JPH08315430A - Production of disk substrate and disk substrate produced by that method - Google Patents

Abstract

PURPOSE: To obtain a producing method of disk substrate to avoid swelling out of an adhesive from the inner and outer edges of a disk and to omit a trimming process, and to obtain a disk substrate produced by this method. CONSTITUTION: Recorded information is transferred to at least one of two disks 1, 1, and at least a reflecting film 5 is formed on the disk plane having the recorded information. These disks are laminated with an adhesive 8 to obtain a disk substrate 10. In each disk 1, annular steps 2 or grooves to be used as a reservoir of the adhesive which is swollen out in the adhering process are formed in the outer and inner edges of the disk planes facing each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a commonly used LD, and further two discs such as a DVD (digital video disc) which is expected to be developed as a recording medium for a video department or a computer in the future. The present invention relates to a disc manufacturing method of a type in which the layers are bonded together and a disc structure thereof.

[0002]

2. Description of the Related Art The conventional disc structure has an outer diameter of 120 m.
It is a disc having a thickness of m and a thickness of 1.2 mm, and has a three-layer structure of a transparent substrate, a reflective layer, and a protective layer. The signal is recorded as the length and spacing of protrusions, called bits, on the reflective surface, with a string of bits spiraling from inside to outside forming tracks. The spot diameter of the laser beam applied to extract a signal is as small as 1.5 μm on the reflecting surface, but it is as large as 1 mm on the disk surface, so that the optical signal is not easily disturbed by scratches and dust. .

This optical disk (including a magneto-optical disk) has come to be used as an information recording medium in a wide range of fields such as audio, video, computers, etc., but in recent years, one of them is an improvement in recording capacity. For this purpose, an integrated disc substrate was developed by stacking two disc-shaped thin substrates (also simply referred to as discs) formed separately from each other.
Application to D etc. is considered.

According to such a structure, since signals can be recorded on each disk-shaped thin substrate, it is more than twice as large as that having a conventional single disk substrate structure. It is possible to secure the recording capacity.

By the way, such an overlapping type disc substrate has a thickness of 1.2 mm in LD and 0.6 mm in DVD, and a pair of these disc-shaped thin substrates is used. , Each of which is formed by using a stamper similarly to a normal single-structured disc substrate, and after forming a reflection film and a protective layer such as aluminum on the signal recording surface,
A pair of disk-shaped thin substrates are adhered back to back (both sides serve as a signal recording surface) by using a hot-melt adhesive or an ultraviolet curable adhesive, so that they are overlapped and formed.

Examples of the method of applying this adhesive include a spin coating method and a roll coating method which will be described later. However, in the bonding of the discs performed after the application of the adhesive, it is necessary to perform trimming (edging) on the inner diameter and the outer diameter of the disc because the adhesive may be extruded at the time of bonding.

This trimming is to remove the adhesive by cutting, but during the trimming, the cut adhesive powder scatters and sticks to the surface of the disk substrate, which is a major cause of defects. .

[0008]

In view of the above circumstances, the present invention provides a disk substrate in which the trimming process is omitted by eliminating the protrusion of the adhesive from the inner and outer edges of the disk when the disk substrates are bonded together. It is intended to provide a manufacturing method and a disk substrate used for the manufacturing method.

[0009]

In order to achieve the above object, a method of manufacturing a disk substrate according to the present invention is such that an annular step portion or a circumferential groove is formed on an outer peripheral edge and an inner peripheral edge on the one surface side of the disk, and At least one of the two disks is prepared by transferring two pieces of recording information to the disk surface side having the stepped portion or the like, and a reflecting film such as aluminum is formed on the disk surface having the recording information. Next, each step of bonding two disks by applying an adhesive agent to the surface side of each disk to be faced and making the bonded surfaces of the disks face each other and overlapping them is characterized. I am trying.

In the disc substrate of the present invention, recording information is transferred onto at least one of the two discs, at least a reflecting film is formed on the disc surface having the recording information, and the discs facing each other are superposed and bonded. In the structure of bonding with an agent, each disk is characterized in that an annular stepped portion or a circumferential groove, which serves as a reservoir for the adhesive that sticks out at the time of bonding, is formed on the outer and inner peripheral edges of the disk surfaces facing each other. There is.

[0011]

With such a structure, the excess adhesive protruding from the superposed surfaces of the discs flows into the pool of the adhesive, that is, the annular stepped portion or the circumferential groove of the outer peripheral edge and the inner peripheral edge of the disc, There is no need to trim the adhesive, as it does not stick out from the outer and inner edges of the disc.

[0012]

An embodiment of the present invention will be described with reference to the drawings.
1 and 2 are cross-sectional views showing one disk cross-sectional shape of a disk substrate in an embodiment of the present invention.

Referring to FIG. 1, the disk substrate 10 of the present invention.
The disc 1 for superposition for manufacturing is formed by injection molding, and the bit 11 as recording information is formed on the signal surface side 1a thereof, and at the same time, the outer peripheral edge and the inner peripheral edge of the signal surface side 1a are annular. A step 2 is provided. The dimension of the step 2 at the outer peripheral edge is the thickness dimension L = 0.
6 mm, the depth dimension A and the radial dimension B are both about 0.3 mm, and the step 2 at the inner peripheral edge has a depth dimension C of 0.2 mm and a radial dimension D of 0.5 mm. Has become.

FIG. 2 shows another embodiment in which a circumferential groove 3 is formed instead of the step portion 2 shown in FIG. 1, and the depth dimension E of the circumferential groove at the outer peripheral edge is about 0.2 mm. The radial dimension F is about 0.3 mm, the depth G of the circumferential groove on the inner peripheral edge is about 0.2 mm, and the radial dimension H is about 0.2 mm.

Here, the circumferential groove 3 at the inner peripheral edge may be the step portion 2 as in FIG. The edge 4 on the end side of the inner and outer edges
The thickness M is about 0.1 to 0.2 mm, and the height dimension may be lower than the depth dimension E instead of being flush with the signal surface. The reason is that the edge 4 on the end side has a function of blocking the adhesive that has flowed into the groove or does not expose the adhesive surface to the end side as much as possible.

The disc 1 having the same shape is formed by injection molding, and the disc substrate 10 is formed by adhering the discs with the signal surfaces facing each other and adhering them by the manufacturing method described below.

In the present invention, the disc 1 has bits as recording information formed on the signal surface side.
Of course, in the case where the image information is satisfied only on one side of the disc substrate 10 rather than on both sides, it goes without saying that the recorded information may be a disc having only one side.

A method of manufacturing the disk substrate 10 of the present invention will be described below with reference to FIG.

First, a bit 11 as recording information is formed on one surface side of the disk 1, and a disk in which a step portion 2 or a circumferential groove 3 is formed on the outer peripheral edge and the inner peripheral edge of the signal surface side is manufactured by injection molding. To do. Two discs having this step portion or the like, or when the video information is on one side of the disc substrate, one of the two discs is a dummy disc.

In this dummy disk, no bits are formed on the signal surface side, and only the step portion 2 or the circumferential groove 3 is formed on the outer peripheral edge and the inner peripheral edge of the disk surface.

FIG. 3a shows only one of the two disks having the step portion and the like.

Then, as shown in FIG. 3B, in this disc 1, a reflection film 5 of aluminum or the like is formed on the surface of the disc having recorded information. The reflective film 5 made of aluminum or the like in this manufacturing process is formed by sputtering.

When using a dummy disk as one of the disks, it is not necessary to form this reflective film.

Next, as shown in FIG. 3c, a protective layer 6 is formed on the reflective film 5 of the disk having the reflective film 5 formed thereon. Then, as shown in FIG. 3D, a hot melt adhesive 7 or an ultraviolet curable adhesive 8 is applied onto the protective layer 6. On the other hand, in the case of using a dummy disk, only the adhesive is directly applied to the disk surface having a step or the like without forming a reflection film or a protective layer.

In the case where the ultraviolet curing adhesive 8 is used in the above adhesive applying step, this applying method is usually
It is based on the spin coating method. In this spin coating method, the signal surface of the disc 1 is directed upward, and the disc 1 is placed horizontally on a turntable. The adhesive 8 is dropped onto the center of the rotating disc 1 from above and the adhesive is removed by centrifugal force. Application is performed by spreading on the signal surface.

However, this spin coating method is possible when the diameter of the disk is 120 mm like a DVD, but it is difficult to apply it when the diameter is large like an LD, and an adhesive is applied by a roller. It is designed to be applied by a roller coating method. Further, since the hot melt adhesive 7 has a high viscosity, the spin coating method cannot be used, and when the adhesive is used, the application to the disc is usually performed by the roller coating method in principle. There is.

Furthermore, as shown in FIG. 3e, when the ultraviolet curing adhesive 8 is used as the adhesive, this adhesive is made of the same composition material as the protective layer, and the protective layer is formed by spin coating or the like. Since it can be applied, the adhesive 8 can also be used as the protective layer 6. Therefore, it is possible to omit the method of forming the protective layer in the formation of the reflective film and the protective layer as the procedure of the step of forming the disc substrate 10.

Thus, before laminating and adhering two discs to each other, each disc is formed with a reflection film 5 of aluminum or the like, and an ultraviolet curing adhesive 8 is applied thereon (FIG. 3e). When a dummy disk is used, the adhesive is directly applied to the disk surface of this disk only.
Furthermore, when the hot-melt adhesive 7 is used as the adhesive, each disk has a protective layer 6 formed on the reflective film 5 as shown in FIG. The agent 7 is applied.

In the next bonding step, when the disk shown in FIG. 3e is used as an example, as shown in FIG. 4, the disk 1 coated with the ultraviolet adhesive 8 and the other disk 1 similarly formed are used. Are superposed with the disk surfaces having stepped portions and the like facing each other.

In this bonding step, two disks are bonded together by using a low pressure press or the like. In the manufacture of the disk substrate 10 of the present invention, as shown in FIG. Of the adhesive 8 from the outer and inner peripheral edges of the disk 1 by flowing into the stepped portion 2 or the circumferential groove 3 as a pool portion of the disk 1.
The bonding is completed without protruding.

Further, the bonding of the disks is carried out by the same drying or heat treatment as in the conventional case in order to dry and solidify the adhesive, and for example, in the case of DVD,
A desired disk substrate is formed simply by a method of low pressure pressing, and in the case of LD, a method of hot pressing or the like.

The disc substrate 10 of the present invention thus completed has, for example, a sectional shape as shown in FIG. 5, that is, a reflective film 5 is formed on each disc so as to face the signal surface of the disc 1. An adhesive 8 is interposed between the reflective films 5 and 5 and the disk 1 is laminated.

As is apparent from the above description, this layered structure has the layer formed between the disks 1 and 1 in the disk substrate 10 of the present invention, as shown in FIG. -In addition to the three-layer structure of the reflective film, the reflective film-protective layer-adhesive-protective layer-reflective film has a five-layer structure, and when a dummy disk is used, the reflective film-adhesive A two-layer structure and a three-layer structure including a reflective film-protective layer-adhesive are possible.

In the above-described shape of the step portion 2 or the circumferential groove 3 of the disk of the present invention, the step portion at the outer peripheral edge and the step portion at the inner peripheral edge are different from each other. This is because the amount is larger on the outer circumference than on the inner circumference. In the actual measurement results, the outer circumference is at least 0.2 mm x 0.2 m.
A space of m or more is sufficient, and even a slight step on the inner circumference side has achieved a considerable effect.

1 and 2, the step portion 2 or the circumferential groove 3 has a square cross section, but it may have a semicircular shape, and in any case, an adhesive agent is used when the disks are stuck together. Any shape may be used so long as it does not protrude from the outside of the disc.

[0036]

According to the present invention, by carrying out the above-mentioned manufacturing steps in sequence, the excess adhesive flows into the stepped portion or the circumferential groove to be solidified, and the two discs are superposed on each other without protruding from the discs. It can be pasted.

As a result, the trimming process of the adhesive can be omitted, and the DV of the type in which two discs are bonded together
A disc such as D can be easily manufactured.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a first embodiment showing a cross-sectional shape of a disc in manufacturing a disc substrate of the present invention.

FIG. 2 is a cross-sectional view of a second embodiment showing the cross-sectional shape of the disk in the manufacture of the disk substrate according to the present invention similar to FIG.

FIG. 3 is a schematic view showing a pattern of a layer structure formed on one disk of the disk substrate of the present invention.

FIG. 4 is a schematic view of an embodiment showing a state before the disc substrates of the present invention are superposed on each other.

FIG. 5 is a schematic view of an embodiment showing a state after the disc substrates of the present invention are superposed on each other.

[Explanation of symbols]

 1 Disc 2 Step 3 Circumferential Groove 4 Edge 5 Reflective Film 6 Protective Layer 7 Adhesive 10 Disc Substrate 11 Bit

Claims (3)

[Claims] 1. An annular step portion or a circumferential groove is formed on the outer peripheral edge and the inner peripheral edge of one surface of a disc, and recording information is transferred to the disc surface side having the step portion or the like on at least one disc. Two discs thus prepared are prepared, a reflective film such as aluminum is formed on the disc surface having the recorded information, and then an adhesive is applied to the surface side of each disc to be faced, A method of manufacturing a disc substrate, comprising: laminating two discs by causing the adhesive surfaces to face each other and superimposing them on each other. 2. A step of forming a protective layer between the step of forming a reflective film of aluminum or the like and the step of applying an adhesive on the disk surface having recorded information. The method for manufacturing a disk substrate according to claim 1. 3. A disc substrate in which recording information is transferred to at least one of two discs, at least a reflecting film is formed on a disc surface having the recording information, and discs facing each other are superposed and bonded with an adhesive. A disk substrate, wherein each disk has an annular stepped portion or a circumferential groove, which serves as a reservoir for the adhesive that protrudes at the time of bonding, is formed on the outer and inner peripheral edges of the disk surfaces facing each other.