JP2810379B2 - Information recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an information recording medium having a recording layer containing a polymer liquid crystal.

More specifically, the present invention relates to an information recording medium in the form of a disk, tape, or card format suitable for use in an optical recording and reproducing apparatus, wherein the recording layer of the recording medium contains a polymer liquid crystal.

[Conventional technology]

2. Description of the Related Art In recent years, rewritable recording media for applications such as large-capacity memories and displays have been actively developed. One of them is known which utilizes a phase transition of a liquid crystal.

For example, a pair of transparent electrodes or a liquid crystal phase that maintains its alignment aligned with a suitable substrate is optically transparent. Therefore, raise the temperature of this liquid crystal layer,
The liquid crystal layer does not return to the original transparent state but shows a light scattering state when the temperature is raised to a phase transition temperature (nematic phase → liquid phase or smectic phase → nematic phase) or higher, and the liquid crystal layer is rapidly cooled. That is,
Recording and reading are performed based on this contrast difference.

Further, after writing, by applying an electric field between the electrodes of the recording medium, or by heating or gradually cooling, the transition to the original smectic phase or the like is performed and the data can be erased.

In addition, heating can be performed while applying a voltage, or erasing can be performed by heating without applying a voltage. Recently, polymer liquid crystals having a glass transition point and excellent memory properties have been attracting attention.

Usually, a small and inexpensive semiconductor laser is often used to heat the polymer liquid crystal layer, but the oscillation wavelength of this laser is usually 650 nm or more, and generally, an argon laser, a helium-neon laser, etc. Laser light power is smaller than gas laser. Since ordinary liquid crystals do not have such absorption in the near infrared region, it is known that a soluble light absorbing dye is contained in the liquid crystal. (Japanese Unexamined Patent Publication No. 62-246
However, dyes having absorption in the near-infrared region are generally not sufficiently thermally stable in the liquid crystal, and have a problem in that, when writing and erasing are repeated, a part of the dye is decomposed and a sufficient contrast cannot be obtained.

It has been reported that phthalocyanine, which is a very stable pigment, is provided as a light absorbing layer or dispersed in polymer liquid crystal to absorb light. However, the provision of a light-absorbing layer and the dispersion of the pigment in the recording layer cause a decrease in efficiency when light is absorbed and converted into heat. When recording a fine pit, the S / N ratio is lowered or scattered by particles, which is not preferable.

As a solution to this problem, attempts have been made to solubilize stable pigments such as phthalocyanine, and solubilization has been reported in low-molecular liquid crystals, which may improve the durability of optical recording systems in low-molecular liquid crystals. It is shown. (See Japanese Patent Application Laid-Open No. 62-25191) In addition to this, although it is not a recording medium using liquid crystal or polymer liquid crystal, a method using a chemical bond between a polymer and a pigment has been reported as a method for solubilizing a stable pigment. I have. (Japanese Unexamined Patent Publication No. 61
However, other than the method of fixing the structure by using a polymer liquid crystalline compound as a recording layer in the rewritable information recording medium by light absorption described above and utilizing its phase transition, melting point or glass transition point. Are often chemically and physically unstable in their recording, playback, and erasure,
The recording layer itself tends to deteriorate. Further, the contrast in the recording state is low, and the detection / reproduction system tends to be complicated. In that respect, the information recording medium having a high-molecular liquid crystalline compound in the recording layer shows excellent stability and high contrast,
When light is used as recording energy, a high-molecular liquid crystalline compound itself does not absorb light in the visible to near-infrared range, so some light absorber is required. Moreover, in order to obtain a medium having good recording sensitivity, contrast ratio, S / N ratio, etc., it is necessary that the light absorbing agent is dissolved in a large amount as much as possible in a liquid crystalline polymer compound as much as possible. .

A dye mixed with a conventional polymer liquid crystal has low solubility in a polymer liquid crystal compound or, even if dissolved, significantly lowers the melting point or glass transition point of a liquid crystal phase. In many cases, the liquid crystal phase itself is destabilized, the clearing point is lowered, and the liquid crystal phase itself is erased.

Because of these drawbacks, it has been difficult to achieve both high light absorption efficiency and a stable recording state by adding a light absorber.

[Object of the invention]

An object of the present invention is to be able to record a large optical density difference with excellent reversibility compared to other recording media, and by using its phase transition and melting point or glass transition point, it is essentially stable. In a recording medium containing a polymer liquid crystal capable of recording, sufficient and stable light absorption for optical recording is realized without lowering the melting point, glass transition point, and destabilizing the liquid crystal phase. Is to provide a means.

[Specific description of the invention]

It is generally known that a dye having a rod-like shape similar to a liquid crystal molecule has excellent solubility and does not hinder the liquid crystal phase. However, even with such a shape, even in the case where the solubility is high in the polymer liquid crystal, there is a disadvantage that the melting point and the glass transition point of the polymer liquid crystal are significantly reduced due to the low molecular weight of the dye. Was.

On the other hand, the inventors of the present invention say that a soluble organic macrocyclic dye having not less than a rod shape but a flat plate shape, particularly having 10 or more carbon atoms, more preferably 20 or more, is recorded, reproduced, and erased as a polymer liquid crystal composition. High extinction coefficient, good S / N ratio, low by not only having excellent durability against repetition of optical recording process, but also showing good solubility in polymer liquid crystal as a characteristic of its shape It is possible to obtain a bit error rate (BER), and because the dye has a two-dimensional spread, it does not impair the liquid crystallinity of the liquid crystal phase of the polymer liquid crystal, and has a clear point (Tcl), It has been found that the glass transition point (Tg) and the melting point (Tm) are significantly reduced, and the mobility does not increase to decrease the liquid crystal phase.

The organic macrocyclic dyes include azaannulene and annulene. Alkyl substituents are provided for solubility, but other substituents may be provided as long as solubility is not impaired.

More specifically, phthalocyanines, naphthalocyanines, tetrabenzoporphyrins and other substituted and unsubstituted polyfilins are used.

Particularly effective ones include phthalocyanine and naphthalocyanine represented by the following general formula (I).

(The middle code of the general formula (I) Indicated by

[However, R _{1 to} R _{20 represent a} hydrogen atom, a linear or branched alkyl group having 4 to 20 carbon atoms, an alkoxy group, an alkenyl group, or a substituent selected from the following.

-SiQ ₁ Q ₂ Q ₃ -SQ ₄ -COQ ₅ --COOQ ₆ -NQ ₇ Q ₈ (Q _{1 to} Q ₈ : a hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 20 carbon atoms. )] M represents Ge, Sn, a transition metal, Al, Ga, In, an alkaline earth metal, a lanthanide metal, an aphtin metal and an oxide, a halogen compound or an alkoxylated compound thereof. It is important to use a semiconductor laser having a wavelength from near-infrared to red-visible when performing optical recording, which is important for miniaturization and high performance of a recording / reproducing apparatus. Naphthalocyanines are particularly excellent as soluble organic macrocyclic dyes.

Particularly, those represented by the general formula (II) are suitable for the recording medium of the present invention because of their excellent solubility.

(In the general formula (II), M: Ge, Sn, transition metal, Al, Ga, In, alkaline earth metal, lanthanide metal or aftinide metal X: halogen group, alkyl group, carboxyl group, alkoxy group, ether group or alkenyl Xm ₁ to Xm ₄ : a halogen group, an alkyl group, a sulfaceyl group, an ether group or an alkenyl group; a to d: 0 to 4;

(However, a + b + c + d ≧ 1). These compounds can be easily synthesized by the method disclosed in JP-A-62-90291 and the like.

Examples of the polymer liquid crystal compound include the following main-chain polymer liquid crystal compounds, side-chain polymer liquid crystal compounds, main-chain side-chain polymer liquid crystal compounds, and discotic polymer liquid crystal compounds.

The main chain type liquid crystalline compound includes the following compounds.

(N1 ≧ 5, x = 1-20) The side chain type polymer liquid crystalline compound includes the following.

(N1 ≧ 5, x = 1-20) As the main chain-side chain type polymer liquid crystal, (n1 ≧ 5) The following are examples of discotic polymer liquid crystals.

The amount of the soluble organic macrocyclic dye added to the polymer liquid crystal is about 0.01 to 40% by weight, preferably about 0.1 to 40%.
It is 1 to 25%, most preferably 5 to 20%. The polymer liquid crystal composition of the present invention has at least one of a nematic phase, a chiral nematic phase, a smectic phase, a chiral smectic phase, and a discotic phase, and uses the liquid crystal phase.

In the present invention, the polymer liquid crystal can be used as a mixture with several different kinds of polymer liquid crystals. It is also possible to use a mixture of a high-molecular liquid crystal and a low-molecular liquid crystal.
Preferably it is 3 or less. The low-molecular liquid crystal is not particularly limited, and ordinary low-molecular liquid crystals can be used.

Furthermore, a ferroelectric polymer liquid crystal composition having a chiral asymmetric carbon can be used as the recording layer of the present invention, and it has been confirmed that the compound shown in the present invention has good compatibility with the organic macrocyclic dye. Was done.

If necessary, ordinary polymers (for example, olefin resin, acrylic resin, polystyrene resin, polyester resin, polyurethane resin, polycarbonate resin, etc.), oligomers, various antioxidants, etc.
Various plasticizers, various ultraviolet absorbers, quenchers and the like may be contained.

In addition, this organic macrocyclic dye and other near-infrared absorbing dyes and 2
Coloring dyes may be combined. Representative examples of near infrared absorbing dyes that can be suitably combined include cyanine, merocyanine, naphthoquinone, tetrahydrocholine, dioxazine, anthraquinone, triphenodithiazine, xanthene, triphenylmethane, pyrylium, croconium, azulene and triphenylamine. And a metal chelate compound.

These are used in a range that does not adversely affect the glass transition point and melting point of the polymer liquid crystal, usually in the range of 0.01 to 2%.

In addition, an ultraviolet absorber or an antioxidant low-molecular liquid crystal can be similarly added and used within a range that does not adversely affect the glass transition point and the melting point of the high-molecular liquid crystal.

Polymer liquid crystal thinning is performed by dissolving the polymer liquid crystal in a solvent, coating it on a substrate by spin coating, dipping, etc., and then drying it. The film may be used beforehand. Note that the thickness of the liquid crystal layer is preferably about 0.01 to 100 μm.

When using a liquid crystal phase-isotropic phase transition and recording / erasing by fixing each phase using a glass transition point,
It is not necessary to orient the recording layer containing the polymer liquid crystal compound, and it is possible to simply use the polymer liquid crystal composition of the present invention simply by applying it.

On the other hand, in order to uniformly align the polymer liquid crystal in a certain direction, a generally known alignment method can be used.

For example, the orientation method includes a stretching method, a rubbing method, an oblique evaporation method, a method of applying shear stress between two substrates, a method of slowly performing a phase transition while applying a magnetic field, and a method of aligning with a spacer ET. Etc. are available.

FIGS. 2 and 3 are cross-sectional views showing one embodiment of the information recording medium of the present invention. In FIG. 2, reference numeral 1 denotes a substrate, 2 denotes an alignment film, 3 denotes a recording layer of the present invention, and 4 denotes a reflection layer.

In FIG. 3, reference numerals 1, 2 and 3 are the same as those in FIG. Reference numeral 5 denotes a transparent electrode, and reference numeral 6 denotes an electrode / reflection layer.

FIG. 4 is a schematic view of an apparatus for writing and reading by irradiating a recording medium with a laser. In FIG.
For writing, a laser beam emitted from a semiconductor laser 8 as a laser oscillator is focused on an optical system 11 and is incident on a recording medium 10.

Reading is performed by irradiating a laser beam emitted from a semiconductor laser 8 which is a laser oscillator to a recording medium 10 through an optical system 11 and a beam splitter 7, and using the reflected light again through a beam splitter 7 with a light detecting device 9. Perform a read.

Example 1 The following polymer liquid crystal and a soluble naphthalocyanine (IRD2001 manufactured by Yamamoto Gosei Co., Ltd.) were dissolved and mixed in 1,2-dichloroethane, and then dried under reduced pressure to remove the solvent, thereby obtaining a polymer liquid crystal composition. I got something. FIG. 1 shows a phase diagram confirmed by DSC and a microscope.

The dye concentration is most preferably 5-20 wt% (further 20 wt%
The liquid crystal phase was stable and the glass transition point was stable in the range of 30 to 70 ° C.

Example 2 A polyamic acid solution (manufactured by Hitachi Chemical Co., Ltd., PIQ) was applied to a disk-shaped glass substrate having a diameter of 130 mm and a thickness of 1.2 mm, heated, and then subjected to a rubbing treatment to give a polyimide alignment film.

The following side-chain type polymer liquid crystal and soluble naphthalocyanine (IRD1001 manufactured by Yamamoto Gosei Co., Ltd.) are mixed with 1,1,2-trichloroethane, applied by a spinner method, dried, and dried to a thickness of 1 μm. A layer was formed. The addition amount of the metal chelate compound is 5.0 wt% with respect to the liquid crystal. This polymer liquid crystal composition had Tg = 35 ° C. and Tce = 75 ° C., Tcl did not change much, Tg was slightly reduced, and the liquid crystal temperature range was good.

Further, a substrate provided with a polyimide alignment film in the same manner as described above on a glass substrate having a reflective film (aluminum deposited film) formed on the polymer liquid crystal layer via a spacer (thickness of 1 μm) on the outer peripheral portion. I combined. FIG. 2 shows a part of the sectional configuration. The above-described laminate was heated to 90 ° C. and gradually cooled to bring the liquid crystal layer into a nematic layer state, thereby producing an information recording medium.

As shown in FIG. 4, when the recording medium was irradiated from the transparent substrate side at a recording power of 3.0 mW with a semiconductor laser 8 of 830 nm as shown in FIG. 4, the orientation of the irradiated part was disturbed, and the recording medium was scattered. Next, reproduction was performed at a readout light wavelength of 780 nm and a power of 0.3 mW, and the reproduction light was measured by the photodetector 9 to determine the contrast ratio. Was calculated.

Further, the substrate on which the recording was performed was heated to 90 ° C. and gradually cooled, and erasing was performed according to the orientation of the recording portion.

Further, recording and erasing were repeated, and at the time of repeating 300 times, reproduction was performed and the contrast ratio was measured.

Good durability was obtained with a contrast of 0.4 before the repeated test and a contrast of 0.39 after the test, and neither Tg nor Tcl was changed.

Comparative Example 1 An information recording medium was produced in the same manner as in Example 2 except that the following dyes were mixed in the polymer liquid crystal. The dye content is 5% by weight based on the polymer liquid crystal.

This composition did not show any liquid crystal phase.

Example 3 ITO having a diameter of 130 mm and a thickness of 1.2 m deposited with ITO as a transparent electrode layer
A polyamic acid solution (PIQ manufactured by Hitachi Chemical Co., Ltd.) was applied onto a glass substrate of m, heated, and rubbed to form a polyimide alignment film.

A ferroelectric polymer liquid crystal and a soluble phthalocyanine (PC-494, manufactured by Nippon Shokubai) shown below are dissolved in 1,1,2-trichloroethane, applied by a spinner method, and dried to form a liquid crystal layer having a thickness of 3 μm. Formed.

In the same manner as in Example 2, a substrate provided with a polyimide alignment film by a method similar to that described above was superposed on a glass substrate on which an electrode layer and a reflective layer (aluminum-deposited film) had been formed via a spacer. FIG. 3 shows a part of the cross-sectional configuration.

The above-mentioned laminated body is heated to 90 ° C., and then gradually cooled, so that the liquid crystal layer is in a smectic phase state in which the liquid crystal layer is uniaxially oriented, and a voltage is applied between the electrodes to align the polarization direction in a certain direction, thereby producing an information recording medium. did. Applying a reverse electric field between the transparent electrode (ITO) and the AI electrode in this recording medium,
The recording part was heated by irradiating the recording part from the transparent electrode side with a recording power of 3.0 mW with a 30 nm semiconductor laser, and writing was performed by reversing the direction of spontaneous polarization.

Then, without applying an electric field, a laser beam is irradiated through a polarizer with a reproduction output of 0.3 mW, and the reflected light contains a difference in birefringence due to a difference in polarization direction. The light intensity was measured and the contrast ratio was calculated.

While applying a forward electric field again between the ITO-Al electrodes,
Irradiation was performed with a laser power of 3.5 mW to erase the recorded part or the entire surface. The contrast ratio was 0.4.

Comparative Example 2 An information recording medium was produced in exactly the same manner as in Example 3, except that the dye used in Comparative Example 1 was used as the organic dye.

Similarly, an electric field was applied, but no contrast was obtained.

〔The invention's effect〕

According to the information recording medium of the present invention configured as described above, in a recording / reproducing / erasing process using light absorption-heat conversion by a compound made of a polymer liquid crystal and a light absorber, high sensitivity and good S / N, the bit error rate (BER)
In addition to excellent repetition durability, a stable liquid crystal phase is exhibited, so that an excellent effect that storage stability of recording is also good can be obtained.

[Brief description of the drawings]

FIG. 1 shows a phase diagram of the polymer liquid crystal composition of the present invention. Second
FIG. 3 and FIG. 3 are cross-sectional views of the information recording medium of the present invention, and FIG. 4 is a schematic view of an optical system for recording / reproducing / erasing. DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Alignment film 3 ... Recording layer 4 ... Reflective layer 5 ... Transparent electrode 6 ... Electrode / reflective layer 7 ... Beam splitter 8 ... Semiconductor laser 9 ... Light Detector 10: Recording medium, 11: Optical system 12: Reflector, 13: Polarizer

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tsuyoshi Mitou 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (56) References JP-A-59-10930 (JP, A) JP-A Sho 61-215662 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B41M 5/26

Claims (1)

(57) [Claims] A recording layer having a liquid crystal phase in which a plate-shaped soluble organic macrocyclic dye represented by the following general formula (I) is added to a high-molecular liquid crystalline compound at a concentration of 5 to 20% by weight. Information recording medium having. (In the general formula (I), A, B, C, and D are Indicated by [However, R _{1 to} R _{20 represent a} hydrogen atom, a linear or branched alkyl group having 4 to 20 carbon atoms, an alkoxy group, an alkenyl group, or a substituent selected from the following. −SiQ ₁
Q ₂ Q ₃ , -SQ ₄ , -COQ _5- , -COOQ ₆ , -NQ ₇ Q ₈ (Q _{1 to} Q ₈ :
A hydrogen atom, a linear or branched alkyl or alkenyl group having 1 to 20 carbon atoms)] M is Ge, Sn, a transition element, Al, Ga, In, an alkaline earth metal, a lanthanide metal, an aphtinide metal and oxidation thereof. , Halides and alkoxylates. )