JP2000113529A - Method and device for manufacturing optical disk and production of substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an effective production method and device for optical disk with good flatness by suppressing generation of warping with the lapse of time as well as at the time of production. SOLUTION: A manufacturing method of a stuck type optical disk contains a process (1) in which a pair of substrates, at least one of which has ruggedness on a main surface of one side, are molded out of a transparent resin, a process (2) in which a metallic thin film is formed on the main surface of one side having ruggedness and a process (3) in which a pair of substrates are laminated so that the metallic thin film is located inside and the substrates are joined by an adhesive supplied between the substrates. After the process (1), a stand-by process, in which temp. of the substrate is dropped till moisture absorption amount of the substrate becomes <=0.1 wt.% and temp. difference between the molded substrates and the environment becomes <=5 deg.C, is executed and then the process (2) is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for manufacturing an optical disk, particularly a bonded optical disk, and a method for manufacturing a substrate to be bonded for manufacturing such an optical disk. Such an optical disk includes, for example, an optical disk for a DVD (Digital Video Disk).

[0002]

2. Description of the Related Art As an optical disk for DVD, it is known to manufacture a single optical disk having a plurality of recording layers by laminating a plurality of substrates having recording layers. Such a method and an apparatus therefor are disclosed, for example, in WO 97/35720, the contents of which are hereby incorporated by reference and which are suitable for the invention described hereinafter. Constitute.

[0003] Specifically, an optical disk can be manufactured by, for example, the following method: (1) Fine unevenness is formed on one main surface in advance by injection molding of a transparent resin, and gold, aluminum, or the like is formed thereon. A pair of the same or different substrates (usually a circular substrate, which may have a circular opening in the center) on which the metal thin films are formed are prepared, and (2) the metal thin films are opposed to each other. Holding a pair of substrates in a state where there is a gap between the substrates, and (3) supplying an adhesive, for example, an ultraviolet curable adhesive, to the gap to spread the whole of the gap to obtain a laminate of substrates,
(4) By curing the adhesive, the pair of substrates is joined (or joined) with the adhesive.

To read data (or information) recorded on an optical disk or to write data to the optical disk, a laser beam having a predetermined wavelength is emitted from the outer or inner circumference of the optical disk while rotating the optical disk at a high speed. The irradiation is performed by irradiating the optical disk with the substrate. Since the data recorded on the recording layer or the density of the data to be recorded is very high, it is necessary to irradiate a predetermined position on the optical disk with laser light. At this time, if the flatness of the entire optical disc is poor, the laser beam cannot be irradiated with the focal point adjusted to a predetermined position, and errors are likely to occur when reading or writing data. Therefore, in the production of an optical disc, warpage of the optical disc as a final product, the presence of deformation such as distortion is suppressed, and even after the production, such deformation is suppressed, and as a result, improved. It is desired that flatness can be maintained.

[0005]

Under the above-described background, as a result of studying the deformation occurring on the optical disk, it is considered that one possibility is that the deformation is generated by the following mechanism: Deformation is the result of temporal deformation occurring in the resin molded substrate. In particular, a substrate in a high temperature and dry state immediately after molding tends to absorb moisture from the surrounding environment of the substrate, and as a result, the substrate is deformed as the substrate absorbs moisture.

Therefore, the molded substrate is left in a predetermined environment for a sufficiently long time to reach a stable state in which the amount of moisture absorbed by the substrate is constant, and then a metal thin film is formed on the substrate. Methods for performing the steps have been proposed.
This leaving of the substrate is sometimes called "annealing treatment", and is usually left for several hours to 24 hours.

However, when mass production of optical discs is to be performed, it is very inefficient to perform annealing that requires a long time in the middle of a production line. In order to perform the annealing process, a large space for temporarily storing a large amount of substrates after removing the substrates from the molding machine is required. If the environment for storing the substrate changes during the execution of the annealing process, the effect of the annealing process varies. In addition, it takes a long time from the start of forming the substrate to the completion of obtaining a finished optical disk.

Further, there is a warp that increases with time after the optical disc is manufactured, and a warp that occurs depending on the use environment of the optical disc. At the time the optical disk is manufactured, even if it is confirmed by various product inspections that the amount of warpage of the optical disk is within a predetermined range, the optical disk can be stored for a long period of time or repeatedly used. In some cases, the amount of warpage may increase, which may adversely affect writing or reading of data. It is considered that this is because the internal stress, strain, and the like built in the optical disk at the time of manufacturing are released over time or due to the use environment, and thus warpage is additionally generated.

In view of the above, in the production of a bonded optical disk, it is an object of the present invention to suppress the occurrence of warpage during production and over time, and to efficiently produce an optical disk having a good flatness. Is the problem to be solved.

[0010]

In a first aspect, the present invention provides a method for manufacturing a bonded optical disk,
The method includes: (1) a step of molding a pair of substrates from a transparent resin, at least one of which has irregularities on one main surface;
(2) a step of forming a metal thin film on the one-sided main surface having the irregularities; and (3) bonding a pair of substrates so that the metal thin film is located inside and bonding the substrates with an adhesive supplied between the substrates. (Or combining), comprising:
After that, the moisture absorption of the substrate is 0.1% by weight or less, and
Step (2) is performed after performing a standby process of lowering the temperature of the substrate until the temperature difference between the molded substrate and the environment becomes 5 ° C. or less.

In the present invention, at least one of the pair of substrates has one side main surface having fine irregularities. That is,
Only one substrate may have such irregularities on one major surface, but usually both substrates have such irregularities on each major surface. In the case of a read-only type (ie, ROM type) optical disk, the unevenness is a pits corresponding to data to be recorded, and is a rewritable type (ie, RAM type) or a write-once type (ie, R type). In the case of an optical disk, the irregularities correspond to lands and grooves. Also, in any type of optical disc, one or both main surfaces of the substrate may include irregularities corresponding to format information originally required for use of the optical disc.

The metal thin film is a light-reflective film formed on the one-side main surface of the substrate having irregularities, and this film is semi-transparent (ie, translucent) to light. Good.
For example, it is formed by sputtering gold or aluminum. This metal thin film functions as a reflection layer that reflects the laser light applied to the optical disk. When both substrates have irregularities, a metal thin film is formed on one of the irregular main surfaces of each substrate.

In an optical disk of a type in which laser light is irradiated from one side of the optical disk, a metal thin film formed on one substrate is translucent. In an optical disk of a type that irradiates laser light from both sides of the optical disk, the metal thin film formed on both substrates may be opaque to light.
When only one substrate has irregularities, it is sufficient to form a metal thin film on one irregular main surface of one substrate, and it is not necessary to form a thin film on the other substrate.

In the case of a read-only optical disk,
The metal thin film, together with the unevenness of the substrate, reflects the irradiated laser light in accordance with the pre-recorded data. Therefore, in this sense, in the case of a read-only optical disk, the metal thin film can be called a recording layer.

As is well known, in the case of a rewritable or write-once optical disk, the metal thin film is irradiated together with the unevenness of the substrate and the reversibly or irreversibly changeable layer separately provided thereon. Record the data to be written by the applied laser light, and read the pre-recorded data by the irradiated laser light together with the unevenness of the substrate and the separately provided reversibly or irreversibly changed layer. . As described above, in the case of the rewritable or write-once optical disc, the unevenness, the layer that can be changed reversibly or irreversibly, and the metal thin film are involved in the function of writing and reading data, but they are mainly reversible or irreversible. A layer that can be changed reversibly acts on this function, so a layer that can be changed reversibly or irreversibly can be called a recording layer.

Therefore, in the case of a rewritable or write-once optical disk, a reversibly or irreversibly changeable layer is formed on one main surface of a substrate having irregularities, and a metal thin film is further formed thereon. . Therefore, in the method for manufacturing an optical disk according to the present invention, in order to manufacture a rewritable or write-once optical disk, the step (2) is performed after the standby process.
, An additional step of providing such a reversibly or irreversibly changeable layer is performed. In other words, in the step (2) of forming the metal thin film, before forming the metal thin film, a reversibly or irreversibly changeable layer is provided on one side main surface of the substrate having irregularities, and This is a step of forming a metal thin film. Of course, in the case of a read-only optical disk, such an additional step is not required.

In this specification, the term “recording layer” also means
It is used in the above sense, and the elements corresponding to the recording layer are different depending on the type of the optical disc. Less than,
The present invention will be described mainly with reference to a read-only optical disk. However, in the case of a rewritable or write-once optical disk, a layer that can be changed reversibly or irreversibly is formed before forming a metal thin film. There is no substantial difference except that the additional step is carried out, and the reversibly or irreversibly changeable layer can be formed in a conventional manner.

In one embodiment, the standby treatment of the present invention is carried out such that the amount of moisture absorption preferably does not exceed 0.08% by weight, more preferably does not exceed 0.05% by weight. In the present specification, the amount of moisture absorption is based on the dry state of the substrate (so-called dry base). In another aspect, the standby process of the present invention is performed such that the temperature difference from the environment is preferably 5 ° C. or less, more preferably 3 ° C. or less. In a more preferred embodiment, the standby treatment is performed so that the temperature difference from the environment is 5 ° C. or less without the moisture absorption amount exceeding 0.05% by weight, for example, a room temperature of 20 ° C. to 35 ° C.
This can be performed by leaving the substrate taken out of the molding machine in an environment of a relative humidity of 10% to 60% for about 1 to 6 minutes. In addition, the environment means a space where the substrate is subjected to standby processing,
The space usually has a predetermined temperature and humidity (for example, 25
° C, 30% relative humidity). The amount of moisture absorption as described above may be measured by any appropriate method, for example, by measuring a change in weight of a molded substrate in a predetermined environment.

In a second aspect, the present invention provides a bonded optical disk by bonding a first substrate formed by a first molding machine and a second substrate formed by a second molding machine as a pair of substrates. A method of manufacturing, wherein (1) a first substrate and a second substrate, which are a pair of substrates having at least one having irregularities on one main surface, are molded from a transparent resin by a first molding machine and a second molding machine, respectively. (2)
Forming a metal thin film on one main surface having the irregularities,
And (3) a step of laminating a pair of substrates so that the metal thin film is located inside and joining (or bonding) the substrates by an adhesive supplied between the substrates, and a mold of the first molding machine. Providing a temperature difference between 2C and 6C between the temperature and the mold temperature of the second molding machine. In the manufacturing method according to the second aspect, in a preferred embodiment, the standby processing according to the first aspect is performed.

Here, the mold temperature means that the substrate is formed by injecting and molding a molten transparent resin into a cavity (or void) of a mold composed of a pair of mold halves (mold half). In manufacturing, it refers to the arithmetic average temperature of the temperature of the pair of mold parts that define the cavity corresponding to the substrate. Normally, in a bonded optical disk, one of a pair of substrates has a rib (or a stack rib) and the other has no rib, but the mold temperature of a molding machine for molding a substrate having a rib is increased. Is preferred.

According to a third aspect, the present invention is a method of manufacturing an optical disk substrate by injection molding in which a molten transparent resin is supplied to a cavity in a mold, the method comprising the steps of: mold halves) temperature is 0
A method characterized in that the temperature differs between 6C and 6C. The substrate manufactured by this method is preferably used in the method of manufacturing an optical disc according to the first or second aspect.

According to a fourth aspect, the present invention provides (a) a molding section for molding a substrate with a resin, (b) a film forming section for forming a metal thin film on the surface of the substrate by a thin film forming means, and (c) a pair of Having a bonding portion for bonding the substrates through an adhesive,
An apparatus for manufacturing an optical disk by bonding a pair of substrates with an adhesive is also provided. In this apparatus, a substrate is sent from a molding unit to a bonding unit via a film forming unit to a bonding unit, and the molding unit and the film forming unit are formed. A temporary standby unit for holding the substrate between the unit and the unit for a predetermined time. The standby unit has the predetermined environment and performs the standby process described above. The forming unit forms a pair of substrates, at least one of which has irregularities on one side main surface, and the film forming unit forms a metal thin film on one side main surface of the substrate having irregularities.

In the present invention, the manufacturing of an optical disc or a substrate is performed except that a standby process is performed, a pair of substrates is formed by changing a mold temperature, and a temperature difference is provided in a mold portion at the time of forming. The method includes forming the substrate,
Including the formation of the metal thin film and the joining (or bonding) of the substrate, the method can be carried out by a known method using known materials and equipment under known conditions, as exemplified below.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The components of an optical disk, a method of manufacturing an optical disk, a substrate for forming an optical disk, and a method of manufacturing the same according to the present invention will be described below in more detail.

[Optical Disk] The present invention relates to a ROM type,
It is intended for the manufacture of various types of M-type and R-type optical disks. For example, in addition to DVD, CD (Compact Disk), P
Among various optical disks such as a D (Phase change Disk) and an LD (Laser Disk), a bonded optical disk constituted by bonding a plurality of substrates is targeted. Such a laminated optical disc may have a single recording layer, and generally has two recording layers.

[Substrate] The substrate used for manufacturing the optical disk of the present invention is manufactured by appropriately combining materials such as a synthetic resin and a metal thin film in accordance with the purpose of use of the optical disk. In the case of a DVD optical disk, the substrate is molded from a transparent resin such as a polycarbonate resin, and one main surface of the substrate has predetermined fine irregularities corresponding to data to be recorded, or lands and grooves, as described above. Having. At least one of the pair of substrates has a one-sided main surface having irregularities.

A metal thin film is formed on the main surface of the substrate having the irregularities. This metal thin film is a metal layer that reflects a laser beam applied to an optical disk, and is formed of a metal such as gold, aluminum, or silicon, and can be formed by a method such as sputtering. The formed metal thin film is
Opaque or translucent to light. A protective film (for example, a layer of zinc sulfide) may be formed on the surface of the metal thin film as necessary.

In the case of a read-only optical disk,
Although a substrate as described above is used, a write-once or write-once optical disc is formed on a main surface of a substrate having irregularities before forming a metal thin film on a main surface of a substrate having a concavo-convex pattern by using a reversibly changeable material (eg, GeSbTe) in a conventional manner. ) Or a layer of irreversibly changeable material (eg, TePdO) is formed as the recording layer.

Two such substrates are bonded together. Usually, the surface on the side where the recording layer is arranged is the bonding surface.
In this case, the two substrates may have a texture and a thin metal film as described above, and optionally a layer of a reversibly changeable or irreversibly changeable material.
In this case, the substrates may have the same material and structure, or may have different materials or structures. In the case of the ROM type, usually, at least a pair of substrates to be bonded are different from each other in at least the concavo-convex shape, and therefore the structure of the recording layer. In the case of another type, at least the concavities and convexities of both substrates, and thus the structure of the recording layer, may be the same except for the portion corresponding to the format data. In another embodiment, one is a substrate having such irregularities and a metal thin film, and the other is a disk-shaped substrate having neither flats nor a metal thin film and having two flat main surfaces made of a simple resin. Good. Even if the protective film does not exist,
Alternatively, at least one of the substrates may have it.

When the substrate is used for an ordinary optical disk, it has a thin disk shape and has a circular opening at the center. Usually, one of the substrates has a rib around the opening. Depending on the purpose of use of the bonded substrates, the substrates may have a shape other than a circular plate, and the shapes of the substrates may be processed after bonding. When laminating substrates for lamination, the paired substrates are arranged such that the metal thin film is located on the inner side, that is, on the side closer to the lamination surface.

[Process of Forming Substrate] Basically, a forming apparatus and a forming method similar to those of a normal optical disc substrate are employed. As the molding method and apparatus, an injection molding method and an injection molding apparatus are used. In the injection molding apparatus, the mold is composed of a pair of mold parts arranged vertically or horizontally,
A cavity having a shape corresponding to the outer shape of the substrate is formed between the mold portions. Since the substrate is provided with pits (in the case of ROM type) or lands and grooves (in the case of RAM type or R type) which constitute the above-mentioned fine irregularities for recording information, one side of the cavity is provided with a fine surface of the substrate. It has a fine uneven shape corresponding to a rough uneven structure.

In the injection molding, a resin material heated and melted at a high temperature is injected and supplied to a cavity of a mold at a high pressure. The forming conditions such as the injection pressure and the injection temperature may be the same as the conditions for manufacturing a substrate for an ordinary optical disk. In order to improve the flow of the molten resin injected and supplied into the mold, the mold is heated to a predetermined temperature. As will be described later, by adjusting the heating temperature of the mold, the shape accuracy and the amount of warpage of the formed substrate can be controlled.

The temperature difference between the temperature of the mold portion forming the front surface of the substrate and the temperature of the mold portion forming the rear surface of the substrate is from 6 ° C. to 10 ° C. (preferably from 7 ° C. to 10 ° C.). 9 ℃)
It has been found that by setting the substrate in the range described above, the warp of the optical disk finally manufactured can be reduced. In addition, this temperature difference is set to 0 ° C. or more and 6 ° C.
If the temperature difference is set in the range of less than 2 ° C. (preferably 2 ° C. to 5 ° C.), the warpage of the optical disk immediately after manufacturing slightly increases compared to the case where the temperature difference is 6 ° C. or more and 10 ° C. or less. It has also been found that the increase in

In the method of the present invention, an optical disk is manufactured by laminating a pair of substrates. As described above, these two substrates are manufactured by different molding machines, and in this case, the metal mold of the molding machine is used. It has been found that different mold temperatures are preferred. In this case, the temperature difference between the mold temperatures is preferably from 2 ° C to 6 ° C, and preferably from 3 ° C to
More preferably, it is 4 ° C.

According to the method of the present invention, an optical disk is manufactured by bonding a pair of substrates. As described above, the pair of substrates constituting the optical disk are divided into the first and second substrates.
In this case, a change in the amount of warpage of the optical disk with time can be controlled by setting a difference in the mold temperature between the two molding machines. In a specific example, 1
Of the pair of substrates, the temperature of the mold of a molding machine for molding a substrate (having ribs in shape) for forming a semi-permeable metal thin film is set to the other substrate (having no ribs). By increasing the temperature by 2 ° C. to 6 ° C. higher than the temperature of a mold of a molding machine for molding the optical disk, it is possible to suppress an increase in warpage of the optical disk with time. For example, the change Δt in the amount of warpage can be suppressed to within ± 0.3 °.

[Formation (Deposition) Step of Metal Thin Film] A metal thin film to be a reflection film is formed on the surface of the substrate by using a thin film forming means in the same manner as an ordinary optical disk. The metal thin film is directly on the main surface of the substrate having fine irregularities such as pits,
Alternatively, it is formed on a reversibly or irreversibly changeable layer provided on the unevenness. As the material of the metal thin film, gold, aluminum, and other metal materials used for ordinary optical disks are used. Vacuum deposition, C
VD (Chemical Vapor Deposition), PVD (Physica
l Vapor Deposition) is adopted.

[Standby Process] As described above, a standby process is performed before forming a metal thin film, and then a film forming process is performed. Normally, after a standby process for a predetermined period of time, for example, a standby period of 1 to 6 minutes, a film forming process is performed. The waiting time generally starts from the time when the formed substrate is taken out of the mold of the molding machine and is the time until the formation of the metal thin film in the film forming process. Therefore, for example, the time required to transfer the substrate from the molding process to the film forming process is also included in the standby time, and the standby process is performed during that time.

In order to suppress the warpage of the optical disk as the final product, the difference between the temperature of the substrate and the temperature of the surrounding environment must be 5 or less.
It is preferable to lower the temperature of the substrate until the temperature becomes lower than or equal to ° C. It is desirable that the time required for the temperature drop be at least about 2 minutes. Such a decrease in the temperature of the substrate may be confirmed by any appropriate means, for example, it can be measured using an infrared thermometer.

The substrate immediately after molding varies depending on the substrate material, but is usually in a high temperature state of about 70 to 100 ° C.
The temperature of such a substrate is lowered by a standby process. The environment in which the standby process is performed is outside the molding machine of the optical disk production line, and is a room where the production line is located. In order to lower the temperature of the substrate, the substrate may be left alone at an ambient temperature, or may be forcibly cooled by blowing cold air or contacting a low-temperature object. However, the occurrence of thermal stress and thermal distortion due to rapid cooling must be avoided. As described above, the standby process is performed, and the temperature of the environment is generally 15 ° C. to 35 ° C., and is usually about room temperature (20 ° C. to 25 ° C.).

In the stand-by process, the moisture absorption of the substrate does not exceed 0.1% by weight (based on the weight of the dried substrate containing no water), preferably does not exceed 0.08% by weight, more preferably. Should not exceed 0.05% by weight. In order to suppress the increase in the amount of absorbed moisture, it is possible to adjust the humidity of the environment from the molding process to the film forming process through the standby process. For example, the transfer path may be a tunnel-like closed space between these steps, and the humidity in the space may be adjusted. The smaller the moisture absorption, the more the warpage of the optical disc is suppressed.

If the substrate is cooled down to a temperature equal to or slightly higher than the temperature of the environment while maintaining the above-mentioned moisture absorption, the warping deformation due to the thermal deformation or thermal stress of the substrate. Is suppressed. If the film forming process is performed in a state where the substrate temperature is higher than the environmental temperature or in a state where the amount of moisture absorption is too large, the variation in the warp angle of the manufactured optical disk increases. Generally, a temperature of 20 ° C. to 3
The standby treatment is preferably performed in an environment of 5 ° C. and a relative humidity of 10% to 60%. In such an environment, the amount of moisture absorption and the temperature difference can be within the above ranges by a standby time of 1 minute to 6 minutes. .

In other words, in the present invention, the standby time is set to such a time that the molded substrate cools down to the above-mentioned temperature range and at the same time, the amount of moisture absorption becomes less than the above-mentioned amount. If the standby time from the molding step to the film forming step is too short, the film is formed on the substrate whose temperature is not sufficiently lowered, and the substrate is likely to be deformed at the time of film forming, and particularly heat is applied at the time of film forming. In this case, thermal deformation of the substrate occurs, and the manufactured optical disk is likely to be warped.

If the waiting time is too long, for example, more than 40 minutes, the amount of moisture absorption of the substrate may vary, and the substrate may be easily warped. If a sufficiently long standby time of several hours to 24 hours is taken as the standby time as in the conventional annealing treatment, the amount of moisture absorption becomes constant, and the variation in the warping deformation due to the moisture absorption is eliminated, but the work efficiency becomes poor. . Also, variations in the temperature and / or humidity of the environment during the long standby time may cause variations in the warpage of the optical disc.

In the present invention, the predetermined standby time can be set by adjusting the transfer time of the substrate from the molding step to the film forming step. For example, the standby time can be changed by adjusting the speed and length of a conveyor serving as a substrate transfer unit. In another method, the forming step and the film forming step are continuously performed in a fixed cycle, and the substrate is temporarily retained between the forming step and the film forming step.
Temporary standby means for performing standby processing may be provided.

[Temporary Standby Means] In one specific embodiment, a substrate running on the conveyor is taken out of the conveyor and stacked at another location in the middle of the conveyor for transferring the substrate from the molding process to the film forming process. , Or side by side,
After a lapse of a predetermined time, an apparatus may be employed in which the taken out substrate is returned to the conveyor again and sent to the film forming step.

When such a temporary standby means is provided, it is not necessary to change the setting of the speed and length of the transfer conveyor in order to adjust the standby time. Even if the waiting time is long, the transfer conveyor does not become long and the equipment space does not increase.

[Substrate Bonding Step] After the film forming step, a pair of substrates is bonded together with an adhesive. For this purpose, the same processing method and processing apparatus as in the case of manufacturing an ordinary optical disk are used.

As the adhesive, various light-curing types can be used depending on the material of the substrate to be bonded, the conditions of use of the optical disk (for example, the place of use (for example, for vehicle use), the temperature of use, the purpose of use (for example, audio), etc. Is used. In particular, for a DVD optical disk, it is preferable to use an ultraviolet-curable transparent adhesive. Adhesives that cure with light of a wavelength other than ultraviolet light can also be used. An adhesive may be supplied to one or both of the pair of substrates by using a normal coating means or a coating means, and the substrates may be overlapped with each other and then cured with ultraviolet light or the like. When both substrates have a metal thin film or irregularities, the bonding is performed on the substrate having both the metal thin film or the irregularities so that the main surface of the substrate having the metal thin film or the irregularities is located inside. This is performed so that the main surface is located inside (that is, opposed).

As a preferable bonding method, the following method can be applied: a pair of substrates is opposed to each other and held at a relatively small interval, and an adhesive discharge nozzle is inserted into the gap, and the discharge nozzle is inserted. By rotating the pair of substrates about an axis perpendicular to the surface while discharging the adhesive from the substrate, the adhesive is annularly arranged in the gap. Thereafter, by narrowing the gap between the substrates and further rotating the two substrates, the annular adhesive spreads in the radial direction, and the gap between the substrates can be filled with a thin adhesive layer.

In order to cure the adhesive layer by light, usually, a light irradiation lamp is arranged above a pair of substrates placed horizontally on a flat mounting table, and the light irradiated from the light irradiation lamp is set. Is passed through a transparent substrate material on the upper surface side and, if present, a semi-transparent metal thin film to reach the adhesive layer to perform photo-curing of the adhesive. Such a bonding method is specifically disclosed in detail in International Publication No. WO97 / 35720 cited above.

[Other Steps] When a pair of substrates are bonded with an adhesive, the optical disk of the present invention is completed.
An inspection process for inspecting the shape and dimensions of the optical disk and verifying whether necessary data information is recorded can be performed. It is also possible to add a step of printing characters or the like on a surface or a portion of the surface of the optical disk which does not hinder information reading.

[0052]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical disk according to the present invention is manufactured on the basis of a manufacturing line 100 comprising a forming step (1), a film forming step (2) and a joining step (3), as shown in FIG. . In the illustrated embodiment, a ROM optical disk is manufactured.

In the molding step (1), donut disk-shaped substrates d1 and d2 are molded using an injection molding apparatus. On one main surface of each of the substrates d1 and d2, pits forming fine irregularities corresponding to information to be recorded are formed.
As one of the substrates d1 and d2, a smooth substrate having no unevenness on the surface can be used.

In the film forming step (2), a metal thin film is formed on the surfaces of the substrates d1 and d2 by using a thin film forming means such as a vacuum evaporation apparatus. For example, a thin film of gold can be formed on the substrate d1, and a thin film of aluminum can be formed on the substrate d2. In the case of single-sided recording, film formation may not be performed on one substrate.

In the joining step (3), the substrates d1 and d2 are bonded with an adhesive g to manufacture the optical disc D. This step includes (i) supplying an adhesive, (ii) laminating a substrate, and (i)
ii) Consists of a sub-step of curing the adhesive.

First, in the adhesive supply sub-step (i), a pair of substrates d1 and d2 are arranged so that the surfaces on the side having fine irregularities and on which the metal thin film is formed face each other. By horizontally rotating the substrates d1 and d2 while discharging the adhesive g from the tip nozzle of the adhesive supply device G, the adhesive g is arranged in an annular shape. At this time, if the distance between the upper and lower substrates d1 and d2 is narrowed so that the adhesive g discharged from the adhesive supply device g is disposed in contact with the upper and lower substrates d1 and d2, the adhesive g is placed securely,
In the next laminating sub-step, it is possible to prevent air bubbles from entering between the substrates d1 and d2 and to prevent application unevenness of the adhesive g.

In the laminating sub-step (ii), the substrates d1 and d2 are brought close to each other and horizontally rotated, so that the adhesive g interposed therebetween is thinly stretched over the entire surface between the substrates d1 and d2, and the substrates d1 and d2 are thinned. And d2 are adhered and laminated. In the adhesive curing sub-step (iii), ultraviolet light is irradiated from one side of the laminate of the substrates d1 and d2 by the ultraviolet irradiation lamp L, and the ultraviolet light cures the adhesive g through the transparent substrate d1. When the adhesive g is cured, the substrates d1 and d1
2 is obtained.

[Manufacturing Apparatus] FIG. 2 schematically shows an optical disk manufacturing apparatus which can carry out the optical disk manufacturing method of the present invention as viewed from above. This apparatus includes a forming unit 20 (and 20 ′), a temporary standby unit 30, a film forming unit 40, and a joining unit 50. Each process unit is arranged along a transfer conveyor 10 running rightward.

The molding units 20 and 20 ′ are provided on the transfer conveyor 1.
0 and on both sides of the transfer conveyor 10 respectively. The molding units 20 and 20 'are composed of two series of injection molding devices, and continuously mold the substrates d1 and d2. The formed substrates d1 and d2 are alternately supplied onto the transfer conveyor 10 by the transport arm 22 that rotates. On the transfer conveyor 10, the substrates d1 and d2
Are transferred alternately.

The temporary standby means 30 disposed between the forming units 20 and 20 ′ and the film forming unit 40
By the operation of 2, the substrates d1 and d2 transferred on the transfer conveyor 10 are transferred to the stand 34 arranged on the side of the transfer conveyor 10. In the stand 34, the substrates d1 and d2
Are sequentially stacked. The substrates d1 and d2 that have been on standby for a predetermined time on the standby table 34 are
Is returned onto the transfer conveyer 10 by the operation of. Substrate d
By adjusting the time during which 1 and d2 are placed on the standby table 34, the standby time can be changed.

In the film forming section 40, the substrates d1 and d2 transferred on the transfer conveyor 10 are sequentially taken in by the reciprocating arm 42, and a metal thin film corresponding to each of the substrates d1 and d2 is formed. Return to top. When gold and aluminum are used as the metal thin film, the film forming unit 40 is provided with a thin film forming mechanism corresponding to each metal.
The substrates d <b> 1 and d <b> 2 conveyed to the downstream of the transfer conveyor 10 after the film forming process is completed are sent to the joint 50 by the operation of the turning arm 12.

At the joint 50, the substrates d1 and d2 are held opposite to each other, the adhesive g is supplied by the adhesive supplier G,
And d2 are laminated, the adhesive is stretched, and a curing process using an ultraviolet lamp L is performed. Thus, an optical disc D is obtained. The obtained optical disk D is placed on the collection conveyor 60 and transported.

[Electrostatic Elimination Device] In the above manufacturing apparatus, an electrostatic elimination device for preventing static electricity from accumulating on the substrates d1 and d2 can be provided. In particular, as described above, it is preferable to reduce the moisture absorption of the substrates d1 and d2 in the path from the molding step to the film forming step via the standby processing. For this purpose, it is preferable to keep the substrates d1 and d2 in a dry state, but the substrates d1 and d2 in a dry state are liable to generate static electricity. When static electricity accumulates on the substrates d1 and d2, dust adheres to the surface. If they are bonded as they are, it will interfere with writing and reading of records.
Therefore, if the static electricity accumulated on the substrates d1 and d2 is removed, the above-mentioned problem caused by the static electricity can be solved. If the transfer conveyor 10 is provided with a static electricity removing device, static electricity can be effectively removed from the substrates d1 and d2 during the manufacturing process.

[Injection Molding Apparatus] FIG. 3 schematically shows an injection molding apparatus 20 in which a mold is shown in a sectional view. Using this apparatus 20, the substrates d1 and d2 are formed by injection molding.
The resin chips stored in the hopper 210 are heated and melted while being kneaded in the screw cylinder 220. The molten resin supplied to the injection cylinder 230 is supplied to the mold 240 at high speed and high pressure.

The mold 240 includes a pair of upper mold portions 242.
And a lower mold part 244. The mold parts 242 and 244 are provided with heating means such as a heater (not shown).
44 can each be heated to a predetermined temperature. Between the two mold parts 242 and 244, a cavity (or gap) 246 composed of a disk-shaped space corresponding to the shape of the substrate d1 or d2 is defined.

[Changes in Moisture Absorption and Warpage after Molding] The graph shown in FIG. 4 shows the moisture absorption over time of the substrates d1 and d2 (made of polycarbonate) used for manufacturing the DVD optical disk molded by the above-described injection molding apparatus. Represents the change. In addition, a change in the warp angle (tilt angle) immediately after the manufacture occurs in the manufactured optical disc due to a difference in a standby time of a standby process from molding to film formation.

The substrate was molded from polycarbonate at a mold temperature of 90 ° C., and after molding, was heated to 23 ° C. and a relative humidity of 50%.
Environment. In the graph, △ is a warp angle at a position of 58 mm from the center of the optical disk, □ is a warp angle at a position of 40 mm from the center of the optical disk,
○ indicates a warp angle at a position 23 mm from the center of the optical disc. The warpage angle was measured based on DVD Specifications using a commercially available optical disk deformation measuring device. The amount of moisture absorption was measured by a change in the weight of the substrate.

As is apparent from FIG. 4, the substrates d1 and d1
The moisture absorption (broken line) of No. 2 sharply increases immediately after molding, and thereafter increases with time. The warp angle fluctuates with a large fluctuation width as the standby time becomes longer, but is approximately 4000.
When the time exceeds about sec (70 minutes), the fluctuation range becomes smaller,
It changes relatively smoothly and then approaches a nearly constant value.

In the annealing treatment in the prior art, after the substrates d1 and d2 after molding are allowed to stand until such a change in the warpage angle becomes stable, the variation in the warpage of each optical disk is performed by performing a film forming process. I was holding it down.

In the present invention, the moisture absorption of the substrates d1 and d2 is kept at 0.1% by weight or less. For this purpose, the standby time may be set within a range of about 1 to 40 minutes (60 to 2400 sec). You can see that. In this case, the absolute value of the warp angle is not so large. In a particularly preferred embodiment of the present invention,
It is understood that the amount of moisture absorption is maintained at 0.05% by weight or less, and for this purpose, the standby time may be set within a range of about 2 to 6 minutes (120 to 360 seconds). In this case, the film is formed before the variation of the warp angle occurs, and the variation of the warp angle is reduced.

[Environmental Test] FIG. 5 shows the discs of an optical disk manufactured by the manufacturing method of the present invention (standby time: 4 minutes) and an optical disk manufactured by a conventional manufacturing method in which annealing is performed for 24 hours. The results of evaluating the change in warpage over time in the long term after production by an environmental test under an accelerated environment (80 ° C., relative humidity 85%, corresponding to 4 days) are shown. As the disk, the same disk as used when the change in the amount of moisture absorption was measured was used. The standby treatment or the annealing treatment of the substrate was performed by maintaining the substrate in an environment at 23 ° C. and a relative humidity of 50%. The substrate had a temperature of 26 ° C. after the completion of the standby treatment, and had a moisture absorption of 0.04% by weight.
Met. The temperature of the substrate was 23 ° C. after the completion of the annealing treatment, and the moisture absorption was 0.21% by weight.

FIG. 5A shows the warp angle of the optical disk obtained by the manufacturing method of the present invention. The waiting time between the forming step and the film forming step was 4 minutes. When the difference between the warp angles of the ten disks before and after the test was measured, the average Δt was −0.54 °. FIG. 5 (b)
This shows the warp angle of an optical disc on which a film is formed after performing a conventional annealing process (24 hours) after molding. When the difference in the warp angles before and after the test was measured for 10 disks,
The average value Δt was −0.46 °.

Therefore, when comparing the test results of FIGS. 5A and 5B, the change in the warp angle before and after the environmental test is different between the conventional annealing process and the short-time standby process of the present invention. No substantial difference was observed from a practical point of view. However, considering the time of the conventional annealing process and the standby process of the present invention, the method of the present invention is 1 /
It took less than 200 hours, demonstrating that the method of the present invention significantly improves production efficiency.

[Adjustment of Mold Temperature] When the mold temperature or mold part temperature is changed in the above-described substrate molding process, the influence of the change on the warpage of the optical disk finally manufactured is described above. The evaluation was made based on the change in the warpage angle over time due to the test. Note that the environment for the standby process is temperature 2
5 ° C., relative humidity 38%, standby time 4 minutes,
As a result, the temperature of the substrate becomes 28 ° C.
0.04% by weight.

<Temperature difference between upper and lower mold parts> The upper mold part 2 when molding the substrate d1 with the injection molding apparatus shown in FIG.
The temperature of 42 and the temperature of the lower mold part 244 were changed. The waiting time between the forming step and the film forming step was 4 minutes.

In each of Test Examples 1 and 2, 15 samples were manufactured and subjected to the same environmental test as above. The results are shown in FIG. In Table 1, Δt represents the average value of the difference between the warp angles before and after the test. The substrate is made of polycarbonate.

[0077]

Table 1 Test Example 1 Test Example 2 Upper mold part temperature (° C.) 87 87 Lower mold part temperature (° C.) 92 94 Temperature difference 57 Δt (°) +0.19 +0.44

As a result of the above test, Test Example 1 in which the temperature difference between the mold portions 242 and 244 for forming the substrates d1 and d2 was reduced (FIG. 6A), and Test Example in which the temperature difference was under normal molding conditions Compared with FIG. 2 (FIG. 6B), the warp angle before the start of the environmental test is smaller in Test Example 2 in which the temperature difference between the mold portions is large.

The change Δt in the warp angle before and after the environmental test is smaller in Test Example 1 than in Test Example 2 in which the temperature difference between the mold portions is small. Looking at the slope of the straight line in each graph of FIG. 6, the slope of Test Example 1 is smaller than that of Test Example 2. This indicates that the variation in the warpage angle over time can be suppressed by reducing the temperature difference in the mold portion.

Therefore, in order to reduce the warpage at the time of manufacturing the optical disk, it is better to provide a certain temperature difference between the mold portions. Is small (for example, 2
(In the range of 5 ° C. to 5 ° C.) is more preferable. Normally, if the warpage deformation at the time of manufacturing satisfies the standard conditions, it is preferable that the change of the warpage deformation with time is small.
C.).

<Temperature difference between molds when a pair of substrates is molded by different molding machines> In each of the molding machines 20 and 20 'for molding the pair of substrates d1 and d2, the mold temperature of each molding machine ( = The arithmetic average of the temperature of the upper mold part and the temperature of the lower mold part) was evaluated for the effect on the warpage of the optical disk. Note that the substrate d1 is a substrate on which a semi-transmissive film is formed, and has a rib in shape.
The substrate d2 is a substrate on which a non-transmissive film is formed, and does not have a rib in shape.

The temperature difference ΔT is calculated by the following equation. ΔT = T1−T2 (1) T1 = (T11 + T12) / 2 (2) T2 = (T21 + T22) / 2 (3) where T1: the upper mold part temperature T11 and the lower mold temperature in the molding machine for substrate d1. Arithmetic average value with side mold part temperature T12 T2: Upper mold part temperature T2 in molding machine for substrate d2
It is an arithmetic mean value of 1 and the lower mold part temperature T22.

For evaluation, an optical disk was manufactured using the obtained substrate, and the environmental test described above was performed on the optical disk to evaluate it. The evaluation results of the warp angle are shown in FIG. The difference between the upper mold part temperature and the lower mold part temperature was 6 ° C. The environment for the standby processing was a temperature of 25 ° C. and a relative humidity of 38%, and the standby time was 4 minutes, whereby the substrate reached 28 ° C. and its moisture absorption was 0.04
% By weight.

[0084]

Table 2 Test Example 1 2 3 4 5 First molding machine mold temperature T1 (° C) 87 89 91 89.5 90.5 Second molding machine mold temperature T1 (° C) 89 89 89 83.5 83.5 Temperature difference ΔT = T1-T2 (℃) -2 0 +2 +6 +7 Variation of warpage angle Δt (°) -0.72 -0.52 -0.25 +0.19 +0.44

As a result, the change Δt in the warp angle before and after the environmental test changes depending on the difference in the mold temperature between the molding machines, and the mold temperature difference is appropriately set (for example, 2 ℃ -6
° C), it can be seen that warpage over time can be reduced.

[0086]

According to the method and apparatus for manufacturing an optical disk of the present invention, the warpage of the optical disk caused by the processing conditions, particularly the processing conditions from the molding step to the film forming step, is effectively prevented, and the flatness is improved. The optical disk with high performance can be manufactured, and the working efficiency of the manufacturing can be improved.

[Brief description of the drawings]

FIG. 1 is a process diagram schematically showing steps of a method for manufacturing an optical disc according to the present invention.

FIG. 2 is a plan view schematically showing the optical disk manufacturing apparatus of the present invention as viewed from above.

FIG. 3 is a partial cross-sectional elevational view schematically showing a molding section of the optical disk manufacturing apparatus of the present invention.

FIG. 4 is a graph showing a change in a moisture absorption amount and a warp angle over time after molding of a substrate.

FIGS. 5A and 5B are graphs showing the results of an environmental test of an optical disc.

FIGS. 6A and 6B are graphs showing another environmental test result of the optical disc.

FIG. 7 is a graph showing still another environmental test result of the optical disc.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Conveyer conveyor, 20, 20 '... Molding part, 30 ... Temporary standby means, 40 ... Film formation part, 50 ... Joining part, 60 ... Collection conveyor, 240 ... Dies 242,244 ... Die part, 246 ... Cavity D: optical disk, d1, d2: substrate, g: adhesive, L:
Curing lamp

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuyuki Sawada 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. 72) Inventor Takaaki Higashida 1006 Kadoma Kadoma, Kadoma City, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd.

Claims (10)

[Claims] 1. A method for manufacturing a bonded optical disk, comprising: (1) at least one of which has irregularities on one main surface;
Forming a pair of substrates from a transparent resin, (2) forming a metal thin film on the one-sided main surface having the irregularities, and (3) laminating the pair of substrates such that the metal thin film is positioned inside. A step of bonding the substrates with an adhesive supplied between the substrates, and after the step (1), the substrate has a moisture absorption of 0.
A step of performing a step (2) after performing a standby process of lowering the temperature of the substrate until the temperature difference between the formed substrate and the environment is 5 ° C. or less and 1% by weight or less. Method. 2. The method according to claim 1, wherein the temperature of the environment is 20 ° C. to 35 ° C., the relative humidity of the environment is 10% to 60%, and the waiting process is performed for 1 minute to 6 minutes. . 3. The method according to claim 1, wherein the standby treatment is performed while maintaining the moisture absorption of the substrate at 0.05% by weight or less. 4. A method of manufacturing a bonded optical disk by bonding a first substrate formed by a first molding machine and a second substrate formed by a second molding machine as a pair of substrates, 1) at least one has irregularities on one side main surface;
Forming a first substrate and a second substrate, which are a pair of substrates, from a transparent resin using a first molding machine and a second molding machine, respectively; (2) forming a metal thin film on the one-sided main surface having the irregularities; (3) a step of laminating a pair of substrates so that the metal thin film is located on the inside and joining the substrates by an adhesive supplied between the substrates, the mold temperature of the first molding machine and the second molding A manufacturing method, wherein a temperature difference of 2 ° C. to 6 ° C. is provided between the temperature of the mold and the temperature of the machine. 5. The manufacturing method according to claim 4, wherein after the step (1), the standby processing according to any one of claims 1 to 3 is performed, and then the step (2) is performed. 6. A method for manufacturing an optical disk substrate by injection molding in which a transparent resin is supplied to a cavity in a mold, wherein a temperature of one of a pair of mold portions defining a cavity during molding is 0% with the other. A method for manufacturing a substrate, wherein the temperature is different from 6 ° C to 6 ° C. 7. The manufacturing method according to claim 6, wherein a substrate used in the method for manufacturing an optical disk according to claim 1 is manufactured. 8. A molding section for resin molding a substrate,
(B) bonding a pair of substrates comprising a film forming unit for forming a metal thin film on the surface of the substrate by the thin film forming means, and (c) a bonding unit for bonding the pair of substrates via an adhesive An apparatus for manufacturing an optical disk by bonding with an agent, in which a substrate is sent from a forming unit to a bonding unit via a film forming unit by a transfer unit, and the substrate is held between the forming unit and the film forming unit for a predetermined time. An optical disk manufacturing apparatus, comprising: a temporary standby unit having a changing environment. 9. The temperature of the environment of the temporary standby means is from 20 ° C.
The manufacturing apparatus according to claim 8, wherein the temperature is 35C and the relative humidity of the environment is 10% to 60%. 10. The manufacturing apparatus according to claim 8, which is used in the manufacturing method according to claim 1.