JP4834955B2 - Liquid crystal composition - Google Patents

Description

  The present invention relates to a liquid crystal composition used for a variable function device in which a liquid crystal layer is disposed between a conductor line constituting a high frequency line and a ground conductor, and a variable function device using the same.

  In order to use a system with various functions by switching it with a single piece of hardware or using software to switch it programmatically, a device that can electronically change the frequency band, bandwidth, etc., at a high-frequency analog stage is required. It is. For this reason, for example, development of devices capable of variably controlling performance and functions such as variable circuits and devices such as electronic tuning filters, voltage controlled oscillators, variable characteristic amplifiers, phase shifters / attenuators, and the like has been underway.

  As a high-frequency device using a liquid crystal medium as a variable function device, the phase shift of the electromagnetic wave propagating through the microstrip line can be varied or delayed by changing the dielectric constant of the liquid crystal layer depending on whether the drive voltage is applied or not applied. There is disclosed a microwave band variable phase shifter that can be made (see Non-Patent Document 1). In addition, a technique using a polymer dispersed liquid crystal (see Patent Document 1) and a dual frequency drive liquid crystal (see Patent Document 2) as a liquid crystal layer of a variable function device using a liquid crystal medium has been reported.

  In the liquid crystal compositions conventionally used in the variable function devices, the problem is that the phase control range cannot be increased, but this is considered to be caused by the fact that Δε of the liquid crystal composition used is not sufficiently large. It is done. Δε described here refers to Δε in the GHz band rather than Δε in the low frequency region that is often discussed in liquid crystal compositions, but generally a special measuring device is required to measure Δε in the GHz band. However, it cannot be measured easily. However, it is known that the birefringence Δn in the visible light region and Δε in the GHz band are in a proportional relationship, and indirectly in the GHz band by measuring Δn in the visible light region. Δε can be relatively observed.

Based on these findings, in the liquid crystal composition that has been used in the past (see Patent Document 3), Δn in the visible light region is significantly lower than 0.3, so Δε in the GHz band is small, and the range of phase control in variable function devices is reduced. It turned out that it was difficult to make it large enough. However, the development of liquid crystal compositions having Δn exceeding 0.3 is problematic, and even if Δn increases to some extent, there is a problem that the nematic phase-isotropic liquid phase transition temperature T _NI is low, and visible light Development of a liquid crystal composition having a large Δn in the region has been demanded.

JP 2000-315902 A (1 page) JP 2001-237606 A (1 page) Japanese Laid-Open Patent Application No. 08-005996 (pages 5 and 6) D. Dolfi, “Electronics Letters” (UK), 1993, 29, 10, p. 926-927

  An object of the present invention is to develop a composition having a large birefringence Δn and a large dielectric anisotropy Δε in the GHz band in a liquid crystal composition for a variable function device.

  The inventors of the present invention have intensively studied to solve the above-mentioned problems. As a result, it has been found that Δn of the liquid crystal composition can be increased by using a specific liquid crystal compound as a constituent member. It came. The present invention relates to the general formula (I)

（式中、R¹は炭素数が４から１２で二重結合の置換位置が３位以上であるアルケニル基を表し、X¹及びX²はそれぞれ独立してフッ素原子又は水素原子を表す。）で表される化合物及び一般式(II)

(Wherein R ¹ represents an alkenyl group having 4 to 12 carbon atoms and a double bond substitution position of 3 or more, and X ¹ and X ² each independently represents a fluorine atom or a hydrogen atom.) And a compound represented by the general formula (II)

(式中、R²は炭素原子数１から１５のアルキル基、炭素原子数２から１５のアルケニル基又は水素原子を表し、該アルキル基又はアルケニル基は非置換であるか又は置換基として1個又は2個以上のフッ素原子、塩素原子、メチル基又はトリフルオロメチル基を有することができ、該アルキル基又はアルケニル基中に存在する１個又は２個以上のメチレン基は、−CO−で置換されていても良く、酸素原子が相互に直接結合しないものとして、−S−、−O−、−OCOO−、−OCO−又は−COO−で置換されていても良く、
C¹及びC²はそれぞれ独立して、

(Wherein R ² represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, or a hydrogen atom, and the alkyl group or alkenyl group is unsubstituted or represents one substituent. Or two or more fluorine atoms, chlorine atoms, methyl groups or trifluoromethyl groups, and one or more methylene groups present in the alkyl group or alkenyl group are substituted with -CO- May be substituted with -S-, -O-, -OCOO-, -OCO- or -COO-, as oxygen atoms are not directly bonded to each other,
C ¹ and C ² are each independently

(i) trans-1,4-cyclohexylene group (one methylene group present in this group or two or more methylene groups not adjacent to each other may be replaced by -O- or -S-) ),
(ii) a 1,4-phenylene group (one —CH═ present in the group or two or more non-adjacent —CH═ may be replaced by a nitrogen atom);
(iii) 1,4-cyclohexenylene group, 1,4-bicyclo (2.2.2) octylene group, piperidine-1,4-diyl group, naphthalene-2,6-diyl group, 1,2,3,4 A group selected from the group consisting of -tetrahydronaphthalene-2,6-diyl group and decahydronaphthalene-2,6-diyl group, wherein the group (i), group (ii) or group (iii) is cyano Group, fluorine atom or chlorine atom may be substituted,
K ¹ and K ² are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —COO—, —OCO— or —C≡. C-
X ³ , X ⁴ and X ⁶ each independently represent a hydrogen atom or a fluorine atom,
p represents 0, 1 or 2;
X ⁵ represents a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a fluoromethoxy group, a difluoromethoxy group, a trifluoromethoxy group or a 2,2,2-trifluoroethyl group. ), A liquid crystal composition for a variable function device comprising a liquid crystal layer disposed between a conductor line constituting a high frequency line and a ground conductor, and a variable comprising the liquid crystal composition as a constituent member. Provide functional devices.

  Since the liquid crystal composition of the present invention has excellent characteristics such as a large birefringence Δn in the visible light region and a large dielectric anisotropy Δε in the GHz band, the liquid crystal composition is used as a constituent member. It has an excellent effect of expanding the range of phase control in the variable function device. The variable function device of the present invention is useful as a microwave band variable phase shifter or the like.

  In the liquid crystal composition of the present invention, the content of the compound represented by the general formula (I) is preferably 5 to 50% by mass, more preferably 5 to 40% by mass, and particularly preferably 10 to 30% by mass.

In general formula (I), R ¹ is an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, 2 to 10 alkenyl groups, or an alkenyloxy group having 2 to 10 carbon atoms. Are preferred, an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, and an alkenyloxy group are more preferred, and an alkyl group having 1 to 5 carbon atoms, an alkoxy group, and the number of carbon atoms. A alkenyl group having 2 to 5 carbon atoms or an alkenyloxy group having 2 to 5 carbon atoms is particularly preferable. When R ¹ represents an alkenyl group, a structure of the following formula (a) or formula (b) is preferred,

（構造式は右端で環に連結しているものとする。）
特に式（a）が最も好ましい。

(The structural formula shall be connected to the ring at the right end.)
Particularly preferred is formula (a).

X ¹ and X ² each independently represent a fluorine atom or a hydrogen atom, but X ¹ and X ² are both hydrogen atoms, X ¹ is a fluorine atom and X ² is a hydrogen atom or X ¹ is a hydrogen atom and X ² is A compound represented by a fluorine atom is preferred. Specifically, general formula (c), general formula (d), or general formula (e)

（式中、Ｒ^１は炭素数が４から１２で二重結合の置換位置が３位以上であるアルケニル基を表す。）で表される構造が好ましく、特に一般式（ｄ）が最も好ましい。

(Wherein R ¹ represents an alkenyl group having 4 to 12 carbon atoms and a double bond substitution position of 3 or more ), and general formula (d) is most preferred.

  The content of the general formula (II) is 95 to 50% by mass, and the total content of the general formula (I) and the general formula (II) is preferably 60% by mass or more, and the general formula (II) 95 to 60% by mass, and the total content of the general formula (I) and the general formula (II) is more preferably 70% by mass or more, and the general formula (II) is 90 to 70% by mass, and The total content of general formula (I) and general formula (II) is particularly preferably 80% by mass or more.

Although the compound represented by general formula (II) contains many compounds, the following embodiments are preferred. R ² is preferably an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, but an alkyl group having 1 to 8 carbon atoms or 1 carbon atom. More preferred is an alkoxy group having 8 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 5 carbon atoms.

Preferably, C ¹ and C ² each independently represent a structure selected from the group consisting of formula (i), formula (j) and formula (k).

Ｋ^１及びＫ^２はそれぞれ独立して単結合又は−Ｃ≡Ｃ−を表すことが好ましい。

Preferably, K ¹ and K ² each independently represent a single bond or —C≡C—.

X ³ , X ⁴ and X ⁶ each independently represent a hydrogen atom or a fluorine atom.
X ⁵ is preferably a cyano group, a fluorine atom, an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms or an alkenyl group having 2 to 15 carbon atoms, but a fluorine atom, a cyano group or a carbon atom An alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms is more preferable, and an alkyl group having 1 to 5 carbon atoms is particularly preferable.

  Specifically, the compound represented by the general formula (II) includes the following general formula (III-a), general formula (III-b), general formula (IV-a), and general formula (IV-b). Or the compound represented by general formula (V) is preferable.

（式中、Ｒ^３は炭素原子数１〜１５のアルキル基、炭素原子数１〜１５のアルコキシ基又は炭素原子数２〜１５のアルケニル基を表す。）
一般式（III−ａ）又は一般式（III−ｂ）で表される化合物を含有する場合、その含有量は５〜３０質量％が好ましいが、１０〜２０質量％が特に好ましい。
一般式（II）においてＲ³は、炭素原子数１〜８のアルキル基、炭素原子数１〜８のアルコキシ基又は炭素原子数２〜８のアルケニル基が好ましく、炭素原子数１〜５アルキル基がより好ましい。

(In the formula, R ³ represents an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms.)
When the compound represented by the general formula (III-a) or the general formula (III-b) is contained, the content is preferably 5 to 30% by mass, particularly preferably 10 to 20% by mass.
In general formula (II), R ³ is preferably an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and an alkyl group having 1 to 5 carbon atoms. Is more preferable.

(In the formula, R ⁴ and R ⁵ each independently represents an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms.)
When the compound represented by the general formula (IV-a) or the general formula (IV-b) is contained, the content is preferably 10 to 40% by mass, more preferably 15 to 30% by mass, and more preferably 20 to 20% by mass. 30% by mass is particularly preferred.

R ⁴ is more preferably an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms, or an alkenyl group having 2 to 8 carbon atoms, and particularly preferably an alkyl group having 1 to 5 carbon atoms.
R ⁵ is more preferably an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and particularly preferably an alkyl group having 1 to 5 carbon atoms.

（式中、Ｒ⁶は炭素原子数１〜１５のアルキル基、炭素原子数１〜１５のアルコキシ基又は炭素原子数２〜１５のアルケニル基を表す。）
一般式（V−ａ）又は一般式（V−ｂ）で表される化合物を含有する場合、その含有量は１０〜３０質量％が好ましく、１５〜２５質量％がより好ましい。

(In the formula, R ⁶ represents an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms.)
When the compound represented by the general formula (Va) or the general formula (Vb) is contained, the content is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass.

R ⁵⁶ is more preferably an alkyl group having 1 to 8 carbon atoms, an alkoxy group having 1 to 8 carbon atoms or an alkenyl group having 2 to 8 carbon atoms, and particularly preferably an alkyl group having 1 to 5 carbon atoms.

  The birefringence Δn of the liquid crystal composition of the present invention is preferably 0.25 or more at a wavelength of 589 nm, more preferably 0.30 or more, and a larger phase shift conversion is possible by increasing it. It can be.

  In the present invention, the variable function device is not particularly limited as long as the transmission characteristics of the device can be varied by the liquid crystal layer, but it is useful to use as a variable frequency high-frequency transmission line in the microwave band. It is preferably used as a microwave band variable phase shifter that varies the phase characteristics. A microwave band variable phase shifter can also be applied as a beam scanning antenna.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is further explained in full detail, this invention is not limited to these Examples. Further, “%” in the compositions of the following examples and comparative examples means “mass%”.
In the examples, the measured characteristics are as follows.
T _NI : Nematic phase-isotropic liquid phase transition temperature (° C)
Δn: birefringence (20 ° C. and 589 nm)
Vth: Threshold voltage (V) (25 ° C)
The following abbreviations are used in the description of compounds.
-Terminal n (number): -C _n H _{2n + 1} ndm-: C _n H _{2n + 1} -CH = CH- (CH ₂ ) _m-1-
-T-: -C≡C- -ndm:-(C _n H _{2n + 1} -CH = CH- (CH ₂ ) _m-1 )
-F: -F -On: -OC _n H _{2n + 1}
-VO-: -COO- -CN: -C≡N
-Z-: -CH = NN = CH- -CF ₂ O-: -CF ₂ -O-

  For example, abbreviations are used as shown below.

(Examples 1, 2, and 3 and Comparative Examples 1 and 2)
Liquid crystal composition No. 1 (Example 1), No. 2 (Example 2), No. 3 (Example 3) and liquid crystal composition M1 (Comparative Example 1), liquid crystal composition M2 (Comparative Example 2) Table 1 shows the physical property values prepared.

Compared to the liquid crystal compositions of Comparative Examples 1 and 2, the liquid crystal compositions of the examples all have a high birefringence of 0.3 or more, and the nematic phase-isotropic liquid phase transition temperature (T _NI ) is also high. It has high characteristics.

It is a figure which shows the structure of the variable characteristic high frequency electric transmission line which concerns on this invention.

Explanation of symbols

1, 6 ... Ceramic substrate
2 ... Liquid crystal layer
3 ... Conductor line (metal line)
4 ... Alignment film
5 ... Ground surface (metal film)

Claims (9)

Formula (I)

(Wherein R ¹ represents an alkenyl group having 4 to 12 carbon atoms and a double bond substitution position of 3 or more, and X ¹ and X ² each independently represents a fluorine atom or a hydrogen atom.) And a compound represented by the general formula (II)

(Wherein R ² represents an alkyl group having 1 to 15 carbon atoms, an alkenyl group having 2 to 15 carbon atoms, or a hydrogen atom, and the alkyl group or alkenyl group is unsubstituted or represents one substituent. Or two or more fluorine atoms, chlorine atoms, methyl groups or trifluoromethyl groups, and one or more methylene groups present in the alkyl group or alkenyl group are substituted with -CO- May be substituted with -S-, -O-, -OCOO-, -OCO- or -COO-, as oxygen atoms are not directly bonded to each other,
C ¹ and C ² are each independently
(i) a 1,4-phenylene group (one —CH═ present in the group or two or more non-adjacent —CH═ may be replaced by a nitrogen atom);
(ii) a group selected from the group consisting of naphthalene-2,6-diyl groups, wherein the group (i) or group (ii) may be substituted with a cyano group, a fluorine atom or a chlorine atom, respectively. ,
K ¹ and K ² are each independently a single bond, —CH ₂ CH ₂ —, — (CH ₂ ) ₄ —, —OCH ₂ —, —CH ₂ O—, —COO—, —OCO— or —C≡. C-
X ³ , X ⁴ and X ⁶ each independently represent a hydrogen atom or a fluorine atom,
p represents 1 or 2,
X ⁵ represents a hydrogen atom, a fluorine atom, a chlorine atom, a cyano group, a trifluoromethyl group, a fluoromethoxy group, a difluoromethoxy group, a trifluoromethoxy group or a 2,2,2-trifluoroethyl group. ), The content of the compound represented by the general formula (I) is 5 to 50% by mass, and the content of the compound represented by the general formula (II) is 95 to 50% by mass. %, A liquid crystal composition for a variable function device comprising a liquid crystal layer disposed between a conductor line constituting a high frequency line and a ground conductor. The liquid crystal composition according to claim 1, wherein R ¹ represents a structure of the formula (a) or the formula (b).

(The above formula is assumed to be linked to the ring structure on the right side.) The liquid crystal composition according to claim 1, comprising a compound represented by general formula (c), general formula (d), or general formula (e).

(In the formula, R ¹ represents an alkenyl group having 4 to 12 carbon atoms and having a double bond substituted at position 3 or more.) 2. The liquid crystal composition according to claim 1, wherein the total content of the compounds represented by the general formula (I) and the general formula (II) is 60% by mass or more. The liquid crystal composition according to claim ^1, wherein C ¹ and C ² each independently represent a structure of formula (i), formula (j), or formula (k).

The liquid crystal composition according to claim ^1, wherein K ¹ and K ² each independently represent a single bond or —C≡C—. As a compound represented by general formula (II), general formula (III-a), general formula (III-b), general formula (IV-a) , general formula (Va) or general formula (Vb) Compound represented by

(In the formula, R ³ represents an alkyl group having 1 to 15 carbon atoms, an alkoxy group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms, and R ⁴ and R ⁵ are each independently carbon. An alkyl group having 1 to 15 atoms, an alkoxy group having 1 to 15 carbon atoms, or an alkenyl group having 2 to 15 carbon atoms, R ⁶ represents an alkyl group having 1 to 15 carbon atoms, or 1 to 15 carbon atoms. Represents an alkoxy group or an alkenyl group having 2 to 15 carbon atoms.)
The liquid crystal composition according to claim 1, comprising: In the variable function device formed by disposing a liquid crystal layer between a conductor line constituting a high frequency line and a ground conductor, the liquid crystal layer is made of the liquid crystal composition according to any one of claims 1 to 7. Feature variable function device. The variable function device according to claim 8 , wherein the birefringence Δn of the liquid crystal layer is 0.25 or more at a wavelength of 589 nm.

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