resin film that has been stretched and dyed with iodine in a liquid containing a phenolic compound. A resin film that has been stretched and dyed with iodine is a laminate or a resin film (typically a PVA resin layer) obtained by forming a resin layer (typically a PVA resin layer) on a resin base material. (resin film) by stretching and dyeing with iodine. Hereinafter, details of the method for producing a resin film subjected to stretching and dyeing treatment with iodine will be explained using a case where a laminate is used as an example.

The above-mentioned laminate is produced, for example, by applying a coating liquid containing a PVA-based resin and a halide onto a thermoplastic resin base material and drying it to form a PVA-based resin layer. The thickness of the thermoplastic resin base material is preferably 20 μm to 300 μm, more preferably 50 μm to 200 μm. If it is less than 20 μm, it may be difficult to form a PVA-based resin layer. If it exceeds 300 μm, for example, in underwater stretching described below, it may take time for the thermoplastic resin base material to absorb water, and an excessive load may be required for stretching.

The water absorption rate of the thermoplastic resin base material is preferably 0.2% or more, more preferably 0.3% or more. Such a thermoplastic resin base material absorbs water and can be plasticized by the water acting as a plasticizer. As a result, the stretching stress can be significantly reduced and the film can be stretched to a high magnification. On the other hand, the water absorption rate of the thermoplastic resin base material is preferably 3.0% or less, more preferably 1.0% or less. According to such a water absorption rate, it is possible to prevent problems such as a significant decrease in the dimensional stability of the thermoplastic resin base material during production and deterioration of the quality of the obtained polarizer. Furthermore, it is possible to prevent the thermoplastic resin base material from breaking or the PVA resin layer from peeling off during underwater stretching. The water absorption rate of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material. Note that the water absorption rate is a value determined according to JIS K 7209.

The glass transition temperature (Tg) of the thermoplastic resin base material is preferably 120°C or lower. By using such a thermoplastic resin base material, it is possible to sufficiently ensure the stretchability of the laminate while suppressing crystallization of the PVA-based resin layer. Furthermore, in consideration of plasticizing the thermoplastic resin base material with water and performing underwater stretching well, Tg is more preferably 100°C or less, and even more preferably 90°C or less. On the other hand, the Tg of the thermoplastic resin base material is preferably 60°C or higher. According to such a Tg, defects such as deformation of the thermoplastic resin base material (e.g., occurrence of unevenness, sagging, wrinkles, etc.) when applying and drying the above-mentioned coating solution can be prevented, and good lamination can be achieved. body can be created. Further, the resin layer can be stretched well at a suitable temperature (for example, about 60° C.). The Tg of the thermoplastic resin base material can be adjusted, for example, by introducing a modifying group into the constituent material and heating it using a crystallizing material. Note that the glass transition temperature (Tg) is a value determined according to JIS K 7121.

Any suitable thermoplastic resin may be employed as the constituent material of the thermoplastic resin base material. Examples of thermoplastic resins include ester resins such as polyethylene terephthalate resins, cycloolefin resins such as norbornene resins, olefin resins such as polypropylene, polyamide resins, polycarbonate resins, and copolymer resins thereof. Can be mentioned. Among these, norbornene resins and amorphous polyethylene terephthalate resins are preferred.

In one embodiment, an amorphous (non-crystallized) polyethylene terephthalate resin is preferably used. Among these, amorphous (hard to crystallize) polyethylene terephthalate resin is particularly preferably used. Specific examples of the amorphous polyethylene terephthalate resin include copolymers further containing isophthalic acid and/or cyclohexane dicarboxylic acid as a dicarboxylic acid, and copolymers further containing cyclohexanedimethanol or diethylene glycol as a glycol.

In another embodiment, a polyethylene terephthalate resin having isophthalic acid units is preferably used. This is because it has extremely excellent stretchability and can suppress crystallization during stretching. This is thought to be due to the fact that the introduction of the isophthalic acid unit imparts a large bend to the main chain. Polyethylene terephthalate resin has a terephthalic acid unit and an ethylene glycol unit. The content of the isophthalic acid unit is preferably 0.1 mol% or more, more preferably 1.0 mol% or more, based on the total of all repeating units. This is because a thermoplastic resin base material with extremely excellent stretchability can be obtained. On the other hand, the content of isophthalic acid units is preferably 20 mol% or less, more preferably 10 mol% or less, based on the total of all repeating units. This is because the degree of crystallinity can be favorably increased in the drying process described below.

The thermoplastic resin base material may be stretched in advance (eg, before forming the PVA-based resin layer). In one embodiment, the elongated thermoplastic resin base material is stretched in the lateral direction. The lateral direction is preferably a direction perpendicular to the stretching direction of the laminate described below. In addition, in this specification, "orthogonal" also includes a case where they are substantially orthogonal. Here, "substantially orthogonal" includes a case where the angle is 90°±5.0°, preferably 90°±3.0°, and more preferably 90°±1.0°. The stretching temperature of the thermoplastic resin base material is preferably Tg-10°C to Tg+50°C with respect to the glass transition temperature (Tg) of the thermoplastic resin base material. The stretching ratio of the thermoplastic resin base material is preferably 1.5 times to 3.0 times. Any suitable method may be employed as a method for stretching the thermoplastic resin base material. Specifically, fixed end stretching or free end stretching may be used. The stretching method may be a dry method or a wet method. Stretching may be performed in one step or in multiple steps. When performing multi-stage stretching, the stretching ratio is the product of the stretching ratios of each stage.

The coating liquid is typically a solution in which a PVA-based resin and a halide are dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. These can be used alone or in combination of two or more. Among these, water is preferred. The content of the PVA resin in the coating liquid is preferably 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. According to such a range, a uniform coating film that adheres to the thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight based on 100 parts by weight of the PVA resin.

Examples of the PVA resin include polyvinyl alcohol and ethylene-vinyl alcohol copolymer. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. Ethylene-vinyl alcohol copolymer can be obtained by saponifying ethylene-vinyl acetate copolymer. The degree of saponification of the PVA resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, more preferably 99.0 mol% to 99.93 mol%. It is. By using a PVA resin having such a degree of saponification, a polarizer with excellent durability can be obtained. If the degree of saponification is too high, there is a risk of gelation. Note that the degree of saponification can be determined according to JIS K 6726-1994.

The average degree of polymerization of the PVA resin is usually 1,000 to 10,000, preferably 1,200 to 4,500, and more preferably 1,500 to 4,300. Note that the average degree of polymerization can be determined according to JIS K 6726-1994.

Any suitable halide may be employed as the halide. Examples include iodides such as potassium iodide, sodium iodide, and lithium iodide, and chlorides such as sodium chloride. Among these, potassium iodide is preferred. By using a halide, a polarizer with excellent optical properties can be obtained. Specifically, the crystallization of the PVA-based resin after the aerial auxiliary stretching described below is promoted, and the orientation of polyvinyl alcohol molecules is disturbed and the orientation is reduced in subsequent wet treatments (e.g., dyeing and underwater stretching described below). can be suppressed, and a polarizer having excellent optical properties can be obtained.

In preparing the coating liquid, it is preferable to mix 5 parts by weight to 20 parts by weight of a halide, more preferably 10 parts by weight to 15 parts by weight, per 100 parts by weight of PVA-based resin. Specifically, the content of halide in the resulting PVA resin layer is preferably 5 parts by weight to 20 parts by weight, more preferably 10 parts by weight to 15 parts by weight, based on 100 parts by weight of PVA resin. It is. If the amount of halide relative to the PVA-based resin is large, for example, the halide may bleed out and the resulting polarizer may become cloudy.

Additives may be added to the coating liquid. Examples of additives include plasticizers and surfactants. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These are used, for example, for the purpose of improving the uniformity, dyeability, and stretchability of the resulting PVA-based resin layer.

Examples of methods for applying the above coating liquid include roll coating, spin coating, wire bar coating, dip coating, die coating, curtain coating, spray coating, and knife coating (comma coating, etc.). It will be done. The coating and drying temperature of the coating liquid is preferably 50°C or higher.

The thickness of the PVA resin layer is preferably 3 μm to 40 μm, more preferably 3 μm to 20 μm.

Before forming the PVA-based resin layer, the thermoplastic resin base material may be subjected to surface treatment (for example, corona treatment, etc.), or an easily adhesive layer may be formed on the thermoplastic resin base material. By performing such a treatment, the adhesion between the thermoplastic resin base material and the PVA resin layer can be improved.

The above-mentioned stretching is preferably carried out by subjecting the laminate to dry stretching (in-air auxiliary stretching) and then underwater stretching. By auxiliary stretching, the thermoplastic resin base material can be stretched while suppressing crystallization, and this solves the problem that the stretchability is reduced due to excessive crystallization of the thermoplastic resin base material during stretching in boric acid water. The laminate can be stretched to a higher magnification. Furthermore, when a thermoplastic resin base material is used, the coating temperature may be set low, which may cause a problem that crystallization of the PVA-based resin becomes relatively low and sufficient optical properties cannot be obtained. On the other hand, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be improved even when a thermoplastic resin is used. Further, by increasing the orientation of the PVA resin in advance, problems such as a decrease in orientation and dissolution of the PVA resin can be prevented during subsequent wet processing. In this way, a polarizer with excellent optical properties can be obtained.

The method of aerial auxiliary stretching may be fixed-end stretching (e.g., stretching using a tenter stretching machine) or free-end stretching (e.g., uniaxial stretching by passing the laminate between rolls with different circumferential speeds). . Preferably, free end stretching is employed. For example, heating roll stretching may be employed, in which the laminate is stretched in the longitudinal direction by a difference in circumferential speed between heating rolls. In one embodiment, the aerial assisted stretching includes a zone stretching step in a thermal space (zone) and a heated roll stretching step. Although the order of the zone stretching step and the heating roll stretching step is not limited, for example, the zone stretching step and the heating roll stretching step are performed in this order. In another embodiment, in a tenter stretching machine, the ends of the film are held and the film is stretched by widening the distance between the tenters in the machine direction (the widening of the distance between the tenters becomes the stretching ratio). At this time, the tenter distance in the width direction (perpendicular to the flow direction) is preferably set to be closer to the free end stretching than the stretching ratio in the flow direction. In the case of free end stretching, the shrinkage rate in the width direction is calculated by the formula: shrinkage rate in the width direction=(1/stretching ratio) ^1/2 .

The stretching ratio of the aerial auxiliary stretching is preferably 2.0 times to 3.5 times. Aerial assisted stretching may be performed in one step or in multiple steps. In the case of multi-stage stretching, the stretching ratio is the product of the stretching ratios of each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching described below.

The stretching temperature of the in-air auxiliary stretching is set to any appropriate value depending on, for example, the thermoplastic resin base material used, the stretching method, and the like. The stretching temperature is preferably at least the glass transition temperature (Tg) of the thermoplastic resin base material, more preferably at least Tg+10°C, even more preferably at least Tg+15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin and to suppress defects caused by the crystallization (for example, preventing the orientation of the PVA-based resin layer due to stretching). can.

The above-mentioned underwater stretching is typically performed by immersing the laminate in a stretching bath. According to underwater stretching, it is possible to stretch the PVA resin layer at a temperature lower than the glass transition temperature (typically about 80° C.) of the thermoplastic resin base material and the PVA resin layer, and the PVA resin layer can be stretched at a temperature lower than the glass transition temperature (typically about 80° C.). It is possible to stretch to a high magnification while suppressing the stretching. As a result, a polarizer with excellent optical properties can be obtained.

The underwater stretching method may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching by passing the laminate between rolls having different circumferential speeds). Preferably, free end stretching is employed. The laminate may be stretched in one step or in multiple steps. When performing multi-stage stretching, the stretching ratio of the laminate described below is the product of the stretching ratios of each stage.

Stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, it is possible to impart rigidity to the PVA-based resin layer to withstand tension applied during stretching, and water resistance that does not dissolve in water. Specifically, boric acid can generate a tetrahydroxyborate anion in an aqueous solution and crosslink with the PVA-based resin through hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer, and it can be stretched well, making it possible to obtain a polarizer having excellent optical properties.

The aqueous boric acid solution is preferably obtained by dissolving boric acid and/or a borate salt in water, which is a solvent. The boric acid concentration is preferably 1 to 10 parts by weight, more preferably 2.5 to 6 parts by weight, even more preferably 3 to 5 parts by weight, based on 100 parts by weight of water. It is. By setting the boric acid concentration to 1 part by weight or more, dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizer with higher characteristics can be manufactured. In addition to boric acid or a borate salt, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, etc. in a solvent can also be used.

Preferably, iodide is added to the stretching bath (boric acid aqueous solution). By blending iodide, it is possible to suppress elution of iodine adsorbed to the PVA-based resin layer. Examples of iodides include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. can be mentioned. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight, based on 100 parts by weight of water.

The stretching temperature (the liquid temperature of the stretching bath) is preferably 40°C or higher, more preferably 60°C or higher. At such a temperature, it is possible to stretch to a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin base material is preferably 60° C. or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40° C., there is a possibility that the stretching cannot be performed satisfactorily even if the plasticization of the thermoplastic resin base material by water is taken into consideration. On the other hand, the stretching temperature is, for example, 70°C or lower, preferably 67°C or lower, and more preferably 65°C or lower. As the stretching temperature becomes higher, the solubility of the PVA-based resin layer becomes higher, and there is a possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by underwater stretching is preferably 1.5 times or more, more preferably 3.0 times or more. The total stretching ratio of the laminate (stretching ratio combining aerial auxiliary stretching and underwater stretching) is preferably 5.0 times or more, more preferably 5.5 times or more, relative to the original length of the laminate. Yes, and more preferably 6.0 times or more. By achieving such a high stretching ratio, a polarizer with extremely excellent optical properties can be manufactured. Such a high stretching ratio can be achieved by employing an underwater stretching method (boric acid underwater stretching).

The above-mentioned dyeing is typically performed by adsorbing iodine to the PVA-based resin layer. Iodine adsorption methods include, for example, immersing a PVA resin layer (laminate) in a dyeing solution containing iodine, coating the PVA resin layer with the dyeing solution, and applying the dyeing solution to the PVA resin layer. The method of spraying is mentioned. Preferably, the method involves immersing the laminate in a dyeing solution (dyeing bath). This is because iodine can be adsorbed well.

The staining solution is preferably an aqueous iodine solution. The amount of iodine blended is preferably 0.05 part by weight to 0.5 part by weight per 100 parts by weight of water. In order to increase the solubility of iodine in water, it is preferable to add iodide to the iodine aqueous solution. Specific examples of iodides are as described above. Preferably potassium iodide is used. The amount of iodide to be blended is preferably 0.1 parts by weight to 10 parts by weight, more preferably 0.3 parts by weight to 5 parts by weight, based on 100 parts by weight of water. The temperature of the dyeing solution during dyeing is preferably 20° C. to 50° C. in order to suppress dissolution of the PVA resin. When the PVA resin layer is immersed in the dyeing liquid, the immersion time is preferably 5 seconds to 5 minutes, more preferably 30 seconds to 90 seconds, in order to ensure the transmittance of the PVA resin layer.

The dyeing conditions (concentration, liquid temperature, immersion time) are set, for example, so that the single transmittance of the final polarizer is 42.0% or more and the degree of polarization is 99.98% or more. can do. As for such staining conditions, for example, it is preferable that the content ratio of iodine and potassium iodide in the iodine aqueous solution that is the staining solution is 1:5 to 1:20, more preferably 1:5 to 1. :10.

When dyeing is performed continuously after immersing the laminate in a treatment bath containing boric acid (for example, insolubilization treatment described below), boric acid mixes into the dyeing bath and the boric acid concentration in the dyeing bath changes. Staining properties may become unstable. In order to suppress such destabilization of dyeability, the concentration of boric acid in the dyeing bath is adjusted to preferably 4 parts by weight or less, more preferably 2 parts by weight or less, based on 100 parts by weight of water. be done. On the other hand, the concentration of boric acid in the dyeing bath is preferably 0.1 parts by weight or more, more preferably 0.2 parts by weight or more, and even more preferably 0.5 parts by weight, based on 100 parts by weight of water. That's all. In one embodiment, the dyeing is performed in advance using a dyeing bath containing boric acid. According to such a form, the rate of change in boric acid concentration when boric acid is mixed into the dyeing bath can be reduced. The amount of boric acid blended in advance in the dyeing bath (the content of boric acid not derived from the above treatment bath) is preferably 0.1 parts by weight to 2 parts by weight, more preferably 0.1 parts by weight to 2 parts by weight, based on 100 parts by weight of water. is from 0.5 parts by weight to 1.5 parts by weight.

If necessary, an insolubilization treatment is performed after the above-mentioned auxiliary stretching in the air and before the underwater stretching and dyeing. The insolubilization treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing the insolubilization treatment, it is possible to impart water resistance to the PVA-based resin layer and prevent a decrease in orientation of PVA when immersed in water. The concentration of the aqueous boric acid solution in the insolubilization treatment is preferably 1 part by weight to 4 parts by weight per 100 parts by weight of water. The temperature of the insolubilization treatment (the temperature of the boric acid aqueous solution) is preferably 20°C to 50°C.

If necessary, crosslinking treatment is performed after dyeing and before underwater stretching. The crosslinking treatment is typically performed by immersing the PVA resin layer in a boric acid aqueous solution. By performing crosslinking treatment, water resistance can be imparted to the PVA-based resin layer, and deterioration in orientation of PVA can be prevented during subsequent underwater stretching. The concentration of the boric acid aqueous solution in the crosslinking treatment is preferably 1 to 5 parts by weight per 100 parts by weight of water. It is preferable to mix iodide with the boric acid aqueous solution. By blending iodide, it is possible to suppress elution of iodine adsorbed to the PVA-based resin layer. Specific examples of iodides are as described above. The amount of iodide to be blended is preferably 1 to 5 parts by weight per 100 parts by weight of water. The temperature of the crosslinking treatment (the temperature of the boric acid aqueous solution) is preferably 20°C to 50°C.

As mentioned above, a resin film that has been stretched and dyed with iodine (a laminate that has been subjected to the various treatments described above) is immersed in a liquid containing a phenolic compound (hereinafter sometimes referred to as an immersion liquid). A polarizer can be obtained. As the immersion liquid, for example, a solution in which a phenolic compound is dissolved in any suitable solvent is used. Water is preferably used as the solvent for dissolving the phenolic compound. The concentration of the phenolic compound in the immersion liquid is, for example, 5% to 20% by weight, preferably 7% to 18% by weight. It is preferable that the immersion liquid contains an iodide such as potassium iodide. The iodide concentration of the immersion liquid is preferably between 1% and 7% by weight.

The temperature of the immersion liquid is preferably 20°C to 50°C. The immersion time of the resin film (laminate) in the immersion liquid may be, for example, 1 second to 30 seconds.

After being immersed in a liquid containing a phenolic compound, the resin film (laminate) may be subjected to any appropriate treatment. For example, after immersion in a liquid containing a phenolic compound, the resin film can be washed with water. Water washing is typically performed by immersing the resin film in a water bath. The temperature of the water bath can be, for example, 15°C to 30°C. The immersion time of the resin film in the water bath can be, for example, 1 second to 30 seconds.

After the water washing, it is preferable to dry the resin film (laminate). Drying may be performed in any suitable manner. Specifically, the heating may be performed by heating the entire zone (zone heating method) or by heating the conveyance roll (heating roll method). Preferably, a heated roll method is employed, and more preferably both are employed. By using a heating roll, heating curling of the laminate can be efficiently suppressed, and a polarizer with excellent quality can be manufactured. Specifically, by drying the laminate along a heating roll, it is possible to efficiently promote crystallization of the thermoplastic resin base material and increase the degree of crystallinity, which is relatively low. Even at drying temperatures, the degree of crystallinity of the thermoplastic resin base material can be increased favorably. As a result, the thermoplastic resin base material has increased rigidity and is in a state where it can withstand shrinkage of the PVA resin layer due to drying, thereby suppressing curling. Furthermore, by using a heating roll, the laminate can be dried while maintaining it in a flat state, so that not only curling but also wrinkles can be suppressed.

By drying, the laminate can be shrunk in the width direction and its optical properties can be improved. This is because the orientation of PVA and PVA/iodine complex can be effectively improved. The shrinkage rate of the laminate in the width direction upon drying is preferably 1% to 10%, more preferably 2% to 8%, and even more preferably 4% to 6%. By using a heating roll, the laminate can be continuously contracted in the width direction while being conveyed, and high productivity can be achieved.

The drying conditions can be controlled by adjusting the heating temperature of the conveying roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, etc. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, even more preferably 70°C to 80°C. According to such a temperature, the degree of crystallinity of the thermoplastic resin can be increased to suppress curling, and at the same time, extremely excellent durability can be imparted to the laminate. Note that the temperature of the heating roll can be measured with a contact thermometer. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and even more preferably 1 to 10 seconds.

The heating roll may be provided within a heating furnace (for example, an oven) or may be provided on a normal production line (at room temperature). Preferably, it is provided in a heating furnace equipped with air blowing means. By using both heating roll drying and hot air drying, a sharp temperature change between the heating rolls can be suppressed, and shrinkage in the width direction can be easily controlled. The temperature of hot air drying is preferably 30°C to 100°C. Further, the hot air drying time is preferably 1 second to 300 seconds. The wind speed of the hot air is preferably about 10 m/s to 30 m/s. Note that the wind speed is the wind speed within the heating furnace, and can be measured with a mini-vane digital anemometer.

B-2. Manufacturing method 2
The polarizer includes, for example, coating a liquid containing a phenolic compound on at least one principal surface (first principal surface) of a resin film containing iodine and having a first principal surface and a second principal surface facing each other. This can be obtained by In one embodiment, a liquid containing a phenolic compound (hereinafter sometimes referred to as a coating liquid) is applied to the first main surface of the resin film with the protective material disposed on the second main surface of the resin film. Coat. Specifically, a laminate of a resin film and a protective material is prepared, and a liquid containing a phenolic compound is applied to the first principal surface of the resin film of this laminate.

FIG. 2 is a schematic cross-sectional view showing the general structure of a laminate used for manufacturing a polarizer in one embodiment of the present invention. The laminate 100 includes a resin film 10 and a protective material 1. The resin film 10 has a first main surface 10a and a second main surface 10b facing each other, and the protective material 1 is disposed on the second main surface 10b of the resin film 10.

The resin film included in the laminate may be produced by any suitable method. In one embodiment, a hydrophilic polymer film such as a polyvinyl alcohol (PVA) film, a partially formalized PVA film, or a partially saponified ethylene/vinyl acetate copolymer film is coated with iodine, dichroic dye, etc. It is produced by a method that includes dyeing with a dichroic substance and stretching. The method may further include insolubilization treatment, swelling treatment, crosslinking treatment, and the like. Since such a manufacturing method is well known and commonly used in the art, detailed explanation will be omitted.

In another embodiment, the resin film included in the laminate is produced using a laminate of a resin base material and a resin layer (typically, a PVA-based resin layer). For example, applying a PVA-based resin solution to a resin base material and drying it to form a PVA-based resin layer on the resin base material to obtain a laminate of the resin base material and the PVA-based resin layer; the laminate by stretching and dyeing. In this embodiment, preferably, a PVA-based resin layer containing a halide and a PVA-based resin is formed on one side of the resin base material. Stretching typically includes immersing the laminate in an aqueous boric acid solution and stretching. Furthermore, the stretching may further include stretching the laminate in air at a high temperature (for example, 95° C. or higher) before stretching in the boric acid aqueous solution, if necessary. In addition, in the present embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction to shrink by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an in-air auxiliary stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process in this order. By introducing auxiliary stretching, even when applying PVA onto a thermoplastic resin base material, it becomes possible to improve the crystallinity of PVA and achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, it is possible to prevent problems such as deterioration of orientation and dissolution of PVA when it is immersed in water during the subsequent dyeing and stretching processes, resulting in high optical properties. can be achieved. Furthermore, when the PVA-based resin layer is immersed in a liquid, disturbance of the orientation of PVA molecules and deterioration of the orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide, and high optical properties can be achieved. It can be achieved. Furthermore, high optical properties can be achieved by shrinking the laminate in the width direction through drying shrinkage treatment. The resin base material may be used as it is as a protective layer of the obtained polarizer, or may be peeled off from the resin base material/PVA resin layer laminate. Details of the method for manufacturing such a resin film (polarizer) are described in, for example, Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire descriptions of these publications are incorporated herein by reference.

As the protective material 1 disposed on the second main surface 10b of the resin film 10, any appropriate member (eg, film, layer) can be used. For example, the resin base material described above can be used as the protective material. Furthermore, as the protective material, at least one of a protective layer or a retardation layer of a polarizer, which will be described later, may be used. In this case, the protective material may be laminated to the resin film via an adhesive or adhesive.

As the coating liquid, for example, a solution in which a phenolic compound is dissolved in any suitable solvent is used. As the solvent for dissolving the phenolic compound, for example, water, alcoholic solvents such as methanol, ethanol, etc. are used. These may be used alone or in combination of two or more. The concentration of the phenolic compound in the coating liquid is, for example, 1% to 20% by weight, preferably 5% to 15% by weight.

Examples of coating methods for liquids containing phenolic compounds include roll coating, spin coating, bar coating, dip coating, die coating, curtain coating, spray coating, knife coating (comma coating, etc.). ).

After coating a resin film with a liquid containing a phenolic compound, it is preferable to dry it. The drying temperature is, for example, 50°C to 80°C. The drying time is, for example, 10 seconds to 10 minutes.

At the time of coating the liquid containing the phenolic compound, the coated surface may be surface-modified. For example, by increasing the surface energy of the coated surface through surface modification, the coating liquid can be uniformly applied to the coated surface, for example. Surface modification is performed, for example, by corona treatment or plasma treatment. These may be used alone or in combination.

For example, it is preferable to lower the contact angle of the coated surface (first principal surface) by 5° or more by coating a liquid containing a phenolic compound, or by surface modification and coating a liquid containing a phenolic compound, It may be lowered by 10 degrees or more, 15 degrees or more, 20 degrees or more, or 25 degrees or more.

C. Polarizing Plate A polarizing plate according to an embodiment of the present invention has the above polarizer. Typically, it includes the above polarizer and at least one of a protective layer and a retardation layer. Polarizing plates according to embodiments of the present invention are typically used in image display panels. Specifically, it is placed on the viewing side of the image display panel main body.

FIG. 3 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 200 includes a polarizer 10, a first protective layer 21 disposed on the first principal surface 10a side (visible side) of the polarizer 10, and an adhesive layer disposed on the second principal surface 10b side of the polarizer 10. It has an agent layer 40 and a release film 50. A phenolic compound may exist on the first main surface 10a of the polarizer 10. The phenolic compound that may exist on the first main surface 10a is not visible from the first protective layer 21 side because the adhesive layer described below is provided adjacent to the first main surface 10a, and is not visible from the first protective layer 21 side, for example, on the image display panel. Even if it is placed on the visible side, it will not be visible. In the image display panel, by arranging the first principal surface 10a where a phenolic compound may exist on the viewing side, decolorization due to influence from the external environment can be effectively suppressed. Note that, unlike the illustrated example, the adhesive layer 40 and the release film 50 are arranged on the first main surface 10a side where a phenolic compound may exist, and the first protective layer 21 is arranged on the second main surface 10b side (visible side). may be placed.

The release film 50 is peelably bonded to the adhesive layer 40 and can protect the adhesive layer 40. By using the release film 50, for example, the laminate 100 can be formed into a roll. Practically speaking, the polarizing plate 200 can be attached to the image display panel body using the adhesive layer 40. The release film 50 can function as a release liner to which the polarizing plate 200 is temporarily attached until it is ready for use.

Although not shown, a second protective layer may be disposed between the polarizer 10 and the adhesive layer 40. Moreover, the polarizing plate may have a retardation layer. Specifically, it may be a polarizing plate with a retardation layer. The retardation layer is arranged between the polarizer 10 and the adhesive layer 40, for example.

Each member constituting the polarizing plate may be laminated via any appropriate adhesive layer (some not shown). Specific examples of the adhesive layer include an adhesive layer and a pressure-sensitive adhesive layer. The polarizing plate may be elongated or sheet-like. Here, "elongated shape" refers to an elongated shape whose length is sufficiently longer than its width, for example, an elongated shape whose length is 10 times or more, preferably 20 times or more as compared to its width. The elongated polarizing plate can be wound into a roll.

C-1. Protective Layer The protective layer may be formed of any suitable film that can be used as a protective layer of a polarizer. Specific examples of materials that are the main components of the film include cellulose resins such as triacetylcellulose (TAC), polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, and polysulfones. , polystyrene, cycloolefin such as polynorbornene, polyolefin, (meth)acrylic, acetate, and other transparent resins.

The polarizing plate is typically placed on the viewing side of the image display device, and the first protective layer 21 is placed on the viewing side. Therefore, the first protective layer 21 may be subjected to surface treatments such as hard coat (HC) treatment, antireflection treatment, antisticking treatment, and antiglare treatment, as necessary.

The thickness of the protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, even more preferably 15 μm to 35 μm. In addition, when the above-mentioned surface treatment is performed, the thickness of the first protective layer 21 is the thickness including the thickness of the surface treatment layer.

In one embodiment, the second protective layer is preferably optically isotropic. In this specification, "optically isotropic" means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) is -10 nm to +10 nm. say. The thickness of the second protective layer is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, even more preferably 10 μm to 30 μm.

C-2. Adhesive layer The thickness of the adhesive layer 40 is preferably 10 μm to 20 μm. Any suitable configuration may be adopted as the adhesive constituting the adhesive layer 40. Specific examples include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and blending ratio of monomers that form the base resin of the adhesive, as well as the amount of crosslinking agent, reaction temperature, reaction time, etc., adhesives can have desired characteristics depending on the purpose. can be prepared. The base resin of the adhesive may be used alone or in combination of two or more types. The base resin is preferably an acrylic resin (specifically, the adhesive layer is preferably composed of an acrylic adhesive).

C-3. Release Film The release film may be comprised of any suitable plastic film. Specific examples of plastic films include polyethylene terephthalate (PET) film, polyethylene film, and polypropylene film. A release film can function as a release liner. Specifically, as the release film, a plastic film whose surface is coated with a release agent is preferably used. Specific examples of the release agent include silicone release agents, fluorine release agents, and long-chain alkyl acrylate release agents.

The thickness of the release film is preferably 20 μm to 80 μm, more preferably 35 μm to 55 μm.

C-4. Retardation Layer The retardation layer may be a single layer or may have a laminated structure of two or more layers. The retardation layer may be composed of any suitable material. Specifically, the retardation layer may be an oriented solidified layer of a liquid crystal compound, a stretched film, or a combination thereof. The thickness of the retardation layer is, for example, 1 μm or more and 50 μm or less. In one embodiment, the thickness of the retardation layer is preferably 10 μm or less, more preferably 8 μm or less, and still more preferably 6 μm or less. In addition, when a retardation layer has a laminated structure, "thickness of a retardation layer" means the total thickness of each retardation layer. Specifically, the "thickness of the retardation layer" does not include the thickness of the adhesive layer.

As the retardation layer, for example, an alignment fixed layer of a liquid crystal compound (liquid crystal alignment fixed layer) is used. By using a liquid crystal compound, for example, the difference between nx and ny of the obtained retardation layer can be made much larger than that of a non-liquid crystal material. The thickness can be significantly reduced. Therefore, it is possible to realize a remarkable reduction in the thickness of the polarizing plate with a retardation layer. As used herein, the term "orientation-fixed layer" refers to a layer in which a liquid crystal compound is oriented in a predetermined direction and the orientation state is fixed. In addition, the "alignment hardened layer" is a concept that includes an orientation hardened layer obtained by curing a liquid crystal monomer as described below. In the retardation layer, rod-shaped liquid crystal compounds are typically aligned in the slow axis direction of the retardation layer (homogeneous alignment).

The liquid crystal alignment solidified layer is produced by subjecting the surface of a predetermined base material to an alignment treatment, applying a coating liquid containing a liquid crystal compound to the surface to align the liquid crystal compound in a direction corresponding to the alignment treatment, and forming the liquid crystal alignment solidified layer. It can be formed by fixing the orientation state. Any suitable orientation treatment may be employed as the orientation treatment. Specifically, mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment can be mentioned. Specific examples of mechanical alignment treatment include rubbing treatment and stretching treatment. Specific examples of physical alignment treatment include magnetic field alignment treatment and electric field alignment treatment. Specific examples of chemical alignment treatment include oblique vapor deposition and photo alignment treatment. As the treatment conditions for various orientation treatments, any appropriate conditions may be adopted depending on the purpose.

The alignment of the liquid crystal compound is carried out by treatment at a temperature at which it exhibits a liquid crystal phase depending on the type of liquid crystal compound. By performing such temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is oriented in accordance with the orientation treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound oriented as described above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound oriented as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of the liquid crystal compound and details of the method for forming the alignment solidified layer are described in JP-A No. 2006-163343. The description of the publication is incorporated herein by reference.

In one embodiment when the retardation layer is a single layer, the retardation layer can function as a λ/4 plate. Specifically, Re(550) of the retardation layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and even more preferably 110 nm to 160 nm. The thickness of the retardation layer can be adjusted to obtain a desired in-plane retardation of the λ/4 plate. When the retardation layer is the liquid crystal alignment solidified layer described above, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and still more preferably 44°. The angle is between 46° and 46°. Further, it is preferable that the retardation layer exhibits inverse dispersion wavelength characteristics in which the retardation value increases depending on the wavelength of the measurement light.

In another embodiment where the retardation layer is a single layer, the retardation layer can function as a λ/2 plate. Specifically, Re(550) of the retardation layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and even more preferably 230 nm to 280 nm. The thickness of the retardation layer can be adjusted to obtain a desired in-plane retardation of the λ/2 plate. When the retardation layer is the above-mentioned liquid crystal alignment solidified layer, its thickness is, for example, 2.0 μm to 4.0 μm. In this embodiment, the angle between the slow axis of the retardation layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and even more preferably 12°. It is between 16° and 16°.

In one embodiment where the retardation layer has a laminated structure, the retardation layer includes a first retardation layer (H layer) and a second retardation layer (Q layer) arranged in order from the polarizer side. It also has a two-layer laminated structure. The H layer can typically function as a λ/2 plate, and the Q layer can typically function as a λ/4 plate. Specifically, Re (550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and still more preferably 230 nm to 280 nm; Re (550) of the Q layer is preferably The wavelength is 100 nm to 180 nm, more preferably 110 nm to 170 nm, even more preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted to obtain a desired in-plane retardation of the λ/2 plate. When the H layer is the liquid crystal alignment solidified layer described above, its thickness is, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted to obtain a desired in-plane retardation of the λ/4 plate. When the Q layer is the liquid crystal alignment solidified layer described above, its thickness is, for example, 1.0 μm to 2.5 μm. In this embodiment, the angle between the slow axis of the H layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and still more preferably 12°. ~16°; The angle between the slow axis of the Q layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and even more preferably 72°. ~76°. Note that the arrangement order of the H layer and the Q layer may be reversed, and the angle between the slow axis of the H layer and the absorption axis of the polarizer, and the angle between the slow axis of the Q layer and the absorption axis of the polarizer. The angle may be reversed. Further, each layer (for example, the H layer and the Q layer) may exhibit inverse dispersion wavelength characteristics in which the retardation value increases depending on the wavelength of the measurement light, or the retardation value increases depending on the wavelength of the measurement light. It may exhibit a positive wavelength dispersion characteristic that decreases, or it may exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes depending on the wavelength of the measurement light.

The retardation layer (at least one layer when having a laminated structure) typically exhibits a refractive index characteristic of nx>ny=nz. Note that "ny=nz" includes not only the case where ny and nz are completely equal but also the case where they are substantially equal. Therefore, there may be cases where ny>nz or ny<nz as long as the effects of the present invention are not impaired. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3.

As mentioned above, the retardation layer is preferably a liquid crystal alignment solidified layer. Examples of the liquid crystal compound include a liquid crystal compound whose liquid crystal phase is a nematic phase (nematic liquid crystal). As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for developing liquid crystallinity of a liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (that is, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or crosslinking the liquid crystal monomers, the alignment state can be fixed. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Therefore, the formed retardation layer does not undergo transition to a liquid crystal phase, a glass phase, or a crystalline phase due to a temperature change, which is characteristic of liquid crystal compounds, for example. As a result, the retardation layer becomes an extremely stable retardation layer that is not affected by temperature changes.

The temperature range in which a liquid crystal monomer exhibits liquid crystallinity differs depending on its type. Specifically, the temperature range is preferably 40°C to 120°C, more preferably 50°C to 100°C, and most preferably 60°C to 90°C.

Any suitable liquid crystal monomer may be employed as the liquid crystal monomer. For example, described in Special Table 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, and GB2280445, etc. Polymerizable mesogenic compounds and the like can be used. Specific examples of such polymerizable mesogenic compounds include, for example, BASF's product name LC242, Merck's product name E7, and Wacker-Chem's product name LC-Sillicon-CC3767. As the liquid crystal monomer, nematic liquid crystal monomers are preferred.

In another embodiment, the retardation layer includes, from the polarizer side, a first retardation layer that can function as a λ/4 plate, and a second retardation layer whose refractive index characteristics exhibit a relationship of nz>nx=ny. (so-called positive C plate). Details of the λ/4 plate are as described above. In this embodiment, the angle between the slow axis of the first retardation layer and the absorption axis of the polarizer is preferably 40° to 50°, more preferably 42° to 48°, and even more preferably is 44° to 46°. Moreover, it is preferable that the first retardation layer exhibits inverse dispersion wavelength characteristics in which the retardation value increases depending on the wavelength of the measurement light.

The retardation Rth (550) in the thickness direction of the positive C plate is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, still more preferably -90 nm to -200 nm, and particularly preferably is −100 nm to −180 nm. Here, "nx=ny" includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. The in-plane retardation Re (550) of the positive C plate is, for example, less than 10 nm.

The second retardation layer having a refractive index characteristic of nz>nx=ny may be formed of any suitable material, but preferably consists of a film containing a liquid crystal material fixed in a homeotropic alignment. The liquid crystal material (liquid crystal compound) that can be homeotropically aligned may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compound and the method for forming the retardation layer described in [0020] to [0028] of JP-A No. 2002-333642. In this case, the thickness of the second retardation layer is preferably 0.5 μm to 5 μm.

C-5. Preparation of Polarizing Plate The polarizing plate according to the embodiment of the present invention can be obtained by laminating each layer on the above polarizer (resin film). Lamination of each layer is performed, for example, while being conveyed by rolls (so-called roll-to-roll). The protective layer is laminated using an adhesive, for example. Lamination of the retardation layer is typically performed by transferring a liquid crystal alignment solidified layer formed on a base material. When the retardation layer has a laminated structure, each retardation layer may be sequentially laminated (transferred) on the polarizer (resin film), or a laminate of retardation layers may be laminated (transferred). good. Transfer is performed using, for example, an active energy ray-curable adhesive. The thickness of the active energy ray-curable adhesive after curing (the thickness of the adhesive layer) is preferably 0.4 μm or more, more preferably 0.4 μm to 3.0 μm, and even more preferably 0.6 μm to 3.0 μm. It is 1.5 μm.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to these Examples. Note that the thickness and contact angle are values measured by the following measurement method. Furthermore, unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.
<Thickness>
The thickness of 10 μm or less was measured using a scanning electron microscope (manufactured by JEOL Ltd., product name “JSM-7100F”). Thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name “KC-351C”).
<Contact angle>
The water contact angle on the surface of the polarizer formed on the resin base material was measured using a contact angle meter (manufactured by Kyowa Kaimen Kagaku Co., Ltd., trade name "Model DMo-501", control box "DMC-2'' and control/analysis software ``FAMAS (version 5.0.30)''). The amount of distilled water dropped was 2 μL, and the contact angle was calculated using the θ/2 method from an image 5 seconds after dropping. The values listed are the average values of five measurements.

[Example 1-1]
As the thermoplastic resin base material, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a water absorption rate of 0.75% and a Tg of about 75° C. was used. One side of the resin base material was subjected to corona treatment.
100 weight PVA resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefaimer Z410") at a ratio of 9:1. 13 parts by weight of potassium iodide was added to 13 parts by weight of potassium iodide to prepare a PVA aqueous solution (coating liquid).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched free end to 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 130° C. (in-air assisted stretching).
Here, the laminate was cut into a rectangle with a length of 100 mm in the longitudinal (MD) direction and 50 mm in the (TD) direction perpendicular to the longitudinal direction.

Next, the cut laminate was immersed in an insolubilization bath (boric acid aqueous solution with a boric acid concentration of 3% by weight) at a liquid temperature of 30° C. for 60 seconds (insolubilization treatment).
Next, the final polarizer was added to a dyeing bath (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 to 100 parts by weight of water) at a liquid temperature of 30°C. The sample was immersed for 60 seconds while adjusting the concentration so that the single transmittance (Ts) was 38% or less (staining). Note that the single transmittance was set low in order to facilitate the evaluation of decolorization, which will be described later.
Next, it was immersed in a crosslinking bath (boric acid aqueous solution having a potassium iodide concentration of 3% by weight and a boric acid concentration of 3% by weight) at a liquid temperature of 30° C. for 60 seconds (crosslinking treatment).
Thereafter, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 1.5% by weight, potassium iodide concentration 5% by weight) at a liquid temperature of 67°C, the total stretching ratio in the longitudinal direction is increased to 5.5 times. Uniaxial stretching was performed as shown (underwater stretching). At this time, both ends in the longitudinal direction (a range of 20 mm from each opposing end) were held between clips and stretched.
Thereafter, the laminate was immersed in an immersion liquid (a liquid in which 250 g of catechol was dissolved in 3 L of an aqueous solution with a potassium iodide concentration of 4% by weight) at a temperature of 30°C.
Thereafter, the laminate was immersed in a water bath with a liquid temperature of 25° C. for 5 seconds (water washing).
Thereafter, it was dried for 4 minutes in an oven maintained at 60°C (drying).
In this way, a polarizer with a thickness of 5 μm was formed on the resin base material.

[Example 1-2]
A polarizer was obtained in the same manner as in Example 1-1, except that a solution prepared by dissolving 500 g of catechol in 3 L of an aqueous solution having a potassium iodide concentration of 4% by weight was used as the immersion liquid.

[Comparative example 1]
A polarizer was prepared in the same manner as in Example 1-1, except that an aqueous solution having a potassium iodide concentration of 4% by weight was used as the immersion liquid (catechol was not mixed), and subsequent washing with water was not performed. I got it.

<Evaluation 1>
Examples 1-1, 1-2 and Comparative Example 1 were evaluated as follows.
The obtained resin base material/polarizer laminate was bonded to an alkali glass plate via an acrylic adhesive having a thickness of 20 μm. At this time, the laminate was bonded so that the resin base material of the laminate was on the alkali glass plate side. Thereafter, both longitudinal ends of the laminate were fixed to an alkali glass plate with polyimide tape to obtain a sample for evaluation.
The obtained evaluation sample was placed in an oven at 85° C. and 85% RH, and then taken out from the oven every 5 minutes to measure the single transmittance (Ts). Single transmittance was measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-7100). Note that the single transmittance is a Y value measured using a 2-degree field of view (C light source) according to JIS Z8701 and subjected to visibility correction.
The evaluation results are shown in Figure 4. Note that the line graph shown in FIG. 4 shows the average value of the values measured three times.

From FIG. 4, it can be seen that decolorization is suppressed in the example.

[Example 2]
(Preparation of laminate)
As the thermoplastic resin base material, a long, amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) with a Tg of about 75°C was used, and one side of this resin base material was subjected to corona treatment. .
100 parts by weight of a PVA resin prepared by mixing polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Gosei Kagaku Kogyo Co., Ltd., trade name "Gosefaimer") at a ratio of 9:1. to which 13 parts by weight of potassium iodide was added was dissolved in water to prepare a PVA aqueous solution (coating solution).
The PVA aqueous solution was applied to the corona-treated surface of the resin base material and dried at 60° C. to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times in the vertical direction (longitudinal direction) in an oven at 130° C. (in-air auxiliary stretching treatment).
Next, the laminate was immersed for 30 seconds in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. (insolubilization treatment).
Next, the single transmittance of the resulting resin film was added to a dyeing bath (an aqueous iodine solution obtained by blending iodine and potassium iodide at a weight ratio of 1:7 to 100 parts by weight of water) at a liquid temperature of 30°C. It was immersed for 60 seconds while adjusting the concentration so that (Ts) was 45% (staining treatment).
Next, it was immersed for 30 seconds in a crosslinking bath (an aqueous boric acid solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C. (Crosslinking treatment).
Thereafter, while immersing the laminate in a boric acid aqueous solution (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 70°C, the laminate was completely rolled in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds. Uniaxial stretching was performed so that the stretching ratio was 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, while drying in an oven kept at about 90°C, it was brought into contact with a SUS heating roll whose surface temperature was kept at about 75°C (drying shrinkage treatment).
In this way, a resin film with a thickness of about 5 μm was formed on the resin base material, and a laminate having a resin base material/resin film configuration was obtained.

An ethanol solution (coating liquid) containing 10% by weight of catechol was applied to the exposed surface of the resin film of the obtained laminate using a wireless bar, dried at 60°C for 3 minutes, and the contact angle was adjusted on the resin base material. A 64° polarizer was formed.

[Comparative example 2-1]
A polarizer (contact angle of 73°) was obtained in the same manner as in Example 2 except that the coating solution did not contain catechol.

[Comparative example 2-2]
A polarizer (contact angle of 92°) was obtained in the same manner as in Example 2, except that the coating liquid was not applied to the resin film and the coating was not dried.

<Evaluation 2>
The following evaluations were performed for Example 2 and Comparative Examples 2-1 and 2-2. The evaluation results are summarized in Table 1.
Ultraviolet curing is applied to the surface of a polarizer formed on a resin base material (in this evaluation, the resin film was corona-treated in advance and a coating liquid was applied to the corona-treated surface to obtain the polarizer). An acrylic film (manufactured by Toyo Kohan Co., Ltd., "HX40UF") having a thickness of 40 μm was bonded to each other via a mold adhesive to obtain a polarizing plate. Note that before bonding, an undercoat layer with a thickness of 200 nm was formed on the bonding surface of the acrylic film. Next, the resin base material was peeled off from the polarizing plate (polarizer), the polarizing plate was cut into a size of 30 mm in length x 30 mm in width, and an acrylic adhesive layer with a thickness of 20 μm was formed on the surface from which the resin base material was peeled off. A polarizing plate was attached to an alkali glass plate. After leaving this state in an oven at 85°C and 85% RH for 48 hours, the single transmittance (Ts) and polarization degree (P) of the polarizing plate before and after the moist heat test were measured, and the single transmittance and polarization degree by the moist heat test were measured. The change in polarization degree was calculated. Single transmittance and polarization degree were measured using an ultraviolet-visible spectrophotometer (manufactured by JASCO Corporation, V-7100). Note that the single transmittance is a Y value measured using a 2-degree field of view (C light source) according to JIS Z8701 and subjected to visibility correction. ΔTs listed in Table 1 is the value obtained by subtracting the single transmittance before and after the heat and humidity test from the single transmittance after the heat and humidity test, and ΔP is the value obtained by subtracting the degree of polarization before and after the heat and humidity test from the degree of polarization after the heat and humidity test. All values are average values of three measurements.
In addition, the range (bleaching width) from the edge where each edge (vertical edge and horizontal edge) of the polarizing plate was bleached by the moist heat test was observed and measured using a microscope. The decolorization width shown in Table 1 is the average value of values measured at several locations on each edge.

Table 1 shows that decolorization is suppressed in Examples.

Polarizers according to embodiments of the present invention are used, for example, in image display devices such as liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

1 Protective material 10 Polarizer (resin film)
21 First protective layer 40 Adhesive layer 50 Release film 100 Laminate 200 Polarizing plate

Claims (10)

It is composed of a resin film containing iodine and having a first principal surface and a second principal surface facing each other,
Contains phenolic compounds,
polarizer. The polarizer according to claim 1, wherein the phenolic compound includes catechol. The polarizer according to claim 1 or 2, wherein the phenolic compound is present on at least the first main surface of the resin film. The polarizer according to any one of claims 1 to 3, wherein the first principal surface has a contact angle of 85° or less. The polarizer according to any one of claims 1 to 4, having a thickness of 8 μm or less. including immersing a resin film containing iodine in a liquid containing a phenolic compound,
A method for manufacturing a polarizer according to claim 1 or 2. Coating a liquid containing a phenolic compound on at least the first main surface of a resin film containing iodine and having a first main surface and a second main surface facing each other,
A method for manufacturing a polarizer according to any one of claims 1 to 5. 8. The manufacturing method according to claim 7, further comprising surface-modifying the surface to be coated before said coating. 9. The manufacturing method according to claim 8, wherein the surface modification is performed by at least one of corona treatment and plasma treatment. The polarizer according to any one of claims 1 to 5,
At least one of a protective layer or a retardation layer,
A polarizing plate.

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