JPS63236689A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To enhance storage stability, by containing a cyanine dye and an acrylic resin in a recording layer. CONSTITUTION:A cyanine dyestuff is represented by formula (I) (wherein A and A' are respectively a condensed aromatic ring, R1 and R'1 are a 3 or less C alkyl group, L is a coupling group for forming carbocyanine and X<-> is an anion). An acrylic resin is represented by formula (IV) (wherein R2 is a hydrogen atom or a methyl group and R3 is a 1-4C alkyl group and this atomic group is contained as a repeating unit) and, for example, polymethyl methacrylate and a copolymer based on methyl methacrylate are designated. This recording medium is obtained by coating a support with a solution prepared by dissolving the cyanine dyestuff, the acrylic resin and, if necessary, other additives in a proper solvent.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical recording medium such as an optical disk containing a /anine dye as a light absorbing agent in a recording layer.

(Prior Art and its Problems) In recent years, various materials containing dyes that absorb in the near-infrared region have attracted attention as recording materials that use laser beams.

In particular, the development of materials for use in so-called heat mode DRAW recording media, in which information is recorded by drilling minute bits or forming minute alteration points in the recording layer using a laser beam, is being actively conducted. This material must (a) have good absorption in the near-infrared region, (b) be easy to form a thin film, and (c) have no change over time during storage of the formed thin film.

Many materials of this type have already been proposed, including cyanine-based (polymethine-based), azo-based, anthraquinone-based, indanthrene-based, triarylmethane-based, naphthoquinone-based, phthalocyanine-based, porphyrin-based, Compounds such as dithiolate complex systems, croconic methine systems, squarylium systems, and indoaniline systems are mainly studied. However, there is still no one that completely satisfies the above conditions required for a DRAW recording medium.

Now, the light source used to record and reproduce information using laser light is an -AtGaAs semiconductor laser (
Among them, semiconductor lasers are particularly small and lightweight, and can be produced at low cost. It became like this,
Since it is practically superior to the available laser light sources, there is a need for recording materials that support this oscillation wavelength.

On the other hand, it is advantageous for substrate materials used in optical recording media to be made from synthetic resins that are easy to mold, such as polymethyl methacrylate (PMMA), polycarbonate, epoxy, polyvinyl chloride, polymethylpentene, porsulfone, and polyether. Polymethyl methacrylate resin, which can be manufactured with a disk-shaped substrate having a large diameter (for example, a diameter of 300wnφ with excellent optical properties and low birefringence), has been proposed, and injection molding Polycarnate resin, which has excellent heat resistance and moisture absorption resistance, is particularly preferred as an optical disk substrate material because it can simultaneously mold and transfer so-called concentric or spiral pregrooves that serve as guide grooves for laser beams. It is.

Furthermore, methods for forming a recording layer on the substrate can be roughly divided into a dry process in which the recording material is deposited in a vacuum system and a wet process in which the recording material is attached or coated onto the substrate using a spin coater, dipping, or other means. The former requires sublimation or evaporation by heating under high vacuum, so the compound used for this process must first be thermally stable, and if a thermal decomposition point exists, , it is essential to operate at lower heating temperatures and is more cost-effective than wet processes. In other words, the latter is economically advantageous. However, in the coating method, the compound used is dissolved in a suitable solvent, coated on the surface of the substrate material according to the purpose, and after the solvent evaporates, forms a continuous thin layer with uniform optical properties. is required.

That is, in order to form a thin layer having an appropriate thickness as a recording layer, the solubility of the compound used in the solvent must preferably be 0.5% by weight or more, although it depends on the type of solvent. Furthermore, it is necessary that the solvent used does not cause changes in the surface condition of the substrate material, such as dissolution, swelling, or penetration. When the substrate material is glass, there are no such restrictions on the solvent used.
The selection of the light absorber used as the recording medium can be made relatively freely, taking into consideration the magnitude of absorption in the near-infrared region and chemical stability, etc.; This point is important when using glass with poor quality.

Furthermore, materials for optical recording media are required to be stable when a recording layer is formed thereon.

In other words, in order to be able to use the recording material for a long time and to prevent the recorded information from disappearing, it is necessary not only to form information bits by drilling holes in the layer of the recording material during recording, but also to ensure that it is chemically stable during storage. Furthermore, it is required that there be no changes over time such as crystallization, and that there should be no change in the light absorption rate, reflectance, etc. of the recording layer as a result.

As mentioned above, when creating an optical information recording medium by forming a recording layer on a Zolastra substrate by a coating method, the material used must meet at least three requirements: (1) absorbance at a wavelength of around 800 nm; (2) The solubility is high and the solvent does not adversely affect the substrate material; (3) There is no change over time in the recording layer during storage;
It is necessary to satisfy.

Among the materials being researched for use in DRAW-type recording media as exemplified above, cyanine dyes are dyes that can have large absorption at wavelengths around 800 nm, and are known to have relatively good solubility in various solvents. However, there were problems with chemical stability, crystallization in the recording layer, etc.

For example, JP-A-59-67092 attempts to solve these problems by using a cyanine dye having an alkyl group having 4 or more carbon atoms. The patent further proposes the use of a mixture of the cyanine dye having an alkyl group and a resin. However, it is not advisable to introduce an alkyl group having as many as 9 carbon atoms into a cyanine dye because it leads to a decrease in the extinction coefficient.

In view of this situation, the present inventor searched for various substances that could stabilize the cyanine dye in the recording layer, and as a result, discovered an acrylic resin and completed the present invention.

(Object of the invention) Therefore, the object of the present invention is to
The laser beam obtained from an aAs semiconductor laser can be used for recording and reproduction, and can be used to directly form films on easily available substrate materials such as glass substrates as well as various resin substrates, especially injection-molded polycarbonate substrates, using a coating method. The object of the present invention is to provide an optical recording medium that can be manufactured by using the same method and has good storage stability.

(Structure of the Invention) The present invention provides an optical information recording medium comprising a support and a recording layer formed on the support, wherein the recording layer contains a cyanine dye and an acrylic resin. It is a medium.

In the present invention, the cyanine dye has the following formula (1) (in the above formula (1), A and A' each represent a fused aromatic ring, R4 and R'1 represent an alkyl group having 3 or less carbon atoms, L represents a linking group for forming cardocyanine, and X- represents an anion) is preferably used. Specific examples of such dyes include the following formula (II) (Japan Photosensitive Pigment Research Institute YoshiM←12
5) and the following formula @) (commercially available as NK-2014) CH
3a(.

etc. can be exemplified.

On the other hand, the acrylic resin in the present invention is an atomic group represented by the following formula % (in the above formula, R2 represents a hydrogen atom or a methyl group, and R3 represents an alkyl group having 1 to 4 carbon atoms). Typical examples include polymethyl methacrylate and copolymers containing methyl methacrylate as a main component.

In the present invention, the support can have any shape such as a disk, card, tape, etc., and a disk shape is particularly desirable. The material can be plastic, metal, glass, ceramics, or any other material, but plastic is particularly desirable.

Any material other than acrylic resin such as polycarbonate resin, epoxy resin, or polymethylpentene resin can be used as the above-mentioned plastic, but it is preferable to use transparent glass used in the backside recording method (so-called Ph1lips method), and among them, polycarbonate is particularly preferred as it has excellent heat resistance and moisture absorption resistance.

Therefore, it is particularly preferable as the support in the present invention that a resin typified by polycarbonate is molded into a disk shape by injection molding. Note that the pregroove may or may not be transferred during injection molding.

In addition to the cyanine dye and the acrylic resin, additives such as stabilizers such as quenchers, lubricants, antistatic agents, surfactants, and plasticizers may be added to the recording layer of the present invention, if necessary.

The thickness of the recording layer is 100× to 5 μm, preferably 200×
It is appropriately selected within a range of 1 μm from X. Note that the recording layer of the present invention can be used in combination with another recording layer and/or a protective layer and an underlayer to form a laminated film.

The present invention can be practiced by dissolving the cyanine dye represented by formula (1) above, the acrylic resin, and other additives as necessary in a suitable solvent, and coating the resulting solution on the support. .

The above-mentioned solvents include ketones such as acetone, cellosolves such as methyl cellosolve, amides such as dimethylformamide, tD ethers such as diethyl ether, esters such as methyl acetate, halogenated hydrocarbons such as chloroform, and benzene. Aromatics such as the following can be used alone or in combination. Application or attachment of the above solution can be performed by any means such as spin coating, dip coating, roller coating, etc.

The present invention will be explained below using Examples.

Examples 1-3. Comparative Examples 1 to 3 Cyanine dyes and polymethyl methacrylates represented by formulas (If) and (g) above, and polycaprolactone (Plaxel H manufactured by Daicel Chemical Industries, Ltd.) for comparison.
-7) and 212131314.4 at the concentrations shown in Table 1.
, 5.5-octafluoro, dissolved in ethyl alcohol and filtered with Teflon (pore size 0.2 microns)
The mixture was filtered to obtain six types of coating solutions.

Each of these coating solutions was coated by a spin code method onto a polycarbonate substrate onto which groups of 92.5 micron pitch were transferred by injection molding, and air-dried to obtain six types of recording media. The reflectance of these optical information recording media at 830 nm was measured from the substrate side and was as shown in Table I. On the other hand, 830 nm semiconductor laser light was focused on these media and irradiated from the substrate side. Signal recording was performed by irradiating with IE las light at a linear velocity of 4.2 rrv/sec, an irradiation surface power of 7 mW, and a recording frequency of IMHz.

A semiconductor laser with an irradiation surface iR power of 5 mW was focused on this recording section, and the reflected light signal was reproduced, as shown in Table 1.
The ratio shown in is obtained.

Further, the optical recording medium was placed in a constant temperature and humidity chamber kept at 60°C and 90° relative humidity, left for 200 hours, and the reflectance was measured in the same manner. After repeated regenerations, the values shown in Table I were obtained.

From these results, the effect of improving the durability of the cyanine-based recording material of the present invention is clear.

Claims (1)

[Claims] 1) An optical information recording medium comprising a support and a recording layer formed on the support, wherein the recording layer contains a cyanine dye and an acrylic resin. Medium. 2) The optical information recording medium according to claim 1, wherein the support is a plastic molded product. 3) The optical information recording medium according to claim 2, wherein the support is an injection molded disk of polycarbonate resin with or without pregrooves.