JPS619848A - Guide groove forming method of optical recording medium - Google Patents

Abstract

PURPOSE:To improve the tracking capacity, the read S/N ratio, and the productivity by forming patterns of an optical recording layer consisting of optical recording medium materials on a foundation layer by the lift-off process and forming gap parts of this optical recording layer into guide grooves. CONSTITUTION:A photoresist is applied to the flat surface of a foundation layer 1 to form a photoresist film 2, and a mask 3 is used as shown in a figure B to expose guide groove patterns 3a to a light L on the photoresist film 2. After exposure of guide groove patterns 3a, the resist made insoluble by exposure is developed to remain as shown in a figure C to form resist patterns 4 for predeterminate guide grooves. Optical recording medium materials 5 are stuck to the surface of upper sides of resist patterns and the surface of the foundation layer 1 separately from each other as shown in a figure D. Finally, resist patterns 4 are removed by lift-off to leave optical recording medium materials 5 on the foundation layer 1 as they are, and these materials are used as optical recording layers 6, and gap parts between optical recording layers 6 are used as guide grooves 7 as shown in a figure E.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium, and particularly to a method for forming guide grooves therein.

(Prior Art) In the field of information technology, with the rapid increase in the amount and diversification of information, there has been a marked increase in the demand for a significant increase in the recording density of recording media.

Therefore, as an alternative to the conventional recording method, an optical recording method using an optical recording medium has been proposed. This optical recording method uses, for example, optical recording media using irreversible recording materials such as metal thin films or polymer materials, or optical recording media using reversible recording materials such as thermoplastics, chalcogenide alloys, TeOx, or magneto-optical materials. Media are being put into practical use or being developed.

Optical recording systems using these optical recording media are required to be able to perform random access, so recording and reading must be performed along a line, but guide grooves for tracking are not formed. This makes random access extremely difficult.

By the way, three methods are currently being used to form the guide groove.

The first method is to use a plastic substrate and form guide grooves during molding.

The second method is to use a glass substrate that does not deform, does not absorb moisture, and has excellent optical properties, and etches the glass substrate to form guide grooves.

The third method is to form guide grooves on the recording medium itself by forming a recording medium material on the substrate and then applying a treatment depending on the medium material, without providing guide grooves on the substrate itself. be.

(Problems to be Solved by the Invention) However, in the first method, since a plastic material is used, the material itself is easily deformed and warps occur, and S et al. The formation conditions for forming the recording medium material layer on the substrate become significantly stricter;
There are disadvantages such as the recording medium material being easily corroded because it easily absorbs moisture and having a high refractive index.

In the second method, the etching process involves first applying a photoresist to a glass substrate, then exposing the resulting photoresist film to light using a mask or directly using a laser or the like, and then , develop the resist,
The process involves at least four steps: etching the glass substrate; in particular, glass etching is extremely difficult to achieve selectivity in the etching direction because glass does not have anisotropy. Therefore, there was a drawback that it was difficult to form a pattern of perfectly aligned unevenness.

Furthermore, in the third method described above, for example, a thin metal film medium such as Te is directly irradiated with a laser to form irregularities, or a magneto-optical material is burnt out by laser irradiation, thereby changing the shape. Although there is no unevenness, a structural change occurs and a guide groove is formed due to the difference in reflectance. The drawback was that it did not improve sex. Furthermore, when forming irregularities on a Te or other metal thin film, the etching of the convex portion, which is the recording portion, may curl up, and in the case of a method that causes burnout of the magneto-optical material,
Since the difference in reflectance was insufficient, there was a drawback that it could not be used as a guide groove.

In this way, the conventional method for forming guide grooves in optical recording media is as follows:
As mentioned above, the reality is that there are various problems and many points to be improved.

A first object of the present invention is to provide a method for forming a guide groove of an optical recording medium in which the guide groove has an ideal shape so that it can fully perform its function as a guide groove.

A second object of the present invention is to provide a method for forming guide grooves that can increase the productivity of optical recording media and enable Langmuth access as a high-density recording medium.

(Means for Solving the Problem) In order to achieve this object, according to the method for forming a guide groove for an optical recording medium of the present invention, when forming a guide groove for an optical recording medium, a lift-off process is performed to form a base layer. It is characterized in that a pattern of an optical recording layer made of an optical recording medium material is formed thereon, and the gaps between the optical recording layers are formed as guide grooves.

(Function) According to this method, a guide groove is formed using a lift-off process, and specifically, for example, a photoresist is applied on a base layer to form a photoresist film, and then a photoresist film is formed. The film is exposed to light using a mask or directly drawn, then developed, an optical recording medium material is deposited to form an optical recording layer, and then lift-off is performed to form a pattern on the optical recording layer. This process involves forming the gap between the optical recording layers as a guide groove, so it can be applied regardless of the substrate material used for the underlayer as well as the type of magneto-optical material used for the optical recording layer, and the productivity is extremely high. improves.

Furthermore, according to the lift-off process, the guide groove and the recording layer are formed at the same time, with a sharp separation between the two, and since the guide groove exposes the base layer having a flat surface, there is no diffused reflection and its reflectance is also low. On the other hand, since the surface of the optical recording layer can be formed into a flat surface and its reflectance is high, the dB of the tracking signal, focusing signal, and readout signal can be increased, and noise can be reduced. Therefore, the guide groove can obtain its full function.

Furthermore, according to the lift-off process, since the optical recording layer is three-dimensionally separated by the guide groove, it is possible to record across the entire width of the optical recording layer in the lateral direction, and moreover, information does not leak into the adjacent optical recording layer. Since there are no holes, high-density recording is possible.

(Example) Hereinafter, an example of the method for forming a guide groove for an optical recording medium according to the present invention will be described with reference to the drawings.

FIGS. 1A to 1E are process diagrams for explaining a method for forming a guide groove by a lift-off process of the present invention.

In FIG. 1(A), reference numeral 1 denotes a base layer, which may be a substrate made of glass, plastic, or other materials, or may be provided with a dielectric layer or an organic layer in advance on these substrates. It may be something like that. A photoresist is applied to the flat surface of this base layer 1 to form a photoresist film 2.

Next, as shown in FIG. 1B, the guide groove pattern 3a is exposed to light using the mask 3 on the photoresist film 2. Then, as shown in FIG. In this embodiment, the mask 3 is used for exposure, but direct writing can also be performed using a laser or other radiation.

Next, after exposing the guide groove pattern 3a, as shown in FIG.
As shown in FIG.
form.

Next, as shown in FIG. 1(D), the optical recording medium material 5 is applied to the entire surface of the base layer l including the resist pattern 4.
to adhere to. In this case, as the optical recording medium material 5, for example, a magneto-optical material such as Tb-Fe can be deposited by vacuum deposition. As a result, the magneto-optical material 5 is deposited on the upper surface of the resist pattern 4 and on the surface of the underlayer 1 while being separated from each other.

As the material for this optical recording medium, materials other than Tb--Fe, such as Te, chalcogenide, TeOx, and other materials can be used regardless of the type. In addition to vacuum deposition, deposition methods include sputtering,
Ion blating method can be used.

Finally, as shown in FIG. 1(E), the resist pattern 4
is removed by lift-off to leave the optical recording medium material 5 on the underlayer 1, which is used as an optical recording layer 6, and the gap between the optical recording layers 6 is used as a guide groove 7.

FIG. 2 is a perspective view showing the pattern of the optical recording layer formed by the above process. As is clear from this figure, it is possible to pattern the cross-sectional shape of the optical recording layer 6 made of convex portions of the optical recording material into a substantially rectangular shape. For this reason, the optical recording layer 6 has this rectangular cross-sectional shape, is three-dimensionally separated from each other by the guide groove 7, and the surface of the base layer 1 is exposed in the guide groove 7, so that other substances cannot be absorbed. It has the characteristic that it does not exist, making it an extremely ideal structure as an optical recording medium.

These features will be explained below.

First, a convex optical recording layer 6 formed of an optical recording medium material
is completely separated from the adjacent optical recording layer 6, so that the optical recording layer (
In this embodiment, the recording portion 8 can be formed by recording (writing) over the entire width of the recording portion 6 (which is made of a magneto-optical material). Therefore, it is possible to completely confine the expansion of the recorded portion 8 in the horizontal direction perpendicular to the tracking direction, making it suitable for high-density recording. The N ratio can be improved. Furthermore, there is no lateral heat diffusion, so
Writing sensitivity can also be improved. Furthermore, since the surface of the recording portion 8 can be formed flat, scattering of the laser during writing and reading can be suppressed and noise can be reduced.

Second, since the base layer 1 is exposed in the portion of the guide groove 7 where the optical recording layer 6 is not formed, the difference in reflectance between the optical recording layer 6 and the base layer 7 directly becomes a tracking signal. , I-racking accuracy is improved. In this case, base layer 1
When a glass substrate is used, the reflectance is about 8%, and the reflectance from the surface of the optical recording layer 6 made of magneto-optical material is about 50%, so there is a large difference between the two, and therefore, the method of the present invention The resulting recording medium with guide grooves can be produced by a conventional method, that is, by forming an optical medium material on a substrate with guide grooves and utilizing the phase difference, or by forming a magneto-optical material on a substrate without grooves and using a laser beam. A significantly larger tracking signal can be obtained compared to a method in which a guide groove is formed by causing burnout by direct writing and the difference in reflectance between the burnt part and the untreated part is utilized.

In addition, since the surface of the base layer l with a high degree of flatness is exposed at the guide groove 7, it is possible to reduce noise in the tracking signal, focus signal, and readout signal due to diffused reflection of the irradiated light, which can lead to errors. can be expected to decrease.

Therefore, the optical recording medium formed by the method of the present invention improves the tracking signal and reproduction signal by several dB, and reduces the recording power by 20% compared to the case where a magneto-optical material layer is formed on a conventional grooved substrate. It is possible to reduce the degree.

(Effects of the Invention) As is clear from the above explanation, according to the method for forming guide grooves in an optical recording medium according to the present invention, the guide grooves are formed by a lift-off process, so unlike the conventional method, the guide grooves are formed by the lift-off process. The material and the optical recording medium material may be any material, and there is an advantage that productivity is improved.

Further, according to the method of the present invention, the guide layer and the optical recording layer of the optical recording medium are clearly separated, and the surfaces of the guide groove and the optical recording layer are flat, and the reflectance between them is greatly different. Therefore, the optical recording medium obtained by this invention has significantly improved tracking performance, readout S/N ratio, and focusing performance compared to the optical recording medium obtained by the conventional method, and also has higher recording (writing) power. It has the advantage that it can be significantly reduced.

Furthermore, since the above-mentioned effects are provided, the recording medium can be simplified.

According to the present invention, it is possible to form a guide groove for tracking that has the above-described effects, so that random access can be performed without difficulty using this guide groove.

[Brief explanation of the drawing]

FIGS. 1(A) to (E) are process diagrams for explaining the method for forming guide grooves in an optical recording medium of the present invention, and FIGS. 2 and 3 show guide grooves formed by the method of the present invention. 2 is a partial perspective view and a partial plan view schematically showing the structure of an optical recording medium having an optical recording layer. FIG. DESCRIPTION OF SYMBOLS 1... Base layer, 2... Photoresist film 3... Mask, 3a... Guide groove pattern 4... Resist pattern, 5... Optical recording medium material 6... Optical recording layer, 7...Guide groove 8...
Recording part. Patent applicant Oki Electric Industry Co., Ltd. Figure 1

Claims (1)

[Claims] In forming the guide groove of the optical recording medium, a pattern of an optical recording layer made of an optical recording medium material is formed on the underlayer by a lift-off process, and the gap between the optical recording layers is formed as a guide groove. A method for forming a guide groove in an optical recording medium.