JPS6034171B2 - Video disk master using optical recording method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a video disc master used in manufacturing a video disc, and particularly to a video disc master using an optical recording method in which recording is performed by an optical method.

When manufacturing a video disc, first obtain a master disc, form a concavo-convex pattern on it according to the recorded content, create a stamper based on this master disc, press-mold the video disc using this stamper, and apply a protective film on the surface. Obtained by depositing.

Normally, this master disc consists of a positive type (a type that becomes soluble when irradiated with light) photoresist layer coated on a substrate, this photoresist layer is exposed to light according to a recording signal, and then this photoresist layer is developed. Then, the exposed portion is removed to form a concavo-convex pattern corresponding to the recording, so to speak, optical recording is performed using photographic technology.

FIG. 1 shows an example of optical recording on a master disc. In the figure, 1 is the master disc, and this master disc is made up of a substrate 2 coated with a positive photoresist layer 3.

This master disc 1 is placed on a rotating surface disc 4 (turntable). The surface of the face plate 4 is, for example, subjected to a blackening treatment to prevent light from being reflected. In this way, with respect to the master disk 1 rotated by the surface plate 4, a recording beam, for example, a laser beam 5 modulated by a recording signal, is moved in the radial direction and scanned onto the photoresist layer 3 of the master disk 1 for exposure. . In the figure, 6 is a laser source, 7 is an optical modulator controlled by a recording signal, 8 and 9 are a lens system, and 10 is a mirror. The laser light source 5 is focused onto the photoresist layer 3 by means of a lens system, in particular an objective lens 9, as shown in FIG. The photoresist layer 3 subjected to the exposure treatment in this manner is developed and the exposed portion is removed to form an exposure pattern, that is, unevenness corresponding to the recording signal. When recording by such an optical method, the track pitch is, for example, 1.6.
In order to perform high-density recording such as 7mm, the photoresist layer 3 is required to be formed as a layer with no particular thickness unevenness and good flatness. The substrate 2 is made of a glass substrate that provides excellent surface properties. Further, the laser beam 5 for exposing the photoresist layer 3 is also required to be focused to a diameter as small as possible. However, when recording is performed using such a method, fogging or peeling of the photoresist layer may occur. As a result of various experimental studies, the inventors of the present invention have found that this fogging and peeling is caused by the reflection of exposure light on the back surface of the glass substrate, ie, the transparent substrate, that constitutes the master.

That is, when the substrate 2 of the master 1 is made of a transparent substrate such as glass, the exposure light beam 5 for the photoresist layer 3 enters the substrate 2 as shown in FIG. 2, i.e., the surface opposite to the side coated with the photoresist layer 3, and the air (an interface b is formed between the back surface of the master disk 1 and the surface layer 4 on the surface disk 4 as explained in FIG. 1). However, optically, there is a gap between the master disk 1 and the surface disk 4, resulting in a boundary fold), and some light is reflected as shown by the broken line, and this is reflected onto the photoresist layer 3. Further, the light that diverges after being focused reaches the interface b. It was determined that the total reflection is greatly influenced by the arrival of light at an angle of incidence greater than that of the critical surface. That is, now the refractive index of air is n,
Assuming that the refractive index of the glass substrate 2 is ~ from the refractive index of the photoresist layer, these refractive indices have a relationship of n, so that at each interface Q and Q on the back and front surfaces of the substrate 2, there is a When the angle of incidence of light toward the other direction exceeds the critical angle, it is totally reflected. Therefore, when the light that is focused and then diverges enters the interface b through the photoresist layer 3 and the substrate 2 at an angle greater than the critical angle, it is totally reflected and directed toward the interface Q, and the incident angle to the interface b2 is If the critical angle is greater than or equal to the critical angle, the light is totally reflected again at step 2), and the light spreads along the plane of the substrate 2, but in this case, some of the light Since it enters the photoresist layer 3, it becomes soluble in the developing solution after exposure. The spread of light due to total reflection becomes more pronounced as the focusing is strengthened in order to obtain a narrower diameter exposure beam 5 for high-density recording, as the divergence angle of the light after focusing becomes larger. arise. Note that when the glass and the photoresist have substantially the same refractive index, the light is repeatedly totally reflected between the lower surface of the substrate 2 and the upper surface of the photoresist layer 3, thereby exposing the photoresist layer. Therefore, fogging occurs in the obtained recording pattern, and especially when high-density recording is to be performed, the photoresist layer 3 may be
peels off from the substrate 2. In the present invention, such “
In order to investigate the cause of "fogging" and "peeling", we can effectively avoid the above-mentioned "fogging" and "peeling" even if we use a glass substrate with excellent surface properties as the substrate that makes up the master disc. The present invention provides a video disc master using a new optical recording method that makes it possible to record video discs using a new optical recording method.

The master disk according to the present invention will be described with reference to FIGS. 5 to 7. In the figures, reference numeral 11 generally indicates a video disk master according to the optical recording method according to the present invention. In the present invention, a positive photoresist layer 13 is coated on a glass substrate with excellent surface properties, that is, an optically transparent substrate 12. In particular, a positive photoresist layer 13 is coated on the back surface of the substrate 12, that is, the photoresist layer 12. Apply anti-reflection treatment to the side opposite to the side to which No. 13 was applied.

This light reflection prevention treatment is, for example, as shown in FIG.
A light absorption layer 14 is applied to the back surface of the substrate 12. This light-absorbing layer 14 is coated with a resin colored clear, red, or black, so that it absorbs the exposure light to the photoresist layer 13, especially the light at a wavelength to which the photoresist layer 13 exhibits photosensitivity. can be formed by
Alternatively, as shown in FIG. 6, the back surface of the substrate 12 is etched with hydrogen fluoride or subjected to a matte treatment using a mechanical method to form a finely textured surface 15 on which light is diffusely reflected. Alternatively, as shown in FIG. 7, a material layer 16 having a refractive index n4 intermediate between the refractive index w of the substrate 12, that is, the refractive index w of glass and the refractive index n of air, is applied to the back surface of the substrate 12. This material layer 16 is not limited to a single-layer structure, but may have a multi-layer structure, and is made of a material whose refractive index gradually approaches n from France as the distance from the substrate 12 side increases. In this way, the light absorption layer 1 is formed on the back surface of the substrate 12.
4. Optical recording as explained in FIGS. 1 to 3, for example, is performed on the master disc 11 according to the present invention, which has been subjected to light reflection prevention treatment such as the rough surface 15 and the material layer 16.

Even if such optical recording is performed, the master disc 11 according to the present invention
It was confirmed that the occurrence of fogging and peeling was reliably and effectively avoided. That is, in any of the examples shown in FIGS. 5 to 7, a phenomenon in which the exposure light beam is reflected at the optical interface formed on the back surface of the substrate 12 and directed toward the photoresist layer 13 is avoided. As described above, according to the configuration of the present invention, since fogging and peeling can be effectively eliminated, video disks with high-density recording can be easily manufactured, and the industrial benefits thereof are great.

Incidentally, the light reflection prevention treatment for the substrate 12 can be performed in multiple ways by roughening each structure explained in FIGS. 5 to 7.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing a series of optical recording methods on a video disc master, Figs. 2 and 3 are similar explanatory diagrams, and Fig. 4
The figure shows the mode of light reflection in a conventional master disc.
7 through 7 are enlarged cross-sectional views of essential parts of each example of the master disc according to the present invention. 11 is a master disk, 12 is a transparent substrate, 13 is a photoresist layer, and 14, 15, and 16 are antireflection treated layers. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Claims] 1. In a video disc master in which a photoresist layer is coated on a transparent substrate, and optical recording is performed by exposing the photoresist layer to light according to a recording signal, the back surface of the transparent substrate is treated to prevent light reflection. A video disc master using the optical recording method.