JP4656013B2 - Manufacturing method of optical disk medium - Google Patents

Description

This invention can be formed in a uniform thickness of the light transmissive film in high-density recording optical disk, a method of manufacturing an optical disc medium on which Ru possible to prevent the occurrence of projections of the outer peripheral portion.

  High-density recording of an optical disk can be realized, for example, by shortening the wavelength of laser light used in an optical pickup, increasing the numerical aperture NA (Numerical Aperture) of the objective lens, and reducing the size of the focused spot.

  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). A DVD-ROM (Digital Versatile Disc-ROM) has a laser beam wavelength of 650 nm and a numerical aperture of 0.6, and has a recording capacity of 4.7 GB (gigabytes).

  Further, in the next generation high-density recording optical disc, the wavelength of the laser beam is 450 nm or less, and the NA is 0.78 or more, which makes it possible to increase the capacity of 22 GB or more with a single layer. In a high-density recording optical disk, a light-transmitting protective film called a light-transmitting film so-called cover layer is formed on the signal reading surface side of the disk. The cover layer has a thickness of, for example, 100 μm (0.1 mm).

  In CD and DVD, the distance from the signal reading surface (disc surface) of the disc to the information recording layer where the signal is recorded is relatively large. In the case of CD, this distance is about 1 mm. In the case of DVD, This distance is about 0.6 mm.

  On the other hand, in a high-density recording optical disk, this distance is about 0.1 mm. When a high-density recording optical disk having two information recording layers is formed, the intermediate layer between the two information recording layers needs to be as thin as about 20 μm to 30 μm. In some cases, a lubricant layer such as a hard coat is formed on the surface of the cover layer, the surface of the cover layer is protected by the lubricant layer, and is processed smoothly. This lubricant layer is formed with a very thin thickness.

  The cover layer, the intermediate layer, and the lubricant layer described above are required to have high thickness accuracy. For example, a cover glass structure and a resin cover structure are known as the structure of the cover layer. The cover glass structure is a structure in which a transparent film or a thin glass plate is pasted on a signal layer via an adhesive or an adhesive material to form a cover layer. The resin cover structure is a cover structure in which an energy absorption / curing liquid resin represented by UV (ultraviolet) curable resin or a semi-cured material is applied and then cured.

  The advantage of the cover glass structure is that the film thickness distribution can be formed relatively stably. However, there is a problem of misalignment between the cover member and the substrate. If a protruding portion where the cover member protrudes from the outer periphery of the substrate is generated, the cover member is easily peeled off during handling or when the disk is dropped. Moreover, the bubble mixing part and edge flash may occur due to the deviation of the bonding. Furthermore, since the cover member is required to have high thickness accuracy and no defects / scratches due to its properties, the cover member becomes expensive, which causes a large increase in the cost of the disk. Further, since the cover member is manufactured in advance, it is difficult to delicately control the film thickness in order to correct disc characteristics and process variations.

  As a method for forming a cover layer having a resin cover structure, a spin coating method has been proposed. The spin coating method is a method in which a liquid resin material is applied to a thin film forming surface of a substrate, and the substrate is spread at high speed around the center of the substrate by rotating the substrate at a high speed with a spin coater. .

  Hereinafter, the formation of the cover layer by the spin coating method will be described with reference to FIG. First, as shown in FIG. 1A, a liquid ultraviolet curable resin (hereinafter referred to as UV resin) 102 is dropped on the inner periphery of a substrate 101 on which irregularities are formed by injection molding and a recording film is formed. To do. Next, as shown in FIG. 1B, the substrate 101 is rotated at a high speed to spread the UV resin uniformly over the entire surface of the substrate, and the excess UV resin 102 on the substrate 101 is shaken off. Thereafter, the high-speed rotation is stopped, and the UV resin 102 is cured by irradiating the substrate 101 with ultraviolet rays by the ultraviolet lamp 103 as shown in FIG. 1C. Thus, the cover layer is formed.

  However, since the above-mentioned spin coating method has a hole in the center part, the dropping position of the UV resin cannot be the center position of the substrate 101, and therefore, a uniform thickness from the inner periphery to the outer periphery. A cover layer having a thickness cannot be obtained. That is, as shown in FIG. 2, the UV resin 102 applied to the substrate 101 on which the information recording layer 104 is formed has a thicker layer from the inner periphery to the outer periphery, and has an inner periphery and an outer periphery of about 5 μm to 10 μm. The difference in thickness occurs. In addition, as indicated by reference numeral 105, there is a problem that a rim-like raised portion is generated in the outer peripheral portion of the substrate due to the influence of the surface tension. The height of the raised portion 105 is, for example, 10 μm to 50 μm. Further, there are known problems that the resin reaches the outer peripheral edge to become dirt and burrs, and further, goes around the back surface to contaminate the substrate.

  Patent Document 1 below describes a method for preventing the bulge of the outer peripheral portion by covering the bulge with a mask. In this method, the outermost peripheral part of the substrate is covered with a light-shielding mask so that the outermost peripheral part of the substrate is not irradiated with light. Next, the photocurable resin other than the raised portion is cured. Then, the substrate is rotated again, and the photocured resin at the resin bulge portion is shaken off and removed. Next, the remaining photocurable resin is cured by irradiation with light. By the above, the resin layer without a bulge part in an outer peripheral part can be formed.

Japanese Patent Laid-Open No. 11-73691

In order to prevent the film thickness from increasing from the inner periphery to the outer periphery, the following method has been proposed.
1. In synchronism with the spin coating, the outer peripheral portion of the substrate is warmed with an infrared lamp or the like, and the viscosity of the liquid resin in this portion is lowered to facilitate flow to make the film thickness uniform, and UV curing is performed in this state.
2. As shown in FIG. 3, the hole 111 in the disk center portion is closed and flattened with a cap 112 as another member, and the liquid resin 102 is dropped onto the center and spin-coated to make the film thickness uniform. UV cure. Next, the rotation of the spinner is stopped, the cap 112 closing the hole 111 in the center of the disk is removed, and the cap 112 is cleaned for reuse. As described above, the UV resin 102 is applied to the substrate 101, and a cover layer is formed on the substrate 101.
3. As shown in FIG. 4, spot UV irradiation is performed. That is, the substrate 101 is placed on the spinner table 106 and the UV resin 102 is applied on the substrate 101. The spinner table 106 is rotated at a high speed, the UV resin is spread on the substrate 101 by centrifugal force, and the excess UV resin 102 on the substrate 101 is shaken off. During this high-speed rotation, the spot UV head 107 is moved from the inner periphery to the outer periphery in the radial direction of the substrate 101, so that the spot UV is irradiated from the inner periphery to the outer periphery of the substrate 101. In this way, the time of rotating in the liquid state is lengthened as it goes to the outer periphery, thereby making the film thickness uniform, and UV curing is performed in this state.

  When the cap 112 is used, operations such as attaching / detaching and cleaning the cap 112 are indispensable, and workability is deteriorated and the apparatus is complicated. Further, when the cap 112 that is not sufficiently cleaned is used, a cover layer having a uniform thickness cannot be formed.

  In the method of curing the UV resin by moving the spot UV head 107, the area of the irradiated light is small, and the light is irradiated concentrically with respect to the UV resin. For this reason, there is a problem that unevenness of irradiation is likely to occur, and a history of irradiation remains on the cured surface, resulting in insufficient surface uniformity.

Accordingly, an object of the present invention, it is possible to uniform radial thickness, is to provide a method of manufacturing an optical disk medium that can form the cover layer has no unevenness of light during irradiation on the surface.

In order to solve the above-described problems, the present invention provides:
In an optical disc manufacturing method in which an information layer and a light transmission layer are sequentially laminated on a substrate,
A first layer forming step of forming a first light-transmitting resin layer on the information layer by spin coating so that the film thickness decreases from the inner periphery toward the outer periphery;
And a second layer forming step of forming a second light-transmissive resin layer is laminated by spin coating to the first light transmitting resin layer,
The first layer forming step
Rotate the substrate to stretch the photocurable resin on the information layer,
By moving the spot light irradiation means in the radial direction of the substrate and controlling the irradiation power and / or moving speed of the spot light irradiation means, the film thickness increases from the inner periphery to the outer periphery of the second light transmissive resin. The thickness of the first light transmissive resin layer is formed so as to cancel the change in
The second layer forming step
Rotating the substrate to stretch the photocurable resin onto the first light transmissive resin layer,
This is a method of manufacturing an optical disk medium in which light is radiated to a photocurable resin at once to completely cure the photocurable resin to form a second light transmissive resin layer .

Preferably, after the completion of the first layer forming step, the thickness of the first light transmissive resin is measured,
In the second layer forming step, the second measured value of the thickness of the first light transmissive resin is used so that the total film thickness of the first and second light transmissive resins becomes a predetermined value. The film thickness of the light transmissive resin layer is controlled.

  According to this invention, the light transmissive layer is formed by the laminated structure of the first and second light transmissive resin layers, and occurs when the second light transmissive resin layer is formed by ordinary spin coating. Since the film thickness of the first light-transmitting resin layer is decreased from the inner periphery toward the outer periphery so as to cancel the increase in film thickness from the periphery to the outer periphery, the film thickness is made uniform in the radial direction of the light-transmitting layer. be able to.

  Embodiments of the present invention will be described below with reference to the drawings. First, an example of an optical disc to which an embodiment of the present invention can be applied will be described. FIG. 5 shows an example of a high-density recording optical disk according to an embodiment of the present invention. In this optical disc, information signals are recorded and reproduced by irradiating the information recording layer 2 with laser light from the cover layer 3 side. For example, a laser beam having a wavelength of 400 nm to 410 nm is collected by the objective lens 4 having a numerical aperture of 0.84 to 0.86 and irradiated to the information recording layer 2 from the cover layer 3 side, thereby Recording and playback are performed.

  This optical disc has a configuration in which an information recording layer 2 and a cover layer 3 are sequentially laminated on one main surface of a substrate 1. The optical disk has a substantially disk shape with a center hole (not shown) opened at the center. The optical disk has, for example, a disk diameter of 120 mm, a center hole diameter of 15 mm, a disk thickness of 1.2 mm, and a substrate thickness of 1.1 mm.

  As the substrate 1, for example, a low-absorbency resin such as polycarbonate (PC) or cycloolefin polymer can be used. The information recording layer 2 is a reflective film, a recording film or the like formed on the unevenness of the substrate. The information recording layer 2 is a reflective film made of, for example, gold (Au), silver (Ag), silver alloy, aluminum (Al), aluminum alloy or the like when the optical disk is a read-only type. When the optical disc is a write-once type, the information recording layer 2 is configured by sequentially laminating a recording layer made of a reflective film and an organic dye material, for example. When the optical disc is of a rewritable type, the information recording layer 2 is configured by sequentially laminating a reflective film, a lower dielectric layer, a phase change recording layer, and an upper dielectric layer, for example.

  As the cover layer 3, a UV resin can be used. Further, if necessary, a lubricant layer (not shown) such as a hard coat may be formed on the surface of the cover layer 3. The lubricant layer is for protecting the surface of the cover layer 3 and smoothing the surface.

  Another example of a high-density recording optical disk to which an embodiment of the present invention can be applied will be described with reference to FIG. As shown in FIG. 6, this optical disc has a configuration in which an L0 layer, an intermediate layer 12, an L1 layer, and a cover layer 13 are sequentially laminated on a substrate 11. The substrate 11 is made of a low-absorbency resin such as polycarbonate (PC) or cycloolefin polymer.

  The L0 layer and the L1 layer that are information recording layers are a reflective film, a recording film, and the like formed on the unevenness of the substrate 11. The L0 layer and the L1 layer are reflective films made of, for example, gold (Au), silver (Ag), silver alloy, aluminum (Al), or aluminum alloy when the optical disk is a read-only type. When the optical disc is a write-once type, the L0 layer and the L1 layer are configured by sequentially laminating, for example, a reflective film and a recording layer made of an organic dye material. When the optical disc is a rewritable type, the L0 layer and the L1 layer are configured by sequentially laminating, for example, a reflective film, a lower dielectric layer, a phase change recording layer, and an upper dielectric layer.

  An intermediate layer 12 is formed on the L0 layer formed on the substrate 11. An L1 layer is formed on the intermediate layer 12. A cover layer 13 is formed on the L1 layer formed in the intermediate layer 12. The cover layer 13 is formed for the purpose of protecting the optical disc. Information signals are recorded and reproduced, for example, by focusing laser light on the information recording layer through the cover layer 13 by the objective lens 14.

  A UV resin can be used as the intermediate layer 12 and the cover layer 13. The thickness of the intermediate layer 12 is, for example, 25 μm, and the thickness of the cover layer 13 is, for example, 75 μm, and it is required to form a layer having a uniform thickness.

  In one embodiment in which the present invention is applied to the formation of the cover layers 3 and 13, as shown in FIG. 7, a UV resin 5 as a first light-transmitting resin layer is spin coated on the substrate 1 as shown in FIG. Further, the UV resin 6 as a second light-transmitting resin layer is formed on the cured UV resin 5 by spin coating, the UV resin 6 is cured, and the laminated two layers of the UV resin 5 are laminated. And 6 constitute the cover layer 3 or 13. The film thickness of the first UV resin 5 is formed so as to cancel out the film thickness that increases from the inner periphery to the outer periphery of the UV resin 6. FIG. 7 schematically shows from the outer peripheral side of the center hole of the substrate 1 to the outermost peripheral portion of the substrate 1.

  Thus, in order to control the film thickness of the UV resin 5 of the first layer, the UV resin 5 is cured by a spot UV head as a spot light irradiation means for moving the UV resin stretched by spin coating in the radial direction. It is formed by the forming process. In this case, the UV resin 5 can be formed such that the film thickness decreases from the inner periphery toward the outer periphery by controlling the irradiation power and / or moving speed (referred to as scan speed as appropriate) of the spot UV head. .

  The UV resin 6 of the second layer is formed by a forming process in which the UV resin is stretched by spin coating on the cured UV resin 5 of the first layer, and the UV resin is cured by batch irradiation. The spin coating for forming the second layer of the UV resin 6 is the same as in the prior art. Irradiation unevenness is less likely to occur due to collective irradiation, and no trace of UV irradiation remains on the surface of the UV resin 6.

  With reference to FIG. 8, a cover layer forming process according to an embodiment of the present invention will be described. The substrate 1 is mounted on a spinner table (not shown) of the first spin coater. Next, while rotating the substrate 1, the first layer UV resin 5a is dropped from the nozzle around the center hole, for example, over one round. As the UV resin 5a, for example, one having a viscosity of about 1000 mPa · s is used. The substrate 1 has irregularities (pits, grooves, etc.) formed on its surface by injection molding or the like, and an information recording layer formed on the irregularities. The information recording layer is a reflective film in the case of a read-only disk, and a recordable film such as a phase change film in the case of a writable disk.

  Next, the spinner table is rotated at a high speed to form the UV resin 5b stretched on the substrate 1, and the UV resin 5b stretched by the spot UV head 24 is irradiated with the spot UV 25 to cure the UV resin 5b. The spot UV head 24 is moved from the inner peripheral side to the outer peripheral side of the substrate 1 so as to follow the UV resin 5b flowing from the inner peripheral side toward the outer peripheral side, and the region irradiated with the spot UV 25 is cured. For example, it is completely cured. Here, the spot UV is ultraviolet light that irradiates the substrate 1 with a spot in a fine range. On the surface of the substrate 1, the spot size of the spot UV is preferably about 1 mm to 10 mm in diameter, and more preferably about 2 mm to 5 mm in diameter.

  As an example, it is assumed that an 80 μm cover layer is formed by two layers of UV resins 5 and 6, the thickness of the first layer UV resin 5 is set to 60 μm, for example, and the thickness of the second layer UV resin 6 is set to 20 μm, for example. . For example, in the case of the substrate 1 having a diameter of 120 mm, the first layer UV resin 5 has a thickness of 60 μm on the innermost peripheral side (radius 30 mm) when the radial position is defined with the center being 0, and the thickness gradually increases. In the outermost periphery (radius 60 mm), the predetermined thickness is reduced to, for example, 52 μm. The inclination (change) at which the film thickness decreases can cancel the inclination (change) at which the film thickness increases when the UV resin 6 of the second layer is formed by spin coating and batch irradiation. As a result, when the second layer UV resin 6 is formed on the UV resin 5, the thickness of the cover layer having a two-layer structure can be made substantially uniform.

  The amount of increase in film thickness in the radial direction when the second layer UV resin 6 is formed by spin coating and collective UV irradiation varies depending on the type of UV resin used, the diameter of the substrate 1, and the like. For example, in the case of the substrate 1 having a diameter of 50 mm, the thickness is about 5 μm at the outermost periphery. Therefore, what kind of change in film thickness the first layer UV resin 5 should have depends on the type of UV resin used, the diameter of the substrate 1 and the like.

  The film thickness of the first layer UV resin 5 can be controlled as described above by controlling the irradiation power of the spot UV 25 and / or the scanning speed of the spot UV head 24. FIG. 9A shows the first layer UV in the radial direction (direction from the inner peripheral side to the outer peripheral side) of the substrate 1 when the irradiation power of the spot UV 25 is changed when the scanning speed of the spot UV head 24 is set to a predetermined speed. The change of the film thickness of the resin 5 is shown.

  As shown by the film thickness change 7a by a certain irradiation power, when a certain film thickness can be formed, if the irradiation power is made smaller, the curing speed of the UV resin is slowed down, so that it cures in the inner peripheral region. The amount of UV resin decreases, and the film thickness gradually increases toward the outer periphery as shown by the film thickness change 7b. On the other hand, when the irradiation power is increased, the curing speed of the UV resin increases, so that the amount of the UV resin that cures in the inner peripheral region increases, and as shown by the film thickness change 7c, the UV resin cures toward the outer peripheral side. The film thickness gradually decreases.

  FIG. 9B shows the first layer UV in the radial direction (direction from the inner peripheral side toward the outer peripheral side) of the substrate 1 when the scanning speed of the spot UV head 24 is changed when the irradiation power of the spot UV 25 is set to a predetermined value. The change of the film thickness of the resin 5 is shown. As shown by the film thickness change 8a at a certain scanning speed, when a constant film thickness can be formed, if the scanning speed is further increased, the UV that cures in the region on the inner peripheral side is the same as when the irradiation power is reduced. The amount of the resin decreases, and the film thickness gradually increases toward the outer peripheral side as shown by the film thickness change 8b. On the other hand, when the scanning speed is further reduced, the amount of UV resin that is cured in the inner peripheral region increases as in the case of increasing the irradiation power, and as shown by the film thickness change 8c, toward the outer peripheral side. The film thickness gradually decreases.

  In one embodiment of the present invention, the film thickness change 7c is generated by increasing the irradiation power, or the film speed change 8c is generated by lowering the scanning speed. Furthermore, by controlling both the irradiation power and the scanning speed, the first layer UV resin 5 is formed so that the film thickness decreases toward the outer periphery.

  As shown in FIG. 8, in order to form the second layer UV resin 6, the substrate 1 on which the first layer UV resin 5 is formed is mounted on a spinner table (not shown) of the second spin coater. In this case, the first layer UV resin 5 and the second layer UV resin 6 can be formed by the same spin coater. Next, while rotating the substrate 1, the second layer UV resin 6a is dropped from the nozzle around the center hole, for example, over one turn. The UV resin 6a does not have to be the same resin as the UV resin 5a.

  Next, the spinner table is rotated at a high speed to form the UV resin 6b stretched on the substrate 1. The UV resin 6b stretched by the collective UV irradiation device 26 is collectively irradiated with UV to completely cure the UV resin 6b. The collective UV irradiation device 26 has a plurality of, for example, three UV lamps 27a, 27b, and 27c arranged in series in the diameter direction of the substrate 1, and is provided on the upper surface of the substrate 1 that rotates the UVs 28a, 28b, and 28c. Uniform irradiation is possible.

  Thus, the second layer UV resin 6 is formed by normal spin coating and collective UV irradiation, and the rotation speed is adjusted so that the thickness becomes a predetermined one, for example, 20 μm. Since the second layer UV resin 6 cannot center on the dropping position of the UV resin 6a, the film thickness increases from the inner periphery toward the outer periphery. However, as described above, since the underlying first layer UV resin 5 is formed so that the film thickness decreases from the inner periphery toward the outer periphery, the increase in the film thickness of the second layer UV resin 6 is offset. The film thickness of the cover layer in which the UV resins 5 and 6 are laminated can be made almost constant.

  It is also possible to form the second layer UV resin 6 by spin coating and UV spot irradiation. In one embodiment, since the second layer UV resin 6 is formed by normal spin coating and batch UV irradiation, a smooth and stable surface can be formed.

  As shown in FIG. 10, the spin coater for forming the first layer UV resin 5 includes a spinner table 21, a center pin 22, a single-axis robot 23, and a spot UV head installed at the tip of the single-axis robot 23. 24. By controlling the single-axis robot 23, the spot UV head 24 is moved in the radial direction of the substrate 1 at a desired moving speed.

  The spinner table 21 is a table on which the substrate 1 is placed when performing spin coating. Further, the dispenser mechanism for supplying the UV resin may be provided in the spin coater, or the substrate pre-coated with the UV resin in another place may be transported to the spin coater. The spinner table 21 rotates integrally with the substrate 1. The shaken UV resin is stored in the chamber. The center pin 22 has a function of positioning the substrate 1 placed on the spinner table 21 and closing the opening at the center of the substrate 1. A spot UV head 24 is installed in the single-axis robot 23, and the spot UV can be irradiated from the inner periphery to the outer periphery of the substrate 1.

  The spot UV head 24 is coupled to the light source unit via an optical fiber, and irradiates UV from the light source unit to the outside. UV irradiation and non-irradiation can be switched by a shutter or the like, and the irradiation power of the light source unit can be controlled.

  The spot UV head 24 may have a structure having a lens holder (not shown). The lens holder has a lens disposed therein, and has a structure that can be removed from the spot UV head and replaced. By exchanging the lens holder, light can be condensed, or diffused light and parallel light can be obtained. That is, the irradiation range for the substrate can be changed. Further, the spot UV may be emitted by using a power source that can be used even in a dimmed state with an inverter type.

  FIG. 11 shows an example of a measured value of the film thickness when a disk having a diameter of 50 mm is used. The first layer UV resin 5 is 65 μm at the innermost peripheral position (12 mm at the radial position) as shown by the change 31 in the film thickness, and the film thickness gradually decreases toward the outer peripheral position. At the position 24 mm), it is 58 μm. A second layer UV resin 6 having a thickness of about 20 μm is formed thereon by ordinary spin coating. The film thickness change 32 of the second layer UV resin 6 is such that the film thickness of the underlying UV resin 5 decreases toward the outer periphery. )

  In the measurement example of FIG. 11, since the degree of decrease in the film thickness of the first layer UV resin 5 is too large, the entire film thickness decreases toward the outer peripheral side. If the degree of decrease in the film thickness of the first layer UV resin 5 is made smaller, for example, 4 μm or 5 μm at the outermost peripheral position, the entire film thickness can be made more uniform.

  Here, assuming that the change width of the film thickness of the UV resin is 10 μm, the change in the film thickness can be expressed as shown in FIG. The horizontal axis in FIG. 12 is an axis representing the film thickness of the first layer UV resin 5, and the vertical axis is an axis representing the film thickness of the second layer UV resin 6. The first layer UV resin 5 has a film thickness of 65 μm at the innermost peripheral position (12 mm at the radial position), the film thickness gradually decreases toward the outer periphery, and 55 μm at the outermost peripheral position (24 mm at the radial position). To change. On the other hand, the second layer UV resin 6) has a film thickness of 15 μm at the innermost peripheral position (12 mm in the radial position), and the film thickness gradually increases toward the outer periphery. 24 mm), it changes to 25 μm. Therefore, the thickness of the cover layer composed of the two layers of the UV resins 5 and 6 can be constant at 80 μm at any radial position.

  Furthermore, in order to prevent variation in the cover layer between individuals during mass production, after forming the first layer UV resin 5, the thickness of the first layer UV resin 5 is measured, and the second layer is determined according to the measurement result. The thickness of the UV resin 6 during spin coating is corrected so that the cover layer has a predetermined thickness. FIG. 13 shows an example of thickness correction. For example, as described above, an example in which a cover layer having a thickness of 80 μm is formed on a substrate having a diameter of 50 mm will be described.

The first layer UV resin 5 is formed in step ST1 by spin coating and UV spot irradiation. In the film thickness measurement step ST2, the film thickness of the first layer UV resin 5 is measured using an optical microscope or the like. There are one or more measurement points. For example, a film thickness with a radial position of 20 mm is measured. The measurement result is compared with a predetermined film thickness, for example, 60 μm. When the measurement result coincides with 60 μm (meaning coincidence within the allowable error range), the rotation speed of the spinner table of the spin coater for forming the second layer UV resin 6 (referred to as the spin rotation speed as appropriate) is standard. The rotation speed is A [rpm] (step ST3). Then, the second layer UV is formed by ordinary spin coating.
Resin 6 is formed (step ST6). At the standard rotation speed A [rpm], the second layer UV resin 6 can be formed with a film thickness of 20 μm at a radial position of 20 mm.

In the measurement step ST2, when the measurement result is thinner than the predetermined film thickness, the spin rotation speed is slower than the standard rotation speed A [rpm]. For example, when the measurement result is 59 μm, the spin rotation speed is set to A-100 [rpm] in step ST4. And process ST6
The second layer UV resin 6 is formed. Since the spin rotation speed is lower than the standard rotation speed, the film thickness of the second layer UV resin 6 is increased, for example, 21 μm, and the total film thickness can be 80 μm.

In the measurement step ST2, when the measurement result is thicker than the predetermined film thickness, the spin rotation speed is set to be faster than the standard rotation speed A [rpm]. For example, when the measurement result is 61 μm, the spin rotation speed is set to A + 100 [rpm] in step ST5. And process ST6
The second layer UV resin 6 is formed. Since the spin rotation speed is increased from the standard rotation speed, the film thickness of the second layer UV resin 6 is reduced to, for example, 19 μm, and the total film thickness can be 80 μm.

  The above-described embodiment of the present invention is uniform in comparison with the conventional method using a cap, without causing problems such as a decrease in workability due to work such as attaching and detaching the cap and cleaning, and a problem that the apparatus becomes complicated. A thick cover layer can be formed. In addition, since the UV resin is cured by batch irradiation on the surface, the problem of insufficient surface uniformity does not occur unlike the method of curing the UV resin by spot UV, and the cover layer has a uniform thickness. Can be formed.

  In addition, the two-layer structure of the UV resin can reduce the thickness per layer, so that the shrinkage stress for each layer when each layer is cured can be reduced. In addition, since the second layer is formed after the first layer of the UV resin 5 is cured, the polymerization reaction takes time and the shrinkage stress at the time of curing can be alleviated, and the problem of warping of the disk can be improved. it can. Furthermore, it is possible to use a UV resin having hard coat characteristics and antifouling properties as the second layer UV resin 6. The second layer UV resin 6 that forms the surface is formed by spin coating as in the prior art and cured by batch UV exposure, so that it is easy to obtain a smooth and process-stable surface.

  The present invention is not limited to the above-described embodiment of the present invention, 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 countermeasure for the bulging portion generated at the outermost peripheral portion of the substrate is not mentioned, but when forming the second layer UV resin, the outermost peripheral portion is masked and the outermost peripheral UV resin is masked. You may use together the method of suppressing the rising part which shakes off. Further, the optical disk according to the above-described embodiment has been described by taking a single-layer optical disk as an example. However, the present invention is not limited to this, and the optical disk according to the embodiment is not limited to this. Applicable.

It is a basic diagram which shows the conventional spin coat method. It is a basic diagram for demonstrating the problem in the conventional spin coat method. It is a basic diagram for demonstrating the conventional spin coat method which blocks the center hole with a cap. It is a basic diagram for demonstrating the conventional spin coat method by spot UV irradiation. It is sectional drawing which shows an example of the optical disk in one embodiment of this invention. It is sectional drawing which shows the other example of the optical disk which can apply this invention. 1 is a schematic cross-sectional view of an optical disc according to an embodiment of the present invention. It is a basic diagram for demonstrating the process of the cover layer formation method in one embodiment of this invention. It is a basic diagram for demonstrating the film thickness control method at the time of 1st layer formation in one embodiment of this invention. It is the front view and side view of an example of the spin coater which can be used at the time of 1st layer formation in one embodiment of this invention. It is a graph which shows an example of the film thickness measurement result of the 1st layer UV resin and the 2nd layer UV resin which were formed by one embodiment of this invention. It is a graph which shows an example of the change width of the film thickness of the 1st layer UV resin and the 2nd layer UV resin formed by one embodiment of this invention. It is a flowchart of an example of the correction | amendment process of the film thickness at the time of 2nd layer formation in one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Information recording layer 3 ... Cover layer 4 ... Objective lens 5 ... 1st layer UV resin 6 ... 2nd layer UV resin 11 ... Substrate 12 ... Intermediate layer 13: Cover layer 14 ... Objective lens 15 ... Cover layer 21 ... Spinner table 22 ... Center pin 24 ... Spot UV head 26 ... Batch UV irradiation device

Claims (2)

In an optical disc manufacturing method in which an information layer and a light transmission layer are sequentially laminated on a substrate,
A first layer forming step of forming a first light-transmitting resin layer on the information layer by spin coating so that the film thickness decreases from the inner periphery toward the outer periphery;
And a second layer forming step of forming a second light-transmissive resin layer is laminated by spin coating on the first light-transmissive resin layer,
The first layer forming step includes
Rotating the substrate to stretch the photocurable resin on the information layer,
By moving the spot light irradiation means in the radial direction of the substrate and controlling the irradiation power and / or moving speed of the spot light irradiation means, the second light transmitting resin increases from the inner periphery toward the outer periphery. Forming the film thickness of the first light-transmitting resin layer so as to cancel the change in film thickness
The second layer forming step includes
Rotating the substrate to stretch the photocurable resin onto the first light transmissive resin layer,
A method of manufacturing an optical disc medium , wherein the second light-transmitting resin layer is formed by irradiating light to the photo-curing resin to cure the photo-curing resin completely . After the completion of the first layer forming step, the thickness of the first light transmissive resin is measured,
In the second layer forming step, using the measured value of the thickness of the first light transmissive resin, the total film thickness of the first and second light transmissive resins becomes a predetermined value. The method of manufacturing an optical disk medium according to claim 1, wherein the film thickness of the second light transmissive resin layer is controlled.

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