JP2804322B2 - recoding media - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a recording medium capable of reversibly recording and erasing information.

[Prior Art] In recent years, with the spread of OA and the like, the amount of various types of information data has been steadily increasing. For this reason, optical disk recording devices are being actively developed as means for storing such information data at high density. However, in order to organize and edit information or to access a computer, it is indispensable that information can be recorded and erased reversibly as a recording material. Development using a semiconductor or a thermoplastic resin as a recording material is in progress. However, the former has the disadvantage that the cost is high because of the toxicity or the steps of vapor deposition, and the latter has a short lifespan of the recording material or the contrast because the dye is used as a light absorbing agent. However, there is a problem that the S / N ratio is low and a sufficient SN ratio cannot be obtained. As a solution to the above-mentioned drawbacks and problems, Japanese Patent Application Laid-Open No. 58-125247 discloses that the transparent alignment state and opaque random state of a polymer liquid crystal are reversibly changed by heat or heat and an electric field. A recording material is disclosed. Here, heat can be generated by irradiating the light absorber with laser light, that is, laser light can be used as writing means. Such an example is also disclosed in JP-A-60-114823, in which polysiloxane is used as a liquid crystal polymer.

In a recording medium using such a polymer liquid crystal, it is necessary to preferentially orient the liquid crystal in one direction for the purpose of improving the contrast. Many studies have been made on the fact that the orientation treatment has a great effect on the characteristics of these recording media.

Conventional methods for aligning polymer liquid crystals include oblique deposition of inorganic oxides, rubbing of organic polymer coatings, application of a constant direction, pressure shear stress, and use of electric and magnetic fields. Are known, but none are satisfactory.

[Problems to be Solved by the Invention] An object of the present invention is to provide a recording medium that can improve the orientation of a polymer liquid crystal and obtain good recording and erasing characteristics by using a specific orientation layer. .

[Means for Solving the Problems] The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that it is effective to use a liquid crystal silane coupling agent as the alignment layer, and have reached the present invention. Was.

That is, the present invention provides a recording medium having a polymer liquid crystal layer on a substrate and an alignment layer for aligning the polymer liquid crystal, wherein a liquid crystalline silane coupling agent is used as a component for forming the alignment layer. It is a recording medium characterized by the following.

 Hereinafter, the present invention will be described with reference to the drawings.

First, the present invention will be described with reference to the drawings, in which the present invention utilizes a control force from an alignment layer.

FIG. 1 is a cross-sectional view of a recording medium of the present invention, wherein 1 is a substrate, 7 is a liquid crystalline silane coupling agent, and 9 is a liquid crystal polymer layer. FIG. 2 is a sectional view showing another embodiment of the present invention, and 5 is an inorganic oxide film or an organic polymer film.

A uniform orientation state can be obtained by annealing the recording medium manufactured as described above at the liquid crystal temperature. When writing information on this recording medium, irradiation is performed by locally irradiating high-density energy light such as laser light, for example, by heating through a phase transition temperature or a transparent point, and then cooling by cooling. Variations in light scattering, optical activity, birefringence, or absorption occur in the portion, and a recording point is formed. In this state, information can be read. The entered information can be erased again by heating locally or completely.

FIG. 2 illustrates a case where the present invention is used in combination with the control force from the alignment layer and the electric field.

In FIG. 3, reference numerals 1 and 2 denote substrates, reference numerals 3 and 4 denote electrodes, reference numerals 7 and 8 denote liquid crystal silane coupling agents, and reference numeral 9 denotes a polymer liquid crystal layer.
In FIG. 4, reference numerals 5 and 6 denote an inorganic oxide film or an organic polymer film.

For simplicity, a polymer liquid crystal having a positive dielectric anisotropy will be described. By heating the recording medium thus prepared to an isotropic liquid and then cooling it while applying a voltage, a vertical alignment state can be obtained. When information is written on this recording medium, recording can be performed in the same manner as in the first case. The written information can be erased again by heating locally or entirely and then cooling while applying a voltage.

Examples of the substrate used for the recording medium of the present invention include synthetic resin films such as glass and polyester. Further, a reflective layer made of Al, Cr, Ni, Ag or the like may be provided between the substrate and the recording layer for the purpose of improving the S / N ratio at the time of reproducing information and improving the sensitivity at the time of recording. Further, in FIGS. 3 and 4, the electrode 3 may also serve as these reflection layers.

For the electrode provided on this substrate, for example, known indium tin oxide (ITO) can be used.

The organic polymer film or the inorganic oxide film material used for the recording medium of the present invention includes polyimide, polyvinyl alcohol (PVA), polyamide, polyvinylidene fluoride (PVD).
Organic polymer materials such as F), silane coupling agents, oxides such as SiO, and the like can be mentioned, and these can be formed by vapor deposition or the like. In the embodiment shown in FIG. 1 and FIG. 2, if necessary, an epoxy resin,
A protective layer made of silicon resin, acrylic resin, urethane resin or the like may be provided on the recording layer.

The silane coupling agent used as a component for forming the alignment layer in the present invention is, for example, a silane coupling agent having liquid crystallinity represented by the following general formulas (I) and (II).

_{(R 1 O) 3 Si-} CH 2 CH 2 R 2 M (II) ( wherein, R ₁ represents a lower alkyl group, n an integer of 1 to 6, R ₂ is a spacer group, M represents a mesogen group. ) R ₂ represents a group forming a so-called spacer, i.e. a constant distance.

Examples of suitable groups R ₂ (spacer group), for example _{-CH 2 -, CH 2 2,} CH 2 3, CH 2 4, CH 2
_{5, CH 2 6, CH 2} 7, CH 2 8, CH 2 9,
CH _{2 10} , CH _{2 11} , -CH ₂ -OCH _{2 3} , -CH ₂ -O
_{CH 2 4, -CH 2 -OCH 2} 6, CH 2 3 OCH
_{2 3, CH 2 3 OCH 2} 4, CH 2 3 OCH 2 6, -C
_{H 2 NHCH 2 2, -CH 2} -N (CH 3) CH 2 2, CH 2 3
NHCH _{2 2} or And so on.

Examples of suitable groups M are Wherein R ³ is a C ₁ -C ₁₂ -alkyl group, a C ₁ -C ₁₂ alkoxy group, a C ₁
-C ₁₂ -alkoxycarbonyl group, C ₁ -C ₁₂ alkanoyloxy group, hydrogen, fluorine atom, chlorine atom, cyano group, 4-
It represents a cyanophenyl group or a nitro group, and R ⁴ is C ₁ -C ₁₂ - alkyl group.

These liquid crystalline silane coupling agents can be obtained according to the following reaction formula.

First, the general formula (I) is obtained by heating and reacting an isocyanatoalkyl trialkoxysilane (III) and an alcohol compound (IV) in a solvent such as toluene or tetrahydrofuran.

The general formula (II) can be obtained from a trialkoxysilane (V) and an ethylene compound (VI) by a known hydrosilation reaction. The reaction is carried out in a suitable organic solvent, for example, in a solvent such as benzene, toluene, tetrahydrofuran or the like at room temperature to 20 ° C.
The reaction is carried out in a temperature range of about 0 ° C. in the presence of a known hydrosylation catalyst, for example, a chloroplatinic acid catalyst, for 10 minutes to 100 hours. The concentration of the catalyst used is from 0.001 to
It is used in an amount in the range of 1%.

_{(R 1 O) 3 SiH (} V) + CH 2 = CH-R 2 -M (VI) → (R 1 O) 3 Si-CH 2 CH 2 -R 2 -M (II) liquid silane coupling below Specific examples of the agent will be given. In the following, * indicates an asymmetric carbon atom.

It is not clear why the alignment film made of the liquid crystalline silane coupling agent shows good alignment, but it is thought to be due to the interaction between the mesogen group in the silane coupling agent and the liquid crystal material.

In another aspect of the present invention, good alignment is obtained by sequentially laminating an organic polymer film, which is an inorganic oxide film, and a thin film made of a liquid crystalline silane coupling agent as an alignment layer. At this time, the inorganic oxide film or the organic polymer film has been treated by oblique deposition or lapping, and has an effect of aligning the mesogen group of the liquid crystalline silane coupling agent laminated thereon. Therefore, the liquid crystal can be oriented by the mesogenic group of the oriented liquid crystalline silane coupling agent.

To form these liquid crystal silane coupling agent layers on a substrate, an inorganic oxide film or an organic polymer film, these liquid crystal silane coupling agents are dissolved in a solvent such as 1,2-dichloroethane, toluene, and tetrahydrofuran. And
Spin coating, dipping, plate coating, roll coating or screen printing, flexographic printing, etc., are applied on a substrate, inorganic oxide film, or organic polymer film, heated to 80 to 120 ° C, and then unreacted liquid crystal It is obtained by washing and drying the hydrophilic silane coupling agent with the above-mentioned solvent.

As the polymer liquid crystal used in the present invention, a known liquid crystal can be used, which has a mesogen group in a main chain or a side chain, and has an average molecular weight of 500 or more.

Further, the polymer liquid crystal may be cross-linked. Further, the crosslinking is more preferably a photocrosslinking.

Specific examples of the polymer liquid crystal to be used are described below. In the following, * indicates an asymmetric carbon atom.

Such high-molecular liquid crystals are usually used singly or as a mixture, and other low-molecular liquid crystals can be added and used. This low-molecular liquid crystal is intended to improve the recording characteristics and erasing characteristics by controlling the viscosity, phase transition temperature and the like of the high-molecular liquid crystal, and known low-molecular liquid crystals of nematic, smectic or costeric liquid crystals can be used.

Using such a polymer liquid crystal, for example, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, butyl acetate, ethyl acetate, carbitol acetate, ester systems such as butyl carbitol acetate, methyl cellosorb, ethyl cellosolve, tetrahydrofuran, etc. Dissolved in a solution such as an ether system, an aromatic system such as toluene or xylene, an alkyl system such as dichloroethane, N, N-dimethylformamide, or an alcohol system, for example, by spin coating or dip coating. Can be created.

It is also possible to directly fill a recording medium having a cell type structure as shown in FIGS. 3 and 4.

In some cases, the temperature is raised once and then gradually cooled to form a phase. At that time, an electric field or a magnetic field is applied as needed.

 Note that the thickness of the liquid crystal layer is about 0.01 to 100 μm.

Further, the polymer liquid crystal layer may contain one or more light absorbing substances.

The light-absorbing substance is used when controlled by light such as a laser, and in some cases, a polychromatic dye is also used. The light absorption of these light absorbing materials should be adapted to the wavelength of the laser used. When the recording and reading processes are to be performed using various laser wavelengths, it is preferable to use a mixture of light-absorbing substances exhibiting high absorption in the wavelength range of the laser used.

The light absorbing substance may be provided as a separate layer on the substrate. In that case, the light absorbing substance layer is formed by dissolving or dispersing the light absorbing substance in an epoxy resin, a silicone resin, an acrylic resin, a urethane resin, or the like, and applying or vapor depositing the light absorbing substance.

Known light-absorbing substances can be used, and specific examples thereof include the following.

Azo dyes, for example Perylene derivatives Anthraquinone dyes, for example Azulene dyes Phthalocyanine Naphthalocyanine Or a metal complex such as It is.

These light-absorbing substances are used by dissolving or dispersing in a polymer liquid crystal, and the polymer liquid crystal further contains an appropriate molecularly dispersed additive such as a UV stabilizer, an antioxidant, or a softener. be able to.

[Examples] Hereinafter, the present invention will be described with reference to examples, but the present invention is not limited to these examples.

Production Example 1 Production of liquid crystalline silane coupling agent represented by general formula (I) [In the general formula (I), R ₁ = −C ₂ H ₅ , n = 3, R ₂ = CH
_{2 6,} Compound No. S-11], 4- (6-hydroxyhexyloxy) benzoic acid-4'-hexyloxyphenyl ester 2.07 g (0.005 mol) and 3-isocyanatopropyltriethoxysilane 1.48 g (0.006 mol) Was dissolved in 100 ml of toluene and reacted under reflux for 20 hours. After the reaction, toluene was distilled off, and the obtained crude product was recrystallized from hexane to obtain 2.24 g of the desired product.

Clearing point: 62.0 ° C Elemental analysis Observed value Calculated value C (%) 63.41 63.51 H (%) 8.46 8.38 N (%) 2.10 2.12 The structure of this product was confirmed by an infrared absorption spectrum. The infrared absorption spectrum is shown in FIG.

Production Example 2 Production of liquid crystalline silane coupling agent represented by general formula (II) [In the general formula (I), R ₁ = —C ₂ H ₅ , R ₂ = —CH ₂ —, Compound No. S-17] 4- (2-propeneoxy) -4'-cyano-biphenyl 4.71 g (0.02 mol), triethoxysilane 4.93 g (0.
03 mol) and 5 mg of hexachloroplatinic acid hexahydrate were reacted in toluene for 12 hours under reflux. After the reaction, toluene and triethoxysilane were distilled off to obtain 8.0 g of an oily target product.

Elemental analysis Actual value Calculated value C (%) 65.93 66.13 H (%) 7.60 7.32 N (%) 3.42 3.51 The structure of this product was confirmed by an infrared absorption spectrum.

Example 1 Substrate: Cr-deposited glass plate (glass plate thickness 1.2 mm, Cr layer thickness 1
000 °) Orientation layer: After forming a film with a thickness of 1000 ° by dipping using polyvinyl alcohol, rubbing treatment was performed 5 times at a pressure of 100 g / cm ² .

Alignment film: The liquid crystalline silane coupling agent of Preparation Example 1 was adjusted to 1 wt% with toluene, formed into a film by dipping, heated at 100 ° C. for 30 minutes, washed with toluene, and heated at 100 ° C. Dry for 1 hour.

Polymer liquid crystal: Dissolve Lc33 in tetrahydrofuran (10wt
%) A film having a thickness of 2 μm was formed by spin coating.

A recording medium was prepared from the above materials as shown in FIG.
This recording medium was annealed at 150 ° C. to obtain a recording medium having very good orientation. Recording was performed on this recording medium with a semiconductor laser (780 nm) at 8 mW and 1 μs.
The contrast ratio between the recorded area and the non-recorded area was 10: 1 when measured with a weak light (0.1 mW) of a semiconductor laser (780 nm). Furthermore, when this recording medium was annealed at 150 ° C., the recording was erased, and the recording medium returned to the original orientation state and repeated recording was possible.

Example 2 Substrate: (the above substrate) ITO vapor-deposited glass plate (glass plate 1.2 mm,
ITO layer thickness 1000 mm) (Lower substrate) Cr-deposited glass plate (glass plate 1.2 mm, C
r layer, thickness 1000 mm) Alignment film: The liquid crystalline silane coupling agent of Production Example 2 was adjusted to 1 wt% with toluene, formed into a film on the upper substrate by dipping, and heated at 100 ° C. for 30 minutes. The surface was washed with toluene and dried at 100 ° C. for 1 hour.

Polymer liquid crystal: Dissolve Lc30 in tetrahydrofuran (10wt
%) A film having a thickness of 2 μm was formed by spin coating.

A recording medium was prepared from the above materials as shown in FIG.
This recording medium was annealed at 140 ° C. to obtain a recording medium having very good orientation. Recording was performed on this recording medium with a semiconductor laser (780 nm) at 5 mW and 1 μs.
The contrast ratio between the recorded area and the non-recorded area was 8: 1 when measured with a weak light (0.1 mW) of a semiconductor laser (780 nm). Further, when an electric field of 1 kHz and 25 kV / cm was applied between the Cr layer and the ITO layer in the same manner as the laser beam irradiation at the time of recording, the recording medium returned to the original alignment state and could be erased.

Comparative Example 1 A recording medium was prepared in the same manner as in Example 1 except that only the polyvinyl alcohol was used as the alignment layer and the silane coupling agent was not used, the recording medium was processed under the same conditions, and recording was performed. 5: 1 contrast ratio of non-recorded area
Met.

Comparative Example 2 Except that a known vertical alignment agent octadecyldimethyl [3- (trimethoxysilyl) propyl] ammonium chloride (AY43-021 manufactured by Toray Silicone Co., Ltd.) was used instead of the liquid crystalline silane coupling agent as the alignment film. Prepared a recording medium in the same manner as in Example 2, processed the recording medium under the same conditions, and performed recording. As a result, the contrast ratio between the recorded part and the non-recorded part was 3: 1.

Further, this recording medium could not be erased under the same conditions as in Example 2.

[Effects of the Invention] As described above, by using a liquid crystalline silane coupling agent as a component for forming an alignment layer, the alignment of a polymer liquid crystal is improved, and very good recording and erasing characteristics are obtained. be able to.

[Brief description of the drawings]

1 to 4 are cross-sectional views of a polymer liquid crystal device showing an example of the present invention, and FIG. 5 is an infrared absorption spectrum diagram of the liquid crystalline silane coupling agent obtained in Production Example 1. In the figure, 1, 2 are substrates, 3, 4 are electrodes, 5, 6, 7, and 8 are alignment layers, and 9 is a polymer liquid crystal layer.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-167389 (JP, A) JP-A-63-259623 (JP, A) JP-A-62-194229 (JP, A) JP-A-62-194229 299814 (JP, A) JP-A-60-114823 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G02F 1/1337-1/1337 530

Claims (2)

(57) [Claims] 1. A recording medium comprising a substrate and a polymer liquid crystal layer and an alignment layer for aligning the polymer liquid crystal, wherein a liquid crystal silane coupling agent is used as a component for forming the alignment layer. Recording medium. 2. A recording medium according to claim 1, wherein said liquid crystalline silane coupling agent is formed as an alignment layer on an inorganic / oxide film or an organic polymer film.