JP2008084440A - Double sided optical disk and optical disk unit using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a double-sided optical disk and optical disk unit using the same which can simply color disk surfaces by adding layers with a different refraction index on reflection films. <P>SOLUTION: In the double-sided optical disk comprising a first recording layer which has a first recording plane to record information and the reflection film deposited on the first recording plane on the side which is irradiated with a red laser beam, and a second recording layer which has a second recording plane to record information and the reflection film deposited on the second recording plane on the side which is irradiated with a blue laser beam, the reflection films consist of interference films which execute interference of light and total reflection films which totally reflect the laser beams. The interference films satisfy a following equation: d=λ×(2m+1)/4n (m=0, 1, 2, ..., λ: wavelength to be absorbed, n: refraction index), when the refraction index is denoted by n, and the thickness by d (nm). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a double-sided optical disc on which information is recorded on both the front and back surfaces, and more particularly to a double-sided optical disc that allows easy visual identification of the front and back surfaces. The present invention also relates to an apparatus using this double-sided optical disc.

For playback-only DVDs with recorded sound and video information, a disk substrate having a recording surface with a signal transferred on one side and a flat plate disk substrate having no signal (non-recording surface) on the other side There is a so-called single-sided optical disc that is bonded to each other, and a double-sided optical disc in which two non-recording surfaces are bonded to each other on their non-recording surfaces and recording surfaces are formed on both sides.

In recent years, HD DVD (High densi
ty DVD) and BD (Blu-ray disc) are being commercialized, and one of the recording surfaces is DV
D. Double-sided optical discs have also been devised in which the other recording surface is HD DVD. In any case, a single-sided optical disc can read information from only one side, and a double-sided optical disc can read information from both sides.

Single-sided optical discs can be printed on the side where information cannot be read,
A double-sided optical disc from which information can be read from both sides has almost no space for label printing. Therefore, usually for the identification, in the transparent non-recording area near the center hole,
Labels for identifying the front and back surfaces were attached.

However, since the label may be mistakenly applied during optical disc production or the label may be peeled off during use, the identification means by label attachment has not been fully satisfactory. Therefore, in recent years, double-sided optical discs have been devised in which double-sided optical discs are provided with reflective films of different colors on each recording surface side, and the front and back sides can be visually identified from the outside (see Patent Document 1). ).
JP-A-8-297863

According to Patent Document 1, in order to provide reflective films of different colors on the recording surface sides of the front surface and the back surface, two single-sided optical disks having different reflective film colors are simply bonded together with an adhesive. . Specifically, a reflective film is provided on a transparent disk substrate. The reflective film is an aluminum vapor deposition film and the other is a gold vapor deposition film, so that the aluminum vapor deposition film is a transparent disk substrate. Through the transparent disk substrate, the gold deposited film looks like gold. As a result, the front and back surfaces can be visually identified from the outside, and the color of the reflective film does not disappear even when used for a long time.

However, in the reflective film coloring method of Patent Document 1, for example, when a double-sided optical disk has one recording surface with a DVD and the other recording surface with an HD DVD, whichever surface is silver or gold, the surface is DVD. It ’s hard to tell if it ’s an HD DVD.

Further, the coloring method uses the color of the material of the vapor deposition film itself, and there is no idea about the coloring method by dyeing the plastic substrate or multilayering the reflective film material.
Accordingly, an object of the present invention is to solve the above-described problems, and provides a double-sided optical disk in which a plastic substrate is dyed in coloring a disk surface and an optical disk apparatus using the double-sided optical disk.

Another object of the present invention is to solve the above-mentioned problems, and provides a double-sided optical disk in which a reflective film material is multilayered for coloring the disk surface and an optical disk apparatus using the double-sided optical disk. .

In order to solve the above problems, the present invention has a first recording surface on which information is recorded and a reflective film formed on the first recording surface on the side irradiated with the red laser beam. A second recording surface including the first recording layer, on which the information is recorded on the side irradiated with the blue laser light, and the second recording surface
In the double-sided optical disc including the second recording layer having the reflection film formed on the recording surface, the reflection film includes an interference film that interferes with light and a total reflection film that totally reflects the laser light; When the interference film has a refractive index n and a thickness d (nm),

d = λ · (2m + 1) / 4n
m = 0, 1, 2,...
λ: wavelength of the color to be absorbed (nm)
n: It is configured to satisfy the relationship of refractive index.

According to the present invention, each surface is colored so that information can be read. For example, when one recording surface of a double-sided optical disc is a current DVD and the other recording surface is a next-generation DVD,
The current DVD is red and the next generation DVD is blue. In other words, a DVD that reads information with a red laser is an HD DVD (or BD) that reads information with a red or blue laser.
By making the disc surface have a color that matches the user's image, such as blue, it compensates for the shortcomings of double-sided optical discs that label printing is not possible, and the user can easily determine the information recording surface. Can be effective.

In addition, according to the present invention, the disk coloring method can easily color the disk surface by introducing a simple dyeing process after the molding process or by additionally providing a layer having a different refractive index in front of the reflective film. It is also an advantage that it can be carried out by modifying the production line with a minimum cost and without interfering with the production of a normal single-sided optical disc.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a structural diagram of a double-sided optical disc according to an embodiment of the present invention. FIG. 2 is a structural diagram of a single-sided optical disk.
As an example, the one shown in FIG. 1 is a double-sided type optical disc, and one recording layer 11 is D.
For VD, the other recording layer 12 is for HD DVD. The DVD layer reproducing light (laser beam) 13 having a wavelength of 650 nm is irradiated on the recording layer 11 from the lower side of the double-sided optical disk in the drawing, and the HD DVD information reproducing beam 14 (laser beam) having a wavelength of 405 nm is irradiated on the recording layer 12 from the upper side in the drawing. Is irradiated. Incidentally, here, the side irradiated with the laser beam 13 is a DVD surface, and the side irradiated with the laser beam 14 is an HD DVD surface.

In addition, in a normal single-sided disc (FIG. 2), the other side is a dummy and is a surface that is not related to recording / reproduction, so that it is easy for a consumer to determine which side is an information recording side by label printing or the like. Can be distinguished. However, in the double-sided type optical disk, as shown in the figure, since the reading surface by the laser beam is double-sided, both surfaces need to be transparent to at least the wavelength of the laser beam, and label printing or the like cannot be performed. .

Therefore, in the present invention, the DVD of the current generation optical disc is a red laser for reproduction light, and the HD DVD (or BD) of the next generation optical disc is a blue laser for reproduction light, so that the DVD surface is red and the HD DVD surface is blue (or On the contrary, the back side of the DVD surface is colored red and the back side of the HD DVD surface is colored blue, so that the consumer can easily understand which one to reproduce visually or imageically. However, since it must be transparent to the reproduction laser beam so as not to hinder the information reproduction, in the present invention, as a coloring method, for example, a plastic molding material is dyed or a reflective film is formed in multiple layers, and color is generated by the interference. Take measures to make it happen.

A method of manufacturing this double-sided type optical disc will be described with reference to FIG. Note that the flow of the manufacturing method is the same for a single-sided, dual-layer type optical disc except for the difference in whether the reflective film is semi-transmissive or totally reflective.

First, the DVD layer is formed. Raye by injection molding from mold 15 and Ni stamper 17
A DVD molded substrate 10 to which r0 is transferred is produced (ST21). In this method, a plastic disk is produced by injection molding using a Ni stamper or the like as a mold, and polycarbonate is generally used as a molding material. The Ni stamper is manufactured by nickel plating a glass master disc in which information is engraved with a pit-like uneven pattern by means such as lithography. A reflective film 21 is formed on the information pattern recording surface 2 of the DVD plastic disk thus formed (ST22). Here, since a double-sided disk is assumed, the reflection film 21 is a metal (generally aluminum or silver alloy) total reflection film. In the case of a single-sided type disk, a translucent film is formed.

In parallel with this, the HD DVD layer is also formed. In this process as well, the HD DVD molded substrate 23 is produced using a Ni stamper as in the case of DVD (ST23). Polycarbonate is used as the molding material. The difference is the recording density of information, and HD DVD records about three times as much information as DVD. HD DVD plastic disk (H
The reflective film 21 is similarly formed on the information pattern recording surface 3 of the D DVD molding substrate) 23 (ST24). The reflection film is a total reflection film of metal (generally, aluminum or silver alloy).

The DVD molded substrate 10 and the HD DVD molded substrate 23 thus manufactured are bonded to each other with an adhesive (
In general, it is bonded with an ultraviolet curable adhesive) to form a disk (ST25). D
Since VD and HD DVD have the same dimensions, they can be bonded together without any problem.

In this way, a double-sided type optical disc is completed, but label printing cannot be performed because both sides of the disc are information reading surfaces. Therefore, which user is DVD
It is impossible to determine which is the HD DVD surface. Of course, if the wrong side is inserted into the player, the desired information is not read out, so some sort of discriminating means is required.

Therefore, in the present invention, the disc surface is colored so that the user can easily discriminate between DVD / HD DVD and a coloring method is provided.
Since DVD reads information with a red laser and HD DVD reads information with a blue laser, these two colors are used for coloring. Whether the DVD surface is colored red or the back surface corresponding to the DVD label surface (HD DVD surface) is colored red may be either as long as the same kind of product can be unified. However, in order to reproduce information with laser light, it must be transparent to the laser light wavelength. For this reason, it is of course necessary to color the film moderately thinly, but it is necessary to color it with a color that does not absorb the laser light wavelength. In this regard, red absorbs light of the complementary cyan wavelength, and blue absorbs the complementary yellow light, but does not absorb the reproduction laser light wavelengths (red and blue). Therefore, it is preferable also in this point.

As an example of the coloring method, dyeing of a plastic material can be mentioned. As a specific example, since the polycarbonate of the disk molding material has no polar group, it is desirable to color with an image in which a dye molecule is entangled with a polycarbonate polymer rather than coloring due to chemical bonding of molecules. For example, a glycol ether type dye is used. It is possible. In this case, by attaching the molded disk to the dye, it is possible to achieve a semi-transparent light coloring, and to separate the dyeing process without contaminating the conventional molding process. There is merit that can be produced and mass-produced. However, it goes without saying that the resin pellets may be kneaded with the dye and injection molded, or may be injection molded using originally colored resin pellets.

As another example of the coloring method, a reflective film is formed in multiple layers (simply two layers) and colored using light interference. FIG. 4 shows a part of a double-sided type optical disc having a two-layer reflection film.

As shown in FIG. 4, the optical disk is made of polycarbonate 3 in order from the incident laser beams 1 and 2 side.
6, the interference film 30, the reflection film 32, the ultraviolet curable resin 34, and the like. In particular, the reflection film has two layers, the interference film 30 has a refractive index n and a thickness d (nm), and the reflection film 32 has total reflection. At this time, the incident laser light can take the optical paths of the incident laser light 1 and the incident laser light 2 in the figure, but when the optical path difference is equal to the half wavelength of the incident laser light wavelength, they cancel each other and the light of that wavelength becomes weak. .

As described above, in order to develop red and blue colors, it is only necessary to absorb the complementary colors cyan and yellow.
d = λ · (2m + 1) / 4n
(M = 0, 1, 2,..., Λ: cyan or yellow wavelength)
The reflective film may be designed so that the above relationship is established. If the complementary color is absorbed by the reflective film in this way, it will appear to be colored red or blue as a result.
By such a dyeing of the disk molding material and a device for the reflective film, it is possible to make the disk surface look red or blue when visually observed. Label printing can be achieved by giving the disc surface a color that matches the user's image, such as red for information reading with a red laser and blue for HD DVD (or BD) for reading information with a blue laser. This makes it possible to compensate for the shortcomings of the double-sided type optical disc, such that the user cannot easily determine the information recording surface.

In addition, the disk coloring method of this embodiment has a minimum cost such as introducing a simple dyeing process after the molding process, or additionally providing a layer having a different refractive index in front of the reflective film. It is also an advantage that it can be implemented by remodeling the production line in a form that does not interfere with this.

Next, an optical disk device that reproduces information recorded on the above-described optical disk will be described. FIG. 5 is a block diagram showing a schematic configuration of an optical disc apparatus for reproducing an optical disc. As shown in FIG. 5, the optical disc is, for example, the double-sided type optical disc shown in FIG. A short wavelength semiconductor laser light source 120 is used as the light source. The wavelength of the emitted light is, for example, in the violet wavelength band in the range of 400 nm to 410 nm. The emitted light 100 from the semiconductor laser light source 120 is converted into parallel light by the collimator lens 121, passes through the polarization beam splitter 122 and the λ / 4 plate 123, and enters the objective lens 124. Thereafter, the light passes through the substrate of the optical disc D and is condensed on each information recording layer. The reflected light 101 from the information recording layer of the optical disc D is transmitted again through the substrate of the optical disc D, and the objective lens 124, λ
/ 4 plate 123, and after being reflected by the polarization beam splitter 122, the condensing lens 125
And is incident on the photodetector 126.

The light receiving unit of the photodetector 127 is normally divided into a plurality of parts, and outputs a current corresponding to the light intensity from each light receiving unit. The output current is converted into a voltage by an unillustrated I / V amplifier (current / voltage conversion) and then input to the arithmetic circuit 140. The input voltage signal is arithmetically processed by the arithmetic circuit 140 into a tilt error signal, HF signal, focus error signal, track error signal, and the like. The tilt error signal is for tilt control, the HF signal is for reproducing information recorded on the optical disc D, the focus error signal is for focus control, and the track error The signal is used for tracking control.

The objective lens 124 can be driven by the actuator 128 in the vertical direction, the disc radial direction, and the tilt direction (radial direction and / or tangential direction), and is controlled by the servo driver 150 so as to follow the information track on the optical disc D. Is done. There are two types of tilt directions. There is a “radial tilt” that occurs when the disc surface tilts toward the center of the optical disc, and a “tangential tilt” that occurs in the tangential direction of the track. Of these, radial tilt is generally caused by warping of the disk. It is necessary to consider not only the tilt that occurs during disk manufacture, but also the tilt that occurs due to aging and sudden changes in the usage environment. By using such an optical disk device, the optical disk of the present invention can be reproduced.

Note that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention in the implementation stage. For example, in this embodiment, DVD and H
D: A double-sided disc of DVD was taken as an example, but in addition to a normal 120 mm outer diameter disc, if the double-sided disc has a surface to be played with a red laser and a surface to be played with a blue laser, the outer diameter An 80 mm disc or a combination of DVD and BD may be used.
Also, a disc having two or more layers per side may be used. Regarding the material, for example, the disk molding material may be acrylic or cycloolefin polymer in addition to polycarbonate, and the reflective film material may be metal oxide or dielectric other than metal.

The figure which shows the structure figure of the double-sided optical disk which concerns on embodiment of this invention. The figure which shows the structure figure of a single-sided type optical disk. The figure which showed the flow of the manufacturing method of a double-sided optical disk. The figure which shows a part of structure of the double-sided optical disk of this invention. The block diagram which shows schematic structure of the optical disk apparatus for reproducing | regenerating an optical disk.

Explanation of symbols

10 ... DVD molded substrate, 15 ... mold, 17 ... Ni stamper, 21 ... reflective film, 27 ...
HD DVD molded substrate, 30 ... interference film, 32 ... reflection film, 34 ... UV curable resin

Claims (3)

A first recording layer having a first recording surface on which information is recorded and a reflective film formed on the first recording surface is provided on the side irradiated with the red laser beam, and the blue laser beam is irradiated with the first recording layer. A double-sided optical disc including a second recording layer having a second recording surface on which the information is recorded and the reflective film formed on the second recording surface;
The reflection film is composed of an interference film that interferes with light and a total reflection film that totally reflects the laser light, and the interference film has a refractive index n and a thickness d (nm).
d = λ · (2m + 1) / 4n
m = 0, 1, 2,...
λ: wavelength of the color to be absorbed (nm)
n: A double-sided optical disk characterized by satisfying the relationship of refractive index. The method of claim 1, wherein light of cyan wavelength that is a complementary color of red is absorbed in order to visually show red color, and light of yellow wavelength that is complementary color of blue is absorbed in order to visually appear blue. Item 1
Double-sided optical disc as described. Irradiation means for irradiating the double-sided optical disk of claim 1 with laser light;
A light receiving means for receiving reflected light from the laser light irradiated by the irradiation means;
An optical disc apparatus comprising: a reproducing unit that reproduces the double-sided optical disc based on the reflected light received by the light receiving unit.

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