JP2591941B2 - Optical recording method and optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording method and an optical recording medium.

[Prior Art] Conventionally, as an optical recording medium, there are known a type in which pits (holes) are formed, a type in which bubbles are formed, and a type in which phase transformation is performed by irradiation of a light beam, for example, a laser beam.

Among these, those that form pits (holes) are formed on the support by low-melting-point metals such as Te, Bi, Sn, Sb, and In, cyanine, squalium, phthalocyanine, tetradehydrocholine, and methine. And a dye / pigment (organic dye) such as a naphthoquinone-based or benzenedithiol-nickel complex, and a composite thin film of these organic dye and metal.

These thin films are irradiated with a light beam, converted into thermal energy in accordance with the absorptivity, and form recording pits in the heat mode.

At this time, as shown in FIG. 3, the peripheral portion of the recording pit 5 of the recording pit rises, and a projection called a rim 8 occurs.

This rim is caused by the melting-solidification process of the optical recording medium, but the process is very complicated, its shape and size are not always constant, and it leads to errors in retransmission signals when reading. Had become.

[Problems to be Solved by the Invention] An object of the present invention is to solve the above-mentioned conventional drawbacks, and to provide an optical recording capable of forming a recording pit having no rim and always having a constant size and shape. It provides a method.

Another object of the present invention is to provide a highly reliable optical recording medium having a small error rate of a reproduced signal.

[Means for Solving the Problems] and [Operation] That is, the present invention provides an optical recording layer composed of a laminate of a light reflecting layer and a porous light absorbing layer such that the light absorbing layer faces the substrate. The optical recording medium disposed on the substrate is irradiated with a light beam to deform the light beam irradiating portion of the light absorbing layer into a concave shape, and the light reflecting layer is deformed into a concave shape along with the deformation of the absorbing layer. An optical recording method characterized by recording information by forming recording pits in the light reflecting layer at least.

Further, the present invention provides an optical recording layer in which a light reflection layer and a porous light absorption layer are laminated, the light reflection layer is disposed on the substrate such that the light reflection layer faces the substrate, and the optical recording layer In an optical recording medium on which information is recorded, the information is recorded on the optical recording medium by recording pits formed by a concavely deformed light absorbing layer and a light reflecting layer deformed concavely along the deformation of the light absorbing layer. An optical recording medium characterized by being recorded in a layer.

 Hereinafter, a specific configuration of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view showing a typical configuration example of the present invention. In FIG. 1, the optical recording medium of the present invention forms an optical recording layer 2a by laminating a light reflecting layer 6 and a porous light absorbing layer 7, and the optical recording layer 2a is disposed below the optical recording layer 2a. The protective layer 4 is provided on the outermost layer to protect the light reflecting layer 6.

In the present invention, the substrate 3 is a glass plate, a ceramic plate, an aluminum plate, a metal plate such as a stainless steel plate, PVC.PMMA.PC
Such as a plastic plate can be used. The substrate may be transparent or opaque, and its size is not particularly limited as long as it satisfies the function of the support of the optical recording medium, and the light absorbing layer may also serve as the substrate.

In the present invention, one of the features of the present invention is that the optical recording layer 2a includes the light reflecting layer 6 and the porous light absorbing layer 7.

The optical recording layer receives the light beam, absorbs the light, converts the light into heat, and forms a recording pit by the heat. It is required to be a so-called heat mode recording material and to have a reflection for reading a signal.

In view of this point, the present invention is to form an optical recording layer by laminating the light reflecting layer 6 and the light absorbing layer 7 as shown in FIG. 1. Particularly, the light absorbing layer 7 is porous. It is a feature.

In the present invention, the light reflection layer is an important factor that determines the S / N of recorded information, and is required to have a large ratio between the reflection intensity before recording and the reflection intensity after recording. In addition, the reflection signal from the light reflection layer becomes a signal for operating AT and AF which are important for recording / reproducing of the optical recording medium.

Considering these points, the higher the reflectivity of the light reflecting layer is, the more preferable it is.
A rational apportionment of both is required. Therefore, the reflectance of the light reflecting layer is preferably 10 to 85%, and more preferably 15 to 60%.

The light reflecting layer is formed by depositing a metal such as gold, silver, or copper, by electroless plating, or by dispersing and applying these metal particles in a vehicle.

The thickness of the light reflecting layer is determined by the reflectance determined by the relationship with the light absorbing layer constituting the optical recording layer and the processing method, that is, whether to select vapor deposition or electroless plating, or application of a dispersion medium. It is determined, and the range is several m to m / m, preferably 20 m to 1.0 m / m.

In the present invention, the light absorbing layer has both a function of absorbing the irradiated light energy and converting it to heat energy, and a function of forming the recording pit and the laminated reflective layer by itself deforming by the heat. is there.

The light-absorbing layer is formed by dispersing substances such as dyes and pigments having absorption characteristics at the wavelength of the recording beam at the time of optical recording, or these substances in Bekhill and a binder, and furthermore, these are porous. It is adjusted as it is.

As the light absorbing layer, low melting point metals such as Te, Bi, Sn, Sb, In and alloys thereof and metal particles such as Au, Ag, Cu, cyanine, squalium, phthalocyanine, tetradehydrocholine, methine, Naphthoquin-based dyes and pigments, organic metal complexes such as benzenedithiol nickel complex, and black dyes and pigments such as carbon black and nigrosine can be preferably used.

Further, as a binder for dissolving or dispersing these light absorbing materials, polyvinyl chloride, polyvinyl alcohol, vinyl acetate such as polyvinyl acetate, olefins such as polyethylene and polypropylene, polymethyl methacrylate, polymethyl acrylate and the like Acrylic, polyester, polyamide, polystyrene,
Examples include organic polymer substances composed of cellulose-based, polycarbonate-based, and ionomer-based resins and copolymers and mixtures thereof, organic carboxylic acids such as stearic acid, palmitic acid, phthalic acid, and succinic acid, and solid paraffin.

That is, these substances cause thermal deformation such as melting and thermal softening at a low temperature of 400 ° C. or lower, preferably 200 ° C. or lower.

Such a light absorbing layer can be made porous by the following means.

(1) A method of performing casting while allowing a swelling agent to act during film formation.

(2) A method in which a foaming agent such as azodicarbonamide or dinitropentamethylenetetramine is allowed to act upon film formation.

(3) A method in which at the time of film formation, a film is formed using two or more kinds of resins or a copolymer composed of two or more components as a dispersant, and then a solvent is applied to dissolve at least one component of the dispersant.

As the copolymer, a PVA-acrylonitrile-based graft polymer, a PVA-acrylic-based graft polymer, an ethyl acrylate-methyl methacrylate copolymer, or the like can be used.

(4) A method of using a diazo compound such as p-diethylaminobenzene chloride or a zinc chloride double salt of p-dimethylaminobenzenediazonium chloride or an azide compound as a binder, and irradiating the film with light.

(5) A method of producing a porous material by controlling the rate of volatilization of a solvent during solvent casting.

The porous voids may be continuous or independent, and the ratio of the voids per unit volume, that is, the porosity is preferably 10% or more, preferably 10 to 90%, particularly preferably 20 to 80%. .

The thickness of the light-absorbing layer is several to several m / m, preferably 700
~ 1.8m / m is desirable.

In the present invention, the optical recording layer is provided on the substrate 3. In this case, even if the optical recording layer is set by coating or depositing a porous light absorbing layer and a light reflecting layer on the substrate in order, The optical recording layer may be provided via an adhesive layer such as a laminating agent.

If the optical recording layer is coated on a thin film or the like in advance, such as a silver halide photographic material, the entire film can be set on a substrate via an adhesive.

In the present invention, the protective layer 4 imparts mechanical, chemical and physical resistance to the environment of the optical recording layer, and covers the optical recording layer with a material transparent to recording / reproducing light.

For example, a glass plate or a ceramic plate, a plastic plate such as polymethyl methacrylate, polycarbonate, vinyl chloride, polyethylene terephthalate, polystyrene, CR-39, or polymethylpentene is provided on the optical recording layer via an adhesive layer as necessary. .

In another example, the plastic material described above is coated directly on the optical recording layer and cured to form a protective layer. in this case,
A radiation-curable resin can also be used.

The protective layer is provided on the optical recording layer, but does not have to be in close contact with the optical recording layer, and may be provided via air or an inert gas.

On the outer surface of the protective layer, anti-abrasion treatment, hardening treatment, anti-fouling / dye-proofing treatment, anti-static treatment, anti-static treatment and anti-moisture treatment to prevent adhesion of scratches and dust during handling processing,
Anti-ultraviolet treatment, oxygen-proof transmission treatment (O ₂ gas barrier treatment)
Can be applied as needed.

The optical recording medium according to the present invention has an optical recording layer as shown in FIG.
When information is written by irradiating the laser beam 1 from the side 2a, recording pits 5 are formed in the light-irradiated portion of the optical recording layer 2a. When information is written by this light irradiation, the porous voids in the light irradiation part are reduced due to the softening and melting of the porous light absorbing layer 7, so that the shape of the recording pit is shaped, that is, the rim is formed. A pit having a stable size that does not occur can be formed, and an excellent reproduction signal can be given.

Furthermore, the optical recording medium of the present invention has a high absorption for converting light into heat energy due to the high sensitivity of the optical recording layer, and has an appropriate reflectance for detecting a signal with good contrast. In addition, it has excellent durability (withstands storage for at least 10 years or more).

[Example] Hereinafter, the present invention will be described more specifically with reference to examples.

Example 1 Cyanine dye; NK1414 (manufactured by Nikko Sensitive Dye Co., Ltd.) 30
Parts by weight, and 15 parts by weight of dinitropentamethylenetetramine as a foaming agent were mixed with 50 parts by weight of an ethanol solution containing 20% by weight of polyvinyl butyral and uniformly mixed, and this was mixed on a polycarbonate substrate having a thickness of 1.0 mm. Was coated with a bar coater to form a film, and a porous light absorbing layer having a thickness of 5 μm and a porosity of 65% was provided.

Subsequently, gold was vacuum-deposited on the absorption layer to provide a light reflecting layer having a thickness of 50 ° to obtain an optical recording medium having a porous optical recording layer.

As a result of writing a semiconductor laser having a wavelength of 830 nm on this optical recording layer with a beam diameter of 3 μm and a power of 3 mW on the recording surface, a reproduction signal of 0.10 mW provided a reproduction signal of 0.80 or more contrast.

As a result of observing the recording pit at this time by a scanning electron microscope, no rim was formed, and a recording pit having a very stable size with a pit diameter of 3 ± 0.1 μm was obtained.

Example 2 Carbon black (manufactured by Columbia Carbon Co., Ltd.) was added to a 15% by weight solution of cellulose triacetate (manufactured by Kodak Company) in methylene chloride, and 1/2 of the cellulose triacetate was used.
After mixing for about 2 hours, apply a bar coat on a 1.0 mm thick transparent polymethyl methacrylate substrate, immerse it in an ethanol solution, and dry it. A membrane was obtained.

Subsequently, an aluminum vapor-deposited film was formed on the light absorbing layer for 200 hours.
An optical recording medium having a porous optical recording layer provided with a thickness of Å was obtained.

When recording and reproduction were performed on the optical recording layer under the same conditions as in Example 1, a contrast of 0.60 or more was obtained with the reproduction signal.

When the recording pits were observed with a scanning electron microscope, no rim was formed, and recording pits having a very stable size with a pit diameter of 3.0 ± 0.2 μm were obtained.

Example 3 Azodicarbonamide and Mordant Black 86 (trade name: Mitsui) in a 10% by weight solution of polyvinyl acetate (molecular weight: 1400 to 1600, manufactured by Wako Pure Chemical Industries, Ltd.) in ethylene dichloride
Chrome Black ME (manufactured by Mitsui Toatsu Chemicals, Inc.) was added in an amount of 20 parts by weight, and after sufficient stirring, a bar coat was applied on a 0.18 μm thick transparent polyethylene terephthalate substrate to give a dry film thickness of 6.5 μm and a porosity of 85. % Of a porous light absorbing layer was obtained.

Next, a 90-mm-thick copper film was formed on the light-absorbing layer by chemical plating to provide a light-reflecting layer, thereby obtaining an optical recording medium having a porous optical recording layer.

When recording and reproduction were performed on this optical recording layer under the same conditions as in Example 1, a contrast of 0.5 or more was obtained in the reproduction signal.

When the recording pit was observed with a scanning electron microscope, no rim was formed, and the pit system had a stable size of 3.0 ± 0.3 μm and a uniform shape.

Comparative Example 1 A film having a thickness of 4. was obtained using the same procedure and conditions except that dinitropentamethylenetetramine was not used in Example 1.
An optical recording medium having a 5 μm optical recording layer was obtained.

When recording was performed on this optical recording layer under the same conditions as in Example 1, a contrast of 0.40 or more was obtained. However, a rim having a width of about 0.1 to 0.5 μm was found around the pit, and variations in the pit diameter and shape were observed.

[Effects of the Invention] As described above, according to the optical recording method and the optical recording medium of the present invention, it is possible to always keep the shape of the recording pit constant and to reduce the error rate of the reproduced signal at the time of reading. There are advantages such as possible.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a typical configuration example of an optical recording medium of the present invention, FIG. 2 is a cross-sectional view showing a state of writing information, and FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Laser light, 2a, 2b ... Optical recording layer 3 ... Substrate 4, Protective layer 5 ... Recording pit, 6 ... Light reflecting layer 7 ... Light absorbing layer, 8 ... Rim

Continuing on the front page (72) Inventor Hitoshi Yoshino 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Sachiko Igarashi 3-30-2 Shimomaruko 3-chome, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Seijiro Kato 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-54-5447 (JP, A) JP-A-57-150149 (JP, A) JP-A-57-55540 (JP, A) JP-A-56-124135 (JP, A) JP-A-62-33349 (JP, A) JP-A-61-95991 (JP, A)

Claims (2)

(57) [Claims] An optical recording layer comprising a laminate of a light reflecting layer and a porous light absorbing layer is provided on an optical recording medium disposed on a substrate such that the light absorbing layer faces the substrate. To irradiate the light-absorbing layer of the light-absorbing layer with a concave shape to deform the light-reflecting layer along with the deformation of the light-absorbing layer to form recording pits in the light-reflecting layer. An optical recording method, comprising: 2. An optical recording layer on which a light reflecting layer and a porous light absorbing layer are laminated is disposed on the substrate such that the light absorbing layer faces the substrate, and information is recorded on the optical recording layer. In the optical recording medium in which is recorded, the information is recorded in the optical recording layer by the recording pits formed by the concavely deformed light absorbing layer and the concavely deformed light reflecting layer along the deformation of the light absorbing layer. An optical recording medium characterized by being recorded.