Photocurable resin composition and method for manufacturing image display device

Abstract

To provide a photocurable resin composition capable of obtaining good adhesion after main curing.SOLUTION: A photocurable resin composition for cured resin layer 3 is used for manufacturing an image display device 1 in which an image display member 2 and a front face plate 4 are joined to each other through the cured resin layer 3, and contains a photoradical reactive component, a photopolymerization initiator and an ultraviolet absorber, in which the photopolymerization initiator is a photopolymerization initiator having a molar absorption coefficient to light at a wavelength of 365 nm of 1.2×102 ml / (g cm) or more, and the ultraviolet absorber is an ultraviolet absorber that absorbs light at a wavelength of 365 nm or more.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present technology relates to a photocurable resin composition and a method for producing an image display device. [Background technology]

[0002] In image display devices such as liquid crystal display panels used in information terminals such as smartphones, a photocurable resin composition is first disposed between an image display member such as a liquid crystal display panel or an organic EL panel and a front panel to form a curable resin layer. The curable resin layer is then irradiated with light to cure and become a cured resin layer. In this manner, the image display device is manufactured by adhering and laminating the image display member and the front panel.

[0003] As a method for manufacturing an image display device, for example, a method has been proposed that includes a step of irradiating light to a photocurable resin composition applied to at least one of a front panel and an image display member to form a provisionally cured layer, a step of bonding the front panel and the image display member via the provisionally cured layer, and a step of irradiating light to the provisionally cured layer after bonding to fully cure it (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-30274 A Summary of the Invention [Problem to be solved by the invention]

[0005] As a result of investigations conducted by the present inventors, it was found that when a material that transmits only long-wavelength ultraviolet light (e.g., wavelengths of 320 to 400 nm) is used as a front panel, it is difficult to obtain sufficient adhesion with conventional photocurable resin compositions.

[0006] Specifically, when considering the use of a member that transmits only long-wave ultraviolet light as the front panel, the photopolymerization initiator that is cleaved by long-wave ultraviolet light must remain in the provisionally cured layer during the final curing of the provisionally cured layer. However, the photopolymerization initiator that is cleaved by long-wave ultraviolet light is cleaved very quickly, and is unlikely to remain after the provisional curing of the photocurable resin composition.

[0007] The present technology has been proposed in view of the above-mentioned conventional circumstances, and provides a photocurable resin composition that provides good adhesion after main curing. [Means for solving the problem]

[0008] The present inventors have discovered that by using a photocurable resin composition containing a photopolymerization initiator that is cleaved by long-wave ultraviolet light and an ultraviolet absorber that absorbs long-wave ultraviolet light, it is possible to leave the photopolymerization initiator that is cleaved by long-wave ultraviolet light in the provisionally cured layer when the provisionally cured layer is fully cured, thereby making it possible to obtain good adhesion after fully cured.

[0009] The present technology relates to a photocurable resin composition for a cured resin layer, which is used for manufacturing an image display device in which an image display member and a front panel are bonded via a cured resin layer, and which contains a photoradical reactive component, a photopolymerization initiator, and an ultraviolet absorber, and the photopolymerization initiator has a molar absorption coefficient of 1.2 × 10 for light with a wavelength of 365 nm. 2 ml / (g cm) or more, and the ultraviolet absorber is an ultraviolet absorber that absorbs light with a wavelength of 365 nm or more.

[0010] The present technology relates to a photocurable resin composition for a cured resin layer, which is used for manufacturing an image display device in which an image display member and a front panel are bonded via a cured resin layer, and which contains a photoradical reactive component, a photopolymerization initiator, and an ultraviolet absorber, wherein the photopolymerization initiator is a photopolymerization initiator having a light absorption peak in a wavelength range of 350 to 400 nm, and the ultraviolet absorber is an ultraviolet absorber having a light absorption peak in a wavelength range of 340 to 400 nm.

[0011] The present technology is a manufacturing method of an image display device in which an image display member and a front panel are bonded via a cured resin layer, the method including the steps of: forming a curable resin layer made of a photocurable resin composition containing a photoradical curable component, a photopolymerization initiator, and an ultraviolet absorber on a surface of the image display member or the front panel; irradiating the curable resin layer with light to form a provisionally cured layer; bonding the image display member and the front panel via the provisionally cured layer; and irradiating the provisionally cured layer with light via the front panel to form the cured resin layer, the photopolymerization initiator having a molar absorption coefficient of 1.2×10 for light with a wavelength of 365 nm. 2 ml / (g·cm) or more, and the ultraviolet absorber in the photocurable resin composition is an ultraviolet absorber that absorbs light with a wavelength of 365 nm or more.

[0012] The present technology is a manufacturing method for an image display device in which an image display member and a front panel are bonded via a cured resin layer, the method including the steps of: forming a curable resin layer made of a photocurable resin composition containing a photoradical curable component, a photopolymerization initiator, and an ultraviolet absorber on a surface of the image display member or the front panel; irradiating the curable resin layer with light to form a provisionally cured layer; bonding the image display member and the front panel via the provisionally cured layer; and irradiating the provisionally cured layer with light via the front panel to form the cured resin layer, wherein the photopolymerization initiator is a photopolymerization initiator having a light absorption peak in the wavelength range of 350 to 400 nm, and the ultraviolet absorber is an ultraviolet absorber having a light absorption peak in the wavelength range of 340 to 400 nm. Effect of the Invention

[0013] According to the present technology, it is possible to provide a photocurable resin composition that exhibits good adhesion after main curing. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a cross-sectional view showing an example of an image display device. [Diagram 2]FIG. 2 is a cross-sectional view showing an example of step (A) of the method for producing an image display device. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of step (B) of the method for producing an image display device. [Figure 4] FIG. 4 is a cross-sectional view showing an example of step (B) of the method for producing an image display device. [Diagram 5] FIG. 5 is a cross-sectional view showing an example of step (C) of the method for producing an image display device. [Figure 6] FIG. 6 is a cross-sectional view showing an example of step (D) of the method for producing an image display device. [Figure 7] FIG. 7 is a perspective view illustrating a method for dropping a photocurable resin composition into openings in a spacer on a glass plate in the production of a laminate for evaluation. [Figure 8] FIG. 8 is a perspective view illustrating a method for adjusting the thickness of a curable resin layer using a squeegee in producing a laminate for evaluation. [Figure 9] FIG. 9 is a perspective view illustrating a method for provisionally curing a curable resin layer in the production of a laminate for evaluation. [Figure 10] FIG. 10(A) is an oblique view illustrating a method for fully curing a curable resin layer in producing a laminate for evaluation, FIG. 10(B) is a cross-sectional view illustrating an adhesive strength test of the laminate, and FIG. 10(C) is a plan view illustrating an adhesive strength test of the laminate. [Figure 11] FIG. 11 is a graph showing the transmittance of the polycarbonate plates used in the laminate for evaluation to light with wavelengths of 300 to 500 nm. [Figure 12] FIG. 12 is a graph showing the light transmittance of the cured resin layer. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] <Photocurable resin composition> The photocurable resin composition according to the present embodiment is a composition for a curable resin used for manufacturing an image display device in which an image display member and a front panel are bonded via a cured resin layer. The photocurable resin composition contains a photoradical reactive component, a photopolymerization initiator, and an ultraviolet absorber. The photopolymerization initiator has a molar absorption coefficient of 1.2×10 for light with a wavelength of 365 nm. 2 The photocurable resin composition according to the present embodiment contains a photopolymerization initiator having a light absorption peak in the wavelength range of 350 to 400 nm as a photopolymerization initiator, and a UV absorber having a light absorption peak in the wavelength range of 340 to 400 nm as a UV absorber. The UV absorber contains a UV absorber that absorbs light with a wavelength of 365 nm or more (hereinafter referred to as a UV absorber that absorbs long-wave UV light) as a photopolymerization initiator.

[0016] Here, the molar absorption coefficient ε (ml / (g cm)) of a photopolymerization initiator refers to the value calculated from the absorbance in the absorption spectrum obtained by dissolving the initiator in methanol or acetonitrile and measuring the absorption spectrum using a UV-Visible spectrophotometer.

[0017] [Photoradical reactive components] The photoradical reactive component includes, for example, a photoradical polymerizable poly(meth)acrylate and a photoradical polymerizable (meth)acrylate monomer.

[0018] [Photo-radical polymerizable poly(meth)acrylate] The photo-radical polymerizable poly(meth)acrylate may be a (meth)acrylate having an isoprene, urethane, isobutene, butadiene, etc., skeleton. In this specification, the (meth)acrylate includes both acrylate and methacrylate.

[0019] For example, the (meth)acrylate having a urethane bond is preferably an oligomer (urethane (meth)acrylate oligomer). The urethane (meth)acrylate oligomer preferably has, for example, 1 to 4 (meth)acrylic groups, and more preferably has 2 to 3 (meth)acrylic groups. Commercially available examples of (meth)acrylates having a urethane bond include Shikoh (registered trademark) UV-2000B, UV-2750B, UV-3000B, UV-3200B, UV-3210EA, UV-3300B, UV-3310B, UV-3500BA, UV-3520EA, UV-3700B, and UV-6640B (all manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), and Art Resin UN-6200, UN-6202, UN-6300, UN-6301, UN-7600, and UN-7700 (all manufactured by Negami Chemical Industry Co., Ltd.).

[0020] Commercially available polyisobutylene products include Oppanol B10SFN, Oppanol B11SFN, Oppanol B12SFN, Oppanol B13SFN, and Oppanol B14SFN manufactured by BASF.

[0021] The weight average molecular weight of the photoradically polymerizable poly(meth)acrylate is not particularly limited, and is, for example, 2,000 to 80,000.

[0022] In the photocurable resin composition, the content of the photoradical polymerizable poly(meth)acrylate is preferably 5 to 50 mass%, more preferably 5 to 30 mass%. The photoradical polymerizable poly(meth)acrylate may be used alone or in combination of two or more. When two or more types of photoradical polymerizable poly(meth)acrylate are used in combination, it is preferable that the total amount thereof satisfies the above content range.

[0023] [Photo-radical polymerizable (meth)acrylate monomer] The photoradical polymerizable (meth)acrylate monomer is used, for example, as a reactive diluent for imparting sufficient reactivity and coatability to a photocurable resin composition in the manufacturing process of an image display device. The photoradical polymerizable (meth)acrylate monomer is not particularly limited, but from the viewpoint of compatibility with other components, it is preferable to use a (meth)acrylate monomer having a cyclic structure or an alkyl (meth)acrylate monomer having 5 to 20 carbon atoms.

[0024] As the (meth)acrylate monomer having a cyclic structure, an acrylic monomer having a heterocycle such as a morpholine ring, a furan ring, or a dioxolane ring, or an acrylic monomer having an alicyclic hydrocarbon group can be used. The cyclic structure may be saturated or unsaturated. The cyclic structure may have a substituent. Specific examples include acryloylmorpholine, tetrahydrofurfuryl (meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolane-4-yl)methyl (meth)acrylate, isobornyl (meth)acrylate, etc. In addition, as the alkyl (meth)acrylate monomer having 5 to 20 carbon atoms, lauryl (meth)acrylate, isodecyl (meth)acrylate, stearyl (meth)acrylate, etc. can be mentioned.

[0025] In the photocurable resin composition, the content of the photoradical polymerizable (meth)acrylate monomer can be 10 to 80% by mass, or can be 20 to 50% by mass. The photoradical polymerizable (meth)acrylate monomer may be used alone or in combination of two or more. When two or more monomers are used in combination, it is preferable that the total amount thereof satisfies the above content range.

[0026] [Photopolymerization initiator] The photopolymerization initiator used in the present embodiment is cleaved by long-wave ultraviolet light, and is activated by irradiation with light having a wavelength of, for example, 365 nm or more, and is a component capable of curing the above-mentioned photoradical reactive component. The photopolymerization initiator has a light absorption peak in the wavelength range of 350 to 400 nm.

[0027] As such a photopolymerization initiator that is cleaved by long-wave ultraviolet light, for example, an acylphosphine-based photopolymerization initiator is preferable, and specific examples include 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, etc.

[0028] In the photocurable resin composition, the content of the photopolymerization initiator is preferably 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, based on 100 parts by mass of the total of the above-mentioned photoradical reactive components. By setting the content within such a range, it is possible to more effectively prevent insufficient curing during light irradiation and to more effectively prevent an increase in outgassing due to cleavage. In addition, in the photocurable resin composition, the content of the photopolymerization initiator is preferably, for example, 0.5 to 5% by mass. The photopolymerization initiator may be used alone or in combination of two or more types. When two or more types of photopolymerization initiators are used in combination, it is preferable that the total amount thereof satisfies the above range.

[0029] [Ultraviolet absorber] The photocurable resin composition according to the present embodiment contains an ultraviolet absorber that absorbs light with a wavelength of 365 nm or more (long-wave ultraviolet light), and in particular, preferably contains an ultraviolet absorber having a transmittance of 5% or less for light with a wavelength of 365 nm. The ultraviolet absorber has a light absorption peak in the wavelength range of 340 to 400 nm. By using such an ultraviolet absorber that absorbs long-wave ultraviolet light, when a member that transmits only long-wave ultraviolet light is used as a front plate in a manufacturing method for an image display device described later, the photopolymerization initiator that is cleaved by long-wave ultraviolet light can be left in the provisionally cured layer during the main curing of the provisionally cured layer, and good adhesion can be obtained after the main curing.

[0030] As the ultraviolet absorbing agent that absorbs long-wave ultraviolet light, a benzotriazole-based ultraviolet absorbing agent is preferable, and an ultraviolet absorbing agent represented by the following general formula is more preferable.

[0031] [ka] (In the formula, R 1 represents a substituent, R 2 represents a hydrogen atom or a substituent.

[0032] R 1 R is preferably an alkyl group or a phenyl group. The alkyl group is preferably a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms. 2 When represents a substituent, it is preferably an alkyl group. The alkyl group is preferably a linear alkyl group having 1 to 6 carbon atoms or a branched alkyl group having 3 to 6 carbon atoms, and more preferably a branched alkyl group having 3 to 6 carbon atoms substituted with a phenyl group.

[0033] Preferred specific examples of the benzotriazole-based ultraviolet absorber include 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN 900, manufactured by BASF), 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol (TINUVIN 928, manufactured by BASF), and 2-(2-hydroxy-5-t-butylphenyl)-2H-benzotriazole (TINUVIN PS, manufactured by BASF).

[0034] In the photocurable resin composition, the content of the ultraviolet absorber is preferably 0.5% by mass or more. By making the content of the ultraviolet absorber 0.5% by mass or more, the photopolymerization initiator cleaved by long-wave ultraviolet light can be more reliably left in the provisionally cured layer during the final curing of the provisionally cured layer, and good adhesion can be obtained after the final curing. In addition, the upper limit of the content of the ultraviolet absorber is not particularly limited, but is preferably 10% by mass or less. This can suppress the inhibition of the cleavage of the photopolymerization initiator during the provisional curing of the photocurable resin composition, and more effectively suppress insufficient curing. The ultraviolet absorber may be used alone or in combination of two or more types. When two or more types of ultraviolet absorbers are used in combination, it is preferable that the total amount thereof satisfies the above content range.

[0035] In addition, in the photocurable resin composition, the mass ratio (photopolymerization initiator / ultraviolet absorber) of the photopolymerization initiator cleaved by long-wave ultraviolet light to the ultraviolet absorber absorbing long-wave ultraviolet light is preferably 0.5 to 2.0. By setting the mass ratio at such a level, it is possible to effectively prevent insufficient effect during provisional curing of the photocurable resin composition, and to obtain good adhesion during final curing of the provisionally cured layer.

[0036] The photocurable resin composition may further contain other components in addition to the above-mentioned components, as long as the effects of the present technology are not impaired. Examples of the other components include a plasticizer and an antioxidant.

[0037] [Plasticizer] The plasticizer does not photo-cure by itself, for example, when irradiated with light, but gives flexibility to the cured resin layer after photo-cure. Examples of the plasticizer that can be used include a plasticizer having a weight-average molecular weight of 2000 or more and derived from ethylene glycol and propylene glycol, and a plasticizer having a weight-average molecular weight of 2000 or more and derived only from propylene glycol (a plasticizer made of polypropylene glycol).

[0038] The plasticizer preferably contains, for example, a compound represented by the following general formula. H-(-OC2H4-) n -(-OC3H6) m -OH In the formula, m is an integer of 25 to 138, preferably 35 to 100, more preferably 40 to 80, and further preferably 50 to 55. n is an integer of 8 to 50, preferably 10 to 30, and more preferably 15 to 20.

[0039] The weight average molecular weight of the plasticizer represented by the above general formula may be, for example, 3000 or more, 3500 or more, or 4000 or more. The upper limit of the weight average molecular weight of the plasticizer represented by the above general formula is not particularly limited, and may be, for example, 10000 or less, 8000 or less, or 6000 or less. As a commercially available product of the plasticizer represented by the above general formula, for example, EXCENOL 510 (Mw=4000) manufactured by Asahi Glass Co., Ltd. can be used.

[0040] In addition to the above-mentioned plasticizers, solid tackifiers and liquid oil components can also be used. Examples of solid tackifiers include terpene resins such as terpene resins, terpene phenol resins, and hydrogenated terpene resins, rosin resins such as natural rosin, polymerized rosin, rosin ester, and hydrogenated rosin, and terpene hydrogenated resins. In addition, non-reactive oligomers obtained by previously polymerizing the above-mentioned acrylic monomers to low molecular weight can also be used, and specific examples include copolymers of butyl acrylate, 2-hexyl acrylate, and acrylic acid, and copolymers of cyclohexyl acrylate and methacrylic acid. Examples of liquid oil components include polybutadiene oils and polyisoprene oils.

[0041] When the photocurable resin composition contains a plasticizer, the total content of the plasticizer in the photocurable resin composition is preferably 40 to 85% by mass, more preferably 40 to 60% by mass. The plasticizer may be used alone or in combination of two or more. When two or more plasticizers are used in combination, the total amount thereof preferably satisfies the above range.

[0042] [Antioxidants] The antioxidant is used, for example, for the purpose of preventing discoloration of the photocurable resin composition. The antioxidant is not particularly limited, and a known antioxidant can be used. For example, a compound having a hindered phenol structure, a compound having a hindered amine structure, a compound having a thioether structure, etc. can be mentioned.

[0043] Examples of commercially available compounds having a hindered phenol structure, which are examples of antioxidants, include: Examples include "IRGANOX1010", "IRGANOX1035", "IRGANOX1076", "IRGANOX1098", "IRGANOX1135", "IRGANOX1330", "IRGANOX1726", "IRGANOX1425WL", "IRGANOX1520L", "IRGANOX245", "IRGANOX259", "IRGANOX3114", "IRGANOX565", and "IRGAMOD295" (all manufactured by BASF).

[0044] When the photocurable resin composition contains an antioxidant, the total content of the antioxidant in the photocurable resin composition can be 0.1 to 10 mass%, or can be 0.5 to 3 mass%. The antioxidant may be used alone or in combination of two or more. When two or more antioxidants are used in combination, it is preferable that the total amount thereof satisfies the above content range.

[0045] As described above, the photocurable resin composition according to the present embodiment is a photocurable resin composition containing a photopolymerization initiator cleaved by long-wave ultraviolet light and an ultraviolet absorber absorbing long-wave ultraviolet light, and the light transmittance of a 150 μm-thick cured product (cured resin layer) at a wavelength of 365 nm is preferably 5% or less, more preferably 2% or less. By satisfying such physical properties, the photopolymerization initiator cleaved by long-wave ultraviolet light can be more reliably left in the provisionally cured layer during the main curing of the provisionally cured layer, and good adhesion can be obtained after the main curing. In addition, the photocurable resin composition according to the present embodiment is preferably a 150 μm-thick cured product (cured resin layer) at a wavelength of 405 nm, more preferably 80% or more, and even more preferably 90% or more. In addition, the photocurable resin composition according to the present embodiment is preferably a 150 μm-thick cured product (cured resin layer) at a wavelength of 550 nm, more preferably 90% or more. The light transmittance herein refers to a value measured at 25° C. using an ultraviolet-visible spectrophotometer (device name: UV-2450, manufactured by Shimadzu Corporation).

[0046] The photocurable resin composition is preferably in a liquid state at room temperature. For example, the photocurable resin composition preferably has a viscosity of 0.01 to 100 Pa·s at 25° C. as measured with a Brookfield viscometer.

[0047] The photocurable resin composition can be prepared by uniformly mixing the above-mentioned components according to a known mixing method.

[0048] <Image display device> As shown in FIG. 1, an image display device 1 according to the present embodiment includes an image display member 2, a cured resin layer 3, and a front panel 4 in this order.

[0049] The image display member 2 is, for example, an image display panel in which a polarizing plate is formed on the viewing side surface of an image display cell. Examples of the image display cell include a liquid crystal cell and an organic EL cell. Examples of the liquid crystal cell include a reflective liquid crystal cell and a transmissive liquid crystal cell. The image display member 2 is, for example, a liquid crystal display panel, an organic EL display panel, a touch panel, etc. Here, the touch panel means an image display / input panel that combines a display element such as a liquid crystal display panel with a position input device such as a touch pad.

[0050] The front plate 4 may be any material having optical transparency that allows the image formed on the image display member 2 to be visible, and examples of such materials include plate-like and sheet-like materials such as glass, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and polycarbonate. These materials may be hard-coated or anti-reflective on one or both sides. The physical properties of the front plate 4, such as the thickness and elastic modulus, may be appropriately determined depending on the intended use. The front plate 4 may be not only a relatively simple member as described above, but also a laminate of various sheets or film materials such as a touch panel module.

[0051] As described above, when a member that transmits only long-wave ultraviolet light (for example, light with a wavelength of 380 nm or more) is used as the front plate, the photopolymerization initiator that is cleaved by long-wave ultraviolet light must remain in the provisionally cured layer when the provisionally cured layer is fully cured. However, the photopolymerization initiator that is cleaved by long-wave ultraviolet light cleaves very quickly, and is unlikely to remain after the provisional curing of the photocurable resin composition, making it difficult to obtain good adhesion after the fully cured layer. Therefore, in the present technology, as described above, by using a photocurable resin composition containing a photopolymerization initiator that is cleaved by long-wave ultraviolet light and an ultraviolet absorber that absorbs long-wave ultraviolet light, the photopolymerization initiator that is cleaved by long-wave ultraviolet light can remain in the provisionally cured layer when the provisionally cured layer is fully cured, and good adhesion can be obtained after the fully cured layer.

[0052] A light-shielding layer 5 may be provided on the periphery of the front panel 4 to improve the contrast of the image. The light-shielding layer 5 can be formed, for example, by applying a paint colored black or the like by screen printing or the like, and then drying and curing the paint. The thickness of the light-shielding layer 5 is usually 5 to 100 μm.

[0053] The cured resin layer 3 is a cured product of the above-mentioned photocurable resin composition, and is obtained, for example, by photoradical polymerization of the photocurable resin composition by light irradiation in the atmosphere, so that the average reaction rate (curing rate) of the entire cured product is 90% or more (preferably 97% or more).

[0054] Here, the reaction rate is a value defined as the ratio (consumption rate) of the amount of (meth)acryloyl groups present after light irradiation to the amount of (meth)acryloyl groups present in the curable resin layer before light irradiation, and the larger this value is, the more curing has progressed. Specifically, the reaction rate is measured at 1640 to 1620 cm from the baseline in the FT-IR measurement chart of the curable resin layer before light irradiation. -1 and the absorption peak height (X) of 1640 to 1620 cm from the baseline in the FT-IR measurement chart of the curable resin layer (cured resin layer 3) after light irradiation. -1 and the absorption peak height (Y) of the sample in the above formula. Reaction rate (%)=[(XY) / X]×100

[0055] The cured resin layer 3 preferably has a transmittance of 90% or more in the visible light region. By satisfying such a range, the visibility of the image formed on the image display member 2 can be improved. The refractive index of the cured resin layer 3 is preferably approximately equal to the refractive index of the image display member 2 and the front panel 4. The refractive index of the cured resin layer 3 is preferably, for example, 1.45 or more and 1.55 or less. This can increase the brightness and contrast of the image light from the image display member 2, thereby improving visibility. The thickness of the cured resin layer 3 can be, for example, about 25 to 200 μm.

[0056] <Manufacturing method for image display device> The manufacturing method of the image display device according to this embodiment includes a step (A) of forming a curable resin layer made of the above-mentioned photocurable resin composition on the surface of a front panel, a step (B) of irradiating the curable resin layer with light to form a provisionally cured layer, a step (C) of bonding the image display member and the front panel via the provisionally cured layer, and a step (D) of irradiating the provisionally cured layer with light via the front panel to form a cured resin layer.

[0057] [Process (A)] In step (A), as shown in FIG. 2, for example, a photocurable resin composition 6 is applied to the surface of an image display member 2 to form a curable resin layer 7. Specifically, the photocurable resin composition 6 is preferably applied to the entire surface of the image display member 2 so as to form a flat layer. The thickness of the curable resin layer 7 may be, for example, 25 to 350 μm. The photocurable resin composition 6 may be applied in one step or multiple steps so long as a required thickness is obtained.

[0058] [Process (B)] In step (B), as shown in Fig. 3, the curable resin layer 7 formed in step (A1) is irradiated with light (e.g., ultraviolet light) to form a provisionally cured layer 8 as shown in Fig. 4. The reason for provisionally curing the curable resin layer 7 is to change the photocurable resin composition from a liquid state to a state in which it does not flow significantly, and to improve handleability by preventing the composition from flowing even when the composition is turned upside down.

[0059] The temporary curing of the curable resin layer 7 is preferably carried out so that the reaction rate of the temporary cured layer 8 is 10 to 99%, and may be 40 to 95%. The conditions of the light irradiation are not particularly limited as long as the temporary cured layer 8 can be cured so that the reaction rate is, for example, 10 to 99%. For example, an ultraviolet irradiation device (UV-LED) is used to irradiate ultraviolet light having an emission wavelength of 365±5 nm with an illuminance of 100 to 300 mW / cm. 2 , Accumulated light intensity 500~1500mJ / cm 2 It is preferable to irradiate under the conditions of the following. The remaining rate (%) of the photopolymerization initiator in the obtained provisionally cured layer 8 is preferably 40% or more, more preferably 44% or more, and even more preferably 50% or more. The method for measuring the remaining rate (%) of the photopolymerization initiator in the provisionally cured layer 8 is the same as the measurement method in the examples described later.

[0060] [Process (C)] [In step (C), as shown in Fig. 5, an image display member 2 is placed on the surface of the provisionally cured layer 8, and the image display member 2 and the front panel 4 are bonded together via the provisionally cured layer 8. The bonding can be performed, for example, by applying pressure at 10 to 80°C using a known pressure bonding device.

[0061] [Process (D)] In step (D), as shown in Fig. 6, the provisionally cured layer 8 is irradiated with light (e.g., ultraviolet light) through the front panel 4 to fully cure it. This provides an image display device 1 (see Fig. 1) in which the image display member 2 and the front panel 4 are laminated with the cured resin layer 6 interposed therebetween.

[0062] The partially cured layer 8 is preferably cured so that the reaction rate of the cured resin layer 6 is 90% or more, and more preferably 95% or more. The conditions for the partially cured layer 8 are not particularly limited as long as the cured resin layer 6 can be cured so that the reaction rate of the cured resin layer 6 is 90% or more. For example, an ultraviolet ray irradiation device (metal halide lamp) is used, and an integrated light amount of 1000 to 6000 mJ / cm is used. 2 It is preferable to carry out the reaction under the following conditions.

[0063] As described above, in the manufacturing method of the image display device according to the present embodiment, by using the photocurable resin composition 6 containing a photopolymerization initiator cleaved by long-wave ultraviolet light and an ultraviolet absorber that absorbs long-wave ultraviolet light, the photopolymerization initiator cleaved by long-wave ultraviolet light can be left in the provisionally cured layer 8 during the final curing of the provisionally cured layer 8, and good adhesion can be obtained after the final curing. In addition, by using the photocurable resin composition 6 containing a photopolymerization initiator cleaved by long-wave ultraviolet light and an ultraviolet absorber that absorbs long-wave ultraviolet light, the process margin during lamination after provisional curing can be improved.

[0064] In the above-mentioned manufacturing method for the image display device, an example has been described in which the photocurable resin composition 6 is applied to the surface of the image display member 2 in step (A), but the photocurable resin composition 6 may also be applied to the surface of the front panel 4 on which the light-shielding layer 5 is formed.

[0065] In addition, in the above-mentioned manufacturing method of the image display device, the case where the front panel 4 having the light-shielding layer 5 is used has been described, but the present invention is not limited to this example. For example, the image display device may be manufactured using a front panel that does not have the light-shielding layer 5.

[0066] As another method for manufacturing an image display device, a so-called dam-fill process may be adopted. The dam-fill process is a method in which, for example, a dam material is used to form a coating area of ​​a fill material on the surface of an image display member, the fill material is coated on the coating area, the image display member and a light-transmitting member are bonded together via the fill material, and light is irradiated onto the fill material to form a cured resin layer. EXAMPLES

[0067] Hereinafter, examples of the present technology will be described. Note that the present technology is not limited to these examples.

[0068] <Photoradical reactive components> UV-3700B: UV-curable urethane acrylate, manufactured by Nippon Synthetic Chemical Industry Co., Ltd. Oppanol B12SFN: Polyisobutylene, manufactured by BASF MEDOL-10: Monofunctional monomer ((2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl acrylate), manufactured by Osaka Organic Chemical Industry Co., Ltd. IBXA: Isobornyl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. LA: Lauryl acrylate, manufactured by Osaka Organic Chemical Industry Co., Ltd. <Plasticizer> EXCENOL 510: Polyether polyol (Mw: 4000), manufactured by Asahi Glass Co., Ltd. <Photopolymerization initiator> IRGACURE 184: 1-hydroxy-cyclohexyl-phenyl ketone, manufactured by BASF, absorption peak: around 240 nm, molar absorption coefficient for light with a wavelength of 365 nm: 8.864 x 10 1 ml / (g cm) (using MeOH) IRGACURE TPO: 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, manufactured by BASF, absorption peak: around 380 nm, molar absorption coefficient for light with a wavelength of 365 nm: 4.720 × 10 2 ml / (g cm) (MeOH used), molar absorption coefficient for light with a wavelength of 405 nm: 1.650×10 2 ml / (g cm) (using MeOH) IRGACURE 819: Bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, manufactured by BASF, Absorption peak: around 370 nm, Molar absorption coefficient for light with a wavelength of 365 nm: 2.309 x 10 3 ml / (g cm) (MeOH used), molar absorption coefficient for light with a wavelength of 405 nm: 8.990×10 2ml / (g cm) (using MeOH) <Antioxidants> IRGANOX 1135: Octyl 3-(4-hydroxy-3,5-diisopropylphenyl)propionate, manufactured by BASF <Ultraviolet absorbing agent> TINUVIN 928: 2-(2H-benzotriazol-2-yl)-6-(1-methyl-1-phenylethyl)-4-(1,1,3,3-tetramethylbutyl)phenol, manufactured by BASF, absorption peak: around 349 nm (in toluene, using 1 cm cell) TINUVIN PS: 2-(2-hydroxy-5-t-butylphenyl)-2H-benzotriazole, manufactured by BASF, absorption peak: around 342 nm (in toluene, using a 1 cm cell)

[0069] <Preparation of Photocurable Resin Composition> <Example 1> A photocurable resin composition was prepared consisting of 20 parts by mass of ultraviolet-curable urethane acrylate (UV-3700B), 30 parts by mass of monofunctional monomer (MEDOL-10), 1 part by mass of photopolymerization initiator (IRGACURE TPO), 1 part by mass of antioxidant (IRGANOX 1135), 50 parts by mass of plasticizer (EXCENOL 510), and 1 part by mass of ultraviolet absorber (TINUVIN 928).

[0070] <Comparative Example 1> A photocurable resin composition was prepared in the same manner as in Example 1, except that the ultraviolet absorber (TINUVIN 928) was not added.

[0071] <Example 2> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.5 parts by mass.

[0072] <Comparative Example 2> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.4 parts by mass.

[0073] <Comparative Example 3> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.3 parts by mass.

[0074] <Comparative Example 4> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.2 parts by mass.

[0075] <Comparative Example 5> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.1 parts by mass.

[0076] <Example 3> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the photopolymerization initiator (IRGACURE TPO) was changed to 0.5 parts by mass.

[0077] <Example 4> A photocurable resin composition was prepared in the same manner as in Example 1, except that the amount of the photopolymerization initiator (IRGACURE TPO) was changed to 5 parts by mass, and the amount of the ultraviolet absorber (TINUVIN 928) was changed to 3 parts by mass.

[0078] <Example 5> A photocurable resin composition was prepared in the same manner as in Example 4, except that 10 parts by mass of TINUVIN PS was used as the ultraviolet absorbent.

[0079] <Example 6> A photocurable resin composition was prepared in the same manner as in Example 1, except that the photopolymerization initiator (IRGACURE TPO) was changed to an equal amount of IRGACURE 819.

[0080] <Example 7> A photocurable resin composition was prepared in the same manner as in Example 6, except that the amount of the photopolymerization initiator (IRGACURE 819) was changed to 0.5 parts by mass.

[0081] <Example 8> A photocurable resin composition was prepared in the same manner as in Example 1, except that the ultraviolet absorber (TINUVIN 928) was changed to an equal amount of TINUVIN PS.

[0082] <Example 9> A photocurable resin composition was prepared in the same manner as in Example 8, except that the amount of the ultraviolet absorber (TINUVIN 928) was changed to 0.5 parts by mass.

[0083] <Comparative Example 6> A photocurable resin composition was prepared in the same manner as in Comparative Example 1, except that the photopolymerization initiator (IRGACURE TPO) was changed to an equal amount of IRGACURE 184.

[0084] <Example 10> A photocurable resin composition was prepared consisting of 30 parts by mass of Oppanol B12SFN, 40 parts by mass of IBXA, 30 parts by mass of LA, 1 part by mass of a photopolymerization initiator (IRGACURE TPO), and 1 part by mass of an ultraviolet absorber (TINUVIN 928).

[0085] [Preparation of laminate for evaluation] 7, a spacer 10 having a thickness of 150 μm and an opening with a diameter of 6 mm was placed on a glass plate 9 having a thickness of 1 mm. A photocurable resin composition 6 was dropped onto the spacer so as to cover the opening.

[0086] 8, the photocurable resin composition 6 on the spacers 10 was removed using a squeegee 11, and the thickness of the curable resin layer 7 was adjusted to 150 μm. Thereafter, the spacers 10 were removed from the glass plate 9.

[0087] As shown in FIG. 9, the curable resin layer 7 is irradiated with an ultraviolet ray irradiation device 12 (UV-LED, model: H-4MLH200-V1, manufactured by HOYA Corporation) shown in Table 1 below, with an accumulated light amount of 1000 mJ / cm 2 2 So, 200mW / cm 2The coating was irradiated with strong ultraviolet light (emission wavelength: 365±5 nm) for 5 seconds to form a provisionally cured layer 8. As shown in Table 2, the reaction rate of the provisionally cured layer 8 obtained in each of the examples and comparative examples was in the range of 40 to 99%.

[0088] [Table 1]

[0089] As shown in Fig. 10(A), a glass plate 9 with a provisionally cured layer 8 was attached to the surface of a polycarbonate plate 13 (thickness 2.0 mm) via the provisionally cured layer 8, to obtain a laminate in which the glass plate 9 and the polycarbonate plate 13 were joined via the provisionally cured layer 8. The provisionally cured layer 8 of the obtained laminate was irradiated with an integrated light amount of 5000 mJ / cm2 via the polycarbonate plate 13 using an ultraviolet irradiation device 14 (metal halide lamp). 2 The provisionally cured layer 8 was completely cured (mainly cured) by irradiating it with ultraviolet light so that the provisionally cured layer 8 became completely cured (mainly cured). As a result, a laminate for evaluation was obtained in which the polycarbonate plate 13 and the glass plate 9 were bonded together via the cured resin layer 3 having a diameter of 6 mm and a thickness of 150 μm.

[0090] [Initiator remaining rate after temporary curing] The residual rate (%) of the photopolymerization initiator in the provisionally cured layer 8 was measured by the following method. In the preparation of the laminate for evaluation described above, the same amount of the photocurable resin composition 6 before provisional curing and the provisionally cured layer 8 were weighed out, and each was contacted with a predetermined solvent at room temperature for a certain time to extract the photopolymerization initiator contained therein. The obtained extract was subjected to an ultra-high performance liquid chromatograph (manufactured by Shimadzu Corporation, product name: Nexera X2) to measure the height of the peak derived from the photopolymerization initiator, and the ratio (H2 / H1) between the height (H1) of the peak derived from the photopolymerization initiator extracted from the photocurable resin composition 6 and the height (H2) of the peak derived from the photopolymerization initiator extracted from the provisionally cured layer 8 was calculated, and the residual rate (%) of the photopolymerization initiator was calculated by the calculation formula of the ratio (H2 / H1) x 100. In practical use, it is desirable that the residual rate of the photopolymerization initiator is 40% or more. The results are shown in Table 2.

[0091] [Adhesiveness after temporary curing] In producing the laminate for evaluation described above, the process margin during lamination after forming the provisionally cured layer 8 was evaluated. Specifically, the time from forming the provisionally cured layer 8 until laminating the glass plate 9 with the provisionally cured layer 8 on the surface of the polycarbonate plate 13 was set to several seconds, and the case where no air bubbles were generated in the provisionally cured layer 8 was evaluated as OK, and the case where air bubbles were generated in the provisionally cured layer 8 was evaluated as NG. The results are shown in Table 2.

[0092] [Adhesive strength after full curing] As shown in Figures 10(B) and (C), for the laminate for evaluation obtained by the above-mentioned preparation of the laminate for evaluation, the glass plate 9 located on the lower side of the laminate was fixed, and the polycarbonate plate 13 located on the upper side was lifted up vertically at a speed of 5 mm / min using a jig 15, and the adhesive state was evaluated according to the following criteria. Shimadzu Corporation's AGS-X was used to measure the adhesive strength. Adhesive strength (N / cm 2 ) was calculated by measuring the stress required until the glass plate 9 and the polycarbonate plate 13 separated at 25°C and dividing the stress by the unit area of ​​the cured resin layer 3. In practice, the adhesive strength is 10 N / cm 2 The results are shown in Table 2.

[0093] [Light transmittance] In preparing the laminate for evaluation described above, the transmittance (25°C) of the cured resin layer 3 for light with wavelengths of 365 nm, 405 nm, and 550 nm was measured using an ultraviolet-visible spectrophotometer (device name: UV-2450, manufactured by Shimadzu Corporation). The results are shown in Table 2. For practical purposes, it is desirable that the transmittance of the cured resin layer 3 for light with a wavelength of 365 nm is 5% or less. Note that FIG. 11 is a graph showing the transmittance of the polycarbonate plate 13 used in the laminate for evaluation for light with a wavelength of 300 to 500 nm. From this result, it can be seen that the polycarbonate plate 13 transmits only long-wave ultraviolet light (light with a wavelength of 380 nm or more).

[0094] Fig. 12 is a graph showing the light transmittance of a cured resin layer made of a photocurable resin composition containing an ultraviolet absorber, measured at 25° C. Specifically, Fig. 12(A) to (D) show the results for the cured resin layer in the evaluation laminate produced using the photocurable resin compositions of Examples 1, 2, 8, and 9.

[0095] [Table 2]

[0096] As shown in the examples, it was found that a photocurable resin containing a photoradical reactive component, a photopolymerization initiator that is cleaved by long-wave ultraviolet light, and an ultraviolet absorber that absorbs long-wave ultraviolet light can provide better adhesion after full curing. It was also found that the process margin during lamination after temporary curing is wider.

[0097] As in Comparative Examples 1 to 5, if the content of the ultraviolet absorbing agent that absorbs long-wave ultraviolet rays is too small or if no ultraviolet absorbing agent that absorbs long-wave ultraviolet rays is contained, the residual rate of the photopolymerization initiator in the provisionally cured layer becomes low, and it is found that good adhesion cannot be obtained after main curing. Also, in Comparative Example 1, it was found that the process margin during lamination is narrow.

[0098] It was found that, when only the photopolymerization initiator cleaved by short-wave ultraviolet light was contained as in Comparative Example 6, the residual rate of the photopolymerization initiator after provisional curing was good, but good adhesion could not be obtained after main curing. This is thought to be because the provisionally cured layer did not contain a photopolymerization initiator cleaved by long-wave ultraviolet light, and therefore the provisionally cured layer could not be crosslinked even when irradiated with ultraviolet light through a polycarbonate plate. [Explanation of symbols]

[0099] REFERENCE SIGNS LIST 1 image display device, 2 image display member, 3 cured resin layer, 4 front panel, 5 light-shielding layer, 6 photocurable resin composition, 7 curable resin layer, 8 provisionally cured layer, 9 glass plate, 10 spacer, 11 squeegee, 12 ultraviolet ray irradiation device, 13 polycarbonate plate, 14 ultraviolet ray irradiation device, 15 tool

Claims

1. A photocurable resin composition for the cured resin layer, which is used for producing an image display device in which an image display member and a front panel are bonded via a cured resin layer, A photoradical reactive component; A photopolymerization initiator; An ultraviolet absorber; A plasticizer is included, The photopolymerization initiator has a molar absorption coefficient of 1.2×10 ２ ml / (g cm) or more, The ultraviolet absorber is an ultraviolet absorber that absorbs light having a wavelength of 365 nm or more, the photoradical reactive component includes a polyether-based urethane acrylate which is a photoradical polymerizable poly(meth)acrylate, and a photoradical polymerizable (meth)acrylate monomer, the photoradical polymerizable (meth)acrylate monomer includes a (meth)acrylate monomer having a heterocycle; The content of the photoradical polymerizable poly(meth)acrylate is 5 to 50% by mass, The content of the photoradical polymerizable (meth)acrylate monomer is 10 to 80% by mass, The content of the ultraviolet absorber is 0.5% by mass or more, A photocurable resin composition in which the mass ratio of the photopolymerization initiator to the ultraviolet absorber (photopolymerization initiator / ultraviolet absorber) is 0.5 to 2.

0.

2. A photocurable resin composition for the cured resin layer, which is used for producing an image display device in which an image display member and a front panel are bonded via a cured resin layer, A photoradical reactive component; A photopolymerization initiator; An ultraviolet absorber; A plasticizer is included, The photopolymerization initiator is a photopolymerization initiator having a light absorption peak in a wavelength range of 350 to 400 nm, The ultraviolet absorber is an ultraviolet absorber having a light absorption peak in a wavelength range of 340 to 400 nm, the photoradical reactive component includes a polyether-based urethane acrylate which is a photoradical polymerizable poly(meth)acrylate, and a photoradical polymerizable (meth)acrylate monomer, the photoradical polymerizable (meth)acrylate monomer includes a (meth)acrylate monomer having a heterocycle; The content of the photoradical polymerizable poly(meth)acrylate is 5 to 50% by mass, The content of the photoradical polymerizable (meth)acrylate monomer is 10 to 80% by mass, The content of the ultraviolet absorber is 0.5% by mass or more, A photocurable resin composition in which the mass ratio of the photopolymerization initiator to the ultraviolet absorber (photopolymerization initiator / ultraviolet absorber) is 0.5 to 2.

0.

3. The photocurable resin composition according to claim 1 or 2, wherein the photopolymerization initiator contains an acylphosphine-based photopolymerization initiator.

4. A method for manufacturing an image display device in which an image display member and a front panel are bonded via a cured resin layer, comprising the steps of: forming a curable resin layer on a surface of the image display member or the front panel, the curable resin layer being made of a photocurable resin composition containing a photoradical reactive component, a photopolymerization initiator, an ultraviolet absorber, and a plasticizer; A step of irradiating the curable resin layer with light to form a provisionally cured layer; a step of bonding the image display member and the front panel via the provisionally cured layer; and irradiating the provisionally cured layer with light through the front plate to form the cured resin layer. The photopolymerization initiator has a molar absorption coefficient of 1.2×10 ２ ml / (g cm) or more, The ultraviolet absorber is an ultraviolet absorber that absorbs light having a wavelength of 365 nm or more, the photoradical reactive component includes a polyether-based urethane acrylate which is a photoradical polymerizable poly(meth)acrylate, and a photoradical polymerizable (meth)acrylate monomer, the photoradical polymerizable (meth)acrylate monomer includes a (meth)acrylate monomer having a heterocycle; In the photocurable resin composition, the content of the photoradical polymerizable poly(meth)acrylate is 5 to 50 mass %, the content of the photoradical polymerizable (meth)acrylate monomer is 10 to 80 mass %, the content of the ultraviolet absorber is 0.5 mass % or more, and the mass ratio of the photopolymerization initiator to the ultraviolet absorber (photopolymerization initiator / ultraviolet absorber) is 0.5 to 2.

0.

5. A method for manufacturing an image display device in which an image display member and a front panel are bonded via a cured resin layer, comprising the steps of: forming a curable resin layer on a surface of the image display member or the front panel, the curable resin layer being made of a photocurable resin composition containing a photoradical reactive component, a photopolymerization initiator, an ultraviolet absorber, and a plasticizer; A step of irradiating the curable resin layer with light to form a provisionally cured layer; a step of bonding the image display member and the front panel via the provisionally cured layer; and irradiating the provisionally cured layer with light through the front plate to form the cured resin layer. The photopolymerization initiator is a photopolymerization initiator having a light absorption peak in a wavelength range of 350 to 400 nm, The ultraviolet absorber is an ultraviolet absorber having a light absorption peak in the wavelength range of 340 to 400 nm, the photoradical reactive component includes a polyether-based urethane acrylate which is a photoradical polymerizable poly(meth)acrylate, and a photoradical polymerizable (meth)acrylate monomer, the photoradical polymerizable (meth)acrylate monomer includes a (meth)acrylate monomer having a heterocycle; In the photocurable resin composition, the content of the photoradical polymerizable poly(meth)acrylate is 5 to 50 mass %, the content of the photoradical polymerizable (meth)acrylate monomer is 10 to 80 mass %, the content of the ultraviolet absorber is 0.5 mass % or more, and the mass ratio of the photopolymerization initiator to the ultraviolet absorber (photopolymerization initiator / ultraviolet absorber) is 0.5 to 2.

0.

6. The method for manufacturing an image display device according to claim 4 , wherein the temporarily cured layer has a residual rate of the photopolymerization initiator of 40% or more.

7. 7. The method for manufacturing an image display device according to claim 4, wherein the front panel has a light transmittance of 0% at a wavelength of 365 nm and a light transmittance of 80% or more at a wavelength of 405 nm.

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