Front plate, optical laminate, and image display device

Abstract

To provide a high-quality front plate, optical laminate, and image display device.SOLUTION: A front plate 4 provided herein comprises a protective resin layer 12 and a hard coat layer 13 arranged in order in a thickness direction. A difference Δ between a refractive index of the protective resin layer 12 and a refractive index of the hard coat layer 13 is 0.04 or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a front panel, an optical laminate, and an image display device. [Background technology]

[0002] As a front panel, for example, a front panel including a hard coat layer made of an acrylic resin and a resin film made of a polyimide resin has been proposed (see, for example, Patent Document 1 below). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-102443 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, there has been a demand for higher quality front panels.

[0005] The present invention provides a high-quality front panel, an optical laminate, and an image display device. [Means for solving the problem]

[0006] The present invention (1) includes a front panel having a protective resin layer and a hard coat layer in that order in the thickness direction, and the difference in refractive index between the protective resin layer and the hard coat layer is 0.04 or less.

[0007] In this front panel, the difference in refractive index between the protective resin layer and the hard coat layer is small, at 0.04 or less, so the front panel is of high quality and does not suffer from the problem of unevenness caused by the difference in refractive index.

[0008] The present invention (2) includes the front panel according to (1), in which the molar ratio of structural units derived from aromatic compounds in the main component of the material of the protective resin layer is 5.0 mol % or less.

[0009] In this front panel, the molar proportion of structural units derived from aromatic compounds in the main components of the material of the protective resin layer is low, at 5.0 mol % or less, so the high quality of the front panel can be more reliably ensured.

[0010] The present invention (3) includes the front panel according to (1) or (2), in which the material of the protective resin layer is an acrylic resin or a polycarbonate resin, and the material of the hard coat layer is an acrylic resin.

[0011] In this front panel, the material of the protective resin layer is acrylic resin or polycarbonate resin, and the material of the hard coat layer is acrylic resin, so the refractive index of the protective resin layer and the refractive index of the hard coat layer are similar, and the difference between the refractive index of the protective resin layer and the refractive index of the hard coat layer is reliably reduced, thereby reliably maintaining high quality.

[0012] The present invention (4) further includes the front panel according to any one of (1) to (3), which comprises a substrate and an adhesive layer, the substrate, the adhesive layer, the protective resin layer, and the hard coat layer being arranged in that order in the thickness direction, and the substrate comprising a thin glass plate.

[0013] This front panel further comprises a substrate and an adhesive layer, with the substrate, adhesive layer, protective resin layer, and hard coat layer arranged in that order in the thickness direction, and since the substrate includes a thin glass plate, the occurrence of marks (such as wrinkles) after bending can be suppressed, thereby maintaining high quality.

[0014] The present invention (5) includes an optical laminate comprising, in order toward the viewing side, a polarizing film and the front plate according to any one of (1) to (4).

[0015] This optical laminate is of high quality because it includes the front plate described above.

[0016] The present invention (6) includes an image display device comprising an image display member and the optical laminate according to (5) in this order toward the viewing side.

[0017] This image display device includes the above-described optical laminate, and therefore does not suffer from the problem of unevenness caused by refractive index differences, and is of high quality. [Effects of the Invention]

[0018] The front panel, optical laminate, and image display device of the present invention are of high quality without the problem of unevenness caused by refractive index differences. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a cross-sectional view of an organic EL display device as an embodiment of the image display device of the present invention. [Figure 2] FIG. 2 is a cross-sectional view of one embodiment of the optical laminate of the present invention. [Figure 3] FIG. 3 is a cross-sectional view of one embodiment of the front plate of the present invention. [Figure 4] FIG. 4 is a cross-sectional view illustrating the bent state of the front panel in the bending test. DETAILED DESCRIPTION OF THE INVENTION

[0020] [Organic EL display device] An organic electroluminescence display device, which is one embodiment of the image display device of the present invention, will be described with reference to Fig. 1. Hereinafter, the organic electroluminescence display device will be abbreviated as an organic EL display device.

[0021] The organic EL display device 1 has, for example, a flat plate shape, and is preferably configured to be bendable around a bending portion 25 located between two opposing sides 27 spaced apart in the surface direction (a direction perpendicular to the front-to-back direction), and more preferably configured to be foldable. Each of the members described below is preferably configured to be bendable, and more preferably configured to be foldable.

[0022] 1, the organic EL display device 1 includes an image display member 3 and an optical laminate 2, arranged in this order toward the viewing side. That is, in this organic EL display device 1, the optical laminate 2 and the image display member 3 are arranged in this order toward the side opposite the viewing side, which is the side viewed by a user. In the organic EL display device 1, the viewing side corresponds to the front side, and the side opposite the viewing side corresponds to the back side.

[0023] [Optical laminate] The optical laminate 2 includes a front plate 4 and a polarizing film 5 in this order toward the back side.

[0024] [Front plate] The front panel 4 is sometimes called a cover window or a window film. The front panel 4 includes a protection member 6 and a substrate 7 in this order toward the back side.

[0025] [Adhesive layer and layer structure] The organic EL display device 1 also includes an adhesive layer 8 located between adjacent members in the front-to-back direction. The adhesive layer 8 includes, in order toward the back side, a first adhesive layer 9, a second adhesive layer 10, and a third adhesive layer 11, which are examples of adhesive layers. Therefore, in the organic EL display device 1, the protective member 6, the first adhesive layer 9, the substrate 7, the second adhesive layer 10, the polarizing film 5, the third adhesive layer 11, and the image display member 3 are arranged in this order toward the back side.

[0026] [Protective material] The protective member 6 protects the front side of the substrate 7. The protective member 6 has a flat plate shape extending in the planar direction. The protective member 6 includes a protective resin layer 12 and a hard coat layer 13, which are arranged in this order toward the front side.

[0027] [Protective resin layer] The protective resin layer 12 forms the back surface of the protective member 6. The protective resin layer 12 extends in the plane direction. There are no particular limitations on the material of the protective resin layer 12, as long as it is a resin that satisfies the in-plane retardation Re(550) and thickness direction retardation Rth(550), which will be described later.

[0028] The molar ratio of structural units derived from aromatic compounds in the main component of the material of protective resin layer 12 is, for example, 10 mol % or less, preferably 5.0 mol % or less, more preferably 3.0 mol % or less, even more preferably 2.0 mol % or less, and most preferably 0.0 mol %. If the molar ratio of structural units derived from aromatic compounds in the main component of the material of protective resin layer 12 is equal to or less than the above-mentioned upper limit, the high quality of front panel 4 can be more reliably maintained.

[0029] The molar proportion of structural units derived from aromatic compounds in the main component of the material of the protective resin layer 12 is measured, for example, as follows: The protective resin layer 12 is decomposed into structural units by a known decomposition method. For example, it is immersed in an alcohol solvent (e.g., methanol) to obtain soluble components as decomposition products. The structural units of the decomposition products (soluble components) are then identified by a known analytical method (e.g., gas chromatography-mass spectrometry (GC-MS)).

[0030] Separately, a protective resin layer 12 1 Specifically, the protective resin layer 12 is subjected to H-NMR measurement. 1 The solution containing the main component of the protective resin layer 12 is then dissolved in a solvent for H-NMR to prepare a solution containing the main component of the protective resin layer 12. 1 The resulting mixture is subjected to H-NMR measurement. Next, based on the structural units identified by the above analytical method, the molar ratio of structural units derived from aromatic compounds and the molar ratio of structural units derived from non-aromatic compounds are determined from the integral ratio of protons directly connected to aromatic rings and the integral ratio of other protons. An aromatic compound is a compound having at least one aromatic ring. A non-aromatic compound is a compound having no aromatic rings. The molar ratio of structural units derived from aromatic compounds in the main components of the material of the protective resin layer 12 is then determined as a percentage.

[0031] Examples of materials for the protective resin layer 12 include resins such as acrylic resins and polycarbonate resins. As materials for the protective resin layer 12, acrylic resins and polycarbonate resins are preferred from the viewpoint of reducing the in-plane retardation Re(550) and thickness direction retardation Rth(550), and acrylic resins are more preferred from the viewpoint of suppressing fluctuations in the in-plane retardation Re(550) and thickness direction retardation Rth(550) before and after bending at the bent portion 25. Furthermore, the above-mentioned resins preferably do not have structural units derived from aromatic compounds.

[0032] The acrylic resin has, for example, a glutarimide unit and an unsaturated carboxylic acid alkyl ester unit. The acrylic resin preferably does not have a structural unit derived from an aromatic compound. Specifically, the acrylic resin has a glutarimide unit represented by the following formula (1) and an unsaturated carboxylic acid alkyl ester unit represented by the following formula (2).

[0033] [ka]

[0034] (In formula (1), R 1 and R 2 R each independently represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms. 3 represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group having 3 to 12 carbon atoms, or an aryl group having 6 to 10 carbon atoms.

[0035] [ka]

[0036] (In formula (2), R 4 and R 5 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

[0037] In formula (1), R 1and R 2 Examples of the alkyl group having 1 to 8 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, and octyl.

[0038] R 1 As the aryl group, preferably, methyl is mentioned.

[0039] R 2 is preferably a hydrogen atom.

[0040] R 3 Examples of the alkyl group having 1 to 18 carbon atoms represented by the formula (I) include, in addition to the alkyl groups having 1 to 8 carbon atoms exemplified above, nonyl, decyl, dodecyl, undecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, etc. Examples of the cycloalkyl group having 3 to 12 carbon atoms include cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, etc. Examples of the aryl group having 6 to 10 carbon atoms include phenyl, naphthyl, etc. R 3 As the alkyl group, preferably, an alkyl group is used, and more preferably, methyl is used.

[0041] In formula (2), R 4 and R 5 Examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include methyl, ethyl, propyl, butyl, and pentyl, and a preferred example of the alkyl group is methyl.

[0042] R 4 A preferred example of the group is a hydrogen atom.

[0043] R 5 As the alkyl group, preferably, methyl is mentioned.

[0044] The content of glutarimide units in the acrylic resin is, for example, 5 mol% or more, preferably 15 mol% or more, and for example, 50 mol% or less, preferably 40 mol% or less. When the content of glutarimide units is equal to or more than the above-mentioned lower limit and equal to or less than the above-mentioned upper limit, the retardation can be reduced.

[0045] The imidization rate of the acrylic resin, which is the proportion of imide carbonyl groups in all carbonyl groups, is, for example, 2.5% or more, and, for example, 7.5% or less, preferably 5.0% or less. If the imidization rate of the acrylic resin is equal to or higher than the above-mentioned lower limit, a decrease in heat resistance and a decrease in transparency can be suppressed. If the imidization rate of the acrylic resin is equal to or lower than the above-mentioned upper limit, excellent moldability and transparency can be achieved. The imidization rate of the acrylic resin can be measured by NMR spectroscopy, IR spectroscopy, etc. of the acrylic resin.

[0046] The content of unsaturated carboxylic acid alkyl ester units in the acrylic resin, which is the remainder of the content of glutarimide units, is, for example, 50 mol% or more, preferably 60 mol% or more, and for example, 95 mol% or less, preferably 85 mol% or less. The content of acrylic acid ester units in the acrylic resin (specifically, acrylic acid ester units in the total amount of glutarimide units, methacrylic acid units, and acrylic acid ester units) is, for example, less than 1 mass%, preferably less than 0.5 mass%. When the content of acrylic acid ester units is not more than the above-mentioned upper limit, the acrylic resin has excellent thermal stability and can suppress deterioration of the physical properties of the acrylic resin during resin production or molding processing. The acid value of the acrylic resin is, for example, 0.10 mmol / g or more, for example, 0.50 mmol / g or less. When the acid value is within the above range, an acrylic resin having an excellent balance of heat resistance, mechanical properties, and molding processability can be obtained.

[0047] The acid value of an acrylic resin is the content of carboxylic acid units and carboxylic anhydride units in the acrylic resin. The acid value can be calculated, for example, by the titration method described in WO2005-054311 or the titration method described in JP2005-23272A.

[0048] The acrylic resin may contain other copolymerizable vinyl monomer units other than those mentioned above. Examples of other vinyl monomers include alkenyl aromatic monomers such as styrene, α-methylstyrene, vinyltoluene, and divinylbenzene.

[0049] The weight-average molecular weight of the acrylic resin is, for example, 1,000 or more, preferably 5,000 or more, more preferably 10,000 or more, and for example, 2,000,000 or less, preferably 1,000,000 or less, more preferably 500,000 or less. The weight-average molecular weight of the acrylic resin is determined in terms of polystyrene using a gel permeation chromatograph (GPC system).

[0050] The polycarbonate resin contains, for example, a structural unit derived from a dihydroxy compound. The structural unit derived from a dihydroxy compound includes, for example, a structural unit derived from an isosorbide-based dihydroxy compound and a structural unit derived from at least one first dihydroxy compound selected from the group consisting of an alicyclic diol, an alicyclic dimethanol, a di-, tri-, or polyethylene glycol, and an alkylene glycol or a spiroglycol. The first dihydroxy compound excludes an isosorbide-based dihydroxy compound. Furthermore, the structural units derived from the dihydroxy compound may contain structural units derived from a fluorene-based dihydroxy compound. Preferably, the structural units derived from the dihydroxy compound do not contain structural units derived from a fluorene-based dihydroxy compound. In this case, the proportion of structural units derived from aromatic ring compounds in the protective resin layer 12 can be reduced or eliminated. This improves the quality of the protective resin layer 12. The proportion of the isosorbide-based dihydroxy compound in the dihydroxy compounds is, for example, 40 mol% or more, preferably 55 mol% or more, and for example, 90 mol% or less, preferably 75 mol% or less. The proportion of the first dihydroxy compound in the dihydroxy compounds is, for example, 60 mol% or less, preferably 45 mol% or less, and for example, 10 mol% or more, preferably 25 mol% or more. The proportion of the fluorene-based dihydroxy compound in the dihydroxy compounds is, for example, 25 mol% or less, preferably 10 mol% or less, more preferably 0 mol%.

[0051] The thickness of the protective resin layer 12 is, for example, 10 μm or more, preferably 20 μm or more, more preferably 30 μm or more, and for example, 150 μm or less, preferably 100 μm or less, more preferably 80 μm or less. If the thickness of the protective resin layer 12 is equal to or greater than the above-mentioned lower limit, a decrease in impact resistance can be suppressed when the substrate 7 is a thin glass plate. If the thickness of the protective resin layer 12 is equal to or less than the above-mentioned upper limit, foldability can be improved.

[0052] The total light transmittance of the protective resin layer 12 is, for example, 85% or more, preferably 88% or more, more preferably 90% or more, and is, for example, 100% or less. The total light transmittance of the protective resin layer 12 is determined in accordance with JIS K 7361-1. The total light transmittance of other members is determined in the same manner as above.

[0053] The in-plane retardation Re(550) of the protective resin layer 12 is, for example, 10 nm or less, preferably 5 nm or less, and particularly preferably 0 nm, i.e., no in-plane retardation Re(550). The thickness direction retardation Rth(550) of the protective resin layer 12 is, for example, 30 nm or less, preferably 10 nm or less, and particularly preferably 0 nm, i.e., no thickness direction retardation Rth(550).

[0054] If the in-plane retardation Re(550) and thickness direction retardation Rth(550) of the protective resin layer 12 are each below the above-mentioned upper limit, the in-plane retardation Re(550) and thickness direction retardation Rth(550) (described later) of the front panel 4 including the protective resin layer 12 can be set within the desired range.

[0055] Note that "in-plane retardation Re(550)" means the in-plane retardation Re measured with light having a wavelength of 550 nm. "Thickness direction retardation Rth(550)" means the thickness direction retardation Rth measured with light having a wavelength of 550 nm. Even if the number 550 in parentheses changes, the definition of retardation remains the same as above.

[0056] The in-plane retardation Re(550) and the thickness direction retardation Rth(550) are measured by a retardation measurement device. The following retardations are also measured by a retardation measurement device.

[0057] The refractive index of the protective resin layer 12 is appropriately adjusted so that the refractive index difference Δ with the hard coat layer 13 described below falls within a desired range. Specifically, if the protective resin layer 12 is isotropic, the refractive index n thereof is, for example, 1.40 or more, preferably 1.48 or more, and for example, 1.60 or less, preferably 1.55 or less, more preferably 1.53 or less, and even more preferably 1.52 or less.

[0058] Protective resin layer 12 is soft, specifically, has a pencil hardness of, for example, 6B or less. Pencil hardness is measured in accordance with JIS K 5400-5-4. However, if the pencil hardness of protective resin layer 12 is equal to or less than the above-mentioned upper limit, front panel 4 is also soft, meaning that the pencil hardness of front panel 4 is likely to decrease, for example, to 2B or less. However, in this embodiment, front panel 4 includes substrate 7 made of a thin glass plate with excellent hardness, and this thin glass plate can reinforce front panel 4. As a result, front panel 4 can have excellent hardness, specifically, a pencil hardness of, for example, B or more, preferably H or more, and more preferably 2H or more.

[0059] The composition, physical properties, manufacturing method, etc. of the protective resin layer 12 are described in detail in, for example, JP 2016-151696 A.

[0060] [Hard coat layer] The hard coat layer 13 is a protective member that suppresses damage caused by friction on the surface of the organic EL display device 1. For example, when the optical laminate 2 is manufactured by roll-to-roll production, the hard coat layer 13 suppresses damage caused by pressing or friction during lamination when the optical laminate 2 is laminated in the radial direction of the rolls.

[0061] The hard coat layer 13 forms the surface of the protective member 6. The hard coat layer 13 is disposed on one side in the thickness direction of the protective resin layer 12. Specifically, the hard coat layer 13 is in contact with the surface (one side in the thickness direction) of the protective resin layer 12. The hard coat layer 13 extends in the planar direction.

[0062] The hard coat layer 13 is made of, for example, a cured product of a curable composition or a molded product of a thermoplastic composition. That is, examples of materials for the hard coat layer 13 include a curable composition and a thermoplastic composition. Examples of materials for the hard coat layer 13 include preferably a curable composition, more preferably an active energy ray-curable composition, and even more preferably an ultraviolet ray-curable composition.

[0063] Furthermore, the main component of the material of the hard coat layer 13 does not have, for example, an aromatic ring. The main component is the component contained in the hard coat layer 13 in the largest amount, or a component that accounts for 25% or more of the hard coat layer 13.

[0064] Specifically, the hard coat layer 13 is preferably made of a cured product of a curable composition (cured resin), and more preferably made of a cured product of a curable acrylic composition (cured acrylic resin).

[0065] The curable composition contains an ultraviolet-curable compound, which may be any of a monomer, an oligomer, and a prepolymer.

[0066] Specifically, the curable compound may be, for example, an acrylic compound (monomer and / or oligomer) having a plurality of ultraviolet-polymerizable functional groups, preferably a curable compound having a plurality of (meth)acryloyl groups. The number of functional groups ((meth)acryloyl groups) in the curable compound is, for example, 3 or more, preferably 5 or more, and for example, 30 or less, preferably 20 or less.

[0067] Furthermore, the curable compound preferably further contains a hydroxyl group in the molecule.

[0068] Examples of curable monomer compounds include tricyclodecane dimethanol diacrylate, pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, trimethylolpropane triacrylate, pentaerythritol tetra(meth)acrylate, dimethylolpropane tetraacrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol (meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, dipropylene glycol diacrylate, isocyanuric acid tri(meth)acrylate, ethoxylated glycerin tri(meth)acrylate, ethoxylated pentaerythritol tetraacrylate, and oligomers or prepolymers thereof. These can be used alone or in combination.

[0069] Examples of the curable compound that is a monomer or oligomer include urethane (meth)acrylate and / or urethane (meth)acrylate oligomer. The number of (meth)acryloyl groups in the urethane (meth)acrylate and / or urethane (meth)acrylate oligomer is, for example, 3 or more, preferably 4 or more, more preferably 6 or more, and for example, 25 or less, preferably 20 or less.

[0070] The weight average molecular weight (or theoretical molecular weight) of the urethane (meth)acrylate and / or urethane (meth)acrylate oligomer is, for example, 3000 or less, preferably 2500 or less, more preferably 2000 or less, and for example, 500 or more, preferably 800 or more. When the urethane (meth)acrylate and / or urethane (meth)acrylate oligomer is a commercially available product, the theoretical molecular weight described in the catalog attached to the commercially available product is used.

[0071] To form the hard coat layer 13, if the hard coat layer 13 is a cured product, a varnish containing a curable composition is applied and then the curable composition is cured. Alternatively, the hard coat layer 13 made of a thermoplastic resin is directly molded from a thermoplastic composition.

[0072] The tensile storage modulus E' of the hard coat layer 13 at 25°C is, for example, 3 GPa or less, preferably 2.5 GPa or less, and for example, 1.5 GPa or more, preferably 2 GPa or more. The tensile storage modulus E' of the hard coat layer 13 at 25°C is obtained by measuring dynamic viscoelasticity in a temperature dispersion mode under conditions of a frequency of 1 Hz and a temperature increase rate of 5°C / min. When the tensile storage modulus E' of the hard coat layer 13 is equal to or less than the above-mentioned upper limit, the hard coat layer 13 has excellent bending properties (foldability). When the tensile storage modulus E' of the hard coat layer 13 is equal to or greater than the above-mentioned lower limit, damage to the protective resin layer 12 due to friction can be effectively suppressed.

[0073] The pencil hardness of the hard coat layer 13 is, for example, F or more, more preferably H or more, and even more preferably 2H or more. The pencil hardness is measured in accordance with JIS K 5400-5-4. When the pencil hardness of the hard coat layer 13 is equal to or greater than the above-mentioned lower limit, damage to the protective resin layer 12 due to friction can be effectively suppressed.

[0074] The hard coat layer 13 has an in-plane retardation Re(550) of, for example, 10 nm or less, or preferably 5 nm or less. The hard coat layer 13 has a thickness direction retardation Rth(550) of, for example, 30 nm or less, or preferably 10 nm or less.

[0075] The refractive index of the hard coat layer 13 is appropriately adjusted so that the refractive index difference Δ between the hard coat layer 13 and the protective resin layer 12 described below falls within a desired range. Specifically, if the protective resin layer 12 is isotropic, the refractive index n thereof is, for example, 1.40 or more, preferably 1.48 or more, and for example, 1.60 or less, preferably 1.53 or less.

[0076] The hard coat layer 13 has a thickness of, for example, 5 μm or more, or preferably 7 μm or more, and for example, 30 μm or less.

[0077] The total light transmittance of the hard coat layer 13 is, for example, 85% or more, or preferably 90% or more, and for example, 100% or less.

[0078] The composition, physical properties, manufacturing method, etc. of the hard coat layer 13 are described in detail in, for example, JP 2016-151696 A.

[0079] [Protective material properties] The thickness of the protective member 6 is, for example, 15 μm or more, preferably 35 μm or more, and for example, 170 μm or less, preferably 130 μm or less, more preferably 90 μm or less.

[0080] The total light transmittance of the protective member 6 is, for example, 85% or more, or preferably 90% or more, and for example, 100% or less.

[0081] The protective member 6 has an in-plane retardation Re(550) of, for example, 10 nm or less, or preferably 5 nm or less. The protective member 6 has a thickness direction retardation Rth(550) of, for example, 30 nm or less, or preferably 10 nm or less.

[0082] The protective member 6 is bent 180 degrees with the hard coat layer 13 facing inward and having a diameter of 4 mm, and then placed in an environment of 85°C and 85% RH for 100 hours. The protective member 6 is then opened, and the difference Δ between the in-plane retardation Re(550) of the bent portion 25 and the in-plane retardation Re(550) of the bent portion 25 before the bending test is, for example, 10 nm or less. The difference Δ between the thickness direction retardation Rth(550) of the bent portion 25 after the bending test and the thickness direction retardation Rth(550) of the bent portion 25 before the bending test is, for example, 30 nm or less. Details of the bending test will be described later in "Another Feature of One Embodiment."

[0083] [substrate] The substrate 7 forms the rear surface of the front panel 4. The substrate 7 is adhered to the protective resin layer 12 via a first adhesive layer 9, which will be described later. The substrate 7 is, for example, flexible.

[0084] The substrate 7 may be, for example, a resin film such as a polyimide film, or a thin glass plate. From the viewpoint of obtaining excellent bendability, as well as excellent foldability, hardness, and transparency, a thin glass plate is preferably used as the substrate 7. In this embodiment, the substrate 7 is preferably made of a thin glass plate.

[0085] The substrate 7 ensures the mechanical strength and toughness of the front plate 4. The substrate 7 supports the rear side of the protective member 6. The substrate 7 has a flat plate shape extending in the surface direction.

[0086] The thickness of the substrate 7 is, for example, 10 μm or more, and, for example, 100 μm or less, or preferably 80 μm or less.

[0087] The total light transmittance of the substrate 7 is, for example, 80% or more, or preferably 85% or more, and is, for example, 95% or less.

[0088] The thin glass plate is preferably isotropic. The refractive index n of the thin glass plate is, for example, 1.45 or more and, for example, 1.55 or less. If the thin glass plate is isotropic, it does not have an in-plane retardation Re(550) or a thickness direction retardation Rth(550).

[0089] [Polarizing film] The polarizing film 5 is disposed on the back side of the front plate 4. This protects the polarizing film 5 from the front plate 4. The polarizing film 5 is adhered to the substrate 7 via a second adhesive layer 10, which will be described later. The polarizing film 5 has a flat plate shape extending in the planar direction.

[0090] The polarizing film 5 has a thickness of, for example, 15 μm or more, preferably 25 μm or more, and for example, 300 μm or less, preferably 250 μm or less. The polarizing film 5 has a total light transmittance of, for example, 40% or more, preferably 42% or more, and for example, 45% or less.

[0091] The polarizing film 5 includes a polarizer protective film 17, a polarizer 18, and an optical compensation layer 19, which are arranged in this order toward the back side.

[0092] [Polarizer protective film] The polarizer protective film 17 forms the surface of the polarizing film 5. The polarizer protective film 17 extends in the plane direction. The polarizer protective film 17 protects the polarizer 18, which will be described next, from the front side.

[0093] The material of the polarizer protective film 17 is not particularly limited, and examples thereof include polyethylene terephthalate resin, polyethylene naphthalate resin, acetate resin, polyethersulfone resin, polycarbonate resin, polyamide resin, polyimide resin, polyamideimide resin, polyolefin resin, acrylic resin, polyvinyl chloride resin, polyvinylidene chloride resin, polystyrene resin, polyvinyl alcohol resin, polyarylate resin, and polyphenylene sulfide resin. These may be used alone or in combination. To ensure high quality of the optical laminate 2, examples of the material for the polarizer protective film 17 include acrylic resins, more preferably acrylic resins having unsaturated carboxylic acid alkyl ester units and glutarimide units. Specific examples include the acrylic resins exemplified for the protective resin layer 12.

[0094] The polarizer protective film 17 has a thickness of, for example, 10 μm or more, and for example, 100 μm or less, preferably 80 μm or less. The polarizer protective film 17 has an in-plane retardation Re(550) and a thickness direction retardation Rth(550) of, for example, 10 nm or less, preferably 5 nm or less. When the polarizer protective film 17 is isotropic, its refractive index n is, for example, 1.40 or more, preferably 1.48 or more, and for example, 1.60 or less, preferably 1.53 or less.

[0095] The composition, physical properties, production method, etc. of the polarizer protective film 17 are described in detail in, for example, JP-A-2016-151696.

[0096] [Polarizer] The polarizer 18 is in contact with the rear surface of the polarizer protective film 17. The polarizer 18 has a flat plate shape extending in the plane direction. Examples of the polarizer 18 include a hydrophilic film such as a PVA film that has been dyed and stretched, a PVA film that has been dehydrated, and a polyvinyl chloride film that has been dehydrochlorinated. The polarizer 18 is a single layer or multiple layers. The thickness of the polarizer 18 is, for example, 1 μm or more, preferably 3 μm or more, and for example, 15 μm or less, preferably 10 μm or less. The material, composition, physical properties (birefringence, retardation, refractive index, etc.), and manufacturing method of the polarizer 18 are described in detail in, for example, JP 2016-151696 A.

[0097] [Optical compensation layer] The optical compensation layer 19 is in contact with the rear surface of the polarizer 18. The optical compensation layer 19 has a flat plate shape extending in the plane direction. The optical compensation layer 19 is a retardation film, specifically, functions as a λ / 4 plate. This allows the polarizing film 5 including the polarizer 18 and the optical compensation layer 19 to have excellent circular polarization. Materials for the optical compensation layer 19 include materials having the following optical properties, such as polycarbonate resin, polyvinyl acetal resin, cycloolefin resin, acrylic resin, and cellulose ester resin. Polycarbonate resin is preferred. The polycarbonate resin, for example, contains a structural unit derived from a fluorene-based dihydroxy compound, a structural unit derived from an isosorbide-based dihydroxy compound, and a structural unit derived from at least one dihydroxy compound selected from the group consisting of an alicyclic diol, an alicyclic dimethanol, a di-, tri-, or polyethylene glycol, and an alkylene glycol or a spiroglycol.

[0098] The in-plane retardation Re(550) of the optical compensation layer 19 is, for example, 100 nm or more, preferably 135 nm or more, and for example, 180 nm or less, preferably 155 nm or less. The in-plane retardation Re(550) of the optical compensation layer 19 is greater than the in-plane retardation Re(450) and less than the in-plane retardation Re(650). Specifically, Re(450) / Re(550) is, for example, less than 1, preferably 0.95 or less, or, for example, 0.8 or more. Re(550) / Re(650) is, for example, less than 1, preferably 0.97 or less, or, for example, 0.8 or more.

[0099] The composition, physical properties, manufacturing method, etc. of the optical compensation layer 19 are described in detail in, for example, JP 2017-102443 A.

[0100] The substrate 7 and polarizing film 5 having the polarizer protective film 17, the polarizer 18, and the optical compensation layer 19 are described in detail in JP-A-2017-102443.

[0101] [Adhesive layer] The adhesive layer 8 is an adhesive layer that adheres (pressure-sensitively bonds) the above-mentioned members in the front-to-back direction. The adhesive layer 8 includes the first adhesive layer 9, the second adhesive layer 10, and the third adhesive layer 11, as described above. The first adhesive layer 9, the second adhesive layer 10, and the third adhesive layer 11 each extend in the planar direction. The thickness of each of the first adhesive layer 9, the second adhesive layer 10, and the third adhesive layer 11 is, for example, 1 μm or more, preferably 5 μm or more, more preferably 10 μm or more, and for example, 200 μm or less, preferably 150 μm or less, more preferably 100 μm or less.

[0102] The total light transmittance of each of the first adhesive layer 9, the second adhesive layer 10, and the third adhesive layer 11 is, for example, 85% or more, preferably 88% or more, more preferably 90% or more, and is, for example, 100% or less.

[0103] In particular, the first adhesive layer 9 has an in-plane retardation Re(550) of, for example, 10 nm or less, and a thickness direction retardation Rth(550) of, for example, 30 nm or less.

[0104] The composition, physical properties, manufacturing method, etc. of the adhesive layer 8 including the first adhesive layer 9 are described in detail in, for example, JP 2018-28573 A.

[0105] [First adhesive layer] The first adhesive layer 9 adheres the protective member 6 to the substrate 7 in the front-to-back direction. Specifically, the first adhesive layer 9 contacts (adheres to) the back surface of the protective resin layer 12 and the front surface of the substrate 7.

[0106] [Second adhesive layer] The second adhesive layer 10 adheres the front plate 4 and the polarizing film 5 in the front-to-back direction. Specifically, the second adhesive layer 10 contacts (adheres to) the back surface of the substrate 7 and the front surface of the polarizer protective film 17.

[0107] [Third adhesive layer] The third adhesive layer 11 adheres the optical laminate 2 and the image display member 3 in the front-to-back direction. Specifically, the third adhesive layer 11 contacts the back surface of the optical compensation layer 19 and the front surface of the optical laminate 2. [Adhesive layer material] Examples of materials for the first adhesive layer 9, the second adhesive layer 10, and the third adhesive layer 11 include acrylic adhesives, rubber adhesives, vinyl alkyl ether adhesives, silicone adhesives, polyester adhesives, polyamide adhesives, urethane adhesives, fluorine adhesives, epoxy adhesives, and polyether adhesives.

[0108] In particular, from the viewpoint of reducing the in-plane retardation Re(550) and thickness direction retardation Rth(550) of front panel 4, the material of first adhesive layer 9 is preferably an acrylic adhesive.

[0109] Examples of acrylic adhesives include crosslinked adhesives obtained by crosslinking a copolymer of an alkyl (meth)acrylate containing an alkyl moiety having 3 to 8 carbon atoms and a hydroxyalkyl (meth)acrylate containing a hydroxyalkyl moiety having 3 to 8 carbon atoms with a crosslinking agent.

[0110] Examples of alkyl(meth)acrylates containing an alkyl moiety having 3 to 8 carbon atoms include n-propyl(meth)acrylate, isopropyl(meth)acrylate, n-butyl(meth)acrylate, s-butyl(meth)acrylate, t-butyl(meth)acrylate, isobutyl(meth)acrylate, n-pentyl(meth)acrylate, isopentyl(meth)acrylate, n-hexyl(meth)acrylate, isohexyl(meth)acrylate, isoheptyl(meth)acrylate, 2-ethylhexyl(meth)acrylate, and n-octyl(meth)acrylate. A preferred example of the alkyl(meth)acrylate is n-butyl(meth)acrylate.

[0111] Examples of hydroxyalkyl (meth)acrylates containing a hydroxyalkyl moiety having 3 to 8 carbon atoms include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 5-hydroxypentyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 7-hydroxyheptyl (meth)acrylate, and 8-hydroxyoctyl (meth)acrylate. A preferred example of the hydroxyalkyl (meth)acrylate is 4-hydroxybutyl (meth)acrylate. The number of parts by mass of the hydroxyalkyl (meth)acrylate relative to 100 parts by mass of the alkyl (meth)acrylate is, for example, 0.5 parts by mass or more and, for example, 5 parts by mass or less.

[0112] Examples of crosslinking agents include isocyanate-based crosslinking agents, peroxide-based crosslinking agents, epoxy-based crosslinking agents, and imine-based crosslinking agents. These can be used alone or in combination. Preferably, an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent are used in combination. Examples of isocyanate-based crosslinking agents include bifunctional and trifunctional agents, preferably trifunctional agents, and specific examples include trimethylolpropane adducts of xylylene diisocyanate. Examples of peroxide-based crosslinking agents include acyl peroxides, preferably benzoyl peroxide. The proportion of the crosslinking agent is, for example, 0.01 parts by mass or more and, for example, 1 part by mass or less, per 100 parts by mass of the copolymer. Furthermore, when an isocyanate-based crosslinking agent and a peroxide-based crosslinking agent are used in combination, the number of parts by mass of the isocyanate-based crosslinking agent is, for example, 0.05 parts by mass or more and less than 0.2 parts by mass, and the number of parts by mass of the oxide-based crosslinking agent is, for example, 0.2 parts by mass or more and 0.5 parts by mass or less, relative to 100 parts by mass of the copolymer.

[0113] [Image display section] The image display member 3 forms the rear surface of the organic EL display device 1. The image display member 3 is disposed on the rear side of the optical laminate 2 via a third adhesive layer 11. The image display member 3 has a generally flat plate shape extending in the surface direction, and specifically, an organic EL element can be used. For example, although not shown, the image display member 3 includes a display substrate, two electrodes, an organic EL layer sandwiched between the two electrodes, and a sealing layer. The thickness of the image display member 3 is, for example, 1 μm or more, and, for example, 100 μm or less. The configuration, physical properties, manufacturing method, etc. of the image display member 3 are described in detail in, for example, JP 2018-28573 A.

[0114] [Touch panel input display device] 1, the organic EL display device 1 can further include a conductive layer 15 and a shielding layer 16. This allows the organic EL display device 1 to function as a touch panel input display device.

[0115] [Conductive layer] The conductive layer 15 is provided in the optical laminate 2, and specifically, is disposed on the back side of the third adhesive layer 11. The conductive layer 15 is embedded, for example, in the middle part of the third adhesive layer 11 in the front-to-back direction (the middle part in the thickness direction).

[0116] Examples of materials for the conductive layer 15 include metal oxides, conductive fibers, and metals.

[0117] Examples of metal oxides include composite oxides such as indium zinc oxide (IZO), indium gallium zinc oxide (IGZO), indium gallium oxide (IGO), indium tin oxide (ITO), and antimony tin oxide (ATO). The conductive layer 15 made of a metal oxide has a total light transmittance of, for example, 85% or more, preferably 88% or more, and more preferably 90% or more, and is, for example, 100% or less.

[0118] Examples of conductive fibers include metal nanowires and carbon nanotubes.

[0119] Examples of metals include gold, platinum, silver, and copper. When the material of the conductive layer 15 is a metal, the conductive layer 15 is a metal mesh having a mesh shape in a planar view. The width of the lines constituting the mesh is, for example, 100 μm or less, preferably 30 μm or less, more preferably 10 μm or less, and is, for example, 1 μm or more.

[0120] Details of the conductive layer 15 are described in, for example, JP 2017-102443 A, JP 2014-113705 A, JP 2014-219667 A, etc. The conductive layer 15 integrally includes a sensor electrode portion 20 located at the center in the surface direction and a lead-out wiring portion (not shown) located around the sensor electrode portion 20.

[0121] [Hidden layer] The concealing layer 16 is provided on the front panel 4, and specifically, is disposed (specifically, printed) on the peripheral portion of the back surface of the protective resin layer 12. In a plan view, the concealing layer 16 has a pattern that encompasses the lead-out wiring portion (or routed wiring) of the conductive layer 15. Examples of materials for the concealing layer 16 include a composition containing a black component and a resin. The total light transmittance of the concealing layer 16 is, for example, 10% or less, preferably 5% or less. The concealing layer 16 is a layer in the organic EL display device 1 that prevents a user from viewing the lead-out wiring portion (not shown) from the viewing side. When projected in the thickness direction, the optical laminate 2 includes a non-display region 21 that overlaps with the concealing layer 16 and a display region 22 that does not overlap with the concealing layer 16 and overlaps with the sensor electrode portion 20 of the conductive layer 15. When the concealing layer 16 is provided on the front panel 4, the in-plane retardation Re(550) and thickness direction retardation Rth(550) of the front panel 4 are the in-plane retardation Re(550) and thickness direction retardation Rth(550) measured in the display area 22 of the front panel 4.

[0122] Salient Features of One Embodiment Next, prominent features of this embodiment will be described.

[0123] The difference Δ between the refractive index n of the protective resin layer 12 and the refractive index n of the hard coat layer 13 is, for example, 0.04 or less, preferably 0.03 or less, and more preferably 0.02 or less.

[0124] <1> Specifically, if both the protective resin layer 12 and the hard coat layer 13 are isotropic, the difference Δ between the refractive index n of the protective resin layer 12 and the refractive index n of the hard coat layer 13 is 0.04 or less, preferably 0.03 or less, and more preferably 0.02 or less.

[0125] <2> If both the protective resin layer 12 and the hard coat layer 13 are birefringent, the difference Δ in the refractive index nx in their slow axis direction is 0.04 or less, preferably 0.03 or less, more preferably 0.02 or less, and even more preferably 0.01 or less, and the difference Δ in the refractive index nx in their fast axis direction is 0.04 or less, preferably 0.03 or less, and more preferably 0.02 or less.

[0126] <3> When one of the protective resin layer 12 and the hard coat layer 13 is isotropic and the other is birefringent, the difference Δ between the refractive index n of one and the refractive index nx of the other in the slow axis direction is 0.04 or less, preferably 0.03 or less, and more preferably 0.02 or less.

[0127] If the refractive index difference Δ exceeds the upper limit, it will be impossible to obtain a high-quality front panel 4, a high-quality optical laminate 2, and a high-quality organic EL display device 1, and problems of unevenness due to the refractive index difference Δ will occur.

[0128] Other Features of an Embodiment The front panel 4 has an in-plane retardation Re(550) of 10 nm or less, and a thickness direction retardation Rth(550) of 30 nm or less.

[0129] If the in-plane retardation Re(550) of the front panel 4 exceeds 10 nm, or if the thickness direction retardation Rth(550) of the front panel 4 exceeds 30 nm, it may not be possible to obtain a high-quality front panel 4.

[0130] The in-plane retardation Re(550) of the front panel 4 is preferably 5 nm or less, more preferably 1 nm or less. The thickness direction retardation Rth(550) of the front panel 4 is preferably 15 nm or less, more preferably 10 nm or less.

[0131] Furthermore, the front panel 4 is bent at 180 degrees with the hard coat layer 13 facing inward and having a diameter of 4 mm, and then fixed in an environment of 85°C and 85% RH for 100 hours. After that, the front panel 4 is opened and the difference Δ between the in-plane retardation Re(550) of the bent portion 25 and the in-plane retardation Re(550) of the bent portion 25 before the bending test is, for example, 10 nm or less, and the difference Δ between the thickness direction retardation Rth(550) of the bent portion 25 after the bending test and the thickness direction retardation Rth(550) of the bent portion 25 before the bending test is, for example, 30 nm or less.

[0132] In the bending test, as shown in Fig. 4, front panel 4 is bent while being supported from the back side by two glass plates 35 so that the hard coat layer (not shown in Fig. 4) of front panel 4 faces inward. At this time, distance L between the surfaces of front panel 4 facing each other in the thickness direction is 4 mm. In other words, if bent portion 25 has a semicircular arc shape, its diameter (inner diameter) is 4 mm.

[0133] The absolute value of the photoelastic coefficient of the front panel 4 at 23°C is, for example, 150.0 × 10 -13 cm 2 / dyn or less, preferably 100.0 x 10 -13 cm 2 / dyn or less, more preferably 50.0 × 10 -13 cm 2 / dyn or less, particularly preferably 30.0 × 10 -13 cm 2 / dyn or less, most preferably 10.0 × 10 -13 cm 2 / dyn or less. If the absolute value of the photoelastic coefficient of front panel 4 is equal to or less than the above-mentioned upper limit, the difference Δ in Re(550) before and after the bending test and the difference Δ in Rth(550) can be set to be equal to or less than the above-mentioned upper limit. Therefore, front panel 4 has excellent bendability and foldability.

[0134] [Effects of one embodiment] Furthermore, in the front panel 4 of this organic EL display device 1, the difference Δ between the refractive index of the protective resin layer 12 and the refractive index of the hard coat layer 13 is small, at 0.04 or less, so the front panel 4 is of high quality and does not suffer from the problem of unevenness caused by the refractive index difference Δ.

[0135] Furthermore, in this front panel 4, if the molar ratio of structural units derived from aromatic compounds in the main components of the material of protective resin layer 12 is low, at 5.0 mol % or less, the high quality of front panel 4 can be ensured even more reliably.

[0136] Furthermore, in this front panel 4, if the material of the protective resin layer 12 is an acrylic resin or a polycarbonate resin and the material of the hard coat layer 13 is an acrylic resin, the refractive index of the protective resin layer and the refractive index of the hard coat layer are similar, and the difference Δ between the refractive index of the protective resin layer 12 and the refractive index of the hard coat layer 13 can be reliably reduced, thereby reliably maintaining high quality.

[0137] On the other hand, as described above, protective resin layer 12 made of acrylic resin or polycarbonate resin (especially acrylic resin) has a low tensile storage modulus E', which reduces mechanical strength and is likely to cause a decrease in the strength of front panel 4.

[0138] However, in this organic EL display device 1, if the substrate 7 is made of a thin glass plate, the protective resin layer 12 can be reinforced, and therefore the reduction in strength of the front panel 4 can be suppressed.

[0139] Furthermore, this front panel 4 comprises a substrate 7 including a thin glass plate and a first adhesive layer 9, and the substrate 7, first adhesive layer 9, protective resin layer 12, and hard coat layer 13 are arranged in order in the thickness direction, thereby suppressing the occurrence of marks (such as wrinkles) after bending and maintaining high quality.

[0140] This optical laminate 2 and organic EL display device 1 include the front panel 4 described above, and therefore do not suffer from the problem of unevenness caused by the refractive index difference Δ, and are of high quality.

[0141] [Variations] In the following modifications, the same components and steps as those in the above-described embodiment are denoted by the same reference numerals, and detailed descriptions thereof will be omitted. Furthermore, each modification can achieve the same effects as those in the above-described embodiment unless otherwise specified. Furthermore, the embodiment and its modifications can be combined as appropriate.

[0142] Although not shown, the back surface of the conductive layer 15 may be in direct contact with the surface of the image display member 3 .

[0143] In the embodiment, an organic EL display device 1 is exemplified as an example of the image display device of the present invention, but the image display device is not limited to this, and may also be, for example, a liquid crystal display device (LCD).

[0144] The protective member 6 may further include a second hard coat layer 14. The second hard coat layer 14 is disposed on the surface of the hard coat layer 13. That is, the protective member 6 includes, in order from the front side, a protective resin layer 12, a hard coat layer 13, and a second hard coat layer 14. The second hard coat layer 14 has the same physical properties and thickness as the hard coat layer 13, except for the following differences. The tensile storage modulus E' of the second hard coat layer 14 at 25°C is, for example, lower than the tensile storage modulus E' of the second hard coat layer 14. The tensile storage modulus E' of the second hard coat layer 14 at 25°C is, for example, less than 2 GPa, preferably less than 1.5 GPa, and for example, 0.5 GPa or more, preferably 1 GPa or more. The tensile storage modulus E' of the second hard coat layer 14 at 25°C is obtained by measuring dynamic viscoelasticity in a temperature dispersion mode under conditions of a frequency of 1 Hz and a heating rate of 5°C / min.

[0145] As shown in Fig. 2, the optical laminate 2 of this modified example is not provided on the image display member 3, and does not have to constitute the organic EL display device 1. Specifically, the optical laminate 2 is a component for producing the organic EL display device 1, and is not yet adhered to the optical laminate 2. In this case, a release sheet 26 shown by the imaginary line is laminated on the back surface of the third adhesive layer 11. The optical laminate 2 is distributed as a component alone, and is an industrially applicable device.

[0146] Although not shown, the front panel 4 may not be provided on the polarizing film 5 and may not constitute the optical laminate 2. Specifically, the front panel 4 is a component for producing the optical laminate 2 and is not yet adhered to the polarizing film 5. The front panel 4 may be provided with a second adhesive layer 10. The front panel 4 is distributed as a component alone and is an industrially applicable device.

[0147] As shown in Fig. 3, the front panel 4 of the modified example does not include the substrate 7, and can include only the protective member 6. Specifically, the front panel 4 shown in the modified example of Fig. 3 does not include the first adhesive layer 9 and the substrate 7, and is made up of only the protective member 6.

[0148] Preferably, front panel 4 further includes first adhesive layer 9 and substrate 7, and substrate 7 further includes a thin glass plate. This configuration makes it possible to suppress the occurrence of marks (such as wrinkles) after bending (and further folding), thereby maintaining high quality. [Example]

[0149] The present invention will be described in more detail below with reference to examples and comparative examples. It should be noted that the present invention is not limited to these examples and comparative examples. The specific numerical values ​​of the blending ratios (content ratios), physical property values, parameters, etc. used in the following description can be replaced with the upper limit (a numerical value defined as "equal to or less than") or lower limit (a numerical value defined as "equal to or more than" or "exceeding") of the corresponding blending ratios (content ratios), physical property values, parameters, etc. described in the "Description of the Invention" above.

[0150] First, the method for measuring the physical properties of each layer will be described below.

[0151] [Refractive Index] The refractive index of each layer at a wavelength of 589 nm was measured using an Abbe refractometer (model number: DR-M2, manufactured by Atago Co., Ltd.) at a temperature of 23°C.

[0152] [Measurement of the molar proportion of structural units derived from aromatic compounds in the protective resin layer 12] [Identifying structural units] The protective resin layer 12 was immersed in methanol. The methanol-soluble matter (decomposition products) was measured by GC-MS. As a result, the structural unit of the protective resin layer 12 was identified.

[0153] [Measurement of aromatic compound percentage based on integrals] The protective resin layer 12 was dissolved in deuterated chloroform to prepare a solution. 1 H-NMR was measured. 1In the H-NMR measurement, the molar ratio of structural units derived from aromatic compounds and the molar ratio of structural units derived from non-aromatic compounds were calculated from the integral ratio of protons directly bonded to aromatic rings and the integral ratio of other protons based on the structural units identified by the GC-MS measurement. Then, the molar ratio of structural units derived from aromatic compounds in the protective resin layer 12 was calculated as a percentage. 1 For H-NMR measurements, an NMR evaluation device (AVANCEIII-600 with Cryo Probe, manufactured by Bruker Biospin) was used.

[0154] [Example 1] A coating agent was prepared by mixing 100 parts by mass of a multifunctional acrylate (manufactured by AICA Kogyo Co., Ltd., product name "Z-850-16"), 5 parts by mass of a leveling agent (manufactured by DIC Corporation, product name: GRANDIC PC-4100), and 3 parts by mass of a photopolymerization initiator (manufactured by Ciba Japan Co., Ltd., product name: Irgacure 907), and diluting the mixture with methyl isobutyl ketone to a solids concentration of 50% by mass.

[0155] Separately, a protective resin layer 12 made of an acrylic film manufactured by Nitto Denko Corporation (product name "HX-40N", thickness 40 μm) was prepared. The refractive index of the protective resin layer 12 was 1.51. The molar proportion of structural units derived from aromatic compounds in the protective resin layer 12 was 0.0 mol%.

[0156] A coating agent was applied to one side of the prepared protective resin layer 12 to form a coating layer, and the coating layer together with the protective resin layer was heated at 90°C for 2 minutes. Next, ultraviolet light was irradiated onto the coating layer using a high-pressure mercury lamp with an integrated light dose of 300 mJ / cm. 2 A hard coat layer 13 was formed by irradiating the hard coat layer 13 with light at a wavelength of 1000 nm. The thickness of the hard coat layer 13 was 10 μm. The refractive index of the hard coat layer 13 was 1.49. In this way, a protective member 6 including a protective resin layer 12 and a hard coat layer 13 was produced, as shown in FIG. 3 . In other words, a front panel 4 including the protective member 6 was produced.

[0157] [Example 2] A front panel 4 shown in Fig. 3 was produced in the same manner as in Example 1. However, protective resin layer 12 was changed to a polycarbonate film produced in the following manner.

[0158] 81.98 parts by mass (0.56 mol) of isosorbide (manufactured by Roquette Fleuret, trade name "POLYSORB"), 47.19 parts by mass (0.24 mol) of tricyclodecane dimethanol, 175.1 parts by mass (0.81 mol) of diphenyl carbonate (manufactured by Mitsubishi Chemical Corporation), and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst were charged into a reaction vessel, and in a nitrogen atmosphere, as the first step of the reaction, the heating bath temperature was heated to 150 ° C., and the raw materials were dissolved (about 15 minutes) while stirring as necessary. Next, the pressure was increased from atmospheric pressure to 13.3 kPa, and the heating bath temperature was increased to 190 ° C. over 1 hour, while the generated phenol was withdrawn from the reaction vessel. After the entire reaction vessel was maintained at 190°C for 15 minutes, the second step involved reducing the pressure inside the reaction vessel to 6.67 kPa, raising the heating bath temperature to 230°C over 15 minutes, and removing the generated phenol from the reaction vessel. As the stirring torque of the agitator increased, the temperature was raised to 250°C over 8 minutes. To further remove the generated phenol, the pressure inside the reaction vessel was lowered to 0.200 kPa or less. After reaching the predetermined stirring torque, the reaction was terminated, and the resulting reaction product was extruded into water to obtain polycarbonate resin pellets. The resulting polycarbonate resin was vacuum-dried at 80°C for 5 hours. A protective resin layer 12 consisting of a 135 μm-thick polycarbonate film was then produced using a film-forming device equipped with a single-screw extruder (manufactured by Toshiba Machine Co., Ltd., cylinder temperature setting: 250°C), a T-die (width: 300 mm, temperature setting: 250°C), a chill roll (temperature setting: 120-130°C), and a winder. The refractive index of the protective resin layer 12 was 1.51. The molar proportion of structural units derived from aromatic compounds in the protective resin layer 12 was 1.0 mol %.

[0159] [Example 3] A front panel 4 shown in Fig. 3 was produced in the same manner as in Example 1. However, protective resin layer 12 was changed to a polycarbonate film produced in the following manner.

[0160] 38.06 parts by weight (0.059 mol part) of bis[9-(2-phenoxycarbonylethyl)fluoren-9-yl]methane, 53.73 parts by weight (0.368 mol part) of isosorbide (manufactured by Rocket Fleuret, trade name "POLYSORB"), 9.64 parts by weight (0.067 mol part) of 1,4-cyclohexanedimethanol (cis-trans mixture, manufactured by SK Chemicals), 81.28 parts by weight (0.379 mol part) of diphenyl carbonate (manufactured by Mitsubishi Chemical), and 3.83 × 10 calcium acetate monohydrate as a catalyst. -4 Weight part (2.17×10 -6 (parts by mole) were charged into a reaction vessel, and the reactor was purged with nitrogen under reduced pressure. The raw materials were dissolved under a nitrogen atmosphere at 150°C for approximately 10 minutes while stirring. In the first stage of the reaction, the temperature was raised to 220°C over 30 minutes, and the reaction continued at atmospheric pressure for 60 minutes. The pressure was then reduced from atmospheric pressure to 13.3 kPa over 90 minutes, and maintained at 13.3 kPa for 30 minutes, during which the generated phenol was removed from the reaction system. In the second stage of the reaction, the heat transfer medium temperature was raised to 240°C over 15 minutes, while the pressure was reduced to 0.10 kPa or less over 15 minutes, and the generated phenol was removed from the reaction system. After reaching the predetermined stirring torque, the pressure was restored to atmospheric pressure with nitrogen to terminate the reaction. The resulting polyester carbonate was extruded into water, and strands were cut to obtain polycarbonate resin pellets. Polycarbonate films were then produced from the resulting polycarbonate resin pellets. The refractive index of the obtained polycarbonate film (unstretched) was 1.53. The obtained polycarbonate film was stretched obliquely by 2 to 3 times. The stretching direction was set at 45° with respect to the longitudinal direction of the film. In this way, a protective resin layer 12 made of a polycarbonate film was produced. The refractive index of the protective resin layer 12 was 1.53. The molar proportion of structural units derived from aromatic compounds in the protective resin layer 12 was 6.6 mol %.

[0161] [Comparative Example 1] A front panel 4 shown in Figure 3 was produced in the same manner as in Example 1. However, the protective resin layer 12 was changed to a polyethylene terephthalate film manufactured by Mitsubishi Chemical Corporation (product name: T912E50-N). The refractive index of this protective resin layer 12 was 1.57. The molar proportion of structural units derived from aromatic compounds in the protective resin layer 12 was 50 mol%.

[0162] [evaluation] The following items were evaluated for the front panels 4 of Examples 1 to 3 and Comparative Example 1. The evaluation results are shown in Table 1.

[0163] [Refractive index difference] The difference between the refractive index of the protective resin layer 12 and the refractive index of the hard coat layer 13 was calculated.

[0164] [Dignity] A black acrylic plate was attached to the protective resin layer 12 of the front panel 4 via an acrylic adhesive. Next, the surface of the hard coat layer 13 was visually observed under a three-wavelength fluorescent lamp. The evaluation was ⊚ when almost no unevenness in appearance was visible, ◯ when slight unevenness in appearance was visible, and × when unevenness in appearance was clearly visible.

[0165] [Table 1] [Explanation of symbols]

[0166] 1 Organic EL display device 2 Optical laminate 3 Image display components 4 Front plate 6 Protective materials 7. Circuit Board 9 First adhesive layer 12 Protective resin layer 13 Hard coat layer

Claims

1. A protective resin layer and a hard coat layer are provided in this order in the thickness direction, A front panel characterized in that the difference in refractive index between the protective resin layer and the hard coat layer is 0.04 or less.

2. 2. The front panel according to claim 1, wherein the molar ratio of structural units derived from aromatic compounds in the main components of the material of said protective resin layer is 5.0 mol % or less.

3. 3. The front panel according to claim 1, wherein the material of the protective resin layer is an acrylic resin or a polycarbonate resin, and the material of the hard coat layer is an acrylic resin.

4. Further, the device includes a substrate and an adhesive layer, the substrate, the adhesive layer, the protective resin layer, and the hard coat layer are arranged in this order in a thickness direction; The front panel according to any one of claims 1 to 3, characterized in that the substrate comprises a thin glass plate.

5. A polarizing film; and the front panel according to any one of claims 1 to 4. An optical laminate characterized in that the layers are arranged in order toward the viewing side.

6. an image display member; The optical laminate according to claim 5 An image display device characterized in that the display devices are arranged in order toward the viewing side.

Images