UV-curable adhesive composition and interior film comprising adhesive layer formed thereof

Abstract

The present invention relates to a UV-curable adhesive composition and an interior film comprising same, wherein the UV-curable adhesive composition comprises: a urethane (meth)acrylate-based oligomer; a (meth)acrylate-based monomer; a caprolactam-based compound; and a UV initiator, wherein the urethane (meth)acrylate-based oligomer includes two functional groups, and has a weight average molecular weight of 500 g / mol to 2,000 g / mol.

Description

An interior film comprising a UV-curable adhesive composition and an adhesive layer formed therefrom

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0077002, filed June 15, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an interior film having excellent adhesion and durability between an ink layer and a transparent protective layer, including a UV-curable adhesive composition having excellent storage stability at room temperature (25°C) and high temperature (60°C) and excellent adhesion to an ink layer, and an adhesive layer formed therefrom.

[0003] Various printing methods such as flexo printing, gravure printing, inkjet printing, and screen printing are utilized to apply specific colors or form patterns on various types of substrates. In particular, gravure printing and flexo printing are widely used because they can be mass-produced at high speeds. However, gravure printing and flexo printing have limitations such as requiring additional costs and time, such as producing copper plates, for design changes, and insufficient resolution of the image after printing. In addition, conventional printing methods typically use solvent-based inks containing organic solvents. These solvent-based inks have the problem of causing environmental problems by emitting large amounts of volatile organic compounds (VOCs) due to the organic solvents contained in the ink.

[0004] As an alternative to this, digital printer printing and the use of water-based inks have been proposed. When using a digital printer printing method, for example, a laminate can be manufactured by printing an ink layer on a substrate layer using a digital printer, forming an adhesive layer on the ink layer, and then laminating and curing a transparent protective layer on the adhesive layer. Specifically, Japanese Patent No. 5945902 (Patent Document 1) discloses an ink composition for inkjet, which comprises a pigment, a water-soluble organic solvent, a surfactant, at least one of a urethane (meth)acrylate having a weight average molecular weight of 1,000 to 10,000 and a crosslinked urethane (meth)acrylate having a structural unit including the urethane (meth)acrylate, a compound having a radical polymerizable group, a photoradical polymerization initiator, and water.

[0005] When using this digital printer printing method, the adhesion between the ink layer and the transparent protective layer must be excellent so that the transparent protective layer does not peel off, and there must be no problems such as reduced printability due to differences in surface tension between the ink layer and the adhesive.

[0006] Therefore, there is a need for research and development on an adhesive composition that has excellent adhesion to a printed ink layer, improves the adhesion between the ink layer and the transparent protective layer, prevents peeling of the transparent protective layer, and can be applied to digital printing.

[0007] The present invention provides an adhesive composition having excellent adhesion to a printed ink layer and improving the adhesion between the ink layer and a transparent protective layer to prevent peeling of the transparent protective layer, applicable to a digital printing method, and further having excellent storage stability at room temperature (25°C) and high temperature (60°C), so that the adhesive layer manufactured therefrom has excellent adhesion even after storage.

[0008] In addition, the present invention aims to provide an interior film having excellent durability with less occurrence of appearance defects such as cracks, excellent flexibility, and less occurrence of cracks even when folded, including an adhesive layer formed from the adhesive composition, and further having excellent coating properties for an ink layer.

[0009] The present invention comprises a urethane (meth)acrylate oligomer, a (meth)acrylate monomer, a caprolactam compound and an ultraviolet initiator,

[0010] The above urethane (meth)acrylate oligomer contains two functional groups and provides an ultraviolet-curable adhesive composition having a weight average molecular weight of 500 to 2,000 g / mol.

[0011] In addition, the present invention comprises a substrate layer;

[0012] An ink layer formed on the above substrate layer;

[0013] An adhesive layer formed on the ink layer and formed from the ultraviolet-curable adhesive composition; and

[0014] An interior film is provided, including a transparent protective layer formed on the adhesive layer.

[0015] The ultraviolet-curable adhesive composition according to the present invention has excellent storage stability at room temperature (25°C) and high temperature (60°C), and excellent adhesion to a printed ink layer.

[0016] In addition, the adhesive layer formed from the adhesive composition according to the present invention can improve the adhesion between the ink layer and the transparent protective layer, thereby preventing peeling of the transparent protective layer, resulting in excellent interlayer adhesion and product reliability. Furthermore, the interior film comprising the adhesive layer according to the present invention has fewer appearance defects such as cracks, and has excellent flexibility, resulting in fewer cracks even when folded, resulting in excellent durability. In addition, the interior film according to the present invention has excellent coating properties for the ink layer due to the adhesive layer formed from the adhesive composition.

[0017] The present invention is described in detail below.

[0018] In this specification, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0019] Additionally, in this specification, when it is said that a layer is located "on" another layer, this includes not only cases where the layer is in contact with the other layer, but also cases where another layer exists between the two layers.

[0020] “Weight average molecular weight” can be measured by a method well known in the art, and can represent a value measured by, for example, a GPC (gel permeation chromatography) method.

[0021] The "particle size", which is the diameter of the particle, is measured by a conventional method known in the relevant technical field, and can be measured by laser light scattering (LLS), for example, and the "average particle size" is the cumulative distribution 10% (D) of the particle size distribution measured as described above. 10 ) to 90%(D 90 ) may be the average value of the particle diameter.

[0022] Additionally, “viscosity” is measured by a conventional method known in the art, and can be measured using, for example, a Brookfield viscometer (rotating spindle viscometer).

[0023] A “functional group” is a functional group involved in a polymerization reaction, and may be, for example, a (meth)acrylate group, and “(meth)acrylate” means “acrylate” and / or “methacrylate”.

[0024]

[0025] UV-curable adhesive composition

[0026] The ultraviolet-curable adhesive composition according to the present invention comprises a urethane (meth)acrylate-based oligomer, a (meth)acrylate-based monomer, a caprolactam-based compound, and an ultraviolet initiator.

[0027]

[0028] Urethane (meth)acrylate oligomer

[0029] Urethane (meth)acrylate oligomers are the main raw material that governs the properties of adhesive compositions, and they play a role in imparting adhesive strength to adhesive layers manufactured from compositions containing them. Specifically, the urethane (meth)acrylate oligomers include a soft urethane structure, thereby enhancing the melting and adhesive properties of the adhesive composition, resulting in excellent adhesion to ink layers and transparent protective layers, and enhancing the flexibility and elongation of manufactured products such as interior films.

[0030] The above urethane (meth)acrylate oligomer contains two functional groups. When the urethane (meth)acrylate oligomer contains two functional groups, the flexibility of the manufactured adhesive layer and the adhesion to the ink layer and the transparent protective layer are excellent, so that the interior film can be commercialized. On the other hand, when the urethane (meth)acrylate oligomer contains one functional group, the curing property of the adhesive composition is insufficient, which may cause the adhesive layer to not be cured and the adhesion to be reduced. When the urethane (meth)acrylate oligomer contains three or more functional groups, the hardness of the interior film increases, which may cause cracks to occur when the film is folded or when forming an embossing, thereby causing damage to the film.

[0031] In addition, the urethane (meth)acrylate oligomer has a weight average molecular weight (Mw) of 500 to 2,000 g / mol. When the weight average molecular weight of the urethane (meth)acrylate oligomer is within the above range, excellent adhesion between the ink layer and the adhesive layer is achieved during digital printing.

[0032] Specifically, the urethane (meth)acrylate-based oligomer may have a weight average molecular weight of 700 to 1,700 g / mol, or 1,000 to 1,500 g / mol. If the weight average molecular weight of the urethane (meth)acrylate-based oligomer is less than the above range, the adhesive composition may not be cured or the adhesion may be reduced, and if it exceeds the above range, the hardness of the adhesive layer may increase, causing cracks to occur when folding or embossing an interior film containing the same.

[0033] The viscosity of the urethane (meth)acrylate-based oligomer at 25°C may be 1,000 to 5,000 cps, 2,000 to 4,800 cps, or 3,000 to 4,500 cps. If the viscosity of the urethane (meth)acrylate-based oligomer at 25°C is below the above range, there is a problem of insufficient adhesive strength of the manufactured adhesive layer, and if it exceeds the above range, the viscosity of the adhesive composition may increase, resulting in insufficient workability.

[0034] In addition, the urethane (meth)acrylate-based oligomer may be included in an amount of 25 to 40 wt%, 27 to 38 wt%, or 29 to 37 wt% based on the total weight of the adhesive composition. If the amount of the urethane (meth)acrylate-based oligomer is less than the above range, there is a problem of insufficient adhesive strength of the manufactured adhesive layer due to insufficient content of the effective ingredient in the adhesive composition, and if it exceeds the above range, the obtainable effect (improvement in adhesive strength) is small compared to the amount of the urethane (meth)acrylate-based oligomer used, which may result in poor economic feasibility.

[0035]

[0036] (meth)acrylate monomer

[0037] (Meth)acrylate monomers improve workability by controlling the viscosity of the adhesive composition and play a role in improving the adhesion of the adhesive layer manufactured therefrom.

[0038] Specifically, the (meth)acrylate monomer may be a monofunctional monomer containing one functional group. When the (meth)acrylate monomer contains one functional group, the manufactured adhesive layer is flexible, which prevents the problem of cracks occurring when using the interior film, and has the advantage of allowing for heat-extension construction.

[0039] Meanwhile, if the above (meth)acrylate monomer is bifunctional or more containing two or more functional groups, the adhesive layer may have high hardness, which may reduce the flexibility of the interior film, or cracking may occur during the embossing process, or the film may not be stretchable during film construction, or cracks may occur when the film is folded.

[0040] At this time, the functional group may include a (meth)acrylate group.

[0041] In addition, the (meth)acrylate monomer may include a first (meth)acrylate monomer containing a heterocyclic group and a second (meth)acrylate monomer containing an aryl group.

[0042] The above first (meth)acrylate monomer serves to improve adhesion to the adhesive layer during the manufacture of the interior film. For example, the first (meth)acrylate monomer may be tetrahydrofurfuryl acrylate (THFA).

[0043] The second (meth)acrylate monomer serves to appropriately control the viscosity of the adhesive composition and to improve the solubility of the ultraviolet initiator. For example, the second (meth)acrylate monomer may be phenoxyethyl acrylate (PHEA).

[0044] The weight average molecular weight of the (meth)acrylate monomer may be 100 to 1,000 g / mol, 100 to 700 g / mol, or 100 to 500 g / mol. If the weight average molecular weight of the (meth)acrylate monomer is less than the above range, the adhesive strength of the manufactured adhesive layer may be insufficient, and if it exceeds the above range, the hardness of the adhesive layer may be increased, resulting in insufficient flexibility.

[0045] In addition, the (meth)acrylate monomer may include the first (meth)acrylate monomer and the second (meth)acrylate monomer in a weight ratio of 1:0.5 to 1:2.0, a weight ratio of 1:0.6 to 1:1.5, or a weight ratio of 1:0.7 to 1:1.3.

[0046] If the (meth)acrylate monomer contains a smaller amount of the second (meth)acrylate monomer than the above-mentioned range for the first acrylate monomer, a problem with dissolution of the ultraviolet initiator may occur. In addition, if the (meth)acrylate monomer contains an excess amount of the second (meth)acrylate monomer than the above-mentioned range for the first acrylate monomer, the adhesive strength of the manufactured adhesive layer may be reduced.

[0047] In addition, the (meth)acrylate monomer may be included in an amount of 40 to 60 wt%, or 40 to 56 wt%, based on the total weight of the adhesive composition. If the amount of the (meth)acrylate monomer is less than the above range, the viscosity of the adhesive composition may increase, thereby reducing the coating workability of the adhesive composition. If the amount exceeds the above range, the viscosity of the adhesive composition may decrease, or the adhesive strength of the adhesive layer may deteriorate due to a decrease in the oligomer content.

[0048] Specifically, the adhesive composition may include 20 to 30 wt%, 20 to 28 wt%, or 22 to 28 wt% of the first (meth)acrylate-based monomer, and 20 to 30 wt%, 20 to 28 wt%, or 22 to 28 wt% of the second (meth)acrylate-based monomer, based on the total weight of the adhesive composition. If the content of the first (meth)acrylate-based monomer is out of the above range, the adhesion between the ink layer and the adhesive layer may be reduced during digital printing. In addition, if the content of the second (meth)acrylate-based monomer is less than the above range, a problem of dissolution of the ultraviolet initiator may occur, and if it exceeds the above range, the viscosity of the adhesive composition may decrease or the adhesion of the manufactured adhesive layer may be reduced.

[0049] In addition, the adhesive composition may include a urethane (meth)acrylate-based oligomer and a (meth)acrylate-based monomer in a weight ratio of 1:0.5 to 1:2.0, or a weight ratio of 1:0.9 to 1:1.7. If the adhesive composition includes a smaller amount of the (meth)acrylate-based monomer than the aforementioned range based on the content of the urethane (meth)acrylate-based oligomer, the content of the (meth)acrylate-based monomer may be insufficient, thereby increasing the viscosity of the adhesive composition and reducing workability. In addition, if the adhesive composition includes an excess amount of the (meth)acrylate-based monomer than the aforementioned range based on the content of the urethane (meth)acrylate-based oligomer, the content of the urethane (meth)acrylate-based oligomer may be relatively insufficient, thereby reducing the adhesive strength of the manufactured adhesive layer.

[0050]

[0051] caprolactam compounds

[0052] Caprolactam compounds play a role in improving the adhesion to the ink layer when manufacturing an adhesive layer using an adhesive composition and improving the heat resistance of the manufactured adhesive layer.

[0053] The caprolactam compound may have a weight average molecular weight of 50 to 500 g / mol, 80 to 400 g / mol, or 100 to 300 g / mol. If the weight average molecular weight of the caprolactam compound is less than the above range, the adhesion and heat resistance of the manufactured adhesive layer may be reduced, and if it exceeds the above range, the color of the ink layer may change during digital printing, and the performance improvement effect compared to the amount of the caprolactam compound used may be insignificant, resulting in poor economic feasibility.

[0054] Additionally, the caprolactam compound may be, for example, n-vinylcaprolactam.

[0055] The caprolactam-based compound may be included in an amount of 10 to 20 wt%, or 10 to 18 wt%, based on the total weight of the adhesive composition. If the content of the caprolactam-based compound is less than the above range, the adhesiveness of the adhesive layer may be reduced, and the heat resistance of the adhesive layer may be weak, which may cause a problem of color change of the film during the interior film lamination process. If the content exceeds the above range, a color change inherent in the ink layer may occur during digital printing, or the adhesive layer may be over-cured, and the performance enhancement effect is insignificant compared to the amount of the caprolactam-based compound used, which is not desirable in terms of economic feasibility.

[0056] In addition, the adhesive composition may include a urethane (meth)acrylate-based oligomer and a caprolactam-based compound in a weight ratio of 1:0.2 to 1:1.0, or a weight ratio of 1:0.25 to 1:0.70. If the adhesive composition includes a smaller amount of a caprolactam-based compound than the aforementioned range based on the content of the urethane (meth)acrylate-based oligomer, the adhesion of the manufactured adhesive layer may be reduced, and the heat resistance of the adhesive layer may be low, which may cause a problem of color change of the film during the interior film lamination process. In addition, if the adhesive composition includes an excessive amount of a caprolactam-based compound than the aforementioned range based on the content of the urethane (meth)acrylate-based oligomer, a change in the inherent color of the ink layer may occur during digital printing, or over-curing of the adhesive layer may occur, and the performance improvement effect relative to the amount of the caprolactam-based compound used is insignificant, which is not desirable in terms of economic feasibility.

[0057]

[0058] UV initiator

[0059] The ultraviolet initiator absorbs ultraviolet rays to initiate polymerization and harden the adhesive composition, thereby forming an adhesive layer and controlling the curing speed of the adhesive composition.

[0060] The above ultraviolet initiator may include a phosphine oxide-based compound containing an acyl group. Specifically, the above ultraviolet initiator may be a phosphine oxide-based compound containing one acyl group.

[0061] For example, the acyl group-containing phosphine oxide compound may be diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO).

[0062] The above UV initiator may be included in an amount of 2 to 6 wt%, or 3 to 5 wt%, based on the total weight of the adhesive composition. If the amount of the UV initiator is less than the above range, the adhesive layer may not be cured, and if it exceeds the above range, the excessive amount of UV initiator may not be dissolved.

[0063]

[0064] additives

[0065] The above UV-curable adhesive composition may additionally contain additives such as a surface tension control agent, a surfactant, and a preservative, and may also contain additives that are typically applicable to adhesives.

[0066] For example, the surface tension control agent improves coatability by controlling the wetting properties of the manufactured adhesive layer, thereby reducing the surface tension difference between the ink layer and the adhesive layer. Specifically, the surface tension control agent may be a polyether-modified polydimethylsiloxane.

[0067] The surface tension modifier may be included in an amount of 0.5 to 2.0 wt% or 0.8 to 1.5 wt% based on the total weight of the adhesive composition. If the amount of the surface tension modifier exceeds the above range, a clumping phenomenon may occur when applying the adhesive layer due to a difference in surface tension between the ink layer and the adhesive layer during digital printing.

[0068] The above UV-curable adhesive composition may have a viscosity at 25°C of 40 to 90 cps, or 50 to 80 cps.

[0069] The ultraviolet-curable adhesive composition according to the present invention as described above has excellent storage stability at room temperature (25°C) and high temperature (60°C), and excellent adhesion to a printed ink layer.

[0070]

[0071] Interior film

[0072] In addition, an interior film according to the present invention includes a substrate layer; an ink layer formed on the substrate layer; an adhesive layer formed on the ink layer and formed from the ultraviolet-curable adhesive composition; and a transparent protective layer formed on the adhesive layer.

[0073]

[0074] Substrate layer

[0075] The above-mentioned substrate layer can be used without any special restrictions as long as it is generally applicable to interior films or decorative films, and may include, for example, a vinyl chloride-based resin.

[0076] The above vinyl chloride resin may be at least one selected from the group consisting of polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and vinyl chloride and a vinyl chloride copolymer containing a monomer copolymerized therewith.

[0077] The above-mentioned substrate layer may be a commercially available product that is typically applicable to interior films or decorative films, and may have an average thickness of, for example, 30 to 200 ㎛ or 50 to 150 ㎛.

[0078]

[0079] ink layer

[0080] The ink layer can be used without any special restrictions as long as it is an ink composition that can be applied to interior films or decorative films.

[0081] The ink layer may be formed using a digital printing method. For example, the ink layer may be formed by printing an ink composition on a substrate layer using a digital printing method. Specifically, the ink composition may include an oligomer, a monomer, an ultraviolet initiator, and the like.

[0082]

[0083] adhesive layer

[0084] The adhesive layer is formed from the UV-curable adhesive composition described above. The adhesive layer according to the present invention has excellent adhesion to the ink layer and provides excellent adhesion between the ink layer and the transparent protective layer, thereby preventing interlayer peeling.

[0085] The above adhesive layer can be applied without any special limitation as long as it has a thickness that can be typically applied to interior films or decorative films, and for example, the average thickness may be 1 to 20 μm, or 2 to 10 μm. If the average thickness of the adhesive layer is outside the above range, the adhesive strength between the ink layer and the transparent protective layer may be weakened, resulting in delamination between layers, or the thick adhesive layer may adversely affect the color development of the ink layer.

[0086]

[0087] transparent protective layer

[0088] The transparent protective layer can be used without any special restrictions as long as it is generally applicable to interior films or decorative films, and may include, for example, a vinyl chloride-based resin.

[0089] The above vinyl chloride resin may be at least one selected from the group consisting of polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), and vinyl chloride and a vinyl chloride copolymer containing a monomer copolymerized therewith.

[0090] The above transparent protective layer can be formed by a method that is typically applicable to interior films or decorative films, and for example, can be formed by laminating it on the adhesive layer and then curing it by irradiating it with ultraviolet rays.

[0091] In addition, the transparent protective layer may be a commercially available product typically applicable to interior films or decorative films, and may have an average thickness of, for example, 50 to 200 μm or 80 to 130 μm. If the average thickness of the transparent protective layer is outside the above range, the deep embossing effect may not be achieved, resulting in poor texture, or the film may become expensive due to the thick thickness, resulting in poor economic efficiency.

[0092] The interior film may have a 180° peel strength between the ink layer and the transparent protective layer of 4.0 kgf / inch or more, 4.0 to 6.0 kgf / inch, or 4.5 to 5.5 kgf / inch, as measured by a tensile tester.

[0093] As described above, the interior film according to the present invention exhibits excellent adhesion between the ink layer and the transparent protective layer, thereby preventing peeling of the transparent protective layer. This results in excellent interlayer adhesion, resulting in superior product reliability. Furthermore, the interior film according to the present invention exhibits minimal appearance defects, such as cracks, and has excellent flexibility, resulting in minimal cracking even when folded, resulting in superior durability.

[0094] Hereinafter, the present invention will be described in more detail through examples.

[0095] [Example]

[0096] Experimental Examples 1 to 18. Preparation of UV-curable adhesive composition

[0097] A UV-curable adhesive composition was prepared by adjusting the composition as described in Tables 1 to 3.

[0098] Ingredients (% by weight) Experimental Example 1 Experimental Example 2 Experimental Example 3 Experimental Example 4 Experimental Example 5 Experimental Example 6 Oligomer 130.0 33.0 35.0 30.0 30.0 Oligomer 2 30.0 Oligomer 3 Oligomer 4 Oligomer 5 Monomer 125.0 25.0 25.0 25.0 22.0 28.0 Monomer 225.0 25.0 25.0 25.0 28.0 22.0 Monomer 3 Monomer 4 Monomer 5 Caprolactam compound 15.0 12.0 10.0 15.0 15.0 15.0 Ultraviolet initiator 4.0 4.0 4.0 4.0 4.0 Surface tension Regulator 1.01.01.01.01.01.0 Total 100.0100.0100.0100.0100.0100.0

[0099] Component (weight%) Experimental Example 7 Experimental Example 8 Experimental Example 9 Experimental Example 10 Experimental Example 11 Experimental Example 12 Oligomer 137.0 30.0 30.0 Oligomer 2 Oligomer 3 30.0 Oligomer 4 30.0 Oligomer 5 30.0 Monomer 120.0 25.0 25.0 25.0 25.0 25.0 25.0 Monomer 220.0 25.0 25.0 25.0 Monomer 3 25.0 Monomer 4 25.0 Monomer 5 Caprolactam compound 18.0 15.0 15.0 15.0 15.0 15.0 Ultraviolet initiator 4.0 4.0 4.0 4.0 4.0 4.0 Surface tension Regulator 1.01.01.01.01.01.0 Total 100.0100.0100.0100.0100.0100.0

[0100] Ingredients (% by weight) Experimental Example 13 Experimental Example 14 Experimental Example 15 Experimental Example 16 Experimental Example 17 Experimental Example 18 Oligomer 130.022.037.0 45.033.0 Oligomer 2 Oligomer 3 Oligomer 4 Oligomer 5 Monomer 125.050.050.025.025.029.0 Monomer 2 25.025.029.0 Monomer 3 Monomer 4 30.0 Monomer 525.0 Caprolactam compound 15.023.08.015.0 5.0 Ultraviolet initiator 4.04.04.04.04.04.0 Surface tension regulator 1.01.01.01.01.0 Total 100.0100.0100.0100.0100.0100.0100.0

[0101] The manufacturer, product name, and other characteristics of each component used in the above experimental example are shown in Table 4 below, and Mw is the weight average molecular weight.

[0102] Ingredients Oligomer 12-functional urethane acrylate oligomer (Mw 1,000 g / mol, viscosity (25℃) 3,550 cps) Oligomer 22-functional urethane acrylate oligomer (Mw 1,500 g / mol, viscosity (25℃) 4,470 cps) Oligomer 31-functional urethane acrylate oligomer (Mw 440 g / mol, viscosity (25℃) 910 cps) Oligomer 42-functional urethane acrylate oligomer (Mw 3,700 g / mol, viscosity (25℃) 7,630 cps) Oligomer 53-functional epoxy acrylate oligomer (Mw 1,800 g / mol, viscosity (25℃) 4,830 cps) Monomer 11-functional monomer (tetrahydrofurfuryl methacrylate, THFA) Monomer 21-Functional Monomer (Phenoxyethyl Acrylate, PHEA) Monomer 32-Functional Monomer (1,6-Hexanediol Diacrylate, HDDA) Monomer 43-Functional Monomer (Ethoxylated Trimethylolpropane Triacrylate, ETPTA) Monomer 54-Functional Monomer (Pentaerythritol Tetraacrylate, PETA) Caprolactam Compound N-Vinyl Caprolactam (NVC) UV Initiator Diphenyl (2,4,6-Trimethylbenzoyl) Phosphine Oxide Surface Tension Control Agent Polyether-Modified Polydimethylsiloxane (Product Name: BYK-UV3510)

[0103]

[0104] Test Example: Characteristic Evaluation

[0105] The properties of the UV-curable adhesive composition of the experimental example were measured using the following method, and the results are shown in Table 5.

[0106]

[0107] (1) Viscosity at 25℃

[0108] Measurements were made using a viscometer (Brookfield spindle viscometer, Brookfield Viscometer LVDV-II, CPE-40 spindle) at room temperature (25℃).

[0109]

[0110] (2) Whether cracks occur after 360° folding

[0111] An ink layer was formed on a colored PVC film (manufacturer: Geumgang Enterprise, product name: KKP PRINT, thickness: 80 μm) using a digital printing device equipped with a KONIKA 1024i series, RICHO GEN5 head, and AGFA ANUVIA 1550 ink. Then, an adhesive layer was formed by applying about 7 μm of the UV-curable adhesive composition of the experimental example on the ink layer. Thereafter, a PVC transparent film (manufacturer: Geumgang Enterprise, product name: KKP DECO, thickness: 110 μm) was laminated on the adhesive layer and irradiated with UV rays using an LED light source having a wavelength of 395 nm to manufacture a specimen.

[0112] A specimen in which a colored PVC film, an ink layer, an adhesive layer, and a PVC transparent film were sequentially laminated was stored at 25°C or -20°C for 24 hours, and then the specimen was folded 360° to visually check whether cracks occurred.

[0113]

[0114] (3) Whether cracks occur

[0115] After manufacturing the specimen in the same manner as in item (2), the specimen was passed through a 200㎛ deep roll made of SUS at 170℃ under a pressure of 6MPa to create an embossed texture. Afterwards, it was visually inspected to confirm that the printed surface of the area pressed to a depth of 200㎛ was maintained intact.

[0116]

[0117] (4) Coating suitability for ink layer

[0118] A digital printing device equipped with a KONIKA 1024i series RICHO GEN5 head was used, and a UV ink composition (manufacturer: AGFA, product name: ANUVIA 1550) was used to form an ink layer on a colored PVC film (manufacturer: Kumkang Enterprise, product name: KKP PRINT, thickness: 80㎛). Then, the UV-curable adhesive composition of the experimental example was applied to the ink layer with a thickness of about 7㎛ to form an adhesive layer, and it was visually checked whether the surface of the adhesive layer was evenly coated over time. If beading (clumping in the shape of water droplets) occurred within 5 minutes after application, it was considered defective, and if the coated surface was evenly coated without beading, it was considered good.

[0119]

[0120] (5) Peel strength

[0121] A specimen was manufactured in the same manner as in item (2), and a specimen was manufactured in which a colored PVC film, an ink layer, an adhesive layer, and a PVC transparent film were laminated in that order. After storing the specimen at 25°C for 1 day, the 180° peel strength between the ink layer and the PVC transparent film was measured using a tensile tester (Universal Testing Machine, manufacturer: SALT, model number: ST-1003).

[0122]

[0123] (6) Peeling strength after storage

[0124] After preparing the specimens in the same manner as in item (2), they were stored at 60°C or -20°C for 2 weeks and then the peel strength was measured in the same manner as in item (5).

[0125]

[0126] Viscosity (25℃) (cps) Cracks after folding Cracks (200㎛ embossing) Coating aptitude Peeling strength (kgf / inch) Peeling strength after storage (kgf / inch) 25℃-20℃ 60℃-20℃ Experimental example 151XXX Good 5.3 5.15.4 Experimental example 260XXX Good 5.25 5.3 Experimental example 371XXX Good 4.9 4.8 5.1 Experimental example 462XXX Good 5.0 5.15.3 Experimental example 552XXX Good 4.9 5.35.1 Experimental example 653XXX Good 5.4 5.5 5.1 Experimental example 775XXX Good 5.35 5.1 Experimental example 848XXX Good 2.12 2.6 Experimental example 9106XXX Poor 5.15 35.1 Experimental example 1072OOO Good 5.6 5.15.2 Experimental example 1160XXO Good 4.3 4.3 4.5 Experimental example 1262XOO Good 4.6 4.6 4.8 Experimental example 1378OOO Good 4.1 4.2 4.9 Experimental example 1451XXX Good 2.8 2.7 2.7 Experimental example 1578XXX Good 4.2 3.4 4.6 Experimental example 1628XXO Good 1.1 1.2 1.0 Experimental example 17102XXX Bad 4.6 3.7 4.8 Experimental example 1875XXX Bad 3.5 3.4 3.7

[0127]

[0128] As shown in Table 5, the compositions of Experimental Examples 1 to 7 had an appropriate viscosity at 25°C and thus had excellent workability, and the adhesive layer manufactured therefrom did not crack and did not crack even when folded, had excellent coating suitability for the ink layer, and had excellent peel strength and peel strength even after storage.

[0129] On the other hand, Experimental Example 8 including Oligomer 3 containing a monofunctional urethane acrylate oligomer, Experimental Example 14 including a small amount of urethane acrylate oligomer and an excess of a caprolactam-based compound, Experimental Example 16 not including a urethane acrylate oligomer, and Experimental Example 18 including a small amount of a caprolactam-based compound had insufficient peel strength and peel strength after storage. In particular, Experimental Example 16 had insufficient workability due to the low viscosity of the composition, and cracks also occurred in the cured product. In addition, Experimental Example 18 also had insufficient coating suitability for an ink layer.

[0130] In addition, Experimental Example 9, which includes Oligomer 4, a bifunctional urethane acrylate oligomer having a high viscosity and weight average molecular weight at 25°C, and Experimental Example 17, which includes an excessive amount of urethane acrylate oligomer and does not include a caprolactam compound, had high viscosity of the adhesive composition, resulting in poor workability and poor coating suitability for the ink layer.

[0131] Experimental Example 10, which includes Oligomer 5, a trifunctional epoxy acrylate oligomer, and Experimental Example 13, which includes Monomer 5, a tetrafunctional acrylate monomer, showed cracks in the manufactured adhesive layer and cracks even after 360° folding during storage.

[0132] In addition, cracks occurred in the adhesive layer produced in Experimental Example 11, which included Monomer 3, a bifunctional acrylate monomer, and Experimental Example 12, which included Monomer 4, a trifunctional acrylate monomer. In particular, cracks occurred in the specimen of Experimental Example 12 after 360° folding at -20°C.

[0133] Experimental Example 15, which contained an excess of urethane acrylate oligomer and a small amount of caprolactam compound, showed insufficient peel strength after storage at 60°C for two weeks.

Claims

1. Contains urethane (meth)acrylate oligomer, (meth)acrylate monomer, caprolactam compound and ultraviolet initiator, A UV-curable adhesive composition, wherein the above urethane (meth)acrylate oligomer contains two functional groups and has a weight average molecular weight of 500 to 2,000 g / mol.

2. In claim 1, The viscosity of the above urethane (meth)acrylate oligomer at 25°C is 1,000 to 5,000 cps, A UV-curable adhesive composition wherein the weight average molecular weight of the above (meth)acrylate monomer is 100 to 1,000 g / mol.

3. In claim 1, A UV-curable adhesive composition, wherein the above (meth)acrylate monomer comprises a first (meth)acrylate monomer containing a heterocyclic group and a second (meth)acrylate monomer containing an aryl group.

4. In claim 1, A UV-curable adhesive composition, wherein the UV-curable initiator comprises an acyl group-containing phosphine oxide compound.

5. In claim 1, A UV-curable adhesive composition comprising 25 to 40 wt% of a urethane (meth)acrylate oligomer, 40 to 60 wt% of a (meth)acrylate monomer, 10 to 20 wt% of a caprolactam compound, and 2 to 6 wt% of an ultraviolet initiator.

6. Base layer; An ink layer formed on the above substrate layer; An adhesive layer formed on the ink layer and formed from the ultraviolet-curable adhesive composition of any one of claims 1 to 5; and An interior film comprising a transparent protective layer formed on the adhesive layer.