JPS6399990A - Optical recording disk - Google Patents

Abstract

PURPOSE:To provide an optical recording disk not affected by environments and retaining favorable sensitivity and S/N and facilitate the production of the disk, by incorporating a fluorine-containing hydrophobic substance in a coating composition so that the hydrophobic substance separates out after application of the composition to form a hydrophobic film containing the hydrophobic substance on a recording layer so as to face a gap layer. CONSTITUTION:To separately provide a recording layer 4 and a hydrophobic film 5, a fluorine-containing hydrophobic substance is added to a solution of a coating composition. The fluorine-containing hydrophobic substance may be a fluorine-containing oil, resin, oligomer, surface active agent or the like having a perfluoroalkyl group. The amount of the hydrophobic substance added is preferably about 0.1-5 pts.wt. per 100 pts.wt. of a coloring matter, and the viscosity of the coating composition solution is 20-50 cp. When the coating composition solution is applied to a substrate 31 by spin coating, the hydrophobic film 5 comprising the fluorine-containing oil or the like is separately and partly provided on the recording layer 4 comprising the coloring matter or the like as the coat film is dried. After spin coating is finished, a heat treatment is further conducted to effect complete separation of the hydrophobic film 5.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical recording discs, particularly heat mode optical recording discs.

Prior art optical recording disks have the characteristic that the recording disk does not deteriorate due to wear and tear because the medium and the writing or reading head are not in contact with each other, and for this reason, research and development of various optical recording media are being carried out.

Among such optical recording disks, heat mode optical recording disks are being actively developed because they do not require development in a dark room.

This heat mode optical recording disk is an optical recording disk that uses recording light as heat. For example, a part of the medium is melted or removed using recording light such as a laser, and a part of the medium is melted or removed to create a pit. There is a pit-forming type in which small holes are formed and δ is recorded, information is recorded using the pits, and the bits are detected with readout light and read out.

Until now, most of these pit-forming type disks, especially those using a semiconductor laser as a light source, which allows for miniaturization of the device, have a recording layer made of a material mainly composed of Te.

In addition, in recent years, organic materials mainly containing dyes have been used instead of Te-based materials due to the toxicity of Te-based materials and the need for higher sensitivity and lower manufacturing costs. An increasing number of proposals and reports have been made regarding media using recording layers of the above-mentioned type (Japanese Patent Application No. 19715-1980, etc.).

In a pit-forming optical recording medium having such a dye recording layer, a so-called air sandwich structure is preferably used in order to improve sensitivity and S/N ratio.

In this case, the air sandwich structure uses a pair of optical recording parts having a recording layer on a transparent resin substrate, and integrates them so that the recording layers face each other with a predetermined gap in between.

In order to integrate both optical recording parts in a disc with such an air sandwich structure, a resin ring-shaped connecting member is interposed as a spacer in the center part and the peripheral part, and this and the substrate of both optical recording parts are interposed. A method in which a plurality of rod-shaped protrusions are provided on the outer and/or inner circumference of the board, and the two boards are integrated via these protrusions (
There is a patent application No. 59-203284, etc.).

Some of the optical recording disks produced in this manner have ventilation holes in order to prevent distortion of the substrate due to the difference in pressure between the outside and the inside.

Such ventilation holes conversely cause dust and dirt to enter the gaps of the optical recording disk, adversely affecting recording and reproduction. For this reason, filters are often placed in the vents to prevent dust and dirt from entering.

Incidentally, the sensitivity of these various optical recording disks may decrease due to changes in the environment in which they are stored or used.

One of the causes of the decrease in sensitivity is due to moisture entering the gap of the optical recording disk, particularly through the vents, or condensation of the moisture originally present. This is thought to be because partial dissolution of the recording layer occurs due to dew condensation, and after the dew condensation evaporates, the film thickness becomes non-uniform, which causes reflection to be disturbed, resulting in a decrease in sensitivity and variations.

In such a case, there are known examples in which an inorganic compound is provided as a protective film on the surface, but in all cases the film thickness is 0.2 μm or more, and in such a case, the sensitivity itself decreases.

Therefore, the present inventors have reported that a hydrophobic film containing fluorine-based oil or the like is formed on the recording layer (Japanese Patent Application No. 1986-18
No. 3282).

Although this solves the above problem, it is necessary to add one more step after forming the recording layer to form a hydrophobic film.

Therefore, it is desired to develop new means that can simplify the process and reduce costs.

Note that in the case of single-sided recording in which the optical recording portion and the protective plate are integrated, the same procedure as described above is applied when the recording layer is brought into contact with the protective plate through the gap layer.

■ Purpose of the Invention The purpose of the present invention is to integrate a pair of optical recording portions each having a recording layer on a disc-shaped substrate so that the recording layer faces each other with a gap in between, or to form a protective layer with the optical recording portion. An optical recording disk that is integrated with a plate so as to seal the recording layer with a gap, which is not affected by the environment during storage and use, maintains a good sensitivity S/N ratio, and is easy to manufacture. The purpose is to provide discs.

■Disclosure of the invention Such objects are achieved by the invention described below.

That is, the present invention has a pair of disk-shaped substrates, and has a recording layer made of a dye or a dye composition formed by coating a coating composition containing a dye on at least one of the substrates,
In an optical recording disk in which both substrates are integrated so that the recording layer is located on the inside and a void layer is present on the recording layer, the coating composition contains a fluorine-based hydrophobic substance, and after application of the coating composition, The optical recording disk is characterized in that the hydrophobic substance is separated and a hydrophobic film containing the hydrophobic substance is formed on the recording layer so as to be in contact with the void layer.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

In the case of single-sided recording, the optical recording disk 1 of the present invention has a recording layer 4 provided on a disk-shaped substrate 31 and a hydrophobic film 5 on the recording layer 4, as shown in FIG. It has an optical recording portion 2 and a protection plate 35.

The substrate 31 used has a disk shape with a hole in the center into which the rotating shaft is inserted, and is made of resin that is substantially transparent (preferably with a transmittance of 80% or more) to writing light and reading light.

This allows writing and reading from the back side of the substrate.

Note that the resin material used may be any of acrylic resin, polycarbonate resin, nylon, TPX, and the like.

Further, the protection plate 35 may be made of the same material as the substrate 31. The protection plate 35 may be opaque.

A plurality of protrusions for integration with the substrate may be provided on the outer circumferential portion and/or the inner circumferential portion of at least one of the substrate and the protection plate. Further, integration may be performed using a connecting member as a spacer.

In FIG. 1, a plurality of projections 61, 71 are provided on the inner and outer peripheral portions of the protection plate 35, and the protection plate 35 is integrated via these projections.

The recording layer of the present invention preferably consists of a dye alone or a dye composition.

The dye to be used may be appropriately determined from among those that effectively absorb the wavelengths of the writing light and reading light. In this case, these light sources are
Since it is preferable to use a semiconductor laser because the device can be made smaller, the dyes may be cyanine-based, phthalocyanine-based, anthraquinone-based, azo-based, triphenylmethane-based,
Pyrylium or thiapyrylium salts are preferred.

Further, when the dye composition is used as a recording layer, it can contain a self-oxidizing resin such as nitrocellulose, or a thermoplastic resin such as polystyrene or nylon. Furthermore, a quencher may be included in order to prevent oxidative deterioration of the dye. Furthermore, other additives may also be included.

In such a case, a mixture of an indolenine cyanine dye and a quencher such as bisphenyldithiol is particularly preferred.

It is also preferable to use these as an ionic bond between a dye cation and a quencher anion.

For forming the recording layer, a ketone type, ester type, ether type, aromatic type, alkyl halide type, alcohol type, etc. may be used as a coating solvent.

The dye concentration in the coating solution may be about 1.5 to 3%.

In the present invention, in order to form the recording layer 4 and the hydrophobic film 5 separately, a fluorine-based hydrophobic substance is added to the coating composition solution.

Examples of fluorine-based hydrophobic substances include fluorine oils, resins, oligomers, and surfactants having perfluoroalkyl groups.

The perfluoroalkyl group of these fluorine-based hydrophobic substances preferably has about 1 to 3 carbon atoms or more.

In these cases, fluorine-based oligomers or resins are suitable, and commercially available products include Surflon S-381 and S-382 (Asahi Glass Co., Ltd.), which are fluorine-based oligomers.
, water-soluble fluorine-containing comb polymer LF-100W, L
F-200W, perfluoroalkylated graft copolymerized acrylic resin (<C type polymer LF-40, LF-45
) (Souken Kagaku) etc. are suitable.

These are graft polymers or oligomers having perfluoroalkyl groups in their side chains.

As the graft polymer or oligomer used in the present invention, a graft polymer synthesized using a reactive polymeric monomer having a polymerizable functional group at one end of the molecule in is particularly preferable. In this case, the polymeric material preferably has a fluororesin skeleton. One end of such a skeleton has a vinyl polymerization type or polycondensation type polymerizable functional group, and this is copolymerized.

In this case, the fluorine-based hydrophobic substance may be added directly to the coating solution, or may be a ketone type such as cyclohexanone or ME, a halogenated alkyl type such as dichloroethane or dichloromethane, an aromatic hydrocarbon type such as toluene, It is also possible to add propatool diluted with an alcohol-based solvent such as butanol.

Further, the amount of the fluorine-based hydrophobic substance added is preferably about 0.1 to 5 parts by weight per 100 parts by weight of the dye.

The viscosity of such a coating composition solution is 20 to 50 cp.

Application is usually by spin cord.

The rotation speed of the spinner is set to about 400 to 1000 r, p, m to form a coating film on the substrate.

When such a coating composition solution is spin-coated onto a substrate, as the coating film dries, a hydrophobic film 5 containing a portion of fluorine-based oil or the like is usually separated and formed on the recording layer 4 containing a dye or the like.

After the spin code is completed, further heat treatment is performed to complete the separation of the hydrophobic film 5.

The heat treatment may be carried out at 100° C. or less after maturation, and generally for about 10 to 60 minutes.

In this case, the hydrophobic film is formed by separating a hydrophobic substance such that, for example, perfluoroalkyl groups are arranged on the surface of the coating film, and the hydrophobic film is formed so as to cover the recording layer.

In this case, the thickness of the recording layer 4 is preferably about 0.01 to 10 μm.

In addition, when providing grooves for tracking control as described later, the thickness of the recording track portion in the recording layer is 0.2 μm.
The thickness is preferably 0.05 to 0.15 μm, more preferably 0.05 to 0.15 μm.

At this time, writing sensitivity is improved. Further, due to multiple reflections in the recording layer, the reflectance becomes extremely high, and the read S/N ratio becomes extremely high. Then, the difference in reflectance based on the difference in thickness between the recording track portion and other areas increases, making tracking control easier.

Further, the hydrophobic film 5 is about 2 to 50 λ, preferably 5 to 1
It is preferable to have a thickness of approximately Oλ.

If the thickness of the hydrophobic film is less than 2λ, a continuous coating of the hydrophobic film will not be formed and the effects of the present invention will not be achieved.

Moreover, if the number of hydrophobic films exceeds 50, disadvantages such as a decrease in sensitivity will arise.

The hydrophobic film 5 thus formed forms a continuous film on the surface of the recording layer 4 facing the void layer, and the contact angle of the hydrophobic film with water is 6.
It is preferable that the angle is 0° or more.

If the contact angle is less than 60°, the effects of the present invention will not be fully exhibited due to insufficient water repellency of the hydrophobic film.

By providing such a hydrophobic film, even if dew condensation occurs due to environmental changes, it will only exist as water droplets on the hydrophobic layer, completely eliminating negative effects V (reduction in sensitivity and S/N ratio) on the recording layer. can be prevented.

Note that although the above-described separation formation of the recording layer 4 and the hydrophobic film 5 from the coating film may be completed after the spin code is completed, it is usually formed only partially. Then, as described above, heat treatment is performed after the spin cord to complete the separation, and both layers thus formed are extremely stable.

Ultrasonic fusion may normally be used to integrate the substrate 31 having the recording layer 4 and the hydrophobic film 5 with the protection plate 35 and the like via the protrusions 61 and 71.

Ultrasonic welding forms an airtight outer peripheral wall over the entire surface.

Also, vents can be formed between the partition walls.

Fixing can also be achieved by injecting adhesive.

Alternatively, a hot melt resin may be applied as an adhesive to the peripheral edge of the substrate, and then both substrates may be combined and subjected to ultrasonic fusion, so that they may be integrated using a combination of so-called adhesion and fusion.

In order to form such a plurality of rod-shaped protrusions, a master or a stamper may be processed and integrally formed when molding the substrate.

Above, we have explained the integration using rod-shaped protrusions, but
In addition, various known integrated structures are possible.

It is preferable that tracking grooves be formed on the surface of the substrate 31 on which the recording layer 4 is formed.

The depth of the groove is about λ/8n, especially λ/7n to λ/
12 n (where n is the refractive index of the substrate). Further, the width of the groove is approximately the width of a track.

Formation of such grooves on the substrate may be performed by a resin injection molding method, or by a so-called 2P method using a photopolymer.
It may be done by law.

In the case of the 2P method, a photopolymer is applied to a predetermined thickness on a flat substrate made of the various resins mentioned above, and a stamper is pressed onto the photopolymer to cure it with ultraviolet rays to form grooves.

The grooves formed by the No. 22 method have a sharp shape;
It has the advantage that the recording layer has good reflectance.

It is preferable that the recording layer 5 located in the recessed portion of the groove be used as a recording track portion, and write light and read light are irradiated from the back side of the substrate.

With this configuration, the writing sensitivity and the reading S/N ratio are improved, and the tracking control signal is also increased.

Note that a known base layer of yuzu can be formed between the recording layer and the substrate.

Note that although we have discussed the case of single-sided recording above,
In the present invention, a double-sided recording medium may be used in which recording layers are provided on both substrates. In this case, both substrates need to be substantially transparent (preferably with a transmittance of 80% or more).

(2) Specific Effects of the Invention The optical recording disk of the present invention irradiates reading light from the back side of the substrate while rotating. As a result, pits are preferably formed in a track shape in the recording track portion located in the groove recess.

The bits formed in this manner are detected by emitting readout light from the back side of the substrate while rotating and detecting the reflected light.

In order to control tracking, the reflected light is usually split while writing and reading.
Introduce it to a pair of sensors divided into two. At this time, when the beam spot begins to deviate from the recording track section, the primary light due to the interference effect due to the phase difference due to the step of the groove is biased toward one sensor, so the signals from both sensors are detected.
A track error signal is detected.

Note that if the recording layer is formed from a dye composition containing a thermoplastic resin, once formed pits can be erased by light or heat and writing can be performed again.

In addition, the light source used for writing and reading is
Although various lasers can be used, it is particularly preferred to use semiconductor lasers.

(2) Specific Effects of the Invention In the present invention, a hydrophobic film is separated and formed on the recording layer after one-part coating of the recording layer coating composition.

Therefore, even if dew condensation occurs due to changes in the environment in which the optical recording disk is stored or used, it will only exist as water droplets on the hydrophobic crotch.

Therefore, it is possible to prevent bad i99 caused by water from entering the recording layer, and it is possible to provide an optical recording disk that always maintains good sensitivity and S/N ratio.

Furthermore, since the formation of the hydrophobic film of the present invention can be carried out in the same process as the formation process of the recording layer, it is possible to simplify the manufacturing process and reduce costs.

Furthermore, when forming a hydrophobic film after forming a recording layer, the dye may be dissolved by the hydrophobic film coating solvent, but the present invention solves this problem.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown and the present invention will be explained in more detail.

EXAMPLE A base layer containing a partial hydrolyzate of silicate ester was formed on a disc-shaped substrate of PMMA resin material with a diameter of 12 cm and a thickness of 1.2 mm, which had a pre-group, and an indolenine cyanine dye was formed on this. Coating was performed by a spin cord method using a coating solution containing a nickel bisphenyldithiol stabilizer and a fluorine-based hydrophobic substance.

The coating solvent was cyclohexanone, and the dye concentration was 2.2.
%, and the hydrophobic substance concentration was 0.5%.

The hydrophobic substances used are as follows.

Fluororesin 1: Surflon S-382 (manufactured by Asahi Glass Co., Ltd.) Fluororesin 2: Comb-shaped polymer LF-40 (manufactured by Soken Kagaku Co., Ltd.) After the spin cord was completed, the coating film was heated at 100° C. for 60 minutes.

The thickness of the recording layer was 0.05 μm, and the thickness of the hydrophobic film was about 10λ.

Next, this optical recording portion and a protection plate (made of PMMA resin) were integrated by ultrasonic welding so as to enclose the recording portion to form an optical recording disk.

Each disk produced in this way was heated at 80°C and 80% R.
After leaving it in H for 24 hours, it was cooled to 10°C and dew condensed.
Thereafter, it was left at room temperature for 2 days.

Then, variations in the reflectance of the recording surface of each of these disks were measured.

The results are shown in Table 1.

Table 1 Sample hydrophobic film reflectance No.
(Contact angle) Variation 1 Fluororesin 1 None 115°) 2 Fluororesin 2 None 120°) 3 Yes

[Brief explanation of the drawing]

FIG. 1 is a cut end view showing an example of the optical recording disk of the present invention. Explanation of symbols 1... Optical recording disk, 2...
...Optical recording part, 31...Substrate, 35...Protection plate, 4...Recording layer, 5...・・・・・・Hydrophobic membrane, 61.71・・・Rod-like protrusion Patent applicant TDC Co., Ltd. Agent Patent attorney Yo Ishii -Fl (3,1

Claims (1)

[Scope of Claims] A pair of disc-shaped substrates, a recording layer made of a dye or a dye composition formed by coating a coating composition containing a dye on at least one of the substrates; is located on the inside, and the two substrates are integrated so that a void layer is present on the recording layer. 1. An optical recording disk characterized in that a hydrophobic film containing the hydrophobic substance is formed on the recording layer so as to be in contact with the void layer.