Patent Application
20240151878
The present invention relates to an optical film and a display device.
Self-luminous display devices that include self-luminous elements such as organic light-emitting elements are, unlike liquid crystal display devices and the like, easy to downsize and have good characteristics such as low power consumption, high luminance, and high response speed, and thus have potential as next-generation display devices. Electrodes and wiring made of metal are provided in a region on the display surface of a self-light-emitting display device. Thus, light incident on the display screen from the outside (i.e., external light) is reflected by the electrodes or the wirings, easily leading to lower display quality such as lower contrast.
In order to solve the above problem, for example, a configuration has been proposed in which a polarizing plate and a phase retardation plate are provided on the surface of a self-light-emitting display device. However, in the configuration using a polarizing plate and a phase retardation plate, when light emerging from the display device passes through the polarizing plate and the phase retardation plate to the outside, most of the light is lost, easily leading to a shorter life of elements.
Furthermore, display devices are required to have high color purity. Color purity indicates the range of colors that can be displayed by a display device, and is also referred to as a color reproduction range. Thus, high color purity means a large color reproduction range and high color reproducibility. Known methods of achieving higher color reproducibility include a technique in which a light source that emits white light is subjected to color separation using a color filter, and a technique in which a light source that emits monochromatic light in the three primary colors R, G, and B is subjected to correction to produce a narrow half-value using a color filter. In order to achieve higher color reproducibility of a display device using a color filter, a color filter having a larger thickness and a color material at a higher concentration are required, thus leading to lower display quality such as a poor pixel shape or poor viewing angle characteristics. For a display device including a light source that emits monochromatic light in the three primary colors R, G, and B, a process of forming a color filter is required, thus leading to higher cost.
As a display device having a configuration different from the configuration using a polarizing plate and a phase retardation plate or the configuration using a color filter described above, for example, Patent Literature 1 discloses an organic light-emitting display device that includes a display substrate including an organic light-emitting element, and a sealing substrate provided apart from the display substrate and in which a space between the display substrate and the sealing substrate is filled with a filler that selectively absorbs external light for each wavelength range to adjust the transmittance. In this configuration, reflection of external light is reduced to provide better visibility, and of light emerging from the display device, in particular, light in a wavelength range that leads to lower color purity is selectively absorbed to achieve higher color purity. However, the disclosed technique is insufficient to reduce reflection of external light, and causes coloration of the reflected light. Furthermore, a color material that absorbs light having a specific wavelength may have insufficient reliability in terms of light resistance or the like, and is thus difficult to put into practical use.
[PTL 1] JP 5673713 B.
The conventional technique as described above has the following problems.
In a device using a polarizing plate and a phase retardation plate, the amount of reflected light arising from external light can be reduced, but the amount of display light generated by organic light-emitting elements is also reduced.
Furthermore, Patent Literature 1 proposes, as the filler having wavelength selective absorption properties disclosed in Patent Literature 1, a configuration containing a colorant having an absorption maximum wavelength in the wavelength region of 480 nm to 510 nm and a colorant having an absorption maximum wavelength in the wavelength region of 580 nm to 610 nm. Thus, it is difficult to remove the influence of external light in the wavelength range of less than 480 nm and the wavelength range of more than 610 nm. Failure to reduce external light in such wavelength ranges leads to an insufficient reflectance reduction effect and deterioration in reflection hue.
Furthermore, a colorant having wavelength selective absorption properties as described above has insufficient reliability in terms of light resistance or the like, and is thus difficult to put into practical use unless the reliability of the colorant is improved.
In view of the above circumstances, an object of the present invention is to provide an optical film achieving higher display quality and a longer life of light-emitting elements, and a display device including the optical film.
A first aspect of the present invention is an optical film including a transparent substrate, one or more colored layers that contain a colorant and are provided on the transparent substrate, and one or more functional layers that are provided on a side opposite to the transparent substrate with the one or more colored layers interposed therebetween.
The one or more colored layers contain a first color material in which a maximum absorption wavelength is in a range of 470 nm or more and 530 nm or less and a half-width of an absorption spectrum thereof is 15 nm or more and 45 nm or less, and a second color material in which a maximum absorption wavelength is in a range of 560 nm or more and 620 nm or less and a half-width of an absorption spectrum thereof is 15 nm or more and 55 nm or less.
At least the one or more functional layers or the one or more colored layers contain a black organic pigment.
The one or more functional layers as a whole have an ultraviolet shielding rate of 85% or more.
A surface of the optical film on the side closer to the one or more functional layers has a pencil hardness of H or more at a load of 500 g.
Each of values a* and b* of a hue of the optical film that are defined by the following formulas (1) to (9) is in a range of −5 or more and +5 or less.
In this case, λ is a variable representing a wavelength, and t is a variable representing a ratio of X, Y, and Z to Xn, Yn, and Z.
The values a* and b* calculated from the formulas (1) to (3) are calculated according to a calculation method for a CIE 1976 L*a*b* color space, which is a CIELAB color space. In the formulas (1) and (2), Xn, Yn, and Z n are tristimulus values at a white point of illuminant D65.
In the formula (4), RE (λ) is a function representing a reflectance [%] of a perfect reflecting diffuser, which is 100% at each wavelength, R2 (λ) is a function representing a surface reflectance [%] of an outermost surface of the one or more functional layers, and T(λ) is a function representing a transmittance [%] of the optical film.
In formulas (6) to (9), PD65(λ) is an illuminant D65 spectrum, and
The definite integrals in formulas (6) to (9) are obtained by appropriate numerical integration. The numerical integration is performed at a wavelength interval of, for example, 1 nm.
In the formula (5), R (λ) represents the reflectance of the optical film for incident light from the side most distant from the transparent substrate, considering internal reflection in the transparent substrate of the optical film.
X, Y, and Z represented by the formulas (6) to (8) are tristimulus values at a white point of illuminant D65.
A second aspect of the present invention is a display device including a light source, and the optical film according to the first aspect.
The present invention provides an optical film and a display device achieving higher display quality by external light reflection and a longer life of light-emitting elements of the display device.
Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings to be referred, components identical with or similar to each other are given the same or similar reference signs. It should be noted that the drawings are only schematically illustrated, and thus the relationship between thickness and two-dimensional size of the components, and any thickness ratios, are not to scale. Therefore, specific thicknesses and dimensions should be understood in view of the following description. As a matter of course, dimensional relationships or ratios may be different between the drawings.
Further, the embodiments described below are merely examples of configurations for embodying the technical idea of the present invention. The technical idea of the present invention does not limit the materials, shapes, structures, arrangements, and the like of the components to those described below. The technical idea of the present invention can be modified variously within the technical scope defined by the claims. In addition, the drawings are exaggerated as appropriate to facilitate understanding.
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
An optical film and a display device according to a first embodiment of the present invention will be described.
A display device 50A of the present embodiment whose cross section in the thickness direction is shown in
The display unit 20 includes a substrate 21, light-emitting elements 22, and a color filter unit 23.
The substrate 21 is composed of, for example, a silicon substrate.
The light-emitting elements 22 emit white light. The light-emitting elements 22 may be, for example, organic EL (electroluminescent) devices. In an organic EL device, a direct-current voltage is applied between an anode and a cathode to cause an electron and a positive hole to be injected into an organic light-emitting layer and recombined to form an exciton, and light generated when the exciton is deactivated is used to emit light. Light from the light-emitting elements 22 is emitted in a light emission direction from the lower side toward the upper side of
The light-emitting elements 22 are produced on the substrate 21, for example, using a semiconductor manufacturing process.
An electrode of each of the light-emitting elements 22 is connected to a driving circuit (not shown) through a metal wiring provided on the substrate 21. The driving circuit controls the ON and OFF states of the light-emitting elements 22 based on an image signal.
The light-emitting elements 22 include, for example, a first light-emitting element 22R that is turned on in response to a red component image signal, a second light-emitting element 22G that is turned on in response to a green component image signal, and a third light-emitting element 22B that is turned on in response to a blue component image signal. The first light-emitting element 22R, the second light-emitting element 22G, and the third light-emitting element 22B are provided in each pixel that performs color display.
The color filter unit 23 is provided in the light emission direction with respect to the light-emitting elements 22.
The color filter unit 23 includes red filters that allow red light to pass through, green filters that allow green light to pass through, and blue filters that allow blue light to pass through. The red filters are provided to face the first light-emitting elements 22R, the green filters are provided to face the second light-emitting elements 22G, and the blue filters are provided to face the third light-emitting elements 22B.
The color filter unit 23 may include a lens that collects light passing through each of the red filters, the green filters, and the blue filters.
The optical film 10A of the present embodiment is provided on the color filter unit 23 of the display unit 20. The optical film 10A provides higher color purity in a display region of the display unit 20 to achieve higher display quality in the presence of external light reflection.
The optical film 10A includes a transparent substrate 11, a colored layer 12, an ultraviolet absorption layer 13 (functional layer), and a low refractive index layer 14A (functional layer) in this order in the light emission direction of the display unit 20.
The transparent substrate 11 is a plate or a sheet that has a first surface 11a and a second surface 11b in the thickness direction. The second surface 11b of the transparent substrate 11 is located closer to the color filter unit 23 of the display unit 20 with the colored layer 12 interposed therebetween. The transmittance of visible light in the material of the transparent base material 11 is preferably as close to 100% as possible. Visible light is light in the visible light wavelength range of 380 nm or more and 780 nm or less.
The material of the transparent substrate 11 may include transparent resins for example polyolefins such as polyethylenes or polypropylenes, polyesters such as polybutylene terephthalate or polyethylene naphthalate, polyacrylates such as polymethyl methacrylate, polyamides such as nylon 6 or nylon 66, polyimides, polyarylates, polycarbonates, triacetyl cellulose, polyvinyl alcohols, polyvinyl chloride, cycloolefin copolymers, norbornene-containing resins, polyether sulfones, or polysulphones, or inorganic glass. Of these, a film made of polyethylene terephthalate (PET), a film made of triacetyl cellulose (TAC), a film made of polymethyl methacrylate (PMMA), and a film made of polyester are preferable. The thickness of the transparent substrate 11 is not particularly limited, but is preferably 10 μm to 100 μm.
The colored layer 12 is a layer portion containing a colorant and is provided on the first surface 11a of the transparent substrate 11 to overlap with the transparent substrate 11. Thus, the colored layer 12 is located between the ultraviolet absorption layer 13 and the transparent substrate 11.
The colored layer 12 contains, as a colorant, a first coloring material and a second color material.
In the first color material, the maximum absorption wavelength is in the range of 470 nm or more and 530 nm or less, and the half-width (full width at half maximum) of the absorption spectrum thereof is 15 nm or more and 45 nm or less. The maximum absorption wavelength indicates a wavelength at which the highest maximum absorbance is obtained in an absorbance spectrum (absorption spectrum). In a transmittance spectrum, this wavelength indicates a wavelength at which the lowest minimum transmittance is obtained. The same applies to the following description.
In the second color material, the maximum absorption wavelength is in the range of 560 nm or more and 620 nm or less, and the half-width of the absorption spectrum thereof is 15 nm or more and 55 nm or less.
The colored layer 12 may contain, for color adjustment, a third color material that is different from the first color material and the second color material. For example, in the third color material, a wavelength in the wavelength range of 400 nm or more and 780 nm or less at which the transmittance is lowest is in the range of 650 nm or more and 780 nm or less. In the third color material, the half-width of the absorption spectrum thereof is, for example, 10 nm or more and 300 nm or less, but is not particularly limited.
In the following description, the first color material and the second color material may be collectively referred to simply as a “color material”.
The color materials contained in the colored layer 12 may contain one or more compounds selected from the group consisting of compounds having a porphyrin structure, compounds having a merocyanine structure, compounds having a phthalocyanine structure, compounds having an azo structure, compounds having a cyanine structure, compounds having a squarylium structure, compounds having a coumarin structure, compounds having a polyene structure, compounds having a quinone structure, compounds having a tetradiporphyrin structure, compounds having a pyrromethene structure, compounds having an indigo structure, and metal complexes thereof. The color materials particularly preferably contain, for example, a compound having a porphyrin structure, a pyrromethene structure, a phthalocyanine structure, or a squarylium structure in molecules thereof.
In the optical film 10A of the present invention, each of values a* and b* of a hue of the optical film represented by the formulas (1) to (9) is in the range of −5 or more and +5 or less, where a reflectance R (λ) is the reflectance of the optical film 10A measured from the side closer to a surface 10a which is the outermost surface of the functional layers, the ultraviolet absorption layer 13 and the low refractive index layer 14A, on the side closer to the first surface 11a of the transparent substrate 11 when the optical film 10A is irradiated with illuminant D65 light from the side closer to the surface 10a, and the light is perfectly diffusely reflected on the side closer to a lowermost surface 10b of the optical film. A hue is represented by a three-dimensional orthogonal coordinate system with axes representing three values: the value represented by the formula (1), the value represented by the formula (2), and a lightness index L* represented by the following formula (10). The three-dimensional orthogonal coordinate system is a uniform color space defined by the International Commission on Illumination (CIE) (also referred to as CIE 1976 L*a*b* color space or CIELAB color space).
In this case, Y is a tristimulus value for reflected light with the reflectance R (λ) for illuminant D65, and is calculated from the formulas (4), (5), (7) and (9), and Yn is a tristimulus value at the white point of illuminant D65.
The method of calculating the values a* and b* as characteristics of an external light reflection hue of the optical film of the present invention will be described in detail with reference to
When the optical film 10A is irradiated with illuminant D65 light from the surface 10a which is the outermost surface of the functional layers of the optical film 10A in the thickness direction, light emerging from the optical film 10A can be divided into a surface reflection component and an internal reflection component. The surface reflection component is defined by R2 (λ) [%], which is the surface reflectance of the surface 10a. The internal reflection component is defined by R1 (λ) [%] calculated from the formula (4) using a reflectance RE (λ) [%] of a perfectly diffuse reflector, which is 100% irrespective of the wavelength, a transmittance T (λ) of the optical film 10A, and the surface reflectance R2 (λ) [%] of the surface 10a.
R (λ) [%] is calculated from formula (5), where R (λ) is the reflectance of the optical film 10A on the side closer to the surface 10a irradiated with illuminant D65 light.
R (λ) is a function of wavelength k as with R1 (λ) and R2 (λ), and thus tristimulus values X, Y, and Z are determined by calculating a definite integral fork in the formulas (6) to (9). The definite integral may be obtained by appropriate numerical integration. For example, numerical integration may be performed at a wavelength interval such as an equal interval of, for example, 1 nm.
As described above, X, Y, and Z in formulas (1) and (2) are tristimulus values for reflected light with the reflectance R (λ) to illuminant D65 of the optical film 10A on the side closer to the surface 10a, and Xn, Yn, and Zn represent the tristimulus values at the white point of illuminant D65. These values can be used to calculate the values a* and b* as the indicators of the external light reflection hue of the optical film 10A. Each of the values a* and b* of the external light reflection hue of the optical film 10A is preferably in the range of −5 or more and +5 or less from the viewpoint of achieving higher display quality by external light reflection. The internal reflectance for light reflected by the inner surface such as a display unit or an electrode wiring portion of a self-light-emitting display device such as an organic light-emitting display device typically has different values at different wavelengths in the wavelength range of 380 nm to 780 nm. However, as a result of intensive study, the inventors of the present invention have found that when each of the values a* and b* of the external light reflection hue of the optical film 10A is in the range of −5 or more and +5 or less, and R E PO as the reflectance of a perfectly diffuse reflector, which is 100% at all wavelengths, is substituted with the internal reflectance of the display unit 20 of an actual self-luminous display device, the values a* and b* as the indicators of the external light reflection hue are in the range of −5 or more and +5 or less, achieving high display quality.
The colored layer 12 having such a configuration has, as a whole, a maximum absorption wavelength, that is, a minimum transmittance, in the range of 470 nm or more and 530 nm or less and in the range of 560 nm or more and 620 nm or less, thus achieving a spectral absorption spectrum having a minimum absorption wavelength, that is, a maximum transmittance, in the range of 620 nm or more and 780 nm or less. This allows most of red light, green light, and blue light emerging from the display unit 20 to pass through the colored layer 12.
On the other hand, the colored layer 12 reduces the amount of transmitted light for part of each of a wavelength component between the maximum wavelength of red light and the maximum wavelength of green light, a wavelength component between the maximum wavelength of green light and the maximum wavelength of blue light, ultraviolet light, and infrared light. Thus, for example, of reflected light arising from external light reflected by wiring or the like of the display unit 20, wavelength components that reduce the color purity of the display light are absorbed by the colored layer 12.
The colored layer 12 may contain, as an additive, at least one of a radical scavenger, a peroxide decomposer, and a singlet oxygen quencher. When the colored layer 12 contains such an additive, as described below, it is possible to prevent the color materials contained in the colored layer 12 from fading due to light, heat, or the like, thus achieving higher durability.
A radical scavenger serves to prevent autooxidation by capturing radicals when oxidative degradation of a colorant occurs, and prevents deterioration (fading) of the colorant. When the colored layer 12 contains, as a radical scavenger, a hindered amine light stabilizer (HALS) having a molecular weight of 2000 or more, the colored layer 12 has a high fading prevention effect.
If the colored layer 12 contains a radical scavenger having a low molecular weight, which is easily evaporated, only a small number of molecules remain in the colored layer, making it difficult for the colored layer 12 to have a sufficient fading prevention effect. Materials suitable as the radical scavenger include, for example, Chimassorb (registered trademark) 2020 FDL, Chimassorb (registered trademark) 944 FDL, or Tinuvin (registered trademark) 622 manufactured by BASF, or LA-63P manufactured by Adeka Corporation.
A singlet oxygen quencher serves to inactivate highly reactive singlet oxygen that easily causes oxidative degradation (fading) of a colorant, to prevent oxidative degradation (fading) of the colorant. Examples of a singlet oxygen quencher include transition metal complexes, colorants, amines, phenols, and sulfides. A material particularly suitable as a singlet oxygen quencher is a transition metal complex of dialkyl phosphate, dialkyl dithiocarbanate, or benzenedithiol, and a material suitable as central metal is nickel, copper, or cobalt. The singlet oxygen quencher may be, for example, NKX1199, NKX113, or NKX114 manufactured by Hayashibara Biochemical Laboratories, Inc., Research Institute for Photosensitizing Dyes, or D1781, B1350, B4360, or T3204 manufactured by Tokyo Chemical Industry Co., Ltd.
A peroxide decomposer serves to decompose peroxide generated when oxidative degradation of a colorant occurs, and stop the autooxidation cycle to prevent deterioration (fading) of the colorant. A material used as a peroxide decomposer may be a phosphorus-based antioxidant or a sulfur-based antioxidant.
Examples of a phosphorus-based antioxidant include 2,2′-methylenebis(4,6-di-t-butyl-1-phenyloxy)(2-ethylhexyloxy)phosphorus, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and 6-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-t-butyldibenz[d,f][1,3,2] dioxaphosphepine.
Examples of a sulfur-based antioxidant include 2,2-bis({[3-(dodecylthio)propionyl]oxy}methyl)-1,3-propanediyl-bis[3-(dodecylthio)propionate], 2-mercaptobenzimidazole, dilauryl-3,3′-thiodipropionate, dimyristyl-3,3′-thiodipropionate, distearyl-3,3′-thiodipropionate, pentaerythrityl-tetrakis(3-laurylthiopropionate), and 2-mercaptobenzothiazole.
The ultraviolet absorption layer 13 is a layer portion having an ultraviolet shielding rate of 85% or more. The ultraviolet shielding rate is measured and calculated in accordance with JIS L 1925, and is represented by a value [%] obtained by subtracting, from 100%, the average transmittance (unit: [%]) in the wavelength range of 290 nm to 400 nm.
The absorption wavelength range in the ultraviolet region of the ultraviolet absorption layer 13 is more preferably the range of 290 nm or more and 370 nm or less. The absorption wavelength range is defined as a wavelength region in which the ultraviolet absorption rate is 90% or more.
The ultraviolet absorption layer 13 is provided on the side opposite to the transparent substrate 11 with the colored layer 12 interposed therebetween.
In the example shown in
The color materials contained in the colored layer 12 have a good color correction function, but have insufficient resistance to light, particularly ultraviolet light, and when irradiated with ultraviolet light, deteriorate with time and can no longer absorb light having a wavelength near the maximum absorption wavelength.
In the present embodiment, the optical film 10A includes the ultraviolet absorption layer 13 provided so that external light enters the ultraviolet absorption layer 13 before entering the colored layer 12, thus reducing the amount of ultraviolet light contained in external light that enters the colored layer 12. This allows the colored layer 12 to have higher resistance to ultraviolet light.
The ultraviolet absorption layer 13 is formed by applying and drying a composition containing an energy ray-curable resin, a photopolymerization initiator, an ultraviolet absorber, and a solvent, followed by irradiation with energy rays such as ultraviolet light to cure the composition.
The energy ray-curable resin contained in the ultraviolet absorption layer 13 is a resin that is polymerized and cured by irradiation with an active energy ray such as ultraviolet light or an electron beam, and may be, for example, monofunctional, bifunctional, or tri- or more functional (meth)acrylate monomer. Herein, “(meth)acrylate” collectively refers to both acrylate and methacrylate, and “(meth)acryloyl” collectively refers to both acryloyl and methacryloyl.
Examples of a monofunctional (meth)acrylate compound include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, glycidyl (meth)acrylate, acryloylmorpholine, N-vinylpyrrolidone, tetrahydrofurfuryl acrylate, cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isobornyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate, benzyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 3-methoxybutyl (meth)acrylate, ethyl carbitol (meth)acrylate, phosphoric acid (meth)acrylate, ethylene oxide-modified phosphoric acid (meth)acrylate, phenoxy (meth)acrylate, ethylene oxide-modified phenoxy (meth)acrylate, propylene oxide-modified phenoxy (meth)acrylate, nonylphenol (meth)acrylate, ethylene oxide-modified nonylphenol (meth)acrylate, propylene oxide-modified nonylphenol (meth)acrylate, methoxy diethylene glycol (meth)acrylate, methoxy polyethylene glycol (meth)acrylate, methoxy propylene glycol (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, 2-hydroxy-3-phenoxy propyl (meth)acrylate, 2-(meth)acryloyloxyethyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hydrogen phthalate, 2-(meth)acryloyloxypropyl hexahydro hydrogen phthalate, 2-(meth)acryloyloxypropyl tetrahydro hydrogen phthalate, dimethylaminoethyl (meth)acrylate, trifluoroethyl (meth)acrylate, tetrafluoropropyl (meth)acrylate, hexafluoropropyl (meth)acrylate, octafluoropropyl (meth)acrylate, and adamantane derivative mono(meth)acrylates such as adamantyl acrylate having a monovalent mono(meth)acrylate derived from 2-adamantane or adamantane diol.
Examples of a bifunctional (meth)acrylate compound include di(meth)acrylates such as ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, nonanediol di(meth)acrylate, ethoxylated hexanediol di(meth)acrylate, propoxylated hexanediol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, ethoxylated neopentyl glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, and hydroxypivalic acid neopentyl glycol di(meth)acrylate.
Examples of a tri- or higher functional (meth)acrylate compound include trifunctional (meth)acrylate compounds such as tri(meth)acrylates such as trimethylolpropane tri(meth)acrylate, ethoxylated trimethylolpropane tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, tris 2-hydroxyethyl isocyanurate tri(meth)acrylate, and glycerin tri(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, and ditrimethylolpropane tri(meth)acrylate, tri- or higher functional (polyfunctional) (meth)acrylate compounds such as pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, ditrimethylolpropane penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, and ditrimethylolpropane hexa(meth)acrylate, and polyfunctional (meth)acrylate compounds obtained by substituting part of any of these (meth)acrylates with an alkyl group or ε-caprolactone.
As an active energy ray-curable resin, urethane (meth)acrylate may be used. Urethane (meth)acrylate may be obtained, for example, by reacting a (meth)acrylate monomer having a hydroxyl group with a product obtained by reacting an isocyanate monomer or a prepolymer with a polyester polyol.
Examples of urethane (meth)acrylate include pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate toluene diisocyanate urethane prepolymer, dipentaerythritol pentaacrylate toluene diisocyanate urethane prepolymer, pentaerythritol triacrylate isophorone diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate isophorone diisocyanate urethane prepolymer.
The above resins may be used singly or in combination of two or more. The above resins may be a monomer or a partially polymerized oligomer in a composition for forming a hard coat layer.
The ultraviolet absorber contained in the ultraviolet absorption layer 13 may be, for example, a benzophenone-based compound, a benzotriazole-based compound, a triazine-based compound, an oxanilide-based compound, or a cyanoacrylate-based compound. The ultraviolet absorption layer 13 preferably contains one or more of these compounds so that the absorption wavelength range in the ultraviolet region of the ultraviolet absorber is the range of 290 nm to 370 nm.
The ultraviolet absorption layer 13 preferably contains one or more photopolymerization initiators having an absorption wavelength range in the ultraviolet region different from the absorption wavelength range in the ultraviolet region of the ultraviolet absorber. In such a case, an energy ray-curable compound can be cured by irradiation with light in the ultraviolet region that is not absorbed by the ultraviolet absorber, thus leading to efficient formation of a cured film. When the absorption wavelength range of the ultraviolet absorber is the range of 290 nm to 370 nm, an acylphosphine oxide-based photopolymerization initiator having an absorption wavelength range different from the absorption wavelength range of the ultraviolet absorber can be suitably used, and the photopolymerization initiator may be, for example, diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, or the like. The use of an ultraviolet absorber and a photopolymerization initiator having an absorption wavelength range different from the absorption wavelength range of the ultraviolet absorber can prevent inhibition of curing during formation of an ultraviolet absorption layer containing the ultraviolet absorber, and can prevent, after curing, deterioration of the colorant contained in the colored layer 12 due to ultraviolet light.
Other examples of the photopolymerization initiator contained in the composition for forming the ultraviolet absorption layer 13 include 2,2-ethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, dibenzoyl, benzoin, benzoin methyl ether, benzoin ethyl ether, p-chlorobenzophenone, p-methoxybenzophenone, Michler's ketone, acetophenone, and 2-chlorothioxanthone. These materials may be used singly or in combination of two or more.
Examples of the solvent used in the composition for forming the ultraviolet absorption layer 13 include ethers such as dibutyl ether, dimethoxymethane, dimethoxyethane, diethoxyethane, propylene oxide, 1,4-dioxane, 1,3-dioxolane, 1,3,5-trioxane, tetrahydrofuran, anisole, and phenetole, ketones such as acetone, methyl ethyl ketone, diethyl ketone, dipropyl ketone, diisobutyl ketone, methyl isobutyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone, esters such as ethyl formate, propyl formate, n-pentyl formate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, n-pentyl acetate, and γ-butyrolactone, and cellosolves such as methyl cellosolve, cellosolve, butyl cellosolve, and cellosolve acetate. These materials may be used singly or in combination of two or more.
In the present embodiment, the surface of the optical film 10A including the ultraviolet absorption layer 13 on the side closer to the functional layers has a pencil hardness of H or more at a load of 500 g. The pencil hardness is measured based on JIS-K 5600-5-4:1999.
Thus, the ultraviolet absorption layer 13 of the present embodiment serves as an ultraviolet protective layer that protects the colored layer 12 from ultraviolet light entering from the outside of the optical film 10A, and also serves as a hard coat layer that protects the colored layer 12 from a load imposed from the outside of the optical film 10A.
The ultraviolet absorption layer 13 having both a function of protecting the colored layer from ultraviolet light and a hard coat function as in the present embodiment can be obtained, for example, by producing a hard resin layer using any of the materials described above as an energy ray-curable resin and adjusting the balance between the absorption wavelength of an ultraviolet absorber and the absorption wavelength of a photopolymerization initiator to prevent inhibition of curing.
The ultraviolet absorption layer 13 may contain metal oxide fine particles to adjust the refractive index and have a high hardness. Examples of such metal oxide fine particles include fine particles of zirconium oxide, titanium oxide, niobium oxide, antimony trioxide, antimony pentoxide, tin oxide, indium oxide, indium tin oxide, and zinc oxide.
In order to impart at least one of water repellency and oil repellency to the ultraviolet absorption layer 13 to achieve higher antifouling properties, the ultraviolet absorption layer 13 may contain any of a silicon oxide, a fluorine-containing silane compound, fluoroalkylsilazane, fluoroalkylsilane, a fluorine-containing silicon compound, and a perfluoropolyether group-containing silane coupling agent.
The ultraviolet absorption layer 13 may further contain, as other additives, a leveling agent, an antifoaming agent, an antioxidant, a photostabilizer, a photosensitizer, a conductive material, and the like.
In the optical film 10A applied to the display device 50A, the low refractive index layer 14A is located closest to a user (viewer) who views a display. In the present embodiment, the low refractive index layer 14A is laminated on the surface of the ultraviolet absorption layer 13 facing away from the transparent substrate 11. The thickness of the low refractive index layer 14A is not particularly limited, but is preferably 40 nm to 1 μm.
The low refractive index layer 14A is made of a material having a lower refractive index than the ultraviolet absorption layer 13. Thus, interference occurs between reflected light of external light entering from the outside that is reflected by the interface between the ultraviolet absorption layer 13 and the low refractive index layer 14A and reflected light reflected by the surface of the low refractive index layer 14A, achieving a lower surface reflectance for external light.
The low refractive index layer 14A can reduce surface reflection of external light, achieving better visibility of the display device 50A.
The low refractive index layer 14A is a layer portion made of an inorganic material or an inorganic compound. The inorganic material or inorganic compound may be, for example, fine particles of LiF, MgF, 3NaF·AlF, AlF, or Na3AlF6, silica fine particles, or the like. As silica fine particles, fine particles having voids inside the particles such as porous silica fine particles or hollow silica fine particles are effective to allow the low refractive index layer 14A to have a low refractive index. A composition for forming the low refractive index layer 14A may appropriately contain, in addition to an inorganic material or an inorganic compound, any of the materials described as an active energy ray-curable resin, a photopolymerization initiator, a solvent, and other additives for the ultraviolet absorption layer 13.
The composition for forming the low refractive index layer 14A may contain any of a silicon oxide, a fluorine-containing silane compound, fluoroalkylsilazane, fluoroalkylsilane, a fluorine-containing silicon compound, and a perfluoropolyether group-containing silane coupling agent. Such a material can impart at least one of water repellency and oil repellency to the low refractive index layer 14A, achieving higher antifouling properties.
In the optical film 10A of the present embodiment, the ultraviolet absorption layer 13 and the low refractive index layer 14A constitute one or more functional layers that are provided on the side opposite to the transparent substrate 11 with the colored layer 12 interposed therebetween.
The optical film 10A may include an appropriate functional layer between the colored layer 12 and the ultraviolet absorption layer 13 as long as the optical film 10A can achieve the necessary front luminance, visibility in the presence of external light reflection, and color purity for display light.
In the optical film 10A, at least the functional layers or the colored layer 12 contains a black organic pigment. In the optical film 10A including a plurality of functional layers, two or more of the functional layers may contain a black organic pigment.
Suitable examples of a black organic pigment include a bisbenzofuranone compound, an azomethine compound, a perylene compound, and an azo compound.
Herein, the black organic pigment does not include carbon black. A study by the inventors has found that the use of carbon black leads to a coating film having a high haze value due to compatibility with a resin and thus is not preferable.
The black organic pigment contained in at least the colored layer or the functional layers can reduce the amount of color material contained in the optical film 10A. This prevents a significant deterioration in any of low reflection, luminance efficiency, and reliability.
The optical film 10A can be produced by forming, on the first surface 11a of the transparent substrate 11, the colored layer 12, the ultraviolet absorption layer 13, and the low refractive index layer 14A in this order.
The colored layer 12, the ultraviolet absorption layer 13, and the low refractive index layer 14A each can be formed, for example, by applying and drying a coating liquid containing the constituent materials of the corresponding layer, followed by irradiation with active energy rays such as ultraviolet light to cure the coating liquid.
A composition for forming the colored layer 12 contains an active energy ray-curable resin, a photopolymerization initiator, a colorant, and a solvent. The composition for forming the colored layer 12 may further contain a black organic pigment and an additive as necessary. The composition for forming the colored layer 12 may contain any of the materials described as an active energy ray-curable resin, a photopolymerization initiator, and a solvent for the ultraviolet absorption layer 13.
The composition for forming the colored layer 12 contains, as a colorant, the first color material and the second color material described above. The composition for forming the colored layer 12 may contain, as an additive, at least one of a radical scavenger, a peroxide decomposer, and a singlet oxygen quencher.
The ultraviolet absorption layer 13 can be formed by applying a composition containing at least an energy ray-curable compound, a photopolymerization initiator, an ultraviolet absorber, and a solvent onto the colored layer 12, followed by irradiation with an energy ray for starting photopolymerization to cure the composition.
The low refractive index layer 14A can be formed by applying a material for forming the low refractive index layer 14A onto the ultraviolet absorption layer 13, followed by irradiation with an energy ray for starting photopolymerization to cure the composition, as with the ultraviolet absorption layer 13.
The low refractive index layer 14A can also be formed by vapor deposition, sputtering, or the like.
The display device 50A can be produced by preparing the display unit 20, and bonding and fixing the transparent substrate 11 of the optical film 10A to a surface of the color filter unit 23 via an adhesive layer or the like.
In the display device 50A of the present embodiment, when the light-emitting elements 22 are turned on in response to an image signal, display light generated by the light-emitting elements 22 passes through the color filter unit 23. Thus, light from the first light-emitting elements 22R, light from the second light-emitting elements 22G, and light from the third light-emitting elements 22B pass, as red light, green light, and blue light, respectively, the transparent substrate 11, the colored layer 12, the ultraviolet absorption layer 13, and the low refractive index layer 14A to the outside of the optical film 10A.
In this case, the colored layer 12 has good transmittance to light having red, green, and blue wavelengths of display light, and thus can prevent reduction in luminance of the display light for each color, achieving higher color purity for the display light for each color. The ultraviolet absorption layer 13 mainly absorbs light in the ultraviolet region, and thus allows display light to pass through with substantially no reduction in luminance. The low refractive index layer 14A has good transmittance for visible light, and thus allows display light to pass through to the outside with substantially no reduction in luminance.
On the other hand, external light enters the display device 50A through the optical film 10A.
The low refractive index layer 14A reduces the surface reflectance to external light, and thus prevents poor visibility due to excessive surface reflection of the external light.
When external light enters the ultraviolet absorption layer 13, a wavelength component in the ultraviolet region of the external light is absorbed by the ultraviolet absorption layer 13, and the light then enters the colored layer 12.
The colored layer 12 further absorbs wavelength components of external light near the absorption wavelengths of the color materials contained in the colored layer 12. Then, the external light passes through the color filter unit 23 and reaches the substrate 21. The substrate 21 includes, for example, metal portions having a high reflectance such as a wiring and an electrode.
Thus, the external light is reflected by the wirings, electrodes and the like, and sequentially passes through the color filter unit 23, the transparent substrate 11, the colored layer 12, the ultraviolet absorption layer 13, and the low refractive index layer 14A to the outside.
An observer of the display device 50A observes, in addition to display light, reflected light obtained by combining surface reflected light of external light from the display device 50A and internal reflected light of external light transmitted through and reflected by the inner portion of the display device 50A.
In the present embodiment, external light passes through the colored layer 12 twice to the outside to reduce wavelength components other than wavelength components of display light; thus, it is possible to prevent reduction in luminance of display light while reducing internal reflection of external light, achieving higher color purity for the display light.
Even while the display device 50A performs no display, when the values a* and b* as the indicators of the external light reflection hue of the optical film 10A are −5 or more and +5 or less, the influence of the color of the optical film is small, and thus the blackness of the display screen is maintained.
In the present embodiment, the ultraviolet absorption layer 13 absorbs an ultraviolet light component of external light, preventing deterioration of the color materials when the colored layer 12 is exposed to ultraviolet light. Thus, the spectral characteristics of the color materials of the colored layer 12 are more likely to be maintained with time.
An optical film and a display device according to a second embodiment of the present invention will be described.
A display device 50B of the present embodiment whose cross section in the thickness direction is shown in
The optical film 10B has the same configuration as the optical film 10A except that the optical film 10B includes an oxygen barrier layer 15 between the colored layer 12 and the ultraviolet absorption layer 13.
The following description will focus on differences from the first embodiment.
The oxygen barrier layer 15 is a transparent layer that allows light to pass through. The oxygen barrier layer 15 has an oxygen permeability of 10 cc/m2·day·atm or less. The main constituent material of the oxygen barrier layer 15 is preferably a polyvinyl alcohol (PVA), ethylene-vinyl alcohol copolymer (EVOH), vinylidene chloride, siloxane resin, or the like, and may be, for example, MAXIVE (registered trademark) manufactured by Mitsubishi Gas Chemical Company, Inc., EVAL (registered trademark) or Poval manufactured by Kuraray Co., Ltd., or Saran latex (registered trademark) or Saran (registered trademark) resin manufactured by Asahi Kasei Corporation. In the oxygen barrier layer 15, inorganic particles such as silica particles, alumina particles, silver particles, copper particles, titanium particles, zirconia particles, or tin particles may be dispersed to reduce the oxygen permeability.
When the optical film 10B is attached to the display device 50B, oxygen contained in the outside air needs to pass through the oxygen barrier layer 15 to reach the colored layer 12. This prevents deterioration of the color materials of the colored layer 12 due to light or heat in the presence of oxygen in the outside air. Thus, the light absorption performance of the colored layer 12 is maintained for a long time.
In the present embodiment, instead of or in addition to the oxygen barrier layer 15, the optical film 10B may include an oxygen barrier layer on the side closer to the second surface 11b of the transparent substrate 11. In such a case, the oxygen barrier layer protects the color materials of the colored layer 12 from oxygen present in the display device 50B.
The optical film 10B and the display device 50B of the present embodiment include the colored layer 12, the ultraviolet absorption layer 13, and the low refractive index layer 14A as in the first embodiment, and thus have the same actions as in the first embodiment.
In particular, the optical film 10B of the present embodiment further includes the oxygen barrier layer 15, and can thus prevent oxidative degradation of the colorants of the colored layer 12 due to the influence of oxygen.
An optical film and a display device according to a third embodiment of the present invention will be described.
A display device 50C of the present embodiment whose cross section in the thickness direction is shown in
The optical film 10C has the same configuration as the optical film 10A except that the optical film 10C includes an ultraviolet absorption antiglare layer 16 (ultraviolet absorption layer, functional layer, antiglare layer) instead of the low refractive index layer 14A and the ultraviolet absorption layer 13.
The following description will focus on differences from the first embodiment.
The ultraviolet absorption antiglare layer 16 is a layer portion having ultraviolet absorption properties and an antiglare function.
The ultraviolet absorption antiglare layer 16 has an ultraviolet shielding rate of 85% or more as with the ultraviolet absorption layer 13. The absorption wavelength range of the ultraviolet absorption antiglare layer 16 is more preferably the range of 290 nm or more and 370 nm or less.
The antiglare function is a function of scattering external light using a fine uneven structure on the surface to reduce glare of the external light.
The ultraviolet absorption antiglare layer 16 has a pencil hardness of H or more as with the ultraviolet absorption layer 13.
The ultraviolet absorption antiglare layer 16 can be formed by curing a coating liquid containing the same composition as the composition for forming the ultraviolet absorption layer 13 and at least organic fine particles or inorganic fine particles that impart an antiglare function. The organic fine particles are to form a fine uneven structure on the surface of the ultraviolet absorption antiglare layer 16 to impart a function of diffusing external light, and may be, for example, resin particles of a translucent resin material such as an acrylic resin, a polystyrene resin, a styrene-(meth)acrylic ester copolymer, a polyethylene resin, an epoxy resin, a silicone resin, a polyvinylidene fluoride, or a polyethylene fluoride resin. The organic fine particles may be a mixture of two or more types of resin particles of different materials (with different refractive indexes) in order to adjust the refractive index and the dispersibility of the resin particles. The inorganic fine particles are to adjust the precipitation and aggregation of the organic fine particles in the ultraviolet absorption antiglare layer 16, and may be silica fine particles, metal oxide fine particles, various mineral fine particles, or the like. The silica fine particles may be, for example, colloidal silica, or silica fine particles surface-modified with a reactive functional group such as a (meth)acryloyl group. The metal oxide fine particles may be fine particles of, for example, alumina, zinc oxide, tin oxide, antimony oxide, indium oxide, titania, zirconia, or the like. The mineral fine particles may be fine particles of, for example, mica, synthetic mica, vermiculite, montmorillonite, iron montmorillonite, bentonite, beidellite, saponite, hectorite, stevensite, nontronite, magadiite, ilerite, kanemite, layered titanate, smectite, synthetic smectite, or the like. The mineral fine particles may be a natural product or a synthetic product (including a substitution product and a derivative), or may be a mixture of a natural product and a synthetic product. The mineral fine particles are more preferably made of layered organoclay. Layered organoclay is a clay in which organic onium ions are introduced between layers of swelling clay. Layered organoclay may contain any organic onium ions that can organically modify swelling clay using the cation exchange properties of the swelling clay. When layered organoclay mineral particles are used as mineral fine particles, synthetic smectite can be suitably used as described above. Synthetic smectite has a function of increasing the viscosity of a coating liquid for forming an antiglare layer to prevent precipitation of resin particles and inorganic fine particles, adjusting the uneven shape of the surface of an optical functional layer.
The composition for forming the ultraviolet absorption antiglare layer 16 may contain any of a silicon oxide, a fluorine-containing silane compound, fluoroalkylsilazane, fluoroalkylsilane, a fluorine-containing silicon compound, and a perfluoropolyether group-containing silane coupling agent. Such a material can impart at least one of water repellency and oil repellency to the ultraviolet absorption antiglare layer 16, allowing the optical film 10C to have improved antifouling properties.
The ultraviolet absorption antiglare layer 16 may be configured such that a layer having a relatively high refractive index and a layer having a relatively low refractive index are sequentially laminated from the side closer to the colored layer 12. The ultraviolet absorption antiglare layer 16 containing unevenly distributed materials can be formed, for example, by applying a composition containing a low refractive index material containing surface-modified silica fine particles or hollow silica fine particles and a high refractive index material, and performing phase separation using the difference in surface free energy between the two materials. When the ultraviolet absorption antiglare layer 16 is composed of two layers obtained by phase separation, the ultraviolet absorption antiglare layer 16 is preferably configured such that the layer having a relatively high refractive index on the side closer to the colored layer 12 has a refractive index of 1.50 to 2.40 and that the layer having a relatively low refractive index on the side closer to the surface of the optical film 10C has a refractive index of 1.20 to 1.55.
The optical film 10C of the present embodiment is an example in which the ultraviolet absorption antiglare layer 16 as an ultraviolet absorption layer also serves as an antiglare layer.
The optical film 10C and the display device 50C of the present embodiment include the colored layer 12 as in the first embodiment, and the ultraviolet absorption antiglare layer 16 having the ultraviolet absorption properties as with the ultraviolet absorption layer 13, and thus have the same actions and effects as in the first embodiment.
In particular, the optical film 10C of the present embodiment includes the ultraviolet absorption antiglare layer 16 that also serves as an antiglare layer, causing external light to be scattered in the ultraviolet absorption antiglare layer 16. This reduces surface reflection and glare of external light, achieving better visibility of the display screen and display light, thus preventing lower display quality due to external light reflection.
An optical film and a display device according to a modification (first modification) of the third embodiment of the present invention will be described.
A display device 50D of the present modification whose cross section in the thickness direction is shown in
The optical film 10D has the same configuration as the optical film 10C except that the optical film 10D includes the ultraviolet absorption layer 13 as in the first embodiment and an antiglare layer 17 (functional layer) instead of the ultraviolet absorption antiglare layer 16.
The following description will focus on differences from the third embodiment.
The antiglare layer 17 is a layer portion having an antiglare function. The placement of the antiglare layer 17 is not particularly limited as long as the antiglare layer 17 is placed on the side of the ultraviolet absorption layer 13 facing away from the transparent substrate 11 with the colored layer 12 and the ultraviolet absorption layer 13 between it and the transparent substrate 11. The antiglare layer 17 located closer to the surface of the optical film 10D is more preferable. For example, in the example shown in
The optical film 10D of the present modification is an example in which the ultraviolet absorption layer 13 as an ultraviolet absorption layer, and the antiglare layer 17 are separate layers.
The optical film 10D and the display device 50D of the present modification include the colored layer 12 and the ultraviolet absorption layer 13 as in the first embodiment, and thus have the same actions and effects as in the first embodiment.
In particular, the optical film 10D of the present modification includes the antiglare layer 17, causing external light to be scattered in the antiglare layer 17. This reduces surface reflection and glare of external light, achieving better visibility of the display screen and display light, thus preventing lower display quality due to external light reflection.
An optical film and a display device according to a fourth embodiment of the present invention will be described.
A display device 50E of the present embodiment whose cross section in the thickness direction is shown in
The optical film 10E has the same configuration as the optical film 10C except that the optical film 10E includes a low refractive index layer 14E (functional layer) that is laminated on the ultraviolet absorption antiglare layer 16.
The following description will focus on differences from the third embodiment.
The low refractive index layer 14E is the same as the low refractive index layer 14A of the first embodiment except that the low refractive index layer 14E has a lower refractive index than the ultraviolet absorption antiglare layer 16.
Thus, interference occurs between reflected light of external light entering from outside that is reflected by the interface between the ultraviolet absorption antiglare layer 16 and the low refractive index layer 14E and reflected light reflected by the surface of the low refractive index layer 14E, achieving a lower surface reflectance for external light.
The low refractive index layer 14E can reduce surface reflection of external light, achieving better visibility of the display device 50E.
The material of the low refractive index layer 14E is not particularly limited as long as the material is a transparent material having a lower refractive index than the ultraviolet absorption antiglare layer 16. The material of the low refractive index layer 14E may be the same as that of the low refractive index layer 14A of the first embodiment.
The optical film 10E and the display device 50E of the present embodiment include the colored layer 12 and the ultraviolet absorption antiglare layer 16 as in the third embodiment, and thus have the same actions and effects as in the third embodiment.
In particular, the optical film 10E of the present embodiment includes the low refractive index layer 14E on the outer side, and this reduces surface reflection and glare due to external light, achieving better visibility of the display screen and display light, thus preventing lower display quality by external light reflection.
In the examples described in the embodiments and modification described above, the light-emitting elements are organic EL devices, but the light-emitting elements are not limited to organic EL devices. The light-emitting elements may be, for example, white LED devices, inorganic phosphor light-emitting elements, or quantum dot light-emitting elements. When a light source that emits monochromatic light in the three primary colors R, G, and B is used, the display unit 20 may be configured not to include the color filter unit 23.
In the above embodiments and modification, various functional layer configurations are described; however, the functional layer configuration is not limited to these.
For example, in the above description, the ultraviolet absorption layer 13 serves as both an ultraviolet absorption layer and a hard coat layer; however, the optical film may include an ultraviolet absorption layer having a pencil hardness of less than H, and a hard coat layer having a pencil hardness of H or more. In such a case, the hard coat layer is more preferably located closer to the outer side of the optical film than the ultraviolet absorption layer.
For example, the low refractive index layer or the antiglare layer may also serve as a hard coat layer.
For example, the optical film may further include, as a functional layer, at least one of an antistatic layer that contains an antistatic agent and an antifouling layer that has water repellency. However, the various functional layers described above may also serve as an antistatic layer and an antifouling layer.
The optical film according to the present invention will be further described by way of examples and comparative examples. The technical idea of the present invention is not limited only by the specific content of the examples.
Table 1 shows layer configurations of optical films of the examples, and Table 2 shows layer configurations of optical films of the comparative examples. In the optical films including a plurality of functional layers, a functional layer with a higher number is located closer to the colored layer.
Table 3 shows a composition used to form a colored layer in the examples and the comparative examples.
The method of forming each layer will be described.
The following materials were contained in the colored layer. The maximum absorption wavelength and half-width of color materials were calculated as characteristic values of a cured coating film from the spectral transmittance.
First Color Material:
Dye-1 Pyrromethene cobalt complex dye represented by the following chemical formula 1 (maximum absorption wavelength: 493 nm; half-width: 26 nm)
Second Color Material:
Dye-2 Tetraazaporphyrin copper complex dye (FDG-007 manufactured by Yamada Kagaku Co., Ltd.; maximum absorption wavelength: 595 nm; half-width: 22 nm)
Dye-3 Tetraazaporphyrin copper complex dye (PD-311S manufactured by Yamamoto Chemicals, Inc.; maximum absorption wavelength: 586 nm; half-width: 22 nm)
Third Color Material:
Dye-4 Phthalocyanine copper complex dye (FDN-002 manufactured by Yamada Kagaku Co., Ltd.; maximum absorption wavelength: 800 nm; minimum transmittance wavelength in the range of 400 to 780 nm: 780 nm)
Dye-5 Phthalocyanine cobalt complex dye (FDR-002 manufactured by Yamada Kagaku Co., Ltd.; maximum absorption wavelength: 683 nm; minimum transmittance wavelength in the range of 400 to 780 nm: 683 nm)
Black Organic Pigment:
Black organic pigment dispersion (IRBK-001 manufactured by Tokushiki Co., Ltd.)
Hindered amine light stabilizer Chimassorb (registered trademark) 944 FDL (manufactured by BASF Japan Ltd.; molecular weight: 2000 to 3100)
Hindered amine light stabilizer Tinuvin (registered trademark) 249 (manufactured by BASF Japan Ltd.; molecular weight: 482)
Singlet oxygen quencher D1781 (manufactured by Tokyo Chemical Industry Co., Ltd.)
Ultraviolet Absorber:
Tinuvin (registered trademark) 479 (manufactured by BASF Japan Ltd.; maximum absorption wavelength: 322 nm)
LA-36 (manufactured by Adeka Corporation; maximum absorption wavelength: 310 nm, 350nm)
Active Energy Ray-Curable Resin:
UA-306H (manufactured by Kyoeisha Chemical Co., Ltd.; pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer)
DPHA (dipentaerythritol hexaacrylate)
PETA (pentaerythritol triacrylate)
Initiator:
Omnirad (registered trademark) TPO (manufactured by IGM Resins B.V.; absorption wavelength peak: 275 nm, 379 nm)
As a transparent substrate, a TAC film having a thickness of 60 μm was used. The composition for forming a colored layer shown in Table 3 was applied to a surface of the transparent substrate, and dried in an oven at 80° C. for 60 seconds. Then, the coating films were cured by irradiation with ultraviolet light at an exposure dose of 150 mJ/cm2 using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan K.K., light source H bulb) to form each of colored layers 1 to 10 so that the corresponding colored layer after curing had a thickness of 5.0 μm. The addition amounts shown in Table 3 are expressed as mass ratios.
Composition for Forming Oxygen Barrier Layer:
PVA117 (manufactured by Kuraray Co., Ltd.) 80% aqueous solution
The composition for forming an oxygen barrier layer was applied onto the colored layer and dried to form an oxygen barrier layer having an oxygen permeability of 1 cc/m2·day·atm.
Table 4 shows a composition used to form a hard coat layer in the examples and the comparative examples.
Of the materials shown in Table 4, a material that has not been described above is as follows.
Photopolymerization Initiator:
Omnirad (registered trademark) 184 (manufactured by IGM Resins B.V.; absorption wavelength peak: 243 nm, 331 nm)
The corresponding composition for forming a hard coat layer was applied onto a predetermined layer, and dried in an oven at 80° C. for 60 seconds. Then, the coating film was cured by irradiation with ultraviolet light at an exposure dose of 150 mJ/cm2 using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan K.K., light source H bulb) to form each of hard coat layers 1 to 4 so that the corresponding hard coat layer after curing had a thickness of 5.0 μm.
Table 5 shows a composition used to form an antiglare layer in the examples and the comparative examples.
50%
50%
Of the materials shown in Table 5, materials that have not been described above are as follows.
Active Energy Ray-Curable Resin:
Light Acrylate PE-3A (manufactured by Kyoeisha Chemical Co., Ltd.; refractive index: 1.52)
Organic Fine Particles:
Styrene-methyl methacrylate copolymer particles (refractive index: 1.515; average particle size: 2.0 μm)
Inorganic Fine Particles:
Alumina nanoparticles, average particle size: 40 nm
The corresponding composition for forming an antiglare layer was applied onto a predetermined layer, and dried in an oven at 80° C. for 60 seconds. Then, the coating film was cured by irradiation with ultraviolet light at an exposure dose of 150 mJ/cm2 using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan K.K., light source H bulb) to form an antiglare layer 1 or 2 so that the corresponding antiglare layer after curing had a thickness of 5.0 μm. The antiglare layer 2 corresponds to the ultraviolet absorption antiglare layer 16 described above.
The following materials were contained in a composition for forming a low refractive index layer.
Refractive Index Adjusting Agent:
Dispersion of porous silica fine particles (average particle size: 75 nm; solid content: 20%; solvent: methyl isobutyl ketone) 8.5 parts by mass
Antifouling Agent:
OPTOOL (registered trademark) AR-110 (manufactured by Daikin Industries, Ltd.; solid content: 15%; solvent: methyl isobutyl ketone) 5.6 parts by mass
Active Energy Ray-Curable Resin:
Pentaerythritol triacrylate 0.4 parts by mass
Initiator:
Omnirad 184 0.07 parts by mass
Leveling agent:
RS-77 (manufactured by DIC Corporation) 1.7 parts by mass
Solvent:
Methyl isobutyl ketone 83.73 parts by mass
The composition for forming a low refractive index layer was applied onto a predetermined layer, and dried in an oven at 80° C. for 60 seconds. Then, the coating film was cured by irradiation with ultraviolet light at an exposure dose of 200 mJ/cm2 using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan K.K., light source H bulb) to form a low refractive index layer so that the low refractive index layer after curing had a thickness of 100 nm.
The optical films of the examples and the comparative examples were evaluated for the following items.
The functional layers were peeled off from the optical films of the examples using a cellophane tape in accordance with JIS-K5600 adhesion test. The transmittance of the functional layers was measured by using an automatic spectrophotometer (U-4100 manufactured by Hitachi, Ltd.) using, as a reference, a cellophane tape to which no functional layer was adhered. Then, the transmittances were used to calculate the average transmittance [%] in the ultraviolet region (290 nm to 400 nm), and the ultraviolet shielding rate [%] was calculated as a value obtained by subtracting the average transmittance [%] in the ultraviolet region (290 nm to 400 nm) from 100%.
The surface of the optical films of the examples on a first surface side (on the side closer to the functional layers) was subjected to a test using a pencil (uni manufactured by Mitsubishi Pencil Co., Ltd.; pencil hardness: H) at a load of 500 gf (4.9 N) (hereinafter, a load of 500 g) in accordance with JIS-K5600-5-4: 1999 by using a Clemens-type scratch hardness tester (HA-301 manufactured by Tester Sangyo Co., Ltd.), and the optical films were evaluated by visual observation for a change in appearance due to scratching. Optical films on which no scratching was observed were determined to be good (“Good” in the tables), and optical films on which scratching was observed were determined to be poor (“Poor” in the table).
The optical films of the examples were subjected to a test using a xenon weather meter (X75 manufactured by Suga Test Instruments Co., Ltd.) at a xenon lamp illumination of 60 W/cm2 (300 nm to 400 nm) at a temperature of 45° C. and a humidity of 50% RH in the tester for 120 hours.
Before and after the test, the transmittance of the optical films was measured using an automatic spectrophotometer (U-4100), and the transmittance was used to calculate a transmittance difference ΔTλ1 before and after the test at a wavelength λ1 at which the minimum transmittance before the test was in the wavelength range of 470 nm to 530 nm, and a transmittance difference ΔTλ2 before and after the test at a wavelength λ2 at which the minimum transmittance before the test was in the wavelength range of 560 nm to 620 nm. An optical film having a transmittance difference closer to zero is better. An optical film in which |ΔTλN|≤20 (N=1 to 2) is preferable, and an optical film in which |ΔTλN|≤10 (N=1 to 2) is more preferable.
The optical films of Examples 8 and 10 and Comparative Examples 4 to 7 were evaluated for display device characteristics. The optical film of Example 8 had the same color material configuration as the optical films of Examples 1 to 7 and 9, and thus the optical films of Examples 1 to 7 and 9 can be expected to have the same display device characteristics as the optical film of Example 8.
(White Display Transmission Characteristic)
The transmittance of the optical films of the examples was measured using an automatic spectrophotometer (U-4100). The transmittance was used to calculate the efficiency of light transmission through the optical films during white display, and the efficiency was evaluated as a white display transmission characteristic. The efficiency was calculated as a ratio of the light intensity at each wavelength of light transmitted through the optical films to the light intensity at each wavelength during white display in which light was emitted from a white organic EL light source and output through a color filter. A higher light intensity ratio indicates higher luminance efficiency of the light source.
The transmittance T (λ) and the surface reflectance R2 (λ) of the optical films of the examples were measured using an automatic spectrophotometer (U-4100). In the measurement of the surface reflectance R2 (λ), the optical films were subjected to antireflection treatment by applying a matte black coating material to the surface of the transparent substrate on which neither the colored layer nor the functional layer was provided, and the spectral reflectance at an incidence angle of 5° to the optical films was measured to obtain the surface reflectance R2 (λ). A relative reflection value relative to the intensity of reflected light from illuminant D65 when no optical film was provided was calculated, without considering interface reflection in the layers or surface reflection, based on the formulas (4), (5), (7), and (9), where the electrode reflectance RE (λ) was 100% at all wavelengths in the wavelength range of 380 nm to 780 nm, and the relative reflection value was evaluated as a display device reflection characteristic 1. A lower relative reflection value indicates a lower intensity of reflected light and higher display quality.
(Display device Reflection Hue 1)
The transmittance T (λ) and the surface reflectance R2 (λ) of the optical films of the examples that were obtained in the evaluation for the display device reflection characteristic 1 were used to calculate the values a* and b* of the reflection hue for illuminant D65, without considering interface reflection in the layers or surface reflection, based on the formulas (1) to (9), where the electrode reflectance RE (λ) was 100% at all wavelengths in the wavelength range of 380 nm to 780 nm, and the values a* and b* were evaluated as a display device reflection hue 1.
Values a* and b* closer to zero indicate better values with less color. The values a* and b* are preferably −5 or more and +5 or less.
A relative reflection value was calculated in the same manner as the display device reflection characteristic 1 except that the value used as the electrode reflectance RE (λ) was an electrode reflectance obtained by reflectance measurement using an organic light-emitting display device (organic EL TV OLED55C8PJA manufactured by LG Electronics), and the obtained relative reflection value was evaluated as a display device reflection characteristic 2. As with the display device reflection characteristic 1, a lower relative reflection value indicates a lower intensity of reflected light and higher display quality.
The values a* and b* of the reflection hue were calculated in the same manner as the display device reflection hue 1 except that the value used as the electrode reflectance RE (λ) was an electrode reflectance obtained by reflectance measurement using an organic light-emitting display device (organic EL TV OLED55C8PJA manufactured by LG Electronics), and the obtained values a* and b* were evaluated as a display device reflection hue 2. As with the display device reflection hue 1, values a* and b* closer to zero indicate better values with less color. The values a* and b* are preferably −5 or more and +5 or less.
The transmittance of the optical films of the examples was measured using an automatic spectrophotometer (U-4100). A CIE 1931 chromaticity value was calculated using the transmittance and a spectrum of light for each of red display, green display, and blue display shown in
Table 6 shows the optical film characteristics of the optical films of the examples, and Table 7 shows the optical film characteristics of the optical films of the comparative examples. In this case, ΔEab is represented by the distance between two points in L*a*b* color space (CIE1976) with illuminant C before and after the test. An optical film in which ΔEab is closer to zero is better, and an optical film in which ΔEab≤3 is preferable.
Table 8 shows the evaluation results for the display device characteristics. Table 8 also shows values relative to the values of the optical film of Comparative Example 7 including no colored layer.
The evaluation results for the optical film characteristics of the optical film of Example 2 compared with the evaluation results for the optical film characteristics of the optical films of Comparative Examples 1 and 3 show that a functional layer having an ultraviolet shielding rate of 85% or more located above the colored layer maintained the hardness of the optical film and achieved significantly less fading of the colored layer. In the optical film of Comparative Example 2, the colored layer contained the ultraviolet absorber, but the optical film of Comparative Example 2 had a lower fading prevention effect than the optical films of the examples.
The evaluation results of the optical films of Examples 3 to 5 show that the optical films including the antiglare layer as a functional layer also had a similar hardness and light resistance.
The light resistance test results of the optical films of Examples 2 and 6 show that an optical film including a colored layer containing a HALS had higher light resistance.
The light resistance test results of the optical films of Examples 6 and 7 show that an optical film containing a HALS having a high molecular weight had higher light resistance than the optical film containing a HALS having a low molecular weight.
The light resistance test results of the optical films of Examples 7 and 8 show that an optical film containing a singlet oxygen quencher in combination with a HALS having a high molecular weight had even higher light resistance.
The light resistance test results of the optical films of Examples 2 and 11 show that an optical film including an oxygen barrier layer had even higher light resistance.
The results of the optical film of Example 10 show that an optical film including a colored layer containing the third color material also had higher light resistance.
The results of the optical film of Example 9 show that an optical film in which a black organic pigment was contained not in the colored layer but in the functional layer also had higher light resistance of the colored layer.
In the optical film of Comparative Example 4, the colored layer contained the first color material, the second color material, and the black organic pigment, but the reflection hue was significantly shifted, leading to low display quality. Thus, in order to achieve the values a* and b* in the preferable range described above, it is important for the optical film to contain the color materials and the black organic pigment at a proper ratio.
The black organic pigment contained in the optical film according to the present invention can reduce the amount of colorant contained in the colored layer. This makes it possible to provide an optical film achieving all of low reflection, high luminance efficiency, and high reliability.
The display devices according to Examples 8 and 10 had significantly lower values for the reflection characteristics than the display device according to Comparative Example 7 including no colored layer. In general, the use of a circular polarizing plate is expected to lead to a reduction in transmittance by half; however, as shown in the evaluation values for the white display transmission characteristic, the display devices according to Examples 8 and 10 had high luminance efficiency and high color reproducibility.
In the display device according to Comparative Example 5 containing no black organic pigment, the reflection hue was significantly shifted, leading to low display quality.
In the display device according to Comparative Example 6, the colored layer contained the first color material, the second color material, and the third color material, but did not contain the black organic pigment; thus, the display device according to Comparative Example 6 had low light resistance, leading to low reliability.
In the optical films according to the examples, the colored layer was configured such that each of the values a* and b* of the display device reflection hue 1 was in the range of −5 or more and +5 or less; thus, a neutral reflection hue was also maintained for the display device reflection hue 2 obtained in the presence of electrode reflectance of an actual organic light-emitting display device.
The embodiments, examples, and the like of the present invention have been described; however, the specific configuration of the present invention is not limited to these, and includes modifications and combinations of the configurations without departing from the gist of the present invention.
For example, when the optical film includes a functional layer composed of a plurality of layers, the optical film may be configured such that one of the layers of the functional layer alone has an ultraviolet shielding rate of 85% or more or that even though any of the layers of the functional layer alone does not have an ultraviolet shielding rate of 85% or more, the functional layer composed of a plurality of layers as a whole has an ultraviolet shielding rate of 85% or more.
The present invention provides an optical film and a display device achieving higher display quality by external light reflection and a longer life of light-emitting elements of the display device.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-113003 | Jul 2021 | JP | national |
This application is a continuation application filed under 35 U.S.C. § 111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) of International Patent Application No. PCT/JP2022/026962, filed on Jul. 7, 2022, which is based upon and claims the benefit of priority to Japanese Patent Application No. 2021-113003, filed on Jul. 7, 2021, the disclosures of which are incorporated herein by reference in their entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2022/026962 | Jul 2022 | US |
| Child | 18403955 | US |
