JPH03266235A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enable writing, reading and erasing of data at low cost by laminating a shape-memory resin layer, thermosetting resin layer, metallic reflecting layer and protective layer on a disk substrate. CONSTITUTION:A styrene-butadiene shape-memory resin to which cyanine dye is added is dissolved in tolunene and applied on a disk substrate by spin coating. Then an epoxy resin, which is a thermosetting resin, which a polyamide resin as a hardening agent and cyanine dye as the light-absorbing dye for laser light is dissolved in methylethylketone and applied on the shape-memory resin layer by spin coating to form the thermosetting resin layer. Further, a metallic reflecting layer such as aluminum or gold is formed by vacuum vapor deposition, and a UV-curing resin is applied by spin coating as the protective coating film and cured with UV-ray to form the protective layer. Thus, the obtd. optical recording medium can be used for a user to rewrite data freely at low cost.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a rewritable type optical recording medium.

Conventional technology Conventionally, for rewritable type optical recording media using laser light, materials such as MnB1 alloy or Co ferrite are magnetized and irradiated with laser light to raise the temperature above the cue point. A magneto-optical recording method that changes the size and writes and erases data, and a chalcogenide thin film that is irradiated with a laser to cause a reversible phase change from the crystalline phase to the amorphous phase. There is a phase change recording method that performs reading using the difference in reflectance of laser light.

All of these methods use high-vacuum forming techniques such as vacuum cutting and nupanotaring when producing recording films.

Regarding writing, technical documents related to the present invention include Japanese Patent Application Laid-Open No. 60-45953.

JP-A-60-46954, JP-A-60-6193
Regarding the structure in which two layers of an elastic body and a resin layer are provided on a substrate, there are US Pat. No. 4,780,867 and US Pat. No. 4,719,615.

Problems to be Solved by the Invention In such conventional optical recording media, a high vacuum film forming technique such as a vacuum apparatus or puttering is used when producing a recording film, making the optical recording medium itself very expensive.

Furthermore, since the device mechanism is fundamentally different from that of currently widely used CD players, it is not compatible with CD players.

The present invention solves the above problems and is inexpensive and C
The purpose of the present invention is to provide a rewritable optical recording medium that is compatible with D players.

Means for Solving the Problems In order to achieve the above object, the present invention constitutes an optical recording medium by laminating a shape recording resin layer, a thermosetting resin layer, a metal reflective layer, and a protective layer on a disk substrate. It is something.

Effect: With the above-described configuration, the present invention causes a shape change and recovery action, that is, the formation and erasure of pits, due to the thermal expansion force of the thermosetting resin layer and the temperature change of the shape memory resin layer when irradiated with laser light. It will be possible to write, read and erase data.

EXAMPLE An example of the present invention will be described below. First, a cyanine dye was added to a styrene-butadiene shape memory resin, dissolved in toluene, and coated using a spin code method on a polycarbonate disk substrate on which groups (grooves) had been formed in advance. It was dried at ℃ for 30 minutes to form a shape memory resin layer with a thickness of 0.6 μm.

In the molecular structure of the shape memory resin layer formed in this way,
It consists of a stationary phase consisting of molecular crosslinks and crystals, and a reversible phase that can become rubbery at temperatures above a certain temperature.

Next, on the shape memory resin layer, a mixture of epoxy resin, which is a thermosetting resin using polyamide resin as a curing agent, and a cyanine dye as a laser light absorption dye is dissolved in methyl ethyl ketone and applied to the spin code method. The thermosetting resin layer was dried and cured at 120° C. for 30 minutes to obtain a thermosetting resin layer with a thickness of 6 μm. Further, aluminum or gold is formed thereon to a thickness of 0.05 μm by vacuum evaporation to obtain a metal reflective layer. Subsequently, an ultraviolet curable resin is applied onto the metal reflective layer using a spin code method, and is cured by irradiating ultraviolet rays to provide a protective layer with a thickness of 20 μm, thereby completing an optical recording medium. In this state, the aforementioned shape memory resin layer remembers the shape of the initial primary molding.

This optical recording medium is written at a wavelength of 630 am, 30! from the disk substrate side. When IW laser light is irradiated for 150 ns, it is absorbed by the thermosetting resin layer through the shape memory resin layer, and the temperature instantly rises and expands.

At this time, the shape memory resin layer also slightly absorbs the laser with a wavelength of 630 nm, and due to heat conduction from the heated thermosetting resin layer, the temperature rises from the glass transition temperature Tq or higher to the next molding temperature T1 or higher. Increase the temperature to.

Here, the elastic modulus of the thermosetting resin layer after heating is calculated as follows: Galanu transition temperature Tq or higher of the shape memory resin layer - Temperature at the time of next molding T1
By using a material that is molecularly designed to have a higher elastic modulus in confirmed. The shape memory resin layer memorizes the deformed state as the shape of the secondary molding.

Next, this pit is read out using a laser beam of 780 nm and 3 mW. This wavelength 7BOnrn was selected for compatibility with CD players. The laser light intensity during reading is much lower than that during writing described above. Furthermore, the laser light reflectance during readout is required to be 70% or more in areas without pits, but it was actually confirmed that the reflectance was 25% and 72%, respectively, depending on the presence or absence of pits.

Next, erasing was performed using a laser beam of 780 nm and 15 mW. Energy is selectively absorbed in the shape memory resin layer and not in the thermosetting resin layer to a much greater extent than in the previously described readout. The shape memory resin layer that has absorbed this laser beam is heated to a temperature that is equal to or higher than the Galanu transition temperature Tq and equal to or lower than the temperature during subsequent molding T1, and recovers to the initial primary molded shape. It was experimentally confirmed that the pits actually disappeared. In this way, information is written, read and erased.

At this time, the thermosetting resin layer and the shape memory resin layer satisfy the following characteristics from the viewpoint of repeated writing and erasing characteristics and reflectance characteristics during reading.

The thermosetting resin layer absorbs the laser beam with the wavelength λW during writing and thermally expands as the temperature rises, but it has a large coefficient of thermal expansion at that time and has high heat resistance, and it also absorbs the laser beam with the wavelength λR during reading. It has high transmittance and low birefringence. Further, the shape memory resin layer must undergo plastic deformation due to thermal expansion of the thermosetting resin, have a low birefringence, and have low adhesion to the thermosetting resin layer.

In this way, by optimizing the molecular design of the thermosetting resin layer and shape memory resin layer and matching the wavelength and energy of the irradiated laser light, it is possible to create a rewritable material that can be written, read, and erased. Moreover, since the coating is performed using an inexpensive nupinner without using an expensive vacuum evaporation apparatus as in the past, a very inexpensive optical recording medium can be provided.

Also, the reading method based on the intensity of reflected light in areas without pits and areas with pits is the same as in CD players.
By designing a disc that complies with the RedBook standard, which is an international standard for players, it is possible to provide an optical recording medium that can be played on CD players that have been widely used.

In this embodiment, a case has been described in which a disk substrate made of polycarbonate is used, but a disk substrate made of glass, polymethyl methacrylate, or the like may also be used.

Although the description has been made regarding the disk substrate on which groups have been formed, the same can be achieved in the case where no groups have been formed.

In addition, as for the formation order of each layer, the case where the shape memory resin layer, the thermosetting resin-1 metal reflective layer, and the protective layer were laminated in this order on the disk substrate was described. You can also bring it in between. However, in this case, it is necessary to perform laser irradiation from the protective layer side.

Furthermore, in the two cases described above, there is also a structure in which the formation order of the shape memory resin layer and the thermosetting resin layer is reversed.

Next, other embodiments will be described. That is, a polyurethane resin is used as the shape memory resin layer in the above embodiment, and is melted and applied together with an azulenium dye in dimethylformamide. An optical recording medium was obtained in the same manner as in the previous example except that the polyurethane resin and the azulenium dye were dissolved in dimethylformamide and applied.

At this time, the azulenium dye contained in the shape memory resin layer and the azulenium dye contained in the thermosetting resin layer have selective absorption at 630 nm and 780 mm, respectively.

A 630 nm, 20 mW laser beam for writing is transmitted 200 m from the polycarbonate disk substrate side.
s irradiation, pits are formed according to the same principle as in the previous embodiment, and data can be read by irradiating the pits with a 780 nm, 3 mW laser beam. The reflectance of laser light with and without pits was 38% and 71%, respectively.

Furthermore, a 780 nm, 10 mW laser beam was applied to the
The pits were erased by m5 irradiation.

In addition to the above-described embodiments, other resin compositions that can serve as the shape-memory resin layer described above and other materials as the thermosetting resin can also be used. It goes without saying that other pigment materials that absorb laser light and whose molecules are designed to match the material properties and laser properties can be widely used.

Effects of the Invention As is clear from the above examples, the optical recording medium in which a shape memory resin layer, a thermosetting resin layer, a metal reflective layer, and a protective layer are laminated on a disk substrate according to the present invention is inexpensive. , the data can be freely rewritten by the user, and there is a possibility of compatibility with CD players.
This will greatly contribute to industry in that it will enable the widespread use of optical recording media for consumer use.

Claims (5)

[Claims] (1) An optical recording medium in which a shape memory resin layer, a thermosetting resin layer, a metal reflective layer, and a protective layer are sequentially laminated on a disk substrate. (2) An optical recording medium in which a metal reflective layer, a shape memory resin layer, a thermosetting resin layer, and a protective layer are sequentially laminated on a disk substrate. (3) The optical recording medium according to claim (1) or (2), wherein the stacking order of the shape memory resin layer and the thermosetting resin layer is changed so that the stacking order of the thermosetting resin layer and the shape memory resin layer is changed. (4) Claim (1) wherein the shape memory resin layer and thermosetting resin layer contain a dye that selectively absorbs laser light of a specific wavelength.
, (2) or (3). (5) Claim in which grooves are formed in advance on the disk substrate (
The optical recording medium according to 1), (2), (3) or (4).