JP2007317287A - Method for manufacturing optical recording medium substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an optical recording medium substrate made of a transesterification process polycarbonate resin, capable of suppressing coating failures, when a recording layer, especially a pigment layer which is the recording layer of a WORM (write-once-read-many) optical recording medium, and to provide a method for manufacturing the WORM optical recording medium. <P>SOLUTION: The method for manufacturing an optical recording medium substrate, wherein an optical recording medium resin molding, prepared by molding an aromatic polycarbonate resin of viscosity average molecular weight of 25,000 or smaller, obtained from an aromatic dihidroxy compound and diester carbonate by the transesterification process, is brought into contact with positive and negative ions generated by an ion generator for alternately generating positive and negative ions cyclically, and an information recording layer is disposed on the optical recording medium substrate obtained. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a substrate (optical recording medium substrate) for an optical recording medium or a magneto-optical recording medium (hereinafter also referred to as “optical recording medium”), which is a high-density recording medium. In particular, the present invention relates to a write-once type optical recording medium substrate using an organic dye for an information recording layer and an optical recording medium manufacturing method using the same.

  Optical recording media are available in various recording methods as low-priced and large-capacity information recording media, and their production volume is increasing year by year. Specifically, for example, read-only optical recording media such as CD-ROM, CD-DA, V-CD, DVD-ROM, DVD-Video, and DVD-Audio, and write-once light such as CD-R and DVD-R Recording media and rewritable optical recording media such as CD-RW, MO, DVD-RAM, DVD-RW, and DVD + RW are known.

  In particular, write-once optical recording media are becoming cheaper with rapid spread, and the demand for improvement in signal characteristics and productivity has become stricter. In particular, production of substrates for optical recording media (optical recording media substrates) Sex has been emphasized.

  The optical recording medium substrate is usually transparent, and as its material, polycarbonate resin, polymethyl methacrylate resin, amorphous polyolefin resin or the like which is a thermoplastic amorphous resin is used. Among them, polycarbonate resin is most frequently used in terms of strength, heat resistance, dimensional stability, price, and the like.

  Among polycarbonate resins, polycarbonate resins obtained by transesterification (transesterification) from aromatic dihydroxy compounds and carbonic acid diesters can be obtained without using phosgene gas or organic solvents as in the conventional method (interface method). The feature is that the load on the surrounding environment is small. Further, the transesterification method has a great advantage that the production process is simplified as compared with the interface method, and a polycarbonate resin having a stable quality can be obtained.

  Furthermore, the transesterification method has many advantages such as environmental friendliness, stable quality, and low price because it can be used as a raw material for producing raw material monomers, such as phenol, which is a by-product generated by the reaction. . For this reason, studies have been made on the use of polycarbonate resins obtained by the transesterification method as resins for optical recording media substrates. In recent years, the use of polycarbonate resins produced by this transesterification method (transesterification method polycarbonate resins) has expanded. It's getting on.

  On the other hand, transesterification polycarbonate resins, especially aromatic polycarbonate resins, have a high melt viscosity and poor fluidity during injection molding. Therefore, when an optical recording medium substrate on which pits and grooves serving as information signals are formed by injection molding using this transesterified aromatic polycarbonate resin, the transferability of pits and grooves may be lowered. In addition, there is a problem that distortion occurs in the substrate and birefringence increases, causing an error in signal reproduction.

  To solve these problems, a method of increasing the fluidity by lowering the viscosity average molecular weight of the transesterification aromatic polycarbonate resin can be mentioned. However, there is a problem that a significant decrease in viscosity average molecular weight causes a decrease in substrate strength. Furthermore, the injection-molded resin molding produced using the transesterification polycarbonate resin has a problem that it is easily charged to a negative polarity as compared with the polycarbonate resin obtained by the interface method.

  When the surface of the optical recording medium substrate is negatively charged, there are problems such as adhesion of fine particles such as dust in the air and reduction of the wettability of the dye of the write once optical recording medium. For this, a technique of adding several kinds of antistatic agents has been proposed (see, for example, Patent Document 1).

  On the other hand, several methods have been proposed in the past for removing the charge on a substrate or the like in an optical recording medium manufacturing process. Specifically, for example, a method has been proposed in which the surface of the substrate is neutralized by a neutralization bar or ionizer after being taken out from the mold (see, for example, Patent Document 2). In addition, a method has been proposed in which air is removed by blowing air containing ions having a polarity opposite to the polarity of charging on the substrate surface (see, for example, Patent Document 3). Furthermore, a method of blowing positive polarity ionized air in a direction parallel to the substrate surface has been proposed (see, for example, Patent Document 4).

JP 11-279396 A JP-A-7-57307 Japanese Patent Laid-Open No. 10-177744 JP 2003-85835 A

  However, as described in Patent Document 1, the addition of an antistatic agent to polycarbonate has a problem that the transparency of the polycarbonate resin is lowered and the resin is easily decomposed when used for a long time under high temperature and high humidity. there were. Further, Patent Documents 2 and 3 did not describe or suggest a problem related to improvement of the coating property of the dye in the method for producing an optical recording medium or negative charging characteristic of the transesterification polycarbonate. In addition, in the method described in Patent Document 4, the improvement of the dye characteristics after coating in the production of the optical recording medium remains insufficient.

  An object of the present invention is to provide an information recording layer provided on this substrate, particularly a dye layer which is an information recording layer of a write once optical recording medium, particularly in a method for producing an optical recording medium substrate made of a transesterified polycarbonate resin. An object of the present invention is to provide a method for manufacturing an optical recording medium substrate and a method for manufacturing a write-once type optical recording medium, in which coating failure is suppressed.

  The present inventors first analyzed in detail the surface of the resin molded product for an optical recording medium substrate in a method for producing an optical recording medium substrate using a transesterified polycarbonate resin. As a result, although most of the surface is negatively charged, it is found that there is a portion that is locally positively charged, and this positive residual charge is found to be the cause of poor dye application. It was.

  And, as a result of intensive studies on a method for eliminating positive charge from the surface of the resin molded body for an optical recording medium substrate in such a state, a resin for an optical recording medium substrate comprising a transesterification polycarbonate resin having an average molecular weight below a specific value It has been found that this positive charge can be removed by bringing both positive ions and negative ions generated from the ion generator into contact with the surface of the molded body.

  Further, as the ion generator used for this static elimination, an ion generator that periodically generates positive ions and negative ions from an electrode needle portion composed of one or a plurality of electrode needles is preferably used. It has been found that by using a generator that alternately generates positive ions and negative ions from one electrode needle, positive charges can be removed, and the present invention has been completed.

  That is, the gist of the present invention is that a resin molded body for an optical recording medium substrate obtained by molding an aromatic polycarbonate resin having a viscosity average molecular weight of 25000 or less, obtained by an ester exchange method from an aromatic dihydroxy compound and a carbonic acid diester, And a method of manufacturing an optical recording medium substrate, characterized by contacting with positive ions and negative ions generated from an ion generator having electrode needle portions that periodically and negatively generate negative ions, and obtained thereby The present invention also relates to a method for manufacturing an optical recording medium, comprising providing an information recording layer on the optical recording medium substrate.

  The optical recording medium substrate made of the transesterified polycarbonate resin obtained by the production method of the present invention has been subjected to charge removal at the same level as that obtained by the interface method, suppressing poor dye application, etc. It has the feature that the layer can be formed satisfactorily. The present invention is effective not only in the write-once type optical recording medium substrate but also in the manufacturing method of the ROM type optical recording medium substrate and the rewritable type optical recording medium substrate, and has good signal characteristics and productivity in each optical recording medium. It is expected that.

  Furthermore, an optical recording medium substrate having excellent characteristics can be easily manufactured by using a transesterified polycarbonate resin, thereby reducing the burden on the surrounding environment and providing a stable quality and low price optical recording medium substrate. And an optical recording medium can be provided.

  Hereinafter, the present invention will be described in detail.

Aromatic polycarbonate The aromatic polycarbonate used in the present invention is an aromatic polycarbonate resin obtained by an ester exchange method from an aromatic dihydroxy compound and a carbonic acid diester, and is also referred to as an ester exchange method (or melt method) aromatic polycarbonate resin. It is. The viscosity average molecular weight (hereinafter sometimes referred to as “Mv”) is 25000 or less.

  If the viscosity average molecular weight is higher than 25000, the birefringence of the resin molded product for an optical recording medium substrate, particularly obtained by injection molding, is remarkably increased. On the other hand, even if the viscosity average molecular weight is too low, it may not have sufficient strength as a resin molded body for an optical recording medium substrate or an optical recording medium substrate.

  Therefore, the viscosity average molecular weight of the transesterification aromatic polycarbonate resin used in the present invention is preferably 10,000 or more, particularly preferably 14,000 or more. The viscosity average molecular weight is preferably 23,000 or less, particularly 18000 or less.

Here, the viscosity average molecular weight in the present invention is determined by measuring the intrinsic viscosity (η) at 20 ° C. of a solution using methylene chloride as a solvent using an Ostwald viscometer, and the Schnell viscosity formula ([η] = 1.23 × 10 ⁻⁴ M ^0.83 ). The transesterification aromatic polycarbonate resin used in the present invention may be a mixture of a plurality of types of polycarbonate resins, and the viscosity average molecular weight at that time is a value obtained for the whole mixture.

  The aromatic polycarbonate used in the present invention can be obtained by a transesterification reaction using an aromatic dihydroxy compound and a carbonic acid diester as raw materials in the presence of a transesterification catalyst. Specific examples of the aromatic dihydroxy compound include bis (4-hydroxydiphenyl) methane, 2,2-bis (4-hydroxyphenyl) propane, and 2,2-bis (4-hydroxy-3-methylphenyl). Propane, 2,2-bis (4-hydroxy-3-tert-butylphenyl) propane, 2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane, 2,2-bis (4-hydroxy-) 3,5-dibromophenyl) propane, 4,4-bis (4-hydroxyphenyl) heptane, 1,1-bis (4-hydroxyphenyl) cyclohexane, 4,4′-dihydroxybiphenyl, 3,3 ′, 5 5′-tetramethyl-4,4′-dihydroxybiphenyl, bis (4-hydroxyphenyl) sulfone, bis (4-hydroxypheny ) Sulfide, bis (4-hydroxyphenyl) ether, bis (4-hydroxyphenyl) ketone.

  Among these, it is preferable to use 2,2-bis (4-hydroxyphenyl) propane (hereinafter abbreviated as “bisphenol A”). These aromatic dihydroxy compounds may be used alone or in combination of two or more in any proportion.

  Specific examples of the carbonic acid diester include aliphatic carbonates such as dimethyl carbonate, diethyl carbonate, and di-t-butyl carbonate; aromatic carbonates such as diphenyl carbonate and biphenyl phenyl carbonate; Among these, diphenyl carbonate is preferably used, and these carbonic acid diesters may be used alone or in combination of two or more.

  The aromatic polycarbonate used in the present invention is preferably obtained by a transesterification method, in particular, bisphenol A as an aromatic dihydroxy compound and diphenyl carbonate as a carbonic acid diester.

  The molar ratio of the raw materials in the transesterification method may be appropriately selected and determined. However, if it is too small, the terminal hydroxyl group content of the obtained aromatic polycarbonate resin increases and the thermal stability of the polymer tends to deteriorate. . Conversely, if the molar ratio is too large, the transesterification rate decreases, and it tends to be difficult to produce an aromatic polycarbonate having a desired molecular weight. Therefore, the molar ratio of the raw materials is, for example, that of diphenyl carbonate / bisphenol A is usually 1.001 to 1.3, and preferably 1.02 to 1.2.

  In the transesterification method, a transesterification catalyst is usually used. Any conventionally known transesterification catalyst can be used. Among these, preferred are alkali metal compounds and alkaline earth metal compounds. Further, basic compounds such as basic boron compounds, basic phosphorus compounds, basic ammonium compounds, and amine compounds may be used in combination.

The amount of the catalyst is usually 1 × 10 ^{−7 to} 9 × 10 ⁻⁷ mol with respect to 1 mol of the aromatic dihydroxy compound. If the amount of the catalyst is too small, the polymerization activity necessary for the production of the polycarbonate resin having the predetermined molecular weight and the terminal hydroxyl group content tends to be difficult to obtain. Conversely, if the amount is too large, the hue of the resulting aromatic polycarbonate resin deteriorates. And branching also increases and the moldability of the polymer tends to be impaired. Therefore, the amount of the catalyst is 1.5 × 10 ⁻⁷ to 8 × 10 ⁻⁷ mol, particularly 2 × 10 ^{−7 to} 7 × 10 ⁻⁷ mol, with respect to 1 mol of the aromatic dihydroxy compound. preferable.

  Specific examples of the alkali metal compound include sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, sodium hydrogen carbonate, potassium hydrogen carbonate, lithium hydrogen carbonate, cesium hydrogen carbonate, sodium carbonate, potassium carbonate, Lithium carbonate, cesium carbonate, sodium acetate, potassium acetate, lithium acetate, cesium acetate, sodium stearate, potassium stearate, lithium stearate, cesium stearate, sodium borohydride, potassium borohydride, lithium borohydride, hydrogen Cesium borohydride, sodium phenide boron, potassium phenide boron, lithium phenide boron, cesium phenide boron, sodium benzoate, potassium benzoate, lithium benzoate, cesium benzoate, phosphorus 2 sodium hydrogen, 2 potassium hydrogen phosphate, 2 lithium hydrogen phosphate, 2 cesium hydrogen phosphate, 2 sodium phenyl phosphate, 2 potassium phenyl phosphate, 2 lithium phenyl phosphate, 2 cesium phenyl phosphate, sodium, potassium, Examples thereof include lithium, cesium alcoholate, phenolate, disodium salt of bisphenol A, 2 potassium salt, 2 lithium salt, 2 cesium salt and the like.

  Specific examples of the alkaline earth metal compound include calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium hydroxide, calcium bicarbonate, barium bicarbonate, magnesium bicarbonate, strontium bicarbonate, calcium carbonate, Examples thereof include barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, barium acetate, magnesium acetate, strontium acetate, calcium stearate, barium stearate, magnesium stearate, strontium stearate, and the like.

  Specific examples of the basic boron compound include tetramethyl boron, tetraethyl boron, tetrapropyl boron, tetrabutyl boron, trimethylethyl boron, trimethylbenzyl boron, trimethylphenyl boron, triethylmethyl boron, triethylbenzyl boron, triethylphenyl. Sodium, potassium, lithium, calcium, barium, magnesium, strontium salts such as boron, tributylbenzylboron, tributylphenylboron, tetraphenylboron, benzyltriphenylboron, methyltriphenylboron, butyltriphenylboron Etc.

  Specific examples of the basic phosphorus compound include triethylphosphine, tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine, triphenylphosphine, tributylphosphine, quaternary phosphonium salt, and the like.

  Specific examples of the basic ammonium compound include tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, trimethylethylammonium hydroxide, trimethylbenzylammonium hydroxide, and trimethylphenyl. Ammonium hydroxide, triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide, triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide, tributylphenylammonium hydroxide, tetraphenylammonium hydroxide, benzyltriphenylammonium hydroxide, methyltriphenyl Ammoni Muhidorokishido, butyl triphenyl ammonium hydroxide, and the like.

  Specific examples of the amine compound include 4-aminopyridine, 2-aminopyridine, N, N-dimethyl-4-aminopyridine, 4-diethylaminopyridine, 2-hydroxypyridine, 2-methoxypyridine, 4- Examples include methoxypyridine, 2-dimethylaminoimidazole, 2-methoxyimidazole, imidazole, 2-mercaptoimidazole, 2-methylimidazole, and aminoquinoline.

  The transesterification reaction is generally performed in a multistage process having two or more stages. Specifically, for example, the first stage reaction is performed at 120 to 260 ° C., preferably 180 to 240 ° C. under reduced pressure of 93 to 1.33 kPa for 0.1 to 5 hours, preferably 0.1 to React for 3 hours. Next, there is a production method in which the reaction temperature is raised while raising the degree of vacuum of the reaction system, and finally the polycondensation reaction is performed at a temperature of 240 to 320 ° C. under a reduced pressure of 133 Pa or less.

  The type of reaction may be any of batch type, continuous type, or a combination of batch type and continuous type, and the apparatus used may be a tank type, a tube type or a column type reactor.

  Further, in the production of the aromatic polycarbonate used in the present invention, in order to deactivate the transesterification catalyst after the reaction, an acidic compound or a precursor thereof, specifically, for example, a sulfonic acid compound or a precursor thereof is deactivated. It is preferable to add as. As such a catalyst deactivator, p-toluenesulfonic acid, methyl p-toluenesulfonate, butyl p-toluenesulfonate and the like are preferable, and these are used alone or in an arbitrary ratio of two or more. May be.

  The amount of the catalyst deactivator used for the transesterification catalyst may be appropriately selected and determined. Specifically, for example, in the case of the acidic compound as described above or a precursor thereof, it is used for the polycondensation reaction. It is preferable to add 0.1 to 50 times mol, especially 0.5 to 30 times mol for the neutralized amount of the basic transesterification catalyst.

  The addition time of the catalyst deactivator is arbitrary as long as it is after the polycondensation reaction, and the addition method is not particularly limited. Depending on the properties of the catalyst deactivator and desired conditions, a method of adding directly, a method of adding by dissolving in an appropriate solvent, a method of using pellets or flaky master batch, and the like can be mentioned.

  In the aromatic polycarbonate used in the present invention, any conventionally known resin additive, specifically, for example, a stabilizer, an ultraviolet absorber, a release agent, a colorant, etc., is included within the range not impairing the effects of the present invention. You may contain.

  In the present invention, as described above, an aromatic polycarbonate resin having a viscosity average molecular weight of 25000 or less obtained by an ester exchange method from an aromatic dihydroxy compound and a carbonic acid diester is injection-molded to form a resin molded product for an optical recording medium substrate. Get. Then, the resin molded body is brought into contact with positive ions and negative ions (hereinafter simply referred to as “positive ions and negative ions”) generated from an ion generator to manufacture an optical recording medium substrate. Features.

Formation of resin molded body for optical recording medium substrate In the present invention, a method for producing a substrate of an optical recording medium, for example, a write-once optical recording medium such as a CD-R or a DVD-R, using the aromatic polycarbonate resin as described above Any conventionally known method can be used. Specifically, for example, the surface of the optical recording medium substrate has a plurality of grooves, pits, grooves, and the like having a submicron size that is pre-engraved on a predetermined stamper by injection molding of an aromatic polycarbonate resin. And a method of manufacturing a disk-shaped resin molded body for an optical recording medium substrate having a surface (hereinafter, also referred to as a signal surface) in which these uneven shapes are arranged concentrically.

  In particular, in the present invention, in such a method for producing a resin molded body for an optical recording medium substrate by injection molding, the charging that occurs when the resin molded body for an optical recording medium substrate is peeled from an injection mold is also effective. Static elimination can be achieved, and the effect becomes remarkable.

Contact between the ion generator and the positive ions and the negative ions In the present invention, the electrode needle portion for periodically generating the positive ions and the negative ions in the resin molded body for the optical recording medium substrate obtained in this way. An optical recording medium substrate is manufactured by bringing into contact with positive ions and negative ions generated from an ion generator having the following. The timing of this contact is such that an information recording layer (hereinafter sometimes simply referred to as “recording layer”), a reflective film, a protective layer, scratch resistance / anti-resistance is formed on the signal surface of the resin molded body for the optical recording medium substrate. If it is before forming a rubbing layer etc., there will be no restriction | limiting in particular.

  Among them, there is a method in which positive ions and negative ions are brought into contact with the cooling fluid in the cooling stage of the optical recording medium substrate resin molding after the resin molding process such as injection molding, together with the cooling fluid. preferable.

  Here, specific examples of the cooling fluid include air, nitrogen, etc., and these fluids are usually cleaned fluids from which fine particles have been removed. It is preferable to carry out in a clean environment such as inside. Specifically, for example, it is preferable to contact positive ions and negative ions generated from an ion generator under conditions of FED standard (FED-STD-209E) cleanliness class 10000 or less. In particular, it is preferably class 100 or less.

  A method of bringing both positive and negative ions into contact with the cooling fluid is arbitrary, and there is no particular limitation. Specifically, for example, there is a method in which positive ions and negative ions are brought into contact with a cooling fluid such as cooling air supplied to the entire cooling stage by a down blow method. Further, the cooling fluid supplied from the compressor may be used together with the cooling fluid supplied to the vicinity of the resin molded body for the optical recording medium substrate by a transfer tube such as a flexible tube.

  Among them, the cooling fluid supplied from the compressor is introduced into the static eliminator by means of a transfer tube such as a flexible tube, and as a cooling fluid containing positive and negative ions, resin molding for the optical recording medium substrate from the discharge port of the static eliminator The method of supplying to the body surface is preferable because of its high static elimination effect. An example of such a static eliminator is SJ-R060 manufactured by Keyence Corporation.

  In the present invention, the introduction angle for bringing positive ions and negative ions into contact with the resin molded body for an optical recording medium substrate is arbitrary, and may be appropriately selected and determined. Among them, it is preferable to introduce and contact positive ions and negative ions substantially parallel to the signal surface of the resin molded body for an optical recording medium substrate. Specifically, the introduction of positive ions and negative ions can be performed by the following method, for example.

  The resin molded body for an optical recording medium substrate separated from a resin molding machine such as an injection molding machine has the substrate surface held in a horizontal or vertical direction on a cooling stage in a clean booth. Usually, in order to reduce the installation area of the cooling stage, the substrate surface is held in the vertical direction. On the cooling stage, positive ions and negative ions are introduced and brought into contact with the cooling fluid from the upper part in parallel with the substrate surface held vertically. By such a method, it is possible to efficiently remove static electricity while reducing “warping” of the resin molded body for an optical recording medium substrate.

  The ion generator used in the present invention is not particularly limited, and can be determined by appropriately selecting any conventionally known one as long as it has an electrode needle portion that periodically and alternately generates positive ions and negative ions. Good. Ion generators are roughly classified into a direct current method (DC method) and an alternating current method (AC method).

  In the DC method, a high voltage can be continuously applied, so the amount of ions generated per unit time is large. Only one type of positive or negative ions is generated from one generator, that is, one electrode needle that emits ions. It is something to be made. Therefore, when using a DC-type ion generator, it is composed of two or more electrode needles so that the ion balance is good because the amount of either plus or minus ions is too large to promote charging. What is necessary is just to use the ion generator which has an electrode needle part and has what was used as the electrode needle part which generates a positive ion and a negative ion alternately alternately.

  On the other hand, in the AC method, since an alternating voltage is applied to one electrode needle, both positive and negative ions are emitted from one electrode needle. Therefore, both positive and negative charges can be removed, and the ion balance is good, so that there is little risk of promoting charging, which is preferable. In the AC method, the amount of ions generated per unit time is generally smaller than that in the DC method and the charge removal speed is slow. Therefore, the charge removal may be performed by appropriately increasing the applied voltage and the number of electrode needles used.

  The AC system includes a pulse AC system. The pulse AC method employs a method of alternately applying a DC voltage, and the applied voltage is a rectangular wave. As a result, the amount of ions generated per unit time is greater than the AC voltage (sine wave) used in the AC method, and both positive and negative ions are generated alternately, resulting in a good ion balance.

  The ion generator used in the present invention may be appropriately selected and determined from the conventionally known arbitrary ones as described above. Among them, the pulse AC method is used because the charge removal characteristics and the design of the electrode structure are easy. It is preferable to use an ion generator. When the pulse AC system is used as the ion generator used in the present invention, specifically, for example, it is preferable to use a plurality of electrode bars in which the electrode needles are arranged on a substantially straight line. As a result, the ion balance in the longitudinal direction of the bar is good, and the resin molded body for the optical recording medium substrate can be discharged efficiently.

The pulse AC type ion generator used in the present invention has an output voltage required for ion generation, a flow rate and pressure of a cooling fluid when the ions are brought into contact with a resin molded body for an optical recording medium substrate, and a distance from the resin molded body. The output voltage is generally 1 to 20 kv, the pulse wavelength is 1 to 100 Hz, the cooling fluid flow rate is 1 to 100 m ³ / min, and the cooling fluid pressure is 0.01. ~ 1 MPa, the distance between the substrate surface and the ion generator is 0.1 to 1 m, and such static elimination time (the time of contact with positive ions and negative ions generated from the ion generator) is 1 second to 5 minutes. It is.

  In the present invention, as described above, the positive and negative ions generated from the ion generator are brought into contact with the resin molded body for the optical recording medium substrate to perform static elimination, thereby obtaining the optical recording medium substrate. Next, in the case of an information recording layer (hereinafter sometimes simply referred to as “recording layer”), a reflective film, a protective layer, a scratch- and scratch-resistant layer, and a DVD-R, etc. An optical recording medium is manufactured by providing a transparent substrate again on the outermost layer on the side opposite to the substrate.

  The method for producing an optical recording medium substrate of the present invention can be applied to the production of a substrate used for any optical recording medium. Specific examples of the optical recording medium include CD-R, which is a write-once type optical recording medium in which a dye recording layer, a reflective layer, a protective layer, a kill-resistant layer, and the like are laminated in this order on a substrate. . Further, a write-once type optical recording medium having a configuration similar to that of a CD-R, in which a laminate made of a protective layer and a transparent substrate (dummy plate) are bonded on the reflective layer so that the recording layer is on the inside. Are DVD-R and DVD + R.

  Furthermore, DVD-R and DVD + R, which are rewritable optical recording media having a phase change recording layer as the recording layer and having substrates on both sides of the optical recording medium, can be mentioned. The production method of the present invention is particularly preferred when used in a method for producing a write-once optical recording medium substrate using a dye layer as a recording layer, since the effect becomes remarkable. Specifically, the effect of suppressing the dye application failure when forming the dye layer on the substrate and forming the recording layer satisfactorily becomes remarkable.

  Hereinafter, the method for producing an optical recording medium of the present invention will be described by taking a write-once optical recording medium using a dye layer as a recording layer as an example.

  The optical recording medium substrate used in the method for producing an optical recording medium of the present invention usually has a thickness of 0.5 to 1.5 mm. Specifically, for example, it is 1.2 mm for CD-R and for DVD-R. What is necessary is just to shape | mold so that it may become 0.6 mm. Although the molding method is arbitrary, it is usually manufactured by injection molding. At the time of this injection molding, grooves and / or pits are formed on the signal surface side. The resin molded body for an optical recording medium substrate obtained in this manner is the one obtained by removing electricity as described above, and an optical recording medium substrate is formed, and a dye layer as a recording layer is formed on this substrate.

Recording layer formation (dye application)
In general, in a method for producing a write-once optical recording medium using a dye in the recording layer, the recording layer is formed by directly applying the dye onto the signal surface of the substrate. The method for applying the dye is arbitrary, and may be determined by appropriately selecting from any conventionally known methods. Usually, there is a method of applying a dye solution obtained by dissolving an organic dye in an organic solvent so as to fill a groove formed on the signal surface by using a spin coating method.

  In general, the spin coating method may be performed by using any conventionally known spin coating apparatus including a coating liquid application device (dispensing nozzle), a spinner head, a scattering prevention wall, an exhaust device, and the like. Specifically, for example, an optical recording medium substrate is placed on a spinner head, and then the spinner head is rotated by a drive motor, and is preferably placed on the inner peripheral surface of the substrate, preferably 2 from the innermost peripheral edge of the groove. The coating liquid is supplied from the nozzle of the coating liquid application device to a position within 3 mm. The coating solution supplied on the substrate may be cast radially on the outer peripheral side by centrifugal force to form a coating film.

  The thickness of the dye layer may be appropriately selected and determined, but is usually 10 to 5000 nm for CD-R and 10 to 3000 nm for DVD-R.

  During the spin coating operation, a dry gas such as air is introduced from an opening (gas introducing portion) provided above the anti-scattering wall, the gas is circulated on the coating film, and is exhausted from below the spin coating apparatus. . By this gas flow, the solvent is removed from the coating film, and the coating film is dried. If necessary, the recording layer may be formed by placing the substrate in a drying oven called baking to remove the remaining solvent.

  The dye used in the dye layer which is the recording layer of the write-once type optical recording medium is not limited as long as it is a dye having an absorption region in the laser light wavelength range, for example, 300 to 850 nm. do it. Specifically, for example, azo dyes, cyanine dyes, phthalocyanine dyes, azurenium dyes, squarylium dyes, polymethine dyes, pyrylium dyes, thiopyrylium dyes, indoaniline dyes, naphthoquinone dyes, anthraquinone dyes, triallylmethane dyes, aminium dyes, diimonium dyes And metal chelate dyes composed of azo ligand compounds and metals, metal complexes, and the like, and mixtures thereof.

  Among them, azo dyes, cyanine dyes, phthalocyanine dyes, and the like are preferable because they are excellent in signal sensitivity, easily dissolved in a solvent, have good light resistance, and provide a high-quality write-once optical recording medium.

  The organic solvent for the dye solution may be appropriately selected and determined. Specifically, for example, esters such as butyl acetate and cellosolve acetate, ketones such as methyl ethyl ketone, cyclohexanone and methyl isobutyl ketone, dichloromethane, and 1,2-dichloroethane , Chlorinated hydrocarbons such as chloroform, amides such as dimethylformamide, hydrocarbons such as cyclohexane, ethers such as tetrahydrofuran, ethyl ether and dioxane, alcohols such as ethanol, n-propanol, isopropanol, n-butanol and diacetone alcohol, Fluorine solvents such as 2,2,3,3-tetrafluoropropanol, glycols such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether Ether compounds, and the like.

  These solvents can be used alone or in combination of two or more in consideration of the solubility of the dye used. Among them, it is preferable to use a fluorinated solvent such as 2,2,3,3-tetrafluoropropanol, octafluoropentanol, or dibutyl ether.

  A reflective layer is provided on the recording layer. The reflective layer may be provided by any conventionally known method such as sputtering using a metal such as Ag, Au, or Al. Further, a protective film and further a scratch-resistant layer may be provided on the reflective layer. In the case of CD-R, it is formed of a single plate, but in the case of DVD-R, a transparent substrate may be further bonded onto the protective layer described above via an adhesive layer or the like.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist. Moreover, the following were used for the raw material and the static elimination apparatus.

1. Transesterification method polycarbonate resin Mitsubishi Engineering Plastics Novalex M7020AD2, Mv: 16000

2. Static eliminator and static eliminator such as cooling conditions (a): “SJ-R060” (pulse AC method) manufactured by Keyence Co., Ltd. A static eliminator (electrode needles that periodically generate both positive and negative ions are arranged in the longitudinal direction) thing). Each condition is as follows: output voltage: 7.0 kv, pulse wavelength: 10 Hz (rectangular wave), air flow rate: 40 m ³ / min, air pressure: 0.2 MPa, resin molded body (disc-shaped resin molded body end) and static elimination The distance from the bar was 0.3 m, and the charge removal time was 60 seconds.

Static elimination device (b): “Model 442” manufactured by Hugle Electronics, double DC type static elimination bar (in the longitudinal direction, electrode needles that generate only positive ions and electrode needles that generate only negative on are alternately arranged. thing). Each condition was as follows: output voltage: ± 6.0 kv, air flow rate: 40 m ³ / min, distance between resin molded body (disc-shaped resin molded body end) and static elimination bar: 0.3 m, static elimination time: 60 seconds .

3. When using the static elimination device (a) (pulse AC method) such as cooling conditions , the resin molded body for the optical recording medium substrate is static neutralized in a state where it is allowed to stand almost vertically in the cooling stage (clean booth). The bar was moved horizontally in the longitudinal direction. The ion generator was installed horizontally in the clean booth directly above the moving path of the resin molded body along the moving direction. The cooling air was supplied to the static elimination bar through a flexible tube, and was blown down together with positive and negative ions from the static elimination bar and brought into contact with the horizontally moving resin molded body for the optical recording medium substrate.

  When using the static eliminator (b) (double DC method), the resin molded product for the optical recording medium substrate is moved horizontally in the longitudinal direction of the static eliminator in a clean booth while being left standing almost vertically. I let you. The ion generator is installed in the clean booth directly above the movement path of the resin molding, and the longitudinal direction is horizontally installed along the movement direction, together with the down blow cooling air supplied from the upper part of the clean booth. Positive and negative ions generated from the bar were brought into contact with the surface of the resin molding.

(Example 1, Comparative Examples 1 and 2)
Using an injection molding machine (manufactured by Sumitomo Heavy Industries, model: SD40) equipped with a polycarbonate resin and a mold (stamper) for producing an optical recording medium having a groove depth of 150 nm and a pitch of 0.74 μm, the cylinder temperature is 380 ° C. A transparent, disk-shaped resin molded body for an optical recording medium substrate having a thickness of 0.6 mm and a diameter of 120 mm was obtained under conditions of a mold temperature of 128 ° C. and a molding cycle of 6.0 sec.

  Next, this resin molded body was taken out from the mold, and cooled and coated with a dye in a room with a cleanness class of 10,000. First, in the clean booth installed in this room with the static eliminator installed in the upper part (the clean degree in the clean booth is class 100), cooling is performed with or without static elimination, and the groove is removed. An optical recording medium substrate having was produced.

  Next, while rotating the obtained optical recording medium substrate at 200 rpm, an octafluoropen of an azo dye (Mitsubishi Chemical Media Co., Ltd .: PDS-1861) was formed on the inner periphery 3 mm inward from the innermost periphery of the groove. A 5% solution of tanol was dripped from the nozzle. After dropping the solution, the number of rotations of the substrate was increased to 5000 rpm, and the coating solution supplied on the substrate was cast radially on the outer peripheral side of the disk-shaped substrate to form a coating solution layer filled with the groove. Next, the optical recording medium substrate provided with this coating liquid layer was put into a drying oven maintained at 95 ° C. and allowed to stand for 15 minutes to remove the residual solvent, thereby forming a dye recording layer.

  The following items were evaluated for the optical recording medium substrate provided with the dye layer obtained by the above method. The results are shown in Table 1.

(1) Presence / absence of bright defect: The dye recording layer formed on the substrate after the dye application was visually observed, and a portion where the dye was partially thinned was regarded as a bright defect, and the presence / absence thereof was examined.

(2) Roundness of inner periphery of coated part: The inner peripheral part of the dye recording layer formed on the substrate after the dye application was visually observed to check for the presence of partial disturbance of the perfect circle shape.

  From Table 1, it can be seen that the optical recording medium substrate of the present invention is suitable as an optical recording medium substrate because there are no bright defects or perfect circle disturbance when the dye is applied. However, even with the same transesterification polycarbonate resin optical recording medium substrate, when the resin molded body for the substrate is neutralized with a DC-type static eliminator (Comparative Example 1), there is an appearance defect due to perfect circle disorder, so recording It turns out that it is not suitable as a medium substrate.

In addition, it can be seen that in the case where static elimination is not performed (Comparative Example 2), bright defects exist in addition to the perfect circle disturbance, which affects the signal characteristics and is not suitable as an optical recording medium substrate.

Claims (5)

  A resin molded body for an optical recording medium substrate obtained by molding an aromatic polycarbonate resin having a viscosity average molecular weight of 25000 or less, obtained by an ester exchange method from an aromatic dihydroxy compound and a carbonic acid diester, is used to periodically add positive ions and negative ions. A method for producing an optical recording medium substrate, comprising contacting positive ions and negative ions generated from an ion generator having electrode needle portions that are alternately generated.   2. The method of manufacturing an optical recording medium substrate according to claim 1, wherein positive ions and negative ions generated from an ion generator are brought into contact under a condition of a clean degree of 10,000 or less.   The ion generator has an electrode needle and a power source applied to the electrode needle, and positive ions and negative ions are periodically and alternately generated from one electrode needle. 3. A method for producing an optical recording medium substrate according to 1 or 2.   An optical recording medium manufacturing method comprising providing an information recording layer on an optical recording medium substrate obtained by the manufacturing method according to claim 1. 5. The method of manufacturing an optical recording medium according to claim 4, wherein the optical recording medium is a write-once type optical recording medium.