JP2730038B2 - Manufacturing method of optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an optical disc for optically recording / reproducing information or recording / reproducing / erasing information by irradiating a focused light such as a gas laser or a semiconductor laser, and an optical disc. The present invention relates to an optical recording medium such as a magnetic disk, and more particularly to a method for manufacturing an optical recording medium in which a recording layer is selectively provided only in a track groove of a substrate.

[Prior Art] A conventional optical recording medium will be described by taking a type having a recording layer on one side as an example. As shown in FIGS. 2 and 3, a pre-groove (pre-groove) for focusing and tracking servo is used. groove) (a) transparent substrate (b)
A recording layer (c) provided on the entire surface of the substrate (b);
The main part is composed of a protective layer (d) provided on the entire surface of the recording layer (c), and input of recording information to the optical recording medium (e) is performed as shown in FIG. A predetermined portion of the recording layer (c) is irradiated with a recording focused light (g) from a light source such as a semiconductor laser condensed by an optical lens (f), and a phase change of the recording layer (c) is performed on the irradiated portion. It causes magnetization reversal or deformation, etc.
Alternatively, it is performed by forming recording dots (h) having different Kerr rotation angles (see FIG. 3). In this case, focusing and tracking servo control are performed using the pre-groove (a) in order to reliably irradiate the focused light (g) from the light source to a predetermined portion of the recording layer (c), and the recording dot is recorded. The width dimension (B) of (h) is changed to the fifth
As shown in the figure, the intensity of the focused light spot for recording (i) is set to a half-value width (Ω2) indicating the steepest value, so that recording dots (h) of substantially the same size are formed stably. Has been adjusted.

On the other hand, at the time of reproducing the recorded information, as shown in FIGS. 6 and 7, the focused light for reproduction (g) is irradiated onto the recording surface of the optical recording medium (e), and the reflected light is emitted from a photodiode or the like. The data is input to the light receiving element (j) and reproduced. In this case, the entire light of the reproduction focused light spot is used for reproduction, and as shown in FIG. 5, typically, the light in the 1 / e ² full width (Ωe) region in the reproduction focused light spot (i). Is considered to contribute to the reproduction signal. In addition, (p) in FIG.
Indicates an optical head for reproduction, and a semiconductor laser (p1)
A condenser lens (p2) for forming an image of the laser beam on the surface of the optical recording medium (e), a beam splitter (p3) for polarizing a reflected beam from the optical recording medium (e), and a half mirror (p4). , The servo signal detector (p5) and the reproduced signal light receiver (p6) constitute the main part.

By the way, the conventional optical recording medium (e) has the following various disadvantages since the recording layer (c) is provided on the entire surface of the substrate (b) as described above.

First, in the optical recording medium (e), the track pitch (T
P) can be set as narrow as possible so that the signal on the adjacent track does not mix with the playback signal, and its minimum value (T
Considering only the crosstalk with the adjacent track at the time of reproduction, (P _min ) is obtained from (TP _min ) = B / 2 + (Ωe−B) / 2 + B / 2 = (B + Ωe) / 2 from FIG. be able to.

Here, (B) is the width dimension of the recording dot (h), (Ωe)
Indicates the full width of 1 / e ² in the focused light spot for reproduction (i).

On the other hand, conventionally, the width dimension (B) of the recording dot (h)
Is set to about the half-value width (Ω2) of the recording focused light spot (i) as described above. Therefore, in order to improve the track density in the optical recording medium, the spot diameter (g) of the focused light (g) is eventually reached. Ωe, Ω2) can only be set small, and if the spot diameter (Ω2) is set too small, a recording error occurs due to a slight dimensional error on the substrate surface. For this reason, there is a drawback that the above density improvement has a certain limit.

Further, since the recording material constituting the recording layer (c) usually has thermal conductivity, heat easily leaks to the periphery as the scanning of the recording spot progresses due to the influence of the thermal conductivity, and the recording width is reduced. In some cases, as shown in FIG. 9, the shape of the recording dot (h) became a so-called “tear drop dot”. For this reason, as shown by α in FIG. 16, the reproduced signal is distorted and large jitter is likely to occur, and
There is a drawback that the C / N ratio decreases.

Further, the diameter (Ωe) of the focused light spot for reproduction (i)
Is larger than the diameter (B) of the recording dot (h) as described above, and the optical recording medium (e) is provided with the recording layer (c) on the entire surface of the substrate (b). In some cases, the optical recording medium (e) has a drawback that noise has a large effect on a reproduced signal. That is, the tenth
As shown in the figure, on the surface of the recording layer (c) of the optical recording medium (e), there are a large number of noise generating portions (n1) to (n1) having different reflectances due to defects of the medium itself, crystal grains, and the like. ,And,
Noise generating portions (n2) to (n2) due to dot shape unevenness are also present at the periphery of the recording dot (h), and these noises are mixed into the reproduction signal.
This was a major obstacle to improving the C / N ratio (see the C / N ratio indicated by α in FIG. 18; however, C indicates the carrier signal level and N indicates the noise signal level, respectively).

Furthermore, in the optical recording medium for recording / reproducing / erasing, when erasing the recorded information, the sensitivity of the recording layer is degraded due to aging, the output of the convergence light for erasing is fluctuated, and the tracking error is caused. As shown in FIG. 11, there is a defect that the recorded information cannot be completely erased. On the other hand, in order to solve this defect, the spot diameter (Ω) of the converging light for erasing is set to be smaller than the spot diameter (Ω2) of the converging light for recording. There is a drawback that setting a large value causes a decrease in track density.

In the conventional optical recording medium, since the recording layer (c) is formed on the entire surface of the substrate (b), the recording layer (c)
Due to the stress at the time of formation and the difference in expansion coefficient between the substrate (b) and the recording layer (c), a two-dimensional internal stress (St) is easily applied to the recording layer (c) as shown in FIG. There is a disadvantage that the recording performance is easily deteriorated.

Accordingly, the applicant has conducted intensive studies to solve the above-mentioned drawbacks, and as a result, the track density, the C / N ratio, and the like are high, the reproduction noise and the servo signal noise are small, and the recording performance is long. An optical recording medium that does not deteriorate has already been proposed.

That is, this optical recording medium (e ') comprises a substrate (b') and a track groove (a ') provided on one surface of the substrate (b') at a plurality of intervals as shown in FIG. The recording layer (c ') provided in the track groove (a') and the protective layer (d ') provided on the recording layer (c') side as necessary constitute the main part. Further, the width dimension of the track groove (a ') is set to be equal to or less than about a half-value width of the focused light spot for recording.

Then, as shown in FIGS. 13 to 14, a predetermined portion of the recording layer (c ') is irradiated with a focusing light for recording while performing focusing and tracking control using the track groove (a'). A recording dot (h ') having a diameter of about half width (Ω2) of the focused light spot for recording is formed, and
This recording dot (h ') is read by the focused light for reproduction to obtain a reproduced signal.

In the optical recording medium (e ') thus configured, as shown in FIGS. 14 (b) and (d), the width dimension (B) of the recording dot (h') is the track groove (a '). And the same width dimension (T), and this width dimension (T)
Is set to be equal to or less than the half-width (Ω2) of the focused light spot for recording, so that the minimum value (TP ′ _min ) of the track pitch of the optical recording medium (e ′) is equal to the track pitch of the conventional optical recording medium. The relationship with the minimum value of (TP _min ) is (TP ′ _min ) <(TP _min ), and the track pitch (TP) can be set small, which has the advantage of improving the track density. ing.

Further, in this optical recording medium (e '), the recording layer (c') is regulated by the shape of the track groove (a '), and therefore, differs from the conventional "tear drop shape" as shown in FIG. Thus, a recording dot (h ′) having a shape close to a rectangular shape can be formed.

Therefore, as shown by β in FIG. 16, the reproduced signal waveform at the time of reproduction is not distorted, so that there is an advantage that both the C / N ratio and the jitter are improved.

Further, in this optical recording medium (e '), since the recording layer (c') is not provided in a portion other than the track groove (a '), the medium noise is reduced and the recording dots (h') are reduced. Is not restricted by the track groove (a '), and the unevenness of the reflectance and the magnetic domain distribution at the boundary of the recording dots (h') is reduced, and the C / N ratio in the reproduced signal is improved. have. That is, when the noise of a light source such as a semiconductor laser is sufficiently suppressed, the reproduction signal noise at the time of reproduction is generally caused by medium noise caused by defects, crystal grains and the like of an optical recording medium and unevenness of a recording dot shape. Recording noise is dominant. In the optical recording medium (e '), since the recording layer (c') is not provided in a portion other than the track groove (a '), the medium noise is reduced, and the recording is performed as shown in FIG. Both side edges of the layer (c ') are restricted by the track grooves (a') formed with high precision, and the recording dots (h ') are less likely to have irregular shapes, so that recording noise is also reduced. Therefore, since the above-mentioned noise signal is less likely to be mixed into the reproduction signal, the C / N ratio is significantly improved as indicated by β in FIG.

Furthermore, in the conventional recording / reproducing / erasing optical recording medium, the recorded information is completely lost due to the deterioration of the recording layer sensitivity due to aging deterioration, the output fluctuation of the focusing light for erasing, and the tracking deviation. Although there was a disadvantage that erasure could not be performed, as shown in FIG. 19, there is no recording layer (c ') in an area where erasure remains, so that there is an advantage that erasure does not occur.

Since the recording layer (c ') in the track groove (a') is continuous only in the length direction and not continuous in the width direction, as shown in FIG. Since the internal stress (St) becomes one-dimensional and is greatly reduced, and when the recording material is a phase change type, the atom transfer process of crystallization and amorphization in the recording / erasing process also proceeds one-dimensionally. The composition variation and the in-plane variation of the composition in the recording layer (c ′) hardly occur, and the recording layer (c ′)
In addition to the stability of the recording bit and the recording performance, it has the advantage that the repeatability is improved and the recording performance is stable for a long time.
In addition, since the recording / erasing process proceeds one-dimensionally, there are various advantages such as speeding up of each process and enabling high-speed recording / erasing.

[Problems to be Solved by the Invention] By the way, in manufacturing this improved optical recording medium, unlike a conventional optical recording medium in which a recording layer is provided on the entire surface of a substrate, only a track groove provided in the substrate is provided. It was necessary to selectively form a recording layer.

However, since the width dimension of the track groove is set to an extremely small value, there is a problem that it is difficult to form the recording layer, and it is difficult to manufacture the recording layer accurately and efficiently.

Moreover, if the recording layer is formed erroneously at a portion other than the track groove, the recording layer at this portion causes the medium noise and the recording noise. There was a problem that the N ratio was lowered.

[Means for Solving the Problems] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an optical recording medium having good productivity and good recording accuracy. To provide.

That is, the present invention relates to an optical recording medium for optically recording / reproducing information or recording / reproducing / erasing by irradiating a focused light, comprising: a substrate; and a track groove formed on at least one surface of the substrate at a plurality of intervals. And a recording layer formed in the track groove, on the premise of a method of manufacturing an optical recording medium, a substrate forming step of forming a substrate having the track groove, and the entire surface of the substrate on which the track groove is provided. A recording film forming step of forming a recording layer forming film until the surface on the side opposite to the substrate is flattened; and removing the recording layer forming film on the substrate by a dry etching method and recording in the track groove. A recording layer forming step of forming a recording layer while leaving the layer forming film.

In such technical means, a light-transmitting material is desirable as the substrate in the above-described substrate forming step because of irradiating focused light from the substrate side, for example, glass, polycarbonate, polyacrylonitrile, polymethyl methacrylate, Epoxy resins, polypentene and the like can be mentioned. Further, the substrate may be constituted by a single light-transmitting material, or a plurality of the light-transmitting materials may be stacked to form a substrate. Further, the shape of the substrate is usually circular, but is preferably rectangular when a card-type optical recording medium is used. Incidentally, in an optical recording medium in which recording / reproducing or recording / reproducing / erasing is performed by irradiating a converging light from the opposite side of the substrate, it is a matter of course that the substrate is made of a light-impermeable material other than the above-described light transmissive material. May be configured.

The track groove formed on at least one surface of the substrate at a plurality of intervals is similar to a pregroove conventionally formed for focusing and tracking servo control, and is formed spirally or concentrically on a circular substrate. On the other hand, a rectangular substrate is constituted by a group of concave grooves formed in parallel lines. As a method of forming the track groove, there are a method of forming a groove directly on the substrate, and a method of fixing a plurality of protrusions on the substrate and forming the groove by the protrusion and the substrate. That is,
As the former method, for example, a curable resin such as an ultraviolet curable resin is applied on a glass substrate, and a master plate prepared in advance by a precision device such as a laser cutting machine is brought into close contact with the applied surface to transfer and form the groove pattern. Then, the resin is cured to directly form a concave groove, so-called 2P (Ph
oto-Polymer) method, injection method of casting a thermoplastic resin into a mold created based on the above master disk and directly obtaining a substrate with a concave groove, casting method, or patterning photoresist on a glass substrate There is an etching method and the like in which a concave groove is formed by directly etching the thin film, and on the other hand, as the latter method, a thin layer of the curable resin is formed on a glass substrate, and the thin layer is formed into a pattern. To form a convex groove, and a concave groove is formed between the convex line and the substrate. In order to increase the track density, the C / N ratio, and the like with respect to the width dimension T of the track groove, the half-width (Ω2) or less of the focused light spot for recording, preferably about Ω2 / 3 to 2 × Ω2 / 3. On the other hand, in order to increase the track density with respect to the track groove distance TP, when the total width of the focused light spot for recording 1 / e ² is Ωe, it is set to approximately (T + Ωe) / 2. desirable. However, for the purpose of reducing the internal stress of the recording layer and only stabilizing the recording performance, it is needless to say that the setting range is not limited. Further, the depth of the track groove needs to be such a depth that the recording layer forming film in the track groove can remain for the removal processing of the recording layer forming film in the following recording layer forming step. The dimensions are slightly different between when the dry etching method is selected as the recording layer forming step and when the mechanical polishing method is selected, and even when the dry etching method is selected, the type of etching material used, its concentration, etc. However, it is usually set to about 300 to 3000 angstroms.

Next, as the recording material in the recording film forming step, any material widely known as an optical recording material can be used.

That is, Te, Se, S, Sb, As, P, Pb, Sn, Ge, S
i, Tl, In, Ga, Al, Zn, Au, Ag, Cu, Pt, Mo, Ti, N
A simple substance or a compound containing at least one component among elements such as i, Cr, and W, or a material in which they are dispersed in another material can be used. this house
Te, Se-Te, Pb-Se-Te, Te-C, etc. are non-rewritable records.
Suitable for perforated materials that are reclaimed, TeO _X ,
TeO _X (Ge, Sn added), In-Se, In- Sb, In-Te, Sb 2 S
e, Te-Ge-Sn, Te-Ge-Sn-Au, AS 2 S 3, Sb-Te, Te-
N, Ge-Te, Ag-In, Ag-Zn, Cu-Al, Ag-Al-Cu, Cu
-Al-Ni, Au-Ti, Cr-Ti and the like are suitable for a rewritable recording / reproducing / erasing type phase change recording material.

Also, rewritable magneto-optical recording materials include Fe, Co,
Transition metals such as Ni and Mn, and Tb, Gd, Nd, Pm, Sm, Em, E
n, Dy, Ho, Er, Tm, Yb, a magnetic material containing at least one component among rare earth elements such as Lu, typically Tb-Fe-
Co, Tb-Fe, Dy-Fe, Mn-Bi, Pt-Mn-Sb, etc. can be applied.

Further, as a material constituting the recording layer, other than the above, cyanine dyes, phthalocyanine, naphthoquinone, squarylium, polythiophene, organic dye materials represented by polydiacetylene, and spiropyran, fulgide, photochromic material represented by azobenzene and the like. Can be used.

As a means for forming a recording layer forming film on the entire surface of the substrate, for example, a recording material such as the cyanine dye, phthalocyanine dye, and naphthoquinone dye dissolved or dispersed in a solvent such as dichloromethane, benzene, ethyl alcohol, and methyl alcohol. And a dry process such as a vapor deposition method or a sputtering method for directly forming a recording material such as TeO _X , In—Se, and In—Sb directly on the substrate. When the affinity between the substrate and the recording material is low, a base material having an affinity with the recording material may be formed on the substrate as needed.

Next, in the recording layer forming step, a method of removing the recording layer forming film on the substrate and leaving the recording layer forming film in the track groove to form a recording layer includes dissolving the recording layer forming film with an etching material. The dry etching method for removing is suitable, and the etching material is CF ₄ , CCl
Gases to which appropriate amounts of O ₂ , H ₂ , and N ₂ are added based on ₂ H ₂ or CCl ₄ can be used.

Further, this technical means can be applied to a method of manufacturing an optical recording medium having a recording layer only on one side and a method of manufacturing an optical recording medium having a recording layer on both sides. In this case, the latter can be formed by bonding two recording layers to each other with an adhesive or a spacer interposed therebetween, and the adhesive may be a urethane adhesive or an epoxy adhesive. Hot-melt adhesives such as curable silicone resins and ethylene-vinyl acetate resins, and high-frequency adhesives such as polyvinyl chloride resins can be used.

Further, as a light source for recording / reproducing or recording / reproducing / erasing information by irradiating the recording layer of the optical recording medium obtained by this manufacturing method with focused light, a light source used in a conventional method is used. Specifically, semiconductor lasers such as GaAlAs-based semiconductor laser, GaAlInP-based semiconductor laser, GaInAsP-based semiconductor laser, He-Ne laser, Ar laser, and He laser
And a gas laser such as a -Cd laser.

Further, the optical recording medium manufactured according to the present invention can be applied to various uses such as an optical disc for a computer in addition to a music disc such as a compact disc and an image such as a video desk.

According to the technical means described above, the recording layer forming film is formed in the track groove by the recording film forming step of forming the recording layer forming film on the entire surface of the substrate until the surface opposite to the substrate is flattened. Is provided, and the recording layer forming film other than the track groove is removed by the tri-etching method in the recording layer forming step, so that only the recording layer forming film in the track groove remains. Only with high precision, the recording layer can be formed reliably.

[Example] Hereinafter, an example in which the present invention is applied to an optical recording medium having a recording layer on one side will be described in detail with reference to the drawings.

First, a UV-curable resin (for example, a resin in which 1,1-dimethyl-1-phenylacetophenone is attached to acrylate) (11) is applied on a circular glass plate (10), and a laser is applied to the applied surface in advance. A master disk (not shown) made by a cutting machine is closely attached to transfer and form a groove pattern thereof, and then the resin (11) is irradiated with ultraviolet rays to cure the resin (11), thereby forming a substrate (2) having a track groove (3). (See FIG. 1a).

Incidentally, the width dimension (T) of the track groove (3) is set to 5000 angstroms, and its depth dimension is set to 3000 angstroms.

Then, a resin material containing a cyanine dye (trade name: NK-123, manufactured by Japan Photosensitive Dye Laboratories) is spin-coated on the surface of the resin (11) until the surface is flattened (about 4,000).
Angstrom) to form a recording layer forming film (12) (see FIG. 1b), and this recording layer forming film (12)
A dry etching process is performed from the side to remove the recording layer forming film (12) other than the track groove (3) (see FIG. 1C). The dry etching process needs to be stopped when the recording layer forming film (12) other than the track groove (3) is completely removed. That is, the recording layer forming film (12) formed in the track groove has a larger film thickness than the recording layer forming film (12) other than the track groove (3). Even when the recording layer forming film (12) at the portion is completely removed by the dry etching process, the recording layer forming film (12) in the track groove (3) remains to form the recording layer (4). In other words, when the dry etching process is continued even after the recording layer forming film (12) other than the track groove (3) is removed, the recording layer forming film (12) in the track groove (3). Is also etched and removed. Therefore, in the dry etching process, the recording layer forming film (12) in a portion other than the track groove (3)
Need to be stopped when it is completely removed.

In this embodiment, the dry etching conditions are set as follows: etching material: CCl ₂ H ₂ gas, gas pressure: 10 ⁻² to 10 ¹ Torr, and power density: 0.5 W / cm ² .

Thus, an optical recording medium (1) having the recording layer (4) only in the track groove (3) as shown in FIG. 1 (c) was manufactured.

According to the present invention, a recording layer forming film is provided in a track groove by a recording film forming step of forming a recording layer forming film on the entire surface of a substrate until a surface opposite to the substrate is flattened. At the same time, since the recording layer forming film other than the track groove is removed by the dry etching method in the recording layer forming step, and only the recording layer forming film in the track groove remains, the recording layer is formed only in the track groove. It is possible to form the recording layer accurately and reliably.

Therefore, an optical recording medium having a recording layer only in the track groove can be easily and efficiently manufactured.

[Brief description of the drawings]

1 (a) to 1 (c) show an embodiment of the present invention,
FIG. 2 is a process explanatory view showing a manufacturing process of an optical recording medium according to this embodiment. FIGS. 2 to 12 show a conventional optical recording medium, FIG. 2 is a perspective view thereof, and FIG. And FIG. 6 is a perspective view of a partial cross section thereof, FIG. 4 is an illuminance distribution of a light source such as a semiconductor laser and an illuminance distribution of a convergent light spot, FIG. FIG. 8 (a) is a partial sectional view of an optical recording medium, FIG. 8 (b) is a partial plan view thereof, and FIG. 8 (c) is a recording / reproducing semiconductor laser spot. FIG. 8D is a partial plan view of the optical recording medium when the track pitch is minimized, and FIGS.
FIG. 12 is a plan view showing the shape of a recording layer and recording dots, FIG. 12 is an explanatory diagram showing internal stress applied to the recording layer, and FIG.
FIG. 19 to FIG. 19 show another conventional optical recording medium, FIG. 13 is a partial cross-sectional perspective view, FIG. 14 (a) is a partial cross-sectional view of this optical recording medium, and FIG. 14 (b). 14C is a partial plan view thereof, FIG. 14C is an illuminance distribution of a recording / reproducing semiconductor laser spot, FIG. 14D is a partial plan view of an optical recording medium when a track pitch is minimized, and FIG. 17, FIG. 17, and FIG. 19 are plan views showing the shapes of track grooves, recording layers, and recording dots, FIG. 16 is a diagram showing the relationship between a reproduction signal level and time, and FIG. 18 is a carrier signal level in the reproduction signal. And relational diagrams each showing a relationship between the noise signal level and the noise signal level. [Explanation of Symbols] (1) Optical recording medium (2) Substrate (3) Track groove (4) Recording layer

 ──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hiroyuki Hotta 2274 Hongo, Ebina-shi, Kanagawa Prefecture Fuji Xerox Co., Ltd. Ebina Works (56) References JP-A-1-109552 (JP, A) JP-A-63- 152035 (JP, A)

Claims (2)

(57) [Claims] An optical recording medium for optically recording / reproducing information or recording / reproducing / erasing information by irradiating convergent light,
In a method for manufacturing an optical recording medium comprising: a substrate; a track groove formed on at least one surface of the substrate at a plurality of intervals; and a recording layer formed in the track groove, forming the substrate having the track groove A recording layer forming step of forming a recording layer forming film on the entire surface of the substrate on which the track grooves are provided until the surface opposite to the substrate is flattened; and a recording layer on the substrate. A method for forming a recording layer by removing the film by dry etching and leaving a recording layer forming film in the track groove as a recording layer. 2. An optical recording medium according to claim 1, wherein said recording film forming step is constituted by a wet process method using a recording material dissolved or dispersed in a solvent. Production method.