JPS5898289A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain a recording medium having excellent storability of recorded information as well as a great regenerated SN ratio by adding a coloring substance to convert recording lasers into heat and a high molecular compound to the lasers adsorption layer of an optical information recording medium. CONSTITUTION:On the surface of a base plate 1, a reflection layer 2 of a metal deposit film and a light transmissive heat-insulating layer 3 of SiO2, polymethyl methacrylate, etc., are formed, and then a laser absorptive layer 4 containing a coloring substance and a high molecular compound is formed on said layers. The coloring substance used includes colloidal metal fine particles of Cu, Ag, etc., a carbonaceous substance of carbon black, etc., or inorganic pigments composed primarily of heavy metal salts. Also, the high molecular compound used as a dispersion medium for the coloring substance is a thermoplastic resin (e.g., polystyrene, polymethylmethacrylate, etc.) or a self-oxidizing compound (e.g., methyl cellulose, etc.). These are uniformly dispersed with a water-soluble binder, a surfactant, etc., and then coated on a heat-insulating layer 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical information recording medium having a reflective layer, a thermally insulating layer, and a laser light absorbing layer mainly composed of an organic substance.

In a high-density information recording medium that uses a laser beam that can provide high-intensity and short-time exposure, it is possible to directly read information without any post-processing immediately after writing it.r DRAW J
(Direct Read After Write
) The usefulness of time-sensitive media has been widely pointed out in recent years in the fields of computers, data files, V, T, R, audio discs, duplication recording media, etc. Furthermore, many studies on materials for DRAM recording media have been reported.

Conventionally, many of the recording layers in known laser beam recording media are made of reflective metal thin films such as A' s Rh h Au s Or, amorphous metals such as Te%Bi, Be, or their oxides. or Se-Te-As,
This is a vapor-deposited thin film of a chalcogen compound such as Te-As. In many cases, information is recorded by forming pits (four parts) based on the principle of irradiating these recording layers with a laser beam and melting and vaporizing the recording layer using the energy.

Particularly in conventional optical information recording media in which reproduction is performed using a reflection method, the reflectance of pit portions formed in the recording layer is often relatively lower than that of unrecorded portions.

In addition, since a considerable amount of the recording laser beam is reflected in a dark recording medium, the energy of the recording laser beam cannot be fully used up, which has the disadvantage of requiring the use of a high-output laser beam generator. has. Therefore, in order to improve the efficiency of the recording laser beam in the unrecorded part of such a recording medium, if the surface of the unrecorded part is made as low as possible in reflectance, for example, when the reflectance is set to 30% or less, It is not possible to make the difference in reflectance between the bit portion formed in the recording layer and the unrecorded portion so large. This results in the disadvantage that the information recording and reproducing characteristics, that is, the signal-to-noise ratio (8N ratio) does not become large.

One way to solve the above-mentioned drawbacks of the prior art is to create a recording layer made of a material or structure that increases the reflectance of recorded areas irradiated with laser light during reproduction relative to unrecorded areas. It is to adopt.

P, W, 8pong American Union 13i1 Special Pestle No. 4.
As described in the specification of No. 097.895, the reflection stopper dye layer supported on one substrate is melted and removed by laser light irradiation, and the reflectance of the bit portion formed increases. An example of what is recorded is shown. As the above-mentioned recording layer, examples are known in which, in addition to a dye that absorbs laser light, an amorphous metal such as KTe or an oxide thereof, and a low melting point metal such as Ti are used.

However, these recording materials #'i are mostly vacuum vaporized*
The film must be formed by sputtering or the like, and is manufactured by a so-called batch method, which is not necessarily suitable for mass production.

Historically, dye-deposited films produced by the above-mentioned methods had extremely low film strength and required some kind of preservation means, for example, a plastic protective layer.

Te vapor-deposited film is also easily oxidized by the influence of oxygen or moisture in the air, and the surface characteristics of the vapor-deposited film surface and the focus area change, so there is a concern that dope P7 drop-out of the reproduced signal will occur, and the preservation of information will be a problem. It becomes. In addition, the above-mentioned problems have not been completely solved even with the use of a conventional plastic protective layer due to its poor air permeability. Furthermore, there are concerns that the toxicity of l1le itself may have an impact on the environment not only at the manufacturing site of recording media, but also on the environment during use and storage, and on multiple levels. This is a disadvantage.

Furthermore, a three-layer optical disk using a vapor-deposited metal layer such as Ti has a drawback of low recording sensitivity due to the high thermal conductivity of the metal layer.

The purpose of the present invention is to improve the drawbacks and inconveniences of the prior art, and to provide an optical information recording system that is harmless, free from oxidation, deterioration, etc., has excellent storage stability of recorded information, and is highly sensitive and has a large reproduction signal-to-noise ratio. The goal is to provide a medium.

The above object of the present invention is to provide a thermal insulating layer that transmits both laser beams between a layer that reflects reproduction laser beams and a laser beam absorption layer that corrodes the cough reflection layer and highly absorbs recording laser beams. This is achieved by an optical information recording medium characterized in that the laser light absorption layer contains at least a colored substance and a polymer compound that convert recording laser light into heat.

According to a preferred embodiment of the present invention, there is provided an optical information recording medium characterized in that the colored substance is colloidal metal fine particles, or the colored substance is carbon black. It is an information recording medium,
Alternatively, it is an optical information recording medium characterized in that the colored substance is graphite. According to another preferred embodiment, the optical information recording medium is characterized in that the polymer compound is a thermoplastic resin, or
An optical information recording medium characterized in that the polymer compound is a self-oxidizing compound.

The laser light absorption layer that highly absorbs recording laser light in the present invention is a layer mainly composed of an organic substance. is transmitted, melting or blow off
Bits are formed by (blowing).

The reflectance of the laser light absorption layer at the wavelength of the recording laser light is extremely small compared to the vapor-deposited metal layer, etc., and the thermal conductivity of the coloring substance and the polymer compound as the dispersion medium is low, resulting in low output. It has the advantage that sufficient recording can be performed with a laser beam of .

Furthermore, it has the advantage of not being toxic like Te or Bi, and having extremely high surface strength compared to dye-deposited films and being easy to handle.

As the colored substance contained in the laser light absorption 1- of the present invention,
'(&:K) Carbon-based substances such as carbon black and graphite, inorganic pigments, organic pigments such as phthalocyanine and derivatives thereof, or colloidal metal fine particles can be used. One or more of these can be used in combination. I can say that.

Further, as the polymer compound contained in the laser light absorption layer of the present invention, it is preferable to use a thermoplastic resin that is easily melted and removed by heat, or a self-oxidizing polymer compound that is easy to blow off by heat. preferred for pit formation. These may be used singly or in combination.

According to the present invention, since the laser light absorbing layer containing the polymer compound in which the coloring substance is dispersed is formed by coating a dispersion solution, the recording medium can be manufactured at low cost and in a continuous assembly line. It also has the advantage of being manufacturable.

Recording on the information recording medium according to the present invention is performed, for example, as follows. That is, in the case of recording, recording is performed by making pits (openings) in the laser light absorption layer using a recording laser beam modulated by an input electrical signal. Reproduction is performed by irradiating a reproduction laser beam,
At this time, since the reflection of the laser beam on the bit part is a reflection on the surface of the lower reflective layer 11, C is relatively large compared to other unirradiated parts, so it is reproduced with high sensitivity. S
This makes it possible to remove the reflective layer of an information recording with a large N ratio.

The type of laser used here is determined by the spectral absorption characteristics of the laser light absorption layer containing a colored substance, and for example, He-Ne5 with an output of several milliwatts to several tens of milliwatts.
A gas laser such as HeCd, an ion laser such as ArsKr, or a semiconductor laser is used.

Hereinafter, specific examples of the optical information recording medium according to the present invention will be explained in detail based on the drawings.

4 represents a transparent thermal insulating layer, and 4 represents a laser light absorption layer.

The substrate 1 may be any material as long as it has excellent surface smoothness and dimensional stability, and specific examples include glass, metal, ceramic, or resin, but these may be transparent, translucent, or opaque. I don't mind.

The reflective layer 2 reflects a considerable portion of the incident light having the wavelength of recording and reproducing laser light, and is generally made of a metal such as Kl, Ag, or Au, which exhibits a high reflectance. The reflective layer 2 is deposited on the substrate 1 to a thickness of 200 to 1000 Å by vacuum deposition so as to reflect 50% of the incident light.

In order to reduce the recording energy threshold on the laser light absorption layer 4, the translucent thermal insulating layer 3 has a sufficiently low thermal conductivity in °C compared to the reflective layer 2, and also It is a material that substantially allows light to pass through. For example, 8i
Inorganic materials such as 0□, MgF', WO2, etc., or organic materials such as transparent silicone resin, polyethylene, polyester-based and acrylic-based hydrocarbon intermolecules, and fluorocarbon-based polymers and the like are used. Especially 5i
02. Polymethyl methacrylate (PMMA) is preferred.

The light-transmitting thermal insulating layer 3 is provided on the light-reflecting layer 2 by a vapor deposition method, a glow discharge current, a solution coating method, etc.
lill is 100λ to 10μ.

If it is less than 10 rl A, the thermal insulation effect will not be sufficient, causing an increase in the recording energy threshold. In the case of a reproduction method using interference, the sum of the film thicknesses of the transparent thermal insulation layer 3 and the light absorption layer (recording layer) 4 is n/4 times (n
is an integer), and the thickness of the thermal insulating layer 3 is determined so that He
If a -Ne laser (6328A) is used as a light source for reproduction, its film thickness is preferably about 1500λ.

The colored substance that converts light into heat and is included in the laser light absorption layer of the present invention is, for example, Ou s Ag s Au % N1
%Pd, Pt, Co, Rh, Ir, F”e
, colloidal metal fine particles such as Mn, Or, Ti, etc.
Carbon-based substances such as carbon black and graphite, inorganic pigments whose main constituents are salts of kenkinmagaku, such as lead-based, iron-based, cadmium-based, cobalt-based, ultramarine blue and deep blue pigments, and organic pigments such as anthraquinone. System, anthic P -ry, azo, and Futhalcianin pigments can be used.

The preferred type of metal when using metal fine particles depends on the type of polymer used as a dispersion medium and the particle size of the dispersed fine particles, but according to one preferred embodiment, the average particle size is 3.
The laser light absorbing layer is made by dispersing microparticles of ~00λ in gelatin. The metal used here is not limited to one type, and it is also possible to use a mixed and dispersed layer of two or more metals as the recording layer, and it is also possible for this mixed metal to be the main component. , generally a polymeric binder 50
It is used by dispersing it in % by weight or more.

Further, carbon black, graphite, etc. are also used as one of the preferred coloring substances. As specific examples of these, known ones can be preferably used, such as carbon black (30°, 40%, 50) (Mitsubishi Chemical Corporation a).

The polymer compound as a dispersion medium for dispersing the colored substance is a thermoplastic resin with an appropriate softening point, preferably 20 to 3.
It is desirable that the thermoplastic resin has a softening point 10 to 200 degrees Celsius higher than 0 degrees Celsius (room temperature), and in the laser light absorption layer, the thermoplastic resin has the ability to maintain appropriate binding properties between particles of the colored substance. desirable. The thermoplastic resin is a granular dispersion medium and is in the form of an emulsion, and the thermoplastic resin in the emulsion can have any particle size, but
Particle size from 0.01μ to 100μ, preferably from 0.01μ to 1
It is desirable to have a particle size of μ.

Thermoplastic resins having the above characteristics include polystyrene, polymethyl methacrylate, polyethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyacrynitrile, polyvinyl alcohol, or having a vinyl group or a vinylidene group. Examples include polymeric substances such as monomeric polymers or copolymers, and various ionomer resins. Among these thermoplastic resins, it has been confirmed that a copolymer of vinylidene chloride and acrytolyl exhibits particularly good properties.

The thermoplastic resin used in the present invention is provided in the form of a water-soluble or oil-bath emulsion.

In particular, when a water-soluble emulsion is used, water-based coating is possible, which has the industrial advantage of not requiring the use of harmful organic solvents.

The laser light absorption layer in the present invention may contain arbitrary additives such as a plasticizer, a water-soluble binder, and a surfactant, if necessary. Adding a wooden binder may be effective in improving coating properties and film properties, but if a water-bathable binder is included, the sensitivity tends to decrease, so the amount added should be kept at a minimum of 1IilK. There is a need.

The water bathing pinter is polyvinyl alcohol,
Synthetic hydrophilic polymers such as polyvinylpyridone, polyvinylamine, and polyethylene oxide, or natural or modified natural hydrophilic colloids such as gelatin, glue, casein, zein, hydroxyethyl cellulose, and carboxymethyl cellulose can be used. The amount added is preferably 1:1 or less by weight to the thermoplastic resin.

Self-oxidizing compounds such as methyl cellulose, ethyl cellulose, nitrocellulose, hydroxypropylene methylcellulose, cellulose acetate, cellulose can be used as another polymer compound for dispersing the coloring substance in the laser light absorbing layer of the present invention. Examples of the self-acidic compound used include, but are not limited to, acetate butyrate, hydroxypropylene methylcell p-sphthalate, cellulose diacetate, carboxymethylcellulose, and the like.

Among these autooxidizing compounds, nido-cellulose or hydroxypropylmethylcellulose is particularly preferred.

According to a preferred embodiment of the present invention, the laser light absorbing layer contains 0.001 to 1000 parts by weight, preferably 0.001 to 1000 parts by weight, of a coloring substance per 1 part by weight of the thermoplastic resin emulsion or self-oxidizing compound. After mixing at a weight ratio of 1 to 10 parts by weight and adding a water-soluble binder, plasticizer, surfactant, etc. as necessary, the mixture is uniformly dispersed by means such as a ball mill or ultrasonic dispersion to form a thermal insulation layer. Obtained by applying on top.

The coating method can be wire bar coating, spinner coating, dip coating, air knife coating, bead coating, curtain coating, etc., and the film thickness is 7.

500A to 1μ, especially 100OA to 5
000A 8 degrees is preferred. i.e. less than 500A"'
Company Q It is difficult to obtain a stable thin film, and on the other hand, if it exceeds 1 μm, it is too thick and the recording energy becomes large, which is not preferred in practice.

An optical information recording medium using colloidal particles of metal as a colored substance that converts light into heat can be obtained by coating a polymer solution in which colloidal mold particles are dispersed on a suitable substrate. In order to increase the film strength and reduce the film thickness, the film can be hardened by heat treatment before recording. A radiation method is preferable so that the heating can be performed uniformly over the entire surface of the dispersion layer, but a heating method using a convection type open or contact type heat source may also be used. The heating temperature and heating time are selected so as to minimize the increase in reflectance due to contraction and hardening of the dispersion layer, and although they vary depending on the dispersion metal, 250° C. and 3 minutes are standard. Heating atmosphere The heat treatment is performed in air containing oxygen unless it is necessary to suppress the oxidation reaction of the dispersed metal under expanded pressure or reduced pressure.

The reflectance of the laser light absorbing layer serving as the information recording layer is preferably 20% or less, preferably 10% or less, and the optical density is desirably at least 1.0 or more.

Further, in the recording medium according to the present invention, it is also useful to provide a preservation layer made of an inorganic material such as 8i02 or an organic material made of a natural or synthetic polymer on the laser light absorption layer for preservation. .

The optical information recording medium according to the present invention has excellent stability over time, and even if there are slight fluctuations in conditions such as usage environment and storage environment, good writing alignment and reflective reading can be stably obtained, and it has high sensitivity. It is an optical information recording medium with a high signal-to-noise ratio.

FIG. 2 is an enlarged cross-sectional view schematically showing recording on an optical information recording medium according to the present invention. That is, in the bit portion 5 that has been melted and removed by irradiation with laser light modulated by digital information, the incident laser beam for reproduction is highly reflected on the surface of the reflective layer 20, and compared to the non-reflectivity of the unirradiated portion 6. This produces a sufficient difference in reflectance, and a reproduced signal with a high S/N ratio can be obtained. The information recording medium according to the present invention having such characteristics can be used as a suitable optical information recording medium for computer data files, digital audio discs, IM image transmission, still image reproduction recording, etc. be.

EXAMPLES The present invention will be explained specifically and in detail with reference to Examples below.

Example 1 Excellent smoothness 1, 6. A reflective layer was vacuum-deposited on a thick glass substrate to a thickness of approximately 200 mm at 10 Torr, and then polymethyl methacrylate (P)
A sample was obtained by coating a 1096 acetylacetone solution of MMA) with a light-transmitting heat insulating layer having a thickness of 1.0 μm.

A gelatin-dispersed aqueous solution of colloidal silver particles was bar coated onto the sample. The dispersion was obtained by reducing AgNO3 with dextrin, the weight ratio of silver to gelatin was 32%, and the particle size of colloidal silver particles was 300%.
It was A. The yellow transparent dispersion layer with a dry film thickness of about 1.5μ is heated at 250℃ for 3 minutes using a far-infrared radiant heater to form an opaque, pale green color with a reflectance of 12%.
gave the surface of

A sample of the recording medium according to the present invention manufactured as described above was rotated at a linear velocity of 1j 5 m/see, and He-Ne with a diameter of 1.4 μ was applied to the recording surface with a power of 10 mW.
Recording was performed using gas laser light (6328A). A 2 MHz rectangular wave signal was used as the input signal, and the laser light was modulated by an acousto-optic modulator.

Reproduction was performed using the same optical system as used during recording and a He--Ne laser beam with a power of 1.5 mW, and a reproduction signal contrast ratio of 0.65 was obtained. Note that the reproduced signal contrast ratio is defined as the ratio of the difference and the sum of the reflected light intensities of the reproduction laser beam from the pit portion and the non-bit portion.

This good reproduction signal corresponds to an 8N ratio of 50 dB or more in recording and reproducing information such as video signals.

Example 2 On a 1,6-thick glass substrate with excellent smoothness, about 2 oo
;The reflective layer is made to have a film thickness of L ~ 10-”fort)
(PMMA) was coated with lθ% acetylacetone solution solution, and the film thickness was 1. A sample provided with a transparent heat insulating layer of θμ was obtained.

A silver iodobromide emulsion with an average grain size of 300λ for precision photography was coated on the sample to give a dry film thickness of 0.2 μm, appropriate exposure was given, and normal photographic operations such as testing and fixing were carried out. After that, a thin gelatin film containing filamentous blackened silver was provided. The optical density of the laser light absorption layer was 0.4.

Recording and reproduction were performed using the same recording and reproducing apparatus as in Example 1, and a good reproduced signal contrast ratio of 0.75 was obtained.

Example 3 A recording medium was prepared in the same manner as in Example 2, except that instead of using polymethyl methacrylate (PMMA) as the light-transmissive heat insulating layer in Example 2, a film with a thickness of zoooX was provided by sputtering. Manufactured.

Recording and reproduction were performed using the same recording and reproduction apparatus as in Example 1, and a good reproduction signal contrast ratio of 0.70 was obtained.

Example 4 Except for the laser light absorption layer, it was manufactured in the same manner as in Example 1, and 0u (L+17 Agcua Br6., IQ
An emulsion layer containing photosensitive halogenated steel having the composition I as a main component is provided by an appropriate coating method on a layer having a dry film thickness of 0.2 μm. After appropriate exposure, it was developed for 10 minutes with a methol-L-ascorbic acid developer and fixed to obtain a copper mirror surface with a reflectance of 6%. The recording layer is a fine particle mixed and dispersed layer containing 1 and Ag in gelatin.

Recording and reproduction were performed using the same recording and reproduction apparatus as in Example 1, and a good reproduction signal contrast ratio of 0.65 was obtained.

Example 5 A diethylene glycol dimethyl ether solution of a styrene-vinylpyridine copolymer in which Pd fine particles of 20 OA41 were dispersed was applied onto the heat insulating layer, and a laser beam of 01μ was produced in the same manner as in Example 1 except for the laser light absorption layer. It was used as an absorbent layer.

Recording and reproduction were performed using the same recording and reproduction apparatus as in Example 1, and a good reproduction signal contrast ratio of 0.7 was obtained.

Example 6 A dispersion liquid having the following composition was applied onto the heat insulating layer, except for the laser light absorbing layer, which was manufactured in the same manner as in Example 1.

[Dispersion liquid composition for laser light absorption layer]

A composition comprising glass beads having the above weight ratio of 10
After being dispersed for a minute, it was coated to a dry film thickness of 0.2 μm.

Recording and reproduction were performed using the same recording and reproduction apparatus as in Example 1, and a good reproduction signal contrast ratio of 0.60 was obtained.

Example 7 A recording medium was manufactured in the same manner as in Example 6 except that the composition of the coating liquid for the laser light absorption layer was changed as shown below.

(Dispersion liquid composition for laser light absorption layer) After dispersing for 5 minutes, the coating was applied so that the dry film thickness was 0.2μ.

Recording and reproduction were carried out using the same recording and reproduction apparatus as in Example 1, and a good reproduced signal weight loss ratio of 0.65 was obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an enlarged cross-sectional view showing an embodiment of an optical information recording medium according to the present invention, and FIG. 2 is an enlarged cross-sectional view of the recorded medium. In the figure, 1 is a substrate, 2 is a reflective layer, 3 is a light-transmissive thermal insulation layer,
Reference numeral 4 indicates a laser light absorption layer, 5 indicates a recorded pit, and 6 indicates an unrecorded sickle portion surface. Figure 1 Figure 2

Claims (6)

[Claims] (1) A thermal insulating layer that transmits both laser beams is provided between a layer that reflects the p+ raw laser beam and a laser beam absorption layer that crosses the reflective layer and highly absorbs the recording laser beam. An optical information recording medium characterized in that the laser light absorption layer contains at least a colored substance and a polymer compound that convert recording laser light into heat. (2) The optical information recording medium according to claim 1, wherein the colored substance is colloidal metal fine particles. (3) The optical information recording medium according to claim 1, wherein the colored substance is a carbon blank. (4) The optical information recording medium according to claim 1, wherein the fi color substance is graphite. (5) The optical information recording medium according to claim 1, wherein the polymer compound is a thermoplastic resin. (6) The optical information recording medium according to claim 1, wherein the polymer compound is a self-oxidizing compound.