High-density optical disk with a polymer film featuring thermochromism

Abstract

The present invention relates to a high-density optical disk having thin film layer made from a thermochromic polymer with a red-shift which exhibits self-focusing and optical bleaching. After an incident light beam passes through the polymer medium, not only can the spot size of the beam be reduced but also transmittance can be enhanced due to these kinds of third-order nonlinear optical response. Thus, a high-density disk structured according to the present invention is capable of the signal reproduction resolution beyond the diffraction limit with an efficient reflectivity. Accordingly, data recording density of a high-density disk can be improved greatly.

Description

CROSS REFERENCE TO RELATED ART[0001] This application claims the benefit of Korean Patent Application No. 2001-63491, filed on Oct. 15, 2001, which is hereby incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002] 1. Field of the Invention[0003] The present invention relates to a high-density (HD) optical disk having a thin film layer made from a thermochromic polymer with a red-shift which exhibits self-focusing and optical bleaching.[0004] 2. Description of the Related Art[0005] In general, information signals in an optical disk such as a compact disk (CD) or a digital versatile disk (DVD) is recorded and reproduced with a laser beam incident thereto. The optical disk is classified into two types, one for a read-only optical disk such as a CD or DVD for read only memory (CD-ROM or DVD-ROM), and the other for a rewritable optical disk such as a rewritable CD (CD-R / W) or a DVD for random access memory (DVD-RAM).[0006] FIG. 1 shows a schematic structure of a conve...

AI Technical Summary

Benefits of technology

[0012] Another object of the present invention is to provide a polymer film that exhibits third-order optical nonlinearities. These third-order optical nonlinearities include self-focusing or self-defocusing in the refractive aspect and optical bleaching or saturation in the absorptive aspect, depending on material. In particular, self-focusing reduces the size of beam spot due to the intensity-dependent positive refractive change, while optical bleaching enhances the intensity of transmitted beam due to a lowered extinction coefficient beyond linear optical properties. Since a thermochromic polymer with a red-shift can be shown to have both the properties of self-focusing and optical bleaching at a specific frequency of irradiated beam as explained in detailed description, not only can the size of a beam spot focused on the recording surface be minimized but also the optical efficiency of a light beam reflected from the recording surface can be maximized after a light beam travels in this medium.

[0014] To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a recordable disk medium for use with a light source comprises a transmission layer; a reflection layer; a protective layer; and a polymer film having thermochromism disposed coplanarly with the reflection layer in an incident light beam path of the light source wherein the polymer film refracts an incident light beam beyond a diffraction limit of the incident light beam and allows the formation of a smaller laser beam spot on the reflection layer.

[0018] The disk medium described below is used with a recording and reproduction apparatus. Such apparatus comprises a light source that provides an incident light beam on the disk medium. In particular, the disk medium comprises a transmission layer; a reflection layer; a protective layer; and a polymer film having thermochromism disposed coplanarly with the reflection layer in an incident light beam path of the light source wherein the polymer film refracts the incident light beam beyond a diffraction limit of the incident light beam and allows the formation of a smaller laser beam spot on the reflection layer.

Problems solved by technology

Thus the signal reproduction resolution and density of recorded information are limited to the size of a beam spot at the focal position.

However, it is not possible to make the size of the beam spot, which is focused on the recording layer 11 of the optical disk, to be smaller than the wavelength of the laser beam because of optical restriction posed by the diffraction limit of the laser beam.

Unfortunately, effective solutions for situations such as this example are not available presently and are urgently required.

However, this invention has not been commercialized because the amorphous silicon film excessively absorbs light energy in the wavelength region of visible light.

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