JPH02226529A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To perform precise recording and reproduction and to prevent inconvenience such as deformation, etc., from occurring by providing a ventilating area where ventilation can be performed at the inner peripheral and outer peripheral parts of a protection layer which covers an annular recording layer, and joining the protection layer. CONSTITUTION:In an optical disk 12, an annular recording medium layer 2 is formed on an annular disk shape substrate 1, and the protection layer 3 is formed on the layer 2. The layer 3 is joined with the substrate 1 at the inner peripheral part 4 and the outer peripheral part 5. And the ventilating areas 6a and 6b are formed at a joining part with the substrate 1 at the inner peripheral part 4 and the outer peripheral part 5 of the layer 3. The total area of the area 6a of the inner peripheral part 4 is formed larger than that of the area 6b of the outer peripheral part 5. In the disk 12 formed in such way, an air layer in which the layer 3 is floated over the layer 2 is formed when it is rotated in a direction of arrow head A at high speed and recording and reproduction are performed with a laser beam, and the source of air entering from the area 6a passes through from the area 6a to the outside. Thereby, a normal bit can be formed with an appropriate laser power.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical information recording medium in which information is recorded and reproduced using thermal energy such as a laser beam, and more specifically, the present invention relates to an optical information recording medium in which information is recorded and reproduced using thermal energy such as a laser beam. The present invention relates to an optical information recording medium having the following.

(Prior art) In recent years, recording using high energy density laser beams, etc.
Optical information recording media for reproduction have been put into practical use, and examples of such information recording media include video discs, audio discs, large-capacity still image files, and optical discs used as large-capacity computer disk memories.

The basic structure of such an optical disk is a ring-shaped transparent substrate made of plastic, glass, etc., and a recording layer provided on this substrate.A protective layer is used to protect the recording layer, which is easily influenced by the outside world. In recent years, it has become known that a ring-shaped resin film is bonded above the recording layer. (Unexamined Japanese Patent Publication No. 59-38339, Utility Model Application No. 82-17
No. 5428, Japanese Utility Model Application No. 82-175427).

Such a resin film is bonded to the substrate along the outer and inner peripheries in a manner that seals the recording layer in the non-recording areas of the inner and outer peripheries of the annular substrate described above.

(Problems to be Solved by the Invention) However, as mentioned above, the protective layer made of a resin film is placed in direct contact with the recording layer, so it is difficult to record.

There were some unfavorable points during playback. In other words, for example, recording of signals on these optical disks is performed by heat mode recording, which is performed by injecting a laser beam into the recording layer from the substrate side, partially evaporating or sublimating the recording layer, and forming pits with a diameter of about 1 μm in the traces. However, as mentioned above, if the protective layer is in direct contact with the recording layer, the energy of the laser beam will be diffused into the protective layer, causing energy loss.
In addition, there have been other inconveniences such as partial evaporation or sublimation from the recording layer becoming difficult to occur and normal pits not being formed resulting in recording errors.

On the other hand, unevenness is provided on the surface of the resin film in contact with the recording layer (Japanese Unexamined Patent Publication No. 59-313339), and a porous sheet is interposed between the resin film and the recording layer (Utility Model Application No. 82-175428). ), etc. have been proposed. However, even with these methods, the resin film comes into direct contact with the recording layer locally, so laser energy is dissipated and normal pits are difficult to form.

It is also conceivable to interpose a sealed air layer between the recording layer and the protective layer, but in optical discs with such an air sandwich structure, changes in external pressure, temperature, etc. The air inside may expand, which may cause tension in the resin film, causing the substrate to warp and cause distortion.

Therefore, in order to adjust the difference in atmospheric pressure between the inside of the air layer space and the outside, it is necessary to provide an air inflow hole through which outside air can flow.

However, in a protective layer made of resin film, if the air ventilation holes are too large, foreign matter such as dust from the outside world will accumulate in the air layer through the ventilation holes, causing deterioration and damage to the recording layer.
Furthermore, if the ventilation holes are too small, there is a problem in that the intended atmospheric pressure regulation function is degraded.

In view of the above-mentioned problems, the present invention provides accurate recording,
The object of the present invention is to provide a high-performance optical information recording medium that can be reproduced and does not cause problems such as deformation.

(Means for Solving the Problems) The optical information recording medium of the present invention includes an annular recording medium layer formed on a disk-shaped substrate, and an annular recording medium layer that covers the recording medium layer, and an inner circumferential portion or an outer circumferential portion of the disk-shaped substrate. In an optical information recording medium comprising a protective layer bonded to a protective layer, a ventilation area through which passage can pass is formed in a part of the outer peripheral part of the protective layer, and a part or all of the inner peripheral part of the protective layer is formed. It is characterized by forming a ventilation area that allows ventilation.

Also, said Ho:! ! It is appropriate that the ventilation area formed on the inner periphery of one layer is larger than the ventilation area formed on the outer periphery. Note that the term "large" means that the area of the inner circumferential ventilation area is increased in the relative area between the inner circumferential ventilation area and the outer circumferential ventilation area.

In addition, the ventilation area may be defined as a part of the inner and outer peripheries that are not bonded to the substrate and the non-bonded areas may be used as ventilation areas, but the inner and outer peripheries may be entirely bonded to the substrate and ventilation holes are formed in the inner and outer peripheries. It may also be used as a ventilation area.

(Function) Since the present invention has the above-described structure, when the medium is rotated for recording and reproduction, air enters from the ventilation area and an air layer is formed between the protective layer and the recording layer. In other words, due to the centrifugal force caused by the rotation of the medium, an airflow is generated from the inner circumferential side to the outer circumferential side, causing the protective layer to float above the medium surface, and the air entering from the inner circumferential ventilation area escapes from the outer circumferential ventilation area. An air layer through which air can circulate is formed between the recording layer and the protective layer.

At this time, the air layer can be formed more effectively by making the amount of air flowing in from the inner circumferential ventilation area larger than the air flowing out from the outer circumferential ventilation area.

(Execution N) Hereinafter, the optical information recording medium of the present invention will be explained using the drawings.

FIG. 1 shows an optical information recording medium (optical disk) of the present invention 1
2 is an explanatory plan view of FIG. 2, and FIG. 2 is an explanatory cross-sectional view of FIG. 1 taken along the line ■-■.

The optical disc 12 has an annular recording medium layer 2 coated on an annular disk-shaped substrate 1, and a protective layer 3 for protecting the recording layer 2 formed on the recording layer 2.

This protective layer 3 has substantially the same shape as the substrate 1 and is bonded to the substrate 1 at the inner circumferential portion 4 and outer circumferential portion 5 . Ventilation regions 8a and 6b are formed in the inner circumferential portion 4 and outer circumferential portion 5 of the protective layer 3 at the joint portions to the substrate 1. This ventilation area Ga, 8b is located at the outer peripheral portion 5.
It is provided by forming non-contact parts of the substrate 1 and the protective layer 3 at approximately equal intervals along the circumference of the inner circumferential part 4, and the total area of the ventilation area (ia) of the inner circumferential part 4 is equal to the outer circumference. The area is larger than the total area of the ventilation area 6b of the portion 5.

The ratio of the outer ventilation area 8b to the inner ventilation area 6a is preferably 10% to 90%, more preferably 40%.
% to 70%. Further, when the circumference of the outer circumferential portion 5 is twice as long as the circumference of the inner circumferential portion 4, the ratio of the ventilation area to the entire circumference is the ventilation area of the inner circumference (10 in 3a).
-100% is preferred, more preferably 70-100%
It is. In addition, in the ventilation area 6b on the outer periphery, 5% to 4%
It is preferably 5%, more preferably 15% to 45%.

The material of the resin film forming this protective layer includes acrylic resin, vinyl chloride resin, polystyrene resin, polyamide resin, polyolefin resin, (for example,
polypropylene, polyethylene), polycarbonate,
Examples include polyester resins and thermoplastic resins such as polyvinylidene chloride.

The resin film may be bonded to the surface of the substrate 1 using an adhesive, ultrasonic welding, heat fusion, or the like. Further, the surface of the resin film may be provided with irregularities in order to improve separation between the recording layer 2 and the protective layer 3.

Further, the substrate 1 can be made of various materials used as substrates of general optical information recording media. Examples include acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate, vinyl chloride resins such as polyvinyl chloride copolymers, epoxy resins, amorphous polyolefin resins, and synthetic resins such as polycarbonate. . Among these, polymethyl methacrylate and polycarbonate are preferred from the viewpoint of dimensional stability, transparency, flatness, etc.

An undercoat layer (and/or intermediate layer) is provided on the surface of the substrate on the side where the recording layer 2 is provided for the purpose of improving flatness, increasing adhesive strength, and preventing deterioration of the recording layer 2. Good too.

Next, as an example of the material used for the recording layer 2, T
c5Zns In, Sn, Zr5A'; 1zsT 1
Examples include metals such as s Cu SG Os A u s P 1, semimetals such as B1, As, and Sb, semiconductors such as St, and alloys thereof, or combinations thereof. Further, compounds such as sulfides, oxides, borides, silicide compounds, carbides, and nitrides of these metals, semimetals, or semiconductors, and mixtures of these compounds and metals can also be used in the recording layer 2. . Alternatively, dyes and combinations of dyes, polymeric dyes, and the metals, semimetals, or semiconductors described above may be utilized.

The recording layer 2 may further contain various known metals, semimetals, semiconductors, or compounds thereof. The recording layer 2 can be formed on the substrate directly or via an undercoat layer using the above-mentioned materials by a method such as light blue coating, sputtering, ion blasting, or coating. The recording layer 2
may be a single layer or a multilayer, but the layer thickness is usually in the range of 100 to 5,500 layers, preferably in the range of 150 to 1,000 layers in view of the optical density required for optical information recording.

The surface of the substrate 1 opposite to the side on which the recording layer 2 is provided is coated with an inorganic material such as silicon dioxide, tin oxide, magnesium fluoride, etc., in order to improve the moisture resistance and moisture resistance. A thin film made of a polymeric material such as a thermoplastic resin or a photocurable resin may be provided by a method such as vacuum deposition, sputtering, or coating.

Further, the thickness of the resin film used in this example is usually in the range of 10 to 500 μm, preferably 50 to 2 μm.
It is in the range of 00 μm. Further, it is preferable to use a material having the same main components as the material of the substrate 1, and it is particularly preferable to use a material having the same composition as the material of the substrate 1.

The optical disc 12 having the ventilation areas Oa and Ob as described above is rotated at high speed in the direction of arrow A by fitting the spindle lO into the hole in the inner circumferential part 4, and when recording and reproducing with a laser beam, the optical disc 12 is heated by centrifugal force. The aforementioned inner ventilation area 6a
The air that has entered between the protective layer 3 and the n-layer 2 flows in the direction of the outer ventilation area 6b described above.
becomes. Therefore, an air layer is formed in which the protective layer 3 floats from the recording layer 2, and furthermore, this air flow 8a is transferred to the ventilation area 6 on the outer periphery.
b to the outside (8b>. At this time, since the ventilation area 6a on the inner periphery is wider than the ventilation area 6b on the outer periphery, an air layer is effectively formed by the airflow 8a. Recorded in this way.

++r The protective layer 3 and the recording layer 2 are selectively removed only during recording.
Since an air layer is formed between the wafer and the wafer, a normal bit can be formed with an appropriate laser power, and warpage and distortion of the substrate due to changes in external pressure and temperature can be prevented. Note that when the rotation of the medium stops, the airflows 8a and 8b from the inner circumferential side to the outer circumferential side due to centrifugal force disappear, but since no recording or reproduction is performed in this state, the protective layer may be in contact with the recording layer.

A specific example will be explained below.

(Example 1) Disc-shaped polycarbonate substrate with tracking grooves (outer diameter: 120 M, inner diameter: 15 M, thickness 1.2 N)
A groove with a diameter of 45 mm in inner diameter to 116 am in outer diameter, 0.06 μm deep, 1.1 μm wide, and 1.6 μm pitch was created by injection molding, and used for tracking of this board. A coating solution with the following composition was applied onto the grooved surface using a spin code method (rotation speed: 70 rpm).
) and dried at a temperature of 70° C. for 10 minutes to form a chlorinated polyethylene layer with a dry thickness of 400.

Coating composition Chlorinated polyethylene 0.3 parts by weight (Cz
Ha −y CQJy ) (y = 1.7, nm200) acetic acid n
-Butyl 1 part by weight Methyl ethyl ketone 9 parts by weight cyclohexane
100 parts by weight Next, on this chlorinated polyethylene layer, AuS ln and Gas were each added in a weight ratio of 35 parts by weight.
%, 40%, and 25%, and the layer thickness was 10%.
A recording layer of 00 people was formed. At this time, the heating power source flowing to the Au evaporation source was controlled so that the Au concentration was high on the substrate side and decreased as it approached the surface on the recording layer side.

Note that the Aua degree on the substrate side surface of the formed recording layer was 80%. Furthermore, a polycarbonate film (product name: Mitsubishi Gas Chemical Co., Ltd.) with minute irregularities on the surface (maximum irregularity depth 7.2 umSRa value, 5llTrL)
, Kneepilon Matte Film, FE-2000M Ol
, 130 μTrL) was cut into a piece with a center hole diameter of 35 m and an outer diameter of 120 #, which was laminated concentrically on the surface of the recording layer as a protective layer and bonded to the substrate using a heat fusion machine to produce an optical disc.

In this joint part, several ventilation areas were formed at the joint part of the outer circumferential part and the inner circumferential part. The area of the ventilation area at the inner periphery was twice as large as that of the ventilation area at the outer periphery.

(Example 2) An optical disc having a protective layer was produced in the same manner as in Example 1. The outer periphery of this protective layer was joined in a ring shape with several ventilation regions formed, and the inner periphery was not joined at all, providing a ventilation region over the entire circumference.

(Comparative Example 1) An optical disc having a protective layer was prepared in the same manner as in Example 1. Note that both the inner and outer peripheral portions of this protective layer were joined by a full-circumference thermal exciter, and no ventilation area was formed. Table 1 shows the ventilation area ratios of these three optical discs.

The optical discs obtained as shown in Table 1 and above were evaluated using an optical disc evaluation machine (NakaIllchl Disk Evaluation Apparatus 0M5), and the results are shown in Table 2.

Table 2 also shows the warp after aging in a thermostat for 10 days at 60° C. and 90% RH.

As is clear from Table 2, Example 1.2 has a smaller C/N characteristic than the comparative example (the recording condition is good, the BER is small, there are few bit errors, and there is roughly no warping after thermostat aging. You can see that it's small.

(Effects of the Invention) In the optical information recording medium of the present invention, the protective layer is bonded by providing ventilation areas on the inner and outer circumferences of the protective layer that covers the annular recording layer. During reproduction, as the medium is rotated, an air layer is formed between the protective layer and the recording layer due to air flow. Therefore, when recording and reproducing with a laser beam, the laser energy does not dissipate into the protective layer, so normal pits can be formed with appropriate laser power. Furthermore, since the air layer is an air current, there is no warping or distortion of the substrate due to oxidation due to external pressure, temperature, etc., and the performance is excellent. Furthermore, by providing ventilation from the inner circumferential portion to the outer circumferential portion, it is possible to prevent problems such as dust and the like from accumulating between the protective layer and the recording layer, which would otherwise occur due to the provision of ventilation holes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory plan view of an embodiment of the optical information recording medium of the present invention, and FIG. 2 is an explanatory cross-sectional view of FIG. 1 taken along the line -■. 1... Disc-shaped substrate 2... Recording medium layer 3.
...Protective layer 4...Inner peripheral part 5...Outer peripheral part 13a, [ib...Ventilation area 12.
・・Optical information recording medium

Claims (2)

[Claims] (1) An optical information recording medium comprising an annular recording medium layer formed on a disk-shaped substrate and a protective layer covering the recording medium layer and having an inner peripheral portion or an outer peripheral portion joined to the disk-shaped substrate. In this method, a permeable ventilation area is formed in a part of the outer periphery of the protective layer, and a permeable ventilation area is formed in a part or all of the inner periphery of the protective layer. Optical information recording medium. (2) The optical information recording medium according to claim 1, wherein the ventilation area at the inner circumference of the protective layer is larger than the ventilation area at the outer circumference.