JPH10320850A - Production method of optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of obstructing the progress of coating liquid by a step section, to uniformly spread the liquid and to improve the uniformity of the film thickness by supplying the liquid so that it is completely spread over the section formed in the vicinity of the center section of a substrate main surface side, rotating the substrate within the surface direction, rotatively spreading the liquid and covering the main surface side. SOLUTION: A diameter D1 of a substrate 1 is 120 mm, a thickness T1 is 1.2 mm and a diameter D2 of a hole section 2 is 15 mm. At the center section of a main surface 1a, a projecting section 3, in which a diameter D3 is 30 mm and a thickness T2 is 1.5 mm, is provided and a step section 4 having a height of 0.3 mm is formed. Then, ultraviolet curing resin is supplied as the liquid in a ring manner and is spread over the section 4. Then, the substrate 1 is rotated, the liquid is rotatively expanded, a coating is performed and the resin is hardened by ultraviolet rays. Thus, the dispersion in the film thickness in a peripheral direction at a prescribed radius and the dispersion of the film thickness in a radial direction are reduced compared with the case in which the coating liquid is supplied in a ring manner to the substrate 1 having no section 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for supplying a coating liquid near the center of one principal surface of a substrate, and rotating and stretching the substrate in an in-plane direction to thereby rotationally stretch the coating liquid to provide a coating on one principal surface. The present invention relates to a method for manufacturing an optical recording medium to be applied to a recording medium. More specifically, the present invention relates to a method for manufacturing an optical recording medium that has a convex portion provided on one principal surface side of a substrate and supplies a coating liquid to the vicinity of the convex portion so that the coating liquid can be uniformly applied.

[0002]

2. Description of the Related Art In recent years, in the field of information recording, researches on optical information recording systems have been advanced in various places. This optical information recording system is capable of non-contact recording and reproduction, achieving a recording density that is at least an order of magnitude higher than the magnetic recording system, and can be used in read-only, write-once, and rewritable memory formats. It has a number of advantages such as compatibility, and is considered as a system that can realize an inexpensive large-capacity file for a wide range of uses from industrial use to consumer use.

In particular, digital audio discs and optical video discs, which are optical discs compatible with a read-only type memory, are widely used.

In an optical disk such as the above digital audio disk, a reflective film made of a metal thin film such as an aluminum film is formed on an optical disk substrate which is a transparent substrate on which a concavo-convex pattern such as pits or grooves indicating information signals is formed. A protective film for protecting the reflective film from moisture and O ₂ in the atmosphere is formed on the reflective film. When reproducing the information of such an optical disk, a reproduction light such as a laser beam is applied to the concave / convex pattern from the optical disk substrate side, and the information is detected based on a difference between the reflectance of the incident light and the return light.

When manufacturing such an optical disk, first, an optical disk substrate having the above-mentioned concavo-convex pattern is formed by a technique such as injection molding, and a reflective film made of the metal thin film is formed thereon by a technique such as vapor deposition. The protective film is formed, and an ultraviolet curable resin or the like is applied thereon, and then cured to form the protective film.

[0006]

By the way, as described above, when a protective film is formed by applying an ultraviolet curable resin or the like,
It is difficult to make the film thickness uniform. The optical disk substrate is usually provided with a hole serving as a rotation center at the center. When applying the ultraviolet curable resin or the like on the optical disk substrate as described above, the ultraviolet curable resin or the like is supplied concentrically with the rotation center so as to form a ring,
In general, the optical disk substrate is rotated in an in-plane direction and rotationally stretched.

However, when the ultraviolet curable resin is applied in this manner, the film thickness is extremely uniform in the circumferential direction at a position where the radius from the rotation center is a predetermined radius due to the difference in the supply state at the application start position. May lack sexuality.

[0008] Such a variation in the circumferential direction at a predetermined radius of the film thickness is also explained by the following equation 1 showing the relationship between the film thickness h and the radius r from the center of rotation.

[0009]

(Equation 1)

In the above _{equation (} 1), r ₀ indicates the radius from the rotation center at the coating start position, η indicates the viscosity of the ultraviolet curing resin, ρ indicates the density of the ultraviolet curing resin, and ω indicates the rotational angular velocity. And t indicates the rotation time.

In _equation (1), the difference in the supply state at the coating start position gives a variation in the radius r ₀ from the rotation center at the coating start position, and consequently gives a circumferential variation at a predetermined radius of the film thickness. It will be.

As described above, the optical disk substrate is formed with a hole serving as a center of rotation at the center, and this hole prevents the ultraviolet curable resin from stretching. Centrifugal force is the main force applied to the UV-curable resin during rotational stretching, but in general, if there are holes or steps in the direction of fluid movement, the UV-curable resin cannot proceed further, It is difficult to make the thickness uniform.

In view of this, a method of supplying an ultraviolet curable resin while avoiding the center hole and performing rotational stretching is also conceivable. However, for example, as shown in FIG. 13, the film thickness in the radial direction from the rotational center may vary. . In FIG. 13, the horizontal axis is the radius from the rotation center, the vertical axis is the film thickness, the average of the film thickness at each radius is shown by a curve, and the variation of the film thickness is also shown by the solid line in the vertical axis direction. . This is also explained from Equation 1 shown above. That is, if the radius r ₀ from the rotation center at the coating start position is made as small as possible, a uniform film thickness h independent of the radius r from the rotation center can be obtained. Therefore, it is desirable to supply the ultraviolet curable resin without avoiding the center of rotation, in other words, avoiding the central hole.

Accordingly, the present invention has been proposed in view of the actual situation in the related art, in which a coating liquid such as an ultraviolet curable resin is applied with good uniformity to form a coating film with improved uniformity in film thickness. It is an object of the present invention to provide a method of manufacturing an optical recording medium that enables the following.

[0015]

In order to achieve the above object, a method of manufacturing an optical recording medium according to the present invention comprises a step having a step on one principal surface near a center on the principal surface. The coating liquid is supplied so as to spread over the substrate, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction to apply the coating liquid to one main surface side.

According to another aspect of the present invention, there is provided a method of manufacturing an optical recording medium, comprising: providing a convex portion at a central portion on one main surface side of a substrate; The coating liquid is supplied to the section and the substrate is rotated in an in-plane direction, whereby the coating liquid is rotationally stretched and applied to one principal surface side.

In the method of manufacturing an optical recording medium according to the present invention, it is preferable that the convex portion has a substantially circular plane shape about the center of rotation of the substrate.

Further, as a result of intensive studies by the present inventors, it has been found that in order to suppress the variation in film thickness in the radial direction from the rotation center, it is necessary to supply the ultraviolet curable resin without avoiding the rotation center. It has been found that it is sufficient to supply the ultraviolet curable resin by closing the holes.

That is, according to the method of manufacturing an optical recording medium of the present invention, a substantially plate-like member for closing the hole is provided on one principal surface side of a substrate having a hole at the center, and the protrusion is provided. A coating liquid is supplied to the vicinity, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction to apply the coating liquid to one principal surface side.

In the method of manufacturing an optical recording medium according to the present invention, it is preferable that the coating liquid is supplied to a step between the projection and one main surface of the substrate.

Further, in the method for manufacturing an optical recording medium of the present invention, the coating liquid may be supplied to the surface of the projection.

Further, in the method of manufacturing an optical recording medium according to the present invention, it is preferable that the substantially plate-shaped member is a member having a substantially circular plane shape about the center of rotation of the substrate.

Further, in the method of manufacturing an optical recording medium of the present invention, it is preferable that the substantially plate-shaped member is a member having a convex portion on the side facing the substrate, which fits into the hole of the substrate.

In the method of manufacturing an optical recording medium according to the present invention, a coating liquid is supplied so as to spread over a step near a central portion of the main surface side of a substrate having a step portion on one main surface side. Since the coating liquid is rotated and stretched by being rotated in the in-plane direction to apply the coating liquid to one main surface side, the step portion is prevented from hindering the progress of the coating liquid, and the coating liquid spreads evenly. The uniformity of the thickness is improved.

In the method of manufacturing an optical recording medium according to the present invention, a convex portion is provided at a central portion on one main surface side of the substrate, and a coating liquid is supplied to a step portion between the convex portion and one main surface of the substrate. By rotating the substrate in the in-plane direction, the coating liquid is rotated and stretched so that the coating liquid is applied to one main surface side, and since the coating start position is clearly defined by the step portion, the coating start position is Variations in radius from the center of rotation are suppressed, and variations in the circumferential direction at a predetermined radius of the film thickness are suppressed. Further, even if a hole is formed in the center of the substrate, the coating liquid is not supplied to the vicinity of the hole, and the coating liquid is evenly spread without the rotational stretching of the coating liquid being hindered by the hole. The uniformity of the film thickness is improved.

Further, in the method of manufacturing an optical recording medium according to the present invention, a substantially plate-like member for closing the hole is provided on one principal surface side of a substrate having a hole at the center to provide a projection. The coating liquid is supplied to the vicinity of the convex portion, such as a step portion between the convex portion and one main surface of the substrate or the surface of the convex portion, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction, so that the one main surface side Since the coating liquid is supplied without avoiding the rotation center, the radius from the rotation center at the application start position is very small, and the variation in the film thickness in the radial direction from the rotation center is reduced. Can be suppressed. In addition, since the holes of the substrate are closed, the coating does not hinder the rotational stretching of the coating liquid, and the coating liquid spreads evenly, and the uniformity of the film thickness is improved. Furthermore, if the coating liquid is supplied to the step between the convex portion and the one main surface of the substrate as described above, the application start position is defined by the step, and the radius of the radius from the rotation center at the application start position is determined. Variation is suppressed, and variation in the circumferential direction at a predetermined radius of the film thickness is suppressed.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

That is, in the method of manufacturing an optical recording medium according to the present embodiment, as shown in FIG.
At the center of one main surface 1a of the disc-shaped substrate 1 having a convex shape, a convex portion 3 having a substantially circular shape with respect to the hole 2 is provided. 1A shows a plan view of the substrate 1, and FIG. 1B shows a cross-sectional view of the substrate 1. After a coating liquid such as an ultraviolet curable resin is supplied to the step portion 4 between the convex portion 3 and the one main surface 1a of the substrate 1, the substrate 1 is rotated in the in-plane direction with the hole 2 as a rotation center, and A coating liquid such as a curable resin is rotationally stretched and applied to the one main surface 1a side to form a coating film made of an ultraviolet curable resin or the like.

In the method of manufacturing an optical recording medium according to this embodiment,
The coating start position is clearly defined by the step portion 4, and the variation in radius from the rotation center at the coating start position is suppressed, and the variation in the circumferential direction at a predetermined radius of the film thickness of the formed coating film is suppressed. Even when the hole 2 is formed in the center of the substrate 1, the coating liquid is not supplied in the vicinity of the hole 2, and the hole 2 does not hinder the rotational stretching of the coating liquid. Are spread evenly, and a coating film with improved uniformity of the film thickness can be formed.

Further, as a method for manufacturing an optical recording medium to which the present invention is applied, the following method can be mentioned.

That is, in the method of manufacturing an optical recording medium according to the present embodiment, as shown in FIG.
2 and a disk-shaped plate 13 having a larger diameter than the hole 12 as shown in FIG. FIG. 2A is a plan view of the substrate 11, and FIG.
FIG. 3B is a cross-sectional view of the substrate 11, and FIG.
3 is a plan view, and FIG. 3B is a cross-sectional view of the plate 13.

Then, a plate member 13 is arranged on one main surface 11a of the substrate 11 so as to cover the hole portion 12 to form a projection. Next, a coating liquid such as an ultraviolet curable resin is supplied to the vicinity of the convex portion such as a step portion between the convex portion and one main surface 11a of the substrate 11 or the surface of the convex portion. There is also a method of forming a coating film made of an ultraviolet-curable resin or the like by rotating the coating solution inward, rotating and stretching a coating liquid such as an ultraviolet-curable resin and applying the coating liquid to the one main surface 11a side. However, in this case, one main surface 13a which is the surface of the plate 13 facing the substrate 11
To apply an adhesive.

Further, a manufacturing method as described below can also be mentioned. That is, in the manufacturing method of the optical recording medium of the present embodiment, as shown in FIG. 4, a flat annular shape having a hole 22 which is a through hole at the center and surrounding the hole 22 near the center of one main surface 21a. A disk-shaped substrate 21 having a groove portion 24 and a disk-shaped plate member 23 having a diameter larger than the outer peripheral portion of the groove portion 24 as shown in FIG. 5 are prepared. Here, FIG.
FIG. 4A is a plan view of the substrate 21, and FIG.
5A is a plan view of the plate 23, and FIG. 5B is a cross-sectional view of the plate 23. As shown in FIG. In the plate member 23, the one main surface 23a side is formed in a truncated cone shape having the main surface 25 as the upper surface, and the main surface 23b opposite to the one main surface 23a is fitted into the hole 22. Convex part 2
6 are provided.

Then, the plate material 23 is closed on the one main surface 21a of the substrate 21 by fitting the convex portions 26 into the holes 22 and the groove portions 24 are formed.
It is also arranged so as to cover it to form a projection. Next, a coating liquid such as an ultraviolet curable resin is supplied to the vicinity of the convex portion such as a step portion between the convex portion and one main surface 21a of the substrate 21 or the surface of the convex portion. Rotate inward to rotate and stretch the coating liquid such as UV-curable resin to form one main surface 2
A coating film made of an ultraviolet curable resin or the like is formed by coating on the 1a side. Note that, in this example, the board 21 is
Since the convex portion 26 fitted into the hole portion 22 is provided, the plate member 23 does not separate from the substrate 21 during rotational stretching.

In the method for manufacturing an optical recording medium as described above, since the coating liquid is supplied without avoiding the center of rotation, the radius from the center of rotation at the coating start position is very small, and the distance from the center of rotation is small. Variations in the film thickness in the radial direction can be suppressed. Further, the holes 1 of the substrates 11 and 21 are formed.
Since the holes 2 and 22 are closed, the coating liquid is spread evenly without the holes 12 and 22 obstructing the rotation and stretching of the coating liquid, and a coating film with uniformity of the film thickness can be formed. Becomes In the substrate 21, since the groove 24 is also covered by the plate 23, the coating liquid is not even hindered by the groove 24, and the coating liquid is spread evenly and the uniformity of the film thickness is improved. Can be formed. Furthermore,
As described above, the projections and the main surfaces 11a, 11a of the substrates 11, 21 are provided.
If the coating liquid is supplied to the step portion with respect to 1a, the application start position is defined by the step portion, the variation in the radius from the rotation center at the application start position is suppressed, and the circumference at a predetermined radius of the film thickness is suppressed. Variations in direction are also suppressed.

In the method of manufacturing an optical recording medium in which the plate members are arranged as the convex portions as described above, if the plate members are removed after applying a coating liquid such as an ultraviolet curable resin, the plate members are removed. This is preferable because it can be washed and reused, which contributes to cost reduction during mass production.

[0037]

EXAMPLES Next, in order to confirm the effects of the present invention, the following experiments were conducted.

Experimental Example 1 In this experimental example, one principal surface 1 as shown in FIG.
A substrate 1 having a convex portion 3 on the a-side and a substrate having a similar shape but no convex portion were prepared, and the variation in film thickness when an ultraviolet-curable resin was applied to these was investigated.

[0039] That is, first, the substrate 1 shown in FIG. 1 D ₁
The diameter and 120 (mm), the diameter of the hole 2 shown in figure D ₂ and 15 (mm), the diameter of the convex portion 3 shown in the figure D ₃ and 40 (mm), in the drawing T ₁ and 1.2 the thickness of the portion other than the convex portion 3 of the substrate 1 shown (mm), the thickness of the portion where the convex portion 3 of the substrate 1 shown in the drawing T ₂ are formed 1.5 (m
m) and then, the main surface 1a of the substrate 1 of the convex portion 3 shown in the figure T ₃
From the height, in other words, the height of the step portion 4 is 0.3 (m).
As m), a substrate 1 as previously shown in FIG. 1 was prepared. Further, a substrate having a configuration similar to that of the above-described substrate 1 and having no projection was also prepared.

Next, an ultraviolet-curable coating liquid is applied as a coating liquid at a position of a radius of 20 (mm) from the center of the hole 2 which is the center of rotation of one principal surface 1a of the substrate 1 having the projection 3 on which the projection 3 is formed. The resin was supplied in an annular shape, applied by rotating and stretching, and then cured. That is, here, the ultraviolet curable resin, which is a coating liquid, is supplied to the step portion 4 and is supplied so as to spread over the step portion 4.

On the other hand, even on a substrate having no convex portion, an ultraviolet curable resin is supplied as a coating liquid in a ring shape at a position of a radius of 20 (mm) from the center of the hole serving as the center of rotation, and the substrate is rotated and drawn. And then cured.

Then, the thickness of the coating film made of the ultraviolet curable resin on these substrates was examined. Substrate 1 having convex portion 3
6 and FIG. 7 show the result of the substrate having no projection. 6 and 7, the horizontal axis is the radius from the rotation center, the vertical axis is the film thickness, the average of the film thickness at each radius is shown by a curve, and the variation of the film thickness is also shown by the solid line in the vertical axis direction. Show.

From the results of FIGS. 6 and 7, when the present invention is applied and the substrate having the convex portions 3 is used, the case where the substrate having no convex portions is used is more effective than the case where the substrate having no convex portions is used. It can be seen that the variation in the circumferential direction and the variation in the film thickness in the radial direction from the rotation center are suppressed.

That is, in the case where the present invention is applied, the coating start position is clearly defined by the step portion 4, the variation in the radius from the rotation center at the coating start position is suppressed, and the coating film to be formed is formed. It was confirmed that variation in the circumferential direction at a predetermined thickness radius was suppressed.
Even when the hole 2 is formed in the center of the substrate 1, the coating liquid is not supplied in the vicinity of the hole 2, and the hole 2 does not hinder the rotational stretching of the coating liquid. Was evenly spread and the uniformity of the film thickness was also improved.

Experimental Example 2 In this experimental example, the substrate 11 as shown in FIG.
And a plate material 13 as shown in FIG. 3 is prepared, and in the case where the plate material 13 is arranged on the substrate 11 to form a convex portion and in the case where only the substrate 11 is used, an ultraviolet curable resin is applied, and The variability was investigated.

[0046] That is, first, the substrate 1 shown in FIG. 2 D ₁₁
1 of a diameter and 120 (mm), the hole 1 shown in the figure D ₁₂
The second diameter and 15 (mm), the substrate 11 shown in the figure T ₁₁
Was set to 1.2 (mm), and a substrate 11 as shown in FIG. 2 was prepared. Further, plate member 13 shown in FIG. 3 D ₁₃
The diameter and 37 (mm), was prepared a plate material 13 as shown in FIG. 3 above the thickness of the plate 13 shown in the figure T ₁₃ as 0.14 (mm).

Next, the plate material 1 is placed on one main surface 11a of the substrate 11.
3 is arranged so as to cover the hole portion 12 to form a convex portion.
An ultraviolet-curable resin was supplied as a coating liquid to a position corresponding to the center of the hole portion 12 serving as the rotation center of the substrate 11 on the three surfaces, and the coating was performed by rotating and stretching, followed by curing. That is, here, the ultraviolet curable resin, which is a coating liquid, is supplied to the surface of the projection formed by the plate 13. However, in this case, one principal surface 1 which is a surface of the plate 13 facing the substrate 11.
An adhesive is applied to 3a. The substrate 11 on which the ultraviolet-curable resin was applied in this manner is referred to as Sample 1.

Further, a plate member 13 is disposed on one main surface 11a of the substrate 11 so as to cover the hole portion 12 so as to form a convex portion, and a radius of 12.5 from the center of the hole portion 12 serving as the rotation center of the substrate 11 is formed.
(Mm), an ultraviolet curable resin was supplied in a ring shape as a coating liquid, and the resin was rotated and stretched, and then cured.
That is, the ultraviolet curing resin, which is a coating liquid, is supplied to the step between the projection formed by the plate member 13 and the one main surface 11a of the substrate 11, and is supplied so as to spread over the step. . However, also in this case, an adhesive is applied to one main surface 13a of the plate material 13 facing the substrate 11. The substrate 11 coated with the ultraviolet curable resin in this manner is referred to as Sample 2.

Further, an ultraviolet curable resin is supplied as a coating liquid in a ring shape at a position having a radius of 15 (mm) from the center of the hole portion 12 serving as the rotation center of the substrate 11 as described above, and is rotated and stretched for coating. And then cured. The substrate 11 on which the ultraviolet curable resin was applied in this manner is referred to as Sample 3.

Then, the thickness of the coating film made of the UV-curable resin of these samples was examined. FIG. 8 shows the result of Sample 1, FIG. 9 shows the result of Sample 2, and FIG. 10 shows the result of Sample 3. 8 to 10, the horizontal axis is the radius from the rotation center, the vertical axis is the film thickness, the average of the film thickness at each radius is shown by a curve, and the variation of the film thickness is also shown by the solid line in the vertical axis direction. Show.

Comparing the results of FIGS. 8 and 9 with those of FIG. 10, the case where the present invention is applied and the projections are formed on the substrate 11 by the plate material 13 is larger than the case where only the substrate 11 is used.
It can be seen that the variation in the film thickness in the radial direction from the rotation center is suppressed.

That is, in the case where the present invention is applied, since the coating liquid is supplied without avoiding the center of rotation, the radius from the center of rotation at the application start position is very small, and the radial direction from the center of rotation is small. It was confirmed that the variation of the film thickness was suppressed. Further, when the present invention is applied, since the holes 12 of the substrate 11 are closed, the coating liquid is uniformly spread without the holes 12 hindering the rotational stretching of the coating liquid. It was also confirmed that the uniformity of the composition was improved.

8 and 9, the sample 2 shown in FIG. 9 has a smaller thickness than the sample 1 shown in FIG. 8, for example, at a position where the radius from the rotation center is 25 (mm). The variation in the circumferential direction is suppressed.
9 and FIG.

That is, if the coating liquid is supplied to the step between the projection and the one main surface 11a of the substrate 11, the application start position is defined by the step, and the rotation at the application start position is performed. It was confirmed that the variation in radius from the center was suppressed, and the variation in the circumferential direction at a predetermined radius of the film thickness was suppressed.

Experimental Example 3 In this experimental example, the substrate 21 shown in FIG.
The plate 13 as shown in FIG. 3 was disposed on the first main surface 21a, the hole 22 was closed with the plate 13, and the film thickness was measured when coating was performed.

That is, first, the substrate 2 indicated by D ₂₁ in FIG.
1 is 120 (mm) in diameter, and a groove 2 indicated by D ₂₄ in the drawing
4 has a diameter of 38 (mm), a width of the groove 24 indicated by W ₂₄ in the figure is 1 (mm), and a groove 2 indicated by L ₂₄ in the figure.
4 was prepared at a depth of 0.2 (mm) to prepare a substrate 21 as shown in FIG. Further, the plate 1 shown in FIG. 3 D ₁₃
3 of diameter and 37 (mm), sheet material 13 shown in the figure T ₁₃
Was set to 0.14 (mm) to prepare a plate 13 as shown in FIG.

Next, the plate member 13 is disposed on the one main surface 21a side of the substrate 21 where the groove portion 24 is provided so as to close the hole portion 22. Then, the diameter D _{13 of the} plate 13 is 37 (mm), the diameter D _{24 at} the outer peripheral edge of the groove 24 of the substrate 21 is 38 (mm), and the width W _{24 of the} groove ₂₄ is 1 (mm). Therefore, the plate 13 reaches only the inner peripheral side of the groove 24.

Then, an ultraviolet-curing type coating liquid is applied on the inner peripheral side of a position of a radius 19 (mm) from a hole 22 which is a rotation center on one main surface 21a of the substrate 21 on which the plate member 13 is arranged as described above. The resin was supplied in an annular shape, rotated and stretched to apply an ultraviolet-curable resin, and then cured. That is, the ultraviolet curable resin is supplied into the groove 24. The substrate coated in this way is referred to as Sample 4.

Further, an ultraviolet-curable resin is applied as a coating liquid in an annular shape from the hole 22 serving as the center of rotation on the one main surface 21a of the substrate 21 on which the plate material 13 is arranged as described above to a position of a radius 24 (mm). The resin was supplied, rotated and stretched to apply an ultraviolet curable resin, and then cured. That is, the ultraviolet curable resin is supplied to the outer peripheral side beyond the groove 24. The substrate coated in this way is referred to as Sample 5.

Then, the thickness of the coating film made of the ultraviolet-curable resin of these samples was examined. FIG. 11 shows the result of Sample 4 and FIG. 12 shows the result of Sample 5.
11 and 12, the horizontal axis is the radius from the rotation center, the vertical axis is the film thickness, the average of the film thickness at each radius is shown by a curve, and the variation of the film thickness is also shown by the solid line in the vertical axis direction. Show.

From the results shown in FIGS. 11 and 12, the thickness of Sample 5 in which the coating liquid was supplied to the outer peripheral side beyond the groove 24 was more uniform than that of Sample 4 in which the coating liquid was supplied in the groove 24. I have. That is, it was confirmed that by supplying the coating liquid so as to spread over the step portion, it is possible to prevent the step portion from hindering the progress of the coating liquid.

[0062]

As is apparent from the above description, in the method of manufacturing an optical recording medium according to the present invention, a substrate having a step on one principal surface is provided with a step near the center on the principal surface. Since the coating liquid is supplied so as to spread, the coating liquid is rotated and stretched by rotating the substrate in the in-plane direction so that the coating liquid is applied to one main surface side. And the coating liquid can be spread evenly to form a coating film with improved film thickness uniformity.

In the method of manufacturing an optical recording medium according to the present invention, a convex portion is provided at a central portion on one main surface side of the substrate, and a coating liquid is supplied to a step portion between the convex portion and one main surface of the substrate. By rotating the substrate in the in-plane direction, the coating liquid is rotated and stretched so that the coating liquid is applied to one main surface side, and since the coating start position is clearly defined by the step portion, the coating start position is Variations in radius from the center of rotation are suppressed, and variations in the circumferential direction at a predetermined radius of the film thickness are suppressed. Further, even if a hole is formed in the center of the substrate, the coating liquid is not supplied to the vicinity of the hole, and the coating liquid is evenly spread without the rotational stretching of the coating liquid being hindered by the hole. It is possible to form a coating film with improved uniformity of the film thickness.

Further, in the method of manufacturing an optical recording medium according to the present invention, a substantially plate-like member for closing the hole is provided on one principal surface side of a substrate having a hole at the center to provide a projection. The coating liquid is supplied to the vicinity of the convex portion, such as a step portion between the convex portion and one main surface of the substrate or the surface of the convex portion, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction, so that the one main surface side Since the coating liquid is supplied without avoiding the rotation center, the radius from the rotation center at the application start position is very small, and the variation in the film thickness in the radial direction from the rotation center is reduced. Can be suppressed. In addition, since the holes in the substrate are closed, the coating does not hinder the rotational stretching of the coating liquid, and the coating liquid spreads evenly, enabling the formation of a coating film with improved film thickness uniformity. Becomes Furthermore, if the coating liquid is supplied to the step between the convex portion and the one main surface of the substrate as described above, the application start position is defined by the step, and the radius of the radius from the rotation center at the application start position is determined. Variation is suppressed, and variation in the circumferential direction at a predetermined radius of the film thickness is suppressed.

[Brief description of the drawings]

FIG. 1 is a plan view and a cross-sectional view illustrating an example of a substrate used in a method for manufacturing an optical recording medium to which the present invention is applied.

FIGS. 2A and 2B are a plan view and a cross-sectional view showing another example of a substrate used in a method for manufacturing an optical recording medium to which the present invention is applied.

FIG. 3 is a plan view and a cross-sectional view illustrating an example of a plate material used in a method for manufacturing an optical recording medium to which the present invention is applied.

FIG. 4 is a plan view and a cross-sectional view showing another example of the substrate used in the method for manufacturing an optical recording medium to which the present invention is applied.

FIG. 5 is a plan view and a cross-sectional view showing another example of a plate material used in the method for manufacturing an optical recording medium to which the present invention is applied.

FIG. 6 is a characteristic diagram showing an example of a relationship between a radius and a film thickness.

FIG. 7 is a characteristic diagram showing another example of the relationship between the radius and the film thickness.

FIG. 8 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

FIG. 9 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

FIG. 10 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

FIG. 11 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

FIG. 12 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

FIG. 13 is a characteristic diagram showing still another example of the relationship between the radius and the film thickness.

[Explanation of symbols]

1,11,21 Substrate, 1a, 11a, 21a, 23a
One main surface, 2, 12, 22 holes, 3, 26 protrusions, 4
Step part, 13,23 plate material

Claims (8)

[Claims] 1. A coating liquid is supplied to a substrate having a stepped portion on one principal surface side in the vicinity of a central portion on the principal surface side, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction. A method for manufacturing an optical recording medium to be applied to a main surface, wherein a coating liquid is supplied so as to spread over a step near a central portion on one main surface of a substrate. 2. An optical recording medium for supplying a coating liquid near a central portion on one main surface side of a substrate and rotating and stretching the coating liquid in an in-plane direction to apply the coating liquid on one main surface side. The method for producing an optical recording medium according to claim 1, wherein a convex portion is provided at a central portion on one main surface side of the substrate, and a coating liquid is supplied to a step between the convex portion and the one main surface of the substrate. 3. The method for manufacturing an optical recording medium according to claim 2, wherein the convex portion has a substantially circular shape in a plane about the center of rotation of the substrate. 4. A coating liquid is supplied in the vicinity of a central portion on one main surface side of a substrate having a hole at the center, and the coating liquid is rotated and stretched by rotating the substrate in an in-plane direction, thereby rotating and stretching the coating liquid. In the method for manufacturing an optical recording medium to be applied to a substrate, a substantially plate-shaped member that closes the hole is disposed at a central portion on one main surface side of the substrate, a convex portion is provided, and a coating liquid is supplied near the convex portion. Characteristic method for producing an optical recording medium. 5. The method for manufacturing an optical recording medium according to claim 4, wherein the coating liquid is supplied to a step between the projection and one main surface of the substrate. 6. The method for manufacturing an optical recording medium according to claim 4, wherein the coating liquid is supplied to the surface of the projection. 7. The method for manufacturing an optical recording medium according to claim 4, wherein the substantially plate-shaped member is a member having a substantially circular plane shape about the center of rotation of the substrate. 8. The method for manufacturing an optical recording medium according to claim 4, wherein the substantially plate-shaped member is a member having a convex portion which fits into a hole of the substrate on the side facing the substrate.