JP2001233893A - Liquid crystal compound bearing a photosensitive site, liquid crystal additive and optical recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cholesteric liquid crystal compound that has good photorespontivity and shows high storage stability of the fixed color without acceleration of crystallization, even when it is held at room temperature after the color fixation and provide a optical recording medium comprising the liquid crystal compound. SOLUTION: The objective liquid crystal compound is represented by the following general formula (1) (wherein A is H or a 1-20C organic group, Y is an azo-benzene group; Z is a cholesteryl group; R is a 2-30C divalent organic group), has the molecular weight of <=3,000, the glass transition point of >=35 deg.C and this liquid crystal compound is used to obtain the objective optical recording medium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a liquid crystal compound and an optical recording medium.

[0002]

2. Description of the Related Art A color photograph and a color copy are known as recording materials capable of recording full color and not rewriting. Non-full-color rewritable recording materials include thermosensitive recording materials containing long-chain alkyl carboxylic acid derivatives such as behenic acid, optical recording materials using photochromic compounds such as spiropyran derivatives, and memories such as magnetism and magnetomagnetism. Materials are known.
Recently, as a rewritable full-color thermal recording material, Tamaki et al.
A method using a cholesteric liquid crystal compound having a temperature of 5 ° C. or higher is shown (N. Tamaoki et al., Advanced Materials, 9
(14), 1102 (1997)). There, the cholesteric reflection color is preserved in the glassy solid by a rapid cooling operation from the liquid crystal temperature. Tamaki et al. Further described a rewritable full-color recording material and an image forming method in optical mode having a molecular weight of 200.
This is achieved by irradiating a composition obtained by adding a photochromic compound such as an azobenzene derivative to a cholesteric liquid crystalline compound having a glass transition temperature of 35 ° C. or higher with a temperature of 0 or less. Due to light irradiation at the cholesteric liquid crystal temperature, the reflection color of the light irradiation part changes continuously depending on the light irradiation amount,
It has the property that the reflected color can be maintained even in a glassy solid by a subsequent quenching operation to a glass transition temperature or lower.

Tamaki et al. Have proposed a light-rewritable color recording material comprising a mixture of a cholesteric liquid crystal compound having a molecular weight of 2,000 or less and a glass transition temperature of 35 ° C. or more and a photochromic compound added thereto. However, in the case of this color recording material, if a photochromic compound is added in an amount of 10% by weight or more to enhance the photoresponsiveness, crystallization after color fixation is promoted, and there is a problem in stable storage of the fixed color at room temperature. I understood that.

[0004]

DISCLOSURE OF THE INVENTION The present invention has good photoresponsiveness, and does not promote crystallization even when kept at room temperature after color fixation, and has excellent storage stability of fixed colors. An object of the present invention is to provide a cholesteric liquid crystal compound and an optical recording medium comprising the liquid crystal compound.

[0005]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, have completed the present invention. That is, according to the present invention, the following general formula (1)

Embedded image Z—O—CO—R—CO—O—Y—A (1) (wherein A is a hydrogen atom or an organic group having 1 to 20 carbon atoms;
Is an azobenzene group, Z is a cholesteryl group, and R is carbon number 2.
To 30 divalent organic groups), having a molecular weight of 3000 or less and a glass transition temperature of 35 ° C. or more. Further, according to the present invention, there is provided an optical recording medium comprising the liquid crystalline compound.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The liquid crystalline compound of the present invention is a diester compound represented by the general formula (1).

In the general formula (1), A represents a hydrogen atom or an organic group having 1 to 20 carbon atoms. In this case, the organic group includes an aliphatic group having 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms, an aromatic group having 6 to 20 carbon atoms, preferably 6 to 12 carbon atoms, or 1 to 20 carbon atoms, preferably 1 to 12 carbon atoms. A hydrocarbon oxy group having 12 hydrocarbon groups is shown.

[0008] Aliphatic groups include linear and cyclic saturated or unsaturated aliphatic groups. The chain aliphatic group includes an alkyl group and an alkenyl group. Specific examples thereof include, for example, those having 1 to 1 carbon atoms such as methyl, ethyl, propyl, butyl, hexyl, propenyl, and hexenyl.
6 lower alkyl or alkenyl groups; 7-1 carbon atoms such as heptyl, octyl, decyl, octynyl, decenyl and the like.
1 middle alkyl group or alkenyl group; and higher alkyl or alkenyl groups having 12 to 20 carbon atoms such as dodecyl, octadecyl, behenyl, dodecenyl, octadecenyl and the like. The cycloaliphatic group includes a cycloalkyl group and a cycloalkenyl group. Its carbon number is 5
20, preferably 6-12. Specific examples thereof include, for example, cyclohexyl, cyclohexenyl, cyclooctyl, cyclohexylmethyl, cyclohexyloctyl and the like.

The aromatic groups include those having a condensed polycyclic aromatic ring such as a naphthalene ring and an anthracene ring in addition to a benzene ring, and a chain polycyclic aromatic ring such as biphenyl and terphenyl. Specific examples thereof include aryl groups such as phenyl, tolyl, xylyl, naphthyl, and methylnaphthyl; and alkylaryl groups such as benzyl, phenethyl, naphthylmethyl, and naphthylethyl.

The hydrocarbon oxy group includes those having an aliphatic group and an aromatic group. As a specific example,
Methoxy, ethoxy, propoxy, octyloxy, dodecyloxy, phenoxy, benzyloxy and the like.

Y represents an azobenzene group. This azobenzene group is represented by the following formula (3).

Embedded image In the above formula, two benzene rings may have a substituent.

R has 2 to 30 carbon atoms, preferably 8 to 24 carbon atoms.
Represents a divalent organic group. In this case, the divalent organic group includes an aliphatic group and an aromatic group. In addition, the aliphatic group,
It includes a linear or cyclic saturated or unsaturated divalent aliphatic hydrocarbon group having 2 to 30, preferably 8 carbon atoms.
~ 24. Unsaturated aliphatic groups include those having a double bond or a triple bond. The divalent aromatic group includes a monocyclic aromatic hydrocarbon having one benzene ring (benzene,
Divalent hydrocarbon groups derived from toluene, xylene, etc.) and divalent hydrocarbon groups derived from polycyclic aromatic hydrocarbons having two or more, usually 2 to 4 benzene rings (naphthalene, biphenyl, terphenyl, etc.). Valent hydrocarbon groups.

The divalent organic group R is preferably an unsaturated aliphatic group represented by the following general formula (2).

Embedded image _{- (CH 2) m-C≡C} -C≡C- (CH 2) n- (2) In the formula, m and n is an integer of 1 or more independently, that m and n Is 26 or less, preferably 20 or less, and its lower limit is about 4. Z represents a cholesteryl group which is a residue obtained by removing a hydroxyl group (OH) from cholesterol.

Specific examples of preferred liquid crystalline compounds according to the present invention are as follows.

Embedded image (In the formula, n and m each represent a number of 4 to 10, preferably 8, and Z represents a cholesteryl group.)

Embedded image (Wherein, n represents a number of 10 to 22, preferably 20;
Z represents a cholesteryl group)

Embedded image (Wherein, R ¹ represents an alkyl group having ¹ to 16, preferably 7, carbon atoms, n and m each represent a number of 4 to 10, preferably 8, and Z represents a cholesteryl group)

The compound of the present invention is obtained by stirring cholesterol, the corresponding dicarboxylic acid compound and the corresponding hydroxyazobenzene compound in methylene chloride in the presence of dicyclohexylcarbodiimide and 4-dimethylaminopyridine at room temperature. The precipitate can be separated from the obtained reaction product by a filter, and then purified by column chromatography of the solution and silica gel (developing solvent is a mixture of methylene chloride and hexane at a volume ratio of 3: 2). .

The optical recording medium of the present invention has the general formula (1)
It consists of a liquid crystalline compound represented by these. In this case, the molecular weight of the liquid crystal compound is 3000 or less, preferably 2000 or less, and its lower limit is about 700. Its glass transition temperature is above 35 ° C., preferably 50
° C or higher, and its upper limit is about 90 ° C.

The optical recording medium of the present invention may comprise another cholesteric liquid crystal compound in addition to a single or a mixture of the above liquid crystal compounds. Examples of such a liquid crystal compound include a compound represented by the following general formula (8).

Embedded image ZO—CO—R—CO—O—Y (8) In the above formula, Z and Y each independently represent a cholesteryl group, a hydrogen atom or an alkyl group, and R has 2 to 3 carbon atoms.
0 represents a divalent organic group, and at least one of Z and Y represents a cholesteryl group. Specific examples of R include those shown for the general formula (1). The content of the cholesteric liquid crystal compound represented by the general formula (8) is 1 to 99 by weight in the total liquid crystal compound.
%, Preferably 50 to 98%.

The form of the optical recording medium of the present invention may be a conventionally known form. For example, the optical recording medium of the present invention can have the liquid crystalline compound according to the present invention or a mixture containing the same interposed between two substrates at least one of which is transparent. In this case, a thin glass plate or the like is usually used as the substrate, but a polymer thin film or a metal plate may be used. One of the two sheets needs to be transparent so that at least a part of the light is transmitted. As a method of sandwiching a liquid crystal compound or a mixture between two substrates,
First, the liquid crystalline compound or mixture is heated to a temperature of a molten state or a liquid crystal state, and then added to one substrate and then placed on the other substrate, or a pressure reduction or a capillary phenomenon is caused between two substrates kept in parallel. There is a method of using and adding. The distance between the substrates is not particularly limited, but is preferably about several microns to 100 microns. Partial or total heating of this medium is performed by a thermal head, heating roll,
All methods are possible, such as a laser beam. Heating that requires temperature control to the liquid crystal temperature range can be achieved by controlling the temperature of the thermal head or heating roll, adjusting the intensity or spot diameter of the laser beam, or by heating the whole to a certain temperature and then imaging it. This is possible by lowering the temperature to the required temperature with a flat metal plate or rubber plate. The light source for photoreacting the photosensitive liquid crystal compound according to the present invention can be selected according to the absorption wavelength of the compound, such as a mercury lamp, a xenon lamp, a tungsten lamp, and a laser. The rapid cooling to the glass transition temperature or lower includes a method of immersing the entire sample in a refrigerant or a cooled atmosphere, a method of bringing a part of the sample into contact with a cooled head, and the like.

The optical recording medium according to the present invention is a rewritable color image recording medium that can be recorded by light irradiation for a short time. In order to form an image using this, a liquid crystal compound or a mixture thereof sandwiched between substrates, from the transparent substrate side, the liquid crystal compound or a mixture thereof contains a liquid crystal containing the liquid crystal compound of the present invention. Image information can be written and stored by irradiating light at a temperature indicating a phase and then rapidly cooling to a temperature below the glass transition temperature. Particularly, in the mixture containing the liquid crystal compound of the present invention, the compound to be mixed and the compound to be mixed have commonality such as a molecular weight and a functional group. It is possible to suppress the stored image information for a long time at room temperature.

The image information obtained by the present invention can be erased any number of times by recording once and heating the whole or a part of the image information above the melting point of the liquid crystalline compound or a mixture thereof. Optical recording can be performed by the method. When the liquid crystalline compound according to the present invention is used, image information can be written by only partially irradiating the compound in a liquid crystal state through a mask with light weak enough to cause a photoisomerization reaction, thereby partially changing optical properties. In this case, image information can be stored by fixing the optical properties by a quenching operation. For example, if light irradiation is performed in a cholesteric liquid crystal state having an optical property of reflecting light in the visible region, the reflection color of the unirradiated portion remains unchanged, and the light-irradiated portion is shorter than the unirradiated portion depending on the amount of light irradiation. Since light of a wavelength is reflected, color image information of at least two colors can be recorded. In addition, if light is irradiated to the cholesteric liquid crystal state having reflection in the infrared region, the unirradiated portion is transparent because light in the visible region is not reflected,
The light-irradiated portion reflects light having a shorter wavelength than the unirradiated portion, that is, light in the visible region, depending on the amount of light irradiation, so that color image information with a transparent background can be recorded. Also, by increasing the amount of light irradiation, a phase transition occurs, and the light irradiation part becomes an isotropic liquid state.
Image information having contrast between the light scattering state and the light reflection state can also be recorded. Furthermore, the liquid crystal state is not limited to the cholesteric liquid crystal phase, and since the optical properties of only the light-irradiated part change in the nematic and smectic phases, image information due to the contrast between the light-irradiated part and the non-irradiated part must be recorded. Can be.

[0021]

Next, the present invention will be described in more detail with reference to examples.

Example 1 Synthesis of a liquid crystal compound having the following structural formula

Embedded image (Wherein, Z represents a cholesteryl group)

1.90 g of 10,12-docosadiynedicarboxylic acid, 2.14 of dicyclohexylcarbodiimide
g, a solution of 2.00 g of 4-hydroxyazobenzene and 1.03 g of cholesterol in 40 ml of methylene chloride were slowly added dropwise to a solution of 0.12 g of 4-dimethylaminopyridine in 30 ml of methylene chloride, and the mixture was stirred at room temperature for 6 hours. After filtering the insoluble matter in the reaction mixture, the solution was mixed with a mixed solvent of methylene chloride and n-hexane (volume ratio = 3:
After separation and purification by column chromatography using 2) as a developing solvent, the solvent was removed under reduced pressure to obtain 0.18 g of the desired compound.
I got Molecular weight: 911, isotropic phase → liquid crystal phase: 79 ° C., liquid crystal phase → crystal: 26 ° C., glass transition temperature: 47 ° C. ¹ H-N
MR data (CDCl ₃ ) 0.65 to 2.60 (m, 7
5H), 4.60 (m, 1H), 5.34 (m, 1
H), 7.22 (d, 2H), 7.48 (m, 3H),
7.91 (m, 4H)

Example 2 Synthesis of a liquid crystalline compound having the following structural formula

Embedded image (Wherein, Z represents a cholesteryl group)

1.87 g of docosadicarboxylic acid, dicyclohexane
Hexylcarbodiimide 2.08 g, 4-dimethylamido
Dissolve 0.09 g of pyridine in 60 ml of methylene chloride
1.00 g of 4-hydroxyazobenzene was added to the solution
Dissolve 1.95 g of sterol in 110 ml of methylene chloride
The solution was added dropwise slowly and stirred at room temperature for 15 hours. reaction
After filtration of the insolubles in the mixture, the solution was washed with methylene chloride and n-
Using a mixed solvent of hexane (volume ratio = 3: 2) as a developing solvent
After separation and purification by column chromatography
Removal under pressure yielded 0.25 g of the desired compound. Molecular weight:
919, isotropic phase → liquid crystal phase: 101 ° C., liquid crystal phase → crystal: 8
1 ° C, glass transition temperature: 60 ° C ¹ H-NMR data (CDCl_Three) 0.65 to 2.62
(M, 83H), 4.60 (m, 1H), 5.37
(M, 1H), 7.23 (d, 2H), 7.51 (m,
3H), 7.93 (m, 4H)

Example 3 Synthesis of a liquid crystalline compound having the following structural formula

Embedded image (Wherein, Z represents a cholesteryl group)

10,12-docosadiyne dicarboxylic acid
1.87 g, dicyclohexylcarbodiimide 2,08
g, 4-dimethylaminopyridine 0.09 g in methyl chloride
Add 4-hydroxy-4 'to the solution dissolved in 50 ml
1.49 g of butyl azobenzene, 1.9 of cholesterol
5 g of methylene chloride and 100 ml of methylene chloride
After separation by column chromatography using a solvent,
The solvent is removed from the filtered filtrate by filtration
A crystal was obtained. Recrystallize with ether to obtain the desired compound
0.30 g was obtained. Molecular weight: 1010, isotropic phase → liquid crystal
Phase: 111 ° C, liquid crystal phase → crystal: 33 ° C, glass transition temperature
Degree: 47 ° C ¹ H-NMR data (CDCl_Three) 0.67 to 2.68
(M, 90H), 4.65 (m, 1H), 5.39
(M, 1H), 7.23 (d, 2H), 7, 31 (d,
2H), 7.83 (d, 2H), 7.93 (d, 2H)

Example 4 The compound 9 of Example 1 is sandwiched between two glass plates having a thickness of 0.18 mm, and the whole is heated to 95 ° C. and melted, and the thickness of the sample portion becomes about 10 μm. Was adjusted as follows. Then 7
When the sample was placed on a hot stage maintained at 0 ° C., the whole exhibited a green reflection color. When ultraviolet rays from a mercury lamp were partially irradiated through the mask for 15 seconds, the irradiated portion turned blue and the unirradiated portion remained green. After ultraviolet irradiation, the sample was immersed in ice water and rapidly cooled to 0 ° C., and the color was fixed. The fixed color was stable at room temperature for more than 2 days.

Example 5 The whole color-fixed sample obtained in Example 4 was heated again to 95 ° C. and melted to erase the fixed color. Next, when the sample was placed on a hot stage maintained at 70 ° C., the whole exhibited a green reflection color. When UV light from a mercury lamp was partially irradiated for 1 minute therethrough via a mask, the irradiated part changed to transparent (change from cholesteric liquid crystal to isotropic liquid), and the unirradiated part remained green. After ultraviolet irradiation, the sample was immersed in ice water and rapidly cooled to 0 ° C., whereupon the light-irradiated part was fixed in a light-scattering state and the unirradiated part remained green, but the color was fixed. The fixed color etc. was stable at room temperature for more than 2 days.

Example 6 The compound 10 of Example 2 is sandwiched between two quartz plates having a thickness of 0.18 mm, and the whole is heated to 110 ° C. and melted, and the thickness of the sample portion becomes about 10 μm. Was adjusted as follows. Next, when the sample was placed on a hot stage maintained at 90 ° C., the whole color turned green. When ultraviolet rays from a mercury lamp were partially irradiated through the mask for 15 seconds, the irradiated part turned blue and the unirradiated part remained as it was. After ultraviolet irradiation, the sample was immersed in ice water and rapidly cooled to 0 ° C., and the color was fixed. The fixed color was stable at room temperature for more than 30 days.

Example 7 A mixture of the compound 9 of Example 1 and the compound 10 of Example 2 (1: 1 by weight) was sandwiched between two quartz plates having a thickness of 0.18 mm. Then, the sample was heated and melted, and the thickness of the sample portion was adjusted to about 10 μm. Next, when the sample was placed on a hot stage maintained at 80 ° C., the whole turned yellow-green. When ultraviolet rays from a mercury lamp were partially irradiated through the mask for 30 seconds, the irradiated portion changed to transparent and the unirradiated portion remained unchanged. When the sample was immersed in ice water and rapidly cooled to 0 ° C. after ultraviolet irradiation, the light-irradiated portion was fixed in a light-scattering state and the non-irradiated portion was fixed in yellow-green color. The fixed color etc. was stable at room temperature for 30 days or more.

Example 8 A mixture obtained by mixing 10% by weight of the compound 9 of Example 1 with 10,12-docosadiindicholesteryl ester (compound 12 shown below) which is a cholesteric liquid crystal compound has a thickness of 0.1%.
It was sandwiched between two 18 mm quartz plates, and the whole was heated to 130 ° C. and melted to adjust the thickness of the sample portion to about 10 μm. Next, when the sample was placed on a hot stage maintained at 85 ° C., the whole turned green. When UV light from a mercury lamp was partially irradiated through the mask for 30 seconds, the irradiated portion turned blue, and the unirradiated portion remained unchanged. After UV irradiation, immerse the sample in ice water
Upon quenching to ℃, the color was fixed. When the reflection spectra of the irradiated part and the unirradiated part were measured, the maximum wavelength of the reflection peak was 498 nm and 523 nm, respectively. The fixed color was stable at room temperature for more than 30 days.

[0033]

Embedded image (Wherein, Z represents a cholesteryl group)

Example 9 A mixture obtained by mixing 20% by weight of the compound 9 of Example 1 with the compound 12 which is a cholesteric liquid crystal compound has a thickness of 0.1%.
It was sandwiched between two 18 mm quartz plates, and the whole was heated to 130 ° C. and melted to adjust the thickness of the sample portion to about 10 μm. Next, when the sample was placed on a hot stage maintained at 75 ° C., the whole was green. When UV light from a mercury lamp was partially irradiated through the mask for 30 seconds, the irradiated portion turned blue, and the unirradiated portion remained unchanged. After UV irradiation, immerse the sample in ice water
Upon quenching to ℃, the color was fixed.

Example 10 A mixture obtained by mixing 10% by weight of the compound 11 of Example 3 with the compound 12 as a cholesteric liquid crystal compound was sandwiched between two quartz plates having a thickness of 0.18 mm.
The sample was melted by heating to ℃, and the thickness of the sample portion was adjusted to about 10 μm. Next, when the sample was placed on a hot stage maintained at 90 ° C., the whole became transparent (cholesteric liquid crystal having reflection in an infrared region). When UV light from a mercury lamp was partially irradiated through the mask for 30 seconds, the light-irradiated part changed to blue, the light-irradiated part at 25% changed to green, and the non-irradiated part remained original transparent. After the ultraviolet irradiation, the sample was immersed in ice water and rapidly cooled to 0 ° C., whereupon the unirradiated part was transparent, and the irradiated part was fixed in blue and green. The fixed color was stable at room temperature for more than 10 days.

Example 11 A mixture obtained by mixing 2% by weight of the compound 11 of Example 3 with the above-mentioned compound 12 which is a cholesteric liquid crystal compound has a thickness of 0.1%.
It was sandwiched between two 18 mm quartz plates, and the whole was heated to 130 ° C. and melted to adjust the thickness of the sample portion to about 10 μm. Next, when the sample was placed on a hot stage maintained at 88 ° C., the whole color turned orange.
The UV light from the mercury lamp was partially passed through the mask
Upon irradiation for 0 seconds, the irradiated part turned blue, and the unirradiated part remained unchanged. After ultraviolet irradiation, the sample was immersed in ice water and rapidly cooled to 0 ° C., and the color was fixed. The fixed color was stable at room temperature for more than 10 days.

[0037]

EFFECT OF THE INVENTION By using the liquid crystalline compound of the present invention, it has good photoresponsiveness, furthermore, crystallization is not promoted even if it is kept at room temperature after color fixing, and the storage stability of the fixed color An excellent optical recording medium can be obtained.

Continuation of the front page (71) Applicant 597072464 Hiroo Matsuda 1966-8 Uenomuro, Tsukuba City, Ibaraki Prefecture (72) Inventor Nobuyuki Tamaki 1-1-1, Higashi 1-chome, Tsukuba City, Ibaraki Pref. Hiroo 1-1-1 Higashi, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology (72) Inventor Masaya Moriyama 4-1-8, Honcho, Kawaguchi-shi, Saitama F-term (Reference) 2H111 HA07 HA35 4C091 AA01 BB06 CC01 DD01 EE05 FF01 GG01 HH01 JJ03 KK01 LL01 MM03 NN01 NN05 PA02 PB05 QQ01 4H027 BA02 BD08 DM03

Claims (6)

[Claims] 1. The following general formula (1): ZO—CO—R—CO—O—Y—A (1) (where A is a hydrogen atom or an organic group having 1 to 20 carbon atoms) , Y
Is an azobenzene group, Z is a cholesteryl group, and R is carbon number 2.
A divalent organic group having a molecular weight of 3000 or less and a glass transition temperature of 35 ° C. or more. 2. The divalent organic group represented by R is represented by the following formula (2): — (CH ₂ ) m—C≡C—C≡C— (CH ₂ ) n— (2) Wherein m and n are each independently an integer of 1 or more, provided that the sum of m and n is 26 or less). 3. The liquid crystalline compound according to claim 1, wherein the divalent organic group represented by R is an alkylene group having 2 to 30 carbon atoms. 4. An optical recording medium comprising the liquid crystalline compound of claim 1 alone. 5. The method according to claim 1, wherein the liquid crystalline compound is at least 2
An optical recording medium using a composition in which the types are mixed. 6. A liquid crystal composition obtained by adding at least one kind of the compound of claim 1 to a cholesteric liquid crystal compound having a molecular weight of 2,000 or less and a glass transition temperature of 35 ° C. or more, or a mixture thereof. And an optical recording medium using those compositions.