TWI535818B - Adhesive and optical member using the same - Google Patents

Description

Adhesive and optical component using the same Field of invention

The present invention relates to an adhesive and an optical element using the same. More specifically, the present invention relates to an adhesive having improved transparency, durability, and antistatic property while maintaining excellent productivity and light leakage resistance as advantages of a hard adhesive, and an optical member using the same.

Background of the invention

The optical film includes a polarizing plate for various optical elements including an LCD, a color filter, a phase retardation film, an elliptically polarizing film, a reflective film, an anti-reflection film, a compensation film, a brightness enhancement film, an alignment film, a diffusion film, and a glass resistance. A scattering film, a surface protective film, a plastic LCD substrate, or the like.

When an optical element such as a polarizing plate or a phase retardation film is stacked on a liquid crystal cell to manufacture an LCD, it is preferable to use an adhesion method of an adhesive layer. Since release films or optical components typically include plastic materials with high electrical insulation properties, static electricity is generated during the bonding or stripping process. In particular, static electricity generated by peeling is called a glass electrostatic voltage, which causes a substantial problem. Adhesive sheets charged by the generated static electricity attract foreign materials and cause defects. Further, when the adhesive sheet is attached to the liquid crystal cell, liquid crystal molecules are difficult to match in the alignment due to the residual static electricity. In order to solve these problems, an adhesive layer having antistatic properties is required as a method of preventing charging due to static electricity.

Korean Patent Publication No. 2010-0093470 discloses an adhesive comprising a lithium salt antistatic agent. Further, Korean Patent Publication No. 2010-0067171 discloses an antistatic adhesive comprising a pyridinium salt antistatic agent. Korean Patent Publication No. 2010-0093470 describes a method for improving the effect of a lithium salt antistatic agent by using an ester copolymer. Further, Korean Patent Publication No. 2009-0075360 discloses a method of using an antistatic coating between an adhesive and a release film.

However, although the conventional antistatic agent provides antistatic properties, it may cause a decrease in transparency or light leakage, or a decrease in tolerance, which may deteriorate the performance of the adhesive.

In the adhesive for a polarizing plate, an adhesive sheet including a tolerant adhesive layer is required, so that the adhesive is not used in various environments, for example, in various processes of LCD manufacturing, sales, transportation or long-term use thereof. Will separate and peel off. Moreover, the adhesive layer needs to have light leakage resistance, and light leakage occurs due to a change in size due to dimensional changes such as shrinkage and expansion of the film.

As a conventional method for solving light leakage, Korean Patent Publication No. 1998-0079266 discloses a soft adhesive which exhibits basic creep with external stress and which is easily deformed to ensure stress-relieving performance. However, since the soft adhesive has poor cutting properties, it may be pressed or stuck, resulting in a decrease in productivity and productivity.

In contrast, a hard adhesive has been developed to prevent light leakage. If an adhesive is designed to have hard physical properties, the shrinkage and expansion of the polarizer under high temperature or high humidity conditions are optimally controlled to minimize stress generation and concentrate stress on the outermost area. Thereby obtaining superior optical performance and ensuring productivity. However, the hard adhesive of the polarizing plate has a poor initial bonding strength due to the storage modulus (G'), and thus the durability is remarkably lowered. This phenomenon becomes more serious especially when the polarizing film is sufficiently shrunk.

Summary of invention

Certain aspects of the present invention provide an adhesive that maintains excellent light leakage resistance, has excellent electric chargeability, and has adhesive strength, antistatic properties, durability, transparency, and light leakage resistance. A suitable balance of properties between properties, exhibits excellent creep properties, and is suitable for hard adhesives. Further, a surface of the present invention provides an optical element that uses the adhesive to have excellent properties between creep properties, peel strength, durability, reworkability, and sectility. balance.

One aspect of the present invention provides an adhesive. In one embodiment, the adhesive has a surface resistance of 10 ⁸ to 10 ¹² Ω/sq and a luminance difference (ΔL) between the edge portion and the central portion of greater than 0 and less than 1, the brightness difference Calculated by the following equation:

ΔL=[(a+b+d+e)/4]-c,

Wherein a, b, d, and e are each an average brightness of an edge portion of each side of the optical element covering a total area of 1/16 of the optical element, and c is the optical covering the total area of 1/32 The average brightness of the center of the component.

In another embodiment, the adhesive may include an alkylammonium compound represented by Formula 1:

Wherein n is an integer from 0 to 15.

The adhesive may have an initial bond strength of 100 to 250 gf as determined by a construction analyzer after the spherical probe is adhered to the adhesive for 2 seconds.

The adhesive may have a creep of 1 to 50 μm as measured by a texture analyzer after being attached to a glass substrate and stored for 3 days.

The adhesive may have a haze of 0 to 0.1%.

The adhesive may include a (meth) acrylate copolymer, a crosslinking agent, and an alkyl ammonium compound.

The adhesive may include 100 parts by weight of the (meth) acrylate copolymer, 0.01 to 10 parts by weight of the crosslinking agent, and 0.01 to 10 parts by weight of the alkyl ammonium compound.

The (meth) acrylate copolymer may have a carboxyl group and a hydroxyl group.

The (meth) acrylate copolymer may be a copolymer of a C1 to C16 alkyl (meth) acrylate, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer.

The (meth) acrylate copolymer may have a weight average molecular weight of from 1,000,000 to 1,500,000 g/mol.

The crosslinking agent can be a combination of an isocyanate crosslinking agent and a carbodiimide crosslinking agent.

The adhesive may further include 0.01 to 3 parts by weight of a decane coupling agent.

Another aspect of the invention provides an optical component. In one embodiment, the optical element can include an adhesive layer of the adhesive disposed on one or both sides of the optical film.

Detailed description of the preferred embodiment

Various embodiments of the present invention will now be described in detail.

An adhesive according to an embodiment of the present invention includes an alkylammonium compound represented by Formula 1:

Wherein n is an integer from 0 to 15.

When an alkylammonium compound having the above structure is used, the adhesive is provided with a charge rate to have an antistatic function. In addition, since the alkylammonium compound has good compatibility with the acrylic adhesive, it can be uniformly dispersed in the polymer network after the adhesive is cured, thereby maintaining the transparency of the adhesive. In addition, the alkylammonium compound has no functional groups and thus does not chemically react with the network of the adhesive, so that the acrylic adhesive acts as a low molecular weight polymer in the polymer network while maintaining the existing structure. Therefore, the adhesive has an improved initial bond strength and provides elasticity to promote durability.

In the formula 1, n is from 0 to 15, preferably from 0 to 7.

The alkylammonium compound may be included in an amount of from 0.01 to 10 parts by weight, based on 100 parts by weight of the (meth) acrylate copolymer, preferably from 0.1 to 5 parts by weight, more preferably from 0.5 to 3.5 parts by weight. Within this range, a suitable balance of properties between antistatic properties, compatibility, transparency, and adhesion can be obtained. Specifically, the content of the alkylammonium compound may be 0.6 to 2 parts by weight based on 100 parts by weight of the (meth) acrylate copolymer.

In one embodiment, in addition to the above alkylammonium compound, the above adhesive may further include a (meth) acrylate copolymer and a crosslinking agent.

The above (meth) acrylate copolymer may be any (meth) acrylate copolymer commonly used in the art. Specifically, the (meth) acrylate copolymer may be polymerized from a C1 to C20 alkyl ester of (meth)acrylic acid with a monomer mixture including a monomer copolymerizable therewith.

Examples of the C1 to C20 alkyl ester of (meth)acrylic acid may include, but are not limited to, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, and butyl (meth)acrylate. , (meth) pentyl acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, octyl (meth) acrylate, decyl (meth) acrylate, decyl (meth) acrylate, ( Undecyl (meth)acrylate and lauryl (meth)acrylate, which may be used singly or as a mixture. Herein, the term "(meth)acrylate" as a whole refers to both acrylate and methacrylate.

The copolymerizable monomer may include a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a monomer having a positive birefringence.

For example, the (meth) acrylate copolymer may be a copolymer of a C1 to C20 alkyl ester of (meth)acrylic acid and a carboxyl group-containing monomer and a hydroxyl group-containing monomer. Specifically, the content of the carboxyl group-containing monomer and the hydroxyl group-containing monomer may be 0.01 to 10% by weight based on the total amount of the above copolymer.

Alternatively, the (meth) acrylate copolymer may include a C1 to C20 alkyl ester of (meth)acrylic acid, a hydroxyl group-containing monomer, a carboxyl group-containing monomer, and a monomer having a positive birefringence. Specifically, the (meth) acrylate copolymer may include 60 to 99% by weight of a C1 to C20 alkyl (meth) acrylate, 0.01 to 20% by weight of a hydroxyl group-containing monomer, and 0.01 to 10% by weight of a carboxyl group-containing Monomer and 0 to 10% by weight of a monomer having a positive birefringence.

Examples of the hydroxyl group-containing monomer may include, but are not limited to, 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, (A) 2-hydroxybutyl acrylate, -6-hydroxyhexyl (meth) acrylate, 1,4-cyclohexane dimethanol mono (meth) acrylate, chloro-2-hydroxypropyl (methyl) Acrylate, diethylene glycol mono(meth)acrylate, and allyl alcohol, which may be used singly or as a mixture.

Examples of the carboxyl group-containing monomer may include, but are not limited to, (meth)acrylic acid, 2-carboxyethyl (meth)acrylate, 3-carboxypropyl (meth)acrylate, (meth)acrylic acid-4- Carboxybutyl ester, itaconic acid, crotonic acid, maleic acid, fumaric acid and maleic anhydride, which may be used singly or as a mixture.

The monomer having a positive birefringence may include an aromatic (meth) acrylate. Specifically, examples of the monomer having a positive birefringence may include, but are not limited to, methacrylic acid such as cyclohexyl (meth)acrylate, 2-ethylphenoxy (meth)acrylate, (methyl) ) 2-ethylthiophenyl acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, 2-phenylethyl (meth) acrylate, 3-phenyl (meth) acrylate Propyl ester, 4-phenylbutyl (meth)acrylate, 2-2-methylphenylethyl (meth) acrylate, 2-2-3-phenylphenylethyl (meth) acrylate, 2-4-methylphenylethyl (meth) acrylate, 2-(4-propylphenyl)ethyl (meth) acrylate, 2-(4-(1-methylethyl)phenyl Ethyl (meth) acrylate, 2-(4-methoxyphenyl)ethyl (meth) acrylate, 2-(4-cyclohexyl phenyl) ethyl (meth) acrylate, 2 -(2-chlorophenyl)ethyl (meth) acrylate, 2-(3-chlorophenyl)ethyl (meth) acrylate, 2-(4-chlorophenyl)ethyl (methyl) Acrylate, 2-(4-bromophenyl)ethyl (meth) acrylate, 2-(3-phenylphenyl)ethyl (meth) acrylate and 2-(4-benzylphenyl) Ethyl (meth) acrylate, which may be used alone or as a mixture use.

The above (meth) acrylate copolymer may have a weight average molecular weight of from 1,000,000 to 1,500,000 g/mol, preferably from 1,200,000 to 1,450,000 g/mol.

Crosslinking agents can include, but are not limited to, isocyanates, epoxies, quinones, and acridine crosslinkers, which can be used alone or in admixture.

Examples of the isocyanate crosslinking agent may include, but are not limited to, toluene diisocyanate, xylene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylene diisocyanate, naphthalene. Diisocyanates and their polyols (trimethylolpropane, etc.), which may be used singly or as a mixture.

Examples of the epoxy crosslinking agent may include, but are not limited to, ethylene glycol diglycidyl ether, triglycidyl ether, trimethylolpropane triglycidyl ether, N, N, N', N'-tetrahydration Glyceryl ether ethylenediamine, glycerol diglycidyl ether, etc., which may be used singly or as a mixture.

The quinone imine crosslinker can be a carbodiimide.

In one embodiment, an isocyanate crosslinker and an epoxy crosslinker can be used together. The ratio of the isocyanate crosslinking agent to the epoxy crosslinking agent may be from 1500:1 to 1:1, preferably from 100:1 to 10:1. Within this range, excellent light leakage control effects can be obtained.

Alternatively, the isocyanate crosslinker and the carbodiimide crosslinker can be used together. The ratio of isocyanate crosslinker to carbodiimide crosslinker may range from 3500:1 to 500:1, preferably from 2500:1 to 1000:1. Within this range, excellent light leakage control effects can be obtained.

The content of the crosslinking agent may be from 0.01 to 10 parts by weight, preferably from 0.05 to 8.5 parts by weight, based on 100 parts by weight of the (meth) acrylate copolymer. Within this range, the light leakage control effect can be obtained. Specifically, the content of the crosslinking agent may be 5 to 8.2 parts by weight based on 100 parts by weight of the (meth) acrylate copolymer.

In the present invention, the adhesive may further include a decane coupling agent to further improve adhesion stability and adhesion reliability.

Examples of the decane coupling agent may include γ-glycidoxypropyltrimethoxydecane, γ-glycidoxypropylmethyldiethoxydecane, γ-glycidoxypropyltriethyltriethyl Oxaloxane, 3-mercaptopropyltrimethoxydecane, vinyltrimethoxydecane, vinyltriethoxydecane, γ-methylpropenyloxypropyltrimethoxydecane, γ-methylpropene oxime Oxypropyl propyl triethoxy decane, γ-aminopropyl triethoxy decane, 3-isocyanate propyl triethoxy decane and γ-acetamidine acetate propyl trimethoxy decane, which can be used alone Use or as a mixture.

The content of the decane coupling agent may be from about 0.01 to 3 parts by weight, preferably from about 0.05 to 0.3 parts by weight, based on 100 parts by weight of the (meth) acrylate copolymer. Within this range, suitable adhesion stability and adhesion reliability can be obtained.

In the present invention, the adhesive composition may further include additives selected as needed, such as a UV stabilizer, an antioxidant, a colorant, a reinforcing agent, an antifoaming agent, a surfactant, a plasticizer, and the like.

The above adhesives can be prepared by any method known in the art to which the present invention pertains. In one embodiment, the (meth) acrylate copolymer is uniformly mixed with an alkylammonium compound, a crosslinking agent, and an additive to prepare an adhesive. At this time, a solvent may be added for dilution as needed. Mixing and dilution processes are readily implemented for those of ordinary skill in the art to which the invention pertains.

The adhesive of the present invention has excellent heat resistance, toughness, peel strength, and reworkability, achieves low light leakage, and particularly exhibits excellent antireflection properties.

The above adhesive can be applied to an optical film and aged to form an adhesive layer.

The above adhesive may have an initial bond strength of from 100 to 250 fg, preferably from 120 to 250 gf, and more preferably from 150 to 250 gf, measured by a construction analyzer after attaching the spherical probe to the adherend for 2 seconds.

The 100 mm x 100 mm sample was measured with a Mitsubishi Chemical MCP-HT450 for 10 seconds, and the above adhesive may have 10 ⁸ to 10 ¹² Ω/sq, preferably 10 ⁸ to 10 ¹¹ Ω/sq, and more preferably 10 Surface resistance of ⁸ to 5 × 10 ¹⁰ Ω/sq.

In addition, the above adhesive is observed by the naked eye without strong light leakage at the edge portion, and may have an edge portion and a center portion which are greater than 0 and less than 1, preferably less than or equal to 0.5, more preferably greater than 0 and less than 0.2. The difference in luminance (ΔL) is calculated by the following equation:

ΔL=[(a+b+d+e)/4]-c,

Wherein a, b, d and e are each an average brightness of an edge portion on each side of the optical element covering a total area of 1/16 of the optical element, and c is an average of the central portion of the optical element covering the total area of 1/32. brightness.

After attaching to a glass substrate of 1.5 mm × 1.5 mm and standing for 3 days, and then measuring with a structural analyzer after stretching at 2 kgf, the above adhesive may have 1 to 50 μm, preferably 20 to 50 μm, and more preferably Creep of 40 to 50 μm.

The above adhesive may have a haze of 0.1% or less, preferably 0 to 0.08%, as measured by a haze meter.

Another aspect of the invention provides an optical component. The optical element can include an adhesive layer of the above-described adhesive formed on one side or the opposite sides of the optical film. The adhesive layer can be formed on the optical film by any method. For example, the above adhesive is directly deposited on an optical film and dried, or an adhesive layer is formed on a release substrate and then transferred to an optical film. The adhesive layer may have a thickness of from about 10 to 100 μm, preferably from about 20 to 70 μm.

Examples of the optical film may include a polarizing plate, a color filter, a phase retardation film, an elliptically polarizing film, a reflective film, an antireflection film, a compensation film, a brightness enhancement film, an alignment film, a light diffusion film, a glass anti-scatter film, and surface protection. Film, plastic LCD substrate, etc. The above optical film system can be easily manufactured by those having ordinary skill in the art to which the present invention pertains.

Hereinafter, the present invention will be explained in more detail with reference to the following examples. These examples are provided for illustrative purposes only and are not to be construed as limiting the invention in any way.

Example

(A) (meth) acrylate copolymer: comprising 92.5 wt% of n-butyl acrylate, 2.5 wt% of acrylic acid and 5 wt% of hydroxyethyl methacrylate and having a weight average molecular weight of 1,000,000 g/mol and 25% A solid content (meth) acrylate copolymer.

(B) Crosslinker

(B1) Diisocyanate Crosslinking Agent: Trimethylolpropane Diisocyanate Addition Compound

(B2) quinone imine crosslinker: V-05S (Nisshinbo Chemical Co., Ltd.)

(C) antistatic agent

(C1) Alkyl ammonium compound: A compound having a structure represented by Formula 1, wherein n is 4.

(C2) pyridine antistatic agent: ILP14-2 (KOEI)

(C3) lithium salt antistatic agent: ILA2-2 (KOEI)

(D) decane coupling agent: γ-glycidoxypropyl methoxy decane (KBM-403, Shinetsu Chemical Industries Co., Ltd.)

Examples 1 to 4

The above components were mixed according to the compositions listed in Table 1, and 20 parts by weight of methyl ethyl ketone was added as a diluent to the mixture, and uniformly stirred for 20 minutes to prepare a coating liquid. The adhesive coating liquid was deposited on a release film to a dry thickness of 25 μm to prepare an adhesive sheet, followed by aging at 35 ° C and 45% RH. Then, the performance of the adhesive was evaluated.

Comparative example 1

An adhesive was prepared in the same manner as in Example 1 except that the alkylammonium compound was not added.

Comparative example 2

An adhesive was prepared in the same manner as in Example 2 except that a pyridine antistatic agent was added instead of the alkylammonium compound.

Comparative example 3

An adhesive was prepared in the same manner as in Example 2 except that a lithium salt antistatic agent was added instead of the alkylammonium compound.

Physical performance evaluation (1) Initial bond strength

The polarizing plate was fixed in the construction analyzer with the adhesive facing up, and the spherical probe was bonded to the adhesive for about 2 seconds, and then the force (gf) when the spherical probe was vertically separated was measured.

(2) Peel strength (gf/25mm)

The 180° peel strength between the adhesive and the glass substrate was measured by the JIS 2107 method. The sample was cut into 25 mm x 210 mm sheets laminated on a glass substrate. However, the peel strength between the adhesive layer and the glass substrate was measured with a structural analyzer while peeling at a stretching speed of 300 mm/min.

(3) Creep

The creep was evaluated after attaching the polarizing plate to the glass substrate to have a bonding area of 1.5 cm × 1.5 cm and leaving it at room temperature for 3 days. When the sample was stretched with a load of 2 kgf, the creep was evaluated by measuring the creep of the adhesive with a construction analyzer.

(4) Surface resistance (Ω/sq)

The polarizing plate was cut into a 100 mm × 100 mm sample, and then the surface resistance was measured with a Mitsubishi Chemical MCP-HT450 for 10 seconds.

(5) Light leakage resistance

(i) The polarizing plate was attached to the LCD, left at 70 ° C for 250 hours, and then left at room temperature for 1 hour, and then the light leakage was evaluated by the naked eye and the brightness measuring device. If light leakage occurs, the brightness is higher at the edge portion of the LCD than at the center portion, and uneven brightness is observed.

○: light leakage occurs, X: no light leakage occurs

(ii) After driving the LCD, the brightness of the entire display panel was measured with a brightness measuring device (Lisa) at a distance of 1 m. The degree of light leakage is quantified by the difference in luminance between the central portion and the edge portion where the light leakage occurs. The luminance difference (ΔL) between the edge portion and the center portion is calculated by the following equation. When ΔL is less than 1, light leakage is not clearly observed with the naked eye. However, when ΔL is 1 or more, light leakage is clearly observed at a specific position, or light leakage is observed over a wide range, so that brightness uniformity of the panel is deteriorated.

ΔL=[(a+b+d+e)/4]-c,

Here, a, b, d, and e are each an average brightness of an edge portion of each side of the optical element covering the total area of the optical element of 1/16, and c is a central portion of the optical element covering the total area of 1/32. Average brightness.

(6) Durability

The polarizing plate was cut into 100 mm × 80 mm sheets, which were attached to an LCD or glass substrate and adhered tightly at 50 ° C and 3.5 atm. Then, the sample was allowed to stand under dry heat at 100 ° C for 250 hours, and allowed to stand under heat and humidity conditions of 60 ° C / 90% RH for 250 hours, and then left at room temperature for 1 hour or longer, and then it was verified whether the adhesive was Separation and whether bubbles are generated on the edge portion of the polarizing plate.

○: no separation and no bubbles at the edge

△: slight separation occurred and bubbles were formed at the edges.

X: Separation occurs and bubbles are present at the edge

(7) Haze

The haze was measured with a haze meter (HR-100).

As shown in Table 2, the adhesive using the alkylammonium compound (1) according to Examples 1 to 4 did not exhibit a cohesive (creep) change because it did not affect the main network of the adhesive. Therefore, these adhesives maintain excellent light leakage resistance. Moreover, they are specifically improved in chargeability and initial bond strength depending on the content of the alkylammonium compound (C1). Further, they have enhanced durability due to the addition of an alkylammonium compound (C1) having a soft chain.

Meanwhile, the hard adhesive according to Comparative Example 1 controlled shrinkage and expansion of the polarizing plate to exhibit excellent light leakage resistance, however, it had low initial bonding strength and could not withstand the shrinkage force of the film, thereby exhibiting unsuitable durability. In addition, it has no antistatic properties.

In Comparative Example 2 using a pyridinium salt antistatic agent, when the pyridinium salt antistatic agent was excessively added, its compatibility with the adhesive was deteriorated, resulting in a decrease in transparency and affecting the cohesive property of the adhesive, so that Can not maintain light leakage resistance.

The lithium salt antistatic agent in Comparative Example 3 did not affect cohesiveness, but had lower antistatic properties than the examples. In addition, it does not function properly to improve the initial bond strength and durability.

While the invention has been described herein, it will be understood by those skilled in the art Changes and replacements. Therefore, the scope of the invention should be limited only by the scope of the appended claims and their equivalents.

Claims (10)

An adhesive comprising a (meth) acrylate copolymer, a crosslinking agent, and an alkyl ammonium compound represented by Formula 1, wherein the crosslinking agent is an isocyanate crosslinking agent and a carbodiimide crosslinking agent. Combination, and wherein the adhesive has a creep of 1 μm to 50 μm as determined by a construction analyzer after being attached to a glass substrate and placed for 3 days: Wherein n is an integer from 0 to 15. The adhesive according to claim 1, wherein the adhesive has a surface resistance of 10 ⁸ to 10 ¹² Ω/sq and a luminance difference between an edge portion and a central portion of greater than 0 and less than 1 ( ΔL), the luminance difference is calculated by the following equation: ΔL = [(a + b + d + e) / 4] - c, wherein a, b, d and e are each covering the total area of the optical element The average brightness of the edge portion on each side of the optical element of 1/16, and c is the average brightness of the central portion of the optical element covering the total area of 1/32. The adhesive according to claim 1, wherein the adhesive is applied to the structure after the spherical probe is adhered to the adhesive for 2 seconds. (Texture analyzer) The initial bond strength was measured from 100 gf to 250 gf. The adhesive of claim 1, wherein the adhesive has a haze of 0 to 0.1%. The adhesive according to claim 1, wherein the adhesive comprises 100 parts by weight of the (meth) acrylate copolymer, 0.01 to 10 parts by weight of the crosslinking agent, and 0.01 to 10 parts by weight. Parts of the alkyl ammonium compound. The adhesive according to claim 1, wherein the (meth) acrylate copolymer comprises a carboxyl group and a hydroxyl group. The adhesive according to claim 6, wherein the (meth) acrylate copolymer is a copolymer of a C1 to C16 alkyl (meth) acrylate, a carboxyl group-containing monomer, and a hydroxyl group-containing monomer. Things. The adhesive according to claim 1, wherein the (meth) acrylate copolymer has a weight average molecular weight of from 1,000,000 g/mol to 1,500,000 g/mol. The adhesive according to claim 5, wherein the adhesive further comprises 0.01 to 3 parts by weight of a decane coupling agent. An optical element comprising an adhesive layer formed of an adhesive as described in claim 1 or 2 disposed on one side or the opposite side of the optical film.