JPH0688458B2 - Optical recording medium - Google Patents

Description

TECHNICAL FIELD The present invention relates to an erasable optical recording medium.

[Conventional technology]

As typical erasable optical recording media, magneto-optical recording media and phase change media are known.

[Problems to be solved by the invention]

Regarding the above-mentioned media, the magneto-optical recording media have problems that it is difficult to improve signal quality, that overwriting cannot be performed, manufacturing cost is high, and light resistance is low. On the other hand, the phase change medium is toxic and has a problem of high cost because it is manufactured by a manufacturing method such as sputtering. As a method for solving these problems, an optical recording medium using a polymer liquid crystal has been proposed (JP-A-59-10930, 59-3598).
9).

In such a medium, a glass transition temperature (Tg) and an isotropic liquid transition temperature (Tc) that are considerably higher than room temperature are required for stable retention of the recording state, and therefore, generally, a high molecular weight is required. However, when the molecular weight is high, there is a tendency to form a polydomain, which causes problems such as deterioration of signal quality and high pumping power.

An object of the present invention is to provide an optical recording medium using a polymer liquid crystal, which has high signal quality with low writing power.

[Means for solving problems]

The optical recording medium of the present invention has at least a transparent electrode on a support,
An optical recording medium provided with an optical recording layer, a light absorbing layer, and a reflective electrode substrate is characterized in that a high molecular compound of nematic liquid crystal and cholesteric liquid crystal having negative dielectric anisotropy is used for the optical recording layer. .

[Action]

The operation principle used by the present invention will be described. When a high electric field is applied to a mixture of liquid crystals with negative dielectric anisotropy and cholesteric liquid crystals, liquid crystal molecules are disturbed and show light scattering. This is preserved even when the electric field is turned off. This is called dynamic scattering with a memory effect. Erasure can be performed by adding an electric field with a frequency higher than the frequency (fc) at which the charge transfer in the process of space charge generation based on the negative anisotropy of liquid crystal molecules cannot follow the change of the electric field. is doing.

The structure of the recording medium according to the present invention is as follows. That is, an optical recording layer, which is a feature of the present invention, is provided on a glass substrate provided with a transparent electrode, and a light absorbing layer and a reflective electrode substrate are provided thereon.

To write information, the semiconductor laser is focused on the light absorption layer to locally heat the optical recording layer and at the same time cutoff frequency (fc).
When a voltage having the following frequency is applied, it is heated to cause dynamic scattering at a place where the viscosity becomes low.
On the other hand, when erasing information, the writing portion and the vicinity thereof are reheated by irradiation with a semiconductor laser beam, and at the same time, an electric field having a cutoff frequency or higher is applied.

The operation of the present invention essentially utilizes the fact that a scattering phenomenon is caused by the application of an electric field in the liquid crystal phase, and heating is carried out in order to reduce the viscosity to such an extent that the above scattering occurs in the liquid crystal phase. Therefore, unlike the conventional medium, writing irradiation can be performed by irradiation with semiconductor laser light of relatively low power, without requiring heating above the isotropic liquid transition temperature (Tc).

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, a transparent electrode 2 was provided on a glass substrate 1 as a support, and the cholesteric polymer liquid crystal shown in FIG. 2 was used as an optical recording layer on the transparent electrode 2. A light absorbing layer 4 was provided on top of this, and a reflective electrode substrate 5 was provided on top of this to obtain an optical recording medium. The optical recording layer 3 was formed by spin-coating a solution of polymer liquid crystal and drying the solvent.
The film thickness is 1 to 20 μm. The light absorption layer 4 was formed by vapor-depositing vanadium oxide phthalocyanine. The film thickness is 0.1 μm. The reflective electrode substrate 5 was formed by depositing aluminum to a thickness of 300 μm by vapor deposition.

A semiconductor laser of 830 nm was used. Write 5
A background electric field ratio of 5 was obtained by applying a DC electric field of 1 to 5 kV / cm simultaneously with the irradiation of laser light of mw and 1 μs.

For erasing, 1kHz, 5kV / c is applied at the same time as irradiation with the same laser light as writing.
This was done by applying an electric field of m.

〔The invention's effect〕

According to the present invention, unlike the conventional medium, it is not necessary to heat above the isotropic liquid transition temperature, and writing irradiation can be performed by semiconductor laser light irradiation of relatively low power, and a high quality signal can be obtained. This has the effect of realizing retention.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG. 2 is a view showing a cholesteric polymer liquid crystal structure. 1 ... Glass substrate, 2 ... Transparent electrode 3 ... Optical recording layer, 4 ... Light absorbing layer 5 ... Reflecting electrode substrate

Claims (1)

[Claims] 1. An optical recording medium comprising at least a transparent electrode, an optical recording layer, a light absorbing layer, and a reflective electrode substrate on a support, wherein the optical recording layer has a high dielectric anisotropy of nematic liquid crystal and cholesteric liquid crystal. An optical recording medium characterized by using a molecular compound.