JPH02101647A - Optical information recording tape and its recording method - Google Patents

Abstract

PURPOSE:To obtain an optical information recording tape reloadable and with a satisfactory memory life and a high contrast ratio and its recording and reproducing method by providing a recording layer consisting of macromolecule liquid crystal whose anisotropy of refractive index can be controlled by an electric field with temp. exceeding glass transition point. CONSTITUTION:An orientation control film 2 is formed on a tape substrate 1 that is the supporting body of the optical information recording tape 5, and the recording layer 3 consisting of the macromolecule liquid crystal with the glass transition point whose anisotropy of refractive index can be controlled by the electric field with temp. exceeding glass transition point is provided on the film. Furthermore, a protection layer 4 is provided on the recording layer 3, and chiral smectic C liquid crystal having ferroelectric property is used as the macromolecule liquid crystal to be used in addition to nematic liquid crystal having dielectric anisotropy. The tape 5 is fed between a pair of transparent guide rollers 6 for tape feed having transparent electrodes 7 in a tape feed direction, and the electric field is applied between the rollers 6 in a direction of thickness of the tape 5 in feeding the tape, then, recording and reproduction can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical information recording tape and a recording method thereof.

[Prior Art] Magnetic recording tape has conventionally been known as an information recording tape, but since magnetic recording tape has a limit in information recording density and also has a limit in improving noise characteristics, optical recording tape has recently been developed. A method using the formula principle has been proposed. An example of a method using an optical principle is a method in which a recording bit consisting of fine holes is formed on a recording layer by irradiation with a laser beam. (Japanese Unexamined Patent Publications No. 57-3:1447, No. 5894145) The recording medium forming the recording layer used here is T
A metal film of e-As-Se or a mixture of carbon and nitrocellulose coated on a plastic base is used. However, in the methods using these recording media, recording is irreversible and cannot be rewritten.

On the other hand, as rewritable optical recording media, there are known phase transition methods that use Of-inverse phase transition between amorphous and crystalline chalcogenide thin films, and methods that use structural changes within the amorphous phase temperature region. There is.

As for organic materials, there are known methods such as a photon mote recording method using a photochromic material and a method that utilizes the change in light reflection between a scattering state and a transparent state or a uniformly oriented state and a non-oriented state of a polymer liquid crystal.

Among these, polymeric liquid crystal materials have the advantage of being easy to mold into a film, and are particularly advantageous when used in tape-shaped optical information recording media.

[Problems to be Solved by the Invention] In the conventional system using the optical principle, recording is irreversible and cannot be rewritten, as well as the problem of reproduction deterioration, which should be improved.

Furthermore, those that utilize the phase transition phenomenon of chalcogenide thin films or those that use photochromic materials have problems with the storage stability and durability of recorded information.

On the other hand, when using polymer liquid crystal as an optical recording medium,
When trying to measure the contrast between the light scattering state (liquid crystal state) and transparent state (isotropic rod state) of a polymer liquid crystal, there is a problem that it is difficult to measure the contrast when the film thickness is thin. Optical information recording tape using polymer liquid crystals has not been put into practical use. Furthermore, the present invention, which has a slow erasing speed and is not suitable for use as a rewritable medium, was developed to solve these conventional problems. It is an object of the present invention to provide an optical information recording tape with a high ratio and a recording method thereof.

[Means for Solving the Problems] That is, the present invention provides an optical information recording tape characterized by having a recording layer made of polymeric liquid crystal whose refractive index anisotropy can be controlled by an electric field above the glass transition point. It is.

The present invention also provides an optical information recording tape having a recording layer made of a polymeric liquid crystal whose refractive index anisotropy can be controlled by an electric field above the glass transition point. Optical information recording, characterized in that information is recorded and reproduced by causing the tape to run between guide rolls, applying an electric field in the thickness direction of the tape, and irradiating recording and reproduction light that passes through the transparent guide rolls. This is a tape recording method.

The present invention will be explained in detail below.

The optical information recording tape of the present invention uses a polymeric liquid crystal having a glass transition point and whose refractive index anisotropy can be controlled by an electric field above the glass transition point as a recording layer.

FIG. 1 is a partial explanatory diagram showing the basic layer structure of the optical information recording tape of the present invention. In FIG. 1, the optical information recording tape of the present invention has an orientation control film 2 formed on a tape base l, which is a tape support, and has a glass transition point or higher. A recording layer 3 made of polymeric liquid crystal whose refractive index anisotropy can be controlled by an electric field is provided, and a protective layer 4 is further provided on the recording layer 3. Further, a laser light absorption layer may be provided as necessary.

For example, a transparent resin such as polyethylene terephthalate, polymethyl methacrylate, or polyimide is used for the tape base l.

Further, as the polymeric liquid crystal that can be used as the recording layer, in addition to nematic liquid crystal having dielectric anisotropy, chiral smect C liquid crystal having ferroelectricity is more preferable. Next, specific examples of the above-mentioned polymeric liquid crystal will be given, but the invention is not limited to these.

Polymer liquid crystal C1l having a nematic phase with Δε>0:
1 (TV) Ferroelectric polymer liquid crystal C1!3 υ (V) (II) Polymer liquid crystal with a nematic phase of ΔSakuO (III) (Vl) Polymer liquid crystal with a nematic phase of Δε〉0 When used as a recording layer, it is desirable that the initial state is horizontally aligned; conversely, when a polymer liquid crystal having a nematic phase with Δε<0 is used as the recording layer, the initial state is vertically aligned. It is preferable to keep it.

In addition, when using a ferroelectric polymer liquid crystal, 0.1 to 10 wt of a suitable dye is added to the liquid crystal to absorb laser light.
It is more preferable to mix 1. There is no particular problem as long as the dye used for this purpose is a commonly used laser light absorbing dye.

The polymer liquid crystal layer of the recording layer can be formed by applying a bar code or roll coating onto a tape substrate on which an alignment film has been formed, or by applying a stretched film-like polymer liquid crystal to the liquid crystal's isometric phase transition temperature. A method of crimping using the above-mentioned condition may also be mentioned. Thereafter, a highly oriented tape-like recording medium can be produced by slow cooling to room temperature or by stretching the substrate together.

Further, the thickness of each layer constituting the optical information recording tape of the present invention is 1 to IO#Ls+ for the tape base.

500-1000 people for the alignment control film, 0.1-1 for the recording layer
0 gm, and the protective layer is preferably in the range of 0.1 to 1 gta.

Next, a method for recording and reproducing an optical information recording tape according to the present invention will be explained. FIG. 2 is a partial explanatory diagram showing the main parts of a recording and reproducing apparatus used in the optical information recording tape recording and reproducing method of the present invention. In FIG. 2, reference numeral 6 indicates a transparent guide roll for running the tape, and is made of a transparent material such as plastic or glass. 7 is a transparent electrode such as ITO provided on the surface of a transparent guide roll, 5 is an optical information recording tape, 8 is a polarizer, 9 is an analyzer, IO is a laser light source, and 12 is an odometer (for reproduction).

To record and reproduce information, the optical information recording tape 5 is run between a pair of transparent tape running guide rolls 6.6 equipped with transparent electrodes 7, and the tape passes through the transparent electrodes 7.7. An electric field is applied in the thickness direction of the intervening tape. At this time, recording/reproducing light is irradiated from the laser light source IO through the transparent guide roll 6, and the portion of the optical information recording tape 5 that is irradiated with the laser light is heated to a temperature higher than the glass transition point of the polymer liquid crystal. When the liquid crystal state is reached, the liquid crystal molecules respond to the electric field, and the alignment direction of the polymer liquid crystal changes, so that the anisotropy of the refractive index changes only in the laser irradiated area. Therefore, contrast can be obtained because the light passing through the polarizer 8 and the analyzer 9 and detected by the photodiode 2 changes between the recorded and non-recorded areas.

When a nematic liquid crystal is used as the recording layer, in order to erase the data, the liquid crystal phase can be heated to the isokichi phase using a laser beam and intensity modulation, and then slowly cooled to restore the initial alignment state.

In addition, when using chiral smectic liquid crystal,
If laser irradiation is applied with an electric field opposite to that used during reading, partial erasure can be performed at the same speed as writing.

In an optical information recording tape using a ferroelectric polymer liquid crystal whose refractive index anisotropy can be controlled by an electric field above the glass transition point in the recording layer, the optical information recording tape is made of two pairs of transparent electrodes. The tape is made to run between transparent guide rolls, and electric fields are applied in opposite directions in the thickness direction of the tape, and recording/reproduction light is irradiated through the transparent guide rolls. Partial recording of information can be rewritten. Specifically, as shown in FIG. 3, using a device equipped with two pairs of transparent guide rolls 6.6a to which an electric field can be applied, the tape is run in the X direction shown in the figure, and the guide rolls are 6a is applied with an electric field in the opposite direction to that of writing and irradiated with the partial erasing laser 13 to perform whole or partial erasing, and then an electric field in the same direction as that during writing is applied by the guide roll 6 to erase the whole or partial area. Only partial rewriting is possible.

[Function] The present invention uses a polymer liquid crystal, which has a glass transition point and whose refractive index anisotropy can be controlled by an electric field above the glass transition point, as a recording layer of an optical information recording tape. By keeping the temperature below the glass transition point, it is possible to obtain a large-capacity recording medium with good memory storage stability and a high contrast ratio due to a large change in refractive index anisotropy.

Furthermore, by performing reproduction using rotation of the plane of polarization, the reproduction contrast ratio can be increased. At the same time, a pair of transparent tape running guide rolls with transparent electrodes on their surfaces apply an electric field in the thickness direction of the tape, and recording/playback light is transmitted through the transparent guide rolls to produce stable playback signals. You can get it. In addition, when a ferroelectric polymer liquid crystal is used, the tape is made to run between two pairs of transparent guide rolls equipped with transparent electrodes, and each electric field is directed in the thickness direction of the tape or in the opposite direction. Partial rewriting is also possible by irradiating recording/reproducing light through a transparent guide roll while applying an electric current.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 After applying polyimide as an alignment film to a thickness of 1000 on a polymethyl methacrylate film having a thickness of 5 μl,
On a flexible substrate that has been subjected to a rubbing process.

Among the polymer liquid crystals represented by the structural formula (Vl), n=
No. 10 (Tg = 30°C) was coated to a thickness of 0.5 gra by wire bar coating, and after drying, a polyethylene terephthalate film with a thickness of 1 cm was further pressure-bonded at the isotonic phase transition temperature of the polymer liquid crystal. A uniaxially oriented tape-shaped recording medium was obtained by slowly cooling to room temperature. however,
Polymer liquid crystals contain dyes (
input + max = 785 nm) is 1 for polymer liquid crystal.
It is contained in the proportion of wt$.

An electric field with a strength of 4 V/pm was applied in the thickness direction of the optical information recording tape formed in this way, and 780r++
After irradiation with a semiconductor laser (power: 8 mW, beam diameter: 1.6 mm), the electric field was turned off. When the written area was observed with a polarizing microscope, a contrast ratio of 1:9 was obtained between the laser irradiated area and the non-irradiated area. Furthermore, the recording section was preserved for more than three months at room temperature even when a reverse electric field was applied, confirming that the memory storage property was good.

Example 2 The rotating optical information recording tape used in Example 1 was used in a second
The tape was set in a cassette housing with a guide roll with transparent electrodes as shown in the figure, and the running speed of the tape was set at 4 rm/s.
Adjusted to ec. A semiconductor laser with a wavelength of 780 nm, a power on the recording surface of 8+aW, and a beam diameter of 1.61 was irradiated with IKIIz modulation, and an electric field was applied so that the electric field strength was 4 V/pm. Recorded.

After recording, the laser power was set to 0.1 mW, and the contrast ratio between the recorded area and the non-recorded area was 1:9 (definition is based on the example). A high contrast ratio (same as that of the 3D image) was obtained. Furthermore, while applying an electric field in the opposite direction to the fortune-telling to the tape recorded in this way,
Using an 80t++s semiconductor laser with the same power as during recording, the beam diameter was widened to 2μ, and the continuous wave rate was 4m/s.
When a running tape was irradiated with EC, the bits in the recording part were completely erased, confirming that erasing was possible.

Example 3 The same optical information recording tape as used in Example 1.2 was set in a cassette housing having two pairs of guide rolls with transparent electrodes as shown in FIG. 3, and the running speed of the tape was adjusted. was set to 4 ta/sec. The bit forming part of the already recorded tape is passed through a guide roll part to which an electric field opposite to that for writing is applied, and a laser beam (wavelength 780n+*,
After performing partial erasure by irradiating with a bit diameter of 2 l),
We used a rewriting laser to write on the non-recorded area, and when we looked at the playback signal, it was confirmed that only partial rewriting was possible.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain an optical information recording tape that is rewritable, has good memory storage properties, and has a high contrast ratio, and a recording and reproducing method thereof. I can do it.

[Brief explanation of drawings]

FIG. 1 is a partial explanatory diagram showing the basic layer structure of the optical information recording tape of the present invention, and FIG. FIG. 3 is an explanatory diagram showing a partial recording rewriting method. ■...Tape base 2...Orientation control film 3.
...Recording layer 4...Protective layer 5...Optical information recording tape 6.6a...Guide roll 7,7a...Transparent electrode 8...Polarizer 9...Analyzer lO...
・Laser light source II...Lens 12...Photograph for reproduction 13...Laser for partial erasure 14...Laser for damage replacement

Claims (5)

[Claims] (1) An optical information recording tape characterized by having a recording layer made of a polymeric liquid crystal whose refractive index anisotropy can be controlled by an electric field at a temperature above the glass transition point. (2) The optical information recording tape according to claim 1, wherein the polymer liquid crystal is a polymer liquid crystal having ferroelectric properties. (3) An optical information recording tape having a recording layer made of polymeric liquid crystal whose refractive index anisotropy can be controlled by an electric field above the glass transition point is placed between a pair of transparent guide rolls for tape running equipped with transparent electrodes. An optical information recording tape is characterized in that information is recorded and reproduced by running the tape, applying an electric field in the thickness direction of the tape, and irradiating recording and reproduction light through a transparent guide roll. Method. (4) The optical information recording tape according to claim 3, wherein the polymer liquid crystal is a polymer liquid crystal having ferroelectric properties. (5) An optical information recording tape having a recording layer made of a ferroelectric polymer liquid crystal whose refractive index anisotropy can be controlled by an electric field at temperatures above the glass transition point is connected to two pairs of tape running transparent tapes equipped with transparent electrodes. The tape is made to run between transparent guide rolls, and electric fields are applied in opposite directions in the thickness direction of the tape, and recording/reproducing light is transmitted through the transparent guide rolls to partially record information. A recording method for an optical information recording tape characterized by rewriting the recording.