JP7310796B2 - liquid crystal display element - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission scattering type liquid crystal display element that becomes a transmission state when a voltage is applied.

A TN (Twisted Nematic) mode has been put into practical use as a liquid crystal display element. In this mode, it is necessary to use a polarizing plate in order to switch light using the optical rotation characteristic of liquid crystal. The use of a polarizing plate lowers the light utilization efficiency.
As a liquid crystal display element that does not use a polarizing plate, there is an element that switches liquid crystal between a transmissive state (also referred to as a transparent state) and a scattering state. In general, liquid crystals using polymer-dispersed liquid crystal (PDLC) or polymer network liquid crystal (PNLC) are known.

In these liquid crystal display elements, a liquid crystal composition containing a polymerizable compound that is polymerized by ultraviolet rays is placed between a pair of substrates provided with electrodes, and the liquid crystal composition is cured by irradiation with ultraviolet rays. It forms a composite with a cured compound (eg, polymer network). In this liquid crystal display element, the scattering state and transmission state of the liquid crystal are controlled by applying a voltage.

In liquid crystal display elements using PDLC or PNLC, when no voltage is applied, the liquid crystal is oriented in random directions, resulting in a cloudy (scattering) state. It becomes a transparent state (also called a normal type element). In this case, since the liquid crystal is random when no voltage is applied, there is no need for a liquid crystal alignment film or alignment treatment for aligning the liquid crystal in one direction. Therefore, in this liquid crystal display element, the electrodes and the liquid crystal layer (the composite of the liquid crystal and the cured product of the polymerizable compound) are in direct contact (see Patent Documents 1 and 2).

Japanese Patent No. 3552328 Japanese Patent No. 4630954

The polymerizable compound in the liquid crystal composition has a role of forming a polymer network to obtain desired optical properties and a role of enhancing adhesion between the liquid crystal layer and the electrodes. However, in order to realize these, it is necessary to form a dense polymer network, which impedes the driving of the liquid crystal molecules with respect to voltage application. for that reason. This element requires a higher driving voltage than a TN mode liquid crystal display element.
In view of the above, it is an object of the present invention to provide a liquid crystal display device that exhibits good optical characteristics and requires a low driving voltage for the liquid crystal display device.

（Ｘ^１は下記式［１－ａ］～式［１－ｊ］を示す。Ｘ^２は単結合、－Ｏ－、－ＮＨ－、－Ｎ（ＣＨ_３）－、－ＣＨ_２Ｏ－、－ＣＯＮＨ－、－ＮＨＣＯ－、－ＣＯＮ（ＣＨ_３）－、－Ｎ（ＣＨ_３）ＣＯ－、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｘ^３は単結合又は－（ＣＨ_２）_ａ－（ａは１～１５の整数である）を示す。Ｘ^４は単結合、－Ｏ－、－ＯＣＨ_２－、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｘ^５はベンゼン環、シクロヘキサン環及び複素環からなる群から選ばれる２価の環状基、又はステロイド骨格を有する炭素数１７～５１の２価の有機基を示し、前記環状基上の任意の水素原子は、炭素数１～３のアルキル基、炭素数１～３のアルコキシ基、炭素数１～３のフッ素含有アルキル基、炭素数１～３のフッ素含有アルコキシ基又はフッ素原子で置換されていてもよい。Ｘ^６は単結合、－Ｏ－、－ＣＨ_２－、－ＯＣＨ_２－、－ＣＨ_２Ｏ－、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｘ^７はベンゼン環、シクロヘキサン環及び複素環からなる群から選ばれる環状基を示し、これらの環状基上の任意の水素原子が、炭素数１～３のアルキル基、炭素数１～３のアルコキシ基、炭素数１～３のフッ素含有アルキル基、炭素数１～３のフッ素含有アルコキシ基又はフッ素原子で置換されていてもよい。Ｘ^８は炭素数１～１８のアルキル基、炭素数２～１８のアルケニル基、炭素数１～１８のフッ素含有アルキル基、炭素数１～１８のアルコキシ基又は炭素数１～１８のフッ素含有アルコキシ基を示す。Ｘｍは０～４の整数を示す。）

（Ｘ^Ａは水素原子又はベンゼン環を示す。）As a result of intensive studies to achieve the above object, the inventors have completed the present invention having the following gist.
That is, the present invention has a liquid crystal layer in which a liquid crystal composition containing a liquid crystal and a polymerizable compound disposed between a pair of substrates provided with electrodes is cured by irradiating with ultraviolet rays, and a scattering state occurs when no voltage is applied. A liquid crystal display element that becomes transparent when a voltage is applied, wherein the liquid crystal has positive dielectric anisotropy, and the liquid crystal composition contains a compound represented by the following formula [1]: A liquid crystal display element characterized by

(X ¹ represents the following formulas [1-a] to [1-j]; X ² is a single bond, -O-, -NH-, -N(CH ₃ )-, -CH ₂ O-, - CONH-, -NHCO-, -CON(CH ₃ )-, -N(CH ₃ )CO-, -COO- or -OCO-, ^{X 3} is a single bond or -(CH ₂ ) _a - (a is is an integer of 1 to 15. X ⁴ represents a single bond, -O-, -OCH ₂ -, -COO- or -OCO-.X ⁵ represents a group consisting of a benzene ring, a cyclohexane ring and a heterocyclic ring. or a divalent organic group having 17 to 51 carbon atoms having a steroid skeleton, wherein any hydrogen atom on the cyclic group is an alkyl group having 1 to 3 carbon atoms, an alkyl group having 1 to 3 carbon atoms, may be substituted with an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms or a fluorine atom, X ⁶ is a single bond, -O-, - CH ₂ —, —OCH ₂ —, —CH ₂ O—, —COO— or —OCO— X ⁷ represents a cyclic group selected from the group consisting of a benzene ring, a cyclohexane ring and a heterocyclic ring, and these cyclic Any hydrogen atom on the group is an alkyl group having 1 to 3 carbon atoms, an alkoxy group having 1 to 3 carbon atoms, a fluorine-containing alkyl group having 1 to 3 carbon atoms, a fluorine-containing alkoxy group having 1 to 3 carbon atoms, or fluorine X ⁸ is an alkyl group having 1 to 18 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, a fluorine-containing alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 18 carbon atoms, or represents a fluorine-containing alkoxy group having 1 to 18 carbon atoms, and Xm represents an integer of 0 to 4.)

(X ^A represents a hydrogen atom or a benzene ring.)

According to the present invention, it is possible to obtain a liquid crystal display device that has good optical characteristics and requires a low driving voltage. Therefore, the element of the present invention is used as a normal type element for a liquid crystal display intended for display, a dimmer window for controlling transmission and blocking of light, an optical shutter element, and the like.
The mechanism by which the liquid crystal display device having the above-described excellent characteristics can be obtained by the present invention is not necessarily clear, but is presumed to be as follows.

The liquid crystal composition used in the present invention contains a liquid crystal having positive dielectric anisotropy, a polymerizable compound, and a compound represented by formula [1] (also referred to as a specific compound). The specific compound has a site with a rigid structure, such as a benzene ring or a cyclohexane ring, and a site that undergoes a polymerization reaction with ultraviolet light, represented by ^X1 in formula [1]. Therefore, when such a specific compound is included in the liquid crystal composition, the rigid structural part of the specific compound enhances the vertical alignment of the liquid crystal, promotes the driving of the liquid crystal with voltage application, and lowers the driving voltage of the liquid crystal display element. can. In addition, the polymer network can be maintained in a dense state by reacting the site of X1 in the formula [ ¹ ] with the polymerizable compound.
From the above points, the liquid crystal display element using the liquid crystal composition of the present invention is a normal type element that has good optical characteristics and a low driving voltage for the liquid crystal display element.

<Liquid crystal composition>
The liquid crystal composition in the invention contains a liquid crystal, a polymerizable compound, and the specific compound represented by the above formula [1].
Nematic liquid crystal, smectic liquid crystal, or cholesteric liquid crystal can be used for the liquid crystal. Among them, in the present invention, it is preferable to have positive dielectric anisotropy. From the viewpoint of low-voltage driving and scattering characteristics, it is preferable that the anisotropy of the dielectric constant is large and the anisotropy of the refractive index is large. In addition, two or more kinds of liquid crystals can be mixed and used for the liquid crystal according to the physical property values of the phase transition temperature, dielectric anisotropy, and refractive index anisotropy.

In order to drive a liquid crystal display element as an active element such as a TFT (Thin Film Transistor), the liquid crystal is required to have a high electric resistance and a high voltage holding ratio (also called VHR). Therefore, it is preferable to use a fluorine-based or chlorine-based liquid crystal, which has a high electrical resistance and does not lower the VHR due to active energy rays such as ultraviolet rays, as the liquid crystal.

Furthermore, the liquid crystal display element can be made into a guest-host type element by dissolving a dichroic dye in the liquid crystal composition. In this case, it is possible to obtain an element that absorbs (scatters) when no voltage is applied and becomes transparent when voltage is applied. Further, in this liquid crystal display element, the direction of the liquid crystal director (orientation direction) changes by 90 degrees depending on the presence or absence of voltage application. Therefore, this liquid crystal display device utilizes the difference in light absorption characteristics of the dichroic dyes to obtain a higher contrast than conventional guest-host type devices that perform switching between random orientation and vertical orientation. In a guest-host type device in which a dichroic dye is dissolved, the device becomes colored when the liquid crystal is aligned in the horizontal direction, and becomes opaque only in the scattering state. Therefore, it is also possible to obtain an element that switches from a colored opaque state when no voltage is applied to a colored transparent state and a colorless transparent state as voltage is applied.

The polymerizable compound in the liquid crystal composition is for forming a curable resin through a polymerization reaction upon irradiation with ultraviolet rays during the production of the liquid crystal display element. Therefore, a polymer obtained by polymerizing a polymerizable compound in advance may be introduced into the liquid crystal composition. However, even if it is made into a polymer, it must have a site that undergoes a polymerization reaction when irradiated with ultraviolet rays. As the polymerizable compound, it is preferable to use a liquid crystal composition containing a polymerizable compound from the viewpoint of handling of the liquid crystal composition, that is, suppression of increase in viscosity of the liquid crystal composition and solubility in liquid crystal.
The polymerizable compound is not particularly limited as long as it dissolves in the liquid crystal, but when the polymerizable compound is dissolved in the liquid crystal, it is necessary that there is a temperature at which part or all of the liquid crystal composition exhibits a liquid crystal phase. Even if a portion of the liquid crystal composition exhibits a liquid crystal phase, the liquid crystal display element should be observed with the naked eye to obtain substantially uniform scattering properties and transparency throughout the element.

Any polymerizable compound may be used as long as it is polymerized by ultraviolet rays, and in that case, the polymerization proceeds in any reaction form to form a curable resin. Specific reaction forms include radical polymerization, cationic polymerization, anionic polymerization, and polyaddition reaction.
Among them, the reaction form of the polymerizable compound is preferably radical polymerization from the viewpoint of the optical properties of the liquid crystal display device. At that time, as the polymerizable compound, the following radical-type polymerizable compound or an oligomer thereof can be used. Moreover, as described above, polymers obtained by polymerizing these polymerizable compounds can also be used.
Specific examples of radical type polymerizable compounds or oligomers thereof include radical type polymerizable compounds described on pages 69 to 71 of International Publication No. 2015/146987 (published October 1, 2015).

The ratio of the radical type polymerizable compound or its oligomer used is preferably 70 to 150 parts by mass with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition, from the viewpoint of adhesion between the liquid crystal layer and the electrode of the liquid crystal display element. , 80 to 110 parts by mass is more preferable. In addition, the radical type polymerizable compound may be used alone or in combination of two or more depending on the properties.
In order to promote the formation of the curable resin, a radical initiator (also referred to as a polymerization initiator) that generates radicals by ultraviolet rays is introduced into the liquid crystal composition for the purpose of promoting radical polymerization of the polymerizable compound. is preferred.
Specific examples include radical initiators described on pages 71 to 72 of International Publication No. 2015/146987.

The ratio of the radical initiator used is preferably 0.01 to 20 parts by mass, preferably 0.05 parts by mass, with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition, from the viewpoint of adhesion between the liquid crystal layer and the electrodes of the liquid crystal display element. ~10 parts by mass is more preferable. Also, the radical initiator can be used alone or in combination of two or more depending on the properties.
The specific compound is a compound represented by the above formula [1].

In formula [1], X ¹ to X ⁸ and Xm are as defined above, and among them, the following are preferred.
X ¹ is preferably the above formula [1-a], formula [1-b], formula [1-c], formula [1-d], formula [1-e] or formula [1-f], and formula [ 1-a], formula [1-b], formula [1-c] or formula [1-e] is more preferred, and formula [1-a] or formula [1-b] is most preferred.
X ² is preferably a single bond, -O-, -CH ₂ O-, -CONH-, -COO- or -OCO-, more preferably a single bond, -O-, -COO- or -OCO-.

X ³ is preferably a single bond or -(CH ₂ ) _a - (a is an integer of 1 to 10), more preferably -(CH ₂ ) _a - (a is an integer of 1 to 10).
X ⁴ is preferably a single bond, -O- or -COO-, more preferably -O-.
^X5 is preferably a C17-51 divalent organic group having a benzene ring, a cyclohexane ring, or a steroid skeleton, more preferably a C17-51 divalent organic group having a benzene ring or a steroid skeleton.
^X6 is preferably a single bond, -O-, -COO- or -OCO-, more preferably a single bond, -COO- or -OCO-.

^X7 is preferably a benzene ring or a cyclohexane ring.
X ⁸ is preferably an alkyl or alkoxy group having 1 to 18 carbon atoms, or an alkenyl group having 2 to 18 carbon atoms, more preferably an alkyl or alkoxy group having 1 to 12 carbon atoms. Xm is preferably an integer of 0-2.

Preferred combinations of X ¹ to X ⁸ and Xm in formula [1] are shown in Tables 1 to 9 below.

Among them, (1-3a) ~ (1-8a), (1-11a) ~ (1-24a), (1-27a) ~ (1-36a), (1-39a), (1-40a) , (1-43a) ~ (1-48a), (1-51a) ~ (1-64a), (1-67a) ~ (1-76a), (1-79a), (1-80a), ( 1-83a) ~ (1-88a), (1-91a) ~ (1-104a), (1-107a) ~ (1-116a), (1-119a), (1-120a), (1- 123a), (1-124a), (1-129a), (1-130a), (1-133a), (1-134a), (1-137a), (1-138a), (1-141a) , (1-142a), (1-145a), (1-146a) or combinations of (1-149a) to (1-172a) are preferred.

More preferably, (1-3a) ~ (1-8a), (1-11a), (1-12a), (1-15a) ~ (1-18a), (1-21a), (1- 22a), (1-27a) to (1-30a), (1-33a), (1-34a), (1-39a), (1-40a), (1-43a) to (1-48a) , (1-51a), (1-52a), (1-55a) ~ (1-58a), (1-61a), (1-62a), (1-67a) ~ (1-70a), ( 1-73a), (1-74a), (1-79a), (1-80a), (1-83a) ~ (1-88a), (1-91a), (1-92a), (1- 95a) ~ (1-98a), (1-101a), (1-102a), (1-107a) ~ (1-110a), (1-113a), (1-114a), (1-119a) , (1-120a), (1-123a), (1-124a), (1-129a), (1-130a), (1-133a), (1-134a), (1-137a), ( 1-138a), (1-141a), (1-142a), (1-145a), (1-146a) or a combination of (1-149a) to (1-172a).

Most preferred are (1-3a) to (1-8a), (1-15a) to (1-18a), (1-29a), (1-30a), (1-43a) to (1- 48a), (1-55a) to (1-58a), (1-69a), (1-70a), (1-83a) to (1-88a), (1-95a) to (1-98a) , (1-109a), (1-110a), (1-123a), (1-124a), (1-133a), (1-134a), (1-141a), (1-142a), ( 1-149a) to (1-152a) or combinations of (1-161a) to (1-172a).

（Ｘ^ａは、－Ｏ－又は－ＣＯＯ－を示す。Ｘ^ｂは、炭素数１～１２のアルキル基を示す。ｐ１は、１～１０の整数を示す。ｐ２は、１又は２の整数を示す。）More specific specific compounds include compounds selected from the group consisting of the following formulas [1a-1] to [1a-11], and these are preferably used.

(X ^a represents -O- or -COO-; X ^b represents an alkyl group having 1 to 12 carbon atoms; p1 represents an integer of 1 to 10; p2 represents an integer of 1 or 2; show.)

（Ｘ^ｃは、単結合、－ＣＯＯ－又は－ＯＣＯ－を示す。Ｘ^ｄは、炭素数１～１２のアルキル基又はアルコキシ基を示す。ｐ３は、１～１０の整数を示す。ｐ４は、１又は２の整数を示す。）

(X ^c represents a single bond, -COO- or -OCO-; X ^d represents an alkyl group or alkoxy group having 1 to 12 carbon atoms; p3 represents an integer of 1 to 10; p4 represents Indicates an integer of 1 or 2.)

（Ｘ^ｅは、－Ｏ－又は－ＣＯＯ－を示す。Ｘ^ｆは、ステロイド骨格を有する炭素数１７～５１の２価の有機基を示す。Ｘ^ｇは、炭素数１～１２のアルキル基又は炭素数２～１８のアルケニル基を示す。ｐ５は、１～１０の整数を示す。）

(X ^e represents -O- or -COO-. X ^f represents a divalent organic group having 17 to 51 carbon atoms and having a steroid skeleton. X ^g represents an alkyl group having 1 to 12 carbon atoms or represents an alkenyl group having 2 to 18 carbon atoms, p5 represents an integer of 1 to 10.)

The content of the specific compound is preferably 0.1 to 30 parts by mass, preferably 0.5 to 30 parts by mass, with respect to 100 parts by mass of the liquid crystal in the liquid crystal composition, from the viewpoint of adhesion between the liquid crystal layer and the electrode of the liquid crystal display element. 20 parts by weight is more preferred, and 1 to 10 parts by weight is most preferred. Also, the specific compound can be used alone or in combination of two or more depending on the properties.

As a method for preparing the liquid crystal composition, a method of adding a mixture of one or more kinds of polymerizable compounds and a specific compound to the liquid crystal, or a method of adding a specific compound to the liquid crystal in advance and adding one or more kinds of and a method of adding a polymerizable compound.
When using a plurality of types of polymerizable compounds, they can be heated according to the solubility of the polymerizable compounds when they are mixed. The temperature at that time is preferably less than 100°C. The same is true when mixing a polymerizable compound and a specific compound, and when mixing a liquid crystal and a specific compound.

<Method for producing liquid crystal display element>
The substrate used for the liquid crystal display element is not particularly limited as long as it is a highly transparent substrate, and in addition to the glass substrate, an acrylic substrate, a polycarbonate substrate, a plastic substrate such as a PET (polyethylene terephthalate) substrate, and films thereof. can be used. In particular, a plastic substrate or film is preferable when used for a light control window or the like. From the viewpoint of process simplification, it is preferable to use a substrate on which an ITO electrode, an IZO (Indium Zinc Oxide) electrode, an IGZO (Indium Gallium Zinc Oxide) electrode, an organic conductive film, or the like is formed for driving the liquid crystal. . In the case of a reflective liquid crystal display element, a silicon wafer, a substrate on which a metal such as aluminum or a dielectric multilayer film is formed can be used if only one substrate is formed.

The liquid crystal composition used for the liquid crystal display element is the liquid crystal composition as described above, and a spacer for controlling the electrode gap (also referred to as gap) of the liquid crystal display element can be introduced thereinto.
The method of injecting the liquid crystal composition is not particularly limited, but includes, for example, the following method. That is, when glass substrates are used as the substrates, a pair of substrates are prepared, four pieces of one substrate are coated with a sealing agent except for a part, and then the electrode surface is turned inside, and the other substrate is coated with a sealant. An empty cell is produced by pasting the substrates together. Then, there is a method of obtaining a liquid crystal composition-injected cell by injecting the liquid crystal composition under reduced pressure from a place where the sealant is not applied. Furthermore, when a plastic substrate or film is used as the substrate, a pair of substrates are prepared, and the liquid crystal composition is dropped onto one of the substrates by an ODF (One Drop Filling) method, an inkjet method, or the like. A method of obtaining a liquid crystal composition-injected cell by bonding the substrates on one side is mentioned. In the liquid crystal display element of the present invention, since the adhesion between the liquid crystal layer and the electrodes is high, it is not necessary to apply a sealant to the four pieces of the substrate.

The gap of the liquid crystal display element can be controlled by the aforementioned spacer or the like. Examples of the method include, as described above, a method of introducing a spacer of a desired size into the liquid crystal composition, a method of using a substrate having a column spacer of a desired size, and the like. Further, when a plastic or film substrate is used for the substrate and the substrates are attached by lamination, the gap can be controlled without introducing a spacer.
The gap size of the liquid crystal display element is preferably 1 to 100 μm, more preferably 1 to 50 μm, and particularly preferably 2 to 30 μm. If the gap is too small, the contrast of the liquid crystal display element will be lowered, and if it is too large, the driving voltage of the element will be high.

A liquid crystal display element is obtained by curing a liquid crystal composition to form a liquid crystal layer. The liquid crystal composition is cured by irradiating the above liquid crystal composition injection cell with ultraviolet rays. Examples of the light source of the ultraviolet irradiation device used at that time include metal halide lamps and high-pressure mercury lamps. At that time, the wavelength of the ultraviolet rays is preferably 250 to 400 nm, more preferably 310 to 370 nm. Further, heat treatment may be performed after irradiation with ultraviolet rays. The temperature at that time is preferably 20 to 120°C, more preferably 30 to 100°C.

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these. The abbreviations used below are as follows.
<Specific compound>

<Polymerizable compound>
R1: IBXA (manufactured by Osaka Organic Chemical Industry Co., Ltd.)
R2: 2-hydroxyethyl methacrylate R3: KAYARAD FM-400 (manufactured by Nippon Kayaku Co., Ltd.)
R4: EBECRYL 230 (manufactured by Daicel Allnex)
R5: Karenz MT PE1 (manufactured by Showa Denko)
<Photoradical initiator>
P1: IRGACURE 184 (manufactured by BASF)
<LCD>
L1: MLC-3018 (manufactured by Merck)

<Production of liquid crystal composition (1)>
R1 (1.20 g), R2 (0.30 g), R3 (1.20 g), R4 (0.90 g) and R5 (0.30 g) are mixed and stirred at 60 ° C. for 2 hours to obtain a polymerizable compound A solution of On the other hand, S1 (0.20 g) and L1 (5.80 g) were mixed and stirred at 25° C. for 2 hours to prepare a liquid crystal containing the specific compound. After that, the prepared solution of the polymerizable compound, the liquid crystal containing the specific compound, and P1 (0.10 g) were mixed and stirred at 25° C. for 6 hours to obtain a liquid crystal composition (1).

<Production of liquid crystal composition (2)>
R1 (1.20 g), R2 (0.30 g), R3 (1.20 g), R4 (0.90 g) and R5 (0.30 g) are mixed and stirred at 60 ° C. for 2 hours to obtain a polymerizable compound A solution of On the other hand, S1 (0.80 g) and L1 (5.20 g) were mixed and stirred at 25° C. for 2 hours to prepare a liquid crystal containing the specific compound. After that, the prepared solution of the polymerizable compound, the liquid crystal containing the specific compound, and P1 (0.10 g) were mixed and stirred at 25° C. for 6 hours to obtain a liquid crystal composition (2).

<Production of liquid crystal composition (3)>
R1 (1.20 g), R2 (0.30 g), R3 (1.20 g), R4 (0.90 g) and R5 (0.30 g) are mixed and stirred at 60 ° C. for 2 hours to obtain a polymerizable compound A solution of On the other hand, S2 (0.40 g) and L1 (5.60 g) were mixed and stirred at 25° C. for 2 hours to prepare a liquid crystal containing the specific compound. Thereafter, the polymerizable compound solution prepared, the liquid crystal containing the specific compound, and P1 (0.10 g) were mixed and stirred at 25° C. for 6 hours to obtain a liquid crystal composition (3).

<Production of liquid crystal composition (4)>
R1 (1.20 g), R2 (0.30 g), R3 (1.20 g), R4 (0.90 g) and R5 (0.30 g) are mixed and stirred at 60 ° C. for 2 hours to obtain a polymerizable compound A solution of On the other hand, S1 (0.20 g), S2 (0.10 g) and L1 (5.70 g) were mixed and stirred at 25° C. for 2 hours to prepare a liquid crystal containing the specific compound. After that, the prepared solution of the polymerizable compound, the liquid crystal containing the specific compound, and P1 (0.10 g) were mixed and stirred at 25° C. for 6 hours to obtain a liquid crystal composition (4).

<Production of liquid crystal composition (5)>
R1 (1.20 g), R2 (0.30 g), R3 (1.20 g), R4 (0.90 g) and R5 (0.30 g) are mixed and stirred at 60 ° C. for 2 hours to obtain a polymerizable compound A solution of After that, the prepared solution of the polymerizable compound, L1 (6.00 g) and P1 (0.10 g) were mixed and stirred at 25° C. for 6 hours to obtain a liquid crystal composition (5).

"Fabrication of liquid crystal display element (glass substrate)"
Two glass substrates with ITO electrodes (length: 100 mm, width: 100 mm, thickness: 0.7 mm) washed with pure water and IPA (isopropyl alcohol) were prepared. A 15 μm spacer (trade name: Micropearl, manufactured by Sekisui Chemical Co., Ltd.) was applied. After that, the above liquid crystal compositions (1) to (5) are dropped on the spacer-coated surface of the substrate by the ODF (One Drop Filling) method, and then the other substrate is attached so that the ITO surface faces each other. They were combined to obtain a liquid crystal display element before treatment.
The liquid crystal display element before this treatment was irradiated with ultraviolet rays for 60 seconds using a metal halide lamp with an illuminance of 20 mW/cm ² to cut wavelengths of 350 nm or less. Thus, a liquid crystal display element (glass substrate) was obtained.

"Fabrication of liquid crystal display element (plastic substrate)"
Two PET substrates with ITO electrodes (length: 150 mm, width: 150 mm, thickness: 0.1 mm) washed with pure water were prepared, and the spacer of 20 µm was applied to the ITO surface of one of the substrates. Thereafter, the above liquid crystal compositions (1) to (5) are dropped by the ODF method on the ITO surface of the substrate coated with the spacer, and then the other substrate is laminated so that the ITO surface faces each other, A liquid crystal display element before treatment was obtained. Note that a glass substrate was used as a support substrate for the PET substrate with the ITO electrodes when the liquid crystal composition was dropped and bonded by the ODF method. After that, the supporting substrate was removed before irradiation with ultraviolet light.
The liquid crystal display element before this treatment was irradiated with ultraviolet rays in the same manner as in the above-mentioned "Preparation of liquid crystal display element (glass substrate)" to obtain a liquid crystal display element (plastic substrate).

"Evaluation of optical properties (scattering properties and transparency)"
This evaluation was carried out by measuring the haze (cloudiness) of the liquid crystal display element (glass substrate and plastic substrate) with no voltage applied (0 V) and with voltage applied (AC drive: 10 V to 50 V). At that time, haze was measured with a haze meter (HZ-V3, manufactured by Suga Test Instruments Co., Ltd.) in accordance with JIS K 7136. In this evaluation, the higher the haze in the non-voltage-applied state, the better the scattering properties, and the lower the haze in the voltage-applied state, the better the transparency. The Haze results are summarized in Table 10.

<Examples 1 to 8 and Comparative Examples 1 and 2>
As shown in Table 10 below, using the liquid crystal compositions (1) to (5), liquid crystal display devices were produced and the optical properties (scattering properties and transparency) were evaluated by the methods described above. .
At that time, in Example 1, Example 3, Example 5, Example 7, and Comparative Example 1, a liquid crystal display element was produced using a glass substrate and each evaluation was performed. 6, in Example 8 and Comparative Example 2, a plastic substrate was used.

As can be seen from Table 10 above, the liquid crystal display elements of the examples have a lower haze in a voltage applied state and a lower haze at a lower voltage than the comparative example. That is, in Examples, good optical characteristics (transparency) are exhibited, and the driving voltage of the liquid crystal display element is low.
Specifically, it is clear from the comparison between Example 1 and Comparative Example 1 and the comparison between Example 2 and Comparative Example 2, which are comparisons under the same conditions. These results were the same even when a plastic substrate was used as the substrate of the liquid crystal display element.

Further, the liquid crystal display element of the present invention can be suitably used as a normal type element which becomes a scattering state when no voltage is applied and becomes a transparent state when a voltage is applied. This element can be used for a liquid crystal display for display purposes, and furthermore, for a light control window or an optical shutter element for controlling the blocking and transmission of light. A substrate can be used.
In addition, the entire contents of the specification, claims, drawings, and abstract of Japanese Patent Application No. 2018-052662 filed on March 20, 2018 are cited here as disclosure of the specification of the present invention. , is to be incorporated.

Claims (4)

It has a liquid crystal layer that is cured by irradiating a liquid crystal composition containing a liquid crystal and a polymerizable compound placed between a pair of substrates with electrodes and by irradiating it with ultraviolet rays. A liquid crystal display element that is in a state,
the liquid crystal has a positive dielectric anisotropy, and
A liquid crystal display element, wherein the liquid crystal composition contains at least one compound selected from the group consisting of the following formulas [1a-1] to [1a-8] .

(X ^a represents -O- or -COO-; X ^b represents an alkyl group having 1 to 12 carbon atoms; p1 represents an integer of 1 to 10; p2 represents an integer of 2; )

(X ^c represents a single bond, -COO- or -OCO-; X ^d represents an alkyl group or alkoxy group having 1 to 12 carbon atoms; p3 represents an integer of 1 to 10; p4 represents indicates an integer of 2.) The content of at least one compound selected from the group consisting of the formulas [1a-1] to [1a-8] is 0.5 to 20 parts by mass with respect to 100 parts by mass of the liquid crystal. 3. The liquid crystal display element according to . 3. The liquid crystal display element according to claim 1, wherein the substrate of said liquid crystal display element is a glass substrate or a plastic substrate. 4. The liquid crystal display element according to claim 1, wherein said liquid crystal display element is a light control window or an optical shutter element.