JPH0362321A - Optical recording device - Google Patents

Abstract

PURPOSE:To improve the recording density of a recording medium part, to realize simultaneous access to the both surfaces thereof and to make the capacity thereof large by adopting veneer structure for the recording medium part and irradiating the recording medium part from the recording film side thereof with light with the aid of using a floating type optical recording head. CONSTITUTION:The recording medium part 4 is constituted of a veneer obtained by forming a recording layer 2 on the both surfaces of a substrate 1 which is optically smooth and forming a protecting layer 3 on it. The optical recording head 10 is constituted of a slider 7, an objective lens 8 and a mirror 9 and made to float on the surface of the medium through an air layer whose thickness is several mum - several tens mum by rotating the medium part 4 at a high speed. Thus, an optical system whose numerical aperture is large is easily used. Besides, the recording density is improved and the capacity is made large.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an optical recording device that records high-density information on a recording medium using a high-density energy flux such as a laser beam.

Conventional technology It is well known that optical recording media can record at a much higher density than conventional magnetic recording media. For example, when comparing magnetic recording media and optical recording media in terms of areal recording density, In the case of magnetic recording, it is necessary to ensure output,
Alternatively, due to the limited tracking accuracy, the track pitch must be increased by an order of magnitude or more compared to the recording mark pitch, whereas in optical recording, grooves for light guides are formed on the substrate in advance, etc. By using this method, the track pitch can be reduced to the order of the wavelength of light, and thereby a high density of several to ten times that of a magnetic recording medium can be easily achieved.

However, when compared in terms of device capacity, there is no large difference as seen in areal recording density.

This is because in the case of optical recording devices, only one recording surface can be accessed at the same time, whereas in magnetic recording devices, there is a stack structure in which many recording media are stacked, and a small magnetic field called a flying hef. This is because by employing a head, many surfaces can be accessed simultaneously, increasing the capacity of the device.

It is said that the means to dramatically increase the recording density of the optical recording medium itself is to change the recording mechanism from conventional heat mode recording to photon mode recording, and PHB
Wavelength multiplexing recording using photochemical hole burning (photochemical hole burning), multilayer recording using photochromic materials, and the like have been proposed.

However, at present, the former requires use at extremely low temperatures, and the latter requires a wavelength tunable laser or multiple lasers with different wavelengths, and its sensitivity is in the ultraviolet region, making it difficult to develop semiconductor lasers. When considered as a device, it is far from a practical level.

Problems to be Solved by the Invention A means for increasing the recording density using conventional recording media as a drive lies in devising the recording means, for example, shortening the wavelength of the laser beam from the current around 80 nm to around 65 nm. , change the numerical aperture (NA) of the aperture lens to the current 0.
For example, it may be increased from about 5 to 0.6 to 0.9. However, for the former, we will have to wait for the development of short wavelength semiconductor lasers, and for the latter, the working distance and depth of focus will be considerably smaller, so we will need to adjust the format, including the configuration of the recording medium and recording head. There is a problem in that current optical recording technology such as cushing servo cannot be applied as is.

Therefore, in the case of optical recording as well, from the perspective of increasing the capacity of the device, a stacked structure of recording media (for example, perforated recording media, phase change recording media, magneto-optical recording media, etc.) is adopted in the same way as magnetic recording devices. This is considered to be effective. However, assuming that the apparatus is configured using a conventional optical recording head and optical recording medium, it becomes difficult to miniaturize the apparatus and it becomes impractical. In other words, in conventional optical recording devices, it is assumed that the size of the optical recording head is much larger than that of the magnetic recording head, and that the distance between the optical head and the recording medium is sufficiently large. There is a problem in that the thickness (height) of the device becomes extremely large simply by stacking the optical recording medium and the optical recording head.

In other words, it has been difficult to increase the capacity by stacking layers as in magnetic disk devices by simply collecting conventional techniques.

As mentioned above, the present invention aims to overcome the various limitations faced by current optical recording media due to increased capacity. In other words, the purpose of the present invention is to enable recording using an optical system with a larger numerical aperture than conventional ones, and to enable a structure in which recording media are stacked in a small device, thereby achieving ultra-high capacity that could only be achieved with optical recording. The idea is to realize a recording device.

Means for Solving the Problems In the present invention, in order to solve the above-mentioned problems and realize an ultra-high density optical recording device as an object of the present invention, both sides of a single substrate are irradiated with a high-density energy flux such as a laser beam. A recording thin film that changes optical properties and, if necessary, a protective layer or a protective layer that is harder than the recording film and transparent and has a thickness of several hundred micrometers at most, for the purpose of protecting the recording film on the surface of the recording film. a recording medium having an abrasion layer; a means for rotating or moving the recording medium; and a means for rotating or moving the recording medium; and a means for rotating or moving the recording medium; A floating floating optical recording head is applied. The movable part of the optical system is a so-called separated optical head consisting only of a reflecting mirror, an objective lens, and a slider for floating to reduce weight.

Furthermore, in order to achieve the above object, the present invention has a structure in which the recording medium, the moving or rotating means, and the optical recording head are enclosed in a single sealed box that is not affected by changes in the outside air. Apply.

Furthermore, in order to realize an ultra-high density recording device, the present invention includes a structure in which a plurality of the recording media are stacked closely together, a means for moving or rotating the recording medium, and a means for moving or rotating the recording medium, and a means for moving or rotating the recording medium, and a A configuration is applied in which the optical recording head and the optical recording head arranged close to each other are enclosed in a single box with a closed structure that is not easily affected by changes in the outside air.

Further, in the present invention, in order to simplify the structure, a recording medium having a thin film of phase change recording material, particularly a thin film of phase change recording material that can be overwritten by a single laser beam, is used as the recording layer.

Furthermore, in the present invention, since the light irradiation to the recording film surface is performed from the recording film side on each surface, the surface of the recording film has a hardness higher than that of the recording film and is optically transparent. 1 (takes a configuration in which a wear-resistant layer with a thickness of 10 micrometers or less is formed).

Another material thin wa1 for optical optimization on the surface of the recording film
1, a wear-resistant layer with higher hardness than that thin film is formed.

Further, in the present invention, as a method for making the flying height of the head constant, a method is applied in which the linear velocity of rotation and movement is constant at any position on the recording medium.

In addition, in the present invention, a slider, an objective lens, and a deflection mirror (prism) are used to facilitate adjustment of the optical recording head.
are integrally molded.

By adopting a working single plate structure and using a floating optical recording head to irradiate light from the recording film side, it is possible to downsize the entire apparatus. At this time, since the distance between the head and the recording surface can be made much smaller than in the past, an optical system with a high numerical aperture can be applied, and the recording density can be improved. At the same time, since both sides of the recording medium can be accessed simultaneously, it is possible to efficiently stack the recording media, and the capacity of the device can be dramatically increased.

Additionally, trash by locking it up in a confidential box.

In addition to eliminating the influence of dust, it is possible to make the protective layer of the recording medium less susceptible to the influence of outside air even if it is made thin.

Embodiment Hereinafter, one embodiment of the optical recording apparatus of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram of an optical recording apparatus of the present invention.

The recording medium unit 4 is fixed to a motor 5 via a rotating shaft 6, and is rotated at high speed by the motor, for example, 18 (10-540
It is driven to rotate at a rotational speed of about 100 psi.

A small optical recording head 10 consisting of a slider 7, an objective lens 8, a mirror 9, or a deflection prism is provided on both surfaces of the recording medium section, and is configured to float as the medium section rotates. Laser light 11 emitted from a laser (not shown in the drawing) installed further outside the outer circumference of the medium section is supplied to the mirror section, and is focused by an objective lens onto the recording layer 2 for recording, rewriting, etc. . The first point of the present invention lies in the structure of the recording medium section and the selection of the type of recording layer. The recording medium section has a structure in which a recording layer 2 is formed on both sides of an optically smooth substrate 1, and a protective layer 3 is placed thereon. It is important for the base material to have an optically smooth surface and to have as little warp, distortion, etc. as possible. For example, it is desirable that the warp size is at most 50 square meters or less. The material is glass plate 1w4. plate, metal plate such as aluminum plate, PM
A resin board such as an MA board, a polycarbonate board, or a vinyl chloride board can be used. However, in the present invention, it is more effective to use a single plate, and a glass plate or a metal plate is preferable because of their high strength and rigidity.

Spiral or concentric grooves and signal pit rows are previously provided on the surface of the substrate for the purpose of tracking recording light and reproduction light during recording and reproduction.

The drawings typically show a case where grooves 12 are formed. Glass plates are superior to metal plates in that grooves can be formed directly on the substrate surface. 2P for metal discs
The grooves can be formed by a method.

The reason for using a double-sided single-plate structure is that the overall thickness can be made thinner than by laminating two sheets together. However, when adopting this structure, the type of recording thin film, especially phase change material, is required. It is valid. First, considering write-once type recording media, for example, in the recording media of write-once type recording devices currently on the market, the temperature of the irradiated area is locally increased by irradiation with a laser beam, and the material in the irradiated area is evaporated. Alternatively, there are methods based on mechanisms such as moving the material to form a hole or changing the state of the material in the irradiated area from an amorphous state to a crystalline state to change the optical properties. The present invention does not involve movement, because, as described later, in the present invention, the recording medium surface and the recording head are set extremely close to each other. That is, in a recording medium that involves material movement, it is impossible in principle to provide a protective layer that is in close contact with the recording layer, so it is difficult to avoid damage to the recording film and loss of data due to collisions with the recording head. Even assuming that there is no collision, it is difficult to avoid the effects of evaporated matter contaminating the optical system, etc. Therefore, the recording thin film applied to the present invention should, in principle, be one that does not involve changes in the shape of substances or large transfers of substances. There is a need for something that can be applied with an adherent protective layer, and phase change material thin films are particularly suitable for meeting this requirement.

Next, when considering rewritable optical recording media, magneto-optical recording materials can be considered in addition to phase change materials as recording media that can have a close contact structure. However, in the case of magneto-optical recording, not only an optical recording head but also an auxiliary magnetic field generating coil for generating a larger magnetic field is required for recording and reproduction, which does not satisfy the purpose of the present invention of miniaturizing the apparatus. In addition, when considering data rewriting, in the case of phase change media, it is possible to overwrite with just an optical head, whereas in the case of magneto-optical recording media, it is possible to overwrite data with the optical head sandwiching the medium between them. A head is required, making it difficult to access both sides of the medium at the same time.

That is, even when a rewritable device is assumed, the present invention can be particularly effective when a phase change medium is employed.

One reason for providing the protective layer is to use optical interference effects to adjust reflectance, and the other is to protect the recording film from damage when a head collides with it. Therefore, the protective layer must have properties such as being optically transparent to the wavelength of the light source used, being resistant to abrasion, and having, for example, higher hardness than the recording film or slider material.

Naturally, oxides are applied to conventional optical recording media.

Thin films of nitrides, sulfides, selenides, and mixtures thereof are effective, but thin films with high hardness such as DLC (diamond-like carbon) films and CBN (cubic boron nitride) films are particularly effective.

The thickness of the protective layer has an upper limit depending on the material (refractive index) of the protective layer and the size (effective diameter) and NA of the objective lens. When the effective diameter of the lens is about 1 mm and the NA is about 0.5, considering that the working distance of the lens system is limited to about several hundred microns at most due to lens design, the thickness of the protective layer is also about several hundred microns at most. In order to increase the NA, it is necessary to make it even thinner, preferably 1 (below 10 microns, ideally less than 10 microns). It is.

The second point of the present invention is that floating optical recording pads 10 are arranged on each surface of the recording medium.

The optical recording head is composed of a slider 7, an objective lens 8, and a mirror 9, and as the recording medium rotates at high speed, it floats above the surface of the recording medium through an air layer of several ξ meters to several tens of micrometers. I will do it.

Laser light 11 emitted from a laser light source such as a semiconductor laser passes through a collimator lens, becomes a parallel beam, reaches an objective lens via a mirror or prism, and is focused onto a recording surface for recording.

In this case, the distance between the objective lens mounted on the slider for narrowing down the laser beam 11 to the surface of the recording medium can be set to a minimum of several ξ meters, so the aperture of the aperture lens can be made as small as possible. For the same reason, it becomes possible to use an objective lens with a larger NA of about 0.6 to 0.9 than the conventional one of about 0.5, and it is possible to improve the recording density.

As the material of the slider, materials used for flying heads in magnetic recording, such as Mn-Zn ferrite, can be used as the material must have a certain degree of hardness and be light. By forming the objective lens and the slider with the same material, that is, by making the bottom shape of the slider and the objective lens as one body, the problem of how to ensure precision in mounting the objective lens 8 to the slider 7 is solved. be able to. The material will be glass or plastic,
When using a material that is relatively easily abraded, such as plastic, a wear-resistant layer 16 such as the above-mentioned DLC film can be formed on the surface of the slider portion (see FIG. 4).

The flying height (distance between the medium surface and the head) of the optical recording head is determined by the relative speed between the head and the medium. Therefore, when a certain rotational speed (in terms of vA speed) is given, the distance between the lens and the medium is uniquely determined, and recording, erasing, and reproducing can be performed without the need for focusing. . The so-called CLV method is an effective method for keeping the linear velocity constant. Although FIG. 1 omits the tracking mechanism, recording medium transport mechanism, etc. that are naturally necessary for an optical recording apparatus, it goes without saying that these mechanisms are necessary.

The third point of the present invention is that the system in which the recording medium and the optical recording head are stacked can be constructed compactly, and this dramatically increases the capacity of the apparatus. FIG. 2 shows a schematic diagram of a recording apparatus of the present invention constructed using a laminated structure. In the figure, reference numeral 14 is an example of the structure of a recording medium having a stacked structure composed of four recording media. The thickness of one recording medium is 0
．． 5 to 2 mm, and the distance between each medium can be selected to be about 3 to 5 mm, so 4 to 10 sheets and full hide (84 mm) can be placed in a device with a height of so-called half hide (42 mm). In the case of ), it is possible to provide a stacked recording medium having about 8 to 20 recording media, and the capacity of the device increases at once by more than 10 times. By arranging independent optical recording heads on each side of the recording layer, each side can be accessed simultaneously.

The recording medium is affected by the surrounding environment, such as dust.

The entire device can be stored in an airtight box to isolate it from the effects of dust, wind, moisture, etc. The airtight box is completely isolated from outside air and nitrogen.

It can be filled with rare gases such as argon, or clean air can be circulated through a filter.

In particular, in the case of the former structure, since there is no fear of temperature deterioration or oxidation of the recording medium, synergistic effects such as the ability to make the protective layer thinner are produced, and the degree of freedom in medium design is increased.

FIGS. 3(A) to 3(P) show the structure of a recording medium used in the recording apparatus of the present invention. In each figure, parts with the same pattern indicate the same constituent elements. FIG. 3(A) shows the simplest structure in which the recording layer 2 is provided on both sides of the substrate 1.

The recording material constituting the recording layer is a thin film that undergoes a phase change, for example, between an amorphous phase and a crystalline phase, or between a crystalline phase and another crystalline phase, depending on the laser beam irradiation conditions.
e, Ge-Te-5n.

Ge-Te-3b, Ge-Te-B1. GeTe-5n
-Au=, Ge-3e-Te, 5b-3e, 5b-3e
-Te, In-Te, 5bTe, In-3e, In-3
b-Te, In5b-Se, In-3e-TIE, In
-3eT4! -Co, Ga-Te-3e, Te-0-G
e-3n, Te-0-Cue-3n-Au, I n-
Thin films based on tellurium and selenium such as Te-Au,
Ga-3b, In-3b, Au-3b, Ge-3b, C
u-3b, B1-3b, Zn-3b.

Antimony-based thin films such as Ag-3b, Ag-
A thin film or the like that utilizes a difference in reflectance due to a change in band structure between metals such as Zn is used.

Among others, GeTe, Ge5bTeInSbTe, GeTe, Ge5bTeInSbTe,
In5eTfICo, 5bSe.

CaSb base threads, especially Ge5bTe series, are effective.

Figure 3 (B) shows a structure in which a layer of material with a higher melting point than the recording layer, for example a dielectric layer 12, is provided between the substrate and each recording layer, and Figure 3 (C) shows a structure in which a similar material layer is provided on both sides of the recording layer. FIG. 3(D) shows a structure in which a dielectric layer is provided only on the surface of the recording layer. When provided above the recording film, it is required to be transparent. The dielectric layer has the function of optimizing the amount of optical change, reflectance, absorption, etc. before and after recording by appropriately selecting the film thickness.
TiO2, Af20. , oxides such as ZrO2, GeO20, Aj! Nitride such as N, SiN, BN, ZnS, Z
A chalcogenide such as n5e, the above-mentioned DLC film, etc. can be used. In cases where the sensitivity of the recording film is insufficient, a material with low thermal conductivity is used for the layer between the recording layer and the substrate to suppress heat diffusion to the substrate.

Figure 3 (1) shows a structure in which a reflective layer 13 is provided between the recording layer and the substrate, and Figure 3 (L) shows the structure in Figure 3 (1) with a dielectric layer formed on the surface. A structural example is shown.

The reflective layer has the function of increasing light absorption efficiency in the recording layer.
! , Au, Pd, Cu, Ti, Ni, Cr
.

Metals such as Ge, Si, Fe, Sb, Sn, Ta, and W can be used alone or as an alloy thin film between them.

Figure 3 (J) shows a structure in which a dielectric layer is sandwiched between the reflective layer and the recording layer, and Figure 3 (K) shows the structure in Figure 3 (J) with an additional dielectric layer on the surface of the recording layer. This shows the structure that formed the .

By providing a dielectric layer between the recording layer and the reflective layer, it is possible to change the distance between the recording layer and the reflective layer, making it possible to optimize not only the optical properties but also the thermal properties.

Figure 3 (E), (F), CG), (H), (M
), (N).

(0) and (P) are respectively shown in Figure 3 (A), (B), and (C).
).

Examples of structures in which the protective layer is provided for the structures of (D), (J), (K), and (L) are shown.

As described above, according to this embodiment, an optical recording device based on a floating optical recording head that can mount an objective lens with a large NA and various types of single-plate double-sided structure recording media has the same performance as that of a conventional optical disk device. It has been shown that it is possible to achieve a capacity that is more than an order of magnitude larger than the device size.

Effects of the Invention The optical recording device of the present invention overcomes several limitations associated with increased capacity that current optical recording media face.

That is, the present invention facilitates the use of an optical system with a larger numerical aperture than conventional ones, and enables a structure in which recording media are stacked in a compact device, thereby making it possible to create an ultra-high capacity recording device that could not be achieved without optical recording. I was able to make it happen.

[Brief explanation of drawings]

FIG. 1 shows the basic configuration of an embodiment of the optical recording device of the present invention, FIG. 2 is a configuration diagram illustrating another embodiment of the optical recording device of the present invention, and FIG. FIG. 4 is a sectional view showing the structure of the recording medium constituting the present invention. FIG. 4 is a diagram showing an embodiment of the structure in which the slider and objective lens of the optical recording head constituting the present invention are integrated. 1...Substrate, 2...Recording layer, 3...
...Protective layer, 4...Recording medium section, 5...
... Motor, 6 ... Rotating shaft, 7 ...
Slider, 8...Objective lens, 9...
- Mirror, 10... Optical recording head, 11.
... Laser light, 12 ... Groove.

Claims (14)

[Claims] (1) A recording medium comprising a recording thin film on both sides of a single substrate that changes reversibly or irreversibly between a plurality of states that can be detected by irradiation with a laser beam, or a recording thin film further provided on the surface of the recording thin film as necessary. a recording medium formed with an optically transparent protective layer having a thickness of at most several hundred micrometers; and means for rotating or moving the recording medium;
disposed close to both sides of the recording medium,
An optical recording head comprising an optical recording head that flies while maintaining a predetermined distance due to the resistance of surrounding environmental gas as the recording medium rotates and moves, and records information on each recording thin film of the recording medium according to the information. Device. (2) A recording medium comprising a recording thin film on both sides of a single substrate that changes reversibly or irreversibly between a plurality of states that can be detected by laser beam irradiation, or a recording thin film further provided on the surface of the recording thin film as necessary. a recording medium formed with an optically transparent protective layer having a thickness of at most several hundred micrometers; and means for rotating or moving the recording medium;
disposed close to both sides of the recording medium,
An objective lens having a numerical aperture of 0.6 or more that floats while maintaining a predetermined distance due to the resistance of surrounding environmental gas as the recording medium rotates and moves, and records information in accordance with each recording thin film of the recording medium. An optical recording device equipped with an optical recording head. (3) A recording medium comprising a recording thin film on both sides of a single substrate that changes reversibly or irreversibly between a plurality of states that can be detected by irradiation with a laser beam, or a recording thin film provided with an optical recording film on the surface of the recording thin film as necessary. A recording medium formed by forming a protective layer that is transparent and has a thickness of at most several hundred micrometers;
a means for rotating or moving the recording medium; and means disposed close to both sides of the recording medium, while maintaining a predetermined distance by resistance of surrounding environmental gas as the recording medium rotates or moves. An optical recording device comprising an optical recording head that floats and records information on each recording thin film of the recording medium in an airtight box for isolating it from changes in the external environment. (4) A recording medium comprising a recording thin film on both sides of a single substrate that changes reversibly or irreversibly between a plurality of states that can be detected by irradiation with a laser beam, or a recording thin film further provided with optical fibers on the surface of the recording thin film as necessary. A laminated recording medium comprising a plurality of laminated recording media formed with a protective layer that is transparent and has a thickness of at most several hundred micrometers, a means for rotating or moving the laminated recording medium, and a laminated recording medium. It is placed close to each surface of the medium, and as the recording medium rotates and moves, it floats while maintaining a predetermined distance due to the resistance of the surrounding environmental gas, and records information on each recording thin film of the recording medium. An optical recording device that includes an optical recording head and an airtight box for isolating it from changes in the external environment. (5) The optical recording device according to any one of claims (1), (2), (3), and (4), wherein the recording medium is moved or rotated at a constant linear velocity. (6) A recording thin film layer is formed on either surface of an optically smooth base material having grooves or pit rows for guiding light on both surfaces, and further recording is performed for the purpose of protecting the recording film. A wear-resistant layer that is harder than the film, transparent, and has a thickness of at most several hundred micrometers is provided on the recording layer on both sides.
An optical recording medium characterized in that recording light is irradiated from the wear-resistant layer side. (7) The optical recording medium according to claim (6), characterized in that a dielectric layer is provided on both sides or on either side of the recording thin film layer. (8) The optical recording medium according to claim (7), characterized in that an optical reflective layer is provided on the surface of the substrate. (9) Using a material that causes a reversible phase change phenomenon between an equilibrium phase and a non-equilibrium phase depending on the laser beam irradiation conditions for the recording thin film,
According to any one of claims (1), (2), (3), and (4), rewritable recording is performed by detecting changes in optical properties associated with phase changes as signals. Optical recording device. (10) The optical recording apparatus according to claim (9), wherein overwriting is performed on each recording surface by simply changing the irradiation intensity of a single laser beam. (11) Rewriting is possible by using a material that causes a reversible phase change between an equilibrium phase and a non-equilibrium phase in the recording thin film depending on the laser beam irradiation conditions, and detecting the change in optical properties accompanying the phase change as a signal. The optical recording medium according to any one of claims (6), (7), and (8), characterized in that recording is performed on the optical recording medium. (12) A recording medium comprising a recording thin film on both sides of a single substrate that changes reversibly or irreversibly between a plurality of states detectable by irradiation with a laser beam, or a recording thin film further provided on the surface of the recording thin film as necessary. A recording medium formed by forming an optically transparent protective layer with a thickness of at most several hundred micrometers, a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium, and a means for rotating or moving the recording medium. an optical recording head that is arranged at a position where the recording medium is rotated and moved, flies while maintaining a predetermined distance due to the resistance of surrounding environmental gas, and performs recording according to information on each recording thin film of the recording medium; An optical recording device comprising: an optical recording head comprising a slider section, an objective lens section, and a deflection prism or mirror section. (13) An optical recording head characterized in that the slider section, objective lens section, and deflection prism or mirror section are integrally molded using the same material. (14) The optical recording head according to claim 13, wherein the lens portion has a numerical aperture of 0.6 or more.