JPH01201838A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium which has a high track density and C/N and decreased medium noises by providing tracks formed of recording layers via intervals on a substrate and setting the width size thereof at about the width equal to the half-amplitude level of a light spot or below. CONSTITUTION:The tracks 4 consisting of the recording layers 3 are formed on the substrate 2 and the width T thereof is set at the half-amplitude level OMEGA2 of the semiconductor laser spot for recording or below. The laser is projected to the prescribed sections of the layer 3 to form recording dots 6 of the width OMEGA2 or below. The width B of the dots 6 is, therefore, the same as the width T of the tracks 4 and since this width is smaller than the width OMEGA2, the track pitch TP can be set smaller and the track density is increased. Since the dots 6 can be formed nearly to a rectangular shape, the waveform distortions at time of reproduction are eliminated and the C/N and jitter are improved; in addition, the layers 3 are not formed except in the tracks 4 and, therefore, the medium noises are decreased. The high-quality medium is thereby obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to optical discs and optical discs that optically record and reproduce information, or record, reproduce, and erase information by irradiating focused light from gas lasers, semiconductor lasers, etc. Regarding optical recording media such as magnetic disks, track density, C/N ratio, etc. are improved, and
The present invention also relates to an improvement of an optical recording medium which has less reproduction noise and servo signal noise and whose recording performance does not deteriorate over a long period of time.

[Prior Art] To explain a conventional optical recording medium using a type having a recording layer on one side as an example, as shown in FIGS. 12 and 13, a pre-group for focusing and tracking servo is used. A transparent substrate (b) on which groove) (a) is applied, a recording layer (C) provided on the entire surface of this substrate (b), and a protective layer (d) provided on the entire surface of this recording JB (c). The main part of the optical recording medium (e) is inputted by recording information from a light source such as a semiconductor laser focused by a condensing lens (f) as shown in FIG. The focused light (CI) is irradiated onto a predetermined portion of the recording layer (C), and the irradiated portion is exposed to the recording layer (C).
This is done by causing a phase change, magnetization reversal, deformation, etc., and forming recording dots (h) (see FIG. 13) having a different reflectance or Kerr rotation angle from the non-irradiated area. In this case, the focused light i) from the light source is recorded above! ! 1
In order to reliably irradiate the predetermined area in (c), focusing and tracking servo control are performed using the pre-group (a), and the width dimension (B) of the recording dot (h) is shown in FIG. The recording dot (
h) is adjusted so that it is stably formed.

On the other hand, when reproducing the recorded information, as shown in FIGS.
e) is irradiated onto the recording surface, and the reflected light is input to a light receiving element (j) such as a photodiode for reproduction. In this case, the light from the entire focused light spot for reproduction is used for reproduction, and typically, as shown in FIG. is considered to contribute to the reproduced signal.

[Problems to be Solved by the Invention] By the way, since the conventional optical recording medium (0) is provided with the recording layer (C) on the entire surface of the substrate (b) as described above, it has various problems as shown below. It had points.

First, the track pitch (TP
) can be set narrowly to the point where signals on adjacent tracks do not mix with the reproduced signal, and its minimum value (TP
・ ) is the result of Figure 18 (
d) to (TPlo) =8/2+ (Ωe-B)/2+8/2=(B+Ωe)
/2.

However, (B) shows the width dimension of the recording dot (h), and (Ωe) shows the 1/e2 full width at the focused light spot for reproduction (i).

On the other hand, conventionally, the width dimension (B) of the recording dot (h) is equal to the half width of the recording focused light spot (i), Ω.
2), in order to improve the track density on an optical recording medium, the focused light (
The only way is to set the spot diameter (Ωe1Ω2) in a) small, and if the spot diameter (Ω2) is set too small, a slight dimensional error on the substrate surface will cause a recording malfunction, so it must be kept below a certain level. Since there are restrictions that cannot be set, there is a problem in that the density improvement described above has a certain limit.

Furthermore, since the recording material constituting the recording layer (C) usually has thermal conductivity, as the scanning of the recording spot progresses, heat tends to leak to the periphery due to the influence of this thermal conductivity, and the recording width decreases. As shown in FIG. 19, recording dots (h
) sometimes took the form of a so-called "teardrop-shaped dot."

For this reason, the reproduced signal is distorted as shown by α in FIG. 5, which tends to cause large jitter, and the C/
There was a problem that the N ratio decreased.

Furthermore, the diameter (Ωe) of the focused light spot for reproduction (+) is larger than the diameter (B) of the recording dot (h) as described above, and moreover, for the optical recording medium (e), its substrate (b) ) Since the recording layer (C) is provided on the entire surface, there is a drawback that the noise of the optical recording medium (e) greatly affects the reproduced signal during reproduction.

That is, as shown in FIG. 20, on the surface of the recording layer (C) of the optical recording medium (e), there are noise generation sites (nl) to (nl) with different reflectances due to defects in the medium itself, crystal grains, etc. There are a large number of noise generation areas (n2) due to the unevenness of the dot shape also at the peripheral edge of the recording dot (h).
(n2) and these noises are mixed into the reproduced signal, which has been an obstacle to improving the C/N ratio of the reproduced signal (see the C/N ratio indicated by α in FIG. 7).

However, C indicates the main 1 serial signal level, and N indicates the noise signal level.)

In addition, in optical recording media for recording, reproduction, and erasing, when erasing recorded information, it is difficult to erase due to factors such as a decrease in sensitivity of the recording layer due to aging, fluctuations in the output of the focused light for erasing, and tracking deviation. As shown in Figure 21, there is a drawback that recorded information cannot be completely erased, but on the other hand,
In order to eliminate this drawback, the spot diameter of the focused light for erasing (Ω
) is set larger than the spot diameter (Ω2) of the focused recording light, there is a problem in that the track density decreases.

In addition, in conventional optical recording media, the recording layer (C) is formed on the entire surface of the substrate (b), so stress during formation of the recording layer (C) and the stress between the substrate (b) and the recording layer (c) are also important. Due to differences in expansion rates, etc., two-dimensional internal stress (St) tends to be applied to the recording layer (C) as shown in FIG. 22, resulting in a problem that the recording performance tends to deteriorate over time.

Incidentally, Japanese Patent Application Laid-Open No. 58-37857 discloses an optical recording medium in which a recording layer is formed in a track shape without forming a recording layer on the entire surface of the substrate, but the means disclosed in this publication is different from the conventional one. The formation of the pre-group for tracking servo in the above is omitted, and this is merely an attempt to reduce the manufacturing cost of the optical recording medium.

Therefore, the above-mentioned publication does not make any mention of the above-mentioned problems, and the above-mentioned problems are still unresolved except for forming the recording layer in a track shape to reduce manufacturing costs. .

[Means for Solving the Problems] The present invention has been made in view of the above-mentioned problems. To provide an optical recording medium with less noise and whose recording performance does not deteriorate over a long period of time.

That is, the present invention is based on an optical recording medium in which information is optically recorded and reproduced, or recorded and erased by irradiation with focused light, and includes a substrate and a recording layer formed on at least one surface of the substrate with a gap therebetween. It consists of multiple tracks,
The width of the track is set to be equal to or less than the half width of the focused recording light spot.

In such technical means, the substrate is desirably made of a light-transmissive material since focused light is irradiated from the substrate side, such as glass, polycarbonate, polyacrylonitrile, polymethyl methacrylate, epoxy resin, polybenthene, etc. can be mentioned. Further, the substrate may be made of a single light-transmitting material, or the substrate may be formed by laminating a plurality of the light-transmitting materials. Furthermore, although the shape of the substrate is usually circular, it is preferably rectangular in the case of a card-type optical recording medium. In addition, this technical means makes it possible to perform focusing and tracking servo control during recording, playback, and erasing by using multiple tracks formed on the recording layer at intervals on the substrate. However, it is also possible to use a substrate that does not have a conventional pre-group. In addition, in optical recording media in which recording/reproduction or recording/reproduction/erasing is performed by irradiating focused light from the opposite side of the substrate, the substrate is naturally made of a light-opaque material other than the above-mentioned light-transmitting material. may be configured.

Further, the recording layer forming tracks on the substrate is composed of a plurality of spirally or concentrically formed strip layers or a single strip layer in the case of a circular substrate,
On the other hand, a rectangular substrate is composed of a plurality of strip-like layers formed parallel to each other.

As a method for forming the recording layer, a method can be applied in which a recording material is uniformly formed on the substrate, and then the recording material is removed from areas other than the tracks.

Specifically, methods for uniformly forming the recording material include, for example, dry processes such as vapor deposition and sputtering in which the recording material is directly formed on the substrate; A wet process for coating and forming on a substrate can be applied.

On the other hand, as means for removing excess recording material formed in areas other than the above-mentioned tracks, etching methods that partially remove it using a solvent, mechanical removal methods such as puff polishing, laser cutting, etc. are applied. can.

Furthermore, as another method for forming a recording layer, a resist layer is formed in a pattern on a substrate, and then a recording material is uniformly formed on the entire surface of the resist layer, and then the resist layer and the layer formed on the resist layer are formed on the substrate. This is also possible by removing the recording material layer.

Note that the width dimension (2) of the recording layer formed by these means, that is, the track, is approximately equal to or less than the half width (Ω2) of the focused recording light spot in order to increase the track density, C/N ratio, etc.
Preferably, it is set to about Ω2/3 to 2XΩ2/3. On the other hand, the track pitch TP is approximately ( T+Ωe)/2
It is desirable to set it to .

Next, as the recording material constituting the recording layer, all materials widely known as optical recording materials can be used.

That is, Te, Se, S,, Sb, As%P, Pb
, Sn, Ge, S i , Tj, 1n1Qa.

AI, Zn, Au, AoS Cu, Pt, Mo, Ti,
A single substance or a compound containing at least one component of elements such as Ni, Cr, and W, or a material in which these elements are dispersed in another material can be used. Of this, 10% is 5e-Te.

Pb-8e-Te, Te-C, etc. are non-rewritable recording/reproducing types. Holes are suitable for shaped materials, and TeO, T
eax (Ge, Sn added), In-x Se, In-8b1 In-Te, 5b2Se.

"re-Ge-3n, Te-Ge-8n-Au, As2
S3.5b-Te, Te-N, Ge-Te.

Aa-1n, Ao-Zn, Cu-Al, Ag-Al-C
u, Cu-Al-Ni, Au-Ti, and Cr-T
i, etc. are suitable for phase change recording materials that are rewritable recording/reproducing/erasing plates.

In addition, rewritable magneto-optical recording materials include Fe, CO
1 Transition metals such as Ni and Mn, and Tb, Gd, Nd, and P
m, Sm1En1Dy, Ho, Er, 4m, Yb, lu
Magnetic materials containing at least one component of rare earth elements such as Tb-Fe-Co, Tb-Fe, Dy
-Fe.

Mn-Bi, Pt-Mn-8b, etc. can be applied.

In addition to the above materials, materials constituting the recording layer include organic dye materials such as cyanine dyes, phthalocyanine, naphthoquinone, squarylium, polythiophene, and polydiacetylene, and photochromic materials such as subpyran, fulgide, and azobenzene. etc. are available.

Furthermore, this technical means can be applied not only to an optical recording medium having a recording layer on one side only, but also to an optical recording medium having recording layers on both sides. In this case, the latter can be formed by placing two recording layers facing each other and bonding them together with an adhesive, and examples of this adhesive include urethane adhesive, epoxy adhesive, and curable silicone. Resins, hot melt adhesives such as ethylene-vinyl acetate resin, high frequency adhesives such as polyvinyl chloride resin, etc. can be used.

On the other hand, in the former case, a protective layer for protecting the recording layer may be provided on the entire surface of the substrate on the recording layer side, and this material may be SiO2, ZnS1zr02, AlN1Si3N.
4th class is available.

In addition, the light source used in conventional methods can be used as a light source for recording/reproducing information or recording/reproducing/erasing information by irradiating the recording layer of this optical recording medium with focused light. GaAlAs semiconductor laser, GaAI
Semiconductor lasers such as InP semiconductor lasers and Ga1nAsP semiconductor lasers, He-Ne lasers, Ar lasers,
Examples include gas lasers such as He-Cd lasers.

Furthermore, the optical recording medium according to the present invention can be applied to various uses such as optical discs for a total of n machines in addition to music recording media such as compact discs, and image recording media such as video desks.

[Function] According to the technical means described above, this optical recording medium can:
It is composed of a substrate and a plurality of tracks formed of a recording layer at intervals on at least one surface of the substrate, and no recording layer is formed between adjacent tracks.
Media noise during playback is reduced, and unerased information is less likely to occur when erasing recorded information, and the recording layer in the track is continuous only in the length direction and not in the width direction, so the recording layer On the other hand, since the width of the track is set to less than the half width of the focused recording light spot, the track pitch can be set smaller, and the shape of the recording dot can be made approximately rectangular. It becomes possible to approximate.

[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. As shown in the figure, a circular glass substrate (2), a track (4) formed by a recording layer (3) provided concentrically on this substrate (2), and the recording layer (3) Side board (2)
The main part is composed of a protective layer (5) uniformly formed on the surface.

The width T of the recording layer (3), that is, the track (4) is the half width (Ω2) of the recording semiconductor laser spot.
[See Figures 3 (b) and (C)] The thickness is set to 5000 angstroms below, and the above record B (3)
is made of 300 angstrom thick TeOx.

Then, while performing focusing and tracking control using the tracks (4) formed by the concentric recording layer (3), a predetermined position of the recording layer (3) is performed as shown in FIGS. A recording semiconductor laser is irradiated onto the site to form recording dots (6) whose diameter is about the half-width (Ω2) of the semiconductor laser spot, and recording information is input.
This recording dot (6) is read by a reproducing semiconductor laser to obtain a reproduced signal.

In addition, (7) in Fig. 1 shows the optical head for reproduction.
A semiconductor laser (71) and the laser beam are transferred to an optical recording medium (
1) A condensing lens (72) that forms an image onto a surface, a beam splitter (73) that polarizes the reflected beam from the optical recording medium (1), a half mirror (74), a servo signal detector (75), and The main part thereof is composed of a reproduced signal receiver (76). Further, as in the conventional case, it is considered that the light in the 1/e2 full width (Ωe) region of the reproducing semiconductor laser spot contributes to the reproduced signal.

Here, this optical recording medium (1) has various effects as shown below compared to conventional optical recording media in which a recording layer is formed on the entire surface of the substrate.

First, this optical recording medium (1) allows the track pitch (TP) to be set significantly smaller than that of conventional optical recording media.

That is, the minimum value of the track pitch (TP
As mentioned above, (TPffiin) =8/2+ (Ωe-B)/2+B/2=(B+Ωe
)/2.

However, (B) shows the width dimension of the recording dot, and (Ωe>) shows the 1/e2 full width of the focused light spot for reproduction.

On the other hand, in this optical recording medium (1), as shown in FIG.
And as shown in (d), the width dimension (B) of the recording dot (6) is the same as the width dimension (T) of the track (4), and this width dimension (T) is different from that of the conventional optical Since it is set smaller than the recording dot diameter (Ω2) in the recording medium, the minimum track pitch (TP', ') of the optical recording medium (1) according to the embodiment and the 1n track pitch of the conventional optical recording medium The relationship with the minimum value (TP, ) is 1n (TP” ・ ) < (TP・ ) 111n 1lIn,
This has the advantage that the track pitch (TP) can be set significantly smaller than in the past, and the track density can be improved.

In addition, in the optical recording medium (1) according to the embodiment, the track (4) is composed of a strip-shaped recording layer (3), so it is different from the conventional "teardrop shape" as shown in FIG. Thus, recording dots (6) having a nearly rectangular shape can be formed.

Therefore, as shown by β in FIG. 5, the reproduced signal waveform during reproduction is not distorted, and this has the advantage of improving both the C/N ratio and jitter compared to the conventional method.

Furthermore, since this optical recording medium (1) does not have a recording layer (3) in any part other than the track (4), medium noise is reduced, and the shape of the recording dots (6) is
The recording dots (
6) has the advantage that reflectance unevenness and magnetic domain distribution unevenness at the boundary are reduced and the C/N ratio of the reproduced signal is improved.

In other words, when the noise of a light source such as a semiconductor laser is sufficiently suppressed, the reproduced signal noise during reproduction generally consists of medium noise caused by defects, crystal grains, etc. in the optical recording medium, and recording noise caused by unevenness in the shape of recording dots. Noise becomes dominant. In this optical recording medium, track (4)
Since the recording layer (3) is not provided in other parts, the medium noise is reduced, and as shown in FIG. 3), recording noise is also reduced because shape irregularities are less likely to occur. Therefore, since the above-mentioned noise signal is less likely to be mixed into the reproduced and raw signal, the C/N ratio has the advantage of being significantly improved as shown by β in FIG.

In addition, in this optical recording medium (1), the recording dot (6)
Since the width dimension (T) of the carrier signal is narrower than that of the conventional one, the carrier signal level C decreases slightly as shown in FIG.
Since the noise signal level N is also significantly reduced, the C/N ratio increases as a result. Furthermore, since servo signal noise is similarly reduced, it also contributes to stabilization of servo control. In particular, tracking servo control has the advantage of being able to set a large difference in reflectance between the track section and the tracks, and also greatly stabilizing the structure.

Furthermore, when the present invention is applied to an optical recording medium for recording, reproduction, and erasing, conventional causes such as a decrease in sensitivity of the recording layer due to deterioration over time, fluctuations in the output of the focused light for erasing, and tracking deviation are caused. However, as shown in Fig. 8, there is no recording layer (3) in the area where unerased information occurs, so it has the advantage that no unerased information occurs. ing.

Further, a strip-shaped recording layer (3) constituting the track (4) is also provided.
) is continuous only in the length direction and not in the width direction, so the internal stress (St) of the recording layer (3) becomes -dimensional and is significantly alleviated as shown in Fig. 8. When the recording material is of a phase change type, the atomic movement processes of crystallization and amorphization in the recording and erasing process also proceed one-dimensionally, making it difficult for composition fluctuations and in-plane composition variations in the recording layer (3) to occur. In addition to the stability of the recording layer (3) and recording bits, it has the advantage of improved repeatability and stable recording performance over a long period of time. This process has the advantage of speeding up each process and enabling high-speed recording and erasing.

◎Manufacture of optical recording medium A method of manufacturing the optical recording medium (1) according to the example will be described below.

(First manufacturing method example) First, a circular glass substrate (2) shown in FIG. 9(a)
A positive type 7-otoresist material (manufactured by Hoechst, trade name AZ1350J) was applied onto the surface using a spin code method, and a 2000 angstrom thick 7-otoresist layer (
10) (see Figure 9). Next, the photoresist layer (10) at the exposed area is changed in quality by exposure through a photomask (not shown) and made soluble in an alkaline aqueous solution as a developer, and the first exposed area is dissolved and removed by the alkaline aqueous solution to form a width. A groove (11) having a T of 5000 angstroms and a depth of about 2000 angstroms is formed (see FIG. 9C). The depth of the groove (11) is 500 to 6000 angstroms, preferably 10 angstroms.
It is desirable to set the thickness to about 0.00 to 4000 angstroms.

The reason for this is that the recording layer (3) is formed at a predetermined location based on the following steps using the step of the groove (11).
This is because if the depth dimension is too shallow, it becomes impossible to remove the recording film between the tracks (5), while if it is too deep, it becomes difficult for the recording film to adhere to the shadow part of the step.

Next, a 300 angstrom thick TeO thin layer (12) is deposited on the side surface of the photoresist layer (11) of the substrate (2).
is uniformly formed by a vapor deposition method (see Figure 9d). Furthermore, this? The layer thickness of the first layer (12) varies depending on the type of recording material, but is usually 100 to 200 mm.
It is set to about 0 angstrom. Furthermore, if the substrate (2) has a weak affinity with the recording material, a base material may be coated on the surface of the substrate (2) if necessary.

Next, the photoresist layer (10) in the exposed area and the thin layer (12) on the photoresist layer (10) are dissolved and removed using an organic solvent such as acetone, and a width T of 5 is formed on the substrate (2).
A recording layer (3) having a thickness of 300 angstroms and a thickness of 300 angstroms is formed (see FIG. 9e).

Furthermore, as shown in FIG. 9(f), a protective layer (5) made of SiO2 is formed on the surface of the substrate (2) on the side of the recording layer (3).
An optical recording medium (1) was manufactured which includes tracks (4) formed by recording layers (3) arranged concentrically on a substrate (2).

(Second manufacturing method example) First, a circular glass substrate (2
), a 300 angstrom thick TeOx thin layer (20) doped with Qe and 3n was formed uniformly by vapor deposition, and a photoresist material (manufactured by Hoechst) was deposited on the surface by spin cording. name A11350J)
A photoresist layer (21) having a thickness of 5000 angstroms is formed (see FIG. 10C).

Next, as shown in FIG. 10(b), a photomask (22) prepared by patterning thin Cr I was brought into close contact with the photoresist layer (21), and then an excimer laser beam using KrF was applied. (wavelength 2490 angstroms)
is irradiated to partially change the photoresist layer (21) to be soluble in a developer, and the master pattern is transferred.

In addition to the above, the exposure light source may include excimer laser light (wavelength: 3080 angstroms) using XeC1;
X-rays etc. can be used. Moreover, instead of bringing the photomask (22) into close contact with the surface of the photoresist layer (21), the photoresist layer (21) and the photomask (22)
An imaging lens may be interposed therebetween, and the master pattern may be transferred by projection exposure.

Next, the exposed portion of the photoresist layer (21) is dissolved and removed using an alkaline aqueous solution as a developer, and the width T is 5000.
Form a track pattern of angstroms (first
(See Figure 0C). Furthermore, the above TeOx il! (20) is protected by the remaining photoresist layer (21) and etched to remove the exposed TeOx i.
The EI layer (20) is dissolved and removed (see Figure 10C). Here, as the etching method, a dry etching (reactive ion etching) method using CCl2H2 as an etching gas was used. In addition, instead of dry etching method
A wet etching method using a solvent mainly composed of C,1 may be applied.

Next, the remaining photoresist layer (21) is dissolved and removed using an organic solvent such as acetone, and then the recording layer (21) is removed.
3) A protective layer (5) composed of SiO2 is uniformly formed on the side substrate (2) surface, and tracks are formed with a recording layer (3) provided concentrically on the substrate (2). (4
) was produced (see FIG. 10C).

In this manufacturing method example, a photomask (22) is used to transform the photoresist II (21) into a track pattern. A method may also be adopted in which the surface of the photoresist layer (21) is irradiated track by track with a focused laser beam while rotating, thereby changing the photoresist layer (21) into a developer-soluble one in a track pattern. In this case, Ar laser light (wavelength 4579 angstroms), Kr ion laser light (wavelength 4131 angstroms), and He-Cd laser light (1 length 4416 angstroms) are used.
．． It is possible to use a laser beam such as a laser beam such as a laser beam (e.g.

(Third manufacturing method example) This method is performed by a laser cutting process in which a thin layer of TeOx formed on the entire surface of a glass substrate (2) is irradiated with a laser beam, as shown in FIGS. 11(a) to (, C). A recording layer (3) is formed by partially removing it, and an optical recording medium (1) in which a spiral track (4) can be seen is manufactured.

In this case, a method is adopted in which a groove (30) for tracking servo is formed in the substrate (2) to ensure that the laser beam is irradiated to a predetermined location.

In addition, the groove (30) is used during the laser cutting process as described above, and is not used when recording or reproducing the optical recording medium (1). As shown in Figure (b), the width dimensions of the groove (30) and the recording layer (3) do not have to match.

[Effects of the Invention] As described above, the present invention makes it possible to set the track pitch to a smaller value, reduce medium noise, and approximate the shape of the recording dots to a rectangular shape. It not only makes it possible to improve the C/N ratio and jitter, but also has the effect of reducing reproduction noise, etc. Moreover, since the internal stress of the recording layer is reduced, recording performance deteriorates over a long period of time. It has no effect.

[Brief explanation of the drawing]

1 to 11 show embodiments of the present invention.
The figure is a perspective view of an optical recording medium according to an embodiment, FIG. 2 is a partial cross-sectional perspective view thereof, FIG. 3(a) is a partial cross-sectional view of the optical recording medium, and FIG. 3(b) is a partial plan view thereof. Figure 3 (C) shows the illuminance distribution of the recording and reproducing semiconductor laser spot, Figure 3 (d)
) is a partial plan view of the optical recording medium when the track pitch is minimized, FIGS. 4, 6, and 8 are plan views showing the shapes of the recording layer, tracks, and recording dots, and FIG. 5 is a plan view of the optical recording medium when the track pitch is minimized. A diagram showing the relationship between signal level and time. Figure 7 is a diagram showing the relationship between the carrier signal level and noise signal level in the reproduced signal. Figures 9 (a) to (f) are manufacturing examples of optical recording media. 10(a) to (e) are process explanatory diagrams showing a second manufacturing example of an optical recording medium, and FIG. 11(a)
12 to 22 show conventional optical recording media, and FIG. 12 is a perspective view thereof. Figures 13 and 16 are partial cross-sectional perspective views, Figure 14 is the illuminance distribution of a light source such as a semiconductor laser and its convergent light spot, Figure 15 is an enlarged view of I in Figure 14, and Figure 17 is an enlarged view of I in Figure 14. Explanatory diagram when reproducing an optical recording medium, FIG. 18(a)
18(b) is a partial plan view of the optical recording medium, FIG. 18(C) is the illuminance distribution of the recording and reproducing semiconductor laser spot, and FIG. 18(d) is the minimum track pitch. Partial plan view of the optical recording medium in the case of
FIG. 21 is a plan view showing the shapes of tracks, recording layers, and recording dots, and FIG. 22 is an explanatory diagram showing internal stress applied to the recording layer. [Explanation of symbols] (1)... Optical recording medium (2) -... Substrate (3)... Recording layer (4)... Track (5)... Storage layer (6)...・Recording dot (7)... Optical head patent Applicant: Fuji Xerox Co., Ltd. Agent: Patent attorney: Tomohiro Nakamura (3 others) Figure 1 Figure 3 Figure 4 Figure 5 Time Figure 6 Fig. 7 Reproduction signal level (dB) Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 14 Fig. 15 Fig. 16 Fig. 17 Fig. 19 Fig. 20 Fig. 21 Fig. 22

Claims (2)

[Claims] (1) An optical recording medium that optically records, reproduces, or erases information by irradiating it with focused light, which includes a substrate and a plurality of recording layers formed at intervals on at least one surface of the substrate. an optical recording medium, characterized in that the width of the track is set to be approximately equal to or less than the half width of a focused recording light spot. (2) The track pitch is set to approximately (T+Ωe)/2, where T is the width of the track and Ωe is the 1/e^2 full width of the focused recording light spot. An optical recording medium according to claim 1.