JPS6192453A - Optical recording method - Google Patents

Abstract

PURPOSE:To attain high-density recording by using a specific organic amorphous compound as a recording medium, increasing the temperature of the recording medium while applying an electric field in a direction with a tilt angle to the read direction, cooling it and irradiating light on the recording at recording together with the electric field in the reading direction or singly so as to rise the temperature. CONSTITUTION:An organic amorphous compound is used where an isotropy is caused to a refractive index by arranging a dipole with an electric field and the orientation relax temperature of the radical causing the dipole is >=40 deg.C is used as the recording medium. A preparatory processing the same as erasure of recording is executed before recording for the recording medium. In the preparatory processing, electrodes 2a, 2b are provided in a direction with a tile angle theta in the read direction to a part to be recorded on the recording medium 1, an electric field is applied to a direction with a tilt in the reading direction and the recording medium 1 is heated to a temperature more than the orientation relax temperature or over of the polar radical. In the recording of the recording medium 1 subject to preparatory processing, a ray T2 is irradiated on the recording medium 1, the recording part is heated to relax the orientation of the oriented dipole and then cooled and fixed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Objective) The present invention provides optical recording/reading. This invention relates to a recording method that is excellent in terms of possible optical recording.

(Results of the Invention) There are two methods of optical recording: one that utilizes the photon effect and one that utilizes the thermal effect. The present invention relates to a recording method that utilizes thermal effects. Thermal effects that have been studied for optical recording include in-phase/vapor phase transitions, amorphous/crystalline transitions, metal/semiconductor transitions, and magnetic transitions. Looking at these from the perspective of recording methods, solid-state-to-vapor phase transition is a method that creates holes in the recording layer using heat, while amorphous-to-crystal transition and metal-to-semiconductor transition are methods that change the refractive index of the recording layer before and after the transition. This is a recording method that uses changes in light, reflectance, and light absorption coefficient.

Magnetic transition is a recording method that utilizes the difference in the rotational direction of the vibration plane of light depending on the magnetization direction of the magnetic material forming the recording layer.

The present invention utilizes the presence or absence of refractive index anisotropy in the dipole orientation state and disordered state.

Examples of methods that have been considered in the past for utilizing orientation of dipoles by an electric field include liquid crystal displays and dielectric treatments that impart piezoelectricity or pyroelectricity to ferroelectric materials. The latter involves orienting dipoles through polarization treatment in order to impart piezoelectricity or pyroelectricity, and cannot be used for optical recording.

The former optically utilizes the change in orientation caused by an electric field, but since it is necessary to continue applying an electric field in order to use it for recording, it is used exclusively for display purposes.

The present inventors have arrived at the present invention as a result of intensive research into the orientation of dipoles caused by an electric field and the use of the anisotropy of the refracting portion based thereon for optical recording.

If you put something that is optically isotropic when viewed from the viewing direction between crossed polarizers and the light passes through it, you won't see anything, but when you look from the viewing direction, you can put something that is optically anisotropic between crossed polarizers. It is generally known that if the long axis or short axis of the refractive index ellipsoid does not coincide with the axis of the orthogonal polarizer, part of the light will be transmitted.

It is also generally known that in the case of low molecular weight liquid crystals, molecules are oriented by an electric field and exhibit optical anisotropy.

This phenomenon is used in liquid crystal displays, but in order to use it for display, it is usually only necessary to control the orientation of a part with a size of about 0.1m + nX001 or more, and it is necessary to control the orientation of a part that is small enough to be used for recording. No attempt has been made to control the orientation, nor has there been any attempt to freeze and fix this orientation.

The orientation and change of dipoles contained in ordinary materials other than liquid crystals due to electric fields has been studied as a dielectric relaxation phenomenon, but it has not been studied in relation to optical properties.

Usually, such research uses a film sample and conducts experiments with electrodes attached to both sides of the film, so optical measurements cannot be performed unless the electrodes are removed, and when viewed from the direction perpendicular to the film surface, This is thought to be due to the lack of optical anisotropy.

When trying to utilize the orientation of dipoles caused by an electric field for optical recording, it is not enough to simply orient the dipoles due to the electric field and thereby produce optical anisotropy; it is also necessary to be able to record with high density and high speed change. is necessary.

(Summary of the Invention) The present invention provides an organic amorphous compound that produces anisotropy in the refractive index by orienting dipoles by an electric field, and in which the orientation relaxation temperature of the group that produces the dipole is 40°C or higher. is used as a recording medium, and the recording medium is heated while applying an electric field in a direction with an inclination angle to the reading direction to orient the dipoles, and then cooled. The present invention provides an optical recording method characterized by irradiating light onto a recording area independently to raise its temperature, which allows the recording unit area to be extremely small, thus enabling high-density recording, and Recording and erasing can be repeated at high speed.

(Detailed Description of the Invention) The recording material used in the present invention contains a dipole whose direction can be easily changed by an electric field at the recording temperature, and the optical anisotropy caused by the orientation of the dipole is It does not relax at least 40°C, preferably below 50°C, and its glass transition temperature is 50°C or higher, preferably Vi60.
An organic amorphous compound having a temperature of ℃ or higher is used.

As such an organic amorphous compound, a polymer compound having a polar group in the main chain or side chain and a large dipole moment is suitable, and a polymer compound having a large dipole moment as a negative group (a group having a large dipole moment) is suitable. is aromatic ring, heterocycle, -CN-1-CO
OH, -4-COO), M (M is a metal element), etc. can be used.

Such materials include various oligomers and polymers, such as polycarbonate, polystyrene, styrene-acrylonitrile copolymers, and polyacrylonitrile.

Further, even if a substance having a low-molecular dipole that is oriented along with the orientation of the dipole in such a substance is included, it is sufficient that the substance has the above-mentioned temperature characteristics as a whole.

In order to convert light into heat when it is irradiated, a substance that absorbs light at the wavelength used for recording is dissolved in the recording layer at an appropriate concentration, or when it comes into contact with the recording layer, it absorbs the light and converts it into heat. It is necessary to provide layers. Such a recording layer may be formed on the substrate by coating or the like.

A recording medium is produced by molding these organic amorphous compounds into a disc, tape, or line, or by coating the surface of another base material.

Before recording is performed on the recording medium, a preprocessing operation similar to the erasing operation of the recording is performed.

As shown in FIG. 1, in the preliminary processing, electrodes 2a and 2b are provided on the portion of the recording medium 1 to be recorded in a direction having an inclination angle θ with respect to the reading direction. An electric field is applied to the recording medium 1, and the recording medium 1 is heated to a temperature higher than the orientation relaxation temperature of the polar group.

In the present invention, "printing" and "cutting direction" mean the direction of light irradiated when reading a record, and mean the direction of the light beam in FIG. 3.

The inclination angle θ of the electric field is 5° or more, preferably 10° or more.

In addition, the heating of the recording medium 1 is performed by heating the orientation of polar groups with a relaxation temperature μ
Recording medium 1 is processed by processing it in a constant temperature bath.
It is possible to raise the temperature of the entire recording medium, but in order to fix the orientation of the dipoles by rapidly cooling it after processing, it is possible to heat the recording medium as a whole to fix the orientation of the dipoles, as shown in Figure 1. Electrodes 2a, 2
A preferred method is to apply heat ray T1 at the same time as irradiation with heat ray T1, to locally raise the temperature of the area to be recorded to a temperature higher than the orientation relaxation temperature of the polar group by means of heat ray Tl, and to run the irradiation position of this heat ray TI and the electrode position.

When recording on a preprocessed recording medium l, the procedure shown in Fig. 2 (
As shown in b), the recording medium l is irradiated with the light beam T2,
By raising the recording section, the orientation of the oriented dipoles is relaxed and then cooled and fixed.

In addition, in order to increase the recording speed, as shown in Figure 2 ←), light T2 is irradiated and electrodes 3a and 3b are provided in the same direction as the reading direction, and an electric field is applied in the P reading direction. Preferably, the dipoles of the recording medium 1 are oriented in the reading direction.

Through these operations, the orientation of the heated portions and dipoles is relaxed or oriented in the reading direction, so that the recording part becomes optically isotropic with respect to the reading direction, and the tilt angle A region that is optically different from other regions oriented in the direction of θ is formed, and recording is fixed by rapidly cooling this region. It is heated to a temperature below which the orientation of the organic compound can be relaxed, and preferably above the glass transition point of the organic compound.

In order to obtain the records recorded in this way, as shown in FIG. By receiving the light with the analyzer 5, it is possible to read the record based on changes in the intensity of the transmitted light caused by the presence or absence of dipole orientation or the difference in the direction of orientation, and it is also possible to use reflected light.

The polarization direction of the incident light for the purpose of dipping must be deviated by at least 5° from the direction in which the electric field is applied to the recording surface, most preferably at an angle of 45°. It is necessary that the direction of the polarizer 4b on the side of the analyzer 5 is orthogonal to this polarization direction. The recording light does not need to be polarized.

EXAMPLE Thin films of five types of polymers, polystyrene, styrene-acrylonitrile copolymer, polyacrylonitrile, polycarbonate, and polymethyl methacrylate, were formed on a substrate, and an electric field was applied at an angle of 30 to 60' with respect to the normal to the thin plane. While its glass transition temperature flf (Tg)
The temperature was raised to a temperature between Tg and 25° C., and then cooled. In the case of polystyrene, the strength of the applied electric field is 100
0 KV/m, 900 KV/l' for styrene-acrylonitrile copolymer and polymethyl methacrylate
1900Kv/C for In% polyacrylonitrile
1 polycarbonate, it should be 880 KV/.

The ratio of the brightness of transmitted light between orthogonal polarizers was determined for the part with refractive index anisotropy and the part without anisotropy in this way, and it was found to be ij 9.5 for polystyrene.
times, 3.8 times for styrene-acrylonitrile copolymer
2 times for polyacrylonitrile, 10,2 times for polycarbonate, ij for polymethyl methacrylate
It was 1.3 times. Those having a phenyl group or phenylene group in the main chain or side chain are easy to use because of their relatively low voltage and large light intensity ratio, but other types are also fully usable. By partially raising the temperature of the material that had been imparted with optical anisotropy to a temperature above Tg, it was possible to eliminate the optical anisotropy only in the portion where the humidity was higher than or equal to the wet temperature. It was also possible to eliminate the optical anisotropy by adding +JOFJsL to the entire optically anisotropic part. Furthermore, Pc was able to repeat these steps with good reproducibility.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram (longitudinal cross-sectional view) showing the pretreatment method;
FIGS. 2A and 2B are explanatory diagrams (longitudinal cross-sectional view) showing the recording method, and FIG. 3 is an explanatory diagram (thread cross-sectional view) when reading the recording. l: Recording medium θ: Inclination angle L: Light beam Patent applicant Mitsubishi Yuka Co., Ltd. agent Patent attorney Hidetoshi Furukawa (and 1 other person) Figure 1 Figure 2

Claims (1)

[Claims] The recording medium is an organic amorphous compound that produces anisotropy in the refractive index by orienting the dipoles by an electric field and has an orientation relaxation temperature of 40° C. or higher for the group that produces the dipoles. The temperature is raised while applying an electric field in a direction at an angle to the reading direction to orient the dipoles, and then cooled. During recording, light is irradiated onto the recording area together with the electric field in the reading direction or alone. An optical recording method characterized by heating.