JPH0244538A - Optical recording material - Google Patents

Abstract

PURPOSE:To obviate the degradation of resolution with age by utilizing an orientation change of a liquid crystal by light to record information. CONSTITUTION:A molecular layer 2 of a high-polymer compd. having the residual group to generate a reversible structure change by light is fixed onto a transparent substrate 1 and further, a liquid crystal layer 3 is provided thereon. Since the arrangement of the liquid crystal is defined by the photochromic high-polymer layer 2, the definition by the liquid crystal having flowability is excellent and the deterioration thereof with age is obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a novel optical recording element that utilizes the change in orientation of liquid crystal caused by light. More specifically, the present invention causes a change in the orientation of the liquid crystal layer through the action of a polymer compound having a residue that undergoes a reversible structural change when exposed to light, and utilizes this to temporarily or permanently transfer information. This relates to an element for recording.

There are two known types of recording elements using liquid crystals: those that store information using electrical effects and those that use light to store information; the former is mainly used for display purposes. .

By the way, LCD displays that use electrical effects to write information lose their information when the power supply stops.
To preserve this permanently, special measures must be taken, and since patterned electrodes are used, the resolution is low and it is unsuitable as a recording element for high-capacity insects.

On the other hand, methods that use heat such as laser beams to store information using the action of light can be applied to high-density optical recording, but are limited to pit recording.
The scope of its use is inevitably limited. In addition, a compound that mixes a compound whose structure changes photochemically and changes its phase under the action of light shows excellent resolution when the information is first input manually, but because liquid crystals flow, it takes a long time. There is a tendency for resolution to drop significantly over time. For example, photochromic cholesteric liquid crystals obtained by dissolving chiral azobenzene in nematic liquid crystals change to an isotropic phase under the action of ultraviolet light, and this can be used to record information, but over time The liquid crystal flows and the recorded image becomes unclear. (Refer to the proceedings of the 52nd Spring Annual Meeting of the Chemical Society of Japan, 1986).

Problems to be Solved by the Invention The present invention records information using changes in the orientation of liquid crystals caused by light, and moreover uses polychromatic light that does not cause a decrease in resolution over time due to its fluidity. This was made for the purpose of providing a recording element.

Means to Solve the Problem In order to develop an optical recording device that takes advantage of changes in the orientation of liquid crystals caused by light, the present inventors conducted intensive research by creating a polymer layer containing residues that cause changes in the amount of the molecules. If a liquid crystal layer is provided on the layer, the liquid crystals will be reversibly aligned in parallel or perpendicularly according to the two types of structures of the residues that change reversibly with light. Based on this knowledge, we discovered that even when the molecules overlap more than 10,000 times, the information is transmitted quickly, and that unless the light conditions change, the liquid crystal layer does not change and information is retained for a long period of time. The present invention has been accomplished.

That is, the present invention provides an optical recording element in which a liquid crystal layer is provided on a transparent substrate via a polymer layer having a residue that undergoes a structural change reversibly when exposed to light.

The transparent substrate used in the present invention may be a sheet of ordinary silica glass, hard glass, quartz, various plastics, etc., or a surface thereof coated with silicon oxide, tin oxide, indium oxide, aluminum oxide, titanium oxide, chromium oxide, zinc oxide, etc. A material coated with metal oxide or modified silicon carbide is used. Furthermore, these may be surface-treated in advance with a silylating agent or the like by a known method.

Normally, a liquid crystal is used as a sandwich structure filled between two substrates, but in the present invention, at least one of these two substrates may be a transparent substrate, and the other may be made of copper or iron. It can also be a sheet of metal such as aluminum, platinum, or a sheet coated with these metals. These substrates are normally used as sheets with a smooth surface and a thickness of 0.01=1 mm.

In the present invention, it is necessary to provide on the above-mentioned substrate a polymer layer having a residue that undergoes a reversible structural change when exposed to light, and photochromic compounds are the most suitable compounds for forming this residue. Commonly used.

Photochromic compounds are compounds that undergo structural changes under the action of light and change their behavior toward light, such as color tone. A wide variety of compounds are known that utilize the isomerization reaction of heavy bonds. [For example, published by Wiley Interscience, edited by G. H. Brown,
"Photochromism J (1971)]. Examples of photochromic compounds based on photogeometric isomerization include abbenzene, indigo, anruinnogo, thioindigo, selenoindigo, berinaphthoindigo, hemiindigo, Examples of photochromic compounds based on a heterolytic photocyclic ring closure reaction include hemitioindigo, azomethine, etc. Examples of photochromic compounds based on a photocyclization reaction include pyran and spiroindolizine; examples of photochromic compounds based on a photocyclization reaction include stilbene and fulgide; and examples of photochromic compounds based on a phototautomerization reaction include salicylideneanyl, Compounds each having a basic skeleton of -hydroxyazobenzene, 0-nitrobenzyl, etc. can be mentioned.

The polymer having such a photochromic residue used in the present invention may be produced by preparing a monomer having a photochromic unit in advance and then subjecting it to a polymerization reaction, or by using a known photochromic compound. (See Masahiro Irie, "Synthesis and Applications of Photofunctional Polymers J (1984)," published by CMC Co., Ltd.).In this case, the photochromic residue is the main component of the polymer. The photochromic residue may be incorporated into the chain or bound to the side chain, but from the standpoint of efficient reversible structural changes due to light, it is better to bind the photochromic residue to the side chain. preferable.

The backbone polymer that provides the polymer having photochromic residues used in the present invention has a molecular weight of 1000 to 1.
The type does not matter as long as it is within the 12x range of 000000. If the molecular weight is below this range, the physical strength will be poor and the durability as an optical recording element will be reduced; if the molecular weight is above this range, a uniform coating film will be formed.
This becomes difficult. Examples of such base polymers include polyvinyl alcohol, polyimide resin, poly(meth)acrylic acid ester, poly(meth)acrylic acid amide, poly(L-glutamic acid ester), and poly(L-glutamic acid ester). -lysine), polystyrene, polyester, polyamide, etc., but are not limited thereto.

The rate of introduction of photochromic units into these basic polymers is desirably set so that the molecular weight per photochromic unit is in the range of 0 to 500 as calculated by dividing the photochromic unit. If the value is higher than this, or in other words, if the introduction rate is lower than this, reversible alignment change of the liquid crystal will not be observed.

In order to provide the polymer having a photochromic residue according to the present invention on a transparent substrate, a conventional method such as casting a polymer solution or spin coating is used. The thickness of this polymer film, even if it is a monomolecular layer, is suitable for the purposes of the present invention, and any thickness in the range from several meters to several tens of meters is acceptable. In particular, in order to obtain an ultra-thin film, the so-called Langmuir-Prodgett method is suitable, in which a solution of the polymer according to the present invention is spread on a water surface, and after the solvent has evaporated, it is scooped onto a transparent substrate. Alternatively, in order to process large-area substrates more easily, physical or
A polymer having photochromic units may be chemically adsorbed. For this purpose, it is appropriate to provide a polymer with photochromic units on a transparent substrate that is untreated or treated with a silylation agent, heat it, and then wash it with a solvent to remove most of the polymer. It is.

In order to obtain a clear recorded image by reversibly changing the orientation of the liquid crystal, it is desirable that the long sleeves of the liquid crystal molecules be homonoidally oriented in one direction. For this purpose, it is necessary to impart anisotropy to a transparent substrate coated with a polymer having photochromic residues. For this purpose, it is effective to deposit an oxide such as 5iOz on the transparent substrate itself from an oblique direction, or to apply a rubbing treatment to finely deform the surface. Alternatively, after coating the transparent substrate with a polymer having 27 q ki of photochromic acid, rubbing treatment q may be performed. Furthermore, if the substrate is a polymer sheet, it can be stretched after being coated with a polymer having photochromic residues.

Next, as the liquid crystal for the liquid crystal layer provided on the polymer layer that undergoes a reversible structural change when exposed to light, any liquid crystal material can be selected from among the conventionally known nematic, smectic, and cholesteric liquid crystal materials. However, in the case of smectic liquid crystal materials, it is necessary to choose one that takes a nematic liquid crystal phase at a certain temperature. It goes without saying that liquid crystal substances include not only low molecular weight substances but also high molecular weight substances.

Such liquid crystal materials are, for example, Nie Pekin (A, Be
``Molecular Crystals and Liquid Crystals (M. Qu in) et al.

1ecular crystals and 1
iquid Crystals) J, Volume 115, Page 1. Polymeric liquid crystal materials are, for example, manufactured by Advances in Polymer Science (A
dvances in Polymar 5cf
ence), Volume 60/61 (1984). These liquid crystal substances may be used alone or in combination of two or more.

Next, the present invention will be explained in more detail with reference to the accompanying drawings.

Figure 1 is a cross-sectional view showing the basic structure of the present invention, in which a molecular layer 2 of a polymer compound having residues that undergoes a reversible structural change when exposed to light is fixed on a transparent substrate l, and In order to prevent this, this is further covered with a substrate. This substrate may be transparent or opaque, and its surface may be coated with a molecular layer of a polymer compound having a residue that undergoes a reversible structural change when exposed to light. It is also possible to use one coated with a homogeneous alignment layer that has the function of aligning liquid crystals parallel to the surface.

FIG. 2 shows a substrate 1 illustrating an example of a preferred embodiment of the present invention.
In this figure, f shows the state after light irradiation, and before light irradiation, it has a sandwich structure with a liquid crystal layer sandwiched between them. In the liquid crystal layer, liquid crystals are regularly arranged in a direction (homeotropic) perpendicular to the substrate surface (1). Next, when part (A) of this optical recording element is irradiated with light, the photochromic residue undergoes a structural change, so the vertical alignment marked ff'J in that part is destroyed, and the liquid crystal becomes parallel to the surface ( parallel or homogeneous) arrangement.

Therefore, when placed between two orthogonal polarizers, the area not irradiated with light (B) will be dark and the area irradiated with light (A) will be bright. Therefore, optical information can be read based on the light transmittance. It can be performed. Since light at a wavelength that does not cause photochromism can be used to read information, the information will not be destroyed.

Next, FIG. 3 is an example of an embodiment different from that shown in FIG. 2, and is an example in which a homogeneous orientation calendar 4 is provided on one of the two substrates. This homogeneous alignment layer is
It can be provided by rubbing the substrate surface with polyvinyl alcohol, polyimide resin, polyoxyethylene, etc., or by obliquely vapor-depositing an oxide such as Sin. In this example, on the polymer layer side with photochromic residues, the liquid crystals are aligned perpendicular to the substrate surface, as shown in Figure 3 (■), but on the homogeneous alignment layer side, they are aligned parallel to the substrate. It has a structure arranged in the direction. When this is irradiated with light, the liquid crystals in the irradiated area (A) are aligned parallel to the surface of the photochromic polymer layer, so the whole becomes a homogeneous array, and optical information is transmitted by polarized light in the same way as above. Can be read.

In the optical recording element of the present invention, if it is desired to erase information that has been recorded, the dichroic dye is dissolved in advance in the photochromic liquid crystal layer by irradiating it with light of a different wavelength from the light used during recording. By placing the dye on the screen, it is possible to read out information based on the shading of the dye without using a polarizing plate.

Examples of dichroic pigments include Naotake Matsuzawa, “Dyeing Industry”
, Vol. 32, p. 2!5 (198) is used.

In this case, if you use a temperature-dependent liquid crystal material, for example, a liquid crystal material that does not change its structure when irradiated with light at room temperature, but undergoes a structural change when heated above a certain temperature, it is possible to develop dichroism. A permanent record can be obtained based on the shade of the pigment.

Effects of the Invention The optical recording element of the present invention has the advantage that it does not exhibit the disadvantages of conventional information recording using photochromic residues, such as the disadvantage that information once recorded gradually disappears due to repeated reading. Since the alignment of the liquid crystal is controlled by the photochromic polymer layer, the resolution of the fluid liquid crystal is much better than that of the conventional liquid crystal in which a photochromic compound is added.

Further, the optical recording element of the present invention can be suitably used not only for reversible optical information storage but also for optically addressed display.

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

Example 1 4-hexyl-4′-hydroxyazobenzene (1) 5
．． 039. 3.579 of ethyl bromoacetate and 3.699 of anhydrous potassium carbonate were added to 15xQ of acetone, which was heated to reflux with stirring for 2 hours. After completion of the reaction, the filtrate was filtered and the solvent was distilled off to obtain crystalline 4-hexyl-4°-ethoxycarbonylmethoxyazobenzene. This was dissolved in dioxane 4QxQ, filtered through this for 1.44 hours, collected, suspended in water, acidified with hydrochloric acid, and stirred with heating for 1 hour. The crystals were collected by filtration and recrystallized from isopropyl alcohol to yield 4.809 4-hexyl-4°-carboxymethoxyazobenzene with a melting point of 188-191°C. 1.739 of this carboxylic acid was added to benzene LOx (l), 3.59 thionyl chloride and 5 drops of dimethylformamide were added, and the mixture was heated under reflux for 2 hours. Excess thionyl chloride was distilled off, and the solvent was distilled off to crystallize The acid chloride was obtained.

Polymerization degree 500, completely saponified polyvinyl alcohol (Nippon Gosei ML-05) 200ml was suspended in 8x dimethylformamide (l), and 1g of pyridine was added to make 11
While heating and stirring at 0°C, 4z (l) of a solution of this acid chloride in methylformamide was added and reacted for 1 hour.

After adding benzene 5zQ, the reaction was further continued for 2 hours. The reaction product was reprecipitated in methanol 2003+12, yellow,! i: The lees were collected by filtration and thoroughly washed with methanol. After drying, a polymer having 1.40 g of abbenzene in the side chain was obtained. From the absorption spectrum, the introduction rate of azobenzene units was 50 mol%.

A 1% toluene solution of this polymer was prepared and spin coated on two glass slides at 80 rpm. A cyclohexanecarboxylic acid phenyl ester mixed liquid crystal (K-17-N-73-1) containing an 8 pm glass rod spacer was sandwiched between these two glass plates and sealed with epoxy resin to create a sandwich cell. This colorless and transparent cell was placed between crossed nicols, and the amount of transmitted light was monitored using a He-Ne laser. It can be seen that the cell before irradiation with ultraviolet rays has zero transmitted light I under crossed Nicol conditions, indicating that the cell is homeotropically aligned as a liquid crystal. When this was irradiated with 365 nm ultraviolet rays, the amount of transmitted light increased as abbenzene photoisomerized from trans to cis. Next, when visible light of 440 nm or more was irradiated, the amount of transmitted light decreased again as trans isomerization occurred. The amount of transmitted light changed reversibly in response to alternate irradiation with ultraviolet light and visible light. In addition, when the same cell was irradiated with ultraviolet rays through a negative film, a clear image was obtained with crossed nicols. Heat treatment was performed at ℃ for 30 minutes. After allowing it to cool, it was immersed in toluene for 1 minute to remove most of the polymer. The absorbance at 340n+n was 0.002, confirming that the polymer was adsorbed on the glass plate. The mixed liquid crystal used in Example 1 was sandwiched between these glass plates,
configured the cell.

When irradiated with ultraviolet rays and visible light alternately, a reversible change in the amount of transmitted light was observed under crossed Nicols conditions. After the entire surface was irradiated with ultraviolet rays, a clear image was obtained when the film was exposed to 488 nm light from an Ar laser through a negative film.

Example 3 Azobenzene-bonded polyvinyl alcohol prepared in the same manner as in Example 1 was spin-coated onto two glass slides, and then heat-treated at 120° C. for 30 minutes. These were rubbed with a cotton cloth so that the rubbing directions matched, and an 8 ptm mixed liquid crystal sandwich cell was constructed in the same manner as in Example 1. When irradiated with ultraviolet rays and visible light alternately, a reversible change in the amount of transmitted light was observed under crossed Nicols conditions.

Example 4 Azobenzene-bonded polyvinyl alcohol prepared in the same manner as in Example 1 was spin-coated onto a slide glass, and then heat-treated at 120° C. for 30 minutes. A 5% solution of partially saponified polyvinyl alcohol with a degree of polymerization of 1400 was spin-coated on another glass sheet at 1+10Q rpm, dried, and rubbed with a cotton cloth. A liquid crystal cell was constructed in the same manner as in Example 1 using these two glass plates.

When a cell was placed between two orthogonal polarizers and alternately irradiated with ultraviolet light and visible light, a reversible change in the amount of transmitted light was observed. At this time, when the rubbing direction between the polarizer and the polyvinyl alcohol film was 45 degrees, the light amount change was greatest.

Example 5 Azobenzenecarboxylic acid in Example 1 1. (+(l
y was converted into an acid chloride using thionyl chloride, and then made into a solution of dimethylacetamide (3112), which was diluted with 2.00
9, polymerization degree 1400, partially saponified polyvinyl alcohol (Nippon Gosei Kaji type GM-14) was added to a dimethylacetamide solution (25g &) heated and dissolved at 110"C.
It was stirred for 2 hours. The reaction product was poured into 300 ml of acetone and reprecipitated to obtain a yellow polymer. This was dissolved again in dimethylacetamide and precipitated again in acetone. This was dried in vacuum. This polymer was dissolved in dimethylacetamide to make a 1% solution, which was spin-coated onto two glass slides and dried at 110°C. The liquid crystal used in Example 1 was sandwiched between these glass plates to form a cell. When this was irradiated with ultraviolet light through the negative image,
A clear image was observed by placing it between two orthogonal polarizing plates.

Example 6 4-cyclohexyl azobenzene was used in place of 4-hexyl-4'-hydroxyazobenzene in Example 1, and reacted with polyvinyl alcohol in the same manner as in Example 1 to obtain a yellow polymer. This was similarly spin-coated onto a glass plate, and then a liquid crystal cell was constructed. When this was irradiated with ultraviolet light through the negative image, a clear image was observed by placing it between two orthogonal polarizing plates.

Example 7 A liquid crystal cell was constructed in exactly the same manner as in Example 1 except that 4-year-old ctyl-4°-hydroxyazobenzene was used instead of 4-hexyl-4°-hydroxyazobenzene. When this was irradiated with ultraviolet light through the negative image,
A clear image was observed by placing it between two orthogonal polarizing plates.

Example 8 Polymer containing azobenzene obtained in Example 1 5. lz9 was dissolved in chloroform 2031+2, and this was irradiated with ultraviolet rays to isomerize abbenzene from trans to cis form. Thereafter, this solution 120)+1 was dropped onto the trough of a Lauda film balance, and it was observed that a monomolecular film was attached. It was confirmed by UV-visible spectrophotometer that an abbenzene group was bonded. When a liquid crystal cell was constructed using the two slopes prepared in this manner and alternately irradiated with visible light and ultraviolet light, the amount of transmitted light changed reversibly.

Example 9 Abbenzene-bonded polyvinyl alcohol prepared in the same manner as in Example 5 was spin-coated onto two glass slides, and then heat-treated at 120° C. for 30 minutes. After rubbing these with cotton cloth, a cell was constructed using the liquid crystal used in Example 1. At this time, the glass plates were arranged so that the respective rubbing directions were perpendicular to each other. Alternate irradiation with ultraviolet and visible light showed homeotropic and twisted orientation changes, and the amount of transmitted light was reversibly changed.

Example 10 Two glass plates spin-coated with azobenzene-bonded polyvinyl alcohol prepared in Example 1 were coated with 4-octyl-4'-cyanobiphenyl (K-21-S-33), which is in a smectic liquid crystal phase at room temperature. -N-40-1) sandwich cell (cell thickness: 81 Jm) was constructed. Even when the cell was irradiated with ultraviolet rays at room temperature (approximately 20°C), no phase change was observed in the liquid crystal, but when the cell was heated to 35°C and then irradiated with ultraviolet rays, a change in the amount of transmitted light was observed under crossed Nicols conditions. Admitted. An image obtained by passing a negative through this cell and irradiating it with ultraviolet rays at 35° C. remained stable for 6 months at room temperature.

This image did not disappear even when the cell was irradiated with visible light. From this, a memory effect due to the smectic liquid crystal was recognized.

Example 11 The polymer containing abbenzene used in Example 1 was made to have a thickness of 50 mm.
)Ill polyester film and cut it into 5CII+×5CI11. 2% by weight of anthracene dichroic dye (structural formula A) was dissolved in a cyclohexanecarboxylic acid phenyl ester mixed liquid crystal containing an 8PII+ glass spacer, and this was sandwiched between two prepared '7'lf lumes. When this was irradiated with ultraviolet light through a mask, a deep blue image with a pale blue background appeared in the exposed areas. When this was illuminated with visible light, the image disappeared and turned pale blue again.

Structural warrior

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 is a sectional view showing one example of the structure of the optical recording element of the present invention, FIG. 2 is a sectional view showing another example and the alignment state of liquid crystal before and after light irradiation, FIG. 3 is a cross-sectional view showing yet another example and the arrangement state of liquid crystals before and after light irradiation. In the figure, reference numeral I indicates a substrate, 2 a polymer layer having a residue that undergoes a reversible structural change when exposed to light, 3 a liquid crystal layer, and 4 a homogeneous alignment layer. Nu 1 figure 21211 (ri (ff) 3 figures (I) (n)

Claims (1)

[Claims] An optical recording material in which a liquid crystal layer is provided on a transparent substrate with a polymer layer containing residues that undergo structural changes reversibly when exposed to light.