JP2003281781A - Optical recording medium and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical recording medium of high density having the track pitch, the groove width and the minimum mark length shorter than those of a DVD+R/RW even though a special exposure device using an electron beam or the like is not used, in a multilayered structure type optical recording medium having a plurality of layers for recording and reproducing a signal by using light. <P>SOLUTION: The optical recording medium formed by laminating a substrate, a recording layer and a light transmission layer is characterized in that the light transmission layer consists of a heat shrinkable film and grooves and/or pits are formed on at least one surface of the heat shrinkable film. <P>COPYRIGHT: (C)2004,JPO

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 and its manufacturing method. In particular, the present invention relates to an optical recording medium that enables high-density recording and a manufacturing method thereof.

[0002]

2. Description of the Related Art As a writable or rewritable optical recording medium, a CD-Recordable / ReWr
itable (Fig. 1, hereinafter abbreviated as CD-R / RW)
And DVD + Recordable / ReWritable
e (FIG. 2, hereinafter abbreviated as DVD + R / RW) is already on sale. CD-R / RW and DVD + R
/ RW is generally created by the following steps. The process will be described by taking a rewritable DVD + RW as an example. As shown in FIG. 3, first, a resist material 22 is applied onto a glass master 21 (1), and laser light (λ = Ar364 or Kr413 nm, NA = 0.
After exposing in 9) (2), a nickel film is formed by a sputtering method in the groove obtained by the developing treatment (3), and electrolytic plating treatment is applied to perform nickel plating.
4 is formed (4). After the nickel father plate 24 is peeled off from the glass master plate (5), the inner / outer diameter is punched with a press die, and the groove and the facing surface are ground to form a stamper 26 (6). Next, the stamper 26 is attached to an injection molding die, and a substrate having a thickness of 0.6 mm is molded by injection molding or the like (7). Next, a recording film and a reflective film are formed in the groove of the substrate (8). Finally, the two substrates are bonded together to obtain a finished product (here, DVD + RW) (9).

In response to the demand for further improvement in recording density, DVD
Optical recording media having a recording density exceeding + R / RW have been proposed. For example, Japanese Patent Publication No. 2991443, JP-A-8-23.
The optical recording mediums described in JP-A-5638 and JP-A-11-273147 are one of the above proposals (Table 1). N of the lens
It is a proposal to make the laser spot diameter further smaller than that of DVD + R / RW by setting A to 0.85 and shortening the wavelength of the laser beam for writing or reading to 405 nm to achieve higher density. This high-density optical recording medium has a structure in which a reflective film and a recording film (which may include a recording protective film) are formed on a substrate on which a groove is formed, and a light-transmissive adhesive layer (for example, an ultraviolet curable type) is used. Resin etc.).
The recording density is 20 to 25 GB, and the thickness of the light transmission layer is 0.1 m.
m, track pitch 0.30 to 0.35 μm, groove width 0.15 μm or less, minimum mark length 0.13 to 0.18 μm
m. The above-mentioned high-density optical recording medium is a CD-R / RW.
Track pitch, groove width, compared to DVD + R / RW
Since the minimum mark length is small, a general exposure machine (λ = Ar
364 or Kr413nm, NA = 0.9),
It was not possible to form grooves or pits.

In order to solve these problems, a stamper manufacturing method using an electron beam instead of laser light has been proposed. For example, JP-A-11-288532 and JP-A-1
Examples thereof include 1-288535 and JP-A-11-328750. However, the electron beam exposure machine has drawbacks that it is more difficult to handle than general laser light, a vacuum system is required, the apparatus cost is high, and the resist agent must be changed.

[0005]

SUMMARY OF THE INVENTION The present invention provides a multilayer structure type optical recording medium having a plurality of layers for reproducing and recording signals by using light without using a special exposure device such as an electron beam. , DVD + R / RW, track pitch, groove width,
To obtain a high-density optical recording medium having a small minimum mark length, specifically, a general exposure device (λ = Ar364 or K
r413 nm, NA = 0.9) or a resist agent, the laser beam spot of the exposure device (for example, 364 nm / 0.9 =
The purpose is to be able to form a track pitch and groove width smaller than 0.4 μm.

[0006]

The present invention relates to an optical recording medium in which a substrate, a recording layer and a light transmitting layer are laminated, wherein the light transmitting layer is a heat shrink film, and the heat shrink film comprises The above problem can be solved by providing an optical recording medium having a groove and / or a pit formed on at least one surface.

The heat-shrinkable film used in the present invention is a molecule that is permeable to the wavelength of laser light and has a glass transition point or higher and a melting point or lower and is stretched only in the longitudinal or transverse direction or in the longitudinal and transverse directions. It is a heat-shrinkable film that is oriented, does not shrink at normal temperature by controlling heat treatment, and has shrinkage characteristics by reheating. If the heat shrink temperature is too low, the heat shrink film used in the present invention has a general environment (-20
(About -40 ° C), warpage occurs and the reliability of the optical recording medium itself becomes low. If the shrinkage ratio is too small, the track pitch and groove width cannot be reduced. If the shrinkage anisotropy is large, concentric circular grooves cannot be formed. Therefore, the heat-shrinkable film has an isotropic shrinkage and a temperature of 50 ° C.
It is preferable that the shrinkage rate is 10% or more. Further, as the heat shrinkable film, a thermoplastic resin film having a relatively large dielectric loss is preferable.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below based on Examples. Embodiment 1 The inventions of claims 1 to 3 will be explained based on FIGS. 5 and 6. In FIG. 5, an optical recording medium 1 includes a substrate 2, a recording layer 4, and a light transmitting layer 5, which are laminated, the light transmitting layer 5 is made of a heat shrinkable film, and the heat shrinkable film 5 has a groove on at least one surface thereof. Pits are formed. Further, the light transmitting layer 5 and the substrate 2 are joined by an adhesive layer 6. Polycarbonate having a thickness of 1.1 mm was used as the substrate 2, but the substrate is not limited to this. In order to prevent the warp of the optical recording medium due to the difference in hygroscopic expansion between the light transmitting layer 5 and the substrate 2 (bimetal effect), it is preferable to use the same material for the light transmitting layer and the substrate, but it has a high elastic modulus. There is no problem even if a warp due to the difference in hygroscopic expansion is suppressed by using a plastic or glass plate. As the high elastic modulus plastic, glass fiber,
Examples include glass whiskers, carbon fiber inclusions, and the like.

The recording layer 4 includes a reflective film. Examples of the material of the reflective film include Au, Pt, Ag, Al, and alloys containing these elements, but are not limited thereto. In the present invention, an inorganic compound mainly containing Al or Ag is used in terms of price and function. Examples of the material of the recording film include phase change type materials that cause a change in refractive index and hue due to light and heat, but are not limited to this, and are merely holes, bubble types, and textures that change due to heat and light. There is no problem with the type. In the present invention, a chalcogen-based material obtained by adding several kinds of elements to a material mainly containing an SbTe compound is used. Further, in order to protect the recording film,
A dielectric (eg, SiO ₂ —ZnS) film is laminated on and under the recording film to form a recording layer. Further, there is no problem even if an organic dye is used for the recording film. The optical recording medium using the organic dye does not require the dielectric film. On the other hand, RO
In the case of M, there is no recording film or dielectric film, and only the reflective film is used.

Examples of the light transmitting layer 5 (heat shrinkable film having grooves or pits) include, but are not limited to, polycarbonate, acrylic resin, and polyolefin resin. In this embodiment, a polycarbonate, polyethylene relephthalate or amorphous polyolefin film having a thickness of 0.1 mm is used.
A material with 50% heat shrinkage is used in an environment of ℃ or above.
Acrylic ultraviolet curable resin was used as the material of the adhesive layer 6, but the material is not limited to this. An adhesive such as a hot melt or a double-sided pressure-sensitive adhesive, or a thermoplastic film may be fused, as long as the substrate and the light transmitting layer are not separated.

The manufacturing process of the optical recording medium will be described by dividing it into steps (1) to (8) with reference to FIG. (1) Apply the resist agent 22 on the glass master. The resist agent 22 used was a positive type in which the exposed portion was dissolved in the developing solution. In coating, an adhesion reinforcing agent such as HMDS (hexamethyldisilazane) is also used. The adhesion reinforcing agent is dropped on a glass master, spin-rolled with a spinner, dried, and then coated with a resist agent using the same spinner. After the application, a pre-baking process is performed for the purpose of removing the solvent from the resist film to obtain a predetermined resist film thickness. Also, as the material for the glass master, a diameter of 300 mm called soda lime glass
Although soda lime glass of was used, but it is not limited to this, it is necessary to polish the glass surface with a cerium oxide chiller having a particle size of 0.5 μm or less and to finish it to a certain roughness with a scrubber, There is no problem as long as the material has a relatively fine surface roughness. (2) Exposing with an exposure machine. Kr laser 4 for exposure
An optical system of 13 nm and NA = 0.9 was used to expose a track pitch of 0.70 μm, a groove width of 0.3 μm, and a groove depth of 60 nm, but pits used in ROM may be exposed. (3) Conductivity treatment 23 is applied to the groove 3 obtained by the development treatment. Generally, the material of the conductive film is Ag.
And Ni are used. In this embodiment, a Ni film is formed by the sputtering method. The film forming method may be electroless plating or may be Ag film forming by a vacuum vapor deposition method. However, in the present invention, the Ni film quality obtained by the sputtering method is dense, and it is obtained by electroforming in the next step. Nickel was used because a surface layer made of the same metal as that of the obtained nickel father was integrated and the father could be used as it is as a stamper. (4) Nickel father board 24 after electrolytic plating
To form. (5) After the nickel father board 24 is separated from the glass master board, the inner / outer diameter is punched out by a press die, and the groove and the facing surface are ground to form a stamper 26. (6) The stamper 26 is attached to a molding die or a drum, and grooves or pits are transferred by molding heat on a heat shrinkable film. (7) The heat-shrinkable film is heat-treated and shrunk to form a light-transmitting layer. (8) The recording layer 4 is formed on the groove of the light transmitting layer 5 or on the pit surface.
Is formed by a sputtering method. (9) Finally, it is attached to the substrate 2 having a thickness of 1.1 mm obtained by injection molding to obtain an optical recording medium.

The optical recording medium obtained through the above steps is
The track pitch is 0.35 μm, the groove width is 0.15 μm, and the groove depth is 30 nm. Since a heat-shrinkable film is used, the laser beam diameter of the exposure machine can be used without using a special exposure machine such as an electron beam. An optical recording medium having a narrower track pitch and groove width can be obtained. Further, since the permeable layer is made of a material that does not cause heat shrinkage under a general environment (-20 to 40 ° C), it does not change with time.

Example 2 A heat shrinkable film used in the present invention will be described with reference to FIGS. 7 and 8. FIG. 7 is a schematic view of a biaxial stretch extrusion molding machine (generally called a tenter method or a flat method) for explaining the steps (6) and (7) described in Example 1. The extrusion molding machine mainly includes an extrusion unit, a stretching unit, a heat transfer unit, a heat shrinking unit, a cooling unit, and a winding unit. After supplying the dried resin to the hopper and melting the resin in the extruding section, the molten resin extruded from the T-die slit is stretched in the stretching section (longitudinal by a heating roll between the slow drive roll and the fast drive roll). Direction, then enters the tenter, is heated while holding both ends of the film, and is stretched in the transverse direction.) To form a film. In the stretching part, temperature control and temperature gradient control in units of 0.1 ° C. are possible. Further, in this embodiment, a general T-die is used, but other solution casting method (casting method) or calender method may be used.

Next, the grooves and pits of the stamper are transferred to the film at the thermal transfer section. This thermal transfer will be described with reference to FIG. In FIG. 8, since the stamper 26 is attached to the drum 41 and the heater 43 is coated on the inner surface of the drum 41, the temperature can be freely controlled. Furthermore, since each of the two drums can be moved up and down and pressure can be applied to the film, the transferability of the grooves and pits can be freely controlled. Although the drum is used in the present embodiment, the present invention is not limited to this, and a mold or the like may be used. Next, the heat-shrinkable film 42 is reheated in the heat-shrinkable portion and heat-shrinked. The heat-shrinkable portion can also be temperature-controlled and temperature-gradient controlled in units of 0.1 ° C. Finally, it is cooled in the cooling unit to obtain the light transmission layer.

The light transmitting layer of this embodiment has a thickness of 30 μm or more. Therefore, it is possible to form the light transmission layer having a thickness of 30 μm or more only by improving a part of a general biaxially-stretching and extruding machine. When the thickness of the light transmission layer is 30 μm or less, handling in subsequent steps (punching, film formation, bonding) becomes very difficult, and the heat capacity is small, so that the recording layer film formation method. Will be restricted. On the other hand, in the stretching section and the thermal transfer section, the temperature, tension,
The pressure and the like can be controlled, and the shrinkage rate of the heat shrinkable film can be adjusted relatively freely.

Example 3 An optical recording medium according to claim 4 will be described with reference to FIG. The recording layer 4 manufactured in Examples 1 and 2 and having a thickness of 0.1 m
m light transmitting layer 5 ′ and a substrate having a second recording layer 4 formed on a 1.2 mm-thick grooved substrate formed by general injection molding or injection compression molding. Pasted together. Polycarbonate having a transmittance of 88% or more for 780 nm laser light (3 ″) is used for each substrate. Although no particular material is specified, the same material as that of the light transmission layer is used in order to secure the warpage reliability described in detail in the first embodiment. In the optical recording medium of this example, the substrate side is formed with grooves conforming to the CD-R / RW standard, while the opposite side is formed with the grooves of the high density recording medium manufactured in Example 1.

When a certain image or photograph is distributed as an advertisement, or when a personal video or the like is recorded and stored and viewed by a family, a drive for reading the optical recording medium is required. The DVD + R / RW and the high-density recording medium in the present invention are not popular at this stage as compared with the CD-R / RW. For such a user, the present invention is provided with one side compliant with the CD-R / RW of 0.65 GB on one side (CD-R / RW is a CD-ROM equipped with a general personal computer). But it can be read.) Of course, since the capacity is too small, it serves as a digest board for the high-density recording medium on the facing surface. On the other hand, of course, pits used for ROM instead of grooves may be used.

Example 4 An optical recording medium according to claim 5 will be described with reference to FIG. In this embodiment, the recording layer of the optical recording medium is made into two layers. Grooves are formed on both sides of the first light transmitting layer 5 (thickness 30 μm), and the first and second recording layers 4 and 4 ′ are formed on the grooves. Next, the thickness of 1.1mm molded by injection molding
After being bonded to the substrate 2 of 1. with an adhesive layer (ultraviolet curable resin), a second light transmitting layer 5'having a thickness of 0.1 mm is fused to the surface of the second recording layer (4 '). . As the adhesive layer 6 on the facing surface, a double-sided adhesive or thermoplastic resin may be used in addition to the ultraviolet curable resin. A thermoplastic film was fused as the second light-transmitting layer 5 ′ having a thickness of 0.1 mm, but this was also a single-sided adhesive (a polycarbonate film with an adhesive on one side), a polycarbonate film with an ultraviolet curable resin. They may be attached to each other, or may be only an ultraviolet curable resin.
The optical recording medium of the present embodiment can double the recording capacity of the first embodiment (40 to 50 GB).

Embodiment 5 The invention of claim 6 will be described with reference to FIGS. 11 and 12. FIG. 11 shows the structure of the optical recording medium in this embodiment, and FIG. 12 shows its manufacturing process. The optical recording medium in this embodiment includes a substrate, a first light transmitting layer 5, a first recording layer 4, a second light transmitting layer 5 ′, a second recording layer 4 ′, and a third light transmitting layer. It is manufactured by quasi-layering with 5 ''. The substrate 2 having a thickness of 1.1 mm is molded by general injection molding (2). Next, the first heat-shrinkable film with grooves (first light-transmitting layer) prepared in Example 1 is fused to the substrate 2 by heat (2). At this time, the first recording layer is not formed. Next, after the inner / outer diameters of the first light transmitting layer 5 are punched out by a press die, the first recording layer 4 is formed by a sputtering method (3). Next, the second grooved heat-shrinkable film (second light-transmitting layer) is heat-sealed to the first light-transmitting layer, the inner / outer diameter is punched, and the second recording layer is formed (4 ). Finally, a third light transmitting layer having a thickness of 0.1 mm is fused to obtain an optical recording medium (5). Compared with Examples 1 to 4, since the heat capacity of the substrate to be sputtered is large, even if the film is formed by a general sputtering apparatus, the substrate and the groove are not melted, and the high capacity (40 to 40
An optical recording medium of 50 GB) can be manufactured.

[0020]

[Table 1]

[0021]

Effect of the Invention Since the heat shrink film is used, an optical recording medium having a track pitch and a groove width narrower than the laser beam diameter of the exposure machine can be obtained without using a special exposure machine such as an electron beam. Can be done. In addition, the light transmission layer is under a general environment (-20 to 4).
At 0 ° C., since a material that does not cause heat shrinkage is used, warpage does not change over time. 2. 4. A CD-ROM that is generally popular because at least one surface is formed with a groove conforming to CD-R / RW or a groove and / or pit conforming to CD-ROM.
It is possible to read the recorded contents with the drive. 3. A fifth aspect of the present invention is capable of providing a high-capacity optical recording medium because it has at least two recording layers. Specifically, the recording capacity is 40 to 50 GB or more. 4. 6. A substrate, a first transparent layer, a first recording layer, a second transparent layer, a second recording layer, and a cover layer, which are quasi-laminated, are formed by a general sputtering apparatus. However, a high capacity (40 to 50 GB) optical recording medium can be manufactured without melting the substrate or the groove.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing the structure of an optical recording medium (CD-R / RW).

FIG. 2 is a schematic cross-sectional view showing the structure of an optical recording medium (DVD + R / RW).

FIG. 3 is a diagram showing a manufacturing process of an optical recording medium (DVD + RW).

FIG. 4 is a schematic sectional view showing a structure of an optical recording medium according to the present invention.

FIG. 5 is a schematic cross-sectional view showing the structure of the optical recording medium in Example 1.

FIG. 6 is a diagram illustrating a manufacturing process of the optical recording medium according to the first embodiment.

FIG. 7 is a diagram illustrating an optical recording medium manufacturing apparatus according to a second embodiment.

FIG. 8 is a diagram illustrating a thermal transfer unit of an optical recording medium manufacturing apparatus according to a second exemplary embodiment.

FIG. 9 is a schematic cross-sectional view showing the structure of the optical recording medium in Example 3.

FIG. 10 is a schematic cross-sectional view showing the structure of the optical recording medium in Example 4.

FIG. 11 is a schematic cross-sectional view showing the structure of the optical recording medium in Example 5.

FIG. 12 is a diagram illustrating the manufacturing process of the optical recording medium in Example 3.

[Explanation of symbols]

1 Optical recording medium 2 substrates 3 grooves and / or pits 4 recording layers 4'recording layer 5, light transmission layer 5'light transmitting layer 5 '' light transmitting layer 6 Adhesive layer 7 Center hole 8 print layers (print label) 9 Reflective film 10 Dielectric film 11 Recording film 12 track pitch 12 'track pitch 13 Groove width 14 Groove depth 21 glass master 22 Resist agent 23 Conductivity treatment (nickel film formation) 24 Nickel Father Edition 25 inner diameter 26 Stamper 31 lens 31 'lens 31 '' lens 32 laser light 32 'laser light 32 '' laser light 41 Drum with stamper 42 (heat shrink) film 43 heater

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G11B 7/24 538 G11B 7/24 538R

Claims (6)

[Claims] 1. An optical recording medium in which a substrate, a recording layer and a light transmitting layer are laminated, wherein the light transmitting layer comprises a heat shrink film, and grooves and / or pits are formed on at least one surface of the heat shrink film. An optical recording medium characterized by being formed. 2. The optical recording medium according to claim 1, wherein the heat-shrinkable film is made of a thermoplastic resin and isotropically shrinkable. 3. The heat-shrinkable film is heat-shrinkable by 10% or more in an environment of 50 ° C. or higher,
The optical recording medium according to claim 1. 4. An optical recording medium in which at least a substrate, a recording layer, and a light transmission layer are laminated, wherein grooves and / or pits are formed on both surfaces of the light transmission layer, and at least the light transmission layer is formed. The grooves and / or pits on one side of the layer are C
The optical recording medium according to any one of claims 1 to 3, which is compliant with the D-R / RW standard. 5. A substrate, at least two or more first light transmission layers having grooves and / or pits formed on both sides thereof;
5. The recording layer formed on the groove and / or the pit of the light transmitting layer, and the second light transmitting layer are at least laminated to form a structure. The optical recording medium according to the item. 6. An optical recording medium in which a substrate, at least two or more recording layers, and at least two or more light transmitting layers are laminated, and at least two pairs of the light transmitting layers and the recording layers are laminated in order. The optical recording medium manufacturing method according to any one of claims 1 to 5, wherein the pair is laminated by fusion bonding.