Adhesive sheet and optical semiconductor device

Abstract

To provide an adhesive sheet having high light extraction function and excellent reliability.SOLUTION: An adhesive sheet 1 comprises a substrate part 4, and an adhesive part 2 formed on one side of substrate part 4. The adhesive part 2 includes a first adhesive layer 21 and a second adhesive layer 22. The adhesive sheet 1 has a lamination structure in which the first adhesive layer 21, the second adhesive layer 22 and the substrate part 4 are laminated in this order. A visible light transmittance T1 of the first adhesive layer 21 and a visible light transmittance T2 of the second adhesive layer 22 satisfy T1<T2. A storage modulus G1'of the first adhesive layer 21 at 90°C is 35 to 100 kPa.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a pressure-sensitive adhesive sheet and an optical semiconductor device. [Background technology]

[0002] In recent years, self-emitting display devices, such as mini / micro light-emitting diode displays (LED displays), have been devised as next-generation display devices. Mini / micro LED displays basically use a substrate, on which optical semiconductor elements such as many tiny LED light-emitting elements (LED chips) are densely arranged, as a display panel, with the LED chips sealed with a sealing material and a cover member such as a resin film or glass plate laminated on the outermost surface.

[0003] There are several types of self-luminous display devices such as mini / micro LED display devices, including a white backlight type, a white-emitting color filter type, and an RGB type. In the white-emitting color filter type and RGB type, a black encapsulant is sometimes used to prevent reflection of metal wiring and metal oxides such as ITO arranged on the display panel substrate (see, for example, Patent Documents 1 to 3). In particular, in RGB-type mini / micro LED display devices in which LED chips are arranged, the black encapsulant can also contribute to preventing RGB color mixing and improving contrast. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-204905 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-203810 [Patent Document 3] Special Publication No. 2018-523854 Summary of the Invention [Problem to be solved by the invention]

[0005] When the black sealing material described in Patent Documents 1 to 3 is used, the upper part (image display side) of an optical semiconductor element such as an LED chip is covered with a black sealing material having a reduced transmittance for visible light, resulting in a problem that the light extraction function deteriorates and the image becomes dark.

[0006] In order to suppress the deterioration of the light extraction function, it is conceivable to reduce the thickness of the black sealing material when sealing the optical semiconductor element. For example, it is conceivable to increase the flexibility of the black sealing material so that the thickness of the black sealing material is reduced by compression when sealing the optical semiconductor element. However, if the flexibility of the black sealing material is high, there is a problem of poor reliability, such as a change in the transmittance of the black sealing material or the generation of voids (foaming) when exposed to high temperatures.

[0007] The present invention has been conceived under such circumstances, and its object is to provide an adhesive sheet having a high light extraction function and excellent reliability.

Means for Solving the Problems

[0008] As a result of intensive studies to achieve the above object, the present inventors have found that according to a specific adhesive sheet, the light extraction function is high and the reliability is excellent. The present invention has been completed based on these findings.

[0009] That is, the present invention includes a base material portion and an adhesive portion formed on one surface of the base material portion, The adhesive portion includes a first adhesive layer and a second adhesive layer, The first adhesive layer, the second adhesive layer, and the base material portion have a laminated structure laminated in this order, The visible light transmittance T1 of the first adhesive layer and the visible light transmittance T2 of the second adhesive layer satisfy T1 < T2, The storage elastic modulus G1' of the first adhesive layer at 90°C is 35 to 100 kPa, and an adhesive sheet is provided.

[0010] The storage modulus G1' and the storage modulus G2' at 90°C of the second pressure-sensitive adhesive layer preferably satisfy the relationship G1' / G2'<1.3.

[0011] The first pressure-sensitive adhesive layer preferably contains a colorant.

[0012] The colorant preferably contains carbon black.

[0013] The thickness of the first pressure-sensitive adhesive layer is preferably 5 to 10 μm.

[0014] The pressure-sensitive adhesive sheet is preferably a sheet for encapsulating one or more optical semiconductor elements arranged on a substrate.

[0015] The present invention also provides an optical semiconductor device comprising: a substrate; an optical semiconductor element disposed on the substrate; and the pressure-sensitive adhesive sheet or a cured product thereof that seals the optical semiconductor element. [Effects of the Invention]

[0016] The pressure-sensitive adhesive sheet of the present invention has high light extraction function and excellent reliability, and can therefore be preferably used as a sheet for encapsulating optical semiconductor elements. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of a pressure-sensitive adhesive sheet according to one embodiment of the present invention. [Figure 2] 2 is a partial cross-sectional view showing one embodiment of a state in which an optical semiconductor element is encapsulated using the pressure-sensitive adhesive sheet shown in FIG. 1. FIG. [Figure 3] 2 is a partial cross-sectional view showing one embodiment of an optical semiconductor device using the pressure-sensitive adhesive sheet shown in FIG. 1. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0018] [Adhesive sheet] An adhesive sheet according to one embodiment of the present invention comprises at least a substrate and an adhesive portion formed on one surface of the substrate. The adhesive portion comprises at least a first adhesive layer and a second adhesive layer. The adhesive sheet has a layered structure in which the first adhesive layer, the second adhesive layer, and the substrate are layered in this order. The adhesive sheet may also have layers other than these layers.

[0019] The pressure-sensitive adhesive sheet is preferably used for bonding to the uneven surface of an adherend having an uneven shape, and is particularly preferably a sheet for encapsulating optical semiconductor elements. In this specification, the term "sheet for encapsulating optical semiconductor elements" refers to a sheet for encapsulating one or more optical semiconductor elements arranged on a substrate with an adhesive sheet. In this specification, "encapsulating an optical semiconductor element" refers to embedding at least a portion of the optical semiconductor element within the adhesive sheet (particularly within the adhesive portion) or covering the optical semiconductor element with the adhesive sheet (particularly the adhesive portion). The adhesive sheet (particularly the adhesive portion) has flexibility that allows it to embed at least a portion of the optical semiconductor element or to cover the optical semiconductor element with the adhesive sheet (particularly the adhesive portion).

[0020] Each layer constituting the adhesive portion (such as the first adhesive layer and the second adhesive layer) may be a single layer or multiple layers having the same or different compositions. When multiple layers are included, the multiple layers may be stacked in contact with each other or may be stacked separately.

[0021] In the above adhesive sheet, the visible light transmittance T1 of the first adhesive layer and the visible light transmittance T2 of the second adhesive layer satisfy T1 < T2. That is, the visible light transmittance of the first adhesive layer is lower than that of the second adhesive layer. Such a configuration is preferable when the adhesive sheet is used as a sheet for encapsulating an optoelectronic device in that the first adhesive layer prevents reflection by metal wiring or the like on the display panel and prevents color mixing between the arranged optoelectronic devices, thereby improving the contrast. Also, in such a configuration, the second adhesive layer having a higher visible light transmittance than the first adhesive layer is positioned above the optoelectronic device (image display side), improving the light extraction function, brightening the image, and reducing the power consumption due to an increase in output for enhancing the emission luminance. That is, according to the above adhesive sheet, by having the above configuration, it is possible to improve the light extraction function and also achieve effects such as an antireflection function for metal wiring or the like, prevention of color mixing of RGB, and improvement of contrast, which are in a trade-off relationship with this.

[0022] (First adhesive layer) The storage elastic modulus (storage elastic modulus G1') of the first adhesive layer at 90°C is 35 to 100 kPa, preferably 37 to 95 kPa, more preferably 40 to 90 kPa. When the storage elastic modulus G1' is 35 kPa or more, the fluidity of the first adhesive layer at high temperature is low, and aggregation of components that may be contained in the first adhesive layer such as pigments hardly occurs. Therefore, for example, when used by bonding to an adherend having an uneven shape, even when exposed to a high temperature during bonding such as encapsulation of an optoelectronic device or in other use processes, the optical properties of the first adhesive layer and the adhesive sheet hardly change, and voids hardly occur, and the reliability is excellent. Also, when the storage elastic modulus G1' is 100 kPa or less, when used by bonding to an adherend having an uneven shape, the first adhesive layer is easily compressed appropriately, so that the thickness of the first adhesive layer positioned above the optoelectronic device (image display side) becomes appropriate, the light extraction function is high, and voids are hardly formed.

[0023] The storage modulus G1' of the first pressure-sensitive adhesive layer is measured by the following method using a laminate in which the first pressure-sensitive adhesive layer is laminated to a thickness of 1 mm as a measurement sample. Specifically, the laminate is cut to a diameter of 8 mm to prepare a test piece. Using an 8 mm diameter jig, temperature dispersion is performed from -50 to 150°C using a TA Instruments viscoelasticity analyzer "ARES-G2." The temperature rise rate is 5°C / min, the frequency is 1 Hz, and the strain is 0.1%, and the modulus at 90°C is taken as the storage modulus. In more detail, it can be measured by the method described in the Examples below.

[0024] The storage modulus G1' of the first adhesive layer can be adjusted, for example, by the type and amount of monomer components constituting the base polymer that can be contained in the adhesive layer, the amount of other monomer components, the type and amount of crosslinking agent, etc.

[0025] The visible light transmittance (visible light transmittance T1) of the first pressure-sensitive adhesive layer is not particularly limited, and may be, for example, 80% or less, and may be 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less. When the visible light transmittance T1 of the first pressure-sensitive adhesive layer is 80% or less, the transmittance can be made lower than the visible light transmittance T2 of the second pressure-sensitive adhesive layer, and by sealing the gap between the metal wiring and the optical semiconductor element when the optical semiconductor element is encapsulated, reflection of the metal wiring and the like can be prevented, color mixing between the optical semiconductor elements can be prevented, and contrast can be further improved.

[0026] The visible light transmittance T1 of the first pressure-sensitive adhesive layer can be measured in detail by the method described in the Examples below.

[0027] The visible light transmittance T1 of the first pressure-sensitive adhesive layer can be adjusted, for example, by the type and amount of colorant that can be contained in the pressure-sensitive adhesive layer.

[0028] The first pressure-sensitive adhesive layer is preferably a layer intended to prevent light reflection from metal wiring or the like provided on a substrate in an image display device.

[0029] The adhesive constituting the first adhesive layer can be any known or commonly used adhesive and is not particularly limited. For example, depending on the type of base polymer, examples include acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine-based adhesives, and styrene adhesives. Among these, acrylic adhesives are preferred as adhesives constituting the adhesive layer in terms of adhesion, weather resistance, cost, and ease of adhesive design. One or more of the above adhesives may be used.

[0030] The acrylic pressure-sensitive adhesive contains an acrylic polymer as a base polymer. That is, the base polymer is preferably an acrylic polymer. In this specification, the base polymer refers to a main component among the polymer components in the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer, for example, a polymer component contained in an amount of more than 50% by mass. The content of the base polymer in the pressure-sensitive adhesive layer is preferably 60% by mass or more, more preferably 70% by mass or more, relative to the total amount of the pressure-sensitive adhesive layer (100% by mass).

[0031] The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth)acryloyl group in the molecule) as a monomer component constituting the polymer. That is, the acrylic polymer contains a structural unit derived from the acrylic monomer. Only one type of acrylic polymer may be used, or two or more types may be used. Furthermore, the acrylic polymer may contain only one type of acrylic monomer as a monomer component, or two or more types. In this specification, "(meth)acrylic" refers to "acrylic" and / or "methacrylic" (either one or both of "acrylic" and "methacrylic"), and the same applies to other terms.

[0032] The acrylic polymer is preferably a polymer containing the largest amount of structural units derived from (meth)acrylic acid esters by mass. Examples of the (meth)acrylic acid ester include hydrocarbon group-containing (meth)acrylic acid esters. Examples of the hydrocarbon group-containing (meth)acrylic acid ester include (meth)acrylic acid alkyl esters having a linear or branched aliphatic hydrocarbon group, (meth)acrylic acid esters having an alicyclic hydrocarbon group such as (meth)acrylic acid cycloalkyl esters, and (meth)acrylic acid esters having an aromatic hydrocarbon group such as (meth)acrylic acid aryl esters. The hydrocarbon group-containing (meth)acrylic acid esters may be used singly or in combination of two or more.

[0033] Examples of the (meth)acrylic acid alkyl ester include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, butyl (meth)acrylate, isobutyl (meth)acrylate, s-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate, isopentyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, and methyl (meth)acrylate. Examples of the acrylate include isooctyl (meth)acrylate, nonyl (meth)acrylate, isononyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate (lauryl (meth)acrylate), tridecyl (meth)acrylate, tetradecyl (meth)acrylate, pentadecyl (meth)acrylate, hexadecyl (meth)acrylate, heptadecyl (meth)acrylate, octadecyl (meth)acrylate, nonadecyl (meth)acrylate, and eicosyl (meth)acrylate.

[0034] Among the above (meth)acrylic acid alkyl esters, (meth)acrylic acid alkyl esters having a linear or branched aliphatic hydrocarbon group with a carbon number of 1 to 20 (preferably 2 to 12, more preferably 2 to 8) are preferred. When the carbon number is within the above range, the storage stability tends to be better.

[0035] In the first pressure-sensitive adhesive layer, the (meth)acrylic acid alkyl ester preferably includes a (meth)acrylic acid alkyl ester having a linear or branched aliphatic hydrocarbon group having 1 to 6 carbon atoms (sometimes referred to as "(meth)acrylic acid alkyl ester (A)") and a (meth)acrylic acid alkyl ester having a linear or branched aliphatic hydrocarbon group having 7 to 12 carbon atoms (sometimes referred to as "(meth)acrylic acid alkyl ester (B)"), from the viewpoint of facilitating the setting of the storage modulus G1' within the above range.

[0036] In order to properly exhibit the basic properties such as adhesiveness of the (meth)acrylic acid alkyl ester in the adhesive layer, the proportion of the (meth)acrylic acid alkyl ester is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. Also, from the viewpoint of copolymerizing other monomer components and obtaining the effects of the other monomer components, the proportion is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0037] The proportion of the (meth)acrylic acid alkyl ester (A) in the (meth)acrylic acid alkyl ester is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, relative to the total amount (100% by mass) of the (meth)acrylic acid alkyl ester, from the viewpoint of easily adjusting the storage modulus G1' within the above range. Moreover, the proportion is preferably 90% by mass or less, more preferably 80% by mass or less, and even more preferably 70% by mass or less.

[0038] The proportion of the (meth)acrylic acid alkyl ester (B) in the (meth)acrylic acid alkyl ester is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more, relative to the total amount (100% by mass) of the (meth)acrylic acid alkyl ester, from the viewpoint of easily setting the storage modulus G1' within the above range. Moreover, the proportion is preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 40% by mass or less.

[0039] Examples of the (meth)acrylic acid ester having an alicyclic hydrocarbon group include (meth)acrylic acid esters having a monocyclic aliphatic hydrocarbon ring such as cyclopentyl (meth)acrylate, cyclohexyl (meth)acrylate, cycloheptyl (meth)acrylate, and cyclooctyl (meth)acrylate; (meth)acrylic acid esters having a bicyclic aliphatic hydrocarbon ring such as isobornyl (meth)acrylate; and (meth)acrylic acid esters having a tricyclic or higher aliphatic hydrocarbon ring such as dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, tricyclopentanyl (meth)acrylate, 1-adamantyl (meth)acrylate, 2-methyl-2-adamantyl (meth)acrylate, and 2-ethyl-2-adamantyl (meth)acrylate.

[0040] The proportion of the (meth)acrylic acid ester having an alicyclic hydrocarbon group is preferably 0.6% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more, relative to the total amount (100% by mass) of monofunctional monomers constituting the acrylic polymer, and is preferably 20% by mass or less, more preferably 12% by mass or less.

[0041] Examples of the (meth)acrylic acid ester having an aromatic hydrocarbon group include (meth)acrylic acid phenyl ester and (meth)acrylic acid benzyl ester.

[0042] The proportion of the (meth)acrylic acid ester having an aromatic hydrocarbon group is preferably less than 33% by mass, more preferably 32% by mass or less, relative to the total amount (100% by mass) of monofunctional monomers constituting the acrylic polymer, and may be 5% by mass or more, or 10% by mass or more.

[0043] The proportion of the hydrocarbon group-containing (meth)acrylic ester is preferably 40% by mass or more, more preferably 60% by mass or more, and even more preferably 70% by mass or more, based on the total amount (100% by mass) of monofunctional monomers constituting the acrylic polymer. From the viewpoint of copolymerizing other monomer components and obtaining the effects of the other monomer components, the proportion is preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less.

[0044] The acrylic polymer may contain structural units derived from other monomer components copolymerizable with the hydrocarbon group-containing (meth)acrylic acid ester for the purpose of improving cohesive strength, heat resistance, etc. Examples of the other monomer components include polar group-containing monomers such as hydroxy group-containing monomers, nitrogen atom-containing monomers, carboxy group-containing monomers, acid anhydride monomers, keto group-containing monomers, alkoxysilyl group-containing monomers, glycidyl group-containing monomers, sulfonic acid group-containing monomers, and phosphate group-containing monomers. Of the polar group-containing monomers, hydroxy group-containing monomers are preferred. The polar group-containing monomers may be used alone or in combination of two or more.

[0045] Examples of the hydroxy group-containing monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 10-hydroxydecyl (meth)acrylate, 12-hydroxylauryl (meth)acrylate, and (4-hydroxymethylcyclohexyl)methyl (meth)acrylate.

[0046] Examples of the nitrogen atom-containing monomer include amide group-containing monomers, amino group-containing monomers, cyano group-containing monomers, and monomers having a nitrogen atom-containing ring. Examples of the amide group-containing monomer include (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-butyl(meth)acrylamide, N-methylol(meth)acrylamide, N-methylolpropane(meth)acrylamide, N-methoxymethyl(meth)acrylamide, and N-butoxymethyl(meth)acrylamide. Examples of the amino group-containing monomer include aminoethyl(meth)acrylate, N,N-dimethylaminoethyl(meth)acrylate, and t-butylaminoethyl(meth)acrylate. Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile. Examples of the monomer having a nitrogen atom-containing ring include N-vinyl-2-pyrrolidone, N-methylvinylpyrrolidone, N-vinylpyridine, N-vinylpiperidone, N-vinylpyrimidine, N-vinylpiperazine, N-vinylpyrazine, N-vinylpyrrole, N-vinylimidazole, N-vinyloxazole, N-vinylmorpholine, N-vinylcaprolactam, and N-(meth)acryloylmorpholine.

[0047] Examples of the carboxy group-containing monomer include acrylic acid, methacrylic acid, carboxyethyl (meth)acrylate, carboxypentyl (meth)acrylate, itaconic acid, maleic acid, fumaric acid, crotonic acid, etc. Examples of the acid anhydride monomer include maleic anhydride, itaconic anhydride, etc.

[0048] Examples of the keto group-containing monomer include diacetone (meth)acrylamide, diacetone (meth)acrylate, vinyl methyl ketone, vinyl ethyl ketone, allyl acetoacetate, and vinyl acetoacetate.

[0049] Examples of the alkoxysilyl group-containing monomer include 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, 3-(meth)acryloxypropylmethyldimethoxysilane, and 3-(meth)acryloxypropylmethyldiethoxysilane.

[0050] Examples of the glycidyl group-containing monomer include glycidyl (meth)acrylate and methylglycidyl (meth)acrylate.

[0051] Examples of the sulfonic acid group-containing monomer include styrenesulfonic acid, allylsulfonic acid, 2-(meth)acrylamido-2-methylpropanesulfonic acid, (meth)acrylamidopropanesulfonic acid, sulfopropyl (meth)acrylate, and (meth)acryloyloxynaphthalenesulfonic acid.

[0052] Examples of the phosphate group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

[0053] The proportion of the polar group-containing monomer is not particularly limited, but from the viewpoint of better exerting the effect of using the polar group-containing monomer, it is preferably 0.1% by mass or more, more preferably 0.5% by mass or more, and even more preferably 1% by mass or more, relative to the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. Furthermore, the proportion is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 15% by mass or less. Furthermore, it is preferable that the proportion of the hydroxy group-containing monomer is within the above range.

[0054] The monomer components constituting the acrylic polymer may further contain other monomers. Examples of the other monomers include vinyl ester monomers such as vinyl acetate, vinyl propionate, and vinyl laurate; aromatic vinyl compounds such as styrene, substituted styrenes (such as α-methylstyrene), and vinyltoluene; olefin monomers such as ethylene, propylene, isoprene, butadiene, and isobutylene; chlorine-containing monomers such as vinyl chloride and vinylidene chloride; alkoxy group-containing monomers such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; and vinyl ether monomers such as methyl vinyl ether and ethyl vinyl ether. Each of the other monomer components may be used singly or in combination of two or more.

[0055] Examples of the alkoxy group-containing monomer include those in which one or more hydrogen atoms in the hydrocarbon group of the hydrocarbon group-containing (meth)acrylic ester are substituted with alkoxy groups, and examples include hydrocarbon group-containing (meth)acrylic esters having an alkoxy group, such as methoxymethyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, 2-methoxybutyl (meth)acrylate, 2-ethoxyethyl (meth)acrylate, and ethoxyethoxyethyl (meth)acrylate (ethyl carbitol (meth)acrylate).

[0056] The proportion of the other monomers may be, for example, 0.05% by mass or more, 0.5% by mass or more, 5% by mass or more, or 10% by mass or more relative to the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. The proportion may be, for example, 20% by mass or less, 10% by mass or less, 5% by mass or less, or may be substantially zero.

[0057] The acrylic polymer may contain a structural unit derived from a polyfunctional (meth)acrylate copolymerizable with the monomer components constituting the acrylic polymer to form a crosslinked structure in the polymer skeleton. Examples of the polyfunctional (meth)acrylate include hexanediol di(meth)acrylate, (poly)ethylene glycol di(meth)acrylate, (poly)propylene glycol di(meth)acrylate, neopentyl glycol di(meth)acrylate, pentaerythritol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol hexa(meth)acrylate. The polyfunctional monomer may be used alone or in combination of two or more.

[0058] In order to properly exhibit the basic properties of the hydrocarbon group-containing (meth)acrylic acid ester, such as adhesiveness and adhesion to the adherend, in the adhesive layer, the content of the polyfunctional monomer relative to 100 parts by mass of the total amount of monofunctional monomers constituting the acrylic polymer is preferably 0.001 to 1 part by mass, more preferably 0.01 to 0.1 part by mass.

[0059] The acrylic polymer can be obtained by polymerizing the various monomer components described above. The polymerization method is not particularly limited, but examples thereof include solution polymerization, emulsion polymerization, bulk polymerization, and polymerization by active energy ray irradiation (active energy ray polymerization). The obtained acrylic polymer can be any of a random copolymer, a block copolymer, a graft copolymer, and the like.

[0060] Various common solvents may be used in the polymerization of the monomer components. Examples of the solvent include organic solvents such as esters such as ethyl acetate and n-butyl acetate; aromatic hydrocarbons such as toluene and benzene; aliphatic hydrocarbons such as n-hexane and n-heptane; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; and ketones such as methyl ethyl ketone and methyl isobutyl ketone. One or more of the solvents may be used.

[0061] The polymerization initiator, chain transfer agent, emulsifier, etc. used in the radical polymerization of the monomer components are not particularly limited and can be appropriately selected and used. The weight-average molecular weight of the acrylic polymer can be controlled by the amounts of the polymerization initiator and chain transfer agent used and the reaction conditions, and the amounts used are appropriately adjusted depending on the types of these.

[0062] As the polymerization initiator used for polymerizing the monomer components, a thermal polymerization initiator, a photopolymerization initiator (photoinitiator), etc. can be used depending on the type of polymerization reaction. Only one of the above polymerization initiators may be used, or two or more of them may be used.

[0063] The thermal polymerization initiator is not particularly limited, but examples thereof include azo-based polymerization initiators, peroxide-based polymerization initiators, redox-based polymerization initiators, etc. The amount of the thermal polymerization initiator used is preferably 1 part by mass or less, more preferably 0.005 to 1 part by mass, and even more preferably 0.02 to 0.5 parts by mass, per 100 parts by mass of the total amount of the monofunctional monomers constituting the acrylic polymer.

[0064] Examples of the photopolymerization initiator include benzoin ether-based photopolymerization initiators, acetophenone-based photopolymerization initiators, α-ketol-based photopolymerization initiators, aromatic sulfonyl chloride-based photopolymerization initiators, photoactive oxime-based photopolymerization initiators, benzoin-based photopolymerization initiators, benzyl-based photopolymerization initiators, benzophenone-based photopolymerization initiators, ketal-based photopolymerization initiators, thioxanthone-based photopolymerization initiators, acylphosphine oxide-based photopolymerization initiators, titanocene-based photopolymerization initiators, etc. Among these, acetophenone-based photopolymerization initiators are preferred.

[0065] Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, 4-(t-butyl)dichloroacetophenone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and methoxyacetophenone.

[0066] The amount of the photopolymerization initiator used is preferably 0.005 to 1 part by mass, more preferably 0.01 to 0.7 parts by mass, and even more preferably 0.18 to 0.5 parts by mass, relative to 100 parts by mass of the total amount of the monofunctional monomers constituting the acrylic polymer. When the amount used is 0.005 part by mass or more, it is easy to control the molecular weight of the acrylic polymer to be small, and the conformability to the uneven structure tends to be better.

[0067] The acrylic polymer may have a structural moiety derived from a crosslinking agent. For example, the acrylic polymer may be crosslinked to further reduce low-molecular-weight substances in the pressure-sensitive adhesive layer. Furthermore, the weight-average molecular weight of the acrylic polymer may be increased. The crosslinking agent may be used alone or in combination with two or more other crosslinking agents.

[0068] Examples of the crosslinking agent include an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, a melamine-based crosslinking agent, a peroxide-based crosslinking agent, a urea-based crosslinking agent, a metal alkoxide-based crosslinking agent, a metal chelate-based crosslinking agent, a metal salt-based crosslinking agent, a carbodiimide-based crosslinking agent, an oxazoline-based crosslinking agent, an aziridine-based crosslinking agent, an amine-based crosslinking agent, a silicone-based crosslinking agent, and a silane-based crosslinking agent.

[0069] Examples of the isocyanate-based crosslinking agent (polyfunctional isocyanate compound) include lower aliphatic polyisocyanates such as 1,2-ethylene diisocyanate, 1,4-butylene diisocyanate, and 1,6-hexamethylene diisocyanate; alicyclic polyisocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate, isophorone diisocyanate, hydrogenated tolylene diisocyanate, and hydrogenated xylene diisocyanate; and aromatic polyisocyanates such as 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and xylylene diisocyanate. Examples of the isocyanate crosslinking agent include a trimethylolpropane / tolylene diisocyanate adduct, a trimethylolpropane / hexamethylene diisocyanate adduct, and a trimethylolpropane / xylylene diisocyanate adduct.

[0070] The content of the crosslinking agent is not particularly limited, but is preferably 5 parts by mass or less, more preferably 0.001 to 5 parts by mass, and even more preferably 0.01 to 3 parts by mass, relative to 100 parts by mass of the total amount of monofunctional monomers that form the acrylic polymer.

[0071] The first pressure-sensitive adhesive layer preferably contains a colorant. The colorant may be a dye or a pigment, as long as it is soluble or dispersible in the first pressure-sensitive adhesive layer. Dyes are preferred because they can achieve low haze even with a small amount of addition, do not sediment like pigments, and are easily distributed uniformly. Pigments are also preferred because they provide high color expression even with a small amount of addition. When using a pigment as a colorant, it is preferable that it has low or no conductivity. When using a dye, it is preferable to use it in combination with an antioxidant, etc., as described below. The above colorants may be used alone or in combination with two or more types.

[0072] The colorant is preferably a black colorant. Known or commonly used black colorants (pigments, dyes, etc.) can be used as the black colorant. Examples include carbon black (furnace black, channel black, acetylene black, thermal black, lamp black, pine soot, etc.), graphite, copper oxide, manganese dioxide, aniline black, perylene black, titanium black, cyanine black, activated carbon, ferrite (non-magnetic ferrite, magnetic ferrite, etc.), magnetite, chromium oxide, iron oxide, molybdenum disulfide, chromium complexes, anthraquinone-based colorants, and zirconium nitride. A colorant functioning as a black colorant may also be used by combining colorants exhibiting colors other than black. Among the colorants, carbon black and zirconium nitride are preferred, and carbon black is more preferred, from the viewpoint of further reducing the visible light transmittance T1 even when the thickness of the first adhesive layer is thin.

[0073] When the first pressure-sensitive adhesive layer is a radiation-curable pressure-sensitive adhesive layer, the colorant preferably absorbs visible light and is transparent to light of a wavelength at which the radiation-curable pressure-sensitive adhesive layer can be cured.

[0074] From the viewpoint of imparting an appropriate anti-reflection function to the adherend, the content of the colorant in the first pressure-sensitive adhesive layer is preferably 0.04% by mass or more, more preferably 0.1% by mass or more, or even 0.2% by mass or more, or 0.4% by mass or more, relative to 100% by mass of the total amount of the first pressure-sensitive adhesive layer. The content of the colorant is, for example, 20% by mass or less, preferably 10% by mass or less, and more preferably 5% by mass or less. The content may be appropriately set depending on the type of colorant, the color tone and light transmittance of the pressure-sensitive adhesive layer, and the like. The colorant may be added to the composition as a solution or dispersion dissolved or dispersed in an appropriate solvent.

[0075] The first pressure-sensitive adhesive layer may contain other components in addition to the above-mentioned components, provided that the effects of the present invention are not impaired. Examples of such other components include curing agents, crosslinking accelerators, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), antioxidants, fillers (metal powders, organic fillers, inorganic fillers, etc.), antioxidants, plasticizers, softeners, surfactants, antistatic agents, surface lubricants, leveling agents, light stabilizers, UV absorbers, polymerization inhibitors, granular materials, foil-like materials, silane coupling agents, light-diffusing fine particles, crosslinking catalysts, and crosslinking inhibitors. Only one of the above other components may be used, or two or more may be used.

[0076] When the first pressure-sensitive adhesive layer contains the silane coupling agent, the adhesive reliability to glass (particularly the adhesive reliability to glass in a high-temperature, high-humidity environment) is improved.

[0077] Examples of the silane coupling agent include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-phenyl-aminopropyltrimethoxysilane, and 3-acryloxypropyltrimethoxysilane. Among these, γ-glycidoxypropyltrimethoxysilane is preferred. The silane coupling agents may be used alone or in combination of two or more.

[0078] The content of the silane coupling agent in the first pressure-sensitive adhesive layer is not particularly limited, but is preferably 0.01 to 1 part by mass, and more preferably 0.03 to 0.5 parts by mass, per 100 parts by mass of the total amount of the base polymer.

[0079] The thickness of the first pressure-sensitive adhesive layer (total thickness of the multiple layers when multiple layers are present) is preferably 0.5 μm or more, more preferably 2 μm or more, and even more preferably 5 μm or more, from the viewpoint of imparting an appropriate anti-reflection function to the adherend. Furthermore, from the viewpoint of making the first pressure-sensitive adhesive layer thinner on the upper part (image display side) of the optical semiconductor element, the thickness is preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 10 μm or less. The thickness of the first pressure-sensitive adhesive layer is the thickness when uncompressed before being attached to the adherend.

[0080] Furthermore, from the viewpoint of imparting an appropriate anti-reflection function to the adherend, the thickness of the first pressure-sensitive adhesive layer is preferably 0.1 times or more, more preferably 0.2 times or more, and even more preferably 0.3 times or more, the height of the optical semiconductor element. Furthermore, from the viewpoint of making the first pressure-sensitive adhesive layer thinner on the upper part (image display side) of the optical semiconductor element, the thickness is preferably 2.0 times or less, more preferably 1.5 times or less, and even more preferably 1.2 times or less, the height of the optical semiconductor element. The thickness of the first pressure-sensitive adhesive layer is the thickness in an uncompressed state before being attached to the adherend.

[0081] (Second adhesive layer) The visible light transmittance (visible light transmittance T2) of the second pressure-sensitive adhesive layer is not particularly limited, but may be, for example, 85% or more (upper limit 100%), 88% or more, 90% or more, or 92% or more. When the second pressure-sensitive adhesive layer has high transmittance, the light extraction efficiency is further improved when the pressure-sensitive adhesive sheet is used as a sheet for encapsulating an optical semiconductor element.

[0082] The visible light transmittance T2 of the second pressure-sensitive adhesive layer can be measured in detail by the method described in the Examples below.

[0083] The visible light transmittance T2 of the second pressure-sensitive adhesive layer can be adjusted, for example, by the type and amount of colorant that can be contained in the pressure-sensitive adhesive layer.

[0084] The storage modulus (storage modulus G2') of the second pressure-sensitive adhesive layer at 90°C is preferably 20 to 600 kPa, more preferably 30 to 300 kPa, and more preferably 40 to 200 kPa. When the storage modulus G2' is within the above range, the first pressure-sensitive adhesive layer can be appropriately compressed when attached to an adherend having an uneven surface, and the light extraction function is further improved.

[0085] The storage modulus G2' of the second pressure-sensitive adhesive layer is measured by the following method using a laminate in which the second pressure-sensitive adhesive layer is laminated to a thickness of 1 mm as a measurement sample. Specifically, the laminate is cut to a diameter of 8 mm to prepare a test piece. Using an 8 mm diameter jig, temperature dispersion is performed from -50 to 150°C using a TA Instruments viscoelasticity analyzer "ARES-G2." The temperature rise rate is 5°C / min, the frequency is 1 Hz, and the strain is 0.1%, and the modulus at 90°C is taken as the storage modulus. In more detail, it can be measured by the method described in the Examples below.

[0086] The storage modulus G2' of the second adhesive layer can be adjusted, for example, by the type and amount of monomer components constituting the base polymer that can be contained in the adhesive layer, the amount of other monomer components, the type and amount of crosslinking agent, etc.

[0087] The second adhesive layer is preferably a layer (non-colored layer) that is not intended to prevent light reflection from metal wiring or the like provided on the substrate of the display. The second adhesive layer may be a colorless layer or may be slightly colored. The second adhesive layer may be transparent or non-transparent.

[0088] The content of the colorant in the second adhesive layer is preferably less than 0.2% by mass, more preferably less than 0.1% by mass, and even more preferably less than 0.05% by mass, relative to 100% by mass of the total amount of the second adhesive layer, and may be less than 0.01% by mass or less than 0.005% by mass.

[0089] The adhesive constituting the second adhesive layer can be any known or commonly used adhesive and is not particularly limited. Examples of such adhesives include, depending on the type of base polymer, acrylic adhesives, rubber adhesives (natural rubber, synthetic rubber, mixtures thereof, etc.), silicone adhesives, polyester adhesives, urethane adhesives, polyether adhesives, polyamide adhesives, fluorine-based adhesives, and styrene adhesives. Among these, acrylic adhesives are preferred as adhesives constituting the adhesive layer in terms of adhesion, weather resistance, cost, and ease of adhesive design. One or more of the above adhesives may be used.

[0090] The acrylic pressure-sensitive adhesive contains an acrylic polymer as a base polymer. The acrylic polymer may contain only one type of acrylic monomer as a monomer component, or may contain two or more types of acrylic monomers.

[0091] The acrylic polymer is preferably a polymer containing the largest amount of structural units derived from (meth)acrylic acid esters by mass. Examples of the (meth)acrylic acid esters include those exemplified and explained as hydrocarbon group-containing (meth)acrylic acid esters in the acrylic polymer that may be contained in the first pressure-sensitive adhesive layer. The hydrocarbon group-containing (meth)acrylic acid esters may be used singly or in combination of two or more.

[0092] As the (meth)acrylic acid alkyl ester as the hydrocarbon group-containing (meth)acrylic acid ester, among others, a (meth)acrylic acid alkyl ester having a linear or branched aliphatic hydrocarbon group having 1 to 20 carbon atoms (preferably 2 to 12, more preferably 2 to 8) is preferred. When the carbon number is within the above range, the storage stability tends to be better.

[0093] In order to properly exhibit the basic properties such as adhesiveness of the (meth)acrylic acid alkyl ester in the adhesive layer, the proportion of the (meth)acrylic acid alkyl ester is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, based on the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. Also, from the viewpoint of copolymerizing other monomer components and obtaining the effects of the other monomer components, the proportion is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 85% by mass or less.

[0094] The acrylic polymer may contain structural units derived from other monomer components copolymerizable with the hydrocarbon group-containing (meth)acrylic acid ester for the purpose of improving cohesive strength, heat resistance, etc. Examples of the other monomer components include those exemplified and explained as polar group-containing monomers and other monomers in the acrylic polymer that may be contained in the first pressure-sensitive adhesive layer. One type of the other monomer may be used, or two or more types may be used.

[0095] Of the polar group-containing monomers, hydroxy group-containing monomers and nitrogen atom-containing monomers are preferred.

[0096] The proportion of the polar group-containing monomer is not particularly limited, but from the viewpoint of better exerting the effect of using the polar group-containing monomer, it is preferably 0.1% by mass or more, more preferably 1% by mass or more, and even more preferably 5% by mass or more, based on the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. Moreover, the proportion is preferably 60% by mass or less, more preferably 40% by mass or less.

[0097] The proportion of the other monomers may be, for example, 0.05% by mass or more, 0.5% by mass or more, 5% by mass or more, or 10% by mass or more relative to the total amount (100% by mass) of the monofunctional monomers constituting the acrylic polymer. The proportion may be, for example, 20% by mass or less, 10% by mass or less, 5% by mass or less, or may be substantially zero.

[0098] The acrylic polymer may contain a structural unit derived from a polyfunctional (meth)acrylate copolymerizable with the monomer components constituting the acrylic polymer to form a crosslinked structure in the polymer skeleton. Examples of the polyfunctional (meth)acrylate include those exemplified and explained as polyfunctional (meth)acrylates in the acrylic polymer that may be contained in the first pressure-sensitive adhesive layer. The polyfunctional monomer may be used alone or in combination of two or more.

[0099] In order to properly exhibit the basic properties of the hydrocarbon group-containing (meth)acrylic acid ester, such as adhesiveness and adhesion to the adherend, in the adhesive layer, the content of the polyfunctional monomer relative to 100 parts by mass of the total amount of monofunctional monomers constituting the acrylic polymer is preferably 0.001 to 1 part by mass, more preferably 0.01 to 0.1 part by mass.

[0100] The second pressure-sensitive adhesive layer may contain other components in addition to the above-mentioned components, as long as the effects of the present invention are not impaired. Examples of the other components include those exemplified and explained as other components that may be contained in the first pressure-sensitive adhesive layer. Only one of the other components may be used, or two or more of the other components may be used.

[0101] The thickness of the second pressure-sensitive adhesive layer (the total thickness of the multiple layers when the pressure-sensitive adhesive layer is a continuous layer) is preferably 100 μm or less, more preferably 99 μm or less, and may be 95 μm or less, 85 μm or less, 75 μm or less, or 50 μm or less, from the viewpoint of imparting an appropriate anti-reflection function to the adherend. If the thickness is 100 μm or less, the pressure-sensitive adhesive sheet is more susceptible to the hardness of the substrate when sealing the optical semiconductor element, and the stress relaxation property of the second pressure-sensitive adhesive layer is reduced, resulting in a thinner first pressure-sensitive adhesive layer located on the upper side (image display side) of the optical semiconductor element. This allows for further improvement in light extraction function. The thickness is preferably 5 μm or more, more preferably 10 μm or more, and may be 20 μm or more, or 25 μm or more.

[0102] The pressure-sensitive adhesive layers (first pressure-sensitive adhesive layer, second pressure-sensitive adhesive layer) constituting the pressure-sensitive adhesive sheet may be in any form, such as an emulsion type, a solvent type (solution type), an active energy ray-curable type, or a hot melt type (hot melt type). Among these, solvent-type and active energy ray-curable pressure-sensitive adhesive layers are preferred because they are easy to obtain pressure-sensitive adhesive layers with excellent productivity. The first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer may be in the same form or different forms (for example, the first pressure-sensitive adhesive layer may be an emulsion type or a solvent type, and the second pressure-sensitive adhesive layer may be an active energy ray-curable type).

[0103] Examples of the active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, and electron beams, as well as ultraviolet rays, and ultraviolet rays are particularly preferred. That is, the active energy ray-curable pressure-sensitive adhesive layer is preferably an ultraviolet-curable pressure-sensitive adhesive layer.

[0104] The pressure-sensitive adhesive layer can be produced, for example, by applying (coating) a pressure-sensitive adhesive composition for forming the pressure-sensitive adhesive layer onto a release liner and drying and curing the resulting pressure-sensitive adhesive composition layer, or by applying (coating) the pressure-sensitive adhesive composition onto a release liner and irradiating the resulting pressure-sensitive adhesive composition layer with active energy rays to cure it. If necessary, the resulting pressure-sensitive adhesive composition may be further dried by heating.

[0105] Examples of the pressure-sensitive adhesive composition include a mixture of monomer components (sometimes referred to as a "monomer mixture") or a composition containing a partially polymerized product thereof as an essential component.

[0106] The mixture of monomer components may be composed of a single monomer component or two or more monomer components. The "partially polymerized product" may also be called a "prepolymer" or "syrup," and refers to a composition in which one or more of the monomer components in the monomer mixture are partially polymerized.

[0107] The storage modulus G1' and the storage modulus G2' preferably satisfy G1' / G2'<1.3. In this case, when the pressure-sensitive adhesive sheet is used as a sheet for encapsulating an optical semiconductor element, the first pressure-sensitive adhesive layer is more easily compressed, the thickness of the first pressure-sensitive adhesive layer located on the upper part (image display side) of the optical semiconductor element becomes appropriately thin, and the light extraction function is further improved. The G1' / G2' ratio is more preferably 1.2 or less. Furthermore, the G1' / G2' ratio is preferably 0.3 or more, more preferably 0.4 or more. When the G1' / G2' ratio is 0.3 or more, voids are less likely to form between the pressure-sensitive adhesive sheet and the optical semiconductor element.

[0108] The thickness of the pressure-sensitive adhesive portion is not particularly limited, but is preferably equal to or greater than the height of the convex portions of an optical semiconductor element or the like, from the viewpoint of more adequately sealing the convex portions. The thickness is, for example, preferably 1.0 to 13.0 times the height of the convex portions, more preferably 1.3 to 11.0 times, even more preferably 1.6 to 10.0 times, and particularly preferably 2.0 to 9.0 times. Furthermore, it is preferable that the total thickness of the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer be within the above range.

[0109] The total thickness of the first and second pressure-sensitive adhesive layers is, for example, about 5.0 to 200 μm, and may be 5.0 μm or more, 10.0 μm or more, 15.0 μm or more, or 20.0 μm or more. The total thickness may be, for example, 200 μm or less, 160 μm or less, 120 μm or less, or 90 μm or less. When a plurality of first pressure-sensitive adhesive layers are present, the thickness of the first pressure-sensitive adhesive layers is the sum of the thicknesses of the first pressure-sensitive adhesive layers located closer to the adherend than the second pressure-sensitive adhesive layer located closest to the adherend. When a plurality of second pressure-sensitive adhesive layers are present, the thickness of the second pressure-sensitive adhesive layer is the thickness of the second pressure-sensitive adhesive layer located closest to the adherend, and when a continuous multi-layer structure is present, it is the total thickness of the multi-layer structure.

[0110] The ratio of the thickness of the second pressure-sensitive adhesive layer to the thickness of the first pressure-sensitive adhesive layer [thickness of second pressure-sensitive adhesive layer / thickness of first pressure-sensitive adhesive layer] is not particularly limited, but is, for example, about 0.1 to 200.0, preferably 1.0 to 100.0, more preferably 2.0 to 50.0, and more preferably 2.5 to 15.0. When a plurality of first pressure-sensitive adhesive layers are present, the thickness of the first pressure-sensitive adhesive layers is the sum of the thicknesses of the first pressure-sensitive adhesive layers located closer to the adherend than the second pressure-sensitive adhesive layer located closest to the adherend. When a plurality of second pressure-sensitive adhesive layers are present, the thickness of the second pressure-sensitive adhesive layer is the thickness of the second pressure-sensitive adhesive layer located closest to the adherend, and when a continuous multi-layer structure is present, it is the total thickness of the multi-layer structure.

[0111] (Base material part) The pressure-sensitive adhesive sheet includes a substrate. In the pressure-sensitive adhesive sheet, the substrate is located closer to the second pressure-sensitive adhesive layer than the first pressure-sensitive adhesive layer. When the pressure-sensitive adhesive sheet is used as a sheet for encapsulating optical semiconductor elements, the substrate is located on the side of the sheet opposite the optical semiconductor element, allowing the surface of the pressure-sensitive adhesive portion to be flat, thereby reducing the occurrence of diffused reflection of light and improving the appearance of the optical semiconductor device both when the light is off and when the light is on. In addition, by forming an anti-glare layer or anti-reflection layer described below on the substrate, it is possible to impart anti-glare properties and anti-reflection properties to the optical semiconductor device. In addition, the substrate serves as a support for the pressure-sensitive adhesive portion in the pressure-sensitive adhesive sheet, and the pressure-sensitive adhesive sheet is therefore easy to handle.

[0112] The substrate may be a single layer, or may be multiple layers that are the same or have different compositions, thicknesses, etc. When the substrate is multiple layers, each layer may be bonded to another layer such as a pressure-sensitive adhesive layer. Note that the substrate layer used in the substrate is the part that is attached to the adherend together with the pressure-sensitive adhesive portion, and does not include a release liner that is peeled off when the pressure-sensitive adhesive sheet is used (attached) or a surface protection film that simply protects the surface of the substrate.

[0113] Examples of the substrate layer constituting the substrate part include glass and plastic substrates (particularly, plastic films). Examples of resins constituting the plastic substrate include low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, high-density polyethylene, very low-density polyethylene, random copolymer polypropylene, block copolymer polypropylene, homopolypropylene, polybutene, polymethylpentene, ionomer, ethylene-(meth)acrylic acid copolymer, ethylene-(meth)acrylic acid ester (random, alternating) copolymer, ethylene-vinyl acetate copolymer (EVA), ethylene-propylene copolymer, cyclic olefin polymer, ethylene-butene copolymer, ethylene-hexene copolymer, etc. Examples of suitable resins include polyolefin resins, polyurethanes, polyesters such as polyethylene terephthalate (PET), polyethylene naphthalate, and polybutylene terephthalate (PBT), polycarbonates, polyimide resins, polyether ether ketones, polyetherimides, polyamides such as aramids and wholly aromatic polyamides, polyphenyl sulfides, fluororesins, polyvinyl chloride, polyvinylidene chloride, cellulose resins such as triacetyl cellulose (TAC), silicone resins, acrylic resins such as polymethyl methacrylate (PMMA), polysulfones, polyarylates, and polyvinyl acetates. The above resins may be used singly or in combination. The substrate layer may be any of various optical films, such as antireflection (AR) films, polarizing plates, and retardation plates.

[0114] The thickness of the plastic substrate is preferably 20 to 300 μm, more preferably 40 to 250 μm. When the thickness is 20 μm or more, the supportability and handleability of the pressure-sensitive adhesive sheet are further improved. When the thickness is 300 μm or less, the pressure-sensitive adhesive sheet can be made thinner.

[0115] The surface of the base material portion on the side provided with the adhesive portion may be subjected to surface treatments such as physical treatments such as corona discharge treatment, plasma treatment, sand mat processing treatment, ozone exposure treatment, flame exposure treatment, high-voltage electric shock exposure treatment, ionizing active energy ray treatment, etc.; chemical treatments such as chromic acid treatment; easy adhesion treatment with a coating agent (primer), etc., for the purpose of enhancing adhesion, retention, etc. with the adhesive portion. The surface treatment for enhancing adhesion is preferably applied to the entire surface on the adhesive portion side in the base material portion.

[0116] From the viewpoint of excellent functions as a support and scratch resistance of the surface, the thickness of the base material portion is preferably 5 μm or more, more preferably 10 μm or more. From the viewpoint of more excellent transparency, the thickness of the base material portion is preferably 300 μm or less, more preferably 250 μm or less.

[0117] The visible light transmittance T1 of the first adhesive layer and the visible light transmittance (visible light transmittance T3) of the base material portion preferably satisfy T1 < T3. With such a configuration, the base material portion having a higher visible light transmittance than the first adhesive layer is located above the optical semiconductor element (image display side), the light extraction function is improved, the image can be brightened, and the power consumption due to the output increase for enhancing the emission luminance can be reduced. The visible light transmittance T3 of the base material portion is not particularly limited, but is, for example, 85 to 100%, and may be 88% or more, 90% or more, or 92% or more.

[0118] <Adhesive sheet> The pressure-sensitive adhesive sheet may include a layer having antiglare and / or antireflection properties. Such a configuration can suppress gloss and light reflection when an optical semiconductor element is encapsulated, improving the appearance. An example of the antiglare layer is an antiglare-treated layer (anti-glare treated layer). An example of the antireflection layer is an antireflection-treated layer. The antiglare treatment and the antireflection treatment can be performed by known or conventional methods. The antiglare layer and the antireflection layer may be the same layer or different layers. The antiglare and / or antireflection layer may have only one layer or two or more layers. It is preferable that the pressure-sensitive adhesive sheet has a layer having antiglare and / or antireflection properties on one outermost surface of the pressure-sensitive adhesive sheet.

[0119] When the optical semiconductor element is encapsulated with the pressure-sensitive adhesive sheet, the pressure-sensitive adhesive portion preferably has a flat surface on the side opposite to the side encapsulating the optical semiconductor element, which reduces the occurrence of diffuse reflection of external light on the surface of the pressure-sensitive adhesive sheet when the optical semiconductor element is encapsulated, improving the appearance of the image display device both when the light is off and when the light is on.

[0120] The thickness of the pressure-sensitive adhesive sheet is preferably 10 to 600 μm, more preferably 20 to 550 μm, even more preferably 30 to 500 μm, still more preferably 40 to 450 μm, and particularly preferably 50 to 400 μm, from the viewpoint of more efficiently reducing color shift while improving the anti-reflection function and contrast of metal wiring, etc. Note that the thickness does not include the thickness of the release liner.

[0121] [Release liner] The release-treated surface of a release liner may be attached to the surface of the pressure-sensitive adhesive portion. The release liner is used as a protective material for the pressure-sensitive adhesive sheet and is peeled off when the sheet is attached to an adherend such as an optical semiconductor element. However, the release liner is not necessarily provided.

[0122] Examples of the release liner include polyethylene terephthalate (PET) film, polyethylene film, polypropylene film, plastic film and paper whose surface is coated with a release agent such as a fluorine-based release agent or a long-chain alkyl acrylate-based release agent.

[0123] The thickness of the release liner is, for example, 10 to 200 μm, preferably 15 to 150 μm, and more preferably 20 to 100 μm. When the thickness is 10 μm or more, the release liner is less likely to break due to cuts made during processing. When the thickness is 200 μm or less, the release liner is more easily peeled from the pressure-sensitive adhesive sheet during use.

[0124] FIG. 1 is a cross-sectional view showing one embodiment of the pressure-sensitive adhesive sheet. As shown in FIG. 1, the pressure-sensitive adhesive sheet 1 can be used to encapsulate one or more optical semiconductor elements arranged on a substrate, and includes a base member 4 and a pressure-sensitive adhesive portion 2 formed on the base member 4. The base member 4 is composed of a base film 41 and a functional layer 42, which is a surface treatment layer, but may also be composed of the base film 41 without the functional layer 42. The pressure-sensitive adhesive portion 2 is formed of a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22. The first pressure-sensitive adhesive layer 21 is laminated directly on the second pressure-sensitive adhesive layer 22, and the second pressure-sensitive adhesive layer 22 is laminated directly on the base member 4. A release liner 3 is attached to the first pressure-sensitive adhesive layer 21, and the base member 4 is attached to the second pressure-sensitive adhesive layer 22.

[0125] The functional layer 42 is a layer not included in the adhesive portion 2, and can impart various functions to the adhesive sheet. Examples of the functional layer include a layer including a surface treatment layer. Such a configuration allows the adhesive sheet having the functional layer including the surface treatment layer laminated thereon to have excellent light diffusion properties and light extraction efficiency. Examples of the surface treatment layer include an anti-glare treatment layer, an anti-reflection treatment layer, and a hard coat treatment layer. The functional layer may be laminated on the adhesive portion of the adhesive sheet, or, if the substrate portion is provided, on the substrate portion; however, it is preferably laminated on the substrate portion, and is preferably laminated on the side of the substrate portion opposite the side on which the adhesive portion is provided.

[0126] [Manufacturing method of adhesive sheet] One embodiment of a method for producing the pressure-sensitive adhesive sheet will now be described. For example, the pressure-sensitive adhesive sheet 1 shown in Fig. 1 is produced by separately sandwiching a first pressure-sensitive adhesive layer 21 and a second pressure-sensitive adhesive layer 22 between the release-treated surfaces of two release liners. One of the release liners bonded to the first pressure-sensitive adhesive layer 21 is release liner 3.

[0127] Next, one of the release liners attached to second pressure-sensitive adhesive layer 22 is peeled off to expose the surface of second pressure-sensitive adhesive layer 22, and the exposed surface is bonded to substrate 4. Thereafter, one of the release liners attached to first pressure-sensitive adhesive layer 21 (a release liner other than release liner 3) is peeled off, and the release liner on the surface of second pressure-sensitive adhesive layer 22 is peeled off, and the exposed surface of first pressure-sensitive adhesive layer 21 is bonded to the exposed surface of second pressure-sensitive adhesive layer 22. Note that the lamination of the various layers can be carried out using a known roller or laminator. In this manner, the pressure-sensitive adhesive sheet 1 shown in FIG. 1 can be produced, in which second pressure-sensitive adhesive layer 22, second pressure-sensitive adhesive layer 21, and release liner 3 are laminated in this order on substrate 4.

[0128] [Optical semiconductor device] The pressure-sensitive adhesive sheet can be used to produce an optical semiconductor device such as an image display device. The optical semiconductor device produced using the pressure-sensitive adhesive sheet comprises a substrate, an optical semiconductor element disposed on the substrate, and the pressure-sensitive adhesive sheet or a cured product of the sheet that encapsulates the optical semiconductor element. When the pressure-sensitive adhesive sheet comprises a radiation-curable pressure-sensitive adhesive layer, the cured product is a cured product of the radiation-curable pressure-sensitive adhesive layer that has been cured by irradiation with radiation.

[0129] Examples of the optical semiconductor element include light emitting diodes (LEDs) such as blue light emitting diodes, green light emitting diodes, red light emitting diodes, and ultraviolet light emitting diodes.

[0130] In the optical semiconductor device, the adhesive sheet preferably encapsulates multiple optical semiconductor elements collectively, since it has excellent conformability to unevenness when the optical semiconductor elements are convex and the gaps between multiple optical semiconductor elements are concave, and has excellent conformability and embeddability for the optical semiconductor elements.

[0131] The height of the optical semiconductor element on the substrate (the height from the surface of the substrate to the front end of the optical semiconductor element) is preferably 500 μm or less. When the height is 500 μm or less, the adhesive portion has better ability to conform to the uneven shape.

[0132] FIG. 2 shows one embodiment of an optical semiconductor device using the pressure-sensitive adhesive sheet 1 shown in FIG. 1. The optical semiconductor device 10 shown in FIG. 2 includes a substrate 5, a plurality of optical semiconductor elements 6 arranged on one surface of the substrate 5, an encapsulating resin layer 7 that encapsulates the optical semiconductor elements 6, and a base material 4 laminated on the encapsulating resin layer 7. The plurality of optical semiconductor elements 6 are encapsulated collectively in the encapsulating resin layer 7. The encapsulating resin layer 7 is formed by laminating a first pressure-sensitive adhesive layer 71 and a second pressure-sensitive adhesive layer 72. The first pressure-sensitive adhesive layer 71 adheres closely to the optical semiconductor elements 6 and the substrate 5, conforming to the uneven shape formed by the plurality of optical semiconductor elements 6, thereby embedding the optical semiconductor elements 6. The interface of the first pressure-sensitive adhesive layer 71 on the optical semiconductor element 6 side has an uneven shape conforming to the uneven shape, and the other interface is flat.

[0133] The encapsulating resin layer 7 is formed by the adhesive portion 2. More specifically, the first adhesive layer 71 is formed by the first adhesive layer 21, and the second adhesive layer 72 is formed by the second adhesive layer 22. Specifically, when the adhesive portion 2 in the adhesive sheet 1 does not have a radiation-curable adhesive layer, the adhesive portion 2 becomes the encapsulating resin layer 7 in the optical semiconductor device 10. On the other hand, when the adhesive portion 2 in the adhesive sheet 1 has a radiation-curable adhesive layer, for example, when the second adhesive layer 22 is a radiation-curable adhesive layer, the second adhesive layer 22 is cured to form the second adhesive layer 72, which becomes the encapsulating resin layer 7.

[0134] 2, the optical semiconductor element 6 is completely embedded and sealed in the first pressure-sensitive adhesive layer 71, and is indirectly sealed by the second pressure-sensitive adhesive layer 72. That is, the optical semiconductor element 6 is sealed by the sealing resin layer 7 made of a laminate of the first pressure-sensitive adhesive layer 71 and the second pressure-sensitive adhesive layer 72. The optical semiconductor device is not limited to this embodiment, and may be, for example, as shown in FIG. 3, in which the optical semiconductor element 6 is completely embedded and sealed in the first pressure-sensitive adhesive layer 71 and the second pressure-sensitive adhesive layer 72.

[0135] The optical semiconductor device may be a tiled structure of individual optical semiconductor devices, i.e., the optical semiconductor device may be a structure in which a plurality of optical semiconductor devices are arranged in a tiled pattern in a planar direction.

[0136] The image display device preferably includes a self-luminous display device. The self-luminous display device can also be combined with a display panel, if necessary, to form an image display device. In this case, the optical semiconductor elements are LED elements. Examples of the self-luminous display device include LED displays, backlights, and organic electroluminescence (organic EL) display devices. The backlight is preferably a full-surface direct backlight. The backlight includes, as at least a part of its components, a laminate including the substrate and a plurality of optical semiconductor elements arranged on the substrate. For example, in the self-luminous display device, a metal wiring layer is laminated on the substrate for transmitting light emission control signals to each LED element. LED elements emitting red (R), green (G), and blue (B) light are alternately arranged on the substrate via the metal wiring layer. The metal wiring layer is made of a metal such as copper, and adjusts the light emission intensity of each LED element to display each color.

[0137] The pressure-sensitive adhesive sheet can be used in optical semiconductor devices that are used by folding, for example, optical semiconductor devices having a foldable image display device (flexible display) (particularly, a foldable image display device (foldable display)). Specifically, it can be used in foldable backlights and foldable self-luminous display devices.

[0138] The pressure-sensitive adhesive sheet has excellent conformability and embeddability for optical semiconductor elements, and can therefore be preferably used when the optical semiconductor device is either a mini LED display device or a micro LED display device.

[0139] [Method of manufacturing optical semiconductor device] The optical semiconductor device can be produced, for example, by attaching the pressure-sensitive adhesive sheet to a substrate on which an optical semiconductor element is arranged, sealing the optical semiconductor element with the pressure-sensitive adhesive portion, and curing the sheet as necessary.

[0140] (Sealing process) The method for manufacturing an optical semiconductor device using the pressure-sensitive adhesive sheet includes a sealing step of bonding the pressure-sensitive adhesive sheet to a substrate on which optical semiconductor elements are arranged and sealing the optical semiconductor elements with the adhesive portion. Specifically, the sealing step first involves peeling the release liner from the pressure-sensitive adhesive sheet to expose the adhesive portion. Then, of a laminate (such as an optical component) comprising a substrate and optical semiconductor elements (preferably multiple optical semiconductor elements) arranged on the substrate, the adhesive surface (the exposed surface of the pressure-sensitive adhesive sheet) is bonded to the substrate surface on which the optical semiconductor elements are arranged. If the laminate comprises multiple optical semiconductor elements, the adhesive portion is further positioned so that it fills the gaps between the multiple optical semiconductor elements, thereby collectively sealing the multiple optical semiconductor elements. Specifically, the release liner 3 is peeled from the pressure-sensitive adhesive sheet 1 shown in FIG. 1 , exposing the first adhesive layer 21, which is exposed by peeling it from the pressure-sensitive adhesive sheet 1, so that it faces the surface of the substrate 5 on which the optical semiconductor elements 6 are arranged. The pressure-sensitive adhesive sheet 1 is then bonded to the surface of the substrate 5 on which the optical semiconductor elements 6 are arranged, embedding the optical semiconductor elements 6 in the adhesive portion 2.

[0141] The temperature during the lamination is, for example, within a range from room temperature to 110°C. Furthermore, reduced pressure or pressure may be applied during the lamination. This reduced pressure or pressure can prevent voids from forming between the adhesive portion and the substrate or optical semiconductor element. Furthermore, in the sealing step, it is preferable to apply pressure after laminating the adhesive sheets under reduced pressure. When reduced pressure is applied, the pressure is, for example, 1 to 100 Pa, and the depressurization time is, for example, 5 to 600 seconds. When pressurized, the pressure is, for example, 0.05 to 0.5 MPa, and the pressurization time is, for example, 5 to 600 seconds.

[0142] (Radiation irradiation process) When the adhesive portion comprises a radiation-curable adhesive layer, the manufacturing method may further comprise a radiation irradiation step of irradiating a laminate comprising the substrate, an optical semiconductor element disposed on the substrate, and the adhesive sheet encapsulating the optical semiconductor element with radiation to cure the radiation-curable adhesive layer and form a cured product layer. As described above, examples of the radiation include electron beams, ultraviolet rays, α rays, β rays, γ rays, and X-rays. Among these, ultraviolet rays are preferred. The temperature during radiation irradiation is, for example, within a range from room temperature to 100°C, and the irradiation time is, for example, from 1 minute to 1 hour.

[0143] (dicing process) The manufacturing method may further include a dicing step of dicing a laminate including the substrate, an optical semiconductor element disposed on the substrate, and the pressure-sensitive adhesive sheet encapsulating the optical semiconductor element. The dicing may be performed on a laminate that has undergone the radiation irradiation step. When the laminate includes a cured material layer formed by curing a radiation-curable pressure-sensitive adhesive layer by radiation irradiation, the dicing step involves dicing and removing the cured material layer of the pressure-sensitive adhesive sheet and the side edges of the substrate. This allows the surface of the cured material layer, which has been sufficiently cured and has reduced adhesiveness, to be exposed on the side. The dicing can be performed by a known or conventional method, such as a method using a dicing blade or laser irradiation.

[0144] (Tiling process) The manufacturing method may further include a tiling step of arranging the plurality of optical semiconductor devices obtained in the dicing step so that they are in contact with each other in a planar direction. In the tiling step, the plurality of stacks obtained in the dicing step are tiled so that they are in contact with each other in a planar direction. In this manner, a single large image display device can be manufactured.

[0145] In this manner, an optical semiconductor device can be manufactured. When the adhesive portion 2 of the adhesive sheet 1 does not have a radiation-curable adhesive layer, the adhesive portion 2 becomes the encapsulating resin layer 7 of the optical semiconductor device 10. On the other hand, when the adhesive portion 2 of the adhesive sheet 1 has a radiation-curable adhesive layer, for example, when the second adhesive layer 22 is a radiation-curable adhesive layer, the second adhesive layer 22 is cured to form the second adhesive layer 72, which becomes the encapsulating resin layer 7.

[0146] The pressure-sensitive adhesive sheet has high light extraction function and excellent reliability. Therefore, the pressure-sensitive adhesive sheet can be preferably used as a sheet for encapsulating optical semiconductor elements. Furthermore, even when exposed to high temperatures during lamination, such as encapsulation of optical semiconductor elements, or other use processes, the optical properties of the pressure-sensitive adhesive sheet are unlikely to change, voids are unlikely to occur, and the pressure-sensitive adhesive sheet has excellent reliability. [Example]

[0147] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples in any way.

[0148] Preparation Example 1 (Preparation of Acrylic Polymer A-Containing Composition) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 27 parts by weight of 2-ethylhexyl acrylate (2EHA), 64 parts by weight of ethyl acrylate (EA), 5 parts by weight of methyl methacrylate (MMA), 4 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). This resulted in a polymer solution containing acrylic polymer A. The weight-average molecular weight (Mw) of the acrylic polymer in this polymer solution was 600,000.

[0149] Preparation Example 2 (Preparation of Acrylic Polymer B-Containing Composition) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 96 parts by weight of 2-ethylhexyl acrylate (2EHA), 4 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). This resulted in a polymer solution containing acrylic polymer B. The weight-average molecular weight (Mw) of the acrylic polymer in this polymer solution was 600,000.

[0150] Preparation Example 3 (Preparation of Acrylic Polymer C-Containing Composition) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 82 parts by weight of ethyl acrylate (EA), 10 parts by weight of N-vinyl-2-pyrrolidone (NVP), 8 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). This resulted in a polymer solution containing acrylic polymer C. The weight-average molecular weight (Mw) of the acrylic polymer in this polymer solution was 600,000.

[0151] Preparation Example 4 (Preparation of Black Pigment Dispersion) A black pigment dispersion was prepared by mixing 25 parts by mass of carbon black, 8 parts by mass of dispersant, and 67 parts by mass of ethyl acetate in a conventional manner.

[0152] Preparation Example 5 (Preparation of First Pressure-Sensitive Adhesive Composition 1) To the acrylic polymer A-containing composition obtained in Preparation Example 1, 0.4 parts by mass (solids equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 parts by mass (solids equivalent) of Narthem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer A so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 1.

[0153] Preparation Example 6 (Preparation of First Pressure-Sensitive Adhesive Composition 2) To the acrylic polymer A-containing composition obtained in Preparation Example 1, 0.6 parts by mass (solids equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 parts by mass (solids equivalent) of Narcem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer A so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 2.

[0154] Preparation Example 7 (Preparation of First Pressure-Sensitive Adhesive Composition 3) To the acrylic polymer A-containing composition obtained in Preparation Example 1, 1.0 part by mass (solid content equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 part by mass (solid content equivalent) of Narcem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer A so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 3.

[0155] Preparation Example 8 (Preparation of First Pressure-Sensitive Adhesive Composition 4) To the acrylic polymer B-containing composition obtained in Preparation Example 2, 0.4 parts by mass (solid content equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 parts by mass (solid content equivalent) of Narthem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer B so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 4.

[0156] Preparation Example 9 (Preparation of First Pressure-Sensitive Adhesive Composition 5) To the acrylic polymer B-containing composition obtained in Preparation Example 2, 0.6 parts by mass (solid content equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 parts by mass (solid content equivalent) of Narcem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer B so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 5.

[0157] Preparation Example 10 (Preparation of First Pressure-Sensitive Adhesive Composition 6) To the acrylic polymer C-containing composition obtained in Preparation Example 3, 1.0 part by mass (solid content equivalent) of an isocyanate crosslinking agent (product name "Coronate HX", manufactured by Tosoh Corporation) as a crosslinking agent, 0.01 part by mass (solid content equivalent) of Narcem ferric iron (manufactured by Nippon Chemical Industry Co., Ltd.) as a crosslinking catalyst, 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst), and the black pigment dispersion obtained in Preparation Example 4 were added and mixed per 100 parts by mass of acrylic polymer C so that the pigment concentration in the adhesive layer was 3.2% by mass, to obtain a first adhesive composition 6.

[0158] Preparation example 1 (Preparation of First Pressure-Sensitive Adhesive Layers 1 to 6) A first PSA composition shown in Table 1 was applied to the release-treated surface of a 38-μm-thick polyester film A (trade name "DiaWheel MRF," manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, to form a coating. The coating was then dried at 130°C for 3 minutes to form an 8-μm-thick PSA layer. The release-treated surface of a 38-μm-thick polyester film B (trade name "DiaWheel MRE," manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, was then bonded to this PSA layer. The resulting film was then aged at 50°C for 5 days to promote a crosslinking reaction in the PSA layer. This yielded first PSA layers 1-6, sandwiched between two release liners: polyester film A and polyester film B. Information about first PSA layers 1-6 is shown in Table 1.

[0159] [Table 1]

[0160] Preparation example 2 (Preparation of Acrylic Polymer D-Containing Composition) In a reaction vessel equipped with a stirrer, thermometer, reflux condenser, and nitrogen gas inlet tube, a mixture containing 60 parts by weight of 2-ethylhexyl acrylate (2EHA), 20 parts by weight of N-vinyl-2-pyrrolidone (NVP), 10 parts by weight of methyl methacrylate (MMA), 10 parts by weight of 2-hydroxyethyl acrylate (HEA), 0.2 parts by weight of 2,2'-azobisisobutyronitrile (AIBN) as a polymerization initiator, and 200 parts by weight of ethyl acetate as a solvent was stirred at 60°C for 7 hours under a nitrogen atmosphere (polymerization reaction). This resulted in a polymer solution containing acrylic polymer D. The weight-average molecular weight (Mw) of the acrylic polymer in this polymer solution was 1.2 million.

[0161] (Preparation of second adhesive composition 1) To the above acrylic polymer D-containing composition, 2.5 parts by mass (solids equivalent) of an isocyanate crosslinking agent (trade name "Takenate D110N", manufactured by Mitsui Chemicals, Inc.) as a crosslinking agent, 0.02 parts by mass (solids equivalent) of dibutyltin dilaurate (trade name "OL-1", 1 mass% ethyl acetate solution, manufactured by Tokyo Fine Chemicals Co., Ltd.) as a crosslinking catalyst, and 3 parts by mass of acetylacetone as a crosslinking inhibitor (ligand for the crosslinking catalyst) were added and mixed per 100 parts by mass of acrylic polymer D to obtain a second adhesive composition 1.

[0162] (Preparation of second adhesive layer 1) The second PSA composition 1 was applied to the release-treated surface of a 38 μm-thick polyester film A (trade name "DiaWheel MRF", manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, to form a coating. The coating was then dried at 130°C for 3 minutes to form a 75 μm-thick PSA layer. The release-treated surface of a 38 μm-thick polyester film B (trade name "DiaWheel MRE", manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, was then bonded to this PSA layer. The resulting adhesive was then aged at 50°C for 5 days to promote a crosslinking reaction in the PSA layer. This resulted in a second PSA layer 1, in which a 75 μm-thick PSA layer, a cured product of the second PSA composition 1, was sandwiched between two release liners, polyester film A and polyester film B. Information about second PSA layer 1 is shown in Table 2.

[0163] [Table 2]

[0164] Preparation Example 11 (Preparation of Acrylic Prepolymer A-Containing Composition) A separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube was charged with 75 parts by mass of 2-ethylhexyl acrylate (2EHA), 15 parts by mass of N-vinyl-2-pyrrolidone (NVP), 10 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.04 parts by mass of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF), and 0.04 parts by mass of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF). After that, nitrogen gas was introduced and the mixture was purged with nitrogen for about 1 hour while stirring. 2 The reaction rate was adjusted to 5 to 15%, and an acrylic prepolymer A-containing composition was obtained.

[0165] Preparation Example 12 (Preparation of Acrylic Prepolymer B-Containing Composition) A separable flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas inlet tube was charged with 40 parts by mass of lauryl acrylate (LA), 40 parts by mass of 2-ethylhexyl acrylate (2EHA), 10 parts by mass of N-vinyl-2-pyrrolidone (NVP), 10 parts by mass of 4-hydroxybutyl acrylate (HBA), 0.04 parts by mass of a photopolymerization initiator (trade name "Irgacure 184", manufactured by BASF), and 0.04 parts by mass of a photopolymerization initiator (trade name "Irgacure 651", manufactured by BASF). After that, nitrogen gas was introduced and the mixture was purged with nitrogen for about 1 hour while stirring. After that, 5 mW / cm 2 The reaction rate was adjusted to 5 to 15%, and a composition containing acrylic prepolymer B was obtained.

[0166] Preparation Example 13 (Preparation of second adhesive composition 2) A photopolymerizable second adhesive composition 2 was prepared by adding 20 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.1 parts by mass of 1,6-hexanediol diacrylate (HDDA) as a polyfunctional monomer, and 0.4 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent to the acrylic prepolymer A-containing composition obtained in Preparation Example 11 (total amount of prepolymer being 100 parts by mass).

[0167] Preparation Example 14 (Preparation of second adhesive composition 3) A photopolymerizable second adhesive composition 3 was prepared by adding 20 parts by mass of 2-hydroxyethyl acrylate (HEA), 0.3 parts by mass of 1,6-hexanediol diacrylate (HDDA) as a polyfunctional monomer, and 0.4 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent to the acrylic prepolymer A-containing composition obtained in Preparation Example 11 (total amount of prepolymer being 100 parts by mass).

[0168] Preparation Example 15 (Preparation of Second Pressure-Sensitive Adhesive Composition 4) A photopolymerizable second adhesive composition 4 was prepared by adding 0.1 parts by mass of 1,6-hexanediol diacrylate (HDDA) as a polyfunctional monomer and 0.4 parts by mass of 3-glycidoxypropyltrimethoxysilane as a silane coupling agent to the acrylic prepolymer B-containing composition obtained in Preparation Example 12 (total amount of prepolymers: 100 parts by mass).

[0169] Preparation example 3 (Preparation of second pressure-sensitive adhesive layers 2 to 4) The second adhesive composition shown in Table 3 was applied to the release-treated surface of a 38 μm-thick polyester film A (trade name "DiaWheel MRF", manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, so that the thickness after curing would be 75 μm. This was then covered with a 38 μm-thick polyester film B (trade name "DiaWheel MRE", manufactured by Mitsubishi Chemical Corporation), one side of which had been release-treated with a silicone-based release agent, to produce a laminate, which was then sealed off from air. A black light (trade name "FL15BL", manufactured by Toshiba Corporation) was used to illuminate one side of this laminate at an illuminance of 5 mW / cm. 2 , cumulative light intensity 1300mJ / cm 2The adhesive was irradiated with ultraviolet light under the following conditions. As a result, second adhesive layers 2 to 4 were obtained, in which a 75 μm-thick adhesive layer, which was a cured product of the second adhesive composition, was sandwiched between two release liners, polyester film A and polyester film B. The illuminance of the black light was measured using an industrial UV checker (product name "UVR-T1", manufactured by Topcon Corporation, light-receiving unit model "UD-T36") with a peak sensitivity wavelength of approximately 350 nm. Table 3 shows information on second adhesive layers 2 to 4.

[0170] [Table 3]

[0171] Examples 1 to 5, Comparative Examples 1 to 3 Polyester film B was peeled off from a 50 mm x 50 mm cut piece of the second pressure-sensitive adhesive layer, and the exposed adhesive surface was attached to a 50 mm x 50 mm PET substrate (trade name "Lumirror U34", manufactured by Toray Industries, Inc.), after which polyester film A was peeled off to expose the adhesive surface. Polyester film B was then peeled off from a 50 mm x 50 mm cut piece of the first pressure-sensitive adhesive layer, and the exposed adhesive surface was attached to the adhesive surface of the first pressure-sensitive adhesive layer, to obtain a pressure-sensitive adhesive sheet consisting of [substrate / second pressure-sensitive adhesive layer / first pressure-sensitive adhesive layer / release liner (polyester film A)]. The first pressure-sensitive adhesive layer and second pressure-sensitive adhesive layer used in each example are shown in Table 4.

[0172] <Evaluation> The pressure-sensitive adhesive layers used and the pressure-sensitive adhesive sheets produced in the Examples and Comparative Examples were evaluated as follows. The results are shown in Table 4.

[0173] (1) Transmittance For the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer used in the examples and comparative examples, the visible light transmittance T1 of the first pressure-sensitive adhesive layer and the visible light transmittance T2 of the second pressure-sensitive adhesive layer were measured by the following procedure. First, polyester film B was peeled off from the pressure-sensitive adhesive layer, and the exposed adhesive surface was attached to alkali-free glass. Then, polyester film A was peeled off from the pressure-sensitive adhesive layer to obtain an evaluation sample in which the pressure-sensitive adhesive layer was attached to the alkali-free glass. Using this evaluation sample, the transmittance of the evaluation sample was measured in accordance with JIS K7361-1 using a visible-ultraviolet spectrophotometer (product name "HSP-150Vis", manufactured by Murakami Color Research Laboratory Co., Ltd.). The transmittance of the obtained evaluation sample was then taken as the visible light transmittance of the pressure-sensitive adhesive layer.

[0174] (2) Storage modulus For the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer used in the Examples and Comparative Examples, the storage modulus G1' of the first pressure-sensitive adhesive layer and the storage modulus G2' of the second pressure-sensitive adhesive layer were measured. Two release liners were peeled off and the pressure-sensitive adhesive layers were laminated to a thickness of approximately 1 mm. The laminate was cut to a diameter of 8 mm to prepare a test piece. Using an 8 mm diameter jig, the temperature dispersion of the test piece was measured at temperatures from -50 to 150°C using a viscoelasticity measuring device (product name "ARES-G2", manufactured by TA Instruments). The heating rate was 5°C / min, the frequency was 1 Hz, and the strain was 0.1%. The modulus at 90°C was taken as the storage modulus (kPa) of the pressure-sensitive adhesive layer.

[0175] (3) Presence or absence of voids after sealing An 8-inch wafer (protrusion size: 20 μm length × 40 μm width × 10 μm height, protrusion spacing: 20 μm lengthwise and widthwise) with convex processing (shaped to form convex portions) was prepared as a simulated panel. The release liner was peeled off from the PSA sheets obtained in the Examples and Comparative Examples, and the exposed adhesive surface was attached to the side of the simulated panel having the convex portions. The sheet was then autoclaved to obtain an evaluation sample consisting of [substrate / second PSA layer / first PSA layer / simulated panel]. The sheets were differentially attached using an MSV300 device manufactured by Nitto Seiki Co., Ltd. The differential attachment conditions were a vacuum of 20 Pa, attachment pressure of 0.1 MPa, and simulated panel (wafer) surface temperature of 90°C. The autoclave conditions were a pressure of 0.5 MPa, a temperature of 90°C, and a time of 90 seconds. A cross section was cut out from the evaluation sample prepared above, and the obtained cross section was observed by SEM. If no voids were observed, it was judged as "○", and if voids were observed, it was judged as "×".

[0176] (4) Thickness of the first adhesive layer on the chip The thickness of the first adhesive layer on the convex portions of the simulated panel was measured from the SEM images obtained in the evaluation of the presence or absence of voids after sealing, and the average value of three points was taken as the thickness on the chip.

[0177] (5) Presence or absence of voids after reliability testing The release liner was peeled from the pressure-sensitive adhesive sheets obtained in the Examples and Comparative Examples, and the exposed adhesive surface was bonded to alkali-free glass. The sheets were then autoclaved to obtain evaluation samples each consisting of [substrate / second pressure-sensitive adhesive layer / first pressure-sensitive adhesive layer / alkali-free glass]. The autoclave conditions were a pressure of 0.5 MPa, a temperature of 50°C, and a time of 15 minutes. These evaluation samples were left in an environment at 105°C for 500 hours. After the 500 hours had elapsed, the evaluation samples were visually observed, and were rated as "Good" if no voids were observed, and "Poor" if voids were observed.

[0178] (6) Change in transmittance before and after reliability testing Regarding the evaluation sample after 500 hours obtained in the evaluation of the presence or absence of voids after the above reliability test, the transmittance was measured in accordance with JIS K7361-1 using a visible ultraviolet spectrophotometer (trade name "HSP-150Vis", manufactured by Murakami Color Technology Co., Ltd.). Then, the change in transmittance before and after being placed in an environment of 105°C for 500 hours was calculated by the following formula. Change in transmittance [%] = Transmittance after reliability test - Transmittance before reliability test

[0179]

Table 4

[0180] As shown in Table 4, the adhesive sheet of the example had a thinner thickness on the convex portion in the first adhesive layer with the same pigment concentration, and was evaluated to have a high light extraction function. Also, no voids occurred before and after the reliability test, and the change in transmittance before and after the reliability test was small, and it was evaluated to have excellent reliability. On the other hand, when the storage elastic modulus G1' of the first adhesive layer at 90°C was small (Comparative Examples 1 and 2), the occurrence of voids was confirmed before or after the reliability test, and it was evaluated to have poor reliability. Also, when the storage elastic modulus G1' of the first adhesive layer at 90°C was high (Comparative Example 3), the thickness on the convex portion in the first adhesive layer with the same pigment concentration was thick, and it was evaluated to have a low light extraction function, and the occurrence of voids was confirmed before the reliability test, and it was evaluated to have poor reliability.

[0181] Hereinafter, variations of the invention according to the present disclosure will be described. [Appendix 1] A substrate portion and an adhesive portion formed on one surface of the substrate portion, The adhesive portion includes a first adhesive layer and a second adhesive layer, The first adhesive layer, the second adhesive layer, and the substrate portion have a laminated structure laminated in this order, The visible light transmittance T1 of the first adhesive layer and the visible light transmittance T2 of the second adhesive layer satisfy T1 < T2, The storage elastic modulus G1' of the first adhesive layer at 90°C is 35 to 100 kPa, an adhesive sheet. [Appendix 2] The pressure-sensitive adhesive sheet according to Appendix 1, wherein the storage modulus G1' and the storage modulus G2' of the second pressure-sensitive adhesive layer at 90°C satisfy the relationship G1' / G2'<1.3. [Appendix 3] The pressure-sensitive adhesive sheet according to appendix 1 or 2, wherein the first pressure-sensitive adhesive layer contains a colorant. [Appendix 4] The pressure-sensitive adhesive sheet according to Appendix 3, wherein the colorant contains carbon black. [Appendix 5] The pressure-sensitive adhesive sheet according to any one of Appendices 1 to 4, wherein the thickness of the first pressure-sensitive adhesive layer is 5 to 10 μm. [Appendix 6] The pressure-sensitive adhesive sheet according to any one of Appendices 1 to 5, which is a sheet for encapsulating one or more optical semiconductor elements arranged on a substrate. [Appendix 7] An optical semiconductor device comprising: a substrate; an optical semiconductor element disposed on the substrate; and the pressure-sensitive adhesive sheet or a cured product thereof according to Appendix 6 that encapsulates the optical semiconductor element. [Explanation of symbols]

[0182] 1 adhesive sheet 2 Adhesive part 21 1st adhesive layer 22 Second adhesive layer 3 Release liner 4 Base material layer 41 Base film 42 Surface treatment layer 5. Substrate 6. Optical semiconductor elements 7 Sealing resin layer 71 1st adhesive layer 72 Second adhesive layer 10 Optical semiconductor device

Claims

1. A substrate and an adhesive portion formed on one surface of the substrate, the adhesive portion includes a first adhesive layer and a second adhesive layer, a laminated structure in which the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer, and the base material are laminated in this order; a visible light transmittance T1 of the first pressure-sensitive adhesive layer and a visible light transmittance T2 of the second pressure-sensitive adhesive layer satisfy T1<T2; The pressure-sensitive adhesive sheet, wherein the first pressure-sensitive adhesive layer has a storage modulus G1' at 90°C of 35 to 100 kPa.

2. The pressure-sensitive adhesive sheet according to claim 1 , wherein the storage modulus G1′ and the storage modulus G2′ at 90° C. of the second pressure-sensitive adhesive layer satisfy the relationship G1′ / G2′<1.

3.

3. The pressure-sensitive adhesive sheet according to claim 1 , wherein the first pressure-sensitive adhesive layer contains a colorant.

4. The pressure-sensitive adhesive sheet according to claim 3 , wherein the colorant contains carbon black.

5. The pressure-sensitive adhesive sheet according to claim 1 or 2, wherein the thickness of the first pressure-sensitive adhesive layer is 5 to 10 μm.

6. The pressure-sensitive adhesive sheet according to claim 1 or 2, which is a sheet for encapsulating one or more optical semiconductor elements arranged on a substrate.

7. An optical semiconductor device comprising: a substrate; an optical semiconductor element disposed on the substrate; and the pressure-sensitive adhesive sheet or a cured product thereof according to claim 6 that encapsulates the optical semiconductor element.

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