JPS6297149A - Optical disk and its production - Google Patents

Abstract

PURPOSE:To obtain an optical disk which is free from exfoliation even after resting at the under a high temp. and high humidity and has high long-term reliability by providing a tightly adhered layer consisting of a mixture composed of a photosetting resin and transparent inorg. material between a transparent resin substrate and recording layer. CONSTITUTION:The tightly adhered layer 21 consisting of the material mixture composed of the photosetting resin and transparent dielectric material is provided between the transparent resin substrate 1 as represented by a polymethyl methacrylate, polycarbonate, epoxy, etc. and the recording layer 3 consisting of a metal, semiconductor, metallic compd., etc., which cause an optical change by the irradiation of light. The formation of the tightly adhered layer is executed by uniformly coating the photosetting resin having about several 10 - several 100[Cp] viscosity in the environment where light is shielded onto the substrate, installing the transparent resin substrate in a thin film forming device and irradiating near UV - blue visible light to the uncured photosetting resin layer to cure the photosetting resin simultaneously with deposition of the transparent inorg. material by sputtering vapor deposition or vacuum deposition on the uncured photosetting resin layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an optical disc on which information is recorded and reproduced by irradiation with a light beam from a semiconductor laser or the like.

[Technical background of the invention and its problems]

Optical discs record and reproduce information by irradiating them with a light beam, typically a semiconductor laser. (1) The recording area per bit is about the same as the spot diameter of the light beam (~1 μmφ); The density is extremely high. (11) Since information is recorded and reproduced without contact, there is no wear of the medium by the head.

(Due to the advantages of easy high-speed access of iD to several 100m5+EC, it is expected to become the mainstream of next-generation peripheral memory.Such original disks are basically made of a disk substrate and some kind of optical It consists of a recording layer that causes optical changes.Some optical changes include (i)
) The irradiated part is deformed (holes, bulges), and the reflectance of the deformed part is different from that of the undeformed part. The (i+)@ radiation part undergoes a phase change, and the reflectance of the phase change part is different from that of the non-phase change part. (iii) There is a type in which the magnetization of the irradiated part is reversed and the biased force state of the reversed part is different from that of the non-reversed part. In any of the above-mentioned types, it is practical to irradiate the recording layer with the recording/reproducing light beam through the substrate. This is because dirt and dust adhere to the air side of the recording layer, so if a light beam is irradiated onto the recording layer from the air side, many errors will occur.
If the disc manufacturer pays sufficient attention to the substrate side of the recording layer, it is possible to prevent dust from entering the substrate, and on the side of the substrate where the recording layer is not provided, the light beam is defocused. Therefore, dirt and dust attached to this surface are unlikely to cause errors for two reasons. However, the substrate of an optical disk is required to be transparent, and furthermore, in order to lower the noise level, it is also required to have as low a birefringence as possible. or,
In order to quickly move the optical head to a predetermined position on the disk surface to record and reproduce desired information, a group is required to guide the original head, and this group is not provided in the recording layer. Even if it is provided on the substrate surface in advance, it is far more technically advantageous from the standpoint of recording layer formation technology. Polymethyl methacrylate is a substrate material that simultaneously satisfies the three basic requirements mentioned above (transparency, low birefringence, and group formability).

Transparent resin materials such as polycarbonate and epoxy. However, since such transparent resin materials have extremely poor adhesion with inorganic materials, it is extremely difficult to form a recording layer made of a metal or metal compound well on a transparent Vli lipid-based substrate. is the current situation. For example, rare earth-transition metal amorphous ferrimagnetic films (hereinafter abbreviated as RE-TM films), which are currently most promising as recording layers for erasable optical discs, have poor adhesion to transparent resin substrates. This is one of the reasons for delaying the practical application of RE-TM optical discs.

[Purpose of the invention]

The present invention was made in view of the problems of the prior art described above, and uses polymethyl methacrylate.

The purpose of this invention is to provide a technology for forming a recording layer made of a metal or metal compound with good adhesion on an optical disk substrate typically made of polycarbonate, epoxy, or the like.

[Summary of the invention]

The optical disc of the present invention consists of a transparent resin substrate typically made of polymethyl methacrylate, polycarbonate, epoxy, etc., and a metal (metallic material) that causes an optical change when irradiated with a light beam.
RE-TM film, shape memory alloy film, etc.), a semiconductor, a recording layer made of a metal compound, etc., and a mixed material of a photocurable ML resin and a transparent dielectric between the transparent resin substrate and the recording layer. It is characterized by having an adhesive layer made of
It is cured by irradiation with light of 50 mm). Resins such as methyl methacrylate or epoxy can be used, and transparent inorganic materials include Si3N4. A.I.N.

5i02. SiO, ZnO, CaF2. In addition to dielectric materials such as MgF2, ITO.

A wide variety of transparent conductors such as 5n02 can be used.

In addition, as a means for forming the adhesive layer, powdered Butsuma inorganic material is mixed in an uncured photocurable resin, and the mixture is applied onto a transparent resin substrate, and then light is irradiated to form the adhesive layer. The first method is to harden the photocurable resin, but this method has the drawback that it is difficult to control the viscosity of the photocurable resin, which tends to cause unevenness during application, and that transparent inorganic materials Since the particle size of the powder is generally large, about several micrometers, it has the disadvantage that it diffusely reflects the recording/reproducing beam, which is unfavorable for memory operation. However, a preferred manufacturing method is to uniformly apply a photocurable resin with a viscosity of several tens to several hundreds of Cp in an environment that is exposed to light, and then place the transparent resin substrate in a thin film forming apparatus. Another method is to harden the photocurable finger by sputtering or vacuum depositing a transparent inorganic material on the uncured photocurable resin layer and simultaneously irradiating near ultraviolet to blue visible light.

〔Effect of the invention〕

According to the invention, polymethyl methacrylate.

A thin film of metal, semiconductor, metal compound, etc. can be formed with good adhesion on the original disk substrate made of transparent ml resin such as polycarbonate or epoxy, so it will not peel off even if left under high temperature and high humidity, ensuring long-term reliability. We can provide optical discs with high performance.

[Embodiments of the invention]

Hereinafter, the optical disc of the present invention will be explained in detail with reference to the drawings.

(Example-1) Fig. 1 is a cross-sectional view of the configuration of an embodiment of the optical disc of the present invention.
FIG. 2 is a sectional view of the structure of a conventional optical disc implemented as a comparative example with respect to the present invention. In Figures 1 and 2, (1) is a polycarbonate substrate with groups, c
! υ is the photocurable resin (epoxy type) and transparent dielectric (S
i3N4) mixed adhesion layer, (〃 is Si3N4 base layer,
(3) is a TbCo recording layer, 14) is a Si3N4 interference layer,
(5) is the AI reflection. FIG. 3 is a conceptual diagram of one embodiment of the apparatus used for manufacturing the optical discs shown in FIGS. 1 and 2. FIG. In Figure 3, (6) is a vacuum container, (
7) is a substrate holder, (8) is a substrate, (9) is a substrate rotating jig, (1 is a sputtering source, and aQ is an RF power source.

aQ is the shutter, (13 is the ultraviolet (254)) lamp house, ■ is the Lang power supply, (ts is the gas supply system, aQ
is the exhaust system. The optical disc of the present invention shown in FIG. 1 was produced using the apparatus having the configuration shown in FIG. 3 using the above procedure.

First, a substrate (8) on which a 0.3 μm thick photocurable ML fat layer was provided by spin-coding an epoxy photocurable resin on a grouped polycarbonate plate in a dark room was placed in a vacuum container (as shown in Fig. 3). 6), the pressure of the container (6) was reduced by the exhaust system OeI, and 5 (mTorr) of N2-Ar mixed gas with a partial pressure ratio of 10 inches of N2 was introduced from the gas supply system Kasumi. Next, with shutter az closed, RF1t! source αυ
The sample was put into the svarter source α1 containing the i3N4 target, and blur sputtering was performed for 5 minutes to clean the target surface. Move the jig (9) and attach the substrate holder (7)
was rotated at 60 (rpn), and at the same time the shutter 02 was opened, the rung power supply 0 was turned on to light the ultraviolet lamp (13). The time required for the hardening resin to harden was set to 10 minutes, and the power input to the Si3N4 target was set to 50X thickness per minute.
4 is set so that it enters into the photocurable resin layer, and the adhesion layer Qυ
I got it. Next, the substrate (1) provided with the adhesion layer was placed in a different sputtering device, and the surface of the adhesion layer was heated to an R of 300W.
After cleaning the surface by sputter etching with F power for 5 minutes, the TbCo recording layer 250X, Si
3N4 interference layer z5oX'AA! Reflection Nj toooA
Sputtering film formation was performed continuously to obtain the original disk sample of the present invention (FIG. 1). Conventional optical disc (
Figure 2) The sample was prepared using a Si3N4 underlayer 1000 on a grouped polycarbonate substrate based on the prior art.
After forming A and sputter etching the surface of this underlayer, a TbCo recording layer 25oX, Si3N4
A 25oX interference layer and an A1 reflective layer were laminated in this order. The thus obtained optical disc of the present invention and the conventional optical disc were heated at 65°C-90%RH, 24Hrs←room temperature IHr.
It was subjected to an accelerated deterioration test of 4 cycles.

Figure 4 shows the results. FIG. 4-(a) shows the surface state of the optical disc of the present invention after accelerated deterioration, and FIG. 4-(b) shows the surface state of the conventional optical disc after accelerated deterioration. As is clear from Fig. 4, the zero-source disc of the present invention maintains a good surface condition even after accelerated deterioration, whereas the conventional optical disc has many striped parts in the form of stripes or hexagonal shells. .

(Comparative Example 2) In Example 1, an example of an optical disk having a 5hN4 underlayer on a transparent resin substrate was described as Comparative Example 1, but even in the case of a film other than Si3N4, the present invention can be applied. For those without an adhesion layer, all peeling occurred after the υ mouth aging/deterioration test.The structure was the same as that shown in Figure 2, and S was used as the base layer.
In addition to the i3N4 membrane, the inventors have also developed a 5iOzS10. ZnS
, AIN, TiO2, CaF2. We made a prototype of a single-source disk using ITO, and the state after accelerated deterioration is shown in Figure 4.
The result was similar to that shown in (b). Father, the Si3N4 shown in Example-1 and the underlayer described above are transparent dielectric CI.
Although TO is a transparent conductor), a sample in which a recording layer was directly formed on a ml resin substrate was also prototyped and evaluated. FIG. 5 is a block diagram of this embodiment. In FIG. 5, (1) is a polycarbonate substrate with groups.

(31) is a recording layer, and examples of the recording layer include, for example, a TbCo film that uses magneto-optical effect, a CuM film that uses shape memory effect, 5eTe that uses crystal structure change, and InSb that uses crystal structure change. Either can be used.

The recording layer was formed using a sputtering device. It was found that in the optical discs having each of the recording layers, the recording layer peeled off from the substrate after accelerated deterioration, as shown in FIG. 4-(b).

<Example 2> An original disc of the present invention was produced using the recording layer used in the above comparative example. FIG. 6 is a block diagram of this embodiment. In FIG. 6, (1) is a polycarbonate substrate with groups, Cυ is a mixed adhesion layer of epoxy photocurable ml fat and Si3N4, and (3t) is the recording layer shown in Comparative Example-2. The adhesion layer was formed using the apparatus shown in Figure 3. As a result of subjecting these optical discs to accelerated deterioration tests, the original disc of the present invention was found to have a mixed adhesive layer of epoxy photocuring resin and 513N4.

Figure 4-(a) exhibits delamination for all recording layer materials.
), there was no alteration of the surface.

<Example-3> In Examples 1 and 2, epoxy photocurable resin and Si3N
As mentioned above, the mixed adhesion layer consisting of A6!4 and A6! N,
A mixed adhesion layer was formed using 5tOz, ZnS, CaFz, and ITO in the same manner as in Example 1 using the apparatus shown in FIG. 3, and its adhesion was evaluated by a beer-off test using an adhesive tape.

No peeling occurred in the mixed adhesive layers on the polymethyl methacrylate and epoxy substrates. Also, when a methyl methacrylate type resin was used as the photocurable resin, the adhesion was good.

Comparative Example 3 In Examples 1 to 3, the means for forming a mixed adhesion layer of a photocurable finger and a transparent inorganic material was to apply a transparent, clear inorganic material on an uncured photocurable resin. We have described a product formed by sputtering and irradiating light at the same time, but for comparison, we used the apparatus shown in Figure 3 to create a base layer in which a transparent inorganic material was formed by sputtering on a photocurable resin layer after curing. form,
A TbCo film was sputtered on top of the base layer at 65°C.
Figure 4-(b)
Similarly, numerous hectic detachments were observed. From this, when a transparent inorganic material is sputtered onto a photocurable resin layer after curing, the resin layer and inorganic material do not mix and wrinkle in any way, forming a clear interface and improving adhesion. On the other hand, when a transparent inorganic material is sputtered on the uncured photocurable resin layer of the present invention and light is irradiated at the same time, the sputtered particles penetrate into the resin layer and the photocurable resin layer is deposited near the interface. It can be determined that a mixed layer of resin and transparent inorganic material is formed, and that adhesion and adhesion are significantly improved.

<Example-4> In Examples 1 to 3, as a means for forming the mixed adhesion layer,
In addition to sputtering a transparent organic material on an uncured photocurable resin layer and irradiating it with light at the same time, there are other methods of mixing transparent inorganic material powder into an uncured photocurable resin. The mixed adhesion layer can also be formed by a method such as spin-coating the mixture onto the substrate. The inventors mixed powdered Si3N4 into an epoxy-based photocurable resin liquid.

Thereafter, a mixed adhesion layer was created by irradiating the polycarbonate substrate with a 254 nm Hg lamp using a spin code, and a beer-off test was conducted.

No peeling was observed when the 5i02 mixing ratio was 50VoJ or less. Moreover, TbC is placed on this mixed adhesion layer.

When the film was formed by sputtering and subjected to accelerated deterioration in 65° C.-90SR, ), almost no streak-like peeling occurred. However, the uniformity over a large area was inferior to that of the mixed adhesion layer described in Example 1. Furthermore, the transmittance for light with a wavelength of 833 nm was 85% for the mixed fE in Example-1, whereas in Example-4, Si3N4
Mixing ratio 20%, 60%, 5iaN4 mixing ratio 50V
The oA'% decreased to 40 inches, and it became clear that the method of Example 1 was superior in terms of optical memory operation.

The mixed adhesion layer of the photocurable resin and transparent inorganic material of the present invention can be expected to significantly improve adhesion regardless of the layer thickness, but it is difficult to maintain the shape of the groups pre-prepared on the substrate. The thickness of the adhesion layer should be as thin as possible, and should be at most 0.5 μm, preferably 0.3 μm or less.

[Brief explanation of drawings]

Fig. 1 is a block diagram of an optical disc of the present invention, Fig. 2 is a block diagram of an embodiment of a conventional optical disc, and Fig. 3 is an implementation of an apparatus for manufacturing the optical disc of the present invention. A conceptual diagram of an example, FIG. 4 is a diagram showing four metal structures showing the surface condition after accelerated deterioration tests of the optical disc of the present invention and a conventional optical disc, and FIG. 5 is a diagram of the configuration of another example of the conventional optical disc. , FIG. 6 is a block diagram of another embodiment of the original disk of the present invention. 1... Transparent ml fat substrate, 21... Adhesive layer, 22...
・Underlying layer, 3, 31... Recording layer, 4... Interference layer, 5
. . . Reflective layer, 6 . Vacuum container, 7 . Substrate holder, 8 . 12...shutter, 13...lung, 14...
Lamp power supply, 15... gas supply system, 16... exhaust system. Agent Patent Attorney Noriyuki Chika Yudo Kikuo Takehana Figure 2 Figure 8 Figure 4

Claims (2)

[Claims] (1) A transparent resin substrate and a recording layer that causes an optical change upon irradiation with a light beam, and a mixture of a photocurable resin and a transparent inorganic material is provided between the transparent resin substrate and the recording layer. An optical disc characterized by being provided with an adhesive layer. (2) After applying an uncured photocurable resin layer to a transparent resin substrate, a transparent dielectric material is sputtered or vacuum deposited on the transparent resin substrate coated with this photocurable resin layer and irradiated with light. A method of manufacturing an optical disc, comprising: curing a photocurable resin layer to form an adhesive layer; and forming a recording layer that causes an optical change upon irradiation with a light beam on the adhesive layer.