Information recording medium and recording method

Details Information recording medium and recording method Information recording medium and recording method

2001-02-16

2003-02-25

Mulvaney, Elizabeth (Department: 1774)

Stock material or miscellaneous articles

Circular sheet or circular blank

C428S064800, C430S270180

Reexamination Certificate

active

06524678

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to an optical information recording medium capable of recording and reproducing information using a laser and also to a method for recording information. More specifically, the present invention relates to a heat mode-type optical information recording medium suitable for the recording of information using a short wavelength laser at a wavelength of 550 nm or less, such as recordable optical disk (CD-R) and digital video disk (DVD-R).
BACKGROUND OF THE INVENTION
Conventionally, an optical information recording medium (optical disk) capable of only once recording information by a laser is known. This optical disk is called CD recordable (so-called CD-R) and in a representative structure thereof, a recording layer comprising an organic disk, a light-reflecting layer comprising a metal such as gold, and a resin-made protective layer are provided in a stacked layer state on a transparent disk-like substrate. The recording of information on this CD-R is performed by irradiating a laser in the near infrared region (usually a laser at a wavelength in the vicinity of 780 nm) on the CD-R. The irradiated portion of the recording layer absorbs light and causes local elevation of the temperature, as a result, physical or chemical changes (for example, production of pits) are generated and the optical properties thereof are changed, thereby recording the information. On the other hand, the reading (reproduction) of information is also performed by irradiating a laser at the same wavelength as the laser for recording, and while detecting the difference in the reflectance between the portion changed in the optical properties (recorded portion) and the portion not changed (unrecorded portion) of the recording layer, the information is reproduced.
In recent years, an optical information recording medium having a higher recording density is being demanded. To cope with this requirement, an optical disk called recordable digital video disk (so-called DVD-R) has been proposed (see,
Nikkei New Media,
extra number “DVD”, issued in 1995). This DVD-R has a structure such that two sheets of disks each obtained by providing a recording layer comprising a dye on a transparent disk-like substrate having formed thereon a guide groove (pregroove) for tracking of the irradiated laser to a width as narrow as a half or less (0.74 to 0.8 &mgr;m) as compared with CD-R and usually on the recording layer, providing a light-reflecting layer and if desired, further a protective layer, or the disk and a disk-like protective substrate having the same shape as the disk, are laminated with an adhesive while disposing said recording layer in the inner side. The recording and reproduction of information in the DVD-R is performed by irradiating a visible laser (usually a laser at the wavelength of 630 to 680 nm), where higher density recording than in CD-R can be achieved.
Also in recent years, networks such as internet, and high-vision TV are abruptly propagating and to cope with this tendency, demands for a high-capacity recording medium capable of inexpensively and easily recording the image information are increasing. The DVD-R can ensure the position as a large-capacity recording medium to a certain extent but cannot be said to have a recording capacity highly enough to be responsible to the requirements in the future. Therefore, studies are proceeding to develop an optical disk having a larger recording capacity by using a laser having a further shorter wavelength than DVD-R and thereby improving the recording density. For example, JP-A-4-74690 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), JP-A-5-38878, JP-A-6-40161, JP-A-11-53758, JP-A-2000-108513 and JP-A-2000-263938 disclose an optical information recording medium using an organic dye as the recording dye, such as monomethine cyanine dye, styryl-base dye, metal azo-base dye, quinophthalone-base dye and trimethine cyanine dye, and a recording/reproducing method for recording and reproducing information by irradiating a laser having a wavelength of 550 nm or less on this optical information recording medium.
SUMMARY OF THE INVENTION
According to the studies made by the present inventors, it has been found that the optical disk described in JP-A-11-53758 is not yet satisfied in the sensitivity in practice and in the recording properties such as reflectance and modulation factor and still in need of improvement.
An object of the present invention is to provide an information recording medium capable of recording/reproducing information by a laser having a shorter wavelength than those used for CD-R or DVD-R, particularly a laser having a wavelength of 550 nm or less, and at the same time, exhibiting excellent recording properties.
Another object of the present invention is to provide an information recording method capable of performing high-density recording of information by using an optical information recording medium in which a recording layer containing a dye compound having high sensitivity to a laser is provided.
Other objects and effects of the present invention will become apparent from the following description.
As a result of investigations, the present inventors have found that when a dye compound represented by formula (I), (II) or (III) is used as the recording material of the recording layer, an optical information recording medium capable of exhibiting high sensitivity even to a laser having a short wavelength of 550 nm or less, and favored with good recording/reproducing properties of giving high reflectance and high modulation factor can be produced.
The present invention also relates to an information recording method of recording information by irradiating a laser having a wavelength of 550 nm or less on the above-described information recording medium.
That is, the above-described objects of the present invention have been achieved by providing the following optical information recording media and information recording method.
(1) An optical information recording medium comprising a substrate having thereon a recording layer capable of information recording by laser irradiation, wherein said recording layer contains a dye compound represented by the following formula (I), (II) or (III):
R
11
R
12
N
+
═L
11
—L
12
—L
13
—NHR
13
·(1/m)(X
1
)
m−
  (I)
wherein R
11
, R
12
and R
13
each independently represents an alkyl group, an aryl group, an aralkyl group or a heterocyclic group, L
11
, L
12
and L
13
each independently represents a methine group which may have a substituent, (X
1
)
m−
represents an organic or inorganic m-valent anion, m represents an integer of 1 to 5, and any two of R
11
, R
12
, R
13
, L
11
, L
12
and L
13
may combine to form a ring;
R
21
R
22
N—L
21
═L
22
—L
23
═NR
23
  (II)
wherein R
21
, R
22
and R
23
each independently represents an alkyl group, an aryl group, an aralkyl group or a heterocyclic group, L
21
, L
22
and L
23
each independently represents a methine group which may have a substituent, and any two of R
21
, R
22
, R
23
, L
21
, L
22
and L
23
may combine to form a ring;
R
31
R
32
N
+
═L
31
—L
32
═L
33
—NR
33
R
34
·(1
)(X
3
)
n−
  (III)
wherein R
31
and R
32
each independently represents an alkyl group, an aryl group, an aralkyl group or a heterocyclic group, R
33
and R
34
each independently represents an alkyl group, an aralkyl group or a heterocyclic group, L
31
, L
32
and L
33
each independently represents a methine group which may have a substituent, (X
3
)
n−
represents an organic or inorganic n-valent anion, n represents an integer of 1 to 5, and any two of R
31
, R
32
, R
33
, R
34
, L
31
, L
32
and L
33
may combine to form a ring.
(2) The optical information recording medium according to item (1) above, wherein R
11
, R
12
, R
13
, R
21
, R
22
, R
23
, R
31
and R
32
in formulae (I), (II) and (III) each independently represents an alkyl group having from 1 to 20 carbon atoms, which may have a sub

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