JPH0426934A - Optical recording medium - Google Patents

Abstract

PURPOSE:To facilitate increase in recording density by preformatting many recessed parts which can form the respective information pits constituting information pit arrays by each one in the beam scanning direction of a data recording part. CONSTITUTION:The many recessed parts 14 are preformatted in the light beam scanning direction of the data recording part 4. The recessed parts 14 are formed by having the pitches equal to the bit pitches of the information pit arrays recorded by scanning signal-modulated light beams on an optical disk medium, i.e. the pitches which can form the respective information pits constituting the information pit arrays by each one. The thermal influence to be exerted on the adjacent recessed parts 14 and memory tracks is, therefore, decreased at the time of writing of the information. The pit pitches and track pitches are narrowed in this way and the recording density is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical recording medium, and particularly to a surface structure of a data recording portion formed along a recording track.

[Prior Art] Write-once or rewritable optical recording media having a data recording section on which information can be optically written are conventionally known.

FIG. 10 is a plan view of essential parts showing an example of this type of optical recording medium that has been known in the past, and FIG.
-
A header portion 3 having an uneven shape and a flat data recording portion 4 are alternately preformatted. The guide groove 1 and the header pit 2 are formed on a transparent substrate 5, as shown in FIG. 11, and a recording film 6 is adhered to the signal surface of the transparent substrate 5.

In this optical recording medium, a desired address can be detected from the header part 3 by tracking a light beam between the guide grooves 1, and information can be recorded/reproduced from the synchronization pit to the address. The lock can be retracted as needed to do so. Therefore, by accessing the data recording section 4 at a desired address with a light beam and irradiating it with a signal-modulated light beam, it is possible to write the information pit string 7 corresponding to the discontinuation of the light beam.

In addition, conventionally known optical recording media of this type include those in which a header portion 3 and a data recording section 4 are preformatted on a guide groove l, and those in which a light beam is tracked instead of a guide groove. There is one in which pairs of wobbling pits and synchronization pits are periodically formed, and a data recording section is formed in a flat area following the synchronization pits.

[Problems to be Solved by the Invention] Incidentally, in such optical recording media, increasing the recording density is one of the most important technical issues, and reducing the pit pitch Pp and narrowing the track pitch P8. is being explored.

In order to reduce the pit pitch Pp and narrow the track pitch P, the information pits 8 constituting the information pit row 7 must be
In order to miniaturize the information pits 8, it is necessary to reduce the diameter of the light beam spot focused on the optical recording medium and to increase the sensitivity of the recording film 6.

In the past, efforts have been made to design optical systems with high light collection efficiency and research into recording films with high recording sensitivity, but so far nothing has been provided that can dramatically increase recording density.

Note that if the power of the recording light beam is lowered, the amount of heat generated will be reduced, so small information pits 8 can be partially formed in the recording layer 6, but depending on the thickness and composition of the recording layer 6. Due to subtle non-uniformities, fluctuations in the focus servo that focuses the light beam spot on the optical recording medium, etc., it is difficult to form stable information pits, and so-called missed shots are likely to occur. Therefore, in order to form stable information pits, it is necessary to sufficiently increase the power of the recording light beam, and it is difficult to increase the recording density by making the information pits smaller due to the decrease in the power of the recording light beam. .

The present invention has been made to solve the problems of the prior art described above, and an object of the present invention is to provide an optical recording medium with high recording density.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a data recording unit in which, by scanning a signal-modulated light beam, information pit strings corresponding to the discontinuation of the light beam are written. The optical recording medium is characterized in that a large number of recesses are preformatted in the light beam scanning direction of the data recording section in which each information pit constituting the information pit row can be formed one by one.

[Function] When a resin substrate is used as the transparent substrate, the recess is formed on the surface of the resin substrate, and when a glass substrate is used as the transparent substrate, the recess is formed on the resin layer transferred to the glass substrate. formed on the surface of Since the resin material constituting the resin substrate and resin layer has a much lower heat transfer coefficient than the recording layer, the peripheral surface of the recess serves as a heat insulating wall, reducing the thermal influence on the adjacent recess and recording track. can do. Also, the length of the recording film from bottom to bottom of adjacent recesses in the same data recording area, and the length of the recording film from bottom to bottom of adjacent recesses between adjacent recording tracks. Since the length is extended, the thermal influence on adjacent recesses and recording tracks can be reduced from this point as well.

Therefore, the pit pitch and track pitch can be reduced, and the recording density can be increased. Furthermore, since a light beam of sufficiently large power can be irradiated, information pits with a stable shape and uniform size can be formed.

〔Example〕

First, a first embodiment of the present invention will be described with reference to FIGS. 1 to 5. The second embodiment of the present invention is an embodiment in which the present invention is applied to a continuous servo type optical disk medium. In addition, in FIGS. 1 to 5, parts corresponding to those shown in FIGS. 10 and 11 described above are designated by the same reference numerals for easy understanding.

FIG. 5 is an explanatory diagram of a continuous servo type optical disc medium, in which a ring-shaped area excluding the innermost and outermost parts of a transparent substrate 5 formed in a disc shape is a recording area 11. In this recording area 11, a spiral or concentric guide groove 1 is formed concentrically with the center hole 12.

Further, the recording area 11 has a plurality of sectors 13a in the circumferential direction,
13b, 13c, . The area following the second header part 3 is a data recording section 4. In addition, actually header part 3
are minute areas, and when the optical disk medium is viewed from the plane, they are observed as radial lines extending in the radial direction of the recording area 11, but in this figure, for ease of understanding, each sector 13a, 13b, 13c.

..., header pit 2 is displayed at the 13X delimiter.

Figure 1 is an enlarged plan view of each sector, Figure 2 is A of Figure 1,
-A sectional view, and FIG. 3 is a BB sectional view of FIG.

As shown in these figures, the optical disc medium of this embodiment has a large number of concave grooves in the light beam scanning direction of the data recording section 4.
(114 is preformatted. This recess 14
is a pitch that is equal to the pit pitch of an information pit string recorded by scanning a signal-modulated light beam on the optical disk medium, that is, a pitch that allows each information pit forming the information pit string to be formed one by one. It is formed with.

In order to provide a contrast between the header pit 2 and the information pit and to make them optically distinguishable, the depth d of the recess 14 is set to λ/, where λ is the wavelength of the reproduction light beam.
It is formed to a depth of 20 to λ/4. In addition, this recess 14
In order to increase the recording density, the area S of the opening is at least smaller than the size of an information pit formed in a conventional optical disk medium, that is, 1 μm or less. In addition,
The area S of the opening of this recess] 4 can be formed to be approximately the same size as the header pit 2 or smaller,
It can also be formed slightly larger than the header pit 2.

In this embodiment, the recess 14 is formed on the surface of the transparent substrate 5 together with the guide groove 1 and the header pit 2, as shown in FIGS. 2 and 3. In producing such a transparent substrate 5, first, a master disk on which a photoresist film is uniformly formed is laser cut, a metal stamper is copied from the obtained cut master disk, and a transparent substrate 5 is further duplicated from this metal stamper. Conventional optical disk medium duplication techniques such as the above can be applied as is.

As the recording film 6 adhered to the signal surface of the transparent substrate 5, a so-called write-once type recording film, such as a low melting point metal recording film, on which information can be added only once, may be used. It is also possible to use a so-called erasable type recording film, such as a magneto-optical recording film or a phase change recording film, in which information can be rewritten any number of times. Therefore, in this specification, information pits include those formed by a change in the shape of the recording film 6, those formed by a phase change of the recording film 6, and those formed by a change in the magnetic polarity of the recording film 6. including.

The optical recording medium of this example can detect a desired address from the header part 3 by tracking the light beam 15 on the flat part between the guide grooves 1, and can also detect the desired address from the synchronization pit. A lock can be inserted as necessary to record/reproduce information. Therefore, by accessing the data recording section 4 at a desired address with a light beam and irradiating the signal-modulated light beam 15, it is possible to write the information pit string 7 corresponding to the discontinuation of the light beam.

Each information pit 8 constituting the information pit row 7 is shown in FIG.
As shown in a) and (b), one is formed in each recess 14. FIG. 4(a) shows the information pits 8 recorded on the perforated recording film 6, and FIG. 4(b) shows the information pits 8 recorded on the magneto-optical or phase-change recording film 6. show. As shown in these figures, the information pit 8 must be formed at least within the opening area of the recess 14,
It is necessary to adjust the intensity of the light beam, etc. so as to satisfy such conditions. On the other hand, if the size of the information pits 8 becomes too small, the signal level read from the optical disk medium will decrease and the S/N ratio of the reproduced signal will decrease. Ratio is 50-10
It is preferable to adjust it so that it is in the range of 0%.

In the optical disk medium of the above embodiment, the recess 14 is formed on the surface of the transparent substrate 5, and the information pits 8 are recorded in the recess 14. Therefore, the circumferential surface of the recess 14 becomes a heat insulating wall, and the adjacent Thermal influence during recording on the recessed portion 14 and the recording track can be reduced. In addition, the length of the recording film 6 from the bottom surface to the bottom surface of the four adjacent portions 14 in the same data recording section 4, and the length from the bottom surface to the bottom surface of the adjacent recessed portions 14 between adjacent recording tracks. Since the length of the recording film 6 is extended, it is also possible to reduce the thermal influence on the adjacent recesses 14 and recording tracks during recording.

Therefore, the pit pitch P and track pitch P of the information pits 8 can be reduced, and the recording density can be increased. Further, since a light beam of sufficiently large power can be irradiated, information pits 8 having a stable shape and uniform size can be formed.

Next, a second embodiment of the present invention will be described with reference to FIGS. 6 to 9. A second embodiment of the present invention is an embodiment in which the present invention is applied to a sample servo type optical disk medium.

In the sample servo type optical disk medium, pit pairs called wobbling pit pairs for guiding the light beam are periodically formed on the left and right sides of the recording track instead of guide grooves, and sampling is performed from the reproduced signal of the wobbling pit pairs. This method uses a tracking error signal to apply tracking servo. A synchronization pit and a flat data recording section are arranged behind each pair of wobbling pits, and information is recorded/reproduced by scanning the light beam guided by the pair of wobbling pits. be able to.

FIG. 6 is a plan view of essential parts of the optical disk medium of this system, FIG. 7 is a sectional view taken along line CC in FIG. 6, FIG. 8 is a sectional view taken along line DD in FIG. It is a sectional view taken along line E-E in the figure.

In these figures, 21 is a pair of wobbling pits, 2
Reference numeral 2 indicates a synchronization pit, and other portions corresponding to those shown in FIGS. 1 to 5 described above are designated by the same reference numerals for easy understanding.

In the optical disc medium of this example, as shown in FIG.
4 are formed so as to be shifted from each other by half a pitch. In addition, the pitch of the recessed portion 14, the depth d, the area S of the opening, etc. are the same as in the second embodiment.

The optical disk medium of this example has the same effect as the optical disk medium of the first example described above, and also has four portions 14 formed in the data recording portions 4 of adjacent recording tracks so as to be shifted by a half pitch from each other. If the concave portions 14 are arranged in parallel at the same position and the track pitch P7 can be made relatively small, an optical disc medium with a high -layer recording density can be obtained.

In the first embodiment, a so-called on-land recording type optical disk medium in which recording tracks are set in flat areas between adjacent guide grooves 1 is taken as an example of a continuous servo type optical disk medium. Although described above, the present invention can be implemented in exactly the same manner for an optical disk medium of a so-called in-group recording method in which recording tracks are set on guide grooves.

Further, although the above embodiments have been described using an optical disk medium as an example, the present invention can be implemented in exactly the same manner for optical recording media of other shapes, such as card-shaped optical recording media.

Furthermore, in the above embodiment, the header pits 2 and the recesses 14 were formed on the surface of the transparent substrate 5 made of resin, but when a glass substrate is used as the transparent substrate, the resin layer is transferred to the glass substrate. These header pits and recesses can be formed on the surface of.

[Effects of the Invention] As explained above, according to the present invention, it is possible to reduce the thermal influence on adjacent recesses and recording tracks when writing information, so it is possible to reduce the pit pitch and track pitch. It is possible to increase the recording density. Furthermore, since a light beam of sufficiently large power can be irradiated, information pits with a stable shape and uniform size can be formed.

[Brief explanation of drawings]

1 to 5 are explanatory diagrams of the first embodiment, in which FIG. 1 is an enlarged plan view of a sector, FIG. 2 is a sectional view taken along line A-A in FIG. 1, and FIG. BB cross-sectional view, Fig. 4(a,),
(b) is a cross-sectional view of main parts showing the formation state of information pits;
The figure is a plan view of a continuous servo type optical disk medium. 6 to 9 are explanatory diagrams of the second embodiment, in which FIG. 6 is a plan view of the main part of the optical disk medium of this system, and FIG.
8 is a sectional view taken along line CC in the figure, FIG. 8 is a sectional view taken along line DD in FIG. 6, and FIG. 9 is a sectional view taken along line EE in FIG. 10 and 11 are explanatory diagrams of the prior art, in which FIG. 10 is a plan view of a main part of an optical recording medium, and FIG. 11 is a sectional view taken along line XX in FIG. 10. 1...Guide groove, 2...Header pit,
3...Part of header, 4...Data recording section, 5...Transparent substrate, 6...Recording film, 7
...Information pit row, 8 ...Information pit. Figure 3 Figure 4 (b) Figure 2 Figure 5 Figure 6 Figure 7 Figure 8

Claims (6)

[Claims] (1) In an optical recording medium having a data recording section in which information pit strings corresponding to discontinuities of the light beam are written by scanning a signal-modulated light beam, in the light beam scanning direction of the data recording section, An optical recording medium characterized in that a large number of recesses are preformatted in which each information pit constituting the information pit row can be formed one by one. (2) In claim 1, where the wavelength of the reproduction light beam is λ, the depth of the recess is λ/20 to λ/4, and the area of the opening of the recess is 1 μm^2. An optical recording medium characterized by being formed as follows. (3) The optical recording medium according to claim 1, wherein the information pits are formed in a range of 50 to 100% of the opening area of the recess. (4) In claim 1 or 2, the information pits are formed by a change in the shape of the recording film, a change in the phase of the recording film, or a change in the magnetic polarity of the recording film. An optical recording medium characterized in that it is any of the following. (5) The optical recording medium according to any one of claims 1 to 3, wherein the recess is formed on the surface of a transparent substrate. (6) The optical recording medium according to any one of claims 1 to 3, wherein the recess is formed on the surface of a resin layer transferred onto a transparent substrate.