Provided are a resin composition for sealing an optical semiconductor providing both UV transmission and heat resistance, and a molded resin product for sealing an optical semiconductor, an optical semiconductor-sealing material, and an optical semiconductor device each including the same. The resin composition satisfies the relationship X=(A1×A2)/A3+(B1×B2)/B3+ . . . <0.0005 wherein A1 represents the mass ratio of an aromatic compound, A2 represents the number of aromatic rings per molecule of the aromatic compound, A3 represents the molecular weight of the aromatic compound, and A, B, . . . each represent an aromatic compound. The composition contains an epoxy, an alicyclic acid anhydride, and an antioxidant. When formed into a cured product (size: 50 mm in width×50 mm in length×1 mm in thickness), a linear transmittance at 300 nm is 80% or higher and a linear transmittance at 400 nm is 95% or higher.

Provided are a resin composition for sealing an optical semiconductor providing both UV transmission and heat resistance, and a molded resin product for sealing an optical semiconductor, an optical semiconductor-sealing material, and an optical semiconductor device each including the same. The resin composition satisfies the relationship X=(A1×A2)/A3+(B1×B2)/B3+ . . . <0.0005 wherein A1 represents the mass ratio of an aromatic compound, A2 represents the number of aromatic rings per molecule of the aromatic compound, A3 represents the molecular weight of the aromatic compound, and A, B, . . . each represent an aromatic compound. The composition contains an epoxy, an alicyclic acid anhydride, and an antioxidant. When formed into a cured product (size: 50 mm in width×50 mm in length×1 mm in thickness), a linear transmittance at 300 nm is 80% or higher and a linear transmittance at 400 nm is 95% or higher.

A novel photosensitive adhesive composition including the following components (A), (B), (C), and (D): Component (A): a polymer having a structural unit of the following formula (1) and a structure of the following formula (2) at a terminal, Component (B): a polymer having the structural unit of formula (1), and a carboxy group or hydroxy group at a terminal, Component (C): a radical photopolymerization initiator, and Component (D): a solvent, wherein the content by mass of the component (B) is larger than that of the component (A), ##STR00001##
(wherein X is a C.sub.1-6 alkyl group, a vinyl group, an allyl group, or a glycidyl group, m and n are each independently 0 or 1, Q is a divalent C.sub.1-16 hydrocarbon group, Z is a divalent C.sub.1-4 linking group, the divalent linking group being bonded to an O group in formula (1), and R.sup.1 is a hydrogen atom or a methyl group.)

A novel photosensitive adhesive composition including the following components (A), (B), (C), and (D): Component (A): a polymer having a structural unit of the following formula (1) and a structure of the following formula (2) at a terminal, Component (B): a polymer having the structural unit of formula (1), and a carboxy group or hydroxy group at a terminal, Component (C): a radical photopolymerization initiator, and Component (D): a solvent, wherein the content by mass of the component (B) is larger than that of the component (A), ##STR00001##
(wherein X is a C.sub.1-6 alkyl group, a vinyl group, an allyl group, or a glycidyl group, m and n are each independently 0 or 1, Q is a divalent C.sub.1-16 hydrocarbon group, Z is a divalent C.sub.1-4 linking group, the divalent linking group being bonded to an O group in formula (1), and R.sup.1 is a hydrogen atom or a methyl group.)

A novel photosensitive adhesive composition including the following components (A), (B), (C), and (D): Component (A): a polymer having a structural unit of the following formula (1) and a structure of the following formula (2) at a terminal, Component (B): a polymer having the structural unit of formula (1), and a carboxy group or hydroxy group at a terminal, Component (C): a radical photopolymerization initiator, and Component (D): a solvent, wherein the content by mass of the component (B) is larger than that of the component (A),

##STR00001##

(wherein X is a C.sub.1-6 alkyl group, a vinyl group, an allyl group, or a glycidyl group, m and n are each independently 0 or 1, Q is a divalent C.sub.1-16 hydrocarbon group, Z is a divalent C.sub.1-4 linking group, the divalent linking group being bonded to an O group in formula (1), and R.sup.1 is a hydrogen atom or a methyl group.)

One embodiment is a pressure sensitive adhesive label or tape that comprises a facestock, and a pressure sensitive adhesive composition disposed on the facestock and the pressure sensitive adhesive composition includes a product made from reacting an epoxidized naturally occurring oil or fat with a dimer acid. Another embodiment of the invention is a method that comprises reacting an epoxidized naturally occurring oil or fat with a dimer acid to form a PSA precursor; coating the PSA precursor onto a carrier and curing the PSA precursor via UV radiation to form a pressure sensitive adhesive.