Label for optical disks and optical disk adhered with the label

Details Label for optical disks and optical disk adhered with the label Label for optical disks and optical disk adhered with the label

1998-10-09

2001-09-11

Ahmad, Nasser (Department: 1772)

Stock material or miscellaneous articles

Circular sheet or circular blank

Recording medium or carrier

C369S275100, C369S283000, C369S288000, C428S040100, C428S064400, C428S065200, C428S201000, C428S202000, C428S412000

Reexamination Certificate

active

06287661

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a label for optical disks and an optical disk adhered with the label.
2. Description of Related Art
In recent years, optical disks such as a compact disk (CD), a laser disk (LD) and a digital video disk (DVD) have prevailed. The optical disks are recorded with various informations such as computer informations, music, image and the like, and the recorded informations are reproduced by a ray irradiate.
The optical disks are structured with an aluminum vapor deposition film formed on a surface of a substrate such as a polycarbonate substrate and a hard coat layer formed on the aluminum vapor deposition film for protecting the aluminum vapor deposition film.
For displaying the recorded informations in the optical disk and et. al., printing has been applied directly on the hard coat layer.
Therefore, there is a problem that if the printing is unsuccessful on the hard coat layer, all of the optical disk must be rejected. Also, there is another problem that the kinds of applicable printings are restricted because of a shape, material characteristic and et. al. of the optical disk, and it is difficult to apply the display on the hard coat layer by high technical printings such as photoengraving process printing and phologram.
SUMMARY OF THE INVENTION
The present invention is provided to resolve the problems described above.
One object of the present invention is to provide a label for optical disks which is not rejected because of printing failure, can be applied on the surface of the optical disk with displays such as various printings and pholograms, and can provides an optical disk having beauty and fineness in an aesthetic outward appearance.
Extensive investigations undertaken by the present inventors directed to the objects described above have led to an idea of beforehand forming the display on the optical disk with a label having the display by printing, instead of forming the display by printing directly on the hard coat layer of the optical disk. And further detail investigations undertaken by the present inventors directed to the adaptation of the label material to the optical disk have led to the discovery that such objects can be achieved by using a base sheet having a coefficient of linear expansion of 1.0×10
−5
to 12.0×10
−5
and a thermal shrinkage ratio of 3 or below percent as the base sheet of the label.
Thus, the present invention is directed to a label for optical disks which comprises a base sheet having a coefficient of linear expansion of 1.0×10
−5
to 12.0×10
−5
and a thermal shrinkage ratio of 3 or below percent, a display formed on at least one surface of the base sheet, and an adhesive layer formed on the surface of the base sheet or the display. Also, the present invention is directed to an optical disk which is composed of a polycarbonate resin substrate and is adhered with the label for optical disks as described above.
DESCRIPTION OF PREFERRED EMBODIMENTS
The base sheet of the label for optical disks of the present invention has a coefficient of linear expansion of 1.0×10
−5
to 12. 0×10
−5
, preferably 3.0×10
−5
to 10.0×10
5
, more preferably 5.0×10
−5
to 8.0×10
−5
. When the coefficient of linear expansion is less than 1.0×10
−5
, the substrate of the optical disk composed of a polycarbonate resin or the like generates warpage after adhering the label for optical disks on the optical disk and the recorded data are reproduced insufficiently or not at all. When the coefficient of linear expansion is more than 12.0×10
−5
, the label generates distortion and wrinkle, and is damaged aesthetically after adhering the label for optical disks on the optical disk.
Further, the base sheet of the label for optical disks of the present invention has a thermal shrinkage ratio of 3 or below percent, preferably 2 or below, more preferably 1 or below. The thermal shrinkage ratio needs to be within the range described above in both of machine direction (hereinafter called “MD”) and transverse direction (hereinafter called “TD”). When the thermal shrinkage ratio is more than 3 percent, the substrate of the optical disk generates warpage after adhering the label for optical disks on the optical disk and the recorded data are reproduced insufficiently or not at all.
Examples of the base sheet satisfying the above-mentioned condition of the coefficient of linear expansion and the thermal shrinkage ratio are, for example, a polycarbonate resin film, a polyester resin film such as a polyethyleneterephthalate resin, a polybutyleneterephthalate resin and a polyethylenenaphthalate resin (PEN resin), a polyvinylchloride resin film, and a norbornene resin film, preferably a polycarbonate resin film.
The base sheet has preferably a glass transition temperature of not less than 60° C. When the glass transition temperature is less than 60° C., the base sheet are shrunk largely and the substrate of the optical disk easily generates warpage and the label easily generates distortion and wrinkle.
The base sheet is a single-layer structure or multi-layers structure of same or different films.
The base sheet can be oriented in uniaxially or biaxially, or is not oriented.
Further, the base sheet is transparent, translucent or opaque.
The thickness of the base sheet can be selected properly, and is generally in the range of 10 to 200 micrometers, preferably 20 to 150 micrometers.
The display is formed on at least one surface of the base sheet of the label for optical disks of the present invention. The display is formed by printing, phologram treatment or the like. The printing includes various printing technologies such as offset printing, flexographic printing, silk screen printing and gravure printing.
A pattern of the display includes various patterns such as a letter, a symbol, a figure, a picture, a photograph and a combination of two or more members.
Further, the display can be covered with a protect film, a coating agent layer or the like. When the display is covered with a protect film or a coating agent layer, the coefficient of linear expansion and the thermal shrinkage ratio of the covering layer such as the protect film and the coating agent layer are preferably in the range of that of the base sheet of the label for optical disks.
The adhesive layer is formed on at least one surface of the base sheet of the label for optical disks of the present invention. The adhesive layer can be composed of one or more various adhesives. Examples of the adhesives are a pressure sensitive adhesive and a heat sensitive adhesive. Preferable adhesive is the pressure sensitive adhesive.
Examples of the pressure sensitive adhesives are, for example, a natural rubber, a synthetic rubber, an acrylic resin, a polyvinylether resin, an urethane resin and a silicone resin pressure sensitive adhesives. Examples of the synthetic rubber are a styrene-butadiene rubber, a polyisobutylene rubber, an isobutylene-isoprene rubber, an isoprene rubber, a styrene-isoprene block copolymer, a styrene-butadiene block copolymer and a styrene-ethylene-butylene block copolymer. Examples of the acrylic resin are a homopolymer or copolymer of acrylic acid, methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, ethyl methacrylate, butyl methacrylate, acrylonitrile or the like. Examples of the polyvinylether resin are polyvinylether, polyvinyisobutylether, or the like. Examples of the silicone resin are dimethylpolysiloxane or the like.
Examples of the heat sensitive adhesives are, for example, a polyethylene resin, an ethylene-vinylacetate resin, a polyester resin, a polyurethane resin and a synthetic rubber.
The adhesive can be used singly or in combination of two or more members.
The adhesives can contain a tackifier, a filler, a softening agent, a wax, an antioxidant, an ultraviolet absorber or a crosslinking agent as required. The tackifier includes rosin res

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