JPS61123593A - Recording medium - Google Patents

Abstract

PURPOSE:To obtain a photo recording medium which is easy to be prepared, of low noise level, and highly sensitive and able to be re-written by having a protective layer containing organic compound which produces three dimension al cross-linked network through reaction to irradiation of light. CONSTITUTION:On a surface of one side of a substrate 1 of a thickness of 1.2mm [for instance; glass plate, polymethyl methacrylate (PMMA) plate etc.], a protective layer 2 in which crosslinking action has been taken place between photo-setting organic compounds (for instance; trimethylol-propane triacrylate etc.) which has three or more reactive portions in a moleculel; and a sensitizer (for instance; benzophenone etc.) is provided in a preferable thickness of 10nm-2mm, and on the top of it, a chalcogenide film 3 is formed by vacuum distillation or spattering. Then, another protective layer 4 of a preferable thickness of 10nm-2mm is provided with the same or a different material as that of the protective layer 2, resulting in obtaining of subject recording medium.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a maintenance layer of a recording film in which recording is performed using an energy beam such as a laser beam. It was measured.

[Background of the invention]

Conventionally, an inorganic layer such as 5iOz has been considered as a protective film in a rewritable optical recording medium that utilizes a mutual phase change (transition) between crystal and amorphous in a chalcogenide recording film. When a crystalline state is transformed into an amorphous state by a laser beam, the irradiated portion of the recording film is once melted and then rapidly cooled to become amorphous. The role of the protective film is to prevent the recording film from being perforated or deformed when it melts. However, although an inorganic protective layer is advantageous in terms of preventing the above-mentioned deformation, it has the disadvantage that the recording sensitivity of the optical recording film is lowered due to its relatively high thermal conductivity. Another drawback is that the method for creating the inorganic layer is complicated. Furthermore, as described in Japanese Patent Publication No. 52-2783, there are some that use epoxy resin, polystyrene, etc. as part of the protective film. However, the degree of crosslinking is low or
It is not cross-linked at all and is weak in hardness.
The disadvantage was that the noise level was high.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to overcome the drawbacks of conventional recording sensitivity such as low recording sensitivity and high noise level, and to provide a rewritable optical recording medium that is easy to produce and has high sensitivity.

[Summary of the invention]

In the present invention, a highly hard organic adhesive layer is used in place of the conventional inorganic protective layer. Generally, organic materials have lower thermal conductivity than inorganic materials.

The laser light beam is absorbed by the chalcogenide film and converted into thermal energy. The heat generated at this time is also transferred to the protective layer, and the lower the heat conductivity of this protective layer, the more effectively this heat is used. I become extremely sensitive. On the other hand, it is essential to increase the number of reseeding times that the cal;genide material undergoes little change in shape when melting.

Therefore, the protective layer must have high hardness to suppress changes in the shape of the recording film. Further, when creating an organic layer, an extremely simple method of coating can be used.

In addition, an extremely thin inorganic layer is provided between the organic protective layer and the recording film, for example, a 5-ins layer with a thickness of about 5 to 80 nm.
A layer may be provided. As a result, 111! Can be reinforced to a certain degree. Furthermore, since the inorganic layer is an extremely thin layer, there is little heat diffusion due to thermal conduction, so there is little deterioration in sensitivity. In this case as well, it is necessary to use an organic substance with high hardness for the organic substance protective layer. The main layer that suppresses changes in the shape of the recording film is not an inorganic layer but an organic layer.

By using such a highly hard organic material as a protective layer, an optical recording medium with high sensitivity and a high number of rewrites can be obtained. Also, if you record only one time without exchanging honors, it will be too busy.
Contributes to improved reliability such as N ratio, error rate, and shelf life.

[Embodiments of the invention]

The present invention will be explained below with reference to FIG. 1.2. As the substrate 1 in FIG. 1, a 12 m thick glass plate or a plastic substrate such as a PMMA plate is used.

A highly hard organic layer 2 is provided on one surface of this substrate.

An organic layer with high hardness can be obtained by proceeding with a network crosslinking reaction in a three-dimensional structure. Organic compounds that easily form three-dimensional network structures include:
It is desirable to have three or more reactive sites in the molecule. Due to this, organic substances that are complexly bonded to each other can be formed. A thin film is formed by applying unreacted substances and then reacting them. Photocurable organic compounds having three or more reactive sites in the molecule include trimethylolpropane triacrylate;
Trimethylolpropane trimethacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, 1°3.5-tris(β-acryloyloxyethyl)in cyanurate, 113,5
- Tris(β-methacryloyloxyethyl)in cyanurate, pentaerythritol tetraacrylate,
Pentaerythritol tetramethacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, dipentaerythritol hexamethacrylate, dipentaerythritol hexa(ω-acryloyloxy-6-caproate), dipentaerythritol hexa(ω-methacrylate) royloxy-C-caproate) and the like, and these can be used singly or in mixtures. Further, these monomers having three or more functional groups can be used in combination with other monomers, for example, monomers having two functional groups.

Furthermore, there are no restrictions on the sensitizer, and those conventionally used can be used as they are. Examples include benzophenone, θ-carbomethoxypentuphenone, 4
．． 4'-dichlorobenzophenone, 4.4'-dimethylaminobenzophenone, 4.4'-diethylaminobenzophenone, acetophenone, benzyl, benzoin, penzoin inglobil ether, penzyl dimethyl acetal, 1,1-dimethoxyacetophenone, 2 −
Ethyl anthraquinone, 2-t-7' tylanthraquinone, 2-70 lothioxanthone, 2,4-diethylthioxanthone, 2,4-diisopropylthioxanthone, etc. are used alone or in combination of two or more. It is also possible to use this th crab sensitization adjuvant. Examples of the sensitizing adjuvant include tertiary amines such as dimethylethanolamine, triethanolamine, p-dimethylaminobenzoic acid alkyl ester, and mercaptans.

The thickness of this S-holding film is from 1Q nm to 2emj.

A particularly preferable thickness is in the range of 0.2 μm or more and 100 μm or less. A chalcogenide film 3 is formed on this protective film by vacuum evaporation or sputtering.

Chalcogenide materials are required to reversibly change between crystalline and amorphous states. The material for this is TeQx(x(λO), Te.

Te-8e, 'I'e-86-Get Te-86-8
There are many compositions such as n, As-'fe-G6, etc. It is preserved on this chalcogenide film! An M film 4 is provided. This protective layer 4 can use the organic material of the protective layer 2 described above. The protective layer 4 and the protective layer 2 do not need to be made of the same material. The thickness of the protective layer 4 is 2 nm from 1Q nm. Particularly preferred thickness is 0.2 μm or more and 100 μm
The range is as follows. It is better for the protective layer 4 to have a large thickness in order to prevent deformation of the recording film. Further, a structure in which a glass or plastic substrate is laminated onto the protective layer 4 using an adhesive is also possible. Generally, it is preferable for the protective layer to be present on both sides as in this example, rather than on one side.

The laser beam may be irradiated from the substrate side or from the protective layer 4 side.

Next, we will briefly describe the apparatus for the recording medium obtained and the method for evaluating the number of exchanges.

A semi-integrated laser beam with a wavelength of 830 nm is irradiated through the substrate of the recording medium. This laser pulse is shown in FIG. This is one cycle of amorphous/crystalline. By the write pulse 5, the recording film in a crystalline state is once melted and changed into an amorphous state. If the pulse height and light intensity are small enough to cause this change, then the sensitivity is high. On the other hand, the narrower the pulse width, the higher the sensitivity. The read pulse 6 is used to read out the crystalline and amorphous states as a difference in reflected light intensity without changing the recording film. The erasing pulse 7 is used to change the state from an amorphous state to a crystalline state, and in this case, the change occurs while remaining in a solid state without passing through a molten state. In this case, the pulse height is generally lower than that of the write pulse and the reached temperature is also lower, but the pulse width is wide and damage may occur if the material of the retention film layer is not appropriate.

The number of rewrites is evaluated by fixing the recording medium, continuously applying the pulse shown in FIG. 2 to one point on its surface, and reading the change in the magnitude of the signal output due to the read pulse. In this case, the signal output corresponding to the crystalline state is large, and the signal output corresponding to the amorphous state is small. As the number of repetitions increases, these signal outputs decrease at a certain number of times. This is due to deformation of the recording film. The number of times until this decrease starts is referred to as the number of rewrites.

Example 1 Dipentaerythritol hexa-(ω-acrylocarproate (hereinafter referred to as DPCA-
60 parts), 60 parts of 2'-bis-(4-acryloxyethoxyethyloxyphenyl)propane (common name: tetraoxyethylated bisphenol-A diacrylate, hereinafter referred to as Hiscoat +700), Ethylene glycol diacrylate (hereinafter referred to as A-4G)
), 5 parts of benzophenone, 2゜2'-
A photosensitive composition containing 0.2 parts of methylenebis(4-ethyl-6-t-butylphenol) (hereinafter referred to as AW-500) was added to a mold with tracking grooves made in advance under conditions where ultraviolet light was removed. and apply it to a thickness of 1.2
A glass substrate was placed in between. Exposure was carried out for 30 seconds at a distance of 10 cPn from a 4 kW high pressure mercury lamp from the direction of the glass substrate. Thereafter, the gold film was peeled off to obtain a protective film having tracking grooves formed on the glass substrate. Next, the protective film was heat-treated for 150,060 minutes. Protect WI! The thickness of the film was approximately 50 μm. Next, a recording film was deposited on this protective film. The recording film composition is 'I' e -f3 e-Qe. The film thickness is about 13 Qnm. The mixture having the above composition was again spin-coated onto this recording film, exposed to light under the same conditions as above, and heat treated to obtain a protective layer. The thickness of this protective layer was 30 μm. With this heat treatment, the f! The film becomes crystalline. The recording sensitivity and number of replacements of this sample were measured and compared with a sample using 5iOz with a thickness of 1001 mm as a protective layer. As a result, the sensitivity of the protective layer sample of this example was approximately twice as high.

The number of repetitions was approximately 5×10” times.

The number of repetitions of the 5iOz layer sample was 10 times or more. In the protective layer of this example, 5 jOz does not reach any repeating number, but the sensitivity is about twice as high, and it is promising as a rewritable high-sensitivity optical recording medium.

Example 2 In Example 1, a composition containing 10 parts of DPCA-60, 70 parts of Viscoat◆700, and other compositions having the same composition as in Example 1 was treated in the same manner as in Example 1, and the sensitivity and The number of repetitions was evaluated. As a result, almost the same effect as in Example 1 was obtained, but because the composition ratio of DPCA-60 was reduced, the number of repetitions was slightly smaller at 4×10' times.

Example 3 In Example 1, 30 parts of trimethylolpropane triacrylate having three photoreactive sites, 60 parts of Skort φ700, and A-4G were used.

10 parts, 5 parts of 1,1-dimethoxyacetophenone, A
Example 1 Photosensitive composition containing 0.2 parts of W-500
A film with a thickness of 60 μm was prepared on a 1.2 m glass substrate using the same method as above. 'L' as a recording film is placed on this protective film.
An e-Se-3n film was deposited.

Next, the photosensitive composition of Example 3 was formed on the recording film by spin coating to a film thickness of 8 μm, and after heat treatment at -150C for 1 hour, the sensitivity and number of repetitions were evaluated.

As a result, the same sensitivity as in Example 1 and the number of repetitions of 2×10′ were obtained.

Example 4 In Example 1, 50 parts of pentaerythritol tetraacrylate having four photoreactive sites,
Multiple samples were prepared in the same manner as in Example 1 using a photosensitive composition consisting of 40 parts of hexanediol diacrylate, 10 parts of A-4G, 5 parts of benzophenone, and 0.2 parts of AW-500. The thickness of the protective film was 60 μm on the glass substrate side and 70 μm on the opposite side. As a result, the sensitivity was approximately twice that of the 8102 protective film, and the number of repetitions was 4×10' times.

Example 5 A protective film was formed on a 1.2 mm glass substrate using the photosensitive composition of Example 1 in the same manner as in Example 1, and heat-treated. The thickness of the protective film was approximately 40 μm. Next, a 5jCh film of p20 is deposited on this protective film by sputtering.
It was formed with a film thickness of nm.

Next, Te-3e-Qe as a recording film is placed on the Brow film.
A film was formed. Next, a 5i (h film) was formed on this recording film with a thickness of p2Qnm by sputtering.Finally, a protective film was formed using the photosensitive composition of Example 1 in the same manner as in Example 1. .

The thickness of this protective film was approximately 10 μm. As a result, the sensitivity of SiO! The reduction was approximately 20% compared to the case without the membrane. Further, the number of repetitions was 106 times or more.

Example 6 In Example 1, a thermosetting epoxy resin was used instead of the ultraviolet curable resin. Apply an epoxy resin consisting of 50 parts of bisphenol A diglycidyl ether (trade name: Ebicoat 828), 50 parts of hexahydrophthalic anhydride, and 1 part of benzyltrimethylammonium chloride,
A protective film was obtained by heat treatment at 150C for 30 minutes. the result,
The sensitivity and number of repetitions were the same as in Example 1. However, when the CN ratio was measured after repeated use for 10 seconds, it was about 3 dB lower than in Example 1.

This is presumed to be because the recording film was slightly attacked by the acid present inside the epoxy resin.

〔Effect of the invention〕

According to the present invention, the sensitivity is high and the number of rewrites is 105.
An optical recording medium that can be rewritten more than once is obtained. Further, the protective film of the present invention is also effective for recording films based on other recording principles such as magneto-optical recording.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of the optical recording medium of the present invention, and FIG. 2 is a diagram showing optical pulses used to evaluate the sensitivity of the recording medium and the number of rewrites. DESCRIPTION OF SYMBOLS 1... Substrate, 2, 4... Protective layer, 3... Chalcogenide recording film, 5... Write pulse, 6... Read bar 1st rod 20

Claims (1)

[Claims] 1. A photocurable organic compound having at least three or more sites on one side or both sides of a recording film on which recording is performed using an energy beam such as a laser beam, which binds to other organic compounds upon irradiation with light. A recording medium comprising a protective layer containing at least one type of. 2. Claim 1, wherein at least one of the protective layers on one side of the recording film further has an inorganic material layer laminated between the protective layer and the recording film side. recording medium. 3. The recording medium according to claim 2, wherein the inorganic material layer is silicon dioxide. 4. The recording medium according to claim 3, wherein the silicon dioxide film has a thickness of 5 to 80 nm.