Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
72~
BACKGROUND OF T~E INVENTION
Field of the Invention
The present invention relates to a disc-
shaped, optically readable information carrier having high
storage density comprising a transparent carrier disc
exhibiting a center hole and having an information-carrylng
side which exhibits the information in the form of a micro-
structure disposed in a concentric annular surface and
covered with a reflective film, being covered with an outer
protective layer.
Description of the Prior Art
Information carriers of the type generally
set forth above are known, for example, from the German
allowed application 23 41 338. The information structure
existing on the one side of the transparent carrier plate is
read through the plate during reproduction by a focused laser
beam, whereby the optical structure is made insensitive to
dust and damage to a certain degree. The protective layer on
that side of the carrier plate carrying the information can
be a paper layer or a synthetic film provided with an
adhesive. It is also possible to realize the layer by, for
example, a sprayed-on lacquer layer whose thickness exceeds
the depth of the information structure.
As practice has shown, paper layers or
synthetic films provided with adhesive are generally not suitable
as protective layers because a grain-oriented paper layer
promotes warping of the disc, as does also the coefficient of
thermal expansion of a synthetic film which is generally
different relative to -the material of the carrier plate. Such
,
o
warping phenomena are ex-tremely critical, since the admissible
tolerance limits to be required given such plates for the
planarity of the plates, in consideration of the op-tical read
system, are very narrow. For the same reasons, it must be re-
quired that a protec-tive layer realized, for example, by a spray-
on lacquer layer, exhibits practically no fluctuations in
thickness over the entire surface.
~ dded thereto is that the dangerof warping is further
increased by labels which are to be applied to the structure.
Independently of the protective layer itself, the influence of
paper or synthetic film labels on the warping tendency of such a
disc is all the more pronounced the smaller the ratio of the disc
diameter to the label diameter. Particularly critical considera-
tions are therefore given for the digital audio disc which has
entered the literature under the designation Compact Disc, -this
exhibiting a disc diameter of only approximately 12 cm, and
given which the label to be applied to the protective layer can-
not be selected with as small a diameter as desired in view of
the generally extensive informational data.
SUMMARY OF THE INVENTION
The object of the presen-t invention, therefore, is to
provide a solution for the protec-tive layer in conjunction with
the label, particularly for a Compact Disc, which overcomes the
aEoremen-tioned difficulties which have heretofore occurred.
Given a disc-shaped, optically readable information
carrier having high storage density of the type generally set
forth above, -this object is achieved, according to the present
inven-tion, in that the outer protective layer is an over print
2--
of a primary color of thickness greater -than the microstructure
which, in turn, carries written and figurative information
applied thereto monochromatically or polychromatically.
The present invention is based on the precept -that the
required protec-tive layer can be realized in an extremely simple
mallner by applying a color of sufficient thickness which simulta-
neously represen-ts the underlay for the lahel to be applied. In
addition, the application of the primary color by printing also
makes a very uniform texture of -the layer of printing ink pos-
sible across the surface of the carrier plate. By so doing, alabel extendiny over the entire surface of one side of the
information carrier is simultaneously realized in an extremely
advantageous manner, the label, in contrast to paper or synthetic
film labels, exerting no warping forces on the disc.
In order to promote a rapid drying of the color to be
printed and in order to promote the same to a sufficient degree,
it is entirely meaningful to construct the color impression of
two or more layers,namely, in such a manner that an applied color
layer is dried in an intermediate step before the nex-t color
layer is printed.
ior the purpose of a better adhesion of the primary
or fla-t color to the side of the carrier plate carrying -the
inEormation, it can also be meaningful to first apply a primary
coat in the form of an underlayer which is expedien-tly likewise
printed on but, however, can also be applied under certain con-
ditions by a centrifuyal or spray operation.
The -tampon printing method set forth in -the German
Le-tters Pa-tent 23 04 723, column 2, lines 26-72, is particularly
suited for the impression of the primary color, as well as for
--3--
the figurative and wri-tten information to be printed onto -the
primary color, the printing method, in turn, leading to optimum
work results with the printing device specified in the above
mentioned letters patent.
BRIEF DESCRIPTION OF THE DRAWINGS
O-ther objects, features and advantages of the invention,
its organization, construction and operation will be best under-
stood from the following detailed descrip-tion, taken in conjunc-
tion wi-th the accompanying drawings, on which:
Figure 1 is a plan view Or an information carrier
having a first surface shape of the label protective layer;
Figures 2 and 3 are sectional views of the information
carrier of Figure 1 having different primary color layer formats;
Figure 4 is a plan view of an information carrier
having a second surface shape of the label protective layer;
Figures 5 and 6 are sectional views of the informatipn
carrier of Figure 4 having various primary color layer formats;
Figure 7 is a plan view of an information carrier
having a third surface shape of the label protective area;
7~
FIGS. 8 and 9 are sectional views of the
information carrier of FIG. 7 having different primary color
layer formats;
FIG. 10 is a plan view of an information
carrier having a fourth surface shape of the label protective
layer; and
FIGS. 11 and 12 are sectional views of the
information carrier according to FIG. 1.0 having different
primary color layer formats.
~ESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, the information carrier
disc 1 has a label protective area which is only limited by a
center hole M and by the edge of the disc. As the sectional
illustration of FIG. 2 further illustrates, it is applied to
the information side of the carrier plate 1 in a single primary
color layer 2. The information printing 3 applied to the
primary color layer 2, as in all other sectional illustrations
of FIGS. 5, 6, 8, 9, 11 and 12, is indicated in a broken
line extending over the primary color layer 2.
In addition to the color layer 2, the
alternative shown in the sectional illustration of FIG. 3
also exhibits an underlayer 4 which can either likewise
comprise the same primary color as the primary color layer 2
or, cn the other hand, is a priming coat serving the purpose
of better adhesion of the primary color layer 2 to the
information side of the carrier plate 1.
The information carrier plate 1 illustrated
in FIG. 4 includes a second surface shape of the protective
layer which is limited by the center hole M and by a narrow,
-- 5 -
information-free, outer annular zone AR. Thereby, the
sectional illustra-tions of FIGS. 5 and 6 correspond -to the
sectional illustrations of FIGS. 2 and 3. Under certain
conditions, the outer annular zone AR can be required for
reasons of printiny technology.
The information carrier plate 1 according to
FIG. 7 comprises a third surface shape of the label protective
layer which is limited/ on the one hand, by the outer edge
of the disc and, on the other hand, by the outer edge of the
information-free, concentric, inner annular zone IR. This
surface shape can also prove meaningful in view of requirements
of printing technology. The sectional illustrations of the
information carrier plate 1 according to FIG. 7 in FIGS. 8 and
9 again correspond to the sectional illustrations of FIGS. 2,
5 and 3, 6.
Finally, th~plan view of the information
carrier plate 1 according to FIG. 10 illustrates a fourth
surface shape of the label protective area which is limited
both by a narrow, information-free outer annular zone AR and
by an inner, information-free annular zone IR. The sectional
illustrations of the information carrier plate 1 according -to
FIG. 10 in FIGS. 11 and 12 again correspond to the sectional
illustrations of FIGS. 2, 5, 8 and 3, 6, 9.
Although we have described our invention by
reference to particular illustrative embodiments thereof,
many changes and modifications of the invention may become
apparent to those skilled in the art withou-t departing from
the spirit and scope of the invention. We therefore intend
to include within the patent warranted hereon all such changes
and modifications as may reasonably and properly be included
within the scope of our contribution to the art.
