阅读说明：本技术 紫外线固化型涂料组合物 (Ultraviolet-curable coating composition ) 是由 金康洙 朴圭烨 柳晳化 曺畅贤 于 2018-05-31 设计创作，主要内容包括：本发明涉及一种汽车前照灯用无溶剂型紫外线固化型涂料组合物,提供一种环保且具有优异物性的无溶剂型紫外线固化型涂料组合物,其包含一定比例的二官能以下丙烯酸酯单体。(The invention relates to a solvent-free ultraviolet curing coating composition for an automobile headlamp, and provides a solvent-free ultraviolet curing coating composition which is environment-friendly and has excellent physical properties, and comprises a certain proportion of difunctional or less acrylate monomers.)

1. A solvent-free ultraviolet-curable coating composition comprising, based on 100 parts by weight of the total composition:

10 to 20 parts by weight of a tetrafunctional or higher urethane (meth) acrylate oligomer, 35 to 55 parts by weight of a trifunctional or higher (meth) acrylate monomer, 15 to 25 parts by weight of a monofunctional (meth) acrylate monomer having a hydroxyl group, 10 to 20 parts by weight of a difunctional or lower aliphatic cyclic (meth) acrylate monomer, and 5 to 10 parts by weight of a photopolymerization initiator.

2. The solvent-free ultraviolet curable coating composition according to claim 1,

the tetrafunctional or higher urethane (meth) acrylate oligomer has a weight average molecular weight (Mw) of 1000 to 2500g/mol and a viscosity of 2500cps or less at 25 ℃.

3. The solvent-free ultraviolet curable coating composition according to claim 1,

the trifunctional or higher (meth) acrylate monomer has a viscosity of 2000cps or less at 25 ℃.

4. The solvent-free ultraviolet curable coating composition according to claim 1,

the monofunctional (meth) acrylate monomer having a hydroxyl group has a viscosity of 30cps or less at 25 ℃,

the difunctional or lower aliphatic cyclic (meth) acrylate monomer has a viscosity of 150cps or less at 25 ℃.

5. The solvent-free ultraviolet curable coating composition according to claim 1,

the total content of the monofunctional (meth) acrylate monomer having a hydroxyl group and the difunctional or less aliphatic cyclic (meth) acrylate monomer is in the range of 35 to 60 parts by weight based on 100 parts by weight of the entire (meth) acrylate monomer.

6. The solvent-free ultraviolet curable coating composition according to claim 1,

the photopolymerization initiator is an initiator which absorbs ultraviolet rays with the wavelength of 230 to 340 nm.

7. The solvent-free ultraviolet curable coating composition according to claim 1,

the composition also comprises more than one additive in 0.5 to 6 weight portions based on 100 weight portions of the whole composition.

8. A headlamp, comprising:

a substrate; and

a cured coating layer formed on one or both sides of the substrate and formed of the ultraviolet curable coating composition described in any one of claims 1 to 7.

Technical Field

The present invention relates to a solvent-free ultraviolet curable coating composition and an automobile headlamp reflector using the same.

Background

A head light (headlamp) is a lamp that illuminates the front of a vehicle for safe driving at night. The lamp reflector for such a headlamp, which is being replaced by a synthetic resin material from a metal material, is made in the following manner: a Bulk Molding Compound (BMC) obtained by adding glass fibers, a weight material, a low shrinkage material, a mold release agent, and the like to an unsaturated polyester resin was injection-molded to prepare a mirror as a BMC molded body, and then aluminum was deposited on the surface of the mirror to form a mirror surface.

Vacuum deposition Ultraviolet (UV) curable coatings for automotive headlamps, which are currently in widespread use, include vacuum deposition coatings for spray coating (Air spray) using a solvent, and vacuum deposition coatings for Flow coating (Flow coating). Among them, the vacuum vapor deposition coating for spray coating using a solvent is easy to handle and does not greatly affect the surface state and shape of the injection-molded article, and thus occupies most of the headlamp market. However, when the solvent-based coating material is used, there is a problem in that not only a Regenerative Thermal Oxidizer (RTO) facility for removing VOCs needs to be operated in compliance with Volatile Organic Compounds (hereinafter, VOC) regulations, but also fuel costs and filter costs incurred thereby are continuously paid out. Further, a drying process required for volatilizing the solvent is required, and thus there is a problem that productivity is lowered.

A flow coating is a coating that has been developed as a substitute for spray coatings that use volatile organic solvents. Since the coating film thickness of the coating material applied by the flow coating material is in the form of a thin film, defects due to the surface state of the injection-molded article are likely to occur, and if the shape is complicated, the coating omission and/or the coating retention are likely to occur. Further, since a single solvent is used, the amount of VOC generated is small compared to a coating material for spray coating, but there is a problem in that VOC is continuously generated.

Disclosure of Invention

Problem of the invention

The invention provides a solvent-free ultraviolet curing coating composition, wherein a certain proportion of difunctional or lower acrylate monomer is used as a component of a UV coating composition, so that the composition is environment-friendly and can exert excellent adhesiveness at high temperature.

Further, the present invention provides a lens or a reflector for an automobile headlamp, which comprises a cured coating layer formed from the solvent-free ultraviolet curable coating composition.

Means for solving the problems

The present invention provides a solvent-free Ultraviolet (UV) curable coating composition comprising, based on 100 parts by weight of the total composition: 10 to 20 parts by weight of a tetrafunctional or higher urethane (meth) acrylate oligomer, 35 to 55 parts by weight of a trifunctional or higher (meth) acrylate monomer, 15 to 25 parts by weight of a monofunctional (meth) acrylate monomer having a hydroxyl group, 10 to 20 parts by weight of a difunctional or lower aliphatic cyclic (meth) acrylate monomer, and 5 to 10 parts by weight of a photopolymerization initiator.

Furthermore, the present invention provides a headlamp comprising: a substrate and a cured coating layer formed on one or both surfaces of the substrate and formed from the solvent-free ultraviolet curable coating composition.

Effects of the invention

The present invention provides a solvent-free ultraviolet curable coating composition which can be directly used for conventional spray coating (Air spray coating) and can improve productivity and can exhibit coating film properties such as high-temperature adhesion, appearance characteristics, initial adhesion, heat resistance, moisture resistance, and rapid cooling and heating resistance equivalent to those of conventional coating materials using solvents.

In addition, the solvent-free ultraviolet curing coating composition of the invention does not use volatile organic solvent, thus solving the problems of human harmfulness and environmental pollution caused by using solvent, and simultaneously eliminating preparation equipment and procedures required by solvent volatilization, thus improving productivity and economy.

Furthermore, the solvent-free ultraviolet curable coating composition of the present invention can satisfy not only the korean VOC environmental regulation in the regulatory standards protocol of the ministry of enviroment, but also all the overseas environmental regulations in china, india, etc. under development, and can minimize the use and management costs of the existing environmental equipments.

Detailed Description

The present invention will be described in detail below. However, the present invention is not limited to the following, and various modifications and optional combinations of the respective constituent elements may be made as necessary. Therefore, it should be understood that all changes, equivalents and substitutions included in the spirit and technical scope of the present invention are included in the present invention.

In the present specification, "(meth) acrylate" means acrylate and methacrylate.

In the present specification, "monomer" and "monomer" have the same meaning. In the present invention, monomers are distinguished from oligomers and polymers by weight-average molecular weight of less than 1000 g/mol. In the present specification, "polymerizable functional group" means an unsaturated group participating in polymerization reaction, such as a (meth) acrylate group.

Since the conventional ultraviolet curable coating composition for an automobile headlamp has a high viscosity, it is necessary to adjust the viscosity to a sprayable viscosity before it is applied to various plastic materials, and therefore, it is diluted with a solvent which is a volatile organic compound before the application. However, the solvent used as the diluent is harmful to the human body, causes environmental pollution, and requires additional preparation equipment and processes to cope with solvent volatilization, so that productivity and economy are deteriorated.

Further, a solventless UV coating has been developed as a coating for simple surface protection, but it has not been used for applications as a headlamp. In fact, since the coating material has a high viscosity, the coating workability is poor, the smoothness of the coating film is lowered, and the coating material is not suitable for a plastic injection-molded article having a complicated shape which is not a flat material. Even when the solvent-free UV coating material is used for a headlamp material, the solvent-free UV coating material is not practically used because light distribution is lowered due to reduction in smoothness of a coating film, peeling of a highly heat-resistant coating film due to poor curing of an excessively coated portion, and a rainbow-pattern phenomenon due to surface wrinkles occur.

The ultraviolet-curable coating composition to be developed according to the present invention can be applied by conventional spray coating, and can minimize the content of volatile organic compounds, thereby minimizing environmental regulations concerning the use of the coating and the influence on the environment.

Accordingly, the present invention provides a solventless ultraviolet curable coating composition in which a tetrafunctional or higher urethane (meth) acrylate oligomer, a trifunctional or higher (meth) acrylate monomer, a low-viscosity monofunctional or difunctional (meth) acrylate monomer, and a photopolymerization initiator are mixed and the content thereof is adjusted to a specific range.

< solvent-free ultraviolet-curable coating composition >

The solvent-free ultraviolet curable coating composition according to the present invention is a photocurable composition comprising a photocurable oligomer, a photocurable monomer and a photopolymerization initiator, wherein a tetrafunctional or higher urethane (meth) acrylate oligomer is used as the photocurable oligomer component, and three or more monofunctional, difunctional and trifunctional or higher (meth) acrylate monomers are used in combination as the photocurable monomer. Conventional additives such as adhesion enhancer, leveling agent, etc. may be further included as necessary.

The composition of the solventless ultraviolet curable coating composition will be specifically described below.

Tetrafunctional or higher urethane (meth) acrylate oligomer

In the solvent-free ultraviolet curable coating composition of the present invention, the urethane acrylic oligomer having four or more functions is a main component for forming a coating film, and plays a role in controlling the crosslinking density of the entire coating film to exert the strength and high-temperature durability of the coating film.

The tetrafunctional or higher urethane (meth) acrylate oligomer may have 4 or more (e.g., 4 to 15) polymerizable functional groups, which are polymerizable unsaturated groups, and may include 6 or more (e.g., 6 to 15) as another example. When the number of polymerizable functional groups in one molecule of the urethane (meth) acrylate oligomer is less than 4, poor appearance of the cured coating film and reduction in heat resistance and strength may result.

The tetrafunctional or higher urethane (meth) acrylate oligomer may be obtained by using conventional components known in the art, for example, a reaction product of a difunctional aliphatic isocyanate compound (e.g., hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, etc.) and a hydroxy (meth) acrylate monomer having 3 or more polymerizable unsaturated groups per molecule (e.g., pentaerythritol tri (meth) acrylate, dipentaerythritol tri (meth) acrylate, etc.).

The tetrafunctional or higher urethane (meth) acrylate oligomer may have a viscosity of 2500cps or less at 25 ℃, and as another example may have a viscosity of 2200cps or less. The weight average molecular weight (Mw) of the tetrafunctional or higher urethane (meth) acrylate oligomer may be 1000 to 2500g/mol, and may be 1000 to 2000g/mol, as another example. When the viscosity and the weight average molecular weight are within the above ranges, excellent reactivity and heat resistance can be exhibited, and physical properties such as processability and moisture resistance are excellent.

The content of the tetrafunctional or higher urethane (meth) acrylate oligomer is not particularly limited, and may be, for example, 10 to 20 parts by weight based on 100 parts by weight of the total solvent-free ultraviolet curable coating composition. When the content of the tetrafunctional or higher urethane (meth) acrylate oligomer satisfies the foregoing range, excellent strength and heat resistance of the coating film can be exerted, and adhesion to other substrates can be improved.

Trifunctional or higher (meth) acrylate monomer

In the solvent-free ultraviolet curable coating composition of the present invention, the trifunctional or higher (meth) acrylate monomer functions as a crosslinking agent for adjusting the crosslink density between polymers, and assists in the curing properties such as hardness, adhesion, appearance characteristics, etc. of the coating film.

The trifunctional or higher (meth) acrylate monomer may have 3 or more (e.g., 3 to 10) polymerizable functional groups in a molecule, and may have 4 to 8 polymerizable functional groups in another example.

The trifunctional or higher (meth) acrylate monomer may have a viscosity of 2000cps or less at 25 ℃, and as another example, may have a range of 50 to 1800 cps.

Non-limiting examples of more than three functional (meth) acrylate monomers that may be used are trimethylolpropane tri (meth) acrylate (TMPTA), pentaerythritol tri (meth) acrylate (pentaerythrityl tri (meth) acrylate, PETA), ethoxylated trimethylolpropane tri (meth) acrylate (ethoxylated trimethylolpropane tri (meth) acrylate), ditrimethylolpropane tetra (meth) acrylate (ditrimethylolpropane tetra (meth) acrylate, DTMPTTA), dipentaerythritol penta (meth) acrylate, DPPA), dipentaerythritol hexa (meth) acrylate (DPHA), or combinations of more than one thereof, and the like. As an example, trimethylolpropane triacrylate (TMPTA), pentaerythritol triacrylate (PETA), or a combination thereof may be used.

The content of the trifunctional or higher (meth) acrylate monomer is not particularly limited, and may be 35 to 55 parts by weight, for example, 35 to 45 parts by weight, based on 100 parts by weight of the total solvent-free ultraviolet curable coating composition. When the content of the trifunctional or higher (meth) acrylate monomer is within the above range, the high-temperature adhesive force of the coating film can be improved, and excellent strength, heat resistance and appearance characteristics can be exhibited, thereby improving adhesion to other substrates.

Monofunctional (meth) acrylate monomer having hydroxyl group

In the solvent-free ultraviolet curable coating composition of the present invention, a monofunctional (meth) acrylate monomer having a hydroxyl group is used as a reactive diluent for a photoreactive polymer, thereby adjusting the viscosity of the resin composition to impart fluidity and workability and assisting curing properties such as curing speed, adhesion, flexibility, appearance characteristics, and hardness of a photopolymerizable coating film.

As the monofunctional (meth) acrylate monomer having a Hydroxyl group, a known (meth) acrylate monomer having a Hydroxyl group (Hydroxyl group) in the molecule and containing 1 polymerizable functional group can be used without limitation. These monofunctional (meth) acrylate monomers having hydroxyl groups function as diluents to maintain the viscosity of the composition at a low level.

The monofunctional (meth) acrylate monomer having a hydroxyl group may have a viscosity of 30cps or less at 25 ℃, and as another example, may have a range of 7 to 10 cps. When the viscosity is set as described above, the coating material has a controlled fluidity, and thus has excellent physical properties such as processability and moisture resistance.

Non-limiting examples of monofunctional (meth) acrylate monomers having a hydroxyl group that can be used are hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxypentyl (meth) acrylate, or combinations of one or more thereof, and the like. For example, hydroxyethyl methacrylate (HEMA) can be used.

The content of the monofunctional (meth) acrylate monomer having a hydroxyl group is not particularly limited, and may be 15 to 25 parts by weight based on 100 parts by weight of the total solvent-free ultraviolet curable coating composition, as an example. When the content of the monofunctional (meth) acrylate monomer having a hydroxyl group satisfies the aforementioned range, the adhesion and flexibility of the coating film can be promoted, and better high-temperature adhesion and excellent strength, heat resistance, and appearance characteristics can be exerted.

Difunctional or less aliphatic cyclic (meth) acrylate monomers

In the solvent-free ultraviolet curable coating composition of the present invention, the aliphatic cyclic acrylate monomer is used as a reactive diluent for the photoreactive polymer, thereby providing workability by adjusting the viscosity of the resin composition and assisting the curing properties such as curing speed, adhesion, appearance characteristics, and hardness of the photopolymerizable coating film.

As the aliphatic cyclic (meth) acrylate monomer, a known (meth) acrylate monomer having an alicyclic ring (alicyclic) and having a polymerizable functional group in a molecule of 2 or less, for example, 1 or 2, may be used without limitation. These aliphatic cyclic (meth) acrylate monomers are suitably used because they have a low viscosity and therefore have a high diluting power and a low polymerization shrinkage (low shrinkage) after curing.

The difunctional or lower aliphatic cyclic (meth) acrylate monomer may have a viscosity of 150cps or less at 25 ℃, and as another example, 140cps or less. When the viscosity is set as described above, the fluidity of the coating material is adjusted, and therefore, the coating material is easy to handle and excellent in physical properties such as processability and moisture resistance.

Non-limiting examples of aliphatic cyclic (meth) acrylate monomers that can be used include tricyclodecane dimethanol di (meth) acrylate, cyclohexyl di (meth) acrylate, norbornyl di (meth) acrylate, combinations of one or more thereof, and the like. For example, tricyclodecane dimethanol diacrylate (TCDDA) can be used.

The content of the difunctional or lower aliphatic cyclic (meth) acrylate monomer is not particularly limited, and may be, for example, 10 to 20 parts by weight, and may be, for another example, 10 to 15 parts by weight, based on 100 parts by weight of the total solvent-free ultraviolet curable coating composition. When the content of the difunctional or less aliphatic cyclic (meth) acrylate monomer satisfies the foregoing range, workability is excellent, and excellent strength, heat resistance, and appearance characteristics of the coating film can be promoted.

According to one embodiment of the present invention, the total amount of the difunctional or less (meth) acrylate monomer (the monofunctional (meth) acrylate monomer having a hydroxyl group and the difunctional or less aliphatic cyclic (meth) acrylate monomer) may be 35 to 60 parts by weight based on 100 parts by weight of the entire acrylate monomer (the trifunctional or more (meth) acrylate monomer, the monofunctional (meth) acrylate monomer having a hydroxyl group and the difunctional or less aliphatic cyclic (meth) acrylate monomer).

According to another embodiment of the present invention, the ratio of the trifunctional or higher (meth) acrylate monomer to the monofunctional (meth) acrylate monomer having a hydroxyl group to the difunctional or lower aliphatic cyclic (meth) acrylate monomer may be in the range of 1.5 to 4 by weight: 0.5-2: 1.

photopolymerization initiator

In the solventless ultraviolet curable coating composition of the present invention, the photopolymerization initiator is a component which is excited by ultraviolet rays or the like to exert photopolymerization initiation action, and a photopolymerization initiator which is conventional in the art can be used without limitation.

Non-limiting examples of the photopolymerization initiator that can be used are photoinitiator (Irgacure 184), photoinitiator (Irgacure 369), photoinitiator (Irgacure 651), photoinitiator (Irgacure 819), photoinitiator (Irgacure 907), benzoin alkyl ether (benzinalkylether), Benzophenone (Benzophenone), benzil dimethyl ketal (Benzophenone), hydroxycyclohexyl phenyl acetone (hydroxycyclohexyl phenyl acetone), chloroacetophenone (chloroacetophenone), 1-dichloroacetophenone (1, 1-dichloroacetophenone), diethoxyacetophenone (dioxyacetophenone), oxybenzophenone (hydroxyacetophenone), 2-chlorothioxanthone (2-c chlorothiophenone), 2-ethylxanthoquinone 2-AQothioquinone 2-hydroxy 2-cyclohexyl acetone (1-hydroxy 2-hydroxy phenyl acetone), 1-dichloroacetophenone, 1-hydroxy phenyl acetone (hydroxy phenyl acetone), and 1, 1-hydroxy phenyl acetone (hydroxy phenyl acetone), and the like phenyl-1-propanone), 2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-propanone (2-hydroxy-1- [4- (2-hydroxyethoxy) phenyl ] -2-methyl-1-propanone), methyl benzoylformate (methyl benzoylformate), and the like. These may be used alone or in combination of two or more.

According to an example of the present invention, as the photoinitiator, a short-wavelength initiator that absorbs wavelengths of 300nm or less, a long-wavelength initiator that absorbs wavelengths of more than 300nm, or a combination of all of them may be used. According to another example of the present invention, the photopolymerization initiator may absorb a wavelength of 230 to 340 nm.

The content of the photopolymerization initiator may be 5 to 10 parts by weight, and as another example, 5 to 8 parts by weight, based on 100 parts by weight of the total solvent-free ultraviolet curable coating composition. When the content of the photoinitiator is within the above range, photopolymerization reaction can be sufficiently performed without deteriorating the physical properties of the coating film.

Additive agent

In addition to the above components, the solvent-free ultraviolet curable coating composition of the present invention may use additives known in the art without limitation within the range not to inhibit the effect of the present invention. At this time, the content of the additive may be appropriately adjusted within a range known in the art.

Adhesion enhancing agent

The solventless ultraviolet curable coating composition of the present invention may further contain an adhesion enhancer if necessary. The adhesion enhancer is used in an appropriate amount in the composition, and has the effects of enhancing the adhesion of the ultraviolet-curable composition, preventing silver oxidation, and the like.

The adhesion enhancer may use a phosphate adhesion enhancer. As an example, the phosphate adhesion enhancer has a number average molecular weight of 500 to 1000, and has an oxide group, an oxyhydroxide group, and/or an acid ester (trifunctional acid ester) group, so that the adhesion of the coating film to the surface of the substrate can be increased. For example, a hydroxyl/carboxyl-functional phosphate ester (Hydroxy/carboxyl-functional phosphate ester) can be used.

The content of the adhesion enhancer may be appropriately adjusted within a known content range. For example, the solvent-free ultraviolet curable coating composition may be used in an amount of 2 to 5 parts by weight, based on 100 parts by weight of the total amount of the composition. When the content of the adhesion enhancer is within the above range, the adhesion enhancing effect can be exhibited without causing fog (haze).

Leveling agent

The solvent-free ultraviolet curable coating composition of the present invention may further contain a leveling agent as needed. The leveling agent can be used for leveling to ensure that the solvent-free UV curing composition can be smoothly coated during coating, thereby further improving the adhesion in the composition.

The leveling agent may be any one of those known in the art without limitation, and as an example, one or a mixture of two or more of acrylic and silicone may be used. For example, polyether modified polydimethylsiloxane may be used, and the polyether chain may further contain (meth) acryloyl groups. Among them, the siloxane-based compound can impart wettability (wetting).

The content of the leveling agent may be appropriately adjusted within a known content range. For example, the solvent-free ultraviolet curable coating composition may be used in an amount of 0.5 to 1 part by weight, based on 100 parts by weight of the total weight of the composition. When the content of the leveling agent falls within the above range, a desired effect of improving the adhesion and adhesion of the coating film can be exhibited.

Other additives

In addition to the above components, the solvent-free ultraviolet curable coating composition of the present invention may use additives known in the art without limitation within the range not to inhibit the effect of the present invention. At this time, the content of the additive may be appropriately adjusted within a range known in the art.

Examples of the additives that can be used are ultraviolet absorbers (e.g., triazines), light stabilizers (e.g., Hindered Amine Light Stabilizers (HALS)), antioxidants (e.g., phenol antioxidants), lubricants, surface conditioners, surfactants, defoamers (e.g., dimethylpolysiloxane), slip aids, solvents, wetting agents, antifouling agents, flexibilizers, thickeners, polymers, and the like. These may be used alone or in combination of two or more.

The method for producing the solventless ultraviolet curable coating composition of the present invention is not particularly limited, and can be produced by the following conventional methods, as an example: the above-mentioned tetrafunctional or higher urethane (meth) acrylate oligomer, trifunctional or higher (meth) acrylate monomer, monofunctional (meth) acrylate monomer having a hydroxyl group, difunctional or lower aliphatic cyclic (meth) acrylate monomer, and photopolymerization initiator (if necessary, a known additive is added) are charged into a mixing device such as a dissolver, a stirrer, and the like, and then mixed at an appropriate temperature (for example, room temperature).

The solventless ultraviolet curable coating composition of the present invention containing the foregoing components may have a viscosity of 50 to 300cps at 25 c, and as another example, 60 to 200 cps. Thus, the coating composition has appropriate fluidity even when the coating composition does not contain an organic solvent, and therefore can be used for spray coating.

The solvent-free ultraviolet curable coating composition of the present invention can be used for coating components of a headlamp, such as a headlamp lens or a reflector. But is not limited thereto, and can be used in various process steps and applications.

< headlamp >

The present invention provides a headlamp, such as a lens or a reflector for an automobile headlamp, having a cured coating layer formed by curing the solvent-free ultraviolet curable coating composition. The headlamp comprises a substrate (substrate) and a cured coating layer formed on one or both surfaces of the substrate and formed from the solvent-free ultraviolet curable coating composition.

The base material may be any conventional component used in the field of headlamps without limitation, and examples thereof include metal materials such as iron, aluminum, and magnesium, and plastic materials such as engineering plastics, thermoplastic plastics, and thermosetting plastics.

Non-limiting examples of plastic substrates that can be used are polyphenylene sulfide, polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), cellulose Triacetate (TAC), Polycarbonate (PC), Polyimide (PI), Polyethylene (PE), polypropylene (PP), Polyethersulfone (PEs), polyvinyl alcohol (PVA), polyvinyl chloride (PVC), or combinations of 2 or more thereof, and the like. As another example, there is a bulk molding compound for molding, which is obtained by adding glass fibers, a weighting material, a low shrinkage material, a mold release agent, and the like to an unsaturated polyester resin, and is prepared by injection molding. When the substrate of the above-mentioned components is used, the solvent-free ultraviolet curable coating composition of the present invention is excellent in initial and high-temperature adhesion.

The thickness of the cured coating layer composed of the composition may be variously adjusted depending on the use purpose, and may be 5 to 25 μm as an example, and may be in a range of 5 to 20 μm as another example. When the thickness is as described above, the adhesion to the surface of the substrate is excellent, and the appearance failure can be prevented.

According to one embodiment of the present invention, the solvent-free ultraviolet curable coating composition is applied to a surface of a substrate, dried, and then cured by ultraviolet irradiation to form a cured coating layer. The solvent-free uv curable coating composition may be applied to a substrate by a conventional coating method in the art, such as spray coating, brush coating, dip coating (dipcoating), spin coating (spin coating), roll coating (roll coating), flow coating, air coating (air coating), and the like. Solvent-based coatings are often used for spray coating, but low viscosity solventless coatings may also be suitable for spray coating. The amount of ultraviolet irradiation is not particularly limited, and may be in the range of 500 to 3000mJ/cm, for example²。

The substrate on which the cured coating is formed as described above may be an automotive headlamp, and for example, may be a lens or a mirror of a headlamp on the surface of which the cured coating is formed. Such a headlamp is excellent in adhesion between a plastic substrate (e.g., BMC material) and a metal vapor deposited film (e.g., aluminum), and also excellent in overall physical properties of the coating film such as appearance, heat resistance, moisture resistance, and rapid cooling and heating resistance.

The present invention will be described more specifically with reference to examples. However, the following examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[ examples 1 to 9]

Solvent-free ultraviolet curable coating compositions of examples 1 to 9 were prepared according to the compositions shown in table 1 below. In table 1 below, the amount of each composition is in parts by weight.

Comparative examples 1 to 8

The ultraviolet-curable compositions of comparative examples 1 to 8 were prepared according to the compositions shown in Table 1 below.

[ Table 1]

A-1: hexafunctional urethane acrylate oligomer (Mw: 1,800, viscosity: 2000cps, trade name: CN968NS)

A-2: difunctional aliphatic urethane acrylic oligomer (trade name: Miramer PU2100)

B: pentaerythritol triacrylate (PETA, Mw: 298, viscosity: 1000-1800cps)

C-1: 2-hydroxyethyl methacrylate (HEMA, Mw: 131, viscosity: 7-10cps)

C-2: hexanediol diacrylate (HDDA, Mw: 226.27, viscosity: 12cps)

D: dicidol diacrylate (TCDDA, Mw: 305, viscosity: 130cps)

E: photopolymerization initiator (2-hydroxy-2-methyl-1-phenyl-1-propanone) trade name IRGACURE 184)

F: phosphate adhesion enhancer (bis (2-methacryloyloxy) ethyl) phosphate)

G: flatting agent (BYK310)

[ Experimental example: evaluation of physical Properties of ultraviolet-curable coating composition for automobile headlamp

The solvent-free type ultraviolet curable coating compositions prepared in examples 1 to 9 and comparative examples 1 to 8 were air-sprayed at a thickness of about 12 μm (upper layer, based on the thickness of the dried coating film) onto a BMC test piece (trade name: KPI SN203), and then dried at a temperature of 80 ℃ for about 300 seconds, and then hard coated test pieces cured by an ultraviolet curing apparatus were evaluated as follows. The results are shown in table 3 below. With ultraviolet energy (UV energy): 2500mj/cm²Intensity (intensity): 300mW/cm²The UV curing conditions of (1) are applied. The evaluation method of the physical properties of the cured product is shown in Table 2 below.

[ Table 2]

[ Table 3]

As described above, according to examples 1 to 9 of the present invention, by containing the four-or more-functional acrylate oligomer, the three-or more-functional acrylate monomer, the monofunctional acrylate monomer having a hydroxyl group, the two-or less-functional aliphatic cyclic acrylate monomer, the photopolymerization initiator, and the additives (such as the phosphate adhesion enhancer and the leveling agent) in a specific composition ratio, the external gloss can be improved, the excellent initial adhesion to the plating layer can be ensured, the heat resistance is excellent, the peeling and the swelling of the coating film do not occur at a high temperature of 200 ℃.

On the contrary, comparative examples 1 and 2 did not use the urethane acrylic oligomer having four or more functions and the monofunctional acrylate monomer having a hydroxyl group, respectively, and showed poor results in one or more of adhesion, heat resistance and quenching heat resistance.

In comparative example 3, the content of trifunctional or higher acrylate monomer B was high, the content of monofunctional acrylate monomer C having a hydroxyl group was low, and the viscosity of the composition was high, so that the leveling property of the appearance was lowered, the coating film was easily broken, the adhesion at the initial stage and after heat resistance was lowered, and cracks were generated after the rapid cooling and rapid heating resistance test, as compared with the entire coating composition. In comparative examples 4 to 6, the content of the trifunctional or higher acrylate monomer B was low and the amount of the difunctional or lower aliphatic cyclic acrylate monomer D was excessive as compared with the bulk coating composition, and the physical properties were found to be inferior to those of two or more items. In comparative example 7, the coating film was easily broken and the initial adhesion and the appearance and adhesion after heat resistance and rapid cooling and heating resistance were reduced compared to the examples according to the present invention, which included an excessive amount of the photopolymerization initiator. From the above results, it is clear that the physical properties exhibited are not good when the content ratio of each component according to the present invention is not satisfied.

In comparative example 8, the total content of the difunctional below (meth) acrylate monomers (components C and D) was 31.25 based on 100 parts by weight of the entire acrylate monomers (components B, C and D), and the use ratio of the trifunctional or higher (meth) acrylate monomer B, the monofunctional (meth) acrylate monomer C having a hydroxyl group, and the difunctional below aliphatic cyclic (meth) acrylate monomer D was 5.5: 1.5: 1. from the results, it is understood that the physical properties exhibited are not satisfactory when the content ratios of the respective components ((C + D)/(B + C + D) and B: C: D) according to the present invention are not satisfied.

From the above experimental results, it is apparent that the solvent-free ultraviolet curable coating composition and the vehicle component substrate using the same according to the present invention are environmentally friendly since they are excellent in appearance, initial adhesion, heat resistance, moisture resistance, and rapid cooling and heating resistance, and contain a minimum amount of Volatile Organic Compounds (VOC) without using an organic solvent.

Industrial applicability

The present invention provides a solvent-free ultraviolet curable coating composition which can be used as it is for conventional spray coating (Air spray) coating, can improve productivity, and can exhibit coating film properties such as high-temperature adhesion, appearance characteristics, initial adhesion, heat resistance, moisture resistance, and rapid cooling/heating resistance equivalent to those of conventional coating materials using solvents.

In addition, the solvent-free ultraviolet curing coating composition of the invention does not use volatile organic solvent, thus solving the problems of human harmfulness and environmental pollution caused by using solvent, and simultaneously eliminating preparation equipment and procedures required by solvent volatilization, thereby improving productivity and economy.

Furthermore, the solvent-free ultraviolet curable coating composition of the present invention can satisfy not only the korean VOC environmental regulation in the regulatory standards protocol of the ministry of enviroment, but also all the overseas environmental regulations in china, india, etc. under development, and can minimize the use and management costs of the existing environmental equipments.