Spacer holder arrangement

Abstract: A spacer holder arrangement includes a support sheet (1) of a self-supporting nature, at least one side of the support sheet (1) having a low adhesive-bonding ability. A pair of concentric inner (2) and outer (3) spacer elements of an annular shape are disposed on the one side of the support sheet (1) to provide a preformed spacer (S), each of the inner (2) and outer (3) spacer elements having adhesive layers (4) formed respectively on opposite sides thereof. One of the adhesive layers (4) is interposed between each of the inner (2) and outer (3) spacer elements and the support sheet (1) to releasably bond them together. The inner spacer element (2) has a central hole therethrough which is coaxial with an aperture (5) formed through the support sheet (1) so that a guide rod (7) can be passed through the aperture (5) and the central hole.

Description: BACKGROUND OF THE INVENTION Field of the Invention This invention relates generally to a spacer for holding a pair of disc-shaped bases of an optical disc of the air-sandwich type in spaced relation to each other, and more particularly to a spacer holder arrangement removably holding such a spacer. Prior Art Generally, an optical disc of the air-sandwich type comprises a pair of disc-shaped bases or substrates and a pair of inner and outer ring-shaped spacer elements interposed between and adhesively bonded to the pair of bases to hold them in spaced relation to each other to form an annular space defined by the pair of bases and the inner and outer spacer elements. The bonding between the bases of the optical disc and the spacer elements has heretofore been made using an adhesive, for example, of the ultraviolet curing type or the thermosetting type. In this method, the adhesive is applied to the spacer elements immediately before assembling the optical disc, and therefore the spacer elements are liable to be displaced out of position relative to the disc bases. For this reason, it has been necessary to keep the assembled optical disc standstill under a constant pressure until the coated adhesive is cured or set. In this respect, this conventional method is not suited for mass production. To overcome the problem of keeping such standstill condition, it has been proposed to use inner and outer spacer elements each having preformed adhesive layers provided respectively on opposite sides thereof. A protective film is attached to the outer side of each adhesive layer. This method overcomes the difficulty encountered with the first-mentioned prior art in which the adhesive is used, but it has been found still not suited for mass production because each spacer element has to be carefully positioned relative to the bases of the optical disc when adhesively bonding them together after removal of the protective film. A prior art that is of interest is: OPTICAL ENGINEERING, vol. 22, no. 4, July/August 1983, pages 464-472, Belingham, Washington, USA; D. C. Kowalski et al.: "Multichannel digital optical disk memory system". This document discloses what is termed as being a structure for sealing and protecting a recording media and is described with reference to an exploded view of the several components. The exploded view shows a central vertically extending rod on which is fitted a first annular spacer element 6. Concentric with the first annular spacer element there is illustrated a much larger second annular spacer element lying in the same plane as the first annular element and concentric therewith. No means are disclosed for arranging or maintaining the second annular element in position relative to the first annular element. Slidably mounted on the post above the annular elements is an upper vacuum chuck supporting on its under face an optical disk that is to be secured to the upper faces of the two annular elements. Also slidably mounted on the post below the annular elements is a lower vacuum chuck supporting on its upper face an optical disk that is to be secured to the underfaces of the two annular elements. The two annular elements each have double-sided adhesive paper mounted on their upper and lower surfaces, the exposed surface of said adhesive paper being protected by a removable cover paper. Just before the two vacuum chucks are slid along the rod to move them towards the annular elements to clamp them between the optical disks carried by the upper and lower vacuum chucks, the protective paper is removed from the adhesive paper. Thus when the chucks have pressed their associated optical disks against the two annular elements said optical disks adhere to the annular elements. The vacuum to the vacuum chucks is then released and the vacuum chucks are slid off the rod. The rod can then be removed from the central annular member. SUMMARY OF THE INVENTION It is an object of the present invention to provide means for use in manufacturing an optical disk by which an optical disc can be easily assembled without the assembler having to correctly position the two annular spacer elements relatively to each other, thereby facilitating mass production of the optical discs. The invention is as defined in the accompanying claims. The means of the present invention that is used for manufacturing an optical disk of the type comprising a pair of concentric inner and outer spacer elements of an annular shape and in which said inner annular spacer element defines a central hole such that a guide rod can be passed therethrough, adhesive layers being formed respectively on opposite sides of each of said inner and outer spacer elements; comprises a support sheet of a self suporting nature having at least one aperture formed therethrough so that said aperture can be coaxially aligned with the central hole through the inner spacer element, and at least one side of the support sheet having a low adhesive-bonding ability so that one of said adhesive layers of each of said inner and outer spacer elements can releasably bond said spacer elements to said support sheet via said side of low adhesive-bonding ability of said sheet. The inner and outer annular spacer elements, each having the adhesive layers on the opposite sides thereof, are concentrically held in position on the support sheet to provide the preformed spacer. Further, since the support sheet has the aperture disposed coaxially with the inner spacer element, the spacer can be easily attached in position to each base of the optical disc through the guide rod. Thus, the spacer is supported on the support sheet in a preformed condition and can be attached to the bases of the optical disc without changing the relative position between the inner and outer spacer elements. Therefore, there is no need to position the inner and outer spacer elements relative to each other when assembling the optical disc. This greatly facilitates the mass production of the optical discs. BRIEF DESCRIPTION OF THE INVENTION Fig. 1 is a top plan view of a spacer holder arrangement provided in accordance with the present invention; Fig. 2 is a cross-sectional view taken along the line II-II of Fig. 1; Fig. 3 is a cross-sectional view of the spacer holder arrangement, showing a preformed spacer to be attached to a base of an optical disc; and Fig. 4 is a view similar to Fig. 2 but showing a modified spacer holder arrangement. DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The invention will now be described with reference to the drawings. A spacer holder arrangement shown in Figs. 1 to 3 comprises a support sheet or film 1 and a preformed spacer S removably mounted on the support sheet 1. The support sheet 1 is flexible and has a self-supporting nature, and at least one side or face of the support sheet 1 has a low adhesive-bonding ability. The preformed spacer S is releaseably attached to the one side of the support sheet 1. It is preferred that the support sheet 1 should have a thickness of not less than about 50 µm to retain the self-supporting properties although this value varies slightly depending on the material of which the support sheet 1 is made. For example, the support sheet 1 is made of a polyester film, a polypropylene film, a laminate composed of a substrate such as Kraft paper and polyolefin film laminated on one side of the substrate, or a resin treated material composed of a substrate of one of a polyester film, a polypropylene film of the above-mentioned laminate and a coating of a release agent, such as a polyvinyl N-octadecyl carbamate compound and a silicone compound, formed on one side of the substrate. The preformed spacer S comprises a pair of inner and outer annular or ring-shaped spacer elements 2 and 3 each having a pair of upper and lower adhesive layers 4a (4b) and 4′a (4′b) formed respectively on the opposite sides thereof. The inner and outer annular spacer elements 2 and 3 are releaseably bonded to the one side of the support sheet 1 through the respective lower adhesive layers 4′a and 4′b in such a manner that the two spacer elements 2 and 3 are disposed in concentric relation to each other. The adhesive layers 4a and 4′a (4b and 4′b) on the opposite sides of each of the inner and outer spacer elements 2 and 3 are annular and equal in width to their mating spacer element and are disposed coaxially therewith. The plane in which the upper adhesive layers 4a and 4b are disposed is parallel to the plane in which the lower adhesive layer 4′a and 4′b lie. Each of the annular spacer elements 2 and 3 is made of a rigid plastics material such as polycarbonate and methyl methacrylate. The adhesive layers 4a, 4b, 4′a and 4′b are made of an adhesive which is pressure sensitive either at room temperature (hereinafter referred to as "cold adhesive type") or upon heating (hereinafter referred to as "hot adhesive type"). The upper and lower adhesive layers 4a, 4b, 4′a and 4′b may all be made of the same or similar adhesive. Also, the lower adhesive layers 4′a and 4′b may be of the cold adhesive type while the upper adhesive layers 4a and 4b are of the hot adhesive type. In the latter case, it is not particularly necessary to protect the outer surface of the upper adhesive layers 4a and 4b during storage of the spacer holder arrangement. In the case where the upper adhesive layers 4a and 4b are of the cold adhesive type, a protective film is releaseably bonded to the outer surface of each of these upper adhesive layers. In this case, also, the other side of the support sheet 1 may be so arranged to have a low adhesive-bonding ability so that during storage, a plurality of the spacer holder arrangements can be stacked one upon another, with the other side of each support sheet 1 releaseably bonded to the upper adhesive layers 4a and 4b of the spacer holder arrangement disposed immediately therebelow. Each of the upper and lower adhesive layers 4a, 4b, 4′a and 4′b can be made entirely of an adhesive which is composed predominantly of a synthetic resin and/or rubber and is pressure sensitive at room temperature, or can comprise a thin substrate coated and impregnated at opposite sides thereof with such an adhesive. Also, each adhesive layer can be made entirely of an adhesive which is composed predominantly of a synthetic resin and/or rubber and is pressure sensitive upon heating, or can comprise a thin substrate coated and impregnated at opposite sides thereof with such a hot-type adhesive. The support sheet 1 has an aperture 5 of a circular cross-section formed therethrough, the aperture 5 having a diameter equal to the inner diameter of the inner annular spacer element 3 and being disposed coaxially therewith. For example, the spacer holder arrangement is produced by preparing a spacer structure composed of inner and outer spacer elements 2 and 3 and starting adhesive layers formed on the opposite sides of the inner and outer spacer elements, attaching this spacer structure to the support sheet 1, sealing the starting adhesive layers at those regions corresponding to the adhesive layers 4a, 4b, 4′a and 4′b to be formed, and removing unnecessary portions of the starting adhesive layers. At this time, the aperture 5 is formed through the support sheet 1. With this method, the inner and outer spacer elements 2 and 3 can be accurately positioned in concentric relation to each other on the support sheet 1. For assembling an optical disc using the spacer holder arrangement (Fig. 3), a guide rod 7 is passed through the aperture 5 in the support sheet 1 and the center hole of the inner spacer element 2. Then, one disc-shaped base 6 of the optical disc is brought into contact with the upper adhesive layers 4a and 4b, with the guide rod 7 inserted in the center hole of the base 6, and then is bonded to these adhesive layers by application of either pressure or pressure and heat. Then, the support sheet 1 is removed from the lower adhesive layers 4′a and 4′b, and the other disc-shaped disc of the optical disc is bonded to these adhesive layers 4′a and 4′b in a similar manner. As shown in Fig. 4, the support sheet 1 can be elongated so that a plurality of preformed spacers S can be carried by the support sheet 1 and spaced from one another along the length thereof. In this case, the elongated support sheet 1 can be formed into a roll or be folded in a zigzag or corrugated manner when the spacer holder arrangement is stored. In this case, a protective film may be wound or folded together with the elongated sheet 1. As described above, the inner and outer ring-shaped spacer elements 2 and 3, each having the upper and lower adhesive layers 4a, 4b, 4′a and 4′b on the opposite sides thereof, are concentrically held in position on the support sheet 1 to provide the preformed spacer S. Further, since the support sheet 1 has the aperture 5 having the diameter equal to the inner diameter of the inner spacer element 2 and disposed coaxially therewith, the spacer can be easily attached in position to each base of the optical disc through the guide rod 7. Thus, the spacer S is supported on the support sheet 1 in a preformed condition and can be attached to the bases of the optical disc without changing the relative position between the inner and outer spacer elements 2 and 3. Therefore, there is no need to position the inner and outer spacer elements 2 and 3 relative to each other when assembling the optical disc. This greatly facilitates the mass production of the optical discs.

Claims: Means for use in manufacturing an optical disk of the type comprising a pair of concentric inner (2) and outer (3) spacer elements of an annular shape to provide a preformed spacer (S), said inner spacer element (2) defining a central hole such that a guide rod (7) can be passed therethrough, adhesive layers (4) being formed respectively on opposite sides of each of said inner (2) and outer (3) spacer elements; the said means being characterised in that they comprise: a support sheet (1) being of a self supporting nature and having at least one aperture (5) formed therethrough so that said aperture (5) can be coaxially aligned with said central hole through the inner spacer element (2), and at least one side of the support sheet (1) having a low adhesive-bonding ability so that one of said adhesive layers (4) of each of said inner (2) and outer (3) spacer elements can releasably bond said spacer elements (2, 3) to said support sheet (1) via said side of low adhesive-bonding ability of said sheet. Means according to Claim 1, in which said adhesive layers (4) on the the opposite sides of each of said inner (2) and outer (3) spacer elements are annular and equal in width to their mating spacer element (2, 3) and are disposed coaxially herewith. Means according to claim 1, in which said aperture (5) in said support sheet (1) is of a circular cross-section, the inner diameter of said inner spacer element (2) defined by an edge of said central hole being equal to a diameter of said aperture (5). Means according to claim 1, in which said adhesive layers (4) are pressure sensitive at room temperature. Means according to claim 1, in which said adhesive layers (4) are pressure sensitive upon heating. Means according to claim 1, in which said one adhesive layer (4) interposed between each of said inner (2) and outer (3) spacer elements and said support sheet (1) is pressure sensitive at room temperature while the other adhesive layer (4) on the side of each of said inner (2) and outer (3) spacer elements facing away from said support sheet (1) is pressure sensitive upon heating. Means according to claim 1, in which said support sheet (1) is elongated and has a plurality of said apertures (5) spaced from one another along the length of said support sheet (1), there being provided a plurality of said preformed spacers (S) spaced from one another along the length of said support sheet (1).

Inventors: MISAWA YOZI, MITOH YASUO, SEKIGUCHI HIDEO, MISAWA, YOZI, MITOH, YASUO, SEKIGUCHI, HIDEO
Applicants: NITTO DENKO CORP, NITTO DENKO CORPORATION
Application year: 1989
Main classification: G11B7
IPC codes: G11B7