Optical laminate, and polarizing plate, display panel, and image display device using the same.

Abstract

The present invention provides an optical laminate that eliminates the need for peeling of the substrate and further improves the interlayer adhesion and orientation of the phase difference layer of the optical laminate. [Solution] An optical laminate 100 having a substrate having a first surface S1 and a second surface S2 opposite to the first surface, and a phase difference layer 40 disposed on the first surface S1 side of the substrate, wherein the substrate is an acrylic substrate 10, and a hard coat layer 20 is provided between the acrylic substrate 10 and the phase difference layer 40, and when the average height of the acrylic substrate 10 on the first surface S1 side is defined as Ha [nm], the average of the maximum heights of the acrylic substrate 10 on the first surface S1 side is defined as Hm [nm], and the average thickness of the hard coat layer 20 is defined as Ta [nm], Ha is 2.2 nm or more, Ha / Ta is 0.02720 or less, and Ta-Hm is 2200 nm or more.

Description

Technical Field

[0001] The present disclosure relates to an optical laminate, a polarizing plate, a display panel, and an image display device using the same.

Background Art

[0002] Conventionally, various optical laminates have been used in image display devices. For example, an optical laminate having a function of a circular polarizing plate may be disposed on an emission surface of a display element. The optical laminate having a function of a circular polarizing plate can suppress reflection of external light on the surface of an image display panel. Therefore, the optical laminate having a function of a circular polarizing plate is useful for display elements having a high reflectance, such as an organic EL display element. In this specification, the "circular polarizing plate" means "circular polarizing plate and elliptical polarizing plate" unless otherwise specified.

[0003] The optical laminate having a function of a circular polarizing plate, for example, has a configuration in which an optical laminate including a retardation layer and a polarizer are laminated. As an optical laminate including a retardation layer, for example, an optical laminate in which a retardation layer is formed on a triacetyl cellulose substrate having good optical isotropy is disclosed (Patent Document 1). Further, as an optical laminate including a retardation layer, a release film having a retardation layer on a substrate and the retardation layer being peelable from the substrate is disclosed (Patent Document 2).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the optical laminate described in Patent Document 1, in which a phase difference layer is formed on a triacetylcellulose substrate, there were cases where the interlayer adhesion of the optical laminate and the orientation of the phase difference layer were insufficient. The optical laminate described in Patent Document 2 has the problem of increased manufacturing costs because it requires a process to peel off the substrate. Furthermore, if the optical laminate described in Patent Document 2 is used without peeling off the substrate, there is a problem of poor interlayer adhesion of the optical laminate. [Means for solving the problem]

[0006] The inventors conducted research to solve the above problems. First, the inventors considered forming a phase difference layer on an acrylic substrate. However, when a phase difference layer was formed on an acrylic substrate, cases frequently occurred where the interlayer adhesion of the optical laminate and the orientation of the phase difference layer were insufficient. Through further research, the inventors discovered that by providing a hard coat layer between the acrylic substrate and the phase difference layer, and by ensuring that the shape of the hard coat layer side of the acrylic substrate and the thickness of the hard coat layer meet predetermined conditions, the interlayer adhesion of the optical laminate and the orientation of the phase difference layer can be improved, leading to the completion of this disclosure.

[0007] This disclosure is as follows: <1> ~ <4> To provide. <1> A substrate having a first surface and a second surface opposite to the first surface, An optical laminate having a phase difference layer disposed on the first surface side of the substrate, The substrate is an acrylic substrate, and a hard coat layer is provided between the acrylic substrate and the phase difference layer. When the average height of the first surface of the acrylic substrate is defined as Ha [nm], the average of the maximum heights of the first surface of the acrylic substrate is defined as Hm [nm], and the average thickness of the hard coat layer is defined as Ta [nm], An optical laminate in which Ha is 2.2 nm or greater, Ha / Ta is 0.02720 or less, and Ta-Hm is 2200 nm or greater. <2> The polarizer comprises a polarizer, a first protective film disposed on one side of the polarizer, and a second protective film disposed on the other side of the polarizer, wherein the first protective film is <1> A polarizing plate, which is an optical laminate described above. <3> On the light-emitting surface of the display element, <1> A display panel with the optical laminate described above arranged on it. <4> <3> An image display device, including the display panel described above. [Effects of the Invention]

[0008] According to the optical laminate of this disclosure, and the display panel and image display device using the same, peeling of the substrate of the optical laminate is unnecessary, and furthermore, the interlayer adhesion and orientation of the phase difference layer of the optical laminate can be improved. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing one embodiment of the optical laminate of the present disclosure. [Figure 2] This is a schematic diagram illustrating the interface profile between the acrylic substrate and the hard coat layer. [Figure 3] This is a cross-sectional view showing one embodiment of a polarizing plate in this disclosure. [Figure 4] This is a cross-sectional view showing one embodiment of the display panel of the present disclosure. [Modes for carrying out the invention]

[0010] The embodiments of this disclosure are described below. In this specification, "acrylic" means acrylic-based and / or methacrylic-based materials. In this specification, the in-plane phase difference and the phase difference in the thickness direction are defined as values ​​expressed by the following formula, where Nx is the refractive index in the X-axis direction, which is the axis direction with the highest refractive index in the plane, Ny is the refractive index in the Y-axis direction, which is perpendicular to the X-axis in the plane, Nz is the refractive index in the thickness direction, and d [nm] is the thickness. In-plane phase difference=(Nx-Ny)×d Phase difference in the thickness direction = ((Nx+Ny) / 2-Nz)×d

[0011] [Optical laminate] The optical laminate of the present disclosure a base material having a first surface and a second surface on the opposite side of the first surface an optical laminate having a retardation layer disposed on the first surface side of the base material, where the base material is an acrylic base material, and has a hard coat layer between the acrylic base material and the retardation layer, when the average height on the first surface side of the acrylic base material is defined as Ha [nm], the average of the maximum heights on the first surface side of the acrylic base material is defined as Hm [nm], and the average thickness of the hard coat layer is defined as Ta [nm], Ha is 2.2 nm or more, Ha / Ta is 0.02720 or less, and Ta−Hm is 2200 nm or more.

[0012] FIG. 1 is a cross-sectional view showing an embodiment of the optical laminate of the present disclosure. The optical laminate 100 in FIG. 1 has an acrylic base material 10 having a first surface S1 and a second surface S2 on the opposite side of the first surface. The optical laminate 100 in FIG. 1 has a retardation layer 40 disposed on the first surface S1 side of the acrylic base material 10. The optical laminate 100 in FIG. 1 has a hard coat layer 20 and an alignment layer 30 between the acrylic base material 10 and the retardation layer 40. FIG. 1 is a schematic cross-sectional view. That is, the scales of each layer constituting the optical laminate 100 and the scale of the concavo-convex shape of the first surface S1 are schematized for easy illustration and are different from the actual scales. The same applies to the figures other than FIG. 1.

[0013] <Ha, Ha / Ta, Ta−Hm, θa> The optical laminate of the present disclosure requires that when the average height on the first surface side of the acrylic base material is defined as Ha [nm], the average of the maximum heights on the first surface side of the acrylic base material is defined as Hm [nm], and the average thickness of the hard coat layer is defined as Ta [nm], Ha is 2.2 nm or more, Ha / Ta is 0.02720 or less, and Ta−Hm is 2200 nm or more.

[0014] When forming a hard coat layer on an acrylic substrate, components of the hard coat layer may flow into the acrylic substrate, or components of the acrylic substrate may flow into the hard coat layer. When the amount of these components flowing in increases, the surface shape of the first surface of the acrylic substrate becomes rougher, which tends to improve the adhesion between the acrylic substrate and the hard coat layer. For this reason, by setting Ha to 2.2 nm or more, the interlayer adhesion of the optical laminate can be improved. On the other hand, if Ha is less than 2.2 nm, it is not possible to improve the adhesion between the acrylic substrate and the hard coat layer, and therefore the interlayer adhesion of the optical laminate cannot be improved either.

[0015] The larger the Ha / Ta ratio, the more easily the surface shape of the first surface of the acrylic substrate is reflected in the surface shape of the hard coat layer (Note: In this specification, "surface shape of the hard coat layer" means the surface shape of the hard coat layer opposite to the acrylic substrate). When the surface shape of the acrylic substrate is reflected in the surface shape of the hard coat layer, the orientation of the phase difference layer tends to deteriorate. For this reason, when Ha / Ta exceeds 0.02720, it is not possible to achieve good orientation of the phase difference layer. On the other hand, by setting Ha / Ta to 0.02720 or less, it is possible to achieve good orientation of the phase difference layer. The orientation of the phase difference layer refers to, for example, the orientation of the liquid crystal molecules in the phase difference layer.

[0016] When forming a hard coat layer on an acrylic substrate, components of the acrylic substrate may flow into the hard coat layer. The thinner the hard coat layer, the easier it is for these acrylic substrate components to reach the phase difference layer or orientation layer. The hard coat layer has a thickness distribution, and the Ta-Hm value corresponds to locally thin areas within the hard coat layer. Therefore, the smaller the Ta-Hm value, the easier it is for the acrylic substrate components that flow into the hard coat layer to reach the phase difference layer or orientation layer. When these acrylic substrate components reach the phase difference layer or orientation layer, the orientation of the phase difference layer decreases. Consequently, if Ta-Hm is less than 2200nm, it is not possible to achieve good orientation of the phase difference layer. On the other hand, by setting Ta-Hm to 2200nm or higher, it is possible to achieve good orientation of the phase difference layer.

[0017] Ha, Hm, and θa (described later) can be adjusted by the degree of dissolution of the acrylic substrate. Specifically, Ha, Hm, and θa tend to increase as the degree of dissolution of the acrylic substrate increases, and tend to decrease as the degree of dissolution of the acrylic substrate decreases. The degree of dissolution of the acrylic substrate can be adjusted, for example, by the resin components and solvents contained in the hard coat coating solution, as well as the drying temperature and drying time of the hard coat coating solution. Using materials that readily dissolve the acrylic substrate as the resin components and solvent tends to increase the degree of dissolution of the acrylic substrate. Lowering the drying temperature and increasing the time it takes for the solvent to evaporate also tends to increase the degree of dissolution of the acrylic substrate.

[0018] The Ha wavelength is preferably 2.5 nm or greater, more preferably 2.7 nm or greater, and even more preferably 2.9 nm or greater. If Ha is too large, the average thickness of the hard coat layer required to achieve a Ha / Ta ratio of 0.02720 or less may become too thick. For this reason, Ha is preferably 300.0 nm or less, more preferably 200.0 nm or less, and even more preferably 160.0 nm or less.

[0019] Ha / Ta is preferably 0.02500 or less, more preferably 0.02300 or less, and even more preferably 0.02200 or less. If Ha / Ta is too small, the average thickness of the hard coat layer may become too thick. For this reason, Ha / Ta is preferably 0.00078 or higher, more preferably 0.00100 or higher, and even more preferably 0.00200 or higher.

[0020] Ta-Hm is preferably 2300 nm or more, more preferably 2400 nm or more, and even more preferably 2500 nm or more. If Ta-Hm is too large, the average thickness of the hard coat layer becomes too thick, which can cause curling in the optical laminate. For this reason, Ta-Hm is preferably 10,000 nm or less, more preferably 8,000 nm or less, and even more preferably 7,000 nm or less.

[0021] By increasing Ta, it is easier to suppress the components of the acrylic substrate that have flowed into the hard coat layer from reaching the phase difference layer or orientation layer. Also, by increasing Ta, it is easier to suppress the solvent of the coating liquid for the phase difference layer from passing through the hard coat layer to reach the acrylic substrate. Furthermore, by not making Ta excessively large, it is easier to suppress curling of the optical laminate. For this reason, Ta is preferably between 2300 nm and 11000 nm, more preferably between 4300 nm and 9000 nm, and even more preferably between 2600 nm and 7300 nm.

[0022] Hm is preferably 20 nm to 1000 nm, more preferably 40 nm to 800 nm, and even more preferably 60 nm to 760 nm.

[0023] The average inclination angle θa on the first surface side of the acrylic substrate is preferably 0.6 degrees or more and 14.2 degrees or less, more preferably 0.7 degrees or more and 12.6 degrees or less, and even more preferably 0.8 degrees or more and 11.5 degrees or less. By setting θa to 0.6 degrees or more, it becomes easier to improve the interlayer adhesion of the optical laminate. By setting θa to 14.2 degrees or less, it becomes easier to improve the orientation of the phase difference layer.

[0024] Ha, Hm, Ta, and θa shall be calculated using the following steps 1 and 2.

[0025] Step 1: A vertical cross-sectional image of the optical laminate in the thickness direction is captured using a scanning electron microscope (SEM). Step 2: Extract 10 measurement regions from the photograph obtained in Step 1. The width of each measurement region should be 5 μm. Calculate Ha, Hm, Ta, and θa from the 10 measurement regions.

[0026] 《Process 1》 In step 1, a vertical cross-sectional image of the optical laminate in the thickness direction is captured using a scanning electron microscope.

[0027] In step 1, "a cross-section perpendicular to the thickness direction of the optical laminate" means a cross-section perpendicular to the XY plane, assuming that the second surface of the acrylic substrate is the XY plane. The vertical cross-sectional image in step 1 is taken by preparing a sample in which the vertical cross-section in the thickness direction of the optical laminate is exposed, and then imaging using the sample. In step 1, one location of the sample may be imaged, or two or more locations of the sample may be imaged as needed. That is, in step 1, one vertical cross-sectional image may be taken, or two or more vertical cross-sectional images may be taken. In step 1, it is preferable that the magnification during imaging be between 5,000x and 20,000x.

[0028] The aforementioned sample can be prepared, for example, by the following steps (A1) to (A2). If the interfaces of each layer are difficult to distinguish due to insufficient contrast, the sample may be stained with a dye such as osmium tetroxide, ruthenium tetroxide, or phosphotungstic acid. If the liquid crystal molecules in the phase difference layer are liquid crystal molecules oriented horizontally, it is preferable that the cutting direction in (A2) be parallel to the orientation axis of the liquid crystal molecules.

[0029] (A1) Prepare cut samples by cutting the optical laminate into strips 2 mm wide. The length of the samples can be any length. (A2) Cut the ends of the strip-shaped sample with a diamond knife. The cross-section of the end cut with the diamond knife will be the cross-section to be imaged in step 1.

[0030] 《Process 2》 In step 2, 10 measurement regions are extracted from the photograph obtained in step 1. The width of each measurement region is set to 5 μm. Then, Ha, Hm, Ta, and θa are calculated from the 10 measurement regions.

[0031] In step 2, the 10 measurement areas, each 5 μm wide, may be extracted from a single photograph, or from multiple photographs to total 10. However, the ranges of each measurement area should not overlap.

[0032] In step 2, Ha, the average height of the first surface of the acrylic substrate, Hm, the average of the maximum heights of the first surface of the acrylic substrate, and θa, the average inclination angle of the first surface of the acrylic substrate, are calculated using the following procedure (B1) to (B4). The 5 μm wide profile (B1) to (B4) corresponds to the measurement area in step 2 with a width of 5 μm.

[0033] (B1) Obtain a profile of the interface between the acrylic substrate and the hard coat layer from the photograph taken in step 1. The profile refers to data quantified with the measurement area on the horizontal axis and the unevenness height in the cross-sectional direction on the vertical axis. Obtain 10 profiles with a width of 5 μm. The 10 profiles may be extracted from a single photograph, or they may be extracted from multiple photographs so that the total is 10.

[0034] By binarizing the photographic data captured in step 1 using image analysis software, it becomes easier to obtain a profile of the interface between the acrylic substrate and the hard coat layer.

[0035] The lowest height of each of the 10 profiles obtained in (B2)(B1) is set as 0 nm, which is the baseline height for each profile. The average height of the first surface of the acrylic substrate is calculated for each of the 10 profiles. The average of the average heights of the 10 profiles is set as Ha.

[0036] The lowest height of each of the 10 profiles obtained in (B3)(B1) is set as 0 nm, which is the baseline height for each profile. For each of the 10 profiles, the maximum height on the first surface side of the acrylic substrate is calculated. The average of the maximum heights of the 10 profiles is set as Hm. Figure 2 is a schematic diagram of the profile P at the interface between the acrylic substrate and the hard coat layer. In Figure 2, the symbol BP indicates the lowest point in the profile. In Figure 2, the symbol Hm1 indicates the highest point in the profile. The maximum height of the profile in Figure 2 corresponds to the difference in height between Hm1 and BP.

[0037] For each of the 10 profiles obtained in (B4)(B1), calculate the average tilt angle on the first surface side of the acrylic substrate. Let θa be the average of the average tilt angles of the 10 profiles. The average slope angle of each profile is tan -1The extreme value is calculated as (total height difference of the profile / 5 μm). The total height difference of the profile is the sum of the height differences of adjacent extreme values ​​within the profile. The extreme values ​​of the profile are the points where the height difference of the profile changes from increasing to decreasing, and the points where the height difference of the profile changes from decreasing to increasing. In the profile in Figure 2, the black circles correspond to the extreme values. In some cases, it can be difficult to identify extreme values ​​from a profile. For example, if the profile is a gentle curve, it can be difficult to identify the extreme values. When it is difficult to identify the extreme values, the sum of the height differences between adjacent measurement points at all measurement points that make up the profile may be considered as the total height difference of the profile.

[0038] In step 2, the average thickness of the hard coat layer, Ta, is calculated using the following procedure (C1) to (C2).

[0039] (C1) In the first of the 10 measurement areas extracted in step 2, the thickness of the hard coat layer is measured from a vertical cross-sectional image taken with a scanning electron microscope. The thickness of the hard coat layer is measured at five arbitrarily selected locations in the 5 μm width direction. However, these five locations are selected so as not to be concentrated in any particular area in the 5 μm width direction. The average of the thicknesses at the five locations is taken as the thickness of the hard coat layer in the first measurement area. Perform the same procedure as in (C2) and (C1) for the 2nd to 10th measurement areas, and define Ta as the average thickness of the hard coat layer in the 1st to 10th measurement areas.

[0040] <Base material (acrylic base material)> The substrate has a first surface and a second surface opposite to the first surface. In this disclosure, an acrylic substrate is used as the substrate. In this specification, "acrylic" means acrylic and / or methacrylic.

[0041] The acrylic substrate serves, for example, as a support for the phase difference layer and the hard coat layer. Acrylic substrates are preferred because they offer excellent light transmittance, optical isotropy, and light resistance.

[0042] The acrylic substrate preferably has (meth)acrylic resin as its main component. "Main component" means that the proportion of (meth)acrylic resin to the total amount of the acrylic substrate is 60% by mass or more, preferably 80% by mass or more, and more preferably 90% by mass or more. In this specification, "(meth)acrylic" is a general term for "acrylic" and "methacrylic". Also, in this specification, "(meth)acrylate" is a general term for "acrylate" and "methacrylate".

[0043] Examples of (meth)acrylic resins include (meth)acrylic acid esters alone or copolymers thereof, and copolymers of (meth)acrylic acid esters and comonomers. Examples of (meth)acrylic acid esters include methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, dimethylaminoethyl (meth)acrylate, and glycidyl (meth)acrylate. Examples of comonomers include vinyl acetate, (meth)acrylonitrile, (meth)acrylamide, styrene, (meth)acrylic acid, itaconic acid, and maleic anhydride. The (meth)acrylic resin may be modified with fluorine.

[0044] Examples of (meth)acrylic resins include polyalkyl (meth)acrylates such as polymethyl (meth)acrylate, polyethyl (meth)acrylate, polypropyl (meth)acrylate, and polybutyl (meth)acrylate. Among these, polymethyl (meth)acrylate is preferred. The (meth)acrylic resin may be a (meth)acrylic resin having a ring structure such as a lactone ring structure or an imide ring structure.

[0045] The acrylic substrate may contain organic particles, inorganic particles, and other particles to the extent that they do not impair the effects of the present disclosure. On the other hand, if the acrylic substrate contains particles, Ha and Ha / Ta tend to increase. For this reason, it is preferable that the acrylic substrate is substantially free of particles. Substantially free of particles means that the particle content relative to the total amount of the acrylic substrate is 0.3% by mass or less, preferably 0.1% by mass or less, and more preferably 0.01% by mass or less.

[0046] To enhance the optical isotropy of the acrylic substrate, it is preferable that the in-plane phase difference at a wavelength of 550 nm is 100 nm or less, more preferably 10 nm or less, and even more preferably 2 nm or less.

[0047] The thickness of the acrylic substrate is preferably 5 μm to 150 μm, more preferably 20 μm to 100 μm, and even more preferably 30 μm to 50 μm. By making the acrylic substrate thickness 5 μm or more, the handling properties of the optical laminate can be improved. By making the acrylic substrate thickness 150 μm or less, it is possible to make polarizing plates, display panels, and image display devices thinner.

[0048] <Hard coat layer> The optical laminate of this disclosure requires having a hard coat layer between the acrylic substrate and the phase difference layer. By providing a hard coat layer such that Ha, Ha / Ta, and Ta-Hm are within predetermined ranges, the interlayer adhesion of the optical laminate and the orientation of the phase difference layer can be improved. On the other hand, if the orientation layer and phase difference layer described later are provided on the acrylic substrate without a hard coat layer, it is difficult to ensure sufficient interlayer adhesion of the optical laminate and the orientation of the phase difference layer. This is because the orientation layer is usually a thin film and cannot fully perform the function of the hard coat layer. Furthermore, because the orientation layer is a thin film, it is difficult to mitigate defects on the acrylic substrate.

[0049] The hard coat layer preferably contains the cured product of an ionizing radiation-curable resin composition as its main component. Specifically, it is preferable that the hard coat layer contains 50% by mass or more of the cured product of the ionizing radiation-curable resin composition, more preferably 70% by mass or more, and even more preferably 90% by mass or more, relative to the total solid content of the hard coat layer. By including the cured product of the ionizing radiation-curable resin composition as the main component of the hard coat layer, the crosslinking density of the hard coat layer is improved. This makes it easier to suppress the reach of components of the acrylic substrate that have flowed into the hard coat layer to the phase difference layer or orientation layer, and also makes it easier to suppress the reach of the coating liquid for the phase difference layer to the acrylic substrate. Therefore, it is easier to improve the orientation of the phase difference layer.

[0050] An ionizing radiation-curable resin composition is a composition containing a compound having an ionizing radiation-curable functional group (hereinafter also referred to as "ionizing radiation-curable compound"). Examples of ionizing radiation-curable functional groups include ethylenically unsaturated bonding groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, as well as epoxy groups and oxetanyl groups. As the ionizing radiation-curable compound, a compound having an ethylenically unsaturated bonding group is preferred, a compound having two or more ethylenically unsaturated bonding groups is more preferred, and among these, a polyfunctional (meth)acrylate compound having two or more ethylenically unsaturated bonding groups is even more preferred. Both monomers and oligomers can be used as the polyfunctional (meth)acrylate compound. Ionizing radiation refers to electromagnetic waves or charged particle beams that possess energy quanta capable of polymerizing or bridging molecules. Typically, ultraviolet (UV) or electron beams (EB) are used, but other electromagnetic waves such as X-rays and gamma rays, as well as charged particle beams such as alpha rays and ion beams, can also be used.

[0051] The ionizing radiation-curable compound preferably contains polyfunctional (meth)acrylate monomers and monofunctional (meth)acrylate monomers. Because polyfunctional (meth)acrylate monomers have a high crosslinking density, they can help suppress the reach of components of the acrylic substrate to the phase difference layer or orientation layer, and also help suppress the reach of solvents in the coating solution for the phase difference layer to the acrylic substrate. On the other hand, monofunctional (meth)acrylate monomers readily dissolve the acrylic substrate. Therefore, by including polyfunctional (meth)acrylate monomers and monofunctional (meth)acrylate monomers in the ionizing radiation-curable compound, it is possible to improve the interlayer adhesion and orientation of the phase difference layer of the optical laminate. The mass ratio of polyfunctional (meth)acrylate monomer to monofunctional (meth)acrylate monomer (polyfunctional (meth)acrylate monomer: monofunctional (meth)acrylate monomer) is preferably 30:70 to 90:10, more preferably 40:60 to 80:20, and even more preferably 50:50 to 70:30. By setting the mass ratio within the above range, a good balance of the effects of the polyfunctional (meth)acrylate monomer and monofunctional (meth)acrylate monomer is achieved, making it easier to improve the interlayer adhesion and phase difference layer orientation of the optical laminate.

[0052] Among polyfunctional (meth)acrylate compounds, examples of difunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiaacrylate, bisphenol A tetrapropoxydiaacrylate, and 1,6-hexanediol diacrylate. Examples of (meth)acrylate monomers with three or more functionalities include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate.

[0053] Examples of monofunctional (meth)acrylates include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, and isobornyl (meth)acrylate.

[0054] The above (meth)acrylate monomer may have a modified molecular skeleton. For example, the above (meth)acrylate monomer may also be one in which a part of the molecular skeleton has been modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc. The above (meth)acrylate monomer preferably contains a hydroxyl group in order to improve adhesion with the orientation layer.

[0055] When the ionizing radiation-curable compound is an ultraviolet-curable compound, the ionizing radiation-curable resin composition preferably contains additives such as photopolymerization initiators and photopolymerization accelerators. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzyldimethyl ketal, benzoylbenzoate, α-acyloxime ester, thioxanthones, etc. Photopolymerization accelerators reduce polymerization inhibition caused by air during curing and can accelerate the curing speed. Examples of accelerators include isoamyl p-dimethylaminobenzoate and ethyl p-dimethylaminobenzoate.

[0056] The hard coat layer may further contain a thermoplastic resin. The thermoplastic resin is less likely to dissolve the acrylic substrate, yet adheres easily to it. Therefore, by including the cured product of the ionizing radiation-curable resin composition and the thermoplastic resin in the hard coat layer, it is possible to improve the interlayer adhesion and orientation of the phase difference layer of the optical laminate. On the other hand, if the thermoplastic resin content increases too much, components of the acrylic substrate may more easily reach the phase difference layer or orientation layer, or the solvent of the coating liquid for the phase difference layer may more easily reach the acrylic substrate. For this reason, the mass ratio of the cured product of the ionizing radiation-curable resin composition to the thermoplastic resin (cured product of the ionizing radiation-curable resin composition: thermoplastic resin) is preferably 90:10 to 60:40, more preferably 85:15 to 65:35, and even more preferably 80:20 to 70:30.

[0057] Examples of thermoplastic resins include polystyrene resin, polyolefin resin, ABS resin, AS resin, AN resin, polyphenylene oxide resin, polycarbonate resin, polyacetal resin, acrylic resin, polyester resin, polysulfone resin, and polyphenylene sulfide resin. Among these, acrylic resin is preferred as it is easier to achieve good adhesion with the acrylic substrate. It is preferable that the thermoplastic resin contains hydroxyl groups to facilitate good adhesion with the orientation layer.

[0058] The weight-average molecular weight of the thermoplastic resin is preferably 20,000 to 200,000, more preferably 30,000 to 150,000, and even more preferably 50,000 to 100,000. In this specification, weight-average molecular weight is the average molecular weight measured by GPC analysis and converted to standard polystyrene.

[0059] A hard coat layer can be formed by applying, drying, curing, etc., a hard coat coating solution containing the components and solvents that make up the hard coat layer.

[0060] Examples of solvents include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ethers such as dioxane and tetrahydrofuran; aliphatic hydrocarbons such as hexane; alicyclic hydrocarbons such as cyclohexane; aromatic hydrocarbons such as toluene and xylene; halogenated carbons such as dichloromethane and dichloroethane; esters such as methyl acetate, ethyl acetate, and butyl acetate; alcohols such as isopropanol, butanol, and cyclohexanol; cellosolves such as methyl cellosolve and ethyl cellosolve; glycol ethers such as propylene glycol monomethyl ether acetate; cellosolve acetates; sulfoxides such as dimethyl sulfoxide; and amides such as dimethylformamide and dimethylacetamide. To adequately dissolve the acrylic substrate, it is preferable to include one or more solvents selected from methyl ethyl ketone, methyl isobutyl ketone (MIBK), propylene glycol monomethyl ether acetate (PGME), ethyl acetate, and butyl acetate.

[0061] The proportion of solvent to the total amount of the coating liquid for the hard coat layer is preferably 40% by mass or more and 90% by mass or less, more preferably 50% by mass or more and 80% by mass or less, and even more preferably 55% by mass or more and 75% by mass or less. By setting the proportion of solvent within the above range, it is easier to set Ha, Ha / Ta, and Ta-Hm within the above range.

[0062] The drying temperature of the coating liquid for the hard coat layer is preferably 60°C to 110°C, more preferably 70°C to 100°C, and even more preferably 75°C to 95°C. The drying time for the hard coat layer coating solution is preferably 15 seconds to 120 seconds, more preferably 20 seconds to 80 seconds, and even more preferably 30 seconds to 60 seconds. By setting the drying conditions, such as temperature and time, within the above ranges, it becomes easier to bring Ha, Ha / Ta, and Ta-Hm into these ranges.

[0063] <Retardation layer> The retardation layer is disposed on the first surface side of the acrylic substrate. When the retardation layer is disposed on the first surface side of the acrylic substrate, the interlayer adhesion of the optical laminate and the orientation of the retardation layer may be insufficient. However, the optical laminate of the present disclosure has a hard coat layer between the acrylic substrate and the retardation layer, and by setting Ha, Ha / Ta, and Ta-Hm within the above-described ranges, the interlayer adhesion of the optical laminate and the orientation of the retardation layer can be improved.

[0064] Examples of the retardation layer include a positive A layer, a positive C layer, etc. The retardation layer may be a single layer or two or more layers. When the optical laminate of the present disclosure is used as a circular polarizing plate in combination with a polarizer, it is preferable to include a positive A layer as the retardation layer. When the retardation layer is made into two layers, a combination of a positive A layer and a positive C layer may be used. Also, as the positive A layer, a combination of two positive A layers of a λ / 4 retardation layer and a λ / 2 retardation layer may be used. In this specification, the positive A layer is a layer that satisfies the relationship Nx>Ny≒Nz when the refractive index in the X-axis direction, which is the direction of the axis with the highest refractive index in the plane of the retardation layer, is defined as Nx, the refractive index in the Y-axis direction perpendicular to the X-axis in the plane of the retardation layer is defined as Ny, and the refractive index in the thickness direction of the retardation layer is defined as Nz. Also, in this specification, the positive C layer is a layer that satisfies the relationship Nx≒Ny<Nz.

[0065] The retardation layer such as the positive A layer and the positive C layer preferably contains a structural unit derived from a liquid crystal compound as a main component. The main component means that the ratio of the structural unit derived from the liquid crystal compound to the total amount of the retardation layer is 50% by mass or more, preferably 70% by mass or more, and more preferably 90% by mass or more.

[0066] The liquid crystal compound preferably contains a polymerizable liquid crystal compound having polymerizable functional groups within its molecule. Having polymerizable functional groups allows the liquid crystal compound to be polymerized and fixed, resulting in excellent alignment stability and reduced likelihood of changes in phase difference over time. It is more preferable that the polymerizable liquid crystal compound has two or more polymerizable functional groups within its molecule. Having two or more polymerizable functional groups further stabilizes the three-dimensional orientation of the liquid crystal compound, reducing the likelihood of changes in phase difference over time.

[0067] Examples of polymerizable functional groups include those that polymerize through the action of ultraviolet light, ionizing radiation such as electron beams, or heat. Examples of polymerizable functional groups include radical polymerizable functional groups. Typical examples of radical polymerizable functional groups include functional groups having at least one addition polymerizable ethylenically unsaturated double bond, and specific examples include vinyl groups with or without substituents, acrylate groups (a general term encompassing acryloyl groups, methacryloyl groups, acryloyloxy groups, and methacryloyloxy groups). Furthermore, generally known cationic polymerizable functional groups may be used as polymerizable functional groups. Examples of cationic polymerizable functional groups include alicyclic ether groups (epoxy groups, oxetanyl groups, etc.), cyclic acetal groups, cyclic lactone groups, cyclic iminoether groups, cyclic thioether groups, spiroorthoester groups, and vinyloxy groups. Among these, alicyclic ether groups and vinyloxy groups are preferred, and epoxy groups, oxetanyl groups, and vinyloxy groups are more preferred.

[0068] Liquid crystal compounds are preferably those having polymerizable functional groups at their terminals. By using such liquid crystal compounds, for example, the terminals of the liquid crystal compounds can polymerize with each other to form a three-dimensionally oriented state, which makes it easier to improve stability.

[0069] Liquid crystal compounds can be used individually or in combination of two or more. When used individually, the liquid crystal compound is preferably a polymerizable liquid crystal compound. When used in combination of two or more, it is preferable that at least one is a polymerizable liquid crystal compound, and more preferably that all of them are polymerizable liquid crystal compounds.

[0070] The liquid crystal compound for the positive A layer may be a homogeneously oriented liquid crystal compound. The homogeneously oriented liquid crystal compound may be a material made of a liquid crystalline polymer or a material made of a liquid crystalline monomer. Homogeneous orientation means that the long axes of the molecules of the liquid crystal compound are oriented in the horizontal direction. Furthermore, it is preferable that the positive A layer exhibits a smectic phase. A smectic phase refers to a state in which molecules aligned in one direction have a layered structure.

[0071] Examples of liquid crystal compounds for the positive A layer include disc-shaped liquid crystal materials and rod-shaped liquid crystal materials, with rod-shaped liquid crystal materials being preferred as they tend to exhibit inverse dispersion. Examples of polymerizable liquid crystal compounds exhibiting inverse dispersion include those represented by general formula (1) in Japanese Patent Application Publication No. 2019-73712 and those represented by general formula (II) in International Publication No. 2017 / 043438. Inverse dispersion refers to the characteristic where the in-plane phase difference increases as the wavelength increases. Conversely, positive dispersion refers to the characteristic where the in-plane phase difference decreases as the wavelength increases.

[0072] The liquid crystal compound for the positive A layer can be made from a general-purpose material, such as the compound represented by general formula (I) described in Japanese Patent Publication No. 2008-297210, the compound represented by general formula (1) described in Japanese Patent Publication No. 2010-84032, and the liquid crystal compound A0 described in Japanese Patent Publication No. 2016-53709. The liquid crystal compound for the positive A layer can also be made from the compounds shown in the following formulas (1) to (19).

[0073] [ka]

[0074] [Chemistry]

[0075] [Chemistry]

[0076] When the in-plane retardation at a wavelength of 450 nm of the positive A layer is defined as R450, the in-plane retardation at a wavelength of 550 nm is defined as R550, and the in-plane retardation at a wavelength of 650 nm is defined as R650, it is preferable that the relationship of R450 < R550 < R650 is shown. That is, it is preferable that the positive A layer has inverse dispersibility. By the positive A layer having inverse dispersibility, it becomes easy to make the optical laminate have inverse dispersibility. And by making the optical laminate have inverse dispersibility, it becomes easy to improve optical properties such as antireflection properties in a wavelength range deviated from 550 nm.

[0077] R450, R550, and R650 of the positive A layer are not particularly limited. When the positive A layer is a λ / 4 retardation layer, R550 is preferably 100 nm or more and 180 nm or less, more preferably 110 nm or more and 160 nm or less, and even more preferably 135 nm or more and 150 nm or less. By setting the in-plane retardation of the λ / 4 retardation layer within the above range, when the λ / 4 retardation layer and a polarizer are combined, it becomes easy to exhibit an antireflection function as a circular polarizing plate. In addition, by using a λ / 4 retardation layer and a λ / 2 retardation layer as the positive A layer, it is also possible to broaden the wavelength range in which optical properties such as antireflection properties are improved.

[0078] The lower limit of the thickness of the positive A layer is preferably 0.1 μm or more, more preferably 0.5 μm or more, and even more preferably 1.5 μm or more. The upper limit of the thickness of the positive A layer is preferably 5.0 μm or less, more preferably 4.0 μm or less, and even more preferably 3.0 μm or less. The thickness of the phase difference layer, such as the positive A layer, and the thickness of the orientation layer, which will be described later, can be calculated using the same method as the thickness of the hard coat layer.

[0079] The liquid crystal compound for the positive C layer can be a liquid crystal compound that exhibits vertical orientation (homeotropic orientation). Furthermore, the liquid crystal compound for the positive C layer preferably exhibits a smectic phase or a nematic phase, and more preferably a smectic phase. When it is in a smectic phase, the center of gravity of the liquid crystal molecules is aligned, resulting in a highly ordered layer structure, which makes it easier for the positive C layer to adopt homeotropic orientation. A rod-shaped liquid crystal compound is preferred as the liquid crystal compound for the positive C layer.

[0080] Preferred examples of rod-shaped liquid crystal compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyanosubstituted phenylpyrimidines, alkoxysubstituted phenylpyrimidines, phenyldioxanes, trans, and alkenylcyclohexylbenzonitriles. In addition to the low-molecular-weight liquid crystal compounds described above, high-molecular-weight liquid crystal compounds can also be used. It is more preferable to fix the orientation of the rod-shaped liquid crystal compound by polymerization. The liquid crystal compound preferably has a substructure that can undergo polymerization or crosslinking reactions by active light, electron beams, heat, etc., and more preferably has polymerizable groups. As polymerizable rod-shaped liquid crystal compounds, compounds described in Makromol. Chem., Vol. 190, p. 2255 (1989), Advanced Materials, Vol. 5, p. 107 (1993), U.S. Patent No. 4,683,327, U.S. Patent No. 5,622,648, U.S. Patent No. 5,770,107, International Publication No. 95 / 22586, International Publication No. 95 / 24455, International Publication No. 97 / 00600, International Publication No. 98 / 23580, International Publication No. 98 / 52905, Japanese Patent Publication No. 1-272551, 6-16616, 7-110469, 11-80081, and Japanese Patent Publication No. 2001-328973 can be used. Specific examples of rod-shaped liquid crystal compounds include the compounds shown in formulas (1) to (19) above.

[0081] The positive C layer preferably contains a vertical alignment promoter from the viewpoint of facilitating uniform vertical orientation of the liquid crystal compound molecules. Examples of vertical alignment promoters include boronic acid compounds and / or onium salts. The amount of the vertical alignment promoter is preferably 0.1% to 25% by mass, and more preferably 0.5% to 20% by mass, relative to the total solid content of the positive C layer.

[0082] The phase difference in the thickness direction of the positive C layer at a wavelength of 550 nm is preferably -100 nm or more, more preferably -90 nm or more, and preferably -50 nm or less, more preferably -60 nm or less, at the upper limit. By setting the phase difference in the thickness direction of the positive C layer within the above range, it is easier to improve visibility in oblique directions.

[0083] From the viewpoint of not affecting the in-plane phase difference of the optical laminate, the positive C layer preferably has an in-plane phase difference of 20 nm or less at a wavelength of 550 nm, more preferably 10 nm or less, even more preferably 5 nm or less, and even more preferably 2 nm or less.

[0084] The thickness of the positive C layer is preferably 0.01 μm or more at the lower limit, more preferably 0.05 μm or more, and even more preferably 0.10 μm or more, and preferably 5 μm or less at the upper limit, more preferably 3 μm or less, and even more preferably 2 μm or less.

[0085] The phase difference layers, such as the positive A layer and the positive C layer, may contain additives such as polymerization initiators, leveling agents, orientation promoters, antioxidants, and ultraviolet absorbers.

[0086] Phase difference layers such as the positive A layer and the positive C layer can be formed by applying, drying, curing, etc., a coating solution for phase difference layers containing the components and solvents that make up the phase difference layer. The liquid crystal compound content relative to the total volume of the coating solution for the phase difference layer is preferably 5% by mass or more and 30% by mass or less. If the amount of liquid crystal compound is less than 5% by mass, a large amount of solvent removal will be required, which is likely to lead to a deterioration in reliability due to residual solvent. On the other hand, if it exceeds 30% by mass, the viscosity of the coating solution becomes too high, which reduces its suitability for coating.

[0087] The solvent for the phase difference layer coating solution is preferably a solvent that can dissolve liquid crystal compounds. Examples of such solvents include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and N-methyl-2-pyrrolidone; ether-based solvents such as dioxolane and tetrahydrofuran; and alcohol-based solvents.

[0088] The drying temperature of the coating liquid for the phase difference layer is preferably 60°C to 150°C, more preferably 70°C to 130°C, and even more preferably 80°C to 120°C. The drying time for the phase difference layer coating solution is preferably 15 seconds to 180 seconds, more preferably 30 seconds to 100 seconds, and even more preferably 45 seconds to 75 seconds. By setting the drying conditions, such as temperature and time, within the above range, it becomes easier to suppress the solvent of the phase difference layer coating solution from passing through the hard coat layer to reach the acrylic substrate, and it also becomes easier to reduce residual solvent.

[0089] <Oriented layer> The optical laminate of this disclosure preferably has an alignment layer between the phase difference layer and the hard coat layer. An orientation layer can be formed, for example, by applying an orientation layer coating solution containing an orientation-oriented material onto a hard coat layer to impart an orientation-regulating force. Examples of orientation-oriented materials include photo-oriented materials. The orientation layer coating solution may contain a solvent as needed.

[0090] Examples of photo-oriented materials include photoisomerized and photodimerized resins. Examples of photodimerized resins include resins having structures such as cinnamate, coumarin, benzylidenephthalimidine, benzylideneacetophenone, diphenylacetylene, stilbazole, uracil, quinolinone, maleimide, and cinnamyridene acetate derivatives. Examples of photoisomerized resins include resins containing azo compounds.

[0091] The means for imparting orientation-regulating force to the orientation layer can be conventionally known methods, such as the rubbing method, the photo-alignment method, and the shaping method. The thickness of the orientation layer is preferably 1 nm to 1000 nm, and more preferably 60 nm to 300 nm.

[0092] <Other layers> The optical laminates of this disclosure may have other layers, provided that they do not impair the effects of this disclosure. Examples of other layers include gas barrier layers, adhesive layers, and surface protection layers.

[0093] <Physical properties of optical laminates> In an optical laminate, when the in-plane phase difference at a wavelength of 550 nm is defined as R550, R550 is preferably between 100 nm and 180 nm, more preferably between 110 nm and 160 nm, and even more preferably between 135 nm and 150 nm. By setting the R550 of the optical laminate to the above range, it becomes easier to achieve anti-reflective properties as a circular polarizer when the optical laminate and polarizer are combined.

[0094] When the in-plane retardation at a wavelength of 450 nm is defined as R450, the in-plane retardation at a wavelength of 550 nm is defined as R550, and the in-plane retardation at a wavelength of 650 nm is defined as R650, it is preferable that the optical laminate exhibits the relationship of R450 < R550 < R650. That is, the optical laminate preferably has inverse dispersibility. When the optical laminate has inverse dispersibility, when the optical laminate and a polarizer are combined, it is easy to improve optical properties such as antireflection properties even in a wavelength range deviated from 550 nm.

[0095] The haze of the optical laminate according to JIS K7136:2000 is preferably 1.0% or less, more preferably 0.9% or less, and even more preferably 0.8% or less. Further, the total light transmittance of the optical laminate according to JIS K7361-1:1997 is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. By setting the haze or total light transmittance of the optical laminate within the above ranges, it is easy to improve the visibility of the image display device.

[0096] <Size, shape, etc.> The optical laminate may be in the form of a leaf-shaped piece cut to a predetermined size, or may be in the form of a roll obtained by winding a long sheet in a roll shape. The size of the leaf-shaped piece is not particularly limited, but the general maximum diameter is 2 inches or more and 500 inches or less. The "maximum diameter" refers to the maximum length when any two points of the optical laminate are connected. For example, when the optical laminate is rectangular, the diagonal of the rectangle is the maximum diameter. When the optical laminate is circular, the diameter of the circle is the maximum diameter. The width and length of the roll shape are not particularly limited, but generally, the width is 500 mm or more and 3000 mm or less, and the length is 500 m or more and 5000 m or less. The optical laminate in the roll form can be cut into leaf-shaped pieces and used according to the size of an image display device or the like. When cutting, it is preferable to exclude the roll ends where the physical properties are not stable. The shape of the leaflets is not particularly limited; for example, they may be polygonal (triangle, quadrilateral, pentagon, etc.), circular, or randomly irregular in shape.

[0097] [Polarizing plate] The polarizing plate of this disclosure comprises a polarizer, a first protective film disposed on one side of the polarizer, and a second protective film disposed on the other side of the polarizer, wherein the first protective film is the optical laminate of this disclosure described above.

[0098] Figure 3 is a cross-sectional view showing an embodiment of the polarizing plate of this disclosure. As shown in Figure 3, the polarizing plate 200 includes a polarizer 201, a first protective film 202 positioned on one side of the polarizer, and a second protective film 203 positioned on the other side of the polarizer. In the polarizing plate 200 of Figure 3, the optical laminate 100 described above is used as the first protective film 202.

[0099] <Polarizer> Examples of polarizers include sheet-type polarizers such as polyvinyl alcohol film, polyvinyl formal film, polyvinyl acetal film, and ethylene-vinyl acetate copolymer saponified film dyed with iodine or the like and stretched; wire grid-type polarizers consisting of numerous parallel metal wires; coated polarizers coated with lyotropic liquid crystal or dichroic guest-host material; and multilayer thin-film polarizers. These polarizers may also be reflective polarizers that have the function of reflecting polarization components that do not transmit through them.

[0100] <Protective film> A first protective film is placed on one side of the polarizer, and a second protective film is placed on the other side of the polarizer. The optical laminate, which is the first protective film, may be arranged so that the surface on the acrylic substrate side faces the polarizer side, or so that the surface on the phase difference layer side faces the polarizer side. Examples of the second protective film include plastic films and glass. Examples of plastic films include polyester films, polycarbonate films, cycloolefin polymer films, and acrylic films, and stretched films of these are preferred from the viewpoint of mechanical strength. Examples of glass include alkali glass, nitride glass, soda-lime glass, borosilicate glass, and lead glass.

[0101] The polarizer and the protective film may be bonded together using the adhesive properties of the polarizer, or they may be bonded together using an adhesive. A general-purpose adhesive can be used, and a PVA-based adhesive is preferred.

[0102] When the positive A layer is a λ / 4 phase difference layer, it is preferable to position the polarizer's absorption axis and the positive A layer's slow axis at 45 degrees ± 5 degrees, more preferably at 45 degrees ± 3 degrees, and even more preferably at 45 degrees ± 1 degree. By positioning them according to the aforementioned angle relationship, they can be made to function as a circular polarizer.

[0103] The polarizing plate of this disclosure is preferably used as a polarizing plate placed on the light-emitting surface side of a display element. Furthermore, when used as described above, it is preferable to position the polarizing plate so that the side of the optical laminate, which is the first protective film, faces the display element side.

[0104] [Display Panel] The display panel of this disclosure has the optical laminate described above arranged on the surface of the display element facing the light emission surface.

[0105] Figure 4 is a cross-sectional view showing an embodiment of the display panel 500 of the present disclosure. In the display panel 500 of Figure 4, an optical laminate 100 is laminated on the light-emitting surface of the display element 300.

[0106] When the display element of a display panel is a liquid crystal display element, a backlight (not shown) is required behind the liquid crystal display element. Both edge-lit and direct-lit backlights can be used. Examples of backlight light sources include LEDs and CCFLs. Quantum dot backlights are also an option.

[0107] The display panel preferably has a polarizer on the side opposite to the display element of the optical laminate. By adopting this configuration, an anti-reflective function for external light can be added to the image display device, and the degradation of color when viewed from an oblique angle can be suppressed.

[0108] <Display element> Examples of display elements include liquid crystal display elements, EL display elements (organic EL display elements, inorganic EL display elements), plasma display elements, and LED display elements such as microLED display elements. These display elements may also have a touch panel function inside. Examples of liquid crystal display methods for liquid crystal display elements include IPS, VA, multi-domain, OCB, STN, and TSTN methods.

[0109] The display panel of this disclosure may be a display panel with a touch panel, having a touch panel between the display element and the optical laminate.

[0110] The size of the display panel is not particularly limited, but the typical maximum diameter is between 2 inches and 500 inches. The maximum diameter refers to the maximum length when connecting any two points within the surface of the display panel.

[0111] [Image display device] The image display device disclosed herein includes the display panel disclosed herein.

[0112] The image display device of the present disclosure is not particularly limited as long as it includes the panel of the present disclosure. Preferably, the image display device of the present disclosure comprises the panel of the present disclosure, a drive control unit electrically connected to the panel, and a housing that houses these. If the display element is a liquid crystal display element, the image display device of this disclosure requires a backlight. The backlight is positioned on the side opposite to the light-emitting surface of the liquid crystal display element.

[0113] The size of the image display device is not particularly limited, but the maximum diameter of the effective display area is generally between 2 inches and 500 inches. The effective display area of ​​an image display device is the area in which an image can be displayed. For example, if an image display device has a housing that surrounds the display element, the area inside the housing becomes the effective image area. The maximum diameter of the effective image area refers to the maximum length when connecting any two points within the effective image area. For example, if the effective image area is rectangular, the diagonal of that area is the maximum diameter. If the effective image area is circular, the diameter of that area is the maximum diameter.

[0114] This disclosure is as follows: <1> ~ <12> Includes. <1> A substrate having a first surface and a second surface opposite to the first surface, An optical laminate having a phase difference layer disposed on the first surface side of the substrate, The substrate is an acrylic substrate, and a hard coat layer is provided between the acrylic substrate and the phase difference layer. When the average height of the first surface of the acrylic substrate is defined as Ha [nm], the average of the maximum heights of the first surface of the acrylic substrate is defined as Hm [nm], and the average thickness of the hard coat layer is defined as Ta [nm], An optical laminate in which Ha is 2.2 nm or greater, Ha / Ta is 0.02720 or less, and Ta-Hm is 2200 nm or greater. <2> Ha is between 2.5 nm and 300.0 nm. <1> The optical laminate described above. <3> Ha / Ta is between 0.00078 and 0.02720. <1> or <2> The optical laminate described above. <4> The optical laminate according to any one of <1> to <3>, wherein Ta-Hm is 2300 nm or more and 10000 nm or less. <5> The optical laminate according to any one of <1> to <4>, wherein Ta is 2300 nm or more and 11000 nm or less. <6> The optical laminate according to any one of <1> to <5>, wherein the average inclination angle θa on the first surface side of the acrylic substrate is 0.6 degrees or more and 14.2 degrees or less. <7> The optical laminate according to any one of <1> to <6>, having an alignment layer between the retardation layer and the hard coat layer. <8> The optical laminate according to any one of <1> to <7>, wherein when the in-plane retardation at a wavelength of 550 nm is defined as R550, R550 is 100 nm or more and 180 nm or less. <9> The optical laminate according to any one of <1> to <8>, wherein when the in-plane retardation at a wavelength of 450 nm is defined as R450, the in-plane retardation at a wavelength of 550 nm is defined as R550, and the in-plane retardation at a wavelength of 650 nm is defined as R650, the relationship R450 < R550 < R650 is shown. <10> A polarizing plate having a polarizer, a first protective film disposed on one side of the polarizer, and a second protective film disposed on the other side of the polarizer, wherein the first protective film is the optical laminate according to any one of <1> to <9>. <11> A display panel having the optical laminate according to any one of <1> to <9> disposed on the light-emitting surface of a display element. <12> An image display device including the display panel according to <11>.

Examples

[0115] Next, the present disclosure will be described in more detail with reference to examples, but the present disclosure is not limited to these examples. In addition, "parts" and "%" are based on mass unless otherwise specified.

[0116] 1. Measurement and Evaluation The following measurements and evaluations were performed on the optical laminates obtained in the examples and comparative examples. The results are shown in Table 1.

[0117] 1-1. In-plane phase difference The in-plane phase difference of the optical laminates of the examples and comparative examples was measured using the "RETS-100" product manufactured by Otsuka Electronics Co., Ltd. The in-plane phase difference was measured at a wavelength of 450 nm (R450), at a wavelength of 550 nm (R550), and at a wavelength of 650 nm (R650). In the optical laminates of the examples and comparative examples, the in-plane phase difference of layers other than the phase difference layer is approximately 0. Therefore, R450, R550, and R650 of the optical laminate can be considered as R450, R550, and R650 of the phase difference layer.

[0118] In section 1-1 above, the in-plane phase difference was measured using the following procedure (1) to (4). (1) To stabilize the light source of the RETS-100, leave it for at least 60 minutes after turning on the light source. Then, select the rotational analyzer method and the θ mode (mode for angular phase difference measurement and Rth calculation). By selecting this θ mode, the stage becomes a tilting rotation stage. (2) Next, input the following measurement conditions into the RETS-100. <Measurement conditions> • Measurement range of in-plane phase difference: Rotation analyzer method • Measurement spot diameter: φ5mm • Inclination angle range: 0° • Measurement wavelength range: 400nm to 800nm • The average refractive index of the phase difference layer (The average refractive index N can be calculated using the formula (N = (Nx + Ny + Nz) / 3) based on Nx, Ny, and Nz. Since the phase difference of the optical laminates in the examples and comparative examples is governed by the phase difference of the phase difference layer, the average refractive index of the phase difference layer should be input.) • Thickness of the phase difference layer (Enter the thickness of the phase difference layer measured separately) (3) Next, background data is obtained without placing a sample in the apparatus. The apparatus is a closed system, and this is done each time the light source is turned on. (4) After that, the sample is placed on the stage inside the apparatus and measured.

[0119] 1-2. Calculation of Ta, Ha, Hm, and θa (1) Sample preparation Samples were prepared in which the cross-section in the thickness direction of the optical laminate was exposed. The samples were prepared using the processes (A1) to (A2) described in the main text of the specification. In (A2), a Leica Microsystems "Ultramicrotome EM UC7" was used as the device for cutting the edges of the strip-shaped sample. When cutting the edges of the sample, rough trimming was performed first, followed by precise trimming. For precise trimming, the feed rate was set to 0.1 μm, and the feed speed was manually controlled at the slowest possible speed of approximately 0.4 mm / min.

[0120] (2) IO The aforementioned samples were imaged using a scanning electron microscope. The scanning electron microscope used was a Hitachi High-Technologies Corporation model "SU-8000". The imaging conditions were as follows: From the captured images, 10 measurement areas with a width of 5 μm were obtained. <Imaging conditions> Mode: SE(U) Acceleration voltage: 3kV Emission current: 10μA WD (Working Distance): 8.0mm Magnification: 10,000x in High magnification mode

[0121] (3) Calculation of Ha, Hm, and θa From the 10 measurement areas obtained in (2) above, 10 profiles with a width of 5 μm were acquired. Specifically, after obtaining image data by binarizing the photographic data captured in (2) above, a profile was obtained by extracting the area corresponding to the interface between the acrylic substrate and the hard coat layer from the binarized image data. For binarization and profile extraction, the public domain image analysis software "ImageJ 1.53" was used. Next, Ha, Hm, and θa were calculated based on steps (B2) to (B4) in the main text of the specification.

[0122] (4) Calculation of Ta From the 10 measurement areas obtained in (2) above, Ta was calculated based on the steps (C1) to (C2) in the main text of the specification.

[0123] 1-3. Adhesion The adhesion of the optical laminates of the examples and comparative examples was evaluated using the following method. The evaluation sample was cross-cut into a grid pattern of 10 squares vertically and 10 squares horizontally, for a total of 100 squares. The cut interval was 1 mm. When cutting, the cutter blade was inserted from the phase difference layer side, and the cross-cut was performed so that the cutter blade reached the top of the acrylic substrate. Adhesive tape (manufactured by Nichiban Co., Ltd., product name "Sellotape®") was applied to the surface of a cross-cut sample, and a peel test was performed in accordance with the cross-cut method specified in JIS K 5600-5-6:1999. The number of remaining squares after the peel test was counted out of 100 squares. The results were evaluated according to the following criteria based on the number of remaining squares. A: The number of remaining squares is 100 B: The number of remaining squares is between 80 and 99. C: The number of remaining squares is 79 or less.

[0124] 1-4. Orientation of the phase difference layer Samples were prepared by cutting the optical laminates of the examples and comparative examples to 5 cm × 5 cm. The samples were placed between the polarizer and analyzer of a polarizing microscope. In a crossed nicol state, where the absorption axes of the polarizer and analyzer of the polarizing microscope were orthogonal, the number of bright spots was counted and evaluated according to the following criteria. The polarizing microscope used was Olympus's "BX51" model. The field of view for counting the number of bright spots was approximately 2.2 mm × 1.7 mm. The magnification of the eyepiece and objective lens was set to 10x. A+: Number of bright spots is 10 or less A: The number of bright spots is between 10 and 30. B: Number of bright spots is between 30 and 100. C: Number of bright spots exceeds 100

[0125] 1-5. Curl Samples of the optical laminates of the examples and comparative examples were prepared by cutting them into 10cm x 10cm sections. Each sample was placed on a flat table, and the height at which each of the four edges lifted off the table was measured. The average of the four heights was calculated and evaluated according to the following criteria. A: Height is 1 mm or less B: Height is between 1mm and 2mm C: Height 3mm or more

[0126] 2. Synthesis of Compounds Based on the synthesis of compound 4 in Example 4 of Japanese Patent No. 5962760, the polymerizable liquid crystal compound (A) shown below was synthesized.

[0127] [ka]

[0128] 3. Fabrication of optical stacks [Example 1] A hard coat layer coating solution with the following formulation was applied to a 40 μm thick acrylic substrate (OXIS-PMMA, manufactured by Okura Industries Co., Ltd.) and dried (drying temperature: 90°C, drying time: 60 seconds). Then, it was irradiated with ultraviolet light (cumulative light intensity: 80 mJ / cm²). 2 A hard coat layer with an average thickness of 3.5 μm was formed. Next, the orientation layer coating solution with the following formulation was applied to the hard coat layer and dried (drying temperature: 90°C, drying time: 60 seconds). Then, it was exposed to polarized light with ultraviolet light at a wavelength of 310 nm (integrated light intensity: 15 mJ / cm²). 2 A oriented layer with an average thickness of 200 nm was formed. Next, the phase difference layer coating solution described below was applied to the orientation layer using a bar coater so that the thickness after drying was 3500 nm, and then dried (120°C, 60 seconds). Then, it was irradiated with ultraviolet light (integrated light intensity: 400 mJ / cm²). 2 A phase difference layer (positive A layer) was formed, and the optical laminate of Example 1 was obtained. The optical laminate of Example 1 has an acrylic substrate, a hard coat layer, an alignment layer, and a phase difference layer in this order. In Examples 1-6 and Comparative Examples 1-2, the thickness of the hard coat layer after drying was adjusted by the amount of hard coat coating solution applied per unit area in its wet state.

[0129] <Coating liquid for hard coat layer 1> • Polyfunctional acrylate monomer 60 parts by mass (Toa Gosei Co., Ltd., Product name: M-405) • Monofunctional acrylate monomer 40 parts by mass (Toa Gosei Co., Ltd., Product name: M-5700) • Photopolymerization initiator 5 parts by mass (IGM Resins BV, product name Omnirad 907) • Solvent 1 (PGME) 125 parts by mass • Solvent 2 (MIBK) 125 parts by mass

[0130] <Coating liquid for orientation layer> • Polycinnamate compound 100 parts by mass • Solvent 1 (PGME) 2000 parts by mass

[0131] <Coating liquid for phase difference layer> • 100 parts by mass of the polymerizable liquid crystal compound (A) obtained in step 2 above • Photopolymerization initiator 5 parts by mass (IGM Resins BV, product name "Omnirad 369") • Toluene 500 parts by mass • N-methylpyrrolidone 400 parts by mass

[0132] [Examples 2-6], [Comparative Examples 1-2] Optical laminates of Examples 2-6 and Comparative Examples 1-2 were obtained in the same manner as in Example 1, except that the formulation of the coating solution for the hard coat layer, the average thickness Ta of the hard coat layer, and the drying conditions of the hard coat layer were as shown in Table 1. The formulation of the coating solution 2 for the hard coat layer used in Examples 2-3 and Comparative Example 2 is shown below.

[0133] <Coating liquid for hard coat layer 2> • 50 parts by mass of polyfunctional acrylate monomer (Toa Gosei Co., Ltd., Product name: M-405) • Monofunctional acrylate monomer 20 parts by mass (Toa Gosei Co., Ltd., Product name: M-5700) • Thermoplastic acrylic resin 30 parts by mass (Taisei Fine Chemical Co., Ltd. Product name: 8DL-100) • Photopolymerization initiator 5 parts by mass (IGM Resins BV, product name: Omnirad 907) • Solvent 1 (PGME) 150 parts by mass • Solvent 2 (MEK) 100 parts by mass

[0134] [Table 1]

[0135] As is clear from the results in Table 1, it can be confirmed that the optical laminate of the example can improve the interlayer adhesion and orientation of the phase difference layer of the optical laminate. [Explanation of Symbols]

[0136] 10: Acrylic substrate 20: Hard court layer 30: Orientation layer 40: Retardation layer S1: 1st page S2: 2nd side 100: Optical laminate 200: Polarizing plate 201: Polarizer 202: First protective film 203: Second protective film 300: Display element 500: Display Panel

Claims

1. A substrate having a first surface and a second surface opposite to the first surface, An optical laminate having a phase difference layer disposed on the first surface side of the substrate, The substrate is an acrylic substrate, and a hard coat layer is provided between the acrylic substrate and the phase difference layer. When the average height of the first surface of the acrylic substrate is defined as Ha [nm], the average of the maximum heights of the first surface of the acrylic substrate is defined as Hm [nm], and the average thickness of the hard coat layer is defined as Ta [nm], An optical laminate in which Ha is 2.2 nm or greater, Ha / Ta is 0.02720 or less, and Ta-Hm is 2200 nm or greater.

2. The optical laminate according to claim 1, wherein Ha is 2.5 nm or more and 300.0 nm or less.

3. The optical laminate according to claim 1, wherein Ha / Ta is 0.00078 or more and 0.02720 or less.

4. The optical laminate according to claim 1, wherein Ta-Hm is 2300 nm or more and 10000 nm or less.

5. The optical laminate according to claim 1, wherein Ta is 2300 nm or more and 11000 nm or less.

6. The optical laminate according to claim 1, wherein the average inclination angle θa of the first surface side of the acrylic substrate is 0.6 degrees or more and 14.2 degrees or less.

7. The optical laminate according to claim 1, further comprising an orientation layer between the phase difference layer and the hard coat layer.

8. The optical laminate according to claim 1, wherein when the in-plane phase difference at a wavelength of 550 nm is defined as R550, R550 is between 100 nm and 180 nm.

9. The optical laminate according to claim 1, wherein when the in-plane phase difference at a wavelength of 450 nm is defined as R450, the in-plane phase difference at a wavelength of 550 nm is defined as R550, and the in-plane phase difference at a wavelength of 650 nm is defined as R650, the relationship R450 < R550 < R650 is observed.

10. A polarizing plate comprising a polarizer, a first protective film disposed on one side of the polarizer, and a second protective film disposed on the other side of the polarizer, wherein the first protective film is an optical laminate according to any one of claims 1 to 9.

11. A display panel comprising an optical laminate according to any one of claims 1 to 9 arranged on the light-emitting surface of a display element.

12. An image display device including the display panel described in claim 11.

Images