Adhesive composition and transparent adhesive tape comprising same

Abstract

The present invention relates to an adhesive composition which suppresses bubble generation and has excellent transparency, adhesiveness, mechanical properties, and long-term reliability, and a transparent adhesive tape comprising same.

Description

Adhesive composition and transparent adhesive tape comprising the same

[0001] The present invention relates to an adhesive composition that suppresses bubble generation and has excellent transparency, adhesiveness, mechanical properties and long-term reliability, and a transparent adhesive tape comprising the same.

[0002]

[0003] Optically clear adhesives (OCAs) are widely used in bonding glass, LCDs, and display modules containing them, and various studies are underway to improve their properties. For example, Korean Patent No. 10-1288238 discloses an acrylic resin composition suitable for use as a durable adhesive that does not change the appearance of an optical laminate even under high-humidity heat and humidity conditions and after repeated heating and cooling.

[0004] Recently, due to cost concerns and safety concerns surrounding electric vehicles, attempts to use plastic plates, including polycarbonate (PC) and polymethyl methacrylate (PMMA), in addition to glass, have been increasing. Applying conventional optical adhesives to these plastic plates can lead to the generation of bubbles due to outgassing from the plastic material.

[0005] Accordingly, there is a need for development of an adhesive composition that suppresses bubble generation due to gas emission when applied to a plastic substrate.

[0006]

[0007] The present invention provides an adhesive composition that suppresses bubble generation and has excellent transparency, adhesiveness, mechanical properties and long-term reliability, and a transparent adhesive tape comprising the same.

[0008]

[0009] The present invention provides an adhesive composition comprising monomers including 2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA) and 2-hydroxyethyl acrylate (HEA) and a hexanediol diacrylate (HDDA) crosslinking agent, wherein the adhesive composition comprises 50 to 60 wt% of 2-ethylhexyl acrylate (EHA), 20 to 30 wt% of isobornyl acrylate (IBOA) and 15 to 25 wt% of 2-hydroxyethyl acrylate (HEA) based on the total weight of the monomers, and 0.05 to 0.5 wt% of hexanediol diacrylate (HDDA) based on 100 wt% of the monomers.

[0010]

[0011] The present invention provides a pressure-sensitive adhesive composition that suppresses bubble formation and exhibits excellent transparency, adhesiveness, mechanical properties, and long-term reliability, and a transparent pressure-sensitive adhesive tape comprising the same. The pressure-sensitive adhesive composition according to the present invention suppresses bubble formation due to gas release when applied to a plastic substrate under high temperature or high temperature and high humidity conditions, and is therefore suitable for use as an optical pressure-sensitive adhesive for plastic substrates. In addition, the pressure-sensitive adhesive composition of the present invention exhibits excellent transparency, adhesiveness, mechanical properties, and long-term reliability, and exhibits excellent adhesion to both glass and plastic substrates. A transparent pressure-sensitive adhesive tape comprising the pressure-sensitive adhesive composition of the present invention can be applied as a transparent pressure-sensitive adhesive tape for vehicles.

[0012]

[0013] Figure 1 illustrates a process for manufacturing a transparent adhesive tape from an adhesive composition.

[0014]

[0015] The present invention will be described in detail below. However, it is not limited to the following description, and each component may be modified or selectively mixed as needed. Therefore, it should be understood that all modifications, equivalents, and alternatives included within the spirit and technical scope of the present invention are included.

[0016] The “viscosity” used herein is measured by a conventional method known in the art, and can be measured, for example, using a Brookfield rotational viscometer at room temperature (25°C).

[0017]

[0018] Adhesive composition

[0019] The adhesive composition of the present invention comprises monomers including 2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA) and 2-hydroxyethyl acrylate (HEA).

[0020] 2-Ethylhexyl acrylate (EHA) acts as an adhesive. 2-Ethylhexyl acrylate (EHA) may be present in an amount of 50 to 60 wt%, for example, 55 to 60 wt%, based on the total weight of the monomer. If the content of 2-ethylhexyl acrylate is below 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] Isobornyl acrylate (IBOA) plays a role in controlling adhesion. Isobornyl acrylate (IBOA) may be included in an amount of 20 to 30 wt%, for example, 20 to 25 wt%, based on the total weight of the monomer. If the amount of isobornyl acrylate is below the aforementioned range, adhesion to the plastic may be reduced, and if it exceeds the aforementioned range, brittleness may occur.

[0022] 2-Hydroxyethyl acrylate (HEA) acts as an anti-fogging agent. 2-Hydroxyethyl acrylate (HEA) may be present in an amount of 15 to 25 wt%, for example, 15 to 20 wt%, based on the total weight of the monomer. If the amount of 2-hydroxyethyl acrylate (HEA) is below the aforementioned range, fogging may occur, and if it exceeds the aforementioned range, adhesion may be reduced.

[0023] The adhesive composition of the present invention includes hexanediol diacrylate (HDDA) as a crosslinking agent. Hexanediol diacrylate (HDDA) may be included in an amount of 0.05 to 0.5 parts by weight, for example, 0.1 to 0.3 parts by weight, based on 100 parts by weight of the monomer. If the content of hexanediol diacrylate (HDDA) is less than the above-mentioned range, the gel content may decrease, and the storage modulus and elongation characteristics may deteriorate. If the content exceeds the above-mentioned range, the composition may become brittle.

[0024] The adhesive composition of the present invention includes a photoinitiator. Any photoinitiator used in the relevant technical field can be used without particular limitation. The photoinitiator may be included in an amount of 0.01 to 0.5 parts by weight, for example, 0.1 to 0.4 parts by weight, based on 100 parts by weight of the monomer. If the content of the crosslinking agent 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 may become excessively low.

[0025] The adhesive composition of the present invention can be manufactured by a manufacturing method including a step (first step) of mixing monomers including 2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA), and 2-hydroxyethyl acrylate (HEA) and a photoinitiator, a step (second step) of manufacturing a resin by irradiating the mixture with UV, and a step (third step) of mixing a crosslinking agent, hexanediol diacrylate (HDDA), and a photoinitiator into the resin.

[0026] With respect to 100 parts by weight of the monomer, the content of the photoinitiator added in the first step may be 0.005 to 0.1 parts by weight, for example, 0.01 to 0.1 parts by weight, and the content of the photoinitiator added in the third step may be 0.01 to 0.4 parts by weight, for example, 0.1 to 0.3 parts by weight.

[0027] If the photoinitiator content in the first step is below the aforementioned range, the polymerization rate may slow down, thereby reducing the reaction yield. If it exceeds the aforementioned range, the molecular weight may decrease, thereby reducing the gel content and solid content after coating and curing, and deteriorating the mechanical properties. If the photoinitiator content in the third step is below the aforementioned range, the curing rate may slow down, thereby reducing the coating yield and solid content. If it exceeds the aforementioned range, the degree of crosslinking may decrease, thereby reducing the gel content, and deteriorating the mechanical properties.

[0028] The above UV irradiation can be performed using low-pressure UV until the resin becomes a viscous liquid state with a viscosity (at 25°C) of 800 to 5,000 cPs. The resin is a mixed state of a monomer and a polymer, and may include, for example, 4 to 10 wt% of a polymer and 90 to 96 wt% of an unreacted monomer. The final product, an adhesive composition, is a viscous liquid state with a viscosity (at 25°C) of 800 to 5,000 cPs. If the viscosity of the resin and the adhesive composition is less than the above-mentioned range, it may be difficult to control the thickness during coating, making it difficult to obtain a coating film with a desired thickness, and if it exceeds the above-mentioned range, the coating workability deteriorates, and it may be difficult to obtain a film with a uniform thickness.

[0029]

[0030] Transparent adhesive tape

[0031] The present invention provides a transparent adhesive tape comprising the aforementioned adhesive composition. The transparent adhesive tape may comprise a lower layer release film, an adhesive layer comprising the adhesive composition, and an upper layer release film. The transparent adhesive tape may be manufactured by a manufacturing method comprising the steps of manufacturing a laminate comprising the lower layer release film, the adhesive layer comprising the adhesive composition, and the upper layer release film, and the step of irradiating the upper layer release film and the lower layer release film of the laminate with UV light.

[0032] For example, the laminate may be manufactured by injecting an adhesive composition between a lower layer release film and an upper layer release film. As another example, the laminate may be manufactured by coating an adhesive composition on a lower layer release film and laminating an upper layer release film on the coating.

[0033] For example, the lower layer release film may be a medium-peel release film, and the release peel strength may be 100 gf / in or less. For example, the upper layer release film may be a light-peel release film, and the release peel strength may be 5 to 30 gf / in. The release peel strength of the lower layer release film may be 2 to 4 times the release peel strength of the upper layer release film.

[0034] The above UV irradiation may include first irradiation and second irradiation, and the second irradiation intensity may be greater than the first irradiation intensity. If the second irradiation intensity is lower than the first irradiation intensity, unreacted monomers may remain, resulting in a lower solid content and bubbles may be generated after bonding.

[0035] For example, the first irradiation intensity may be 5 mW / cm2 or less, and the second irradiation intensity may be greater than the first irradiation intensity. If irradiation is performed with a strong irradiation intensity from the beginning, for example, a first irradiation intensity exceeding 5 mW / cm2, the degree of crosslinking and molecular weight may decrease, which may result in a deterioration in storage modulus and elongation characteristics, and as a result, the gel content and solid content may decrease.

[0036] For example, as shown in Fig. 1 below, UV irradiation can be performed through six UV zones spaced at 5 m intervals. The first irradiation can be performed in the early UV zone (UV zones 1 to 3), and the second irradiation can be performed in the late UV zone (UV zones 4 to 6). In this case, excellent properties such as transparency, adhesiveness, mechanical properties, and long-term reliability can be secured through the early UV zone, and the adhesive composition can be completely cured through the late UV zone, and high gel content and solid content can be secured while suppressing bubble generation.

[0037] The total light irradiation dose during the above UV irradiation may be 1,500 mJ / cm2 or more, for example, 1,500 to 3,000 mJ / cm2, or as another example, 2,000 to 3,000 mJ / cm2. If the total light irradiation dose is less than the above-mentioned range, bubbles may be generated, and the gel content and solid content may be reduced.

[0038] The transparent adhesive tape of the present invention has a high solid content and crosslinking degree. The transparent adhesive tape has a solid content of 98.5% or more, for example, 98.5 to 99.8%, and a gel content of 85% or more, for example, 85 to 98%. If the solid content is less than the above-mentioned range, bubbles may be generated at the adherend surface during bonding due to the generated volatile matter, and if the gel content is less than the above-mentioned range, the storage modulus and elongation characteristics may be deteriorated.

[0039]

[0040] Hereinafter, the present invention will be described in more detail through examples. However, the following examples are intended only to aid understanding of the present invention and are not intended to limit the scope of the present invention in any way.

[0041]

[0042] [Example 1-8: Preparation of adhesive composition]

[0043] According to Table 1 below, the resin components were introduced into the reactor, nitrogen was injected for 30 minutes to remove dissolved oxygen, and then UV was irradiated with a low-pressure UV lamp (TL-8W from Philips). After the polymerization reaction began, the reaction was terminated while observing an increase in viscosity. The reaction was terminated by turning off the low-pressure UV lamp and injecting air. The crosslinking compound was uniformly mixed with the manufactured resin (viscosity (25°C) 2,000-4,000 cps, solid content 5-10%) to prepare an adhesive composition of each example.

[0044]

[0045] [Comparative Example 1-10: Preparation of adhesive composition]

[0046] The adhesive compositions of each comparative example were prepared in the same manner as in the examples, except as indicated in Table 2 below.

[0047]

[0048]

[0049]

[0050] EHA: 2-ethylhexyl acrylate

[0051] IBOA: Isobornyl acrylate

[0052] HEA: 2-hydroxyethyl acrylate

[0053] HDDA: Hexanediol diacrylate

[0054] Photoinitiator: Igacure 651

[0055]

[0056] [Transparent Adhesive Tape Manufacturing]

[0057] As illustrated in Fig. 1, the adhesive compositions of each example and comparative example were injected between two upper and lower release films to a thickness of 400 μm, and UV was irradiated with a low-pressure UV lamp according to the conditions of Tables 3 and 4 below, thereby manufacturing transparent adhesive tapes of each example and comparative example. The length of each UV Zone was set to 5 m.

[0058]

[0059]

[0060]

[0061]

[0062] [Physical property evaluation]

[0063] According to the following method, the physical properties of the transparent adhesive tapes of each example and comparative example were evaluated, and the results are shown in Tables 5 and 6 below.

[0064]

[0065] Gel content (Gel%)

[0066] The transparent adhesive tapes of each example and comparative example were immersed in acetone for more than 24 hours, filtered, and dried in an oven at 120°C for 30 minutes. The gel content was evaluated by the mass change rate before and after immersion.

[0067]

[0068] Solids content (NV%)

[0069] The transparent adhesive tapes of each example and comparative example were dried in a 120°C forced circulation oven for 30 minutes, and the solid content was evaluated by the mass change rate before and after drying.

[0070]

[0071] adhesiveness

[0072] The transparent adhesive tapes of each example and comparative example were adhered to a 25 ㎛ PET film, cut to a width of 1 inch, adhered to sodalime glass, and left for 24 hours to prepare specimens. Using UTM equipment (Salt, ST-1003), the adhesive strength of each specimen was evaluated by performing a 180º peel test at a speed of 300 mm / min at room temperature.

[0073]

[0074] Transmittance, turbidity

[0075] Two sheets of sodalime glass were laminated using the transparent adhesive tape of each example and comparative example to produce a specimen with a glass / transparent adhesive tape / glass structure. After allowing each specimen to stand for 24 hours, the transmittance and turbidity were measured using a penetrameter (BYK, Haze gard-i).

[0076]

[0077] Tensile strength, elongation

[0078] The transparent adhesive tapes of each example and comparative example were overlapped to a thickness of 1 mm, cut to a width of 1 cm, and measured using UTM equipment (Salt, ST-1003, speed of 100 mm / min).

[0079]

[0080] long-term reliability

[0081] Using the transparent adhesive tape of each example and comparative example, two sheets of sodalime glass were laminated to produce specimens with a glass / transparent adhesive tape / glass structure. After storing each specimen for 1,000 hours under each condition, the transmittance, turbidity, and color difference (b*) were analyzed to evaluate long-term reliability according to the following criteria.

[0082] [metewand]

[0083] Good: Transmittance 90% or more, turbidity less than 1%, b* change 0.3 or less

[0084]

[0085] Foaming inhibition power

[0086] Each specimen was manufactured by sequentially laminating the PC surface of a PC / PMMA coextruded sheet, the transparent adhesive tape of each example and comparative example, and glass. After leaving each specimen for 24 hours, it was placed in a constant temperature and humidity chamber at 85°C and 85% RH, and the occurrence of bubbles was observed for one week.

[0087]

[0088]

[0089]

[0090]

[0091] As shown in Tables 5 and 6 above, the transparent adhesive tapes of Examples 1-8 using the adhesive composition according to the present invention exhibited excellent properties overall in terms of gel content, solid content, adhesive strength, transmittance, turbidity, mechanical properties (tensile strength, elongation), long-term reliability, and bubble generation. On the other hand, the transparent adhesive tapes of Comparative Examples 1-9 using the adhesive composition not satisfying the composition of the present invention exhibited generally inferior properties compared to the transparent adhesive tapes of the Examples. On the other hand, in the case of Comparative Example 10, polymerization occurred insufficiently, forming an adhesive composition with low viscosity, and an adhesive tape with a uniform thickness could not be formed, so the physical properties could not be evaluated.

[0092]

[0093] The present invention provides an adhesive composition that suppresses bubble generation and has excellent transparency, adhesiveness, mechanical properties and long-term reliability, and a transparent adhesive tape comprising the same.

Claims

Containing monomers including 1.2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA) and 2-hydroxyethyl acrylate (HEA) and a crosslinking agent including hexanediol diacrylate (HDDA), Based on the total weight of the above monomers, it comprises 50 to 60 wt% of 2-ethylhexyl acrylate (EHA), 20 to 30 wt% of isobornyl acrylate (IBOA), and 15 to 25 wt% of 2-hydroxyethyl acrylate (HEA). An adhesive composition comprising 0.05 to 0.5 parts by weight of hexanediol diacrylate (HDDA) per 100 parts by weight of the above monomer. A step of mixing monomers and a photoinitiator including 2.2-ethylhexyl acrylate (EHA), isobornyl acrylate (IBOA) and 2-hydroxyethyl acrylate (HEA), A step of manufacturing a resin by irradiating the above mixture with UV, and A method for producing an adhesive composition, comprising a step of mixing hexanediol diacrylate (HDDA) and a photoinitiator into the above resin.

3. In the second paragraph, based on the total weight of the monomer, 50 to 60 wt% of 2-ethylhexyl acrylate (EHA), 20 to 30 wt% of isobornyl acrylate (IBOA), and 15 to 25 wt% of 2-hydroxyethyl acrylate (HEA) are included. A method for producing an adhesive composition comprising 0.05 to 0.5 parts by weight of hexanediol diacrylate (HDDA) per 100 parts by weight of the above monomer.

4. A method for producing an adhesive composition in the second paragraph, wherein the viscosity (25°C) of the resin is 800 to 5,000 cPs, and the viscosity (25°C) of the adhesive composition is 800 to 5,000 cPs.

5. A step of manufacturing a laminate including a lower layer release film, an adhesive layer, and an upper layer release film; and A step of irradiating UV to the upper layer release film and the lower layer release film of the above laminate, A method for manufacturing a transparent adhesive tape, wherein the adhesive layer is made of the adhesive composition of claim 1.

6. A method for manufacturing a transparent adhesive tape in the fifth paragraph, wherein the UV irradiation includes first irradiation and second irradiation, the first irradiation light intensity is 5 mW / ㎠ or less, and the second irradiation light intensity is greater than the first irradiation light intensity.

7. A method for manufacturing a transparent adhesive tape in the fifth paragraph, wherein the total light irradiation amount during the UV irradiation is 1,500 mJ / ㎠ or more.

Images