JPH01236437A - information recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an information recording medium.

[Prior Art] Conventionally, in information recording media, especially optical information recording media (hereinafter referred to as optical carts), grooves (guide grooves) are formed on a substrate at regular intervals in order to write and read information. A commonly used method is to form it in advance. Track control is performed using the difference in the amount of reflected light between the guide groove section and the recording section, thereby enabling high-speed access. Also, write-once type,
In the rewritable type, necessary information is recorded in advance as a preformat.

Methods for forming such a substrate include: (1) when the substrate is made of a thermoplastic resin, a method of transferring a mold having a concave-convex preformat pattern by an injection method or a heat press method; After applying a photocurable resin composition onto a transparent resin plate made of thermoplastic resin, a mold is brought into close contact with the transparent resin plate, and energy such as ultraviolet rays is applied from the side of the transparent resin plate to cure the photocurable resin composition. The so-called 22 method, in which a replica of the mold is transferred onto a transparent resin plate, or ■Groups are formed in advance on one or both sides when casting a prepolymer containing a resin monomer or solvent. A method of casting using a casting mold is known.

[Problems to be Solved by the Invention] However, thermoplastic resin substrates obtained by the injection method or dry press method described in (2) above tend to warp after molding due to residual stress and molecular orientation due to thermal history during molding. However, since optical anisotropy may occur, problems remain as a substrate for optical cards.

In addition, in the substrate obtained by the 2P method described in (1) above, the polymerization initiator and sulfuric acid used during photocuring tend to remain in the resin after photocuring, and these may affect the optical recording layer of the recording medium. The problem often occurs that the recording characteristics are degraded.

As a method for manufacturing an optical card substrate that does not cause these problems, the above-mentioned cast molding method (2) is sometimes used. The substrate obtained by this method does not have warpage or optical anisotropy because almost no pressure is applied during molding compared to the above methods ① and ②. Since any of thermosetting resins, thermosetting resins, and photocuring resins can be used, it is possible to select a resin that does not adversely affect the recording layer.

The conventional method for manufacturing a cast molding mold in cast molding is to form a thin film of 7-otoresist on a glass plate or metal plate, and then perform laser cutting of groups and information bits with predetermined specifications. The method used was to perform etching to remove the remaining resist to obtain a cast molding mold in which convex portions for track grooves and signal bits were formed.

When a recording layer is formed by a coating method on a substrate having a preformat pattern having signal bits and track grooves manufactured by a cast molding method using the cast molding mold, the signal bits are particularly In areas where signal bits are provided close to each other, the recording medium that forms the recording layer gets into the signal bits, so there is a problem that the thickness of the recording layer in the recording area between the signal bits becomes thinner than in other recording areas. arise. As a result, there is a problem in that a sufficient amount of reflected light cannot be obtained in the recording section where the film thickness of the preformat section is thin, and there is also a large variation in the amount of reflected light within the card.

The present invention has been made in view of the problems of the prior art, and by forming the depth of the signal bit of the uneven preformat provided on the substrate to be smaller than the depth of the track groove, the recording layer can be It is an object of the present invention to provide an information recording medium that reduces the difference in the film thickness of the card, thereby increasing reliability in reading preformat, and having low variation in reflectance within the card.

[Means for Solving the Problems] According to one aspect of the present invention, in an information recording medium having a recording layer formed by a coating method on a concavo-convex preformat provided on a substrate, the signal bits of the concavo-convex preformat are The information recording medium is characterized in that the depth is smaller than the depth of the track groove.

The present invention will be explained in detail below.

FIG. 1 is a sectional view showing one embodiment of the information recording medium of the present invention. In FIG. 1, the information recording medium of the present invention is formed on a substrate l having a concave-convex preformat on the surface, and the depth of the signal bit 5 of the concavo-convex preformat is formed to be smaller than the depth of the track groove 6. A recording layer 2 formed by coating a recording material such as a dye is provided, and the recording layer 2 and a backing material 4 for protection or support of the recording carrier are bonded together by an adhesive layer 3'.
It is made by adhering it through.

In the present invention, the depth of the signal bit of the uneven preformat provided on the substrate is formed to be smaller than the depth of the track groove, and specifically, the depth of the signal bit is preferably 0.5 pm or less. is 0.03~0.3μ garden,
and 415 times or less the depth of the track groove, preferably 21
A range of 5 to 4/S times is desirable; if it exceeds 415 times, the reflectance between signal bits decreases, which is not preferable.

In the present invention, the substrate 1 is not particularly limited, and any commonly used base material can be used as long as it is transparent and does not cause any inconvenience in optical recording/reproduction.For example, the substrate 1 may be made of a material such as glass or plastic. The material should be suitable, and it should have a high transmittance for the light to be used.

For forming the recording layer 2, a solution type material in which a dye is dissolved or dispersed is used, and any material that can be applied to the substrate l by a commonly used coating method may be used.For example, anthraquinone derivatives, dioxazine compounds, and derivatives thereof. , triphuedithiazine compounds, phenanthrene derivatives, cyanine compounds, merocyanine compounds, azo dyes, methine dyes.

Examples include sulfur dyes and the like.

The adhesive layer 3 is a hot melt type adhesive, such as ethylene-vinyl acetate copolymer and its modified resin, and ethylene-ethyl acrylate copolymer.

Examples include vinyl acetate-acrylate copolymer and polyimide resin.

The backing material 4 can be made of any material such as glass, plastic, metal, etc., but preferably it is made of the same material as the substrate 1.

As a manufacturing method for the substrate used in the present invention, for example, the substrate for preformat is formed by casting using a casting mold in which the track grooves and the signal pits for concave and convex preformat have different heights. A preferred method is to obtain a substrate in which the depth of the signal pit is smaller than the depth of the track groove.

[Function] In the information recording medium of the present invention, the depth of the signal pits of the uneven preformat provided on the substrate is smaller than the depth of the track grooves, and the recording layer formed thereon by a coating method is provided. As a result, the amount of recording medium that enters the preformat signal pits is reduced, and the difference in recording layer thickness between the preformat signal bit part and other recording parts is reduced, which increases the reliability in reading the preformat. This improves the reflectivity and reduces the variation in reflectance within the card.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A cast mold used for producing a substrate used in the present invention was
It was manufactured by the steps shown in FIGS. 2(a) to 2(g). First, a resist 8 is formed on a base material such as a glass plate or a metal plate. (FIG. 2(a)) Next, the track groove pattern 1O is exposed and developed, and the resist is removed (FIG. 2(b)). A metal film 9 of Cr or the like is formed to a thickness of approximately 1000 mm. (Fig. 2 (C)), remove the resist part (Fig. 2 (D)), repeat the process to form a cyst again (Fig. 2 (E)), and remove the resist part (Fig. 2 (D)). Expose, develop and remove the pattern (second
Figure (f)).

Next, after forming a metal film such as Cr to a thickness of 500 mm, the resist portion is removed to obtain a casting mold having a signal pit convex portion 15 and a track groove convex portion 16. . (FIG. 2(g)) In this step, the preformatted signal pit portion may be formed before the track groove pattern.

Next, as shown in FIG. 3, a mirror surface mold made of a metal plate is placed on the cast mold 11 produced in the above manner through a spacer 13 so that the surface in contact with the casting resin becomes a mirror surface. 12 were provided facing each other to assemble the casting device.

A liquid acrylic resin having the following composition was injected into the casting device as the liquid bripolymer 14.

(Blend composition) Methyl methacrylate 70 parts Tert-butyl methacrylate 25 parts by weight Boy ethylene glycol dimethacrylate (molecular weight tzo) s parts by weight After pouring the liquid resin into a casting device, heat it at 135°C for 6 hours to harden it. The mold was released to obtain a substrate having a thickness of 0.5 am, a signal pit depth of 500 µl, a width of 5 µl, a track groove depth of 1000 µm, a width of 51 µm, and a pitch of 15 µm.

A solution prepared by dissolving 3 parts by weight of polymethine dye (PM-2) in 97 parts by weight of diacetone alcohol was applied to a substrate having an uneven preformat by gravure coating. The thickness of the recording layer in the flat recording portion was approximately 1,000 layers, and the thickness between signal bits was also approximately 950 layers.

A backing material made of polymethyl methacrylate having a thickness of 0.5 liters was adhered onto the recording layer via a hot melt type ethylene vinyl acetate copolymer adhesive to obtain an optical card.

When the reflectance of the obtained optical card was measured using a semiconductor laser beam with a wavelength of 830 ns, a laser power of 0.51 W, and a beam diameter of 5 pm, the reflectance was approximately 18% in the recording section.
A reflectance of about 17 to 18% was also obtained between signal pits.

On the other hand, if the depth of the track groove and the signal pit are the same (10
00 persons), the recording part had a reflectance of about 18%, whereas the reflectance between the signal bits was only about 10 to 14%.

Example 2 FIGS. 4(a) to 4(c) show another example of a method for manufacturing a casting mold.

First, a resist 8 is placed on a base material 7 such as a metal plate or a glass plate.
Negative pattern 1 of track grooves and signal pits
0 with a Xe lamp (Fig. 4(a)), and then expose the signal pit pattern for preformat from above with weak light (approximately 1 gJ) of an Ar'' laser (Fig. 4(b)). During etching, the portions weakly exposed by the Ar'' laser are etched at a slower rate than the portions exposed by the XE laser. As a result, as shown in FIG. 4(C), it is possible to produce a casting mold in which the signal pit convex portion 15 and the track groove convex portion 16 have different heights.

Incidentally, since the exposure energy and the etching speed are proportional, these heights can be adjusted by changing the exposure energy.

Using the obtained casting mold, an optical card was produced in the same manner as in Example 1, and when the optical card was tested, similar results were obtained.

[Effects of the Invention] As explained above, according to the information recording medium of the present invention,
Since the depth of the signal pit of the uneven preformat provided on the substrate is smaller than the depth of the track groove, the difference in film thickness of the recording layer between the signal bit part of the preformat and other recording parts is small. , which increases reliability in reading preformats,
Moreover, variations in reflectance within the card can be kept low.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one embodiment of the information recording medium of the present invention, and FIGS. 2(a) to (g) show a method for manufacturing a casting mold used for producing a substrate used in the present invention. Process diagram, 3rd
The figure is an explanatory diagram of a casting apparatus, and FIGS. 4(a) to 4(C) are process diagrams showing another example of a method for manufacturing a casting mold used for producing a substrate. l... Substrate 2... Recording layer 3... Adhesive layer 4... Back material 5... Signal pit
6...Track groove 7...Base material 8...
Resist 9...Metal 1511G-...Pattern 11-
...Mold for cast molding 12-...Mirror mold 13-...Spacer 14-...Liquid prepolymer 15...
Convex portion for signal bit 16 - Convex portion for track groove

Claims (1)

[Claims] (1) In an information recording medium having a recording layer formed by a coating method on a concavo-convex preformat provided on a substrate, the depth of the signal pit of the concavo-convex preformat is formed to be smaller than the depth of the track groove. An information recording medium characterized by: