JP7633792B2 - Method for manufacturing a polarizing plate with a retardation layer - Google Patents

Description

The present invention relates to a method for manufacturing a polarizing plate with a retardation layer.

Image display devices, such as liquid crystal display devices and electroluminescence (EL) display devices (e.g., organic EL display devices, inorganic EL display devices), are rapidly becoming popular. A polarizing plate and a retardation plate are typically used in image display devices. In practice, retardation layer-attached polarizing plates in which a polarizing plate and a retardation plate are integrated are widely used (e.g., Patent Document 1). In recent years, the possibility of bending, bending, folding, and rolling up image display devices using flexible substrates (e.g., resin substrates) has been studied. As a retardation layer-attached polarizing plate to be used in such image display devices, a thin retardation layer-attached polarizing plate is desired. However, a thin retardation layer-attached polarizing plate has a problem in that it is prone to warping.

Patent No. 3325560

The present invention has been made to solve the above-mentioned problems in the conventional art, and its main objective is to provide a retardation layer-attached polarizing plate with reduced warping and with a high yield.

According to an embodiment of the present invention, a method for manufacturing a polarizing plate with a retardation layer is provided. The manufacturing method includes preparing a laminate having a first protective film, a polarizing plate including a polarizer and a protective layer arranged on at least one side of the polarizer, a retardation layer, and a second protective film in this order, the sum of the thickness of the polarizing plate and the thickness of the retardation layer is 50 μm or less, and the ratio of the thickness of the polarizing plate to the thickness of the retardation layer is 5 or more, and placing the laminate on a placement surface in an environment with a water vapor amount of 10.5 g/ ^m3 or more to perform a humidification treatment, and placing the laminate on the placement surface in a state where the main surface of the laminate is angled.
In one embodiment, the production method includes laminating the polarizing plate and the retardation layer to obtain a laminate precursor.
In one embodiment, the manufacturing method includes cutting the laminate precursor into sheets.
In one embodiment, the humidification treatment is performed with a plurality of the laminates arranged in an array.
In one embodiment, the first protective film has a moisture permeability of 30 g/m ² ·24 h or less at 40° C. and 92% RH.
In one embodiment, the second protective film has a moisture permeability of 30 g/m ² ·24 h or less at 40° C. and 92% RH.
In one embodiment, the production method includes laminating the polarizing plate and the retardation layer while transporting them with rolls.
In one embodiment, the production method includes laminating the polarizing plate and the retardation layer using an active energy ray-curable adhesive.
In one embodiment, the active energy ray-curable adhesive has a thickness of 0.4 μm or more after curing.
In one embodiment, the laminate has a pressure-sensitive adhesive layer arranged on the side of the retardation layer on which the polarizing plate is not arranged, and the weight increase per unit area of the laminated portion of the polarizing plate, the retardation layer, and the pressure-sensitive adhesive layer due to the humidification treatment is 0.1% or more.
In one embodiment, the humidification treatment time is 6 hours or more.
In one embodiment, the amount of water vapor during the humidification treatment is 10.5 g/m ³ to 30 g/m ³ .
In one embodiment, the manufacturing method includes laminating the polarizing plate and the retardation layer in an environment with a water vapor amount of 10.2 g/m ³ or less.
In one embodiment, the amount of water vapor during the humidification treatment is 0.5 g/m ³ or more higher than the amount of water vapor during lamination of the polarizing plate and the retardation layer.
In one embodiment, the retardation layer or the protective layer has a moisture permeability of 300 g/m ² ·24 h or more at 40° C. and 92% RH.
In one embodiment, in the polarizing plate, a protective layer is arranged only on the side of the polarizer on which the retardation layer is not arranged.
In one embodiment, the center of gravity in the thickness direction of the polarizer is located closer to the retardation layer than the center of gravity in the thickness direction of a laminated portion of the polarizing plate and the retardation layer.
In one embodiment, the retardation layer is a layer in which a liquid crystal compound is aligned and fixed.

According to an embodiment of the present invention, by subjecting a laminate having a first protective film, a polarizing plate, a retardation layer, and a second protective film in this order to a humidification treatment under specified conditions, it is possible to manufacture a polarizing plate with a retardation layer that is suppressed in warping with good yield, even if the polarizing plate and the retardation layer have a specified thickness.

1 is a schematic cross-sectional view showing an outline of a laminate according to a first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view showing an outline of the configuration of a laminate according to a second embodiment of the present invention. FIG. 2 is a cross-sectional view showing an example of a warped state of a laminate precursor. FIG. 2 is a cross-sectional view showing an example of a laminated portion from a polarizing plate to a pressure-sensitive adhesive layer. FIG. 2 is a cross-sectional view showing an example of a state in which a laminate is placed on a placement surface.

The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

(Definition of terms and symbols)
The definitions of terms and symbols used in this specification 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., the slow axis direction), "ny" is the refractive index in the direction perpendicular to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction.
(2) In-plane phase difference (Re)
"Re(λ)" is the in-plane retardation measured with light having a wavelength of λ nm at 23° C. For example, "Re(550)" is the in-plane retardation measured with light having a wavelength of 550 nm at 23° C. Re(λ) is calculated by the formula: Re(λ)=(nx−ny)×d, where d (nm) is the thickness of the layer (film).
(3) Retardation in the thickness direction (Rth)
"Rth(λ)" is the 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 calculated 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 calculated by Nz=Rth/Re.
(5) Angle When referring to an angle in this specification, the angle includes both clockwise and counterclockwise angles with respect to a reference direction. Thus, for example, "45°" means ±45°.

A method for producing a polarizing plate with a retardation layer according to one embodiment of the present invention includes preparing a laminate having a polarizing plate including a polarizer and a retardation layer, and placing the laminate on a mounting surface in a predetermined environment.

A. Laminate FIG. 1 is a schematic cross-sectional view showing the outline of the laminate according to the first embodiment of the present invention. The laminate 100 has a first protective film 31, a polarizing plate 10, a retardation layer 20, and a second protective film 32 in this order from the viewing side. In the illustrated example, the polarizing plate 10 includes a polarizer 11 and a protective layer 12 arranged on the viewing side of the polarizer 11 (the side on which the retardation layer 20 is not arranged), and no protective layer is arranged between the polarizer 11 and the retardation layer 20. According to such a form, for example, the thickness, total thickness, thickness ratio, and moisture permeability of the polarizing plate described later can be achieved well. Typically, the center of gravity in the thickness direction of the polarizer is located on the retardation layer side of the center of gravity in the thickness direction of the laminated portion of the polarizing plate and the retardation layer.

Although not shown, a protective layer may further be included on the other side of the polarizer 11 (between the polarizer 11 and the retardation layer 20).

Figure 2 is a schematic cross-sectional view showing the general configuration of a laminate according to a second embodiment of the present invention. In the first embodiment, the retardation layer 20 is a single layer, whereas in the second embodiment, the retardation layer 20 has a laminated structure including a first retardation layer 21 and a second retardation layer 22. Unlike the illustrated example, the retardation layer 20 may have a laminated structure of three or more layers.

Although not shown, the laminate may further have other functional layers. The type, characteristics, number, combination, arrangement, etc. of the functional layers that the laminate may have can be appropriately set according to the purpose. For example, the laminate may further have a conductive layer or a conductive layer-attached isotropic substrate. The conductive layer or the conductive layer-attached isotropic substrate is typically arranged between the retardation layer 20 and the second protective film 32. Note that a laminate (polarizing plate with retardation layer) having a conductive layer or a conductive layer-attached isotropic substrate is applied to, for example, a so-called inner touch panel type input display device in which a touch sensor is incorporated inside an image display panel. As another example, the laminate may further have other retardation layers. The optical characteristics (e.g., refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, arrangement position, etc. of the other retardation layers can be appropriately set according to the purpose. As a specific example, the viewing side of the polarizer 11 may be provided with other retardation layers (typically, a layer that imparts (elliptical) polarization function, a layer that imparts ultra-high retardation) that improve visibility when viewed through polarized sunglasses. By having such layers, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the resulting polarizing plate with retardation layers can be suitably applied to image display devices that can be used outdoors.

Each member constituting the laminate may be laminated via any suitable adhesive layer (not shown). Specific examples of adhesive layers include an adhesive layer and a pressure-sensitive adhesive layer. For example, the first protective film 31 is attached to the polarizing plate 10 via a pressure-sensitive adhesive layer. The first protective film 31 may be peeled off before the retardation layer-attached polarizing plate obtained by the embodiment of the present invention is used (before it is laminated on an image display panel) or during the manufacturing process of the final product (image display device), or it may be mounted directly on the final product.

For example, the second protective film 32 is attached to the retardation layer 20 via an adhesive layer. In practice, the second protective film 32 can function as a release film (separator) that is temporarily attached until the retardation layer-attached polarizing plate obtained by the embodiment of the present invention is used. By temporarily attaching the release film, for example, the adhesive layer is protected and the laminate can be formed into a roll.

For example, the retardation layer 20 is bonded to the polarizing plate 10 via an adhesive layer (preferably, using an active energy ray curable adhesive). When the retardation layer 20 has a laminated structure of two or more layers, each retardation layer is bonded via an adhesive layer (preferably, using an active energy ray curable adhesive).

A-1. Polarizing Plate The polarizing plate includes a polarizer and a protective layer. The thickness of the polarizing plate depends on the number of protective layers included, but is preferably 20 μm or more, more preferably 25 μm or more. On the other hand, the thickness of the polarizing plate is preferably 40 μm or less, more preferably 36 μm or less, and even more preferably 33 μm or less. Note that, in the case where an adhesive layer is used when laminating the polarizer and the protective layer, the thickness of the adhesive layer is not included in the thickness of the polarizing plate.

The polarizer is typically a resin film containing a dichroic material (e.g., iodine). As described above, examples of the resin film include hydrophilic polymer films such as polyvinyl alcohol (PVA)-based films, partially formalized PVA-based films, and partially saponified ethylene-vinyl acetate copolymer-based films.

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

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.5% to 46.0%, preferably 42.0% to 46.0%, and more preferably 44.5% to 46.0%. The degree of polarization of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more.

The protective layer can be formed of any suitable film that can be used as a protective layer for a polarizer. Specific examples of materials that are the main component of the film include cellulose-based resins such as triacetyl cellulose (TAC), and transparent resins such as polyesters, polyvinyl alcohols, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, polynorbornenes, polyolefins, (meth)acrylics, and acetates.

The polarizing plate with a retardation layer obtained by the embodiment of the present invention is typically placed on the viewing side of an image display device, and the protective layer 12 is placed on the viewing side. Therefore, the protective layer 12 may be subjected to surface treatment such as hard coat (HC) treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment, as necessary.

The thickness of the protective layer 12 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm. If the above-mentioned surface treatment has been applied, the thickness of the protective layer 12 includes the thickness of the surface treatment layer.

In one embodiment, the protective layer (not shown) disposed between the polarizer 11 and the retardation layer 20 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 retardation in the thickness direction Rth(550) is -10 nm to +10 nm. The thickness of the protective layer disposed between the polarizer 11 and the retardation layer 20 is preferably 5 μm to 80 μm, more preferably 10 μm to 40 μm, and even more preferably 10 μm to 30 μm.

The polarizing plate may be produced by any suitable method. Specifically, the polarizing plate may include a polarizer produced from a single layer of resin film, or may include a polarizer obtained by using a laminate of two or more layers.

A typical method for producing a polarizer from the above-mentioned single-layer resin film includes subjecting the resin film to a dyeing process using a dichroic substance such as iodine or a dichroic dye, and a stretching process. As the resin film, for example, a hydrophilic polymer film such as a polyvinyl alcohol (PVA)-based film, a partially formalized PVA-based film, or an ethylene-vinyl acetate copolymer-based partially saponified film is used. The method may further include an insolubilization process, a swelling process, a crosslinking process, or the like. A polarizing plate can be obtained by laminating a protective layer on at least one side of the obtained polarizer. This manufacturing method is well known and commonly used in the industry, so a detailed description will be omitted.

Specific examples of polarizers obtained using the above laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer coated on the resin substrate can be produced, for example, by applying a PVA-based resin solution to a resin substrate and drying the substrate to form a PVA-based resin layer on the resin substrate to obtain a laminate of the resin substrate and the PVA-based resin layer; stretching and dyeing the laminate to make the PVA-based resin layer into a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Furthermore, the stretching may further include air-stretching the laminate at a high temperature (e.g., 95°C or higher) before stretching in the boric acid aqueous solution, as necessary. In addition, in this embodiment, the laminate is preferably subjected to a drying shrinkage treatment in which the laminate is heated while being conveyed in the longitudinal direction, thereby shrinking the laminate by 2% or more in the width direction. Typically, the manufacturing method of this embodiment includes subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, it is possible to increase the crystallinity of PVA even when PVA is applied onto a thermoplastic resin, and it is possible to achieve high optical properties. At the same time, by increasing the orientation of PVA in advance, problems such as a decrease in the orientation of PVA or dissolution can be prevented when the PVA is immersed in water in the subsequent dyeing step or stretching step, and it is possible to achieve high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to when the PVA-based resin layer does not contain a halide. This can improve the optical properties of the polarizer obtained by immersing the laminate in a liquid in a treatment process such as a dyeing process and an underwater stretching process. Furthermore, the optical properties can be improved by shrinking the laminate in the width direction by a drying shrinkage process. The obtained resin substrate/polarizer laminate may be used as it is (i.e., the resin substrate may be used as a protective layer for the polarizer), or any suitable protective layer may be laminated on the peeled surface obtained by peeling the resin substrate from the resin substrate/polarizer laminate, or on the surface opposite to the peeled surface. Details of the manufacturing method of such a polarizer are described in, for example, JP 2012-73580 A and JP 6470455 A. The entire disclosures of these publications are incorporated herein by reference.

A-2. Retardation layer The thickness of the retardation layer depends on its structure (whether it is a single layer or has a laminated structure), but is preferably 8 μm or less, more preferably 5 μm or less. On the other hand, the thickness of the retardation layer is, for example, 1 μm or more. In addition, when the retardation layer has a laminated structure, the "thickness of the retardation layer" means the sum of the thicknesses of each retardation layer. Specifically, the "thickness of the retardation layer" does not include the thickness of the adhesive layer.

As the retardation layer, a liquid crystal compound alignment solidified layer (liquid crystal alignment solidified layer) is preferably used. By using a liquid crystal compound, the difference between nx and ny of the obtained retardation layer can be significantly increased compared to non-liquid crystal materials, so the thickness of the retardation layer to obtain the desired in-plane retardation can be significantly reduced. Therefore, a polarizing plate with a retardation layer can be significantly thinned. In this specification, the "alignment solidified layer" refers to a layer in which the liquid crystal compound is aligned in a predetermined direction within the layer and the alignment state is fixed. The "alignment solidified layer" is a concept that includes an alignment hardened layer obtained by hardening a liquid crystal monomer as described later. In the retardation layer, typically, rod-shaped liquid crystal compounds are aligned in the slow axis direction of the retardation layer (homogeneous alignment).

The liquid crystal alignment solidified layer can be formed by performing an alignment treatment on the surface of a predetermined substrate, 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 fixing the alignment state. Any appropriate alignment treatment can be adopted as the alignment treatment. Specific examples include mechanical alignment treatment, physical alignment treatment, and chemical alignment treatment. 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 deposition method and photoalignment treatment. Any appropriate conditions can be adopted as the treatment conditions for various alignment treatments depending on the purpose.

The alignment of liquid crystal compounds is achieved by treating them at a temperature that exhibits a liquid crystal phase according to the type of liquid crystal compound. By carrying out such temperature treatment, the liquid crystal compounds take on a liquid crystal state, and the liquid crystal compounds are aligned according to the alignment treatment direction of the substrate surface.

In one embodiment, the alignment state is fixed by cooling the liquid crystal compound aligned 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 aligned as described above to a polymerization treatment or a crosslinking treatment.

Specific examples of liquid crystal compounds and details of the method for forming the alignment solidification layer are described in JP 2006-163343 A. The disclosure of this publication is incorporated herein by reference.

As described above, the retardation layer 20 may be a single layer or may have a laminated structure of two or more layers.

As shown in FIG. 1, in one embodiment in which the retardation layer 20 is a single layer, the retardation layer 20 can function as a λ/4 plate. Specifically, the 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 the desired in-plane retardation of the λ/4 plate. When the retardation layer is the above-mentioned liquid crystal alignment solidified layer, the 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 even more preferably 44° to 46°. In this embodiment, the retardation layer preferably exhibits an inverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light. In this embodiment, the laminate may further include a layer (another retardation layer, not shown) that exhibits a refractive index characteristic of nz>nx=ny and is disposed between the retardation layer 20 and the second protective film 32.

In another embodiment in which the retardation layer 20 is a single layer, the retardation layer 20 can function as a λ/2 plate. Specifically, the 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 so as 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, the 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° to 16°.

2, when the retardation layer 20 has a laminated structure, the retardation layer 20 has a two-layer laminated structure in which, for example, a first retardation layer (H layer) 21 and a second retardation layer (Q layer) 22 are arranged in order from the polarizing plate side. The H layer can typically function as a λ/2 plate, and the Q layer can typically function as a λ/4 plate. Specifically, the Re (550) of the H layer is preferably 200 nm to 300 nm, more preferably 220 nm to 290 nm, and even more preferably 230 nm to 280 nm; the Re (550) of the Q layer is preferably 100 nm to 180 nm, more preferably 110 nm to 170 nm, and even more preferably 110 nm to 150 nm. The thickness of the H layer can be adjusted so as to obtain the desired in-plane retardation of the λ/2 plate. When the H layer is the above-mentioned liquid crystal alignment solidified layer, its thickness is, for example, 2.0 μm to 4.0 μm. The thickness of the Q layer can be adjusted so as to obtain the desired in-plane retardation of the λ/4 plate. When the Q layer is the above-mentioned liquid crystal alignment solidified layer, 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 even more preferably 12° to 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° to 76°. When the retardation layer 20 has a laminated structure, each layer (for example, the H layer and the Q layer) may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light, or may exhibit a flat wavelength dispersion characteristic in which the retardation value hardly changes depending on the wavelength of the measurement light.

The retardation layer 20 (or each layer when it has a laminated structure) typically exhibits the following refractive index characteristic: nx>ny=nz. Note that "ny=nz" does not only include the case where ny and nz are completely equal, but also includes the case where they are substantially equal. Therefore, there may be cases where ny>nz or ny<nz, as long as the effect of the present invention is not impaired. The Nz coefficient of the retardation layer is preferably 0.9 to 1.5, and more preferably 0.9 to 1.3.

As described above, the retardation layer is preferably a liquid crystal alignment solidified layer. Examples of the liquid crystal compound include liquid crystal compounds whose liquid crystal phase is a nematic phase (nematic liquid crystals). Examples of such liquid crystal compounds that can be used include liquid crystal polymers and liquid crystal monomers. The mechanism by which the liquid crystallinity of the liquid crystal compound is expressed may be either lyotropic or thermotropic. The liquid crystal polymer and 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 orientation state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (i.e., curing) the liquid crystal monomer. After the liquid crystal monomer is aligned, for example, the liquid crystal monomers can be polymerized or crosslinked with each other, thereby fixing the above-mentioned orientation state. Here, a polymer is formed by polymerization, and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystals. Therefore, the formed retardation layer does not undergo transition to a liquid crystal phase, a glass phase, or a crystalline phase due to temperature changes, which are specific to liquid crystal compounds. As a result, the retardation layer becomes a retardation layer that is not affected by temperature changes and has excellent stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity varies depending on the type of the monomer. 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 used as the liquid crystal monomer. For example, the polymerizable mesogen compounds described in JP-A-2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171, GB2280445, etc. may be used. Specific examples of such polymerizable mesogen compounds include BASF's product name LC242, Merck's product name E7, and Wacker-Chem's product name LC-Sillicon-CC3767. As the liquid crystal monomer, a nematic liquid crystal monomer is preferred.

A-3. Relationship between the thickness of the polarizing plate and the thickness of the retardation layer The sum of the thickness of the polarizing plate and the thickness of the retardation layer (hereinafter, sometimes simply referred to as "total thickness") is 50 μm or less, preferably 45 μm or less, and more preferably 40 μm or less. On the other hand, the total thickness is, for example, 25 μm or more.

The ratio of the thickness of the polarizing plate to the thickness of the retardation layer (thickness of polarizing plate/thickness of retardation layer, hereinafter sometimes simply referred to as "thickness ratio") is 5 or more, preferably 8 or more, and more preferably 10 or more. On the other hand, the thickness ratio is preferably 30 or less, and more preferably 25 or less.

The laminate used in the manufacturing method according to the embodiment of the present invention has a small total thickness and a large ratio of the polarizing plate thickness to the total thickness (a small ratio of the retardation layer thickness). The inventors have found that the above-mentioned warping problem is likely to occur when the total thickness and thickness ratio are within the above-mentioned specified range. More specifically, when the difference between the thickness of the polarizing plate and the thickness of the retardation layer is not large, and when the thickness of the polarizing plate is excessively large, the warping problem is unlikely to occur in the polarizing plate with the retardation layer. Based on this new knowledge, the inventors have intensively studied the suppression of warping and found that the manufacturing method according to the embodiment of the present invention can efficiently suppress warping.

A-4. First Protective Film The first protective film 31 may be formed of any appropriate material. Specific examples of the forming material include polyester-based polymers such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), etc.; cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose; polycarbonate-based polymers; (meth)acrylic polymers such as polymethyl methacrylate; and cycloolefin-based polymers such as polynorbornene. These may be used alone or in combination of two or more.

The first protective film preferably has a moisture permeability of 30 g/ ^m2 ·24 h or less at 40° C. and 92% RH, more preferably 20 g/ ^m2 ·24 h or less. With such a first protective film, moisture can be appropriately added to the laminate (preferably the polarizer) in the humidification treatment described below, and a retardation layer-attached polarizing plate with suppressed warping can be obtained. On the other hand, the moisture permeability of the first protective film at 40° C. and 92% RH is, for example, 5 g/ ^m2 ·24 h or more.

The thickness of the first protective film is preferably 15 μm to 50 μm, and more preferably 25 μm to 40 μm.

As described above, the first protective film 31 can be attached to the polarizing plate 10 via the adhesive layer. Any suitable configuration can be adopted for the adhesive layer. 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 compounding ratio of monomers forming the base resin of the adhesive, as well as the compounding amount of the crosslinking agent, reaction temperature, reaction time, and the like, an adhesive having desired properties according to the purpose can be prepared. The base resin of the adhesive may be used alone or in combination of two or more kinds. The base resin is preferably an acrylic resin (specifically, the adhesive layer is preferably composed of an acrylic adhesive). The thickness of the adhesive layer is, for example, 5 μm to 15 μm. The storage modulus of the adhesive layer at 25° C. is, for example, 1.0×10 ⁵ Pa to 1.0×10 ⁷ Pa.

In one embodiment, a laminate in which the above-mentioned pressure-sensitive adhesive layer is formed on a first protective film (hereinafter referred to as a "surface protective film") is used. The thickness of the surface protective film is preferably 30 μm to 60 μm, and more preferably 30 μm to 50 μm. As described above, when the first protective film is peeled off, it can be peeled off together with the pressure-sensitive adhesive layer (together with the surface protective film).

A-5. Second Protective Film The second protective film 32 may be made of any suitable plastic film. Specific examples of the plastic film include a polyethylene terephthalate (PET) film, a polyethylene film, and a polypropylene film. As described above, the second protective film 32 may function as a separator. Specifically, a plastic film whose surface is coated with a release agent is preferably used as the second protective film 32. Specific examples of the release agent include a silicone-based release agent, a fluorine-based release agent, and a long-chain alkyl acrylate-based release agent.

The second protective film preferably has a moisture permeability of 30 g/ ^m2 ·24h or less at 40°C and 92% RH, more preferably 20 g/ ^m2 ·24h or less. With such a second protective film, moisture can be appropriately added to the laminate (preferably the polarizer) in the humidification treatment described below, and a retardation layer-attached polarizing plate with suppressed warping can be obtained. On the other hand, the moisture permeability of the second protective film at 40°C and 92% RH is, for example, 5 g/ ^m2 ·24h or more.

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

A-6. Preparation of Laminate The laminate 100 can be obtained, for example, by laminating the polarizing plate 10 and the retardation layer 20 to prepare a laminate precursor, and laminating the first protective film 31 and the second protective film 32 on the obtained laminate precursor.

The polarizing plate 10 and the retardation layer 20 are laminated, for example, while they are transported by rolls (so-called roll-to-roll). The lamination is typically performed by transferring a liquid crystal alignment solidified layer formed on a substrate. As shown in FIG. 2, when the retardation layer has a laminated structure, each retardation layer may be laminated (transferred) sequentially onto the polarizing plate, or a laminate of retardation layers may be laminated (transferred) onto the polarizing plate.

The transfer is performed, for example, using an active energy ray curable adhesive. The thickness of the active energy ray curable adhesive after curing (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 1.5 μm. The warping of the retardation layer-attached polarizing plate having the above-mentioned predetermined total thickness and thickness ratio is mainly caused by the adhesive used to laminate the polarizing plate and the retardation layer (specifically, shrinkage during curing of the active energy ray curable adhesive), and warping may occur in the laminate precursor obtained by laminating the polarizing plate 10 and the retardation layer 20.

Figure 3 is a cross-sectional view showing an example of the warped state of a laminate precursor. In Figure 3, hatching has been omitted from the cross section of the laminate precursor to make the drawing easier to see. In the example shown in Figure 3, the laminate precursor 90 has a convex warp toward the polarizing plate 10. The warp tends to occur along the absorption axis direction of the polarizing plate 10 (polarizer 11).

The lamination of the polarizing plate 10 and the retardation layer 20 is preferably performed in an environment in which the amount of water vapor (A1) is 10.2 g/m ³ or less. The amount of water vapor (A1) in the lamination is more preferably 6.0 g/m ³ to 10.0 g/m ³ , and even more preferably 8.0 g/m ³ to 9.5 g/m ^3. By performing the lamination in an environment in which the amount of water vapor (A1) is in such a range, for example, the effect of the humidification treatment described later becomes remarkable. Such an amount of water vapor (A1) in the lamination can be realized, for example, by changing the relative humidity according to the temperature in the range of 18°C to 25°C. The amount of water vapor (A1) can be realized, for example, by setting the relative humidity to 65% RH or less when the temperature is 18°C; or, for example, by setting the relative humidity to 55% RH or less when the temperature is 20°C; or, for example, by setting the relative humidity to 45% RH or less when the temperature is 23°C. The lower limit of the relative humidity may be, for example, 30% RH.

In one embodiment, the moisture permeability of either the protective layer 12 or the retardation layer 20 at 40°C and 92% RH is preferably 300 g/m2·24h or more, more preferably 400 g/m2·24h to 1000 g/m2·24h, and even more preferably 400 g/m2·24h to 800 g/m2·24h. If either the protective layer 12 or the retardation layer 20 has such moisture permeability, the effect of the humidification treatment described below can be significantly obtained.

As described above, if the laminate further has other functional layers (e.g., a conductive layer, other retardation layers), the functional layers can be laminated or formed at predetermined positions by any suitable method.

The laminate precursor having at least the polarizing plate 10 and the retardation layer 20 is laminated with the first protective film 31, for example, by bonding the above-mentioned surface protection film. The laminate precursor is laminated with the second protective film 32, for example, by using an adhesive. The thickness of the adhesive (the thickness of the adhesive layer disposed between the retardation layer 20 and the second protective film 32) is, for example, 10 μm to 20 μm.

B. Moisture Treatment The laminate is subjected to a humidification treatment. By subjecting the laminate to a humidification treatment, moisture is added to the laminate (preferably, the polarizer), and a retardation layer-attached polarizing plate with suppressed warping can be obtained. For example, the laminate is placed in an environment with a water vapor amount of 10.5 g/m ³ or more to perform the humidification treatment. The water vapor amount (A2) during the humidification treatment is preferably 10.5 g/m ³ to 30 g/m ³ , and more preferably 11 g/m ³ to 20 g/m ³ .

The amount of water vapor (A2) during the humidification process can be achieved, for example, by setting the relative humidity to 80% RH or more when the temperature is 18°C; or, for example, by setting the relative humidity to 60% RH or more when the temperature is 20°C; or, for example, by setting the relative humidity to 50% RH or more when the temperature is 23°C. The upper limit of the relative humidity can be, for example, 100% RH.

In one embodiment, the laminate is subjected to a humidification treatment under an environment that satisfies a water vapor amount greater than the water vapor amount (A1). More specifically, the difference between the water vapor amount (A2) during the humidification treatment and the water vapor amount (A1) is preferably 0.5 g/m ³ or more, more preferably 1.0 g/m ³ to 28 g/m ³ , even more preferably 1.0 g/m ³ to 12 g/m ³ , particularly preferably 1.5 g/m ³ to 10 g/m ³ , and most preferably 1.5 g/m ³ to 8 g/m ^3. By humidifying under such conditions, an appropriate amount of moisture can be imparted to the laminate. More specifically, moisture can be imparted to the laminate without shrinking the laminate. If the amount of moisture imparted to the laminate in the humidification treatment is too large, for example, warping in a direction opposite to the initial warping and/or warping in a direction perpendicular to the initial warping direction in the plane may occur.

In one embodiment, the laminate is preferably subjected to a humidification treatment so that the weight per unit area of the laminated portion from the polarizing plate to the adhesive layer increases by 0.1% or more. The weight increase per unit area of the laminated portion from the polarizing plate to the adhesive layer due to the humidification treatment is more preferably 0.1% to 2.0%, even more preferably 0.1% to 1.0%, and particularly preferably 0.1% to 0.5%. By setting the weight increase within such a range, the polarizer can absorb a desired amount of moisture. As a result, the warping of the resulting retardation layer-attached polarizing plate can be effectively suppressed. Here, the laminated portion from the polarizing plate to the adhesive layer refers to, for example, the laminated portion 80 of the polarizing plate 10, the adhesive layer 40, the retardation layer 20 (including the adhesive layer if it has a laminated structure) and the adhesive layer 50, as shown in FIG. 4. In FIG. 4, the cross section of the laminated portion is not hatched.

The time for the humidification treatment is preferably 6 hours or more, more preferably 12 hours or more, and even more preferably 24 hours or more. With such a treatment time, for example, the desired weight gain (moisture absorption) can be satisfactorily achieved. On the other hand, the time for the humidification treatment is, for example, 150 hours or less. Since the effect remains the same even if the humidification treatment time is excessively long, the upper limit of the humidification treatment time can be determined by balancing the desired amount of weight gain and production efficiency.

During the humidification process, the laminate is placed with its main surface at an angle to the placement surface. FIG. 5 is a cross-sectional view showing an example of the state in which the laminate is placed on the placement surface. Note that in FIG. 5, hatching has been omitted from the cross section of the laminate to make the drawing easier to see. In the illustrated example, the laminate 100 is placed on the placement surface S such that the main surface 100a of the laminate 100 forms an angle θ with the placement surface S. The angle θ is greater than 0° and equal to or less than 90°, preferably 70° to 90°, and more preferably 80° to 90°.

In the illustrated example, n sheets of the laminate 100 are arranged so that the main surfaces of adjacent laminates 100 overlap. Typically, prior to the humidification treatment, the laminate is cut into sheets of a predetermined size. The sheet-shaped laminate is preferably obtained by cutting a long laminate precursor. Specifically, it is preferable to obtain a sheet-shaped laminate precursor by cutting a long laminate precursor, and then laminate a first protective film and a second protective film on the sheet-shaped laminate precursor to obtain a sheet-shaped laminate. According to this embodiment, for example, since a large-scale roll conveying (roll-to-roll) facility is not required, the manufacturing efficiency can be improved. It is preferable to cut the laminate precursor having a warp so that the obtained sheet-shaped laminate is superimposed on the laminate precursor having a warp, as shown in FIG. 5. In one embodiment, the long laminate precursor is cut along a direction at 45° to the longitudinal direction. In another embodiment, the long laminate precursor is cut along the longitudinal direction and the width direction (direction perpendicular to the longitudinal direction).

According to this embodiment, moisture can be efficiently absorbed into the laminate (polarizer), and a polarizing plate with a retardation layer in which warping is suppressed can be manufactured with good yield. Specifically, by adopting a state in which the main surface of the laminate has an angle with respect to the mounting surface, as shown in FIG. 5, a humidification treatment can be performed on multiple laminates at once in a uniform state (e.g., a state in which the force applied to the laminate is uniform), as shown in FIG. 5. As a result, moisture can be uniformly applied to multiple laminates (e.g., a single humidification treatment can satisfactorily achieve an increase in weight of the laminated portion of the polarizing plate and the retardation layer in multiple laminates), and a polarizing plate with a retardation layer in which warping is suppressed can be manufactured with good yield. In addition, the obtained polarizing plate with a retardation layer can also have an excellent appearance.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The thickness and moisture permeability are values measured by the following measuring methods. Furthermore, unless otherwise specified, "parts" and "%" in the 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"), and the thickness of more than 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name "KC-351C").
<Moisture permeability>
The moisture permeability was determined by the cup method (JIS Z 0208).

[Example 1]
(Preparation of Polarizing Plate)
As a thermoplastic resin substrate, a long amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a Tg of about 75° C. was used, and one side of this resin substrate was subjected to a corona treatment.
A PVA aqueous solution (coating solution) was prepared by adding 13 parts by weight of potassium iodide to 100 parts by weight of a PVA-based resin prepared by mixing polyvinyl alcohol (polymerization degree 4,200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., product name "GOHSEFFIMER") in a ratio of 9:1, and dissolving the resultant in water.
The above PVA aqueous solution was applied to the corona-treated surface of a resin substrate and dried at 60° C. to form a PVA-based resin layer having a thickness of 13 μm, thereby producing a laminate.
The obtained laminate was uniaxially stretched 2.4 times in the longitudinal direction (machine direction) in an oven at 130° C. (auxiliary in-air stretching treatment).
Next, the laminate was immersed in an insolubilizing bath (a boric acid aqueous solution obtained by mixing 4 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (insolubilizing treatment).
Next, the film was immersed in a dye bath (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with 100 parts by weight of water) having a liquid temperature of 30° C. for 60 seconds while adjusting the concentration so that the single transmittance (Ts) of the finally obtained polarizer would have a desired value (dyeing treatment).
Next, the plate was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with 100 parts by weight of water) at a liquid temperature of 40° C. for 30 seconds (crosslinking treatment).
Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration: 4 wt %, potassium iodide concentration: 5 wt %) at a liquid temperature of 70° C., and uniaxially stretched in the longitudinal direction (longitudinal direction) between rolls with different peripheral speeds to a total stretch ratio of 5.5 times (underwater stretching treatment).
Thereafter, the laminate was immersed in a cleaning bath (an aqueous solution obtained by mixing 4 parts by weight of potassium iodide with 100 parts by weight of water) at a liquid temperature of 20° C. (cleaning treatment).
Thereafter, the film was dried in an oven maintained at about 90° C., while being brought into contact with a SUS heated roll whose surface temperature was maintained at about 75° C. (drying shrinkage treatment).
In this manner, a polarizer having a thickness of about 5 μm was formed on the resin substrate, and a laminate having a resin substrate/polarizer structure was obtained.

An HC-COP film (thickness 27 μm) was attached as a protective layer to the polarizer side of the obtained laminate via an ultraviolet-curable adhesive. The HC-COP film is a film in which an HC layer (thickness 2 μm) is formed on a cycloolefin resin (COP) film (thickness 25 μm), and the COP film was attached to the polarizer side. The resin substrate was then peeled off from the polarizer to obtain a polarizing plate having a HC-COP film (protective layer)/polarizer configuration.

(Preparation of Retardation Layer)
A liquid crystal composition (coating liquid) was prepared by dissolving 10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: product name "Paliocolor LC242", represented by the following formula) and 3 g of a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: product name "Irgacure 907") in 40 g of toluene.

The surface of a polyethylene terephthalate (PET) film (thickness 38 μm) was rubbed with a rubbing cloth and subjected to an orientation treatment. The orientation treatment direction was set to be 15° from the viewing side with respect to the direction of the absorption axis of the polarizer when it was laminated to the polarizing plate. The liquid crystal coating liquid was applied to this orientation treatment surface with a bar coater, and the liquid crystal compound was aligned by heating and drying at 90 ° C for 2 minutes. The liquid crystal layer thus formed was irradiated with light of 1 mJ / cm ² using a metal halide lamp, and the liquid crystal layer was hardened to form a liquid crystal alignment solidified layer A (H layer) on the PET film. The thickness of the liquid crystal alignment solidified layer A was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Furthermore, the liquid crystal alignment solidified layer A showed a refractive index characteristic of nx > ny = nz.

A liquid crystal alignment solidified layer B (Q layer) was formed on a PET film in the same manner as above, except that the coating thickness was changed and the orientation treatment direction was set to a 75° angle from the viewing side to the absorption axis direction of the polarizer. The liquid crystal alignment solidified layer B had a thickness of 1.5 μm and an in-plane retardation Re (550) of 140 nm. Furthermore, the liquid crystal alignment solidified layer B exhibited refractive index characteristics of nx>ny=nz.

(Preparation of Laminate)
The obtained liquid crystal alignment solidified layer A (H layer) and liquid crystal alignment solidified layer B (Q layer) were transferred in this order to the polarizer side of the obtained polarizing plate. At this time, the transfer (lamination) was performed so that the angle between the absorption axis of the polarizer and the slow axis of the alignment solidified layer A was 15°, and the angle between the absorption axis of the polarizer and the slow axis of the alignment solidified layer B was 75°. Each transfer was performed via an ultraviolet-curing adhesive (thickness 1.0 μm). In this way, a laminate precursor was obtained. The transfer (lamination) was performed while being transported by rolls. Furthermore, the transfer (lamination) was performed in an environment with a water vapor amount of 9.3 g/ ^m3 (23°C and 45% RH).
The total thickness of the obtained laminate precursor was 36 μm, and the thickness ratio was 8.

The obtained long laminate precursor was cut in a direction at 45° to the longitudinal direction and the width direction (direction perpendicular to the longitudinal direction) to obtain a 165 mm x 80 mm sheet of laminate precursor. The longitudinal direction corresponds to the absorption axis direction of the polarizer.

Next, a surface protection film (thickness 48 μm) was attached to the protective layer side of the polarizing plate of the laminate precursor. The surface protection film was a film in which a pressure-sensitive adhesive layer (thickness 10 μm) was formed on a PET film (thickness 38 μm, moisture permeability 18 g/ ^m2 ·24 h).
Furthermore, a separator (thickness 38 μm, moisture permeability 18 g/ ^m2 ·24 h) was attached to the liquid crystal alignment solidified layer B (Q layer) side of the laminate precursor via an adhesive layer (thickness 15 μm) to obtain a sheet-shaped laminate of 165 mm × 80 mm.
Similarly, a total of 500 sheet-shaped laminates measuring 165 mm×80 mm were prepared.

(Humidification treatment)
500 sheets of the obtained sheet-like laminate were stacked to form a laminate assembly, and the laminate was subjected to a humidification treatment in a state where the main surface of each laminate was placed at an angle of 90° with respect to the placement surface as shown in Fig. 5. Specifically, 500 sheets of laminate (laminate assembly) were housed in a case having a predetermined size, and the humidification treatment was performed in a state where the main surface of each laminate was placed at an angle of 90° with respect to the inner bottom surface (placement surface) of the case. Here, the humidification treatment was performed in a state where the long side of each laminate was in contact with the inner bottom surface of the case, and the vacant space in the case (the space between the main surface of the laminate located at the front end and the rear end of the laminate assembly and the inner side surface of the case) was filled with an unfoamed polystyrene (PS) sheet. The humidification treatment was performed for 24 hours at 23°C and 60% RH (water vapor amount 12.4 g/m ³ ).
In this way, a polarizing plate with a retardation layer was obtained.

[Example 2]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that a TAC film (thickness: 27 μm) was used as the protective layer instead of the HC-COP film.

[Comparative Example 1]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the long laminate precursor was not cut and that the long laminate was produced and wound into a roll and subjected to the humidification treatment.

[Comparative Example 2]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that in the humidification treatment, the laminate assembly was placed so that the main surface of each laminate was at an angle of 0° with respect to the mounting surface (500 laminates were stacked and placed on the mounting surface).

[Comparative Example 3]
A polarizing plate with a retardation layer was obtained in the same manner as in Example 1, except that the humidification treatment was carried out at 23° C. and 45% RH (water vapor amount: 9.3 g/m ³ ) for 24 hours.

[Reference Example 1]
A long roll of a PVA-based resin film having a thickness of 60 μm was uniaxially stretched in the longitudinal direction by a roll stretching machine so that the total stretch ratio was 6.0 times, while simultaneously undergoing swelling, dyeing, crosslinking and washing treatments, and finally drying treatment to produce a polarizer having a thickness of 22 μm. A TAC film (thickness 71 μm) with an HC layer was bonded to one surface of the obtained polarizer. Furthermore, a polycarbonate resin retardation film (thickness 58 μm) showing reverse dispersion wavelength dependency and having Re (550) of 140 nm was bonded to the other surface of the polarizer. Here, the retardation film was bonded so that the angle between the slow axis of the retardation film and the absorption axis of the polarizer was 45°. In this way, a retardation layer-attached polarizing plate was obtained. The total thickness of the retardation layer-attached polarizing plate was 151 μm, and the thickness ratio was 1.6. This retardation layer-attached polarizing plate was cut into a size of 165 mm x 80 mm and placed on a flat surface, and no warping was observed.

[Reference Example 2]
A polarizer having a thickness of 22 μm was prepared in the same manner as in Reference Example 1. A TAC film with an HC layer (thickness 91 μm) was attached to one surface of the obtained polarizer, and a TAC film (thickness 80 μm) was attached to the other surface to obtain a polarizing plate. A polarizing plate with a retardation layer having a structure of a TAC film with an HC layer/polarizer/TAC film/adhesive layer/retardation layer (H layer)/adhesive layer/retardation layer (Q layer) was obtained in the same manner as in Example 1 except that this polarizing plate was used. The total thickness of the polarizing plate with a retardation layer was 197 μm, and the thickness ratio was 48. This polarizing plate with a retardation layer was cut into a size of 165 mm x 80 mm and placed on a flat surface, and no warping was observed.

The following evaluations were carried out for the Examples and Comparative Examples. The evaluation results are summarized in Tables 1 and 2.
<Evaluation>
1. Weight Change per Unit Area The weight of the laminated portion from the polarizing plate to the pressure-sensitive adhesive layer (laminate portion 80 shown in FIG. 4) was measured using an electronic balance before and after humidification, and the weight change was calculated from the obtained measured values.
2. Amount of Warping The laminate precursor and the retardation layer-attached polarizing plate in the form of a sheet were placed on a flat surface with the retardation layer side facing the flat surface, and the height of the highest part from the flat surface was measured to obtain the amount of warping.
In addition, a convex warp toward the stationary surface is represented as "positive (+)" and a convex warp toward the opposite side to the stationary surface is represented as "negative (-)." In the table, "(MD)" corresponds to the transport direction of the roll transport and corresponds to the absorption axis direction of the polarizer.
The appearance of the obtained polarizing plate with a retardation layer was visually observed, and the evaluation criteria were as follows:
(Evaluation Criteria)
Good: No dents observed Bad: Dents observed

As is clear from Table 1, in Examples 1 and 2, the weight change due to the humidification treatment was confirmed to be within the range of 0.1% to 0.4%, and the warpage of the obtained retardation layer-attached polarizing plate was within the range of -20 mm to +20 mm (- indicates warpage in the MD direction, and + indicates warpage in the TD direction perpendicular to the MD direction). Thus, in Examples 1 and 2, moisture could be uniformly added to multiple laminates, and the degree of correction of the warpage generated in the laminate precursor was also highly uniform.
In contrast, in Comparative Example 2 in which the laminates were placed on the mounting surface, the weight change due to the humidification treatment was found to vary. Specifically, the laminates located at the top of the laminate assembly were subjected to a smaller force than the laminates located at the bottom, and the laminates located at the top absorbed more moisture than the laminates located at the bottom, and the laminates located at the top were found to have a warp in the opposite direction to the warp that occurred in the laminate precursor. On the other hand, the warp that occurred in the laminate precursor was improved in the laminates located at the bottom. Thus, the degree of correction of the warp that occurred in the laminate precursor was also found to vary. In addition, dents were also found in the obtained polarizing plate with a retardation layer.

In Comparative Example 1, in which the film was subjected to a humidification treatment in a rolled state, the weight per unit area of the inner part wound into the roll did not change, and warping was not improved.
As is clear from the reference examples, such warping is a problem specific to polarizing plates with a retardation layer, which have a small total thickness and a large ratio of the thickness of the polarizing plate to the total thickness.

The polarizing plate with a retardation layer according to one embodiment of the present invention is used as a polarizing plate with a retardation layer for an image display device, and can be particularly suitably used for an image display device that is curved, or that can be bent, folded, or rolled up. Representative examples of image display devices include liquid crystal display devices, organic EL display devices, and inorganic EL display devices.

10 Polarizing plate 11 Polarizer 12 Protective layer 20 Retardation layer 21 First retardation layer (H layer)
22 Second retardation layer (Q layer)
90 Laminate precursor 100 Laminate

Claims (16)

preparing a laminate having, in this order, a first protective film, a polarizing plate including a polarizer and a protective layer disposed on at least one side of the polarizer, a retardation layer, and a second protective film, the sum of the thickness of the polarizing plate and the thickness of the retardation layer being 50 μm or less, and the ratio of the thickness of the polarizing plate to the thickness of the retardation layer being 5 or more; and
The laminate is placed on a placement surface and placed in an environment with a water vapor amount of 10.5 g/ ^m3 or more to perform a humidification treatment;
preparing the laminate includes laminating the polarizing plate and the retardation layer using an active energy ray-curable adhesive;
The laminate is placed with a main surface of the laminate at an angle to the placement surface,
The humidification treatment is performed in a state where a plurality of the laminates are arranged so as to overlap each other.
A method for producing a polarizing plate with a retardation layer. The manufacturing method according to claim 1, which includes laminating the polarizing plate and the retardation layer to obtain a laminate precursor. The manufacturing method according to claim 2, which includes cutting the laminate precursor into sheets. The method according to claim 1 , wherein the first protective film has a moisture permeability of 30 g/m ² ·24 h or less at 40° C. and 92% RH. The method according to claim 1 , wherein the second protective film has a moisture permeability of 30 g/m ² ·24 h or less at 40° C. and 92% RH. The method according to claim 1 , further comprising laminating the polarizing plate and the retardation layer while transporting them with a roll. The method according to claim 1 , wherein the active energy ray-curable adhesive has a thickness of 0.4 μm or more after curing. the laminate has a pressure-sensitive adhesive layer disposed on a side of the retardation layer on which the polarizing plate is not disposed,
The method according to claim 1 , wherein the weight increase per unit area of the laminated portion of the polarizing plate, the retardation layer and the pressure-sensitive adhesive layer due to the humidification treatment is 0.1% or more. The method according to claim 1 , wherein the humidification treatment is carried out for 6 hours or more. The method according to any one of claims 1 to 9 , wherein the amount of water vapor during the humidification treatment is 10.5 g/m ³ to 30 g/m ³ . The method according to claim 1 , further comprising laminating the polarizing plate and the retardation layer in an environment having a water vapor amount of 10.2 g/m ³ or less. The method according to claim 1 , wherein the amount of water vapor during the humidification treatment is 0.5 g/m ³ or more higher than the amount of water vapor during lamination of the polarizing plate and the retardation layer. The method according to claim 1 , wherein the retardation layer or the protective layer has a moisture permeability of 300 g/m ² ·24 h or more at 40° C. and 92% RH. The method according to claim 1 , wherein the polarizing plate has a protective layer disposed only on a side of the polarizer on which the retardation layer is not disposed. The method according to claim 1 , wherein the center of gravity of the polarizer in the thickness direction is located closer to the retardation layer than the center of gravity of a laminated portion of the polarizing plate and the retardation layer in the thickness direction. The method according to claim 1 , wherein the retardation layer is a layer in which a liquid crystal compound is aligned and fixed.

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