JPH05241151A - Method for orienting liquid crystal and liquid crystal optical element - Google Patents

Abstract

(57) [Summary] [Structure] A dichroic molecule having at least one double bond selected from C = C, C = N, and N = N as a light-absorbing portion is chemically formed on at least one substrate surface. By providing a liquid crystal layer through a molecular layer that is chemically bonded to achieve a planar alignment and irradiating linearly polarized light in the wavelength range absorbed by the dichroic molecule, the liquid crystal is oriented in a direction at an angle to the polarization axis. And a liquid crystal optical element obtained by this method. [Effect] Information can be written by changing only the polarization axis without changing the wavelength, and stable and high-resolution information storage is possible. Overwriting only requires changing the polarization axis, and has an advantage over conventional optical recording or display. Therefore, it can be suitably used for high density rewritable optical recording and optical address type display.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal alignment method and a novel liquid crystal optical element using the same. More specifically, the present invention relates to a method of aligning liquid crystal molecules in a direction different from the polarization axis by the action of linearly polarized light absorbed by a certain type of dichroic molecule layer chemically bonded to the substrate surface, and an optical method using the method. The present invention relates to a liquid crystal optical element having controlled physical properties.

[0002]

2. Description of the Related Art In order for an optical element suitable for display or recording using a liquid crystal to operate, the liquid crystal medium sandwiched between substrates must be aligned in the same direction, and the alignment direction of the liquid crystal must be It is essential to change by the action of external fields. Among them, in order to orient the liquid crystal molecules in the same direction, a rubbing treatment in which the surface of the substrate is covered with a polymer film of some kind and rubbed with a cloth in one direction is widely adopted (J. Cogner ( J. Cognard) "Molecular
Crystals and Liquid Crystals (Mo
lecular Crystals and Liquid Cryatals) ", Supplement 1 (1982)).

In order to drive the liquid crystal device thus treated on the surface of the substrate, it is necessary to coat the substrate with a transparent conductive material that is patterned in advance and apply an electric field. Liquid crystal optical elements based on this principle
It is used in various fields by incorporating it into a display device that can be viewed by humans, but the conventional one has a low resolution because it uses patterned electrodes, and is used for high-density, high-resolution display applications. Has a limit, and furthermore, the information is usually lost when the power supply is stopped, so that it is not suitable for application to a record for permanently storing the information.

On the other hand, there is a liquid crystal element for displaying or recording information by utilizing the phase change of liquid crystal due to the action of light. The phase change is caused by the thermal energy generated by high density light such as a laser beam, or the molecular structure change caused by the photochemical reaction of photochromic molecules coexisting in the liquid crystal medium. However, these have drawbacks such as reduction in resolution due to heat conduction and high laser energy required.

Further, a liquid crystal recording element utilizing a photochemical reaction to improve the resolution is also known. This is a liquid crystal element in which a molecular layer whose structure is reversibly changed by light is provided on the surface of the substrate, and the alignment of the liquid crystal molecules is perpendicular to the substrate according to the photochromic reaction of the molecules bound to the surface (homeo It changes between the state (parallel alignment) and the parallel state (tropic alignment). In this method, the alignment film itself performs reversible liquid crystal alignment without applying an electric field, but like other reversible optical recording or display principles, it is stored in order to write new information. The information has to be erased by irradiating the entire surface with light of another wavelength, and two kinds of wavelengths of light are indispensable, and overwriting cannot be performed for display and recording.

On the other hand, as a method of arranging molecules in liquid crystal, a method of controlling the orientation of the liquid crystal medium by irradiating linearly polarized light absorbed by anisotropic absorbing molecules existing in a liquid crystal medium or a substrate in contact with the liquid crystal medium Has been proposed (see Japanese Laid-Open Patent Publication No. 2-277025). However, in the case of this method, the liquid crystal alignment generated by the linearly polarized light absorbed by the anisotropic absorbing molecules in the liquid crystal medium is unstable, and the amount of light energy required for the liquid crystal alignment is extremely high. In particular, when anisotropically absorbing molecules are embedded in a substrate, high energy is required. In addition, a method has also been proposed in which a photochromic compound layer is provided on a substrate, a liquid crystal layer is laminated, and linearly polarized light is applied to this to orient the liquid crystal in a predetermined manner. However, even in this case, the photochromic compound is generally inferior in durability because it undergoes a large reversible molecular structure change by the action of light, and the changed molecular structure thermally returns to the original structure naturally. Therefore, there are inevitable drawbacks in using the liquid crystal alignment method for display and rewritable optical recording, such as unstable alignment.

The method of controlling the liquid crystal orientation by such linearly polarized light is a method of displaying or recording information by a single light source, which has a very advantageous characteristic in principle. There are serious drawbacks such as a remarkably high amount of exposure energy and poor durability.

[0008]

DISCLOSURE OF THE INVENTION In order to solve the above-mentioned conventional drawbacks, the present invention provides a substrate with a dichroic molecule having a certain structure which changes the molecular axis with high sensitivity by irradiation of linearly polarized light. Provided is a method of reversibly changing the alignment direction of liquid crystal molecules depending on the direction of the linear polarization axis by chemically bonding to the above and facilitating contact with the liquid crystal molecules. Then, based on this method, with a small amount of exposure energy,
An object of the present invention is to provide a liquid crystal optical element capable of overwriting by using a light source in a single wavelength range while maintaining excellent resolution and stably holding written information for an arbitrary time. ..

[0009]

The present inventor has conducted extensive studies to develop an optical recording or display device utilizing reversible alignment change of liquid crystal by a single light source, and as a result, a linearly polarized light was formed on a substrate. To form a liquid crystal cell by chemically bonding a kind of dichroic molecular layer that easily changes the molecular axis by
By irradiating it with linearly polarized light in the wavelength range absorbed by the dichroic molecule, the liquid crystal molecules are aligned in a direction different from the polarization axis, and further, the alignment state is stably maintained for a long time. Based on these findings, the present invention has been completed.

That is, according to the present invention, C = C, C = N,
Planar alignment by providing a liquid crystal layer with a dichroic molecule having at least one double bond selected from N = N as a light absorbing part chemically bonded on the surface of at least one substrate Then, by irradiating the linearly polarized light in the wavelength range absorbed by the dichroic molecule, the liquid crystal is aligned in a direction having an angle with respect to the polarization axis.

The substrate used in the present invention may be transparent or opaque as long as it can bind dichroic molecules. As a transparent substrate, ordinary silica glass,
Metal oxides such as silicon oxide, tin oxide, indium oxide, aluminum oxide, titanium oxide, chromium oxide, and zinc oxide, silicon nitride, silicon carbide, etc. are formed on the surface of hard glass, quartz, various plastics, etc. or their surfaces. The coated one is used. As the opaque substrate, a metal or glass or plastic sheet on which a metal layer or a metal oxide layer is attached is used.

Usually, a sandwich structure in which a liquid crystal is filled between two substrates is used. In this case, at least one of the substrates needs to be transparent. These boards are usually 0.
Used as a sheet having a smooth surface with a thickness of 01 to 1 mm. This structure is configured by combining one or two polarizers. In the present invention, it is necessary to provide a dichroic molecule that causes a change in molecular axis orientation on the above substrate by linearly polarized light. The dichroic molecule means light energy in a certain wavelength range absorbed by the molecule. Have different properties depending on the two directions of the molecule. The wavelength of the light absorbed by the dichroic molecule is not limited to the visible light region, and includes the ultraviolet and infrared regions that cannot be observed by the naked eye.

The dichroic molecule used in the present invention is one that can change its molecular axis orientation by the action of light. The change in molecular axis orientation referred to here is a phenomenon in which the direction of the molecular axis is changed without changing the molecular structure after absorbing linearly polarized energy and passing through a photoexcited state. At least one of C = C, C = N, and N = N as a light absorbing portion
A dichroic molecule containing a double bond selected from the following is used in the present invention as one that easily causes a change in molecular axis orientation, and this phenomenon was first discovered by the inventor of the present invention. .. In the ground state of the ethylene molecule, two carbon atoms and four hydrogen atoms are on the same plane, whereas in the photoexcited state, the planes formed by the two sets of H-C-H atomic groups are twisted perpendicular to each other. It is well known that the structure is the same, and the dichroic molecule used in the present invention similarly loses the planarity formed by the above double bond in the photoexcited state, and then undergoes a twisted structure to be accompanied by It is presumed that the molecular axis orientation change occurs in the process of returning to the state. Therefore, even if the molecular structure change based on the geometrical isomerization before and after the light irradiation is not caused, the molecular axis orientation change proceeds.

A specific example of the dichroic molecule used in the present invention is as follows. First, as a compound having an N = N bond,
Aromatic azo compounds such as azobenzene, azonaphthalene, aromatic heterocyclic azo compounds, bisazo compounds and formazan, as well as those having azoxybenzene as a basic skeleton. For example, many azobenzene compounds undergo a photogeometric isomerization reaction from the trans isomer to the cis isomer by ultraviolet light, but most of the azobenzene compound is converted to the light isomer due to the conversion of the cis isomer to the trans isomer with respect to longer wavelength light. It is well known that geometric isomerization does not occur. In the present invention, such apparent photoisomerization reaction, that is, the fact that molecular axis alignment changes easily by irradiation with linearly polarized light in a wavelength range that does not show photochromism is utilized. Furthermore, a compound in which a photoisomerization reaction is not substantially observed can be used in the present invention because the change from the cis form to the trans form occurs rapidly thermally. Examples of these are shown below, but the present invention is not limited thereto.

[0015]

[Chemical 1]

Examples of the compound having a C = N bond include the following aromatic Schiff bases and aromatic hydrazones. These can become geometrical isomers upon irradiation with light, but since they are extremely unstable, they quickly return to the thermodynamically stable original structure.For example, no substantial photoisomerization is observed at room temperature. It does not show chromism.

[0017]

[Chemical 2]

Examples of the compound having a C = C bond include the following polyene, stilbene, stilbazole, stilbazolium, cinnamic acid, and hemithioindigo. Most of these undergo photogeometric isomerization reaction, but similar to the case of azobenzene, the light in the wavelength range suitable for isomerization from cis form to trans form does not allow geometric isomerization to be recognized. Can be used.

[0019]

[Chemical 3]

Further, a dichroic compound in which the photogeometric isomer is immediately unstable to return to the original structure and a substantial photoisomerization reaction is not recognized by irradiation with light is also used. For example, the following cyanines and merocyanines can be mentioned. Furthermore, the following compounds which do not show any photogeometric isomerization reaction can also be used in the present invention.

[0021]

[Chemical 4]

These dichroic molecules are listed as examples of the basic skeleton, and these skeletons have an alkyl group,
Alkoxy group, allyl group, allyloxy group, cyano group,
One or more residues such as an alkoxycarbonyl group and a hydroxy group may be bonded. In particular, an alkyl group, an alkoxy group, a cyano group and an alkoxycarbonyl group which give a structure similar to that of a liquid crystal molecule are preferable.

These dichroic molecules must have a substituent with a residue for binding to the substrate surface. This kind of substituent is attached at a site located on the molecular axis parallel to the transition moment that absorbs light of a longer wavelength, and when it is not on the molecular axis but in the direction of the transition moment. In some cases, they are joined at an angle. In the former case, the dichroic molecules tend to be arranged perpendicular to the substrate, but a residue or a spacer between the dichroic molecule and the binding group to the substrate surface may be introduced. The spacer is a chain residue in which atoms selected from carbon, oxygen, nitrogen or sulfur atoms are arranged in series, and the number of atoms is 3 or more, preferably 5 or more. If it is less than this, the major axis of the dichroic molecule tends to be oriented in the direction perpendicular to the substrate surface, which is not suitable for the present invention. A more preferable binding form of the dichroic molecule is such that the residues necessary for binding the dichroic molecule to the substrate are
It is to bind at a position, not on its molecular axis.

The above embodiment will be described by taking azobenzene as an example of a dichroic molecule. That is, azobenzene causes a photogeometric isomerization reaction by the action of light, and the molecular long axis that absorbs the light energy that causes the reaction is substantially in line with the para-position of two phenyl groups. Therefore, when the para-position of azobenzene is substituted with a substrate surface-bonding group, the azobenzene unit is likely to maintain a position perpendicular to the substrate surface. To avoid this, a spacer of sufficient length is necessary. Also, when the meta or ortho position of the phenyl group constituting the azobenzene skeleton is replaced with a substrate surface bonding group, the bonding position is not on the molecular axis, so the long axis direction of the azobenzene skeleton becomes perpendicular to the substrate surface. Hateful. Especially when it is bound to the ortho position,
This is more preferable for the present invention because the molecular axis of the dichroic molecule is necessarily parallel to the substrate surface.

In the present invention, in order to provide the dichroic molecular layer which causes such a reversible change in molecular axis orientation on the substrate, a method of physically or chemically bonding depending on the surface characteristics of the substrate, There is a method in which dichroic molecules are bound in advance to prepare a polymer, and the polymer is applied as a thin film on a substrate. Either method is acceptable. First, a method for binding dichroic molecules to the substrate surface will be described. For this purpose, for example, if the substrate is silyl glass, a method in which liquid crystal alignment is used can be adopted (J. Cognar
d) "Molecular Crystals and Liquid Cry"
stals) ", Supplement 1 (1982)).

As a first method for this purpose, a surface active group is bound to the dichroic molecule and adsorbed and bound to the substrate surface. Examples of the surface active group include a carboxylic acid residue, a malonic acid residue, a carbamoyl group, an alkylaluminum residue, a tetraalkylammonium group, an alkylpyridinium residue, an alkylquinolinium residue, a carboxylatochromium residue, and an ester. A residue, a nitrile residue, a urea residue, an amino group, a hydroxyl group, a betaine residue, etc. can be mentioned. In order to apply such a dichroic molecule having a surface active group to the surface of the substrate, it may be applied directly to the surface of the substrate or may be dissolved in a liquid crystal substance before use. In the latter case, the addition amount of the dichroic compound having a surface active group is 0.01 to 5.0% by weight, preferably 0.
It is in the range of 5 to 3.0% by weight.

As a second method, the Langmuir-Blodgett method in which the dichroic molecule having the above surface active group is developed as a monomolecular layer on the water surface by a known method, and at least one of the layers is transferred onto a substrate. Can be adopted. For this purpose, a carboxyl group, a carbamoyl group, an amino group, an ammonium group, a tetraalkylammonium group and a hydroxyl group are particularly preferable as the surface active group.

As a third method, it is also effective to bond to the surface with a dichroic molecule having a silyl group substituted with at least one halogen atom or an alkoxy group (E.
"Silane coupling agents" by EP Pluedemann,
Plenum Press (1982)). For this purpose, one kind of these silyl groups is introduced into the dichroic molecule in advance, and the surface of the silica glass is treated with this by a usual method. Alternatively, the surface of the substrate may be treated with a silylating agent having an amino group, and then the dichroic molecule having a carboxyl group or an acryl group may be introduced by a condensation reaction or an addition reaction. The operation of binding these dichroic molecules to the surface may be performed in the coexistence of another silylation treating agent. Examples of the silylation agent for this purpose, methyltriethoxysilane, dimethyldiethoxysilane, trimethylchlorosilane, ethyltriethoxysilane, diethyldiethoxysilane, propyltriethoxysilane, butyltriethoxysilane, butylmethyldiethoxysilane, Pentyltriethoxysilane, Hexyltriethoxysilane, Heptyltriethoxysilane, Octyltriethoxysilane, Octyltrichlorosilane, Nonyltriethoxysilane, Decyltriethoxysilane, Undecyltriethoxysilane, Dodecyltriethoxysilane, 3-Aminopropyltriethoxysilane Ethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-aminopropyldimethylethoxysilane, 3-cyanopropyltriethoxysilane,
Examples thereof include 3-dimethylaminopropyltriethoxysilane, but not limited thereto.

As a fourth method, in the case where the polymer substance forms the substrate itself or the substrate surface layer, it is treated with the dichroic compound having the above-mentioned surface active group for adsorption bonding. Alternatively, the dichroic molecule may be bound to the active group exposed on the polymer surface by a covalent bond. For example, when the polymer substance is polyvinyl alcohol, the dichroic molecule is bound to the surface layer by an acetal bond or an ester bond. For this purpose, a dichroic molecule having a formyl group or a chloroformyl group may be prepared, dissolved in a solvent that does not dissolve polyvinyl alcohol, and a substrate having a polyvinyl alcohol film may be dipped in the solution to react. To increase the treatment reaction rate, a catalyst acid such as p-toluenesulfonic acid may be added in the case of acetalization, and triethylamine, pyridine, etc. may be added in order to remove hydrogen chloride generated in the reaction in the case of esterification. It is effective to add the above base.

The fifth method for introducing a dichroic molecule into a substrate is gold on the surface of the substrate by a known method such as vacuum deposition,
A metal thin film layer of copper or the like may be provided, and a dichroic molecule having a residue such as a sulfhydryl group that binds to a metal may be reacted on the surface layer. This type of dichroic molecule may be dissolved in a solvent such as alkane, benzene, toluene and methylene chloride, and the substrate may be dipped or applied in the solution.

In order to adjust the amount of the dichroic molecule bound to the surface of the substrate, the treatment is carried out in the presence of other surface-bound molecules as described in the description of the second method. The molar ratio of the treatment agent composed of a dichroic molecule to another treatment agent is
1: 0 to 1: 1000, preferably 1: 0 to 1:
500. When the molar ratio of the other treating agent exceeds this range, the alignment of the liquid crystal does not change even when irradiated with linearly polarized light.

Next, a method of using a polymer having a dichroic molecule bound thereto will be described. In order to bond the dichroic molecule to the side chain or main chain of the polymer, a monomer composed of the dichroic molecule is polymerized in advance by a known method, or a polymer substance having a chemical structure A dichroic molecule with a suitable reactive residue is attached. In the former polymerization method, a dichroic molecule having an acrylic or methacrylic group having radical polymerization ability is particularly suitable as a monomer, and a polymer having a dichroic molecule bonded to its side chain can be easily obtained. .. In the case of a polymer obtained by polycondensation reaction of polyester, polyamide, polyimide or the like or polyaddition reaction of polyurethane or the like, a bifunctional monomer containing a dichroic molecule may be prepared. The binding amount of the dichroic molecule can be adjusted by changing the copolymerization ratio of the dichroic molecule-containing monomer. The copolymerization ratio of the dichroic monomer and the other monomer suitable for the present invention depends on the structure of the copolymerizable monomer,
1: 0 to 1: 100, more preferably 1: 0 to 1:
The range is 50. Examples of the reactive polymer used in the present invention include, but are not limited to, polyvinyl alcohol, styrene-maleic anhydride copolymer, polyglycidyl methacrylate or its copolymer, and the like.

In order to provide such a polymer thin film having a dichroic molecule in the main chain or side chain on the substrate surface, the spin coating method is preferable. A film thickness of 1 μm or less is sufficient. Alternatively, this type of polymer may be provided on the substrate by the Langmuir Project. The dichroic molecule of the present invention binds to the substrate surface in the above-described method,
It is necessary to maintain dichroism while being in contact with the liquid crystal layer. That is, the molecular axis of the dichroic molecule is not perpendicular to the substrate, and the ratio of absorbed linearly polarized light by the molecules bound to the substrate varies depending on the direction. is necessary. Such a state brings the alignment of the liquid crystal molecules in parallel or close thereto, and is an essential condition for the present invention. Next, as the liquid crystal of the liquid crystal layer provided on the dichroic molecular layer that undergoes a structural change by linearly polarized light, any one of conventionally known nematic, smectic, and cholesteric liquid crystal substances should be selected. However, in the case of a smectic liquid crystal substance, it is necessary to select one that takes a nematic liquid crystal layer at a certain temperature. This is because even if the smectic liquid crystal layer is irradiated with linearly polarized light, the liquid crystal alignment is not changed by the dichroic molecular layer.

Such a liquid crystal substance is, for example,
A. Bequin et al., "Molecular Crystals and Liquid Crystals"
and Liquid Crystals), Vol. 115, page 1. These liquid crystal substances may be used alone or in combination of two or more. Polymeric liquid crystals can also be used. Further, a dichroic dye may be dissolved in these liquid crystal substances. In this case, since the dichroic dyes are aligned in parallel with the substrate surface in synchronization with the alignment of the liquid crystal layer, they can be detected as dichroic at the dye absorption wavelength. Further, an antioxidant may be added to prevent decomposition of the dichroic molecular layer.

The present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing the basic structure of the present invention, in which a liquid crystal layer 3 is provided on a transparent substrate 1 with a dichroic molecular layer 2 which causes a structural change caused by light. Usually, in order to fix the liquid crystal layer and prevent dissipation, a liquid crystal layer is further covered with a protective layer or a substrate. The protective layer or substrate may be transparent or opaque, and the surface thereof may be coated with a dichroic molecular layer that undergoes a structural change by light.

FIG. 2 is a sectional view showing an example of a preferred embodiment of the present invention, in which a liquid crystal layer is sandwiched between two substrates 1 having a dichroic molecular layer 2 on the surface. It has a sandwich structure. Before irradiation with linearly polarized light, the long axes of the liquid crystal molecules are aligned substantially parallel to the surface of the substrate prepared by the above method, but the directions are not uniform (random parallel alignment). FIG. 2 (a) shows the alignment state of the liquid crystal layer after being irradiated with the linearly polarized light absorbed by the dichroic molecule. When the liquid crystal layer is sufficiently irradiated, the liquid crystal molecules are aligned in the direction orthogonal to the polarization axis (homogeneous alignment). ) Do. FIG. 2B shows that a part (A) of this liquid crystal element is irradiated with the polarization axis changed to a position β which forms, for example, 45 degrees with respect to the direction α of the axis of the linearly polarized light which is first irradiated. The alignment direction of the liquid crystal is approximately 45 degrees with respect to the direction in the unirradiated portion. For this reason,
When this liquid crystal element is placed between two orthogonal polarizers and viewed, when the linear polarization axis direction α coincides with the axial direction of the polarizer, the exposed portion is dark with respect to the second linear polarization. In Although,
The exposed portion transmits light and appears bright. This light-dark relationship is reversed by tilting the polarization axis of the polarizer by 45 degrees. This is optically obvious, and so is it. When the third linearly polarized light is changed again so that the polarization axis coincides with the direction α and the exposed portion is irradiated, the alignment of the liquid crystal layer in that portion again coincides with the unexposed portion, and the information written by the polarized light is erased. It was done. On the other hand, if the polarization axis at this time is set to the direction γ different from the former two, it means that new information is immediately written. Thus, the fact that the orientation of dichroic molecules on the substrate surface is controlled only by the change of the polarization axis to determine the orientation direction of the liquid crystal was first discovered by the inventors of the present invention.

FIG. 3 is an example of an embodiment different from that of FIG. 2, and is an example of a hybrid liquid crystal element in which a homogeneous alignment layer 4 is provided on one of the two substrates. The homogeneous alignment layer 4 is provided by coating the surface of the substrate with a polymer film of polyvinyl alcohol, polyimide resin, polyamino acid, etc., and then rubbing or vapor-depositing an oxide such as SiO ₂ from an oblique direction. be able to. In this example, when the whole surface is irradiated with the linearly polarized light whose polarization axis coincides with the direction of homogeneous alignment, the liquid crystal alignment becomes homogeneous alignment in the orthogonal direction in the vicinity of the surface of the substrate covered with the dichroic molecular layer (a). Therefore, in a nematic liquid crystal element, it becomes a twisted nematic layer. If exposure is performed by changing the polarization axis, only the exposed portion changes the alignment direction of the liquid crystal, and therefore it is possible to easily distinguish from the unexposed portion by the polarizer. By selecting the direction of this second polarization axis, a twisted nematic optical element having an arbitrary angle is prepared (b).

FIG. 4 shows a hybrid cell type embodiment different from that of FIG. 3, in which a homeotropic alignment layer 5 is provided on one of the two substrates. The homeotropic alignment layer 5 is prepared by a known substrate surface treatment method using lecithin or a long-chain alkylsilylating agent. In this example, when the whole surface is irradiated with the linearly polarized light in the polarization axis direction α and then exposed with (a) the linearly polarized light changed to the polarization axis direction β, only the exposure part changes the alignment direction of the liquid crystal. Information is written as the same difference in birefringence direction.

FIG. 5 shows an example in which a dichroic dye is dissolved in the liquid crystal layer in the device structure shown in FIG. 4, and the dichroic dye is added in the direction orthogonal to the polarization axis direction β of the second linearly polarized light. Arrange. Therefore, the change in transmittance due to the absorption of the dye is detected by one polarizer. The linearly polarized light used in the present invention is a combination of a polarizer with a light source such as an ultra-high pressure mercury lamp, a xenon lamp, and a fluorescent lamp, or using various lasers such as a helium-neon laser, an argon laser, a helium-cadmium laser, and a semiconductor laser. You can

The information written by the linearly polarized light in the element structure shown in the above example is not lost or is very difficult to be lost even if it is the light of the wavelength absorbed by the dichroic molecular layer if it is natural light. This means that the optical element of the present invention which stores information can be stored in a bright place, and it is possible to write information having a threshold value while using a photochemical reaction.

Therefore, in the present invention, if the entire surface is first irradiated with linearly polarized light so that the alignment direction of the liquid crystal molecules is orthogonal to the polarization axis, writing of information simply changes the linear polarization axis. Is possible and
Rewriting is also possible if linearly polarized light having a polarization axis in a new direction is used. This point is important when this optical element is used for recording or display. On the other hand, conventional optical recording materials, such as magneto-optical recording and photochromic recording, are based on the principle of erasing the record once and then rewriting it in order to rewrite it. Alternatively, it was necessary to devise a special method.

[0042]

EXAMPLES Example 1 p-Hexylaniline was used as a diazonium salt in hydrochloric acid-methanol-water to diazotize benzoic acid resorcinol ester to obtain 4- (2-benzoyloxy-4-hexylphenyl) azophenol. .. The azophenol and hexyl bromide were stirred with anhydrous potassium carbonate in dimethylformamide. Sufficient water was added to the reaction product, the product was extracted with hexane, washed thoroughly with water, and then dried over anhydrous potassium carbonate. The obtained 1-hexyloxy-4- (2-benzoyloxy-4-hexylphenyl) azobenzene was hydrolyzed to give 1-hexyloxy-4- (2-hydroxy-4-hexylphenyl) azobenzene. This exhibited liquid crystallinity and became an isotropic phase. The hydroxyazobenzene and 5-bromocaproic acid tetrahydropyranyl ester were stirred in dimethylformamide in the presence of anhydrous potassium carbonate at 80 ° C. for 4 hours. Water was added to the reaction solution, and then the product was extracted with hexane, and hexane was distilled off to prepare a solution of dioxane, and 6N hydrochloric acid was added thereto to hydrolyze.
The precipitated crystals were collected by filtration to give 5- [3-hexyloxy-6- (4-hexylphenyl) azophenyl] caproic acid.

This azophenylcaproic acid was condensed with 3-aminopropyltriethoxysilane in dichloromethane with dicyclohexylsulbodiimide. The urea derivative formed was filtered off, the solvent was distilled off, and the product was dissolved in ethanol to give a 1% solution. Place a quartz plate of 1 × 3 cm ² on acetone, deionized water, concentrated nitric acid, deionized water, sodium bicarbonate solution, deionized water in the order 15
The surface was cleaned by treating with ultrasonic waves for a minute. This quartz plate was immersed in the above ethanol solution for 20 minutes and heated at 120 ° C. for 30 minutes. This was sonicated twice in chloroform for 15 minutes. The absorption spectrum of the quartz plate thus obtained has a maximum value at 340 nm,
Although it showed an absorbance of 0.005, it was actually colorless and transparent.

Cyclohexanecarboxylic acid phenyl ester mixed liquid crystal (DON-103: K-17-N-73-1 manufactured by Rhodic Corporation) containing spherical glass spacers having a diameter of 5 μm was used on two quartz plates thus treated. A sandwich cell was prepared by sandwiching and sealing with an epoxy resin. This colorless and transparent cell was bright under crossed Nicols, but its transmittance did not show angle dependence, and it was confirmed that it was randomly parallel aligned. This cell at 120 ° C for 10
After heating for a minute, let the light from the mercury lamp pass through a glass filter that cuts light with a wavelength of 430 nm or less.
The cell was illuminated through the polarizer for 2 minutes. When this cell was placed between orthogonal Nicols, it was dark when the polarization axis of the linearly polarized light irradiated to the polarization axis of the polarizer was 0 ° or 90 °.
It was confirmed that the image was bright at the position of 5 degrees and had a homogeneous orientation. Moreover, it was confirmed that the light of this wavelength hardly caused the photoisomerization of azobenzene from the trans form to the cis form. Through this film through a negative film, the light with a polarization axis that forms 45 degrees with the initial irradiation polarization axis
When the cells were exposed for a minute and then observed under a crossed Nicols, a clear image was obtained. This image remained clear at room temperature for more than half a year even when stored under room light.

Even when a non-fluorescent slide glass is used in place of the quartz plate and the surface treatment is performed in the same manner, and a mixed liquid crystal is sandwiched between two glass plates to form a cell, a clear image can be obtained under the same irradiation conditions. I was able to. In this case as well, the image was saved for more than half a year without any change. Example 2 A thin cyclohexanecarboxylic acid phenyl ester mixed liquid crystal was spin-coated at 600 rpm on the quartz plate obtained in Example 1, linearly polarized light of 430 nm or more was irradiated through the quartz plate, and then the polarization axis was rotated by 45 degrees. Then, when the film was irradiated through the negative film for 2 minutes, a clear image was observed under the crossed Nicols.

Example 3 Two surface-treated glass plates obtained in Example 1 were used to prepare a nematic liquid crystal cell of a cyanobiphenyl mixed liquid crystal (RO-507 manufactured by Roddick). When this cell was heated at 120 ° C. for 10 minutes and then irradiated with light having a wavelength of 430 nm or more by changing the polarization axis to 45 ° twice as in Example 1, a clear image could be obtained. ..

Example 4 A liquid crystal cell of a cyclohexene-cyclohexane nematic mixed liquid crystal (LVI-035L by Rodick Co., TN ₁ = 26.6 ° C.) was prepared in the same manner from two surface-treated glass plates obtained in Example 1. did. This cell was irradiated with light having a wavelength of 430 nm or more at 23 ° C. in the same manner as in Example 1 so that the polarization axis was set to 45 °
Irradiation was performed at different degrees, and a clear image could be obtained.

Example 5 A saponification rate of 8 was obtained at a polymerization degree of 1700 on a quartz plate of 1 × 3 cm ^2.
A 3% by weight aqueous solution of 7% polyvinyl alcohol was spin-coated and dried at 100 ° C. for 20 minutes. This was rubbed with tissue paper in one direction. This quartz plate 1
A liquid crystal cell was prepared by sandwiching the cyclohexanecarboxylic acid ester-based mixed liquid crystal between the single plate and the surface-treated quartz plate obtained in Example 1. This cell is heated at 120 ° C for 10 minutes and then it has a polarization axis parallel to the rubbing direction.
Irradiation with light having a wavelength of 30 nm or more was performed for 2 minutes. When this cell is placed between two polarizers whose polarization axes are parallel, the cell becomes dark, but when the polarization axes of the polarizers are made orthogonal, the cell becomes bright and a twisted nematic phase of about 90 degrees is obtained. It has been confirmed that When this cell was irradiated with light through a negative film with the polarization axis orthogonal to the rubbing treatment direction, a clear image was observed between the two polarizers. At this time, the image was observed as both negative and positive by changing the polarization axes of the cell and the polarizer. Heat the cell again to 120 ° C for 10 minutes, then
When another image was written by the same operation, the previous image disappeared completely and a new image was observed. This image was completely preserved under room light for over half a year.

Example 6 A 1 × 3 cm ² quartz plate was immersed in an ethanol solution of 1% by weight octadecyltriethoxysilane for 20 minutes, and 120
Surface treatment was performed by heating at 30 ° C. for 30 minutes. This quartz plate 1
A cell was prepared by sandwiching the cyclohexanecarboxylic acid ester-based mixed liquid crystal between the sheet and one surface-treated quartz plate obtained in Example 1. While maintaining this cell at 80 ° C., the same operation as in Example 1 was carried out by irradiating with a linearly polarized light of a wavelength of 430 nm for 2 minutes, then a negative image was placed on the cell and the polarization axis was rotated at 45 °. Irradiation was carried out for 2 minutes. The cell between two orthogonal polarizing plates showed clear light and dark in the exposed and unexposed areas.

Example 7 In the same manner as in Example 6, 2% by weight of diaminoanthraquinone type dichroic dye was added to the liquid crystal (DON-1-3) in advance, and the quartz plate obtained in Example 1 was used. Enclosed between quartz plates treated with octadecyltriethoxysilane
A liquid crystal cell having a cell thickness of m was prepared. While keeping the temperature at 80 ° C., the azobenzene-treated quartz plate was used as the front surface and irradiated with polarized light having a wavelength of 430 nm or more for 2 minutes by the same operation as in Example 1, and this cell was placed on or below the polarizing plate. Dichroism was observed in the condition. 80 more cells
While maintaining the temperature at 0 ° C., the polarization axis of the irradiation line polarization was rotated to 90 ° C. over the negative image and irradiation was performed for 2 minutes. When this cell was observed through a polarizing plate so as to be orthogonal to the polarization axis of the irradiation line polarized light, a clear blue image was recognized.

Example 8 A surface treatment agent synthesized from the azophenylcaproic acid obtained in Example 1 and 3-aminopropyltriethoxysilane by a condensation reaction was added with ethyltriethoxysilane (ET
S) are 1, 3, 5, 20, 50, 10 in molar ratios, respectively.
It was added so as to be 0, 500 and 1000 to obtain a 1 wt% ethanol solution. Add two clean quartz plates to these solutions.
Soak each piece for 20 minutes, air dry for 10 minutes, then add 120
Heat at 30 ° C. for 30 minutes. Irradiation of these quartz plates with visible light of 430 nm or longer hardly changed the absorption spectrum of azobenzene. A cell of a mixed liquid crystal of cyclohexanecargonate ester was prepared by using two quartz plates. The image was written by irradiating it with linearly polarized light having a wavelength of 430 nm or more in the same manner as in Example 1. as a result,
Image formation was observed up to a molar ratio of ethyltriethoxysilane of 500, but no image formation was observed at a molar ratio of 1000.

Example 9 2-hydroxy-4-hexyloxy-obtained in Example 1
4'-hexylazobenzene was reacted with bromoacetic acid tert-butyl ester to give 2-carboxymethoxy-4-hexyloxy-4'-hexylazobenzene. This was condensed with aminopropyltriethoxysilane and dicyclohexylcarbodiimide and then similarly prepared as an ethanol solution. The washed quartz plate was immersed in this solution and then heated at 120 ° C. for 30 minutes. This is sonicated in chloroform and dimethylformamide for 30 minutes each, washed with chloroform and then at 120 ° C.
And dried for 10 minutes. A cell was prepared by sandwiching a nematic mixed liquid crystal (DON-103, manufactured by Roddick) containing a spherical glass spacer of 5 μm between the quartz plate and the lecithin-treated quartz plate. While heating the entire surface of the cell to 80 ° C., linearly polarized light was irradiated for 3 minutes under the same conditions as in Example 1. When a cell was placed between two orthogonal polarizers and observed, it was confirmed that the position at 45 ° corresponding to the linear polarization axis was the brightest and was homogeneously aligned. While maintaining the cell at 80 ° C., linear polarization with the polarization axis rotated by 45 ° was irradiated through the negative image for 2 minutes, and when the cell was observed between the crossed polarizers, a clear image was observed.

Example 10 In Example 10, the corresponding azobenzenecarboxylic acid was synthesized by using ω-bromoundecanoic acid tetrahydropyranyl ester instead of bromoacetic acid tert ester. After condensing this with aminopropyltriethoxysilane, the surface of the similarly washed quartz plate was subjected to surface treatment. 5 with this quartz plate and the quartz plate surface treated with lecithin
A nematic mixed liquid crystal (DON-103 manufactured by Roddick) containing a spherical glass spacer of μm was sandwiched to prepare a cell. Example 1 while heating the entire surface of the cell to 80 ° C.
The linearly polarized light was irradiated for 3 minutes under the same conditions as in. When a cell was placed between two orthogonal polarizers and observed, it was confirmed that the position at 45 ° corresponding to the linear polarization axis was the brightest and was homogeneously aligned. While maintaining the cell at 80 ° C., linear polarization with the polarization axis rotated by 45 ° was irradiated through the negative image for 2 minutes, and when the cell was observed between the crossed polarizers, a clear image was observed.

Example 11 In the same manner as in Example 1, 4-cyano-4'-hydroxyazobenzene was reacted with 5-bromocaproic acid tetrahydropyranyl ester to obtain the corresponding cyanoazobenzenecarboxylic acid. This was reacted with equimolar amounts of aminopropyltriethoxysilane and dicyclohexylcarbodiimide in dichloromethane at room temperature for 3 hours, and then the reaction solution was diluted with ethanol to 0.5% by weight. A quartz plate was immersed in this solution and heated at 120 ° C. for 30 minutes.
This was soaked in the order of chloroform, dimethylformamide, ethanol, and chloroform, subjected to ultrasonic treatment for 20 minutes, washed, and dried. 5 μm between the quartz plate surface-treated in this way and the quartz plate surface-adsorbed with lecithin
Cyclohexanecarboxylic acid-cyclohexene-based mixed nematic liquid crystal (EXP-CIL: N-31.8-I manufactured by Rodick Co.) in which the spherical glass spacers of No. 3 were suspended to form a cell, which was sealed with an epoxy resin. While maintaining this cell at 60 ° C., light of 430 nm or more from an ultra-high pressure mercury lamp was exposed through a polarizer for 1 minute. A cell exposed between a polarized He-Ne laser and a polarizer having a polarization axis orthogonal to the polarization axis is placed with its surface perpendicular to the laser beam, and the amount of laser transmitted light when the cell is rotated is measured. did. Almost no transmitted light was observed at (0 + 90xn) degrees with respect to the polarization axis of the linearly polarized light, but about 20% transmittance was observed at (45 + 90xn) degrees.

While the cell was heated again to 60 ° C., the polarization axis of the linearly polarized light was rotated by 60 ° and exposure was carried out for 1 minute. When the amount of polarized He-Ne laser transmitted light of this cell was measured, almost no transmitted light was observed at (60 + 90xn) degrees, but the transmittance at (-15 + 90xn) degrees was about 20.
%, And it was confirmed that the liquid crystal alignment axis was rotated by 60 degrees. Further, even when this cell was exposed to unpolarized natural light for 10 minutes at room temperature, the liquid crystal alignment state did not change.

Example 12 N-carboxymethylated merocyanine, aminopropyltriethoxysilane and dicyclohexylcarbodiimide were dissolved in dichloromethane and stirred at room temperature for one day.
A reaction solution containing a compound having the following structural formula was diluted with ethanol, a clean quartz plate was immersed in this solution for 20 minutes, and then heated at 120 ° C. for 30 minutes. Ultrasonic treatment was performed in each of chloroform and dimethylformamide, washed with chloroform, and then heated at 120 ° C. for 10 minutes to be dried.
A cell was prepared by sandwiching a cyclohexanecarboxylic acid-cyclohexene-based mixed nematic liquid crystal (Rhodick EXP-CIL: N-31.8-I) in which a spherical glass spacer of 5 μm was suspended between the quartz plate and the lecithin surface-treated quartz plate. And sealed with epoxy resin. While maintaining this cell at 60 ° C., light of 430 nm or more from an ultra-high pressure mercury lamp was exposed through a polarizer for 1 minute. Then, over the negative image, while the cell was heated again to 60 ° C., the polarization axis of the linearly polarized light was rotated by 45 ° and exposure was performed for 1 minute. When this cell was cooled to room temperature and then observed under crossed Nicols, a clear image was recognized.

[0057]

[Chemical 5]

[0058]

According to the liquid crystal optical element of the present invention, information can be written by changing only the polarization axis without changing the wavelength, and moreover, stable and high-resolution information storage is possible. Overwriting only requires changing the polarization axis, and has an advantage over conventional optical recording or display. Therefore,
It can be suitably used for high density rewritable optical recording and optical address type display.

[0059]

[Brief description of the figure]

[0060]

FIG. 1 shows an optical element in which a dichroic molecular layer 2 is provided on a transparent substrate 1 and a liquid crystal layer 3 is provided thereon.

[0061]

FIG. 2 (a) shows an optical element formed by sandwiching a liquid crystal layer 3 between two transparent substrates 1 provided with a dichroic molecular layer, as an alignment state of the liquid crystal layer after irradiation with linearly polarized light. FIG. 6B is a cross-sectional view schematically showing the liquid crystal array of the element in which the polarization axis is changed only in the portion A and the linearly polarized light is irradiated.

[0062]

FIG. 3 (a) is a transparent substrate 1 provided with a dichroic molecular layer 2.
FIG. 3 is a cross-sectional view showing an optical element formed by sandwiching a liquid crystal layer 3 with a transparent substrate 1 provided with a homogeneous alignment layer 4 and further irradiating the optical element with linearly polarized light parallel to the homogeneous alignment direction. FIG. 3B) is a cross-sectional view schematically showing the liquid crystal array of the element in which the polarization axis is changed only in the portion A and the linearly polarized light is irradiated.

[0063]

FIG. 4A shows a transparent substrate 1 provided with a dichroic molecular layer 2.
And (b) a transparent substrate 1 provided with a homeotropic alignment layer 5, an optical element sandwiching the liquid crystal layer 3, and a cross-sectional view showing an optical element obtained by irradiating the liquid crystal layer 3 with linearly polarized light.
[FIG. 3] is a cross-sectional view schematically showing a liquid crystal array of an element in which a polarization axis is changed only in a portion A and linearly polarized light is irradiated.

[0064]

FIG. 5 (a) is a transparent substrate 1 provided with a dichroic molecular layer 2.
And a transparent substrate 1 provided with a homeotropic alignment layer 5 sandwiching a liquid crystal layer 3 containing a dichroic dye, and an optical element irradiated with linearly polarized light. FIG. 3B is a cross-sectional view schematically showing the liquid crystal array of the element in which the polarization axis is changed only in the portion A and the linearly polarized light is irradiated.

[0065]

[Explanation of symbols]

 1 substrate 2 dichroic molecule layer 3 liquid crystal layer 4 homogeneous alignment layer 5 homeotropic alignment layer

Claims (2)

[Claims] 1. A dichroic molecule having at least one double bond selected from C = C, C = N, and N = N as a light-absorbing part is chemically bonded on the surface of at least one substrate. A liquid crystal layer is provided through a molecular layer formed by
A method for aligning liquid crystals, which comprises arranging liquid crystals in a direction at an angle to a polarization axis by irradiating linearly polarized light in a wavelength range absorbed by dichroic molecules. 2. A dichroic molecule having at least one double bond selected from C = C, C = N and N = N as light absorption is chemically bonded onto at least one substrate surface. By aligning the liquid crystal layer through the molecular layer formed by the above to achieve the planar alignment and irradiating the linearly polarized light in the wavelength range absorbed by the dichroic molecule, the liquid crystal is aligned in the direction having an angle with respect to the polarization axis. A liquid crystal optical element characterized by: