SPECIFICATION

Technical Field

The invention relates to a composite sheet material used to make packaging and other storage devices for compact discs.

Background of Invention

The compact disc (CD) provides a significant advance over previous recording media due to its capability of storing a large amount of digital computer data and/or audio program material in digitally encoded form per unit area of the disc. However, great care must be taken to protect the optically readable surface of the compact disc from factors which can adversely affect the CD playback performance, such as scratches, dust, and fingerprints. For these purposes, various types of compact disk storage devices have been developed. A widely used CD storage device is the so-called jewel box, which consists of two transparent panels of molded polycarbonate plastic hinged along a common side and holding a carrying tray for the CD on one opened side and printed graphics sheet material facing outwardly through the transparent panel on the other opened side. However, the jewel box has the disadvantages that it is difficult to open and remove the disc, is fragile and breaks easily, is expensive to manufacture, and represents an excessive amount of packaging.

Several alternatives to the jewel box have been proposed. A flexible sleeve for storing an individual compact disc, e.g., as disclosed in U.S. Patent 4,850,731 of Ross Youngs, is fabricated from a transparent vinyl front sheet that is folded over itself and joined on three sides to form a pocket with an overflap, and has an inner divider formed by a nonwoven fabric bonded to a backing sheet of vinyl. The CD is stored in the pocket with its optical surface in contact with the nonwoven fabric, while printed graphics material is inserted between the divider

and front sheet. However, a sequence of assembly steps using different stock materials is required to form the flexible sleeve, the graphics material must be separately printed and inserted in the pocket, and the sleeve itself may not have sufficient rigidity to prevent damage to the disc. Another form of CD packaging that has been proposed include various types of paperboard sleeves or wallets on which desired graphics material can be printed on their external surfaces. However, paperboard can abrade the disc after numerous insertions and has no ability to wipe or clean the disc or static control, and paper debris can contaminate the disc. Attempts to adhere a soft liner to the paperboard to avoid abrasion have the deficiency of possible chemical outgassing or bleed-through from adhesives which can attack of the polycarbonate material of the compact disc.

Summary of Invention

It is therefore a principal object of the invention to provide a single stock material that can be used to form various styles and designs of packaging for compact discs and allow for simplified and low cost manufacturing. It is a further object that such single stock material bring together a combination of desirable properties for packaging compact discs, including sufficient rigidity to protect the disc, an exterior surface suitable for printing high resolution graphics, non-abrasion of the disc despite repeated insertions, a disc cleaning ability, minimizing of debris that can contaminate the disc, and provision of a clean, debris- free, and adhesive-free package environment.

In accordance with the present invention, a composite stock material in sheet form for use in making various types of packaging for compact discs comprises an outer layer of paperboard material of sufficient thickness and rigidity for packaging compact discs, an inner layer of bonded nonwoven fibers, and an intermediary layer of

thermoplastic material thermally bonding the paperboard outer layer and the nonwoven inner layer together without adhesives, said thermoplastic material of the intermediary layer having a melting point lower than that of the fibers of the nonwoven inner layer.

Preferably, the paperboard is solid bleached sulfate (SBS) boardstock of from 12 pt. to 24 pt. , preferably 18 pt. , caliper, the nonwoven is 100% low denier, staple length polypropylene fibers thermally bonded together with about a 20% bond area, and the intermediary layer is a low density polyethylene (LDPE) film of a low weight of about 10 lbs. /ream. The LDPE film can be coated on the paperboard layer or on the nonwoven layer prior to thermally bonding the two layers together between a pair of heated nipping rolls. The composite sheet material is a single stock material that can be manufactured into envelopes, cartons, sleeves, wallets, or any other type of desired packaging for compact discs. The paperboard outer surface can be printed with graphics directly, and may have a clay filler coating for enhanced printing quality. The nonwoven layer provides a soft, adhesive-free, debris-free layer that largely eliminates abrasion, cleans the disc, and protects it with an anti-static environment.

Other objects, features, and advantages of the present invention will be explained in the following detailed description of the invention having reference to the appended drawings.

Brief Description of Drawings

Fig. 1 is a side sectional view of the single stock material in accordance with the invention for use in making various types of packaging for compact discs.

Fig. 2 is a side sectional view of a type of wallet for packaging compact discs made from the single stock material. Fig. 3 is a plan view of the wallet for packaging compact discs shown in Fig. 2.

Detailed Description of Invention

Referring to Fig. 1, a single stock material for use in making various types of packaging for compact discs is a composite 10 in sheet form of an outer layer 12 of paperboard material, an inner layer 14 of nonwoven fibers bonded together, and an intermediary layer 16 of thermoplastic material. The paperboard layer may be made of any paper-based boardstock of sufficient thickness and rigidity for packaging compact discs. For example, boardstock of from 12 pt. to 24 pt. , preferably 18 pt. , caliper, is found to be suitable. The nonwoven layer may be made of any suitable fibrous material bonded together without adhesives. For example, thermalbond, wetlaid, spunbond, and hydroentangled fibers may be used. The paperboard and nonwoven layers are fused together by the thermoplastic intermediary layer through application of heat and pressure through a pair of heated nipping rolls. The intermediary material must have a melting point lower than that of the fibers of the nonwoven layer. Various materials for the composite have been tested for suitability to be manufactured into packaging for compact discs, and the following composite has been found to be particularly suitable. The preferred paperboard material is 18 pt . solid bleached sulfate (SBS) boardstock, although other calipers from 12 pt. to 24 pt. could be used. The SBS boardstock is coated with a clay filler layer on its external side for enhancing printing thereon. The preferred nonwoven is 27 gsy, 100% thermally bonded polypropylene fibers of 3 denier by 1-7/8" staple length with a hydrophilic finish. The polypropylene fibers are bonded in a conventional quilted pattern with diamond- shaped bond points taking up about a 20% bond area. This provides a distinctive pillow-type look and depth of .050" found to provide a soft, debris-free, cleaning surface for the compact disc. Other nonwoven materials, such as 100% rayon chembond, 80%/20% polyester/cellulose wetlaid, 100% polypropylene spunbond, and 30%/70% rayon/polyester

hydroentangled, and other basis weights and nonwoven bond patterns may also be used, although those of a higher cost would be less acceptable. Nonwovens having a complete absence of binders are preferred, since the binders existing in chembond adhesives and wetlaids are likely to attack the polycarbonate surface of the discs.

The preferred intermediary layer is a low density polyethylene (LDPE) film of a low weight of about 10 lbs. /ream. The LDPE film can be coated on the paperboard layer prior to lamination and then thermally fused to the nonwoven via calendaring, or can be extruded onto the boardstock or nonwoven at the time the nonwoven layer is supplied. The preferred weight of LDPE is established so as to provide a fiber-free separation between the board and nonwoven and to ensure that there would be no bleed through of chemicals from the boardstock into the nonwoven which can attack the CD surface while also minimizing for economy.

The various preferred composites were tested for their cleaning ability and the results were found to be as follows:

Composite/Nonwoven Material % ipeability

SBS boardstock unfinished 97.3 (high abrasion)

SBS boardstock finished 88.2 (high abrasion) SBS + polypropylene thermalbond 99.5 SBS + rayon chembond 99.4

SBS + polyester/cellulose wetlaid 99.1

The results show that all composites with the nonwoven layer provided significantly better cleaning than the SBS-finished boardstock alone, which has been the packaging material of choice for paperboard packaging of CDs. The test CDs were subjected to 100 cycles of contact under an 8.46 psi load which simulates the finger pinch pressure of actual use. The tests showed that the paperboard-only material had a very high abrasion of the CDs compared to the nonwoven composite material. The 100%

polypropylene nonwoven showed significantly less abrasion as determined by visual inspection. The rayon and polyester fibers have a higher relative hardness than the polypropylene. The composite sheet material is a single stock material that can be manufactured by simple scoring, folding, and seaming steps into envelopes, cartons, sleeves, wallets, or any other type of desired packaging for compact discs. As shown in Figs. 2 and 3, a wallet type of package 20 for an individual CD 30 has the composite stock material 10 scored at hinge lines 22, bent at the pocket fold 24, and seamed at side flaps 26 to form the pocket half 28 and catch-fold half hinged in the center. The outer surface 16a of the paperboard can be printed with graphics directly. The nonwoven-lined pocket provides a soft, clean, adhesive-free, debris-free, abrasion-free environment for the discs. Many other types of CD packaging, such as sleeves, mailers, envelopes, storage containers, multi-disc holders, etc., can be manufactured readily and at a low per unit cost using the single composite stock material .

Various modifications and variations may be devised given the above-described embodiments of the invention. It is intended that all embodiments and modifications and variations thereof be included within the scope of the invention as it is defined in the following claims.