JPH0660423A - Thin optical recording medium - Google Patents

Abstract

PURPOSE:To decrease surface vibration of the recording medium and to improve C/N, erasing ratio characteristics and rewriting life by using a flexible substrate having a rugged pattern part to generate optical signals. CONSTITUTION:The thin optical information recording medium consists of a flexible substrate 1 having preformat of pits 100 for servo, and a recording medium layer 2. By forming the recording medium layer 2 on the substrate, deformation of the substrate during film forming can be prevented, and thereby, tracking performance and rewriting characteristics of the thin information recording medium can be improved. By this constitution, tracking performance of recording and reproducing and thermal fatigue characteristics of the recording medium film can be improved to prevent peeling or cracking, and moreover, C/N and erasing ratio chatracteristics of the optical disk and rewriting life are increased.

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 such as an optical disk, and more particularly to a thin optical recording medium having high sensitivity and long life even when the optical recording medium is made small and thin.

[0002]

2. Description of the Related Art An optical recording system using an optical disk or the like is vigorously developed as a recording medium that can replace conventional magnetic disks because it can perform high-density recording and can read and write at high speed without contacting the medium.

As a rewritable optical disc, a magneto-optical system and a phase-change recording medium system utilizing the phase change of crystals are known. The magneto-optical method is a combination of light and magnetism, in which the local magnetic anisotropy of the medium near the Curie temperature is reversed and recorded, and the magnetic Faraday effect and the magnetic field of the polarized incident light at that portion are recorded. It is reproduced by the amount of rotation of the polarization plane due to the Kerr effect, and has already been put to practical use. However, in this method, since both the optical and magnetic heads are used, it is difficult to reduce the weight and size of the optical head.

On the other hand, in the case of the phase change type recording medium system, the phase change between crystals or the phase change between amorphous and crystal is utilized. As the medium used for the former, Cu-Al-Ni described in JP-A-60-46339 is used.
Alloys and In-Sb alloys are known. The medium used for the latter is mainly a chalcogenite-based substance,
For example, it is described in JP-B-47-26897. Further, tellurium compounds are disclosed in JP-A-60-253034, and In is disclosed in JP-A-63-251290.
-Sb-Te based alloys are described respectively.

On the other hand, when the optical disk is used as a memory of a laptop computer or other portable information processing device, it is required to make the recording medium thinner. In order to reduce the thickness of the recording medium, it is necessary to reduce the thickness of the substrate of the optical recording medium from 1.2 mm to 1.2 mm or less. Here, if the substrate is thinned, as the substrate becomes thinner,
Deformation of the substrate due to film formation stress during film formation of the recording medium is remarkable. Such a deformation of the substrate increases the surface wobbling of the recording medium and impairs the tracking performance at the time of recording / reproducing, the C / N of the recording / reproducing signal, or the rewriting characteristic, and therefore a countermeasure is required.

As a technique for thinning the substrate, Japanese Patent Application Laid-Open No. 60-79581 discloses an example using a thin metal substrate on which a preform for a servo is not formed.

Further, an optical information recording medium, particularly an optical disc using a phase change recording medium, is provided with a dielectric film in order to utilize the interference effect of light for the purpose of improving recording / reproducing characteristics, It is generally practiced to further provide a reflective film to enhance the effect. For example, JP-A-63
The rewritable optical disk described in Japanese Patent Application Laid-Open No. 251290 uses an In-Sb-Te based alloy as a recording medium and is a transparent rigid substrate / dielectric film / In-Sb-Te recording medium / dielectric film / reflection film / protection. It is composed of layers. As the dielectric film, a nitride, an oxide, a sulfide, a carbide or a boride of silicon, zirconium, aluminum, zinc, titanium, tantalum or the like having a large refractive index and transmittance is used. The reflective film is usually made of aluminum, gold, silver, copper,
A high reflectance material made of platinum, nickel or an alloy thereof is used.

[0008]

As described above, when the dielectric film or the reflective film is formed for the purpose of improving the characteristics of the optical disc, a large film forming stress acts on the rigid substrate. The film-forming stress acting on this rigid substrate often deforms the rigid substrate, impairing the tracking performance at the time of recording / reproducing, the C / N of the recording / reproducing signal, or the rewriting characteristic.
In particular, when the rigid substrate of an optical recording medium is thinned from 1.2 mm to 1.2 mm or less as a memory of a laptop computer or other portable information processing device, the thinner the rigid substrate is, the more deformed the recording medium is. The amount increases. As described above, such deformation of the rigid substrate impairs the tracking performance at the time of recording / reproducing, the C / N of the recording / reproducing signal, or the rewriting characteristic, and therefore a countermeasure is required.

On the other hand, as an example of using a thin substrate, an example using a thin metal substrate on which a preformat for a servo is not formed is described in Japanese Patent Laid-Open No. 60-79581. In this case, since the substrate preform is not formed on the substrate, it cannot be applied as a recording medium of the portable information processing device. Further, in the case of a metal substrate, it has been difficult to form a servo preform on the metal substrate.

The object of the present invention is to solve such a problem,
An object of the present invention is to provide an information recording medium which has less surface wobbling and which has a good C / N and erasing ratio characteristics and a good rewriting life.

[0011]

SUMMARY OF THE INVENTION The present invention provides a multi-layered optical recording medium for the purpose of improving the recording / reproducing efficiency of an optical disc and increasing the reliability thereof. In order to be suitable as a memory for other portable information processing devices, when the thickness of the optical recording medium is reduced from 1.2 mm to 1.2 mm or less, the deformation due to the film formation of the substrate is prevented, It improves the tracking performance at the time of recording / reproducing, the C / N of the recording / reproducing signal, or the rewriting characteristics.

To achieve the above object, according to the present invention, in an optical recording medium having a substrate and a recording layer for storing an optical signal, the substrate being provided with an optical signal. There is provided an optical recording medium characterized by being a flexible substrate provided with an uneven portion for transmitting.

[0013]

When the recording layer is formed on the substrate, film-forming stress is generated in the recording layer, so that the rigid substrate is deformed by the action of the film-forming stress. In particular, the film structure of the optical recording medium
For example, when a multilayer film structure of transparent rigid substrate / dielectric film / recording medium film / dielectric film / reflection film / protective layer is used as in the prior art, film formation stress is generated in each layer. The rigid substrate is deformed by the action of the film stress. The deformation of the rigid substrate increases as the number of film forming layers increases and the thickness of the film forming layers increases. This is because the film forming stress in each film forming layer is added to the deformation of the rigid substrate. Therefore, the thinner the rigid substrate is, the greater the film forming stress is, and the deformation of the thin optical recording medium is increased.

Here, in order to prevent deformation of the recording medium,
It is necessary to reduce the film formation stress caused by the difference in shrinkage between the rigid substrate and the film formation material during film formation. Therefore, as a means for reducing the film formation stress in the sputter film formation method, an attempt was made to reduce the film formation stress by changing the sputtering conditions such as sputtering current and voltage or sputtering gas. However, it has been impossible to prevent the deformation of the rigid substrate even if the sputtering conditions are changed variously.

Therefore, the inventors have found the present invention as a result of various studies on a method for preventing the deformation of the substrate. That is, in the case of forming a film on the recording medium by the sputtering method,
When a substrate having high rigidity is used as the substrate, the film formation stress derived from the film formation increases with an increase in the film formation amount. Thus, when the above-mentioned recording medium is formed into a film on a rigid substrate by the sputtering method, the deformation of the substrate caused by the film forming stress of the sputtering cannot be reduced, but when a flexible substrate with low rigidity is used as the substrate. Have found that the film-forming stress derived from each film-forming layer of the recording medium is reduced, and the deformation of the substrate can be prevented. That is, it has been found that when a flexible substrate having low rigidity is used as the substrate, each film forming layer can be formed without deteriorating the flexible characteristics of the substrate, and therefore deformation of the substrate due to film forming stress can be prevented. Sputter deposition on this flexible substrate
It has been confirmed that even when a plurality of materials and film forming layers are formed, the same film forming behavior as in the case of single layer film formation is exhibited.

Here, when a flexible substrate having a small rigidity is used as the substrate of the optical recording medium, the optical recording medium can be formed into a film on the substrate while having the flexible characteristics, so that tracking performance and recording can be performed on the substrate. Playback signal C /
Deformation such as warpage or the like of the substrate, which is a factor that impairs N or rewriting characteristics, is reduced.

Therefore, by forming the optical recording medium layer on the flexible substrate, it is possible to provide a thin optical recording medium suitable as a memory for a laptop computer or other portable optical information processing device.

As described above, only the optical recording medium in which the optical recording medium layer is formed on the flexible substrate can be sufficiently applied as a suitable memory for the above-mentioned laptop computer and other portable information processing devices.

Further, in the recording medium of the present invention, after forming an optical recording medium layer on a flexible substrate on which a preformat for outputting an optical signal for servo is formed, a rigidity of the flexible optical recording medium and that of the flexible optical recording medium are formed. By bonding the protective substrates together, it is possible to fabricate a thin optical recording medium having a small amount of deformation such as warpage.

That is, as described above, when the conventional rigid substrate is thinned to 1.2 mm or less, the flexible substrate is used to prevent the deformation of the substrate due to the sputter deposition, which increases as the rigid substrate becomes thinner. A thin optical recording medium having rigidity is provided by bonding a flexible substrate on which an optical recording medium is formed into a film to a rigid substrate.

In the thin optical recording medium of the present invention produced by bonding the above-mentioned flexible substrate on which the recording medium is formed into a film and the rigid substrate, the preform for the servo is formed on the flexible substrate. It That is, a rigid substrate having a preform for servo,
When making a thin optical recording medium with a flexible substrate,
When the recording medium is directly formed on the thin rigid substrate, the deformation of the substrate due to the film forming stress cannot be prevented as described above. Therefore, the recording recording medium layer is formed on the flexible substrate to prevent the deformation of the substrate. There is a need to.

In this case, if the preform is formed on a rigid substrate, the recording medium is formed on a flexible substrate on which the preform is not formed, and these are adhered, the following drawbacks occur. That is, when a thin optical recording medium is manufactured by laminating a flexible substrate having a recording medium layer formed on a rigid substrate formed by the preformat, the preformat and the recording medium layer are separated by an adhesive layer formed by the lamination. This is because it becomes difficult to obtain the simultaneous focus of the preformat and the recording medium layer. Of course, when the simultaneous pre-focus between the pre-format and the recording medium layer cannot be obtained, C /
Since N, or various characteristics such as tracking performance deteriorate,
It cannot be applied as a memory of a portable information processing device. Therefore, the thin optical recording medium of the present invention is characterized in that the recording medium is formed into a film on a flexible substrate on which a preform for a servo is formed.

Here, the flexible substrate may be transparent or opaque, but when a reflective film and an interstitial film are used, the recording layer of the thin optical recording medium depends on the transparency or opacity of the substrate used for the thin optical recording medium. The film composition is different. That is, when a transparent substrate is used, an optical recording medium layer is formed on the substrate from the side on which light is incident with the film configuration of optical interference film / optical recording film / optical interference film / light reflecting film. However, when an opaque substrate is used, light is necessarily incident from the opposite side of the opaque substrate, and therefore the optical recording medium layer is an opaque flexible substrate / light reflecting film / optical interference film / optical recording medium film / light. The optical recording medium layer is formed with the film structure of the interference film.

That is, as described above, according to the present invention, as a result of various studies on the problem that the recording / reproducing characteristics of the optical recording medium are deteriorated and the problem that the information rewriting life is shortened, the deformation of the substrate derived from the rigid substrate is prevented. This is based on the discovery by experiments described later that the reduction can be achieved by applying a flexible substrate. That is, as shown in FIG. 3, it has been found that when the substrate is thin and the film is formed by sputtering on a flexible substrate, the deformation of the substrate due to the film formation by sputtering can be significantly reduced.

Generally, in the case of an optical recording medium using a phase change recording medium, information is recorded and reproduced by utilizing the phase change between amorphous and crystalline. In this case, the amorphous state of the recording medium is used. In order to cause a reversible phase change between the quality and the crystal, the recording medium is repeatedly heated to a high temperature above the melting point.

Therefore, the optical interference film formed in contact with the recording medium undergoes a large thermal strain due to repeated expansion and contraction accompanying the melting and solidification of the recording medium. In the optical recording medium using the phase change recording medium, when recording and reproducing information repeatedly, due to the repeated action of this thermal strain,
Thermal fatigue occurs, and peeling or cracking easily occurs in the optical interference film. In this case, when film forming stress remains in the constituent films of these optical recording media, peeling or cracking of the constituent films is promoted.

If peeling or cracking occurs in the constituent film of the optical recording medium, the recording layer melts and flows out at the time of recording melting, and the interference effect of the dielectric film is reduced. Come different. For this reason, the C / N and erase ratio characteristics of the optical disk and the rewriting characteristics are deteriorated. However, according to the present invention, a flexible substrate is used as a substrate for forming the optical recording medium to reduce the film forming stress of each recording layer. The thin optical recording medium improves the tracking performance of recording / reproducing and the thermal fatigue property of the recording medium constituting film, prevents the occurrence of peeling or cracking, and increases the C / N and erasing ratio characteristics of the optical disc and the rewriting life. .

[0028]

Embodiments of the present invention will be described below with reference to the drawings.

Example 1 FIG. 1 shows a schematic sectional view of a thin optical information recording medium of an example of the present invention. The thin optical information recording medium of FIG. 1 comprises a recording medium layer 2 on a flexible substrate 1 on which servo pits 100 are preformatted. By forming the recording medium layer 2 as a film, the deformation that occurs in the substrate during the film formation is prevented, and the tracking performance and rewriting characteristics of the thin optical information recording medium are improved. By forming a recording medium layer on the flexible substrate 1,
The reason for reducing the deformation amount of the substrate 1 will be described later.

Next, referring to FIG. 2, as another embodiment of the present invention, in order to impart a horizontal holding force to the thin optical information recording medium shown in FIG. 2 shows a basic cross-sectional schematic diagram of a thin optical information recording medium.
With this film structure of the thin optical information recording medium of FIG. 2, it is possible to manufacture a thin optical information recording medium which has flexibility of the substrate 1 and rigidity of the protective substrate 4 and has a reduced deformation amount of the substrate. . That is, the amount of deformation of the recording medium layer 2 is reduced by forming the recording medium layer 2 on the flexible substrate 1, and the adhesive layer 3 made of an adhesive is used on the recording medium layer 2 to provide a rigid protective substrate. By bonding 4 to each other, a rigid thin optical information recording medium is manufactured. Of course, if a flexible substrate is used as the protective substrate 4, a flexible thin optical information recording medium can be manufactured.

The present embodiment is intended to provide a thin optical information recording medium suitable for a small-sized information processing apparatus, and its gist will be described below. That is, when the optical disk is used as a memory of a laptop computer or other portable information processing device, it is required to make the recording medium thin. In order to make the recording medium thinner, it is necessary to make the substrate of the optical recording medium thinner than before. However, if the substrate is thin, in the case of the conventional rigid substrate, the deformation due to the film formation stress when forming the recording medium is remarkable. Such deformation of the substrate increases the surface wobbling of the recording medium and impairs the tracking performance at the time of recording / reproducing, the C / N of the recording / reproducing signal, or the rewriting characteristic, and therefore a countermeasure is desired.
This embodiment provides a novel technique for reducing the deformation of the substrate, which is caused when the recording medium is formed, by forming the recording medium on the flexible substrate. This is based on the finding that the deformation of the substrate, which was difficult to avoid when the recording medium is formed on the rigid substrate, can be reduced by forming the recording medium on the flexible substrate. . That is, as will be described later with reference to FIG. 3, as a result of various investigations and examinations regarding the flexibility of the substrate 1 and the deformation of the substrate 1 after the recording medium layer 2 is formed, the substrate 1 having flexibility has the recording medium layer 2 It was discovered that the film formation stress during the film formation is relaxed and the substrate deformation is reduced.

FIG. 3 shows plastic substrates 1 having different thicknesses.
The results of investigation of the deformation amount of the substrate when the recording medium layer 2 is formed and formed are shown in FIG. In FIG. 3, PMMA (polymethylmethacrylate) with a diameter of 64 mm is used as the plastic substrate 1.
No. described in Table 1 to be described later. 9 shows the results of investigation of the deformation amount of the substrate when the recording medium layer 2 having the film configuration D1 is formed.

As is apparent from FIG. 3, it is known that the deformation of the substrate 1 is significantly reduced when the thickness of the substrate 1 is 0.3 mm or less. In the case of PMMA (polymethylmethacrylate), it has good flexibility with a thickness of the substrate 1 of 0.3 mm or less. From this experimental result, it is confirmed that the flexible substrate 1 is a film-forming substrate for a thin optical information recording medium. It was found that the application as No. 1 is effective. In addition, in FIG. 3, a PMM is used as a film formation substrate of the recording medium.
An example of the result of investigation of the deformation amount of the substrate in the case of A is shown.
It has been confirmed that a thin optical information recording medium with less deformation can be produced by using the flexible substrate 1 when the recording medium layer 2 is formed, not limited to MA.

As described above, by forming the recording medium layer 2 on the flexible substrate 1, a thin optical information recording medium with little deformation can be manufactured with the film structure shown in FIGS. In principle, all of these are stored in a cartridge and applied as a measure against dust.

Here, the flexible substrate 1 may be either transparent or opaque as long as it has flexibility according to the application conditions described later. That is, first, when light is incident on the thin optical recording medium from the flexible substrate 1 side, it is necessary to use a transparent material for the flexible substrate 1. As a transparent flexible substrate,
PMMA (polymethylmethacrylate) thinned into a shape
An acrylic resin or an epoxy resin represented by PC or PC (polycarbonate) is suitable.

When light is incident from the transparent flexible substrate 1 side, the protective substrate 4 shown in FIG.
Is not particularly concerned with the transparency and rigidity of the material. If a material having rigidity is used for the protective substrate 4, a thin optical information recording medium having rigidity can be manufactured as described above. As a material of the protective substrate 4, a lightweight and high-strength aluminum alloy, a metal material such as stainless steel having excellent corrosion resistance, or polyvinyl chloride,
Thermoplastic resins such as polyethylene, phenolic resins, thermosetting resins such as unsaturated polyesters and silicon resins, mixtures of these polymers, and composite plastics combined with a reinforcing material are used.

Then, the incidence of light on the thin optical recording medium is
When the flexible substrate 1 is formed on the opposite side of the flexible substrate 1, the flexible substrate 1 may be either transparent or opaque as long as it has flexibility. However, it is necessary to use a transparent material for the protective substrate 4 shown in FIG. In this case, the protective substrate 4 may be a transparent substrate, and transparent plastic such as acrylic resin or epoxy resin typified by PMMA or PC described above and glass are applied.

In this case, the flexible substrate 1 may be any material as long as it is flexible and has good adhesion to the recording medium layer 2, for example, PMMA, PC, polyester, polyvinyl chloride, polyamide, etc. described above. Is preferred. These have excellent workability when forming the pits 100 on the flexible substrate, and all have excellent flexibility when the substrate 1 is thin. Here, the flexibility of these substrates 1 is more excellent as the substrate thickness is smaller, but if the substrate thickness is less than 0.01 mm, defects such as pinholes occur in the substrate, and thus the above-mentioned thin type It is not preferable as a flexible substrate for an optical information recording medium. Further, if the thickness of the substrate 1 is thicker than 0.3, the flexible characteristics of the substrate 1 are deteriorated, which is not preferable as the flexible substrate of this embodiment. Therefore, when the flexible substrate 1 applied to the thin optical information recording medium is made of the above-mentioned organic material, the substrate thickness is 0.01.
It is preferable to set it in the range of mm to 0.3 mm.

In the case of the film structure shown in FIG. 2, the protective substrate 4 is attached by using the adhesive layer 3 made of an adhesive,
For this adhesive, a room temperature and thermosetting epoxy adhesive, a hot melt adhesive, and an ultraviolet curing adhesive are suitable.

When light is incident from the transparent protective substrate 4 side, the amount of information can be increased by forming a structure in which transparent flexible substrates are attached to both surfaces of the protective substrate 4. However, when the light is incident from the transparent flexible substrate 1 side, the thickness of the flexible substrate is thin in the range of 0.01 to 0.3 mm, and therefore, as a measure against dust that causes a light focusing error, The thin optical recording medium is used by being housed in a cartridge described later.

In the thin optical recording medium having the film structure shown in FIGS. 1 and 2, even when the substrate is thinned, the recording medium having a small amount of substrate deformation and film-forming stress is formed into a film. The thin optical recording medium having good characteristics can be obtained.

Example 2 A process for manufacturing a flexible substrate having guide grooves or pits for servo preformed as used in this example will be described below with reference to FIGS. 4 and 5. 4 and 5 are perspective views showing a manufacturing process of the flexible substrate for forming the pre-format such as the guide groove and the pit described above. As shown in FIGS. 4 and 5, the manufacturing apparatus includes two belt drive rolls 10.
And a stamper transport belt 7 wound around two belt drive rolls 10. A plurality of stamper support bases 13 that support the stamper 6 are attached to the stamper transport belt. A heating plate 8 and a cooling plate 9 are arranged below the stamper conveying belt 7. In addition, a sheet transport roll 11 for transporting the substrate
Are arranged.

As shown in FIG. 4, first, the flexible sheet 5 is conveyed onto the heating plate 8 by the driving roll 11 and heated to the softening temperature or higher. A pre-format such as a guide groove and a pit is stamped and formed by a stamper 6 on the flexible sheet 5 heated above the softening temperature. Next, the flexible sheet 5 is conveyed on the cooling plate 9 while being marked by the stamper 6 and cooled to a temperature of about 50 ° C., and then the flexible sheet 5 and the stamper 6 are separated. Further, although not shown in the drawing, the stamp forming portion of the preformat is punched out to manufacture a flexible substrate.

Here, the above-mentioned thermoplastic plastic material is used for the flexible sheet 5, but when light is incident from the flexible substrate side, a transparent PMMA is used.
(Polymethylmethacrylate) and PC (Polycarbonate)
Acrylic resin or epoxy resin represented by G) is suitable. However, when light is not incident from the flexible substrate side, any material having thermoplasticity may be used. Also, the peeling of the flexible sheet 5 and the stamper 6 is 50
A good preformat can be formed when applied at a temperature near ℃. That is, when peeling is carried out at a temperature of 50 ° C. or higher, deviation of the size or shape of the preformat easily occurs due to elongation of the sheet during peeling. Further, when the peeling temperature is low, the marking transfer accuracy of the preformat is good, but on the other hand, the peeling is difficult. Therefore, the peeling temperature of the stamper 6 from the flexible sheet 5 is 50
-20 ° C is preferred.

The stamper 6 is a flexible sheet 5
When the preformat is imprinted and transferred, the stamper 6 needs to be imprinted and transferred under the same stress condition at each position of the stamper 6. That is, when the stamper 6 and the flexible sheet 5 have different stress states at corresponding positions during the imprint transfer, the imprint transfer accuracy decreases.

Therefore, as shown in FIG. 5, the stamper 6 is preferably installed on a rigid stamper support and mounted on the conveyor belt of the stamper. FIG. 5 shows an example of how the stamper is mounted on the stamper transport belt. In the figure, 6 is a stamper, 7 is a stamper conveyor belt,
12 is a roll and 13 is a stamper support. As shown in the figure, by mounting the stamper 6 on the conveyor belt 7 via the stamper support base 13, the flexible sheet 5 can be mounted.
It has been confirmed by an experiment that the accuracy of the imprinting on the stamp is significantly improved. This is because when the conveyor belt 7 is mounted via the stamper support base 13, the opposition between the stamper 6 and the flexible sheet 5 is improved, and by providing the stamper support base. This is because it becomes easy to apply stress to the stamper by means of rolls, rolls or the like. When the stamper 6 is mounted on the stamper support base 13, the stamp transfer accuracy is better when a plurality of stampers 6 are mounted than the single stamper.

Example 3 The film structure and film forming method of the recording medium layer 2 of the thin optical recording medium of Example 1 described above will be described below. First, the gist of the film structure of the recording medium layer 2 of the thin optical recording medium will be described with reference to FIGS. According to the experiments by the authors, when a phase change recording medium is used as the recording medium of the thin optical recording medium, C /
In order to improve N and erase ratio characteristics or rewriting characteristics, it is effective to provide a dielectric film serving as an interference film for utilizing the light interference effect or to have a multilayer film structure provided with a reflection film. I know there is.

6 to 11 are schematic cross-sectional views of the recording layer 2 of an example of the thin optical recording medium of the present example having a multilayer film structure. As shown in FIGS. 6 to 11, on the transparent flexible substrate 1a or the opaque flexible substrate 1b, the light interference films 14 to 18, the recording medium film 19, and the light reflection film 20 are laminated on the protective substrate 4a or 4b. . Here, the optical interference films 14 to 15 are formed in front of the recording medium film 19 with respect to the light incident direction, and the optical interference film 16 is formed.
Numerals 18 to 18 are formed behind the recording medium film 19 with respect to the light incident direction. Thus, the optical interference film 1
Nos. 4 to 18 are formed before and after the recording medium film 19 with respect to the incident direction of light to enhance the light absorption efficiency to the recording medium film 19 and amplify the reflected light amount at the time of reproduction, Further, the recording medium film 19 is provided to prevent the recording medium film 19 from being destroyed when recording and reproduction are repeated. Here, the dielectric films of the light interference films 14 to 18 may be those having a large refractive index and transmittance, and nitrides, oxides, sulfides of silicon, zirconium, aluminum, tantalum, titanium, zinc and the like. , Carbides or borides are used.

Further, in order to enhance the interference effect, a reflection film 20 is provided to reflect the light transmitted through the interference films 14 to 18 and the recording medium film 19. Reflective film 2
For 0, a substance having a high reflectance, which is usually made of aluminum, gold, silver, copper, platinum, nickel, or an alloy thereof, is used.

6 to 9 show basic cross-sectional schematic views of the recording layer of the thin optical recording medium of this embodiment as a relationship with the incident direction of light. FIG. 6 is a schematic cross-sectional view of the recording layer of the thin optical recording medium when light is incident from the flexible substrate side 1a and FIG. 7 is incident from the opposite side of the flexible substrate 1b. Also, in FIG.
9 has a film structure in which the protective substrate 4a or 4b is attached in the case of FIGS. 6 and 7. As shown in FIGS. 6 and 8, when light is incident from the flexible substrate side 1a, it is necessary to use a transparent material such as PMMA or polycarbonate for transmitting light. When light is incident from the opposite side of the flexible substrate 1b, the flexible substrate 1b does not need to be a transparent material, and an opaque material can be used. On the other hand, when light enters from the flexible substrate 1a side shown in FIG. 8, the protective substrate 4a can be made of any material regardless of whether it is transparent or opaque. However, when light is incident from the side opposite to the flexible substrate 1b in FIG. 9, the protective substrate 4b is limited to a transparent material.

As shown in FIGS. 6 to 11, the basic structure of the medium recording layer of the thin optical recording medium is a light interference film / recording medium film / light interference film / light reflection film in the light incident direction. In the case of imparting rigidity to the thin optical recording medium, the protective substrate 4a or 4b is bonded to the thin optical recording medium to form a film.

As described above, the optical interference films 14 to 18
Is destroyed in order to increase the light absorption efficiency to the recording medium film 19 by utilizing the multiple interference effect of light, to amplify the reflected light amount at the time of reproducing, and when the recording medium film 19 is repeatedly recorded and reproduced. It is provided to prevent
As shown in FIG. 11, the effect is great when the multilayer film structure is used.

Further, the light reflection film 20 enhances the absorption efficiency of incident light in the recording medium film 19, or is associated with the refractive index n, extinction coefficient k, and film thickness d of the other layers, so as to achieve thin optical recording. It is provided to increase the optical characteristics of the medium and to serve as a suitable coolant for increasing the phase change efficiency of the recording layer 2. Also in the case of the light reflection film 20, in order to improve adhesion, it is often a multilayer film structure with elements such as carbides and nitrides such as chromium, titanium, molybdenum, and tungsten, which are easy to form compounds such as nitrides.

Tables 1 and 2 show examples of specific film structures of the thin optical recording medium of this example. In the table, No. C1-N
o. C3 and No. C7 shows an example of the material of each specific film configuration shown in FIG. C4 to No.
C6 indicates a material example of each film configuration in FIG. Similarly, N
o. D1 to No. E6 shows an example of a material in the case where the light interference film and the light reflection film have a multilayer film structure. C1 is a transparent flexible substrate 1a made of PC having a thickness of 0.2 mm formed with a preform for a servo by the method of the second embodiment, and ZnS is used as the optical interference film 14 with 20 mol% SiO 2 as the optical interference film 14. _After a dielectric film mixed with ₂ was formed to a thickness of 70 nm, the recording film 19 was made of the In ₃ SbTe ₂ alloy of the phase change recording medium of 30 nm and then Zn.
A thin optical recording medium is formed by forming S-20 Mol% SiO ₂ in a thickness of 120 nm and then forming an Al alloy containing Ti in a thickness of 2 nm and Ti in an amount of 3% as a light reflection film 20 to a thickness of 200 nm. It was made.

Here, the thin film optical recording medium described above is formed by forming a film by using a sputtering method.
In the case of ol% SiO _2, a target having a mixed composition with a purity of 99.9% or higher was used, and an In ₃ SbTe ₂ alloy for a phase change recording medium was used under the conditions of an output RF of 200 watts and an argon gas pressure of 0.67 Pa. Is a target of this alloy composition. Under the conditions of an output RF of 200 watts and an argon gas pressure of 0.67 Pa, Ti and Al-3% Ti alloys are targeted at a purity of 99.9% or more. Output RF 200 watts, argon gas pressure 0.67
The film was formed by sputtering under the condition of Pa.

Nos. Shown in Tables 1 and 2 were used. C2-N
o. Also in the case of the thin optical recording medium of E6, sputter deposition was performed using each target corresponding to each constituent film of the film structure. That is, No. Si ₃ N used as a constituent film in C2
_For No. 4, a target having a Si ₃ N ₄ purity of 99.9% or more was used and a film was formed under the conditions of an output RF of 200 watts and a mixed gas pressure of argon + nitrogen of 0.67 Pa. Similarly, Si ₃ N ₄
In the case of a nitride such as −20 Mol% SiO ₂ and AlN,
Using each target with a purity of 99.9% or more,
A film was formed under the conditions of an output RF of 200 watts and a mixed gas pressure of argon + nitrogen of 0.67 Pa. In addition, Al ₂ O ₃ and Ta
_In the case of oxides and fluorides such as ₂ O ₅ , ZrO ₂ and MgF ₂ , each target having a purity of 99.9% or more is used, output RF 400 watts, argon gas pressure 0.67.
The film was formed by sputtering under the condition of Pa.

The thin optical recording media shown in Tables 1 and 2 above have different film structures, but in each case, the warp deformation amount of the substrate is small and good tracking characteristics are exhibited. A thin optical recording medium having good reproduction signal C / N and repetitive rewriting characteristics could be produced.

Example 4 In the case of the thin optical recording medium of this example, a flexible thin optical recording medium having a small thickness is produced when the optical recording medium structure of FIG. 1 is produced. Therefore, the recording medium may be housed in a cartridge for use in order to prevent damage to the recording medium or to prevent dust from adhering to the recording medium to cause a focus error of light.

FIG. 12 shows the thin optical recording medium of the present embodiment.
It is drawing which shows the example accommodated in the ridge. 12A is a cross-sectional view showing an example of mounting the thin optical recording medium on a cartridge, FIG. 12B is a sectional view of the thin optical recording medium stored in the cartridge, and FIG. It is drawing which shows the mounting condition example of a thin optical recording medium. As shown in FIG. 12, the cartridge for the thin optical recording medium of the present embodiment has a hub 23 for transmitting the rotational driving force of the information recording / reproducing apparatus to the thin optical recording medium 26 and a shirt 24. Case 2 provided
5 has a structure for accommodating the thin optical recording medium 26.
That is, as shown in FIG. 12 (b), the shirt 24 is closed during storage to prevent dust from entering the case 25. As shown in FIG. 12C, at the time of use, the shirt 24 is opened to have a function of allowing recording / reproducing light to enter. Of course, the cartridge can accommodate the thin optical recording medium manufactured with the medium structure shown in FIG.

Next, a concrete example of the cartridge accommodating the thin optical recording medium of this embodiment will be described. Since the thin optical recording medium 26 is housed in the protective case 25, it has an outer diameter of 6 mm.
A PC board having a size of 4 mm × 0.2 mmt was used to manufacture a substrate on which a sample servo system preformat was formed under the manufacturing conditions of Example 2, and the No. A thin optical recording medium D1 was produced under the film forming conditions of Example 3.

That is, ZnS-20Mol% SiO ₂ having a thickness of 100 nm was formed as an optical interference film 14 on the surface of the flexible substrate on which the sample servo type preform was formed, and then In ₃ SbTe ₂ of the phase change recording medium was used. 30n alloy
Then, ZnS-20Mole% as the optical interference film 16
SiO ₂ of 120 nm, Si ₃ N ₄ of 140 nm is formed as the light interference film 17, and Ti of 2 nm is formed as the reflection film 20.
It was manufactured by sequentially forming a 200 nm Al film.

It has been found that the cartridge containing the thin optical recording medium is effective for preventing damage to the recording medium and preventing dust from adhering to the recording medium.

Example 5 With respect to the thin optical recording medium of the present example, a rewriting test by a semiconductor laser output was carried out when the film configuration of the recording medium was changed. That is, an outer diameter of 64 mm × 0.2 mmt formed with a sample servo type preformat.
No. 1 in Table 1 and Table 2 using the flexible PC board of No.
Thin optical recording media C1 and D1 were prepared under the film forming conditions of Example 3, housed in the cartridge described in Example 4, and subjected to the test.

The test results are shown in FIG. In FIG. 13, 21 is a thin optical recording medium No. C1 and C22 are thin optical recording medium Nos. The rewriting test result of D1 is shown. As is clear from the figure, the above No. With the thin optical recording media of C1 and D1, a semiconductor laser output of 8 mW or more and a C / N of 50 dB or more were obtained.

Example 6 FIG. 14 shows the rewriting life test result of the thin optical recording medium of this example. In FIG. 14, No. 2 shown in the fifth embodiment is shown. The rewriting life test results for the thin optical recording media C1 and D1 are shown.

The thin optical recording medium used in the test was a flexible PC having an outer diameter of 64 mm × 0.2 mmt formed with a sample servo system preformat as in the case described above.
It was manufactured using a substrate and was stored in a cartridge and used for the test. The rewriting life test was conducted under the conditions of a disk rotation speed of 2400 rpm and a laser light film surface output of 8 mW at recording, and a laser light film surface output of 4 mWat at erasing. In the case of the optical disk 10 as an example, repeated writing and erasing were performed under the test conditions of the laser light film surface output at the time of recording of 8 milliwatts, and the life was compared by the change of the C / N of the recording / reproducing signal. .

From the figure, the thin optical recording medium of this embodiment is
o. It can be seen that both C1 and D1 exhibit excellent rewriting life. That is, in both cases, the C / N of the recording / reproducing signal is not deteriorated even when the rewriting is repeated 5 × 10 ⁵ times. As described above, the thin optical recording medium using the flexible substrate of this embodiment has an excellent rewriting life, and is suitable as an optical recording medium for a laptop top computer and other small and thin information recording / reproducing devices. I know there is.

As shown in each of the above-mentioned embodiments, in this embodiment, an optical recording medium composed of a flexible substrate on which a servo preform is formed and an optical recording medium layer, and these optical recording media. The optical recording medium manufactured by bonding the protective substrate to the substrate can prevent the recording medium from being deformed such as warpage during film formation, and thus can improve the recording / reproducing tracking performance. Further, since the recording medium is formed into a film on the flexible substrate, the film forming stress of the recording medium can be reduced, which has the effects of improving the rewriting life and increasing the C / N of the recording / reproducing signal.

The reason why the repeated rewriting life is improved is as follows.
It is considered that by reducing the film forming stress of the optical recording medium, thermal strain or the like on the optical recording medium at the time of rewriting is alleviated and the thermal fatigue life of the constituent films is improved.

That is, there is an effect of increasing the thermal fatigue strength of the optical recording medium by reducing the film forming stress of the optical recording medium. For this reason, it is considered that the recording medium has an action of preventing the film from peeling and cracking, which has conventionally occurred, and can improve the rewriting life and the C / N and erasing ratio characteristics of the recording / reproducing signal.

Further, according to the present invention, it is possible to produce the thin optical recording medium having a small deformation such as a warp. Therefore, it is possible to create a thin optical recording medium having rigidity, which has been conventionally difficult to prevent deformation such as warpage, while preventing deformation such as warpage. Therefore, the device can be downsized by using the thin optical recording medium.

When the rewritable thin optical recording medium is mounted on a card or the like, a disk incard having a large information recording / reproducing capacity can be obtained.

When the present invention is applied to an optical recording medium such as a CD (compact disk) and an optical card, the size of the apparatus can be reduced and the CD and the optical card having a good recording and reproducing life can be manufactured.

[0074]

[Table 1]

[0075]

[Table 2]

[0076]

As described above, according to the present invention, since the film forming stress of the constituent films of the optical recording medium is reduced, the film peeling of each film forming layer at the time of recording and erasing is prevented and reduced, and the life is increased. The C / N characteristics of the optical recording medium can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a layer structure of a thin optical recording medium according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the layer structure of a thin optical recording medium according to another embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the substrate thickness of the optical recording medium and the amount of substrate warpage due to film formation.

FIG. 4 is a perspective view showing a manufacturing process of a flexible substrate having a preformat according to an embodiment of the present invention.

5 is an explanatory view showing in detail a mounting portion of the stamper of FIG.

FIG. 6 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an embodiment of the present invention.

FIG. 7 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an example of the present invention.

FIG. 8 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an example of the present invention.

FIG. 9 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an example of the present invention.

FIG. 10 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an example of the present invention.

FIG. 11 is a sectional view showing the structure of a recording layer of a thin optical recording medium according to an example of the present invention.

12A and 12B are a cross-sectional view and a plan view showing the configuration of a thin optical recording medium according to an embodiment of the present invention and a cartridge that houses the thin optical recording medium.

FIG. 13 is a graph showing the results of a rewriting test by laser output of the thin optical recording medium of one example of the present invention.

FIG. 14 is a graph showing the results of rewriting life test of a thin optical recording medium according to an example of the present invention.

[Explanation of symbols]

1 ... Flexible substrate, 1a ... Transparent flexible substrate,
1b ... Opaque flexible substrate, 2 ... Recording medium layer, 3 ...
Adhesive layer, 4 ... Protective substrate, 5 ... Flexible sheet, 6 ...
Stamper, 7 ... Stamper-conveying belt, 8 ... Heating plate,
9 ... Cooling plate, 10 ... Belt drive roll, 11 ... Sheet transport roll, 12 ... Roll, 13 ... Stamper support stand, 1
4 to 18 ... Optical interference film, 19 ... Recording medium film, 20 ... Light reflecting film, 21-22 ... Thin optical recording medium of the present invention, 23 ... Hub,
24 ... Shutter, 25 ... Case.

Front page continued (72) Inventor Yoshinori Maeda 4026 Kujimachi, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Ltd. (72) Yoshimi Kato 4026 Kujicho, Hitachi City, Ibaraki Hitachi Research Institute, Ltd. In-house (72) Atsuko Naruse 4026 Kuji-machi, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Inc. (72) Inventor Yoshio Sato 4026, Kuji-cho, Hitachi City, Ibaraki Hitachi Research Laboratory, Hitachi Ltd. (72) Inventor Yoshito Tsunoda 4026 Kuji Town, Hitachi City, Hitachi, Ibaraki Prefecture Hitachi Research Laboratory, Hitachi, Ltd.

Claims (16)

[Claims] 1. An optical recording medium having a substrate and a recording layer for storing an optical signal, which is provided on the substrate, wherein the substrate is provided with an uneven portion for transmitting the optical signal. An optical recording medium, which is a substrate having flexibility. 2. The recording layer according to claim 1, wherein the recording layer has a recording medium film and a reflection film for reflecting the irradiation light, and the recording medium film and the light reflection film are provided in this order on the substrate. An optical recording medium, wherein the substrates are stacked, and the substrate is transparent to light emitted to the recording layer. 3. The optical recording medium according to claim 2, further comprising a protective substrate for protecting the recording layer, wherein the protective substrate is adhered to the reflective film side. 4. The recording layer according to claim 1, wherein the recording layer has a recording medium film and a reflection film for reflecting the irradiation light, and the reflection film is provided on the substrate. An optical recording medium comprising a recording medium film laminated in this order. 5. The protective substrate according to claim 4, further comprising a protective substrate for protecting the recording layer, the protective substrate being adhered to the recording layer side, and the protective substrate being irradiated on the recording layer. An optical recording medium, which is transparent to light. 6. The recording layer according to claim 2, further comprising a first interference film above the recording medium film and a second interference film below the recording medium film. Optical recording medium. 7. The thickness of the substrate according to claim 1,
An optical recording medium having a size of 0.01 mm or more and 0.3 mm or less. 8. The optical recording medium according to claim 6, wherein the light interference film and the light reflection film each have a multilayer film structure. 9. The optical recording medium according to claim 1, wherein the substrate is made of an organic material. 10. The optical recording medium according to claim 2, wherein the recording medium film is made of an In—Sb—Te-based material. 11. The optical recording medium according to claim 1, wherein the uneven portion of the substrate is a groove portion or a pit for transmitting at least one of a tracking signal and a preformatted signal. 12. A method of manufacturing a substrate for an optical recording medium, wherein a flexible organic sheet is heated to a softening point temperature or higher, and a stamper having irregularities is pressure-bonded to the heated organic sheet. Then, in the pressure-bonded state, the organic material sheet and the stamper are set to 50
A method for producing a substrate for an optical recording medium, which comprises cooling the substrate to a temperature of ℃ or less, and then peeling the organic sheet and the stamper to produce a flexible substrate having an uneven portion. . 13. A plurality of stampers, an endless belt on which the plurality of stampers are mounted, two rollers for conveying the endless belt, driving means for rotating the rollers, and an upstream side of the belt. A heating means arranged, a cooling means arranged on the downstream side of the belt, a conveying means for conveying a sheet between the heating means and the belt, and a punching means for punching the sheet into a disc shape. A sheet is conveyed between the heating means and the endless belt to be heated, and the stamper is pressure-bonded to the sheet to form irregularities, and then punched into a disc shape by the punching means for an optical recording medium. Manufacturing equipment for manufacturing substrates. 14. An optical disc comprising a disc-shaped optical recording medium having a substrate and a recording layer for storing optical signals, and a cartridge having a shutter portion for exposing the optical recording medium, The optical disc according to claim 1, wherein the substrate of the optical recording medium is a flexible substrate provided with an uneven portion for transmitting an optical signal. 15. An optical disc having a substrate and a recording layer for storing optical signals, a drive unit for rotating the optical disc, a light source for irradiating the optical disc with light, and a light for detecting reflected light from the optical disc. An information recording apparatus including a detector, wherein the substrate of the optical disc is a flexible substrate provided with a concave and convex portion for transmitting an optical signal. 16. The optical disc according to claim 14, wherein the optical recording medium has a diameter of 30 mm or more and 64 mm or less.