JP2563631B2 - Optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an optical recording medium for recording and reproducing by using an organic dye.

2. Description of the Related Art Conventionally, an optical recording medium using an organic dye is produced as a thin film dispersed in a polymer film by a spin coating method or the like.

An optical recording medium provided with a recording layer and a separation layer has also been proposed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the conventional recording medium and configuration, the recording layer without the control layer is continuously formed, and the organic dye moves in the recording layer, and the dye forms an aggregate. . The formation of aggregates is promoted, especially with increasing temperature.

As a result, the concentration of the organic dye in the recording medium becomes high or low,
Recording with a recording diameter smaller than the size of the aggregate becomes difficult, and the recording density decreases.

Further, since the conventional separation layer is simply provided to spatially separate the two layers, it is impossible to suppress aggregation in the recording layer.

An object of the present invention is to reduce the aggregate of organic dye formed in the recording layer of an optical recording medium.

Means for Solving the Problems In order to achieve the above object, a recording layer made of an ultrathin film containing an organic dye and a control layer are alternately laminated,
An optical recording medium in which at least the uppermost layer is the control layer is used.

When the recording layer and the control layer are alternately laminated, and when the recording medium has the uppermost layer as the control layer, the aggregate of dyes becomes small.

It is considered that this is because the recording layer was divided into the ultra-thin film by the control layer, so that the migration of the organic dye molecules did not easily occur and the aggregation of the molecules in the film was suppressed.

Examples The organic dye of the present invention is an organic substance having absorption in the visible region, and changes such as absorption and reflection due to photoreaction and thermal reaction accompanying light irradiation.

Photoreactions include oxidation, reduction, cis-trans isomerization,
Proton transfer, counterion formation, ring-opening ring-closing reaction, etc.

Organic substances that cause photoreaction include viologen-based, endoperoxide-based, stilbene-based, azobenzene-based, indigo-based, spiropyran-based, azomethine imine-based, dihydroindolizine-based, fulgide-based and the like.

 The thermal reaction includes sublimation, deformation and decomposition.

Cyanine-based, merocyanine-based, porphyrin-based, azo-based, styryl-based, phthalocyanine-based, xanthene-based, thiazole-based, carbonium-based, azine-based, pyridine-based, quinoline-based, anthraquinone-based, benzophenone-based, as an organic substance in which a thermal reaction is utilized Benzonequinone type, naphthoquinone type, flavone type, xathone type, pyrazolone type,
There are nitro type, nitroso type, squarinium type, croconium type, etc.

The recording layer of the recording medium of the present invention is composed of an ultrathin film, and the thin film can be formed by any of the Langmuir-Blodgett method (hereinafter abbreviated as LB method), spin coating method, vapor deposition method and the like. Is.

In particular, when the LB method is applied, the dye needs to have amphiphilicity. At this time, a dye having a long-chain hydrocarbon chain or the like bonded to the dye to make it hydrophobic is applied.

The number of carbon atoms in the long hydrocarbon chain attached to the dye is 11 to 31.
A good balance between hydrophilicity and hydrophobicity is obtained by setting
It is preferable that a film can be obtained. Further, the recording layer in the recording medium is preferably composed of one or two monomolecular films. At this time, the thinner recording layer is sandwiched between the control layers, so that the migration of the dye is suppressed. As a result, the aggregate of the dye becomes smaller.

Further, if the recording layer is composed of a mixed film of organic dyes, the effect of suppressing the formation of aggregates is further improved, and it becomes difficult to form aggregates even at high temperatures.

Examples of the mixture with the dye in the recording layer include esters, ethers, fatty acid metal salts, fatty acids, alcohols, amines, amides and hydrocarbons. Among them, as the mixture, at least one of fatty acid metal salt, fatty acid, alcohol, amine, amide, and hydrocarbon is preferable because the structure of the dye in the recording layer is stabilized.

This is probably because the mixture mixed in the recording layer further hinders the migration and aggregation of dye molecules.

Of course, when a recording layer is formed by the LB method, a mixture of these mixtures with a long-chain hydrocarbon chain or the like is used like the dye used.

Materials applicable to the control layer include esters, ethers, fatty acid metal salts, fatty acids, alcohols, amines and amides.

Among them, the control layer is preferably a fatty acid metal salt, fatty acid, alcohol, amine, amide or the like. Although the details of this reason are not clear, it is assumed that the control layer composed of the above-mentioned compound, which has a relatively high melting point as compared with the dye, is adjacent to each other, whereby the migration and aggregation of the dye molecules in the recording layer can be further suppressed. It

When a plurality of recording layers are present in the recording medium via the control layer, the number of monomolecular films in each recording layer may be different from each other.

That is, for example, as shown in FIG. 1, the recording layer 1 is composed of only one kind of dye, and the recording layer 1 is composed of one monolayer.
When the recording layer 2 composed of two monomolecular films is a recording medium in which the control layer 3 and the control layer 3 are alternately laminated, these recording layers exhibit absorption maximum wavelengths that differ depending on the number of laminated layers. This is because the molecular arrangement of dye molecules differs depending on the number of monolayers in the recording layer, and the absorption maximum wavelength shifts.

When such a recording medium is used, for example, US Pat.
Wavelength multiplex recording as described in 4,737,427 becomes possible, and the recording density can be doubled by using one kind of dye.

Recording on a recording medium using these dyes is performed by irradiating a visible laser to reduce absorption or reflection in the visible portion, and reproduction is performed by irradiating weak visible light to detect absorption or reflected light. To do.

What has been described above will be described with reference to the drawings.

In the following examples, as a representative example of organic dyes for convenience of description, organic dyes represented by the following chemical structural formulas (hereinafter, SP
7, SP1822, SP1801, and CN18) and copper phthalocyanine were used, but it goes without saying that the present invention is not limited to these five types of dyes.

For SP1822 and SP1801, see Thin Solid Films, 1985, Vol. 133, p. 21 (E. Ando et al. Thin Solid F
ilms, 133 , 21 (1985)), Thin Solid Films 1
988, 160, 279 (E. Ando et al. Thin Solid Films, 1
60, 279 are described in detail in (1988)), it can be synthesized accordingly. SP7 can also be synthesized by a method similar to these.

Copper phthalocyanine is commercially available from ordinary chemical manufacturers, and CN18 is commercially available, for example, as Japan Photosensitive Dye.

Of these, SP7, SP1822, and SP1801 are organic dyes that undergo photoreaction, and can be recorded by initializing them as colored bodies by irradiation with ultraviolet light and irradiating with a visible laser to return to colorless bodies. It can be erased by irradiating it with external light and returning it to the colored body.

A dye having a long-chain carbon number of 32 or more was difficult to obtain and could not be confirmed easily, but similar experiments are considered to be possible.
Further, when the number of carbon atoms is 10 or less, it is difficult to form a film by the LB method because the hydrophobicity is insufficient, but the present invention can be applied without using the LB method.

In addition, if the recording layer is accumulated using the LB method,
Neither the X type as shown in the figure nor the Z type as shown in FIG. 5 does not depend on the accumulated form of the dye in the recording layer.

Substrates in the following examples include polycarbonate,
Polymer materials such as acrylic and polyolefin, quartz, glass and various metals, and inorganic materials such as CaF ² can be used.

Example 1 A recording medium was formed by the spin coating method, and the effect of the control layer was investigated.

As shown in FIG. 2, SP7 is formed as the recording layer 9 on the substrate 4.
A thin film of A was formed, and a polyvinyl alcohol film was formed thereon as a control layer 10 to form a recording medium 1a.

 The conditions for spin coating are shown below.

○ Recording layer thinning condition 1 SP7 1.5 wt% toluene solution 3000 rpm ○ Control layer thinning condition 1 Polyvinyl alcohol 0.3 wt% aqueous solution 3000 rpm When this is irradiated with ultraviolet light for 30 minutes at 35 ° C with an ultraviolet lamp, colorless substance is colored. The reaction to the body progressed.

When the recording layer was observed with an optical microscope, the size of the aggregate was 2.0 μm or less, and the uniformity of the recording layer was good.

Further, this recording layer could be erased by irradiation with ultraviolet light in addition to recording with a visible laser.

These results show that high density recording with recording pits of 2 μm or less is possible and adaptability to a rewritable recording medium.

Comparative Example 1 Only the recording layer of SP7 was formed on the substrate by the spin coating method as in Example 1 to obtain a recording medium 1b. The spin coating was performed under the recording layer thinning condition 1. The thickness of the recording medium was 120A.

This recording medium 1b was exposed to UV light at 30 ° C with an UV lamp at 30 ° C.
Irradiated for minutes.

When observing this recording layer with an optical microscope, 8-12
Aggregates of μm were observed.

As described above, in the conventional recording medium 1b, large aggregates are observed in the recording layer, but in the recording medium 1a of Example 1, the provision of the control layer has an effect of suppressing the formation of aggregates. It was

Example 2 A recording medium was formed using SP1822 as an organic dye,
The effect of the control layer was investigated.

As a material for the recording layer, a 1 mmol / l benzene solution of SP1822 was prepared.

 SP1822 was accumulated by the LB method under the following accumulation condition 1.

Accumulation condition 1 Sub-phase: pH 7 / phosphate buffer, temperature 18 ° C Compression rate: 2800 mm ² / min Cumulative pressure: 20 mN / m The control layer is a 1 mmol / l benzene solution of stearic acid dissolved in barium salt. The monolayer of barium stearate formed on the sub-phase was accumulated and formed.

The accumulation condition of this control layer by the LB method is as follows.
Is.

At this time, as shown in FIG. 3, the recording layer 2 has a film thickness of 50 A consisting of two monomolecular films of the dye SP1822, and the control layer 3 consists of two barium stearate monomolecular films of 50 A.
The recording layer 2 and the control layer 15 were alternately laminated once each.

○ Cumulative condition 2 Sub-phase: pH8.6 / BaCl ₂ = 4 × 10 ^-4 mol / l / KHCO ₃ = 5 × 10 ^-5 mol / l, temperature 18 ° C Compression rate: 2800 mm ² / min Cumulative pressure: 30 mN / m When the recording medium 2a thus formed was irradiated with ultraviolet light for 30 minutes at 35 ° C. by an ultraviolet lamp, a reaction from a colorless body to a colored body proceeded.

When the recording layer 2 of this recording medium was observed with an optical microscope, the size of the aggregate was 1.0 μm or less, and the uniformity of the recording layer was good.

In addition to recording with a visible laser, this recording layer 2
It was possible to erase by irradiation with ultraviolet light.

These results show that high density recording with recording pits of 1 μm or less is possible and adaptability to a rewritable recording medium.

In this embodiment, the accumulation of the recording layer 2 showed the Y type, but the accumulation type of the recording layer X type shown in FIG. 4 and Z type shown in FIG. The size of the collection is 1.
The thickness was 0 μm or less, and the uniformity of the recording layer was good.

Comparative Example 2 As the material for the recording layer, the SP1822 monolayer two layers were used in Example 2
Under the cumulative condition 1 of No. 3, the recording medium 2b was formed by stacking on the substrate.

This recording medium 2b has a structure when the control layer 3 of barium stearate shown in FIG. 3 is not present.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

Observation with an optical microscope revealed that the size of aggregates in this recording layer was as large as 5 to 10 μm.

As described above, in the conventional recording medium 2b, large aggregates are observed in the recording layer, but the recording medium 2a of Example 2 has the effect of suppressing the formation of aggregates by providing the control layer 3. there were.

Example 3 A recording medium was formed using SP1801 as an inorganic dye, and the effect of the control layer was examined.

As shown in FIG. 6, SP180 is used as the material of the recording layer 1.
1 and a monolayer film of barium stearate as a material for the control layer 13 are laminated on the substrate 4 one by one, and a recording medium
Formed 3a.

The accumulation of the recording layer 1 was performed under the same conditions as the accumulation condition 1 of Example 2, and the accumulation of the control layer 13 was performed under the same conditions as the accumulation condition 2 of Example 2.

The film thickness of the recording layer 1 was 25A, and the film thickness of the control layer 13 was 25A.

The recording medium 3a was irradiated with ultraviolet light from an ultraviolet lamp at 35 ° C. for 30 minutes to completely form a colored body.

The recording layer was observed by an optical microscope, but no formation of aggregates was observed.

Therefore, this shows the possibility of forming recording pits of about the recording wavelength and dramatically improving the storage capacity.

In addition to recording with a visible laser, this recording layer
It was possible to erase by irradiation with ultraviolet light.

These results show the applicability to a high density rewritable recording medium having recording pits of 0.5 μm or less.

Comparative Example 3 As shown in FIG. 7, SP180 was used as the material for the recording layer 1.
1 and a monolayer film of barium stearate as a material for the control layer 13 are laminated on the substrate 4 one by one, and a recording medium
Formed 3b. The configuration of the recording medium 3b differs from the recording medium 3a of the third embodiment in that the uppermost layer is the recording layer.

The accumulation conditions were the same as in Example 3, the accumulation of the recording layer 1 was performed under the accumulation condition 1 of Example 2, and the control layer 13 was performed under the accumulation condition 2 of Example 2.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

Observation with an optical microscope revealed that aggregates in the recording layer were 4μ
More than m were observed.

As described above, in the conventional recording medium 3b, large aggregates are observed in the recording layer, but the recording medium 3a of Example 3 has the effect of suppressing the formation of aggregates by providing the control layer. It was

Example 4 A recording medium was formed using CN18 as a dye, and the effect of the control layer was investigated.

A 1 mmol / l benzene solution of CN18 was prepared as a material for the recording layer, and two monomolecular films were accumulated on the substrate by the LB method. Next, two monomolecular films of barium stearate as a material for the control layer were accumulated on the recording layer to form a recording medium 4a.

The accumulation of the recording layer was performed under the accumulation condition 1 of Example 2, and the accumulation of the control layer was performed under the accumulation condition 2 of Example 2.

The recording medium 4a has a Y-shape similar to that shown in FIG. The recording layer 2 had a film thickness of 50A and the control layer 3 had a film thickness of 50A.

 This was heated to 35 ° C. for 30 minutes and allowed to cool.

When the recording layer 2 was observed with an optical microscope, the size of the aggregate was 1.0 μm or less, and the uniformity of the recording layer 2 was good.

These results show applicability to high density recording media.

Comparative Example 4 A recording medium 4b was formed by laminating only two CN18 monomolecular films as recording layers on a substrate. That is, the recording medium 4b does not have the barium stearate control layer 3 shown in FIG.

The accumulation was performed under the same conditions as those for the recording layer of Example 4.

 This was heated to 35 ° C. for 30 minutes and allowed to cool.

Observation of this recording medium with an optical microscope revealed that the aggregate size was as large as 5 to 10 μm.

As described above, in the conventional recording medium 4b, large aggregates are observed in the recording layer, but the recording medium 4a of Example 4 has the effect of suppressing the formation of aggregates by providing the control layer. It was

Example 5 SP1822 was used as the dye, the recording layer was composed of a mixed monolayer, and the effect of the mixture was investigated. Octadecane was used for the mixture.

As a material for the recording layer, a benzene solution of SP1822 / octadecane = 1/2 was adjusted so that the concentration of SP1822 was 1 mmol / l, and the monomolecular film 2 was formed on the substrate under cumulative condition 1 of Example 2.
The layers were accumulated.

Further, as a material for the control layer, barium stearate was laminated on the recording layer under the cumulative condition 2 of Example 2 to form the recording medium 5.

The recording medium used in Example 2 was SP instead of the SP1822 monolayer.
1822 / octadecane = 1/2 monolayer was included (see Fig. 3).

 The thickness of the recording layer of the recording medium 5 was 50A.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

Observation of the recording medium 5 with an optical microscope revealed that the size of the aggregates in the recording layer was as small as 0.5 μm or less.

By thus forming the recording layer as a mixed film containing an organic dye, there is an effect that aggregates in the recording layer in the recording medium are further reduced.

In addition to recording with a visible laser, this recording layer
It was possible to erase by irradiation with ultraviolet light.

These results show the possibility of adapting to a rewritable recording medium in addition to the possibility of high density recording of recording pits of the recording medium 5 of 0.5 μm or less.

When stearic acid, stearylamine, steramide, stearyl alcohol, or barium stearate was used as a mixture instead of octadecane, the same effect as in this example was obtained.

Example 6 The effect of the mixture was investigated when SP1822 was used as the dye and the recording layer was composed of a mixed monolayer.

 Stearine was used for the mixture.

As shown in FIG. 8, as the material of the recording layer 14, SP is formed on the substrate 4.
A recording medium 6 was formed by laminating one monolayer of 1822 / stearic acid = 1/8 and two monolayers of barium stearate as a material for the control layer 13.

SP1822 / stearic acid = 1 as a developing solution on the recording layer 14.
/ 8 1 mmol / l benzene solution was used to accumulate under the accumulating condition 1 of Example 2, and the control layer 13 was laminated under accumulating condition 2 of Example 2.

At this time, the film thickness of the recording layer 14 was 25 A, and the film thickness of the control layer 13 was 25 A each.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

When the recording layer 14 of the recording medium 6 was observed by an optical microscope, formation of aggregates was not observed.

Furthermore, this was heated to 50 ° C. for 30 minutes, but no aggregate was formed.

That is, it becomes possible to form recording pits of about the recording wavelength,
Memory capacity has improved dramatically.

In addition to recording with a visible laser, this recording layer
It was possible to erase by irradiation with ultraviolet light.

These results show the adaptability to the rewritable recording medium in addition to the adaptability to the high density recording medium having the recording pits of the medium 6 having the recording wavelength.

In addition, instead of stearic acid, octadecane, stearylamine, stearoamide, stearyl alcohol,
Similar effects were obtained when barium stearate was used as a mixture.

Example 7 The effect when one recording layer in the recording medium is formed of a multi-layered monomolecular film was examined.

As shown in FIG. 9, four layers of SP1822 / stearic acid = 1/8 were accumulated as the material of the recording layer 16, and two layers of barium stearate were accumulated as the material of the control layer 3 to form the recording medium 7.

The recording medium 7 was irradiated with ultraviolet light from an ultraviolet lamp for 30 minutes at 35 ° C., and the reaction from a colorless body to a colored body proceeded.

When this recording layer 16 was observed by an optical microscope, the size of the aggregate was 1 μm or less and the uniformity was good.

As described above, even when one recording layer is formed of a multi-layered monomolecular film, the formation of aggregates is effectively reduced.

Further, this recording layer 16 could be erased by irradiation with ultraviolet light in addition to recording with a visible laser.

These results show the applicability to a high density rewritable recording medium having recording pits of 1.0 μm or less.

Example 8 The effect of the control layer when the recording medium has a plurality of recording layers was examined. SP1822 was used as the dye.

As shown in FIG. 10, as the material of the recording layer 1, SP1822, control layer
Barium stearate is used as the material of the recording medium 8 and the monomolecular films are alternately accumulated one by one on the substrate 4 to form the recording medium 8.
Was formed.

 The recording medium 8 has 10 recording layers.

The accumulation of the recording layer 1 was performed under the accumulation condition 1 of Example 2, and the accumulation of the control layer 13 was performed under the accumulation condition 2.

The thickness of each control layer 13 and recording layer 1 was 25A.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

When the recording layer 1 was observed with an optical microscope, formation of aggregates was not observed. At this time, the absorbance was about 10 times that of Example 6.

Providing the control layer in this way has the effect of reducing the aggregates regardless of the number of recording layers.

At the same time, increasing the number of recording layers has the effect of increasing the absorbance and facilitating reproduction.

The recording layer 1 could be erased by irradiation with ultraviolet light in addition to recording with a visible laser.

These results show the possibility of adapting to a rewritable recording medium at a high density by forming recording pits of about the wavelength of the recording light source.

Example 9 The effect when two or more recording layers having different numbers of layers in the recording medium was examined.

 Only one type of SP1822 was used as the dye.

As shown in FIG. 1, the dye SP18 is used as the material for the recording layers 1 and 2.
The recording medium 9 was formed by accumulating two monolayers of monolayers and two layers of 22 monolayers of barium stearate as materials for the control layer 3 on the substrate 4.

Recording layers 1 and 2 were accumulated under accumulation condition 1 of Example 2, and control layer 3 was accumulated under accumulation condition 2.

Two recording layers were formed in the recording medium: a recording layer 1 having a thickness of 25 A and a recording layer 2 having a thickness of 50 A and a single monolayer. The thickness of each control layer 3 is 50
It was A.

This was irradiated with ultraviolet light for 30 minutes at 35 ° C. using an ultraviolet lamp.

When the recording medium 9 was observed with an optical microscope, only agglomerates of 10 μm or less were observed and the uniformity was good.

Also, the absorption of the recording medium had a maximum at 618 nm and 585 nm.

Incidentally, unlike the recording layer 1 having the absorption maximum at 585 nm, the recording layer 2 having the absorption maximum at 618 nm has a wavelength of 632.8 nm.
Recording with the He-Ne laser is now possible.

These results show that the adaptability of the recording medium to the high density rewritable recording medium can be improved by the light of different wavelengths.
Possibility of wavelength-multiplexed recording in which recording is performed on recording layers 1 and 2 using different dyes, and possibility of expanding light source selectivity by changing the number of monolayers in the recording layer Is shown.

Example 10 The carbon chain length of the control layer material and the effect of the control layer were investigated.

First, SP1822 was vapor-deposited on the substrate as a recording layer under the conditions of a vacuum degree of 5 × 10 ⁻⁶ Torr and an evaporation source temperature of 200 ° C., and two monolayers of n-C ₃₁ H ₆₃ COOH were recorded as a control layer. The recording medium 10 was formed by accumulating on the layers.

For the control layer, n-C ₃₁ H ₆₃ COOH was used in a benzene solution of 1 mmol / l, and the cumulative pressure was changed to 30 mN / m under the cumulative condition 1 of Example 2 and cumulative.

The recording medium 10 has the same configuration as that of the first embodiment. (See FIG. 2) The recording layer had a thickness of 120A and the control layer had a thickness of 80A.

This recording medium 10 was exposed to ultraviolet light at 35 ° C with an ultraviolet lamp.
Irradiated for 30 minutes.

When the recording layer 9 was observed with an optical microscope, the size of the aggregate was 1.0 μm or less, and the uniformity of the recording layer 9 was good.

Regarding the method of forming the recording layer, the recording medium 10 is formed by the vacuum evaporation method, but the recording layer is formed by the spin coating method under the same conditions as those for thinning the recording layer in Example 1.
The same treatment was observed for the recording medium 1a formed as a thin film of 0 A and the recording medium 2a formed as a thin film of 50 A by the LB method under the same conditions as the cumulative condition 1 of Example 2. The size of the aggregate is 2 μm or less for the recording medium 1a,
The recording medium 2a was 1 μm or less, and the uniformity of the recording layer was good.

As described above, regardless of which recording layer forming method, the formation of the agglomerates can be suppressed by providing the control layer, and moreover, it is effective regardless of the material of the control layer and the method of forming the thin film.

Further, as a material for the control layer, stearic acid (C) was used instead of n-C ₃₁ H ₆₃ COOH for the recording layer described above in the recording medium 10.
₁₈ H ₃₇ COOH) and C ₁₁ H ₂₇ COOH were used to form control layers to prepare recording media.

The accumulation of each long-chain fatty acid monomolecular film was performed under the same accumulation condition as that for n-C ₃₁ H ₆₃ COOH.

In each case, as with the recording medium 10, the ultraviolet light was irradiated for 30 minutes at 35 ° C. by the ultraviolet lamp.

The size of the aggregates observed was 1.0 μm or less, and the uniformity of the recording layer was good. Even if the carbon number of the fatty acid constituting the control layer was changed, the formation of aggregates of the dye in the recording layer There was a suppressive effect.

Further, when the control layer was formed using cadmium stearate, stearyl alcohol, stearyl amine, stearoamide instead of n-C ₃₁ H ₆₃ COOH under the same conditions as the recording medium 10, the aggregate size was 1.0 μm. The following was obtained, the uniformity of the recording layer was good, and it was effective in suppressing the formation of aggregates.

Incidentally, these recording layers could be erased by irradiation with ultraviolet rays in addition to recording with a visible laser.

This result shows the adaptability of any of these recording media to a high density rewritable recording medium.

Further, as a material for the recording layer, a recording medium was formed by using copper phthalocyanine instead of SP1822 of the recording medium 10.

When a recording layer of 120 A is formed by a vapor deposition method under the conditions of a vacuum degree of 5 × 10 ^-6 Torr and a vapor deposition source temperature of 450 ° C., and a control layer is formed on the recording layer with the same formulation and film thickness as the recording medium 10. After the same treatment as the recording medium 10, the size of aggregates observed is 1
It was less than or equal to μm and was effective in suppressing the formation of aggregates.

Example 11 The effect of the control layer was investigated using a mixture of short chains as the material for the control layer.

SP1822 was formed as the recording layer material under the recording layer thinning condition 1 of Example 1, and zinc valerate as the control layer material was thinned by the spin coating method under the following conditions to form the recording medium 11.

 The structure of this recording medium 11 was the same as in FIG.

 The recording layer had a thickness of 120A and the control layer had a thickness of 150A.

○ Control layer thinning condition 2 Zinc valerate 1.0% by weight aqueous solution 2000 rpm This recording medium 11 was exposed to ultraviolet light from an ultraviolet lamp at 35 ° C.
Irradiated for 30 minutes.

When the recording layer was observed with an optical microscope, the size of the aggregate was 2.0 μm or less, and the uniformity of the recording layer was good.

Regarding the method of forming the recording layer, although the recording medium 11 is formed by the spin coating method, the recording layer formed by the vapor deposition method under the same conditions as in Example 10 and the LB under the same conditions as cumulative condition 1 in Example 2. For the recording layer formed by the method,
The same control layer as in this example was formed, and the size of the agglomerates observed after the same treatment was observed both when the recording layer was formed by the vapor deposition method and when the recording layer was formed by the LB method. It was 1 μm or less, and the uniformity of the recording layer was good.

Thus, no matter which recording layer formation method is used, the control layer is provided, and the carbon number of the control layer material is short-chain compounds such as valeric acid (C ₄ H ₉ COOH). However, the formation of aggregates is effectively suppressed.

Further, when the control layer was formed by using barium propionate or zinc caproate instead of zinc valerate of the recording medium 11 as the material of the control layer, the same effect was obtained.

Further, these recording layers could be erased by irradiation with ultraviolet light in addition to recording with a visible laser.

This result shows the applicability of the above medium to a high density rewritable recording medium.

Further, as the material of the recording layer, the recording layer material of the recording medium 11 is used.
Instead of SP1822, using copper phthalocyanine described in Example 10 to form a recording layer under the same vapor deposition conditions as in Example 10,
The same control layer as the recording medium 11 was deposited to form the recording medium.

Also in this recording medium, the size of aggregates observed after the same treatment was 1 μm or less, and it was effective in suppressing the formation of aggregates.

EFFECT OF THE INVENTION The optical recording medium of the present invention is an optical recording medium in which a recording layer made of an ultra-thin film containing an organic dye and a control layer are alternately laminated, and the uppermost layer is the control layer. Agglomerates of dyes in the layer are small, and the recording density is high.

Moreover, since the absorption wavelength in the recording layer changes by changing the number of monolayers of the recording layer, there is an effect that the selection of the recording / reproducing light source is expanded.

Further, even when a single dye is used, wavelength multiplexing recording corresponding to different absorption wavelengths becomes possible by changing the number of laminated monomolecular films of the recording layer, which also has an effect of improving recording density.

[Brief description of drawings]

1 to 10 are schematic views showing accumulation patterns in the embodiment of the present invention. 1, 2, 9, 11, 12, 14, 15, ... Recording layer, 3, 10, 13,
Control layer, 5 hydrophilic part, 6 hydrophobic part, 7
Hydrophilic part, 8 ... Hydrophilic part, 4 ... Substrate

Claims (7)

(57) [Claims] 1. An optical recording medium comprising a recording layer and a control layer, which are made of an ultra-thin film containing an organic dye and are alternately laminated, and at least the uppermost layer is composed of the control layer. 2. The optical recording medium according to claim 1, wherein the recording layer is one monolayer or two monolayers. 3. The optical recording medium according to claim 1, wherein the organic dye is a photochromic compound. 4. The optical recording medium according to claim 1 or 2, wherein the recording layer contains at least one kind of fatty acid, fatty acid metal salt, alcohol, amine, hydrocarbon and amide. 5. The optical recording medium according to claim 1, wherein the control layer is composed of a monomolecular film. 6. The optical recording medium according to claim 1, wherein the control layer contains at least one of fatty acid, fatty metal salt, alcohol, amine and amide. 7. The optical recording medium according to claim 2, wherein the monomolecular film is formed by the LB method.