KR20230042028A - An image display device including a polarizing plate, a polarizing plate with a retardation layer, and the polarizing plate or the polarizing plate with the retardation layer - Google Patents

Abstract

Provided is a polarizing plate that is extremely thin and suppresses cracking in a release processing part. The polarizing plate of the present invention includes a polarizer and a protective layer disposed on at least one side of the polarizer, and has a shape other than rectangular. The protective layer is composed of a resin film having a thickness of 10 µm or less. The polarizer is composed of a PVA-based resin film containing a dichroic material. In one embodiment, the polarizer satisfies the following formula (1) when the single transmittance is x% and the birefringence of the PVA-based resin is y. In another embodiment, the polarizer satisfies the following formula (2) when the single transmittance is x% and the in-plane retardation of the PVA-based resin film is znm. In another embodiment, the polarizer satisfies the following formula (3) when the single transmittance is x% and the orientation function of the PVA-based resin is f. In another embodiment, the polarizer has a puncture strength of 30 gf/μm or more.
y<-0.011x+0.525 (1)
z<-60x+2875 (2)
f<-0.018x+1.11 (3)

Description

An image display device including a polarizing plate, a polarizing plate with a retardation layer, and the polarizing plate or the polarizing plate with the 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 typified by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) are rapidly spreading. Due to the image forming method of the image display device, a polarizing plate is disposed on at least one side of the image display device. In recent years, as the demand for thinning of image display devices has increased, the demand for thinning has also increased for polarizing plates. By the way, in recent years, processing of a polarizing plate into a shape other than a rectangular shape (special shape processing: formation of notches and/or through holes, for example) is sometimes required. However, there is a problem that cracks tend to occur in the release processing part of the thin polarizing plate.

Japanese Unexamined Patent Publication No. 2001-343521

The present invention has been made in order to solve the above conventional problems, and its main object is to provide a polarizing plate that is extremely thin and suppresses cracking in a release processing part.

A polarizing plate according to one embodiment of the present invention includes a polarizer and a protective layer disposed on at least one side of the polarizer, and has a shape other than rectangular. The protective layer is composed of a resin film having a thickness of 10 µm or less. When the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y, Equation (1) is satisfied:

y<-0.011x+0.525 (1).

A polarizing plate according to another embodiment of the present invention includes a polarizer and a protective layer disposed on at least one side of the polarizer, and has a shape other than rectangular. The protective layer is composed of a resin film having a thickness of 10 µm or less. The polarizer 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 z nm, the following formula ( 2) satisfies:

z<-60x+2875 (2).

A polarizing plate according to another embodiment of the present invention includes a polarizer and a protective layer disposed on at least one side of the polarizer, and has a shape other than rectangular. The protective layer is composed of a resin film having a thickness of 10 µm or less. The polarizer 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 ) satisfies:

f<-0.018x+1.11 (3).

A polarizing plate according to another embodiment of the present invention includes a polarizer and a protective layer disposed on at least one side of the polarizer, and has a shape other than rectangular. The protective layer is composed of a resin film having a thickness of 10 µm or less. The polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and has a puncture strength of 30 gf/μm or more.

In one embodiment, the thickness of the polarizer is 10 μm or less.

In one embodiment, the polarizer has a single transmittance of 40.0% or more, and a polarization degree of 99.0% or more.

In one embodiment, the irregular shape is a through hole, a V-shaped notch, a U-shaped notch, a concave portion having a shape approximate to a ship shape when viewed in plan view, a rectangular concave portion when viewed in plan view, and a concave portion having a shape approximated to a ship shape when viewed in plan view. It is selected from the group consisting of an R-shaped concave portion approximate to a bathtub shape, and a combination thereof.

In one embodiment, the radius of curvature of the U-shaped notch is 5 mm or less.

In one embodiment, the resin film contains at least one type of resin selected from epoxy resins and (meth)acrylic resins.

In one embodiment, the resin film is composed of a photo-cationic cured material 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 material of a 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 material of a 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 situation of this invention, the polarizing plate with a retardation layer is provided. The polarizing plate with the retardation layer includes the polarizing plate and the retardation layer, and the retardation layer is disposed on the opposite side of the polarizer on which the protective layer is disposed.

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 and the polarizer The angle formed by the absorption axis of is 40° to 50°.

In one embodiment, the retardation layer is laminated on the polarizing plate with an adhesive layer interposed therebetween.

According to another aspect of the present invention, an image display device is provided. The said image display device contains the said polarizing plate or the said polarizing plate with a retardation layer.

According to an embodiment of the present invention, in a polarizing plate having a mold release (release processing part), by controlling the alignment state of the polyvinyl alcohol (PVA)-based resin of the polarizer, while being extremely thin, cracking in the release processing part is suppressed A polarizing plate can be realized. Further, such a polarizer (as a result, a polarizing plate) can exhibit practically acceptable optical properties.

1 is a schematic cross-sectional view of a polarizing plate according to one embodiment of the present invention.
2 is a schematic plan view illustrating an example of a release or release processing part in a polarizing plate according to an embodiment of the present invention.
3 is a schematic plan view illustrating a modified example of a release or release processing unit in a polarizing plate according to an embodiment of the present invention.
4 is a schematic plan view illustrating another modified example of a release or release processing unit in a polarizing plate according to an embodiment of the present invention.
5 is a schematic plan view illustrating another modified example of a release or release processing unit in a polarizing plate according to an embodiment of the present invention.
6 is a schematic view showing an example of drying shrinkage treatment using a heating roll in the manufacturing method of a polarizer that can be used for a polarizing plate according to an embodiment of the present invention.
7 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
8 is a graph showing the relationship between the single transmittance of polarizers produced in Examples and Comparative Examples and the birefringence of PVA-based resin.
9 is a graph showing the relationship between the single transmittance of light polarizers produced in Examples and Comparative Examples and the in-plane retardation of the PVA-based resin film.
10 is a graph showing the relationship between the single transmittance of light polarizers produced in Examples and Comparative Examples and the orientation function of PVA-based resin.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment.

A. Polarizer

A-1. Overall configuration of polarizer

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 includes a polarizer 10 and a protective layer 20 disposed on one side of the polarizer 10 . Depending on the purpose, another protective layer (not shown) may be provided on the side opposite to the protective layer 20 of the polarizer 10 . The protective layer 20 is composed 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 as a rear-side polarizing plate. A polarizing plate is typically used as a viewing-side polarizing plate. In this case, the protective layer 20 may be disposed on the viewing side (opposite to the image display cell).

A polarizing plate according to an embodiment of the present invention has a shape other than rectangular. In this specification, 'having a non-rectangular shape' means that the planar view shape of the polarizing plate has a shape other than rectangular. The mold release is typically a mold release processed part. Therefore, 'a polarizing plate having a non-rectangular shape' (hereinafter sometimes referred to as 'a different type polarizing plate') is not only a case where the entire hetero-shaped polarizing plate (ie, the outer edge defining the planar view shape of the polarizing plate) is other than a rectangular shape, The case where a mold release process part is formed in the part separated inward from the outer edge of a rectangular polarizing plate is also included. In a polarizing plate, cracks tend to occur in such a mold release part, but according to the embodiment of the present invention, such cracks can be remarkably suppressed. More specifically, it is as follows. In a normal (ie, non-release) polarizer (substantially a polarizer), cracks occur along the absorption axis (stretching direction) of the polarizer in many cases. On the other hand, L-shaped cracks (cracks in an oblique direction with respect to the absorption axis) may occur in the molded part. According to the embodiment of the present invention, as will be described later, by making the orientation in the direction of the absorption axis of the molecular chain of the PVA-based resin of the polarizer gentler than that of the conventional polarizer, not only ordinary cracks but also such L-shaped cracks are remarkable. can be suppressed.

As the release (release processing part), for example, as shown in Figs. 2 and 3, those obtained by chamfering corners into R shapes, through holes, and cutting parts that become concave parts in the case of planar view are exemplified. Representative examples of the concave portion include a shape approximating a linear shape, a rectangle, an R shape approximating a bathtub shape, a V-shaped notch, and a U-shaped notch. As another example of the release (release processing part), as shown in Figs. 4 and 5, a shape corresponding to the meter panel of an automobile can be given. The shape includes a portion where the outer edge is formed in an arc shape along the rotational 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 release (release processing part) is not limited to the illustrated example. For example, the shape of the through hole may be any suitable shape (eg, elliptical, triangular, quadrangular, pentagonal, hexagonal, octagonal) depending on the purpose other than the approximate circular shape shown in the illustrated example. Further, the through hole is provided at any suitable position depending on the purpose. As shown in Fig. 3, the through hole may be provided in the substantially central portion of the longitudinal end of the rectangular polarizing plate, may be provided in a predetermined position of the longitudinal end, or may be provided in the corner portion of the polarizing plate; Although not shown, it may be provided at the short end of the rectangular polarizing plate; As shown in Fig. 4 or Fig. 5, the center portion of the release polarizing plate may be provided. As shown in Fig. 3, a plurality of through holes may be provided. Moreover, you may combine the shapes of an illustration suitably according to a purpose. For example, a through hole may be formed at an arbitrary position of the heterogeneous polarizing plate of FIG. 2, or a V-shaped notch and/or a U-shaped notch may be formed at an arbitrary appropriate position on the outer edge of the heteromorphic polarizing plate of FIG. 4 or 5. . Such a release polarizer can be suitably used for image display devices such as meter panels of automobiles, smart phones, tablet PCs, or smart watches. Further, for example, when the irregular shape includes an R shape, the radius of curvature thereof is, for example, 0.2 mm or more, and is, for example, 1 mm or more, and is, for example, 2 mm or more. On the other hand, the radius of curvature is, for example, 10 mm or less, and for example, 5 mm or less. Further, for example, when the irregular shape is a U-shaped notch, its radius of curvature (the radius of curvature of the U-shaped portion) is, for example, 5 mm or less, and is, for example, 1 mm to 4 mm, and, for example, 2 mm to 3 mm.

The mold release (release processing part) 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 polarizer is composed of a PVA-based resin film containing a dichroic material. In one embodiment, the polarizer satisfies the following formula (1) when x% is the single transmittance and birefringence of the polyvinyl alcohol-based resin constituting the polarizer is y. In one embodiment, the polarizer satisfies the following formula (2), when the single transmittance is x% and the in-plane retardation of the polyvinyl alcohol-based resin film constituting the polarizer is znm. In one embodiment, a polarizer satisfies the following formula (3), when x% is the single transmittance and the orientation function of the polyvinyl alcohol-based resin constituting the polarizer is f. In one embodiment, the polarizer has a puncture strength of 30 gf/μm or more.

y<-0.011x+0.525 　(1)

z<-60x+2875 (2)

f<-0.018x+1.11 (3)

Birefringence of the PVA-based resin in the polarizer (hereinafter referred to as birefringence of PVA or Δn of PVA), in-plane retardation of the PVA-based resin film (hereinafter referred to as 'in-plane retardation of PVA'), orientation of the PVA-based resin Both the function (hereinafter referred to as 'PVA orientation function') and the piercing strength of the polarizer are values related to the degree of orientation of the molecular chains of the PVA-based resin constituting the polarizer. Specifically, the birefringence, in-plane retardation, and orientation function of PVA may become large values as the degree of orientation increases, and the puncture strength may decrease as the degree of orientation increases. The polarizer according to the embodiment of the present invention (that is, the polarizer satisfying the above equations (1) to (3) or the stabbing strength) has a more gentle orientation of the molecular chain of the PVA-based resin in the direction of the absorption axis than the conventional polarizer. Due to this, heating shrinkage in the direction of the absorption axis is suppressed. As a result, such a polarizer (as a result, a polarizing plate) can be suppressed from cracking in the release processing part while being extremely thin. In addition, such a polarizer (as a result, a polarizing plate) is also excellent in flexibility and bending durability, so it is preferably a curved image display device, more preferably a bendable image display device, and still more preferably a foldable image display device can be applied to Conventionally, it has been difficult to obtain acceptable optical characteristics (typically single transmittance and polarization degree) with a polarizer having a low degree of orientation. Optical properties are compatible.

The polarizer preferably satisfies the following formula (1a) and/or formula (2a), and more preferably satisfies the following formula (1b) and/or formula (2b).

-0.004x+0.18<y<-0.011x+0.525 (1a)

-0.003x+0.145<y<-0.011x+0.520 (1b)

-40x+1800<z<-60x+2875 (2a)

-30x+1450<z<-60x+2850 (2b)

In the present specification, the in-plane retardation of the 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 near-infrared region as the measurement wavelength, the influence of iodine absorption in the polarizer can be eliminated, and it becomes possible to measure the phase difference. In addition, the birefringence (in-plane birefringence) of the PVA is a value obtained by dividing the in-plane retardation of the PVA by the thickness of the polarizer.

The in-plane retardation of PVA was evaluated as follows. First, phase difference values are measured at a plurality of wavelengths with a wavelength of 850 nm or more, and a plot of the measured phase difference values: R(λ) and wavelength: λ is performed, and these are fit to the following Selmeier equation by the least square method. Here, A and B are fitting parameters and are coefficients determined by the least squares method.

R(λ)=A+B/(λ ² −600 ² )

At this time, this retardation value R(λ) can be separated into an in-plane retardation value (Rpva) of PVA having no wavelength dependence and an in-plane retardation value (Ri) of iodine having a strong wavelength dependence as follows.

Rpva=A

Ri=B/(λ ² -600 ² )

Based on this separation equation, the in-plane retardation of PVA at a wavelength of λ = 1000 nm (ie, Rpva) can be calculated. In addition, the evaluation method of the in-plane retardation of the said PVA is also described in Japanese Patent Publication No. 5932760, and can be referred as needed.

In addition, birefringence (Δn) of PVA can be calculated by dividing this retardation by the thickness.

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

The orientation function (f) of the polarizer preferably satisfies the following formula (3a), and more preferably satisfies the following formula (3b). When the orientation function is too small, acceptable single transmittance and/or polarization degree 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 can be obtained by attenuated total reflection (ATR) measurement using, for example, a Fourier transform infrared spectrophotometer (FT-IR) and using polarized light as measurement light. Specifically, germanium is used as the crystallizer for adhering the polarizer, the incident angle of the measurement light is 45° incident, and the incident polarized infrared light (measurement light) is polarized light that oscillates parallel to the surface of the germanium crystal that adheres the sample. (s-polarization), measurement was performed in a state where the stretching direction of the polarizer was arranged parallel and perpendicular to the polarization direction of the measurement light, and the absorbance spectrum obtained at 2941 cm ^-1 was used to calculate according to the following formula. do. Here, intensity I is a value of 2941 cm ^{-1 /} 3330 cm ^{-1 with 3330 cm -1} as a reference peak. Also, when f = 1, the orientation is perfect, and when f = 0, it becomes random. The peak at 2941 cm ^-1 is considered to be absorption due to vibration of the PVA main chain (-CH ₂ -) in the polarizer.

f=(3<cos ² θ>-1)/2

=(1-D)/[c(2D+1)]

=-2×(1-D)/(2D+1)

step,

c=(3cos ² β-1)/2, and in case of vibration of 2941cm ^-1, β=90°.

θ: angle of the molecular chain with respect to the stretching direction

β: angle of the transition dipole moment with respect to the molecular chain axis

D=(I _⊥ )/(I _// ) (in this case, D increases as the PVA molecules are oriented)

I _⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are perpendicular to each other

I _// : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are parallel

The thickness of the polarizer is preferably 10 μm or less, more preferably 8 μm or less. The lower limit of the thickness of the polarizer may be, for example, 1 μm. The thickness of the polarizer 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 polarizer very thin in this way, heat shrinkage can be made very small. It is inferred that such a configuration can also contribute to suppression of crack generation in the release processing part of the polarizing plate.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of single transmittance may be, for example, 49.0%. The single transmittance of the polarizer is 40.0% to 45.0% in one embodiment. The degree of polarization of the polarizer is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization may be, for example, 99.999%. The degree of polarization of the polarizer is 99.0% to 99.9% in one embodiment. Although the polarizer according to the embodiment of the present invention has a lower degree of orientation of the PVA-based resin constituting the polarizer than before, and has the above in-plane retardation, birefringence and / or orientation function, such a practically acceptable single transmittance and a degree of polarization can be realized. It is guessed that this originates in the manufacturing method mentioned later. Incidentally, the single transmittance is typically a Y value measured using an ultraviolet/visible ray spectrophotometer and corrected for visibility. The degree of polarization can be obtained by the following formula, typically based on the parallel transmittance Tp and the orthogonal transmittance Tc measured using an ultraviolet/visible spectrophotometer and corrected for visibility.

Polarization degree (%) = {(Tp-Tc)/(Tp+Tc)} ^1/2 × 100

The puncture strength of the polarizer 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. am. The upper limit of the piercing strength may be, for example, 80 gf/μm. By making the puncture strength of a polarizer into such a range, it can suppress remarkably that a crack arises in a mold release process part, and that a polarizer is torn along an absorption axis direction. As a result, a polarizer (as a result, a polarizing plate) having very excellent flexibility can be obtained. The puncture strength represents the crack resistance of the polarizer when the polarizer is pierced with a predetermined strength. The puncture strength can be expressed as, for example, the strength at which the polarizer cracks (breaking strength) when a predetermined needle is attached to a compression tester and the needle is pierced into the polarizer at a predetermined speed. In addition, as is clear from the unit, the piercing strength means the piercing strength per unit thickness (1 μm) of the polarizer.

As described above, the polarizer is composed of a PVA-based resin film containing a dichroic substance. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially the polarizer) contains an acetoacetyl-modified PVA-based resin. With such a structure, a polarizer having a desired piercing strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably from 5% by weight to 20% by weight, more preferably from 8% by weight to 12% by weight, based on 100% by weight of the entire PVA-based resin. If the blending amount is in such a range, the piercing strength can be made into a more suitable range.

A polarizer can be typically manufactured using a laminate of two or more layers. As a specific example of the light polarizer obtained using a laminated body, the polarizer obtained using the laminated body of the resin base material and the PVA system resin layer applied and formed on the said resin base material is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate, for example, by applying a PVA-based resin solution to the resin substrate, drying it, forming a PVA-based resin layer on the resin substrate, Obtaining a laminated body of a resin substrate and a PVA-based resin layer; It can be produced by: stretching and dyeing the layered product to make the PVA-based resin layer a polarizer. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically involves immersing the layered product in an aqueous solution of boric acid and extending the laminate. Further, the stretching preferably further includes air stretching the laminate at a high temperature (eg, 95° C. or higher) prior to stretching in an aqueous solution of boric acid. 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 such a total magnification of stretching, a polarizer having acceptable optical characteristics can be obtained by a combination of halide addition and drying shrinkage treatment. Further, in the embodiment of the present invention, the draw ratio of air assisted stretching is preferably greater than the draw ratio of stretching in boric acid water. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has acceptable optical characteristics can be obtained. Further, the laminate is preferably subjected to a drying shrinkage treatment in which it shrinks by 2% or more in the width direction by heating while conveying in the longitudinal direction. In one embodiment, the manufacturing method of a light polarizer includes giving a laminated body an air assisted stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process in this order. By introducing auxiliary stretching, even when the PVA-based resin is applied on a thermoplastic resin, it becomes possible to increase the crystallinity of the PVA-based resin and achieve high optical properties. In addition, by simultaneously increasing the orientation of the PVA-based resin in advance, problems such as deterioration in orientation and dissolution of the PVA-based resin when immersed in water in a subsequent dyeing step or stretching step can be prevented, and high optical properties can be obtained. it becomes possible to achieve Further, in the case where the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizer obtained through the processing process performed by immersing a layered product in liquid, such as a dyeing process and an underwater extension process, can be improved. In addition, optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The obtained laminate of the resin substrate/polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), and the resin substrate is peeled from the laminate of the resin substrate/polarizer, and the peel surface is used for the purpose. Any suitable protective layer according to the above may be laminated and used. The details of the manufacturing method of the polarizer are described in section A-3.

A-3. Manufacturing method of polarizer

The method for producing the polarizer is preferably to form a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate, Forming a laminate, and subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment for shrinking by 2% or more in the width direction by heating while conveying in the longitudinal direction in this order. include 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 layered product by the drying shrinkage treatment is preferably 2% or more. In addition, the draw ratio of air assisted stretching is preferably larger than that of underwater stretching. According to such a manufacturing method, the polarizer described in the above section A-2 can be obtained. In particular, a laminate comprising a PVA-based resin layer containing a halide is produced, and stretching of the laminate is multi-step stretching including air-assisted stretching and underwater stretching, and the laminate after stretching is heated with a heating roll to obtain a width By shrinking by 2% or more in the direction, a polarizer having excellent optical properties (typically single transmittance and polarization degree) can be obtained.

A-3-1. Fabrication of the laminate

Arbitrary suitable methods can be adopted as a method of producing the laminated body of a thermoplastic resin base material and a PVA system resin layer. Preferably, a PVA-based resin layer is formed on the thermoplastic resin substrate by applying a coating liquid containing a halide and a PVA-based resin to the surface of the thermoplastic resin substrate and drying it. 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.

As a method of applying the coating liquid, any suitable method can be employed. For example, roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spray coating method, knife coating method (comma coating method etc.), etc. are 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. A polarizer having allowable single transmittance and polarization degree despite a lower degree of orientation of the PVA-based resin than before by making the thickness of the PVA-based resin layer before stretching extremely thin in this way and reducing the total magnification of the stretching as described below. can be obtained.

Before forming the PVA-based resin layer, surface treatment (for example, corona treatment, etc.) may be performed on the thermoplastic resin substrate, or an easily bonding layer may be formed on the thermoplastic resin substrate. By performing such a process, the adhesiveness of a thermoplastic resin base material and a PVA system resin layer can be improved.

A-3-1-1. Thermoplastic resin substrate

As the thermoplastic resin substrate, any suitable thermoplastic resin film can be employed. About the detail of a thermoplastic resin base material, it describes, for example in Unexamined-Japanese-Patent No. 2012-73580. The entire description of the publication is incorporated herein by reference.

A-3-1-2. coating liquid

As described above, the coating liquid contains a halide and a PVA-based resin. The coating liquid is typically a solution obtained by dissolving the halide and the PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. can These can be used individually or in combination of 2 or more types. Among these, water is preferable. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhering to the thermoplastic resin substrate can be formed. 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.

You may mix|blend additives with a coating liquid. Examples of additives include plasticizers and surfactants. Examples of the plasticizer include polyhydric alcohols such as ethylene glycol and glycerin. As surfactant, a nonionic surfactant is mentioned, for example. These can be used for the purpose of further improving the uniformity, dyeability, and stretchability of the obtained PVA-based resin layer.

As the PVA-based resin, any suitable resin can be employed. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification 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. A light polarizer excellent in durability can be obtained by using PVA-type resin of such a degree of saponification. When the saponification degree is too high, there exists a possibility of saponification. As described above, the PVA-based resin preferably includes an acetoacetyl-modified PVA-based resin.

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

As the halide, any suitable halide can be employed. Examples include iodide and sodium chloride. As iodide, potassium iodide, sodium iodide, and lithium iodide are mentioned, for example. 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. When the amount of the halide with respect to 100 parts by weight of the PVA-based resin exceeds 20 parts by weight, the halide may bleed out and the polarizer finally obtained may become cloudy.

In general, when the PVA-based resin layer is stretched, the orientation of the polyvinyl alcohol molecules in the PVA-based resin layer increases, but when the stretched PVA-based resin layer is immersed in a liquid containing water, the orientation of the polyvinyl alcohol molecules is disturbed. , the orientation may decrease. In particular, in the case of stretching the laminate of the thermoplastic resin substrate and the PVA-based resin layer in boric acid water, in the case of stretching the laminate in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin substrate, the lowering of the orientation The trend is remarkable. For example, while it is common for stretching of a PVA film alone in boric acid to be carried out at 60°C, the stretching of a laminate of A-PET (thermoplastic resin substrate) and a PVA-based resin layer is performed at a high temperature of around 70°C. In this case, the orientation of PVA in the initial stage of stretching may be lowered in the stage before rising by underwater stretching. In contrast, by preparing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and stretching the laminate in air at high temperature (auxiliary stretching) before stretching the laminate in boric acid, the PVA of the laminate after auxiliary stretching Crystallization of the PVA-based resin in the resin-based layer can be promoted. As a result, in the case where the PVA-based resin layer is immersed in the liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in the orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizer obtained through the processing process performed by immersing a layered product in liquid, such as a dyeing process and an underwater extension process, can be improved.

A-3-2. Air Assisted Stretching Treatment

In particular, in order to obtain high optical properties, a method of two-step stretching is selected in which dry stretching (auxiliary stretching) and stretching in boric acid are combined. Like the two-stage stretching, by introducing auxiliary stretching, the thermoplastic resin substrate can be stretched while suppressing crystallization. Furthermore, in the case of applying the PVA-based resin on a thermoplastic resin substrate, in order to suppress the influence of the glass transition temperature of the thermoplastic resin substrate, it is necessary to lower the application temperature compared to the case of applying the PVA-based resin on a normal metal drum. As a result, the crystallization of the PVA-based resin is relatively low, resulting in a problem that sufficient optical properties cannot be obtained. In contrast, by introducing auxiliary stretching, the crystallinity of the PVA-based resin can be increased even when the PVA-based resin is applied on the thermoplastic resin, and high optical properties can be achieved. In addition, by simultaneously increasing the orientation of the PVA-based resin in advance, it is possible to prevent problems such as deterioration in the orientation of the PVA-based resin and dissolution when immersed in water in a subsequent dyeing step or drawing step, thereby achieving high optical properties. it becomes possible to do

The stretching method of air assisted stretching may be fixed end stretching (eg, stretching using a tenter stretching machine) or free end stretching (eg, uniaxial stretching by passing a laminate between rolls having different circumferential speeds). However, in order to obtain high optical properties, free end stretching may be actively employed. In one embodiment, the air stretching treatment includes a heating roll stretching step of stretching the laminate by a circumferential speed difference between heating rolls while conveying the laminate in its longitudinal direction. The aerial stretching treatment typically includes a zone stretching process and a heated roll stretching process. In addition, the order of the zone stretching process and the hot roll stretching process is not limited, and the zone stretching process may be performed first, or the hot roll stretching process may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching process and the hot roll stretching process are performed in this order. Further, in another embodiment, the film is stretched by gripping an end portion of the film in a tenter stretching machine and extending the distance between tenters in the flow direction (expansion of the distance between tenters becomes a stretching ratio). At this time, the distance of the tenter in the width direction (direction perpendicular to the flow direction) is set to be arbitrarily close. Preferably, with respect to the stretching ratio in the flow direction, it can be set to be approached by free end stretching. In the case of free end stretching, the shrinkage ratio in the width direction = (1/stretching ratio) is calculated as ^1/2 .

Air assisted stretching may be performed in one step or may be performed in multiple steps. When performing in multiple steps, the draw ratio is the product of the draw ratios of each step. The stretching direction in air assisted stretching is preferably approximately the same as that in underwater stretching.

The draw ratio in air assisted stretching is preferably 1.0 to 4.0 times, more preferably 1.5 to 3.5 times, still more preferably 2.0 to 3.0 times. If the draw ratio of air-assisted stretching is within this range, when combined with underwater stretching, the total stretching magnification can be set within a desired range, and desired birefringence, in-plane retardation, and/or orientation function can be realized. As a result, it is possible to obtain a polarizer (as a result, a polarizing plate) in which the generation of cracks in the release processing part is suppressed. Moreover, as mentioned above, it is preferable that the draw ratio of air assisted stretching is larger than the draw ratio of stretching in boric acid water. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has acceptable optical characteristics can be obtained. More specifically, the ratio of the draw ratio in air-assisted stretching to the draw ratio in underwater stretching (underwater stretching/air-assisted stretching) is preferably 0.4 to 0.9, more preferably 0.5 to 0.8.

The stretching temperature of the air-assisted stretching can be set to any suitable value depending on the forming material of the thermoplastic resin substrate, the stretching method, and the like. The stretching temperature is preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably equal to or higher than the glass transition temperature (Tg) of the thermoplastic resin substrate (Tg) + 10°C, particularly preferably equal to or higher than Tg + 15°C. On the other hand, the upper limit of the stretching temperature is preferably 170°C. By stretching at such a temperature, rapid crystallization of the PVA-based resin can be suppressed, and problems caused by the crystallization (for example, obstruction of orientation of the PVA-based resin layer by stretching) can be suppressed.

A-3-3. Insolubilization treatment, dyeing treatment and cross-linking treatment

If necessary, insolubilization treatment is performed after the air-assisted stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. Details of the insolubilization treatment, dyeing treatment, and crosslinking treatment are described, for example, in Japanese Unexamined Patent Publication 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, stretching can be performed at a temperature lower than the glass transition temperature (typically about 80° C.) of the thermoplastic resin substrate or the PVA-based resin layer, and the PVA-based resin layer can be stretched while suppressing its crystallization. . As a result, a polarizer having excellent optical properties can be manufactured.

Arbitrary suitable methods can be employed for the stretching method of the laminate. Specifically, fixed-end stretching or free-end stretching (for example, a method of uniaxially stretching a laminate by passing it between rolls having different circumferential speeds) may be used. Preferably, free end stretching is selected. Stretching of the laminate may be performed in one step or in multiple steps. When carried out in multiple stages, the total stretching ratio is the product of the stretching ratios of each stage.

Stretching in water is preferably performed by immersing the layered product in an aqueous boric acid solution (stretching in boric acid water). By using a boric acid aqueous solution as a stretching bath, rigidity that can withstand the tension applied during stretching and water resistance that does not dissolve in water can be imparted to the PVA-based resin layer. Specifically, boric acid generates tetrahydroxyboric acid anions in an aqueous solution and can be crosslinked with PVA-based resins by hydrogen bonding. As a result, rigidity and water resistance can be imparted to the PVA-based resin layer so that it can be stretched satisfactorily, and a polarizer having excellent optical properties can be manufactured.

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

Preferably, iodide is incorporated into the stretching bath (boric acid aqueous solution). By blending iodide, elution of iodine adsorbed to the PVA-based resin layer can be suppressed. Specific examples of iodide are as described above. The concentration of iodide is preferably from 0.05 parts by weight to 15 parts by weight, more preferably from 0.5 parts by weight to 8 parts by weight, based on 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, it can be extended at a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60°C or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40°C, there is a risk that satisfactory stretching may not be possible even if plasticization of the thermoplastic resin substrate by water is taken into consideration. On the other hand, as the temperature of the stretching bath becomes higher, the solubility of the PVA-based resin layer increases, and there is a possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

The draw ratio by underwater stretching is preferably 1.0 to 2.2 times, more preferably 1.1 to 2.0 times, even more preferably 1.1 to 1.8 times, still more preferably 1.2 to 1.6 times. If the stretching magnification in the underwater stretching is within such a range, the total stretching magnification can be set within a desired range, and desired birefringence, in-plane retardation and/or orientation function can be realized. As a result, it is possible to obtain a polarizer (as a result, a polarizing plate) in which the generation of cracks in the release processing part is suppressed. The total stretching ratio (total stretching ratio when air assisted stretching and underwater stretching are combined) is, as described above, preferably 3.0 to 4.5 times, more preferably 3.0 times the original length of the laminate. times to 4.3 times, more preferably 3.0 times to 4.0 times. By appropriately combining the addition of a halide to the coating liquid, adjustment of the draw ratio of air assisted extension and underwater extension, and drying shrinkage treatment, a polarizer having acceptable optical properties can be obtained even at the total magnification of such extension.

A-3-5. dry shrink treatment

The drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or may be performed by heating the conveying roll (using a so-called heating roll) (heating roll drying method). Preferably, both of them are used. By drying using a heating roll, heating curl of a layered product can be suppressed efficiently and a light polarizer excellent in external appearance can be manufactured. Specifically, by drying in a state where the laminate is attached to a heating roll, the crystallization of the thermoplastic resin substrate can be efficiently promoted to increase the crystallinity, and even at a relatively low drying temperature, the crystallinity of the thermoplastic resin substrate can be increased satisfactorily. can As a result, the rigidity of the thermoplastic resin base material is increased, and curling is suppressed in a state capable of withstanding shrinkage of the PVA-based resin layer due to drying. In addition, since it is possible to dry the layered product while maintaining it in a flat state by using a heating roll, not only curling but also occurrence of wrinkles can be suppressed. At this time, the optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. This is because the orientation properties of PVA and PVA/iodine complexes can be effectively increased. The shrinkage in the width direction of the laminate by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 2% to 6%.

6 is a schematic diagram showing an example of drying shrinkage treatment. In the drying shrinkage treatment, the laminate 200 is dried while being conveyed by conveyance rolls R1 to R6 and guide rolls G1 to G4 heated to a predetermined temperature. In the illustrated example, the transport rolls R1 to R6 are arranged so that the PVA resin layer surface and the thermoplastic resin substrate surface are alternately and continuously heated. You may arrange conveyance rolls R1-R6 so that only may be heated continuously.

Drying conditions can be controlled by adjusting the heating temperature of the conveying rolls (temperature of the heating rolls), the number of heating rolls, and the contact time with the heating rolls. 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. While the crystallinity of the thermoplastic resin can be increased satisfactorily and curling can be suppressed satisfactorily, an optical laminate having extremely excellent durability can be manufactured. In addition, the temperature of a heating roll can be measured with a contact thermometer. Although six conveyance rolls are provided in the illustrated example, there is no particular restriction as long as there are a plurality of conveyance rolls. The conveyance rolls are usually provided in 2 to 40 pieces, preferably 4 to 30 pieces. 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, still more preferably 1 to 10 seconds.

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

A-3-6. other processing

Preferably, washing treatment is performed after the underwater stretching treatment and before the drying shrinkage treatment. The washing treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of potassium iodide.

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 reducing the thickness of the polarizing plate. Conventionally, a protective layer having a thickness of 20 μm or more is used from the viewpoint of following the shrinkage of the polarizer during heating and protecting the polarizer. On the other hand, as described above, the polarizer used in the embodiment of the present invention has a lower degree of orientation of the PVA-based resin than before, and as a result, shrinkage due to heating is small, so that a protective layer having a thickness of 10 μm or less is used. Even in this case, generation of cracks during heating is suppressed. Moreover, such a polarizer can also contribute to crack suppression in a mold release processing part.

The thickness of the protective layer is preferably 7 μm or less, more preferably 5 μm or less, still more 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 may be used depending on the purpose. Specific examples include (meth)acrylic, cellulose-based such as triacetyl cellulose (TAC), polyester-based, polyurethane-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based. thermoplastic resins such as pon-based, polystyrene-based, polynorbornene-based, polyolefin-based, and acetate-based resins; (meth)acrylic, urethane-based, (meth)acrylurethane-based, epoxy-based, silicone-based thermosetting resins or active energy ray-curable resins; Glassy type polymers, such as a siloxane type polymer, are mentioned. In one embodiment, an epoxy resin and (meth)acrylic resin are mentioned as resin which forms a resin film. These may be used independently or may be used in combination.

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

In one embodiment, the protective layer is a solidified product of a coating film of an organic solvent solution of a thermoplastic (meth)acrylic resin (hereinafter, (meth)acrylic resin is sometimes simply referred to as 'acrylic resin'), photo cations of an epoxy resin It may be a cured product or a solidified product of a coating film of an organic solvent solution of an epoxy resin. Hereinafter, it demonstrates concretely.

A-4-1. Solidified material of coating film of organic solvent solution of thermoplastic acrylic resin

In one embodiment, the protective layer is composed of a solidified material of a coating film of an organic solvent solution of a thermoplastic acrylic resin. 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, from the viewpoint of humidification durability. , From the viewpoint of moldability, it is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, and particularly preferably 160°C or less.

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 also becomes approximately 100°C or higher. When the Tg of the acrylic resin is 100° C. or higher, the polarizing plate including the protective layer obtained from such a resin can have excellent humidification durability in addition to crack resistance. The Tg of the acrylic resin is more preferably 110°C or higher, still more 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. When the Tg of the acrylic resin is within this range, moldability may be excellent.

As the acrylic resin, any suitable acrylic resin can be employed as long as it has the above Tg. Acrylic resin typically contains an alkyl (meth)acrylate as a main component as a monomer unit (repeating unit). In the present specification, '(meth)acryl' means acryl and/or methacryl. As the alkyl (meth)acrylate constituting the main skeleton of the acrylic resin, those having 1 to 18 carbon atoms in a linear or branched alkyl group can be exemplified. These can be used alone or in combination. In addition, you may introduce|transduce arbitrary appropriate copolymerization monomers into acrylic resin by copolymerization. An acrylic resin capable of forming a desired protective layer can be obtained by appropriately setting the type, number, combination and blending ratio of alkyl (meth)acrylates, the type and number, combination and blending ratio of copolymerized monomers, and polymerization conditions. there is.

Acrylic resin preferably has a repeating unit containing a ring structure. As a repeating unit containing a ring structure, a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit are mentioned. As for the repeating unit containing ring structure, only 1 type may be included in the repeating unit of acrylic resin, and 2 or more types may be included. An acrylic resin having a lactone ring unit is described, for example, in Japanese Unexamined Patent Publication No. 2008-181078. An acrylic resin having a glutarimide unit is, for example, Japanese Patent Application Laid-open No. 2006-309033, Japanese Patent Laid-Open No. 2006-317560, Japanese Laid-Open Patent No. 2006-328334, Japanese Laid-Open Patent No. 2006-337491 , Japanese Unexamined Patent Publication No. 2006-337492, Japanese Unexamined Patent Publication No. 2006-337493, and Japanese Unexamined Patent Publication No. 2006-337569. Descriptions of these publications are incorporated herein by reference.

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

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

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

As the organic solvent, any appropriate 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 concentration of the acrylic resin in 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 adhering to the polarizer can be formed.

The solution may be applied to any suitable substrate or may be applied to a polarizer. In the case of application to a substrate, the solidified material of the coating film formed on the substrate is transferred to the polarizer. When applying to a polarizer, a protective layer is formed directly on a polarizer by drying (solidifying) a coating film. Preferably, the solution is applied to the polarizer, and a protective layer is formed directly on the polarizer. With such a structure, since the adhesive layer or pressure-sensitive adhesive layer required for transfer can be omitted, the polarizing plate can be made thinner. As a method of applying the solution, any suitable method can be employed. 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 (such as a comma coating method).

A protective layer can be formed by drying (solidifying) the coated film of the solution. The drying temperature is preferably 100°C or less, more preferably 50°C to 70°C. If the drying temperature is within this range, adverse effects on the polarizer can be prevented. The drying time may vary depending on the drying temperature. The drying time may be, for example, 1 minute 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 an epoxy resin. By using such a protective layer, occurrence of cracks can be suppressed and excellent humidification durability can be obtained. As described above, since the protective layer is a photo-cationic cured product, the composition for forming a protective layer contains a photo-cationic polymerization initiator. The photocationic polymerization initiator is a photosensitizer having a function of a photoacid generator, and examples thereof include ionic onium salts containing a cation portion and an anion portion. In this onium salt, the cation portion absorbs light, and the anion portion becomes a source of acid. The ring-opening polymerization of an epoxy group advances with the acid generated from this photocationic polymerization initiator. The resulting protective layer, which is a photocationically cured product, has a high softening temperature and can reduce the amount of iodine adsorbed. Therefore, it is possible to provide a polarizing plate in which occurrence of cracks is suppressed and which has excellent 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, even more preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, from the viewpoint of humidification durability. , From the viewpoint of moldability, it is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, and particularly preferably 160°C or less.

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. As an aromatic skeleton, a benzene ring, a naphthalene ring, a fluorene ring etc. are mentioned, for example. An epoxy resin may be used alone or in combination of two or more. Preferably, an epoxy resin having a biphenyl skeleton or a bisphenol skeleton or an additive 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 backbone is an epoxy resin comprising the following structure. The epoxy resin having a biphenyl skeleton may be used alone or in combination of two or more.

(In the formula, R ^{14 to} R ²¹ are Each independently represents 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 backbone is an epoxy resin represented by the following formula.

(In the formula, R ¹⁴ to ^{R 21} are As described above, n represents an integer of 0 to 6).

In one embodiment, the epoxy resin having a biphenyl backbone is an epoxy resin having only a biphenyl backbone. 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 chemical structures other than the biphenyl skeleton. As chemical structures other than a biphenyl skeleton, a bisphenol skeleton, an alicyclic structure, an aromatic ring structure, etc. are mentioned, for example. In this case, the ratio (molar ratio) of chemical structures other than the biphenyl skeleton is preferably smaller than that of the biphenyl skeleton.

The epoxy resin (epoxy resin after photocationic curing) preferably has a glass transition temperature (Tg) of 100°C or higher. As a result, the softening temperature of the protective layer also becomes approximately 100°C or higher. When the Tg of the epoxy resin is 100°C or higher, the resultant polarizing plate including the protective layer tends to have excellent durability. The Tg of the epoxy resin is more preferably 110°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 epoxy resin is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, and particularly preferably 160°C or less. When the Tg of the epoxy resin is within this range, moldability may be excellent.

The epoxy equivalent of the epoxy resin is preferably 100 g/equivalent or more, more preferably 150 g/equivalent or more, still more preferably 200 g/equivalent or more. Further, 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 within the above range, a more stable protective layer (a sufficiently cured protective layer with few residual monomers) can be obtained. In addition, in this specification, "epoxy equivalent" refers to "mass of an epoxy resin containing an epoxy group of 1 equivalent", and can be measured according to JIS K 7236.

In this embodiment, you may use together the said epoxy resin and another resin. That is, a blend of the above epoxy resin (for example, an epoxy resin having at least one selected from the group consisting of an aromatic backbone and a hydrogenated aromatic backbone) and another resin may be used for molding the protective layer. 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 a (meth)acrylic compound, for example, a (meth)acrylic compound having one (meth)acryloyl group in a molecule (hereinafter also referred to as a 'monofunctional (meth)acrylic compound'), or a (meth)acrylic compound having two or more (meth)acrylic compounds in a molecule. ) A (meth)acrylic compound having an acryloyl group (hereinafter, also referred to as a 'multifunctional (meth)acrylic compound'). These (meth)acrylic compounds may be used alone or in combination of two or more. About these acrylic resins, it describes, for example in Unexamined-Japanese-Patent No. 2019-168500. The entire description of the publication is incorporated herein by reference.

As the oxetane resin, any suitable compound having at least one oxetanyl group 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, 3-ethyl-3-(oxiranylmethoxy)oxetane, (meth)acrylic acid (3-ethyloxetan-3-yl)methyl, etc. oxetane compounds with dogs; 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 4 oxetane compounds having two or more oxetanyl groups in the molecule, such as 4'-bis[(3-ethyl-3-oxetanyl)methoxymethyl]biphenyl; etc. can be mentioned. These oxetane resins may use only 1 type, and may combine 2 or more types. As the oxetane resin, preferably 3-ethyl-3-hydroxymethyloxetane, 1,4-bis[(3-ethyl-3-oxetanyl)methoxymethyl]benzene, 3-ethyl-3-( 2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, (meth)acrylic acid (3-ethyloxetan-3-yl)methyl, 3-ethyl-3{[( 3-ethyloxetan-3-yl)methoxy]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, from the viewpoint of compatibility and adhesiveness, an oxetane resin preferably having a molecular weight of 500 or less and liquid at room temperature (25°C) is used. In one embodiment, preferably an oxetane compound containing two or more oxetanyl groups in a molecule, an oxetane compound containing one oxetanyl group and one (meth)acryloyl group or one epoxy group in a molecule is used, more preferably 3-ethyl-3{[(3-ethyloxetan-3-yl)methoxy]methyl}oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, ( Meth)acrylic acid (3-ethyloxetan-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. photo cationic polymerization initiator

The photocationic polymerization initiator is a photosensitizer having a function of a photoacid generator, and examples thereof include ionic onium salts containing a cationic moiety and an anionic moiety. In this onium salt, the cation portion absorbs light, and the anion portion becomes a source of acid. The ring-opening polymerization of an epoxy group advances with 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. Photocationic polymerization initiators may be used alone or in combination of two or more.

As a photocationic polymerization initiator, for example, triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfonium hexafluoroantimonate, p-(phenyl Thio) phenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluorophosphate, 4-chlorophenyldiphenylsulfonium hexafluoroantimonate, bis[4-(diphenylsulfonio )phenyl]sulfidebishexafluorophosphate, bis[4-(diphenylsulfonio)phenyl]sulfidebishexafluoroantimonate, (2,4-cyclopentadien-1-yl)[(1-methyl Ethyl) benzene] -Fe- hexafluorophosphate, diphenyliodonium hexafluoroantimonate, etc. are mentioned. 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, for example, may be formed by applying a composition containing the epoxy resin and a photocationic polymerization initiator to form a coating film, and irradiating the coating film with light (eg, ultraviolet rays).

The epoxy resin concentration in the composition is preferably 10 to 30 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhering to the polarizer can be formed.

The composition may be applied to any suitable substrate or may be applied to a polarizer. In the case of applying to a substrate, the cured product of the coating film formed on the substrate is transferred to the polarizer. In the case of application to a polarizer, a protective layer is directly formed on the polarizer by curing the coating film by, for example, light irradiation. Preferably, the composition is applied to a polarizer, and a protective layer is directly formed on the polarizer. With such a structure, since the adhesive layer or pressure-sensitive adhesive layer required for transfer can be omitted, the polarizing plate can be made thinner. The coating method of the composition is as described above.

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

A-4-3. Solidified material of coating film of organic solvent solution of epoxy resin

In one embodiment, the protective layer is composed of a solidified material of a coating film of an organic solvent solution of an epoxy resin. The softening temperature of the protective layer of the present embodiment is preferably 100 ° C. or higher, more preferably 110 ° C. or higher, even more preferably 120 ° C. or higher, particularly preferably 125 ° C. or higher, from the viewpoint of humidification durability. , From the viewpoint of moldability, it is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, and particularly preferably 160°C or less.

A-4-3-1. epoxy resin

In this 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 also becomes approximately 100°C or higher. If Tg of an epoxy resin is 100 degreeC or more, the polarizing plate containing the protective layer obtained from such resin tends to be excellent in durability. The Tg of the epoxy resin is more preferably 110°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 epoxy resin is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, and particularly preferably 160°C or less. When the Tg of the epoxy resin is within this range, moldability may be excellent.

As the epoxy resin, any suitable epoxy resin can be employed as long as it has the above Tg. An 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. As an aromatic ring in the epoxy resin which has an aromatic ring in molecular structure, a benzene ring, a naphthalene ring, a fluorene ring etc. are mentioned, for example. An epoxy resin may be used alone or in combination of two or more. When using 2 or more types of epoxy resins, you may use combining the epoxy resin containing an aromatic ring, and the epoxy resin which does not contain an aromatic ring.

As the epoxy resin having an aromatic ring in the molecular structure, specifically, bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diglycidyl ether type epoxy resin, resorcindiglyc Cydyl ether type epoxy resin, hydroquinone diglycidyl ether type epoxy resin, terephthalic acid diglycidyl ester type epoxy resin, bisphenoxyethanol fluorene diglycidyl ether type epoxy resin, bisphenol fluorene diglycidyl Epoxy resins having two epoxy groups, such as ether type epoxy resins and biscresol fluorene diglycidyl ether type epoxy resins; Novolac type epoxy resin, N,N,O-triglycidyl-P- or -m-aminophenol type epoxy resin, N,N,O-triglycidyl-4-amino-m- or -5-amino- epoxy resins having three epoxy groups such as o-cresol type epoxy resins and 1,1,1-(triglycidyloxyphenyl)methane type epoxy resins; Epoxy resins having four epoxy groups, such as glycidylamine type epoxy resins (for example, diaminodiphenylmethane type, diaminodiphenylsulfone type, and metaxylenediamine type); and the like. Moreover, you may use glycidyl ester type epoxy resins, 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.

The epoxy equivalent of the epoxy resin is preferably 1000 g/equivalent or more, more preferably 3000 g/equivalent or more, still more preferably 5000 g/equivalent or more. Further, the epoxy equivalent of the epoxy resin is preferably 30000 g/equivalent or less, more preferably 25000 g/equivalent or less, still more preferably 20000 g/equivalent or less. When the epoxy equivalent is within the above range, a more stable protective layer can be obtained. In addition, in this specification, "epoxy equivalent" refers to "mass of an epoxy resin containing an epoxy group of 1 equivalent", and can be measured according to JIS K 7236.

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

The protective layer of the present embodiment may 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 concentration of the epoxy resin in the organic solvent solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhering to the polarizer 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 may be applied to a polarizer. In the case of application to a substrate, the solidified material of the coating film formed on the substrate is transferred to the polarizer. When applying to a polarizer, a protective layer is formed directly on a polarizer by drying (solidifying) a coating film. Preferably, the solution is applied to the polarizer, and a protective layer is formed directly on the polarizer. With such a structure, since the adhesive layer or pressure-sensitive adhesive layer required for transfer can be omitted, the polarizing plate can be made thinner. The application method of the solution is as described above.

By drying (solidifying) the coating film of the solution, a protective layer, which is a solidified product of the coating film, can be formed. The drying temperature is preferably 100°C or less, more preferably 50°C to 70°C. If the drying temperature is within this range, adverse effects on the polarizer can be prevented. The drying time may vary depending on the drying temperature. The drying time may be, for example, 1 minute to 10 minutes.

B. Polarizing plate with retardation layer

B-1. Overall configuration of polarizing plate with retardation layer

7 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention. The polarizing plate 200 with a retardation layer in the illustrated example includes the polarizing plate 100 described in the above item A and the retardation layer 120. Therefore, the polarizing plate 200 with the retardation layer has the same mold release 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 polarizer 10 . The retardation layer 120 is typically laminated on the polarizing plate 100 (the polarizer 10 in the illustrated example) with an adhesive layer (not shown) interposed therebetween. The adhesive layer is an adhesive layer or a pressure-sensitive adhesive layer, and is preferably a pressure-sensitive adhesive layer (eg, an acrylic pressure-sensitive 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 polarizer 10 as needed. In addition, the polarizing plate with a retardation layer may have another retardation layer (not shown) on the side opposite to the polarizing plate 100 of the retardation layer 120 as needed. The other retardation layer is typically a so-called positive C plate whose refractive index characteristic shows the relationship nz > nx = ny.

Re(550) of the retardation layer 120 is preferably 100 nm to 190 nm, and Re(450)/Re(550) is preferably 0.8 or more and less than 1. In addition, the angle between the slow axis of the retardation layer 120 and the absorption axis of the polarizer 10 is preferably 40° to 50°.

B-2. phase contrast layer

The retardation layer 120 may have any suitable optical and/or mechanical properties depending on the purpose. The retardation layer typically has a slow axis. In one embodiment, the angle θ formed by the slow axis of the retardation layer and the absorption axis of the polarizer 10 is, as described above, preferably 40° to 50°, more preferably 42° to 48°, and It is preferably about 45°. When the angle θ is within this range, a polarizing plate with a retardation layer having excellent circular polarization characteristics (as a result, excellent antireflection characteristics) can be obtained by using a λ/4 plate as the retardation layer as described later.

The retardation layer preferably has a refractive index characteristic of nx > ny > nz. The retardation layer is typically provided to impart antireflection properties to the polarizing plate, and in one embodiment, it can function as a λ/4 plate. 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, still more preferably 130 nm to 160 nm. In addition, 'ny=nz' here includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny<nz is satisfied within a range that does not impair the effects of the present invention.

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, when the obtained polarizing plate with a retardation layer is used for an image display device, an extremely excellent reflected color can be achieved.

The retardation layer may exhibit reverse dispersion wavelength characteristics in which the retardation value increases with the wavelength of the measurement light, or may exhibit a positive wavelength dispersion characteristic in which the retardation value decreases with the wavelength of the measurement light. A flat wavelength dispersion characteristic that hardly changes may be exhibited. In one embodiment, the retardation layer exhibits reverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the retardation layer is preferably 0.8 or more and less than 1, more preferably 0.8 or more and 0.95 or less. With such a configuration, very excellent antireflection characteristics can be realized.

The retardation layer has an absolute value of the photoelastic coefficient of 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 /N, still more preferably contains a resin of 1.0×10 ⁻¹² m ² /N to 1.2× ^{10 −11} m ² /N. If the absolute value of the photoelastic coefficient is in this range, phase difference change is unlikely to occur when shrinkage stress occurs during heating. As a result, heat unevenness of the resulting image display device can be favorably 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 in such a range, curling at the time of bonding can be favorably adjusted while suppressing curling at the time of heating favorably. As will be described later, in an embodiment in which the retardation layer is composed of a polycarbonate-based resin film, the thickness of the retardation layer is preferably 40 μm or less, more preferably 10 μm to 40 μm, and still more preferably It is 20 μm to 30 μm. When the retardation layer is composed of a polycarbonate-based resin film having such a thickness, it is possible to contribute to improvement of bending durability and reflection color while suppressing curling.

The retardation layer may be composed of any appropriate resin film capable of satisfying the above characteristics. Representative examples of such resins include polycarbonate-based resins, polyester carbonate-based resins, polyester-based resins, polyvinyl acetal-based resins, polyarylate-based resins, cyclic olefin-based resins, cellulose-based resins, polyvinyl alcohol-based resins, Polyamide-based resins, polyimide-based resins, polyether-based resins, polystyrene-based resins, and acrylic resins are exemplified. These resins may be used alone or in combination (for example, blend or copolymerization). When the retardation layer is composed of a resin film exhibiting reverse dispersion wavelength characteristics, a polycarbonate-based resin or a polyester carbonate-based resin (hereinafter sometimes simply referred to as a polycarbonate-based resin) can be suitably used.

As the polycarbonate-based resin, any appropriate polycarbonate-based resin can be used as long as the effects of the present invention are obtained. For example, the polycarbonate-based resin includes a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and an alicyclic diol, alicyclic dimethanol, di, tri, or polyethylene. It includes a structural unit derived from glycol, and at least one dihydroxy compound selected from the group consisting of alkylene glycol or spiroglycol. Preferably, the polycarbonate-based resin comprises 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 alicyclic dimethanol, and/or contains structural units derived from di, tri or polyethylene glycol; More preferably, a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from di, tri, or polyethylene glycol are included. The polycarbonate-based resin may contain structural units derived from other dihydroxy compounds as needed. Further, details of the polycarbonate-based resin that can be suitably used in the present invention are, for example, Japanese Patent Laid-Open No. 2014-10291, Japanese Laid-Open Patent Publication No. 2014-26266, and Japanese Unexamined Patent Publication No. 2015-212816 , Unexamined-Japanese-Patent No. 2015-212817, and Unexamined-Japanese-Patent No. 2015-212818, and the description is incorporated herein as a reference.

The glass transition temperature of the polycarbonate-based resin is preferably 110°C or higher and 150°C or lower, more preferably 120°C or higher and 140°C or lower. When the glass transition temperature is excessively low, heat resistance tends to deteriorate, dimensional change may occur after film forming, and image quality of the obtained organic EL panel may be lowered in some cases. 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 in some cases. In addition, the glass transition temperature can be obtained according to JIS K 7121 (1987).

The molecular weight of the polycarbonate-based resin can be expressed as a reduced viscosity. The reduced viscosity was measured using an Uberode viscometer at a temperature of 20.0° C.±0.1° C. using methylene chloride as a solvent, accurately preparing a polycarbonate concentration of 0.6 g/dL. The lower limit of the reduced viscosity is usually preferably 0.30 dL/g, more preferably 0.35 dL/g or more. The upper limit of the reduced viscosity is usually preferably 1.20 dL/g, more preferably 1.00 dL/g, still more preferably 0.80 dL/g. When the reduced viscosity is less than the lower limit, there may be a problem that the mechanical strength of the molded article is reduced. On the other hand, when the reduced viscosity is greater than the above upper limit, there may be a problem that the flowability during molding is lowered, and productivity and moldability are lowered.

A commercially available film may be used as the polycarbonate-based resin film. Specific examples of commercially available products include "Pure Ace WR-S", "Pure Ace WR-W" and "Pure Ace WR-M" manufactured by Teijin, and "NRF" manufactured by Nitto Denko.

The retardation layer can be obtained, for example, by stretching a film formed of the polycarbonate-based resin. As a method for forming a film from a polycarbonate-based resin, any suitable molding processing method can be employed. Specific examples include compression molding method, transfer molding method, injection molding method, extrusion molding method, blow molding method, powder molding method, FRP molding method, cast coating method (eg casting method), calender molding method, hot press method and the like. An extrusion molding method or a cast coating method is preferred. It is because the smoothness of the obtained film can be improved and favorable optical uniformity can be obtained. Molding conditions can be appropriately set according to the composition or type of resin used, desired characteristics of the retardation layer, and the like. In addition, since many film products of polycarbonate-type resin are marketed as mentioned above, you may use the said commercially available film for extending|stretching processing as it is.

The thickness of the resin film (unstretched film) can be set to any appropriate value depending on the desired thickness of the retardation layer, desired optical properties, stretching conditions described later, and the like. Preferably they are 50 micrometers - 300 micrometers.

For the stretching, any suitable stretching method and stretching conditions (eg, stretching temperature, stretching ratio, stretching direction) may be employed. Specifically, various stretching methods such as free end stretching, fixed end stretching, free end contraction, and fixed end contraction may be used alone or simultaneously or sequentially. As for the stretching direction, it can be performed in various directions or dimensions, such as a longitudinal direction, a width direction, a thickness direction, and an oblique direction. The temperature of the stretching is preferably Tg-30°C to Tg+60°C, more preferably Tg-10°C to Tg+50°C relative 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 properties (eg, refractive index characteristics, in-plane retardation, and Nz coefficient) can be obtained.

In one embodiment, the retardation film is produced by uniaxial stretching or fixed-end uniaxial stretching of a resin film. As a specific example of the fixed-end uniaxial stretching, a method of stretching in the width direction (transverse direction) while running the resin film in the longitudinal direction is exemplified. The draw ratio is preferably 1.1 to 3.5 times.

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

Examples of the stretching machine used for oblique stretching include a tenter type stretching machine capable of applying feed force, tensile force, or pulling force at different speeds on the left and right sides in the transverse and/or longitudinal directions. Although tenter-type stretching machines include transverse uniaxial stretching machines, simultaneous biaxial stretching machines, and the like, any suitable stretching machine may be used as long as it can continuously obliquely stretch a long resin film.

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

The stretching temperature of the film may vary depending on the desired in-plane retardation value and thickness of the retardation layer, the type of resin used, the thickness of the film used, and the stretching ratio. 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 suitable characteristics in the present invention can be obtained. In addition, Tg is the glass transition temperature of the constituent material of a film.

C. Image display device

The polarizing plate or polarizing plate with a retardation layer may be applied to an image display device. Accordingly, embodiments of the present invention include an image display device including such a polarizing plate or a polarizing plate with a retardation layer. Representative examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device and an inorganic EL display device). An image display device according to an embodiment of the present invention includes the polarizing plate described in the above item A or the polarizing plate with a retardation layer described in the item B on its viewing side. Polarizing plates with a retardation layer are laminated so that the retardation layer is on the side of an image display cell (for example, a liquid crystal cell, an organic EL cell, or an inorganic EL cell) (so that the polarizer is on the viewing side). The image display device preferably has a shape other than rectangular. In such an image display device, the effect according to the embodiment of the present invention is remarkable. Specific examples of the image display device having a mold release include an automobile meter panel, a smartphone, a tablet PC, and a smart watch.

[Example]

Hereinafter, the present invention will be specifically described by examples, but the present invention is not limited by these examples. The measurement method of each characteristic is as follows. In addition, unless otherwise specified, 'parts' and '%' in Examples and Comparative Examples are based on weight.

(1) Thickness

It was measured using an interference film thickness meter (manufactured by Otsuka Electronics, product name 'MCPD-3000'). The calculated wavelength range used for thickness calculation was 400 nm to 500 nm, and the refractive index was 1.53.

(2) In-plane retardation of PVA (Re)

With respect to the polarizer (polarizer alone) obtained by peeling and removing the resin substrate from the laminate of the polarizer / thermoplastic resin substrate obtained in Examples and Comparative Examples, using a retardation measuring device (product name 'KOBRA-31X100 / IR' manufactured by Oji Instruments Co., Ltd.), The in-plane retardation (Rpva) of PVA at a wavelength of 1000 nm was evaluated (a value obtained by subtracting the in-plane retardation (Ri) of iodine from the total in-plane retardation at a wavelength of 1000 nm, according to the principle described). The absorption edge wavelength was 600 nm.

(3) Birefringence of PVA (Δn)

Birefringence (Δn) of PVA was calculated by dividing the in-plane retardation of PVA measured in (2) by the thickness of the polarizer.

(4) single transmittance and degree of polarization

With respect to the polarizer (polarizer alone) obtained by peeling and removing the resin substrate from the laminate of the polarizer/thermoplastic resin substrate obtained in Examples and Comparative Examples, using an ultraviolet / visible ray spectrophotometer ("V-7100" manufactured by Nippon Bunko Co., Ltd.) Transmittance Ts, parallel transmittance Tp, and orthogonal transmittance Tc were measured. These Ts, Tp, and Tc are Y values measured with a 2-degree field of view (C light source) in accordance with JIS Z 8701 and corrected for visibility. From the obtained Tp and Tc, the polarization degree P was calculated|required by the following formula.

Degree of polarization P(%)={(Tp-Tc)/(Tp+Tc)} ^1/2 × 100

In addition, as for the spectrophotometer, "LPF-200" manufactured by Otsuka Electronics Co., Ltd. can perform equivalent measurements, and it has been confirmed that equivalent measurement results can be obtained even when any spectrophotometer is used.

(5) Puncture strength (breaking strength per unit thickness)

The polarizer was peeled off from the laminate of the polarizer/thermoplastic resin substrate used in Examples and Comparative Examples, and placed in a compression tester equipped with a needle (manufactured by Katotech, product name 'NDG5' needle penetration measurement specification), In a room temperature (23°C ± 3°C) environment, it was stabbed at a stabbing speed of 0.33 cm/sec, and the strength when the polarizer was cracked was defined as the breaking strength. The evaluation value measured the breaking strength of 10 sample pieces, and used the average value. In addition, a needle having a tip diameter of 1 mmφ and a diameter of 0.5R was used. For the polarizer to be measured, a jig having a circular opening with a diameter of about 11 mm was clamped and fixed from both sides of the polarizer, and a needle was pierced into the center of the opening to conduct a test.

(6) Orientation function of PVA

Regarding the polarizer (polarizer alone) obtained by peeling and removing the resin substrate from the polarizer / thermoplastic resin substrate laminate obtained in Examples and Comparative Examples, with respect to the surface opposite to the surface from which the resin substrate was peeled, a Fourier transform infrared spectrophotometer (FT -IR) (manufactured by Perkin Elmer, trade name: 'Frontier') was used, and polarized infrared light was used as measurement light to measure attenuated total reflection (ATR) on the surface of the polarizer. . Germanium was used as a crystallite for adhering the polarizer, and the incident angle of the measurement light was 45° incident. The orientation function was calculated in the following procedure. Incident polarized infrared light (measurement light) is polarized light (s-polarized light) that oscillates parallel to the surface of the germanium crystal on which the sample is brought into close contact. Each absorbance spectrum was measured in a state of being arranged in parallel (//). From the obtained absorbance spectrum, (2941 cm ^-1 intensity) I was calculated with reference to (3330 cm ^-1 intensity). I _⊥ is It is (2941 cm ^-1 intensity) / (3330 cm ^-1 intensity) obtained from the absorbance spectrum obtained when the polarizer is stretched perpendicularly (⊥) to the polarization direction of the measurement light. In addition, I _// is (2941 cm ^-1 intensity) / (3330 cm ^-1 intensity) obtained from the absorbance spectrum obtained when the polarizer is arranged parallel to the polarization direction of the measurement light (//). Here, (2941 cm ^-1 intensity) is the bottom of the absorbance spectrum. Absorbance ^at 2941 cm -1 when 2770 cm ^-1 and 2990 cm ^-1 are used as baselines, (3330 cm ^-1 intensity) is 2990 cm ^-1 and It is the absorbance at 3330 cm ^-1 when 3650 cm ^-1 is taken as the baseline. An orientation function f was calculated according to Equation 1 using the obtained I _⊥ and I _// . In addition, when f = 1, it becomes perfect orientation, and when f = 0, it becomes random. The peak at 2941 cm ^-1 is said to be absorption due to vibration of the PVA main chain (-CH ₂ -) in the polarizer. In addition, the peak at 3330 cm ^-1 is said to be absorption due to vibration of the hydroxyl group of PVA.

(Equation 1) f=(3<cos ² θ>-1)/2

=(1-D)/[c(2D+1)]

step,

c=(3cos ² β-1)/2

Therefore, when 2941 cm ^-1 is used as described above, β = 90 ° ⇒ y = -2 × (1-D) / (2D + 1).

θ: angle of the molecular chain with respect to the stretching direction

β: angle of the transition dipole moment with respect to the molecular chain axis

D=(I _⊥ )/(I _// )

I _⊥ : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are perpendicular to each other

I _// : Absorption intensity when the polarization direction of the measurement light and the stretching direction of the polarizer are parallel

(7) Crack occurrence rate

A surface protection film was temporarily attached to the surface of the protective layer of the polarizing plate (or 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 polarizing plate with a retardation layer). This laminate was cut into about 130 mm x about 70 mm. At this time, the polarizer was cut so that the absorption axis was in the short direction. A U-shaped notch having a width of 5 mm, a depth (length of the concave portion) 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 laminate. The U-shaped notch was formed by end milling. The outer diameter of the end mill was 4 mm, the feed speed was 500 mm/min, the rotation speed was 35000 rpm, and the cutting amount and number of cuts were 0.2 mm/time for rough cutting and 0.1 mm/time for finishing cutting, total of 2 times. The separator was peeled off from the laminate in which the U-shaped notch was formed, and it was affixed to a glass plate (thickness: 1.1 mm) through an acrylic pressure-sensitive adhesive layer. Finally, the surface protection film was peeled off, and a test sample having a configuration of protective layer/polarizer/adhesive layer/glass plate (or protective layer/polarizer/adhesive layer/phase contrast layer/adhesive layer/glass plate) was obtained. This test sample was subjected to a heat shock test in which holding at -40°C for 30 minutes and then holding at 85°C for 30 minutes was repeated 300 cycles, 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 retardation layers), and the number of polarizing plates (or polarizing plates with retardation layers) in which cracks (substantially L-shaped cracks) occurred was evaluated.

[Example 1]

1. Fabrication of polarizer

As the thermoplastic resin substrate, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 μm) having a long shape, water absorption of 0.75%, and Tg of about 75° C. was used. Corona treatment (treatment conditions: 55 W·min/m 2 ) was performed on one side of the resin substrate.

Polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., trade name 'Gosefimer Z410') were mixed in a ratio of 9:1 to 100 parts by weight of a PVA-based resin, potassium iodide 13 weight parts were added and the PVA aqueous solution (coating liquid) was prepared.

A PVA-based resin layer having a thickness of 13.5 μm was formed by applying the PVA aqueous solution to the corona-treated surface of the resin substrate and drying at 60° C. to prepare a laminate.

The obtained layered product was uniaxially stretched at the free end by 2.4 times in the machine direction (longitudinal direction) between rolls having different circumferential speeds in a 130°C oven (air assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (boric acid aqueous solution obtained by blending 4 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (insolubilization treatment).

Next, in a dyeing bath (water = 100 parts by weight, iodine and potassium iodide obtained by blending iodine and potassium iodide at a weight ratio of 1:7) at a liquid temperature of 30 ° C., the single transmittance (Ts) of the finally obtained polarizer is 40.5% or more. It was immersed for 60 seconds while adjusting the concentration so as to be (dyeing treatment).

Then, it was immersed in a crosslinking bath (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 at a liquid temperature of 40 ° C. (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous boric acid solution (boric acid concentration = 4.0% by weight, potassium iodide 5.0% by weight) at a liquid temperature of 62°C, while the total stretching ratio in the machine direction (longitudinal direction) was 3.0 between rolls having different circumferential speeds. Uniaxial stretching was performed so as to double (underwater stretching treatment: the stretching ratio in the underwater stretching treatment is 1.25 times).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by blending 4 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Thereafter, while drying in an oven maintained at 90°C, it was brought into contact with a heating roll made of SUS whose surface temperature was maintained at 75°C for about 2 seconds (dry shrinkage treatment). The shrinkage rate in the width direction of the layered product by the drying shrinkage treatment was 2%.

In this way, a polarizer having a thickness of 7.4 μm was formed on the resin substrate.

2. Fabrication of polarizer

15 parts of an epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical Corporation, trade name: jER (registered trademark) YX4000) and 10 parts by weight of an oxetane resin (manufactured by Toagosei Co., Ltd., trade name: Aronoxetane (registered trademark) OXT-221) It was dissolved in 73 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 2 parts of photocationic polymerization initiator (trade name: CPI (registered trademark) -100P, manufactured by San-Apro Corporation) was added to obtain a protective layer forming composition. The obtained protective layer forming composition was applied directly to the polarizer surface of the laminate of the resin substrate/polarizer obtained in 1. above (ie, without forming an easily adhesive layer) using a wire bar, and the coating film was dried at 60 ° C. for 3 minutes. Subsequently, the cumulative light intensity is 600 mJ/cm 2 using a high-pressure mercury lamp. A protective layer was formed by irradiating ultraviolet rays as much as possible. The thickness of the protective layer was 3 μm. Then, the resin substrate 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 configuration of a protective layer (photo-cationic cured layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Examples 2 to 4]

A polarizer (thickness: 7.4 μm) was formed on a resin substrate in the same manner as in Example 1 except that dye baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Example 5]

A polarizer (thickness: 6.7 μm) was formed on the resin substrate in the same manner as in Example 1 except that the draw ratio of the underwater extension was increased to 1.46 times (as a result, the total stretch magnification was increased to 3.5 times). The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Example 6-1]

A polarizer (thickness: 6.7 μm) was formed on a resin substrate in the same manner as in Example 5 except that dye baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Example 6-2]

It carried out similarly to Example 6-1, and obtained the laminated body of resin base material/polarizer (thickness: 6.7 micrometer). On the other hand, 20 parts of an 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 to obtain an epoxy resin solution (20%). . This epoxy resin solution was applied to the polarizer surface of the layered product using a wire bar, and the coating film was dried at 60°C for 3 minutes to form a protective layer constituted as a solidified product of the coating film. The thickness of the protective layer was 3 μm. Next, the resin substrate was peeled off, and an acrylic pressure-sensitive adhesive layer similar to Example 1 was provided on the peeled surface. In this way, a polarizing plate having a configuration of a protective layer (solidified layer of an epoxy resin coating film)/polarizer/adhesive layer was obtained.

[Example 6-3]

It carried out similarly to Example 6-1, and obtained the laminated body of resin base material/polarizer (thickness: 6.7 micrometer). On the polarizer surface of the obtained laminate, as an easily adhesive layer, a polyurethane-based aqueous dispersion resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., product name: Superflex SF210) was applied to a thickness of 0.1 μm to form an easily adhesive layer. On the other hand, 20 parts by weight of 100% polymethyl methacrylate acrylic resin (manufactured by Kusumoto Chemical Co., Ltd., product name: B-728) 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 easily bonding layer using a wire bar, and the coated film was dried at 60°C for 5 minutes to form a protective layer constituted as a solidified material of the coated film. The thickness of the protective layer was 2 μm. In addition, a hard coat layer (thickness: 3 μm) was further formed on the side opposite to the easily bonding layer of the protective layer. The hard coat (HC) layer is 70 parts by weight of dimethylol-tricyclodecane diacrylate (manufactured by Kyoeisha Chemical, trade name: Light Acrylate DCP-A), isobornyl acrylate (manufactured by Kyoei Shagaku, trade name: Light Acrylate IB-XA) 20 parts by weight, 1,9-nonanediol diacrylate (manufactured by Kyoeisha Chemical, trade name: Light Acrylate 1.9NA-A) 10 parts by weight, and a photopolymerization initiator (BASF) Manufacture, brand name: Irgacure 907) 3 parts by weight were mixed using an appropriate solvent, and the obtained coating solution was applied on the surface of the protective layer so as to have a thickness of 3 μm after curing, and then the solvent was dried and a high-pressure mercury lamp was used. 300mJ/㎠ of integrated light It was formed by irradiating ultraviolet rays as much as possible under a nitrogen atmosphere. Finally, the resin substrate was peeled off, and an acrylic pressure-sensitive adhesive layer similar to Example 1 was provided on the peeled surface. In this way, a polarizing plate having a configuration of HC layer/protective layer (solidified layer of acrylic resin coating film)/easy adhesion layer/polarizer/adhesive layer was obtained.

[Examples 7 to 8]

A polarizer (thickness: 6.7 μm) was formed on a resin substrate in the same manner as in Example 5 except that dye baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Examples 9 to 12]

EXAMPLES EXCEPT EXAMPLES Except for using a dyeing bath having a different iodine concentration (weight ratio of iodine and potassium iodide = 1:7), the draw ratio of the underwater drawing was increased to 1.67 times (as a result, the total stretching ratio was increased to 4.0 times). It carried out similarly to 1, and formed the polarizer (thickness: 6.2 micrometer) on the resin substrate. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Examples 13 to 16]

Example except that the draw ratio of the underwater drawing was increased to 1.88 times (as a result, the total extension ratio of the drawing was increased to 4.5 times), and dyeing baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. It carried out similarly to 1, and formed the polarizer (thickness: 6.0 micrometer) on the resin substrate. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Comparative Example 1]

A polarizer (thickness: 5.5 μm) was formed on a resin substrate in the same manner as in Example 1 except that the draw ratio of the underwater extension was increased to 2.29 times (as a result, the total stretch magnification was increased to 5.5 times). The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Comparative Example 2-1]

A polarizer (thickness: 5.5 μm) was formed on a resin substrate in the same manner as in Comparative Example 1 except that dye baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Comparative Example 2-2]

Except for forming a protective layer using the same epoxy resin solution as in Example 6-2, in the same manner as in Comparative Example 2-1, having a protective layer (solidified layer of epoxy resin coating film) / polarizer / pressure-sensitive adhesive layer configuration A polarizer was obtained.

[Comparative Examples 2 to 3]

Except for forming a protective layer using the same acrylic resin solution as in Example 6-3, in the same manner as in Comparative Example 2-1, having a protective layer (solidified layer of acrylic resin coating film) / polarizer / adhesive layer configuration A polarizer was obtained.

[Comparative Examples 3 to 4]

A polarizer (thickness: 5.5 μm) was formed on a resin substrate in the same manner as in Comparative Example 1 except that dye baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. The following procedure was carried out similarly to Example 1, and the polarizing plate which has the structure of protective layer (photocationic curing layer of epoxy resin)/polarizer/adhesive layer was obtained.

[Example 17]

1. Production of retardation film constituting the retardation layer

Polymerization was carried out using a batch polymerization apparatus composed of two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100°C. Bis [9- (2-phenoxycarbonylethyl) fluoren-9-yl] methane 29.60 parts by mass (0.046 mol), isosorbide (ISB) 29.21 parts by mass (0.200 mol), spiroglycol (SPG) 42.28 mass part (0.139 mol), 63.77 parts by mass (0.298 mol) of diphenyl carbonate (DPC), and 1.19 × 10 ^-2 parts by mass (6.78 × 10 ^-5 mol) of calcium acetate monohydrate as a catalyst were added. After replacing the inside of the reactor with reduced pressure nitrogen, heating was performed with a heating medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was started, and after reaching 220°C, it was set to 13.3 kPa in 90 minutes. Phenol vapor produced by-product along with the polymerization reaction was led to a reflux condenser at 100°C, a small amount of monomer components contained in the phenol vapor was returned to the reactor, and uncondensed phenol vapor was led to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor to once restore the pressure to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Subsequently, the temperature increase and pressure reduction in the second reactor were started, and the internal temperature was 240°C and the pressure was 0.2 kPa in 50 minutes. Thereafter, polymerization was allowed to proceed until a predetermined agitation power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor to restore pressure, the resulting 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 ° C.), A long resin film with a thickness of 130 μm was produced using a film forming apparatus equipped with a cooling roll (set temperature: 120 to 130° C.) and a winder. The obtained elongated resin film was stretched while adjusting so as to obtain a predetermined phase difference, and a phase difference film having a thickness of 48 µm was obtained. The stretching conditions were a stretching temperature of 143°C and a stretching ratio of 2.8 times in the width direction. Re(550) of the obtained retardation film was 141 nm, Re(450)/Re(550) was 0.86, and the Nz coefficient was 1.12.

2. Production of Polarizing Plate with Retardation Layer

It carried out similarly to Example 6-1, and obtained the laminated body of resin base material/polarizer (thickness: 6.7 micrometer). It carried out similarly to Example 1 on the surface of the polarizer of a laminated body, and formed the protective layer (photocationic hardening layer of epoxy resin). Next, the resin substrate was peeled off, and the retardation film (retardation layer) obtained above was bonded 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 polarizer formed an angle of 45° and bonded together. Finally, an acrylic pressure-sensitive adhesive layer similar to Example 1 was provided on the surface of the retardation layer. In this way, a polarizing plate with a retardation layer having a configuration of protective layer (photocationic cured layer of epoxy resin) / polarizer / adhesive layer / retardation layer / adhesive layer was obtained.

[Comparative Example 5]

In the same manner as in Comparative Example 2-1, a laminate of resin substrate/polarizer (thickness: 5.5 µm) was obtained. A polarizing plate with a retardation layer having a configuration of protective layer (photocationic cured layer of epoxy resin) / polarizer / adhesive layer / retardation layer / adhesive layer was obtained in the same manner as in Example 17 except that this laminate was used.

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

[Table 1]

As is clear from Table 1, in the polarizing plate and the polarizing plate with a retardation layer of the examples, cracking of the mold release portion (U-shaped notch portion) is suppressed.

8 to 10, respectively, the relationship between the single transmittance of the polarizer obtained in Examples and Comparative Examples and Δn of PVA, in-plane retardation or orientation function is shown. As shown in FIGS. 8 to 10, even if the birefringence, in-plane retardation, or orientation function is about the same (as a result, the degree of orientation is about the same), when the single transmittance is high, it can be seen that cracks tend to occur in the release processing part. there is. For example, when Δn is around 35 (×10 ^-3 ) in FIG. 8 , when the single transmittance is greater than about 44.2%, equation (1) is not satisfied, and cracks occur as in Comparative Example 4 as a result. Therefore, it can be seen that, in addition to the degree of orientation of the PVA-based resin, it is also important to adjust the single transmittance (resulting in the adsorption amount of the dichroic substance) in order to effectively suppress the occurrence of cracks in the mold release processing part. In addition, it can be seen that the polarizer satisfying Expression (1), Expression (2) and/or Expression (3) is one in which these adjustments have been suitably performed, and generation of cracks in the release processing part can be suitably suppressed. can

The polarizing plate of the present invention is used in an image display device, and is particularly suitably used in an image display device having a different shape such as a meter panel of an automobile, a smartphone, a tablet type PC, and a smart watch.

Claims (17)

A polarizing plate comprising a polarizer and a protective layer disposed on at least one side of the polarizer,
The polarizing plate has a shape other than a rectangle,
The protective layer is composed of a resin film having a thickness of 10 μm or less,
When the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y, A polarizing plate that satisfies the following formula (1):
y<-0.011x+0.525 (1). A polarizing plate comprising a polarizer and a protective layer disposed on at least one side of the polarizer,
The polarizing plate has a release shape other than rectangular,
The protective layer is composed of a resin film having a thickness of 10 μm or less,
The polarizer 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 z nm, the following formula ( 2), a polarizer that satisfies:
z<-60x+2875 (2). A polarizing plate comprising a polarizer and a protective layer disposed on at least one side of the polarizer,
The polarizing plate has a release shape other than rectangular,
The protective layer is composed of a resin film having a thickness of 10 μm or less,
The polarizer 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 ), a polarizer that satisfies:
f<-0.018x+1.11 (3). A polarizing plate comprising a polarizer and a protective layer disposed on at least one side of the polarizer,
The polarizing plate has a release shape other than rectangular,
The protective layer is composed of a resin film having a thickness of 10 μm or less,
The polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and has a puncture strength of 30 gf/μm or more. According to any one of claims 1 to 4,
A polarizing plate having a thickness of the polarizer of 10 μm or less. According to any one of claims 1 to 5,
A polarizing plate having a single transmittance of the polarizer of 40.0% or more and a polarization degree of 99.0% or more. According to any one of claims 1 to 6,
The deformation is a through hole, a V-shaped notch, a U-shaped notch, a concave portion having a shape approximate to a linear shape when viewed in plan view, a rectangular concave portion when viewed in plan view, and an R approximated to a bathtub shape when viewed in plan view. A polarizing plate selected from the group consisting of concave portions of a shape, and combinations thereof. According to claim 7,
A polarizing plate in which the radius of curvature of the U-shaped notch is 5 mm or less. According to any one of claims 1 to 8,
The polarizing plate in which the said resin film contains at least 1 type of resin chosen from an epoxy resin and (meth)acrylic-type resin. According to any one of claims 1 to 9,
The polarizing plate, wherein the resin film is composed of a photocationic cured material of an epoxy resin, and the resin film has a softening temperature of 100° C. or higher. According to any one of claims 1 to 9,
The polarizing plate, wherein the resin film is composed of a solidified material of a coating film of an organic solvent solution of an epoxy resin, and the softening temperature of the resin film is 100°C or higher. According to any one of claims 1 to 9,
The polarizing plate, wherein the resin film is composed of a solidified material of a 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. According to claim 12,
The polarizing plate which has at least one selected from the group which the said thermoplastic (meth)acrylic-type resin consists of a lactone ring unit, a glutaric acid anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide unit. Comprising the polarizing plate according to any one of claims 1 to 13 and a retardation layer;
The polarizing plate with a retardation layer, wherein the retardation layer is disposed on a side of the polarizer opposite to the side on which the protective layer is disposed. According to claim 14,
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,
A polarizing plate with a retardation layer, wherein an angle between a slow axis of the retardation layer and an absorption axis of the polarizer is 40° to 50°. The method of claim 14 or 15,
The polarizing plate with the retardation layer in which the retardation layer is laminated on the polarizing plate with an adhesive layer interposed therebetween. An image display device provided with 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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