JP2006048878A - Manufacturing method of optical recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an optical recording medium by which the variation of the film thickness of a formed thin film can be reduced by controlling accurately a film thickness distribution in the radial direction when the thin film of a light transmission layer that requires the high accuracy of a film thickness is formed on the substrate by a spin coat method. <P>SOLUTION: A disk substrate 1 is placed on a spin table 2 and fixed, a center hole of the disk substrate 1 is closed by a center cap 8, and a resin material is dropped on the center cap 8 so as to come into contact with a peripheral plane of a resin contact part 15. The spin table 2 is rotated and the dropped resin material is expended on the whole main plane of the disk substrate 1. When the thickness of the resin material extended on the main plane of the disk substrate 1 is thinned as approaching the outer peripheral side, the diameter of the resin contact part 15 is expanded, when the thickness is thickened as approaching the outer peripheral side, the diameter A of the resin contact part 15 is optimized by reducing the diameter of the resin contact part 15. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing an optical recording medium such as an optical disk.

  High-density recording of an optical recording medium can be achieved by shortening the wavelength of laser light used in the optical pickup, increasing the numerical aperture (NA) of the objective lens, and reducing the size of the focused spot UV.

  For example, a CD (Compact Disc) has a laser beam wavelength of 780 nm, a numerical aperture (NA) of 0.45, and a recording capacity of 650 MB (megabytes). In a DVD-ROM (Digital Versatile Disc-ROM), the laser beam wavelength is 650 nm, the numerical aperture (NA) is 0.6, and the recording capacity is 4.7 GB (gigabytes). ing. Further, in the next-generation disc-shaped optical recording medium (so-called Blu-ray Disc (trade name), hereinafter abbreviated as BD disc as appropriate), light transmission of about 100 μm (0.1 mm) on the signal reading surface side of the disc. By forming a protective film with a laser beam wavelength of 450 nm or less and NA of 0.78 or more, a single layer can have a large capacity of 22 GB or more.

  In CD and DVD, the dimension from the signal reading surface (disk surface) of the disk to the reflective film on which the signal is recorded is relatively large. That is, it is about 1.2 mm for CD and about 0.6 mm for DVD. On the other hand, in a BD disc, this dimension is about 0.1 mm. When a single-sided dual-layer optical disc is formed, the intermediate layer formed between the two optical recording layers needs to be thinned to about 20 μm to 30 μm. A high thickness accuracy is required for the light-transmitting layers such as the protective film and the intermediate layer.

  As an example of a method for forming a film-like layer such as a protective film and an intermediate layer on a substrate, a spin coating method is known. For example, in the formation of the light transmitting layer, a resin material such as a light transmissive ultraviolet curable resin is dropped on the disk substrate, and the dropped resin material is spread evenly on the entire surface of the disk substrate by a spin coater. A curing method is generally used.

  FIG. 10 is an example of a spin coater used for forming a light transmission layer of an optical disc. The center hole of the disk substrate 101 is fitted to the center pin 104, and the disk substrate 101 is placed on the spin table 102. The disk substrate 101 placed on the spin table 102 is attracted and fixed to the spin table 102 by a vacuum channel 103 connected to a vacuum source (not shown). In this state, while rotating the spin table 102 at a low speed with a spindle motor (not shown) or the like, a light-transmitting ultraviolet curable resin is dropped from the dropping nozzle 105, and then the spin table 102 is rotated at a high speed, thereby dropping the ultraviolet curable resin. Is extended over the entire main surface of the disk substrate 101. Thereafter, by irradiating with ultraviolet rays, the ultraviolet curable resin is cured to form a light transmission layer. However, this method has a problem that the film thickness of the inner peripheral portion of the disk substrate 101 becomes thin.

  Therefore, a method of closing the center hole of the disk substrate with a closing member and dropping a resin material such as an ultraviolet curable resin from the vicinity of the center of the disk substrate is conceivable.

  For example, Patent Document 1 below describes a method using a closing member that includes a disk part for closing a center hole of a disk substrate and a support shaft integrated in the center of the disk part. .

JP 2001-351275 A

  According to this method, the film thickness difference between the inner peripheral portion and the outer peripheral portion of the disk substrate can be greatly improved. Moreover, since the support shaft is provided in the disc part, handling of the closing member is facilitated.

  However, the film thickness cannot be delicately controlled by simply closing the center hole of the disk substrate and dropping the resin material near the center of the disk substrate. In particular, in a next-generation high-density recording optical disk such as a Blu-ray Disc, the standard of variation in the film thickness of the light transmission layer in the disk surface is the average value of the film thickness in the inner periphery (R22 mm to R23 mm). On the other hand, it is defined very strictly as ± 2 μm. For this reason, it is necessary to minimize the variation in the thickness in the radial direction and to eliminate as little as possible the difference in thickness between the inner and outer circumferences, but it is difficult to control the thickness easily and accurately. there were.

  Therefore, the object of the present invention is to form a film by controlling the film thickness distribution in the radial direction with high precision when a thin film such as a light transmission layer, which requires high film thickness accuracy, is formed on a substrate by spin coating. It is an object of the present invention to provide a method for manufacturing an optical recording medium that can reduce variations in the thickness of a thin film.

  In order to achieve the above object, the present invention provides a method for manufacturing an optical recording medium having an information signal layer and a thin film formed by spin coating on a main surface of a substrate. The center hole of the substrate is placed at the center of the disk portion and the shaft by a closing member having a step of placing and fixing, a disc portion covering the center hole, and a shaft having one end attached to the center of the disc portion. A step of closing the spin table so as to be positioned on the rotation axis of the spin table; a step of dropping a resin material on the closing member so as to contact the peripheral surface of the shaft; and a resin dropped on the closing member by rotating the spin table Extending the material to the entire main surface of the substrate, and when the thickness of the resin material stretched on the main surface of the substrate becomes thinner as it approaches the outer peripheral side of the substrate, the diameter of the shaft is increased, If the thickness of the resin material stretched on the main surface of the plate is increased as it approaches the outer peripheral side, a method of manufacturing an optical recording medium and performing optimized to reduce the diameter of the shaft.

  According to the present invention, the substrate having the center hole is placed and fixed on the spin table, and by a closing member having a disc portion covering the center hole, and a shaft having one end attached to the center of the disc portion, The center hole of the substrate is closed so that the center of the disk and the shaft is located on the rotation axis of the spin table, and a resin material is dropped on the closing member so as to contact the peripheral surface of the shaft, and the spin table is rotated. When the resin material dripped on the closing member is stretched over the entire main surface of the substrate, if the thickness of the resin material stretched on the main surface of the substrate decreases as it approaches the outer peripheral side of the substrate, If the diameter of the resin material is increased and the thickness of the resin material stretched on the main surface of the substrate becomes thicker as it approaches the outer peripheral side, by optimizing to reduce the diameter of the shaft, in the radial direction of the substrate Variation in film thickness can be reduced.

  Therefore, when forming a thin film that requires high film thickness accuracy, such as a light-transmitting layer of Blu-ray Disc, on the substrate by spin coating, the film thickness distribution in the radial direction can be controlled with very high accuracy. And variation in film thickness within the main surface of the substrate is reduced. Accordingly, even when a thin film such as a light-transmitting layer of Blu-ray Disc whose film thickness accuracy is strictly regulated is formed, the yield can be improved and the manufacturing cost can be suppressed.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of the configuration of a spin coater applicable to an embodiment. Reference numeral 1 denotes a disk substrate on which a thin film is formed by spin coating. The disk substrate 1 is formed in a disk shape having a center hole.

  The spin table 2 has a mounting surface on which the disk substrate 1 is mounted, and is formed of a metal material such as aluminum, for example. The spin table 2 is configured to be rotatable at a predetermined rotational speed in a direction perpendicular to the placement surface (for example, a direction indicated by an arrow) by a drive source such as a spindle motor (not shown). In addition, the rotation direction and rotation speed of the spin table 2 can be changed as desired.

  The spin table 2 has a center pin 3 on which the center hole of the disk substrate 1 is fitted on the mounting surface. The center pin 3 protrudes on the mounting surface located on the rotation axis of the spin table 2 and positions the disc substrate 1 and the center cap 8 installed on the disc substrate 1.

  In this example, the center pin 3 is composed of one member integrated with the spin table 2, but the center pin 3 is composed of a member different from the spin table 2, and is placed on the mounting surface of the disk substrate 1. It may be detachable. In the center portion of the center pin 3, a recess 4 into which the center cap 8 is fitted is provided. Further, the peripheral end portion of the center pin 3 is chamfered so that the center hole of the disk substrate 1 can be easily fitted.

  The spin table 2 is provided with a vacuum channel 5 for adsorbing the main surface of the disk substrate 1 to the mounting surface and a vacuum channel 6 for adsorbing the center cap 8 to the mounting surface side.

  One end of the vacuum channel 5 communicates with the mounting surface of the spin table 2 and the other end communicates with a vacuum source outside the spin table 2 (not shown). For example, a suction port is provided on the placement surface of the spin table 2, and the placement surface of the spin table 2 and the vacuum channel 5 communicate with each other through this suction port. For example, the suction port is constituted by a plurality of holes provided at equal intervals on a concentric circle with the center of the placement surface. The suction port is not limited to a hole, and may be configured by a groove.

  One end of the vacuum channel 6 communicates with the recess 4 of the center pin 3, and the other end communicates with a vacuum source outside the spin table 2 (not shown). The vacuum source may be the same as that communicating with the other end of the vacuum channel 5 or may be different.

  The disk substrate 1 placed on the spin table 2 is positioned by fitting a center hole to the center pin 3, and suction of a vacuum source (not shown) communicating through the vacuum channel 5 allows Fixed in close contact with the mounting surface.

  The fixing of the disk substrate 1 to the mounting surface of the spin table 2 is not limited to this. For example, the positioning of the disk substrate 1 on the mounting surface of the spin table 2 may be configured such that the outer periphery of the disk substrate 1 is regulated.

  A detachable center cap 8 is installed on the disk substrate 1 placed on the spin table 2. By fitting the center cap 8 into the recess 4 of the center pin 3, the center cap 8 is positioned, and the center cap 8 is moved by the suction of a vacuum source (not shown) passing through the vacuum flow path 6. 2 is fixed in a state of being adsorbed to the mounting surface side.

  The fixing of the center cap 8 to the spin table 2 is not limited to this. For example, the center cap 8 may be fixed to the spin table 2 using a magnetic force such as a magnet chuck, instead of sucking and fixing the center cap 8 using the vacuum flow path 6.

  The dropping nozzle 7 is connected to a resin supply unit (not shown), and is a nozzle that drops a resin material for forming a thin film such as an ultraviolet curable resin supplied from the resin supply unit. The dripping nozzle 7 is movable on the spin table 2, for example, and the dripping position of the resin material can be adjusted.

  Here, with reference to FIG. 2, the center cap 8 that closes the center hole of the disk substrate 1 placed on the spin table 2 will be described in detail. The center cap 8 is made of, for example, a metal material such as stainless steel, and has a configuration in which the fitting portion 9, the disc portion 10, and the shaft portion 11 are integrated.

  The fitting portion 9 has a shape that fits into the recess 4 provided in the center pin 3. By fitting the fitting portion 9 into the recess 4, the center cap 8 is positioned on the center pin 3. A disc portion 10 is provided on the fitting portion 9, that is, on the dropping surface side of the resin material of the fitting portion 9.

  The disc portion 10 has a disc shape that covers the center hole of the disc substrate 1 placed on the placement surface and covers the inner peripheral portion of the disc substrate 1. The disc portion 10 is provided in the fitting portion 9 so that the center of the disc is located on the rotation axis of the spin table 2.

  The disc part 10 has the horizontal part 12, the inclination part 13, and the support part 14 in order from the inner peripheral side. The horizontal portion 12 has a parallel surface substantially parallel to the mounting surface of the disk substrate 1 on the resin material dropping surface side. The inclined portion 13 has an inclined surface inclined toward the placement surface side from the inner peripheral side toward the outer peripheral direction on the dropping surface side of the resin material. The support portion 14 has a vertical surface that is substantially perpendicular to the mounting surface, and a contact surface that contacts the inner periphery of the disk substrate 1 in an annular shape.

  A gap 17 is provided between the disc portion 10 and the center pin 3, and the contact surface of the support portion 14 contacts and supports the inner peripheral portion of the disk substrate 1 with no gap by the gap 17. Is done.

  The disk portion 10 is not limited to such a shape, and may have other shapes as long as the dropped resin material extends on the main surface of the disk substrate 1 by the rotation of the spin table 2. May be. For example, the dropping surface side of the resin material of the disc portion 10 is configured by a parallel surface, an inclined surface, and a vertical surface, but is not limited thereto, and is configured only by an inclined surface, or by only a parallel surface and an inclined surface. Alternatively, it may be composed of only parallel planes and vertical planes. Moreover, it is good also as a structure using a curved surface.

  One end of a shaft portion 11 for facilitating handling such as attachment / detachment of the center cap 8 is attached to the resin dropping surface side of the disc portion 10 so as to be positioned on the rotation axis of the spin table 2. The shaft portion 11 includes a resin contact portion 15 on the mounting surface side, and a gripping portion 16 that is the protruding end side, that is, the other end side of the shaft portion 11. The resin material dropped on the center cap 8 by the dropping nozzle 7 is in contact with the peripheral surface of the resin contact portion 15.

  As a result of trial and error, the inventor of the present application changes the radius of the thin film formed on the main surface of the disk substrate 1 by changing the diameter of the shaft of the resin contact portion 15 in contact with the resin material dropped on the center cap 8. It came to know that the dispersion | variation in the film thickness average in a direction can be controlled. Specifically, it has been found that as the diameter of the shaft of the resin contact portion 15 is increased, the film thickness in the radial direction becomes thinner on the inner peripheral side of the disk substrate 1 and thicker on the outer peripheral side. Thus, it has been found that by appropriately optimizing the diameter of the shaft of the resin contact portion 15, the variation in the film thickness in the radial direction can be easily improved.

  Therefore, the diameter A of the shaft of the resin contact portion 15 is configured with this optimized value. That is, when the thickness of the resin material stretched on the main surface of the disk substrate 1 becomes thinner as it approaches the outer peripheral side of the disk substrate 1, the diameter of the shaft of the resin contact portion 15 is increased to increase the main diameter of the disk substrate 1. In the case where the thickness of the resin material stretched on the surface becomes thicker as it approaches the outer peripheral side, the diameter of the shaft of the resin contact portion 15 is reduced to appropriately optimize the diameter of the shaft, and the optimized diameter Is the diameter A of the resin contact portion 15.

  The gripping portion 16 is a portion that is gripped when the center cap 8 detaching machine (not shown) detaches the center cap 8. The shaft diameter B of the gripping portion 16 is configured to have a value corresponding to the attachment / detachment machine. The shape of the gripping portion 16 is not particularly limited. If the gripping portion 16 is suitable for a detachable machine, for example, a portion corresponding to the shaft portion 11 is made of a resin having a diameter A such as a center cap 18 shown in FIG. It is good also as a structure which comprised only the contact part 19 and eliminated the level | step difference of the axis | shaft.

  Next, an example of forming a thin film by the spin coat method using the center cap 8 will be described with reference to FIG. First, as shown in FIG. 4A, the disk substrate 1 is placed on the spin table 2 of the spin coater. Next, a center cap 8 is attached to the center pin 3 of the disk substrate 1 to close the center hole of the disk substrate 1. The disc substrate 1 and the center cap 8 are adsorbed and fixed to the mounting surface side of the spin table 2 by vacuum channels 5 and 6 connected to a vacuum source (not shown).

  When the disk substrate 1 is fixed to the spin table 2 and the center cap 8 is attached to the center pin 3, a thin film is formed on the center cap 8 by the dropping nozzle 7 while rotating the spin table 2 at a low speed as shown in FIG. 4B. A resin material 20 such as an ultraviolet curable resin for forming is dropped. The dropping position at this time is, for example, within 5 mm from the peripheral surface of the resin contact portion 15.

  After the application of the resin material 20, the spin table 2 is rotated at a high speed, for example, at 3000 to 3500 rpm, and the resin material 20 applied on the center cap 8 is stretched. As a result, a thin film of the resin material 20 is formed on the disk substrate 1 as shown in FIG. 4C. These operations are repeated when spin coating is repeated to increase the film thickness.

  When a thin film of the resin material 20 having a desired thickness is formed on the disk substrate 1, the center cap 8 is gripped by a detachable machine (not shown), and the center cap 8 is removed from the center pin 3. For example, two center caps 8 are used alternately. When one center cap 8 is used for spin coating, the other used center cap 8 is made usable by emptying and washing with alcohol.

  When the center cap 8 is removed, the resin material 20 formed on the disk substrate 1 is cured. For example, when the resin material 20 is an ultraviolet curable resin, ultraviolet rays are irradiated. As a result, a thin film is formed on the disk substrate 1.

  In the case of optimizing the diameter of the shaft of the resin contact portion 15, if the thickness of the thin film formed on the disk substrate 1 becomes thinner as it approaches the outer peripheral side of the disk substrate 1, If the diameter of the shaft is increased and the thickness of the resin material stretched on the main surface of the disk substrate 1 increases as it approaches the outer peripheral side, the diameter of the shaft of the resin contact portion 15 is decreased. By repeating this, the diameter of the resin contact portion 15 suitable for forming a thin film is found, and a good thin film can be formed by using the center cap 8 having the resin contact portion 15 having the diameter. Thereby, the variation in the film thickness distribution in the radial direction of the disk substrate 1 is improved.

  Here, an example of an optical recording medium on which a thin film is formed by spin coating will be described. FIG. 5 is an enlarged cross-sectional view showing an example of the configuration of a single-layer optical disc. The optical disk 21 is configured by sequentially laminating a reflective film 23 and a light transmission layer 24 on one main surface of a disk substrate 22.

  The disk substrate 22 is made of a resin material such as polycarbonate. The reflection film 23 is irradiated with the laser beam condensed by the lens 25 having a high numerical aperture (NA). For example, the lens 25 has a configuration in which two lenses are bonded together, and the NA is 0.85.

  The optical disk 21 has a substantially disk shape with a center hole (not shown) opened at the center. As an example, the disk diameter is 120 mm, the center hole diameter is 15 mm, and the disk thickness is 1.2 mm. The thickness of the disk substrate 22 is 1.1 mm, for example, and the thickness of the light transmission layer 24 is 0.1 mm, for example.

  On one main surface of the disk substrate 22, a reflective film 23 is formed, and an optical recording layer as an information signal layer is formed. For the reflective film 23, for example, a film material made of aluminum, silver, gold, or an alloy containing these is used. The optical recording layer made of the reflective film 23 is formed with a pit pattern having a fine uneven shape. The pit has a pit length modulated according to the recording data.

  On the reflective film 23, a light transmission layer 24 is formed as a protective film. The light transmission layer 24 is formed of a resin material such as an ultraviolet curable resin having light transmittance, for example.

  Laser light that passes through the lens 25 is applied to the reflective film 23 of the optical disc 21 from the light transmission layer 24 side. The distance of the lens 25 from the optical disk 21 is adjusted to focus on the reflective film 23, and the return light reflected by the reflective film 23 is received by the light receiving element, and reproduction is performed.

  For example, by forming the light transmission layer 24 of the optical disc 21 by the spin coating method using the center cap 8 described above, it is possible to form the light transmission layer 24 with a highly accurate radial thickness distribution.

  Although the optical disk 21 has a single-layer structure, the present invention can be applied to the manufacture of an optical disk having a multilayer structure. FIG. 6 is an enlarged cross-sectional view showing an example of the configuration of an optical disk having a multilayer structure. The optical disc 31 is configured by sequentially laminating a reflective film 33, a light transmissive layer 36, a semi-transmissive reflective film 37, and a light transmissive layer 34 on a disk substrate 32.

  The disk substrate 32 is made of a resin material such as polycarbonate. The laser light collected by the lens 35 having a high numerical aperture (NA) is applied to the reflective film 33 or the semi-transmissive reflective film 37. For example, the lens 35 has a configuration in which two lenses are bonded together, and the NA is 0.85.

  The optical disc 31 has a substantially disk shape with a center hole (not shown) opened at the center. As an example, the disk diameter is 120 mm, the center hole diameter is 15 mm, and the disk thickness is 1.2 mm. The thickness of the disk substrate 32 is 1.1 mm, for example, the thickness of the light transmission layer 36 is 25 μm, for example, and the thickness of the light transmission layer 34 is 75 μm, for example.

  On one main surface of the disk substrate 32, a reflective film 33 is formed, and an optical recording layer (L0 layer) which is a first information signal layer is formed. For the reflective film 33, for example, a film material made of aluminum, silver, gold, or an alloy containing these is used. The optical recording layer formed of the reflective film 33 is formed with a pit pattern having a fine uneven shape. The pit has a pit length modulated according to the recording data.

  On the reflection film 33, a light transmission layer 36 is formed as an intermediate layer. The light transmission layer 36 is formed of a resin material such as an ultraviolet curable resin having light transmittance, for example.

  A transflective film 37 is formed on the light transmission layer 36, and an optical recording layer (L1 layer) which is a second information signal layer is formed. For the transflective film 37, for example, a film material made of silver or a compound containing silver is used. The optical recording layer made of the semi-transmissive reflective film 37 has a pit pattern having a fine uneven shape. The pit has a pit length modulated according to the recording data.

  On the transflective film 37, a light transmission layer 34 is formed as a protective film. The light transmissive layer 34 is formed of a resin material such as an ultraviolet curable resin having light transmittance, for example.

  Laser light through the lens 35 is irradiated from the light transmission layer 34 side to the reflective film 33 or the semi-transmissive reflective film 37 of the optical disk 31. The distance of the lens 35 from the optical disk 31 is adjusted to focus on one of the reflective film 33 and the semi-transmissive reflective film 37, and reproduction is performed on one of the reflective film 33 or the semi-transmissive reflective film 37. The semi-transmissive reflective film 37 is semi-transmissive, and the reflective film 33 is irradiated with laser light through the semi-transmissive reflective film 37 and the light transmissive layer 36. The return light reflected by one recording layer on which the reflective film 33 and the semi-transmissive reflective film 37 are focused is received by the light receiving element, and reproduction is performed.

  For example, the light transmission layer 34 and the light transmission layer 36 of the optical disc 31 are formed by the spin coating method using the center cap 8 described above, so that the light transmission layer 34 and the light having a highly accurate radial thickness distribution can be obtained. The transmission layer 36 can be formed.

  The inventor of the present application actually formed the light transmission layer 24 of the optical disc 21 by spin coating using the center cap 8 described above. The diameter A of the resin contact portion 15 was set to φ8.0 mm as a result of experiment and optimization. Moreover, the diameter B of the holding part 16 was set to φ2.0 mm according to the attachment / detachment machine. As the resin material, an ultraviolet curable resin made of an acrylic resin having a viscosity of about 2300 mPaS was used. The disk substrate 22 having a diameter of 120 mm was used.

  While rotating the spin table 2 on which the disk substrate 22 on which the reflective film 23 is formed is rotated at a low speed, about 2.0 g of ultraviolet curable resin is dropped on the center cap 8, and the disk substrate 22 is mounted. The spin table 2 is rotated at a desired number of revolutions, and the dropped ultraviolet curable resin is stretched over the entire main surface of the disk substrate 22, and then the stretched ultraviolet curable resin is irradiated with ultraviolet rays to form a light transmission layer 24. did.

  FIG. 7 shows the film thickness distribution in the radial direction of the light transmission layer 24 formed as described above. The variation in film thickness between R22 mm and R56 mm was 0.7 μm, and a very good result was obtained.

  For comparison, the inventors of the present application actually formed a thin film on the disk substrate 22 using the center cap 38 having the shape shown in FIG. The shape is the same as that of the center cap 8 described above except that the diameter C of the resin contact portion 39 with which the resin material contacts is φ2.0 mm. The coating conditions were also the same as described above, and the light transmission layer 24 was formed.

  FIG. 9 shows the film thickness distribution in the radial direction of the light transmission layer 24 thus formed. The variation in film thickness between R22 mm and R56 mm was 2.1 μm, and the film thickness became thinner toward the outer periphery of the disk substrate 22.

  Therefore, it can be seen that it is effective to increase the diameter of the shaft with which the resin material contacts when the film thickness becomes thinner as the outer periphery of the disk substrate 22 is approached. Similarly, when the film thickness increases as it approaches the outer periphery of the disk substrate 22, it is effective to reduce the diameter of the shaft with which the resin material contacts. There is an optimum value for the diameter of the axis that the resin material touches to form a thin film that can suppress variations in the film thickness distribution in the radial direction, and a highly accurate film thickness can be formed by using the axis of the diameter of that value. I understand.

  The present invention is not limited to the above-described embodiment, and various modifications and applications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, the read-only optical disk has been described. However, the present invention is not limited to this, and can be applied to a writable optical disk. The thin film formed by spin coating is not limited to a light transmission layer such as a protective film or an intermediate layer, but can be applied to other thin films formed by spin coating such as a coating layer. Further, the present invention can be applied to the formation of a thin film that requires high film thickness accuracy of other optical recording media such as a magneto-optical disk as well as an optical disk.

It is a figure for demonstrating the structure of an example of the spin coater in one Embodiment. It is a figure which shows an example of a structure of a center cap. It is a figure which shows the other example of a structure of a center cap. It is a figure for demonstrating formation of the thin film using a center cap. It is a figure which shows an example of a structure of an optical disk (single layer). It is a figure which shows an example of a structure of an optical disk (multilayer). It is a graph which shows the film thickness distribution of the radial direction in one Embodiment. It is a figure which shows an example of a structure of the center cap which is not optimized. It is a graph which shows the film thickness distribution of the radial direction for comparing with one Embodiment. It is an example of the conventional spin coater.

Explanation of symbols

1, 22, 32 ... disk substrate 2 ... spin table 3 ... center pin 4 ... concave portion 5, 6 ... vacuum channel 7 ... drip nozzle 8, 18 ... center cap DESCRIPTION OF SYMBOLS 9 ... Fitting part 10 ... Disc part 11 ... Shaft part 15, 19 ... Resin contact part 16 ... Grasping part 20 ... Resin material 21, 31 ... Optical disk 24, 34, 36 ... Light transmission layer

Claims (3)

In a method for manufacturing an optical recording medium having an information signal layer and a thin film formed by spin coating on a main surface of a substrate,
Placing and fixing a substrate having a center hole on a spin table;
By means of a closing member having a disc part covering the center hole and a shaft having one end attached to the center of the disc part, the center hole of the substrate is arranged so that the center of the disc part and the shaft is the spin table. A step of closing so as to be located on the rotation axis of
Dropping a resin material on the closing member so as to contact the peripheral surface of the shaft;
Extending the resin material dropped on the closing member by rotating the spin table over the main surface of the substrate,
When the thickness of the resin material stretched on the main surface of the substrate becomes thinner as it approaches the outer peripheral side of the substrate, the diameter of the shaft is increased and the thickness of the resin material stretched on the main surface of the substrate is increased. When the thickness of the optical recording medium becomes thicker as it approaches the outer peripheral side, optimization is performed so as to reduce the diameter of the shaft. In claim 1,
The method for producing an optical recording medium, wherein the dropping position of the resin material is within 5 mm from the peripheral surface of the shaft. In claim 1,
The other end of the shaft has a shape suitable for gripping the closing member, and the closing member is attached and detached by gripping the other end of the shaft. A method for manufacturing a medium.

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