JP2002067035A - Method for recovering substrate resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an industrially advantageous method which can recover the substrate resin at a high quality from an information recording medium after usage and off-specification products produced in the manufacturing process. SOLUTION: By this recovering method, the substrate resin is recovered from the optical information recoding medium comprising the resin substrate wherein a metal thin film layer and/or a coated layer are formed on the surface. In such a recovering method, to the surface, on which the metal thin film layer and/or the coated layer are formed, of the recording medium, a powder stream containing a powder formed of a resin is jetted. Thus, the film layer component other than the substrate resin is removed from the surface of the recording medium by the recovering method for the substrate resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for recovering a substrate resin from an optical information recording medium comprising a resin substrate having a metal thin film layer and / or a coating layer formed on a surface thereof. More specifically, the present invention relates to a method for effectively removing a metal thin film layer and / or a coating layer formed on the surface of the optical information recording medium and recovering a resin substrate made of a resin.

[0002]

2. Description of the Related Art Conventionally, a method of detecting fine irregularities provided on a disk substrate by a laser beam to reproduce a sound or an image, a method of recording / reproducing information by an information recording layer provided on a substrate surface, or a method of recording. Various optical information recording media have been developed and marketed, such as a system capable of erasing or overwriting recorded information, and a system in which these are pasted to increase the recording capacity. Such an information recording medium is required to have a large amount and an extremely high density storage capacity and an extremely high quality, so that even if it has minute defects, it must be a defective product. In addition, a large number of test samples must be taken from various parts of the production process to maintain high quality. In particular, a large number of compact discs exclusively for reproduction are produced, and there is a problem in processing a large number of resin plates such as samples, defective products, and recovered products from the market and the like.

Hitherto, such information recording media have been manufactured from transparent resins such as polycarbonate resin, polymethyl methacrylate resin, and amorphous cyclic polyolefin resin. Among them, polycarbonate resin is used for most discs and large-scale production is required. On the other hand, a large number of samples, defective products, etc. are simultaneously generated. These samples,
In the processing of defective products and the like, the transparent optical substrate before the information recording layer or the reflective layer is applied can be directly pulverized or repelletized, mixed with a general polycarbonate resin or an alloy with another resin, and reused without any problem. However, a resin plate provided with an information recording layer and a reflective layer, further provided with a protective coat layer such as a UV coat and an adhesive layer for bonding (hereinafter, referred to as a resin plate).
Reuse of the "coated resin plate") is severely limited. For example, a UV-coated resin plate
Since the UV coating layer is incompatible with the polycarbonate resin, simply mixing it with a general polycarbonate resin causes irregularities on the surface of the obtained molded product, which significantly impairs the appearance. In the case of a laminated resin plate, the heat stability of the adhesive is inferior to that of the resin, so that the hue may be deteriorated or the molecular weight of the resin may be reduced. Therefore, it has been proposed to selectively remove the information recording layer, the reflective layer and the protective coat layer from the resin substrate to recover the resin itself.

[0004] Some of the proposals will be described below. (I) JP-A-4-305414 (European Patent No. 47)
No. 6,475, U.S. Pat. No. 5,151,452) and JP-A-5-200379 (European Patent No. 537,567).
No. 5,214,072) and JP-A-6-214.
No. 223416 (European Patent No. 601,719, U.S. Pat. No. 5,306,349): These methods involve chemically treating a coated resin plate with, for example, an aqueous solution of an acid or alkali. . In other words, these methods dissolve the metal part of the information recording layer and the reflective layer,
This method removes the V coat layer and the label print layer, and has the disadvantage that the layer cannot be removed, such as a part without a metal part or a defective resin plate subjected to a coat test, a label print test, etc. An increase in running costs, such as necessity of a neutralization process and a neutralization step of wastewater, was unavoidable. (Ii) Japanese Patent Application Laid-Open No. 5-345321:
This is a method in which the coated resin plate is immersed in hot water for a long time, and is excellent in that the neutralization treatment in the above method is not required. However, this method has a drawback that the polycarbonate resin substrate is apt to be immersed in hot water for a long time, so that the molecular weight is reduced and whitening is apt to occur in the case of a polycarbonate resin substrate. Therefore, this method is not a preferable method for recycling the recovered resin. (Iii) JP-A-5-210873 and US Pat. No. 5,203,067:

In these methods, the surface of the coating layer of the coated resin plate is mechanically cut and polished with a blade or an abrasive to remove the surface. These methods require a device for reading the cut surface and a device for reversing the surface of the resin plate, so the initial investment amount is large, and there are disadvantages such as a decrease in the resin recovery rate due to cutting, and it is difficult to spread the method. there were. Further, as a recent technique, a technique of attaching a thin resin plate for the purpose of increasing the recording capacity has been developed, but a new problem has arisen that grinding is impossible because the resin portion is outside. (Iv) WO 97/39868 In this method, the optical information recording medium is rolled, heat-treated, pulverized, and then heat-treated again to remove the coating film layer and the metal thin film layer and recover the substrate resin. Is the way. Although this method is industrially advantageous, its steps are relatively complicated, and simpler steps are required.

[0006]

The above-mentioned method of recovering a resin from a resin plate covered with a metal thin film layer and / or a coating layer is not economically and industrially satisfactory. From the viewpoint of reusing the resin, the quality and the recovery were hardly satisfactory. Further, when the resin molded product to be reused requires transparency and high quality, the conventional method cannot be said to be a satisfactory method. Therefore, an object of the present invention is to provide an industrially advantageous method capable of effectively removing a coating layer from an optical information recording medium and selectively recovering a resin component.

In order to achieve the above object, the present inventor has sprayed a powder stream containing a solid powder onto the surface of an information recording medium to separate a metal thin film layer and / or a coating layer from the recording medium. We focused on the removal method and conducted various studies. For example, considering the polishing efficiency, using a powder stream containing an inorganic powder having a higher hardness than the substrate resin, and conducting an experiment,
Although the metal thin film layer and / or the coating layer could be peeled off and removed relatively efficiently, the problem with this method is that a very small part of the inorganic powder adheres and buries on the substrate surface, making it difficult to remove. is there. With respect to the reuse of the substrate resin to which the inorganic powder has adhered, the range of its use is significantly limited.

Therefore, the present inventor uses a powder formed of a resin having a hardness close to that of a substrate resin or a coating layer, particularly a powder formed of a resin forming a substrate, as the powder. Is sprayed onto the surface of the information recording medium, whereby the metal thin film layer and / or the coating film layer is easily peeled and removed, and the metal thin film layer and / or the coating film layer is substantially contained in the substrate. , And a transparent resin substrate was recovered. Since this method does not use an inorganic powder, it can be seen that an excellent advantage that the inorganic powder does not adhere to the substrate and a base made of a high-quality resin component that can be easily reused is recovered is obtained. Was issued.

[0009]

According to the present invention, there is provided a method for recovering a substrate resin from an optical information recording medium comprising a resin substrate having a metal thin film layer and / or a coating layer formed on a surface thereof. Spraying a powder stream containing a powder formed of a resin onto the surface of the medium on which the metal thin film layer and / or the coating layer is formed, thereby removing film layer components other than the substrate resin from the surface of the recording medium; A method for collecting a substrate resin is provided. Hereinafter, the present invention will be described in more detail.

[0010] The optical information recording medium in the present invention is:
It is an information recording medium that records and reproduces information by so-called laser light irradiation. As such information recording media, digital audio discs (so-called compact discs), optical video discs (so-called laser discs), various write-once discs, magneto-optical discs, phase change discs, and the like have been put to practical use. Of these, compact discs and laser discs are read-only (Read
It is an only memory (ROM) type optical disk. In these optical disks, pits corresponding to information signals are formed in an uneven shape on a transparent substrate, and an Al reflective layer is formed thereon with a thickness of 40 nm or more. In such an optical disc, an information signal is reproduced by detecting a change in reflectance caused by optical interference generated in the pit.

On the other hand, a write-once optical disc has an R (Recordable) on which arbitrary information can be written by a user.
e) type optical disk, a magneto-optical disk and a phase change type disk are RAMs (Random Access Memory) in which arbitrary information can be repeatedly written.
y) type optical disc. That is, the R-type optical disc is formed of a write-once recording layer on a transparent substrate, the optical characteristics of which are irreversibly changed by irradiation of a laser beam, or the uneven shape is formed. As the recording layer, for example, a cyanine-based, phthalocyanine-based, or azo-based organic dye that is decomposed by heating by laser light irradiation, changes its optical constant, and causes deformation of the substrate due to volume change is used.

A magneto-optical disk allows a user to repeatedly write and erase information.
This is a rewritable optical disk that has a T
A perpendicular magnetization film having a magneto-optical effect (for example, the Kerr effect) such as a b-Fe-Co amorphous alloy thin film is formed. In this magneto-optical disk, recording pits are formed by magnetizing a small region of a perpendicular magnetization film upward or downward in response to an information signal. The information signal is reproduced by utilizing the fact that the rotation angle θk (Kerr rotation angle) of the linearly polarized light in the reflected light differs depending on the direction of magnetization of the perpendicular magnetization film.

A phase change disk is a rewritable disk like a magneto-optical disk. For example, a phase change disk exhibits a crystalline state in an initial state, and changes its phase to an amorphous state when irradiated with a laser beam. A phase change material or the like is used. In this recording layer, recording pits are formed by phase-changing a minute area in response to an information signal.
The information signal is reproduced by detecting a change in the reflectance between the amorphous portion corresponding to the pit and the other crystal region. In such magneto-optical disks and phase change disks,
For the purpose of preventing the oxidation of the recording layer and increasing the signal modulation degree due to multiple interference, a four-layer structure is often adopted in which both sides of the recording layer are sandwiched between transparent dielectric layers and an Al reflective layer is further laminated thereon. . In addition, as the dielectric layer, a silicon nitride film, a Zn—SiO ₂ mixed film, or the like is used.

Recently, digital versatile disks have been developed as high-density recording media. A digital video disc (DVD), which is one of the digital versatile discs, has a diameter of 120 mm, the same as a CD, and records video information equivalent to one movie, and can reproduce the same picture quality as a current television. It was done as such.

Such a digital versatile disk is provided on a recording layer formed on a substrate, as described in JP-A-6-274940, in order to compensate for a decrease in disk strength due to the thinning of the substrate. In addition, a so-called bonding structure in which substrates are further bonded is adopted. As the recording layer of the bonded optical disk, any of the ROM-type recording layer, the R-type recording layer, and the RAM-type recording layer used in the above-described single-plate configuration can be adopted. Further, the bonded optical disks include a single-sided bonded optical disk using only one surface thereof and a double-sided bonded optical disk using both surfaces thereof.

The resin for the substrate of the information recording medium applied to the resin collecting method of the present invention may be a light-transmitting resin.
Usually, an aromatic polycarbonate resin, a polymethyl methacrylate resin or an amorphous cyclic polyolefin resin is used. Among them, an aromatic polycarbonate resin or a polymethyl methacrylate resin is preferable, and an aromatic polycarbonate resin is most preferable. Next, these resins will be described. The polycarbonate resin is usually produced by reacting a dihydric phenol with a carbonate precursor in a solvent (interfacial polymerization method) or in a molten state (melt polymerization method). Basic means of these manufacturing methods will be briefly described.

In the case of the interfacial polymerization method using, for example, phosgene as a carbonate precursor, the reaction is usually carried out in the presence of an acid binder and a solvent. Examples of the acid binder include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide and amine compounds such as pyridine. As the solvent, for example, halogenated hydrocarbons such as methylene chloride and chlorobenzene are used. For promoting the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt may be used. At that time, the reaction temperature is usually 0 to 4
0 ° C. and the reaction time is a few minutes to 5 hours.

In the melt polymerization method (ester exchange reaction) using a carbonic acid diester as a carbonate precursor, a predetermined ratio of a dihydric phenol component is stirred with a carbonic acid diester while heating under an inert gas atmosphere to distill off the formed phenols. It is done by the method of letting out. The reaction temperature depends on the boiling point of the phenols formed, etc.
It is in the range of 00 ° C. The reaction is completed at a reduced pressure from the beginning while distilling off phenols produced. Further, a catalyst usually used in a transesterification reaction to promote the reaction can be used. Examples of the carbonic acid diester used in the transesterification reaction include diphenyl carbonate, dinaphthyl carbonate, bis (diphenyl) carbonate and the like. Of these, diphenyl carbonate is particularly preferred.

A typical example of the above dihydric phenol is 2,2-bis (4-hydroxyphenyl) propane.
[Bisphenol A], bis (4-hydroxyphenyl)
Methane, 1,1-bis (4-hydroxyphenyl) ethane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2- (4-hydroxy-3-methylphenyl) propane, Bis (4-hydroxyphenyl) sulfone and the like can be mentioned. Preferred dihydric phenols are bis (4-hydroxyphenyl) alkanes, especially bisphenol A.

In producing the polycarbonate resin, the above dihydric phenols can be used alone or in combination of two or more. In addition, a suitable molecular weight regulator, a branching agent, a catalyst for accelerating the reaction, and the like can be used. Two or more of the polycarbonate resins thus obtained may be mixed. The molecular weight of such a polycarbonate resin is preferably 10,000 to 20,000, more preferably 13,000 to 16,000, in terms of viscosity average molecular weight.

The polymethyl methacrylate resin is a resin obtained by polymerizing a methyl methacrylate monomer as a main raw material. For optical applications, a homopolymer is usually used, but other copolymerizable monomers, specifically, methyl acrylate, ethyl acrylate,
Acrylates such as propyl acrylate and butyl acrylate, and methacrylates such as ethyl methacrylate, propyl methacrylate and butyl methacrylate
Those copolymerized at 0 mol% or less can also be used. The polymerization method is not particularly limited, and a production method such as bulk polymerization, suspension polymerization, solution polymerization, or emulsion polymerization is used.

Examples of the amorphous cyclic polyolefin resin include a hydrogenated product of a ring-opened polymer of a norbornene-based monomer and a hydrogenated product of polystyrene or a derivative thereof. Examples of such norbornene monomers include norbornene, dimethanooctahydronaphthalene, trimethanododecahydroanthracene and their alkyl-substituted or alkylidene-substituted products, dicyclopentadiene, 2,3-dihydrodicyclopentadiene, dimethanooctahydrobenzoin Examples thereof include den, dimethanodecahydrobenzoindene, dimethanodecahydrofluorene, and alkyl-substituted products thereof. Further, those having a polar substituent such as a halogen atom, an ester-type residue, an ether-type residue, and a cyano group may be used. Among them, those having two or more functionalities make injection molding difficult, and those having one or more functionalities are preferably used. These norbornene-based monomers may be used alone or in combination of two or more.

In the present invention, when recovering the substrate resin from the optical information recording medium described above, the resin formed on the surface of the recording medium on which the metal thin film layer and / or the coating layer is formed is formed. A powder stream containing powder is sprayed to peel and remove film components other than the substrate resin from the surface. The powder used at that time is a powder formed of a resin, and preferably a powder formed of a thermoplastic resin.

The resin forming the powder used includes:
The above polycarbonate resin, polyolefin resin (polyethylene resin, polypropylene resin, etc.), acrylic resin, styrene resin, ABS resin, polyamide resin, polyester resin (polyethylene terephthalate resin, polyethylene naphthalate resin, polybutylene terephthalate resin, etc.), vinyl chloride resin And the like, and a polycarbonate resin is particularly preferably employed. The molecular weight of the polycarbonate resin forming the resin powder is preferably 10,000 to 50,000 in terms of viscosity average molecular weight,
000 to 35,000 are more preferred. A polycarbonate resin having such a viscosity average molecular weight is suitable for efficiently removing film layer components other than the substrate resin of the optical information recording medium.

It is practically preferable that the powder used in the present invention is formed of the same resin as the substrate resin to be recovered. Here, the same type means a resin belonging to the same polymer class as the substrate resin, and does not necessarily need to be the same resin. For example, when the substrate resin is a polycarbonate resin, for example, the same resin, the same resin but a different polycarbonate resin, the terminal group-modified polycarbonate resin, the copolymerized polycarbonate resin, and a mixture containing the polycarbonate resin Other types of polycarbonate resins having different dihydric phenols as well as the resin are also included in the category of the same type of resin.

The shape of the resin powder in the present invention includes a columnar shape, a spherical shape, a rectangular shape, a cocoon shape, a powder shape, and the like, and the average particle size is 0.05 to 3.0 m.
m is preferable, and 0.1 to 2.0 mm is more preferable. In particular, it is more preferably from 0.2 to 1.0 mm. In carrying out the method of the present invention, in order to spray a powder fluid containing powder on the surface of a resin substrate of an information recording medium, a method using a powder fluid composed of powder and air (dry method) and powder There is a method (wet method) of using a powder fluid composed of a liquid medium or a powder fluid further containing air therein (wet method). However, in order to peel the metal thin film layer and / or the coating film layer from the recording medium in a short time and efficiently, it is suitable to use a wet method.

The wet method is preferable because it is practical to use water as the liquid medium, and the recovery operation of the resin substrate after the peeling treatment and the treatment of the treated water are easy. The powder fluid is air containing resin powder, liquid medium containing resin powder, or a mixture containing resin powder air and liquid medium.
In order to spray the powder fluid onto the surface of the resin substrate, the flow velocity is suitably from 10 to 1000 m / sec, preferably from 50 to 1000 m / sec.
500 m / sec, more preferably 100 to 400 m
/ Sec. In the case of wet spraying, for example, low pressure air (for example, 1.1 to 2 atmospheres, that is, about 110 MPa to 200 MPa)
It is common to blow out MPa) together with water containing powder from a nozzle and spray it on the substrate surface.

The distance from the spray nozzle to the substrate surface is usually 30 to 1000 mm, preferably 50 to 500 mm.
mm, and more preferably 50 to 300 mm.
When water is used as the liquid medium, the proportion of the powder in the water is 0.1 to 30% by weight, preferably 0.2 to 10% by weight.
Is advantageous. In the spraying, the angle and position of the nozzle should be set so that the powder fluid efficiently collides with the substrate surface, and for that purpose, the angle and position of the nozzle can be moved. Usually, the metal thin film layer and / or the coating film layer can be effectively peeled and removed in 10 to 300 seconds, preferably 20 to 200 seconds, and the resin substrate having relatively high transparency is recovered after the treatment. be able to.

Thus, according to the present invention, a high-quality resin substrate substantially free of a metal thin film layer and / or a coating layer can be recovered in a short time, and the recovered resin substrate is made of an inorganic material. Since the resin does not contain any particles and the deterioration of the resin is extremely small, it can be advantageously reused as it is.

[0030]

Hereinafter, the present invention will be described in detail with reference to examples. In the examples, the following resin substrates and powders were used. The transparency and overall judgment of the substrate after the spraying treatment were performed according to the following methods. Polycarbonate resin substrate with dihydric phenol component bisphenol A having an information recording medium viscosity average molecular weight of 15000 (1.2 mm) / aluminum deposited layer (0.05 μm)
/ UV coating layer (5-10 μm) / label printing layer (2
0 μm) resin substrate A (120 mm in diameter)
It was used. Powder (1) PC powder: A polycarbonate resin powder having a viscosity average molecular weight of 25,000 and a dihydric phenol component of bisphenol A (average particle size: 0.4 mm). (2) Alumina powder: average particle size 0.2 mm (3) Sand powder: sand for sandblasting, average particle size 0.3 mm

Transparency of the substrate A black circle having a diameter of 1 cm is drawn on white paper (the circle is painted with an HB pencil). Place the substrate after spraying on this black circle, slowly move the substrate upward from the paper while visually observing, until the black circle can no longer be confirmed,
The distance between the paper and the substrate was measured. Therefore, the longer the distance, the higher the transparency of the substrate. In this measurement, a water drop was dropped on the sprayed surface of the substrate, and a transparent polycarbonate sheet having a thickness of 2 mm was stacked thereon. Comprehensive judgment ：: A highly transparent substrate was recovered, the spraying time was short, the amount of remaining powder was extremely small, and the recyclability was extremely excellent. ：: A highly transparent substrate was recovered and excellent in recyclability. ×: The releasability of the metal film and the coating film is good, but the powder remains, and the recyclability has some difficulty.

Example 1 A surface of a resin substrate A having a metal thin film layer and a coating layer was coated with P
Water containing 5% by weight of the C powder was sprayed from a nozzle having a diameter of 14 mm using pressure air of about 150 MPa (about 1.5 atm). The speed of this powder flow was 200 m / sec, and the distance between the nozzle and the resin substrate A was 150 mm. The nozzle angle was controlled so that the powder stream would strike the entire surface of the resin substrate A almost at right angles. The spraying of the powder stream was continued for a period of time until the metal thin film layer and the coating layer (UV coating layer and label printing layer) of the resin substrate A were substantially peeled off. The same operation was performed on five resin substrates A. The results are shown in the table.

Example 2 PC was applied to the surface of the resin substrate A having the metal thin film layer and the coating layer.
Air containing powder was blown from a nozzle having a diameter of 14 mm at a pressure of about 150 MPa (about 1.5 atm). The same operation was performed for five resin substrates A. The results are shown in the table below.

Comparative Example 1 The procedure of Example 1 was repeated, except that alumina powder was used instead of PC powder. The results are shown in the table below. Comparative Example 2 The procedure of Example 2 was repeated, except that alumina powder was used instead of PC powder. The results are shown in the table below. Comparative Example 3 The procedure of Example 2 was repeated, except that sand powder was used instead of PC powder. The results are shown in the table below.

[0035]

[Table 1]

Claims (13)

[Claims] 1. A method for recovering a substrate resin from an optical information recording medium comprising a resin substrate having a metal thin film layer and / or a coating layer formed on a surface thereof, wherein the metal thin film layer and / or the coating film of the recording medium is provided. A method for recovering a substrate resin, comprising spraying a powder stream containing a powder formed of a resin onto a surface on which a layer is formed, thereby removing a film layer component other than the substrate resin from the surface of the recording medium. 2. The method according to claim 1, wherein said powder has an average particle size of 0.05 to 3 mm. 3. The method according to claim 1, wherein the powder is a powder formed of a thermoplastic resin. 4. The recovery method according to claim 1, wherein the powder is a powder formed of the same kind of resin as the resin forming the resin substrate. 5. The method according to claim 1, wherein the resin is a polycarbonate resin, a polymethyl methacrylate resin, or an amorphous cyclic polyolefin resin. 6. The method according to claim 1, wherein the resin is a polycarbonate resin. 7. The method according to claim 1, wherein the powder stream is sprayed at a speed of 10 to 1000 m / sec. 8. The method according to claim 1, wherein the powder stream is composed of powder formed of resin and air. 9. The method according to claim 1, wherein the powder stream is composed of a powder formed of a resin and a liquid medium. 10. The method according to claim 1, wherein the powder stream is composed of a powder formed of a resin, air and a liquid medium. 11. The recovery method according to claim 9, wherein the liquid medium is water. 12. The recovery method according to claim 1, wherein the optical information recording medium is an optical disk having an aluminum metal thin film layer. 13. The method according to claim 1, wherein the film layer components other than the substrate resin are a metal thin film layer component and a coating layer component.