JPS6369046A - Optical recording medium - Google Patents

Abstract

PURPOSE:To decrease the jitter quantity of signals as against a temp. and humidity change of external environment by coating the section of an optical recording medium where the medium contacts the outside field with a dielectric film having 1.35<=n<=1.75 refractive index n. CONSTITUTION:The composite dielectric film 2 consisting of the composite dielectric film composed of Al nitride and Si nitride is formed on a polycarbonate substrate 1 with guide grooves. A magneto-optical recording film 3 consisting of NdDyFeCoTi is formed thereon and the composite dielectric film composed of Al nitride and Si nitride is formed thereon. The composite dielectric film 6 composed of Al nitride and Si nitride is formed on a PC substrate 5. The substrates 1, 5 are tightly stuck to each other by using a UV curing resin 7 and an SiO2 film 8 is deposited by evaporation thereon to 5,000Angstrom thickness. The section of the optical recording medium where the medium contacts the outside field is coated with the dielectric film having 1.35<=n<=1.75 refractive index n in the above-mentioned manner, by which the jitter quantity of the signals as against the temp. and humidity change of the external environment is decreased and since the surface hardness of the substrates is increased, the scratching resistance is improved.

Description

[Detailed description of the invention] [Industrial application field] Misfire@11 relates to the structure of optical recording media.

[Conventional technology]

Optical recording media that can be optically recorded, reproduced, or erased are
Research and development has been actively conducted. In particular, in recent years, a nine-optical magnetic recording medium that utilizes the a-optical effect is on the verge of being put into practical use as an erasable and rewritable optical recording medium.

However, since the recording film of the magneto-optical recording medium is a rare earth transition gold R film, it has poor weather resistance. As a result of intensive research efforts, the inventors of the present invention developed a composite dielectric film as a protective film (
% patent application Sho 6l-747943, and laminated structure (patent application Sho 6
Through the development of 1-122767), it became possible to provide a magneto-optical recording medium with long-term reliability sufficient for practical use.

[Problem that the invention seeks to solve]

However, with the above-mentioned conventional technology, it has become possible to provide a medium with long-term reliability, but the substrate is a translucent resin substrate (PC,
PMMA, epoxy resin, etc.) Because it uses t'', it has a serious drawback that the humidity and temperature expansion is large and the deviation (jitter) of the signal once written becomes large.Therefore, in the past, when performing accelerated test sounds, Please be sure to remove the medium from the constant temperature and humidity chamber and leave it at room temperature and humidity for one day and night.

The present invention is intended to solve these problems, and its purpose is to provide an optical recording medium in which the amount of signal jitter does not change even when the temperature and humidity of the usage environment change. .

[Next method to solve the problem]

The optical recording medium of the present invention records, reproduces, or erases information by irradiating an optical recording layer formed on a transparent resin substrate with light. The optical recording medium in which this method is applied is characterized in that the portion of the optical recording medium that comes into contact with the outside world is coated with a dielectric film having a refractive index n of 1.35≦n≦1.75.

[Effect]

According to the above configuration of the present invention, by coating the portion t1 of the optical recording medium that comes into contact with the outside world with the dielectric film, it is possible to prevent moisture (moisture) from penetrating into the translucent resin substrate, and furthermore, the dielectric Since it is made of ceramic, it has a small coefficient of thermal expansion, and by suppressing the thermal expansion of the translucent resin substrate, the change in the jitter amount of the signal can be completely heated.Moreover, the refraction of the dielectric film By setting the ratio n to 1.55≦n≦1.75, the difference between the refractive index of the translucent resin substrate (near n = 1.5) is small, so the difference between the translucent resin substrate and the dielectric film is Since there is little reflection at the interface, it is possible to reduce the amount of light loss during reproduction.

The present invention will be described in detail below based on examples.

〔Example〕

FIG. 1 is a schematic cross-sectional view of the magneto-optical recording medium of the present invention. 1 is a polycarbonate (PC) substrate with guide grooves, and on this, as 2, a composite dielectric film of 1000 At of aluminum nitride and silicon nitride is formed by a sputtering method. NiDyFeC
oτ1 optical recording film 400 A'i bottom film, and 4 aluminum nitride and silicon nitride composite dielectric film 1000
A complete film was formed. Next, 500 A't of composite dielectric film of aluminum nitride and silicon nitride (6) was placed on the grooveless PC board (5).
- Films were formed, and the film-formed PC board with guide grooves and the PG board without grooves t7 were closely bonded together using an ultraviolet (U/V) curing resin. Finally, a 5io25000A film of 8 was formed by vapor deposition on the entire surface of the bonded magneto-optical recording medium in contact with the outside world.

Recording and reproduction were performed using the medium of the present invention thus prepared and a conventional medium not coated with a 5in2 film, and the amount of jitter in the signal was measured. The temperature at the time of recording was 25℃ and the humidity was 50%.
It is. Then, these inventive and conventional media were combined into 25
Figure 2 is a diagram showing the humidity dependence of jitter 1, which shows how the amount of jitter changes when the temperature is kept constant and the humidity is changed.

21 is S10.21 according to the present invention. The coated medium, 22 is a conventional uncoated medium, and as is clear from this figure, the jitter of the medium of the present invention is constant at 60 nsec regardless of humidity, but the jitter of the conventional medium increases as the humidity changes. This is a sign that a signal shift occurs due to humidity expansion (contraction). However, the jitter at 50% humidity is the same as the inventive media! 0 n5ec, but this is because the humidity at the time of recording was 50%. That's ninety-nine.

Next, with the total absolute humidity of these two media kept constant and the temperature raised, the jitter-tt-measurement was carried out in FIG. 3, which shows the temperature dependence of the amount of jitter.

21' is a coated medium of the present invention, and 22' is a conventional uncoated medium. It is clearly seen from this figure that the medium of the present invention shows little change in the amount of jitter. On the other hand, it can be seen that the amount of jitter in conventional media has a large humidity dependence.

The reason why the inventive medium and the conventional medium have the same amount of jitter at 25°C is because the recording temperature is 25°C.

It can be seen from FIGS. 2 and 3 that the medium of the present invention is extremely stable against changes in temperature and humidity in the external environment.

Furthermore, the signal amplitude can be improved by changing the film composition of the covering dielectric film. The film composition used was A40a (n=1.53)O
aF, (n==1i83, 0eF(n=t603,
KEr (n=1.50).

KO2 (n=1.53), LaF3 (n=1.58
3, 810 (n=1.73).

Sin, (n=1.463, ThF, (n=1.3
63, WO3 (n=1.70.).

C5Br (n=1.673, Os engineering (n=1.733,
MgO (n=1.63).

NaF (n = 145 3, The, (n = 1.
753, MgF, (n=145).

AtN (n=2.03, 81gN, (n=1.83)
, Zn8 (n=2.2).

AtFs (n==1.30). Membrane J! G? ′
150QQA constant ratio. FIG. 4 is a diagram showing the dependence of signal amplitude on the refractive index of the covering dielectric film. As is clear from this figure, the signal amplitude of the medium with a refractive index n of 1.35≦n≦1.75 does not change, but the signal amplitude of n (1, 55 and n) 1.75 becomes smaller. There is. This means that the refractive index of the substrate n =
This is a very different message from 1.5.

In addition, the humidity dependence of the amount of jitter was examined by changing the thickness of the covering dielectric film. In other words, we prepared all the media with various film thicknesses, and
FIG. 5 shows the jitter i total ratio of the signal recorded in a ambient environment of 5° C. and 50% RH and reproduced in a 98XRH atmosphere at 25° C., and is a graph of the dependence of the amount of jitter on the coating dielectric film thickness. The dielectric used here is 910. (n=1.46). It is clear from this figure that the thickness of the dielectric film is required to be 50A or more.

Similarly, although the structure of the recording medium used in this example is a closely bonded structure, the present invention is also effective with an air sandwich structure and a single plate, and is also applicable to write-once optical recording media as well as magneto-optical recording media. The present invention is effective. Furthermore, the structure on the recording layer side of this example is a three-layer structure sandwiched between the magneto-optical recording layer Vvjt body film, but other than this, a four-layer structure or a third dielectric layer may be used. A three-layer structure in which the film is replaced with a reflective film is also effective. In this example, the covering dielectric film was formed using a vapor deposition method, but there is no problem in using a sputtering method, an ion plating method, a sol-glu method, or the like.

〔Effect of the invention〕

As mentioned above, according to the present invention, the portion of the optical recording medium that comes into contact with the outside world is coated with a dielectric film having a refractive index n of 1.35≦n≦1.75, thereby increasing the temperature of the external environment. It is possible to reduce the amount of signal jitter due to humidity changes, and as a result, B
It is also possible to reduce changes in Ratθ. or,
Scratch resistance is also improved because the substrate surface becomes harder.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view of the magneto-optical recording medium of the present invention. FIG. 2 is a humidity dependence diagram of the amount of jitter. FIG. 3 is a temperature dependence diagram of the amount of jitter. FIG. 4 is a diagram showing the dependence of signal amplitude on the refractive index of the covering dielectric film. FIG. 5 is a diagram showing the dependence of the amount of jitter on the thickness of the coating EG electric material. 1... Polycarbonate with guide groove 1 (PC) board 2.
...Composite current visitor body of aluminum nitride and silicon nitride!
l [1000A thickness 3 --- NdDyFeooTi original magnetic recording 8 film 400A
Thickness 4... Composite dielectric film of aluminum nitride and silicon nitride 1000A Thickness 5... PC board without IW 6... Composite dielectric film of aluminum nitride and silicon nitride 111i500A Jun 7... Ultraviolet 1 噸 (σz") ) Cured resin layer 8...sio
, 5000A thickness 21...810. according to the present invention. Covered medium 22...
Conventional uncoated medium 21'...Sin according to the present invention, coated medium 22/...
...Conventional uncoated media. Applicant: Seiko Epson Corporation No. 2 Intention 3

Claims (3)

[Claims] (1) In an optical recording medium in which recording, reproduction, or erasing is performed by irradiating an optical recording layer formed on a transparent resin substrate with light, the portion of the optical recording medium that touches the outside world has a refractive index n. An optical recording medium characterized in that it is coated with a dielectric film satisfying 1.35≦n≦1.75. (2) The components of the dielectric film are Al_2O_3, CaF
_2, CeF, KBr, KCl, LaF_3, NdF_
3, SiO, SiO_2, ThF_4, WO_3, Cs
Br, CsI, MgO, NaF, ThO_2, MgF_
2. The optical recording medium according to claim 1, wherein the optical recording medium contains at least one component of 2. (3) The optical recording medium according to claim 1, wherein the dielectric film has a thickness of 50 Å or more.