JPH01105340A - Information recording medium, its production and optical information recording method - Google Patents

Abstract

PURPOSE:To obtain a Direct Read After Write (DRAW) type recording medium having high recording sensitivity and high reflectivity by constituting a recording layer of a metallic layer which contains metals respectively having specific m.p. and thermal conductivities at prescribed weight % and is crystallized to have a specific reflectivity. CONSTITUTION:The recording layer on a substrate is formed of the metallic layer which contains the metal having <=700K m.p. and the metal having <=0.5W/cm.K thermal conductivity at the weight % ranging 70:30-30:70 and is so crystallized as to have >=60% reflectivity. The recording medium which has the high recording sensitivity and high reflectivity and is advantageous for DRAW type recording is then obtd.

Description

Detailed Description of the Invention [Field of the Invention] The present invention relates to an information recording medium that can be advantageously used to record and reproduce compact disc (CD) format signals using light, a method for manufacturing the same, and CD format signals, etc. The present invention relates to a method for recording information on an information recording medium.

[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 (CDs) generally contain EFM (Eight to Four) signals such as CD format signals.
(teenModulation) It consists of a plastic disk-shaped transparent substrate in which holes (pits) containing digital audio signal information are formed in advance, and a reflective thin film and a protective film made of metal such as aluminum provided on this substrate. . Information from a CD is read by irradiating the optical disc with a laser beam, and CD format signals and the like are read by changes in reflectance depending on the presence or absence of pits.

Based on the CD standard, the CD length is 1.2 to 1.4 m.
By rotating and recording at a constant linear speed of /second, the maximum recording time is 63 to 74 minutes with a bit width of 0.8 μm and a track pitch of 1.6 μm within the range of a signal surface inner diameter of 45 mm and a signal surface outer diameter of 116 mm. It is required to have time. Conventional audio CDs have pits formed on the substrate in advance (therefore, they do not have a recording layer) and are only for playback, and have the disadvantage that information cannot be recorded or edited. Therefore, D RA W (Direct Re
adAfter Write, writable) type CD
development is desired.

In addition, files such as documents, data, and still images can also be stored on CD-ROM (Read Only Memory).
y) or a DRAW type optical disc for CD-1 (Interactive).

The basic structure of a normal DRAW type information recording medium is as follows:
A disc-shaped transparent substrate made of plastic, glass, etc.
It has a recording layer provided thereon. For the recording layer, for example, metals such as In, Zn, Cd, Pb, and Sn with a melting point of 700 or less, and metals with a conductivity of 0.5 W/cm・K or less such as Bi, Sb, Se, and Te are used. Metal layers consisting of combinations with metals are known. 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 done by irradiating the optical disc with a laser beam.
Information is reproduced by detecting reflected light or transmitted light according to changes in the optical characteristics of the recording layer.

However, in such conventional DRAW-type information recording media, since the optical disk is rotated at a high linear velocity during recording, information cannot be recorded unless a wide pit interval is maintained, and it is not possible to record information at a high density at a slow linear velocity. Depending on the CD method used for recording, information could not be written.

Further, even if information could be recorded, commercially available CD players, which require a high reflectance to the laser beam during reproduction, could not read the information.

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 an optical information recording method using the optical disc have been proposed (Japanese Patent Laid-Open No. 61-237239).
However, these optical discs cannot be said to be sufficient for practical use in terms of recording sensitivity, reproduction sensitivity, etc.

[Object of the Invention] An object of the present invention is to provide a novel RAW type information recording medium, a method for manufacturing the same, and a method for optically recording on the information recording medium.

Another object of the present invention is to provide a method for optically recording a CD format signal on a DRAW type information recording medium.

A further object of the present invention is to provide an information recording medium on which a CD format signal can be recorded by the above method and which can be played back by a commercially available CD player.

[Summary of the Invention] The present invention provides information writing and/or optical information on a substrate.
Alternatively, in an information recording medium provided with a readable recording layer, the recording layer is made of a metal having a melting point of 700 or less and a metal having a thermal conductivity of 0.5 W/cm·K or less at a weight ratio of 700.
: Contains in the range of 30 to 30 : 70 and 60%
An information recording medium characterized by being a crystallized metal layer having a reflectance of 700 or more; The following manufacturing method can advantageously obtain the above information recording medium; and,
After forming a metal layer containing a metal with a thermal conductivity of 0.5 W/cm K or less in a weight ratio of 70:30 to 30:70, the entire surface thereof is irradiated with light to crystallize it. A method for producing an information recording medium, comprising: changing the metal layer into a recording layer having a reflectance of 60% or more; and: producing a digital signal by irradiating the recording layer of the information recording medium with light to form pits. An optical information recording method consists of recording information.

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

1゜The following metals with a melting point of 700 are In, Zn, Cd,
The information recording medium described above is made of at least one metal selected from Pb and Sn.

2゜The metal whose thermal conductivity is 0.5 W/cm・K or less is B
The information recording medium described above is made of at least one metal selected from i, -3b, Se, and Te.

3゜The metal with a melting point of 700 or less is In, and the metal with a thermal conductivity of 0.5 W/am・K or less is Se or Te.
The above information recording medium is characterized in that:

4゜Metal with melting point 700 and thermal conductivity 0.5W/c
The ratio of m/K to metal is 65:35 to 35 by weight
: The above-mentioned information recording medium is characterized in that it is within the range of 65.

5゜The above information characterized in that the metal layer is formed by co-evaporating or co-sputtering a metal having a melting point of 700 or less and a metal having a thermal conductivity of 0.5 W/cm K or less. recoding media.

Preferred embodiments of the method for manufacturing an information recording medium of the present invention are as follows.

1. The method for manufacturing the information recording medium, characterized in that the crystallization of the metal layer is carried out by irradiating the entire surface of the metal layer with light from a projector.

2゜Crystallization of the metal layer occurs when the light irradiation energy on the surface of the metal layer is 0.01 to 1, OOjo
The method for manufacturing an information recording medium as described above, characterized in that the method is carried out by irradiating light in the range of ule/cm2.

3. The method for producing the above information recording medium, characterized in that the crystallization of the metal layer is carried out by irradiating the entire surface of the metal layer with light from a xenon lamp.

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

1° The above digital signal causes the information recording medium to
The optical information recording method described above is characterized in that recording is performed by irradiating light onto the recording layer to form pits while rotating at a constant linear speed of 2.8 m/sec.

[Effects of the Invention] The information recording medium of the present invention is provided with a recording layer having the above structure and has high recording sensitivity and high reflectance.

Therefore, when a CD format signal is recorded on the information recording medium by forming pits at a slow linear velocity using the above method, since the recording layer of the information recording medium has a high reflectance, the recorded signal can be read with high precision using a commercially available CD player.

Further, the information recording medium used in the present invention can write EFM signals with an irradiation power of 10 mW or less. Therefore, the information recording medium of the present invention can be advantageously used as a DRAW type compact disc.

[Detailed Description of the Invention The information recording medium used in the optical information recording method of the present invention includes:
For example, it can be manufactured 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: polyethylene terephthalate. etc. Polyesters:
Mention may be made of polycarbonates and amorphous polyolefins. Among these, preferred are polymethyl methacrylate, polycarbonate, epoxy resin, amorphous polyolefin and polyethylene terephthalate, with polycarbonate being particularly preferred.

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, nitrocellulose, polyethylene,
Polymer substances such as polypropylene and polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (Si02, An, 0. etc.), inorganic fluorides (MgF2)
Inorganic substances such as

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 consisting of a polymer containing groups is provided.

The undercoat layer can be formed by, for example, 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 cording, dip coating, or extrusion coating.

Further, a layer of pregrooves may be provided on the substrate for the purpose of tracking grooves, or a layer of prepits may be provided for the purpose of forming unevenness representing information such as address signals. As a material for the layer such as the pregroove, a mixture of at least one type of acrylic acid monoester, diester, triester, and tetraester (or oligomer) and a photopolymerization initiator can be used.

The layer thickness of the layer such as pregroove is generally 0.05 to 100
It is in the range of μm, preferably in the range of 0.1 to 50 μm. Furthermore, in the case of a plastic substrate, pregrooves or the like may be formed directly on the substrate surface.

An intermediate layer such as chlorinated polyolefin, nitrocellulose, polystyrene, etc. may be provided on the substrate of the information recording medium of the present invention (via a pregroove layer or an undercoat layer if desired). For example, when a chlorinated polyolefin layer is provided, this can reduce the loss of thermal energy due to laser beam irradiation from the recording layer to the substrate due to thermal conduction, and also reduce the loss of thermal energy from the irradiated portion of the chlorinated polyolefin layer. Since gas is generated, bits can be easily formed, thereby increasing recording sensitivity and reducing reading errors (pit error rate).

The chlorinated polyolefin layer can be provided by dissolving the above-mentioned chlorinated polyolefin in a solvent to prepare a coating solution, and then applying and drying this coating solution onto the substrate (via an undercoat layer, etc. if desired). .

As a coating method, a spray method, a spin code method, a dip method, a roll coating method, a blade coating method, a doctor roll method, a screen printing method, etc. can be used. The layer thickness of the chlorinated polyolefin layer is generally 10 to 10
It is in the range of 00 or more, preferably in the range of 100 to 500 or more.

A recording layer is provided on the chlorinated polyolefin layer or on the substrate.

The recording layer of the present invention is a metal layer containing a metal with a melting point of 700 or less and a metal with a thermal conductivity of 0.5 W/cm·K or less, and the entire surface of the metal layer cannot be irradiated with light or heated. This is a recording layer in which the reflectance of the metal layer has been changed to a sufficiently high reflectance. The weight ratio of the metal with a melting point of 700 or less and the metal with a thermal conductivity of 0.5 W/cm·K or less is required to be in the range of 70:30 to 30:70.

The metals below the melting point of 700 are In, Zn, Cd, P
b and Sn are preferred, and In is particularly preferred.

In addition, the above metals with a thermal conductivity of 0.5 W/cm・K or less,
Bi, Sb%Se and Te are preferred, and Se is particularly preferred.

A metal with a melting point of 700 and a thermal conductivity of 0.5W/
A particularly preferred combination of Cm and the following metals is In.
and Se or In and Te.

Metals with a melting point of 700 and a thermal conductivity of 0.5 W/cm
・The ratio with metals below K is 65:35 to 35 by weight.
: The range of 65 is preferable, and the range of 55:45 is particularly preferable.
~45:55.

A metal layer formed by vacuum deposition using a combination of the above two types of metals itself exhibits relatively high recording sensitivity, but has a low reflectance. The reason for this is that the deposited metal is in an amorphous state.

Therefore, such an amorphous metal layer has a low reflectance and cannot be said to have sufficient performance as a recording layer that allows recorded signals to be read with high precision by a commercially available CD player.

The phase state of the metal layer changes from an amorphous state to a crystalline state by heat treatment, and the reflectance increases. The present inventors can efficiently change the metal layer from an amorphous state to a crystalline state by irradiating the metal layer with light,
It has been found that this allows a crystallized metal layer with high reflectance to be obtained. The recording layer thus obtained has a high reflectance sufficient to allow recorded signals to be read with high precision by a commercially available CD player. The information recording medium of the present invention has high sensitivity as described above,
By using a recording layer with a high reflectance, information is recorded not by phase change but by bit formation. This recorded information can then be read by a commercially available CD player.

When irradiating light to increase the reflectance of the metal layer (change it from an amorphous state to a crystalline state), the light irradiation energy on the surface of the metal layer is 0.01 to 1.00.
It is preferably in the range of 0.05 to 0.50 joule/cm', more preferably 0.05 to 0.50 joule/cm
The range is m2.

In addition, light sources used to irradiate the metal layer with light include a xenon lamp, high-pressure mercury lamp, carbon arc lamp, sodium lamp, laser light (gas: Ne,
He-Ne, Xe, C02-N2-He, solid nilby, glass, YAG, etc.) are preferred, and a xenon lamp is particularly preferred.

Further, the thickness of the recording layer is preferably in the range of 100 to 3000×, particularly preferably in the range of 200 to 1200×, from the viewpoint of ease of writing information and reflectance.

The recording layer is formed on the substrate by a known method such as vapor deposition, sputtering, or ion blasting using the above recording layer material. Since two or more metals are used in the present invention, co-evaporation or co-sputtering is preferably used.

However, if desired, an intermediate layer may be interposed between the substrate and the recording layer. The recording layer may be a single layer or a multilayer.

Preferably, a protective layer is provided on the recording layer. The protective layer is preferably a laminate of a soft protective layer made of a soft resin material and a hard protective layer made of a hard resin material. This laminate is laminated on the recording layer with the soft protective layer side facing the recording layer side. Examples of the soft resin material include polyurethane, polyvinylidene chloride, ethylene/vinyl acetate copolymer, silicone rubber, styrene/butadiene rubber, polyvinylidene chloride, and polyacrylic acid ester. Usually these are solution application, tex application,
It is applied onto the recording layer by a method such as melt coating, and is subjected to treatments such as drying and heating if necessary to form a soft protective layer. The thickness of the soft protective layer is usually in the range of 100λ to 5 μm, preferably in the range of 0.3 to 3 μm. Examples of hard resin materials include ultraviolet curing resins and thermosetting resins. Usually, these are applied onto the soft protective layer by a method such as solution coating, and if necessary UV irradiation is applied.
A hard protective layer is formed by processing such as heating. The thickness of the hard protective layer is usually in the range of 0.1 to 10 μm, preferably in the range of 1 to 3 μm.

The surface of the substrate opposite to the side on which the recording layer is provided is coated with inorganic substances such as silicon dioxide, tin oxide, and magnesium fluoride, or thermoplastic resins and photocurable resins to improve scratch resistance and moisture resistance. A thin film made of a polymeric material such as mold resin may be provided by a method such as vacuum deposition, sputtering, or coating.

A bonded type information recording medium can be manufactured by bonding two substrates having the above structure using an adhesive or the like. In an air sandwich type recording medium, at least one of the two disk-shaped substrates has the above-described structure, and the substrate is attached to one or both of the substrates via a ring-shaped outer spacer and an inner spacer, or to one or both of the substrates. Manufacture 1 can be carried out by joining via provided protrusions.

Next, information can be recorded using the above information recording medium by the optical information recording method of the present invention as described below. The present invention is particularly advantageous when recording CD format signals etc. at a slow constant linear velocity.
A method for recording a D format signal will be explained as an example.

First, while rotating the information recording medium at a constant linear velocity within the range of 1.2 to 2.8 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. The information recording medium of the present invention can record with a laser power of 10 mW or less, and has high sensitivity.

As a result, bits having a length of 0.70 to 4.0 μm are formed concentrically or spirally at intervals of 0.70 to 4.0 μm in the recording layer. EFM signal information such as a CD format signal is then written to the recording layer.

Signals may be recorded either on the grooves or between the grooves. At this time, recording for 60 minutes or more is possible with a recording medium whose signal surface has an inner diameter of 50 mm and an outer diameter of 115 mm.

During recording, it is preferable to perform tracking control using a tracking pregroove. If the recording medium is provided with pregrooves, the signal may be recorded either at the bottom of the group or in the area between the groups. With this method, for example, recording for 60 minutes or more is possible on a recording medium whose signal surface has an inner diameter of 50 mm and an outer diameter of 115 mm.

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. In the present invention, since the recording layer has a high reflectance of 60% or more on a plain plane, 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 of the present invention will be described. However, each of these aspects does not limit the invention.

[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.
07 μm in width, 0.8 μm in width, and 1.6 μm in pitch grooves were provided in a spiral shape), a chlorinated polyolefin was applied using a spin cord to a layer thickness of 200 to provide an intermediate layer. Then, on this intermediate layer,
In and Se were co-deposited at a ratio of 60% by weight: 40% by weight, respectively, to form a recording layer with a layer thickness of 1000X.

Next, the obtained recording layer was exposed to the light of a xenon lamp with an output of 1200W (manufactured by Tokyo Zenon ■, 5UNSTAR-5TOR).
OBOV8-2400S type) was irradiated from a distance of 20 cm. As a result, a crystallized recording layer was formed.

In this way, an information recording medium consisting of a substrate, an intermediate layer portion, and a recording layer was manufactured.

[Example 2] A record crystallized in the same manner as in Example 1 except that the ratio of In and Se in Example 1 was changed from 60% by weight: 40% by weight to 50% by weight: 50% by weight. An information recording medium having layers was manufactured.

[Comparative Example 1] An information recording medium was manufactured in the same manner as in Example 1 except that an amorphous recording layer was formed without irradiating the recording layer with a xenon lamp.

[Comparative Example 2] An information recording medium was manufactured in the same manner as in Example 1 except that In and A1 were co-deposited in a ratio of 60% by weight: 40% by weight, respectively, instead of In and Se.

[Comparative Example 3] An information recording medium was manufactured in the same manner as in Comparative Example 2, except that an amorphous recording layer was formed without irradiating the recording layer with a xenon lamp.

[Evaluation of information recording medium] A disc evaluation device (Naka
michi Disk evaluation device 0MS-1000) and E
Using an FM, IT-encoder (KEN-WOOD), a reference signal (8.15 Hz) was recorded as an EFM-CD format signal at a recording power of 8.0 mW and a constant linear velocity of 1.3 m/sec. The evaluation was AA if it was possible to record, and CC if it was not possible.

Next, the information recorded on the recording medium was reproduced using a commercially available CD player (Sony, D-50MKII). The evaluation was AA if playback was possible, and CC if playback was not possible.

The reflectance was measured using a spectrophotometer model 330 (manufactured by JASCO ■). (The light used for the measurement had a wavelength of 780 nm) The above measurement results are shown in Table 1.

Table 1 Reflectance (%) Recording Reproduction Example 1 70 AA AA2
7 2 A.A.
Comparative example 1 to A 50 A
ACC.

2 70 CG CG3
70 CG CG As is clear from the above table, the recording layer in Comparative Example 1 has a sensitivity that allows recording, but has a low reflectance for playback on a CD player. By irradiating it with xenon lamp light, the reflectance increases and reproduction becomes possible.

Comparative Example 2.3 uses Al1, which has a high reflectance, so the reflectance is high, but the sensitivity is low and recording is impossible.

Claims (1)

[Claims] 1. An information recording medium provided with a recording layer on a substrate that allows information to be written and/or read by light, in which the recording layer is made of a metal with a melting point of 700K or less and a thermal conductivity. 70:30 weight ratio with metal of 0.5 W/cm・K or less
30:70 and has a reflectance of 60% or more. 2. On the substrate, a metal with a melting point of 700K or less and a metal with a thermal conductivity of 0.5W/cm・K or less are placed in a weight ratio of 70:30.
After forming a metal layer containing a ratio within the range of ~30:70, the entire surface is irradiated with light to crystallize it, thereby changing the metal layer into a recording layer having a reflectance of 60% or more. A method for manufacturing an information recording medium. 3. On the substrate, there is a metal with a melting point of 700K or less and a thermal conductivity of 0.
．． Weight ratio of 70:30 to 5W/cm・K or less metal
Recording digital signal information by irradiating light onto the recording layer of an information recording medium provided with a crystallized recording layer including the ratio of 30:70 and having a reflectance of 60% or more to form pits. An optical information recording method consisting of: