JP3113072B2 - Optical recording medium - Google Patents

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 for recording / reproducing information with light such as laser light, and more particularly to a guide groove for performing tracking control using a difference signal between two light beams.

[0002]

2. Description of the Related Art When recording / reproducing information on / from an optical recording medium, a guide groove is provided as a tracking track on the optical recording medium, and this is performed by tracking the guide groove. As a tracking method for tracking the guide groove, there are mainly two methods of (1) push-pull method and (2) three-beam method.

The push-pull method (1) is mainly used for an optical disk or the like. As shown in FIG. 3A, the width 41 of the guide groove 40 is about 1/2 of the beam diameter 51, and Is substantially the same as the beam diameter 51, and the tracking method is the two-part sensor 2 through the lens 21, the beam splitter 22, and the lens 23.
The reflected light from the guide groove 40 that reaches the sensor 4 is detected by the sensor 24-
The control is performed so that the light amount becomes equal to I on the sensor 24-II. In this method, since the recording / reproducing beam and the tracking beam can be shared, there is an advantage that the configuration of the optical head is simplified. However, in a medium that is thin and easy to bend, such as an optical card, the image formed on the sensors 24-I and 24-II is easily distorted due to the inclination of the medium, and correct tracking cannot be performed. Is generally used.

As shown in FIG. 3B, the three-beam system uses center beams 31 and 2 used for recording / reproduction.
Tracking two side beams 32I and 32II. The tracking method is the side beam 32 detected by the sensors 25-I and 25-II of the split sensor 25.
By setting the difference signal (α ₁ −α ₂ ) to 0 when the amplitudes of the reflected lights of I and 32II are respectively α ₁ and α ₂ , the center beam 31 is positioned at the center of the recording unit 33. Is controlled.

[0005]

Of the above-mentioned conventional optical recording medium tracking methods, the three beams (2) used for an optical card are side beams 32I and 3I.
When 2II is applied to the guide groove and the amount of reflected light decreases due to interference, the change in signal amplitude, that is, the shape of the track traversing signal has a large effect on the tracking characteristics.

FIG. 4 shows the signal intensity α ₁ of the reflected light amount of the side beams 32I and II corresponding to the position of the center beam 31,
The waveforms of α ₂ and their difference signal (α ₁ −α ₂ ) are shown. In order to improve the tracking characteristics, (1) track crossing shown in FIGS. In the shape of the signal waveform, the rate at which the amount of reflected light decreases as the side beams 32I and 32II traverse the track;
That is, the cross-track contrast (β / α) has a large value. (2) In FIG. 4C, the slope portion (δ portion) of the difference signal (α ₁ −α ₂ ) is linear and wide.

[0007] The above two are desired. Where δ
Is an allowable range of tracking for correctly positioning the center beam, and is called a pull-in range.

Heretofore, in order to improve the tracking signal, there have been proposed some types in which the shape of the guide groove is specified. For example, the shape of the guide groove is trapezoidal and the length of the slope is defined, or the shape of the guide groove is V-shaped.

[0009] However, the V-shaped groove has a drawback that it is difficult to stably manufacture it, although the cross-track contrast is high. Also, since the length and angle of the slope of the trapezoidal groove have a close correlation with the track crossing signal, it is also difficult to stably produce the track crossing signal, and the track crossing signal cannot obtain a very large value. There were drawbacks.

Furthermore, in a coating type optical recording medium using an organic dye or the like, the groove needs to have a depth of 2000 to 4000 angstroms in order to obtain a certain high cross-track contrast. ,
As shown in FIG. 5, the transparent substrate 10 is formed when the recording layer 12 is formed.
There is a drawback that the expected tracking characteristics cannot be obtained because the recording layer accumulates in the guide groove and uneven thickness occurs.

An object of the present invention is to provide a stable production when a three-beam type tracking method is used. It is to provide an optical recording medium.

[0012]

The optical recording medium of the present invention comprises:
The guide groove is composed of three auxiliary grooves having the same width, and the width of the guide groove measured at the outer edges of both outer auxiliary grooves among the three auxiliary grooves is W, and the light beam for performing tracking control is W. when the diameter and d _B, W and d _B is substantially the same value.

Further, the present invention includes a case where the diameter d _B of the width W and the light beam of the guide groove is 0.8d _B ≦ W ≦ 1.2d _B, furthermore, the depth of the guide groove 500 to 1500 Angstrom range is included.

[0014]

Since the guide groove is composed of three auxiliary grooves having the same width, the depth of the guide groove can be made relatively shallow, so that when the recording layer is formed by coating, coating unevenness occurs. , The cross-track contrast of the cross-track signal of the side beam used for tracking control is increased, and the pull-in range is widened, so that the tracking characteristics are improved. Further, since it is not necessary to make the cross section of the groove V-shaped or trapezoidal, it is possible to easily produce a product with good yield.

[0015]

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the optical recording medium of the present invention, and FIG. 2 is a graph showing a track crossing signal of side beam reflected light by the optical recording medium of FIG. 1 and another optical recording medium. .

This optical recording medium is an optical card comprising a transparent substrate 1, a recording layer 2, an adhesive layer 3, a protective substrate 4, and a hard coat layer 5.

The transparent substrate 1 has a thickness of 0.4 mm and a size of 76 mm.
It is made of a × 54 mm polycarbonate resin. here,
Since recording / reproduction is performed on the transparent substrate 1 through this substrate, the transparent substrate 1 only needs to be transparent to a laser beam to be used.
Plastics such as polyamide, polyolefin resin, phenol resin, epoxy resin, and polyimide, glass, and the like can be used. The tracking track 11 is formed on one surface of the transparent substrate 1 using a photopolymer (30 × 717 made by Three Bond). The transferred tracking track pattern has a tracking track width 14 of 3 μm, a pitch of 12 μm, and 1
The tracking track 11 is composed of three auxiliary grooves 12, and the auxiliary groove 12 has a width 15 of 0.6 μm and a depth 16 of 1
It has a rectangular shape of 000 angstroms and is arranged at equal intervals. In this case, the auxiliary groove 12 is formed directly on the transparent substrate 1, but may be additionally formed using a photopolymer resin or the like.

The recording layer 2 is formed by mixing organic dyes of the following formulas [I] and [II] at a ratio of 3: 1 and applying the mixture on a transparent substrate 1 with a diacetone alcohol solution. Recording section 13 on which information is recorded by light 6
Is about 1000 angstroms.

[0020]

Embedded image

[0021]

Embedded image In this case, the recording layer 2 is an organic dye but may be an inorganic material, and may be a write-once type or a rewritable phase change type.
For example, organic dyes include polymethine, azulene, pyrylium, squarium, croconium,
Tripherylmethane, xanthene, anthraquinone, cyanine, phthalocyanine, dioxazine,
There are tetrahydrocholine-based, triphenothiazine-based, phenanthrene-based, aminium-salt / diimonium-salt-based, and metal-chelate rust-based dyes. If necessary, these dyes may be mixed and used for improving stability.

The adhesive 3 is a hot-mel adhesive (Evaflex EV150, manufactured by Du Pont-Mitsui Chemicals Co., Ltd.). The adhesive layer may be any adhesive as long as it does not deteriorate the recording layer. Vinyl acrylic, vinyl acetate copolymer, vinyl acetate emulsion, acrylic, acrylate, acrylic copolymer, ethylene, ethylene vinyl acetate, ethylene vinyl acetate copolymer, polyethylene, methylene chloride,
Polyamide-based, polyamide-amine-based, polyimide-based,
Urea, epoxy, epoxy urethane, epoxy acrylate, urethane acrylate, polyester, chloroprene, chloroprene rubber, nitrile, nitrile rubber, urethane, vinyl urethane,
Polyurethane, olefin, cyanoacrylate, alkyl acrylate, vinyl chloride, phenol SBR (styrene butadiene rubber), polyol, silica-alumina, synthetic rubber, emulsion, oligoester, cellulose, Formaldehyde-based, ultraviolet-curable adhesives, and organic solvents can also be used. At the time of bonding, materials requiring energy such as heat, light, and an electron beam are also effective as long as the energy does not deteriorate the function of the optical recording material.

The protective substrate 4 is made of a polycarbonate resin, is formed to a thickness of 0.3 mm, and is laminated and adhered to the transparent substrate 1 using the adhesive layer 3. The hard coat layer 5 is an ultraviolet curing agent, and is used for hard coat processing on the surface of the transparent substrate 1.

In this optical card, despite the recording layer 2 being formed by a coating method, there is not much unevenness in thickness, and a track crossing signal is measured at a beam diameter of 3 μm and a wavelength of 830 μm. The result obtained is as shown in the amplitude on the vertical axis corresponding to the distance from the center of the tracking track on the horizontal axis in FIG. 2A, and the cross-track contrast is 0.67. And the retraction range was 20 μm, and good results were obtained in both cases.

Next, in this embodiment, the tracking track 11 is constituted by three auxiliary grooves 12. Next, another embodiment of the present invention will be described with reference to Embodiments 2 and 3. (1) First Comparative Example FIG. 6 is a longitudinal sectional view of a first comparative example of the optical recording medium of the present invention.

This optical recording medium is an optical card, in which a tracking track 61 is formed on a transparent substrate 60. The tracking track 61 is composed of two auxiliary grooves 62, the width 65 of the auxiliary groove 62 is 1 μm and the depth 66. Is 1000 angstroms and the width 6 of the tracking track 61 is
4 is 3 μm and the pitch 67 is 12 μm. The recording layer 68 is formed on the transparent substrate 60, and the other configuration is the same as that of the embodiment.

The cross-track signal waveform of the reflected light amount of the side beam measured for this optical card is as shown in FIG. 2B. At this time, the cross-track contrast is 0.45, and the pull-in range is 1.0 μm. Was. When this is compared with the embodiment, as shown in Table 1, this optical card has a smaller cross-track contrast than the embodiment,
Further, it can be seen that the tracking characteristics are inferior because the pull-in range is narrow.

[0028]

[Table 1] (2) Second Comparative Example FIG. 7 is a longitudinal sectional view of a second comparative example of the optical recording medium of the present invention.

This optical recording medium is also an optical card, in which a tracking track 71 is formed on a transparent substrate 70, the tracking track 71 is composed of four auxiliary grooves 72, and the width 75 of the auxiliary grooves 72 is 0.47 μm and deep. 76 is 1000
Angstrom and tracking track 71
Has a width 74 of 3 μm and a pitch 77 of 12 μm. The recording layer 78 is formed on the transparent substrate 71, and the other configuration is the same as that of the embodiment.

The cross-track signal waveform of the reflected light amount of the side beam measured for this optical card is as shown in FIG. 2 (c), and the cross-track contrast at this time is 0.68 as shown in Table 1, so that it was implemented. Although almost the same as the example, the pull-in range is 0.8 μm, and the tracking characteristic is inferior to the example.

As can be seen from the above comparative example, when three auxiliary grooves are used, the tracking characteristics are particularly excellent as compared with the case where two or four auxiliary grooves are used, which is a preferable embodiment.

In the optical recording medium of the present embodiment, the auxiliary groove may be simply formed into a rectangular shape as a tracking track, so that stable production can be easily performed. In addition, since the auxiliary groove is shallow, the recording layer is formed by coating. In this case, coating unevenness is small, high cross-track contrast and a wide pull-in range are obtained, so that tracking characteristics are good. Further, although the present embodiment is an optical card, application to an optical disk is also possible.

[0033]

As described above, according to the present invention, a tracking track having a width substantially equal to the diameter of a light beam for performing tracking control is constituted by three auxiliary grooves having the same width. The auxiliary groove has a small depth, and the best results can be obtained especially in the range of 500 to 1500 angstroms. Even if the recording layer is formed by coating, the coating unevenness becomes small, and the track crossing signal of the side beam track crossing signal is used. Since the contrast is high and the drawing-in range is wide, good tracking characteristics can be obtained, and the cross-sectional shape of the groove does not need to be V-shaped or trapezoidal, so that there is an effect that manufacturing is easy and the yield is improved. .

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of one embodiment of an optical recording medium of the present invention.

FIG. 2A is a graph of a signal waveform across a track of the optical recording medium of FIG. 1; (B) is a graph of a track crossing signal waveform of the first comparative example. (C) is a graph of a track crossing signal waveform of the second comparative example.

FIG. 3A is a longitudinal sectional view of a first conventional example of an optical recording medium. (B) is a longitudinal sectional view of a second conventional example of the optical recording medium.

FIGS. 4A and 4B are graphs of the amount of side beam reflected from the optical recording medium. (C) is (a)
5 is a graph of a difference signal between the light amount of FIG.

FIG. 5 is a longitudinal sectional view showing a conventional recording layer of an optical recording medium.

FIG. 6 is a longitudinal sectional view of a first comparative example of the optical recording medium.

FIG. 7 is a longitudinal sectional view of a second comparative example of the optical recording medium.

[Explanation of symbols]

1, 60, 70 transparent substrate 2 recording layer 3 adhesive layer 4 protective substrate 5 hard coat layer 6 laser beam 11, 61, 71 tracking track 12, 62, 72 auxiliary groove 13 recording section 14, 64, 74 tracking track width 15, 65,75 Auxiliary groove width 16,66,76 Depth α ₁ , α ₂ signal δ Pull-in range

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hisanori Hayashi 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-1-286134 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) G11B 7/24

Claims (3)

(57) [Claims] 1. An optical recording medium having a tracking track for performing tracking control using a difference signal between two light beams and recording / reproducing information with light such as a laser beam, the tracking tracks have the same width. It is composed of three auxiliary groove, and the width of the tracking tracks measured at the outer edge of both the outer auxiliary grooves of the three auxiliary grooves is W, the diameter of the light beam for tracking control and d _B having to time, the optical recording medium, characterized in that W and d _B is substantially the same value. Wherein 0.8d _B ≦ W ≦ 1.2d _B The optical recording medium according to claim 1, wherein. 3. The optical recording medium according to claim 1, wherein the depth of the auxiliary groove is in a range of 500 to 1500 angstroms.