JPH01118236A - Production of optical memory element - Google Patents

Abstract

PURPOSE:To obtain an element which is less degraded in signal by hygroscopic deformation, thermal deformation and double refractions and is hardly cracked by subjecting a plastic substrate to a treatment by UV rays. CONSTITUTION:The substrate is molded by injection of polycarbonate of a carbonate type of bisphenol A. While a disk is kept rotated, the disk is uniformly subjected to intermittent irradiations of 30sec intervals at 80W/cm intensity by using a UV lamp which well emits light of <=300nm wavelength before the double refractions stabilize. The element which is less degraded in the signal by the hygroscopic deformation, thermal deformation and the double refractions is thereby obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing an optical memory element that records, reproduces, or erases 1a information using light.

[Conventional technology]

Conventional optical memory elements use glass, acrylic resin, polycarbonate resin, or the like as a substrate. Glass is made by photopolymer method or photoetching method.
Tracking grooves and bits are formed using acrylic resin or polycarbonate resin by injection molding, injection compression molding, or photopolymer method. Furthermore, in order to reduce birefringence of polycarbonate resin, attempts have been made to use an annealing method in which the substrate is heated.

[Problem that the invention seeks to solve]

However, the conventional technology has the following problems.

Glass has a high specific gravity, and a disk-shaped element has a high rotational resistance and is easily broken, making it difficult to handle. Furthermore, it is difficult to process, resulting in high costs. Acrylic resin has a large amount of moisture deformation and thermal deformation, so it is difficult to maintain ceramics.
When using m, the ceramic layer tends to crack (low reliability).Polycarbonate resin has small moisture deformation and thermal deformation, but has a large photoelastic constant, so birefringence increases and the signal decreases. Therefore, attempts have been made to reduce birefringence by changing molding conditions or by annealing, but it is extremely difficult to reduce birefringence by simply changing molding conditions. If the substrate is heated enough to reduce refraction, the heat will deform the substrate.

Therefore, the present invention is intended to solve these problems, and its purpose is to use a plastic substrate without any problems with moisture absorption deformation or thermal deformation, and without the problem of signal deterioration due to birefringence. The object of the present invention is to provide a reliable optical memory element whose protective layer is less likely to be cracked.

[Means for resolving gaps]

The optical memory device of the present invention records information using light,
In an optical memory element that is read or erased, a plastic substrate is used and the plastic substrate is treated with ultraviolet rays.

〔Example〕

The present invention will be explained below based on the drawings.

FIG. 1 is a schematic diagram of a method for manufacturing an optical memory element according to the present invention. The treatment with ultraviolet rays in the process shown in FIG. 1 will be explained using polycarbonate as an example. Polycarbonate that can be injection molded into disc canes is currently called Bisphe/-
A carbonate ester type of Le A is used, and its glass transition temperature is usually 130°C to 150°C. Interpal was applied at an intensity of 80 W/cm while rotating the disk so that the ultraviolet rays were applied uniformly to the surface of the disk whose birefringence was to be reduced.
Intermittent irradiation for 30 seconds was performed for 10 minutes. Polycarbonate absorbs light of approximately 300 nm or less, so 300 nm
It is preferable to use an ultraviolet lamp that emits light with a wavelength of nm or less. The treatment temperature varies depending on the temporary glass transition temperature, and is preferably 10°C to 30°C lower than the glass transition temperature. In this example, since 135'C polycarbonate was used, the treatment temperature was 120C. Furthermore, since this treatment with ultraviolet rays is more effective if it is performed before the substrate is molded and the birefringence is not stabilized, in this example, this treatment was performed 30 seconds after molding.

Figure 2 shows a case in which the recording layer part was formed using a substrate treated according to the present invention, a recording layer part formed using a substrate without any treatment, and annealing treatment. FIG. 3 is a diagram showing the relationship between the radial position and C/N of a disk when a transparent substrate and an ultraviolet curing resin are used to bond the disk. 1 is when the treatment of the present invention was applied, 2 is when no treatment was applied, and 3 is when annealing treatment was performed at 120° C. for 5 hours. The i2 recording section uses a 5i NdDYFeCo recording layer.
It has a sandwich structure with a protective layer of AIN.

As the transparent substrate used for bonding, a polycarbonate substrate having the same thickness (1 to 2 mm) as the substrate on which the film was formed was used. The ultraviolet curing resins used for lamination were 20% by weight of butanediol diacrylate, 25% by weight of neopentyl glycol diacrylate, 50% by weight of dipentaerythritol hexaacrylate, and 5% by weight of Irgacure 907 from Ciba Geigy (West Germany). A mixture was used. Then, the ultraviolet curing resin was cured by irradiating it with ultraviolet light using a high-pressure mercury lamp. This, 1 to 3 at 75℃85
% RH (7), cracks occurred in those annealed at 120° C. and those not subjected to any treatment. Although the C/N of a substrate annealed at 120° C. was not much different from that of a substrate treated according to the present invention, many cracks were generated in the ceramic layer. Table 1 shows the occurrence of cracks at various annealing temperatures and times. As can be seen from the results in Table 1, cracks occurred at 65°C in the case of no treatment and at 70°C in the case of annealing at 120°C for 5 hours. However, in the case of using a substrate treated according to the present invention, no cracks occurred even at 75°C. As can be seen from the results in Table 1 and the results in FIG. 2, it can be seen that by using a substrate treated according to the present invention, an optical memory element with a high C/N and strong against cracks can be obtained.

Table 1 Note that the present invention is not limited to these examples, and various changes can be made without departing from the gist of the present invention. For example, although polycarbonate resin is used as an example in the present invention, epoxy resin, polystyrene, acrylic resin, etc. may also be used, and metal halide lamps, chemical lamps, halogen lamps, etc. may be used instead of high-pressure mercury lamps (as appropriate). It is also good to use an infrared filter or a cold mirror.Also, NdDyFeC can be used as the
In addition to the o layer, TbFeCo5, GdTbFeFi, GdT
bFeCoG, S m D y F e Co layer, C
In addition to magneto-optical recording layers such as eDyFeCo layers, Te-T
There is no problem in using an eOx layer, a photochangeable writing layer such as Ag-ZnA'J, or a writing layer using any number of dyes. The same goes for the protective layer, 5i
In addition to the AIN layer, there is a SiN layer, AIN, 5iA1ONff
l etc. may also be used. Furthermore, the contact layer may also be of a thermosetting type, an anaerobic curing type, a roll coating type, etc. in addition to an ultraviolet curing type.

〔Effect of the invention〕

The optical memory element of the present invention has no problems with moisture absorption deformation or thermal deformation even when using a plastic Jλ plate, and there is no problem of signal deterioration due to birefringence, and it is reliable and does not easily cause cracks in the protective layer. This has the effect of providing an optical memory element.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a method for manufacturing an optical memory element according to the present invention. FIG. 2 is a diagram showing the relationship between the radial position of the disk and the C/N when a substrate treated according to the present invention is used and when no treatment is applied. 1... When using a substrate treated with ultraviolet light according to the present invention 2... When using a substrate that has not been subjected to any treatment 3... When annealing at 120'C for 5 hours Up

Claims (1)

[Claims] 1. A method of manufacturing an optical memory element that records, reproduces, or erases information using light, using plastic as a substrate, and treating the plastic substrate with ultraviolet rays.