JP2008222829A - Chiral agent, polymerizable liquid crystal composition, optical element and optical recording/reproducing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a chiral agent and the like exhibiting high light resistance against blue laser light, and an optical element using the same. <P>SOLUTION: The chiral agent is represented by general formula (1) (wherein P<SP>1</SP>and P<SP>2</SP>are each independently a 10-20C hydrocarbon group which bears one 1,4-cyclohexylene group and may bear an ether oxygen or an ester bond therein and the hydrogen atoms of which may be replaced by a fluorine atom; and one of P<SP>1</SP>and P<SP>2</SP>further contains a polymerizable functional group). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a chiral agent, a polymerizable liquid crystal composition containing the same, an optical element using the same, and an optical recording / reproducing apparatus.

  The liquid crystal molecules in the cholesteric liquid crystal have a helically twisted orientation and have a property of selectively reflecting one of the left and right circularly polarized light components corresponding to the helical pitch. For this reason, cholesteric liquid crystals are used in various optical elements. Such a cholesteric liquid crystal can be obtained by adding a chiral agent having an asymmetric center to a liquid crystal material such as a nematic liquid crystal material.

  As the cholesteric liquid crystal, a polymer type cholesteric liquid crystal is useful because of its good temperature characteristics and high reliability. The polymer cholesteric liquid crystal can be obtained by polymerizing a polymerizable liquid crystal composition containing a liquid crystalline compound having a polymerizable functional group and a chiral agent having a polymerizable functional group.

  Conventionally, various chiral agents added to a liquid crystal material in order to obtain a cholesteric liquid crystal have been developed. For example, a chiral agent having an isosorbide skeleton structure is disclosed.

  As a chiral agent having an isosorbide skeleton structure, for example, Patent Document 1 discloses a compound having a symmetric structure centered on an isosorbide skeleton structure and 2 to 6 polymerizable groups. Further, Patent Document 2 discloses a chiral dopant having an isosorbide skeleton structure but having no polymerizable functional group. Furthermore, Patent Document 3 discloses a chiral compound having an isosorbide skeleton structure and having different numbers of rings on both sides of the isosorbide skeleton structure.

  However, when the compound disclosed in Patent Document 1 is mixed with a polymerizable liquid crystal compound and polymerized as a polymerizable liquid crystal composition to obtain a polymer cholesteric liquid crystal, the following problems have occurred. The polymerization rate of the compound having 2 to 6 polymerizable groups as disclosed in Patent Document 1 is faster than the polymerization rate of the monofunctional polymerizable liquid crystalline compound. For this reason, at the initial stage of the polymerization reaction, a large proportion of the compound having 2 to 6 polymerizable groups as disclosed in Patent Document 1 contributes to the polymerization reaction, while at the later stage of the polymerization reaction. Has a large proportion of contribution to the polymerization reaction of a monofunctional polymerizable liquid crystalline compound. Therefore, the composition of the polymer obtained by the polymerization reaction may vary between the initial stage of polymerization and the late stage of polymerization. As a result, the selective reflection band of the polymer cholesteric liquid crystal obtained may be wider than the selective reflection band in the liquid crystal composition before polymerization, or the rectangular shape of the selective reflection band may collapse. The selective reflection band of the polymer cholesteric liquid crystal means a wavelength region of light in which the polymer cholesteric liquid crystal selectively reflects one of the left and right circularly polarized components.

Further, a chiral dopant having an isosorbide skeleton structure but not having a polymerizable functional group as disclosed in Patent Document 2 may have low compatibility with a polymerizable liquid crystal compound.
For this reason, when polymerizing a polymerizable liquid crystalline compound, phase separation may occur between the obtained polymer and the chiral dopant. Moreover, a chiral dopant may precipitate after superposition | polymerization of a polymeric liquid crystalline compound. Furthermore, since the chiral dopant as disclosed in Patent Document 2 does not have a polymerizable functional group, a high molecular cholesteric liquid crystal cannot be produced.

  In recent years, in order to increase the capacity of optical disks, it has been promoted to shorten the wavelength of laser light used for writing and reading information and to reduce the size of concave and convex pits on the optical disk. Laser light with a wavelength of 780 nm is used for CDs and laser light with a wavelength of 660 nm is used for DVDs, but the use of laser light with a wavelength of 300 to 450 nm is being studied for next-generation optical disks. Accordingly, there is a demand for an optical element for modulating laser light with a wavelength of 300 to 450 nm (hereinafter also referred to as blue laser light).

  However, the conventionally known chiral agents described in Patent Documents 1 and 3 have insufficient light resistance against blue laser light, and have been problematic for use in optical elements for next-generation optical disks.

JP 9-506088 gazette Special Table 2000-51596 JP 2003-137877 A

  An object of the present invention is a photocurable chiral agent having high light resistance to blue laser light, which is excellent in compatibility with a polymerizable liquid crystal compound and is mixed with the polymerizable liquid crystal compound to obtain a polymerizable liquid crystal composition. It is to provide a chiral agent capable of uniform polymerization even when polymerized as.

The inventors of the present invention are compounds having a sorbitol skeleton, and a compound having a specific group as a substituent exhibits high light resistance against blue laser light and is excellent in compatibility with a polymerizable liquid crystal compound. It was found that even when mixed with a polymerizable liquid crystal compound and polymerized as a polymerizable liquid crystal composition, uniform polymerization is possible and an optical element having excellent characteristics can be obtained.
That is, the present invention provides the following inventions.

[1] A chiral agent represented by the following general formula (1),
P ¹ and P ² are each carbon number independently containing one 1,4-cyclohexylene group is 10 to 20 hydrocarbon group, optionally having an oxygen atom or an ester bond of an ether bonding in the radical A chiral agent, wherein a hydrogen atom in the group may be substituted with a fluorine atom, and ^one of P ¹ and P ² further contains a polymerizable functional group.

[2] A chiral agent represented by the following general formula (1A) or the following general formula (1B),
Q ¹ and Q ⁴ are each independently
_{^{CH 2 = CR 1 -COO- (L}} ) m -E 1 -
A group represented by
Q ² and ^{Q 3} are each independently,
-E ² -R ²
A group represented by
R ¹ is a hydrogen atom or a methyl group,
R ² is a group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, an alkoxy group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, and a fluorine atom. A group selected from
m is 0 or 1,
L is optionally substituted by fluorine atom _{(CH 2) p O -,} - (CH 2) q - or _{- (CH} 2) r OCO-, or a combination of the same group or different groups thereof,
p, q and r are integers of 2 or more and 8 or less when used alone, and in the case of a combination of the same group or different groups, the total number of methylene groups is 2 or more and 8 or less,
E ¹ and E ² are the chiral agents according to the above [1], which is a 1,4-cyclohexylene group.

[3] The chiral agent according to [2], wherein R ² is a group selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a fluorine atom.

[4] The chiral agent according to any one of [1] to [3], which has a molar extinction coefficient of 20000 or less at a wavelength of 250 nm.

[5] A polymerizable liquid crystal composition comprising a polymerizable liquid crystal compound and the chiral agent according to any one of [1] to [4].

[6] An optical element comprising a polymer liquid crystal obtained by polymerizing a polymerizable liquid crystal composition according to [5] sandwiched between a pair of substrates whose surfaces are subjected to alignment treatment .

[7] A first optical material having an isotropic refractive index and a polymer liquid crystal obtained by polymerizing the polymerizable liquid crystal composition according to the above [5] have an anisotropic second refractive index. A diffractive optical element, wherein optical materials are arranged in a lattice pattern.

[8] The refractive index of the first optical material with respect to the first circularly polarized light is substantially equal to the refractive index of the second optical material with respect to the first circularly polarized light, and is opposite to the first circularly polarized light. The refractive optical element according to [7], wherein a refractive index of the first optical material with respect to the rotating second circularly polarized light is different from a refractive index of the second optical material with respect to the second circularly polarized light.

[9] An optical information recording / reproducing apparatus for recording information on an optical recording medium and / or reproducing information recorded on an optical recording medium, including the diffractive optical element according to [7] or [8] An optical recording / reproducing apparatus.

Since the chiral agent of the present invention has a cyclohexylene group having a small absorption coefficient in the wavelength region of 300 to 450 nm in the structure, light deterioration due to blue laser light is suppressed, and as a result, light resistance to blue laser light is excellent. A chiral agent can be provided. In addition, since P ¹ and P ² each have only one cyclohexylene group, it is easy to improve compatibility with other polymerizable liquid crystal compounds. In addition, by providing a polymerizable functional group on ^{one of} the materials P ¹ and P ² , there is less change in properties at the initial and final stages due to the early polymerization of only the chiral agent, and a uniform polymer is obtained. It becomes easy to be done.

Next, embodiments of the present invention will be described with reference to the drawings.
The chiral agent of the present invention is a chiral agent represented by the following general formula (1),
P ¹ and P ² are each independently a hydrocarbon group having 10 to 20 carbon atoms including one 1,4-cyclohexylene group, and has an etheric oxygen atom or ester bond in the group. Alternatively, a hydrogen atom in the group may be substituted with a fluorine atom, and ^one of P ¹ and P ² further contains a polymerizable functional group.
That is, the compound represented by the general formula (1) is a chiral agent having an asymmetric carbon atom.

Here, each of P ¹ and P ² is a hydrocarbon group having 10 to 20 carbon atoms including one 1,4-cyclohexylene group. This hydrocarbon group may have an etheric oxygen atom or ester bond in the group, and the hydrogen atom in the group may be substituted with a fluorine atom. That is, each of P ¹ and P ² contains only one 1,4-cyclohexylene group. Thereby, the light resistance with respect to a blue laser beam can be improved, and compatibility with another polymeric liquid crystal compound can also be improved. Further, since the absorption is small even in the ultraviolet region, the transparency is high.

  This is because the use of a cyclohexylene group instead of a phenyl group as the ring structure shortens the absorption wavelength and improves the light resistance against blue lasers. Moreover, it is because a crystallization point becomes small compared with a polycyclic ring by making one ring on both sides of sorbitol. When preparing a composition containing a chiral agent and a polymerizable liquid crystal compound, if these materials have a high melting point, heating is necessary to sufficiently mix them. Due to this heating, a non-uniform thermal polymerization reaction tends to proceed, and it may be difficult to obtain a uniform polymer cholesteric liquid crystal. Further, when the crystallization point is high, a chiral agent is likely to be precipitated in the composition, and the polymer cholesteric liquid crystal may be nonuniform.

Moreover, ^one of P ¹ and P ² contains a polymerizable functional group. In other words, ^one of P ¹ and P ² contains a polymerizable functional group, and the other does not contain a polymerizable functional group. The polymerizable functional group is a functional group containing a carbon-carbon double bond (—C═C—). Examples of the polymerizable functional group include an acryloyl group (CH ₂ ═CHCOO—) and a methacryloyl group (CH ₂ ═C (CH ₃ ) COO—).

P ¹ and P ² are each preferably a group in which the hydrogen atom of the carboxyl group of 4-substituted-cyclohexanecarboxylic acid is removed. One of 4-positions of P ¹ and P ² has a substituent having a polymerizable unsaturated group, and the other 4-position has a substituent having no polymerizable unsaturated group. As the substituent having no polymerizable unsaturated group, R ² described later is preferable, and an alkyl group having 8 or less carbon atoms is particularly preferable. The substituent having a polymerizable unsaturated group is preferably CH ₂ ═CR ¹ —COO— (L) _m — (R ¹ , L and m are the same as those described later), and in particular, CH ₂ ═CR ¹ —COO. — (CH ₂ ) _r —OCO— (R ¹ and r are the same as those described later) is preferable.

In the present invention, a chiral agent having high light resistance against blue laser light can be provided. The term light resistance Kr laser at temperature 80 ° C. (wavelength 407 nm, multimode 413 nm), in an acceleration test for the total irradiation exposure energy 15W · hour / mm ^2, is determined from the variation value of the light transmittance at 405nm . When this fluctuation value is small, it is assumed that the light resistance is high.

Further, the chiral agent of the present invention can have a high HTP (Helical Twisting Power). Chiral HTP is
HTP = (PC) ⁻¹
P represents the pitch (μm) of the cholesteric liquid crystal by the chiral agent, and C represents the concentration (mass%) of the chiral agent in the composition containing the chiral agent.
Furthermore, the change in HTP of the chiral agent with respect to the temperature change of the chiral agent of the present invention is relatively small.

The chiral agent of the present invention is preferably a chiral agent represented by the following general formula (1A) or the following general formula (1B). The compound represented by the following general formula (1A) or general formula (1B) is a chiral agent having an asymmetric carbon atom.
Larger HTP can be produced by linking an ester bond-cyclohexylene group to the skeleton of isosorbide. In addition, the structure is similar to that of the liquid crystal compound, so that the compatibility with the liquid crystal compound and the composition is good, and phase separation hardly occurs during polymerization. In particular, the addition amount of the chiral agent for moving the selective reflection region from 400 nm to 500 nm is small, and the compatibility with the liquid crystal composition as the host is good, and the crystallization point is relatively mixed by mixing with the chiral agent. A low liquid crystal composition can be provided.

Here, Q ¹ and Q ⁴ are each independently a group represented by CH ₂ ═CR ¹ —COO— (L) _m —E ¹ —. Q ² and Q ³ are each independently a group represented by -E ² -R ² .

R ¹ is a hydrogen atom or a methyl group, and preferably a hydrogen atom. R ² is a group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, an alkoxy group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, and a fluorine atom. It is a group selected more.

  The alkyl group having 1 to 8 carbon atoms is a linear or branched alkyl group having 1 to 8 carbon atoms, and is a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, s -Butyl group, t-butyl group, n-pentyl group, n-hexyl group, n-heptyl group, n-octyl group and the like. The alkoxy group having 1 to 8 carbon atoms is a linear or branched alkoxy group having 1 to 8 carbon atoms, and includes a methoxy group, an ethoxy group, a propoxy group, a butoxy group, an n-pentyloxy group, and an n-hexyl group. An oxy group, n-heptyloxy group, n-octyloxy group, etc. are mentioned.

In the chiral agent of the present invention, preferably, from the viewpoint of increasing HTP, R ² is a group selected from the group consisting of an alkyl group having 1 to 8 carbon atoms and an alkoxy group having 1 to 8 carbon atoms. It is preferable. Specifically, an n-propyl group, a pentyl group, and an n-heptyl group are preferable.

m is 0 or 1, and 1 is preferable. L is — (CH ₂ ) _p O—, — (CH ₂ ) _q — and — (CH ₂ ) _r OCO—, or a combination of these same or different groups. That _is, - the _{(CH 2) p3 O- (CH} 2) r1 OCO- different groups as _{- (CH 2) p1 O- (} CH 2) may be combined p2 O-same groups _as, You may combine. Among them, _{- (CH} 2) preferably includes a r OCO-.

p, q, and r are integers of 2 or more and 8 or less when used alone. In the case of a combination of the same group or different groups, the total number of methylene groups is 2 or more and 8 or less. That is, as in the above _example, - _(CH 2) if p1 _{O- (CH 2)} p2 _O- of, and a p1 + p2 2 to 8 _{integer, - (CH 2) p3 O-} (CH 2 In the case of _r1 OCO-, p3 + r1 is an integer of 2 or more and 8 or less. In particular, it is preferable to use an integer of 2 or more and 4 or less because temperature characteristics are improved.

E ¹ and ^{E 2,} 1,4-cyclohexylene to a xylene group includes one each as a ring structure ^{Q 1} and ^{Q 2} or ^{Q 3} and ^{Q 4.} This 1,4-cyclohexylene group improves the light resistance to blue laser light. This 1,4-cyclohexylene group can be used in cis or trans, unlike a normal liquid crystal, but is a trans-1,4-cyclohexylene group in terms of compatibility with a polymerizable liquid crystal compound. It is preferable.

As the chiral agent of the present invention, the following compounds are preferable. ^A preferable embodiment of the Q 1 to Q ⁴ are illustrated in the following compounds.

Thus, the chiral agent of the present invention has one 1,4-cyclohexylene group on each side of the isosorbide-derived central skeleton, and a polymerizable functional group only on one side of the isosorbide-derived central skeleton. , preferably a -COO- _CH 2 ⁼ CR 1.

  The chiral agent of the present invention is characterized by high light resistance to blue laser light and large HTP. Furthermore, it is excellent in compatibility with other polymerizable liquid crystal compounds, and a uniform polymer is easily obtained.

  The compound of general formula (1A) and the compound of general formula (1B) of the chiral agent of the present invention can be synthesized, for example, by the following method. In the formula, EDC represents 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride, and DMAP represents 4-dimethylaminopyridine.

[Synthesis Method 1]
Among the chiral agents of the present invention, the compound represented by the general formula (1A) obtains a compound (3A) by a condensation reaction between isosorbide (2) and a predetermined first carboxylic acid (Q ² COOH), then compound (3A), to give compound (1A) by reacting a second acid ^(Q 1 COOH).

[Synthesis Method 2]
In addition, the compound represented by the general formula (1B) is obtained by a condensation reaction between isosorbide (2) and a predetermined carboxylic acid (Q ⁴ COOH), and then the compound (3B) and an acid salt are obtained. Compound (1B) can be obtained by reaction with the product (Q ³ COCl).

As Q ¹ COOH, Q ² COOH, Q ³ COCl, and Q ⁴ COOH, commercially available compounds can be used as they are, or derived from commercially available compounds.

  The chiral agent of the present invention is used as a polymerizable liquid crystal composition by mixing with a polymerizable liquid crystal compound. The chiral agent of the present invention is contained in 1 to 20 parts by weight in 100 parts by weight of the polymerizable liquid crystal composition. Components other than the chiral agent include 50 to 98 parts by weight of a polymerizable liquid crystal compound, 0 to 30 parts by weight of a polymerizable non-liquid crystal compound, 0.1 to 5 parts by weight of a photocuring initiator, and 0 to 10 parts by weight of other additives. Yes, the final composition may have liquid crystallinity. In particular, a composition curable by photopolymerization is preferable because it can be easily cured while maintaining liquid crystallinity.

  This polymerizable liquid crystal composition is used by being sandwiched between a pair of substrates whose surfaces are subjected to alignment treatment and polymerized. Specifically, an alignment film is formed by forming a polyimide film or the like on the surface of a substrate such as glass or plastic and rubbing or oblique deposition. This substrate is disposed so that the alignment treatment surfaces face each other, and the polymerizable liquid crystal composition is sandwiched.

  For this purpose, a sealing material is arranged around the substrate, the two substrates are bonded together with a certain gap to form an empty cell, and a polymerizable liquid crystal composition is injected from the injection port. What is necessary is just to harden. Moreover, it can also manufacture using the method of arrange | positioning a sealing material around the one board | substrate, pouring a polymeric liquid crystal composition, and adhere | attaching a sealing part, pressing the other board | substrate on it.

  In the above description, only the alignment film has been touched for the sake of simplicity, but an electrode is provided for controlling the optical characteristics, a reflective film is provided for use as a reflective element, and the surface of the substrate is Fresnel. A lens configuration, a grating for diffraction grating, a colored layer for color tone adjustment, a low reflection layer for suppressing stray light, and the like may be provided.

  When used as a diffractive optical element, it is necessary to form a grating on the inner surface of the substrate. Usually, it is obtained by forming a grating of the first optical material having an isotropic refractive index in advance and filling the remaining portion with the polymerizable liquid crystal composition containing the chiral agent of the present invention for polymerization. A second optical material made of a polymer liquid crystal and having an anisotropic refractive index is disposed. Thereby, a polarization diffractive optical element can be formed. Although the process is complicated, on the contrary, a grating of the second optical material having an anisotropic refractive index is formed in advance by the polymerizable liquid crystal composition, and then the refractive index is isotropic in the remaining portion. It is also possible to fill and cure the first optical material.

  In this case, the refractive index of the first optical material with respect to the first circularly polarized light is substantially equal to the refractive index of the second optical material with respect to the first circularly polarized light, and is opposite to the first circularly polarized light. The refractive index of the first optical material with respect to the rotating second circularly polarized light can be different from the refractive index of the second optical material with respect to the second circularly polarized light. Thereby, the first circularly polarized light can be transmitted, and the diffraction amount of the second circularly polarized light can be adjusted by the thickness of the grating.

The optical element of the present invention can be used for a polarization diffraction optical element, a phase difference plate, a wavefront correction element, and the like. Such an optical element is suitable for use in an optical information recording / reproducing apparatus that records information on an optical recording medium and / or reproduces information recorded on the optical recording medium in the optical path of a laser beam. .
In particular, it is suitable for an optical head for an optical information recording / reproducing apparatus using blue laser light such as BD and HDDVD which has recently been put into practical use.

Example 1 Synthesis of Chiral Agent (B1) Compound (B1) was synthesized according to Synthesis Method 2 described above.

(1) Synthesis of Compound Q ⁴ COOH (B1-1) In a 500 mL three-necked flask equipped with a stirrer, a dropping funnel and a reflux tube, 17.2 g (0. 1) of trans-1,4-cyclohexanedicarboxylic acid (4) was added. 1 mol), 23.6 g (0.2 mol) of thionyl chloride, 2 drops of DMF, and 500 mL of toluene were added, and the mixture was heated to reflux at 110 ° C. for 3 hours. After completion of the reaction, the solution was concentrated at 70 ° C. Trans-1,4-cyclohexanedicarboxylic acid chloride (5), which is an acid chloride obtained by completely distilling off the solvent, was dissolved in 1 L of dichloromethane.

  A solution of 14.4 g (0.1 mol) of 4-hydroxybutyl acrylate (6) and 7.9 g (0.1 mol) of pyridine in 1 L of dichloromethane was dissolved in a dichloromethane solution of the acid chloride over 3 hours. It was dripped slowly. After stirring at room temperature for 1 hour, 100 mL of water was added to stop the reaction. After completion of the reaction, the organic layer was recovered by washing with water and dichloromethane. The organic layer was dried over anhydrous magnesium sulfate, then anhydrous magnesium sulfate was removed by filtration under reduced pressure, and the filtrate was concentrated. The filtrate was purified by column chromatography (ethyl acetate: hexane = 1: 1 as a developing solvent) to obtain compound (B1-1). The yield was 13.4 g, the yield was 45%, and the GC purity was 97%.

¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
1.41-2.11 (m, 12H), 2.30-2.35 (m, 2H), 4.28-4.38 (m, 4H), 5.86-6.46 (m, 3H) )

(2) Synthesis of Compound (B1-2) 15.8 g (0.042 mol) of Compound (B1-1), 6.1 g (0.042 mol) of isosorbide (2), 1-ethyl-3 in a 500 mL three-necked flask -(3-dimethylaminopropyl) carbodiimide hydrochloride 16 g (0.083 mol), 4-dimethylaminopyridine 0.7 g and dichloromethane 200 mL were added and stirred at room temperature overnight, and then 100 mL of 1 mol / L aqueous ammonium chloride solution was added. The reaction was stopped. Subsequently, water and dichloromethane were added to the reaction solution for washing, and the collected organic layer was washed with 5% hydrochloric acid aqueous solution and saturated sodium chloride aqueous solution. The organic layer was dried over anhydrous magnesium sulfate, the anhydrous magnesium sulfate was removed by filtration under reduced pressure, and the solvent was concentrated. The obtained filtrate was purified by column chromatography (hexane: ethyl acetate = 5: 5 as a developing solvent) to obtain compound (B1-2). The yield was 12.3 g, and the yield was 68.7%.

¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
1.26 to 3.57 (m, 15H), 3.58 to 3.76 (m, 1H), 3.76 to 4.62 (m, 10H), 5.23 (s, 1H), 5. 82-7.30 (m, 3H)

(3) Synthesis of Compound (B1-3) In a 500 mL three-necked flask under nitrogen atmosphere, trans-4-n-pentylcyclohexanecarboxylic acid (7) 6.55 g (0.033 mol), thionyl chloride 7.8 g (0 0.066 mol), 2 drops of DMF and 200 mL of toluene were added, and the mixture was refluxed at 100 ° C. for 3 hours. Thereafter, the reaction solution was concentrated to obtain trans-4-n-pentylcyclohexanecarbonyl chloride (B1-3).

(4) Synthesis of Compound (B1) In a 500 mL three-necked flask equipped with a stirrer and a reflux tube, 6.56 g (0.022 mol) of the compound (B1-2) synthesized above and 3.34 g (0.32 g) of triethylamine were added. 033 mol) and 150 mL of dichloromethane were added and the mixture was stirred at room temperature. Next, 5.7 g (0.026 mol) of trans-4-n-pentylcyclohexanecarbonyl chloride (B1-3) synthesized above was dissolved in 50 mL dichloromethane and slowly added dropwise to the mixture over 5 minutes. After stirring overnight at room temperature, the reaction was quenched with 50 mL of water. The organic layer was recovered by partitioning with dichloromethane and water. Further, the organic layer was sufficiently separated with an aqueous sodium hydrogen carbonate solution, and unreacted carboxylic acid was transferred to the aqueous layer.
The collected organic layer was washed with a 5% aqueous hydrochloric acid solution, and then the organic layer was dried over anhydrous magnesium sulfate, filtered, and the solvent was concentrated. The obtained filtrate was purified by column chromatography (hexane: ethyl acetate = 3: 2 as a developing solvent) and recrystallized from methanol to obtain compound (B1). The yield was 7.9 g, and the yield was 60%. The NMR analysis result of the compound (B1) was as follows.

¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
0.86-2.29 (m, 35H), 3.92-4.21 (m, 8H), 4.44-4.84 (m, 2H), 5.12-5.19 (m, 2H) ) 5.82-6.43 (m, 3H)

Example 2 Synthesis of Chiral Agent (B2) Compound (B2) was synthesized according to Synthesis Method 2 described above.

In the same manner as in Example 1, compound (B1-2) was reacted with trans-4-n-propylcyclohexanecarbonyl chloride, which is an acid chloride obtained from trans-4-n-propylcyclohexanecarboxylic acid, to give compound ( B2) was obtained. The yield of the compound (B2) was 60.0%, and the NMR analysis result for the compound (B2) was as follows.
¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
0.86-2.29 (m, 31H), 3.91-4.46 (m, 8H), 4.44-4.83 (m, 2H), 5.12-5.18 (m, 2H) ) 5.82-6.43 (m, 3H)

Example 3 Synthesis of Chiral Agent (B3) Compound (B3) was synthesized according to Synthesis Method 2 described above.

(1) Synthesis of Compound Q ⁴ COOH (B3-1) Trans-1,4-cyclohexanedicarboxylic acid in the same reaction as in Example 1, except that 2-hydroxyethyl acrylate (8) was used instead of 4-hydroxybutyl acrylate. Compound (B3-1) was synthesized by a reaction with an acid chloride obtained from an acid. The yield was 42%.

¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
1.41-2.11 (m, 8H), 2.3-2.35 (m, 2H), 4.28-6.46 (m, 4H), 5.88-6.46 (m, 3H) )

(2) Synthesis of Compound (B3-2) The compound (B3-2) was reacted with isosorbide (2) using the compound (B3-1) instead of the compound (B1-1) by the same reaction as the compound of Example 1. -2) was synthesized. The yield was 70%.

¹ HNMR (400 MHz, solvent: CDCl _3, internal standard: TMS) δ (ppm)
1.26 to 3.57 (m, 11H), 3.58 to 3.76 (m, 1H), 3.76 to 4.65 (m, 10H), 5.23 (s, 1H), 5. 8-6.43 (m, 3H)

(3) Synthesis of Compound (B3) Acid chloride (trans-4-n-pentyl) obtained from compound (B3-2) and trans-4-n-pentylcyclohexanecarboxylic acid by the same reaction as the compound of Example 1 Compound (B3) was synthesized by reaction with cyclohexanecarbonyl chloride. The yield was 65.0%, and the NMR analysis result for the compound (B3) was as follows.

¹ HNMR (400 MHz, solvent: CDCl ₃ , internal standard: TMS) δ (ppm)
0.88-2.29 (m, 31H), 3.91-3.96 (m, 4H), 4.35-4.36 (m, 5H), 4.82-5.18 (m, 3H) ) 5.82-6.43 (m, 3H)

[Example 4] Evaluation of physical properties of chiral agent (1)
The melting point, HTP (helical twisting power), and optical rotation of the chiral agents synthesized in Examples 1 to 3 were measured as follows.

(1) Method for Measuring Melting Point of Chiral Agent A cell was formed by sandwiching synthesized chiral agent crystals between two preparations, and the cell was heated at a rate of 5 ° C./min. While the temperature of the cell was raised, the cell was observed with a microscope, and the temperature at which the melting of the chiral agent crystal began to be observed was taken as the melting point of the chiral agent.

(2) Preparation of polymerizable liquid crystal composition 90 parts by weight of the following polymerizable liquid crystal compound (R1) and the following polymerizable liquid crystal compound (R2) mixed at 11: 9 (molar ratio) is a compound that is a chiral agent ( The polymerizable liquid crystal composition 1 was prepared by adding 10 parts by weight of B1). Next, 0.5 part by weight of a photopolymerization initiator was added to the polymerizable liquid crystal composition 1 with respect to 100 parts by weight of the liquid crystal composition 1 to obtain a polymerizable liquid crystal composition 1A. Similarly, a polymerizable liquid crystal composition 2A to which 10 parts by weight of the compound (B2) was added and a polymerizable liquid crystal composition 3A to which 10 parts by weight of the compound (B3) were added were also prepared. In addition, “Irgacure 754” manufactured by Ciba Specialty Chemicals was used as the photopolymerization initiator.

As a comparative example, a chiral agent (9) in which E ¹ and E ² in the present invention are not 1,4-cyclohexylene groups but 1,4-phenylene groups was prepared. Further, an ^{E 1} is 1,4-phenylene group, ^{E 2} was prepared 1,4-cyclohexylene group of the chiral agent (10). 10 parts by weight of the chiral agent (9) is added to 90 parts by weight of the following polymerizable liquid crystal compound (R1) and the following polymerizable liquid crystal compound (R2) mixed at 11: 9 (molar ratio), and the same as above. A liquid polymerization composition 4A was prepared by adding 0.5 parts by weight of a photopolymerization initiator.

(3) Measurement of HTP of chiral agent Each of the prepared polymerizable liquid crystal compositions 1A to 4A was injected into a wedge-shaped cell in which the value of tan θ was measured in an isotropic phase. The cell was cooled to room temperature, and the HTP of the chiral agent was calculated by the Grandjean-Cano wedge method using a microscope. The results are shown in Table 1.

(4) Measurement of optical rotatory power of chiral agent One part by weight of two kinds of chiral agents whose optical rotations are levorotatory and dextrorotatory are respectively added to 99 parts by weight of a cyanobiphenyl-based nematic liquid crystal (“5CB” manufactured by Aldrich). By mixing, liquid crystal compositions 9 and 10 for optical rotation test were prepared. Similarly, 1 part by weight of each of compounds (B1) to (B3) and the compound (9) of Comparative Example was mixed with 5CB to prepare liquid crystal composition parts 5 to 8. A two-hole cell made by EHC (cell gap: 10 μm) was prepared, liquid crystal compositions 5 to 8 were injected from the left hole of the cell, and the above optical rotation was the left or right optical rotation from the right hole. The liquid crystal compositions 9 and 10 for test were injected, and the optical rotation was judged by a method (contact method) of observing the contact portion of the liquid near the center of the cell. The results are shown in Table 1.

[Example 5] Evaluation of physical properties of chiral agent (2)
The chiral agent (B1) of the present invention, the compound (9) and the compound (10) described above as comparative examples were each dissolved in THF so as to have a concentration of 10 ⁻⁵ mol / L, and the absorption maximum wavelength (λmax), absorption Table 2 shows the results of measuring the molar absorption coefficient ε at the edge wavelength and 250 nm.

A graph showing the relationship between the molar extinction coefficient and the wavelength of the chiral agent (B1) of the present invention and the chiral agents (9) and (10) of the comparative examples is shown in FIG. In the above table, the molar extinction coefficient at 250 nm is shown, but in the graph, the molar extinction coefficient depending on the wavelength can be seen in more detail.
The chiral agent having a cyclohexane ring of the present invention exhibits a lower molar extinction coefficient to the shorter wavelength side than the chiral agent containing a benzene ring of Comparative Example. The chiral agent of the comparative example rapidly increases in molar extinction coefficient from around 290 nm, whereas the chiral agent of the present invention has a gradual increase in molar extinction coefficient, and a molar extinction coefficient of about 20000 or less even in the 250 nm wavelength region. Indicates.

[Example 6] Preparation of optical element (1) Preparation of polymerizable liquid crystal composition 90 parts by weight of the following polymerizable liquid crystal compound (R3) and the following polymerizable liquid crystal compound (R4) mixed at 1: 1 (molar ratio) 10 parts by weight of the compound (B1) which is the chiral agent of the present invention was added to prepare a polymerizable liquid crystal composition 11. Next, 0.5 part by weight of a photopolymerization initiator (“Irgacure 754” manufactured by Ciba Specialty Chemicals Co., Ltd.) is added to the polymerizable liquid crystal composition 11 with respect to 100 parts by weight of the polymerizable liquid crystal composition 11 to perform polymerization. Liquid crystal composition 11A was obtained.

  As a comparative example, similarly, the following polymerizable liquid crystal compound (R3) and the following polymerizable liquid crystal compound (R4) were mixed at a 1: 1 (molar ratio) to 90 parts by weight, and the compound (4) as the chiral agent described above. 10 parts by weight was added to prepare a polymerizable liquid crystal composition 12. Similarly, 0.5 part by weight of the same photopolymerization initiator as described above was added to the polymerizable liquid crystal composition 12 with respect to 100 parts by weight of the polymerizable liquid crystal composition 12 to obtain a polymerizable liquid crystal composition 12A.

(2) Production of optical element A polyimide substrate was coated on a glass plate having a length of 5 cm, a width of 5 cm, and a thickness of 0.5 mm using a spin coater and dried, followed by rubbing treatment with nylon cloth in a certain direction to produce a glass substrate.
Two glass substrates were bonded to each other with an adhesive so that the surfaces subjected to the alignment treatment face each other to produce a cell. Glass beads having a diameter of 4 μm were added to the adhesive, and the distance between the glass substrates was adjusted to 4 μm.

Next, the polymerizable liquid crystal composition 11A was injected into the cell at 105 ° C. At 50 ° C., an optical element 11 was obtained by performing photopolymerization by irradiating ultraviolet rays having an intensity of 135 mW / cm ^{2 so} that the integrated light amount became 72900 mJ / cm ² .
Similarly, a polymerizable liquid crystal composition 12A was injected into the cell at 105 ° C. At 50 ° C., ultraviolet light having an intensity of 135 mW / cm ² was irradiated so that the integrated light amount was 72900 mJ / cm ² to perform photopolymerization, whereby the optical element 12 was obtained.

(3) Evaluation of optical element Kr laser (wavelength 407nm, multimode of 413nm) was irradiated to the optical element 11 created above, and the blue laser beam exposure acceleration test was done. The irradiation conditions were a temperature of 80 ° C. and an integrated exposure energy of 15 W · hour / mm ² . The variation range of the transmittance after the test with respect to the transmittance of 405 nm before the acceleration test was less than 1%. Similarly, a blue laser light exposure acceleration test was performed on the optical element 12. In the optical element 12, the variation width of the transmittance after the test with respect to the transmittance of 405 nm before the acceleration test was 3.2%.
The chiral agent having only one cyclohexane ring as a ring structure on both sides of the isosorbide structure of the present invention exhibits a low molar extinction coefficient to the short wavelength side, and exhibits a molar extinction coefficient of 20000 or less even in the 250 nm wavelength region. It was confirmed that the optical element produced using this chiral agent was excellent in light resistance against blue laser light.

  According to the present invention, a chiral agent excellent in light resistance with little photodegradation by blue laser light can be obtained, and therefore it is used for optical elements using a blue laser, particularly for reading and writing high-density optical recording media. It is suitable for an optical element for an optical head and an optical head using the optical element.

FIG. 1 is a graph showing the relationship between the molar extinction coefficient and the wavelength of the chiral agent of the present invention and the chiral agent of the comparative example.

Claims (9)

A chiral agent represented by the following general formula (1),
P ¹ and P ² are each independently a hydrocarbon group having 10 to 20 carbon atoms including one 1,4-cyclohexylene group, and has an etheric oxygen atom or ester bond in the group. A chiral agent, wherein a hydrogen atom in the group may be substituted with a fluorine atom, and ^one of P ¹ and P ² further contains a polymerizable functional group.

A chiral agent represented by the following general formula (1A) or the following general formula (1B),
Q ¹ and Q ⁴ are each independently
_{^{CH 2 = CR 1 -COO- (L}} ) m -E 1 -
A group represented by
Q ² and ^{Q 3} are each independently,
-E ² -R ²
A group represented by
R ¹ is a hydrogen atom or a methyl group,
R ² is a group consisting of a hydrogen atom, an alkyl group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, an alkoxy group having 1 to 8 carbon atoms which may be substituted with a fluorine atom, and a fluorine atom. A group selected from
m is 0 or 1,
L is optionally substituted by fluorine atom _{(CH 2) p O -,} - (CH 2) q - or _{- (CH} 2) r OCO-, or a combination of the same group or different groups thereof,
p, q and r are integers of 2 or more and 8 or less when used alone, and in the case of a combination of the same group or different groups, the total number of methylene groups is 2 or more and 8 or less,
The chiral agent according to claim ^1, wherein E ¹ and E ² are 1,4-cyclohexylene groups.

The chiral agent according to claim 2, wherein R ² is a group selected from the group consisting of an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, and a fluorine atom.   The chiral agent according to any one of claims 1 to 3, which has a molar extinction coefficient of 20000 or less at a wavelength of 250 nm.   A polymerizable liquid crystal composition comprising a polymerizable liquid crystal compound and the chiral agent according to claim 1.   6. An optical element comprising a polymer liquid crystal obtained by polymerizing a polymerizable liquid crystal composition according to claim 5 sandwiched between a pair of substrates subjected to alignment treatment on the surface.   A second optical material having an anisotropic refractive index composed of a polymer liquid crystal obtained by polymerizing the first optical material having an isotropic refractive index and the polymerizable liquid crystal composition according to claim 5 is a lattice. A diffractive optical element characterized by being arranged in a shape.   The refractive index of the first optical material with respect to the first circularly polarized light is substantially equal to the refractive index of the second optical material with respect to the first circularly polarized light, and is rotated in a direction opposite to the first circularly polarized light. The diffractive optical element according to claim 7, wherein a refractive index of the first optical material with respect to the second circularly polarized light is different from a refractive index of the second optical material with respect to the second circularly polarized light.   9. An optical information recording / reproducing apparatus for recording information on an optical recording medium and / or reproducing information recorded on an optical recording medium, comprising the diffractive optical element according to claim 7 or 8. Recording / playback device.

Images