Optical information recording substrate and method of making thereof

An optical information recording substrate having a legible matter formed in a groove area thereof or a pit array area thereof, wherein the legible matter includes a plurality of grooves or pit arrays being partially different in the breadth or depth thereof. The grooves or arrays may be partially dislocated in the radial direction of the optical information recording substrate from a predetermined track. The visually legible matter may include a plurality of laser generated pit arrays wherein remaining portions of the legible matter have a plurality of continuous grooves formed therein. The legible matter may also include a plurality of continuous grooves wherein remaining portions of the legible matter includes a plurality of laser generated pit arrays formed therein.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an optical information recording substrate 
on which visually comprehensible legible matter is formed and a method of 
making thereof. 
2. Discussion of the Background 
Conventionally, a substrate for composing an optical record disc such as a 
compact disc, is produced by a stamper made of a primary disc. 
In such a substrate for producing an optical disc, legible matter 
(hereinafter a mark) is formed on an area outside of a recording area 
thereof, for identifying, for instance, the contents of a recording or 
production number. As a method of forming the mark, a method is known, for 
instance, wherein the mark is physically made at the inner periphery of 
the stamper for producing the optical information recording substrate by a 
punch or by a marking-off pin, or a method is known disclosed in Japanese 
Unexamined Utility Model Publication No. 181119/1988, wherein the mark is 
provided on the stamper by an ultrasonic machining. 
The substrate is formed using the stamper provided with the mark, by 
injection molding or the like. 
However, in the method of marking the mark by the conventional technology, 
especially when the mark is produced on the stamper by a physical method, 
burrs and shavings are generated, which impairs the record or the play 
back portion of the substrate. As the result, in the optical record disc 
utilizing the substrate produced by such method, errors are generated in 
the recording or the play back signal. 
Furthermore as is described in the conventional technology, when the mark 
is physically produced on the stamper, a recess is generated on the 
surface thereof by physical force. As the result, when the substrate for 
the optical record disc produced by such a stamper is utilized, in forming 
another layer on the substrate, defects such as nonuniformity of film 
thickness or a cometary defect in the layer formation by spin coating 
method, are generated. In the case of the ultrasonic machining, it is 
necessary to provide a tool for the ultrasonic machining, which increases 
the production cost thereof. 
SUMMARY OF THE INVENTION 
In view of the above problems of the conventional technology, it is an 
object of the present invention to provide an optical information 
recording substrate which has little influences on characteristic values 
as an optical record disc which is caused by the mark formation on the 
stamper. It is another object of the present invention to provide a method 
of making the optical information recording substrate in which the surface 
of the stamper is not impaired, a protrusion or recess is not formed and 
the mark is easily formed. 
According to an aspect of the present invention, there is provided an 
optical information recording substrate having a legible matter formed in 
a groove area thereof or a pit array area thereof, wherein the legible 
matter comprises a plurality Of grooves or pit arrays which are partially 
different in terms of the breadth or depth thereof. 
According to another aspect of the present invention there is provided an 
optical information recording substrate having a legible matter formed in 
a groove area thereof or a pit array area thereof, wherein the legible 
matter comprises a plurality of grooves or pit arrays, the tracks of which 
are partially dislocated in the radial direction of the optical 
information recording substrate from a predetermined track. 
According to another aspect of the present invention there is provided an 
optical information recording substrate having visually comprehensible 
legible matter formed in a groove area thereof or a pit array area 
thereof, wherein the legible matter comprises a plurality of pit arrays, 
17 the other portion of which a plurality of continuous grooves are 
formed. 
According to another aspect of the present invention there is provided an 
optical information recording substrate having visually comprehensible 
legible matter formed in a groove area thereof or a pit array area 
thereof, wherein the legible matter comprises a plurality of continuous 
grooves, 17 the other portion of which a plurality of pit arrays are 
formed. 
According to another aspect of the present invention there is provided a 
method of making an optical information recording substrate, wherein a 
plurality of grooves or a plurality of pit arrays are formed by 
irradiating laser beam on a primary disc on which a photo resist is made 
and the optical recording substrate is formed by using a stamper made of 
the primary disc, characterized in that a legible matter is produced by 
partially changing a power density or a size or a shape of a beam spot of 
the laser beam, or partially dislocating an irradiated location of the 
laser beam in the radial direction of the optical information recording 
substrate when the plurality of grooves or the plurality of pit arrays are 
formed on the primary disc. 
According to another aspect of the present invention there is provided a 
method of making an optical information recording substrate, wherein a 
plurality of grooves or a plurality of pit arrays are formed by 
irradiating a laser beam on a primary disc on which a photo resist is made 
and the optical recording substrate is formed by using a stamper made of 
the primary disc, characterized in that visually comprehensible legible 
matter, composed of a portion of the plurality of grooves or the plurality 
of pit arrays is produced by intermittently irradiating partially the 
laser beam for forming grooves, or by continuously irradiating partially 
the laser beam for forming pit arrays when the plurality of grooves or the 
plurality of pit arrays are formed on the primary disc. 
According to an optical information recording substrate of the first and 
the second embodiment of the invention, an identifiably different portions 
which is optically different with the other portions is formed, by 
partially changing the width or the depth of continuous grooves or pit 
arrays, or by partially dislocating the tracks thereof. Accordingly, by 
aggregating of these portions, a legible mark is formed. 
Furthermore, as for the groove or the pit array, although the width or the 
depth thereof is partially changed, or the track is partially dislocated, 
since the continuity thereof is maintained, tracking thereof is possible 
along the groove or the pit array passing through the portions wherein the 
mark is formed, in the recording of the information in the optical 
information recording carrier or the playing back thereof. 
Furthermore, according to the an optical information recording substrate of 
the third and the fourth embodiments of the invention, identifiably 
different portions which optically differ from other portions can be 
formed, by partially forming pit arrays or continuous grooves in parts of 
the continuous grooves or the pit arrays, respectively. Accordingly, by 
aggregating the portions a legible mark can be formed. 
Furthermore, the above pit array or the continuous groove can be tracked 
along the groove or pit array through the portion wherein the mark is 
formed, as in the continuous grooves or pit arrays before and after the 
mark forming portion, in the recording of information on the optical 
information recording carrier or the playing back thereof. 
According to a method of making the optical information recording substrate 
of the first and the second inventions, in order to change the sectional 
shape of the groove or pit array, a laser beam is utilized. The mark is 
formed on the primary disc by (partially) changing the power density or a 
size or a shape of a beam spot of the laser beam, or by dislocating the 
laser beam. This mark can be formed on the substrate by using the stamper 
made of the primary disc. Accordingly, it is possible to easily form the 
mark by utilizing the laser beam which is originaly used for forming pits 
or grooves in the record portion of the substrate. At that occasion, no 
physical force is applied on the primary disc nor the stamper. Therefore 
no protrusion or recess which influences on the spin coating of the 
surface of the substrate is produced by the stamper. 
This is similar to a method of the making the optical information recording 
substrate of the third and the fourth embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS following discussion, a detailed 
explanation will be given of the embodiments of the present invention 
referring to the drawings. 
FIG. 4 shows a device for imprinting the mark on a primary disc for 
producing the substrate by the method of making the optical information 
recording substrate according to the present invention. In FIG. 4, the 
primary disc 20 is composed of a glass disc painted with photo resist by a 
spinner method or the like after polishing the surface thereof, is placed 
on the spindle motor 12. A laser spot of Ar laser or He--Cd laser or the 
like generated by the laser beam generator 18 is irradiated on the surface 
of the primary disc 20 and the surface thereof is exposed. Afterwards the 
grooves or the pit arrays are formed on the surface thereof by etching or 
the like. 
In FIG. 4, reference numeral 11 designates a controller for controlling the 
revolution of the spindle motor 12, 14 denotes an object lens for focusing 
the laser beam by the laser beam generator 18 on the spot, and 15 
indicates a feed mechanism for feeding the beam in the radial direction of 
the primary disc, by reflecting the laser beam and by moving it at a 
predetermined velocity (for instance, 1.6 .mu.m per one revolution of the 
spindle motor). Numeral 19 designates a modulator which modulates the 
laser beam in accordance with signals generated by the CD signal generator 
17 based on data of the data source 16. 
According to the present invention, the mark on the optical information 
recording substrate imprinted by the above device can be formed in any 
area such as inner periphery or outer periphery of the primary disc, 
despite whether the area is in the information recording area of the 
primary disc 20 for producing optical information recording carrier as 
shown in FIG. 5 (in FIG. 5, hatched part), inasmuch as the continuous 
grooves or pit arrays are formed. 
The grooves or the pit arrays are transcribed from a primary disc made as 
maintained above to a stamper. 
The optical information recording substrate is formed using the stamper 
obtained as above indicated, by means of injection molding or the like. 
Generally speaking, in case of producing an optical information recording 
carrier capable of recording information by optical means from this 
substrate, a coloring agent is painted on the surface of the substrate, 
which forms a thin recording layer, and furthermore a reflection layer and 
a protection layer are formed on top of the recording layer. Furthermore, 
it is possible to produce from such a substrate, an optical information 
recording carrier of a ROM type, wherein optically legible information is 
recorded when it is produced, such as in a compact disc, and successive 
recording is impossible. Such optical information recording carrier can be 
produced generally by forming a reflection layer and a protection layer on 
the surface of the substrate. 
FIG. 1A shows an enlarged view of a part of the formed substrate. As 
apparent in the drawing, a profile of a visually legible letter such as an 
alphabetical a mark (in this example, in shape of "A" as an alphabet) is 
formed by thickening the plurality of grooves 21 (that is, the thick 
groove portion 21D). Furthermore, the groove width of the thick grooves 
21D should be larger than that of the surrounding thin grooves 21T, so 
that the profile of the letter is recognizable to human eyes, as a whole. 
FIG. 1B shows an alphabet "A" which is formed by the thick grooves 21D. In 
contrast with FIGS. 1A and 1B, FIGS. 2A and 2B show an example in which 
the surrounding portion is formed by the thick grooves 21D and the letter 
portion is formed by the thin grooves 21T. 
By the way, when the width of the groove or the pit is enlarged, the groove 
or the pit on the surface of the substrate is deepened by reason of the 
transcribability thereof in forming. 
FIGS. 3A and 3B show a substrate formed by a stamper obtained by a method 
wherein the plurality of continuous grooves 21 are dislocated in the 
radial direction of the primary disc 20 in the letter portion, as a method 
of forming the letter without changing the width of the plurality of 
continuous grooves 21. 
As a track of the groove to be dislocated 21, for instance, as shown in 
FIG. 3A, a track which is dislocated on the outer side or the inner side 
of the primary disc 20, is a general pattern. Furthermore, a track is 
proposed in which the track is dislocated alternatively and in away manner 
on the outer side or on the inner side of the primary disc 20, or the 
track is dislocated wavily only at a starting point and at an end point of 
the mark. Generally speaking, the dislocated track which clarifies the 
mark is most desirable. However the dislocated track is pertinently 
determined also considering the request of simplification for the 
production procedure. 
FIG. 6 shows an example wherein the intermittent pit arrays 22 are arranged 
in the midst of the continuous grooves 21, and the mark is formed by 
aggregating the pit arrays 22. Conversely, it is possible to form the mark 
by aggregating the continuous grooves 21, by arranging continuous grooves 
21 in the midst of the intermittent pit arrays 22. The substrate is 
produced by such a stamper which is produced by such a primary disc, the 
method of production of which is basically the same as the above method. 
However, instead of dislocating the laser beam or changing the power 
thereof, the continuous grooves are partially replaced with the pit 
arrays, or the pit arrays are partially replaced with the continuous 
grooves. 
As mentioned above, according to the present invention, in the grooves or 
pit arrays for forming the mark on the optical information recording 
substrate, the continuity thereof is maintained throughout the portion 
wherein the mark is formed, and the tracking thereof is possible. 
Therefore the mark can be formed at any area in spite of whether it is in 
the record area or not. It is possible to record information and play back 
the recorded information at the area on a recording carrier wherein the 
mark is formed. Furthermore, when the mark is formed at the outside of the 
record area, it is possible to perform the tracking control by moving an 
optical pick up outside of the record area, by recording a tracking servo 
information such as an ATIP information. 
As apparent in the above explanation, according to an optical information 
recording substrate of the present invention, it is possible to form 
another layer on the substrate without causing errors in recording or in 
playing back signals, caused by the mark formation, since no flaw is 
generated in the record or the play back area. 
Furthermore in the grooves or the pit arrays for forming the mark, the 
continuity for tracking is maintained through the mark forming portion, 
and the continuous tracking is possible around the grooves or the pit 
arrays. Therefore the location for forming mark is not restricted, and the 
mark can be formed at any location on the recording carrier. 
Furthermore, in the method of making the optical information recording 
substrate according to the present invention, no flaw is caused on the 
surface of the stamper, and no protrusion or recess is caused. Therefore 
no corresponding protrusion or recess which influences on the spin coating 
on the substrate is formed by the stamper. Furthermore, it is possible to 
easily form the mark on the primary disc for forming the stamper, by using 
the laser beam device for forming originally the pits or the grooves on 
the record or on the play back area of the optical information recording 
carrier. Therefore it is not necessary to provide another working device, 
which is economically enforceable.