JPH03263629A - Optical recording medium - Google Patents

Abstract

PURPOSE:To lower a surface wobbling acceleration and to provide the excellent adapta bility to driving of a high rotating speed by providing square notched parts in the peripheral edges of the substrates of the optical recording medium of a sticking type having recording layers via an adhesive layer between two sheets of the substrates. CONSTITUTION:Two sheets of the substrates 1a and 1b, with their surfaces having the recording layers positioned on the inner side are disposed to face each other and are stuck via the adhesive layer 2. The outer peripheral edge parts on the inner side of such substrates 1a and 1b are formed with the notched parts 3a and 3b. Namely, the outer peripheral edge parts on the inner side of the substrates disposed to face each other have the step by the notched parts 3a and 3b. The application of a pressure to the notched parts 3a and 3b is low and the strains generated within the substrate planes are relieved therein when the pressure is applied by a press to the substrates at the time of sticking of the substrates. The planes of the substrates 1a and 1b having the recording layers are thereby relatively flattened. There is not much increase in the surface wobbling acceleration in spite of an increase in the rotating speed in this way and the recording medium is hardly affected by a change in the rotating speed of recording, reproducing and erasing. The excellent interchangeability of driving is obtd. as well.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an optical recording medium on which information is recorded, reproduced, and erased using a light beam, and in particular is used under conditions where the linear velocity of recording and reproduction is high. The present invention relates to an optical recording medium suitable for recording.

[Prior art and its problems]

In recent years, optical recording media have a large storage capacity, so
It is put into practical use for large-capacity data files, etc.

Optical recording media usually take the form of a disc with a thin recording layer on a transparent substrate such as glass or plastic.
Based on the difference in recording method and recording layer, they can be classified into ROM type, WO type, magneto-optical recording medium, etc.

Furthermore, by making at least one recording layer a so-called bonded type medium that is provided between two substrates via an adhesive layer, the recording layer is kept away from the outside air and has excellent weather resistance. The medium can also be a double-sided recording type medium.

On the other hand, a common problem with optical recording systems is that the transfer speed is slow. In order to deal with this problem, increasing the rotation speed of the drive is being considered.

In the past, it was sufficient to design optical recording media based on the premise that the rotational speed of the drive was constant, but from now on, for the reasons mentioned above, practical characteristics such as recording and playback characteristics and erasing characteristics will need to be optimized for drives with different rotational speeds. There is a growing demand for media designs with less fluctuation.

In other words, there is a need for an optical recording medium with low linear velocity dependence, which can record and erase data with the same laser power even if the rotational speed of the drive increases and the transfer rate exceeds that of the current one.

Also, the degree of vertical displacement of the disk surface of the medium due to the rotation of the recording medium, which greatly affects the accuracy of recording and reproduction,
The so-called surface run-out acceleration increases in proportion to the square of the rotation speed, so if you increase the recording linear velocity in an attempt to improve the transfer speed problem, an increase in the surface run-out acceleration is unavoidable, and as a result, the focus servo There is a growing concern that this could lead to a serious error in which the connector cannot be removed and becomes detached.

In order to reduce the surface runout acceleration of an optical recording medium, for example, Japanese Patent Application No. 3-31Tbubu No. 7 discloses that the substrate after injection molding is heated and annealed to remove molding distortion.
A method is disclosed for reducing surface runout acceleration as a result.

However, although this method was effective for single-plate media, it was difficult to sufficiently eliminate surface runout acceleration for the laminated type media.

And 3AOOr, which is currently being considered for practical use.
When the rotational speed was as high as pm, jl, 100 rprn, the problem of surface runout acceleration due to debris became serious.

In particular, in the case of the above-mentioned bonded type media, when bonding two substrates each having a recording layer thereon, an adhesive such as a hot melt adhesive or an ultraviolet curing adhesive is applied and a press is applied. When pressing the substrate, pressure is not sufficiently released to the outer periphery of the substrate, resulting in local protrusions around the outer periphery. This is thought to be mainly because the distortion caused by the warp of the substrate itself is concentrated on the outer periphery due to the correction effect caused by the application of pressure during bonding. In addition, the highly viscous adhesive gathers around the outer periphery of the substrate, resulting in a build-up of adhesive on the outer periphery. These protrusions and bulges formed on the outer periphery of the substrate also cause local deterioration of surface runout acceleration.

As a result, the optical head could not follow the recorded signal, resulting in poor tracking.

In order to eliminate the influence of the true melt adhesive that is extruded and accumulated on the end surface of the substrate, an optical recording medium having a tapered portion on the outer peripheral edge of the substrate is disclosed in Japanese Patent Application Laid-Open No. 4-T1. There is a method of creating grooves in the non-recording area of the substrate surface.
It is disclosed in 1982-2!2j177.

However, with these methods, as the rotation speed increases,
1 was not sufficient to address the problem of increased surface runout acceleration.

Problems to be Solved by #J from C] The present invention was made in view of the problems of the prior art described above, and is a so-called adhesive tape in which a recording layer is provided between two substrates via an adhesive layer. It is an object of the present invention to provide a laminated type optical recording medium that is less prone to surface runout acceleration and capable of recording and reproducing at a high linear velocity.

[Means to solve problems]

The object of the present invention is to provide an optical recording medium having at least one recording layer between two substrates facing each other via an adhesive layer. The optical recording medium is characterized by having a rectangular notch on its periphery.

FIG. 1 is a schematic cross-sectional view of an optical recording medium according to the present invention, in which two substrates /a and /b have a recording layer (not shown in the drawing) on at least one side thereof. They are placed facing each other with their surfaces facing inward and bonded together with an adhesive layer 2 interposed therebetween.

There are notches s3a and 3b on the inner outer periphery of the substrates /a and /b. That is, on the inner outer peripheral edge of each of the substrates disposed opposite to the optical recording medium of the present invention, there is a difference between the notches 3a and 3b. When pressure is applied to the press when bonding the substrates /a and /b, the notch is formed within the plane of the substrate because the pressure is relatively lower on the parts 3a and 3b. As the strain escapes there, the planes of the substrates /a and /b on which the recording layer is located become relatively flat.

Ota. Since the excess adhesive protruding from between the substrates /a and /b is accommodated in the regions of the notches 3a and 3b, it becomes a mound, etc., and affects the shape change of the end surface of the substrate. This will be prevented. In other words, by smoothing the transfer of the adhesive during the adhesion process), it is possible to prevent the adhesive from remaining on the outer peripheral edge surface of the laminated type optical recording medium or #'i.
Eliminates shape abnormalities and dirt caused by protrusion.

Therefore, the optical recording medium of the present invention has the advantage that the surface runout acceleration does not increase even when the rotational speed increases, and is less susceptible to changes in the rotational speed during recording, playback, and erasing. It also has excellent drive compatibility.

The advantages of the present invention can be further enhanced by the dimensions of the notches 3a and 3b. That is, when the thickness of the adhesive layer 2 is D, the length d2 of the notches 3a and 3b in the thickness direction of the substrate is D/co or more, or 1 housing, or D or more, Furthermore, the substrate/a
and /bLv diameter is R1, when the diameter of the outermost circumference of the recording track area of the substrates /a and /b is r, the length dl of the notches in the in-plane direction of the substrate of the portions 3a and 3b is 01l.
The object of the present invention can still be effectively achieved by setting the layer to be at least x (R-r), or at least 1 ton, or at least 0,0 x (R-r).

In the shape of the notch, if the above d2 is less than D/C, the thickness unevenness of the hot melt e applied to the lower step of the notch cannot be sufficiently absorbed and the part is filled with a local hot melt layer. Because of this, the distortion during pressing described earlier is
There will be some areas where "escape" is not performed locally,
If d1 is less than 0.7 x (R-r), the farther the pressure release part is from the outermost recording circumference, the more difficult it is to release the strain accumulated there, and the effect of improving surface runout acceleration will decrease. Well, that's not desirable.

That is, the length dl of the notches 3a and 3b in the in-plane direction of the substrate is 7/70 of the width of the non-recording area on the substrate.
With the above, the length d2 of the notches 3a and 3b in the thickness direction of the substrate is preferably 1/2 or more of the thickness D of the adhesive layer, preferably 0 or more. 1 cabinet.

Further, in the optical recording medium of the present invention, the notch is formed in the portion 3a.
When forming the notches 3b and 3b, the surface contact acceleration is further reduced by limiting the gap formed at the end of the notch to a specific size. That is, in FIG. 2 showing an enlarged view of the outer peripheral end portion A of the optical recording medium of the present invention in FIG. is d3 and the width is d4, then d3/
d4 to a2×10-4 or less, 1 case i;l:/X10
-4 or less.

By making the height of the paris considerably smaller than the width, 2
When the two substrates are crimped together, the pressure is smoothly released to the outside, and deformation of the end surfaces of the substrates due to contact between the edges is prevented, thereby preventing the above-mentioned surface contact acceleration from occurring.

The notches 3a and 3b of the optical recording medium of the present invention may be buttoned in advance on the substrates /a and /b before the bonding process, or may be formed by cutting after the casing or bonding. It may be formed.

The thickness of the adhesive layer of the optical recording medium of the present invention is preferably /10μm or less, preferably /00p from the viewpoint of adhesive strength.
m or less.

Various conventionally known adhesives can be used as the adhesive for the adhesive layer, but hot melt adhesives, ultraviolet curing adhesives, and epoxy adhesives are particularly preferred. True melt adhesives are desirable because they have fewer problems in terms of suitability for mass production and toxicity to the human body.

As a specific example of the adhesive, for example, Takahei Chemical Co., Ltd.
Synthetic rubber adhesive ◆XW-i3゜UV curable adhesive LI-Tough J' manufactured by LOCTITE, Nagas
The ultraviolet curable adhesive XNRrφRIO manufactured by e-CIBA can be used.

The shape and dimensions of the substrates /a and lb of the optical recording medium of the present invention are determined by standards defined for each type of optical recording medium of the present invention.

For example, 1. ．． In the case of a 23-inch magneto-optical recording medium substrate, thickness/, 2 mrn, outer diameter/JOmm, inner diameter/j
It is mm.

The optical recording medium of the present invention! As the material for the substrates/a and lb, polycarbonate, polymethyl methacrylate, epoxy resin, glass, etc. are used. Among them,
A plastic substrate such as polycarbonate, polymethyl methacrylate, or epoxy resin is preferred, and polycarbonate is particularly preferred since it has advantages such as low water absorption and high glass transition temperature.

The optical recording medium of the present invention! is formed by bonding two substrates each having a recording layer on one or both sides with the recording layer facing inward using the various adhesives described above.

By forming recording layers on both substrates, a double-sided recording medium can be obtained.

Note that on the surface of the substrate having the recording layer, a guide groove for recording and reproduction is formed in advance (5i-i), and the area where the guide groove is formed substantially coincides with the recording area, and is an area with a diameter r in FIG. 1. .

Then, an adhesive is applied onto the recording layer using a roll coater or the like and bonded under pressure to form the adhesive layer having a predetermined thickness. The press pressure when adhering under pressure is 0.3~/0kg7cm2 or preferably V~7k
g/cm2.

The optical recording medium of the present invention! When is a magneto-optical recording medium, the recording layer can be made of various oxides and metal magnetic materials. For example, MnAJGe.

Crystal materials such as MnCuB1, GdIG, BiSmEr
GaIG.

Even if the form is a single layer, it may be an amorphous layer made of single crystal materials such as BiSmYbCoGeIG, or transition metals or rare earth metals, or an "i-layer" in which thin films of different magnetic materials are alternately layered in a casing. It may be a stacked layer.

Among them, a recording layer mainly containing transition metals and rare earth metals is particularly preferable in terms of characteristics, and the transition metals include, for example, Fe.
, Co, Ni, etc., and the rare earth metals include Tb, Gd,
Nd, Dy, Sm, etc. can be used. A specific example of the composition of the recording layer is GdCo%GdFe%Tb.
Fe, DyFe.

GdFeTb, TbFeCo%DyFeCo, TbFe
Examples include Ni, ()dFeCo, NdDyFeCo, and the like. Among them, TbFeCo is the most preferable, and in order to further improve the corrosion resistance of the recording layer, Cr, Ta, AI
.

It is preferable to contain Pt, V, etc., especially Cr.
is the most effective, its content is 20 a
t 4, Nozomi! It's really FiJ to /fat Yu.

The recording layer is formed by a vacuum film forming method such as a sputtering method, and has a film thickness of 200 to 3000 Å.

Usually, a thin dielectric film Is is formed between the recording layer and the substrate as an enhancement layer of the recording layer.

Then, an inorganic protective layer for protecting the recording layer is formed on the recording layer.

As materials for the enhancement layer and the inorganic protective layer, dielectrics such as oxides, nitrides, and sulfides such as 8i0x, SiNx, Al1Nx, and Zn8 are used.

Among these, 8i nitride, Al nitride, or a mixture thereof is preferable from the viewpoint of optical properties and protective function.

Further, a metal reflective layer is provided on the inorganic protective layer, and further C
/N can also be improved. The material of the metal reflective layer is a thin metal film with a thickness of 300 to 400 mm mainly made of A/N or Ni, and is formed by sputtering like the other layers.

There are no particular restrictions on the film-forming conditions for the enhancement layer and the protective layer, but the thickness of the enhancement layer is usually 100%.
The thickness of the inorganic protective layer is 00 to 1 rooh.

Furthermore, in order to improve the characteristics of the magneto-optical recording layer, a metal reflective layer can be formed to a thickness of 300 to 600 nm on the inorganic aN storage layer.

After forming a magneto-optical recording layer consisting of thin films such as the above-mentioned recording layer, enhancement layer, inorganic protective layer, metal reflective layer, etc., the top and side surfaces are coated with an organic resin protective layer such as an ultraviolet curing resin. It is also possible to further improve the storage stability of the magnetic recording medium.

When the optical recording medium of the present invention is a WO type, the recording layer thereof is Te, Te0%TeSe, TeC82, Te5eP.
b, Te-TeO2,5bSe%Te8eAs.

Metal thin films such as T e Ge, cyanine, merocyanine, 7-talocyanine, methine dyes or their derivatives, and dye thin films such as benzenethiol nickel complexes and tetrahydrocholine complexes are used.

Then, to improve recording performance, an undercoat layer such as a thin metal film, a dielectric material, or an organic material, and an overcoat layer using a dielectric film such as 8i02 to improve corrosion resistance are formed. It can be a structure. The thickness of the recording layer is usually 300 to 100 mm/ooh.

When the optical recording medium of the present invention is a ROM type, its recording layer is usually a metal thin film with a high reflectance, such as kl, Au,
Single substances or alloys of Pt, Ta, Cr, Ni, Ti, etc. are used, and among them, Al or trik1 alloy is particularly desirable because of its low cost and relatively good reflectance! Yes. As for the film thickness of the recording layer,! 0θ~/! 00).

〔Effect of the invention〕

By providing a rectangular notch at the periphery of a bonded type optical recording medium in which a recording layer is placed between two substrates via an adhesive layer, an optical recording medium with low surface contact acceleration can be created. This makes it possible to achieve excellent suitability for drives with a large number of rotations.

The novel features of the present invention will be specifically explained by the following Examples and Comparative Examples.

(Example-7) Diameter on one side just like injection molding! A disk is fixed on the rotating body on the surface with the guide groove of a polycarbonate substrate with a diameter of 30 mm and a thickness of 7° and 2 mm, with a guide groove provided between Cutting was performed by feeding the cutting tool so that the shape was cut. The feeding direction of the cutting tool is the radial direction of the disk, and may be perpendicular to the disk surface. In addition, if d3 and d4 did not satisfy the condition that the cracks caused by this cutting were the main cause, additional polishing was performed using 2000 or more during lapping.

In the above method, a rectangular notch in which dl is 2 mm on one side of the outer periphery and dl is varied in the range of 4t to 34 μm forms a part, and at the same time, the notch formed at that time is inside the part. A substrate was prepared in which the height d3 and width d4 of the burr at the peripheral edge were measured using a stylus-type step meter.

The substrate was set on a rotating substrate holder in a sputtering chamber of a magnetron sputtering device.

Then, argon gas was introduced into the sputtering chamber, and the gas pressure was set to /mTorr.

Then, a thin film of SiNx with a thickness of 1100 Å was formed as an enhancement layer by magnetron sputtering.

Next, electric power was applied to the FeCoCr alloy target and the Tb target to form a recording layer having a composition of Tb1gFe66Co8Cr6 to a thickness of ruoA on the enhancement layer by dual simultaneous sputtering.

After that, an inorganic protective layer of SiN is formed on the recording layer.
2 thin films of x! A film was formed to a thickness of OA.

Furthermore, Al-Ta (Taja
t%) with a thickness of 4ook.

A magneto-optical recording layer having a four-layer structure consisting of an enhancement layer, a recording layer, an inorganic protective layer and a metal reflective layer was formed on the substrate.

After that, an ultraviolet curable resin φSD-/7 manufactured by Dainippon Ink ■ was coated on the magneto-optical recording layer using a spin code method.
The coating was applied to a thickness of 1 μm under the conditions of rpm, and was cured by irradiating ultraviolet rays at 10 omW/Cm for 2.7 minutes using a high-pressure mercury lamp to form an organic resin protective layer.

Under similar conditions, another medium having the magneto-optical recording medium provided on one side of a substrate having the same shape was prepared, and each of the substrates was turned with the surface without the magneto-optical recording layer facing outward, and the organic resin was Hot melt adhesive φXW- made by Toagosei Kagaku ■ on the protective layer
13/! Melt it at O0C and apply it with a roll coater,
Pressure bonding was carried out under conditions of a press pressure of J kgf/cm for 2.20 seconds to obtain an adhesive layer with a thickness of aOμm, and the recording layer was attached to the rectangular notch through the adhesive layer to the outer periphery. A sample of a double-sided recording type magneto-optical recording medium provided between two substrates at the periphery was prepared.

The surface runout acceleration of the optical recording medium sample obtained as described above was measured and evaluated under the following conditions.

Surface runout acceleration ``Rotational speed iro'' using a disk mechanical property measuring device LM10θ manufactured by Ono Saiki ■.

The evaluation was performed using rpm and a radius of 40 mm.

The measurement results are as shown in Fig. 3, and the length of the rectangular notch in the thickness direction of the substrate is equal to the thickness of the adhesive layer It Op.
It was found that the surface contact acceleration decreases after m//2.

At the same time, the surface contact acceleration tends to increase as d3/d4 increases, and the value of the notch is 2×10-4
I found that the size below becomes smaller.

(Example-2) In Example-/, the shape of the notch is 2.
A substrate with mm and d2 of 30 μm was used, and the adhesive was an ultraviolet curing adhesive LI- manufactured by LOCTITE.
A sample of a double-sided recording type magneto-optical recording medium was prepared under the same conditions as in Example 7 except that Y7t was used.

The relationship between the shape of the notch formed at the inner circumferential end of the notch and the surface contact acceleration is evaluated as shown in FIG.

The height to width ratio d a/d of the Paris is JXlo-4
It was found that the surface contact acceleration increases when the

(Example-3) In Example-/, d2 is 30 μm, and dl is 0 to
Change in the range of 7 mm and d a / d 4 is I
A sample of a magneto-optical recording medium was prepared under the same conditions as in Example-/, except that Ox10-4 and d3/d4 were 2x10-4.

FIG. 1 shows the results of measuring surface runout acceleration under the same measurement conditions.

[Brief explanation of drawings]

FIG. 7 is a schematic cross-sectional view of the optical recording medium of the present invention. FIG. 2 is an enlarged view of the outer periphery of the optical recording medium of the present invention. FIG. 3 shows the relationship between the shape of the rectangular notch provided on the outer periphery of the substrate of the optical recording medium of the present invention, the shape of the inner edge of the notch, and the surface contact acceleration. Graph showing. FIG. 4 is a graph showing the relationship between the shape of the inner circumferential end of the notch and surface contact acceleration of the optical recording medium of the present invention. /a, lb... board! . . . Adhesive layers 3a, 3b . . . Notches are at portion μ19. Paris! ...Optical recording medium Figure 1

Claims (3)

[Claims] (1) In an optical recording medium having at least one recording layer between two substrates placed facing each other with an adhesive layer interposed therebetween, a rectangular cut is formed on the inner outer periphery of the two substrates. An optical recording medium characterized by having a notch. (2) When the diameter of the substrate is R, the outermost circumferential diameter of the recording track area on the substrate is r, and the distance between the two substrates facing each other is D, the cutout portion is directed in the plane of the substrate. The length d_1 of the notch is larger than 0.1×(R-r), and the length d_2 of the notch in the thickness direction of the substrate is D
2. The optical recording medium according to claim 1, wherein the optical recording medium is larger than /2. (3) When the height of the burr at the inner peripheral end of the notch is d_3 and the width is d_4, d_3/d_4 is 2
The optical recording medium according to claim 1, wherein the optical recording medium is not more than ×10^-^4.