JPS60231926A - Production of master disk for recording - Google Patents

Abstract

PURPOSE:To enable development monitoring and detection of an end point by providing a developement monitor zone equal approximately to the signal of the blank groove or ruggedness of the groove depth having the longest section to the position of a master disk corresponding to the outside of the recording and reproducing region of an information recording medium in the stage of manufacturing a replica disk. CONSTITUTION:The zone 15 for monitoring development has the blank groove approximately equal to the groove depth having the longest recording section in the master disk for recording and a recording width of about 2-3 times (about 2-3mm.) the diameter of the irradiating spot during development monitoring. The recording position is preferably the outside circumferential position on the master disk where the zone 15 does not exist on the replica in the stage of manufacturing a die from the master disk and making the replica. The diffraction in the tangent direction by the signal is thus eliminated and the intensity of the 1st order or second order diffracted light of the monitor light is increased. The monitor signal having good S/N is thus obtd.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to information recording and reproducing devices used in information recording and reproducing devices, such as digital data files, that write and read information on a radiation-sensitive recording layer using light such as a laser. The present invention relates to a method of manufacturing a master disk for making a mold for forming a substrate of a recording medium.

In addition, the present invention particularly relates to a master disc for providing a preformatted board, and in particular, a blank groove in an information recording area used by a user, and a signal area for formatting position information, etc. used for random access etc. Furthermore, it is an object of the present invention to provide a suitable method for manufacturing a recording master disc having a structure including clock information recorded for use during recording and reproduction.

(Constitution of Conventional Example and Its Problems) Types of optical discs can be roughly divided into read-only discs and recordable discs. Read-only discs are already on the market and mass production is progressing, and various improvements and countermeasures have already been taken regarding the master disc manufacturing method. Examples of read-only discs include optical video discs and compact discs. All of this information is recorded in the form of uneven surfaces on the master disc.

The master structure of an optical video disc will be explained with reference to FIG. In FIG. 1, 1 is a glass substrate, 2 is a track,
28 to 2d indicate recorded signal areas. Track (−
As an example, 2a) shows the recesses (3', 4') corresponding to the information.
, 5', 6') and convex portions (3, 4, 5, 6). Here, the recessed portions are obtained by irradiating a photosensitive material layer such as a photoresist with light and performing development.

In the case of a read-only disc with such a structure, the information is composed only of the uneven parts, and the photoresist layer on the four parts is removed to the glass substrate surface after exposure and development, and the film thickness of the protruding parts is not exposed and the film thickness decreases even after development. It does not change and becomes the same mirror surface as the land between tracks. Therefore, the groove (or pit) depth is only a fraction d of the difference between the depression and the protrusion.

Therefore, it is possible to monitor development by using a portion of the signal area instead of providing a development monitoring zone.

An example of such a developing device is described in Japanese Patent Application No. 57-4078 filed by the present applicant, and the principle of a method for monitoring development is also known.

Furthermore, as a method for manufacturing recording master discs with a conventional disc structure with higher precision, the provision of a development monitoring zone for a constant signal of a recording wavelength approximately equal to the minimum recording wavelength is also described in Japanese Patent Application No. 136874/1987 by the present applicant. has been done. However, this proposal is aimed at recording masters in which the conventional groove (or pit) depth has only a - value.

On the other hand, recordable disks are currently being developed as memories for data files, document files, still images, etc., and the groove (or pit) structure suitable for these systems is different from the conventional one. There is.

FIG. 2 shows an example of a record-once type master structure. In FIG. 2, 11 is a track address section, 12 is a sector separator, 13 is a part of a sector, and 148 to 14C are tracks. The track address section 11 has groove (or pit) depths dl and d2 for land portions between tracks.
Information is recorded in the form of concavities and convexities, and the sector part 13 is configured as an information recording/reproducing area as an empty groove with a groove depth d2 in the land between the tracks.

As mentioned above, recordable discs have a track address section,
A part of the sector separator and a part of the sector have different structures, and the groove (or pit) depth has two different values for the land between tracks in the recording master.

The development monitor of such a recording master simply irradiates light onto the signal area recorded on the master and monitors the development state using diffracted light, similar to a read-only disc. It is extremely difficult because it has a large number of sectors and a large number of sectors. For example, as a detection method for a development monitor to solve this problem, a method may be considered in which sampling is performed only while the detection light for the development monitor passes through one of the grooves. However, in general, the rotational drive system of the developing device has no rotational speed control, there are many rotational irregularities, and the rotational speed is very low. It is difficult to determine accurately. Therefore, even if a complicated and expensive developing device is manufactured, the detection accuracy will be significantly degraded.

(Object of the Invention) The present invention provides one or at least two suitable for a recordable disc.
It is an object of the present invention to provide a suitable method for manufacturing a recording master disc having groove (or pit) depths of two or more.

The present invention also relates to a method for producing a master disc that allows highly accurate development monitoring, especially at the time of developing a master disc.

(Structure of the Invention) The present invention enables the development process of a master disc having a structure having at least two or more different groove (or pit) depths, such as a recordable disc, to a master disc that is recorded in the form of convexes and convexities in the conventional manner. By using the monitor system of the developing device that was used for the original disc, we created a developing monitor zone with the same signal all around, with the desired groove depth, outside the information recording and reproducing area, so that the developing state could be controlled with precision. It is characterized by providing.

(Explanation of Examples) FIG. 3 shows the structure of a master disc according to an embodiment of the present invention.

In FIG. 3, 10 to 14c show the same parts as in FIG. 2. Reference numeral 15 denotes a development monitoring zone, in which an empty groove approximately equal to the groove depth dl having the longest recording section in the recording master is spread over the entire circumference, with a diameter of 2 to 3 times the diameter of the irradiation spot at the time of development monitoring.
It has a recording width approximately twice that (approximately 2 to 3 nwn). Further, the recording position is preferably a peripheral position on the master where the development monitor zone does not exist on the replica when a mold is made from the master and a replica is made. In this case, the master disc size is, for example, in the case of a disc with an information recording and playback area of 30 square meters.
The recording position of the development monitor zone is desirably about 35 An in diameter, and the recording position of the development monitor zone is preferably a position close to the outermost periphery when making a replica prototype, for example, about 30.5 An in diameter. Further, as another embodiment of the present invention, if a clock that is approximately equal to the groove depth of a part of the sector is superimposed and recorded over the entire circumference of the track, the monitor zone is formed with irregularities that are approximately equal to this clock signal. Signals are recorded over the entire circumference and used as a development monitor zone. A part of the cross section of the address mark and a part of the sector in this case is shown in FIG. 4(a), and a part of the corresponding cross section of the development monitor zone is shown in FIG. 4(b). The clock usually has a groove depth that is the shallowest compared to other signals recorded in the master so that the modulation degree of the clock is the lowest compared to the address mark of the readout light during reproduction and the reproduction signal of the written information. It is formed as follows.

If this clock frequency is very high and the pit depth of the uneven part is very shallow, the diffracted light by the development monitor zone of the temporary irradiation beam of the development monitor will concentrate on the 0th order light, and the ±1st or ±2nd order light will be The intensity of the folded light becomes very weak.

In this case, as an embodiment of the present invention, as shown in FIG. 4(c), an empty groove having a groove depth approximately close to the uneven portion of the clock signal is recorded as a development monitor. The reason for this is shown in FIG. This will be explained using the relationship between the exposure amount and the film thickness remaining rate of a positive photoresist. In FIG. 5, the vertical axis shows the film thickness remaining rate, and the horizontal axis shows the exposure amount E. I is the maximum exposure amount without exposure, ■1°. indicates the minimum exposure amount required for 100% exposure. This I. ,■□. . varies depending on the type of photoresist and the concentration of the developer. The gamma characteristic of the resist in this case is expressed by the following equation.

1 γ = (log I□../manufacturing) When using such gamma characteristics to prototype a master disc with a groove structure as explained in Fig. 2, the exposure amount is equal to the signal depth d□. The section is El, and the section of groove depth dl is E2. In this case, the exposure amount for the signal depth dl is 110
If the development speed etc. are adjusted so that the desired line width and signal length can be obtained at an exposure amount greater than fl, the exposure amount E1
Even if the signal changes, the desired signal can be recorded. However, the exposure amount E2 of the empty groove with the groove depth dl and the signal section is ΔB2
If there is a change, the groove depth will correspondingly change by Δd. Therefore, in order to obtain a master disk with a desired disk structure, it is desirable to record grooves or signals in the area of the shallowest film thickness in the development monitor zone, monitor the development state, and control the development. Also, in master discs with structures other than those used in Figure 2, the groove depth is not large enough. ~Even if there are multiple corresponding signals or grooves within Loa,
By recording the shallowest groove or signal in the recording zone, the development state of other grooves or signals can be controlled because the gamma characteristics of the resist can be approximated as approximately linear.

Furthermore, if a clock signal is superimposed, the region with the shallowest signal depth corresponds to the clock signal. In this case, when this region is irradiated with development monitoring light, the transmitted or reflected diffracted light is mostly concentrated in the zero-order light.

Therefore, in order to increase the intensity of the first or second-order diffracted light, an empty groove approximately equal to the groove depth of this clock signal should be recorded in the development recording zone. By doing this,
The tangential diffraction caused by the signal is eliminated, and the monitor light is
The intensity of the next or second-order diffracted light increases, and a monitor signal with a good S/N ratio can be obtained.

(Effects of the Invention) As described above, in the method for manufacturing a recording master disc of the present invention, a clock is superimposed on a disc having a structure having two or more groove depths or signal depths different from conventional read-only optical discs, or Even in the case of a disc having a structure similar to the above, a development monitoring zone approximately equal to the groove depth or unevenness signal having the longest section should be provided at the master position corresponding to the outside of the recording/playback area of the information recording medium when manufacturing the replica disc. This makes it possible to monitor development and detect the end point by using the conventional development monitor device with a disk structure as is.

Furthermore, among two or more different groove depths or signal depths recorded in the master disk as a development monitor zone,
By recording an empty groove approximately equal to the shallowest groove depth as a development monitoring zone, irradiating this area with monitor light, and controlling development using this diffracted light, development can be controlled with good S/N and high precision. is possible.

In the recording master of the present invention, the development monitor zone may be located at any position as long as it is outside the information reproduction area, and the groove structure of the master also allows signals having two or more different groove depths. Alternatively, it can be applied to any structure in which air grooves are present.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the master structure of a conventional video disc.
FIG. 2 is a diagram showing the structure of a write-once master disc, FIG. 3 is a diagram showing the master disc structure according to an embodiment of the present invention, and FIG. 4 is a diagram showing a case where a clock is superimposed according to an embodiment of the present invention. FIG. 5 is a diagram showing the groove shape of the development monitoring zone, and FIG. 5 is a diagram showing the gamma characteristics of a positive type photoresist. 11... Track address section, 12... Sector separator, 13... Sector part, 148-14c.
... Track, 15...Zone for development monitor. Patent Applicant Matsushita Electric Industrial Co., Ltd. Agent Koji Hoshino Figure 1 Figure 3 Figure 4 rllll (a) (b) (C) Figure 5 IO↑11oo f (mJ/crn')22 El

Claims (2)

[Claims] (1) A light spot having at least two or more different intensities is irradiated on the master disc provided with the photosensitive material layer according to the information signal, and at least two or more different groove depths or signal depths are formed. Information about the groove depth or information that is approximately equal to the empty groove that has the longest recording section recorded within the recording area over the entire circumference outside the recording area of the information signal or the empty groove. Alternatively, a method for producing a recording master disc includes recording an empty groove as a development monitoring zone, irradiating the development monitoring zone with a light spot that does not affect the photosensitive material layer during development, and detecting the development state from the diffracted light. (2) As the development monitor zone, an empty groove approximately equal to the shallowest groove depth among two or more different groove depth information or empty grooves recorded in the recording master disk is recorded over the entire circumference. A method for manufacturing a recording master according to claim (1), characterized in that: