JP2007231167A - Liquid crystal element, optical path-deflecting element and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal element that exhibits excellent orienting properties, permits drive of an optical axis in a low electric field and exhibits excellent response and/or optical properties, to provide an optical path-deflecting element that is comprised of the liquid crystal element and brings about parallel shift of an optical path at a high speed, and to provide an image display device that is capable of highly precise display by incorporation of the optical path-deflecting element though using an image display element with less picture elements. <P>SOLUTION: In the liquid crystal element 1 comprising a pair of transparent substrates 2, a liquid crystal layer 5 filled between the pair of substrates 2 and forming a homeotropically aligned chiral smectic C phase, and an electrode 4 generating an electric field (parallel electric field) applied at least to the liquid crystal layer 5 in the direction parallel to the main surface of the substrate 2, the liquid crystal layer 5 comprises a base liquid crystal material having a phase series, from the higher temperature side, of an isotropic liquid phase, a nematic phase, a smectic A phase, and a smectic C phase and, incorporated therewith, at least two chiral compounds. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a liquid crystal element that changes the tilt direction of the optical axis of a uniaxial substance by an electric signal, an optical path deflecting element that is composed of the liquid crystal element and deflects an optical path of light by an electric signal, and the optical path deflecting element. The present invention relates to an image display device. The optical path deflecting element is used in a projector, a head mounted display, an optical switch, an imaging optical system, and the like.

Prior to the description of the prior art, terms used in this specification are defined.
“Optical path deflecting element” means that the optical path of light is deflected by an electrical signal from the outside, that is, the outgoing light is shifted in parallel to the incident light, rotated at a certain angle, or both Means an optical element capable of switching the optical path. In this description, the magnitude of the shift with respect to the optical path deflection due to the parallel shift is referred to as “shift amount”, and the amount of rotation with respect to the optical path deflection due to rotation as the “rotation angle”. The “optical path deflecting device” means a device that includes such an optical path deflecting element and deflects the optical path of light.

  In addition, the “pixel shift element (pixel shift element)” is an image display element in which a plurality of pixels that can control light according to image information is two-dimensionally arranged, a light source that illuminates the image display element, and an image display An optical member for observing an image pattern displayed on the element, and an optical path deflecting unit for deflecting an optical path between the image display element and the optical member for each of a plurality of subfields obtained by temporally dividing the image field, An image display in which the apparent number of pixels of the image display element is multiplied and displayed by displaying an image pattern in which the display position is shifted in accordance with the deflection state of the optical path for each subfield by the optical path deflecting means. It means the optical path deflecting means in the apparatus. Therefore, basically, it can be said that the optical path deflecting element and the optical path deflecting device defined above can be applied as optical path deflecting means (pixel shift element (pixel shifting element)).

Conventionally, various techniques relating to an optical path deflecting element (or an optical deflecting element) or a pixel shift element using a liquid crystal material, an image display device using these, and the like have been proposed (see, for example, Patent Documents 1 to 6). However, in the conventional optical path deflection element and pixel shift element,
・ High cost due to the complicated structure, large equipment, loss of light, optical noise such as ghost, or reduced resolution,
・ Position accuracy and durability, especially in the case of a configuration with moving parts, vibration and sound problems,
・ Response speed problem in nematic liquid crystal, etc.
There are various problems.

  Therefore, the applicant first improved the problem in the conventional optical path deflecting element, i.e., the high cost, the large size of the apparatus, the loss of light amount, the optical noise, and the like due to the complicated structure. For the purpose of providing an optical path deflecting element and apparatus that are simple and small in size, have little light loss, optical noise, resolution reduction, and can be reduced in cost, an optical path deflecting element having a novel configuration has been proposed (Patent Document 7). reference).

  The optical path deflecting element 1 has a pair of transparent substrates 2 and 3, an alignment film 4 provided on at least one of the pair of substrates 2 and 3, and a homeotropic alignment filled between the pair of substrates 2 and 3. A liquid crystal layer 5 composed of a chiral smectic C phase, and an electrode pair 6 composed of at least one pair of electrodes 6a and 6b for applying an electric field to the liquid crystal 5; the electrode pair 6 is connected to a power source 7; It is set as the structure which applies an electric field to. Since this optical path deflecting element 1 uses a liquid crystal 5 composed of a chiral smectic C phase, compared to a conventional optical path deflecting element, the cost is increased due to the complicated configuration, the size of the apparatus, the light loss, The problem of optical noise can be improved, and the dullness of responsiveness in conventional smectic A liquid crystals and nematic liquid crystals can also be improved, enabling high-speed response.

  In order to obtain a practical optical path shift amount of about several μm to several tens of μm with such an optical path deflecting element, it is necessary to set the thickness of the liquid crystal layer to a very large value of several tens μm to several hundred μm (non- (See Patent Document 1). In general, when the liquid crystal layer is thicker, the influence of the alignment regulating force from the substrate surface is reduced at the center of the liquid crystal layer, so that it is difficult to maintain uniform alignment of the entire liquid crystal layer. For example, the alignment at the center of the liquid crystal layer may be disturbed, resulting in white turbidity. Therefore, in the optical path deflecting element as described above, it is the most important issue to form and maintain a uniform alignment state of the entire liquid crystal layer.

  Therefore, the applicant of the present invention has previously described an optical path deflecting element (see Patent Document 8) in which the liquid crystal layer is formed of a liquid crystal material that does not form a smectic A phase at a higher temperature than the chiral smectic C phase. A monomer or the like is contained, the liquid crystal layer is maintained at a temperature at which a smectic A phase is formed, molecular orientation is adjusted, photopolymerization is performed to form a fibrous or network structure composed of a polymer material, and then a chiral smectic C A method of cooling to a temperature at which a phase is formed (see Patent Document 9) is proposed. However, Patent Document 8 may have some side effects such as a limited range of liquid crystal materials, and Patent Document 9 may have some side effects such as an effect on response speed and optical characteristics due to the presence of a polymer structure.

In addition, for ferroelectric liquid crystal mixtures and display devices with large spontaneous polarization and excellent orientation, the amount of chiral compound added, the number and relative concentration of chiral compounds, and the helical pitch of the nematic (N ^* ) phase of the mixture are adjusted. And the like have been proposed (see Patent Document 10). In this document, a display element using a plane-aligned surface stable ferroelectric liquid crystal is targeted.

In general, in a surface stable ferroelectric liquid crystal element, the liquid crystal thickness is set to about 2 μm in order to obtain alignment uniformity (single plane alignment: monodomain alignment with a spiral), fast response, and good contrast. In particular, it is specified that the helical pitch in the nematic (N ^* ) phase needs to be about 5 times the thickness of the liquid crystal layer, that is, about 10 μm or more in order to realize a single plane alignment. Moreover, it illustrates about the addition method of the doping agent for satisfy | filling such conditions. In addition, it is stated that in the case of display layers operated in a thicker layer than usual, for example in guest-host mode, the helical pitch must be relatively larger, and the helical pitch by the mixture of this document is described. The effectiveness of the effect of increasing the value is shown. Further, since the helical pitch is sufficiently larger than the thickness in the operating temperature range of the surface stable type element, the size of the helical pitch in the smectic C phase hardly affects the operation of the element.

  On the other hand, as in the liquid crystal element used as the optical path deflecting element of the present invention, the chiral smectic C phase is vertically aligned (alignment not untwisted by a helix) and the liquid crystal layer has a very thick liquid crystal thickness of about several tens of μm. In the case of an element, the design concept of the above-described surface-stable liquid crystal material does not apply.

That is, as described in Patent Document 10, it is not sufficient to simply improve the orientation by adjusting the helical pitch of the nematic (N ^* ) phase or increase the spontaneous polarization, and the spiral pitch of the smectic C phase in the actual operating temperature range is insufficient. It is important to improve device characteristics by optimization. For example, when a liquid crystal mixture having a sufficiently long helical pitch in the nematic (N ^* ) phase is used, the helical pitch in the smectic C phase tends to be long. When a vertical alignment liquid crystal element having a very thick liquid crystal layer of about several tens of μm with such a material is used, alignment uniformity is not necessarily obtained, and liquid crystal domains are easily generated during operation. Deterioration of characteristics due to light scattering.

Japanese Patent Laid-Open No. 6-18940 JP-A-9-133904 Japanese Patent No. 2939826 JP-A-5-313116 JP-A-6-324320 JP-A-10-133135 JP 2002-328402 A JP 2003-280041 A JP 2004-184522 A Japanese Patent No. 3034024 “Crystal optics”, Applied Physics Society, Optical Society, p198

  The present invention has been made in view of the above-described problems in the prior art, and provides a liquid crystal element that is excellent in orientation, can drive an optical axis with a low electric field, and has excellent response and / or optical characteristics. It is an object of the present invention to provide an optical path deflecting element comprising the liquid crystal element and capable of parallel-shifting the transmitted optical path at high speed. It is another object of the present invention to provide an image display device capable of high-definition display while using an image display element having a small number of pixels by providing the optical path deflecting element.

  The invention of claim 1 provided to solve the above-described problems includes a pair of transparent substrates, a liquid crystal layer forming a chiral smectic C phase having a homeotropic orientation filled between the pair of substrates, and at least the above-mentioned In a liquid crystal element having an electrode for generating an electric field (parallel electric field) in a direction parallel to the main surface of the substrate with respect to the liquid crystal layer, the liquid crystal layer has an isotropic liquid phase, a nematic phase, a smectic A phase from the high temperature side. A liquid crystal element comprising a base liquid crystal material having a phase series which is a smectic C phase and containing at least a chiral compound of the following general formula (I) and a chiral compound of the following general formula (II).

（式中、Ｒ^１は炭素数が３から１２の直鎖状のアルキル基あるいはアルコキシ基を表し、Ｒ^２は炭素数が３から１２の分岐していても良いアルキル基を表す。なお、式中の＊はカイラル中心を表す。また、ｈ，ｊは０か１か２、ｉ，ｋは０か１、ｌは０か１か２、ただしｈとｊが同時もしくは片方が０の時ｉは０、ｌが０の時ｋは０、またｈ + j + lは２もしくは３である。
また、式中Ａ^１，Ａ^２は式（ａ）から選択される基を示し、Ａ^３は式（ｂ）から選択される基を示す。
また、Ｂ^１，Ｂ^２は-ＣＯ-Ｏ-、 -Ｏ-ＣＯ-、 -ＣＨ_２Ｏ-、ＯＣＨ_２-である。）

(In the formula, R ¹ represents a linear alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ² represents an optionally branched alkyl group having 3 to 12 carbon atoms. The * in the middle represents the chiral center, and h and j are 0, 1 or 2, i, k is 0 or 1, l is 0 or 1 or 2, if h and j are the same or one is 0 Is 0, and when l is 0, k is 0, and h + j + l is 2 or 3.
In the formula, A ¹ and A ² represent a group selected from the formula (a), and A ³ represents a group selected from the formula (b).
B ¹ and B ² are —CO—O—, —O—CO—, —CH ₂ O—, and OCH ₂ —. )

（式中、Ｒ^３は炭素数が３から１２の分岐していても良いアルキル基あるいはアルコキシ基を表し、Ｒ^４およびＲ^５は炭素数が３から５の直鎖状のアルキル基、もしくは末端同士が結合した六員環以上の環状構造のアルキル基を表す。Ａ^１，Ａ^２，Ａ^３，Ｂ^１，Ｂ^２，ｈ，ｉ，ｊ，ｋ，ｌは前記式(Ｉ)と同じ定義であり、それぞれ独立に式(Ｉ)と同じであっても異なっても良い。）

(Wherein R ³ represents an optionally branched alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ⁴ and R ⁵ are linear alkyl groups having 3 to 5 carbon atoms, or terminal groups. Represents an alkyl group having a cyclic structure of 6 or more members bonded to each other, wherein A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l are the same as defined in the formula (I). And each may independently be the same as or different from formula (I).)

  The invention of claim 2 provided to solve the above-mentioned problems is characterized in that in the liquid crystal element according to claim 1, a chiral compound of the following general formula (III) is further added to the liquid crystal layer. It is a liquid crystal element.

（式中、Ａ^１，Ａ^２，Ａ^３，Ｂ^１，Ｂ^２，ｈ，ｉ，ｊ，ｋ，ｌは前記式（Ｉ）と同じ定義であり、それぞれ独立に式(Ｉ)または式（II）と同じであっても異なっても良い。Ｒ^６は炭素数が３から１２の分岐していても良いアルキル基あるいはアルコキシ基または前記Ｙ基であり、Ｒ⁷は炭素数が３から１２の分岐していても良いアルキル基を表す。）

(In the formula, A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l have the same definition as in the above formula (I), and each independently represents formula (I) or formula ( II) may be the same as or different from R), R ⁶ is an optionally branched alkyl group or alkoxy group having 3 to 12 carbon atoms, or the Y group, and R ⁷ is 3 to 12 carbon atoms. Represents an alkyl group which may be branched.)

  Further, the invention of claim 3 provided to solve the above problem is that in the liquid crystal device according to claim 2, the chiral compound of the general formula (I) is represented by the following formula (IV), and The liquid crystal device is characterized in that the chiral compound of the general formula (II) is the following formula (V), and the chiral compound of the general formula (III) is the following formula (VI).

（式中、ｎおよびｍは３から１２の整数である。ｎとｍは同一数値でも良い。またＭ^１はメソゲニック芳香族単位(メソゲン基)であり、式（ｃ）から選択される基を示す。）

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. M ¹ is a mesogenic aromatic unit (mesogenic group), and a group selected from the formula (c)). Show.)

（式中、ｎは３から１２の整数である。またＭ^１は前記式(IV)と同じ定義であり、式(IV)と同じであっても異なってもよい。）

(In the formula, n is an integer of 3 to 12. M ¹ has the same definition as in the formula (IV) and may be the same as or different from the formula (IV).)

（式中、ｎおよびｍは３から１２の整数である。ｎとｍは同一数値でも良い。なお、式(IV)から式(VI)でのnとｍとは互いに独立した数値でも良い。またＭ^１は前記式(IV)と同じ定義であり、式(IV)または式（V）と同じであっても異なってもよい。）

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VI) may be independent values). M ¹ has the same definition as in formula (IV) and may be the same as or different from formula (IV) or formula (V).

  Further, the invention of claim 4 provided to solve the above-described problem is the liquid crystal device according to claim 3, wherein a compound of the following formula (VII) is further added as the chiral compound of the general formula (I): This is a liquid crystal element.

（式中、ｎおよびｍは３から１２の整数である。ｎとｍは同一数値でも良い。またＭ^２はメソゲニック芳香族単位(メソゲン)であり、式（ｄ）から選択される基を示す。）

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. M ² is a mesogenic aromatic unit (mesogen) and represents a group selected from the formula (d)). .)

  Further, the invention of claim 5 provided to solve the above problem is that in the liquid crystal device according to claim 2, the chiral compound of the general formula (I) is the formula (IV), and The liquid crystal device is characterized in that the chiral compound of the general formula (II) is the above formula (V) and the chiral compound of the general formula (III) is the following formula (VIII).

（式中、ｎおよびｍは３から１２の整数である。ｎとｍは同一数値でも良い。なお、式(IV)から式(VIII)でのnとｍとは互いに独立した数値でも良い。またＭ^１は前記式(IV)と同じ定義であり、式(IV)または式（V）と同じであっても異なってもよい。）

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VIII) may be independent values). M ¹ has the same definition as in formula (IV) and may be the same as or different from formula (IV) or formula (V).

  The invention of claim 6 provided to solve the above-described problem further adds the compound of the formula (VII) as the chiral compound of the general formula (I) in the liquid crystal device according to claim 5. This is a liquid crystal element.

  Further, the invention of claim 7 provided to solve the above-mentioned problem is that in the liquid crystal element according to any one of claims 1 to 6, the ratio of the chiral compound contained in the liquid crystal layer is 15 wt. % Or more and 40% by weight or less.

  The invention of claim 8 provided to solve the above-mentioned problem is the liquid crystal element according to any one of claims 1 to 7, wherein the base liquid crystal material contains at least a phenylpyrimidine compound. A liquid crystal element.

  The invention of claim 9 provided to solve the above-mentioned problem is an optical path deflecting element that deflects the optical path of light in accordance with an electric signal, from the liquid crystal element according to claim 1. The incident light to the liquid crystal element is linearly polarized light, and the plane of polarization of the linearly polarized light is set in a direction orthogonal to the direction in which the parallel electric field is applied in the element. An optical path deflecting element that is shifted in parallel.

  The invention of claim 10 provided to solve the above-mentioned problem is an image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, and a light source and an illumination device for illuminating the image display element An optical device for observing the image pattern displayed on the image display element, display driving means formed by a plurality of subfields obtained by temporally dividing the image field, and deflecting the optical path of the emitted light from each pixel And displaying an image pattern corresponding to a state in which a display position is shifted according to a deflection state of an optical path for each subfield by the optical path deflection element on the image display element. An image display device that displays an image by multiplying the apparent number of pixels, wherein the optical path deflecting element according to claim 9 is provided as the optical path deflecting element. It is a device.

As an effect of the present invention, according to the invention of claim 1, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, a liquid crystal layer having a relatively small saturation electric field intensity at the optical axis tilt angle can be obtained, and a sufficient optical axis tilt angle can be obtained even at a low electric field.
According to the invention of claim 2, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, a liquid crystal element having a relatively small saturation electric field intensity at the optical axis tilt angle and excellent response can be obtained.
According to the invention of claim 3, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, the spontaneous polarization of the liquid crystal layer can be increased, and a liquid crystal element with excellent response can be obtained.
According to the invention of claim 4, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, a liquid crystal element having a very small saturation electric field intensity at the optical axis tilt angle and excellent response can be obtained. In particular, when a 2,5-diphenylpyrimidine group is used as the mesogenic group, the effect of reducing the saturation electric field is remarkable.
According to the invention of claim 5, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, a liquid crystal element having a very small saturation electric field strength at the optical axis tilt angle and excellent MTF characteristics during electric field driving can be obtained.
According to the invention of claim 6, a liquid crystal layer having no alignment defect can be obtained even in a vertically aligned liquid crystal element having a thick liquid crystal layer, and light scattering can be prevented. In addition, a liquid crystal element having a very short response time and excellent MTF characteristics during electric field driving can be obtained. In particular, when a 2,5-diphenylpyrimidine group is used as the mesogenic group of the formula (VII), the effect of improving the vertical alignment and responsiveness is remarkable.
According to the seventh aspect of the present invention, when the chiral compound ratio is 15% by weight or more, the spontaneous polarization is increased, and the response time can be as high as 1.0 ms or less. Moreover, deterioration of optical characteristics, such as generation of white turbidity due to phase separation, can be prevented by setting it to 40% by weight or less.
According to the invention of claim 8, a stable smectic phase is formed near room temperature, and a liquid crystal layer having a low viscosity and a high-speed response can be obtained.
According to invention of Claim 9, the optical path which permeate | transmits is shifted in parallel with the inclination direction inversion operation | movement of the optical axis tilt angle of a liquid crystal layer. Since the above-described ferroelectric liquid crystal material is used, the optical axis can be reversed quickly and the optical path can be shifted at high speed.
According to the invention of claim 10, since the optical path deflecting element having good orientation and excellent high-speed response is used, the optical path can be deflected at high speed corresponding to the subfield image, and apparently high. Fine image display is possible. Further, since the switching time of the subfield image can be shortened by the high-speed response, the temporal light utilization efficiency is improved.

The configuration of the present invention will be described below.
First, the form of the liquid crystal element of the present invention will be described with reference to FIG.
FIG. 1 is a diagram schematically showing a cross section of a liquid crystal element. In the figure, reference numeral 1 is a liquid crystal element, 2 is a substrate, 3 is a vertical alignment film, 4 is an electrode, and 5 is a liquid crystal layer composed of a smectic C phase.

  The liquid crystal element 1 of the present invention is provided with a pair of transparent substrates 2 arranged to face each other. As the transparent substrate 2, glass, quartz, plastic or the like can be used, but a transparent material having no birefringence is preferable. The substrate 2 has a thickness of several tens of μm to several mm.

A vertical alignment film 3 is formed on the inner side surfaces (surfaces facing each other) of the substrate 2. The vertical alignment film 3 is not particularly limited as long as it is a material for vertically aligning liquid crystal molecules with respect to the surface of the substrate 2 (homeotropic alignment), but a vertical alignment agent for a liquid crystal display, a silane coupling agent, a deposited film of SiO or SiO ₂ Etc. can be used. The vertical alignment (homeotropic alignment) referred to in the present invention includes not only a state in which liquid crystal molecules are aligned perpendicularly to the substrate surface but also an alignment state in which the liquid crystal molecules are tilted to several tens of degrees.

  The distance between the two substrates 2 is defined with a spacer in between, and an electrode 4 and a liquid crystal layer 5 are formed between the substrates 2. As the spacer, a sheet member having a thickness of several μm to several mm or particles having the same particle diameter is used, and is preferably provided outside the effective region of the element. As the electrode 4, a metal such as aluminum, copper, or chromium, or a transparent electrode such as ITO is used. However, in order to apply a uniform horizontal electric field in the liquid crystal layer 5, the electrode 4 has a thickness comparable to the liquid crystal layer thickness. A metal sheet is preferably used and is provided outside the effective area of the element. In FIG. 1, as a more preferable example, the spacer member and the metal sheet member are common, and the thickness of the liquid crystal layer is defined by the thickness of the metal sheet member.

  As the liquid crystal layer 5, a chiral compound is added to a base liquid crystal material having a phase sequence of an isotropic liquid phase, a nematic phase, a smectic A phase, and a smectic C phase from the high temperature side, and the chiral smectic C phase is formed in a practical temperature range. The liquid crystal material to be formed is used. By applying a voltage between the electrodes 4, an electric field is applied in the horizontal direction of the liquid crystal layer.

  Further, in order to apply a uniform horizontal electric field over a larger area, a plurality of line-shaped transparent electrodes 4L are provided on the substrate surface as shown in FIGS. 5 and 6, and a voltage value that sequentially changes to each transparent electrode 4L. May be applied to forcibly form a potential gradient in the horizontal direction to form a uniform horizontal electric field. Further, a transparent dielectric layer 6 may be provided between the surface of the substrate 2 on which the line-shaped transparent electrode is provided and the liquid crystal layer 5. As a method of applying a sequentially changing voltage value to each transparent electrode 4L, it is preferable to connect each transparent electrode 4L in series with a resistor 8. 5 and 6 can increase the effective area of the liquid crystal element 10 to about several centimeter squares, which is preferable when applied to an application that requires a relatively large area, such as an image display device.

Here, the liquid crystal layer 5 forming the chiral smectic C phase will be described.
A “smectic liquid crystal” is a liquid crystal layer in which the major axis direction of liquid crystal molecules is arranged in a layered manner (smectic layer). With regard to such a liquid crystal, a liquid crystal in which the normal direction of the layer (layer normal direction) and the major axis direction of the liquid crystal molecules coincide with each other is referred to as “smectic A phase”, and a liquid crystal that does not coincide with the normal direction is referred to as “ It is called “smectic C phase”. A ferroelectric liquid crystal composed of a smectic C phase generally has a so-called spiral structure in which the direction of the liquid crystal director is spirally rotated for each smectic layer in a state where an external electric field does not work, and is called a “chiral smectic C phase”. . Further, the chiral smectic C reciprocal ferroelectric liquid crystal faces the direction in which the liquid crystal directors face each other. Since the liquid crystal composed of these chiral smectic C phases contains a chiral compound having an asymmetric carbon in the molecular structure and is spontaneously polarized by this, the liquid crystal molecules are rearranged in a direction determined by the spontaneous polarization Ps and the external electric field E. By doing so, the optical characteristics are controlled. In the present embodiment and the like, a liquid crystal element and an optical path deflecting element will be described by taking a ferroelectric liquid crystal as an example of the liquid crystal layer. However, the liquid crystal layer can be similarly used in the case of an antiferroelectric liquid crystal.

The operation principle of the liquid crystal element of the present invention will be described with reference to FIG.
FIG. 2 schematically shows the electric field direction and the tilt direction of the liquid crystal molecules in the configuration shown in FIG. The side where the width of the liquid crystal molecules 5a is drawn wide is shown as being inclined to the upper side of the paper, and the side where the width is drawn is inclined to the lower side of the paper. In addition, the spontaneous polarization of the liquid crystal (denoted by the symbol Ps) is indicated by an arrow. When the direction of the electric field E is reversed, the direction of the tilt angle of the substantially vertically aligned liquid crystal molecules 5a is reversed. Here, the relationship between the electric field application direction and the tilt direction of the liquid crystal molecules is shown in the case where the spontaneous polarization is positive. Here, when the direction of the tilt angle is reversed, it is considered that it rotates in a virtual cone-shaped plane as shown in the perspective views of FIGS.

  Here, FIG. 3 shows a model of the liquid crystal molecular arrangement of the chiral smectic C phase. The molecular layers having the tilt angle θ overlap each other while being shifted from each other to form a helical structure. In the electric field E = 0, the liquid crystal director directions are spatially averaged by a symmetrical spiral structure as shown in FIG. The averaged optical axis of the liquid crystal layer 5 faces the normal direction of the layer, and is optically isotropic with respect to incident light parallel to the optical axis. When a conoscopic image is observed with a polarizing microscope from the normal direction of the chiral smectic C phase liquid crystal layer under no electric field, the cross image is located in the center and has a uniaxial optical axis. Can be confirmed. Next, when a relatively small electric field 0 <E <Es is applied in the horizontal direction of the liquid crystal layer, a rotational moment is generated in the liquid crystal molecules due to the action of the electric field E on the spontaneous polarization Ps, as shown in FIG. The spiral structure is distorted and asymmetric, and the average optical axis is tilted in one direction. At this time, distortion increases as the electric field strength increases, and the average tilt angle of the optical axis also increases. This can be confirmed from the movement of the cross image of the conoscopic image. When the electric field strength is further increased, the spiral structure disappears as shown in FIG. 3 (c) above a certain threshold electric field Es and a uniform alignment state is obtained. The tilt angle of the optical axis at this time is equal to the tilt angle θ of the liquid crystal director. Further, even if the electric field is increased, the tilt angle θ does not change, and the tilt angle of the optical axis becomes constant.

  FIG. 4 schematically shows the alignment state of the liquid crystal molecules 5a in the liquid crystal element 1, and the vertical alignment film 3, the spacer, and the electrode 4 are omitted. In FIG. 4, for the sake of convenience, a voltage is applied in the front and back direction of the paper, and the electric field E acts in the front and back direction of the paper. The direction of the electric field is switched by a power source (not shown) corresponding to the target light deflection direction.

  When an electric field to the front side of the paper is applied as shown in FIG. 4A, if the spontaneous polarization of the liquid crystal molecules 5a is positive, the number of molecules in which the liquid crystal director is inclined to the upper right of the figure increases, and the average as the liquid crystal layer 5 is increased. A typical optical axis also tilts in the upper right direction of the figure and functions as a birefringent plate. Above the threshold electric field (hereinafter referred to as the saturation electric field Es) at which the chiral smectic C-phase helical structure can be solved, all the liquid crystal directors exhibit a tilt angle θ, and the liquid crystal element 5a has a complex structure in which the optical axis is inclined upward at an angle θ. Functions as a refracting plate. For example, the linearly polarized light L0 incident as extraordinary light from the left side of the liquid crystal element 5a in the figure is shifted in parallel upward in the figure. Here, the parallel shift amount S of the optical path where the refractive index in the major axis direction of the liquid crystal molecules 5a is ne, the refractive index in the minor axis direction is no, and the thickness (gap) of the liquid crystal layer 5 is d is expressed by the following equation (1). (See, for example, “Crystal Optics” Applied Physics Society, Optical Society, p198).

S = [(1 / no) ² − (1 / ne) ² ] sin (2θ) × d
÷ [2 ((1 / ne) ² sin ² θ + (1 / no) ² cos ² θ)] ………… Equation (1)

  Similarly, as shown in FIG. 4B, when the applied voltage to the electrode 4 is reversed and the electric field E is applied to the back side of the paper, the liquid crystal director is located at the lower right of the figure if the spontaneous polarization of the liquid crystal molecules 5a is positive. The liquid crystal element 1 is inclined and functions as a birefringent plate whose optical axis is inclined downward at an angle θ. Similarly, linearly polarized light L0 incident as extraordinary light from the left side of the liquid crystal element 1 in the figure is shifted in parallel downward in the figure. Therefore, an optical path shift amount of 2S can be obtained by reversing the direction of the electric field applied in the liquid crystal element 1. For example, when no = 1.55, ne = 1.70, d = 30 μm, and θ = 35 ° in Expression (1), an optical path shift amount of 2S = 5 (μm) is obtained. As described above, in the case of a general chiral smectic liquid crystal, in order to obtain an optical path shift amount of about several μm to several tens of μm, it is necessary to set the thickness of the liquid crystal layer to a very large value of several tens μm to several hundred μm. .

  Further, the liquid crystal layer 5 composed of the chiral smectic C phase of homeotopic orientation used in the present invention is more homogeneous than the liquid crystal director when it is in a homogeneous orientation (the liquid crystal director is oriented parallel to the substrate surface). However, it is difficult to receive the regulating force from the alignment film 3, and it is easy to control the direction of the optical axis by adjusting the direction of the external electric field. On the other hand, when the liquid crystal layer 5 is thick, the alignment regulating force from the alignment film 3 on the substrate surface is also reduced at the center of the liquid crystal layer 5, so that it is difficult to maintain uniform alignment of the entire liquid crystal layer 5. For example, the alignment at the center of the liquid crystal layer 5 is likely to be disturbed or cloudy. Therefore, in the present invention, as a result of examining combinations of various chiral compounds added to the base liquid crystal material, even when the thickness of the liquid crystal layer 5 is sufficiently large, the vertical alignment is excellent, and the responsiveness and optical characteristics are also excellent. A liquid crystal device could be obtained.

Embodiments of the liquid crystal element according to the present invention will be described below.
(First embodiment)
First, the first embodiment is characterized by containing at least a chiral compound of the following general formula (I) and a chiral compound of the general formula (II).

In formula (I), R ¹ represents a linear alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ² represents a linear alkyl group having 3 to 12 carbon atoms. In addition, * in a formula represents a chiral center. H and j are 0 or 1 or 2, i and k are 0 or 1, l is 0 or 1 or 2, but when h and j are simultaneous or one is 0, i is 0, and l is 0 Is 0, and h + j + l is 2 or 3. R ² preferably has 3 to 5 carbon atoms.
In the formula, A ¹ and A ² represent a group selected from the formula (a), and A ³ represents a group selected from the formula (b). B ¹ and B ² are —CO—O—, —O—CO—, —CH ₂ O—, and OCH ₂ —.

In the formula (II), A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l have the same definitions as in the formula (I), and each independently represents the formula (I) R ³ represents a linear alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ⁴ and R ⁵ represent a linear alkyl group having 3 to 5 carbon atoms. Represents an alkyl group having a cyclic structure of 6 or more members in which the groups or ends are bonded to each other. In particular, any of A ¹ , A ² , and A ³ is a pyrimidine ring, and i and k are preferably 0.

  In addition, it is considered that the base liquid crystal has a low skeletal viscosity and exhibits a high-speed response, and has a phase sequence of isotropic liquid phase, nematic phase, smectic A phase, smectic C phase, and crystal phase from the high temperature side. In particular, it is preferable to use a phenylpyrimidine compound exhibiting a stable smectic C phase around room temperature.

The epoxide ester group of the above formula (I) has a cis isomer with the R center at the chiral center. It has the property of inducing positive spontaneous polarization and inducing a right-handed spiral direction in the nematic (N ^* ) phase. A trans isomer having a similar structure has a relatively small effect on the expression of spontaneous polarization, and the cis isomer is more effective and more preferable.

On the other hand, in the dioxolane ether group of the formula (II), the chiral center has an S configuration and is a trans isomer. It has the property of inducing positive spontaneous polarization and inducing a left-handed spiral direction in the nematic (N ^* ) phase. That is, the addition of the formula (II) has the effect of canceling the effect of winding the spiral of the formula (I), but since the polarities of the spontaneous polarization are the same, the addition amount of the formula (I) and the formula (II) By appropriately adjusting the ratio, the helical pitch in the nematic (N ^* ) phase can be adjusted from short to long while maintaining a large spontaneous polarization.

The helical pitch in the nematic (N ^* ) phase is thought to affect the alignment during the production of liquid crystal elements. By setting the optimal pitch according to the characteristics of each element, the liquid crystal element has excellent reliability Is obtained. Further, the helical pitch in the chiral smectic C phase can be adjusted by the combination of the formulas (I) and (II). When the helical pitch in the chiral smectic C phase is short, a domain structure is hardly generated in the liquid crystal layer when the liquid crystal element is stopped from the driving state, but the saturation electric field strength of the optical axis tilt angle tends to increase. On the other hand, if the helical pitch in the chiral smectic C phase is long, the saturation electric field strength of the optical axis tilt angle tends to decrease, but a domain structure is likely to occur in the liquid crystal layer when the liquid crystal element is stopped from the driven state. Become.

  In the liquid crystal element of the present invention, it is preferable that the spiral pitch of the chiral smectic C phase is shorter than the thickness of the liquid crystal layer in order to ensure alignment stability. By setting the optimal pitch according to the characteristics of each element, a liquid crystal layer with excellent alignment stability and a relatively small saturation electric field strength at the optical axis tilt angle can be obtained, and sufficient optical axis tilt can be achieved even at low electric fields. A corner is obtained.

(Second Embodiment)
In the second embodiment, a chiral compound of the following general formula (III) is further added to the liquid crystal layer in the liquid crystal element of the first embodiment.

In formula (III), A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l have the same definitions as those in formula (I), and each independently represents formula (I) or It may be the same as or different from formula (II), R ⁶ is a linear alkyl group having 3 to 12 carbon atoms or an alkoxy group or the Y group, and R ⁷ is 3 to 12 carbon atoms. Represents a linear alkyl group. R ⁷ preferably has 3 to 5 carbon atoms.

The epoxide ether group represented by the Y group in the formula (III) has a chiral center in the S configuration and is a trans isomer. It has the property of inducing positive spontaneous polarization and inducing a left-handed spiral direction in the nematic (N ^* ) phase. Therefore, the combination with the above formula (I) is particularly effective for adjusting the helical pitch in the nematic (N ^* ) phase. In this structure, the effect of spontaneous polarization is relatively small. However, the combination of a cis ester system such as formula (I) and a trans ether group such as formula (III) changes other physical property values. It is possible to adjust the helical pitch in the nematic (N ^* ) phase while reducing the amount of. By adding the chiral compound of the formula (III) to the chiral compounds of the formulas (I) and (II), a liquid crystal element having a large spontaneous polarization and excellent responsiveness and excellent orientation can be obtained.

(Third embodiment)
In the third embodiment, in the liquid crystal element of the second embodiment, the chiral compound of the general formula (I) is the following formula (IV), and the chiral compound of the general formula (II) is the following formula The chiral compound of the general formula (III) that is (V) is the following formula (VI).

In formula (IV), n and m are integers of 3 to 12. n and m may be the same numerical value. In the formula (V), n is an integer of 3 to 12. Further, in the formula (VI), n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VI) may be numerical values independent of each other. In formulas (IV), (V), and (VI), M ¹ is a mesogenic aromatic unit (mesogenic group), which represents a group selected from the following formula (c).

  When a phenylpyrimidine group is used as the mesogenic group of formula (IV) and the same orientation as the pyrimidine ring of the base liquid crystal material is used, the compatibility is improved and the stability of the liquid crystal layer is improved, such as prevention of crystallization. It is considered effective. In addition, the formula (V) is characterized in that the end of the chiral moiety has a cyclohexane structure. Although the relationship with the molecular structure is not clear, the use of this formula (V) is effective in improving and maintaining the vertical alignment. Furthermore, since the formula (VI) has two chiral centers, it has the effect of inducing large spontaneous polarization. Therefore, the spontaneous polarization can be further increased, and a liquid crystal element with excellent response can be obtained.

(Fourth embodiment)
In the fourth embodiment, in the liquid crystal device of the third embodiment, a compound of formula (VII) is further added as another chiral compound of general formula (I).

In formula (VII), n and m are integers of 3 to 12. n and m may be the same numerical value. M ² is a mesogenic aromatic unit (mesogenic group) and represents a group selected from the following formula (d).

  In formula (VII), the mesogenic group has a tricyclic structure, and generally has the effect of improving the phase transition temperature by addition. In the present invention, in particular, when a 2,5-diphenylpyrimidine group is used as the mesogenic group of the formula (VII), the effect of reducing the saturation electric field is remarkable. The cause of this is not clear, but it is thought to be a specific effect due to interaction with other chiral compounds. As a result, a liquid crystal element having a very small saturation electric field strength at the optical axis tilt angle and a very excellent response can be obtained.

(Fifth embodiment)
In the fifth embodiment, in the liquid crystal element of the second embodiment, the chiral compound of the general formula (I) is the formula (IV), and the chiral compound of the general formula (II) is The formula (V) is similar to the above-described third embodiment, but is characterized in that the chiral compound of the general formula (III) is the following formula (VIII).

In formula (VIII), n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VIII) may be numerical values independent of each other. M ¹ is a mesogenic group, and the same mesogenic group as described above can be used.

  Formula (VIII) differs from the structure of formula (VI) described above in that there is one chiral center. Therefore, the effect of inducing spontaneous polarization is relatively small, but in particular, when a phenylpyrimidine group is used as the mesogenic group of formula (VIII), the structure is similar to other chiral compounds and base liquid crystal materials, so compatibility is improved. It has the effect of improving the orientation. In particular, the MTF characteristic (Modulation Transfer Function) which is an optical characteristic during driving of the liquid crystal element is improved.

(Sixth embodiment)
In the sixth embodiment, the formula (VII) is further added as another chiral compound of the general formula (I) in the liquid crystal element of the fifth embodiment. In this formula (VII), n and m are integers of 3 to 12. n and m may be the same numerical value. M ² is a mesogenic group, and those described above can be used.

  In formula (VII), the mesogenic group has a tricyclic structure, and generally has the effect of improving the phase transition temperature by addition. In the present invention, in particular, when a 2,5-diphenylpyrimidine group is used as the mesogenic group of the formula (VII), the effect of improving the vertical alignment and responsiveness is remarkable. The cause of the improvement in the orientation is not clear, but it is considered that the responsiveness has been greatly improved by the effect of increasing the spontaneous polarization. However, there was a tendency for the saturation electric field to increase, contrary to the effect of the fourth embodiment described above. Although the cause of this is not clear, it is considered that different effects occur even when the same compound is added because the interaction with other chiral compounds is effective. A liquid crystal element having excellent vertical alignment, a very short response time, and excellent MTF characteristics during electric field driving can be obtained.

(Seventh embodiment)
In the seventh embodiment, in the liquid crystal elements of the first to sixth embodiments, the ratio of the chiral compound contained in the liquid crystal layer is 15 wt% or more and 40 wt% or less. .

When the chiral compound ratio is less than 15% by weight, that is, when the base liquid crystal is 85% by weight or more, the spontaneous polarization becomes small and the response time is lowered to 1.0 msec or more. If the response time is longer than 1.0 msec, the characteristics of the ferroelectric liquid crystal material are not utilized. Therefore, when the chiral compound ratio is 15% by weight or more, that is, the base liquid crystal is less than 85% by weight, the spontaneous polarization becomes larger than about 40 nC / cm ^{2 and} the response time of the liquid crystal element can be increased to 1.0 ms or less. However, if the number of chiral compounds is increased too much for speeding up, side effects such as phase separation and white turbidity due to crystallization will occur. Therefore, when the chiral content is 40% by weight or less, deterioration of the optical characteristics of the liquid crystal element such as generation of white turbidity can be prevented.

  More preferably, the ratio of the chiral compound contained in the liquid crystal layer is 20% by weight or more and 40% by weight or less. By setting the chiral compound ratio to 20% by weight or more, the spontaneous polarization is further increased, and the response time of the liquid crystal element can be as high as 0.5 ms or less.

(Eighth embodiment)
In the eighth embodiment, in the liquid crystal elements of the first to seventh embodiments, the base liquid crystal material contains at least a phenylpyrimidine compound.

  The phenylpyrimidine compound has an isotropic liquid phase, a nematic phase, a smectic A phase, a smectic C phase, and a crystalline phase sequence from the high temperature side, and particularly exhibits a smectic C phase near room temperature. As a result, a liquid crystal element capable of forming a ferroelectric liquid crystal layer that is stable in the operating temperature range can be provided.

  Here, examples of the compound having a preferred phenylpyrimidine skeleton include those represented by the following formulas (e) and (f).

In the formula (e), R ₄ and R ₅ are linear or branched alkyl or alkenyl groups having 3 to 15 carbon atoms, and at least one H may be substituted with F or Cl. Further, the CH ₂ group may be —O—, —CO—, —O—CO—, —CO—O, —O—CO—O—.

  An optical path deflecting element according to the present invention deflects an optical path of light in accordance with an electric signal, and includes the liquid crystal element according to any one of the first to eighth embodiments. Incident light to the linearly polarized light, and the plane of polarization of the linearly polarized light is set in a direction orthogonal to the direction of application of the parallel electric field in the element, thereby shifting the position of the outgoing optical path with respect to the incident optical path in parallel An optical path deflecting element characterized by That is, the optical path transmitted through the liquid crystal layer 5 is shifted in parallel with the inversion operation of the tilt angle of the optical axis tilt angle. Since the ferroelectric liquid crystal material is used as shown in FIG. 4 described above, the optical axis can be reversed quickly and the optical path can be shifted at high speed.

Next, the image display apparatus according to the present invention will be described.
An image display device of the present invention includes an image display element in which a plurality of pixels that can control light according to image information are two-dimensionally arranged, a light source and an illumination device that illuminate the image display element, and a display on the image display element An optical device for observing the image pattern, display driving means formed by a plurality of subfields obtained by dividing the image field in time, and the optical path deflection of the present invention described above for deflecting the optical path of the emitted light from each pixel An image pattern corresponding to a state in which a display position is shifted in accordance with a deflection state of an optical path for each subfield by the optical path deflecting element is displayed on the image display element. The display is performed by multiplying the number of pixels.

  FIG. 7 shows a configuration example of the image display device. In FIG. 7, reference numeral 21 denotes a light source in which LED lamps are arranged in a two-dimensional array. In the traveling direction of light emitted from the light source 21 toward the screen 26, a diffusion plate 22, a condenser lens 23, and an image display element are used. A transmissive liquid crystal panel 24 and a projection lens 25 as an optical member for observing the image pattern are sequentially arranged. Reference numeral 27 denotes a light source drive unit for the light source 21, and reference numeral 28 denotes a drive unit for the transmissive liquid crystal panel 24.

  Here, an optical path deflecting element 20 functioning as a pixel shift element is interposed on the optical path between the transmissive liquid crystal panel 24 and the projection lens 25, and is connected to the drive unit 30. As such an optical path deflecting element 20, the liquid crystal element as described above is used.

  The illumination light that is controlled by the light source drive unit 27 and emitted from the light source 21 becomes illumination light that is made uniform by the diffusion plate 22, and is controlled by the condenser lens 23 in synchronization with the illumination light source by the liquid crystal drive unit 28 and is transmissive. The liquid crystal panel 24 is illuminated. The illumination light spatially modulated by the transmissive liquid crystal panel 24 enters the optical path deflecting element 20 as image light, and the optical path deflecting element 20 shifts the image light by an arbitrary distance in the pixel arrangement direction. The light transmitted through the optical path deflecting element 20 is magnified by the projection lens 25 and projected onto the screen 26.

  Here, an apparent pixel of the transmissive liquid crystal panel 24 is displayed by displaying an image pattern in which the display position is shifted according to the shift position of the optical path for each of the plurality of subfields obtained by dividing the image field in time. The number is multiplied and displayed. Thus, the shift amount by the optical path deflecting element 20 is set to ½ of the pixel pitch because the image multiplication is performed twice as much as the pixel arrangement direction of the transmissive liquid crystal panel 24. By correcting the image signal for driving the transmissive liquid crystal panel 24 by the shift amount according to the shift amount, an apparently high-definition image can be displayed. At this time, an optical path deflecting element with good orientation and high-speed response is used, so that high-speed optical path deflection is possible in correspondence with subfield images, and apparently high-definition image display is possible. It becomes. Further, since the switching time of the subfield image can be shortened by the high-speed response, the temporal light utilization efficiency is improved.

Hereinafter, examples in which the present invention is actually implemented will be described.
In this example, the chiral compound added as the liquid crystal material was selected from the compounds shown in Table 1 below.

Example 1
(1) Preparation of liquid crystal element A liquid crystal element was prepared by the following procedure.
First, 400 transparent electrode lines having a width of 10 μm were formed in parallel at a pitch of 100 μm on the surface of a glass substrate having a thickness of 1.1 mm. The effective length of the transparent electrode line was 10 mm. The effective area of the transparent electrode line group is 40 mm square, and a glass having a thickness of 150 μm is laminated thereon with an ultraviolet curable adhesive. The thickness of the adhesive was about 10 μm. As a result, the transparent line electrode 4L is embedded in the transparent glass as shown in the sectional view of the liquid crystal element in FIG.

  A vertical (homeotropic) alignment film 3 of a polyimide compound having a thickness of 0.06 μm was formed on the surface of the substrate. As the polyimide alignment film, a polyamic acid solution was applied by spin coating, and a polyimide film was obtained by imidization treatment by heat treatment at about 180 ° C. Then, a cell was created by sandwiching a 50 μm spacer sheet outside the effective area and facing the two substrates. At this time, the transparent electrode lines within the effective area of the upper and lower substrates were bonded to each other so as to be alternately positioned as viewed from above. Next, in a state where the cell was heated to about 95 ° C., a liquid crystal material described later was injected into the space between the substrates by a capillary method. After cooling, it was sealed with an adhesive to prepare a liquid crystal element 10 having a liquid crystal thickness of 70 μm and an effective area of 4 cm square.

  As shown in FIG. 6, the resistor 8 made of a CrSiO vapor deposition film is formed so that each transparent electrode line 4L of the substrate 2 is directly connected. By connecting a power source composed of a pulse generator and a high-speed amplifier to both ends of the resistor 8, a current flows through the resistor array, a voltage is distributed, and a potential distribution is formed inside the effective area.

(2) Liquid crystal material In this example, the following compounds were mixed and used as the liquid crystal material.
-Base liquid crystal mixed at the composition ratio shown in Table 2 below: 87 wt%
As an example of the chiral compound of formula (I), compound A shown in Table 1: 4 wt%
And Compound B: 5 wt%
As an example of the chiral compound of formula (II), compound E shown in Table 1: 4 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 75 ° C., smectic A phase / nematic phase: 85 ° C., nematic phase / isotropic phase: 90 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +35 nC / cm ² .

(3) Characteristic evaluation of liquid crystal element After preparing a liquid crystal element sample, the vertical alignment in an initial state was evaluated by target observation and polarization microscope observation. The evaluation was rank evaluation, and the evaluation criteria were as follows.
The orientation of the liquid crystal element of this example was within the practical range at rank 2.

(Orientation evaluation criteria)
Rank 1: There is an alignment defect that does not transmit light.
Rank 2: The transmittance is good but slightly cloudy. The white turbidity is eliminated by driving the electric field, making it practical.
Rank 3: Good transmittance and no cloudiness. However, domains of several tens to several hundreds μm are observed.
Rank 4: Good transmittance, almost no domain is observed, and a wide and uniform orientation state.

Next, various characteristics of the liquid crystal element were measured using the apparatus shown in FIG.
The light from the light source 41 passes through an optical system (ND filter 42, diffuser plate 43, F4.1 50mm lens 44) for setting an illumination angle and a polarizing plate 45, and a sinusoidal density with a spatial frequency of 100 periods / mm (10 μm pitch). The MTF chart 46 having a distribution was illuminated. Then, the light transmitted from the MTF chart 46 through the liquid crystal element 10 was observed with a high-speed camera with a microscope or a high-definition CCD camera as the camera 47.

  At this time, by applying a rectangular wave AC voltage with a driving frequency of the liquid crystal element 10 of 100 Hz, an optical path shift phenomenon due to switching of the optical axis of the liquid crystal layer 5 occurs, and the position of the pattern (MTF pattern) of the MTF chart 46 is displaced. The situation was observed. The displacement of this pattern was photographed with the high-speed camera 47, and the response time was measured by analyzing the image. The time for displacement from 10% to 90% with respect to the maximum displacement was defined as response time, and the comparison was made with the response time at an electric field strength of 150 V / mm.

  When a high-definition CCD camera is used instead of the high-speed camera, the MTF pattern appears to move relatively slowly on the image of the CCD camera due to the difference between the frame frequency of the CCD camera and the driving frequency of the liquid crystal element 10. In this case, an image in which the MTF pattern was shifted in one direction and stopped still was taken into a computer, and the MTF value of the liquid crystal element was obtained. Further, the MTF ratio attributed to the liquid crystal layer 5 was determined by normalizing the MTF value with the MTF value of the reference element.

  Further, the optical path shift amount was obtained from the comparison of the stationary positions on both sides of the MTF pattern. Further, when the electric field strength was increased, the saturation electric field strength of the optical axis was obtained from the electric field at the time when the optical path shift amount was saturated to a constant value.

The evaluation results of the liquid crystal element of this example are shown below.
-Response time: 1.2 msec (when electric field E = 150 V / mm)
・ Saturation electric field: 45V
-MTF ratio: 0.6 (when driving at 100 Hz)

  The liquid crystal of this embodiment is excellent in that the saturation electric field is as small as 45V. However, the orientation was slightly inferior to rank 2, and the response time was 1.2 ms, which was relatively slow. However, it has practical performance as a vertically aligned ferroelectric liquid crystal element.

(Example 2)
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 2: 82 wt%
As an example of the chiral compound of formula (I), compound A shown in Table 1: 5 wt%
And Compound B: 5 wt%
As an example of the chiral compound of formula (II), compound E shown in Table 1: 3 wt%
As an example of a chiral compound of formula (III), compound C shown in Table 1: 5 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 77 ° C., smectic A phase / nematic phase: 87 ° C., nematic phase / isotropic phase: 93 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +60 nC / cm ² .

Further, the orientation of the liquid crystal element of this example was relatively good at rank 3.
Moreover, the characteristic evaluation result of the liquid crystal element was as follows.
Response time (VAFLC element): 0.6 msec (when electric field E = 150 V / mm)
・ Saturation electric field (VAFLC element): 40V
-MTF ratio (VAFLC element): 0.85 (when driven at 100 Hz)
In the liquid crystal element of Example 2, the saturation electric field was as small as 40 V, and the response time was further improved to 0.6 ms.

(Comparative example)
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 2: 82 wt%
As an example of the chiral compound of formula (I), compound A shown in Table 1: 6 wt%
And Compound B: 6 wt%
-Does not include the chiral compound of formula (II).
As an example of the chiral compound of formula (III), compound C shown in Table 1: 6 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 80 ° C., smectic A phase / nematic phase: 86 ° C., nematic phase / isotropic phase: 93 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +77 nC / cm ² .

  Further, the alignment of the liquid crystal element of this comparative example was determined to be rank 1 because a cloudy portion due to an alignment defect occurred in a part of the effective portion. This is presumably because the vertical alignment was deteriorated because the compound of formula (II) was not included. Since the SSFLC element for spontaneous polarization measurement showed good orientation, this phenomenon is considered to be a phenomenon peculiar to a vertically aligned element having a relatively large cell thickness. Due to the occurrence of white turbidity, no other evaluation was performed.

(Example 3)
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 2: 70 wt%
As an example of the chiral compound of formula (IV), the compound H shown in Table 1: 13 wt%
As an example of the chiral compound of formula (V), compound E shown in Table 1: 4 wt%
As an example of the chiral compound of the formula (VI), the compound C shown in Table 1: 13 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 67 ° C., smectic A phase / nematic phase: 82 ° C., nematic phase / isotropic phase: 89 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +67 nC / cm ² .

Further, the orientation of the liquid crystal element of this example was relatively good at rank 3.
Moreover, the characteristic evaluation result of the liquid crystal element was as follows.
Response time (VAFLC element): 0.4 msec (when electric field E = 150 V / mm)
・ Saturation electric field (VAFLC element): 70V
-MTF ratio (VAFLC element): 0.80 (when driven at 100 Hz)
In the liquid crystal element of Example 3, the response time was as high as 0.4 ms. However, the saturation electric field at the optical axis tilt angle was relatively large at 70V.

Example 4
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 2: 72 wt%
As an example of the chiral compound of formula (IV), the compound H shown in Table 1: 8 wt%
As an example of the chiral compound of formula (VII), compound B shown in Table 1: 4 wt%
As an example of the chiral compound of formula (V), compound E shown in Table 1: 4 wt%
As an example of the chiral compound of formula (VI), compound C shown in Table 1: 8 wt%

The phase transition temperature of the liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 77 ° C., smectic A phase / nematic phase: 92 ° C., nematic phase / isotropic phase: 95 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +94 nC / cm ² .

Further, the orientation of the liquid crystal element of this example was relatively good at rank 3.
Moreover, the characteristic evaluation result of the liquid crystal element was as follows.
Response time (VAFLC element): 0.4 msec (when electric field E = 150 V / mm)
・ Saturation electric field (VAFLC element): 30V
-MTF ratio (VAFLC element): 0.85 (when driven at 100 Hz)
In the liquid crystal element of Example 4, the response time was as short as 0.4 ms, and the saturation electric field of the optical axis tilt angle was as small as 30V. On the other hand, although MTF is sufficient as 0.85, further improvement is desired.

(Example 5)
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 3 below: 70 wt%
As an example of the chiral compound of formula (IV), the compound H shown in Table 1: 13 wt%
As an example of the chiral compound of formula (V), compound E shown in Table 1: 4 wt%
As an example of the chiral compound of formula (VIII), compound I shown in Table 1: 13 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −10 ° C., smectic C phase / smectic A phase: 68 ° C., smectic A phase / nematic phase: 90 ° C., nematic phase / isotropic phase: 96 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +50 nC / cm ² .

Further, the orientation of the liquid crystal element of this example was relatively good at rank 3.
Moreover, the characteristic evaluation result of the liquid crystal element was as follows.
Response time (VAFLC element): 0.5 msec (when electric field E = 150 V / mm)
・ Saturation electric field (VAFLC element): 35V
-MTF ratio (VAFLC element): 0.90 (at 100 Hz drive)
In the liquid crystal element of Example 5, the saturation electric field of the optical axis tilt angle was as small as 35 V, and the MTF during electric field driving was very good at 0.9. That is, the use of Compound I improved the MTF characteristics. Although the response time is slightly delayed at 0.5 ms, it is a characteristic that is not problematic in practical use.

(Example 6)
In Example 1, a liquid crystal element was produced in the same manner as in Example 1 except that the liquid crystal material having the following composition was used.
-Base liquid crystal having the composition shown in Table 2: 66 wt%
As an example of the chiral compound of formula (IV), the compound H shown in Table 1: 13 wt%
As an example of the chiral compound of formula (VII), compound B shown in Table 1: 4 wt%
As an example of the chiral compound of formula (V), compound E shown in Table 1: 4 wt%
As an example of the chiral compound of formula (VIII), compound I shown in Table 1: 13 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −17 ° C., smectic C phase / smectic A phase: 69 ° C., smectic A phase / nematic phase: 88 ° C., nematic phase / isotropic phase: 89 ° C. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was +86 nC / cm ² .

Also, the orientation of the liquid crystal element of this example was very good at rank 4.
Moreover, the characteristic evaluation result of the liquid crystal element was as follows.
・ Response time (VAFLC element): 0.3 msec (when electric field E = 150 V / mm)
・ Saturation electric field (VAFLC element): 70V
-MTF ratio (VAFLC element): 0.90 (at 100 Hz drive)
The liquid crystal element of this Example 6 had a good initial alignment rank of 4, a fast response time of 0.3 ms, and a very good MTF of 0.9 during electric field driving. That is, the initial orientation was improved by the addition of Compound B. However, although the saturation electric field of the optical axis tilt angle is slightly increased to 75 V, there is no problem in practical use.

  Table 4 shows the evaluation results of Examples 1 to 6.

(Example 7)
In this example, the correlation between the total concentration and the response time for various combinations of chiral compounds was investigated. Specifically, in Example 1, among the chiral compounds shown in Table 1, the combination of compounds A, B, C and E (symbol ●), the combination of compounds A, B and E (symbol ○), compound H, Combination of B, I and E (symbol ▲), combination of compounds H, B, C and E (symbol △), combination of compounds H, C and E (symbol x), combination of compounds H, I and E (symbol) The liquid crystal material was prepared in the same manner as in Example 1 except that the total concentration was changed every time and the liquid crystal material mixed with the base liquid crystal having the composition shown in Table 2 or Table 3 was used. The response time of the liquid crystal element when the electric field E = 150 V / mm was measured.

FIG. 9 shows the correlation between the total concentration and the response time in the combination of the various chiral compounds with respect to the base liquid crystal shown in Table 2 or Table 3.
Even if the combination of chiral compounds is different, the change in response time with respect to the total amount of addition shows almost similar characteristics. When the chiral compound ratio is less than 15% by weight, that is, when the base liquid crystal is 85% by weight or more, the spontaneous polarization becomes small and the response time is lowered to 1.0 msec or more. If the response time is longer than 1.0 msec, the characteristics of the ferroelectric liquid crystal material are not utilized. Therefore, when the chiral compound ratio is 15% by weight or more, that is, the base liquid crystal is less than 85% by weight, the spontaneous polarization becomes larger than about 40 nC / cm ^{2 and} the response time of the liquid crystal element can be increased to 1.0 ms or less. More preferably, when the chiral compound ratio is 20% by weight or more, the spontaneous polarization is further increased, and the response time of the liquid crystal element can be as high as 0.5 ms or less.

Next, the MTF ratio was measured for the liquid crystal elements manufactured by changing the total concentration for each combination of the chiral compounds.
FIG. 10 shows the result. Although there are variations depending on the combination of the chiral compounds, the MTF ratio tends to deteriorate as the total concentration increases. In particular, when it exceeds 40% by weight, it rapidly decreases, but this is considered to be due to phase separation and crystallization of the chiral compound.

  From the above, in the liquid crystal element of the present invention, the ratio of the chiral compound contained in the liquid crystal layer is preferably 15% by weight or more and 40% by weight or less, and more preferably 20% by weight or more and 40% by weight or less. preferable.

(Example 8)
The image display apparatus shown in FIG. 7 was produced using the liquid crystal element of Example 6 as an optical path deflecting element. A diagonal TFT 0.9 inch XGA (1024 × 768 dots) polysilicon TFT liquid crystal light valve was used as the image display element (transmission type liquid crystal panel 24). At this time, the pixel pitch is about 18 μm both vertically and horizontally, and the aperture ratio of the pixel is about 50%. In addition, a microlens array is provided on the light source side of the image display element (transmission type liquid crystal panel 24) to increase the collection rate of illumination light. In this embodiment, an RGB three-color LED light source is used as a light source, and a so-called field sequential method is adopted in which color display is performed by switching the color of light applied to the one liquid crystal panel 24 at high speed.

  In this embodiment, the frame frequency for image display is 60 Hz, and the subfield frequency for quadruple pixel multiplication by pixel shift is quadruple 240 Hz. Further, in order to further divide one subframe into three colors, images corresponding to the respective colors were switched at 720 Hz. By turning ON / OFF the LED light source of the corresponding color in accordance with the display timing of each color image on the liquid crystal panel, the observer can see a full color image.

  In this example, two sets of the liquid crystal elements of Example 6 are used as the optical path deflecting elements 20, the incident side is the first optical path deflecting element, the exit side is the second optical path deflecting element, and the directions of the line electrodes are orthogonal to each other. The image display element (transmission type liquid crystal panel 24) is arranged so as to coincide with the pixel arrangement direction.

  Further, in this embodiment, the light emitted from the liquid crystal light valve is already linearly polarized light, and the polarization direction thereof is arranged so as to coincide with the optical path deflection direction of the first optical path deflection element. In order to ensure the degree of polarization of light, a linearly polarizing plate was provided as a polarization direction control means on the incident surface side of the optical path deflecting element 20. Thereby, generation | occurrence | production of the noise light which goes straight without being deflected by the 1st light deflection | deviation element can be prevented.

  Further, a polarization plane rotating element is provided between the first and second optical path deflecting elements. The polarization plane rotating element was prepared as follows. That is, a polyimide-based alignment material was spin-coated on a thin glass substrate (3 cm × 4 cm, thickness 0.15 mm) to form an alignment film having a thickness of about 0.1 μm. A rubbing process is performed after the annealing process of the glass substrate. An empty cell is fabricated by sandwiching an 8 μm thick spacer between the two glass substrates and bonding the upper and lower substrates so that the rubbing directions are orthogonal to each other. In this cell, a nematic liquid crystal having a positive dielectric anisotropy and an appropriate amount of a chiral material mixed with a chiral material is injected under normal pressure to produce a TN liquid crystal cell in which the orientation of liquid crystal molecules is twisted by 90 degrees. A polarization plane rotation element was obtained. Since this cell is not provided with an electrode, it functions as a simple polarization rotation element.

  When placing the polarization plane rotation element, the polarization plane of the light emitted from the first optical path deflection element is sandwiched between two optical path deflection means so that the rubbing directions of the incident plane of the polarization rotation element coincide with each other. Arranged. This polarization plane rotating element rotates the polarization plane of the outgoing light from the first optical path deflecting element by 90 degrees to coincide with the deflection direction of the second optical path deflecting element. The pixel shift element composed of the first optical path deflecting element, the polarization plane rotating element, and the second optical path deflecting element thus manufactured was installed immediately after the image display element (transmission type liquid crystal panel 24).

  In this embodiment, the rectangular wave voltage for driving the pixel shift element is set to ± 6 kV, the frequency is set to 60 Hz, the vertical and horizontal phases of the two sheets are shifted by 90 degrees, and the drive timing is set so as to shift the pixels in four directions. Set. The shift amount of the light deflection element under this condition was 9 μm.

  In this example, the subfield image displayed on the image display element was rewritten at 240 Hz, so that a high-definition image in which the apparent number of pixels was multiplied by four in the vertical and horizontal directions could be displayed. The switching time of the optical path deflecting element was about 0.3 msec, and sufficient light utilization efficiency was obtained. Also, no flicker was observed.

It is sectional drawing which shows the structure of the liquid crystal element which concerns on this invention. FIG. 2 is a schematic diagram showing an electric field direction and a tilt direction of liquid crystal molecules in the liquid crystal element of FIG. 1. It is a model figure of the liquid crystal molecular arrangement | sequence of a chiral smectic C phase. It is also a schematic diagram showing the alignment state of liquid crystal molecules and the principle of optical path deflection. It is sectional drawing which shows another structure of the liquid crystal element which concerns on this invention. It is a figure which shows the arrangement | sequence and connection state of the transparent line electrode of the liquid crystal element of FIG. It is the schematic which shows the structure of the image display apparatus which concerns on this invention. It is the schematic which shows the structure of the apparatus which performs the characteristic evaluation of a liquid crystal element. It is a correlation diagram of the amount of chiral compound added to the liquid crystal layer and the response time. It is a correlation diagram of the amount of chiral compound added to the liquid crystal layer and the MTF ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 Liquid crystal element 2 Substrate 3 Vertical alignment film 4 Electrode 4L Transparent line electrode 5 Liquid crystal layer 5a Liquid crystal molecule 6 Dielectric layer 7 Spacer 8 Resistor 20 Optical path deflecting element 21 Light source 22 Diffusion plate 23 Condenser lens 24 Transmission type liquid crystal panel 25 Projection lens 26 Screen 27 Light source drive unit 28 Drive unit 30 Optical path deflection element drive unit 41 Lamp 42 ND filter 43 Diffuser plate 44 F1.4 50 mm lens 45 Polarizing plate 46 MTF chart 47 Microscope camera (CCD camera)
C virtual cone E electric field L0 incident linearly polarized light Ps spontaneous polarization

Claims (10)

A pair of transparent substrates, a liquid crystal layer forming a chiral smectic C phase having a homeotropic orientation filled between the pair of substrates, and an electric field in a direction parallel to the main surface of the substrate at least with respect to the liquid crystal layer ( In a liquid crystal element having an electrode for generating a parallel electric field)
In the base liquid crystal material in which the liquid crystal layer has a phase series of isotropic liquid phase, nematic phase, smectic A phase, and smectic C phase from the high temperature side, at least a chiral compound of the following general formula (I) and the following general formula ( A liquid crystal device comprising the chiral compound of II).

(In the formula, R ¹ represents a linear alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ² represents an optionally branched alkyl group having 3 to 12 carbon atoms. The * in the middle represents the chiral center, and h and j are 0, 1 or 2, i, k is 0 or 1, l is 0 or 1 or 2, if h and j are the same or one is 0 Is 0, and when l is 0, k is 0, and h + j + l is 2 or 3.
In the formula, A ¹ and A ² represent a group selected from the formula (a), and A ³ represents a group selected from the formula (b).
B ¹ and B ² are —CO—O—, —O—CO—, —CH ₂ O—, and OCH ₂ —. )

(Wherein R ³ represents an optionally branched alkyl group or alkoxy group having 3 to 12 carbon atoms, and R ⁴ and R ⁵ are linear alkyl groups having 3 to 5 carbon atoms, or terminal groups. Represents an alkyl group having a cyclic structure of 6 or more members bonded to each other, wherein A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l are the same as defined in the formula (I). And each may be the same as or different from formula (I).) 2. The liquid crystal device according to claim 1, wherein a chiral compound represented by the following general formula (III) is further added to the liquid crystal layer.

(In the formula, A ¹ , A ² , A ³ , B ¹ , B ² , h, i, j, k, and l have the same definition as in the above formula (I), and each independently represents formula (I) or formula ( II) may be the same as or different from R), R ⁶ is an optionally branched alkyl group or alkoxy group having 3 to 12 carbon atoms, or the Y group, and R ⁷ is 3 to 12 carbon atoms. Represents an optionally branched alkyl group.) The liquid crystal device according to claim 2, wherein the chiral compound of the general formula (I) is the following formula (IV), and the chiral compound of the general formula (II) is the following formula (V): A liquid crystal device wherein the chiral compound of the general formula (III) is the following formula (VI).

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. M ¹ is a mesogenic aromatic unit (mesogenic group), and a group selected from the formula (c)). Show.)

(In the formula, n is an integer of 3 to 12. M ¹ has the same definition as in the formula (IV) and may be the same as or different from the formula (IV).)

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VI) may be independent values). M ¹ has the same definition as in formula (IV) and may be the same as or different from formula (IV) or formula (V). 4. The liquid crystal device according to claim 3, wherein a compound of the following formula (VII) is further added as the chiral compound of the general formula (I).

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. M ² is a mesogenic aromatic unit (mesogen) and represents a group selected from the formula (d)). .)

The liquid crystal device according to claim 2, wherein the chiral compound of the general formula (I) is the formula (IV), and the chiral compound of the general formula (II) is the formula (V). And the chiral compound of the said general formula (III) is following formula (VIII), The liquid crystal element characterized by the above-mentioned.

(In the formula, n and m are integers of 3 to 12. n and m may be the same numerical value. Note that n and m in the formulas (IV) to (VIII) may be independent values). M ¹ has the same definition as in formula (IV) and may be the same as or different from formula (IV) or formula (V).   6. The liquid crystal device according to claim 5, wherein the compound of the formula (VII) is further added as the chiral compound of the general formula (I).   The liquid crystal element according to claim 1, wherein the ratio of the chiral compound contained in the liquid crystal layer is 15% by weight or more and 40% by weight or less.   The liquid crystal element according to claim 1, wherein the base liquid crystal material contains at least a phenylpyrimidine compound. An optical path deflecting element that deflects an optical path of light according to an electrical signal,
The liquid crystal device according to claim 1, wherein light incident on the liquid crystal device is linearly polarized light, and a polarization plane of the linearly polarized light is orthogonal to a direction in which a parallel electric field is applied in the device. An optical path deflecting element characterized by shifting the position of the outgoing optical path with respect to the incident optical path in parallel by setting the direction. An image display element in which a plurality of pixels capable of controlling light according to image information are two-dimensionally arranged, a light source and an illumination device that illuminate the image display element, and an image pattern displayed on the image display element An optical device, display driving means formed by a plurality of subfields obtained by dividing an image field in time, and an optical path deflecting element for deflecting an optical path of light emitted from each pixel, and each subfield by the optical path deflecting element An image display device that displays an image pattern corresponding to a state in which the display position is shifted according to the deflection state of the optical path on the image display element, thereby increasing the number of apparent pixels of the image display element. In
An image display apparatus comprising the optical path deflecting element according to claim 9 as the optical path deflecting element.

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