JP4622896B2 - High density recording optical disc surface protective layer composition, cured film and optical disc having surface protective layer - Google Patents

Description

  The present invention relates to a composition for a surface protective layer of a high-density recording optical disk having a high refractive index, high hardness and excellent transparency. Furthermore, the present invention relates to a high density recording optical disc having a cured film obtained by curing the composition and a surface protective layer comprising the cured film.

  In recent years, optical discs that record and / or reproduce using laser light, such as CDs and DVDs, are widely used as recording media for recording large volumes of digital data. Laser light applied to the optical disk is collected by an optical system and forms a beam spot having a predetermined diameter in a layer for recording information.

  In order to achieve a higher density of the optical disk, it has been studied to reduce the irradiation area of the focused beam by shortening the wavelength of the laser beam used or increasing the numerical aperture of the lens.

  Recently, in order to narrow the condensing spot, the numerical aperture (NA) of the condensing lens is increased to about 0.85, and the wavelength of the laser beam used is shortened to about 405 nm, thereby dramatically increasing the recording capacity. Blu-ray discs with increased capacity have been proposed and put into practical use. In this Blu-ray disc, a recording layer and a transparent cover layer are laminated on a substrate, blue laser light is incident from the transparent cover layer side, and writing and / or reading is performed on the recording layer.

  The transparent cover layer is formed, for example, by applying an ultraviolet curable resin composition on a recording layer and performing ultraviolet curing, and requires transparency and hardness (Patent Document 1).

With the start of digital broadcasting, the environment surrounding video information has changed significantly. When recording more beautiful video and sound as digital data, a large-capacity recording medium is required, and an optical disc with higher recording density is required.
Japanese Patent Laid-Open No. 11-273147

  An object of the present invention is to provide a composition for a surface protective layer of a high-density recording optical disk that can further increase the recording density.

  The present inventors have obtained a film having a high refractive index, high hardness, and excellent transparency with a composition containing rutile-type titanium oxide particles having a major axis of 100 nm or less in a specific ratio, and a high-density recording optical disc. It has been found that the recording density can be further increased by using it for the surface protective layer, and the present invention has been completed.

That is, the present invention
(A) Rutile-type titanium oxide particles having a major axis of 10 to 60 nm,
(B) 65 to 85% by mass of component (A) with respect to the total of the components containing 2 or more (meth) acryloyl groups in one molecule and (C) solvent, excluding the solvent, A composition for a surface protective layer of a high-density recording optical disk containing 15 to 35% by mass of the component (B) is provided.

  The present invention also provides a cured film obtained by curing the composition and an optical disc having the cured film.

  The composition for the surface protective layer of the high-density recording optical disk of the present invention provides a cured film having a high refractive index, high hardness and excellent transparency, and an optical disk having a high recording density can be obtained.

  The rutile-type titanium oxide particles of the component (A) used in the present invention have an average particle size of 100 nm or less, preferably 10 to 60 nm, and are preferable because the resulting coating has high transparency. The average particle diameter can be measured using an electron microscope.

  As such titanium oxide particles, for example, commercially available products such as titanium oxide slurry 884T (manufactured by Teika) can be used.

  The titanium oxide particles are contained in an amount of 65 to 85% by mass, preferably 65 to 75% by mass, based on the total of components excluding the solvent of the composition. If it is less than 65% by mass, a film having a high refractive index cannot be obtained. If it exceeds 85% by mass, the particle filling tolerance may be exceeded and the curability may be lowered.

  In the present invention, the solvent refers to a component that volatilizes when the composition is cured and that dissolves or disperses other components. Specific examples include ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monopropyl ether, isopropyl alcohol, toluene and the like.

  (C) A solvent can be used 1 type or in combination of 2 or more types, Although the content is not specifically limited, It is preferable to contain 50-70 mass% in the whole composition.

  The component (B) used in the present invention is a compound having two or more (meth) acryloyl groups in one molecule, and is polymerizable and multifunctional, thereby increasing the cross-linking density of the coating and increasing the hardness. A coating can be obtained. Examples of such compounds include polyethylene glycol diacrylate, tricyclodecanediyldimethylene di (meth) acrylate, di (meth) acrylate of bisphenol A to which ethylene oxide is added, tris (2-hydroxyethyl) iaocyanurate tri ( And (meth) acrylate, hexanediol diacrylate, dipentaerythritol hexa (meth) acrylate, and the like. As these commercial products, for example, light acrylate 9EG-A, 4EG-A (above, manufactured by Kyoeisha Chemical Co., Ltd.), Iupimer UV, SA1002 (above, manufactured by Mitsubishi Chemical Corporation), Aronix M-215, M-315, M -325 (manufactured by Toagosei Co., Ltd.), KAYARAD DPHA (manufactured by Nippon Kayaku Co., Ltd.), VR-90 (manufactured by Showa Kogyo Co., Ltd.) and the like.

  The compound of a component (B) can be used 1 type or in combination of 2 or more types, and 15-35 mass% with respect to the sum total of the component except a solvent, Preferably it contains 20-30 mass%. Within this range, the coating film strength can be maintained, which is preferable.

  The composition of the present invention may contain a photoinitiator for photocuring. Examples of the photoinitiator include 1-hydroxycyclohexyl phenyl ketone, 2,2-dimethoxy-2-phenylacetophenone, xanthone, fluorenone, benzaldehyde, fluorene, anthraquinone, triphenylamine, carbazole, 3-methylacetophenone, 4-chloro. Benzophenone, 4,4'-dimethoxybenzophenone, 4,4'-diaminobenzophenone, Michler's ketone, benzoin propyl ether, benzoin ethyl ether, benzyl dimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane- 1-one, 2-hydroxy-2-methyl-1-phenylpropan-1-one, thioxanthone, diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothi Xanthone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino-propan-1-one, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, bis- (2,6-dimethoxybenzoyl)- 2,4,4-trimethylpentylphosphine oxide and the like.

  These commercially available products include Irgacure 184, 369, 651, 500, 907, 819, CGI 1700, CGI 1850, CGI 1870, CG 2461, Darocur 1116, 1173 (above, manufactured by Ciba Specialty Chemicals), LUCIRIN TPO (manufactured by BASF) And Ubekrill P36 (manufactured by UCB).

  The photoinitiator can be used alone or in combination of two or more, and is contained in an amount of 0.1 to 5% by mass, particularly 0.5 to 2% by mass, based on the total of components excluding the solvent. This is preferable because an efficient reaction proceeds.

  Moreover, the composition of this invention can contain a particle | grain dispersing agent, surfactant, a surface modifier, etc. other than the said component.

  The composition of this invention can be manufactured by mixing the said component.

  The composition of the present invention is applied onto the recording layer of an optical disc, dried and then photocured to form a cured film.

  The method for applying the composition is not particularly limited, and methods such as spin coating, roll coating, slit coating, and bar coating can be used.

  A method of photocuring after coating and drying is a high-pressure mercury lamp, a metal halide lamp, or the like.

  In addition, although the composition of this invention is hardened | cured with a radiation, a radiation means infrared rays, visible light, an ultraviolet-ray, an X-ray, an electron beam, an alpha ray, a beta ray, a gamma ray etc. here.

  The thickness of the cured film obtained in the present invention is preferably 1 to 3 μm, particularly preferably 1 to 2 μm from the viewpoint of surface protection performance.

  Moreover, as the cured film, a film having a refractive index at 25 ° C. of 1.80 or more, particularly about 1.80 to 1.93 is obtained, and since it has a high refractive index, the irradiation area of the focused beam is reduced. The recording density in the recording layer of the optical disc can be increased.

EXAMPLES Next, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these Examples at all.
Example 1
The composition for the surface protective layer of the high-density recording optical disk having the composition shown in Table 1 was produced, and the refractive index of the coating film obtained by curing was measured. The results are also shown in Table 1. In addition, scratch resistance was evaluated.

In addition, in the components ((1) to (3) and (6)) other than the solvent, the ratio of the rutile-type titanium oxide particles was 68.6% by mass in Example 1, and 49.0 in Comparative Example 1. % By mass.
(Production method)
After the raw material components were mixed and IPA and toluene were evaporated and concentrated so that the solid content was 45 ± 5 mass%, ethyl lactate was added so that the solid content was 35 mass%.
(Measurement method of refractive index)
A composition having a solid content of 35% by mass was diluted 5-fold with ethyl lactate and applied to a Si wafer with a thickness of 110 to 150 nm using a spin coater. After drying at 80 ° C. for 3 minutes, it was cured at 1 J / cm ² (energy amount at 365 nm) using a UV lamp.

  About the obtained film, the refractive index in 589 nm was measured at 25 degreeC using the ellipsometer (made by Otsuka Electronics Co., Ltd.).

（耐擦傷性の測定方法）
ＤＶＤディスクに上記の組成物を、厚さ１μｍとなるように塗布した。８０℃のオーブンで３分間乾燥させた後、ＵＶランプを用い、１Ｊ／ｃｍ²（３６５ｎｍでのエネルギー量）で硬化させた。このディスクを、イソプロピルアルコールを浸したベンコットＳ−２（旭化成せんい社製）で軽く塗膜表面を擦り、傷がないことを確認した。

(Measurement method of scratch resistance)
The above composition was applied to a DVD disk so as to have a thickness of 1 μm. After drying in an oven at 80 ° C. for 3 minutes, it was cured at 1 J / cm ² (energy amount at 365 nm) using a UV lamp. The disc surface was lightly rubbed with Bencot S-2 (Asahi Kasei Fibers Co., Ltd.) soaked in isopropyl alcohol, and it was confirmed that there was no scratch.

Claims (4)

(A) Rutile-type titanium oxide particles having a major axis of 10 to 60 nm,
(B) 65 to 85% by mass of component (A) with respect to the total of the components containing 2 or more (meth) acryloyl groups in one molecule and (C) solvent, excluding the solvent, A composition for a surface protective layer of a high-density recording optical disk containing 15 to 35% by mass of the component (B).   Furthermore, the composition for surface protection layers of the high-density recording optical disk of Claim 1 which contains 0.1-5 mass% of photoinitiators with respect to the sum total of the component except a solvent.   A cured film obtained by curing the composition according to claim 1. An optical disk having the cured film according to claim 3 .