Transparent adhesive sheet
View Patent ↗A photocurable adhesive sheet that can be photocured even if there are places such as print-concealed sections that are difficult for light to reach, and even if the adhesive sheet has a certain degree of thickness, the entire sheet can be cured. A transparent adhesive sheet formed from an adhesive composition containing: (A) a thermoplastic resin; (B) a crosslinking agent; (C) a photopolymerization initiator that reacts with light having a wavelength of at least 380 to 430 nm; and (D) a wavelength conversion agent that is excited by light having a wavelength shorter than 380 nm and that emits light having a wavelength of 380 to 550 nm. The transparent adhesive sheet is characterized by the adhesive sheet absorbance X at a wavelength of 390 nm and the adhesive sheet thickness Y satisfying relational formula (1): 0.5≤ X/Y ≤12. Formula (1):
1. A transparent adhesive sheet, comprising an adhesive composition comprising:
(A) a thermoplastic resin;
(B) a crosslinking agent;
(C) a photopolymerization initiator that reacts with light having a wavelength of at least 380 to 430 nm; and
(D) a wavelength conversion agent that is excited by light having a wavelength shorter than 380 nm and that emits light having a wavelength of 380 to 550 nm,
wherein an absorbance X of the transparent adhesive sheet at a wavelength of 390 nm and a thickness Y (mm) of the transparent adhesive sheet satisfy the following relational formula (1):
0.5≤ X/Y≤ 12, Formula (1):
provided that:
X =-Log ( T/ 100),
where T is a transmittance (%) for a wavelength of 390 nm, and
the thermoplastic resin (A) is an acrylic series copolymer which comprises a graft copolymer having a macromonomer as a branch component.
2. The transparent adhesive sheet according to claim 1 , wherein the wavelength conversion agent (D) is a material compatible with the thermoplastic resin (A).
3. The transparent adhesive sheet according to claim 1 , having a hot-melting property of being softened or flowed by heating in an uncrosslinked state, and photo-crosslinkability of being crosslinked by light.
4. A transparent adhesive sheet, comprising an adhesive composition comprising:
(A) a thermoplastic resin;
(B) a crosslinking agent;
(C) a photopolymerization initiator that reacts with light having a wavelength of at least 380 to 430 nm; and
(D) a wavelength conversion agent that is excited by light having a wavelength shorter than 380 nm and that emits light having a wavelength of 380 to 550 nm,
wherein an absorbance X of the transparent adhesive sheet at a wavelength of 390 nm and a thickness Y (mm) of the transparent adhesive sheet satisfy the following relational formula (1):
0.5≤ X/Y≤ 12, Formula (1):
provided that:
X =-Log ( T/ 100),
where T is a transmittance (%) for a wavelength of 390 nm,
the thermoplastic resin (A) is formed by copolymerization of a monomer a having a glass transition temperature (Tg) of less than 0° C., a monomer b having a glass transition temperature (Tg) of 0° C. or more and less than 80° C., and a monomer c having a glass transition temperature (Tg) of 80° C. or more in a mole ratio of a:b:c=10 to 40:90 to 35:0 to 25, and
the thermoplastic resin (A) is a resin containing a (meth)acrylic acid ester copolymer or a vinyl copolymer having a weight average molecular weight of 50,000 to 400,000.
5. A transparent adhesive sheet, comprising an adhesive composition comprising:
(A) a thermoplastic resin;
(B) a crosslinking agent;
(C) a photopolymerization initiator that reacts with light having a wavelength of at least 380 to 430 nm; and
(D) a wavelength conversion agent that is excited by light having a wavelength shorter than 380 nm and that emits light having a wavelength of 380 to 550 nm,
wherein an absorbance X of the transparent adhesive sheet at a wavelength of 390 nm and a thickness Y (mm) of the transparent adhesive sheet satisfy the following relational formula (1):
0.5≤ X/Y≤ 12, Formula (1):
provided that:
X =-Log ( T/ 100),
where T is a transmittance (%) for a wavelength of 390 nm, and
the adhesive sheet has a release film on one of the front and back sides or on both sides, and at least the release film on one of the front and back sides is a film having a light transmittance of 40% or less of the light having a wavelength shorter than 380 nm.
6. The transparent adhesive sheet according to claim 4 , wherein the wavelength conversion agent (D) is a material compatible with the thermoplastic resin (A).
7. The transparent adhesive sheet according to claim 4 , having a hot-melting property of being softened or flowed by heating in an uncrosslinked state, and photo-crosslinkability of being crosslinked by light.
8. The transparent adhesive sheet according to claim 5 , wherein the wavelength conversion agent (D) is a material compatible with the thermoplastic resin (A).
9. The transparent adhesive sheet according to claim 5 , having a hot-melting property of being softened or flowed by heating in an uncrosslinked state, and photo-crosslinkability of being crosslinked by light.
10. The transparent adhesive sheet according to claim 5 , wherein the thermoplastic resin (A) is an acrylic series copolymer which comprises a graft copolymer having a macromonomer as a branch component.
11. The transparent adhesive sheet according to claim 5 ,
wherein the thermoplastic resin (A) is formed by copolymerization of a monomer a having a glass transition temperature (Tg) of less than 0° C., a monomer b having a glass transition temperature (Tg) of 0° C. or more and less than 80° C., and a monomer c having a glass transition temperature (Tg) of 80° C. or more in a mole ratio of a:b:c=10 to 40:90 to 35:0 to 25, and
the thermoplastic resin (A) is a resin containing a (meth)acrylic acid ester copolymer or a vinyl copolymer having a weight average molecular weight of 50,000 to 400,000.