JPH01192035A - Method for adhering optical disk - Google Patents

Abstract

PURPOSE:To enhance the reliability of recording and reproduction by welding substrates on an inside circumferential spacer side by an ultrasonic welding method and the substrates on an outside circumferential spacer side by using an adhesive agent having rubber elasticity. CONSTITUTION:Two sheets of the doughnut-shaped polycarbonate substrates 1 formed with tracking grooves are used and such substrates on which thin films are provided as recording layers 2 are used as the carrier substrates for an optical disk. Two sheets of these substrates are welded by using an inside circumferential spacer 3 and outside circumferential spacer 4 made of polycarbonate and by using an ultrasonic welding machine from above the spacer 3. The two-liquid curing type silicone rubber adhesive agent is previously coated on both faces face of the spacer 4 and the spacers are held in place between the substrates in such a manner that the recording layers are positioned on the inner side, then the substrates are ultrasonically welded. The substrates are thereafter sandwiched and fixed from both the front and rear faces of the air sandwich disk by glass plates 7 and are rested for 12hr in a room in this state. The glass plates 7 are removed and further, the disk is rested for 12hr.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to bonding of air sandwich type optical discs. More specifically, it is an adhesion method related to bonding.

(Prior Art) In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk and can be used as a video disk, an audio disk, a large-capacity still image file, and a large-capacity computer disk memory. The basic structure of an optical disk is a disc-shaped transparent plate made of plastic or glass, and a recording layer made of a metal or semimetal such as Bi, Sn, In, Te, etc., provided thereon. Information is written on an optical disc by, for example, irradiating the optical disc with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in physical or chemical changes. Information is recorded by changing its optical properties. Reading information from an optical disc is also performed by irradiating the optical disc with a laser beam, and the information is reproduced by detecting reflected or transmitted light according to changes in the optical characteristics of the recording layer. Recently, as a disk structure for protecting the recording layer, a recording layer is provided on at least one of two disk-shaped substrates, and the recording layer is located inside the two substrates, and An air sandwich structure has been proposed in which a ring-shaped inner spacer and a ring-shaped outer spacer are sandwiched and joined to form a space. In optical discs with such a structure, the recording layer is not in direct contact with the outside air, and information is recorded and reproduced using laser light that passes through the substrate, so the recording layer is generally not subject to physical or chemical damage. There is no possibility that the recording or reproduction of information will be hindered by dust particles or dust particles adhering to the surface.

(Problems to be Solved by the Invention) However, the optical disc of this air sandwich structure may be deformed, warped, or curved due to applied strain at the bonding point between the disk substrate and the spacer during bonding or storage. Even if there is no apparent deformation, applied strain at the bonding point will cause a shift (jitter) in the signal position in the outermost group on a small disk with a diameter of 130 mm, and on a large disk with a diameter of 300 mm. The group on the outer periphery has a wavy phenomenon (Sn
ake) When such a phenomenon occurs, correct recording and reproduction cannot be performed even if a laser beam is irradiated.

(Means for Solving the Problems) The optical disc bonding method of the present invention is such that, in an air sandwich type optical disc, the inner circumferential spacer side is welded by ultrasonic welding, and the outer circumferential spacer side is welded using an adhesive having rubber elasticity. It is characterized by the fact that it can be bonded together using

(Preferred mode for carrying out the invention) The optical disk adhesive and bonding method of the present invention uses polymethyl methacrylate (PMMA) as a disk substrate,
A plastic molded product such as polycarbonate (PC) is used. Plastic substrates are less likely to break than glass substrates, and can be easily mass-produced using injection molding machines, resulting in low costs.

However, plastic substrates have a higher coefficient of thermal expansion and contraction than glass substrates or metal substrates, and because they are absorbent and have oxygen permeability, they are susceptible to dimensional changes in response to environmental changes such as changes in temperature and humidity. This dimensional change causes a large deviation, especially between the outer spacer and the outer circumference of the disk, resulting in applied distortion, resulting in Jitter, 5n.
This causes phenomena such as ake. In order to solve this problem, there is no choice but to use an adhesive that relieves the applied strain on the outer periphery, and an adhesive having rubber elasticity is used as the adhesive.

First, if the inner circumferential spacer is centered and fixed by welding using ultrasonic welding, then the outer circumference (where the outer circumferential substrate and outer circumferential spacer are bonded) is fixed by inner circumferential bonding. You can temporarily avoid the effects of applied strain caused by dimensional changes. (Since the outer periphery has not yet solidified) Next, under the bonding environment conditions, the outer periphery substrate and spacer are bonded with an adhesive having rubber elasticity, so that they are solidified in a state where no applied distortion occurs. go. The important point here is that the outer periphery adhesive is in a semi-cured state (
The problem is to remove the fixing jig before it completely hardens. This is to allow the adhesive layer to follow the dimensional changes due to expansion and contraction of the outer periphery of the substrate and the outer periphery spacer, and if this operation is not performed, jitter will occur.

5nake phenomenon cannot be completely eliminated.

Next is the ultrasonic welding method, which is the inner spacer.

If ultrasonic welding is performed on both the outer periphery spacer, signal jitter will occur with respect to the outer periphery group, which is undesirable. Furthermore, if a rubber adhesive is used on both the inner and outer peripheries, eccentricity is likely to occur. Therefore, the inner circumference is ultrasonically welded, and the adhesive having rubber elasticity used for the outer circumference includes urethane rubber, synthetic rubber, and silicone rubber adhesives. As for the bonding process, for example, if an ultrasonic welding method is used to bond the inner periphery and a two-component silicone rubber thread gripper is used for the outer periphery, the ultrasonic welding method will bond almost instantaneously, and the silicone rubber bond The agent requires 24 hours to fully cure. In this case, the inner circumferential spacer is sandwiched between two disk substrates and ultrasonically welded. However, silicone rubber adhesive is applied to both the top and bottom surfaces of the outer circumferential spacer, and the two disk substrates are attached with the recording layer inside. Sandwich the air sand disk by ultrasonic welding from the top surface to center and fix the center. Then sandwich the disk between two glass plates (upper and lower) and leave it as it is for 12 hours. With the adhesive layer on the outer periphery semi-hardened, attach the disk to the glass plate. Remove. The bonding process is completed by leaving it in this state for another 12 hours.

(Effects of the Invention) In an air sandwich type optical disc, the inner circumferential spacer side is welded using an ultrasonic welding method, and the outer circumferential spacer side is bonded using an adhesive having rubber elasticity. In the optical disc bonding method of the present invention, J
Compared to the case where the same adhesive is used to bond the outer periphery spacer, a small disk with a diameter of 130 mm will have no jitter when writing and reading signals on the outer periphery, and a large disk with a diameter of 300 mm will have less jitter on the outer periphery. This eliminates the groove waving phenomenon (snake) and improves the reliability of recording and reproduction.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 A donut-shaped polycarbonate (PC) substrate 1 with a groove width of 0.611 mm for tracking was formed in a spiral shape. 2. Molded with a groove depth of 700 mm and a pitch width of 1.611 mm.
Te and S are used on each group surface as the recording layer 2.
A thin film consisting of E, Ti, and Ag was deposited by sputtering to a thickness of 500 mm, and was used as an optical disk carrier substrate. These two optical disk carrier substrates are covered with a 0.9 mm thick polycarbonate (PC) inner peripheral spacer 3. The outer circumferential spacer 4 is welded from the top surface of the inner circumferential spacer 3 using an ultrasonic welding machine (Model 9800, manufactured by Branson), but both sides of the outer circumferential spacer 4 are coated with a two-component hardening base silicone rubber adhesive (KE67). .

CatRC2.0% (Shin-Etsu Chemical Co., Ltd. product) is applied, and the recording layer is placed on the inside, a spacer is inserted, and the inner circumference is ultrasonically welded. After that, the air sand disk was sandwiched between the top and bottom sides of the glass plate, which is a fixing jig, and fixed by sandwiching the glass plate with eyeball clips, left as it was indoors for 12 hours, and then removed the glass plate and left for another 12 hours. did. When the jitter of the outer periphery of this Sunful was measured, it was found to be the same value as that of a single disk that was not bonded.

Comparative Example 1 Both sides of the inner and outer circumferential spacers were ultrasonically welded using the ultrasonic welding machine used in Example 1. The rest was treated in the same manner as in Example 1. Jitter on the outer periphery of this sample
When measured, the values changed significantly, indicating that the recorded and reproduced signals deviated greatly from the group.

Example 2 A donut-shaped polymethyl methacrylate (PMMA) substrate 1 with an outer diameter of 300 mm, an inner diameter of 35 mm, and a thickness of 1.2 mm is spirally formed with a groove width o4 as a tracking groove.
Two sheets molded with a groove depth of 900 mm and a pitch width of 1.611 were used as the recording layer 2, and each group surface was coated with Te.

An optical disk carrier substrate was prepared by depositing a thin film of Se, Ti, and Ag to a film thickness of 500 Å using a sputtering method. These two optical disk carrier substrates are bonded using a special spacer (core material, JP-A-6O-251535) made of PMMA and an iron core, and the disk substrates are attached to the inner periphery of the spacer alternately on one side using an ultrasonic welding machine. 98
Ultrasonic welding is performed using 0 (1!!, manufactured by Branson Corporation), but two-component curing type silicone rubber adhesive (KE68, 2.0% catalyst RC mixture, Shin-Etsu Chemical Co., Ltd. product) is applied to the outer periphery of the spacer on both sides. , sandwich the spacers so that the recording layer of the substrate is on the inside, and weld the inner circumferential spacers alternately from the top and bottom surfaces of the air sand disk using an ultrasonic welding machine. Next, use a fixing jig. I fixed it with a glass plate and placed a weight on it. After 12 hours, the weight and the glass plate were removed, and the sample was left indoors for another 12 hours to completely cure the adhesive layer on the outer periphery. 5nake on the outer periphery of this sample
When measured, the value was the same as that of a single disk without bonding.

Comparative Example 2 Both sides of the inner and outer circumferential spacers were coated with the silicone rubber adhesive of Example 2, and otherwise treated in the same manner as in Example 2. When the eccentricity of the outer periphery of this sample was measured, it was found that the value changed greatly, and the groups (grooves) were largely deviated.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a state immediately after the inner circumferential portion of an air sandwich optical disk sandwiched between two glass plates in Example 1 of the present invention is ultrasonically welded. (Explanation of symbols) 1, ...Disc substrate 2, ...Recording layer 3, ...Inner spacer 4, ...Outer spacer 5, ...Inner Circumferential ultrasonic welding layer 6,... Outer silicone rubber welding layer 7,...
... Glass plate 8, ... Eyeball clip

Claims (1)

[Claims] A method for adhering an optical disc, which is characterized in that, in an air sandwich type optical disc, the inner spacer side is welded by ultrasonic welding, and the outer spacer side is bonded using an adhesive having rubber elasticity.