JPH07169105A - Production of optical disk - Google Patents

Abstract

PURPOSE:To prevent the occurrence of unevenness in coating by regulating the ratio between the peripheral speed of a coating roller and the speed of a conveyor for conveying a substrate to a specified range. CONSTITUTION:A roll coater is composed essentially of a coating roller 1, an under roller 2 and a conveyor 3 for conveying a substrate 6. In this structure, the ratio between the peripheral speed of the coating roller 1 for coating the top of the substrate 6 with a resin layer 5 of a hot-melt adhesive and the speed of the conveyor 3 is regulated to 7:1 to 17:1. In the case of <7:1, entrapment phenomenon is liable to occur. In the case of >17:1, entrapment phenomenon does not occur but unevenness in coating in the longitudinal direction is liable to increase.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an optical disk, in which a hot melt adhesive is applied on a substrate having a recording film formed thereon.

[0002]

2. Description of the Related Art Optical recording media capable of storing information at high density are expected to become widespread as large-capacity external memories. Among them, optical disks can be reproduced at high speed. It is attracting attention as an external memory for computers. Various types of optical recording media with different information storage methods and sizes have been proposed. Among them, the write-once type and the rewriting of information in which the information can be written only once with the size of 5.25 inches in diameter are proposed. Possible magneto-optical types, ROM type that is read-only for 3.5-inch diameter, magneto-optical type, and partial ROM type that mixes magneto-optical and ROM are standardized by ISO standard. It is expected to become even more widely marketed.

Recently, optical discs have begun to be applied in the digital audio field. For example,
A player using a write-once type optical disk or a magneto-optical disk has been put on the market as a master source in 24-48 digital multi-track recording. In addition to such products for professionals, CD-Rs (light once type compact discs) and MDs (mini discs) have also appeared in products for general consumers, and future trends are drawing attention.

On these optical discs, guides for orderly arranging the information marks by the laser beam from the optical pickup of the recording / reproducing apparatus, that is, for tracking are formed in the form of concave or convex grooves from the inner circumference of the disc. It is formed in a spiral shape toward the outer circumference. This groove is called a guide groove. If the guide groove is further described in detail, as defined in the ISO standard,
A portion that is concave when viewed from the optical pickup, that is, a portion that is distant is called a land, and a portion that is convex when viewed from the pickup, that is, a portion that is near is called a groove. Information is recorded on either lands or grooves. Recording on a land is called a land recording method, and recording on a groove is called a groove recording method. A route for recording information is called a track. From the center of the track to the center of the next track,
We call it track pitch.

As a material for the substrate, glass or synthetic resin is used as a transparent substrate, but for the glass substrate, synthetic resin such as polymethylmethacrylate or polycarbonate is used in view of manufacturing cost and safety. In general, a protective film, a recording film, and a protective film are sequentially formed on this using a vacuum deposition method or a sputtering method. Further, in order to protect the surface of the substrate from dust adhesion, scratches, etc., a light-transmitting organic protective film may be formed on the surface of the substrate.

By the way, there are two types of optical discs, one of which is composed of one substrate having a recording film formed thereon and the other of which is composed of two substrates or protective substrates bonded together.
Of these, the latter is 2 with the recording film forming side facing inward.
By adhering two substrates so that they face each other, the mechanical protection of the recording film and the environmental resistance are improved. There are many types of adhesives that can be used for such adhesion. For example, the UV-curable adhesive that has been often used in the past can be configured simply because it is quickly cured by irradiation with UV light for a short time, but the recording film does not transmit UV light. I can't. Therefore, there is a problem in manufacturing an optical disc having excellent durability. Also,
Although a thermosetting adhesive such as an epoxy resin has sufficient adhesive strength, it takes 10 hours to several days to be completely cured, which causes a problem of poor productivity.

On the other hand, the hot melt adhesive is
Since it does not contain an organic solvent, there is no adverse effect on the recording layer,
Due to its excellent mass productivity and simple process, it has come into the spotlight. Bonding with hot melt adhesive
The recording film side of the substrate on which the recording film is formed is roll-coated (applied) with a hot-melt hot-melt adhesive by a roll coater, and similarly processed. It is to bond them together.

[0008]

However, when actually applying a hot-melt type adhesive with a roll coater, the viscosity of the hot-melt type adhesive, which melts the substrate, is often involved in the application roller. was there. In this case, slip marks were recognized on the surface of the hot-melt adhesive applied on the substrate, and horizontal stripe-shaped uneven coating was generated. It was also found that when an accelerated test at 80 ° C. and 85% RH is performed after such substrates are bonded to each other to manufacture an optical disk, peeling is likely to occur at the bonded portion, and the life of the optical disk becomes a problem.

[0009]

As a result of earnest research, the present inventor has found that the substrate melts by adjusting the speed ratio of the outer peripheral speed (or the number of rotations) of the coating roller and the conveyor speed for conveying the substrate to a certain range. The present invention has been completed by finding that the problem of causing the coating roller to be caught due to the viscosity of the hot-melt adhesive that is being applied, which causes uneven coating, has been achieved.

Therefore, according to the present invention, "a recording film is formed on a substrate, an organic protective film is formed on the recording film, and a hot-melt type adhesive is further applied on the organic protective film, and another In the method of manufacturing an optical disk in which substrates are bonded together, the ratio of the peripheral speed of the coating roller for coating the resin layer of the hot melt adhesive to the conveyor speed for substrate transportation is 7: 1 to 1 in the previous period.
Method for manufacturing optical disc characterized by being 7: 1 "
Is provided.

[0011]

As shown in FIG. 1, the roll coater is mainly composed of a coating roller, an under roller, and a conveyer for conveying the substrate. The substrate is rolled up on the surface of the coating roller due to the viscosity (tackiness) of the hot-melt adhesive on the coating roller. The substrate enters between the coating roller and the under roller, and the hot-melt adhesive is almost coated on the substrate. It is time to finish and be discharged. The substrate wound on the surface of the coating roller peels off from the surface of the roller due to its own weight. That is, when the disk substrate is rolled up, the front side of the substrate tilts upward, and then the disk substrate falls off while peeling off from the surface of the coating roller due to its own weight, resulting in uneven coating.

This phenomenon is related to the ratio between the rotation speed of the coating roller and the passing speed of the substrate, and the ratio of the rotation speed (or peripheral speed) of the coating roller to the conveyer conveyor speed is 7:
A good coating film was obtained in the range of 1 to 17: 1, and 8: 1 to 1
3: 1 is more preferable. When the speed ratio is less than 7: 1, the above-mentioned entrainment phenomenon easily occurs, and the speed ratio is 17:
If it exceeds 1, there is no entrainment phenomenon, but coating unevenness in the front-back direction tends to increase.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto.

[0014]

[Example] Diameter 130 mm (5.25 inches), plate thickness 1.2 mm
A polycarbonate substrate with a guide groove was prepared. On the guide groove side of the substrate, a protective film of Si ₃ N ₄ with a thickness of 75 nm,
A TbFeCo recording film with a thickness of 100 nm and a Si ₃ N ₄ protective film are used.
It was formed to a thickness of 75 nm by the sputtering method. UV-curing resin OVD-002 is formed on the protective film of this optical disk substrate.
(Nippon Kayaku Co., Ltd.) was spin-coated, and after nitrogen substitution (after discharging oxygen), ultraviolet rays were irradiated for 1 minute by a high pressure mercury lamp to cure. At this point, the thickness of the substrate is measured.

Next, a roll coater R400T-DW (manufactured by Matsushita Industrial Co., Ltd.) was used to apply a hot melt adhesive to the recording film side of the optical disk substrate. Aronmelt PPET-XW-30 (manufactured by Toagosei) was used as the hot melt adhesive, and the resin melting temperature was 130 ° C. The number of rotations of the coating roller is 100, 2
The speed was 00, 400, 500, 600, 800 rpm, and the conveyer conveyor speed was 25, 30, 35 cm / sec. The thickness of the disk substrate after coating was measured with a digital micrometer (manufactured by Tsugami). The four measurement points are front, rear, left and right with respect to the feeding direction. The results are shown in Table 1.

From Table 1, when the ratio of the coating roller rotation speed to the substrate passage speed is within the range of the present invention,
It can be seen that good adhesion with small coating unevenness is performed.

[0017]

EFFECTS OF THE INVENTION According to the present invention, in the step of adhering substrates by a roll coater, the coating unevenness can be suppressed by controlling the number of revolutions of the coating roller or the peripheral speed and the conveying conveyor speed within the range of the present invention. As a result, a highly reliable optical disk can be supplied.

[0018]

[Table 1]

[Brief description of drawings]

FIG. 1 is a sectional view of an optical disk manufacturing apparatus according to the present invention.

[Explanation of symbols]

 1 ... Coating roller 2 ... Under roller 3 ... Conveyor for transport 4 ... Tank (heating tank) 5 ... Hot melt adhesive 6 ... Substrate and above

Claims (1)

[Claims] 1. An optical disk in which a recording film is formed on a substrate, an organic protective film is formed on the recording film, a hot-melt adhesive is applied on the organic protective film, and another substrate is bonded. 2. The method for producing an optical disc as described in 1 above, wherein the ratio of the peripheral speed of the application roller for applying the resin layer of the hot melt adhesive to the substrate transfer conveyor speed is 7: 1 to 17: 1.