JPH05250724A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide an optical recording medium having high sensitivity and high recording speed and excellent in safety and manufacturability. CONSTITUTION:Light absorbent substance is added to a recording layer 2 formed on a light transmissive substrate by dispersing a thermally expansive substance, where thermal deformation can be sustained even after cooling, into an elastic rubberlike material or to layers 5, 6 adjoining to the recording layer 2.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a writable optical recording medium having at least a recording layer on a transparent substrate.

[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), utilizing the change between compatible and phase-separated states by polymer blend (Hyundai Kagaku Special Edition 8,134,1986)
Etc. However, these have the drawbacks that the temperature at which the phase change and the change between the compatible and phase separated states occur is high and the time required for the change is long. On the other hand, for a recording method in which a recording material is irradiated with a laser beam and thermally deformed by melting, evaporation, aggregation, expansion, etc., it has been proposed to use a polymer material for the recording layer (Japanese Patent Laid-Open No. 60-69846). .. However, the polymer material itself, which is deformed by heat, has high transparency and has a low ability to absorb light such as laser light, which is problematic in practical use. Therefore, at present, a satisfactory recording method and recording element have not been developed.

[0003]

An object of the present invention is to provide an optical recording medium which is excellent in manufacturability and stability, has a high recording speed, and has a high photothermal conversion efficiency (high sensitivity).

[0004]

An optical recording medium according to the present invention comprises a substrate having a light-transmitting property, in which a substance that is thermally expanded and deformed by heating and the deformed state can be maintained by subsequent cooling is dispersed in a rubber-like elastic body. In an optical recording medium having a recording layer of, a light absorbing substance is contained in the recording layer or a layer in contact with the recording layer. Examples of the light absorbing substance used in the present invention include imidazoxoxaline dyes represented by the following general formula (I).

[Chemical 5] (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. May be formed, and A ₃ is N
Or C—R ₄ (R ₄ is a hydrogen atom, an alkyl group, an aryl group), R ₁ , R ₂ and R ₃ are an alkyl group, an aryl group,
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. ) Further, there are light absorbing substances having the structural formulas represented by the following formulas (A), (B) and (C).

[Chemical 6]

[Chemical 7]

[Chemical 8] In the optical recording material of the present invention, when a part of the surface is heated, for example, by irradiation with light of a semiconductor laser to heat,
In the heated portion, the substance expands and deforms to deform the rubber-like elastic body around it. The expanded and deformed state due to this substance is maintained even after cooling, and the surface of the irradiated portion is formed as a bulge. This bulge has different refraction, diffraction, and reflection states compared to the non-heated portion. Therefore, desired recording can be performed depending on the difference in light transmittance. In addition, in the recording method using the deformation of the rubber-like elastic body, unlike the metal thin film, there is no modification such as oxidation and corrosion, so that the recording characteristics are not deteriorated and the storage stability can be improved. As a substance that undergoes thermal expansion deformation by heating, and this deformed state can be maintained by subsequent cooling,
A heat-expandable thermoplastic resin, for example, a thermoplastic resin containing a compound having a low boiling point is preferable, but the thermoplastic resin is not limited to this as long as it meets the purpose of the present invention. In this case, the thermoplastic resin is more preferably a fine powder. A substance that undergoes thermal expansion deformation by such heating and can maintain this deformation state by subsequent cooling can be compounded not only in the recording layer having rubber-like elasticity but also in the adjacent layer to the recording layer. However, the different layer may be a layer newly provided to contain the thermal expansion deformable substance, or may be a layer such as a protective layer adjacent to the recording layer. The amount of the substance used is 0.01 with respect to the rubber-like elastic body.
It is desirable to use in the range of ˜20 parts by weight. 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 brittle. As the rubber elastic body, those having a large light transmittance, and those having transparency are preferable. Specifically, for example, styrene rubber, butadiene rubber, nitrile rubber, butyl rubber, acrylic rubber, urethane rubber, silicon rubber, fluororubber, chlorosulfonated polyethylene, ethylene vinyl acetate copolymer, chlorinated polyethylene, polyisobutylene, alfin rubber. Synthetic rubbers such as polyester rubber, epichlorohydrin rubber, chlorinated butyl rubber, nitrile isoprene rubber and thermoplastic styrene rubber can be used. However, the rubber-like elastic body that can be used in the present invention is not limited to the above-mentioned examples, and has a large light transmittance, and the heat-deformable substance as described above is thermally expanded by heating. The type is not particularly limited as long as it can be deformed to form a bulge. The substrate material is not limited in type as long as it is transparent to the laser light used, but acrylic resin, vinyl chloride copolymer resin, plastic such as polycarbonate, or glass or the like can be used.
As the recording medium of the present invention, the one having the recording layer provided on the substrate as described above is the most basic, but other layers, for example, the following layers may be provided if necessary. On one side or both sides of the substrate, especially on the surface of the substrate where the recording layer is provided, for the purpose of improving the flatness, improving the adhesive force with the recording layer, improving the sensitivity due to the heat insulating effect, and preventing alteration of the recording layer. An undercoat layer may be provided. Further, a pre-groove layer can be provided if necessary. This pre-groove layer is made of, for example, a radiation curable resin,
It can be formed by irradiating ultraviolet rays or the like. Furthermore, in order to increase the reflectance of the optical information recording medium, as a reflective film,
It is preferable to provide a metal film. For example, gold, silver, aluminum, or an alloy containing these can be formed by a method such as an evaporation method or a sputtering method. Further, it is preferable to provide a protective layer formed of a resin having excellent impact resistance on the reflective film. The protective layer is formed by applying a UV curable resin by a spin coating method and irradiating it with an ultraviolet ray to cure it. It can be formed by The above-described configuration of the present invention will be specifically 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, a reflective layer made of a metal such as Al, Ni, Cr, or Ag may be provided between the substrate and the recording layer or on the recording layer (FIGS. 5 and 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 described above, the optical recording medium of the present invention, the thermal deformation of the recording layer, for example, maintains the deformed state due to the thermal expansion that occurs when irradiated with laser light,
Bulge on the surface. Since the surface state and the internal state of the bulged portion are different from those of the unirradiated portion, the optical characteristics such as refraction, diffraction, and reflection are different. In this state, if the light for recording reproduction is applied to the light-irradiated part, the incident angle of the light changes due to the bulge, which changes the light transmission amount. Since the light is refracted, reflected, and scattered to be scattered, the light transmission amount in the bulge portion is smaller than that in the non-irradiated portion of the laser light. That is, in the bulged part irradiated with laser light and the unirradiated part,
Since the light transmittance is different, it is possible to write information on the recording medium by utilizing such a state.

[0005]

According to the optical recording medium of the present invention, a substance that is thermally expanded and deformed by heating and the deformed state can be maintained by subsequent cooling is dispersed in a rubber-like elastic body or adjacent to the recording layer. Since the layer contains the light absorbing substance,
It is possible to provide an optical recording medium having high sensitivity, high recording speed, and excellent safety and manufacturability.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a basic structure of a recording medium of the present invention composed of a substrate 1 and a recording layer 2.

FIG. 2 is a cross-sectional view schematically showing a structure in which a light absorbing substance 4 is dispersed in a recording layer 1.

FIG. 3 is a cross-sectional view schematically showing a configuration in which a light absorbing layer 3 is provided between a substrate 1 and a recording layer 2.

FIG. 4 is a cross-sectional view schematically showing a structure in which a light absorbing layer 3 is provided on a recording layer 2.

FIG. 5 is a cross-sectional view schematically showing a configuration in which a reflective layer 5, a recording layer 2 having a light absorbing substance 4 dispersed therein, and a protective layer 6 are sequentially formed on a substrate 1.

FIG. 6 is a cross-sectional view schematically showing a structure in which a reflective layer 5, a light absorbing layer 3, a recording layer 2 and a protective layer 6 are sequentially formed on a substrate 1.

[Explanation of symbols]

 1 substrate 2 recording layer 3 light absorbing layer 4 light absorbing material 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 (3)

[Claims] 1. A light having, as a recording layer, a substance which is thermally expanded and deformed by heating and is dispersed in a rubber-like elastic body on a light-transmissive substrate so that the deformed state can be maintained by subsequent cooling. An optical recording medium, wherein a recording medium or a layer adjacent to the recording layer contains a light absorbing substance. 2. The optical recording medium according to claim 1, wherein the light absorbing substance is an imidazoquinoxaline dye represented by the following general formula (I). [Chemical 1] (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. May be formed, and A ₃ is N
Or C—R ₄ (R ₄ is a hydrogen atom, an alkyl group, an aryl group), R ₁ , R ₂ and R ₃ are an alkyl group, an aryl group,
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. ) 3. The light-absorbing substance has the following structural formula (A):
The optical recording medium according to claim 1, which is selected from the group of compounds represented by (B) and (C). [Chemical 2] [Chemical 3] [Chemical 4]