JP2007231166A - 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 and forms a stable ferroelectric liquid crystal layer in a service temperature region, 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 one specific chiral compound. <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 is referred to as “shift amount” with respect to the optical path deflection due to the parallel shift, and the rotation amount is referred to as “rotation angle” with respect to the optical path deflection due to rotation. 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.

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

  The present invention has been made in view of the above-described problems in the prior art, and provides a liquid crystal element that forms a ferroelectric liquid crystal layer that is excellent in orientation and stable in the operating temperature range. An object of the present invention is to provide an optical path deflecting element that parallel shifts a transmitted optical path at high speed. Another object of the present invention is 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 high-path deflection 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. The base liquid crystal material having a phase series which is a smectic C phase contains at least a chiral compound of the following general formula (I).

（式中Ｒ^１は炭素数が１から１５の非置換、または一つが−ＣＮで置換、もしくは少なくとも一つの水素原子がＦかＣｌで置換されたアルキル基またはアルケニル基である。また、ＣＨ_２基が−Ｏ−，−ＣＯ−，−Ｏ−ＣＯ−，−ＣＯ−Ｏ，−Ｏ−ＣＯ−Ｏ−であってもよい。
また、式中Ａ^２は、１，４−フェニレン基、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイル、１，３，４−チアジアゾール−２，５−ジイル、１，２，４−チアジアゾール−３，５−ジイル、であり、１つか２つの水素がＦで置換されていてもよい。Ｚ^１、Ｚ^２、は互いに独立に−ＣＯ−Ｏ−，−Ｏ−ＣＯ−もしくは単結合である。また、ｍ＝１，２であり、１≦ｌ≦９である。）

(Wherein R ¹ is an unsubstituted or substituted alkenyl group having 1 to 15 carbon atoms, or one substituted with —CN, or at least one hydrogen atom substituted with F or Cl. CH ₂ The group may be —O—, —CO—, —O—CO—, —CO—O, —O—CO—O—.
In the formula, A ² represents 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4. -Thiadiazole-3,5-diyl, wherein one or two hydrogens may be replaced by F. Z ¹ and Z ² are each independently —CO—O—, —O—CO— or a single bond. M = 1, 2 and 1 ≦ l ≦ 9. )

  The invention of claim 2 provided to solve the above-mentioned problems is characterized in that, in the liquid crystal device of claim 1, the chiral compound of the general formula (I) is the following formula (II): It is a liquid crystal element.

（式中Ａ^３，Ａ^４は、それぞれ独立に１，４−フェニレン基、ピリジン−２，５−ジイル、ピリミジン−２，５−ジイルから選ばれ、１つか２つの水素がＦで置換されていてもよい。
また、式中Ｒ^２は炭素数が1から１５のアルキル基またはアルケニル基であり、１≦ｌ≦９である。）

(Wherein A ³ and A ⁴ are each independently selected from a 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, and one or two hydrogens are substituted with F. May be.
In the formula, R ² is an alkyl group or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9. )

  According to a third aspect of the present invention, there is provided the liquid crystal device according to the second aspect, wherein the chiral compound of the formula (II) is the following formula (III): It is an element.

（式中Ｒ^３は炭素数が１から１５のアルキル基またはアルケニル基であり、１≦ｌ≦９である。）

(Wherein R ³ is an alkyl or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9)

  According to a fourth aspect of the present invention, there is provided the liquid crystal device according to any one of the first to third aspects, wherein the base liquid crystal material contains at least one phenylpyrimidine compound. The liquid crystal element characterized by the above.

  The invention of claim 5 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 any one of claims 1 to 4. 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 6 provided to solve the above-mentioned problems is 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 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 apparatus for multiplying and displaying the apparent number of pixels comprises the optical path deflecting element according to claim 5 as the optical path deflecting element. It is the location.

As an effect of the present invention, according to the first to third aspects of the present invention, 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.
According to the invention of claim 4, it is possible to form a stable smectic phase near room temperature and to obtain a liquid crystal layer having a low viscosity and a high speed response.
According to the fifth aspect of the invention, the optical path transmitted through the liquid crystal layer is shifted in parallel with the inversion operation of the tilt direction of the optical axis tilt angle of the 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 6, since the optical path deflecting element having good orientation and excellent high-speed response is used, it becomes possible to deflect the optical path at high speed corresponding to the subfield image, and it is 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 changed 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, so that the required electric field is relatively low. 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 general formula (I).

In formula (I), R ¹ is an alkyl or alkenyl group having 1 to 15 carbon atoms, and one carbon atom is substituted with —CN, or at least one H is substituted with F or Cl. May be. The CH ₂ group may be —O—, —CO—, —O—CO—, —CO—O, —O—CO—O—. A ² represents 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4-thiadiazole. -3,5-diyl, wherein one or two hydrogens may be replaced by F. Z ¹ and Z ² are each independently —CO—O—, —O—CO— or a single bond. M = 1, 2 and 1 ≦ l ≦ 9.

The chiral compound of the general formula (I) is preferably the following formula (II).

At this time, A ³ and A ⁴ in formula (II) are each independently selected from 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, and one or two hydrogen atoms are It may be substituted with F. In the formula, R ² is an alkyl group or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9.

  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.

  Although the reason is not clear, since the spiral pitch of the chiral smectic C phase is appropriate, a liquid crystal layer having a good alignment with stable alignment and no alignment defects can be obtained even with a vertically aligned liquid crystal element having a thick liquid crystal layer.

(Second Embodiment)
The second embodiment is characterized in that, in the first embodiment, the chiral compound of the formula (II) is the following formula (III).

In the formula (III), R ³ is an alkyl group or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9. The reason is not clear, but since the helical pitch of the chiral smectic C phase is appropriate, a liquid crystal layer having a very good alignment property with stable alignment and no alignment defects can be obtained even in a vertically aligned liquid crystal device with a thick liquid crystal layer. .

(Third embodiment)
In the third embodiment, in the liquid crystal element of the first embodiment or the second embodiment, the base liquid crystal material contains a compound having at least one phenylpyrimidine skeleton.

  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 (a) and (b).

In formulas (a) and (b), 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 third embodiments, and the liquid crystal element 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.
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 1 below: 90 wt%
As an example of a chiral compound of formula (I), compound A shown by the following formula: 10 wt%

The phase transition temperature of this liquid crystal material is as follows: crystal / smectic C phase: −15 ° C., chiral smectic C phase / smectic A phase: 81 ° C., smectic A phase / nematic phase: 89 ° C., nematic phase / isotropic phase: It was 101-103 degreeC. Moreover, the result of measuring the spontaneous polarization by the SSFLC element was −24 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. As a result, the transmittance was good, almost no domain was observed, and a uniform alignment state was exhibited over a wide range.

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: 1.3 msec (when electric field E = 150 V / mm)
・ Saturation electric field: 270V
-MTF ratio: 0.883 (when driving at 100 Hz)

  The liquid crystal of this example has very good orientation and MTF is as high as 0.883. Although the response time is relatively slow at 1.3 ms and the saturation electric field strength is relatively large at 270 V, it has practical performance as a vertically aligned ferroelectric liquid crystal element.

(Example 2)
The image display apparatus shown in FIG. 7 was produced using the liquid crystal element of Example 1 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 1 are used as the optical path deflecting elements 20, the incident side is the first optical path deflecting element, the outgoing 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 6 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 1.3 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.

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 (6)

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 that generates a parallel electric field)
The liquid crystal layer contains at least a chiral compound of the following general formula (I) in a base liquid crystal material having a phase sequence that is an isotropic liquid phase, a nematic phase, a smectic A phase, and a smectic C phase from the high temperature side. A characteristic liquid crystal element.

(Wherein R ¹ is an unsubstituted or substituted alkenyl group having 1 to 15 carbon atoms, or one substituted with —CN, or at least one hydrogen atom substituted with F or Cl. CH ₂ The group may be —O—, —CO—, —O—CO—, —CO—O, —O—CO—O—.
In the formula, A ² represents 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,2,4. -Thiadiazole-3,5-diyl, wherein one or two hydrogens may be replaced by F. Z ¹ and Z ² are each independently —CO—O—, —O—CO— or a single bond. M = 1, 2 and 1 ≦ l ≦ 9. ) 2. The liquid crystal device according to claim 1, wherein the chiral compound of the general formula (I) is the following formula (II).

(Wherein A ³ and A ⁴ are each independently selected from a 1,4-phenylene group, pyridine-2,5-diyl, pyrimidine-2,5-diyl, and one or two hydrogens are substituted with F. May be.
In the formula, R ² is an alkyl group or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9. ) 3. The liquid crystal device according to claim 2, wherein the chiral compound of the formula (II) is the following formula (III).

(Wherein R ³ is an alkyl or alkenyl group having 1 to 15 carbon atoms, and 1 ≦ l ≦ 9)   4. The liquid crystal device according to claim 1, wherein the base liquid crystal material contains at least one phenylpyrimidine compound. 5. An optical path deflecting element that deflects an optical path of light according to an electrical signal,
5. 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 device comprising the optical path deflecting element according to claim 5 as the optical path deflecting element.

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