JPH0827986B2 - Optical information recording medium - Google Patents

Description

The present invention relates to an optical information recording medium such as an optical disc, and more particularly to a material of a recording film underlayer.

[Prior Art] One of the recording methods of an optical disk is a CAV (Constant Angular Velocity) method in which the angular velocity in the recording area is constant, but in this method, the recording density gradually increases toward the outer peripheral side of the disk. It has the drawback of going down. In order to eliminate this drawback and increase the recording density, CLV (Constant Linear V
elocity) method or MCAV (Modified Constant Ang
Regular Velocity (MCV) method, MCLV (Modified Constant Linea)
r Velocity) method is adopted.

These systems are configured so that the recording density is almost constant in the inner peripheral portion, the middle portion, and the outer peripheral portion of the disk, but especially in the MCAV type and MCLV type disks, the recording area is arranged along the radial direction of the disk. It is divided into blocks of several to several tens of stages, and the number of sectors in the block increases as it goes to the outer periphery. FIG. 8 is an explanatory diagram of this format, and 7 in the figure is an example of a set of prepits in which a large number of prepits 8 (see FIG. 9) are arranged. As shown in the figure, the end portions of most of the prepet set rows 7 are displaced from the end portions of the prepet set rows 7 of the adjacent blocks and face the sector portions of the adjacent blocks.

On the other hand, as one of the methods for manufacturing an optical disk, for example, an ultraviolet coin resin is spread between a transparent substrate such as glass and a stamper on which an inversion pattern of a signal pattern is formed, and an inversion pattern of the stamper is formed. Is transferred to the underlayer of the recording film. The so-called 2P method is known.

In this way, a groove (pre-group) for tracking is formed on the surface of the optical disk, and by guiding the groove, laser light is focused on the recording layer on the disk surface at the spot,
By melting locally, a hole (prepit) was formed and desired information was recorded.

[Problems to be Solved by the Invention] FIG. 9 is an enlarged cross-sectional view in the AA direction in the circle of FIG. In the figure, 3 is a recording film underlayer made of an ultraviolet curable resin or the like, 5 is a recording layer, and 9 is a pregroup.

By the way, since the recording layer 5 is formed by using a thin film forming technique such as vapor deposition or sputtering, the peripheral surface 10 of the concave prepit 8 having a deeper groove than the pregroup 9 is extremely thin. Further, the ultraviolet curable resin used in the optical disc contains an organic compound having hydro-oxygen such as hydroxymethylmethacrylate for improving the adhesiveness to the transparent substrate, so that the water absorption of the cured product is relatively high. .
Therefore, during assembly of the optical disk, moisture in the air permeates the recording film underlayer 3 from the peripheral surface 10 of the prepit 8 as indicated by the dotted arrow. As described above, since a large number of prepets 8 are arranged in a row to form the prepite aggregated array 7, the permeation of the moisture locally occurs near the prepite aggregated array 7, and as a result, the recording film underlayer 3 is formed. Partially swells.

When the prepit aggregate rows 7 of adjacent blocks are arranged on a straight line, there is no problem because the swelling of the recording film underlayer 3 cancels each other in the radial direction of the disk. However, it is extremely rare that the prepet set rows 7 are arranged in a straight line with each other between the blocks, and in most cases, the ends of the prepet set rows 7 face the sector portions of the adjacent blocks. In such a case, as shown in FIG. 9, the swelling of the recording film underlayer 3 extends to the sector part of the adjacent block. Therefore, in the above-mentioned CLV system, MCAV system and MCLV system, near the boundary between the blocks. The laser pick-up is swung to the left and right of the track over hundreds to thousands of tracks in. Therefore, the tracking noise becomes high, and there is an area (dead zone) that cannot be used for recording. In an optical disc with a large number of blocks, this dead zone increases,
The recording capacity is significantly reduced, and in some cases, the recording density is lower than that of the CAV method.

Note that, as known techniques related to the present invention, there are inventions described in, for example, JP-A-62, 144938 and JP-A-63-210118.

An object of the present invention is to eliminate such drawbacks of the prior art and provide a highly reliable optical information recording medium that reduces tracking noise.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides at least a transparent substrate and a recording film having a large number of signal recesses such as pits and pregroups formed on the transparent substrate. The present invention is intended for an optical information recording medium such as an optical disk, which is provided with an underlayer and a recording layer formed on the underlayer by a thin film forming technique such as vapor deposition or sputtering. The ultraviolet curable resin that constitutes the recording film underlayer has (a) an acrylic group or a methacrylic group at the terminal,
And an organic compound having a polybutadiene skeleton or a poly-1-butene skeleton in the molecule, (b). An organic compound having one acrylic group or methacrylic group in one molecule and having no polar group such as a hydroxyl group, a carboxyl group, a thiol group, or an amine group in the molecule; (c). An organic compound having two or more acryl groups or methacryl groups in one molecule and not having a polar group such as a hydroxyl group, a carboxyl group, a thiol group or an amine group in the molecule, (d). It is characterized in that the composition is mixed with a photopolymerizing agent and the composition is cured.

[Operation] (a) organic compound, (b) organic compound, (c)
The recording film underlayer cured from the composition containing the organic compound and the organic compound (d) has an extremely low water absorption rate of 0.3%.
In addition to the above, the (a) organic compound imparts appropriate toughness to the recording film underlayer, and the (b) organic compound reduces stress in the recording film underlayer to increase adhesion to the transparent substrate. Further, the organic compound (c) can impart appropriate rigidity to the underlayer of the recording film to improve the releasability from the stamper.

As a result, swelling of the recording film underlayer due to moisture absorption can be suppressed, and as a result, tracking noise can be reduced and a highly reliable optical information recording medium can be obtained.

[Embodiment] FIGS. 1A to 1D are process diagrams for explaining a manufacturing process of a recording single plate of an optical disk according to Embodiment 1. FIGS.
As shown in (a) of the figure, the groove (depth 0.09 μm,
Width 0.40 μm) and pit (depth 0.16 μm, width 0.60 μm)
A nickel stamper 1 having an outer diameter of 300 mm and having a diameter of m) is prepared.

Outside diameter 300 after baking silane coupling agent (γ-methacryloxypropyltrimethoxysilane) at 110 ℃ for 30 minutes
The thickness of the resin layer 3 is obtained by pressing the transparent substrate 2 to the stamper 1 side by interposing an ultraviolet curable resin 3 described later between the transparent substrate 2 made of a glass disk having a thickness of 1.2 mm and a thickness of 1.2 mm and the stamper 1. Is maintained at about 80 μm.

Then, as shown in FIG. 1 (b), an energy ray having a light intensity of 150 mw / cm ^{2 at} a wavelength of 320 to 400 nm is irradiated from the transparent substrate 2 side for 30 seconds by using a high-pressure mercury lamp 4, and the ultraviolet curable resin layer 3 is cured to form a recording film base layer.

Next, as shown in FIG. 1 (c), the stamper 1 is peeled off from the resin layer 3 (recording film base layer) to obtain a transparent substrate 2 with an information pattern. Thereafter, as shown in FIG. 1 (d), a Te—Se—Pb based recording layer 5 is vacuum-deposited on the resin layer 3 to a thickness of 30 nm.

2 (a) to 2 (d) are manufacturing process diagrams showing a modified example of the recording veneer, which is different from the optical disc shown in FIG.
First underlayer 3 made of UV curable resin and nitrocellulose or polytetrafluoroethylene (fluorine resin)
A second base layer 6 made of, for example, is provided.

The underlayer 6 is provided to improve the recording sensitivity and the peelability from the stamper 1.

3 to 5 are sectional views of an optical disk using these recording single plates.

In the case of the optical disc shown in FIG. 3, the recording layer 5 side of two recording single plates are placed inside each other, and the recording layer 5 side is laminated with the inner peripheral spacer 11 and the outer peripheral spacer 12 bonded to each other. It has become.

In the case of the optical disc shown in FIG. 4, one recording single plate and one protective plate 13 are attached to each other via the inner peripheral spacer 11 and the outer peripheral spacer 12 so that the recording layer 5 is located inside. It has a record-type Air Sun Germany type structure.

The optical disc shown in FIG. 5 has a single-plate structure in which a moisture-resistant protective layer 14 is formed by coating on the recording layer 5 of the recording single plate.

In any of the structures shown in FIGS. 3 to 5, the recording layer 5 has a closed structure that is shielded from the atmosphere when the optical disc is completely assembled.

The ultraviolet curable resin that constitutes the recording film underlayer 3 is (a). It has an acrylic group or a methacrylic group at the terminal and has a polybutadiene skeleton or poly-1-
An organic compound having a butene skeleton, (b). An organic compound having one acryl group or methacryl group in one molecule and having no polar group such as a hydroxyl group, a carboxyl group, a thiol group or an amine group in the molecule; (c). An organic compound having two or more acryl groups or methacryl groups in one molecule and not having a polar group such as a hydroxyl group, a carboxyl group, a thiol group or an amine group in the molecule, (d). It is composed of a mixture of a photopolymerizing agent and a cured composition.

Among the organic compounds (a), those having a polybutadiene skeleton in the molecule include compounds represented by the following formula (1) or formula (2).

Further, among the organic compounds (a), compounds having a poly-1-butene skeleton in the molecule include compounds represented by the following formula (3).

The average molecular weight of the organic compound (a) is preferably 500 to 10,000. If the average molecular weight is less than 500, the mechanical strength of the recording film underlayer decreases, while the average molecular weight is 10,000.
If it exceeds the range, the viscosity of the photocurable composition becomes high, resulting in a decrease in workability.

Examples of the organic compound (b) include methyl acrylate, methyl methacrylate, ethyl acrylate,
Ethyl methacrylate, n-propyl acrylate, isopropyl acrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, 2-ethylhexyl acrylate, 2-Ethylhexyl methacrylate, isodecyl acrylate, isodecyl methacrylate, lauryl acrylate, lauryl methacrylate, isobornyl acrylate, inbornyl methacrylate and the like are used.

Examples of the organic compound (c) include ethylene glycol diacrylate, ethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butanediol diacrylate, and 1,4. -Butanediol methacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, 1,1
0-decanediol diacrylate, 1,10-decanediol dimethacrylate, tripropylene glycol diacrylate, tripropylene glycol dimethacrylate and the like are used.

The photopolymerization agent which is the organic compound (d) is not particularly limited as long as it produces a radical upon irradiation with light and radically polymerizes an acrylic group or a methacrylic group. For example, benzyls, benzoins, thioxanthones, anthraquinones, Benzyl ketals, 1-hydroxy chlorhexyl phenyl ketone, etc. are effective.

As the nitrocellulose used for the above-mentioned underlayer 6, the nitrogen content is 11.9 to 12.2%, the average substitution degree is about 2.1 to 2.3,
Nitrocellulose (product name: HI-1000 manufactured by Asahi Kasei) having a viscosity of 850 to 1000 (seconds) at a solid content of 12.2% is suitable.

Specific composition (parts by weight) of the composition that forms the underlayer of the recording film
Is shown in FIG. Compounds 1 to 9 in the figure are the following organic compounds.

Compound 1 Poly (1,2-butadiene) containing methacrylic groups at both ends (average molecular weight 2000: TE-2000, each manufactured by Nippon Tanka Co.) Compound 2 Poly-1-butene containing an acrylic group at both ends (average molecular weight 1000, product name TEAI-1000, manufactured by Nippontandan Co., Ltd.) Compound 3 Poly-1-butene containing both ends acryl groups (average molecular weight 3000, product name TEAI-3000 manufactured by Nippon Tanka Co., Ltd.) The molecular structural formula is the same as that of the compound 3.

The following various tests were performed on Examples 1 to 14 shown in FIG. 6, and the results are shown in the following table.

(Test item) Test 1: Water supply rate of the recording film underlayer after immersion in water at 20 ° C for 7 days. [Unit%] Test 2: Track noise after vapor deposition of recording layer and aging for 24 hours at 20 ° C, 50% RH under aeration. [Unit%] Test 3: Crosshatch adhesion test between substrate and recording film underlayer. In this test, a recording film underlayer was formed on a substrate, and 11 cuts were made in the recording film underlayer so that 1 cut was perpendicular to each other, and the cuts were made until reaching the substrate. To form. And 3 with adhesive tape
The number of remaining square portions was checked by performing a peeling operation. [JIS K5400 Reference Units] Test 4: Peelability test from stamper.

Test 5: Transferability test of pattern from stamper.

Test 6: Workability of the recording film underlayer forming process. In Tests 4 to 6, ⊚ indicates a very good condition, and ∘ indicates a good condition.

In the case of an optical information recording medium in which the underlayer 3 made of an ultraviolet curable resin and the underlayer 6 made of nitrocellulose are formed as shown in FIG. 2, the composition constituting the underlayer 3 is substantially compatible with nitrocellulose. It is better to choose a material that is not soluble. In the present specification, a material substantially incompatible with nitrocellulose means, in addition to a material having no compatibility at all,
It is meant to include those that do not affect the reflectance even if they have some compatibility.

As a result of various investigations by the present inventors on compositions that are substantially incompatible with nitrocellulose, (a) organic compounds used are those represented by the above-mentioned molecular structural formulas, and (b) As the organic compound, one having the following molecular structural formula can be used.

As the organic compound (c), one having the following molecular structural formula can be used.

In these molecular structural formulas, R is H or CH.
₃ is shown.

Next, as a result of studying the composition ratio of each of these organic compounds, it was found that those within the range of the diagonal line surrounded by the straight line connecting points A, B and C in FIG. 7 are preferable. The composition ratios of the organic compounds (a), (b) and (c) at the points A, B, C and D are shown in the following table.

Using the organic compounds (a), (b), and (c) described above, and blending within the range of the diagonal line surrounded by the straight line connecting points A, B, C, and D in FIG. There is no adverse effect on the stratum. The average reflectance with the recording layer formed is
40%, and in the case of an optical disc having a recording film underlayer compounded within the range of the diagonal line surrounded by the straight line connecting the points A to D, the variation range of reflectance was measured to be about 38 to
It was 42%. On the other hand, even if the same organic compounds (a) to (c) are used, the optical disk having the recording film underlayer compounded outside the range of the oblique line has a reflectance variation range of about 30.
The result was as wide as ~ 42%.

[Effects of the Invention] The following table shows the composition of the conventionally known recording film underlayer. The compounds in the table are as follows.

Compound 8 The same substance as compound 8 shown in the above-mentioned Example Compound 10 Polycarbonate diacrylate (product name: Nippon Polyurethanes, product name: DN-981, molecular weight 1000) Compound 11 Polyurethane diacrylate (Sumitomo Bayer product name: Desmofuen 2020E, molecular weight 2000) Various test results of each sample (Comparative Examples 1 to 3) are shown in the following table. The various test conditions are the same as those described in the above embodiment.

As is clear from this table, the test 4 (peel test), the test 5 (pattern transfer test), and the test 6 (workability) have relatively good results.
The adhesion to the transparent substrate (glass plate) was poor, and the track noise could not be measured because the underlayer of the recording film peeled off from the substrate during vapor deposition of the recording layer.

On the other hand, the one of the present invention does not peel off the recording film underlayer due to its good adhesion to the substrate, and further, since the recording film underlayer has a low water absorption rate, the occurrence of tracking noise is small,
Highly reliable optical information recording medium that has a flat surface even on a hard track, can be used near the block boundary, prevents a decrease in recording capacity, and can fully demonstrate the features of the CLV, MCAV, or MCLV method. Can be obtained.

[Brief description of drawings]

1 (a) to 1 (d) are manufacturing process diagrams of a recording veneer according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (d) are manufacturing process diagrams showing modified examples of the recording veneer. 3, 4 and 5 are sectional views of an optical disk according to an embodiment of the present invention, FIGS. 6 and 7 are composition diagrams, and FIG. 8 is an optical disk by CLV system, MCAV system or MCLV system. Partly enlarged plan view of No. 9
The drawing is an enlarged sectional view taken along the line AA in FIG. 2 ... Transparent substrate, 3 ... Recording film base layer, 5 ... Recording layer,
6 ... Underlayer.

Claims (7)

[Claims] 1. At least a transparent substrate, and a recording film underlayer having a large number of signal recesses formed on the transparent substrate,
In an optical information recording medium having a recording layer formed on the recording film underlayer by a thin film forming technique, the ultraviolet curable resin constituting the recording film underlayer is
(A). Having an acrylic group or a methacrylic group at the terminal and having a polybutadiene skeleton or poly-1-
An organic compound having a butene skeleton, (b). An organic compound having one acryl group or methacryl group in one molecule and having no polar group such as a hydroxyl group, a carboxyl group, a thiol group or an amine group in the molecule; (c). An organic compound having two or more acryl groups or methacryl groups in one molecule and not having a polar group such as a hydroxyl group, a carboxyl group, a thiol group or an amine group in the molecule, (d). An optical information recording medium, characterized by comprising a photopolymerizing agent and curing the composition. 2. The optical information recording according to claim 1, wherein the organic compound (a) has a molecular structural formula represented by the following formulas (1) to (3). Medium. 3. An optical information recording medium according to claim 1, wherein a base layer made of fluorine resin is provided between the transparent substrate and the recording layer. 4. An optical information recording medium according to claim 1, wherein an underlayer made of nitrocellulose is provided between the transparent substrate and the recording layer. 5. The optical information recording according to claim 4, wherein the UV-curable resin material of the recording film underlayer is a material substantially incompatible with the layer made of nitrocellulose. Medium. 6. The organic compound of (5) above has a molecular structural formula represented by the following formula (4) or (5), and the organic compound of (c) below: An optical information recording medium having a molecular structural formula represented by the formula (6). However, R in the formula is H or CH ₃ . 7. The method according to claim 6, wherein the (a),
The organic compounds of (b) and (c) are the points in FIG.
An optical information recording medium, characterized in that it is compounded within a range of a diagonal line surrounded by a straight line connecting A, B, C, D.