JPH01243252A - Medium and method for recording optical information - Google Patents

Abstract

PURPOSE:To improve sensitivity and recording quality by forming a groove on the plane on one side of a transparent substrate, constituting a part on which the groove is formed of a thermosoftening member, forming a light absorptive reflection layer on the plane where the groove of the substrate is formed, and setting a prescribed ratio of a reflecting level for a laser beam projecting the depth and the width of the groove at the part where the groove is formed to the part where no groove is formed. CONSTITUTION:Groove parts 7a, 7b, 7c... are formed on the plane on one side of an optical information recording medium 1, and the transparent substrate 2 in which the parts where the groove parts 7a, 7b, 7c... are formed are constituted of the thermosoftening member is used. On the plane where the groove parts 7a, 7b, 7c... are formed, the light absorptive reflection layer 3 and a protective layer 4 are formed sequentially. The depth and the width of the groove parts 7a, 7b, 7c... of the recording medium 1 constituted in such way that the reflected light levels of the groove parts 7a, 7b, 7c... for a laser convergence beam projected from the substrate 2 side are set at values of 10-50% of that of the parts where no groove part 7a, 7b, 7c... are formed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to an optical information recording medium, such as an optical disk, on which information is optically recorded using a focused laser beam, and a recording method.

[Prior art]

2. Description of the Related Art In recent years, optical discs have been used in video and audio recording devices, external storage devices for computers, and the like to optically record information using a focused laser beam with a diameter of about one door. Conventionally, in such information recording, a method has been adopted in which a light-absorbing and reflective thin film is provided on a substrate, a focused laser beam is irradiated, and small holes are formed in the thin film to record information.

However, in conventional optical discs, metals, alloys, and organic dyes are used as light-absorbing and reflective thin films, and their melting points, evaporation temperatures, and decomposition temperatures are as high as 200°C to 1000°C, making it difficult to increase sensitivity. could not. Furthermore, there is a drawback that the material removed when forming small holes in the thin film deteriorates signal quality.

〔the purpose〕

The present invention has been made to solve the drawbacks of the prior art, and an object of the present invention is to provide an optical information recording medium and a recording method with improved sensitivity and recording quality.

〔composition〕

According to the present invention, a first aspect of the present invention includes a transparent substrate having a groove formed on one surface and at least a portion where the groove is formed is made of a thermosoftening material; and a surface of the transparent substrate where the groove is formed. and a light absorption/reflection layer provided on the transparent substrate, and the depth and width of the groove are such that the level of light reflected from the groove portion to the laser beam irradiated from the transparent substrate side is such that the level of light reflected from the groove portion is the same as the reflection of the portion where the groove is not formed. An optical information recording medium is provided, characterized in that the light level is set to a value of 10% to 50% of the light level.

Further, as a second invention, information is recorded by irradiating the light absorbing and reflecting layer provided on the groove portion of the optical information recording medium with a focused laser beam from the transparent substrate side and deforming the groove structure by the heat effect. A recording method is provided that is characterized by performing the following steps.

Next, the optical information recording medium and recording method of the present invention will be explained with reference to the drawings. FIG. 1 is a sectional view perpendicular to the scanning direction showing the optical information recording medium of the present invention, and FIG.
shows an unrecorded state, and (b) shows a recorded state. In FIG. 1, reference numeral 1 denotes an optical information recording medium such as an optical disk, which basically includes a transparent substrate 2 with grooves formed on one surface, and a light absorbing/reflecting medium provided on the transparent substrate 2. Consists of layer 3. In the optical information recording medium 1 of the present invention, a protective layer 4 may be provided in order to protect the recording surface, depending on the case. In the figure, 5 is a condenser lens, 6 is a laser light forming beam, and 7a, 7b, and 7c are groove portions of the light absorption and reflection layer 3.

The entire transparent substrate 2 may be made of a heat-softening material, or a portion, that is, a portion where the grooves are formed, may be made of a heat-softening material. In the case of FIG. 1, the grooves formed in the transparent substrate 2 are concave grooves toward the substrate side, but they may also be concave grooves toward the recording layer side, that is, convex grooves toward the substrate side.

This concept of groove is relative, and in this specification, both grooves will be collectively referred to as grooves.

Information is recorded on the optical information recording medium 1 as follows. As shown in FIG. 1(a), for example, the condenser lens 5 creates a groove with a diameter of 1
A focused laser beam 6 with a spot diameter of around μm and a power of a predetermined value or more is irradiated. The laser focused beam 6 is absorbed by the light absorption/reflection layer 3, and as the temperature of the groove portion 7b rises, the heat-softening material in the vicinity thereof softens, and the groove portion 7b becomes 7b in FIG. 1(b) due to surface tension. '
It decreases, that is, becomes shallower. Note that 7b' may be in a state where the groove structure completely disappears. 7b' in FIG. 1(b) is a recording state, and recording is performed when the laser irradiation power exceeds a predetermined value. When the laser irradiation power is lower than a predetermined value, the deformation temperature is not reached, so no change in shape of the groove portion occurs. Therefore, depending on the strength of the power of the laser focused beam 6, portions 11a, llb, llc... where the groove structure disappears or is reduced are formed on the track 10 made of grooves as shown in FIG. Information can be recorded.

To read information from the optical information recording medium 1, a track is traced with a focused laser beam of low irradiation power that does not change the groove structure, and the intensity of the reflected light can be read. For example, when tracing a track as shown in FIG. 2(b), corresponding to the parts 11a, ilb, and 1.1c where the groove structure has disappeared or deteriorated, the groove structure shown in FIG.
) are reflected light signals such as 9a, 9b, and 9c. 8 in the figure is the level of light reflected by the groove portion. That is, the reflected light level is low in the groove portion due to the diffraction effect, but the reflected light level is high in the portion where the groove structure has disappeared or decreased. Therefore, in the present invention, the depth and width of the groove are set such that the level of reflected light from the groove is 10% to 50%, preferably 20% to 40%, of the level of reflected light at the portion without the groove (mirror surface). It is necessary to do so. For this purpose, the effective depth of the groove is preferably 0.13λ to 0.24λ (λ is the wavelength of light), and the half width of the groove is preferably 0.2 to 0.5 times the focused spot diameter (full width at half maximum). The maximum depth of the groove varies somewhat depending on the shape of the groove, and in the case of a rectangular groove, 1 times the effective depth is appropriate, and in the case of a V-shape, 1.6 times the effective depth is appropriate.

Figure 3 shows the full width at half maximum of 0.2 to 0.4 of the laser beam.
An example of the relationship between the maximum depth of a groove having double the half width and the reflected light ratio is shown. The figure (a) shows the case of a rectangular groove, and the figure (b) shows the case of a V-shaped groove. In the case of a rectangular groove with a depth of 0.2λ, the reflected light ratio increases from 0.35 to 0.85 by turning the groove into a 0.1λ groove by laser beam irradiation. In the case of a V-shaped groove,
By irradiating a 0.26λ groove with a laser beam, the groove becomes 0°1λ, thereby increasing the reflected light ratio from 0.4 to 0.85.

The protective layer 4 protects the recording surface and is effective for preventing damage to recorded information, and is also effective for preventing part of the light absorbing reflective layer 3 from scattering during excessive laser beam irradiation. The protective layer 4 may not necessarily be necessary if the surface of the light-absorbing reflective layer 3 is not contaminated (for example, when it is open in the air gap of an air sandwich structure).

Examples of materials constituting the transparent substrate 2 of the optical information recording medium 1 of the present invention include glass, transparent plastics (acrylic resin (PMMA), polycarbonate resin, polyester resin, polyvinyl chloride resin, nylon resin, polyolefin resin, polystyrene). resin, epoxy resin,
silicone resin, etc.), but it is necessary to select a heat-softening transparent resin at least for the groove forming portion.

Examples of the material constituting the light absorption and reflection layer 3 include Te.
, Bi, Se, Ti, Pb, Sn
Metals, alloys, oxides such as cyanine dyes, merocyanine dyes, triphenylmethane dyes, phthalocyanine dyes,
Organic dyes such as squarylium dyes and pyrylium dyes are used.

The material constituting the protective layer 4 is, for example, Ap.

Metals and alloys such as Au, Ag, Pd; Sin, MgF,
Metal oxides, metal fluorides, metal nitrides such as SiN;
Acrylic resin (PMMA), polycarbonate resin, polyester resin, polyvinyl chloride resin, nylon resin,
Resins such as epoxy resin, silicone resin, gelatin, and polystyrene resin are used. Further, the protective layer 4 can contain a lubricant, a stabilizer, a pigment, a dye, and the like.

〔effect〕

=7- According to the present invention, information is recorded by deforming (disappearing or lowering) the groove structure using a focused laser beam, so it is possible to record information at a lower temperature than the small hole formation method. Since it can be recorded, sensitivity is improved. Furthermore, since the recording film (light absorbing and reflecting layer) is not scattered during recording, the surface of the recording film is not contaminated with foreign matter, improving reliability. Furthermore, since there is no need for an air sand inch structure, manufacturing costs can be reduced and warping due to the influence of external pressure will not occur.

〔Example〕

Next, the present invention will be explained in detail, but it is not limited thereto.

Example 1 Groove width 0.3 μm, depth 0.12 in polycarbonate resin
Using an optical disk substrate in which a trapezoidal groove with a slightly rounded shape was spirally formed at a track pitch of 1.6ρ, a 5eTe film was deposited to a thickness of 400 mm as a light absorbing and reflecting layer. Furthermore, a 10 μm thick silicone resin was applied thereon to form a protective film. Then, using a semiconductor laser with a wavelength of 780 nm and a condensing lens with a numerical aperture of 0.47, the full half maximum @ 0.
Laser light was focused on a 9 μm spot and irradiated onto the recording medium. Linear velocity 2.1. m/see, irradiation power 2.3
As a result of recording at d, a C/N ratio of 50 dB was obtained. At this time, no holes were formed in the 5eTe film, and the grooves in the substrate became shallow.

Example 2 A cyanine dye having the following structural formula was coated on the same substrate as in Example 1 to a thickness of 0.05 mm, and a protective film of SiO was coated on it to a thickness of 0.05 mm.
It was deposited to a thickness of 7 μm.

Then, the same laser beam as above is focused, and the linear velocity is 2
．． As a result of recording at 1 m/see and irradiation power of 2.2 mW, a C/N ratio of 52 dB was obtained. At this time, no holes were formed in the dye film, and the grooves in the substrate became shallow. Similar results were obtained when a layer of gelatin with a thickness of 30 μm was applied as a protective film.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the structure of an optical information recording medium according to the present invention, with FIG. 1(a) showing an unrecorded state and FIG. 1(b) showing a recorded state. FIG. 2 is an explanatory diagram of information reading from the optical information recording medium according to the present invention, and FIG. FIG. 2(b) shows the signal pattern on the track. FIG. 3 is a graph showing the relationship between the maximum depth of the groove and the reflected light ratio. FIG. 3(a) shows the case of a rectangular groove, and FIG. 3(b) shows the case of a V-shaped groove. 1... Optical information recording medium 2... Transparent substrate 3... Light absorption reflective layer 4... Protective layer 6... Laser condensed beam 7a,
7b, 7cm groove part

Claims (2)

[Claims] (1) A transparent substrate with grooves formed on one surface and at least the portion where the grooves are formed is made of a thermosoftening material, and a light absorbing/reflecting substrate provided on the surface of the transparent substrate where the grooves are formed. The depth and width of the groove are such that the level of light reflected at the groove portion with respect to the laser beam irradiated from the transparent substrate side is 10% to 50% of the level of light reflected at the portion where the groove is not formed. An optical information recording medium characterized by being set to a value such that . (2) Information is recorded by irradiating the light absorbing and reflecting layer provided in the groove portion of the optical information recording medium according to claim 1 with a focused laser beam from the transparent substrate side and deforming the groove structure by the heat effect. A recording method characterized by performing the following.