Optical recording material and optical recording medium

Details Optical recording material and optical recording medium Optical recording material and optical recording medium

1997-10-27

1998-10-13

Evans, Elizabeth

Stock material or miscellaneous articles

Circular sheet or circular blank

428 642, 428 644, 428 648, 428913, 43027017, 43027019, 43027021, 4304951, 430945, 369288, B32B 300

Patent

active

058209620

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an optical recording medium which permits the writing and reading of data with laser light. More specifically, it relates to an optical recording film material, a recording film composition and a medium constitution for a write-once compact disk (CD-R).


TECHNICAL BACKGROUND

As a write-once optical disk having an edit function, at present, there is practically used a CD-R having a reflection film of gold formed on a recording film formed of an organic dyestuff such as cyanine, in which CD format or CD-ROM format signal is recorded at a wavelength of 780 nm and data is read out with a CD or CD-ROM reproducer. Since, however, the cyanine dystuff is generally poor in light stability, a CD or CD-ROM having a single surface structure has a risk of its data reliability being questioned under a use condition where it is directly exposed to sunlight.
Attempts have been therefore made to use a physicochemically stable phthalocyanine dyestuff as a recording film material in place of the cyanine dyestuff. JP-B-4-53713, JP-A-4-214388 and JP-A-5-1272 propose the use of phthalocyanine compounds, and some of them are practically used. CR-Rs using the above phthalocyanine materials have characteristics equivalent to those of CD-R using the cyanine dyestuff and work as media based upon "Orange Book", and some of them are excellent over medium using the cyanine dye in light resistance.
As CD-ROMS have been widely increasingly used in recent years, CD-R media are required to satisfy fast-access storage and fast-access reading, and one medium is required to comply with not only random-access storage but also double-speed and quad-speed storage. Since the phthalocyanine dyestuff is generally poor in recording sensitivity as compared with the cyanine dyestuff as described above, the phthalocyanine dyestuff does not satisfy all of these requirements. For improving recording sensitivity, therefore, it is necessary to modify the dyestuff structure by introducing a highly pyrolyzable substituent as is disclosed in JP-A-7-20550, or it is necessary to use a pyrolysis-promoting additive in combination as is disclosed in JP-A-59-92448. The above techniques succeed in attaining recording sensitivity which can satisfy fast-access storage, while it is generally attained at the sacrifice of durability and light resistance. Further, as a result of an improvement in recording sensitivity, the stability of storage characteristics becomes insufficient due to unstable forms of recording pits, and it is consequently further difficult to provide CD-R with good compatibility with all of commercially available CD players. As shown in JP-B-5-58915 and JP-A-7-98887, therefore, attempts are made to stabilize characteristics of stored signals by incorporating an agent which improves the properties of a surface layer of a recording film or an agent which controls the form of recording pits. However, the recording layer has a complicated constitution, and the productivity is inferior as compared with a case using a dyestuff alone. Otherwise, there is another problem that the reliability is poor since these agents themselves are poor in light resistance.
The present inventors have made diligent studies to overcome the above problems, and as a result, have found that an optical recording medium having recording sensitivity adequate for fast-access storage, having improved reliability with regard to light resistance and durability and having stabilized recording characteristics can be obtained by incorporating a phthalocyanine compound having a specific structure as an organic dyestuff to be incorporated into a recording layer, and the present invention has been accordingly arrived at.


DISCLOSURE OF THE INVENTION

The present invention 1 is an optical recording material which is a phthalocyanine compound having a specific structure of the formula (1) and is used as an organic dyestuff used for a recording layer in an optical recording medium formed of four layers comprising a transparent substrate, the r

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