JPH05250729A - Optical recording medium - Google Patents

Abstract

PURPOSE:To enhance contrast between transparent and colloidal state by adding a specified coloring matter to a recording layer or a layer contacting therewith. CONSTITUTION:When an imidazoquinoxaline coloring matter shown by formula I is added to a recording layer or a layer contacting therewith, durability and contrast between transparent and colloidal states can be enhanced. In formula I, A1 and A2 represent an alkyly group, an aryl group or an alkenyl group, respectively, A3 represents N or C-R4(R4 represents a hydrogen atom, an alkyl group, or an aryl group), R1, R2, and R3 couple, respectively, with an alkyl group, an aryl group, an alkenyl group, or L to form a ring, X<-> is an anion, Q is group coupled with N-R3 to form a five or six-membered ring, L is a trivalent group coupled with three, five or seven methine groups to form a conjugated double bond.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an optical information recording medium and an optical information recording method using the same.

[0002]

2. Description of the Related Art In recent years, a method of recording information using a beam having a high energy density such as a laser beam has been developed and some have already been put into practical use. The information recording medium is basically composed of a substrate made of plastic, glass or the like and a recording layer provided thereon. Known recording materials used in the recording layer include metals or semimetals such as Bi, Sn, In, Te and Se, and dyes such as cyanine, phthalocyanine, quinone and metal complex dyes. Information is written by, for example, irradiating a laser beam, and as a result of locally increasing the temperature of the irradiated portion of the recording layer, information is recorded by changing its optical characteristics by causing physical or chemical changes. To be done. Known methods for changing the recording layer include bit formation, recess formation, bubble formation, a method utilizing phase change, and a method utilizing magnetization reversal. Particularly, a rewritable recording medium is typified by a method utilizing phase change and a method utilizing magnetization reversal. As a system for recording using phase change, As-T
An e-Ge-based amorphous recording material and a Tb-Fe-Co-based amorphous alloy are known as a recording system utilizing magnetization reversal. As described above, as recording materials, inorganic materials such as metals and metalloids or dyes have been used conventionally. Further, recently, various methods of using a polymer material, which is excellent in safety, manufacturability, and cost, as a recording material have been announced. For example, one utilizing the phase change of a polymer (Japanese Patent Laid-Open No. 63-27944).
0), which utilizes the thermal expansion of the polymer (JP-A-60-
69846). However, the one using the phase change of the polymer has the drawback that the temperature of the phase change is high and the rate of the phase change is slow, and the one using the thermal expansion is because the recording is essentially a shape change. However, there are drawbacks such as difficulty in forming a single plate, and at present, satisfactory recording methods and materials have not been developed. On the other hand, research on polymer blends in which two or more kinds of polymers are mixed has been advanced in order to impart properties that cannot be obtained by a single material. Above all, application of polymer blends that change state between compatible and phase-separated states by temperature change to optical memory has been proposed (Hyundai Kagaku Special Edition 8,134,19).
86). That is, in the compatible state, the blended polymers are uniformly mixed and transparent, but in the phase-separated state, the respective component polymers have different refractive indexes and thus become cloudy. Since this transparent-white turbid phenomenon occurs reversibly under temperature control, it is expected to be applied to a recording medium. Among polymer blends exhibiting such characteristics, there are an LCST type polymer having a compatible state at a low temperature and a phase separated state at a high temperature, and a VCST type polymer having a phase separated state at a low temperature and a compatible state at a high temperature. However, since the blend itself has a small absorption for light such as a laser beam, it is necessary to dispose a light-absorbing substance in the recording layer or in another layer in contact with the recording layer to improve the photothermal conversion efficiency. However, when a light-absorbing substance is dispersed in the recording layer, the problem is that the recording material itself becomes brittle and the contrast between the transparent and opaque states is reduced depending on the amount of the light-absorbing substance dispersed. ..

[0003]

An object of the present invention is to provide an optical information recording medium and an optical information recording method using the same, which are free from problems such as embrittlement of a recording medium or reduction of contrast between transparent and opaque states.

[0004]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have made extensive studies on a light absorbing substance to be contained in a recording medium using a composition comprising a polymer blend or in a separate layer in contact with the recording layer, When the dye having the structure represented by the general formula (I) is used as the light absorbing substance, the light absorption of the recording layer portion with respect to the light such as the laser beam irradiated by irradiating only a small amount of the dye in the polymer blend composition. The inventors have found that the heat conversion efficiency can be improved and have completed the present invention.

[Chemical 2] (However, A ₁ and A ₂ represent an alkyl group, an aryl group, an alkenyl group or a group having a substituent, which may be the same or different from each other, or A ₁ and A ₂
May be linked to each other to form a ring, A ₃ is N or C—R ₄ (R ₄ is a hydrogen atom, an alkyl group or an aryl group), R ₁ , R ₂ and R ₃ are an alkyl group or an aryl group. Base,
Represents an alkenyl group or these groups having a substituent,
They may be the same or different from each other, or at least one of these groups may combine with L to form a ring, and
^- represents an anion, Q is linked to a N-R ₃ 5 or 6
Represents a group for forming a member ring, and L represents a methine group or a trivalent group formed by connecting 3, 5 or 7 methine groups so as to form a conjugated double bond. ,
The methine group may be substituted. The present invention relates to an optical recording medium containing a dye consisting of an imidazoquinoxaline dye. That is, as a laser beam used for recording / reproducing of an optical recording medium, a semiconductor laser that oscillates near-infrared light has been put into practical use, and in order to improve the light absorption and heat conversion efficiency of the recording partial layer, It is necessary to incorporate a light-absorbing substance having a high absorptivity for light having a wavelength of about 780 nm into a recording medium or a separate layer in contact with the recording layer. For such a purpose, the above general formula ( It has been found that a dye having the structure shown in I) is suitable.

The use amount of the dye of the general formula (I) varies depending on the kind of the blended resin composition and the like, but the use amount is 0.
Although it can be used in the range of 01 to 20 parts by weight,
A small amount of 5 parts by weight can sufficiently exert the effect. If the amount used is less than 0.01 part by weight, heat conversion will not be sufficient. On the other hand, if the amount is more than 20 parts by weight, the recording layer becomes fragile. Further, the dye of the general formula (I) may be not only a single dye but also a mixture of two or more kinds of dyes. These dyes can be blended not only in the recording layer but also in a separate layer adjacent to the recording layer as described above, and the separate layer is a layer newly provided for containing the dye. It may be a layer such as a protective layer adjacent to the recording layer.

Examples of the blend composition containing the light absorbing substance represented by the general formula (I) in the present invention include the following. Examples of LCST type polymer blends include (1) Combination of amorphous polymers: polystyrene and polyvinyl methyl ether, styrene / acrylonitrile copolymer and poly-ε-caprolactone, styrene / acrylonitrile copolymer and polymethyl methacrylate, Polyvinyl acetate and polymethyl acrylate, ethylene / vinyl acetate copolymer and chlorinated rubber, poly-ε-caprolactone and polycarbonate (bisphenol A type), p-
Chlorostyrene / o-chlorostyrene copolymer and poly (2,6-dimethyl-1,4-phenylene oxide), polycarbonate (bisphenol A type) and ethylene oxide block copolymer, butylene terephthalate / tetrahydrofuran block copolymer Polyvinyl chloride, thermoplastic polyurethane [poly-ε-caprolactone soft block] and polyvinyl chloride: (2) Combination of crystalline polymer and amorphous polymer: polyvinylidene fluoride and polymethyl acrylate, polyvinylidene fluoride and polyethyl Acrylate, polyvinylidene fluoride and polymethylmethacrylate, polyvinylidene fluoride and polyethylmethacrylate, polyvinylidene fluoride and polyvinyl methyl ketone: and (3) combination of crystalline polymer and crystalline monomer: polyethylene Oxide and trioxane, poly-ε-caprolactone and trioxane: may be mentioned. UC
Examples of ST type polymer blends include combinations of amorphous polymers such as polystyrene and polyisoprene, polystyrene and polyisobutene, polypropylene oxide and polybutadiene, and polyisobutene and polydimethylsiloxane. These polymer blends are used in a solution state using a solvent that dissolves each polymer constituting the polymer blend.

The substrate is not limited in kind as long as it is transparent to the laser light used, but as the substrate material, acrylic resin, vinyl chloride copolymer resin, plastic such as polycarbonate, or glass is used. it can. In addition, a pre-format for address signals or a pre-groove for a guide groove may be formed on the surface of the substrate.

The most basic optical recording medium of the present invention is one in which a recording layer is provided on a substrate as described above, but if necessary, an undercoat layer may be provided between the substrate and the recording layer. It may be provided, a protective layer may be provided on the recording layer, or a light reflection layer may be provided on the recording layer. The undercoat layer has improved adhesiveness with the recording layer, a barrier against water or gas,
It is used for the purpose of improving the storage stability of the recording layer, improving the reflectance, protecting the substrate from a solvent, forming pre-rubbing, and the like.

Preferred embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the optical recording medium basically comprises a recording layer and a substrate. In the present invention, in order to increase the light-heat conversion efficiency, a light absorbing substance is dispersed in the recording layer as shown in FIG. As shown in FIGS. 3 and 4, the light absorption layer may be provided as another layer. If necessary, Al, Ni, Cr, A may be provided between the substrate and the recording layer or on the recording layer.
A reflective layer made of a metal such as g may be provided (FIG. 5,
6). Further, a protective layer made of epoxy resin, silicon resin, acrylic resin, polyurethane resin or the like may be provided on the recording layer (FIGS. 5 and 6). As a material for the reflective layer formed on the light absorption layer, a metal or a semimetal having a high reflectance can be used. For example, Zn, Cu, Ni, C can be used.
r, Au, Ag, Al, etc. can be mentioned. Especially A
u and Al are preferable. A protective layer may be further provided on the reflective layer, and as the material thereof, various polymer materials such as polyamide resin, vinyl resin, silicone, and liquid rubber,
Inorganic compounds such as SiO, SiO ₂ , TiO ₂ , TiN, Si ₃ N _{4 and the} like, ultraviolet curable resins and the like can be used alone or in a laminated form.

[0010]

Example A copolymer of vinylidene fluoride and hexafluoropropylene having a copolymerization ratio of 91: 9 (manufactured by Central Glass Co., Ltd.) (Component 1) and polymethylmethacrylate (manufactured by BR-Mitsubishi Rayon) (Component 2) were used. Using methyl ethyl ketone, which is a common solvent for both, a dye having a structure shown in the following formula was mixed and applied to a solution prepared by adjusting the blend ratio (weight ratio) of component 1 / component 2 to 1/1. The liquid was adjusted.
The mixing ratio of the polymer blend and the dye in this coating solution was 100: 1 (weight ratio). The thus-prepared solution was applied onto a glass substrate having a thickness of 1 mm by a spin coating method and dried under reduced pressure at 100 ° C. for 1 hour to prepare a recording medium sample having a polymer blend film having a film thickness after drying of about 5 μm. ..

[Chemical 3] The absorption spectrum of this dye in a 1,2-dichloroethane solution was λmax = 704 mm, ε = 3.56 ×
It is 10 ⁵ liter / mol · cm, and shows large absorption in the vicinity of 780 nm which is the wavelength of the semiconductor laser light. Next, when the produced recording medium was heated to 147 ° C. by a heater, the component 1 and the component 2 of the polymer blend film were phase-separated, and as a result, the recording layer became cloudy. When this cloudy sample was put into water and rapidly cooled, the cloudy state was fixed. When this recording medium was again heated to 147 ° C. by a heater and gradually cooled by turning off the heater and naturally lowering the temperature, the component 1 and the component 2 of the polymer blend film became compatible with each other and became transparent. Next, the produced optical recording medium was irradiated with a semiconductor laser light (oscillation wavelength 780 nm, beam diameter 5 μm) at a frequency of 10 KHz from the glass substrate side in a cloudy state, and a transparent circular bit was obtained with an irradiation power of 4 mW or more. The circular bit was erased by illuminating it with focused light.

[0011]

As described above, in the present invention, the polymer blend composition is used for the recording layer, and the general formula (I) is used as the light-absorbing substance to be contained in the recording layer or another layer in contact with the recording layer. When the dye having the structure shown in (1) is used, since the light absorption coefficient is high, the light-heat conversion efficiency can be increased by using it in a small amount in the blend composition. Therefore, it is possible to obtain a strong optical recording medium having a high contrast between the transparent and opaque states.

[Brief description of drawings]

FIG. 1 is a model view showing a cross-sectional structure of an optical recording medium including a recording layer and a substrate.

FIG. 2 shows the recording layer of FIG. 1 containing a light absorbing substance.

FIG. 3 is a model view showing a cross-sectional structure of an optical recording medium in which a light absorbing material layer and a recording layer are sequentially provided on a substrate.

FIG. 4 is a model view showing a cross-sectional structure of an optical recording medium in which a recording layer and a light absorbing material layer are sequentially provided on a substrate.

FIG. 5 is a model view showing a cross-sectional structure of an optical recording medium in which a reflective layer, a recording layer and a protective layer are sequentially provided on a substrate.

FIG. 6 is a model view showing a cross-sectional structure of an optical recording medium in which a reflective layer, a light absorbing layer, a recording layer and a protective layer are sequentially provided on a substrate.

[Explanation of symbols]

 1 substrate 2 recording layer 3 light absorbing layer 4 light absorbing material layer 5 reflective layer 6 protective layer

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Noboru Sasa 1-3-6 Nakamagome, Ota-ku, Tokyo Within Ricoh Co., Ltd.

Claims (2)

[Claims] 1. An optical recording medium having a recording layer on a light-transmissive substrate that utilizes a change in optical characteristics associated with a compatible state and a phase-separated state due to a temperature change, in the recording layer or the recording layer. In another layer in contact with the layer, the following general formula (I): [Wherein A ₁ and A ₂ represent an alkyl group, an aryl group, an alkenyl group or a group having a substituent, which may be the same or different from each other, or A ₁ and A ₂
May be linked to each other to form a ring, A ₃ is N or C—R ₄ (R ₄ is a hydrogen atom, an alkyl group or an aryl group), R ₁ , R ₂ and R ₃ are an alkyl group or an aryl group. Base,
Represents an alkenyl group or these groups having a substituent,
They may be the same or different from each other, or at least one of these groups may combine with L to form a ring, and
^- represents an anion, Q is linked to a N-R ₃ 5 or 6
Represents a group for forming a member ring, and L represents a methine group or a trivalent group formed by connecting 3, 5 or 7 methine groups so as to form a conjugated double bond. ,
The methine group may be substituted. ] An optical recording medium containing a dye consisting of an imidazoquinoxaline dye. 2. The optical recording medium according to claim 1, wherein the content of the dye represented by the general formula (I) in the recording layer is 20.
An optical recording medium characterized by being less than or equal to parts by weight.