JPH0474688A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical recording medium to which dirt and dust hardly apply and to prevent the occurrence of an error in writing or reading by a method wherein in the optical recording medium on which information can be written or read by a laser light, a layer containing a light transmitting particle having conductive properties is provided on the laser light incident surface of the optical recording medium. CONSTITUTION:As conductive light-transmitting fine particle, indium oxide can be exemplified. By adding, mixing, and stirring the conductive light- transmitting fine particle in an inactive organic solvent, such as a silane coupling agent, the silane coupling agent is adsorbed on the surface of the conductive light-transmitting fine particle, and the surface treatment is completed. The particle surface-treated with the silane coupling agent is uniformly mixed with a multifunctional-base acrylic material. This is applied on an optical disk substrate 2 and cured by an ultraviolet radiation or an electron beam. This organic protective film 5 is provided on the laser light incident surface of the optical disk.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to an optical recording medium on which information can be written and/or read using a laser beam.

[Background of the invention]

As a method for recording and reproducing information, methods that write and/or read information using magnetism have been widely used until now, but recently, methods for recording high-density information using fine beams such as laser light have been widely used. In addition, optical recording media that perform playback have been proposed, and some have already been put into practical use and are attracting attention. According to this method, it is possible to record several thousand times more information on a medium of the same size than with conventional magnetic recording and reproducing methods, making it an extremely useful recording medium in an information-oriented society. Such optical recording media include optical disks such as optical cards, video disks, digital audio disks, large-capacity still image file disks, and large-capacity computer disk memories. The basic structure of an optical recording medium such as such an optical disk is to form a reflective film and/or a recording film on a substrate on which recording pits and guide grooves have been formed in advance, and to make laser light incident on one side of the substrate, and to form a reflective film and/or a recording film on the substrate. Alternatively, the light reflected by the recording film is received, and the received light is converted by a photoelectric conversion element and reproduced as information. Transparent glass, plastics such as polymethyl methacrylate, polycarbonate, and amorphous polyolefin are used for the substrates of optical discs, and various film materials and film configurations have been proposed for the recording and reflective films depending on the recording and reproducing method. ing. Incidentally, although glass is a very hard and scratch-resistant material for use as a substrate for optical discs, it is difficult to form recording pits, guide grooves, etc. thereon. In addition, there is an etching method in which grooves etc. are formed directly on the glass substrate, and 2) in which the glass substrate is coated with a photopolymer and then pressed against a mold to form grooves etc.
Although the P method has been proposed, these methods lack mass productivity. On the other hand, plastics have the advantage that once a stamper is made through a mastering process, it can be mass-produced by injection molding based on this stamper. However, since this plastic is softer than glass, it is easily damaged, and it is said that it is necessary to form a protective film on the substrate surface after forming the recording film and reflective film to increase the surface hardness. That is, when writing and/or reading information to and from an optical disc, if there is damage such as a scratch on the surface of the optical disc where the laser beam enters the optical disc, it will cause an error. Therefore, when such plastic is used as a substrate,
For example, ultraviolet curable resin is applied using a spin coater method and cured to form a transparent organic protective film with relatively high hardness, or a transparent scratch-resistant film is attached to prevent scratches. Furthermore, when writing and/or reading information on an optical disc, if there is dust or dirt on the side of the laser beam incident on the optical disc, this can also cause errors. Regarding this dust problem, the first method is to mix an antistatic agent into the substrate during the injection molding stage of the substrate, or to
As a means for this, a method of providing an antistatic function by forming a conductive film, and as a third means, a method of adding a conductive material such as a surfactant, metal, or carbon to the organic protective film is considered. However, the first method has problems with adhesion with the recording film and reflective film and film corrosion, and is still not sufficient.
When a conductive film is formed on the surface of an optical disk substrate using the above method, the problem of scratches occurs. Furthermore, adding a conductive material to the organic protective film in the third method causes problems such as deterioration of optical properties due to non-uniformity of the film and generation of new dust. In this case, the surfactant becomes a negative factor, as can be seen in the durability test under high temperature conditions.
There is a problem that the board becomes cloudy.

[Disclosure of the invention]

A first object of the present invention is to provide an optical recording medium that is less likely to be scratched and less prone to errors in writing and/or reading. A second object of the present invention is to provide an optical recording medium that is less likely to attract dirt and dust and less prone to errors in writing and/or reading. A third object of the present invention is to provide an optical recording medium with high productivity. The object of the present invention is to provide an optical recording medium on which information can be written and/or read using a laser beam, the surface of which the laser beam enters the optical recording medium contains conductive light-transmitting particles. This is achieved by an optical recording medium characterized by comprising a layer of. In this optical recording medium, it is preferable that the layer containing conductive light-transmitting particles is formed using a radiation-curable resin, and the conductive light-transmitting particles are preferably formed using a silane cup. It is preferable that the surface be treated with at least one selected from the group of ring agents and titanium coupling agents. That is, the present inventors focused on the structure of the organic protective film as a means to solve the above-mentioned problems, particularly scratches. Damage to an optical recording medium (optical disk) substrate due to scratches depends on the hardness of the plastic material. Usually, thermoplastic resins such as polymethyl methacrylate, polycarbonate, and polyolefin are used as plastic raw materials for optical disk substrates, and their hardness is not very high. Furthermore, in consideration of the optical properties of the substrate, such as injection moldability and birefringence, raw material resins with relatively low molecular weights are used, and as a result, the hardness is becoming increasingly low. Therefore, the surface of a typical plastic optical disk substrate is relatively easily damaged. By the way, it has been found that using methods other than injection molding or changing the raw material resin in order to prevent scratches on the substrate is extremely difficult in order to maintain the characteristics of the optical disk substrate. It's here. Therefore, we investigated a technique to form an organic protective film on the laser light incident surface of the substrate. As a result, in order to form this organic protective film, that is, to form a strong and hard film and have a scratch prevention function, it is important to increase the elastic modulus of the organic protective film material and increase the crosslink density. It has been found that it is sufficient to form an organic protective film having a three-dimensional network structure. As a result of further research, various materials such as polyfunctional epoxy materials, acrylic materials, and unsaturated polyesters can be considered as materials for forming such a protective film. It is preferable to construct the organic protective film using an acrylic material. For example, monofunctional acrylates such as ethyl acrylate, hydroxyethyl acrylate, n-butyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, phenyl cellosolve acrylate, isobornyl acrylate, dicyclopentadieneoxyethyl acrylate, diethylene glycol diacrylate, neopentyl glycol diacrylate, ■, 6-hexanediol diacrylate,
Bifunctional acrylates such as polyethylene glycol diacrylate, trimethylolpropane triacrylate,
A type selected from acrylic acid ester monomers that are polyfunctional acrylates such as trimethylolethane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol hexaacrylate, polyurethane acrylate, polyester acrylate, polyol acrylate, etc. When an acrylic organic protective film composed of the above-mentioned monomers or polymers is provided on the side of the laser beam incident surface on the optical disk, the above object can be effectively achieved. Note that although only acrylate-based materials have been mentioned as the acrylic-based materials, methacrylate-based materials are also included. Furthermore, regarding acrylic acid ester monomers,
It may also contain caprolactam, ethylene oxide, propylene oxide, etc. Further, in order to improve the scratch resistance of the organic protective film, it is preferable to use a film based on polyfunctional acrylenide, which can increase the crosslinking density after curing by radiation and easily forms a three-dimensional network structure. Various acrylates are then mixed in consideration of properties such as viscosity adjustment and film adhesion. The cause of errors during writing and/or reading due to the adhesion of dust and dirt is largely due to electrostatic charge, and as a result of intensive study to solve this problem as well as preventing scratches, we found that, for example, the acrylic material mentioned above is electrostatically charged. It has been found that adhesion of dust and dirt due to static electricity can be prevented by mixing conductive, light-transmitting fine particles with a prevention function and curing the mixture with radiation such as ultraviolet rays or electron beams. Examples of such conductive light-transmitting fine particles include indium oxide, indium tin oxide, tin oxide, antimony tin oxide, tin cadmium oxide, tin oxide fluoride, zinc oxide, zinc aluminum oxide, and the like. When the above fine particles are mixed with acrylic material,
Since phenomena such as aggregation and sedimentation of fine particles easily occur, it is preferable to surface-treat the fine particles with a silane coupling agent or a titanium coupling agent. As such a silane coupling agent, γ-(2-
aminoethyl)aminopropyltrimethoxysilane, T
-(2-aminoethyl)aminopropylmethyldimethoxysilane, T-methacryloxypropyltrimethoxysilane, T-glycidoxypropyltrimethoxysilane,
Examples of titanium coupling agents include methyltrimethoxysilane, methyltriethoxysilane, γ-anilinopropyltrimethoxysilane, and vinyltrimethoxysilane. Examples of titanium coupling agents include tetra-1-propoxytitanium and tetra-
Examples include n-butoxytitanium, titanium stearate, isopropyl trimethyl methacrylic titanate, dimethacryl ethylene natanate, isopropyl triacryl titanate, isopropyl trioctanoyl titanate, isopropyl tristearoyl titanate, and the like. Then, in an inert organic solvent such as benzene, toluene, xylene, methyl ethyl ketone, etc., to which such a silane coupling agent or titanium coupling agent is added,
By adding, mixing, and stirring the conductive light-transmitting fine particles, the silane coupling agent and the titanium coupling agent are adsorbed onto the surface of the conductive light-transmitting fine particles, and the surface treatment is completed. The amount of the silane coupling agent and titanium coupling agent used is about 1 to 10 parts by weight based on 100 parts by weight of the conductive, light-transmitting fine particles. The present invention can be achieved by uniformly mixing fine particles whose surface has been treated with this coupling agent with a polyfunctional-based acrylic material, applying the mixture onto an optical disk substrate using a spin coater method, and curing it with ultraviolet rays or electron beams. An optical recording medium is obtained. In the case of ultraviolet curing, a photopolymerization initiator such as 1-hydroxycyclohexylphenylketone, benzophenone, acetophenone, benzoin ethyl ether, etc. is added in advance. In addition, the proportion of conductive light-transmitting fine particles contained in an organic resin material such as an acrylic material is 10 to 70.
It is about % by weight, and from the viewpoint of antistatic properties, it is preferable that the number of conductive, light-transmitting fine particles is large, but from the viewpoint of uniform dispersion, it is preferable that there are not many.
From this point of view, about 20 to 50% by weight is preferable. The optical recording medium of the present invention configured as described above is hard to be scratched, hard to attract dirt and dust, and hard to cause errors in writing and/or reading. The medium can be obtained with good productivity. τEmbodiment 1 FIG. 1 is a schematic cross-sectional view showing one embodiment of an optical recording medium according to the present invention. In the figure, 1 is a recording bit or guide groove, 2 is a substrate on which the recording pit or guide groove 1 is formed, 3 is a reflective film or recording film, 4 is a protective film, and 5 is an organic protective film having the features of the present invention. and
It is configured such that a laser beam enters from above the substrate 2, the reflected light from a reflective film or recording [13] is received, and the received light is converted by a photoelectric conversion element and reproduced as information. The recording film 3 for write-once discs is made of a material in the oscillation wavelength range of a semiconductor laser, such as a phthalocyanine dye, a naphthalocyanine dye, a cyanine dye, a naphthoquinone dye, an anthraquinone dye, or a benzenedithiol metal complex dye. A dye having absorption and reflection properties can be applied by dissolving it in a solvent that does not dissolve the substrate material, or by vapor deposition to form a thin film, typically 20 to 500 nm thick. In this case, a soluble resin component may be used in combination with the dye, or different types of dye thin films may be laminated. For rewritable disks, SiN, AIN, S
After forming a dielectric film with a thickness of 10 to 200 nm, a thin film of a rare earth transition metal such as TbFeCo is formed with a thickness of 20 to 110 nm.
A thickness of 0n was formed, and a protective film of SiN,
AIN, SiO□, etc. are formed to a thickness of 20 to 1100 nm by a method such as sputtering. The above configuration is for a magneto-optical recording medium,
A linearly polarized laser is input, and information is written or read using the Kerr rotation angle at that time. Further, the reflective film can be formed by depositing, for example, an aluminum material. The organic protective film 5 on the substrate 2 of this optical recording medium was produced by the following steps. That is, 70 parts by weight of an ultraviolet curing hard coating agent (EX-704 manufactured by Dainippon Ink and Chemicals) and 30 parts by weight of antisedimentation-treated tin antimony oxide particles were uniformly mixed and coated to a predetermined thickness using a spin coater method. UV irradiation was performed. Incidentally, since the hard coating agent contains a photopolymerization initiator and a photosensitizer, no new addition is necessary. In order to investigate the characteristics of the optical disc constructed in this way, a scratch test was performed using steel wool on a polycarbonate substrate on which an organic protective film with the same composition as organic protective film 5 was provided with a thickness of 10 IJm. There were significantly fewer scratches compared to rubbing. In addition, in order to investigate the antistatic property that indicates the adhesion of dust and dirt, we measured the surface electrical resistance, and found that the product of this example was coated with an ultraviolet curing hard coating agent (EX-704) without mixing antimony tin oxide particles. The surface electrical resistance value was much lower than that of the organic protective film formed by coating only the organic protective film, and it was difficult for dust and dirt to adhere to it. Furthermore, the light transmittance was also good.

Example 2 The following materials were used for the organic protective film 5 in Example 1. 40 parts by weight of pentaerythritol triacrylate, 35 parts by weight of trimethylolpropane, 10 parts by weight of urethane acrylate, diethylene glycol diacrylate) 12
Part by weight and 3% of 1-hydroxycyclohexylphenyl ketone as a photopolymerization initiator are mixed to prepare an ultraviolet curable resin. Then, 20 parts by weight of indium tin oxide fine particles subjected to silane coupling treatment using 3 parts by weight of r-(2-aminoethyl)aminopropyltriethoxysilane and 80 parts by weight of the ultraviolet curable resin were uniformly mixed. , in the same manner as in Example 1. The scratch test, antistatic properties indicating the adhesion of dust and dirt, and light transmittance properties were as good as in Example 1.

[Example 3] In Example 2, 35 parts by weight of tin oxide fine particles were treated with titanium coupling using 3 parts by weight of tetra-1-propoxytitanium instead of γ-(2-aminoethyl)aminopropyltriethoxysilane. and 65 parts by weight of the ultraviolet curable resin of Example 2 were uniformly mixed, and the same procedure as in Example 2 was carried out. The scratch test, antistatic properties indicating the adhesion of dust and dirt, and light transmittance properties were as good as in Example 2.

【effect】

The optical recording medium according to the present invention is an optical recording medium on which information can be written and/or read using laser light, and includes:
Since a layer containing conductive, light-transmitting particles is formed on the side of the laser beam incident on the optical recording medium, it is free from scratches and dust that can cause errors during writing and/or reading. , can effectively prevent dust adhesion, and
The conductive layer has excellent transparency and has the advantage of being able to provide high-quality optical recording media with good productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of one embodiment of an optical recording medium according to the present invention. DESCRIPTION OF SYMBOLS 1... Recording pit, 2... Substrate, 3... Reflective film or recording film, 4... Protective film, 5...
Organic protective film.

Claims (3)

[Claims] (1) An optical recording medium on which information can be written and/or read using a laser beam, and a layer containing conductive light-transmitting particles is formed on the side of the surface where the laser beam enters the optical recording medium. An optical recording medium characterized by: (2) In the optical recording medium according to claim 1, the layer containing conductive, light-transmitting particles is formed using a radiation-curable resin. (3) In the optical recording medium according to claim 1 or 2, the electrically conductive, light-transmitting particles are at least one type selected from the group of silane coupling agents and titanium coupling agents. Something that has been surface-treated.