JPH09128812A - Optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical recording medium on the reading surface side of which characters and pictures are displayed with good visibility. SOLUTION: This optical recording medium A is constituted by forming dyestuff films 3 templating at least characters, designs, etc., on a substrate 2 formed with pits 1 or tracks. These dyestuff films 3 have a spectral characteristic to allow the transmission of reproducing light in a reproducing wavelength region and to absorb visible light in a visible light region exclusive the reproducing wavelength region. In addition, the film thickness thereof is specified to an integer times of λ/(2.n) (where λ: the reproducing wavelength, n: the refractive index of the dyestuff films 3 at the reproducing wavelength and the times are an integer).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical recording medium in which characters and pictures are printed on a reading surface.

[0002]

2. Description of the Related Art The structure of an optical disk currently in practical use is divided into a double-sided bonded structure and a single-plate structure. Among these, only a laser disk (registered trademark) is a read-only memory (ROM) type disk that has a double-sided laminated structure and is used only for reproduction. Compact disks (CDs), CD-ROs are used as ROM-type disks excluding this laser disk.
There are M, video CD, etc., but all of these discs have a single plate structure.

For this reason, these single-plate discs have a label or the like printed on the side opposite to the reading side. On the other hand, in the laser disc, a printed label is attached to the center (near the center hole) where reading is not hindered.

[0004]

By the way, there is a tendency that the density of optical discs is increased and the disc size is reduced. For example, a high-density optical disk recently proposed as a standard has a double-sided laminated structure. In this high density optical disc, substrates having a diameter of 120 mm and a plate thickness of 0.6 μm are bonded together, and laser light having a wavelength of 600 nm is used to achieve a memory capacity 10 times or more that of a CD.

However, in such a high density optical disc having a relatively small size, it is possible to print a character, a design or the like, or to attach a label on which the character, the design or the like is printed, in the central portion which does not hinder reading. It is said that
Since the area here is small, the visibility of the print or label is poor.

The above-mentioned high-density optical disc types include
There are a random access memory (RAM) type capable of recording and reproducing and a ROM type dedicated to reproduction. Of these, RA
Since the M type high density optical disc records and reproduces various information, it is not necessary to print a label or the like for the purpose of displaying the memory contents, whereas the ROM type high density optical disc has the memory contents. There is a problem that it is important to be able to print on most of the disk surface in terms of product design.

In order to solve this problem, JP-A-59-
There is a disk manufacturing method disclosed in Japanese Patent No. 177739. In this method, an information recording layer such as a photoresist that can be exposed to laser light is formed on a transparent substrate when cutting a CD or the like, and the surface of the substrate opposite to the surface on which the information recording layer is formed is formed. Characters, pictures, etc. drawn with a material having a relatively high absorptivity for laser light are opposed to each other. Then, the information recording layer is irradiated with laser light so as to form tracks (pits) with high density in a spiral or concentric pattern with respect to the center, and there are the above-mentioned materials for the characters, pictures, etc. The track width (pit width) corresponding to the part and the part that does not exist is changed, and due to this change, characters and pictures are displayed on the reading surface side (transparent to the disk surface side where the information recording layer is formed. And you can see the letters and pictures well).

However, JP-A-59-177739
In the disc manufacturing method disclosed in Japanese Patent Publication, characters and pictures are displayed by minute changes in the pit width, so the visibility is poorer than screen printing such as a CD, and the contents of software can be used as a decoration. There was a drawback that it was not suitable for displaying titles and titles. Therefore, an object of the present invention is to provide an optical recording medium in which characters and pictures are displayed on the reading surface side with good visibility.

[0009]

In order to solve the above problems, the present invention provides an optical recording medium having the following constitutions (1) to (3).

(1) As shown in FIG. 1, at least
Optical recording medium A in which a dye film 3 in the shape of characters or patterns is formed on a substrate 2 having pits 1 or tracks formed thereon.
And the dye film 3 has a reproduction wavelength range (wavelength 600 n
m has a spectral characteristic of transmitting reproduction light (reading laser light) and absorbing visible light outside the reproduction wavelength range (wavelength 380 nm to 760 nm), and the film thickness is λ.
/ (2 · n) (where λ is the reproduction wavelength, n is the refractive index of the dye film 3 at the reproduction wavelength, and the multiple is an integer).

(2) An optical recording medium comprising at least a transparent dielectric film in which characters, patterns, etc. are formed on a substrate 2 having pits 1 or tracks formed thereon, wherein the transparent dielectric film is , Has a refractive index that does not cause wavelength dispersion of reproduction light (reading laser light) in the reproduction wavelength range (wavelength of the order of 600 nm) and wavelength dispersion in the visible light range outside the reproduction wavelength range, and has a film thickness of λ / An optical recording medium characterized by being a multiple of (2 · n) (where λ is a reproduction wavelength, n is a refractive index of the transparent dielectric film at the reproduction wavelength, and a multiple is an integer).

(3) The optical recording medium as described in (1) or (2) above, wherein the optical recording medium is a double-sided bonded disc, and both sides thereof can be reproduced. The optical recording medium according to the present invention is almost transparent to a reproduction wavelength region in a character or a picture part, and has a dye film or a refractive index which has absorption of visible light outside the reproduction wavelength to be visually recognized as a color. A transparent dielectric film having wavelength dispersion in the visible light region is used, and these film thicknesses are λ / (2 · n) (λ: reproduction wavelength, n: refractive index of dye film or transparent dielectric film at reproduction wavelength). ) Is a multiple of.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the optical recording medium of the present invention will be described below with reference to FIGS. FIG. 1 is a longitudinal sectional view of an embodiment of the optical recording medium of the present invention, FIG. 2 is a view showing a mask, and FIG. 3 is a view for explaining conditions of the film thickness of the dye film.

(Structure of Optical Recording Medium A) As shown in FIG. 1, the optical recording medium A of the present invention has a dye film 3 in which characters, patterns, etc. are formed on a substrate 2 such as polycarbonate in which pits 1 are molded. Is formed (formed), an aluminum film 4 similar to a CD or the like is formed thereon, and a protective film 5 is further formed thereon. 7 is a land. Substrate 2 described above
Form a series of concentric or spiral information tracks by the pits 1 and the lands 7. Thus, by irradiating the laser beam from the substrate 2 side (the arrow a side in FIG. 1) of the optical recording medium A, it becomes possible to read the information and also to visually recognize characters and pictures. Also,
This optical recording medium A is a high density optical disc and has a diameter of 12
By bonding substrates of 0 mm and a plate thickness of 0.6 μm and using a reading laser beam with a reproduction wavelength of 600 nm, C
It is a ROM-type disk that has a memory capacity 10 times as large as that of D.

Although only one substrate 2 having a plate thickness of 0.6 μm is shown here, the optical recording medium of the present invention has another substrate (plate) such as polycarbonate having pits formed on the upper surface of the protective film 5. Needless to say, it may be a double-sided laminated disk having a thickness of 0.6 μm) bonded together. In this case, both sides thereof can be regenerated, but since characters and patterns can be seen from the front side from the substrate 2, the meaning can be immediately visually recognized. Of course, the optical recording medium A, which is a high-density optical disc, has a single plate structure with a diameter of 120 mm and a plate thickness of 1.2 μm as shown in FIG.
It goes without saying that a ROM type disk having a memory capacity 10 times or more that of a CD may be used by using a laser beam in the 0 nm range. Also, plate thickness 1.2 μm
C using a laser beam with a wavelength of 780 nm in the single plate structure of C
It may be D.

(Manufacturing Method of Optical Recording Medium A) Next, the optical recording medium A having the above structure is manufactured in the order of 1 to 4 described below. For convenience of description, only the optical recording medium A having a single plate structure will be described here. 1. On a substrate 7 such as a polycarbonate having a diameter of 120 mm and pits 1 molded therein, a mask 1 in which characters, patterns and the like are shaped is overlaid. As shown in FIG. 1, the mask 1 is obtained by stamping out only the character portion "OPTICAL DISC". 2. The dye film 3 is vacuum-deposited on the mask 1. After this, the mask 1 is removed. As a result, the dye film 3 is formed only on the portion on the substrate 7 where the character portion "OPTICAL DISC" overlaps. 3. The aluminum film 4 is vacuum-formed on all the substrates 7 including the portion where the dye film 3 is formed. 4. A protective film 5 is formed by coating on the aluminum film 4. In this way, one optical recording medium A is manufactured.

(Regarding Dye Film 3) As a material for forming the dye film 3, a substance that is almost transparent in the reproduction wavelength range and has absorption of visible light outside the reproduction wavelength for visual recognition as a color. Preferred (eg phthalocyanine etc.). The film thickness of the dye film 3 is a multiple of λ / (2 · n) (λ: reproducing wavelength, n: refractive index of the dye film 3 at the reproducing wavelength, the multiple is an integer).

Next, the conditions of the film thickness of the dye film 3 are shown in FIG.
This will be described with reference to FIG. In the optical recording medium A having the above-mentioned structure, the laser light beam is focused on a small spot, which is the pit 1.
A signal is detected by utilizing the fact that the amount of light diffracted at that point and returning to the objective lens (not shown) is reduced. At this time, when the phase difference between the light 9 reflected and returned to the land 7 of the optical recording medium A and the light 10 reflected and returned to the bottom of the pit 1 becomes an odd multiple of π, the effect of diffraction Will be the maximum. The phase difference of π means that the optical path difference between the light 9 and the light 10 is λ / 2, which is the depth 11 of the pit 1.
Is λ / 4.

The depth 11 of the pit 1 in the actual optical recording medium A is λ / (4.multidot.4), where n'is the refractive index of the substrate 2.
It is set to a value slightly shallower than n '). This is to obtain the tracking error signal. When the dye film 3 is provided between the substrate 2 and the aluminum film 4 which is a reflective film,
The light reflected and returned to the pigment film 3 is as 12.
If the film thickness of the dye film 3 is set so that the phase difference between the light 12 and the light 10 in the portion where the dye film 3 is not present becomes 0, the diffraction effect becomes the minimum (substantially “0”). Therefore, the influence on the reproduction signal can be suppressed.

If the phase difference is 0, it means that the optical path difference between the light 10 and the light 12 is λ. Therefore, the film thickness of the dye film 3 may be set to λ / (2 · n) where n is the refractive index of the dye film 3 at the reproduction wavelength.

In the above-mentioned optical recording medium A, characters, pictures and the like can be visually confirmed by the dye film 3, but a transparent dielectric film may be used instead of the dye film 3. Needless to say, if the transparent dielectric film satisfies the following two conditions, it is possible to visually recognize characters, patterns, etc. without affecting reproduction conditions. 1. 1. The refractive index of the transparent dielectric film has wavelength dispersion in the visible light range. The thickness of the transparent dielectric film should be a multiple of λ / 2 · n.

From the above, the substrate 2 of the optical recording medium A is
To provide an optical recording medium having a label or the like printed on the reproducing surface which is the side (the arrow a side in FIG. 1) or the protective film 5 side,
In particular, both sides are playback surfaces, like a double-sided bonded disc,
Label printing is possible even with conventional technology that cannot print a large printing area. In addition, C, which is already widespread
If it is applied to a D or a laser disk, it becomes possible to achieve design differentiation. Furthermore, among the next-generation optical discs that are being standardized at present, the double-sided laminating method does not allow label printing like a CD, and since it is small in size, it should be affixed to the center part like a laser disc. Is also difficult. However, by using the optical recording medium according to the present invention, label printing with good visibility becomes possible.

[0023]

As described above, the optical recording medium of the present invention
Since a pigment film or a transparent dielectric film that displays characters and patterns with good visibility and does not adversely affect reproduction is provided on the substrate, for example, a substrate other than the conventional display place such as near the center hole of an optical disk. Since characters and pictures can be displayed on the upper part of the screen, a display area much larger than the conventional one can be taken, and as a result, the characters and pictures can be surely made more visible. Further, it is possible to display a label or the like having good visibility even on a disc having a reproduction surface on both sides, such as a double-sided laminated disc, which cannot have a large printing area in the conventional technique.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of an example of an optical recording medium of the present invention.

FIG. 2 is a diagram showing a mask.

FIG. 3 is a diagram for explaining conditions of the film thickness of a dye film.

[Explanation of symbols]

 1 pit 2 substrate 3 dye film A optical recording medium

Claims (3)

[Claims] 1. An optical recording medium comprising at least a dye film in the shape of characters or pictures formed on a substrate having pits or tracks formed thereon, wherein the dye film is a reproduction light beam in a reproduction wavelength range. Has a spectral characteristic of transmitting visible light outside the reproduction wavelength range and absorbing visible light, and the film thickness is a multiple of λ / (2 · n) (however,
λ: reproduction wavelength, n: refractive index of the dye film at the reproduction wavelength,
An optical recording medium characterized by being configured as: 2. An optical recording medium comprising at least a transparent dielectric film in the shape of characters, patterns, etc. formed on a substrate having pits or tracks formed thereon, wherein the transparent dielectric film has a reproduction wavelength. Has a refractive index that does not cause wavelength dispersion of the reproduced light in the region and wavelength dispersion in the visible light region outside the reproduction wavelength region, and the film thickness is a multiple of λ / (2 · n) (where λ: reproduction Wavelength, n: refractive index of the transparent dielectric film at the reproduction wavelength, multiple is an integer), and an optical recording medium. 3. The optical recording medium according to claim 1 or 2, wherein the optical recording medium is a double-sided bonded disc, and both sides thereof can be reproduced.