JPH01217737A - Information recording medium - Google Patents

Abstract

PURPOSE:To enable optical recording by a CD system and reading of the recorded signal only by a commercially marketed CD player by incorporating fluoroplastic into an intermediate layer and In, GeS and Au into a recording layer. CONSTITUTION:The fluoroplastic is incorporated into the intermediate layer of the information recording medium which is provided with the recording layer capable of writing and/or reading information by a laser via the intermediate layer and is used for recording of the CD format signal and the In, GeS and Au are incorporated into the recording layer. The recording medium consisting of the combination of the fluoroplastic and the In, GeS and Au has an extremely high sensitivity and allows writing of the signal at a low irradiation power; in addition, said medium has >=60% reflectivity at a plain plane. The reading with the commercially marketed CD player is thereby enabled and the medium is usable as the DRAW (direct-read-after-write) type CD.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a DRAW type information recording medium used for optical recording in the CD system.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk, and can be used as a video disk, an audio disk, a large-capacity still image file, and a large-capacity computer disk memory. Among these information recording media, compact discs (CDs) are widely used for audio reproduction of music and the like.

Compact discs are generally CD four? -/Eight to Four signals, etc. (1) E F M (Eight to Four
(teenModulation) A plastic disk-shaped transparent substrate in which holes (pits) containing digital audio signal information are formed in advance, and an antenna provided on the plastic disk-shaped transparent substrate.
It consists of a reflective thin film and a protective film. C
Information is read from the optical disc by irradiating the optical disc with a laser beam, and the CD format signal and the like are read based on changes in reflectance depending on the presence or absence of pits.

Based on the CD standard, the CD is 11.2 to 1.4 m.
By rotating and reproducing at a constant linear speed of /sec, within the range of signal surface inner diameter 45 mm and signal surface outer diameter 116 mm, pit @ 0.81Lm,) rack pitch 1.61
Lm is required to have a maximum playback time of 74 minutes. Conventionally, such audio CDs have pits formed on the substrate in advance and are only for playback.
It had the disadvantage that information could not be recorded or edited.

Therefore, D RA W (Direct Read A
fterWrite, writable) type CD is desired.

In addition, files such as various documents, data, and still images can be stored on CD-ROM (Read On 12Mem).
or CD-I (Interactive)
) is desired.

On the other hand, the commonly known DRAW type information recording medium is
The basic structure is a disc-shaped transparent substrate made of plastic, glass, etc., and Bi, Sn, In,
It has a recording layer made of metal or metalloid such as Te.

Information is written on a recording medium by, for example, irradiating the recording medium with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in physical changes such as pit formation. Alternatively, information can be recorded by causing a chemical change such as a phase change to change its optical properties. Reading information from optical discs is also
This is performed by irradiating an optical disk with a laser beam, etc., and information is reproduced by detecting reflected light or transmitted light according to changes in the optical characteristics of the recording layer.

However, in such a RAW type information recording medium, information cannot be recorded unless it is rotated at a high linear velocity to ensure a wide pit interval. It was not possible to write information.

Further, even if information could be recorded, commercially available CD players, which require high reflectance, could not read the information.

Various studies have been conducted to increase the sensitivity of normal DRAW type information recording media, and optical discs with an intermediate layer between the substrate and the recording layer are attracting particular attention.For example, fluorine-based The invention using resin was published in Japanese Unexamined Patent Application Publication No. 5
It is disclosed in various publications such as JP-A No. 7-172535, JP-A-59-90246, and JP-A-55-163639.

However, these optical discs do not have high reflectance, and there is a problem in that commercially available CD players cannot read the information.

On the other hand, as an optical disc for recording CD format signals, an optical disc having a recording layer made of a dye or a pigment composition on a substrate and for recording CD format signals, and an optical information recording method using the optical disc have been proposed. However, these optical discs cannot be said to be sufficient for practical use in terms of recording sensitivity and reproduction sensitivity.

[Object of the Invention] An object of the present invention is to provide a RAW type information recording medium on which CD format signals can be optically recorded.

Another object of the present invention is to provide a DRAW type information recording medium on which a CD format signal that can be played by a commercially available CD player is recorded.

[Summary of the Invention] The present invention provides an information recording medium used for recording CD format signals, which is provided with a recording layer on a substrate through which information can be written and/or read by a laser via an intermediate layer. The information recording medium is characterized in that the intermediate layer contains a fluororesin, and the recording layer contains In, GeS, and Au.

Preferred embodiments of the information recording medium of the present invention are as follows.

l) The information recording medium, wherein the fluororesin is polytetrafluoroethylene.

2) The information recording medium, wherein the recorded signal is reproducible by a CD player.

3) The information recording medium, wherein the concentration of the metal on the substrate side is higher than the concentration on the recording layer surface side.

4) The concentration of the metal on the substrate side surface is 10 to 100
The above-mentioned information recording medium is characterized in that the content is within a range of % by weight.

[Effects of the Invention] As described above, the present invention basically consists of a substrate, an intermediate layer, and a recording layer, the intermediate layer containing a fluororesin, and the recording layer containing In%GeS and Au. By adopting such a configuration, optical recording can be performed using the CD method, and since the recording layer has a high reflectance, the recorded signals can be read by a commercially available CD player.

That is, the information recording medium of the present invention, which is a combination of the above-mentioned fluororesin and In, GeS, and Au, has extremely high sensitivity, allows EFM signals to be written with an irradiation power of less than (10n)W, and can be written on a flat surface. Since it has a reflectance of 60% or more, it can be read by a commercially available CD player and can be used as a DRAW MCD.

In particular, when the intermediate layer is formed by sputtering a fluororesin, the recording layer is also formed by a vapor deposition method such as sputtering, so the production line only requires a sputtering process.

This can be said to be very advantageous in terms of manufacturing.

Further, when the recording layer is formed by making Au, which is a highly reflective metal, exist with a high concentration gradient on the substrate side, recording and reproduction in the CD system can be performed with even higher accuracy.

[Detailed Description of the Invention] The information recording medium used for recording the CD format signal of the present invention can be manufactured, for example, by the following method.

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Optical properties, flatness, processability of the substrate,
In terms of ease of handling, stability over time, and manufacturing cost,
Examples of substrate materials include glass such as soda lime glass; acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; and polycarbonate. can be mentioned.

Among these, polymethyl methacrylate, polycarbonate, epoxy resin, and glass are preferred from the viewpoint of dimensional stability, transparency, and flatness.

The surface of the substrate on which the recording layer is provided has improved flatness,
An undercoat layer may be provided for the purpose of improving adhesive strength and preventing deterioration of the recording layer. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, and nitro. cellulose, polyethylene,
High molecular substances such as polypropylene and polycarbonate; organic substances such as nitrogen coupling agents; and inorganic oxides C3i02. A! 120 etc.), inorganic fluoride (MgF2 etc.), inorganic fluoride (MgF2
) and other inorganic substances.

In the case of a glass substrate, hydrophilic groups such as styrene/maleic anhydride copolymer and/or maleic anhydride are added to prevent adverse effects on the recording layer due to alkali metal ions and alkaline earth metal ions liberated from the substrate. Preferably, a subbing layer made of a polymer having acid groups is provided.

The undercoat layer can be formed, for example, by dissolving or dispersing the above-mentioned substance in a suitable solvent and then applying this coating solution to the substrate surface by a coating method such as spin cord, tip coat, or extrusion coat.

Also, on the substrate, for the purpose of forming tracking grooves or irregularities representing information such as address signals.

The material of the pre-groove layer, which may be provided with the pre-groove layer, is a mixture of at least one monomer (or oligomer) of acrylic acid monoester, diester, triester, and tetraester and a photopolymerization initiator. can be used.

The pre-groove layer is formed by first coating a mixture of the above acrylic ester and polymerization initiator on a precisely made matrix (stamper), then placing the substrate on top of this coating solution layer. , the substrate and the liquid phase are fixed by curing the liquid layer by irradiating ultraviolet rays through the substrate or the matrix.
Next, by peeling the substrate from the mother mold, a substrate provided with a pregroove layer is obtained. The thickness of the pregroove layer generally ranges from 0.05 to 100 gm, preferably from 0.1 to 50 pm.

Furthermore, in the case of a plastic substrate, pregrooves may be provided directly on the substrate surface.

The information recording medium of the present invention requires that an intermediate layer made of a fluororesin be provided on the substrate (via an undercoat layer and/or a pregroove layer if desired).

Examples of fluororesins include polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl trifluoride, polyhexafluoropropylene, polyvinyl fluoride, polyvinylidene fluoride, and tetrafluoroethylene-hexafluoroethylene copolymer. can be mentioned.

Among these, polytetrafluoroethylene (eg, Teflon, manufactured by Du Pont) is preferred.

The method of providing the above resins on the substrate as an intermediate layer is to use these resins as targets and introduce an inert gas such as Ar into a sputtering device to perform sputtering; or to perform sputtering using an organic solvent containing fluorine oil. A method is used in which the fluororesin is dissolved, a coating solution thereof is applied onto a substrate using a coating machine such as a spin cord, and then dried.

This makes it possible to reduce the loss of thermal energy due to laser beam irradiation from the recording layer to the substrate, etc., and also facilitates the formation of pits due to the generation of gas from the irradiated portion of the fluororesin layer. Therefore, recording sensitivity can be increased and reading errors (pit error rate) can be reduced. Therefore, it can be said that the information recording medium of the present invention using a fluororesin as an intermediate layer has extremely high sensitivity. Furthermore, since fluororesin has excellent water resistance, it also has the effect of protecting the recording layer by preventing moisture from entering from the substrate.

Furthermore, unlike many other resins, fluororesin is difficult to decompose at high temperatures, so it is possible to form a film by sputtering. Since the intermediate layer is formed by sputtering, and the recording layer is usually formed by a vapor deposition method such as sputtering, the production line requires only a sputtering process, which is very advantageous in terms of manufacturing.

The layer thickness of the fluororesin intermediate layer is generally 10 to 1000
It is in a large range, preferably in a range of 100 to 500.

Next, a recording layer is provided on the intermediate layer.

In, GeS, and Au are used as materials for the recording layer.

In addition to the above-mentioned In, GeS, and Au, the following metals and metal compounds may be included if desired.

Examples of metal compounds include CrS, Cr25. Cr
25=,MoS2,MnS,FeS,FeS2,Co
d, Co253, NiS, N12S, P b
S, Cu2S, Ag2
S, Z n S, In2S3, In252, G
e5x (0,5<X≦2.0), SnS, 5n
Metal sulfides such as S2, As2S3.5b2S* and Bi2S3; MgF2, CaF2 and Rh
Metal fluorides such as F s; and M o 01In2
0. Mention may be made of metal oxides such as In2O3, GeO and PbO.

Examples of metals include low melting point metals such as Te, Sn, Pb, and Bi, as well as Ag, An, Cu, Ga, Go, Mo, Ni, and S.
t, v, Be, Cr, Fe, Mn, Nb, Pd, Ti
, and metals with high surface tension such as Zn.

Metals with high surface tension such as Au also. From melting point and melting point 3
It has a high surface tension of 600 dyn/cs or more in the temperature range above 00°C, and by mixing and containing In and GeS, which have low boiling points, in the same layer, the recording layer material can be improved by the interaction between these substances. It is possible to improve the so-called r-drawing J during melting of the recording layer, and it is possible to easily form well-shaped beats in the recording layer. In particular, the composition of the recording layer of the present invention, ie, the combination of Au, In and GeS, facilitates the formation of good pits.

The indium content in the recording layer is generally 30 to 8
It is in the range of 0% by weight, preferably in the range of 30-50% by weight. GeS content is generally 10-50% by weight
It is preferably in the range of 20 to 30% by weight. The content of Au, which is a metal with high reflectivity, is generally in the range of 10 to 50% by weight, particularly preferably 2% by weight.
It is in the range of 5 to 40% by weight.

Further, in order to improve recording sensitivity and reading accuracy, in the present invention, the high reflectance metal Au is contained in the recording layer so that the concentration on the substrate side is higher than the concentration on the opposite recording layer surface side. For example, Au is present in the recording layer with a concentration gradient such that the concentration gradually decreases from the substrate side to the recording layer surface side.

The concentration of Au is 10 to 1 on the substrate side surface of the recording layer.
It is preferably in the range of 0.00% by weight.

Here, the concentration of Au in the recording layer refers to the ratio of the metal present on the cut surface when the recording layer is cut parallel to the surface direction, and the surface side of the recording layer refers to the proportion of the metal present on the cut surface when the recording layer is cut parallel to the surface direction. Refers to the surface that does not touch.

The recording layer is formed on the substrate by a method such as vapor deposition, sputtering, or ion blasting using the above-mentioned material. In order to increase the concentration of high-reflectance Au on the substrate side, for example, the heating current flowing through the high-reflectance Au evaporation source during the evaporation process can be controlled to change the amount of evaporated. This can be done by letting

The recording layer may be a single layer or a multilayer, but its layer thickness is generally from 300 to 20 mm in terms of optical density required for optical information recording.
It is in the range of 00 or more, preferably in the range of 700 to 1500 or more.

Since the above-mentioned high-reflectance Au exists with a high concentration gradient on the substrate side, pits are likely to be formed when information is recorded by laser light, so the output of the laser light can be reduced, and the recording sensitivity can be improved. Furthermore, since pits with good shapes can be formed, reading errors can be reduced when reading information.

Note that the surface of the substrate opposite to the side on which the recording layer is provided is coated with an inorganic substance such as silicon dioxide, tin oxide, or magnesium fluoride in order to improve scratch resistance and moisture resistance.
Alternatively, a thin film made of a polymeric substance such as a thermoplastic resin or a photocurable resin may be provided by a method such as vacuum evaporation, sputtering, or coating.

Note that a bonded type information recording medium can be manufactured by bonding two substrates having the above structure using an adhesive or the like. Furthermore, an air sandwich type recording medium can be manufactured by joining two disk-shaped substrates, at least one of which has the above configuration, via a ring-shaped outer spacer and an inner spacer. can.

Next, information is recorded on the information recording medium of the present invention by a recording method as described below.

First, while rotating the information recording medium at a constant linear velocity within the range of 1.2 to 1.4 m/sec, recording light such as semiconductor laser light is irradiated from the substrate side. Generally, a semiconductor laser beam having an oscillation wavelength in the range of 750 to 850 nm is used as the recording light. In addition, in the present invention, recording can be performed with an irradiation power of 10 mW or less,
High sensitivity.

As a result, pits with a length of 0.70 to 4.0 gm are formed in the recording layer. They are formed concentrically or spirally at intervals of OILm. EFM signal information such as a CD format signal is then written to the recording layer. Signals can be recorded either on the groove or between the grooves.
At this time, the inner diameter of the signal surface is 50 mm, and the outer diameter is 115 mm.
It is possible to record for more than 60 minutes using this recording medium.

Note that during recording, it is preferable to perform tracking control using tracking grooves.

Information can be reproduced by rotating the recording medium at the same constant linear velocity as described above, irradiating semiconductor laser light from the substrate side, and detecting the reflected light. Since it has a high reflectance of more than 60% on a plain surface, it can be read satisfactorily using a commercially available CD player.

Note that the information recording medium of the present invention includes a CD-ROM, a CD-ROM, and a CD-ROM.
It is essentially compatible with media recorded in CD format such as I.

Next, Examples and Comparative Examples of the present invention will be described.

However, each of these aspects does not limit the invention.

Blank space below [Example 1] Disc-shaped polycarbonate substrate with tracking grooves (outer diameter: 120 mm, inner diameter: 15 mm, thickness: 1.2
mm, depth 0.0mm in the range of inner diameter 45mm to outer diameter 116mm.
07JLm, width 0.8gm, pitch 1.6ILm grooves are provided in a spiral shape)
A Teflon intermediate layer having a thickness of 200 mm was provided by sputtering Teflon (manufactured by Nu Pant).

Then, on this Teflon intermediate layer, Au.

In and GeS were co-deposited at weight ratios of 35%, 40% and 25%, respectively, to form a recording layer having a layer thickness of 1000 layers. At this time, the heating current flowing through the Au evaporation source was controlled so that the elegance of Au was high on the substrate side and decreased as it approached the surface of the recording layer. Note that the Au concentration on the surface of the substrate side of the formed recording layer was 80% by weight.In this way, an information recording medium consisting of the substrate, the Teflon intermediate layer, and the recording layer was manufactured in this order.

[Comparative Example 1] In Example 1, T was used instead of Au, In and GeS.
An information recording medium consisting of a substrate, a Teflon intermediate layer, and a recording layer was manufactured in this order by performing the same operations as in Example 1 except that a recording layer of the same thickness was formed by using e alone.

[Evaluation of information recording medium 1 The recording layer of the above samples A and B was coated with a disc evaluation device (N
akamichi Disk evaluation device 0MS-1000
) and EFMzy: +-dar (KEN-WOOD), recording power 8.0 mW and constant linear velocity 1.3 m
A reference signal (8,15 Hz) was recorded as an EFM-CD format signal.

In addition, the recorded information can be stored on a commercially available CD player (5 on
y, Rho 50MKII).

As a result, the information recording medium of the present invention obtained in the example was able to perform both recording and reproduction using the CD method with high accuracy, but the information recording medium of Comparative Example 1 (conventional information recording medium) could be recorded, but playback was not possible.

This is because the reflectance of the recording layer (plain portion) of Example 1 was 60% at a wavelength of 780 nm, whereas the reflectance of the recording layer (plain portion) of Comparative Example 1 was 45%. It is estimated that a commercially available CD player designed with a reflectance of 70 to 80% could not reproduce information from the information recording medium obtained in Comparative Example 1.

Claims (1)

[Claims] 1. An information recording medium used for recording CD format signals, which is provided with a recording layer on a substrate through which information can be written and/or read by a laser via an intermediate layer, the intermediate layer containing a fluororesin. , and the recording layer contains In, GeS, and Au.