Photocurable composition and method for manufacturing image display device

Abstract

Provided is a photocurable composition that, when manufacturing an image display device having a light-shielding part, does not require thermal curing, exhibits excellent curability of the light-shielding part, and is less affected regarding turbidity and / or coloration in a visible-light region. This photocurable composition is characterized by comprising a photocurable compound, a photopolymerization initiator, and a phosphor having an inorganic substance, and is characterized in that the phosphor has a volume average particle diameter of 10-400 nm.

Description

Photocurable Composition and Method for Manufacturing Image Display Device

[0001] The present invention relates to a photocurable composition and a method for manufacturing an image display device.

[0002] As an image display device used in a mobile phone or the like, for example, as shown in FIG. 2, there is known one having a transparent protective part 103 made of glass or plastic on a liquid crystal panel 102. In this case, in order to protect the liquid crystal panel 102 and a polarizing plate (not shown), a spacer 104 is interposed between the liquid crystal panel 102 and the protective part 103, and a gap 105 is provided between the liquid crystal panel 102 and the protective part 103. However, due to the presence of the gap 105 between the liquid crystal panel 102 and the protective part 103, light scattering occurs, and as a result, the contrast and brightness decrease.

[0003] In view of such problems, a technique of filling the gap between the liquid crystal panel and the protective part with a cured product of a resin composition having an adjusted refractive index has been studied (for example, refer to Patent Document 1 and the like). The resin composition used in this technique usually contains an ultraviolet curable resin and a photoinitiator. In this technique, the resin composition is filled between the liquid crystal panel and the protective part, and the filled resin composition is photocured to fill the gap between the liquid crystal panel and the protective part with the cured product of the resin composition.

[0004] On the other hand, from the viewpoint of design, the protective part is mainly printed in black as decorative printing. However, the lower part of the decorative printing is a light-shielding part where light does not reach, and the photocurable resin composition in the light-shielding part is insufficiently cured.

[0005] Patent Document 2 discloses a technique of using a resin composition containing a photoinitiator and a thermal initiator, performing photocuring and thermal curing on the resin composition, and filling the cured product of the resin composition between a liquid crystal panel and a protective part in order to improve the curability of the light-shielding part.

[0006] Further, Patent Documents 3 to 5 disclose a technique of improving the curability of the light-shielding part by including an organic compound that is excited by absorbing a specific wavelength and emits fluorescence in a photocurable resin composition.

[0007] Japanese Patent Publication No. 2012-46658, International Publication No. 2008 / 126860, Japanese Patent Publication No. 2013-144760, International Publication No. 2013 / 105163, International Publication No. 2021 / 019920

[0008] The technology disclosed in Patent Document 2 requires thermal curing in addition to photocuring, which increases the number of steps in the manufacturing of image display devices.

[0009] Furthermore, while the technologies disclosed in Patent Documents 3 to 5 can improve the curability of the light-shielding portion without thermal curing, there is a risk that the organic compounds used may cause problems due to the influence of coloration in the visible light region.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a photocurable composition that does not require thermal curing when manufacturing an image display device having a light-shielding portion, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region. Furthermore, the present invention aims to provide a method for manufacturing an image display device that does not require thermal curing, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region.

[0011] The gist of the present invention, which solves the above problems, is as follows.

[0012] [1] A photocurable composition comprising a photocurable compound, a photopolymerization initiator, and a phosphor having an inorganic substance, wherein the phosphor has a volume average particle diameter of 10 to 400 nm.

[0013] [2] The photocurable composition according to [1], wherein the phosphor is excited by light with a wavelength of 800 to 1200 nm and emits fluorescence with a wavelength of 365 to 405 nm.

[0014] [3] The photocurable composition according to [1], wherein the phosphor is excited by light with a wavelength of 325 to 395 nm and emits fluorescence with a wavelength of 365 to 405 nm.

[0015] [4] The photocurable compound is at least one selected from the group consisting of compounds having a (meth)acrylic group and compounds having an epoxy group, according to any one of [1] to [3].

[0016] [5] A method for manufacturing an image display device, wherein a display panel having an image display unit and a frame surrounding the image display unit and a protective unit are laminated with a cured material layer in between, the method comprising: interposing a photocurable composition described in any of [1] to [4] between the display panel and the protective unit so as to extend across the image display unit and the frame to form a photocurable composition layer; and photocuring the photocurable composition layer to form a cured material layer.

[0017] According to the present invention, when manufacturing an image display device having a light-shielding portion, it is possible to provide a photocurable composition that does not require thermal curing, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region. Furthermore, according to the present invention, it is possible to provide a method for manufacturing an image display device that does not require thermal curing, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region.

[0018] This is a schematic diagram illustrating the step of forming a photocurable composition layer in a method for manufacturing an image display device according to one embodiment of the present invention. This is a schematic diagram illustrating the step of forming a cured material layer in a method for manufacturing an image display device according to one embodiment of the present invention. This is a schematic cross-sectional view of an image display device manufactured using a method for manufacturing an image display device according to one embodiment of the present invention. This is a schematic cross-sectional view illustrating a conventionally known image display device.

[0019] Embodiments of the present invention will be described in detail below. In this specification, "(meth)acrylic group" means at least one of an acrylic group and a methacrylic group. In this specification, "(meth)acrylate" means at least one of an acrylate and the corresponding methacrylate. In this specification, "(meth)acrylic acid" means at least one of an acrylic acid and the corresponding methacrylic acid.

[0020] (Photocurable Composition) A photocurable composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the photocurable composition of this embodiment") contains a photocurable compound, a photopolymerization initiator, and a phosphor having an inorganic substance, wherein the phosphor has a volume average particle diameter of 10 to 400 nm.

[0021] As a result of the inventors' diligent research, it was found that when using phosphors containing inorganic materials in the manufacture of image display devices, there is a risk of problems with coloration and light diffusion in the visible light region; that is, there is a risk of coloration and / or turbidity occurring when visible light is incident on the phosphor. It was found that this is due to the particle size of the phosphors containing inorganic materials. As a result of further diligent research by the inventors, it was found that the effect of coloration and / or turbidity in the visible light region can be reduced by keeping the volume-average particle size of the phosphors containing inorganic materials within a specific range. Furthermore, as a result of the inventors' diligent research, it was found that when the photocurable composition of this embodiment is placed in the light-shielding part of an image display device, the photopolymerization initiator present in the light-shielding part absorbs the light (fluorescence) emitted by the phosphors present in the non-light-shielding parts, generating radicals or cations, and that these radicals or cations cure the photocurable composition present in the light-shielding part. Moreover, it was found that the photocurable composition of this embodiment can be cured by light alone and does not require thermal curing. Therefore, the photocurable composition of the present invention does not require thermal curing when manufacturing an image display device, exhibits excellent curability of light-shielding areas, and has minimal influence of coloration and / or turbidity in the visible light region.

[0022] Photocurable compounds are compounds that polymerize by radicals or ions generated by a photopolymerization initiator in response to light (e.g., ultraviolet light), and have one or more polymerizable functional groups. Examples of polymerizable functional groups include functional groups containing ethylenically unsaturated bonds such as vinyl groups, allyl groups, styryl groups, and (meth)acrylic groups; epoxy groups, etc.

[0023] The photocurable compound may be a monomer, oligomer, or prepolymer. The photocurable compound may be used alone or in combination of two or more types.

[0024] In the photocurable composition of this embodiment, the photocurable compound is preferably at least one selected from the group consisting of compounds having a (meth)acrylic group and compounds having an epoxy group. These compounds allow for easy adjustment of the refractive index required for the applications of the present invention, and also offer diverse chemical structures, making it easy to adjust the intensity and other properties required for image display devices.

[0025] Compounds having (meth)acrylic groups are acrylic monomers having one or more (meth)acrylic groups in the molecule, or acrylic oligomers having one or more (meth)acrylic groups in the molecule.

[0026] The above acrylic monomers are further classified into monofunctional monomers having one (meth)acrylic group in the molecule, difunctional monomers having two (meth)acrylic groups in the molecule, and polyfunctional monomers having three or more (meth)acrylic groups in the molecule.

[0027] Examples of the above monofunctional monomers include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, 2-cyanoethyl (meth)acrylate, 2-(2-ethoxyethoxy)ethyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, isopropyl (meth)acrylate, cyclohexyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and neopentyl glycol. Examples include di(meth)acrylate, pentaerythritol(meth)acrylate, hydroxypropyl(meth)acrylate, isobutyl(meth)acrylate, 2-hydroxybutyl(meth)acrylate, isobornyl(meth)acrylate, decyl(meth)acrylate, octyl(meth)acrylate, lauryl(meth)acrylate, 2-methoxyethyl(meth)acrylate, 2-phenoxyethyl(meth)acrylate, tetrahydrofurfluryl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and N,N-dimethylaminopropyl(meth)acrylate.

[0028] Examples of the above-mentioned difunctional monomers include ethylene glycol diacrylate, diethylene glycol diacrylate, and tri(propylene glycol) di(meth)acrylate.

[0029] Examples of the above-mentioned polyfunctional monomers include trimethylolpropane tri(meth)acrylate, tetramethylolmethane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol penta(meth)hexaacrylate, and ditrimethylolpropane tetra(meth)acrylate.

[0030] Examples of acrylic oligomers include polyurethane (meth)acrylate, polyether (meth)acrylate, polybutadiene (meth)acrylate, and polyisoprene (meth)acrylate.

[0031] The weight-average molecular weight of the acrylic oligomer is preferably 1,000 to 200,000, and more preferably 30,000 to 100,000.

[0032] Polyurethane (meth)acrylate has a polyurethane backbone in its main chain. Preferred specific examples of polyurethane (meth)acrylate include aliphatic urethane acrylate (e.g., CN9014, Sartomer Japan Co., Ltd.; UA-1, Light Chemical Industry Co., Ltd.).

[0033] Polyether (meth)acrylates have a polyether backbone such as polyethylene glycol or polypropylene glycol in their main chain. Preferred specific examples of polyether (meth)acrylates include terminally acrylic-modified polyethers (e.g., UN-6202, Negami Kogyo Co., Ltd.; EBECRYL230, Daicel Cytec Co., Ltd.).

[0034] Polybutadiene (meth)acrylate has a polybutadiene skeleton or a hydrogenated polybutadiene skeleton in its main chain. Preferred specific examples of polybutadiene (meth)acrylate include esters of polybutadiene polymers and 2-hydroxyethyl methacrylate (e.g., EMA-3000, Nippon Soda Co., Ltd.).

[0035] Polyisoprene (meth)acrylate has a polyisoprene skeleton in its main chain. Preferred specific examples of polyisoprene (meth)acrylate include esterified products of a maleic anhydride adduct of a polyisoprene polymer and 2-hydroxyethyl (meth)acrylate (for example, UC102 (polystyrene equivalent molecular weight 17,000), Kuraray Co., Ltd.; UC203 (polystyrene equivalent molecular weight 35,000), Kuraray Co., Ltd.).

[0036] Compounds having epoxy groups are monomers, oligomers, or prepolymers having one or more epoxy groups in their molecule. Examples of compounds having epoxy groups include various bisphenol-type epoxy resins (bisphenol A type, bisphenol F type, etc.), hydrogenated bisphenol A type epoxy resins, novolac-type epoxy resins, various modified epoxy resins such as rubber and urethane, naphthalene-type epoxy resins, biphenyl-type epoxy resins, phenol novolac-type epoxy resins, stilbene-type epoxy resins, triphenolmethane-type epoxy resins, dicyclopentadiene-type epoxy resins, triphenylmethane-type epoxy resins, cyclohexene oxide-type epoxy resins, and prepolymers thereof.

[0037] The content of the photocurable compound in the photocurable composition of this embodiment is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 20% by mass or more and 99% by mass or less, more preferably 30% by mass or more, and even more preferably 90% by mass or less, based on the total amount of the photocurable composition of this embodiment.

[0038] The photopolymerization initiator is not particularly limited, and known ones can be used. Examples of photopolymerization initiators include photoradical polymerization initiators and photocationic polymerization initiators.

[0039] Examples of photoradical polymerization initiators include molecular cleavage type photoradical polymerization initiators such as 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methyl-propylonyl)benzyl]phenyl}-2-methyl-1-propan-1-one, 2-methyl-4'-(methylthio)-2-morpholinopropiophenone, 2-benzyl-2-(dimethylamino)-4'-morpholinopropiophenone, and diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide; and hydrogen abstraction type photoradical polymerization initiators such as benzophenone, 2,4-diethylthioxanthone, and 4,4'-bis(dimethylamino)benzophenone.

[0040] As the photo cationic polymerization initiator, for example, onium salts such as iodonium salts, sulfonium salts, aromatic diazonium salts, phosphonium salts, selenonium salts, etc., metal arene complexes, complex compounds such as silanol / aluminum complexes, benzoin tosylate, o-nitrobenzyl tosylate, etc. can be mentioned. Further, as the counter anion when forming a salt, propylene carbonate, hexafluoroantimonate, hexafluorophosphate, tetrafluoroborate, tetrakis(pentafluorophenyl)borate, etc. can be mentioned.

[0041] The photoinitiator may be used alone or in combination of two or more. The photoinitiator is appropriately selected according to the type of the photocurable compound.

[0042] The content of the photoinitiator in the photocurable composition of the present embodiment is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 0.1% by mass or more and 15% by mass or less, more preferably 3% by mass or more, and more preferably 10% by mass or less, based on the total amount of the photocurable composition of the present embodiment.

[0043] The phosphor having an inorganic substance is excited by light of a specific wavelength and emits light (fluorescence) having a wavelength different from the excitation wavelength. When the photocurable composition of the present embodiment is disposed in the light shielding portion of the image display device, the photoinitiator present in the light shielding portion absorbs the light (fluorescence) emitted by the phosphor present in the portion other than the light shielding portion and generates radicals or cations. Then, the photocurable composition present in the light shielding portion is cured by the radicals or cations. Therefore, the photocurable composition of the present embodiment is excellent in the curability of the light shielding portion. Further, since the photocurable composition of the present embodiment can be cured only by light, heat curing is not required.

[0044] When manufacturing an image display device, if an organic compound is used as the phosphor in the photocurable composition, there is a possibility that the pot life (usable time) of the photocurable composition cannot be sufficiently ensured. On the other hand, since the photocurable composition of the present embodiment uses a phosphor having an inorganic substance, it is possible to sufficiently ensure the pot life.

[0045] As the phosphor having an inorganic substance (hereinafter, may be simply referred to as "phosphor"), known ones can be used. Examples of the inorganic substance include metal compounds such as metal oxides, metal sulfides, and metal halides. The metal constituting the metal compound is not particularly limited, and examples thereof include one or more selected from the group consisting of Ag, Al, Au, Bi, Cd, Cr, Cu, Ga, In, Mn, Mo, Pb, Sn, Sr, Ti, Tl, Zn, Zr, and rare earth metals. The rare earth metal is a lanthanoid metal selected from the group consisting of La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu.

[0046] The phosphor has a volume average particle diameter of 10 to 400 nm. By having a volume average particle diameter of 400 nm or less, the influence of coloring and / or turbidity in the visible light region can be reduced. From the same viewpoint, the phosphor preferably has a volume average particle diameter of 300 nm or less, more preferably 250 nm or less, still more preferably 200 nm or less, and particularly preferably 100 nm or less. Also, if the volume average particle diameter is less than 10 nm, the luminous efficiency of the phosphor may deteriorate. From the same viewpoint, the phosphor preferably has a volume average particle diameter of 20 nm or more, more preferably 30 nm or more, still more preferably 40 nm or more, and particularly preferably 50 nm or more.

[0047] The above-mentioned "volume average particle diameter" can be measured using a dynamic light scattering type or a laser diffraction / scattering type particle size distribution measuring device. The adjustment of the volume average particle diameter of the phosphor having an inorganic substance is not particularly limited, but can be performed by adjusting the particle diameter of the raw material when producing the phosphor having an inorganic substance. Also, if necessary, the phosphor having a desired particle diameter may be sorted using a sieve or the like.

[0048] The excitation wavelength of the phosphor is preferably 800 to 1200 nm. In other words, it is preferable that the phosphor is excited by light with a wavelength of 800 to 1200 nm. In some cases, materials with low ultraviolet light transmittance, such as colorless polyimide, may be used for the protective part. In this case, even if ultraviolet light is irradiated from the protective part side, a sufficient amount of ultraviolet light will not reach the photocurable composition, and therefore the photocurable composition cannot be photocured. On the other hand, light with a wavelength of 800 to 1200 nm can be transmitted even through materials with low ultraviolet light transmittance. Therefore, even if a material with low ultraviolet light transmittance is used for the protective part, if the excitation wavelength of the phosphor in the photocurable composition is 800 to 1200 nm, the photocurable composition can be cured by irradiating light with a wavelength of 800 to 1200 nm from the protective part side. Furthermore, the fluorescence wavelength of the phosphor can be appropriately selected according to the absorption wavelength of the photopolymerization initiator. The fluorescence wavelength of the phosphor is preferably 365 to 405 nm. In other words, it is preferable that the phosphor emits fluorescence at a wavelength of 365 to 405 nm. Since light with a wavelength of 365 to 405 nm is outside the visible light region, having a fluorescence wavelength of 365 to 405 nm can further reduce the influence of coloration in the visible light region. For the above reasons, it is preferable that the phosphor is excited by light with a wavelength of 800 to 1200 nm and emits fluorescence at a wavelength of 365 to 405 nm.

[0049] Furthermore, it is preferable that the excitation wavelength of the phosphor be 325 nm or higher. In other words, it is also preferable that the phosphor be excited by light of 325 nm or higher. Light of 325 nm or higher is less likely to be absorbed by the protective part, photocurable composition, etc., so photocuring can be performed more reliably. In addition, the excitation wavelength of the phosphor may be 395 nm or lower. For the above reasons, it is preferable that the phosphor be excited by light with a wavelength of 325 to 395 nm and emit fluorescence with a wavelength of 365 to 405 nm.

[0050] The excitation wavelength and fluorescence wavelength of the phosphor can be adjusted, for example, by adjusting the type and content of the inorganic substance mentioned above.

[0051] The phosphor preferably further contains an organic dye. The presence of an organic dye (i.e., an organic-inorganic hybrid phosphor) increases the light absorption efficiency and improves the luminescence efficiency. The organic dye is not particularly limited, but examples include phthalocyanine dyes, squarium dyes, indigo dyes, and the like.

[0052] The phosphor content in the photocurable composition of this embodiment is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferable that the phosphor content be 0.05% by mass or more and 25% by mass or less of the total amount of the photocurable composition of this embodiment. By having a phosphor content of 0.05% by mass or more, the curability of the light-shielding portion can be more reliably improved. From a similar viewpoint, it is more preferable that the phosphor content be 5% by mass or more. Furthermore, it is even more preferable that the phosphor content be 10% by mass or less.

[0053] The photocurable composition of this embodiment may optionally further contain a plasticizer. The plasticizer typically does not have polymerizable functional groups and does not polymerize upon irradiation with light. The plasticizer is not particularly limited, but examples include terpene resins such as terpene resins, terpene phenol resins, and hydrogenated terpene resins; rosin resins such as natural rosin, polymerized rosin, rosin esters, and hydrogenated rosin; and petroleum resins such as polybutadiene and polyisoprene.

[0054] The content of the plasticizer in the photocurable composition of this embodiment is not particularly limited and can be appropriately selected according to the purpose. For example, it is preferably 0% by mass or more and 70% by mass or less, more preferably 40% by mass or more, and even more preferably 60% by mass or less, based on the total amount of the photocurable composition of this embodiment.

[0055] The photocurable composition of this embodiment may further contain other components as needed. There are no particular limitations on the other components, and they can be appropriately selected depending on the purpose. Examples include chain transfer agents such as 2-mercaptoethanol, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-ethylhexyl thioglycolate, 2,3-dimethylcapto-1-propanol, and α-methylstyrene dimer; adhesion improvers such as silane coupling agents; and antioxidants.

[0056] The photocurable composition of this embodiment has a phosphor volume-average particle size of 10 to 400 nm, which reduces the influence of coloration and / or turbidity in the visible light region. Preferably, the photocurable composition of this embodiment has a visible light transmittance of 90% or more in a cured product with a thickness of 100 μm.

[0057] The "transmittance in the visible light region" mentioned above is a value measured using an ultraviolet-visible spectrophotometer.

[0058] The photocurable composition of this embodiment has a storage modulus (at 25°C) of 1 × 10⁻¹⁶ of the cured product obtained by photocuring. ７ It is preferable that the pressure be Pa or less. The storage modulus of the cured product (at 25°C) is 1 × 10⁻⁶. ７ By keeping the pressure below Pa, stress due to curing shrinkage can be suppressed when the photocurable composition is photocured. Therefore, when the photocurable composition is interposed between the display panel and the protective part and photocured, distortion is less likely to occur. From a similar viewpoint, the storage modulus of the cured product (at 25°C) is 1 × 10⁻⁶. ６ It is more preferable that the pressure be less than or equal to Pa. Furthermore, the storage modulus of the cured product (at 25°C) is 1 × 10⁻⁶. ３ It may be Pa or higher.

[0059] The "storage modulus (25°C)" mentioned above was measured using a viscoelasticity measuring device with a cured product thickness of 2 mm, at a temperature of 25°C and a measurement frequency of 1 Hz. The "storage modulus (25°C)" can be adjusted by appropriately adjusting the components and their content of the photocurable composition described above.

[0060] In this embodiment, the photocurable composition preferably has a cured product shrinkage rate of 5% or less. A curing shrinkage rate of 5% or less reduces the internal stress accumulated in the cured product when the photocurable composition is photocured. Therefore, when the photocurable composition is interposed between the display panel and the protective part and photocured, distortion is less likely to occur in the display panel and the protective part.

[0061] The "curing shrinkage rate" described above is calculated by measuring the "specific gravity of the photocurable composition" and the "specific gravity of the cured product" using an electronic hydrometer, and using the following formula: Curing shrinkage rate = ("Specific gravity of the cured product" - "Specific gravity of the photocurable composition") × 100 / "Specific gravity of the cured product" Note that the "curing shrinkage rate" of the photocurable composition in this embodiment can be adjusted by appropriately adjusting the components of the photocurable composition and their content as described above.

[0062] The internal stress accumulated in the cured product when a photocurable composition is photocured can be evaluated by measuring the average surface roughness of the cured product obtained by dropping the photocurable composition onto a flat plate and photocuring it. In this embodiment, the "average surface roughness of the cured product" is preferably 6 nm or less.

[0063] The "average surface roughness of the cured product" mentioned above can be measured by the following procedure: 2 mg of the photocurable composition is dropped onto a glass plate and cured by ultraviolet light irradiation to a curing rate of 90% or more to obtain a cured product. The average surface roughness of the cured product is measured using a three-dimensional non-contact surface roughness analyzer.

[0064] In this embodiment, the photocurable composition preferably has an elongation of 700% or more at 25°C and 400% or more at 80°C. Furthermore, the cured product preferably has an adhesion strength of 0.4 N / cm or more at 25°C and 0.3 N / cm or more at 80°C to the protective part. Here, the protective part is the same as that described later.

[0065] The reason for selecting 25°C and 80°C as the temperatures that define the elongation rate and adhesion is that the normal operating environment for image display devices is 25°C, and when the photocurable composition is irradiated with light during the manufacturing process, the temperature rises to approximately 80°C. If the elongation rate and / or adhesion of the cured product are within the above range, the cured product will be able to follow the warping of the protective part if warping occurs, thereby suppressing the separation of the cured product layer formed by the photocurable composition from the protective part.

[0066] The "elongation rate" mentioned above was obtained by cutting the cured material into a sample measuring 0.6 mm thick, 10 mm wide, and 25 mm long, and then measuring and calculating the value using a tensile tester under the conditions of an ambient temperature of 25°C or 80°C, a load of 5 kgf, and a tensile speed of 5 mm / min. The elongation rate is calculated using the following formula: Elongation rate (%) = L / L ０ ×100 (where L ０ (where L is the reference length, and L is the displacement length until fracture.)

[0067] The aforementioned "adhesion strength" is measured in accordance with JIS K6854-1.

[0068] Furthermore, the "elongation" and "adhesion" of the photocurable composition in this embodiment can be adjusted by appropriately adjusting the components of the photocurable composition and their content as described above.

[0069] In this embodiment, the photocurable composition preferably uses an acrylic monomer (more preferably at least one selected from isobornyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate) as the photocurable compound, and also uses at least one selected from an acrylic oligomer (more preferably polyurethane (meth)acrylate or polyisoprene (meth)acrylate) as the photocurable compound, polybutadiene as the plasticizer, and hydrogenated terpene resin as the plasticizer. In the above case, it is preferable to select a photoradical polymerization initiator as the photopolymerization initiator.

[0070] In the above case, the "storage modulus (25°C)" and "curing shrinkage rate" can be more reliably adjusted to fall within the above range. Therefore, when a photocurable composition is interposed between the display panel and the protective part and photocured, distortion is less likely to occur between the display panel and the protective part. In addition, the "elongation rate" and "adhesion rate" can be more reliably adjusted to fall within the above range. Therefore, if warping occurs in the protective part, the cured material can follow that warping, and delamination between the cured material layer formed by the photocurable composition and the protective part can be suppressed.

[0071] The photocurable composition of this embodiment preferably contains a cycloalkyl group or an acrylic monomer having an alkyl group, an acrylic oligomer, a photoradical polymerization initiator, and a phosphor having an inorganic substance. In this case, the photocurable composition exhibits excellent curability for light-shielding areas. From a similar viewpoint, the content of the cycloalkyl group or the acrylic monomer having an alkyl group is preferably 5 to 45% by mass and 20 to 35% by mass, based on the total amount of the photocurable composition of this embodiment.

[0072] Here, the acrylic monomer having an alkyl group may have a hydroxyl group, an aryl group such as a phenyl group, or a heterocycloalkyl group bonded to the alkyl group. The number of carbon atoms in the alkyl group is preferably 4 to 18, more preferably 8 to 12. Examples of acrylic monomers having an alkyl group include isobornyl (meth)acrylate, lauryl (meth)acrylate, octyl (meth)acrylate, and decyl (meth)acrylate.

[0073] In this embodiment, the photocurable composition preferably has a glass transition temperature of -40 to 20°C when the cured product obtained by photopolymerization by ultraviolet irradiation in air is cured to a degree that exceeds 90% curing of the outermost surface. In this case, the photocurable composition has the effect of improving the shape retention, adhesion, and adhesion retention of the cured resin layer.

[0074] The aforementioned "glass transition temperature" is measured using a dynamic viscoelasticity analyzer (DMA, compression mode, 1 Hz, variable temperature). The glass transition temperature can be adjusted by appropriately adjusting the components and their content of the photocurable composition described above.

[0075] The method for producing the photocurable composition of this embodiment is not particularly limited, and it can be produced by kneading the various components described above using a kneader such as a roller.

[0076] <Method for Manufacturing an Image Display Device> A method for manufacturing an image display device according to one embodiment of the present invention (hereinafter sometimes referred to as "the manufacturing method of this embodiment") is a method for manufacturing an image display device in which a display panel having an image display unit and a frame surrounding the image display unit and a protective unit are laminated with a cured material layer in between, and is characterized by comprising the steps of interposing the photocurable composition of this embodiment between the display panel and the protective unit so as to extend across the image display unit and the frame to form a photocurable composition layer, and photocuring the photocurable composition layer to form a cured material layer.

[0077] The manufacturing method of this embodiment does not require thermal curing, has excellent curability of the light-shielding portion, and makes it possible to manufacture an image display device with minimal influence of coloring and / or cloudiness in the visible light region.

[0078] Below, an example of the manufacturing method of this embodiment will be described in detail, using drawings as needed. Some of the components disclosed in Figures 1A to 1C are schematically represented with different scales and shapes than the actual components for the sake of explanation.

[0079] In the manufacturing method of this embodiment, a display panel is used as a component of the image display device. As shown in Figures 1A to 1C, the display panel 2 in the manufacturing method of this embodiment has an image display unit 6 and a frame 7 surrounding the image display unit 6. The display panel 2 in the manufacturing method of this embodiment may further have a backlight 8 on the back of the image display unit 6.

[0080] In the manufacturing method of this embodiment, a protective part is used as a component of the image display device. The protective part 3 is formed, for example, from a rectangular, flat transparent member 4. Examples of the transparent member 4 include glass plates, acrylic resin plates, polyethylene terephthalate resin plates, polyethylene naphthalate resin plates, polycarbonate resin plates, colorless polyimide resin plates, and other resin material plates.

[0081] The protective portion 3 may be provided with decorative printing 5, such as black printing, and it is preferable that the decorative printing 5 be provided on the peripheral edge of the transparent member 4.

[0082] The protective portion 3 may have a hard coat treatment, anti-reflective treatment, or the like applied to one or both sides.

[0083] The thickness of the transparent member 4 is not particularly limited and can be appropriately selected according to the purpose, but it is preferable to select it from a range of 50 μm to 5000 μm, for example.

[0084] The step of forming the photocurable composition layer involves, for example, dropping a predetermined amount of the photocurable composition of this embodiment onto the surface of the protective part 3 that has decorative printing. Next, as shown in Figure 1A, the protective part 3 is inverted so that the surface of the protective part 3 with decorative printing 5 and the surface of the display panel 2 with the image display section 6 face each other, and the display panel 2 and the protective part 3 are placed on top of each other. As a result, the photocurable composition 11 is interposed between the display panel 2 and the protective part 3 so as to extend across the image display section 6 and the frame 7, and a photocurable composition layer 12 is formed as shown in Figure 1B.

[0085] The process of forming the cured layer involves, for example, irradiating the photocurable composition layer 12 with light 21 from the protective part 3 side, as shown in Figure 1B, to photocur it. This forms the cured layer 13 as shown in Figure 1C.

[0086] The direction of irradiation of light 21 is not particularly limited, but from the viewpoint of uniformly photocuring the photocurable composition in the photocurable composition layer 12, it is preferable that it be in a direction perpendicular to the surface of the protective portion 3.

[0087] Referring to Figure 1B, light 21 typically has the same wavelength as the excitation wavelength of the phosphor 14 containing inorganic material. By irradiating with light 21, the phosphor 14 containing inorganic material is excited and emits fluorescence including fluorescence 22. At this time, the photopolymerization initiator (not shown) present in the lower part of the decorative print 5, i.e., the light-shielding part, absorbs the fluorescence including fluorescence 22 and emits radicals or cations. As a result, the photocurable compound present in the light-shielding part polymerizes and curing proceeds. Therefore, the manufacturing method of this embodiment has excellent curing properties for the light-shielding part. Note that the photocurable composition present in the part that is not the light-shielding part may be photocured by fluorescence 22 alone, or by fluorescence 22 and light 21.

[0088] Furthermore, the manufacturing method of this embodiment allows the photocurable composition in the light-shielding portion to be cured solely by photocuring, thus eliminating the need for thermal curing.

[0089] Since the phosphor 14 has a volume-average particle diameter of 400 nm or less, the photocurable composition layer 12 and the cured product layer 13 are less affected by coloring and / or turbidity in the visible light region. Therefore, the manufacturing method of this embodiment is less affected by coloring and / or turbidity in the visible light region. Since the phosphor 14 has a volume-average particle diameter of 10 nm or more, it has good luminescence efficiency. Therefore, the manufacturing method of this embodiment can sufficiently cure the photocurable composition layer 12.

[0090] The thickness of the cured layer 13 is not particularly limited, and can be appropriately selected depending on the purpose, but it is preferable to select it from a range of 50 μm to 250 μm.

[0091] The image display device manufactured by the manufacturing method of this embodiment comprises a display panel having an image display section and a frame surrounding the image display section, and a protective section disposed on the display panel, wherein a cured material layer is interposed between the display panel and the protective section, and the cured material layer is formed by photocuring the photocurable composition of this embodiment. Since the image display device manufactured by the manufacturing method of this embodiment is manufactured using the photocurable composition of this embodiment, thermal curing is not required when manufacturing the image display device, the curing of the light-shielding section is excellent, and the influence of coloration in the visible light region is small.

[0092] The image display device manufactured by the manufacturing method of this embodiment is not particularly limited and can be applied to a variety of devices, including instrument panels and center information displays for mobile phones, portable game devices, vehicles, and display devices for amusement machines.

[0093] According to the present invention, when manufacturing an image display device having a light-shielding portion, it is possible to provide a photocurable composition that does not require thermal curing, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region. Furthermore, according to the present invention, it is possible to provide a method for manufacturing an image display device that does not require thermal curing, has excellent curability of the light-shielding portion, and has little influence of coloring and / or turbidity in the visible light region.

[0094] 2: Display panel 3: Protective part 4: Transparent component 5: Decorative printing 6: Image display section 7: Frame 8: Backlight 11: Photocurable composition 12: Photocurable composition layer 13: Cured material layer 14: Inorganic phosphor 21: Light 22: Fluorescence

Claims

1. A photocurable composition comprising a photocurable compound, a photopolymerization initiator, and a phosphor having an inorganic substance, wherein the phosphor has a volume-average particle diameter of 10 to 400 nm.

2. The photocurable composition according to claim 1, wherein the phosphor is excited by light with a wavelength of 800 to 1200 nm and emits fluorescence with a wavelength of 365 to 405 nm.

3. The photocurable composition according to claim 1, wherein the phosphor is excited by light with a wavelength of 325 to 395 nm and emits fluorescence with a wavelength of 365 to 405 nm.

4. The photocurable composition according to any one of claims 1 to 3, wherein the photocurable compound is at least one selected from the group consisting of compounds having a (meth)acrylic group and compounds having an epoxy group.

5. A method for manufacturing an image display device, wherein a display panel having an image display unit and a frame surrounding the image display unit and a protective unit are laminated with a cured material layer in between, the method comprising: interposing a photocurable composition according to any one of claims 1 to 3 between the display panel and the protective unit so as to extend across the image display unit and the frame to form a photocurable composition layer; and photocuring the photocurable composition layer to form a cured material layer.

Images