JPH0422289B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to optical discs.

Conventionally, substrates for optical disks include glass,
Polymethyl methacrylate (PMMA), vinyl chloride, and a copolymer of vinyl chloride and vinyl acetate are used. When forming grooves on a substrate as a tracking guide, a pressing method is usually used for substrates that mainly contain vinyl chloride, and an injection molding method is used for substrates that mainly contain polymethyl methacrylate. A hard mold, such as nickel, is made from the irregularities, and the grooves are replicated by pressing or pouring a heated organic material into the mold. However, organic substances that can reproduce in this way are easily deformed even at room temperature.
Also, the surface is easily scratched.

Made of hard material that does not easily deform under mechanical pressure,
It is said that bonding the groove with a material whose grooves can be easily replicated is effective in preventing deformation and scratches. However, since there is usually a difference in coefficient of thermal expansion between these materials, unless the thickness of one is made thinner, warping will occur due to temperature changes and faithful reproduction will not be possible. However, if this easy-to-replicate soft material is thin, it is difficult to replicate the unevenness using a press method or an injection molding method.

An object of the present invention is to provide an optical disk having an extremely stable and long-life optical disk substrate that does not have the above-mentioned drawbacks.

The optical disc of the present invention has the following structure as an example.

At least a second organic material layer having a film thickness larger than the average amplitude of the tracking unevenness and a first organic material layer formed by injection into a mold are laminated on a substrate made of chemically strengthened glass. First, the first organic material thin film is dissolved with an organic solvent at room temperature, or a low-viscosity organic material solution is spread to every corner of the tracking groove or hole, and then solidified, so the shape of the groove or hole is accurate and faithful. transcribed into. Moreover, since the second organic material thin film layer is formed on the first organic material thin film layer with the above-mentioned predetermined thickness, mechanical strength is maintained. In addition, since it is formed thin in this way, even when it is bonded to a substrate, no warpage, distortion, cracks, etc. are introduced, and excellent recording characteristics such as high sensitivity and small recording holes can be obtained.

This will be explained in detail below using examples.

FIGS. 1a to 1f are schematic diagrams of manufacturing steps for an optical disk substrate according to an embodiment of the present invention.
All figures are cross-sectional views of the substrate. The board is circular;
This is an example in which there is an opening in the center through which the rotating shaft passes.

Board thickness: 1.1mm, outer diameter: 330mm, inner diameter: 70mm
Chemically strengthened glass made by the ion exchange method was prepared in advance, and a cellulose acetate film with a thickness of 0.05 mm was prepared as a soft organic thin film.

First, methyl acetate 2 was poured into a mold 1 having groove-like irregularities serving as a tracking guide to uniformly wet the mold 1, and a cellulose acetate sheet 3 was pasted thereon. At this time, cellulose acetate dissolved in methyl acetate forms layer 2 and solidifies. Next, apply epoxy adhesive 4 to the opposite side of this cellulose acetate sheet, and apply the above chemically strengthened glass 5.
pasted. Next, when the mold 1 was peeled off from one end, the cellulose acetate 3 remained on the chemically strengthened glass side, and a grooved surface was exposed. Next, this substrate was placed in a vacuum deposition apparatus, and an As-te-Se recording film 8 was deposited on the cellulose acetate layer 2 to a thickness of about 40 nm. Next, a part of the periphery of the membrane 8 is wiped off with acetone or the like. Next, a spacer 6 with a thickness of 0.1 mm is pasted on the inner and outer peripheries of the side on which the vapor-deposited film is attached, and a protective chemically strengthened glass 7 with the same thickness, inner diameter, and outer diameter as above is pasted. Ta. This chemically strengthened glass also has a sheet of organic material (not shown) pasted on the opposite side of the chemically strengthened glass.
Even better if reinforced. If the spacer 6 is not provided with this organic sheet or cellulose acetate sheet, the adhesion will be stronger.

The laser light for recording and reading may be incident from the chemically strengthened glass 5 side that is a transparent substrate, or may be incident from the chemically strengthened protective glass 7 side.

Chemically strengthened glass can be made thin and has high strength, making it ideal for substrates and protection.

The bonding of chemically strengthened glass and cellulose acetate or the like is not limited to the method using the above-mentioned adhesive, but various methods such as applying a solvent, pasting and solidifying the glass, thermocompression bonding, etc. can also be used. This will be discussed later. In addition to the above-mentioned cellulose acetate, it is also possible to use organic substances that rapidly solidify after being dissolved in a solvent.

Furthermore, as described above, the optical disk of the present invention mainly uses a hard material called chemically strengthened glass for the substrate, so it is hard to deform, hard to get scratched, and does not change over time. The strength of this chemically strengthened glass is increased by introducing atoms, molecules, ions, etc. with a large radius into the glass surface by ion exchange method or the like to generate compressive stress.

FIGS. 2a to 2e are schematic diagrams of the manufacturing process of an optical disk substrate according to another embodiment of the present invention.

As a board made of hard material, the thickness is 1mm, the outer diameter is 330mm,
A donut-shaped PMMA plate with an inner diameter of 70 mm and two types of cellulose acetate solutions (the solvent is cyclohexanone) with different concentrations (solvent to solute weight ratio) or solute molecular weights are prepared as soft organic thin films. First, a cellulose acetate solution with a concentration or molecular weight suitable for obtaining a thin film is applied to a mold 21 having an uneven surface using a spinner to an average film thickness of about 150 nm, and dried to form a first coating layer 22. (2a). Next, a high viscosity cellulose acetate solution suitable for obtaining a thick film, for example, is poured on top of this 2b, and the PMMA board 25 is pressed from one end to avoid bubbles, until it is completely pasted 2c. . Second cellulose acetate layer 2
2d separated from the mold 21 after solidifying. Mold 2
If 1 has information such as video, audio, digital, etc., the information can be read out as it is by depositing metal on the uneven surface of the thus formed replica. In the case where the mold 21 has irregularities for a tracking guide, the replica thus formed is used as a substrate, an information recording member is adhered thereon, and information can be recorded in the same manner as in Example 1 described above. 2e, which can be an optical disk. Note that 26 is a spacer, and 27 is a protective chemically strengthened glass.
If the thickness of the cellulose acetate 23 exceeds 0.5 mm, which is 1/2 of the thickness of the PMMA plate 25, a large warpage will occur after separation from the mold, making recording and reading difficult, so the thickness should be less than this. It is necessary.
On the other hand, if the average thickness of the cellulose acetate layer 23 is less than 80 mm, which is the average amplitude of the unevenness, the thickness of the cellulose acetate layer at the bottom of the unevenness will be uneven, so a thickness greater than this is required. . Also, if the cellulose acetate layer 23 becomes particularly thin,
It is even better to use an ultraviolet curing adhesive (for example, Photobond (trade name)) to attach the PMMA plate 25.

In this example, cellulose acetate dissolved in a solvent was used, but it is also preferable to apply a monomer or a low molecular weight material and polymerize it, since this simplifies the process.

A more preferable average thickness of the cellulose acetate layer 23 is in the range of 300 nm or more and 200 μm or less.
This is common to all organic thin films forming layer 23.

In addition to PMMA, of course the chemically strengthened glass mentioned above,
Other resins that are difficult to deform, such as CR-39 (polyglycol diallyl carbonate), ABS resin, AS resin (acrylonitrile styrene resin)
etc. may also be used.

As detailed above, the present invention provides an excellent optical disk substrate by providing an organic thin film layer on a chemically strengthened glass substrate, and the use of this substrate as an optical disk has great industrial benefits. It is. In addition to the method described in the Examples, it is not impossible to form the organic layer having irregularities by a pressing method (also called compression, embossing, etc.). Further, those skilled in the art will easily infer that the present invention is also applicable to a type of disk in which reading is performed using a probe. Using chemically strengthened glass for the substrate,
It is also effective for thermomagnetic recording disks and magnetic disks.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the manufacturing process of one embodiment of the substrate used in the present invention, and FIG. 2 is a schematic diagram of the manufacturing process of another embodiment of the substrate used in the invention. DESCRIPTION OF SYMBOLS 1... Mold, 2... First cellulose acetate layer, 3... Second cellulose acetate layer, 4... Adhesive layer, 5... Chemically strengthened glass, 6... Spacer, 7
...Protective chemically strengthened glass, 8... Information recording member (As-Te-Se recording film).

Claims (1)

[Claims] 1. An optical disk characterized in that an organic material layer is provided on a chemically strengthened glass, the surface of which has irregularities for tracking or irregularities representing video, audio, or digital information.