JPH0883444A - Optical recording medium and its production as well as its recording method - Google Patents

Abstract

PURPOSE: To obtain a disk for reproduction only or writing once which enables a super-resolution reproducing operation at a low operating temp. and is recorded at a high density by varying the coercive forces of recording films in correspondence to the information to be recorded. CONSTITUTION: Regions 11a, 11b of a part of the magneto-optical films 1 on a substrate are composed of parts which are 10 to 50nm and 3 to 20mn respectively in the average sizes in the intra-surface direction and perpendicular direction of surface roughness and parts which are <=10μm or 3nm respectively in the average size in the intra-surface direction and perpendicular direction of surface roughness. The coercive force of the recording films consisting of rare earth to transition metal magnetic films formed on the substrate are varies in the respective parts of 11a, 11b on the substrate. As a result, the super- resolution reproducing operation at a low operating temp. is made possible and the narrowing of track pitches is made possible. Further, the optical recording medium for reproduction only which can be arranged on the same plane as the plane of the reloadable recording medium is obtd.

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 used for recording information. In particular, it is used for an external storage device of a computer, a video or audio recording device, a storage device such as a game machine, or a multimedia in which these are integrated.

[0002]

2. Description of the Related Art In recent years, read-only optical recording media are CDs,
It is widely used for audio, video and data files such as LD and CD-ROM. However, with the spread of today's optical recording media, the data to be handled has become widespread, and the demand for higher density has increased.

As one of the solutions, there has been proposed a method of reproducing a recording domain having a diameter smaller than the laser spot diameter by a method described below for a re-recordable optical recording medium. This is a structure in which the recording film and the reproducing film are separately provided, and the information recorded on the recording film is transferred to the reproducing film only in a limited narrow area of the reproducing beam irradiation area. This is a method of reproducing while forming a film, which is a method called super-resolution reproduction.

This is the method disclosed in Japanese Patent Laid-Open No. 03-93058, which basically comprises two layers of perpendicularly magnetized films, a recording film having a high coercive force and a reproducing film having a low coercive force. Has a structure in which the exchange coupling force acts. Next, the reproduction principle of the optical recording medium having this structure will be briefly described. At room temperature,
Due to the strong external magnetic field (3 Koe or more), only the magnetization of the reproducing film is aligned in one direction. On the other hand, the coercive force of the reproducing film is drastically decreased in the region where the reproducing light is irradiated and the temperature is raised to a certain temperature or higher, and the recording domain in the recording film is transferred to the reproducing film as the direction of magnetization by the exchange coupling action. Therefore, the recording domain is detected and reproduced only from the reproducing film portion whose temperature has risen above a certain temperature in the reproducing light spot, and no signal is reproduced from the portion where the temperature has not risen to the certain temperature.

This system, like the conventional magneto-optical recording,
Although it is an effective means for an optical recording medium recorded by a user, it is not applied to a read-only optical recording medium. As a method of performing super-resolution reproduction on a reproduction-only optical recording medium,
There is a method that utilizes the difference between the reflectance in the solid state and the reflectance in the liquid state (Yasuda et al., International Symposium Off-Axis Memory Memory Off-Axis Optical Data Storage / Yasuda et al. Internati
onal Symposium Optical Memory and Optical Data St
orage '93 Th3.2, 1993). This optical recording medium has a structure in which a GeSbTe film is provided on a substrate on which information is recorded in the form of phase pits, and a reflective film is laminated to improve thermal sensitivity.

Next, the reproducing principle of the optical recording medium having this structure will be briefly described. When light is input from the substrate side for reproduction, GeSbTe is in a solid state at a low temperature portion, and
Since the reflectance of eSbTe is high, reflected light that reflects the phase pit information on the substrate can be obtained. However, in the portion where the temperature rises above a certain temperature due to the reproduction light, GeSb
Since Te is in a liquid phase and the reflectance of GeSbTe is drastically reduced, the reflected light that reflects the phase pit information on the substrate becomes extremely small. Therefore, the phase pit signal is detected and reproduced only from the low temperature part in the reproduction light spot,
Super-resolution reproduction is possible in a reproduction-only optical recording medium.

[0007]

However, the structure of the above-mentioned read-only super-resolution reproducing medium has the following drawbacks.

[0008] The first drawback is that in order to constantly regenerate the GeSbTe while raising the temperature to the liquid state, GeSbTe must be heated to several hundred degrees or more (600 ° C. or more in the above example) during regeneration, and is exclusively for regeneration. However, it means that extremely large power is required. This not only requires a high-power laser, but also causes an increase in noise due to thermal deterioration of the substrate due to repeated reproduction, or a decrease in reproduction SN ratio due to deterioration of the characteristics of the GeSbTe film itself.

The second problem is that the high temperature portion of the light beam irradiation area is masked and only the low temperature portion is reproduced, so that crosstalk between adjacent tracks is easily picked up and it is difficult to reduce the track pitch. There is.

A third problem is that a part of the recording medium is read-only and the other part is re-recordable, so-called partial ROM, or rewritable with read-only address information and management information. It is difficult to achieve both the use as a data file and the super-resolution reproduction function. That is, the GeSbTe film itself is a rewritable recording film that uses a reversible change between a crystalline state and an amorphous state. However, in order to perform super-resolution reproduction of the GeSbTe film, the film must always be in the liquid phase state, that is, the information Even if is recorded, it is reproduced while erasing it, and the information recorded in the phase change cannot be reproduced again.

In view of the above problems, the present invention can perform a super-resolution reproducing operation at a low operating temperature, can reduce a track pitch, and can dispose the recording medium on the same surface as a rewritable recording medium. An optical recording medium for reproduction only is provided.

[0012]

In order to solve the above-mentioned problems, one optical recording medium of the present invention has at least a partial area on a substrate, the surface roughness of which is a constant value corresponding to recording information. However, the coercive force of the recording film formed on the substrate is made different in each part.

In another optical recording medium of the present invention, the magnitude of magnetic anisotropy is changed in at least a part of the area by changing the composition of the magnetic film, which is a recording film, corresponding to the recorded information. By forming different portions, the coercive force of the recording film is made different in each portion.

Furthermore, in another optical recording medium of the present invention, a microstructure (composition, density, crystallinity, etc.) observed in a recording film by a transmission electron microscope in at least a part of the area, corresponding to recording information. (Due to fluctuations in the recording film) or different sizes of crystal grains are formed to make the coercive force of the recording film different in each part.

Further, according to the method of recording on the optical recording medium of the present invention, at the time of information recording, the laminated magnetic films constituting the recording film and the film of the additional element are recorded with a light intensity capable of mutually diffusing. , A structure in which portions having different magnitudes of magnetic anisotropy are formed in accordance with recording information and the coercive force of the recording film is made different in each portion, or observed by a transmission electron microscope in the recording film. By recording with a light intensity capable of growing the fine structure or crystal grain size, a portion having different fine structure or crystal grain size is formed corresponding to the recorded information, and the coercive force of the recording film is increased. It has a configuration in which each part is different.

[0016]

The present invention provides an optical recording medium for reproduction only or a write-once optical recording medium having a high SN ratio, which is capable of performing super-resolution reproducing operation at a low operating temperature and having a narrow track pitch by the above-described structure. However, it is possible to arrange the recording medium on the same surface as the rewritable recording medium.

The principle will be described in more detail.
First, a means for changing the coercive force of the recording film will be described.

If there is a fine structure or grain boundaries due to fluctuations in composition, density, crystallinity, etc. observed by a transmission electron microscope in the magnetic film as a recording film, the homogeneity in the film is impaired at that portion. As a result, the domain wall energy is disturbed. Here, since the domain wall energy is the energy stored in the domain wall, when the domain wall energy changes depending on the position, a force represented by its differential value is required to move the domain wall. On the other hand, the domain wall is a region in which the direction of spin, which is the source of magnetization, gradually transitions and has a constant width. Therefore, if the fine structure or the size of crystal grains becomes smaller than the width of the domain wall, As a result, the inhomogeneities caused by them are averaged, so that the interaction between them and the domain wall becomes small, and the domain wall moves easily.

When the crystalline magnetic film has a large magnetocrystalline anisotropy, the magnetization in each crystal grain tends to be oriented in the direction of the easy axis of magnetization. In a normal polycrystalline film, the crystal plane orientation of each crystal grain (that is, the orientation of the easy axis of magnetization) is randomly distributed. Therefore, when the magnetic film is magnetized in one direction, it differs for each crystal grain. It takes a process in which the magnetization of the direction rotates and aligns in one direction. Here, if the size of the crystal grain is sufficiently larger than the width of the domain wall, the domain wall is likely to exist at the boundary of each crystal grain and the movement of the domain wall is hindered. If it gets smaller,
Since the domain wall extends over a plurality of crystal grains, the magnetocrystalline anisotropy of each crystal grain is averaged within the domain wall, and as a result, the interaction with the domain wall is reduced and the magnetization is facilitated.

That is, it is possible to change the coercive force by a certain magnitude relationship between the width of the domain wall and the fine structure or the size of the crystal grain.

By the way, when a certain surface roughness is present on the substrate, the magnetic film formed on the substrate by the sputtering method, the vapor deposition method or the like is oriented in the direction of each minute surface constituting the rough surface during the formation process. It has the property of growing with nature. Since the minute surface forming the rough surface has various orientations, the magnetic film formed on the rough surface becomes heterogeneous in density, crystallinity, etc. near the boundary of the minute surface. Further, when a crystalline magnetic film having a large magnetocrystalline anisotropy is formed on a rough surface, the orientation of each crystal grain (that is, the orientation of the easy axis of magnetization) becomes different.

Therefore, when a certain surface roughness is present on the substrate, the magnetic film formed on the substrate has a fine structure or a fine structure derived from fluctuations in density, crystallinity, etc., which reflect the surface roughness. Grain boundaries will be generated.

When such a fine structure and grain boundaries exist,
As described above, the coercive force can be changed by the constant magnitude relationship between the width of the domain wall and the fine structure or the size of the crystal grain.

However, if the fine structure or the size of the crystal grains exceeds a certain level, it is detected as noise during optical reproduction, and the reproduction SN ratio is lowered. Therefore, it is necessary that the fine structure and the size of the crystal grains are equal to or less than a certain dimension so as not to cause noise generation.

Furthermore, when a certain element is added to the magnetic film, the magnetic anisotropy of the magnetic film may increase or decrease. For example, it is a case where a heavy rare earth metal element or another 3d transition metal element is added to a rare earth-transition metal magnetic film or a 3d transition metal magnetic film. Generally, there is a positive relationship between the magnitude of coercive force and the magnitude of magnetic anisotropy, and if the magnetic anisotropy is large, the coercive force is large for almost the same material, and if the magnetic anisotropy is small, the coercive force is small. Become. Therefore, if there are portions having different magnetic anisotropies due to composition changes in the magnetic film that is the recording film, the coercive force can be changed at each portion.

Next, the reproducing principle of the optical recording medium according to the present invention will be described. In FIG. 1, reference numeral 11 is a recording film made of a magneto-optical film, and a low coercive force portion 11a corresponding to recorded information.
And a high coercive force portion 11b. Reference numeral 12 is a reproducing light spot, 13 is a magnetic field for initialization, and 14 is a bias magnetic field. A curve 15 is a curve showing the temperature of the magneto-optical film at the time of reproduction, and corresponds to the position of the reproduction light spot 12. Curve 16 shows the temperature characteristic of the coercive force of the high coercive force portion 11b, and curve 17 shows the temperature characteristic of the coercive force of the low coercive force portion 11a.

During reproduction, the magneto-optical film is uniformly magnetized upward (or downward) by the initializing magnetic field 13 prior to irradiation of reproducing light. At this time, the magnetic field strength H2 of the initializing magnetic field 13 is required to be equal to or higher than the coercive force H3 of the high coercive force portion 11b at room temperature. When the recording medium moves and passes the reproducing light spot 12, the temperature of the magneto-optical film changes as shown by a curve 15. At this time, a weak bias magnetic field 14 having a direction opposite to that of the initializing magnetic field 13 is applied, and its magnetic field strength is H1.

The temperature of the magneto-optical film rises as the reproducing light spot 12 passes, but both the low coercive force portion 11a and the high coercive force portion 11b have a coercive force larger than that of the bias magnetic field 14 until the temperature T1 is reached. Since it has, the direction of magnetization does not change at all. However, in the temperature region higher than T1 and lower than T2, the bias magnetic field strength H1 is superior to the coercive force in the low coercive force portion 11a shown by the curve 17, so that the magnetization is reversed according to the direction of the bias magnetic field 14. On the other hand, in the high coercive force portion 11b, the bias magnetic field strength H
Since the coercive force shown by the curve 16 is superior to 1, the magnetization does not reverse and remains in the direction determined by the initializing magnetic field 13. In the temperature region where the temperature further rises and is higher than T2, the high coercive force portion 11 shown by the curve 16 is formed.
Also in b, the bias magnetic field strength H1 is superior to the coercive force, and the magnetization is inverted according to the direction of the bias magnetic field 14. That is, in the reproducing light spot 12, only in the region X where the temperature is equal to or higher than T1 and equal to or lower than T2, the state in which the magnetization is inverted according to the recorded information is created, which contributes to the detection and reproduction of the recorded information. . That is, it is possible to detect a recording domain having a reproducing light spot diameter or less, which is difficult to detect by a normal reproducing method, and it becomes possible to reproduce.

In the above description of the reproducing method, the reproducing light intensity is set so that the maximum temperature of the magneto-optical film is T2 or more, but the reproducing light intensity may be set so that the maximum temperature is T1 or more and T2 or less. The temperature in the reproduction light spot 12 is T1
Only in the area above and below T2, the state in which the magnetization is inverted is created according to the recorded information, so that the super-resolution reproducing operation is possible.

The optical recording medium for realizing such super-resolution reproduction has different coercive force depending on the recorded information.
Any magnetic film having a relatively large magneto-optical effect can be realized.

By the way, as a reproducing method for realizing such super-resolution reproduction using the optical recording medium of the present invention, reproduction is performed while the temperature of the magneto-optical film is raised to T1 or higher, and a bias magnetic field is used. 14 is required, but the initialization magnetic field 13 is not always necessary. That is, in the principle diagram of FIG. 1, an initializing magnetic field is provided to align the magnetization upward before the reproducing operation. However, when reproducing while increasing the temperature of the magneto-optical film to T2 or more, a downward bias magnetic field is applied. ,
Since the magnetization is uniformly downward after passing through the reproduction light spot 12, the initialization magnetic field can be omitted by making the bias magnetic field upward during the next reproduction.

These reproduction methods are convenient for ensuring compatibility with the conventional super-resolution reproduction method.

Further, a method of recording on some of the optical recording media of the present invention will be described.

Generally, in a magnetic film as it is formed on a substrate by a sputtering method or the like, fine structures and crystal grains due to fluctuations in density, crystallinity, etc. are likely to be fine, and the film is formed especially at low pressure. If you do, the tendency is strong. This state is a metastable state as the energy state of the substance, and the fine structure and crystal grains grow in a form in which adjacent fine structures or crystal grains are integrated in order to transition to a more stable state by heating. To go.

Therefore, a magnetic film in a film-forming state having a fine structure or crystal grain size smaller than the width of the magnetic domain wall of the magnetic film is used as a recording film, and the fine structure or crystal grain size in the recording film at the time of information recording. By recording with a light intensity that can grow
A fine structure or a coarse portion of crystal grains can be formed corresponding to the recorded information. When there are such portions having different fine structures or crystal grains, as described above, the coercive force can be changed by the constant magnitude relationship between the width of the domain wall and the fine structure or crystal grains.

By the way, the fine structure formed by the above-mentioned recording method or the coarsened portion of the crystal grains can be made finer by heating the magnetic film to a melting temperature or higher and quenching it. It is also possible to erase the recorded information depending on the size of.

Further, an optical recording medium having a laminated film of a magnetic film having a certain magnetic anisotropy and a film made of an additive element for increasing or decreasing the magnetic anisotropy of the magnetic film as a recording film is as it is. There is no portion in the recording film where the magnetic anisotropy is obviously different. However, when the recording film is heated to a certain temperature or higher, the laminated magnetic film and the film of the additional element begin to diffuse into each other and start alloying. In the alloyed portion, the magnetic anisotropy of the recording film increases or decreases, and as a result, the coercive force also increases or decreases.

Therefore, at the time of recording information, by recording the laminated magnetic film and the film of the additional element with a light intensity that allows mutual diffusion, the magnitude of magnetic anisotropy varies depending on the recorded information. By forming the portions, the coercive force of the recording film can be made different in each portion.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical recording medium according to an embodiment of the present invention will be described below with reference to the drawings.

<First Embodiment> FIG. 2 is a sectional view showing the structure of an optical recording medium according to the first embodiment of the present invention.
FIG. 3 is a perspective view and a sectional view of a substrate in the optical recording medium of this embodiment.

In FIG. 2, the first protective film 22, the recording film 23, the second protective film 24, and the reflective film 25 are formed on the substrate 21 by R.
Sequentially formed by the F sputtering method and the DC sputtering method,
Further, the protective coat layer 26 is formed by the spin coat method. Here, as an example of the material of each component, the substrate 21 is a transparent plastic such as polycarbonate or glass, the first protective film 22 and the second protective film 24 are nitride films such as SiN, and the recording film 23. Is GdTbFeC
The rare earth-transition metal magnetic film such as an o film and the reflective film 25 are made of Al.
The metal film such as a film and the protective coating layer 26 are acrylic UV resins. An example of the thickness of each film is the first protective film 22.
Is 100 nm, the recording film 23 is 15 to 40 nm, the second protective film 24 is 10 to 20 nm, the reflective film 25 is 40 nm, and the protective coat layer 26 is 5 μm.

FIG. 3 is an enlarged schematic view of the substrate 21. In FIG. 3A, the hatched portion represents the recording domain 31 formed on the surface of the substrate corresponding to the recording information, and the sectional view taken along the line AA ′ is FIG. 3B. In the optical recording medium of this embodiment, the recording domain portion 3 is formed on the substrate.
The recorded information is expressed by roughening 1 in comparison with other portions. The concave and convex groove formed by 32 and 33 is a guide for tracking control of the light spot during reproduction.

In order to manufacture the substrate 21 as described above, a master having a rough surface portion and a mirror surface portion (smooth surface portion) corresponding to recorded information is used, and a conventional mass copying method of the substrate such as injection molding is used. You can easily. The manufacturing procedure will be described below for two methods with reference to the drawings.

First, the first method will be described. This method is a method for expressing recording information by roughening the recording domain portion in comparison with other portions as in the present embodiment. In FIG. 4A, 41 is a glass master, 42 is a photoresist, 43 is an argon laser beam, 44 is an etching ion particle beam, 45 is an ultraviolet ray, 46 is a Ni film, 47 is a Ni electroformed layer, and 48 is a stamper. 21 is a substrate. The manufacturing procedure is 1) 2) 3) in Fig. 4 (a).
・ In order. 1) ... After heat-treating the photoresist 42 applied on the glass master 41 polished to a mirror surface, cutting exposure is performed with an argon laser beam 43 whose intensity is modulated according to the information to be recorded. 2) ... By developing with a developer, a portion where the photoresist 42 is removed and a portion where the photoresist 42 is not removed are formed depending on the information to be recorded. The procedure up to this point is exactly the same as the conventional procedure. 3) ... In this embodiment, plasma ion etching is next performed. This step is performed for the purpose of roughening the surface of the portion where the glass master 41 is exposed by the development. In this embodiment, a mixed gas of CF ₄ gas and Ne gas or a mixed gas of CF ₄ gas and Ar gas is used, and a pressure of 1 to 20 mTorr,
Etching was performed for 20 to 120 seconds with a power of 0.7 to 2.0 W / cm ² . Here, mixing He gas is
This is because it has an effect of reducing noise generated by roughening the surface of the glass master. For example, when a half amount of Ne gas was mixed with CF ₄ gas and etching was performed, the noise amount could be reduced by about 2 dB. 4) ... After completion of the plasma ion etching, the exposed portion of the glass master 41 and the surface of the photoresist 42 are roughened. 5) ... Further, the entire surface is irradiated with ultraviolet rays 45, and 6).
All the photoresist 42 formed on 1 is removed. 7) ... Next, a Ni film 46 is formed by sputtering on the glass master 41, and then a nickel electroformed layer 47 is formed to a certain thickness using the Ni film 46 as an electrode to form a stamper 48. 8) After that, the stamper 48 is peeled off from the glass master 41, and the stamper 48 in which the rough surface portion and the mirror surface portion are formed according to the information to be recorded is completed. In this case, the recording domain portion has a rough surface. 9) ... Using this stamper 48, the substrate 21 corresponding to the surface roughness of the stamper 48 is manufactured by an injection molding method or the like.

If the substrate material is glass and it is difficult to reproduce it by injection molding or the like, the glass substrate may be regarded as a glass master and the above production steps 1) to 6) may be performed to directly produce the substrate. .

Next, the second method will be described. This method is different from the present embodiment in that the recording information is expressed by smoothing the recording domain portion in comparison with other portions (roughening the portion other than the recording domain). In FIG. 4 (b), although each numeral indicates the same as that in FIG. 4 (a), the photoresist 42 has the property of being softened by being exposed to an argon laser or being softened in a high temperature state by irradiation with an argon laser. Use one. The manufacturing procedure is in the order of 1) 2) 3) ... Of FIG. 1) ... A photoresist 42 is applied on a glass master 41 having a mirror surface, and heat treatment is performed. The procedure up to this point is exactly the same as the conventional procedure. 2) ... In this embodiment, plasma ion etching is next performed. This step is performed for the purpose of roughening the entire surface of the photoresist 42. In this embodiment, a mixed gas of N ₂ gas and He gas or a mixed gas of O ₂ gas and He gas is used, with a pressure of 1 to 20 mTorr and a power of 0.2 to 0.5 W / cm ² , and 20 to 120. Second etching was performed. The He gas is mixed here because it has an effect of reducing noise generated by roughening the photoresist surface. For example, when a half amount of He gas was mixed with N ₂ gas for etching, the noise amount could be reduced by about 2 dB. 3) ... After completion of the plasma ion etching, the surface of the photoresist 42 is roughened. 4) ... Irradiating the roughened photoresist 42 with an argon laser beam 43 whose intensity is modulated according to the information to be recorded, to soften and smooth the roughened photoresist surface. Turn into. Therefore, a smooth surface portion and a rough surface portion are formed on the surface of the photoresist 42 according to the information to be recorded. 5) ... Next, a Ni film 46 is formed by sputtering on the photoresist 42, and the nickel electroformed layer 47 is formed by using the Ni film 46 as an electrode.
To a certain thickness to form the stamper 48. 6) After that, the glass master 41 and the photoresist 42
The stamper 48 is peeled off from the stamper 48, and the stamper 48 in which the smooth surface portion and the rough surface portion are formed according to the information to be recorded is completed. 7) ... Using this stamper 48, the substrate 21 corresponding to the surface roughness of the stamper 48 is manufactured by an injection molding method or the like.

Here, returning to FIG. 3, the surface roughness in the recording domain portion 31 is represented by an in-plane dimension α and a vertical dimension β, and respective average values in the recording domain portion 31 are represented. Represented by <α> and <β>. At this time, <β>
FIG. 5 shows the relationship between the coercive force of the recording film (GdTbFeCo film) 23 and <α> in the case of 5 nm.
FIG. 6 shows the relationship between the coercive force of the recording film 23 and <β> in the case of ˜45 nm.

From FIG. 5, the average dimension of the surface roughness in the in-plane direction <
It can be seen that the coercive force starts to increase when α> is about 10 nm or more, and from FIG. 6, the coercive force increases when the average surface roughness <β> in the vertical direction is about 3 nm or more. I know you will start.

By the way, since the magnetic anisotropy constant Ku of the GdTbFeCo film is Ku˜2 × 10 ⁶ erg / cc and the exchange stiffness constant A is 2 × 10 ⁻⁷ erg / cm, the width of the domain wall δ˜π (A /
Ku) ^1/2 is about 10 nm.

This corresponds well with the fact that the coercive force starts to increase when the average dimension <α> of the surface roughness in the in-plane direction in FIG. 5 becomes about 10 nm or more. This result shows that there is a fine structure that reflects the surface roughness on the substrate, and due to the constant magnitude relationship between the width of the domain wall and such fine structure,
This supports the above-mentioned effect of the present invention that the coercive force changes. In addition, the width δ of the domain wall of other rare earth-transition metal magnetic films such as TbFe film and GdTbFe film is 1
It is estimated to be about 0 to 20 nm, but the above GdTbFe
Similar to the Co film, a correspondence relationship between the coercive force and the surface roughness dimension was confirmed.

FIG. 7 shows that <α> to 40 nm, <β on the substrate.
Rough surface portion of> ~ 5 nm, and <α> ~ 80 nm, <β
The temperature dependence of the coercive force in each part of the optical recording medium of the present example provided with a smooth surface part of> ~ 1 nm is shown. A curve 71 shows a rough surface portion, and a curve 72 shows a smooth surface portion. Here, the recording film GdTbFe
The Curie temperature of the Co film is about 210 ° C. in this embodiment, but a coercive force difference of about double is obtained in the entire temperature range from room temperature to the Curie temperature.

From the above, in correspondence with the recorded information, the portions where the average surface roughness in the in-plane direction and the average direction in the vertical direction are 10 nm or more and 3 nm or more, respectively, and the average surface roughness in the in-plane direction and the vertical direction, respectively. If a recording film made of a rare earth-transition metal magnetic film is formed on a substrate having a dimension of 10 nm or less or 3 nm or less, an optical recording medium having a portion having a different coercive force corresponding to recorded information is obtained. be able to.

However, in order to increase the coercive force, the average of the surface roughness in the in-plane direction and the average size in the vertical direction are each 10 nm.
The above and 3 nm or more are not necessary and sufficient for the optical recording medium of the present embodiment. That is, it is necessary to prevent the occurrence of noise during reproduction due to the roughened surface. In FIG. 8, using a laser with a wavelength of 830 nm,
<Β> ~ 5 nm average surface roughness in the in-plane direction <
The relationship between α> and playback noise is shown, but <α> is approximately 50 nm.
When it becomes above, the reproduction noise has increased rapidly. Furthermore, <
When α> 45 nm, average surface roughness in the vertical direction <β
When> was 20 nm or more, the reproduction noise increased and the reflectance at that portion decreased to 90% or less. If the reflectance change corresponding to such recorded information is large, the recording domain that should originally be super-resolution-reproduced as a magneto-optical signal is normally detected as a reflectance change signal, which is unsuitable.

From the above, it is desirable that the average dimensions of the surface roughness in the in-plane direction and in the vertical direction are 50 nm or less and 20 nm or less, respectively.

Next, the minimum dimension of a portion having different coercive force (that is, the recording domain) corresponding to the recorded information is set to the wavelength 8
This optical recording medium set to 0.6 μm or less, which is difficult to detect with a light spot of 30 nm, is reproduced by the reproducing method described in the above-mentioned “Action” section.

The initialization magnetic field 13 in FIG. 1 is set to 3 kOe,
FIG. 9 shows a change in the CN ratio (curve 91) when reproducing this optical recording medium in which the recording domain size was variously set under the condition that the bias magnetic field 14 was 500 Oe and the linear velocity was 5 m / s. For reference, the change in the CN ratio (curve 92) during normal recording and reproduction is also shown. The CN ratio on the vertical axis is
The CN ratio when the recording domain size is 2 μm is plotted as 0 dB. As can be seen from FIG. 9, according to the present embodiment, a large C is obtained even for a smaller recording domain size.
The N ratio can be secured and a high density optical recording medium can be realized.

Further, as is clear from FIG. 7, the temperature rise required for regeneration is as low as 200 ° C. or lower, and
Since the detection area in the light spot is a high-temperature portion with a relatively narrow width in the track direction, super-resolution reproduction operation is possible at a low operating temperature, and reproduction with a high SN ratio can reduce the track pitch. It is possible to realize a dedicated optical recording medium.

Further, as is clear from the principle of the present invention, the material and thickness of each constituent element are not limited to these. For example, for the first or second protective film, another nitride film or ZnS film is used. It may be a chalcogenized film such as SiO 2 film, an oxide film such as SiO film, or a film of a mixture thereof. For the recording film, TbFe, Gd having a relatively high magneto-optical effect are used.
TbFe, TbFeCo, DyFe, GdDyFe, D
Other rare earth-transition metal based magnetic films such as yFeCo, GdDyFeCo, NdTbFeCo may be used.

That is, regarding the film structure, the existence of a recording film having a different coercive force corresponding to the information to be recorded is an essential constituent requirement of the present invention, and the protective film, the reflective film, the protective coat layer, etc. are reliable. It is provided as appropriate in order to secure or improve various characteristics relating to performance, signal quality, heat distribution during recording or reproduction, and the like.

Further, in this optical recording medium, a portion where the surface roughness of the substrate differs by a constant value in accordance with the recorded information is a partial region on the substrate (for example, the inner peripheral side region or the outer peripheral side region or the like). )), Since the rare earth-transition metal magnetic film itself is a rewritable recording film, the rewritable area may be an optical recording medium (so-called partial ROM) arranged on the same surface. It will be possible.

By the way, in the present embodiment, the recording domain portion 31 is made rougher than the portion other than the recording domain 31 to have a large coercive force. On the contrary, the portion other than the recording domain 31 is the recording domain portion 31. Even in the case where the surface is roughened and the coercive force is large, the super-resolution reproducing operation which is the object of the present invention can be performed by the reproducing method described in the above-mentioned "Operation" section.

<Second Embodiment> An optical recording medium according to a second embodiment of the present invention has a noble metal / transition metal multilayer film having a relatively high magneto-optical effect as the recording film 23 in the medium structure of FIG. , A transition metal oxynitride film, a ferrite film or the like is used, and glass is used as the substrate 21. In the optical recording medium of the present embodiment, the constituent elements other than the recording film 23 may be the same as in the first embodiment.

First, in the case of a noble metal / transition metal-based multilayer film such as Pt / Co or Pd / Co formed on a dielectric film such as a SiN film by the DC sputtering method or the like, the perpendicular magnetic anisotropy constant Ku is 0. Since the exchange stiffness constant A is about 7 to 2 × 10 ⁶ erg / cc and the exchange stiffness constant A is about 0.8 to 1.3 × 10 ⁻⁶ erg / cm, the width δ of the domain wall is estimated to be about 20 to 43 nm. Here, the film thickness per noble metal film is 0.8 to 3.5.
nm, the thickness of each transition metal film is 0.1 to 1.5 n
m, the total thickness of the noble metal / transition metal multilayer film is 15 to 40 n
m.

Further, the reactive film is formed on the dielectric film such as the SiN film.
FeON, FeCo produced by the on-beam sputtering method or the like
For transition metal oxynitride films such as ON, the perpendicular magnetic anisotropy is determined.
Number Ku is 4-8x10^Fiveerg / cc, exchange stiffness
Constant A is 0.6 to 1.2x10 ^-6erg / cm
Therefore, the width δ of the domain wall is estimated to be about 30 to 50 nm.
Be done. Here, the film thickness of the transition metal oxynitride film is 20 to 60.
nm.

Further, Co ferrite, Bi.C, etc. prepared on the dielectric film such as SiN film by the reactive RF sputtering method or the like.
o In the case of ferrite film such as substituted garnet ferrite,
Perpendicular magnetic anisotropy constant Ku is 0.2 to 1.5 × 10 ⁶ erg / cc
Degree, exchange stiffness constant A is 0.3 to 1.5x10 ^-6
Since it is about erg / cm, the width δ of the domain wall is 30 to
It is estimated to be about 50 nm. Here, the film thickness of the ferrite film was 100 to 300 nm.

By the way, in FIG. 3 which is an enlarged schematic view of the substrate 21, the surface roughness in the recording domain portion 31 is expressed by the dimension α in the in-plane direction and the dimension β in the vertical direction, as in the case of the first embodiment. The respective average values in the recording domain portion 31 are represented by <α> and <β>.

Further, as in the case of the first embodiment, the substrate 21 as described above is manufactured by an injection molding method using a master having a rough surface portion and a mirror surface portion (smooth surface portion) corresponding to recorded information. It can be easily performed by a conventional method such as mass replication of substrates.

FIG. 10 shows a recording film (Pt / Co multilayer film, FeCoON film, Bi.Co) when the average surface roughness in the recording domain portion 31 in the vertical direction <β> to 7 nm.
3 shows the relationship between the coercive force of the (replacement YIG film) 23 and the average surface roughness in the in-plane direction <α>. FIG. 11 shows
It shows the relationship between the coercive force of the recording film 23 and the average vertical surface roughness dimension <β> in the case of α> 45 nm.

From FIG. 10, the average in-plane dimension <α> of the surface roughness at which the coercive force begins to increase is about 20 nm for the Pt / Co multilayer film, about 30 nm for the FeCoON film, and Bi · Co.
It can be seen that the substituted YIG film has a thickness of about 30 nm. Further, from FIG. 11, the average vertical dimension <β> of the surface roughness at which the coercive force starts to increase is as follows: Pt / Co multilayer film, FeCoO
It can be seen that both the N film and the Bi / Co substituted YIG film have a thickness of about 5 nm.

The result is that the coercive force changes according to a certain size relationship between the width of the domain wall and the microstructure, etc., which has a microstructure reflecting surface roughness on the substrate. It supports the action.

<Α> to 45 nm, <β> to 7n on the substrate
m, <α> to 80 nm, <β> to 1.5 n
When the temperature dependence of the coercive force in each part of the optical recording medium of the present example provided with the part m is measured, the coercive force difference of about 1.6 times is found in the entire temperature range from room temperature to the Curie temperature. It was confirmed that it was obtained.

From the above, in correspondence with the recorded information, the portions where the average dimensions of the surface roughness in the in-plane direction and the vertical direction are 20 nm or more and 5 nm or more, respectively, and the average of the surface roughness in the in-plane direction and the vertical direction, respectively. Pt / Co is formed on a substrate having portions each having a dimension of 20 nm or less or 5 nm or less.
If a recording film made of a noble metal / transition metal-based multilayer film such as a multilayer film, a transition metal oxynitride film such as a FeCoON film, or a ferrite film such as a Bi / Co-substituted YIG film is formed, the coercive force corresponding to the recorded information is different. An optical recording medium having a portion can be obtained.

However, in the same manner as described in the first embodiment, in order to achieve the super-resolution reproducing operation of the present invention by preventing the occurrence of noise and the change in reflectance during reproduction due to the roughening of the surface,
The average dimension <α> of the surface roughness in the in-plane direction is 50 nm or less, and the average dimension <β> of the surface roughness in the vertical direction is 20 nm or less.
It must be less than or equal to nm.

Therefore, by reproducing this optical recording medium by the reproducing method described in the above section "Operation" as in the case of Example 1, the super-resolution reproducing operation is possible at a low operating temperature. Moreover, it is possible to realize a read-only optical recording medium with a high SN ratio that can reduce the track pitch.

Further, as is clear from the principle of the present invention, the material and thickness of each constituent element are not limited to these. For example, for the first or second protective film, another nitride film or ZnS film is used. It may be a chalcogenized film such as the above, an oxide film such as a SiO film, or a film of a mixture thereof, and in particular, the second protective film may be appropriately omitted. The recording film may be another 3d transition metal-based magnetic film having a domain wall width δ of about 20 to 50 nm and a relatively high magneto-optical effect.

That is, regarding the film structure, the existence of the recording film having a different coercive force corresponding to the information to be recorded is an essential constituent requirement of the present invention, and the protective film, the reflective film, the protective coat layer, etc. are reliable. It is provided as appropriate in order to secure or improve various characteristics relating to performance, signal quality, heat distribution during recording or reproduction, and the like.

Further, in this optical recording medium, a portion where the surface roughness of the substrate is different by a constant value in accordance with the recorded information is defined as a partial region on the substrate (for example, the inner peripheral region or the outer peripheral region). )), Since the rare earth-transition metal magnetic film itself is a rewritable recording film, the rewritable area may be an optical recording medium (so-called partial ROM) arranged on the same surface. It will be possible.

By the way, in the present embodiment, the recording domain portion 31 is made rougher than the portion other than the recording domain 31 to have a large coercive force. On the contrary, the portion other than the recording domain 31 is the recording domain portion 31. Even in the case where the surface is roughened and the coercive force is large, the super-resolution reproducing operation which is the object of the present invention can be performed by the reproducing method described in the above-mentioned "Operation" section.

<Third Embodiment> FIG. 12 shows the third embodiment of the present invention.
FIG. 13 is a cross-sectional view showing the structure of the optical recording medium in the example of FIG. 13, and FIG. 13 is a view for partially making the magnetic anisotropy of the recording film different corresponding to the recording information in the optical recording medium of the example. 1 shows an outline of a recording device.

In FIG. 12, the first protective film 122, the magnetic film 123, the additional element film 124, the second protective film 125, and the reflective film 126 are formed on the substrate 121 by the RF sputtering method and DC.
The protective coat layer 1 is formed in order by the sputtering method.
27 is formed by a spin coating method, and a recording film 128 is composed of the magnetic film 123 and the additional element film 124. Here, if the material of each component is shown as an example,
The substrate 121 is made of transparent plastic such as polycarbonate or glass, and has a first protective film 122 and a second protective film 125.
Is a nitride film such as SiN, and the magnetic film 123 is GdTbF.
Rare earth-transition metal based magnetic film such as eCo film, additional element film 1
24 is a heavy rare earth metal film such as a Tb film, and the reflective film 126 is Al.
The metal film such as a film and the protective coat layer 127 are epoxy UV resin. An example of the thickness of each film is the first protective film 1
22 is 100 nm, the magnetic film 123 is 15 to 30 nm, the additional element film 124 is 0.1 to 0.4 nm, and the second protective film 125.
Is 10 to 20 nm, the reflective film 126 is 40 nm, and the protective coat layer 127 is 5 μm.

In FIG. 13, reference numeral 131 is an optical recording medium in which the above-mentioned films are formed on the substrate (for convenience, the films other than the magnetic film and the additive element film are not shown), 121 is the substrate. Reference numeral 123 is a magnetic film, 123a is a recorded domain portion, 124 is an additive element film, 132 is a recording laser beam,
33 is an optical head, and 134 is a spindle motor.

The optical recording medium 131 is rotated at a constant speed of 1.4 m / sec, and the recording laser beam 132 is emitted to the optical head 1.
While being scanned at 33, the rewritable recording film G
dTbFeCo film (Gd18Tb6Fe71C in this embodiment)
The Curie temperature is about 230 ° C. with the composition of o5. ) Is irradiated at an intensity of about 1.5 times or more higher than the normal recording power of), corresponding to the recorded information. By this recording process, in the recording domain portion 123a, the magnetic film GdTbFeCo film and the additional element film Tb film are mutually diffused and integrated, and the Tb amount of the composition of the magnetic film 123 increases only in this portion.

As a result, the magnetic anisotropy of the recording domain portion 123a increases corresponding to the recording information, and the coercive force of this portion becomes larger than that of the other portions.

FIG. 14 shows the T in the GdTbFeCo film.
The relationship between the b amount and the coercive force is shown. Tbx [Gd19Fe76Co
5] When the composition is expressed by 100-x, the coercive force increases from 1 kOe to 1.8 kOe when the Tb amount x increases from 6 at% to 6.5 at%.
You can see that it increases.

That is, the composition of the recording film is partially changed by performing the recording process on the optical recording medium having the recording film composed of the laminated film of the magnetic film and the additional element film as in this embodiment, as described above. An optical recording medium having portions having different coercive forces corresponding to recorded information can be obtained. Actually, when the temperature dependence of the coercive force in each part of the optical recording medium thus obtained was measured, a coercive force difference of about 1.5 times was obtained in the entire temperature range from room temperature to the Curie temperature. Was confirmed.

By the way, the reflectance of the recording film is hardly changed by such a slight increase of the additive element, and the form of the recording film is hardly changed, so that it does not cause an increase in reproduction noise.

Therefore, by reproducing this optical recording medium by the reproducing method described in the above-mentioned "Operation" as in the case of Example 1, the super-resolution reproducing operation is possible at a low operating temperature. Moreover, it is possible to provide a read-only optical recording medium having a high SN ratio that can reduce the track pitch. Further, since the method of forming a recording domain as shown in this embodiment can be carried out by an ordinary optical disk drive, it can be used not only as a read-only disk but also as a write-once disk. Obviously, the material and thickness of each component are not limited to these, and for example, for the first or second protective film, other nitride film, chalcogenized film such as ZnS film, SiO film, etc. It may be an oxide film or a film of a mixture thereof, and the magnetic film may be TbFe, GdTbFe, TbFeCo, DyF having a relatively high magneto-optical effect.
e, GdDyFe, DyFeCo, GdDyFeCo,
It may be another rare earth-transition metal magnetic film such as NdTbFeCo or a 3d transition metal magnetic film such as a transition metal oxynitride film or a ferrite film, and the additive element film is another heavy rare earth metal film such as Tb. May be.

That is, regarding the film structure, the existence of the recording film having a different coercive force corresponding to the information to be recorded is an essential constituent requirement of the present invention, and the protective film, the reflective film, the protective coat layer, etc. are reliable. It is provided as appropriate in order to secure or improve various characteristics relating to performance, signal quality, heat distribution during recording or reproduction, and the like.

Further, in this optical recording medium, a portion having a different composition of the recording film is provided only in a partial area (for example, the inner peripheral area or the outer peripheral area) corresponding to the recorded information. In this case, since the rare earth-transition metal magnetic film itself is a rewritable recording film, the rewritable region is also arranged on the same surface (so-called partial RO).
M).

By the way, in this embodiment, the magnetic anisotropy of the recording domain portion 123a is determined by the recording domain 123a.
The recording domain portion 123a is made to have a large coercive force by changing the composition so that the recording domain portion 123a has a larger magnetic anisotropy than that of the recording domain portion 123a. Even if the composition is changed to a recording domain portion 123a having a small coercive force, the reproducing method described in the above section "Action" enables the super-resolution reproducing operation which is the object of the present invention.

The optical recording medium in this case can be obtained by using the GdTbFeCo film as the magnetic film 123 in FIG. 12 and the Fe film as the additional element film 124 and performing the above-described recording process in the recording apparatus in FIG. This means that the relationship between the amount of Fe and the coercive force in the GdTbFeCo film shown in FIG.
That is, when the composition is expressed by Fex [Gd62Tb20Co18] 100-x, it can be understood that the coercive force decreases from 1.7 kOe to 0.9 kOe when the Fe amount x increases from 70.5 at% to 71.5 at%. Here, the additional element film may be another 3d transition metal film such as Co.

<Fourth Embodiment> FIG. 16 shows a fourth embodiment of the present invention.
3 is a cross-sectional view showing the configuration of the optical recording medium in Example of FIG.

In FIG. 16, a first protective film 162, a recording film 163, a second protective film 164 and a reflective film 165 are sequentially formed on a substrate 161 by an RF sputtering method, a DC sputtering method and the like, and a protective coating layer is further formed. 166 is formed by the spin coating method. Here, as an example of the material of each constituent element, the substrate 161 is glass, the first protective film 162 and the second protective film 164 are nitride films such as SiN, and the recording film 163 is Bi / Co substituted YIG. A ferrite film such as a film, a transition metal oxynitride film such as FeCoON, a reflective film 165 is a metal film such as an Al film, and a protective coating layer 166 is an epoxy UV resin. In addition, an example of the thickness of each film is
The first protective film 162 has a thickness of 100 nm, and the recording film 163 has a thickness of 100 nm.
˜300 nm, the second protective film 164 is 10 to 20 nm, the reflective film 165 is 40 nm, and the protective coat layer 166 is 5 μm.

Further, in the optical recording medium of the present embodiment, in order to partially differ the fine structure or the size of crystal grains observed by the transmission electron microscope in the recording film according to the recorded information, The recording apparatus shown in FIG. 12 used in the third embodiment is used.

The optical recording medium 121 is rotated at a constant speed of 1.4 m / sec, and the recording laser beam 122 is supplied to the optical head 1.
The recording film B which is originally rewritable while scanning at 23
i.Co-substituted YIG film ((Bi, Y) 3Fe in this embodiment)
Curie temperature about 30 with composition of 3.4 (Co, Ge) 1.6 O12
0 ° C. ) Is irradiated at an intensity of about 2.0 times or more of the normal recording power of), corresponding to the recorded information. By this recording process, the Bi / Co-substituted YIG film is heat-treated in the recording domain part 123a, and the crystal grains of the recording film grow only in this part.

As a result, the average size of the crystal grains becomes larger in the recording domain portion 123a than in other portions, corresponding to the recording information.

By the way, if there is a fine structure or a grain boundary derived from fluctuations in composition, density, crystallinity, etc. observed by a transmission electron microscope in the recording film, homogeneity in the film is impaired at that portion. The domain wall energy is disturbed. Here, since the domain wall energy is the energy stored in the domain wall, when the domain wall energy changes depending on the position, a force represented by its differential value is required to move the domain wall. On the other hand, the domain wall is a region in which the direction of spin, which is the source of magnetization, gradually transitions and has a constant width. Therefore, if the fine structure or the size of crystal grains becomes smaller than the width of the domain wall, As a result, the inhomogeneities caused by them are averaged, so that the interaction between them and the domain wall becomes small, and the domain wall moves easily. That is, it becomes possible to change the coercive force by a certain magnitude relationship between the width of the domain wall and the fine structure or the size of the crystal grain.

In the case of a ferrite film such as Bi / Co-substituted garnet ferrite formed on the dielectric film such as SiN film by the reactive RF sputtering method, the perpendicular magnetic anisotropy constant Ku is 0.2 to 1.5 × 10 ^6. Since the exchange stiffness constant A is about erg / cc and the exchange stiffness constant A is about 0.3 to 1.5 × 10 ⁻⁶ erg / cm, the width δ of the domain wall is estimated to be about 30 to 50 nm.

Further, a reactive film is formed on the dielectric film such as the SiN film.
FeON, FeCo produced by the on-beam sputtering method or the like
For transition metal oxynitride films such as ON, the perpendicular magnetic anisotropy is determined.
Number Ku is 4-8x10^Fiveerg / cc, exchange stiffness
Constant A is 0.6 to 1.2x10 ^-6erg / cm
Therefore, the width δ of the domain wall is estimated to be about 30 to 50 nm.
Be done.

Therefore, first, by appropriately adjusting the substrate temperature at the time of forming the recording film, an optical recording medium having a fine structure in the recording film and a crystal grain size of 30 nm or less is manufactured,
Next, by using the recording apparatus of FIG. 13 to perform the recording process, the fine structure and the size of the crystal grains in the recording domain portion 123a are grown to 30 nm or more which is the domain wall width of the recording film. The coercive force at is larger than the other parts.

An optical recording of this embodiment was carried out by forming a Bi.Co-substituted YIG film having an average crystal grain size of about 15 nm on a substrate and heat-treating a part of the film to grow the average crystal grain size to about 45 nm. As a result of examining the temperature dependence of the coercive force in each part of the medium, it was confirmed that a coercive force difference of about 1.5 times was obtained in the entire temperature range from room temperature to the Curie temperature.

As described above, if a recording film having a fine structure or a portion having an average size of crystal grains of 30 nm or more and 30 nm or less is formed corresponding to the recording information, the recording information is It is possible to obtain an optical recording medium having portions having different coercive forces corresponding to.

However, even if the fine structure in the recording film or the average size of the crystal grains is 30 nm or more in order to increase the coercive force, it is not necessary and sufficient for the optical recording medium of this embodiment. That is, it is necessary to prevent generation of noise at the time of reproduction due to enlargement of the fine structure in the recording film or the average size of crystal grains. In order to suppress the noise generation, the fine structure in the recording film and the average size of the crystal grains should be 50 n.
It is preferably m or less.

From the above, the average size of the fine structure and crystal grains in the recording film in the high coercive force portion is 30 nm to 50 nm.
Is desirable.

Therefore, by reproducing this optical recording medium by the reproducing method described in the above section "Operation" as in the case of Example 1, the super-resolution reproducing operation can be performed at a low operating temperature. Moreover, it is possible to provide a read-only optical recording medium having a high SN ratio that can reduce the track pitch. Further, since the method of forming a recording domain as shown in this embodiment can be carried out by an ordinary optical disk drive, it can be used not only as a read-only disk but also as a write-once disk. Obviously, the material and thickness of each component are not limited to these, and for example, for the first or second protective film, other nitride film, chalcogenized film such as ZnS film, SiO film, etc. It may be an oxide film or a film of a mixture thereof, and the recording film has a domain wall width δ of 20 to 5
Other 3d transition metal-based magnetic film having a relatively high magneto-optical effect of about 0 nm (other ferrite film such as Co ferrite or transition metal oxynitride film such as FeON or FeCoON) may be used.

That is, regarding the film structure, the existence of a recording film having a different coercive force corresponding to the information to be recorded is an essential constituent requirement of the present invention, and the protective film, the reflective film, the protective coat layer, etc. are reliable. It is provided as appropriate in order to secure or improve various characteristics relating to performance, signal quality, heat distribution during recording or reproduction, and the like.

Further, in this optical recording medium, a portion where the fine structure in the recording film and the average size of the crystal grains are different by a constant value in correspondence with the recording information is set as a partial region (for example, the inner circumference). If it is provided only in the side area or the outer peripheral side area), the 3d transition metal-based magnetic film itself is a rewritable recording film, so that the rewritable area is also arranged on the same plane (so-called partial recording). ROM).

[0108]

As described above, according to the present invention, by changing the coercive force of the recording film according to the information to be recorded, the super-resolution reproducing operation can be performed at a low operating temperature, and the track pitch can be improved. The present invention realizes a high-density read-only or write-once or partial ROM optical recording medium that can be filled with a high density, and provides a specific manufacturing method thereof.

[Brief description of drawings]

FIG. 1 is a principle diagram illustrating a reproducing operation of an optical recording medium of the present invention.

FIG. 2 is a configuration diagram of an optical recording medium according to a first embodiment of the present invention.

FIG. 3 is a perspective view and a sectional view of a substrate in the optical recording medium according to the first embodiment of the present invention.

FIG. 4 is a view showing a procedure for manufacturing a substrate in the optical recording medium of the first embodiment of the present invention.

FIG. 5 is a diagram showing the relationship between the in-plane dimension of the surface roughness of the substrate and the coercive force of the recording film in the optical recording medium of the first embodiment of the present invention.

FIG. 6 is a diagram showing the relationship between the vertical dimension of the surface roughness of the substrate and the coercive force of the recording film in the optical recording medium of the first embodiment of the present invention.

FIG. 7 is an optical recording medium of the first embodiment of the present invention,
The figure which shows the temperature dependence of the coercive force of the recording film in the part where surface roughness of a substrate differs.

FIG. 8 is a diagram showing the relationship between the in-plane dimension of the surface roughness of the substrate and the reproduction noise in the optical recording medium of the first embodiment of the present invention.

FIG. 9 is a diagram showing a relationship between a recording domain size and a signal level when super-resolution reproduction is performed on the optical recording medium of the first embodiment of the present invention.

FIG. 10 is a diagram showing the relationship between the in-plane dimension of the surface roughness of the substrate and the coercive force of the recording film in the optical recording medium of the second embodiment of the present invention.

FIG. 11 is a diagram showing the relationship between the vertical dimension of the surface roughness of the substrate and the coercive force of the recording film in the optical recording medium of the second embodiment of the present invention.

FIG. 12 is a configuration diagram of an optical recording medium according to a third embodiment of the present invention.

FIG. 13 is a schematic diagram of a recording device for an optical recording medium in a third embodiment of the present invention.

FIG. 14 is a diagram showing a relationship between a Tb amount and a coercive force in a GdTbFeCo film.

FIG. 15 is a graph showing the relationship between the amount of Fe and the coercive force in a GdTbFeCo film.

FIG. 16 is a configuration diagram of an optical recording medium according to a fourth embodiment of the present invention.

[Explanation of symbols]

 11 magneto-optical film 11a low coercive force portion 11b high coercive force portion 12 reproducing light spot 13 initialization magnetic field 14 bias magnetic field 15 temperature curve of magneto-optical film 16 coercive force temperature curve of high coercive force portion 17 coercive force of low coercive force portion Temperature curve 21 Substrate 22 First protective film 23 Recording film 24 Second protective film 25 Reflective film 26 Protective coating layer 41 Master disc 42 Photoresist 43 Argon laser beam 44 Etching ion particle beam 45 Ultraviolet ray 46 Ni film 47 Nickel electroformed layer 48 Stamper 121 Substrate 122 First Protective Film 123 Magnetic Film 124 Additional Element Film 125 Second Protective Film 126 Reflective Film 127 Protective Coating Layer 128 Recording Film 131 Optical Recording Medium 132 Recording Laser Light 133 Optical Head 134 Spindle Motor 161 Substrate 162 First Protection Film 163 recording film 1 64 Second protective film 165 Reflective film 166 Protective coating layer

Claims (13)

[Claims] 1. At least a part of a region on a substrate corresponding to recorded information, a portion having an average surface roughness in the in-plane direction and an average dimension in the vertical direction of 10 nm to 50 nm and 3 to 20 nm, respectively, and a surface. The recording film is formed of a portion having an average in-plane roughness of 10 nm or less or a vertical average size of 3 nm or less, and a coercive force of a recording film made of a rare earth-transition metal magnetic film formed on the substrate. An optical recording medium characterized in that parts are different. 2. At least a part of the area on the substrate corresponding to the recorded information, the surface roughness and the surface in which the average dimensions of the in-plane direction and the vertical direction are 20 nm to 50 nm and 5 to 20 nm, respectively. The roughness of the recording film is made up of a portion having an average in-plane direction and an average dimension in the vertical direction of 20 nm or less or 5 nm or less, respectively. An optical recording medium characterized by being different. 3. The optical recording medium according to claim 2, wherein the 3d transition metal-based magnetic film is any one of a noble metal / transition metal-based multilayer film, a transition metal oxynitride film, and a ferrite film. 4. A step of applying a photoresist on a glass master and heat treating it, a step of exposing the photoresist surface with a laser whose intensity is modulated according to recording information, and a developing solution after cutting. After the development, the surface of the glass master portion exposed by the development is roughened by plasma ion etching using a mixed gas of CF ₄ gas and Ne gas or a mixed gas of CF ₄ gas and Ar gas from the photoresist surface side after development. And a step of removing all the photoresist formed on the glass master after plasma ion etching, a step of forming a stamper by electroforming on the glass master after removing the photoresist, and a glass stamper. The process of peeling from the master disc and the part with different surface roughness corresponding to the recorded information using the stamper A step of molding the formed substrate,
A method of manufacturing an optical recording medium, comprising: forming a magnetic film, which is a recording film, on the substrate. 5. A step of applying a photoresist on a glass master and heat treating it, and plasma ion etching the photoresist surface using a mixed gas of N ₂ gas and He gas or a mixed gas of O ₂ gas and He gas. A roughening step, and a cutting step of softening and smoothing the roughened photoresist surface with a laser whose intensity is modulated according to recorded information after plasma ion etching,
After cutting, a step of electroforming on the photoresist to form a stamper, a step of peeling the stamper from the glass master and the photoresist, and a portion having different surface roughness corresponding to recorded information using the stamper A method of manufacturing an optical recording medium, comprising: a step of molding a substrate on which is formed, and a step of forming a magnetic film as a recording film on the substrate. 6. The recording by forming a portion having a different magnetic anisotropy by changing the composition of a magnetic film, which is a recording film, in at least a part of the area in accordance with recording information. An optical recording medium characterized in that the coercive force of the film is made different in each part. 7. The optical recording medium according to claim 6, wherein the recording film is a rare earth-transition metal magnetic film. 8. The optical recording medium according to claim 6, wherein the recording film is a laminated film of a rare earth-transition metal magnetic film and a heavy rare earth metal film or a transition metal film. 9. When recording information on an optical recording medium using a laminated film of a magnetic film having a certain magnetic anisotropy and a film of an additive element for increasing or decreasing the magnetic anisotropy of the magnetic film as a recording film. In addition, by recording the laminated magnetic film and the film of the additional element with a light intensity capable of mutually diffusing, a portion having different magnetic anisotropy is formed corresponding to recorded information,
A recording method for an optical recording medium, wherein the coercive force of the recording film is made different in each part. 10. The optical recording according to claim 9, wherein the laminated magnetic film is a rare earth-transition metal based magnetic film, and the film of the additional element is a heavy rare earth metal film or a transition metal film. Media recording method. 11. At least a part of the area is formed with a portion having a different fine structure or crystal grain size observed by a transmission electron microscope in the recording film, corresponding to recorded information. An optical recording medium characterized in that the coercive force of the recording film is made different in each part. 12. A recording film comprising a fine structure or a crystal grain size of 30 nm to 50 nm and 30 nm or less, wherein the recording film is either a transition metal oxynitride film or a ferrite film. The optical recording medium according to claim 11, wherein 13. When recording information on an optical recording medium having a recording film made of a crystalline magnetic film, recording is performed with a light intensity capable of growing a fine structure or crystal grains observed by a transmission electron microscope or the like in the recording film. Accordingly, a recording method of an optical recording medium, wherein portions having different fine structures or different crystal grain sizes are formed in accordance with recording information, and the coercive force of the recording film is made different in each portion. .