KR100856431B1 - UV Curable Coating Composition for Blu-ray Disc - Google Patents

Abstract

The present invention is chemically bonded by (i) a urethane acrylate oligomer, (ii) a monomer of a multifunctional group, (iii) a nanosize silica having a particle size of 5 to 50 nm and an acrylate having an isocyanate functional group. It provides a UV-curable coating composition for a Blu-ray disc comprising a silica-bonded acrylate monomer, (iv) a photoinitiator.

Photoprotective film according to the composition of the present invention is cured by ultraviolet irradiation of 200 ~ 1000mJ / m ² , expressing excellent mechanical and optical properties of surface pencil hardness of 4H or more, light transmittance of 90% or more, reflectance of 5% or less In particular, there is no heat deformation or yellowing.

Description

UV curable coating composition for Blu-ray Discs {UV CURABLE HARD COATING COMPOSITION FOR BLUE-RAY DISC}

The present invention relates to an ultraviolet curable coating composition used as a light protection film of a Blu-ray disc, and more particularly, a urethane acrylate-based coating material having a pencil hardness of 4H or higher, a light transmittance of 90% or more, and a reflectance of 5%. The present invention relates to a UV-curable hard coating composition for protecting the surface of a Blu-ray disc having no aging or deformation due to heat and ultraviolet rays, and having excellent mechanical and optical properties.

While a conventional DVD uses a red laser with a wavelength of 650 nanometers as a light source, the newly developed blue-ray disc uses a blue violet laser with a wavelength of 405 nanometers, which is about five times the recording capacity of a DVD. In addition, tera-class optical disc technology has also been developed by multilayering the recording layer.

This blue-ray disc is a next-generation storage medium capable of storing 25 GB on a single-sided basis, and has a track pitch interval of 1/22 micrometers smaller than DVD and a pitch length of about 0.15 micrometers smaller than that of DVD. In addition, since the 405nm wavelength optical pickup is used, performance is determined by small foreign matter such as dust and scratches on the disk surface.

Therefore, there is a need for a technology capable of preventing foreign substances and scratches on the surface of the disk, and also considering the fact that the Blu-ray disk is a high-capacity disk, long-term reliability must also be essential.

In the Blu-ray Disc, which is a next-generation optical disc, a protective film made of polycarbonate is adhered to the information recording layer to protect the information recording layer, similarly to a conventional optical disc. Extremely substitute

Due to the high volume and high density, even a small scratch on the protective film may cause an error in reading or writing information, and in reality, a Blu-ray disc is stored in a cartridge and handled.

Therefore, a cartridgeless type bare disk is also desired for compacting as a medium of a Blu-ray disc and reducing manufacturing cost.

For this reason, for example, as disclosed in Japanese Patent Laid-Open No. 2003-157579, it is considered to form a hard coat layer on a protective film for an information recording layer, but in the conventional protective film on which a hard coat layer is formed, The distortion caused by hardening shrinkage of the hard coating agent is large, and the resulting disk also has distortion, which may cause problems in signal characteristics. Therefore, in order to suppress such distortion, the thickness of the hard coat layer had to be made thin, specifically, 1-3 micrometers. However, with such a thin hard coat layer, surface hardness sufficient for preventing a wound could not be obtained.

It is also possible to use the resin composition disclosed in Japanese Patent Laid-Open No. 2000-273272 as a hard coating agent, but in this case as well, in order to make the surface hardness of the obtained hard coating layer sufficient, the thickness of the hard coating layer is not increased to some extent. Therefore, it was difficult to suppress the occurrence of distortion in the protective film and the resulting disk.

In addition, Korean Patent Laid-Open Publication No. 2005-41899 discloses a composition for coating a Blu-ray disc, comprising: reactive particles obtained by chemically bonding an inorganic oxide particle to an organic compound having at least one polymerizable unsaturated group in a molecule, and two or more in the molecule. Although a monomer or oligomer of an organic compound having a polymerizable unsaturated group and an organic compound having a weight average molecular weight of 1500 or more having one or more polymerizable unsaturated groups in a molecule have been disclosed, there is sufficient coating resistance. Did not secure.

In the present invention, the coating composition of the present invention is developed to improve the problems and to introduce a high reliability UV hard coating having excellent optical properties, which are essential for mass production and popularization, on the Blu-ray Disc surface to reduce the ease of use and the significant cost. It became.

In order to solve the problems of the prior art as described above, an object of the present invention is a UV-curable urethane acrylate superhard coating including nano-size silica, excellent optical properties having a transmittance of 90% or more and a reflectance of 5% or less at a wavelength of 405nm It is to provide a protective coating composition for a Blu-ray disc that can provide a mechanical property that does not scratch at 250 times the hardness of pencil, steel wool (steel wool # 0000) of 4H or more.

In addition, in view of the optical storage medium to provide a coating composition having a physical property of the error occurrence frequency of less than 1% even after accelerated test for 200 hours or more at high temperature and high humidity (85 ℃, 85% relative humidity).

In order to achieve the above object, in the present invention,

(i) urethane acrylate oligomers,

(ii) monomers of polyfunctional groups,

(iii) silica-bonded acrylate monomers chemically bonded by chemical reaction of nanosized silica having a particle size of 5-50 nm with an acrylate having an isocyanate functional group,

(iv) Provides an ultraviolet curable coating composition for a Blu-ray disc comprising a photoinitiator.

Since the nano-sized silica particles in the coating composition have a small refractive index and do not optically scatter or interfere with the coating, irregularities are added to the surface during coating. Thus, when coating the coating composition to the surface of a Blu-ray disc, scratch resistance or surface hardness It serves to be very good. However, simple mixing of such nano-sized silica may cause layer separation of particles, and it is difficult to form a stable coating film. In addition, even when artificially dispersed in the nano-size silica using a dispersing agent, yellowing phenomenon, coating cracks may occur. Therefore, the present invention is characterized in that it is used after synthesis to enable chemical bonding with the acrylate monomers, rather than simply mixing nano-size silica as described below.

Hereinafter will be described in detail for each component of the present invention.

urethane Acrylate Oligomer

In the present invention, a urethane acrylate oligomer having excellent light transmittance and low haze is used as the photocurable compound. A small amount of one or two polyester-based or epoxy-based oligomers can be added thereto to improve adhesion and surface hardness. Polyester-based oligomers have poor high temperature and high humidity reliability characteristics, and epoxy-based oligomers should be used within 5 to 20% of the total composition because of yellowing.

The oligomers that can be used for the Blu-ray Disc photoprotective film are urethane acrylate oligomers based on acrylics, polyesters, polyethers, butadienes, polyvinyls, etc., and when the molecular weight is less than 100, stable reliability cannot be expected. Since it is difficult to maintain uniformity in the disc coating operation, the molecular weight is suitable between 100 and 350.

The urethane acrylate oligomer is preferably used 10 to 60% by weight of the total weight of the coating composition. If it is 10% or less, it is difficult to express the oligomer properties, and if it exceeds 60%, the manufacturing cost increases and the viscosity rises, so that the defoaming force falls, thereby increasing the defective rate.

In the present invention, various urethane acrylates can be used as the composition of the present invention as long as they have excellent adhesive strength with polycarbonate, which is mainly used as a cover layer of a Blu-ray disc, and satisfy light transmittance and haze characteristics. Since such urethane acrylates are very diverse, the present invention does not limit the specific urethane acrylate.

Nano size  Silica bonding Acrylate  Monomer Synthesis

In the present invention, the nano-sized silica obtained through the sol-gel method or the precipitation method is prepared using a ball mill or a high-speed disperser to prepare a colloidal nano silica solution of 5 ~ 50nm size dispersed in the monomer. Colloidal technology of such silica is a very well known technology, and since it is not the scope of the present invention, a detailed description thereof will be omitted.

In the present invention, the nano-sized silica colloidal solution has a particle size of 5 to 50 nm, and crushed and dispersed for 2 to 10 hours by adding an acrylate monomer thereto. If the dispersion time is less than 2 hours, a stable colloidal solution cannot be obtained. If the dispersion time is 10 hours or more, the productivity decreases.

The acrylate monomer having an isocyanate functional group is stirred while maintaining at 30 to 70 ° C, and the nano-sized silica colloidal solution obtained above is slowly added thereto. Dosing time is about 0.1 ~ 10ml / min. If it is added faster than 0.1ml / min, it hardens by gelation reaction, and if it is slower than 10ml / min, phase separation occurs due to the reactivity of nano-size silica. In addition, the content of the nano-size silica is added to 0.1 to 5% by weight based on solids. When less than 0.1% by weight, the silica properties are not expressed, and when more than 5%, a haze phenomenon occurs.

By using an acrylate monomer having an isocyanate functional group, the hydroxyl group (OH) of the nano-sized silica and the isocyanate functional group (N = C = 0) of the acrylate monomer react with each other, and the silica and the acrylate monomer are chemically bonded. Will be The reason why the silica is reacted with the acrylate monomer having an isocyanate functional group is so that the mixture with the urethane acrylate which is the photocurable oligomer is well achieved. That is, it has been known that the wear resistance is increased by using silica as described above, but in the related art, by simply mixing the nano-sized silica, particle separation may occur, and it is difficult to form a stable coating film. However, in the present invention, the separation of the urethane acrylate, which is the main material of the coating layer, does not occur, and the acrylate is chemically bonded to the silica to be mixed well so that the silica does not occur with the urethane acrylate.

After the reaction is continued for 1 to 5 hours, the mixture is stirred while cooling to room temperature, whereby an acrylate monomer containing transparent silica can be obtained.

Acrylate monomers usable in the reaction include isocyanate and hydroxyl groups, tri 2-hydroxy ethyl isocyanate triacrylate, tri 2-hydroxy ethyl isocyanate diacrylate And so on.

Nano-size silica-bonded acrylate monomer is added to 1 to 40% by weight of the total weight of the total coating composition and thoroughly mixed. If it is less than 1% by weight, the surface hardness is low. If it is more than 40% by weight, haze increases, and surface uniformity is poor, which makes it difficult to record stably.

Multifunctional  Monomer

In addition, in order to secure the mechanical or reliability characteristics of the protective film, a monomer having a multifunctional group such as a bifunctional or trifunctional compound is added. The monomers help to crosslink urethane acrylates during photocuring due to the polyfunctional groups in the molecule, thereby controlling viscosity and curing rate, and also acting as a kind of diluent. In particular, the polyfunctional monomer for securing mechanical and optical properties is preferably aliphatic acrylate or cyclic acrylate, and the number of functional groups is about one to six.

Such monomers may be added in an amount of 5 to 40% by weight based on the total weight of the coating composition. It is preferable to add such an amount as the number of functional groups increases. It is preferable to use the trifunctional or more than trifunctional monomer especially at 5 weight% or less. If it is more than 40% by weight, the surface hardness is improved, but the impact cracking or disc deformation is caused. By adding polyfunctional monomers, the crosslinking reaction of the urethane acrylate oligomers occurs more actively.

Photoinitiator

The photoinitiator used for UV curing of the urethane acrylate oligomer is free from yellowing, and in particular, it is advantageous to use a photoinitiator that does not generate black spots or corrosion on the surface of the disk due to the free of acid or base at high temperature and high humidity. Therefore, it is advantageous to use an appropriate combination of an alpha-hydroxy-ketone system and a phosphine system that is advantageous for internal curing, and the photoinitiator is used at 2 to 20% by weight of the total weight of the composition. . If less than 2% by weight does not completely cure, if greater than 20% by weight may cause surface sunspots or corrosion in high temperature and high humidity reliability. In addition, the phosphine-based photoinitiator is useful for internal curing, but if it exceeds 20% by weight, a lot of sunspots or corrosion may occur.

Other ingredients

Silicone or fluorine additives such as silicone acrylic modified polymers, silicone urethane modified polymers, fluorine modified acrylics, fluorine modified silicones, etc. may be used to improve bubbles or film uniformity that may occur during the production of blue discs. Use within 1% of limit. When the content of the additive is 1% or more, the surface glossiness is degraded at high temperature and high humidity reliability, and the adhesion is lowered.

The optical protective film hard coating agent of the ultraviolet curable Blu-ray disc manufactured by the above manufacturing method has a viscosity of about 200 to 1000 cps. If it is less than 200 cps, it is difficult to expect a thick film property, and if it exceeds 1000 cps, it is difficult to maintain the uniformity of thickness.

Hereinafter, preferred examples are provided to help understanding of the present invention, but the following examples are merely to illustrate the present invention, and the scope of the present invention is not limited to the following examples.

EXAMPLE

Nano size  Silica included Acrylate  Monomer Production Example  One ( Sample name S1 )

500 g of tetraethoxysilane was added to a 3000 ml beer bottle, and 1,000 ml of ethanol was poured and stirred sufficiently using a stirrer. 500 g of distilled water was added thereto, followed by pouring 2 g of ammonia water while stirring and stirring rapidly. After stirring for about 5 minutes, an opaque silica colloidal solution is prepared. This was placed in a dialysis machine, 2000 ml of ethylcellulose solution was added, and dialyzed 10 times to remove water and ethanol, and concentrated to obtain 500 ml of a colloidal solution in which nano-sized silica was dispersed.

In a 1000 ml three-necked flask equipped with a stirrer and a cooler, 500 g of trihydroxyethyl isocyanate acrylate (SR368, Sartomer) was weighed and stirred, and 100 ml of the nano-size silica colloidal solution (solid content of 30% by weight) was 2ml / min. It heated up to 65 degreeC, adding at the speed of. After reacting for 3 hours, the volatile component was removed using a cooler to obtain an acrylate monomer containing silica (hereinafter, abbreviated as "S1" for convenience).

Nano size  Silica included Acrylate  Monomer Production Example  2 ( Sample name S2 )

600 g of tetraethoxysilane was added to a 3000 ml beer bottle, 1,500 ml of ethanol was poured, and the mixture was sufficiently stirred using a stirrer. 20 g of distilled water was added thereto, followed by pouring 1 g of ammonia water while stirring and stirring rapidly. After stirring for about 5 minutes, the silica colloidal solution is prepared. The solid was separated using a centrifuge to recover the precipitate and dried at 60 ° C. for 24 hours. 60 g of the dried nano-size silica was placed in an ultra-fine dispersion machine (Ultra-apex mill, Kotobuki), and 140 g of tripropylglycol diacrylate was added thereto, and dispersed at 4800 rpm for 4 hours to obtain 190 g of the nano-size silica colloidal solution.

 Hereinafter, using the nano-sized silica colloidal solution prepared above in the same manner as the sample S1, to obtain a nano-sized silica-containing acrylate monomer (hereinafter abbreviated as "S2" for convenience).

[ Comparative example  One / Example  One / Example  2]

The coating compositions of Comparative Examples 1, 1 and 2 were prepared as described in Table 1, and the properties of the compositions were evaluated. Evaluation of the composition was spin-coated the coating compositions of Examples 1 to 3 on a 1.1 mm thick round polycarbonate substrate and cured at 500 mJ / m ² light with a mercury lamp.

Table 1

ingredient Comparative Example 1 Example 1 Example 2 Remarks CN966H90 45 45 45 aliphatic polyester based urethane acrylate CN9009 5 5 5 hexafunctional urethane acrylate S1 10 Sample S1 prepared above S2 10 Sample S2 prepared above HDDA 10 5 5 hexadiol diacrylate DPGDA 15 15 15 dipropylene glycol diacryalte SR-399 10 5 5 dipentaerythritol pentaacrylate SR-531 10 10 10 cyclic trimethylopropane formal acrylate Ir-184 3 3 3 alpha hydroxy ketone TPO 2 2 2 result Pencil hardness (H) 4H 5H 5H or more ASTM D3363 Wear resistance 80 scratches 250 times good 250 times good steel wool # 0000 250g, 250times Adhesion 100/100 100/100 100/100 ASTM D3359 Light transmittance (%) 93 94 93 ASTM D1003 Haze 0.4 0.4 0.5

** The content of each composition is weight percent.

As shown in the results of Table 1, in the composition of Comparative Example 1, when the nano-size silica-bonding acrylate monomer was not used, it showed unsatisfactory results in wear resistance and pencil hardness compared to Examples 1 and 2 of the present invention. And it was found.

[ Comparative example  2 and 3]

The coating compositions of Comparative Examples 2 and 3 were prepared as follows to evaluate the properties of the composition. In Comparative Examples 2 and 3, instead of using "S1" or "S2" produced by the synthesis of silica and an acrylate monomer having an isocyanate functional group like the silica-bonded acrylate monomer used in the present invention, nano-sized silica was simply used. Prepared by simple mixing.

Comparative Example 2 was added to the composition without synthesizing the nano-size silica having a particle size of 25nm, Comparative Example 3 was used without adding a silica having a particle size of 100nm. It was spin-coated on a 1.1 mm thick polycarbonate substrate and cured with a mercury lamp at 500 mJ / m ² light. As a result, the result of Table 2 was obtained.

TABLE 2

Furtherance Comparative Example 2 Comparative Example 3 Remarks CN966H90 45 45 aliphatic polyester based urethane acrylate CN9009 5 5 hexafunctional urethane acrylate Silica-25nm 0.5 Silica-100nm 0.5 HDDA 10 10 hexadiol diacrylate DPGDA 15 15 dipropylene glycol diacryalte SR-399 9.5 9.5 - SR-531 10 10 - Ir-184 3 3 TPO 2 2 result Pencil hardness (H) 3H 3H ASTM D3363 Wear resistance 250 times good 250 times good steel wool # 0000 250g, 250times Adhesion 100/100 100/100 ASTM D3359 Light transmittance (%) 90 86 ASTM D1003 Haze 1.1 6.3

As described in Comparative Examples 2 and 3, when silica was not used in combination with acrylate as in the present invention and simply mixed with silica, very poor results were obtained in pencil hardness, light transmittance, and haze characteristics.

Blue disk photoprotective coating composition comprising nano-size silica according to the present invention, by chemically bonding nano-size silica to the monomer in a simple process, showing excellent mechanical properties without deterioration of light transmittance and haze properties, mass production of Blu-ray disc And effective use in commercialization. In addition, it can be applied to coating of display panels such as LCD, PDP or the like for mobile communication components or display window, which requires similar protective film coating properties in addition to Blu-ray discs.

The photoprotective film prepared by applying the coating composition of the present invention is cured by ultraviolet irradiation of 200 ~ 1000mJ / m ² , excellent mechanical properties and optical properties of surface pencil hardness of 4H or more, light transmittance of 90% or more, reflectance of 5% or less It is characterized by no heat deformation or yellowing.

Claims (7)

(i) urethane acrylate oligomers, (ii) monomers of polyfunctional groups, (iii) silica-bonded acrylate monomers chemically bonded by chemical reaction of nanosized silica having a particle size of 5-50 nm with an acrylate having an isocyanate functional group, (iv) UV-curable coating composition for a Blu-ray disc comprising a photoinitiator. According to claim 1, wherein the urethane acrylate oligomer 10 to 60% by weight, 5 to 40% by weight of the multifunctional monomer, 1 to 40% by weight of silica-bonded acrylate, Blu-ray disc, characterized in that 2 to 20% by weight photoinitiator UV curable coating composition. The UV curable coating composition for a Blu-ray disc according to claim 1 or 2, further comprising a polyester or epoxy oligomer in an amount of 5 to 20% by weight. The UV curable coating composition for a Blu-ray disc according to claim 1 or 2, wherein the monomer of the multifunctional group is aliphatic acrylate or cyclic acrylate of 1 to 6 functional groups. The UV curable coating composition for a Blu-ray disc according to claim 1 or 2, wherein the photoinitiator is aliphatic acrylate or cyclic acrylate. The UV curable coating composition for a Blu-ray disc according to claim 1 or 2, wherein the urethane acrylate oligomer has a molecular weight of 100 to 350. The ultraviolet ray for the Blu-ray disc according to claim 1 or 2, further comprising a silicone-based additive or a fluorine-based additive such as silicone acrylic modified polymer, silicone urethane modified polymer, fluorine-modified acrylic, fluorine-modified silicone, etc., within 1% by weight. Curable coating composition.