JPH03254436A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To make improvement in the transferability of prepits by forming guide grooves shallower than the other parts in the whole or a part of the regions inclusive of the parts adjacent to the prepit arrays among the guide grooves. CONSTITUTION:A substrate 1 is formed by an injection molding method. The guide grooves 2 and the prepits 3 are transferred thereto simultaneously with the injection molding of the substrate 1. The guide grooves 2a shallower than the other parts are formed in the whole or a part of the regions inclusive of the parts adjacent to the prepit arrays 3 among the guide grooves 2. Namely, a stamper is provided with the projecting parts for the low guide grooves corresponding thereto to smooth the flow of the resin flowing through these parts to the circumference of the projecting parts for the prepits and to prevent the generation of turbulence. The transferability of the prepits is improved in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording medium, and more particularly to the shape of a guide groove in an optical information recording medium in which a pre-pit array is formed between adjacent guide grooves. .

[Conventional technology]

Conventionally, as shown in FIGS. 10 and 11, there has been known an optical information recording medium in which pre-pit rows 12 are formed between guide grooves 11 formed at equal intervals (Japanese Unexamined Patent Application Publication No. 1983-1999).
No. 41446).

This optical information recording medium is characterized in that since the track signal read from the guide groove 11 is not superimposed on the information signal read from the pre-pit row 12, a read signal with a high S/N ratio can be obtained. It is attracting attention as a recording method for magneto-optical recording media, etc., which reads minute changes in the Kerr rotation angle as information signals.

[Problem to be solved by the invention]

By the way, the guide groove 11 and prepit row 12 are transferred onto one side of the substrate by a transfer technique. The method for transferring the guide grooves 11 and pre-pit rows 12 is as follows: (1) uniformly spreading a photocurable resin between the substrate and a stamper having a concavo-convex pattern that is reversed with respect to the desired guide grooves 11 and pre-pit rows 12; 5. After the resin has hardened, the photocurable resin is peeled off from the stamper to form a resin layer on one side of the substrate with the guide grooves 11 and pre-pit rows 12 transferred thereto (2P method); is formed into the shape of a desired substrate, and a part of the cavity surface is formed by the stamper, and injects and fills the mold with molten resin;
There is a method (injection molding method) in which a substrate having the desired guide grooves 11 and pre-pit rows 12 on one side is integrally formed.

The injection molding method is characterized by much higher productivity than the 2P method, and now that optical information recording media have reached the mass production stage, establishing this technology is the most important technological This is one of the challenges.

However, as mentioned above, the pre-pit row 1 is formed between the guide grooves 11.
When an optical information recording medium having the above-mentioned number 2 is manufactured by the injection molding method, the transferability of the pre-pits 12 is poor, making it difficult to manufacture a normal optical information recording medium.

As a result of research into the causes of such defects, the inventors of the present application have obtained the following knowledge. That is, as shown in FIG. 12, the stamper 13 is formed with a guide groove protrusion 14 which is an inverted pattern of the guide groove 11 and a prepit protrusion 15 which is an inverted pattern of the prepit 12. When the molten resin 16 is injected at high speed from one side of the stamper 13, the molten resin 16 that advances inside the cavity along the stamper 13 collides with the guide groove protrusion 14, creating a turbulent flow and entraining air. When air entrainment occurs in this way, the width w1 of the guide groove protrusion 14 and the pre-pit protrusion 1
5 has a width W2 of about 0.4 μm to 0.8 μm, and a height hl of the guide groove protrusion 14 and a depth h2 of the pre-pit protrusion 15 is about 61 nm to 138 nm or an integral multiple thereof (
However, when the wavelength of the reproduction light is 830nrn and the refractive index of the substrate is 1.5), the interval (track pitch) P between the two adjacent guide groove protrusions 14 and 14 is approximately 1.6.
Since the pre-pit protrusion 1 is extremely fine as μm,
5 side, especially the back side of the pre-pit projections 15, the resin does not wrap around sufficiently, and normal prepit transfer is inhibited.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned deficiencies of the prior art and to provide an optical information recording medium in which pre-pits can be transferred with high precision by injection molding.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an optical information recording medium in which a pre-pit row is formed between guide grooves formed at equal intervals. A guide groove that is shallower than other parts is formed in all or a part of the area including the part adjacent to the pre-pit row.

[Effect]

In order to injection mold such an optical information recording medium, it is necessary to use a stamper in which all or part of the area of the guide groove protrusion that includes the part adjacent to the pre-pit protrusion is formed lower than other parts. There is. When this stubber is installed in a mold and molten resin is injection-molded, the flow of the resin passing through the low guide groove protrusion and around the pre-pit protrusion becomes smooth and turbulent flow is less likely to occur. The transferability of the pre-pits is improved because the entanglement of the pre-pits is reduced. As a result, an optical information recording medium on which pre-pits are transferred with high precision can be provided at a low cost.

〔Example〕

First, an outline of the present invention will be explained based on FIGS. 1 to 4.

FIG. 1 is a sectional view of an optical information recording medium according to the present invention, FIG. 2 is an enlarged sectional view of FIG. 1, FIG. 3 is a plan view of this optical information recording medium, and FIG. 1 is a sectional view showing a cross-sectional shape, and 1 is a substrate, 2 is a guide groove, 3 is a pre-pit, and 4 is a recording film.

The substrate 1 is made of, for example, polycarbonate, acrylic resin such as polymethyl methacrylate, or polyolefin resin such as polymethylpentene.

It is made of a transparent thermoplastic resin such as polysulfone, polyethersulfone, polyarylate, etc., and the guide groove 2 and pre-pit 3 are integrally formed on one side thereof. This substrate 1 is formed by an injection molding method, and the substrate 1
The guide grooves 2 and pre-pits 3 are transferred simultaneously with the injection molding.

The guide groove 2 is formed in a concentric or spiral shape in the plane direction of the substrate 1. Further, the pre-pit 3 is a second pre-pit.
As shown in the figure and Fig. 3, two adjacent guide grooves 2
, 2. A guide groove 2a that is shallower than other parts is formed in all or part of the area of the guide groove 2 that includes a part adjacent to the pre-pit row 3.

The cross-sectional shape of each prepit constituting the guide grooves 2, 2a and the prepit row 3 may be any shape, such as a 7-shape, a U-shape, a rectangle, or a trapezoid, as shown in FIGS. 4(a) to 4(d). can be formed into

The depth dl of the guide groove 2 (a portion other than the shallow guide groove 2a) can be formed to any depth, but in order to strengthen the contrast of the readout light in the detector and obtain a high S/N, If the wavelength of light is λ and the refractive index of the substrate is n, then λ/8 n or λ/6 n or λ/4
It is preferable to form an integer multiple of n. The depth dl of the shallow guide groove 2a can be formed to any depth shallower than the guide groove 2, but in order to smooth the flow of resin during injection molding, the depth dl of the shallow guide groove 2a should be at least the same as the depth of the guide groove 2. These guide grooves are preferably about 80% or less of dl.
Although the width w1 of 28 can be formed arbitrarily, it is preferable to form it to 0.4 μm - 0.8 μm in order to improve the recording density. The pitch P between two adjacent guide grooves 2.2 is approximately 1.6 μm.

Moreover, the depth d3 and width W2 of the pre-pit 3 are also formed in the same range as the guide groove 2.

Hereinafter, the forming portions of the shallow guide grooves 2 for the pre-pit rows 3 are illustrated in FIGS. 5 to 8.

The shallow guide grooves 2a can be formed in any arrangement in all or part of the area including the portion adjacent to the pre-pit row 3.

For example, as shown in FIG. 5(a), the shallow guide groove 2a having the same length as the length 1 of the prepit row 3 can be formed in a portion adjacent to the prepit row 3, Furthermore, as shown in FIG. 5(b), the shallow guide groove 2a, which is slightly longer than the length 111 of the pre-pit row 3, can be formed in the same portion.

Further, as shown in FIGS. 6(a) and 6(b), among the pre-pits constituting the prepit row 3, the address signal pit row 3a is adjacent to the address signal pit row 3a formed by a combination of pits that are longer than the normal value prepits. It is also possible to form the shallow guide groove 2a only in that portion. In this case, as shown in FIG. 6(a), the shallow guide groove 2a having the same length as the length of the address signal pit row 3a can be formed, or ), it is also possible to form the shallow guide groove 2a slightly longer than the length ILz of the address signal pit row 3a. When the length of the shallow guide groove 2a is formed to be slightly longer than the length ILz of the address signal pit row 3a, pit-free portions (land portions) arranged before and after the address signal pit row 3a. It can be formed to have a length of 5 and 3.

Further, as shown in FIGS. 7(a) and 7(b), the shallow guide groove 2a is formed only in a portion of the pre-pits constituting the address signal pit row 3a that is adjacent to the sector mark signal pit row 3b. You can also do it. In this case, as shown in FIG. 7(a), the sector mark signal pit row 3
The shallow guide s2a can be formed to have the same length as the length i14 of b, or, as shown in FIG. The shallow guide groove 2a may also be formed.

When the length of the shallow guide groove 2a is made slightly longer than the length 4 of the sector mark signal pit row 3b,
It can be formed to have a length that is the sum of the length j2s of the land portions 5 arranged before and after the sector mark signal pit row 3b.

Further, as shown in FIGS. 8(a) and 8(b), the shallow guide grooves 2a may be formed only in the portions adjacent to the individual pits 3C constituting the pre-pit row 3a. In this case, as shown in FIG. 8(a), the shallow guide grooves 2a can be formed at positions adjacent to all the pits 3C, or as shown in FIG. Among the prepits forming the prepit row 3a, the prepits are relatively long.

For example, a shallow guide groove can be selectively formed only in a region including a portion adjacent to a pre-pit having a pit length of 1 μm or more. Of course, in this case as well, the shallow guide groove 2
A can be formed to have the same length as each pre-pit 3C, or can be formed longer than each pre-pit 3C.

In each of the above embodiments, a case has been described in which shallow guide grooves 2a are formed in both guide grooves located on both sides of the pre-pit row 3, but the gist of the present invention is not limited to this. For example, in optical information recording media such as CLV (Constant Linear Velocity) optical information recording discs in which the pre-pit forming portions are not aligned in the radial direction of the disc, resin injection for the pre-pit rows 3 is required. It is also possible to form a shallow guide groove 2a in the guide groove 2 located on the direction side.

The recording film 4 is made of, for example, a low melting point metal such as TeSe, an organic dye containing a certain kind of dye, T e Fe Co, G
It can be formed using any known heat mode recording material, such as a magneto-optical recording material such as dTbFe, TeDyFe, GdCo, or TbFe, or a phase change recording material such as TeOx or As-Te-Ge.

Examples of methods for forming the recording film 4 include vacuum evaporation, sputtering, ion blasting, electroless plating,
Appropriate thin film forming means such as plasma deposition or spin code method can be applied.

Next, four specific examples will be given and the effects of the present invention will be described.

1st Example By injection molding polycarbonate (optical grade), a plate with a diameter of 130 mm and a plate thickness of 1 and 2 mm was formed with guide grooves having shallow guide grooves in some parts and pre-pit rows transferred thereto.
A substrate of m m was prepared. The guide groove had a triangular groove shape with a depth of about λ/8n and a width of about 0.6 μm, and was formed in a spiral shape with a pitch of about 1.6 μm. The pre-pit row was formed into a rectangular groove shape with a depth of about λ/4n and a width of about 0.6 μm, and was arranged between the guide grooves. The shallow guide groove is shaped like a triangular groove having the same width as the guide groove and a depth of about 80% of the depth of the guide groove, and is formed from a plurality of sector mark signal pits in the pre-pit row. It is formed at a position adjacent to the part from the start end to the end end of the sector mark signal pit row (see FIG. 7(a)).

The molding conditions for the substrate were: cylinder temperature of 350°C, mold temperature of 100°C, injection speed of 150 questions/sec, and injection pressure of 1500 kg/CIK.

Next, a tellurium-based recording film was sputtered onto the surface of this substrate on which the guide grooves and pre-pit rows were formed, thereby producing an optical information recording disk.

Second Embodiment In an optical information recording disk similar to the first embodiment,
The shallow guide groove was formed at a position adjacent to a portion from the start end to the end end of each sector mark signal pit (see FIG. 8(b)).

The material of the substrate, the injection molding conditions, the shapes and dimensions of the guide grooves and pre-pits, the recording film material and the method of forming the same are the same as in the first embodiment.

Third Embodiment In an optical information recording disk similar to the first embodiment,
The guide groove is a rectangular groove with a depth of approximately λ/6n and a width of approximately 0.6μm, and the pre-pit row also has a depth of approximately λ/6n.
It was formed into a rectangular groove shape with a width of about 0.6 μm. Also,
A shallow guide groove is formed with a rectangular groove having the same width as the guide groove and a depth of about 80% of the depth of the guide groove, and a sector mark signal consisting of a plurality of sector mark signal pits in a pre-pit row. It was formed at a position adjacent to the portion from the start end to the end of the pit row (see FIG. 7(a)).

The material of the substrate, the injection molding conditions, the recording film material and the film forming method thereof are the same as in the first embodiment.

Fourth Embodiment In an optical information recording disk similar to the third embodiment,
The shallow guide groove was formed at a position W (see FIG. 8(b)) adjacent to a portion from the start end to the end end of each sector mark signal pit.

The material of the substrate, the injection molding conditions, the shapes and dimensions of the guide grooves and pre-pits, the recording film material and the method of forming the same are the same as in the third embodiment.

FIG. 9 shows changes in the amount of waveform distortion of the read signal when the depth of the shallow pre-pits is varied. The horizontal axis of this graph is the depth of the normal guide groove, and the depth D of the shallow guide groove.
The ratio of p (DP/Do) is scaled, and the vertical axis shows the ratio of the amplitude Vo of this signal to the amplitude Vo of the signal read out from a normal guide groove and the difference ■ between the amplitude Vo of this signal and the amplitude of the signal read out from the shallow guide groove. (V/vO) is graduated. O in the graph is the same optical information recording disk as the first embodiment, and data is obtained by varying the depth of the shallow guide groove, and Δ is the data for the second embodiment.
The data is an optical information recording disk similar to that of the embodiment, but the depth of the shallow guide groove is varied; ◇ indicates data for the same optical information recording disk as in the first embodiment, but with various depths of the shallow guide grooves. The readout conditions were as follows: NA O, 5° laser wavelength, 830 nm, reproducing drive with reproducing laser power of 1.0 mW, and rotational speed of 120 rpm.

As is clear from this graph, when D p / Do is set to 80%, ■ / vo becomes 30% or less, and a practically sufficient signal amplitude is obtained, which reduces pre-pit reading errors and improves the S/N ratio. It turns out that improvements can be made.

Although each of the above embodiments has been explained using an optical information recording disk as an example, the gist of the present invention is not limited thereto, and can be applied to other optical information recording media such as an optical cart. Of course.

〔Effect of the invention〕

As explained above, according to the present invention, during injection molding of a substrate, all or a part of the region of the guide groove protrusion including the portion adjacent to the pre-pit protrusion is formed to be lower than other parts. The resin can flow smoothly around the pre-pit protrusion through the low guide groove protrusion, and the pre-pit transferability is improved. Therefore, the waveform distortion of the signal read from the pre-pits is improved, and it is possible to improve the S/N ratio and reduce the error rate.

[Brief explanation of drawings]

FIG. 1 is a sectional view schematically showing the optical information recording medium according to the present invention, FIG. 2 is an enlarged sectional view of FIG. 1, FIG. 3 is a plan view of the optical information recording medium of FIG. 1, and FIG. (a) to (d) are cross-sectional views illustrating the cross-sectional shapes of the guide groove, the shallow guide groove, and the blip pit;
7(a), 8(b) and 8(a) and 8(b) are plan views of main parts illustrating the arrangement of shallow guide grooves, and FIG. 9 is a graph 2 and 10 showing the effects of the present invention. 1 is a plan view of essential parts of a conventionally known optical information recording medium, the first engineering drawing is a sectional view of the optical information recording medium shown in FIG. 10, and FIG. 12 is an explanatory diagram showing problems with the conventional optical information recording medium. It is. 2: Guide groove, 2a: Shallow guide groove, 3: Pre-bit row, 4: Recording film 3 Figure 4 Figure 2 (3) 2 (3) 2 (3) 2 (3) The same groove shallow ν111 Inner can 3 Riji 0 Shito Ryori Ichimai Figure 6 Figure 8 Figure Umbrella τ Wandering 1 Figure (0) (b) 0 0 0 0 00 (Dp/Do)X100 C% no 0 Illustration procedure amendment (method) % formula % Indication of the case Name of the patent application patent invention Relation to the case of the person who made the optical information recording medium amendment No. 1-313358

Claims (8)

[Claims] (1) In an optical information recording medium in which a pre-pit row is formed between guide grooves formed at equal intervals, there is a An optical information recording medium characterized in that a guide groove is formed that is shallower than the portion of the optical information recording medium. (2) The optical information recording medium according to claim 1, wherein the shallow guide groove is formed in a region of the pre-pit row that includes a portion adjacent to an address signal pit row. (3) The optical information recording medium according to claim 1, wherein the shallow guide groove is formed in a region of the address signal pit row that includes a portion adjacent to the sector mark signal pit row. Medium. (4) The optical information recording medium according to claim 1, wherein the shallow guide groove is formed in an area including a portion adjacent to each prepit forming the prepit row. (5) The optical information recording medium according to claim 1, wherein the shallow guide groove includes a portion adjacent to a prepit having a pit length of 1 μm or more among the portions adjacent to individual prepits constituting the prepit row. An optical information recording medium characterized in that an optical information recording medium is formed in a region. (6) In the optical information recording medium according to any one of claims 1 to 5, of the two guide grooves adjacent to the prepit row, the guide groove is located on the upstream side of the resin flow from the prepit row during injection molding of the substrate. An optical information recording medium characterized in that the shallow guide groove is formed only in the guide groove arranged in the . (7) In the optical information recording medium according to any one of claims 1 to 6, the shallow guide groove is defined by the length of the pre-pit row, the address signal pit row, the sector mark signal pit row, or the length of each pit, and An optical information recording medium characterized in that the optical information recording medium is formed to have a total length of the land portions arranged before and after the land portions. (8) In the optical information recording medium according to any one of claims 1 to 7, the cross-sectional shape of the guide groove and the shallow guide groove is
An optical information recording medium characterized in that it is formed into a letter shape, a U shape, a rectangle, or an inverted trapezoid.