JPS63268150A - Formation of film for information carrier - Google Patents

Abstract

PURPOSE:To prevent expansion of surface defects originating from the deposited foreign matter, flaws, etc., on a disk surface by spraying a coating liquid for a hard protective film to the region exclusive of the part near a center hole and drying the coating to cure. CONSTITUTION:The center hole 12 of the disk 11 is coated with a disk-shaped label 17 and thereafter, the coating liquid 19 for the hard protective film is sprayed in the form of mists from a nozzle 18 and is coated on the disk at the time of forming the hard protective film 22. The coating is thereafter dried to cure and the label 17 is stripped to form the film 22. The expansion of the defects originating from the deposited foreign matter and flaws is, therefore, obviated even if the surface has such deposited matter and flaws. The small flaws are conversely embedded and the surface flaws are annihilated. Since the coating liquid 19 is not blown near the center hole, the shape of the center hole does not change at all and the generation of a run-out and surface waving is obviated even if the film 22 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a surface coating on the surface of a disk-shaped object, and relates to a method for forming a surface coating on the surface of a disk-shaped information carrier disk (hereinafter simply referred to as a disk). It can be used in the process of forming a protective film to protect the surface.

2. Description of the Related Art Conventionally, a recording medium layer is provided on one side of a disc-shaped transparent substrate, and a predetermined information signal is recorded as concave and convex pits, with the surfaces of the recording medium layer facing each other. 2
Alternatively, a disk has been put into practical use in which a protective plate is simply pasted together to form a disk, and information is recorded, reproduced, or erased using a laser beam.

Resin materials such as cast acrylic and polycarbonate are often used for these disk substrates from the viewpoint of economy and safety. These resin materials have a problem in that their outer surfaces are easily scratched during use. For this reason, it has been considered to protect the disk surface by forming a coating with high hardness. As shown in FIG. 4, a conventional method for forming this protective film is to place a disk 4 with a center hole 6 fixed to a rotating shaft 3 in a dip tank 2 containing a coating liquid 1;
After applying the coating liquid 1 while rotating at low speed while immersed in the vicinity of the center hole 5, the disk 4 is pulled up from the dip tank 2 and rotated at high speed to remove excess coating liquid and harden. The so-called spin coating method was mainly used to form a protective film 6 as shown in the figure (for example, Japanese Patent Laid-Open No. 58-43267).

Problems to be Solved by the Invention However, with the conventional method of forming a protective film using the spin coating method explained in FIGS. Surface waviness of the protective coating occurs in the radial direction of the disk starting from the defect, and
There was a drawback that defects such as small foreign matter adhesion were greatly magnified. Further, when holding a disk in the center hole, if there is a burr or the like on the edge of the center hole, the burr or the like adheres to the disk surface, causing a similar defect to occur and expand. As described above, the spin coating method has the problem that the smoothness of the protective coating is impaired due to defects such as foreign matter and scratches, and the number of defects that affect recording, reproduction or erasing is greatly increased.

Means for Solving the Problem In order to solve this problem, the present invention sprays a hard protective film coating liquid over the entire surface of the disk except for the vicinity of the center hole of the disk, applies it in a spray state, and then dries and hardens it. This process forms a hard protective coating on the disk surface.

In other words, by spraying the coating solution for the hard protective film and applying it in a spray state, even if there is a defect due to adhesion of foreign matter, the defect will not enlarge, and on the contrary, thin scratches etc. will be buried and surface defects will be removed. A hard protective film can be formed even when the amount is reduced.

In addition, since a hard protective coating is formed in the area excluding the vicinity of the center hole, the shape of the disk surface near the center hole and center hole, which is the reference for center runout and surface runout when the disk rotates, does not change in any way. Even if a hard protective film is formed, there is no change in the two-plane runout.

Example Hereinafter, one embodiment of the present invention will be described based on the drawings.

In FIG. 1, reference numeral 11 is a disk, and as shown in FIG. 2, the cross-sectional structure thereof is shown, a recording medium layer 14 is formed on one surface of a disk substrate 13 made of polycarbonate resin and has a center hole 12, and an adhesive layer is formed on the disk substrate 13. Disk substrate 1 through 16
It is constructed by bonding together a protective substrate 16 having the same shape and the same material as 3. In FIG. 1, reference numeral 17 is a circular label attached to the center of the disk 11 with the center hole 12 as its center.

Reference numeral 18 denotes a nozzle for spraying the coating liquid for the hard protective film in a spray state, and 19 indicates the atomized coating liquid discharged from the nozzle 18.

In FIGS. 1 and 2, recording and reproduction on the disk 11 is first performed by irradiating the laser beam 20 from the side of the disk substrate 13 in FIG. It is something to do. The method for forming the hard protective film is as shown in Fig. 1, with the disk substrate 1.3 side facing up, a circular label 17 is pasted approximately in the center so as to cover the center hole 12, and then an ultraviolet curable coating is applied. By passing the liquid 19 under the nozzle 18 which is spraying the liquid 19 in the form of a spray, a layer of the hard protective coating 22 can be applied to the entire surface of the disk substrate. After this, the diluent of the coating liquid 19 is evaporated and dried, and the coating liquid 19 is cured by irradiation with ultraviolet rays. In addition to ultraviolet curable materials, thermosetting materials can also be used. Thereafter, by peeling off the label 17, a hard protective coating 22 can be formed in the area excluding the vicinity of the center hole. Note that this label 17 is not limited to a structure in which it is pasted with an adhesive and then peeled off after forming a hard protective film, but for example, as shown in FIG. Even with the member 23, similar effects can be obtained. When applying the coating liquid by spraying it in the form of a spray, there were concerns about the entrainment of air bubbles, foreign matter, and surface smoothness.
By adjusting the viscosity of the coating liquid, it was possible to apply the coating without entrainment of air bubbles. Concerning the entrainment of foreign matter, by keeping the atmosphere clean and the disk surface clean, it was possible to perform coating without the inclusion of foreign matter. Regarding the surface smoothness, a surface roughness of RmaxO0o4 .mu.m could be achieved by optimizing the coating conditions, and the film thickness at this time was 8 to 10 .mu.m. As described above, even when the coating liquid is applied by spraying or spraying, sufficient surface properties and film thickness can be obtained as a hard protective coating for the disk.

In addition, in the case of the spin coating method, after coating the disk surface sufficiently, excess coating liquid is removed by high-speed rotation.
Since this removed coating liquid cannot be reused, the efficiency of using the coating liquid is poor, but this method also has the effect of improving the efficiency of using the coating liquid compared to this spin coating method. In this example, the explanation was made using a disk in which a disk substrate and a protection substrate were bonded together.
A hard protective coating can be similarly formed on a double-sided disk made by bonding two disk substrates together. It can also be applied to disks with a single-plate structure.6 Effects of the Invention The present invention involves spraying a hard protective film coating liquid onto an area of the disk surface other than the vicinity of the center hole, applying it in a spray state, and drying it.・By curing, it is possible to prevent the expansion of surface defects caused by foreign matter, scratches, etc. on the disk surface, and the center hole, which is the center of rotation of the disk, and its vicinity do not form a hard protective coating. Therefore, it is possible to form a hard protective coating that does not cause any change in the center hole, which is the center of rotation of the disk, that is, an increase in runout, or a change in the shape of the support area of the turntable that holds the disk, and does not cause an increase in surface runout. It is something.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a state in which the method for forming a film on an information carrier of the present invention is carried out, FIG. 2 is a cross-sectional side view of the same information carrier, and FIG. 3 is a cross-sectional side view of another information carrier of the present invention. FIGS. 4 and 5 are diagrams showing a conventional method of forming a film on an information carrier and an information carrier. DESCRIPTION OF SYMBOLS 11... Disk, 13... River/disk substrate, 14... Recording medium layer, 18... Nozzle, 19... Group/coating liquid, 22...・Hard protective coating. Figure 1 Figure 2/Do Figure 3 Figure 4

Claims (2)

[Claims] (1) After applying a hard protective film coating liquid in a spray state to the entire surface of the disc-shaped body excluding the vicinity of the center hole on at least one side of the disc-shaped body having a center hole, A method for forming a film on a cured information carrier. (2) A method for forming a film on an information carrier according to claim 1, wherein a removable adhesion prevention member is provided near the center hole of the disc-shaped body and a coating liquid is applied thereto.