JPH11191240A - Optical record medium and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure the hardness of a light transparent layer surface and to assure good reliability by suppressing the shrinkage of the light transparent layer, thereby suppressing a skew to a small level. SOLUTION: A reflection film 3 is formed on at least one main surface 1a of a substrate 1 having a thickness of 0.3 to 1.2 (mm) and the light transparent layer 5 of a thickness of 3 to 177 (μm) consisting of a photosetting resin at least partly cured by a cation polymn. reaction is formed thereon. The one main surface 1a of the substrate 1 preferably has uneven parts. The medium preferably has at least a recording film 4 between the reflection film 3 and the light transparent layer 5. The photosetting resin which forms at least part of the light transparent layer 5 and is cured by the cation polymn. reaction is photoset and is preserved in an atmosphere of 20 to 100 ( deg.C). The photosetting described above is preferably executed in the atmosphere of relative humidity <=60 (%RH). The resin is preferably irradiated with far IR rays of a wavelength below 300 (nm) after the photosetting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a light-emitting device, comprising: at least a reflection film on one principal surface side of a substrate; a recording layer thereon if necessary; and a light transmission layer formed thereon. The present invention relates to an optical recording medium for reproducing or recording / reproducing information by irradiating a laser beam from a transmission layer side. More specifically, the present invention relates to an optical recording medium in which skew is suppressed and surface hardness is secured by defining a material for forming a light transmitting layer, and good reliability is secured, and a method of manufacturing the same. .

[0002]

2. Description of the Related Art In recent years, in the field of data recording, researches on optical data recording methods have been conducted in various places.
This optical data recording system enables non-contact recording and reproduction, achieves recording densities that are at least an order of magnitude higher than magnetic recording systems, and is designed for read-only, write-once, and rewritable memory types. It has a number of advantages such as compatibility, and is considered as a system that can realize an inexpensive large-capacity file for a wide range of uses from industrial use to consumer use.

[0003] Among them, in particular, an optical disk corresponding to a read-only type memory format, such as a digital audio disk on which music data is recorded and an optical video disk on which image data is recorded, are widely used.

An optical disc such as the above digital audio disc has an uneven pattern of a transparent substrate having a thickness of about 1.2 (mm) on which an uneven pattern such as pits or grooves indicating data signals is formed. A reflective film made of a metal thin film such as an aluminum film is formed as a recording layer, and a protective film for protecting the reflective film from atmospheric moisture and O ₂ is formed on the reflective film. Is done.

[0005] Recently, DVDs (Digital Video Recorders) for recording various data such as images, music, computer data and the like have been developed.
digital Versatile Disc,
It is called DVD. ) Is also on the market. In this DVD, the thickness of the substrate is set to about 0.6 (mm) so as to be compatible with an optical system having a short wavelength and to be compatible with an optical system having a high numerical aperture so as to have a high recording density. .

[0006] In addition, a magneto-optical disk and a phase-change optical disk can be cited as ones corresponding to the rewritable memory mode.

[0007] For example, a magneto-optical disk corresponding to the rewritable memory mode has the following configuration. That is, a transparent dielectric film such as silicon nitride is formed on one principal surface of a transparent substrate having a thickness of about 1.2 (mm), and a magneto-optical recording film such as TbFeCo is formed thereon as a recording layer. The structure is such that a transparent dielectric film such as silicon nitride is formed, a reflective film such as an aluminum film is formed, and a protective film made of an ultraviolet curable resin or the like is further formed. As such a magneto-optical disk, for example, a small-sized magneto-optical disk having a diameter of about 64 (mm) is widely used.

A phase-change type optical disk corresponding to the above-mentioned rewritable type memory has the following configuration. That is, a transparent dielectric film made of silicon nitride or the like is formed on one main surface of a transparent substrate, a phase change recording film made of a chalcogen compound or the like is formed thereon, and a transparent dielectric film made of silicon nitride or the like is further formed. Thus, a recording layer is formed, and a reflection film such as an aluminum film is formed. Then, light is irradiated from the transparent substrate side to optically record and reproduce information.

[0009]

In such a situation,
As a next-generation optical recording medium, Japanese Patent Application No. 9-1096
No. 60, NTSC (Nation
al Television System Comm
There has been proposed an optical recording medium capable of reproducing or recording / reproducing for 4 hours by the (itte) method.

[0010] Since there is an increasing demand for large-capacity optical discs and large-capacity DVDs corresponding to the above-mentioned read-only type of memory, the above-mentioned optical recording medium has a large capacity in place of these optical discs and DVDs. It is intended to provide a function as a new recording medium having

Further, in the above-mentioned optical recording medium, by enabling recording and reproduction for four hours as a home video disk recorder, a video tape recorder (Video Tape Recorder), which is currently mainstream, is used.
It is intended to provide a function as a new recording medium replacing der).

In this optical recording medium, a digital audio disk or DVD on which music data is recorded is provided.
The same shape and size as a read-only type optical disk such as a small-sized magneto-optical disk with a diameter of about 64 (mm), etc., so that these disks are easy to use and easy to use for users who are familiar with their usability. Is also considered. Further, in this optical recording medium, by making the shape of a disk, utilizing the speed of access which is the greatest feature of the disk shape, not only a compact and simple recording medium, but also an instant recording and reproduction Various functions such as trick play and editing are also considered.

Therefore, the above-mentioned optical recording medium is required to have a storage capacity of 8 (GB) or more in order to incorporate such various functions.

However, none of the conventional optical recording media on which information is recorded on one principal surface side of the substrate achieve a storage capacity of 8 (GB). For example,
Even a DVD having a high storage capacity has a wavelength λ of 0.65 (μm) and a numerical aperture (hereinafter, referred to as NA) of the optical system of 0.6, and stores 4.7 (GB). Only capacity is secured.

Therefore, the above-mentioned optical recording medium can be adapted to an optical system having a shorter wavelength than that of the above-mentioned DVD, thereby increasing the recording density and also to an optical system having a higher numerical aperture. Therefore, it is desired to increase the recording density by reducing the spot diameter of the reproduction light and performing recording in accordance with this.

If the optical system having a short wavelength and the optical system having a high numerical aperture can be used as described above, the thickness of the portion where the reproduction light is irradiated and transmitted therethrough is reduced. There is a need to. This is due to the high numerical aperture,
This is because the allowable amount of aberration caused by the angle (tilt angle) at which the disk surface deviates from the perpendicular to the optical axis of the optical pickup is reduced. The aberration caused by the tilt angle is the thickness of the portion through which the reproduction light is transmitted. This is because the larger the thickness is, the larger it becomes.

Therefore, in the above-mentioned optical recording medium, for example, an uneven portion is formed on one main surface of a substrate, a reflective film is provided thereon to form a recording layer, and a thin film that transmits light is further formed thereon. A light-transmitting layer, and irradiate the reproducing light from the light-transmitting layer side to reproduce the data in the recording layer, or provide a reflective film on one main surface of the substrate, and at least a phase change Type recording film, a magneto-optical recording film, an organic dye type recording film and the like to form a recording film to form a recording layer, and further provide a light transmitting layer that is a thin film that transmits light thereon,
Light is irradiated from the light transmission layer side to record and reproduce data on and from the recording layer. With this configuration, it is possible to cope with a high numerical aperture of the optical system by reducing the thickness of the light transmission layer.

[0018]

In the above-mentioned optical recording medium, the thickness of the substrate is set to 0.3 to 1.2.
(Mm), and the thickness of the light transmitting layer is 3 to 177 (μm).
m). Then, in manufacturing this, an uneven portion is formed on one main surface side of the substrate as necessary, at least a reflective film is formed on the main surface, and a recording film is further formed as necessary. And on this is a photocurable resin cured by, for example, a radical polymerization reaction,
For example, an epoxy acrylate-based UV-curable resin is provided and cured to form a light transmitting layer.

However, the ultraviolet-curable resin is
Shrinks during photo-curing, and its volume shrinkage is about 7 to 12 (%)
This shrinkage causes a problem that the entire optical recording medium is warped. For example, an epoxy acrylate ultraviolet curable resin having a volume shrinkage of 8 (%) and a Young's modulus of 28 (MPa) is used, and has a thickness of 100 (μm).
m), the skew, which is the warp in the radial direction of the optical disk, is 0.8 at the position of the radius 40 (mm).
{1.1} at the position of the radius 55 (mm). In the optical recording medium, in consideration of the wavelength of the recording / reproducing optical system and the thickness of the light transmitting layer, the skew is preferably set to 0.4 ° or less, and in the optical recording medium manufactured as described above, This is difficult to achieve.

In such an optical recording medium,
The skew of the optical recording medium increases with the stress and the change with time due to the shrinkage of the ultraviolet curable resin, and the light transmitting layer may peel off from the portion of the substrate where information is recorded.

Examples of the material for forming the light transmitting layer as described above include urethane acrylate resins which have a high shrinkage but a low Young's modulus and are cured by a radical polymerization reaction. When the light transmitting layer is formed of such a material, although the skew of the entire optical recording medium can be reduced, the surface of the light transmitting layer is soft and a scratch is generated on the surface when an optical pickup device or the like collides. This makes it difficult to reproduce information.

Further, when the light transmitting layer is formed of a photocurable resin which is cured by the radical polymerization reaction as described above, the photocurable resin is usually formed by a spin coating method conventionally used in the production of optical recording media. A resin is applied, and the resin is irradiated with light and cured to form a light transmitting layer. For this reason,
For example, when a light transmitting layer having a thickness of 100 (μm) is to be formed, the photocurable resin is required to have a viscosity characteristic of about 1000 to 8000 (mPa · s) in an atmosphere of 25 ° C. You. However, it is cured by a radical polymerization reaction that satisfies both such viscosity characteristics and characteristics such as low cost, low volume shrinkage, high hardness, environmental resistance, high transmittance, and adhesion to recording films and reflection films. No photo-curable resin has been developed at present.

The present invention has been proposed in view of the actual situation in the related art, and the optical pickup device has been proposed in which the shrinkage of the light transmitting layer is suppressed, the skew is suppressed, and the hardness of the surface of the light transmitting layer is ensured. It is an object of the present invention to provide an optical recording medium in which the surface of the light transmitting layer is hardly damaged even when the light strikes, etc. and good reliability is secured, and a method of manufacturing the same.

[0024]

Means for Solving the Problems As a result of intensive studies conducted by the present inventors to achieve the above-mentioned object, among the photocurable resins, the photocurable resin cured by a cationic polymerization reaction has a terminal portion. Only the primary resin contributes to the reaction, and the main resin reacts linearly, so that the reaction is accelerated in a three-dimensional network structure, such as an epoxy acrylate-based UV-curable resin or urethane acrylate-based resin cured by a radical polymerization reaction. No shrinkage was found.

In the photocurable resin cured by the cationic polymerization reaction, the number of functional groups of monomers directly involved in the reaction is determined by the epoxy acrylate ultraviolet curable resin or the urethane acrylate resin cured by the radical polymerization reaction. From this, it was found that it was difficult to form a network structure and the shrinkage was small.

That is, in the optical recording medium of the present invention, at least a reflection film is formed on one principal surface of a substrate having a thickness of 0.3 to 1.2 (mm), and a thickness of 3 to 177 (μm A) a light-transmitting layer is formed, and at least a part of the light-transmitting layer is made of a photocurable resin cured by a cationic polymerization reaction.

In the optical recording medium according to the present invention, it is preferable that at least one principal surface of the substrate on which the reflection film is formed has an uneven portion.

Further, in the optical recording medium of the present invention, it is preferable that at least a recording film is provided between the reflection film and the light transmission layer of the substrate, and the recording film is a phase change recording film, a magneto-optical recording film. Or an organic dye type recording film.

Further, in the optical recording medium of the present invention, it is preferable that the light-curable resin which forms the light-transmitting layer and is cured by a cationic polymerization reaction contains an epoxy resin, and the epoxy resin is a cyclic resin. By containing the monomer, volume shrinkage due to polymerization is further suppressed, and higher hardness is secured from the skeleton of the molecule of the epoxy resin.

In the optical recording medium of the present invention, the light transmitting layer is formed, and the wavelength of the cured photocurable resin cured by a cationic polymerization reaction is from 400 to 800.
It is preferable that the spectral transmittance in (nm) is 80 (%) or more.

In the optical recording medium of the present invention, the light transmitting layer is made of a photocurable resin cured by a radical polymerization reaction and has a thickness of 1 to 100 (μm).
Is disposed on the reflective film side, and has a thickness of 2 to 176 made of a photocurable resin cured by a cationic polymerization reaction.
(Μm), the total thickness of the laminated second layers is 3
To 177 (μm).

As a method of manufacturing the optical recording medium of the present invention as described above, a thickness of 0.3 to 1.2 (mm)
When at least a reflection film is formed on one principal surface of the substrate and a light transmission layer having a thickness of 3 to 177 (μm) is formed thereon, at least a part of the light transmission layer is cured by a cationic polymerization reaction. A method of manufacturing an optical recording medium, comprising arranging a photocurable resin to be formed and irradiating the resin with light to form a photocurable resin.

In the method of manufacturing an optical recording medium, it is preferable that the photocurable resin is irradiated with light to be photocured, and then stored in an atmosphere of 20 to 100 (° C.).

Further, in such a method for manufacturing an optical recording medium, it is preferable that the photocuring is performed by irradiating the photocurable resin with light in an atmosphere having a relative humidity of 60 (% RH) or less.

Furthermore, in such a method for manufacturing an optical recording medium, it is preferable that the photocurable resin is irradiated with light and cured by light, and then irradiated with far ultraviolet rays having a wavelength of 300 (nm) or less. .

In the optical recording medium of the present invention, at least a reflection film is formed on one main surface of the substrate, and a thickness of 3 to 177 is formed thereon.
(Μm), and at least a part of the light transmitting layer is made of a photocurable resin cured by a cationic polymerization reaction. In the photocurable resin cured by the above cationic polymerization reaction, only the terminal portion contributes to the reaction, and the main resin reacts linearly, so that the reaction does not accelerate in a three-dimensional network structure. Since the number of functional groups of the monomer directly involved is small and it is difficult to form a network structure, the shrinkage is small. Therefore, in the optical recording medium of the present invention, the shrinkage of the light transmitting layer is suppressed, and the skew of the entire optical recording medium is suppressed.

In the optical recording medium of the present invention, if the light-transmitting layer is formed and the photocurable resin cured by the cationic polymerization reaction contains an epoxy resin, the epoxy resin is a cyclic monomer. , The volume shrinkage due to the polymerization is further suppressed, the higher hardness is secured from the skeleton of the epoxy resin molecules, and the occurrence of scratches when the optical pickup or the like collides with the light transmitting layer surface is suppressed.

Further, in producing the optical recording medium of the present invention, at least a part of the light transmitting layer is provided with a photocurable resin which is cured by a cationic polymerization reaction, and is irradiated with light to cure the photocurable resin. If the photocurable resin is stored in an atmosphere of 20 to 100 (° C.) after photocuring, the curing speed of the photocurable resin is increased.

Further, if the photo-curing resin is irradiated with light by photo-curing in an atmosphere having a relative humidity of 60 (% RH) or less, the curing speed of the photo-curing resin is increased.

Furthermore, if the photocurable resin is irradiated with light and cured by light, and then irradiated with far ultraviolet rays having a wavelength of 300 (nm) or less, the reaction on the surface of the photocurable resin is promoted. Thus, the curing speed of the photocurable resin increases. At the same time, the coefficient of kinetic friction on the surface of the photocurable resin decreases, and the occurrence of scratches when an optical pickup or the like collides with the surface of the light transmitting layer can be suppressed.

[0041]

Embodiments of the present invention will be described below with reference to the drawings.

In the optical recording medium according to the present invention, for example, as shown in FIG. 1, a concave portion 2 is formed on one main surface 1a, and as a result, a reflective film 3 is formed on the one main surface 1a of the substrate 1 having the uneven portion. The recording film 4 is sequentially laminated, and the light transmitting layer 5 is further formed thereon.

The substrate 1 has a thickness of 0.3 to 1.2 (m
m) The substrate is made of, for example, polycarbonate, and irregularities are formed on one main surface 1a as necessary. Further, the reflection film 3 is formed along the uneven portion of the one main surface 1a. Further, the recording film 4 is preferably any one of a phase change type recording film, a magneto-optical recording film, and an organic dye type recording film, and is also formed along the uneven portion of one main surface 1a,
What is necessary is just to form the reflection film 3 in accordance with the characteristics of the recording layer 4. The reflection film 3 and the recording film 4 are formed as needed. If the recording film 4 is not formed, the recording film 4 becomes a read-only optical recording medium. It becomes an optical recording medium.

The light transmitting layer 5 has a thickness of 3 to 17
7 (μm), and one main surface 5a serving as a surface thereof is a flat surface covering the uneven portion.
Further, at least a part of the light transmitting layer 5 is made of a photocurable resin cured by a cationic polymerization reaction.

The light-curable resin which forms the light-transmitting layer 5 and is cured by a cationic polymerization reaction preferably contains an epoxy resin. Further, it is preferable that the light-transmitting layer 5 is formed and the spectral transmittance at a wavelength of 400 to 800 (nm) after curing of the photocurable resin cured by the cationic polymerization reaction be 80 (%) or more.

[0046] Then, in case of reproducing or recording and reproducing of information for the optical recording medium, as shown in FIG. 1, the lens 6 from the light transmission layer 5 side, as shown by the arrow L ₁ By irradiating light, reproduction or recording / reproduction of information is performed by a predetermined method.

In the optical recording medium of the present invention, at least a part of the light transmitting layer 5 is made of a photocurable resin cured by a cationic polymerization reaction. In the photocurable resin cured by the above cationic polymerization reaction, only the terminal portion contributes to the reaction, and the main resin reacts linearly, so that the reaction does not accelerate in a three-dimensional network structure. Since the number of functional groups of the monomer directly involved is small and it is difficult to form a network structure, the shrinkage is small. Therefore, in the optical recording medium of the present invention, the shrinkage of the light transmitting layer is suppressed, the skew of the entire optical recording medium is suppressed, and good reliability is ensured.

In the optical recording medium of the present invention, if the light transmitting layer 5 is formed and the photocurable resin cured by the cationic polymerization reaction contains an epoxy resin, the epoxy resin is cyclic. Since the monomer is contained, volume shrinkage due to polymerization is further suppressed, higher hardness is secured from the skeleton of the epoxy resin molecule, and the occurrence of scratches when an optical pickup or the like collides with the light transmitting layer surface is suppressed, Better reliability is ensured.

To manufacture the optical recording medium as described above,
First, a substrate 1 as shown in FIG. 1 is prepared, and a reflection film 3 and a recording film 4 are formed thereon as necessary.

Subsequently, a light-transmitting layer 5 is formed thereon. At least a part of the light-transmitting layer 5 is provided with a photocurable resin which is cured by a cationic polymerization reaction, and is irradiated with light to be light-cured. Form.

The general reaction mechanism at the time of photocuring of the photocurable resin cured by the above cationic polymerization reaction is shown in Chemical formulas (1) to (5). Here, an example in which the photocurable resin contains an epoxy resin will be described.

[0052]

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[0053]

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[0054]

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[0055]

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[0056]

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That is, as shown in Chemical Formulas 1 and 2, the photoinitiator is photolyzed by irradiation of light (ultraviolet light) to generate a Lewis acid. The Lewis acid reacts with water to produce H ⁺ , as shown in Chemical formula 3 (wherein, only examples of BF ₃ are shown). Next, as shown in Chemical formula 4, the above H
⁺ Is reacted with a compound having an epoxy group, and a cationic polymerization reaction of an oligomer containing an epoxy group such as an epoxy resin is started using the reaction product as shown in Chemical formula 5. A typical example of this type of cationic polymerization initiator is an allyldiazonium salt.

Incidentally, such a cationic polymerization reaction stops when a polar solvent such as water is present in the atmosphere. Therefore, the light curing is performed at a relative humidity of 60.
(% RH) It is preferable to carry out the reaction in the following atmosphere. Specific methods include a method of introducing dry nitrogen or dry air into the atmosphere, a method of disposing a desiccant such as silica gel in the atmosphere, and the like. Thus, by suppressing the relative humidity, the cationic polymerization reaction is promoted, the curing reaction is accelerated, and the productivity is improved.

As the above-mentioned epoxy resin, a condensation product of bisphenol A and epichlorohydrin is generally exemplified. As a characteristic of this bisphenol A-based epoxy resin, it is very excellent in adhesiveness to other substances, and is widely used particularly as an adhesive for metals and glass. In addition, this resin is preferable since it does not produce water or other volatile substances during curing and has a small volume shrinkage.

When the epoxy resin is contained as described above, the epoxy resin can secure excellent mechanical strength and chemical resistance only after reacting with the curing agent. Also in the reaction with such a curing agent, when a cationic polymerization reaction is used, unlike the case where a radical polymerization reaction is used, there is no oxygen polymerization inhibitory effect.

Such a curing agent is roughly classified into two types, and includes an amine-based curing agent and an organic acid anhydride-based curing agent. The former is suitable as a normal- and medium-temperature curing agent, and the latter is suitable as a high-temperature curing agent. As the amine-based curing agent, for example, an addition compound having an amino group at a terminal by adding an epoxy resin, acrylonitrile, ethylene oxide, or the like is often used. In addition, aliphatic polyamines and adducts such as BF ₃ and monoethylamine are also used.

When the photocurable resin is irradiated with light and cured as described above, and stored in an atmosphere of 20 to 100 (° C.), the curing speed of the photocurable resin is increased. , And productivity is improved.

After irradiating the photo-curable resin with light in this way and photo-curing it, irradiating it with far ultraviolet rays having a wavelength of 300 (nm) or less promotes the reaction on the photo-curable resin surface. Thus, the curing speed of the photocurable resin is increased, and the productivity is improved. At the same time, the coefficient of kinetic friction on the surface of the photocurable resin is reduced, and the occurrence of scratches when an optical pickup or the like collides with the surface of the light transmitting layer is suppressed, further improving reliability.

Examples of the photocurable resin cured by the cationic polymerization reaction include a bisphenol AD epoxy resin having a structure shown in Chemical formula 6 in addition to the above-mentioned bisphenol A epoxy resin.

[0065]

Embedded image

The bisphenol A epoxy resin is
Even at room temperature, the viscosity is high, and when a light transmitting layer is to be formed, it is difficult to apply by a normal spin coater, and a special coater is required.

It is conceivable to use various reactive diluents mixed with the bisphenol A-based epoxy resin. However, in this case, although the viscosity is suppressed, the characteristics of the light transmitting layer itself are deteriorated. Not preferred.

The bisphenol AD type epoxy resin has solved these disadvantages, has little residual chlorine, and has stable quality. Naturally, the shrinkage due to the reaction is small, and no volatile components are generated. further,
The viscosity at 25 (° C) is 3000 to 4000 (mPa
S) and low viscosity, so that workability at the time of forming the light transmitting layer is also good. Further, it is amorphous and has good storage stability.

As the diluent for the bisphenol resin, a cycloaliphatic resin is preferably exemplified. This cycloaliphatic resin has a low viscosity, a small epoxy equivalent, and is easy to handle. Further, since the molecule does not contain an aromatic ring, discoloration is difficult. That is, 400 to 800 (nm)
It is possible to realize a high transmittance in the wavelength region of.

As such a bisphenol-based resin containing a cyclic aliphatic resin and cured by a cationic polymerization reaction, 31X028 (trade name) manufactured by Three Bond Co., Ltd. is exemplified. FIG. 2 shows the transmittance of a coating film obtained by applying this resin to a thickness of 100 (μm).

As is apparent from FIG.
It shows a transmittance of 90 (%) or more for light of (nm) or more, and it can be seen that blue semiconductor laser light having a wavelength of around 400 (nm) can be sufficiently used for information reproduction or recording / reproduction. . That is, it was confirmed that the above cycloaliphatic resin was suitable as a diluent for bisphenol resin.

The above-mentioned 31X02 manufactured by Three Bond Co., Ltd.
8 (trade name) does not react well with an amine in reactivity with a curing agent, but reacts well with an acid anhydride. Further, since this resin has a low molecular weight and a cyclic structure, if it is cured, a hard cured product having a high crosslinking density can be obtained, and the resin has excellent high-temperature characteristics.

That is, even if the light transmitting layer is formed of a bisphenol resin containing such a cyclic aliphatic resin and cured by a cationic polymerization reaction, it is sufficiently practical.

In the above-described example, the optical recording medium in which at least a part of the light transmitting layer is made of a photocurable resin cured by a cationic polymerization reaction and a method of manufacturing the same have been described. As the optical recording medium and the method for manufacturing the same, the light transmitting layer has a thickness of 1 to 10 made of a photocurable resin cured on the reflective film side by a radical polymerization reaction.
A first layer of 0 (μm) is disposed thereon, and a thickness of 2-1 of a photocurable resin cured on the first layer by a cationic polymerization reaction.
An optical recording medium having a total thickness of 3 to 177 (μm), in which a second layer of 76 (μm) is laminated and arranged, and a method of manufacturing the same are also included.

[0075]

EXAMPLES Next, in order to confirm the effects of the present invention, the following experiments were conducted.

Experimental Example 1 In this experimental example, the influence on the skew when a light transmitting layer made of a photocurable resin cured by a cationic polymerization reaction was formed on a substrate was investigated.

That is, a photo-curable resin cured by a cationic polymerization reaction is applied on a substrate made of a polycarbonate having a thickness of 1.2 (mm) and having a diameter equivalent to that of a digital audio disc by a thickness of 50 (μm). ) And uniformly cured by light curing to form an optical disc as a light transmitting layer, and the change in skew of the entire optical disc was investigated.

As the photocurable resin, 3102 (trade name) manufactured by Three Bond Co. was used. Then, the skew of the optical disc is determined by disc radius 35 (mm) and 50
(Mm), immediately after the formation of the light transmitting layer, at a temperature of 60 mm.
(° C.) and a relative humidity of 90 (% RH). For comparison, the skew of the substrate itself was also measured. Table 1 shows the results.

[0079]

[Table 1]

As can be seen from the results shown in Table 1, by forming the light transmitting layer on the substrate, the skew is increased by + 0.00 ° at the position of the disk radius 35 (mm) and by the disk radius of 50 (mm). The position shows an increase of + 0.06 °. In addition, looking at the skew after being left in a predetermined environment, it was found that + 0.06 ° at the position of the disk radius 35 (mm),
An increase of + 0.03 ° is shown at the position of the disk radius 50 (mm).

That is, it is confirmed that, when the light transmitting layer is formed of the above-mentioned materials, the shrinkage during light curing is suppressed, the skew of the entire optical recording medium is suppressed, and good reliability is secured. Was done. Furthermore, it was confirmed that when the light transmitting layer was formed from the above-mentioned materials, the light transmitting layer hardly changed over time, and good reliability was secured.

From these facts, if the light transmitting layer is formed by using the above-mentioned materials, if the skew of the substrate is about 0 °, the light transmitting layer can be formed even if the light transmitting layer is formed. The skew of the entire recording medium is kept within + 0.2mm,
In addition, it was confirmed that the skew was suppressed to within + 0.2 ° even when the change with time was taken into consideration, and characteristics that could sufficiently endure practical use were secured.

That is, it has been confirmed that, when the present invention is applied, the shrinkage of the light transmitting layer is suppressed, the skew of the entire optical recording medium is suppressed, and good reliability is secured.

Experimental Example 2 In this experimental example, a first layer composed of a photocurable resin cured by a radical polymerization reaction on a substrate and a second layer composed of a photocurable resin cured by a cationic polymerization reaction The influence on the skew when a light transmission layer, which is a laminated film made of a film, was formed was investigated.

That is, on a substrate made of a disc-shaped polycarbonate having a thickness of 1.2 (mm) and having a diameter equivalent to that of a digital audio disc, a thickness of 4 (made of a photo-curable resin cured by a radical polymerization reaction) μm), and a total thickness of a second layer 36 (μm) made of a photocurable resin cured by a cation polymerization reaction is disposed on the first layer. An optical disc was formed by forming a light transmitting layer, which was a 40 (μm) laminated film, and the skew of the entire optical disc was examined. The first layer and the second layer may be formed by applying respective photo-curable resins and then photo-curing.

As the photocurable resin for forming the first layer, SK-3100 (trade name) manufactured by Sony Chemical Corporation is used.
Is used as the photo-curable resin for forming the second layer,
Three Bond 3102 (trade name) was used. Among the photocurable resins cured by the cationic polymerization reaction, there are materials that easily corrode metals or recording films. As described above, the above-described phenomenon can be prevented by forming a two-layer structure with the photocurable resin cured by the radical polymerization reaction.

The skew of the optical disk is as follows: at the positions of the disk radii of 35 (mm) and 50 (mm), immediately after forming the light transmitting layer, the temperature is 60 (° C.) and the relative humidity is 90 (% R).
The measurement was carried out after allowing to stand for 96 hours in the environment of H). Also,
For comparison, the skew of the substrate itself was also measured. Table 2 shows the results.

[0088]

[Table 2]

As can be seen from the results shown in Table 2, by forming the light transmitting layer on the substrate, the skew was increased by + 0.00 ° at the position of the disk radius 35 (mm) and by the disk radius of 50 (mm). The position shows an increase of + 0.04 °. When the skew after standing in a predetermined environment is seen, at the position of the disk radius 35 (mm), −0.06 °,
A decrease of -0.09 ° is shown at the position of the disk radius 50 (mm).

Such a change in skew after standing is not caused by a change such as shrinkage in the photocurable resin cured by the cationic polymerization reaction, but by an extension in the photocurable resin cured by the radical polymerization reaction. Is caused.
SK-3100 manufactured by Sony Chemical Co., Ltd., which is a photocurable resin that is cured by a radical polymerization reaction used here.
(Trade name) is a urethane acrylate resin. The urethane acrylate resin has a low glass transition temperature and tends to expand under a high-temperature and high-humidity environment such as the above-described storage condition, and thus the above-described expansion occurs. Therefore, for confirmation, a light-transmitting layer having a thickness of 4 (μm) made of SK-3100 (trade name) manufactured by Sony Chemical Co., Ltd. was formed on a substrate similar to the above substrate, and the skew was similarly reduced. Upon investigation, similar results were obtained.

That is, it has been confirmed that even when the light transmitting layer is a laminated film as described above, shrinkage during light curing is suppressed, the skew of the entire optical recording medium is suppressed, and good reliability is secured. Was. Further, it was confirmed that even when the light transmitting layer was a laminated film as described above, the light transmitting layer hardly changed with time, and good reliability was secured.

From the above, when the light transmitting layer is formed as a laminated film as described above, if the skew of the substrate is about 0 °, the optical recording medium can be formed even if the light transmitting layer is formed. The overall skew is kept within + 0.4mm,
It was confirmed that characteristics sufficient for practical use were secured.

Therefore, it was confirmed that, when the present invention was applied, the shrinkage of the light transmitting layer was suppressed, the skew of the entire optical recording medium was suppressed, and good reliability was secured.

Experimental Example 3 In this experimental example, the effect of the treatment conditions after photocuring of a photocurable resin cured by a cationic polymerization reaction on the surface hardness of the photocurable resin was investigated.

That is, 31X-028 (trade name) manufactured by Three Bond Co., Ltd., which is an epoxy resin cured by a cationic polymerization reaction, was applied onto the substrate used in Experimental Example 1, and this was photo-cured. Sample 1 left in an atmosphere of 20 (° C.), similarly cured with light, and Sample 2 left in an atmosphere of 80 (° C.). Similarly, after photo-curing, far ultraviolet rays were applied at an intensity of 1 (J / cm ² ). Irradiated Sample 3 was prepared, and in these Samples 1 to 3, the relationship between the time during which a predetermined treatment was performed and the pencil hardness of the photocurable resin surface was examined.

FIG. 3 shows the results. The horizontal axis in FIG. 3 indicates the time for performing the predetermined processing, the vertical axis indicates the pencil hardness, 中 in FIG. 3 indicates the result of Sample 1, ◎ in FIG. The middle square shows the result of Sample 3.

If the predetermined processing is further continued for any of the samples 1 to 3, the final pencil hardness becomes F. However, as is clear from the results of Sample 1 and Sample 2 in FIG. 3, the curing of Sample 2 in which the standing temperature condition after photocuring is relatively high is faster than that of Sample 1.

This is expressed by the relationship between the Arrhenius velocity and temperature shown in the following equation 1.

K = Aexp (−E / RT) (Equation 1) (k: rate constant, A: frequency factor, E: activation free energy, R: gas constant, T: absolute temperature) It can be seen that the higher the temperature and the storage, the faster the curing speed, and the higher the temperature, the faster the curing speed. That is, heating after photocuring in this way shortens the manufacturing tact time, leading to an improvement in productivity. However, this temperature must not exceed the glass transition temperature of the photocurable resin and must not exceed the thermal deformation temperature of the substrate. Examples of the substrate forming material include polycarbonate forming the substrate of a digital audio disk or a DVD, and the heat deformation temperature of the polycarbonate is about 100 (° C.). No inconvenience is expected.

That is, after applying the present invention and irradiating the photo-curable resin forming the light-transmitting layer with light to photo-cur the resin,
It was confirmed that when stored in an atmosphere of 0 to 100 (° C.), the curing speed of the photocurable resin was increased, and the productivity of the optical recording medium was improved.

As is clear from FIG. 3, Sample 3 has a faster curing speed than Sample 2 left at a temperature of 80 (° C.), and is completely cured after 45 minutes. This seems to be due to the following reasons.
A low-pressure mercury lamp is generally used as a light source for far-ultraviolet light, and the wavelength of this lamp is 254 (nm) and 18 nm.
5 (nm) and the emission line energy is 47
1 (kJ / mol) and 647 (kJ / mol).
On the other hand, the chemical bond energy of the CO bond of the epoxy group which is a functional group involved in the chain reaction of the epoxy resin is 353.
(KJ / mol). That is, far-ultraviolet light is very effective in breaking these bonds, and the cut epoxy groups react one after another and cure, and the curing speed becomes very fast.

Therefore, if the present invention is applied and the photocurable resin forming the light transmitting layer is irradiated with light to be photocured, and then irradiated with far ultraviolet rays having a wavelength of 300 (nm) or less, the photocurable resin is cured. It was confirmed that the reaction on the resin surface was accelerated, the curing speed of the photocurable resin was increased, and the productivity of the optical recording medium was improved.

[0103]

As described above, the optical recording medium of the present invention
At least a reflection film is formed on one principal surface of the substrate, and a light transmission layer having a thickness of 3 to 177 (μm) is formed thereon. At least a part of the light transmission layer is formed by cationic polymerization. It is made of a photocurable resin cured by a reaction. For this reason, in the optical recording medium of the present invention, the contraction of the light transmitting layer is suppressed, the skew of the entire optical recording medium is suppressed, and good reliability is secured.

In the optical recording medium of the present invention, if the light-transmitting layer is formed and the photo-curable resin cured by the cationic polymerization reaction contains an epoxy resin, the volume shrinkage due to the polymerization is reduced. It is further suppressed, and a higher hardness is secured from the skeleton of the epoxy resin molecule, and the occurrence of scratches when an optical pickup or the like collides with the surface of the light transmitting layer is suppressed, and better reliability is secured.

Further, at the time of manufacturing the optical recording medium of the present invention, at least a part of the light transmitting layer is provided with a photocurable resin which is cured by a cationic polymerization reaction, and this is irradiated with light to form a photocurable resin. If the photocurable resin is stored in an atmosphere of 20 to 100 (° C.) after photocuring, the curing speed of the photocurable resin is increased, and the productivity is improved.

Further, if the photocuring is performed by irradiating the photocurable resin with light in an atmosphere having a relative humidity of 60 (% RH) or less, the curing speed of the photocurable resin is increased, and the productivity is increased. Is improved.

Furthermore, if the photocurable resin is irradiated with light and cured by light, and then irradiated with far ultraviolet rays having a wavelength of 300 (nm) or less, the reaction on the surface of the photocurable resin is promoted. Thus, the curing speed of the photocurable resin is increased, and the productivity is improved. At the same time, the coefficient of kinetic friction on the surface of the photocurable resin is reduced, and the occurrence of scratches when the optical pickup or the like collides with the surface of the light transmitting layer is suppressed, and further reliability is obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a main part of an optical recording medium according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between wavelength and transmittance.

FIG. 3 is a characteristic diagram showing a change in pencil hardness with respect to time.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Substrate, 1a, 5a One main surface, 2 concave parts, 3 reflective films, 4 recording films, 5 light transmission layers

Claims (11)

[Claims] At least a reflection film is formed on one principal surface of a substrate having a thickness of 0.3 to 1.2 (mm), and a light transmission layer having a thickness of 3 to 177 (μm) is formed thereon. An optical recording medium, wherein at least a part of the light transmission layer is made of a photocurable resin cured by a cationic polymerization reaction. 2. The optical recording medium according to claim 1, wherein at least one principal surface of the substrate on which the reflection film is formed has a concave and convex portion. 3. The optical recording medium according to claim 1, wherein at least a recording film is provided between the reflection film and the light transmission layer of the substrate. 4. The optical recording medium according to claim 3, wherein said recording film is one of a phase change recording film, a magneto-optical recording film, and an organic dye recording film. 5. The optical recording medium according to claim 1, wherein the photo-curable resin which forms the light transmitting layer and is cured by a cationic polymerization reaction contains an epoxy resin. 6. A light-curable resin which forms the light-transmitting layer and is cured by a cationic polymerization reaction.
2. The optical recording medium according to claim 1, wherein the spectral transmittance at a wavelength of 800 to 800 (nm) is 80 (%) or more. 7. The light transmitting layer according to claim 1, wherein said light transmitting layer is made of a photocurable resin cured by a radical polymerization reaction.
m) is disposed on the reflective film side, and a second layer having a thickness of 2 to 176 (μm) made of a photocurable resin cured by a cationic polymerization reaction is disposed thereon. 2. The optical recording medium according to claim 1, wherein the total thickness of the optical recording medium is 3 to 177 (μm). 8. A reflection film is formed on at least one principal surface of a substrate having a thickness of 0.3 to 1.2 (mm), and a light transmitting layer having a thickness of 3 to 177 (μm) is formed thereon. In this case, at least a part of the light-transmitting layer is provided with a photo-curable resin that is cured by a cationic polymerization reaction, and is irradiated with light to form a photo-curable resin. Method. 9. The method for manufacturing an optical recording medium according to claim 8, wherein the photocurable resin is irradiated with light to be photocured, and then stored in an atmosphere at 20 to 100 ° C. . 10. The method for manufacturing an optical recording medium according to claim 8, wherein the photocuring by irradiating the photocurable resin with light is performed in an atmosphere having a relative humidity of 60 (% RH) or less. 11. The method of manufacturing an optical recording medium according to claim 8, wherein the photocurable resin is irradiated with light to be photocured, and then irradiated with far ultraviolet rays having a wavelength of 300 (nm) or less. .