JPS62143243A - Optical disk - Google Patents

Abstract

PURPOSE:To obtain an optical disk having a substrate for an optical disk which is stable and has a long life by providing a thin org. film layer on a substrate consisting of chemically tempered glass. CONSTITUTION:The chemically tempered glass by an ion exchange method and a cellulose acetate film as a soft thin org. material film are preliminarily prepd. A methyl acetate 2 is poured into a metallic mold 1 to uniformly wet the mold and a cellulose acetate sheet 3 is stuck thereto. An epoxy adhesive agent 4 is coated thereon and the chemically tempered glass 5 is stuck thereto. The mold 1 is stripped from one end and such substrate is put into a vacuum vapor deposition device where an As-Te-Se recording film 8 is deposited by evaporation on the cellulose acetate layer 2. A spacer 6 is stuck thereto and the chemically tempered glass 7 for protection which is the same in thickness, inside diameter and outside diameter is stuck thereto.

Description

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

Conventionally, glass, polymethyl methacrylate (PMMA), vinyl chloride, a copolymer of vinyl chloride and vinyl acetate, and the like have been used as substrates for optical disks. When forming grooves on the substrate as tracking guides,
Usually, in the case of materials mainly containing vinyl chloride, press method,
Injection molding is used for products that mainly contain polymethyl methacrylate. In these cases, a hard mold such as nickel is made from the irregularities of the master disk in which the grooves have been formed, and a heated organic material is pressed or poured into this mold to form the grooves. Replicate. However, such replicable organic substances are easily deformed even at room temperature, and their surfaces are easily scratched.

It is said that it is effective to use a combination of a hard material that does not deform under mechanical pressure and a material that allows grooves to be easily reproduced to prevent deformation and scratches. However, since there is usually a difference in coefficient of thermal expansion between these materials, unless one of the materials is made thinner, warping will occur due to temperature changes and faithful reproduction will not be possible. However, it has been done.

An object of the present invention is to provide an optical disc having an extremely stable and long-life optical disc 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 top of a substrate made of chemically strengthened glass. First, the first organic material film is bathed in an organic solvent at room temperature, or a low-viscosity organic material bath liquid is spread to every corner of the tracking groove or hole, and then solidified to form the groove or hole. is accurately and faithfully transcribed.

Moreover, since the five layers of the second organic material thin film are 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, there is no introduction of warping, distortion, cracks, etc., 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. 13 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. In this example, the substrate is circular and has an opening in the center through which the rotating shaft passes.

The board has a thickness of 1.1 mm, an outer diameter of 330 mm, and an inner diameter of 7.
Q mm of chemically strengthened glass by ion exchange method, and a cellulose acetate film with a thickness of 0.05 mm as a soft organic thin film were prepared in advance.

First, methyl acetate 2 was poured into a mold 1 having groove-like irregularities serving as a tracking guide, and the mold was allowed to melt at 16k, and a cellulose acetate sheet 3 was pasted thereon.

At this time, cellulose acetate dissolved in methyl acetate forms 12 and is rubbed hard. Next, the chemically strengthened glass 5 described above was attached to the opposite surface of this cellulose acetate sheet using an epoxy adhesive 4. 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-8e recording film 8 was deposited on the cellulose acetate layer 2 to a thickness of about 4 Q 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 Q, 1 mm is pasted on the inner and outer peripheries of this disk on the side on which the vapor-deposited film is applied, and a protective chemically strengthened glass 7 having the same thickness, inner diameter, and outer diameter as above is attached. pasted.

It would be even better if this chemically strengthened glass was reinforced by pasting an organic sheet (not shown) on the opposite side of the chemically strengthened glass.This organic sheet or cellulose acetate sheet can be used at the spacer 6. Without it, the adhesion will be even stronger.

Even if the laser beam for recording and reading is incident from the chemically strengthened glass 5 side, which is a transparent substrate, the chemically strengthened glass for storage 70
The light may be input from 111.

Chemically strengthened glass can be made thinner and has greater strength, making it ideal for substrates and protection.0 Bonding of chemically strengthened glass with cellulose acetate or other materials is not limited to the method using the adhesive described above. It is also possible to use various methods such as a method of applying a solvent, pasting and solidifying, and thermocompression bonding. This will be discussed later. Furthermore, in addition to the cellulose acetate mentioned above, it is also possible to use organic substances that rapidly solidify after being used as a heating medium.

Furthermore, as described above, the optical disc 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. This chemically strengthened glass is made by introducing atoms, molecules, ions, etc. with large radii into the glass surface using ion exchange method etc.
Strength is increased by creating compressive stress.

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

A donut-shaped PMMA plate with a thickness of 1 mm, outer diameter of 330 mm, and inner diameter of 79 mm serves as a hard material base, and two types of cellulose acetate solutions with different concentrations (solvent to solute weight ratio) or solute molecular weight serve as soft organic thin films. (The solvent is cyclohexanone). Mold 2I with unevenness
First, a cellulose acetate solution with a concentration or molecular weight suitable for obtaining a thin film is mixed with a spinner for about 15 minutes.
Coated to an average thickness of 0 nm and dried to form coating layer 2 of $1.
2 (2a). Next, pour a cellulose acetate solution with high viscosity suitable for obtaining a thick film 2b) onto this, and press the above PMMA board 25 from one end so as not to create bubbles to completely adhere it. (2C
). After the second cellulose acetate layer 23 was solidified, it was separated into two molds (2d). Mold 21 has video, audio,
In the case of digital information, the information can be read out directly by depositing metal on the uneven surface of the replica thus formed. In the case where the mold 21 has irregularities for use as a tracking guide, the thus formed replica is used as a substrate, an information recording member is adhered thereon, and a recordable optical disc is produced in the same manner as in Example 1 described above. (2e). Note that 26 is a spacer, 2
7 is chemically strengthened protective glass. If the thickness of the cellulose acetate 23 exceeds Q, 5 mm, which is 1/2 of the thickness of the PMMA plate 25, it will cause a large warp after separation from the mold, making recording and reading difficult. It needs to be thick. On the other hand, if the average thickness of the cellulose acetate layer 23 is less than 8Qmm, which is the average imaging width of the unevenness, the thickness of the cellulose acetate 1 at the bottom of the unevenness becomes uneven, so a thickness greater than this is required. It is. Moreover, when the cellulose acetate layer 23 becomes particularly thin, P M
It is even better to use an ultraviolet curing adhesive (for example, Photobond (trade name)) to attach the MA plate 25. In this example, cellulose acetate dissolved in a solvent was used.
It is even better to apply and polymerize a material with a low molecular weight, such as a sulfuric acid, because the process can be simplified.

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 i1 forming layer 23.

In addition to PMMA, not only the above-mentioned chemically strengthened glass, but also other resins that are difficult to deform, such as CR-39 (polyglycol diallyl carbonate), AB8 resin, AS resin (acrylonitrile styrene resin), etc. may 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 is of great industrial benefit. In addition to the method described in the examples, it is not impossible to form the organic material 1 having irregularities by a pressing method (also called combination method, embossing, etc.). Further, those skilled in the art will easily infer that the present invention is also applicable to discs in which reading is performed using a probe. Using chemically strengthened glass for the substrate 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 present invention. ... first cellulose acetate layer, 3 ... second cellulose acetate layer, 4 ... adhesive layer, 5 ... chemically strengthened glass, 6 ... spanner,
7...Protective chemically strengthened glass, 8...Information recording member (As-Te-8e recording film) 0 Agent: Patent attorney Katsuo Ogawa Figure 7 (lL)

Claims (1)

[Claims] An optical disc characterized by using chemically strengthened glass as a substrate.