JPH0448438A - Optical memory cell - Google Patents

Abstract

PURPOSE:To obtain an optical memory cell whose quality is satisfactory by providing a track guiding groove which has a narrow width in a section adjacent to a preformat area, as the density of a pre-pit is increased. CONSTITUTION:A track guiding groove 2 has a width W1 in a first section 2a adjacent to a pre-format 4, which is formed in order to be narrower than a width 2 of a second section 2b adjacent to an information recording area 5, according to the density of a pre-pit 3. That is, the width W1 is successively formed in order to be narrower than the width W2, according to the density of the pre-pit 3. Therefore, a value such as a VFO signal at the time of regeneration can be enlarged, and also the value of a track cross signal can be reduced in areas except for those in which the VFO signal or the like is recorded. Because of this, there is plenty of room for a standard value, and it is not necessary to precisely formed the width of the track guiding groove. Thus, the optical memory call whose quality is stable can be formed, and the yield is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application This invention relates to an optical memory element that can optically record, reproduce, erase, etc. information using a light beam such as a laser beam.

(b) Conventional technology In general, optical memory elements (optical disks) that can optically record, reproduce, and erase information are formed in a concentric or spiral shape at high density using a laser beam focused to a diameter of 1 μm or less. Information is recorded and reproduced by forming minute recording bits on the recording film on the r-track.

In order to guide the laser beam to a designated position, pre-pits are formed in advance on the recording surface of the optical memory element along the above-mentioned tracks to record a pre-format Z2 consisting of track guide grooves and VF○ signal address information. There is. That is, the laser beam is scanned according to the track guide groove,
By obtaining information such as an address in the pre-pit section where the pre-pit is formed, the pre-pit is guided to a designated position. Substrates for such memory devices include glass and plastic, and glass substrates have excellent mechanical properties, quality, reliability, and the like.

As a method for directly forming track guide grooves and pre-pits on such a glass substrate, a resist pattern is formed on a resist-coated mask surface using a laser beam, or a resist pattern is formed using an exposure device through a glass mask. A method is known in which a pattern matching a resist pattern is formed on a glass substrate by dry etching.

Conventionally, track guide grooves have been formed to have a uniform width and a uniform depth over the entire surface of a glass substrate, regardless of its inner or outer circumference. This is shown in FIG.

In FIG. 5 showing a part of the track IO, the track guide groove 11 is divided into a pre-pit section (VFO section) 10a of the track IO and an information recording section 10 without a pre-pit 12.
b are both formed with the same width.

(c) Problems to be Solved by the Invention The reproduced signal characteristics of the track guide groove and pre-pit section, that is, the signal strength when reproducing the optical memory element, are those of push-pull signals, track cross signals, sector mark signals, VFO signals, etc. is required to meet standard values. These are related to the shape of the track guide groove and pre-pit.

However, in the above configuration, among these characteristics, the push-pull signal is close to the upper limit of the standard value, and the VFO signal is
Since the ML value is close to the lower limit, in order to satisfy both, the width and depth of the track guide groove and pre-pit must be controlled with great precision, and with the current production technology, it is difficult to achieve this precision. It was difficult. Moreover, there was a tendency for the yield to decrease. The standard value for the VFO signal is 0.25 or more, and the standard value for the Bupunyuburu signal is 0.4.
It is 0.65 or less.

The present invention has been made in consideration of the above circumstances, and it is an object of the present invention to provide an optical memory element in which track guide grooves and pre-pits can be manufactured with high precision.

(d) Means and operation for solving the problem This invention includes:
A preformat area in which preformat prepits including a VFO signal are formed is formed at a predetermined position,
It is an optical memory element in which a track in which information is recorded in an area following the preformat area, and a track guide groove provided along the track are formed directly on a glass substrate, and the track guide groove is formed in the area following the preformat area. The optical memory element is characterized in that adjacent sections have widths that become narrower in accordance with at least an increase in the density of pre-pits.

With the above configuration, the value of the VFO signal etc. during playback is large, and the value of the track cross signal can be kept low in areas other than one area where the VFO signal etc. are recorded, so there is sufficient margin for the standard value. There is no need to precisely form the width of the guide groove. Therefore, products with stable quality can be produced and the yield is improved.

(E) Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to the following examples.

In FIGS. 1 to 4, a plurality of tracks l are formed concentrically on one surface of a disk-shaped glass substrate 7. In FIGS. The track l is formed between track guide grooves 2,
It is composed of a preformat area 4 in which a preformat formed by prepits 3 is recorded, and an information recording area 5 following the preformat area 4 in which no prepits 3 are formed.

In the first section 2a adjacent to the preformat area 4, the width W1 of the track guide groove 2 is narrower than the width W2 of the second section 2b adjacent to the information recording area 5, corresponding to the density of the pre-pits 3. It is well formed. That is, as shown in FIG. 2, the width W1 is formed to be narrower than the width W2 in accordance with the density of the pre-pits 3. Here, when the VFO signal is formed in the preformat area 4 by the pre-pit 3, the width W of the track guide groove 2
l is, for example, approximately 02 μm, and width W2 is, for example, 0.4 μm.
It is m. In this example, the VF◯ signal value was approximately 0.33, and the Bounyupuru signal value was approximately 055.

When the planar shape of the prepits is approximately circular, the density of the prepits is determined by the number of prepits in a predetermined length in the preformat area. Further, when the planar shape of the prepit is oval, the predetermined length is determined by the proportion occupied by the length of the prepit.

6 is a recording film, tracks 1. ) After the rack guide grooves 2 and pre-pits 3 are formed on the glass substrate 7, they are formed by a method such as vacuum evaporation, sputtering, or spin cording. Then, if necessary, a protective substrate is pasted on the recording film 6 or a hard coat agent is applied thereto.

To create an optical memory element having the above configuration, first, a positive film is deposited on the glass substrate 7 to a thickness of about 5000 Å.
, formed by . Next, this positive resist film is patterned by scanning a laser beam with a cutting machine to form tracks L) rack guide grooves 2 and pre-pits 3, respectively. When patterning a track guide groove, the intensity of the laser beam at that time is changed depending on at least the density of prepits adjacent to the track guide groove.

This controls the groove width of the track guide groove, for example, V
The area adjacent to the prepit of the FO signal is patterned to 02 μm, and the other areas are patterned to 0.4 ua.

The intensity of the laser beam may be changed depending on the shape of the pre-pit.

After the positive resist film is patterned as described above, it is developed and then the tracks 1, track guide grooves 2 and pre-pits 3 are etched to a depth of about 01 μm. After etching is completed,
The recording film 6 is formed on the surface of the glass substrate 7 including the bottom surfaces of the tracks 1, track guide grooves 2, and pits 3 by the above-mentioned method such as vacuum evaporation or spin code.

Note that when the above-mentioned cutting machine is not used, the positive film may be patterned by using a glass mask and transferring the pattern with an exposure device.

The optical memory element formed as described above may be used as a master for producing copies thereof, or may itself be made into an individual finished product.

In the above, we have explained the width of the track guide groove adjacent to the pre-pit that becomes the VFO signal, but in the case of the pre-pit that becomes other signals such as sector mark signals, the groove width can be narrowed in accordance with the signal. good.

(F) Effects of the Invention According to this invention, since the width of the track guide groove changes in accordance with at least the density of the adjacent pre-pits, that is, becomes narrower, the width of the track guide groove is hardly affected by the track guide groove, and the pre-pits Diffraction development of the irradiated light beam occurs efficiently, and a high-quality optical memory element whose reproduced signal characteristics of the signal generated by the pre-pits satisfies standard values can be obtained.

Furthermore, since the reproduced signal characteristics fully satisfy the standard values, it can be produced with high yield.

[Brief explanation of drawings]

FIG. 1 is an enlarged plan view of a main part showing the configuration of an optical memory element according to an embodiment of the present invention, and FIG. 2 is an enlarged plan view of a main part showing changes in groove width of a track guide groove when the density of pre-pits is different in the embodiment. 3 is a sectional view taken along the YIYI line in FIG. 1, and FIG. 3 is a sectional view taken along the line yt-y in FIG. 1, and FIG. ■ Trunk, 2. Track guide groove, 3. Pre-pit, 4. Pre-format area.

Claims (1)

[Claims] 1. A track in which a preformat area in which a preformat prepit including a VFO signal is formed is formed at a predetermined position, and information is recorded in an area following the preformat area, and a track guide provided along the track. An optical memory element in which a groove is formed directly on a glass substrate, wherein the track guide groove has a width that becomes narrower in accordance with at least an increase in the density of pre-pits in adjacent sections of a preformat area. Optical memory device with