JPS615986A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide an optical recording medium having excellent heat resistance and free of optical anisotropy, by a method wherein a polyether sulfone resin is dissolved in an organic solvent, the resultant solution is applied to a mirror surface of a surface having rugged signals, then the solvent is removed, thereafter the film thus formed is released from the surface, and is used as a base for an optical recording medium. CONSTITUTION:An amorphous polyether sulfone resin having a structural unit of the formula is dissolved in an organic solvent such as acetone and THF, preferably, in a concentration of 10-40wt%, the resultant solution is applied to a mirror surface of a surface having rugged signals (e.g., a glass plate), and the solvent is removed by evaporation. Then, the film thus formed is released from the surface to obtain a film preferably having a thickness of 50-200mum. By using the film as a base, a recording layer is provided thereon by, for example, vapor-depositing a low melting point inorganic material such as tellurium and a tellurium-carbon alloy, to obtain the objective optical recording medium for use in optical recording which involves optical writing, reading or the like of signals.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium used for so-called optical recording, in which signals are written or read, or both written and read, using light.

[Prior art]

Optical recording includes, for example, read-only optical recording media that carry uneven signals, write-once optical recording media in which desired information is written and read by the user using light such as a laser, and furthermore, written information There are erasable optical recording media, etc., on which signals can be repeatedly written and read again using light such as a laser.

The base material for each of these optical recording media has been used by molding, for example, methacrylic resin or polycarbonate resin into a disc-shaped sheet by injection molding or spray molding, due to its high productivity. However, due to its low heat resistance, there is a serious drawback that warping, twisting, and surface deformation are likely to occur during the process of vapor-depositing low-melting metals such as tellurium as a recording layer, and optical It produces anisotropy (birefringence) and becomes a source of noise.

In addition, the vapor deposition of the reflective layer and recording layer causes a difference in the rate of fold moisture from the inner surface, which causes warpage to occur easily during storage of optical recording media (recovery of warpage in recording media with a thickness of more than 1 mm). It is difficult.

As described above, there is a strong desire for a substrate material that is heat resistant, free of optical anisotropy, and capable of avoiding warpage during storage of optical recording media.

[Purpose of the invention]

An object of the present invention is to provide a high-quality optical recording medium that has heat resistance, is free from optical anisotropy, and can recover from warpage that occurs during storage of the optical recording medium during use.

[Disclosure of the invention]

The first optical recording medium of the present invention is characterized in that the substrate is a film obtained by dissolving polyether sulfone resin in an organic solvent, applying it to a mirror surface or a surface having an uneven signal, removing the solvent, and then peeling it off. That is.

The present inventors focused on the high heat resistance of polyether sulfone resin and its solubility in organic solvents, and after dissolving polyether sulfone resin in a soluble organic solvent, applied it to a glass plate, etc. It has been found that the film obtained by drying and removing the organic solvent and peeling off from a glass plate, etc., has no optical anisotropy and has excellent heat resistance, and is extremely useful as a substrate for an optical recording medium. In addition, instead of using a material with a smooth surface such as a glass plate, it is coated on a material with unevenness signals, and the unevenness information is accurately transferred to the film obtained in the same way, making it possible to create a read-only optical recording medium. In addition,
It is also extremely effective for forming uneven signals corresponding to guide grooves and preformats of write-once or erasable optical recording media.

[Embodiment]

It is a non-grade resin containing a polyether sulfone tree used in the present invention and has a glass transition temperature of 200°C or higher. Polyether sulfone resin can be manufactured by injection molding or press molding to produce sheets and films, but the molded products, sheets, films, etc. obtained by these molding methods have optical anisotropy. Therefore, it is unsuitable for use in the optical recording medium of the present invention.

Examples of organic solvents that can dissolve the polyether sulfone resin include acetone, cyclohexanone, methyl ethyl ketone, methylene chloride, trichloroethylene, and tetrahydrofuran, but they are not necessarily limited to these solvents. Any solvent may be used as long as it can be used as a solvent, or a mixture of one or more of them may be used.

Usually polyether sulfone resin is 10~40fi 3
It is applied at a concentration of 1%, and at this time, it is desirable to apply filtration to prevent contamination by foreign substances, and to perform application and drying under clean environmental conditions.

Glass plates are the most common surface material with a smooth surface to be coated, but any material with a mirror surface that cannot be immersed in organic solvents may be used, such as metal plates, glass with metal vapor deposition,
Ceramics, solvent-resistant resins, etc. may be used, and metals, metal-deposited glass, etc. are used as surface materials having uneven signals on the surface to be coated. It can be produced in accordance with the manufacturing technology of a photomask, etc., in which a stub bar used in media molding or a metal-deposited glass is etched by the 7-photoresist method.

Drying is usually carried out by first evaporating at least 70% of the organic solvent at room temperature to below the boiling point of the organic solvent, then at a temperature above 80°C and below the glass transition temperature, and if necessary, under reduced pressure to evaporate the organic solvent used. Remove as much as possible by evaporation, but take care not to create bubbles in the film during drying, and limit the above conditions as long as the amount of organic solvent in the film is 3% by weight or less, preferably lt% or less. It is not something that will be done.

Further, when the amount of organic solvent in the film becomes 30% or less, it may be peeled off from the face material and dried, and since the solvent can be removed from both sides, the drying time can be shortened.

The thickness of the polyether sulfone resin film prepared as described above is preferably 20 to 500P, especially 50P.
-2 oop is preferable, less than 20 uL is undesirable as it tends to cause wrinkles and folds in the finished recording medium, and more than 500 uL makes it difficult to write on the recording medium.
Alternatively, when the film is set in a reading device, if warpage occurs due to moisture absorption from one side, the warp cannot be easily restored, and it is difficult to remove the solvent in the film, which is not preferable. Since the optical recording medium of the present invention has appropriate flexibility, even if it becomes slightly warped due to moisture absorption, it can be easily restored and corrected by applying pressure from both sides when it is old or when being installed in a reading device. I can do it.

Using the above polyether sulfone resin film as a substrate, various optical recording media can be obtained as follows.

As described above, read-only optical recording media are obtained by transferring recorded information using a surface material having a concave and convex signal surface, and usually a light reflective material such as aluminum is deposited on the concave and convex signal surface, and if necessary, The reflective layer can be formed by applying a protective layer or laminating other film materials. Furthermore, a thermoplastic resin or photocurable resin is applied onto the polyether sulfone resin that forms the mirror surface, and the resin is superimposed on a stand bar having a concavo-convex signal, and heated, pressurized, or exposed to ultraviolet rays as necessary. It is also possible to obtain a read-only optical recording medium by separately forming a concavo-convex signal on the film by irradiating it with an electron beam or the like, and then forming a reflective layer or a protective layer as described above.

The write-once optical recording medium is produced by depositing a low melting point inorganic material such as tellurium, tellurium oxide, tellurium tin alloy, tellurium carbon alloy, tellurium bismuth alloy, tellurium dicarbon composite film, etc. on the above polyether sulfono resin film. The recording layer is formed by vapor-depositing or coating a material containing various dyes that absorb the writing laser beam and can be used as a heat-transforming material. It is obtained by laminating a dielectric layer, a protective layer, etc. for formation either above or below the recording layer, and the recorded signal is read out by a change in the reflectance of the laser beam irradiation area or a change in transmitted light, and The guide grooves and preformat may be formed by the above-described method for creating a flat uneven signal in a read-only optical recording medium, and then the above-described recording layer may be formed.

Erasable light record J! In the medium, an erasable material is used as the recording layer, such as a material such as tellurium oxide, whose reflectance can be reversibly changed in accordance with the TIT plastic change in crystalline state depending on heating conditions, or a material such as manganese bismuth. Materials such as alloys, gadolinium cobalt alloys, terbium iron alloys, etc. that have a low Curie temperature and are heated by laser irradiation change their magnetism, and the polarization plane of the readout laser changes by forming the material by means such as vapor deposition. It will be done. Moreover, it is of course possible to form a primer layer, a dielectric layer having a high refractive index, or a protective layer on top and bottom of these recording layers, and also to form guide grooves in the same manner as write-once optical recording media. Alternatively, a preformat may be formed, and then the recording layer described above may be formed.

The optical recording medium of the present invention described above is disc-shaped.

It can be used in either card or tape form.

〔Effect of the invention〕

The optical recording medium of the present invention has excellent heat resistance, has no optical anisotropy, and can avoid the problem of warpage causing focus control of a writing or reading optical beam to exceed an allowable range.

EXAMPLES The present invention will be explained in more detail by showing Examples and Comparative Examples below.

Example 1 Polyether sulfone resin (product name Vic manufactured by ICI)
trex 200P) 200ft volume of dimethylacetamide 40% by weight, methylene dichloride 2011
After dissolving in 800 parts by weight of a mixed solvent of 1% and 20% by weight of toluene and filtering with a cartridge type filter, a spacer was applied around the periphery on a glass plate having a mirror surface,
After drying at room temperature for 6 hours, it was further dried at 100°C for 2 hours, peeled off from the glass plate, and further dried in vacuum for 30 minutes to obtain a polyether sulfone resin film with a thickness of 75 μm.

The birefringence of this film was examined using a polarized wJ microscope, but there was no birefringence at all. A dye solution consisting of a cyanine dye (max 795nm), an aromatic dithiol-based nickel complex dye (max 8?onm), and polyvinyl butyral resin was spin-coded onto this film, dried to remove the solvent, and a 2000A thick film was formed. A recording medium (write-once type) of the present invention was obtained by forming an organic dye-containing recording layer.

The above film was sandwiched between glass plates, fixed on a turntable and rotated at 110 Or, p, a.
Using an optical head equipped with a semiconductor laser with an output of 20 mW and an oscillation wavelength of nm, a signal was written at 2.4 MHz through polyether sulfone resin while automatically controlling the focus, and the optical head was used to write a signal through polyether sulfone resin. The signal was read out with the output set to 1 mW. At this time, the C/N ratio was 60 dB, and an extremely excellent result was obtained.

Example 2 A toluene solution of a photosensitive resin containing polymethylmethacrylate and trimethylolpropane acrylate as main components was applied to a polyethersulfone resin film prepared in the same manner as in Example 1, and dried. A photosensitive layer with a thickness of u is formed, a nickel stamper having uneven signals on the surface of the photosensitive layer is pressed using a vacuum press at a pressure of 10 kg/cm2, and a high pressure mercury lamp is passed through the polyether sulfone resin surface. After exposure with a light intensity of 500 mJ/cm2, the film was peeled off to obtain a film to which the uneven signal was transferred. Next, an 800 angstrom aluminum vapor deposition layer is formed on the uneven signal surface, and an acrylic lacquer is applied to the aluminum vapor deposition surface to form a protective layer, and a disk shape of 200 mm diameter is punched out. type) was obtained.

The above optical recording medium is sandwiched between glass plates and fixed to a turntable, and the signal is read out using an automatic focus control optical head equipped with a semiconductor laser with an oscillation wavelength of 830n layer (output IW) through polyethersulfone resin. The F2 optical recording medium that was subjected to
Signals were read out in the same manner for those that had been left at ℃ for 8 hours.

As a result, signals could be reproduced without any problems.

Example 3 Polyether sulfone resin (product name: Vic manufactured by IC1)
trex 1100P) 250 was dissolved in a mixed solvent of 50% by weight N-methylpyrrolidone and 50% by weight methyl ethyl ketone and filtered with a cartridge type filter.
The above solution was coated on a master board having concentric grooves corresponding to the guide grooves formed using 700 angstrom chromium-deposited soda lime glass using a photoresist method using an argon laser, with spacers around it, and the solution was applied at room temperature for 3 minutes. Dry at 80°C for 3 hours, then peel off from the master board and vacuum dry for 2 hours to a thickness of 75mm with guide grooves. obtained the film.

No optical birefringence was observed in the above film when observed using a polarized JL microscope.

Next, tellurium oxide was sputtered on the pre-group groove supporting surface using tungsten as a reducing agent to form a toughened tellurium (1200 angstrom thick).
Te: 0=1+1.1) Form a film with a diameter of 20
The optical recording medium of the present invention was obtained by punching out a disk shape of 0.5 mm.

Using the above-mentioned optical recording medium, signals were written onto and read from the guide grooves through the polyether sulfon resin under the same conditions as in Example 1.

At this time, the C1M ratio was 82 dB, which was an extremely excellent result.

Comparative Example 1 A circular disc having a guide groove and having a diameter of 200 m+* and a thickness of 1.2 mm was injection molded using methacrylic resin (trade name: Acryvet 1llF, manufactured by Mitsubishi Rayon Co., Ltd.).

Observation with an optical microscope revealed birefringence around the center.

A thickness of 1200 mm was formed on the guide groove surface of the substrate in the same manner as in Example 3.
An angstrom tellurium oxide film was formed to obtain a comparative optical recording medium (write-once type). This recording medium warped during the sputtering process, and the warp width at the center and periphery was 0.12 mm. ■ = Optical recording medium in Example 1
However, the peripheral area was outside the range of automatic focus control of the laser beam and no signal could be obtained.

Comparative Example 2 When the dye solution used in Example 1 was applied to the entire surface of the guide of Comparative Example 1, it was observed by microscopic observation that fine racks were generated on the substrate and at the same time the guide grooves were deformed.

Comparative Example 3 A stambar carrying a concavo-convex recording signal was mounted on a mold, and a disk-shaped disc made of methacrylic resin having a diameter of 200 I and a thickness of 1.2 mm was injection-molded in the same manner as in Example 1. Similar to Comparative Example 1, birefringence was observed around the center. Aluminum vapor deposition and protective layer formation were performed on the uneven signal transfer surface in the same manner as in Example 2 to obtain a comparative optical recording medium (read-only type). When the same moisture resistance test and heat resistance test as in Example 2 were conducted, warpage occurred, and signal reproduction could not be performed using the same device as in Example 2.

Claims (1)

[Claims] 1) Dissolve polyether sulfone resin in an organic solvent,
An optical recording medium whose substrate is a film obtained by coating a mirror surface or a surface having uneven signals, evaporating the solvent, and then peeling the film.