KR20220074857A - Polarizing plate with retardation layer, and image display device using same - Google Patents

Abstract

The present invention provides a polarizing plate with a retardation layer in which crack generation during heating is suppressed. A polarizing plate with a retardation layer according to an embodiment of the present invention includes a polarizer, a polarizing plate including a protective layer disposed on one side of the polarizer, and a retardation layer. The polarizer is composed of a polyvinyl alcohol-based resin film, and the orientation function of polyvinyl alcohol is 0.30 or less, the retardation layer is an alignment-solidified layer of a liquid crystal compound, and the thickness of the protective layer is 10 µm or less. Moreover, the polarizing plate with retardation layer which concerns on another embodiment of this invention contains the polarizing plate containing a polarizer, the protective layer arrange|positioned at one side of this polarizer, and retardation layer. The piercing strength of this polarizer is 30 gf/micrometer or more, the said retardation layer is an orientation-solidified layer of a liquid crystal compound, and the thickness of this protective layer is 10 micrometers or less.

Description

Polarizing plate with retardation layer, and image display device using same

The present invention relates to a polarizing plate with a retardation layer and an image display device using the same.

BACKGROUND ART In recent years, an image display device typified by a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device, an inorganic EL display device) has spread rapidly. A polarizing plate and a retardation plate are typically used for an image display apparatus. Practically, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (eg, Patent Document 1). In recent years, as the demand for thickness reduction of an image display apparatus increases, the request|requirement for thickness reduction is also increasing about a polarizing plate with a retardation layer. Moreover, in recent years, the request|requirement with respect to the curved image display apparatus and/or the bendable or bendable image display apparatus is increasing. Therefore, further thinning and further softening of the thickness are calculated|required also about a polarizing plate and a polarizing plate with a retardation layer.

As a method of thinning a polarizing plate, making the thickness of a protective layer thin, and laminating|stacking a protective layer only on one side of a polarizer are proposed. However, by these methods, a polarizer cannot fully be protected, and there exists room for improvement in durability. Moreover, there exists a problem that a crack becomes easy to generate|occur|produce by heat processing.

Japanese Patent Laid-Open 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 with a retardation layer in which crack generation during heating is suppressed.

A polarizing plate with a retardation layer according to an embodiment of the present invention includes a polarizer, a polarizing plate including a protective layer disposed on one side of the polarizer, and a retardation layer. This polarizer is composed of a polyvinyl alcohol-based resin film, and the polyvinyl alcohol has an orientation function of 0.30 or less, the retardation layer is an alignment-solidified layer of a liquid crystal compound, and the protective layer has a thickness of 10 µm or less.

A polarizing plate with a retardation layer according to another embodiment of the present invention includes a polarizer, a polarizing plate including a protective layer disposed on one side of the polarizer, and a retardation layer. The polarizer has a puncture strength of 30 gf/µm or more, the retardation layer is an alignment-solidified layer of a liquid crystal compound, and the protective layer has a thickness of 10 µm or less.

In one embodiment, the total thickness of the polarizing plate with a retardation layer is 30 µm or less.

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

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

In one embodiment, the protective layer is at least one selected from the group consisting of a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, a photocationically cured product of an epoxy resin, and a solidified product of a coating film of an organic solvent solution of an epoxy resin. It is made up of species.

In one embodiment, the thermoplastic acrylic resin has at least one repeating unit 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.

In one embodiment, the protective layer is a photocationically cured product of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton.

In another aspect of the present invention, an image display apparatus is provided. This image display apparatus contains the said polarizing plate with a retardation layer.

According to an embodiment of the present invention, there is provided a polarizing plate with a retardation layer comprising a polarizer having an orientation function of polyvinyl alcohol (PVA) of 0.30 or less, a protective layer having a thickness of 10 μm or less, and a retardation layer of an alignment-solidified layer of a liquid crystal aligning compound do. Further, according to another embodiment of the present invention, there is provided a polarizing plate with a retardation layer comprising a polarizer having a puncture strength of 30 gf/μm or more, a protective layer having a thickness of 10 μm or less, and a retardation layer of an alignment solidification layer of a liquid crystal aligning compound. . By setting it as such a polarizing plate with a retardation layer, the thickness of a polarizing plate with a retardation layer can be made thin, and crack generation at the time of heating can be suppressed. Moreover, crack generation at the time of bending can also be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of the polarizing plate with retardation layer which concerns on one Embodiment of this invention.
Fig. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention.
Fig. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to still another embodiment of the present invention.
4 : is schematic which shows an example of the drying shrinkage process using the heating roll in the manufacturing method of the polarizer used for the polarizing plate with retardation layer of this invention.

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

(Definition of terms and symbols)

Definitions of terms and symbols in the present specification are as follows.

(1) refractive index (nx, ny, nz)

'nx' is the refractive index in the direction in which the in-plane refractive index is maximum (ie, the slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the fast axis direction), and 'nz' is the refractive index It is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

'Re(λ)' is an in-plane retardation measured with light having a wavelength of λ nm at 23°C. For example, 'Re(550)' is an in-plane retardation measured with light having a wavelength of 550 nm at 23°C. Re(λ) is obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is d(nm).

(3) retardation in thickness direction (Rth)

'Rth(λ)' is the retardation in the thickness direction measured with light having a wavelength of λnm at 23°C. For example, 'Rth (550)' is the retardation in the thickness direction measured with light having a wavelength of 550 nm at 23°C. Rth(λ) is obtained by the formula: Rth(λ)=(nx-nz)×d when the thickness of the layer (film) is d(nm).

(4) Nz coefficient

The Nz coefficient is obtained by Nz=Rth/Re.

(5) angle

When referring to an angle in the present specification, the angle includes both a clockwise direction and a counterclockwise direction with respect to the reference direction. Thus, for example, '45°' means ±45°.

A. Overall configuration of polarizing plate with retardation layer

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic sectional drawing of the polarizing plate with retardation layer which concerns on one Embodiment of this invention. The polarizing plate 100 with a retardation layer of this embodiment contains the polarizing plate 10 and the retardation layer 20. As shown in FIG. The polarizing plate 10 includes a polarizer 11 , a first protective layer 12 disposed on one side of the polarizer 11 , and a second protective layer 13 disposed on the other side of the polarizer 11 . do. Depending on the purpose, one of the first protective layer 12 and the second protective layer 13 may be omitted. For example, when the retardation layer 20 can also function as a protective layer of the polarizer 11, the 2nd protective layer 13 may be abbreviate|omitted. The retardation layer 20 is laminated on the polarizer 11 or the second protective layer 13 via any appropriate pressure-sensitive adhesive layer or adhesive layer (not shown). In embodiment of this invention, the polarizer 11 is comprised from the polyvinyl alcohol-type resin film, and the orientation function of polyvinyl alcohol is 0.30 or less. In another embodiment of the present invention, the polarizer 11 has a puncture strength of 30 gf/μm or more. In addition, the thickness of the protective layer is 10 µm or less. When the polarizing plate 100 includes the first protective layer 12 and the second protective layer 13, the thickness of at least one protective layer may be 10 μm or less, preferably the first protective layer 12 and The thickness of both sides of the 2nd protective layer 13 is 10 micrometers or less. In one embodiment, in the polarizing plate 100 , a hard code layer may be formed on a side that is not in contact with the polarizer 11 of the viewing-side protective layer (eg, the first protective layer 12 ). In this embodiment, it is preferable that the sum total of the thickness of a protective layer and the thickness of a hard-coat layer be set to 10 micrometers or less.

Fig. 2 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to another embodiment of the present invention. As shown in FIG. 2 , in the polarizing plate 101 with a retardation layer according to another embodiment, another retardation layer 50 and/or an isotropic substrate 60 with a conductive layer or a conductive layer may be provided. The other retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically provided on the outer side of the retardation layer 20 (opposite to the polarizing plate 10). The other retardation layers typically exhibit a relationship of refractive index characteristics of nz>nx=ny. The other retardation layer 50 and the conductive layer or the isotropic substrate 60 with a conductive layer are typically provided in this order from the retardation layer 20 side. The other retardation layer 50 and the conductive layer or the isotropic base material 60 with a conductive layer are arbitrary layers typically provided as needed, and either one or both may be abbreviate|omitted. In addition, for convenience, the retardation layer 20 is referred to as a first retardation layer and the other retardation layer 50 is referred to as a second retardation layer in some cases. In addition, when a conductive layer or an isotropic substrate with a conductive layer is provided, the polarizing plate with a retardation layer is a so-called inner touch panel type input display device in which a touch sensor is incorporated between the image display cell (eg, organic EL cell) and the polarizing plate. can be applied.

Fig. 3 is a schematic cross-sectional view of a polarizing plate with a retardation layer according to still another embodiment of the present invention. In the embodiment of the present invention, the first phase difference layer 20 is an alignment-solidified layer of a liquid crystal compound. The 1st phase difference layer 20 may be a single layer of the alignment-solidified layer as shown in FIGS. 1 and 2, and the 1st alignment-solidified layer 21 and the 2nd alignment-solidified layer 22 as shown in FIG. may have a laminated structure of

The above embodiments may be appropriately combined, and modifications apparent in the art may be added to the constituent elements in the above embodiments. For example, the 2nd retardation layer 50 and/or the isotropic base material 60 with a conductive layer or a conductive layer may further be provided in the polarizing plate 102 with a retardation layer of FIG. Further, for example, the configuration in which the isotropic substrate 60 with a conductive layer is provided outside the second retardation layer 50 is replaced with an optically equivalent configuration (eg, a laminate of the second retardation layer and the conductive layer) also be

The polarizing plate with a retardation layer which concerns on embodiment of this invention may further contain the other retardation layer. Other optical characteristics (eg, refractive index characteristics, in-plane retardation, Nz coefficient, and photoelastic coefficient), thickness, arrangement position, and the like of the retardation layer may be appropriately set according to the purpose.

Sheet shape may be sufficient as the polarizing plate with retardation layer which concerns on embodiment of this invention, and long picture shape may be sufficient as it. As used herein, the term 'long shape' means an elongate shape having a sufficiently long length with respect to the width, and includes, for example, an elongated shape with a length of 10 times or more, preferably 20 times or more with respect to the width. The elongate polarizing plate with retardation layer can be wound in roll shape.

Practically, an adhesive layer (not shown) is provided on the opposite side to the polarizing plate of the retardation layer, and the polarizing plate with a retardation layer can be affixed to an image display cell. Moreover, it is preferable that the peeling film is temporarily attached to the surface of an adhesive layer until the polarizing plate with retardation layer is provided for use. By temporarily adhering a peeling film, while protecting an adhesive layer, roll formation becomes possible.

The total thickness of the polarizing plate with a retardation layer becomes like this. Preferably it is 30 micrometers or less, More preferably, it is 25 micrometers or less, More preferably, it is 20 micrometers or less. The total thickness may be, for example, 10 μm or more. According to the embodiment of the present invention, an extremely thin polarizing plate with a retardation layer can be realized in this way. Moreover, crack generation at the time of heating can also be suppressed. Such a polarizing plate with a retardation layer may have extremely excellent flexibility and bending durability. Such a polarizing plate with a retardation layer can be applied especially suitably to a curved image display apparatus and/or a bendable or bendable image display apparatus. In addition, the total thickness of the polarizing plate with a retardation layer means the sum total of the thickness of all the layers constituting the polarizing plate with a retardation layer, except for the pressure-sensitive adhesive layer for making the polarizing plate adhere to an external adherend such as a panel or glass (that is, retardation) The total thickness of the polarizing plate with a layer does not include a pressure-sensitive adhesive layer for affixing the polarizing plate with a retardation layer to an adjacent member such as an image display cell and the thickness of a release film that can be temporarily adhered to the surface thereof).

The unit weight of the polarizing plate with a retardation layer according to an embodiment of the present invention is, for example, 6.5 mg/cm ² or less, preferably 2.0 mg/cm ² to 6.0 mg/cm ² , and more preferably 3.0 mg/cm ² to 5.5 mg/cm ² , more preferably 3.5 mg/cm ² to 5.0 mg/cm ² . When a display panel is thin, a panel deform|transforms minutely by the weight of a polarizing plate with a retardation layer, and there exists a possibility that a display defect may arise. According to the polarizing plate with a retardation layer having a unit weight of 6.5 mg/cm ² or less, such deformation of the panel can be prevented. In addition, the polarizing plate with a retardation layer having the above unit weight has good handling properties even when it is thinned, and can exhibit extremely excellent flexibility and bending durability.

Hereinafter, the components of a polarizing plate with a retardation layer are demonstrated in detail.

B. Polarizer

B-1. polarizer

The polarizer according to the embodiment of the present invention is composed of a polyvinyl alcohol (PVA)-based resin film, and has an orientation function of 0.30 or less. If it is such a structure, generation|occurrence|production of the crack at the time of heating, especially generation|occurrence|production of the crack along the absorption axis direction of a polarizer can be suppressed. Moreover, it can suppress remarkably that the polarizer is torn (cracked) along the absorption axis direction even at the time of heating. As a result, a polarizer (as a result, a polarizing plate) extremely excellent in flexibility can be obtained. Such a polarizer (as a result, a polarizing plate) can be preferably applied to a curved image display device, more preferably a bendable image display device, and still more preferably a foldable image display device. The orientation function is preferably 0.28 or less, more preferably 0.26 or less, and still more preferably 0.25 or less. The orientation function may be, for example, greater than or equal to 0.05. When the orientation function is too small, an acceptable single transmittance and/or polarization degree may not be obtained.

The orientation function f is obtained by, for example, attenuated total reflection (ATR) measurement using a Fourier transform infrared spectrophotometer (FT-IR), using polarized light as measurement light. Specifically, with respect to the polarization direction of the measurement light, the measurement is performed in a state in which the stretching directions of the polarizer are parallel and perpendicular, and the obtained absorbance spectrum is calculated using the intensity of 2941 cm ^-1 , according to the following formula. Here, the intensity I is a value of 2941 cm ^-1 /3330 cm ^-1 with 3330 cm ^-1 as a reference peak. Also, when f=1, it is fully oriented, and when f=0, it becomes random. Moreover, the peak at 2941 cm ^-1 is considered to be absorption resulting from the vibration of the main chain (-CH ₂ -) of PVA in the polarizer.

f=(3<cos ² θ>-1)/2

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

=-2×(1-D)/(2D+1)

only,

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

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

β: angle of 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 elongation direction of the polarizer are perpendicular

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

The thickness of a polarizer becomes like this. Preferably it is 10 micrometers or less, More preferably, it is 8 micrometers or less, More preferably, it is 7 micrometers or less. The thickness of the polarizer may be, for example, 1 μm or more. The thickness of the polarizer is 2 μm to 6 μm in one embodiment, 2 μm to 4 μm in another embodiment, 2 μm to 3 μm in still another embodiment, 5.5 μm to 7.5 μm in another embodiment, another embodiment In a form, 6 micrometers - 7.2 micrometers may be sufficient. By making the thickness of a polarizer very thin in this way, thermal contraction can be made very small. It is presumed that such a configuration can also contribute to suppression of fracture in the absorption axis direction.

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, and more preferably 41.0% or more. The single transmittance may be, for example, 49.0% or less. In one embodiment, the single transmittance|permeability of a polarizer is 40.0 % - 45.0 %. The polarization degree of the polarizer is preferably 99.0% or more, and more preferably 99.4% or more. The degree of polarization may be, for example, 99.999% or less. The polarization degree of the polarizer is 99.0% to 99.99% in one embodiment. According to the present invention, although the orientation function is very small as described above, the single transmittance and the degree of polarization that are acceptable for practical use can be realized. It is guessed that this originates in the manufacturing method mentioned later. In addition, the single transmittance|permeability is the Y value which measured using the ultraviolet/visible spectrophotometer typically and performed visibility correction|amendment. The degree of polarization is typically obtained by the following formula based on the parallel transmittance (Tp) and the orthogonal transmittance (Tc) measured using an ultraviolet/visible light spectrophotometer and corrected for visibility.

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

In the embodiment of the present invention, the piercing strength of the polarizer is 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, particularly preferably is 50 gf/㎛ or more. The puncture strength may be, for example, 80 gf/μm or less. By making the puncture strength of a polarizer into such a range, it can suppress remarkably that a polarizer is torn along an absorption axis direction. As a result, a polarizer (as a result, a polarizing plate) extremely excellent in flexibility can be obtained. The puncture strength shows 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 (breaking strength) at which the polarizer cracks 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.

The polarizer is composed of a PVA-based resin film as described above. Preferably, the PVA-based resin constituting the PVA-based resin film (substantially a polarizer) contains an acetoacetyl-modified PVA-based resin. If it is such a structure, the polarizer which has a desired puncture intensity|strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5 to 20% by weight, more preferably 8 to 12% by weight, when the total PVA-based resin is 100% by weight. The puncture strength can be made into a more suitable range as a compounding quantity is such a range.

The polarizer may be typically manufactured using a laminate of two or more layers. As a specific example of the polarizer obtained using a laminated body, the polarizer obtained using the laminated body of the resin base material and the PVA-type resin layer apply|coated to the said resin base material is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer applied and formed on the resin substrate is, for example, a PVA-based resin solution applied to a resin substrate, dried to form a PVA-based resin layer on the resin substrate, obtaining a laminate of a resin substrate and a PVA-based resin layer; It can be produced by; stretching and dyeing the laminate to make the PVA-based resin layer a polarizer. In this embodiment, Preferably, the polyvinyl alcohol-type resin layer containing a halide and polyvinyl alcohol-type resin is provided on one side of a resin base material. Stretching typically includes stretching by immersing the laminate in an aqueous boric acid solution. In addition, the stretching preferably further includes aerial stretching of the laminate at a high temperature (eg, 95° C. or higher) before stretching in an aqueous boric acid solution. In embodiment of this invention, the total magnification of extending|stretching is 3.0 times - 4.5 times, for example, and it is remarkably small compared with usual. Even at such a total magnification of extending|stretching, the polarizer which has an allowable optical characteristic can be obtained by the combination of addition of a halide and drying shrinkage process. Moreover, in embodiment of this invention, it is preferable that the draw ratio of aerial auxiliary drawing is larger than the draw ratio of boric-acid underwater drawing. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has an acceptable optical characteristic can be obtained. In addition, the laminate is preferably subjected to a drying shrinkage treatment for shrinking 1% to 10% in the width direction by heating while conveying in the longitudinal direction. In one embodiment, the manufacturing method of a polarizer includes giving an aerial auxiliary extending|stretching process, a dyeing|staining process, an underwater extending|stretching process, and a drying shrinkage process to a laminated body in this order. By introducing auxiliary stretching, even when applying PVA on a thermoplastic resin, it becomes possible to increase the crystallinity of PVA, and it becomes possible to achieve high optical properties. In addition, by raising the orientation of PVA in advance at the same time, when immersed in water in a subsequent dyeing process or stretching process, problems such as a decrease in orientation and dissolution of PVA can be prevented, and high optical properties can be achieved becomes In addition, in the case where the PVA-based resin layer is immersed in a liquid, as compared to the case in which the PVA-based resin layer does not contain a halide, disorder in the orientation of polyvinyl alcohol molecules and a decrease in orientation can be suppressed. Thereby, the optical characteristic of the polarizer obtained through the processing process performed by immersing a laminated body in a liquid, such as a dyeing process and an underwater extending|stretching process, can be improved. Moreover, an optical characteristic can be improved by shrinking|contracting a laminated body in the width direction by dry shrinkage process. The obtained laminated body of resin substrate / polarizer may be used as it is (that is, the resin substrate may be used as a protective layer of polarizer), and the resin substrate is peeled from the laminate of resin substrate / polarizer, and the said peeling surface is used for the purpose. Any suitable protective layer may be laminated and used. The detail of the manufacturing method of a polarizer is mentioned later in B-2.

B-2. Method for manufacturing a polarizer

In the method for manufacturing a polarizer according to an embodiment of the present invention, a polyvinyl alcohol-based resin layer (PVA-based resin) comprising a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate Formation layer) to form a laminate, and drying shrinkage to shrink 1% to 10% in the width direction by heating while conveying in the longitudinal direction with air-assisted stretching treatment, dyeing treatment, and underwater stretching treatment. This includes performing the processing in this order. The content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. It is preferable to process dry shrinkage using a heating roll, The temperature of a heating roll becomes like this. Preferably it is 60 degreeC - 120 degreeC. The shrinkage ratio in the width direction of the laminate following the drying shrinkage treatment is preferably 1% to 10%. According to such a manufacturing method, the polarizer demonstrated in said B-1 term can be obtained. In particular, producing a laminate including a PVA-based resin layer containing a halide, stretching the laminate in multi-step stretching including air-assisted stretching and underwater stretching, and heating the laminate after stretching with a heating roll Accordingly, it is possible to obtain a polarizer having excellent optical properties (typically, single transmittance and unit absorbance).

B-2-1. Fabrication of laminates

Any suitable method may be employed as a method for producing a laminate of the thermoplastic resin substrate and the PVA-based resin layer. Preferably, a coating liquid containing a halide and a PVA-based resin is applied to the surface of the thermoplastic resin substrate and dried to form a PVA-based resin layer on the thermoplastic resin substrate. As described above, the content of the halide in the PVA-based resin layer is preferably 5 to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

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

The thickness of the PVA-based resin layer is preferably 2 µm to 30 µm, more preferably 2 µm to 20 µm. By making the thickness of the PVA-based resin layer before stretching very thin in this way and reducing the total stretching ratio as described later, a polarizer having an acceptable single transmittance and polarization degree despite the very small orientation function can be obtained. .

Before forming the PVA-based resin layer, the thermoplastic resin substrate may be subjected to surface treatment (eg, corona treatment, etc.), or an easily adhesive 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-type resin layer can be improved.

B-2-1-1. Thermoplastic resin substrate

As the thermoplastic resin substrate, any suitable thermoplastic resin film may be employed. About the detail of a thermoplastic resin base material, it describes in Unexamined-Japanese-Patent No. 2012-73580 and Unexamined-Japanese-Patent No. 6470455, for example. As for the said publication, the description in its entirety is incorporated herein by reference.

B-2-1-2. coating liquid

The coating solution contains a halide and a PVA-based resin as described above. The coating liquid is typically a solution in which the halide and the PVA-based resin are dissolved in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. can be heard 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 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. If it is such a resin concentration, a uniform coating film closely_contact|adhered to a thermoplastic resin base material can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

You may mix|blend an additive with a coating liquid. As an additive, a plasticizer, surfactant, etc. are mentioned, for example. 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.

Any suitable resin may be employed as the PVA-based resin. For example, polyvinyl alcohol and an ethylene-vinyl alcohol copolymer are mentioned. Polyvinyl alcohol is obtained by saponifying polyvinyl acetate. The ethylene-vinyl alcohol copolymer is obtained by saponifying the ethylene-vinyl acetate copolymer. The saponification degree of PVA-type resin is 85 mol% - 100 mol% normally, Preferably they are 95.0 mol% - 99.95 mol%, More preferably, they are 99.0 mol% - 99.93 mol%. The degree of saponification can be obtained according to JIS K 6726-1994. A polarizer excellent in durability can be obtained by using the PVA-type resin of such a saponification degree. When the degree of saponification is too high, there is a possibility of gelation. 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 according to the purpose. The average degree of polymerization is usually 1000 to 10000, preferably 1200 to 4500, more preferably 1500 to 4300. In addition, an average degree of polymerization can be calculated|required according to JISK6726-1994.

As the halide, any suitable halide may be employed. Examples include iodide and sodium chloride. Examples of the iodide include potassium iodide, sodium iodide and lithium iodide. Among these, potassium iodide is preferable.

The amount of the halide in the coating liquid is preferably 5 to 20 parts by weight based on 100 parts by weight of the PVA-based resin, and more preferably 10 to 15 parts by weight based on 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 finally obtained polarizer 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 increases. This may become disturbed, and the orientation may fall. In particular, in the case of stretching a laminate of a thermoplastic resin and a PVA-based resin layer in boric acid water, when stretching the laminate in boric acid water at a relatively high temperature in order to stabilize the stretching of the thermoplastic resin, the tendency of the orientation degree to decrease is remarkable do. For example, compared to the general case that the PVA film alone is stretched in boric acid water at 60° C., the stretching of the laminate of A-PET (thermoplastic resin substrate) and the PVA-based resin layer is performed at a high temperature of around 70° C. It is carried out at a temperature, and in this case, the orientation of the PVA at the initial stage of stretching may be lowered at a stage before it is raised by stretching in water. On the other hand, by producing a laminate of a PVA-based resin layer containing a halide and a thermoplastic resin substrate, and stretching the laminate at a high temperature in air (auxiliary stretching) before stretching the laminate in boric acid water, the laminate after auxiliary stretching Crystallization of the PVA-based resin in the PVA-based resin layer can be promoted. As a result, when the PVA-based resin layer is immersed in a liquid, as compared to the case where the PVA-based resin layer does not contain a halide, disorder in the orientation of polyvinyl alcohol molecules and a decrease in orientation can be suppressed. Thereby, the optical characteristic of the polarizer obtained through the processing process performed by immersing a laminated body in a liquid, such as a dyeing process and an underwater extending|stretching process, can be improved.

B-2-2. Aerial Auxiliary Stretch Treatment

In particular, in order to obtain high optical properties, a method of two-stage stretching in which dry stretching (auxiliary stretching) and stretching in boric acid water is combined is selected. Like two-stage stretching, by introducing auxiliary stretching, stretching can be performed while suppressing crystallization of the thermoplastic resin substrate. Furthermore, when applying the PVA-based resin on the 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 conventional metal drum. As a result, the crystallization of the PVA-based resin is relatively low, which may cause a problem that sufficient optical properties are not obtained. On the other hand, even when apply|coating PVA-type resin on a thermoplastic resin by introduce|transducing auxiliary stretching, it becomes possible to improve the crystallinity of PVA-type resin, and it becomes possible to achieve high optical characteristic. In addition, by increasing the orientation of the PVA-based resin in advance at the same time, when it is immersed in water in a subsequent dyeing process or stretching process, problems such as a decrease in the orientation or dissolution of the PVA-based resin can be prevented, and high optical properties It becomes possible to achieve

The stretching method of the aerial 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) do. In order to obtain high optical properties, free-end stretching can be actively employed. In one embodiment, the aerial stretching process includes the heating roll stretching process of extending|stretching with the circumferential speed difference between heating rolls conveying the said laminated body in the longitudinal direction. The aerial stretching treatment typically includes a zone stretching process and a hot roll stretching process. In addition, the order of a zone extending|stretching process and a heated roll extending process is not limited, A zone extending|stretching process may be performed first, and a hot roll extending|stretching process may be performed first. The zone stretching step may be omitted. In one embodiment, the zone stretching process and the heated roll stretching process are performed in this order. Moreover, in another embodiment, it is a tenter stretching machine, and it is extended|stretched by holding|gripping a film edge part and extending the distance between tenters in a flow direction (widening of the distance between tenters becomes a draw ratio). At this time, the distance of the tenter in the width direction (direction perpendicular to the flow direction) is set so as to be arbitrarily close. Preferably, with respect to the draw ratio in the flow direction, it can be set to be close to the free end drawing. In the case of free-end stretching, it is calculated as the shrinkage ratio in the width direction = (1/stretch ratio) ^1/2 .

Aerial auxiliary extending|stretching may be performed in one step, and may be performed in multiple steps. When carrying out in multiple steps, the draw ratio is the product of the draw ratios of each step. The stretching direction in the aerial assisted stretching is preferably approximately the same as the stretching direction in the underwater stretching.

The draw ratio in aerial auxiliary stretching becomes like this. Preferably they are 1.0 times - 4.0 times, More preferably, they are 1.5 times - 3.5 times, More preferably, they are 2.0 times - 3.0 times. If the draw ratio of the aerial assisted stretching is within such a range, the total magnification of the stretching can be set in a desired range when combined with the underwater stretching, and a desired orientation function can be realized. As a result, the polarizer in which the fracture|rupture along the absorption axis direction was suppressed can be obtained. Moreover, as mentioned above, it is preferable that the draw ratio of air-assisted drawing is larger than the draw ratio of boric-acid water drawing. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has an acceptable optical characteristic can be obtained.

The stretching temperature of the aerial auxiliary stretching can be set to any appropriate value according to the forming material of the thermoplastic resin substrate, the stretching method, and the like. The stretching temperature is preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate, more preferably not less than the glass transition temperature (Tg) of the thermoplastic resin substrate +10°C, particularly preferably not less than Tg+15°C. On the other hand, the upper limit of extending|stretching temperature becomes like this. Preferably it is 170 degreeC. By stretching at such a temperature, it is possible to suppress the rapid progress of crystallization of the PVA-based resin, thereby suppressing problems due to the crystallization (eg, hindering the orientation of the PVA-based resin layer by stretching).

B-2-3. Insolubilization treatment, dyeing treatment and crosslinking treatment

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

B-2-4. 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. can As a result, it is possible to manufacture a polarizer having excellent optical properties.

Any suitable method can be employ|adopted for the extending|stretching method of a laminated body. Specifically, fixed-end stretching may be used, or free-end stretching (eg, a method of uniaxial stretching by passing a laminated body between rolls having different circumferential speeds) may be employed. Preferably, free-end stretching is selected. Extending|stretching of a laminated body may be performed in one step, and may be performed in multiple steps. When carrying out in multiple stages, the total magnification of stretching is the product of the stretching magnifications of each stage.

Stretching in water is preferably performed by immersing the laminate in an aqueous boric acid solution (stretching in boric acid water). By using an aqueous boric acid solution as a stretching bath, rigidity to withstand the tension applied at the time of stretching and water resistance insoluble in water can be imparted to the PVA-based resin layer. Specifically, boric acid can generate a tetrahydroxyborate anion in an aqueous solution and crosslink with a PVA-based resin by hydrogen bonding. As a result, rigidity and water resistance can be provided to a PVA-type resin layer, can be extended|stretched favorably, and the polarizer which has the outstanding optical characteristic can be manufactured.

The aqueous boric acid solution 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 with respect to 100 parts by weight of water. By making boric-acid density|concentration into 1 weight part or more, melt|dissolution of a PVA-type resin layer can be suppressed effectively, and the polarizer of a higher characteristic can be manufactured. In addition to boric acid or borate, an aqueous solution obtained by dissolving a boron compound such as borax, glyoxal, glutaraldehyde, or the like in a solvent can also be used.

Preferably, iodide is mix|blended with the said stretching bath (boric acid aqueous solution). By mix|blending an iodide, the elution of the iodine made to adsorb|suck to the PVA-type resin layer can be suppressed. Specific examples of the iodide are as described above. The concentration of iodide is preferably 0.05 parts by weight to 15 parts by weight, more preferably 0.5 parts by weight to 8 parts by weight with respect to 100 parts by weight of water.

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. If it is such a temperature, it can extend|stretch at a high magnification, suppressing melt|dissolution of a PVA-type 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, when extending|stretching temperature is less than 40 degreeC, even if it considers plasticization of the thermoplastic resin base material by water, there exists a possibility that extending|stretching may not be satisfactory. On the other hand, as the temperature of the stretching bath increases, the solubility of the PVA-based resin layer increases, and there is a fear that excellent optical properties may not be obtained. The immersion time for the stretching bath of the laminate is preferably 15 seconds to 5 minutes.

The draw ratio by extending|stretching in water becomes like this. Preferably they are 1.0 times - 3.0 times, More preferably, they are 1.0 times - 2.0 times, More preferably, they are 1.0 times - 1.5 times. If the draw ratio in the underwater stretching is within such a range, the total stretching ratio can be set in a desired range, and a desired orientation function can be realized. As a result, the polarizer in which the fracture|rupture along the absorption axis direction was suppressed can be obtained. The total magnification of stretching (the sum of the magnifications in the case of combining aerial assisted stretching and underwater stretching) is, for example, 3.0 to 4.5 times, preferably 3.0 to 4.0 times, with respect to the original length of the laminate, as described above. and more preferably 3.0 to 3.5 times. By appropriately combining the addition of a halide to the coating liquid, adjustment of the draw ratios of air-assisted stretching and underwater stretching, and drying shrinkage treatment, a polarizer having acceptable optical properties even at such a total stretching ratio can be obtained. .

B-2-5. dry shrinkage treatment

The said drying shrinkage process may be performed by zone heating performed by heating the whole zone, and may be performed by heating a conveyance roll (using what is called a heating roll) (heating roll drying method). Preferably, both are used. By drying using a heating roll, the heating curl of a laminated body can be suppressed efficiently and the light polarizer excellent in an external appearance can be manufactured. Specifically, by drying in a state in which the laminate is poured on 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 satisfactorily increased. can As a result, the rigidity of a thermoplastic resin base material increases, it becomes a state which can withstand the shrinkage of the PVA-type resin layer accompanying drying, and curl is suppressed. Moreover, by using a heating roll, since it can dry, maintaining a laminated body in a flat state, not only curl but also generation|occurrence|production 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. It is because the orientation of PVA and PVA/iodine complex can be improved effectively. The shrinkage ratio 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 4% to 6%.

4 is a schematic diagram showing an example of a drying shrinkage treatment. In a dry shrinkage process, it is made to dry, conveying the laminated body 200 with conveyance rolls R1-R6 heated to predetermined temperature, and guide rolls G1-G4. In the illustrated example, the conveying rolls R1 to R6 are disposed so as to alternately and continuously heat the surface of the PVA resin layer and the surface of the thermoplastic resin substrate. For example, one surface of the laminate 200 (eg, the surface of the thermoplastic resin substrate) You may arrange|position conveyance rolls R1-R6 so that a bay may be continuously heated.

Drying conditions are controllable by adjusting the heating temperature (temperature of a heating roll) of a conveyance roll, the number of heating rolls, contact time with a heating roll, etc. 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 degree of crystallinity of a thermoplastic resin can be increased favorably and curl can be suppressed favorably, the optical laminated body extremely excellent in durability can be manufactured. In addition, the temperature of a heating roll can be measured with a contact thermometer. In the example of illustration, although six conveyance rolls are provided, if there are several conveyance rolls, there will be no restriction|limiting in particular. 2-40 pieces of conveyance rolls are normally provided, Preferably 4-30 pieces are provided. The contact time (total contact time) of the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, and still more preferably 1 to 10 seconds.

A heating roll may be provided in a heating furnace (for example, oven), and may be provided in a normal production line (under a room temperature environment). Preferably, it is provided in the heating furnace provided with the blowing means. By using together drying with a heating roll and hot air drying, the rapid temperature change between heating rolls can be suppressed and the shrinkage|contraction of the width direction can be controlled easily. The temperature of hot air drying becomes like this. Preferably it is 30 degreeC - 100 degreeC. In addition, the hot air drying time becomes like this. Preferably it is 1 second - 300 second. The wind speed of the hot wind is preferably about 10 m/s to 30 m/s. In addition, the said wind speed is a wind speed in a heating furnace, and can be measured with a mini vane type digital anemometer.

B-2-6. other processing

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

B-3. protective layer

In the embodiment of the present invention, the thickness of the protective layer is 10 µm or less. When the thickness of a protective layer is 10 micrometers or less, it can contribute also to thickness reduction of a polarizing plate. In the polarizing plate with a retardation layer, crack generation during heating can be prevented even when the protective layer has a thickness of 10 μm or less. The thickness of the protective layer is preferably 7 µm or less, more preferably 5 µm or less, and still more preferably 3 µm or less. The thickness of the protective layer is, for example, 1 µm or more.

The protective layer may be formed of any suitable material. Cellulose resins such as triacetyl cellulose (TAC), polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, polynorbornene, polyolefin Transparent resins, such as a system, (meth)acrylic system, and an acetate system; thermosetting resins or ultraviolet curable resins such as (meth)acrylic, urethane, (meth)acrylic urethane, epoxy, and silicone; Glassy type polymers, such as a siloxane type polymer, are mentioned.

A film may be sufficient as a protective layer, the solidified material of a coating film may be sufficient, and hardened|cured material (for example, photocationic hardened|cured material) may be sufficient as it. In one embodiment, the protective layer is a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin (hereinafter simply referred to as an acrylic resin), a photocationically cured product of an epoxy resin, and a solidified product of a coating film of an organic solvent solution of an epoxy resin It is composed of at least one selected from the group consisting of. Hereinafter, it demonstrates concretely.

B-3-1. Solidified material of coating film of organic solvent solution of thermoplastic acrylic resin

In one Embodiment, the protective layer is comprised from the solidified material of the coating film of the organic-solvent solution of a thermoplastic acrylic resin.

B-3-1-1. Acrylic resin

The acrylic resin preferably has a glass transition temperature (Tg) of 100° C. or higher. As a result, the Tg of the protective layer is 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 may have excellent durability. Tg of acrylic resin becomes like this. Preferably it is 110 degreeC or more, More preferably, it is 115 degreeC or more, More preferably, it is 120 degreeC or more, Especially preferably, it is 125 degreeC or more. On the other hand, Tg of acrylic resin becomes like this. Preferably it is 300 degrees C or less, More preferably, it is 250 degrees C or less, More preferably, it is 200 degrees C or less, Especially preferably, it is 160 degrees C or less. When the Tg of the acrylic resin is within such a range, the moldability may be excellent.

As the acrylic resin, any suitable acrylic resin may be employed as long as it has the above Tg. The acrylic resin typically contains an alkyl (meth)acrylate as a main component as a monomer unit (repeating unit). As used herein, '(meth)acryl' refers to acryl and/or methacryl. As the alkyl (meth)acrylate constituting the main skeleton of the acrylic resin, a linear or branched alkyl group having 1 to 18 carbon atoms can be exemplified. These may be used alone or in combination. Moreover, you may introduce|transduce arbitrary appropriate copolymerization monomers into acrylic resin by copolymerization. The repeating unit derived from alkyl (meth)acrylate is typically represented by the following general formula (1):

In the general formula (1), R ⁴ represents a hydrogen atom or a methyl group, and R ⁵ represents a hydrogen atom or an optionally substituted aliphatic or alicyclic hydrocarbon group having 1 to 6 carbon atoms. As a substituent, halogen and a hydroxyl group are mentioned, for example. Specific examples of the alkyl (meth)acrylate include methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic acid n-propyl, (meth)acrylic acid n-butyl, (meth)acrylic acid t-butyl, (meth)acrylic acid n-hexyl, (meth)acrylic acid cyclohexyl, (meth)acrylic acid 2-ethylhexyl, (meth)acrylic acid benzyl, (meth)acrylic acid dicyclopentanyloxyethyl, (meth)acrylic acid dicyclopentanyl, (meth)acrylic acid chloromethyl , (meth) acrylic acid 2-chloroethyl, (meth) acrylic acid 2-hydroxyethyl, (meth) acrylic acid 3-hydroxypropyl, (meth) acrylic acid 2,3,4,5,6-pentahydroxyhexyl, ( and 2,3,4,5-tetrahydroxypentyl meth)acrylic acid, methyl 2-(hydroxymethyl)acrylate, ethyl 2-(hydroxymethyl)acrylate, and methyl 2-(hydroxyethyl)acrylate. In the general formula (1), R ⁵ is preferably a hydrogen atom or a methyl group. Accordingly, particularly preferred alkyl(meth)acrylates are methyl acrylate or methyl methacrylate.

Acrylic resin may contain only a single alkyl (meth)acrylate unit, and may contain the some alkyl (meth)acrylate unit from which R< ⁴ > and R< ⁵ > in the said General formula (1) differ.

The content of the alkyl (meth)acrylate unit in the acrylic resin is preferably 50 mol% to 98 mol%, more preferably 55 mol% to 98 mol%, still more preferably 60 mol% to 98 mol%, Especially preferably, it is 65 mol% - 98 mol%, Most preferably, it is 70 mol% - 97 mol%. When the content ratio is less than 50 mol%, there is a possibility that the effect (eg, high heat resistance, high transparency) derived from the alkyl (meth)acrylate unit may not be sufficiently exhibited. When the content is more than 98 mol%, the resin becomes brittle and cracks easily, high mechanical strength cannot be sufficiently exhibited, and there is a fear that the productivity may be lowered.

The acrylic resin preferably has a repeating unit containing a ring structure. Examples of the repeating unit having a ring structure include a lactone ring unit, a glutaric anhydride unit, a glutarimide unit, a maleic anhydride unit, and a maleimide (N-substituted maleimide) unit. As for the repeating unit containing a ring structure, only 1 type may be contained in the repeating unit of an acrylic resin, and 2 or more types may be contained.

The lactone ring unit is preferably represented by the following general formula (2):

In the general formula (2), R ¹ , R ² , and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. Moreover, the organic residue may contain the oxygen atom. The acrylic resin may contain only a single lactone ring unit, and may contain the some lactone ring unit from which R< ¹ >, R< ² > and R< ³ > in the said General formula (2) differs. Acrylic resin which has a lactone ring unit is described, for example in Unexamined-Japanese-Patent No. 2008-181078, description of this publication is taken in here as a reference.

The glutarimide unit is preferably represented by the following general formula (3):

In the general formula (3), R ¹¹ and R ¹² each independently represent hydrogen or an alkyl group having 1 to 8 carbon atoms, R ¹³ is an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or a cycloalkyl group having 6 to 10 carbon atoms represents an aryl group. In the general formula (3), preferably, R ¹¹ and R ¹² are each independently hydrogen or a methyl group, and R ¹³ is hydrogen, a methyl group, a butyl group or a cyclohexyl group. More preferably, R ¹¹ is a methyl group, R ¹² is hydrogen, and R ¹³ is a methyl group. The acrylic resin may contain only a single glutarimide unit, and may contain the some glutarimide unit from which ^R11 , R12 and ^R13 in the said General formula ( ³ ) differ. Acrylic resins having a glutarimide unit are, for example, JP 2006-309033 , JP 2006-317560 , JP 2006-328334 , JP 2006-337491 , JP It describes in Unexamined-Japanese-Patent No. 2006-337492, Unexamined-Japanese-Patent No. 2006-337493, and Unexamined-Japanese-Patent No. 2006-337569, The description of this publication is taken in here as a reference. In addition, with respect to the glutaric anhydride unit, the above description regarding the glutarimide unit applies except that the nitrogen atom substituted by R ¹³ in the said general formula (3) becomes an oxygen atom.

As for the maleic anhydride unit and the maleimide (N-substituted maleimide) unit, their structures are specified from the names, and thus, detailed descriptions thereof are omitted.

The content ratio of the repeating unit containing a 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% . When there is too little content rate, Tg may become less than 100 degreeC, and the heat resistance, solvent resistance, and surface hardness of the protective layer obtained may become inadequate. When there are too many content rates, a moldability and transparency may become inadequate.

Acrylic resin may contain repeating units other than the repeating unit containing an alkyl (meth)acrylate unit and a ring structure. As such a repeating unit, the repeating unit (other vinylic monomeric unit) derived from the vinylic monomer copolymerizable with the monomer which comprises the said unit is mentioned. Examples of other vinyl monomers include acrylic acid, methacrylic acid, crotonic acid, 2-(hydroxymethyl)acrylic acid, 2-(hydroxyethyl)acrylic acid, acrylonitrile, methacrylonitrile, ethacrylonitrile, allyl Glycidyl ether, maleic anhydride, itaconic anhydride, N-methylmaleimide, N-ethylmaleimide, N-cyclohexylmaleimide, aminoethyl acrylate, propylaminoethyl acrylate, dimethylaminoethyl methacrylate, methacrylic acid Ethylaminopropyl acid, cyclohexylaminoethyl methacrylate, N-vinyldiethylamine, N-acetylvinylamine, allylamine, metaallylamine, N-methylallylamine, 2-isopropenyl-oxazoline, 2- Vinyl-oxazoline, 2-acryloyl-oxazoline, N-phenylmaleimide, phenylaminoethyl methacrylate, styrene, α-methylstyrene, p-glycidylstyrene, p-aminostyrene, 2-styryl -oxazoline, etc. are mentioned. These may be used independently and may be used together. The type, number, combination, content ratio, and the like of the other vinylic monomer units may be appropriately set according to the purpose.

The weight average molecular weight of the acrylic resin is preferably 1000 to 2000000, more preferably 5000 to 1000000, still more preferably 10000 to 500000, particularly preferably 50000 to 500000, and most preferably 60000 to 150000. A weight average molecular weight can be calculated|required by polystyrene conversion using, for example, a gel permeation chromatography (GPC system, Tosoh Corporation). In addition, tetrahydrofuran can be used as a solvent.

The acrylic resin may be polymerized by any suitable polymerization method using an appropriate combination of the above monomer units.

In embodiment of this invention, you may use together acrylic resin and other resin. That is, the monomer component constituting the acrylic resin and the monomer component constituting the other resin may be copolymerized, and the copolymer may be used for forming a protective layer described later; A blend of an acrylic resin and another resin may be used for forming the protective layer. Examples of other resins include thermoplastics such as styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, and the like. and resin. The kind and compounding quantity of resin used together can be set suitably according to the objective, characteristics desired for the film obtained, etc. For example, a styrenic resin (preferably an acrylonitrile-styrene copolymer) may be used in combination as a retardation controlling agent.

When the acrylic resin and other resin are used together, the content of the acrylic resin in the blend of the acrylic resin and other resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight to 100% by weight, still more preferably preferably 70% to 100% by weight, particularly preferably 80% to 100% by weight. When content is less than 50 weight%, there exists a possibility that the high heat resistance which an acrylic resin originally has and high transparency may not fully be reflected.

B-3-2. Photo-cation cured product of epoxy resin

In one embodiment, the protective layer is composed of a photocationically cured product of an epoxy resin. By using such a protective layer, the polarizing plate which made the outstanding durability and the outstanding flexibility compatible, and the polarizing plate with retardation layer can be provided. As described above, since the protective layer is a photocationically cured product, the composition for forming a protective layer contains a photocationic polymerization initiator. A photocationic polymerization initiator is a photosensitizer which has the function of a photo-acid generator, and the ionic onium salt which consists of a cation part and an anion part is typically mentioned. In this onium salt, the cation moiety absorbs light, and the anion moiety serves as a source of acid. Ring-opening polymerization of an epoxy group advances by the acid which generate|occur|produced from this photocationic polymerization initiator. The protective layer, which is the obtained photocationically cured product, has a high glass transition temperature, so that the amount of iodine adsorption can be reduced. Therefore, the polarizing plate which can make the outstanding durability and the outstanding flexibility compatible can be provided.

B-3-2-1. epoxy resin

Any suitable epoxy resin can be used as an epoxy resin. In embodiment of this invention, Preferably the epoxy resin which has at least 1 sort(s) selected from the group which consists of aromatic skeleton and hydrogenated aromatic skeleton can be used. As aromatic skeleton, a benzene ring, a naphthalene ring, a fluorene ring, etc. are mentioned, for example. Only 1 type may be used for an epoxy resin, and may be used in combination of 2 or more type. Preferably, an epoxy resin having a biphenyl skeleton is used as the aromatic skeleton. By using the epoxy resin which has a biphenyl skeleton, the polarizing plate which makes the more excellent durability and the more outstanding flexibility compatible can be provided. Hereinafter, an epoxy resin having a biphenyl skeleton as a representative example will be described in detail.

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin comprising the following structure. Only 1 type may be used for the epoxy resin which has a biphenyl skeleton, and may be used in combination of 2 or more type.

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

R ¹⁴ to R ²¹ 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. Examples of the linear or branched substituted or unsubstituted hydrocarbon group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n- pentyl group, isopentyl group, neopentyl group, tert-pentyl group, cyclopentyl group, n-hexyl group, isohexyl group, cyclohexyl group, n-heptyl group, cycloheptyl group, methylcyclohexyl group, n-oxyl group Tyl group, cyclooctyl group, n-nonyl group, 3,3,5-trimethylcyclohexyl group, n-decyl group, cyclodecyl group, n-undecyl group, n-dodecyl group, cyclododecyl group, phenyl group, benzyl group, A methylbenzyl group, a dimethylbenzyl group, a trimethylbenzyl group, a naphthylmethyl group, a phenethyl group, 2-phenylisopropyl group, etc. are mentioned. As a C1-C12 linear or branched substituted or unsubstituted hydrocarbon group, Preferably, a C1-C4 alkyl group, such as a methyl group, an ethyl group, n-propyl group, isopropyl group, and n-butyl group, is mentioned. As a halogen element, Preferably, fluorine and bromine are mentioned.

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

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

In one embodiment, the epoxy resin having a biphenyl skeleton is an epoxy resin having only a biphenyl skeleton. By using the epoxy resin which has only a biphenyl skeleton, the durability of the protective layer obtained can further be improved.

In one embodiment, the epoxy resin which has a biphenyl skeleton may contain chemical structures other than a biphenyl skeleton. As a chemical structure other than a biphenyl skeleton, a bisphenol skeleton, an alicyclic structure, an aromatic ring structure, etc. are mentioned, for example. In this embodiment, it is preferable that the ratio (molar ratio) of chemical structures other than a biphenyl skeleton is less than a biphenyl skeleton.

As an epoxy resin which has a biphenyl skeleton, you may use a commercial item. As a commercial item, the Mitsubishi Chemical company make, brand name: jER YX4000, jER YX4000H, jER YL6121, jER YL664, jER YL6677, jER YL6810, jER YL7399 etc. are mentioned, for example.

The epoxy resin having a biphenyl skeleton preferably has a glass transition temperature (Tg) of 90°C or higher. As a result, the Tg of the protective layer becomes 90°C or higher. When Tg of the epoxy resin which has a biphenyl skeleton is 90 degreeC or more, the polarizing plate containing the protective layer obtained will become the thing excellent in durability easily. Tg of the epoxy resin which has a biphenyl skeleton becomes like this. Preferably it is 100 degreeC or more, More preferably, it is 110 degreeC or more, More preferably, it is 120 degreeC or more, Especially preferably, it is 125 degreeC or more. On the other hand, Tg of the epoxy resin having a biphenyl skeleton is preferably 300°C or less, more preferably 250°C or less, still more preferably 200°C or less, particularly preferably 160°C or less. If the Tg of the epoxy resin having a biphenyl skeleton is within such a range, moldability may be excellent.

The epoxy equivalent of the epoxy resin having a biphenyl skeleton is preferably 100 g/equivalent or more, more preferably 150 g/equivalent or more, and still more preferably 200 g/equivalent or more. Moreover, the epoxy equivalent of the epoxy resin which has a biphenyl skeleton becomes like this. Preferably it is 3000 g/equivalent or less, More preferably, it is 2500 g/equivalent or less, More preferably, it is 2000 g/equivalent or less. When the epoxy equivalent of the epoxy resin having a biphenyl skeleton is within the above range, a more stable protective layer (a protective layer with few residual monomers and sufficiently cured) is obtained. In addition, in this specification, "epoxy equivalent" means "the mass of an epoxy resin containing 1 equivalent of an epoxy group", and can be measured according to JISK7236.

In embodiment of this invention, you may use together the epoxy resin which has at least 1 sort(s) chosen from the group which consists of aromatic skeleton and hydrogenated aromatic skeleton, and other resin. That is, a blend of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton and another resin may be used for forming the protective layer. Examples of other resins include styrene-based resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, etc. A thermoplastic resin, an acrylic resin, an oxetane resin, etc. are mentioned. Preferably, an acrylic resin and an oxetane resin are used. The kind and compounding quantity of resin used together can be set suitably according to the objective, characteristics desired for the film obtained, etc. For example, a styrenic resin may be used together as a retardation controlling agent.

Any suitable acrylic resin can be used as acrylic resin. For example, as the (meth)acrylic compound, for example, a (meth)acrylic compound having one (meth)acryloyl group in the molecule (hereinafter also referred to as a 'monofunctional (meth)acrylic compound'), two or more (meth)acryloyl group in the molecule ) (meth)acrylic compounds having an acryloyl group (hereinafter also referred to as 'polyfunctional (meth)acrylic compounds') are mentioned. These (meth)acrylic compounds may be used independently and may be used in combination of 2 or more types. About these acrylic resins, it describes in Unexamined-Japanese-Patent No. 2019-168500, for example. As for the said publication, the description in its entirety is incorporated herein by reference.

As the oxetane resin, any suitable compound having one or more oxetanyl groups in the molecule is used. For example, 3-ethyl-3-hydroxymethyloxetane, 3-ethyl-3-(2-ethylhexyloxymethyl)oxetane, 3-ethyl-3-(phenoxymethyl)oxetane, 3-ethyl-3 -(cyclohexyloxymethyl)oxetane, 3-ethyl-3-(oxiranylmethoxy)oxetane, (meth)acrylic acid (3-ethyloxetan-3-yl)methyl, etc. in the molecule of oxetanyl group 1 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; and the like. 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 can be easily obtained, and can be excellent in dilution (low viscosity) and compatibility.

In one embodiment, from the point of compatibility and adhesiveness, Preferably it has a molecular weight of 500 or less, and liquid oxetane resin is used at room temperature (25 degreeC). In one embodiment, preferably an oxetane compound containing two or more oxetanyl groups in the molecule, an oxetane compound containing one oxetanyl group and one (meth)acryloyl group or one epoxy group in the 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, sclerosis|hardenability and durability of a protective layer can be improved.

As oxetane resin, you may use a commercial item. Specifically, Aronoxetane OXT-101, Aronoxetane OXT-121, Aronoxetane OXT-212, and Aronoxetane OXT-221 (both manufactured by Agosei Co., Ltd.) can be used. Preferably, Aronoxetane OXT-101 and Aronoxetane OXT-221 can be used.

When an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton and another resin are used together, an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton The content of the epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton in a blend with another resin is preferably 50% by weight to 100% by weight, more preferably 60% by weight % to 100% by weight, more preferably 70% to 100% by weight, particularly preferably 80% to 100% by weight. When content is less than 50 weight%, there exists a possibility that the heat resistance of a protective layer and sufficient adhesiveness with a polarizer may not be acquired.

When using together an epoxy resin and oxetane resin having a biphenyl skeleton, the content of the oxetane resin is preferably 1 part by weight to 50 parts by weight with respect to 100 parts by weight of the total amount of the epoxy resin and oxetane resin having a biphenyl skeleton. It is a weight part, More preferably, it is 5 weight part - 45 weight part, More preferably, it is 10 weight part - 40 weight part. By setting it as the said range, sclerosis|hardenability improves and the adhesiveness of a protective layer and a polarizer can also improve.

B-3-2-2. photo cationic polymerization initiator

A photocationic polymerization initiator is a photosensitizer which has the function of a photoacid generator, and the ionic onium salt which consists of a cation part and an anion part is typically mentioned. In this onium salt, the cation moiety absorbs light, and the anion moiety serves as a source of acid. Ring-opening polymerization of an epoxy group advances by the acid which generate|occur|produced from this photocationic polymerization initiator. As the photocationic polymerization initiator, any suitable compound capable of curing an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton by irradiation with light such as ultraviolet rays can be used. Only 1 type may be used for a photocationic polymerization initiator, and may be used in combination of 2 or more type.

Examples of the photocationic polymerization initiator include triphenylsulfonium hexafluoroantimonate, triphenylsulfonium hexafluorophosphate, p-(phenylthio)phenyldiphenylsulfoniumhexafluoroantimonate, and 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.

As a photocationic polymerization initiator, you may use a commercial item. As a commercial item, SP-170 of a triphenylsulfonium salt type hexafluoroantimonate type (made by ADEKA), CPI-101A (made by San Apro Corporation), WPAG-1056 (made by Wako Pure Chemical Industries, Ltd.), diphenyl iodonium WPI-116 (manufactured by Wako Pure Chemical Industries, Ltd.) of the salt-based hexafluoroantimonate type; and the like.

Content of a photocationic polymerization initiator with respect to 100 weight part of epoxy resins which has at least 1 sort(s) selected from the group which consists of an aromatic skeleton and hydrogenated aromatic skeleton, Preferably it is 0.1 weight part - 3 weight part, More preferably 0.25 parts by weight to 2 parts by weight. When content of a photocationic polymerization initiator is less than 0.1 weight part, even if it irradiates light (ultraviolet rays), it may not fully harden|cure.

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

In one embodiment, the protective layer is composed of a solidified product of a coating film of an organic solvent solution of an epoxy resin.

B-3-3-1. epoxy resin

In this embodiment, the epoxy resin preferably has a glass transition temperature (Tg) of 90°C or higher. As a result, the Tg of the protective layer becomes 90°C or higher. When Tg of an epoxy resin is 90 degreeC or more, the polarizing plate containing the protective layer obtained from such resin tends to be excellent in durability. Tg of the epoxy resin is preferably 100°C or higher, more preferably 110°C or higher, still more preferably 120°C or higher, and particularly preferably 125°C or higher. On the other hand, Tg of an epoxy resin becomes like this. Preferably it is 300 degrees C or less, More preferably, it is 250 degrees C or less, More preferably, it is 200 degrees C or less, Especially preferably, it is 160 degrees C or less. If the Tg of the epoxy resin is within such a range, moldability may be excellent.

As the epoxy resin, any suitable epoxy resin may be employed as long as it has the above Tg. The epoxy resin typically refers to a resin having an epoxy group in its molecular structure. As the epoxy resin, preferably, an epoxy resin having an aromatic ring in the molecular structure is 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. Only 1 type may be used for an epoxy resin, and may be used in combination of 2 or more type. 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.

Specific examples of the epoxy resin having an aromatic ring in the molecular structure include bisphenol A diglycidyl ether type epoxy resin, bisphenol F diglycidyl ether type epoxy resin, bisphenol S diglycidyl ether type epoxy resin, resorcindi Glycidyl ether type epoxy resin, hydroquinone diglycidyl ether type epoxy resin, terephthalic acid diglycidyl ester type epoxy resin, bisphenoxyethanol fluorenedi glycidyl ether type epoxy resin, bisphenol fluorenediglycy an epoxy resin having two epoxy groups, such as a dilether type epoxy resin and a biscresol fluorenediglycidyl ether type epoxy resin; 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; and epoxy resins having four epoxy groups, such as glycidylamine-type epoxy resins (eg, diaminodiphenylmethane-type, diaminodiphenylsulfone-type, meta-xylenediamine-type). Moreover, you may use glycidyl ester type epoxy resins, such as a hexahydro phthalic anhydride type epoxy resin, a tetrahydro phthalic anhydride type epoxy resin, a dimer acid type epoxy resin, and a p-oxybenzoic acid type|mold.

The weight average molecular weight of the epoxy resin is preferably 1000 to 2000000, more preferably 5000 to 1000000, still more preferably 10000 to 500000, particularly preferably 50000 to 500000, and most preferably 60000 to 150000. A weight average molecular weight can be calculated|required by polystyrene conversion using, for example, a gel permeation chromatography (GPC system, Tosoh Corporation). In addition, tetrahydrofuran can be used as a solvent.

The epoxy equivalent of an epoxy resin becomes like this. Preferably it is 1000 g/equivalent or more, More preferably, it is 3000 g/equivalent or more, More preferably, it is 5000 g/equivalent or more. Moreover, the epoxy equivalent of an epoxy resin becomes like this. Preferably it is 30000 g/equivalent or less, More preferably, it is 25000 equivalent or less, More preferably, it is 20000 g/equivalent or less. When the epoxy equivalent is in the above range, a more stable protective layer is obtained. In addition, in this specification, "epoxy equivalent" means "the mass of an epoxy resin containing 1 equivalent of an epoxy group", and can be measured according to JISK7236.

In embodiment of this invention, you may use together an epoxy resin and other resin. That is, a blend of an epoxy resin and another resin may be used for forming the protective layer. Examples of other resins include thermoplastics such as styrene resins, polyethylene, polypropylene, polyamide, polyphenylene sulfide, polyether ether ketone, polyester, polysulfone, polyphenylene oxide, polyacetal, polyimide, polyetherimide, and the like. and resin. The kind and compounding quantity of resin used together can be set suitably according to the objective, characteristics desired for the film obtained, etc. For example, a styrenic resin may be used together as a phase difference controlling agent.

When using an epoxy resin and another resin together, content of the epoxy resin in the blend of an epoxy resin and another resin becomes like this. Preferably it is 50 weight% - 100 weight%, More preferably, it is 60 weight% - 100 weight%, further Preferably it is 70 weight% - 100 weight%, Especially preferably, it is 80 weight% - 100 weight%. When content is less than 50 weight%, there exists a possibility that the heat resistance of a protective layer and sufficient adhesiveness with a polarizer may not be acquired.

B-3-4. Composition and properties of the protective layer

In one embodiment, as described above, the protective layer is selected from the group consisting of a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, a photocationically cured product of an epoxy resin, and a solidified product of a coating film of an organic solvent solution of an epoxy resin. It is composed of at least one selected type. If it is such a protective layer, compared with an extrusion film, thickness can be made thin remarkably. The thickness of the protective layer is 10 μm or less as described above. Also, although it is not clear theoretically, such a protective layer exhibits smaller shrinkage during film molding compared to cured products of other thermosetting resins or active energy ray-curable resins (eg, ultraviolet curable resins), and does not contain residual monomers. It has the advantage that deterioration of the film itself is suppressed, and the bad influence to the polarizing plate (polarizer) resulting from a residual monomer etc. can be suppressed. In addition, since hygroscopicity and moisture permeability are small compared to a solidified product of an aqueous coating film such as an aqueous solution or an aqueous dispersion, it has the advantage of excellent humidification durability. As a result, it is possible to realize a polarizing plate having excellent durability that can maintain optical properties even in a heating and humidifying environment.

Tg of the protective layer is the same as described for the acrylic resin and the epoxy resin, respectively.

The protective layer is preferably substantially optically isotropic. In the present specification, 'substantially optically isotropic' means that the in-plane retardation Re (550) is 0 nm to 10 nm, and the retardation Rth (550) in the thickness direction is -20 nm to +10 nm. The in-plane retardation Re(550) is more preferably 0 nm to 5 nm, still more preferably 0 nm to 3 nm, and particularly preferably 0 nm to 2 nm. The retardation Rth (550) in the thickness direction is more preferably -5 nm to +5 nm, still more preferably -3 nm to +3 nm, and particularly preferably -2 nm to +2 nm. When Re(550) and Rth(550) of the protective layer are within such ranges, adverse effects on display characteristics can be prevented when a polarizing plate including the protective layer is applied to an image display device. In addition, Re(550) is the in-plane retardation of the film measured with the light of wavelength 550nm at 23 degreeC. Re(550) is obtained by the formula: Re(550)=(nx-ny)×d. Rth (550) is the retardation in the thickness direction of the film measured with light having a wavelength of 550 nm at 23°C. Rth(550) is obtained by the formula: Rth(550)=(nx-nz)×d. Here, nx is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction), ny is the refractive index in the direction orthogonal to the slow axis in the plane (ie, the fast axis direction), and nz is the refractive index in the thickness direction and d is the thickness (nm) of the film.

The higher the light transmittance at 380 nm in the thickness of the protective layer 3 µm, the more preferable. Specifically, the light transmittance is preferably 85% or more, more preferably 88% or more, still more preferably 90% or more. If the light transmittance is within such a range, desired transparency can be ensured. The light transmittance can be measured, for example, by a method according to ASTM-D-1003.

The lower the haze of the protective layer, the more preferable. Specifically, the haze is preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, particularly preferably 1% or less. When the haze is 5% or less, a good feeling of clearness can be imparted to the film. Moreover, even when using for the visual recognition side polarizing plate of an image display apparatus, display content can be visually recognized favorably.

YI in the thickness of 3 micrometers of a protective layer becomes like this. Preferably it is 1.27 or less, More preferably, it is 1.25 or less, More preferably, it is 1.23 or less, Especially preferably, it is 1.20 or less. When YI exceeds 1.3, optical transparency may become inadequate. In addition, YI is obtained by the following formula according to the tristimulus values (X, Y, Z) of the color obtained by measurement using, for example, a high-speed integrating sphere type spectral transmittance meter (trade name: DOT-3C: manufactured by Murakami Color Technology Lab). can

YI=[(1.28X-1.06Z)/Y]×100

The b-value (a color scale according to Hunter's color system) at a thickness of 3 µm of the protective layer is preferably less than 1.5, more preferably 1.0 or less. When the b value is 1.5 or more, an undesired color may appear. In addition, the b value is, for example, a sample of the film constituting the protective layer is cut to 3 cm square, and the color is measured using a high-speed integrating sphere type spectral transmittance meter (trade name DOT-3C: Murakami Color Technology Research Institute), and the corresponding color can be obtained by evaluating according to the Hunter's color space system.

A protective layer (for example, the solidified material of a coating film, or photocationic hardened|cured material) may contain arbitrary appropriate additives according to the objective. Specific examples of the additive include a UV absorber; leveling agent; antioxidants such as hindered phenolic, phosphorus, and sulfur; Stabilizers, such as a light stabilizer, a weathering stabilizer, and a heat stabilizer; Reinforcing materials, such as glass fiber and carbon fiber; near infrared absorbers; flame retardants such as tris (dibromopropyl) phosphate, triallyl phosphate, and antimony oxide; antistatic agents such as anionic, cationic, and nonionic surfactants; colorants such as inorganic pigments, organic pigments, and dyes; organic or inorganic fillers; resin modifiers; organic or inorganic fillers; plasticizer; lubricant; antistatic agent; A flame retardant etc. are mentioned. An additive may be added at the time of superposition|polymerization of an acrylic resin, and may be added to a solution at the time of film formation. The type, number, combination, addition amount, etc. of the additives may be appropriately set according to the purpose.

An easily adhesive layer may be formed in the polarizer side of a protective layer. The easily adhesive layer contains, for example, a water-based polyurethane and an oxazoline-based crosslinking agent. By providing such an easily bonding layer, the adhesiveness of a protective layer and a polarizer can be improved. Moreover, the hard-coat layer may be formed in the protective layer. Further, when the hard coat layer is formed, the hard coat layer may be formed such that the sum of the thickness of the protective layer (eg, the solidified product of the coating film) and the thickness of the hard coat layer is 10 µm or less. The hard coat layer may be formed when the protective layer is used as a protective layer on the viewer side of the viewer side polarizing plate. When both the easily adhesive layer and the hard coat layer are formed, typically they may each be formed on different sides of the protective layer.

C. First retardation layer

The first retardation layer 20 is an alignment-solidified layer of the liquid crystal compound as described above. By using the liquid crystal compound, the difference between nx and ny of the retardation layer obtained can be significantly increased compared to that of a non-liquid crystal material, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be remarkably reduced. As a result, further thinning and weight reduction of the polarizing plate with a retardation layer can be implement|achieved. In the present specification, the term "alignment-solidified layer" refers to a layer in which the liquid crystal compound is oriented in a predetermined direction in the layer and the alignment state is fixed. In addition, the "orientation-solidified layer" is a concept including the orientation hardening layer obtained by hardening a liquid crystal monomer so that it may mention later. In this embodiment, the rod-shaped liquid crystal compounds are typically oriented in a line in the slow axis direction of the first retardation layer (homogeneous alignment).

As a liquid crystal compound, the liquid crystal compound (nematic liquid crystal) whose liquid crystal phase is a nematic phase is mentioned, for example. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The liquid crystal expression mechanism of the liquid crystal compound may be either lyotropic or thermotropic. A liquid crystal polymer and a liquid crystal monomer may be used individually, respectively, and may be combined.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (ie, curing) the liquid crystal monomer. After aligning the liquid crystal monomers, for example, by polymerizing or crosslinking the liquid crystal monomers, the alignment state can thereby be fixed. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystalline. Accordingly, in the formed first phase difference layer, for example, transition to a liquid crystal phase, a glass phase, and a crystal phase due to a temperature change peculiar to the liquid crystal compound does not occur. As a result, the first retardation layer becomes a retardation layer that is not affected by temperature changes and is extremely excellent in stability.

The temperature range in which the liquid crystal monomer exhibits liquid crystallinity differs depending on the type thereof. Specifically, the said temperature range becomes like this. Preferably it is 40 degreeC - 120 degreeC, More preferably, it is 50 degreeC - 100 degreeC, More preferably, it is 60 degreeC - 90 degreeC.

As the liquid crystal monomer, any suitable liquid crystal monomer may be employed. For example, the polymerizable mesogenic compounds described in Japanese Patent Application Publication Nos. 2002-533742 (WO00/37585), EP358208 (US5211877), EP66137 (US4388453), WO93/22397, EP0261712, DE19504224, DE4408171 and GB2280445, etc. can be used. Specific examples of such a polymerizable mesogenic compound include LC242 by BASF, trade name E7 by Merck, and LC-Sillicon-CC3767 by Wacker-Chem. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment-solidified layer of the liquid crystal compound is formed by performing an alignment treatment on the surface of a predetermined substrate, coating the surface with a coating solution containing a liquid crystal compound to align the liquid crystal compound in a direction corresponding to the alignment treatment, and the alignment It can be formed by fixing the state. In one embodiment, the substrate is any suitable resin film, and the alignment-solidifying layer formed on the substrate can be transferred to the surface of the polarizing plate 10 . In another embodiment, the substrate may be the second protective layer 13 . In this case, the transfer step is omitted, and since lamination can be performed by roll-to-roll successively from the formation of the orientation-solidified layer (first retardation layer), productivity is further improved.

As the alignment treatment, any appropriate alignment treatment may be employed. Specifically, a mechanical orientation process, a physical orientation process, and a chemical orientation process are mentioned. As a specific example of a mechanical orientation process, a rubbing process and an extending|stretching process are mentioned. As a specific example of a physical orientation process, a magnetic field orientation process and an electric field orientation process are mentioned. As a specific example of a chemical orientation process, an oblique vapor deposition method and a photo-alignment process are mentioned. Any suitable conditions may be employed as the treatment conditions for various orientation treatments depending on the purpose.

The alignment of the liquid crystal compound is performed by processing at a temperature showing a liquid crystal phase depending on the kind of the liquid crystal compound. By performing such a temperature treatment, a liquid crystal compound takes a liquid crystal state, and the said liquid crystal compound orientates according to the orientation treatment direction of the surface of a base material.

In one embodiment, fixing of an orientation state is performed by cooling the liquid crystal compound orientated as mentioned above. When the liquid crystal compound is a polymerizable monomer or a crosslinkable monomer, the alignment state is fixed by subjecting the liquid crystal compound aligned as described above to a polymerization treatment or a crosslinking treatment.

The specific example of a liquid crystal compound and the detail of the formation method of an orientation-solidified layer are described in Unexamined-Japanese-Patent No. 2006-163343. The disclosure of this publication is incorporated herein by reference.

As another example of the alignment-solidified layer, a form in which the discotic liquid crystal compound is oriented in any one of a vertical alignment, a hybrid alignment, and an oblique direction is exemplified. Typically, in the discotic liquid crystal compound, the disk plane of the discotic liquid crystal compound is oriented substantially perpendicular to the film plane of the first retardation layer. When the discotic liquid crystal compound is substantially perpendicular, the average value of the angle between the film plane and the disk plane of the discotic liquid crystal compound is preferably 70° to 90°, more preferably 80° to 90°, still more preferably means 85° to 90°. In general, a discotic liquid crystal compound has a cyclic parent nucleus such as benzene, 1,3,5-triazine, calixarene, etc. arranged at the center of the molecule, and a straight-chain alkyl group, alkoxy group, substituted benzoyloxy group, etc. is a side chain thereof It refers to a liquid crystal compound having a radially substituted disk-shaped molecular structure. As a representative example of a discotic liquid crystal, a study report by C. Destrade et al., Mol. Crystal. Liq. Crystal. Benzene derivatives, triphenylene derivatives, truxene derivatives, phthalocyanine derivatives, and research reports by B. Kohne et al., Angew. Chem. cyclohexane derivatives described in Vol. 96, p. 70 (1984), and a study report by J. M. Lehn et al., J. Chem. Soc. Chem. Commun., pp. 1794 (1985), a study report by J. Zhang et al., J. Am. Chem. Soc. and macrocycles of the azacrown type or phenylacetylene type described in Volume 116, page 2655 (1994). As a further specific example of a discotic liquid crystal compound, the compound of Unexamined-Japanese-Patent No. 2006-133652, Unexamined-Japanese-Patent No. 2007-108732, and Unexamined-Japanese-Patent No. 2010-244038 is mentioned, for example. The descriptions of these documents and publications are incorporated herein by reference.

In one embodiment, the 1st retardation layer 20 is a single layer of the alignment solidification layer of a liquid crystal compound as shown to FIG. 1 and FIG. When the 1st retardation layer 20 is comprised with the single layer of the alignment-solidified layer of a liquid crystal compound, the thickness becomes like this. Preferably it is 0.5 micrometer - 7 micrometers, More preferably, it is 1 micrometer - 5 micrometers. By using a liquid crystal compound, the in-plane retardation equivalent to a resin film can be implement|achieved with thickness remarkably thinner than a resin film.

The first retardation layer typically has a refractive index characteristic of nx>ny=nz. The first retardation layer is typically provided to impart antireflection properties to the polarizing plate, and when the first retardation layer is a single layer of the alignment solidification layer, it may function as a λ/4 plate. In this case, the in-plane retardation Re (550) of the first 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, here, 'ny=nz' includes not only the case where ny and nz are completely equal, but also the case where ny and nz are substantially equal. Therefore, there may be a case where ny>nz or ny<nz is not impaired in the effect of the present invention.

The Nz coefficient of the first retardation layer is preferably 0.9 to 1.5, more preferably 0.9 to 1.3. By satisfying such a relationship, when the obtained polarizing plate with retardation layer is used for an image display apparatus, the very excellent reflection hue can be achieved.

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

The angle θ between the slow axis of the first retardation layer 20 and the absorption axis of the polarizer 11 is preferably 40° to 50°, more preferably 42° to 48°, further preferably about 45°. If the angle θ is within such a range, a polarizing plate with a retardation layer having very excellent circular polarization characteristics (as a result, very excellent antireflection characteristics) is obtained by using the first retardation layer as a λ/4 plate as described above. can get

In another embodiment, the first retardation layer 20 may have a stacked structure of the first alignment-solidified layer 21 and the second alignment-solidified layer 22 as shown in FIG. 3 . In this case, either one of the first alignment-solidified layer 21 and the second alignment-solidified layer 22 can function as a λ/4 plate, and the other can function as a λ/2 plate. Accordingly, the thicknesses of the first alignment-solidified layer 21 and the second alignment-solidified layer 22 can be adjusted so that a desired in-plane retardation of the λ/4 plate or the λ/2 plate is obtained. For example, when the first orientation-solidified layer 21 functions as a λ/2 plate and the second orientation-solidified layer 22 functions as a λ/4 plate, the thickness of the first orientation-solidified layer 21 is, for example, 2.0 It is a micrometer - 3.0 micrometers, and the thickness of the 2nd orientation-solidified layer 22 is 1.0 micrometer - 2.0 micrometers, for example. In this case, the in-plane retardation Re(550) of the first alignment-solidified layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, and still more preferably 250 nm to 280 nm. The in-plane retardation Re(550) of the second alignment-solidified layer is the same as described above with respect to the single-layered alignment-solidified layer. The angle between the slow axis of the first alignment-solidified layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, and still more preferably about 15°. The angle between the slow axis of the second alignment-solidified layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, and still more preferably about 75°. With such a configuration, it is possible to obtain a characteristic close to the ideal reverse wavelength dispersion characteristic, and as a result, a very excellent antireflection characteristic can be realized. The liquid crystal compound constituting the first alignment-solidified layer and the second alignment-solidified layer, the method of forming the first alignment-solidified layer and the second alignment-solidified layer, and optical properties are as described above for the single-layered alignment-solidified layer.

D. Second retardation layer

As described above, the second retardation layer may be a so-called positive C plate having a refractive index characteristic of nz>nx=ny. By using the positive C plate as the second retardation layer, reflection in the oblique direction can be prevented favorably, and the wide viewing angle of the antireflection function can be increased. In this case, the retardation Rth (550) in the thickness direction of the second retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, further preferably -90 nm to -200 nm, particularly preferably is -100 nm to -180 nm. Here, 'nx=ny' includes not only the case where nx and ny are strictly equal, but also the case where nx and ny are substantially equal. That is, the in-plane retardation Re (550) of the second retardation layer may be less than 10 nm.

The second retardation layer having a refractive index characteristic of nz>nx=ny may be formed of any suitable material. The second retardation layer preferably comprises a film comprising a liquid crystal material fixed in homeotropic orientation. The liquid crystal material (liquid crystal compound) capable of homeotropic alignment may be a liquid crystal monomer or a liquid crystal polymer. Specific examples of the liquid crystal compound and the method for forming the retardation layer include the liquid crystal compound described in [0020] to [0028] of Japanese Patent Application Laid-Open No. 2002-333642 and a method for forming the retardation layer. In this case, the thickness of the second retardation layer is preferably 0.5 µm to 10 µm, more preferably 0.5 µm to 8 µm, and still more preferably 0.5 µm to 5 µm.

E. Conductive layer or isotropic substrate with conductive layer

The conductive layer may be formed by depositing a metal oxide film on any suitable substrate by any suitable film forming method (eg, vacuum vapor deposition, sputtering, CVD, ion plating, spraying, etc.). Examples of the metal oxide include indium oxide, tin oxide, zinc oxide, indium-tin composite oxide, tin-antimony composite oxide, zinc-aluminum composite oxide, and indium-zinc composite oxide. Among them, indium-tin composite oxide (ITO) is preferable.

When a conductive layer contains a metal oxide, the thickness of this conductive layer becomes like this. Preferably it is 50 nm or less, More preferably, it is 35 nm or less. The thickness of the conductive layer is preferably 10 nm or more.

The conductive layer may be transferred from the substrate to the first retardation layer (or the second retardation layer if present), and the conductive layer alone may be a constituent layer of a polarizing plate with a retardation layer, or a laminate with a substrate (with a conductive layer). As a base material), it may be laminated on the first retardation layer (or the second retardation layer if present). Preferably, the substrate is optically isotropic, and therefore the conductive layer can be used in a polarizing plate with a retardation layer as an isotropic substrate with a conductive layer.

As the optically isotropic substrate (isotropic substrate), any suitable isotropic substrate can be employed. As a material constituting the isotropic substrate, for example, a material having a main skeleton of a resin having no conjugated system such as norbornene-based resin or olefin-based resin, or having a cyclic structure such as a lactone ring or a glutarimide ring in the main chain of an acrylic resin materials, and the like. When such a material is used, when an isotropic base material is formed, the expression of the phase difference accompanying the orientation of molecular chains can be suppressed small. The thickness of the isotropic substrate is preferably 50 µm or less, and more preferably 35 µm or less. The thickness of the isotropic substrate is, for example, 20 µm or more.

The conductive layer and/or the conductive layer of the isotropic substrate with the conductive layer may be patterned as necessary. A conductive portion and an insulating portion may be formed by patterning. As a result, an electrode can be formed. The electrode may function as a touch sensor electrode that senses a contact to the touch panel. Any suitable method can be employ|adopted as a patterning method. Specific examples of the patterning method include a wet etching method and a screen printing method.

F. Image display device

The polarizing plate with a retardation layer as described in item A to E above can be applied to an image display device. Accordingly, the present invention includes an image display device using such a polarizing plate with a retardation layer. As representative examples of the image display device, a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device, an inorganic EL display device) are mentioned. The image display apparatus which concerns on embodiment of this invention equips the visual recognition side with the said polarizing plate with a retardation layer as described in the said A to E terms. The polarizing plate with a retardation layer is laminated|stacked so that a retardation layer may become an image display cell (for example, liquid crystal cell, organic electroluminescent cell, inorganic EL cell) side (a polarizer may become a visual recognition side). In one embodiment, the image display device has a curved shape (substantially curved display screen) and/or is bendable or bendable. In such an image display apparatus, the effect of the polarizing plate with retardation layer of this invention becomes remarkable.

Example

Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by these Examples. The measuring method of each characteristic is as follows. In addition, unless otherwise specified, 'part' and '%' in Examples and Comparative Examples are based on weight.

[Example 1]

1. Fabrication of polarizer

As the thermoplastic resin substrate, an amorphous isophthalic copolymerized polyethylene terephthalate film (thickness: 100 µm) having a long water absorption rate of 0.75% and a 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.

Potassium iodide 13 in 100 parts by weight of a PVA-based resin in which polyvinyl alcohol (polymerization degree 4200, saponification degree 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Nihon Kosei Chemical Industry Co., Ltd., trade name 'Kosefimer Z410') were mixed at 9:1 A weight part was added, and the PVA aqueous solution (coating liquid) was prepared.

On the corona-treated surface of the resin substrate, the PVA aqueous solution was applied and dried at 60° C. to form a PVA-based resin layer with a thickness of 12 μm to prepare a laminate.

The obtained laminate was uniaxially stretched at the free end at a length of 2.4 times in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds in an oven at 130°C (air-assisted stretching treatment).

Next, the laminate was immersed in an insolubilization bath (a 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).

Then, in a dyeing bath (aqueous iodine solution obtained by mixing iodine and potassium iodide in a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30° C. so that the single transmittance (Ts) of the finally obtained polarizer is 41.8% It was immersed for 60 seconds while adjusting the density|concentration (dyeing process).

Next, 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) with a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, while the laminate was immersed in an aqueous boric acid solution (boric acid concentration of 4.0 wt%, potassium iodide 5.0 wt%) having a liquid temperature of 62°C, the total draw ratio was 3.0 in the longitudinal direction (longitudinal direction) between rolls having different circumferential speeds. Uniaxial stretching was performed so that it might be doubled (underwater stretching treatment: the draw ratio in the underwater stretching treatment was 1.25 times).

Then, the laminated body was immersed in the washing|cleaning bath (aqueous solution obtained by mix|blending 4 weight part of potassium iodide with respect to 100 weight part of water) with a liquid temperature of 20 degreeC (washing process).

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 ratio in the width direction of the laminate by the drying shrinkage treatment was 2%.

In this way, the 6.9-micrometer-thick polarizer was formed on the resin base material.

2. Fabrication of polarizing plate

A water-based polyurethane resin (manufactured by Daiichi Kogyo Pharmaceutical Co., Ltd., trade name: Super Flex 210-R) was dissolved in a mixed solvent of pure water and isopropyl alcohol, and the resulting solution was applied to the surface of the polarizer formed on the resin substrate obtained above. Then, the solvent was removed by drying at 60° C. to form an easily adhesive layer having a thickness of 0.15 μm. 20 parts of an acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Chemical Co., Ltd., trade name: B728) was dissolved in 80 parts of methyl ethyl ketone to obtain an acrylic resin solution (20%). This acrylic resin solution was applied to the easily adhesive layer using a wire bar, and the coating film was dried at 60° C. for 5 minutes to form an acrylic resin layer constituted as a solidified product of the coating film. The thickness of the acrylic resin layer was 2 micrometers, and Tg was 111 degreeC. Then, 70 parts by weight of dimethylol-tricyclodecanediacrylate (manufactured by Kyoeisha Chemical, trade name: light acrylate DCP-A), isobornyl acrylate (manufactured by Kyoeisha Chemical, 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 (manufactured by BASF, trade name: Irgacure) 907) 3 parts by weight were mixed in a solvent to obtain a coating solution. The obtained coating liquid was apply|coated on the said protective layer so that it might become 3 micrometers after hardening. Then, the solvent was dried, and ultraviolet rays were irradiated in a nitrogen atmosphere so that the accumulated light amount was 300 mJ/cm ² using a high-pressure mercury lamp to form a hard coat layer. The thickness of the hard-coat layer was 3 micrometers. Next, in order to perform the bonding operation|work with the subsequent retardation layer stably, the adhesive layer of a polyethylene terephthalate (PET) film with an adhesive layer was bonded together to a protective layer, and it reinforced. Then, the resin base material was peeled and the polarizing plate which has the structure of PET film with an adhesive layer / protective layer (hard-coat layer / acrylic resin layer (solidified material of a coating film) / easily adhesive layer / polarizer) was obtained.

3. Preparation of the first alignment-solidified layer and the second alignment-solidified layer constituting the retardation layer

10 g of a polymerizable liquid crystal exhibiting a nematic liquid crystal phase (manufactured by BASF: trade name 'Paliocolor LC242', represented by the following formula), and a photopolymerization initiator for the polymerizable liquid crystal compound (manufactured by BASF: trade name 'Irugacure 907') 3 g was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating solution).

The PET film (thickness 38 micrometers) surface was rubbed using the rubbing cloth, and orientation treatment was performed. The direction of orientation treatment was made so that it might become a 15 degree direction as seen from the visual recognition side with respect to the direction of the absorption axis of a polarizer, when bonding it together to a polarizing plate. The liquid crystal compound was orientated by coating the said liquid-crystal coating liquid on the surface of this orientation treatment with a bar coater, and heat-drying at 90 degreeC for 2 minute(s). The liquid crystal layer formed in this way was irradiated with light of 100 mJ/cm ² using a metal halide lamp to cure the liquid crystal layer, thereby forming the liquid crystal alignment solidified layer A on the PET film. The thickness of the liquid-crystal alignment solidification layer A was 2.5 micrometers, and the in-plane retardation Re(550) was 270 nm. Moreover, the liquid-crystal orientation solidification layer A had refractive index distribution of nx>ny=nz.

It carried out similarly to the above, and formed the liquid-crystal orientation solidification layer B on the PET film except having changed the coating thickness and having made the orientation treatment direction a 75 degree direction as seen from the visual side with respect to the direction of the absorption axis of a polarizer. The thickness of the liquid-crystal alignment solidification layer B was 1.3 micrometers, and the in-plane retardation Re(550) was 140 nm. Moreover, the liquid-crystal orientation solidification layer B had refractive index distribution of nx>ny=nz.

4. Preparation of polarizing plate with retardation layer

On the polarizer surface of the polarizing plate obtained in said 2., the liquid-crystal orientation solidified layer A and the liquid-crystal orientation solidified layer B obtained in said 3. were transcribe|transferred in this order. At this time, transfer (bonding) was performed so that the angle between the absorption axis of the polarizer and the slow axis of the alignment-solidified layer A was 15°, and the angle formed between the absorption axis of the polarizer and the slow axis of the alignment-solidified layer B was 75°. In addition, each transcription|transfer (bonding) was performed through the ultraviolet curing adhesive agent (1.0 micrometer in thickness) used in said 2. Next, the PET film with an adhesive layer was peeled. In this way, the protective layer (hard coat layer / acrylic resin layer (solidified product of the coating film)) / easily adhesive layer / polarizer / adhesive layer / retardation layer (first orientation solidified layer / adhesive layer / second orientation solidified layer) phase difference having the configuration A polarizing plate with a layer was obtained. The total thickness of the obtained polarizing plate with retardation layer was 18 micrometers.

[Example 2]

A polarizer having a thickness of 6.4 µm was obtained in the same manner as in Example 1 except that the draw ratio of the underwater stretching treatment was 1.46 times and the total draw ratio was 3.5 times. Except having used the obtained polarizer, it carried out similarly to Example 1, and obtained the polarizing plate 2 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 17 micrometers.

[Example 3]

The draw ratio of the underwater stretching process was 1.67 times, and except having made the total draw ratio 4.0 times, it carried out similarly to Example 1, and obtained the 6.0-micrometer-thick polarizer. Except having used the obtained polarizer, it carried out similarly to Example 1, and obtained the polarizing plate 3 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 17 micrometers.

[Example 4]

Except having made the draw ratio of an underwater extending|stretching process into 1.88 times and having made the total draw ratio into 4.5 times, it carried out similarly to Example 1, and obtained the polarizer with a thickness of 5.6 micrometers. Except having used the obtained polarizer, it carried out similarly to Example 1, and obtained the polarizing plate 4 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 16 micrometers.

[Example 5]

Example 2 except for using an acrylic resin (30 mol% of lactone ring unit) that is polymethyl methacrylate having a lactone ring unit instead of an acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Chemical Co., Ltd., trade name: B728) It carried out similarly to and obtained the polarizing plate 5 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 17 micrometers.

[Example 6]

Instead of an acrylic resin having a methyl methacrylate unit (manufactured by Kusumoto Chemical Co., Ltd., trade name: B728), an acrylic resin that is a polymethyl methacrylate having a glutarimide ring unit (4 mol% of glutarimide ring units) was used. Except for that, it carried out similarly to Example 5, and obtained the polarizing plate 6 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 17 micrometers.

[Example 7]

Instead of the acrylic resin solution, 20 parts of an epoxy resin (manufactured by Mitsubishi Chemical Co., Ltd., trade name: jER (registered trademark) YX6954BH30, weight average molecular weight: 36,000, epoxy equivalent: 13000) were dissolved in 80 parts of methyl ethyl ketone, an epoxy resin solution (20%) ), except that a protective layer constituted as a solidified product of the coating film was formed, a hard coat layer was not formed, and an easily adhesive layer was not formed in the polarizer, in the same manner as in Example 5 to produce a polarizing plate with a retardation layer did Specifically, this epoxy resin solution was applied directly to the polarizer using a wire bar, and the coating film was dried at 60° C. for 3 minutes to form a protective layer. The thickness of the protective layer was 3 μm, and the Tg was 130°C. In this way, except having provided the protective layer, it carried out similarly to Example 5, and obtained the polarizing plate 7 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 15 micrometers.

[Example 8]

A polarizing plate 8 with a retardation layer was obtained in the same manner as in Example 2 except that the protective layer was formed as follows, the easily adhesive layer was not formed in the polarizer, and the hard coat layer was not formed. The total thickness of the obtained polarizing plate with retardation layer was 15 micrometers.

15 parts of an epoxy resin having a biphenyl skeleton (manufactured by Mitsubishi Chemical, trade name: jER (registered trademark) YX4000) was dissolved in 83.8 parts of methyl ethyl ketone to obtain an epoxy resin solution. To the obtained epoxy resin solution, 1.2 parts of a photocationic polymerization initiator (manufactured by San Apro, trade name: CPI (registered trademark)-100P) was added to obtain a composition for forming a protective layer. The obtained composition for forming a protective layer was directly applied to the polarizer using a wire bar, and the coating film was dried at 60°C for 3 minutes. Then, a protective layer was formed by irradiating ultraviolet light using a high-pressure mercury lamp so that the amount of accumulated light was 600 mJ/cm ² . The thickness of the protective layer was 3 μm.

[Example 9]

A polarizing plate 9 with a retardation layer was obtained in the same manner as in Example 8 except that a bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical, trade name: jER (registered trademark) 828) was used instead of the epoxy resin having a biphenyl skeleton. The total thickness of the obtained polarizing plate with retardation layer was 15 micrometers.

[Example 10]

A polarizing plate with a retardation layer 10 was prepared in the same manner as in Example 8 except that a hydrogenated bisphenol-type epoxy resin (manufactured by Mitsubishi Chemical, trade name: jER (registered trademark) YX8000) was used instead of the epoxy resin having a biphenyl skeleton. got it The total thickness of the obtained polarizing plate with retardation layer was 15 micrometers.

[Example 11]

15 parts of hydrogenated bisphenol epoxy resin (manufactured by Mitsubishi Chemical, trade name: jER (registered trademark) YX8000) and 10 parts by weight of oxetane resin (manufactured by Toagosei, trade name: Aronoxetane (registered trademark) OXT-221) methyl ethyl It was made to melt|dissolve in 73 parts of ketones, and the epoxy resin solution was obtained. To the obtained epoxy resin solution, 2 parts of a photocationic polymerization initiator (manufactured by San Apro, trade name: CPI (registered trademark)-100P) was added to obtain a composition for forming a protective layer. Except having used the obtained protective layer formation composition, it carried out similarly to Example 8, and obtained the polarizing plate 11 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 15 micrometers.

[Example 12]

Except having set the thickness of the protective layer to 8 micrometers, it carried out similarly to Example 11, and obtained the polarizing plate 12 with retardation layer.

[Example 13]

Except having made the thickness of a protective layer into 10 micrometers, it carried out similarly to Example 11, and obtained the polarizing plate 13 with retardation layer.

[Example 14]

A protective layer (cured product) was formed in the same manner as in Example 8 except that an ultraviolet curable epoxy resin (manufactured by Daicel, product name 'Celoxide 2021P') was used. Specifically, a composition containing 95% by weight of the epoxy resin and 5% by weight of a photopolymerization initiator (CPI-100P, manufactured by San Apro) is applied on the easily adhesive layer, and accumulated light quantity is 500mJ/ by using a high-pressure mercury lamp in an air atmosphere. A cured layer (protective layer) was formed by irradiating UV rays at cm ² . Except having used this protective layer, it carried out similarly to Example 2, and produced the polarizing plate with retardation layer. The thickness of the polarizing plate was 15 µm.

(Comparative Example 1)

In preparation of the polarizer, in the same manner as in Example 1, except that the draw ratio of the underwater stretching treatment was 2.3 times, the total draw ratio was 5.5 times, and the liquid temperature of the stretching bath was 70° C., a polarizer having a thickness of 5.1 μm was obtained . A polarizing plate C1 with a retardation layer was obtained in the same manner as in Example 1 except that an acrylic resin film having a thickness of 40 µm was laminated on the surface of the obtained polarizer via an ultraviolet curing adhesive to form a protective layer. The total thickness of the obtained polarizing plate with retardation layer was 52 micrometers.

(Comparative Example 2)

As a protective layer, except having used the 20-micrometer-thick acrylic film, it carried out similarly to the comparative example 1, and obtained the polarizing plate C2 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 32 micrometers.

(Comparative Example 3)

Except having used the polarizer obtained in the comparative example 1, it carried out similarly to Example 1, and obtained the polarizing plate C3 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 16 micrometers.

(Comparative Example 4)

In preparation of a polarizer, except having made the liquid temperature of the extending|stretching bath of an underwater stretching process into 64 degreeC, it carried out similarly to the comparative example 1, and obtained the 5.1-micrometer-thick light polarizer. Except having used the obtained polarizer, it carried out similarly to the comparative example 3, and obtained the polarizing plate C4 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 16 micrometers.

(Comparative Example 5)

It carried out similarly to Example 7, except having formed the protective layer, it carried out similarly to the comparative example 3, and obtained the polarizing plate C5 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 14 micrometers.

(Comparative Example 6)

It carried out similarly to Example 8, and except having formed the protective layer, it carried out similarly to the comparative example 3, and obtained the polarizing plate C6 with retardation layer. The total thickness of the obtained polarizing plate with retardation layer was 14 micrometers.

[evaluation]

The following evaluation was performed using the polarizing plate with retardation layer obtained by the Example and the comparative example. A result is shown in Table 1.

(1) thickness

The thickness of the polarizer 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. In addition, the thickness of the protective layer was measured by appropriately selecting the calculated wavelength range and refractive index using an interference film thickness measuring meter (manufactured by Otsuka Electronics, product name 'MCPD-3000'). The thickness of the easily adhesive layer was calculated|required from scanning electron microscope (SEM) observation. The thickness exceeding 10 μm was measured using a digital micrometer (manufactured by Anritsu Corporation, product name 'KC-351C').

(2) orientation function

For the polarizers used in Examples and Comparative Examples, a Fourier transform infrared spectrophotometer (FT-IR) (manufactured by Perkin Elmer, trade name: 'Frontier') was used, and the polarized infrared light was used as measurement light. , atenuateted total reflection (ATR) measurement of the surface of the polarizer was performed. Germanium was used for the crystallizer to adhere the polarizer, and the incident angle of the measurement light was set to 45°. The orientation function was calculated in the following procedure. The incident polarized infrared light (measurement light) is polarized light (s-polarized light) that vibrates parallel to the surface on which the sample of the germanium crystal is in close contact, and the direction of elongation of the polarizer is perpendicular to the polarization direction of the measurement light (⊥) and Each absorbance spectrum was measured in a state arranged in parallel (//). From the obtained absorbance spectrum, (2941 cm ^-1 intensity) I was calculated with reference to (3330 cm ^-1 intensity). I _⊥ is (2941 cm ⁻¹ intensity)/(3330 cm ⁻¹ intensity) obtained from the absorbance spectrum obtained when the elongation direction of the polarizer is perpendicular (⊥) 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 extending direction of the polarizer is arranged parallel (//) with respect to the polarization direction of the measurement light. Here, (2941 cm ^-1 intensity) is the absorbance at 2941 cm ^-1 when 2770 cm ^-1 and 2990 cm ^-1 , which are the bottoms of the absorbance spectrum, are used as baselines, and (3330 cm ^-1 intensity) is 2990 The absorbance is 3330 cm ^-1 when cm ^-1 and 3650 cm ^-1 are used as baselines. Using the obtained I _⊥ and I _// , the orientation function (f) was calculated according to Equation 1. Also, when f=1, it is fully oriented, and when f=0, it becomes random. In addition, the peak at 2941 cm ^-1 is called absorption due to vibration of the main chain (-CH ₂ -) of PVA in the polarizer. In addition, the peak at 3330 cm ^-1 is called absorption due to vibration of the hydroxyl group of PVA.

(Equation 1) f=(3<cos ² θ>-1)/2

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

only

c=(3cos ² β-1)/2

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

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

β: angle of 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 elongation direction of the polarizer are perpendicular

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

(3) crack rate

The polarizing plate with retardation layer obtained in the Example and the comparative example was cut out to 10 mm x 10 mm size. The cut-off polarizing plate with a retardation layer was affixed to the glass plate (1.1 mm in thickness) through the 20-micrometer-thick acrylic adhesive layer. After putting the sample affixed on the glass plate in 100 degreeC oven for 120 hours, the presence or absence of the crack generation in the absorption axis direction (MD direction) of a polarizer was visually confirmed visually. This evaluation was performed using the polarizing plate with retardation layer of 3 sheets, and the number of the polarizing plate with retardation layer which a crack generate|occur|produced was evaluated.

(4) bending resistance

The polarizing plate with retardation layer obtained in the Example and the comparative example was cut out to 50 mm x 100 mm size. At this time, it cut so that the absorption axis direction of a polarizer might become a long side direction. Using a bending tester (manufactured by Yuasa Systems Co., Ltd., product name: DLDM111LH), the cut out polarizing plate with a retardation layer was subjected to a bending test at room temperature. Specifically, for a polarizing plate with a retardation layer, a bending diameter of 1 mmφ (R is 0.5 mm) under the condition of a rotation speed of 60 rpm in the absorption axis direction so that the retardation layer side is the inner side and the protective layer or the hard coat layer formed on the protective layer is the outer side was set, and the polarizing plate with a retardation layer was bent 50,000 times. Next, the presence or absence of the crack of the polarizing plate with retardation layer after a test was visually confirmed, and the thing by which a crack could not be confirmed was made into good thing and the thing by which a crack was confirmed was made into impossibility. Further, the bending direction is the transmission axis direction of the polarizer.

(5) Single transmittance and polarization degree

Using a UV/visible spectrophotometer (manufactured by Nippon Bunko, product name 'V-7100') for the polarizer (single polarizer) in which the resin substrate was peeled and removed from the polarizer / thermoplastic resin substrate laminate used in Examples and Comparative Examples The measured single transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) were respectively taken as Ts, Tp, and Tc of the polarizer. These Ts, Tp, and Tc are Y values which measured by the 2 degree field of view (C light source) of JIS Z8701, and performed the visibility correction|amendment.

From the obtained Tp and Tc, the polarization degree (P) was calculated|required by the following formula.

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

(6) piercing strength

The polarizer was peeled from the polarizer/thermoplastic resin substrate-based laminate used in Examples and Comparative Examples, and placed in a compression tester equipped with a needle (manufactured by Kato Tech, product name 'NDG5' needle penetrating force measurement specification), and placed at room temperature (23 ° C.) ±3°C) environment, the piercing speed was 0.33 cm/sec, and the strength when the polarizer was cracked was defined as the breaking strength (piercing 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 0.5R was used. About the polarizer to be measured, the jig which has a circular opening part with a diameter of about 11 mm was pinched|interposed from both surfaces of the polarizer, and it fixed, and the test was performed by stabbing a needle in the center of the opening part.

As is evident from Table 1, in the polarizing plates with retardation layer of Examples 1 to 14, crack generation was suppressed even when subjected to heat treatment. Moreover, it was excellent also in the durability at the time of bending.

The polarizing plate with a retardation layer of this invention is used suitably for an image display apparatus.

10 Polarizer
11 Polarizer
12 first protective layer
13 second protective layer
20 retardation layer
100 Polarizing plate with retardation layer
101 Polarizing plate with retardation layer
102 Polarizing plate with retardation layer

Claims (9)

A polarizer and a polarizing plate including a protective layer disposed on one side of the polarizer, and a retardation layer,
The polarizer is composed of a polyvinyl alcohol-based resin film, and the orientation function of polyvinyl alcohol is 0.30 or less,
The retardation layer is an alignment-solidified layer of the liquid crystal compound,
The thickness of the said protective layer is 10 micrometers or less, The polarizing plate with retardation layer. A polarizer and a polarizing plate including a protective layer disposed on one side of the polarizer, and a retardation layer,
The piercing strength of the polarizer is 30 gf / μm or more,
The retardation layer is an alignment-solidified layer of the liquid crystal compound,
The thickness of the said protective layer is 10 micrometers or less, The polarizing plate with retardation layer. 3. The method of claim 1 or 2,
A polarizing plate with a retardation layer whose total thickness is 30 micrometers or less. 4. The method according to any one of claims 1 to 3,
The polarizing plate with a retardation layer whose thickness of the said polarizer is 10 micrometers or less. 5. The method according to any one of claims 1 to 4,
A polarizing plate with a retardation layer, wherein the polarizer has a single transmittance of 40.0% or more and a polarization degree of 99.0% or more. 6. The method according to any one of claims 1 to 5,
The protective layer is composed of at least one selected from the group consisting of a solidified product of a coating film of an organic solvent solution of a thermoplastic acrylic resin, a photocationically cured product of an epoxy resin, and a solidified product of a coating film of an organic solvent solution of an epoxy resin, Polarizing plate with retardation layer. 7. The method of claim 6,
A polarizing plate with a retardation layer, wherein the thermoplastic acrylic resin has at least one repeating unit selected from the group consisting of a lactone ring unit, glutaric anhydride unit, glutarimide unit, maleic anhydride unit and maleimide unit. 7. The method of claim 6,
The polarizing plate with a retardation layer, wherein the protective layer is a photocationically cured product of an epoxy resin having at least one selected from the group consisting of an aromatic skeleton and a hydrogenated aromatic skeleton. The image display device containing the polarizing plate with retardation layer in any one of Claims 1-8.

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