KR102289244B1 - Low reflection adhesive composition, adhesive film comprising the cured product thereof, and optical member comprising thereof - Google Patents

Abstract

The present specification relates to a low-refractive adhesive composition, a low-refractive adhesive film including a cured product thereof, and an optical member including the same.

Description

Low-refractive adhesive composition, low-refractive adhesive film comprising a cured product thereof, and an optical member comprising the same

The present specification provides a low-refractive adhesive composition, a low-refractive adhesive film including a cured product thereof, and an optical member including the same.

Various members are attached to the electronic device by means of an adhesive layer. For example, various optical members such as a polarizing plate, a retardation plate, an optical compensation film, a reflective sheet, a protective film, and a luminance enhancing film may be attached to a liquid crystal display (LCD) by an adhesive film.

The pressure-sensitive adhesive film used for an optical member such as a touch panel may be applied to a substrate having a printing step, or the like. At this time, if the pressure-sensitive adhesive film does not have sufficient step absorbency to absorb the printing step, it is difficult to exhibit sufficient adhesiveness, and further, delayed bubbles are generated near the step, thereby causing a problem in the durability of the product.

In addition, if the pressure-sensitive adhesive film itself has a characteristic of low refraction in order to improve the visibility of the optical member, there is an advantage in that more various choices can be made at the time of optical design.

Accordingly, there is a need for research on an adhesive film that has high step absorption and can implement a low refractive index.

Korean Publication: KR 10-2013-0131795 A

An object of the present specification is to provide a low-refractive adhesive composition, a low-refractive adhesive film including a cured product thereof, and an optical member including the same.

However, the problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

An exemplary embodiment of the present invention is an acrylic copolymer comprising a polysiloxane-based monomer unit, and a fluorinated polyolefin-based monomer unit, at least one low-refractive monomer unit, and a photoreactive functional group-containing (meth)acrylate monomer unit; and an isocyanate-based curing agent; provides a low-refractive adhesive composition comprising.

An exemplary embodiment of the present invention provides a low-refractive adhesive film comprising a cured product of the low-refractive adhesive composition.

An exemplary embodiment of the present invention provides an optical member including the low-refractive adhesive film.

Since the low-refractive adhesive film according to an exemplary embodiment of the present invention has a low refractive index, various optical designs of the optical member including the low-refractive adhesive film are possible.

Since the low-refractive adhesive composition according to an exemplary embodiment of the present invention has high step absorbency, the reliability of a product including the same can be increased.

The low-refractive film according to an exemplary embodiment of the present invention can implement excellent high-temperature durability.

In the present specification, when a part "includes" a certain component, this means that other components may be further included rather than excluding other components unless otherwise stated.

In the present specification, when a member is said to be located "on" another member, this includes not only a case in which a member is in contact with another member but also a case in which another member exists between the two members.

In the present specification, "(meth)acrylate" may mean acrylate or methacrylate.

In the present specification, the unit “parts by weight” may mean a ratio of weight between each component.

As used herein, the term “copolymer” may refer to a substance composed of molecules formed as a linkage of one or more “monomer units”.

As used herein, the term “monomer” may refer to a substance capable of forming a covalent bond with a series of additionally identical or different molecules under the polymer-forming reaction conditions. That is, a "monomer" may be converted into a repeating unit of a polymer sequence, ie, a monomer unit, in a polymerization reaction to form a polymer.

Hereinafter, the present specification will be described in more detail.

An exemplary embodiment of the present invention is an acrylic copolymer comprising a polysiloxane-based monomer unit, and a fluorinated polyolefin-based monomer unit, at least one low-refractive monomer unit, and a photoreactive functional group-containing (meth)acrylate monomer unit; and an isocyanate-based curing agent; provides a low-refractive adhesive composition comprising.

The acrylic copolymer may be a prepolymer prepared by copolymerization of a monomer group including at least one (meth)acrylate monomer. The (meth)acrylate monomer unit may mean derived from a (meth)acrylate monomer, and may be a monomer unit constituting the acrylic copolymer.

The low refractive monomer unit may allow a low refractive index adhesive film prepared by using the low refractive adhesive composition to have a low refractive index. Specifically, by the low-refractive monomer unit, the low-refractive adhesive film prepared using the low-refractive adhesive composition may implement a very low refractive index compared to the refractive index of a general acrylic adhesive film.

In addition, the low-refractive monomer unit may serve to improve the high-temperature durability of the low-refractive adhesive film prepared by using the low-refractive adhesive composition. Specifically, the low-refractive adhesive film prepared by using the low-refractive adhesive composition may have high high-temperature durability of the polysiloxane-based compound or the fluorinated polyolefin-based compound.

According to an exemplary embodiment of the present invention, the polysiloxane-based monomer unit may be derived from a compound including a polysiloxane skeleton, and a (meth)acryloyl group, a hydroxyl group, or an amino group bonded to at least one terminal. Specifically, the polysiloxane-based monomer unit may be derived from a compound in which (meth)acryloyl groups are bonded to one or both ends of the polysiloxane-based compound. More specifically, the polysiloxane-based monomer unit may be a polysiloxane-based (meth)acrylate monomer unit.

According to an exemplary embodiment of the present invention, the polysiloxane-based compound may be polydialkylsiloxane, specifically, polydimethylsiloxane.

According to an exemplary embodiment of the present invention, the fluorinated polyolefin-based monomer unit may be derived from a compound including a fluorinated polyolefin backbone and bonded to at least one terminal with a (meth)acryloyl group, a hydroxyl group, or an amino group. Specifically, the fluorinated polyolefin-based monomer unit may be derived from a compound in which (meth)acrylate groups are bonded to one or both terminals of the fluorinated polyolefin-based compound. More specifically, the fluorinated polyolefin-based monomer unit may be a fluorinated polyolefin-based (meth)acrylate monomer unit.

According to an exemplary embodiment of the present invention, the fluorinated polyolefin-based compound is polytetrafluoroethylene, polyvinylidene fluoride, a copolymer of trifluoroethylene and vinylidene fluoride, or tetrafluoroethylene and hexafluoro It may be a copolymer of propylene.

According to an exemplary embodiment of the present invention, the content of the low refractive monomer unit may be 25 parts by weight or more and 75 parts by weight or less based on 100 parts by weight of the acrylic copolymer. Specifically, the content of the low refractive monomer unit may be 30 parts by weight or more and 70 parts by weight or less based on 100 parts by weight of the acrylic copolymer.

When the content of the low refractive monomer unit is within the above range, the adhesive film prepared using the low refractive adhesive composition may implement a low refractive index of 1.46 or less at a wavelength of 605 nm.

The photoreactive functional group-containing (meth)acrylate monomer unit may enable the low-refractive adhesive composition to perform photocrosslinking. Specifically, the photoreactive functional group-containing (meth)acrylate monomer unit may induce photocuring in the secondary photocuring step of the low-refractive adhesive composition.

According to an exemplary embodiment of the present invention, the photoreactive functional group-containing (meth) acrylate monomer unit, an acetphenone-based (meth) acrylate monomer unit; benzoin-based (meth)acrylate monomer units; acylphosifine oxide-based (meth)acrylate monomer units; titanocene-based (meth)acrylate monomer units; benzophenone-based (meth)acrylate monomer units; anthracene-based (meth)acrylate monomer units; and thioxanthone-based (meth)acrylate monomer units; It may include at least one of Specifically, the photoreactive functional group-containing (meth)acrylate monomer unit may be a benzophenone-based (meth)acrylate monomer unit.

According to an exemplary embodiment of the present invention, the content of the photoreactive functional group-containing (meth)acrylate monomer unit may be 0.1 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the acrylic copolymer. Specifically, the content of the photoreactive functional group-containing (meth)acrylate monomer unit is 0.1 parts by weight or more and 5 parts by weight or less, 0.1 parts by weight or more and 3 parts by weight or more, 0.1 parts by weight or more based on 100 parts by weight of the acrylic copolymer. It may be 1 part by weight or less.

When the content of the photoreactive functional group-containing (meth)acrylate monomer unit is within the above range, the low-refractive adhesive composition may enable an increase in curing degree by additional photocuring after thermal curing. Furthermore, when the content of the photoreactive functional group-containing (meth)acrylate monomer unit is within the above range, it is possible to prevent excessive curing by additional photocuring, so the low-refractive adhesive produced using the low-refractive adhesive composition The film can realize excellent appearance such as low haze.

According to an exemplary embodiment of the present invention, the acrylic copolymer is at least one of an alkyl group-containing (meth)acrylate monomer unit, a cycloalkyl group-containing (meth)acrylate monomer unit, and a polar functional group-containing (meth)acrylate monomer unit. It may include more species.

According to an exemplary embodiment of the present invention, the alkyl group-containing (meth)acrylate monomer unit may be derived from an alkyl group-containing (meth)acrylate monomer.

In the present specification, "alkyl group" may mean including a carbon chain structure in which an unsaturated bond does not exist in a functional group, and may mean including a straight or branched carbon chain structure having 1 to 20 carbon atoms. there is.

According to an exemplary embodiment of the present invention, the alkyl group-containing (meth)acrylate monomer may be a (meth)acrylate having an alkyl group having 1 to 20 carbon atoms. Specifically, the alkyl group-containing (meth) acrylate monomer is methacrylate, 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, 2-ethylhexyl (meth) acrylate, 2-ethylbutyl (meth) acrylic It may include at least one selected from the group consisting of rate, n-octyl (meth) acrylate, and isooctyl (meth) acrylate.

According to an exemplary embodiment of the present invention, the alkyl group-containing (meth)acrylate monomer may include methacrylate and (meth)acrylate having an alkyl group having 2 to 20 carbon atoms. Specifically, according to an exemplary embodiment of the present invention, the alkyl group-containing (meth)acrylate monomer may include methacrylate and 2-ethylhexyl (meth)acrylate.

According to an exemplary embodiment of the present invention, the content of the alkyl group-containing (meth)acrylate monomer unit may be 20 parts by weight or more and 60 parts by weight or less based on 100 parts by weight of the acrylic copolymer.

The alkyl group-containing (meth)acrylate monomer unit may serve to form an acrylic skeleton of the acrylic copolymer.

According to an exemplary embodiment of the present invention, the cycloalkyl group-containing (meth)acrylate monomer unit may be derived from a cycloalkyl group-containing (meth)acrylate monomer.

In the present specification, the "cycloalkyl group" may include a carbon ring structure in which an unsaturated bond does not exist in the functional group, and means including a monocyclic ring or polycyclic ring having 3 to 20 carbon atoms. can do.

According to an exemplary embodiment of the present invention, the cycloalkyl group-containing (meth)acrylate monomer is cyclohexyl acrylate (CHA), cyclohexyl methacrylate (CHMA), isobornyl acrylate (IBOA), isobornyl methacrylate (IBOMA) and 3,3,5-trimethylcyclohexylacrylate (TMCHA, 3,3,5-trimethylcyclohexylacrylate) may include at least one selected from the group consisting of.

According to an exemplary embodiment of the present invention, the content of the cycloalkyl group-containing (meth)acrylate monomer unit may be 20 parts by weight or more and 60 parts by weight or less based on 100 parts by weight of the acrylic copolymer.

When the content of the cycloalkyl group-containing (meth)acrylate monomer unit is within the above range, the low-refractive adhesive film prepared using the low-refractive adhesive composition may implement high initial adhesive strength.

According to an exemplary embodiment of the present invention, the polar functional group-containing (meth)acrylate monomer unit may be derived from a polar functional group-containing (meth)acrylate monomer.

According to an exemplary embodiment of the present invention, the polar functional group-containing (meth) acrylate monomer is at least one of a hydroxyl group-containing (meth) acrylate monomer, a carboxy group-containing (meth) acrylate monomer, and a nitrogen-containing (meth) acrylate monomer It may include species.

According to an exemplary embodiment of the present invention, the hydroxyl group-containing (meth) acrylate monomer is 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylic the group consisting of rate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 2-hydroxyethylene glycol (meth) acrylate and 2-hydroxypropylene glycol (meth) acrylate It may include one or more selected from.

According to an exemplary embodiment of the present invention, the carboxyl group-containing (meth) acrylate monomer is acrylic acid, methacrylic acid, 2-ethyl acrylic acid, β-CEA (2-CARBOXYETHYL ACRYLATE), 2- (meth) acryloyloxy acetic acid , 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, and may include at least one selected from the group consisting of acrylic acid duplex.

According to an exemplary embodiment of the present invention, the nitrogen-containing (meth)acrylate monomer is 2-isocyanatoethyl (meth)acrylate, and 3-isocyanatopropyl (meth)acrylate, 4-isocy It may be at least one selected from the group consisting of anatobutyl (meth) acrylate.

According to an exemplary embodiment of the present invention, the content of the polar functional group-containing (meth)acrylate monomer unit is 5 parts by weight or more and 30 parts by weight or less, 5 parts by weight or more and 20 parts by weight or less, based on 100 parts by weight of the acrylic copolymer; Or 5 parts by weight or more and 15 parts by weight or less.

When the content of the polar functional group-containing (meth)acrylate monomer unit is within the above range, gelation can be prevented during polymerization of the low-refractive adhesive composition, and the cohesive force of the adhesive film prepared using the low-refractive adhesive composition is excessive. It can be raised to prevent haze from occurring. Furthermore, when the content of the polar functional group-containing (meth)acrylate monomer unit is within the above range, rework can be facilitated by appropriately adjusting the adhesive force of the pressure-sensitive adhesive film prepared using the low-refractive pressure-sensitive adhesive composition.

According to an exemplary embodiment of the present invention, the weight average molecular weight of the acrylic copolymer may be 500,000 g/mol or more and 2,000,000 g/mol or less. Specifically, the weight average molecular weight of the acrylic copolymer may be 500,000 g/mol or more and 1,500,000 g/mol or less, or 500,000 g/mol or more and 1,000,000 g/mol or less.

When the weight average molecular weight of the acrylic copolymer is within the above range, high-temperature durability of the low-refractive adhesive film produced by using the low-refractive adhesive composition can be secured. Furthermore, when the weight average molecular weight of the acrylic copolymer is within the above range, the internal cohesive force of the low-refractive adhesive film prepared by using the low-refractive adhesive composition can be appropriately adjusted, so that the low-refractive adhesive film has high adhesive strength and excellent appearance can be realized.

According to an exemplary embodiment of the present invention, the refractive index of the acrylic copolymer at a wavelength of 605 nm may be 1.46 or less. Specifically, the refractive index of the acrylic copolymer at a wavelength of 605 nm may be 1.0 or more and 1.46 or less, or 1.0 or more and 1.455 or less.

In the present specification, the refractive index is measured using a Prism coupler (Metricon 2010) at 532 nm, 632 nm, and 830 nm wavelengths at any three points, and then the refractive index of the 605 nm wavelength is obtained by Cauchy fit. can For example, the refractive index of the acrylic copolymer may be determined by measuring the refractive index of the 605 nm wavelength by the above method after forming the solid content from which the solvent is removed to a thickness of 50 μm. In addition, the refractive index of the low-refractive adhesive film can be measured by the method after preparing the low-refractive adhesive film to a thickness of 50 ㎛, the refractive index of the 605 nm wavelength.

According to an exemplary embodiment of the present invention, the isocyanate-based curing agent may induce thermal curing in the first thermal curing step of the low-refractive adhesive composition to form the low-refractive adhesive composition into a semi-cured adhesive film.

According to an exemplary embodiment of the present invention, the isocyanate-based curing agent may be a compound having at least two isocyanate groups. Specifically, the isocyanate-based curing agent is tolylene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, methylenebis(4-cyclohexyl isocyanate), trimethyl It may include at least one of hexamethylene diisocyanate and naphthalene diisocyanate. In addition, the isocyanate-based curing agent is a diisocyanate modified with trimethylol propane, an adact body, a trimer of diisocyanate (isocyanurate), a biuret body by reaction of diisocyanate and water, etc. 1 type or 2 It may be a combination of more than one species. However, the present invention is not limited thereto, and any isocyanate-based compound used as a curable compound in the art may be used without limitation.

According to an exemplary embodiment of the present invention, the content of the isocyanate-based curing agent may be 0.5 parts by weight or more and 5 parts by weight or less based on 100 parts by weight of the acrylic copolymer. By controlling the content of the isocyanate-based curing agent within the above range, the degree of curing of the semi-cured pressure-sensitive adhesive film through primary heat curing of the low-refractive pressure-sensitive adhesive film can be controlled.

According to an exemplary embodiment of the present invention, the low-refractive adhesive composition may further include a solvent. The low-refractive adhesive composition may be dissolved, or an appropriate viscosity may be imparted.

According to an exemplary embodiment of the present invention, the solvent may include at least one selected from the group consisting of an aromatic hydrocarbon solvent, an acetate ester solvent, an alcohol solvent, a petroleum solvent, and an amide solvent.

Specifically, the solvent may include ketones such as methyl ethyl ketone and cyclohexanone; aromatic hydrocarbons such as toluene, xylene, and tetramethylbenzene; Ethylene glycol monoethyl ether, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether , glycol ethers such as dipropylene glycol diethyl ether and triethylene glycol monoethyl ether (Cellosolve); Ethyl acetate, butyl acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, dipropylene glycol monomethyl ether acetate Acetic acid esters, such as; alcohols such as ethanol, propanol, ethylene glycol, propylene glycol, and carbitol; aliphatic hydrocarbons such as octane and decane; petroleum solvents such as petroleum ether, petroleum naphtha, hydrogenated petroleum naphtha, and solvent naphtha; and amides such as dimethylacetamide and dimethylformamide (DMF); may include one or more solvents selected from the group consisting of.

According to an exemplary embodiment of the present invention, the content of the solvent may be 10 parts by weight or more and 50 parts by weight or less based on 100 parts by weight of the low-refractive adhesive composition.

Within the content range of the solvent, the low-refractive adhesive composition maintains an appropriate viscosity to increase coatability, and may be easily dried.

According to an exemplary embodiment of the present invention, the low-refractive adhesive composition is selected from the group consisting of a silane coupling agent, a tackifier, an epoxy resin, a crosslinking agent, a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, a filler, an antifoaming agent, a surfactant, and a plasticizer. It may further include one or more selected additives. The additive may be applied by appropriately adjusting substances and contents known in the art as long as the performance of the low-refractive adhesive composition is not reduced.

According to an exemplary embodiment of the present invention, the pressure-sensitive adhesive composition may be capable of multi-step curing. Specifically, the multi-step curing may include a first thermal curing step and a second photo-curing step.

The low-refractive adhesive composition may be prepared as a low-refractive adhesive film in a semi-cured state through a first heat curing step. The low-refractive adhesive film in the semi-cured state may have a low modulus and high step absorption (step difference embedding). When the low-refractive adhesive film in the semi-cured state is attached to a member having a step portion such as a substrate having a printed step portion, the step portion can be sufficiently filled to prevent lifting, and the step portion is fully cured through the secondary photocuring. can be Through such multi-step curing, when the low-refractive adhesive film using the low-refractive adhesive composition is applied to a member having a step portion, it is possible to prevent the occurrence of delayed bubbles due to lifting in the step portion, and thereby It can help improve reliability.

An exemplary embodiment of the present invention provides a low-refractive adhesive film comprising a cured product of the low-refractive adhesive composition.

According to an exemplary embodiment of the present invention, the low-refractive adhesive film may be in a semi-cured state by primary heat curing of the low-refractive adhesive composition. As described above, the low-refractive adhesive film in the semi-cured state has a high step absorbency and has the advantage of being easy to handle.

According to an exemplary embodiment of the present invention, the storage elastic modulus of the low-refractive adhesive film in the semi-cured state may be 10,000 Pa or more and 100,000 Pa or less. Specifically, the storage modulus of the low-refractive adhesive film in the semi-cured state may be 40,000 Pa or more and 80,000 Pa or less, or 50,000 Pa or more and 70,000 Pa or less.

When the storage elastic modulus of the low-refractive adhesive film in the semi-cured state is within the above range, when the low-refractive adhesive film is attached to a member having a step portion, the step embedding property is excellent, so that after the second photocuring, the delay bubble formation can be minimized.

According to an exemplary embodiment of the present invention, the gel content of the low-refractive adhesive film in the semi-cured state may be 35% or more and 55% or less.

When the gel content of the low-refractive adhesive film in the semi-cured state is within the above range, the flowability of the low-refractive adhesive film is appropriately adjusted to provide excellent workability, and also to attach to a member having a step portion In this case, the step filling property may be excellent.

According to an exemplary embodiment of the present invention, the gel content of the low-refractive adhesive film in the fully cured state may be 60% or more and 80% or less, or 65% or more and 75% or less.

When the gel content of the low-refractive adhesive film in the fully cured state is within the above range, the low-refractive adhesive film may have appropriate hardness and adhesive strength. Furthermore, when the gel content of the low-refractive adhesive film in the fully cured state is within the above range, the low-refractive adhesive film in the semi-cured state is attached to a member having a step portion to maintain a state in which the step portion is embedded and the hardness is increased. Since it can be maintained, the generation of delayed bubbles can be minimized.

In the present specification, the gel content is 0.3 g of a sample put in an ethyl acetate solvent and left for 1 day, filtered through a #200 mesh wire mesh to obtain a solid content remaining in the wire mesh, and then left at 110° C. for 2 hours to obtain the residual It can be measured using the weight after removing the solvent and the weight of the sample.

According to an exemplary embodiment of the present invention, the low-refractive adhesive film may be in a fully cured state by primary heat curing and secondary photo curing of the low refractive adhesive composition. As described above, the low-refractive pressure-sensitive adhesive film in the fully cured state may be processed in a semi-cured state and then fixed in shape through post-curing and bonding members. In this way, it is possible to prevent the occurrence of air-flammable bubbles in the member with the step portion and improve the reliability of the product.

According to an exemplary embodiment of the present invention, the storage elastic modulus of the low-refractive adhesive film in the fully cured state may be 30,000 Pa or more and 150,000 Pa or less. Specifically, the storage modulus of the low-refractive adhesive film in the fully cured state may be 40,000 Pa or more and 120,000 Pa or less, 50,000 Pa or more and 110,000 Pa or less, or 60,000 Pa or more and 90,000 Pa or less.

In the present specification, the storage modulus may be measured by raising the temperature from -20 °C to 100 °C by 5 °C per minute under the condition of a strain of 10% 1rad/sec using ARES G2.

When the storage elastic modulus of the low-refractive adhesive film in the semi-cured state is within the above range, the low-refractive adhesive film may prevent a decrease in adhesive strength due to excessively high cohesive force and implement an excellent appearance.

According to an exemplary embodiment of the present invention, the storage elastic modulus in the fully cured state of the low refractive adhesive film is 10,000 Pa to 40,000 Pa, or 10,000 Pa to 20,000 Pa higher than the storage elastic modulus in the semi-cured state of the low refractive adhesive film can

According to an exemplary embodiment of the present invention, the refractive index at a wavelength of 605 nm of the low-refractive adhesive film in the fully cured state may be 1.46 or less.

An exemplary embodiment of the present invention provides an optical member including the low-refractive adhesive film. Specifically, the optical member may include the low refractive film in a fully cured state.

According to an exemplary embodiment of the present invention, the optical member may be a display panel, a touch panel, a polarizing film, a brightness enhancing film, or a retardation film. Specifically, the low-refractive adhesive film may be attached to at least one surface of the optical member.

An exemplary embodiment of the present invention provides a display device including the optical member.

Hereinafter, examples will be given to describe the present invention in detail. However, the embodiments according to the present invention may be modified in various other forms, and the scope of the present invention is not to be construed as being limited to the embodiments described below. The embodiments of the present specification are provided to more completely explain the present invention to those of ordinary skill in the art.

[ Example One]

About 50 parts by weight of polydimethylsiloxane (MAT-PDMS) (FM-0721) modified at the terminal with a methacryloxypropyl group, about 32.5 parts by weight of 2-ethylhexyl acrylate (2-EHA), about methacrylate (MA) 7.5 parts by weight, about 10 parts by weight of 2-hydroxyethyl acrylate (2-HEA), and about 0.5 parts by weight of benzophenone methacrylate (BPMA) were copolymerized to prepare an acrylic copolymer syrup. AIBN Azobisisobutyronitrile) was used as a thermal initiator when preparing the acrylic copolymer syrup, and toluene was used as a solvent.

The acrylic copolymer prepared as described above had a solid content of 49.47%, a conversion rate of 99%, and a weight average molecular weight of 880,000 g/mol.

Further, an isocyanate-based curing agent (TKA100) was mixed in an amount of about 1 part by weight based on 100 parts by weight of the acrylic copolymer syrup, and aged at 50° C. for 24 hours to prepare a low-refractive adhesive composition.

Low-refractive adhesive compositions according to Examples 2 and 3 and adhesive compositions according to Comparative Examples 1 and 2 were prepared in the same manner as in Example 1, except that the acrylic copolymer was prepared with the composition shown in Table 1 below.

Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Acrylic copolymer MAT-PDMS
(parts by weight) 50 70 30 - 50 2-EHA
(parts by weight) 32.5 19.5 45.5 65 32.5 MA
(parts by weight) 7.5 4.5 10.5 15 7.5 2HEA
(parts by weight) 10 6 14 20 10 BPMA
(parts by weight) 0.5 0.5 0.5 0.5 - Acrylic copolymer
Mw (g/mol) 880,000 820,000 780,000 1,000,000 860,000

After the prepared low-refractive adhesive composition was applied to the substrate, a first heat curing was performed at 120° C. to prepare a semi-cured low-refractive adhesive film with a thickness of 50 μm. Furthermore, secondary photocuring was performed using a 3 J metal halide lamp to prepare a fully cured low-refractive adhesive film.

Table 2 shows the physical properties of the low-refractive adhesive films prepared by using the low-refractive adhesive compositions according to Examples 1 to 3 and Comparative Examples 1 to 2.

refractive index after final curing
(@605nm) Gel content after first heat curing
(%) Gel content after secondary photocuring
(%) Storage modulus after first heat curing
(Pa) Storage modulus after secondary photocuring
(Pa) Example 1 1.438 40 72 60,000 80,000 Example 2 1.419 51 73 70,000 90,000 Example 3 1.451 45 70 50,000 60,000 Comparative Example 1 1.472 50 70 40,000 50,000 Comparative Example 2 1.435 50 50 60,000 60,000

According to Table 2, Examples 1 to 3 containing an acrylic copolymer prepared by applying a photoreactive functional group-containing (meth)acrylate monomer (BPMA) are gels through secondary photocuring after primary thermal curing. It can be seen that the content and storage modulus increased significantly. This means that the reliability of the product can be improved by attaching a semi-cured, low-refractive adhesive film having a low gel content to a member with a step to fill the step, and then fix the buried state through additional curing. do.

In addition, in Examples 1 to 3, it can be seen that the refractive index of the low-refractive adhesive film produced after the first thermal curing and the secondary photo-curing is 1.46 or less, thereby realizing a very low refractive index.

In the case of Comparative Example 1 using an acrylic copolymer that does not include a low refractive monomer unit such as MET-PDMS, it can be confirmed that the refractive index is higher than in Examples 1 to 3.

In addition, in the case of Comparative Example 2 using an acrylic copolymer that does not include a photoreactive functional group-containing (meth)acrylate monomer unit such as BPMA, it can be confirmed that there is no change in the degree of crosslinking and storage modulus through additional photocuring. That is, in the case of Comparative Example 2, since additional curing cannot be performed when attached to a member having a step portion, it can be expected that the state in which the step portion is embedded is difficult to be fixed.

Claims (16)

an acrylic copolymer comprising a polysiloxane-based monomer unit, a fluorinated polyolefin-based monomer unit, at least one low-refractive monomer unit, and a (meth)acrylate monomer unit containing a photoreactive functional group; and an isocyanate-based curing agent. The method according to claim 1,
The content of the low-refractive monomer unit is a low-refractive adhesive composition that is 25 parts by weight or more and 75 parts by weight or less based on 100 parts by weight of the acrylic copolymer. The method according to claim 1,
The content of the photoreactive functional group-containing (meth) acrylate monomer unit is 0.1 parts by weight or more and 10 parts by weight or less based on 100 parts by weight of the acrylic copolymer low-refractive adhesive composition. The method according to claim 1,
The photoreactive functional group-containing (meth)acrylate monomer unit may include an acetphenone-based (meth)acrylate monomer unit; benzoin-based (meth)acrylate monomer units; acylphosifine oxide-based (meth)acrylate monomer units; titanocene-based (meth)acrylate monomer units; benzophenone-based (meth)acrylate monomer units; anthracene-based (meth)acrylate monomer units; and thioxanthone-based (meth)acrylate monomer units; A low-refractive adhesive composition comprising at least one of The method according to claim 1,
The acrylic copolymer may further include at least one of an alkyl group-containing (meth)acrylate monomer unit, a cycloalkyl group-containing (meth)acrylate monomer unit, and a polar functional group-containing (meth)acrylate monomer unit. adhesive composition. The method according to claim 1,
The acrylic copolymer has a weight average molecular weight of 500,000 g/mol or more and 2,000,000 g/mol or less of a low-refractive adhesive composition. The method according to claim 1,
The refractive index of the acrylic copolymer at a wavelength of 605 nm is 1.46 or less, the low-refractive adhesive composition. The method according to claim 1,
The adhesive composition is a low-refractive adhesive composition capable of multi-step curing. 9. The method of claim 8,
The multi-step curing is a low-refractive adhesive composition comprising a first thermal curing step and a secondary photo-curing step. A low-refractive adhesive film comprising a cured product of the low-refractive adhesive composition according to claim 1. 11. The method of claim 10,
The low-refractive adhesive film is a low-refractive adhesive film that is in a semi-cured state by primary heat curing of the low-refractive adhesive composition. 12. The method of claim 11,
The storage elastic modulus of the low-refractive adhesive film in the semi-cured state is 10,000 Pa or more and 100,000 Pa or less. 11. The method of claim 10,
The low-refractive adhesive film is a low-refractive adhesive film in a fully cured state by primary heat curing and secondary photocuring of the low refractive adhesive composition. 14. The method of claim 13,
The storage elastic modulus of the low-refractive adhesive film in the fully cured state is 30,000 Pa or more and 150,000 Pa or less. 14. The method of claim 13,
The refractive index at a wavelength of 605 nm of the low-refractive adhesive film in the fully cured state is a low-refractive adhesive film of 1.46 or less. An optical member comprising the low-refractive adhesive film according to claim 10 .