JPH02187939A - Optical recording medium and optical recording and reproducing method - Google Patents

Abstract

PURPOSE:To form the optical recording medium which is hardly flawed and corroded, is strong to repetitive reproduction and is light in weight by changing the refractive index of an optical recording layer at the wavelength of reproducing light equal to the wavelength of recording light before and after the irradiation of the recording light. CONSTITUTION:The optical recording layer 2 having the low light absorbability in the specific wavelength region and a reflecting layer 3 are provided on a transparent substrate 1. The reflecting layer 3 reflects the reproducing light at a high reflectivity, for which gold, platinum, Al, etc., are used. The refractive index of the recording layer 2 at the wavelength of the reproducing light equal to the wavelength of the recording light changes before and after the irradiation of the recording light and with such medium, the recording layer 2 is irradiated and condensed with the recording light of the wavelength at which the recording layer 2 exhibits the low light absorbability from the side of the substrate 1, by which refractive index changing parts 5 are formed in the recording layer 2 and signals are thus recorded thereon. Reproducing is executed by detecting the signals recorded on the recording layer 2 as the refractive index changing parts 5 by the reproducing light of the wavelength equal to the wavelength of the recording light and small energy.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording medium capable of recording and reproducing information using a focused laser beam, and an optical recording and reproducing method.

2. Description of the Related Art Optical recording media, especially optical disks, have been making remarkable progress in recent years, and are expected to be used for a wide variety of purposes and applications as the market expands. Generally, optical discs are broadly classified into two types: read-only discs and writable discs. The former uses a stamper with information recorded on it and forms a reflective layer on a transparent substrate onto which the information on the stamper is transferred by molding, thereby producing tens of thousands of discs with the same information. A typical example is the compact disc (hereinafter referred to as CD). On the other hand, many recordable and reproducible optical recording media using organic dyes as recording materials have been announced because of their mass production and versatility in material selection. Such a recordable and reproducible optical recording medium has a structure as shown in FIG. 3, as shown in Japanese Patent Laid-Open No. 112794/1983. That is, an optical recording layer 2 made of an organic dye that absorbs laser light and decomposes or sublimates is formed on a transparent substrate 1. In the optical recording medium with this configuration, the focused laser beam is absorbed by the optical recording layer 2 and converted into heat, so that
The organic dye decomposes or sublimates to form bit 6, and recording is performed.

Problems to be Solved by the Invention Conventionally, in order to manufacture read-only optical discs such as CDs, stampers were required, which could only be manufactured using expensive manufacturing equipment.
was required for each software. Because the production of this stamper requires a high cost and the production equipment is extremely precise and large-scale, it is difficult for anyone to make just a few or even dozens of discs. I did not go. Furthermore, since the pits of recordable and reproducible optical recording media are exposed on the surface of the medium and exposed to the atmosphere, they are easily scratched and susceptible to corrosion and oxidation. In the case of an air sandwich structure in which another protective substrate is attached via a spacer to prevent scratches on the medium surface, the medium becomes thick and heavy. Furthermore, when an organic dye is used as a recording material, it is susceptible to repeated reproduction because of its large absorption at the wavelength of reproduction light. Furthermore, organic dyes have a low reflectance of about 10 to 30%, and the reflection level of the reproduced signal is low, resulting in problems such as not being able to be reproduced by reproduction-only decks such as CD players currently available on the market.

In view of the above problems, the present invention eliminates the need for expensive stampers and stamper manufacturing equipment for each software, is resistant to scratches and corrosion, and is resistant to repeated playback.
Furthermore, the present invention provides a lightweight single-plate optical recording medium that can be played on conventional commercially available CD players, and an optical recording and reproducing method.

Means for Solving the Problems In order to solve the above problems, the optical recording medium and optical recording/reproducing method of the present invention include an optical recording layer having low light absorption in a specific wavelength range on a transparent substrate, and an optical recording layer on the transparent substrate. It consists of a reflective layer, and the refractive index of the optical recording layer at the wavelength of the reproduction light, which is equal to the wavelength of the recording light, changes before and after irradiation with the recording light, and the optical recording layer exhibits low light absorption. A signal is recorded on the optical recording layer by irradiating it with light, and the signal recorded on the recording layer is detected as a change in the refractive index by the reproduction light, which has the same wavelength as the recording light and has low energy, and is reproduced. be.

Effect With the above-described structure and method, when the recording layer is irradiated with high-energy recording light at a wavelength that exhibits low light absorption, the optical recording layer absorbs the light and generates heat in the irradiated area, thereby recording a signal. It will be done. Since this recording portion has low light absorption at the wavelengths of recording light and reproduction light, it can be regarded as a portion where the refractive index has changed rather than a portion where the absorption coefficient of the optical recording layer has changed. When the reproduction light is irradiated here, the reproduction light is in a medium with a homogeneous refractive index,
The recorded portion will be detected as a portion where the refractive index has changed. In other words, the amount of reflected light decreases in the refractive index change area due to the effects of light diffraction and interference, and in other areas, the light absorption of the optical recording layer is relatively low, and the amount of light reflected on the optical recording layer decreases. Since it has a layer, high reflectance can be obtained.

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

Embodiments of the present invention are illustrated in FIGS. 1 and 2. The optical recording medium of the present invention includes a transparent substrate 1, an optical recording layer 2, a reflective layer 3,
It is also possible to further form a protective layer on the first reflective layer 3 consisting of. The material for the transparent substrate l needs to be transparent to the light used for recording and reproduction, and various transparent plastics such as glass, polycarbonate, polymethyl methacrylate, polyimide, and polymethylpentene can be used. When using transparent plastic as the transparent substrate, a transparent protective layer may be formed between the transparent substrate 1 and the optical recording layer 2 to prevent damage to the substrate. Further, the guide groove 4 on the surface of the transparent substrate 1 may be made by injection molding or may be made using a photocurable resin. As a method for forming the optical recording layer 2 on the transparent substrate 1, a vacuum evaporation method or a solution coating method is selected depending on the material of the optical recording layer.

As the solution coating method, spin coating, dip coating, etc. are suitable.

As an optical recording material, an organic dye-based material that absorbs only in a specific wavelength range is suitable. Specifically, it can be selected from cyanine dyes, zuquarylium dyes, phthalocyanine dyes, cholines, triphenylmethane dyes, metal complex compounds, and the like.

These organic dye-based materials may be used alone or in combination as an optical recording layer, or may be dispersed in a binder such as a transparent resin. Optical recording N
A reflective layer 3 is formed on 2, but the reflective layer 3 itself needs to reflect the reproduced light with a high reflectance, and gold, platinum, 11
．． One type or alloy of aluminum, indium, copper, etc. is formed by vacuum evaporation, sputtering, etc. The thickness of the optical recording layer 2 depends on the change in refractive index of the optical recording layer 2 before and after recording at the wavelength of the reproduction light, and can be selected to allow the reproduction light to be efficiently diffracted and interfered with.

Recording is performed by focusing recording light onto the optical recording layer 2 from the side of the transparent substrate 1, and a refractive index changing portion 5 is formed. Reproduction is performed by focusing reproduction light onto the optical recording layer 2 from the side of the transparent substrate 1 and detecting the refractive index changing portion 5. The wavelength of the reproduction light is equal to the wavelength of the recording light, and the power is lowered to reduce the energy. In addition, when an organic dye having an absorption maximum in a wavelength range different from that of the recording light and reproduction light is used as a recording material, if the wavelength of the recording light and reproduction light is selected at the absorption edge of the dye. good.

Example 1 1.1'-diethyl was deposited on a polycarbonate substrate with a diameter of 12 am and a thickness of 1.2 mm+, on which tracking servo grooves with a width of 0.6 μm and a depth of 70 nm were spirally formed on the surface at a pitch of 1.6 μm. A methanol solution of -4,4'quinocarbocyanine iodide was applied.

At this time, the absorption wavelength range of the optical recording layer is from 550 nm to 840 nm.
nm, and the maximum absorption wavelength was 760 nm. Aluminum was vacuum-deposited thereon to a thickness of 1100 nm to obtain an optical disk. While tracking servo was applied to the guide groove, an 830 nm semiconductor laser was irradiated onto the dye recording layer, and an EFM signal was recorded as a single signal with a frequency of 500 KHz and a sound signal. Recording was performed by irradiating light from the transparent substrate side at a linear velocity of 1.3 m/s. The reflectance of the signal surface after recording was 60% at 830 nm. The reproduction C/N is 45 when the recorded signal is reproduced with a tracking servo and the laser burley is reduced using a semiconductor laser of 830 nm, which is the same wavelength as the absorption edge of the recording layer.
It was dB. Further, this optical disc could be played on a CD player using an 830 nm semiconductor laser.

Example 2 Victoria blue and near-infrared absorption were placed on a glass substrate with a diameter of 12 cm and a thickness of 1.2 mm, on which a tracking servo groove with a width of 16 μm and a depth of 70 nm was formed in a spiral shape with a 1.6 μm pinch. A chloroform solution containing dye IR-820 (manufactured by Nippon Kayaku Co., Ltd.) mixed at a weight ratio of 40:1 was applied. At this time, the absorption wavelength range of the optical recording layer is 45
0nm to 880nm, maximum absorption wavelength is 600n
m and 840 nm. Gold was formed thereon to a thickness of one meter, and a protective layer was further formed with an ultraviolet curable resin to obtain an optical disk. While tracking servo was applied to the guide groove, an 830 nm semiconductor laser was irradiated onto the dye recording layer, and an EFM signal was recorded as a single signal with a frequency of 500 KHz and a sound signal. Recording is done by irradiating light from the transparent substrate side, with a laser output of 20 mW and a linear velocity of 1.3.
It was performed at m/s.

The reflectance of the signal plane after recording was 73% at 830 nm. When the recorded single signal of 500 KHz was reproduced using an 830 nm semiconductor laser with a laser output of 0.6 mW, the reproduced C/N was 43 dB. In addition, this optical disc is a CD using an 830 nm semiconductor laser.
I was able to play it on the player.

Example 3 In Example 1, the organic dye was 111'-diethyl-4
, 4'-quinotricarbocyanine iodide was used, but an optical disk was obtained using the same manufacturing process. The absorption wavelength range of this optical recording layer is from 750nm to 11050n,
The absorption maximum wavelength was 950 nm. A single signal of 500 KHz and a sound signal were recorded on the obtained optical disc using a 780 nm semiconductor laser in the same manner as in Example 1.

The reflectance of the signal plane after recording was 70% at 780 nm. Reproduction C when reproduction is performed by reducing the laser power with a semiconductor laser of 780 nm, which is the same wavelength as the absorption edge of the recording layer.
/N was 46 dB. Also, this optical disc is 78
It could be played on a CD player using a 0 nm semiconductor laser.

Effects of the Invention As described above, the present invention consists of an optical recording layer and a reflective layer that have low light absorption in a specific wavelength range on a transparent substrate. The refractive index of the optical recording layer changes depending on the wavelength, and a signal is recorded on the optical recording layer by irradiating recording light with a wavelength at which the optical recording layer exhibits low light absorption. By detecting and reproducing the signal recorded in the recording layer by equal and low-energy reproduction light as a change in refractive index, there is no need for an expensive standber and standber manufacturing equipment for each software, and the recording The effect is that the layer is less susceptible to scratches and corrosion. Furthermore, it is possible to obtain a lightweight, single-plate optical recording medium that is resistant to repeated playback and can be played on commercially available CD players.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing the structure of the optical recording medium of the present invention, and FIG.
The figure is a perspective view of the optical recording medium of the present invention, and FIG. 3 is a sectional view of a conventional optical recording medium. 1... Transparent substrate, 2... Optical recording layer, 3
...Reflection layer, 4...Guide groove, 5...
...Refractive index changing part, 6...Focus. Name of agent Patent attorney Shigetaka Awano 1 person 1- row 1111 ink temporary 2-- light examination, 1 5-.

Claims (6)

[Claims] (1) An optical recording medium consisting of a transparent substrate, an optical recording layer having low light absorption in a specific wavelength range, and a reflective layer, in which the light is emitted at the wavelength of the reproduction light equal to the wavelength of the recording light before and after irradiation with the recording light. An optical recording medium characterized in that the refractive index of the recording layer changes. (2) Claim (1) characterized in that the recording layer contains an organic dye that has an absorption maximum in a wavelength range different from the wavelengths of the recording light and the reproduction light, and whose absorption edge is at the wavelength of the reproduction light. )
The optical recording medium described. (3) The optical recording medium according to claim (1), wherein the recording layer contains two or more types of organic dyes having different absorption maxima. (4) In an optical recording medium consisting of a transparent substrate, an optical recording layer that has low light absorption in a specific wavelength range, and a reflective layer, the optical recording layer is irradiated with recording light of a wavelength that shows low light absorption. A signal is recorded in the optical recording layer, and the signal recorded in the optical recording layer is detected as a change in refractive index by reproduction light having a wavelength equal to that of the recording light and having a small energy, and reproduction is performed. Optical recording and playback method. (5) Claim (4) characterized in that the recording layer contains an organic dye that has an absorption maximum in a wavelength range different from the wavelengths of the recording light and the reproduction light, and whose absorption edge is at the wavelength of the reproduction light. )
The optical recording and reproducing method described. (6) The optical recording and reproducing method according to claim (4), wherein the recording layer contains two or more types of organic dyes having different absorption maxima.