JPH02101650A - Optical information recording tape - Google Patents

Abstract

PURPOSE:To obtain the optical tape which is always stable tracking controllable and is rewritable by providing a position signal region formed with the irreversible and fixed position signals which do not change the optical characteristics of the optical information recording tape. CONSTITUTION:Prewobbling holes of a prescribed diameter are formed by a semiconductor laser of a prescribed wavelength to the servo area of the optical recording tape so as to be shifted to the right and left of the line connecting the centers of data bits. The magnitudes of the reflected light from the prewobbling holes is compared by a sample hold system and after the application of tracking is confirmed, writing of the data is executed by throttling the laser power to form the transparent data bits on the surface of the turbid recording layer. The optical recording tape is passed through heating rollers the surface of which is kept at about 90 deg.C, by which the total erasing of the recording bits is executed. The previously formed holes are not erased so that the exact tracking at the time of executing the recording and reproducing again is assured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an optical information recording tape (hereinafter referred to as an optical recording tape) with an erasing section.

[Prior Art] Conventionally, magnetic recording tapes have been known as information recording tapes, but magnetic recording tapes have limitations in information recording density and in improving noise characteristics. A method using an optical principle has been proposed. An example of a method using an optical principle is a method in which recording bits consisting of fine holes are formed on a recording layer by irradiation with a laser beam. (JP-A-57-3:1447, JP-A-5894145) The recording medium forming the recording layer used here is a metal film of D-As-SC or a mixture of carbon and nitrocellulose. The body is coated with a plastic base. However, in the systems 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 a reversible phase transition between amorphous and crystalline chalcogenide thin films, and methods that use structural changes within the amorphous phase temperature region. ing.

In addition, in organic material systems, there are known methods such as a photon mote recording method using a photochromic material and a method that utilizes changes in light reflectance 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.

[Problem to be solved by the invention] In the tape-shaped optical information recording medium as described above, data for position signal detection is written in a predetermined area as a tracking method during recording and playback. This method is often used. For example, one method for rewriting optical recording tapes that uses polymeric liquid crystal in the recording layer is to completely erase the previously recorded portion of the recording layer by passing it through a heating roller or applying an electric field, and then rewriting it again. A method of #I writing may be considered, but if the position signal is formed using the same writing method as the data signal, there is a problem that the position signal will also be erased when the entire surface is erased.

The present invention was made in order to improve these conventional problems, and it is possible to use fixed bits that cannot be recorded or erased in a rewritable optical recording tape that uses polymeric liquid crystal for the recording layer. It is an object of the present invention to provide a rewritable optical recording tape that can prevent the position signal from being erased by forming it in the position signal area, and can perform stable tracking control without track grooves.

[Means for Solving the Problems] and [Operations] Namely, 1, the present invention uses a polymeric liquid crystal having a glass transition point as a recording layer, and reversibly changes the optical characteristics of the recording layer by heat or the action of heat and an electric field. This optical information recording tape is characterized in that it has a position signal area that forms an irreversible fixed position signal whose optical characteristics do not change.

The present invention will be explained in detail below.

The polymeric liquid crystal that can be used in the present invention is a thermotropic liquid crystal, and nematic, smectic, or cholesteric types can be used as the intermediate phase. Polymer thermotropic liquid crystals have the advantage of not only being able to form a thin film but also being easy to maintain a recorded state.

For example, polymer thermotropic liquid crystals, which are polymer liquid crystals that can be used in the present invention, are classified into the following two types.

■Mesogenic groups, or relatively rigid long atomic groups or those connected by flexible chains.

■Having a mesogen group or a relatively rigid and long atomic group in the side chain.

These polymer liquid crystals can be used in combination with several different polymer liquid crystals. It is also possible to use a mixture of a polymer liquid crystal and a low molecular liquid crystal, or a mixture of a polymer liquid crystal and a polymer.

Specific examples of polymer liquid crystals are shown below, but the invention is not limited thereto.

R: 8 OCs.

R: 0Cffl! ? n: CN CI+.

e Since these polymeric liquid crystals have the characteristic of being able to maintain their structural state at temperatures below the glass transition point, a recording mode such as the first order is possible, for example.

In the (+) recording mode, the polymer liquid crystal is first maintained in a liquid crystal phase or a polydomain state consisting of a large number of domains. Next, recording is performed by heating the polymeric liquid crystal to a temperature higher than the temperature at which it exhibits the isokitic phase, and then rapidly cooling it to below the glass transition point to maintain the polymeric liquid crystal in the isokitic phase state.

In the recording mode (2), the polymer liquid crystal is first maintained in a liquid crystal phase or a monodomain state consisting of a single domain using an electric field or the like. Next, recording is performed by heating the polymeric liquid crystal above its glass transition point and then cooling it to maintain the liquid crystal phase in a polydomain state.

In addition, ferroelectric polymer liquid crystals can also be used as polymer liquid crystals, and in this case, (3) electric field birefringence control type recording mode using polarization inversion of ferroelectric polymer liquid crystals may be used. Recording is performed by

In any of these recording modes (1), (2), and (3), it is possible to return the recording state to the initial state by slow cooling after heating, or by a combination of heating and electric field application, so rewriting is not possible. It can be used as a possible optical recording tape. Therefore, it is also possible to reverse the 6-shape yE of first non-scattering and light scattering to form a recording top.

A common method for heating the polymeric material in the recording layer of an optical memory is to add a light-absorbing dye into the recording layer or an adjacent layer to convert irradiated light into heat.

The irradiation light is preferably a laser beam that is monochromatic and has excellent straightness, and a semiconductor laser is particularly preferable from the viewpoint of compactness and low power consumption. Examples of light-absorbing dyes having absorption in the near-infrared wavelength region such as semiconductor laser light include the following.

(Note) However, n is a positive integer, R is an aromatic cyamine residue, A is an aromatic tetracarboxylic acid residue, a and b are each independently O or an integer from 1 to 50, and a+b is an integer from 1 to +00.

In addition, l1e-Ne laser light, Ar ion laser
If light or the like is used, it is possible to use light-absorbing dyes that have absorption at each wavelength. In particular, when adding it to a polymeric liquid crystal, it is preferable to use a dichroic dye from the viewpoint of compatibility.

Furthermore, additives such as ultraviolet absorbers, antioxidants, and nucleating agents may be added to the recording layer.

The rewritable optical recording tape of the present invention uses a polymeric liquid crystal having a glass transition point as a recording layer, and has a fixed recording layer in which either irreversible recording whose optical properties do not change or erasing is impossible. It has a position signal area in which a position signal is formed. As a specific method for forming a fixed position signal that cannot be recorded or erased, the recording layer may be thermally deformed into pits or holes, or the recording layer may be crystallized or altered. .

To form pits or holes in a polymer liquid crystal recording layer, for example, recording of a rewritable optical memory is possible.

The output of the laser beam used for reproduction and erasing is greatly increased, and the polymer liquid crystal is heated to a temperature higher than the temperature at which it exhibits the isotonic phase, and the viscosity of the polymer liquid crystal is extremely reduced and thermally changed to form the recording layer. Either by forming areas of reduced thickness (pits) or by decomposing and removing the polymeric liquid crystal, areas without a recording layer (
This is done by forming holes).

In the areas where these pits or holes are formed, the recording layer is completely absent or the thickness of the recording layer is thinner than in other areas, and the light transmittance and light reflectance are high. Therefore, even if an attempt is made to reduce the light transmittance or light reflectance by irradiating a position signal area in which a pit or hole-shaped position signal is formed with a laser beam used in a rewritable optical recording medium, recording will not be possible. When the layer thickness is small, there is almost no change, so the position signal area in which pits or holes are formed becomes a fixed area that cannot be recorded or erased.

Further, the size of the pit or hole may be such that tracking can be performed, and for example, the diameter is preferably Ig+a or more, preferably in the range of 1.5 to 2.0 μm.

In the present invention, this fixed area is used for a position signal of a rewritable optical recording tape. More specifically,
As shown in FIG. 1, a tracking line 3 is a line connecting the center line of the recording pit 2 to the tracking signal area.
A position signal consisting of pits or holes (ring hits or tracking pits) l shifted to the left and right from the position is formed. Note that the tracking line 3 also indicates the scanning direction of the laser beam.

In the sample servo method, when recording or reproducing light moves along a tracking line, tracking servo is performed by detecting the difference in reflected light from two tracking bits, but according to the present invention, when erasing the entire surface, Since this position signal will not be erased, tracking control can be carried out with peace of mind.

The fixed position signal in the present invention may be attached to the end face of the tape in the width direction. In this case, it can be used for searching for a specific data area. In addition, as shown in Fig. 2, such hardened pits or holes are continuously formed in a linear shape, and this is used as a tracking track 4 exclusively for tracking, and the area sandwiched between the tracking tracks 4 is By setting the area as a data write-only area, it is possible to use the three-beam tracking method and to perform stable tracking without mixing in recording data.

In the present invention, there are no particular limitations on the base material, and ordinary materials can be used.For example, a film made of synthetic resin or the like can be used.

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

Example 1 A polymer liquid crystal represented by the following structural formula (12) was placed on a polyethylene terephthalate film with a thickness of 10 pm,
0.5 wt% of the following structural formula (13
) The concentration of non-volatile matter containing the pigment represented by is 10wt.
% dichloroethane solution was coated with a bar coater, the solvent was removed, the mixture was heated to a temperature above the clearing point of the liquid crystal, and slowly cooled to room temperature to produce an optical recording tape with a recording layer having a thickness of 6 mm. . The initial state of this optical recording tape was a cloudy state.

A semiconductor laser with a wavelength of 8:1 Ons was applied to this optical recording tape so that the output on the recording layer surface was adjusted to 20 W, and a pre-wobble hole with a diameter of 1.6 #L was created as shown in Figure 1. The servo area of the optical recording tape was formed so that it was slightly shifted to the left and right of the line connecting the centers of the data bits.

After confirming that tracking can be performed using a sample servo method that compares the magnitude of the reflected light from this pre-wobbling hole, we reduced the laser power to 5 mW and wrote data at a frequency of I MHz.
Transparent data bits were formed on the cloudy surface of the recording layer.

Either this optical recording tape is passed through a heated roller whose surface is heated to 90°C to completely erase the recorded pits, or the previously formed holes are not erased and accurate tracking is not possible when recording/playing again. I was able to do it.

Structural formula (12) Structural formula (13) Example 2 A polyethylene terephthalate film with a thickness of 5 μm was adhered onto the recording layer of the same optical recording tape used in Example 1, and the recording layer was heated using a transparent electrode and a heater. Applying an 80V electric field in the thickness direction of the tape while maintaining the liquid crystal temperature,
Polymer liquid crystals were vertically aligned. In this state, the state of the pre-wobble hole did not change. Even when a thermal head for writing was added to this information recording tape, the tape was rapidly cooled, and the orientation state was disturbed and writing was performed, the pre-wobble holes did not change and accurate recording and reproduction were repeatedly performed.

Example 3 A polymeric liquid crystal represented by the following structural formula (14) was deposited on a polyethylene terephthalate film with a thickness of 5μ.
A wt% dichloroethane solution was applied in the same manner as in Example 1 to a thickness of 5 μm. However, the same dye used in Example 1 was used in the polymer liquid crystal layer at 3 wt% of the liquid crystal.
Contains only A polyethylene terephthalate film having a thickness of 5 cm and a thickness of 5 #Lm was adhered onto the recording layer thus formed.

This was slowly cooled from a temperature above the clearing point of the liquid crystal to room temperature.

A burbling pit was formed in this in the same manner as in Example 1. This tape is sandwiched between a pair of transparent electrodes, the part sandwiched between the electrodes is heated with a heater to the liquid crystal temperature, an electric field of 50 V and 5 Hz is applied between the electrodes, and the state of light transmission is observed in a crossed nicol state. It was confirmed that the optical properties of the pit-formed area did not change due to changes in the electric field, and that this area could not be erased.

Structural formula (14) A rewritable optical recording tape can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a method of forming a fixed position signal on an optical recording tape according to the present invention, and FIG. 2 is a partial explanatory diagram showing a position signal area formed on the optical recording tape. l... Pit or hole 2... Recording bit 3 - Tracking line 4... Tracking track 5... Main spot 6... Side spot [Effects of the invention]

Claims (4)

[Claims] (1) A polymer liquid crystal having a glass transition point is used as a recording layer,
In an optical information recording tape in which the optical properties of the recording layer can be reversibly changed by the action of heat or heat and an electric field, a position signal area that forms an irreversible fixed position signal whose optical properties do not change. An optical information recording tape characterized by having. (2) The optical information recording tape according to claim 1, wherein the fixed position signal is a bit or a hole. (3) The position signal area is formed from a continuous line of bits or holes, the position signal area is used as a tracking track, and the area sandwiched between the tracking tracks is used as a data writing area. Optical information recording tape. (4) The optical information recording tape according to claim 1, 2 or 3, wherein the fixed position signal is a wobbling bit shifted to the left or right from a line connecting the centers of recording bits.