JPH04335223A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain the recording medium which is high in both of a modulation degree and reflectivity and is excellent in tracking property as well by providing specific relations between the depth of prepits and the film thickness of a recording layer and between the depth of pregrooves and the film thickness of the recording layer. CONSTITUTION:The following relation is provided between the depth of the prepits 8 and the film thickness of the recording layer 2: 0.15lambda<=nsdp- nd tp<=0.24l. The following relation is provided between the depth of the pregrooves and the film thickness of the recording layer 2: 0.02lambda<=nsdg- nd tg<=0.08lambda, where, ns is the refractive index of the substrate 1; nd is the refractive index of the recording layer 2; dp is the depth of the prepits; tp is the difference between the film thickness of the recording layer in the bottom of the prepits and the film thickness in the inter-prepit part; dg is the depth of the pregrooves; tg is the difference between the film thickness of the recording layer in the bottom of the pregrooves and the film thickness in the inter- pregroove part; lambda is the wavelength of a reproducing laser.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium on which information can be recorded using light.

0002

2. Description of the Related Art In recent years, information recording media using high energy density beams such as laser beams 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.

General DRAW (Direct Read)
The basic structure of an After Write (writable) type information recording medium is a disc-shaped transparent substrate made of plastic, glass, etc., and a Bi provided on this.
It has a recording layer made of a metal or metalloid such as Sn, In, Te, etc., or a dye such as a cyanine dye. 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 chemical changes to change its optical properties. Information is also read from an optical disk by irradiating the optical disk with a laser beam, and the information is reproduced by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

[0004] Compact discs (CDs), which are optical discs for information reproduction, generally contain EFM (Eight to Fourteen M) such as CD format signals.
It is composed of a plastic disc-shaped transparent substrate in which holes (pits) containing digital audio signal information are formed in advance, and a reflective thin film such as Al and a protective film provided thereon. 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, such CDs have a CD rating of 1.2~
By rotating and recording at a constant linear speed of 1.4 m/sec, it is possible to have a maximum recording time of 74 minutes at 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. requested. Conventionally, such audio CDs are play-only CDs with pits formed in advance on the substrate as described above. In addition, recently, instead of music information, CD-ROMs (Read Only) have been pre-recorded with information such as various documents and still images.
y Memory) has also been put into practical use. Such optical discs naturally have the disadvantage that information cannot be recorded or edited. Therefore, DRAW (Direct R
Ead After Write (writable) type CDs are being developed and some have been put into practical use.

[0005] The DRAW type CD is required to be able to play recorded information on a commercially available CD player. Since it is necessary for an optical disc to have a high reflectance in order to play it on a CD player, an optical disc with a high reflectance is desired. Since the reflectance of both the dye recording layer and the metal recording layer is generally as low as about 30 to 40%,
Dyes that can be easily coated to form a recording layer have manufacturing advantages over metals. Therefore, DRAW type C in which a dye recording layer and a reflective layer are laminated on a substrate.
D is being considered. As an example of such a DRAW type CD, an optical disc having a structure in which a dye recording layer, an Au reflective layer, and a protective layer are laminated in this order on a polycarbonate substrate is published by Nikkei Electronics (p. 107, 1989, 1).
published on the 23rd of May).

[0006] Such a DRAW type CD (conventional DR
(The same is true for AW type optical discs), generally there is a pre-pit area where pits are formed for recording information such as address information on the inner circumference side of the substrate, and a laser for recording information is guided on the outer circumference side of the pre-pit area. A pregroove for recording has a pregroove area (recording area) provided on the substrate. Furthermore, recently, an optical disc has been proposed that has the functions of both a playback CD and a DRAW type CD in a single disc (Japanese Patent Laid-Open No. 2-42652). That is, it is an optical disc having a recordable area having a pregroove on the substrate on the outer circumference side of a CD for reproduction, and a ROM area containing information such as music, that is, a reproduction-only area on the inner circumference side. This allows the user to record data and memos on the same disc while sharing the same information (music and programs) with other people.

A method for creating an optical disc having such a ROM area and a recordable area is disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2-4265.
According to Publication No. 2, the read-only area (ROM area) of the board
A dye recording layer is formed by coating a dye coating liquid on a groove having a diameter of 80 to 117 mm on the substrate, which is closer to the outer circumferential side. A reflective layer is formed on the read-only area and the recording layer. That is, a recording layer is not formed in the read-only area consisting of pre-pits, but a recording layer is provided only in the pre-groove area. Formation of such a recording layer is carried out by applying a dye coating liquid for the recording layer to the read-only area. However, if the dye coating liquid for the recording layer is applied to the read-only area, the pre-pits are filled with the coating liquid, so the actual pre-pits are The depth becomes shallower than the planned depth and the modulation degree decreases,
It becomes almost impossible to read the reproduced signal. Therefore, as described above, the dye recording layer is provided only in the pregroove area.

However, the above-mentioned Japanese Patent Application Laid-Open No. 2-42652
In an information recording medium that does not provide a dye recording layer in the read-only area and only provides a dye recording layer in the recordable area, as described in the publication, the portion where the dye recording layer is provided and the dye recording layer It is difficult to form a boundary with good reproducibility at a boundary with a portion where no Alternatively, there is a problem that the film thickness tends to become non-uniform at the end portion of the dye recording layer corresponding to the boundary portion, and a problem that eccentricity of the dye recording layer formed in an annular shape tends to occur. Therefore, during playback, errors such as loss of focus at this boundary are likely to occur. Furthermore, the information recording medium is actually divided into two areas: a read-only area and a recordable area on the outer circumference side. can only be manufactured. That is, it is difficult to provide a pregroove recordable area on the inner circumferential side of the read-only area or to provide a mix of the read-only area and the recordable area. Furthermore, there are restrictions on pre-recording application software in the reproduction-only area and on how to use the software.

[0009]

[Problems to be Solved by the Invention] In order to solve the above-mentioned problems, the present applicant formed a dye recording layer over the entire read-only area consisting of pre-pits and the recordable area consisting of pre-grooves, thereby eliminating the above-mentioned drawbacks. An application has already been filed for information recording media. Japanese Patent Application No. 2-264786 discloses that in consideration of the fact that pre-pits (and pre-grooves) are filled with a coating liquid, the pre-pits formed on the substrate are made deep in advance so that the reproduced signal does not become small. It is described that a designed board is used. In addition, the patent application Hei 2-
No. 191,257 describes an improved coating method that allows the dye coating solution to be applied so that the pre-pits (and pre-grooves) are not filled with the coating solution.

As a method for forming the dye recording layer, according to the method disclosed in Japanese Patent Application No. 2-191257, the film thickness at the bottom of the pre-pits and the film thickness at the space between the pre-pits, or the film thickness at the bottom of the pre-groove and the film thickness at the space between the pre-pits is adjusted. It is possible to form a film with a substantially uniform thickness. Of course, it is not possible to form a uniform film using conventional methods. Even if the above formation method is used, the shapes (particularly the depths) of the pre-pits and pre-grooves are not the same, so the way the pigment layer is filled into the pre-pits and pre-grooves is often uneven. Therefore, it is necessary to determine the depths of pre-grooves and pre-pits in consideration of how each dye layer is filled, but such a determining method is not known. Therefore, it is necessary to experimentally create a substrate by forming pre-pits and pre-grooves with different depths and in various combinations of depths, and then select a preferable substrate by repeating the formation of a dye layer on this. be. Furthermore, when the dye is changed, there is a problem in that a solvent composition suitable for the dye must be prepared in order to form a uniform film. On the other hand, even with the method of preparing the pre-pits to be formed on the substrate deep in advance as described in Japanese Patent Application No. 2-264786, if the dye coating liquid is changed, the filling method and the uniformity of the film thickness will differ. Experiments are required, and as mentioned above, there is also the problem that the degree of filling varies depending on the depth of the pre-pits (and pre-grooves).

Therefore, it is an object of the present invention to provide an information recording medium that has a read-only area and a recordable area, can obtain a reproduced signal with a high degree of modulation in both areas, and has excellent tracking characteristics. With the goal. Moreover, the present invention
It is an object of the present invention to provide an information recording medium having a read-only area and a recordable area that can be easily manufactured.

0012

[Means for Solving the Problems] The object is to provide a disc-shaped substrate having a read-only area consisting of pre-pits and a recordable area consisting of pre-grooves on its surface, on which information can be recorded by laser. In an information recording medium in which a recording layer and a reflective layer are provided in this order, the relationship between the depth of the pre-pits and the thickness of the recording layer is expressed by the following formula (I):
0.15λ≦ns dp −nd Δtp ≦
0.24λ (I), and the relationship between the depth of the pregroove and the thickness of the recording layer is expressed by the following formula (II): 0.02λ≦ns dg −nd Δtg
≦0.08λ (II) [However, ns represents the refractive index of the substrate, nd represents the refractive index of the recording layer, dp represents the depth of prepits (nm), and Δt
p represents the difference (nm) between the thickness of the recording layer at the bottom of the pre-pits and the thickness of the recording layer between the pre-pits, dg represents the depth of the pre-groove (nm), and Δtg represents the thickness of the recording layer at the bottom of the pre-groove. represents the difference (nm) between the film thickness of the recording layer and the film thickness of the recording layer between the pregrooves, and λ represents the wavelength of the laser used during reproduction. This can be achieved by an information recording medium that satisfies the following.

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

1) The above-mentioned information recording medium, wherein the recording layer is a layer made of a dye.

2) The formula (I) is the following formula (III):
0.17λ≦ns dp −nd Δtp
≦0.22λ (III) [However, ns
, nd, dp, Δtp and λ have the same meanings as defined above].

3) The formula (II) is the following formula (IV):
0.03λ≦ns dg −nd Δtg ≦
0.06λ (IV) [However, ns, nd
, dg, Δtg and λ have the same meanings as defined above].

4) The above information recording medium, wherein the dp is in the range of 80 to 300 nm.

5) The above-mentioned information recording medium, wherein the above-mentioned dg is in a range of 10 to 230 nm.

6) The above-mentioned information recording medium, wherein the above-mentioned Δtp is in a range of 0 to 120 nm.

7) The above-mentioned information recording medium, wherein the above-mentioned Δtg is in a range of 0 to 110 nm.

8) The information recording medium described above, wherein the recording layer is a phase change type recording layer made of a metal and/or a metal compound.

9) The information recording medium described above, further comprising a protective layer formed on the reflective layer.

10) An information recording medium characterized in that the information in the read-only area is an EFM signal in CD format.

[0024]

[Effects of the Invention] As described above, the depth of the pre-pit and the thickness of the recording layer satisfy the above formula (I), and the depth of the pre-groove and the thickness of the recording layer satisfy the formula (II) above. The created information recording medium having a read-only area and a recordable area has a high degree of modulation of a reproduced signal in both areas, and also has excellent tracking characteristics. That is, according to the present invention, for example, when using a new substrate, the thickness of the recording layer at the bottom of the pre-pits and pre-grooves can be determined by measuring the depth of the pre-pits and pre-grooves of the already created substrate. By coating and forming in a manner that satisfies the above formula, it is possible to easily manufacture an information recording medium having excellent properties as described above. In addition, for example, when changing the dye coating liquid, the dye coating liquid is applied to a substrate with known pre-pit and pre-groove dimensions, and a film is formed. Then, create a substrate with pre-pit and pre-groove depths that satisfy the above formula,
The above information recording medium can be easily manufactured by forming a dye recording layer on the substrate. In addition, in the case of a phase-change metal recording layer, the reflectance itself is low, and in order to obtain a high reflectance it is necessary to provide a reflective layer on top of the recording layer. In the case of an optical disc having a recordable area consisting of a region and a pregroove, it is possible to easily reproduce a reproduced signal with a high degree of modulation by using the relationship between the film thickness of the prepit, pregroove, and recording layer of the present invention. It is possible to easily obtain an information recording medium with excellent tracking characteristics.

[Detailed Description of the Invention] The information recording medium of the present invention has a basic structure in which a recording layer made of a dye and a reflective layer are formed in this order on a disk-shaped substrate.

The structure of the information recording medium of the present invention will be explained with reference to the accompanying drawings. FIG. 1 is a half-sectional perspective view showing an example of the information recording medium of the present invention. The information recording medium shown in FIG. 1 includes a disc-shaped substrate 1, a recording layer 2 provided on the substrate, a reflective layer 3 provided on the recording layer, and a protective layer 4 provided on the reflective layer. have. The above-mentioned information recording medium has a read-only area 5 in which prepits are provided as recording signals on the inner substrate, and a recordable area 6 in which information can be recorded in which pre-reg grooves are formed on the outer substrate. There is. Two or more read-only areas and two or more recordable areas may be provided. For example, even if a recordable area is provided on the inner circumferential side of the read-only area 5, a read-only area may be provided outside the recordable area 6. It's okay to be beaten. Note that, in general, the vicinity of the inner peripheral edge and the vicinity of the outer peripheral edge of the substrate are plain surfaces on which pits and grooves are not formed (not shown).

FIG. 2 is a partially enlarged sectional view of the vicinity of the boundary between the read-only area and the recordable area in FIG. The surface of the disc-shaped substrate 1 includes a read-only area 5 consisting of pre-pits 8 on which information is recorded, and a recordable area 6 consisting of pre-grooves 9 for guiding a laser for recording (or reproduction).
It consists of The dye recording layer 2 is formed on the entire surface of the read-only area 5 and the recordable area 6. A reflective layer 3 is provided to completely cover the dye recording layer, and a protective layer 4 is formed on the reflective layer.

Next, the relationship between the depth of the pre-pit and the thickness of the recording layer and the relationship between the depth of the pre-groove and the thickness of the recording layer according to the present invention will be explained.

FIG. 3 is a radial cross-sectional view of the prepits showing the relationship between the depth of the prepits and the thickness of the recording layer according to the present invention. Pre-pits 8 (within the read-only area 5) are formed on the surface of the disc-shaped substrate 1, and a recording layer 2 is formed on the surface so as to follow the shape of the pre-pits. A reflective layer and a protective layer are provided on the recording layer, but are not shown here. dp is the depth (nm) of the prepit, and tp is the film thickness (nm) at the bottom of the prepit of the recording layer.
), and tbp is the film thickness (nm) between prepits. Then, the difference between the film thickness tp at the bottom of the prepits of the recording layer and the film thickness tbp between the prepits is expressed as Δtp (=tp −tbp
).

In the present invention, the relationship between the depth of the prepits and the thickness of the recording layer (preferably the dye recording layer) is expressed by the following formula (I
) is satisfied. 0.15λ≦ns dp −nd Δtp
≦0.24λ (I)ns represents the refractive index of the substrate 1, nd represents the refractive index of the recording layer, and λ represents the wavelength of the laser used during reproduction. In the prepit portion, it is preferable that the reflectance is 0 because the signal strength is large, and generally the phase difference may be set to 1/4λ. However, it is also necessary to generate a push-pull signal for controlling tracking based on this phase difference, and this signal needs to be approximately equal to the signal strength of the pregroove within the same disc. For this reason, the inventors of the present invention have repeatedly studied and found that the phase difference {the above (ns
dp-nd Δtp ) is within the range of the above formula (I), it has become clear that a signal with a high modulation degree can be obtained in the pre-pit region and tracking can also be good.

FIG. 4 is a radial cross-sectional view of the pregroove of the present invention showing the relationship between the depth of the pregroove and the thickness of the recording layer. A pregroove 9 (inside the recordable area 6) is formed on the surface of the disc-shaped substrate 1, and a recording layer 2 is formed on the surface so as to follow the shape of the pregroove. A reflective layer and a protective layer are provided on the recording layer, but are not shown here. dg is the pregroove depth (n
m), tg is the film thickness (nm) at the bottom of the pregroove of the recording layer, and tbg is the film thickness (nm) at the part between the pregrooves (land part). Then, the difference between the film thickness tg at the bottom of the pregroove of the recording layer and the film thickness tbg between the pregrooves is expressed as Δ in the following formula (I).
This corresponds to tg (=tg-tbg).

In the present invention, the relationship between the depth of the pregroove and the thickness of the recording layer (preferably the dye recording layer) is expressed by the following formula (
II) is satisfied. 0.02λ≦ns dg −nd Δtg
≦0.08λ (II) ns represents the refractive index of the substrate 1, nd represents the refractive index of the recording layer, and λ represents the wavelength of the laser used during reproduction. In the pre-groove area, the reflectance is high in the unrecorded state (
For example, a CD) is preferable, and the phase difference may be set to 0 for that purpose. However, it is also necessary to generate a push-pull signal for controlling tracking based on this phase difference, and this signal needs to be approximately equal in signal strength to the signal intensity of prepits in the same disk. Therefore, after repeated studies by the present inventors, the fact that the phase difference {which corresponds to (ns dp - nd Δtp ) above} is within the range of formula (II) above is the reason for the high reflectance in the pregroove region. It became clear that a signal could be obtained and tracking was also good.

The above formula (I) is further transformed into the following formula (III)
: 0.17λ≦ns dp −nd Δt
p ≦0.22λ (III) [However, n
s , nd , dp , Δtp and λ have the same meanings as defined above], and the above formula (II) preferably satisfies the following formula (IV): 0.
03λ≦ns dg −nd Δtg ≦0.06λ
(IV) [However, ns, nd, dg,
Δtg and λ have the same meanings as defined above].

[0034] Furthermore, the above dp (depth of the bottom of the pre-pit) is preferably in the range of 80 to 300 nm,
The above dg (depth of the bottom of the pregroove) is 10 to 23
It is preferably in the range of 0 nm. Furthermore, the above Δtp
(Film thickness at the bottom of the pre-pits and between the pre-pits)
The difference is preferably in the range of 0 to 120 nm,
The above Δtg (film thickness at the bottom of the pregroove and the area between the pregrooves) is preferably in the range of 0 to 110 nm. ns (refractive index of the substrate) is generally between 1.4 and 1.7 for plastic substrates, for example 1.58 for polycarbonate substrates. , nd (refractive index of the dye recording layer) is generally between 1.4 and 4.0, for example, in the case of indolenine cyanine dyes, it is between 2.0 and 3.5.
It is in.

[0035] The information recording medium of the present invention can be created by, for example,
A dye recording layer is coated and formed on a substrate having pre-pits and pre-grooves of a certain size, and the way the dye recording layer is filled into the pre-pits and pre-grooves, that is, the film thickness at each part, is measured, and then the above formula is satisfied. A substrate having pre-pit and pre-groove depths as described above is prepared, and then manufacturing is performed. Alternatively, by measuring the depth of pre-pits and pre-grooves in already created substrates,
The coating method may be changed so that the film thickness at the bottom of the pre-pits and pre-grooves satisfies the above formula, and after the coating method is established, manufacturing may be performed.

The information recording medium of the present invention can be manufactured, for example, by the method described below.

The disc-shaped substrate of the present invention can be arbitrarily selected from various materials used as substrates of conventional information recording media. Examples of the substrate material of the present invention include glass; polycarbonate; acrylic resin such as polymethyl methacrylate; vinyl chloride resin such as polyvinyl chloride and vinyl chloride copolymer; epoxy resin; amorphous polyolefin and polyester. They may be used together if desired. Note that these materials can be used in the form of a film or as a rigid substrate. Among the above materials, polycarbonate is preferred in terms of moisture resistance, dimensional stability, cost, and the like.

An undercoat layer may be provided on the surface of the substrate on which the recording layer is provided for the purpose of improving planarity, adhesion, sensitivity, and preventing deterioration of the recording layer. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, styrene/maleinate anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene/vinyltoluene copolymer, and chlorosulfonated polyethylene. , nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, polyimide, vinyl acetate/vinyl chloride copolymer,
Examples include polymeric substances such as ethylene/vinyl acetate copolymer, polyethylene, polypropylene, and polycarbonate; and organic substances such as silane coupling agents.

The undercoat layer is prepared by, for example, dissolving or dispersing the above-mentioned substance in a suitable solvent to prepare a coating solution, and then applying this coating solution to the substrate surface by a coating method such as spin coating, dip coating, or extrusion coating. It can be formed by The thickness of the undercoat layer is generally 0.
It is in the range of 0.005 to 20 μm, preferably 0.01 to 20 μm.
The range is 10 μm.

Pre-pits and tracking grooves (pre-grooves) representing information such as address signals or music information are formed on the disc-shaped substrate (or undercoat layer) of the present invention. When using a resin material such as the above-mentioned polycarbonate, it is preferable that pre-pits and pre-grooves are provided directly on the substrate by injection molding or extrusion molding of the resin material.

[0041] Pregroove and the like may also be formed by providing a pregroove layer. As the material for the pregroove layer, 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 pregroove layer is formed by first coating a mixture of the above-mentioned acrylic ester and polymerization initiator on a precisely made matrix (stamper), and then placing the substrate on top of this coating layer. The liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase. Next, by peeling the substrate from the mother mold, a substrate provided with a pregroove layer is obtained. The thickness of the pregroove layer is generally 0.
In the range of 0.05 to 100 μm, preferably 0.1 to 5
It is in the range of 0 μm.

A recording layer is provided on the disk-shaped substrate. When forming a dye recording layer as a recording layer, examples of dyes used in the present invention include indolenine dyes,
Cyanine dyes such as imidazoquinoxaline dyes, indolizine dyes, phthalocyanine dyes, naphthalocyanine dyes, pyrylium/thiopyrylium dyes,
Azulenium pigment, squalirium pigment, Ni, C
Metal complex dyes such as r, naphthoquinone/anthraquinone dyes, indophenol dyes, indoaniline dyes, triphenylmethane dyes, triallylmethane dyes, merocyan dyes, oxonol dyes, aminium/diimmonium dyes Mention may be made of dyes and nitroso compounds.

To form the dye layer, a coating solution is prepared by dissolving the above dye, and optionally a binder, a metal complex dye, or an aminium/diimmonium dye (quencher) in a solvent. This can be done by coating the surface of the substrate to form a coating film and then drying it.

Examples of the solvent for preparing the dye coating solution include esters such as ethyl acetate, butyl acetate, and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone, and methyl isobutyl ketone, dichloromethane,
, halogenated hydrocarbons such as 2-dichloroethane and chloroform, ethers such as tetrahydrofuran, ethyl ether and dioxane, alcohols such as ethanol, n-propanol, isopropanol and n-butanol, amides such as dimethylformamide, 2, 2, 3, 3
- Fluorinated solvents such as tetrafluoropropanol can be mentioned. In addition, these non-hydrocarbon organic solvents may include aliphatic hydrocarbon solvents, as long as the amount is within 50% by volume.
It may also contain hydrocarbon solvents such as alicyclic hydrocarbon solvents and aromatic hydrocarbon solvents. Various additives such as antioxidants, UV absorbers, plasticizers, and lubricants may be further added to the coating liquid depending on the purpose.

[0045] When a binder is used, the binder includes:
For example, cellulose derivatives such as gelatin, nitrocellulose, and cellulose acetate, natural organic polymer substances such as dextran, rosin, and rubber; and hydrocarbon resins such as polyethylene, polypropylene, polystyrene, and polyisobutylene, polyvinyl chloride, polyvinylidene chloride, Vinyl resins such as polyvinyl chloride and polyvinyl acetate copolymers,
Synthetic organic polymers such as initial condensates of acrylic resins such as polymethyl acrylate and polymethyl methacrylate, polyvinyl alcohol, chlorinated polyolefins, epoxy resins, butyral resins, rubber derivatives, and thermosetting resins such as phenol/formaldehyde resins. Can list substances. Application methods include spray method, spin coating method,
Examples include a dip method, a roll coating method, a blade coating method, a doctor roll method, and a screen printing method. When a binder is used in combination as a material for the dye layer, the ratio of the dye to the binder is generally in the range of 0.01 to 99% (weight ratio), preferably in the range of 1.0 to 95% (weight ratio). It is in.

[0046] A method for forming the film thickness at the bottom and the intervening part of pre-pits and pre-grooves to be almost the same is disclosed in Japanese Patent Application No.
The method described in Japanese Patent No.-191257 can be used. The solvent for the dye coating solution is a good solvent for the dye to be used (preferably a solvent that can dissolve 2% by weight or more of the dye to be used at the coating temperature of the dye solution) and a poor solvent for the dye to be used (preferably a dye solution). It is preferable to use a mixture with a solvent that does not dissolve 2% by weight or more of the dye used at the coating temperature. In this case, it is necessary that the good solvent and the poor solvent are compatible, and that the evaporation rate of the poor solvent is not greater than the evaporation rate of the good solvent at the above coating temperature. When applying the dye coating liquid onto the substrate by a spin coating method, a device and method known per se can be used. The above dye solution,
Generally 0-100°C, especially 5-80°C, more especially 10-80°C
Preferably, it is applied at a temperature of 60°C. The rotation speed of the substrate is generally 10 to 1000 when applying the dye solution.
r. p. m. , especially from 100 to 500 r. p. m. When drying the pigment coating, it is generally
00~10000r. p. m. , especially 500-7000
r. p. m. , more particularly from 700 to 4000 r. p. m.
It is preferable to

Further, when forming a phase change type recording layer made of metal as the recording layer, the recording layer material may be Te, G
e, Sn, O, In, Se, Tl, Co, Sb, Se,
Mention may be made of Ag and Zn. Among these,
Te, Sn, In, Se, Ge, Sb and Se are preferred. These may be used alone or in combination of two or more. The phase change recording layer can be formed on the substrate, for example, by vacuum evaporation, sputtering or ion plating of the above metals. For example, In
- The thickness of the recording layer made of Sb.Te is preferably 15 to 25 nm. When a phase change type recording layer is provided, it is preferable to form layers of oxide films such as Al2O3 above and below the recording layer to prevent the recording layer from undergoing changes beyond phase change, such as the formation of pits. Al2O3 on recording layer
The thickness of the layer is preferably 80 to 120 nm, and the thickness of the Al2O3 layer below the recording layer is preferably 50 to 200 nm.

An intermediate layer made of chlorinated polyolefin, nitrocellulose or fluororesin may be provided between the recording layer and the substrate.

A reflective layer is provided on the substrate and the recording layer. The light reflective material that is the material of the reflective layer is a material that has a high reflectance to laser light, examples of which are:
Mg, Se, Y, Ti, Zr, Hf, V, Nb, Ta,
Cr, Mo, W, Mn, Re, Fe, Co, Ni, Ru
, Rh, Pd, Ir, Pt, Cu, Ag, Au, Zn,
Cd, Al, Ga, In, Si, Ge, Te, Pb, P
Mention may be made of metals and metalloids such as O, Sn, Bi, etc. Among these, preferred are Al, Au, and C.
r and Ni. These substances may be used alone, or in combination of two or more or as an alloy. The reflective layer can be formed on the substrate, for example, by vacuum deposition, sputtering, or ion plating of the light reflective material described above. The thickness of the reflective layer is generally in the range of 10 to 300 nm.

Further, it is preferable that a protective layer is provided on the reflective layer for the purpose of physically and chemically protecting the recording layer and the like. This protective layer may also be provided on the side of the substrate where the recording layer is not provided for the purpose of increasing scratch resistance and moisture resistance. Examples of materials used for the protective layer include Si
O, SiO2, MgF2, SnO2, Si3 N4
and organic substances such as thermoplastic resins, thermosetting resins, and UV curable resins.

The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic onto the recording layer (reflection layer) and/or the substrate via an adhesive layer. Alternatively, it may be provided by methods such as vacuum deposition, sputtering, and coating. In the case of a thermoplastic resin or a thermosetting resin, it can also be formed by dissolving these in an appropriate solvent to prepare a coating liquid, then applying this coating liquid and drying it. In the case of a UV curable resin, it can also be formed by preparing a coating liquid as it is or by dissolving it in an appropriate solvent, applying this coating liquid, and curing it by irradiating it with UV light. Various additives such as antistatic agents, antioxidants, and UV absorbers may be further added to these coating liquids depending on the purpose. When coating the protective layer forming material directly on the recording layer, coat polybutadiene or the like on the recording layer to protect the recording layer from the dissolving action of the coating liquid for the protective layer (in this case, use a solvent that does not dissolve the recording layer). It is preferable to provide the intermediate layer by using The middle class is
A thin film of metal or the like may be provided by vapor deposition. The thickness of the protective layer is generally in the range of 0.1 to 100 μm.

Furthermore, instead of forming a protective layer on the recording layer, the recording layer may be protected by providing a plastic film on the recording layer by welding it to the inner and outer peripheries of the substrate.

In the present invention, the information recording medium may be a single substrate having the above-described structure, or alternatively, two substrates having the above-described structure may be placed facing each other so that the recording layer is on the inside, and an adhesive or the like is applied to the medium. A laminated type recording medium can also be manufactured by bonding using. Alternatively, an air sandwich type recording medium is manufactured by using a substrate having the above structure as at least one of two disc-shaped substrates and joining them via a ring-shaped inner spacer and a ring-shaped outer spacer. You can also. The information recording medium of the present invention can be manufactured by the method described above.

The information recording and reproducing method is carried out using the above information recording medium, for example, as follows. First, the information recording medium is moved at a constant linear velocity (1.
Recording light such as semiconductor laser light is irradiated from the substrate side while rotating at a constant angular velocity (2 to 1.4 m/sec) or at a constant angular velocity. Irradiation of this light causes pits (holes) to be formed in the recording layer, resulting in deformation and alteration of the substrate surface, or by discoloration of the recording layer, changes in the state of association, etc., and the refractive index changes. It is thought that information is recorded by. Recording light is 550nm to 850nm
A semiconductor laser beam having an oscillation wavelength in the range of is used.

Reproduction of the information recorded in the above manner is carried out by irradiating semiconductor laser light from the substrate side while rotating the information recording medium at the same constant linear velocity as above, and detecting the reflected light. be able to. Incidentally, in the case of a flexible disk, etc., the laser beam irradiation may be performed from the recording layer side.

[0056]

[Examples] Examples and comparative examples of the present invention will be described below. However, these examples do not limit the invention.

[Example 1] Disc-shaped polycarbonate substrate; (1) Dimensions: outer diameter 120 mm, inner diameter 15 mm, thickness 1.2 mm, refractive index 1.58 (2) Diameter 44-47 mm region: track pitch is 1
．． 6 μm, pre-groove half-value width of 0.8 μm, and a groove with a depth of 37 nm. (3) Diameter 47-70 mm region: Track pitch is 1
．． 6μm, pre-pit half width 0.6μm, depth 1
A concave portion of 10 nm was formed. (4) A region with a diameter of 70 to 116 mm: a groove with a track pitch of 1.6 μm, a pregroove half width of 0.8 μm, and a depth of 37 nm was prepared as a substrate for an optical disk.

The following dye A (refractive index: 2.8): Dye A

[0059]

[Chemical formula 1]

[0060] 3.25g Dye B below: Dye B

[0061]

[Case 2]

0.325 g was dissolved in a mixed solvent consisting of 75 ml of 2,2,3,3-tetrafluoro-1-propanol, 20 ml of ethyl cellosolve, and 5 ml of tetrachloroethane by applying ultrasonic waves for 1 hour to record the dye. A layer coating solution was prepared.

[0063] The coating solution was applied from the inner peripheral side of the disc-shaped polycarbonate substrate by spin coating at a rotation speed of 20.
After applying for 5 seconds at a speed of 0 rpm, apply at a speed of 50 rpm per second.
Increase the speed by pm to 2000 rpm, 2000
It was dried by holding at rpm for 30 seconds to form a dye recording layer having the thickness shown below. (1) Bottom of prepits in diameter 47-70mm region: 125nm (2) Part between prepits in diameter 47-70mm region: 120nm (3) Diameter 7
Pregroove bottom in 0-116mm area: 125n
m (4) Area between pregrooves in diameter 70-116mm region: 120nm

A reflective layer having a thickness of 100 nm was formed on the dye recording layer by DC sputtering (Ar pressure: 2 Pa, power: 200 W) in an area having a diameter of 42 to 118 mm.

Furthermore, on the reflective layer, an ultraviolet curing resin (
Product name: 3070, manufactured by Three Bond Co., Ltd.) was applied by spin coating at a rotation speed of 200 rpm, leveled at a rotation speed of 1500 rpm for 30 seconds, and then irradiated with ultraviolet rays (high pressure mercury lamp 200 W/cm) for 10 seconds. Cured, layer thickness 2 μm (layer thickness 2 μm on outer peripheral end surface)
A protective layer of ~10 μm) was formed.

In this manner, an information recording medium consisting of a substrate, a dye recording layer, a reflective layer and a protective layer was manufactured.

[Example 2] In Example 1, the pre-pit depth was set to 110 mm as a disc-shaped polycarbonate substrate.
Changed the pregroove depth from 37 nm to 105 nm.
An information recording medium having a recording layer having the following thickness was manufactured in the same manner as in Example 1 except that the thickness was changed from nm to 25 nm. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
0nm

[Example 3] Example 1 except that a disk-shaped polycarbonate substrate was used in which the pre-pit depth was changed from 110 nm to 115 nm and the pre-groove depth was changed from 37 nm to 40 nm. An information recording medium having a recording layer having the thickness shown below was manufactured in the same manner as in Example 1. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
0nm

[Example 4] A recording layer having the following film thickness was prepared in the same manner as in Example 1, except that a disk-shaped polycarbonate substrate was used in which the pre-pit depth was changed from 110 nm to 90 nm. An information recording medium having the following was manufactured. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
0nm

[Example 5] The following film thickness was recorded in the same manner as in Example 1, except that a disk-shaped polycarbonate substrate was used with the pregroove depth changed from 37 nm to 50 nm. An information recording medium having layers was manufactured.

[Comparative Example 1] In Example 1, the prepit depth was set to 110 mm as a disc-shaped polycarbonate substrate.
Change the pregroove depth from 37 nm to 170 nm.
An information recording medium having a recording layer having the following thickness was manufactured in the same manner as in Example 1 except that the thickness was changed from nm to 80 nm. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
0nm

[Comparative Example 2] Example 1 except that a disk-shaped polycarbonate substrate was used in which the pre-pit depth was changed from 110 nm to 80 nm and the pre-groove depth was changed from 37 nm to 50 nm. An information recording medium having a recording layer having the thickness shown below was manufactured in the same manner as in Example 1. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
0nm

[Example 6] In Example 1, the mixed solvent of the dye coating solution was changed to 2,2,3,3-tetrafluoro-
1-propanol 68ml, ethyl cellosolve 25ml
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1, except that the mixed solvent was changed to 7 ml of tetrachloroethane and 7 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 115 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 11
5nm

[Example 7] In Example 1, the mixed solvent of the dye coating solution was changed to 2,2,3,3-tetrafluoro-
1-propanol 70ml, ethyl cellosolve 20ml
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1, except that the mixed solvent was changed to 10 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 110 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 11
0nm

[Example 8] A disc-shaped polycarbonate substrate in Example 1 with the pre-pit depth changed from 110 nm to 170 nm and the pre-groove depth changed from 37 nm to 80 nm was used, and dye coating was performed. The mixed solvent of the liquid is 2,2,3,3-tetrafluoro-
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1 except that 100 ml of 1-propanol was used as the single solvent. (1) Bottom of pre-pit: 135 nm (2) Area between pre-pits: 95 nm (3) Bottom of pre-groove: 125 nm (4) Area between pre-groove:
95nm

[Comparative Example 3] In Example 1, the mixed solvent for the dye coating solution was 45 ml of 2,2,3,3-tetrafluoro-1-propanol and 40 ml of ethyl cellosolve.
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1, except that the mixed solvent was changed to 15 ml of tetrachloroethane and 15 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 105 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 10
5nm

[Example 9] In Example 1, a disc-shaped polycarbonate substrate was used in which the pre-pit depth was changed from 110 nm to 140 nm, and the pre-groove depth was changed from 37 nm to 60 nm, and dye coating was performed. The mixed solvent of the liquid is 2,2,3,3-tetrafluoro-
1-propanol 45ml, ethyl cellosolve 40ml
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1 except that the mixed solvent was changed to 15 ml of tetrachloroethane. (1) Pre-pit bottom: 130 nm (2) Pre-pit space: 105 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 10
5nm

[Example 10] In Example 1,
A disk-shaped polycarbonate substrate was used in which the pre-pit depth was changed from 110 nm to 180 nm and the pre-groove depth was changed from 37 nm to 95 nm, and the dye in the dye coating solution was 1.75 g of the following dye C and the above dye. Change to 0.175g of B, and change the mixed solvent to 2, 2, 3,
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1 except that 100 ml of 3-tetrafluoro-1-propanol was used as the single solvent. (1) Pre-pit bottom: 145 nm (2) Pre-pit space: 100 nm (3) Pre-groove bottom: 140 nm (4) Pre-groove space: 10
0nm dye C (refractive index: 2.9):

[0079]

[Chemical formula 3]

[Example 11] In Example 1, the depth of the pre-pits was set to 11 for the disc-shaped polycarbonate substrate.
Change the pregroove depth from 0nm to 250nm,
Using a dye whose wavelength was changed from 37 nm to 165 nm, the dye in the dye coating solution was 2.6 g of the following dye D and 0.2 g of the above dye B.
An information recording medium having a recording layer with the following thickness was prepared in the same manner as in Example 1 except that the mixed solvent was changed to 100 ml of 2,2,3,3-tetrafluoro-1-propanol as a single solvent. was manufactured. Dye D (refractive index: 2.7):

[0081]

[Chemical formula 4] (1) Pre-pit bottom: 210 nm (2) Pre-pit space: 120 nm (3) Pre-groove bottom: 200 nm (4) Pre-groove space: 12
0nm

[Example 12] In Example 1,
A disc-shaped polycarbonate substrate with pre-pit depth changed from 110 nm to 105 nm and pre-groove depth changed from 37 nm to 30 nm was used, and the mixed solvent of the dye coating solution was 2,2,3,3- 75 ml of tetrafluoro-1-propanol, 20 ml of propylene glycol monomethyl ether and 5 ml of tetrachloroethane
An information recording medium having a recording layer having the thickness shown below was manufactured in the same manner as in Example 1 except that the mixed solvent was changed to ml. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 125 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
5nm

[Example 13] In Example 1,
A disk-shaped polycarbonate substrate with pregroove depth changed from 37 nm to 35 nm was used, and the mixed solvent of the dye coating solution was 75 ml of 2,2,3,3-tetrafluoro-1-propanol and 2 diisobutyl ketone.
An information recording medium having a recording layer with the following thickness was produced in the same manner as in Example 1 except that the mixed solvent was changed to 0 ml and 5 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 122 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
2nm

[Example 14] In Example 1,
The mixed solvent of the dye coating solution was 75 ml of 2,2,3,3-tetrafluoro-1-propanol and 20 ml of ethyl caprylate.
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1, except that the mixed solvent was changed to 5 ml of tetrachloroethane and 5 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 122 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
2nm

[Example 15] In Example 1,
The mixed solvent of the dye coating solution was 75 ml of 2,2,3,3-tetrafluoro-1-propanol and 20 ml of 1-pentanol.
An information recording medium having a recording layer having the thickness shown below was produced in the same manner as in Example 1 except that the mixed solvent was changed to 5 ml of 1 and 5 ml of tetrachloroethane. (1) Pre-pit bottom: 125 nm (2) Pre-pit space: 122 nm (3) Pre-groove bottom: 125 nm (4) Pre-groove space: 12
2nm

[Example 16] In Example 1,
Change dye A to dye C, and change the mixed solvent of the dye coating solution to 2,2
, 3,3-tetrafluoro-1-propanol 82ml,
13 ml of ethyl cellosolve and 5 ml of tetrachloroethane
An information recording medium having a recording layer having the thickness shown below was manufactured in the same manner as in Example 1 except that the mixed solvent was changed to ml. (1) Pre-pit bottom: 140 nm (2) Pre-pit space: 135 nm (3) Pre-groove bottom: 140 nm (4) Pre-groove space: 13
5nm

[Example 17] In Example 1,
Instead of the dye recording layer, Al2O3 is added as follows.
An information recording medium having a laminate having the following layer thickness was manufactured in the same manner as in Example 1 except that a laminate consisting of a phase change metal recording layer and an Al2O3 layer was formed. On the above substrate, an Al2O3 layer having a thickness of 100 nm was formed by vacuum evaporating Al2O3. On top of this layer, (In3SbTe2) and (In22Sb37T
Co-sputtering (Ar
Pressure: 2Pa, power: 200W) (In
3SbTe2)50(In22Sb37Te41)
A recording layer having a layer thickness of 20 nm was formed. An Al2O3 layer with a thickness of 100 nm was further formed on the recording layer by vacuum evaporation. (1) Pre-pit bottom: 20 nm (2) Pre-pit space: 20 nm (3) Pre-groove bottom:
20 nm (4) Area between pre-grooves: 20 nm The depth of the pre-pits and pre-grooves of the above substrate,
The layer thickness of the recording layer and the like was obtained by measuring its cross section using an ultra-high resolution SEM (scanning electron microscope).

[Evaluation of Information Recording Medium] 1) Modulation degree Information was recorded and reproduced on the information recording medium obtained under the following conditions. Optical disc evaluation machine D as a recording/playback evaluation device
Recording was performed using DU1000 (manufactured by Pulstech Co., Ltd.). That is, the oscillation wavelength is 780 nm and the NA
Using an optical head with a power of 0.5, a power of 7.4 mW, a linear velocity of 1.4 m/s, a CD format EFM signal,
Recording was made from a position with a diameter of 72 mm on the substrate. To evaluate the modulation degree, reproduce the prepit part at a position of 66 mm in diameter.
The recorded information was reproduced at a position with a diameter of 72 mm. Using the same laser used for recording, playback was performed at a playback power of 0.5mW and a linear velocity of 1.4m/sec, and the DC playback signal at each of the above positions was measured. High level is Itop, low level is Ibot
The modulation degree was calculated from the following formula. Modulation degree = {(Itop − Ibot )/Itop }
Evaluation of ×100 modulation degree is good when it exceeds 60, 70
It can be said that it is excellent when it exceeds.

2) The unrecorded portion of the reflectance pregroove is reproduced at a position of 71 mm under the above conditions, and the average voltage of the DC reproduction signal (I
g). The reflectance (Ro) of the innermost mirror part of a commercially available CD was measured with a reflectance meter, and the average voltage (Io) was measured at that position in the same playback state as above, and the reflectance was determined from the following formula. . Reflectance==(Ig/Io)×Ro×100 When evaluating the reflectance, it can be said that when it exceeds 63, it is good, and when it exceeds 70, it is said that it is excellent.

3) Fluctuation rate of push-pull signal The obtained information recording medium is reproduced using the above-mentioned evaluation machine, and the tracking error signals output in each of the pre-pit area and pre-groove area are observed, and each The maximum amplitude in the area is A, the minimum amplitude is B, 2×(A-B
)/(A+B) was determined as the above fluctuation rate. Regarding the evaluation of the fluctuation rate of the push-pull signal, it can be said that 0.03 to 0.12 is good and 0.04 to 0.09 is excellent. Table 1 shows the configurations of the information recording media obtained in the Examples and Comparative Examples, and Table 2 shows the results.

[0091]

[Table 1]

a: 2,2,3,3-tetrafluoro-1-
Propanol b: Ethyl cellosolve c: Tetrachloroethane d: Propylene glycol monoethyl ether e: Diisobutyl ketone f: Ethyl caprylate g: 1-pentanol

[0093]

[Table 2]

As is clear from the above results, the pre-pit depth, pre-groove depth, and
The information recording medium of the present invention has a recording layer thickness of
It has high modulation degree and reflectance, and also has excellent tracking performance.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an information recording medium of the present invention.

FIG. 2 is a partially enlarged sectional view of FIG. 1;

FIG. 3 is a cross-sectional view of a prepit portion for explaining the relationship between the depth of the prepit and the thickness of the recording layer according to the present invention.

FIG. 4 is a cross-sectional view of a pre-pit portion for explaining the relationship between the depth of a pre-groove and the thickness of a recording layer according to the present invention.

[Explanation of symbols]

1 Disk-shaped substrate 2 Recording layer 3 Reflection layer 4 Protective layer 5 Play-only area 6 Recordable area 8 Prepit 9 Pregroove

Claims (2)

[Claims] Claim 1: A recording layer capable of recording information using a laser and a reflective layer are provided on a disk-shaped substrate having a read-only area consisting of pre-pits and a recordable area consisting of pre-grooves on the surface thereof. In the information recording medium provided in this order, the relationship between the depth of the prepits and the thickness of the recording layer is expressed by the following formula (I): 0.15λ≦ns dp −nd Δtp
≦0.24λ (I), and the relationship between the depth of the pregroove and the thickness of the recording layer is expressed by the following formula (II): 0.02λ≦ns dg −nd Δtg
≦0.08λ (II) [However, ns represents the refractive index of the substrate, nd represents the refractive index of the recording layer, dp represents the depth of prepits (nm), and Δt
p represents the difference (nm) between the thickness of the recording layer at the bottom of the pre-pits and the thickness of the recording layer between the pre-pits, dg represents the depth (nm) of the pre-groove, and Δtg represents the difference (nm) between the thickness of the recording layer at the bottom of the pre-pits and the thickness of the recording layer between the pre-pits. It represents the difference (nm) between the thickness of the recording layer and the thickness of the recording layer between the pregrooves, and λ represents the wavelength of the laser used during reproduction. ] An information recording medium characterized by satisfying the following. 2. The information recording medium according to claim 1, wherein the recording layer is a layer made of a dye.