JPH07122935B2 - Optical information recording medium and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical information recording medium, in particular, a ROM area which is a read-only area in which information is recorded in advance, and information writing at any time or additionally. It is a recordable area that can be performed
The present invention relates to a write-once type optical information recording medium having a RAM area and having compatibility with a compact disc, and a manufacturing method thereof.

(Prior Art) In recent years, as the demand for recording various information signals at a high recording density has increased, it has been possible to improve the information signal quality by using information recording media made based on various constitutional principles and operation principles. Density recording / reproduction has come to be performed,
For example, unevenness corresponding to the information signal is formed on the signal surface of the information recording medium, the information signal is recorded, and the recorded information signal is reproduced by optical means, or the capacitance value changes. The recording / reproducing apparatus adapted to reproduce by detecting the above has already been put into practical use for recording / reproducing video signals and audio signals.

In order to meet the demand for high-density recording and reproduction in various technical fields, the recording layer of the information recording medium is irradiated with a beam whose intensity is modulated by the information signal, so that the recording layer of the information recording medium responds to the information signal. Studies have also been conducted on information recording media in which information signals are recorded by causing physical changes or chemical changes, but in recent years, it has become easier to obtain semiconductor lasers that operate stably. As a result, various optical recording media (hereinafter also referred to as optical discs) capable of high-density recording / reproduction using laser light have already been put into practical use, or have been put into practical use. It is well known that research and development are currently underway.

That is, a recorded optical disk (playback-only optical disk) that is reproduced in large quantities from an original disk on which information signals are recorded by pits formed as geometrical recesses or projections is, for example, a video disk or a compact disk. In addition to the fact that it is beginning to spread to general households, 1
Optical discs (write-once optical discs) that can be additionally recorded by a user only once, erasable optical discs, and the like are being actively researched and developed for practical use in, for example, office file memories and other applications.

By the way, a compact disc known as one of the information recording media in which information signals are recorded at a high density due to the arrangement of pits corresponding to the information signals on the signal surface of the information recording medium has a wavelength of 780 nm. The information signal is recorded on the signal surface by the arrangement of pits having a depth set to a specific relationship with, and the entire signal surface is covered with a thin film of aluminum or the like. , The reflectance of the land portion on the signal surface is set to 70% to 90% with respect to the light having the wavelength of 780 nm, and the reading of the information signal from the signal surface of the information recording medium is performed at the wavelength of 780 nm. It is done by the spot of light.

Then, when reading an information signal from the compact disc, the amount of reflected light from the pit portion on the signal surface of the compact disc causes the amount of reflected light from the land portion as a result of light interference occurring at the pit portion. It is performed by making use of the fact that the amount of light is smaller than the amount of light, and tracking error information also uses the difference between the amount of light reflected from the recorded mark and the amount of light reflected from the land. It is supposed to be obtained.

Now, with the spread of the compact discs described above, as an optical disc compatible with a compact disc that can be played back using a compact disc player, for example, a prerecorded area dedicated to playback (hereinafter, ROM area ... may be described as read-only memory area ...) and recording area that can be used as a write-once optical disc (hereinafter, referred to as RAM area ... random access memory area ...) Various proposals have been made for a write-once type optical disc of a configuration mode provided with a) or an optical disc having an entire recording area. However, in the optical disc of the configuration mode having the RAM area as described above. A guide groove for tracking is provided on the transparent substrate so that tracking control is performed even during recording.

By the way, as an optical disc that is compatible with compact discs,
Playback standards established for discs,
That is, it must satisfy the standard values for reflectance, modulation of high frequency signals, symmetry of high frequency signals, tracking signal output, crosstalk, etc. When trying to obtain a write-once type optical disc having power compatibility, various standards relating to reproduction on a compact disc that are particularly problematic include reflectance, modulation degree of high frequency signal, tracking signal output, etc. To be

Here, in the case of constructing a write-once optical disc compatible with a compact disc, various standards relating to the reflectance, the modulation degree of a high frequency signal, the tracking signal output, etc. which are prescribed for the compact disc. The problem that occurs when a write-once optical disc that can satisfy the above conditions is constructed will be outlined below.

First of all, the standard value for the reflectance of compact discs is to have a reflectance of 70% or more when viewed from the reading side of the optical disc when laser light with a wavelength of 780 nm is incident from the reading side of the optical disc. However, since a reflection loss of about 8% occurs on the surface of the optical disk, it is necessary to consider the reflection loss on the surface of the optical disk only in order to set the reflectance on the reading side of the optical disk to 70% or more. , The reflectance of the metal reflective film is at least
80% or more will be required.

It is well known that a compact disc uses an aluminum reflective film having a reflectance of 80% or more and satisfies the above-mentioned standard value of reflectance.

However, in the write-once type optical disc, when recording is performed on the recording film, the recording film absorbs energy for recording, and as described above, the write-once type optical disc is used for tracking control during recording. In addition, since a guide groove for tracking control is provided on the transparent substrate, a light amount loss due to the incident light being diffracted by the guide groove is also added, so that the reflectance on the read side of the optical disk is reduced. It has been conventionally difficult to obtain the standard value of the reflectance in.

Further, when a write-once type optical disc compatible with a compact disc is to be constructed, the write-once type optical disc that can satisfy the standard for the modulation degree of the high frequency signal defined for the compact disc is constructed. In this case, there are the following problems.

That is, since the information signal is read out using the diffraction of light by the pit in the compact disc, it is easy to meet the standard value for the modulation degree of the high frequency signal, but it has been proposed in the past. In a general write-once optical disc, the recording mode on the recording film is, for example, due to perforation or phase change, and the recorded information signal is read by changing the reflectance. Therefore, the difference between the light reflectance of the land and the light reflectance of the recording portion (corresponding to the pit) due to the phase change or the phase change, that is, the modulation degree of the high frequency signal is small, It was not possible to meet the standard for the modulation degree of high-frequency signals specified for compact discs.

In order to satisfy the standard value of the compact disc for the modulation of the high frequency signal, even in the case of the write-once optical disc, the information signal is read using the diffraction of light by the pits. Similarly, it may be necessary for the phase structure to allow the reading of the information signal.

Next, when a write-once optical disc compatible with a compact disc is to be constructed, a write-once optical disc capable of satisfying the standard for the output level of the tracking signal specified for the compact disc is constructed. When doing, there are the following problems.

That is, the output level of the tracking signal on the optical disc is determined by the phase structure that is determined by the shape of the pit or the tracking guide groove formed on the transparent substrate, but the write-once optical disc also satisfies other characteristics. In addition, it is necessary to make the output level of the tracking signal satisfy the standard value.

However, in the case of a general write-once type optical disc that has been conventionally proposed, when the recording mode on the recording film is performed by, for example, making a hole, the shape of the guide groove for tracking is determined by the hole. Since the phase structure is disturbed, it is difficult to obtain a tracking signal having a desired output level.

From the above description, when trying to construct a write-once optical disc compatible with the compact disc, the compact disc having various characteristics such as the reflectance of light at the time of reproduction, the modulation degree of the high frequency signal, the output of the tracking signal, etc. There are many problems in satisfying the standard stipulated in the above, and it was difficult to provide a write-once optical disc compatible with a compact disc by using a conventional write-once optical disc. .

FIG. 5 is a vertical cross-sectional view of an example configuration of an optical recording medium disc disclosed in Japanese Patent Laid-Open No. 132656/1990. This optical recording medium disc has tracking guide grooves G, G ... Provided transparent substrate made of, for example, polycarbonate resin
A metal film 12 for light reflection in the ROM area, which is a read-only area, and a protective film made of, for example, an ultraviolet curable resin are provided on the board surface on which the guide groove G for tracking in 10 is provided.
13 is sequentially adhered, and in the RAM area which is the recordable area, a recording laser beam having a predetermined wavelength is formed on the plate surface of the transparent substrate 10 on which the guide groove G for tracking is provided. When irradiated with, the organic material film 11 absorbs an appropriate amount of the laser light and changes its refractive index (hereinafter, also referred to as the organic material recording film 11)
Then, a metal film 12 for light reflection and a protective film 13 made of, for example, an ultraviolet curable resin are sequentially attached.

The ROM area of the above-mentioned optical recording medium disc is the same as the configuration of a normal compact disc, and its reproducing operation is well known.

Further, the RAM area in the above-mentioned optical recording medium disk is on the board surface of the transparent substrate 10 provided with the tracking guide grooves G, G. When irradiated with a recording laser beam having a predetermined wavelength, the organic material recording film 11 attached to the transparent substrate 10 absorbs an appropriate amount of the laser beam and the refractive index changes. To do.

Then, the tracking guide grooves G, G on the transparent substrate 10 in the laser light incident from the side of the board where the guide grooves G, G for tracking on the transparent substrate 10 are not provided. Compared with the phase difference obtained in the absence of the organic material recording film 11 described above, the phase difference generated between the part and the part of the transparent substrate 10 other than the guide grooves G for tracking G, G ... Reduced due to the change in the optical path length due to the difference in the film thickness of the material recording film 11, the substantial phase difference of the laser light becomes smaller than the value of the phase difference determined by the groove shape in the transparent substrate 10,
Further, due to the advance of the phase caused by the change of the organic material recording film 11 in the recorded portion, the optical phase of the laser beam in the recorded portion is substantially advanced as compared with the actual recorded portion. Enables compatibility with optical recording medium discs, that is, compact discs, in which characteristics such as light reflectance during playback, modulation of high-frequency signals, and output of tracking signals can meet the standards stipulated for compact discs. It is possible to provide a write-once type optical disc having the above.

(Problems to be Solved by the Invention) By the way, in a write-once optical disc having compatibility with the already proposed compact disc having the ROM area which is the reproduction-only area and the RAM area which is the recordable area, , Transparent substrate 1 in ROM area as shown in FIG.
The metal film 12 for light reflection and the protective film 13 made of, for example, an ultraviolet curable resin are sequentially attached on the plate surface on which the guide groove G for tracking in 0 is provided, in contrast to the RAM. In the area, the organic material recording film 11, the light reflecting metal film 12, and the protective film made of, for example, an ultraviolet curable resin are provided on the plate surface of the transparent substrate 10 on which the guide groove G for tracking is provided. When the organic material recording film 11 is formed by applying the spin coat method only on the transparent substrate 10 corresponding to the ROM area in manufacturing it, the ROM area is Since it is necessary to prevent the above-mentioned organic material recording film 11 from being formed on the substrate, for example, a track pitch of 500
Approximately 1500 times as large as the interval (the portion illustrated by the reference numeral 14 in FIG. 5) having a very large dimension is the ROM area and R
Since it is required to be provided between the optical disc and the AM area, there is a drawback that the total recording capacity of the optical recording medium disc is reduced.

When the organic material recording film 11 is formed by applying the spin coating method as described above, the ROM area is provided in the inner peripheral portion of the optical recording medium disk, and the RAM area is provided in the outer peripheral portion rather than the ROM area. In addition to the restriction that it is necessary to provide the optical recording medium disk, it is impossible to make an optical recording medium disk in which a plurality of RAM areas and a plurality of ROM areas are mixed.

On the other hand, as a solution of these problems, a recording layer made of an organic material is formed over the entire area of a ROM area which is a read-only area and a RAM area which is a recordable area as Japanese Patent Application No. 2-36190 from the applicant company. Have filed an optical disc compatible with compact discs.

FIG. 4 is a side sectional view showing an example of the structure of the optical disc. In the figure, the same parts as those of the related art are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 4, G _O is a pit formed by an information signal in the ROM area, and Ga is a guide groove for tracking provided in the RAM area.

The width of the pit C _{O and} the width of the tracking guide groove Ga are the width of the pit G _{O in} the direction orthogonal to the extending direction of the recording trace (track) of the optical recording medium disk and the tracking guide. It is the width of the groove Ga.

The transparent substrate having the pit G _O in the ROM area and the guide groove Ga for tracking in the RAM area.
An organic material recording film 11 whose refractive index changes by absorbing an appropriate amount of a recording laser beam having a predetermined wavelength (for example, a wavelength of 780 nm) in all areas of the ROM area and the RAM area on the surface 10
Are formed by applying the spin coating method. The organic material recording film 11 is, for example, a heat mode optical recording material, a photon mode optical recording material, or both a heat mode and a photon mode, which uses an organic dye or a material in which an organic dye is dispersed in an organic material. It is possible to use an organic optical recording material selected from an optical recording material using an organic dye that operates in a mode or a material in which an organic dye is dispersed in an organic material, for example, in a state where a laser beam for recording is not irradiated. For example, a cyanine-based organic dye material having a refractive index n of +2.65 in the real part and −0.05 in the imaginary part can be used.

12 is a metal film for light reflection provided on the above-mentioned organic material recording film 11 by applying, for example, a vapor deposition method or a sputtering method, and the metal film 12 has a high reflectance, for example, Au, Al,
It is made of a metal such as Cu or an alloy having a high reflectance.

Reference numeral 13 is a protective film provided on the metal film 12 and made of, for example, an ultraviolet curable resin.

According to the configuration of FIG. 4, the ROM area and the RAM area can be freely mixed, the decrease in recording density can be prevented, and the spin coating method can be used as it is. The setting of the liquid dropping position is also easy.

However, this structure is important for information RO
Since the dye layer is also present in the M region, there is a problem that this region is easily affected by photobleaching of the dye.

The present invention has been made in view of the above point, a highly productive spin coating method can be applied, and a highly reliable optical information in which the boundary between the pit portion and the vacant groove portion is clear and the recording density is not deteriorated. It is an object of the present invention to provide a recording medium and a manufacturing method thereof.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and as a first invention, a read-only area and a V-shaped groove are formed on the same surface of an optical information recording medium. An optical information recording medium having a recordable area formed as a recording layer, the recording layer being formed only in the recordable area, and the recording layer and the read-only area including the read-only area and the recordable area. An optical information recording medium comprising a reflective layer continuously formed on the reflective layer and a protective layer formed on the reflective layer, and as a second invention, on the same surface of the optical information recording medium. A method of manufacturing an optical information recording medium having a read-only area and a recordable area, the method comprising: forming a reflective layer only in the read-only area; and forming a recording layer only in the recordable area. Including a reflective layer formed in the reproduction-only area, It is intended to provide a method for manufacturing an optical information recording medium, which comprises a step of forming a reflective layer on a recording layer formed in a recordable area and a step of forming a protective layer on the reflective layer.

(Example) FIG. 1 is a vertical sectional view of an optical information recording medium according to the present invention, and FIGS. 2 (A) to 2 (E) are vertical sectional views showing the manufacturing process thereof.

In FIG. 1, reference numeral 1 denotes a transparent substrate made of, for example, a polycarbonate resin. For example, in the main surface of the transparent substrate 1 having a diameter of 120 mm, a ROM area having a radius of 25 mm to 35 mm has a CD of 110 nm depth.
Pit G _O of -ROM signal is formed in accordance with the desired information. The RAM area with a radius of 35 mm to 58 mm has a depth of 40
A V-shaped guide groove Ga for tracking that is absolute time modulated is formed by a wobbling having a width of .about.70 nm, a width of 0.4 to 0.8 .mu.m, a pitch of 1.6 .mu.m and an amplitude of 30 nm.

The RAM region on the surface of the transparent substrate 1 on which the pit G _O in the ROM region and the V-shaped guide groove Ga for tracking in the RAM region are provided has a predetermined wavelength (for example, 7
When irradiated with a recording laser beam having a wavelength of 80 nm), an organic material recording film (hereinafter sometimes simply referred to as a recording layer) which absorbs an appropriate amount of the laser beam and changes its refractive index 2 Are formed by spin coating.

As the organic material recording film 2, an indolenine cyanine dye represented by the general formula shown in FIG. 3 is used.

In the equation, R1, R2 is CH3 ^-, C2 H5 ^- is any one of, R3, R4 is
It is an alkyl group of C1 to C5, and R3 = R4 or R3 ≠ R4 may be used. In addition, X ⁻ represents an anion.

When forming this organic material recording film 2,
First, the RAM area is masked with a metal or resin material so as not to enter the ROM area, and then 40 to 50 nm of Au serving as a reflection layer is formed on the ROM area pit G _{O by} , for example, a sputtering method. After that, the organic material recording film 2 is formed.

Here, a method of attaching the indolenine cyanine dye by spin coating will be described.

First, the indolenine cyanine dye as described above,
Dissolve 6% by weight concentration in diacetone alcohol to prepare a coating solution for recording layer.

Then, this coating solution is dripped from the inner peripheral side of the transparent substrate 1 in the vicinity of the boundary with the reflective layer, and 1500 to 3000 rpm.
Then, the transparent substrate 1 is rotated and shaken off to form the recording layer 2 by coating on a predetermined RAM area.

When the recording layer 2 is formed, since the reflective layer is previously provided on the ROM area,
There is no such thing as going into the area.

Then, after the recording layer 2 is dried, the entire area of the ROM area and the RAM area is a pit G _O in the ROM area which is the read-only area and the recordable area and covers the entire surface of the organic material recording film 2. For example, a metal film 3 for light reflection (hereinafter, also simply referred to as a reflection layer) 3 is attached by applying, for example, a vapor deposition method or a sputtering method.

As the metal film 3 for light reflection, a metal having a high reflectance, for example, a metal such as Au, Al, Cu or an alloy having a high reflectance is used.
It is deposited and formed with a thickness of 70 nm.

4 is, for example, an ultraviolet curable resin monomer provided over the entire upper surface of the metal film 3 is formed into a film having a thickness of, for example, 2 to 5 μm by a spin coating method, and further cured by ultraviolet irradiation. It is a protective film formed by tearing.

In this case, if the outer peripheral side end of the recording layer 2 and the outer peripheral side end of the reflective layer 3 are respectively covered with the protective layer 4, the protective layer 4 dissolves and removes the recording layer 2 and the like. 4 will be formed. Therefore, the protective layer 4 reaches the transparent substrate 1 and the entire area including the recording layer 2 and the reflective layer 3 is covered with the protective layer 4, so that the adhesion between the transparent substrate 1 and the protective layer 4 is extremely high. It will be good.

When this optical disk was played back with an appropriate CD player, the ROM area was left as it was with a normal CD.
I was able to play it as well.

In addition, when the CI error rate, symmetry, modulation degree, and the like of the reproduced signal at this time were measured, the CD standard was satisfied in all cases. In the RAM area, the recording power is 6.5 to 9 m using laser light with a wavelength of 780 nm.
As a result of trying to record the EFM-modulated signal with W, the recording was satisfactorily performed, and the CD player could reproduce the same as the ROM area.

Next, a manufacturing method of the optical information recording medium shown in FIG. 1 will be described with reference to FIGS.

For example, in the center of the transparent substrate 1 in which a tracking guide groove having a pitch of 1.6 μm is formed, a hole having a predetermined diameter is formed as well known, although not shown.

The diameter of the transparent substrate 1 is 120 mm, for example, and polycarbonate is used as the material thereof.

Of the main surface of this transparent substrate 1, ROM with a radius of 25 mm to 35 mm
In the region, pits G _O of a CD-ROM signal having a depth of 110 nm are formed according to desired information.

In the RAM area with a radius of 35 mm to 58 mm, the depth is 110 nm and the width is
Absolute time-modulated V-shaped guide groove for wobbling with 0.5 μm pitch 1.6 μm and amplitude of 30 nm
Ga is formed. (FIG. 2 (A)) First, a mask made of metal or resin is placed on the RAM region of the transparent substrate 1, and Au is deposited in a thickness of 40 to 50 nm only on the pit G _O portion of the ROM region by the sputtering method. (FIG. 2 (B)) After the Au film is formed, the metal or resin mask is removed from the RAM region.

Next, an indolenine cyanine dye represented by the general formula shown in FIG. 3 is formed in the RAM region by a spin coating method, which is performed by the following method.

That is, an indolenine cyanine dye is dissolved in diacetone alcohol at a concentration of 6% by weight, and the dissolved coating solution for recording is dropped near the boundary between the reflective layer 3 and the inside thereof, and transparent at 1500 to 3000 rpm. The substrate 1 is rotated, the solution is shaken off, and the recording layer 2 is applied and formed on a predetermined RAM area. (FIG. 2 (C)) The recording layer 2 is dried after coating.

After drying, Au was added again to 50 to 50 by a sputtering method over all of these upper portions where the reflective layer 3 and the recording layer 2 were formed.
The reflective layer 3 is formed by depositing it to a thickness of 70 nm. (FIG. 2 (D)) Next, an ultraviolet curable resin monomer is applied by a spin coat method so as to cover the entire main surface of the transparent substrate 1 on which the reflective layer 3 is formed as described above, and an ultraviolet lamp is used. It is photo-crosslinked and cured by irradiation with ultraviolet rays to be cured to form a protective layer of about 5 μm. (FIG. 2 (E)).

(Comparative Example) Next, a comparative example was manufactured to compare the characteristics.

This comparative example has a radius on the transparent substrate 1 used in the above-mentioned example.
At a position of 35 to 40 mm, the same dye solution as in the example is dropped,
An optical disk was obtained by forming a recording layer by a spin coating method and then sequentially laminating a reflective layer and a protective layer in the same manner as in the above-mentioned embodiment. According to this, the boundary between the pit portion and the vacant groove portion was obtained. It was difficult to correctly set the position of R = 35 mm as the boundary of the recording layer, and a preferable appearance was not obtained.

The optical disc of this comparative example was reproduced by a CD player in the same manner as the example, but the obtained signal was out of the CD standard in symmetry and mag, and a good result was not obtained.

(Other Embodiments) In the optical information recording medium and the method for manufacturing the same according to the present invention, the groove shape provided in the recordable area is illustrated as a V shape, but the shape is not limited to this and is, for example, a rectangular shape. There is no difference in terms of things. If you have a rectangular shape,
Pits in the ROM area, which is the read-only area, and R, which is the recordable area
Since the tracking groove depth in the AM area can be made the same, it is possible to easily set the conditions for pit formation and tracking groove formation during mastering, and it is also compatible with CDs. .

(Effects of the Invention) As described in detail above, according to the optical information recording medium and the method for manufacturing the same of the present invention, the recording layer is formed only in the recordable area, so that it is less susceptible to the photobleaching of the dye, A highly reliable optical disc of this type can be obtained, and a highly productive spin coating method can be applied. In addition, the boundary between the pit portion and the vacant groove portion is clear, there is no decrease in recording density, and there is a read-only area. Is an ordinary read-only optical disc, has the same structure, has the same recordable area as an ordinary recordable disc, and has good recording and playback characteristics, so it is easily compatible with ordinary CDs. Is a great thing.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an optical information recording medium according to the present invention, FIGS. 2 (A) to (E) are the process diagrams of the optical information recording medium, and FIG. The chemical formulas of indolenine cyanine dyes used in Examples are shown in FIG. 4 and FIG.
FIG. 6 is a vertical sectional view of an optical information recording medium as a conventional example. 1 ... Transparent substrate, 2 ... Recording layer, 3 ... Reflective layer, 4 ... Protective layer.

Claims (2)

[Claims] 1. An optical information recording medium having a read-only area and a recordable area formed as a V-shaped groove on the same surface of the optical information recording medium, the optical information recording medium being formed only in the recordable area. A recording layer, a reflective layer continuously formed on the recording layer and the read-only area so as to include the read-only area and the recordable area, and a protective layer formed on the reflective layer. A characteristic optical information recording medium. 2. A method of manufacturing an optical information recording medium having a read-only area and a recordable area on the same surface of the optical information recording medium, the method comprising forming a reflective layer only in the read-only area. A step of forming a recording layer only in the recordable area, a step of forming a reflective layer on the recording layer formed in the recordable area including a reflective layer formed in the read-only area, and the reflective layer A method of manufacturing an optical information recording medium, comprising the step of forming a protective layer on the top.