WO2022024798A1 - Polarizing plate, polarizing plate with phase difference layer, and image display device including said polarizing plate or said polarizing plate with phase difference layer - Google Patents

Abstract

Provided is a polarizing plate in which the occurrence of cracking in a deformed portion is suppressed although being extremely thin. This polarizing plate includes a polarizer, and a protective layer provided on at least one side of the polarizer, and has a deformed shape other than a rectangular shape. The protective layer comprises a resin film having a thickness of 10 μm or less. The polarizer comprises a PVA-based resin film containing a dichroic material. In one embodiment, expression (1) is satisfied when the single transmittance of the polarizer is denoted by x%, and the birefringence of PVA-based resin is denoted by y. In another embodiment, expression (2) is satisfied when the single transmittance of the polarizer is denoted by x%, and the in-plane phase difference of the PVA-based resin film is denoted by z nm. In still another embodiment, expression (3) is satisfied when the single transmittance of the polarizer is denoted by x%, and the orientation function of the PVA-based resin is denoted by f. In yet another embodiment, the piercing strength of the polarizer is 30 gf/μm or more.　(1): y < -0.011x+0.525 (2): z < -60x+2875 (3): f < -0.018x+1.11

Description

An image display device including a polarizing plate, a polarizing plate with a retardation layer, and the polarizing plate or a polarizing plate with a retardation layer.

The present invention relates to a polarizing plate, a polarizing plate with a retardation layer, and an image display device including the polarizing plate or the polarizing plate with a retardation layer.

In recent years, image display devices represented by liquid crystal displays and electroluminescence (EL) display devices (for example, organic EL display devices and inorganic EL display devices) have rapidly become widespread. Due to the image forming method of the image display device, a polarizing plate is arranged on at least one of the image display devices. In recent years, as the demand for thinner image display devices has increased, the demand for thinner polarizing plates has also increased. By the way, in recent years, it may be desired to process a polarizing plate to a shape other than a rectangle (deformed processing: for example, formation of a notch and / or a through hole). However, there is a problem that cracks are likely to occur in the deformed portion of the thin polarizing plate.

Japanese Unexamined Patent Publication No. 2001-343521

The present invention has been made to solve the above-mentioned conventional problems, and a main object thereof is to provide a polarizing plate which is extremely thin and in which crack generation in a deformed portion is suppressed.

The polarizing plate according to one embodiment of the present invention has a polarizing element and a protective layer arranged on at least one side of the polarizing element, and has a non-rectangular shape. The protective layer is made of a resin film having a thickness of 10 μm or less. When the polarizing element is made of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y, the following formula (1) is used. Meet:
y <−0.011x + 0.525 (1).
A polarizing plate according to another embodiment of the present invention has a polarizing element and a protective layer arranged on at least one side of the polarizing element, and has a non-rectangular shape. The protective layer is made of a resin film having a thickness of 10 μm or less. The polarizing element is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and when the single transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm, the following formula is used. Satisfy (2):
z <-60x + 2875 (2).
The polarizing plate according to still another embodiment of the present invention has a polarizing element and a protective layer arranged on at least one side of the polarizing element, and has a non-rectangular shape. The protective layer is made of a resin film having a thickness of 10 μm or less. The polarizing element is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and when the single transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is f, the following formula (3) is used. Meet:
f <−0.018x + 1.11 (3).
The polarizing plate according to still another embodiment of the present invention has a polarizing element and a protective layer arranged on at least one side of the polarizing element, and has a non-rectangular shape. The protective layer is made of a resin film having a thickness of 10 μm or less. The polarizing element is made of a polyvinyl alcohol-based resin film containing a dichroic substance, and the piercing strength of the polarizing element is 30 gf / μm or more.
In one embodiment, the thickness of the polarizing element is 10 μm or less.
In one embodiment, the simple substance transmittance of the above-mentioned extruder is 40.0% or more, and the degree of polarization is 99.0% or more.
In one embodiment, the variant has a through hole, a V-shaped notch, a U-shaped notch, a recess with a shape similar to a ship shape when viewed in plan view, a rectangular recess when viewed in plan view, and a bathtub when viewed in plan view. It is selected from a group consisting of R-shaped recesses that approximate the shape and combinations thereof.
In one embodiment, the radius of curvature of the U-shaped notch is 5 mm or less.
In one embodiment, the resin film comprises at least one resin selected from epoxy resins and (meth) acrylic resins.
In one embodiment, the resin film is composed of a photocationically cured product of an epoxy resin, and the softening temperature of the resin film is 100 ° C. or higher.
In one embodiment, the resin film is composed of a solidified coating film of an organic solvent solution of an epoxy resin, and the softening temperature of the resin film is 100 ° C. or higher.
In one embodiment, the resin film is composed of a solidified coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin, and the softening temperature of the resin film is 100 ° C. or higher. In one embodiment, the thermoplastic (meth) acrylic resin has at least one selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit. ..
According to another aspect of the present invention, a polarizing plate with a retardation layer is provided. The polarizing plate with a retardation layer includes the above-mentioned polarizing plate and the above-mentioned retardation layer, and the retardation layer is arranged on the side opposite to the side where the above-mentioned protective layer of the above-mentioned polarizing element is arranged.
In one embodiment, Re (550) of the retardation layer is 100 nm to 190 nm, Re (450) / Re (550) is 0.8 or more and less than 1, and the slow axis of the retardation layer. The angle formed by the above-mentioned polarizing element with the absorption axis is 40 ° to 50 °.
In one embodiment, the retardation layer is laminated on the polarizing plate via an adhesive layer.
According to yet another aspect of the present invention, an image display device is provided. The image display device includes the above-mentioned polarizing plate or the above-mentioned polarizing plate with a retardation layer.

According to the embodiment of the present invention, in a polarizing plate having a deformed shape (deformed portion), by controlling the orientation state of the polyvinyl alcohol (PVA) -based resin of the polarizing element, the polarizing plate is extremely thin, but the deformed portion is formed. It is possible to realize a polarizing plate in which crack generation is suppressed. Further, such a polarizing element (as a result, a polarizing plate) can exhibit practically acceptable optical characteristics.

It is a schematic sectional drawing of the polarizing plate by one Embodiment of this invention. It is a schematic plan view explaining an example of the deformed or deformed processed part in the polarizing plate by embodiment of this invention. It is a schematic plan view explaining the deformation example of the deformed or deformed part in the polarizing plate by embodiment of this invention. It is a schematic plan view explaining the further modification of the deformed or deformed processed portion in the polarizing plate according to the embodiment of the present invention. It is a schematic plan view explaining the further modification of the deformed or deformed processed portion in the polarizing plate according to the embodiment of the present invention. It is a schematic diagram which shows an example of the drying shrinkage process using a heating roll in the method of manufacturing a polarizing element which can be used for a polarizing plate by embodiment of this invention. It is the schematic sectional drawing of the polarizing plate with a retardation layer by one Embodiment of this invention. It is a graph which shows the relationship between the simple substance transmittance of the polarizing element produced in an Example and the comparative example, and the birefringence of a PVA-based resin. It is a graph which shows the relationship between the simple substance transmittance of the elemental transmittance and the in-plane phase difference of a PVA-based resin film produced in an Example and a comparative example. It is a graph which shows the relationship between the simple substance transmittance of the elemental transmittance and the orientation function of a PVA-based resin produced in an Example and a comparative example.

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

A. Polarizing plate A-1. Overall Configuration of Polarizing Plate FIG. 1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention. The polarizing plate 100 of the illustrated example has a polarizing element 10 and a protective layer 20 arranged on one side of the polarizing element 10. A separate protective layer (not shown) may be provided on the opposite side of the protector 10 from the protective layer 20 depending on the purpose. The protective layer 20 is made of a resin film having a thickness of 10 μm or less. The polarizing plate may be used as a viewing-side polarizing plate of an image display device, or may be used as a back-side polarizing plate. The polarizing plate is typically used as a viewing-side polarizing plate. In this case, the protective layer 20 may be arranged on the visual recognition side (the side opposite to the image display cell).

The polarizing plate according to the embodiment of the present invention has a variant shape other than a rectangle. As used herein, the term "having a variant other than a rectangle" means that the planar view shape of the polarizing plate has a shape other than a rectangle. The irregular shape is typically a deformed portion that has been deformed. Therefore, in the "polarizing plate having a deformed shape other than a rectangle" (hereinafter, may be referred to as a "deformed polarizing plate"), the entire deformed polarizing plate (that is, the outer edge defining the planar view shape of the polarizing plate) is other than a rectangle. This includes not only a certain case but also a case where a deformed portion is formed in a portion inwardly separated from the outer edge of the rectangular polarizing plate. In the polarizing plate, cracks are likely to occur in such a deformed portion, and according to the embodiment of the present invention, such cracks can be remarkably suppressed. More details are as follows. In a normal (ie, non-deformed) polarizing plate (essentially a polarizing element), cracks often occur along the absorber's absorption axis (stretching direction). On the other hand, L-shaped cracks (cracks in the diagonal direction with respect to the absorption axis) may occur in the deformed portion. According to the embodiment of the present invention, as will be described later, by making the orientation of the molecular chain of the PVA-based resin of the polarizing element in the direction of the absorption axis gentler than that of the conventional polarizing element, not only ordinary cracks but also this crack can be achieved. Such L-shaped cracks can also be remarkably suppressed.

Examples of the irregular shape (deformed portion) include a chamfered corner portion in an R shape, a through hole, and a cutting portion that becomes a concave portion when viewed in a plan view, as shown in FIGS. 2 and 3. Typical examples of the recess include a shape similar to a ship shape, a rectangle, an R shape similar to a bathtub shape, a V-shaped notch, and a U-shaped notch. As another example of the irregular shape (deformed portion), as shown in FIGS. 4 and 5, there is a shape corresponding to the instrument panel of an automobile. The shape includes a portion where the outer edge is formed in an arc shape along the rotation direction of the meter needle and the outer edge forms a V-shape (including an R shape) convex inward in the plane direction. Needless to say, the shape of the deformed shape (deformed portion) is not limited to the illustrated example. For example, as the shape of the through hole, any appropriate shape (for example, ellipse, triangle, quadrangle, pentagon, hexagon, octagon) may be adopted depending on the purpose other than the substantially circular shape in the illustrated example. Further, the through hole is provided at an arbitrary appropriate position according to the purpose. As shown in FIG. 3, the through hole may be provided at a substantially central portion of the longitudinal end portion of the rectangular polarizing plate, or may be provided at a predetermined position at the longitudinal end portion of the polarizing plate. It may be provided at the corners; although not shown, it may be provided at the lateral end of the rectangular polarizing plate; at the center of the deformed polarizing plate as shown in FIG. 4 or FIG. It may be provided. As shown in FIG. 3, a plurality of through holes may be provided. Further, the shapes of the illustrated examples may be appropriately combined according to the purpose. For example, a through hole may be formed at any position on the modified polarizing plate of FIG. 2; a V-shaped notch and / or a U-shaped notch may be formed at any appropriate position on the outer edge of the modified polarizing plate of FIG. 4 or FIG. It may be formed. Such a deformed polarizing plate can be suitably used for an image display device such as an automobile meter panel, a smartphone, a tablet PC or a smart watch. For example, when the variant includes an R shape, the radius of curvature thereof is, for example, 0.2 mm or more, for example, 1 mm or more, and for example, 2 mm or more. On the other hand, the radius of curvature is, for example, 10 mm or less, and is, for example, 5 mm or less. Further, for example, when the irregular shape is a U-shaped notch, the radius of curvature (the radius of curvature of the U-shaped portion) is, for example, 5 mm or less, for example, 1 mm to 4 mm, and for example, 2 mm to 3 mm.

The variant (deformed portion) can be formed by any suitable method. Specific examples of the forming method include cutting with an end mill, punching with a punching blade such as a Thomson blade, and cutting with laser light irradiation. These methods may be combined.

A-2. Polarizer The polarizing element is composed of a PVA-based resin film containing a dichroic substance. In one embodiment, the polarizing element satisfies the following formula (1) when the simple substance transmittance is x% and the birefringence of the polyvinyl alcohol-based resin constituting the polarizing element is y. In one embodiment, the substituent satisfies the following formula (2) when the simple substance transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film constituting the polarizing element is znm. In one embodiment, the polarizing element satisfies the following formula (3) when the simple substance transmittance is x% and the orientation function of the polyvinyl alcohol-based resin constituting the polarizing element is f. In one embodiment, the puncture strength of the polarizing element is 30 gf / μm or more.
y <-0.011x + 0.525 (1)
z <-60x + 2875 (2)
f <-0.018x + 1.11 (3)

Double refraction of PVA-based resin in the above deflector (hereinafter referred to as PVA double refraction or PVA Δn), in-plane phase difference of PVA-based resin film (hereinafter referred to as “PVA in-plane phase difference”). , The orientation function of the PVA-based resin (hereinafter referred to as "orientation function of PVA") and the piercing strength of the modulator are both values related to the degree of orientation of the molecular chains of the PVA-based resin constituting the modulator. .. Specifically, the birefringence, in-plane phase difference and orientation function of PVA can be large as the degree of orientation increases, and the puncture strength can decrease as the degree of orientation increases. In the polarizing element according to the embodiment of the present invention (that is, the polarizing element satisfying the above formulas (1) to (3) or the piercing strength), the orientation of the molecular chain of the PVA-based resin in the absorption axis direction is larger than that of the conventional polarizing element. Due to the gradualness, heat shrinkage in the absorption axis direction is suppressed. As a result, such a polarizing element (as a result, a polarizing plate) can suppress the occurrence of cracks in the deformed portion while being extremely thin. Further, since such a polarizing element (as a result, a polarizing plate) is also excellent in flexibility and bending durability, a curved image display device is preferable, a bendable image display device is more preferable, and a folding image display device is more preferable. It can be applied to possible image display devices. Conventionally, it has been difficult to obtain acceptable optical characteristics (typically, simple substance transmittance and degree of polarization) with a polarizing element having a low degree of orientation. It is possible to achieve both a lower degree of orientation of the PVA-based resin and an acceptable optical property.

The polarizing element preferably satisfies the following formulas (1a) and / or the following formula (2a), and more preferably the following formulas (1b) and / or the formula (2b).
-0.004x + 0.18 <y <-0.011x + 0.525 (1a)
-0.003x + 0.145 <y <-0.011x + 0.520 (1b)
-40x + 180 <z <-60x + 2875 (2a)
-30x + 1450 <z <-60x + 2850 (2b)

In the present specification, the in-plane retardation value of PVA is the in-plane retardation value of the PVA-based resin film at 23 ° C. and a wavelength of 1000 nm. By setting the measurement wavelength in the near-infrared region, the influence of absorption of iodine in the polarizing element can be eliminated, and the phase difference can be measured. The birefringence of PVA (in-plane birefringence) is a value obtained by dividing the in-plane phase difference of PVA by the thickness of the polarizing element.

The in-plane phase difference of PVA is evaluated as follows. First, the phase difference value is measured at a plurality of wavelengths having a wavelength of 850 nm or more, the measured phase difference value: R (λ) and the wavelength: λ are plotted, and this is fitted to the following Selmeyer equation by the least squares method. Let me. Here, A and B are fitting parameters and coefficients determined by the least squares method.
R (λ) = A + B / (λ ^{2-600 2 )}
At this time, the phase difference value R (λ) is divided into the in-plane phase difference (Rpva) of PVA having no wavelength dependence and the in-plane phase difference value (Ri) of iodine having a strong wavelength dependence as follows. Can be separated.
Rpva = A
Ri = B / (λ ^{2-600 2 )}
Based on this separation formula, the in-plane phase difference (that is, Rpva) of PVA at a wavelength of λ = 1000 nm can be calculated. The method for evaluating the in-plane phase difference of the PVA is also described in Japanese Patent No. 5923760, and can be referred to as necessary.
Further, the birefringence (Δn) of PVA can be calculated by dividing this phase difference by the thickness.

Examples of commercially available devices for measuring the in-plane phase difference of PVA at a wavelength of 1000 nm include KOBRA-WR / IR series and KOBRA-31X / IR series manufactured by Oji Measurement Co., Ltd.

The orientation function (f) of the polarizing element preferably satisfies the following formula (3a), and more preferably the following formula (3b). If the orientation function is too small, acceptable single transmittance and / or degree of polarization may not be obtained.
-0.01x + 0.50 <f <-0.018x + 1.11 (3a)
-0.01x + 0.57 <f <-0.018x + 1.1 (3b)

The orientation function (f) is obtained by total internal reflection spectroscopy (ATR) measurement using, for example, a Fourier transform infrared spectrophotometer (FT-IR) and polarized light as measurement light. Specifically, germanium is used as the crystallite to which the polarizing element is brought into close contact, the incident angle of the measurement light is 45 °, and the polarized infrared light (measurement light) to be incident is the surface to which the sample of the germanium crystal is brought into close contact. The polarization (s ^- polarized light) that vibrates in parallel with the light is used, and the measurement is performed with the extension directions of the substituents arranged parallel and perpendicular to the polarization direction of the measurement light. Is calculated according to the following formula. Here, the intensity I is a ^value of 2941 cm -1/3330 cm ^-1 with 3330 cm ^-1 as a reference peak. When f = 1, it is completely oriented, and when f = 0, it is random. Further, the peak of 2941 cm ^-1 is considered to be absorption caused by the vibration of the main chain (-CH _2- ) of PVA in the polarizing element.
f = (3 <cos ² θ> -1) / 2
= (1-D) / [c (2D + 1)]
= -2 x (1-D) / (2D + 1)
However,
In the case of vibration of 2941 cm ^-1 with c = (3cos ² β-1) / 2, β = 90 °.
θ: Angle of molecular chain with respect to stretching direction β: Angle of transition dipole moment with respect to molecular chain axis D = (I _⊥ ) / (I _// ) (In this case, D becomes larger as the PVA molecule is oriented)
I _⊥ : Absorption intensity when the polarization direction of the measurement light and the extension direction of the modulator are perpendicular I _// : Absorption intensity when the polarization direction of the measurement light and the extension direction of the modulator are parallel

The thickness of the polarizing element is preferably 10 μm or less, more preferably 8 μm or less. The lower limit of the thickness of the transducer can be, for example, 1 μm. The thickness of the polarizing element may be 2 μm to 10 μm in one embodiment and 2 μm to 8 μm in another embodiment. By making the thickness of the stator very thin in this way, the heat shrinkage can be made very small. It is presumed that such a configuration can also contribute to suppressing the occurrence of cracks in the deformed portion of the polarizing plate.

The polarizing element preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The simple substance transmittance of the polarizing element is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of the single transmittance can be, for example, 49.0%. The simple substance transmittance of the polarizing element is 40.0% to 45.0% in one embodiment. The degree of polarization of the polarizing element is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization can be, for example, 99.999%. The degree of polarization of the polarizing element is 99.0% to 99.9% in one embodiment. Despite the fact that the polarizing element according to the embodiment of the present invention has a lower degree of orientation of the PVA-based resin constituting the polarizing element than the conventional one and has the above-mentioned in-plane phase difference, birefringence and / or orientation function. One of the features is that such a practically acceptable single-unit transmittance and degree of polarization can be realized. It is presumed that this is due to the manufacturing method described later. The single transmittance is typically a Y value measured with an ultraviolet-visible spectrophotometer and corrected for luminosity factor. The degree of polarization is typically determined by the following equation based on the parallel transmittance Tp and the orthogonal transmittance Tc measured with an ultraviolet-visible spectrophotometer and corrected for luminosity factor.
Polarization degree (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100

The puncture strength of the polarizing element is, for example, 30 gf / μm or more, preferably 35 gf / μm or more, more preferably 40 gf / μm or more, still more preferably 45 gf / μm or more, and particularly preferably 50 gf / μm or more. That is all. The upper limit of the piercing strength can be, for example, 80 gf / μm. By setting the piercing strength of the polarizing element within such a range, it is possible to remarkably suppress the occurrence of cracks in the deformed portion and the splitting of the polarizing element along the absorption axis direction. As a result, a polarizing element having very excellent flexibility (as a result, a polarizing plate) can be obtained. The piercing strength indicates the cracking resistance of the polarizing element when the polarizing element is pierced with a predetermined strength. The piercing strength can be expressed as, for example, the strength (breaking strength) at which the polarizing element is cracked when a predetermined needle is attached to a compression tester and the needle is pierced into the polarizing element at a predetermined speed. As is clear from the unit, the piercing strength means the piercing strength per unit thickness (1 μm) of the polarizing element.

As described above, the polarizing element is composed of a PVA-based resin film containing a dichroic substance. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially, a polarizing element) contains an acetoacetyl-modified PVA-based resin. With such a configuration, a polarizing element having a desired piercing strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight, when the total amount of the PVA-based resin is 100% by weight. .. When the blending amount is in such a range, the piercing strength can be in a more suitable range.

The decoder can typically be made using a laminate of two or more layers. Specific examples of the polarizing element obtained by using the laminated body include a polarizing element obtained by using a laminated body of a resin base material and a PVA-based resin layer coated and formed on the resin base material. The polarizing element obtained by using the laminate of the resin base material and the PVA-based resin layer coated and formed on the resin base material is, for example, a resin base material obtained by applying a PVA-based resin solution to the resin base material and drying it. It is produced by forming a PVA-based resin layer on the PVA-based resin layer to obtain a laminate of a resin base material and a PVA-based resin layer; and stretching and dyeing the laminate to make the PVA-based resin layer a stator. obtain. In the present 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 base material. Stretching typically involves immersing the laminate in an aqueous boric acid solution for stretching. Further, stretching preferably further comprises stretching the laminate in the air at a high temperature (eg, 95 ° C. or higher) prior to stretching in an aqueous boric acid solution. In the embodiment of the present invention, the total magnification of stretching is preferably 3.0 to 4.5 times, which is significantly smaller than usual. Even at the total magnification of such stretching, a stator having acceptable optical properties can be obtained by combining the addition of a halide and the drying shrinkage treatment. Further, in the embodiment of the present invention, the stretching ratio of the aerial auxiliary stretching is preferably larger than the stretching ratio of the boric acid water stretching. With such a configuration, it is possible to obtain a polarizing element having acceptable optical characteristics even if the total magnification of stretching is small. In addition, the laminate is preferably subjected to a drying shrinkage treatment of shrinking by 2% or more in the width direction by heating while transporting in the longitudinal direction. In one embodiment, the method for producing a polarizing element includes subjecting a laminate to an aerial auxiliary stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment in this order. By introducing the auxiliary stretching, even when the PVA-based resin is coated on the thermoplastic resin, the crystallinity of the PVA-based resin can be enhanced, and high optical characteristics can be achieved. At the same time, by increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration of the orientation of the PVA-based resin and dissolution when immersed in water in the subsequent dyeing step or stretching step. , It becomes possible to achieve high optical characteristics. Further, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecule and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical characteristics of the polarizing element obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water. Further, the optical characteristics can be improved by shrinking the laminated body in the width direction by the drying shrinkage treatment. The obtained resin base material / polarizing element laminate may be used as it is (that is, the resin base material may be used as a protective layer for the polarizing element), and the resin base material is peeled off from the resin base material / polarizing element laminate. Then, an arbitrary appropriate protective layer according to the purpose may be laminated on the peeled surface and used. The details of the method for manufacturing the stator will be described in Section A-3.

A-3. Method for manufacturing a polarizing element In the above method for manufacturing a polarizing element, a polyvinyl alcohol-based resin layer (preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin base material (preferably A PVA-based resin layer) is formed to form a laminated body, and the laminated body is heated in the width direction by performing an aerial auxiliary stretching treatment, a dyeing treatment, and an underwater stretching treatment while transporting the laminated body in the longitudinal direction. It includes performing a dry shrinkage treatment for shrinking by% or more in this order. The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60 ° C. to 120 ° C. The shrinkage rate in the width direction of the laminated body by the dry shrinkage treatment is preferably 2% or more. Further, the stretch ratio of the aerial auxiliary stretch is preferably larger than the stretch ratio of the underwater stretch. According to such a manufacturing method, the modulator described in Section A-2 above can be obtained. In particular, a laminate containing a PVA-based resin layer containing a halide is prepared, the stretching of the laminate is a multi-step stretching including aerial auxiliary stretching and underwater stretching, and the stretched laminate is heated with a heating roll to have a width. By shrinking by 2% or more in the direction, a stator having excellent optical properties (typically, single transmittance and degree of polarization) can be obtained.

A-3-1. Preparation of Laminate As a method for preparing a laminate of a thermoplastic resin base material and a PVA-based resin layer, any appropriate method can be adopted. Preferably, a coating liquid containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin base material and dried to form a PVA-based resin layer on the thermoplastic resin base material. As described above, the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Any appropriate method can be adopted as the application method of the coating liquid. For example, a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, a knife coating method (comma coating method, etc.) and the like can be mentioned. The coating / drying temperature of the coating liquid is preferably 50 ° C. or higher.

The thickness of the PVA-based resin layer is preferably 2 μm to 30 μm, more preferably 2 μm to 20 μm. By making the thickness of the PVA-based resin layer before stretching very thin in this way and reducing the total magnification of stretching as described later, it is acceptable even though the degree of orientation of the PVA-based resin is lower than before. It is possible to obtain a polarizing element having a possible single transmittance and a degree of polarization.

Before forming the PVA-based resin layer, the thermoplastic resin base material may be surface-treated (for example, corona treatment or the like), or the easy-adhesion 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-based resin layer can be improved.

A-3-1-1. Thermoplastic resin base material As the thermoplastic resin base material, any suitable thermoplastic resin film can be adopted. Details of the thermoplastic resin base material are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580. The entire description of the publication is incorporated herein by reference.

A-3-1-2. Coating liquid The coating liquid contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethyl sulfoxide, 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 preferable. The PVA-based resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, it is possible to form a uniform coating film in close contact with the thermoplastic resin base material. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

Additives may be added to the coating liquid. Examples of the additive include a plasticizer, a surfactant and the like. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. Examples of the surfactant include nonionic surfactants. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

Any suitable resin can be adopted as the PVA-based resin. For example, polyvinyl alcohol and ethylene-vinyl alcohol copolymers can be mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. .. The degree of saponification can be determined according to JIS K 6726-1994. By using a PVA-based resin having such a degree of saponification, a polarizing element having excellent durability can be obtained. If the degree of saponification is too high, gelation may occur. As described above, the PVA-based resin preferably contains an acetoacetyl-modified PVA-based resin.

The average degree of polymerization of the PVA-based resin can be appropriately selected according to the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, and more preferably 1500 to 4300. The average degree of polymerization can be determined according to JIS K 6726-1994.

As the above-mentioned halide, any suitable halide can be adopted. For example, iodide and sodium chloride can be mentioned. Iodides include, for example, potassium iodide, sodium iodide, and lithium iodide. Among these, potassium iodide is preferable.

The amount of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, and more preferably 10 parts by weight to 15 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is a department. If the amount of the halide exceeds 20 parts by weight with respect to 100 parts by weight of the PVA-based resin, the halide may bleed out and the finally obtained polarizing element may become cloudy.

Generally, the stretching of the PVA-based resin layer increases the orientation of the polyvinyl alcohol molecules in the PVA-based resin layer. However, when the stretched PVA-based resin layer is immersed in a liquid containing water, the polyvinyl alcohol molecules become higher. The orientation of the plastic may be disturbed and the orientation may decrease. In particular, when the laminate of the thermoplastic resin base material and the PVA-based resin layer is stretched in boric acid water, the laminate is stretched in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin base material. In the case of stretching, the tendency of the degree of orientation to decrease is remarkable. For example, while stretching a PVA film alone in boric acid water is generally performed at 60 ° C., stretching of a laminate of A-PET (thermoplastic resin base material) and a PVA-based resin layer is performed. It is carried out at a high temperature of about 70 ° C., and in this case, the orientation of PVA at the initial stage of stretching may decrease before it is increased by stretching in water. On the other hand, by preparing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin base material, and stretching the laminate in air at a high temperature (auxiliary stretching) before stretching it in boric acid water. , Crystallization of the PVA-based resin in the PVA-based resin layer of the laminated body after the auxiliary stretching can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecule and the decrease in the orientation can be suppressed as compared with the case where the PVA-based resin layer does not contain a halide. This makes it possible to improve the optical characteristics of the polarizing element obtained through a treatment step of immersing the laminate in a liquid, such as a dyeing treatment and a stretching treatment in water.

A-3-2. Aerial auxiliary stretching treatment In particular, in order to obtain high optical properties, a two-stage stretching method that combines dry stretching (auxiliary stretching) and boric acid water stretching is selected. By introducing auxiliary stretching as in the case of two-step stretching, it is possible to stretch while suppressing the crystallization of the thermoplastic resin base material. Furthermore, when the PVA-based resin is applied on the thermoplastic resin base material, it is compared with the case where the PVA-based resin is applied on a normal metal drum in order to suppress the influence of the glass transition temperature of the thermoplastic resin base material. Therefore, it is necessary to lower the coating temperature, and as a result, the crystallization of the PVA-based resin becomes relatively low, which may cause a problem that sufficient optical characteristics cannot be obtained. On the other hand, by introducing auxiliary stretching, it is possible to improve the crystallinity of the PVA-based resin even when the PVA-based resin is applied on the thermoplastic resin, and it is possible to achieve high optical characteristics. Become. At the same time, by increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration of the orientation of the PVA-based resin and dissolution when immersed in water in the subsequent dyeing step or stretching step. , It becomes possible to achieve high optical characteristics.

The stretching method of the aerial auxiliary stretching may be fixed-end stretching (for example, a method of stretching using a tenter stretching machine) or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Although good, free-end stretching can be positively adopted in order to obtain high optical properties. In one embodiment, the aerial stretching treatment includes a heating roll stretching step of stretching the laminate by the difference in peripheral speed between the heating rolls while transporting the laminated body in the longitudinal direction thereof. The aerial stretching treatment typically includes a zone stretching step and a heating roll stretching step. The order of the zone stretching step and the heating roll stretching step is not limited, and the zone stretching step may be performed first, or the heating roll stretching step may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching step and the heating roll stretching step are performed in this order. Further, in another embodiment, in the tenter stretching machine, the film is stretched by grasping the end portion of the film and widening the distance between the tenters in the flow direction (the widening of the distance between the tenters is the stretching ratio). At this time, the distance of the tenter in the width direction (perpendicular to the flow direction) is set to approach arbitrarily. Preferably, it can be set to be closer to the free end stretch with respect to the stretch ratio in the flow direction. In the case of free end stretching, it is calculated by shrinkage rate in the width direction = (1 / stretching ratio) ^1/2 .

The aerial auxiliary stretching may be performed in one step or in multiple steps. When performed in multiple stages, the draw ratio is the product of the draw ratios in each stage. The stretching direction in the aerial auxiliary stretching is preferably substantially the same as the stretching direction in the underwater stretching.

The draw ratio in the aerial auxiliary stretching is preferably 1.0 to 4.0 times, more preferably 1.5 to 3.5 times, and further preferably 2.0 to 3.0 times. be. If the stretch ratio of the aerial auxiliary stretch is in such a range, the total stretch ratio can be set to a desired range when combined with the underwater stretch, and the desired birefringence, in-plane retardation and / or orientation can be set. Functions can be realized. As a result, it is possible to obtain a polarizing element (as a result, a polarizing plate) in which the generation of cracks in the deformed portion is suppressed. Further, as described above, it is preferable that the stretching ratio of the aerial auxiliary stretching is larger than the stretching ratio of the underwater stretching. With such a configuration, it is possible to obtain a polarizing element having acceptable optical characteristics even if the total magnification of stretching is small. More specifically, the ratio of the stretching ratio of the aerial auxiliary stretching to the stretching ratio of the underwater stretching (underwater stretching / aerial auxiliary stretching) is preferably 0.4 to 0.9, more preferably 0.5 to 0. It is 8.8.

The stretching temperature of the aerial auxiliary stretching can be set to an arbitrary appropriate value depending on the forming material of the thermoplastic resin base material, the stretching method, and the like. The stretching temperature is preferably the glass transition temperature (Tg) or higher of the thermoplastic resin base material, more preferably the glass transition temperature (Tg) of the thermoplastic resin base material (Tg) + 10 ° C. or higher, and particularly preferably Tg + 15 ° C. or higher. 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 suppress defects due to the crystallization (for example, hindering the orientation of the PVA-based resin layer due to stretching). can.

A-3-3. Insolubilization treatment, dyeing treatment and cross-linking treatment If necessary, an insolubilization treatment is performed after the aerial auxiliary stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing a PVA-based resin layer in a boric acid aqueous solution. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, a cross-linking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The cross-linking treatment is typically performed by immersing a PVA-based resin layer in an aqueous boric acid solution. Details of the insolubilization treatment, the dyeing treatment and the crosslinking treatment are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580.

A-3-4. Underwater stretching treatment The underwater stretching treatment is performed by immersing the laminate in a stretching bath. According to the underwater stretching treatment, the thermoplastic resin base material or the PVA-based resin layer can be stretched at a temperature lower than the glass transition temperature (typically, about 80 ° C.), and the PVA-based resin layer is crystallized. Can be stretched while suppressing. As a result, it is possible to manufacture a polarizing element having excellent optical characteristics.

Any appropriate method can be adopted as the stretching method of the laminated body. Specifically, it may be fixed-end stretching or free-end stretching (for example, a method of uniaxial stretching through a laminate between rolls having different peripheral speeds). Preferably, free-end stretching is selected. The stretching of the laminate may be carried out in one step or in multiple steps. When performed in multiple stages, the total stretching ratio is the product of the stretching ratios in each stage.

The underwater stretching is preferably carried out by immersing the laminate in a boric acid aqueous solution (boric acid water stretching). By using the boric acid aqueous solution as the stretching bath, it is possible to impart rigidity to withstand the tension applied during stretching and water resistance that does not dissolve in water to the PVA-based resin layer. Specifically, boric acid can generate a tetrahydroxyboric acid anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, the PVA-based resin layer can be imparted with rigidity and water resistance, can be stretched satisfactorily, and a polarizing element having excellent optical characteristics can be produced.

The boric acid aqueous solution is preferably obtained by dissolving boric acid and / or borate in water as a solvent. The boric acid concentration is preferably 1 part by weight to 10 parts by weight, more preferably 2.5 parts by weight to 6 parts by weight, and particularly preferably 3 parts by weight to 5 parts by weight with respect to 100 parts by weight of water. Is. By setting the boric acid concentration to 1 part by weight or more, the dissolution of the PVA-based resin layer can be effectively suppressed, and a polarizing element having higher characteristics can be produced. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde or the like in a solvent can also be used.

Preferably, iodide is added to the above stretching bath (boric acid aqueous solution). By blending iodide, the elution of iodine adsorbed on the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, and more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.

The stretching temperature (liquid temperature of the stretching bath) is preferably 40 ° C to 85 ° C, more preferably 60 ° C to 75 ° C. At such a temperature, the PVA-based resin layer can be stretched at a high magnification while suppressing dissolution. 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., it may not be stretched well even in consideration of the plasticization of the thermoplastic resin base material by water. On the other hand, the higher the temperature of the stretching bath, the higher the solubility of the PVA-based resin layer, and there is a possibility that excellent optical characteristics cannot be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The stretching ratio by stretching in water is preferably 1.0 to 2.2 times, more preferably 1.1 times to 2.0 times, and further preferably 1.1 times to 1.8 times. , Even more preferably 1.2 to 1.6 times. When the stretching ratio in underwater stretching is in such a range, the total stretching ratio can be set in a desired range, and the desired birefringence, in-plane retardation and / or orientation function can be realized. As a result, it is possible to obtain a polarizing element (as a result, a polarizing plate) in which the generation of cracks in the deformed portion is suppressed. As described above, the total stretching ratio (the total stretching ratio when the aerial auxiliary stretching and the underwater stretching are combined) is preferably 3.0 to 4.5 times with respect to the original length of the laminated body. , More preferably 3.0 to 4.3 times, still more preferably 3.0 to 4.0 times. By appropriately combining the addition of a halide to the coating liquid, the adjustment of the stretching ratios of the aerial auxiliary stretching and the underwater stretching, and the drying shrinkage treatment, even the total magnification of such stretching has acceptable optical properties. A modulator can be obtained.

A-3-5. Drying Shrinkage Treatment The drying shrinkage treatment may be performed by heating the entire zone by zone heating, or by heating the transport roll (using a so-called heating roll) (heating roll drying method). Preferably both are used. By drying using a heating roll, it is possible to efficiently suppress the heating curl of the laminate and produce a polarizing element having an excellent appearance. Specifically, by drying the laminated body along the heating roll, the crystallization of the thermoplastic resin base material can be efficiently promoted and the crystallinity can be increased, which is relatively low. Even at the drying temperature, the crystallinity of the thermoplastic resin substrate can be satisfactorily increased. As a result, the rigidity of the thermoplastic resin base material is increased, and the PVA-based resin layer is in a state of being able to withstand shrinkage due to drying, and curling is suppressed. Further, by using the heating roll, the laminated body can be dried while being maintained in a flat state, so that not only curling but also wrinkles can be suppressed. At this time, the laminated body can be improved in optical characteristics by shrinking in the width direction by a drying shrinkage treatment. This is because the orientation of PVA and the PVA / iodine complex can be effectively enhanced. The shrinkage ratio in the width direction of the laminate by the dry shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 2% to 6%.

FIG. 6 is a schematic view showing an example of the drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being transported by the transport rolls R1 to R6 heated to a predetermined temperature and the guide rolls G1 to G4. In the illustrated example, the transport rolls R1 to R6 are arranged so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin base material. For example, one surface of the laminate 200 (for example, thermoplasticity) is arranged. The transport rolls R1 to R6 may be arranged so as to continuously heat only the resin substrate surface).

Drying conditions can be controlled by adjusting the heating temperature of the transport roll (temperature of the heating roll), the number of heating rolls, the contact time with the heating roll, and the like. The temperature of the heating roll is preferably 60 ° C. to 120 ° C., more preferably 65 ° C. to 100 ° C., and particularly preferably 70 ° C. to 80 ° C. The crystallinity of the thermoplastic resin can be satisfactorily increased, curling can be satisfactorily suppressed, and an optical laminate having extremely excellent durability can be produced. The temperature of the heating roll can be measured with a contact thermometer. In the illustrated example, six transport rolls are provided, but there is no particular limitation as long as there are a plurality of transport rolls. The number of transport rolls is usually 2 to 40, preferably 4 to 30. 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 further preferably 1 to 10 seconds.

The heating roll may be provided in a heating furnace (for example, an oven) or in a normal production line (in a room temperature environment). Preferably, it is provided in a heating furnace provided with an air blowing means. By using both drying with a heating roll and hot air drying together, a steep 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. 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. The wind speed is the wind speed in the heating furnace and can be measured by a mini-vane type digital anemometer.

A-3-6. Other Treatments Preferably, a washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The cleaning treatment is typically performed by immersing a PVA-based resin layer in an aqueous potassium iodide solution.

A-4. Protective layer The thickness of the protective layer is 10 μm or less. When the thickness of the protective layer is 10 μm or less, it can contribute to the thinning of the polarizing plate. Further, conventionally, from the viewpoint of protecting the polarizing element by following the shrinkage of the polarizing element during heating, a protective layer having a thickness of 20 μm or more has been used. On the other hand, as described above, the polarizing element used in the embodiment of the present invention has a lower degree of orientation of the PVA-based resin than the conventional one, and as a result, shrinkage due to heating is small, so that the protective layer has a thickness of 10 μm or less. Even when the above is used, the generation of cracks during heating is suppressed. Further, such a polarizing element can also contribute to crack suppression in the deformed portion.

The thickness of the protective layer is preferably 7 μm or less, more preferably 5 μm or less, and further preferably 3 μm or less. The thickness of the protective layer is, for example, 1 μm or more.

The protective layer is composed of a resin film. As the resin forming the resin film, any suitable resin can be used depending on the purpose. Specific examples include (meth) acrylic, cellulose-based such as triacetylcellulose (TAC), polyester-based, polyurethane-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, polysulfone-based, and polystyrene. Thermoplastic resins such as (meth) acrylic, urethane, (meth) acrylic urethane, epoxy, silicone, etc., or active energy ray-curable resins. Resin: Glassy polymers such as siloxane-based polymers can be mentioned. In one embodiment, examples of the resin forming the resin film include an epoxy resin and a (meth) acrylic resin. These may be used alone or in combination.

The resin film constituting the protective layer may be, for example, a molded product of a molten resin, or may be a solidified coating film of a resin solution obtained by dissolving or dispersing the resin in an aqueous solvent or an organic solvent. , A cured product of a curable resin (for example, a photocationic cured product) may be used.

In one embodiment, the protective layer is a solidified coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin (hereinafter, the (meth) acrylic resin may be simply referred to as “acrylic resin”). , A photocationically cured product of an epoxy resin, or a solidified product of a coating film of an organic solvent solution of an epoxy resin. Hereinafter, a specific description will be given.

A-4-1. Solidification of the coating film of the organic solvent solution of the thermoplastic acrylic resin In one embodiment, the protective layer is composed of the solidification of the coating film of the organic solvent solution of the thermoplastic acrylic resin. From the viewpoint of humidification durability, the softening temperature of the protective layer of the present embodiment is preferably 100 ° C. or higher, more preferably 115 ° C. or higher, still more preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, and molding. From the viewpoint of properties, it is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower.

The acrylic resin has a glass transition temperature (Tg) of preferably 100 ° C. or higher. As a result, the softening temperature of the protective layer is also approximately 100 ° C. or higher. When the Tg of the acrylic resin is 100 ° C. or higher, the polarizing plate containing the protective layer obtained from such a resin can be excellent in humidification durability in addition to crack resistance. The Tg of the acrylic resin is more preferably 110 ° C. or higher, further preferably 115 ° C. or higher, still more preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the acrylic resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. If the Tg of the acrylic resin is in such a range, the moldability can be excellent.

As the acrylic resin, any suitable acrylic resin can be adopted as long as it has Tg as described above. Acrylic resins typically contain an alkyl (meth) acrylate as a main component as a monomer unit (repeating unit). As used herein, the term "(meth) acrylic" means acrylic and / or methacrylic. Examples of the alkyl (meth) acrylate constituting the main skeleton of the acrylic resin include linear or branched alkyl groups having 1 to 18 carbon atoms. These can be used alone or in combination. Further, any suitable copolymerization monomer may be introduced into the acrylic resin by copolymerization. Acrylic that can form a desired protective layer by appropriately setting the type, number, combination and compounding ratio of the alkyl (meth) acrylate, the type, number, combination and compounding ratio of the copolymerization monomer, and the polymerization conditions. A based resin can be obtained.

The acrylic resin preferably has a repeating unit containing a ring structure. Examples of the repeating unit including a ring structure include a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. Only one type of the repeating unit including the ring structure may be contained in the repeating unit of the acrylic resin, or two or more types may be contained. Acrylic resins having a lactone ring unit are described in, for example, Japanese Patent Application Laid-Open No. 2008-181078. Acrylic resins having a glutarimide unit are, for example, JP-A-2006-309033, JP-A-2006-317560, JP-A-2006-328334, JP-A-2006-337491, JP-A-2006-337492. It is described in JP-A-2006-337493 and JP-A-2006-337569. The description of these publications is incorporated herein by reference.

The content ratio of the repeating unit including the ring structure in the acrylic resin is preferably 1 mol% to 50 mol%, more preferably 10 mol% to 40 mol%, and further preferably 20 mol% to 30 mol%. If the content ratio is too small, Tg may be less than 100 ° C., and the heat resistance, solvent resistance and surface hardness of the obtained protective layer may be insufficient. If the content is too high, moldability and transparency may be insufficient.

In the embodiment of the present invention, an acrylic resin and another resin may be used in combination. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be used for molding the protective layer described later; the acrylic resin and the other resin. The blend of may be used for forming the protective layer.

The protective layer of the present embodiment can be formed, for example, by applying an organic solvent solution of an acrylic resin to the surface of a polarizing element to form a coating film, and solidifying the coating film.

As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the acrylic resin can be used. Specific examples of the organic solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The acrylic resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the polarizing element can be formed.

The solution may be applied to any suitable substrate or to a polarizing element. When applied to a substrate, the solidified material of the coating film formed on the substrate is transferred to the polarizing element. When applied to a polarizing element, a protective layer is directly formed on the polarizing element by drying (solidifying) the coating film. Preferably, the solution is applied to the polarizing element and a protective layer is formed directly on the polarizing element. With such a configuration, the adhesive layer or the pressure-sensitive adhesive layer required for transfer can be omitted, so that the polarizing plate can be further thinned. Any suitable method can be adopted as the method for applying the solution. Specific examples include a roll coating method, a spin coating method, a wire bar coating method, a dip coating method, a die coating method, a curtain coating method, a spray coating method, and a knife coating method (comma coating method, etc.).

A protective layer can be formed by drying (solidifying) the coating film of the solution. The drying temperature is preferably 100 ° C. or lower, more preferably 50 ° C. to 70 ° C. When the drying temperature is in such a range, it is possible to prevent an adverse effect on the polarizing element. The drying time can vary depending on the drying temperature. The drying time can be, for example, 1 to 10 minutes.

A-4-2. Photocationic cured product of epoxy resin In one embodiment, the protective layer is composed of a photocationic cured product of epoxy resin. By using such a protective layer, the generation of cracks can be suppressed and excellent humidification durability can be obtained. As described above, since the protective layer is a photocationic cured product, the composition for forming the protective layer contains a photocationic polymerization initiator. The photocationic polymerization initiator is a photosensitizer having a function of a photoacid generator, and a typical example thereof is an ionic onium salt composed of a cation portion and an anion portion. In this onium salt, the cation part absorbs light and the anion part becomes a source of acid. Ring-opening polymerization of the epoxy group proceeds by the acid generated from this photocationic polymerization initiator. The protective layer, which is the obtained photocationic cured product, has a high softening temperature, and the amount of iodine adsorbed can be reduced. Therefore, it is possible to provide a polarizing plate in which the occurrence of cracks is suppressed and has excellent humidification durability.

From the viewpoint of humidification durability, the softening temperature of the protective layer of the present embodiment is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, further preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, and molding. From the viewpoint of properties, it is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower.

A-4-2-1. Epoxy resin As the epoxy resin, any suitable epoxy resin can be used, and an epoxy resin having an aromatic ring or an alicyclic ring can be preferably used. In the present embodiment, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton can be preferably used. Examples of the aromatic skeleton include a benzene ring, a naphthalene ring, a fluorene ring and the like. Only one type of epoxy resin may be used, or two or more types may be used in combination. Preferably, an epoxy resin having a biphenyl skeleton or a bisphenol skeleton or a hydrogenated product thereof is used as the aromatic skeleton. By using such an epoxy resin, a polarizing plate having more excellent durability and excellent flexibility can be provided.

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin containing the following structure. Only one type of epoxy resin having a biphenyl skeleton may be used, or two or more types may be used in combination.

(In the formula, R ¹⁴ to R ²¹ each independently represent a hydrogen atom, a linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms, or a halogen element).

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin represented by the following formula.

(In the equation, R ¹⁴ to R ²¹ are as described above, and n represents an integer of 0 to 6).

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin having only a biphenyl skeleton. By using an epoxy resin having only a biphenyl skeleton, the durability of the obtained protective layer can be further improved. In another embodiment, the epoxy resin having a biphenyl skeleton may contain a chemical structure other than the biphenyl skeleton. Examples of the chemical structure other than the biphenyl skeleton include a bisphenol skeleton, an alicyclic structure, an aromatic ring structure and the like. In this case, the ratio (molar ratio) of the chemical structure other than the biphenyl skeleton is preferably smaller than that of the biphenyl skeleton.

The epoxy resin (epoxy resin after photocation curing) preferably has a glass transition temperature (Tg) of 100 ° C. or higher. As a result, the softening temperature of the protective layer is also approximately 100 ° C. or higher. When the Tg of the epoxy resin is 100 ° C. or higher, the obtained polarizing plate including the protective layer tends to have excellent durability. The Tg of the epoxy resin is more preferably 110 ° C. or higher, further preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the epoxy resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the epoxy resin is in such a range, the moldability can be excellent.

The epoxy equivalent of the epoxy resin is preferably 100 g / equivalent or more, more preferably 150 g / equivalent or more, and further preferably 200 g / equivalent or more. The epoxy equivalent of the epoxy resin is preferably 3000 g / equivalent or less, more preferably 2500 g / equivalent or less, still more preferably 2000 g / equivalent or less. When the epoxy equivalent is in the above range, a more stable protective layer (a protective layer having less residual monomer and sufficiently cured) can be obtained. In the present specification, "epoxy equivalent" means "mass of epoxy resin containing 1 equivalent of epoxy group" and can be measured according to JIS K7236.

In this embodiment, the above epoxy resin may be used in combination with another resin. That is, even if a blend of the above epoxy resin (for example, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton) and another resin is used for molding the protective layer. good. Examples of other resins include acrylic resins and oxetane resins.

As the acrylic resin, any suitable (meth) acrylic compound can be used. For example, as the (meth) acrylic compound, for example, a (meth) acrylic compound having one (meth) acryloyl group in the molecule (hereinafter, also referred to as “monofunctional (meth) acrylic compound”), intramolecular. Examples thereof include (meth) acrylic compounds having two or more (meth) acryloyl groups (hereinafter, also referred to as “polyfunctional (meth) acrylic compounds”). These (meth) acrylic compounds may be used alone or in combination of two or more. These acrylic resins are described in, for example, Japanese Patent Application Laid-Open No. 2019-168500. The entire description of the publication is incorporated herein by reference.

As the oxetane resin, any suitable compound having one or more oxetanyl groups in the molecule is used. For example, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane, 3-ethyl-3- (phenoxymethyl) oxetane, 3-ethyl-3- (cyclohexyloxymethyl). Oxetane compound having one oxetane group in the molecule such as oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) methyl; 3-ethyl- 3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 4,4'-bis [(3-ethyl) -3-Oxetane) methoxymethyl] An oxetane compound having two or more oxetane groups in a molecule such as biphenyl; and the like. Only one kind of these oxetane resins may be used, or two or more kinds thereof may be combined. The oxetane resin is preferably 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3-oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (2-ethylhexyloxymethyl). Oxetane, 3-Ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic acid (3-ethyloxetane-3-yl) methyl, 3-ethyl-3 {[(3-ethyloxetane-3-yl) Methyl] methyl} oxetane and the like are used. These oxetane resins are easily available and can be excellent in dilutability (low viscosity) and compatibility.

In one embodiment, an oxetane resin having a molecular weight of 500 or less and liquid at room temperature (25 ° C.) is preferably used from the viewpoint of compatibility and adhesiveness. In one embodiment, it preferably contains an oxetane compound containing two or more oxetanel groups in the molecule, one oxetaneyl group and one (meth) acryloyl group or one epoxy group in the molecule. Oxetane compounds are used, more preferably 3-ethyl-3 {[(3-ethyloxetane-3-yl) methoxy] methyl} oxetane, 3-ethyl-3- (oxylanylmethoxy) oxetane, (meth) acrylic. Acid (3-ethyloxetane-3-yl) methyl is used. By using these oxetane resins, the curability and durability of the protective layer can be improved.

A-4-2-2. Photocationic polymerization initiator The photocationic polymerization initiator is a photosensitive agent having a function of a photoacid generator, and a typical example thereof is an ionic onium salt composed of a cation portion and an anion portion. In this onium salt, the cation part absorbs light and the anion part becomes a source of acid. Ring-opening polymerization of the epoxy group proceeds by the acid generated from this photocationic polymerization initiator. As the photocationic polymerization initiator, any suitable compound capable of curing an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton by irradiation with light such as ultraviolet rays. Can be used. Only one type of photocationic polymerization initiator may be used, or two or more types may be used in combination.

Examples of the photocationic polymerization initiator include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p- (phenylthio) phenyldiphenylsulfonium hexafluoroantimonate, p- (phenylthio) phenyldiphenylsulfonium hexafluorophosphate, and the like. 4-Chlorphenyl diphenyl sulfonium hexafluorophosphate, 4-chlorphenyl diphenyl sulfonium hexafluoroantimonate, bis [4- (diphenyl sulfonio) phenyl] sulfide bishexafluoro phosphate, bis [4- (diphenyl sulfonio) phenyl ] Sulfoxybishexafluoroantimonate, (2,4-cyclopentadiene-1-yl) [(1-methylethyl) benzene] -Fe-hexafluorophosphate, diphenyliodonium hexafluoroantimonate and the like. Preferably, a triphenylsulfonium salt-based hexafluoroantimonate type photocationic polymerization initiator and a diphenyliodonium salt-based hexafluoroantimonate type photocationic polymerization initiator are used.

The protective layer of the present embodiment is formed by, for example, applying a composition containing the epoxy resin and a photocationic polymerization initiator to form a coating film, and irradiating the coating film with light (for example, ultraviolet rays). Can be done.

The epoxy resin concentration in the above composition is preferably 10 parts by weight to 30 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the polarizing element can be formed.

The above composition may be applied to any suitable substrate or may be applied to a polarizing element. When applied to a substrate, the cured product of the coating film formed on the substrate is transferred to the polarizing element. When the coating film is applied to the polarizing element, the protective layer is directly formed on the polarizing element by, for example, curing the coating film by irradiation with light. Preferably, the composition is applied to a polarizing element and a protective layer is formed directly on the polarizing element. With such a configuration, the adhesive layer or the pressure-sensitive adhesive layer required for transfer can be omitted, so that the polarizing plate can be further thinned. The method for applying the composition is as described above.

Curing of the coating film can be performed by irradiating light (typically ultraviolet rays) with an arbitrary appropriate light source so as to obtain an arbitrary appropriate irradiation amount. After the light irradiation, further heat treatment may be performed to complete the curing by the light reaction. The heat treatment can be performed at any suitable temperature and time.

A-4-3. Solidification of the coating film of the organic solvent solution of the epoxy resin In one embodiment, the protective layer is composed of the solidification of the coating film of the organic solvent solution of the epoxy resin. From the viewpoint of humidification durability, the softening temperature of the protective layer of the present embodiment is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, further preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, and molding. From the viewpoint of properties, it is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower.

A-4-3-1. Epoxy resin In the present embodiment, the epoxy resin preferably has a glass transition temperature (Tg) of 100 ° C. or higher. As a result, the softening temperature of the protective layer is also approximately 100 ° C. or higher. When the Tg of the epoxy resin is 100 ° C. or higher, the polarizing plate containing the protective layer obtained from such a resin tends to have excellent durability. The Tg of the epoxy resin is more preferably 110 ° C. or higher, further preferably 120 ° C. or higher, and particularly preferably 125 ° C. or higher. On the other hand, the Tg of the epoxy resin is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, still more preferably 200 ° C. or lower, and particularly preferably 160 ° C. or lower. When the Tg of the epoxy resin is in such a range, the moldability can be excellent.

As the epoxy resin, any suitable epoxy resin can be adopted as long as it has Tg as described above. The epoxy resin typically refers to a resin having an epoxy group in its molecular structure. As the epoxy resin, an epoxy resin having an aromatic ring in the molecular structure is preferably used. By using an epoxy resin having an aromatic ring, an epoxy resin having a higher Tg can be obtained. Examples of the aromatic ring in the epoxy resin having an aromatic ring in the molecular structure include a benzene ring, a naphthalene ring, a fluorene ring and the like. Only one type of epoxy resin may be used, or two or more types may be used in combination. When two or more kinds of epoxy resins are used, an epoxy resin containing an aromatic ring and an epoxy resin not containing an aromatic ring may be used in combination.

Specific examples of the epoxy resin having an aromatic ring in its molecular structure include bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diglycidyl ether type epoxy resin, and resorcin diglycidyl ether. Type epoxy resin, hydroquinone diglycidyl ether type epoxy resin, terephthalic acid diglycidyl ester type epoxy resin, bisphenoxyethanol full orange glycidyl ether type epoxy resin, bisphenol full orange glycidyl ether type epoxy resin, biscresol full orange glycidyl ether type epoxy resin, etc. Epoxy resin having two epoxy groups; novolak type epoxy resin, N, N, O-triglycidyl-P- or -m-aminophenol type epoxy resin, N, N, O-triglycidyl-4-amino-m -Or-5-Amino-o-cresol type epoxy resin, 1,1,1- (triglycidyloxyphenyl) methane type epoxy resin and other epoxy resins with three epoxy groups; glycidylamine type epoxy resin (eg, diamino) Examples thereof include epoxy resins having four epoxy groups such as diphenylmethane type, diaminodiphenylsulfone type, and metaxylene diamine type). Further, a glycidyl ester type epoxy resin such as a hexahydrophthalic anhydride type epoxy resin, a tetrahydrophthalic anhydride type epoxy resin, a dimer acid type epoxy resin, and a p-oxybenzoic acid type may be used.

The epoxy equivalent of the epoxy resin is preferably 1000 g / equivalent or more, more preferably 3000 g / equivalent or more, and further preferably 5000 g / equivalent or more. The epoxy equivalent of the epoxy resin is preferably 30,000 g / equivalent or less, more preferably 25,000 g / equivalent or less, and further preferably 20,000 g / equivalent or less. When the epoxy equivalent is in the above range, a more stable protective layer can be obtained. In the present specification, "epoxy equivalent" means "mass of epoxy resin containing 1 equivalent of epoxy group" and can be measured according to JIS K7236.

In this embodiment, the epoxy resin and another resin may be used in combination. That is, a blend of the epoxy resin and another resin may be used for molding the protective layer. Other resins may be appropriately selected depending on the intended purpose.

The protective layer of the present embodiment can be formed, for example, by applying an organic solvent solution containing the epoxy resin to form a coating film and solidifying the coating film. The epoxy resin concentration in the organic solvent solution is preferably 3 parts by weight to 20 parts by weight with respect to 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film in close contact with the polarizing element can be formed.

As the organic solvent, any suitable solvent capable of dissolving or uniformly dispersing the epoxy resin can be used. Specific examples of the solvent include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone.

The solution may be applied to any suitable substrate or to a polarizing element. When applied to a substrate, the solidified material of the coating film formed on the substrate is transferred to the polarizing element. When applied to a polarizing element, a protective layer is directly formed on the polarizing element by drying (solidifying) the coating film. Preferably, the solution is applied to the polarizing element and a protective layer is formed directly on the polarizing element. With such a configuration, the adhesive layer or the pressure-sensitive adhesive layer required for transfer can be omitted, so that the polarizing plate can be further thinned. The method of applying the solution is as described above.

By drying (solidifying) the coating film of the solution, a protective layer that is a solidified coating film can be formed. The drying temperature is preferably 100 ° C. or lower, more preferably 50 ° C. to 70 ° C. When the drying temperature is in such a range, it is possible to prevent an adverse effect on the polarizing element. The drying time can vary depending on the drying temperature. The drying time can be, for example, 1 to 10 minutes.

B. Polarizing plate with retardation layer B-1. Overall Configuration of Polarizing Plate with Difference Layer FIG. 7 is a schematic cross-sectional view of the polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate with a retardation layer 200 in the illustrated example includes the polarizing plate 100 according to the above item A and the retardation layer 120. Therefore, the polarizing plate 200 with a retardation layer has the same variant shape as the polarizing plate 100. In the polarizing plate 200 with a retardation layer, the retardation layer 120 can also function as a protective layer for the polarizing element 10. The retardation layer 120 is typically laminated on a polarizing plate 100 (polarizer 10 in the illustrated example) via an adhesive layer (not shown). The adhesive layer is an adhesive layer or an adhesive layer, and is preferably an adhesive layer (for example, an acrylic adhesive layer) from the viewpoint of reworkability and the like. Although not shown, the polarizing plate with a retardation layer may have another protective layer (not shown) on the retardation layer 120 side of the polarizing element 10, if necessary. Further, if necessary, the polarizing plate with a retardation layer may have another retardation layer (not shown) on the opposite side of the polarizing plate 100 of the retardation layer 120. Another retardation layer is typically a so-called positive C plate whose refractive index characteristic shows a relationship of nz> nx = ny.

The Re (550) of the retardation layer 120 is preferably 100 nm to 190 nm, and the Re (450) / Re (550) is preferably 0.8 or more and less than 1. Further, the angle formed by the slow axis of the retardation layer 120 and the absorption axis of the polarizing element 10 is preferably 40 ° to 50 °.

B-2. Phase difference layer The phase difference layer 120 may have any suitable optical and / or mechanical properties depending on the intended purpose. The retardation layer typically has a slow phase axis. In one embodiment, the angle θ formed by the slow axis of the retardation layer and the absorption axis of the polarizing element 10 is preferably 40 ° to 50 °, more preferably 42 ° to 48 ° as described above. Yes, more preferably about 45 °. If the angle θ is in such a range, as will be described later, by using a λ / 4 plate as the retardation layer, a very excellent circularly polarized light characteristic (as a result, a very excellent antireflection characteristic) can be obtained. A polarizing plate with a difference layer can be obtained.

The retardation layer preferably shows a relationship in which the refractive index characteristic is nx> ny ≧ nz. The retardation layer is typically provided to impart antireflection properties to the polarizing plate and can function as a λ / 4 plate in one embodiment. In this case, the in-plane retardation Re (550) of the retardation layer is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and even more preferably 130 nm to 160 nm. Here, "ny = nz" includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, ny <nz may be satisfied as long as the effect of the present invention is not impaired.

The Nz coefficient of the retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. .. By satisfying such a relationship, a very excellent reflected hue can be achieved when the obtained polarizing plate with a retardation layer is used in an image display device.

The retardation layer may exhibit a reverse dispersion wavelength characteristic in which the retardation value increases according to the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases according to the wavelength of the measurement light. It is also possible to exhibit a flat wavelength dispersion characteristic in which the phase difference value hardly changes depending on the wavelength of the measured light. In one embodiment, the retardation layer exhibits inverse dispersion wavelength characteristics. In this case, Re (450) / Re (550) of the retardation layer is preferably 0.8 or more and less than 1, and more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be realized.

In the retardation layer, the absolute value of the photoelastic coefficient is preferably 2 × 10 ^-11 m ² / N or less, more preferably 2.0 × 10 ^-13 m ² / N to 1.5 × 10 ^-11 m ² /. It contains N, more preferably 1.0 × ^10-12 m ² / N to 1.2 × ^10-11 m ² / N. When the absolute value of the photoelastic coefficient is in such a range, the phase difference change is unlikely to occur when the shrinkage stress during heating occurs. As a result, thermal unevenness of the obtained image display device can be satisfactorily prevented.

The retardation layer is typically composed of a stretched film of a resin film. In one embodiment, the thickness of the retardation layer is preferably 70 μm or less, more preferably 45 μm to 60 μm. When the thickness of the retardation layer is within such a range, it is possible to satisfactorily adjust the curl at the time of bonding while satisfactorily suppressing the curl at the time of heating. Further, as described later, in the embodiment in which the retardation layer is made of a polycarbonate resin film, the thickness of the retardation layer is preferably 40 μm or less, more preferably 10 μm to 40 μm, and further preferably 20 μm. It is ~ 30 μm. By forming the retardation layer with a polycarbonate-based resin film having such a thickness, it is possible to contribute to the improvement of bending durability and the reflected hue while suppressing the generation of curl.

The retardation layer may be composed of any suitable resin film that can satisfy the above characteristics. Typical examples of such resins include polycarbonate resins, polyester carbonate resins, polyester resins, polyvinyl acetal resins, polyarylate resins, cyclic olefin resins, cellulose resins, polyvinyl alcohol resins, and polyamide resins. , Polyethylene resin, polyether resin, polystyrene resin, acrylic resin and the like. These resins may be used alone or in combination (eg, blending, copolymerization). When the retardation layer is composed of a resin film exhibiting a reverse dispersion wavelength characteristic, a polycarbonate-based resin or a polyester carbonate-based resin (hereinafter, may be simply referred to as a polycarbonate-based resin) can be preferably used.

As the above-mentioned polycarbonate-based resin, any suitable polycarbonate-based resin can be used as long as the effects of the present invention can be obtained. For example, the polycarbonate-based resin has a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, an alicyclic diol, an alicyclic dimethanol, di, tri or polyethylene glycol, and an alkylene. Includes structural units derived from at least one dihydroxy compound selected from the group consisting of glycols or spiroglycols. Preferably, the polycarbonate-based resin is a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, a structural unit derived from an alicyclic dimethanol, and / or di, tri or polyethylene glycol. Containing structural units derived from; more preferably structural units derived from fluorene dihydroxy compounds, structural units derived from isosorbide dihydroxy compounds, and structural units derived from di, tri or polyethylene glycol. .. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds, if necessary. Details of the polycarbonate-based resin that can be suitably used for the present invention are, for example, JP-A-2014-10291, JP-A-2014-226666, JP-A-2015-212816, JP-A-2015-21217. , 2015-21218, and the description is incorporated herein by reference.

The glass transition temperature of the polycarbonate resin is preferably 110 ° C. or higher and 150 ° C. or lower, more preferably 120 ° C. or higher and 140 ° C. or lower. If the glass transition temperature is excessively low, the heat resistance tends to deteriorate, dimensional changes may occur after film molding, and the image quality of the obtained organic EL panel may be deteriorated. If the glass transition temperature is excessively high, the molding stability during film molding may be deteriorated, and the transparency of the film may be impaired. The glass transition temperature is determined according to JIS K7121 (1987).

The molecular weight of the polycarbonate resin can be expressed by the reducing viscosity. The reduced viscosity is measured by using methylene chloride as a solvent, precisely adjusting the polycarbonate concentration to 0.6 g / dL, and using a Ubbelohde viscous tube at a temperature of 20.0 ° C. ± 0.1 ° C. The lower limit of the reduction viscosity is usually preferably 0.30 dL / g, more preferably 0.35 dL / g or more. The upper limit of the reduction viscosity is usually preferably 1.20 dL / g, more preferably 1.00 dL / g, and further preferably 0.80 dL / g. If the reduced viscosity is smaller than the lower limit, there may be a problem that the mechanical strength of the molded product is reduced. On the other hand, if the reduced viscosity is larger than the upper limit value, the fluidity at the time of molding is lowered, and there may be a problem that the productivity and the moldability are lowered.

A commercially available film may be used as the polycarbonate resin film. Specific examples of commercially available products include Teijin's product name "Pure Ace WR-S", "Pure Ace WR-W", "Pure Ace WR-M", and Nitto Denko's product name "NRF". Will be.

The retardation layer can be obtained, for example, by stretching a film formed of the above-mentioned polycarbonate resin. As a method for forming a film from a polycarbonate-based resin, any appropriate molding processing method can be adopted. Specific examples include a compression molding method, a transfer molding method, an injection molding method, an extrusion molding method, a blow molding method, a powder molding method, an FRP molding method, a cast coating method (for example, a casting method), a calendar molding method, and a hot press. The law etc. can be mentioned. Extrusion molding method or cast coating method is preferable. This is because the smoothness of the obtained film can be enhanced and good optical uniformity can be obtained. The molding conditions can be appropriately set according to the composition and type of the resin used, the characteristics desired for the retardation layer, and the like. As described above, since many film products of the polycarbonate resin are commercially available, the commercially available film may be subjected to the stretching treatment as it is.

The thickness of the resin film (unstretched film) can be set to an arbitrary appropriate value according to a desired thickness of the retardation layer, desired optical characteristics, stretching conditions described later, and the like. It is preferably 50 μm to 300 μm.

For the above stretching, any appropriate stretching method and stretching conditions (for example, stretching temperature, stretching ratio, stretching direction) can be adopted. Specifically, various stretching methods such as free-end stretching, fixed-end stretching, free-end contraction, and fixed-end contraction can be used alone or simultaneously or sequentially. As for the stretching direction, it can be performed in various directions and dimensions such as a length direction, a width direction, a thickness direction, and an oblique direction. The stretching temperature is preferably Tg-30 ° C to Tg + 60 ° C, more preferably Tg-10 ° C to Tg + 50 ° C with respect to the glass transition temperature (Tg) of the resin film.

By appropriately selecting the stretching method and stretching conditions, a retardation film having the desired optical characteristics (for example, refractive index characteristics, in-plane retardation, Nz coefficient) can be obtained.

In one embodiment, the retardation film is produced by uniaxially stretching or fixed-end uniaxially stretching the resin film. Specific examples of the fixed-end uniaxial stretching include a method of stretching the resin film in the width direction (lateral direction) while running the resin film in the longitudinal direction. The draw ratio is preferably 1.1 to 3.5 times.

In another embodiment, the retardation film can be produced by continuously diagonally stretching a long resin film in the direction of the above angle θ with respect to the longitudinal direction. By adopting diagonal stretching, a long stretched film having an orientation angle of an angle θ with respect to the longitudinal direction of the film (a slow axis in the direction of the angle θ) can be obtained. Roll-to-roll is possible, and the manufacturing process can be simplified. The angle θ may be an angle formed by the absorption axis of the polarizing element and the slow axis of the retardation layer in the polarizing plate with a retardation layer. As described above, the angle θ is preferably 40 ° to 50 °, more preferably 42 ° to 48 °, and even more preferably about 45 °.

Examples of the stretching machine used for diagonal stretching include a tenter type stretching machine capable of applying a feeding force, a pulling force, or a pulling force at different speeds in the lateral and / or vertical directions. The tenter type stretching machine includes a horizontal uniaxial stretching machine, a simultaneous biaxial stretching machine, and the like, but any suitable stretching machine can be used as long as the long resin film can be continuously and diagonally stretched.

By appropriately controlling the left and right velocities in the stretching machine, a retardation layer having the desired in-plane phase difference and having a slow phase axis in the desired direction (substantially long). A phase difference film) can be obtained.

The stretching temperature of the film can change depending on the in-plane retardation value and thickness desired for the retardation layer, the type of resin used, the thickness of the film used, the stretching ratio, and the like. Specifically, the stretching temperature is preferably Tg-30 ° C to Tg + 30 ° C, more preferably Tg-15 ° C to Tg + 15 ° C, and most preferably Tg-10 ° C to Tg + 10 ° C. By stretching at such a temperature, a retardation layer having appropriate characteristics in the present invention can be obtained. Tg is the glass transition temperature of the constituent material of the film.

C. Image display device The above-mentioned polarizing plate or a polarizing plate with a retardation layer can be applied to an image display device. Therefore, an embodiment of the present invention includes an image display device including such a polarizing plate or a polarizing plate with a retardation layer. Typical examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (for example, an organic EL display device and an inorganic EL display device). The image display device according to the embodiment of the present invention includes the polarizing plate according to the above item A or the polarizing plate with a retardation layer according to the item B on the visible side thereof. The polarizing plate with a retardation layer is laminated so that the retardation layer is on the image display cell side (for example, a liquid crystal cell, an organic EL cell, an inorganic EL cell) (so that the polarizing element is on the visual recognition side). The image display device preferably has a variant shape other than a rectangle. In such an image display device, the effect of the embodiment of the present invention is remarkable. Specific examples of the image display device having a deformed shape include a meter panel of an automobile, a smartphone, a tablet PC, and a smart watch.

Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited to these Examples. The measurement method of each characteristic is as follows. Unless otherwise specified, "parts" and "%" in Examples and Comparative Examples are based on weight.

(1) Thickness Measured using an interference film thickness meter (manufactured by Otsuka Electronics Co., Ltd., product name "MCPD-3000"). The calculated wavelength range used for the thickness calculation was 400 nm to 500 nm, and the refractive index was 1.53.
(2) In-plane phase difference (Re) of PVA
A phase difference measuring device (product name manufactured by Oji Measuring Instruments Co., Ltd.) is used for the polarizing element (polarizer unit) obtained by removing the resin base material from the laminate of the polarizing element / thermoplastic resin base material obtained in Examples and Comparative Examples. KOBRA-31X100 / IR ”) was used to evaluate the in-plane phase difference (Rpva) of PVA at a wavelength of 1000 nm (according to the explained principle, from the total in-plane phase difference at a wavelength of 1000 nm, the in-plane phase difference of iodine. (Ri) is subtracted). The absorption edge wavelength was set to 600 nm.
(3) Birefringence of PVA (Δn)
The birefringence (Δn) of PVA was calculated by dividing the in-plane phase difference of PVA measured in (2) above by the thickness of the substituent.
(4) Single Transmittance and Polarization Degree The ultraviolet-visible spectrophotometric degree of the polarizing element (polarizer unit) obtained by peeling and removing the resin base material from the polarizing element / thermoplastic resin base material laminates obtained in Examples and Comparative Examples. A single transmittance Ts, a parallel transmittance Tp, and a orthogonal transmittance Tc were measured using a meter (“V-7100” manufactured by Nippon Spectroscopy Co., Ltd.). These Ts, Tp and Tc are Y values measured by the JIS Z 8701 2 degree field of view (C light source) and corrected for luminosity factor. From the obtained Tp and Tc, the degree of polarization P was determined by the following formula.
Polarization degree P (%) = {(Tp-Tc) / (Tp + Tc)} ^1/2 × 100
It should be noted that the spectrophotometer can be used for the same measurement with "LPF-200" manufactured by Otsuka Electronics Co., Ltd., and the same measurement result can be obtained regardless of which spectrophotometer is used. Has been confirmed.
(5) Puncture strength (breaking strength per unit thickness)
Compression tester (manufactured by Kato Tech Co., Ltd., product name "NDG5" needle penetration force measurement specification) in which the stator is peeled off from the laminate of the stator / thermoplastic resin base material obtained in Examples and Comparative Examples and a needle is attached. ), And pierced at a piercing speed of 0.33 cm / sec under a room temperature (23 ° C ± 3 ° C) environment, and the strength when the polarizing element was broken was defined as the breaking strength. As the evaluation value, the breaking strength of 10 sample pieces was measured, and the average value thereof was used. The needle used had a tip diameter of 1 mmφ and 0.5R. The polarizing element to be measured was fixed by sandwiching a jig having a circular opening having a diameter of about 11 mm from both sides of the polarizing element, and a needle was pierced into the center of the opening to perform a test.
(6) PVA Orientation Function The resin base material was peeled off from the spectrometer (separator alone) from which the resin base material was peeled off from the laminate of the spectrometer / thermoplastic resin base material obtained in Examples and Comparative Examples. A Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: "Frontier") is used for the surface opposite to the surface, and polarized infrared light is used as measurement light for polarization. Total internal reflection spectroscopy (ATR) measurement of the child surface was performed. Germanium was used as the crystallite to which the polarizing element was brought into close contact, and the incident angle of the measured light was 45 °. The orientation function was calculated according to the following procedure. The incident polarized infrared light (measurement light) is polarized light (s-polarized light) that vibrates parallel to the surface to which the germanium crystal sample is in close contact, and the extension direction of the substituent is perpendicular to the polarization direction of the measurement light (measurement light). ⊥) and parallel (//) were arranged, and the respective absorbance spectra were measured. From the obtained absorbance spectrum, (2941 cm ^-1 intensity) I was calculated with reference to (3330 cm ^-1 intensity). I _⊥ is (2941 cm ^-1 intensity) / (3330 cm ^-1 intensity) obtained from the absorbance spectrum obtained when the stretching direction of the modulator is arranged perpendicularly (⊥) with respect to the polarization direction of the measurement light. Further, I _// is obtained from the absorbance spectrum obtained when the stretching direction of the splitter is arranged parallel (//) with respect to the polarization direction of the measurement light (2941 cm ^-1 intensity) / (3330 cm ^-1 intensity). Is. Here, (2941 cm ^-1 intensity) is the absorbance of 2941 cm ^-1 when 2770 cm ^-1 and 2990 cm ^-1 , which are the bottoms of the absorbance spectrum, are used as baselines, and (3330 cm ^-1 intensity) is 2990 cm ⁻ . It is the absorbance of 3330 cm ^-1 with ¹ and 3650 cm ^-1 as the baseline. Using the obtained I _⊥ and I _// , the orientation function f was calculated according to Equation 1. When f = 1, it is completely oriented, and when f = 0, it is random. Further, the peak of 2941 cm ^-1 is said to be absorption caused by vibration of the main chain (-CH _2- ) of PVA in the polarizing element. The peak of 3330 cm ^-1 is said to be absorbed due to the vibration of the hydroxyl group of PVA.
(Equation 1) f = (3 <cos ² θ> -1) / 2
= (1-D) / [c (2D + 1)]
However, c = (3cos ² β-1) / 2
Then, when 2941 cm ^-1 is used as described above, β = 90 ° ⇒ y = -2 × (1-D) / (2D + 1).
θ: Angle of molecular chain with respect to stretching direction β: Angle of transition dipole moment with respect to molecular chain axis D = (I _⊥ ) / (I _// )
I _⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing element are perpendicular to each other I _// : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizing element are parallel (7) Crack occurrence rate A surface protective film was temporarily attached to the surface of the protective layer of the polarizing plate (or the polarizing plate with a retardation layer) obtained in Examples and Comparative Examples. Next, a separator was temporarily attached to the pressure-sensitive adhesive layer of the polarizing plate (or a polarizing plate with a retardation layer). This laminate was cut out to a size of about 130 mm × about 70 mm. At this time, the absorber was cut out so that the absorption axis was in the lateral direction. A U-shaped notch having a width of 5 mm, a depth (length of the recess) of 6.85 mm, and a radius of curvature of 2.5 mm was formed in the central portion of the short side of the cut-out laminate. The U-shaped notch was formed by end milling. The outer diameter of the end mill was 4 mm, the feed rate was 500 mm / min, the rotation speed was 35,000 rpm, the amount of cutting and the number of times of cutting were 0.2 mm / time for rough cutting and 0.1 mm / time for finish cutting, for a total of 2 times. The separator was peeled off from the laminate having the U-shaped notch formed, and attached to a glass plate (thickness 1.1 mm) via an acrylic pressure-sensitive adhesive layer. Finally, a test in which the surface protective film is peeled off and has a structure of a protective layer / a polarizing element / an adhesive layer / a glass plate (or a protective layer / a polarizing element / an adhesive layer / a retardation layer / an adhesive layer / a glass plate). A sample was obtained. This test sample was held at −40 ° C. for 30 minutes and then held at 85 ° C. for 30 minutes for 300 cycles of repeated heat shock tests, and the presence or absence of L-shaped cracks after the test was visually confirmed. This evaluation was performed using three polarizing plates (or polarizing plates with a retardation layer), and the number of polarizing plates (or polarizing plates with a retardation layer) in which cracks (substantially L-shaped cracks) were generated was determined. evaluated.

[Example 1]
1. 1. Preparation of A Polarizer As a thermoplastic resin base material, an amorphous isophthal copolymer polyethylene terephthalate film (thickness: 100 μm) having a long shape, a water absorption of 0.75%, and a Tg of about 75 ° C. was used. One side of the resin base material was subjected to corona treatment (treatment conditions: 55 W · min / m ² ).
100 weight of PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name "Gosefimer Z410") are mixed at a ratio of 9: 1. 13 parts by weight of potassium iodide was added to the part 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 having a thickness of 13 μm, and a laminate was prepared.
The obtained laminate was stretched 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different peripheral speeds in an oven at 130 ° C. (aerial auxiliary stretching treatment).
Next, the laminate was immersed in an insolubilizing bath at a liquid temperature of 40 ° C. (a boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with 100 parts by weight of water) for 30 seconds (insolubilization treatment).
Next, in a dyeing bath having a liquid temperature of 30 ° C. (an aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1: 7 with respect to 100 parts by weight of water), the polarizing element finally obtained is charged. It was immersed for 60 seconds while adjusting the concentration so that the simple substance transmittance (Ts) was 40.5% (staining treatment).
Then, it was immersed in a cross-linked bath having a liquid temperature of 40 ° C. (a boric acid aqueous 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) for 30 seconds. (Crossing treatment).
Then, while immersing the laminate in a boric acid aqueous solution (boric acid concentration 4.0% by weight, potassium iodide 5.0% by weight) having a liquid temperature of 62 ° C., the rolls having different peripheral speeds are subjected to the longitudinal direction (longitudinal direction). ) Was uniaxially stretched so that the total stretching ratio was 3.0 times (underwater stretching treatment: the stretching ratio in the underwater stretching treatment was 1.25 times).
Then, the laminate was immersed in a washing bath having a liquid temperature of 20 ° C. (an aqueous solution obtained by blending 4 parts by weight of potassium iodide with 100 parts by weight of water) (cleaning treatment).
Then, while drying in an oven kept at 90 ° C., it was brought into contact with a heating roll made of SUS whose surface temperature was kept at 75 ° C. for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the laminated body by the dry shrinkage treatment was 2%.
In this way, a polarizing element having a thickness of 7.4 μm was formed on the resin substrate.

2. 2. Fabrication of Plate Plate 15 parts of epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) YX4000) and oxetane resin (manufactured by Toagosei Co., Ltd., trade name: Aron Oxetane (registered trademark) OXT-221) 10 parts by weight and 73 parts of methyl ethyl ketone were dissolved to obtain an epoxy resin solution. To the obtained epoxy resin solution, two parts of a photocationic polymerization initiator (manufactured by San-Apro Co., Ltd., trade name: CPI (registered trademark) -100P) was added to obtain a protective layer forming composition. The obtained protective layer forming composition can be used in the above 1. It was applied directly (that is, without forming an easy-adhesion layer) to the polarizing element surface of the resin substrate / polarizing element laminate obtained in 1), and the coating film was dried at 60 ° C. for 3 minutes. Then, using a high-pressure mercury lamp, ultraviolet rays were irradiated so that the integrated light amount was 600 mJ / cm ² , and a protective layer was formed. The thickness of the protective layer was 3 μm. Next, the resin base material was peeled off, and an acrylic pressure-sensitive adhesive layer (thickness 15 μm) was provided on the peeled surface. In this way, a polarizing plate having a structure of a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer was obtained.

[Examples 2 to 4]
A polarizing element (thickness: 7.4 μm) was formed on the resin substrate in the same manner as in Example 1 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used. did. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Example 5]
The polarizing element (thickness:: 6.7 μm) was formed. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Example 6-1]
A polarizing element (thickness: 6.7 μm) was formed on the resin substrate in the same manner as in Example 5 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used. did. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Example 6-2]
A laminate of resin base material / polarizing element (thickness: 6.7 μm) was obtained in the same manner as in Example 6-1. On the other hand, 20 parts of epoxy resin (manufactured by Mitsubishi Chemical Corporation, trade name: jER (registered trademark) YX6954BH30, weight average molecular weight: 36000, epoxy equivalent: 13000) was dissolved in 80 parts of methyl ethyl ketone, and an epoxy resin solution (20%) was added. Obtained. This epoxy resin solution was applied to the surface of the polarizing element of the laminate using a wire bar, and the coating film was dried at 60 ° C. for 3 minutes to form a protective layer formed as a solidified product of the coating film. The thickness of the protective layer was 3 μm. Next, the resin base material was peeled off, and the same acrylic pressure-sensitive adhesive layer as in Example 1 was provided on the peeled surface. In this way, a polarizing plate having a structure of a protective layer (solidified layer of an epoxy resin coating film) / a polarizing element / an adhesive layer was obtained.

[Example 6-3]
A laminate of resin base material / polarizing element (thickness: 6.7 μm) was obtained in the same manner as in Example 6-1. A polyurethane-based water-based dispersion resin (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., product name: Superflex SF210) was applied as an easy-adhesion layer to the polarizing surface of the obtained laminate so that the thickness was 0.1 μm. An adhesive layer was formed. On the other hand, 20 parts by weight of an acrylic resin (manufactured by Kusumoto Kasei Co., Ltd., product name: B-728) which is 100% polymethylmethacrylate was dissolved in 80 parts by weight of methyl ethyl ketone to obtain an acrylic resin solution (20%). This acrylic resin solution was applied to the surface of the easy-adhesion layer using a wire bar, and the coating film was dried at 60 ° C. for 5 minutes to form a protective layer composed of a solidified coating film. The thickness of the protective layer was 2 μm. Further, a hard coat layer (thickness 3 μm) was further formed on the surface of the protective layer opposite to the easy-adhesion layer. The hard coat (HC) layer is 70 parts by weight of dimethylol-tricyclodecanediacrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate DCP-A), isobornyl acrylate (manufactured by Kyoeisha Chemical Co., Ltd., trade name: light acrylate IB-XA). ) 20 parts by weight, 1,9-nonanediol diacrylate (Kyoeisha Chemical Co., Ltd., trade name: Light Acrylate 1.9NA-A) 10 parts by weight, and a photopolymerization initiator (BASF Co., Ltd., trade name: Irgacure 907). 3 parts by weight were mixed using an appropriate solvent, and the obtained coating liquid was applied onto the protective layer surface so as to be 3 μm after curing, and then the solvent was dried and integrated using a high-pressure mercury lamp. It was formed by irradiating ultraviolet rays in a nitrogen atmosphere so that the amount of light was 300 mJ / cm ² . Finally, the resin base material was peeled off, and the same acrylic pressure-sensitive adhesive layer as in Example 1 was provided on the peeled surface. In this way, a polarizing plate having a structure of an HC layer / a protective layer (a solidified layer of an acrylic resin coating film) / an easy-adhesion layer / a polarizing element / an adhesive layer was obtained.

[Examples 7 to 8]
A polarizing element (thickness: 6.7 μm) was formed on the resin substrate in the same manner as in Example 5 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used. did. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Examples 9 to 12]
The stretch ratio of stretching in water was 1.67 times (as a result, the total ratio of stretching was 4.0 times), and the dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1). A polarizing element (thickness: 6.2 μm) was formed on the resin substrate in the same manner as in Example 1 except that: 7) was used. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Examples 13 to 16]
The stretching ratio of stretching in water was 1.88 times (as a result, the total ratio of stretching was 4.5 times), and the dyeing baths with different iodine concentrations (weight ratio of iodine and potassium iodide = 1). A polarizing element (thickness: 6.0 μm) was formed on the resin substrate in the same manner as in Example 1 except that: 7) was used. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Comparative Example 1]
The polarizing element (thickness:: 5.5 μm) was formed. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Comparative Example 2-1]
A polarizing element (thickness: 5.5 μm) was formed on the resin substrate in the same manner as in Comparative Example 1 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used. did. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Comparative Example 2-2]
Protective layer (solidified layer of epoxy resin coating film) / polarizing element / adhesive in the same manner as in Comparative Example 2-1 except that the protective layer was formed using the same epoxy resin solution as in Example 6-2. A polarizing plate having a layer structure was obtained.

[Comparative Example 2-3]
Protective layer (solidified layer of acrylic resin coating film) / polarizing element / adhesive in the same manner as in Comparative Example 2-1 except that the protective layer was formed using the same acrylic resin solution as in Example 6-3. A polarizing plate having a layer structure was obtained.

[Comparative Examples 3 to 4]
A polarizing element (thickness: 5.5 μm) was formed on the resin substrate in the same manner as in Comparative Example 1 except that dyeing baths having different iodine concentrations (weight ratio of iodine to potassium iodide = 1: 7) were used. did. The following procedure was the same as in Example 1 to obtain a polarizing plate having a protective layer (photocationic curing layer of epoxy resin) / polarizing element / adhesive layer.

[Example 17]
1. 1. Preparation of a retardation film constituting the retardation layer Polymerization was carried out using a batch polymerization apparatus consisting of two vertical reactors equipped with a stirring blade and a reflux condenser controlled at 100 ° C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] 29.60 parts by mass (0.046 mol) of methane, 29.21 parts by mass (0.200 mol) of isosorbide (ISB), 42 of spiroglycol (SPG) .28 parts by mass (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC) and calcium acetate monohydrate 1.19 x 10 ^-2 parts by mass (6.78 x 10- ⁾ as a catalyst. ⁵ mol) was charged. After substituting nitrogen under reduced pressure in the reactor, heating was performed with a heat medium, and stirring was started when the internal temperature reached 100 ° C. The internal temperature was brought to 220 ° C. 40 minutes after the start of the temperature rise, and the depressurization was started at the same time as controlling to maintain this temperature, and the temperature was 13.3 kPa 90 minutes after reaching 220 ° C. The phenol vapor produced by the polymerization reaction was guided to a reflux condenser at 100 ° C., the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the non-condensed phenol vapor was guided to a condenser at 45 ° C. for recovery. Nitrogen was introduced into the first reactor and the pressure was once restored to atmospheric pressure, and then the oligomerized reaction solution in the first reactor was transferred to the second reactor. Then, the temperature rise and depressurization in the second reactor were started, and the internal temperature was 240 ° C. and the pressure was 0.2 kPa in 50 minutes. Then, the polymerization was allowed to proceed until the stirring power became a predetermined value. When the predetermined power was reached, nitrogen was introduced into the reactor to repressurize, the produced polyester carbonate-based resin was extruded into water, and the strands were cut to obtain pellets.

After vacuum-drying the obtained polyester carbonate-based resin (pellet) at 80 ° C. for 5 hours, a single-screw extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250 ° C.), T-die (width 200 mm, set temperature: 250). A long resin film having a thickness of 130 μm was prepared by using a film forming apparatus equipped with a chill roll (set temperature: 120 to 130 ° C.) and a winder. The obtained long resin film was stretched while adjusting so that a predetermined retardation was obtained, to obtain a retardation film having a thickness of 48 μm. The stretching conditions were a stretching temperature of 143 ° C. and a stretching ratio of 2.8 times in the width direction. The Re (550) of the obtained retardation film was 141 nm, the Re (450) / Re (550) was 0.86, and the Nz coefficient was 1.12.

2. 2. Preparation of polarizing plate with retardation layer A laminate of resin base material / polarizing element (thickness: 6.7 μm) was obtained in the same manner as in Example 6-1. A protective layer (photocationic curing layer of epoxy resin) was formed on the surface of the polarizing element of the laminate in the same manner as in Example 1. Next, the resin base material was peeled off, and the retardation film (phase difference layer) obtained above was attached to the peeled surface via an acrylic pressure-sensitive adhesive layer having a thickness of 5 μm. At that time, the slow axis of the retardation layer and the absorption axis of the polarizing element were bonded so as to form an angle of 45 °. Finally, the same acrylic pressure-sensitive adhesive layer as in Example 1 was provided on the surface of the retardation layer. In this way, a polarizing plate with a retardation layer having a structure of a protective layer (photocationic curing layer of epoxy resin) / polarizing element / pressure-sensitive adhesive layer / retardation layer / pressure-sensitive adhesive layer was obtained.

[Comparative Example 5]
A laminate of resin base material / polarizing element (thickness: 5.5 μm) was obtained in the same manner as in Comparative Example 2-1. A retardation layer having a structure of a protective layer (photocationic curing layer of epoxy resin) / polarizing element / pressure-sensitive adhesive layer / retardation layer / pressure-sensitive adhesive layer in the same manner as in Example 17 except that this laminate is used. A polarizing plate was obtained.

The polarizing plates obtained in Examples and Comparative Examples or the polarizing plates with a retardation layer were subjected to the evaluations (2) to (7) above. The results are shown in Table 1.

As is clear from Table 1, in the polarizing plate of the embodiment and the polarizing plate with a retardation layer, the generation of cracks in the deformed portion (U-shaped notch portion) is suppressed.

Further, FIGS. 8 to 10 show the relationship between the simple substance transmittance of the polarizing element obtained in Examples and Comparative Examples, Δn of PVA, the in-plane phase difference, or the orientation function, respectively. As shown in FIGS. 8 to 10, even if the birefringence, the in-plane phase difference, or the orientation function is the same (as a result, the degree of orientation is the same), if the single transmittance is high, the deformed shape is processed. It can be seen that cracks are likely to occur in the portion. For example, when Δn is around 35 (× 10 ^-3 ) in FIG. 8, when the simple substance transmittance becomes larger than about 44.2%, the equation (1) is not satisfied, and as a result, cracks are generated as in Comparative Example 4. appear. Therefore, in order to effectively suppress the occurrence of cracks in the deformed portion, it is important to adjust the single transmittance (as a result, the amount of adsorbed dichroic substance) in addition to the degree of orientation of the PVA-based resin. I understand. Further, the polarizing element satisfying the formula (1), the formula (2) and / or the formula (3) is preferably adjusted, and the generation of cracks in the deformed portion can be suitably suppressed. You can see that.

The polarizing plate of the present invention is used for an image display device, and is particularly preferably used for an image display device having a deformed shape such as an automobile meter panel, a smartphone, a tablet PC, or a smart watch.

Claims (17)

1. A polarizing plate having a polarizing element and a protective layer arranged on at least one side of the polarizing element.
   The polarizing plate has a shape other than a rectangle and has a variant shape.
   The protective layer is made of a resin film having a thickness of 10 μm or less.
   When the polarizing element is made of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y, the following formula (1) is used. Satisfying, polarizing plate:
   y <−0.011x + 0.525 (1).
2. A polarizing plate having a polarizing element and a protective layer arranged on at least one side of the polarizing element.
   The polarizing plate has a shape other than a rectangle and has a variant shape.
   The protective layer is made of a resin film having a thickness of 10 μm or less.
   The polarizing element is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and when the single transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film is znm, the following formula is used. A polarizing plate that satisfies (2):
   z <-60x + 2875 (2).
3. A polarizing plate having a polarizing element and a protective layer arranged on at least one side of the polarizing element.
   The polarizing plate has a shape other than a rectangle and has a variant shape.
   The protective layer is made of a resin film having a thickness of 10 μm or less.
   The polarizing element is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and when the single transmittance is x% and the orientation function of the polyvinyl alcohol-based resin is f, the following formula (3) is used. Satisfying, polarizing plate:
   f <−0.018x + 1.11 (3).
4. A polarizing plate having a polarizing element and a protective layer arranged on at least one side of the polarizing element.
   The polarizing plate has a shape other than a rectangle and has a variant shape.
   The protective layer is made of a resin film having a thickness of 10 μm or less.
   The polarizing element is a polarizing plate made of a polyvinyl alcohol-based resin film containing a dichroic substance and having a piercing strength of 30 gf / μm or more.
5. The polarizing plate according to any one of claims 1 to 4, wherein the polarizing element has a thickness of 10 μm or less.
6. The polarizing plate according to any one of claims 1 to 5, wherein the single-unit transmittance of the polarizing element is 40.0% or more, and the degree of polarization is 99.0% or more.
7. The irregular shape is a through hole, a V-shaped notch, a U-shaped notch, a concave portion having a shape similar to a ship shape when viewed in a plane, a rectangular concave portion when viewed in a plane, and an R shape which is similar to a bathtub shape when viewed in a plane. The polarizing plate according to any one of claims 1 to 6, which is selected from the group consisting of recesses and combinations thereof.
8. The polarizing plate according to claim 7, wherein the radius of curvature of the U-shaped notch is 5 mm or less.
9. The polarizing plate according to any one of claims 1 to 8, wherein the resin film contains at least one resin selected from an epoxy resin and a (meth) acrylic resin.
10. The polarizing plate according to any one of claims 1 to 9, wherein the resin film is composed of a photocationically cured product of an epoxy resin, and the softening temperature of the resin film is 100 ° C. or higher.
11. The polarizing plate according to any one of claims 1 to 9, wherein the resin film is composed of a solidified coating film of an organic solvent solution of an epoxy resin, and the softening temperature of the resin film is 100 ° C. or higher.
12. The method according to any one of claims 1 to 9, wherein the resin film is composed of a solidified coating film of an organic solvent solution of a thermoplastic (meth) acrylic resin, and the softening temperature of the resin film is 100 ° C. or higher. The polarizing plate according to the description.
13. 12. According to claim 12, the thermoplastic (meth) acrylic resin has at least one selected from the group consisting of a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit and a maleimide unit. Polarizer.
14. The polarizing plate according to any one of claims 1 to 13 and a retardation layer are included.
    A polarizing plate with a retardation layer, wherein the retardation layer is arranged on the side opposite to the side on which the protection layer of the polarizing element is arranged.
15. The Re (550) of the retardation layer is 100 nm to 190 nm, and Re (450) / Re (550) is 0.8 or more and less than 1.
    The polarizing plate with a retardation layer according to claim 14, wherein the angle formed by the slow axis of the retardation layer and the absorption axis of the polarizing element is 40 ° to 50 °.
16. The polarizing plate with a retardation layer according to claim 14 or 15, wherein the retardation layer is laminated on the polarizing plate via an adhesive layer.
17. An image display device comprising the polarizing plate according to any one of claims 1 to 13 or the polarizing plate with a retardation layer according to any one of claims 14 to 16.

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