JP2721878B2 - Optical recording medium and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical storage device that stores optical read-only information.
The present invention relates to an optical recording medium that is a ROM (read only memory) medium and a method for manufacturing the same. (Related Art) Among optical recording media, a read-only medium is a medium in which information is divided into pits in advance and the pits are recorded on the optical recording medium. There are roughly two types of pit recording / reproducing methods. One is to record data as uneven pits, and when irradiating with laser light, the laser light is diffracted with a phase difference caused by the uneven pits. The other is a method in which pits with different reflectivities are recorded as, for example, the presence or absence of a metal thin film, and the read / reproduce is performed as a signal based on the difference in reflectivity when laser light is irradiated. However, in any of the methods, reading of information is performed by detecting reflected light such as an irradiated laser beam. For example, optical cards that are becoming popular are light and inexpensive, but are thinner than optical disks (0.76 mm thick according to the magnetic card standard), are easily bent, and have poor flatness. Therefore, the reading accuracy is low, and the signal reading method is usually a method based on the difference in reflected light, and the pits to be recorded are large. Reading errors are prevented. Such a difference in the reflectance of the recording portion is generally performed by a method of forming a portion where the light reflective metal thin film exists and a portion where the light reflective metal thin film does not exist. As one method of generating the difference in the reflectance, there is a method in which a low melting point thin film is destroyed by a laser beam used for a write-once optical recording medium to form a low reflectance pit. It takes time because it forms pits and ROM
It is not suitable for mass production of optical recording media. As another method, there is a method by a photo etching method. According to this method, predetermined pits are formed in a silver salt emulsion in advance by a photographic method, a photoresist is separately applied to a recording medium having a uniform light-reflective thin film, a pattern of the silver salt emulsion is printed, and an etching solution is used. The thin film is locally etched to form the presence or absence of a light-reflective thin film.
Suitable for the production of optical recording media. In addition to the above methods, photomechanical methods using the principle of batch duplication have been developed. (Problems to be Solved by the Invention) However, in a medium for reading information by detecting a difference in reflected light such as an irradiated laser beam as described above,
The reader has a problem in that the irradiation unit and the light receiving unit must be in the same direction, and there is a lack of freedom in device design, and a problem that if the irradiation unit and the light receiving unit are designed to face each other, the device becomes extremely complicated. was there. In the production of a medium, the method of batch duplication described above optically prints a fine pit pattern from a photographic master onto a duplication recording medium, and records information by pits by various post-processing. The problem is that the entire process is long and the probability of generating pit defects is high, and it is difficult to increase the yield of sufficient non-defective products even if great care is taken so that fine dust and the like are not mixed in the manufacturing process. There was a problem. (Means for Solving the Problems) The present invention has been made to solve the above problems. That is, in the first invention of the present invention, a pattern of a portion of a smooth surface and a portion of a relief surface of a diffraction grating is formed on a light-transmitting substrate, and the entire pattern portion is higher than the light-transmitting substrate. A film having a refractive index is formed to a thickness of 50 to 1000 °, and a data signal is obtained by a difference in the amount of transmission or reflection of light from the portion of the smooth surface and the portion of the diffraction grating surface. Of the present invention, the second aspect of the present invention
The second invention uses a premaster plate in which a pattern of a smooth surface portion corresponding to data recorded on a support and a pattern of a diffraction grating relief surface is formed and pressed against the surface of the light-transmitting substrate. After duplicating the pattern of the pre-master plate, on the surface where the pattern is duplicated, a film having a higher refractive index than the light-transmitting substrate is formed to a thickness of 50 to 1000 mm by vapor deposition or sputtering, and the optical recording medium In a third aspect of the present invention, a pattern of a smooth surface portion and a diffraction grating relief surface portion corresponding to data to be recorded is formed. After being replicated on a metal plate and using the metal plate as a mold to replicate the pattern on the light-transmitting substrate by the injection method, the surface on which the pattern is replicated is higher than the light-transmitting substrate. With refractive index Film was formed in a thickness 50Å~1000Å by a deposition or sputtering method, it is an gist method of manufacturing the optical recording medium, characterized in that to produce the optical recording medium. (Function) The basic principle of the present invention is to use a pattern composed of a smooth surface portion and a diffraction grating relief surface portion as data recording means, and further provide a higher refractive index on this pattern than on the material forming the pattern. By forming a film of the rate, by detecting either transmitted light or reflected light from the smooth surface portion and the diffraction grating surface portion, it is possible to read the recorded information, In producing the medium, the press method was used to duplicate the pattern. Hereinafter, the principle and operation of the present invention will be described in detail with reference to the drawings. FIG. 1 is a plan view of an example of the optical recording medium of the present invention,
2 and 3 are enlarged partial sectional views of FIG. In the optical recording medium 10 of the present invention, a pattern of the smooth surface 2 and the diffraction grating relief surface 3 is formed in a pattern corresponding to the recording data on the light transmitting base material 1 and the entire pattern portion is formed. A high-refractive-index film 4 made of a metal, alloy, metal oxide, metal sulfide, or nonmetal having a higher refractive index than the material of the light-transmitting substrate 1 is formed. The trajectory of light in the method of reading data using transmitted light in the optical recording medium of the present invention will be described with reference to FIG. When the laser beam 5 is irradiated onto the optical recording medium 10 at an incident angle θ, the light 5 is refracted from the smooth surface 2 by the refractive index n of the high refractive index film 4 and is emitted as transmitted refracted light 6 at an angle θ _1. I do. On the other hand, on the diffraction grating relief surface 3 on which the diffraction grating relief is formed, the light 5 incident at an angle θ is transmitted and refracted light 6 at an angle θ ₁ and the so-called transmission diffraction that transmits and diffracts at a specific angle α. Light 7 is produced. (Reference numeral 7 in the figure is a first-order diffracted light, and strictly speaking, an n-th-order diffracted light is generated, but the first-order diffracted light is the largest, and the second and lower orders have a small intensity.) The ratio between the incident light and the transmitted light at is approximately as follows, assuming that there are no factors other than diffraction. Incident light: transmitted refracted light: transmitted diffracted light = 100: 70: 30 Therefore, if the photodetector is installed at the position of the angle θ ₁ , the amount of transmitted refracted light of 100 with respect to the incident light 100 from the smooth surface portion 2 On the other hand, from the diffraction grating relief surface 3, light is divided into transmitted refracted light and transmitted diffracted light, so that the amount of transmitted refracted light obtained is about 70. (In fact, since the n-order diffracted light exists, the transmitted refraction light amount can be reduced to a minimum of 0.) That is, data can be read by detecting the difference in the light amount. If the photodetector is installed in the direction of the angle α of the transmitted diffracted light, light cannot be detected from the smooth surface 2, but from the diffraction grating relief surface 3, about 3/10 of the amount of incident light. Can be detected, and data can be read from the difference. In this case, the ratio of light from the portion of the smooth surface 2 to the portion of the diffraction grating relief surface 3 is infinite at the position of the detector, and the S / N ratio is the best. As described above, the reason why the diffraction effect of the diffraction grating occurs in the transmitted light is that the organic material constituting the light transmitting substrate 1, for example, the organic material having a refractive index substantially equal to the refractive index (1.4 to 1.6) of the plastic film. When the films of the above are laminated, the diffraction grating relief is buried and the difference in refractive index disappears, so that there is no diffraction overhead. However, a film having a higher refractive index than that of the light transmitting substrate 1 (for example, ZnS: 2.2, Sb ₂ S ₃ :
3.0), the difference between the two refractive indices is 0.7 or 1.
5, which is because the diffraction effect of the diffraction grating is exhibited. In order to transmit light in the optical recording medium as described above, it is necessary to set the incident angle θ of the incident light 5,
For example, a diffraction grating relief having a pitch (0.1 to 2.0 μ) and a depth (0.05 to 1.0 μ), and a substrate refractive index of 1.4 to 1.6
In this case, the incident angle θ of the light may be set to about 56 ° or less. Next, the trajectory of light in the method of reading data by reflected light will be described with reference to FIG. When the laser beam 5 is irradiated on the optical recording medium at the incident angle ψ, only the regular reflected light at the angle ψ is generated on the smooth surface 2 and no diffracted light is generated. On the other hand, on the diffraction grating relief surface 3 on which the diffraction grating relief is formed, the light 5 incident at an angle ψ becomes a regular reflection light 8 at an angle ψ and a so-called reflected diffraction light 9 reflected and diffracted at a specific angle β. Occurs. (9 in the figure is 1
Although it is the next order diffracted light, strictly speaking, the nth order diffracted light is generated,
The first-order diffracted light is the maximum, and the second-order and lower-order diffracted lights are omitted because the intensity is low. Assuming that there is no factor other than diffraction, the ratio of incident light to reflected light on the diffraction grating relief surface 3 is approximately the following (considering a good reflective thin film). Incident light: specular reflected light: reflected diffracted light = 100: 70: 30 Accordingly, if the photodetector is installed at the position of the angle β, light from the smooth surface 2 is not detected, and the diffraction grating relief surface 3 is not detected.
Only the reflected diffraction light from the portion can be detected, and data can be read from the difference in the amount of light. (Examples) Hereinafter, the present invention will be described based on examples. Master plate The master plate is the basis of a press master plate for manufacturing optical recording media. In manufacturing an optical recording medium, first, information to be recorded is converted into a predetermined data format. This data is input to a device for exposing a data pattern to a photosensitive material for producing a master plate, and this device generates white spots, laser light, and an electron beam of minute spots for exposing the photosensitive material constituting the master plate. Irradiated. Incidentally, it is naturally possible to produce a mask on which a data pattern is formed without using such an apparatus and to perform pattern exposure on the photosensitive material via the mask. As the photosensitive material constituting the master plate, a general high-resolution silver salt emulsion or a photosensitive resin can be used. Here, in the conventional method, the data exposure is performed by directly exposing the photosensitive material provided on the substrate and developing the master plate. However, in the present invention, the master plate having a diffraction grating surface is pre-processed by pre-processing. Is prepared. The pre-processing is to form a diffraction grating relief having an appropriate diffraction effect over the entire surface of the master plate substrate. This diffraction grating relief has a pitch of 0.1 to 2.0 μ and a depth of 0.05 to 1.0
It is about μ, but is not particularly limited to this. Such a relief of the diffraction grating can be obtained by recording the interference fringes of two light beams on a photosensitive material using mechanical precision cutting, etching, precision processing by an electron beam, or holography on the substrate surface. . In this diffraction grating, if the grating interval is constant, the diffraction angle φ varies depending on the wavelength of light, and if the wavelength of light is constant, the diffraction angle φ varies depending on the grating interval. This relationship is shown by the following equation. λ = d (sin ω + sin φ) λ: wavelength, d: grating interval, ω: incident angle, φ: diffraction angle Generally, the wavelength of light used for reading data is determined, and a predetermined diffraction angle φ is obtained by the above method. It is good to determine the lattice spacing for the. Here, in the case where a diffraction grating is produced using holography, if the photosensitive material used is a silver halide photographic material, the recorded diffraction grating is recorded as a smooth black-and-white grating, and if it is a photoresist, it is recorded as fine relief. You. Since the master plate substrate of the present invention must have fine relief, a smooth black-and-white lattice made of a silver halide photographic material must be printed on a photosensitive material or the like applied to another substrate to produce a new fine relief. Must. In this step, a defect is likely to occur in the grating due to dust or duplication means, and the number of steps itself increases. Therefore, a method of recording a diffraction grating directly on a photoresist is preferable. Next, a photosensitive resin is applied to the master plate substrate surface having the diffraction grating relief manufactured as described above. As the photosensitive resin, those commonly used can be widely used, and may be either a negative type or a positive type. For example, a photosensitive resin for semiconductor production is used. The photosensitive resin surface of the master plate substrate surface is exposed, developed, and dried by an apparatus for exposing the data pattern described above or through a mask on which the data pattern is formed,
A master plate 30 whose sectional view is shown in FIG. 4 can be obtained. The master plate 30 has a smooth surface portion 12 in which the relief of the diffraction grating formed on the support 20 is covered with the photosensitive resin film 11 having a pit pattern shape of the copied data, and a portion 13 in which the diffraction grating relief is exposed. Consists of Then, a data pattern to be recorded is constituted by the smooth surface portion 12 covered with the photosensitive resin film 11 and the portion 13 where the minute relief is exposed. Using this master plate, the pattern of the smooth surface portion and the diffraction grating relief surface portion can be transferred and duplicated on a light-transmitting base material. However, in the case of mass production, the sub-master Preferably, a plate is prepared and used. Sub-master plate The sub-master plate can be produced by the following methods: (1) A curable resin having an appropriate viscosity is applied to the master plate surface and cured, and the substrate for the sub-master plate is adhered to the surface with an adhesive, and then separated from the master plate. As a result, a submaster plate in which the pattern of the smooth surface portion and the pattern of the diffraction grating relief surface portion are duplicated can be obtained. Incidentally, if the adhesiveness between the cured resin and the sub master plate is good, it is not necessary to use an adhesive. As the hardening resin, a thermosetting, light-curing, or reactive-curing resin is used, but in order to replicate fine irregularities, the shrinkage ratio during hardening is small, and no reaction products such as gas are generated. Those having high strength are preferred. (2) A thermoplastic resin is applied to the substrate for the sub-master plate in advance, and the master plate is pressed against this surface in a heated state to duplicate the pattern of the smooth surface portion and the diffraction grating relief surface portion on the sub-master substrate. You can get a submaster version. (3) After the master plate is sufficiently washed, electroless plating is performed to form a metal film layer, and then electroplating is further performed.
After forming a metal film on the metal film layer and obtaining a required thickness, the metal sublayer is separated from the master plate to obtain a metallic submaster plate in which the pattern of the smooth surface portion and the diffraction grating relief surface portion is duplicated. be able to. As the activating liquid used for the electroless plating, for example, a liquid mainly containing palladium chloride is used, and as the plating metal, for example, nickel is used. This metal submaster plate has good reproducibility of minute unevenness, high durability and high strength. Production of Optical Recording Medium An optical recording medium is produced using the master plate or the sub-master plate obtained as described above as a press master plate. (1) In the case of small-volume production A curable resin having an appropriate viscosity is applied to the master plate surface and cured, and a light-transmissive substrate is adhered to the surface with an adhesive,
By peeling off the master plate, an intermediate of the optical recording medium in which the data pattern of the smooth surface portion and the diffraction grating relief surface portion is duplicated can be obtained. Note that an adhesive may not be used as long as the adhesiveness between the cured resin and the light-transmitting substrate is good. As the hardening resin, a thermosetting, light-curing, or reactive-curing resin is used, but in order to replicate fine irregularities, the shrinkage ratio during hardening is small, and no reaction products such as gas are generated. Those having high strength are preferred. The material for the light-transmitting substrate is not limited as long as it is light-transmitting. For example, a general plastic, for example, a film, sheet, or plate of vinyl chloride, polycarbonate, acryl, polymethyl methacrylate, or the like is used. Next, on the surface on which the pattern of the smooth surface portion and the diffraction grating relief surface portion is formed, a high refractive index film made of a metal, an alloy, a metal oxide, a metal sulfide, or a nonmetal having a higher refractive index than the substrate is formed. The optical recording medium of the present invention can be obtained by forming by means of coating, plating, vapor deposition, sputtering or the like. Examples of metals, alloys, metal oxides, metal sulfides, and nonmetals that form the high refractive index film include CdSe (3.5) and ZnTe
(2.6), Ge (4.0 to 4.4), HfO ₂ (2.2), PbTe (5.
6), Si (3.4), Te (4.9), TiCl (2.6), ZnTe (2.
8), Sb ₂ S ₃ (3.0), Fe ₂ O ₃ (2.7), PbO (2.6), ZnSe
(2.6), CdS (2.6), Bi ₂ O ₃ (2.4), TiO ₂ (2.3), Pb
Cl ₂ (2.3), CeO ₂ (2.2), Ta ₂ O ₅ , ZnS (2.2), ZnO
(2.1), CdO (2.1) , Nd 2 O 3 (2.1), Sb 2 O 3 (2.0), S
iO (2.0), InO ₃ (2.0), Y ₂ O ₃ (1.9), TiO ₂ (1.9),
ThO ₂ (1.9), Si ₂ O ₃ (1.9), PbF ₂ (1.8), Cd ₂ O ₃ (1.
8) etc. can be used. [The numerical value in parentheses indicates the refractive index.] The thickness of the high refractive index film is desirably about 50 to 1000, preferably 100 to 500. (2) In the case of mass production After forming a resin layer, preferably a thermoplastic resin layer, on a light-transmitting substrate, the submaster plate obtained above is hot-pressed to form a smooth surface portion and a diffraction grating relief surface. After duplicating the pattern with the portion on the resin surface, a high refractive index film is formed by the same method as in the above (1) to obtain the optical recording medium of the present invention. The resin layer in which the pattern is duplicated has excellent storability, durability and physical properties when cured by heat or light. The above-mentioned metallic submaster plate is used as a mold, or an injection mold is separately prepared therefrom, and a light-transmissive resin is injected into the mold, and the injection method is used.
An intermediate of the optical recording medium in which the pattern of the smooth surface portion and the diffraction grating relief surface portion is duplicated is obtained, and a high refractive index layer is formed by the same method as in the above (1) to obtain the optical recording medium of the present invention. Obtainable. In the optical recording medium of the present invention obtained as described above, the data area surface (data pattern forming surface) has scratches,
A protective layer for protecting dust and the like can be formed. This protective layer is formed by uniformly applying a light-transmitting resin, or by laminating a film or sheet having such optical characteristics, and the thickness is about 0.1 mm to 1.0 mm, but is 0.4 mm to When the thickness is 0.6 mm, the optical card which is an example of the optical recording medium of the present invention is suitable for preventing erroneous reading due to adhesion of dust and dirt. An acrylic resin or a polycarbonate resin is preferably used as the light-transmitting resin, and a film or sheet made of such a resin is suitably used as the film or sheet. The optical recording medium of the present invention having the above-described basic structure can be used as a flexible disk, card, tape, or the like, and is applied to, for example, the following applications. (1) Financial distribution industry: cash card, credit card, prepaid card. (2) Medical health industry: health certificate, medical chart, medical card,
Emergency card. (3) Entertainment industry: software media, membership cards, admission tickets, game machine control media, video game media. (4) Transportation travel industry: tourist cards, licenses, commuter passes,
passport. (5) Publishing industry: electronic publishing. (6) Information processing industry: external recording devices and filing of electronic machines. (7) Education industry: Teaching material programs, grade management cards, library access control and book management. (8) Automobile industry: security records, operation management. (9) FA: Program recording media such as MC, NC, and robot. (10) Other: building control, home control, ID card, vending machine medium, cooking card. (Effects of the Invention) In the optical recording medium of the present invention, data is read because a smooth surface portion and a diffraction grating relief surface portion are used as data pits and a high refractive index film is formed on the surface on which these patterns are formed. Can be read by transmitted light or reflected light of a laser beam to be irradiated, and the degree of freedom in designing a reading device is expanded. Further, when the transmitted light detection is used in reading the optical recording medium of the present invention, the transmitted light has less loss of light than the reflected light, so that the data can be read with higher sensitivity than the conventional reflected light detection. it can.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of an example of the optical recording medium of the present invention, and FIGS. 2 and 3 are diagrams of FIG. 1 for explaining the trajectories of light in the optical recording medium of the present invention. FIG. 4 is an enlarged partial sectional view of a master plate used in the present invention. DESCRIPTION OF SYMBOLS 1 ... Transparent base material 2 ... Smooth surface 3 ... Diffraction grating relief surface 4 ... High refractive index film 10 ... Optical recording medium 30 ... Master plate

Claims (1)

(57) [Claims] A pattern of a smooth surface portion and a diffraction grating relief surface portion pattern is formed on the light transmitting base material, and a film having a higher refractive index than the light transmitting base material has a thickness of 50 to
An optical recording medium which is formed at an angle of 1000 ° and obtains a data signal based on a difference in light transmission or reflection from the smooth surface portion and the diffraction grating surface portion. 2. Using a premaster plate in which a pattern of a smooth surface portion and a diffraction grating relief surface portion corresponding to the data recorded on the support is formed, the premaster plate is pressed against the surface of the light-transmissive base material. After duplicating the pattern, a film having a refractive index higher than that of the light-transmitting substrate on the surface on which the pattern was duplicated was deposited to a thickness of 50 by a vapor deposition or sputtering method.
A method for manufacturing an optical recording medium, comprising forming an optical recording medium at {1000}. 3. A patent wherein the premaster plate is a premaster plate in which a photosensitive resin layer and a diffraction grating relief surface are formed in a pattern corresponding to data on a support having a diffraction grating surface formed by holography. A method for manufacturing an optical recording medium according to claim 2. 4. Copy the pattern of the part of the smooth surface and the part of the diffraction grating relief surface corresponding to the data to be recorded on a metal plate,
After duplicating the pattern on a light-transmitting substrate by the injection method using the metal plate as a mold, a film having a higher refractive index than the light-transmitting substrate is deposited on the surface where the pattern is duplicated. Alternatively, a film thickness of 50 to 10
A method for manufacturing an optical recording medium, comprising: forming an optical recording medium;