JPH02297732A - Information recording medium and its inspection method - Google Patents

Abstract

PURPOSE:To enable simple and accurate inspection of a medium by manufacturing such an optical disk that has a mirror area with a mirror surface for measurement of reflectance in the inner area of the substrate and then by measuring the reflectance of the mirror area. CONSTITUTION:The surface of the optical disk is composed of an annular groove area 13 for recording having helical grooves, a mirror area 14 having a mirror surface, an inspection groove area 15 having the same groove pattern as the area 13. The optical disk is judged by photoirradiation on the mirror area 14, measuring the reflectance and comparing the reflectance to the specified value. Some types of medium, depending on the purpose of its use, can be judged enough only by the reflectance, but it is preferable to inspect the medium by measuring the recording/reproducing characteristics such as C/N and jitter by use of the inspection groove region 15. Thereby, recording medium having excellent characteristics can be easily selected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to an information recording medium that can be advantageously used for recording or reproducing information using a high-energy-density laser beam, and a method for inspecting the same after manufacturing. be.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk, and includes video disks, audio disks, large-capacity still image files, large-capacity computer disk memories, and the like. Among these information recording media, compact discs (CDs) are widely used for reproducing audio such as music, and other media are gradually being put into practical use.

Read-only CDs (compact discs) are made based on the CD standard and are read (played) while rotating the CD at a constant linear speed of 1.2 to 1.4 m/s.
Within the range of signal surface inner diameter 45mm and signal surface outer diameter 116mm, bit width 0°8μm, track pitch 1.6μm
It is required to have a maximum recording time of 74 minutes. Conventional audio CDs are playback-only CDs with bits pre-formed on the substrate (therefore, they do not have a recording layer), and have the disadvantage that information cannot be recorded or edited. Therefore, D RA W (DirectRead
After WriLe (writable) type CDs have been developed, some of which have already been put into practical use.

In addition, files such as documents, data, and still images can also be stored on CD-ROM (Read Only Memory).
y) or CD-1 (Interactive), read-only type optical discs especially for computers are being developed. Furthermore, CD-ROM
CD-WORM (Write
E0nce 1lead Memory) is also being developed.

DRAW type information recording media (optical disks) are l5O(
Both the International Organization for Standardization) compatible type and the CD compatible type are already known. These information recording media have the following basic structure:
A disc-shaped transparent substrate made of plastic, glass, etc.
It has a recording layer made of metal or semimetal such as Bi, Sn, In, Te, etc. provided thereon. Information is written on an optical disk by, for example, irradiating the optical disk with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in physical changes such as bit formation or phases. Information is recorded by causing a chemical change such as a change in its optical properties. Reading information from optical discs is also done by irradiating the optical disc with a laser beam, etc.
Information is reproduced by detecting reflected light or transmitted light according to changes in the optical characteristics of the recording layer.

Furthermore, an erasable type (E-DRAW type) optical disk that is not only capable of recording and reproducing as described above, but also allows repeated recording, has been developed and is attracting attention.

Such optical disks are manufactured by, for example, forming a substrate having pregrooves on its surface, forming a recording layer made of metal or the like, and providing a protective layer or the like as necessary. During processes such as substrate molding or recording layer formation, optical discs with characteristics outside the predetermined range naturally occur due to differences in working conditions. Therefore, in order to inspect whether the obtained optical disk has predetermined characteristics, an inspection area is provided on the optical disk. This inspection is carried out by actually irradiating a laser beam onto the manufacturing areas (having a recording layer on a pregroove) set on the inner and outer circumferential sides of the disk to perform recording and reproduction. However, the optical disc has no boundary between the manufacturing area and the user area where recording is performed, and requires an expensive device to search the manufacturing area. In addition, with this type of recording and reproducing inspection method, the operation is complicated;
Another problem is that it takes a considerable amount of time. Furthermore, in order to eliminate this complexity, even if the number of samples obtained above is limited and the test is performed by measuring the characteristics thereof, there is a problem that the reliability of the test is lowered. Therefore,
A simple and highly reliable optical disk inspection method is desired.

[Object of the Invention] An object of the present invention is to provide a simple and accurate method for inspecting information recording media in order to select information recording media having predetermined characteristics.

Further, the present invention provides a tube for selecting information recording media having predetermined characteristics by measuring the reflectance of the rear-packed mirror area after manufacturing an information recording medium having a mirror area on the inner circumferential side. The purpose of this research is to provide an accurate inspection method for information recording media.

A further object of the present invention is to provide an information recording medium that has a reflectance measurement mirror area on the inner circumferential side of the disk, which is used to select information recording media having predetermined characteristics.

[Summary of the Invention] The present invention provides a ring having an annular recording groove area formed of a spiral or concentric groove on its surface, and a surface provided adjacent to the inner peripheral side of the groove area having a mirror surface. A laser is used to write information on a disk-shaped substrate with a hole in the center and a ring-shaped inspection groove area provided adjacent to the inner circumferential side of the mirror area on the right side. Or an information recording medium provided with a readable recording layer.

The information recording medium has a ring-shaped recording groove area on the surface that includes a spiral or concentric groove, and a ring-shaped mirror that is provided adjacent to the inner circumferential side of the groove area and has a mirror surface. On a disk-shaped substrate with a hole in the center and a ring-shaped inspection groove area provided adjacent to the inner circumferential side of the mirror area, a laser beam is used to record or read information. between the recording groove area and the inspection groove area in order to obtain an information recording medium having predetermined characteristics from the information recording medium. The present invention can be advantageously used in an information recording medium inspection method that involves selecting information recording media having predetermined characteristics by irradiating light onto a certain mirror area and measuring the reflectance.

Preferred embodiments of the information recording medium of the present invention are as follows.

1) The mirror area between the recording groove area and the inspection groove area is 22,5 to 2 inches from the center of the substrate.
The above-mentioned information recording medium is characterized in that it is in the range of 3.0 mm.

2) The inspection groove area is located 20 minutes from the center of the substrate.
．． 0~. The above-mentioned information recording medium is characterized in that it is in the range of 22.5 mm.

3) The information recording medium, wherein the disk-shaped substrate is made of acrylic resin or polycarbonate resin.

Preferred embodiments of the method for inspecting an information recording medium of the present invention are as follows.

1) The above-mentioned information recording medium, which is characterized in that the information recording medium selected by measuring the reflectance is recorded with information by irradiating the inspection groove area with a laser beam, and then the recorded signal is inspected. inspection method.

[Detailed Description of the Invention] The information recording medium of the present invention basically comprises a substrate having a pregroove on its surface and a recording layer formed on the substrate made of metal or the like. A mirror region having a mirror surface for measuring reflectance is provided inside the substrate.

This mirror area.

It is provided between the recording groove and the inspection groove area.

Since optical disks are obtained through processes such as substrate molding and recording layer formation, some of the obtained disks do not satisfy predetermined characteristics. Conventionally, inspection of optical discs was performed by actually irradiating laser light onto the manufacturing areas (having a recording layer on the pregroove) set on the inner and outer sides of the disc to record and play back. was. However, such an inspection method has the problem that, as mentioned above, it requires expensive equipment, the five operations are complicated, and it takes a considerable amount of time.

Therefore, the present inventors have been studying a method that can easily test whether an optical disc has predetermined recording/reproducing characteristics. As a result, we found that items with high reflectance have good other physical properties (C/N, jitter, etc.), and inspection can be performed by measuring reflectance in the inner mirror area. I understand. Conventional optical discs are subjected to temperature inspection using the manufacturing areas (inspection groove areas in the present invention) set on the inner and outer circumferential sides of the disc. Since the manufacturing area (groove area) and the manufacturing area are continuous, and the boundary between them cannot be visually distinguished, it was necessary to use expensive equipment to search for their position and evaluate their recording characteristics. Further, even if it were attempted to measure the reflectance, there was a problem in that it existed only outside the manufacturing area, making it difficult to search and measure it.

The present invention solves the above problem, and after manufacturing an optical disk having a mirror area whose surface for measuring reflectance is a mirror surface on the inside of a substrate, a predetermined reflection is obtained by measuring the reflectance in the mirror area. This is an information recording medium inspection method in which optical discs are sorted based on whether or not they have reached a certain level.

An information recording medium suitable for use in the above inspection method of the present invention will be explained with reference to FIGS. 1 and 2.

FIG. 1 shows the surface of an information recording medium of the present invention in which a recording layer is provided on a disc-shaped substrate having grooves on the surface.
FIG. 3 is an example of a perspective view for explaining the functions of a groove area and a mirror area.

FIG. 1 shows an optical disc in which a recording layer is provided on a disk-shaped substrate 12 having a hole 11 in the center and grooves, and the functional structure of the surface is a helical/V-shaped concave groove. It consists of an annular recording groove area (also referred to as user area) 13, a mirror area 14 having a surface or mirror surface, and an inspection groove area (also referred to as manufacturing area) 15 consisting of the same concave groove as 13. .

The recording groove area 13 is a recording area used by the user who purchased the optical disc to record information.

The inspection groove area 15 is an area for inspecting the obtained optical disc, and in the present invention, for discs whose reflectance is within a predetermined value range, the recording and reproducing characteristics are evaluated here depending on the case. , perform further selection.

Conventionally, inspection has been performed only by evaluating the recording and reproducing characteristics in the inspection groove area 15. In addition, since the recording groove area 13 and the inspection groove area 15 are continuous and the boundary cannot be visually distinguished, the position search and evaluation of recording characteristics etc. are all performed using expensive equipment. Ta. The mirror region 14 whose surface is a mirror surface is
This is a characteristic feature of the present invention, and conventionally a mirror area has never been provided in the middle of a groove area. In the present invention, the mirror area 14 is irradiated with light to measure the reflectance, and the resulting optical disc is inspected to see if it has a value within a predetermined range. Obtained optical disc (product)
Depending on the application, the above reflectance alone may be sufficient for inspection, but it is preferable to measure recording/reproducing characteristics such as C/N and jitter in the inspection groove area 15 for inspection.

Thereby, it is possible to easily select information recording media having excellent characteristics.

When the information recording medium is a 5-inch disk, the mirror area 14 is 22 degrees 5 to 23.0 meters from the center of the substrate.
It is preferably in the range of m.

In addition, the inspection groove area 15 is 20 mm from the center of the substrate.
．． It is preferably in the range of 0 to 22.5 mm, particularly preferably in the range of 22.0 to 22.5 mm. The above range is changed as appropriate depending on the size of the disc and taking into account the characteristics of the recording drive and reproduction drive.

FIG. 2 is an enlarged view of a cross section of the substrate in the radial direction of the mirror region 14 and inspection groove region 15 of FIG. 1.

FIG. 2 shows an optical disc in which a recording layer (not shown because it is an extremely thin layer) is provided on a disc-shaped substrate 22 having a hole 21 in the center and grooves, and the functional structure of the surface. The recording groove area 23 includes a recording groove area 23 having a concave groove, a mirror area 24 having a mirror surface, and an inspection groove area 15 having a concave groove. As can be seen from Figure 2,
The mirror region 24 is an extremely smooth mirror surface, which is convenient for measuring reflectance. Further, since the mirror area 24 is surrounded by groove areas on both sides and its position can be visually confirmed, the reflectance at this position can be easily measured. On the other hand, if this mirror area is set on the outer circumferential side, the reflectance is likely to change because the outer circumferential portion of the substrate has many changes in birefringence, and the outer circumferential side has a larger area.
It is effective to provide a mirror area on the inner circumferential side as in the present invention for reasons such as reducing the j area. Further, this mirror area on the inner circumferential side can be used for positioning the optical disc when the optical disc is inserted into a drive (recording or reproducing device). That is, since the position of the mirror area of the optical disc is fixed, the drive can detect the position where the reflectance is high and adjust the optical disc to an appropriate positional relationship with the drive.

The inspection method of the present invention, which is performed using the above-mentioned mirror part, can be applied to any type of optical disc, such as DRAW type, E-DRAW type, read-only type, as well as ISO compatible type and CD compatible type. It is. However, in the case of a read-only optical disc, a reflective layer made of metal is generally provided in place of the recording layer.

The information recording medium of the present invention is manufactured, for example, by the following method.

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information storage media. In terms of optical properties, flatness, processability, handling, stability over time, and manufacturing cost, examples of substrate materials include glass such as soda lime glass; cell-cast polymethyl methacrylate, and injection-molded polymethyl methacrylate. Acrylic resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins; polyesters such as polyethylene terephthalate; polycarbonates and amorphous polyolefins. Among these, preferred are polymethyl methacrylate, polycarbonate, epoxy resin, amorphous polyolefin and polyethylene terephthalate, with polycarbonate being particularly preferred.

The surface of the substrate on which the recording layer is provided has improved flatness,
An undercoat layer may be provided for the purpose of improving adhesive strength and preventing deterioration of the recording layer. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, nitrocellulose, polyethylene,
Polymer substances such as polypropylene and polycarbonate; organic substances such as silane coupling agents; and inorganic oxides (Si02, AIL203, etc.), inorganic fluorides (MgF2
) and other inorganic substances.

In the case of a glass substrate, hydrophilic groups such as styrene/maleic anhydride copolymer and/or maleic anhydride are added to prevent adverse effects on the recording layer due to alkali metal ions and alkaline earth metal ions liberated from the substrate. Preferably, a subbing layer consisting of a polymer containing groups is provided.

The undercoat layer can be formed by, for example, dissolving or dispersing the above-mentioned substance in a suitable solvent, and then applying this coating solution to the substrate surface by a coating method such as spin cording, dip coating, or extrusion coating.

Furthermore, as mentioned above, pre-grooves are formed on the substrate for the purpose of good tracking, and/or pre-pits are formed by molding a resin material for the purpose of forming unevenness representing information such as address signals, or a pre-groove layer is formed on the substrate. It is provided by the formation of etc. As a material for the layer such as the pregroove, a mixture of at least one type of acrylic acid monoester, diester, triester, and tetraester (or oligomer) and a photopolymerization initiator can be used. The layer thickness of the pre-groove etc. layer is
It is generally in the range of 0.05 to 100 μm, preferably in the range of 0.1 to 50 μm. Further, in the case of a plastic substrate, an intermediate layer may be provided directly on the substrate groove layer.

Examples of the intermediate layer include, in addition to the heat insulating layer, an adhesive layer, a reflective layer, a sensitivity enhancement layer (gas generation layer), and the like.

When the intermediate coating layer is a heat insulating layer, for example, polymethyl methacrylate, acrylic acid/methacrylic acid copolymer,
Styrene/maleic anhydride copolymer, polyvinyl alcohol, N-methylol/acrylamide copolymer, styrene/vinyltoluene copolymer, chlorinated polyethylene,
Chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, polyester, polyimide, vinyl acetate/vinyl chloride copolymer, ethylene/vinyl acetate copolymer, polyethylene, polypropylene, polycarbonate,
It can be formed using a coating liquid in which a polymeric substance such as fluorinated polyolefin is dissolved in a solvent. Preferably, a coating solution using fluorinated polyolefin, chlorinated polyethylene or nitrocellulose is used, and chlorinated polyethylene is particularly preferable.

The layer thickness (average layer thickness) of the intermediate coating layer is determined in consideration of the characteristics required of the intermediate layer. The layer thickness of the intermediate coating layer is usually in the range of 100 to 1000 angstroms.

The intermediate layer formed as described above, preferably the chlorinated polyethylene layer, can reduce the loss of thermal energy due to laser beam irradiation from the recording layer to the substrate due to thermal conduction, and the chlorinated polyethylene layer Since gas force 9 is generated from the irradiated area, pits can be easily formed and recording sensitivity can be increased.

When forming the chlorinated polyethylene layer, the concentration of the coating solution in which chlorinated polyethylene is dissolved in a solvent is preferably within the range of 0.1 to 0.4%. The concentration of this coating liquid is 0.
If it is less than 1%, the role of the sensitivity enhancing layer, such as the function of facilitating the formation of bits in the chlorinated polyethylene layer, is undesirably reduced.

Additionally, if it exceeds 0.4%, uneven coating tends to occur when applying the chlorinated polyethylene coating solution, which may result in variations in sensitivity on the same disk and an increase in burst errors. I don't like it.

A recording layer is provided on the substrate or on the intermediate layer. The material used for the recording layer may be any material conventionally used in optical discs.

Examples of materials used for the recording layer include Te, Zn, I
Metals such as n, Sn, Zr, All, Cu, Ge; Bi
, As, Sb, and other metalloids; Ge, Si, and other semiconductors; and alloys thereof, or combinations thereof. Compounds such as sulfides, oxides, borides, silicon compounds, carbides, and nitrides of these metals or semimetals; and mixtures of these compounds and metals can also be used in the recording layer. Further, dyes such as cyanine dyes may be used in the recording layer, or polymer compounds used for rough phase change recording may be used.

The recording layer can be formed on the substrate or on the intermediate coating layer by using the above-mentioned recording material by vapor deposition, sputtering, ion blasting, or other methods. Colorants, polymer compounds, etc. can be provided by coating. If desired, an undercoat layer may be interposed below the intermediate layer.

The recording layer may be a single layer or a multilayer, but the layer thickness is generally 100 to 500 ml from the viewpoint of optical density required for optical information recording.
It is in the range of 500 angstroms. In addition, when providing dyes or polymer compounds by coating, if the dye is used instead of the intermediate layer material when forming the intermediate layer, it will be possible to form the recording layer and to coat both corners of the grooves on the substrate. It is also possible to simultaneously form a tracking guide in which the top of the side wall is arcuate.

Preferably, a protective layer is provided on the recording layer. Examples of the protective layer include a laminate of a soft protective layer made of a soft resin material and a hard protective layer made of a hard resin material.

This laminate is laminated on the recording layer with the soft protective layer side facing the recording layer side. Examples of the soft resin material include polyurethane, polyvinylidene chloride, ethylene/vinyl acetate copolymer, silicone rubber, styrene/butadiene rubber, polyvinylidene chloride, and polyacrylic acid ester. Usually, these are applied onto the recording layer by methods such as solution coating, latex coating, and melt coating, and are subjected to treatments such as drying and heating as necessary to form a soft protective layer. The thickness of the soft protective layer is usually in the range of 100λ to 5 μm, preferably in the range of 0.3 to 3 μm. Examples of hard resin materials include ultraviolet curing resins and thermosetting resins. Usually, these are applied onto a soft protective layer by a method such as solution coating, and if necessary, a treatment such as ultraviolet irradiation or heating is performed to form a hard protective layer. The thickness of the hard protective layer is usually in the range of 0.1 to 10 μm, preferably in the range of 1 to 3 μm.

In the present invention, in order to protect the recording layer, it is preferable to use a protective film instead of the above-mentioned protective layer and to cover the recording layer by bonding it to the inner and outer peripheral sides of the substrate. The bonding is preferably performed by ultrasonic fusion or thermal fusion. Moreover, it is preferable to adopt a sandwich structure having the following protective function instead of the above-mentioned protective layer.

A bonded type information recording medium can be manufactured by bonding two substrates having the above structure using an adhesive or the like.In an air sandwich type recording medium, By joining at least one of the disk-shaped substrates having the above structure via a ring-shaped outer spacer and an inner spacer, or via a protrusion provided on one or both of the substrates. can be manufactured.

The surface of the substrate opposite to the side on which the recording layer is provided is coated with inorganic substances such as silicon dioxide, tin oxide, and magnesium fluoride, or thermoplastic resins and photocurable resins to improve scratch resistance and moisture resistance. A thin film made of a polymeric material such as mold resin may be provided by a method such as vacuum deposition, sputtering, or coating.

Next, a method for optically recording information on the information recording medium will be described. This is an example of a recording method used in the present invention.

First, while rotating the information recording medium at a constant linear velocity or constant angular velocity, a recording light such as a semiconductor laser beam is irradiated from the substrate side to the groove of the pregroove to generate an EFM signal of a CD format. Signals are recorded by forming bits in the recording layer of the groove.

Generally, a semiconductor laser beam having an oscillation wavelength in the range of 750 to 850 nm is used as the recording light.

Generally recorded with a laser power of 3-15 mW.

As a result, bits having a length of 0.70 to 4.0 μm are formed concentrically or spirally at intervals of 0.70 to 4.0 μm in the recording layer.

During recording, tracking control is performed by a push-pull method or the like using the tracking pregroove. Information is recorded in the grooves of the pregroove or in the lands between the grooves.

Information is reproduced by performing tracking control using a three-beam method, etc. by irradiating semiconductor laser light from the substrate side and detecting the reflected light while rotating the recording medium at the same constant linear velocity or constant angular velocity as described above. information can be played back while

[Effects of the Invention] As described above, the inspection of the present invention selects information recording media having predetermined characteristics by measuring the reflectance of the information recording medium of the present invention having a mirror area on the inner peripheral side of the substrate. This method can be said to be a simpler and more accurate inspection method than the conventional inspection method of evaluating recording and reproducing characteristics in the manufacturing area.

In other words, the manufacturing areas (inspection groove areas) set on the inner and outer sides of conventional discs.
In optical discs that are inspected using , the user area where information is recorded and the manufacturing area mentioned above are continuous, and the boundary cannot be visually distinguished, so it is difficult to search for the location, record characteristics, etc. All evaluations were conducted using expensive equipment. Therefore, the operation is complicated and the test method requires a relatively long time.

On the other hand, in the above inspection method of the present invention, since the mirror area, which is the reflectance measurement position, is sandwiched between two groove areas, it can be easily confirmed, and if the reflectance value is within a predetermined range, then Since it can be said that the optical disc has good recording and reproducing characteristics, it can be said that it is a simple and accurate inspection method.

Furthermore, the inner mirror area of the present invention can also be used to align the optical disk when the optical disk is inserted into a drive (recording or reproducing device).

[Brief explanation of the drawing]

FIG. 1 shows the surface of an information recording medium of the present invention in which a recording layer is provided on a disc-shaped substrate having grooves on the surface.
FIG. 3 is an example of a perspective view for explaining the functions of a groove area and a mirror area. FIG. 2 is an enlarged view of a cross section in the radial direction of the substrate in the mirror region and inspection groove region of FIG. 1. FIG. Hole: 11, 21 Disc-shaped substrate: 12, 22 Recording groove area: 13, 23 Mirror area: 14, 24

Claims (1)

[Claims] 1. An annular recording groove area formed of a spiral or concentric groove on the surface, a ring-shaped mirror area provided adjacent to the inner peripheral side of the groove area and having a mirror surface, and the mirror area. A recording layer on which information can be written or read using a laser beam is provided on a disk-shaped substrate with a hole in the center and a ring-shaped inspection groove area provided adjacent to the inner circumference of the disk. An information recording medium made up of 2. An annular recording groove area formed of a spiral or concentric groove on the surface, a ring-shaped mirror area provided adjacent to the inner peripheral side of the groove area and having a mirror surface, and the mirror area. A recording layer on which information can be written or read using a laser beam is formed on a disk-shaped substrate with a hole in the center and a ring-shaped inspection groove area provided adjacent to the inner circumference of the disk. After manufacturing an information recording medium by doing this, the mirror area between the recording groove area and the inspection groove area is irradiated with light and the reflectance is measured to produce an information recording medium having predetermined characteristics. A method for inspecting information recording media, which consists of sorting.