JPH05144081A - Optical recording medium - Google Patents

Abstract

PURPOSE:To ameliorate the troubles, such as lowered productivity and degraded substrate arising from the provision of a transmittance changing material for reducing the spot diameter of a light beam for recording or reproducing. CONSTITUTION:A substrate 10 is obtd. by mingling the transmittance changing material with a high-polymer matrix material and subjecting the material mixture to desired molding including pits 12. A reflection film 14 and a protective film 16 are formed in this order on the main surface of such substrate 10. The incident light beam on the optical recording medium as shown by an arrow FA is reduced in its spot diameter by the effect of the transmittance changing material at the time of the passage through the substrate. The thickness of the substrate 10 is kept uniform by the accuracy at the time of molding and the thickness thereof is larger than the film thickness of the conventional transmittance changing materials. The spot diameter is, therefore, eventually effectively reduced. The light reflected by the reflection film 14 is outputted in the direction of an arrow FB.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium for optically recording or reproducing information such as an optical disk, an optical card, an optical tape, etc., and is particularly suitable for recording information at high density. To an improved optical recording medium.

[0002]

2. Description of the Related Art CD is generally used as an optical recording medium, but recently, attempts have been made to record information at a higher density. Japanese Patent Application No. 2-969
Japanese Patent Laid-Open No. 26-26 discloses a technique that attempts such a high density. According to this, a nonlinear optical layer is provided on the light incident side of the record carrier. Then, due to the action of this nonlinear optical layer, the beam spot diameter of the incident light becomes small,
As a result, it becomes possible to perform high density information recording and reproducing.

As the non-linear optical layer, the light transmittance is increased by the light irradiation, and the light transmittance is almost restored to the original value when the light irradiation is stopped or other light irradiation is performed, such as gallium arsenide or indium. Antimony or the like is used. The transmittance changing substance has a nonlinear transmittance characteristic with respect to the incident light intensity, for example, as shown by a solid line GA in FIG.

Such transmittance characteristics have the effect of substantially reducing the spot diameter of the incident light beam. For example, when the incident light intensity and the transmittance are proportional to each other as shown by a dotted line GB in the figure, the light spot diameter is reduced to about 3/4. In the case of the graph GA in the same figure, the light spot diameter is further reduced to about 3/5.

According to the above-mentioned conventional technique, as shown in FIG. 4A, the transmittance changing film 102 is first formed on the main surface of the substrate 100 on which the unevenness corresponding to the pit row (or the guide groove) is formed. It is formed. Then, the transmittance changing film 102
A reflective film 104 and a protective film 106 are respectively formed on top.
When a light beam having a spot diameter SA as shown in FIG. 2B is incident on such an optical disc, the spot diameter SA is substantially reduced to SB by the action of the transmittance changing film 102, which is a pit. Will be incident on.
Therefore, even if the track interval is narrowed due to the high density of information recording, the information can be read out satisfactorily.

[0006]

However, when the transmittance changing substance is formed as a film by itself as in the prior art as described above, there are the following inconveniences. (1) Since a layer made of a transmittance changing substance is newly provided, productivity is reduced. (2) When the transmittance changing substance is formed by dissolution coating, the base material is dissolved and swelled by the solvent, resulting in damage to the base material. Further, with this method, it is difficult to make the thickness constant.

(3) When the transmittance changing substance is formed by a method such as vapor deposition with a vacuum film, it is difficult to increase the film thickness. For this reason, it is not possible to use a substance with a low efficiency of transmittance change, and the range of material selection is reduced. The present invention focuses on these points, and an object of the present invention is to provide an optical recording medium with good productivity that can effectively obtain good transmittance change characteristics.

[0008]

DISCLOSURE OF THE INVENTION The present invention uses a moldable polymer matrix material as a substrate material of an optical recording medium in which information is recorded or reproduced by irradiation of a light beam, and a light beam is used. The transmittance changing substance whose light transmittance changes according to the irradiation of 1) is mixed in the polymer matrix material.

[0009]

According to the present invention, the transmittance changing substance is dispersed or mixed in the substrate material, and a layer having only that substance is not formed. The spot diameter of the recording or reproducing light beam is reduced by the action of the transmittance changing substance when passing through the substrate.
The thickness of the substrate can be made uniform with good precision during molding, and a sufficient thickness can be obtained, so that the spot diameter can be reduced satisfactorily and effectively.

[0010]

Embodiments of the optical recording medium according to the present invention will be described below with reference to the accompanying drawings. <First Embodiment> First, a first embodiment of the present invention will be described with reference to FIG. This embodiment is a CD-RO
This is an example in which the present invention is applied to M and the like, and a part of a cross section orthogonal to the pit track is shown in the same figure. In the figure, the unevenness 12 corresponding to a pit is formed on the main surface of the substrate 10. On the main surface of the substrate 10, a reflective film 1 is further provided.
4. The protective film 16 is formed in order.

Of these, the substrate 10 is formed by mixing the transmittance changing substance in the substrate material. As the substrate material, an amorphous polymer such as PC (polycarbonate), PMMA (polymethylmethacrylate, acrylic), or polyolefin is used. Further, as the transmittance changing substance, for example, an inverse photochromic substance which is compatible with the matrix of the polymer or a metal coordination bond substance of a cyclic organometallic complex is used.

As the reverse photochromic substance, for example, a spiroselenazoline type substance such as spiroselenazolinobenzopyran is used. This material has a wavelength of 600n
It has a maximum absorption of light in the vicinity of m, and easily changes to a colorless body by irradiation with light of 600 nm, and the light transmittance remarkably increases. Further, it has a transmittance change characteristic that it returns to its original state immediately after the light is blocked.

Next, as the metal coordination bond substance of the cyclic organometallic complex, an appropriate ligand (for example, metal complex such as nickel, aluminum, iron, tin, other transition metal) is added to the phthalocyanine skeleton. , Pyridine, NH
A polar molecule such as _3, or an anion such as Cl ⁻ is bound to it. This substance causes the separation of coordination bonds upon irradiation with light having a wavelength of 600 nm to 700 nm to change the light absorption spectrum, which causes a large change in the light transmittance. However, it is returned to the original state by the recombination of ligands by light blocking. Even if such separation and recombination of the ligands is utilized, good light transmittance change characteristics can be obtained.

The substrate 10 is obtained by uniformly dispersing the transmittance changing substance in the substrate material as described above and then molding it into a predetermined shape by a known method such as injection molding. When PC and iron phthalocyanine (ligand pyridine) are used as the materials, the transmittance changing substance is dispersed in the substrate material by, for example, a kneading method. Specifically, the mixing ratio of PC and iron phthalocyanine is PC: iron phthalocyanine =
The weight ratio of 100: 0.2 is set to 3 near the melting temperature of PC.
The dispersion is carried out by heating to 00 ° C. and kneading with a screw in an injection molding machine. For injection molding, for example, the mold temperature is 100 ° C., the material filling time is 1 second, and the holding pressure is 20 kg /
cm ² 0.3 seconds, cylinder temperature 320 ℃, mold clamping pressure 2
It is carried out under the condition of 65 kg / cm ² .

When the substrate material is a UV curable polymer,
The substrate 10 is obtained by uniformly dispersing the transmittance changing substance therein and then molding it into a predetermined shape by irradiation with ultraviolet rays. For example, urethane-modified acrylate is used as the ultraviolet curable polymer, and spiroselenazolinobenzopyran is used as the transmittance changing substance. Specifically, the mixing ratio of the urethane-modified acrylate and the spiroselenazolinobenzopyran is the urethane-modified acrylate:
The weight ratio of spiroselenazolinobenzopyran = 100: 0.2 is used, and the wavelength of ultraviolet rays to be irradiated is 200 to 380 n.
m, the intensity is 120 W / cm ² , and the irradiation time is 3 seconds. At this time, by appropriately selecting the glass transition point and the viscosity of the ultraviolet curable polymer, it is possible to adjust the light change speed and the homodispersibility of the transmittance changing substance. The reflection film 14 and the protective film 16 are sequentially formed on the substrate 10 obtained as described above by a known method.

Next, the operation of the above embodiment will be described. The light beam for irradiating the pits 12 and reading information is incident on the optical disk from the substrate 10 side as shown by an arrow FA. By the way, in this embodiment, the substrate 10 has a composition in which the transmittance changing substance is mixed. Therefore, when the light beam travels into the substrate 10, the spot diameter is reduced by the transmittance changing substances.

The light beam with the reduced spot diameter is incident on the pit 12, reflected by the reflection film 14, further passes through the substrate 10, and is output from the optical disc as indicated by an arrow FB. This reflected light beam enters a photoelectric detection means (not shown), is converted into an electric signal here, and is then processed by a known method.

As described above, according to this embodiment, since the transmittance changing substance is mixed in the substrate material, the substrate 10 itself has a transmittance changing function. Therefore, in the case where the transmittance changing substance is formed alone, the inconvenience such as the decrease in productivity and the deterioration of the base does not occur.

Further, since the thickness of the substrate 10 is controlled by the precision of the mold at the time of molding, the variation in the thickness direction can be reduced and a uniform change in transmittance can be obtained. Since the transmittance can be effectively changed depending on the direction,
A large change in transmittance, that is, the effect of reducing the spot diameter can be obtained. In other words, it is possible to obtain a favorable change in transmittance even if a substance having a small change in transmittance is used.

<Second Embodiment to Fifth Embodiment> Next, the second to fifth embodiments of the present invention will be described with reference to FIG. The same reference numerals will be used for the same or corresponding components as those of the above-described embodiment.

First, the second embodiment will be described with reference to FIG. In this embodiment, the present invention is applied to an additionally recordable or rewritable optical recording medium.
As shown in the figure, the main surface of the substrate 10 is provided with irregularities corresponding to the guide grooves. The recording film 20 is formed on the main surface.
The reflective film 14 and the protective film 16 are formed on the recording film 20, respectively. The recording film 20 is made of a material such as an amorphous metal magnetic film capable of recording information by the magneto-optical effect or the like.

The third embodiment is shown in FIG. This embodiment has a structure in which the reflection film 14 is removed from the second embodiment, and information can be recorded and reproduced by any method of reflection and transmission of a light beam.

A fourth embodiment is shown in FIG. This embodiment is also an example of an optical recording medium on which additional recording or rewriting is possible similarly to the second and third embodiments. The enhancement film 30, the recording film 20, and the heat insulating film 3 are formed on the main surface of the substrate 10.
2, a reflective film 14, and a protective film 16 are laminated in that order. Among these, the enhancement film 30 is provided to increase the signal output by the interference effect, and the heat insulating film 32 is provided to reduce the heat conduction and improve the sensitivity.

A fifth embodiment is shown in FIG. This embodiment is an example of a read-only optical recording medium having a pit train similar to that of the first embodiment. A dielectric film 40, a reflective film 14, and a protective film 16 are formed in this order on the main surface of the substrate 10 having the irregularities corresponding to the pit rows. The dielectric film 40 is for increasing the signal output by the interference effect. In any of the above embodiments, the substrate 10
It is the same as the conventional one except.

The present invention is not limited to the above embodiment, and includes, for example, the following. (1) Any of various types of read-only discs, write-once discs, and rewritable discs other than those shown in the above embodiment are effective, and can be applied to cards, tapes, etc. other than discs.

(2) As a substrate material, PC, PMMA
However, other polymer materials such as polyolefin and epoxy resin are also applicable. The same applies to the transmittance changing substance, and for example, a fluorescent substance, a reversible temperature indicating ink, a phase change substance, etc. are also applicable. (3) In the above embodiment, the injection molding and ultraviolet curing methods are shown, but other methods such as compression molding and injection compression molding may be used.

[0027]

As described above, according to the optical recording medium of the present invention, the transmittance changing substance is mixed in the substrate material, so that the transmittance changing layer is formed at the same time when the substrate is molded and produced. There is an effect that the lightness can be improved and the light spot can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a first embodiment of an optical recording medium according to the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the light intensity incident on the transmittance changing film and the light transmittance of the transmittance changing film.

FIG. 4 is an explanatory diagram showing a relationship between a conventional read-only optical recording medium and a light spot.

[Explanation of symbols]

10, 100 ... Substrate, 12 ... Pit, 14, 104 ... Reflective film, 16, 106 ... Protective film, 20 ... Recording film, 30 ... Enhance film, 32 ... Thermal insulation film, 40 ... Dielectric film, 102 ...
Transmittance change film, FA, FB ... Arrow, GA, GB ... Graph, SA, SB ... Spot diameter.

Claims (1)

[Claims] 1. An optical recording medium in which information is recorded or reproduced by irradiation of a light beam, a moldable polymer matrix material is used as a substrate material of the medium, and light transmission is performed in response to the irradiation of the light beam. An optical recording medium, wherein a transmittance changing substance having a changing ratio is mixed in the polymer matrix material.