Adhesive composition

Abstract

The present invention relates to an adhesive composition which adheres well to glass and plastic substrates and is reliably durable and resistant to reddening.

Description

Adhesive composition

[0001] The present invention relates to an adhesive composition having excellent adhesion to glass and plastic substrates, while simultaneously having excellent durability, reliability, and anti-scattering properties.

[0002]

[0003] Optically clear adhesives (OCAs) are widely used in the process of bonding glass or plastic cover plates to display modules, and various studies are being conducted to improve their physical properties. For example, Korean registered patent 10-1288238 discloses an acrylic resin composition that is desirable for an adhesive with excellent durability, which does not cause changes in the appearance of an optical laminate even under high humidity and heat conditions and even when heating and cooling are repeated.

[0004] Optical transparent adhesives are also used in the process of bonding a display module with glass and a polarizing plate as the top layer. However, the polarizing plate undergoes hydrolysis in a high-temperature environment and releases iodine (I2), which causes redness in the display. To prevent this, techniques such as coating the surface of the polarizing plate with a porous material have been proposed, but the introduction of a separate process complicates the manufacturing process and increases costs.

[0005] Accordingly, there is a need to develop an adhesive composition that exhibits excellent adhesion to glass and plastic substrates, while simultaneously possessing excellent durability, reliability, and anti-fogging properties.

[0006]

[0007] The present invention provides an adhesive composition having excellent adhesion to glass and plastic substrates, while also having excellent durability, reliability, and anti-scattering properties.

[0008]

[0009] The present invention provides an adhesive composition comprising a (meth)acrylate monomer mixture, a crosslinking agent, and a moisture absorbent, wherein the (meth)acrylate monomer mixture comprises an alkyl (meth)acrylate and a (meth)acrylate containing a hydroxyl group, and the moisture absorbent comprises one or more selected from the group consisting of a silane compound, polyethylene glycol (PEG), polypropylene glycol (PPG), and acrylic acid (AA), and wherein the composition comprises 0.1 to 2.5 parts by weight of the moisture absorbent per 100 parts by weight of the (meth)acrylate monomer mixture.

[0010]

[0011] The present invention provides an adhesive composition that exhibits excellent adhesion to glass and plastic substrates, as well as excellent durability reliability and anti-reddening properties. The adhesive composition according to the present invention can delay the occurrence of reddening at high temperatures (e.g., 120°C) for a significant period (e.g., 24 hours or more), has excellent adhesion to plastic or glass materials (e.g., 1,500 g / in or more), and exhibits excellent durability reliability against various environments such as high temperatures, low temperatures, thermal shock, and UV. The adhesive composition of the present invention is applicable for bonding polarizers.

[0012]

[0013] The present invention will be described in detail below. However, it is not limited to the following description, and each component may be modified in various ways or selectively combined as needed. Accordingly, it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0014] The term "viscosity" as used in this specification is measured by conventional methods known in the art, for example, using a Brookfield rotational viscometer at room temperature (25°C).

[0015] The adhesive composition of the present invention comprises a (meth)acrylate monomer mixture, a crosslinking agent, and a moisture absorbent.

[0016]

[0017] (Meta)acrylate monomer mixture

[0018] The adhesive composition of the present invention comprises a mixture of (meth)acrylate monomers including alkyl (meth)acrylate and (meth)acrylate containing hydroxyl groups.

[0019] Alkyl (meth)acrylates serve to impart adhesiveness. The alkyl (meth)acrylates may include alkyl (meth)acrylates having linear or branched alkyl groups having 1 to 20 carbon atoms and (meth)acrylic acid esters. For example, the alkyl (meth)acrylates may include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, butyl (meth)acrylate, pentyl (meth)acrylate, hexyl (meth)acrylate, ethylhexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate, nonyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, dodecyl (meth)acrylate, etc. These may be used alone or in a mixture of two or more types. For example, the alkyl (meth)acrylate may include 2-ethylhexyl (meth)acrylate (EHA), n-butyl (meth)acrylate (BA), or a mixture thereof.

[0020] Based on the total weight of the above (meth)acrylate monomer mixture, the above alkyl (meth)acrylate may contain 30 to 85 weight%, for example, 70 to 80 weight%. If the content of the alkyl (meth)acrylate is less than the aforementioned range, the adhesive strength may be reduced, and if it exceeds the aforementioned range, the storage modulus and elongation characteristics may be reduced.

[0021] For example, based on the total weight of the above (meth)acrylate monomer mixture, it may contain 30 to 80 weight%, for example 50 to 60 weight%, of 2-ethylhexyl (meth)acrylate (EHA) and 0.1 to 45 weight%, for example 15 to 25 weight%, of n-butyl (meth)acrylate (BA). If the content of 2-ethylhexyl (meth)acrylate (EHA) is less than the aforementioned range, the adhesive strength may decrease, and if it exceeds the aforementioned range, the cohesive strength of the adhesive may decrease, thereby reducing the elongation and tensile strength. If the content of n-butyl (meth)acrylate (BA) exceeds the aforementioned range, the elongation and tensile strength may decrease.

[0022] Hydroxyl group-containing (meth)acrylates serve to prevent fogging and increase cohesiveness. The above hydroxyl group-containing (meth)acrylates may include C1-C20 alkyl group-containing (meth)acrylates having hydroxyl groups, and C5-C20 cycloalkyl group-containing (meth)acrylates having hydroxyl groups. For example, the above hydroxyl group-containing (meth)acrylate may include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 6-hydroxyhexyl (meth)acrylate, 1,4-cyclohexanedimethanol mono(meth)acrylate, chloro-2-hydroxypropyl (meth)acrylate, diethylene glycol mono(meth)acrylate, etc. These may be used alone or in a mixture of two or more. As an example, the above hydroxyl group-containing (meth)acrylate may include 2-hydroxybutyl (meth)acrylate (HBA).

[0023] Based on the total weight of the above (meth)acrylate monomer mixture, the above (meth)acrylate containing hydroxyl groups may contain 10 to 40 weight%, for example, 20 to 30 weight%. If the content of the (meth)acrylate containing hydroxyl groups is less than the aforementioned range, the anti-fogging effect may be insufficient, and if it exceeds the aforementioned range, the adhesive strength may be reduced.

[0024] The above (meth)acrylate monomer mixture may contain 2-ethylhexyl (meth)acrylate (EHA), n-butyl (meth)acrylate (BA), and 2-hydroxybutyl (meth)acrylate (HBA) in a weight ratio of 1:0.001 to 1.5:0.3 to 0.85. If the content of n-butyl (meth)acrylate (BA) relative to 2-ethylhexyl (meth)acrylate (EHA) exceeds the aforementioned range, elongation and tensile strength may decrease. If the content of 2-hydroxybutyl (meth)acrylate (HBA) relative to 2-ethylhexyl (meth)acrylate (EHA) is less than the aforementioned range, the anti-fogging effect may be insufficient, and if it exceeds the aforementioned range, the adhesive strength may decrease.

[0025] The viscosity (25°C) of the resin prepared from the above (meth)acrylate monomer mixture may be 400 to 10,000 cPs, for example, 800 to 5,000 cPs. If the viscosity of the resin is below the aforementioned range, it may be difficult to control the thickness during coating, making it difficult to obtain a coating film of the desired thickness, and if it exceeds the aforementioned range, the workability of the coating may be reduced, making it difficult to obtain a film of uniform thickness.

[0026] The total solid content of the resin prepared from the above (meth)acrylate monomer mixture may be 2 to 20 weight%, for example, 4 to 10 weight%. If the total solid content of the resin is less than the aforementioned range, the viscosity may be low, making it difficult to control the coating thickness, and if it exceeds the aforementioned range, the viscosity of the resin may be high, which may reduce the workability of the coating.

[0027]

[0028] crosslinking agent

[0029] The adhesive composition of the present invention includes a polyfunctional (meth)acrylate as a crosslinking agent. The above-mentioned polyfunctional (meth)acrylates are 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, neopentyl glycol adipate di(meth)acrylate, dicyclofentanyl di(meth)acrylate, caprolactone-modified dicyclofentenyl di(meth)acrylate, ethylene oxide-modified di(meth)acrylate, di(meth)acryloxyethyl isocyanurate, allylated cyclohexyl di(meth)acrylate, tricyclodecane dimethanol (meth)acrylate, dimethylol dicyclopentane di(meth)acrylate, and ethylene oxide-modified hexahydrophthalic acid di(meth)acrylate. Difunctional (meth)acrylates such as tricyclodecane dimethanol (meth)acrylate, neopentyl glycol-modified trimethylpropane di(meth)acrylate, adamantane di(meth)acrylate, and 9,9-bis[4-(2-acryloyloxyethoxy)phenyl]fluorene; trifunctional (meth)acrylates such as trimethylolpropane tri(meth)acrylate, dipentaerythritol tri(meth)acrylate, propionic acid-modified dipentaerythritol tri(meth)acrylate, pentaerythritol tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, trifunctional urethane (meth)acrylate, and tris(meth)acrylates such as tris(meth)acrylate; It may include tetrafunctional (meth)acrylates such as diglycerin tetra(meth)acrylate and pentaerythritol tetra(meth)acrylate; pentafunctional acrylates such as dipentaerythritol penta(meth)acrylate; and hexafunctional (meth)acrylates such as dipentaerythritol hexa(meth)acrylate and caprolactone-modified dipentaerythritol hexa(meth)acrylate. These may be used alone or in a mixture of two or more types. For example, the polyfunctional (meth)acrylate may include hexanediol diacrylate (HDDA).

[0030] For every 100 parts by weight of the above (meth)acrylate monomer mixture, 0.01 to 0.5 parts by weight, for example 0.01 to 0.1 parts by weight, of a crosslinking agent may be included. If the content of the crosslinking agent is less than the aforementioned range, the gel content decreases, and the modulus and elongation properties may decrease, and if it exceeds the aforementioned range, it may become excessively hard.

[0031]

[0032] moisture absorbent

[0033] The adhesive composition of the present invention includes a moisture absorbent. When the polyvinyl alcohol (PVA) material constituting the polarizing plate is exposed to high temperatures in a humid environment, it undergoes hydrolysis, causing iodine (I2) to dissociate and resulting in reddening. In the present invention, by using a moisture absorbent, the hydrolysis of PVA is suppressed, thereby preventing or delaying reddening caused by the polarizing plate. Furthermore, the moisture absorbent reacts with the glass surface over the long term to improve long-term adhesion and thus improve durability.

[0034] The above moisture absorbent may include one or more selected from the group consisting of silane compounds, polyethylene glycol (PEG), polypropylene glycol (PPG), and acrylic acid (AA).

[0035] The above silane compound plays a role in effectively suppressing lifting phenomena by supplementing adhesive strength. In particular, when using a hydrophilic silane compound, an increase in solubility can also be induced. As the above silane compound, tetraethyl orthosilicate, 3-glycidoxypropyl trimethoxysilane, 3-methacryloxypropyl trimethoxysilane, etc., can be used. These can be used alone or in a mixture of two or more types.

[0036] With respect to 100 parts by weight of the above (meth)acrylate monomer mixture, the above moisture absorbent may be included in an amount of 0.1 to 2.5 parts by weight, for example, 0.5 to 1.5 parts by weight. If the content of the moisture absorbent is less than the aforementioned range, the moisture absorption effect may be insufficient and the anti-reddening effect may be insufficient, and if it exceeds the aforementioned range, durability may be reduced or whitening may occur.

[0037]

[0038] Photoinitiator

[0039] The adhesive composition of the present invention may include a photoinitiator. As the photoinitiator, any photoinitiator used in the relevant technical field may be used without special limitations. For every 100 parts by weight of the (meth)acrylate monomer mixture, the composition may include 0.01 to 0.5 parts by weight, for example, 0.01 to 0.2 parts by weight of a photoinitiator. If the content of the photoinitiator is less than the aforementioned range, polymerization and crosslinking may proceed insufficiently, and if it exceeds the aforementioned range, the molecular weight of the resin becomes excessively small and soft, which may cause lifting phenomena.

[0040]

[0041] The adhesive composition of the present invention can be manufactured by a manufacturing method comprising the steps of: synthesizing a resin by mixing a monomer containing an alkyl (meth)acrylate and a (meth)acrylate containing a hydroxyl group and a photoinitiator and irradiating with UV light (Step 1); mixing a polyfunctional (meth)acrylate, which is a crosslinking agent, a photoinitiator and an additive with the resin (Step 2); and coating the mixture to an appropriate thickness and curing by irradiating with UV light (Step 3).

[0042] When UV irradiating in the third step above, photocuring is performed with an irradiation dose of 1,000 to 4,000 mJ / ㎠, and photocuring can be performed by gradually increasing the irradiation dose within the above range. If strong light is applied from the beginning, the degree of crosslinking and molecular weight may decrease, and if the irradiation dose is insufficient, bubbles may form.

[0043] The adhesive composition according to the present invention exhibits excellent adhesion to glass and plastic substrates, as well as excellent durability reliability and anti-reddening properties. The adhesive composition of the present invention can significantly delay the occurrence of reddening at high temperatures, possesses excellent adhesion to plastic or glass materials, and exhibits excellent durability reliability against various environments such as high temperature, low temperature, thermal shock, and UV, making it suitable for application as an adhesive for polarizers. For example, the adhesive composition of the present invention can delay the occurrence of reddening at 120°C for more than 24 hours and has an adhesion of 1,500 g / in or more to plastic or glass materials.

[0044]

[0045] The present invention will be explained in more detail below through examples. However, the following examples are intended only to aid in understanding the present invention and do not imply that the scope of the present invention is limited to these examples in any way.

[0046]

[0047] [Examples 1-9: Preparation of Adhesive Compositions]

[0048] According to Table 1 below, the resin components were introduced into a reactor, and dissolved oxygen was removed by injecting nitrogen for 30 minutes, after which UV was irradiated using a low-pressure UV lamp (Philips TL-8W). The reaction was terminated while observing an increase in viscosity after the polymerization reaction began. The reaction was terminated by turning off the low-pressure UV lamp and injecting air. The adhesive composition of each example was prepared by uniformly mixing a crosslinking solution with the resin prepared above. The physical properties of each resin prepared above are shown in Table 1 below.

[0049]

[0050] [Comparative Example 1-7: Preparation of Adhesive Composition]

[0051] The adhesive compositions of each comparative example were prepared in the same manner as the examples, except for those according to Table 2 below.

[0052]

[0053]

[0054]

[0055]

[0056] 2-EHA: 2-ethylhexyl acrylate

[0057] BA: n-butyl acrylate

[0058] HBA: 2-hydroxybutyl acrylate

[0059] Photoinitiator: Igacure 651

[0060] HDDA: Hexanediol diacrylate

[0061] Moisture absorbent 1: Polyethylene glycol (PEG)

[0062] Moisture absorbent 2: Polypropylene glycol (PPG)

[0063] Moisture absorbent 3: 3-glycidoxypropyl trimethoxysilane

[0064] Moisture absorbent 4: 3-methacryloxypropyl trimethoxysilane

[0065] Moisture absorbent 5: Tetraethyl orthosilicate (TEOS)

[0066] Moisture absorbent 6: Acrylic acid (AA)

[0067] Moisture absorbent 7: Calcium chloride

[0068]

[0069] [Physical Property Evaluation]

[0070] The physical properties of the adhesive compositions of each example and comparative example were evaluated as follows, and the results are shown in Tables 3 and 4 below.

[0071]

[0072] Transparent adhesive tape manufacturing

[0073] The adhesive compositions of each example and comparative example were applied to a thickness of 250 μm on a release film, and after covering with a release film, 2,100 mJ / cm² 2 Transparent adhesive tapes of each example and comparative example were prepared by UV irradiation.

[0074]

[0075] Gel content (Gel%)

[0076] The transparent adhesive tapes of each example and comparative example were immersed in ethyl acetate for at least 24 hours, filtered, and dried in a 120°C oven for 30 minutes, after which the gel content was evaluated based on the rate of mass change before and after immersion.

[0077]

[0078] Solid content (NV%)

[0079] After drying the transparent adhesive tapes of each example and comparative example in a forced circulation oven at 120°C for 30 minutes, the solid content was evaluated based on the rate of change in mass before and after drying.

[0080]

[0081] transmittance, turbidity

[0082] Two sheets of soda-lime glass were laminated using the transparent adhesive tape of each example and comparative example to prepare specimens with a glass / transparent adhesive tape / glass structure. After leaving each specimen for 24 hours, transmittance and turbidity were measured using a transmittance meter (BYK, Haze Guard-i).

[0083]

[0084] Tensile strength and elongation

[0085] A specimen was prepared by laminating the transparent adhesive tapes of each example and comparative example to a thickness of 1 mm, cutting them to a width of 1 cm, and then removing the release films from both sides. Using a UTM device (Salt, ST-1003), a tensile test was performed at room temperature at a speed of 100 mm / min to measure the tensile strength and elongation at the highest point at the moment the transparent adhesive tape broke.

[0086]

[0087] adhesiveness

[0088] Transparent adhesive tapes of each example and comparative example were adhered to a 38 μm PET film, cut to a width of 1 inch, adhered to soda-lime glass, and left for 24 hours to prepare specimens. Adhesion strength was evaluated by performing a 180º Peel test at room temperature at a speed of 300 mm / min using a UTM instrument (Salt, ST-1003).

[0089]

[0090] bubbles

[0091] Each specimen was prepared by sequentially laminating a soda-lime glass, a polarizing plate, the transparent adhesive tape of each example and comparative example, and the soda-lime glass. After leaving each specimen for 24 hours, it was placed in a forced-circulation oven at 105°C and the occurrence of bubbles was observed for one week.

[0092]

[0093] Red fire occurrence

[0094] Each specimen was prepared by sequentially laminating a soda-lime glass, a polarizing plate, the transparent adhesive tape of each example and comparative example, and the soda-lime glass. After leaving each specimen for 24 hours, it was placed in a forced-circulation oven at 120°C, and the occurrence of redness was observed visually at 12-hour intervals.

[0095]

[0096] Long-term reliability

[0097] Specimens with a Glass / transparent adhesive tape / Glass structure were prepared by laminating two sheets of Soda-lime glass using the transparent adhesive tapes of each example and comparative example. After storing each specimen for 1,000 hours under each condition, haze and turbidity were analyzed. Long-term reliability was evaluated as good when haze was 99% or higher and turbidity was 1% or lower.

[0098]

[0099]

[0100]

[0101]

[0102]

[0103] As shown in Tables 3 and 4 above, the adhesive compositions of Examples 1-9 according to the present invention exhibited excellent physical properties across all measured items. On the other hand, the adhesive compositions of Comparative Example 1, which does not contain a moisture absorbent; Comparative Examples 2-5, which contain a moisture absorbent in an amount outside the scope of the present invention; Comparative Example 6, which does not contain a hydroxyl group-containing (meth)acrylate; and Comparative Example 7, which contains a moisture absorbent outside the scope of the present invention, exhibited inferior physical properties compared to the examples across all measured items.

[0104]

[0105] The present invention provides an adhesive composition having excellent adhesion to glass and plastic substrates, while also having excellent durability, reliability, and anti-scattering properties.

Claims

It comprises a (meth)acrylate monomer mixture, a crosslinking agent, and a moisture absorbent, The above (meth)acrylate monomer mixture comprises alkyl (meth)acrylate and hydroxyl group-containing (meth)acrylate, and The above moisture absorbent comprises one or more selected from the group consisting of silane compounds, polyethylene glycol (PEG), polypropylene glycol (PPG), and acrylic acid (AA), and An adhesive composition comprising 0.1 to 2.5 parts by weight of the moisture absorbent per 100 parts by weight of the above (meth)acrylate monomer mixture. In claim 1, the alkyl (meth)acrylate comprises 2-ethylhexyl (meth)acrylate (EHA) and n-butyl (meth)acrylate (BA), and The above hydroxyl group-containing (meth)acrylate includes 2-hydroxybutyl (meth)acrylate (HBA), and An adhesive composition comprising one or more silane compounds selected from the group consisting of tetraethyl orthosilicate, 3-glycidoxypropyl trimethoxysilane, and 3-methacryloxypropyl trimethoxysilane. An adhesive composition according to claim 1, comprising 30 to 85 weight% of the alkyl (meth)acrylate and 10 to 40 weight% of the hydroxyl group-containing (meth)acrylate based on the total weight of the (meth)acrylate monomer mixture. An adhesive composition according to claim 2, comprising, based on the total weight of the (meth)acrylate monomer mixture, 30 to 80 weight% of 2-ethylhexyl (meth)acrylate (EHA), 0.1 to 45 weight% of n-butyl (meth)acrylate (BA), and 10 to 40 weight% of 2-hydroxybutyl (meth)acrylate (HBA). In claim 2, the adhesive composition comprises the (meth)acrylate monomer mixture containing 2-ethylhexyl (meth)acrylate (EHA), n-butyl (meth)acrylate (BA), and 2-hydroxybutyl (meth)acrylate (HBA) in a weight ratio of 1:0.001 to 1.5:0.3 to 0.

85. An adhesive composition according to claim 1, comprising 0.01 to 0.5 parts by weight of the crosslinking agent per 100 parts by weight of the (meth)acrylate monomer mixture. An adhesive composition according to claim 1, wherein the viscosity (25°C) of the resin prepared from the (meth)acrylate monomer mixture is 400 to 10,000 cPs and the total solid content is 2 to 20 weight%. An adhesive composition according to claim 1 that delays the occurrence of redness at 120°C for at least 24 hours and has an adhesion of at least 1,500 g / in to plastic or glass materials.

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