KR20230029665A - Polarizing plate with retardation layer, and image display device using the same - Google Patents

Abstract

The present invention provides a polarizing plate with a retardation layer that is thin and suppresses cracking during heating. A polarizing plate with a retardation layer of the present invention includes a polarizing plate including a polarizer, and a retardation layer provided on one side of the polarizing plate, and the polarizing plate includes a protective layer on the opposite side of the polarizer on which the retardation layer is provided. It does not, and the said retardation layer is an orientation hardening layer of a liquid crystal compound. In one embodiment, the polarizer is composed of a PVA-based resin film containing a dichroic material, the single transmittance is x%, and the birefringence of the PVA-based resin is y, the following formula (1) meets In another embodiment, the polarizer is composed of a PVA-based resin film containing a dichroic material, the single transmittance is x%, and the in-plane retardation of the PVA-based resin film is znm, the following formula (2) is satisfied. Further, in another embodiment, the polarizer is composed of a PVA-based resin film containing a dichroic material, the single transmittance is x%, and when the orientation function of the PVA-based resin is f, the following formula (3) is satisfied. Further, in another embodiment, the polarizer is composed of a PVA-based resin film containing a dichroic material, and has a puncture strength of 30 gf/m or more.
y<-0.011x+0.525 (1)
z<-60x+2875 (2)
f<-0.018x+1.11 (3)

Description

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

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

In recent years, image display devices typified by liquid crystal display devices and electroluminescence (EL) display devices (eg, organic EL display devices and inorganic EL display devices) are rapidly spreading. A polarizing plate and a retardation plate including a polarizer and a protective layer that protects the polarizer are usually used in the image display device. In practical terms, a polarizing plate with a retardation layer in which a polarizing plate and a retardation plate are integrated is widely used (for example, Patent Document 1). In recent years, along with the increase in the demand for thickness reduction of image display devices, the demand for thickness reduction is also increasing for polarizing plates with retardation layers.

As a method of reducing the thickness of the polarizing plate, reducing the thickness of the protective layer and laminating the protective layer only on one side of the polarizer have been proposed. However, in these methods, there is a problem that the polarizer cannot be sufficiently protected, there is room for improvement in durability, and cracks easily occur in the polarizer due to heat treatment.

Japanese Unexamined Patent Publication No. 2001-343521

The present invention has been made to solve the above conventional problems, and its main object is to provide a polarizing plate with a retardation layer in which cracking during heating is suppressed while being thin.

According to one aspect of the present invention, a polarizing plate including a polarizer, and a retardation layer provided on one side of the polarizing plate, and the polarizing plate includes a protective layer on the opposite side of the polarizer on which the retardation layer is provided. The retardation layer is an orientation-fixed layer of a liquid crystal compound, the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, and the polyvinyl alcohol-based polarizer is made of a dichroic substance. A polarizing plate with a retardation layer that satisfies the following formula (1) when the birefringence of the resin is y is provided.

y<-0.011x＋0.525　　　　　　　　　(1)

According to another aspect of the present invention, a polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate is included, and the polarizing plate does not include a protective layer on the opposite side of the polarizer on which the retardation layer is provided. , the retardation layer is an orientation-solidified layer of a liquid crystal compound, the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, the polyvinyl alcohol-based resin A polarizing plate with a retardation layer that satisfies the following formula (2) when the in-plane retardation of the film is znm is provided.

z<-60x＋2875　　　　　　　　　(2)

According to another aspect of the present invention, a polarizing plate including a polarizer, and a retardation layer provided on one side of the polarizing plate, wherein the polarizing plate includes a protective layer on the opposite side of the polarizer on which the retardation layer is provided. The retardation layer is an orientation-fixed layer of a liquid crystal compound, the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, and the single transmittance is x%, and the polyvinyl alcohol-based polarizer is made of a dichroic substance. A polarizing plate with a retardation layer that satisfies the following formula (3) when the orientation function of the resin is set to f is provided.

f<-0.018x＋1.11　　　　　(3)

According to another aspect of the present invention, a polarizing plate including a polarizer, and a retardation layer provided on one side of the polarizing plate, wherein the polarizing plate includes a protective layer on the opposite side of the polarizer on which the retardation layer is provided. However, a polarizing plate with a retardation layer is provided in which the retardation layer is an alignment-fixed layer of a liquid crystal compound and the puncture strength of the polarizer is 30 gf/m or more.

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

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

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

In another situation of this invention, the image display apparatus containing the said polarizing plate with a retardation layer is provided.

According to the present invention, by using a polarizer in which the orientation state of a polyvinyl alcohol (PVA)-based resin is controlled, even if a protective layer is not provided on at least one side of the polarizer, generation of cracks during heating can be suppressed. As a result, a polarizing plate with a retardation layer can be obtained that is extremely thin and suppressed from cracking during heating. Moreover, such a polarizer can exhibit practically acceptable optical characteristics.

1A is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
1B is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
1C is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
1D is a schematic cross-sectional view of a polarizing plate with a retardation layer according to one embodiment of the present invention.
Fig. 2 is a schematic view showing an example of drying shrinkage treatment using a heating roll in the manufacturing method of a polarizer used for a polarizing plate with a retardation layer of the present invention.
3 : is a figure which shows the relationship between the single transmittance of the polarizer produced by the Example and the comparative example, and the birefringence of PVA-type resin.
4 : is a figure which shows the relationship between the single transmittance of the polarizer produced by Example and a comparative example, and the in-plane retardation of a PVA-type resin film.
5 : is a figure which shows the relationship between the single transmittance of the polarizer produced by the Example and the comparative example, and the orientation function of PVA-type resin.

EMBODIMENT OF THE INVENTION Hereinafter, although embodiment of this invention is described, this invention is not limited to these embodiment. In addition, each embodiment can be combined suitably.

(Definition of Terms and Symbols)

Definitions of terms and symbols in this specification are as follows.

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

'nx' is the refractive index in the direction in which the in-plane refractive index is maximized (ie, the slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis within the plane (ie, the fast axis direction), and 'nz' is 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) can be obtained by the formula: Re(λ)=(nx-ny)×d when the thickness of the layer (film) is set to d(nm).

(3) Phase difference in thickness direction (Rth)

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

(4) Nz factor

The Nz coefficient can be obtained by Nz=Rth/Re.

(5) Angle

When an angle is referred to in this specification, the angle includes both clockwise and counterclockwise directions with respect to the reference direction. Thus, for example, '45°' means ±45°.

A. Overall configuration of polarizing plate with retardation layer

A polarizing plate with a retardation layer according to an embodiment of the present invention includes a polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate, and the retardation layer is an alignment-fixed layer of a liquid crystal compound. Schematic cross-sectional views of an example of a polarizing plate with a retardation layer according to an embodiment of the present invention are shown in FIGS. 1A to 1D, respectively.

A polarizing plate 100A with a retardation layer illustrated in FIG. 1A includes a polarizing plate 10 and a retardation layer 20 provided on one side thereof. The polarizing plate 10 includes the polarizer 11 and the protective layer 12 provided on the side of the retardation layer 20, and the protective layer is not provided on the side opposite to the side on which the retardation layer 20 is provided.

A polarizing plate 100B with a retardation layer illustrated in FIG. 1B includes a polarizing plate 10 and a retardation layer 20 provided on one side thereof. The polarizing plate 10 includes the polarizer 11, and no protective layer is provided on either side.

The polarizing plate 100C with a retardation layer illustrated in FIG. 1C includes a polarizing plate 10 and a retardation layer 20 provided on one side thereof. The polarizing plate 10 includes the polarizer 11, and no protective layer is provided on either side. The retardation layer 20 has a laminated structure of a first alignment-fixed layer 21 and a second alignment-fixed layer 22 .

1D 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 polarizing plate 100D with a retardation layer illustrated in FIG. 1D , in addition to the polarizing plate 10 and the retardation layer 20 (the first orientation-fixed layer 21 and the second orientation-fixed layer 22), another phase difference layer ( 30) and a conductive layer (or an isotropic substrate with a conductive layer) 40 are provided in this order on the opposite side of the phase difference layer 20 to the side where the polarizing plate 10 is provided. The other retardation layer 30 typically has a refractive index characteristic of nz>nx=ny. The other retardation layer 30 and the conductive layer (or the isotropic substrate with a conductive layer) 40 are typically arbitrary layers provided as needed, and any one or both of them may be omitted. For convenience, the retardation layer 20 is sometimes referred to as a first retardation layer and the other retardation layer 30 is referred to as a second retardation layer. In addition, when a conductive layer or an isotropic base material with a conductive layer is provided, the polarizing plate with a retardation layer is a so-called inner touch panel type input display in which a touch sensor is introduced between an image display cell (eg, an organic EL cell) and a polarizing plate. Applicable to devices.

The polarizing plate with a retardation layer according to the embodiment of the present invention may further contain other retardation layers. Other optical characteristics of the retardation layer (eg, refractive index characteristics, in-plane retardation, Nz coefficient, photoelastic coefficient), thickness, placement position, etc. may be appropriately set according to the purpose.

The polarizing plate with a retardation layer according to the embodiment of the present invention may be sheet-shaped or long-length. In the present specification, 'long' refers to an elongated shape having a sufficiently long length relative to the width, and includes, for example, an elongated shape having a length equal to or more than 10 times, preferably 20 times or more, relative to the width. A long polarizing plate with a retardation layer can be wound in a roll shape.

Practically, the outer surface of either one or both of the polarizing plate with a retardation layer, specifically, the outer surface of the polarizing plate with a retardation layer on the image display cell side and/or the opposite side (typically, the viewer side) has an adhesive layer. (not shown) is provided, and sticking to an adjacent member is possible. Moreover, it is preferable that the release film is temporarily attached to the surface of the pressure-sensitive adhesive layer until the polarizing plate with the retardation layer is put into use. Roll formation becomes possible while protecting an adhesive layer by temporarily attaching a peeling film.

The total thickness of the polarizing plate with the retardation layer is preferably 30 µm or less, more preferably 25 µm or less, still more preferably 20 µm or less. The total thickness may be, for example, 10 μm or more. According to the embodiment of the present invention, such an extremely thin polarizing plate with a retardation layer can be realized. Also, cracking during heating can be suppressed. Moreover, such a polarizing plate with a retardation layer can have extremely excellent flexibility and bending durability. Therefore, such a polarizing plate with a retardation layer can be particularly suitably applied to a curved image display device and/or a curved or bendable image display device. In addition, the total thickness of the polarizing plate with a retardation layer refers to the total thickness of all layers constituting the polarizing plate with a retardation layer, excluding the pressure-sensitive adhesive layer for adhering the polarizing plate with the retardation layer to an external adherend such as a panel or glass ( That is, the total thickness of the polarizing plate with a retardation layer does not include the thickness of the pressure-sensitive adhesive layer for attaching the polarizing plate with a retardation layer to an adjacent member such as an image display cell and a peeling film that can be attached to the surface thereof).

The basis weight of the polarizing plate with a retardation layer according to the 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 -5.5 mg/cm ² , more preferably 3.5 mg/cm ² -5.0 mg/cm ² . When the display panel is thin, the panel is slightly deformed by the weight of the polarizing plate with the retardation layer, and display defects may occur. According to the polarizing plate with a retardation layer having a basis 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-mentioned basis weight has good handleability even when it is reduced in thickness, and can exhibit extremely excellent flexibility and bending durability.

Hereinafter, the constituent elements of the polarizing plate with the retardation layer will be described in more detail.

B. Polarizer

A polarizing plate includes a polarizer composed of a PVA-based resin film containing a dichroic substance. The polarizing plate may or may not further include a protective layer on the side of the polarizer on which the retardation layer is provided, but does not include a protective layer on the side opposite to the side on which the retardation layer of the polarizer is provided. An extremely thin polarizing plate with a retardation layer can be obtained by omitting the protective layer on at least one side, preferably both sides, and employing an alignment-fixed layer of a liquid crystal compound as the retardation layer.

B-1. polarizer

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

y<-0.011x＋0.525　　　　　(1)

z<-60x＋2875　　　　　　　(2)

f<-0.018x＋1.11　　　　　 (3)

Birefringence of the PVA-based resin in the polarizer (hereinafter referred to as birefringence of PVA or Δn of PVA), in-plane retardation of the PVA-based resin film (hereinafter referred to as 'in-plane retardation of PVA'), orientation of the PVA-based resin Both the function (hereinafter referred to as 'PVA orientation function') and the stabbing strength of the polarizer are values related to the degree of orientation of the molecular chains of the PVA-based resin constituting the polarizer. Specifically, the birefringence of PVA, the in-plane retardation, and the orientation function may become large values as the degree of orientation increases, and the puncture strength may decrease as the degree of orientation increases. The polarizer used in the present invention (that is, the polarizer satisfying the above equations (1) to (3) or the stabbing strength) is due to the fact that the orientation of the molecular chain of the PVA-based resin in the direction of the absorption axis is gentler than that of conventional polarizers. Thus, heat shrinkage in the direction of the absorption axis is suppressed. As a result, a polarizing plate with a retardation layer can be obtained which is extremely thin and suppresses cracking during heating. In addition, since such a polarizer is also excellent in flexibility, it is possible to obtain a polarizing plate with a retardation layer excellent in flexibility and bending durability, preferably a curved image display device, more preferably a bendable image display device, still more preferably may be applied to a foldable image display device. Conventionally, it has been difficult to obtain acceptable optical properties (typically single transmittance and polarization degree) in a polarizer having a low degree of orientation. Therefore, the polarizer used in the present invention has a lower degree of orientation of PVA-based resin and acceptable optical properties than before. can be compatible.

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

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

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

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

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

In the present specification, the in-plane retardation of the PVA is the in-plane retardation value of the PVA-based resin film at 23° C. and a wavelength of 1000 nm. By setting the near-infrared region as the measurement wavelength, the influence of iodine absorption in the polarizer can be eliminated, and it becomes possible to measure the phase difference. In addition, the birefringence (in-plane birefringence) of the PVA is a value obtained by dividing the in-plane retardation of the PVA by the thickness of the polarizer.

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

R(λ)=A+B/(λ ² -600 ² )

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

Rpva=A

Ri =B/(λ ² -600 ² )

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

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

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

The orientation function (f) of the polarizer used in the present invention preferably satisfies the following formula (3a), and more preferably satisfies the following formula (3b). When the orientation function is too small, acceptable unit transmittance and/or polarization degree may not be obtained in some cases.

-0.01x+0.50<f<-0.018x+1.11 (3a)

-0.01x+0.57<f<-0.018x+1.1 (3b)

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

f=(3<cos ² θ>-1)/2

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

=-2×(1-D)/(2D+1)

step,

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

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

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

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

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

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

The thickness of the polarizer is preferably 10 μm or less, more preferably 8 μm or less. The lower limit of the thickness of the polarizer may be, for example, 1 μm. The thickness of the polarizer may be 2 μm to 10 μm in one embodiment, and 2 μm to 8 μm in another embodiment. By making the thickness of the polarizer very thin in this way, heat shrinkage can be made very small. It is speculated that such a configuration can also contribute to suppression of crack generation due to heating.

The polarizer preferably exhibits absorption dichroism at any wavelength of 380 nm to 780 nm. The single transmittance of the polarizer is preferably 40.0% or more, more preferably 41.0% or more. The upper limit of single transmittance may be, for example, 49.0%. The single transmittance of the polarizer is 40.0% to 45.0% in one embodiment. The degree of polarization of the polarizer is preferably 99.0% or more, more preferably 99.4% or more. The upper limit of the degree of polarization may be, for example, 99.999%. The degree of polarization of the polarizer is 99.0% to 99.9% in one embodiment. Although the polarizer used in the present invention has a lower degree of orientation of the PVA-based resin constituting the polarizer than before, and has the above in-plane retardation, birefringence and / or orientation function, such a practically acceptable single transmittance and polarization degree It is characterized by being able to realize. It is guessed that this originates in the manufacturing method mentioned later. Incidentally, the single transmittance is typically a Y value measured using an ultraviolet/visible ray spectrophotometer and corrected for visibility. In addition, when measuring the single transmittance of a polarizer using a polarizing plate having a configuration of [polarizer/resin substrate (protective layer)], the single transmittance of the polarizer is determined by setting the refractive index of one surface of the polarizing plate to 1.50 and the other surface of the polarizer. This is the value when the refractive index of is converted to 1.53. The degree of polarization can be obtained by the following formula, typically based on the parallel transmittance Tp and the orthogonal transmittance Tc measured using an ultraviolet/visible spectrophotometer and corrected for visibility.

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

The puncture strength of the polarizer is, for example, 30 gf/μm or more, preferably 35 gf/μm or more, more preferably 40 gf/μm or more, still more preferably 45 gf/μm or more, and particularly preferably 50 gf/μm or more. am. The upper limit of the piercing strength may be, for example, 80 gf/μm or less. By setting the puncture strength of the polarizer within such a range, it is possible to remarkably suppress generation of cracks in the polarizer during heating and tearing of the polarizer along the absorption axis direction. As a result, a polarizer (as a result, a polarizing plate) having very excellent flexibility can be obtained. The puncture strength represents the crack resistance of the polarizer when the polarizer is pierced with a predetermined strength. The puncture strength can be expressed as, for example, the strength at which the polarizer cracks (breaking strength) when a predetermined needle is attached to a compression tester and the needle is pierced into the polarizer at a predetermined speed. In addition, as is clear from the unit, the piercing strength means the piercing strength per unit thickness (1 μm) of the polarizer.

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

A polarizer can be typically manufactured using a laminate of two or more layers. As a specific example of the light polarizer obtained using a laminated body, the polarizer obtained using the laminated body of the resin base material and the PVA system resin layer applied and formed on the said resin base material is mentioned. A polarizer obtained by using a laminate of a resin substrate and a PVA-based resin layer coated and formed on the resin substrate, for example, by applying a PVA-based resin solution to the resin substrate, drying it, forming a PVA-based resin layer on the resin substrate, Obtaining a laminated body of a resin substrate and a PVA-based resin layer; It can be produced by: stretching and dyeing the layered product to make the PVA-based resin layer a polarizer. In this embodiment, preferably, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is formed on one side of the resin substrate. Stretching typically involves immersing the layered product in an aqueous solution of boric acid and extending the laminate. Further, the stretching preferably further includes air stretching the laminate at a high temperature (eg, 95° C. or higher) prior to stretching in an aqueous solution of boric acid. In the embodiment of the present invention, the total magnification of stretching is preferably 3.0 to 4.5 times, which is significantly smaller than usual. Even at such a total magnification of stretching, a polarizer having acceptable optical characteristics can be obtained by a combination of halide addition and drying shrinkage treatment. Further, in the embodiment of the present invention, the draw ratio of air assisted stretching is preferably greater than the draw ratio of stretching in boric acid water. By setting it as such a structure, even if the total magnification of extending|stretching is small, the polarizer which has acceptable optical characteristics can be obtained. Further, the laminate is preferably subjected to a drying shrinkage treatment in which it shrinks by 2% or more in the width direction by heating while conveying in the longitudinal direction. In one embodiment, the manufacturing method of a light polarizer includes giving a laminated body an air assisted stretching process, a dyeing process, an underwater stretching process, and a drying shrinkage process in this order. By introducing auxiliary stretching, even when the PVA-based resin is applied on a thermoplastic resin, it becomes possible to increase the crystallinity of the PVA-based resin and achieve high optical properties. In addition, by simultaneously increasing the orientation of the PVA-based resin in advance, problems such as deterioration in orientation and dissolution of the PVA-based resin when immersed in water in a subsequent dyeing step or stretching step can be prevented, and high optical properties can be obtained. it becomes possible to achieve Further, in the case where the PVA-based resin layer is immersed in a liquid, the disorder of the orientation of the polyvinyl alcohol molecules and the decrease in orientation can be suppressed compared to the case where the PVA-based resin layer does not contain a halide. Thereby, the optical characteristics of the polarizer obtained through the processing process performed by immersing a layered product in liquid, such as a dyeing process and an underwater extension process, can be improved. In addition, optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. The obtained laminate of the resin substrate/polarizer may be used as it is (that is, the resin substrate may be used as a protective layer for the polarizer), and the resin substrate is peeled from the laminate of the resin substrate/polarizer, and the peel surface is used for the purpose. Any suitable protective layer according to the above may be laminated and used. The details of the manufacturing method of the polarizer are described in detail in section B-2.

B-2. Manufacturing method of polarizer

The method for producing the polarizer is preferably to form a polyvinyl alcohol-based resin layer (PVA-based resin layer) containing a halide and a polyvinyl alcohol-based resin (PVA-based resin) on one side of a long thermoplastic resin substrate, Forming a laminate, and subjecting the laminate to an air-assisted stretching treatment, a dyeing treatment, an underwater stretching treatment, and a drying shrinkage treatment for shrinking by 2% or more in the width direction by heating while conveying in the longitudinal direction in this order. include The content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin. The drying shrinkage treatment is preferably performed using a heating roll, and the temperature of the heating roll is preferably 60°C to 120°C. The shrinkage rate in the width direction of the layered product by the drying shrinkage treatment is preferably 2% or more. In addition, the draw ratio of air assisted stretching is preferably larger than that of underwater stretching. According to such a manufacturing method, the polarizer described in the above section B-1 can be obtained. In particular, a laminate comprising a PVA-based resin layer containing a halide is produced, and stretching of the laminate is multi-step stretching including air-assisted stretching and underwater stretching, and the laminate after stretching is heated with a heating roll, and the width By shrinking by 2% or more in the direction, a polarizer having excellent optical properties (typically single transmittance and polarization degree) can be obtained.

B-2-1. Fabrication of the laminate

Arbitrary suitable methods can be adopted as a method of producing the laminated body of a thermoplastic resin base material and a PVA system resin layer. Preferably, a PVA-based resin layer is formed on the thermoplastic resin substrate by applying a coating liquid containing a halide and a PVA-based resin to the surface of the thermoplastic resin substrate and drying it. As described above, the content of the halide in the PVA-based resin layer is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

As a method of applying the coating liquid, any suitable method can be employed. For example, roll coating method, spin coating method, wire bar coating method, dip coating method, die coating method, curtain coating method, spray coating method, knife coating method (comma coating method etc.), etc. are mentioned. The coating/drying temperature of the coating liquid is preferably 50°C or higher.

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

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

B-2-1-1. Thermoplastic resin substrate

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

B-2-1-2. coating liquid

As described above, the coating liquid contains a halide and a PVA-based resin. The coating liquid is typically a solution obtained by dissolving the halide and the PVA-based resin in a solvent. Examples of the solvent include water, dimethylsulfoxide, dimethylformamide, dimethylacetamide, N-methylpyrrolidone, various glycols, polyhydric alcohols such as trimethylolpropane, and amines such as ethylenediamine and diethylenetriamine. can These can be used individually or in combination of 2 or more types. Among these, water is preferable. The concentration of the PVA-based resin in the solution is preferably 3 to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film adhering to the thermoplastic resin substrate can be formed. The content of the halide in the coating liquid is preferably 5 parts by weight to 20 parts by weight with respect to 100 parts by weight of the PVA-based resin.

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

As the PVA-based resin, any suitable resin can be employed. Examples include polyvinyl alcohol and ethylene-vinyl alcohol copolymers. Polyvinyl alcohol can be obtained by saponifying polyvinyl acetate. An ethylene-vinyl alcohol copolymer can be obtained by saponifying an ethylene-vinyl acetate copolymer. The degree of saponification of the PVA-based resin is usually 85 mol% to 100 mol%, preferably 95.0 mol% to 99.95 mol%, and more preferably 99.0 mol% to 99.93 mol%. The degree of saponification can be determined according to JIS K 6726-1994. A light polarizer excellent in durability can be obtained by using PVA-type resin of such a degree of saponification. When the saponification degree is too high, there exists a possibility of saponification. As described above, the PVA-based resin preferably includes an acetoacetyl-modified PVA-based resin.

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

As the halide, any suitable halide can be employed. Examples include iodide and sodium chloride. As iodide, potassium iodide, sodium iodide, and lithium iodide are mentioned, for example. Among these, potassium iodide is preferable.

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

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

B-2-2. Air Assisted Stretching Treatment

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

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

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

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

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

B-2-3. Insolubilization treatment, dyeing treatment and cross-linking treatment

If necessary, insolubilization treatment is performed after the air-assisted stretching treatment and before the underwater stretching treatment or the dyeing treatment. The insolubilization treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. The dyeing treatment is typically performed by dyeing the PVA-based resin layer with a dichroic substance (typically iodine). If necessary, a crosslinking treatment is performed after the dyeing treatment and before the underwater stretching treatment. The crosslinking treatment is typically performed by immersing the PVA-based resin layer in an aqueous solution of boric acid. Details of the insolubilization treatment, dyeing treatment, and crosslinking treatment are described, for example, in Japanese Unexamined Patent Publication No. 2012-73580.

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. . As a result, a polarizer having excellent optical properties can be manufactured.

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

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

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

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

The stretching temperature (liquid temperature of the stretching bath) is preferably 40°C to 85°C, more preferably 60°C to 75°C. At such a temperature, it can be extended at a high magnification while suppressing dissolution of the PVA-based resin layer. Specifically, as described above, the glass transition temperature (Tg) of the thermoplastic resin substrate is preferably 60°C or higher in relation to the formation of the PVA-based resin layer. In this case, if the stretching temperature is lower than 40°C, there is a risk that satisfactory stretching may not be possible even if plasticization of the thermoplastic resin substrate by water is taken into consideration. On the other hand, as the temperature of the stretching bath becomes higher, the solubility of the PVA-based resin layer increases, and there is a possibility that excellent optical properties may not be obtained. The immersion time of the laminate in the stretching bath is preferably 15 seconds to 5 minutes.

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

B-2-5. dry shrink treatment

The drying shrinkage treatment may be performed by zone heating performed by heating the entire zone, or may be performed by heating the conveying roll (using a so-called heating roll) (heating roll drying method). Preferably, both of them are used. By drying using a heating roll, heating curl of a layered product can be suppressed efficiently and a light polarizer excellent in external appearance can be manufactured. Specifically, by drying in a state where the laminate is attached to a heating roll, the crystallization of the thermoplastic resin substrate can be efficiently promoted to increase the crystallinity, and even at a relatively low drying temperature, the crystallinity of the thermoplastic resin substrate can be increased satisfactorily. can As a result, the rigidity of the thermoplastic resin base material is increased, and curling is suppressed in a state capable of withstanding shrinkage of the PVA-based resin layer due to drying. In addition, since it is possible to dry the layered product while maintaining it in a flat state by using a heating roll, not only curling but also occurrence of wrinkles can be suppressed. At this time, the optical properties can be improved by shrinking the laminate in the width direction by drying shrinkage treatment. This is because the orientation properties of PVA and PVA/iodine complexes can be effectively increased. The shrinkage in the width direction of the layered product by the drying shrinkage treatment is preferably 1% to 10%, more preferably 2% to 8%, and particularly preferably 4% to 6%.

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

Drying conditions can be controlled by adjusting the heating temperature of the conveying rolls (temperature of the heating rolls), the number of heating rolls, and the contact time with the heating rolls. The temperature of the heating roll is preferably 60°C to 120°C, more preferably 65°C to 100°C, and particularly preferably 70°C to 80°C. While the crystallinity of the thermoplastic resin can be increased satisfactorily and curling can be suppressed satisfactorily, an optical laminate having extremely excellent durability can be manufactured. In addition, the temperature of a heating roll can be measured with a contact thermometer. Although six conveyance rolls are provided in the illustrated example, there is no particular restriction as long as there are a plurality of conveyance rolls. The conveyance rolls are usually provided in 2 to 40 pieces, preferably 4 to 30 pieces. The contact time (total contact time) between the laminate and the heating roll is preferably 1 second to 300 seconds, more preferably 1 to 20 seconds, still more preferably 1 to 10 seconds.

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

B-2-6. other processing

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

B-3. protective layer

The protective layer may be formed of any suitable material depending on the purpose. Specific examples of the material for forming the protective layer include cellulose-based resins such as triacetyl cellulose (TAC), polyester-based, polyvinyl alcohol-based, polycarbonate-based, polyamide-based, polyimide-based, polyethersulfone-based, and polysulfone-based transparent resins such as polystyrene-based, polynorbornene-based, polyolefin-based, (meth)acrylic-based, and acetate-based; (meth)acrylic, urethane-based, (meth)acrylurethane-based, epoxy-based, silicone-based thermosetting resins or ultraviolet curable resins; Glassy type polymers, such as a siloxane type polymer, are mentioned.

The protective layer may be a resin film or a solidified material of a coating film of a resin solution. When a protective layer is a resin film, typically, a protective layer is bonded to a polarizer via an adhesive bond layer. Further, when the protective layer is a solidified product of a coating film of a resin solution, the protective layer may be formed by forming an easily adhesive layer on the surface of the polarizer, applying the resin solution thereon, and solidifying the coating film.

The thickness of the protective layer is preferably 2 μm to 80 μm, more preferably 5 μm to 40 μm, still more preferably 5 μm to 25 μm, still more preferably 5 μm to 20 μm.

The protective layer is preferably substantially optically isotropic. 'Substantially optically isotropic' in this specification means that the in-plane retardation Re (550) is 0 nm to 10 nm and the thickness direction retardation Rth (550) 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 phase difference 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. If Re (550) and Rth (550) of the protective layer are within these ranges, adverse effects on display characteristics can be prevented when a polarizing plate including the protective layer is applied to an image display device.

C. The first retardation layer

As described above, the first retardation layer 20 is an alignment hardening layer of a liquid crystal compound. By using a liquid crystal compound, the difference between nx and ny of the retardation layer obtained can be significantly increased compared to non-liquid crystal materials, so that the thickness of the retardation layer for obtaining a desired in-plane retardation can be significantly reduced. As a result, further thinning and weight reduction of the polarizing plate with the retardation layer can be realized. In this specification, the 'alignment fixed layer' refers to a layer in which liquid crystal compounds are aligned in a predetermined direction within the layer and the alignment state is fixed. In addition, the 'alignment hardened layer' is a concept including an alignment hardened layer obtained by curing a liquid crystal monomer as will be described later. In this embodiment, the rod-like liquid crystal compounds are typically aligned in a state aligned in the slow axis direction of the first retardation layer (homogeneous alignment).

Examples of the liquid crystal compound include a liquid crystal compound (nematic liquid crystal) in which the liquid crystal phase is a nematic phase. As such a liquid crystal compound, for example, a liquid crystal polymer or a liquid crystal monomer can be used. The mechanism for developing the liquid crystalline properties of the liquid crystal compound may be either lyotropic or thermotropic. The liquid crystal polymer and the liquid crystal monomer may be used alone or in combination.

When the liquid crystal compound is a liquid crystal monomer, the liquid crystal monomer is preferably a polymerizable monomer and a crosslinkable monomer. This is because the alignment state of the liquid crystal monomer can be fixed by polymerizing or crosslinking (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 be fixed accordingly. Here, a polymer is formed by polymerization and a three-dimensional network structure is formed by crosslinking, but these are non-liquid crystal. Therefore, the formed first retardation layer does not undergo transition into a liquid crystal phase, a glass phase, or a crystal phase due to a temperature change peculiar to a liquid crystal compound, for example. As a result, the first retardation layer becomes a retardation layer that is not affected by temperature change and has excellent stability.

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

As the liquid crystal monomer, any suitable liquid crystal monomer may be employed. For example, 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 can be used. Specific examples of such a polymerizable mesogenic compound include, for example, BASF's trade name LC242, Merck's trade name E7, and Wacker-Chem's trade name LC-Sillicon-CC3767. As the liquid crystal monomer, for example, a nematic liquid crystal monomer is preferable.

The alignment hardening layer of the liquid crystal compound is obtained by performing alignment treatment on the surface of a predetermined base material, coating the surface with a coating solution containing the liquid crystal compound, and orienting the liquid crystal compound in a direction corresponding to the orientation treatment, thereby aligning the alignment treatment. It can be formed by fixing the state. In one embodiment, the substrate is any suitable resin film, and the orientation hardening layer formed on the substrate can be transferred to the surface of the polarizing plate 10 . In other embodiments, the substrate may be the protective layer 12 . In this case, since the transfer process is omitted and lamination can be performed by roll-to-roll continuously from the formation of the orientation-fixed layer (first retardation layer), productivity is further improved.

As the orientation treatment, any appropriate orientation treatment may be employed. Specifically, a mechanical orientation treatment, a physical orientation treatment, and a chemical orientation treatment are mentioned. Specific examples of the mechanical orientation treatment include rubbing treatment and stretching treatment. Specific examples of the physical orientation treatment include magnetic field orientation treatment and electric field orientation treatment. Specific examples of the chemical orientation treatment include an oblique deposition method and an optical orientation treatment. Arbitrary appropriate conditions may be employed for the treatment conditions of various alignment treatments depending on the purpose.

Alignment of the liquid crystal compound is performed by treatment at a temperature exhibiting a liquid crystal phase depending on the type of the liquid crystal compound. By performing such a temperature treatment, the liquid crystal compound assumes a liquid crystal state, and the liquid crystal compound is oriented along the orientation treatment direction of the surface of the substrate.

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

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

Another example of the alignment hardening layer is a form in which the discotic liquid crystal compound is aligned in any one of vertical alignment, hybrid alignment, and oblique alignment. In the discotic liquid crystal compound, the disk surface of the discotic liquid crystal compound is typically aligned substantially perpendicular to the film surface 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°, and still more preferably means that it is 85 ° to 90 °. In discotic liquid crystal compounds, generally, a cyclic parent nucleus such as benzene, 1,3,5-triazine, calixarene, etc. is arranged at the center of the molecule, and a straight-chain alkyl group, alkoxy group, substituted benzoyloxy group, etc. are attached to the side chain thereof. It refers to a liquid crystal compound having a disk-shaped molecular structure substituted radially. Representative examples of discotic liquid crystals include a research report by C. Destrade et al., Mol. Cryst. Liq. Cryst. 71, page 111 (1981), benzene derivatives, triphenylene derivatives, thruxene derivatives, phthalocyanine derivatives, and research reports by B. Kohne et al., Angew. Chem. Cyclohexane derivatives described in Vol. 96, page 70 (1984), and the research report of J. M. Lehn et al., J. Chem. Soc. Chem. Commun., p. 1794 (1985), J. Zhang et al., J. Am. Chem. Soc. Azacrown type and phenylacetylene type macrocycles described in Volume 116, page 2655 (1994) are exemplified. As another specific example of the discotic liquid crystal compound, compounds described in, for example, Japanese Unexamined Patent Publication Nos. 2006-133652, 2007-108732, and 2010-244038 are exemplified. Descriptions of the above documents and publications are incorporated herein by reference.

In one embodiment, the 1st retardation layer 20 is a single layer of the alignment hardening layer of a liquid crystal compound, as shown to FIG. 1A and FIG. 1B. When the first retardation layer 20 is composed of a single layer of an orientation fixing layer of a liquid crystal compound, its thickness is preferably 0.5 μm to 7 μm, more preferably 1 μm to 5 μm. By using a liquid crystal compound, an in-plane retardation equivalent to that of a resin film can be achieved with a significantly thinner thickness than that of the 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 may function as a λ/4 plate when the first retardation layer is a single layer of an orientation hardening layer. 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. Also, here, 'ny=nz' includes not only the case where ny and nz are completely equal, but also the case where they are substantially equal. Therefore, there may be cases where ny>nz or ny<nz is satisfied within a range that does not impair 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 a retardation layer is used for an image display device, an extremely excellent reflected color can be achieved.

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

The 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°, still more preferably about It is 45°. When the angle θ is within this range, a polarizing plate with a retardation layer having extremely excellent circular polarization characteristics (as a result, excellent antireflection characteristics) can be obtained by using the λ/4 plate as the first retardation layer as described above.

In another embodiment, the first retardation layer 20 may have a laminated structure of a first alignment-fixed layer 21 and a second alignment-fixed layer 22, as shown in FIGS. 1C and 1D. In this case, one of the first alignment-fixed layer 21 and the second alignment-fixed 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-fixed layer 21 and the second alignment-fixed layer 22 can be adjusted so as to obtain a desired in-plane retardation of the λ/4 plate or the λ/2 plate. For example, when the first alignment-fixed layer 21 functions as a λ/2 plate and the second alignment-fixed layer 22 functions as a λ/4 plate, the thickness of the first alignment-fixed layer 21 is, for example, 2.0 μm to 3.0 μm, and the thickness of the second alignment-fixed layer 22 is, for example, 1.0 μm to 2.0 μm. In this case, the in-plane retardation Re(550) of the first alignment-fixed layer is preferably 200 nm to 300 nm, more preferably 230 nm to 290 nm, still more preferably 250 nm to 280 nm. The in-plane retardation Re (550) of the second alignment-hardened layer is as described above with respect to the single-layer alignment-hardened layer. The angle between the slow axis of the first alignment-fixed layer and the absorption axis of the polarizer is preferably 10° to 20°, more preferably 12° to 18°, still more preferably about 15°. The angle between the slow axis of the second alignment-fixed layer and the absorption axis of the polarizer is preferably 70° to 80°, more preferably 72° to 78°, still more preferably about 75°. With such a configuration, it is possible to obtain characteristics close to ideal reverse wavelength dispersion characteristics, and as a result, extremely excellent antireflection characteristics can be realized. The liquid crystal compounds constituting the first alignment fixed layer and the second alignment fixed layer, the formation method of the first alignment fixed layer and the second alignment fixed layer, optical properties, etc. are as described above with respect to the single-layer alignment fixed 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, it is possible to favorably prevent reflection in an oblique direction, and a wide viewing angle of the antireflection function becomes possible. In this case, the phase difference 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, still more preferably -90 nm to -200 nm, particularly preferably is -100 nm to -180 nm. Here, 'nx=ny' includes not only a case where nx and ny are strictly equal, but also a 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 includes a film containing a liquid crystal material fixed in a 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 Unexamined Patent Publication No. 2002-333642 and the 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, still more preferably 0.5 μm to 5 μm.

E. Conductive layer or isotropic substrate with conductive layer

The conductive layer can be formed by forming a metal oxide film on any suitable substrate by any suitable film formation method (eg, vacuum deposition method, sputtering method, CVD method, ion plating method, spray method, 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 preferred.

When the conductive layer contains a metal oxide, the thickness of the conductive layer is preferably 50 nm or less, more preferably 35 nm or less. The lower limit of the thickness of the conductive layer is preferably 10 nm.

The conductive layer may be transferred from the substrate to the first retardation layer (or, if present, the second retardation layer), and the conductive layer alone may become a constituent layer of a polarizing plate with a retardation layer, or a laminate with the substrate (with a conductive layer) substrate) 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 for 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 the material constituting the isotropic base material, for example, a material whose main skeleton is a resin without a conjugated system such as norbornene resin or olefin resin, and a cyclic structure such as lactone ring or glutarimide ring in the main chain of acrylic resin. Materials etc. are mentioned. When such a material is used, when an isotropic substrate is formed, the expression of phase difference accompanying orientation of molecular chains can be suppressed to a small level. The thickness of the isotropic substrate is preferably 50 μm or less, and more preferably 35 μm or less. The lower limit of the thickness of the isotropic substrate is, for example, 20 µm.

The conductive layer and/or the conductive layer of the isotropic substrate with a conductive layer may be patterned as needed. By patterning, a conductive portion and an insulating portion can be formed. As a result, electrodes can be formed. The electrodes may function as touch sensor electrodes that detect contact with the touch panel. As the patterning method, any suitable method can be employed. 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 may be applied to an image display device. Therefore, the present invention includes an image display device using such a polarizing plate with a retardation layer. Representative examples of the image display device include a liquid crystal display device and an electroluminescence (EL) display device (eg, an organic EL display device and an inorganic EL display device). An image display device according to an embodiment of the present invention includes a polarizing plate with a retardation layer on its viewing side. Polarizing plates with a retardation layer are laminated so that the retardation layer is on the side of an image display cell (for example, a liquid crystal cell, an organic EL cell, or an inorganic EL cell) (so that the polarizer is on the viewing side). In one embodiment, the image display device has a curved shape (substantially a curved display screen) and/or is bendable or bendable. In such an image display device, the effect of the polarizing plate with a retardation layer of the present invention becomes remarkable.

[Example]

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

(1) Thickness

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

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

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

(3) Birefringence of PVA (Δn)

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

(4) single transmittance and degree of polarization

With respect to the polarizer (polarizer alone) obtained by peeling and removing the resin base material from the laminate of the polarizer/thermoplastic resin base material obtained in Examples and Comparative Examples, using an ultraviolet / visible ray spectrophotometer ('V-7100' manufactured by Nippon Spectroscopy Co., Ltd.), a single element was used. Transmittance (Ts), parallel transmittance (Tp), and orthogonal transmittance (Tc) were measured. These Ts, Tp, and Tc are Y values measured with a JIS Z8701 2-degree field of view (C light source) and corrected for visibility. From the obtained Tp and Tc, the polarization degree P was calculated|required by the following formula.

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

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

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

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

(6) Orientation function of PVA

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

(Equation 1) f=(3<cos ² θ>-1)/2

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

step,

c=(3cos ² β-1)/2

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

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

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

D=(I _⊥ )/(I _// )

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

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

(7) Crack occurrence rate

The polarizing plate with the retardation layer obtained in Examples and Comparative Examples was cut into a size of 10 mm × 10 mm. The cut out polarizing plate with the retardation layer was attached to a glass plate (thickness: 1.1 mm) through an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm so that the retardation layer side was on the glass plate side. After the sample affixed to the glass plate was left to stand in an oven at 100°C for 120 hours, the presence or absence of cracks in the absorption axis direction (MD direction) of the polarizer was visually confirmed. This evaluation was performed using three polarizing plates with retardation layers, and the number of polarizing plates with retardation layers in which cracks occurred was evaluated.

[Example 1]

1. Production of polarizer (polarizer)

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

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

A PVA-based resin layer having a thickness of 13 μm was formed by applying the PVA aqueous solution to the corona-treated surface of the resin substrate and drying at 60° C. to prepare a laminate.

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

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

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

Then, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by blending 3 parts by weight of potassium iodide and 5 parts by weight of boric acid) with respect to 100 parts by weight of water at a liquid temperature of 40 ° C. (crosslinking treatment).

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

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

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

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

2. Preparation of the first alignment-fixed layer and the second alignment-fixed 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 ' 3 g of Irgacure 907') was dissolved in 40 g of toluene to prepare a liquid crystal composition (coating liquid).

The surface of a polyethylene terephthalate (PET) film (thickness: 38 μm) was rubbed using a rubbing cloth, and alignment treatment was performed. The direction of the orientation treatment was made to be 15° direction when viewed from the viewing side with respect to the direction of the absorption axis of the polarizer when bonding to the polarizing plate. The liquid crystal compound was aligned by coating the liquid crystal coating solution on the orientation treated surface with a bar coater and heating and drying at 90°C for 2 minutes. 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 a first alignment hardened layer on the PET film. The thickness of the first alignment-fixed layer was 2.5 μm, and the in-plane retardation Re (550) was 270 nm. Moreover, the 1st orientation hardening layer had the refractive index distribution of nx>ny=nz.

A second alignment hardened layer was formed on the PET film in the same manner as above except that the coating thickness was changed and the orientation treatment direction was set to be 75 ° direction when viewed from the viewing side with respect to the direction of the absorption axis of the polarizer. The thickness of the second alignment-fixed layer was 1.3 μm, and the in-plane retardation Re (550) was 140 nm. Moreover, the 2nd orientation hardening layer had the refractive index distribution of nx>ny=nz.

3. Production of Polarizing Plate with Retardation Layer

The 1st alignment hardened layer and the 2nd alignment hardened layer obtained by said 2. were transcribe|transferred to the polarizer surface of the laminated body which has the structure of [polarizer/resin base material] obtained by said 1. in this order. At this time, the angle formed between the absorption axis of the polarizer and the slow axis of the first alignment hardening layer is 15 °, and the angle formed between the absorption axis of the polarizer and the slow axis of the second alignment hardening layer is 75 °. did In addition, each transfer (bonding) was performed through an ultraviolet curable adhesive (thickness: 1.0 µm). The resin substrate was peeled off from the obtained laminate to obtain a polarizing plate with a retardation layer having a structure of [polarizer/adhesive layer/retardation layer (first orientation-fixed layer/adhesion layer/second orientation-fixed layer)]. The total thickness of the obtained polarizing plate with a retardation layer was 13.2 µm.

[Examples 2-4]

A polarizer (thickness: 7.4 μm) was formed on a resin substrate in the same manner as in Example 1 except that dyeing baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used.

Except for using the laminate having the configuration of the [polarizer / resin substrate], in the same manner as in Example 1, the configuration of [polarizer / adhesive layer / retardation layer (first orientation hardened layer / adhesive layer / second orientation hardened layer)] A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 13.2 µm.

[Examples 5 to 8]

Example except that the draw ratio of the underwater extension was increased to 1.46 times (as a result, the total extension ratio of the extension was increased to 3.5 times), and dyeing baths having different iodine concentrations (weight ratio of iodine and potassium iodide = 1:7) were used. In the same manner as in 1, a polarizer (thickness: 6.7 µm) was formed on the resin substrate.

Except for using the laminate having the configuration of the [polarizer / resin substrate], in the same manner as in Example 1, the configuration of [polarizer / adhesive layer / retardation layer (first orientation hardened layer / adhesive layer / second orientation hardened layer)] A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 12.5 µm.

[Examples 9 to 12]

EXAMPLES EXCEPT EXAMPLES Except for using a dyeing bath having a different iodine concentration (weight ratio of iodine and potassium iodide = 1:7), the draw ratio of the underwater drawing was increased to 1.67 times (as a result, the total extension ratio of the drawing was increased to 4.0 times). It carried out similarly to 1, and formed the polarizer (thickness: 6.2 micrometer) on the resin substrate.

Except for using the laminate having the configuration of the [polarizer / resin substrate], in the same manner as in Example 1, the configuration of [polarizer / adhesive layer / retardation layer (first orientation hardened layer / adhesive layer / second orientation hardened layer)] A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 12.0 µm.

[Examples 13 to 16]

EXAMPLES EXCEPT EXAMPLES Except for using a dyeing bath having a different iodine concentration (weight ratio of iodine and potassium iodide = 1:7), the draw ratio of the underwater extension was increased to 1.88 times (as a result, the total extension ratio of the extension was increased to 4.5 times). It carried out similarly to 1, and formed the polarizer (thickness: 6.0 micrometer) on the resin substrate.

Except for using the laminate having the configuration of the [polarizer / resin substrate], in the same manner as in Example 1, the configuration of [polarizer / adhesive layer / retardation layer (first orientation hardened layer / adhesive layer / second orientation hardened layer)] A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 11.8 µm.

[Comparative Examples 1 to 4]

EXAMPLES EXCEPT EXAMPLES Except for using a dyeing bath having a different iodine concentration (weight ratio of iodine and potassium iodide = 1:7), the draw ratio of the underwater extension was increased to 2.29 (as a result, the total extension ratio of the extension was increased to 5.5). It carried out similarly to 1, and formed the polarizer (thickness: 5.5 micrometers) on the resin substrate.

Except for using the laminate having the configuration of the [polarizer / resin substrate], in the same manner as in Example 1, the configuration of [polarizer / adhesive layer / retardation layer (first orientation hardened layer / adhesive layer / second orientation hardened layer)] A polarizing plate with a retardation layer was obtained. The total thickness of the obtained polarizing plate with a retardation layer was 11.3 µm.

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

[Table 1]

As is clear from Table 1, the polarizing plate with the retardation layer of the examples did not contain a protective layer, had a configuration extremely thin, and was suppressed from generating cracks due to heating.

3 to 5, respectively, the relationship between the single transmittance of the polarizer obtained in Examples and Comparative Examples and Δn of PVA, in-plane retardation or orientation function is shown. As shown in FIGS. 3 to 5, even if the birefringence, in-plane retardation or orientation function were the same (as a result, the degree of orientation was the same), when the single transmittance was high, cracks were easily generated by heating. can Therefore, in order to effectively suppress the generation of cracks due to heating, in addition to the degree of orientation of the PVA-based resin, it is understood that adjustment of the single transmittance (resulting in the adsorption amount of the dichroic substance) is also important. In addition, it can be seen that the polarizers satisfying Formula (1), Formula (2) and/or Formula (3) have been suitably adjusted, and generation of cracks due to heating can be suitably suppressed. .

The polarizing plate with a retardation layer of the present invention is suitably used for an image display device.

10: polarizer
11: polarizer
20: phase difference layer
100: polarizing plate with retardation layer

Claims (8)

A polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate,
The polarizing plate does not include a protective layer on the side opposite to the side of the polarizer on which the retardation layer is provided,
The retardation layer is an alignment solidified layer of a liquid crystal compound,
When the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the birefringence of the polyvinyl alcohol-based resin is y, the following formula (1) Polarizer with retardation layer that meets:
y<-0.011x+0.525 (1). A polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate,
The polarizing plate does not include a protective layer on the side opposite to the side of the polarizer on which the retardation layer is provided,
The retardation layer is an alignment solidified layer of a liquid crystal compound,
When the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the in-plane retardation of the polyvinyl alcohol-based resin film is znm, the following formula (2 ), a polarizing plate with a retardation layer that satisfies:
z<-60x+2875 (2). A polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate,
The polarizing plate does not include a protective layer on the side opposite to the side of the polarizer on which the retardation layer is provided,
The retardation layer is an alignment solidified layer of a liquid crystal compound,
When the polarizer is composed of a polyvinyl alcohol-based resin film containing a dichroic substance, the single transmittance is x%, and the orientation function of the polyvinyl alcohol-based resin is f, the following formula (3) A polarizing plate with a retardation layer that satisfies:
f<-0.018x+1.11 (3). A polarizing plate including a polarizer and a retardation layer provided on one side of the polarizing plate,
The polarizing plate does not include a protective layer on the side opposite to the side of the polarizer on which the retardation layer is provided,
The retardation layer is an alignment hardening layer of a liquid crystal compound,
A polarizing plate with a retardation layer, wherein the polarizer has a stabbing strength of 30 gf/m or more. According to any one of claims 1 to 4,
A polarizing plate with a retardation layer having a total thickness of 30 µm or less. According to any one of claims 1 to 5,
The polarizing plate with a retardation layer whose thickness of the said polarizer is 10 micrometers or less. According to any one of claims 1 to 6,
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. An image display device comprising the polarizing plate with a retardation layer according to any one of claims 1 to 7.

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