JPH07334869A - Information recording member - Google Patents

Abstract

PURPOSE:To decrease the crosstalk and to surely reproduce information such as data and address by making the reflectivity from marks of a preformat area and ROM area to be <=5%. CONSTITUTION:A ZnS-SiO2 protective layer 2 of about 90nm thickness is formed on a polycarbonate substrate 1 having 13cm diameter and 1.2mm thickness, on which a Ge22Sb22Te55Co1 recording film 3 of 30nm thickness is formed. The recording film is subjected to sputter etching with Ar ion to decrease the film thickness in the projection part of the fine rugged pattern of the recording film on an embedded mark to obtain of the recording film about 10nm average remaining film thickness on the embedded mark. Then, a ZnS-SiO2 intermediate layer 4 of 40nm thickness is formed, on which an Al-Ti reflecting layer 5 of 100nm thickness is formed. Then, a UV-curing resin layer 6 is applied to obtain a disk. Disks having the same structure are stuck to each other with a hot-melt adhesive 7. Thus, both of lands and grooves formed on surfaces of substrates 1, 1' can be used as tracks for information recording. Reflectivity from the preformat area in the adjacent track or embedded marks of ROM area can be decreased and the crosstalk can be decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal obtained by FM-modulating an analog signal such as video or audio by a recording beam such as a laser beam, or data from an electronic computer, for example.
The present invention relates to an information recording member capable of recording digital information such as a facsimile signal and a digital audio signal in real time.

[0002]

2. Description of the Related Art In recent years, information has been diversified, and a demand for a rewritable optical disk on which a user can record information or rewrite information has increased. In addition, the amount of information has increased, and a large-capacity optical disc has become necessary. Along with this, various research institutes are actively studying how to increase the density of optical disks.

For example, a method of reducing the size of a recording point by shortening a recording laser wavelength, a high NA (aperture ratio) of a focusing lens, or an apparently small spot diameter of a laser beam for reading information. There is a method for increasing the density.

Further, as described in Japanese Patent Publication No. 4466/1980, a method of using a substrate having a guide groove (groove) and recording on both flat portions in the guide groove and between the guide grooves (lands). (Land / groove recording) is proposed. However, in this method, when the groove pitch is smaller than the spot diameter of the read beam, adjacent information may be read (crosstalk) error may occur. As a method of removing this crosstalk, a method of canceling the reflected light from the adjacent recording mark by setting the groove depth to λ / 6 (λ is the laser wavelength) is considered.
According to this method, when there is no recording mark on the adjacent track, the reflectance decreases due to interference when the groove depth becomes deep and becomes the minimum at λ / 4, but the recording mark having almost 0 reflectance on the adjacent track. If present, the light spot returns only from the track on which the center of the light spot is located, so that the reflectance remains constant even if the groove depth is changed. By specifying the groove depth in this way, the reflectance can be made substantially the same and crosstalk can be reduced. That is, when the groove depth is λ / 6n + mλ (λ is the laser wavelength, n is the refractive index of the substrate, and m is 0 or a positive integer), the crosstalk has a minimum value.

[0005]

In land / groove recording, by defining the groove depth to be .lamda. / 6n, crosstalk from recording marks (reflectance close to 0) of adjacent tracks can be suppressed to some extent. be able to. However, the marks on the pre-formatted portion (portions such as addresses), the ROM (read-only memory) portion, and the ROM disk that are formed on the substrate in advance are convex portions or concave portions, and the reflected light from these marks is affected by the groove depth. Receive. Therefore, in the case where the pre-format section and the ROM section are formed in the tracks adjacent to the track to be read, crosstalk from these is large, which is a problem.

An object of the present invention is to provide an information recording member that can reliably reproduce information such as data and addresses in land / groove recording.

[0007]

In order to solve the above-mentioned problems in the prior art, in the information recording member used in the present invention, a pre-formatted portion, a ROM portion or a mark of a ROM disc which is formed in advance ( In the future, these marks will be called embedded marks) and the reflectance will be close to zero. That is, the groove depth is ~ λ / 6n
Further, the crosstalk from the adjacent tracks can be suppressed by making the reflectance from the embedded mark of the preformatted portion, the ROM portion or the ROM disk close to 0. Here, if the reflectance from the embedded mark in the preformat portion or the ROM portion is 5% or less, the effect of crosstalk cancellation is great. A reflectance of 3% or less is particularly preferable.

In the present invention, in order to reduce the reflectance from the embedded mark in the preformat section or the ROM section, the film thickness of the recording film or the dielectric layer at the embedded mark is appropriately selected (multiple interference is caused). Use). At this time, a method of reducing the average film thickness of the recording film at the embedded mark, a method of slightly disturbing light by fine irregularities, or a method of using these in combination is preferable because the reflectance can be easily reduced.

Hereinafter, as an example, a method of reducing the average film thickness of the recording film at the embedded mark will be described. For example, using a substrate in which the embedded mark is formed by a convex portion (plateau) of about 50 nm instead of a conventional uniform concave portion (pit), a lower protective layer is first formed on this substrate, and the lower protective layer is formed on the lower protective layer. The recording film is formed thicker than the target thickness. Then, this recording film is etched by the reverse sputtering method. As a result, the embedded mark portion is easily etched due to the shape effect, and as a result, the recording film thickness of the embedded mark portion can be reduced. The recording film thickness of the embedded mark is determined by the relationship with the film thickness of other protective layers of the disc, etc., but the average thickness of the recording film of the embedded mark portion is the recording film other than the embedded mark portion. 30% or more and 70% or less of the average film thickness of
It is preferably 0% or more and 60% or less.

By forming fine irregularities of about 20 to 100 nm in the embedded mark, the etching effect can be enhanced. The fine irregularities may be formed in the pits or on the terrace-shaped convex portions. When the height of the fine irregularities is as high as 100 nm or more, the reflectance can be lowered by utilizing the scattering of light without performing etching by reverse sputtering depending on the structure.

A substrate having a convex embedded mark used in the present invention was manufactured as follows. First, as described in detail in Examples, two layers of two types of positive photoresists having different sensitivities are applied to an optically polished glass disk, and the argon laser light is irradiated while power-modulating while rotating the glass disk ( cutting). Here, at least a preformat portion such as an address and a groove portion where a user records information are formed. At this time, the embedded mark is formed on the land and the groove at substantially the same depth. When the glass plate is irradiated with argon laser light, the target groove is recorded by moving the glass disk by the amount that corresponds to the groove pitch of the substrate (by exposing the grooves, lands are formed between the grooves. Become). Then, by developing this glass disk with a developing solution, it becomes a master. After that, a nickel stamper having an inverse shape is produced from this master, and further transferred to produce a UV (ultraviolet curing resin) stamper having the same shape as the master. A large number of substrates used in the present invention can be produced from this UV stamper by a method such as injection molding.

A recording film and a dielectric layer are formed on the substrate manufactured as described above by a sputtering method. In this process, a reverse sputtering method is performed to, for example, the film thickness of the recording film at the embedded mark portion. By appropriately thinning, the reflectance of portions other than the embedded mark portion is high and only the reflectance of the embedded mark can be reduced.

The recording film used in the present invention is a crystal-amorphous phase change optical recording film capable of high-speed crystallization, a recording film utilizing a change between amorphous and amorphous, a crystal system and a crystal grain size. The crystal-to-crystal phase change recording film and the magneto-optical recording film are preferable, but other recording films may be used.

[0014]

By using the information recording member of the present invention, it is possible to suppress the crosstalk from the embedded mark in the preformat portion or the ROM portion in the land / groove recording. That is, for example, when the reproduction spot travels on the land, the crosstalk is proportional to the difference in the amount of reflected light from the point where the recording mark or the embedded mark is present in the adjacent groove and the point where it is not present. At this time, it is assumed that the unrecorded portion is crystalline and has high reflectance, the recording mark is amorphous and has low reflectance, and the reflectance from the embedded mark is also low. Then, by making the groove depth close to λ / 6n, it is possible to make the amount of reflected light from the point where the recording mark and the embedded mark of the adjacent track are present and the point where they are not present the same, and the crosstalk is suppressed. Further, the shape of the embedding mark was able to make the recording film in the embedding mark portion thin, whether it was a uniform convex portion or fine irregularities. Here, the film thickness of the recording film is reduced in order to reduce the reflectance from the embedded mark, but the same effect can be obtained by changing the film thickness of at least one of the protective layer and the reflective layer.

Further, the recording medium is not limited to the disk shape, but can be applied to other recording media such as a card shape.

[0016]

【Example】

Example 1 A method for manufacturing the substrate used in this example will be described. First, an organic or inorganic positive photoresist is applied to an optically polished glass disk to a film thickness of about 80 nm, which is about λ / 6n (n is the refractive index of a polycarbonate disk substrate), and the glass disk is rotated. , Wavelength 457.
Exposure is performed by irradiating while changing the power of 9 nm argon laser light (cutting). Here, at least a preformatted portion such as an address and a land portion and a groove portion where a user records information are formed.

Since the embedding marks in the preformatted area of the groove portion are formed by slightly weakening or returning the laser light according to address information or the like, the embedding marks are in the form of a drum-shaped slightly raised embedding mark. The embedded mark in the pre-formatted area of the land portion is formed by slightly strengthening or returning the laser light in accordance with address information or the like, so that it becomes a circular or oval shallow pit row. The preformatted portions of the land portion and the groove portion may be adjacent to each other, but may be alternately shifted back and forth from the inner circumference to the outer circumference of the disc, or may be continuously shifted in one direction. However, it is easier to remove the residual crosstalk when the preformatted areas are adjacent to each other.

The exposed (recorded) portion is dissolved and removed by developing the cut glass disk with a developing solution to form a master. Since the resist is partially removed from both the land portion and the groove embedding mark, minute unevenness is generated on the surface of the embedding mark after development. Note that the photoresist is not a single layer, the low-sensitivity or sparingly soluble resist is thinly applied, and then the above-mentioned photoresist is applied, and in the preformatted area of the groove part, slightly strengthened or restored according to address information etc. May be. In this case, at least a part of the lower photoresist layer is removed into a circle or an ellipse only when the laser beam is strengthened during development, and at other portions, only the upper photoresist layer reaches the interface with the lower photoresist layer. To be removed. Also in this case, the surface of the embedded mark has fine irregularities.

As another method, only the lower photoresist layer is applied first, and only the embedded marks in the preformatted area of the groove are exposed so that only a part of the thickness of the photoresist layer is removed during development. Form by developing. After that, an upper photoresist layer is applied, the groove portion is continuously irradiated with laser light including the preformatted area, and the land portion is irradiated in the same manner as described above. Get the shape.

A nickel layer is formed on this master by a sputtering method. Then, nickel plating is performed using this nickel layer as an electrode to obtain a mold (nickel stamper) having a thickness of about 200 μm. Next, a UV stamper is manufactured using an ultraviolet curable resin (UV resin) so as to have a shape opposite to that of the nickel stamper. Using this UV stamper as a mold, injection molding of polycarbonate was used to fabricate the substrate used in this example. In this embodiment, a cutting device is used so that the groove width is about 0.5 μm, the groove pitch is about 1 μm, the groove depth is about 80 nm, and the height and depth of the embedded mark in the preformat section are about 50 nm. Controlled.

Next, a method of manufacturing a disk using the embedded mark substrate will be described with reference to FIG. First, diameter 13
cm on the polycarbonate substrate 1 with a thickness of 1.2 mm, the thickness of about 90 nm Z by magnetron sputtering method
It was formed nS-SiO ₂ protective layer 2. Next, ZnS-Si
A recording film 3 having a composition of Ge ₂₂ Sb ₂₂ Te ₅₅ Co ₁ was formed on the O ₂ protective layer 2 to have a film thickness of about 30 nm. Then, sputter etching with Ar ions was performed in order to reduce the film thickness of at least the convex portions of the fine irregularities of the recording film on the embedded mark. As a result, the average residual film thickness of the recording film of the embedded mark was significantly reduced to about 10 nm, and the film thickness of the recording film other than the embedded mark was reduced to about 20 nm. Next, ZnS
To form an -SiO ₂ intermediate layer 4 to a thickness of approximately 40 nm. Further, an Al—Ti reflective layer 5 having a thickness of about 100 nm was formed thereon. These films were sequentially formed in the same sputtering device. After that, an ultraviolet curable resin layer 6 was applied on this, and then a hot-melt adhesive 7 was used to adhere and adhere to another disk having the same structure.

FIG. 2 shows the recording film thickness dependence of the reflectance in the crystalline state and the amorphous state of the manufactured disk. As can be seen from this figure, the reflectance is as high as 20% (A in the figure) in the unrecorded portion (crystalline state) in the region other than the embedded mark where the film thickness of the recording film is about 20 nm, and In the crystalline state), the reflectance is as low as 2% (B in the figure). Further, the reflectance is 3 at the embedded mark (crystalline state) in which the recording film has a film thickness of about 10 nm and light is scattered by fine irregularities.
% (C in the figure).

The relationship between the reflectance from adjacent embedded marks and the crosstalk at that time was investigated. The results are shown in Table 1.

[0024]

[Table 1]

From the above results, if the reflectance from the adjacent embedded mark is 5% or less, the crosstalk is -30 dB.
I was able to reduce it to the following. More preferably, the reflectance is −35 dB or less and 3% or less.

Here, it is preferable that the height difference between the embedded mark and its periphery is ± λ / 10n + mλ (n is the refractive index of the substrate, and m is 0 or a positive integer) because crosstalk can be reduced.

Next, the recording / reproducing characteristics of the disk having the structure shown in FIG. 1 were examined. The recording has a ternary level of recording power, erasing power, and reproducing power, and an overwritable waveform is used. First, recording was performed using a semiconductor laser having a wavelength of 780 nm, and the recording power dependence of crosstalk was investigated. The groove depth is ~ λ / 6n (where λ is the laser wavelength,
n is about 80 nm, which is the refractive index of the substrate,
When the recording power was 10 mW or more, the crosstalk from the land and the groove was -35 dB or less, respectively. Further, the crosstalk at the location of the embedded mark was similarly -35 dB or less.

Next, the ratio of the average film thickness of the recording film of the embedded mark portion to the average film thickness of the recording film other than the embedded mark portion (average film thickness of the embedded mark portion / embedded mark portion). The relationship between the average film thickness of the recording film other than the above) and crosstalk was investigated.
The results are shown in Table 2.

[0029]

[Table 2]

The recording film thickness of the embedded mark is determined by the relationship with the film thickness of other protective layers of the disc, but the average thickness of the recording film of the embedded mark portion is not the same as that of the portion other than the embedded mark portion. A film thickness of 30% or more and 70% or less of the average film thickness of the recording film is preferable in terms of reflectance and crosstalk. More preferably, it is 40% or more and 60% or less.

(Embodiment 2) In this embodiment, a case will be described in which an embedded thin film is used to form the embedding mark into fine irregularities of 20 to 100 nm.

A method for manufacturing the substrate used in this embodiment will be described. First, a positive photoresist is applied to an optically polished glass disk to a thickness of about λ / 6n (where λ is the wavelength of the reading light), and the wavelength of 457.9 is applied while rotating the glass disk.
Exposure is performed by irradiating with an argon laser beam of nm 2 (cutting). Here, the user irradiates the groove portion where information is recorded with continuous light.

By developing a cut glass disk with a developing solution, a groove portion in which the exposed (recorded) portion is dissolved and removed and a land portion between the grooves are formed to form a master. Furthermore, Ge ₁ Sb ₂ Te
_{A 4-} phase change recording film is formed by a 75 nm sputtering method. Then, this phase change recording film was sputter-etched with Ar ions. As a result, the recording film is about 50n
It became fine irregularities of about m. The individual protrusions of this fine unevenness are close to a conical shape.

Next, a negative photoresist is coated on the fine irregularities, and the portion to be an embedded mark in a preformatted area such as an address is exposed by modulating the power of an argon laser beam having a wavelength of 457.9 nm. Then, this is developed with a developing solution in which the upper positive photoresist is not dissolved and only the unexposed portion of the negative photoresist is dissolved, and the portion other than the exposed (recorded) portion is dissolved and removed, and then Ge ₁ Sb ₂
The exposed portion of the Te ₄ phase change film is removed with dilute nitric acid, and the photoresist in the embedded mark portion is removed with a plasma asher, whereby an embedded mark having fine irregularities can be formed. Then, a UV stamper is manufactured using an ultraviolet curable resin (UV resin) so as to have a shape opposite to that of the stamper.

Using this UV stamper as a mold, a substrate used in this example was produced by injection molding of polycarbonate. In this embodiment, the groove width is about 0.5 μm,
Groove pitch is about 1 μm and groove depth is about 80 n
m, the cutting device and the sputtering device were controlled so that the height of the fine irregularities of the embedded mark in the preformat portion was about 50 nm.

Next, a method of manufacturing a disk using a substrate having fine uneven embedding marks will be described. The structure is
This is almost the same as FIG. 2 of the first embodiment. First, diameter 13cm,
On a polycarbonate substrate with a thickness of 1.2 mm, ZnS- with a thickness of about 90 nm was formed by a magnetron sputtering method.
A SiO ₂ protective layer was formed. Next, a recording film having a composition of Ge ₂₂ Sb ₂₂ Te ₅₅ Co ₁ is formed on the ZnS-SiO ₂ protective layer by about 3 times _.
It was formed to a film thickness of 5 nm. Then, in order to reduce the thickness of the recording film on the embedded mark, sputter etching with Ar ions was performed. As a result, the average film thickness of the recording film of the embedded mark of fine unevenness is about 10 nm, which is significantly thin,
The average film thickness of the recording film other than the embedded mark was thinned to about 25 nm.

Next, a ZnS-SiO ₂ intermediate layer is applied to about 40 n.
It was formed to a film thickness of m. Further, an Al-Ti reflective layer having a thickness of about 100 nm was formed thereon. These films were sequentially formed in the same sputtering device. After that, an ultraviolet-curable resin layer was applied on this, and then a hot-melt adhesive was used to adhere and adhere to another disk having the same structure.

In this disc, the thickness of the recording film is about 25.
In the region other than the embedded mark having the wavelength of nm, the reflectance is as high as 28% in the unrecorded portion (crystalline state), and the reflectance is as low as 4% in the recorded mark (amorphous state). Further, the reflectance is as low as 2% in the embedded mark (crystalline state) in which the film thickness of the recording film is about 10 nm, and the crosstalk from the recording mark and the embedded mark is as small as -35 dB or less. Was given.

Although the phase change type recording film is used as the recording film in the present embodiment and the first embodiment, the reflectance of the embedded mark is 5 even if the magneto-optical recording film such as Tb-Fe-Co is used.
% Or less, the effect of suppressing the crosstalk from the embedded mark of the adjacent track was obtained as in the above-mentioned embodiment.

[0040]

According to the present invention, both the land and the groove formed on the surface of the substrate can be used as recording tracks for recording information, and the preformat section and the ROM section of adjacent tracks can be filled. By reducing the reflectance from the embedded mark, the crosstalk from these can be reduced, so that information such as data and addresses can be reliably reproduced.

[Brief description of drawings]

FIG. 1 is a sectional view of a disk according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram of reflectance and recording film thickness.

[Explanation of symbols]

1, 1 '... Polycarbonate substrate, 2, 2' ... ZnS-
SiO ₂ protective layer, 3, 3 '... recording film, 4, 4' ... ZnS
-SiO ₂ intermediate layer, 5,5 '... Al-Cu reflective layer, 6,
6 '... UV curable resin layer.

Claims (3)

[Claims] 1. A member for recording information, wherein both a groove and a land formed on the surface of a substrate can be used as a recording track for recording information, in a preformatted portion or RO.
An information recording member having a reflectance of 5% or less from the mark of the M portion. 2. The information recording according to claim 1, wherein the average thickness of the recording film of the marks of the preformatted portion or the ROM portion is 30% or more and 70% or less of the average thickness of the recording film other than the marks. Parts. 3. The member for recording information according to claim 1, wherein fine marks are formed on the marks of the preformat section and the ROM section.