JPH04139630A - Production of optical disk for double-side recording - Google Patents

Abstract

PURPOSE:To prevent the generation of the focusing and tracking defect in the peripheral part of a recording film by executing the radiation with UV rays via a mask larger than the recording film in a stage for tentatively fixing a 1st disk and a 2nd disk by radiating these disks with the UV rays during or after pressure contact. CONSTITUTION:This production process consists of the 1st stage for applying an adhesive 4 which can be set by either of UV rays or heat on the 1st disk; the 2nd stage for bringing the 2nd disk into pressurized contact with the surface of the adhesive 4 by disposing the recording film to face downward; the 3rd stage for tentatively fixing these disks by radiating the disks with the UV rays during or after the pressure contact, and the 4th stage for normally adhering the disks by heating to cure the uncured part of the adhesive 4. The radiation with UV rays in the above-mentioned 3rd stage is executed via the mask 5 larger than the recording film. Consequently, the adhesive 4 is hit by the UV rays only through transparent parts 5b and is thereby cured. The optical disk for double-side recording which does not generate the focusing and tracking defects in the peripheral part of the recording film is thus produced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a double-sided recording optical disc.

[Conventional technology]

Conventionally, recordable optical discs have track grooves for tracking on a circular transparent substrate such as a glass plate (
(excluding the center or periphery) directly or using a groove material, then after forming an opaque recording film on the track groove, a protective glass substrate is bonded using an ultraviolet curing adhesive. It was manufactured in this way.

Opaque recording films include: - Low melting point metal thin films such as Te, Se, Bi (write-once type recording) - Tellurium lower oxide thin films (phase change type recording) -TbFe, TbFeCo, DyFeCo, Tb
DyFeCo, GdFe.

GdCo, GdFeCo, GdTbFe, GdT
There are also amorphous perpendicular magnetization films (magneto-optical recording) such as bFeCo.

Furthermore, in order to increase the recording capacity, a double-sided recording optical disc is manufactured by bonding the two single-sided discs described above using an adhesive.

Figure 2 is a plan view of this disk, and Figure 3 is x-x
' It is a sectional view taken in the direction of arrows.

A conventional method for manufacturing a double-sided recording optical disc will be described below. First, a track groove material layer (2) on a transparent substrate (1),
Two single-sided discs A with an opaque recording film (3) formed on them
, B are prepared. In this case, the trunk region in which the track grooves are formed and the recording film have the same ring shape, and this ring zone has an outer diameter smaller than the outer diameter of the substrate. In other words, the recording film is not formed on the outer peripheral edge of the substrate. The reason for this is to prevent the recording film from being exposed to the end surface of the disk and being corroded.

Here, the two single-sided disks are named the first disk and the second disk. From a structural point of view, a double-sided recording optical disk can be obtained by bonding the first disk A and the second disk B using an adhesive, but since the recording film does not pass ultraviolet rays, UV-curable adhesives cannot bond the recording film to the recording film. Unable to cure areas that are shaded from light.

Therefore, a thermosetting adhesive was used instead of an ultraviolet curable adhesive, but it took time to cure and there was a risk of misalignment during that time, so after the first and second disks were pasted together, a temporary adhesive was used. A stop is necessary. Subsequently, a method was developed that used adhesives that could be cured by both ultraviolet light and heat (hereinafter referred to as double-type adhesives) for bonding disks together.

(Refer to Japanese Patent Application Laid-Open No. 2-214041.) The method for manufacturing a double-sided recording optical disc by this method consists of the following four steps.

First step: Applying double-sided adhesive on the first disk.

Second step: Pressing the second disk onto the adhesive with the recording film facing down.

Third step: Temporary fixing step by irradiating ultraviolet rays during or after crimping. (See FIG. 4) Fourth step: A step of main bonding by heating and curing the uncured portion of the adhesive.

During the third step of temporary fixing, the opaque recording film does not allow ultraviolet rays to pass through. Therefore, the recording film serves as a mask, and the l/rack region, which is annular and has the same shape as the recording film and has track grooves formed therein, is shielded from light.

The adhesive layer corresponding to this portion is uncured and is heated and cured in the fourth step.

[Invention or problem to be solved]

However, optical discs manufactured in this manner have a problem in that focusing and tracking problems often occur at the periphery (near the outer diameter or inner diameter) of the recording film.

[Means to solve the problem]

In order to solve the above problem, we conducted intensive research and found that there was optical distortion in the adhesive layer corresponding to the peripheral area of the recording film, and in severe cases, the track grooves were deformed or raised, resulting in these defects. It turns out that this is the cause of the above problem. As a result of further research, it was found that when the recording film was used as a mask to irradiate ultraviolet rays during the temporary fixing process, a portion of the ultraviolet rays diffracted and penetrated into the adhesive area under the recording film, causing the adhesive to harden. Furthermore, when the adhesive is subsequently heat-cured in the main bonding process, the degree of curing shrinkage of the adhesive differs between the UV-cured area and the heat-cured area, causing a discontinuous change in the degree of shrinkage, which causes mechanical damage to the adhesive layer. It was found that this was caused by distortion caused by the

Therefore, the inventor has developed this strain (discontinuous change portion of shrinkage degree).
The present invention was conceived based on the idea that the above-mentioned problems could be solved by moving the film away from the recording film.

Therefore, the present invention includes a first step of applying an adhesive that can be cured by both ultraviolet rays and heat on the first disk, and a second step of press-bonding the second disk onto the adhesive with the recording film facing downward. , a third step of temporary fixing by irradiating ultraviolet rays during or after crimping, and a fourth step of main bonding by heating to harden the uncured portion of the adhesive,
There is provided a method for manufacturing a double-sided recording optical disc, characterized in that the irradiation of ultraviolet rays in the third step is performed through a mask larger than the recording film.

According to claim 2, the mask has a larger outer diameter than the substrate, and is a ring-shaped transparent mask having an inner diameter larger than the outer diameter of the recording film and smaller than the outer diameter of the substrate. Provided is a method for manufacturing a double-sided recording optical disc characterized by having a portion J.

[Effect]

In the present invention, since a mask larger than the recording film is used without using the recording film as a mask, the boundary between the ultraviolet curing region and the thermosetting region, where the degree of shrinkage changes discontinuously, is kept away from the vicinity of the recording film. This can be done and therefore no problems will occur.

Note that either (1) the outer diameter of the mask may be larger than that of the recording film, or (2) the inner diameter of the mask may be smaller than that of the recording film, or it is preferable that both (2) and (4) be satisfied.

Furthermore, some of the ultraviolet rays may strike an external object and be reflected, obliquely penetrating the adhesive near the outer periphery of the recording film and causing undesirable hardening. To prevent this, it is best to add a light shielding part (5c) on the outside, or, conversely, a larger mask, such as the one shown in Figures 1 (4) and (5).
It is preferable to use a mask having an outer diameter larger than the outer diameter of the substrate and having a "ring-shaped transparent portion having an inner diameter larger than the outer diameter of the recording film and an outer diameter smaller than the outer diameter of the substrate." Transparent part (5
The width of b) is preferably 1 to 2 mm.

〔Example〕

(1) Description of disk A glass substrate (1) with a diameter of 300 mm and a thickness of 2 mm was prepared. However, there is a center hole with a diameter of 60 mm in the center of this board. A center hub is attached to this hole in the final process, but this process is a post-process outside of the manufacturing process of the present invention.

Next, a groove material layer (2) was formed on the substrate (1) by the 2P method. There are many track grooves in a spiral or concentric pattern, and the outermost groove is 4.5 mm from the outer edge of the substrate (1).
The innermost groove is located at a distance of 42 mm from the inner edge of the substrate (1).
mm inside. In other words, the grooves are not formed near the outer and inner peripheral edges of the substrate. Therefore, the annular region where the track grooves are formed is called the track region, and the inner diameter of the track region is larger than the substrate inner diameter of 60 mm.
The outer diameter is smaller than the substrate outer diameter of 300 mm. This will be recorded in the track area later II! ! (3) Although it is formed,
The recording film is easily corroded when exposed to air, so we do not want to expose it to the edge of the disk, and the recording film has poor adhesion with the adhesive (4) compared to the groove material layer (resin), so the surface of the groove material layer should not be exposed. This is due to wanting to expose a part of the image.

Next, an inorganic protective film such as Sl+N is applied on the track area.
4 or without forming an opaque recording layer (3). A specific example of the recording layer (3) is a magneto-optical recording film (rare earth-transition metal alloy-based magnetic thin film) such as TbDyFeCo.

After this, the recording film (3) may be coated with an inorganic protective film and/or
Or cover with an organic protective film.

In this way, a single-sided disc is completed. Two single-sided discs are prepared, and one is named the first disc A and the other is named the second disc B.

(2) Description of Mask A plan view of the mask is shown in FIG. 1 (4). The mask is made of ring-shaped plastic film (inner diameter 60mm, outer diameter 30mm).
It is obtained by dyeing the parts corresponding to the backlit parts (5a) and (5c) of 1 mm thick and 1 mm thick with red dye. The backlight parts (5a) and (5c) do not transmit ultraviolet rays. The essential mask function is performed by the light shielding part (5a). The inner diameter of the annular light shielding part (5a) is 63 to 66 mm, and the outer diameter is 3 mm.
00 to 301 mm.

In other words, the inner diameter of the light shielding part (5a) is 11 to 9 mm smaller than the inside of the recording film (3), and the outer diameter of the light shielding part (5a) is 3 to 6 mm larger than the outside of the recording film.
The radial width of a) is larger than that of the recording film. However, according to the invention, only one or both of the inner diameter and outer diameter may be equal.

In the mask of this embodiment, a larger ring-shaped light-shielding part (5C) is specially provided outside the light-shielding part (5a) with a ring-shaped transparent part (5b) in between.

The transparent portion (5b) is provided to allow ultraviolet rays to pass through, and the light shielding portion (5C) is provided to avoid oblique incidence of ultraviolet rays. Transparent part (5b)
The width in the radial direction of the light shielding part (5C) is 1 to 3 mm, as appropriate, and the width in the radial direction of the light shielding part (5C) is 5 to 10 mm, as appropriate.

This mask has an inner diameter of 60 mm, and the inner diameter of the light shielding part (5a) is 63 to 66 mm, so the inner radial width is 3 to 6 mm.
It has a ring-shaped second transparent part (5d) of mm.

The function of this transparent part (5d) will be explained later.

In addition, instead of such a mask (see Figure 1 (5)),
As shown in Figure 1 (6), a transparent support film (5e
) A mask may be used in which light-shielding portions (5a) and (5C) are formed by adhering a light-shielding film to a predetermined position on the mask.

(3) Explanation of the first step Outer diameter 59.5 mm and height 10 to 30 m as shown in Figure 1 (7)
m cylindrical center tool (6) or protruding pedestal (7)
Prepare.

The center hole in the first disk is fitted with the center tool (6). This is shown in FIG. 1 (7).

A dual-use adhesive (4) is then applied to the track area to the disc. This state is shown in FIG. 1 (1).

(4) Description of the second step Fit the center hole of the second disk B into the center tool (6) with the recording film facing down, and press the disk B against the adhesive. This is Figure 1 (2).

(5) Description of the third step Once the adhesive has spread uniformly, place the mask (5) on the second disk B by fitting the center hole of the mask (5) into the center tool (6). Next, for holding, the board (1)
The same glass plate (not shown) is placed on the mask (5), and then a pot-shaped center cover (not shown) is placed over the center tool (6). The outer diameter of the center cover is larger than the inner diameter of the light-shielding part (5a) of the mask, so that when the center cover is covered, the adhesive (4) near the center tool (6) cannot be seen from above. In this state, UV rays are irradiated from above. This situation is shown in FIG. 1 (3).

However, center tool (6), center cover, pedestal (7)
) and the holding glass plate are not shown.

As a result, the adhesive (4) is exposed to ultraviolet light only through the transparent portion (5b) and is cured. This allows disk ASB
is temporarily fixed.

Furthermore, if ultraviolet rays are irradiated without the center cover, the adhesive (5) near the inner diameter will also be hit by the ultraviolet rays through the second transparent part (5d) and will harden, causing the bonding between the center tool (6) and the disc to become difficult. After temporary fixing, the problem arises that it becomes difficult to remove the disk from the center tool.

Therefore, the temporarily fixed disks A and B are removed from the pedestal (7) along with the mask (5) and placed on another flat pedestal.
Apply ultraviolet light again from above. As a result, the adhesive (5) near the inner diameter is exposed to ultraviolet rays through the second transparent part (5d), and the adhesive near the inner and outer edges is cured. There is no longer any danger that the uncured adhesive will become less viscous and flow out during subsequent heating. In addition, the temporary fixing became stronger.

(6) Explanation of the 4th step Discs A and B temporarily fixed in the previous step are
The uncured adhesive (4) is cured by heating at .degree. This is real gluing.

In this way, the double-sided recording optical disc of this embodiment is manufactured.

Comparative Example: A disk was manufactured in the same manner as in the example except that no mask was used. When I recorded and played back this disc, a large track error occurred at the outermost track.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to manufacture a double-sided recording optical disc that does not cause focusing or tracking defects in the peripheral area (near the outer diameter or inner diameter) of the recording film.

[Brief explanation of the drawing]

FIGS. 1(1) to 1(3) are process diagrams of the method for manufacturing a double-sided recording optical disc of the present invention. (1) is the first step, where dual-use adhesive is applied, (2)
In the second step, the figure (3) shows how two disks are pasted together.
) is a diagram in which ultraviolet rays are irradiated in the third step. FIG. 1(4) is a plan view of the mask in the present invention. FIG. 1(5) is a sectional view taken along YY' arrow in FIG. 1(4). FIG. 1(6) is a sectional view. FIG. 1 (7) is a front view of the first step. FIG. 2 is a plan view of a conventional double-sided recording optical disc. FIG. 3 is a sectional view taken along the line xx' in FIG. 2. Figure 4 shows the conventional manufacturing method for a double-sided recording optical disc.
It is a sectional view in a 3rd process. [Explanation of symbols of main parts] l...Transparent substrate 2...Track groove material layer 3...Recording film 4...Adhesive 5... ... Mask 6 ... Center tool 7 ... Pedestal

Claims (1)

[Claims] 1. Two single-sided disks each consisting of a transparent substrate and "an annular opaque recording film having an outer diameter smaller than the outer diameter of the substrate" formed on the transparent substrate are used as a first disk and a second disk. A first step of applying an adhesive that can be cured by either ultraviolet light or heat onto the first disk; a second step of pressing the second disk onto the adhesive with the recording film facing down; The third step is temporary fixing by irradiating ultraviolet rays during or after crimping.
and a fourth step of performing main adhesion by heating to harden the uncured portion of the adhesive. In the method for manufacturing a double-sided recording optical disc, the ultraviolet ray irradiation in the third step is applied to the recording film. A manufacturing method characterized in that it is carried out through a larger mask. 2. The mask has a larger outer diameter than the substrate and has a "ring-shaped transparent part having an inner diameter larger than the outer diameter of the recording film and an outer diameter smaller than the outer diameter of the substrate." A method for manufacturing a double-sided recording optical disc.