Adhesive bonding and miscellaneous chemical manufacture – Surface bonding means and/or assembly means therefor – With means applying wave energy or electrical energy...
Reexamination Certificate
2000-11-20
2003-03-25
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Surface bonding means and/or assembly means therefor
With means applying wave energy or electrical energy...
C156S379800, C156S556000, C156S578000
Reexamination Certificate
active
06537423
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an optical disc manufacturing apparatus for manufacturing optical discs such as digital video/versatile discs (hereinafter referred to as DVD) adopting particularly a bonding method.
BACKGROUND ART'
When two plate shaped substances are stuck together using UV curable composition as adhesive, UV curable radical polymerization composition has heretofore been applied to surfaces to be bonded uniformly by a spin coating method, a screen printing method and the like, which have been existing technologies, and the surfaces to be bonded have been superposed on another, so as to be opposite, followed lower by curing the UV curable composition by irradiating ultraviolet rays continuously tinuously emitting light thereonto.
A high pressure mercury lamp, a metal halide lamp, a mercury-xenon lamp and the like have heretofore been used as an ultraviolet irradiation source. In such methods, there has been a problem that heat is apt to be caused owing to continuous light emission of the lamps and the heat has adverse effects on deformation of the plate shaped substances and mechanical properties thereof.
Furthermore, in the lamps of such lampes which emit light continuously, since it takes usually a time of more than several minutes until a light emission is stabilized lized after turning on the lamp, turning the lamp off/on is not easy. Accordingly, when the manufacturing is carried out continuously, the lamp must be kept turned on. Assuming that a time (cycle time of a production) required for bonding performed formaed one time (one cycle) be five seconds, and a time required for an ultraviolet irradiation radiation of five seconds be two seconds, the remaining three seconds are consumed uselessly wasting energy.
Furthermore, in the case where the two plate shaped substances are stuck together using the UV curable composition as the adhesive, when at least one of the plate shaped substances offers permeability to ultraviolet light, a severe problem does not occur. However, when the plate shaped substance attenuates an ultraviolet intensity, problems occur.
Specifically, the foregoing DVD and the like have a problem that because of the existence of an Al thin layer or the like in discs, the ultraviolet intensity is significantly attenuated by the thin layer and the layer until ultraviolet rays reach a bonding layer using the foregoing UV curable radical polymerization composition as the adhesive, so that curing-bonding with a high efficiency cannot be performed.
In addition, when it is intended to expedite the cure, lamp equipment having a large capacity is necessary, leading to an inevitable increase in the cost of products. Moreover, use of the lamp having a large capacity causes also a problem producing much conductive heat and radiation heat from the lamp, and a disc tends to be deformed. formed. In order to prevent this, cooling equipment around the lamp is additionally necessary, and the whole of the apparatus has been obliged to be large in size and more intricate.
On the contrary, when it is intended to perform ultraviolet curing with small capacity of the lamp equipment, though the ultraviolet curing is possible, a radiation time of several tens of seconds or more is required, so that the ultraviolet curing has been obliged to be poor in practicability.
A bonding method of a disc for solving the foregoing problems has been proposed in Japanese Patent Application Laid-Open No. 9-193249. Specifically, the bonding method of the disc disclosed in Japanese Patent Application Laid-Open No. 9-193249 has a feature in that ultraviolet rays are not radiated continuously but the ultraviolet rays are radiated in pulses. The method to radiate the ultraviolet ray continuously is the epoch-making one that can restrain power consumption for the ultraviolet radiation and increase the number of plate shaped substances to be stuck per unit of time, and can prevent a warp of the disc from occurring after sticking, compared to the case where the ultraviolet ray is continuously radiated.
Incidentally, there is also the following problem in the method by the flashing ultraviolet radiation. Specifically, when objects to be bonded is a DVD, for reasons of a structure of the DVD, an ultraviolet ray passes through an Al film which offers poor permeability to ultraviolet ray and reaches UV curable composition to cure this compound. Accordingly, when the Al film is thick by a product specification, a curing efficiency is deteriorated. Moreover, among the DVDs, for a DVD-RAM in which a film, for example, a ZnS—SiO
2
film exists, through which ultraviolet rays cannot pass substantially, such a method cannot be adopted, in which the ultraviolet ray is radiated onto UV curable composition existing on sticking planes of two discs to cure the UV curable composition and bond the sticking planes to each other.
An effective bonding method against these problems has been disclosed in Japanese Patent Laid-Open No. 9-69239. The method stated in Japanese Patent Laid-Open No. 9-69239 has a feature in that UV curable cationic composition offering delayed action is used compared to the conventional method in which the UV curable radical polymerization composition has heretofore been used as the adhesive. To be more specific, the UV curable cationic composition is coated on the entire surface of one disc to be stuck, and ultraviolet is radiated onto the UV curable cationic composition after coating thereof Thereafter, the one disc is superposed on the other disc that is a sticking object, and then the UV curable cationic composition is hardened by compressing them to each other.
The method using the UV curable cationic composition stated in Japanese Patent Laid-Open No. 9-69239 is effective one in which bonding is possible when the Al film is thick or even in the DVD-RAM in which the ZnS—SiO
2
film and the like allowing no ultraviolet to pass therethrough substantially stantially exist.
However, also in the method stated in Japanese Patent Laid-Open No. 9-69239, points to be further improved were found out. In other words, in the method in which the ultraviolet is radiated after the UV curable cationic composition position is coated on the disc substrate, though the ultraviolet radiation is required quired only for the UV curable cationic composition essentially, the ultraviolet is radiated also onto the disc substrate formed of polycarbonate and the like inevitably. Such unnecessary ultraviolet radiation onto the disc substrate is apt to cause thermal deformation in the disc substrate such as the DVD having a thickness of 0.6 mm due to heat from a lamp that is an ultraviolet light source.
Moreover, in the curing of the UV curable cationic composition, polymerization is disturbed by humidity of the air. Accordingly, the UV curable cationic composition protruding from an outer periphery of the disc after the superposition is sticky owing to delay of the curing. In addition, some measures must be taken to prevent deformation of the UV curable cationic composition and slippage of the two disc substrates from each other. In the DVD, though it is required for a deflection angle of the disc to be equal to a predetermined value or less according the standard, it is not clear with what measure the deflection angle can be fit in a predetermined range.
Accordingly, the subject of the present invention is to provide an optical disc manufacturing apparatus capable of manufacturing an optical disc having less air bubble trapping and suppressed unevenness in curing even when the UV curable cationic composition is used, and preventing a deformation of the disc due to conductive heat and radiation heat from a lamp that have been considered to be a problem in the conventional methods.
DISCLOSURE OF THE INVENTION
The inventor of this application made investigations to solve the foregoing subjects, and obtained the following knowledge. Specifically, since an ultraviolet ray is radiated onto a disc substrate inevitably in the conventional methods in which ultraviolet radiation is performed
Ebisawa Shoei
Ito Daisuke
Oshima Kiyoshi
Tsunematsu Norio
Armstrong Westerman & Hattori, LLP
Ball Michael W.
Dainippon Ink and Chemicals Inc.
Haran John T.
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