JPH0268741A - optical recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a write-once optical recording medium used for data files, digital audio discs, etc., on which information can be newly recorded and reproduced using light.

2. Description of the Related Art In recent years, optical disks have been increasingly being applied to data files due to their advantages such as high density, large capacity, and high speed access.

There are roughly three types of optical discs. There are three types: a type that only reproduces pre-written information, a write-once type that allows new information to be written in addition to the pre-written information, and a rewritable type that allows repeated writing and erasing. The present invention relates to a write-once type.

There are several types of write-once type. There are types that use the heat of laser light to make holes in the organic dye layer and read changes in the reflectance of the light (for example, Japanese Patent Application Laid-Open No. 154888/1988), and types that use the heat of laser light to read the change in reflectance. A type that forms a focus by foaming a foam layer (for example,
(Japanese Unexamined Patent Publication No. 6348629) and a type that forms a focus by melting a metal layer (for example, Japanese Patent Application Laid-Open No. 52-64905)
A number of methods have been devised, including a type in which pits are formed using thermal phase separation of a polymer blend (polymer alloy) (for example, Gendai Kagaku Special Edition νo1.8 p134-138).

Problems to be Solved by the Invention However, the organic dye perforation type has the drawbacks that the organic dye itself fades over time and that the initial reflectance is low. Furthermore, even in the phase separation type of polymer alloy, the contrast is small, the CN ratio cannot be obtained if the film is thin, and the lifetime of the recorded pits is short due to thermal history and molecular movement over time.

In the type that disperses thermoplastic polymer fine particles and melts them during recording, light scattering (
Reflectance) has the disadvantage of small change.

Furthermore, as for the manufacturing method, a spin code method is used when an organic dye is used as an optical recording medium, and a resistance heating vapor deposition method or a sputtering method is used when a metal thin film is used as an optical recording medium. However, although the spin cord method is inexpensive as an equipment, it is not suitable for mass production and the production cost is high. On the other hand, vacuum equipment such as the resistance heating evaporation method requires very expensive equipment, resulting in high costs.

In view of the above problems, the present invention has a very low manufacturing cost,
The present invention provides an optical recording medium with a relatively high C/N ratio (contrast) and a long recording life.

Means for Solving the Problems In order to solve the above problems, the optical recording medium of the present invention includes at least one layer of hollow polymer particles having a particle size of 1.2 μm or less on a substrate, and The refractive index difference between the inside and the outer shell material is 0.03 or more.

Further, the surrounding material surrounding the hollow polymer particles is a gas or a polymer resin.

As for the method of manufacturing an optical recording medium, when a photocurable resin is used as the surrounding material, it becomes possible to coat the resin onto the substrate using a roll coater and to simultaneously manufacture the overcoat and the optical recording medium layer.

Effect of the present invention In the above-described configuration, in the initial state, polymer hollow fine particles having a refractive index difference with the inside are present on the substrate, which causes fluctuations in the refractive index and reflection on the spherical surface, and the laser beam is transmitted through this layer. is reflected diffusely.

For recording, a high-power laser beam is irradiated from the substrate side and heated above the melting temperature (softening temperature) of the hollow polymer particles to melt them. The molten polymer hollow particles become liquid and exist integrally on the substrate. Therefore, only the part irradiated with laser light becomes transparent. At this time, it is more effective to mix an organic dye that absorbs laser light into the hollow polymer particles in order to improve absorption of laser light and lower recording power.

If the particle size is 0.2 μm or more, noise will be generated when pits with a diameter of 1 μm or less are clearly emitted from the outer edges of the pits. Furthermore, when the polymer hollow fine particles are not composed of more than one layer (when some particles are not present), the periphery of the pit is not clearly visible.

At this time, unless the refractive index difference between the inside of the polymer hollow fine particles and the outer shell material is 0.03 or more, fluctuations in the refractive index will be small, diffuse reflection will be small, and a high C/N ratio will not be obtained.

In addition, when a photocurable resin is used as the surrounding material, the viscosity of the mixed solution with the polymer hollow particles is appropriate, so the coating method using a roll coater used in printing can be used, and the overcoat layer and optical recording The media layer can be formed simultaneously, which significantly reduces manufacturing man-hour costs.

With the above configuration, a write-once optical recording medium can be obtained which has a very low manufacturing cost, a relatively high CN ratio, and excellent long-term reliability.

EXAMPLE Hereinafter, an optical recording medium according to an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of an optical recording medium in a first embodiment of the present invention. In FIG. 1, 11 is a substrate, 1
2 is a polymer hollow fine particle, and 13 is a photocurable resin layer.

FIG. 2 shows a sectional view of the first embodiment during recording. In FIG. 2, 21 is a pit and 22 is a laser beam.

As the substrate 11, a glass substrate on which guide grooves were formed by dry etching was used. Polymer hollow fine particles 12 (functional organic hollow particles manufactured by Dainippon Ink and Chemicals Co., Ltd.) with an average particle diameter of 0.08 μm prepared by emulsion polymerization of a copolymer monomer were added to the above as a surrounding material, and non-anaerobic ( moisture)
photocurable resin (UVX-E401 manufactured by ThreeBond)
A well-mixed mixture of 2:1 by weight was coated on the substrate to a thickness of about 0.5 μm using a roll coater. Next, the substrate was irradiated with ultraviolet rays (45 mW/CM2) to cure the photocurable resin, thereby forming the photocurable resin layer 13.

Here, instead of a roll coater, a spin code is also possible. The polymer hollow fine particles used here have air inside and an acrylic resin outer material, and the difference in refractive index is about 0.5, and the optical recording medium layer in the initial state is cloudy.

When recording, the laser power was 5 mW (linear velocity 1.4 m).
/5ec) on the optical recording medium to melt the polymer hollow particles and form pits 21 (width Q, 7μ
m, length 1. Ollm) was formed.

By melting, the outer shell of the polymer hollow fine particles is torn, and the shape changes from particulate to bulk. Since the number of grain boundaries is reduced, fluctuations in the refractive index are reduced and scattering on the surface of the hollow polymer particles is also eliminated, resulting in a significant decrease in reflectance.

The CN ratio of the optical disc manufactured in this way was 53d.
B, and 1 in the accelerated test at 80"C80%RH.
No deterioration of the CN ratio was observed even after 1,000 hours.

FIG. 3 shows the change in CN ratio with respect to the particle size of hollow polymer particles. Particle size is 0 as polymer hollow particles.
If a material with a diameter of 32 μm or more is used, the outer shell will be difficult to tear, and the CN ratio will be greatly reduced as shown in FIG.

Further, FIG. 4 shows the change in the CN ratio with respect to the film thickness of the optical recording medium layer, and an extreme decrease in the CN ratio was observed at a film thickness of 0.08 μm or less. This is thought to be due to the fact that some hollow polymeric particles are not present, making it difficult for pit outlines to appear. Furthermore, FIG. 5 shows the change in the CN ratio with respect to the refractive index difference between the inside of the polymer hollow fine particles and the outer shell material, and it was found that a high CN ratio could not be obtained unless the refractive index difference was 0.03 or more.

As described above, according to this embodiment, an optical disc can be obtained at low cost, with a relatively large CN ratio, high heat resistance, and long recording pit life.

A second embodiment of the present invention will be described below with reference to the drawings. FIG. 6 is a sectional view of an optical recording medium showing a second embodiment of the present invention.

In the figure, 61 is a substrate, 62 is a hollow polymer particle mixed with an organic dye, 63 is an air layer, and 64 is a ? Fusing layer, 65
is a hot melt film layer.

Figure 7 shows a cross-sectional view during recording, where 71 is a pit;
72 is a laser beam.

A glass substrate 61 with a melting temperature of 9
It is coated with a hot-melt resin at around 0° C., and polymer hollow fine particles 62 (particle size 0.08 μm) mixed with an organic dye are applied thereon. At this time, the temperature of the glass substrate was set to 100
Let it rise to °C. This causes the true melt resin to melt and form a dissolved layer 64. The portions of the hollow polymer particles that are in contact with the dissolved layer are adhered.

Next, a hot melt film is laid on top of this, and the inner and outer peripheral edges are fixed with a hot press, and the recording surface is lightly pressed with a hot plate to fix the upper part of the polymer hollow particles to complete the optical recording medium layer. As an organic dye, IRQ-022 (Nippon Kayaku Co., Ltd.) is a diimonium-based dye that has an absorption band in the range of 700 to 900 nm.
! I used ri.

When recording, the laser power was 4.2 mW (&'!1
Laser light 72 was irradiated at a speed of 1.4 m/5 ec) to dissolve the polymer hollow particles to form bits 71 and generate a difference in reflectance. The CN ratio was as high as 55 dB.

As an organic dye, ethylene 1,2-dithiol foundation W
+ (N i ) Pigments with absorption bands in the near-infrared region are effective, such as tW-forms, cyanine dyes such as phthalocyanine, squalirium dyes, methine-based dyes, naphthoquinone-based dyes, quinone-imine-based dyes, quinone-diimine-based dyes, and anthraquinone-based dyes. Met.

As described above, by mixing an organic dye into the polymer hollow fine particles, the absorption rate of laser light is improved and the recording sensitivity is improved. Furthermore, since the surrounding material of the polymer hollow fine particles is air, there is a large difference in refractive index with the outer shell material, and the CN ratio is improved. By mixing an organic dye into hollow polymer particles used as an optical recording medium in this way, an optical disc with good recording sensitivity and a high C/N ratio can be obtained.

Effects of the Invention As described above, the present invention provides at least one layer of hollow polymer particles having a particle size of 0.2 μm or less on a substrate,
The optical recording medium is composed of an optical recording medium in which the refractive index difference between the inside of the polymer hollow fine particles and the outer material is 0.03 or more, and the CN
The object of the present invention is to provide a low-cost optical recording medium that has a high ratio, has excellent reliability such as heat resistance and service life.

[Brief Description of the Drawings] Figure 1 is a cross-sectional view of an optical recording medium in the first embodiment of the present invention, Figure 2 is a cross-sectional view during recording, and Figure 3 is a CN vs. particle size of hollow polymer particles. Figure 4 is a graph showing changes in the CN ratio with respect to the film thickness of the optical recording medium layer. Figure 5 is a graph showing changes in the CN ratio with respect to the refractive index difference between the inside of the polymer hollow fine particle and the outer shell material. FIG. 6 is a sectional view of an optical recording medium showing a second embodiment of the present invention, and FIG. 7 is a sectional view during recording. 11...Substrate, 12...Polymer hollow fine particles, 13...Photocurable resin layer, 21...
...Focus, 22...Laser light, 61...
... Substrate, 62 ... Polymer hollow fine particles mixed with organic dye, 63 ... Air layer, 64 ...
...? Melting layer, 65... True melt film layer, 71... Bit, 72... Laser light. Name of agent: Patent attorney Shigetaka Awano Haka 1 person 1 Zuzu 3 ++-. Board 2-Katekohikikaishata 13-,-Ichimiba Juutosan 1#Moonhi 2f-m-Binodo 22--1-Boo Hikari

Claims (6)

[Claims] (1) An optical recording medium characterized in that hollow polymer particles are coated on a substrate, and the particles are destroyed by the heat of a laser beam to read changes in reflectance. (2) There is at least one layer of hollow polymer particles with a particle size of 0.2 μm or less on the substrate, and the difference in refractive index between the inside of the hollow polymer particles and the outer shell material is 0.03 or more. The optical recording medium according to claim (1). (3) The optical recording medium according to claim (1), wherein the hollow polymer particles are surrounded by a gas or a polymer resin. (4) The optical recording medium according to claim (1), wherein the interior of the polymer hollow fine particles is gas or polymer resin. (5) The optical recording medium according to claim (1), wherein the polymer resin according to claim (3) is a photocurable resin. (6) Claim (1) characterized in that an organic dye that absorbs laser light is mixed into the outer material of the hollow polymer particles.
) optical recording medium.