JP2003228883A - Information recording medium and method of manufacturing information recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an information recording medium which hardly gives rise to the destruction and peeling of a recording layer and hardly flaws the surfaces of protective layers even when a hard material comes into contact therewith. <P>SOLUTION: The information recording medium which has the recording layer 16 to be recorded with information on a substrate 11 and records and reproduces the information by imparting energy to the medium from the recording layer 16 side has the first protective layer 21 covering the outside surface side of the recording layer 16, the second protective layer 22 covering the first protective layer 21 and the third protective layer 23 which functions as a front surface covering the second protective layer 22, in which the second protective layer 22 is set in its hardness lower than the hardness of the first protective layer 21 and the hardness of the third protective layer 23 and functions to relieve the point pressure acting from the third protective layer 23. <P>COPYRIGHT: (C)2003,JPO

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 for recording information with a recording beam such as a laser beam or an electron beam, and more particularly to an information recording medium having an enhanced protective effect on a recording layer.

[0002]

2. Description of the Related Art In recent years, in addition to computer information and audio information, still image and moving image video information have been digitized, and the amount of information to be handled has become extremely large. Along with this, the capacity of optical recording media for recording and storing such information also tends to increase. A write-once CD-R (Recorda) is widely used as an optical recording medium.
ble) and rewritable CD-RW (Rewritable) exist, but the DVD-RA has a capacity more than 7 times that of these.
Optical recording media such as M and DVD-RW have been commercialized.

This DVD-RAM or DVD-RW has a diameter of 120 mm and has 4.7 GB on one side like other media.
It is a large-capacity rewritable medium having a capacity of 0.
Dielectric layer on 6mm polycarbonate (PC) substrate,
A phase change recording layer, a dielectric layer, and a reflection layer are provided as a basic four-layer structure, and a protective layer made of an ultraviolet curable resin is formed to a thickness of about 10 μm on the reflection layer, which is the uppermost layer. It has a structure in which 0.6 mm substrates are stuck together with a recording layer etc. sandwiched inside. A sputtering method or the like can be used as a film forming method, which is realized by sequentially laminating a dielectric layer, a phase change recording layer, a dielectric layer, and a reflective layer on a substrate.

In order to further increase the capacity, the wavelength (λ) of laser light is shortened to, for example, 405 nm, and the numerical aperture NA of the objective lens is increased to, for example, 0.85. A method of reducing the diameter and thereby increasing the density of DVD-RAM, DVD-RW, etc. has been proposed (Jpn.J.Appl.Phys.Vol.39 (2000) p.
p.756-761, Part1, No.2B, Feb.2000). Here, since the lens numerical aperture NA is increased, the focal length is shortened, and it is no longer possible to irradiate the recording layer with laser light from the substrate side to record and reproduce as in the conventional case. The film surface incidence method is adopted in which recording / reproduction is performed by irradiating laser light from the surface opposite to (the recording layer side, not the substrate side). There are two types of film surface incidence type optical recording media, one using an alloy phase change material for the recording layer and one using a dye material for the recording layer. It is done.

In the method proposed above, the influence on the tilt (angle deviation due to warpage or tilt) of the disk is reduced by using a 0.1 mm substrate which is thinner than the conventional one. Further, this 0.1 mm substrate plays an important role such as mechanical protection and electrochemical protection (corrosion prevention) of the recording layer. A rewritable medium can be obtained by adopting the same laminated structure as the conventional one.
mm It is difficult to maintain the rigidity of the substrate. Therefore, as a stacking order, for example, a reflective layer, a dielectric layer, a layer change recording layer and a dielectric layer are stacked on a thick PC substrate having a thickness of about 1.1 mm in the reverse order of the conventional method, and finally 0 is formed. A method of forming a cover layer corresponding to a substrate of 0.1 mm as a protective layer can be adopted. As a method for forming this protective layer,
There is a method of sticking a 1 mm thick sheet with an ultraviolet curable resin adhesive, but it is difficult to keep the thickness of the adhesive uniform.
On the other hand, a method has been proposed in which an ultraviolet curable resin is uniformly applied by a spin coating method and cured by irradiation with ultraviolet rays to form a protective layer.

[0006]

Since the ultraviolet curable resin used for the protective layer used in the conventional optical disk has low hardness and is soft, it is easy to form a uniform film thickness by the spin coating method. However, scratches are likely to occur in the protective layer when a hard object slides, and when the above-described film surface incidence method is adopted, the information recording layer (recording layer) is irradiated with light from the scratched protective layer. An error is likely to occur when reading the information recorded in. Therefore, it becomes necessary to enhance the effect of protecting the recording layer in the protective layer.

As measures for strengthening the protective layer, a method of covering the information recording layer with a hard protective layer having a high viscosity, a method of covering the information recording layer with a plurality of hard protective layers, and an outer surface of the information recording layer having a low hardness are used. A method of covering with a soft first protective layer and covering the outer surface of the first protective layer with a hard second hard protective layer; and covering the outer surface of the information recording layer with a hard first hard protective layer,
A method of covering the outer surface of the first protective layer with a soft second protective layer having a low hardness has been proposed.

However, if the protective layer covering the information recording layer is made hard, the point pressure applied to the surface of the protective layer is only dispersed, and the point pressure cannot be absorbed. The thickness of the protective layer is naturally limited in order to prevent the warp of the substrate. As a result, it is difficult to reduce the point pressure acting on the information recording layer to a practically sufficient level, and it is impossible to prevent the information recording layer from being destroyed due to the point pressure. Such a drawback is difficult to eliminate even when the information recording layer is covered with a plurality of hard protective layers.

When the outer surface of the information recording layer is covered with a soft first protective layer and the outer surface of the first protective layer is covered with a hard second protective layer, a point pressure is applied by the soft first protective layer. It can be absorbed, and the hard second protective layer can suppress the occurrence of scratches. However, in such a configuration, since the soft protective layer is arranged on the surface of the information recording layer, the force in the surface direction of the protective layer directly acts on the information recording layer. Therefore, when a soft organic compound such as a pigment material is used for the information recording layer, or when the information recording layer is formed by using a phase change material in which the substance easily flows, the destruction of the information recording layer is effectively performed. This cannot be prevented, and peeling between the information recording layer and the first protective layer is likely to occur.

Further, by covering the outer surface of the information recording layer with a hard first protective layer and covering the first protective layer with a soft second protective layer, destruction of the information layer due to point pressure can be prevented. It is possible, but since the soft protective layer is arranged on the surface layer, when a hard object makes sliding contact (contact), scratches are likely to occur on this soft protective layer, and light is irradiated from the protective layer. An error is likely to occur when reading the information recorded on the information recording layer. In addition, once scratches occur, the hard material directly
Since the first pressure protection layer comes into contact with the hard first protection layer, the point pressure acting on the information layer rapidly increases and the information layer is easily broken.

The present invention has been made to solve the above technical problems, and an object of the present invention is to provide an information recording medium or the like in which breakage or peeling of a recording layer is hard to occur. It is in. Another object is to provide an information recording medium or the like in which scratches are unlikely to occur on the surface of the protective layer even when a hard material comes into contact therewith.

[0012]

According to the present invention, at least a recording layer and a protective layer are provided on a substrate, and energy is applied from the side of the protective layer for recording / recording.
In the information recording medium (disc) for reproduction, the protective layer has a three-layer structure, and the hardness of the second protective layer in the middle is made low, so that when a point pressure is applied to the disc surface or a hard object slides. It is possible to suppress scratches on the surface of the disk when a hard object comes into contact with it, such as when it moves, and to further enhance the effect of protecting the recording layer. That is, the present invention relates to a recording layer on which information is recorded.
An information recording medium which comprises a substrate (for example, a phase change recording layer or a dye recording layer) and which records and reproduces information by applying energy from the recording layer side, and which covers the outer surface side of the recording layer. A protective layer and a second layer covering the first protective layer
A protective layer and a third protective layer functioning as a surface layer covering the second protective layer are provided, and the second protective layer has a hardness of the first
The hardness is lower than the hardness of the protective layer and the hardness of the third protective layer. The term “on the substrate” includes not only the case where the substrate is in contact with the substrate but also the case where another layer is interposed therebetween. Further, also in "covering", another layer may be interposed therebetween. The same applies hereinafter.

Here, it is preferable that the first protective layer and the third protective layer have a film thickness of 3 μm or more and 30 μm or less because the protection effect of the recording layer can be enhanced. The distance between the tracks formed on the substrate is 0.5 μm or less, which is particularly effective when information having a wavelength of 500 nm or less is irradiated from the recording layer side to record / reproduce information. Furthermore, the first protective layer, the second protective layer, and the third protective layer have an extinction coefficient k of 0.1 or less, which is represented by a complex refractive index n-ki with respect to light of 500 nm or less. It is preferable that the extinction coefficient k is 0.03 or less, from the viewpoint of preventing an increase in bite error rate and preventing a decrease in reflectance.

From another point of view, the present invention comprises a recording layer on which information is recorded and a protective layer on a substrate, and the protective layer side.
An information recording medium for recording / reproducing information by applying energy from the recording layer side (not the substrate side), the first protective layer covering the outer surface side of the recording layer and suppressing destruction of the recording layer. And a second protective layer that covers the first protective layer and relaxes the acting point pressure, and a third protective layer that covers the second protective layer and suppresses scratches caused by contact with a hard material. It is characterized by that.

Here, it is preferable that the second protective layer contains more components that lower the hardness than the first protective layer and the third protective layer, from the viewpoint of relaxing the acting point pressure. Examples of the component that lowers the hardness include materials having two or less acryloyl groups, for example, materials such as 1,6-hexanediol acrylate and diethylene glycol acrylate, and the content ratio of these materials is, for example, 51% or more. The hardness can be lowered by making the hardness higher than that of the first protective layer and the third protective layer.

On the other hand, the information recording medium to which the present invention is applied has a first protective layer covering the outer surface side of the recording layer, a second protective layer covering the first protective layer, and a surface layer covering the second protective layer. And a third protective layer which is 0.6 N from the third protective layer side.
The byte error rate is 1 × 10 even after applying the load
It can be characterized by being ^-4 or less. When a load of 0.5 N is applied from the third protective layer side, the first
It can be characterized in that peeling does not occur between the first protective layer and the layer on the substrate side in contact with the protective layer. Furthermore, when sapphire glass with a tip angle of 60 degrees is applied from the side of the third protective layer and a load of 0.5 N is applied to slide the sapphire glass on the third protective layer, a sliding contact mark is formed on the third protective layer. Can be characterized by not occurring.

Further, the present invention can be understood as a method of manufacturing an information recording medium. In this manufacturing method, a reflective layer forming step of forming a reflective layer on a substrate having a tracking guide groove on the surface, a recording layer forming step of forming a recording layer for recording information on the reflective layer, and a recording layer forming step. A first protective layer covering the recording layer, a second protective layer covering the first protective layer and softer than the first protective layer, and a third protective layer covering the second protective layer and harder than the second protective layer And a protective layer forming step of forming the resin by coating and then curing the resin. Here, "on the reflective layer" may include other layers in between.

Further, a step of forming at least one dielectric layer between the reflective layer and the recording layer, and the recording layer and the first layer.
And a step of forming at least one dielectric layer between the protective layer and the protective layer, using a phase change recording layer as the recording layer, and obtaining an information recording medium in which this recording layer is effectively protected. Is possible.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. FIG. 1 is a sectional view for explaining the configuration of the optical recording medium in this embodiment. The optical recording medium to which this embodiment is applied prevents the substrate 11, the reflective layer 12, the absorptance correction layer 13, the first dielectric layer 14, and S in the first dielectric layer 14 from diffusing. First diffusion prevention layer 15 for recording, recording layer (information recording layer) 1
6, the second diffusion prevention layer 17, and the second dielectric layer 18 are laminated. Further, as a protective layer, it covers the first protective layer 21 that covers the outer surface side of the recording layer 16, the first protective layer 21, and the second protective layer 22 and the second protective layer 22 that are softer than the first protective layer 21. At the same time, a third protective layer 23, which is harder than the second protective layer 22, is laminated. This optical recording medium achieves high density by irradiating laser light having a wavelength of 500 nm or less from the recording layer 16 side to record and reproduce information.

A tracking guide groove 30 is formed on one surface of the substrate 11. This tracking guide groove 3
0 is formed, for example, by injection molding in a spiral shape that is continuous from the center side of the substrate 11 to the outer peripheral side.
It should be noted that disc identification information, address information and the like are pre-recorded on the substrate 11 by wobbles and prepits of the tracking guide groove 30. Either a groove or a space between the grooves can be used as an information recording track. In addition, the interval is 0.5μ for higher density.
It is less than m. The tracking guide groove 30 and the pits are preferably provided at the time of molding the substrate 11, but may be provided on the substrate 11 by using an ultraviolet curable resin layer.

The material of the substrate 11 is not particularly limited as long as it has required strength and durability. Conventionally used as a substrate material, for example, acrylic resin, methacrylic resin, polycarbonate resin, polyolefin resin (particularly amorphous polyolefin), polyester resin, polystyrene resin, epoxy resin or other resin, glass Any of the above, a glass provided with a resin layer made of a radiation curable resin such as a photocurable resin, and the like can be used as the material of the substrate 11. From the viewpoint of high productivity, cost, moisture absorption resistance, etc., injection molded polycarbonate is preferable. chemical resistance,
From the viewpoint of moisture absorption resistance and the like, amorphous polyolefin is preferable. A glass substrate is preferable from the viewpoint of high-speed response. The substrate 11 need not be transparent to the wavelengths of recording light and reproducing light. Further, in order to prevent vibration during high-speed rotation, a filler such as carbon fiber may be added to a resin such as polycarbonate to increase rigidity.

The reflective layer 12 is preferably composed of a metal or an alloy, particularly an alloy which has good corrosion resistance and is inexpensive.
Specifically, for example, Au, Al, Ag, Cu, Ti,
The metals of Cr, Ni, Pt, Ta, Cr and Pd can be used alone or as an alloy. Among these, Au, Al and Ag have high reflectance and are suitable as materials for the reflective layer. Besides using these as main components, for example, M
g, Se, Hf, V, Nb, Ru, W, Mn, Re, F
e, Co, Rh, Ir, Cu, Zn, Cd, Ga, I
It may also include metals and semi-metals such as n, Si, Ge, Te, Pb, Po, Sn, Bi. Among them, those containing Ag as a main component are particularly preferable from the viewpoints of low cost, high reflectance, and the like. Here, the main component means one having a content rate of 50% or more.

The recording layer 16 may be a phase change recording layer made of a phase change material or a dye recording layer made of a dye material. The recording layer 16 is preferably composed of a single recording film layer made of a heat mode recording material or a photon mode recording material. Among them, the phase change material is excellent in that the recording layer 16 is unlikely to be deformed. . In the phase-change recording layer, data is read and written by changing the state of the material, crystalline / amorphous, that is, the phase, and Ge-Sb-Te series, In-Sb-Te series, Ag-
In-Sb-Te system, MA-Ge-Sb-Te system (MA is A
u, Cu, Pd, Ta, W, Ir, Sc, Y, Ti, Z
r, V, Nb, Cr, Mo, Mn, Fe, Ru, Co,
Rh, Ni, Ag, Tl, S, Se and at least one element of Pt), Sn-Sb-Te system, In-Se-T
1 series, In-Se-Tl-MB series (MB is Au, Cu, P
d, Ta, W, Ir, Sc, Y, Ti, Zr, V, N
b, Cr, Mo, Mn, Fe, Ru, Co, Rh, N
Materials such as i, Ag, Tl, S, Se and at least one element of Pt) and Sn-Sb-Se-based materials can be used.

When a dye recording layer is used as the recording layer 16, the absorptance correction layer 13, the first dielectric layer 14, the first diffusion prevention layer 15, the second diffusion prevention layer 17, and the second dielectric layer 18 are used. Each layer can be omitted. The recording layer 16 contains a dye and has, for example, an absorbance (absorbance measured at a wavelength of 360 nm with air as a reference) of 1.0.
The benzophenone-based recording layer 16 is formed with a thickness of The dye used for the recording layer 16 is preferably an organic dye because it is easy to form a film, and in addition to benzophenone dyes, for example, phthalocyanine dyes, naphthalocyanine dyes, cyanine dyes, azo dyes, squarylium dyes, and the like are included. Metal azo dyes, metal-containing indoaniline dyes, triarylmethane dyes, merocyanine dyes, azurenium dyes, naphthoquinone dyes, anthraquinone dyes, indophenol dyes, xanthene dyes, oxazine dyes, pyrylium dyes Etc. can be used. Among the organic dyes, metal-containing azo dyes are preferable because they are excellent in recording sensitivity and light resistance. The recording layer 16 has a transition metal chelate compound (eg, acetylacetonate chelate, bisphenyldithiol, salicylaldehyde oxime, a singlet oxygen quencher, etc.) in order to improve its stability and light resistance.
Bisdithio-α-diketone, etc.) or a recording sensitivity improving agent such as a metal compound for improving recording sensitivity. Here, the metal-based compound means that a metal such as a transition metal is contained in the compound in the form of an atom, an ion, a cluster, etc., for example, an ethylenediamine-based complex, an azomethine-based complex, a phenylhydroxyamine-based complex, a phenanthroline-based complex, Organometallic compounds such as dihydroxyazobenzene-based complexes, dioxime-based complexes, nitrosoaminophenol-based complexes, pyridyltriazine-based complexes, acetylacetonate-based complexes, metallocene-based complexes, and porphyrin-based complexes are mentioned. The metal atom is not particularly limited, but a transition metal is preferable.

When the recording layer 16 composed of a dye recording layer is adopted, a near infrared laser having a wavelength of about 770 to 830 nm, which is usually used for CD-Rs, or the like, if necessary,
Wavelength 620-690 nm as used for DVD-R
Red laser, wavelength 410nm or 515n
A recording layer 1 for recording with laser light in a plurality of wavelength ranges by using a dye suitable for recording with each of a plurality of wavelengths of recording light such as a so-called blue laser of m or the like.
6 can also be formed. Further, if necessary, a binder, a leveling agent, a defoaming agent, etc. can be used in combination. Preferred binders include polyvinyl alcohol, polyvinylpyrrolidone, nitrocellulose, cellulose acetate, ketone resins, acrylic resins, polystyrene resins, urethane resins, polyvinyl butyral, polycarbonate, polyolefins and the like.

In the protective layer composed of the first protective layer 21, the second protective layer 22, and the third protective layer 23, the second protective layer is the second protective layer.
The hardness of the protective layer 22 is set to the first protective layer 21 and the third protective layer 2.
The hardness is lower than 3. In this way, when the protective layer is composed of the first protective layer 21 having a high hardness, the second protective layer 22 having a low hardness, and the third protective layer 23 having a high hardness, it has three layers.
Even if a point pressure acts on the surface third protective layer 23, the point pressure is applied to the soft second protective layer 2 below the third protective layer 23.
The point pressure is dispersed by the hard first protective layer 21 which is absorbed by the second protective layer 22 and is disposed below the second protective layer 22, so that the recording layer 16 is effectively prevented from being broken due to the action of the point pressure. be able to. Further, even if the soft second protective layer 22 is deformed by the point pressure and a force in the surface direction is generated due to the deformation, the hard first protective layer 21 is arranged below the second protective layer 22. Therefore, the force in the plane direction is applied to the recording layer 16
Even if the recording layer 16 is formed of a soft organic compound such as a dye or a phase change material that easily causes material flow, the layer on the recording layer 16 side (the second dielectric layer 18 in FIG. 1) The peeling between the protective layer and the protective layer (the first protective layer 21 in FIG. 1) is prevented. Furthermore, a hard third protective layer 23 is formed on the surface layer.
Is disposed, the protective layer is less likely to be scratched even when it comes into contact with a hard material, and errors when reading the information recorded in the recording layer 16 are reduced.

As a material for the protective layer of the optical recording medium, an ultraviolet curable resin can be used. UV curable resin
Usually, (A) prepolymer component, (B) monomer component, (C)
It comprises a photopolymerization initiation component, (D) and other components.
The physical properties of the cured product such as viscosity can be changed by adjusting the use ratios of the (A) prepolymer component and the (B) monomer component. Examples of the prepolymer component (A) include polyester acrylate, polyurethane acrylate, epoxy acrylate, and polyether acrylate, and at least one of them is used.

As the monomer component (B), a component for increasing the hardness of the composition (hereinafter referred to as B1 component) and a diluent component for decreasing the viscosity of the composition (hereinafter referred to as B2 component) can be contained. Monomer components B1 and B2 are both 1
Used more than one kind. The component B1 preferably has two or more acryloyl groups in the molecule, and particularly preferably has three or more acryloyl groups. Examples of the compound having two or more acryloyl groups in the molecule include dicyclopentanyl diacrylate and ethylene oxide (EO) -modified bisphenol A acrylate. Examples of the compound having 3 or more acryloyl groups in the molecule include trimethylpropane triacrylate, EO-modified trimethylolpropane triacrylate dipentaerythritol hexaacrylate, dipentaerythritol monohydroxypentaacrylate, alkyl-modified dipentaerythritol pentaacrylate. , Alkyl-modified dipentaerythritol tetraacrylate, pentaerythritol triacrylate,
Examples thereof include pentaerythritol tetraacrylate and ditrimethylolpropane tetraacrylate. The component B2 preferably has 2 or less acryloyl groups in the molecule. Examples of the compound having two acryloyl groups in the molecule include tripropylene glycol diacrylate, 1,6-hexanediol acrylate,
Examples include neopentyl glycol diacrylate and diethylene glycol acrylate. Examples of compounds having one acryloyl group in the molecule include 2-ethyl acrylate, tetrahydrofurfuryl acrylate, and 2
-Hydroxy acrylate, isobornyl acrylate, cyclohexyl acrylate, dicyclopentanyl acrylate, amino acrylates such as acrylmorpholine, and acrylamides such as N-isopropyl acrylamide and N, N, -dimethylaminopropyl acrylamide.

As the photopolymerization initiator component (C), one or more kinds of various photopolymerization initiators and photopolymerization sensitizers used in the ultraviolet curable resin are used. As the open-line type photopolymerization initiator, benzoin, benzoin methyl ether,
Examples thereof include benzoin ethyl ether, benzoin isobutyl ether, 2-methylbenzoin, benzyl dimethyl ketal and the like. Further, as a combination of the hydrogen abstraction type photopolymerization initiator, benzophenone, methyl benzoylbenzoate, benzophenone-based sensitizers such as acrylated benzophenone and an aliphatic amine such as triethylamine, methyldiethanolamine, triethanolamine, bis ( N-methyl-2,2,6,6, -tetramethyl-4-piperidinyl) sebacate, bis (2,2,6,
6, -Tetramethyl-4-piperidinyl) sebacate, 2
-Dimethylaminoethyl benzoate, dimethylamino acephenone, ethyl p-dimethylaminobenzoate, p
Combinations with aromatic amines such as isoamyl dimethylaminobenzoate are conceivable.

As the component (D), various additives such as a tackifier, a polymerization inhibitor and a surfactant are used as required. Since reproduction of recorded information is performed by irradiating light from the protective layer side and utilizing reflected light from the recording layer 16, it is necessary to minimize light absorption in the protective layer.
Therefore, the first protective layer 21, the second protective layer 22, and the third protective layer 23 are composed of a colorless transparent resin layer,
For light having a wavelength of 500 nm or less, the extinction coefficient k represented by the complex refractive index n-ki of each protective layer is 0.1.
The following is preferable, and 0.03 or less is further preferable. Also,
The thickness of each layer constituting the first protective layer 21 and the third protective layer 23 is preferably as thick as possible from the viewpoint of enhancing the protective effect of the recording layer 16, but if it is too thick, the substrate 11 is deformed due to the stress generated when the protective layer is cured. If it is too thin, the protective effect required for practical use cannot be obtained. Therefore,
It is preferable that both the first protective layer 21 and the third protective layer 23 have a thickness of 3 μm or more and 30 μm or less, though it varies depending on the physical properties of the material used. When a dye recording layer is used as the recording layer 16, for example, a resin as an adhesive may be used to form the first protective layer 21 having the above-described function.

In addition to the recording layer 16 alone, the disc structure may be such that the reflection layer 12 and the recording layer 16 are provided in this order.
And other films such as the reflective layer 12 and the dielectric film (the first dielectric layer 14 and the second dielectric layer 18) may be combined. In order to reduce the influence on the tilt of the disc, a protective layer (first protective layer 21 and second protective layer 2
The total thickness of the second and third protective layers 23) is preferably 100 μm. Further, the present embodiment is effective when recording is performed at a high density with a recording track interval of 0.5 μm or less. Further, it is particularly effective when the recording / reproducing laser wavelength is 500 nm or less. When a medium to which this embodiment is applied is used, an information recording / reproducing method and an information recording / reproducing apparatus for irradiating a laser beam having a wavelength of 500 nm or less from the recording layer 16 side to record and reproduce information. Can be provided.

Next, a method of manufacturing the information recording medium according to the present embodiment will be described. First, the substrate 11 is generated. At this time, the substrate 11 is formed by injection molding, for example, and a tracking guide groove 30 having a predetermined pitch and groove depth is formed on the surface thereof. Also, as mentioned above,
Disc identification information, address information, and the like are previously recorded on the substrate 11 by wobbles in the groove. These pieces of information can also be formed by prepits. Next, this board 1
1 is arranged in the first sputtering chamber in the sputtering apparatus which has a plurality of sputtering chambers and is excellent in the uniformity and reproducibility of the film pressure. Then, for example, AgRuAu is sputter-deposited on the surface of the substrate 11 in the argon gas to form the reflective layer 12. Examples of the method of forming the reflective layer 12 include an ion plating method, a chemical vapor deposition method, a vacuum vapor deposition method and the like, in addition to the sputtering method. Next, this substrate 11
After moving to the second sputtering chamber, the absorptance correction layer 13 is formed in argon gas. Next, after moving the substrate 11 to the third sputtering chamber, the first dielectric layer 14 is formed in argon gas. Then, after moving to the 4th sputtering chamber, the 1st diffusion prevention layer 15 is formed in argon gas. Next, the recording layer 16 is formed in argon gas in the fifth sputtering chamber. After that, after moving the substrate 11 to the sixth sputtering chamber, the second diffusion prevention layer 17 is formed in the same manner as the formation of the first diffusion prevention layer 15. Then, it is moved to the seventh sputtering chamber, and the second dielectric layer 18 is formed in the same manner as the formation of the first dielectric layer 14 to obtain a disc material which is a basis of the disc-shaped optical information recording medium. be able to. Subsequently, an ultraviolet curable resin is applied onto the disc material by spin coating and then cured by irradiation with ultraviolet rays to form a protective layer composed of a first protective layer 21, a second protective layer 22, and a third protective layer 23. Is formed with a predetermined thickness.

[0033]

EXAMPLES When manufacturing the information recording medium by the above manufacturing method, the substrate 11 has a diameter of 120 mm and a thickness of 1.1.
The tracking guide groove 30 has a width of 0.16 μm and a depth of 20 nm is 0.3 on the surface of a polycarbonate resin plate of mm.
It is formed with a pitch of 2 μm. For this substrate 11,
Using Ag ₉₈ Ru ₁ Au ₁ (atomic%) as a target,
The AgRuAu reflective layer 12 was formed. Further, Cr _95- (Cr ₂ O ₃ ) ₅ (mol%) was used as a target, and the thickness was 20
absorption layer 13 composed of Cr _95- (Cr ₂ O ₃ ) ₅ nm
Was formed. Then, ZnS and SiO as targets
A mixture of _2, a thickness of _{20nm (ZnS) 80 (SiO 2} )
_A first dielectric layer 14 of ₂₀ (mol%) was formed. Further, Cr ₂ O ₃ is used as a target, and C of 1 nm thickness is used.
The first diffusion barrier layer 15 made of r ₂ O ₃ was formed. Subsequently, a recording layer 16 having a thickness of 20 nm was formed using a Ge ₃₃ Sb ₁₃ Te ₅₄ (atomic%) sintered body target. After that, as in the case of forming the first diffusion prevention layer 15, the thickness 1
The second diffusion barrier layer 17 made of Cr ₂ O ₃ and the first dielectric layer 14 have a thickness of 40 nm (ZnS) ₈₀ (Si
A second dielectric layer 18 made of O ₂ ) ₂₀ (mol%) was formed.

As a protective layer composed of the first protective layer 21, the second protective layer 22, and the third protective layer 23, an ultraviolet curable resin having the component ratio shown in Table 1 was prepared.

[Table 1]

In order to increase the hardness of the compositions 1 and 2,
(B1) The content of the monomer component was increased. There is no problem even if two kinds of the (A) prepolymer component and two kinds of the (B1) monomer component as in the composition 2 are used. In composition 3, the content of the (B2) monomer component was increased in order to lower the hardness. When Composition 1 was formed on a glass plate and the surface was scratched with a pencil, the surface of the cured resin was scratched with a pencil of 2H. When the hardness of the composition 2 was examined in the same manner, the surface of the cured resin was scratched with a pencil hardness of 3H. On the other hand, the composition 3 had a scratch hardness on the surface of the cured resin with a pencil hardness of HB.
Here, the hardness is a pencil hardness when a cured resin is formed on a glass plate. The hardness of the pencil is low B, H
The hardness increases in the order of B, F, and H.

In the present embodiment, the above-mentioned disk material is provided with the first protective layer 21 made of the composition 1 and having a film thickness of 5 μm, the second protective layer 22 made of the composition 3 and having a film thickness of 20 μm, and the composition 2 A third protective layer 23 having a film thickness of 5 μm was formed in this order, and a disc of this example was produced. This disk is called A.

Comparative Example 1 FIG. 2 is a sectional view showing the structure of the information recording medium obtained in Comparative Example 1. A first protective layer 4 composed of the composition 1 and having a film thickness of 15 μm is formed on the disc material.
1 was formed to produce the required disc. This disc is called B. However, the first protective layer 41 was cured by applying ultraviolet rays after applying a resin by a spin coating method. Comparative Example 2 FIG. 3 is a sectional view showing the structure of the information recording medium obtained in Comparative Example 2. A desired disc was produced by forming a first protective layer 42 made of the composition 1 and having a thickness of 5 μm and a second protective layer 43 made of the composition 2 and having a thickness of 10 μm in this order on the disc material. . This disk is C
Call. However, the first protective layer 42 and the second protective layer 43 were cured by irradiation with ultraviolet rays after applying a resin by a spin coating method. Comparative Example 3 FIG. 4 is a sectional view showing the structure of the information recording medium obtained in Comparative Example 3. The above-mentioned disk material is provided with a first protective layer 44 composed of the composition 1 and having a thickness of 5 μm, and a composition 2
A second protective layer 45 having a film thickness of 10 μm, and a composition 3
A third protective layer 46 having a film thickness of 5 μm was formed in this order, and a required disc was produced. This disk is D
Call. However, the first protective layer 44, the second protective layer 45, the third
The protective layer 46 was applied with a resin by a spin coating method and then cured by irradiation with ultraviolet rays. Comparative Example 4 FIG. 5 is a cross-sectional view showing the structure of the information recording medium obtained in Comparative Example 4. A first protective layer 47 made of the composition 3 and having a film thickness of 15 μm and a second protective layer 48 made of the composition 2 and having a film thickness of 5 μm were formed in this order on the disc material to produce a required disc. did. This disk is called E. However, the first protective layer 47 and the second protective layer 48 were cured by irradiation with ultraviolet rays after applying a resin by a spin coating method. Comparative Example 5 FIG. 6 is a sectional view showing the structure of the information recording medium obtained in Comparative Example 5. The disk material was provided with a first protective layer 49 composed of the composition 1 and having a thickness of 5 μm, and a composition 3
A second protective layer 50 having a film thickness of 5 μm was formed in this order to manufacture a required disc. This disk is called F. However, the first protective layer 49 and the second protective layer 50 were cured by irradiation with ultraviolet rays after applying a resin by a spin coating method.

Next, the test apparatus and test method will be described. FIG. 7 is a diagram for explaining the test apparatus and the test method. In the test, as shown in FIG. 7, a recorded disk, which is a sample, is fixed on a table 62 via a non-woven fabric 63, and a sapphire glass 65 having a tip angle of 60 degrees is attached to a tip portion of a load device 64. It was pressed against the protective layer of the disk, and while maintaining this state, the table 62 was transferred in the surface direction thereof and the sapphire glass 65 was relatively moved in the radial direction of the disk to apply a load. The load on the disk is performed by placing a weight 66, which weighs 10 to 50 g, on the axis of the sapphire glass 65, and a radius of 26
~ 29 mm area, radius 31-34 mm area, radius 3
The load was applied to the area of 6 to 39 mm, the area of radius 41 to 44 mm, the area of radius 46 to 49 mm, and the area of radius 51 to 54 mm.

The test methods were compared by the rate of increase in the byte error rate before and after applying a load. Information recording and playback is
The disk was rotated so that the linear velocity was 11.56 m / sec, and the semiconductor laser light with a wavelength of 405 nm was used for the lens numerical aperture N.
The light was collected by an A0.85 objective lens and irradiated on the recording film through a protective layer. Byte error rate is 1-7
It was determined by recording a random pattern by the modulation recording method (shortest mark length 0.156 μm). When a 1-7 random pattern was recorded in the above-mentioned six related areas before loading on the A disk of the above-mentioned example and the B-F disks of comparative examples 1 to 4, the byte error rate at that time was 5 × 1.
0 was ^-5.

Next, the test results will be described. As a result of the above test, the B, C, D and E disks of Comparative Examples 1 to 4 were
After applying a load of 0.3 N, when the 1-7 random pattern recorded on the disc in each relevant area was reproduced, the byte error rate was 8 × 10 ⁻⁴ . The F disk of Comparative Example 5 had a bite error rate of 3 × 10 ⁻⁴ , but after being loaded with a load of 0.5 N,
The byte error rate was 8 × 10 ^-4 . On the other hand, in the A disk of the present embodiment, when a random pattern recorded on the disk was reproduced in each relevant area after applying a load of 0.6 N, the byte error rate was 6
It was × 10 ^-5 , which was almost the same as before the load was applied. Thus, for example, when a load of 0.6 N is applied and the byte error rate is set to 1 × 10 ⁻⁴ as a preferable level from the function of the disk, this value is determined by the A disk which is an example of the present embodiment. You can understand that it has been cleared. That is, it was found that the recording layer protection effect of the protective layer in the A disk, which is an example of the present embodiment, was remarkably improved.

As described above, in this embodiment, as shown in FIG. 1, the protective layer is a three-layer structure including the hard first protective layer 21, the soft second protective layer 22, and the hard third protective layer 23. Since the structure is adopted, even if a point pressure acts on the third protective layer 23 on the surface layer,
The point pressure is absorbed by the soft second protective layer 22 and dispersed by the hard first protective layer 21 disposed under the second protective layer 22, so that the recording layer caused by the action of the point pressure is formed. It is considered that the destruction of 16 can be effectively prevented.
Further, as shown in FIG. 5, in the E disc of Comparative Example 4 in which the soft first protective layer 47 and the hard second protective layer 48 were formed in this order on the disc material, the second dielectric layer 18 Although some peeling occurred between the first protective layer 47 and the first protective layer 47, no peeling occurred in the A disk of this example. This is
In the present embodiment shown in FIG. 3, even if the soft second protective layer 22 is deformed by the point pressure and a force in the surface direction is generated, the lower layer of the second protective layer 22 is hardened. It is considered that the force in the surface direction does not act on the second dielectric layer 18 because the first protective layer 21 having good adhesion to the second protective layer 22 is arranged. Further, as shown in FIG. 6, F of Comparative Example 5 in which a hard first protective layer 49 and a soft second protective layer 50 are formed in this order on the disc material.
In the disc, a sliding contact mark of the sapphire glass 65 is formed on the second protective layer 50 with a load of 0.3 N, and when a load of 0.5 N is applied, the sliding contact mark penetrates the second protective layer 50 and the first
Reaching the protective layer 49, a part of the recording layer 16 is destroyed. On the other hand, in the A disk of this example to which the present embodiment shown in FIG. 1 is applied, since the hard third protective layer 23 is arranged on the surface layer, the sliding contact mark of the sapphire glass 65 is formed. Instead, the recorded random pattern could be reproduced without any problem.

Here, an information recording medium to which the present embodiment is applied, in which a hard first protective layer 21, a soft second protective layer 22, and a hard third protective layer 23 are formed in this order on a disc material, are applied. When a random pattern is recorded under the above recording conditions by changing the extinction coefficient k of the complex optical constant of the first protective layer 21, the second protective layer 22, and the third protective layer 23 at a wavelength of 405 nm. When the bite error rate and reflectance were measured, the results shown in Table 2 were obtained.

[Table 2]

When the extinction coefficients of the first protective layer 21 and the second protective layer 22 are constant below 0.1 and the extinction coefficient of the third protective layer 23 is larger than 0.1, the byte error rate is 4 ×. It becomes 10 ^-4 . Also, the extinction coefficient increases and the reflectance of the disk decreases. Further, as is clear from Table 2, the extinction coefficient of the first protective layer 21 and the third protective layer 23 is constant at 0.1 or less, and the extinction coefficient of the second protective layer 22 is larger than 0.1. Case, and the second protective layer 2
Even if the extinction coefficient of the second and third protective layers 23 is constant at 0.1 or less and the extinction coefficient of the first protective layer 21 is larger than 0.1, the byte error rate also becomes considerably large.

An information recording medium to which the present embodiment is applied, in which a hard first protective layer 21, a soft second protective layer 22, and a hard third protective layer 23 are formed in this order on a disc material, When the thickness of the first protective layer 21 and the thickness of the third protective layer 23 are variously changed, a test for checking the protective effect of the recording layer 16 described above, and a peeling inspection of each protective layer (21 to 23) are performed,
The results shown in Table 3 were obtained.

[Table 3]

The thickness of the third protective layer 23 is constant at 10 μm.
If the thickness of the first protective layer 21 is set to 2 μm or less, the load
After the test, the recorded data is partially disturbed and
8x10 error rate^-FourBecame. Also, the third protective layer
The film thickness of 23 is constant at 10 μm,
When the film thickness is 31 μm or more, it is the uppermost layer of the disc material.
A part is peeled off between the certain second dielectric layer 18 and the first protective layer 21.
Separation occurs and the byte error rate is 5 x 10^-FourBecomes
It was On the other hand, the thickness of the first protective layer 21 is fixed at 10 μm.
If the thickness of the third protective layer 23 is 2 μm or less, the load
After the test, the recorded data is partially disturbed and
Error rate is 5 × 10^-FourBecame. Also, the first protective layer
The thickness of 21 is constant at 10 μm,
When the film thickness is 31 μm or more, the third protective layer 23 and the second protective layer 23
Partial peeling occurred between the protective layer 22 and the bite error trace.
5 x 10 ^-FourBecame. The first protective layer 21 and the second protective layer
Inventive materials for the protective layer 22 and the third protective layer 23
Even when the change is made within the range described in the embodiment,
Similar results were obtained.

As described above in detail, according to the present embodiment, at least the recording layer 16 and the protective layer 21 are formed on the substrate 11.
In the information recording medium in which information is recorded / reproduced by applying energy from the protective layer 23 side (the recording layer 16 side, not the substrate 11 side), a point pressure is applied to the disk surface. Also, it is possible to provide an optical information recording medium which is unlikely to break or peel off the recording layer 16 and which can read the information recorded on the disk without any trouble when a hard material comes into contact (sliding contact). .

Further, in the present embodiment, the recording layer 1
6 has been described by taking a rewritable optical information recording medium as an example, the gist of the present invention is not limited to this, and a write-once optical information recording medium that is not rewritable or a read-only type having only the reflective layer 12 The same can be applied to the optical information recording medium of. Furthermore, in the present embodiment, the phase change recording medium has been described as an example, but the gist of the present invention is not limited to this, and the recording layer 16
The same applies to the dye-based recording medium and the magneto-optical information recording medium provided with a magnetic layer for recording data by using the characteristics of the magnetic force by replacing the magnetic poles (S pole and N pole) of the magnetic substance in the disk Can be applied to. In such a case, the recording layer 16 can be composed of a combination of a recording film, a dielectric film, and a reflective layer.

[0048]

As described above, according to the present invention,
It is possible to effectively prevent the recording layer from being damaged.

[Brief description of drawings]

FIG. 1 is a cross-sectional view for explaining the configuration of an optical recording medium according to the present embodiment.

2 is a sectional view showing the structure of an information recording medium obtained in Comparative Example 1. FIG.

FIG. 3 is a cross-sectional view showing the structure of an information recording medium obtained in Comparative Example 2.

FIG. 4 is a sectional view showing a structure of an information recording medium obtained in Comparative Example 3.

5 is a cross-sectional view showing the structure of an information recording medium obtained in Comparative Example 4. FIG.

FIG. 6 is a cross-sectional view showing the structure of an information recording medium obtained in Comparative Example 5.

FIG. 7 is a diagram for explaining a test apparatus and a test method.

[Explanation of symbols]

11 ... Substrate, 12 ... Reflective layer, 13 ... Absorption rate correction layer, 14
... first dielectric layer, 15 ... first diffusion preventing layer, 16 ... recording layer
(Information recording layer), 17 ... Second diffusion preventing layer, 18 ... Second dielectric layer, 21 ... First protective layer, 22 ... Second protective layer, 23 ... Third protective layer, 62 ... Table, 63 ... Non-woven fabric , 64 ... Load device, 65 ... Sapphire glass, 66 ... Weight

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ identification code FI theme code (reference) G11B 7/24 G11B 7/24 535G 561 561N 7/26 531 7/26 531 (72) Inventor Kazuyo Umezawa 1-88, Toyora, Ibaraki-shi, Osaka Prefecture Hitachi Maxell Co., Ltd. (72) Inventor Makoto Iimura 1-88, Toyora, Ibaraki-shi, Osaka Prefecture F-term (reference) 5D029 JA01 JB18 JB47 in Hitachi Maxell Co., Ltd. LA02 LB07 LB11 LC05 LC13 LC21 5D121 AA04 EE01 EE21 EE23

Claims (13)

[Claims] 1. An information recording medium comprising a recording layer on which information is recorded on a substrate, the first protective layer covering an outer surface side of the recording layer, and the second protective layer covering the first protective layer. And a third protective layer covering the second protective layer, wherein the hardness of the second protective layer is lower than the hardness of the first protective layer and the hardness of the third protective layer. Information recording medium. 2. The information recording medium according to claim 1, wherein information is recorded / reproduced by applying energy from the recording layer side, and the third protective layer functions as a surface layer. 3. The information recording medium according to claim 1, wherein the recording layer is a phase change recording layer. 4. The information recording medium according to claim 1, wherein the first protective layer and the third protective layer have a film thickness of 3 μm or more and 30 μm or less. 5. The track is formed on the substrate at an interval of 0.5 μm or less, and light having a wavelength of 500 nm or less is irradiated from the recording layer side to record / reproduce information. Item 1. The information recording medium according to item 1. 6. The extinction coefficient k of the first protective layer, the second protective layer, and the third protective layer, which is represented by a complex refractive index n−ki with respect to light of 500 nm or less, is 0. .1
The information recording medium according to claim 1, wherein: 7. An information recording medium having a recording layer on which information is recorded on a substrate and recording / reproducing information by applying energy from the recording layer side, the outer surface side of the recording layer being covered. At the same time, a first protective layer that suppresses the destruction of the recording layer, a second protective layer that covers the first protective layer and relaxes the acting point pressure, and a hard material that covers the second protective layer. An information recording medium, comprising: a third protective layer that suppresses scratches caused by contact. 8. The information recording medium according to claim 7, wherein the second protective layer contains more components that reduce hardness than the first protective layer and the third protective layer. 9. An information recording medium having a recording layer on which information is recorded on a substrate, and recording / reproducing information by applying energy from the recording layer side, which covers the outer surface side of the recording layer. A first protective layer, a second protective layer that covers the first protective layer, and a third protective layer that is a surface layer that covers the second protective layer are provided, and a load of 0.6 N is applied from the third protective layer side. An information recording medium having a byte error rate of 1 × 10 ⁻⁴ or less after being added. 10. No peeling occurs between a layer on the substrate side in contact with the first protective layer and the first protective layer when a load of 0.5 N is applied from the third protective layer side. The information recording medium according to claim 9, wherein 11. When the sapphire glass having a tip angle of 60 degrees is applied from the side of the third protective layer and a load of 0.5 N is applied to slide the sapphire glass on the third protective layer, the third protective layer is applied. 11. The information recording medium according to claim 10, wherein no sliding contact mark is formed on the layer. 12. A reflective layer forming step of forming a reflective layer on a substrate having a tracking guide groove on its surface, a recording layer forming step of forming a recording layer for recording information on the reflective layer, A first protective layer on the recording layer, which covers the recording layer;
A second softer layer that covers the protective layer and is softer than the first protective layer.
And a protective layer forming step of forming a protective layer and a third protective layer that covers the second protective layer and is harder than the second protective layer by respectively applying a resin and then curing the resin. Recording medium manufacturing method. 13. A step of forming at least one dielectric layer between the reflective layer and the recording layer, and forming at least one dielectric layer between the recording layer and the first protective layer. 13. The method for manufacturing an information recording medium according to claim 12, further comprising a step.