JPH02289380A - Recording medium - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a high-density recording medium that utilizes a reversible change in crystal state due to the application of thermal energy.

[Prior art]

In recent years, so-called heat mode recording systems have been put into practical use, in which information given by light, for example, is converted into the form of thermal energy and then applied to record changes in the shape or physical properties of a recording material. Examples of such heat mode recording media include Te, Bi, and Se.

Inorganic recording media using metal materials mainly composed of Tb, In, etc., polymethine dyes such as cyanine, macrocyclic azaannulene dyes such as phthalocyanine, naphthalocyanine, and porphyrin, naphthoquinone, anthraquinone dyes, and dithiol. Recording media using organic dyes such as metal complex 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 (pits) 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.

An example of such a reversible recording medium is Gd.

There are magneto-optical recording media that use alloy thin films made of rare earth elements such as Tb and Dy and transition metals such as Fe, Ni and 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, this magneto-optical recording medium...

It has drawbacks such as insufficient sensitivity during reproduction and a poor S/N ratio, and problems such as deterioration of recording sensitivity and recording stability due to effects such as oxidation.

In addition, as reversible recording media, Ge, Te, Ss, Sb, I
There is a method that utilizes the crystal-amorphous phase transition of a recording layer made of a thin film of an inorganic material containing elements such as n and Sn as main components. This recording medium has the advantage of being able to record and erase information in heat mode using only laser light irradiation, but the contrast between recorded and non-recorded areas and recording stability are not sufficient.
It has drawbacks such as problems with the safety of the material of the recording layer.

On the other hand, JP-A-54-119377, JP-A-55-15419
No. 8, No. 63-39378, and No. 63-411136 disclose thermal recording materials comprising a resin matrix material and an organic low-molecular substance present in the matrix material in the form of fine particles dispersed therein. 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 cooled, it becomes transparent, and recording is performed by reversible changes in this light-shielding property. However, Although the contrast caused by this light-shielding property is clear in the case of records that are large enough to be observed with the naked eye, it is difficult to magnify a recorded area formed by changes in a small area of a few houses under a microscope. If the recording layer is to be detected, the contrast will be so low that it cannot be confirmed as a record.In the recording layer, the light scattering properties may change depending on the state of the matrix of the organic low-molecular substance particles. This is because when the size of the recording area becomes a few degrees, the thickness of these particles is no longer small enough to cause such scattering compared to the size of the recording area. To compensate for this, it is possible to make the recording layer much thicker than the size of the recording.
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 an organic material, for example, JP-A-58-199343 discloses an organometallic complex bis(1-p-n-alkylphenylbutane-1
, 3-dionato) (■) and organic polymer mixture, JP-A-1986
No. 3-15793 discloses a mixture of crystalline and immature thermoplastic resins, JP-A-63-95993 and JP-A-96748 disclose a crystalline aromatic vinylene sulfide polymer, and JP-A No. 63-279440 discloses a crystalline aromatic vinylene sulfide polymer. contains a sulfur-containing polymer, and JP-A-63-128993 discloses diazabicyclo (2,
2,2) Octane quaternary salt, JP-A No. 63-259851 discloses the delivery of stretched and oriented polymers and liquid crystalline polymers - a recording medium that utilizes amorphous transition or changes in the degree of orientation. . However, 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, conventional recording media have various problems such as recording stability, recording sensitivity, erasing speed, and contrast between recorded areas and non-recorded areas. Furthermore, from the viewpoint of safety, it is desirable that the recording medium be made of non-toxic materials.

From this viewpoint, the present invention provides a recording medium that can record information, reproduce information, and erase recorded information, and that can be used repeatedly. In addition, we provide recording media that have excellent recording sensitivity and recording speed, good recording stability, high contrast between recorded and non-recorded areas, can record information at high density, and can erase recorded information at high speed. It is something to do. Furthermore, the present invention provides a non-toxic and highly safe recording medium.

[Means to solve the problem]

The inventors studied the thermal changes of various organic materials for two or more purposes, and found that when thin film crystals of n-alkanes or their derivatives with a melting point of 50°C or higher are used in the recording layer, heat changes. It was found that the crystal state of the part where the voltage was applied changes. Furthermore, it was discovered that this changed part can be returned to its original state by being reheated to an appropriate temperature.The present invention is based on the thermal reversible change of thin film-like crystals of n-alkanes or their derivatives. It is.

In other words, the recording medium of the present invention is a recording medium having a recording layer on a substrate, in which the recording layer has an n-
It is characterized by being a thin film-like crystal whose main component is an alkane or a derivative thereof, or a layer containing the thin film-like crystal.

Further, the recording medium of the present invention has a recording layer made of or containing the above-mentioned thin film crystal, and a photothermal conversion layer that absorbs part or all of the light irradiated during recording and converts it into heat. This is a characteristic feature.

Furthermore, in the above two configurations, the recording medium of the present invention absorbs part or all of the light irradiated during recording in the recording layer containing n-alkane or a derivative thereof having a melting point of 50° C. or higher, and absorbs heat. It is characterized by containing a photothermal conversion substance.

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

The recording layer of the recording medium of the present invention has an n-
It is a thin film-like crystal whose main component is an alkane or a derivative thereof, or a layer containing the same, and it may be a single compound or a mixture of two or more types. 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 carbon atoms. It is a compound in which a benzene ring which may be substituted with an alkyl group or an alkoxy group is bonded to an atom. Specifically, n-alkanes include, for example, tetracosane, pentacosane, hexacosane, heptacosane, octacosane, nonacosane, triacontane, todriacontane, tetratriacontane, hexatriacontane,
There are n-alkanes such as octatriacontane and tetracontane, or mixtures containing these as main components, so-called paraffins and paraffin waxes. In addition, as a derivative,
1-hexacosene, 1-heptacosene, ■-octacosene, l-triacontin, 1-tetratriacontin,
1-hexatriacontene, 1-octatriacontene.

1-tetracontin, tocosylbenzene, tetracosylbenzene, hexacosylbenzene, ophtacosylbenzene, triacontylbenzene, tritriacontylbenzene, tetratriacontylbenzene, hexatriacontylbenzene, 1.18- dibrome octadecane,
Examples include 1,20-dibromutocosan and 1,22-dibromutocosan.

The n-alkane or derivative thereof used preferably has a melting point of 50°C or higher, particularly preferably one in the range of 60 to 150°C. 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 of the present invention, one type or a mixture of two or more of these n-alkanes or derivatives thereof can be used. In addition, the recording layer in the present invention may be made of or contain thin film-like crystals mainly composed of these n-alkanes or derivatives thereof, or may contain other resins as necessary to form the layer. can be used.

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. ,
Examples include polyvinylidene chloride, vinylidene chloride-acrylonitrile copolymer, polyester, polyamide, polyacrylate, polymethacrylate, polycarbonate, polyurethane, and silicone resin. When a resin is used in the recording layer, the weight ratio of the resin to 1 part of n-alkane or its derivative in the entire recording layer is preferably 3 or less, particularly 1 or less.

Substrates used in the recording medium of 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 reproduction light. Further, in the case of reading by reflected light, a film of a metal or semimetal such as platinum, titanium, silicon, chromium, nickel, germanium, aluminum, etc. is provided as a reflective layer, if necessary.

In the recording medium of the present invention, recording is performed by applying heat to the recording layer, or when light such as a laser beam is used as the method of applying heat, the irradiated light is used in accordance with the information to be recorded. Will a light-to-heat conversion layer be provided that absorbs some or all of the light and converts it into heat?

Alternatively, it is necessary to include a substance that absorbs light and converts it into heat in the recording layer. As the light-to-heat conversion layer, a metal or metalloid film similar to the reflective layer may be provided, and therefore, this layer can also be used as the reflective layer. The photothermal conversion layer also contains dyes that absorb the irradiated light, such as azo dyes, cyanine dyes, naphthoquinone dyes, anthraquinone dyes, squarylium dyes, phthalocyanine dyes, naphthalocyanine dyes, porphyrin dyes, and indigo dyes. It may be a layer containing a dye, a dithiol complex dye, an azulenium dye, a quinone imine dye, a quinone diimine dye, etc., and the layer is selected depending on the wavelength of the light used for recording. on the other hand.

As the substance to be contained in the recording layer that absorbs light and converts it into heat, various dyes can be used to be contained in the light-to-heat conversion layer, and it is selected depending on the wavelength of the light used for recording.

The recording medium of the present invention has a recording layer on a substrate that is made of or contains a thin film crystal mainly composed of n-alkane or a derivative thereof, and the crystal state of the recording layer changes upon application of heat. Although the structure thereof is not specified, examples of structures of commonly used recording media are shown in FIGS. 1 to 5. In FIG. 1, 1 is a substrate, 2 is a thin film crystal whose main component is n-alkane or a derivative thereof,
Or a recording layer containing this. FIG. 2 shows a photothermal conversion layer 3 between the substrate 1 and the recording layer 2 shown in FIG. It was established. In FIG. 3, a recording layer 2 is provided on a substrate 1, and a photothermal conversion layer 3 is provided thereon.

In FIG. 4, an undercoat layer 4 is provided under the recording layer 2 of FIG. 2 for the purpose of improving the film quality of the recording layer 2, for example. Furthermore, FIG. 5 shows a protective layer 5 on top of the recording layer 2 in FIG.
It has been established.

Various resins can be used for the undercoat layer 4, such as the resins that may be used when forming the recording M2 described above. For the protection M5, these resins may be used, or a glass plate may be used. If a glass plate is used, the surface (the surface in contact with the recording layer) may be coated for the same purpose as the undercoat layer. A similar resin layer may be provided, or the glass surface may be previously treated with a surface treatment agent such as a silane or titanate surface treatment agent that improves the properties of the glass surface.

In order to manufacture the recording medium of the present invention, a light-to-heat converting layer 3 is formed on the substrate 1 by means of vapor deposition, sputtering, plating, etc. using, for example, the metal or metalloid as described above, as required. A recording layer 2 is formed thereon.

For example, there are the following methods for forming the recording layer 2. First, a glass plate or a resin film corresponding to the protective layer 5 is covered over the substrate 1 provided with the light-to-heat conversion layer 3, keeping a gap corresponding to the required thickness of the recording layer 2. In order to create a gap, a spacer layer may be provided around the area where the recording layer 2 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 photothermal conversion layer 3. It may be attached to the side or the protective layer 5 side. Place the entire substrate with the gap formed in this way in a constant temperature bath or place it on a hot plate, keep it at a temperature higher than the melting point of the material used for layer 2, place the molten material at the end of the gap, and Let it soak in between. When the obtained melt layer is slowly cooled and crystallized, a recording layer 2 is formed between the photothermal conversion N3 and the protective layer 5.
Thin film-like crystals can be formed. At this time, in order to maintain the gap interval constant, pressure may be applied using a weight or the like until crystallization. In addition, these operations may be carried out under reduced pressure in order to prevent the formation of bubbles.

In addition, as another manufacturing method, if (f) the material forming the recording layer 2 is a suitable organic solvent (4) (tetrahydrofuran, methyl ethyl ketone, methyl isobutyl ketone,
Dissolve in chloroform, four-base carbon, etc., apply by spin code method, blade coat method, dip coat method, etc. and dry.

Alternatively, a layer with a uniform thickness is formed over the photothermal conversion M3 by a vapor deposition method. A resin dissolved in an appropriate solvent is coated on this as required. Next, this is placed in a constant temperature bath or placed on a hot plate and heated to a temperature higher than the melting point of the material of the penetrating recording layer 2, and then slowly cooled to crystallize the thin film of the recording layer 2. form crystals. Various methods can be used to form the recording layer 2, such as the Banyoko Iya method and the Langmuir-Prodgett method.

In the case of including a photothermal conversion substance in the recording layer z, for example, the dye may be simultaneously dissolved in a solution of the material of the recording layer 2, or dispersed and applied.

When forming the photothermal conversion RIJ3, which absorbs part or all of the light irradiated during recording or erasing and converts it into heat, using the dye described above, it may be formed by a method such as vapor deposition or sputtering, or by a method such as a solvent. It may also be formed by applying a solution dissolved or dispersed in.

In this case, a binding resin may be used if necessary. If a light-reflecting layer is required, a vapor-deposited metal film may be provided separately.

The thickness of the recording layer 2, which is made of or contains thin film crystals mainly composed of n-alkanes or derivatives thereof, is not particularly limited, but is usually 10 to 10 μm.
m, preferably about 10 people to 5 ρ.

The thickness of the photothermal conversion layer 3 is determined in an appropriate range depending on the wavelength and intensity of the light used for recording and the type of material used, but is generally about 50 to 5 μl.

The recording medium of the present invention has a recording layer consisting of or containing a thin film crystal mainly composed of n-alkane or a derivative thereof, and the crystal state of the thin film crystal is reversible by application of heat. It takes advantage of change. Various methods can be considered for recording information, that is, applying heat, but in order to perform high-density recording, a method using focused laser light irradiation is most preferable. In this case, it is necessary to provide the recording medium with the aforementioned photothermal conversion layer that absorbs light and converts it into heat, or to add a substance that absorbs light and converts it into heat into the recording layer.

During recording, the photothermal conversion layer or photothermal conversion material absorbs light and generates heat in the laser beam irradiated area, and the recording layer made of or containing thin film crystals of n-alkane or its derivatives is instantly heated. When the laser beam irradiation stops, it cools down rapidly, forming a recording bit (the pits here are not holes, but areas recorded as changes in the crystal state in the thin film crystal). .

At this time, in the recording layer, a part of the thin film crystal, that is, a part that is instantaneously heated by the heat transmitted from the light-to-heat conversion layer (substance) generated by short-term laser beam irradiation,
A temperature is reached at which the crystals completely melt. However, when the laser beam irradiation stops, the heat diffuses, and this part is instantly cooled and solidified (crystallized).The crystalline state of the part that instantaneously heats, melts, and then cools and crystallizes is the same as the heat applied. The crystal state of the non-recorded portion is different from that of the surrounding non-recorded 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. Also (2)
A change in the direction of the crystal axis or a change in the direction of molecular orientation means, for example, that the crystal structure is basically the same, or that the crystal orientation is different, that is, the direction of the crystal axis is different, or Although it is not as clear as this, it is basically a collection of molecules that are oriented in some way, 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 crystallization is very narrow and the state changes to an amorphous state.

These changes in the crystal state may be due to localized short-term heat application to the thin film crystal, i.e., rapid cooling from the molten state caused by short-term light irradiation, or the cooling rate is mainly due to the rapid cooling from the molten state. 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
μsec is about L5nsec, and the difference in cooling rate is very large. Therefore, the change in the crystal state caused by short-term light irradiation (heat application) also changes depending on the irradiation time and is not constant. For example, in microcrystalization, it is observed that the faster the cooling rate, the more fine the material becomes. It is also related to the state of molecular orientation, and in general, the faster the cooling rate, the more disordered orientation tends to occur, and the range in which one molecule can be regularly arranged becomes narrower, resulting in a state of low crystallinity. Changes in the crystal state due to such recording can be confirmed, for example, by measuring X-ray diffraction of the recording layer. In addition, the above (1), (2), and (3) that occur due to recording
) changes in the crystalline state 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 does not necessarily result. Therefore, the changes in the crystal state of (1), (2), and (3) are compounded in various forms depending on the position even within one recording section. It happens.

Table Loser Light Wavelength: 830 nm The recorded state can be confirmed by optical means such as a 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. This can be done by detecting the intensity of light through the sensor. 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, heat is applied to a part of the thin film crystal mainly composed of n-alkane or its derivative in the recording layer, and the information is recorded as a change in the crystal state by instantaneously melting and recrystallizing it. Erasing can be achieved by heating the recording layer to a temperature lower than the recording temperature, at which the crystalline thin film of the recording layer does not melt, but at which one molecule 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. For example, if a dark recorded area is formed within a non-recorded area that appears uniformly bright, the recorded area will begin to chip at temperatures above a certain level, and eventually the entire area will become as bright as the 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 further raised to reach 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 crystal, whose crystal state has changed, are in a state where they can undergo sufficient thermal movement, they form an arrangement like ■ with the molecules of the surrounding non-recording part. By returning from that temperature to room temperature, the entire crystal becomes a --like thin film state crystal and disappears.

Specifically, erasing can be done by heating the entire recording medium to the above temperature range and cooling it to erase the entire recording, or by heating and cooling the recorded pit area or a slightly wider area locally to the erase temperature. By doing so, 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 is weakened and the temperature of the recorded pit area is adjusted to fall within the erasing temperature range.
You can irradiate it multiple times. 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 is
Similar to the recorded state, it can be confirmed using optical observation means such as a microscope or a polarizing microscope.

The recording medium 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 the thin film-like crystals forming the recording layer or the thin film contained in the recording layer. Recording is performed by changing the crystal state of a portion of a shaped crystal, and the difference between the formed recorded portion and non-recorded portion is detected as, for example, a difference in polarization characteristics. In this respect, the recording medium of 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 medium of the present invention, n-alkane or its derivative 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, resulting in an optical It detects differences in properties. Therefore, the difference between the two is obvious.

〔Effect of the invention〕

Recording and erasing of the recording medium of the present invention is basically based on the difference in temperature reached by thin film crystals of n-alkanes or derivatives thereof forming the recording layer, and this can be adjusted by controlling the intensity of the irradiated laser light. Also, since recording and erasing can be performed at high speed, recording is performed while erasing. So-called override (overwriting) is possible. Further, this recording and erasing can be performed repeatedly and stably. Furthermore, since the recording section is in a stable state like the non-recording section, the recorded information can be stably stored for a long period of time.

〔Example〕

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

EXAMPLE A chromium layer serving as a light reflection layer and a light-to-heat conversion layer was provided by vacuum deposition on an optically polished glass disk having a diameter of 4 inches (101.6 mm) and a thickness of 1.2 mm. The thickness was approximately 900 people. A polyimide resin solution (manufactured by Japan Synthetic Rubber Co., Ltd.: JIB-1) was applied onto this chromium layer and dried at a temperature of 150° C. for 1 hour to provide a polyimide layer with a thickness of about 0.1 μm. On the other hand, the thickness of the protective layer OJmr
Prepare a glass plate of A, and apply a layer of thickness of about 0.1 mm on one side of it.
A similar polyimide layer was provided, and a small amount of silica particles with a diameter of 1 μm were adhered thereon as a gap material. Both were placed in a constant temperature bath at a temperature of 70°C and heated, and then a small amount of paraffin having a melting point of 68 to 70°C was placed on the polyimide layer of the glass disk at the same temperature and melted. Next, one glass plate was gently placed over the paraffin melt from one end with the side to which the gap material was attached facing down, and the melt was spread and sandwiched over the entire surface. Further, a load is applied evenly from the top of the covered glass plate, and the temperature of the thermostat is slowly lowered to crystallize the paraffin and form a recording layer (with a thickness of approx. 1 μm) was formed.

The recording medium thus created is rotated at 90 ORPM, and a semiconductor laser with a wavelength of 830 n+s focused to a diameter of 1 μm is applied to it at a linear velocity of 3500-4000 mm/sec.
It was irradiated in a spiral manner. The laser lighting conditions at this time were set such that the frequency was 200 KHz, the duty ratio was 50%, and the intensity was 8 mW on the recording medium surface.

When this recording medium is observed in a crossed Nicols state using a reflective polarizing microscope, the laser beam irradiated portion of the recording layer has a width of about 1p.
The clear contrast showed that m was recorded. Note that this recording state could hardly be confirmed with a normal optical microscope. Next, while observing this recorded portion with a polarizing microscope, the temperature of the recording medium was increased at a rate of 1° C./min, and the recording was completely erased at 66° C.

[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 of n-alkane or its derivative, 3 is a photothermal conversion layer, and 4 is an undercoat layer. , 5 indicates a protective layer. Patent applicant Rico Co., Ltd.

Claims (3)

[Claims] (1) In a recording medium having a recording layer on a substrate, the recording layer is a thin film crystal whose main component is n-alkane or a derivative thereof with a melting point of 50°C or higher, or a layer containing such a thin film crystal. A recording medium characterized by certain things. (2) The recording medium according to claim (1), further comprising a photothermal conversion layer that absorbs some or all of the light irradiated during recording and converts it into heat. (3) The recording according to claim (1) or (2), characterized in that the recording layer contains a photothermal conversion substance that absorbs part or all of the light irradiated during recording and converts it into heat. Medium.