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WO2024166911A1 - Stratifié et affichage - Google Patents

Stratifié et affichage Download PDF

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Publication number
WO2024166911A1
WO2024166911A1 PCT/JP2024/003925 JP2024003925W WO2024166911A1 WO 2024166911 A1 WO2024166911 A1 WO 2024166911A1 JP 2024003925 W JP2024003925 W JP 2024003925W WO 2024166911 A1 WO2024166911 A1 WO 2024166911A1
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WIPO (PCT)
Prior art keywords
film
resin film
transparent resin
hard coat
laminate
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Ceased
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PCT/JP2024/003925
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English (en)
Japanese (ja)
Inventor
祐介 田口
純 上手
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Kaneka Corp
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Kaneka Corp
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Priority to JP2024576861A priority Critical patent/JPWO2024166911A1/ja
Publication of WO2024166911A1 publication Critical patent/WO2024166911A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B27/00—Layered products comprising a layer of synthetic resin
    • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/022—Mechanical properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/02—Physical, chemical or physicochemical properties
    • B32B7/023—Optical properties
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements
    • G02B1/10—Optical coatings produced by application to, or surface treatment of, optical elements
    • G02B1/14—Protective coatings, e.g. hard coatings
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/30—Polarising elements
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/13363—Birefringent elements, e.g. for optical compensation
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K50/00—Organic light-emitting devices
    • H10K50/80—Constructional details
    • H10K50/86—Arrangements for improving contrast, e.g. preventing reflection of ambient light
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
    • H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
    • H10K59/10—OLED displays

Definitions

  • the present invention relates to a laminate in which multiple films are bonded together, and a display including the laminate.
  • Hard-coated transparent polyimide films are being considered as cover windows for flexible displays (see, for example, Patent Document 1).
  • transparent polyimides have an absorption band that overlaps with the short wavelength region of visible light, so they are colored slightly yellow, which can affect the hue (tone) of the display.
  • Polyimide has a high refractive index, and the difference in refractive index between the air interface and interfaces with other materials results in a lot of light reflection (high reflectance) and low total light transmittance, so using transparent polyimide film as a cover window material can be a factor in reducing the brightness of the display.
  • transparent polyimide film has a large birefringence, so if a transparent polyimide film is implemented as a cover window for a display that has a polarizing plate on the viewing surface, there is an issue that color unevenness occurs when the display is viewed through polarized sunglasses, resulting in poor visibility.
  • Patent Document 1 and Patent Document 2 disclose that by placing a high retardation stretched polyester film on the viewing side of the polarizing plate of a display, it is possible to reduce color unevenness when the display is viewed through polarized sunglasses.
  • Patent Documents 1 and 2 By using a high retardation resin film as shown in Patent Documents 1 and 2 as the cover window of a display, it is possible to reduce color unevenness when the display is viewed through polarized sunglasses. In order to sufficiently suppress color unevenness, a phase difference of 5000 nm or more is necessary, and in order to achieve such a high phase difference, the thickness of the film needs to be large.
  • Thick polyester films have high bending rigidity and therefore insufficient bendability for use as a cover window for flexible displays, particularly foldable displays.
  • foldable displays require excellent restorability, i.e., when the device is folded (bent) and then returned to a flat state, bending marks are unlikely to remain in the bent parts, but thick polyester films have poor restorability.
  • polyester films By laminating multiple polyester films together, it is possible to reduce the thickness of each film, increasing flexibility, while increasing the phase difference of the laminated film.
  • a laminate made by laminating multiple polyester films is placed on the viewing side of a display, the effect of suppressing color unevenness is limited, even if the laminate has the same phase difference as a single polyester film with a large thickness.
  • polyester films like transparent polyimide films, have a high refractive index and high reflectance, which poses the issue of low light transmittance.
  • the present invention aims to provide a cover window material that has excellent flexibility, high light transmittance, and can reduce color unevenness when viewing a display through polarized sunglasses.
  • the laminate of the present invention comprises a first transparent resin film and a second transparent resin film bonded together via a transparent adhesive layer, and a hard coat layer is provided on the outer surface of either the first transparent resin film or the second transparent resin film.
  • the in-plane retardation of the laminate is 5000 nm or more.
  • the total light transmittance of the laminate is preferably 89.0% or more.
  • the laminate of the first embodiment of the present invention has a hard coat layer on the outer surface of a first transparent resin film.
  • the laminate of the second embodiment of the present invention has a hard coat layer on the outer surface of a second transparent resin film.
  • the laminate of the present invention is used as a cover window for a display, it is arranged so that the surface of the laminate on which the hard coat layer is formed becomes the viewing surface.
  • the first transparent resin film is a blended resin film containing a polyimide resin and a solvent-soluble resin other than a polyimide resin.
  • the refractive index of the first transparent resin film is preferably 1.600 or less.
  • the solvent-soluble resin is preferably an acrylic resin, and among these, one containing methyl methacrylate as the main component is preferably used.
  • the polyimide-based resin is a polyimide or polyamide-imide, and contains a tetracarboxylic dianhydride-derived structure and a diamine-derived structure.
  • the polyimide-based resin is preferably a polyimide.
  • the polyimide-based resin preferably contains a fluorine-containing aromatic tetracarboxylic dianhydride and an alicyclic tetracarboxylic dianhydride as the tetracarboxylic dianhydride, and a fluorine-containing diamine as the diamine.
  • the first transparent resin film may be a stretched film.
  • the thickness of the first transparent resin film may be 30 to 80 ⁇ m.
  • the first transparent resin film may have an in-plane retardation of 1000 nm or more and an in-plane birefringence of 0.005 or more.
  • the second transparent resin film is a high-retardation resin film having an in-plane retardation of 2000 nm or more.
  • the in-plane retardation of the second transparent resin film is preferably 4000 nm or more.
  • the thickness of the second transparent resin film is preferably 70 ⁇ m or less.
  • the second transparent resin film may be a polyester film.
  • the angle between the slow axis direction of the first transparent resin film and the slow axis direction of the second transparent resin film is preferably 50° or less.
  • the slow axis direction of the first transparent resin film and the slow axis direction of the second transparent resin film may be parallel.
  • Examples of materials for the hard coat layer include acrylic-based hard coat materials and siloxane-based hard coat materials.
  • the thickness of the hard coat layer may be 1 to 50 ⁇ m.
  • the laminate of the present invention has excellent flexibility and high light transmittance.
  • the front phase difference of the laminate is 5000 nm or more, it is effective in reducing color unevenness when the display is viewed through polarized sunglasses.
  • the laminate of the present invention is suitable for use as a cover window material for flexible displays.
  • FIG. 1 is a cross-sectional view of a laminate according to one embodiment of the present invention.
  • FIG. 1 is a cross-sectional view of a laminate according to one embodiment of the present invention.
  • FIG. 1 is a cross-sectional view of a laminate according to a first embodiment of the present invention
  • FIG. 2 is a cross-sectional view of a laminate according to a second embodiment of the present invention.
  • the laminate of the present invention comprises a first transparent resin film 1 and a second transparent resin film 2, and the first transparent resin film 1 and the second transparent resin film 2 are bonded together via a transparent adhesive layer 9.
  • the first transparent resin film 1 contains a polyimide resin and a solvent-soluble resin other than a polyimide resin.
  • the second transparent resin film 2 has an in-plane retardation of 2000 nm or more.
  • the first transparent resin film may be referred to as a "blend resin film” and the second transparent resin film may be referred to as a "high retardation resin film.”
  • the laminate of the present invention has a hard coat layer on the outer surface of either the first transparent resin film 1 or the second transparent resin film 2.
  • the laminate 11 of the first embodiment shown in FIG. 1 has a hard coat layer 3 on the outer surface (the surface not bonded to the second transparent resin film 2) of the first transparent resin film 1, and the first transparent resin film 1 and the hard coat layer 3 constitute a hard coat film 5.
  • the laminate 12 of the second embodiment shown in FIG. 2 has a hard coat layer 3 on the outer surface (the surface not bonded to the first transparent resin film 1) of the second transparent resin film 2, and the second transparent resin film 2 and the hard coat layer 3 constitute a hard coat film 6.
  • the first transparent resin film 1 is a blended resin film containing one or more polyimide-based resins selected from the group consisting of polyimide and polyamideimide, and a solvent-soluble resin other than a polyimide-based resin (hereinafter, may be referred to as "other resin").
  • other resin a solvent-soluble resin other than a polyimide-based resin
  • Polyimide is obtained by dehydrating and cyclizing polyamic acid obtained by reacting tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") with diamine.
  • Polyamideimide is obtained by replacing a part of the tetracarboxylic dianhydride of polyimide with a dicarboxylic acid derivative such as dicarboxylic acid dichloride.
  • Polyimide and polyamideimide may be used together as the polyimide-based resin. In terms of compatibility with other resins, polyimide may be preferable as the polyimide-based resin.
  • the polyimide resin used in the embodiment of the present invention preferably contains an alicyclic tetracarboxylic dianhydride as an acid dianhydride component.
  • the acid dianhydride component has an alicyclic structure, which tends to improve the compatibility of the polyimide resin with other resins such as acrylic resins.
  • the alicyclic tetracarboxylic dianhydride may have at least one alicyclic structure, and may have both an alicyclic ring and an aromatic ring in one molecule.
  • the alicyclic ring may be polycyclic or may have a spiro structure.
  • Alicyclic tetracarboxylic dianhydrides include 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, meso-butane-1,2,3,4-tetracarboxylic dianhydride, and 1,1'-bicyclohexane-3,3',4,4'-tetracarboxylic acid-3,4:3',4'-dianhydride.
  • 1,2,3,4-cyclobutanetetracarboxylic dianhydride CBDA
  • 1,2,3,4-cyclopentanetetracarboxylic dianhydride CPDA
  • 1,2,4,5-cyclohexanetetracarboxylic dianhydride H-PMDA
  • 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic-3,4:3',4'-dianhydride H-BPDA
  • 1,2,3,4-cyclobutanetetracarboxylic dianhydride being particularly preferred.
  • the content of the alicyclic tetracarboxylic dianhydride relative to 100 mol% of the total amount of the dianhydride components is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, and may be 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more.
  • the amount of the alicyclic tetracarboxylic dianhydride required to provide compatibility with other resins may vary depending on the type of other resin, the type of the alicyclic tetracarboxylic dianhydride amount, etc.
  • the alicyclic tetracarboxylic dianhydride is 1,2,3,4-cyclobutane tetracarboxylic dianhydride (CBDA)
  • CBDA 1,2,3,4-cyclobutane tetracarboxylic dianhydride
  • the content of CBDA relative to 100 mol% of the total amount of the dianhydride components is preferably 6 mol% or more, more preferably 8 mol% or more, and even more preferably 10 mol% or more.
  • the content of the alicyclic tetracarboxylic dianhydride relative to the total amount of the acid dianhydride components is preferably 80 mol% or less, more preferably 78 mol% or less, even more preferably 76 mol% or less, and may be 74 mol% or less, 72 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, or 50 mol% or less.
  • the content of the alicyclic tetracarboxylic dianhydride is preferably 45 mol% or less, more preferably 40 mol% or less, and may be 35 mol% or less.
  • the acid dianhydride component contains, in addition to the alicyclic tetracarboxylic acid dianhydride, a fluorine-containing aromatic tetracarboxylic acid dianhydride and/or a bis(trimellitic anhydride) ester.
  • fluorine-containing aromatic tetracarboxylic acid dianhydrides examples include 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis ⁇ 4-[4-(1,2-dicarboxy)phenoxy]phenyl ⁇ -1,1,1,3,3,3-hexafluoropropane dianhydride, etc.
  • bis(trimellitic anhydride) esters include bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl (abbreviation: TAHMBP).
  • the total content of the fluorine-containing aromatic tetracarboxylic acid dianhydride and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the dianhydride components is preferably 15 mol% or more, more preferably 20 mol% or more, even more preferably 25 mol% or more, and may be 30 mol% or more, 35 mol% or more, 40 mol% or more, 45 mol% or more, or 50 mol% or more.
  • the total content of the fluorine-containing aromatic tetracarboxylic acid dianhydride and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the dianhydride components is preferably 99 mol% or less, more preferably 95 mol% or less, even more preferably 90 mol% or less, and may be 85 mol% or less, 80 mol% or less, 75 mol% or less, or 70 mol% or less.
  • the total content of the alicyclic tetracarboxylic dianhydride, the fluorine-containing aromatic tetracarboxylic dianhydride, and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the acid dianhydride components is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and may be 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more.
  • Polyimide resins may contain, as the acid dianhydride component, acid dianhydrides other than alicyclic tetracarboxylic dianhydrides, fluorine-containing aromatic tetracarboxylic dianhydrides, and bis(trimellitic anhydride) esters.
  • acid dianhydrides other than those mentioned above include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarbox
  • phenyl)ethane dianhydride bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis ⁇ 4-[4-(1,2-dicarboxy)phenoxy]phenyl ⁇ propane dianhydride, 2,2-bis ⁇ 4-[4-(3,4-dicarboxy)phenoxy]phenyl ⁇ propane dianhydride, 2,2-bis ⁇ 4-[3-(1,2-dicarboxy)phenoxy]phenyl ⁇ propane dianhydride, bis ⁇ 4-[4-[3-(1,2-dicarboxy)phenoxy]phenyl
  • the polyimide resin may be a polyamideimide in which a part of the tetracarboxylic dianhydride component is replaced with a dicarboxylic acid derivative.
  • the dicarboxylic acid include aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-oxybisbenzoic acid, 4,4'-biphenyldicarboxylic acid, and 2-fluoroterephthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxy
  • aromatic dicarboxylic acids and alicyclic dicarboxylic acids are preferred as dicarboxylic acids, with aromatic dicarboxylic acids being particularly preferred.
  • aromatic dicarboxylic acids terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, and 4,4'-oxybisbenzoic acid are preferred, with terephthalic acid and isophthalic acid being particularly preferred, with terephthalic acid being particularly preferred.
  • Dicarboxylic acid derivatives used as raw material monomers for polyamide-imide include dicarboxylic acid dichlorides, dicarboxylic acid esters, dicarboxylic acid anhydrides, and other dicarboxylic acid derivatives. Among these, dicarboxylic acid dichlorides are preferred due to their high reactivity.
  • the ratio of the dicarboxylic acid derivative to the total of the tetracarboxylic dianhydride and the dicarboxylic acid derivative is preferably 40 mol% or less, more preferably 35 mol% or less, and even more preferably 30 mol% or less.
  • the polyimide resin may be a polyimide in which the ratio of the dicarboxylic acid derivative is 0 (i.e., it does not contain a structure derived from the dicarboxylic acid derivative).
  • the diamine component of the polyimide resin used in the embodiment of the present invention is not particularly limited.
  • the diamine of the polyimide resin preferably has one or more selected from the group consisting of a fluorine group, a trifluoromethyl group, a sulfone group, a fluorene structure, and an alicyclic structure.
  • the polyimide resin contains a fluorine-containing diamine such as a fluoroalkyl-substituted benzidine as a diamine component.
  • fluoroalkyl-substituted benzidines which are fluorine-containing diamines, include 2-(trifluoromethyl)benzidine, 3-(trifluoromethyl)benzidine, 2,3-bis(trifluoromethyl)benzidine, 2,5-bis(trifluoromethyl)benzidine, 2,6-bis(trifluoromethyl)benzidine, 2,3,5-tris(trifluoromethyl)benzidine, 2,3,6-tris(trifluoromethyl)benzidine, 2,3,5,6-tetrakis(trifluoromethyl)benzidine, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,3'-bis( trifluoromethyl)benzidine, 2,2',3-bis(trifluoromethyl)benzidine, 2,3,3'-tris(trifluoromethyl)benzidine, 2,2',5-tris(trifluoromethyl)benzidine, 2,2',6-tris(trifluoro
  • fluoroalkyl-substituted benzidines having a fluoroalkyl group at the 2-position of the biphenyl are preferred, with 2,2'-bis(trifluoromethyl)benzidine (hereinafter referred to as "TFMB”) being particularly preferred.
  • TFMB 2,2'-bis(trifluoromethyl)benzidine
  • the content of fluoroalkyl-substituted benzidine relative to the total amount of diamine components (100 mol%) is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and may be 80 mol% or more, 85 mol% or more, or 90 mol% or more.
  • a high content of fluoroalkyl-substituted benzidine tends to suppress coloration of the film and increase mechanical strength such as pencil hardness and elastic modulus.
  • the polyimide resin may contain a diamine other than fluoroalkyl-substituted benzidine as a diamine component.
  • diamines other than fluoroalkyl-substituted benzidine include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl Sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 9,9-bis(
  • diaminodiphenyl sulfone as the diamine in addition to fluoroalkyl-substituted benzidine, the solubility in solvents and transparency of the polyimide resin may be improved.
  • diaminodiphenyl sulfones 3,3'-diaminodiphenyl sulfone (3,3'-DDS) and 4,4'-diaminodiphenyl sulfone (4,4'-DDS) are preferred. 3,3'-DDS and 4,4'-DDS may be used in combination.
  • the content of diaminodiphenyl sulfone relative to 100 mol% of the total amount of diamines may be 1 to 40 mol%, 3 to 30 mol%, or 5 to 25 mol%.
  • a polyamic acid is obtained as a polyimide precursor by the reaction of an acid dianhydride with a diamine, and a polyimide is obtained by dehydration and cyclization (imidization) of the polyamic acid.
  • the method for preparing the polyamic acid is not particularly limited, and any known method can be applied.
  • a polyamic acid solution is obtained by dissolving a diamine and a tetracarboxylic dianhydride in approximately equimolar amounts (molar ratio of 90:100 to 110:100) in an organic solvent and stirring the mixture.
  • dicarboxylic acid or its derivative (dicarboxylic dichloride, dicarboxylic anhydride, etc.) may be used as a monomer.
  • the amount of each monomer may be adjusted so that the total amount of tetracarboxylic dianhydride and dicarboxylic acid or its derivative is approximately equimolar to the diamine.
  • the polyimide resin As described above, by adjusting the composition of the polyimide resin, i.e., the type and ratio of the acid dianhydride and diamine, the polyimide resin has transparency and solubility in organic solvents, and is compatible with other resins.
  • the concentration of the polyamic acid solution is usually 5 to 35% by weight, and preferably 10 to 30% by weight. When the concentration is within this range, the polyamic acid obtained by polymerization has an appropriate molecular weight, and the polyamic acid solution has an appropriate viscosity.
  • the diamine When polymerizing polyamic acid, it is preferable to add the diamine to the dianhydride in order to suppress ring-opening of the dianhydride.
  • the diamines or multiple types of dianhydrides When adding multiple types of diamines or multiple types of dianhydrides, they may be added all at once or in multiple portions. By adjusting the order of addition of the monomers, it is also possible to control the physical properties of the polyimide resin.
  • organic solvent used in the polymerization of polyamic acid is not particularly limited as long as it does not react with diamines and acid dianhydrides and can dissolve polyamic acid.
  • organic solvents include urea-based solvents such as methylurea and N,N-dimethylethylurea, sulfoxide or sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone, amide-based solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), ⁇ -butyrolactone, and hexamethylphosphoric acid triamide, halogenated alkyl solvents such as chloroform and methylene chloride, aromatic hydrocarbon solvents such as benzene and toluene, and ether-based solvents such as
  • Polyimide resins are obtained by dehydration and cyclization of polyamic acid.
  • One method for preparing polyimide resins from polyamic acid solutions is to add a dehydrating agent, an imidization catalyst, etc. to the polyamic acid solution and allow imidization to proceed in the solution.
  • the polyamic acid solution may be heated to promote the imidization process.
  • the polyimide resin precipitates as a solid.
  • isolating the polyimide resin as a solid impurities generated during the synthesis of polyamic acid, residual dehydrating agents, imidization catalysts, etc.
  • a solvent suitable for film formation such as a low-boiling point solvent, can be used when preparing a solution for producing a film.
  • the molecular weight of the polyimide resin (weight average molecular weight in terms of polyethylene oxide measured by gel permeation chromatography (GPC)) is preferably 10,000 to 300,000, more preferably 20,000 to 250,000, and even more preferably 40,000 to 200,000. If the molecular weight is too small, the strength of the film may be insufficient. If the molecular weight is too large, the compatibility with other resins may be poor.
  • the polyimide resin is preferably soluble in a low-boiling point solvent such as a ketone solvent or an alkyl halide solvent.
  • a polyimide resin is soluble in a solvent, it means that it is soluble at a concentration of 5% by weight or more.
  • the polyimide resin is soluble in methylene chloride. Since methylene chloride has a low boiling point and residual solvent can be easily removed during film production, the use of a polyimide resin that is soluble in methylene chloride is expected to improve film productivity.
  • the polyimide resin has low reactivity.
  • the acid value of the polyimide resin is preferably 0.4 mmol/g or less, more preferably 0.3 mmol/g or less, and even more preferably 0.2 mmol/g or less.
  • the acid value of the polyimide may be 0.1 mmol/g or less, 0.05 mmol/g or less, or 0.03 mmol/g or less. From the viewpoint of reducing the acid value, it is preferable that the polyimide resin has a high imidization rate. A small acid value increases the stability of the polyimide resin and tends to improve its compatibility with other resins.
  • the first transparent resin film 1 contains a resin other than the polyimide resin ("other resin") in addition to the polyimide resin.
  • the other resin is not particularly limited as long as it is soluble in an organic solvent and can be mixed with the polyimide resin to form a transparent film, and examples of the other resin include those that are compatible with the polyimide resin and those that form a microphase separation structure such as a sea-island structure, a cylindrical structure, or a lamellar structure.
  • the other resin is preferably compatible with the polyimide resin.
  • the film tends to have high transparency and excellent mechanical properties such as elastic modulus and pencil hardness regardless of the processing conditions of the film.
  • the other resin is preferably a transparent resin having a lower refractive index than the polyimide resin.
  • the refractive index of the other resin is preferably 1.600 or less, more preferably 1.550 or less, even more preferably 1.520 or less, and particularly preferably 1.500 or less. Since the other resin has a lower refractive index than the polyimide resin, the blended resin film containing the polyimide resin and the other resin has a lower refractive index than a film of polyimide resin alone, and there is less reflection at the interface, so the total light transmittance tends to be higher.
  • resins include acrylic resins, polycarbonate resins, polyester resins, polyamide resins, polyether resins, cellulose resins, silicone resins, and cyclic olefin resins. Multiple types of these resins may be used. As other resins, acrylic resins, polycarbonate resins, and polyester resins having a fluorene structure are preferred because of their high compatibility with polyimide resins. Among these, acrylic resins are particularly preferred because they are highly compatible with polyimide resins, have a low refractive index, and are easy to form into a film with high hardness.
  • Acrylic resins include poly(meth)acrylic esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic ester copolymers, methyl methacrylate-acrylic ester-(meth)acrylic acid copolymers, and methyl (meth)acrylate-styrene copolymers.
  • Acrylic resins may be modified to introduce glutarimide structural units or lactone ring structural units.
  • the acrylic resin From the viewpoints of transparency, compatibility with polyimide resins, and mechanical strength, it is preferable for the acrylic resin to have methyl methacrylate as the main structural unit.
  • the amount of methyl methacrylate relative to the total amount of monomer components in the acrylic resin is preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more.
  • the acrylic resin may be a homopolymer of methyl methacrylate.
  • the acrylic resin may also be an acrylic polymer having a methyl methacrylate content in the above range, into which a glutarimide structure or a lactone ring structure has been introduced.
  • the glass transition temperature of the acrylic resin is preferably 100°C or higher, more preferably 110°C or higher, and may be 115°C or higher or 120°C or higher.
  • the weight average molecular weight (polystyrene equivalent) of the acrylic resin is preferably 5,000 to 500,000, more preferably 10,000 to 300,000, and even more preferably 15,000 to 200,000.
  • the acrylic resin has a small content of reactive functional groups such as ethylenically unsaturated groups and carboxyl groups.
  • the iodine value of the acrylic resin is preferably 10.16 g/100 g (0.4 mmol/g) or less, more preferably 7.62 g/100 g (0.3 mmol/g) or less, and even more preferably 5.08 g/100 g (0.2 mmol/g) or less.
  • the iodine value of the acrylic resin may be 2.54 g/100 g (0.1 mmol/g) or less or 1.27 g/100 g (0.05 mmol/g) or less.
  • the acid value of the acrylic resin is preferably 0.4 mmol/g or less, more preferably 0.3 mmol/g or less, and even more preferably 0.2 mmol/g or less.
  • the acid value of the acrylic resin may be 0.1 mmol/g or less, 0.05 mmol/g or less, or 0.03 mmol/g or less. A small acid value increases the stability of the acrylic resin and tends to improve compatibility with polyimide resins.
  • the first transparent resin film 1 is a blended resin film containing a polyimide resin and other resins as resin components.
  • the ratio of the polyimide resin to the other resins in the blended resin film is not particularly limited.
  • the mixing ratio (weight ratio) of the polyimide resin to the other resins may be 98:2 to 2:98, 95:5 to 10:90, 90:10 to 15:85, or 65:35 to 50:50.
  • the ratio of the other resin to the total of the polyimide resin and other resins is preferably 10 to 90% by weight, more preferably 15 to 85% by weight, even more preferably 20 to 80% by weight, and may be 30 to 70% by weight, 35 to 65% by weight, or 40 to 60% by weight.
  • the blended resin film may contain organic or inorganic low molecular weight compounds in addition to the above resin components.
  • the blended resin film may contain additives such as bluing agents, ultraviolet absorbers, flame retardants, stabilizers, crosslinking agents, surfactants, leveling agents, plasticizers, and fine particles.
  • the blended resin film may contain organic fine particles such as polystyrene and crosslinked acrylic resin, and inorganic fine particles such as silica and layered silicate, for the purpose of improving blocking resistance and adjusting the refractive index.
  • organic fine particles such as polystyrene and crosslinked acrylic resin
  • inorganic fine particles such as silica and layered silicate
  • the incorporation of fine particles may cause a decrease in the transmittance of the film and an increase in haze.
  • silicon oxides such as silica are useful for lowering the refractive index of the film, but they tend to be poorly dispersed in the resin matrix, which can cause a decrease in transparency, mechanical strength, and bending resistance. Therefore, the content of silicon oxide is preferably 5 parts by weight or less, more preferably 1 part by weight or less, and even more preferably 0.5 parts by weight or less, and may be 0.1 parts by weight or less, relative to 100 parts by weight of the total resin components.
  • the method for forming the blend resin film is not particularly limited, but a solution method in which a solution containing the above-mentioned polyimide resin and other resins is applied onto a support and the solvent is then dried and removed is preferred.
  • the solvent is not particularly limited as long as it is capable of dissolving both polyimide resins and other resins.
  • solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; and alkyl halide solvents such as chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, and methylene chloride.
  • the resin solution can be applied to the support by a known method using a bar coater, a comma coater, or the like.
  • the support can be a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, or the like. From the viewpoint of improving productivity, it is preferable to use an endless support such as a metal drum or a metal belt, or a long plastic film, or the like, as the support and manufacture the film by a roll-to-roll method.
  • a plastic film it is sufficient to appropriately select a material that is not dissolved in the solvent of the resin solution (dope).
  • Heat is preferably applied when drying the solvent.
  • the heating temperature is not particularly limited as long as it is a temperature at which the solvent can be removed and coloring of the resulting film can be suppressed, and is appropriately set between room temperature and about 250°C, with 50°C to 220°C being preferred.
  • the heating temperature may be increased in stages.
  • the resin film may be peeled off from the support after a certain degree of drying has progressed, and then dried. Drying may be performed in air or nitrogen. Heating may be performed under reduced pressure to promote solvent removal.
  • the blended resin film may be stretched in one or more directions to increase the birefringence or improve the mechanical strength of the film.
  • the polymer chains are oriented in the stretching direction, and the refractive index in the stretching direction increases, so the in-plane phase difference of the film increases.
  • Films made of acrylic resin alone may have low toughness, but the strength of the film may be improved by using a compatible system of polyimide resin and acrylic resin.
  • a compatible system of polyimide resin and acrylic resin when stretched, the polymer chains become oriented in the stretching direction, increasing the tensile modulus in the stretching direction, which tends to improve bending resistance.
  • the conditions for stretching the film are not particularly limited.
  • the stretching temperature is about ⁇ 40°C of the glass transition temperature of the film, and may be about 120 to 300°C, 150 to 250°C, or 180 to 230°C.
  • the stretching ratio is about 1 to 200%, and may be 5 to 150%, 10 to 120%, or 20 to 100%. The higher the stretching ratio, the higher the tensile modulus in the stretching direction tends to be. On the other hand, if the stretching ratio is too high, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, and the handling properties of the film may decrease.
  • the film may be biaxially stretched to increase the strength in any direction in the plane.
  • the biaxial stretching may be simultaneous or sequential.
  • the stretching ratio in one direction and the stretching ratio in the perpendicular direction may be the same or different.
  • the refractive index and mechanical strength in the direction with the larger stretching ratio tend to be relatively larger.
  • the thickness of the blend resin film is not particularly limited, and is, for example, 5 to 300 ⁇ m. From the viewpoint of obtaining a film that is both self-supporting and flexible and has high transparency, the thickness of the blend resin film is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 25 ⁇ m or more, particularly preferably 30 ⁇ m or more, and is preferably 100 ⁇ m or less, more preferably 80 ⁇ m or less, and even more preferably 60 ⁇ m or less. When the blend resin film is a stretched film, the thickness after stretching is preferably in the above range.
  • the blended resin film preferably has a single glass transition temperature in differential scanning calorimetry (DSC) and/or dynamic mechanical analysis (DMA).
  • DSC differential scanning calorimetry
  • DMA dynamic mechanical analysis
  • the haze of the blended resin film is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and may be 3.5% or less, 3% or less, 2% or less, 1% or less, or 0.5% or less.
  • a low haze can be achieved by using, as the other resin, an acrylic resin or other resin that is highly compatible with the polyimide-based resin.
  • the total light transmittance of the blended resin film is preferably 89.0% or more, more preferably 90.0% or more, even more preferably 90.5% or more, particularly preferably 91.0% or more, and may be 91.5% or more.
  • the higher the total light transmittance the higher the white brightness of the display and the better the visibility.
  • the refractive index tends to be lower and the total light transmittance tends to be higher compared to the case of using a polyimide-based resin alone.
  • the yellowness index (YI) of the blended resin film is preferably 3.0 or less, more preferably 2.0 or less, and even more preferably 1.0 or less.
  • the yellowness index (YI) of the blended resin film is preferably -3.0 or more, more preferably -2.0 or more, and even more preferably -1.0 or more.
  • the refractive index of the blended resin film is preferably 1.600 or less.
  • the refractive index of the film is the average value of the maximum refractive index (refractive index in the slow layer axis direction) and the minimum refractive index (refractive index in the fast axis direction) in the film plane.
  • the refractive index of the blended resin film is more preferably 1.580 or less, even more preferably 1.560 or less, particularly preferably 1.540 or less, and may be 1.520 or less.
  • the refractive index of a film that contains only polyimide resin as a resin component is generally higher than 1.600, and there is a lot of light reflection (high reflectance) due to the difference in refractive index at the air interface and at interfaces with other components, so the light transmittance is low.
  • a mixed resin system of polyimide resin and other resins has a lower refractive index than polyimide resin alone, so light reflection at the interface is reduced and the total light transmittance is high.
  • acrylic resin has a low refractive index, so when acrylic resin is used as the other resin, the film tends to have a lower refractive index and a higher total light transmittance.
  • Stretched films containing polyimide resins tend to have a large refractive index in the stretching direction (the orientation direction of the polymer chain), so when the blend resin film is a stretched film, it has anisotropy of the refractive index in the plane.
  • the blend resin film preferably has an in-plane birefringence ⁇ n, which is the difference between the refractive index in the maximum in-plane direction (slow axis direction) and the refractive index in the perpendicular direction (fast axis direction), of 0.005 or more.
  • the in-plane birefringence ⁇ n of the blend resin film is more preferably 0.007 or more, even more preferably 0.009 or more, and may be 0.010 or more, 0.020 or more, or 0.030 or more. If the stretching ratio is excessively increased to increase the birefringence, the transparency of the film may decrease. Therefore, the in-plane birefringence of the blend resin film is preferably 0.200 or less, and may be 0.100 or less, 0.070 or less, or 0.050 or less.
  • the in-plane phase difference of the blended resin film is preferably 500 nm or more, more preferably 1000 nm or more, and may be 1100 nm or more, 1200 nm or more, or 1300 nm or more.
  • the larger the in-plane phase difference of the blended resin film the larger the in-plane phase difference of the laminate in which the blended resin film and the high phase difference resin film are bonded together, and the more likely it is that color unevenness will be suppressed when the display is viewed through polarized sunglasses.
  • the tensile modulus of the blended resin film is preferably 3.0 GPa or more, more preferably 3.5 GPa or more, even more preferably 4.5 GPa or more, and may be 5.0 GPa or more, 5.5 GPa or more, or 6.0 GPa or more.
  • the blend resin film may have anisotropy in the tensile modulus in the plane.
  • the tensile modulus in the stretching direction tends to be greater than the tensile modulus in the direction perpendicular to the stretching direction.
  • the blend resin film is a biaxially stretched film or a film uniaxially stretched at its fixed ends, the tensile modulus in all directions in the plane may be greater than before stretching.
  • the blend resin film has anisotropy in the tensile modulus in the plane, it is preferable that the maximum tensile modulus in the plane (generally the tensile modulus in the stretching direction) is within the above range.
  • the second transparent resin film 2 is a high-retardation resin film having an in-plane retardation of 2000 nm or more. Since the second transparent resin film has a large in-plane retardation, color unevenness is suppressed when a display having the laminate of the present invention arranged on the viewing side surface is viewed through a polarizer such as polarized sunglasses.
  • the material constituting the high retardation resin film is not particularly limited as long as it is a material capable of realizing a high retardation of 2000 nm or more in-plane retardation, and examples of such materials include polyester-based resins, acrylic-based resins, polycarbonate-based resins, cycloolefin-based resins, polyamide-based resins, etc. Among these, polyester-based resins are preferred because they have high birefringence, can realize a high retardation, and have high mechanical strength.
  • Polyester-based resins include polyethylene terephthalate (PET) and polyethylene naphthalate (PEN). From the standpoint of versatility and cost, polyethylene terephthalate is preferred.
  • a method for obtaining a high retardation resin film with an in-plane retardation of 2000 nm or more is to stretch an unstretched resin film obtained by melt extrusion molding a resin material such as polyethylene terephthalate while heating it using a stretching machine such as a tenter. Sequential or simultaneous biaxial stretching may also be performed.
  • the stretching ratio is preferably 150% to 500% (2.5 times to 6.0 times). The higher the stretching ratio, the greater the birefringence, and a large in-plane retardation can be achieved with a small thickness.
  • the thickness of the high retardation resin film is preferably 80 ⁇ m or less, more preferably 70 ⁇ m or less, even more preferably 65 ⁇ m or less, and may be 60 ⁇ m or less, 55 ⁇ m or less, or 50 ⁇ m or less.
  • the thickness of the high retardation resin film is preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, even more preferably 25 ⁇ m or more, and may be 30 ⁇ m or more, or 35 ⁇ m or more.
  • the in-plane phase difference of the high retardation resin film is 2000 nm or more, more preferably 3000 nm or more, and even more preferably 4000 nm or more.
  • the thickness of the film is excessively increased in order to increase the phase difference, the flexibility will decrease.
  • the in-plane phase difference of the high retardation resin film is preferably 20,000 nm or less, more preferably 10,000 nm or less, even more preferably 8,000 nm or less, and may be 6,000 nm or less or 5,000 nm or less.
  • the in-plane birefringence ⁇ n of the high phase difference resin film is preferably 0.050 or more, more preferably 0.070 or more, and even more preferably 0.090 or more. If the stretching ratio is excessively increased in order to increase the birefringence, the transparency of the film may decrease. Therefore, the in-plane birefringence is preferably 0.200 or less, and may be 0.150 or less or 0.120 or less.
  • the maximum in-plane refractive index of the high retardation resin film i.e., the refractive index in the slow axis direction
  • the refractive index in the direction perpendicular to the maximum in-plane refractive index direction of the high retardation resin film i.e., the refractive index in the true axis direction
  • the refractive index in the direction perpendicular to the maximum in-plane refractive index direction of the high retardation resin film i.e., the refractive index in the true axis direction
  • the laminate of the present invention has a hard coat layer 3 on one surface of a first transparent resin film (blend resin film) 1 or a second transparent resin film (high retardation resin film) 2.
  • a laminate 11 of a first embodiment shown in Fig. 1 has a hard coat layer 3 on the surface of the first transparent resin film 1.
  • a laminate 12 of a second embodiment shown in Fig. 2 has a hard coat layer 3 on the surface of the second transparent resin film 2.
  • the material constituting the hard coat layer is not particularly limited as long as it has the function of preventing the occurrence of scratches, and examples thereof include polyester-based, acrylic-based, urethane-based, amide-based, siloxane-based, and epoxy-based resins.
  • an acrylic hard coat layer which is a cured product of an acrylic hard coat resin composition, or a siloxane hard coat layer which is a cured product of a siloxane hard coat resin composition is preferred from the viewpoint of preventing the occurrence of scratches.
  • the acrylic hard coat material contains a monomer or oligomer having a (meth)acryloyl group in the molecule as a curable resin component.
  • the molecular weight of the acrylic monomer or oligomer is, for example, about 200 to 10,000.
  • the acrylic hard coat material can control hardness, scratch resistance, bending resistance, optical properties, etc. by combining multiple types of monomers or oligomers having a (meth)acryloyl group. From the viewpoint of curing by photoradical polymerization, the hard coat material preferably has an acryloyl group.
  • oligomers having a (meth)acryloyl group include urethane (meth)acrylate, polyester (meth)acrylate, and epoxy (meth)acrylate.
  • the oligomer may have two or more (meth)acryloyl groups in one molecule.
  • the molecular weight of the oligomer is preferably 10,000 or less.
  • acrylic monomers include compounds with one (meth)acryloyl group, such as methyl (meth)acrylate and 2-ethylhexyl (meth)acrylate; compounds with two (meth)acryloyl groups in one molecule, such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,3-butylene glycol di(meth)acrylate, and 1,6-hexanediol di(meth)acrylate.
  • one (meth)acryloyl group such as methyl (meth)acrylate and 2-ethylhexyl (meth)acrylate
  • compounds with two (meth)acryloyl groups in one molecule such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, propylene glyco
  • Examples of compounds having three or more (meth)acryloyl groups in one molecule include glycerin tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.
  • the acrylic hard coat material contains a polyfunctional (meth)acrylate having three or more functional groups.
  • the functional group equivalent of the (meth)acryloyl group of the polyfunctional (meth)acrylate i.e., the molecular weight per (meth)acryloyl group, is preferably 80 to 150 g/eq.
  • dipentaerythritol hexa(meth)acrylate is particularly preferable.
  • the siloxane-based hard coat material contains a curable compound having a siloxane bond as a curable resin component.
  • the siloxane-based curable compound is preferably one having an epoxy group as a polymerizable functional group, and among them, a polyorganosiloxane compound containing an alicyclic epoxy group is preferable.
  • Such siloxane-based hard coat materials are disclosed in WO2014/204010, WO2018/096729, WO2020/040209, etc., and the descriptions therein can be referred to and incorporated by reference.
  • Siloxane-based hard coat materials that have alicyclic epoxy groups as polymerizable functional groups have little shrinkage when cured, so curling or cracking is unlikely to occur even if the hard coat layer is made thick.
  • the polyorganosiloxane compound having an alicyclic epoxy group can be obtained by condensation of a silane compound represented by the general formula (1). [Y-Si(OR 1 ) x R 2 3-x ] (1)
  • R1 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms.
  • the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an isopropyl group, an isobutyl group, a cyclohexyl group, and an ethylhexyl group.
  • the silane compound represented by the general formula (1) has two or three (-OR 1 ) in one molecule. Since Si-OR 1 is hydrolyzable, a polyorganosiloxane compound is obtained by condensation of the silane compound. From the viewpoint of hydrolysis, it is preferable that the carbon number of R 1 is 3 or less, and it is particularly preferable that R 1 is a methyl group.
  • R2 is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms.
  • hydrocarbon group examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an isopropyl group, an isobutyl group, a cyclohexyl group, an ethylhexyl group, a benzyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a phenethyl group.
  • Y is a monovalent organic group containing an alicyclic epoxy group.
  • examples of Y include an alicyclic epoxy group, an alkyl group having an alicyclic epoxy group as a substituent, and an alkylene glycol group having an alicyclic epoxy group as a substituent. From the viewpoint of heat resistance and bending resistance, an alkyl group having an alicyclic epoxy group as a substituent is preferred.
  • alkyl groups having an alicyclic epoxy group as a substituent include (3,4-epoxycyclohexyl)methyl group, 2-(3,4-epoxycyclohexyl)ethyl group, 3-(3,4-epoxycyclohexyl)propyl group, 4-(3,4-epoxycyclohexyl)butyl group, 5-(3,4-epoxycyclohexyl)pentyl group, 6-(3,4-epoxycyclohexyl)hexyl group, 7-(3,4-epoxycyclohexyl)heptyl group, 8-(3,4-epoxycyclohexyl)octyl group, 9-(3,4-epoxycyclohexyl)nonyl group, 10-(3,4-epoxycyclohexyl)decyl group, 11-(3,4-epoxycyclohexyl)undecyl group, and 12-(
  • silane compounds represented by general formula (1) include (3,4-epoxycyclohexyl)trimethoxysilane, (3,4-epoxycyclohexyl)methyldimethoxysilane, (3,4-epoxycyclohexyl)dimethylmethoxysilane, (3,4-epoxycyclohexyl)triethoxysilane, (3,4-epoxycyclohexyl)methyldiethoxysilane, (3,4-epoxycyclohexyl)dimethylethoxysilane, ⁇ (3,4-epoxycyclohexyl)methyl ⁇ trimethoxysilane, ⁇ (3,4-epoxycyclohexyl)methyl ⁇ methyldimethoxysilane, ⁇ (3,4-epoxycyclohexyl)methyl ⁇ dimethylmethoxysilane, ⁇ (3,4-epoxycyclohexyl)methyl ⁇ dimethylmethoxysilane
  • the polyorganosiloxane compound as a condensation product of a silane compound may be a condensation product of the silane compound of general formula (1) with another silane compound.
  • the Si- OR1 portion of the silane compound is hydrolyzed, and the hydrolyzate is condensed to form a Si-O-Si bond, thereby producing a condensate of the silane compound having an alicyclic epoxy group (a polyorganosiloxane compound).
  • the weight average molecular weight of the polyorganosiloxane compound is preferably 500 or more. Also, from the viewpoint of suppressing volatilization, the weight average molecular weight of the polyorganosiloxane compound is preferably 500 or more. On the other hand, if the molecular weight is excessively large, cloudiness may occur due to reduced compatibility with other components in the composition. Therefore, the weight average molecular weight of the polyorganosiloxane compound is preferably 20,000 or less.
  • the hard coat composition preferably contains a polymerization initiator in addition to the above-mentioned curable resin component.
  • a photopolymerization initiator is preferable.
  • An acrylic hard coat composition containing a compound having a (meth)acryloyl group as a curable resin component preferably contains a photoradical polymerization initiator that generates radicals by light.
  • a siloxane-based hard coat composition containing a polyorganosiloxane compound having an epoxy group as a curable resin component preferably contains a photoacid generator (photocationic polymerization initiator) that generates acid by light.
  • Photoradical polymerization initiators include 2,2-dimethoxy-2-phenylacetophenone, acetophenone, benzophenone, xanthone, 3-methylacetophenone, 4-chlorobenzophenone, 4,4'-dimethoxybenzophenone, benzoin propyl ether, benzil dimethyl ketal, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, 1-(4-isopropylphenyl)-2-hydroxy-2-methylpropan-1-one, and other thioxanthan compounds.
  • Photoacid generators include onium salts that combine anions (strong acids) such as antimony hexafluoride, boron tetrafluoride, phosphorus hexafluoride, fluoroalkyl phosphorus fluoride, and fluoroalkyl gallium fluoride with cations such as sulfonium, ammonium, phosphonium, iodonium, and selenium; iron-arene complexes; silanol-metal chelate complexes; sulfonic acid derivatives such as disulfones, disulfonyldiazomethanes, disulfonylmethanes, sulfonylbenzoylmethanes, imide sulfonates, and benzoin sulfonates; and organic halogen compounds.
  • strong acids such as antimony hexafluoride, boron tetrafluoride, phosphorus hexafluoride
  • the hard coat composition for forming the hard coat layer may contain a solvent and various additives in addition to the curable resin component and the polymerization initiator.
  • the additives include a fluorine-based or silicone-based leveling agent, a sensitizer, a reactive diluent, fine particles, a filler, a dispersant, a plasticizer, an ultraviolet absorber, a surfactant, an antioxidant, a colorant, a viscosity adjuster, and the like.
  • the hard coat composition is applied onto the transparent resin film, and the solvent is dried and removed as necessary, and then cured to form the hard coat layer 3.
  • Methods for applying the hard coat composition include roll coating such as bar coating, gravure coating, and comma coating, die coating such as slot die coating and fountain die coating, spin coating, spray coating, and dip coating.
  • the surface of the transparent resin film may be subjected to surface treatment such as corona treatment or plasma treatment.
  • an easy-adhesion layer or the like may be provided on the surface of the transparent resin film.
  • the curable resin composition contains a photopolymerization initiator and is cured by irradiation with active energy rays.
  • active energy rays irradiated during photocuring include visible light, ultraviolet light, infrared light, X-rays, ⁇ -rays, ⁇ -rays, ⁇ -rays, and electron beams. Since the curing reaction rate is high and the energy efficiency is excellent, ultraviolet light is preferred as the active energy ray.
  • the cumulative irradiation amount of the active energy ray is, for example, about 50 to 10,000 mJ/cm 2 , and may be set according to the type and amount of the photocationic polymerization initiator, the thickness of the hard coat layer, and the like.
  • the curing temperature is not particularly limited, but is usually 150°C or less.
  • the thickness of the hard coat layer 3 is 1 to 50 ⁇ m, preferably 3 ⁇ m or more, and more preferably 5 ⁇ m or more. The thicker the hard coat layer, the more the pencil hardness and scratch resistance tend to improve. On the other hand, if the hard coat layer is too thick, the flex resistance decreases, so the thickness of the hard coat layer is preferably 40 ⁇ m or less, more preferably 30 ⁇ m or less, and even more preferably 25 ⁇ m or less.
  • the first transparent resin film 1 and the second transparent resin film 2 are bonded together via an appropriate transparent adhesive layer 9.
  • the hard coat layer non-forming surface of the hard coat film 5 having the hard coat layer 3 formed on one surface of the first transparent resin film 1 is bonded to the second transparent resin film 2.
  • the hard coat layer non-forming surface of the hard coat film 6 having the hard coat layer 3 formed on one surface of the second transparent resin film 1 is bonded to the first transparent resin film 1.
  • the material constituting the transparent adhesive layer 9 is not particularly limited as long as it is transparent, and various adhesives and pressure-sensitive adhesives (pressure-sensitive adhesives) can be used.
  • adhesives include solvent-type adhesives, reactive adhesives that react and harden when exposed to heat or active energy rays, and hot-melt adhesives.
  • adhesive materials include (meth)acrylic resins, urethane resins, silicone resins, cross-linked rubbers, and thermoplastic elastomers. Among these, (meth)acrylic resins are preferred from the standpoint of transparency and weather resistance.
  • the transparent adhesive layer 9 is preferably an adhesive layer in which an adhesive or pressure sensitive adhesive is molded into a film shape in advance, since this allows the thickness between the transparent resin films 1 and 2 to be kept constant, and among these, a double-sided adhesive sheet is preferred, since it does not require a curing reaction and can be applied as is.
  • the double-sided adhesive sheet may be an adhesive sheet with a substrate in which an adhesive layer is provided on both sides of a transparent substrate film, or a substrateless adhesive sheet consisting only of an adhesive layer. From the viewpoint of transparency and thinness, a substrateless adhesive sheet is preferred.
  • An example of a substrateless adhesive sheet is an optically transparent adhesive tape called OCA (Optical Clear Adhesive).
  • the thickness of the transparent adhesive layer 9 is preferably 5 ⁇ m or more, more preferably 10 ⁇ m or more, more preferably 20 ⁇ m or more, and is preferably 500 ⁇ m or less, more preferably 100 ⁇ m or less, and more preferably 50 ⁇ m or less. If the thickness is too thin, the adhesiveness may be insufficient, and if the thickness is too thick, the bending resistance and flexibility of the laminate may be insufficient. From the viewpoint of providing stress relaxation performance when the laminate is folded, the storage modulus of the transparent adhesive layer at a temperature of 25° C. and a frequency of 1 Hz is preferably 1 ⁇ 10 4 Pa or less, more preferably 5 ⁇ 10 5 Pa or less.
  • a laminate of the first transparent resin film 1 and the second transparent resin film 2 is obtained by bonding the first transparent resin film 1 and the second transparent resin film 2 via a transparent adhesive layer 9.
  • the laminate 11 in Fig. 1 has a hard coat layer 3 on the outer surface of the first transparent resin film 1.
  • the laminate 12 in Fig. 2 has a hard coat layer 3 on the outer surface of the second transparent resin film 2.
  • the hard coat layer 3 may be formed on the transparent resin films 1 and 2 in advance, or the hard coat layer 3 may be formed on the surface of one of the films after the transparent resin films 1 and 2 are bonded together.
  • the laminate of the present invention has an in-plane retardation of 5000 nm or more.
  • the large in-plane retardation of the laminate tends to suppress color unevenness when the display is viewed through polarized sunglasses.
  • a polarizing plate is placed on the viewing surface of the liquid crystal cell, and in organic EL displays, a circular polarizing plate is placed to block external light reflected by metal electrodes, etc. Therefore, the light emitted from the display (image light) is linearly polarized. If a cover window with a phase difference is placed on the surface of a display that emits linearly polarized light, the polarization state of the linearly polarized light emitted from the display changes due to the phase difference of the cover window, and generally becomes elliptically polarized light.
  • the degree of change in the polarization state differs depending on the wavelength of light
  • a polarizer such as polarized sunglasses
  • the amount of light that passes through the polarizer differs depending on the wavelength. Therefore, the image light viewed by an observer wearing polarized sunglasses is colored, and is recognized as color unevenness.
  • phase difference of the cover window placed on the surface of the display is large, at 5,000 nm or more, a slight change in wavelength causes a large difference in the polarization state, so the amount of light passing through a polarizer such as polarized sunglasses (transmittance) changes frequently over a narrow wavelength range (short period) and is perceived as an average. For this reason, an observer wearing polarized sunglasses will find it difficult to recognize this as a color change, reducing color unevenness.
  • polarized sunglasses transmittance
  • the in-plane phase difference of the laminate is more preferably 5,500 nm or more, and may be 6,000 nm or more. From the viewpoint of suppressing color unevenness, there is no particular upper limit to the in-plane phase difference of the laminate, but in order to increase the phase difference of the laminate, it is necessary to increase the thickness of the transparent resin film, which reduces the flexibility of the laminate. From the viewpoint of imparting flexibility to the laminate, the in-plane phase difference of the laminate is preferably 20,000 nm or less, more preferably 10,000 nm or less, and may be 8,000 nm or less or 7,000 nm or less.
  • the in-plane phase difference of the hard coat layer is approximately 0, so the in-plane phase difference of the laminate is determined by the respective front phase differences and arrangement angles of the first transparent resin film 1 and the second transparent resin film 2.
  • the slow axis direction (maximum refractive index direction) of the first transparent resin film and the slow axis direction of the second transparent resin film are parallel, the sum of the in-plane phase difference Re1 of the first transparent resin film and the in-plane phase difference Re2 of the second transparent resin film (Re1 + Re2) becomes the phase difference of the laminate.
  • the angle ⁇ between the slow axis direction of the first transparent resin film and the slow axis direction of the second transparent resin film is small, and ⁇ is preferably 50° or less, more preferably 45° or less, even more preferably 30° or less, particularly preferably 20° or less, and may be 10° or less, 5° or less, 1° or less, or 0°.
  • Polyesters such as PET and PEN exhibit large birefringence when stretched at high magnification, but to achieve an in-plane phase difference of 5000 nm or more with a single film, a thickness of about 70 ⁇ m is required, and when used as a cover window material for a foldable display, flexibility is poor.
  • a laminate made by laminating multiple polyester films does not achieve the same effect of suppressing color unevenness as a single polyester film with an equivalent in-plane phase difference, even if the laminate has an in-plane phase difference of 5000 nm or more.
  • a high phase difference of 5000 nm or more is achieved by laminating a high phase difference resin film such as polyester with a blended resin film having a front phase difference.
  • This configuration provides flexibility and suppresses color unevenness without excessively increasing the thickness of each film.
  • the total thickness of the first transparent resin film and the second transparent resin film is preferably 150 ⁇ m or less, more preferably 120 ⁇ m or less, even more preferably 100 ⁇ m or less, and may be 90 ⁇ m or less.
  • the total thickness of the laminate is preferably 200 ⁇ m or less, more preferably 180 ⁇ m or less, even more preferably 160 ⁇ m or less, and may be 150 ⁇ m or less, or 140 ⁇ m or less.
  • the total thickness of the laminate is preferably 50 ⁇ m or more, more preferably 75 ⁇ m or more, even more preferably 100 ⁇ m or more, and may be 120 ⁇ m or more or 125 ⁇ m or more.
  • the yellowness index (YI) of the laminate is preferably -3.0 to 3.0, more preferably -2.0 to 2.0, and even more preferably -1.0 to 1.0.
  • a small absolute value of YI is preferable in terms of improving the visibility of the display and improving the color tone.
  • the haze of the laminate is preferably 1% or less, more preferably 0.7% or less, and even more preferably 0.5% or less.
  • the total light transmittance of the laminate is preferably 89.0% or more, more preferably 90.0% or more, and even more preferably 90.2% or more, and may be 90.5% or more, 90.8% or more, 91.0% or more, or 91.5% or more.
  • Polyimide-based transparent resin films have higher mechanical strength than transparent resin films such as polyethylene terephthalate, making them suitable as cover window materials for foldable displays.
  • displays that use polyimide-based transparent resin films as cover window materials suffer from color unevenness when the screen is viewed through polarized sunglasses.
  • a high phase difference of 5000 nm or more is achieved and color unevenness is suppressed by laminating a high phase difference resin film and a blended resin film with a front phase difference.
  • Both polyester-based resin films and polyimide-based resin films have a high refractive index and high reflectance at the interface between the film and air and at the interface between the film and the hard coat layer, resulting in a low total light transmittance.
  • Blending polyimide-based resin with other resins such as acrylic resin reduces the refractive index and reduces the reflectance at the interface, so by using a blended resin film as the transparent resin film placed on one side of the laminate, the total light transmittance of the laminate can be increased.
  • a laminate 11 having a hard coat layer 3 on a first transparent resin film (blend resin film) 1 tends to exhibit a high total light transmittance.
  • polyimide-based transparent resin films tend to have a large YI.
  • polyimide-based resin films By using a blend of polyimide-based resin and other resins such as acrylic resin as the first transparent resin film 1, it is possible to reduce coloration and decrease the YI.
  • the laminate of the present invention When the laminate of the present invention is used as a cover window for a display, it is arranged so that the hard coat layer 3 side is the viewing side surface.
  • a display having the laminate 11 of FIG. 1 has, from the viewing side, the hard coat layer 3, the first transparent resin film 1, the transparent adhesive layer 9, and the second transparent resin film 2, with an image display medium such as an organic EL panel or liquid crystal panel arranged underneath.
  • a display having the laminate 12 of FIG. 2 has, from the viewing side, the hard coat layer 3, the second transparent resin film 2, the transparent adhesive layer 9, and the first transparent resin film 1, with an image display medium arranged underneath.
  • the laminate of the present invention When the laminate of the present invention is used as a cover window for a foldable display, by arranging the direction of high mechanical strength of the laminate so that it is perpendicular to the bending axis, even if the film is repeatedly folded, it is difficult for the film to break or crack at the folding point, and a device with high bending resistance can be provided.
  • the first transparent resin film (blend resin film) and the second transparent resin film (high retardation resin film) constituting the laminate are stretched films, the mechanical strength tends to differ between the stretching direction (the direction with the larger stretch ratio in the case of biaxial stretching) and the perpendicular direction.
  • the blend resin film When the blend resin film is arranged so that the stretching direction (slow axis direction) is perpendicular to the bending axis, it tends to be difficult to break or crack.
  • the high retardation resin film is a polyester film, it tends to be difficult to break or crack when it is arranged so that the stretching direction (slow axis direction) is parallel to the bending axis.
  • a laminate in which the blend resin film and the high retardation resin film are arranged so that the slow axis directions of both are parallel tends to have high mechanical strength in the slow axis direction and in the direction perpendicular to it. Therefore, by arranging the bending axis of the display and the slow axis of the laminate so that they are parallel or perpendicular to each other, it is expected that the laminate will be less likely to break or crack when repeatedly bent.
  • the laminate By disposing the laminate on the display medium so that the hard coat layer is the visible surface, scratches and dents caused by pressure from a fingernail or touch pen during touch input, or from external impacts, can be suppressed. It is preferable that the laminate has a pencil hardness of F or more when observed 24 hours after scratching the surface of the hard coat layer with a pencil in accordance with JIS-K5600 (no dents, scratches, or cracks are observed 24 hours after scratching with a pencil of hardness F or more).
  • the pencil hardness of the laminate according to this evaluation standard is more preferably H or more, and may be 2H or more or 3H or more.
  • Polyimide-based resin films have superior mechanical strength compared to polyester-based resin films.
  • blended resin films of polyimide-based resins and other resins tend to exhibit higher pencil hardness compared to films of polyimide-based resins alone, and hard-coated films having a hard-coat layer formed on the surface also tend to exhibit high pencil hardness. Therefore, the laminate 11 having the hard-coat layer 3 on the first transparent resin film 1 has high pencil hardness.
  • the laminate of the present invention also has excellent bending resistance. It is preferable that the laminate is free of cracks and breaks when it is folded 180° with the hard coat layer 3 facing inward at a bending radius of 1.5 mm and then returned to its original flat state.
  • the laminate is preferably capable of being repeatedly bent at a radius of 1.5 mm or more with the hard coat layer 3 on the inside.
  • the absence of cracks in the hard coat layer or breakage of the film during repeated bending is preferable for application to foldable displays in which bending and stretching are repeated at the same location.
  • the laminate 11 having the hard coat layer 3 on the first transparent resin film 1 tends to have excellent bending resistance when repeatedly bent with the hard coat layer 3 on the inside.
  • the laminate preferably has bending recovery.
  • the bending recovery of the laminate is evaluated by folding a rectangular sample of 30 mm x 70 mm at a radius of 3 mm with the center of the long side of the sample as the bending axis, with the hard coat layer 3 facing inward, in an environment of 60°C and 90% relative humidity for 24 hours, removing the bending load, and then storing the sample in an environment of 23°C and 50% RH for 20 minutes, based on the bending angle (included angle).
  • the bending angle folding recovery angle
  • the larger this angle the higher the bending recovery, and the less likely it is that bending marks will remain in the bent portion of the foldable display.
  • the folding recovery angle of the laminate is preferably 95° or more, more preferably 100° or more, even more preferably 110° or more, and may be 115° or more or 120° or more.
  • a polyester film whose thickness is increased to achieve a front retardation of 5000 nm or more has low folding recovery (small folding recovery angle), whereas the laminate of the present invention, which aims to achieve a high retardation by laminating a high retardation resin film and a blended resin film, tends to have excellent folding recovery.
  • the flow direction during application is defined as the MD direction
  • the direction perpendicular to the MD direction is defined as the TD direction.
  • DMF Dimethylformamide
  • tetracarboxylic dianhydride were added thereto in the ratios (mol%) shown in Table 1, and the mixture was reacted by stirring under a nitrogen atmosphere for 5 to 10 hours to obtain a polyamic acid solution with a solid content of 18% by weight.
  • pyridine 5.5 g was added as an imidization catalyst to 100 g of polyamic acid solution, and after complete dispersion, 8 g of acetic anhydride was added and stirred at 90°C for 3 hours. After cooling to room temperature, 100 g of 2-propyl alcohol (IPA) was added at a rate of 2-3 drops/second while stirring the solution, causing polyimide to precipitate. Further, 150 g of IPA was added, and after stirring for about 30 minutes, suction filtration was performed using a Kiriyama funnel. The obtained solid was washed with IPA and then dried for 12 hours in a vacuum oven set at 120°C to obtain polyimide resins 1 and 2 (PI1, PI2).
  • IPA 2-propyl alcohol
  • This solution was applied onto an alkali-free glass plate and heated and dried in air at 60°C for 15 minutes, 90°C for 15 minutes, 120°C for 15 minutes, 150°C for 15 minutes, and 180°C for 15 minutes to obtain a blended resin film with a thickness of about 90 ⁇ m.
  • the obtained film was stretched uniaxially with fixed ends at a temperature of 205°C in the TD direction at a stretching ratio of 80% (TD length 1.80 times that of the film before stretching) using a stretching machine equipped with a heating oven to obtain a stretched film with a thickness of 50 ⁇ m.
  • PI2 polyimide resin 2
  • Tinuvin 477 manufactured by BASF
  • an anthraquinone-based bluing agent an anthraquinone-based bluing agent
  • This solution was applied onto an alkali-free glass plate, and heated and dried in air at 40°C for 60 minutes, 80°C for 30 minutes, 150°C for 30 minutes, 170°C for 30 minutes, and 200°C for 60 minutes to obtain a transparent polyimide film having a thickness of 50 ⁇ m.
  • PEN polyethylene naphthalate
  • ⁇ Tensile modulus> The film was cut into strips with a width of 10 mm, and left to stand at 23°C/55% RH for one day to condition the humidity, after which a tensile test was carried out under the following conditions using a tensile tester "AUTOGRAPH AGS-X" manufactured by Shimadzu Corporation, and the tensile modulus was calculated. The tensile test was carried out in both the MD and TD directions. Distance between grippers: 100 mm Tensile speed: 20.0 mm/min Measurement temperature: 23° C.
  • the refractive index nx in the direction in which the refractive index was maximum and the refractive index ny in the direction perpendicular thereto were measured using a prism coupler (Metricon "2010/M").
  • the refractive index at a wavelength of 589 nm obtained by Cauchy dispersion fitting of the measured values at wavelengths of 404 nm, 594 nm, and 827 nm was taken as the refractive index of the film.
  • the product ⁇ n ⁇ d of the in-plane birefringence ⁇ n of the film and the thickness d of the film measured using a contact thickness meter was taken as the in-plane retardation of the film.
  • ⁇ Siloxane-based hard coat composition In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 66.5 g (270 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane ("SILQUEST A-186" manufactured by Momentive Performance Materials) and 16.5 g of 1-methoxy-2-propanol (PGME) were charged and stirred uniformly. A solution of 0.039 g (0.405 mmol) of magnesium chloride as a catalyst dissolved in a mixture of 9.7 g (539 mmol) of water and 5.8 g of methanol was dropped into this mixture over 5 minutes and stirred until it became uniform.
  • SILQUEST A-186 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane
  • PGME 1-methoxy-2-propanol
  • the weight average molecular weight in terms of polystyrene measured using a Tosoh GPC apparatus "HLC-8220GPC" (columns: TSKgel GMH XL ⁇ 2, TSKgel G3000H XL , TSKgel G2000H XL ) was 3000.
  • the residual rate of epoxy groups calculated from the 1 H-NMR spectrum measured using a Bruker 400 MHz-NMR with deuterated acetone as a solvent was 95% or more.
  • Example 1 (Preparation of hard coat film) An acrylic hard coat composition was applied to one side of the film 1 with a coater so that the dry film thickness was 5 ⁇ m, and the solvent was removed at 120 ° C. Then, under a nitrogen atmosphere, ultraviolet rays were irradiated using a high pressure mercury lamp so that the accumulated light amount was 1950 mJ / cm 2 to harden the hard coat resin composition, and a hard coat film having an acrylic hard coat layer with a thickness of 5 ⁇ m was obtained. The thickness of the hard coat layer is the difference between the thickness of the hard coat film measured using a contact thickness meter and the thickness of the film before the hard coat layer is formed.
  • a 25 ⁇ m-thick transparent adhesive sheet (“8146-1" manufactured by 3M, storage modulus at 25° C. and 1 Hz: 1.2 ⁇ 10 5 Pa) was placed between the above hard coat film and film 4, and they were laminated and pressed with a rubber roller to produce a laminate of the hard coat film and film 4 in which a hard coat layer was formed on film 1.
  • the hard coat film was placed such that the side on which the hard coat layer was not formed was attached to film 4, and the angle between the maximum refractive index direction of film 1 and the maximum refractive index direction of film 4 was 0° (parallel).
  • Example 2 A siloxane-based hard coat composition was applied to one side of the film 1 by a coater so that the dry film thickness was 20 ⁇ m, and the solvent was removed at 120° C. Then, under an atmospheric atmosphere, ultraviolet rays were irradiated using a high-pressure mercury lamp so that the cumulative light amount was 1950 mJ/cm 2 to cure the hard coat resin composition, and a hard coat film having a siloxane-based hard coat layer with a thickness of 20 ⁇ m was obtained. This hard coat film was laminated with the film 4 in the same manner as in Example 1 to prepare a laminate.
  • Example 3 A laminate was produced in the same manner as in Example 3, except that Film 2 was used instead of Film 1 in the production of the hard coat film.
  • Example 4 A hard-coated film was obtained by forming an acrylic hard-coat layer having a thickness of 5 ⁇ m on one surface of the film 4 in the same manner as in Example 1. This hard-coated film and the film 1 were bonded together via a transparent adhesive sheet having a thickness of 25 ⁇ m to prepare a laminate of the hard-coated film having the hard-coat layer formed on the film 4 and the film 1.
  • Example 5 A siloxane-based hard coat layer having a thickness of 20 ⁇ m was formed on one surface of the film 4 in the same manner as in Example 2 to obtain a hard coat film. This hard coat film and the film 1 were bonded together via a transparent adhesive sheet having a thickness of 25 ⁇ m to produce a laminate of the hard coat film having the hard coat layer formed on the film 4 and the film 1.
  • Example 1 A laminate was prepared in the same manner as in Example 1, except that the film 1 and the film 4 were arranged so that the angle between the maximum refractive index direction of the film 1 and the maximum refractive index direction of the film 4 was 90° (orthogonal).
  • the yellowness index (YI) was measured according to JIS K7373 using a spectrophotometer SC-P manufactured by Suga Test Instruments Co., Ltd.
  • ⁇ Pencil hardness> According to JIS K5600, the pencil hardness test was carried out by scratching the hard coat surface of the laminate with a pencil at a load of 750 g. The pencil was scratched in the TD direction of the transparent resin film constituting the hard coat film. Five scratch tests (five locations) were carried out with pencils of each hardness, and visual observation was carried out 24 hours after the test. When no scratches, dents, or cracks were observed in four or more locations (when scratches, dents, or cracks were observed in one location or less), the result was marked as ⁇ , and when scratches, dents, or cracks were observed in two or more locations, the result was marked as ⁇ . The highest hardness that was marked as ⁇ was determined as the pencil hardness of the laminate.
  • ⁇ Repeated bending test> The laminate was cut into a rectangle of 20 mm x 150 mm with the long side in the TD direction to prepare an evaluation sample.
  • the evaluation sample was set in a U-shaped bending durability tester DMLHB manufactured by Yuasa System Equipment, and a bending test was performed 100,000 times with the MD direction as the bending axis at a bending radius of 1.5 mm, a bending angle of 180°, and a speed of 1 time/second so that the hard coat layer was on the inside.
  • the test was performed in a constant temperature and humidity environment set at a temperature of 23°C and a humidity of 55%. After the test, those that did not have cracks or breaks were marked as ⁇ , and those that had cracks or breaks were marked as ⁇ .
  • the laminate was cut into a rectangle with a short side of 30 mm x 70 mm and a long side in the TD direction to prepare an evaluation sample.
  • the sample was folded at a radius of 3 mm and 180° with the hard coat layer on the inside, with the MD direction at the center of the long side as the folding axis, and was kept in an environment of 60°C and 90% relative humidity for 24 hours. After that, the sample was placed on a horizontal table in an environment of 23°C and 55% relative humidity with the folding load removed, and the bending angle (narrow angle) of the sample on the folding axis was measured after 20 minutes.
  • a commercially available liquid crystal display monitor (Princeton's "PTFBKF-24W") was set to display white, a linear polarizing plate was placed on the screen, and the linear polarizing plate was rotated to adjust the arrangement angle so that the luminance was maximized.
  • the laminate was arranged so that the hard coat layer was on the linear polarizing plate side.
  • the transparent resin film constituting the hard coat film is referred to as "Film A”
  • the transparent resin film not forming a hard coat layer is referred to as "Film B”.
  • the difference between the front phase difference of Film A and the front phase difference of Film B was taken as the phase difference of the laminate, and in the other cases (where the slow axes of Films A and B are parallel), the sum of the front phase difference of Film A and the front phase difference of Film B was taken as the front phase difference of the laminate.
  • the laminates of Examples 1 to 5 in which a hard coat layer was provided on either the blended resin film or the high retardation resin film and these films were laminated together, had a front retardation of 5,000 nm or more and excellent color unevenness suppression effects. Furthermore, the laminates had high total light transmittance and excellent transparency.
  • Comparative Example 1 in which two films were laminated so that the slow axis directions were perpendicular to each other, the phase difference of the laminate was small, and the color unevenness suppression effect was inferior to that of the Examples.
  • the laminate of polyester-based film and polyimide-based film is capable of suppressing color unevenness due to its large front retardation.
  • the laminate of Comparative Example 6, in which a high retardation resin film (Film 4) is laminated with a general-purpose PET film (Film 5), and Comparative Example 7, in which a general-purpose PEN film (Film 6) is laminated with a high retardation resin film (Film 4) had poor color unevenness suppression effects, despite having a front retardation of 5,000 nm or more.
  • Comparing Examples 1 to 3 with Comparative Example 7 it can be seen that the blended resin film of polyimide resin and acrylic resin has a lower refractive index than polyester film, which contributes to improving the total light transmittance when a laminate is formed. Comparing Example 2 with Comparative Example 7, it can be seen that the composition comprising a hard coat layer on the blended resin film of polyimide resin and acrylic resin has high pencil hardness and excellent scratch resistance and dent resistance.
  • Comparing Example 2 with Comparative Example 4 it is found that the configuration in which a hard coat layer is provided on a polyimide resin and acrylic resin blend film exhibits a higher pencil hardness than the configuration in which a hard coat layer is provided on a film made of polyimide resin alone.
  • the laminate of the present invention has high transparency, excellent effect in suppressing color unevenness when the screen is viewed through polarized sunglasses, high surface hardness, and excellent bending properties, making it suitable for use as a cover window material for foldable displays.
  • First transparent resin film (blend resin film) 2. Second transparent resin film (high retardation resin film) 3 Hard coat layer 5, 6 Hard coat film 9 Transparent adhesive layer 11, 12 Laminate

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Abstract

Dans ce stratifié (11), un premier film de résine transparent (1) et un second film de résine transparent (2) sont collés ensemble avec une couche adhésive transparente (9) interposée entre ceux-ci, et une couche de revêtement dur (3) est disposée sur la surface externe de l'un du premier film de résine transparent et du second film de résine transparent. La différence de phase dans le plan du stratifié est supérieure ou égale à 5000 nm. Le premier film de résine transparent comprend une résine de polyimide et une résine soluble dans un solvant autre qu'une résine de polyimide. Le second film de résine transparent a une différence de phase dans le plan de 2000 nm ou plus.
PCT/JP2024/003925 2023-02-09 2024-02-06 Stratifié et affichage Ceased WO2024166911A1 (fr)

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KR101831598B1 (ko) * 2016-12-30 2018-02-23 코오롱인더스트리 주식회사 폴리이미드 수지 조성물 및 이의 필름
JP2018119144A (ja) * 2017-01-25 2018-08-02 住友化学株式会社 ポリイミド系フィルム及び積層体
CN109666251A (zh) * 2017-10-13 2019-04-23 南昌欧菲光科技有限公司 一种柔性聚合物共混膜及其制备方法和触摸屏
JP2020086429A (ja) * 2018-11-16 2020-06-04 住友化学株式会社 光学積層体及びそれを備えた画像表示装置
WO2022191329A1 (fr) * 2021-03-12 2022-09-15 株式会社カネカ Film de revêtement dur, son procédé de production et affichage
JP2022139546A (ja) * 2021-03-12 2022-09-26 株式会社カネカ ハードコーフィルムおよびその製造方法
WO2023026982A1 (fr) * 2021-08-24 2023-03-02 株式会社カネカ Composition de résine, article moulé et film

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