JP3440549B2 - Optical recording medium with increased reflectivity - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium of the type in which the reflectance of a recording layer is increased by optical recording such as laser beam irradiation.

[0002]

2. Description of the Related Art A disk type optical recording medium has a tracking control for precisely following a predetermined track with a laser beam of a predetermined size for scanning (writing) and reproducing (reading), and its laser. Focusing control is required to accurately focus the beam. In addition, scanning control in the track direction may be performed in order to remove the jitter component.

Particularly, regarding the above tracking control,
The main control methods are a 3-beam method and a push-pull method, and both have their own advantages and disadvantages. At present, the 3-beam method is a consumer CD (compact disc), LD ( It is often used in optical disk drives such as laser disks,
One of the push-pull methods is often used for optical disk drives for data processing. This three-beam system is a CD, LD
Most used in optical disk drives such as
First, it is said that tracking control is easy, and secondly, it has been used in many cases.

By the way, the specifications of the read-only (read-only) type CD-related optical recording medium are strictly defined by the standard. Specifically, when the recording mode is optical recording, the reflectance of the recording layer is reduced to “High”.
To low ”type, the initial reflectance of the recording layer is set to 70% or more, and the reflectance of the mark portion formed by recording is lowered by the phase structure so that the initial reflectance is higher than a predetermined value. It is configured to obtain the contrast of.

Further, the writable write-once type CD-related optical recording medium has the specifications of Orange Book Part II.
It is regulated by the standard. According to the standard, it is premised that the recording mode is "High to low" type, the initial reflectance of the recording layer is set to 65% or more, and the reflectance of the mark portion is lowered by writing. The contrast above a certain level is generated with respect to the initial reflectance. The reduction of the reflectance of the mark portion is performed by thermally deforming the dye layer in the basic medium structure of Au layer / organic dye layer / substrate by laser beam irradiation.

The 3-beam type tracking control for these optical recording media is performed as follows. That is, in the case of the former medium, the decrease in reflectance at the mark portion is directly detected as the dark and light pits, and in the case of the latter medium, the writing portion is the narrow groove portion () formed on the disc substrate. Narrow groove)
Is set, and before and after writing, a decrease in reflectance at the mark portion along the groove portion is detected as a dark and light pit, which is performed.

As described above, in the normal three-beam type tracking control, the tracking polarity is set so that the control main beam follows the dark portion on the optical recording medium. In short, in the read-only type recording medium, the recorded mark portion (row) functions as a dark track due to the decrease in reflectance, and in the write-once type recording medium, the groove portion is larger than the land portion between them. Since it functions as a track for dark areas, the main beam follows these tracks that become dark areas, and tracking control by the three-beam method is performed.

The present applicant has previously proposed a CD write-once type optical recording medium which can be written at least once using a phase separation type recording material. The CD write-once type optical recording medium to which the phase-separated recording method is applied has “High to low” and “Low to hi” recording modes.
gh ”(optical recording increases the reflectance of the recording layer),
It is possible to adopt three types of modes of "Middle toe and high" (the reflectance of the recording layer having an initial reflectance at an intermediate level is lowered and increased by optical recording).

However, this CD write-once type optical recording medium has a recording mode of "High to l".
ow "or" Middle to low and
In the case of the “high” type, the tracking control of the three-beam method can be applied, but the recording mode is “Low t
In the case of "o high" type, its application is difficult. That is, in the case of the “Low to high” type recording mode, the reflectance of the mark portion becomes higher due to the optical recording, and the average reflectance of the mark portion row becomes higher than that between the mark portion rows. In the container, the mark portion row is detected as a light portion track, and the space between the mark portion rows is detected as a dark portion track. As a result, the control main beam is not drawn into the mark portion row,
This is because they are drawn between the mark portions and follow.

In this way, "Low to high"
Only in the case of the recording mode of the type, that is, the optical recording medium of the reflectance increasing type, it is difficult to apply the tracking control by the three-beam method with the constitution contents so far. Therefore, this type of optical recording medium may not be normally played back by a general popular CD player (playback device).

[0011]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an optical recording medium of a "low to high" recording mode type, that is, a reflectance increasing type, to which a three-beam type tracking control method can be applied. It is in.

Another object of the present invention is to provide an optical recording medium which can be applied to a tracking control method of a three-beam system as an optical recording medium of a reflectance increasing type and at the same time to a tracking control method of a push-pull system. To provide.

[0013]

That is, the reflectance-increasing optical recording medium of the present invention has at least a recording layer, an interference layer, and a reflecting layer on which a reflectance is increased by optical recording on a substrate on which a groove is formed. In the reflectance increasing optical recording medium in which the layers are laminated in this order, the thickness of the interference layer is adjusted so that a difference in lightness and darkness appears between the groove portion and the land portion due to the optical path length difference with respect to the reflection layer. The feature is that they are different.

In the above technical means, the thickness of the interference layer in the groove portion and the land portion (which corresponds to half the optical path length) follows the track where the three-beam tracking control method functions as a dark portion. In consideration of the fact that the tracking polarity is set as described above and that the reflectance of the recording layer is increased by the optical recording in the reflectance increasing type recording medium, the groove portion ( Alternatively, the land portion may be set to have a lower reflectance than the land portion (or groove portion) corresponding to the mark portion row and to be detected as a dark portion.

For example, when the wavelength of the laser beam is λ, the optical thickness of the interference layer in either the groove portion or the land portion forming the mark portion is set to a value of approximately n (λ / 2), and other values. The optical thickness of the interference layer
The value deviates from (λ / 2) (n is an integer). When set in this way, the groove part or the land part in which the thickness of the interference layer is set to n (λ / 2) functions as a “dark part”.

Further, in the reflectance increasing type optical recording medium of the present invention, is the above-mentioned technical means formed such that the interference layer is formed such that the groove is buried so that the surface of the layer becomes a flat surface over the entire surface of the substrate. Alternatively, it is preferable that the interference layer is formed such that a portion of the surface of the layer corresponding to the groove is a recess.

In the case of forming an interference layer composed of a surface having a concave portion, its form is not particularly limited as long as the surface portion of the interference layer corresponding to the groove of the substrate is a concave portion. Then, the recess can be classified into a groove embedding type in which the depth of the recess is smaller than the depth of the groove and a groove emphasizing type in which the depth of the recess is larger than the depth of the groove. The interference layer formed by embedding the groove so that the surface of the layer is a flat surface over the entire surface of the substrate is, in other words, a completely flat surface without the above-mentioned recesses on the surface of the layer. It is an interference layer.

As a method of forming such an interference layer, when forming an interference layer having a flat surface, an organic material (transparent polymer or a material obtained by dissolving it in a solvent,
Alternatively, a method of forming an interference layer material made of SiO ₂ dissolved in an organic solvent) by a spin coating method, an inorganic material (SiO ₂ or SiN,
Alternatively, DLC (Diamond Like Carb)
on)) interference layer material consisting of
Examples thereof include a method of forming by R-CVD method, bias RF sputtering method, ion beam sputtering method and the like.

On the other hand, in the case of forming an interference layer having a surface having a recess, the interference layer may be formed by any method as long as it is a layer forming method in which the recess is finally formed. For example, other than the method of forming by applying the biasing ECR-CVD method, the bias RF sputtering method, the method of forming by the ion beam sputtering method and the like in the same manner and appropriately changing the manufacturing conditions, It is possible to employ a method in which the interference layer material as described above is projected onto the substrate from an oblique direction at a predetermined angle to deposit more material on the land portion than on the groove portion. In particular, as a film forming means from an oblique direction for depositing the interference layer material on the land part more than on the groove part, a thin film forming method such as a sputtering method, an ion beam sputtering method, or a vapor deposition method can be applied. . Examples of the polymer include
UV curable resins, cellulose lacquers, dye polymers and the like are used.

Among these methods for forming an interference layer, the method using an interference layer material of an inorganic material is preferable in that a dry integrated manufacturing process can be adopted, and among them, further, among them,
A bias ECR-CVD method or an ion beam sputtering method, which enables a low temperature process, is desirable. Here, the bias ECR-CVD method is to embed a groove portion by utilizing a reverse sputtering phenomenon by applying a bias. Further, the ion beam sputtering method is a method in which SiO ₂ is sputtered by an ion beam and further an ion beam is applied to the substrate at an angle close to horizontal to perform etching.

Further, in the above technical means, the thickness of the interference layer is further set to a track portion (a region for forming a recording mark) which is a recording layer region set corresponding to the groove portion or the land portion. It is preferable to set the thickness such that the phase of the reflected light in the step (2) leads the phase of the reflected light between the tracks. By forming the interference layer with such a thickness, the optical recording medium can be applied not only to the 3-beam method but also to the push-pull method of tracking control.

Further, in the above technical means, the recording layer is formed by using a known recording material of a type whose reflectance increases by optical recording. In particular, by forming this recording layer with a recording material utilizing phase-separation type spinodal decomposition, a reflectance increasing CD write-once type optical recording medium can be easily constructed.

[0023]

In the reflectance increasing optical recording medium of the present invention,
By appropriately setting the thickness of the interference layer between the portions corresponding to the groove portion and the land portion, optical recording is performed in the recording layer area (track) set corresponding to the groove portion or the land portion functioning as the dark portion. Be seen.

Thus, for example, when the land portion functions as a dark portion by setting the thickness of the interference layer, the land portion on which the mark portion is formed by recording increases the reflectance of the mark portion. Since the reflectance is lower than that of the groove portion where the mark portion is not formed and is detected as a dark portion, the main beam is normally drawn into the land portion where the mark portion is formed even in the tracking control method of the three-beam method. Tracking control is performed.

In some cases, the push-pull type tracking control method cannot be applied to the thickness of the interference layer only by setting the above conditions. When the thickness is set so as to advance from the phase of the reflected light in (3), it can be applied to the push-pull type tracking control simultaneously with the three-beam type.

[0026]

EXAMPLES The present invention will be specifically described below based on examples.

Example 1 As shown in FIG. 1, a polycarbonate substrate 2 having a groove portion 1 (depth 0.2 μm, width 0.5 μm, pitch 1.6 μm) was formed (width of land portion 3). Is 1.1μ
m), in order to prevent deformation, an underlayer of SiO _{2 having} a thickness of 0.08 μm was formed by RF sputtering, and then a recording layer 4 of SbOx having a thickness of 0.04 μm was formed by ion plating. .

Next, an interference layer 5 made of SiO ₂ was formed on the entire surface of the substrate 2 by the bias ECR-CVD method so as to fill the groove portion 1. This bias EC
The R-CVD method uses a magnetic field control type microwave plasma device to generate a cylindrical plasma by oxygen plasma, and the frequency of the bias is 400 kHz,
The power was set to about 100 W. At this time,
Efficient film formation was made possible by the generation of the cylindrical plasma, and the film formation operation could be performed while maintaining the substrate temperature at 50 ° C or lower. In the formed interference layer 5, the layer thickness 5a in the groove portion 1 was 0.26 μm, and the layer thickness 5b in the land portion 3 was 0.06 μm.

Next, a 0.06 μm thick reflective layer 6 made of aluminum is formed on the interference layer 5 by RF sputtering, and then a protective layer 7 made of ultraviolet curable resin having a thickness of several μm is formed by spin coating. Then, a reflectance increasing optical recording medium was prepared.

Using this optical recording medium, an EFM signal was written to the land portion 3 by a writer (optical recording device) and then reproduced by a player adopting a three-beam tracking method. The reproduced signal information could be stably reproduced. The wavelength λ of the laser beam used at this time was 780 nm.

FIG. 2 shows a tracking cross signal (Tc signal) and a tracking error signal (Te signal) before and after writing on the optical recording medium. From this result, the difference in height of the signal level between both signals decreases due to the increase in the reflectance due to recording, but "High to
It can be confirmed that the polarity and level difference are the same as those of a normal CD in the "low" recording mode. In addition,
In the case of the conventional reflectance increasing type, as shown in FIG.
The signal is inverted to have the opposite polarity, which makes tracking control of the 3-beam system difficult.

Example 2 The interference layer 6 in Example 1 was biased by ECR-CVD.
The same optical recording medium as in Example 1 was prepared except that the ion beam sputtering method was used instead of the above method. That is, in this embodiment, a dual ion beam sputtering apparatus is used as shown in FIG. 3, and Ar ⁺ ions generated by passing Ar gas through the ion generation source 8 are applied to the target 9 of SiO ₂ at an irradiation angle of 45 °. irradiates at theta _1, installed and the substrate 2 to the groove portion 1 is formed so that the groove portion face upward position of the target 9 is downward Ar ⁺
The angle θ ₂ between the irradiation direction of the ion beam and the substrate ₂ is about 8
The interference layer 6 was formed by the ion beam sputtering method by setting the angle so that the ion beam was horizontally irradiated. At this time, the acceleration voltage of the ion beam was set to about 200V.

By performing the ion beam sputtering method in this way, it is possible to selectively etch the SiO ₂ deposited on the land portion (projection) while depositing SiO ₂ on the groove portion of the substrate 2. And as a result,
While embedding the groove part, flatten the entire surface with SiO
₂ can be deposited and the same interference layer 6 as in Example 1
Is obtained.

After the EFM signal was written using the obtained optical recording medium in the same manner as in Example 1, reproduction was performed by a player adopting the tracking method of the three-beam method, and normal tracking control was performed. As a result, the written signal information could be stably reproduced.

Example 3 In place of the interference layer 6 in Example 1, the interference is divided into a first interference layer portion in which the groove portion 1 is embedded and a uniform second interference layer portion over the entire surface of the substrate. An optical recording medium of increased reflectance was manufactured in the same manner as in Example 1 except that the layers were formed.

That is, the first interference layer portion also has a function of preventing deformation, and SiO ₂ is formed on the substrate including the groove portion of the substrate after the underlayer is formed by the RF sputtering method in the thickness of the groove portion. Was formed to have a thickness of 0.03 μm. The second interference layer portion was formed by coating a cellulose lacquer on the first interference layer by spin coating. The thickness of the interference layer as a whole is 0.26 μm in the groove portion 1.
m, and the layer thickness in the land portion 3 was 0.06 μm.

After the EFM signal was written using the obtained optical recording medium in the same manner as in Example 1, reproduction was performed by a player adopting the tracking method of the 3-beam method, and normal tracking control was performed. As a result, the written signal information could be stably reproduced.

Embodiment 4 As shown in FIG. 4, a polycarbonate substrate 2 having a groove portion 1 (depth 0.3 μm, width 1.0 μm, pitch 1.6 μm) was formed (width of land portion 3). Is 0.6μ
m), an underlayer of SiO _{2 having} a thickness of 80 nm was formed by RF sputtering, and then a recording layer 4 of SbOx having a thickness of 40 nm was formed by ion plating.

Next, the land thickness 5b is set to 60 on the recording layer 4 by using a dual ion beam sputtering apparatus.
nm and the thickness 5a of the groove portion is 230 nm, and the interference layer 5 made of SiO ₂ is formed on the entire surface of the substrate 2. The recess 8 formed on the surface of the interference layer 5 at this time
The depth of a was 130 nm. Therefore, this interference layer is of a so-called groove filling type.

Next, a thickness 60 of aluminum / titanium alloy is formed on the interference layer 5 by RF sputtering.
After the reflective layer 6 having a thickness of 10 nm was uniformly formed, a protective layer 7 made of an ultraviolet curable resin and having a thickness of about 10 μm was formed by a spin coating method to fabricate an optical recording medium of increased reflectance.

After the EFM signal was written using the obtained optical recording medium in the same manner as in Example 1, reproduction was performed by a player adopting the tracking method of the 3-beam method and the push-pull method. Also in the above, normal tracking control was performed, and as a result, the written signal information could be stably reproduced.

Example 5 As a substrate, a groove portion (depth 0.2 μm, width 0.6 μm)
m, pitch 1.6 μm) formed of a polycarbonate substrate (land width is 1.0 μm), the land portion thickness 5b is 150 nm, and the groove portion thickness 5a is 240 nm as an interference layer. An optical recording medium of increased reflectance was prepared in the same manner as in Example 4 except that the interference layer 5 made of SiO ₂ was formed. At this time, the depth of the concave portion 8a in the interference layer is 110 nm, and therefore this interference layer is also of the groove filling type as in the fourth embodiment.

After the EFM signal was written using the obtained optical recording medium in the same manner as in Example 4, reproduction was performed by a player adopting the tracking method of the 3-beam method and the push-pull method. Also in the above, normal tracking control was performed, and as a result, the written signal information could be stably reproduced.

Example 6 As shown in FIG. 6, an interference layer made of ZnS—SiO ₂ having a land portion 3 having a thickness 5b of 110 nm and a groove portion 1 having a thickness 5a of 40 nm was formed by an oblique sputtering method. An optical recording medium of increased reflectance was produced in the same manner as in Example 4 except that the layer 5 was formed. At this time, the depth of the concave portion 8b formed on the surface of the interference layer 5 was deeper than the initial depth of the groove portion. Therefore, this interference layer is a so-called groove enhancement type.

The formation of the interference layer by the oblique sputtering method means that the sputtered particles are obliquely incident on the substrate to form a layer while making the deposition rate of the sputtered particles on the substrate different between the land portion and the groove portion. Is to do.

After the EFM signal was written using the obtained optical recording medium in the same manner as in Example 4, reproduction was performed by a player adopting the tracking method of the 3-beam method and the push-pull method. Also in the above, normal tracking control was performed, and as a result, the written signal information could be stably reproduced.

[0047]

As described above, although the optical recording medium of the present invention is of the reflectance increasing type, the tracking control method based on the three-beam method can be directly applied without any trouble. Moreover, by setting the thickness of the interference layer so that the phase of the reflected light has the above relationship, it can be applied to the tracking control method by the push-pull method as well as the 3-beam method. For this reason,
For example, even a CD write-once type optical recording medium having a recording layer formed of a phase separation type recording material can be reproduced by a general popular type CD player.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a reflectance increasing optical recording medium showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between the optical recording medium shown in FIG. 1 and a tracking cross signal and a tracking error signal in this recording medium.

FIG. 3 is an explanatory diagram showing a method of forming an interference layer by an ion beam sputtering method.

FIG. 4 is a schematic cross-sectional view of a reflectance increasing optical recording medium showing another embodiment (Example 4) of the present invention.

FIG. 5 is a schematic cross-sectional view of a reflectance increasing optical recording medium showing another embodiment (Example 5) of the invention.

FIG. 6 is a schematic cross-sectional view of a reflectance increasing optical recording medium showing another embodiment (Example 6) of the present invention.

[Explanation of symbols]

1 ... Groove part, 2 ... Substrate, 3 ... Land part, 4 ... Recording layer, 5 ... Interference layer, 5a ... Interference layer thickness in groove part, 5b ... Interference layer thickness in land part, 6 ... Reflection layer , 8a, 8b ... Recesses.

Front page continuation (72) Inventor Kiichi Ueyanagi, Fuji Zerox Co., Ltd., 2274 Hongo, Ebina City, Kanagawa Prefecture (56) Reference JP-A-3-113745 (JP, A) (58) Fields investigated (Int .Cl. ⁷ , DB name) G11B 7/24

Claims (5)

(57) [Claims] 1. A reflectance-increasing optical recording medium comprising a substrate on which a groove is formed, and at least a recording layer whose reflectance increases by optical recording, an interference layer, and a reflection layer, which are laminated in this order. Corresponding layer thickness to its groove and land
Serco different by <br/> optical path length difference of each light reflected by the recording layer and a reflective layer between the site to make a difference in brightness is revealing
The groove part (or run part) where the mark part is formed by
The land part (or group) corresponding to the mark part row
The reflectance is lower than that of the lube part, and it is detected as a dark part.
An optical recording medium of increased reflectivity characterized by the above. 2. The optical recording medium according to claim 1, wherein the interference layer is formed so that the groove is embedded so that the surface of the layer becomes a flat surface over the entire surface of the substrate. recoding media. 3. The optical recording medium according to claim 1, wherein the interference layer is formed such that a portion of the surface of the layer corresponding to the groove is a recess. . 4. The optical recording medium according to claim 1, wherein a thickness of the interference layer is further set in a track portion including a recording layer area set corresponding to the groove portion or the land portion. An reflectance-increasing optical recording medium, characterized in that the thickness of the reflected light is set so as to advance from the phase of the reflected light between the tracks. 5. The optical recording medium according to claim 1, wherein the recording layer is a layer made of a phase separation type recording material.