JP2630381B2 - Optical information recording medium - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical memory medium on which writing, reproduction, and recording are performed using a laser, particularly a semiconductor laser.

[Conventional technology and problems]

Generally, an optical disk is a small optically detectable (eg, about 1 μm) formed on a thin film recording layer provided on a substrate.
The pits can be spiral or circular tracks to store high density information. To write information on such a disc, a laser focused on the surface of the laser sensitive layer is scanned, pits are formed only on the surface irradiated with the laser beam, and the pits are formed into a spiral or circular track. Form in form. The sensitive layer can form pits that are optically detectable by absorbing laser energy. 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 and evaporation or aggregation, thereby causing an optical difference (e.g., reflectance, (Absorption rate etc.) and read. As such an optical recording medium, inorganic materials such as a metal thin film such as an aluminum vapor-deposited film, a bismuth thin film, a tellurium-based thin film, and a chalcogenide-based amorphous glass film have been proposed.

These have the advantage that a thin film can be obtained by a vapor deposition method, a sputtering method, or the like, and have a light absorption even in the near-infrared region, so that a semiconductor laser can be used. There are drawbacks such as large.
In particular, a high reflectivity means that the energy of laser light cannot be used effectively, so that the light energy required for recording increases, and a high-power laser light source is required. As a result, there is a disadvantage that the recording apparatus is large and effective.
Further, a thin film of tellurium, bismuth, selenium or the like has a drawback of being toxic. For these reasons, in recent years, it has become possible to select an absorptivity, a high absorptivity, a low thermal conductivity, and a good productivity and low toxicity. Research proposals are being made. Representative dyes include cyanine dyes (JP-A-58-112790) and anthraquinone dyes (JP-A-
58-224448), naphthoquinone dyes (JP-A-58-22479)
3) and phthalocyanine dyes (JP-A-60-48396). These compounds are used alone or in combination with a self-oxidizing resin on a substrate by a spinner coating dipping method, a plasma method or a vacuum evaporation method. The optical recording medium thus formed. This dye thin film system has the above advantages. In particular, cyanine dyes are structurally capable of having an absorption wavelength in the near infrared, and have many advantages such as low solubility in materials and low melting point. Considerations are being made. On the other hand, there are light deterioration, heat instability and humidity deterioration,
It has been conventionally said that there are problems with long-term storage stability and reproduction stability (stability to read light), and various improvements have been proposed for these problems. Specifically, a protective film is provided on the recording layer (see JP-A-55-22961, 57-66).
541), mixing of a substance for preventing discoloration due to oxygen (JP-A-59-55795), addition of a metal complex having light absorption in a long wavelength region (JP-A-59-215892), and the like have been proposed. However, even with these proposals, the problem has not been sufficiently solved.
There is a problem that the absorption rate decreases.

For these reasons, attention has been paid to a coating type recording medium using a cyanine dye represented by the following general formula from the viewpoint of recording density and reflectivity.

[Where A is O, S, Se, C, X is a halogen anion,
BF ₄ ⁻ , ClO ₄ ⁻ and R represent alkyl] However, the cyanine dye represented by the above general formula also has an essential problem of lacking film-forming properties and thermo-light stability. Regarding film forming properties, it is known that the solubility of the solvent decreases with an increase in the number of methine chains (n), and that the solubility changes depending on the types of heterocyclic rings and substituents at both ends. Regarding the thermo-light stability, it is known that as the number of methine chains increases, the heat and light become unstable and oxidative deterioration easily occurs, and that the stability to heat and light differs depending on the type of heterocycle. Have been.

The present invention has been made in view of the above circumstances, has a high reflectance and a high recording sensitivity, can stably write and reproduce an optical signal, and can perform light, sunlight, and humidity during reproduction. It is an object of the present invention to provide a pollution-free optical information recording medium which is highly stable against light.

[Means and actions for solving the problems]

The present invention has the general formula Wherein R ₁ and R ₂ are a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms or (Ph; phenyl group), R ₃ is an alkyl group having 1 to 6 carbon atoms,
Aralkyl group, phenyl group, X is perchlorate, fluoroborate, iodide, chloride, bromide, anion selected from p-toluenesulfonate, Y is an alkyl group having 1 to 18 carbon atoms, −R ₄ OH, −R ₄ COOH, −R ₄ OR ₅ , −R ₄ COR ₅ , −R ₄ COOR ₅ , (R _4; alkylene group having 1 to 20 carbon atoms, R _5; alkyl group having 1 to 18 carbon atoms), n is an integer of 1 or 2, Z is the case of _{n = 1, -R 6 OH,} -R 6 COOH, −R ₆ OR ₇ , −R ₆ COR ₇ , -R ₆ CN, -OR ₇ , -OH, -COOH, -COR ₇ , phenyl group, -CN,
_{-OCF 3, -OSF 3, -NH 2} N (R 7) 2, -NHCOR 7, (R ₆ ; an alkylene group having 1 to 20 carbon atoms, preferably 1 carbon atom
10 alkylene group, R _7; alkyl group having 1 to 18 carbon atoms,
(Preferably an alkyl group or a phenyl group having 1 to 10 carbon atoms), and in the case of n = 2, an alkyl group or a halogen atom having 1 to 10 carbon atoms]. It is assumed that.

The organic dye used in the present invention is in the methine chain. By introducing a cyclo ring represented by
A recording layer having excellent durability, light resistance, environmental resistance, and high reproduction deterioration characteristics can be formed as compared with an organic dye having the same structure disclosed in JP-A-85791 having only a methine chain. The cyclo ring
R ₁ and R ₂ are as described above, and particularly preferably chlorine, bromine or an alkyl group having 1 to 3 carbon atoms. However, by introducing a cyclo ring into the methine chain, the solvent solubility of the dye is slightly reduced, so that the solvent is limited and it is difficult to form a uniform film.

Therefore, the organic dye of the present invention is obtained by introducing a substituent such as -OH, -COOH, -COR ₇ as Z into the benzene ring constituting indole, as described above, to thereby obtain the tip of the dye, chemical stability and absorption. In addition to controlling the maximum wavelength, solvent solubility and film formability can be improved. Z is as described above,
Especially from the viewpoint of improving the light and chemical stability of the dye -CN,
-OCF _3, - (Cl) it is desirable to use an electron withdrawing group such as _2. In addition, the substitution position of Z to the benzene ring is preferably the 5-position most easily substituted, but any of the positions 4, 6, and 7 are possible. On the other hand, in order to improve solvent solubility and film formability, Z
As-(R ₇ ) ₂ , It is desirable to introduce —R ₆ COOH or the like, but it is preferable to select in consideration of the substituent (Y) introduced into indole.

The organic dye used in the present invention has a structure in which the substituent (Y) described above is introduced into indole. In particular, when thermal stability and chemical stability are improved, an alkyl group as Y is used. It is desirable to introduce R ₄ OR _5, and when considering film formability and solvent solubility, Y is -COOH, -COOR ₅ , -R ₄ COOR ₅ ,
-R ₄ OR ₅ is desirable.

As described above, the organic dye having a structure in which the above-described substituent is introduced,
JP-A-59-150795, light and chemical stability compared with unsubstituted dyes of the following structural formulas disclosed in JP-A-58-194595,
Optical information with excellent solvent solubility and film forming properties, and as a result, by forming a recording layer containing this dye, reduced noise components of the reproduced signal waveform due to poor film forming properties, improved environmental resistance, and improved reproduction deterioration characteristics A recording medium can be obtained.

Specific examples of the dye represented by the above general formula include those represented by the following structural formulas (1) to (21).

The recording layer containing the dye represented by the above general formula, the dye is dissolved in a solvent such as ethyl acetate, toluene, acetone, methyl isobutyl ketone, methylene chloride, alcohol and the like, spinner method, dipping method, doctor blade method,
It is obtained by forming a thin film on a substrate by a roll coater method or the like. As the thickness of the recording layer is smaller, the recording sensitivity is higher, but since the reflectance depends on the film thickness, the thickness is 10 nm or more.
Suitably, it is in the range of 1000 nm, preferably 30 nm to 500 nm. In addition, glass, plastic,
Although generally used materials such as metal can be used, films of acrylic resin, polycarbonate, polyolefin, polyester, and polyimide may be used.

The recording layer is formed by the method described above. Further, by adding a binder resin to the dye at 1 to 40% by weight, preferably 3 to 20% by weight, a film can be formed, and film formability, heat resistance and moisture resistance can be improved. Examples of the binder resin used here include homopolymers of acrylic, ester, nitrocellulose, ethylene, propylene, carbonate, ethylene terephthalate, epoxy, butyral, vinyl chloride, vinyl acetate, styrene and the like, and copolymers thereof. be able to.

In addition, by mixing other dyes instead of the binder resin, or by forming a multilayer structure in which dye layers are stacked, it is possible to improve film forming property and heat resistance, moisture resistance, and light resistance, and as a result, high An optical information recording medium having high density, high sensitivity, and excellent durability without reproduction deterioration can be obtained. In this case, heat resistance, moisture resistance, and light resistance can be improved by laminating another dye. Examples of the dye used here include a cyanine dye, a merocyanine dye, an anthraquinone dye, a triphenylmethane dye, a xanthene dye, and a phthalocyanine dye.

For example, an amine compound represented by the following general formula (A) or (B) or a dithiolate metal complex represented by the following general formula (C) is added to prevent deterioration of optical characteristics of the recording layer due to light, oxygen, and moisture. It is also possible.

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

Here, R in the formula is a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, X is an anion such as perchlorate ion, fluoroborate ion, hexafluoroate ion, and m is O or an integer of 1,2. , A is when m = 0,1; (N = 1 or 2), when m = 2 Is shown. As such amine compounds, for example, commercially available IRG-002 and IRG-003 (both Nippon Kayaku Co., Ltd.)
Product name).

However, in the formula, R _{1 to} R ₄ are an alkyl group or a phenyl group, X,
Y is hydrogen, an alkyl group, a halogen group, M is Ni, Co, Fe, Cr,
And the like. Such metal complexes include:
For example, PA1001 to 1006 (all are Mitsui Toatsu Fine Co., Ltd.)
Brand name), Ni-bis (o-xylene-4,5, diol)
And tetra (orbutyl) ammonium salts.

In addition to the recording layer containing the dye of the above general formula, an intermediate layer and a protective layer can be provided as necessary. The middle layer is
It is provided for the purpose of improving the adhesiveness and protecting from oxygen and moisture, and is mainly formed of a resin or an inorganic compound. As the resin, for example, vinyl chloride, vinyl acetate, acrylic, ester, nitrocellulose, carbonate, epoxy,
A homopolymer or a copolymer of ethylene, propylene, butyral, or the like can be used, and an antioxidant, an ultraviolet light absorber, a leveling agent, a water repellent, and the like can be contained as necessary. These are formed by a spinner method, a dipping method, and 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 configuration as the intermediate layer, and is used for protecting the recording layer from light, oxygen, and moisture, and protecting it 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 configuration of an optical information recording medium.
This is a structure in which a recording layer 2 containing a dye of a 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.

FIG. 3 shows two media having the same configuration arranged via 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 such a configuration, characteristics are good, and further, there is an advantage that the influence of dirt and dust on the recording layer 2 can be controlled.

Further, in the configuration shown in FIGS.
g and other reflective films may be provided between the substrate and the recording layer.

(Example of the invention)

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

Example 1 A dye having the above formula (1) was dissolved in methyl ethyl ketone to form a 2% solution, which was then applied to a 1.2 mm thick glass substrate by a spinner coater and dried to form a 75 nm thick recording layer. Was formed to produce a recording medium.

Example 2 The dye of the above structural formula (5) was dissolved in methylene chloride to form a 2% solution, which was then coated with a spinner coater to a thickness of 2%.
A recording medium was manufactured by coating and drying on a 1.2 mm glass substrate to form a recording layer having a thickness of 80 nm.

Example 3 After dissolving the above-mentioned dye of the structural formula (20) with methylene chloride to form a 2% solution, the solution was adjusted to a thickness of 1.
It was applied on a 2 mm glass substrate and dried to form a 70 nm thick recording layer to produce a recording medium.

Example 4 The above-mentioned dye of the structural formula (21) was dissolved in methylene chloride to form a 2% solution.
It was applied on a 1.2 mm glass substrate and dried to form a recording layer having a thickness of 65 nm, thereby producing a recording medium.

Example 5 An acrylic resin (manufactured by Mitsubishi Rayon Co .; Dianal BR-) was used as a binder resin in addition to the dye of the structural formula (15) described above.
60) was added in an amount of 10% by weight, and the resulting solution was dissolved in methyl ethyl ketone to form a 3% solution. This solution was applied on a glass substrate having a thickness of 1.2 mm with a spinner coater and dried to obtain a solution having a thickness of 95 nm.
Was formed to produce a recording medium.

Example 6 The dye of the above structural formula (8) and an infrared absorbent (trade name, manufactured by Nippon Kayaku Co., Ltd .; IRG-003) were mixed at a weight ratio of 3: 1, and this was dissolved with methyl ethyl ketone. After making a 10% solution, this solution was applied on 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 80 nm, thereby producing a recording medium.

Example 7 The dye of the above structural formula (13) and the dye of the following structural formula were mixed at a weight ratio of 2: 1, and dissolved in the same manner as in Example 1, applied to a substrate and dried. Thus, a recording layer having a thickness of 75 nm was formed to produce a recording medium.

Example 8 A recording layer having a thickness of 60 nm made of the dye of the structural formula (1) was formed on a glass substrate in the same manner as in Example 1,
Aluminum naphthalocyanine represented by the following structural formula was vacuum-heat-deposited on the recording layer under the condition of a degree of vacuum of 1.0 × 10 ⁻⁵ Torr to form a reflective protective layer having a thickness of 30 nm, thereby producing a recording medium.

Comparative Example 1 The dye of the following structural formula (I) was dissolved in methylene chloride to give
% Solution, and the solution was spinned to a thickness of 1.
The composition was applied on a glass substrate of 2 mm and dried to form a recording layer having a thickness of 80 nm, thereby producing a recording medium.

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

The reflectance of the recording layers of the recording media of Examples 1 to 8 and Comparative Examples 1 to 4 with respect to light having a wavelength of 830 nm from the recording layer side was measured by a spectrophotometer. Further, the absorbance of each recording layer with respect to light having a wavelength of 830 nm was measured.
Further, the semiconductor laser light having a wavelength of 830 nm is focused on a spot having a diameter of 1.2 μm so as to have a medium surface output of 4 mW, and the focused laser light is moved at a speed of 9 m / sec from the substrate side of each recording medium.
The recording was performed under the conditions described above, and reproduction was performed using the same laser beam at a reproduction output of 0.4 mW, and the recording sensitivity (recording energy threshold) and the C / N value of the reproduced signal were measured. Further, the recording media of Examples 1 to 8 and Comparative Examples 1 to 4 were left in an atmosphere of 50 ° C. and 95% for 150 hours, and subjected to a heat and humidity resistance test for measuring a decrease in absorbance and a decrease in reflectance before and after the storage. Done. 25 ° C, 60 for each recording medium
A 500 W tungsten light was irradiated to a 50 cm area in a 50% atmosphere for 100 hours, and a light fastness test was performed to measure a decrease in absorbance and a 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 reflectivity and a high recording sensitivity, can stably perform writing and reproduction of an optical signal, and can reproduce light and sunlight, A pollution-free optical information recording medium with high stability to humidity can be provided.

[Brief description of the drawings]

1 to 3 are schematic diagrams each showing an optical information recording medium of the present invention. DESCRIPTION OF SYMBOLS 1 ... board | substrate, 2 ... recording layer, 3 ... laser beam, 4 ... intermediate layer, 5 ... protective layer, 6 ... spacer.

Claims (1)

(57) [Claims] (1) General formula Wherein R ₁ and R ₂ are a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms or (Ph; phenyl group), R ₃ is an alkyl group having 1 to 6 carbon atoms,
Aralkyl group, phenyl group, X is perchlorate, fluoroborate, iodide, chloride, bromide, anion selected from p-toluenesulfonate, Y is an alkyl group having 1 to 18 carbon atoms, −R ₄ OH, −R ₄ COOH, −R ₄ OR ₅ , −R ₄ COR ₅ , −R ₄ COOR ₅ , (R _4; alkylene group having 1 to 20 carbon atoms, R _5; alkyl group having 1 to 18 carbon atoms), n is an integer of 1 or 2, Z is the case of _{n = 1, -R 6 OH,} -R 6 COOH, −R ₆ OR ₇ , −R ₆ COR ₇ , -R ₆ CN, -OR ₇ , -OH, -COOH, -COR ₇ , phenyl group, -CN,
_{-OCF 3, -OSF 3, -NH 2} N (R 7) 2, -NHCOR 7, (R ₆ ; an alkylene group having 1 to 20 carbon atoms, R ₇ ; an alkyl group or a phenyl group having 1 to 18 carbon atoms), and when n = 2, 1 carbon atom
To 10 to 10 alkyl groups or halogen atoms].