Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1998-11-18
2001-02-06
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S160000, C156S275700, C156S285000, C156S295000
Reexamination Certificate
active
06183577
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a manufacturing method and a manufacturing apparatus in which two optical information boards are bonded together.
2.Description of the Related Art
In order to achieve high density of an optical disk, it is necessary to shorten the wavelength of a regenerative laser and to increase the numerical aperture (NA) of an objective lens. For the high-NA objective lens, however, the allowable disk tilt is very small. However, by decreasing the thickness of a board, the allowable range for the disk tilt is widened, so that the high density of a practical optical disk using a high-NA objective lens can be achieved.
For the optical disk using a thin board, two boards are bonded because one board hangs down by gravity. The bonding of two boards not only increases the mechanical strength but also doubles the capacity because both surfaces are used. A conventional method for manufacturing a disk will be explained with reference to
FIG. 4
(Japanese Patent Application Laid-Open No. 8-161771). A board
6
provided with a first information signal surface on its one surface is manufactured by the injection molding method or the like method by using a transparent resin whose principal ingredient is polycarbonate. A reflective film is formed on the information signal surface by the sputtering method or the vacuum deposition method. Also, a board
9
provided with a second information signal surface on its one surface is manufactured by the injection molding method or the like method, and a reflective film is formed on the information signal surface by the sputtering method or the vacuum deposition method. For these reflective films, a metal whose principal ingredient is aluminum is used. While the board
1
is rotated at a low speed, a radiation-curing resin
1
is applied in a doughnut form (FIG.
4
(A)). The second board
2
is lapped on the board
1
in such a manner that the reflective film on the information signal surface faces the radiation-curing resin
1
(FIG.
4
(B)). By rotating the board
6
and the board
9
integrally at a high speed, the radiation-curing resin is spread uniformly between the board
6
and the board
9
(FIG.
4
(C)). After the radiation-curing resin has been spread uniformly, radioacive rays (in
FIG. 4
, ultraviolet rays are used) are irradiated through the board
9
and the reflective film to cure the radiation-curing resin, whereby two boards are bonded together (FIG.
4
(D)).
However, when the radiation-curing resin is applied in a doughnut form while the board is rotated, the other board to be bonded is lapped on the board, and the radiation-curing resin is spread between the two boards by rotating the boards integrally at a high speed, the radiation-curing resin at the inner peripheral portion is moved toward the outer periphery in large quantities by the centrifugal force, so that a variation in thickness of the radiation-curing resin occurs within the board.
This problem is generally solved by contriving the conditions such as the revolutions per minute, rotation time, and viscosity, application amount and application position of radiation-curing resin. Nevertheless, in the method using a rotating force, a disk is produced which has a tendency such that the radiation-curing resin is thinner at the inner peripheral portion than at the middle portion. Although this does not present a very serious problem when the radiation-curing resin has only a bonding function for bonding the two boards, for a disk requiring a function of an intermediate layer for regulating the distance between the two boards, it is difficult to stably form a highly accurate intermediate layer in the whole region of the disk because the accuracy required for the intermediate layer is on the order of micron.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and accordingly an object thereof is to provide a method and an apparatus for manufacturing an optical information medium of bonded disk in which a variation in thickness of a radiation-curing resin caused by the centrifugal force is reduced, and the thickness accuracy of an intermediate layer is high.
To achieve the above object, the present invention provides a method for manufacturing an optical information medium comprising a step of bending at least one of a first board and a second board having a center hole, a step of applying a radiation-curing resin onto the bent board in a doughnut form while the bent board is rotated, and a step of lapping the other board on the bent board and rotating the paired boards integrally.
Also, the present invention provides an apparatus for manufacturing an optical information medium comprising conveying means for conveying a first board and a second board having a center hole, means for bending the first or second board, applying means for applying an ultraviolet-curing resin onto the bent board in a doughnut form while the bent board is rotated, lapping means for putting the remaining board on the bent board, high-speed rotating means for rotating the first and second boards integrally, and radiation irradiating means for irradiating a radiation to the radiation-curing resin by penetrating at least one of the first and second boards.
Thereupon, the present invention can provide a method and an apparatus for manufacturing a bonded disk having a small variation in thickness of the ultraviolet-curing resin and excellent appearance.
According to the present invention, by providing the accumulating place of ultraviolet-curing resin between the two boards, the movement of a large amount of ultraviolet-curing resin to the outer peripheral portion caused by the high-speed rotation can be prevented. Therefore, a uniform ultraviolet-curing resin layer having a small variation in thickness in the whole region of the board can be formed.
REFERENCES:
patent: 5800670 (1998-09-01), Kitano
patent: 8-161771 (1996-06-01), None
patent: 97/36737 (1997-10-01), None
Inoue Kiyoshi
Kozono Toshikazu
Nakanishi Manabu
Yanai Toshio
Ball Michael W.
Matsushita Electric - Industrial Co., Ltd.
Smith, Grambrell & Russell, LLP
Tolin Michael A
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