JPH0729497B2 - Optical information recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical memory medium in which writing, reproduction and recording are performed by a laser, particularly a semiconductor laser.

[Prior art and problems]

In general, an optical disc can store high density information by forming a small (for example, about 1 μm) optically detectable pit formed in a thin film recording layer provided on a substrate into a spiral or circular track form. To write information on such a disc, a laser focused on the surface of the laser sensitive layer is scanned to form pits only on the surface irradiated with this laser beam, and the pits are formed into spiral or circular tracks. Form in the form. This sensitive layer can absorb laser energy to form optically detectable pits. For example, in the heat mode recording method, the recording layer absorbs laser energy and the irradiated portion is locally heated to cause a physical change such as melting, evaporation, or aggregation, and an optical difference (for example, reflectance, Absorption chamber, etc.) and read. As such optical recording media, inorganic substances such as metal thin films such as aluminum vapor deposition films, bismuth thin films, tellurium thin films and chalcogenide amorphous glass films have been proposed so far.

These have the advantage that a semiconductor laser can be used because a thin film can be obtained by a vapor deposition method, a sputtering method, etc. and they also have light absorption in the near infrared region, but on the other hand, they have a large reflectance and a large thermal conductivity and a large specific heat. There are drawbacks such as. In particular, the fact that the reflectance is large means that the energy of the laser light cannot be effectively utilized, so that the light energy required for recording becomes large and a high-power laser light source is required. As a result, there is a drawback that the recording apparatus becomes large and expensive.
Further, a thin film of tellurium, bismuth, selenium, etc. has a drawback that it has toxicity. Therefore, in recent years, it has been possible to select absorptivity, the absorptance is large, the thermal conductivity is small, the productivity is low, and the toxicity is low. Suggestions are coming. Representative dyes include cyanine dyes (JP-A-58-112790), anthraquinone dyes (JP-A-58-112790).
58-224448), naphthoquinone dyes (JP-A-58-22479)
3) and phthalocyanine dyes (JP-A-60-48396), etc., and a compound consisting of them alone or in combination with an auto-oxidizing resin is applied on a substrate by spinner coating, dipping method, plasma method or vacuum deposition method. The optical recording medium is formed on. This dye thin film system has the above-mentioned advantages, and in particular, the cyanine dye is structurally capable of having an absorption wavelength in the near infrared, and has many advantages such as low solubility in a solvent and low melting point. Consideration is being made.
On the other hand, there are problems such as long-term storage stability and reproduction stability (stability against readout light) due to photodegradation, heat instability, humidity deterioration, etc. An improvement plan has been issued. In particular,
Providing a protective film on the recording layer (JP-A-55-22961,57-
66541), mixing an anti-fading substance with oxygen (JP-A-59-55795), and adding a metal complex having light absorption in the long wavelength region (JP-A-59-215892). However, even these proposals have not sufficiently solved the problem, and the film-forming property and reflectance by the additive,
There is a problem that the absorption rate is lowered.

From these points, a coating type recording medium using a cyanine dye represented by the following general formula has attracted attention in terms of recording density and reflectivity.

(However, C in the formula is O, S, Se, C, X is a halogen anion, BF ₄
^-, ClO ₄ ^-, R has an essential problem that alkyl shown), however, also film forming properties for the cyanine dye represented by the above general formula, it lacks thermal light stability. Membrane chain number (n)
It is known that the solubility of the solvent decreases due to an increase in the amount of the solvent, and that the solubility changes depending on the types of heterocycles and the substituents at both ends. Regarding thermophotostability, it is known that the more the number of methine chains increases, the more unstable it is to heat and light, and the more likely it is to undergo oxidative deterioration, and that the stability to heat and light differs depending on the type of heterocycle. Has been.

The present invention has been made in view of the above circumstances, has a high reflectance and a high recording sensitivity, it is possible to write and reproduce an optical signal stably, and light and sunlight at the time of reproduction,
It is intended to provide a pollution-free optical information recording medium having high stability against humidity.

[Means and Actions for Solving Problems]

The present invention is an optical information recording medium comprising a recording layer containing at least one organic dye represented by the following general formula.

However, in the formula, R ₁ is an alkyl group having 1 to 6 carbon atoms, an aralkyl group or a phenyl group, and A is [R ₂ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms], X is an anion selected from perchlorate, fluoroborate, iodide, chloride, bromide, p-toluenesulfonate, and Y is -R ₄ OH, -R ₄ COH, -R ₄ COOH, (R ₄ ; alkylene group having 1 to 20 carbon atoms, R ₅ ; alkyl group having 1 to 18 carbon atoms or phenyl group), Z represents a benzene ring added to a benzene ring forming indole.

The organic dye used in the present invention has a methine chain By introducing a cyclo ring or the like represented by
Disclosed in 59-85791 It is possible to form a recording layer having improved heat resistance and light resistance, and more excellent storage resistance and reproduction deterioration characteristics, as compared with cyanine dyes composed only of methine chains. R ₂ introduced into the cyclo ring or the like is as described above, but particularly when a halogen atom is used, or when Cl, Br or an alkyl group is used, one having 1 to 3 carbon atoms is preferable.

The organic dye used in the present invention is disclosed in JP-A-59-150795 and JP-A-58-194595, for example, by adding a benzene ring as Z to the benzene ring constituting indole. As compared with organic dyes in which the benzene ring that constitutes indole is unsubstituted or substituted with an alkyl group, the hydrophobicity is enhanced, and moisture resistance, which is one of the elements of environmental resistance, can be improved, and photobleaching resistance is also improved. Is improved, so that reproduction deterioration, which is one of the medium characteristics, is improved.

Furthermore, the organic dye used in the present invention has a structure in which the substituent Y described above is introduced into indole. Is introduced, the moisture resistance and heat resistance are relatively improved.
-R ₄ OH, -R ₄ COH, solvent solubility when introducing -R ₄ COOH, improvement in film-forming properties are made as. Therefore, the substituent Y may be appropriately selected depending on the structure and purpose of the recording medium.

Specifically exemplifying the dye represented by the above general formula,
Examples include those represented by the following structural formulas (1) to (13).

The recording layer containing the dye represented by the above general formula is prepared by dissolving the dye in a solvent such as ethyl acetate, toluene, acetone, methyl ethyl ketone, methyl isobutyl ketone, methylene chloride, chloroform, dichloroethane, tetrahydrofuran, alcohol, etc. Law,
It can be obtained by forming a thin film on a substrate by a doctor blade method, a roll coater method or the like. The thinner the recording layer, the higher the recording sensitivity, but since the reflectance depends on the film thickness, it is 10 nm to 1000 nm, preferably 30 nm to 500 nm.
Is appropriate. As the substrate, plastic plates and films such as polyester, acrylic resin, polycarbonate resin, polyolefin resin, phenol resin, epoxy resin, polyamide resin, and polyimide resin, or glass and metals can be used.

The recording layer is formed by the method described above. Furthermore, by adding a binder resin to the dye in an amount of 1 to 40% by weight, preferably 3 to 20% by weight, a film can be formed, and film forming properties, heat resistance, and moisture resistance can be improved. Examples of the binder resin used here include acrylic resins, ester resins, nitrocellulose, ethylene, propylene, carbonate, ethylene terephthalate, urethane resins, epoxy resins, butyral, vinyl chloride, vinyl acetate, and styrene resins. It is also possible to form a composite of these copolymers.

Further, it is possible to improve the film-forming property and heat resistance, humidity resistance, and light resistance by mixing other dyes instead of the binder resin or by forming a multilayer structure in which dye layers are stacked, and consequently high density. Thus, it is possible to obtain an optical information recording medium having high sensitivity and excellent durability without deterioration of reproduction. In this case, other dyes may be laminated to improve heat resistance, humidity resistance and light resistance. As the dye used here,
For example, cyanine dye, merocyanine dye, anthraquinone dye, triphenylmethane dye, xanthene dye,
Examples thereof include phthalocyanine dyes.

Furthermore, for example, an amine compound represented by the following general formulas (A) and (B) or a dithiolate metal complex represented by the following general formula (C) is added, and the optical characteristics of the recording layer are deteriorated by light, oxygen and water. It is also possible to prevent

However, in the formula, R ₁ , R ₂ , R ₄ , and R ₅ are alkyl groups having 1 to 6 carbon atoms, and R ₃ is And R represents an alkyl group having 1 to 6 carbon atoms.

However, in the formula, R is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, X is an anion such as perchlorate ion, fluoroborate ion, or hexafluoroate ion, and m is 0 or an integer of 1 or 2. ,
A is the above m = 0,1, (N = 1 or 2), when m = 2 Indicates. Examples of such amine compounds include commercially available IRG-002 and IRG-003 (both manufactured by Nippon Kayaku Co., Ltd.).
Product name) etc.

However, R _{1 to} R ₄ in the formula are alkyl groups or phenyl groups, X, Y
Represents hydrogen, an alkyl group, a halogen group, and M represents a metal such as Ni, Co, Fe and Cr. Examples of such metal complexes include PA1001 to 1006 (all are trade names manufactured by Mitsui Toatsu Fine Co., Ltd.), Ni-bis (o-xylene-4,5diol) tetra (t-butyl) ammonium salt, and the like.

Incidentally, in addition to the recording layer containing the dye of the above general formula, an intermediate layer and a protective layer can be provided if necessary. The intermediate layer is provided for the purpose of improving adhesiveness and protection from oxygen and moisture, and is mainly formed of a resin or an inorganic compound. As the resin, for example, vinyl chloride, vinyl acetate, acryl, ester, nitrocellulose, carbonate, epoxy, ethylene, propylene, butyral homopolymers or copolymers can be used, and if necessary, an antioxidant,
It is possible to contain an ultraviolet light absorber, a leveling agent, a water repellent, and the like. These are formed by a spinner method, a dipping method, or a doctor blade method. As the inorganic compound, for example, SiO ₂ , SiO, Al ₂ O ₃ , SnO ₂ , MgF ₂ or the like is used, and a thin film is formed by an ion beam, an electron beam or a sputtering method. The protective layer also has the same structure as the intermediate layer and is used for protection of the recording layer from light, oxygen and moisture, and protection from scratches, dust and the like.

Next, a configuration example of the optical information recording medium of the present invention will be described with reference to the drawings.

FIG. 1 shows the basic structure of an optical information recording medium, which has a structure in which a recording layer 2 containing a dye of the general formula is provided on a substrate 1. Recording and reproduction are performed by condensing the laser beam 3 on the recording layer 2 into a spot having a size of 0.8 to 1.5 μm by a condenser lens. The recording / reproducing laser beam 3 may be irradiated from the recording layer 2, but when the substrate 1 is made of a transparent material, irradiation from the substrate 1 side can generally reduce the influence of dirt and dust.

FIG. 2 shows a structure in which an intermediate layer 4 is provided between the substrate 1 and the recording layer 2 and a protective layer 5 is provided on the recording layer 2.

In FIG. 3, two media having the same structure are arranged with a spacer 6 so that the recording layers 2 face each other.
In FIG. 3, 7 is an air gap and 8 is a spindle hole. According to this configuration, the characteristics are good,
Further, there is an advantage that the influence of dirt and dust on the recording layer 2 can be suppressed.

Furthermore, in the structure shown in FIGS. 1 to 3 described above, Al, Ag
Etc. and other reflective films may be provided between the substrate and the recording layer.

Example of Invention

 Hereinafter, examples of the present invention will be described in detail.

Example 1 The dye of structural formula (1) described above was dissolved in methyl ethyl ketone to form a 2% solution, which was then applied onto a 1.2 mm-thick glass substrate with a spinner coater and dried to form a recording layer with a thickness of 75 nm. To form a recording medium.

Example 2 The dye of structural formula (3) described above was dissolved in methylene chloride,
After making 2% solution, spinner coater 1.2m thick
A recording medium was manufactured by forming a recording layer having a thickness of 75 nm on a m glass substrate by coating and drying.

Example 3 The dye of structural formula (5) described above was dissolved in methyl ethyl ketone to form a 2% solution, which was then coated on a 1.2 mm-thick glass substrate with a spinner coater and dried to form a 70 nm-thick recording layer. To form a recording medium.

Example 4 The dye of structural formula (12) above was dissolved in methylene chloride,
After making 2% solution, spinner coater 1.2m thick
A recording medium having a thickness of 75 nm was formed by coating on a m glass substrate and drying to form a recording medium.

Example 5 An acrylic resin (manufactured by Mitsubishi Rayon Co., Ltd .: Dianal BR-6) as a binder resin was added to the dye of the structural formula (7) described above.
0) was added at 10% by weight and dissolved in methyl ethyl ketone to form a 3% solution, which was then applied onto a 1.2 mm thick glass substrate with a spinner coater and dried to a thickness of 85 nm.
A recording layer was formed to produce a recording medium.

Example 6 The above-described dye of structural formula (1) and an infrared absorber (trade name: IRG-003 manufactured by Nippon Kayaku Co., Ltd.) were mixed at a weight ratio of 3: 1 and dissolved in methylene chloride. To make a 2% solution,
This solution was applied onto a glass substrate having a thickness of 1.2 mm with a spinner coater and dried to form a recording layer having a thickness of 70 nm to manufacture a recording medium.

Example 7 The dye of the structural formula (3) described above and the dye of the following structural formula (14) were mixed in a weight ratio of 2: 1, dissolved in the same manner as in Example 1, and applied on a substrate. Then, it was dried to form a recording layer having a thickness of 70 nm, and a recording medium was manufactured.

Example 8 After a recording layer having a thickness of 60 nm made of the dye of structural formula (1) was formed on a glass substrate by the same method as in Example 1,
Aluminum naphthalocyanine represented by the following structural formula (15) is vacuum-heat-deposited on the recording layer under the condition of a vacuum degree of 1.0 × 10 ^-5 Torr to form a reflective protective layer with a thickness of 30 nm, and a recording medium is manufactured. did.

Comparative Example 1 A dye of the following structural formula (I) was dissolved in methylene chloride to obtain 2%.
After making a solution, this solution is 1.2m thick with a spinner coater.
A recording medium was manufactured by applying the composition on a glass substrate of m and drying it to form a recording layer having a thickness of 80 nm.

Comparative Example 2 A dye having the following structural formula (II) was dissolved in the same manner as in Comparative Example 1, coated on a glass substrate and dried to form a recording layer having a thickness of 70 nm, to manufacture a recording medium.

Comparative Example 3 A dye having the following structural formula (III) was dissolved in the same manner as in Comparative Example 1, coated on a glass substrate and dried to form a recording layer having a thickness of 70 nm, to manufacture a recording medium.

Comparative Example 4 A dye having the following structural formula (IV) was dissolved in the same manner as in Comparative Example 1, coated on a glass substrate and dried to form a recording layer having a thickness of 70 nm, and a recording medium was manufactured.

Then, with respect to the recording layers of the recording media of Examples 1 to 8 and Comparative Examples 1 to 4, semiconductor laser light having a wavelength of 830 nm was focused on a spot having a diameter of 1.2 μm so as to have a medium surface output of 7 mW. Optical laser light is written from the substrate side of each recording medium at a moving speed of 9 m / sec to write a signal of 1 MHz, and the same laser light is used to reproduce at a reproduction output of 0.4 mW to achieve recording sensitivity (recording energy threshold) and reproduction. The C / N value of the signal was measured.
Furthermore, the recording media of Examples 1 to 8 and Comparative Examples 1 to 4 were used.
The sample was left to stand in an atmosphere of ℃ at 95% for 150 hours, and a heat and humidity resistance test was performed to measure the rate of decrease in absorbance and the rate of decrease in reflectance before and after standing. Further, each recording medium was irradiated with 500 W tungsten light at 50 ° C. in an atmosphere of 25 ° C. and 60% for 100 hours, and a light resistance test was performed to measure the rate of decrease in absorbance and the rate of decrease in reflectance before and after irradiation with tungsten light. The results are shown in the table below.

[Effects of the Invention] As described in detail above, according to the present invention, it has a high reflectance and a high recording sensitivity, and writing and reproduction of optical signals can be stably performed, and reproduction light and sunlight, It is possible to provide a pollution-free optical information recording medium having high stability against humidity.

[Brief description of drawings]

1 to 3 are schematic views showing the optical information recording medium of the present invention. 1 ... Substrate, 2 ... Recording layer, 3 ... Laser light, 4 ... Intermediate layer, 5 ... Protective layer, 6 ... Spacer.

Claims (1)

[Claims] 1. An optical information recording medium comprising a recording layer containing an organic dye represented by the following general formula. However, in the formula, R ₁ is an alkyl group having 1 to 6 carbon atoms, an aralkyl group or a phenyl group, and A is [R ₂ is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms], X is an anion selected from perchlorate, fluoroborate, iodide, chloride, bromide, p-toluenesulfonate, and Y is -R ₄ OH, -R ₄ COH, -R ₄ COOH, (R ₄ ; alkylene group having 1 to 20 carbon atoms, R ₅ ; alkyl group having 1 to 18 carbon atoms or phenyl group), Z represents a benzene ring added to a benzene ring forming indole.