JP2637147B2 - Optical disk bonding method and optical disk bonding apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Purpose of the Invention] (Industrial application field) The present invention relates to a method and apparatus for bonding optical disks.

(Prior art) In an optical video disk or a laser recording disk (hereinafter referred to as an optical disk) for reading information using a laser, while rotating the disk at a high speed, a laser beam narrowed down to about 1 μm is irradiated and the position is irradiated. Detection and focus adjustment are performed, and pits of only about 1 μm are read and stored. For this reason, in the optical disk, very slight substrate warpage, deviation in parallelism, deformation, scratches, foreign matter, etc. lead to signal errors. Therefore, in an optical disk, a substrate having a high degree of parallelism and a small deformation is used, and the recording portion is set inside to prevent foreign matter from directly contacting the recording surface and the recording film.
Lamination is performed.

The most common manufacturing process for such an optical disc, for example, an optical video disc, will be described in more detail. First,
A photoresist is uniformly applied on a glass plate, and irregularities corresponding to information are deformed by a photolithography method, and the surface is plated with, for example, silver. Next, a stamper made of, for example, nickel is manufactured by electroforming. Using this stamper, a transparent substrate on which information is recorded by, for example, an injection method is manufactured. Next, on the recording surface side of the transparent substrate, a film thickness of 1000
A reflective film made of aluminum having a thickness of about 2000 ° is formed, and a protective film is further formed. Next, a hot-melt adhesive is applied to the protective film side of the two substrates by a roll coater, and the two are adhered to each other using a press device to produce an optical video disc.

By the way, in the above-mentioned manufacturing process, in the step of applying the hot melt adhesive on the protective film side of the substrate with a roll coater, the adhesive is applied in a stripe shape, and a uniform adhesive layer without unevenness cannot be formed. . Therefore, when the two substrates are bonded to each other, an internal bubble is easily formed in the concave portion where the adhesive is not applied. In the process of pressing two substrates with a pressing device, the distribution of pressure applied to the substrate from the upper and lower press plates becomes uneven, and the surface accuracy and parallelism of the pressing surfaces of the upper and lower substrates are easily deviated. The internal air bubbles in the layer are not independent but continuous, and tend to communicate with the outside air.

In the optical disk manufactured as described above, the reflection film and the recording film are in a state of being covered only with a very thin protective film and an adhesive layer. For this reason, as described above, when the bubbles in the adhesive layer are in a continuous state and communicate with the outside air, various substances enter through the pinholes existing in the protective film and the adhesive layer or due to permeation, and the reflective film and the recording film are damaged. to be influenced. For example, aluminum constituting the reflective film is a very active metal and is very thin,
It is corroded by corrosive gases contained in the atmosphere and corrosive substances that come in contact with humans. In particular, when halogen ions are present, aluminum halide is generated, which is hydrolyzed by moisture in the air, and may further corrode aluminum one after another. Further, when such an optical disc is exposed to an environment of high humidity, the adhesive force of the adhesive layer is reduced due to the invasion of moisture, which causes a problem such as peeling.

By the way, conventionally, an optical disk is put in a plastic bag with an open mouth like a record for sound, put in a paper jacket, wrapped with a plastic cover, and is stored as it is. However, in such a package, it is inevitable that corrosive substances and moisture enter the optical disc, and it is difficult to prevent the reflection film from corroding. Therefore, at present, it is sometimes impossible to reproduce recorded information due to corrosion of the reflection film.

Even when independent bubbles are formed in the adhesive layer during bonding by the press device, the internal pressure of the bubbles is increased by receiving pressure from the press device, and the bubbles are caused to change due to changes in environmental temperature and humidity. Are likely to be united into a continuous state, and may eventually communicate with the outside air.
Further, when the internal bubbles do not communicate with the outside air, they expand due to a change in the temperature of the environment and the like, and the internal pressure further increases, which may deform the substrate and generate a signal error.

Therefore, as a method of manufacturing an optical disk, it has been proposed to separately apply a two-component non-mixable adhesive to two disk substrates by a screen printing method, a spin coating method, a spray method, etc., and to bond them under reduced pressure by a press device. (JP-A-61-50231 and JP-A-61-50232). However, in this method, the use of a press device is the same, and the distribution of the pressure applied to the substrate becomes non-uniform depending on the parallelism and surface accuracy of the press plate, and an unbonded portion often occurs. In particular, the substrate manufactured by the injection method often has a non-uniform thickness, and an unbonded portion is easily generated. Therefore, when the pressure is returned to the normal pressure from the reduced pressure state, the unbonded portion communicates with the outside air, so that the same problem as described above occurs. Further, the two-component non-mixing adhesive is more expensive than the hot melt adhesive, and when applied by a spin coating method or the like, the increase in cost due to loss cannot be ignored. In addition, discs bonded in a state in which pressure distribution is non-uniform have a large surface runout and a surface runout acceleration, and as a result, the following of the pickup becomes impossible, which causes a problem that reproduction is impossible.

(Problems to be Solved by the Invention) In any case, in the conventional method, deterioration of characteristics due to corrosion of the reflective film and peeling of the bonding surface, surface runout, and surface runout acceleration are inevitable.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an optical disk having no surface deterioration and a small surface vibration acceleration without deterioration of characteristics due to corrosion of a reflective film and the like and an optical disk having such a low cost can be manufactured. It is an object of the present invention to provide a device capable of performing the following.

[Configuration of the invention]

(Means for Solving the Problems) The present invention is characterized in that in bonding in the production of a double-sided optical disc, a disc on which an adhesive is applied is placed under reduced pressure, and then pressure-bonded with atmospheric pressure or a fluid after decompression. It is assumed that.

In addition, the present invention has a room in which a disk coated with an adhesive is placed, and a room in which atmospheric pressure or fluid is placed, and between both rooms there is a partition made of a polymer film or metal foil having flexibility. Simultaneously, the pressure is reduced, and after the pressure is reduced, the reduced pressure of the room in which the disk is placed is maintained, and the other side is filled with the atmospheric pressure or a fluid and pressurized.

In addition, the part where the disk in the center of the partition of the polymer film or the metal foil touches the disk is provided with a heater that can be heated or heated by using a mirror-polished surface made of a hard material such as metal or ceramic. Are preferred.

(Operation) In the case of using the optical disk manufacturing apparatus of the present invention, the inside of the container having good flexibility and the inside of the container are simultaneously depressurized, and then the inside of the container is returned to normal pressure, and pressure bonding is performed by atmospheric pressure or pressurized fluid. By operating the switching valve as described above, the inside of the adhesive layer can be sufficiently depressurized in the first decompression step, so that the internal bubbles can be reduced and the adhesion of the substrate can be ensured. Further, if air or other fluid as a pressurized medium is heated, the fluidity of the hot melt adhesive can be increased, so that the adhesion of the substrate can be further ensured. Therefore, even when using a low-cost manufacturing process of applying a hot-melt adhesive to two substrates by a roll coater and bonding the two substrates, unlike the bonding by a press device in which pressure is uneven, internal bubbles are generated. It is difficult to be in a continuous state, and since all but small bubbles are adhered to the entire surface, it is possible to reliably prevent the invasion of corrosive substances and moisture, and to prevent the deterioration of the optical disk characteristics due to the corrosion of the reflective film, etc. In addition, during storage, it is subjected to the atmospheric pressure to ensure the adhesion. In addition, since the independent internal air bubbles are also under reduced pressure,
Even if the temperature of the environment changes during storage, the internal bubbles do not expand, and no signal error occurs due to deformation of the optical disk. In addition, since the internal air bubbles in the adhesive layer hardly communicate with the outside air, the possibility of deterioration of the characteristics of the optical disk is much lower than in the past.

Also, by using a metal plate having good surface accuracy, a disk with small surface runout and small surface runout acceleration of the bonded disk can be manufactured. When a metal plate having poor surface accuracy is used, for example, in the case of a film, wrinkles due to reduced pressure are generated, and the pressure is not uniform due to the wrinkles. As a result, a disk with a large surface runout and a large surface runout acceleration of the bonded disk is manufactured. .

The surface runout and the surface runout acceleration of the disk are closely related to the system side, especially to the pickup. If the surface runout and the surface runout acceleration are large, the disk cannot follow and the needle jumps or reproduction becomes impossible. Since such a disk becomes unusable, surface runout and surface runout acceleration of the disk are particularly important.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

First, an aluminum reflective film / protective film is formed on an optical disk substrate, a hot-melt adhesive is applied to the substrate by a roll coater, and the substrate is adhered at a pressing pressure of 500 g / cm ² and a temperature of 50 ° C. using a press device according to the present invention. A comparison was made for three types of bonded substrates with and without a metal plate having good surface accuracy using a manufacturing apparatus.

In order to investigate long-term reliability, a cycle test was conducted in a room and a constant temperature and humidity chamber at 60 ° C and 95%. As a result, peeling of the outer peripheral portion occurred in the second cycle of the adhesive bonded by the press device, and thereafter the peeling proceeded, so that reproduction by the player was completely impossible. On the other hand, the two types bonded using the manufacturing apparatus according to the present invention did not peel off even after 10 cycles, and the aluminum reflective film on the outer periphery was only slightly corroded. This is due to the parallelism of the press and the uniformity of the thickness distribution of the disc when bonding with a press device,
Since no uniform pressure is applied, the adhesion is also non-uniform. As a result, when the cycle test is performed, the disk is deformed due to moisture absorption or the like, and the adhesion is nonuniform, the force balance is lost, and separation occurs. On the other hand, in the manufacturing apparatus of the present invention, since the pressure is applied uniformly, the bonding can be made uniform, and thus, even if the disk is deformed due to moisture absorption, it can be alleviated.

Further, the surface runout and the surface runout acceleration of the disk are closely related to the system side, especially to the pickup. Whether the pickup can follow the signal recorded on the disk depends on this characteristic. Therefore, the characteristics of the three types of disks were measured for the surface runout and the surface runout acceleration. As a measuring method, the number of revolutions was set to 1800 rpm, and the measurement was performed electrically using Microsense. As a result, the disk bonded by the press device has a surface runout of 300 μmp-p or less and a surface runout acceleration of 8 G or less. When bonded with the device according to the present invention, when there is a metal plate with good surface accuracy, the surface runout is within 100 μmp-p, the surface runout acceleration is 2 G or less, and when there is no surface runout, the surface runout is 100 μm.
The metal plate used in the bonding apparatus having a peak-to-peak range and a surface run-out acceleration of 4 G or less can be used as long as the thickness is 1 mm or more and the surface is mirror-polished.

In other words, when there is no metal plate with good surface accuracy, for example, when a bag-shaped film is used, the film becomes wrinkled, pressure is not uniformly applied, and the film is forcibly adhered, so that small irregularities are generated on the disk surface. As a result, the surface runout acceleration increases. When there is a metal plate having good surface accuracy, pressure is uniformly applied to the disk via the metal plate. As a result, the adhesion can be made uniform, and a disk with almost no air bubbles can be formed, and the surface runout acceleration can be reduced.

ADVANTAGE OF THE INVENTION According to the apparatus by this invention, long-term reliability is good and surface run-out and adhesion | attachment of the disk with small surface run-out acceleration are attained.

In trial production of the device according to the present invention, the present inventors prototyped the device shown in FIGS. 1 (a) and (b), for example, in order to solve the problems caused by the use of the press device. 1 (a) and 1 (b), a lower mold 21 is composed of a lower mold plate 22, a support bar 23 which is attached through the center of the lower mold plate 22, and a peripheral portion of the upper surface of the lower mold plate 22. The lower mold ring 24 attached to the lower mold ring 24 and the lower mold flat plate 22 attached to the lower mold ring 24
And a flexible sheet-like member 25 forming a space therebetween and a metal plate 39 with good surface accuracy. Also, the upper mold 26
The upper mold plate 27, a support rod 28 attached to the center of the upper mold plate 27, an upper mold ring 29 attached to the periphery of the upper surface of the upper mold plate 27, and an upper It is composed of a flexible sheet-shaped member 30 forming a space between itself and the mold plate 26 and a metal plate 38 with good surface accuracy. Also, the lower flat plate 22
Is connected to the fluid inlet 31 and the upper flat plate 27 is connected to the fluid inlet 32. Further, a pressure reducing port 33 is connected to a position above the lower die ring 24 where the sheet-like member 25 is mounted. Further, an O-ring 34 is fitted on the upper surface of the lower die ring 4.

The manufacture of an optical disk using this apparatus is performed as follows. First, as shown in FIG. 1 (a), the two disk substrates 35, 35 are coated with a hot melt adhesive 36, and are superposed with the center holes aligned with a center hole jig 37. And the center hole alignment jig 37 is the support rod 23 of the lower die 21
Installed on top. Next, as shown in FIG. 1 (b), the upper mold 26 is lowered so that the lower surface of the upper mold ring 29 contacts the upper surface of the lower mold ring 24 with the O-ring 34 interposed therebetween. The joined body of the disk substrates 35, 35 is sandwiched between good metal plates 38, 39. In this state, a space is formed by joining the lower ring 24, the upper ring 29, the sheet members 25, 30, the metal plates 38, 39 with good surface accuracy, and the disk substrates 35, 35 by evacuating from the pressure reducing port 33. To a reduced pressure. Next, pressurized fluid is caused to flow from the fluid inlets 31 and 32, and the sheet-shaped members 25 and 30
Press 39 to bond. At this time, the fluid inlet
If the pressurized fluid flowing from 31, 32 is heated in advance, the adhesiveness of the hot melt adhesive is improved. The heating may be performed by a heating means such as a heater from the outside via the lower plate 22 and the upper plate 27.

Further, in FIG. 1, it is also possible to bond using only the metal plate 38 with high accuracy on the surface of the sheet member 30 without using the metal plate 39 with high accuracy on the surface of the sheet member 25. In this case, two disk substrates 35, 35 having a hot melt adhesive 36 interposed therebetween are directly disposed on the lower flat plate 22, and the lower flat plate 22 and the sheet tree member 30 are provided with a metal plate 38 having good surface accuracy. The inside of the enclosed space is evacuated from the pressure reducing port 33 to reduce the pressure. Then, the pressurized fluid is caused to flow from only the fluid inlet 32 without using the fluid inlet 31 and is bonded.

As a sheet-like member used in such an apparatus,
Any material that does not break due to the pressure difference and has the flexibility to deform due to the pressure difference may be used. However, since it is repeatedly used, for example, a polymer film that is easily charged may be attached or adhered to dust. In some cases, problems such as difficulty in peeling from the substrate later may occur.
Therefore, a metal foil that satisfies the above conditions (for example, a thickness of 0.
A metal plate that satisfies the above conditions (for example, a stainless steel plate with a thickness of 2 mm) is a hard metal plate that has good surface accuracy and is not easily deformed. It is preferable to use such as.

A single-sided transparent disk was manufactured by using such an apparatus, and observation and tests were performed as follows. In this case, air was used as the pressurized fluid and atmospheric pressure was applied. Observation of the single-sided transparent disk revealed that the internal bubbles were independent. Further, when a red ink test was conducted on this single-sided transparent disk, it was found that there was no permeation of the red ink and no increase in weight, and no internal air bubbles were communicated with the outside air.

Therefore, when an optical disk is manufactured using the above-described apparatus, deterioration of characteristics due to invasion of corrosive substances or moisture hardly occurs.

 FIG. 2 shows a simplified version of the apparatus of the present invention.

This device will be described with reference to FIG. In FIG. 2, the vacuum vessel 1 is composed of a vessel lower part 2 and a vessel upper part 3, which are sealed by assembling them with a packing 4 therebetween. A support base 5 is fixed to the container lower part 2. Further, a pipe 6 having a film suction port 6a, a container suction port 6b, and an air inlet 6c is connected to the container lower part 2 in a state where the film suction port 6a and the container suction port 6b are inserted into the container 1. I have. A switching valve 7 is provided at a branch point of the pipe 6 in three directions. Further, a vacuum pump 8 is connected to the pipe 6 at a position closer to the film suction port 6a than the switching valve 7.

The manufacture of an optical disk using the above apparatus is performed as follows. First, a hot melt adhesive is applied by a roll coater to each of two substrates 11 on which a reflective film and a protective film are formed on a transparent substrate by a normal process, and the adhesive layer 12 side is adhered to each other by aligning the center holes. . This joined body is sandwiched between metal sheets having good surface accuracy, and wrapped in a flexible bag-like film 13 made of, for example, polyethylene.
Place the film 13 on the top and connect the film 13
Connect with In this state, the container lower part 3 is attached, and the container 1 is assembled. Next, the switching valve 7 is set so that the container suction port 6b is connected to the vacuum pump 8 and the air inlet 6c is not communicated with the inside of the container 1, and the vacuum pump 8 is operated. As a result,
The inside of the film 13 and the inside of the container 1 are simultaneously decompressed. Subsequently, after sufficiently reducing the pressure, the vacuum pump 8 is operated to maintain the reduced pressure in the film 13, and the switching valve 7 is connected to the container suction port 6 b without the vacuum pump 8 and the air inlet 6 c is connected to the container 1. It is set in a direction communicating with the inside, and air is introduced into the container 1 to pressurize the bonded body of the substrates 11 and 11 in the film 13 with the atmospheric pressure.

In the above embodiment, atmospheric pressure is applied after the pressure is reduced. However, a medium other than air may be used as the pressure medium.
In this case, a pipe for the pressurized medium may be provided separately from the pipe shown in FIG. Also, as can be seen from the above experiment, it is desirable to heat these pressurized media.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to provide an optical disk having a small characteristic of deterioration of the reflective film due to corrosion of the reflective film, peeling off of the adhesive surface, surface runout, and small surface runout acceleration, and an apparatus capable of manufacturing such an optical disk at low cost. Things.

[Brief description of the drawings]

1 (a) and 1 (b) are cross-sectional views of an optical disk manufacturing apparatus according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view of a simplified optical disk manufacturing apparatus. 1 ... vacuum container, 2 ... lower container, 3 ... upper container, 4 ... packing, 5 ... support base, 6 ... piping, 6a ... film suction port, 6b ... container suction port, 6c ... ... air inlet, 7 ... switching valve, 8 ... vacuum pump, 10 ... optical disk, 11 ... substrate, 12 ... adhesive layer, 13 ... film.

Claims (12)

(57) [Claims] A step of applying an adhesive to an information surface side of two optical disk substrates; a step of superimposing the two optical disk substrates with the information side of the optical disk substrates inside each other; Arranging the substrate under reduced pressure; and pressurizing the two optical disk substrates under the reduced pressure. The pressurizing step includes flowing air or fluid at atmospheric pressure to remove the two optical disk substrates. A method for bonding optical disks, comprising applying pressure. 2. A step of forming a reflective film on each information surface side of two optical disk substrates, a step of forming a protective film on the reflective film, and a step of applying an adhesive to the protective film. Stacking two optical disk substrates with the information surfaces of the optical disk substrates inside each other, arranging the two optical disk substrates under reduced pressure, and pressing the two optical disk substrates under reduced pressure. A method of bonding optical disks consisting of 3. The method for laminating optical disks according to claim 1, wherein a hot melt adhesive is used as said adhesive. 4. The method according to claim 1, further comprising the step of heating the air or fluid at atmospheric pressure. 5. A member for accommodating an optical disk in which two optical disk substrates each having an information surface on one side are superimposed via an adhesive with the respective information surfaces inside each other; An optical disc bonding apparatus, comprising: means for decompressing an enclosed space; a member for enclosing the space decompressed by the means; and means for pressurizing the space enclosed by the member. 6. An optical disk substrate comprising: two optical disk substrates each having an information surface on one surface; a reflective film formed on each of the information surfaces; a protective film formed on each of the reflective films; A member for receiving an optical disk which is superimposed and coated, a means for decompressing a space surrounded by the member, a member for surrounding the space decompressed by the means, and a space for enclosing the member. An optical disc bonding apparatus, comprising: means for pressing. 7. The optical disk bonding apparatus according to claim 5, wherein said pressurizing means causes air or fluid at atmospheric pressure to flow. 8. An optical disk bonding apparatus according to claim 5, further comprising means for heating said atmospheric pressure air or fluid. 9. The optical disk bonding apparatus according to claim 5, wherein the member for inserting the optical disk is a flexible polymer film or metal foil. 10. An optical disk substrate comprising: two optical disk substrates each having an information surface on one surface; a reflective film formed on each of these information surfaces; a protective film formed on each of the reflective films; A member for containing an optical disk which is superimposed and coated with a member, a member for surrounding the member, a means for reducing the pressure of the space surrounded by the member and the space surrounded by the member for containing the optical disk, Means for pressurizing a space surrounded by a member for holding an optical disc, wherein the means for depressurizing and the means for pressurizing are configured to depressurize both spaces simultaneously and then pressurize. Laminating device. 11. A member for inserting two optical disc substrates each having an information surface on one surface, a reflective film formed on each of these information surfaces, applying an adhesive, and superimposing, A member for surrounding the member, a unit for reducing the pressure of the space surrounded by the member and the space for the member for holding the optical disk, and a unit for pressing the space surrounded by the member for holding the optical disk An optical disc bonding apparatus, characterized in that the pressure reducing means and the pressure applying means are configured to simultaneously reduce the pressure in both spaces and then apply the pressure. 12. A member for inserting said optical disk,
11. A flexible film, characterized in that:
12. The optical disk laminating apparatus according to claim 11, wherein: