JPS61236026A - Method of recording information recording master disk - Google Patents

Abstract

PURPOSE:To improve C/N ratio at the time of reproducing information signals by making the width of a guide track section larger than an address signal section. CONSTITUTION:The width W1 of a guide track 11 is made to W1>W2 compared to address information bit width W2 of an address information section 15. Reproduction signal output from the address information section 15 is made to maximum, and reproduction signal output from the guide track section 14 is made to make reproduction signal output by a recording bit 13 as large as possible. One lens diffraction limit is used in tangential direction of guide track and a luminous flux having Gaussian distribution is projected in the direction of width, and the spot at the focus is made anisotropic. The guide track section records at spot size d1 of intensity distribution I1 and the address information bit records at spot size d2 of distribution I2. Accordingly, d1 is larger than d2. By setting to the size range of d1<2d2, it is possible to cope with forming of guide tracks of various width. Thus, C/N can be improved by recording and reproducing information bit.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for recording an information recording master disk such as an optical disk on which video signals, digital signals, etc. can be recorded, reproduced, and erased.

Conventional write-once optical disks or rewritable optical disks on which information signals can be written are 2 times smaller than magnetic disks.
The track density is nearly an order of magnitude higher, and the amount of information that can be recorded is also larger. In order to access such high-density tracks with high precision and high speed, a preformat signal is required for the optical disc. The signal includes a guide track section in which the user can record information and address information for specifying the first location of a track or sector. This involves coating a glass master with photoresist, exposing it to laser light, developing it, and then making a nickel mold from it. A replica disk is made from this mold using various molding methods. A guide track and address information are formed on this replica disk.

A recordable disc is obtained by forming a recording film thereon using a vacuum deposition method or the like.

FIG. 4 shows an enlarged view of the conventional disk preformat signal mentioned above. The width W1 of the guide track 1 and the width W2 of the address information pit 2 are equal.

Information is recorded in this guide track portion. In order to improve the far-field detection efficiency of the tracking error signal, the optical groove depth is usually set to λ/8 (λ: wavelength of the reproduction light source). This is determined by the thickness of the photoresist applied onto the glass master. The photoresist thickness is the optical depth equivalent thickness λ/4 on the replica disk.
A method has also been proposed in which laser power is controlled at the time of master production so that recording is performed at a depth of λ/4 in the address signal pit area and at a depth of λ/8 in the guide track area.

FIG. 5 shows the structure of an optical disc having connected guide tracks and address signal pits formed between the tracks. Information signals are recorded between the guide tracks.

Problems to be Solved by the Invention However, guide tracks are indispensable for high-speed access, but because they have an uneven structure, when irradiated with light, the groove width may change.

Diffraction loss occurs depending on the groove depth, groove shape, etc., and becomes a factor that lowers the C/N ratio (signal-to-noise ratio) during information signal reproduction. In other words, the diffraction loss corresponds to the tracking error signal, and in order to eliminate the diffraction loss, it is sufficient to eliminate the guide track, but this poses various obstacles to access. A sector servo method has also been proposed in which a guide track is eliminated, dozens of sectors are provided on one rotation of the disk, and tracking servo is applied using intermittent tracking error signals from the sectors, but depending on the number of sectors, Tracking has become unstable. In FIG. 4 showing the conventional example, the guide track section 1
The width W1 of the address pit and the width W2 of the address pit part are W1=
W2, and if it were to be possible to read address information efficiently, the diffraction loss due to the guide track would also increase, and the influence on the recorded information signal would also increase.

Furthermore, in the conventional example as shown in FIG. 5, the guide track section and
Since the address information part needs to be recorded separately, two recording spots are required, which complicates the optical system for recording the master disc, and causes problems such as optical axis adjustment and positional stability of the two spots. Means for Solving the Problems The present invention takes into account the above-mentioned problems and provides a recording method for optical disk masters having access preformat information that can be produced stably and of high quality. However, whereas the conventional preformat signal has the same width in both the guide track section and the address signal section, in the present invention,
The conventional problems are solved by a master recording method in which the width of the guide track section is made larger than the width of the address signal section.

Function The present invention reduces diffraction loss for the tracking signal without affecting the address signal output by making the width of the guide track section larger than the width of the address signal section.
This is to increase the reproduction C/N of the recorded information signal. or,
Conventionally, when recording information, the recording focus was formed at a position where the influence of the guide track was most pronounced, so when creating a photoresist master, micro-roughness on the edges of the relief pattern due to exposure and development was caused. The present invention solves the problem of rough guide track edges that are transferred during replica disk production, and when a recording film is formed thereon and information signals are recorded, the roughness of the guide track edges affects the quality of the reproduced signal and lowers the reproduction C/N. The disc has preformat information that forms a recording focus at a position that is less affected by guide trunk edges, minimizes the influence of rough track edges, and facilitates the creation of master discs for producing replica discs.
EMBODIMENT 0 EMBODIMENT OF THE INVENTION Below, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the guide track 110 width W1 of the guide track section 14 is configured so that Wl>W2 when compared with the address information bit width W2 of the address information section 15, and the playback signal output from the address information section 16 is The playback signal output from the guide track section 14 is structured so that the playback signal output from the recording bit 13 is maximized. The distance P between tracks indicates a pitch, and a value of about 2.6 μm to 1.6 μm is usually used. When recording information, recording bits are usually not recorded in the address information section but only in the guide track section 14.

The bit width (groove width) that can efficiently reproduce address information is / of the reproduction light spot. 2 strength (center strength of 13.5
For example, if wavelength 2 of the reproduction light source is 830 nm and N and A of the recording and reproduction lens are 0.53, the spot size φ is φ=0. .83-=1.30 μm A. Therefore, it can be seen that the bit width (groove width) suitable for address signal reproduction is approximately 0.4 μm, 5 μm. Also, when the track pitch P is 1.6 μm, the width W of the guide track section 14 is cannot be larger than pitch P. Therefore, the setting of Wl is W2
A first embodiment is shown in FIG. 2 as a method for recording a master disc having the guide track section 14 and the address information section 16 shown in FIG. 1. FIG. 2 shows the light intensity distribution on the recording lens focal plane corresponding to the guide track 11 and address information bit 12.

Spot size in guide track width direction and tangential direction (
This shows the intensity distribution when Wl, W2 (beam waists) are equal, that is, a round spot. 0Recording lenses are usually in a state close to the lens diffraction limit in order to form as small a groove as possible on the recording master. used in To control the spot size, the N of the recording lens,
There is a method of equivalently changing the N and A of the lens by changing A, or by changing the distribution of the light beam incident on the lens while keeping the N and A of the lens constant. Recording lens N, A
When changing from 0.9 to O, S, the spot size d1 (= d2) is λ, assuming that the lens is used at the diffraction limit, and from d1=o, ss (λ: light source wavelength), d
It changes from 1=O-42prrr to d1=0.76 μm. However, for master recording, λ=467.9% m of the oscillation wavelength of the argon ion laser is used. The photosensitive material used for the master disc must have a concave-convex structure, and this shape must be precisely transmitted to the stamper and replica disc, so a photoresist with good shape accuracy and capable of forming microscopic patterns is needed. used. For example, a commercially available product is Shipley AZ1350.

The width W1 of the guide track part and the bit width W2 of the address information part are W2<
It is preferable to set it in the range of Wl<2W2. In this case, the recording/reproducing light source on the replica disk is a laser diode with λ=830 nm, and the recording/reproducing lens is N.
J=0.53. In order to realize the value of W2 in this range, N and A of the master recording lens should be set as follows: N, A = O-
This can be achieved by using 6 to 0.7 at the diffraction limit.

Also, when using a lens with higher N and A than these, instead of using it at the diffraction limit, the light flux entering the lens entrance pupil should be changed to a plane wave with a uniform intensity, but a light flux with a Gaussian distribution. Therefore, N and A can be equivalently lowered, and the spot size as described above can be realized. The embodiment with a round spot shown in Fig. 2 is useful when recording a guide track! The recording power is increased so that 7 otoresists are exposed with a beam diameter having an intensity distribution of , and when recording address information pits, the recording power is increased so that it can be recorded with a beam diameter having an intensity distribution of I2. need to be lowered and recorded. By doing this, it is possible to form grooves or bit structures having different widths Wl and W2 using a round spot with a centrosymmetric intensity distribution.

Next, a second embodiment will be described using FIG. 3. This example shows an intensity distribution profile when the recording spot size d1 in the guide track width direction is set larger than the spot size d2 in the tangential direction. In this embodiment, one lens diffraction limit is used in the tangential direction of the guide track, a light beam having a Gaussian distribution is made incident in the width direction, and the spot at the focal point is made anisotropic. When the recording lens is used at the diffraction limit only in one axis direction, that is, when the incident light beam has a distribution close to that of a linear light source, the convergence spot size (782 intensity) in the diffraction limit direction is as follows: D = closed, p =
Q-35 μm. By using a light spot that is sufficiently focused to the diffraction limit in the direction tangential to the guide track, the bit edges will be cleaner and the unevenness of development will be reduced. When recording with spots having the distribution shown in FIG. 3, the guide track section records with a spot size d1 having an intensity distribution of 1, so the recording power must be high. Furthermore, when recording address information pits, recording is performed with a spot size d2 with a distribution of T2, so the recording power may be lowered.

The influence exerted in the direction tangential to the guide track is due to the diffraction IJ
Since the direction is focused, there is no problem with the duty ratio, etc. dl is larger than d2
If the size is set within the range of 2d2, it is possible to sufficiently deal with the formation of guide tracks of various widths.

Effects of the Invention By making the width of the guide track part larger than the width of the address information part, it is possible to reduce the diffraction loss due to the track, and also to prevent the occurrence of light scattering due to roughness of the track edge part. It is possible to improve the C/N by bit.

This is effective for both write-once type and rewritable type. Particularly in the case of magneto-optical recording and reproducing, great efforts are being made to improve the C/N ratio, and by increasing the groove width of the disk, it is possible to improve the C/N ratio without significantly affecting the tracking signal.
The effect of improving the reproduced signal C/N is significant.

In the present invention, guide tracks and address information bits of different widths can be formed stably with high yield with a single beam of light, a simple optical system such as a cutting machine is required, and information can be recorded on a replica disk that is copied from the original disk. When performing reproduction, a very large effect can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an enlarged view of an optical disc when the track width is changed, showing the information recording master recording method in the first embodiment of the present invention, and Fig. 2 is a light intensity distribution characteristic diagram showing the recording state with spots in the same direction. , FIG. 3 is a light intensity distribution characteristic diagram showing the recording state with an anisotropic spot in the second embodiment,
FIG. 4 is an enlarged view of an optical disc showing a preformat signal in the case of a conventional track width being constant, and FIG. 5 is an enlarged view of the optical disc in the case of inter-trunk recording. 1... Guide track, 2... Address information pit, 3... Recording bit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure/1-m- is Idotra...Tsuku 13-11 cutting moxibustion bit 2nd figure 3rd figure

Claims (3)

[Claims] (1) A recording light source, a condensing lens for condensing the recording light beam of the recording light source onto the recording master, means for controlling the focus state of the condensing lens, and modulating the recording light according to an information signal. The spot size d_1 at 1/e^2 intensity of the recording spot on the recording master disc in the guide track width direction and the spot size d_2 in the tangential direction of the guide track are set to satisfy d_1≧d_2. An information recording master recording method, characterized in that the recording member irradiation power at the guide track forming portion on the recording master is made higher than the recording member irradiation power at the address information forming portion. (2) The spot size d_1 in the width direction of the guide track and the spot size d_2 in the tangential direction of the guide track are d_
1=d_2, and 0.43μm≦d_1≦0.8μ
An information recording master recording method according to claim (1), characterized in that: m. (3) The spot size d_1 in the width direction of the guide track and the spot size d_2 in the tangential direction of the guide track are d_
2<d_1<2d_2. An information recording master recording method according to claim (1), characterized in that 2<d_1<2d_2.