Optical laminate and image display device using the same

Abstract

The present invention relates to an optical laminate and an image display device using the same, which exhibits excellent bending resistance, pencil hardness, adhesion, and contrast in bright light, while suppressing the occurrence of streaks even at low haze levels. [Solution] An optical laminate comprising a light-transmitting substrate having birefringence and made of a biaxially oriented PEs film, and an optical functional layer provided on one side of the light-transmitting substrate, wherein the total haze is 10% or less, the thickness of the light-transmitting substrate is 20 to 70 μm, and when the retardation measured from a direction perpendicular to the substrate surface is Re(0°) and the retardation measured from a direction tilted at 50° to the substrate surface is Re(50°), the following condition (a) is satisfied in the wavelength range of 360 to 830 nm. 0nm≦|Re(0°)-Re(50°)|≦500nm ···(a)

Description

Technical Field

[0001] The present invention relates to an optical laminate and an image display device using the same.

Background Art

[0002] Since liquid crystal display devices (LCDs) and organic EL display devices (OLEDs) are required to have durability even for use in harsher environments, the polarizing plate disposed on the viewing side is also required to have small changes in its characteristics, that is, high durability, in harsh environments such as high temperature and high humidity.

[0003] Conventionally, as a polarizer protective film, triacetyl cellulose (TAC) has been widely used. On the other hand, from the viewpoint of durability as described above, it has been proposed to use a film excellent in mechanical properties, chemical resistance, and moisture barrier properties, such as polyethylene terephthalate (PET), as a polarizer protective film.

[0004] However, polyester films such as PET have large birefringence in the in-plane and thickness directions of the film due to being highly stretched. Therefore, when a film made of a high-birefringence material such as a polyester film is used as a polarizer protective film disposed between a polarizer and an image display cell, the polarization state is distorted due to the influence of the birefringence, and thus the visibility tends to be significantly reduced, such as the occurrence of rainbow-like unevenness (rainbow unevenness). In particular, with the recent increase in brightness and color purity of image display devices, such rainbow unevenness has become more easily visible, which is one of the reasons for preventing the use of a polyester film as a polarizer protective film.

[0005] Therefore, for example, Patent Document 1 discloses an image display device in which the occurrence of rainbow unevenness is suppressed by using a crystalline PET film having an in-plane retardation, a thickness retardation, and a ratio thereof within a specific range as a protective film.

[0006] Patent Document 2 discloses a film suitable for polarizing plate protective films that does not exhibit color unevenness, mottling, or interference colors, and is made by laminating three or more layers alternately consisting of an A layer mainly composed of crystalline PET and a B layer mainly composed of a thermoplastic resin different from the crystalline PET, wherein the in-plane retardation, thickness retardation, variation in in-plane retardation, and Young's modulus exhibit specific values.

[0007] Patent Document 3 discloses that a laminated film of 10 layers or less, having a polyester A layer and a polyester B layer having a lower melting point than polyester A layer, in which the in-plane retardation and retardation at an angle inclined at 50° with respect to the film surface are specific, can be suitably used as a polarizer protective film without exhibiting interference colors. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2011-112928 [Patent Document 2] Japanese Patent Publication No. 2020-192812 [Patent Document 3] International Publication No. 2015 / 093307 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] The film described in Patent Document 1 cannot be said to sufficiently suppress the occurrence of variegation, and polarizing... It was difficult to apply this to glass. Furthermore, although the films in Patent Documents 2 and 3 suppress the occurrence of variegation with low retardation, their properties as a surface treatment layer for polarizing plates, such as mechanical properties like pencil hardness, are not sufficient, and further improvements are needed.

[0010] The present invention relates to an optical laminate that suppresses the occurrence of streaks even at low haze levels, while also exhibiting excellent bending resistance, pencil hardness, adhesion, and contrast in bright light, as well as an image display device using the same. [Means for solving the problem]

[0011] The present invention relates to the following [1] to [2]. [1] An optical laminate used in an image display device having a polarizing plate, It consists of a biaxially oriented film mainly composed of polyester, and is a light-transmitting substrate with birefringence, It comprises an optical functional layer provided on one side of a light-transmitting substrate, The total haze of the optical stack is 10% or less. The thickness of the light-transmitting substrate is 20 to 70 μm. An optical laminate characterized in that, when the retardation measured from a direction perpendicular to the substrate surface of a light-transmitting substrate is defined as Re(0°) and the retardation measured from a direction inclined at 50° to the substrate surface is defined as Re(50°), the following condition (a) is satisfied in the wavelength range of 360 to 830 nm. 0nm≦|Re(0°)-Re(50°)|≦500nm ···(a) [2] An image display device comprising an image display panel and the optical laminate described in [1] provided on the front surface of the image display panel. [Effects of the Invention]

[0012] The optical laminate of the present invention exhibits excellent effects, including suppression of streaking even at low haze levels, while also providing superior bending resistance, pencil hardness, adhesion, and contrast in bright light. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of the optical laminate of the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view showing another example of the optical laminate of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0014] FIG. 1 is a schematic cross-sectional view showing an example of an optical laminate according to an embodiment.

[0015] The optical laminate 10 includes a light-transmissive substrate 1, and an easy-adhesion layer 2 and a first functional layer 3 in this order on one surface of the light-transmissive substrate 1. In this case, the first functional layer 3 corresponds to an optical functional layer.

[0016] FIG. 2 is a schematic cross-sectional view showing another example of the optical laminate according to the embodiment.

[0017] The optical laminate 10 includes a light-transmissive substrate 1, and an easy-adhesion layer 2, a first functional layer 3, and a second functional layer 4 in this order on one surface of the light-transmissive substrate 1. In this case, the first functional layer 3 and the second functional layer 4 correspond to optical functional layers.

[0018] Hereinafter, details of each layer will be described.

[0019] The light-transmissive substrate is a transparent film that serves as the base of the optical laminate. Examples of the light-transmissive substrate include a biaxially stretched film (biaxially stretched PEs film) mainly composed of polyester having birefringence, and having a thickness of 20 to 70 μm. When the thickness of the light-transmissive substrate is 20 μm or more, the light-transmissive substrate is not too thin, and the strength of the optical laminate can be kept good. Therefore, it is preferably 20 μm or more, more preferably 23 μm or more. On the other hand, when the thickness of the light-transmissive substrate is 70 μm or less, the optical laminate is not too thick, and it can contribute to thinning of the image display device using the optical laminate. Therefore, it is preferably 70 μm or less, more preferably 50 μm or less. In this specification, the thickness of a layer can be measured using a contact-type film thickness gauge Mitutoyo's Lightmatic VL-50A (10.5 mmΦ carbide spherical probe, measurement load 0.06 N).

[0020] As the light-transmitting substrate, when the retardation measured from a direction perpendicular to the substrate surface (normal direction) is defined as Re(0°) and the retardation measured from a direction tilted at 50° to the substrate surface is defined as Re(50°), the substrate that satisfies the following condition (a) over the entire wavelength range of 360 to 830 nm is used. 0nm≦|Re(0°)-Re(50°)|≦500nm ···(a) Here, retardation measured from a direction perpendicular to the substrate surface (normal direction) refers to in-plane retardation (Re), which is defined as Re = (nx - ny) × d, where nx is the refractive index in the slow axis direction (direction with a large refractive index) of the light-transmitting substrate, ny is the refractive index in the fast axis direction, and d is the thickness of the light-transmitting substrate.

[0021] In this invention, it is desirable that the light-transmitting substrate used has retardation measured from each direction relative to the substrate surface within a specific range in order to suppress the occurrence of streaks. To ensure that the difference in visible streaks is not noticeable when the image display device is viewed from the front and from an oblique direction, the difference between Re(0°) and Re(50°) is specified to be small. Specifically, when the absolute difference (|Re(0°)-Re(50°)|) is defined as the difference between Re(0°) and Re(50°), it is sufficient that this absolute difference in the wavelength range of 360 to 830 nm is 500 nm or less. From the viewpoint of suppressing streaks, it is preferably 480 nm or less, more preferably 450 nm or less, and even more preferably 400 nm or less. The lower limit is not particularly limited, and as long as it is 0 nm or more, the effect of suppressing streaks and bending resistance is achieved, so for example, it may be 40 nm or more, or 50 nm or more.

[0022] The |Re(0°)-Re(50°)| range at a wavelength of 360 nm, which is the lower limit of visible light, is preferably 500 nm or less, more preferably 480 nm or less, even more preferably 450 nm or less, even more preferably 400 nm or less, and even more preferably 384 nm or less. The lower limit may be 50 nm or more, or 92 nm or more.

[0023] The |Re(0°)-Re(50°)| wavelength of 450 nm is preferably 500 nm or less, more preferably 470 nm or less, even more preferably 420 nm or less, even more preferably 400 nm or less, and even more preferably 350 nm or less. The lower limit may be 50 nm or more, and may also be 85 nm or more.

[0024] The |Re(0°)-Re(50°)| wavelength of 550 nm is preferably 500 nm or less, more preferably 450 nm or less, even more preferably 400 nm or less, and even more preferably 331 nm or less. The lower limit may be 50 nm or more, and may also be 81 nm or more.

[0025] The |Re(0°)-Re(50°)| wavelength of 589 nm is preferably 500 nm or less, more preferably 450 nm or less, even more preferably 400 nm or less, even more preferably 350 nm or less, and even more preferably 327 nm or less. The lower limit may be 50 nm or more, and may also be 80 nm or more.

[0026] The |Re(0°)-Re(50°)| wavelength of 650 nm is preferably 500 nm or less, more preferably 440 nm or less, even more preferably 390 nm or less, and even more preferably 350 The wavelength is less than or equal to nm, more preferably 321 nm or less. The lower limit should be 50 nm or more, and may also be 79 nm or more.

[0027] The |Re(0°)-Re(50°)| wavelength of 750 nm is preferably 500 nm or less, more preferably 430 nm or less, even more preferably 380 nm or less, even more preferably 350 nm or less, and even more preferably 316 nm or less. The lower limit is 40 nm or more, and may be 50 nm or more, or 77 nm or more.

[0028] The |Re(0°)-Re(50°)| range at a wavelength of 830 nm, which is the upper limit of visible light, is preferably 500 nm or less, more preferably 400 nm or less, even more preferably 350 nm or less, and even more preferably 312 nm or less. The lower limit may be 40 nm or more, and may also be 50 nm or more, or 76 nm or more.

[0029] Furthermore, it is preferable that the wavelength dependence of |Re(0°)-Re(50°)| in the wavelength range of 360 to 830 nm is small, that is, that there is no significant difference in the value of |Re(0°)-Re(50°)| at any wavelength in the visible light range of 360 to 830 nm. Specifically, the difference between the maximum and minimum values ​​of |Re(0°)-Re(50°)| for each wavelength of 360 nm, 450 nm, 550 nm, 589 nm, 650 nm, 750 nm, and 830 nm is not particularly limited to a lower limit, and may be, for example, 3 nm or more or 6 nm or more, while the upper limit is preferably 100 nm or less, more preferably 72 nm or less.

[0030] In the present invention, the light-transmitting substrate has a Re(0°) of 500 nm or less, and more preferably 480 nm or less, across the entire wavelength range of 360 to 830 nm, from the viewpoint of suppressing streaking. The lower limit is not particularly limited across the entire wavelength range of 360 to 830 nm, and if it is 20 nm or more, the effect of suppressing streaking and achieving bending resistance is achieved, so for example, it may be 40 nm or more, or 50 nm or more.

[0031] For example, the Re(0°) at a wavelength of 360 nm, which is the lower limit of visible light, is preferably 500 nm or less, more preferably 480 nm or less, and even more preferably 462 nm or less. The lower limit can be 50 nm or more, and may be 60 nm or more, or 70 nm or more.

[0032] The Re(0°) at a wavelength of 450 nm is preferably 450 nm or less, more preferably 400 nm or less, and even more preferably 394 nm or less. The lower limit may be 50 nm or more, and may also be 55 nm or more, or 62 nm or more.

[0033] The Re(0°) at a wavelength of 550 nm is preferably 400 nm or less, more preferably 370 nm or less, even more preferably 365 nm or less, and even more preferably 362 nm or less. The lower limit is 40 nm or more, and may be 50 nm or more, 55 nm or more, or 58 nm or more.

[0034] The Re(0°) at a wavelength of 589 nm is preferably 400 nm or less, more preferably 380 nm or less, even more preferably 360 nm or less, and even more preferably 354 nm or less. The lower limit is 40 nm or more, and may be 50 nm or more, or 57 nm or more.

[0035] The Re(0°) at a wavelength of 650 nm is preferably 400 nm or less, more preferably 360 nm or less, and even more preferably 344 nm or less. The lower limit may be 40 nm or more, and may also be 50 nm or more, or 55 nm or more.

[0036] The Re(0°) at a wavelength of 750 nm is preferably 380 nm or less, more preferably 360 nm or less, even more preferably 350 nm or less, and even more preferably 331 nm or less. Lower limit The value should be 40nm or greater, but it may also be 45nm or greater, or 54nm or greater.

[0037] The Re(0°) at a wavelength of 830 nm, which is the upper limit of visible light, is preferably 370 nm or less, more preferably 350 nm or less, and even more preferably 324 nm or less. The lower limit may be 40 nm or more, and may also be 45 nm or more, or 53 nm or more.

[0038] Furthermore, it is preferable that the wavelength dependence of Re(0°) in the wavelength range of 360 to 830 nm is small, that is, that there is no significant difference in the value of Re(0°) at any wavelength in the visible light range of 360 to 830 nm. Specifically, the difference between the maximum and minimum values ​​of Re(0°) at each wavelength of 360 nm, 450 nm, 550 nm, 589 nm, 650 nm, 750 nm, and 830 nm is not particularly limited to a lower limit, and may be, for example, 10 nm or more or 16 nm or more, while the upper limit is preferably 150 nm or less, more preferably 138 nm or less.

[0039] While the Re(50°) of the light-transmitting substrate tends to be larger at shorter wavelengths, it is desirable that it be within a specific range across the entire wavelength range of 360 to 830 nm. From the viewpoint of suppressing streaks, the Re(50°) across the entire wavelength range of 360 to 830 nm is preferably 900 nm or less, and more preferably 850 nm or less. The lower limit is not particularly limited across the entire wavelength range of 360 to 830 nm, and if it is 100 nm or more, it is possible to achieve both suppression of streaks and bending resistance, so for example, it may be 120 nm or more, or 140 nm or more.

[0040] For example, the Re(50°) at a wavelength of 360 nm, which is the lower limit of visible light, is preferably 900 nm or less, more preferably 850 nm or less, and even more preferably 812 nm or less. The lower limit can be 140 nm or more, and may be 200 nm or more, or 224 nm or more.

[0041] The Re(50°) at a wavelength of 450 nm is preferably 850 nm or less, more preferably 800 nm or less, and even more preferably 731 nm or less. The lower limit may be 140 nm or more, and may also be 150 nm or more, or 201 nm or more.

[0042] The Re(50°) at a wavelength of 550 nm is preferably 800 nm or less, more preferably 750 nm or less, and even more preferably 685 nm or less. The lower limit may be 140 nm or more, and may also be 150 nm or more, or 187 nm or more.

[0043] The Re(50°) at a wavelength of 589 nm is preferably 800 nm or less, more preferably 750 nm or less, and even more preferably 673 nm or less. The lower limit may be 140 nm or more, and may also be 150 nm or more, or 184 nm or more.

[0044] The Re(50°) at a wavelength of 650 nm is preferably 800 nm or less, more preferably 750 nm or less, even more preferably 700 nm or less, and even more preferably 659 nm or less. The lower limit may be 140 nm or more, and may also be 150 nm or more, or 180 nm or more.

[0045] The Re(50°) at a wavelength of 750 nm is preferably 750 nm or less, more preferably 700 nm or less, and even more preferably 643 nm or less. The lower limit may be 120 nm or more, and may also be 150 nm or more, or 175 nm or more.

[0046] The Re(50°) at a wavelength of 830 nm, which is the upper limit of visible light, is preferably 700 nm or less, more preferably 650 nm or less, and even more preferably 634 nm or less. The lower limit may be 120 nm or more, and may also be 150 nm or more, or 173 nm or more.

[0047] Furthermore, the wavelength dependence of Re(50°) in the 360-830nm range is low. In other words, it is preferable that there is no significant difference in the Re(50°) value at any wavelength in the visible light range from 360 to 830 nm. Specifically, the difference between the maximum and minimum values ​​of the Re(50°) for each wavelength of 360 nm, 450 nm, 550 nm, 589 nm, 650 nm, 750 nm, and 830 nm is not particularly limited to a lower limit, and may be, for example, 40 nm or more or 51 nm or more, while the upper limit is preferably 200 nm or less, more preferably 178 nm or less.

[0048] Furthermore, the light-transmitting substrate used in the present invention preferably has a thickness-direction retardation (Rth') of 0 nm to 1,500 nm at a wavelength of 589 nm, as defined by the following formula. Rth'=(nx-nz)×d nx: Refractive index in the slow axis direction (direction of high refractive index) within the plane of the light-transmitting substrate. nz: Refractive index in the thickness direction of a light-transmitting substrate d: Thickness of the light-transmitting substrate

[0049] For the light-transmitting substrate, a smaller Rth' value at a wavelength of 589 nm is preferable, but a value of 0 nm or greater is preferable because it results in a smaller difference between the refractive index in the in-plane direction and the refractive index in the thickness direction, thereby suppressing the occurrence of streaks. Furthermore, if the Rth' at a wavelength of 589 nm is 1,500 nm or less, the thickness of the light-transmitting substrate does not become too large, which is preferable for thinning the optical laminate. However, from the viewpoint of achieving both suppression of streaks and bending resistance, it is preferably 1,450 nm or less, more preferably 1,400 nm or less, even more preferably 1,380 nm or less, and even more preferably 1,000 nm or less.

[0050] Furthermore, the light-transmitting substrate used in the present invention preferably has an Nz' coefficient defined by the following formula of 18 or less. The definitions of Re and Rth' in the formula are as described above. Nz'=Rth' / Re

[0051] If the Nz' coefficient is 18 or less, the occurrence of streaks depending on the observation angle is suppressed. However, from the viewpoint of achieving compatibility with bending resistance, it is preferably 18.0 or less, more preferably 16.0 or less, even more preferably 14.0 or less, even more preferably 12.0 or less, even more preferably 10.0 or less, even more preferably 8.0 or less, and even more preferably 6.5 or less. The lower limit is not particularly limited, and examples include 1 or more and 1.0 or more.

[0052] In this specification, retardation can be measured using a phase difference film / optical material inspection device (RETS-100, manufactured by Otsuka Electronics) according to the following measurement conditions. [Measurement conditions] • Retardation measurement method: Rotational analyzer method • Measurement spot diameter: φ5mm • Tilt angle range: 0°, 50° • Measurement wavelength range: 360nm to 830nm • The value is calculated using the formula N=(nx+ny+nz) / 3, based on the average refractive index N: nx, ny, and nz of the light-transmitting substrate. In the case of PEs film, N=1.660 Note that retardation values ​​Re(0°) and Re(50°) are for wavelengths of 360, 450, 550, 589, 650, 750, and 830 nm.

[0053] Biaxially oriented PEs film offers excellent low moisture permeability, transparency, heat resistance, and mechanical strength, making it suitable for use as a light-transmitting substrate to improve the durability of optical laminates. Furthermore, biaxially oriented PEs film is inexpensive, offering advantages in terms of manufacturing costs.

[0054] The biaxially oriented PEs film used in the present invention is not limited to any known film in the art, as long as it satisfies the above condition (a). For example, The film may comprise one of a homopolymer layer (film), a random copolymer layer (film), and a block copolymer layer (film), or it may comprise a laminate of two or more of these types. Furthermore, it may comprise multiple laminates of the same type of film. Specifically, examples include a laminate of multiple layers consisting of crystalline polyethylene terephthalate and a thermoplastic resin different from the crystalline polyethylene terephthalate, or a laminate of multiple layers of polyethylene terephthalate with different melting points. Alternatively, it may comprise multiple laminates of crystalline polyethylene terephthalate and an amorphous thermoplastic resin different from the polyethylene terephthalate. The biaxially oriented PEs film may also contain various additives, such as antioxidants, heat stabilizers, weather stabilizers, UV absorbers, pigments, dyes, organic or inorganic fine particles, fillers, antistatic agents, nucleating agents, etc., within limits that do not impair the effects of the present invention.

[0055] When preparing an unstretched film by biaxial stretching, the stretching can be carried out in such a way that the resulting film satisfies condition (a), for example, by a sequential biaxial stretching method in which the unstretched film is stretched longitudinally and then in the width direction, or by stretching in the width direction and then in the longitudinal direction, or by a simultaneous biaxial stretching method in which the longitudinal and width directions of the film are stretched almost simultaneously. The stretching ratio can be appropriately set according to known techniques to satisfy condition (a). Heat treatment may be performed after the stretching process if necessary.

[0056] Biaxially oriented PEs films may be subjected to surface modification treatments to improve adhesion with other layers. Examples of surface modification treatments include alkali treatment, corona treatment, plasma treatment, sputtering, application of surfactants or silane coupling agents, and Si deposition.

[0057] The easy-adhesion layer is laminated on a light-transmitting substrate. The easy-adhesion layer improves adhesion and further enhances bending resistance, even if the first functional layer laminated on top of the easy-adhesion layer is thin. The other side of the light-transmitting substrate may also have the easy-adhesion layer laminated on it to improve adhesion to other layers (e.g., adhesive layers for display lamination) and thus improve adhesion.

[0058] The easy-adhesion layer is formed, for example, by applying an anchor coating agent. However, the easy-adhesion layer is not essential, and the first functional layer may be laminated directly onto the light-transmitting substrate.

[0059] The thickness of the easy-adhesion layer is not particularly limited. For example, a lower limit could be 50 nm or more, and upper limits could be 500 nm or less, or 400 nm or less.

[0060] Examples of the first functional layers include a hard coat layer and an anti-glare layer. The hard coat layer is intended to impart hardness to the optical laminate, and the anti-glare layer allows for an optical laminate that scatters incident light to suppress reflection of external light.

[0061] The hard coat layer (also called the clear hard coat layer) is laminated on top of the easy-adhesion layer to provide flexibility to the optical laminate while also improving impact resistance, thereby enhancing bending resistance and pencil hardness.

[0062] The hard coat layer can be formed by applying and curing a hard coat layer-forming composition containing an active energy ray-curable compound, a photopolymerization initiator, and a solvent.

[0063] As active energy ray curable compounds, for example, monofunctional, bifunctional, or trifunctional or more (meth)acrylate monomers can be used. In this specification, "(meth)acrylate" is a general term for both acrylate and methacrylate, and "(meth)acryloyl" is a general term for both acryloyl and methacryloyl.

[0064] Examples of monofunctional (meth)acrylate compounds include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfluryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and isobornyl (meth)acrylate. Phosphate, Isodecyl (meth)acrylate, Lauryl (meth)acrylate, Tridecyl (meth)acrylate, Cetyl (meth)acrylate, Stearyl (meth)acrylate, Benzyl (meth)acrylate, 2-Ethoxyethyl (meth)acrylate, 3-Methoxybutyl (meth)acrylate, Ethyl carbitol (meth)acrylate, Phosphate (meth)acrylate, Ethylene oxide-modified Phosphate (meth)acrylate, Phenoxy (meth)acrylate, Ethylene oxide-modified Phenoxy (meth)acrylate, Propylene oxide 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate Acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydrohydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydrohydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, 2-adamantane,Examples include adamantane derivative mono(meth)acrylates such as adamantyl acrylate, which has a monovalent mono(meth)acrylate derived from adamantanediol.

[0065] Examples of difunctional (meth)acrylates include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, hydroxypivalate neopentyl glycol di(meth)acrylate, and other di(meth)acrylates.

[0066] Examples of trifunctional (meth)acrylates include trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris-2-hydroxyethyl isocyanurate tri(meth)acrylate, glycerin tri(meth)acrylate, and other trifunctional (meth)acrylate compounds such as pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate, as well as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, and dipentaerythritol Examples include polyfunctional (meth)acrylate compounds with three or more functions, such as methylmethylolpropane hexa(meth)acrylate and ditrimethylolpropane hexa(meth)acrylate, as well as polyfunctional (meth)acrylate compounds in which some of these (meth)acrylates are substituted with alkyl groups or ε-caprolactone.

[0067] Furthermore, urethane (meth)acrylates can also be used as polyfunctional monomers. Examples of urethane (meth)acrylates include those obtained by reacting a product obtained by reacting a polyester polyol with an isocyanate monomer or prepolymer with a hydroxyl group (meth)acrylate monomer.

[0068] Examples of urethane (meth)acrylates include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer.

[0069] The above-mentioned active energy ray curable compounds may be used individually or in combination of two or more. Furthermore, the active energy ray curable compounds may be monomers in the coating solution or oligomers in which a portion has been polymerized.

[0070] The content of the active energy ray-curable compound is not particularly limited, and is, for example, 10 to 90% by mass of the total amount of solid components. In this specification, the total amount of solid components refers to the total content of all components of the composition other than the solvent.

[0071] The photopolymerization initiator can be any substance that triggers a polymerization reaction upon irradiation with ultraviolet light or electron beams, and examples include 2,2-ethoxyacetophenone, 1-hydroxycyclohexylphenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler ketone, acetophenone, and 2-chlorothioxanthone. These may be used individually or in combination of two or more.

[0072] The content of the photopolymerization initiator is not particularly limited, but is, for example, 0.010 to 20% by mass of the total amount of solid components.

[0073] Examples of solvents include ketone solvents such as acetone, methyl ethyl ketone (MEK), and methyl isobutyl ketone (MIBK); alcohol solvents such as ethanol, methanol, isopropyl alcohol (IPA), and isobutanol; ether solvents such as ethylene glycol dimethyl ether and propylene glycol monomethyl ether (PGME); ester solvents such as ethyl acetate, propylene glycol monomethyl ether acetate (PGMEA), and 2-ethoxyethyl acetate; and aromatic hydrocarbon solvents such as toluene. These may be used individually or in combination of two or more.

[0074] The hard coat layer forming composition may contain various additives as needed, such as antistatic agents, defoamers, antioxidants, ultraviolet absorbers, infrared absorbers, colorants, light stabilizers, polymerization inhibitors, photosensitizers, and surface modifiers. The amounts of these additives can be adjusted as appropriate according to known technology.

[0075] The thickness of the hard coat layer is not particularly limited; for example, the lower limit may be 2.0 μm or more and 5.0 μm or more, while the upper limit may be 10 μm or less and 8.0 μm or less.

[0076] The anti-glare layer (also called the anti-glare hard coat layer) can be laminated on top of the easy-adhesion layer to form a fine uneven surface on the outermost surface of the optical laminate.

[0077] The anti-glare layer can be formed by applying and curing an anti-glare layer-forming composition containing an active energy ray-curable compound and organic and / or inorganic fine particles (fillers).

[0078] As the active energy ray curable compound, the polymerizable compound described in the hard coat layer section can be used.

[0079] Organic fine particles are materials that primarily form fine irregularities on the surface of the anti-glare layer, thereby providing a function to diffuse ambient light. As organic fine particles, resin particles made from light-transmitting resin materials such as acrylic resin, polystyrene resin, styrene-(meth)acrylic acid ester copolymer, polyethylene resin, epoxy resin, silicone resin, polyvinylidene fluoride, and polyfluoroethylene resins can be used. To adjust the refractive index and dispersion of the resin particles, two or more types of resin particles with different materials (refractive index) may be mixed and used. The average particle size of the organic fine particles is preferably 0.50 to 10 μm. The content of organic fine particles is not particularly limited, but is, for example, 1.0 to 20% by mass of the total amount of solid components.

[0080] Inorganic microparticles (fillers) are primarily used to regulate the sedimentation and aggregation of organic microparticles in the anti-glare layer. Examples of inorganic microparticles include silica microparticles, metal oxide microparticles, and various mineral microparticles. Examples of silica microparticles include colloidal silica and silica microparticles surface-modified with reactive functional groups such as (meth)acryloyl groups. Examples of metal oxide microparticles include alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, and zirconia. Examples of mineral microparticles include mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, bydelite, saponite, hectorite, stevensite, nontronite, magadiite, islarite, kanemite, layered titanate, smectite, and synthetic smectite. Mineral microparticles may be natural products or synthetic products (including substituted and derivative products), and mixtures of both may be used. Among mineral microparticles, layered organic clay minerals are more preferred. Layered organic clay minerals refer to those in which organic onium ions are introduced between layers of swellable clay. The organic onium ions are not limited as long as they can be organicated by utilizing the cation exchange properties of the swellable clay. When layered organic clay minerals are used as mineral microparticles, the synthetic smectite described above can be suitably used. Synthetic smectite has the function of increasing the viscosity of the anti-glare layer forming composition, suppressing the settling of resin particles and inorganic microparticles, and adjusting the uneven surface shape of the optical functional layer. The average particle size of the inorganic microparticles is preferably 10 to 200 nm. The content of inorganic microparticles is not particularly limited, and is, for example, 1.0 to 20% by mass of the total amount of solid components.

[0081] The anti-glare layer formation composition may contain the above-mentioned photopolymerization initiators and solvents as appropriate. It may also contain various additives as described for the hard coat layer, if necessary. The amounts of these additives can be adjusted as appropriate according to known techniques.

[0082] The thickness of the anti-glare layer is not particularly limited; for example, the lower limit may be 2.0 μm or more and 5.0 μm or more, while the upper limit may be 10 μm or less and 8.0 μm or less.

[0083] As a second functional layer, an anti-reflective layer can be mentioned. The anti-reflective layer is on the surface of the optical laminate. Surface reflection can be reduced.

[0084] An anti-reflective layer can be laminated on top of a hard coat layer or an anti-glare layer to reduce surface reflection of the optical laminate. Examples of anti-reflective layers include low refractive index layers, medium refractive index layers, and high refractive index layers, and depending on the application, they may be used as a single layer or in combination of multiple layers. For example, as a second functional layer, examples include a low refractive index layer only, a layer with a low refractive index layer and a high refractive index layer laminated together, and a layer with a low refractive index layer, a high refractive index layer and a medium refractive index layer laminated together.

[0085] The low refractive index layer has a refractive index lower than that of the underlying hard coat layer or anti-glare layer, and can suppress reflection through optical interference, thereby improving visibility. Examples of refractive indices include approximately 1.25 to 1.45.

[0086] A low refractive index layer can be formed by applying a composition containing an active energy ray curable compound to the surface of an underlying layer, such as a hard coat layer or an anti-glare layer, and curing the coating film. The low refractive index layer may also contain a refractive index adjusting agent for refractive index adjustment.

[0087] Suitable refractive index modifiers include fine particles such as LiF, MgF, 3NaF·AlF or AlF (all with a refractive index of 1.4), or Na3AlF6 (crylcite, refractive index 1.33), or silica fine particles with internal voids. Silica fine particles with internal voids are advantageous for lowering the refractive index of low refractive index layers because the void portion can have the refractive index of air (approximately 1). Specifically, porous silica particles and silica particles with a shell structure can be used. The content of the refractive index modifier is not particularly limited, and is, for example, 1.0 to 20% by mass of the total amount of solid components.

[0088] As the active energy ray curable compound, the polymerizable compound described in the hard coat layer section can be used. In addition, the low refractive index layer formation composition may contain the polymerization initiators, solvents, additives, etc., as appropriate.

[0089] The thickness of the low refractive index layer is not particularly limited; for example, lower limits include 50 nm or more and 75 nm or more, while upper limits include 200 nm or less and 150 nm or less. From the viewpoint of thinning and suppressing reflectivity, the optical film thickness (nd), obtained by multiplying the film thickness of the low refractive index layer by the refractive index of the low refractive index layer, may be designed to be approximately equal to 1 / 4 of the wavelength of visible light (the wavelength to be suppressed).

[0090] High-refractive-index and medium-refractive-index layers, like low-refractive-index layers, suppress reflection through optical interference. Depending on the layering configuration, the refractive index adjusting agent used can be appropriately adjusted to form them in the same manner as the low-refractive-index layer. When using a low-refractive-index layer in combination with a high-refractive-index layer and / or a medium-refractive-index layer, their refractive indices are not particularly limited and can be used based on relative evaluation.

[0091] The optical laminate of the present invention may have one or more other functional layers laminated on it, such as an antistatic layer, an electromagnetic wave shielding layer, an infrared absorption layer, an ultraviolet absorption layer, or a color correction layer, as long as the effects of the present invention are not impaired. Furthermore, a cover glass may be provided on top of the optical functional layer to protect the outermost surface.

[0092] The coating method for each of the above-mentioned layer compositions is not particularly limited, and can be used, for example, with a spin coater, roll coater, reverse roll coater, gravure coater, microgravure coater, knife coater, bar coater, wire bar coater, die coater, dip coater, spray coater, applicator, etc.

[0093] The coated composition can be photocured by heating and drying, followed by irradiation with ultraviolet light using a known light source such as a halogen lamp.

[0094] Thus, the optical laminate of the present invention is obtained. Preferred embodiments of the optical laminate of the present invention include, for example, those laminated in any of the configurations selected from (1) to (4) below. Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer ... (1) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer ... (2) Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer / Anti-reflective layer ... (3) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer / Anti-reflective layer ... (4)

[0095] When the anti-reflective layer is a low refractive index layer, embodiments (3) and (4) are as follows: Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer / Low refractive index layer ... (3-1) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer / Low refractive index layer ... (4-1) Examples include those configured in the manner described above. Furthermore, when the anti-reflective layer consists of a low refractive index layer and a high refractive index layer, embodiments (3) and (4) are as follows: Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer / High refractive index layer / Low refractive index layer ... (3-2) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer / High refractive index layer / Low refractive index layer ... (4-2) Examples include those configured in the manner described above. Furthermore, when the anti-reflective layer consists of a low refractive index layer, a high refractive index layer, and a medium refractive index layer, embodiments (3) and (4) are as follows; Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer / Medium refractive index layer / High refractive index layer / Low refractive index layer ... (3-3) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer / Medium refractive index layer / High refractive index layer / Low refractive index layer ... (4-3) Examples include those composed in the following manner.

[0096] The thickness of the optical laminate of the present invention is not particularly limited and may be, for example, 20 to 100 μm.

[0097] The optical laminate of the present invention preferably has a total haze of 10% or less. In this specification, the total haze can be measured using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136. By having a total haze of 10% or less, an optical laminate with high contrast in bright light can be obtained. If the haze exceeds 10%, it is possible to seemingly suppress light leakage when displaying black in the dark due to transmission loss due to scattering, but this is undesirable because when displaying black in bright light, scattering may cause the black display to appear whitish and reduce contrast.

[0098] The optical laminate of the present invention, when a planar unloaded U-shaped stretch test fixture (DMX-FS) is attached to a desktop durability test machine (manufactured by Yuasa System Equipment), a sample is attached so that it is flat, and the optical functional layer is facing outwards while the distance between opposing surfaces is 2 mm, is continuously folded 180°. Even after 200,000 continuous folds, no fracture at the bend can be visually confirmed. Furthermore, the optical laminate of the present invention can be folded in the same manner when the orientation in which the vertical direction of the display and the slow phase axis of the light-transmitting substrate of the optical laminate are parallel is set as the reference rotation position (0°), and when the optical laminate is rotated 90° clockwise from the reference position. No fracture can be confirmed after testing in each orientation. A higher number of folds without fracture indicates higher bending resistance.

[0099] In this invention, the evaluation of nijimura is performed assuming the use of polarized sunglasses. Specifically, first, the backlight (brightness 5,000 cd / m²) 2 (To the extent) on a display equipped An observation sample is prepared with the following components arranged in order: a first polarizer, the optical laminate of the present invention, and a second polarizer (assuming polarized sunglasses). At this time, the absorption axis of the first polarizer is orthogonal to the vertical direction of the display, and the absorption axis of the second polarizer is orthogonal to the absorption axis of the first polarizer. In addition, the orientation in which the vertical direction of the display and the slow phase axis of the light-transmitting substrate of the optical laminate are parallel is taken as the reference rotation position (0°), and the optical laminate is rotated 90° clockwise (90° from the reference rotation position), and the streaks at each orientation are observed visually. The observer will perform observations from a position directly in front of the display, 50-60 cm away, and from an oblique position 50-60 cm away from the display and tilted 50° to the left or right with respect to the normal direction when viewed from the front. It is preferable that the optical laminate of the present invention does not produce streaks, but even if it does, it is acceptable if it is not a practical problem.

[0100] In accordance with JIS K5400-1900 (250g load), when the pencil hardness of the optical functional layer surface is measured using a pencil (uni, manufactured by Mitsubishi Pencil) and a Clemens scratch tester (HA-301, manufactured by Tester Sangyo), it is preferable that the pencil hardness be H or higher when the change in appearance due to scratching is visually observed and the maximum hardness at which no scratch is observed is used as the evaluation value.

[0101] The optical laminate of the present invention can be subjected to a cross-cut test in accordance with JIS K5600, and the adhesion of the optical functional layer to the light-transmitting substrate can be investigated by determining the percentage of the area of ​​the optical functional layer that remains without peeling. When the peeling state is classified into six stages from 0 to 5, with the least peeling, the optical laminate of the present invention preferably falls into categories 0 to 1, indicating good adhesion.

[0102] The optical laminate of the present invention is attached to a liquid crystal monitor (BUFFALO, FTD-W2023ADSR) via an adhesive or an easy-adhesion layer. When the brightness of the liquid crystal monitor when displaying white (white brightness) and when displaying black (black brightness) is measured using a luminance meter (Konica Minolta, LS-100), and the value obtained by dividing the white brightness by the black brightness is calculated, it is preferable that the rate of change from the contrast calculated in the same manner without the optical laminate is 45% or less. The measurement environment is a brightly lit room with the lighting adjusted to 200 lux in the measurement area. A smaller rate of change in contrast indicates better contrast in bright light.

[0103] The optical laminate according to this embodiment can be used to construct an image display device by laminating it to the outermost surface of an image display panel such as a liquid crystal panel or an organic EL panel. A touch panel may be provided between the optical laminate and the image display panel. Because the optical laminate according to this embodiment uses a biaxially oriented PEs film as the light-transmitting substrate, it has excellent moisture resistance, bending resistance, and surface hardness, and because the unevenness caused by the biaxially oriented PEs film is suppressed, it is suitable as an optical film to be provided on the outermost surface of an image display device having a polarizing plate. Furthermore, since the light-transmitting substrate used in the present invention also has excellent adhesion, the durability of the optical laminate is also excellent. Because the optical laminate of the present invention has bending resistance, it can also be used as an optical film for a foldable image display device.

[0104] As described above, the optical laminate according to this embodiment comprises a biaxially oriented PEs film having specific optical properties as a light-transmitting substrate. Generally, when PET films called medium retardation PET films or low retardation PET films are used as light-transmitting substrates, they have excellent bending resistance because they are biaxially oriented films, but there is a problem that the application is limited because if the haze of the surface treatment layer is low, the unevenness becomes noticeable. Also, when ultra-high retardation PET films are used as light-transmitting substrates, since the film is uniaxially oriented, the occurrence of unevenness is suppressed, but there is a problem that it has poor bending resistance. On the other hand, the optical laminate of the present invention comprises an ultra-low retardation PEs film with a very low retardation value, so even if the haze of the optical laminate is low, the unevenness is not noticeable. This method prevents the occurrence of blemishes and, being a biaxially oriented film, offers excellent bending resistance and allows for thinning. In this embodiment, since the light-transmitting substrate is a biaxially oriented PEs film with specific optical properties, the occurrence of blemishes is suppressed regardless of the type of surface treatment layer. In addition, it offers excellent adhesion to the optical functional layer and ensures the bending resistance, surface hardness, and bright-field contrast required for optical laminates. [Examples]

[0105] The present invention will be specifically described below with reference to examples, but the present invention is not limited in any way by these examples.

[0106] Preparation Example 1 of Light-Transmitting Substrates (PEs Substrates 1-1~17; Ultra-Low RePEs Film) First, the following resins Aa and Ba were prepared as materials for the polyester film. Resin Aa: Polyethylene terephthalate Resin Ba:Ethylene terephthalate 70 mol% - Cyclohexanedimethanol 30 mol% copolymer

[0107] Next, the following materials were prepared as surface coating agent α for the polyester film. Methyl methacrylate 64 parts by mass Acrylic acid 33 parts by mass Melanin-based crosslinking agent: 1.0 part by mass Colloidal silica (80 nm diameter) 1.0 part by mass Fluorine-based surfactant 1.0 part by mass

[0108] Next, each material was extruded through the slit of a T-shaped die at 280°C so that the layer structure was resin Aa(2) / resin Ba(6) / resin Aa(2), and then cooled and solidified on a casting drum (electrostatically charged) at 23°C. Here, the numbers in parentheses indicate the thickness ratio of each material.

[0109] Next, the solidified cast film was heated with a heat roll at 80°C and stretched 3.3 times by the difference in peripheral speed, after which corona discharge treatment was performed on both sides.

[0110] Next, surface coating agent α was applied to both sides as an easy-adhesion coating using a reverse kissing method, so that the film thickness after drying was 0.10 μm.

[0111] Next, the material was stretched 4.3 times in the lateral direction under conditions of 140°C, and then subjected to heat treatment at 225°C.

[0112] Next, a 2% widthwise relaxation treatment was performed at 225°C, followed by a 1% widthwise relaxation treatment at 100°C to obtain a biaxially oriented PEs film with the film thickness shown in Table 1 below. The optical properties are shown in Tables 1-4.

[0113] The thickness of the obtained film layers was measured using a contact-type film thickness gauge, Mitutoyo Lightmatic VL-50A (10.5 mmΦ carbide spherical probe, measuring load 0.06 N).

[0114] Furthermore, retardation was measured using a phase difference film / optical material inspection device (RETS-100, manufactured by Otsuka Electronics) according to the following measurement conditions. [Measurement conditions] • Retardation measurement method: Rotational analyzer method • Measurement spot diameter: φ5mm • Tilt angle range: 0°, 50° • Measurement wavelength range: 360nm to 830nm The value is calculated using the formula N=(nx+ny+nz) / 3, based on the average refractive index N: nx, ny, and nz of the light-transmitting substrate. In the case of PET film, N=1.660 Note that the in-plane retardation (Re) and thickness retardation (Rth') values ​​are for a wavelength of 589 nm. Furthermore, retardations Re(0°) and Re(50°) were measured across the entire wavelength range. Below, as an example, the values ​​for wavelengths 360, 450, 550, 589, 650, 750, and 830 nm, along with the absolute difference between Re(0°) and Re(50°) (|Re(0°)-Re(50°)|), are shown.

[0115] [Table 1]

[0116] [Table 2]

[0117] [Table 3]

[0118] [Table 4]

[0119] Preparation Example 2 of Light-Transmitting Substrates (PET Substrate 2-1; Ultra-High RePET Film) <Unstretched film> Polyethylene terephthalate raw material was melted at 285°C and filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 95% cut of 10μm particles). The resulting material was laminated in a 2-type, 3-layer confluence block, extruded into a sheet from a die, and then cooled and solidified by winding it onto a casting drum with a surface temperature of 30°C using an electrostatic casting method. During this process, the discharge rate of each extruder was adjusted so that the thickness ratio of the three layers was 10:80:10.

[0120] Next, after corona discharge treatment was performed on both sides of the solidified cast film, an easy-adhesion surface coating agent was applied to both sides using a reverse kiss method to a film thickness of 0.1 μm after drying, thereby obtaining an unstretched film.

[0121] <Uniaxially oriented film> The unstretched film obtained above was stretched in the width direction using a tenter stretcher at a stretching temperature of 125°C. Next, while maintaining the stretched width, it was treated at a temperature of 225°C for 30 seconds, and then a 3% relaxation treatment was performed in the width direction to obtain a uniaxially oriented PET film with a film thickness of 80 μm. The optical properties are shown in Tables 5 to 8.

[0122] [Table 5]

[0123] [Table 6]

[0124] [Table 7]

[0125] [Table 8]

[0126] Preparation Examples of Light-Transmitting Substrates 3 (PET Substrates 3-1~7; RePET Film) <Unstretched film> Polyethylene terephthalate raw material was melted at 285°C and filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 95% cut of 10μm particles). The resulting material was laminated in a 2-type, 3-layer confluence block, extruded into a sheet from a die, and then cooled and solidified by winding it onto a casting drum with a surface temperature of 30°C using an electrostatic casting method. During this process, the discharge rate of each extruder was adjusted so that the thickness ratio of the three layers was 10:80:10.

[0127] Next, after performing corona discharge treatment on both sides of the solidified cast film, a surface coating agent was applied to both sides as an easy-adhesion coating using a reverse kiss method to a film thickness of 0.10 μm after drying, thereby obtaining an unstretched film.

[0128] <Biaxially oriented film> The unstretched film obtained above was heated to 105°C using a heated roll group and an infrared heater, then stretched longitudinally using a roll group with different peripheral speeds, and finally stretched widthwise at a stretching temperature of 125°C using a tenter stretcher to obtain a biaxially oriented PET film having the film thickness shown in Table 9 below. The optical properties are shown in Tables 9 to 12.

[0129] [Table 9]

[0130] [Table 10]

[0131] [Table 11]

[0132] [Table 12]

[0133] Preparation Examples of Light-Transmitting Substrates 4 (PET Substrates 4-1~3; Low-RePET Film) <Unstretched film> Polyethylene terephthalate raw material was melted at 285°C and filtered through a stainless steel sintered filter medium (nominal filtration accuracy: 95% cut of 10μm particles). The resulting material was laminated in a 2-type, 3-layer confluence block, extruded into a sheet from a die, and then cooled and solidified by winding it onto a casting drum with a surface temperature of 30°C using an electrostatic casting method. During this process, the discharge rate of each extruder was adjusted so that the thickness ratio of the three layers was 10:80:10.

[0134] Next, after performing corona discharge treatment on both sides of the solidified cast film, a surface coating agent was applied to both sides as an easy-adhesion coating using a reverse kiss method to a film thickness of 0.10 μm after drying, thereby obtaining an unstretched film.

[0135] <Biaxially oriented film> The unstretched film obtained above was heated to 105°C using a heated roll group and an infrared heater, then stretched longitudinally with a roll group having different peripheral speeds, and finally stretched widthwise at a stretching temperature of 125°C using a tenter stretcher to obtain a biaxially oriented PET film having the film thickness shown in Table 13 below. The optical properties are shown in Tables 13-16.

[0136] [Table 13]

[0137] [Table 14]

[0138] [Table 15]

[0139] [Table 16]

[0140] Examples of optical laminate preparation (Examples 1-20 and Comparative Examples 1-12) Optical laminates were fabricated according to the following method to have the layer configuration shown in Tables 17-18.

[0141] <Clear hard coat layer (Clear HC layer)> A mixture of 100 parts by mass of UV-curable acrylic resin, 3.0 parts by mass of a photopolymerization initiator, and 10 parts by mass of a quaternary ammonium salt was diluted with a solvent. This mixture was then coated onto one side of the substrates shown in Tables 17-18 (cured film thickness 5.0 μm), and cured by UV irradiation with a high-pressure mercury lamp in an environment with an oxygen concentration of 1% or less to produce a clear hard coat layer.

[0142] <Anti-glare hard coat layer (AG layer)> A mixture of 100 parts by mass of UV-curable acrylic resin, 3 or 10 parts by mass of organic spherical filler, and 3.0 parts by mass of photopolymerization initiator was diluted with a solvent. This mixture was then coated onto one side of the substrates shown in Tables 17-18 (cured film thickness 5.0 μm), and cured by UV irradiation with a high-pressure mercury lamp in an environment with an oxygen concentration of 1% or less to produce an AG hard coat layer.

[0143] <Anti-reflective layer (low refractive index layer, LR layer)> Hollow silica nanoparticles with a silica outer shell were mixed with an ultraviolet-curable acrylic resin, and 2.0 parts by mass of a photopolymerization initiator was added to 100 parts by mass of the mixture. The mixture was diluted with a solvent so that the cured film thickness would be 138 nm, coated onto a clear HC layer or AG layer, and cured by UV irradiation with a high-pressure mercury lamp in an environment with an oxygen concentration of 1% or less to produce an anti-reflective layer.

[0144] The properties of the obtained optical laminates were evaluated by performing the following tests. In addition, as Reference Example 1, the same evaluation was performed on PEs substrates 1-2. The results are shown in Tables 17-18.

[0145] Test Example 1 [Total Haze] Total haze was measured using a haze meter (NDH4000, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K7136. A total haze of 10% or less is considered acceptable because it indicates high contrast in bright areas.

[0146] Test Example 2 [Bending Resistance] Tabletop durability testing machine (manufactured by Yuasa Systems) with a surface-type unloaded U-shaped expansion and contraction test fixture (DMX-F With S) attached, the test specimen was fixed so that the optical functional layer would be on the side that folded outwards when bent. Then, the specimen was repeatedly folded 180° so that the distance between opposing films was 2 mm. The folding operation was performed once per second for a total of 200,000 times, and cracks on the surface of the optical laminate were visually observed. The test was also performed in two cases: when the orientation in which the vertical direction of the display and the slow phase axis of the light-transmitting substrate of the optical laminate were parallel was set as the reference rotation position (0°), and when the optical laminate was rotated 90° clockwise from the reference position. For each orientation, a "○" was used if no fracture was observed, and a "×" was used if fracture was observed.

[0147] Test Example 3 [Nijimura] Backlight (brightness 5,000 cd / m²) 2An observation sample was prepared by arranging a first polarizer, the optical laminate under test, and a second polarizer (assuming polarized sunglasses) in that order on a display with a certain degree of polarity. At this time, the absorption axis of the first polarizer was orthogonal to the vertical direction of the display, and the absorption axis of the second polarizer was orthogonal to the absorption axis of the first polarizer. Furthermore, the optical laminate was rotated 90° clockwise (90° from the reference rotation position) with the orientation in which the vertical direction of the display and the slow phase axis of the light-transmitting substrate of the optical laminate were parallel as the reference rotation position (0°). The unevenness at each orientation was observed visually. The observer made observations from a position directly in front of the display, 50-60 cm away (incidence angle 0°), and from an oblique position, 50-60 cm away from the display and tilted 50° to the left or right of the normal direction when viewed from the front (incidence angle 50°), and evaluated according to the following evaluation criteria. If no streaks are observed in any of the sample arrangements from any position, it is considered a success with a "◎" rating. If streaks are present but minimal and do not pose a practical problem, it is considered a success with a "〇" rating. (Evaluation Criteria) ×: Nijimura occurs, unusable. △: Some blemishes may occur, but there are no practical problems. ○: Slight blemishes occurred, but there were no practical problems. ◎: No Nijimura (a type of oyster) observed.

[0148] Test Example 4 [Pencil Hardness] In accordance with JIS K5400-1900 (250g load), the pencil hardness of the optical functional layer surface was measured using a pencil (uni, manufactured by Mitsubishi Pencil) and a Clemens-type scratch tester (HA-301, manufactured by Tester Sangyo). The change in appearance due to scratching was observed visually, and the maximum hardness at which no scratch was observed was used as the evaluation value. A pencil hardness of H or higher was considered acceptable.

[0149] Test Example 5 [Adhesion] The adhesion of the optical functional layer to the substrate was investigated by performing a cross-cut test in accordance with JIS K5600 and determining the area ratio of the surface of the optical functional layer that remained without peeling. The peeling state was classified into six stages from 0 to 5, with the least peeling being the most severe. A "○" indicated that the peeling state fell into categories 0 to 1, and a "×" indicated that it fell into categories 2 to 5.

[0150] Test Example 6 [Contrast in Light] An optical laminate was attached to a liquid crystal monitor (BUFFALO, FTD-W2023ADSR) using adhesive, and the brightness of the LCD monitor when displaying white (white brightness) and when displaying black (black brightness) was measured using a luminance meter (Konica Minolta, LS-100). The contrast was defined as the white brightness divided by the black brightness. The measurements were taken in a brightly lit room with the measurement area adjusted to 200 lux. At this time, the rate of decrease from the value measured without the optical laminate was evaluated according to the following evaluation criteria. A rate of decrease of 45% or less under bright room conditions was evaluated as passing. ◎: Decrease rate under bright room conditions is 30% or less ○: Decrease rate under bright room conditions is over 30% and 45% or less. ×: Degradation rate exceeds 45% under bright room conditions

[0151] [Table 17]

[0152] [Table 18]

[0153] From the above results, it can be seen that, compared to Comparative Examples 1 to 12, Examples 1 to 20 have superior bending resistance, pencil hardness, and light-field contrast, and suppress variegation while exhibiting low haze. Furthermore, Examples 13 to 16 have substrate thicknesses of 60 μm or 70 μm, and in addition to the above effects, they exhibit even better pencil hardness. On the other hand, Comparative Example 1, even if the substrate satisfies condition (a), has a high haze of 15%, resulting in inferior light-field contrast. Comparative Example 2, because the substrate is a uniaxially oriented film, has inferior bending resistance and also exhibits short wavelength These methods fail to satisfy condition (a) on the near and long wavelength sides, and cannot suppress the streaking of light incident at an oblique angle. Comparative Examples 3 to 12 use biaxially oriented films as substrates, exhibiting excellent bending resistance and pencil hardness, but they fail to satisfy condition (a) across the entire wavelength range, and were unable to suppress the occurrence of streaking when the haze was 10% or less. [Industrial applicability]

[0154] The optical laminate of the present invention is suitably used as an optical film in an image display device. [Explanation of Symbols]

[0155] 1 Light-transparent base material 2 Easy adhesive layer 3 First functional layer 4 Second functional layer 10 Optical laminate

Claims

1. An optical laminate used in an image display device having a polarizing plate, It consists of a biaxially oriented film mainly composed of polyethylene, and is a light-transmitting substrate with birefringence, The light-transmitting substrate comprises an optical functional layer provided on one side thereof, The total haze of the optical laminate is 10% or less. The thickness of the light-transmitting substrate is 20 to 70 μm. An optical laminate characterized in that, when the retardation measured from a direction perpendicular to the substrate surface of the light-transmitting substrate is defined as Re(0°) and the retardation measured from a direction inclined at 50° to the substrate surface is defined as Re(50°), the following condition (a) is satisfied in the wavelength range of 360 to 830 nm. 0nm≦|Re(0°)-Re(50°)|≦500nm...(a)

2. The optical laminate according to claim 1, having a layer configuration selected from (1) to (4) below. Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer ... (1) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer ... (2) Light-transmitting substrate / Easy-adhesion layer / Anti-glare hard coat layer / Anti-reflective layer ... (3) Light-transmitting substrate / Easy-adhesion layer / Clear hard coat layer / Anti-reflective layer ... (4)

3. The optical laminate according to claim 2, wherein the anti-reflective layer is a low refractive index layer.

4. The optical laminate according to claim 1, wherein an easy-adhesion layer is provided on the side of the light-transmitting substrate that is applied to the polarizer.

5. The optical laminate according to claim 1, wherein no breakage occurs when a test is repeated 200,000 times in which the optical functional layer is placed on the outside and the laminate is folded 180° such that the distance between opposing edges is 2 mm.

6. The optical laminate according to claim 1, wherein a cover glass is laminated on an optical functional layer.

7. Image display panel, An image display device comprising an optical laminate according to any one of claims 1 to 6 provided on the front surface of the image display panel.

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