KR100434274B1 - optical disk of high density and production method of the same - Google Patents

Abstract

The present invention is to manufacture a high-density, high-speed and low-cost disk substrate by solving the vibration problem generated during the reproduction in the high-density optical disk of the inverted structure, inverting the substrate, the light reflection layer, the information recording layer, the protective layer sequentially stacked In the high-density optical disc having a structure, the substrate has a surface layer having information signals in the form of concavities and convexities on the side of the information recording layer on one side, and an engineering having rigidity higher than that of the high flow resin material laminated on the surface layer and formed on the surface layer. By including the core layer formed of plastic, there is an effect to improve the injection characteristics and vibration characteristics at the same time.

Description

Optical disk of high density and production method of the same

The present invention relates to a high density optical disc, and more particularly, to a structure of a high density optical disc having an inverted structure and a method of manufacturing the same.

With the advent of the multimedia era, which covers video signals including moving and still images, audio signals and computer data information, various discs including package media such as CDs and DVDs are widely used. It is a prospect.

Package media such as compact discs (CDs) and digital video discs (DVDs) are largely composed of a substrate and a recording film and a protective film for recording information.

Among these optical disks, read-only memory (ROM) disks have servos, position information, or fine grooves in the form of pits in the circumferential direction, and a reflective layer is present thereunder.

In addition, recordable (R) discs that can only record information once and rewritable (RAM, RW) discs that can write, read, and erase information repeatedly are pre-pits. And a recordable die, a phase change or magneto-optical recording layer, and a protective layer, in addition to the " reflective layer "

To record or read information on these disks, when the laser light source is irradiated, the laser light first passes through a thick portion of the transparent substrate, and then enters the protective layer or the information recording layer on which the information is recorded, and then the reflective layer, and the reflective layer. The disk structure is designed so that it can be reflected from the light and returned to the optical sensor.

CDs and DVDs are currently available. These disc structures have relatively large distances between the focal point and the surface of the substrate, so that the surface of the substrate is scattered or scattered due to dust, fingerprints or contaminants. There are strengths to prevent deterioration.

However, when using a short wavelength light source, for example, a blue light source having a wavelength of 407 nm and an objective lens having a large numerical aperture (NA) (NA = 0.85) to improve recording density, the thickness of the substrate through which the laser beam passes As coma aberration W shown in Equation 1 increases with increasing, when the disk is tilted, there is a problem that the focus is disturbed.

Where t is the distance that the laser beam must pass to reach the information recording surface (the thickness of the substrate)

NA: numerical aperture of the objective lens

alpha: tilt angle

n: refractive index of the substrate

Therefore, an attempt has been made to reduce the thickness t of the substrate from 1.2 mm (CD) to 0.6 mm (DVD) in order to reduce coma aberration.

As another method, a disk structure using a 0.1 mm cover layer has been proposed in a next-generation optical disk having a storage capacity of about 20 gigabytes (GB) or more in a 12 cm diameter cross section.

The disc having the 0.1 mm cover layer structure has a reverse structure in which a reflective layer is positioned on a substrate including land-groove or pre-pit information, and a protective layer or a recording layer is next, unlike a CD or DVD, which is a conventional disc. have.

In other words, the inverted disk has a structure in which the laser beam is incident in the protective layer direction instead of the thick substrate direction. Therefore, the inverted disk does not necessarily have to be transparent, unlike a conventional CD or DVD, which is one of the major differences between the current DVD and HD (High-Density) class optical disk.

On the other hand, in information storage media, recording density, speed, reliability, compatibility, price, etc. are evaluated as important characteristics. Unlike hard disk drives (HDDs), optical discs that can be produced by injection molding have high recording density, reliability, compatibility, and price. Although it has great strength, it has been pointed out that the speed is very slow compared to the computer hard disk drive.

This is one of the important reasons why it is not used as the first storage device.

The reason why the speed of the optical disk is slower than that of the HDD is one of the important reasons of the HDD, which is a high-strength aluminum alloy of the substrate. Because there is a weak disadvantage.

Natural Frequency on Disk Boards , The modulus of elasticity E of the material, disk thickness t, Poisson's ratio v, disk outer diameter a, dimensionless vibration parameters as a function of boundary conditions The following equation 2 holds in between.

As shown in Equation 2, the natural frequency is stiff ( Increases in proportion to the square root of

However, the reason why the polycarbonate is used in the optical disk even though a lot of vibration is generated due to the weak rigidity is because of the strength of the excellent injection characteristics.

In other words, when the grooves, lands and pre-pits formed on the optical disk and the substrate are precisely manufactured, the injection property of the resin is superior to that of any material and the manufacturing cost of the substrate can be significantly lowered. This is because the molding method can be utilized as a manufacturing method.

However, in order to increase the playback or recording speed, which is the biggest disadvantage of the optical information storage medium, the disk must be rotated at high speed, but the vibration problem caused by the low rigidity of the disk acts as an obstacle.

That is, high speed rotation is inevitable in order to increase the speed, but the high speed rotation of the disk causes a problem that makes servo difficult by increasing vibration.

The conventional approach to solve this problem is to use a glass substrate with excellent rigidity, which is impossible to injection molding due to its high melting point, and heavier than plastic, so it is not only large in power consumption but also prone to breakage when dropped. There is a very limited use.

In addition, the method described in Japanese Laid-Open Patent Publication No. Hei 11-242829 and Korean Laid-Open Patent Publication No. 2000-0006267 as another method, since the substrate using the polycarbonate caused a large vibration due to low rigidity, to solve this polycarbonate There has been an attempt to increase the rigidity of the substrate to reduce vibration by introducing fibers or the like into the composite material.

However, this is formed by mixing small-sized pieces of fiber when forming a disc by injection molding, which greatly deteriorates product reliability even when a small number of small pieces of fiber are exposed in the vicinity of the information recording layer. There is a great technical difficulty.

In addition, there are attempts to absorb vibrations due to rotation by introducing a plurality of small bubbles into the polycarbonate, but this also allows the bubbles to enter the position close to the information recording layer as above, but also a method for only absorbing vibrations. It does not bring a great effect.

Accordingly, an object of the present invention is to provide a high-density, high-speed, and low-cost disk substrate by solving the vibration problem generated during reproduction in a high-density optical disk having a reverse structure.

Another object of the present invention is to simultaneously improve the injection characteristics and vibration characteristics in the production of high-density optical disks of inverted structure.

Another object of the present invention is to reduce the thickness of the disk.

1 shows a high density optical disk according to the present invention;

2 shows another embodiment of a high density optical disc according to the present invention;

Figure 3a is a view showing an injection machine used for manufacturing a conventional optical disk substrate

3B and 3C show an embodiment of an injection machine used for manufacturing an optical disk substrate according to the present invention.

* Explanation of symbols for main parts of the drawings

10 core layer 20 surface layer

30: light reflection layer 40: information recording layer

50: protective layer 60: diffusion separation layer

100, 200, 300: Hopper

A feature of the high density optical disc according to the present invention for achieving the above object is a high density optical disc having an inverted structure in which a substrate, a light reflection layer, an information recording layer, and a protective layer are sequentially stacked, wherein the substrate is formed on one side of the high density optical disc. And a core layer formed by an injection molding having uneven shape information signals on the information recording layer side, and a core layer made of an engineering plastic that is in contact with the surface layer and has a rigidity higher than that of the resin material formed on the surface layer.

Another feature of the present invention is to further include a diffusion separation layer formed between the surface layer and the core layer to prevent mixing between the resins generated during injection molding.

The high density optical disk manufacturing method according to the present invention for achieving the above object is characterized by preparing an injection machine consisting of a plurality of hoppers, and excellent fluidity for forming a surface layer on the first hopper located in the first of the plurality of hoppers A step of preparing a molten resin of a carbonate component, and then a molten resin of an engineering plastic component having a large rigidity for forming a core layer into a second hopper located next; And forming a multi-layered substrate by successive injection into a mold for forming a substrate, and a laminating step of sequentially laminating a light reflection layer, an information recording layer, and a protective layer on the substrate.

The method may further include inputting a diffusion separation layer to prevent mutual mixing between molten resins respectively introduced into the first and second hoppers into a third hopper disposed between the first and second hoppers. There are other features.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of a high density optical disc and a method of manufacturing the same according to the present invention will be described with reference to the accompanying drawings.

1 is a view showing a high density optical disc according to the present invention, and FIG. 2 is another embodiment showing a high density optical disc according to the present invention. Referring to FIG. 1, a two-layer structure of the surface layer 20 and the core layer 10 is shown. The light reflection layer 30, the information recording layer 40, and the protective layer 50 are sequentially inverted on the substrate having the reverse direction.

2 shows a diffusion separation layer 60 formed between the surface layer 20 and the core layer 10 to prevent mixing between the surface layer 20 material and the core layer 10 material.

1 and 2, the surface layer 20 and the core layer 10 of the substrate are made of a resin material having different stiffness, and the surface layer 20 has a phase fit, a free group, or the like. A fine concavo-convex pattern is formed to record data information or a tracking servo signal. At this time, the thickness of the surface layer 20 is preferably 100 μm or more.

The surface layer 20 may be produced by injection molding, and a material having high fluidity may be used to increase the precision according to the formation of a predetermined uneven pattern. Polycarbonate may be used as the material of the surface layer 20.

In addition, the core layer 10 is formed on the opposite side to the laser beam is incident, this also uses a material having a rigidity greater than the surface layer 20 to enable injection molding as well as to reduce vibration of the substrate. The material of the core layer 10 is an engineering plastic that can be injection molded but has a relatively high rigidity.

In addition, before forming the surface layer 20 on the core layer 10, the diffusion separation layer 60 may be formed to prevent mixing between materials. In this case, the diffusion separation layer 60 is formed to a thickness of several μm.

At this time, the thickness of the core layer 10 is greater than the thickness of the surface layer 20.

As described above, the substrate has a structure in which the surface layer 20 and the core layer 10 made of engineering plastics having stronger rigidity than the surface layer 20 are composed of one body.

As a result, the optical disk to which the present invention is applied has a rigidity enhanced by the core layer 10, thereby suppressing deformation, such as bending and contraction of the optical disk, and at the same time, the surface layer 20 in which data information, tracking servo signals, etc. are recorded, has high fluidity. By using the material which has, the precision according to predetermined uneven | corrugated pattern formation can be increased.

Looking at the method of manufacturing an optical disk substrate having such a disk substrate structure in detail as follows.

Figure 3a is a view showing an injection machine used for manufacturing a conventional optical disk substrate, Figure 3b and Figure 3c is a view showing an injection machine used for manufacturing an optical disk substrate according to the present invention.

Conventionally, as shown in FIG. 3a, an injection machine having one hopper is used, but in the present invention, an injection machine having a plurality of hoppers is used as shown in FIGS. 3b and 3c.

In more detail, the first hopper 100, the injection material composed of the first hopper 100 and the second hopper 200 as shown in Figure 3b has a high fluidity material (for example, polycarbonate) for forming the surface layer 20 in the first hopper 100 Molten resin is added, and molten resin of an engineering plastic component having great rigidity for forming the core layer 10 is introduced into the second hopper 20.

At this time, the surface layer melt resin and the core layer melt resin is injected into the injection machine at the same time to be manufactured in one injection process.

The molten resin injected into the injection molding machine is sequentially introduced into a mold for forming a substrate.

Then, the molten resin from the first hopper 100 introduced into the mold is introduced into the injection mold before the resin injected from the second hopper 200 and solidified preferentially on the mold surface.

At this time, since the surface layer 20 and the high rigid core layer 10 are configured to be adjacent to each other so that the molten resins of the first hopper 100 and the second hopper 200 are configured separately or in one body, the mixing is performed. As a result, the relative composition ratio is gradually changed.

That is, the surface of the substrate is a polycarbonate excellent in injection characteristics, the lower portion of the substrate is made of a large rigid engineering plastic, the relative ratio has a relative concentration gradient in the thickness direction of the disk.

In another embodiment, the injection molding machine further includes a third hopper 300 as shown in FIG. 3 in order to prevent mutual mixing between the molten resin from the first hopper 100 and the molten resin introduced from the second hopper 200. use.

This prevents mixing between the polycarbonate and the engineering plastic by introducing the diffusion separation layer 60 in the third hopper 300.

At this time, when the injection is performed on the basis of the mold just before injection, first, a resin having high fluidity (for example, polycarbonate) is injected, and then a separation layer for preventing mutual mixing between the two resins, and a high rigid resin (engineering plastic). For example, polyetherimide resin).

As a result, the surface portion of the substrate adjacent to the signal surface is formed with a surface layer 20 made of a highly flexible material (for example, polycarbonate), and a portion of the substrate distant from the laser beam (opposite to the laser incident beam) is made of a high rigid resin. The core layer 10 can be obtained.

In addition, after the injection molding of each of the resins having different properties, respectively, and then the disk in the form of the adhesive is also considered as another application example of the present invention.

The light reflection layer 30 formed of Al alloy and the information recording layer 40 formed of a phase change material or a magnetization reversal material are formed on the substrate constructed as described above by the ion beam sputtering method, the DC sputtering method, the RF sputtering method, and the ion beam sputtering method. Lamination | sequence formation is carried out using etc.

Finally, an ultraviolet curable resin is applied on the information recording layer by a spin coat method, and ultraviolet rays are irradiated to form the protective layer 50, thereby producing a high density optical disc.

The protective layer 50 protects the light reflection layer 30 and the information recording layer 40 from external shocks, and prevents these layers from getting wet or coming into contact with a corrosion medium.

As described in detail above, the optical recording medium related to the present invention has been a major obstacle to speed, production cost, and productivity, which are important characteristics of the information storage medium. Rotation increases the vibration, making it difficult to serve the server.In the information recording layer that requires excellent injection property, high precision materials can be used for precise injection, and the lower part of the injection molding is made of high rigid engineering plastic. , The injection characteristics and vibration characteristics were solved simultaneously.

As described above, the high-density optical disc and the method of manufacturing the same according to the present invention have the following effects.

First, by injecting two kinds of resins having different characteristics sequentially, a high fluidity material is formed on the surface layer of the disk substrate as a signal surface, and the strengths are combined with high rigidity engineering plastics on the core layer as the remaining support part. The disk structure has the effect of simultaneously improving injection and vibration characteristics.

Secondly, when a certain amount of vibration is present in the system, the thickness of the disk can be reduced by providing the disk with improved rigidity as compared to the disk ejected using only polycarbonate. This can reduce the thickness, which is the most problematic of the size of the disk, it is possible to implement a system having a small form factor (form factor).

Third, by using glass to make substrates requiring high rigidity, injection molding is performed by sequentially supplying resins with their own characteristics and increasing the technical limitations and costs, which are disadvantages, through different hoppers. By doing so, the productivity and manufacturing costs can be significantly lowered.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (7)

In a high-density optical disc having an inverted structure in which a substrate, a light reflection layer, an information recording layer, and a protective layer are sequentially stacked, The substrate is a surface layer injection-molded with a highly flexible resin having information signals in the form of unevenness on the side of the information recording layer on one side; A core layer laminated on the surface layer and formed of an engineering plastic having greater rigidity than the resin material formed on the surface layer; And a diffusion separation layer formed between the surface layer and the core layer to prevent mixing between the resins generated during injection molding. delete The method of claim 1, A high density optical disc, characterized in that the thickness of the core layer is larger than the thickness of the surface layer. Prepare an injection machine composed of a plurality of hoppers, inject a high-flow molten resin for forming a surface layer in the first hopper located first of the plurality of hoppers, and then for forming a core layer in a second hopper located Diffusion separation to inject molten resin of engineering plastics component having great rigidity and to prevent mutual mixing between molten resins respectively introduced into the first and second hoppers with a third hopper located between the first and second hoppers. The preparatory step of adding the layers, Forming a multi-layered substrate by sequentially inputting molten resin injected into the injection machine into a mold for forming a substrate; And laminating step of sequentially laminating a light reflection layer, an information recording layer, and a protective layer on the substrate. delete The method of claim 4, wherein In the forming step, when the molten resin of the first hopper and the second hopper is sequentially introduced into the mold, the molten resin from the first hopper solidifies on the surface of the injection mold before the molten resin injected from the second hopper. High density optical disk manufacturing method. The method of claim 4, wherein The diffusion separation layer is a high density optical disc manufacturing method, characterized in that formed to a thickness of several ㎛.