JPH04177636A - Optical information recording medium and manufacture thereof - Google Patents

Abstract

PURPOSE:To eliminate the need for particularly wide space between a ROM region and a RAM region by forming mutual pits or these pits in the ROM region and the bottom of the guide groove of the RAM region on the same plane. CONSTITUTION:A ROM region is formed within a range of a radius of 25-37mm on the main surface of a transparent substrate 1 having a diameter of 120mm, and pits P0 in width of 400-700nm and depth of 80-150nm are formed. A RAM region is shaped within a range of a radius of 37-59mm, and guide grooves Pa in width of 400-700nm and depth of 40-90nm are formed. An organic material recording layer 2, a refractive index of which is changed by the irradiation of a laser for recording, is formed on the whole region of the substrate 1. A metallic layer 3 for reflecting light is shaped onto the layer 2, and a protective layer 4 is formed onto the layer 3. The depth of the pits P0 of the ROM region is set in 130nm and the optical depth of the grooves Pa of the RAM region in 50nm at that time. According to such constitution, the standard of a compact- disc is satisfied, and wide space is unnecessitated particularly between both regions.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical information recording medium, particularly an optical information recording medium having a read-only area and a recordable area, and a method for manufacturing the same.

(Prior Art) In recent years, high-density recording and reproduction of information signals has been performed using information recording media made based on various construction principles. For example, an information signal is recorded by forming irregularities corresponding to the information signal on the signal surface of an information recording medium, and the recorded information signal is reproduced by optical means, or a change in capacitance value is detected. A recording/playback device configured to play back video signals and audio signals has already been put into practical use for recording and playing back video signals and audio signals.

In addition, in order to meet the demands for high-density recording and reproduction in various technical fields, by irradiating the recording layer of the information recording medium with a beam whose intensity is modulated by the information signal, the recording layer of the information recording medium can respond to the information signal. Research has also begun on information recording media in which information signals are recorded by causing physical or chemical changes.

In recent years, as semiconductor lasers that operate stably have become easily available, various optical information recording media (hereinafter referred to as optical disks) that perform high-density recording and reproduction using laser light have become available. It is well known that some technologies have already been put into practical use, or research and development is currently underway to put them into practical use.

In other words, recorded optical discs (read-only optical discs) that are mass-copied from master discs on which information signals are recorded using pits formed as geometrical concave or convex parts are, for example, video discs or compact discs. As such, it is beginning to become popular in ordinary households,
2. Description of the Related Art Optical discs that can be added and recorded only once by a user (write-once optical discs), erasable optical discs, and the like are being actively researched and developed for use as office file memories and other uses.

By the way, the Combat Disk, which is known as an information recording medium in which information signals are recorded at high density by an arrangement of pits corresponding to the information signals on the signal surface of the information recording medium, has a disc size of 780 rosos. Information signals are recorded on the signal surface by an array of pits with depths set in a specific relationship to the wavelength of light, and the entire surface of the signal surface is covered with a thin film such as aluminum. The reflectance of the land portion on the signal surface is set to be 70% to 90% for light with a wavelength of 780 ns, and the readout of information signals from the signal surface of the information recording medium is , a light spot having a wavelength of 780n layer is used.

When reading an information signal from this compact disc, the amount of light reflected from the pit portion on the signal surface is changed from the amount of light reflected from the land portion as a result of light interference occurring at the pit portion. Tracking error information is also obtained by using the difference between the amount of reflected light from the recorded trace area and the amount of reflected light from the land area. It is like that.

Now, with the spread of compact discs, there are now discs that are compatible with compact discs that can be played using compact disc players.
For example, there is a recorded area for playback only (hereinafter referred to as ROM area... read-only memory area...) and a recordable area that can be used as a write-once optical disc (hereinafter referred to as RAM area... Various proposals have been made for write-once optical discs with configurations that include a random-access memory area (sometimes referred to as ``random-access memory area...''), or discs whose entire surface is made up of a recording area. . As described above, an optical disk having a configuration in which a RAM area is provided is configured such that a guide groove for tracking is provided on a transparent substrate so that tracking control is performed even during recording.

By the way, optical discs that are compatible with the above-mentioned compact discs must, of course, comply with various playback standards established for compact discs, such as reflectance, modulation degree of high-frequency signals, and high-frequency signal modulation. It must satisfy standard values regarding symmetry, tracking signal output, crosstalk, etc. When trying to obtain a write-once optical disc that has satisfactory compatibility with various standards regarding playback on compact discs, the various standards regarding playback on compact discs that are particularly problematic include reflectance, Examples include the modulation degree of the high frequency signal and the output of the tracking signal.

When constructing a write-once optical disc that is compatible with compact discs, it must meet the standards for reflectance, high-frequency signal modulation, tracking signal output, etc. stipulated for compact discs. The problems that arise when configuring the write-once type optical disc to be obtained are summarized as follows.

First, the standard value for the reflectance of compact discs is that the wavelength from the reading side of the optical disc is 780 nm.
It is required to have a reflectance of 70% or more when viewed from the reading side of the optical disc when a laser beam of m is incident thereon. Approximately 8% reflection loss occurs on the surface of the optical disk, so even if we consider only the reflection loss on the surface of the optical disk, in order to achieve a reflectance of 70% or more on the read side of the previous disk, we need to increase the reflectance of the metal. The reflectance of the layer is required to be at least 80% or more. Compact discs use an aluminum reflective layer that has a reflectance of 80% or more, and the reflectance standard value mentioned above is used in compact discs. It is well known that the government is satisfied with the following.

However, in write-once optical discs, when recording is performed on the recording layer, energy for recording is absorbed into the recording layer, and since the transparent substrate is provided with guide grooves for tracking control, In addition to the loss of light quantity due to the light being diffracted by the guide groove, it has been difficult to set the reflectance on the read side of the optical disk to the standard value of the reflectance for compact disks.

Furthermore, when attempting to construct a write-once optical disc that is compatible with compact discs, the following problems arise in order to meet the standards for the degree of modulation of high-frequency signals stipulated for compact discs. .

In other words, compact discs use light diffraction by pits to read out information signals, so it is easy to meet the standard value for the degree of modulation of high-frequency signals. In a general write-once optical disc, the recording mode on the recording layer is as follows.
For example, this is done by perforation or phase change, and the recorded information signal is read out by changing the reflectance. Therefore, the difference between the light reflectance of the land portion and the light reflectance of the recording portion (corresponding to the pit) due to the hole or phase change, that is, the degree of modulation of the high frequency signal, is small, making it compact and compact. It was not possible to meet the standards for the degree of modulation of high-frequency signals stipulated for disks.

In order to satisfy the compact disc standard value for the degree of modulation of high-frequency signals, even in write-once optical discs, it is necessary to read out information signals using light diffraction by pits. Similarly, it may be necessary to ensure that the information signal is read out by means of a phase structure.

Next, when attempting to construct a write-once optical disc that is compatible with compact discs, there are the following problems with regard to the output level of the tracking signal specified for compact discs.

In other words, the output level of the tracking signal on an optical disc is determined by the phase structure, which is determined by the shape of the pit or the tracking guide groove provided on the transparent substrate, but even in write-once optical discs, it is necessary to satisfy other characteristics. In addition, it is necessary that the output level of the tracking signal satisfies the standard value. but,
In general write-once optical discs that have been proposed in the past, when recording is performed on the recording layer by making holes, the holes disturb the phase structure determined by the shape of the tracking guide groove. To put it away,
It is difficult to obtain a tracking signal with a desired output level.

From the explanation in J-L4, when constructing a write-once optical disc that is compatible with compact discs, there are problems such as the reflectance of light during playback, the degree of modulation of high-frequency signals, and the output of tracking signals. However, it has been difficult to provide a write-once optical disc that is compatible with compact discs.

FIG. 4 is a partially enlarged sectional view showing a second conventional optical information recording medium disk.

The second conventional disk is disclosed in Japanese Patent Application Laid-Open No. 2-132658, and as shown in the same figure, a transparent substrate 11 made of, for example, polycarbonate resin has guide grooves G, G... In the ROM region, a metal layer 13 for light reflection and a protective layer 14 made of, for example, an ultraviolet curing resin are formed in sequence. Also,
In the RAM area, when a recording laser beam having a predetermined wavelength is irradiated, an organic material layer 12 (hereinafter referred to as an organic material recording layer 12) absorbs an appropriate amount of this laser beam and changes its refractive index. ) and
A metal layer 13 for light reflection and a protective layer 14 made of, for example, an ultraviolet curing resin are sequentially formed.

The ROM area in the optical recording medium disc described above is the same as that of a normal compact disc, and its playback operation is well known.

Further, the RAM area in the optical recording medium disk described above is provided with tracking guide grooves G, G, etc. in the transparent substrate 11, which is provided with tracking guide grooves G, G, and so on.
When a recording laser beam having a predetermined wavelength is irradiated onto the side of the disc surface provided with..., the organic material recording layer 12 formed on this transparent substrate 11 will be exposed to the laser beam. The refractive index changes by absorbing an appropriate amount of

Then, the tracking guide grooves G, G = portions of the transparent substrate 11 in the laser light incident from the side of the board surface where the tracking guide grooves G, G, . . . on the transparent substrate 11 are not provided. , the phase difference that occurs between the tracking guide grooves G, G, etc. in the transparent substrate 11, and the organic material recording layer 12.
(Compared to the phase difference obtained in one state, it decreases due to the change in optical path length due to the difference in film thickness of the organic material recording layer 12, and the substantial phase difference of the laser beam is reduced due to the groove shape in the transparent substrate 11.) It becomes smaller than the determined phase difference value.

Further, due to the phase advance caused by the change in the organic material recording layer 12 in the recorded portion, the optical phase of the laser beam in the recorded portion is substantially advanced compared to the actual recorded portion. The optical recording medium disk, in other words, the compact disk, can meet the standards specified for compact disks in various characteristics such as light reflectivity, modulation degree of high-frequency signals, and output of tracking signals during playback. This makes it possible to provide a compatible write-once optical disc.

(Problem to be solved by the invention: 1) By the way, a write-once optical disc that is compatible with the previously proposed compact disc that is equipped with the above-mentioned ROM area and RAM area is shown in FIG. like,
In the ROM area, the metal layer 13 for light reflection and the protective layer 14 made of, for example, an ultraviolet curing resin are formed in sequence on the surface of the transparent substrate 11 on which the guide groove G for tracking is provided. On the other hand, in the RAM area, the organic material recording layer 12 is formed on the surface of the transparent substrate 11 on which the guide groove G for tracking is provided.
In this structure, a metal layer 13 for light reflection and a protective layer 14 made of, for example, an ultraviolet curable resin are sequentially formed. Therefore, when manufacturing the organic material recording layer 12 by applying the spin code method only on the transparent substrate 11 corresponding to the ROM area, it is necessary to prevent the organic material recording layer 12 from being formed in the ROM area. Must be.

To this end, it is possible to provide a very large gap (the portion 15 in FIG. 5) between the ROM area and the RAM area, which is 50 to 100 times the track pitch. This has the disadvantage of reducing the recording capacity of the optical recording medium disk.

In addition, as described above, when forming the organic material recording layer 12 by applying the spin code method, a ROM area is provided in the inner circumferential portion of the optical recording medium disk, and the ROM area described above is
In addition to the restriction that it is necessary to provide the RAM area on the outer periphery of the area, there is also the problem that it is not possible to create an optical recording medium disk in which multiple RAM areas and multiple ROM areas are mixed. .

On the other hand, as a solution to these problems, the applicant company has proposed a compact disc compatible with a compact disc in which a recording layer made of an organic material is formed over the entire ROM area and RAM area. An application has been filed for an optical disc with

FIG. 3 is a partially enlarged sectional view showing a first conventional optical information recording medium disc.

In the figure, the same parts as those in the second conventional example described above are denoted by the same reference numerals, and detailed explanation thereof will be omitted.

In the figure, GO is a pit formed by information signals in the ROM area, Ga is a tracking guide groove provided in the RAM area, and the width of this pit Go and the width of the tracking guide groove Ca are as follows. This is the width in the direction perpendicular to the direction in which the recording trace (track) of the optical recording medium disk extends.

A predetermined wavelength (for example, 780 nw An organic material recording layer 12 whose refractive index changes by absorbing an appropriate amount of a recording laser beam having a wavelength of 100 nm or more is formed by a spin code method.

This organic material recording layer 12 is a heat mode optical recording material using an organic dye or a material in which an organic dye is dispersed in an organic material, a photon mode optical recording material, or operates in both heat mode and photon mode. The recording material can be formed by selecting from organic dyes that contain organic dyes or optical recording materials in which organic dyes are dispersed in organic materials. For example, it can be constructed using a cyanine-based organic dye material whose refractive index n has a real part of +2.65 and an imaginary part of -0.05 in a state where it is not irradiated with a recording laser beam.

Reference numeral 13 denotes a metal layer for light reflection provided on the organic material recording layer 12 by a vapor deposition method or a sputtering method, and a metal such as Au s Al % Cu having a high reflectance is used.

Reference numeral 14 denotes a protective layer made of, for example, an ultraviolet curing resin, provided on the metal layer 13.

The configuration shown in FIG. 3 allows the ROM area and RAM area to be mixed freely, prevents a decrease in recording density, and allows the conventional spin code method to be used as is.
Setting the drop position of the coating liquid is also easy.

In the figure, it is technically difficult to form a rectangular guide groove in the RAM area, and the V-shaped guide groove shown in the figure generates a lot of noise due to uneven development during master creation, and is unreliable. There are problems.

The present invention has been made in view of these points, and has a clear boundary between the pit portion and the guide groove portion, and there is no reduction in recording density.
It is an object of the present invention to provide a highly reliable optical information recording medium in which a ROM area and a RAM area can coexist, and a method for manufacturing the same.

(Means for Solving the Problems) The present invention has been made to solve the problems as described above. As a first invention, in an optical information recording medium having a structure in which the optical depths of pits in a read-only area and guide grooves in a recordable area are different, the read-only area is formed in an optical information recording medium. This optical information recording medium is configured such that the pits of the area and the bottom of the optical depth of the guide groove of the recordable area are on the same plane. A second invention relates to a method for manufacturing an optical information recording medium according to the first invention, and includes a method for forming pits and guide grooves by exposing a photoresist coated on a glass plate to a laser beam. The optical information recording medium of the first invention is obtained by forming pits or guide grooves with a laser beam and uniformly exposing the upper surface of the pits or guide grooves with a second laser beam.

(Example) Fig. 1 is a partially enlarged cross-sectional view showing an example of an optical recording medium disk which is an embodiment of the optical information recording medium of the present invention, and Fig. 2 shows the manufacturing process of the disk shown in Fig. 1. FIG.

In this embodiment, a compact computer with a ROM area is used.
Experiments and confirmation of the invention were conducted based on the case of a disk (called a CD-ROM).

In Figure 1, 1 is a diameter 12 made of polycarbonate resin.
It is a 0n transparent substrate. Among the main surfaces of this transparent substrate 1,
A read-only ROM area is provided in the range of radius 25~37+ms+, radius 400~700n-1 depth 80~15
A pit PO of 0 nm is formed according to a CD-ROM signal. In addition, a recordable RAM area is provided within a radius of 37 to 59 mm, and the width is 400 to 700 nm.
, a guide groove Pa having a depth of 40 to 90 nl is formed.

As shown in the figure, the pit PO and the guide groove Pa have a rectangular cross-sectional shape in a plane perpendicular to the direction in which the recording trace of the disc of this embodiment extends.

The entire area on the transparent substrate 1 including the ROM area and the RAM area is covered with an organic material recording layer 2 whose refractive index changes by irradiation with a recording laser of a predetermined wavelength (780 ns in this case).
is formed with a thickness of 30 to 60 nm.

This organic material recording layer 2 is a heat mode optical recording material using an organic dye or a material in which an organic dye is dispersed in an organic material, or a photon mode optical recording material using an organic dye or a material in which an organic dye is dispersed in an organic material. Optical recording materials can be selected from optical recording materials that use organic dyes that operate in both heat mode and photon mode, or materials in which organic dyes are dispersed in an organic material. In this example, an indolenine cyanine dye is used.

On this organic material recording layer 2, a metal layer 3 for light reflection is formed by vapor deposition, sputtering, or the like. As the material, gold, copper, aluminum, etc. with high reflectance are selected.

A protective layer 4 is formed on the light reflecting metal layer 3 to protect it from moisture, oxides, dust, etc.

It is necessary that the optical recording medium disk of the configuration shown in FIG. 1 has substantially the same phase structure as a compact disk.

Here, if the refractive index of the organic material layer 2 in the state not irradiated with the recording laser beam is n and the refractive index in the irradiated state is 02, then since the ROM area is not irradiated with the recording light, the organic material layer 2 in the ROM area The refractive index of the material layer 2 is always 01. In order to make the optical depth of the pit portion of the compact disc 110 nm equal to 110 nm, the depth of the pit PO is set to 130 nm in consideration of the refractive index n1 of the organic material layer 2 in this embodiment.

On the other hand, in the RAM area, the guide groove Pa is irradiated with the recording laser beam and the refractive index of the organic material layer 2 is n2, so the optical depth of the guide groove Pa in the RAM area is 50 nsl. There is.

Next, the manufacturing method will be explained based on FIG. 2.

FIG. 2 is a sectional view showing the manufacturing process of the disk of FIG. 1.

(1) As shown in FIG. 4A, a glass plate is cut into a desired shape and then polished to obtain a glass master disk 5 for recording. Next, a photoresist 6 with a thickness of 130 nm was formed on this glass original ff1s by a spin code method, as shown in FIG. 2(A).

(2) Focus the gas laser beam into a shape that corresponds to the pit in the ROM area, and RO
The pit-corresponding parts Qo, Qo, . . . for the M area were sequentially exposed. At this time, as shown in the same figure (B), the pit equivalent part QO
(The shaded area) is exposed to a rectangular shape over a depth of 130n-.

(3) R on the outer periphery of the glass disk (radius 37 to 59 mm)
A guide groove equivalent portion Q3 for forming a guide groove in the AM region was formed by irradiation with the first laser and the second laser. The beam of the first glass laser is narrowed to a shape corresponding to the guide groove Pa of the RAM area, and the beam of the second glass laser is focused so that the irradiation range with the beam spans several tracks, and the exposure of the resist layer 6 is made in a predetermined manner. The output was adjusted so as to achieve the desired depth, and the first laser and second laser were simultaneously irradiated to sequentially expose the entire RAM area, as shown in FIG. In the figure, the dotted line portion is the portion exposed by the second laser irradiation.

(4) Although not shown, development was carried out by a well-known method, and then a nickel film was formed by sputtering, and a nickel film was thickened by wet plating, similar to the normal CD production process, to make a stamper.

(5) Using the above standber, polycarbonate was formed into a desired shape by injection molding to create a polycarbonate substrate 1. See the same diagram.

(6) As shown in Figure (E), the entire surface of the polycarbonate substrate 1 is spin-coded with 2 to 8% by weight of an indolenine cyanine dye dissolved in a polar alcohol solution such as cellosolve or diacetone alcohol. , recording layer 2.

(7) Gold is formed as a reflective layer 3 on the recording layer 2 by a sputtering method, and a protective layer 4 is further formed thereon by a spin coding method, so that the present invention as shown in FIG. An optical information recording medium disk having a structure according to the above was obtained.

After recording on an optical information recording medium disc created in this way with appropriate power, I attempted to play back the recorded signal, but both of the playback signals did not meet the Red Book standards for compact discs. I was able to confirm that there was a statement.

In the embodiment of the present invention having the above configuration,
Since there is no unrecordable area between the ROM area and the RAM area, the recording density is increased, the RAM area and the ROM area can be mixed arbitrarily, and the formation and depth of the guide groove Pa in the RAM area can be controlled. It has the effect of being easy.

In the above-mentioned embodiments, one disc-shaped optical information recording medium has a ROM M area and a RAM M area, or one optical information medium disc has a plurality of ROMs. A configuration in which the area is 6' is also possible. For example, when creating ROM regions with different usage wavelengths on one optical information recording medium disk, the regions with different optical depths can be created at arbitrary locations using the above-described method.

In addition, in the detailed description of the present invention described above, the optical information medium is in the shape of a disc, but is not limited to this shape.
For example, the present invention is also applicable to card-like media.

(Effects of the Invention) The optical information recording medium of the present invention having the above-described configuration satisfies the compact disc standard and does not require a particularly wide space between the ROM area and the RAM area, so it is easy to record. The object of the present invention is to provide an optical information recording medium that does not reduce density, allows a ROM area and a RAM area to coexist, and has high reliability, and a method for manufacturing the same.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged sectional view showing an example of an optical information recording medium disk, which is an embodiment of the optical information recording medium of the present invention, and FIG. 2 is an explanatory diagram showing the manufacturing process of the disk shown in FIG. 1. 3 is a partially enlarged sectional view showing a first conventional optical information recording medium disk, and FIG. 4 is a partially enlarged sectional view showing a second conventional optical information recording medium disk. 1... Polycarbonate substrate (optically transparent substrate)
, 2... Recording layer, 3... Metal layer, 5... Glass plate,
6... Photoresist, Po-pit, Pa...
・Guide groove. Patent applicant: Victor Japan Co., Ltd.

Claims (2)

[Claims] (1) At least one of pits in a read-only area and guide grooves in a recordable area is provided on an optically transparent substrate, and a recording layer is provided on the entire area of the read-only area and the recordable area. In an optical information recording medium in which a reflective metal layer is formed on the recording layer, the pits or the pits and the bottoms of the guide grooves are on the same plane. recoding media. (2) When forming pits and guide grooves by exposing the photoresist coated on a glass plate to laser light, the pits or guide grooves are formed by at least one laser beam, and at least one laser beam is used to form the pits or guide grooves. The optical system according to claim 1, characterized in that by uniformly exposing the upper surface of the pit or the guide groove, a plurality of regions whose bottom surfaces are on the same plane and have different optical depths are formed. A method for manufacturing an information recording medium.