JPS63166037A - Information recording medium and its manufacture - Google Patents

Abstract

PURPOSE:To easily and rapidly form a pre-group layer, by forming the pre-group layer with a thermoplastic polymer and an optical activator. CONSTITUTION:A layer consisting of the thermoplastic polymer including the optical activator possible to generate a photovoltaic effect is provided on a substrate. Next, by projecting an activating beam of light on a group forming layer in a pattern shape by using a photomask, etc., an electromotive force is generated in the group forming layer by the optical activator, and the movement of an electric charge is generated in the layer, thereby, an electrostatic pattern corresponding to a pattern is generated. Next, by heating the group forming layer immediately, the group forming layer is contracted and deformed by an electrostatic force, and a recessed part is formed in the pattern shape. In such a way, it is possible to rapidly and easily form the pre-group layer having a precise tracking guide pattern.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium on which information can be written and/or read using a high-energy-density laser beam, and a method for manufacturing the same.

More specifically, the present invention relates to an information recording medium having a pregroove layer between a substrate and a recording layer, and a method for manufacturing the same.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is, for example, an optical disk such as a video disk or an audio disk, a large-capacity still image file, a large-capacity computer disk memory, an optical card, a micro image recording medium, a super micro image recording medium, or a micro image recording medium. It is applied to facsimiles, original plates for phototypesetting, etc.

An information recording medium basically consists of a disk-shaped transparent substrate made of plastic, glass, or the like, and a recording layer provided thereon. The material of the recording layer is Bi%Sn,
Metals or metalloids such as In and Te; and cyanine-based,
Dyes such as metal complexes and quinones are known.

Information is written on an information recording medium by, for example, irradiating the recording medium with a laser beam.
The irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in a physical or chemical change that changes its optical properties, thereby recording information. Information is also read from a recording medium by irradiating the recording medium with a laser beam, and the information is reproduced by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

Recently, as a disk structure for protecting the recording layer, a recording layer is provided on at least one of the two disk-shaped substrates, and the recording layer is located inside the two disk-shaped substrates. An air sandwich structure has also been proposed in which a ring-shaped inner spacer and a ring-shaped outer spacer are joined together to form a space. In information recording media with such a structure, the recording layer is not in direct contact with the outside air, and information is recorded and reproduced using a single laser beam that passes through the substrate. It will not be damaged or have dust attached to its surface, which will impede information recording and reproduction.

Conventionally, in order to prevent tracking errors when reading information, a pregroove layer having tracking grooves (guide grooves) has been provided between a substrate and a recording layer.

The pre-groove layer is usually created by cutting a master disc with a photoresist layer with a laser beam to create a precise master mold (master disc), and then injecting resin using a mold that includes a stub bar that is copied from this master disc. It is provided by molding to form a plastic substrate having unevenness (guide grooves) on its surface. However, this method requires the stamper to be produced with high precision, and the manufacturing process is complicated, resulting in high manufacturing costs.

[Summary of the Invention] An object of the present invention is to provide an information recording medium that can be manufactured simply and quickly, and a method for manufacturing the same.

Another object of the present invention is to provide an information recording medium with reduced manufacturing costs and a method for manufacturing the same.

The above object is an information recording medium in which a pregroove layer and a recording layer on which information can be written and/or read by a laser are provided on a substrate, in which the pregroove layer is composed of a thermoplastic polymer and a photoactive agent. In the information recording medium of the present invention, and the method for manufacturing the information recording medium in which a pregroove layer and a recording layer on which information can be written and/or read by a laser are provided on a substrate, 1) A step of providing a groove forming layer by applying a coating solution containing a thermoplastic polymer and a photoactive agent onto the substrate and then drying it; and 2) irradiating the groove forming layer with actinic light in a pattern; and This can be achieved by the method for manufacturing an information recording medium of the present invention, which comprises the steps of forming a pattern of concave portions in the groove forming layer to form a pre-groove layer by heating.

The present invention quickly and easily forms a pre-groove layer having a dense tracking guide pattern on a substrate by using a combination of a thermoplastic polymer and a photoactive agent as a material for forming the pre-groove layer, This simplifies the manufacturing process of the information recording medium, shortens manufacturing time, and reduces manufacturing costs.

That is, in the manufacturing method of the present invention, first, a layer (groove forming layer) made of a thermoplastic polymer containing a photoactive agent that produces a photovoltaic effect is provided on a substrate by coating. Next, this groove forming layer is irradiated with actinic light such as ultraviolet rays or visible light in a pattern using a photomask or the like. As a result, an electromotive force is generated in the groove forming layer by the photoactive agent, causing electric charges to move in the layer, and an electrostatic pattern corresponding to the pattern is formed. Next, when the groove forming layer is immediately heated, the groove forming layer contracts and deforms due to electrostatic force, and recesses are formed in a pattern. Note that a similar phenomenon occurs even if the groove forming layer is irradiated with light and heated at the same time.

This deformation phenomenon caused by light irradiation and heating can be achieved using the photocharging method (rPhotocharge Process J).
It is a type of optical pattern forming method.

This photocharging method is described, for example, in J. Gaynor and G. J. Sewe.
ll, Photo.

Sci, Eng, Yu1. P, 204 (1967)
. Here, the layer consisting of a thermoplastic polymer and a photoactive agent is a photosensitive layer, and is also referred to as a photovoltaic thermoplastic layer.

The photoactivator used is, for example, a polyhalogen-substituted hydrocarbon such as iodoform.

Therefore, according to the present invention, grooves can be formed on the surface of the substrate by applying light and heating after coating the resin layer, so there is no need to create a stand bar using complicated processes as in the past. The pre-groove layer can be provided easily in a short time and at low cost. Further, the information recording medium manufactured in this manner has a good tracking guide pattern.

Note that the patterned recesses formed by the method of the present invention may include additional information such as an address signal in addition to the tracking guide pattern, and this tracking guide pattern may include groove tracking and Contains patterns for sampling tracking.

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

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Optical properties, flatness, processability of the substrate,
In terms of ease of handling, stability over time, and manufacturing cost,
Examples of substrate materials include glass such as soda lime glass; acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; polycarbonate resins , amorphous polyolefins, polyesters, polyethylene terephthalate; and ceramics. Among these, preferred are dimethyl methacrylate, polycarbonate resin, epoxy resin, amorphous polyolefin, polyethylene terephthalate, and glass in terms of dimensional stability, transparency, and flatness. Note that these materials can also be used as a rigid substrate with a thickness of 1 to 2 mm, or as a flexible support in the form of a film with a thickness of 200 μm or less.

The surface of the substrate on which the recording layer is provided has improved flatness,
For the purpose of improving adhesive strength and preventing deterioration of the recording layer, an undercoat layer may be provided. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, and styrene.・Maleic anhydride copolymer, polyvinyl alcohol, N-methylol acrylamide, styrene/sulfonic acid copolymer, styrene/vinyltoluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, chlorinated polyolefin, polyester, Polymer substances such as polyimide, vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (s i o 2, aj220 etc.), inorganic substances such as inorganic fluoride (MgF2).

In the case of a glass substrate, hydrophilic groups such as styrene/maleic anhydride copolymer and/or maleic anhydride are added to prevent adverse effects on the recording layer due to alkali metal ions and alkaline earth metal ions liberated from the substrate. Preferably, a subbing layer consisting of a polymer containing groups is provided.

The undercoat layer can be formed, for example, by dissolving or dispersing the above-mentioned substance in a suitable solvent and then applying this coating solution to the substrate surface using a coating method such as spin cording, dip coating, or extrusion coating. Ru. The layer thickness of the undercoat layer is generally in the range of 0.005 to 20 μm, preferably 0.0! ~! It is in the range of 0 μm.

Next, a pregroove layer, which is a characteristic feature of the present invention, is provided on the substrate (or undercoat layer).

The pregroove layer is a layer consisting of a thermoplastic polymer containing a photoactive agent.

A typical example of the thermoplastic polymer used in the present invention is polystyrene. Polystyrene preferably has a molecular weight of about 20,000. In addition, polystyrene exhibits good dielectric properties, has a suitable melting temperature (for example, around 100°C), and has a melt viscosity low enough to allow deformation. Any polymer or polymer blend can be used.

As photoactivators, for example, halogenated aliphatic hydrocarbons can be used, examples of which may include iodoform, carbon tetrabromide, methylene iodide and ethylene tetramonide. Among these, particularly preferred is iodoform.

The pre-groove layer is formed by first preparing a coating solution by dissolving the above thermoplastic polymer and photoactive agent in an appropriate solvent, applying this coating solution to the substrate surface to form a coating film, and then drying it. , a groove forming layer is provided on the substrate.

Solvents for preparing the coating solution include toluene, xylene, ethyl acetate, butyl acetate, cellosolve acetate, methyl ethyl ketone, dichloromethane, 1,2-dichloroethane, dimethylformamide, methyl isobutyl ketone,
Examples include solvents that dissolve thermoplastic polymers and photoactive agents, such as cyclohexanone, cyclohexane, tetrahydrofuran, ethyl ether, dioxane, ethanol, n-propanol, isopropanol, and n-butanol, and mixed solvents thereof.

Furthermore, a small amount of aromatic amine such as diphenylamine, triphenylamine, p-phenylazoaniline, etc. may be added to the coating solution in order to increase the sensitivity and spectral response to light. Various additives such as agents, plasticizers, and lubricants may be added depending on the purpose.

Examples of the coating method include a spray method, a spin code method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method.

The mixing ratio of the thermoplastic polymer and photoactive agent in the coating solution varies depending on the type of thermoplastic polymer and photoactive agent, but is generally 100:100 to 1000:1 (
weight ratio), preferably 100:30 to i
It is in the range of 000:5. The thickness of the groove forming layer is generally in the range of 0.03 to 100 μm, preferably in the range of 0.05 to 20 μm.

Next, a photomask such as a chrome hard mask having a tracking guide pattern is closely attached to this groove forming layer, and then pattern exposure is performed by irradiating light such as ultraviolet rays or visible light. The groove forming layer is heated simultaneously or sequentially with this light irradiation. When the heating is carried out sequentially, it is desirable to carry out the heating immediately after the light irradiation, and the temperature is raised to the pour point of the thermoplastic polymer by heating for a short period of about several seconds.

As a result of the light irradiation, an electromotive force is generated in the groove forming layer by the photoactivator, and an electrostatic image corresponding to the mask pattern is formed. By heating, an electric force is applied to a portion of the groove forming layer where an electromotive force is generated (a portion irradiated with light), causing contraction and forming a depression. That is, the electrostatic pattern formed in the groove forming layer is converted into a deformed pattern and appears on the surface of the layer.

In this way, a pregroove layer having a tracking guide pattern is formed. Note that this tracking guide pattern may be a pattern for groove tracking such as a concentric circular shape or a spiral shape, or may be a pattern for sampling tracking. It is also possible to form a recess representing additional information.

Note that the grooves can also be provided directly on the substrate using a combination of the above thermoplastic polymer and photoactive agent as the substrate material.

A recording layer is provided on the pregroove layer.

As the material for the recording layer, various materials conventionally known as recording materials for information recording media can be used. For example, Te%Zn, In%Sn.

Semiconductors such as Zr, metals such as Aft%Ti, Cu%Ga%Au, Pt, HBi%As, semimetals such as Sb, HGe%St, and alloys thereof or combinations thereof can be mentioned. Sulfides of these metals, semimetals, and semiconductors,
Compounds such as oxides, borides, silicon compounds, carbides and nitrides; and mixtures of these compounds with metals can also be used as recording layer materials. Further, dyes such as cyanine dyes and metal complex dyes can also be used. In addition to the above-mentioned write-once recording material, materials for the recording layer include magneto-optical recording materials made of rare earth-transition metals (for example, TbFe), TeCreSn, 5bTe%5b
Erasable and rewritable recording materials, such as materials that can reversibly change phase between amorphous and crystalline pages such as Se, materials that can phase change between crystals such as AgZn, and recording materials that flow and deform due to dye-polymer systems. can also be suitably used.

When a material such as metal is used, the recording layer can be formed on the pregroove layer by a method such as vapor deposition, sputtering, or ion blasting. The recording layer may be a single layer or a multilayer, but its layer thickness is generally in the range of 100 to 3,000 thick, preferably in the range of 150 to 1,500 thick, from the viewpoint of optical properties required for optical information recording.

Alternatively, when using a material such as a dye, the material and, if necessary, a binder are dissolved in an appropriate solvent to prepare a coating solution, and then this coating solution is applied onto the pregroove layer and dried. I can do it. The thickness of the recording layer is generally in the range of 0.01 to 10 μm, preferably 0.01 to 10 μm.
It is in the range of 0.02 to 1 μm.

Note that the pregroove layer and the recording layer may be provided not only on one side of the substrate but also on both sides.

Furthermore, a protective layer may be provided on the recording layer for the purpose of physically and chemically protecting the recording layer. This protective layer also provides scratch resistance on the side of the substrate where the recording layer is not provided. ,
It may be provided for the purpose of increasing moisture resistance.

Examples of materials used for the protective layer include StO, 5i0
2. Inorganic substances such as MgF2.5n02; thermoplastic resins;
Examples include organic substances such as thermosetting resins and UV curable resins.

The protective layer can be formed, for example, by laminating a film obtained by extrusion of plastic onto the recording layer (or silver salt layer or reflective layer) and/or onto the substrate via an adhesive layer. Alternatively, it may be provided by methods such as vacuum deposition, sputtering, and coating.

In the case of a thermoplastic resin or a thermosetting resin, it can also be formed by dissolving these in an appropriate solvent to prepare a coating liquid, then applying this coating liquid and drying it. In the case of a UV curable resin, it can also be formed by preparing a coating liquid as it is or by dissolving it in an appropriate solvent, applying this coating liquid, and curing it by irradiating it with UV light. Various additives such as antistatic agents, antioxidants, and tJV absorbers may be further added to these coating liquids depending on the purpose.

The thickness of the fi-retention layer is generally in the range of 0.1 to 100 μm.

The information recording medium of the present invention may be a single substrate having the above-mentioned structure, or alternatively, two substrates having the above-mentioned structure may be placed facing each other so that the recording layer is on the inside, and bonded together using an adhesive or the like. By doing so, it may be used as a laminated type information recording medium, or alternatively, by using a substrate having the above configuration as at least one of the two disc-shaped substrates,
By joining via a ring-shaped inner spacer and a ring-shaped outer spacer, an air sandwich type information recording medium may be obtained.

Examples of the present invention are described below. However, the examples do not limit the present invention.

[Example 1] A disc-shaped soda lime glass substrate (outer diameter = 130 mm, inner diameter: 15 mm, thickness: 1.2 mm) was precisely cleaned.

Next, a coating liquid having the following composition was prepared.

1 Blood 1 Iodoform 0.2 g Polystyrene (minutes, molecular weight: 20,00 G) 10 g Toluene 80 mJ2 Methyl ethyl ketone 20 mfL This coating solution was applied onto a glass substrate using a spin code method at a rotation speed of 1000 r.
After coating for 1 minute at a speed of 100 pm, the coating film was dried by heating at a temperature of 80° C. for 5 minutes to form a smooth groove-forming layer with a dry thickness of 1 μm.

A chromium hard mask having a spiral tracking guide pattern with a track width of 1 μm and a track pitch of 3 μm was closely attached to the groove forming layer, and then the groove forming layer was irradiated with flash using a Xe flash lamp through the mask (irradiation energy: 0. 5mJ/c)
. Next, the substrate provided with the groove forming layer was heated to 120°C.
The groove forming layer was placed in an open position and heated for 5 seconds to form recesses on the surface of the groove forming layer, thereby forming a pre-groove layer.

The surface of the obtained pregroove layer was examined using an optical microscope at 60°C.
When observed at a magnification of 0x, it was found that a concave portion (groove) was precisely formed in a spiral shape.

Next, Te is vacuum-deposited on the pre-groove layer at a vacuum degree of 10-5 Torr to form a recording layer having a layer thickness (monitored value) of 500 layers, and an information recording layer consisting of the substrate, the pre-groove layer and the recording layer in this order is formed. Media was manufactured.

[Evaluation of Information Recording Medium] The tracking performance of the obtained information recording medium was evaluated using a recording performance evaluation device.

While rotating the information recording medium at a rotation speed of 1000 rpm, a semiconductor laser (wavelength: 830 nm) was applied.

When a beam (beam diameter: 1 μm) was irradiated from the substrate side, the track could be followed well by the optical system with a tracking servo mechanism.

Claims (1)

[Claims] 1. An information recording medium in which a pregroove layer and a recording layer on which information can be written and/or read by a laser are provided on a substrate, wherein the pregroove layer is composed of a thermoplastic polymer and an optical An information recording medium characterized by comprising an activator. 2. The information recording medium according to claim 1, wherein the photoactivator is a substance that generates photovoltaic force upon irradiation with actinic rays. 3. The information recording medium according to claim 1, wherein the photoactivator is a halogenated aliphatic hydrocarbon. 4. The information recording medium according to claim 1, wherein the thermoplastic polymer is polystyrene. 5. The information recording medium according to claim 1, wherein the mixing ratio of the thermoplastic polymer and the light absorbent is in the range of 100:1 to 10:1 by weight. 6. A method for manufacturing an information recording medium comprising a pre-groove layer and a recording layer on which information can be written and/or read by a laser on a substrate, 1) A thermoplastic polymer and a photoactive agent are provided on the substrate. a step of forming a groove forming layer by applying and drying a coating solution containing the mixture; and 2) irradiating the groove forming layer with actinic rays in a pattern and heating it to form a groove forming layer in a pattern. A method for manufacturing an information recording medium, comprising: a step of providing a recessed portion to form a pregroove layer. 7. The method for producing an information recording medium according to claim 6, wherein in the second step, the groove forming layer is irradiated with actinic rays and heated at the same time. 8. The method for manufacturing an information recording medium according to claim 6, wherein in the second step, the groove forming layer is heated after being irradiated with actinic rays. 9. The method for manufacturing an information recording medium according to claim 6, wherein the groove forming layer generates a photovoltaic force upon irradiation with actinic rays. 10. The method for producing an information recording medium according to claim 6, wherein the photoactivator is a halogenated aliphatic hydrocarbon. 11. The method for producing an information recording medium according to claim 6, wherein the thermoplastic polymer is polystyrene. 12. The method for producing an information recording medium according to claim 6, wherein the mixing ratio of the thermoplastic polymer and the light absorbent is in the range of 100:1 to 10:1 by weight.