JPH10188352A - Information recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the adhesion property of a translucent film and a transparent substrate and to obtain an information recording medium which has multiple layers of recording layers and a translucent film and has excellent environment resistance by forming the translucent film having an element film of a simple substance and dispersing a compd. of superfine particles into the simple substance element film. SOLUTION: The first recording layer 4 having rugged pits 3 of recording data is formed atop the transparent substrate 2 by a stamper. The transparent substrate 2 is introduced into the chamber of a sputtering apparatus. Sputtering of a silicon target and sputtering of an aluminum target are alternately executed to disperse the superfine particles of aluminum oxide or silicon oxide, etc., of 1 to 20nm in diameter into the silicon film or the simple substance element film of aluminum, etc. A space layer 6 is formed on such translucent film 5 and a single plate formed with an aluminum reflection film is stuck onto the transparent substrate 2 formed with the recording layer in such a manner that the first and second recording layers 4, 8 face each other, by which the optical disk is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording medium having a multi-layered recording layer and a light semi-transmissive film to read recording signals of each recording layer from the same surface. The present invention relates to an information recording medium having improved environmental resistance performance of a permeable film.

[0002]

2. Description of the Related Art Conventionally, a read-only optical disk shown in FIG. 4 and a rewritable optical disk shown in FIG. 5 have been known as information media for recording and / or reproducing audio, video, and other various information.

FIG. 4 is a schematic view showing a sectional structure of a read-only optical disk. In FIG. 4, the light irradiation side surface 21a of the read-only optical disk 21 is formed by a transparent substrate 22 of polycarbonate or the like.
On the recording layer 2 having the concave and convex pits 23 of the recording data
4 are formed. On this recording layer 24, a reflection film 25 such as an aluminum vapor-deposited film is formed.
Are covered and protected by a protective film 26 such as an ultraviolet curable resin.

FIG. 5 is a schematic diagram showing a sectional structure of a rewritable optical disk. In FIG. 5, a light irradiation side surface 31a of a rewritable optical disk 31 is formed by a transparent substrate 32 of polycarbonate or the like, and on this transparent substrate 32, an enhanced layer 3 made of a high-refractive-index dielectric is provided.
3 and the recording layer 34 are sequentially formed. On this recording layer 34, a reflective film 36 such as an aluminum vapor-deposited film is formed via a protective layer 35 made of a high refractive index dielectric, and this reflective film 36 is covered with a protective film 37 such as an ultraviolet curing resin. We are protected.

As described above, these optical disks 21 and 3
In the sectional structure of No. 1, each of the recording layers 24 and 34 was a single layer.

However, as the amount of information used increases,
It is necessary to increase the recording density per unit area of the optical disc, and for next-generation optical discs such as digital video discs, use of a high-density optical disc having a multi-layered recording layer has been considered.

FIG. 6 is a schematic view showing a sectional structure of a high-density optical disk. In FIG. 6, the high-density optical disc 41
A first recording layer 44 having pits 43 of recording data is formed on a transparent substrate 42 made of polycarbonate or the like, and a light semi-transmissive film 45 is formed on the first recording layer 44. On the light semi-transmissive film 45, a space layer 46 made of an ultraviolet curable resin or the like is formed. Then, the first recording layer 44 and the second recording layer are bonded together so that the two recording layers 44 and 48 are opposed to each other, with a single plate having an aluminum reflective film formed on a transparent substrate having the recording layer formed thereon. A high-density optical disk 41 having a recording layer 48 was manufactured.

In order to realize such a high-density optical disk 41, the light semi-transmissive film 45 is an extremely important element. That is, the light semi-transmissive film 45 requires a reflectance and a transmittance of 20% to 40%, and when the read focus is set on the first recording layer 44, a recording signal is transmitted from the first recording layer 44. Is read. At this time, the read signal is not focused on the second recording layer 48, so that the recording signals are not mixed at the time of reading. On the other hand, the focus of reading
In this case, only the recording signal of the second recording layer 48 is read out.

The performance required of the light semi-transmissive film 45 is that absorption loss is small in order to make effective use of incident light, and that the amount of return light between the first recording layer 44 and the second recording layer 48 is small. In order to equalize, the reflectance and the transmittance can be adjusted, the adhesion to the space layer 46 is good, and the environment resistance is excellent.

Such a light translucent film 45 is obtained by forming a silicon compound film having a predetermined refractive index and a predetermined thickness by a film forming method such as sputtering or vacuum deposition. Can be described as follows.

In FIG. 7, a light translucent film 45 is interposed between a transparent substrate 42 formed of polycarbonate or the like and a space layer 46 formed of an ultraviolet curable resin or the like. For example, light incident from the transparent substrate 42 side causes multiple reflection in the light semi-transmissive film 45 and interferes.
Therefore, as shown in FIG. 8, the amount of light passing through and the amount of light reflected by the light semi-transmissive film 45 change depending on the thickness and the refractive index of the light semi-transmissive film 45. That is, the reflectance and the transmittance can be arbitrarily selected by changing the refractive index and the film thickness.

FIG. 9 shows that the amount of oxygen is constant (3%), the refractive index of the light translucent film when the amount of nitrogen is changed, and the amount of nitrogen is constant (6%). FIG. 4 is an explanatory diagram showing a change in the refractive index of the light semi-transmissive film when the film is changed. FIG. 9 shows that the refractive index decreases as the total amount of oxygen and nitrogen increases.

The optimum values of the refractive index and the film thickness at this time are determined as follows. The refractive index is set so that the amount of return light from the first recording layer 44 and the second recording layer 48 when viewed from the transparent substrate 32 side is equal. Further, the film thickness is set to a value that minimizes the change in reflectance and transmittance with respect to the change in film thickness in order to obtain a uniform return light amount in the plane.

[0014]

When an optical disk having such a light translucent film is left for a long time in a high-temperature and high-humidity environment, as shown in FIG. 10, jitter and an error rate increase. Was. The cause is that the light semi-transmissive film peels off from the transparent substrate in a high-temperature and high-humidity environment due to poor adhesion between the light semi-transmissive film and the transparent substrate.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. By improving the adhesion between a light semi-transmissive film and a transparent substrate, the light semi-transmissive film is transparent even in a high-temperature and high-humidity environment. It is an object of the present invention to provide an information recording medium which does not peel off from a substrate and has excellent environmental resistance.

[0016]

SUMMARY OF THE INVENTION According to the present invention, there is provided an information processing apparatus comprising a multi-layered recording layer and a light semi-transmissive film for reading a recording signal of each recording layer from the same surface. This is achieved by an information recording medium in which the light semi-transmissive film has a single element film, and a compound of ultrafine particles having a diameter of 1 nm to 20 nm is dispersed in the single element film.

[0017]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. The embodiment described below is a preferred embodiment of the present invention, and therefore, various technically preferable limitations are added. However, the scope of the present invention particularly limits the present invention in the following description. Are not limited to these embodiments unless otherwise described.

FIG. 1 is a schematic view showing an embodiment of a cross-sectional structure of an information recording medium according to the present invention. In FIG.
The information recording medium 1 is configured as, for example, a disc-shaped optical disk, and the light irradiation side of the information recording medium 1 is, for example, polycarbonate,
A transparent substrate 2 such as polymethyl methacrylate, polyethylene, and polystyrene is provided. The transparent substrate 2 may be an optically transparent and moldable one. For example, the transparent substrate 2 is formed in a disk shape by injection molding polycarbonate or the like in a mold, and the upper surface thereof is formed with a stamper to form unevenness of recording data. A first recording layer 4 having pits 3 is formed.

The dispersion of the ultrafine particles 5b in the single element film 5a is performed by using a film forming apparatus 11 as shown in FIG. In FIG. 3, an exhaust port 14 connected to an exhaust system is provided above a chamber 12 of the film forming apparatus 11. A back plate 15 serving as an anode is disposed at a lower portion in the film forming chamber 13, and the transparent substrate 2 is mounted on the back plate 15. Also, in the upper part in the film forming chamber 13,
For example, a silicon target 16 and an aluminum target 1
7 are arranged as a cathode, and are shielded from the anode by a shutter 18. Further, an inert gas, oxygen or carbon gas supply port 19 is provided at an intermediate portion in the film forming chamber 13.
Is arranged. That is, the film forming apparatus 11 is configured as a sputtering apparatus capable of performing co-sputtering.

The sputtering device 11 alternately performs the sputtering of the silicon target 16 and the sputtering of the aluminum target 17 to disperse ultrafine particles 5b such as aluminum oxide or silicon oxide in a single element film 5a such as a silicon film or aluminum. By doing so, the adhesion between the light semi-transmissive film 5 and the transparent substrate 2 is increased. The reason why the adhesion is increased will be described below. The silicon compound film alone is hard and brittle, and has almost no extensibility. for that reason,
A single silicon compound film is formed on a transparent substrate 2 due to changes in temperature and humidity.
The transparent substrate 2 and the light translucent film 5
During this time, stress concentrates, and these adhesions decrease.
The single element film 5a such as a silicon film has a dense structure because atoms in the film form a network that is close to each other. Then, when the ultrafine particles 5b as shown in FIG. 2 are introduced into a single element film 5a such as a silicon film in order to cut off the network between the atoms, the bond of each atom becomes loose and the light semi-transmissive film 5 becomes Become a flexible structure. Therefore,
It is considered that the transparent substrate 2 can flexibly cope with the expansion and contraction of the transparent substrate 2 due to the change of the temperature and the humidity, the stress between the transparent substrate 2 and the light semi-transmissive film 5 is eliminated, and the adhesion between them is improved.

As described above, the information recording medium 1 of the present embodiment
Has a first recording layer 4 and a second recording layer 8, and a single element film 5 a such as a silicon film in which ultrafine particles 5 b are dispersed as a light semi-transmissive film 5 on the first recording layer 4. Is provided to read out the recording signals of the recording layers 4 and 8 from the transparent substrate 2 side.

In this embodiment, the information recording medium 1 having two recording layers has been described. However, the present invention is not limited to this. The information recording medium may have three or more recording layers. .

[0023]

【Example】

Example 1 The information recording medium of Example 1 has the same cross-sectional structure as the information recording medium shown in FIG. 1, and the same reference numerals denote the same members. Polycarbonate is used as the material of the transparent substrate 2. First, polycarbonate was injection-molded in a mold, and a transparent substrate 2 on which a first recording layer 4 having uneven pits 3 was formed by a stamper was produced.

Next, the transparent substrate 2 is subjected to co-sputtering shown in FIG.
2 and placed on the back plate 15 of the anode, and a silicon target 16 and an aluminum target 17 were placed on the cathode. The silicon target 16 is doped with boron in order to increase its conductivity.

After the inside of the chamber 12 is sufficiently evacuated, the silicon target 16 is sputtered for 20 seconds.
ccm of argon gas was introduced from the gas supply port 19,
When sputtering the aluminum target 17, a mixed gas of 15 sccm of argon gas mixed with 3 sccm of oxygen gas is introduced from the gas supply port 19 of the chamber 12, and the mixed gas is deposited on the first recording layer 4 of the transparent substrate 2. The light translucent film 5 was formed. At this time, the deposition rate of the silicon film is 5 nm.
The operation of alternately opening the shutter 18 for 1 second was repeated 10 times, and the light semi-transmissive film 5 was formed with a thickness of 60 nm. The light semi-transmissive film 5 has a refractive index n = 2.95. When the film structure is observed with a transmission electron microscope, ultrafine particles 5b of aluminum oxide having an average diameter of 8 nm are uniformly formed in the silicon film 5a. It was confirmed that they were dispersed.

On the light semi-transmissive film 5 in which the ultrafine particles 5b are dispersed, a space layer 6 made of an ultraviolet curable resin is formed with a thickness of 47 μm. Then, the first recording layer 4 and the second recording layer are bonded together such that the two recording layers 4 and 8 are opposed to each other on a single plate having an aluminum reflective film formed on the transparent substrate on which the recording layer is formed. The optical disc 1 having the recording layer 8 was manufactured.

When the reflectance of the optical disk 1 manufactured as described above was measured, the reflectance of the first recording layer 4 was 2
9%, and the reflectance of the second recording layer 8 was 32%. When the optical disc 1 was focused on the first recording layer 4 or the second recording layer 8 by the optical pickup, the data recorded on each of the optical discs 1 could be read satisfactorily. Further, even after the optical disc 1 was left under a high temperature and high humidity environment of 85% humidity at a temperature of 80 degrees Celsius for 1000 hours, the jitter and the error rate did not change from the initial values.

Embodiment 2 The information recording medium of Embodiment 2 has the same cross-sectional structure as the information recording medium shown in FIG. 1, and the same reference numerals denote the same members. Polycarbonate is used as the material of the transparent substrate 2. First, polycarbonate was injection-molded in a mold, and a transparent substrate 2 on which a first recording layer 4 having uneven pits 3 was formed by a stamper was produced.

Next, the transparent substrate 2 is placed in a chamber 1 of a sputtering apparatus 11 capable of co-sputtering as shown in FIG.
2 and placed on the back plate 15 of the anode, and a silicon target 16 and an aluminum target 17 were placed on the cathode. The silicon target 16 is doped with boron in order to increase its conductivity.

After the inside of the chamber 12 is sufficiently evacuated, an argon gas of 20 sccm is introduced from the gas supply port 19 when sputtering the aluminum target 17, and 1 μm when sputtering the silicon target 16.
A gas mixture of 3 sccm oxygen gas mixed with 5 sccm argon gas was introduced from the gas supply port 19 of the chamber 12, and the light semi-transmissive film 5 was formed on the first recording layer 4 of the transparent substrate 2. At this time, the film formation rate of the aluminum film is 10 nm / sec, the film formation rate of the silicon oxide film is 2 nm / sec, and the operation of alternately opening the shutters 18 for 0.5 seconds is repeated 10 times. 5 was formed with a thickness of 60 nm. This light semi-transmissive film 5 has a refractive index n = 3.05. When the film structure is observed with a transmission electron microscope, ultrafine particles 5b of silicon oxide having an average diameter of 13 nm are uniformly formed in the aluminum film 5a. It was confirmed that they were dispersed.

On the semi-transparent film 5 in which the ultrafine particles 5b are dispersed, a space layer 6 made of an ultraviolet curable resin is formed with a thickness of 47 μm. Then, a single plate in which an aluminum reflective film is formed on a transparent substrate on which a recording layer is formed is attached so that the two recording layers 4 and 8 face each other, thereby forming a first recording layer 4 and a first recording layer. The optical disc 1 having the second recording layer 8 was manufactured.

When the reflectance of the optical disk 1 manufactured as described above was measured, the reflectance of the first recording layer 4 was 2
9%, and the reflectance of the second recording layer 8 was 32%. When the optical disc 1 was focused on the first recording layer 4 or the second recording layer 8 by the optical pickup, the data recorded on each of the optical discs 1 could be read satisfactorily. Further, even after the optical disc 1 was left under a high temperature and high humidity environment of 85% humidity at a temperature of 80 degrees Celsius for 1000 hours, the jitter and the error rate did not change from the initial values.

As described above, according to the embodiment and the examples of the present invention, the light semi-transmissive film 5 is constituted by the single element film 5a, and the compound of ultrafine particles of 1 nm to 20 nm is contained in the single film 5a. Is dispersed, so that the light semi-transmissive film 5
And the transparent substrate 2 can be improved in adhesion, so that the semitransparent film 5 does not peel off from the transparent substrate 2 even in a high-temperature and high-humidity environment, and the information recording medium 1 having excellent environmental resistance is obtained. be able to.

The information recording medium 1 has excellent performance such that it has a small change with time due to excellent adhesion to the transparent substrate 2 and a small light absorption loss.

[0035]

As described above, according to the present invention, by improving the adhesion between the light semi-transmissive film and the transparent substrate, the light semi-transmissive film does not peel off from the transparent substrate even in a high-temperature and high-humidity environment. Thus, an information recording medium having excellent environmental resistance can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a cross-sectional structure of an embodiment of an information recording medium according to the present invention.

FIG. 2 is a schematic diagram showing a structure of a light semi-transmissive film in the information recording medium of the present embodiment.

FIG. 3 is a schematic diagram showing a film forming apparatus used in the present embodiment.

FIG. 4 is a schematic view showing a cross-sectional structure of a conventional read-only optical disc.

FIG. 5 is a schematic diagram showing a cross-sectional structure of a conventional rewritable optical disk.

FIG. 6 is a schematic diagram showing a cross-sectional structure of a conventional high-density optical disk.

FIG. 7 is a conceptual diagram for explaining functions when a silicon compound is used as a light semi-transmissive film.

FIG. 8 is an explanatory diagram showing a relationship between a film thickness, a reflectance, and a refractive index.

FIG. 9 is an explanatory diagram showing the relationship between the oxygen and nitrogen contents and the refractive index.

FIG. 10 is an explanatory diagram showing changes in jitter and an error rate.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Information recording medium, 2 ... Transparent substrate, 3 ... Uneven pit, 4 ... First recording layer, 5 ... Optical translucent film, 5a ... Single element film, 5b ... Ultra fine particles, 6
..Space layer, 7: Uneven pits, 8: Second recording layer, 9: Total reflection film, 10: Protective film

Claims (2)

[Claims] 1. An information recording medium having a multi-layered recording layer and a light semi-transmissive film to read recording signals of each recording layer from the same surface, wherein the light semi-transmissive film is a single element film. And an ultrafine compound having a diameter of 1 nm to 20 nm dispersed in a single element film. 2. The information recording medium according to claim 1, wherein the ultrafine particles are an oxide or a nitride of a base material element.