JPH01140439A - Optical disk of polycarbonate system - Google Patents

Abstract

PURPOSE:To improve the long-period stability of mechanical accuracy by sticking two sheets of disk veneers having polycarbonate substrates to each other via a reinforcing plate consisting likewise of the polycarbonate. CONSTITUTION:Two sheets of the disk veneers formed by laminating optical recording layers 2, 2' and protective layers 3, 3' successively on the polycarbonate substrates 1, 1' are stuck to each other via the reinforcing plate 5 consisting of the polycarbonate by disposing the protective layers 3, 3' to face each other to constitute the optical disk of the polycarbonate system. Although there are no particular limitations on the materials to be used for the optical recordings 2, 2', the materials of a phase transition type are more preferable. The protective layers 3, 3' are formed to prevent the oxidation of the recordings 2, 2' and for example, SiOx, Si3N4, AlN, etc., are used as the material thereof. The full-surface adhesion type optical disk which has the excellent long-period stability of the mechanical accuracy is thereby obtd. without increasing the weight of the disk.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polycarbonate optical disc on which information is recorded and reproduced using laser light. More specifically, the present invention relates to a fully adhesive polycarbonate optical disc that has significantly improved long-term stability in mechanical precision.

Conventional technology Conventionally, there are two main types of optical disc structures: hollow air sand type and full adhesive type, and their constituent materials include:
Those using polycarbonate (PC), polymethacrylate (PMMA), glass, etc. as the substrate material are known, and the recording layer is of the open-hole type, phase change type, bubble-forming type, etc., and these structures, Various optical discs have been developed that combine different constituent materials, types of materials, recording layers, etc.

By the way, since there is air inside the hollow air sand type optical disc, if the optical disc is exposed to a high temperature and high humidity atmosphere for a long time, the recording layer will deteriorate due to oxidation and normal recording will not be possible. There are disadvantages such as not being able to read data or causing large errors during reading. On the other hand, full adhesive type optical discs do not have a structure in which air exists inside like the hollow air sand type, and therefore have the advantage of not having the above-mentioned drawbacks.

However, since the hollow air sand type has spacers on the inner and outer peripheries, it has good long-term stability in mechanical accuracy, whereas the full adhesive type simply attaches two disk veneers together. The drawback is that the long-term stability of mechanical strength is not necessarily sufficient if only the two are combined.

Therefore, in order to compensate for these drawbacks, attempts have been made to use various reinforcing plates in fully adhesive optical discs, and these reinforcing plates are made of plastics such as polyester, polysulfone, nylon, polyolefin, aluminum, and phosphorus. Items made of metals such as bronze and iron have been considered in this section. However, with none of these reinforcing plates, a sufficient effect could be obtained; in order to have an effect, the thickness of the reinforcing plate had to be at least twice that of the base material, and the weight of the optical disc This may cause inconveniences such as the volume becoming significantly heavier. In addition, attempts have been made to use glass fiber reinforced plastic as the reinforcing plate, but using a reinforcing plate made of glass fiber reinforced plastic slightly improves the stability of machine accuracy, but it increases the weight. This results in problems such as an increase in the load on the motor of the optical disk drive and a longer rotation start-up time.

Problems to be Solved by the Invention The present invention has been made with the object of overcoming the drawbacks of the conventional fully adhesive type optical disc and providing a fully adhesive type optical disc with excellent long-term stability in mechanical precision. It is something.

The inventors of the present invention have conducted intensive research to develop a fully adhesive optical disc that is characterized by mechanical precision and long-term stability.As a result, they have developed a material made of polycarbonate as a light-transmissive substrate. The inventors have found that the above object can be achieved by using a reinforcing plate made of polycarbonate, and based on this knowledge, the present invention has been completed.

That is, the present invention provides a disk single plate 2 formed by sequentially laminating an optical recording layer and a protective layer on a polycarbonate substrate.
The present invention provides a polycarbonate-based optical disk characterized in that two discs are bonded together with their protective layers facing each other and a reinforcing plate made of polycarbonate interposed therebetween.

The present invention will be explained in detail below.

The optical disc of the present invention is a fully adhesive type in which two single disc plates are bonded together, and each of the disc plates has a structure in which an optical recording layer and a protective layer are sequentially laminated on a polycarbonate substrate. have. The polycarbonate substrate has been conventionally used as an optical disk substrate, and some are already sold as 5% inch optical disks. This polycarbonate substrate has a saturated water absorption rate of approximately 5%.
It has low hygroscopicity, and the dimensional change rate due to moisture absorption and desorption is 1.
．． Since it is as small as 5.times.10.sup.-8% or less, it has the advantage of extremely high stability against environmental changes in temperature and humidity. Therefore, according to the present invention, in order to obtain an optical disk with excellent long-term stability in mechanical precision, it is necessary to use a substrate made of polycarbonate.

There are no particular restrictions on the material used for the optical recording layer provided on such a polycarbonate substrate, and any material can be selected from those conventionally used for the recording layer of optical discs. Since the optical disc of the invention is of a fully adhesive type, a phase change type material is preferable. Such alloys usually include alloys containing chalcogen elements, such as Te-0, Ge-Te, Ge-T
e-8b, Ge-Te-8e +Te-8n-Pb
, 5b2Se3-Bi2Te5, Engn-6e-Tt,
In-8b, In-8e, Ge-Te-8n, etc. are used.

The protective layer provided on the recording layer is for preventing oxidation of the recording layer, and its material is, for example, SiOx, Si3N4, AtN, or the like.

There are no particular restrictions on the method of forming the recording layer and the protective layer, and Method 1, which is used in the production of ordinary optical discs, may be used.
For example, a sputtering method, a vacuum evaporation method, an ion blating method, etc. can be used.

The optical disc of the present invention is advantageous in this way. Two single discs are formed by sequentially laminating an optical recording layer and a protective layer on a polycarbonate substrate, with the protective layers facing each other. It can be obtained by bonding them together through a reinforcing plate made of. In addition to polycarbonate, there are many materials for the reinforcing plate that have high rigidity and good one-dimensional stability, but reinforcing plates made of these materials can be combined with a polycarbonate substrate to form an optical disk with a fully adhesive structure. death.

When exposed to conditions that change temperature and humidity, subtle differences occur in the rate of dimensional change due to moisture absorption and desorption between the polycarbonate substrate and the reinforcing plate, resulting in a decrease in the stability of machine precision. do not have. On the other hand, when a reinforcing plate made of polycarbonate is used, the reinforcing plate changes in response to changes in the dimensions of the substrate, so the entire optical disk is suitably balanced and the stability of mechanical precision is maintained over a long period of time. maintained over the period.

An adhesive is used to bond the two disc veneers together via the reinforcing plate, but there are no particular restrictions on the type of adhesive, and it has been conventionally used in the production of fully adhesive optical discs. such as hardening adhesives and hot melt adhesives.

An adhesive or the like can be used.

Next, the structure of the polycarbonate optical disc of the present invention will be explained with reference to the accompanying drawings. FIG. 1 shows.

FIG. 2 is a cross-sectional view of one example of the optical disc of the present invention, in which optical recording layers 2 and 2' are provided on polycarbonate substrates 1 and 1', respectively, and protective layers 3 and 2' are provided on the polycarbonate substrates 1 and 1', respectively.
Two disk single plates Y and Y' are provided with
A structure is shown in which protective layers 3 and 3' are bonded to face each other via a reinforcing plate 5 and an adhesive layer 4.4'.

Effects of the Invention The optical disc of the present invention is a fully adhesive type optical disc made by laminating two single discs each having a polycarbonate substrate through a reinforcing plate also made of polycarbonate, and is different from the conventional fully adhesive type optical disc. The long-term stability of 1-machine accuracy is significantly improved compared to the previous model.

EXAMPLES Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to these Examples in any way.

The long-term stability of mechanical precision is generally determined by exposure to 2000 hours at 60°C and 90% RI, which is the maximum temperature and humidity at which optical disks are transported and stored, at 25°C at regular intervals during that time.
Mechanical accuracy was evaluated under 50% RH.

EXAMPLE A disk-shaped smooth PC board with a diameter of 300 mm and a thickness of 165 mm was cleaned with an ultrasonic cleaner, and a recording layer containing Sb, Te, and Ge was provided on one side by sputtering. By the same sputtering on top, S
An iOx protective layer was provided, and then hot melt adhesive (3S49, manufactured by Diabond) was applied thereon to a thickness of G Ottm.

The two disk veneers thus produced were placed with their adhesive coated sides facing each other, and between them a hot melt adhesive (same as above) was coated on both sides to a thickness of 60 μm. A fully adhesive optical disk was fabricated by pressing and bonding them together with a 1 m thick disc-shaped smooth polycarbonate reinforcing plate interposed therebetween.

Using two types of reinforcing plates shown in the attached table, the mechanical precision characteristics of the fully adhesive optical discs A and B were determined, and the results are shown in FIG. FIG. 2 is a graph showing the relationship between the processing time, the amount of recoil, and the amount of surface wobbling, where the solid line is for optical disc A and the broken line is for optical disc B.

Comparative Example Three types of fully adhesive optical discs C, D, and E were prepared in exactly the same manner as in the example except that a reinforcing plate made of the material shown in the attached table was used in place of the polycarbonate reinforcing plate in the example. The mechanical properties were determined. The results are shown in FIG. In FIG. 3, the solid line represents the optical disk C, the broken line represents the optical disk D, and the dashed line represents the optical disk E.

Standards such as mechanical precision of optical discs have not yet been standardized, but write-once and erasable optical discs generally have a rectification of ±250 μm or less and a surface runout of 250 μm.
There are many specifications as below. It can be seen that if the amount of reciprocation and the amount of surface runout are within this range, mechanical precision can be stably maintained over a long period of time in practice, especially by using a reinforcing plate.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of one example of the fully adhesive type optical disc of the present invention. In FIG.
．． 2' is an optical recording layer, 3 and 3' are protective layers, 4 and 4' are adhesive layers, 5 is a polycarbonate reinforcing plate, and Y and Y' are disk single plates. FIG. 2 and FIG. 3 show the processing time and amount of anti-slip for fully adhesive optical discs produced in Examples and Comparative Examples, respectively.
It is a graph showing the relationship with the amount of surface runout. Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] 1. It is characterized by two single disks each consisting of a polycarbonate substrate, with an optical recording layer and a protective layer laminated in sequence, the protective layers facing each other, and bonded together via a reinforcing plate made of polycarbonate. Polycarbonate optical disc.