JP2922632B2 - optical disk - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to optical disks such as rewritable optical recording disks such as magneto-optical recording disks and read-only optical disks such as optical video disks.

<Prior Art> An optical disc, for example, a magneto-optical recording disc, is configured by providing a recording layer as an information carrying unit on a disc substrate.

In order to prevent mechanical damage due to cracking or the like of the recording layer, in the double-sided recording type, a pair of disk substrates are integrated so that the recording layer is enclosed.

By the way, in order to integrate a pair of disk substrates of various optical disks such as a magneto-optical recording disk, usually, a reactive adhesive such as a hot-melt adhesive such as a hot-melt adhesive, an epoxy adhesive, or a UV-curable adhesive is used. Agents, pressure-sensitive adhesives, ie, pressure-sensitive adhesives.

However, when using an epoxy adhesive or a UV-curable adhesive, it takes time to work, which is disadvantageous for mass production.In addition, the curing agent and sensitizer in the adhesive corrode the information carrying parts such as the recording layer. It can be done.

For this reason, it is advantageous to use a pressure-sensitive adhesive or a hot-melt adhesive which does not have the above-mentioned adverse effects.

When using an adhesive or a hot-melt type adhesive, an adhesive layer is formed on the inner sealing surface of the disk substrate, and after bonding both disk substrates, the disk is pressed using a pressing machine to form a pair of disks. Integrate the substrate.

<Problems to be solved by the invention> However, if the inner sealing surface or the adhesive surface of one disk substrate is deformed and irregularities are generated, the other disk substrate is deformed according to the irregularities when pressed. .

For this reason, the mechanical accuracy or dimensional accuracy of the disk is reduced, and the surface runout of the disk is increased when the optical disk is rotated.

A main object of the present invention is to provide an optical disk having high mechanical accuracy in which a pair of disk substrates are integrated via an adhesive layer.

<Means for Solving the Problems> Such an object is achieved by the present invention of the following (1).

(1) Having a pair of disk substrates, forming an information carrying portion on at least one of the disk substrates, and bonding the enclosed surfaces of the pair of disk substrates with an adhesive layer so that the information carrying portion is enclosed. An optical disk integrated by forming an adhesive layer on each of the sealing surfaces of the pair of disk substrates, and covering substantially the entire sealing surface of each of the pair of disk substrates with the adhesive layer. A first adhesive layer formed of an adhesive on one main surface of a base material on at least one of the enclosing surfaces of the pair of disk substrates, and a second adhesive layer formed of an adhesive on the other main surface. A pressure-sensitive adhesive sheet having an adhesive layer of No. 2 through the second adhesive layer, making this at least one of the adhesive layers, and bonding the adhesive through a foam cushioning sheet. Glue the layers together And forming a plurality of grooves in each of the adhesive layers from an outer peripheral edge and / or an inner peripheral edge to an outer peripheral edge and / or an inner peripheral edge through a region facing the disk internal region. optical disk.

<Operation> The optical disk of the present invention is such that after forming an adhesive layer on each of the inner sealing surfaces of a pair of disk substrates, the adhesives are adhered to each other via a foam cushioning material sheet. The board is integrated.

For this reason, even if a convex portion or a concave portion is formed on the enclosing surface or the adhesive surface of one disk substrate, a pair of disk substrates
For example, when pressing and bonding using a press machine, only the portion of the cushioning material sheet facing the convex portion is dented, and the other disk substrate is not deformed.

As a result, an optical disk having high mechanical accuracy close to the surface accuracy of the disk pressing surface of the press machine is realized.

Further, when a predetermined groove is formed in the adhesive layer,
When the pair of disk substrates are integrated, air between the disk substrates flows out of the disk through the groove in the adhesive layer.

Therefore, air bubbles can be prevented from being sealed between the pair of disk substrates, that is, between the cushioning material sheet and the adhesive layer, and the mechanical accuracy of the disk is further improved.

Further, the optical disk of the present invention is formed by forming an adhesive layer on substantially the entire inner sealing surfaces of a pair of disk substrates.

Therefore, in order to prevent air bubbles from being enclosed in the disk, an adhesive layer is partially formed on the disk substrate,
Compared to an optical disk having an air passage, for example, an optical disk having an adhesive layer formed in a stripe shape or the like, in the present invention, the entire surface of the recording layer and the like is sealed with an adhesive, so that corrosion resistance and durability are improved. .

<Specific Configuration of the Invention> Hereinafter, a specific configuration of the present invention will be described in detail.

FIG. 1 shows a preferred embodiment of the optical disk of the present invention.
An example of a double-sided recording type magneto-optical recording disk is shown.

A magneto-optical recording disk 1 shown in FIG. 1 has a pair of disk substrates 2 having a protective layer 4, an intermediate layer 5, a recording layer 6 as an information carrying portion, a protective layer 7, and a protective coat 8 in that order.
2 are integrated by adhesive layers 9 and 9 via a foam cushioning sheet 3.

In the present invention, the disk substrate 2 is transparent to recording light and reproduction light, and is usually made of resin, or may be made of glass as needed.

 The disk substrate 2 has a disk shape.

The outer diameter of the disk substrate 2 is usually about 50 to 360 mm, and the inner diameter is usually about 15 to 35 mm.

In this case, the resin to be used is not limited, but for example, acrylic resin, polycarbonate, epoxy resin, polyolefin and the like are preferable.

 The disk substrate 2 may be manufactured according to a known method.

For example, it is manufactured by simultaneously forming a predetermined pattern such as a pit or a group on a disk substrate surface for tracking, addressing, or the like by injection molding or the like.

Alternatively, after manufacturing the disk substrate, a resin layer having a predetermined pattern such as a group may be formed by the 2P method or the like.

The intermediate layer 5 is provided to improve the C / N ratio, and is preferably formed of various dielectric materials, and preferably has a thickness of about 30 to 150 nm.

Incidentally, such a material for the intermediate layer may be provided as a protective layer 7 on the recording layer 6 described later, and may be used together with the intermediate layer 5.

The protective layer 4 and the protective layer 7, which are provided as necessary,
It is provided to improve the corrosion resistance of the recording layer 6,
It is preferable that at least one of them, and preferably both of them are provided. These protective layers are preferably formed of an inorganic thin film made of various oxides, carbides, nitrides, sulfides, mixtures thereof, or glass. The thickness of the protective layer is preferably about 30 to 300 nm from the viewpoint of improving corrosion resistance.

Such protective layers 4 and 7 and the intermediate layer 5 are preferably formed by various vapor deposition methods such as a sputtering method.

In the recording layer 6, information is magnetically recorded by a modulated heat beam or a modulated magnetic field, and the recorded information is reproduced by magneto-optical conversion.

The material of the recording layer 6 is not particularly limited as long as it can perform magneto-optical recording. An alloy containing a rare earth metal element, particularly an alloy of a rare earth metal and a transition metal, is formed by sputtering,
It is preferably formed as an amorphous film by an evaporation method, an ion plating method, or the like.

The thickness of such a recording layer 6 is usually about 10 to 500 nm.

The protective coat 8 is provided for improving corrosion resistance and abrasion resistance, and is preferably composed of various organic substances. It is preferred to be composed of a material that has been cured by radiation.

The thickness of the protective coat 8 of such a radiation-curable compound is usually about 0.1 to 100 μm, and may be a spinner coat, a gravure coat, a spray coat, a dipping, or the like.
The layers may be formed by combining various known methods.

In the first embodiment of the present invention, as shown in FIG.
A pressure-sensitive adhesive sheet 90 having pressure-sensitive adhesive layers 9 and 99 on both main surfaces of a substrate 91 is used.

The use of the pressure-sensitive adhesive sheet 90 makes it possible to work in a clean room, and in addition, the work can be performed easily and quickly because it can be bonded only by pressing at a pressure of about 1 to 5 kg / cm ^2. You. Furthermore, since the adhesive does not contain a curing agent, a sensitizer, or the like, the recording layer 6 does not corrode.

The adhesive sheet 90 includes a pair of adhesive layers on both main surfaces of the base material 91, that is, an adhesive layer 9 for indirectly attaching the disk, and a second adhesive layer 99 for bonding the disk to the adhesive sheet 90. Is formed between the base material 91 and the adhesive layers 9 and 99.
In some cases, a primer layer or the like is provided.

The shape of the adhesive sheet 90 is usually a disk shape,
The dimensions are appropriately selected according to the dimensions of the disk substrate 2 and the like.

The materials of the adhesive layers 9 and 99, the base material 91, the undercoat layer, and the like are not particularly limited, and any material that is usually used for an adhesive sheet or an adhesive can be used.

In the present invention, the adhesive layers 9 and 99 are, for example, rubber-based,
An acrylic, silicone, or polyvinyl ether-based adhesive may be used.

Such an adhesive is usually composed of a base polymer and various additives such as a tackifier resin, a softener, a filler, an antioxidant, and a crosslinking agent.

The specific gravity of the pressure-sensitive adhesive used is usually about 1.0 to 1.3, and the thickness of the adhesive layers 9 and 99 after pressurization is preferably about 10 to 100 μm.

The thickness of the adhesive layers 9 and 99 of the pressure-sensitive adhesive sheet 90 before pressing is usually about 10 to 200 μm.

For the base material 91, for example, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyimide, cellulose, acetate, 4-fluoroethylene, epoxy resin, or the like may be used, and the thickness is usually about 10 to 50 μm.

For the undercoat layer, for example, a natural rubber-MMA graft, an isocyanate blend, a chlorinated polypropylene, or the like may be used, and its thickness is usually about 1 to 100 μm.

In order to manufacture the magneto-optical disk of the present invention, as shown in FIG. 2, a pair of the pressure-sensitive adhesive sheets 90, 90 are respectively connected to a pair of disk substrates 2, with a second adhesive layer 99 interposed therebetween. 2 is attached to the inner sealing surface, that is, the protective coat 8.

In this case, the adhesive layer 99 is formed so as to cover almost the entire surface of the protective coat 8.

Next, the adhesive layers 9 and 9 of the pair of pressure-sensitive adhesive sheets 90 attached to each other are adhered to each other via the foam cushioning material sheet 3,
The pair of disk substrates 2, 2 are integrated.

By interposing the foam cushioning material sheet 3 between the discs, even if a convex portion or a concave portion is formed on the sealing surface or the adhesive surface of one of the disc substrates 2, the portion of the cushioning material sheet 3 facing the convex portion However, the other disk substrate 2 is not deformed.

In this case, the compression hardness of the cushioning sheet 3 is 10 kgf / cm ²
The following is preferred.

When the compression hardness of the cushioning material sheet 3 exceeds 10 kgf / cm ² ,
The deformation of the disk substrate 2 cannot be sufficiently prevented.

On the other hand, if the compression hardness is too small, a cushion material sheet having a predetermined thickness cannot be obtained.

Therefore, the compression hardness of the cushioning sheet 3 is 0.1 to 10 kgf.
/ cm ² , particularly preferably 0.1 to 5 kgf / cm ² .

The compression hardness may be measured according to a polyethylene foam test method shown in JIS K 6767.

Specifically, first, the length l: 5 of the same quality as the cushioning material sheet 3.
A test piece of 0 cm, width w: 5.0 cm, and thickness h: about 2.5 cm is prepared.

Then, using a predetermined compression hardness tester, the test piece 10mm
/ Min at a rate of 25% of the initial thickness h
The load P (kgf) after 2 seconds is measured.

 Then, the compression hardness H is calculated from the following equation.

Formula H = P / wl The buffer material sheet 3 used in the present invention is not particularly limited as long as it is a foam, but is preferably a foam plastic.

When foamed plastic is used, the portion of the disk substrate 2 facing the convex portion is dented when pressed, and the buffer material sheet 3 retains its shape after pressing, so that the deformation of the disk is further reduced.

Examples of the foam plastic include polyvinyl chloride foam, polyolefin foam, polyethylene foam, polypropylene foam, ethylene-vinyl acetate copolymer (EVA) foam, polystyrene foam, polyurethane foam, and ABS foam. , Polyvinyl alcohol (PVA) foam, acetate cellulose foam, acrylic foam, epoxy resin foam, phenol resin foam, urea resin foam, silicone foam, etc., having a predetermined compression hardness However, in terms of mechanical properties such as sheet workability and compression hardness, polyethylene foam, polyurethane foam, ethylene-vinyl acetate copolymer (EVA) foam,
Polyurethane foams and the like are preferred.

The foam plastic preferably has a density of about 20 to 100 kg / m ³ .

The thickness of the buffer sheet 3 is 50 to 500 μm, especially 100 to 40 μm.
0 μm is preferred.

If the thickness is less than the above range, it is difficult to sufficiently absorb unevenness of the disk substrate 2, and if the thickness exceeds the range, the entire thickness of the disk becomes large.

In order to integrate the pair of disk substrates 2, 2,
For example, after adhering the pressure-sensitive adhesive sheet 90 with a rubber roller or the like, the two disk substrates may be stuck together via the buffer material sheet 3 and pressed at a pressure of about 1 to 5 kg / cm ² .

In the present invention, as shown in FIG. 3, the adhesive layer 9 of the pair of pressure-sensitive adhesive sheets 90, 90 for indirectly attaching the disk is opposed to at least the surface from the outer peripheral edge and / or the inner peripheral edge to the inner region of the disk. It is preferable to form a plurality of grooves 97 reaching the outer peripheral edge and / or the inner peripheral edge through the region where the groove 97 is formed.

No groove 97 is formed in the second adhesive layer 99 for bonding the disk and the adhesive sheet 90.

When the groove 97 is formed in the adhesive layer 9, the ratio of the land 95 between the grooves 97 and 97 to the adhesive layer 9 is preferably 0.3 or more.

When the ratio of the land portions 95 is less than the above range, the adhesive strength is insufficient.

However, if it is too large, the air bubble removal ability tends to decrease, so it is preferably 0.3 to 0.95, particularly preferably 0.5 to 0.9.

Here, the ratio of the land 95 is defined as the land 95 and the groove.
The ratio of the projection area of the land 95 in the thickness direction of the disk substrate 2 to the projection area of the disk substrate 2 in the thickness direction of the disk substrate 97.

The shape and pattern of the groove 97 formed in the adhesive layer 9 are not particularly limited, but FIG. 3 shows a linear groove 97 having a rectangular cross section.
Are formed in parallel at a predetermined pitch.

However, the cross-sectional shape of the groove 97 after pressurization may slightly change from the cross-sectional shape of the groove 97 before pressurization.

FIG. 5 is a cross-sectional view taken along the line VI-VI 'of FIG. 3 showing the adhesive layer 9 in which the groove 97 is formed.

The grooves 97 are formed from the outer peripheral edge to the outer peripheral edge and from the inner peripheral edge to the outer peripheral edge of the disk as shown in FIG.

In this case, by forming the groove 97 in a straight line as in the illustrated example, the formation of the pressure-sensitive adhesive layer 9 is facilitated, and the ability to remove bubbles is improved.

By forming the grooves 97 in parallel,
Control of the ratio of the land portions 95 and the pitch of the grooves 97 described later becomes easy.

Incidentally, in the illustrated example, L ₁ the width of the groove 97, and the width of the land portion 95 between the grooves 97, 97 and L _2, the ratio of the land portion 95 in the adhesive layer 9 of said, L ₂ / (L ₁ + L ₂ ).

_{Thus, L 2 / (L 1 +} L 2) is as described above, 0.3 or more,
More preferably, it is 0.3 to 0.95, particularly preferably 0.5 to 0.9.

Further, it is preferable that one or more grooves 97 exist per 1 cm, that is, the pitch of the grooves 97 is 1 cm or less.

If the pitch exceeds the above range, it is difficult to prevent air bubbles from entering when the ratio of the lands 95 is large, and when the ratio of the lands 95 is small, the mechanical accuracy of the disc deteriorates.

However, if the pitch is too small, it is difficult to form the groove 97. Therefore, the pitch is preferably 0.01 to 1 cm, particularly preferably 0.05 to 0.2 cm.

When the pitch is large, it is preferable to increase the ratio of the land portions 95 to prevent a decrease in the mechanical accuracy of the magneto-optical disk 1.

For example, if the pitch is about 0.1 to 1 cm,
The ratio of 95 is preferably 0.5 or more, more preferably 0.5 to 0.95.

The pitch of the grooves 97 is usually constant, but may be different depending on the case.

The depth of the groove 97 is usually 10% of the thickness of the pressure-sensitive adhesive layer 9.
It may be more than about.

Also, the groove 97 on one disk substrate 2 and the groove 97 on the other disk substrate 2 intersect at a predetermined angle, or the groove 97 on one disk substrate 2 and the groove 97 on the other disk substrate 2 The two disk substrates may be bonded so that the groove 97 is parallel or overlapped.However, in order to further improve the mechanical accuracy of the disk, it is necessary to integrate the two disk substrates so that they intersect at a predetermined angle. Is preferred.

In this case, the crossing angle may be generally about 45 to 90 degrees.

Next, a preferred example in which a groove 97 having another pattern is formed in the adhesive layer 9 will be described.

FIG. 6 is a cross-sectional view of the adhesive layer 9 of the magneto-optical disk of the present invention.

As shown in FIG. 6, the groove 97 is formed radially between the inner peripheral edge and the outer peripheral edge of the disk substrate.

Also in this case, as described above, the shape of the groove 97 is linear,
It is preferable to form at a predetermined pitch.

The number of the grooves 97 is one or more per cm, more preferably 1 to 100, particularly 5 to 20 at the outer peripheral edge of the disk substrate.
It is preferably present. Although the ratio of the land 95 may be directly calculated, the ratio L ₂ of the inner peripheral edge of the disk substrate may be calculated.
/ A (L ₁ + L _2), average may be approximately expressed with the L ₂ / of the outer circumferential edge (L ₁ + L _2).

Even in the case where such radial grooves 97 are provided, similarly to the above, the pitch of the grooves 97 and the ratio of the land portions 95 can be easily controlled, and the inclusion of bubbles can be prevented.

Further, the adhesive layer 9 may be formed so that the lands 95 exist in a scattered manner.

In this case, the ratio of the land 95 is preferably 0.3 to 0.9, more preferably 0.5 to 0.8.

One land part 95 has a size of 1 to 1000 mm ² , more preferably about 10 to 500 mm ² , and 0.03 to 95 pieces / c.
m ² , more preferably about 0.25 to 9 / cm ² .

When the number of land portions 95 per unit area is small, for example, about 0.03 to 1 piece / cm ² , the ratio of the land portions 95 in the adhesive layer 9 is preferably 0.5 to 0.95, more preferably 0.7 to 0.
Preferably it is 9.

The shape and pattern of the groove 97 of the adhesive layer 9 are not limited to those described above, and the cross-sectional shape of the groove 97 may be trapezoidal, triangular, semicircular, or the like. The pattern may be any of a curved shape, a broken line shape, and the like. Further, when the grooves 97 are non-parallel, the grooves 97 may cross each other.

The shape and pattern of the grooves 97 formed in the adhesive layer 9 of the pair of pressure-sensitive adhesive sheets 90 may be the same or different from each other, but should be the same in that the work is easy. It is particularly preferable to form a predetermined angle as described above.

Such an adhesive layer 9 may be usually formed by gravure printing or the like.

Then, an adhesive is applied to the entire surface of the base material 91 to form an adhesive layer 9.
In order to form the groove 97 only on the surface of the adhesive layer 9, for example, if the unevenness is previously formed on the base material 91, the groove 97 can be formed on the surface of the adhesive layer 9 according to the pattern of the base material 91.

Further, the second adhesive layer 9 or the second adhesive layer 99 may be smooth.
May be formed by an ordinary method for producing a pressure-sensitive adhesive sheet.

In the second embodiment of the present invention, as shown in FIG. 4, after forming the adhesive layer 9 directly on almost the entire enclosing surface of one of the pair of disk substrates 2, the above-mentioned foamed cushioning material sheet 3 is formed. The adhesive layer 9 and the pressure-sensitive adhesive sheet 90 are adhered to each other via a pair to integrate the pair of disk substrates.

Then, the adhesive layer 9 is composed of an adhesive or a hot melt type adhesive.

In addition, among adhesives and hot melt adhesives, it is possible to work in a clean room, and it is easy to work,
It is preferable to use an adhesive because it can be performed in a short time.

A hot-melt adhesive is generally composed of a base polymer as a main component and additives such as a tackifier, a softener, a plasticizer, and a wax.

The constituent components of the hot melt adhesive used in the present invention are not particularly limited, and the base polymer may be one or two of polyolefin-based resins, for example, polyethylene, polypropylene, polystyrene, and copolymers containing these. Mixtures of more than one kind, and those obtained by adding other polyolefins, polyolefin-based copolymers, synthetic rubbers, and the like to these may be used.

Also in the second embodiment, as shown in FIG. 5, grooves 97 are formed on both surfaces of the adhesive layers 9, 9 formed on the pair of disk substrates 2, 2, as in the first embodiment. Is preferred.

However, in the second embodiment, when the groove 97 reaching the protective coat 8 is formed in the adhesive layer 9 and the surface of the protective coat 8 is exposed, the corrosion resistance, durability and the like are reduced, and, for example, under high temperature and high humidity. If used or stored for a long time, errors tend to occur during recording and playback.

When the groove 97 is formed in the adhesive layer 9, the groove 97 and the land 95 having a desired shape and dimensions can be easily formed, that is, L ₁ ,
Since it is managed in L ₂ or the like and that a more effective bonding strength can be obtained, it is particularly preferable to use an adhesive.

In order to form the groove 97, for example, an adhesive or the like may be applied once with a nozzle of a special shape or the like, or once applied smoothly with a rubber roll or the like, and then the adhesive is partially applied with a nozzle or the like. It may be applied in a uniform manner, or may be provided with irregularities by means of irregularity processing or the like. Further, an adhesive sheet having no base material may be used.

Also in the second embodiment, the shape, pattern, dimensions,
The pitch and the like are the same as described above, and various forms are possible.

Then, an adhesive sheet 90 having an adhesive layer 9 and a second adhesive layer 99 on both main surfaces of the base material 91 is placed on one disk substrate 2.
After the adhesive layer 9 is formed directly on the inner sealing surface of the other disk substrate 2, the pair of disk substrates 2 and 2 are integrated via the above-mentioned foamed cushioning sheet 3. I do.

The case where the optical disk of the present invention is applied to a double-sided recording type magneto-optical recording disk has been described above, but the present invention can also be applied to a single-sided recording type magneto-optical recording disk.

In the single-sided recording type magneto-optical recording disk, the disk substrate 2 having each of the above-described constituent layers and a protective substrate are adhered to each other with an adhesive layer 9 so that the recording layer 6 as an information carrying portion is enclosed. can get.

As described above, according to the present invention, in the above-described double-sided recording type and single-sided recording type magneto-optical disks, high effects are obtained in terms of corrosion resistance, durability and the like.

In addition, the present invention may be a read-only optical disk such as an optical video disk having an information carrier.

In these cases, the same effects as those of the above-described double-sided recording type magneto-optical recording disk can be obtained.

It should be noted that the information carrying portion in the present invention refers to both a device that carries information in advance, as in a read-only disc, and a recording layer that can carry information, as in a record / playback disc.

<Example> Hereinafter, the present invention will be described in more detail with reference to specific examples of the present invention.

Example 1 A 50 μm thick polyethylene terephthalate disk-shaped base material 91 shown in FIG.
An adhesive sheet A (90) was prepared in which a smooth second adhesive layer 99 μm was formed and a smooth adhesive layer 9 having a thickness of 20 μm was formed on the other main surface.

For the adhesive layers 9 and 99, an acrylic pressure-sensitive adhesive having an alkyl acrylate as a base polymer was used.

The pressure-sensitive adhesive has a shear strength of 10 kg / cm ^{2 in} PC / PC in a shear strength test defined by JIS K 6850, and a creep test in which a 200 g load is applied to an area of 2 cm × 2 cm at a temperature of 60 ° C. It had a holding power of 2 hours.

Also, a disk-shaped cushioning material sheet 3 made of polyethylene foam having a thickness of 300 μm was prepared.

When the compression hardness of the cushioning material sheet 3 was measured according to the polyethylene foam test method shown in JIS K 6767,
It was 1.0 kgf / cm ² .

The density was 30 kg / m ³ .

Next, the glass protective layer 4, the SiNx intermediate layer 5, the TbFeCo recording layer 6, the SiNx protective layer 7, and the ultraviolet curable resin were sequentially formed on a pair of polycarbonate disk substrates 2, 2 in which groups were simultaneously formed by injection molding, respectively. A protective coat 8 was formed.

The polycarbonate disk substrate 2 has an outer diameter of 130 mm,
The protective layer 4, the intermediate layer 5, the recording layer 6, and the protective layer 7 were each formed by a sputtering method.

Next, as shown in FIG. 2, an adhesive sheet A (90) was attached to the surfaces of the protective coats 8 of the pair of disk substrates 2 and 2 via a smooth second adhesive layer 99.

Then, the adhesive layers 9 of both pressure-sensitive adhesive sheets A (90) are adhered to each other via the buffer material sheet 3 to integrate the pair of disk substrates 2 and 2, and the double-sided recording type light shown in FIG. A magnetic recording disk sample No. 1 was produced.

The pressing pressure was 1 kg / cm ^2, and the thickness of the adhesive layers 9 and 99 after pressing was almost the same as the thickness before pressing.

Also, except that the cushioning sheet 3 is not used,
Sample No. 2 for comparison was prepared.

The amount of surface runout in the circumferential direction was measured for both samples using a mechanical accuracy measuring machine ODA02 (manufactured by Shin Denshi Kogyo Co., Ltd.). The measurement was performed at a disk rotation speed of 1800 rpm and a radius of 30 to 60 mm from the disk center at intervals of 5 mm.
The number of measurement samples was three for each magneto-optical recording disk, and the average value of the maximum surface deflection acceleration in the circumferential direction of each sample was determined.

The surface runout is the amount of movement of the optical pickup during focusing servo, and indicates the flatness of the substrate on which the tracking group is formed, similarly to the surface runout acceleration. According to the ISO standard, this value is set to ± 300 μm or less for a magneto-optical recording disk having an outer diameter of 130 mm.

As a result, the maximum runout of sample No.2 (comparison)
The maximum runout of Sample No. 1 (the present invention) was 45 μm, whereas the maximum runout was 98 μm.

In addition, instead of the pressure-sensitive adhesive sheet A (90), an adhesive layer of a pressure-sensitive adhesive or a hot-melt type adhesive was directly formed on the inner sealing surface of the disk substrate to produce various samples, and the same result as above was obtained. Was.

 From these results, the effect of the present invention is clear.

Example 2 An adhesive sheet B (90) shown in FIG. 3 was prepared in which a groove 97 was formed on the surface of the adhesive layer 9 of the adhesive sheet A (90) used in Example 1.

The grooves 97 were formed in a straight line having a rectangular cross section and formed in parallel with each other.

The depth of the groove 97 of the adhesive layer 9 is 10 μm, and the width L _{1 of the} groove 97 is 1 μm.
Was 0.07 cm, the pitch L ₁ + L ₂ of the grooves 97 was 0.17 cm, and the ratio L ₂ / (L ₁ + L ₂ ) of the land 95 in the adhesive layer 9 was 0.6.

Then, in the same manner as in Sample N, except that the adhesive sheet A (90) of Sample No. 1 was replaced with the adhesive sheet B (90).
o.3 was made.

In this case, the groove 97 of the adhesive sheet of one disk substrate
And the two disk substrates were bonded so that the groove 97 of the pressure-sensitive adhesive sheet of the other disk substrate was substantially perpendicular to the groove.

Observation of the obtained sample No. 3 with a shadowgraph revealed that no air bubbles were sealed between the buffer material sheet 3 and the adhesive layer 9.

When sample No. 3 was evaluated in the same manner as in Example 1, it was confirmed that the disk had a small maximum surface run-out amount as in sample No. 1.

And since there is no air bubble in sample No.3,
The instantaneous run-out acceleration was smaller than that of samples No. 1 and No. 2.

Further, when the error rate after storing Sample No. 3 in an environment at a temperature of 80 ° C. and a humidity of 80% RH for 2000 hours was determined, it was almost equal to the error rate before storage.

 Sample No. 3 also had sufficient adhesive strength.

Further, the material and thickness of the buffer material sheet, to produce a magneto-optical recording disk in which the shape or pattern and dimensions of the groove, etc.Moreover, when a double-sided optical video disk for reproduction only was produced, the same The result was obtained.

 The effects of the present invention are clear from the above results.

<Effect of the Invention> The optical disc of the present invention has high mechanical accuracy of the disc.

Therefore, when the optical disk is rotated, the surface of the disk is small, and there is no occurrence of a focusing error, a tracking error, and the like, and good recording and reproduction can be performed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of the optical disk of the present invention. FIGS. 2, 3 and 4 are cross-sectional views each showing a state of the optical disc of the present invention before joining. FIG. 5 is a sectional view taken along the line VI-VI 'of FIG. FIG. 6 is a sectional view showing another example of the adhesive layer of the optical disc of the present invention. DESCRIPTION OF SYMBOLS 1 ... Magneto-optical recording disk 2 ... Disk substrate 4 ... Protective layer 5 ... Intermediate layer 6 ... Recording layer 7 ... Protective layer 8 ... Protective coat 9 ... Adhesive layer 90 ... Adhesion Agent sheet 91: Base material 95: Land portion 97: Groove 99: Second adhesive layer

Claims (1)

(57) [Claims] An information carrying portion is formed on at least one of the disk substrates, and an inner sealing surface of the pair of disk substrates is bonded to an adhesive layer so that the information carrying portion is enclosed. An optical disc integrated by bonding with an adhesive layer on each of the enclosed surfaces of the pair of disk substrates, and the substantially entire enclosed surface of each of the pair of disk substrates is covered by the adhesive layer. Coating, on at least one of the enclosed surfaces of the pair of disk substrates,
A first adhesive layer made of an adhesive on one main surface of the base material, and a second adhesive layer made of an adhesive on the other main surface.
A pressure-sensitive adhesive sheet having an adhesive layer is attached via the second adhesive layer, and this is used as at least one of the adhesive layers. The adhesive layer is provided via a foam cushioning material sheet The pair of disc substrates are integrated by bonding them together, and each of the adhesive layers extends from the outer peripheral edge and / or the inner peripheral edge to the outer peripheral edge and / or the inner peripheral edge through a region facing the disk internal region. Optical disk with multiple grooves.