JPH01221285A - Optical data recording tape and production thereof - Google Patents

Abstract

PURPOSE:To contrive a higher contrast between recorded parts and non-recorded parts at the time of reading, by a construction wherein a protective layer provided on one or both sides of a recording layer using a high molecular weight liquid crystal having a glass transition point comprises a horizontal orientation film of the liquid crystal and/or a polarizing film. CONSTITUTION:A protective layer 2 serves also as a horizontal orientation film of a high molecular weight liquid crystal 5 used in a recording layer 1 and/or as a polarizing film. Where the protective layer 2 serves also as the horizontal orientation layer, for example, an organic insulating film of polyvinyl alcohol, a polyimide or the like is provided on the recording layer, or both layers are laminated and subjected to stretching. Where the protective layer 2 is used as a polarizing plate, for example, a polyvinyl alcohol with polyiodine adsorbed thereon or a polyvinyl alcohol or polyethylene phthalate dyed with a dichromatic dye is uniaxially stretched, and a material thus obtained is used. The liquid crystal 5 is once heated into an isotropic state by writing light, is then fixed by rapid cooling to or below the glass transition point thereof, whereby it is set into a nonoriented state to show an increase in transmittance or reflectance. When the liquid crystal is gradually cooled from the isotropic state into the liquid crystal state by erasing light, it is returned into an initial oriented state.

Description

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

[Prior Art] Magnetic recording tapes have conventionally been known as information recording tapes, but these magnetic recording tapes have limitations in information recording density and improvements in 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. (Japanese Unexamined Patent Publication No. 57-33447, #Open/Close No. 58-94145) The recording medium forming the recording layer used here is T
A metal film of e-As-3e or a mixture of carbon and nitrocellulose coated on a plastic base is used. However, in the systems using these recording media, recording is irreversible and cannot be rewritten.

On the other hand, as a rewritable optical recording medium, a phase transition method using a reversible vicious phase transition between amorphous and crystalline chalcogenide thin films, and a method using a structural change within the amorphous phase temperature region are known.

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. However, until now, there are no known examples of applying polymeric liquid crystal materials to optical information recording tapes.

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

Furthermore, those that utilize the phase transition phenomenon of a chalcogenide thin film 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,
Light scattering state (liquid crystal state) and transparent state of polymer liquid crystal? ! i(
When trying to measure the difference in isotropic S) as contrast, there is a problem that high contrast cannot be measured if the film thickness is thin, and optical information recording tape using polymer liquid crystal has not been put into practical use. .

The present invention was made to solve these conventional problems, and it is rewritable, has high repeat durability, has excellent storage stability of recorded information, does not suffer from playback deterioration, and has a high contrast ratio. An object of the present invention is to provide an optical information recording tape with high performance and a method for manufacturing the same.

[Means for Solving the Problems] That is, the first aspect of the present invention is a recording layer formed using a polymer liquid crystal having a glass transition point, which has a protective layer on at least one surface thereof, and The present invention relates to an optical information recording tape characterized in that the protective layer is composed of a horizontal alignment film or a polarizing film of the polymer liquid crystal.

Further, a second invention provides an optical information recording tape characterized in that a protective layer is adhered to at least one surface of a recording layer formed using a polymeric liquid crystal having a glass transition point, and then co-stretched. This relates to the manufacturing 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 as a recording layer, and has a protective layer on either the upper and lower surfaces of the recording layer, and the protective layer is made of the polymeric liquid crystal. It consists of a liquid crystal horizontal alignment film and/or a polarizing film.

1 and 2 show the basic configuration of the optical information recording tape of the present invention, and FIG. 1 shows a partial configuration diagram of the optical information recording tape of the type in which reading is performed by changing the light transmittance. In the transmission type shown in Fig. 1, basically it is sufficient to have a recording layer 1 and a protective layer 2, and it is desirable to provide the protective layer 2 on both sides of the recording layer 1, but it is preferable to provide the protective layer 2 on only one side. This protective layer may also serve as a flexible substrate, but if necessary, the recording layer and protective layer may be placed on a separate flexible substrate with the structure shown in Figure 1. All you have to do is laminate them.

FIG. 2 shows a partial configuration diagram of an optical information recording tape of a type in which reading is performed by changing the light reflectance. In FIG. 2, a protective layer 2 is provided on both sides of the recording layer l, and the protective layer 2 is
A light reflecting layer 3 and a flexible substrate 4 are sequentially laminated on one surface of the substrate. Although it is more desirable that the protective layer 2 be provided on both sides of the recording layer 1, it may be provided on only one surface of the recording layer 1, and the flexible substrate 4 does not necessarily need to be provided.

The polymer liquid crystal that can be used to form the recording layer may be any polymer liquid crystal having a glass transition point, and specific examples thereof include the following.

However, the ratio in the formula indicates an asymmetric carbon center, and n = 5 to 10
It is 00.

(■, =2~l mouth) (so-called, =2~!0) (s, x2~Is) (m, x2~15) (7)H (layer snow!2++IIJ (8)cns ■ -+ cut- c→- CI! -+ CH, -C→- Proverb (Death=2~15) (■2=2~15) (]2) (x+y =l, q=1~10. Pt=1~I! i
) CI.

CI3 (x+y=1.*,=2~15) CH3 R3=-CFl, CI-(-CH2→-R4=-+el
+, →-(x+y=1,52=2~15) (X+y=1.■2=2~15) (Recommended=1~5) (x+y=1) (Layer,=0~5) B" Record The thickness of the layer is usually 1 to 20p1, preferably 2 to 1O
ILm is preferred.

Next, the protective layer used in the present invention is one that functions both as a protective film and as a horizontal alignment film and/or polarizing film for the polymeric liquid crystal used in forming the recording layer. In the case of a layer that also serves as a horizontal alignment layer as an alignment control layer for polymeric liquid crystal forming a recording layer, polyvinyl alcohol is used, for example.

Polyimide, polyamideimide, polyesterimide,
polyvaraxylene, polyester, polycarbonate,
Organic insulating films such as polyvinyl acetal, polyvinyl chloride, polyvinyl acetate, polyamide, polystyrene, cellulose resin, melamine resin, urea resin, and acrylic resin can be used. By forming such an organic insulating film on the recording layer, or by stretching the two layers after bonding them together, the horizontal alignment of the polymer liquid crystal can be improved.

In addition to the above-mentioned organic insulating film, a polymer liquid crystal having a glass transition point Tg higher than the isotropic phase transition temperature of the polymer liquid crystal used in the recording layer may be used as the protective layer.

In addition, when the protective layer is used as a polarizing plate, for example, after adsorbing an iodine polymer to polyvinyl alcohol and then axially stretching it, or after dyeing a dichroic dye to polyvinyl alcohol or polyethylene terephthalate, it can be axially stretched. A stretched version can be used.

The thickness of the protective layer is usually 300 to 10 ILm, preferably 500 to 1Lm.

Next, the method for manufacturing the optical information recording tape of the present invention includes forming a protective layer in close contact with at least one surface of the recording layer formed using the polymeric liquid crystal having the glass transition point. It can be easily obtained by co-stretching. Co-stretching is usually 50% or more, preferably 100-50%
It is desirable to stretch within a range of 0%.

In order to obtain a light-reflecting optical information recording tape as shown in FIG. 2, after forming a recording layer and a protective layer, a light-reflecting layer is provided by vapor deposition or the like. If a flexible substrate is required, a light reflective film may be provided on the substrate by vapor deposition, etc., and then a protective layer, a recording layer, and a protective layer may be laminated in this order. However, in this case, there are two layers. It is sufficient to have one protective layer, but it is more preferable to have two layers.As a light reflecting layer,
Affll! etc. can be used.

Further, as the flexible substrate, polyimide, polyethylene terephthalate, polycarbonate, etc. can be used.

Next, FIGS. 3(A) to 3(E) are explanatory diagrams showing the initial molecular orientation of a recording layer using a polymeric liquid crystal and changes in the molecular orientation state during recording and after recording and erasing.

During recording, the polymer liquid crystal 5 in the initial alignment state shown in FIG. is fixed, resulting in a non-oriented state and a high transmittance or reflectance. (See Figure 3 (B)) By irradiating this recorded area with erasing light that is intensity-modulated on the writing light, the recording layer is gradually cooled from the isostatic state to the liquid crystal state, resulting in the same state as the initial orientation. . (Figure 3 (
(See C) Erasing does not necessarily have to be by light, but can also be accomplished by heating the portion of the roller through which the tape passes. The writing profile and the extinction profile are shown in FIGS. 3(D) and 3(E), respectively.

Further, an appropriate amount of writing light absorbing dye may be added to the polymeric liquid crystal so that the recording layer can be heated efficiently.

[Function] The optical information recording tape of the present invention has a protective layer on at least one surface of a recording layer formed using a polymeric liquid crystal having a glass transition point, and the protective layer is made of a polymeric liquid crystal having a glass transition point. Since it consists of a horizontal alignment film and/or a polarizing film, the W! Since the layer serves as a horizontal alignment film of polymeric liquid crystal, a polarizing film, or both, it is possible to increase the contrast between the recorded area and the non-recorded area during reading.

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

Example 1 Using a polymeric liquid crystal represented by the following structural formula 30, a film (2) having a thickness of aIL- was obtained by melt extrusion.

Further, a polymeric liquid crystal represented by the following structural formula 31 was similarly molded into a film-like film with a thickness of 6 mm by the melt extrusion method.

Sandwich the film ■ between two sheets of film ■, and add 1:1O
It was sandwiched and crimped between heated rollers set at 'C. This pressed film was passed through heating rollers with different surface speeds at 110° C., stretched to 300%, and then allowed to cool to room temperature in air to obtain a horizontally oriented film. The thickness of this film was 4 mm. Further, the film of the recording layer contains a dye having the structural formula (33) described later at a ratio of 0.5 wt % to the polymer liquid crystal.

Writing was performed on the optical recording tape thus formed using a 10W semiconductor laser (lIL@φ, 100nsec pulse), and a reading light (830nm, 0.5nsec pulse) was used.
The transmittance (W, 14 sec width, 300 Hz) was determined using an optical system that measures through two orthogonal polarizing plates.
Reproduction deterioration was investigated by comparing the S/N ratio immediately after recording and after 1 hour of irradiation. As a result, the S/N ratio was 40 dB in all cases, and it was confirmed that there was no reproduction deterioration. Furthermore, when the writing light was modulated to a pulse width of 500 nsec and irradiated onto the recorded area, it was confirmed that this area was erased, and it was confirmed that rewriting was possible.

Structural formula (30) Structural formula (31) glass ---B N ---P 150° Example 2 A polymeric liquid crystal represented by structural formula 32 was placed on a polyethylene terephthalate film with a thickness of 5 ml, and a polymeric liquid crystal was placed on this polymeric liquid crystal. Against 0. : A dichloroethane solution containing 1 wt % of the dye represented by structural formula 33 (dichloroethane weight percentage of polymer liquid crystal: 10 wt %) was coated to a full thickness with a bar coater. Thereafter, it was dried at 90° C. for 1 hour to remove the solvent and obtain a film ①. Separately, a thin film of polymer liquid crystal represented by structural formula 34 (thickness 4ILs: film ■)
was prepared, and films (1) and (2) were pressed together through a pressure roller set at a temperature of 150°C, and then uniaxially stretched to 300% at this temperature to produce an optical recording tape.

Writing was performed on the film thus produced using a laser with the same power as used in Example 1, and the light transmittance was 70% in the written area and 40% in the non-recorded area, indicating a high contrast ratio recording. Obtained. Furthermore, when the recorded tape was passed between two rollers set at 80° C., the light transmittance returned to its initial value. Even after repeated rewriting durability up to 100 times, the transmittance did not change.

Structural formula (32) Structural formula (33) Structural formula (34) Dichroic dye (Structural formula 35. entered ■ax, 640n■) Structural formula (
35) The colored film was stretched along the l-axis to obtain an oriented film with a final thickness of 20 mm. A 5 wt % solution of the same polymeric liquid crystal in dichloroethane as used for the recording layer in Example 1 was applied to this using a wire bar, and dried at 90° C. for 1 hour to remove the solvent to obtain a recording layer. The thickness of this liquid crystal phase was about 4 JLm. Separately, a polymer liquid crystal film (thickness: 5 haze) represented by the structural formula 34 was prepared, and the two films were placed in a pressure roller set at 150°C with the recording layer facing inside. After crimping, it is further heated at this temperature for 200 min.
% to obtain an optical recording tape.

A 1ie-Ne laser (λ=533
Writing was performed by inputting a laser beam (10 mw, 100 ns pulse) so that the plane of polarization of the laser coincided with the stretching direction (longitudinal direction of the tape). When reading was performed from the same direction as writing with the plane of polarization perpendicular to the writing light, the transmittance of the recorded and non-recorded areas was 35% and 5%, respectively, and a high contrast ratio was obtained. The reproduction deterioration in this state was the same as in Example 1, and the storage stability of the recording portion was also good.

[Effects of the Invention] According to the present invention, it is possible to produce a highly oriented optical recording tape with a simple manufacturing method, and a rewritable high contrast optical information recording tape with excellent environmental stability has been put into practical use. I'll come.

[Brief explanation of the drawing]

Fig. 1 is a partial configuration diagram of an optical information recording tape according to the present invention that performs reading by changing light transmittance, Figure 2 is a partial configuration diagram of a type of optical information recording tape that performs reading by changing light reflectance, and Figure 3 (A) to (E) are explanatory diagrams showing the initial molecular orientation of a recording layer using a polymer liquid crystal and changes in the molecular orientation state during recording and after recording and erasing. l...Recording layer 2...Protective layer 3...Light reflective layer 4...Flexible substrate 5...Polymer liquid crystal

Claims (3)

[Claims] (1) A recording layer formed using a polymeric liquid crystal having a glass transition point has a protective layer on at least one surface, and the protective layer is formed from a horizontal alignment film and/or a polarizing film of the polymeric liquid crystal. An optical information recording tape characterized by: (2) The optical information recording tape according to claim 1, wherein the protective layer is formed of a polymeric liquid crystal having a glass transition temperature higher than the isotropic phase transition temperature of the polymeric liquid crystal forming the recording layer. (3) A method for producing an optical information recording tape, which comprises adhering a protective layer to at least one surface of a recording layer formed using a polymeric liquid crystal having a glass transition point, and then co-stretching the recording layer.