JP2001014736A - Production of optical disk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the warpage of an optical disk and to shorten production time by beat-treating molded substrates before sticking to each other. SOLUTION: A metallic thin film for a recording layer is formed on one face of at least one of substrates having ruggedness optionally by way of a layer of a reversibly or irreversibly changeable material. The resin substrates are disposed with faces having no ruggedness outward and the metallic thin film inward, an adhesive is supplied to one or both of the substrates and the adhesive is cured to stick the substrates to each other. Before this sticking, the substrates are subjected to prescribed heat treatment by holding in a thermostat kept at a prescribed temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an optical disk, and more particularly to a method for manufacturing a bonded optical disk, for example, an optical disk for DVD.

[0002]

2. Description of the Related Art As an optical disk for a DVD, there has been known a technique of manufacturing a bonded optical disk capable of performing multi-layer recording by bonding a plurality of substrates (usually two) having a recording layer.

FIG. 6 schematically shows a method of manufacturing such a bonded optical disk. In FIG. 6, a pair of disk substrates (d1 and d2) having predetermined irregularities on one side are formed by resin molding, and a metal thin film having a predetermined thickness as a reflection film (in this case, metal The thin film functions as a recording layer), and then is allowed to stand naturally for about 24 hours. After that, the ultraviolet curing adhesive g is supplied and laminated between the pair of substrates with the metal films facing each other. Then, the substrates are bonded together by irradiating ultraviolet rays to cure the adhesive, thereby completing the manufacture of the optical disk D. By thus forming the optical disk in a laminated structure, there is an advantage that the recording capacity of the optical disk can be substantially doubled.

[0004] Such a manufacturing method of a bonded optical disk is disclosed, for example, in WO97 / 35702. There, a transparent resin such as polycarbonate is injection-molded to obtain a substrate having irregularities on one side, and a pair of substrates having a metal thin film of gold, aluminum, etc. formed on the irregular surface is separated by a relatively narrow gap. By holding the metal thin film facing each other, an adhesive, for example, an ultraviolet-curable adhesive is discharged into the gap and spread over the entire gap to obtain a laminate, and the adhesive is ultraviolet-cured. An optical disk on which a plurality of substrates are bonded is manufactured.

[0005] On the substrate of the optical disk manufactured as described above, predetermined irregularities are formed in advance by injection molding, and a metal thin film is adhered to the irregularities. The obtained optical disk is read-only (a so-called ROM type). ), But a rewritable type (so-called RAM type) optical disk can be manufactured in the same manner. In that case, land and groove irregularities are previously formed on one surface of the substrate, and then made of a material (for example, a GeSbTe film) capable of reversible change (for example, a phase change between crystal and amorphous). The difference is that a metal thin film as a reflective layer is formed after the recording layer is formed on the uneven surface by, for example, a sputtering method.

Further, a write-once type (so-called R-type) optical disk can be manufactured in the same manner. In this case, instead of a rewritable type reversible phase-changeable recording layer, an irreversibly changeable material is used. (For example, a recording layer made of a light-decomposable organic dye material, an alloy material, or the like) is formed by a sputtering method, and then a metal thin film as a reflection layer is formed. By bonding both of these recordable optical disks (RAM type and R type) after forming the respective substrates, a bonded optical disk can be manufactured.

In the above-described optical disk manufacturing method, in any of the above-described methods, a metal thin film is formed on a substrate, and then these substrates are bonded to each other. Various modifications are possible. For example, in the case of laminating only to achieve a predetermined thickness of the optical disk (thus, without increasing the amount of recorded data),
The recording layer may not be provided on one of the substrates. In another embodiment, after forming the metal thin film, a protective layer made of, for example, a resin may be provided thereon.

[0008] Using such an optical disk, reading of data already recorded by predetermined irregularities from the recording layer or writing of data to the recording layer and reading of the data are performed while rotating the optical disk at high speed.
By irradiating a laser beam of a predetermined wavelength from outside the disc,
This is performed by transmitting light through a transparent substrate. Since the recording density of these data is extremely high, if the flatness (or flatness, for example, the warpage angle is an index) of the disc is poor, it is possible to irradiate the laser beam so as to converge at a predetermined position on the recording layer. Error is likely to occur in writing / reading of information. Therefore, in manufacturing an optical disk, it is important to suppress the occurrence of warpage / distortion and obtain an optical disk having high flatness.

[0009]

Under the above-mentioned background, as a result of various studies on the flatness of the optical disc, the optical disc is warped in the process of photo-curing the adhesive, which causes the flatness of the optical disc as a final product. It has been found to have a significant effect on the degree. This warpage is caused by shrinking of the thermal substrate of the substrate at the time of ultraviolet curing when the resin-molded substrate is bonded, and accompanying this, the disk warps to the side where the shrinkage of the bonded substrate is large. It is presumed that it will.

Since the deformation due to the warpage is greater when the substrate is irradiated with ultraviolet rays at a high temperature, after the substrate is formed or a metal thin film is formed on the substrate, the substrate is left for a sufficiently long time. The substrates are stuck together at a room temperature (that is, naturally left) after the molecular state of the resin of the substrates is stabilized. The process of leaving the substrate in a natural state can be called an annealing process, and is performed for several hours to about 24 hours as described above.

However, when mass-producing optical disks, it is troublesome and inefficient to use such a long-time annealing process in the manufacturing process. Since we started manufacturing optical discs,
It takes a considerably long time to obtain a completed optical disc, and rapid production is not possible. In addition, in order to perform the annealing process, a large space for temporarily storing a large amount of substrates is required.

Also, the warp related to the optical disk includes a warp occurring in a storage or use environment after manufacturing, that is,
There is warpage that occurs over time. At the completion of the manufacture of an optical disc, even if the optical disc warp is confirmed to be within a predetermined specification range by various product inspections, if the optical disc is repeatedly used for a long period of time, the amount of warpage increases and the data Reading / writing is hindered. This is considered to be due to the fact that a larger amount of heat is applied due to heat accumulation due to long-term use, and the above-described warpage due to thermal shrinkage of the substrate further increases.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to suppress the occurrence of deformation such as warpage of an optical disk in the production of a bonded optical disk, and to obtain an optical disk with improved flatness. . As a bonding type optical disk, a DVD optical disk is commercially available. As will be apparent from the following description, the present invention is particularly useful for a DVD optical disk, but is not limited thereto. Instead, the present invention can be applied to other bonded optical disks (eg, CD, PD, LD, etc.) as necessary.

[0014]

As a result of studying the warpage of an optical disk manufactured by bonding substrates that have been subjected to a long-time annealing process as described above, the optical disk is manufactured by bonding the substrates. It has been found that heat treatment of the substrate after forming the substrate and before bonding the substrate can suppress the warpage of the optical disk while shortening the manufacturing time of the optical disk.

First, in a method for manufacturing an optical disk,
A description will be given of the measurement result of the warpage of the optical disk that is supposed to be subjected to the heat treatment. Warpage of an optical disc manufactured using a substrate that has been taken out of a molding machine without being subjected to the long-time annealing described in the prior art and left for 4 minutes (manufactured by omitting only the long-time annealing in the conventional method) Was measured in various ways. The result is shown in FIG. this is,
The warp angle of the optical disk obtained by bonding (ie,
7 is a graph in which the amount of change in the warp angle before and after the disk is subjected to an environmental test is plotted.

The optical disk manufactured to obtain this graph was a DVD substrate made of polycarbonate. After removing the injection-formed substrate from the mold, it was left at room temperature for 4 minutes to form a metal thin film. After that, they were bonded using an ultraviolet curing adhesive. The warp angle was measured using a commercially available optical warp angle measuring device according to the method defined in the SD standard. The environmental test was conducted at a temperature of 80
The test was performed under the conditions of storage for 96 hours in an atmosphere at 85 ° C. and a humidity of 85%.

From this graph, it can be seen that there is a correlation that the smaller the amount of change in the warp angle before and after the environmental test, the larger the warp angle after bonding, as indicated by the solid line. In other words, this means that, when the substrate is deformed and warped in the process of photo-curing the adhesive, the amount of change in the warping due to the thermal history of the environmental test is reduced thereafter. That is, the amount of further deformation of the substrate that has been deformed by heat shrinkage during curing is smaller than the amount of further deformation of the substrate that has not been heat shrunk yet. In other words, the amount of deformation inherent to the substrate as a whole is fixed, and in the case of a disk with a large warpage after bonding, most of the warpage already becomes apparent at the time of bonding, and a small potential warpage However, a disk substrate having a small warpage after bonding has a large potential warpage (this large potential warpage is manifested by an environmental test). It becomes apparent through environmental tests).

Based on such knowledge, it is presumed that, when the deformation of the substrate is made apparent in advance, the deformation that occurs later becomes smaller. In other words, if most of the potential warpage inherent in the substrate is revealed before bonding the substrate, the potential warpage of the substrate after bonding the substrate is reduced, and as a result, photocuring Even when the optical disk is warped after the completion of the optical disk, it has been found that the warp is smaller than that of the conventional optical disk. Further, the inventors have found that it is possible to make most of the potential warpage inherent in the substrate apparent before bonding the substrate by heat-treating the substrate.

Therefore, the present invention can be obtained by laminating a plurality of substrates with an adhesive interposed therebetween.
A method for manufacturing an optical disc having at least one recording layer, comprising: (1) a step of molding a plurality of substrates, wherein at least one substrate has predetermined irregularities on one surface;
(2) a step of forming a metal thin film on the surface of the substrate having irregularities, and (3) laminating the substrates so that the metal thin film is located inside, and bonding the substrates by supplying an adhesive between the substrates. In a method for manufacturing an optical disk, the method includes a step of heat-treating the substrate before performing the step (3) of bonding the substrates.

In the present invention, steps (1) to (3) may be steps conventionally performed in a method for manufacturing a bonded optical disc, except that the substrate is heat-treated. The operation conditions and the materials used in the steps may be those conventionally used in the method of manufacturing a bonded optical disc.

In the present invention, the term “plurality of substrates” means that two or more substrates are bonded together. Usually, two or more substrates are bonded, but if necessary, three or more substrates are bonded together. The method of the present invention can also be applied to the case of manufacturing an optical disk by using the method. Among these substrates, at least one substrate has predetermined irregularities (irregularities corresponding to predetermined recording or irregularities for lands and grooves) on one surface,
The unevenness is covered with a metal thin film that reflects light. Therefore, the other substrate to be bonded may or may not have the predetermined unevenness. When the substrate has the unevenness, the metal thin film is also formed on the unevenness.

In the case of an optical disk which is not read-only, that is, an optical disk on which information can be written later, the method of the present invention uses a light of a predetermined wavelength on the unevenness before the step (2). The method further comprises the step of providing a recording layer that can be converted to a predetermined level or a recording layer that can be changed irreversibly.

In the method of the present invention, the term "heat treatment" means a treatment for rapidly expressing the inherent and potential warpage of a molded substrate under heating. Specifically, 6
0 ° C. to a temperature about 10 ° C. lower than the softening point of the resin used for the substrate (for example, 110 ° C. for polycarbonate), preferably 70 ° C. to 100 ° C., more preferably 70 ° C. to 90 ° C.
At a temperature of, for example, 80 ° C. for a predetermined time, usually 1 second to 6
The heat treatment of the present invention can be carried out by holding for 0 minute, preferably for 1 minute to 30 minutes.

The heat treatment may be carried out in any atmosphere as long as it does not substantially affect the substrate, for example, in air or in an inert gas such as nitrogen. After the heat treatment, the substrate may be left in a room temperature atmosphere for natural cooling for the next bonding step, or may be cooled with a cooling gas (for example, air) on the assumption that the substrate is substantially uniformly cooled. Cooling may be performed forcibly.

The heat treatment may be performed at any time after the step (1) of forming the substrate and before the step (3) of bonding the substrates. For example, after the step (1), the step (2) may be performed. ), Or during or part of step (2). Generally, it is preferable to carry out after step (2).

[0026]

DETAILED DESCRIPTION OF THE INVENTION The method of the present invention will be described in more detail below with reference to preferred features of the present invention, but as described above, may be carried out in a conventional manner, except for heat treatment. The substrate used in the method of the present invention is manufactured in such a manner that predetermined fine irregularities are formed on one surface of the substrate by injection molding from a transparent resin (for example, polycarbonate) according to the specifications of the optical disk to be manufactured. The predetermined irregularities formed on the substrate surface may be irregularities corresponding to data to be read in the case of a read-only optical disk, and may be irregularities corresponding to lands and grooves to write data in the case of a writable optical disk. May be.

Such a substrate can be manufactured by a molding apparatus and a molding method similar to those used for producing an ordinary optical disk substrate. In general, an injection molding apparatus and method can be used. When manufacturing a substrate, a pair of molding dies arranged vertically or horizontally is used to form a cavity defining a gap corresponding to the outer shape of the substrate therebetween. Since it is necessary to provide fine irregularities on one surface of the substrate as described above, the corresponding irregularities are formed in the cavity.

In injection molding, a heated and melted resin material is supplied at a high pressure into a cavity formed by a molding die. The operating conditions such as the injection temperature and the injection pressure may be the same as those employed in the manufacture of a normal optical disk substrate. In order to maintain a good flow of the molten resin supplied into the mold, the mold is usually heated to a predetermined temperature.

For example, in the case of manufacturing an optical disk by bonding two substrates, it is often the case that two lines of molding machines are provided, and each disk is manufactured in a separate line to obtain a pair of substrates. It is difficult to minimize the warpage by matching the warpage characteristics of a pair of substrates manufactured by different types of molding machines as a result. During bonding, the optical disk was warped due to thermal deformation. In the method of the present invention, since the substrate is heat-treated in advance, the potential deformation amount is reduced, so when bonding such a substrate,
Deformation caused by heat during photocuring and the surrounding environment is greatly reduced.

A recording layer is formed on a substrate surface having irregularities. In the case of a read-only optical disk, the metal thin film formed on the uneven surface functions as a recording layer, and in the case of a writable optical disk, the light is reversibly or irreversibly changed by light of a predetermined wavelength formed on the uneven surface. A layer of possible material, together with a thin metal film formed thereon, functions as a recording layer. In the present invention, the recording layer means a layer on which data has already been recorded or a layer on which data can be recorded. On this recording layer, if necessary, for example, a ZnS film, a SiO ₂ film or the like may be formed as a protective film by sputtering.

The metal thin film for the recording layer is formed on the uneven surface of the substrate or on a layer of a reversible or irreversibly changeable substance provided thereon, which comprises: This can be performed in the same manner as in the case of manufacturing an ordinary optical disk. As the material of the metal thin film, gold, aluminum, and other materials used for ordinary optical disks can be used. As a thin film forming method, vacuum deposition, CVD, PVD, or the like can be adopted. When the substrate is heated in forming the thin film, for example, an electric heater, a lamp, or the like can be used as a heating means.

In the case of a writable optical disk, as described above, a layer of a reversible or irreversible changeable material combined with a metal thin film is formed on the uneven surface of the substrate to form a recording layer. This layer can be formed, for example, by vapor deposition, spin coating, sputtering, or the like, as in the case of manufacturing a normal writable optical disk.

Finally, a substrate having a metal thin film as described above (optionally further comprising a layer of a reversible or irreversibly changeable material and / or a protective layer) is attached. At the time of this bonding, the substrate is arranged such that the surface of the resin substrate having no unevenness is located outside and the metal thin film is located inside. For example, when the substrates to be bonded each have a metal thin film, they are arranged so that the metal thin films face each other. Note that the shape of the substrate is generally a thin disk shape (a circular hole may be present at the center),
A shape other than a disk may be used depending on the purpose of use of the bonded substrates. After bonding, the shape of the substrate may be processed into another shape.

This bonding can also be performed using an adhesive, as in the case of manufacturing an ordinary optical disk. As the adhesive, it is preferable to use various photocurable adhesives, particularly an ultraviolet curable transparent adhesive, for example, an acrylic UV curable resin, depending on the material of the substrate to be bonded and the purpose of use.

In this bonding, an adhesive is supplied to one or both of a pair of substrates by using an ordinary adhesive application or coating means, and the substrates are laminated to form a laminate. The adhesive is cured by irradiating light. The following method can be adopted as a particularly preferable bonding method.

One substrate is held facing each other with a relatively small space therebetween, and a discharge nozzle for the adhesive is inserted into the gap, and the pair of substrates is moved to the center while discharging the adhesive from the discharge nozzle. To provide an annular supply of adhesive within the gap. Then, while narrowing the gap between the substrates and rotating both substrates, the adhesive can be spread in the radial direction of the substrate, and the gap between the substrates can be filled with a thin layer of adhesive, and a laminate is obtained. The adhesive is cured by irradiating light. This bonding method is
It is disclosed in WO 97/35702, cited above, the disclosure of which is hereby incorporated by reference.

In order to cure the adhesive layer with light, in particular, ultraviolet light, a lamp which emits predetermined light is usually positioned above a pair of substrate laminates arranged horizontally on a flat mounting table, The lamp is irradiated with light and passes through a transparent substrate and a semi-transparent metal thin film to reach and cure the adhesive layer. In addition, or alternatively, when the light transmittance of the metal thin film is small, light is irradiated from the side of the laminate (that is, irradiation is performed from a direction perpendicular to the thickness direction of the laminate). To perform curing.

As described above, the heat treatment, which is a main feature of the method of the present invention, is performed before the substrates are bonded together by, for example, 6 steps.
It can be carried out by holding the substrate in a constant temperature bath maintained at a temperature of 0 ° C to 110 ° C. In another aspect, the heat treatment may be performed during the formation of the metal thin film. For example, when using CVD or PVD to form a metal thin film, the method can be implemented by heating the substrate with the heat of the plasma used. The substrate formed by resin molding may be cooled to room temperature before heat treatment, or at a higher temperature if the substrate is not substantially deformed in handling the substrate after molding. Is also good. Of course, the heat treatment
Since it may be carried out before the bonding of the substrates, it may be carried out after the formation of the metal thin film.

After the heat treatment and before the next step is performed, the substrate is heated to its environmental temperature (the temperature of the atmosphere of the bonding step when the next bonding step is performed, usually room temperature, or the next metal thin film). In the case where is formed, it is preferable to lower the temperature until the difference from the temperature of the forming atmosphere) becomes about 5 ° C. or less. Usually, it is preferable to spend at least one minute, and preferably at least three minutes, for this temperature drop to approach the environmental temperature of the bonding step.

The temperature of the substrate can be lowered simply by leaving the substrate in the environment, or can be forcibly performed by blowing cool air onto the substrate or by bringing the substrate into contact with a low-temperature object. is there. However, it is necessary to avoid rapid cooling or non-uniform cooling such that thermal stress or thermal strain is generated. The cooling time after this heat treatment is
It can be adjusted by changing the transfer speed of the substrate. For example, the temperature lowering time can be changed by changing the speed or length of the conveyor for transferring the substrate.

FIG. 1 schematically shows one embodiment of the method of the present invention. In the substrate forming step (1), donut-shaped (disks having a circular opening in the center) substrates d1 and d2 are manufactured using an injection molding apparatus. Predetermined irregularities are formed on one surface of each substrate. In another aspect, the one substrate does not need to have unevenness. next,
In the film forming step (2), a metal thin film is formed on the uneven surface of each substrate using a sputtering device. For example, a thin film of gold is formed on the substrate d1, and a thin film of aluminum is formed on the substrate d2. If the substrate has no irregularities,
It is not necessary to form a metal thin film.

Thereafter, a heat treatment is performed before the bonding step (3). In FIG. 1, the heat treatment is performed after the thin film is formed. However, in another embodiment, the heat treatment may be performed in the film forming step (2). In the film formation step (2), for example, heat treatment can be performed using a sputtering apparatus as schematically shown in a sectional view in FIG. In this apparatus, a substrate (1) is placed in a sputtering chamber (10).
2) and the target (14) are opposed to each other, and by changing the distance (T / S distance) between the target (14) and the substrate (12), the thermal energy of the plasma affects the substrate. Can be changed, and as a result, the temperature rise of the substrate can be controlled as predetermined.

The effect of the T / S distance on the temperature of the substrate when forming an aluminum thin film is illustrated in the graph of FIG. For example, when the T / S distance is 40 mm and a DC power supply (16) is applied at about 1500 V, the temperature of the substrate (12) rises to about 70 ° C., and when the T / S distance is shorter, the substrate (12) is heated to a higher temperature. Therefore, in the step of forming the metal thin film, the heat treatment of the present invention can be performed.
In yet another aspect, it is possible to incorporate a heating means, for example an electric heater, into the substrate holder (11) of the sputtering apparatus, or to heat the substrate in a predetermined manner by a lamp.

After the above-mentioned heat treatment, the pair of substrates d1 and d2 are held so that the metal thin films face each other with a gap therebetween, and the tip nozzle of the adhesive supply device G is inserted into the gap to dispose the adhesive g. By rotating the substrates d1 and d2 while discharging, the adhesive is supplied in a ring shape. At this time, if the gap between the substrates is narrowed and the discharged adhesive is arranged so as to be in contact with the upper and lower substrates, air bubbles may enter between the substrates in the next laminating step, or the adhesive may be removed. The occurrence of coating unevenness can be substantially prevented.

In the laminating step, the gap between the substrates d1 and d2 is further narrowed while rotating, so that the adhesive layer interposed in the gap is stretched thinly as a whole between the substrates, and the lamination is performed such that the substrates are in close contact with each other. The body is obtained. Finally, ultraviolet rays are irradiated from one side of the laminate from an ultraviolet lamp L to cure the adhesive, and the bonding is completed. Thus, the optical disc D of the present invention is obtained.

[0046]

According to the method of the present invention, a heat treatment for a relatively short time is performed instead of a long-time annealing treatment before the bonding of the substrates. While greatly reducing the time required for the method of manufacturing an optical disk, it is possible to significantly reduce the time required. As a result, there is no need to temporarily store a large number of substrates required for the annealing process (thus, it is only necessary to temporarily stock a small number of substrates), as schematically shown in FIG. It is possible to realize an integrated production line for laminated optical discs, and productivity is greatly improved.
The production line includes a substrate forming machine (20), a heat treatment device (30), a metal thin film forming device (40), and a substrate bonding device (50).

[Brief description of the drawings]

FIG. 1 is a flow sheet schematically showing a method for manufacturing an optical disk of the present invention.

FIG. 2 is a schematic cross-sectional view of a sputtering apparatus that can be used for heat treatment in the method of the present invention.

FIG. 3 shows substrate temperature and T / in a sputtering apparatus.
It is a graph which shows the relationship with S distance.

FIG. 4 is a graph showing a relationship between a warp angle after bonding substrates and a change in the warp angle due to an environmental test.

FIG. 5 is a schematic diagram of an integrated production line of a bonded optical disk based on the method of the present invention.

FIG. 6 is a flow sheet schematically showing a conventional optical disc manufacturing method.

[Explanation of symbols]

10: sputtering chamber, 11: substrate holder, 12: base, 14: target, 16: DC power supply,
20: molding machine, 30: heat treatment device, 40: sputtering device, 50: bonding device.

Claims (13)

[Claims] 1. A method for manufacturing an optical disk having at least one recording layer, obtained by bonding a plurality of substrates with an adhesive interposed therebetween, wherein (1) at least one substrate has a surface on one side. (2) forming a metal thin film on the surface of the substrate having irregularities, and (3) laminating the substrates such that the metal thin film is located inside. And
A method for manufacturing an optical disc, comprising a step of bonding substrates by supplying an adhesive between the substrates, wherein the substrate is heat-treated before performing the step (3) of bonding the substrates. . 2. A step of forming a layer of a substance which can be reversibly changed by a predetermined light between a surface of a substrate having irregularities and a metal thin film, between the step (1) and the step (2). The production method according to claim 1, further comprising: 3. A step of forming a layer of a substance irreversibly changeable by predetermined light between a surface of a substrate having irregularities and a metal thin film, further comprising a step between the steps (1) and (2). The manufacturing method according to claim 1, comprising: 4. The heat treatment according to claim 1, wherein the heat treatment is performed by holding the substrate in a temperature range of 60 ° C. to 10 ° C. lower than the softening point of the resin used for the substrate for 1 second to 60 minutes. The method described in. 5. The heat treatment is performed after the step (2) and the step (3).
The method according to any one of claims 1 to 4, which is performed before the step (c). 6. The heat treatment is performed after the step (1) and the step (2).
The method according to any one of claims 1 to 4, which is performed before the step (c). 7. The method according to claim 1, wherein the heat treatment is performed during the step (2). 8. Performing step (2) using plasma,
The manufacturing method according to claim 7, wherein the heat treatment is performed by heating the substrate by plasma. 9. The method according to claim 7, wherein the heat treatment is performed by heating the substrate holder holding the substrate in the step (2). 10. The method according to claim 1, wherein after the heat treatment and before performing the next step, the temperature of the substrate is reduced until the difference from the ambient temperature of the next step becomes about 5 ° C. or less. Manufacturing method. 11. The method according to claim 10, wherein the temperature is lowered in at least one minute. 12. The method according to claim 1, wherein the adhesive is an ultraviolet curable adhesive. 13. The method according to claim 1, wherein the optical disk is a DVD optical disk.