JPH02139287A - Recording method - Google Patents

Abstract

PURPOSE:To make it possible to record information at high speed and in high density and to preserve the recorded information stably for a long time by a method wherein a recording medium having a recording layer comprising optically anisotropic organic thin film crystals is heated to melt the crystals, and the melted crystals are rapidly cooled to cause a partial change in the crystal state, thereby recording. CONSTITUTION:For example, a recording layer (about 0.8mum thick) comprising thin film form crystals of stearic acid with a substantially uniform orientation is provided on a chromium layer, and a protective layer (about 0.6mum thick) comprising a vinyl chloride-vinyl acetate copolymer is provided thereon to produce a recording medium. While the recording medium is rotated at 900rpm, the medium is irradiated with a semiconductor laser beam of a wavelength of 830 nm condensed to s beam diameter of 1mum, whereby records can be formed in a spiral form. Next, the medium with the records thus formed is scanned with a semiconductor laser beam of a wavelength of 780 nm condensed to a beam diameter of 5mum, which is continuously turned ON to obtain an intensity on the surface of the recording medium of 1.5mW, 2mW and 3mw, at a linear velocity of 50mm/sec and along a straight line so as to overlap with the record parts previously formed. As a result, the recording layer is brought into an erasing temperature range by irradiation at the intensity of 1.5mW, whereby erasing is performed.

Description

[Detailed Description of the Invention] [Industrial Field] The present invention relates to the recording of information by the application of thermal energy and the heat mode recording of information by light irradiation. This invention relates to a reversible recording method.

[Conventional technology]

In recent years, so-called heat mode recording systems have been put into practical use, in which information is applied in the form of thermal energy and recorded as changes in the shape or physical properties of a recording material. Such heat mode recording media include Te, Bi, Ss, Tb,
Inorganic recording media using metal materials mainly composed of In, polymethine dyes such as cyanine, macrocyclic azaannulene dyes such as phthalocyanine, naphthalocyanine, and porphyrin, naphthoquinone, anthraquinone dyes, and dithiol metal complexes. Recording media using organic dyes such as systematic dyes are known. When thermal energy is applied to these recording media, such as by irradiation with focused laser light, the recording layer in the irradiated area melts or evaporates, forming holes (bits) and recording information. However, these recording media do not have the reversibility of erasing recorded information and recording new information again.

With the development of read-only, write-once type heat mode optical recording media as described above, the need for reversible recording media that can be recorded, read, and erased is increasing.

Examples of such reversible recording media include Gd and Tb.

There is a magneto-optical recording medium that uses an alloy thin film made of a rare earth element such as oy and a transition metal such as Fe, Ni, or Co. This uses a combination of heating by laser beam irradiation and an externally applied magnetic field to record, and reproduces data by utilizing the difference in the rotational direction of the light vibration plane depending on the direction of magnetization. Furthermore, information is erased by heating with a laser and by applying an external magnetic field in the opposite direction to that used during recording. However, although this magneto-optical recording medium performs reproduction using polarized light, the sensitivity during reproduction is insufficient because the difference between the recorded and non-recorded areas is small.
The recording layer has disadvantages such as a poor /N ratio and problems such as deterioration of recording sensitivity and recording stability due to the effects of oxidation on the recording layer.

In addition, as reversible recording media, Ge, Te, Ss,
There is one that utilizes the crystal-amorphous phase transition of a recording layer made of a thin film of an inorganic material mainly composed of elements such as Sb, In, and Sn. This recording medium can perform heat mode recording and erasing using only laser light irradiation, and reproduces data based on the difference in reflectance. However, because the difference in reflectance between the recorded and non-recorded areas is small, the readout speed is low. There are still problems with reliability.

On the other hand, JP-A-54-119377, JP-A-55-15419
No. 8, No. 63-39378, and No. 63-41186 disclose thermal recording materials comprising a resin matrix material and an organic low-molecular substance present in the matrix material in a state of fine particle dispersion. When this recording material is heated above a certain temperature and cooled, it becomes cloudy (light-shielding state), and when heated to a certain temperature range and then cooled, it becomes transparent, and recording is performed by reversible changes in this light-shielding property. However, even if the contrast caused by this light-shielding property is clear in the case of a record that is large enough to be seen with the naked eye, microscopically magnifying a recorded area that is made up of changes in several small areas. However, in the recording layer, the light scattering properties change depending on the state of the matrix of the organic low-molecular-weight particles in the recording layer. This is because when the size of the recording area becomes a few voices, the size of these particles is no longer small enough to cause such scattering compared to the size of the recording area. be. In order to compensate for this, it is possible to make the recording layer much thicker than the recording size.
It is substantially difficult to uniformly heat the entire thick recording layer in the thickness direction to form a small recording portion. Therefore, it cannot be applied to a recording medium that performs high-density recording.

In addition, as an erasable recording medium using organic materials,
For example, in JP-A-199343, an organometallic complex bis(
l-ρ-n-alkylphenylbutane-1,3-dionato) (■) and organic polymer mixture, JP-A-63-1579
3 is a mixture of crystalline and non-crystalline thermoplastic resins, JP-A No. 6
3-95993.96748, a crystalline aromatic vinylene sulfide polymer, JP-A-63-279440, a sulfur-containing polymer, JP-A-63-128993, a diazabicyclo(2,2,2)octane quaternary salt, esp. Kaisho 63-25
No. 9851 discloses a recording method using stretched or oriented polymers, crystals of liquid crystalline polymers, amorphous transitions, or changes in the degree of orientation. All of these have slow recording speeds or slow erasing speeds, making them difficult to put into practical use.

[Problem to be solved by the invention]

As described above, recording methods using conventional recording media have various problems such as recording sensitivity, erasing speed, recording stability, and contrast between recorded and non-recorded areas. Furthermore, from the standpoint of safety, it is desirable that the recording medium used be one made of non-toxic materials.

From this point of view, the present invention provides a recording method that uses a recording medium on which information can be recorded, reproduced, and erased, records information at high speed and with high density, and can store information stably for a long period of time.

[Means to solve the problem]

As a result of studying recording on organic compound crystals for the above purposes, the present inventors found that when heat is instantaneously applied to a thin film-like crystal with optical anisotropy, the crystal state partially changes. They also discovered that by reheating to an appropriate temperature, the crystalline state returns to its original state, and that the polarization properties change significantly as a result. The recording method of the present invention is based on such a reversible change in the crystal state.

That is, in the recording method of the present invention, heat is applied to a recording medium having a recording layer made of or containing an organic thin film crystal having optical anisotropy to melt the thin film crystal. It is characterized by recording after partially changing the crystal state by rapid cooling, and also,
The above-mentioned recording medium is composed of a light-to-heat conversion layer that absorbs part or all of the light irradiated during recording and converts it into heat, and an organic thin film-like crystal that has optical anisotropy, or This is a recording method in which a thin film crystal is irradiated with light to melt it and then rapidly cooled to partially change the crystal state for recording.

Further, the present invention is a recording method in which the above-described change in the crystal state due to heat application or light irradiation includes a change in the orientation direction of molecules, and the above-described change in the crystal state includes a partial change in the thin film-like crystal. This is a recording method that involves microcrystallization.

Further, in the recording method of the present invention, the organic thin film crystal having optical anisotropy described above contains a fatty acid or a fatty acid derivative, a benzoic acid derivative, or an n-alkane having a melting point of 50°C or higher or a derivative thereof as a main component. It is something to do.

The recording method of the present invention will be explained in detail below.

The recording medium used in the recording method of the present invention is provided with a recording layer containing an organic thin film crystal having optical anisotropy. Typical materials for making such a recording layer include: Examples include fatty acids or fatty acid derivatives, benzoic acid derivatives, and n-alkanes or derivatives thereof having a melting point of 50°C or higher.

Fatty acids or fatty acid derivatives as used herein are specifically saturated or unsaturated mono- or dicarboxylic acids or their esters, amides, anilides, hydrazides, ureides, anhydrides, or fatty acid salts such as ammonium salts or metal salts. Esters include esters with compounds having two or more hydroxy groups, such as mono-, di- or triglycerides, and these include halogens, hydroxy groups, acyl groups, acyloxy groups, or substituted or unsubstituted These saturated or unsaturated fatty acids, which may be substituted by aryl groups, may be linear or branched; unsaturated fatty acids may have one double or triple bond, or two. You can have more than that. The carbon number of these saturated or unsaturated fatty acids is preferably 10 or more.

Specific examples of saturated fatty acids include undecanoic acid, lauric acid, myristic acid, pentadecanoic acid, valmitic acid, heptadecanate, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, and melisic acid. Examples of unsaturated fatty acids include oleic acid, elaidic acid, and linoleic acid.

These include sorbic acid and stearolic acid. Specific examples of esters include methyl ester, ethyl ester, hexyl ester, octyl ester, and decyl ester of these fatty acids.

Examples include dodecyl ester, tetradecyl ester, stearyl ester, eicosyl ester, and tocosyl ester. Further, examples of metal salts include metal salts of these fatty acids such as sodium, potassium, magnesium, calcium, nickel, cobalt, zinc, cadmium, and aluminum.

Further, the benzoic acid derivative referred to herein specifically includes benzoic acid represented by the following general formula, and its esters, amides, anilides, and the like. 1. In addition to these, salts such as optionally substituted hydrazides, ureidos, anhydrides, metal salts, and ammonium salts are included. In addition to the compound represented by the general formula (II), esters include esters of aliphatic hydrocarbon compounds with polyhydric alcohols or aromatic hydrocarbons having a plurality of hydroxy groups.

Examples of substituents for R1, R,, R1 and other benzoic acid derivatives in the general formula include hydrogen, an alkyl group, an alkoxy group, or an aryl group such as a phenyl group, a biphenyl group, a naphthyl group, and an anthranyl group. , R1
In addition to these, acyl group, acyloxy group, halogen,
Nitro group, hydroxy group, cyano group, carboxyl group and its ester, optionally substituted carbamoyl group, sulfo group and its ester, or alkyl group, phenyl group, amino group optionally substituted with substituted phenyl group, etc. There is. Further, the above alkyl group, alkoxy group, and aryl group may be substituted with the same substituent as R1. In addition, alkyl groups and alkoxy groups may be linear or branched, and if they have two or more carbon atoms, they may contain one or more unsaturated bonds in the carbon chain. good.

In addition, the n-alkane derivatives mentioned here include compounds containing one or more double bonds or triple bonds in the carbon chain, compounds in which one or more hydrogen atoms are substituted with halogen atoms, and terminal It is a compound in which a benzene ring which may be substituted with an alkyl group or an alkoxy group is bonded to the carbon atom. Specifically, n-alkanes include n-alkanes such as tetracosane, pentacosane, hexacosane, pentacosane, octacosane, nonacosane, triacontane, todoriacontane, tetraliacontane, hexatriacontane, octatriacontane, and tetracontane.
There are alkanes or mixtures containing these as main components, so-called paraffins and paraffin waxes. Derivatives include 1-hexacosene, ■-heptacocene, 1-octacosane, 1-triacontin, l-tetratriacontin, ■-hexatriacontin, ■-octatriacontin, 1-tetracontin, tocosylbenzene. , tetracontanzene, hexacosylbenzene, ophtacosylbenzene, triacontylbenzene, tritriacontylbenzene, tetratriacontylbenzene, hexatriacontylbenzene, 1,18-dibromooctadecane, l,20-di Examples include bromoeicosane and 1,22-dibromotocosane.

The recording layer material used preferably has a melting point of 50 to 20
A temperature in the range of 0°C, particularly 60 to 150°C is preferred.

If it is lower than this, there will be a problem with the storage stability of recording, and if it is higher than this, the energy required for recording will be large and the recording speed will be slow.

In the recording layer of the recording medium used in the present invention, one type or a mixture of two or more of these organic compounds can be used. Further, the recording layer used in the present invention contains thin film-like crystals containing these organic compounds as main components, but resins other than this can be used as necessary to form the layer. Examples of the resin include polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-acrylate copolymer. , polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, polyester, polyamide, polyacrylate, polymethacrylate, polycarbonate,
Examples include polyurethane and silicone resin. When a resin is used in the recording layer, the weight ratio of the resin to the organic compound 1 in the entire recording layer is preferably 3 or less, particularly 1 or less.

Examples of the substrate of the recording medium used in the present invention include glass plates, metal plates, and plastic plates such as polymethyl methacrylate and polycarbonate.

However, if the information is to be read using transmitted light after recording, it is necessary to use a substrate that transmits the reproducing light.

When reading by reflected light, a layer of metal or metalloid such as platinum, titanium, silicon, chromium, nickel, germanium, aluminum or the like is provided as necessary to serve as a reflective layer that reflects a portion of the light.

In the recording method of the present invention, recording is performed by applying thermal energy to the recording layer of the recording medium according to the information to be recorded. It is necessary to provide a layer that absorbs a portion of the emitted light and convert it into heat, or to include a substance in the recording layer that absorbs light and converts it into heat. This light-absorbing layer is made of, for example, platinum or titanium, similar to the reflective layer.

A layer of metal or semimetal such as silicon, chromium, nickel, germanium, or aluminum may be provided, and in this case, it can also be used as a reflective layer. The light absorption layer is a pigment that absorbs the irradiated light.

For example, azo dyes, cyanine dyes, naphthoquinone dyes, anthraquinone dyes, squarylium dyes,
It may be a layer containing phthalocyanine dyes, naphthoquinone dyes, porphyrin dyes, indigo dyes, dithiol complex dyes, azulenium dyes, quinoneimine dyes, quinonediimine dyes, etc., and the dye has a wavelength of light used for recording. Select by. These dyes are also used when a light-absorbing substance is included in the recording layer.

The recording medium used in the present invention is an organic thin film crystal having optical anisotropy, or has a recording layer containing the same, and although its composition is not specified, it is commonly used. Examples of configurations of recording media that can be used are shown in FIGS. 1 to 5.

FIG. 1 shows a recording medium in which a recording layer 2 that is or includes an organic thin film crystal having optical anisotropy is formed on a substrate 1, and FIG. 2 shows a portion of light irradiated onto the substrate 1. A light absorption layer 3 (a layer that reflects part of the light if necessary) is provided, which absorbs some of the light and converts it into heat, and on the light absorption layer 3 is formed an organic thin film-like crystal having optical anisotropy or contains the same. A recording medium with a recording layer 2 provided thereon, FIG. 3 shows a recording medium with a recording layer 2 provided on a substrate 1 and a light absorption layer 3 thereon, and FIG. 4 shows the light absorption of the recording medium shown in FIG. A recording medium in which an undercoat layer 4 is provided between M3 and the recording layer 2 for the purpose of improving the film quality of the recording layer, for example. This is a recording medium provided with a protective layer 5.

For the undercoat layer 4, various resins can be used, such as the resins that may be used when forming the recording layer 2 described above. In addition, these resins may be used for the protective layer 5 as well, or
Alternatively, a glass plate may be used. When using a glass plate, a similar resin layer may be provided on the surface (the surface in contact with the th1 layer) for the same purpose as the undercoat layer, or a surface treatment agent to improve the properties of the glass surface, such as silane. It may be treated with a titanate-based or titanate-based surface treatment agent.

In order to manufacture the recording medium used in the present invention, the above-mentioned substrate]
If necessary, a photothermal conversion layer 3 is formed thereon using, for example, a metal or a metalloid as described above, by vapor deposition, sputtering, plating, or the like, and the recording layer 2 is formed thereon.

For example, there are the following methods for forming the recording layer 2. First, a glass plate or resin film corresponding to the protective layer 5 is placed over the substrate provided with the photothermal conversion layer 3, keeping a gap corresponding to the required thickness of the recording layer. To create a gap, a spacer layer may be provided around the area where the recording layer will be formed, or a gap material having a minute and uniform diameter, such as silica particles or polystyrene beads, may be placed in advance on the side of the light-to-heat conversion layer. Alternatively, it may be attached to the protective layer side. The entire substrate with the gap formed in this way is placed in a constant temperature bath or placed on a hot plate and kept at a temperature higher than the melting point of the material used for the recording layer, and the molten material is placed at the end of the gap and soaked between the gaps. let them get involved. When the obtained melt layer is slowly cooled and crystallized, a thin film-like crystal of the recording layer can be formed between the light-to-heat conversion layer 3 and the protective layer 5. At this time, in order to maintain the gap distance constant, pressure may be applied with a single weight until crystallization, or it may be carried out under reduced pressure to prevent air bubbles from entering. For example, the material for forming the recording layer is dissolved in a suitable organic solvent such as tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone, chloroform, carbon tetrachloride, etc., and the material is coated by a spin code method, a blade coat method, a dip coat method, etc. A layer of uniform thickness is formed on the photothermal conversion layer 3 by drying or by vapor deposition. If necessary, a resin dissolved in an appropriate solvent is applied onto this. 6 Next, this is placed in a constant temperature bath or placed on a hot plate and heated to a temperature equal to or higher than the melting point of the material of the recording layer. Thereafter, it is slowly cooled to crystallize and form a thin film crystal of the recording layer.

In addition to this, various methods such as the Langmuir-Prodgett method can be used to form the recording layer.

When a photothermal conversion substance is included in the recording layer, the dye may be simultaneously dissolved in a solution of the material of the recording layer, or dispersed and applied.

The thickness of the recording layer is not particularly limited, but is usually 10
The number of participants is from 10 to 14 people, preferably from 10 to 5.

The thickness of the layer that absorbs part of the irradiated light and converts it into heat is
The appropriate range is determined by the wavelength and intensity of the light used for recording and the type of material used, but it is approximately 50 people to 511 seconds.

The recording method of the present invention utilizes a partial and reversible change in the crystal state of an organic thin film crystal having optical anisotropy. Recording and erasing information is performed by applying heat, and there are various methods of applying heat.
In order to record information at a higher density, the most preferable method is to use focused laser light irradiation. In this case, the recording medium must have a layer that absorbs light and converts it into heat, or a layer that absorbs light and converts it into heat. It is necessary to add a substance to the recording layer that converts heat into heat.

Information is recorded as follows. The part of the recording layer irradiated with the laser beam is a light-absorbing layer or a light-absorbing substance that absorbs light and generates heat, and the recording layer that is made of or contains an organic thin film-like crystal with optical anisotropy instantly generates heat. It is heated, and when the laser beam irradiation stops, it is rapidly cooled, and a recording pit (bit here does not mean a hole or a depression, but a part recorded as a change in crystal state in a thin film crystal) is formed. (called pits) are formed.

At this time, in the recording layer, a part of the thin film crystal, that is, a part that is instantly heated by the heat transmitted from the light absorption layer (substance) generated by short-term laser beam irradiation, completely melts the crystal. reach the temperature. However, when the laser light irradiation stops, the heat diffuses, and this part is instantly cooled and assimilated (crystallized). The crystalline state of the portion where heat melting and cooling crystallization occurs instantaneously in this manner is different from the crystalline state of the portion to which no heat is applied, that is, the crystalline state of the surrounding non-recording portion.

This change in crystal state includes, for example, (1) a change in the size and form of crystal grains, (2) a change in the direction of crystal axes or the orientation of molecules, and (3) a change in crystal structure.

Before recording is performed, the recording layer is composed of thin film-like crystals that are oriented in approximately the same direction as a whole and have a uniform thickness. Among these changes, (1) a change in the size and form of crystal grains is such that, for example, a recording portion in a thin film crystal becomes a collection of small divided crystals. This change in state can be confirmed by observing the peeled recording layer using, for example, a scanning electron microscope. In addition, the change in the crystal axis direction or the molecular orientation direction in (2) means, for example, that the crystal structure is basically the same, but the direction in which the crystal is oriented, that is, the direction of the crystal axis, is crystallized in a different direction. Or, although it is not as clear as this, it is basically a collection of molecules with some kind of orientation, and the overall orientation direction is different from that of the surrounding non-recording area.

In addition, the change in crystal structure in (3) refers to the crystallization of the recording area to a different crystalline state from the surrounding non-recording area. It also includes cases where the range of properties is very narrow and the amorphous state changes by one degree.

These changes in the crystal state are caused by the rapid cooling from the molten state caused by the local application of short-term heat to the thin film crystal, that is, by short-term light irradiation, but the cooling rate is mainly due to Depends on the time of light irradiation. Since it is difficult to measure temperature changes in minute areas irradiated with focused laser light, we consider the intensity distribution of the laser light, light absorption and heat conduction, and measure the thickness of each layer, light absorption characteristics, and If the thermal properties such as conductivity and specific heat are shown in Table 1, and the temperature change of the recording layer is simulated, for example, from 80°C to 6°C.
The time required to cool down to 0°C is the irradiation time of 10
At 0 μsec, it is approximately 1.7 μsec, and the irradiation time is 0.25
In μsec, it is about 15 nssc, and the difference in cooling rate is very large. Therefore, changes in the crystalline state caused by short-term light irradiation (heat application) also change depending on the irradiation time and are not constant. For example, in microcrystalization, it is observed that the faster the cooling rate, the more fine the crystalline state becomes. It is also related to the state of molecular orientation; the faster the cooling rate, the more disordered orientation tends to occur, and the range in which the molecules are regularly arranged becomes narrower, resulting in a state of low crystallinity. . However, even under such conditions, some kind of orientation state exists at least partially, and in the recording method of the present invention, the orientation of this recording area is characterized by being different from the orientation direction of the surrounding non-recording area. . Changes in the orientation direction due to such recording can be confirmed, for example, by measuring Xa diffraction of the recording layer. Furthermore, the changes in the crystal state (1), (2), and (3) that occur due to recording occur in combination rather than individually. In addition, the temperature and cooling rate of the melted portion of the recording layer that is irradiated with laser light varies greatly depending on the distance from the photothermal conversion layer and the distance from the center of the beam, and each location has different conditions. Because crystallization occurs, a --like state is not necessarily achieved. therefore,
The changes in the crystalline states (1), (2), and (3) occur in a variety of combinations depending on the position even within one recording section.

Table 1 In order to explain in more detail the changes in the crystalline state caused by such recording, we show the case where stearic acid, a typical fatty acid, is used as the recording layer material. Recording layer made of thin film crystals of stearic acid (substrate Nigarasu).

The crystal state of the photothermal conversion layer nichrome vapor-deposited film, protection M: vinyl chloride-vinyl acetate copolymer) before recording is a C-type crystal of stearic acid, with its a-axis and b-axis oriented almost parallel to the substrate. ing. This is the X-ray diffraction diagram of this recording layer (Fig. 6), which shows the long distance between stearic acid C type crystals (39, 8
(however, 5n=:2,3,4,5
, 7, 8, 9, 10.12) are recognized. On the other hand, a semiconductor laser beam with a wavelength of 830 nm and a beam diameter of lμlφ was applied to this aN at a linear velocity of 3500 to 400.
0am/see, continuous lighting at an intensity of 51 on the media surface,
In the xg diffraction diagram (Fig. 7) measured after recording the entire surface in a spiral manner without taking any intervals between recording lines, in addition to the diffraction lines of stearic acid C-type long plane spacing that appeared before recording, new A clear diffraction line appears at 21.6°. This diffraction line is due to the short plane spacing (4, 11) of the C-type crystal, which means that the a-axis and b-axis were oriented almost parallel to the substrate when unrecorded, but the laser beam After irradiation, the orientation direction of the crystal changes, at least partially
This shows that a structure was formed with the axis oriented parallel to the substrate.

The recorded state can be confirmed using optical observation means such as an iR microscope or a polarizing microscope. In particular, such changes in the crystal state are often accompanied by changes in polarization characteristics, which can often be clearly observed as contrast between light and dark or differences in color under crossed Nicol conditions using a polarizing microscope, and therefore cannot be recorded. To reproduce (read) the information, the focused polarized light is incident on the recording medium, and the reflected or transmitted light is transmitted through a polarizer placed so as to transmit the light in the vibration direction perpendicular to the vibration direction of the incident light. through,
This can be done by detecting the intensity of light. The intensity of the light used for reproduction is made sufficiently weaker than the light used for recording and erasing, so that the temperature of the recording layer does not rise to the erasing temperature.

In this way, information recorded as a change in the crystal state by applying heat to a part of the optically anisotropic organic thin film crystal in the recording layer and instantaneously melting and recrystallizing it is transferred to the recording layer. is lower than the recording temperature, and the recording layer does not completely melt, but it can be erased by heating to a temperature at which the molecules can undergo sufficient thermal movement.

The temperature range in which erasing is possible varies depending on the material, purity, etc. of the recording layer, but exists at a temperature lower than the melting point of the thin film crystal forming the recording layer. The manner in which this record is erased can be confirmed by increasing the temperature of the recording layer while observing it with a polarizing microscope. With a polarizing microscope, the recorded area looks like a dark line inside a bright non-recorded area, but as the temperature is increased, the line starts to disappear at a certain temperature and eventually becomes the entire non-recorded area. The record will be erased if it is cooled from this temperature.

At this erasing temperature, there is no change in the brightness of the non-recorded area, but if the temperature is raised further up to the melting point of the recording layer, the entire visual field becomes completely dark. Therefore, when the molecules of the minute recording part formed in the thin film-like crystal with a changed crystal state reach a state where they can undergo sufficient thermal movement, they will take on the same arrangement as the molecules of the surrounding non-recording part. When the temperature returns to room temperature, the entire surface becomes a --like thin film crystal and is erased.

Specifically, recording can be erased by heating the entire recording medium to the above temperature range and cooling it, or by locally erasing the recorded pit area or a slightly wider area. By heating and cooling to the erasing temperature,
It is also possible to erase only part of the recorded information. In the latter case, the intensity of the laser beam irradiated during recording may be weakened, the temperature of the recorded pit portion may be adjusted to fall within the erasing temperature range, and irradiation may be repeated. At this time, the recording pit part (the part where the crystal state has changed) of the thin film crystal of the recording layer is once heated to the erasing temperature, and when it is cooled, the crystal state becomes the same crystal as the surrounding non-recording part. The state returns and the recorded pits are erased. This erased state, like the recorded state, can be detected by optical li! such as a microscope or a polarizing microscope. l! This can be recognized as a means of detection.

The recording method of the present invention basically does not use heat to make holes in the recording layer or change the surface shape of the recording layer, but rather to use the thin film-like crystals forming the recording layer or the thin film contained in the recording layer. The crystalline state of a crystalline crystal is partially changed, and the change is not simply a change from crystalline to amorphous, but is recorded as a change that includes a change in the orientation direction of molecules and partial microcrystalization. The difference between the formed recorded portion and non-recorded portion is detected as a difference in polarization characteristics based on optical anisotropy. In this respect, the recording medium used in the present invention is significantly different from conventional recording media. For example, this is based on a completely different phenomenon from the recording medium described in the prior art section in which an organic low-molecular compound is present in a dispersed state in a resin matrix and the light-shielding property changes depending on the heating temperature. That is, in the recording medium of this example, the organic low-molecular-weight compound exists in the form of fine particles in the recording layer, and the recording section itself is also formed by a large number of fine particles, and the recording is caused by differences in light shielding properties due to the scattering of light due to the dispersed state of the fine particles. In contrast, in the recording method of the present invention, the organic compound exists as a thin film crystal, and the recording is formed as a change in the crystal state in a part of this thin film crystal, and the resulting difference in optical properties is detected. It is something to detect. therefore,
The difference between the two is obvious.

〔Effect of the invention〕

The recording method of the present invention is basically carried out by heating the optically anisotropic organic thin film crystal that forms the recording layer to a temperature higher than its melting temperature, and erasing is performed by heating it to a lower temperature. It is done by Therefore, the intensity of the emitted laser light! llj! Since recording and erasing can be performed at high speed with the i5, so-called override (overwriting), in which recording is performed while erasing, is possible. Further, this recording and erasing can be performed repeatedly and stably. Furthermore, since the recording section is in the same stable state as the non-recording section, recorded information can be stored stably for a long period of time.

〔Example〕

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

Example 1 A chromium layer serving as a light reflecting layer and a light-to-heat converting layer was provided by vacuum deposition on an optically polished glass disk having a diameter of 4 inches (101.6 am) and a thickness of L, 2+ am. There were about 900 people. On this chrome layer,
Vinyl chloride-vinegar is a vinyl copolymer (manufactured by Union Carbide Co., Ltd.: VYl (H)) coated with a 5vt% tetrahydrofuran solution and dried to form a resin layer with a thickness of about 0.2 pm. A 10 wt% tetrahydrofuran solution of stearic acid (manufactured by Sigma, purity 99% or higher) was applied on top and dried at 45°C.Furthermore, a 5 wt% tetrahydrofuran solution of the same vinyl chloride-vinyl acetate copolymer as above was applied on top. The disc was coated and dried at 45°C.The disk was heat treated at 90°C for about 2 minutes, and then slowly cooled to form a thin film of stearic acid crystals with almost -like orientation on the chromium layer. Recording layer (thickness approx. 0.8.)
A protection layer 71 (about 0.6 μm in thickness) made of vinyl chloride-vinyl acetate copolymer was formed thereon.

While rotating the recording medium thus produced at 90 ORPM, it was irradiated with semiconductor laser light of a wavelength of 830 nm focused on a diameter of 1 - under the following conditions (1) and (2), resulting in a spiral-shaped ? 2 records were formed. At this time, the linear velocity in the recording direction of the recorded portion on the disk is approximately 35
00-4000mm/see.

Irradiation conditions (1) Lighting conditions: Frequency 200 KHz, duty ratio 50% Intensity on recording medium surface: 5 mW Recording line spacing: Approximately 3.5. (Center to center) (2) Lighting conditions: Continuous lighting Intensity on recording medium surface: 5 mV Recording line spacing: Approximately lpm (Center to center) The recording medium irradiated with laser light under the conditions of (1) above was examined using a reflective polarizing microscope. When observing wA in the crossed Nicols state, it was observed with clear contrast that a supplementary 1 μm line-shaped recording portion was formed in the laser beam irradiated portion of the recording layer. However, this recorded portion could hardly be confirmed by ordinary optical microscopy. An example observed with a polarizing microscope is shown as a photograph in FIG.

The recording layer of the recorded recording medium is peeled off from the chromium layer,
When the surface (the surface that was in contact with the chromium layer) was observed using a scanning electron microscope, the laser beam irradiated area was a collection of small plate-shaped crystals.

When the recording medium irradiated with the laser beam under the conditions (2) above was similarly observed using a polarizing microscope, it was found that recording was performed over the entire irradiated area of the recording medium with almost no gaps. For the recording medium on which this entire surface recording was performed, X-ray diffraction of the same portion before and after recording was performed at fl19.
Established. The X-ray diffraction before recording is shown in FIG. 6, and the X-ray diffraction after recording is shown in FIG. From Figure 6, before recording, only the diffraction lines based on the long-plane spacing of the C-type crystals of stearic acid were observed, and a
, had a structure in which the b axes were oriented in parallel. However, after recording in Figure 7, the diffraction line (2θ=2
1.6°) appears, indicating that a structure in which the C axis is oriented parallel to the substrate is formed in the recording portion of the recording layer.

Next, with respect to the recording medium recorded under the conditions (1), the temperature of the recording medium was raised from room temperature at a rate of 1'C/min while performing TiftIiA using a polarizing microscope. Then, the recorded area, which had been visible with clear contrast, began to disappear at around 60 degrees Celsius, and at about 68 degrees Celsius, it became completely as bright as the surrounding area and disappeared. Moreover, no change was observed in the state of the surrounding non-recording area up to this temperature. If the temperature continues to rise further, the temperature will reach 69.4℃, and it will become completely dark from one end of the field of view.
It was found that the crystal thin film of the recording layer was completely melted at this temperature, as it quickly spread throughout the area.

Next, on the recording medium recorded under the conditions (1), a semiconductor laser beam with a wavelength of 780 nm focused to a diameter of 5 μ4 was applied at intensities of 1, 5 mV, 2 mV, and 3+a on the recording medium surface.
It was turned on continuously so as to be V, and was scanned linearly at a linear velocity of 50+am/see so as to overlap the previous recorded part. When this recording medium was observed with a polarizing microscope, as shown in the photograph in Figure 9, the irradiation intensity was too strong in the area irradiated with 2IIIv and 3mv intensities, so thin film crystals were observed in the center of the beam. The temperature rose above the melting temperature, and a new line-shaped record was formed. However, in the edge portion of this line, that is, in the portion scanned by the peripheral portion of the beam, the recorded portion previously recorded by the 1/JIIIφ laser beam was erased. on the other hand.

In the area irradiated with an intensity of 1.5+aV, the area recorded by the previous laser beam of 1 φ was erased in a band shape with a width of about 2.574 mm. From the above results, strength 1, 5
It was confirmed that the recording layer entered the erasing temperature range with mW irradiation and erasing was performed.

Example 2 A glass disk having a chromium layer as a light-to-heat conversion layer was prepared in the same manner as that used in Example 1.

Further, a small amount of silica particles having a diameter of about 1-1 mm was attached as a gap material to one side of a glass plate having a thickness of 0.1 m @ to serve as a protective layer. After heating both of these in a constant temperature bath at 100℃, a small amount of behenic acid (manufactured by Sigma, purity 99% or more) was placed on the chromium layer of the glass disk at the same temperature and melted. Gently place the plate over the behenic acid melt from one end with the side with the gap material facing down, spread the melt over the entire surface, sandwich it, and then apply a uniform load from above the covered glass plate. Then, the temperature of the constant temperature bath was slowly lowered, and the behenic acid was crystallized into a thin film of crystals. By the above operations, a recording layer (about 0.8 mm thick) consisting of thin film-like crystals of behenic acid with an approximately -like orientation is formed on the chromium layer, and a recording layer (about 0.8 mm thick) consisting of glass with a thickness of 0.1 m is formed on the chromium layer. A protective layer has been formed.

The recording medium created in this way is rotated at 90 ORPM, and a semiconductor laser beam with a wavelength of 830 nm focused to one tone in diameter is applied to it at a linear velocity of 3500 to 4000 + am/see.
It was irradiated in a spiral manner. The irradiation conditions at this time were two conditions (1) and (2) as in Example 1. However, in (1), the irradiation intensity is 3, 4, 5, 6,
8,10.12ml 1l, (2) te was 8Illv toshi.

The state of the recording recorded under irradiation condition (1) was recorded in the crossed Nicols state using a reflective polarizing microscope. When I guess.

It was confirmed with clear contrast that recording was made at an intensity of 4 mW or more in the laser beam irradiated portion of the recording layer.

Furthermore, as the intensity of the irradiated laser beam increases, the width of the recorded portion, that is, the portion where the crystal state has changed due to melt recrystallization, becomes wider, and in 4I, the width is about 0.4. n, 1
At 2 mV, it was about 1.8 pm.

When observing the recorded area using a polarizing microscope, when the same area was rotated on a sample stage, a reversal of the brightness contrast between the non-recorded area and the recorded area was observed. In other words, if the recorded area appears dark compared to the bright non-recorded area at a certain angle, when the same area is rotated by 45 degrees, the bright recorded area appears in the dark non-recorded area, which is the area recorded at an intensity of 81. Polarized light micrographs are shown in FIGS. 10(a) and (b).

Note that (a) and (b) are the same part rotated by 45 degrees and am-shaped.

Next, as in Example 1, when the temperature of the recording medium was raised while observing the recorded area with a polarizing microscope, the recorded area that had been visible with clear contrast began to disappear at around 60°C.
It was completely erased at about 77°C. Further, at this temperature, no change was observed in the non-recording area, and when the temperature rose to 79.5°C, the entire crystal thin film melted.

Next, another recording medium was irradiated with laser light under the conditions (2) above. When this recording medium is observed with a polarizing microscope,
It was observed that the information was recorded over the entire irradiation range of the recording medium with almost no gaps. After this entire surface recording, the glass plate of the protective layer of the recording medium was peeled off, and the X@ diffraction was measured. on the other hand,
A similarly prepared recording medium was subjected to no recording, the protective layer was peeled off, and X-ray diffraction was measured. Further, the temperature of the recording medium after this recording was raised to 75° C. at a rate of 1° C./min.

The temperature was returned to room temperature, and X-ray diffraction was measured in a state where the recording was almost erased. Not recorded in Figure 12, recorded in Figure 13, 1st
Figure 4 shows an X-ray diffraction diagram after erasing. It can be seen from these that the molecular orientation partially changes after recording, but almost returns to its original state after erasing.

Furthermore, as in Example 1, 5 pm φ laser beams were continuously lit at 2.5, 2, and 1.5 mW, respectively, on the recording medium recorded with l-φ laser light under the conditions (1) above. Then, after scanning at a linear velocity of 50 cm/sec so as to overlap the recorded area, the area irradiated with 2oW was observed as a supplementary 3/7a as shown in the photograph in Figure 11 using a polarizing microscope. erased in strips. Also, 2,5+ov
In the above case, the intensity was too high, so a new line-shaped record was created, and erasure was observed at the edge of the line.
At 5 mW, the recording portion became slightly thinner.

Example 3 A glass substrate (5 cm x
5c++, thickness 1 to 2 mm), a chromium layer as a light-to-heat conversion layer, a recording layer made of behenic acid and a thin film crystal thereon, and a protective layer made of glass on top of the chromium layer. However, the thickness of the recording layer was approximately 0.6 μs.

Semiconductor laser light with a wavelength of 780 nm is focused on this recording medium in five diameter directions, and the intensity is 7.10.14 m on the recording medium surface.
The light was continuously turned on so as to be W, and scanning was performed in a straight line at a linear speed of 200 m++/see. When this recording medium was observed with a polarizing microscope, clear recording was observed as shown in the photograph of FIG. 15(a). Further, when this part was observed by rotating the sample stage by 45 degrees, it was observed that the brightness of the non-recorded part and the recorded part was reversed as shown in the photograph in FIG. 15(b).

Regarding the recording medium created in the same way, the strength was set to 12 m1.
The entire surface of the recording medium was irradiated almost without gaps under the same conditions as above. The thickness of the protective layer of this recording medium is 0.1
Peel off the recording layer from the glass plate of mm, and
Diffraction was measured. For comparison, a recording medium prepared in the same manner was not irradiated with laser light, the glass plate of the protective layer was peeled off, and X-ray diffraction was measured. Before recording (first
Comparing the X-ray diffraction after full-surface recording (Fig. 6) and after full-surface recording (Fig.
Diffraction lines based on humans) are clearly recognized. On the other hand, the change in the short surface interval due to recording is different from that in Example 2, which uses a similar recording medium but has a shorter irradiation time. However, 113! In the observation, the contrast between the non-recorded area and the recorded area is clear, so it can be seen that the way the orientation direction changes due to recording is different between this irradiation condition and the case of Example 2. The difference in conditions is the difference in irradiation time based on the difference in beam diameter and linear velocity:
Example 2 is about 0.25μsec, Example 3 is about 100μsec
sec),.

Example 4 A glass disk having a chromium layer similar to that in Example 1 was prepared. A polyimide resin solution (manufactured by Nippon Gosei Rubber Co., Ltd.: n+3-]) was applied on this chromium layer at a temperature of 150°C.
After drying for 1 hour, a polyimide layer with a thickness of about 0.1 μl was provided. On the other hand, a polyimide layer with a thickness of about 0.1 pm was similarly provided on one side of the glass with a thickness of 0.1 mm to serve as a protective layer.
Further, a small amount of silica particles having a diameter of about 1 prs was attached thereon as a gap material. Place both in a thermostatic chamber,
The materials for the recording layer shown in Table 2 were melted and sandwiched in the same manner as in Example 2, at a temperature 10 to 20"C higher than the melting point of each material.The melt was spread over the entire surface. After that, a load was applied uniformly from above the glass plate of the protective layer, and the temperature of the constant temperature bath was slowly lowered to crystallize the material of the recording layer. Through the above operations, a thin film of each material shown in Table 2 was formed. A recording medium with a crystal recording layer was created.

The recording medium thus produced was irradiated with semiconductor laser light focused to a diameter of 1 μm under the same conditions as in Example 2. However, the intensity of the recording light was as shown in Table 2.

When each recording medium was observed with a polarizing microscope, it was confirmed that recordings similar to those of the recording media of Examples 1 and 2 were formed.

Table 2 Example 5 A glass disk having the same chromium layer as in Example 1 was prepared. On this chromium layer, 5v of vinyl chloride-vinyl acetate copolymer (Union Carbide Co. 11: VV) IH) was applied.
A t% tetrahydrofuran solution was applied and dried to form a resin layer with a thickness of about 0.2p. On top of this, stearic acid (manufactured by Sigma, purity 99% or more) was injected in a 1out% tetrahydrofuran solution. , 3vt for stearic acid
% naphthalocyanine dye (the following structural formula) was applied and dried at 45°C.

Furthermore, a 5w, t% tetrahydrofuran solution of the same vinyl chloride-vinyl acetate copolymer as above was applied on top of it.
It was dried at 5°C. This disk was heat-treated at 90°C for about 2 minutes and then slowly cooled to form a recording layer and a protective layer made of thin film-like crystals of stearic acid containing a naphthalocyanine dye with an almost -like orientation on the chromium layer. did.

A semiconductor laser beam (830 nm) focused to a diameter of 17 All was applied to the recording medium thus created at an intensity of 3 mm.
Irradiation was carried out in the same manner as in the case of irradiation condition (1) of Example 1 except that V was used. When the laser beam irradiated portion of this recording medium was observed with a polarizing microscope, the recorded portion could be observed with clear contrast as in Example 1.

[Brief explanation of the drawing]

1 to 5 are cross-sectional views of the recording medium of the present invention, in which 1 is a substrate, 2 is a recording layer made of an organic thin film crystal having optical anisotropy, 3 is a photothermal conversion layer, and 4 is a photothermal conversion layer. An undercoat layer and 5 indicate a protective layer. FIG. 6 is an X-ray diffraction diagram of a recording medium having a thin film crystal of stearic acid as a recording layer in an unrecorded state, and FIG. 7 is an X-ray diffraction diagram of the same recording medium after recording. Also. Figure 8 is a polarized light micrograph of a portion recorded on this recording medium by IIJsφ laser beam irradiation, and Figure 9 is a polarized light micrograph of a portion recorded on this recording medium by laser beam irradiation of 5-tone φ, and partial erasure was performed by irradiating this recording portion with a 5-tone φ laser beam. This is a polarized light micrograph of a recording medium. Figures 10 (a) and (b) are polarized light micrographs of a recording medium having a thin film crystal of behenic acid as a recording layer, recorded by irradiating a laser beam with a diameter of 1 axis, and (a) and ( b)
is an observation of the same part rotated by 45 degrees. Further, FIG. 11 is a polarized light micrograph of a recording medium in which the recorded portion was irradiated with laser beams of 5 μsφ to partially erase the recording portion. Further, FIGS. 12, 13, and 14 are X-ray diffraction diagrams of the behenic acid recording medium in an unrecorded state, after recording, and after erasing, respectively. Furthermore, FIGS. 15(a) and 15(b) show that a recording medium having a thin film-like crystal of behenic acid as a recording layer is used. This is a polarized light micrograph of a portion recorded by irradiation with a laser beam of φ, (a)
and (b) are obtained by rotating the same part by 45 degrees. Moreover, FIG. 16 and FIG. 17 respectively show the unrecorded state and the XIIA@ folding diagram of this recording medium after recording. Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig.

Claims (5)

[Claims] (1) A recording medium that is made of an organic thin film crystal having optical anisotropy or has a recording layer containing the thin film crystal is crystallized by applying heat to melt the film crystal and then rapidly cooling it. A recording method characterized by recording a state while partially changing it. (2) The above-mentioned recording medium is composed of a light-to-heat conversion layer that absorbs part or all of the light irradiated during recording and converts it into heat, and an organic thin-film crystal having optical anisotropy, or A recording method comprising a recording layer containing crystals, which records by irradiating light to melt the thin film crystals and then rapidly cooling them to partially change the crystal state. (3) Claim (1) wherein the change in the crystal state due to the application of heat or the irradiation of light includes a change in the orientation direction of the molecules.
) or the recording method described in (2). (4) The recording method according to claim (1) or (2), wherein the change in the crystal state due to the application of heat or the irradiation of light includes partial microcrystallization of the thin film crystal. (5) Organic thin film crystals having optical anisotropy are fatty acids or fatty acid derivatives, benzoic acid derivatives, or have a melting point of 5
The recording method according to claim 1 or 2, wherein the main component is n-alkane or a derivative thereof at a temperature of 0°C or higher.