JPS62280082A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To provide an optical information recording medium having high sensitivity and reliability, by providing a recording layer comprising pressure- sensitive microcapsules containing a fluorescent substance coated with a shell comprising a substance for optically hiding the fluorescent substance. CONSTITUTION:A recording layer 7 in which pressure-sensitive microcapsules 3 containing a fluorescent substance coated with a film comprising a substance for optically hiding the fluorescent fubstance are dispersed in a binder layer 2 is provided on a base 1. The fluorescent substance may be fluoroscein, eosine or the like. The substance forming the shells of the pressure-sensitive microcapsules and optically hiding the fluorescent substance may be a copolymer of gelatine and an anionic high molecular weight compount. When this optical information recording medium is irradiated with laser light 8, the light is absorbed by a light-absorbing component in the binder layer 2 with the result of generation of heat, whereby an evaporable or expandable component in the recording layer is evaporated or expanded to generate a pressure, which breaks the microcapsules at an irradiated part 6, and optical characteristic at the irradiated part is changed, thereby achieving recording.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an optical information recording medium, and is particularly suitable for a portable information recording medium such as a cash cart, credit card, or IC card. The present invention also relates to an optical information recording medium on which recording and reproduction are performed optically.

[Prior Art] Conventionally, as a portable information recording medium, a system in which information is magnetically recorded and reproduced, such as a cash card or a credit card, is generally used.

However, in a system in which information is optically recorded and reproduced using a laser beam or the like, information density per same area can easily be achieved several thousand times as much as in the conventional magnetic recording system.

That is, by optically recording information on the area of a conventional information card, it is possible to add a storage capacity of several megabytes, and as a result, the range of application and form of the information card can be expanded.

On the other hand, in comparison with IC cards, optical information recording media
The advantage is that it can be supplied at a lower cost than a built-in IC card.

However, in conventional optical information recording media, metal is often vacuum-deposited as a light-reflecting layer. For example, JP-A-58-15
4087, JP 56-154086, JP 57-109E196, JP 58-820
Examples described in JP-A No. 93, JP-A-58-82094, and the like are optical information recording media of a type in which a metal such as Te is vacuum-deposited. This vacuum deposition method is difficult to perform continuously, is not suitable for mass production, and is expensive.

Furthermore, in conventional optical information recording media, organic dyes or sublimable dyes are often coated on the recording layer to form pits in the light irradiated areas; for example, as described in JP-A-59-82645, Although there are examples, these methods have poor sensitivity during writing and require a high-output laser, making them unsuitable for writing with low-output lasers such as semiconductor lasers.

Furthermore, in the above example, the laser irradiated area becomes heated to a temperature higher than the melting point, and while a portion of it evaporates, the majority moves to the periphery of the pit due to surface tension, causing a phenomenon in which the edge also rises, which causes an increase in the S/N during playback. This caused the ratio value to deteriorate and reliability to deteriorate. This phenomenon occurs because the melted recording layer cannot escape to the substrate surface side.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned drawbacks of the prior art, and uses a recording layer containing pressure-sensitive microcapsules containing a fluorescent substance to produce semiconductor lasers etc. with high sensitivity. The object of the present invention is to provide a highly reliable optical information recording medium that can perform recording using a low-output laser, and does not form pits in the laser irradiated area during recording.

[Means for solving the problem] and [effect], that is,
The present invention is an optical information recording medium characterized by having a recording layer containing pressure-sensitive microcapsules that encapsulate a fluorescent substance and are covered with a shell made of a substance that optically hides the fluorescent substance.

The present invention will be explained in detail below.

FIG. 1 is a sectional view showing one example of a typical configuration of the optical information recording medium of the present invention. In FIG. 1, the optical information recording medium of the present invention includes pressure-sensitive microcapsules 3 that contain a fluorescent substance and are coated with a film made of a substance that optically hides the fluorescent substance, dispersed in a binder layer 2. A recording layer 7 containing the following materials is provided on the substrate 1.

FIG. 2 is a sectional view showing another example of the optical information recording medium of the present invention, in which a recording layer 7 formed by forming a film containing pressure-sensitive microcapsules 3 on the binder layer 2 is placed between A subbing layer 4 is provided on the substrate 1, and a protective layer 5 is provided as the outermost layer on the L of the recording layer 7.

As described above, in the optical information recording medium of the present invention, the recording layer contains pressure-sensitive microcapsules, and specifically, the pressure-sensitive microcapsules absorb light energy by light irradiation and evaporate or expand. The light-absorbing component may be dispersed in a single layer of binder together with the light-absorbing component, or it may be constructed by laminating a single layer of binder containing the light-absorbing component and a film containing pressure-sensitive microcapsules.

The fluorescent substance used in the present invention is not particularly limited, and ordinary fluorescent substances can be used, such as fluorescein, eosin, and the like.

As the material for the substance that optically hides the fluorescent substance forming the shell of the pressure-sensitive microcapsules used in the present invention, materials conventionally used for non-carbon paper etc. can be used, such as gelatin and anion. It is also possible to use a copolymer of polymers. Suitable anionic polymers include carboxymethyl cellulose, polyacrylic acid, methyl vinyl ether, maleic anhydride, and the like.

In addition to the above copolymers, sodium alginate, polyvinyl alcohol, low melting point alloys (e.g. 50% Bi, 2
5%Pb, 12.5%Sn, 12.5%Cd, etc.),
Wax, egg albumin, epoxy resin, etc. can also be used.

In the present invention, the methods of covering and encapsulating the fluorescent substance with a shell to form microcapsules include commonly used interfacial polymerization methods, in situ polymerization methods,
Any method such as an in-liquid curing coating method, a coacervation method, or a condensation polymerization reaction method on the surface of emulsion particles may be used.

For example, in the interfacial polymerization method, a reactant, which is separately added to each liquid, is condensed at the interface of two mutually incompatible liquids to form a polymer film that is insoluble in both liquids at the interface to form a capsule shell. This is the way to make it.

Furthermore, the encapsulation method using in-situ polymerization is a method in which a reactant is supplied from either the inside or outside of the core material to form a polymer shell around the core material.

As can be seen from the above method, the method of microencapsulation can be determined by taking into account the compatibility of the substance forming the capsule shell and the encapsulating substance, the type of carrier layer of the microcapsule, and the like. Furthermore, the outer surface of the microcapsules can be coated with a film of silica or the like.

In the present invention, the heat-absorbing component that is contained in the recording layer and has the function of absorbing light energy irradiated during recording and converting it into thermal energy, and that evaporates or expands itself due to the heat, is an optical recording layer. Examples include light-absorbing substances such as dyes and pigments that have absorption characteristics at the wavelength of the recording beam during recording, and these light-absorbing substances are used by being dispersed in a binder.

The light-absorbing substances include (1) low melting point metals such as Te, Bi, Sn, Sb, and In, and Au.

Metal particles such as Ag and Cu, (2) cyanine-based, squalium-based, phthalocyanine-based, tetradehydrocholine-based, methine-based, naphtoquine-based,
dyes and pigments such as polymethine, (3) organometallic complexes such as benzenedithiol nickel complexes, (4) black dyes and pigments such as nigrosine and carbon black, (5) black toner used in copiers, and magnetite (
Inorganic compounds such as FeO) can be preferably used.

In addition, examples of the binder that dissolves or disperses these light-absorbing substances and/or pressure-sensitive microcapsules to form a binder layer include vinyl-based binders such as polyvinyl chloride, polyvinyl alcohol, and polyvinyl acetate, polyethylene,
Organic polymers made of resins such as olefins such as polypropylene, acrylics such as polymethyl methacrylate and polymethyl acrylate, polyesters, polyamides, polystyrenes, celluloses, polycarbonates, and ionomers, and copolymers and mixtures thereof. Examples include molecular substances, organic carboxylic acids such as stearic acid, valmitic acid, phthalic acid, and succinic acid, and solid paraffin.

The thickness of the recording layer configured in this way ranges from several tens of A to several meters/+
a, preferably 700 A to 1.8 m/m.

In the present invention, when the recording layer 7 is provided on the substrate 1, a layer of a binder containing pressure-sensitive microcapsules, or a layer of binder and a film of pressure-sensitive microcapsules are sequentially applied onto the substrate 1 to form the recording layer. Alternatively, the recording layer may be provided via an adhesive layer such as a dry laminating agent.

In the present invention, a protective layer 5 can be provided as shown in FIG. 2, and the protective layer 5 provides mechanical, chemical, and physical environment resistance to the recording layer, and is used for recording and reproduction. The recording layer 7 is coated with a material transparent to light.

For example, a glass plate, a ceramic plate, a plastic plate such as polymethyl methacrylate, polycarbonate, vinyl chloride, polyethylene terephthalate, polystyrene, CR-39, or polymethylpentene is provided on the recording layer via an adhesive layer as necessary.

In another example, the plastic materials described above are coated directly onto the optical recording layer and cured to form a protective layer. In this case, one option is to use a radiation-curable resin.

To explain the method of recording information on the optical information recording medium of the present invention, when a laser beam 8 is irradiated as shown in FIG. 3, it is absorbed by the light absorbing component contained in the binder layer 2 and heat is generated. Recording can be performed by destroying the pressure-sensitive microcapsules in the irradiated area 6 with the pressure generated by evaporating or expanding the evaporation component or expansion component in the recording layer, thereby changing the optical characteristics of the irradiated area.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 After dissolving fluorescein Ig and terephthaloyl chloride tg in 100mp of monochlorobenzene, this solution was emulsified and dispersed in 250+*j) of sodium bicarbonate,
Furthermore, add 50 mj of diethylene glycol to give 1
The mixture was stirred continuously for hours.

Next, the above suspension was centrifuged at 1500 rpm for 30 seconds, and the generated microcapsules were collected.

On the other hand, a solution in which carbon black was added and dispersed in a 15% acetone solution of nitrocellulose was prepared with thickness], Oam, vertical 5c11, horizontal 8c.
The film was coated on a polycarbonate substrate No. 11 (manufactured by Teijin ■, trade name: Panlite) using a spinner so that the dry film thickness was 51 zm.

Next, on this nitrocellulose-carbon layer, the microcapsules were coated to a thickness of IIL by a casting method,
Furthermore, a polycarbonate film layer having a thickness of 0.05 mm was provided as a protective layer on the microcapsule layer.

The optical recording medium created in this way has a wavelength of 816 nm.
Recording was performed using a semiconductor laser.

The recording conditions were as follows: irradiation was performed for 0.1 m5 ec with a power of 3 mW on the recording surface and a diameter of 3 μm.

When the reflectance was measured using the same laser at a power of 0.31, the reflectance of the recorded portion was 32% and the reflectance of the non-recorded portion was 3.5%.

Example 2 Basic Red L (manufactured by Sumitomo Chemical, trade name Rhodamine 6)
GCP) 10g and sodium polyacrylate 0.5g
was added to 30ml of pure water and dispersed under strong stirring conditions, and a 2.5% by weight aluminum sulfate aqueous solution Log
was added and stirred for 1 hour. This dispersion was passed through with pure water.
0mj), further added 150mf of 40% by weight sodium silicate aqueous solution to this pigment dispersion, filtered,
I did the cleaning.

The pH of the aqueous solution is IN NaOH aqueous solution, pl=1
0, heated to 90 °C, then added 3 wt% sulfuric acid 401 and 30 wt% sodium silicate 40 mB to the above pigment dispersion at the same time, and reacted at 90 °C for about 1 hour to encapsulate. A pigment coated with silica was produced.

The microcapsules were separated in a furnace and dispersed in a 30% methanol solution of cellulose triacetate, and 172 amounts of solvent black of cellulose triacetate were further dispersed therein.

The microcapsule dispersion liquid was coated with a bar code on a polymethyl methacrylate substrate having a thickness of 1.2 m+s and measuring 5 cm in the vertical direction and 8 cm in the horizontal direction. The film thickness when dried was 8 μm.

The optical recording medium created in this way has a wavelength of 830 nm.
Recording was performed using a semiconductor laser.

The recording conditions were 10mW on the recording surface and a beam diameter of 7p.
The irradiation time was 1 m5ec.

When the reflectance was measured using the same laser with a power of 0.5 ■W, the reflectance of the recorded area was 38%, and the reflectance of the non-recorded area was 2.
It was 0%.

[Effects of the Invention] As explained above, by using the optical information recording medium of the present invention, 1) Recording with a low-power laser is possible due to the high sensitivity. To this end, information can be recorded and reproduced using compact recording and reproducing devices that use small light sources such as semiconductor lasers.
It has the following advantages: 2) Reliability of information increases; 3) Low-cost supply becomes possible through mass production.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing one example of a typical configuration of the optical information recording medium of the present invention, FIG. 2 is a cross-sectional view showing another example, and FIG.
The figure is an explanatory diagram showing a method of recording information on an optical information recording medium. l...Substrate 2...Binder single layer 3...
・Pressure sensitive microcapsule

Claims (1)

[Claims] An optical information recording medium comprising a recording layer containing pressure-sensitive microcapsules that encapsulate a fluorescent substance and are covered with a shell made of a substance that optically hides the fluorescent substance.