JPS60256944A - Method for forming disc protection curing film - Google Patents

Abstract

PURPOSE:To prevent granular defect caused by re-adhesion of scattered coating material to a disc during uniforming process by tilting vertically within a specific range and applying uniform film thickness while being turned after a transparent curing coating film material is applied to the disc. CONSTITUTION:In forming a protection curing film to an optical information medium disc, after the transparent curing coating film forming material 2, e.g., an ultraviolet ray curing resin is coated, the disc 1 is turned while being tilted by 20-70 deg. in the vertical direction, and then the resin is cured with uniform film thickness. Then an axcess material 2 is scattered as a locus 7. Thus, troubles such as re-adhesion of scattered material drops on the disc 1 causing granular defect on the cured coating film 2, the resin pooled on the outer circumference drooping downward by gravity causing ununiform film thickness at the lower side of the disc thereby causing the laser beam not normally collected to the information medium layer 8 at information recording and reproduction are prevented and a high quality disc is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for forming a protective hardened coating on an optical information carrier disk, etc. The structure of a conventional example and its problems In general, optical information carrier disks are: An information medium layer is provided on a transparent substrate such as glass or plastic. During reproduction, a laser beam is irradiated and recorded information is read by reflected light or transmitted light from the information medium layer. In this information carrier disk, if the information medium is scratched, it will cause a big problem when recording and reproducing information. Also,
When the information medium layer absorbs moisture in the air, it tends to deteriorate easily. Therefore, it is necessary to protect the information carrier layer from mechanical damage and humidity.

Common methods for protecting the information medium layer include laminating another transparent substrate on top of the information medium layer, or providing a hardened film made of a resin material or the like on top of the information medium layer. It is.

The former has problems such as an increase in the number of steps and costs, and the latter is more effective in manufacturing. Here, the latter method will be explained in more detail.

As a method for providing a cured film on the information medium layer, 1
For example, it is well known to apply an ultraviolet curable liquid organic material and then cure it by irradiating it with ultraviolet rays.Nupin coat is the most productive method for applying a liquid material onto a disc-shaped substrate. is common and common.

Here, when providing a hardened film to protect the information medium layer,
When a hardened coating is provided only on the surface having the information medium layer,
Warpage occurs on the substrate due to curing shrinkage of the cured coating material,
The size of this warpage is approximately proportional to the thickness of the cured film. If the cured coating is made thick enough to strongly protect the information carrier layer, the thickness will increase to such an extent that it cannot be used as an optical information carrier disk. Therefore, in order to increase the thickness of the cured film, it is necessary to provide the cured film on both sides of the substrate.

FIG. 1 is an explanatory diagram showing an example of the process of forming a disk protective cured coating on an optical information disk using an ultraviolet curable resin by a conventional method.

In the coating step (a), the ultraviolet curable resin 2 was applied to the disk 1 from the coating nozzle 3 using a sink while rotating the disk 1, and in the uniformization step (b), the disk 1 was held vertically. Rotate it in the state.

The excess of the ultraviolet curable resin 2 applied to the disk 1 is blown away by centrifugal force to make the film thickness uniform, and in the curing step (C), the disk 1 is rotated while being irradiated with ultraviolet rays 5 from an ultraviolet lamp 4 for ultraviolet curing. When the adhesive resin 2 is cured, a protective cured coating for one disk is formed.

Here, in the equalization step (3), the film thickness of the ultraviolet curable resin on both sides of one disk is made uniform.

If the disk is held vertically, in this case, the ultraviolet curable resin I''ii scattered upward from the disk as shown by arrow 6 during the homogenization step will be gravity-dissolved and easily re-applied to the disk. Items that are re-deposited at the very beginning of the homogenization process are homogenized with the surroundings during this process, but items that are re-applied at a later stage or those with large droplets remain until the curing process and cause particulate defects on the cured film. This not only impairs the aesthetic appearance, but also causes the laser beam to be dispersed during information recording and reproduction, resulting in a problem of deteriorating the performance of the optical information disc. The present invention overcomes the above-mentioned drawbacks and provides a method for forming a disk protective hardened coating that has a good appearance, is uniform in thickness on both sides, and has few defects.

Composition of the invention A method of forming a disk protective hardened coating according to the present invention is as follows.

A coating process in which a transparent hardened coating material is applied to the disc.

A uniformizing step of rotating the disk at an angle of 20 degrees to 70 degrees with respect to the vertical direction to make the thickness of the cured coating material applied to the disk uniform.

It consists of a curing step of curing the cured coating material that has been applied and homogenized on the disk, and it is possible to form a disk protective cured coating that has a good appearance, has a uniform thickness on both sides, and has few defects.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Among the steps of forming a disk protective hardening film according to the present invention. The coating process and the curing process are the same as those in the conventional method, and are carried out as shown in FIGS. 1(a) and 1(C), respectively.

FIG. 2 shows an example of the process of uniformizing the formation of a disk protective hardening film according to the present invention, and the same components as those in the conventional example of FIG. 1 are indicated by the same numbers. This is done by rotating the disk 1 while holding it at an inclination angle of 45 degrees with respect to the vertical direction to make the ultraviolet curable resin 2 uniform.During this process, excess ultraviolet curable resin is The resin scatters as shown by the arrow 7, but in principle it does not roll up a downward trajectory on the disk 1, so it is almost never deposited again.

The closer the inclination angle θ of the disk 1 is to 90 degrees, the smaller the possibility that the scattered ultraviolet curable resin will re-deposit. However,
When the inclination angle θ is close to 90°, the resin accumulated on the outer periphery is pulled by gravity and sag downward, so that even after equalization, the lower surface of the disk remains as shown in Figure 3. The film thickness of the ultraviolet curable resin becomes uneven. This results in unevenness on the surface of the cured film, and the laser beam is not properly focused on the information medium layer during recording and reproduction of newsletters, resulting in a significant deterioration in performance as an optical information medium disc. This film thickness unevenness tends to become larger toward the outer periphery. In addition, the average thickness of the lower layer tends to be larger than that of the upper layer, and since the resin usually shrinks when it hardens, the thicker the lower layer, the stronger the shrinkage force of the lower layer, causing the lower layer to shrink. There also arises the problem that a warp 9 is generated on the disk in the direction of concaveness. Note that 8 is an information medium layer.

A cured film with uniform thickness and few defects on both sides of the disk can be formed when the inclination angle θ of the disk in the uniformization step is between 20 degrees and 70 degrees, and preferably when θ is 40 degrees. ~
This is the case of 50 degrees.

The number of defects on the cured film depends on the viscosity of the ultraviolet curable resin,
Although it varied depending on the rotational speed of the disk in the homogenization process, when θ was 45 degrees, the reduction was approximately % to 1% compared to when θ was 0 degrees.

Effects of the Invention As described above, according to the method of the present invention, it is possible to form a protective cured film on a disc that has a good appearance, has a uniform thickness on both sides, and has few defects. This improves the performance of optical information carrier disks, etc., and improves the quality of the product.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a disc showing an example of the process of forming a disc protective hardening film using an ultraviolet curable resin by a conventional method, and FIG. FIG. 3 is a perspective view of a disk showing an example of the uniformization process of forming a disk protective cured film using an ultraviolet curable resin. FIG. 2 is a perspective view showing the shape of a cured film in a partial cross section of a disk. 1...'disk, 2...UV curable resin, 3...Nozzle, 4...UV rung, 5...UV light, 6° 7... Trajectory of the scattering ultraviolet curable resin, 8. Old... Information medium layer.

Claims (1)

[Claims] A coating step of applying a transparent hardened coating material to a disk, and rotating the disk at an angle of 20 degrees to 70 degrees with respect to the vertical direction to make the thickness of the cured coating material applied to the disk uniform. 1. A method for forming a protective hardened film for a disc, comprising: a uniformizing step of making the hardened film uniform, and a curing step of hardening the hardened film material applied and uniformized on the disc.