JPS61280046A - Optical recording system - Google Patents

Abstract

PURPOSE:To enable the recording of information having high S/N and capable of being reloaded by using different and uniform oriented states of a liq. crystal group in recording and erasing information. CONSTITUTION:A voltage is applied between transparent electrodes 3 and 5, an electric field is impressed on a high molecular liq. crystal 4 to heat the crystal to about 90 deg.C and the liq. crystal is oriented in the direction vertical to a glass substrate. Accordingly, an optical recording medium providing a dark field under crossed Nicols even when cooled is formed. Then when high- density energy light 7 is irradiated while rotating the optical recording medium 1 around the central axis without impressing a voltage between the electrodes 3 and 5, the high molecular liq. crystal at the irradiated part is oriented in the direction different from the initial orientation, namely in the direction parallel to the glass substrate, by the shearing stress due to the rotation and the information can be recorded by the bright field under crossed Nicols. The voltage is applied between the transparent electrodes 3 and 5, light is irradiated on the recorded part of the liq. crystal while impressing an electric field on the high molecular liq. crystal 4 to locally heat the part, hence the crystal is returned to the initial uniform orientation and the information is erased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rewritable information recording system.

[Prior art and its problems]

Conventionally, as rewritable information recording systems, there are known magneto-optical recording systems that use magneto-optical materials and utilize the magneto-optic effect, and rewritable information recording systems that use inorganic materials and utilize phase change.

However, in the magneto-optical recording method, the S/N ratio is ~
In addition to being as low as 40 dB, it has the disadvantage that it cannot be partially erased. Furthermore, in a recording method using an inorganic material and utilizing phase change, although the S/N ratio has improved to 59 dB, the S/N ratio is still not sufficient.

Furthermore, the method of manufacturing a recording medium used in such a recording method uses sputtering or the like, which has the disadvantage of high manufacturing costs.

In order to overcome the above-mentioned drawbacks of the prior art, recording systems using polymeric liquid crystals have been proposed in Japanese Patent Laid-Open Nos. 59-10930 and 1987-35989. In such a method, since the non-aligned state of the liquid crystal is used for writing or erasing, incident light is scattered and the detection mechanism is limited, resulting in a poor S/N ratio.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a rewritable information recording system that uses polymer liquid crystal and can achieve a high S/N ratio.

[Structure of the invention]

In an optical recording method for recording information on an optical recording medium using a polymer liquid crystal and erasing the recorded information, the present invention is directed to the irradiation of a light beam to a polymer liquid crystal with uniform initial molecular orientation. Information is written by applying a molecular orientation force by rotating the recording medium to uniformly orient it in a direction different from the initial orientation, and by applying an electric field at the same time as heating to return the polymer liquid crystal to its initial uniform orientation. It is characterized by erasing information written in the previous period.

[Detailed explanation of configuration]

The basic operating principle of the present invention will be explained. Various types of polymer liquid crystals are known (Publication "Surface J",
Vo 1,20. No. 9 (1982),
P479-491, Koshinsha Publishing), the present invention includes temperature.

It is necessary to use a polymer liquid crystal that has properties that change with electric field and shear stress, and so-called side chain type polymer liquid crystals, in which liquid crystal groups are added to the main chain polymer, are particularly suitable for this purpose. The operation of the present invention is based on the alignment effect of liquid crystal groups.

Glass transition temperature 1 Polymer liquid crystals whose isotropic phase transition temperature has been appropriately adjusted are generally in a solid state at room temperature like ordinary polymers, but at temperatures close to or higher than the isotropic phase, they are in a moderately clayey state. , exhibits external field responsiveness similar to that of low-molecular liquid crystals. That is, for example, in a polymeric liquid crystal having a liquid crystal group with positive dielectric anisotropy, when an electric field is applied, the long axis direction of the molecules of the liquid crystal group is aligned in the direction of the electric field. When the temperature is returned to room temperature, the orientation state is maintained as it is. Similarly, when a polymeric liquid crystal is rotated at a temperature close to or higher than the isotropic phase, it becomes fluidly oriented in the direction of rotation, and when returned to room temperature, the oriented state is maintained as it is.

The present invention records and erases information based on the two different uniform orientation states.

When a temperature T1 necessary for phase change of the polymer liquid crystal and a voltage 1 necessary for alignment are applied, the polymer liquid crystal is uniformly aligned in a certain direction. When cooled in this state, the oriented state of the polymer liquid crystal is maintained even if the voltage is turned off.

The polymer liquid crystal with uniform initial molecular orientation as described above is irradiated with high-density energy light to raise the temperature to T1,
By rotating the polymer liquid crystal and applying shear stress due to rotational flow to the polymer liquid crystal, an orientation state different from the above-mentioned orientation can be obtained, and this state is maintained when the polymer liquid crystal is cooled.

This enables optical recording.

To erase the records made in the above manner, the entire surface of the polymer liquid crystal is heated to a temperature of T1 while a voltage of 1 is applied.
By doing so, it is possible to erase the entire recording by returning the polymer liquid crystal to its initial uniform orientation.

Furthermore, partial erasure is also possible by heating the area locally with a laser beam or the like to a temperature T while applying the voltage (1).

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a schematic cross-sectional view showing an example of an optical recording medium used in an optical recording system according to an embodiment of the present invention, and FIGS. 2 and 3 illustrate writing (recording) and erasing of information, respectively. This is a diagram for

In FIG. 1, the optical recording medium 1 has a diameter of, for example, 20 cm.
ITO was provided as a transparent electrode on a glass substrate 2, and then a polymer liquid crystal 4 having the following structural formula % was applied by heating and dipping, and the thickness was made 10 μm using spacers (not shown). I
It is constructed by providing a glass substrate 6 on which TO is provided as a transparent electrode 5. The structure of the optical recording medium is not limited to this, and a light absorption layer or a light reflection layer may be provided in the optical recording medium in order to increase the absorption efficiency of the light beam.

When a voltage is applied between the transparent electrodes 3 and 5 of the optical recording medium 1 as described above and the polymer liquid crystal 4 is heated to about 90°C while applying an electric field (>3V/μm), the liquid crystal group becomes perpendicular to the glass substrate. An optical recording medium is created which provides a dark field under crossed Nicols even when oriented and cooled.

Next, as shown in FIG. 2, the optical recording medium 1 is rotated 600 to 180 degrees around the central axis without applying a voltage between the transparent electrodes 3 and 5.
High-density energy light 7 while rotating at 0 rpm
For example, when irradiated with a He-Ne laser (10mW, 10m5), the polymer liquid crystal in the irradiated area will be oriented in a direction different from the initial orientation due to the shear core force caused by rotational flow.
In other words, it was possible to record information that was oriented parallel to the glass substrate and provided a bright field under crossed Nicols conditions. The S/N ratio was 70 dB.

To erase the information recorded in the above manner,
As shown in the figure, while applying a voltage between the transparent electrodes 3 and 5 of the optical recording medium 1 and applying an electric field (〉3μ/μm) to the polymer liquid crystal 4, high-density energy is applied to the recorded portion of the polymer liquid crystal. When locally heated to about 90° C. by irradiation with light 7, for example a laser, the initial uniform orientation was restored, the information was erased, and the information recording medium giving a dark field was reproduced again. The above is a case of partial erasing, but it is clear that erasing the entire area becomes possible by heating the entire surface with an appropriate heating means.

Note that the above embodiment describes an example of the present invention, and the present invention is not limited only to this embodiment.

For example, the heating temperature depends on the isotropic phase temperature of the polymer liquid crystal used, and can of course be selected depending on the material under various temperature conditions.

〔Effect of the invention〕

According to the present invention, by using different uniform alignment states of liquid crystal groups in recording and erasing information, the rewritable Information recording becomes possible.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an example of an information recording medium used in an embodiment of the present invention, FIG. 2 is a diagram for explaining recording in the information recording medium of FIG. 1, and FIG. FIG. 3 is a diagram for explaining erasure in the information recording medium shown in the figure. 1... Optical recording medium 2. 6... Glass substrate 3, Transparent electrode 4... Polymer liquid crystal 7... High-density energy light Agent Patent attorney Yoshiyuki Iwasa 1 Light t! tjtd forest fig. 1 fig. 2

Claims (1)

[Claims] (1) Recording information on an optical recording medium using polymer liquid crystal,
In the optical recording method for erasing recorded information, a molecular alignment force is applied to a polymer liquid crystal with a uniform initial molecular orientation by irradiation with a light beam and rotation of an optical recording medium, which causes the molecules to be oriented in a direction different from the initial orientation. An optical recording method characterized in that information is written by uniformly aligning the crystal, and the written information is erased by applying an electric field at the same time as heating to return the polymer liquid crystal to its initial uniform alignment.