JPH0432041A - Optical disk and production thereof - Google Patents

Abstract

PURPOSE:To prevent the bleeding out of an adhesive by interposing a tension resistant sheet into adhesive layers. CONSTITUTION:The tension resistant sheet 9 is interposed into the adhesive layers 7, 8. Extremely high tacky adhesive force is generated between the adhesive layers 7 and 8 and the tension resistant sheet 9 positioned between these layers. The flowability of the adhesive layers 7 and 8 is suppressed by the high adhesive strength to the tension resistant sheet 9 even if the viscosity of these layers tends to decrease as the temp. rises. The bleeding out of the adhesive even by the centrifugal force generated by a high speed rotation at the time of performance or the excessive force generated in the thickness direction by imposing an object thereon during storage is thus obviated.

Description

TECHNICAL FIELD The present invention relates to optical discs such as optical video discs and digital audio discs, and methods of manufacturing the same.

BACKGROUND ART Conventionally, in an optical disc, in order to protect a layer in which information is recorded as a large number of minute pits, that is, a signal recording layer, a pair of circular substrates, at least one of which has a signal recording layer, are used, with the signal recording layer on the inside. It is common practice to connect them facing each other in this way.

An optical disc having such a configuration is particularly suitable for storage at room temperature (20°C).
40°C), the viscosity of the adhesive decreases as the temperature rises; If you rotate it at high speed underneath to create centrifugal force, or place something on it and apply excessive force in the thickness direction, the adhesive will flow and some of it will ooze out. .

Summary of the invention [Object of the invention] The present invention has been made in view of the above points, and its object is to provide an optical disc in which adhesive does not ooze out from the adhesive part and a method for manufacturing the same. It is.

[Structure of the Invention] The optical disc according to the present invention is an optical disc in which a pair of circular substrates, at least one of which has a signal recording layer, are bonded to each other by an adhesive layer made of a hot melt adhesive; It is characterized by having a tension-resistant sheet interposed between it.

Furthermore, in the method for manufacturing an optical disc according to the present invention,
A step of preparing a pair of circular substrates, at least one of which has a signal recording layer, and forming an adhesive layer made of a hot melt adhesive on the main surface of the circular substrate on the signal recording layer side; The present invention is characterized in that it includes a step of attaching a tension-resistant sheet onto the adhesive layer, and a step of attaching the other adhesive layer of the circular substrate to the tension-resistant sheet.

[Operation of the Invention] The fluidity of the adhesive is suppressed by the tension-resistant sheet disposed within the optical disk adhesive layer.

Embodiments Hereinafter, optical discs and methods for manufacturing the same as embodiments of the present invention will be described with reference to the accompanying drawings.

1 and 2 show an optical video disc (hereinafter abbreviated as disc) as a first embodiment of the present invention.

As shown in FIGS. 1 and 2, the disk has two circular substrates 1 and 2 having the same circular dimensions and having central holes 1a and 2a, respectively. The double-sided substrates 1 and 2 are made of synthetic resin and are transparent, and on one side of each is provided with a signal recording layer formed by an information recording track consisting of minute bits (dents) and metal reflective films 3 and 4. and are opposed to each other so that the respective signal recording layers are on the inside. Protective films 5 and 6 are formed to protect this signal recording layer, and adhesive layers 7 and 8 made of a hot melt adhesive are coated on the protective films, and
The disk is formed by bonding both diagonal substrates 1 and 2 via a tension-resistant sheet 9.

Next, a third method for manufacturing a disk having the above-mentioned structure will be described.
This will be explained based on Figures (a) to (e). Note that the following description will be made regarding the processing performed on one of the two circular substrates 1 that are coupled together, and the description of the other circular substrate 2 will be omitted since it is the same.

First, as shown in FIG. 3 (ω), a circular substrate 1 is prepared on which a signal recording layer is formed by depositing a reflective film 3 made of a metal such as aluminum on one side on which information recording tracks are formed. , the reflective film 3 is deposited using a vacuum deposition apparatus.

As shown in FIG. 3(b), for the prepared circular substrate 1,
A protective film 5 is formed on the signal recording layer to protect it. The protective film 5 is obtained by applying a heated hot-melt adhesive that loses its tackiness at room temperature using a roller or the like, and then cooling it at room temperature. Thereafter, as shown in FIG. 3(C), a hot melt adhesive that maintains tackiness at room temperature is applied onto the protective film 5 using a roller or the like to form an adhesive layer 7. Furthermore, as shown in the third drawing, a tension-resistant sheet 9 is attached onto the adhesive layer 7.

On the other hand, the other circular substrate 2 is prepared by performing the same processing as that applied to the circular substrate 1 in the step shown in FIG. 3 (ω-C).

Then, the adhesive layer 8 of the circular substrate 2 is adhered to the tension-resistant sheet 9 on the circular substrate 1, and the two circular substrates are bonded together.

In this way, the disks shown in FIGS. 1 and 2 are obtained, which are then subjected to finishing processes and various inspections to complete the process.

Here, the tension-resistant sheet 9 sandwiched between the two circular substrates 1 and 2 will be described in detail.

First, the tension-resistant sheet 9 is formed into a circular shape with a center hole like the two-day type substrates 1 and 2, and its diameter is set so that it is adhered to almost the entire surface of the two-day type substrate. is desirably suppressed to 100 μm or less. As the material for the tension-resistant sheet 9, a material with high tensile strength is selected, and synthetic resin or natural resin is used in consideration of moldability.

A tension-resistant sheet with a smooth surface may be used, but a tension-resistant sheet 11 with a mesh structure as shown in FIG. It is desirable to use a tension-resistant sheet 12 having round holes 12a formed therein, or a tension-resistant sheet 13 whose main surface is roughened by forming fine irregularities as shown in FIG.

In the disk having the above structure, adhesive layers 7 and 8
An extremely large adhesive force is generated between the tension-resistant sheet 9 and the tension-resistant sheet 9 sandwiched therebetween. Therefore, even though the adhesive layers 7 and 8 decrease their viscosity as the temperature increases,
The large adhesion force to the tension-resistant sheet 9 suppresses its fluidity, and even the excessive force applied in the thickness direction due to centrifugal force due to high-speed rotation during performance, or when objects are placed on it during storage, etc. Adhesive will not ooze out.

Incidentally, when a tension-resistant sheet having a structure with a large surface roughness as shown in FIGS. 4 to 6 is used, the adhesion force between the adhesive layers 7 and 8 and the tension-resistant sheet is further increased. Also, the fourth
Since the tension-resistant sheet having the structure shown in FIG. 5 and FIG. 5 has a mesh-like and porous structure, its weight is reduced, contributing to the weight reduction of the disk as a whole. Furthermore, in the mesh structure shown in FIG. 4, ideal strength can be obtained by forming it from carbon fiber, glass fiber, whiskers, or the like.

FIG. 7 shows a digital audio disc (hereinafter abbreviated as disc) as a second embodiment of the present invention. Note that this disk has the same structure as the disk shown in FIGS. 1 and 2 except for the parts explained below.
I won't go into details. In addition, in the following explanation, the same reference numerals are used for parts that are the same as or correspond to those of the disks shown in Figures 1 and 2, and the compositions are also the same, so the explanation of the materials etc. of each part will be abbreviated. do.

As shown in FIG. 7, this disc does not have a dedicated protective film to protect the reflective films 3 and 4 provided on each circular substrate 1 and 2, respectively, and the adhesive layers 7 and 8 are It is applied directly to the reflective films 3 and 4 and used as a protective film. A tension-resistant sheet 9 is sandwiched between these adhesive layers 7 and 8.

The disk having such a structure can have a smaller thickness than the disk having the structure shown in FIGS. 1 and 2.

The disk shown in FIG. 7 is manufactured by the manufacturing method shown in FIGS. 8(a) to 8(c). The following description of the manufacturing method is based on the processing performed on one of the two circular substrates, ie, the circular substrate 1, and the processing on the other circular substrate 2 is similar. Therefore, the explanation will be omitted.

First, as shown in FIG. 8 (J), a circular substrate 1 on which a signal recording layer is formed by depositing a reflective film 3 on one side on which information recording tracks are formed is prepared.

As shown in FIG. 8), a hot melt adhesive that is sticky at room temperature is applied onto the signal recording layer of the circular substrate 1 using a roller or the like, and the adhesive layer is form 7. Then, as shown in FIG. 8(C), a tension-resistant sheet 9 is attached onto this adhesive layer 7.

On the other hand, the other circular substrate 2 is processed in the same way as the process shown in FIGS. 8(a) and +b+ on the circular substrate 1.
Also give and prepare. After this, the adhesive seat layer 8 of the circular substrate 2 is
is attached to the tension-resistant sheet 9 on the circular substrate 1, and the two circular substrates are combined to obtain the disk shown in FIG.

Similarly to the disks shown in FIGS. 1 and 2, the tension-resistant sheet 9
The effect based on the action of

In each of the above embodiments, optical video disks and digital audio disks, that is, read-only optical disks are shown, but the present application is not limited to these, and also applies to phase-change optical disks such as write-once type and rewritable type optical disks that can also write. It goes without saying that the configuration of the invention is applicable.

Further, in the above embodiment, a double-sided performance disc was shown in which both of the pair of circular substrates forming the optical disc were provided with a signal recording layer, but the signal recording layer was provided only on one circular substrate and the other circular substrate was provided with a signal recording layer. The circular substrate may be a dummy substrate without a signal recording layer and may be an optical disk for single-sided performance.

Effects of the Invention As detailed above, in the optical disc according to the present invention, a tension-resistant sheet is interposed in an adhesive layer made of a hot melt adhesive that adheres a pair of circular substrates.

Furthermore, in the method for manufacturing an optical disc according to the present invention,
Following the step of forming an adhesive layer made of hot melt adhesive on the main surfaces on the signal recording layer side of a pair of circular substrates forming an optical disk, a tension-resistant sheet is attached onto the adhesive layer of one of the circular substrates. Then, the adhesive layer of the other circular substrate is adhered to the tension-resistant sheet.

In such optical discs, a large adhesive force is generated between the adhesive layer and the tension-resistant sheet, which suppresses the fluidity of the adhesive and prevents the adhesive from seeping out.

[Brief explanation of the drawing]

1 and 2 are a perspective view and a partially enlarged cross-sectional view, respectively, of an optical disk according to a first embodiment of the present invention, and a third
Figures (a) to d) are cross-sectional views showing the manufacturing process of the optical disc shown in Figures 1 and 2, and Figures 4 to 6 show the durability included in the optical disc shown in Figures 1 and 2. FIG. 7 is a plan view of each tension sheet, FIG. 7 is a partially enlarged sectional view of an optical disc as a second embodiment of the present invention, and FIG. 8 (Oishuku C)
7 is a sectional view showing the manufacturing process of the optical disc shown in FIG. 7. FIG. Explanation of symbols of main parts

Claims (5)

[Claims] (1) An optical disc comprising a pair of circular substrates, at least one of which has a signal recording layer, bonded to each other by an adhesive layer made of hot melt adhesive, wherein a tension-resistant sheet is interposed in the adhesive layer. An optical disc featuring (2) The optical disc according to claim 1, wherein the tension-resistant sheet has a mesh structure. (3) The optical disc according to claim 1, wherein a large number of holes are formed on the main surface of the tension-resistant sheet. (4) The optical disc according to claim 1, wherein the main surface of the tension-resistant sheet is a rough surface. (5) A step of preparing a pair of circular substrates, at least one of which has a signal recording layer, and forming an adhesive layer made of hot melt adhesive on the main surface of the circular substrate on the signal recording layer side; A method for manufacturing an optical disc, comprising the steps of: adhering a tension-resistant sheet on one of the adhesive layers; and adhering the other adhesive layer of the circular substrate to the tension-resistant sheet.