JP2802661B2 - Manufacturing method of optical recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to the manufacture of an optical recording medium for writing and reading information using light, mainly a semiconductor laser, and in particular, an optical recording medium having a recording layer made of an organic material. About the method.

[Prior Art] Conventionally, as an optical recording medium, various structures having a recording layer formed on a transparent substrate having a guide groove for tracking and having a reflective layer, a protective layer, an undercoat layer, and the like have been proposed. And
There are also many different manufacturing methods.

In particular, as a material for forming the recording layer, for example, Pb, B
Many inorganic metals such as i, Se, and Te and alloys thereof, and organic dyes having an absorption peak near a recording light wavelength have been proposed, and some of them have been put to practical use. As a method for forming a recording layer from these materials, an inorganic thin film is formed by vacuum deposition, sputtering, or the like.

However, in the method of forming a recording layer, there is a problem that a vacuum apparatus is required for vapor deposition and sputtering, which increases the apparatus cost.

On the other hand, an organic dye having good solubility in a solvent can be dissolved or dispersed in the solvent and wet-coated by a dipping method, a doctor blade method, a spinner method or the like, so that a low-cost optical recording medium can be obtained. As the solvent used at this time, conventionally, for example, methanol, ethanol,
Alcohols such as isopropanol and diacetone alcohol; ketones such as acetone, methyl ethyl ketone and cyclohexanone; and amides, ethers, esters, aliphatic halogenated hydrocarbons, aromatics and aliphatic hydrocarbons. Solvents can be mentioned, and are appropriately selected and used depending on the dye used from these.

By the way, it is preferable that the solvent used for coating the recording layer is a solvent having a low boiling point, quick drying, not eroding the substrate, and having good solubility in the dye.

That is, when a high-boiling point solvent, for example, dimethylformamide or toluene, is used as a solvent for coating, it takes time to dry when forming a recording layer by drying after coating, or drying unevenness occurs, There has been a problem that a lateral flow of a coating liquid (hereinafter, referred to as ink) occurs and the thickness of the recording layer is difficult to be constant. In addition, since the ink remains on the substrate for a long time, there is a problem that solvent cracks are easily generated depending on the type of the plastic substrate.

However, few of the currently used coating solvents satisfy all of the above conditions, the dyes used in the recording layer are limited to those having good solubility in those solvents, and the selection range of the dyes is narrow. Was.

On the other hand, phthalocyanine-based dyes, naphthalocyanine-based dyes, naphthoquinone-based dyes, anthraquinone-based dyes, etc., which are suitable for the recording layer material of the optical recording medium in which the coating film exhibits a high reflectance, are generally soluble only in a high-boiling solvent having good solubility. Until now, deposition or the like has been used for film formation, and it has been difficult to form a recording layer by directly applying it on a resin substrate.

[Problems to be Solved by the Invention] The present invention has been made in view of the above problems, and after applying an organic dye using an ink in which a high boiling solvent is dissolved, solvent replacement with a low boiling solvent is performed. As a result, the solvent selection range is widened, and at the same time, organic dyes that could not be used for the coating method due to poor solubility and had to use vacuum deposition or sputtering using a vacuum process were wet-coated. It is an object of the present invention to provide a method for manufacturing an optical recording medium capable of forming a film by using the method described above.

Another object of the present invention is to dry the solvent contained in the ink in a short time, to prevent the occurrence of cracks in the plastic substrate, and to form a recording layer with less thickness unevenness, It is an object of the present invention to provide a method for manufacturing a highly reliable optical recording medium free from uneven reflectance.

[Means for Solving the Problems] That is, the present invention relates to a method for producing an optical recording medium having a recording layer formed using an organic dye, wherein the organic dye is dissolved in a high-boiling solvent and applied to a substrate. A method for producing an optical recording medium, wherein the high-boiling solvent is replaced with a low-boiling solvent, followed by drying and film formation.

 Hereinafter, the present invention will be described in detail.

FIG. 1 is an explanatory view showing a typical example of a method for manufacturing an optical recording medium according to the present invention. In FIG. 1, in the method for manufacturing an optical recording medium of the present invention, a sheet-like substrate 1 is passed through a roll 7,
After applying the high-boiling solvent ink 6 in which the organic dye is dissolved in the high-boiling solvent, the sheet-like substrate 1 is immersed in the low-boiling solvent 2 by the cylindrical roller 5. By this immersion, the high-boiling solvent ink 3 applied to the sheet-like substrate 1 is solvent-substituted and replaced with the ink 4 substituted with the low-boiling solvent, and becomes more drier. A solvent with a very low boiling point results in a dry state that can be eaten by fingers. Thereafter, the film can be formed by natural drying.

Alternatively, the organic dye may be dissolved in a high-boiling solvent and applied to a sheet-like substrate, and then dried so as to be edible by fingers, and then the high-boiling solvent may be replaced with a low-boiling solvent.

In the present invention, a solvent having a boiling point of 100 ° C. or higher is preferable as the high boiling point solvent used for the first coating. Examples of the high boiling point solvent include aprotic solvents such as dimethylformamide and dimethylsulfoxide, toluene,
Examples thereof include aromatic solvents such as xylene, chlorobenzene, and nitrobenzene, and ketone solvents such as cyclohexanone.

On the other hand, as a low boiling point solvent used for solvent replacement, the boiling point is
Those having a temperature of less than 80 ° C are preferred. Examples thereof include alcohol solvents such as methanol, ether solvents such as methyl ethyl ether, diethyl ether and isopropyl ether, aliphatic solvents such as n-hexane and n-pentane, and furan solvents such as tetrahydrofuran. .

As the high boiling point solvent, a solvent having good solubility in an organic dye is preferably selected and used as appropriate. In addition, since the solvent is easily dried by solvent replacement with a low-boiling solvent, any high-boiling solvent can be used as long as it has high solubility in organic dyes. It becomes possible to spread.

Further, as the low boiling point solvent used for the solvent replacement, it is preferable to appropriately select and use a solvent having low solubility in the organic dye, and a solvent which has good compatibility with the above-mentioned high boiling point solvent and can be easily replaced is preferable.

The organic dye that forms the organic dye film of the recording layer is a dye generally known as a near-infrared absorbing dye, and particularly easily soluble in a high-boiling solvent, and in a low-boiling solvent. Those exhibiting poor solubility are preferably used. For example, there are cyanine dyes, merocyanine dyes, croconium dyes, squarium dyes, azurenium dyes, polymethine dyes, pyrylium dyes, phthalocyanine dyes, naphthalocyanine dyes, naphthoquinone dyes, and anthraquinone dyes. These dyes can be used alone or in combination.

In particular, in the present invention, organic dyes which have heretofore been difficult to be formed into a film by a coating method as a dye which is hardly soluble in a solvent, such as phthalocyanine dyes, naphthalocyanine dyes, naphthoquino dyes, anthraquinone dyes Can be easily formed into a film by a coating method to form a recording layer.

To these dyes, a stabilizer having a quenching ability of singlet oxygen such as a triphenylmethane compound, a metal complex, an aminium / diimonium salt compound may be added, or a conjugate of the dye and the stabilizer may be used. It is also possible to use as. The amount of addition is 1 to 60% by weight, preferably 5 to 40% by weight, more preferably 10 to 30% by weight, based on the total solid content.

In addition to these compounds, a binder may be contained in the recording layer composed of the organic dye thin film. Examples of the binder include cellulose esters such as nitrocellulose, cellulose phosphate, cellulose sulfate, cellulose acetate, cellulose propionate, cellulose butyrate, cellulose myristate, cellulose palmitate, cellulose acetate / propionate, cellulose acetate / butyrate, and methylcellulose. , Ethyl cellulose, propyl cellulose, cellulose resins such as butyl cellulose, polystyrene, polyvinyl chloride, polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinyl alcohol, polyvinyl resins such as polyvinyl pyrrolidone,
Copolymer resins such as styrene-butadiene copolymer, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate,
Acrylic resins such as polymethyl acrylate, polybutyl acrylate, polyacrylic acid, polymethacrylic acid, polyacrylamide, polyacrylonitrile, polyesters such as polyethylene terephthalate, poly (4,4'-isopropylidene diphenylene-co-1, 4-cyclohexylenedimethyllencarbonate), poly (ethylenedioxy-3,3'-phenylenethiocarbonate), poly (4,4'-isopropylidenediphenylenecarbonate-co-terephthalate), poly (4,4'- Isopropylidene diphenylene carbonate), poly (4,
Polyarylate resins such as 4'-sec-butylidene diphenylene carbonate), poly (4,4'-isopropylidene diphenylene carbonate-block-oxyethylene), or polyamides, polyimides, epoxy resins, phenolic resins And polyolefins such as polyethylene, polypropylene, and chlorinated polyethylene.

Further, the recording layer may contain a surfactant, an antistatic agent, a stabilizer other than a quencher, a dispersible flame retardant, a lubricant, a plasticizer, and the like.

Further, an undercoat layer may be provided between the recording layer and the substrate, and a protective layer may be provided on the recording layer.

The undercoat layer is used to provide solvent resistance, improve reflectivity, or improve repetitive reproduction. The protective layer is used to protect against scratches, dust, dirt, etc., and to provide environmental stability to the recording layer. Can be The materials used for these are mainly inorganic compounds, metals or organic high molecular compounds. As the inorganic compound, for example, SiO ₂ , MgF ₂ , Si
Examples of metals such as O, TiO ₂ , ZnO, TiN, and SiN include Zn, Cu,
Ni, Al, Cr, Ge, Se, Cd, etc. are used as organic polymer compounds such as ionomer resins, polyamide resins, vinyl resins,
Natural polymers, epoxy resins, silane coupling agents and the like can be used.

As the substrate, plastic such as polyester, polycarbonate, acrylic resin, polyolefin resin, phenol resin, epoxy resin, polyamide, and polyimide, glass, and metals can be used.

The coating can be performed by a coating method such as a dip coating method, a spray coating method, a spinner coating method, a bead coating method, a wire bar coating method, a blade coating method, a roller coating method, and a curtain coating method.

The film thickness (wet) of a high-boiling solvent ink obtained by dissolving an organic dye to be applied on the substrate 1 in a high-boiling solvent is usually from 1000 to 1000 μm.
5000 μm, preferably 4000 ° to 40 μm is suitable.

The thickness of the recording layer formed by replacing such a high-boiling solvent with a low-boiling solvent is 50 to 100 μm, preferably 200 to 1 μm.

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples.

Example 1 An optical recording medium was manufactured by the method shown in FIG. An ink was prepared by dissolving 30 parts by weight of a cyanine dye (trade name: NK-2014, manufactured by Nippon Kogaku Dyeing Co., Ltd.) in 1000 parts by weight of dimethyl sulfoxide (DMSO). Ink was applied by roller coating to a wet film thickness of about 1 μm on a sheet-like substrate in which spiral irregularities were formed by a photopolymer method on a 1.2 mm thick polymethyl methacrylate (PMMA) long sheet. .

At this time, the feeding speed of the sheet-like substrate is 2 m / min.
After the coated surface was dried so as to be capable of finger rubbing, the coated sheet-like substrate was passed through an ether bath to perform solvent replacement. Thereafter, the sheet-like substrate was naturally dried while being conveyed to form a recording layer. .

Examining the formed recording layer, it was found that 600Å ± 50Å
Was obtained. Also, no cracks or the like occurred on the substrate. Table 1 shows the results of measuring the reflectance at this time.

After bonding the backing material of another PMMA substrate to the sheet-like substrate thus obtained with a UV-curable resin adhesive via a spacer, an optical disk was obtained by punching out with a male / female type press.

This was rotated to 1800 rpm, using a semiconductor laser with a wavelength of 830 nm, recording power 8 mW from the substrate side, recording frequency 3 MHz
Was written. Next, when reproduction was performed with a read power of 0.8 mW and the C / N ratio was measured by spectral analysis, it was 50 dB.
Was obtained.

Comparative Example 1 An optical recording medium was prepared in the same manner as in Example 1, except that DMSO was used as a high-boiling-point solvent coating solution and a low-boiling-point solvent for solvent replacement was not used. The ink was not dried only by natural drying, and could not be completely dried even by forcibly blowing air.

Further, since the DMSO solvent was present on the sheet-like substrate for a long time, it became cloudy and could not be used as an optical recording medium.

Example 2 An optical recording medium was manufactured by the method shown in FIG. An ink was prepared by dissolving 2 parts by weight of a naphthalocyanine dye represented by the following general formula (I) in 1000 parts by weight of m-xylene. A polycarbonate (PC) long sheet having a 0.4 mm thick guide groove was prepared. The ink was applied to the substrate to a thickness of about 3 μm by a roller coating method.

At this time, the feeding speed of the sheet-like substrate is 1.6 m / min. Next, the coated sheet substrate was passed through an n-pentane bath to perform solvent replacement, and then the sheet substrate was naturally dried while being transported to form a recording layer.

The formed recording layer had a uniform thickness of 1200 ° ± 60 °.

An optical card was prepared by laminating a PC board having a thickness of 0.3 mm to the sheet-like substrate obtained in this way via an ethylene-vinyl acetate film by a hot roll method and cutting it into a wallet size with a laser. .

This optical card was mounted on a stage driven in the X and Y directions, and a semiconductor laser having an oscillation wavelength of 830 nm was used.
Recording pulse 80μsec at recording power 4.0mW from PC board side
To write information in the Y-axis direction and reproduce it with a read power of 0.4 mW, and its contrast ratio B → signal intensity of the recording section) was measured, and a value of 0.58 was obtained.

Comparative Example 2 An optical recording medium was prepared in the same manner as in Example 2, except that m-xylene was used as the high-boiling-point solvent coating liquid and a low-boiling-point solvent for solvent replacement was not used. During the natural drying of the ink, microcracks were formed on the substrate, and the substrate became cloudy, and could not be used as an optical recording medium.

Comparative Example 3 An ink was prepared by dispersing 2 parts by weight of the dye used in Example 2 in 1000 parts by weight of ether. When this was applied to a polycarbonate long sheet-like substrate and dried in the same manner as in Example 2, a uniform recording layer could not be formed.

[Effects of the Invention] As described above, according to the present invention, after applying using an ink in which an organic dye is dissolved in a high-boiling solvent, the solvent is replaced with a low-boiling solvent and dried to select a solvent. At the same time as the range was widened, it became possible to obtain an optical recording medium having a recording layer in which a dye that could not be used in a coating method because of poor solubility was formed in an amorphous coating film.

In addition, the solvent contained in the ink can be dried in a short time, the occurrence of cracks in the plastic substrate can be prevented, the recording layer with less unevenness in film thickness can be formed, and there is no unevenness in reflectance and high reliability. It has become possible to obtain an optical recording medium.

Further, in the continuous manufacturing process of the optical recording medium, it is possible to reduce a space for drying the coating film, a facility for blowing air, and the like.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a typical example of a method for manufacturing an optical recording medium according to the present invention. DESCRIPTION OF SYMBOLS 1 ... Sheet-like board | substrate 2 ... Low-boiling-point solvent 3 ... High-boiling-point solvent ink 4 ... Ink replaced by low-boiling-point solvent 5 ... Cylindrical roll 6 ... High-boiling-point solvent ink 7 ... Roll

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Masataka Yashima 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (56) References JP-A-64-49683 (JP, A) JP-A-64 -34791 (JP, A) JP-A-63-281240 (JP, A) JP-A-2-1374 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/26 G11B 7/24-7/26

Claims (3)

(57) [Claims] In a method of manufacturing an optical recording medium having a recording layer formed using an organic dye, an organic dye is dissolved in a high-boiling solvent and applied to a substrate, and then the high-boiling solvent is replaced with a low-boiling solvent. And then drying and forming a film. 2. The method for producing an optical recording medium according to claim 1, wherein the high-boiling solvent has high solubility in organic dyes and the low-boiling solvent has low solubility in organic dyes. 3. A film is formed by dissolving an organic dye in a high-boiling solvent and applying it to a substrate, followed by drying to enable finger rubbing, and then replacing the high-boiling solvent with a low-boiling solvent and drying. The method for manufacturing an optical recording medium according to claim 1.