JPH02203441A - Optical recording medium - Google Patents

Abstract

PURPOSE:To additionally stabilize a servo signal and to decrease the error rate at the time of information recording and reproducing by forming the sectional shape of the projecting parts of preformats to a triangular or trapezoidal shape when the preformat surface of a substrate is faced upward. CONSTITUTION:The sectional shape of the projecting parts 4 for tracking is formed to the triangular shape or the trapezoidal shape with which the length of top base b is <=1/10 the spat diameter of irradiation light so that the quantity of reflected light from the projecting parts 4 is sufficiently small compared with that of the recess parts 3. In this case, recording layers are hardly formed in the vertex (top bottom b) parts of the projecting parts or even if the recording layers are formed, the quantity of the reflected light from the projecting parts 4 is hardly detected as the length of (b) is smaller than the spot diameter of the irradiation light. The recording layers are formed along hypotenuses 7 of the projecting parts but the reflected light therein receives the diffraction effect of the hypotenuses, by which the quantity of the reflected light detected by the optical head is sufficiently decreased. As a result, the contrast ratio of the track crossing signal is improved. The identification and detection of the projecting parts which are the track regions are facilitated in this way and the off-tracking of a laser beam for recording and reproducing is decreased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium for optically recording and reproducing information.

[Conventional technology]

2. Description of the Related Art Conventionally, optical recording media have a guide groove for an optical head formed in advance on the substrate surface of the medium in order to record and reproduce information stably and with high density. This guide groove identification is generally performed by detecting the intensity of the converted light based on the phase difference between the reflected light of the irradiated laser beam at the groove and non-groove areas, and by detecting the brightness and darkness due to the difference in the amount of reflected light between the groove and non-groove areas. . This is called a servo signal. On the other hand, as shown in FIG. 3, in the case of a coated type recording medium in which a recording layer such as an organic dye is dissolved in a solvent and coated on a substrate having a concavo-convex preformat to form a recording layer, a coating solution Flows into the concave guide groove, and since the evaporation rate of the solvent dissolving the dye is not uniform within the substrate surface, the thickness of the recording layer becomes thicker in areas where the solvent dries faster.

As a result, the thickness of the recording layer in the concave portions and convex portions is not constant within the recording surface. As shown in FIG. 4, the reflectance of the dye film varies greatly depending on the film thickness, so there were problems such as the servo signal not being stabilized.

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and aims to provide an optical recording medium in which the servo signal is more stabilized and the error rate during recording and reproduction of information is reduced. This is the purpose.

[Means for solving problems]

The present invention provides an optical recording medium in which a concave-convex preformat is formed on a substrate and a recording layer is formed by coating on the preformat, and when the preformat surface of the substrate is placed upward, the convex portions of the preformat are The cross-sectional shape is a triangle or the length of the upper base is a trapezoid with a length of 1/10 or less of the diameter of the light beam, and the angle between the slope and the normal to the lower base is 30° to 70°.
degree, and its height h is greater than or equal to the thickness of the recording layer.

That is, according to the present invention, since there is substantially no recording layer in the convex portions of the preformat, the reflectance of the convex portions is sufficiently smaller than the reflectance of the concave portions, and the servo signal is stabilized.

Next, the present invention will be explained in detail using figures.

FIG. 1 is a drawing showing the features of the present invention, in which 1 is a recording layer;
2 is a substrate, 3 is a preformat concave portion, 4 is a preformat convex portion which is a track area, 5 is an adhesive layer, 6 is a protective material, and 7 is an oblique side of the convex portion.

It has a cross-sectional shape cut at right angles to the guide groove No. 4.

Figure 2 is an enlarged view of the guide groove in Figure 1, and a
, b represent the lower and upper bases of the trapezoidal tracking convex portion.

As shown in FIG. 1, the cross-sectional shape of the tracking convex part 4 is triangular or has a top base as shown in FIG. It is formed into a trapezoid whose length is 1/10 or less of the spot diameter of the irradiation light. When formed in this way, almost no recording layer is formed at the apex (upper base b) of the convex portion, or even if it is formed, the length of b is smaller than the spot diameter of the irradiation light, so that the convex portion 4 Almost no amount of reflected light is detected. or,
The recording layer is formed along the oblique side 7 of the convex portion, but the amount of reflected light detected by the optical head becomes sufficiently small due to the diffraction effect of the slope, and as a result, the amount of reflected light detected by the optical head is defined by the following equation (1). The contrast ratio of the track-crossing signal is improved. As a result, it becomes easier to identify and detect the convex portion which is the track area, and the off-track of the recording/reproducing laser beam is reduced. Further, if the height of the convex portion is set to be equal to or greater than the film thickness of the recording layer, the recording layer is less likely to be formed at the apex (upper base b) of the convex portion in the track area (this is preferable).

Furthermore, in the present invention, the angle formed by the oblique side C of the convex portion and the normal line to the base is preferably 30° or more and 70° or less so as to increase the recording density and ensure that a tracking signal is obtained. That is, if the angle is less than 30 degrees, the width of the track area becomes narrow, and there is a possibility that the laser beam will not detect the track area. Further, if the angle is 70° or more, the bottom side becomes long (and the recording density decreases).

In the present invention, the recording layer 1 is preferably formed of a material that can be dissolved or dispersed in a solvent and can be coated on a substrate. Examples of such materials include pigment materials such as anthraquinone derivatives, dioxazine derivatives, phenanthrene derivatives, cyanine-based, squarylium-based, phthalocyanine-based, merocyanine-based, azo-based, polymethine-based, sulfur dye-based, and mixtures thereof. can be used.

The dye used in the present invention is preferably one that in the form of a thin film absorbs light used for recording and/or reproduction and has a high reflectance.

As such a dye, for example, a dye represented by the following structural formula is suitably used. This dye can be used as a recording layer by itself, and also has light resistance CΦ-CIl=CH-
CH=C (C2HS)2N
In order to improve N(C2H5)2C1!04e, additives such as aminium salts and diimonium salts can be added and used as a recording layer.

Next, a method for manufacturing the optical recording medium of the present invention will be described.

First, the method for forming the guide groove portion on the substrate is not particularly limited, and for example, an injection method, a compression method, a cast molding method, a 2P method, etc. can be used. Among these, in the injection method, compression method, and cast molding method, guide grooves are formed directly on the substrate, and 2P
In this method, after a photocurable resin composition is applied onto a substrate, a master is placed in close contact with the substrate and radiation is irradiated to cure the resin composition and transfer a mask pattern, and a tracking convex is formed on the resin composition. form a section.

In addition, as a method for manufacturing the molds and master discs used in each of the above methods to obtain the shape of the convex portion of the concavo-convex preformat, that is, a triangular or trapezoidal shape, for example, a chromium film is vapor-deposited on a glass stamper substrate. Sometimes, the pressure in the system is gradually increased to produce a deposited film whose physical properties are continuously changed, and then this is etched in a normal photolithography process to obtain a stamper whose grooves have a triangular or trapezoidal cross-sectional shape. Can be done.

Furthermore, the height of the preformat portion can be controlled by controlling the etching process. The material used for the substrate 2 is preferably one that is transparent to the light used when recording and reproducing light is transmitted from the substrate, such as glass, polyvinyl chloride, and polymethyl methacrylate.

Polycarbonate, polymethylpentene, polysulfone, polystyrene, etc. are used, and one is selected from these depending on the manufacturing method. The adhesive layer 4 may be made of any material as long as it does not deteriorate the dye in the recording layer, and in particular, hot melt type adhesives, such as olefin adhesives such as ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, hot melt film, etc. Polyimide resins are preferably used. As the protective material 6, any material that can be used as a normal protective material can be used, and specifically, fluorine-substituted ethylene polymer, vinyl chloride-vinyl acetate copolymer, polyvinylidene chloride, polyvinyl butyral, and acetyl. Cellulose, styrene-butadiene copolymer, polyethylene, polypropylene, epoxy acrylonitrile-butadiene-styrene copolymer, etc. are used.

In some cases, iron, stainless steel, aluminum, tin,
A wide variety of materials can be used depending on the purpose, such as metal sheets such as copper or zinc, synthetic paper, fiber-reinforced plastics, composites of metal powders such as magnetic materials and plastics, and ceramics.

Moreover, the material used for the substrate 2 can also be used.

In the present invention, the contrast is calculated as follows from the waveform obtained from the oscilloscope (Fig. 4) when the amount of reflected light when the laser spot crosses the convex part that is the track area (Fig. 3) is converted into an electrical signal. Define.

Contrast” (Ro Rt)/R.

〔Example〕

Example 1 A photocurable resin was applied to a transparent polycarbonate substrate,
A substrate for an optical recording medium having a tracking preformat convex portion as shown in FIG. 2 was prepared using a stamper mold. The angle between the oblique side of the tracking-like preformat convex part and the normal to the base is 50°
The length of b is 0.2 p m and the height h is 3000 people. However, the spot diameter of the laser beam is 3 μm.

A solution of 3% by weight of the following polymethine dye dissolved in diacetre alcohol is applied to the substrate of the optical recording medium having the tracking preformat convex portions and concave recording portions using a gravure coater to record the concave recording portions. An organic dye recording layer of 1000 parts was obtained.

Next, a polycarbonate protective material is laminated on the organic dye recording layer using a hot melt adhesive whose main component is ethylene-vinyl acetate copolymer (trade name: Elfan-0H504, manufactured by Nippon Matai Co., Ltd.). An optical recording medium of the shape was obtained. The contrast of the transverse signal of the tracking preformat convex portion of the optical recording medium obtained in this way is 0.
．． It was 6. Also, the deviation of the track-crossing signal was within ±5%.

Example 2 Uneven preformat for tracking The angle between the oblique side of the convex part and the normal to the base is 30°, and the length of b is 0.2
An optical recording medium was prepared in the same manner as in Example 1, except that the height h in μm1 was 3000 people.

The contrast ratio of the transverse signal of the tracking preformat convex portion of the optical recording medium obtained in this way is 0.61.
Met. Also, the deviation of the track-crossing signal was within ±5%.

Embodiment 3 Concave/convex preformat for tracking The angle formed by the oblique side of the convex part and the normal to the base is 60'', and the length b is 0.
An optical recording medium was prepared in the same manner as in Example 1 except that the thickness was 2 μm and the height h was 3000 A. The contrast ratio of the cross-track signal of this optical recording medium was 0.59, and its deviation was within ±5%.

〔Effect of the invention〕

As explained above, the cross-sectional contrast value of the tracking convex portion of the optical recording medium of the present invention has been improved, and the deviation of the recording/reproducing light from the track has been significantly reduced, making the optical recording medium highly reliable. I was able to get it.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of one embodiment of the optical recording medium of the present invention. FIG. 2 is an enlarged view of the preformat section of FIG. 1. FIG. 3 is an explanatory diagram of a method for measuring the amount of reflected light in the optical recording medium of the present invention. FIG. 4 is a schematic diagram of the waveform shown on the oscilloscope when the amount of reflected light from the track area and the information recording area is converted into an electrical signal. l... Recording layer 2... Substrate 3... Preformat concave portion 4... Preformat convex portion (track area) 5...
・Adhesive layer 6... Protective material 7... Preformat convex portion Slope 8... Laser beam spot a... Preformat convex portion Lower base b... Preformat convex portion Upper base h... Preformat convex portion height Ro...portion R3 corresponding to the reflectance of the information writing area
...Partial Y10 corresponding to the reflectance of the track area

Claims (4)

[Claims] (1) In an optical recording medium that has an uneven preformat on a substrate and a recording layer is formed on the substrate by coating, when the preformat surface of the substrate is facing up, the cross section of the convex part of the preformat An optical recording medium characterized in that the shape is a triangle or a trapezoid whose upper base length is 1/10 or less of the diameter of a light beam. (2) The optical recording medium according to claim 1, wherein the height of the convex portion of the preformat is greater than or equal to the thickness of the recording layer. (3) Claim 1, wherein the angle between the triangular or trapezoidal slope of the cross section and the normal to the base of the convex portion is 30° to 70°.
optical recording media. (4) The optical recording medium according to claim 1, wherein the recording layer is mainly composed of an organic dye.