JPH06101147B2 - Optical disk manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical information recording member such as a disk for a digital memory, and in particular, to manufacture an optical information recording member with high reliability and long life. The present invention relates to a manufacturing method for doing so.

[Conventional technology]

Optical information recording members (hereinafter referred to as optical discs) include video discs, compact discs, digital memory discs, and the like. Among them, digital memory discs are high in terms of handling digital information. Reliability and long life are required. One measure of high reliability and long life of such disks is 60 ° C, 95% RH.
Even if the disk is left for 1000 hours in an environment of (relative humidity), the information is retained on the disk.

FIG. 2 is a sectional view showing a partial section of a general digital memory disk.

As shown in FIG. 2, the above-mentioned disk for digital memory generally includes a transparent plastic resin substrate 1, a recording film 2 of a chalcogenide compound, a protective film 3 of an ultraviolet curable resin, and an adhesive layer 4 of an adhesive or the like. It consists of and.

Incidentally, examples related to this type of optical disk include, for example, JP-A-61-99951 and JP-A-61-131249.

[Problems to be solved by the invention]

Conventionally, a disk for digital memory configured as shown in FIG. 2 is used in an environment of 60 ° C. and 95% RH for 50 to 100.
When left for a period of time and taken out at room temperature, the third portion of the recording film 2
The swelling 5 shown in the figure may occur, which makes it difficult to read or write information. In FIG. 3, the same parts as those in FIG. 2 are designated by the same reference numerals.

By the way, there have been no reports of the above-mentioned blistering phenomenon until now. This is because a video disk or a compact disk widely used for consumer use has a higher reliability than a digital memory disk that handles digital information.
It is considered that a long life is not required and the harsh environmental test as described above has not been performed.

Therefore, an object of the present invention is to solve the above-mentioned conventional problems, and to cause a blistering phenomenon (hereinafter referred to as a blistering defect) of a recording film even when exposed to a high temperature and high humidity environment for a long time. An object of the present invention is to provide a method of manufacturing an optical disc that does not have any type.

[Means for solving problems]

The inventors of the present invention have thoroughly studied the occurrence of swelling defects, and have found that the cause is that the water contained in the plastic resin substrate is exposed at the interface between the substrate and the recording film.

Furthermore, although the above-mentioned force of ejection largely depends on the physical properties of the plastic resin substrate, the magnitude relationship between the force of ejection and the adhesive force between the substrate and the recording film is greatly related to the occurrence of blistering defects. Focusing attention, among the optical disk manufacturing methods, the present inventors have studied various methods of increasing the adhesive force between the substrate and the recording film, such as the type of the substrate, the substrate pretreatment method, and the recording film forming method.

As a result, in the case of a plastic resin substrate, particularly a polycarbonate resin substrate with high heat resistance, after the plasma irradiation, the recording film (comprising a chalcogenide compound) is sputtered immediately and the UV curable resin is protected. The most suitable method is to produce an optical disk by the steps of forming a film and then performing adhesive bonding.
In particular, it has been found that the formation of the blistering defect can be completely prevented by sputtering the recording film immediately after the surface of the substrate is irradiated with plasma.

Therefore, in order to achieve the above-mentioned object, in the present invention, as a method of manufacturing an optical disk, a first step of irradiating the surface of a plastic resin substrate with plasma and a surface of the plastic resin substrate irradiated with the plasma are performed. And a second step of forming the recording film by sputtering.

[Action]

First, the results of examination of the occurrence status of the blistering defect will be described.

As shown in FIG. 3, the blisters 5 generated on the recording film 2 are substantially circular and have a diameter of 1 to 50 μm. As described above, such blistering defects are not observed immediately after taking out at room temperature after being left in an environment of 60 ° C and 95% RH for 50 to 100 hours, but gradually after 30 minutes to 1 hour. It appears.

By the way, typical transparent plastic resin substrates used as optical disks are acrylic resin substrates and polycarbonate resin substrates. Of these, a polycarbonate resin substrate having high heat resistance is suitable for a substrate as a disk for a digital memory in order to obtain high reliability and a long life. On the other hand, the blistering defect did not occur in the acrylic resin substrate, but occurred in the optical disk using the polycarbonate resin substrate. Even with the polycarbonate substrate, no blister defects were observed when left in a dry state at 60 ° C for 50 to 100 hours.

From the above, it can be inferred that the blistering defect is affected by humidity, but it was necessary to elucidate the reason why the blistering defect occurs in the polycarbonate resin substrate and does not occur in the acrylic resin substrate. In particular, although the water absorption rate of polycarbonate resin is smaller than that of acrylic resin by about one digit, swelling defects occur, and the swelling defects are closely related to humidity. It was necessary to

FIG. 4 (a) is a graph showing the water absorption characteristics of the polycarbonate resin, and FIG. 4 (b) is a graph showing the water absorption characteristics of the acrylic resin.

In Fig. 4 (a), the vertical axis is the water absorption rate, the horizontal axis is the standing time, and in the same figure, the case of standing in water at a temperature of 100 ° C and the case of standing in water at 20 ° C are shown. The respective characteristics when left in the atmosphere are shown. Also, in FIG. 4 (b), the vertical axis is the water absorption rate, the horizontal axis is the number of days left, and in the same figure, 10 ° C, 27 ° C, 60 ° C, 8 ° C.
The characteristics are shown when left in water at each temperature of 0 ° C.

Therefore, the inventors of the present invention, not the above water absorption rate itself,
Attention was paid to the water absorption characteristics as shown in FIG. That is, as shown in FIG. 4, attention was paid to the fact that the polycarbonate resin has a much higher water absorption rate than the acrylic resin, and the difference in the saturated water absorption rate depending on the temperature is large.

In other words, if the optical disk is left in an environment of 60 ° C, 95% RH for a long time and then taken out in a room of about 25 ° C, 50% RH, the temperature will drop relatively quickly, and the moisture in the substrate will Oversaturated and trying to get out. At this time, in the case of the acrylic resin substrate, the water release rate can be expected to be relatively slow due to the water absorption characteristics shown in FIG. 4 (b), but in the case of the polycarbonate resin substrate, it is shown in FIG. 4 (a). As described above, the saturated water absorption rate is greatly different depending on the temperature, and the water discharge rate is fast (about the same as the water absorption rate), so that it is considered that the force of the water to go out of the substrate is very large.

On the other hand, the recording film is a semi-metal or a semiconductor and does not allow water to pass therethrough, so that the above-mentioned force of moisture to be drawn acts on the interface between the recording film and the substrate. Here, if there is a portion where the squeezing force overcomes the adhesive force between the recording film and the substrate, water is squeezed out to that portion, and the recording film appears to swell.

In addition to the above-mentioned causes, as other causes, the inside of the blistering defect is the residual monomer in the substrate (when viewed at the molecular level, it is not chained as an organic substance,
The present inventors have also examined this point, but the fact that there are many blistering defects on the entire surface of the substrate and the hot press plate of polycarbonate resin pellets (residual monomer is an injection molded product). It is very unlikely that the residual monomer is the cause of the blistering defect.

Therefore, from the results of the above studies, the present inventors conclude that the cause of the blistering defect is that the water contained in the plastic resin substrate is exposed at the interface between the substrate and the recording film. Reached

Further, the adhesive force between the polycarbonate resin substrate and the recording film and the adhesive force between the acrylic resin substrate and the recording film were measured by the attracting method (a general method for measuring the adhesive force of the film). As a result, since it was almost equal to 5 to 6 × 10 ⁸ dyne / cm ² , the presence or absence of the blistering defect was determined by the magnitude relationship between the above-mentioned squeezing force and the adhesive force, and the blistering defect was observed in the acrylic resin substrate. It is considered that the reason why the generation is not caused is that the pulling-out force is small.

Since the above-mentioned blowing force is almost determined by the physical properties of the plastic resin (specifically, water permeability and water absorption), it is necessary to increase the adhesive force between the substrate and the recording film in order to prevent blistering defects. Becomes Therefore, the present inventors next examined a method of increasing the adhesive force between the substrate and the recording film.

In the case of inorganic substrates such as glass and S _i, there is a variety of methods as a method for increasing the adhesion of the, for example,
Thin film handbook (Ohm Publishing) P22-P25, P33-P35
It is described in. On the other hand, regarding the plastic resin substrate, the thin film handbooks P881 to P882 are also shown, but the adhesive force between the substrate and the thin film (recording film) is often weak. This is because the release of the internal inclusions peculiar to the plastic resin substrate or the low heat resistance limits the thin film forming conditions.

Therefore, in order to increase the adhesive force between the plastic resin substrate and the recording film, it is necessary to examine various processes of the optical disc manufacturing process and find a manufacturing method suitable for preventing the blistering defect.

From the above, it is naturally conceivable to reduce the contents (for example, water, plasticizer, residual monomer, etc.) contained in the plastic resin substrate in order to prevent the blistering defect.
The present inventors considered that it is impossible to eliminate these due to the injection molding conditions and so on, and intensively studied the surface treatment method of the substrate and the recording film forming method.

First, as a recording film forming method, typical vacuum deposition and sputtering were studied.

In vacuum deposition, B _i, put S _e and S _b, respectively different deposition boat, after the degree of vacuum 5 × 10 ^-3 P _a (Pascal), while rotating the substrate, at the same time current to the evaporation boat flushed, by co-evaporation, to form a S _e -S _b -B _i based recording film.

Further, in the Supatsutaringu, after the vacuum degree of 5 × 10 ^-3 P _a, introduced until the A _r gas 0.7 P _a, while rotating the substrate, B _i -S _e alloy Tagetsuto and S _b -S the high frequency voltage is applied simultaneously to the _e alloy Tagetsuto, by performing simultaneous Supatsutaringu, to form a S _b -S _e -B _i based recording film.

In addition, S _b − formed respectively by these two methods
The film thickness of the S _e -B _i based recording film is approximately 1000 Å. After forming the recording film, a protective film made of an ultraviolet curable resin is formed to a thickness of 30 μm, and the two substrates are bonded together with a hotmelt adhesive to form an optical disc as shown in FIG. Constitute.

Among the transparent plastic resin substrates, typical acrylic resin substrates and polycarbonate resin substrates were used as the substrates. As described above, a polycarbonate resin substrate having high heat resistance is preferable as a substrate of a disk for digital memory in order to satisfy high reliability and long life. Therefore, in the present invention, the focus is on preventing blistering defects in the optical disk using the polycarbonate resin substrate.

Therefore, the above two types of substrates (that is, an acrylic resin substrate and a polycarbonate resin substrate) are used, and each of the above two types of recording film forming methods (that is, vacuum deposition and sputtering).
Fig. 5 shows the results of the cellophane tape peeling test (a method of roughly measuring the magnitude of the adhesive force) of each recording film formed in the case where the recording film was formed by Fig. 6 shows the occurrence of blistering defects in the optical discs.

In addition, in FIG. 6, after left in an environment of 60 ° C. and 95% RH for 100 hours, taken out at room temperature, and after 1 to 2 hours, the occurrence state of blistering defects is observed with a microscope, and the result is ○. , △,
It was classified by x. O marks indicate that no blistering defects occurred, Δ marks indicate that blistering defects occurred but the number was small, and X marks indicate that blistering defects occurred and the number of occurrences was large.

Further, in FIG. 5, as a result of a cellotape peeling test, as a result of the peeling of the recording film, a mark x is given, and a piece without peeling is marked with a mark o. As a result of this test, it is meant that the adhesiveness between the substrate and the recording film is stronger when the recording film is not peeled.

As is clear from FIGS. 5 and 6, in the optical disk using the acrylic resin substrate, the blistering defect may not occur even though the adhesive force is weak, and in the optical disk using the polycarbonate resin substrate, Despite the strong adhesion, the blistering defect occurred. This indicates that, as described above, the presence / absence of a blistering defect is determined based on the magnitude relationship between the pull-out force and the adhesive force.

Further, as shown in FIG. 6, in an optical disc using a polycarbonate resin substrate, swelling defects occur in both of the above two types of recording film forming methods. Therefore, as a method of further increasing the adhesive force between the substrate and the recording film. The surface treatment method of the substrate was examined.

For the surface treatment method, see P22 to P2 of the thin film handbook.
Although there are various methods as described in 5, P33 to P35, the present inventors found a surface treatment method effective in preventing blistering defects in an optical disk using a polycarbonate substrate.

FIG. 7 shows the occurrence status of blistering defects for each surface treatment method of the substrate. Hereinafter, each processing method will be described.

(1) Scrub cleaning with a neutral detergent A brush that rotates while spraying a neutral detergent (a brush is a soft cloth that does not scratch the plastic substrate,
For example, PLUS CHAM (trade name of Kanebo Co., Ltd.) or the like was used. ) To wash the substrate, then spraying pure water,
Scrub cleaning was performed with the same brush, and spin drying was performed while blowing nitrogen gas.

(2) Flon vapor cleaning The substrate was placed in a vapor bath of CFC heated to the boiling point, shaken for 2 to 3 minutes, and then taken out from the bath.

(3) High temperature heating The substrate was heated in vacuum at 80 ° C for 20 minutes. In this treatment method, it is more effective to form the recording film immediately after heating at high temperature, so in practice, the substrate is placed in a vapor deposition apparatus and heated in vacuum at 60 ° C. for 20 minutes. After that, a recording film was formed by vapor deposition in a vacuum chamber. In the case of spattering, we did not consider high temperature heating because of the device.

(4) Ultraviolet / ozone cleaning The substrate was placed in an apparatus equipped with a low-pressure mercury lamp and an ozone generator, and was irradiated with ultraviolet rays for 60 seconds. The distance between the substrate and the mercury lamp is 10 mm, and the ultraviolet intensity is 6 mW / cm.

(5) Plasma irradiation Put the substrate in the sputtering device and set the vacuum degree to 5 × 10 ^-3.
After the P _a, it was introduced to a nitrogen gas or argon gas 0.3P _a. Next, the target side was grounded, a voltage was applied to the substrate side, and a glow discharge was generated to perform plasma irradiation. The input power is 300W and the irradiation time is 90 seconds. As described above, two types of discharge gas, nitrogen gas and argon gas, were examined.

As a result of examining each of the above surface treatment methods, as shown in FIG. 7, an optical disk forming process effective for preventing blistering defects is to combine plasma irradiation and spattering. In vacuum deposition, it was not possible to prevent the occurrence of blistering defects by using any of the surface treatment methods (1) to (5).

By the way, scrub cleaning and Freon vapor cleaning are effective in removing dust adhering to the substrate surface.
The high temperature heating has an effect of removing adsorbed gas, adsorbed water and the like. Ultraviolet / ozone cleaning is effective in removing organic contaminants, and plasma irradiation is effective in removing adsorbed substances. Furthermore, plasma irradiation and ultraviolet / ozone cleaning have the effect of modifying the plastic surface, respectively. Here, one plasma irradiation is more effective in preventing blistering defects, and the other UV / ozone cleaning is not so effective. It can be inferred that it does not play a major role.

Due to the features of the surface treatment method as described above, and the apparent difference in the occurrence state of blistering defects in both vacuum deposition and sputtering, the present inventors have reduced the adhesive force between the substrate and the recording film. We have come to the inference that it is the water contained within the substrate, which is also the water contained on the very surface of the substrate.

That is, in the vacuum deposition and Supatsutaringu, vacuum degree varies greatly during the deposition, the vacuum deposition vacuum of 10 ^-3 P _a degree, in Supatsutaringu a 10 ^-1 P _a. Therefore, spattering, which is performed in a low vacuum with a low degree of vacuum, releases less water from the substrate, and therefore has a stronger adhesive force.
To confirm this, where was the line summer vacuum evaporation by lowering the degree of vacuum 10 ^-2 P _a, less occurrence of defects blister as shown in Figure 7 Natsuta. However, without significantly increasing the temperature of the deposition boat and reduce the degree of vacuum, because it can not be formed, Atsuta 10 ^-2 P _a is the extent.

Further, since the substrate hardly absorbs moisture immediately after being molded, two types of samples having a standing time of 1 hour or less and 1 week or more after molding the substrate were examined.
As shown in the figure, it has been found that a shorter leaving period is more effective in preventing blistering defects. Therefore, if the recording film is formed by spattering within 1 hour after the substrate is formed, the swelling defect can be prevented without performing the above-mentioned surface treatment by plasma irradiation. It is not easy to manage the leaving time after molding in this way on an hourly basis, and it is not suitable for mass production.

As described above, the cause of the blistering defect is investigated. The cause is the moisture contained in the substrate. Therefore, in order to prevent the blistering defect, the moisture contained in the substrate should be removed to form the film. Even inside, it is an important point to suppress the release of water.

Therefore, in the present invention, the moisture contained in the substrate is removed by irradiating the surface of the plastic resin substrate with plasma, and thereafter, the sputtering film is formed on the recording film to remove the moisture from the substrate. The recording film is being formed while suppressing the release. Therefore, according to the present invention, it is possible to completely prevent the occurrence of blistering defects.

By the way, as described above, the surface treatment by plasma irradiation is effective in preventing the blistering defect, but from the viewpoint that the cause of the blistering defect is the water content in the substrate,
High temperature heat treatment also seems to be effective. However, here, it was not possible to study a combination of high-temperature heat treatment and spattering due to the device, but there is a sufficient possibility of preventing the blistering defect.

〔Example〕

 An embodiment of the present invention will be described below.

FIG. 1 is an explanatory view showing the flow of an optical disk manufacturing process in one embodiment of the present invention.

First, as shown in FIG. 1, in step a, a substrate made of a polycarbonate resin having a diameter of 130 mm and a thickness (t) of 1.2 mm is formed by injection molding. Next, step b
In putting the substrate into Supatsutaringu apparatus, after the vacuum degree of 5 × 10 ^-3 P _a, nitrogen (N ₂₎ gas (purity 99.999
The%) was introduced until the 0.3P _a, plasma irradiation.
During plasma irradiation, the target side is grounded and a voltage is applied to the substrate side so that high-energy ions fly to the substrate side. The input power is 300
W, irradiation time is 90 seconds.

Then, in step c, after evacuating again to become the degree of vacuum to 5 × 10 ^-3 P _a, argon (A _r) gas (purity 99.999
%) Was introduced until 0.7 P _a, performs Supatsutaringu formation of the recording film. Tagetsuto is, and B _i -S _e alloy Tagetsuto
S _b -S _e using two alloys Tagetsuto, a high frequency voltage is applied simultaneously to the Tagetsuto, by simultaneous Supatsutaringu, S _b -S _e on the substrate rotating at Tagetsuto above -
A B _i recording film is formed. The thickness of the S _b -S _e -B _i based recording film is approximately 1000 Å. Next, in step d, an ultraviolet curable resin protective film is spin-coated with a spinner to a thickness of 30 .mu.m and cured by ultraviolet irradiation to form a protective film. Finally, in step e, the two disks formed as described above are bonded together with a hot-melt type black adhesive to obtain an optical disk as shown in FIG.

In the optical disk manufactured as above, 60
No blister defects occurred even after leaving the sample at room temperature for 100 hours in an environment of ℃, 96% RH.

Further, an optical disk was manufactured in the same process by using argon gas instead of the above-mentioned nitrogen gas as the gas at the time of plasma irradiation. However, even in this disk, as a result of the above-mentioned test, no blistering defect was generated. .

Next, in the optical disk manufacturing process of this example, the occurrence state of blistering defects when the gas pressure of plasma irradiation and the irradiation time were changed was examined, and the results are shown in FIG.
The gas used was nitrogen gas, and the input power was 300W.

In Fig. 8, when the sample was left in an environment of 60 ° C and 95% RH for 100 hours and taken out at room temperature, the ones that did not have blistering defects were marked with a circle, and those that had even a few blistering defects were marked with ×.
It is indicated by a mark.

As shown in FIG. 8, it is understood that the irradiation time parameter is more important than the gas pressure and the irradiation time is 60 seconds or more in order to prevent the blistering defect.

Then, in this embodiment, the nitrogen gas pressure 0.3P _a, when the input power was 300 W, examined the relationship between plasma exposure time and optical disc of the noise level, and the results are shown in Figure 9.

As shown in FIG. 9, when the plasma irradiation time is longer than 180 seconds, the surface of the substrate is roughened by the plasma and the substrate surface noise increases. Therefore, the plasma irradiation time is suitable between 60 seconds and 180 seconds.

Further, although the input power is fixed at 300 W in the present embodiment, when the input power is lowered, the suitable range of the plasma irradiation time shifts to the long side, and conversely, when the input power is raised, it shifts to the short side. However, if the plasma irradiation time is long, the takt time (processing time) becomes long, and many processes cannot be performed within the set time, which hinders mass production. If it is too short, process stability becomes a problem. Since there is 60 seconds ~
180 seconds is most suitable.

In addition, although the polycarbonate resin substrate has been described in the present embodiment, the present invention is not limited to this, and swelling defects often occur even in resin substrates whose saturated water absorption varies greatly depending on temperature. It goes without saying that the method can be applied.

〔The invention's effect〕

According to the present invention, it is possible to obtain an optical disk that does not cause a blistering defect even when it is exposed to a high temperature and high humidity environment for a long time, and therefore, there is an effect that the reliability of the optical disk is significantly improved. .

[Brief description of drawings]

FIG. 1 is an explanatory view showing a flow of an optical disk manufacturing process in one embodiment of the present invention, FIG. 2 is a sectional view showing a partial section of a general digital memory disk, and FIG.
FIG. 4 is a cross-sectional view showing a partial cross-section of a digital memory disk when a swelling defect occurs, FIG. 4 is a graph showing the water absorption characteristics of plastic resin, and FIG. 5 is for each substrate and each recording film forming method. FIG. 6 is an explanatory view showing the result of the cellophane tape peeling test of the recording film, FIG. 6 is an explanatory view showing the occurrence of blistering defects for each substrate and each recording film forming method, and FIG. 7 is for each surface treatment method of the substrate. FIG. 8 is an explanatory view showing the occurrence of blistering defects, FIG. 8 is an explanatory view showing the occurrence of blistering defects when the gas pressure of plasma irradiation and the irradiation time are changed in the embodiment of FIG. 1, and FIG. 9 is 3 is a graph showing the relationship between the plasma irradiation time and the noise level of the optical disc in the embodiment of FIG. 1. Explanation of reference numerals 1 ... plastic resin substrate, 2 ... recording film, 3 ... protective film, 4 ... adhesive layer, 5 ... blister

Claims (3)

[Claims] 1. A method of manufacturing an optical disk comprising an information recording film on a plastic resin substrate, the first step of irradiating the surface of the plastic resin substrate with plasma, and the plasma resin substrate irradiated with the plasma. A second step of forming the recording film on the surface of the film by sputtering.
A method for producing an optical disk, which comprises at least: 2. The method of manufacturing an optical disk according to claim 1, wherein the plastic resin substrate is a polycarbonate resin substrate. 3. The manufacturing method according to claim 1, wherein the plasma irradiation time in the first step is
A method for producing an optical disk, which is characterized by being 60 seconds to 180 seconds.