JPH07296418A - Information recording medium and its substrate and production - Google Patents

Abstract

PURPOSE:To prevent infiltrating of a coating liquid to another surface side by inclining at least part of the outer end faces of a substrate toward the other surface side on the opposite side from the one surface side of the substrate. CONSTITUTION:The side end face 17 on the outermost periphery of the optically transparent disk substrate 11 inclines rectilinearly inward toward the other surface 18 on the opposite side from the one surface 12 side provided with pits 3 and a recording layer 4. Accordingly, the diameter of one surface is larger than the diameter of other surface 18. The outer end face of the substrate 11 is formed as a slope 17 in such a manner, by which the coating liquid tending to leak from the top end of the outer end face 17 and to infiltrate to the other side is prevented at the time of applying the coating liquid of the recording layer 4 on the substrate 11 while rotating the substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium, in particular a disc-shaped optical information medium, in which information is recorded on one side of a substrate, a substrate and a manufacturing method thereof. .

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 10 and 11, an optical information medium of this type, for example, an optical disk 10, has a pit for recording information on one surface 2 of an optically transparent disk substrate 1. 3 (or pre-groove) is formed in advance in an area of 15 to 25% of the disk effective area, and the recording layer 4 (or light reflecting layer) is formed thereon.

While rotating this medium, laser light 5 is emitted from an optical pickup (not shown) from the side of the other surface 8 having the same diameter as the one surface 2 of the substrate 1, and the reflected light 6 of the reflected light 6 is emitted. The recording signal of the pit and further the optical writing information to the recording layer 4 are read by the difference in the light amount, and the recording information is reproduced. Recording of information on the recording layer 4 is performed by irradiation with a writing laser beam.

Here, a thin film 4 formed by using only an organic dye or a composition of an organic dye and a binder such as a high molecular compound as a main component, and optionally adding an additive or the like for improving light resistance. Is a CD for recording optical information
It is used as a light reflecting layer compliant with the (compact disc) signal standard or as a recording layer of a medium compliant with the MD (mini disc) signal standard.

The recording layer 4 (or the light reflecting layer) is mainly composed of a composition of only an organic dye or an organic dye and a binder such as a polymer compound, and in some cases, an additive or the like for improving light resistance. It is made of blended materials.

In the production of such an information medium, the spin coat method is often employed for forming the recording layer 4 because it has high industrial productivity and can reduce the production cost.

[0007] The spin coating method is to improve the light resistance of the disk-shaped medium, which is mainly composed of the organic dye alone or a composition of the organic dye and a binder such as a polymer compound on the coated surface of the substrate. In this method, a solution prepared by dissolving a material mixed with the additive or the like in an appropriate organic solvent is placed, and then the substrate is rotated to remove the excess solution from the coated surface.
Compared to the vacuum evaporation method and sputtering method, less investment is required for manufacturing equipment and maintenance is easier.

However, in the conventional manufacture of the disc-shaped information medium by the spin coating method, as shown by the phantom line in FIG. 12, the recording layer 4 is rotated while the substrate 1 is rotated.
When spin coating is performed, there is a problem that the coating solution 4a wraps around from the coating surface 2 to the side end surface (outer end surface) 7 on the outer periphery of the substrate, and further to the outer peripheral portion of the surface 8 opposite to the coating surface 2. It was

In this case, not only the commercial value is impaired, but also when the coating solution adheres to the portion where the pits 3 (or grooves) are formed when viewed from the opposite side 8 of the coating surface 2, it is shown in FIG. As described above, the laser light 5 is blocked by the coated portion 4a around which the signal is reproduced or recorded.

Even when the coating solution does not reach the portion where the pits 3 (or grooves) are formed when viewed from the opposite side 8 of the coating surface 2, the coating solution falls off after drying and solidification to form a disc shape. By adhering to a portion of the optical information medium 10 where a groove or a pit is formed, a lens of an optical pickup, or the like, an adverse effect such as an increase in error rate at the time of recording or reproducing a signal is adversely affected.

Until now, several methods have been studied as a method for preventing the coating solution from adhering to the portion 7 in which such grooves or pits are formed. For example, in Japanese Unexamined Patent Publication No. 3-203836, a dye is applied to a substrate-side end face by cutting the periphery of a recording medium obtained by forming a protective layer on a dye layer coated on a transparent substrate. It is described to obtain an unattached optical medium.

Further, in Japanese Laid-Open Patent Publication No. 3-203835, at least a part of the peripheral surface of the optical information recording medium is immersed in a cleaning solution in which the dye is dissolved, and the recording medium is rotated so that the end surface on the substrate side is exposed. A method for obtaining an optical information recording medium on which dyes are not attached is described.

However, in these methods, a step of removing the dyes must be added during the manufacturing process, which lowers the productivity and is difficult to remove a predetermined portion of the dyes reliably and with good reproducibility. There are also cases where even necessary parts are removed.

[0014]

It is an object of the present invention to optimize the cross-sectional shape of the outermost peripheral surface of an information recording medium such as the above-mentioned disc-shaped optical information medium so that it can be manufactured by a conventional manufacturing process. Without increasing the amount of the organic dye alone or a material containing a composition of the organic dye and a binder such as a polymer compound as a main component (in some cases, an additive or the like for improving light resistance is blended) is used as an appropriate organic material. An information medium capable of eliminating the wraparound to the side opposite to the coated surface when a coating solution such as a solution dissolved in a solvent is applied by a spin coating method and remarkably reducing adverse effects due to the wraparound, a substrate and a manufacturing method thereof. To provide.

[0015]

That is, according to the present invention, in an information recording medium configured to record information on one surface side of a substrate, at least a part of an outer end surface of the substrate is the substrate. The present invention relates to an information recording medium characterized by being inclined inward from the one surface side toward the other surface side opposite to the one surface side.

According to the information recording medium of the present invention, at least a part of the outer end surface of the substrate is inclined inward from one surface side on which information is recorded to the other surface side (that is,
Since it has an inwardly inclined surface), when forming a predetermined layer such as a recording layer on one surface by spin coating, the coating liquid leaks from the outer end surface of the medium to the other surface side and wraps around. Even so, the inwardly inclined surface effectively prevents this. This inwardly inclined surface causes the coating liquid to adhere to the outer end surface of the substrate so as to be drawn inward, and the downward flow force due to the weight of the coating liquid itself is dispersed to the inwardly inclined surface side. It is thought that this is because it is done.

As a result, it is possible to prevent the coating liquid from wrapping around (adhering) to the other surface side, so that the reading beam is sufficiently incident and reflected on the pit or groove, and further on the signal recording portion formed of the recording layer. It is possible to perform the signal reproduction without any trouble, and the signal can be reproduced well and the signal can be recorded well. In addition, since the amount of the coating liquid deposited on the outer end surface of the substrate is also reduced, the amount of the coating liquid that has fallen off after drying and solidification is reduced, and the error rate during signal recording or reproduction can be reduced.

In the information recording medium of the present invention having such remarkable effects, by devising the shape of the outer end surface of the substrate (formation of the above-mentioned inwardly inclined surface), the productivity is improved with no additional manufacturing process. You can definitely get it.

In the information recording medium of the present invention, the inwardly inclined surface present on at least a part of the outer end surface of the substrate is one of the one of the substrates in order to more surely reduce the above-mentioned wraparound or adhesion of the coating liquid. It is desirable to have at least one portion that is linearly inclined within the range of 20 to 80 degrees (and further 30 to 80 degrees) with respect to the normal line of the plane. This tilt angle
If it is less than 20 degrees, the above-mentioned wraparound prevention effect is poor, and 80
If it exceeds the limit, the edge of the substrate becomes too sharp and its mechanical strength and the like tend to deteriorate.

The above-mentioned inwardly inclined surface is not limited to a linear one, and may have a concave inclined portion at at least one place. Alternatively, each of the linear inclined portion and the concave inclined portion may be provided in at least one place.

The information recording medium of the present invention may be specifically configured as an optical information medium having pits or grooves formed on one surface side of the substrate. In this case, one surface side of the substrate is formed. In addition, at least one of a recording layer for recording optical information, a light reflection layer and a protective layer may be formed by a spin coating method.

Further, the base is formed in a disk shape, and the inwardly inclined surface existing on at least a part of the outer end surface of the disk-shaped base is directed from one surface side to the other surface side of the disk-shaped base body. It is desirable that the diameter of the substrate is small, and particularly that the diameter of one side of the disk-shaped substrate is larger than the diameter of the other side.

The present invention also provides the above-mentioned substrate for the information recording medium of the present invention.

The information recording medium of the present invention has a predetermined layer (for example, at least one of a recording layer for recording optical information, a light reflecting layer and a protective layer) on one surface side of the above-mentioned substrate. It is desirable to manufacture it by a process of forming by a spin coating method.

In this manufacturing method, when a gas (for example, nitrogen gas) is sprayed from the other surface side of the substrate toward the outer end surface of the substrate during spin coating, the adhesion of the coating liquid to the end surface of the substrate can be further reduced. it can.

In this manufacturing method, the substrate is preferably manufactured by an injection molding method, and a polymer compound such as a polycarbonate resin or an acrylic resin can be used as a molding material.

At this time, the molding space (cavity)
Concavities and convexities opposite to the above-mentioned pits or grooves may be formed in advance on the mold surface on the side, but this can be easily formed through a normal master process (mastering process) and molding process.

[0028]

EXAMPLES Examples of the present invention will be described below.

1 to 5 show a first embodiment in which the present invention is applied to an optical disk. However, Figs. 10 to 12
Portions common to those of the conventional example shown in (1) are denoted by common reference numerals, and description thereof may be omitted (the same applies hereinafter).

As shown in FIGS. 1 and 2, the optical disk 20 of the present embodiment is fundamentally different from the conventional example shown in FIG. 10, and is the outermost peripheral side of the optically transparent disk substrate 11. The end surface (outer end surface) 17 is directed inward from one surface 12 side provided with the pits 3 (or pregrooves) and the recording layer 4 (or light reflection layer) toward the other surface 18 opposite thereto. It is linearly inclined. Therefore, the diameter φ ₁ of the one surface 12 is larger than the diameter φ ₂ of the other surface 18 (see FIG. 2).

As shown in FIG. 3, the linear inclined surface 17 has an angle θ of 20 ° to 80 ° with respect to the normal 30 of the surface 12 of the substrate 11, for example, an angle of about 40 ° on the other surface. Inclined inward toward 18.

By forming the outer end surface of the substrate as the inclined surface 17 in this way, the coating for the recording layer 4 (or the light reflecting layer) is performed while rotating the substrate 11 by the spin coating method as shown by the phantom line in FIG. Even if the coating liquid leaks from the upper end of the outer end surface 17 and wraps around when the liquid 4A is applied, this can be effectively prevented. That is, a phenomenon occurs in which the coating liquid 4A is wet so that it is drawn into the inclined outer end surface 17, and the downward flow force due to the weight of the coating liquid 4A is dispersed to the outer end surface 17 side and the drop amount is significantly reduced. It is believed that

As a result, the coating liquid 4A can be prevented from wrapping around (adhering) to the side of the other surface 18, so that the reading beam is incident and reflected on the signal recording portion composed of the pit or groove and the recording layer (see FIG. 1). (See reference) can be performed sufficiently and without any trouble, and the signal can be reproduced well and the signal can be recorded well. Moreover, since the amount of the coating liquid 4A attached to the outer end surface 17 of the substrate is also reduced, the amount of the coating liquid 4A attached to the signal recording portion or the optical pickup due to the drop after drying and solidification is significantly reduced, and an error during signal recording or reproduction is reduced. The rate can be reduced.

Such a remarkable effect can be ensured with good productivity without adding a manufacturing process by devising the shape of the outer end surface 17 of the substrate as described above (formation of the inward inclined surface). Can be obtained. Therefore, it is possible to improve the yield of the optical disc manufacturing and shorten the manufacturing time. Further, not only the effect of improving the aesthetic appearance of the product can be obtained, but also the reliability of the optical information medium can be improved.

In the present embodiment, a spin coating method is used, which mainly comprises a composition of only an organic dye or an organic dye and a binder such as a polymer compound, and in some cases, an additive or the like for improving light resistance is added. Thin film 4 formed by blending
Is used as a light-reflecting layer for CD (compact disc) signal standard or a recording layer of a medium for MD (mini disk) signal standard for recording optical information.

The substrate 11 for spin-coating the thin film 4 (recording layer or light reflecting layer) can be manufactured by the injection molding method as shown in FIGS. 4 and 5.

That is, in a conventionally known master process (mastering process), for example, a photoresist layer coated on a glass master plate is cut with a laser beam modulated by a recording signal, and a metal plate is electroplated from the resulting recording master plate. Create a master (stamper).

Then, in the disc forming step, the stamper is used as one die 21 as shown in FIG. 4, and the other die 21 is used.
A molding material, for example, a polycarbonate melt 11A is injected and injected into a molding space (cavity) 23 formed between the molding material and the molding material. After solidifying the molding material 11A, as shown in FIG.
The substrate 11 is separated from 22.

Since the molds 21 and 22 are respectively formed with the unevenness 3A corresponding to the pit or groove and the inclined surface 17A, the pit 3 (or groove) is formed on one surface 12 of the molded substrate 11. ), An inclined surface 17 can be formed on the outer end surface.

FIG. 6 shows a second embodiment in which the present invention is applied to an optical disk.

In this embodiment, in the outermost peripheral portion of the optical disk 20, during the spin coating process of the thin film 4 on the substrate 11, from the direction opposite to the coating surface 12 toward the coating surface (that is, , A gas 13 such as air or nitrogen gas is blown against the outer end surface 17).

By this gas spraying, a force for pushing up the coating liquid 4A, which is going to flow down on the outer end surface 17, acts from below to suppress the flowing down of the coating liquid 4A and prevent the coating liquid 4A from flowing around on the other surface 18. Therefore, since the adhesion of the thin film on the outer end surface 17 can be further reduced, the effect obtained in the above-described first embodiment can be further improved.

FIG. 7 shows a third embodiment in which the present invention is applied to an optical disk.

Unlike the first and second embodiments described above, the optical disk 30 according to this embodiment does not form pits or grooves on the coating surface 12 of the substrate 11 but only the organic dye or the organic dye and the binder. The recording layer 24 composed of the composition of
It is formed by leaving the outermost peripheral portion, and an ultraviolet curable film is formed thereon as a protective film 21.

The protective film 21 is formed by the spin coating method. At this time, since the outer end surface 17 of the substrate 11 has the same linear inwardly inclined surface 17 as described above, it is used for the protective film. It is possible to reduce the amount of the coating liquid adhering to the outer end surface 17, and of course to prevent it from flowing around to the other surface 18.

The protective film 21 completely adheres to the outer peripheral edge of the recording layer 24 to sufficiently cover and protect the recording layer 24. It is considered that this is because the adhesion of the protective film 21 is improved by the effect of drawing the coating liquid by the inclined surface 17.

FIG. 8 shows various essential parts of another substrate 11 which can be used for the optical disk to which the present invention is applied.

8A to 8C, each outer end surface 17 of the substrate 11 is a combination of the same linear inwardly inclined surface 17A as described above and a vertical surface 17B parallel to the substrate thickness direction. The vertical surface 17B is connected to the surface 12 (A), the surface 18 is connected to the surface (B), both sides 12 and 18
The example (C) is shown in FIG.

In this way, no matter where the vertical surface 18B exists, if the inwardly inclined surface 17A is formed,
The flow-down phenomenon of the coating liquid can be suppressed on this surface, and as described above, it is possible to achieve the wraparound to the surface 18 and the reduction in the amount of adhesion to the outer end surface 17.

8 (D) to 8 (F) show that each outer end surface 17 of the substrate 11 has an inward concave curved inclined surface 17A 'or a combination thereof with a vertical surface 17B parallel to the substrate thickness direction. And only the curved inclined surface 17A '(D), vertical surface
17B shows an example in which 17B is connected to the surface 12 (E), and an example in which 17B is connected to the surface 18 (F). The vertical surface 17B may be connected to both surfaces 12 and 18 (not shown).

Thus, even if only the curved inclined surface 17A 'exists or the vertical surface 18B exists at any position, if the curved inward inclined surface 17A' is formed,
On this surface, it is possible to suppress the flow-down phenomenon of the coating liquid by the same action as that of the linearly inclined surface described above.
The wraparound and the reduction of the amount of adhesion to the outer end surface 17 can also be achieved.

In this case, the curved inwardly inclined surface 17A '
Can be formed such that the diameter of the substrate 11 gradually decreases from the one surface 12 side to the other surface 18 side (that is, the diameter at the surface 12 becomes larger than the diameter at the surface 18). desirable. Further, the curvature of the curved inclined surface 17A 'is preferably 3 mmφ or less in the case of a circular arc.

8 (G) and 8 (H), each outer end surface 17 of the substrate 11 is a combination of the same linear inwardly inclined surface 17A and curved inwardly inclined surface 17A 'as described above. In addition, an example (G) in which the linear inwardly inclined surface 17A is provided continuously to the surface 12 and an example (H) provided continuously to the surfaces 12 and 18 are shown. The linear inwardly inclined surface 17A may be connected only to the surface 18 (not shown). Also, the inclined surface 17
Instead of A ′, a linear inclined surface 17A may be used, and the gradient may be larger or smaller than that of other linear inclined surfaces.

By combining both inclined surfaces 17A and 17A 'in this way, the flow-down phenomenon of the coating liquid can be further suppressed on both surfaces, and the effect of sneaking into the surface 18 and reducing the amount of adhesion to the outer end surface 17 can be obtained. Further improve.

In FIG. 8 (I), the outer end surface 17 of the substrate 11 is
FIG. 8 (J) shows an example of a combination of the linear inwardly inclined surface 17A and the outwardly convex surface 17C that are connected to the surface 12, and FIG. 17 is surface 12
An example of a combination of the above-described linear inwardly inclined surface 17A and linearly outwardly inclined surface 17D, which are connected to each other, is shown. The inclined surface 17A may be the above-mentioned concave inclined surface 17A '.

Even if the outwardly facing surfaces 17C and 17D are present as described above, if the inwardly inclined surface 17A is formed, the flow-down phenomenon of the coating liquid can be suppressed at this surface, and as described above,
The wraparound to the surface 18 and the reduction of the amount of adhesion to the side end surface 17 can also be achieved.

For reference, FIG. 9 shows an example of a CD (compact disc) in which the pit 43 occupies, for example, 70% or more of the effective area, and the metal reflective film 44 and the protective film 41 are laminated on the pit 43. Show.

In this CD, the protective film 41 is the reflective film 44.
Since it is necessary to sufficiently cover the outer peripheral edge portion of the substrate 11, a step 42 is formed on the outer peripheral portion of the substrate 11 and a protective film is adhered thereto to firmly and firmly adhere the protective film 41.
I am trying.

In this CD, when the inclined surface 17 or 17A, 17A 'is provided on the outer end surface of the substrate 11 as in the above-mentioned embodiment, the amount of the coating liquid adhered to this inclined surface is reduced, so that the above-mentioned sufficient It becomes impossible to form the protective film 41 in the thickness. Therefore, in the case of the CD as shown in FIG. 9, it is not possible to provide an inclined surface on the outer end surface of the substrate, so that the optical disk according to the present invention has a substrate shape significantly different from that of the CD.

Next, the above-described embodiment of the present invention will be described in more detail by way of specific examples.

Concrete Example 1 A surface having a thickness of 1.2 mm and a CD-format signal pit (the above-mentioned 3: same as below) formed on the inner peripheral portion inside the diameter of 117 mm (the above-mentioned 12: same below) ) Outer diameter φ ₁
Is 120 mm, and the outer diameter φ ₂ of the surface on the opposite side to the signal reading side (the above 18: same as below) is 118 mm,
The cross-sectional shape of the outermost peripheral end face (17 described above) in the radial direction of the disk is a straight line (that is, the above-mentioned outer end face 17 (hereinafter, the same) has an inward linear inclined surface as shown in FIG. 1). Such a disk substrate (the above-mentioned 11: hereinafter the same) was produced by injection molding using a polycarbonate resin. The angle formed by the inclined surface and the normal to the disk surface was 40 degrees.

Next, on the signal recording surface of this disk substrate,
A solution in which 2.0% by weight of pentamethine cyanine dye (NK512 manufactured by Nippon Senshoku Co., Ltd.) was dissolved in methyl cellosolve was applied by spin coating.

In this case, the disk substrate is 50 to 300 per minute.
While rotating at a rotational speed selected from among the rotational speeds of rotation, the above dye solution was continuously applied in a ring shape to the innermost peripheral portion using a dispenser for spin coating, and the rotational speed was 1000 per minute. The excess dye solution was removed by increasing the number of revolutions to a number of revolutions selected from 5000 revolutions. After that, the rotation speed was kept at 1500 rotations per minute, and the solvent contained in the dye solution applied on the disk surface was vaporized and dried.
Needless to say, the rotation speed used for drying is not limited to this.

Observation of the thus-produced optical disc showed some adhesion of the dye to the outermost peripheral surface (outer end surface), but the wraparound of the dye to the outermost peripheral portion of the surface opposite to the coated surface was observed. Therefore, the effect of the present invention was confirmed.

Concrete Example 2 As in Concrete Example 1, the thickness is 1.2 mm and the diameter is 117 mm.
The outer diameter φ _{1 of the} surface where the CD format signal pits are formed on the inner inner side is 120 mm, but the outer diameter φ ₂ of the surface on the opposite side of the signal read side is 119 mm, which is the outermost circumference. A disk substrate whose end surface has a linear cross-sectional shape (inwardly inclined surface of the outer end surface) in the radial direction of the disk was produced by injection molding using a polycarbonate resin. The angle formed by the inclined surface and the normal to the disk surface was 22 degrees.

Using this disk substrate, an optical disk produced by applying a dye solution by spin coating in the same manner as in Example 1 has a small amount of the coating solution adhering to the outer end surface as in Example 1, and the opposite surface. I could not see the wraparound.

Specific Example 3 Similar to Specific Example 1, after the dye solution was applied onto the disk surface by using a dispenser, the dye solution was applied from the surface opposite to the application surface toward the outermost peripheral portion (outer end surface) of the disk. Min 500ml
The rotation speed of the spin coater was increased to 2000 rpm with nitrogen gas being blown at.

Observation of the thus-produced optical disc showed that some dye was attached to the outermost peripheral surface, but the extent thereof was remarkably slight as compared with the case where nitrogen gas was not used. Moreover, of course, the coating liquid did not wrap around to the surface opposite to the coating surface.

Concrete Example 4 Similar to Concrete Example 1, the thickness is 1.2 mm and the diameter is 117 mm.
The outer diameter φ _{1 of the} surface on which the CD-format signal pits are formed on the inner inner side is 120 mm, but the outer diameter φ ₂ of the surface on the opposite side of the signal read side is 119.5 mm. It was made. The angle formed by the outermost peripheral end face of this substrate and the normal line to the disc surface was 12 degrees.

An optical disc prepared by applying a dye solution by a spin coating method using this disc substrate in the same manner as in Example 1 has a diameter of 117 mm at the outer periphery of the surface opposite to the coating surface.
Almost no area where the dye wraps around from the mm to the pit forming portion on the inside was seen.

Comparative Example 1 The thickness is 1.2 mm, and the outer diameter of the surface (the surface 2 in FIG. 10: the same applies hereinafter) on which the CD-format signal pits are formed inside the diameter 117 mm is 120 mm. Yes, the surface on the opposite side to the signal read side (surface 8 in FIG. 10: the same hereafter)
The outer diameter of the disk is 120 mm, and the disk substrate of the outermost peripheral end surface (outer end surface 7 in FIG. 10: hereinafter, the same) has a linear cross-section in the radial direction of the disk (substrate 1 in FIG. 10, the same below. Was produced by injection molding using a polycarbonate resin.

Then, the dye solution was applied by the spin coating method under the same conditions as in Example 1, but the dye was found to wrap around at the outermost peripheral portion of the surface opposite to the surface coated with the dye, and the diameter was from 117 mm. 2% of the outer circumference was observed where the dye had reached the inner pit formation area.

Comparative Example 2 The thickness was 1.2 mm, and the outer diameter of the surface on which the signal format pits of the CD format were formed in the inner peripheral portion inside the diameter of 117 mm was
118 mm, the outer diameter of the signal reading side opposite to this is 120 mm, and the outermost peripheral end surface of the disk substrate has a linear cross-section in the radial direction. It was made by injection molding.

Next, on the signal recording surface of this disk substrate,
A solution in which 2.0% by weight of pentamethine cyanine dye (NK512 manufactured by Nippon Senshoku Co., Ltd.) was dissolved in methyl cellosolve was applied by spin coating.

In this case, while rotating the disc at 100 rpm, the above dye solution was continuously applied in a ring shape to the innermost peripheral portion using a dispenser for spin coating, and then the number of revolutions was changed per minute. Excess dye solution was removed by raising to 2000 revolutions. After that, the rotation speed was kept at 1500 rotations per minute, and the solvent contained in the dye solution applied on the disk surface was vaporized and dried.

Observation of the optical disk thus produced showed that the dye wraps around in the outermost peripheral portion of the surface opposite to the surface coated with the dye, and the dye wraps around from the diameter of 117 mm to the inner pit forming portion. The protruding part was seen in 5% of the outer circumference.

Practical Example 5 The thickness is 1.2 mm, and the outer diameter of the surface where the CD-format signal pits are formed on the inner peripheral portion inside the diameter of 117 mm is
A disk substrate having a diameter of 120 mm and an outer diameter on the opposite side of the signal reading side of 118 mm was produced by injection molding using a polycarbonate resin. However, the radial cross-sectional shape of the disk substrate of the outermost peripheral end surface is a straight line portion (17B described above) that starts from the surface on which the signal pit is formed and forms an angle of 0 degrees with the normal line of the disk surface. There is 0.3 mm, and from this point, the straight line portion that is inwardly inclined at 40 degrees with respect to the normal line toward the outermost peripheral portion of the other surface with a diameter of 118 mm (shown in FIG. 8A where 17A described above exists) It has a shape like.

Next, on the signal recording surface of this disk substrate,
A solution prepared by dissolving 2.0% by weight of pentamethine cyanine dye (NK512, manufactured by Nippon Senshoku Co., Ltd.) in hydroxymethylbutanone, diacetone alcohol, methyl cellosolve or the like was applied by spin coating.

In this case, while rotating the disk substrate at 100 revolutions per minute, the above dye solution was continuously applied in a ring shape to the innermost peripheral portion using a dispenser for spin coating, and then the number of revolutions was changed. The excess dye solution was removed by increasing the speed to 1500 rpm or 2000 rpm. After that, the rotation speed was kept at 1500 rotations per minute, and the solvent contained in the dye solution applied on the disk surface was vaporized and dried.

Observation of the thus-produced optical disc revealed that a slight amount of dye was attached to the outermost peripheral surface (outer end surface) where the angle formed by the normal to the disk surface was 0 °, but was opposite to the coated surface. No dye wraparound was observed in the outermost periphery of the surface.

Specific Example 6 As in Specific Example 5, a portion of the outermost peripheral surface in the radial cross-section of the disk that starts from the surface on which the signal pit is formed and forms an angle of 0 degree with the normal line of the disk surface ( The above-mentioned 17B) is 0.3 mm in the normal direction, and the portion which starts from the surface opposite to the pit forming surface and forms an angle of 0 degrees with the normal to the disk surface (17B above) is 0.3 mm in the normal direction. Then, spin coating was performed in the same manner as in Example 5 on the disk substrate (of FIG. 8C) formed by connecting a straight line (17A described above) between 0.6 mm in the normal direction between them. However, the same effect was obtained.

Practical Example 7 Outer diameter φ of a surface having a thickness of 1.2 mm and a CD-format signal pit formed on the inner peripheral portion inside the diameter of 117 mm
_A disk substrate 1 having a diameter of 120 mm and an outer diameter φ ₂ of the surface on the opposite side of the signal reading side of 118 mm of 118 mm was manufactured by injection molding using a polycarbonate resin. The outer edge of this substrate has the above two surfaces on the disk side of 0.1-0.
It had a shape (FIG. 8 (D)) that was connected by an arc (17A ′ described above) so as to form a concave shape of 5 mm.

Next, on the signal recording surface of this disc substrate,
A solution prepared by dissolving 2.0% by weight concentration of a heptapentamethine cyanine dye (NK114 manufactured by Nippon Senshoku Co., Ltd.) in hydroxymethylbutanone, diacetone alcohol, methyl cellosolve, etc. was applied by spin coating.

In this case, while rotating the disk substrate at 100 rpm, the above dye solution was continuously applied to the innermost peripheral portion in a ring shape using a dispenser for spin coating, and then the number of rotations was changed. The excess dye solution was removed by increasing the speed to 1500 rpm or 2000 rpm. After that, the rotation speed was kept at 1500 rotations per minute, and the solvent contained in the dye solution applied on the disk surface was vaporized and dried. Of course, spin coating conditions are not limited to these.

Observation of the thus-produced optical disc revealed that the adhesion of the dye was found in the concave portion of the outermost peripheral end face, but that the dye did not wrap around to the outermost peripheral part of the surface opposite to the coated surface. It was

Comparative Example 3 The thickness was 1.2 mm, and the outer diameter of the surface on which the signal format pits of the CD format were formed on the inner peripheral portion inside the diameter of 117 mm was
A disk substrate having a diameter of 120 mm and an outer diameter on the opposite side to the signal reading side of 120 mm was prepared by injection molding using a polycarbonate resin. In this case, the cross-sectional shape of the disk substrate on the outermost peripheral surface in the radial direction was an arc (0.1 to 0.5 mm from the straight line connecting the outermost peripheral ends of both surfaces to the outside of the disk).

Then, the dye solution was applied to the signal recording surface under the same conditions as in Example 1, but the dye was found to wrap around at the outermost peripheral portion of the surface opposite to the surface on which the dye was applied, and the diameter 1
Dyes were found to wrap around from 17 mm to the inner pit formation area at 5% or more of the outer circumference.

Although the embodiments of the present invention have been described above, the above embodiments can be further modified based on the technical idea of the present invention.

For example, the shape of the outer end surface 17 of the substrate (particularly the shape of the inclined surface) may be variously changed. Further, the forming method thereof may be other than the injection molding method described above, and the planar shape and material of the substrate are not limited to those described above.

The present invention can be applied to optical discs other than those described above, and any one having a coating layer formed by a spin coating method such as a recording layer or a light reflection layer, and further a protective layer is described above. The present invention can be similarly applied.

[0091]

As described above, according to the present invention, in the information recording medium configured to record information on one surface side of the substrate, at least a part of the outer end surface of the substrate is
A predetermined layer such as a recording layer is formed on one surface of the substrate by spin coating, because the substrate is inclined inward from the one surface side to the other surface side opposite to the one surface side. In doing so, even if the coating liquid leaks from the outer end surface of the base body to the other surface side and wraps around, the inclining surface functions to effectively prevent this.

As a result, it is possible to prevent the coating liquid from wrapping around (adhering) to the other surface side of the substrate, so that the reading beam is sufficiently incident and reflected on the signal recording portion including the pits or grooves and the recording layer. In addition, the signal can be reproduced well and the signal can be recorded well. In addition, since the amount of the coating liquid deposited on the outer end surface of the substrate is also reduced, the amount of the coating liquid that has fallen off after drying and solidification is reduced, and the error rate during signal recording or reproduction can be reduced.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view (cross-sectional view taken along line I-I of FIG. 2) of a main part of an optical disc according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of the optical disc.

FIG. 3 is a sectional view similar to FIG. 1, showing a substrate of the optical disc and a situation at the time of spin coating.

FIG. 4 is an enlarged cross-sectional view of a main part of a mold used for injection molding of the same substrate.

FIG. 5 is a cross-sectional view similar to FIG. 4, in which the substrate and the mold formed by the same injection molding are separated.

FIG. 6 is a sectional view similar to FIG. 1, showing a situation in which a coating layer is formed on a substrate by a spin coating method in another embodiment of the present invention.

FIG. 7 is a sectional view of an optical disc according to another embodiment of the present invention, similar to FIG.

FIG. 8 is an enlarged cross-sectional view of a main part of various substrates according to still another embodiment of the present invention.

FIG. 9 is an enlarged cross-sectional view of a main part of another optical disc (CD).

FIG. 10 is an enlarged cross-sectional view (cross-sectional view taken along the line XX of FIG. 11) of a main part of an optical disc according to a conventional example.

FIG. 11 is a schematic plan view of the optical disc.

FIG. 12 is a cross-sectional view similar to FIG. 10, showing a substrate of the optical disc and a situation at the time of spin coating.

[Explanation of symbols]

 1, 11 ... Disk substrate 2, 12 ... One surface 3 ... Pit or groove 4 ... Recording layer or light-reflecting layer 4a ... Encircling portion of coating liquid 5 ... Read beam (Laser light) 6 ... Reflected light 7, 17 ... Outer end surface of substrate (outermost end surface) 17A, 17A '... Inwardly inclined surface 8, 18 ... Other surface 10, 20 ... Optical disk 13 ・ ・ ・ Gas 21, 22 ・ ・ ・ Mold 30 ・ ・ ・ Normal line

Claims (14)

[Claims] 1. An information recording medium configured to record information on one surface side of a substrate, wherein at least a part of an outer end surface of the substrate is separated from the one surface side of the substrate. An information recording medium, which is inclined inward toward the other surface on the opposite side. 2. The inwardly inclined surface existing on at least a part of the outer end surface of the base body with respect to the normal to one surface of the base body.
The information recording medium according to claim 1, wherein at least one portion has a linearly inclined portion in the range of 20 degrees to 80 degrees. 3. The information recording medium according to claim 1, wherein the inwardly inclined surface existing on at least a part of the outer end surface of the substrate has at least one concave inclined portion. 4. The inwardly sloping surface existing on at least a part of the outer end surface of the base body has at least one linear sloping portion according to claim 2 and at least one recessed sloping portion according to claim 3. The information recording medium according to claim 1, which has. 5. The information recording medium according to claim 1, which is configured as an optical information medium having pits or grooves formed on one surface side of a substrate. 6. At least one of a recording layer for recording optical information, a light reflecting layer and a protective layer on one surface side of a substrate.
6. The two are formed by a spin coating method.
The information recording medium described in. 7. The base is formed in a disk shape, and in the inwardly inclined surface existing on at least a part of the outer end surface thereof, the disk shape is provided from one surface side of the disk-shaped base toward the other surface side. The information recording medium according to claim 5, wherein the substrate has a small diameter. 8. The diameter of one surface side of the disk-shaped substrate is larger than the diameter of the other surface side.
The information recording medium described in. 9. A substrate for an information recording medium according to any one of claims 1 to 8. 10. A method for manufacturing an information recording medium, wherein a predetermined layer is formed on one surface side of the substrate according to claim 9 by a spin coating method. 11. The manufacturing method according to claim 10, wherein a predetermined layer is formed as at least one of a recording layer for recording optical information, a light reflection layer, and a protective layer. 12. The manufacturing method according to claim 10, wherein a gas is sprayed from the other surface side of the substrate toward the outer end surface of the substrate during spin coating. 13. The manufacturing method according to claim 1, wherein the base body is manufactured by an injection molding method. 14. The manufacturing method according to claim 10, wherein pits or grooves are formed on one surface side of the substrate.