JP2000040257A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of wrinkles or air bubbles in the adhered parts of a DVD-10 (optical information recording medium writable from both faces) formed by bonding two substrates where recording films and protective layers are formed, with a transparent pressure sensitive adhesive. SOLUTION: Notched shapes 61a, 61b are respectively formed at the outer peripheral ends of the surfaces of disk-shaped light transparent substrates 14a, 14b. Namely, signal pits or grooves are formed on the respective substrate surfaces and recording films 24, 24b including reflection films, etc., are formed thereon in the portions excellent the outer peripheral ends of the substrates. Further, the protective layers 43a, 43b are formed on the recording films and thereafter the substrates 14a, 14b are bonded by the transparent pressure sensitive adhesives 34a so that there protective layers 43a, 43b face each other, to form this optical information recording medium. Conical slopes extending from near the outer periphery ends of the substrate surfaces to the outer peripheral surfaces of the substrate are formed as the notched shapes described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium (DVD or laser disk) formed by bonding two light-transmitting substrates with a transparent adhesive. The present invention relates to a structure of an optical information recording medium having no air bubbles.

[0002]

2. Description of the Related Art An optical information recording medium for reading recorded information, writing information or erasing information by using light of a specific laser wavelength is formed by bonding two light-transmitting substrates. Are already manufactured or sold. For example, a DVD or a laser disk corresponds to this. In the near future, DVDs on which data can be written and rewritten will be manufactured and sold.

FIG. 5 shows a general structure of an optical information recording medium (commonly called DVD-5) in which data can be rewritten only on one side. This DVD-5 is composed of two (disk-shaped) light-transmitting substrates 11a and 11b, a recording film 21 including a reflective film, and an adhesive layer 31. The light transmitting substrate 11a,
11b is made of PC (polycarbonate) or PMMA (commonly called acrylic) resin, amorphous polyolefin resin, amorphous PET (polyethylene terephthalate), the reflective film is made of Au, Ag, Al alloy, etc. UV-curable adhesives are used respectively.

In the general manufacturing process of the DVD-5,
After molding the light-transmitting substrates 11a and 11b, a recording film 21 including a reflective film and the like is formed on the surface of one of the light-transmitting substrates 11b by sputtering or the like. Next, the light-transmitting substrate 11
An ultraviolet-curable adhesive is applied to one or both of the substrates 11a and 11b by a spin coater method, the substrates 11a and 11b are overlapped, and the ultraviolet-curable resin is shaken off at high speed to a desired thickness, and then irradiated with ultraviolet rays. Then, the UV-curable adhesive is cured to form the adhesive layer 31.

In recent years, with the increase in the capacity of recorded information, a recording film including a reflection film and the like is formed on each of two light-transmitting substrates, and these are laminated to face each other. An optical information recording medium (commonly known as DVD-10) capable of writing and rewriting data from a disc has been proposed.

[0006] However, in the case of bonding with an ultraviolet-curing adhesive, if a recording film including a reflection film or the like is formed on both of the two light-transmitting substrates, the ultraviolet light cannot pass through. For this reason, there was a problem that the adhesive could not be cured.

[0007] In order to solve the above problem, bonding with a transparent pressure-sensitive adhesive has recently been proposed. This is described in, for example, Japanese Patent Application Laid-Open Nos.
JP-A-230338, JP-A-4-259935, and JP-A-8-329632.

FIG. 6 shows a general structure of a DVD-10 bonded with a transparent pressure-sensitive adhesive. That is, the recording film 22 including the reflection film or the like is provided on one of the transparent substrates 12a.
a, a protective layer 41a is formed thereon, a recording film 22b including a reflective film or the like is formed on the other transparent substrate 12b, and a recording film 41b is formed thereon, and these substrates 12a, 12b are
The structure is such that the protective layers 41a and 41b are adhered by the adhesive layer 32 in a state where they face each other.

Since the transparent pressure-sensitive adhesive forming the adhesive layer 32 does not require a curing energy source such as light or heat, the recording film 22a including a reflective film and the like on both surfaces of the light-transmitting substrates 12a and 12b. , 22b can be securely bonded.

In the general manufacturing process of the DVD-10 (FIG. 6), after the light-transmitting substrates 12a and 12b are formed, recording films 22a and 22b including a reflection film and the like are formed by sputtering or the like. Next, the protective layer 41 is formed by a spin coater.
a, 41b are applied. Finally, one side of the double-sided adhesive tape is adhered to the protective layer of one substrate, and the protective layer of the other substrate is adhered to the other side. Thereby, the substrate 12
A recording medium having a structure in which a and 12b are pressure-bonded and bonded in a form in which the protective layers 41a and 41b are opposed to each other and in a form in which the protective layers 41a and 41b are overlapped via a transparent pressure-sensitive adhesive (adhesive layer 32).

[0011]

However, as shown in FIG. 7, when the light-transmitting substrates 13a and 13b are bonded with the transparent pressure-sensitive adhesive, the bonding portion between the bonding layer 33 and the protective layers 42a and 42b is formed. In addition, there is a problem that wrinkles 51 and air bubbles 52 are easily generated. One of the causes is uneven coating of the protective layers 42a and 42b. Next, this will be described.

The protective layers 42a and 42b have a viscosity of 10-5.
00c. P. (25 ° C.) UV curable adhesive is used. When these protective layers are formed, a liquid material for forming the protective layers 42a and 42b is applied by a spin coater, and the liquid material is shaken off at a high speed to obtain a desired thickness.
This is cured by ultraviolet light. However, the protective layer rises due to surface tension at the outer peripheral end of the light transmitting substrate until the curing is completed. The height of the swelling varies depending on the conditions, but is usually 5 to 30 μm.
The raised protective layers 42a and 42b are opposed to each other,
The transparent substrate 13a,
13b, wrinkles 5 on the bonding portion as described above.
1 and air bubbles 52 are generated.

The wrinkles 51 and the air bubbles 52 are Tangential
Degradation of Tilt or Radial Acceleration (reduction of recording / reproduction margin) or recording film 23 including reflective film
a, 23b (particularly, a decrease in reliability under high temperature and high humidity).

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and has as its object to form a recording film including a reflective film on at least one of two light-transmitting substrates, and make these transparent to face each other. Writable and rewritable optical information recording media (DVD-5, DVD
-10, DVD-9) is to prevent generation of wrinkles 51 and air bubbles 52 at the bonding portion between the substrates.

[0015]

An optical information recording medium (FIG. 1) according to claim 1 has signal pits or grooves formed on the surfaces of two light-transmitting (disk-shaped) substrates 14a and 14b. After forming recording films 24a and 24b including a reflective film and the like on these signal pits or grooves, and further forming protective layers 43a and 43b on the recording films, the protective layers are opposed to each other. In an optical information recording medium (DVD-10) formed by bonding the two substrates 14a and 14b with a transparent adhesive (for example, a transparent pressure-sensitive adhesive), one or both of the two substrates are used as substrates. A cutout shape is formed at the outer peripheral end of the surface (at least one of 61a and 61b is formed).

In the optical information recording medium according to the present invention (FIG. 2), signal pits or grooves are formed on the surface, and a recording film 25 including a reflection film or the like is formed on these signal pits or grooves. Further, the first light-transmitting (disk-shaped) substrate 15b having the protective layer 44 formed on the recording film 25 and the second light-transmitting (disk-shaped) substrate 15a having a flat surface are formed by the first light-transmitting (disk-shaped) substrate 15a. Optical information formed by bonding these two substrates with a transparent adhesive (for example, a transparent pressure-sensitive adhesive) such that the protective layer 44 of the substrate 15b and the flat surface of the second substrate 15a face each other. In the recording medium (DVD-5), the first
A notch is formed at the outer peripheral end of the surface of the substrate 15b.

According to a third aspect of the present invention, in the optical information recording medium (FIG. 2) according to the first or second aspect, the cutout shape includes a surface perpendicular to the substrate surface and an inclined surface connected to the vertical surface. And the inclined surface intersects the vertical surface at an obtuse angle and extends to the outer peripheral surface of the substrate.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. Embodiment 1 FIG. 1 is a cross-sectional view showing a main structure of a DVD-10. This DVD-10 has disc-shaped light transmissive substrates 14a and 14b.
Pits or grooves are formed on the surface of the substrate, and recording films 24a and 24b including a reflection film and the like are formed on portions other than the outer peripheral edge of the substrate, and protective layers 43a and 43b are formed on the recording film.
The optical information recording medium is formed by bonding substrates 14a and 14b with a transparent pressure-sensitive adhesive 34a such that the protective layers 43a and 43b are opposed to each other after the formation of 43b. 34 is an adhesive layer.

This DVD-10 has substrates 14a and 14b.
Are formed with cutouts 61a and 61b at the outer peripheral end where the recording film is not formed. That is, these notched shapes are formed as conical inclined surfaces extending from the vicinity of the outer peripheral end of the substrate surface to the outer peripheral surface of the substrate, as is apparent from FIG.

The recording films 24a and 24b include, but are not limited to, phase change type inorganic materials and organic dyes, and are not limited to these, and may include external energy (laser light having a certain wavelength, heat, There is no problem as long as it changes depending on ()).

In the DVD-10, the liquid material for forming the protective layer at the outer peripheral edge of the substrate is received in the notches 61a and 61b until the hardening of the liquid material is completed. Therefore, unlike the conventional DVD-10 shown in FIG. 7, the liquid material does not swell at the outer peripheral end of the substrate, so that the generation of wrinkles and air bubbles shown in FIG. 7 is prevented. As described above, the optical information recording medium of the present invention is characterized in that a cutout shape capable of receiving the liquid material for forming the protective layer is formed at the outer peripheral end of the substrate.

Embodiment 2 FIG. 2 is a sectional view showing the structure of a main part of a DVD-5. In this DVD-5, signal pits or grooves are formed on the surface of a disc-shaped light-transmitting substrate 15b, and a recording film 25 including a reflection film or the like is formed on a portion excluding the outer peripheral edge of the substrate. After forming the protective layer 44 on the recording film, the substrate 15
b and a disc-shaped light-transmitting substrate 15a on which a recording layer or the like is not formed, by attaching these substrates to a transparent pressure-sensitive adhesive 35 such that the protective layer 44 and the surface of the substrate 15a face each other.
This is an optical information recording medium bonded by a.
35 is an adhesive layer.

In this DVD-5, the notch shape for receiving the liquid material for forming the protective layer at the outer peripheral edge of the substrate has a surface 62a perpendicular to the substrate surface and an inclined surface 62b connected to the vertical surface 62a. And is formed from The inclined surface 62b is formed as a conical inclined surface that intersects the vertical surface 62a at an obtuse angle and extends to the outer peripheral surface of the substrate.

In the first and second embodiments, the DVD-1
0, DVD-5, but the notch shape of the first embodiment may be applied to DVD-5 or DVD-9, or the notch shape of the second embodiment may be DVD-10 or DV.
D-9 can be adopted, and the same operation and effect as described above can be obtained.

FIG. 3 shows a main structure of a mold 70 when the substrate 14b of FIG. 1 is obtained by injection molding. In this mold 70, the cavity 73 for molding the substrate 14b is formed by the movable side 71 and the fixed sides 72a and 72b, and the portion of the fixed side 72a corresponding to the cutout shape 61b of the substrate 14b has an acute cross section. It becomes the edge 74. Therefore, the mechanical strength of the fixed side 72a may be insufficient.
In FIG. L. Is a parting line.

FIG. 4 shows a main structure of a mold 80 when the substrate 15b of FIG. 2 is obtained by injection molding. In this mold 80, the cavity 83 for molding the substrate 15b is
1 and the fixed sides 82a and 82b,
A portion corresponding to the cutout shape 62a of the substrate 15b of the substrate 2b is an edge 84 having a right angle in cross section, and the cutout shape 62a.
The portion corresponding to b is an edge 85 having an obtuse cross section. Therefore, the fixed side 82a has an advantage that not only the mechanical strength is improved but also the necessity of maintenance is reduced as compared with the fixed side 72a.

[0027]

As apparent from the above description, the following effects can be obtained according to the present invention. (1) Effects According to Claims 1 and 2 In this optical information recording medium, a notch shape is formed at the outer peripheral end of the substrate surface. Since there is no swelling of the protective layer due to surface tension at the outer peripheral end of the substrates, wrinkles and air bubbles do not occur at the bonded portions between the substrates even when the substrates are bonded with a transparent adhesive. Therefore, deterioration of Tangential Tilt or Radial Acceleration (reduction of recording / reproducing margin) or deterioration of a recording film including a reflection film or the like (particularly, reliability under high temperature and high humidity conditions) does not occur. Further, in this optical information recording medium, since the protective layer does not rise, unlike the conventional product, the protective layer does not protrude from the end face of the substrate, so that the appearance is excellent.

(2) Effects Corresponding to Claim 3 In this optical information recording medium, the cutout shape at the outer peripheral end of the substrate is formed by a surface perpendicular to the substrate surface and an inclined surface connected to the vertical surface. Since the inclined surface intersects with the vertical surface at an obtuse angle and extends to the outer peripheral surface of the substrate, there is no sharp edge portion in the mold part for molding the substrate, so that the mold strength is improved. And the need for maintenance is reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of an optical information recording medium according to the present invention.

FIG. 2 is a sectional view showing Embodiment 2 of the optical information recording medium according to the present invention.

FIG. 3 is a sectional view of a main part of a mold for molding a substrate constituting the recording medium of FIG. 1;

FIG. 4 is a sectional view of a main part of a mold for molding a substrate constituting the recording medium of FIG. 2;

FIG. 5 is a cross-sectional view illustrating a configuration example of a DVD-5.

FIG. 6 is a cross-sectional view illustrating a configuration example of a DVD-10.

FIG. 7 is a cross-sectional view illustrating a problem in a conventional optical information recording medium.

[Explanation of symbols]

 11a to 15a Light-transmitting (disk-shaped) substrate 11b to 15b Light-transmitting (disk-shaped) substrate 21, 25 Recording film including reflective film 22a to 24a Recording film including reflective film 22b to 24b Including reflective film Recording film 31-35 Adhesive layer 41a-43a Protective layer 41b-43b Protective layer 44 Protective layer 51 Wrinkle 52 Air bubble 61a, 61b Notch shape 62a Vertical surface 62b Inclined surface 70,80 Mold 73,83 Cavity 74 Edge 84, 85 Edge P.E. L. Parting line

Claims (3)

[Claims] 1. A signal pit or a groove is formed on the surface of two light-transmitting substrates, a recording film including a reflection film or the like is formed on the signal pit or the groove, and a protection film is formed on the recording film. After forming a layer, in an optical information recording medium formed by bonding the two substrates with a transparent adhesive so that these protective layers face each other, one or both of the two substrates may have a substrate surface. An optical information recording medium, wherein a notch shape is formed at an outer peripheral end of the optical information recording medium. 2. A first light in which signal pits or grooves are formed on the surface, a recording film including a reflective film or the like is formed on the signal pits or grooves, and a protective layer is formed on the recording film. A transmissive substrate and a second light transmissive substrate having a flat surface,
In an optical information recording medium which is bonded by a transparent adhesive so that the protective layer of the first substrate and the flat surface of the second substrate face each other, a cut is made at an outer peripheral end of the surface of the first substrate. An optical information recording medium having a notched shape. 3. The notch shape is formed of a surface perpendicular to the surface of the substrate and an inclined surface connected to the vertical surface, the inclined surface intersects the vertical surface at an obtuse angle, and an outer periphery of the substrate. The optical information recording medium according to claim 1, wherein the optical information recording medium is formed so as to extend to a surface.