KR20240092589A - Optical laminate and image display device - Google Patents

Abstract

The present invention provides an optical laminate in which a specific resin layer is disposed adjacent to a polarizer and cracking of the polarizer is suppressed in a high temperature environment.
An optical laminate according to an embodiment of the present invention includes a polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, a resin layer disposed adjacent to the polarizer, and a first layer disposed as the outermost layer on the resin layer side. Includes an adhesive layer. The shrinkage rate of the polarizer in the absorption axis direction is 2.5% or less, the thickness of the first adhesive layer is 17 μm or less, and the storage modulus at 23°C is 0.10 MPa or more.

Description

Optical laminate and image display device {OPTICAL LAMINATE AND IMAGE DISPLAY DEVICE}

The present invention relates to an optical laminated body and an image display device.

In image display devices (e.g., liquid crystal display devices, organic EL display devices, quantum dot display devices), in many cases, a polarizing plate is disposed on at least one side of the display panel due to the image forming method thereof. Additionally, for the purpose of thinning and improving functionality, there are cases where a protective layer is provided on only one side of the polarizer in a polarizing plate, and a specific resin layer is provided on the side where the protective layer is not provided. In a polarizing plate having such a protective layer/polarizer/resin layer structure, cracks often occur in the polarizer in a high-temperature environment. In addition, the polarizing plate is often used integrated with a retardation layer (retardation film), and when a retardation layer is provided on the above-described polarizing plate, cracks in the polarizer often become more noticeable in a high temperature environment.

Japanese Patent Publication No. 2013-072951

The present invention was made to solve the above-described conventional problems, and its main purpose is to provide an optical laminate in which a specific resin layer is disposed adjacent to a polarizer and cracking of the polarizer is suppressed in a high temperature environment. It's in the thing.

[1] An optical laminate according to an embodiment of the present invention includes a polarizer and a protective layer disposed on one side of the polarizer, a resin layer disposed adjacent to the polarizer, and an outermost layer on the resin layer side. It includes a first adhesive layer disposed as. The shrinkage rate of the polarizer in the absorption axis direction is 2.5% or less, the thickness of the first adhesive layer is 17 μm or less, and the storage modulus at 23°C is 0.10 MPa or more.

[2] In [1] above, the optical laminate further includes a retardation layer laminated on a side opposite to the polarizer of the resin layer through a second adhesive layer. The phase contrast layer has a circular polarization function or an elliptical polarization function. The thickness of the second adhesive layer is 7 μm or less, and the storage modulus at 23°C is 0.12 MPa or more.

[3] In [1] or [2], the optical laminate has a total thickness of the polarizer and the protective layer set to A (μm), the resin layer, the second adhesive layer, the retardation layer, and When the total thickness of the first adhesive layer is B (μm), the relationship A<B is satisfied.

[4] In [2] or [3] above, the retardation layer is composed of a stretched resin film, its Re (550) is 100 nm to 200 nm, and the relationship of Re (450) < Re (550) is satisfied, and the angle formed between the slow axis of the retardation layer and the absorption axis of the polarizer is 40° to 50°.

[5] In any one of the above [2] to [4], the optical laminate further comprises another retardation layer on the side opposite to the resin layer of the retardation layer, the refractive index characteristic showing the relationship nz>nx=ny. Includes.

[6] In any one of [1] to [5] above, the resin layer includes a resin having a glass transition temperature of 85°C or higher and a weight average molecular weight (Mw) of 25,000 or higher.

[7] In any one of [1] to [6] above, the indentation elastic modulus of the resin layer is 8 GPa or more.

[8] In any one of [1] to [7] above, the thickness of the resin layer is 1 μm or less.

[9] In any one of [1] to [8] above, the thickness of the polarizer is 8 μm or less, the indentation elastic modulus is 9.5 GPa or less, and the indentation hardness is 0.65 GPa or more.

[10] In any one of [1] to [9] above, the orientation function of the polarizer is 0.30 or more.

[11] In any one of [1] to [10] above, the shrinkage rate of the polarizer in the absorption axis direction is 2.0% or less.

[12] According to another aspect of the present invention, an image display device is provided. This image display device includes an image display panel and the optical laminate of any one of [1] to [11] above, which is bonded to the image display panel through the first adhesive layer.

According to the embodiment of the present invention, an optical laminate in which a specific resin layer is disposed adjacent to the polarizer and cracking of the polarizer is suppressed in a high temperature environment can be realized.

1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention.
Figure 2 is a schematic cross-sectional view of an optical laminate according to another embodiment of the present invention.

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

(Definition of terms and symbols)

The 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 where the in-plane refractive index is maximum (i.e., slow axis direction), 'ny' is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., fast axis direction), and 'nz' is It is the refractive index in the thickness direction.

(2) In-plane phase difference (Re)

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

(3) Phase difference in the thickness direction (Rth)

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

(4) Nz coefficient

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

(5) angle

When referring to an angle in this specification, unless otherwise specified, the angle includes angles in both clockwise and counterclockwise directions.

A. Optical laminate

1 is a schematic cross-sectional view of an optical laminate according to one embodiment of the present invention. The optical laminate 100 of the illustrated example includes a polarizing plate 10, a resin layer 20, and a first adhesive layer 50 in this order from the top of the figure. The upper side of the drawing may correspond to the viewing side when the optical laminate is applied to an image display device; The lower side of the drawing may correspond to the image display panel side. The polarizing plate 10 includes a polarizer 11 and a protective layer 12 disposed on one side (viewer's side) of the polarizer 11. That is, in the embodiment of the present invention, the polarizing plate is a so-called polarizing polarizing plate. If necessary, the protective layer 12 may include a hard coat layer (not shown) on the side opposite to the polarizer 11. The resin layer 20 is disposed adjacent to the polarizer 11. In addition, in this specification, 'disposed adjacent to the polarizer' means that the resin layer is formed directly on the polarizer, or that the resin layer is laminated on the polarizer through an adhesive layer (typically an adhesive layer or adhesive layer). It means that it has been done. In other words, it means that the optical function layer is not interposed between the polarizer and the resin layer. The first adhesive layer 50 is arranged as the outermost layer on the resin layer 20 side. The first adhesive layer 50 enables the optical laminate to be attached to an image display panel.

The resin layer 20 is typically a solidified or cured product of a coating film of an organic solvent solution of a resin. The resin contained in the resin layer 20 typically has a glass transition temperature of 85°C or higher and a weight average molecular weight (Mw) of 25,000 or higher. The resin layer 20 may have a barrier function. The resin layer 20 can suppress the movement of moisture in a high-temperature, high-humidity environment and can suppress discoloration of the ends of the polarizer. Additionally, the resin layer 20 can suppress the movement of iodine that may be included in the polarizer and can reduce the influence that the polarizer may have on other members. For example, when the optical laminate is mounted on an image display device (eg, an organic EL display device), corrosion of metal members of the image display device can be suppressed. By providing such a resin layer adjacent to the polarizer according to the embodiment of the present invention, discoloration of the ends in a high-temperature, high-humidity environment can be further suppressed. Additionally, by providing such a resin layer adjacent to the polarizer, the protective layer can be omitted. Since the resin layer is significantly thinner than the protective layer, it can contribute to thinning of the optical laminated body while maintaining the function of favorably protecting the polarizer. Details of the resin layer will be explained in Section C, which will be described later. In an optical laminate in which such a specific resin layer is disposed adjacent to the polarizer, the effect according to the embodiment of the present invention becomes significant.

In the embodiment of the present invention, the shrinkage rate in the absorption axis direction of the polarizer 11 is 2.5% or less, the thickness of the first adhesive layer 50 is 17 μm or less, and the storage modulus at 23° C. is 0.10 MPa or more. am. With such a structure, cracking of the polarizer in a high-temperature environment can be significantly suppressed in an optical laminate in which the specific resin layer described above is disposed adjacent to the polarizer. Details are as follows. The resin layer as described above is very hard in relation to its characteristics (as described later, the indentation elastic modulus is, for example, 8 GPa or more), and as a result, it is very prone to cracking. As a result of the polarizer also being configured to improve optical properties and suppress discoloration at the ends, it is very hard (as will be described later, the indentation hardness is, for example, 0.65 GPa or more) and is prone to cracking. The present inventors discovered that, in such an optical laminate, the resin layer cracks due to external force or the like, cracks occur in the polarizer following the cracks in the resin layer, and the cracks develop in a high-temperature environment. As a result of a thorough examination of the solution, the present inventors found that it is useful to first suppress the deformation that causes cracking of the resin layer, and optimize the resin layer by combining the thickness and storage modulus of the first adhesive layer adjacent to the resin layer. It was found that deformation could be suppressed well. Specifically, by setting the thickness of the first adhesive layer to 17 μm or less, deformation of the resin layer due to external force or the like can be suppressed. In addition, it was found that by setting the storage modulus of the first adhesive layer to 0.10 MPa or more (by making it hard to some extent), deformation of the resin layer could be suppressed. As a countermeasure against impacts such as external forces, it is common knowledge that the impact is alleviated by absorbing external forces by softening the adhesive layer. According to an embodiment of the present invention, in an optical laminate having the above specific configuration, the adhesive By optimizing the combination of the thickness of the layer and the storage elastic modulus and making the storage elastic modulus hard to some extent, deformation of the resin layer can be suppressed, and as a result, cracking of the polarizer can be suppressed. In this way, the effect according to the embodiment of the present invention is achieved by means contrary to common technical knowledge, and is an unexpected and excellent effect. In addition, according to an embodiment of the present invention, by setting the shrinkage rate in the absorption axis direction of the polarizer to 2.5% or less, even if the resin layer is deformed or cracked, it can be difficult to follow such deformation or cracking, resulting in As a result, cracks can be suppressed. In addition, the above-mentioned mechanism is only a guess, and does not limit the present invention, nor does it limit the present invention to the mechanism.

In one embodiment, like the optical laminate 10 shown in FIG. 2, the retardation layer 30 is laminated on the side opposite to the polarizer 11 of the resin layer 10 via the second adhesive layer 60. ) may be further provided. The phase contrast layer 30 typically has a circular polarization function or an elliptical polarization function. With this configuration, an optical laminate having excellent anti-reflection properties can be obtained. In this case, the optical laminate 101 is located on the side opposite to the resin layer 20 of the retardation layer 30 (for example, between the retardation layer 30 and the first adhesive layer 50), as shown in the example. , it may further include another retardation layer 40 whose refractive index characteristic shows the relationship nz>nx=ny. By providing such a different phase contrast layer, reflection in the oblique direction can be prevented satisfactorily, and wide viewing angle of the anti-reflection function becomes possible. In this case, the thickness of the second adhesive layer is 7 μm or less, and the storage modulus at 23°C is 0.12 MPa or more. It was found that by providing a phase contrast layer, cracking of the resin layer due to external force or the like can be promoted. In contrast, similar to the above, by optimizing the combination of the thickness of the second adhesive layer adjacent to the resin layer and the storage elastic modulus, deformation (as a result, cracking) of the resin layer can be well suppressed. Here, the thickness of the second adhesive layer is 7 μm or less and is thinner than the thickness of the first adhesive layer, and the storage modulus is 0.12 MPa or more and is larger than the storage modulus of the first adhesive layer. Accordingly, even in cases where deformation (as a result, cracking) of the resin layer may be accelerated due to the phase difference layer, such deformation and cracking can be well suppressed. In addition, by setting the thickness and storage modulus of the first adhesive layer as described above, a synergistic effect with the effect of optimizing the thickness and storage modulus of the second adhesive layer in combination can be obtained.

In one embodiment, the optical laminate has a total thickness of the polarizer and the protective layer set to A (μm), and a total thickness of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer. When set to B (㎛), the relationship A<B is satisfied. It was found that cracking of the resin layer is promoted in an optical laminate when the thickness of the resin layer on the visible side and the opposite side is large. According to the embodiment of the present invention, even in such a case, deformation (as a result, cracking) of the resin layer can be suppressed, and cracking of the polarizer can be suppressed. The absolute value of the difference between thickness A and thickness B is preferably 10 μm to 50 μm, and more preferably 20 μm to 40 μm. Moreover, the ratio (B/A) of thickness A to thickness B is preferably 1.1 to 3.0, and more preferably 1.2 to 2.5. In addition, when another retardation layer is provided, the total thickness B includes the thickness of the other retardation layer.

In practical terms, it is preferable that a release liner (not shown) is temporarily attached to the surface of the first adhesive layer 50 until the optical laminate is ready for use. By temporarily attaching the release liner, the first adhesive layer is protected and roll formation of the optical laminated body becomes possible.

Hereinafter, the components of the optical laminate will be described. In addition, the first adhesive layer and the second adhesive layer are collectively described as an adhesive layer. If it is necessary to distinguish between the first adhesive layer and the second adhesive layer, 'first' or 'second' is specified.

B. Polarizer

B-1. polarizer

The polarizer is typically comprised of a polyvinyl alcohol (PVA)-based resin film containing a dichroic substance (for example, iodine). Examples of PVA-based resins include polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene-vinyl alcohol copolymer, and partially saponified products of ethylene-vinyl acetate copolymer.

The PVA-based resin preferably includes acetoacetyl-modified PVA-based resin. With such a structure, a polarizer with desired mechanical strength can be obtained. The blending amount of the acetoacetyl-modified PVA-based resin is preferably 5% by weight to 20% by weight, more preferably 8% by weight to 12% by weight, based on 100% by weight of the total PVA-based resin. If the mixing amount is within this range, a polarizer with better mechanical strength can be obtained.

The polarizer preferably contains iodide or sodium chloride (together, they may be called halides). Examples of iodide include potassium iodide, sodium iodide, and lithium iodide. The content of the halide in the polarizer is preferably 5 parts by weight to 20 parts by weight, and more preferably 10 parts by weight to 15 parts by weight, based on 100 parts by weight of the PVA-based resin. In the manufacturing method described later, the halide is mixed into the coating liquid that forms the PVA-based resin layer, which is a precursor of the polarizer, and can be finally introduced into the polarizer. By introducing a halide into the polarizer, the orientation of the PVA molecules in the polarizer can be improved, making it possible to realize a polarizer with excellent optical properties (typically, both high polarization degree and high single transmittance).

The thickness of the polarizer is preferably 1 μm to 8 μm, more preferably 2 μm to 7 μm, and even more preferably 3 μm to 6 μm. By controlling the shrinkage rate in the absorption axis direction in such a very thin and highly oriented polarizer, the effect according to the embodiment of the present invention becomes significant. Moreover, if the thickness of the polarizer is within this range, curling during heating can be suppressed well, and good external appearance durability during heating is obtained.

As mentioned above, the shrinkage rate of the polarizer in the absorption axis direction is 2.5% or less, preferably 2.2% or less, more preferably 2.0% or less, and even more preferably 1.8% or less. The smaller the shrinkage rate, the more desirable it is, for example, it can be 0.5% or more, and for example, it can be 0.8% or more. Shrinkage can be measured, for example, by thermomechanical analysis (TMA). More specifically, the shrinkage rate means the shrinkage rate at 95°C when measured by TMA under the following conditions.

　Temperature range: -50℃~120℃

　Temperature increase rate: 2℃/min

　Modulation: ±5°C at 300 seconds/cycle

　Tensile load: 0.0196N

The indentation elastic modulus of the polarizer is preferably 7.5 GPa to 9.4 GPa, more preferably 8.0 GPa to 9.3 GPa, further preferably 8.2 GPa to 9.2 GPa, and particularly preferably 8.5 GPa to 9.2 GPa. The indentation hardness of the polarizer is preferably 0.65 GPa to 0.80 GPa, more preferably 0.66 GPa to 0.76 GPa, further preferably 0.67 GPa to 0.74 GPa, and particularly preferably 0.68 GPa to 0.72 GPa. The polarizer used in the embodiment of the present invention has the characteristic of having very high indentation hardness, although the indentation elastic modulus is relatively low. As a result, the polarizer according to the embodiment of the present invention is extremely thin and can significantly suppress discoloration of the ends (particularly, discoloration of the ends in a high-temperature, high-humidity environment). Such a polarizer tends to be prone to cracks, and according to an embodiment of the present invention, the occurrence of cracks can be suppressed. Additionally, the indentation hardness and indentation elastic modulus can be typically measured by a nano-indentation method using an indentation tester (typically a nano indenter). More specifically, the indentation hardness is the maximum load (Pmax) obtained from the displacement-load hysteresis curve obtained by firmly pressing the probe (indenter) on the surface of the polarizer to be measured, and the projected contact area between the indenter and the polarizer ( From A), it is calculated by the following formula.

　　　Indentation hardness (GPa)=Pmax/A

In addition, the indentation elastic modulus is calculated from the contact projection area (A), the slope of the tangent of the unloading curve of the displacement-load hysteresis curve (contact stiffness) (S), and the pi (π) using the following equation.

　　　Indentation elastic modulus (GPa)=(√π/2)×(S/√A)

The orientation function of the polarizer is preferably 0.30 or more, more preferably 0.35 or more, further preferably 0.37 or more, and especially preferably 0.40 or more. If the orientation function of the polarizer is in such a range, it is easy to set the indentation elastic modulus and indentation hardness within the above desired ranges. The upper limit of the orientation function of the polarizer may be, for example, 0.70. The orientation function (y) can be obtained, for example, by measuring attenuated total reflection (ATR) using a Fourier transform infrared spectrophotometer (FT-IR) and using polarized light as the measurement light. Specifically, the measurement is performed with the stretching direction of the polarizer being parallel and perpendicular to the polarization direction of the measurement light, and the intensity of the obtained absorbance spectrum of 2941 cm ^-1 is used to calculate it according to the following formula. Here, the intensity (I) is a value of 2941 cm ^-1 /3330 cm ^-1 with 3330 cm ^-1 as the reference peak. Additionally, when y=1, it is perfectly oriented, and when y=0, it is random. In addition, the peak at 2941 cm ^-1 is thought to be absorption resulting from the vibration of the main chain (-CH ₂ -) of PVA in the polarizer.

y=(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 the case of vibration of 2941 cm ^-1 , β=90°.

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

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

D=(I _⊥ )/(I _// ) (In this case, the more oriented the PVA molecules are, the larger D becomes)

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

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

The polarizer preferably exhibits absorption dichroism at any wavelength between 380 nm and 780 nm. The single transmittance of the polarizer is, for example, 41.0% to 45.0%, preferably 41.5% to 43.5%, and more preferably 42.0% to 43.0%. The polarization degree of the polarizer is preferably 97.0% or more, more preferably 99.0% or more, and even more preferably 99.9% or more. According to an embodiment of the present invention, even if the single transmittance is in the above range, the degree of polarization can be maintained in the above range.

A polarizer can typically be obtained using a laminate of a resin substrate and a PVA-based resin layer. Specific examples of a polarizer obtained using a laminate include a laminate of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a resin substrate and a PVA-based resin layer applied to the resin substrate. A polarizer obtained using a laminated body of the following can be mentioned. A polarizer obtained using a laminate of a resin substrate and a PVA-based resin layer formed by applying to the resin substrate is, for example, applied by applying a PVA-based resin solution to a resin substrate, drying it, and forming a PVA-based resin layer on the resin substrate, Obtaining a laminate of a resin substrate and a PVA-based resin layer; It can be produced by stretching and dyeing the laminate and using the PVA-based resin layer as a polarizer. In this embodiment, a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin is preferably formed on one side of the resin substrate. Stretching typically involves immersing the laminate in an aqueous boric acid solution and stretching it. Additionally, stretching, if necessary, may further include air stretching the laminate at a high temperature (for example, 95°C or higher) before stretching in an aqueous boric acid solution. Additionally, in this embodiment, the laminate is preferably subjected to dry shrinkage treatment to shrink the laminate by 2% or more in the width direction by heating while conveying in the longitudinal direction. Typically, the manufacturing method of this embodiment includes performing aerial auxiliary stretching treatment, dyeing treatment, underwater stretching treatment, and dry shrink treatment on the laminate in this order. By introducing auxiliary stretching, even when applying PVA on a thermoplastic resin, it becomes possible to increase the crystallinity of PVA and achieve high optical properties. Moreover, by simultaneously increasing the orientation of PVA in advance, problems such as a decrease in orientation or dissolution of PVA when immersed in water in the subsequent dyeing or stretching process can be prevented, making it possible to achieve high optical properties. do. Additionally, when the PVA-based resin layer is immersed in a liquid, the disruption of the orientation of 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. As a result, the optical properties of the polarizer obtained through a treatment process performed by immersing the laminate in a liquid, such as dyeing treatment and underwater stretching treatment, can be improved. Additionally, optical properties can be improved by shrinking the laminate in the width direction through dry shrinkage treatment. The obtained resin substrate/polarizer laminate may be used as is (i.e., the resin substrate may be used as a protective layer of the polarizer), or on the peeling surface where the resin substrate is peeled from the resin substrate/polarizer laminate, or on the peeling surface. It may be used by laminating any appropriate protective layer depending on the purpose on the side opposite to the above. Details of the manufacturing method of such a polarizer are described in, for example, Japanese Patent Application Laid-Open No. 2012-73580 and Japanese Patent Application Publication No. 6470455. The entire description of these publications is incorporated herein by reference.

In the embodiment of the present invention, the stretching temperature in the air-assisted stretching process is 140°C or higher, and the stretching ratio is 2.5 times or higher. The stretching temperature is preferably 145°C or higher, more preferably 150°C or higher, and even more preferably 155°C or higher. The upper limit of the stretching temperature may be, for example, 170°C. The draw ratio is preferably 2.5 times to 3.2 times, more preferably 2.6 times to 3.1 times, and still more preferably 2.7 times to 3.0 times. In the conventional method of producing a thin polarizer, the glass transition temperature (Tg) of the thermoplastic resin substrate (typically polyethylene terephthalate (PET)) is +15°C or higher, and rapid crystallization of the PVA-based resin is achieved. Aerial assisted stretching treatment is performed at a temperature that can be suppressed. This stretching temperature is specifically around 130°C. In addition, the draw ratio of the aerial auxiliary stretching process in the conventional method for producing a thin polarizer is usually set to 2.0 times to 2.4 times. Since it is desirable that the total stretching ratio of the air-assisted stretching treatment and the underwater stretching treatment is constant (e.g., 5.5 to 6.0 times), when stretching around 130°C, at a stretching ratio exceeding 2.5 times, the underwater stretching treatment This is because the draw ratio needs to be lowered, and the optical properties may deteriorate due to a decrease in the orientation of iodine. Additionally, at temperatures exceeding 130°C, it is difficult to suppress the rapid crystallization of the PVA-based resin as described above, and control of stretchability is also difficult. The present inventors have found that a rigid thin polarizer can be realized while maintaining the desired optical properties (both high single transmittance and high polarization degree) by performing an aerial auxiliary stretching process at a high temperature and high stretching ratio, which has not been performed before. Found it.

The drying shrink treatment is typically performed by combining zone heating, which is performed by heating the entire zone, and heating roll drying, which is performed by heating the conveyance roll (using a so-called heating roll). In an embodiment of the present invention, the shrinkage rate of the polarizer is reduced to 2.5% or less by controlling the temperature of the heating zone, the temperature of the heating roll, the time from starting zone heating until contact with the heating roll, and the conveyance tension of the laminate. You can do this. The temperature of the heating zone is preferably 80°C to 110°C. The temperature of the heating roll is preferably 60°C to 90°C. The conveyance tension of the laminate is preferably 4 N/cm to 6 N/cm. The time from starting zone heating to contacting the heating roll is preferably 1 second to 10 seconds.

B-2. protective layer

The protective layer 12 is made of any suitable resin film that can be used as a protective film for a polarizer. Representative materials constituting the resin film include cellulose resins such as triacetylcellulose (TAC), cycloolefin resins such as polynorbornene, (meth)acrylic resins, polyethylene terephthalate (PET), and polyethylene naphthalate. Examples include polyester-based resins such as (PEN), polyolefin-based resins such as polyethylene, and polycarbonate-based resins. Representative examples of (meth)acrylic resin include (meth)acrylic resin having a lactone ring structure. (meth)acrylic resins having a lactone ring structure, for example, Japanese Patent Application Laid-Open No. 2000-230016, Japanese Patent Application Publication No. 2001-151814, Japanese Patent Application Publication No. 2002-120326, Japanese Patent Application Publication No. 2002-254544, It is described in Japanese Patent Publication No. 2005-146084. These publications are incorporated herein by reference. From the viewpoint of ease of shape release processing, etc., cellulose resin is preferable, and TAC is more preferable. From the viewpoint of obtaining a polarizing plate with low moisture permeability and excellent durability, cycloolefin-based resin and (meth)acrylic-based resin are preferable.

The optical laminate is typically placed on the viewer side of the image display device, and the protective layer 12 is typically placed on the viewer side. Therefore, the protective layer 12 may be subjected to surface treatment as needed. Examples of surface treatment include hard coat treatment, anti-reflection treatment, anti-sticking treatment, and anti-glare treatment. In embodiments of the present invention, hard coat treatment (formation of a hard coat layer) is preferred. The hard coat layer will be described later. A combination of hard coat treatment and other surface treatments may be performed. Additionally, the protective layer 12 may be treated, as necessary, to improve visibility when viewed through polarized sunglasses (typically, imparting an (other) circular polarization function or imparting an ultra-high phase difference. ) may be implemented. By performing such processing, excellent visibility can be achieved even when the display screen is viewed through polarized lenses such as polarized sunglasses. Therefore, the optical laminate can also be suitably applied to an image display device that can be used outdoors.

The thickness of the protective layer 12 is preferably 10 μm to 80 μm, more preferably 12 μm to 40 μm, and still more preferably 15 μm to 35 μm. In addition, when surface treatment is performed, the thickness of the protective layer is a thickness including the thickness of the surface treatment layer.

The hard coat layer is typically a cured layer of any appropriate active energy ray (eg, ultraviolet ray, visible ray, electron beam) curable resin. Examples of the active energy ray-curable resin include acrylic resin, silicone resin, polyester resin, urethane resin, amide resin, and epoxy resin. The hard coat layer may contain any appropriate additives as needed. Representative examples of the additive include inorganic fine particles and/or organic fine particles. The thickness of the hard coat layer may be, for example, 1 μm to 10 μm, and may be, for example, 3 μm to 7 μm. The hard coat layer preferably has a pencil hardness of H or higher, more preferably 2H or higher, and even more preferably 3H or higher. On the other hand, the pencil hardness of the hard coat layer is preferably 6H or less, and more preferably 5H or less.

C. Resin layer

The resin layer 20 may have a barrier function as described above. In this regard, the resin layer is typically hard. Specifically, the indentation elastic modulus of the resin layer is preferably 8 GPa or more, more preferably 10 GPa to 20 GPa, and still more preferably 11 GPa to 15 GPa. According to the embodiment of the present invention, cracking of the polarizer adjacent to the resin layer can be suppressed even though the resin layer is hard and prone to cracking.

The resin layer is typically a solidified or cured product of a coating film of an organic solvent solution of a resin. According to this configuration, adhesion to the polarizer can be excellent. Specifically, the resin layer can be formed directly on the polarizer without an adhesive layer interposing it. Additionally, the thickness of the resin layer can be made very thin. The thickness of the resin layer is, for example, 10 μm or less, preferably 5 μm or less, more preferably 1 μm or less, and even more preferably 0.7 μm or less. The thickness of the resin layer is preferably 0.05 μm or more, more preferably 0.08 μm or more, further preferably 0.1 μm or more, and particularly preferably 0.2 μm or more.

In one embodiment, the glass transition temperature (Tg) of the resin constituting the resin layer is 85°C or higher, and the weight average molecular weight (Mw) is 25,000 or higher. The Tg of the resin constituting the resin layer is preferably 90°C or higher, more preferably 100°C or higher, further preferably 110°C or higher, and particularly preferably 120°C or higher. Tg may be, for example, 200°C or lower. Moreover, the Mw of the resin constituting the resin layer is preferably 30,000 or more, more preferably 35,000 or more, and still more preferably 40,000 or more. When the Tg and Mw of the resin constituting the resin layer are within this range, an excellent barrier function can be realized despite the thickness being very thin.

As the resin constituting the resin layer, any suitable resin that can form a solidified product or a cured product (for example, a thermoset) of a coating film of an organic solvent solution can be used. As the resin constituting the resin layer, a thermoplastic resin or thermosetting resin having the above Tg and Mw is preferably used, and more preferably a thermoplastic resin is used. Only one type of resin may be used, or two or more types may be used in combination.

Examples of the thermoplastic resin include acrylic resin and epoxy resin. You may use a combination of acrylic resin and epoxy resin.

Acrylic resin typically contains a repeating unit derived from a (meth)acrylic acid ester monomer having a linear or branched structure as a main component. The acrylic resin may contain repeating units derived from any appropriate copolymerization monomer depending on the purpose. Examples of copolymerization monomers include carboxyl group-containing monomers, hydroxyl group-containing monomers, amide group-containing monomers, aromatic ring-containing (meth)acrylates, and heterocycle-containing vinyl monomers. By appropriately setting the type, number, combination, copolymerization ratio, etc. of monomer units, an acrylic resin having the above-mentioned predetermined Mw can be obtained. Specific examples of the acrylic resin include boron-containing acrylic resins described in [0034] to [0056] of Japanese Patent Application Laid-Open No. 2021-117484, acrylic resins containing lactone rings, etc.

As the epoxy resin, an epoxy resin containing an aromatic ring is preferably used. By using an epoxy resin containing an aromatic ring as the epoxy resin, the adhesion between the resin layer and the polarizer can be improved. Additionally, when the adhesive layer is disposed adjacent to the resin layer, the anchoring power of the adhesive layer can be improved. Examples of the epoxy resin containing an aromatic ring include bisphenol-type epoxy resins such as bisphenol A-type epoxy resin, bisphenol F-type epoxy resin, and bisphenol S-type epoxy resin; Novolak-type epoxy resins such as phenol novolak epoxy resin, cresol novolak epoxy resin, and hydroxybenzaldehyde phenol novolac epoxy resin; Polyfunctional epoxy resins such as glycidyl ether of tetrahydroxyphenylmethane, glycidyl ether of tetrahydroxybenzophenone, and epoxidized polyvinyl phenol, naphthol type epoxy resin, naphthalene type epoxy resin, and biphenyl type epoxy resin. etc. can be mentioned. Preferably, bisphenol A-type epoxy resin, biphenyl-type epoxy resin, and bisphenol F-type epoxy resin are used. Only one type of epoxy resin may be used, or two or more types may be used in combination.

The resin layer can typically be formed by applying an organic solvent solution of the resin to form a coating film and solidifying or heat-curing the resulting coating film. As the organic solvent, any suitable organic solvent capable of dissolving or uniformly dispersing the resin can be used. Specific examples of organic solvents include ethyl acetate, toluene, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), cyclopentanone, and cyclohexanone. The resin concentration of the solution is preferably 3 parts by weight to 20 parts by weight based on 100 parts by weight of the solvent. With such a resin concentration, a uniform coating film can be formed.

The solution may be applied to a separately prepared substrate, but is preferably applied to a polarizing plate (polarizer). When applying a solution to a substrate, the solidified or cured product (resin layer) of the coating film formed on the substrate is transferred to a polarizing plate (polarizer). Since transfer is typically performed through an adhesive layer, the resin layer can be formed directly by applying the solution to a polarizing plate (polarizer) and the adhesive layer can be omitted. As a method of applying the solution, any suitable method can be adopted. Specific examples include roll coat method, spin coat method, wire bar coat method, dip coat method, die coat method, curtain coat method, spray coat method, and knife coat method (comma coat method, etc.).

The heating temperature for solidification or heat curing of the coating film is preferably 100°C or lower, and more preferably 50°C to 70°C. If the heating temperature is in this range, adverse effects on the polarizer can be prevented. The heating time may be, for example, 1 minute to 10 minutes.

The resin layer (substantially an organic solvent solution of the resin) may contain any appropriate additives depending on the purpose. Specific examples of additives include ultraviolet absorbers; leveling agent; Antioxidants such as hindered phenol-based, phosphorus-based, and sulfur-based antioxidants; Stabilizers such as light stabilizers, weather stabilizers, and heat stabilizers; Reinforcing materials such as glass fiber and carbon fiber; Near-infrared absorber; Flame retardants such as tris(dibromopropyl)phosphate, triallyl phosphate, and antimony oxide; Antistatic agents such as anionic, cationic, and nonionic surfactants; Colorants such as inorganic pigments, organic pigments, and dyes; Organic or inorganic filler; Resin modifier; Organic or inorganic fillers; plasticizer; lubricant; Flame retardants, etc. can be mentioned. The type, number, combination, addition amount, etc. of additives can be appropriately set depending on the purpose.

D. Phase contrast layer

As described above, the retardation layer 40 typically has a circular polarization function or an elliptical polarization function. The phase contrast layer may be a single layer or may have a laminated structure of two or more layers. When the retardation layer is composed of a single layer, the retardation layer may be a λ/4 plate. When the retardation layer has a laminated structure, the retardation layer may be a laminate of a λ/2 plate and a λ/4 plate. The retardation layer may be composed of any suitable material. Specifically, the retardation layer may be an alignment-fixed layer of a liquid crystal compound, a resin film (typically a stretched film), or a combination thereof. In an embodiment of the present invention, the retardation layer may typically be composed of a stretched resin film. In this case, the phase difference layer may typically be a single layer (λ/4 plate). Hereinafter, a stretched film of a single-layer resin film will be briefly described.

The phase difference layer can function as a λ/4 plate as described above. In this case, the in-plane phase difference Re(550) of the retardation layer is, for example, 100 nm to 190 nm, preferably 110 nm to 170 nm, and more preferably 130 nm to 160 nm. In this case, the retardation layer preferably exhibits a relationship of nx>ny≥nz in refractive index characteristics. Additionally, here, 'ny=nz' includes not only the case where ny and nz are completely the same, but also the case where they are substantially the same. Therefore, there may be cases where ny < nz, within a range that does not impair the effect according to the embodiment of the present invention.

The Nz coefficient of the retardation layer is preferably 0.9 to 3, more preferably 0.9 to 2.5, further preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying this relationship, when the obtained optical laminated body is used in an image display device, very excellent reflected color can be achieved.

The phase difference layer has a slow axis because it typically exhibits the relationship nx>ny as described above. In one embodiment, the angle (θ) formed between the slow axis of the retardation layer and the absorption axis of the polarizer is, for example, 40° to 50°, preferably 42° to 48°, and more preferably about 45°. . If the angle θ is in this range, an optical laminate having very excellent circular polarization properties (as a result, very excellent anti-reflection properties) can be obtained by making the retardation layer a λ/4 plate.

The thickness of the retardation layer can typically be set to a thickness that can properly function as a λ/4 plate. The thickness of the retardation layer may be, for example, 10 μm to 60 μm. If the thickness of the retardation layer is in this range, the total thickness B of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer becomes large. That is, in the optical laminate, the thickness of the resin layer on the visible side and the opposite side increases, which may promote cracking of the resin layer due to external force or the like. According to an embodiment of the present invention, even when a retardation layer having such a thickness is provided, deformation (as a result, cracking) of the resin layer can be suppressed, and cracking of the polarizer can be suppressed.

The phase difference layer may exhibit inverse dispersion wavelength characteristics in which the phase difference value increases depending on the wavelength of the measurement light, or may exhibit positive wavelength dispersion characteristics in which the phase difference value decreases depending on the wavelength of the measurement light. It may exhibit flat wavelength dispersion characteristics that hardly change depending on the wavelength. In one embodiment, the phase difference layer exhibits inverse dispersion wavelength characteristics. In this case, Re(450)/Re(550) of the retardation layer is, for example, 0.8 or more and less than 1, and is preferably 0.8 or more and 0.95 or less. With this configuration, very excellent anti-reflection properties can be achieved.

Representative examples of the resin constituting the retardation layer (resin film) include polycarbonate-based resin, polyestercarbonate-based resin, polyester-based resin, polyvinyl acetal-based resin, polyarylate-based resin, cyclic olefin-based resin, cellulose-based resin, Examples include polyvinyl alcohol-based resin, polyamide-based resin, polyimide-based resin, polyether-based resin, polystyrene-based resin, and acrylic resin. These resins may be used individually or in combination (e.g., blend, copolymerization). When the retardation layer is composed of a resin film exhibiting inverse dispersion wavelength characteristics, polycarbonate-based resin or polyestercarbonate-based resin (hereinafter sometimes simply referred to as polycarbonate-based resin) can be suitably used.

The polycarbonate-based resin contains at least one structural unit selected from the group consisting of a structural unit represented by the following general formula (1) and/or a structural unit represented by the following general formula (2). These structural units are structural units derived from divalent oligofluorene, and may hereinafter be referred to as oligofluorene structural units. Such polycarbonate-based resin has positive refractive index anisotropy.

The retardation layer typically further contains acrylic resin. The content of acrylic resin is 0.5% by mass to 1.5% by mass.

Details of the polycarbonate-based resin that can be suitably used in the retardation layer and the method of forming the retardation layer are, for example, Japanese Patent Laid-Open No. 2014-10291, Japanese Patent Laid-Open No. 2014-26266, and Japanese Patent Laid-Open No. 2015-212816. It is described in Japanese Patent Publication No. 2015-212817, Japanese Patent Publication No. 2015-212818, International Publication No. 2015/159928, and Japanese Patent Publication No. 2021-67762, and the descriptions of these publications are included in this specification. It is used as a reference.

E. Different phase contrast layers

The other retardation layer 40 may be a so-called positive C plate whose refractive index characteristics exhibit the relationship nz>nx=ny, as described above. By using a positive C plate as another phase contrast layer, reflection in the oblique direction can be prevented well, and wide viewing angle of the anti-reflection function becomes possible. In this case, the phase difference Rth (550) in the thickness direction of the other retardation layer is preferably -50 nm to -300 nm, more preferably -70 nm to -250 nm, even more preferably -90 nm to -200 nm, especially Preferably -100nm to -180nm. Here, 'nx=ny' includes not only the case where nx and ny are strictly the same, but also the case where nx and ny are substantially the same. That is, the in-plane phase difference Re(550) of the other phase difference layer may be less than 10 nm.

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

F. Adhesive layer

The first adhesive layer 50 has a storage elastic modulus at 23°C of 0.10 MPa or more as described above, preferably 0.10 MPa to 0.20 MPa, more preferably 0.11 MPa to 0.17 MPa, and even more preferably 0.11 MPa. It is MPa~0.15MPa. The second adhesive layer 60 has a storage elastic modulus at 23°C of 0.12 MPa or more as described above, preferably 0.12 MPa to 0.25 MPa, more preferably 0.13 MPa to 0.20 MPa, and still more preferably 0.13 MPa. It is MPa~0.18MPa. If the storage elastic moduli of the first adhesive layer and the second adhesive layer are in this range, the effect according to the above-described embodiment of the present invention can be more remarkable. Additionally, the storage modulus can be obtained by dynamic viscoelasticity measurement.

The first adhesive layer 50 has a thickness of 17 μm or less as described above, preferably 5 μm to 17 μm, more preferably 8 μm to 16 μm, and still more preferably 10 μm to 15 μm. . The second adhesive layer 60 has a thickness of 7 μm or less as described above, preferably 2 μm to 7 μm, more preferably 3 μm to 6 μm, and still more preferably 4 μm to 5 μm. . If the thickness of the first adhesive layer and the second adhesive layer is in this range, the effect according to the above-described embodiment of the present invention can be more remarkable.

As the adhesive constituting the adhesive layer, any suitable structure may be adopted. Specific examples of the adhesive constituting the adhesive layer include acrylic adhesives, rubber adhesives, silicone adhesives, polyester adhesives, urethane adhesives, epoxy adhesives, and polyether adhesives. By adjusting the type, number, combination, and mixing ratio of the monomers forming the base resin of the adhesive, the amount of crosslinking agent, reaction temperature, reaction time, etc., an adhesive having desired properties according to the purpose can be prepared. The base resin of the adhesive may be used individually, or may be used in combination of two or more types. From the viewpoints of transparency, processability, durability, etc., an acrylic adhesive (acrylic adhesive composition) is preferable. Acrylic adhesive compositions typically contain a (meth)acrylic polymer as a main component. The (meth)acrylic polymer may be contained in the adhesive composition at a rate of, for example, 50% by weight or more, preferably 70% by weight or more, and more preferably 90% by weight or more, based on the solid content of the adhesive composition. The (meth)acrylic polymer contains alkyl (meth)acrylate as a main component as a monomer unit. Additionally, (meth)acrylate refers to acrylate and/or methacrylate. Alkyl (meth)acrylate may be contained in a proportion of preferably 80% by weight or more, more preferably 90% by weight or more, among the monomer components forming the (meth)acrylic polymer. Examples of the alkyl group of the alkyl (meth)acrylate include a linear or branched alkyl group having 1 to 18 carbon atoms. The average number of carbon atoms of the alkyl group is preferably 3 to 9, and more preferably 3 to 6. A preferable alkyl (meth)acrylate is butyl acrylate. Monomers (copolymerized monomers) constituting the (meth)acrylic polymer include, in addition to alkyl (meth)acrylates, monomers containing carboxyl groups, monomers containing hydroxyl groups, monomers containing amide groups, (meth)acrylates containing aromatic rings, and heterocyclic rings. Containing vinyl monomers, etc. can be mentioned. Representative examples of copolymerized monomers include acrylic acid, 4-hydroxybutylacrylate, phenoxyethyl acrylate, and N-vinyl-2-pyrrolidone. The acrylic adhesive composition may preferably contain a silane coupling agent and/or a crosslinking agent. Examples of the silane coupling agent include epoxy group-containing silane coupling agents. Examples of crosslinking agents include isocyanate-based crosslinking agents and peroxide-based crosslinking agents. Additionally, the acrylic adhesive composition may contain an antioxidant and/or a conductive agent. Details of the adhesive layer or acrylic adhesive composition are, for example, Japanese Patent Application Laid-Open No. 2006-183022, Japanese Patent Application Publication No. 2015-199942, Japanese Patent Application Publication No. 2018-053114, Japanese Patent Application Publication No. 2016-190996, International Publication No. It is described in Publication No. 2018/008712, and the descriptions of these publications are incorporated herein by reference.

G. Image display device

The optical laminated body described in items A to F above can be applied to an image display device. Accordingly, embodiments of the present invention also include an image display device using such an optical laminated body. Representative examples of image display devices include liquid crystal display devices and organic EL display devices. An image display device according to an embodiment of the present invention includes an image display panel and the optical laminate described in paragraphs A to F, which is bonded to the image display panel through a first adhesive layer. The optical laminate is typically placed on the viewer's side of the image display panel with the polarizing plate on the viewer's side.

[Example]

Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement and evaluation methods of each characteristic in the examples are as follows.

(1) Shrinkage rate of polarizer

A laminate of the polarizer used in Examples and Comparative Examples and a triacetylcellulose (TAC) film was produced. This laminate was cut out to a size of 4 mm x 16 mm and used as a test sample. The test sample was made so that the long side direction was in the direction of the absorption axis of the polarizer. This test sample was mounted on a TMA device (manufactured by TA Instruments, product name 'Discovery TMA450EM'), and the shrinkage rate at 95°C when measured under the following conditions was taken as the shrinkage rate of the polarizer.

　Temperature range: -50℃~120℃

　Temperature increase rate: 2℃/min

　Modulation: ±5°C at 300 seconds/cycle

　Tensile load: 0.0196N

(2) Indentation elastic modulus and indentation hardness

Measurement was performed by the nanoindentation method using a nanoindenter ('Triboindenter' manufactured by Hysitron Inc.) under the following measurement conditions. Specifically, the probe (indenter) of the nanoindenter was pressed into the surface of the polarizer of the polarizing plate, and the displacement-load hysteresis curve was calculated using the following equation.

　　　Indentation hardness (GPa)=Pmax/A

　　　Indentation elastic modulus (GPa)=(√π/2)×(S/√A)

Here, Pmax is the maximum load obtained from the displacement-load hysteresis curve, A is the projected area of contact between the indenter and polarizer, S is the slope of the tangent of the unloading curve of the displacement-load hysteresis curve (contact stiffness), π is the circumference ratio.

(Measuring conditions)

·Measurement method: single press method

·Measurement temperature: 25℃

·Indentation speed: approximately 2nm/sec

·Indentation depth: approximately 300 nm

·Indenter used: Diamond, Berkovich type (triangular pyramid type)

Additionally, the indentation elastic modulus of the resin layer was similarly measured.

(3) crack

The optical laminated bodies obtained in Examples and Comparative Examples were cut into 80 mm x 150 mm. At this time, the polarizer was cut out so that the absorption axis direction was in the short side direction. The cut pieces are bonded to a glass plate through a first adhesive layer, and cut lines (2 mm in length) are formed at 10 equally spaced locations along the long side, extending in the short side direction (direction of the absorption axis of the polarizer) and penetrating through the glass plate. I put it in. This was used as a test sample. After placing this test sample in an oven at 95°C for 8 hours, the length of the crack extending from the incision line was measured. The average of the lengths of 10 cracks was taken as the crack progress, and was evaluated based on the following criteria.

　A (Excellent): Crack progress is less than 20 mm.

　B (Good): Crack progress is 20 mm or more but less than 40 mm.

　C (Medium): Crack progress is between 40mm and 60mm.

　D (defect): Crack progress is more than 60mm

In addition, the above 'A' to 'D' are relative evaluation standards, and in practical terms, it is good if the crack progress is 30 mm or less, and it is acceptable if the crack progress is 45 mm or less.

[Manufacturing Example 1: Production of polarizer]

As a thermoplastic resin substrate, an amorphous isophthalic copolymerization polyethylene terephthalate film (thickness: 100 μm) with a long shape and a Tg of approximately 75°C was used, and corona treatment was performed on one side of the resin substrate.

100 parts by weight of PVA-based resin, which is a 9:1 mixture of polyvinyl alcohol (degree of polymerization 4200, degree of saponification 99.2 mol%) and acetoacetyl-modified PVA (manufactured by Japan Synthetic Chemical Industry Co., Ltd., brand name 'Gosephimer'), potassium iodide 13 The added weight was dissolved in water to prepare a PVA aqueous solution (coating solution).

The PVA aqueous solution was applied to the corona-treated surface of the resin substrate and dried at 60°C to form a PVA-based resin layer with a thickness of 13 μm, thereby producing a laminate.

The obtained laminate was uniaxially stretched 3.0 times in the longitudinal direction (longitudinal direction) in an oven at 140°C (air auxiliary stretching treatment).

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

Next, in a dyeing bath (iodine aqueous solution obtained by mixing iodine and potassium iodide at a weight ratio of 1:7 with respect to 100 parts by weight of water) at a liquid temperature of 30°C, the single transmittance (Ts) of the polarizer finally obtained is the desired value. It was immersed for 60 seconds while adjusting the concentration to achieve this (dyeing treatment).

Next, it was immersed in a crosslinking bath (a boric acid aqueous solution obtained by mixing 3 parts by weight of potassium iodide and 5 parts by weight of boric acid with respect to 100 parts by weight of water) at a liquid temperature of 40°C for 30 seconds (crosslinking treatment).

Thereafter, the laminate was immersed in an aqueous solution of boric acid (boric acid concentration: 4% by weight, potassium iodide concentration: 5% by weight) at a liquid temperature of 64°C, while the total stretch ratio was stretched in the longitudinal direction (longitudinal direction) between rolls with different circumferential speeds. Uniaxial stretching was performed to increase the size by 5.5 times (underwater stretching treatment).

Thereafter, the laminate was immersed in a washing bath (aqueous solution obtained by mixing 3 parts by weight of potassium iodide with respect to 100 parts by weight of water) at a liquid temperature of 20°C (washing treatment).

Afterwards, it was dried in an oven maintained at about 90°C and brought into contact with a heating roll made of SUS whose surface temperature was maintained at about 75°C (dry shrink treatment). Here, the transport tension of the laminate was set to 6 N/cm, and the time from the oven entrance until the laminate came into contact with the heating roll was set to 5 seconds.

In this way, polarizer P1 with a thickness of 5.5 μm was formed on the resin substrate, and a polarizing plate having the structure of resin substrate/polarizer P1 was obtained. The shrinkage rate in the absorption axis direction of polarizer P1 was 2.5%. Additionally, the single transmittance (Ts) of polarizer P1 was 43.0%, the indentation elastic modulus was 8.77 GPa, and the indentation hardness was 0.688 GPa.

[Manufacturing Example 2: Production of polarizer]

In the heat shrink treatment, the transport tension of the laminate was set to 5 N/cm, and the time from the oven entrance until the laminate came into contact with the heating roll was set to 3.5 seconds, and the resin substrate was prepared in the same manner as in Production Example 1. /A polarizing plate having the structure of polarizer P2 was obtained. The shrinkage rate in the absorption axis direction of polarizer P2 was 1.5%. The single transmittance, indentation elastic modulus, and indentation hardness of polarizer P2 were the same as those of polarizer P1 in Production Example 1.

[Manufacture Example 3: Production of polarizer]

In the heat shrink treatment, a polarizing plate having the structure of resin base material/polarizer P3 was obtained in the same manner as in Production Example 1 except that the conveyance tension of the laminated body was set to 7 N/cm. The shrinkage rate in the absorption axis direction of polarizer P3 was 3.0%. The single transmittance, indentation elastic modulus, and indentation hardness of polarizer P3 were the same as those of polarizer P1 in Production Example 1.

[Preparation Example 4: Preparation of coating liquid for forming resin layer]

97.0 parts of methyl methacrylate (MMA, manufactured by Fujifilm Wako Pure Chemical Industries, brand name 'Methyl Methacrylate Monomer'), 3.0 parts of copolymerization monomer represented by the following formula (1e), polymerization initiator (manufactured by Fujifilm Wako Purely Chemical Industries, brand name ' 0.2 part of 2,2'-azobis(isobutyronitrile)') was dissolved in 200 parts of toluene. Next, a polymerization reaction was performed for 5.5 hours while heating at 70°C in a nitrogen atmosphere to obtain a boron-containing acrylic resin solution (solid content concentration: 33%). The Tg of the obtained boron-containing acrylic polymer (resin) was 110°C and Mw was 80,000. 20 parts of the obtained boron-containing acrylic resin was dissolved in 80 parts of methyl ethyl ketone to obtain a coating liquid for forming a resin layer (20% resin solution).

[Manufacturing Example 5: Production of a laminate of phase contrast layer/other phase contrast layer]

1. Production of retardation film constituting the retardation layer

In a batch polymerization apparatus comprising two vertical reactors equipped with stirring blades and a reflux condenser controlled at 100°C, 29.60 parts by weight (0.046 parts by weight) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane was added. mol), isosorbide (ISB) 29.21 parts by weight (0.200 mol), spiroglycol (SPG) 42.28 parts by weight (0.139 mol), diphenyl carbonate (DPC) 63.77 parts by weight (0.298 mol), and calcium acetate as a catalyst. 1.19×10 ^-2 parts by weight (6.78×10 ^-5 mol) of monohydrate were introduced. After purging the reactor with reduced pressure nitrogen, heating was performed using a heat medium, and stirring was started when the internal temperature reached 100°C. 40 minutes after the start of the temperature increase, the internal temperature reached 220°C, and while controlling to maintain this temperature, pressure reduction was started, and 90 minutes after reaching 220°C, the temperature was set to 13.3 kPa. The phenol vapor produced by-product with the polymerization reaction was guided to a reflux condenser at 100°C, the monomer component contained in a small amount in the phenol vapor was returned to the reactor, and the phenol vapor that did not condense was guided to a condenser at 45°C for recovery. After nitrogen was introduced into the first reactor and the pressure was restored to atmospheric pressure, the oligomerized reaction solution in the first reactor was transferred to the second reactor. Next, the temperature increase and pressure reduction in the second reactor were started, and in 50 minutes, the internal temperature was 240°C and the pressure was 0.2 kPa. Thereafter, polymerization was allowed to proceed until the predetermined stirring power was reached. When the predetermined power was reached, nitrogen was introduced into the reactor, the pressure was restored, and 0.7 parts by mass of PMMA was melt-kneaded with respect to 100 parts by weight of the resulting polyester carbonate-based resin, and then extruded into water and the strands were cut to obtain pellets. .

After vacuum drying the obtained polyester carbonate resin (pellet) at 80°C for 5 hours, a single screw extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250°C), T die (width 200 mm, set temperature: 250°C), cooling roll (Set temperature: 120 to 130°C) and a film forming device equipped with a winder were used to produce a long resin film with a thickness of 105 μm. The obtained long resin film was stretched 2.8 times in the width direction at 138°C while adjusting to obtain a predetermined retardation, and a retardation film (λ/4 plate) with a thickness of 38 μm was obtained. Re(550) of the obtained retardation film was 144 nm, and Re(450)/Re(550) was 0.86.

2. Fabrication of a laminate of phase contrast layer/other phase contrast layer

20 parts by weight of a side-chain liquid crystal polymer represented by the following formula (3) (the numbers 65 and 35 in the formula represent the mole percent of the monomer unit, and are conveniently expressed as a block polymer: weight average molecular weight 5000), representing a nematic liquid crystalline phase. Prepare a liquid crystal coating solution by dissolving 80 parts by weight of polymerizable liquid crystal (manufactured by BASF, brand name: PaliocolorLC242) and 5 parts by weight of a photopolymerization initiator (manufactured by Chiba Specialty Chemicals, brand name: Irgacure 907) in 200 parts by weight of cyclopentanone. did. Then, the coating liquid was applied to the PET base material that had been vertically aligned using a bar coater, and then heated and dried at 80°C for 4 minutes to orient the liquid crystal. By irradiating ultraviolet rays to this liquid crystal layer and curing it, a positive C plate (thickness 3 μm) exhibiting refractive index characteristics of nz>nx=ny was formed on the substrate. The obtained positive C plate was transferred to the above-mentioned retardation film through an adhesive layer, and a laminate of the λ/4 plate and the positive C plate was obtained.

[Preparation Example 6: Preparation of the first adhesive layer]

(Preparation of acrylic polymer A1)

A monomer mixture containing 94.9 parts of butylacrylate, 0.1 part of hydroxyethyl acrylate, and 5 parts of acrylic acid was introduced into a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser. Additionally, with respect to 100 parts of this monomer mixture, 0.1 part of 2,2'-azobisisobutyronitrile was introduced together with 100 parts of ethyl acetate as a polymerization initiator, and nitrogen gas was introduced while gently stirring to replace nitrogen, and then the mixture was purged with nitrogen in the flask. The polymerization reaction was performed for 8 hours while maintaining the liquid temperature at around 55°C to prepare a solution of acrylic polymer A1 with a weight average molecular weight (Mw) of 2.2 million and Mw/Mn = 3.9.

(Preparation of adhesive PSA1)

Based on 100 parts of solid content of the acrylic polymer A1 solution, 0.6 parts of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Tosoh Corporation, brand name 'Colonate L'), 0.3 parts of peroxide crosslinking agent (manufactured by Nippon Yuji Corporation, brand name 'Niper BMT') and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name 'KBM-403') were mixed to obtain adhesive PSA1.

[Preparation Example 7: Preparation of the first adhesive layer]

(Preparation of acrylic polymer A2)

A monomer mixture containing 87.9 parts of butylacrylate, 10 parts of 2-ethylhexyl acrylate, 0.1 part of hydroxyethyl acrylate, and 2 parts of acrylic acid was placed in a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser. introduced. Additionally, with respect to 100 parts of this monomer mixture, 0.1 part of 2,2'-azobisisobutyronitrile was introduced along with 90 parts of ethyl acetate as a polymerization initiator, and nitrogen gas was introduced while gently stirring to purge the mixture into the flask. The polymerization reaction was performed for 8 hours while maintaining the liquid temperature at around 55°C to prepare a solution of acrylic polymer A2 with a weight average molecular weight (Mw) of 2.2 million and Mw/Mn = 4.0.

(Preparation of adhesive PSA2)

Based on 100 parts of solid content of the acrylic polymer A2 solution, 0.6 parts of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Tosoh Corporation, brand name 'Colonate L'), 0.3 parts of peroxide crosslinker (manufactured by Nippon Yuji Corporation, brand name 'Niper BMT') and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name 'KBM-403') were mixed to obtain adhesive PSA2.

[Preparation Example 8: Production of second adhesive layer]

(Preparation of acrylic polymer A3)

A monomer mixture containing 91 parts of butylacrylate, 6 parts of acryloylmorpholine, 2.7 parts of acrylic acid, and 0.3 parts of 4-hydroxybutylacrylate in a four-necked flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser. was introduced. Additionally, with respect to 100 parts of this monomer mixture, 0.1 part of 2,2'-azobisisobutyronitrile was introduced together with 100 parts of ethyl acetate as a polymerization initiator, and nitrogen gas was introduced while gently stirring to replace nitrogen, and then the mixture was purged with nitrogen in the flask. The polymerization reaction was performed for 8 hours while maintaining the liquid temperature at around 55°C to prepare a solution of acrylic polymer A3 with a weight average molecular weight (Mw) of 2.7 million and Mw/Mn = 3.8.

(Preparation of adhesive PSA3)

Based on 100 parts of solid content of the acrylic polymer A3 solution, 0.1 part of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Tosoh Corporation, brand name 'Colonate L'), 0.3 part of peroxide crosslinker (manufactured by Nippon Yuji Corporation, brand name 'Niper BMT') and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name 'KBM-403') were mixed to obtain adhesive PSA3.

[Preparation Example 9: Production of second adhesive layer]

(Preparation of acrylic polymer A4)

In a four-neck flask equipped with a stirring blade, thermometer, nitrogen gas introduction tube, and condenser, 82.7 parts of butylacrylate, 10 parts of 2-ethylhexyl acrylate, 6 parts of acryloylmorpholine, 1 part of acrylic acid, and 4-hydroxyl A monomer mixture containing 0.3 parts of butylacrylate was introduced. Additionally, with respect to 100 parts of this monomer mixture, 0.1 part of 2,2'-azobisisobutyronitrile was introduced along with 90 parts of ethyl acetate as a polymerization initiator, and nitrogen gas was introduced while gently stirring to purge the mixture into the flask. The polymerization reaction was performed for 8 hours while maintaining the liquid temperature at around 55°C to prepare a solution of acrylic polymer A4 with a weight average molecular weight (Mw) of 2.6 million and Mw/Mn = 3.9.

(Preparation of adhesive PSA4)

Based on 100 parts of solid content of the acrylic polymer A4 solution, 0.1 part of trimethylolpropane/tolylene diisocyanate adduct (manufactured by Tosoh Corporation, brand name 'Colonate L'), 0.3 part of peroxide crosslinking agent (manufactured by Nippon Yuji Corporation, brand name 'Niper BMT') and 0.2 parts of an epoxy group-containing silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., brand name 'KBM-403') were mixed to obtain adhesive PSA4.

[Example 1]

The HC-TAC film was bonded to the surface of the polarizer P1 of the polarizing plate obtained in Production Example 1 (the surface on the opposite side to the resin substrate) through an ultraviolet curing adhesive. In addition, the HC-TAC film is a film in which an HC layer (7 μm thick) was formed on a triacetylcellulose (TAC) film (25 μm thick), and the TAC film was bonded to the polarizer side. Next, the resin substrate was peeled to obtain a polarizing plate having the structure of HC layer/TAC film (protective layer)/polarizer P1. Next, the coating liquid for forming the resin layer of Production Example 4 was applied to the surface of the polarizer P1 using a wire bar, and then the coating film was dried at 60° C. for 5 minutes to form a solidified product of the coating film of the organic solvent solution of the resin. A resin layer (thickness 400 nm) was formed. Next, the first adhesive layer PSA1 (thickness 15 μm) obtained in Production Example 6 was placed on the surface of the resin layer, and the structure of HC layer/TAC film (protective layer)/polarizer P1/resin layer/first adhesive layer PSA1 was formed. An optical laminate having was obtained. The obtained optical laminate was subjected to the evaluation of '(3) crack' above. The results are shown in Table 1.

[Examples 2 to 7, Comparative Examples 1 to 7 and Reference Examples 1 to 2]

An optical laminate was obtained in the same manner as in Example 1 except that the polarizer, resin layer, retardation layer, first adhesive layer, and second adhesive layer were combined as shown in Table 1. The obtained optical laminated body was subjected to the same evaluation as Example 1. The results are shown in Table 1. In addition, the 'protective layer' of Reference Examples 1 and 2 in the 'Resin Layer' column of the table indicates that a TAC film was used, not a resin layer.

[Table 1]

[evaluation]

As is clear from Table 1, according to the embodiment of the present invention, in the optical laminate in which a specific resin layer is disposed adjacent to the polarizer, the same configuration (components that do not include a retardation layer, or include a retardation layer) When compared with each other, cracking of the polarizer in a high temperature environment can be suppressed. Additionally, it can be seen that cracks become more noticeable by providing a phase difference layer. In addition, as is clear from Reference Examples 1 and 2, it can be seen that cracks become noticeable in the optical laminate in which a specific resin layer is disposed adjacent to the polarizer.

The optical laminate according to the embodiment of the present invention can be suitably used in an image display device (typically a liquid crystal display device or an organic EL display device).

10: Polarizer
11: Polarizer
12: protective layer
20: Resin layer
30: Phase contrast layer
40: Other phase contrast layer
50: first adhesive layer
60: Second adhesive layer
100: Optical laminate
101: Optical laminate

Claims (12)

A polarizing plate including a polarizer and a protective layer disposed on one side of the polarizer, a resin layer disposed adjacent to the polarizer, and a first adhesive layer disposed as an outermost layer on the resin layer side,
The shrinkage rate of the polarizer in the absorption axis direction is 2.5% or less,
The thickness of the first adhesive layer is 17㎛ or less, and the storage modulus at 23°C is 0.10MPa or more,
Optical laminate. According to paragraph 1,
On the side opposite to the polarizer of the resin layer, it further includes a retardation layer laminated through a second adhesive layer,
The retardation layer has a circular polarization function or an elliptical polarization function,
The thickness of the second adhesive layer is 7 μm or less, and the storage modulus at 23° C. is 0.12 MPa or more,
Optical laminate. According to paragraph 2,
When the total thickness of the polarizer and the protective layer is set to A (㎛), and the total thickness of the resin layer, the second adhesive layer, the retardation layer, and the first adhesive layer is set to B (㎛), A < An optical laminate that satisfies the relationship B. According to paragraph 3,
The retardation layer is composed of a stretched resin film, its Re (550) is 100 nm to 200 nm, satisfies the relationship of Re (450) < Re (550), and the slow axis of the retardation layer and the polarizer are Optical laminates where the absorption axis angle is between 40° and 50°:
(Here, Re(450) and Re(550) are the in-plane retardation measured with light with a wavelength of 450 nm and 550 nm at 23°C, respectively.) According to paragraph 4,
An optical laminate further comprising another retardation layer on the side opposite to the resin layer of the retardation layer, the refractive index characteristic exhibiting the relationship nz>nx=ny. According to paragraph 1,
An optical laminate wherein the resin layer includes a resin having a glass transition temperature of 85° C. or higher and a weight average molecular weight (Mw) of 25,000 or higher. According to clause 6,
An optical laminate wherein the resin layer has an indentation elastic modulus of 8 GPa or more. In clause 7,
An optical laminate wherein the resin layer has a thickness of 1 μm or less. According to clause 8,
An optical laminate in which the thickness of the polarizer is 8 μm or less, the indentation elastic modulus is 9.5 GPa or less, and the indentation hardness is 0.65 GPa or more. According to clause 9,
An optical laminate wherein the polarizer has an orientation function of 0.30 or more. According to paragraph 1,
An optical laminate wherein the shrinkage rate of the polarizer in the absorption axis direction is 2.0% or less. An image display device comprising an image display panel and the optical laminated body according to any one of claims 1 to 11 bonded to the image display panel via the first adhesive layer.