Solvent-free adhesive composition and adhesive film

Abstract

The present invention relates to a solvent-free adhesive composition capable of forming an adhesive material having improved durability under high temperature and high humidity conditions, whilst also having excellent optical properties, and an adhesive film comprising an adhesive layer that comprises a cured product of the composition.

Description

solvent-based adhesive composition and adhesive film

[0001] The present invention relates to an adhesive film comprising an adhesive layer including a solvent-free adhesive composition and a cured product thereof.

[0002] Various components, such as polarizers, TPS, and cover windows, are attached to the display panel as needed. Optical adhesive materials are used to minimize light loss or reflection when attaching these various components.

[0003] Light has the property of refracting or reflecting when it encounters layers of different materials. In display devices, reflection and refraction phenomena occur when light encounters air (air bubbles inside the product, the atmosphere), glass, etc., which can lead to a decrease in the visibility of the display device. To minimize this problem, air gaps within display products are filled with optical adhesive materials that have similar optical properties before and after the passage of light. Meanwhile, to be used in display devices that express color and brightness, optical adhesive materials require high transparency to minimize changes in light, and the transparency at the time of bonding must remain constant over time.

[0004] Optical adhesives widely used in display devices can be classified into OCA (Optically Clear Adhesive), which is manufactured in the form of a film with an adhesive layer formed between two release films, and OCR (Optically Clear Resin), which is supplied in a solution state and applied or injected directly.

[0005] As display devices are required to possess physical properties capable of maintaining excellent optical quality in various environments, adhesive materials used in display devices are also required to possess excellent optical properties and stability.

[0006] The present invention provides a solvent-free adhesive composition capable of realizing an adhesive material with excellent optical properties and improved durability under high temperature and high humidity conditions, and an adhesive film comprising an adhesive layer including a cured product thereof.

[0007] However, the problems that the present invention aims to solve are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below.

[0008] One embodiment of the present invention provides a solvent-free adhesive composition comprising: a (meth)acrylate-based prepolymer comprising a reaction product of a monomer solution comprising a (meth)acrylate-based monomer mixture and a tackifier; and an antioxidant.

[0009] According to one embodiment of the present invention, the tackifier may include a repeating unit represented by the following chemical formula 1:

[0010] [Chemical Formula 1]

[0011]

[0012] In the above chemical formula 1, R1 is a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, and R2 is hydrogen or a methyl group.

[0013] According to one embodiment of the present invention, the weight-average molecular weight of the tackifier may be 5,000 g / mol or more and 20,000 g / mol or less.

[0014] According to one embodiment of the present invention, the monomer solution may have a content of 1 part by weight or more and 10 parts by weight or less of the tackifier with respect to 100 parts by weight of the (meth)acrylate-based monomer mixture.

[0015] According to one embodiment of the present invention, the (meth)acrylate monomer mixture may comprise: a first (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms; a second (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 4 to 10 carbon atoms; and a third (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 1 to 3 carbon atoms.

[0016] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the first (meth)acrylate-based monomer may be 50 parts by weight or more and 75 parts by weight or less.

[0017] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the second (meth)acrylate-based monomer may be 10 parts by weight or more and 30 parts by weight or less.

[0018] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the third (meth)acrylate-based monomer may be 5 parts by weight or more and 15 parts by weight or less.

[0019] According to one embodiment of the present invention, the weight-average molecular weight of the (meth)acrylate-based prepolymer may be 300,000 g / mol or more and 1,000,000 g / mol or less.

[0020] According to one embodiment of the present invention, the antioxidant may comprise at least a phenol group-containing (meth)acrylate-based compound.

[0021] According to one embodiment of the present invention, with respect to 100 parts by weight of the (meth)acrylate-based prepolymer, the content of the antioxidant may be 0.1 parts by weight or more and 1 part by weight or less.

[0022] According to one embodiment of the present invention, the solvent-free adhesive composition further comprises a crosslinking agent, and the content of the crosslinking agent may be 0.05 parts by weight or more and 0.5 parts by weight or less per 100 parts by weight of the (meth)acrylate-based prepolymer.

[0023] According to one embodiment of the present invention, the solvent-free adhesive composition further comprises a photoinitiator, and the content of the photoinitiator may be 0.1 parts by weight or more and 1 part by weight or less with respect to 100 parts by weight of the (meth)acrylate-based prepolymer.

[0024] According to one embodiment of the present invention, the solvent-free adhesive composition further comprises an additive comprising at least one of a coupling agent, a chain transfer agent, and a corrosion inhibitor, and the content of the additive may be 1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the (meth)acrylate-based prepolymer.

[0025] One embodiment of the present invention provides an adhesive film comprising an adhesive layer comprising a cured product of the solvent-free adhesive composition.

[0026] According to one embodiment of the present invention, the yellow index value of the adhesive layer may be 1 or less.

[0027] According to one embodiment of the present invention, the color difference b* of the adhesive layer may be 0.5 or less.

[0028] A solvent-free adhesive composition according to one embodiment of the present invention can effectively realize an adhesive film having excellent adhesive strength and optical properties.

[0029] A solvent-free adhesive composition according to one embodiment of the present invention can effectively realize an adhesive film with excellent durability even under high temperature and high humidity conditions.

[0030] An adhesive film according to one embodiment of the present invention has excellent adhesive strength and optical properties, and may have excellent durability even under high temperature and high humidity conditions.

[0031] The effects of the present invention are not limited to those described above, and unmentioned effects will be clearly understood by those skilled in the art from the present specification and the accompanying drawings.

[0032] Throughout this specification, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0033] Throughout this specification, when a component is described as being located "on" another component, this includes not only cases where a component is in contact with another component, but also cases where another component exists between the two components.

[0034] Throughout the entire specification, the unit "parts by weight" may refer to the ratio of weight between each component.

[0035] Throughout this specification, terms including ordinal numbers, such as “first” and “second,” are used for the purpose of distinguishing one component from another and are not limited by said ordinal numbers. For example, within the scope of the invention, the first component may also be named the second component, and similarly, the second component may be named the first component.

[0036] Throughout the entire specification, the “weight-average molecular weight” and “number-average molecular weight” of a compound can be calculated using the molecular weight and molecular weight distribution of the compound. Specifically, a sample with a compound concentration of 1 wt% is prepared by placing tetrahydrofuran (THF) and the compound in a 50 ml glass vial. After filtering the standard sample (polystyrene) and the sample through a filter (pore size 0.45 μm), the sample is injected into a GPC injector, and the molecular weight and molecular weight distribution of the compound can be obtained by comparing the elution time of the sample with the calibration curve of the standard sample. At this time, an Infinity II 1260 (Agilient) can be used as the measuring instrument, and the flow rate can be set to 1.00 mL / min and the column temperature to 35.0 ℃.

[0037] Throughout the entire specification, the viscosity of a compound (or composition) may be a value measured by a Brookfield viscometer at a corresponding temperature. Specifically, after degassing the compound (or composition) to a bubble-free state, 0.5 mL is sampled using a 5 mL syringe, and the viscosity is measured for 10 minutes while maintaining a constant temperature (20 °C or 25 °C) using a Brookfield HB No. 40 spindle, and the cP value at the point where there is no change in viscosity is measured.

[0038] Throughout this specification, "(meth)acrylate" is used to refer collectively to acrylates and methacrylates.

[0039]

[0040] The present specification will be described in more detail below.

[0041] One embodiment of the present invention provides a solvent-free adhesive composition comprising: a (meth)acrylate-based prepolymer comprising a reaction product of a monomer solution comprising a (meth)acrylate-based monomer mixture and a tackifier; and an antioxidant.

[0042] A solvent-free adhesive composition according to one embodiment of the present invention can effectively realize an adhesive film having excellent adhesive strength and optical properties. In addition, the solvent-free adhesive composition can effectively realize an adhesive film having excellent durability even under high temperature and high humidity conditions.

[0043] According to one embodiment of the present invention, the tackifier may include a repeating unit represented by the following chemical formula 1:

[0044] [Chemical Formula 1]

[0045]

[0046] In the above chemical formula 1, R1 is a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, and R2 is hydrogen or a methyl group.

[0047] By using the tackifier comprising a repeating unit represented by Chemical Formula 1 above, the cured product of the solvent-free adhesive composition can achieve excellent tack and optical properties. In addition, the solvent-free adhesive composition comprising a (meth)acrylate-based prepolymer containing the tackifier in its bonding structure can effectively provide an adhesive layer with excellent durability that does not produce bubbles or delamination under high temperature and high humidity conditions.

[0048] According to one embodiment of the present invention, R1 in Formula 1 may be a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms. Specifically, R1 may be a straight-chain alkyl group, and the number of carbon atoms contained in the alkyl group may be 1 or more and 5 or less, 1 or more and 4 or less, 1 or more and 3 or less, 1 or more and 2 or less, 3 or more and 5 or less, or 4 or more and 5 or less. When R1 is the aforementioned alkyl group, the cured product of the solvent-free adhesive composition comprising a (meth)acrylate-based prepolymer formed using the tackifier may have properties such as tackiness, optical properties, and durability effectively improved.

[0049] According to one embodiment of the present invention, the weight-average molecular weight of the tackifier may be 5,000 g / mol or more and 20,000 g / mol or less. Specifically, the weight-average molecular weight of the tackifier may be 8,000 g / mol or more and 18,000 g / mol or less, 10,000 g / mol or more and 15,000 g / mol or less, 10,000 g / mol or more and 13,000 g / mol or less, 5,000 g / mol or more and 12,000 g / mol or less, 7,000 g / mol or more and 10,000 g / mol or less, 10,000 g / mol or more and 20,000 g / mol or less, or 15,000 g / mol or more and 20,000 g / mol or less. When the weight-average molecular weight of the above-mentioned tackifier satisfies the aforementioned range, the weight-average molecular weight of the above-mentioned (meth)acrylate-based prepolymer can be easily adjusted to the range described below. Through this, the solvent-free adhesive composition containing the above-mentioned (meth)acrylate-based prepolymer can effectively realize an adhesive layer having excellent tackiness while suppressing the occurrence of bubbles and delamination, while maintaining excellent optical properties even under high temperature and high humidity conditions after curing.

[0050] According to one embodiment of the present invention, the monomer solution may contain 1 part by weight or more and 10 parts by weight or less of the tackifier with respect to 100 parts by weight of the (meth)acrylate-based monomer mixture. Specifically, the content of the tackifier included in the monomer solution may be 2 parts by weight or more and 8 parts by weight or less, 3 parts by weight or more and 6 parts by weight or less, 1 part by weight or more and 5 parts by weight or less, 2.5 parts by weight or more and 3.5 parts by weight or less, 3 parts by weight or more and 10 parts by weight or less, 5 parts by weight or more and 10 parts by weight or less, or 7.5 parts by weight or more and 10 parts by weight or less, with respect to 100 parts by weight of the (meth)acrylate-based monomer mixture. When the content of the tackifier included in the monomer solution is within the aforementioned range, the repeating unit represented by Chemical Formula 1 can be stably introduced into the structure of the (meth)acrylate-based prepolymer. Through this, the solvent-free adhesive composition containing the above (meth)acrylate-based prepolymer can easily provide an adhesive layer with excellent adhesiveness, optical properties, and durability.

[0051] According to one embodiment of the present invention, the (meth)acrylate monomer mixture may comprise: a first (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms; a second (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 4 to 10 carbon atoms; and a third (meth)acrylate monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 1 to 3 carbon atoms. Specifically, the above (meth)acrylate monomer mixture comprises a first (meth)acrylate monomer containing an alkyl group, a second (meth)acrylate monomer containing a hydroxyl group but having different carbon atoms in the alkyl group, and a third (meth)acrylate monomer, thereby providing a solvent-free adhesive composition capable of realizing an adhesive layer with excellent adhesion to a target and improved optical properties.

[0052] According to one embodiment of the present invention, the first (meth)acrylate-based monomer may include a straight-chain alkyl group, and the number of carbon atoms contained in the alkyl group may be 1 or more and 10 or less, 1 or more and 8 or less, 1 or more and 6 or less, 1 or more and 4 or less, 3 or more and 7 or less, 4 or more and 5 or less, 4 or more and 10 or less, or 6 or more and 10 or less. When the first (meth)acrylate-based monomer contains the aforementioned alkyl group, the adhesive layer comprising the cured product of the solvent-free adhesive composition can achieve excellent adhesion to a target.

[0053] Specifically, the first (meth)acrylate-based monomer may include at least one of methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, heptyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl-5-(meth)acrylate, isooctyl (meth)acrylate, nonyl (meth)acrylate, and tequila (meth)acrylate.

[0054] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the first (meth)acrylate-based monomer may be 50 parts by weight or more and 75 parts by weight or less. Specifically, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the first (meth)acrylate-based monomer may be 55 parts by weight or more and 70 parts by weight or less, 60 parts by weight or more and 70 parts by weight or less, 65 parts by weight or more and 70 parts by weight or less, 60 parts by weight or more and 75 parts by weight or less, or 70 parts by weight or more and 75 parts by weight or less. By adjusting the content of the first (meth)acrylate monomer included in the above (meth)acrylate monomer mixture to the aforementioned range, the adhesive film containing the cured product of the solvent-free adhesive composition can exhibit excellent adhesive strength.

[0055] According to one embodiment of the present invention, the second (meth)acrylate monomer and the third (meth)acrylate monomer may contain an alkyl group to which a hydroxyl group is bonded. In this case, the number of alkyl groups contained in the second (meth)acrylate monomer and the third (meth)acrylate monomer may be different. By using the second (meth)acrylate monomer and the third (meth)acrylate monomer with different numbers of alkyl groups, the solvent-free adhesive composition can achieve excellent optical properties after curing.

[0056] According to one embodiment of the present invention, the second (meth)acrylate-based monomer may include a straight-chain alkyl group, and a hydroxyl group may be bonded to the alkyl group. In this case, the number of carbon atoms contained in the alkyl group may be 4 or more and 10 or less, 4 or more and 8 or less, 4 or more and 6 or less, 4 or more and 5 or less, 5 or more and 10 or less, or 7 or more and 10 or less. When the second (meth)acrylate-based monomer contains the aforementioned hydroxyl-bonded alkyl group, the adhesive layer comprising the cured product of the solvent-free adhesive composition may have excellent optical properties and improved durability.

[0057] Specifically, the second (meth)acrylate-based monomer may include at least one of hydroxy n-butyl (meth)acrylate, hydroxy t-butyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, hydroxy sec-butyl (meth)acrylate, hydroxypentyl (meth)acrylate, hydroxyhexyl (meth)acrylate, hydroxy 2-ethylbutyl (meth)acrylate, hydroxyheptyl (meth)acrylate, hydroxy 2-ethylhexyl (meth)acrylate, hydroxy n-octyl-5-(meth)acrylate, hydroxyisooctyl (meth)acrylate, hydroxynonyl (meth)acrylate, and hydroxydekyl (meth)acrylate.

[0058] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the second (meth)acrylate-based monomer may be 10 parts by weight or more and 30 parts by weight or less. Specifically, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the second (meth)acrylate-based monomer may be 12.5 parts by weight or more and 27.5 parts by weight or less, 15 parts by weight or more and 25 parts by weight or less, 17.5 parts by weight or more and 22.5 parts by weight or less, 10 parts by weight or more and 25 parts by weight or less, 15 parts by weight or more and 25 parts by weight or less, 20 parts by weight or more and 25 parts by weight or less, 20 parts by weight or more and 30 parts by weight or less, 22.5 parts by weight or more and 27.5 parts by weight or less, or 25 parts by weight or more and 30 parts by weight or less. When the content of the second (meth)acrylate-based monomer is within the aforementioned range, the adhesive layer prepared using the solvent-free composition may have excellent adhesive strength, optical properties, and durability under high temperature and high humidity conditions.

[0059] According to one embodiment of the present invention, the third (meth)acrylate-based monomer may include a straight-chain alkyl group, and a hydroxyl group may be bonded to the alkyl group. In this case, the number of carbon atoms contained in the alkyl group may be 1 or more and 3 or less, 1 or more and 2 or less, or 2 or more and 3 or less. When the third (meth)acrylate-based monomer contains the aforementioned hydroxy-bonded alkyl group, the adhesive layer comprising the cured product of the solvent-free adhesive composition may have excellent optical properties and improved durability. Specifically, the third (meth)acrylate-based monomer may include at least one of hydroxymethyl (meth)acrylate, hydroxyethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and hydroxy n-propyl (meth)acrylate.

[0060] According to one embodiment of the present invention, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the third (meth)acrylate-based monomer may be 5 parts by weight or more and 15 parts by weight or less. Specifically, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of the third (meth)acrylate-based monomer may be 7.5 parts by weight or more and 12.5 parts by weight or less, 10 parts by weight or more and 12.5 parts by weight or less, 5 parts by weight or more and 10 parts by weight or less, 8 parts by weight or more and 10 parts by weight or less, 10 parts by weight or more and 15 parts by weight or less, or 13 parts by weight or more and 15 parts by weight or less. When the content of the third (meth)acrylate-based monomer is within the aforementioned range, the adhesive layer prepared using the solvent-free composition may have excellent adhesive strength, optical properties, and durability under high temperature and high humidity conditions.

[0061] According to one embodiment of the present invention, the content of the second (meth)acrylate monomer included in the (meth)acrylate monomer mixture may be greater than the content of the third (meth)acrylate monomer. Specifically, the weight ratio of the third (meth)acrylate monomer and the second (meth)acrylate monomer may be 1:1.1 to 1:5, 1:1.5 to 1:4, 1:2 to 1:3, 1:1.1 to 1:3, 1:1.5 to 1:2.5, or 1:3 to 1:5. When the weight ratio of the second (meth)acrylate monomer and the third (meth)acrylate monomer included in the above (meth)acrylate monomer mixture is within the aforementioned range, the adhesive layer prepared using the solvent-free composition may have excellent adhesive strength, optical properties, and durability under high temperature and high humidity conditions.

[0062] According to one embodiment of the present invention, the weight-average molecular weight of the (meth)acrylate-based prepolymer may be 300,000 g / mol or more and 1,000,000 g / mol or less. Specifically, the weight-average molecular weight of the (meth)acrylate-based prepolymer may be 400,000 g / mol or more and 800,000 g / mol or less, 500,000 g / mol or more and 600,000 g / mol or less, 300,000 g / mol or more and 700,000 g / mol or less, 450,000 g / mol or more and 650,000 g / mol or less, 500,000 g / mol or more and 1,000,000 g / mol or less, 500,000 g / mol or more and 800,000 g / mol or less, or 700,000 g / mol or more and 1,000,000 g / mol or less. The solvent-free adhesive composition comprising the (meth)acrylate-based prepolymer having the aforementioned weight-average molecular weight can easily realize an adhesive layer with excellent adhesive strength and durability.

[0063] According to one embodiment of the present invention, the antioxidant may comprise at least a phenol group-containing (meth)acrylate-based compound. Specifically, the phenol group-containing (meth)acrylate-based compound may have a phenol group attached to the end of the main chain. Additionally, the phenol group-containing (meth)acrylate-based compound may have a (meth)acrylate group present at the end or inside of the main chain. By using an antioxidant comprising a phenol group-containing (meth)acrylate-based compound, the solvent-free adhesive composition can effectively provide an adhesive film with excellent optical reliability, weather resistance, and light resistance.

[0064] According to one embodiment of the present invention, the content of the antioxidant may be 0.1 parts by weight or more and 1 part by weight or less with respect to 100 parts by weight of the (meth)acrylate-based prepolymer. Specifically, the content of the antioxidant included in the solvent-free adhesive composition may be 0.1 parts by weight or more and 0.8 parts by weight or less, 0.3 parts by weight or more and 0.5 parts by weight or less, 0.1 parts by weight or more and 0.5 parts by weight or less, 0.5 parts by weight or more and 1 part by weight or less, or 0.7 parts by weight or more and 1 part by weight or less with respect to 100 parts by weight of the (meth)acrylate-based prepolymer. By controlling the content of the antioxidant to the aforementioned range, a solvent-free adhesive composition can be provided that enables the realization of an adhesive layer with excellent optical reliability while suppressing the occurrence of cloudiness and lifting under high temperature and high humidity conditions.

[0065] According to one embodiment of the present invention, the solvent-free adhesive composition may further include a crosslinking agent. Specifically, the crosslinking agent may include a polyfunctional (meth)acrylate-based compound. More specifically, the polyfunctional (meth)acrylate-based compound may include (meth)acrylate groups in a number of 2 to 10, 2 to 8, 2 to 6, 2 to 4, or 2 to 3. By using the polyfunctional (meth)acrylate-based compound as a crosslinking agent, the (meth)acrylate-based prepolymer can be stably crosslinked. Through this, the cured product of the solvent-free adhesive composition can achieve improved tackiness and durability.

[0066] Specifically, the polyfunctional (meth)acrylate-based compound may include at least one of hexanediol di(meth)acrylate, tripropylene glycol di(meth)acrylate, ethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane ethoxy tri(meth)acrylate, glycerin propoxylated tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate.

[0067] According to one embodiment of the present invention, with respect to 100 parts by weight of the (meth)acrylate-based prepolymer, the content of the crosslinking agent may be 0.05 parts by weight or more and 0.5 parts by weight or less, 0.1 parts by weight or more and 0.3 parts by weight or less, 0.05 parts by weight or more and 0.2 parts by weight or less, 0.1 parts by weight or more and 0.4 parts by weight or less, or 0.3 parts by weight or more and 0.5 parts by weight or less. When the content of the crosslinking agent is within the aforementioned range, a stable crosslinking reaction can be performed with respect to the solvent-free adhesive composition.

[0068] According to one embodiment of the present invention, the solvent-free adhesive composition may further include a photoinitiator. Any photoinitiator used in the art may be used without limitation. Specifically, the photoinitiator may include at least one of an acetophenone-based compound, a benzophenone-based compound, a thioxantone-based compound, a benzoin-based compound, and a triazine-based compound.For example, the above photoinitiator is an acetophenone-based compound such as 2,2'-diethoxyacetophenone, 2,2'-dibutoxyacetophenone, 2-hydroxy-2-methylpropiophenone, pt-butyltrichloroacetophenone, pt-butyldichloroacetophenone, benzophenone, 4-chloroacetophenone, 4,4'-dimethylaminobenzophenone, 4,4'-dichlorobenzophenone, 3,3'-dimethyl-2-methoxybenzophenone, 2,2'-dichloro-4-phenoxyacetophenone, 2-methyl-1-(4-(methylthio)phenyl)-2-morpholinopropan-1-one, 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one; Benzophenone compounds such as benzophenone, benzoyl benzoic acid, methyl benzoic acid, 4-phenylbenzophenone, hydroxybenzophenone, acrylated benzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone; thioxantone compounds such as thioxantone, 2-chlorothioxantone, 2-methylthioxantone, isopropylthioxantone, 2,4-diethylthioxantone, 2,4-diisopropylthioxantone, 2-chlorothioxantone; benzoin compounds such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, and benzyldimethylketal; and 2,4,6,-trichloros-triazine, 2-phenyl-4,6-bis(trichloromethyl)-s-triazine, 2-(3',4'-dimethoxystyryl)-4,6-bis(trichloromethyl)-s-triazine, 2-(4'-methoxynaphthyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-methoxyphenyl)-4,6-bis(trichloromethyl)-s-triazine, 2-(p-tril)-4,6-bis(trichloromethyl)-s-triazine, 2-phenyl 4,6-bis(trichloromethyl)-s-triazine, bis(trichloromethyl)-6-styryl-s-triazine, 2-(naphtho-1-yl)-4,6-bis(trichloromethyl)-s-triazine, It may include at least one of triazine compounds such as 2-(4-methoxynaphth-1-yl)-4,6-bis(trichloromethyl)-s-triazine, 2-4-trichloromethyl(piperonyl)-6-triazine, and 2-4-trichloromethyl(4'-methoxystyryl)-6-triazine.

[0069] According to one embodiment of the present invention, with respect to 100 parts by weight of the (meth)acrylate-based prepolymer, the content of the photoinitiator may be 0.1 parts by weight or more and 1 part by weight or less, 0.3 parts by weight or more and 0.7 parts by weight or less, 0.1 parts by weight or more and 0.5 parts by weight or less, 0.1 parts by weight or more and 0.3 parts by weight or less, or 0.6 parts by weight or more and 1 part by weight or less. By controlling the content of the photoinitiator to the aforementioned range, stable photocuring of the solvent-free adhesive composition can be achieved, and the curing speed can be improved. Furthermore, when the content of the photoinitiator is within the aforementioned range, the deterioration of optical properties such as transmittance and yellow index of the photocurable of the solvent-free adhesive composition can be effectively prevented.

[0070] According to one embodiment of the present invention, the solvent-free adhesive composition further comprises an additive comprising at least one of a coupling agent, a chain transfer agent, and a corrosion inhibitor, wherein the content of the additive may be 1 part by weight or more and 5 parts by weight or less with respect to 100 parts by weight of the (meth)acrylate-based prepolymer. By controlling the content of the additive to the aforementioned range, the mechanical and optical properties of the photocurable of the solvent-free adhesive composition can be effectively supplemented.

[0071] According to one embodiment of the present invention, the solvent-free adhesive composition may include a coupling agent as an additive. The coupling agent used in the art may be used without limitation. For example, the coupling agent may include at least a silane-based coupling agent. The content of the coupling agent may be 0.1 parts by weight or more and 0.5 parts by weight or less, 0.2 parts by weight or more and 0.3 parts by weight or less, 0.1 parts by weight or more and 0.2 parts by weight or less, or 0.3 parts by weight or more and 0.5 parts by weight or less, based on 100 parts by weight of the (meth)acrylate-based prepolymer. By adjusting the content of the coupling agent to the aforementioned range, the mechanical strength and adhesiveness of the adhesive layer formed using the solvent-free adhesive composition can be improved.

[0072] According to one embodiment of the present invention, the solvent-free adhesive composition may include a chain transfer agent as an additive. The chain transfer agent used in the art may be used without limitation. For example, the chain transfer agent may include at least a styrene-based dimer compound. The content of the chain transfer agent may be 0.1 parts by weight or more and 0.5 parts by weight or less, 0.1 parts by weight or more and 0.3 parts by weight or less, 0.1 parts by weight or more and 0.2 parts by weight or less, or 0.3 parts by weight or more and 0.5 parts by weight or less, based on 100 parts by weight of the (meth)acrylate-based prepolymer. When the content of the chain transfer agent is within the aforementioned range, the crosslinking reaction of the (meth)acrylate-based prepolymer can be appropriately controlled. Through this, the mechanical strength and adhesiveness of the adhesive layer formed using the solvent-free adhesive composition can be improved.

[0073] According to one embodiment of the present invention, the solvent-free adhesive composition may include a corrosion inhibitor as an additive. The corrosion inhibitor may be any one used in the art without limitation. For example, the corrosion inhibitor may include at least one of a benzimidazole-based compound, a triazole-based compound, and a tetrazole-based compound. By adding the corrosion inhibitor, corrosion of copper-containing components inside a display device can be suppressed. The content of the corrosion inhibitor may be 0.1 parts by weight or more and 0.5 parts by weight or less, 0.1 parts by weight or more and 0.3 parts by weight or less, 0.1 parts by weight or more and 0.2 parts by weight or less, or 0.3 parts by weight or more and 0.5 parts by weight or less, based on 100 parts by weight of the (meth)acrylate-based prepolymer. When the content of the corrosion inhibitor is within the aforementioned range, the adhesive layer formed using the solvent-free adhesive composition can effectively prevent copper components from corroding when applied to a display.

[0074] According to one embodiment of the present invention, the solvent-free adhesive composition may include a peel strength enhancer as an additive. The peel strength enhancer may be any used in the art without limitation. For example, the peel strength enhancer may include at least a pyrrolidone-based compound. The content of the peel strength enhancer may be 0.5 parts by weight or more and 2 parts by weight or less, 0.8 parts by weight or more and 1.8 parts by weight or less, 1 part by weight or more and 1.5 parts by weight or less, or 0.5 parts by weight or more and 1.2 parts by weight or less, based on 100 parts by weight of the (meth)acrylate-based prepolymer. When the content of the peel strength enhancer is within the aforementioned range, the peel strength of the adhesive layer formed using the solvent-free adhesive composition can be effectively enhanced.

[0075] According to one embodiment of the present invention, the viscosity of the solvent-free adhesive composition may be 1,000 cps or more and 5,000 cps or less. Specifically, the viscosity of the solvent-free adhesive composition may be 2,000 cps or more and 4,000 cps or less, 2,000 cps or more and 3,000 cps or less, 1,000 cps or more and 3,000 cps or less, or 3,000 cps or more and 5,000 cps or less at 25°C. The solvent-free adhesive composition having the above-mentioned viscosity may have excellent applicability and processability.

[0076] One embodiment of the present invention provides an adhesive film comprising an adhesive layer comprising a cured product of the solvent-free adhesive composition.

[0077] An adhesive film according to one embodiment of the present invention has excellent adhesive strength and optical properties, and may have excellent durability even under high temperature and high humidity conditions. Specifically, the adhesive film can achieve improved adhesive strength, optical properties, and durability under high temperature and high humidity conditions by including an adhesive layer comprising a photocurable of the solvent-free adhesive composition.

[0078] According to one embodiment of the present invention, the yellow index value of the adhesive layer may be 1 or less. The yellow index value of the adhesive layer may be 0.1 or more and 1 or less, 0.2 or more and 0.8 or less, 0.2 or more and 0.7 or less, 0.2 or more and 0.6 or less, or 0.2 or more and 0.5 or less. Specifically, the yellow index value of the adhesive layer after UV irradiation under high temperature conditions may satisfy the aforementioned range. At this time, the high temperature condition may be 50°C or more and 100°C or less. In addition, UV satisfying a wavelength value of 200 nm or more and 400 nm or less is irradiated at 0.5 W / m² 2 1 W / m or more 2It may be irradiated with the following irradiation amount. That is, as the adhesive layer satisfies the yellow index value under the aforementioned conditions, it exhibits less variability under high temperature conditions and light irradiation conditions, and thus can have excellent optical reliability.

[0079] According to one embodiment of the present invention, the color difference b* of the adhesive layer may be 0.5 or less. Specifically, the color difference b* of the adhesive layer may be 0.2 or more and 0.5 or less, 0.2 or more and 0.4 or less, or 0.2 or more and 0.3 or less. The color difference b* is a factor that significantly affects the high-temperature reliability of the adhesive. By including the (meth)acrylate-based prepolymer and the antioxidant together in the solvent-free adhesive composition, the cured product can achieve a color difference b* within the above range, and by exhibiting a color difference b* within the above range, it can exhibit excellent optical reliability even at high temperatures.

[0080] According to one embodiment of the present invention, the color difference Δb* of the adhesive layer after UV irradiation under high temperature conditions may be 0.5 or less. Specifically, the color difference Δb* of the adhesive layer may be 0.2 or more and 0.5 or less, 0.2 or more and 0.4 or less, or 0.2 or more and 0.3 or less. At this time, the high temperature condition may be 50 ℃ or more and 100 ℃ or less. In addition, UV satisfying a wavelength value of 200 nm or more and 400 nm or less is 0.5 W / m² 2 1 W / m or more 2 It may be irradiated with the following amount of irradiation. That is, as the adhesive layer satisfies the color difference Δb* value under the aforementioned conditions, excellent optical reliability can be achieved even under high temperature conditions and light irradiation conditions.

[0081]

[0082] Hereinafter, the present invention will be described in detail with reference to examples to specifically explain the invention. However, the embodiments according to the present invention may be modified in various different forms, and the scope of the present invention is not to be interpreted as being limited to the embodiments described below. The embodiments of this specification are provided to more completely explain the present invention to those with average knowledge in the art.

[0083]

[0084] ingredient

[0085] Butyl acrylate was prepared as the first (meth)acrylate monomer, 4-hydroxybutyl acrylate (4-HBA) as the second (meth)acrylate monomer, and 2-hydroxyethyl acrylate (2-HEA) as the third (meth)acrylate monomer.

[0086] A compound containing a repeating unit of the following chemical formula 1 was prepared as a tackifier.

[0087] [Chemical Formula 1]

[0088]

[0089] At this time, R1 and R2 in Chemical Formula 1 are methyl groups, and the weight-average molecular weight of the compound was 10,000 g / mol.

[0090] Hexanediol diacrylate, a coupling agent (KBM 403, Shin-Etsu), a photoinitiator (Irgacure 651, Ciba Specialty Chemicals), and a chain transfer agent (AMSD-GRH, GOI CHEMICAL) were prepared as crosslinking agents.

[0091] In addition, benzotriazole was prepared as a corrosion inhibitor, and N-vinylpyrrolidone (NVP, Sigma Aldrich) was prepared as a peel strength enhancer.

[0092] The following substances were prepared as antioxidants.

[0093] Primary Antioxidant: Songnox 1010, Songwon

[0094] Secondary Antioxidant: Songnox 1076, Songwon

[0095] Third antioxidant: Songnox 1135, Songwon

[0096] Quaternary Antioxidant: Irganox 1010, BASF

[0097] VIII Antioxidant: Irganox 1076, BASF

[0098]

[0099] Examples

[0100] Example 1

[0101] Synthesis of (meth)acrylate-based prepolymers

[0102] A 1L reactor was prepared with a cooling device installed to facilitate temperature control and nitrogen gas reflux.

[0103] Subsequently, a monomer solution containing a (meth)acrylate-based monomer mixture including butyl acrylate (BA), 4-hydroxybutyl acrylate (4-HBA), and 2-hydroxyethyl acrylate (2-HEA), and a tackifier was added.

[0104] At this time, based on 100 parts by weight of the (meth)acrylate-based monomer mixture, the content of BA was 67 parts by weight, the content of 4-HBA was 23 parts by weight, and the content of 2-HEA was 10 parts by weight. The content of the tackifier was 3 parts by weight with respect to 100 parts by weight of the (meth)acrylate-based monomer mixture.

[0105] Subsequently, the monomer solution was partially polymerized to obtain a (meth)acrylate-based prepolymer with a viscosity of 9,000 cps at 25 °C. At this time, the weight-average molecular weight of the (meth)acrylate-based prepolymer was 550,000 g / mol.

[0106]

[0107] Preparation of solvent-free adhesive composition

[0108] A solvent-free adhesive composition was prepared by mixing the (meth)acrylate-based prepolymer synthesized above with a first antioxidant (Songnox 1010, Songwon), a crosslinking agent, a coupling agent, a photoinitiator, a chain transfer agent, benzotriazole, and N-vinylpyrrolidone.

[0109] At this time, for 100 parts by weight of (meth)acrylate-based prepolymer, the content of the first antioxidant was 0.5 parts by weight, the content of the crosslinking agent was 0.1 parts by weight, the content of the coupling agent was 0.2 parts by weight, the content of the photoinitiator was 0.3 parts by weight, the content of the chain transfer agent was 0.1 parts by weight, the content of the benzotriazole was 0.3 parts by weight, and the content of N-vinylpyrrolidone was 1 part by weight.

[0110] The manufactured solvent-free adhesive composition had a viscosity of about 2,500 cps at 25°C.

[0111]

[0112] Manufacturing of adhesive film

[0113] The prepared solvent-free adhesive composition was coated onto a polyethylene terephthalate film (ROH751, Toray Advanced Materials, thickness: 75 μm) using a bar coater with a release-treated release film to a thickness of 250 μm after UV curing. Subsequently, an adhesive film containing an adhesive layer was prepared by curing it using a UV multi-type curing machine (JH Tech UHFSL-fa4LE) by irradiating it with ultraviolet light (Black light) from a UV lamp at 100% light intensity for 5 minutes. At this time, the thickness of the adhesive layer was approximately 250 μm.

[0114]

[0115] Examples 2 to 7

[0116] A (meth)acrylate-based prepolymer synthesized in Example 1 above was prepared. Subsequently, a solvent-free adhesive composition and an adhesive film were prepared in the same manner as in Example 1, except that the type and content of the antioxidant included in the solvent-free adhesive composition were adjusted as shown in Table 1 below.

[0117]

[0118] Comparative Examples 1 to 2

[0119] A (meth)acrylate-based prepolymer synthesized in Example 1 above was prepared. Subsequently, a solvent-free adhesive composition and an adhesive film were prepared in the same manner as in Example 1, except that the type and content of the antioxidant included in the solvent-free adhesive composition were adjusted as shown in Table 1 below.

[0120]

[0121] (Met)acrylate-based prepolymer Type and Content of Antioxidant Example 1,100 parts by weight 1st Antioxidant 0.5 Example 2,100 parts by weight 2nd Antioxidant 0.5 Example 3,100 parts by weight 3rd Antioxidant 0.5 Example 4,100 parts by weight 4th Antioxidant 0.5 Example 5,100 parts by weight 5th Antioxidant 0.5 Example 6,100 parts by weight 1st Antioxidant 0.1 Example 7,100 parts by weight 1st Antioxidant 1.0 Comparative Example 1,100 parts by weight -- Comparative Example 2,100 parts by weight 1st Antioxidant 1.2

[0122]

[0123] In Table 1 above, the content (parts by weight) of the antioxidant is based on 100 parts by weight of the (meth)acrylate-based prepolymer.

[0124]

[0125] Experimental Example

[0126] 1. Measurement of swelling index

[0127] The swelling index of the adhesive layer prepared in the above examples and comparative examples was measured as follows.

[0128] A sample was prepared by cutting the adhesive layer into small pieces with scissors, 1 g of the sample was placed in 100 g of toluene and stored in a dark room at room temperature for 48 hours, then separated into a sol and a gel, and the swelling index was calculated using the following formula.

[0129] Swelling Index = Weight of swollen gel (g) / Weight of gel (g)

[0130]

[0131] 2. Gel fraction

[0132] The cured product (adhesive) of the solvent-free adhesive composition was cut to a size of 5 cm × 5 cm, placed in a polyethylene bottle, and its weight (a) was measured. Subsequently, ethyl acetate was added to the polyethylene bottle to ensure the adhesive was sufficiently submerged, and the mixture was left at 25°C for 24 hours. Then, the adhesive and ethyl acetate from the polyethylene bottle were poured into a wire mesh (weight: b) cut to a size of 14 cm × 14 cm and filtered. Afterward, the wire mesh filtered with the adhesive was dried in an oven at 110°C for 2 hours, and its weight (c) was measured. Subsequently, the gel fraction (unit: %) was measured by substituting each of the measured weights a, b, and c into the following general formula 1.

[0133] [General Formula 1]

[0134] Gel fraction = ((cb) / a) × 100

[0135]

[0136] 3. Measurement of substrate peel strength

[0137] The adhesive film prepared in the examples and comparative examples was cut to a size of 25 mm × 20 cm (width × height), and after peeling off the release film, it was attached to stainless steel (SUS 304) by reciprocating a 2 kg roller 5 times. After 20 minutes had elapsed, the peel strength was measured using a tensile testing machine (LR5K plus, LLOYD Instruments) under conditions of a peel speed of 300 mm / min and a peel angle of 180°.

[0138]

[0139] 4. Haze and Transmittance Measurement

[0140] After attaching the adhesive layer prepared in the examples and comparative examples to a glass surface with a thickness of 1.1 mm in the form of glass (0.7 mm) / adhesive layer (250 μm), haze and transmittance were measured using NDH 5000 (Nippon Denshoku).

[0141]

[0142] 5. Color difference b* measurement

[0143] After attaching the adhesive layer prepared in the examples and comparative examples to a glass surface with a thickness of 1.1 mm in the form of glass (1.1 mm) / adhesive layer (250 μm), the color difference b* was measured using CM-3600A (Konica Minolta).

[0144]

[0145] 6. Durability Evaluation

[0146] 6-1. High Temperature (105 ℃) Evaluation

[0147] Samples were prepared using the adhesive layers prepared in the examples and comparative examples as shown in the following structure, and after being left at a high temperature (105 ℃) for 500 hours, the presence of bubbles and lifting was visually checked. Performance was evaluated as ○ if no bubbles or lifting occurred, and X if they occurred.

[0148] Sample: Glass(0.7 mm) / PSA / Pol / Adhesive layer(250 µm) / Glass(0.7 mm)

[0149] Pol: LG chem. clear Pol

[0150] PSA: LG Chem

[0151]

[0152] 6-2. Evaluation of Cloudiness / Foam

[0153] The adhesive layer (250 μm) prepared in the example and comparative example was attached to a 1.1 mm thick glass substrate using a 2 kg roller, and a 0.55 mm thick glass substrate was laminated thereon.

[0154] Then, the specimens were placed in an autoclave at 40°C and 4 bar for 20 minutes. Furthermore, using a UV multi-type curing machine (JH Tech UHFSL-fa4LE), the specimens were irradiated with ultraviolet (Black light) at 100% intensity for 5 minutes, placed in an oven at a temperature of 85°C and a relative humidity of 85 RH%, and after 500 hours, the presence of cloudiness and bubbles was visually checked. Performance was evaluated as ○ if no cloudiness or bubbles occurred, and X if they occurred.

[0155]

[0156] 6-3. Evaluation of High Temperature and High Temperature & High Humidity

[0157] Samples were prepared using the adhesive layers prepared in the examples and comparative examples as shown in the following structure, and after being left for 500 hours under high temperature (85 ℃) and high humidity (relative humidity of 85 RH%) conditions, the presence of bubbles and lifting was visually checked. Performance was evaluated as ○ if no bubbles or lifting occurred, and X if they occurred.

[0158] Sample: Glass(0.7 mm) / Adhesive layer(250 µm) / Glass(0.7 mm)

[0159]

[0160] 7. Q-UV Evaluation

[0161] Samples were prepared using the adhesive layers prepared in the examples and comparative examples as shown in the following structure, and after being left for 200 hours under the following operating conditions, changes in yellowing (△b* and Yellow index) were evaluated.

[0162] Sample: Glass(0.7 mm) / Adhesive layer(250 µm) / Glass(0.7 mm)

[0163] Q-UV operating conditions: 0.8W / m² 2 (@340nm), 70 ℃, 200 hours

[0164]

[0165] 1. Swelling index 2. Gel fraction (%) 3. Substrate peel strength (gf / in) 4. Haze 4. Transmittance 5. Optical optics / b* Example 1 28.15 67.9 22,765 0.36 91.63 0.3 Example 2 25.56 65.78 2,723 0.32 92.01 0.28 Example 3 28.10 67.8 2,740 0.25 91.60 0.29 Example 4 27.59 67.51 2,659 0.29 91.95 0.28 Example 5 27.54 67. 842,7950.3491.780.28 Example 6 26.1669.902,5590.2692.000.27 Example 7 31.0565.103,0150.5091.050.35 Comparative Example 1 26.0569.302,5350.2591.80.26 Comparative Example 2 32.0064.583,1000.56910.39

[0166] 6. Durability (500 hours) 7. Q-UV (200 hours) 6-1. High temperature (105℃) 6-2. Cloudiness / Bubbling 6-3. High temperature and high humidity △b*△Yellow index Example 1 0.32 0.50 Example 2 0.41 0.71 Example 3 0.35 0.55 Example 4 0.34 0.52 Example 5 0.37 0.60 Example 6 0.50 0.65 Example 7 0.15 0.21 Comparative Example 1 0.82 1.29 Comparative Example 2 0.15 0.20

[0167] Referring to Tables 1 to 3 above, it was confirmed that the adhesive layers prepared in Examples 1 to 7 of the present invention exhibited excellent adhesiveness, optical properties, and durability. On the other hand, in the case of Comparative Example 1, which did not contain an antioxidant, it was confirmed that the optical properties changed due to yellowing, indicating that the light resistance was inferior. Meanwhile, in the case of Comparative Example 2, in which the content of the antioxidant fell outside the aforementioned range, it was confirmed that although no yellowing occurred, the durability was inferior.

Claims

1. A (meth)acrylate-based prepolymer comprising a reaction product of a monomer solution comprising a (meth)acrylate-based monomer mixture and a tackifier; and A solvent-free adhesive composition comprising an antioxidant.

2. In Paragraph 1, A solvent-free adhesive composition wherein the adhesive promoter comprises a repeating unit represented by the following chemical formula 1: [Chemical Formula 1] In the above chemical formula 1, R1 is a straight-chain or branched-chain alkyl group having 1 to 5 carbon atoms, and R2 is hydrogen or a methyl group.

3. In Paragraph 1, A solvent-free adhesive composition having a weight-average molecular weight of the adhesive agent of the above-mentioned amount of 5,000 g / mol or more and 20,000 g / mol or less.

4. In Paragraph 1, Among the above monomer solution, A solvent-free adhesive composition having a content of 1 part by weight or more and 10 parts by weight or less of the tackifier per 100 parts by weight of the above (meth)acrylate-based monomer mixture.

5. In Paragraph 1, The above (meth)acrylate-based monomer mixture is, A first (meth)acrylate-based monomer containing a straight-chain or branched-chain alkyl group having 1 to 10 carbon atoms; A second (meth)acrylate-based monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 4 to 10 carbon atoms; and A solvent-free adhesive composition comprising: a third (meth)acrylate-based monomer containing a straight-chain or branched-chain alkyl group and a hydroxyl group having 1 to 3 carbon atoms.

6. In Paragraph 5, A solvent-free adhesive composition having a content of 50 parts by weight or more and 75 parts by weight or less of the first (meth)acrylate monomer, based on 100 parts by weight of the above (meth)acrylate monomer mixture.

7. In Paragraph 5, A solvent-free adhesive composition having a content of 10 parts by weight or more and 30 parts by weight or less of the second (meth)acrylate-based monomer based on 100 parts by weight of the above (meth)acrylate-based monomer mixture.

8. In Paragraph 5, A solvent-free adhesive composition having a content of 5 parts by weight or more and 15 parts by weight or less of the third (meth)acrylate-based monomer based on 100 parts by weight of the above (meth)acrylate-based monomer mixture.

9. In Paragraph 1, A solvent-free adhesive composition having a weight-average molecular weight of the above (meth)acrylate-based prepolymer of 300,000 g / mol or more and 1,000,000 g / mol or less.

10. In Paragraph 1, A solvent-free adhesive composition in which the above-mentioned antioxidant comprises at least a phenol group-containing (meth)acrylate-based compound.

11. In Paragraph 1, A solvent-free adhesive composition having a content of 0.1 parts by weight or more and 1 part by weight or less of the antioxidant per 100 parts by weight of the above (meth)acrylate-based prepolymer.

12. In Paragraph 1, It further contains a crosslinking agent, A solvent-free adhesive composition having a crosslinking agent content of 0.05 parts by weight or more and 0.5 parts by weight or less, based on 100 parts by weight of the above (meth)acrylate-based prepolymer.

13. In Paragraph 1, It further includes a photoinitiator, A solvent-free adhesive composition having a content of 0.1 parts by weight or more and 1 part by weight or less of the photoinitiator per 100 parts by weight of the above (meth)acrylate-based prepolymer.

14. In Paragraph 1, It further comprises an additive comprising at least one of a coupling agent, a chain transfer agent, and a corrosion inhibitor, and A solvent-free adhesive composition having a content of 1 part by weight or more and 5 parts by weight or less of the additive, based on 100 parts by weight of the above (meth)acrylate-based prepolymer.

15. An adhesive film comprising an adhesive layer comprising a cured product of a solvent-free adhesive composition according to claim 1.

16. In Paragraph 15, At a temperature of 50 ℃ to 100 ℃, UV light with a wavelength value of 200 nm to 400 nm is applied to the adhesive layer at 0.5 W / m 2 1 W / m or more 2 An adhesive film having a yellow index value of 1 or less measured after irradiation with an irradiation dose below.

17. In Paragraph 15, At a temperature of 50 ℃ to 100 ℃, UV light with a wavelength value of 200 nm to 400 nm is applied to the adhesive layer at 0.5 W / m 2 1 W / m or more 2 An adhesive film having a color difference △b* of 0.5 or less measured after irradiation with an irradiation dose below.

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