JP2002015465A - Optical information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical information recording medium in which a region recording visible information such as the classification of the disk is disposed on the inside of a clamping area and the degree of influence of physical dimensional accuracy necessary for clamping, the total thickness after sticking, etc., on warpage is minimized. SOLUTION: The optical information recording medium 10 is obtained by preparing two disks each with one face having at least a central hole, a clamping region 4 disposed on the outside of the central hole and an information recording region 6 disposed on the outside of the clamping region 4 and sticking the other faces of the disks to each other with an adhesive layer 3. The adhesive layer 3 is disposed between the periphery of the information recording region 6 and the inside 51 of the clamping region 4, a visible information layer 9 is disposed on the stuck face side between the inside 51 and the central hole C1, and the thickness D1 of the layer 9 is made smaller than the thickness D2 of the adhesive layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical information recording medium (hereinafter, referred to as an optical disk) having information recording areas formed on both sides by bonding.

[0002]

2. Description of the Related Art Conventionally, a laminated recording type optical disc has a single-sided recording type optical disc 20 as shown in FIGS.
And a double-sided recording type optical disk 10. In the single-sided recording type optical disc 20 of FIG. 11, 1 is a recording surface, 2 is a non-recording surface, and it is formed by being bonded by a double-sided adhesive layer of 3. Similarly, in the double-sided recording type optical disc 10 shown in FIG. 12, 1 is formed on both sides of the recording surface, and it is formed by being bonded by a three-sided adhesive layer.

In the single-sided recording type optical disc 20 shown in FIG. 11, disc type information (for example, CD, CD-RO) is printed on the non-recording side 2 on the side opposite to the bonding side by printing or the like.
M), side type information (for example, side A and side B), and maker information can be displayed so as to be visually recognized. In the case of the double-sided recording type optical disc 10 in FIG. The non-information recording surface excluding the recording area has only an area (area) in which the above various identification information can be recorded only in the clamp area (area) 4 and the inner peripheral portion 5 on the inner peripheral side (center hole side) thereof. Also, clamp area 4
However, it was necessary to maintain the flatness with high precision, and it was difficult to perform processing such as printing on this surface. Therefore, in the conventional double-sided recording type optical disk 10, various types of identification information are displayed by inserting the optical disk 10 into a cartridge (not shown) and displaying the information on the cartridge. Reference numeral 7 denotes an already recorded area in which address information and the like have already been recorded.

As a method of providing identification information that can be visually recognized on the double-sided recording type optical disk 10 without using a cartridge,
JP-A-8-287522 and JP-A-8-29786
As disclosed in Japanese Unexamined Patent Application Publication No. 7-107, inside the information recording area 6 (center hole side), for example, the clamp area 4
It has been proposed to attach a print label to a region using the region on the side of the bonding surface, for example, as a visible method. In any of the proposals, processing such as reducing the thickness of the disk substrate is necessary in advance in order to make the thickness of the area where the print label is to be applied coincide with the entire thickness of the information recording area 6.
Further, in these conventional methods, since the bonding surface side of the clamp area 4 area is used, it is necessary to set the thickness of the print label so that the total thickness of the information recording area 6 and the total thickness of the clamp area 4 become equal. There is. This arises from the need to suppress the physical dimensional accuracy of the clamp area 4 to a high level, and such a method requires extremely strict management in production.

[0005] In addition, such a method not only prevents the information recording veneer from being shared by both the single-sided recording type and the double-sided recording type and significantly impairs the production efficiency. Such as impairing the fluidity of the resin and deteriorating the birefringence on the inner circumference side, and the warpage of the thin-walled disk substrate will show a different tendency from other clamp parts,
The optical characteristics of the information recording area 6 and the high physical dimensional accuracy required for the clamp portion were not sufficient to maintain a stable level.

As a method other than attaching a print label to the bonding surface side of the clamp area 4, information is recorded in advance in a portion other than the information recording area 6, for example, in a mold for transferring stamper information at the time of veneer molding. Other methods have been proposed, such as transfer during molding. However, this method also has a problem that not only can a single plate be shared with a single-sided recording type and a double-sided recording type, but also if the side identification information is added, the single plate cannot be shared even with the front and back sides of the double-sided plate. there were. Furthermore, in this method, the non-information recording portion is usually transparent, and the recorded identification information is difficult to visually recognize. Therefore, it is necessary to newly form a reflection film on the bonding surface in the corresponding area.

[0007]

As described above, in the prior art, a single plate having a unique information recording surface must be formed for a double-sided recording type. It is necessary to strictly control the lamination thickness and the thickness of the identification information printing label so that the entire thickness is the same at the parts, and there is a great problem in terms of productivity to stably maintain the high dimensional accuracy of the clamp part. Was. Furthermore, in a method other than using a printed label, in particular, a veneer having an information recording surface for front and back is prepared, or a new reflective film is provided on the pasting surface side of the veneer. There was also a problem in terms of productivity, such as having to do so.

[0008] An object of the present invention is to provide, in the non-information recording area of the above-mentioned double-sided recording type optical disc, identification information such as a media type and a side type in terms of production, the same information for the single-sided recording type and the double-sided recording type. The production efficiency can be greatly improved by enabling the use of a recording veneer, and the means for displaying identification information reduces the strict control of thickness, etc., and the high physical dimensional accuracy of the clamp part An object of the present invention is to provide an optical disk capable of maintaining a stable optical disk.

[0009]

According to the present invention, as a first invention, at least a center hole (center hole), a clamp region 4 provided on an outer peripheral side of the center hole (center hole), and the clamp region. And a disc having one surface having an information recording area 6 provided on the outer peripheral side of
An optical information recording medium 10 in which the other surfaces of the two discs are bonded to each other using an adhesive layer 3; provided to the innermost portion 5 _1, made by the information layer 9 visible on the mating surface side bonding between the clamp region innermost portion 5 ₁ to the central hole C ₁ formed, the visible information layer the optical information recording medium 10 having a thickness D ₁ is set so as to be smaller than the thickness D ₂ of the adhesive layer 3 of 9, as a second invention,
2. The information layer 9 which can be visually recognized is provided by printing.
The optical information recording medium according to claim 1, wherein the visible information layer 9 is provided by a printed label, and the adhesive layer 3 is provided as a fourth invention. 5. The optical information recording medium according to claim 3, wherein the optical information recording medium according to claim 1 is formed by a double-sided pressure-sensitive adhesive sheet. Medium 10
Are provided.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below. The optical disc 10 according to the embodiment has an information recording single plate 11 having a thickness of 0.6 m, as apparent from the cross-sectional views of FIGS.
By bonding two disk substrates having the same outer diameter of 120 mm and the same 120 mm as the compact disk, C
The bonded optical disc 10 having the same thickness as D and having an outer diameter of 120 mm is manufactured. 5 _{1 in} both figures
Innermost part clamping area (area) is 8, the information display area 9 is a visible information layer, for example, the information layer disk type information is recorded, C ₁ has a central hole (center hole) It is the inner diameter end. FIG 2 As is clear from the adhesive layer 3 laminated, the information recording area 6 outer periphery than provided to the clamping area (Area) innermost part 5 _1, the center hole inner diameter end of the inner circumferential portion 5 ₁ top clamp area in which the bonding visible in side information layer until C ₁ is formed.

In the optical disk 10 capable of higher-density recording and reproduction, it is necessary to suppress eccentricity and surface runout strictly in order to realize the characteristics. In particular, the area required for clamping and the physical dimensional accuracy must be secured. Must. Therefore, higher accuracy is required for the overall thickness and warpage after bonding as compared with CDs. FIG. 1 shows an embodiment of the present invention.
This will be described with reference to FIGS. The same components as those in the related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a cross-sectional view of an optical disk 10 manufactured according to an embodiment of the present invention, and FIG.
FIG. 3 shows an optical disk 10 manufactured according to one embodiment of the present invention.
4 is a sectional view of an optical disc 10 according to another embodiment of the present invention. FIG. 5 is a sectional view of the optical disc 10 according to the embodiment of the present invention. FIG. FIG. 7 is an enlarged detailed view of a main part of Comparative Example 2, FIG. 8 is an enlarged detailed view of an essential part of Comparative Example 3, FIG. 9 is an enlarged detailed view of a main part of Comparative Example 4, FIG. 13 is an enlarged detailed view of a main part of Comparative Example 5, FIG.
FIG. 4 is an explanatory diagram showing measurement results of the optical discs 10 manufactured in the example and the comparative example.

[0013]

Embodiment 1 FIG. 3 is a cross-sectional view of a main part of an optical disk 10 manufactured in one embodiment of the present invention. In the drawing, reference numeral 12 denotes, for example, side identification information "A" The visible information layer 13 recorded as "" is a visible information layer recorded as side identification information "B" on the other information recording veneer 11, and the visible information layer 14 is, for example, one of the aforementioned information recording units. This is a non-transparent printing layer printed on the visible information layer recorded as side identification information “A” on the plate 11.

In this embodiment, the laminating means is not limited at all. However, in order to further improve the easiness of realization, the uniformity of the thickness D ₂ of the adhesive layer is obtained by laminating with an adhesive sheet. It is possible to set the thickness relatively freely within the range of the full thickness standard specific to the disc,
It is possible to further increase the degree of freedom in selecting the identification information viewing means.

Next, a method of manufacturing the optical disc 10 according to the first embodiment will be described. First, a disk substrate which can be used as a single-sided type having a thickness of 0.6 mm and an outer diameter of 120 mm is manufactured by injection molding. Next, a metal thin film as an information recording layer is formed on the disk substrate by sputtering or vapor deposition, and an information recording single plate 11 is manufactured. The next information recording single area from clamp area innermost portion 5 ₁ of the plate 11 to the center hole inner diameter end C ₁ (clamping area peripheral portion) 5 bonding surface side of the (information display area 8),
Side identification information "A" 1 on one of the disks to be pasted
2 to the other information recording veneer 11 as side identification information.
B ″ 13 are printed at a print thickness of 15 μm using a printing ink by a pad printing method.

Further, a non-transparent color print layer 14 having a print thickness of 15 μm is similarly printed over the entire surface of the side identification information “A” 12. Next, these two information recording veneers 11 are adhered to each other using the double-sided adhesive sheet 3 between non-incident surfaces.
A double-sided recording type optical disk 10 having an adhesive layer thickness of 50 μm with the double-sided pressure-sensitive adhesive sheet 3 was produced. In addition, double-sided adhesive sheet 3
It is formed from the information recording zone outermost periphery to the clamp area innermost portion 5 ₁ of the inner periphery of the clamp area 4.

As described above, by providing the non-transparent printing layer 14, the side identification information "A" 12 or the side identification information "B" 13 is clearly seen when viewed from the front or back of the optical disk 10. Visual recognition becomes possible.

[0018]

Embodiment 2 FIG. 4 is a cross-sectional view of a main part of an optical disk 10 manufactured in another embodiment of the present invention. In the drawing, reference numeral 15 denotes, for example, side identification information A "
Is a non-transparent printing layer printed on the information layer 15, and 17 is a printing layer printed as side identification information "B" on the printing layer 16. It is.

Next, a method of manufacturing the optical disk 10 according to the second embodiment will be described. An information recording veneer 11 is manufactured in the same manner as in the first embodiment. Next, the information recording single center hole (center hole) from the clamp area innermost portion 5 ₁ of the plate 11 region up inside diameter end C ₁ (clamping area peripheral portion) 5 bonding surface side of the (information display area 8) Then, the side identification information “A” 15 is printed on one of the disks to be attached. next,
The printing layer 16 is printed in a non-transparent color on the side identification information “A” 15. Finally, the side identification information “B” 17 is printed on the print layer 16.

Next, the printed information recording veneer 11
And the unprinted information recording veneer 11 are bonded together on the non-incident surfaces using the same double-sided pressure-sensitive adhesive sheet 3 as in Example 1, and the double-sided recording type optical disk having an adhesive layer thickness of 50 μm by the double-sided pressure-sensitive adhesive sheet 3 10 was produced. At this time, the total printing thickness is 40 μm.

[0021]

Embodiment 3 FIG. 5 is a cross-sectional view of a main part of an optical disk 10 manufactured in another embodiment of the present invention. A printed label 19 on which the side identification information "A" is displayed and the side identification information "B" is displayed on the other is a transparent adhesive sheet for sticking the printed label 18 to one of the information recording veneers 11.

Next, a method of manufacturing the optical disk 10 according to the third embodiment will be described. Was prepared in the same manner as the information recording single plate 11 as in Example 1, the region of the clamp area innermost portion 5 ₁ until the disc inner diameter end C ₁ (clamping area peripheral portion) 5
Using a transparent adhesive sheet 19, a printed label 18 on one of the disks to be bonded is displayed on one of the disks to be bonded on the bonding surface side (information display area 8), and the side identification information "A" is displayed on one disk and the side identification information "B" is displayed on the other disk. After that, the two information recording veneers 11 are bonded together on the non-incident surfaces using the same double-sided pressure-sensitive adhesive sheet (adhesive layer) 3 as in Example 1, and the double-sided pressure-sensitive adhesive sheet 3 has an adhesive layer thickness of 50 μm. The double-sided recording type optical disk 10 is manufactured. The total thickness of the print label 18 and its adhesive layer is 25 μm, and the print label 18 is a donut having the same shape as the information display area 8.

When the printed label 18 is used, the visible information layer is the total layer of the adhesive layer and the printed label.

[0024]

Comparative Example 1 FIG. 6 is a sectional view of an essential part of an optical disk 10 manufactured by the method of Comparative Example 1. In the drawing, reference numerals 20 and 20 denote one and the other information recording veneers. 20
The predetermined step portions 20a and 20b are provided on the bonding surface side of the clamp area 4. In addition, 21
Is an adhesive layer for adhering the information recording veneers 20, 20;
Reference numeral 2 denotes a print label displaying the side identification information “A” on one side and the side identification information “B” on the other side.

Next, a method of manufacturing the optical disc 10 according to the first comparative example will be described. First, a disk substrate having a thickness of 0.6 mm and an outer diameter of 120 mm is manufactured by injection molding. At this time, 30 μm steps 20 a and 20 b are provided on the side of the clamping area 4 of the disk substrate to be bonded. Next, a metal thin film as an information recording layer is formed on the disk substrate by sputtering or vapor deposition,
The information recording veneers 20, 20 are manufactured. 2 between non-incident surfaces
When the two pieces of information recording veneers 20 and 20 are pasted together using an adhesive, a printed label 22 having a thickness of 110 μm is sandwiched between the steps 20 a and 20 b of the information recording veneer 20, and an adhesive layer 21 made of an adhesive is applied. A double-sided recording type optical disk having a thickness of 50 μm was manufactured.

[0026]

Comparative Example 2 FIG. 7 is a cross-sectional view of a main part of an optical disk 10 manufactured by the method of Comparative Example 2. In the figure, reference numeral 21 denotes an adhesive layer for bonding information recording veneers 23 and 24, which will be described later. ,
Reference numeral 24 denotes one and the other information recording veneers. The information recording veneers 23 and 24 are provided with steps 23a and 24b similar to those of the comparative example 1 described above.
The side identification information “A” and the side identification information “B” are provided on the bonding surface side of the clamp area 4.

Next, a method of manufacturing the optical disk 10 according to Comparative Example 2 will be described. Disk substrates each having a thickness of 0.6 mm and an outer diameter of 120 mm are manufactured by using two types of stampers, a stamper recording side identification information “A” in the clamp area 4 and a stamper recording “B”. Next, using these disc substrates, information recording single plates 23 and 24 were produced in the same manner as in Comparative Example 1, and two information recording single plates 23 and 24 having different side identification information between non-incident surfaces.
Are bonded by an adhesive, and an adhesive layer 2 of the adhesive is used.
A double-sided recording type optical disk 10 having a thickness of 50 μm was manufactured.

[0028]

Comparative Example 3 FIG. 8 is a cross-sectional view of a main part of an optical disk 10 manufactured by the method of Comparative Example 3. In the drawing, reference numeral 25 denotes a print on the bonding surface side of the clamp area 4 of one information recording single plate 11. The side identification information “A” and 26 are the side identification information “B” printed on the bonding surface side of the clamp area 4 of the other information recording veneer 11. Reference numeral 21 denotes an adhesive layer for bonding the information recording veneers 11, 11.

Next, a method of manufacturing the optical disk 10 according to Comparative Example 3 will be described. An information recording veneer 11 is manufactured in the same manner as in the first embodiment, and the side identification information “A” 25 is attached to one of the information recording veneers 11 in the clamp area 4.
The side identification information “B” 26 is printed on the other information recording veneer 11 with a print thickness of 15 μm. Next, the two information recording veneers 11 and 11 were bonded together using an adhesive between the non-incident surfaces to produce a double-sided recording type optical disc 10 in which the thickness of the adhesive layer 21 of the adhesive was 50 μm.

[0030]

Comparative Example 4 FIG. 9 is a cross-sectional view of a main part of an optical disk 10 manufactured by the method of Comparative Example 4. In the figure, reference numeral 27 denotes one of the disks to be bonded, and the side identification information “A” on one side. Print label displaying side identification information "B", 28
Is a transparent adhesive sheet. In addition, 3 is a double-sided pressure-sensitive adhesive sheet.

Next, a method of manufacturing the optical disk 10 according to Comparative Example 4 will be described. An information recording veneer 11 is manufactured in the same manner as in the first embodiment, and on the bonding surface side (information display area 8) of a region (clamp area inner peripheral portion) 5 from the innermost periphery of the clamp area 4 to the inner peripheral end of the disk. After affixing a printed label 27 displaying side identification information "A" on one side and side identification information "B" on the other side using a transparent adhesive sheet 28 to one of the disks to be bonded, the non-incident surfaces are 2
The two pieces of information recording veneers 11 are bonded together using the same double-sided pressure-sensitive adhesive sheet 3 as in Example 1 to produce a double-sided recording type optical disk 10 having an adhesive layer thickness of 50 μm. The total thickness of the printed label 27 and its adhesive layer is 70 μ
m, and the print label 27 has a donut shape having the same shape as the information display area 8.

[0032]

Comparative Example 5 FIG. 10 is a cross-sectional view of a main part of an optical disk 10 manufactured by the method of Comparative Example 5. In the figure, reference numeral 17 denotes one disk to be bonded and one side identification information “A”.
, And the other side is a printed label displaying side identification information “B”, and 18 is a transparent adhesive sheet. 29 is a double-sided pressure-sensitive adhesive sheet.

Next, a method of manufacturing the optical disk 10 according to Comparative Example 5 will be described. An information recording veneer 11 is manufactured in the same manner as in the first embodiment, and on the bonding surface side (information display area 8) of a region (clamp area inner peripheral portion) 5 from the innermost periphery of the clamp area 4 to the inner peripheral end of the disk. After affixing a printed label 17 displaying side identification information “A” on one side and side identification information “B” on the other side using a transparent adhesive sheet 18 to one of the disks to be bonded, two non-incident surfaces are attached to each other. The two information recording veneers 11 and 11 are stuck together with the double-sided pressure-sensitive adhesive sheet 29, and the thickness of the adhesive layer with the double-sided pressure-sensitive adhesive sheet 29 is
A double-sided recording optical disk 10 of μm is manufactured. The total thickness of the adhesive layer formed by the print label 17 and the transparent adhesive sheet 18 is 30 μm, and the print label 17
It has the same shape as the donut. The double-sided adhesive sheet 29
Are formed from the outer peripheral edge of the disk to the outer peripheral portion of the clamp area 4.

Optical discs 10 manufactured in the examples and comparative examples
FIG. 13 shows the results of measuring the amount of surface runout and examining the commonality of the single-sided recording type / double-sided recording type. Note that the measurement of the surface runout is for evaluating the dimensional accuracy of the clamp area 4, and the maximum surface runout at the position of the disk radius of 57 mm was measured. Regarding the commonality of the single-sided recording type and the double-sided recording type, a case where the same information recording single plate can be used for both the single-sided recording type and the double-sided recording type was evaluated as “good”, and “x” was determined as not. The position of the information layer indicates the position where the visible information layer 9 is formed, and the position of the adhesive layer indicates the inner peripheral end position of the adhesive layer 3.

As is clear from FIG.
Although No. 2 has no problem with the amount of surface runout, the information recording veneer cannot be shared because the information recording veneer is provided with a step or the identification information is formed by a stamper, so that the productivity is inferior. In Comparative Example 3, the position of the adhesive layer was set at the outermost periphery 4 of the clamp area in order to provide a visible information layer in the clamp area.
_{It is} only ₁ and the amount of surface deflection becomes 300 μm or more, the dimensional accuracy is deteriorated, and there is a problem in recording / reproducing of the information recording layer. In Comparative Example 4, since the thickness of the visually recognizable information layer is larger than D2, the amount of surface deflection is large, the dimensional accuracy is deteriorated, and there is a problem in the recording and reproduction of the information recording layer. Comparative Example 5 is the position of the adhesive layer has only to clamp area outermost peripheral portion 4 _1, surface deflection amount deteriorates the dimensional accuracy becomes more than 300 [mu] m, it can be seen that there is a problem in the recording and reproduction of information recording layers.

On the other hand, in the first to third embodiments, the information recording veneer can be shared, the productivity is improved, the visible information layer is provided on the inner peripheral portion of the clamp area, and the adhesive layer is formed on the innermost part of the clamp area. By providing D ₁ to D ₂ or less, the surface runout amount is small, the recording / reproducing of the information recording layer is good, the allowable range of the dimensional accuracy of the clamp area can be widened, and the productivity is improved. I understand.

[0037]

According to the first aspect of the present invention, at least the middle
A center hole (center hole) and the center hole (center hole)
And a clamp area provided on the outer peripheral side of
And an information recording area provided on the outer peripheral side of the
Using two discs with one side, these two discs
The other surfaces of the disks are not bonded together using an adhesive layer.
An optical information recording medium comprising:
Provide from the outermost periphery of the area to the innermost periphery of the clamp area.
Bonding from the innermost periphery of the clamp area to the center hole
A visible information layer is provided on the side of the
Information layer thickness D ₁Is the thickness D of the adhesive layer 3_TwoBecomes
With this setting, high dimensional accuracy of the clamp
Secure and provide visible identification information using various means
Can be

According to the second aspect of the present invention, since the information recording veneer can be shared by the single-sided and double-sided types, the production efficiency can be greatly improved, and the thickness D of the visible information layer can be improved.
_{By 1} was set to suit become thickness D ₂ less adhesive layer paste, it is possible to produce with ease tolerances. Further, by setting the thickness as described above, it is possible to reduce the strict management of the thickness in the identification information display means. Furthermore, depending on the setting of the thickness of the adhesive layer, there is a wider choice of means for providing visible identification information.

According to the third aspect of the present invention, since the information recording veneer can be shared by the single-sided and double-sided types, the production efficiency can be greatly improved, and the thickness D of the visible information layer can be increased.
_{By 1} was set to suit become thickness D ₂ less adhesive layer paste, it is possible to produce with ease tolerances. Further, by setting the thickness as described above, it is possible to reduce the strict management of the thickness in the identification information display means. Furthermore, depending on the setting of the thickness of the adhesive layer, there is a wider choice of means for providing visible identification information.

According to the fourth aspect of the present invention, the uniformity of the thickness of the adhesive layer is enhanced, and the thickness can be set relatively freely within the range of the total thickness standard specific to the disc. It is possible to further increase the degree of freedom in selecting means.

According to the fifth aspect, the uniformity of the thickness is enhanced, and the identification information can be confirmed with high visibility from either side of the double-sided recording type optical disc.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an optical disc 10 manufactured according to an embodiment of the present invention.

FIG. 2 is an enlarged detailed view of a main part of FIG.

FIG. 3 is an optical disc 10 manufactured in one embodiment of the present invention.
It is principal part sectional drawing of.

FIG. 4 is a sectional view of a main part of an optical disc 10 according to another embodiment of the present invention.

FIG. 5 is a sectional view of a main part of an optical disc 10 according to another embodiment of the present invention.

FIG. 6 is an enlarged detailed view of a main part of Comparative Example 1.

FIG. 7 is an enlarged detailed view of a main part of Comparative Example 2.

FIG. 8 is an enlarged detailed view of a main part of Comparative Example 3.

FIG. 9 is an enlarged detailed view of a main part of Comparative Example 4.

FIG. 10 is an enlarged detailed view of a main part of Comparative Example 5.

FIG. 11 is a sectional view of a conventional single-sided recording type bonded optical disc.

FIG. 12 is a sectional view of a conventional double-sided recording type bonded optical disc.

FIG. 13 is an optical disc 10 manufactured in an example and a comparative example.
It is explanatory drawing which shows the measurement result of.

[Explanation of symbols]

3 Double-sided adhesive layer 4 Clamp area 5 Inner circumference of clamp area 5 ₁ Inner circumference of clamp area 6 Information recording area 7 Existing information recording area 8 Information display area 9, 15 Visible information layer 12, 13 Side identification information 14, 16, 17 printing layer 18 printing label 19 transparent adhesive sheet

Claims (5)

[Claims] 1. Two discs each having at least one surface having at least a center hole, a clamp area provided on an outer peripheral side of the center hole, and an information recording area provided on an outer peripheral side of the clamp area. An optical information recording medium in which the other surfaces of the two disks are bonded to each other using an adhesive layer, wherein the adhesive layer extends from the outermost periphery of the information recording area to the innermost periphery of the clamp area. A visible information layer is provided on the bonding surface side between the innermost peripheral portion of the clamp area and the center hole, and the thickness of the visible information layer is equal to or less than the thickness of the adhesive layer 3. An optical information recording medium characterized by setting as described above. 2. The optical information recording medium according to claim 1, wherein said visible information layer is provided by printing. 3. The optical information recording medium according to claim 1, wherein said visible information layer is provided by a printed label. 4. The optical information recording medium according to claim 1, wherein said adhesive layer is formed by a double-sided pressure-sensitive adhesive sheet. 5. The optical information recording medium according to claim 3, wherein said printed label is adhered by a transparent adhesive sheet.