JP2005196906A - Coating film forming apparatus and coating film manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coating film forming apparatus with which an organic protective film having an uniform film thickness is formed from an inner periphery of an optical disk to the neighborhood of an outer peripheral end thereof. <P>SOLUTION: The coating film forming apparatus for forming the organic film on a substrate by a spin-coating method is constituted in such a way that a rectifier plate 4 having the outer diameter larger than that of the substrate by ≥0.1 mm and also having no central hole is arranged on the optical disk substrate 1 and a space between the rectifier plate 4 and the substrate 1 is formed to be smaller continuously or step-wise toward the outer periphery from the inner periphery of the substrate 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a manufacturing apparatus for forming a coating film on a substrate by spin coating. In particular, the present invention relates to a manufacturing apparatus suitable for forming an organic protective film such as a protective coat of an optical disk that records, reproduces, and erases information using a light beam.

  In recent years, a magneto-optical disk characterized by rewritability has been put on the market and is being applied as a data file for computer code information and images. Furthermore, with the spread of mobile computers and the diversification of information, small and large-capacity magneto-optical disks are required.

  In an optical disk manufacturing method, a recording film is generally formed on a resin substrate, and then an organic protective film is formed by a spin coating method.

  The spin coating method has a feature that an arbitrary coating film thickness can be obtained mainly by setting the viscosity and coating amount of the coating solution and the rotation conditions, and is considered to be excellent in productivity. However, various problems have been confirmed as the protective film is required to have higher quality as the size and capacity are increased. In particular, in a high-density magneto-optical disk, keeping the distance between the recording film and the magnetic head constant is an important factor for recording / reproducing characteristics and miniaturization. For this reason, it is required to make the thickness of the protective film formed on the recording film constant from the inner periphery to the outer periphery.

  In the spin coating method, it has been found that a film thickness distribution from the inner periphery to the outer periphery can be formed uniformly in the case of a base material that does not have a center hole such as a master glass. Further, in the vicinity of the outer peripheral portion, the coating material is not sufficiently shaken off by spin, and the film thickness tends to increase. In other words, the spin coating method uses a base material that does not have a central hole and has a sufficiently larger outer diameter than the effective area, as in the case of resist coating on the master glass, thereby providing a uniform film thickness in the effective area. It is possible to form a coating film. However, since the optical disk substrate has step portions such as a center hole and a stamper pressing portion in the vicinity of the center portion, an uncoated region exists in the vicinity of the center portion. As a result, it has been found that the larger the unapplied area on the inner periphery, the worse the film thickness difference between the inner periphery and the outer periphery. Further, as the size is reduced, the difference between the coating start position on the inner periphery and the outer diameter of the substrate is reduced, making it more difficult to form a uniform film thickness in the effective region. Similarly, in the resist coating on the master glass, when the effective area expands to the outer peripheral side and a substrate having a sufficiently large outer diameter cannot be used, an increase in the film thickness near the outer peripheral edge becomes a problem. It was. In addition, as a method for improving the film thickness distribution, it is conceivable to use the volatility of the solvent added to the coating solution, but the solvent addition to the organic protective film material formed on the recording film is applied to the above master glass. Unlike resists, it is difficult because it can be harmful to the recording film or the substrate. For this reason, it is impossible to control the film thickness of the coating film using the volatility of the solvent for the protective film of the optical disk.

  Therefore, as a method for controlling the film thickness of the coating film, it has been conventionally considered to arrange a rectifying plate above the substrate or to provide a rectifying plate above the outer peripheral portion of the substrate in JP-A-11-144330.

  However, it is known that the conventional method has the following problems.

  Although the method of arranging the current plate above the substrate can control turbulent flow during spin coating and is effective in preventing re-adhesion to the coating surface, the coating solution during spinning near the outer peripheral edge of the substrate The problem of increasing the film thickness due to insufficient swing-off has not been solved. In addition, when a solvent-free coating solution is used, the effect of improving the film thickness distribution in the effective region cannot be obtained. The increase in the film thickness in the vicinity of the outer peripheral edge of the substrate depends on the properties of the coating solution, such as the viscosity and surface tension, and the shape of the outer peripheral edge of the substrate at right angles, acute angles, or notches, depending on the spin coating conditions such as the rotational speed and rotational acceleration. Although it is also considered to improve by making the shape of an obtuse angle such as a step or a step, the properties of the coating solution are limited, and even when a specific coating solution is used, the side wall of the outer peripheral edge of the substrate Since the coating liquid stays on the surface and is pulled back to the coating surface by the surface tension of the coating liquid, the insufficient swinging of the coating liquid due to spin cannot be resolved, and the increase in film thickness cannot be reduced sufficiently. . Also, depending on the shape of the outer peripheral edge of the substrate, problems such as substrate transport problems such as generation of injuries in handling of workers, dust generation, and contamination of peripheral devices due to coating liquid adhering to the outer peripheral edge of the substrate, and film due to processing accuracy There was a problem of thickness fluctuation. In the method of arranging the rectifying plate above the substrate, even if the distance between the substrate and the rectifying plate is adjusted, it is not possible to compensate for the lack of shaking of the coating liquid during spinning only by rectifying the air flow during spinning. Further, even if the shape of the outer peripheral edge of the substrate is combined with the method of arranging the rectifying plate above the substrate, the increase in the film thickness at the outer peripheral edge of the substrate cannot be sufficiently reduced. On the other hand, in the case of a coating solution to which a solvent is added, a current plate is disposed above the substrate, and spin coating is performed in a sealed or substantially sealed space, thereby adjusting the volatility of the solvent, thereby controlling the film thickness of the effective region. Although it is possible, it is considered that a material with a small amount of volatile components such as a material to which no solvent is added cannot improve the film thickness distribution because the effect of adjusting the volatility cannot be obtained. Furthermore, as the spin speed increases, the space between the substrate and the rectifying plate becomes negative pressure, the central portion of the rectifying plate is deformed, and the gap between the central portions becomes narrower than the outer peripheral portion. Even in the added material, the film thickness is difficult to control because of restrictions on spin coating conditions.

  That is, in the method in which the current plate is arranged above the substrate, only the centrifugal force and the volatilization amount control by spin are controlled in relation to the film thickness distribution.

  Furthermore, the method of disposing the rectifying plate above only the outer periphery of the substrate shown in JP-A-11-144330 is a method of applying a resist to the master glass as described above, and the purpose of the present invention is different from that of the present invention. This is a method of improving the conventional method in which a uniform film thickness distribution is obtained and increasing the film thickness of the outer peripheral portion. The conventional method in which the current plate is disposed above the outer peripheral portion of the substrate is a method of increasing the film thickness by controlling the volatilization amount of the solvent by increasing the flow velocity in the outer peripheral portion. In the case of liquid, it is difficult to obtain the effect, and the film thickness distribution is deteriorated even if the effect of the current plate is obtained. In addition, no consideration has been given to insufficient shaking of the coating liquid by increasing the flow rate.

That is, in the conventional method, the organic protective film formed on the recording film cannot be formed with a uniform thickness.
JP 11-144330 A

  The present invention has been made in view of the above problems, and improves the film thickness distribution from the inner periphery to the outer periphery of the coating film by the spin coating method, and forms a coating film having a uniform film thickness.

  In other words, the coating solution is applied to the substrate and spread by spin coating, and the film thickness distribution of the inner and outer peripheral coating films is improved, and the coating thickness of the outer peripheral portion is prevented from rising and contains no solvent. A coating film having a uniform thickness is also formed in the coating solution.

  In order to achieve the above object, a coating film forming apparatus of the present invention has a coating liquid supply means for supplying a coating liquid onto a substrate, an outer diameter that is 0.1 mm or more larger than the outer diameter of the substrate, and a center And a current plate disposed above the substrate without a hole, and the distance between the current plate and the substrate changes so as to narrow continuously or stepwise from the inner periphery to the outer periphery of the substrate. It is characterized by that.

  In the present invention, in addition to the scattering of the coating liquid due to the centrifugal force generated by the spin and the film thickness control by adjusting the solvent volatilization amount, by controlling the gas flow velocity on the surface of the coating film, the lack of the centrifugal force generated by the spin is assisted. The amount of scattering of the coating liquid is increased.

  In addition, it is thought that the film thickness distribution of the spin coat method in the base material having the center hole is thicker toward the outer periphery due to the centrifugal force generated by the rotation because the tension pulled back to the inner periphery side of the coating liquid is insufficient. It is considered that the film thickness distribution in the coating liquid with a small volatilization amount is determined by the coating start position on the inner peripheral side, the outer diameter of the substrate, and the film thickness at a predetermined radius. That is, by setting the rotation speed and the viscosity, surface tension, and density of the coating liquid, the film thickness at the predetermined radius position can be obtained arbitrarily, but the coating start position on the inner circumference side is limited. The film thickness distribution on the inner periphery and the outer periphery is determined, and it is impossible to improve the film thickness distribution with the number of rotations and the properties of the coating solution.

  The present invention reduces the film thickness difference between the inner periphery and the outer periphery by reducing the film thickness at the outer periphery by paying attention to the assistance of centrifugal force due to the gas flow velocity on the coating film surface.

  That is, the centrifugal force is assisted by increasing the gas flow rate on the coating film surface toward the outer peripheral part rather than the inner peripheral part of the substrate, and the coating solution remaining excessively is scattered.

  Also, instead of providing a rectifying plate only above the outer periphery of the substrate, by arranging the rectifying plate so as to cover the substrate, it is possible to control the film thickness distribution by controlling the entire air current on the surface of the coating film Yes. This is because when the central part of the rectifying plate is opened, an environment in which gas continuously flows can be obtained, but when the gap between the substrate and the rectifying plate is narrowed, the resistance of the gas passing through the gap increases, thereby causing a reverse flow. This is because it becomes difficult to control the flow rate of the gas. Further, by covering the substrate, it is possible to prevent an unnecessarily large amount of gas from flowing over the uncured coating film, and it is effective in reducing dust defects. Generally, from the viewpoint of productivity, the spin coating time is required to be completed within a few seconds. Since the time from the start of rotation to the stop of rotation is about 5 seconds, the rectification is performed without opening the central portion of the rectifying plate. By setting the shape of the plate and the distance from the substrate, it is possible to obtain a necessary and sufficient airflow on the substrate.

  As described above, according to the present invention, in the spin coater method, by arranging the rectifying plate whose distance from the substrate becomes narrower toward the outer periphery above the substrate, the application start position of the coating solution and the properties of the coating solution are changed. The present invention provides a coating film forming apparatus and manufacturing method, particularly a magneto-optical disk manufacturing apparatus and manufacturing method, which can form a coating film uniformly and with high quality without any restrictions.

(Example 1)
FIG. 1 is a schematic sectional view showing an optical disk manufacturing apparatus according to the present invention.

  As the substrate 1, a polycarbonate resin substrate having a thickness of 0.6 mm, an outer diameter of 50.8 mm, and an inner diameter of 11 mm was used, and a recording film was formed on the substrate. The recording film can be formed by sputtering or vapor deposition of a plurality of laminated magneto-optical recording films and an inorganic protective film and a reflective film on and under the recording film as required.

  The substrate 1 was placed on the turntable 3 holding the substrate with the recording film facing upward, and the substrate was vacuum-sucked in the vicinity 2 of the center of the turntable. The size of the turntable was the same as the outer diameter of the substrate. As a substrate holding method, a magnet chuck method using a magnet or a mechanical clamping method can be used besides vacuum suction.

  Next, the turntable was rotated at a low speed of 20 rpm, and an ultraviolet curable resin having a viscosity of 100 mPaS was used as the coating liquid, and the nozzle for coating on the substrate was moved to a predetermined position to apply the coating liquid. . As the ultraviolet effect type resin, an acrylic solventless resin was used. The coating liquid is applied to the substrate by rotating the substrate and moving the nozzle to form a spiral shape or a concentric circle, or by applying a coating solution to the central portion by capping the opening at the central portion of the substrate. Can be used. When the application amount is large, the rebound and mist reattachment due to the excessive application liquid increase, so that it is desirable to apply the minimum necessary application amount.

  The application start position on the inner peripheral side was a radius of 10 mm.

  Next, the rectifying plate 4 was disposed above the substrate. The cross-sectional shape of the rectifying plate is inclined in a conical shape so that the height is 10 mm with a radius of 26 mm, based on the height of the radius of 0 mm. The gap between the substrate and the current plate was set to 12 mm at the center and 2 mm at the outer periphery of the substrate.

  The current plate is installed in the outer cup 5 which is the outer wall of the spin coater cup, forms a sealed space, and is configured to rotate only the turntable.

  The outer diameter of the rectifying plate may be controlled as long as the gas flow velocity in the gap between the substrate and the rectifying plate can be controlled, and can be controlled if it is 0.1 mm or more larger than the outer diameter of the substrate. The outer peripheral portion of the rectifying plate and the outer wall of the spin coater cup It is also possible to control the turbulent flow due to the rotation of the substrate by providing a gap between the two. When the outer diameter of the rectifying plate is smaller than 0.1 mm than the outer diameter of the substrate, turbulent flow is generated in the vicinity of the outer peripheral portion of the substrate, making it difficult to control the airflow.

  The gap between the rectifying plate and the substrate can be arbitrarily set according to the spin coating conditions such as the properties of the coating liquid, the number of rotations, and the rotation acceleration. It is desirable to provide a gap of 5 mm or more. Moreover, since it will become difficult to raise a flow rate if a clearance gap is expanded too much, it is desirable to set it as a clearance within 10 mm in an outer peripheral part.

  An exhaust hole 6 is provided in the spin coater cup. Although it is possible to perform forced exhaust from the exhaust hole, it is desirable to monitor the exhaust amount and adjust the exhaust amount in order to control the rotating airflow.

  Furthermore, in order to obtain a predetermined film thickness, it is started up at a high speed of 2000 rpm in 0.5 seconds and held for 3 seconds to disperse and remove excess coating solution on the substrate, and a uniform film on the entire surface. Got thick.

  If necessary, the number of revolutions can be controlled in multiple stages to make the film thickness uniform and to remove excess coating solution on the outer periphery of the substrate. Multi-stage control is performed at high speed rotation for a short time so that it is held at 2000 rpm for 2.8 seconds, raised to 5000 rpm for 0.1 second, and held for 0.1 second. In this method, the staying coating liquid is more scattered, and by providing the flow straightening plate, it is possible to increase the air velocity and reduce the outer peripheral bulge by multistage control.

  Next, after the rotation of the substrate was stopped and the current plate was removed, the turntable was taken out of the turntable, irradiated with ultraviolet rays, the coating solution was cured to form a protective film, and a magneto-optical disk was manufactured.

  The coating film at this time was able to obtain a uniform film thickness. The swell at the outer periphery of the substrate was greatly improved because the excess coating solution was scattered and removed.

(Example 2)
FIG. 2 shows a schematic cross-sectional view of an optical disk manufacturing apparatus according to the second embodiment of the present invention.

  A magneto-optical disk was manufactured in the same manner as in Example 1 except that the outer periphery of the rectifying plate was held on the outer periphery of the turntable and rotated with the substrate.

  Although the current plate is held by a magnet, it may be held by a turntable, and a holding method by mechanical clamping or fitting can be performed.

  By rotating the rectifying plate together with the turntable, there is no influence of the rotating touch of the spindle, and the gap between the rectifying plate and the substrate can be kept extremely narrow and accurate. As a result, the gap between the substrate and the current plate in the circumferential direction can be kept constant, and the film thickness uniformity can be further improved. The swell at the outer periphery of the substrate did not occur because excess coating solution was scattered and removed.

(Example 3)
Using a glass master having a thickness of 0.6 mm and no outer diameter of 50.8 mm as a substrate, using a resist of a mixture of a novolac resin, an ethyl cellosolve solvent and a photosensitizer as a coating solution, the center of the substrate A glass master was prepared in the same manner as in Example 1 except that the coating was applied to the part.

  The coating film thickness at this time was 100 nm at a radius of 0 mm and 103 nm at a radius of 24 mm, and a uniform film thickness could be obtained. Swelling at the outer peripheral portion of the substrate hardly occurred because excess coating solution was scattered and removed.

Example 4
Using a glass master having a thickness of 0.6 mm and no outer diameter of 50.8 mm as a substrate, using a resist of a mixture of a novolac resin, an ethyl cellosolve solvent and a photosensitizer as a coating solution, the center of the substrate A glass master was prepared in the same manner as in Example 2 except that the coating was applied to the part.

  The coating film thickness at this time was 100 nm with a radius of 0 mm and 101 nm with a radius of 24 mm, and a uniform film thickness could be obtained. The swell at the outer periphery of the substrate did not occur because excess coating solution was scattered and removed.

(Comparative Example 1)
A magneto-optical disk was manufactured in the same manner as in Example 1 except that the rectifying plate was not provided above the substrate.

  The coating film thickness produced by the method of Comparative Example 1 increased in thickness toward the outer periphery, and increased in the vicinity of the outer periphery. It is considered that the coating liquid remaining excessively in the vicinity of the outer periphery was pulled back to the inner peripheral side after the rotation stopped, and the swell was generated. Further, a defect due to mist adhesion, which did not occur in the above-described embodiment, occurred from the outer peripheral portion of the substrate to the middle peripheral portion.

(Comparative Example 2)
A magneto-optical disk was manufactured in the same manner as in Example 1 except that a rectifying plate having a flat surface facing the substrate was disposed above the substrate, and the distance between the rectifying plate and the substrate was set to 15 mm.

  The coating film prepared by the method of Comparative Example 2 had a coating thickness distribution equivalent to that of Comparative Example 1 although coating defects such as mist reattachment were smaller than those of Comparative Example 1.

  The measurement results of the protective film thickness in the radial direction in the magneto-optical disks formed in Examples 1 and 2 and Comparative Examples 1 and 2 are shown in FIG.

  In the methods of Examples 1 and 2, the film thickness from the inner periphery to the intermediate periphery is substantially the same as that of the comparative example, but the film thickness from the intermediate periphery to the outer periphery is reduced.

  In the inner circumference to the middle circumference, the effect of the rectifying plate installed on the upper side is small, and the film thickness distribution is almost the same as in Comparative Examples 1 and 2. It is estimated that the film thickness distribution was improved.

It is a schematic cross section which shows the manufacturing apparatus of the optical disk in Example 1 of this invention. It is a schematic cross section which shows the manufacturing apparatus of the optical disk in Example 2 of this invention. It is a schematic cross section which shows the manufacturing apparatus of the conventional optical disk. The film thickness distribution of the protective film of the magneto-optical disk manufactured in Examples 1-2 and Comparative Examples 1-2 is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 Turntable adsorption | suction part 3 Turntable 4 Current plate 5 Outer cup 6 Exhaust hole

Claims (1)

  In a coating film forming apparatus for forming an organic film on a substrate by a spin coating method, a coating liquid supply means for supplying a coating liquid on the substrate, an outer diameter that is 0.1 mm or more larger than the outer diameter of the substrate, and A current plate disposed above the substrate without a central hole, and a distance between the current plate and the substrate is narrowed continuously or stepwise from an inner periphery to an outer periphery of the substrate. A coating film forming apparatus characterized in that the coating film is changed.

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