JP2009069297A - Optical deflection element and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ferroelectric liquid crystal element in which a liquid crystal aligning property in an effective region is prevented from deteriorating due to static electricity or deviation of a spontaneous polarization, and in which optical performance is not degraded. <P>SOLUTION: A light deflector has: a pair of transparent substrates stuck to each other by using a sealing material 6; a liquid crystal layer 7 filled between the substrates and forming a homeotropically aligned chiral smectic C phase; and a driving electrode 1 to generate at least an electric field in a direction parallel to the liquid crystal layer 7 (which is called a parallel electric field), and is characterized in that it has an independent electrically floating electrode (a dummy electrode 3) other than the electrode on at least one of the pair of substrates. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an optical deflection element and an image display device, and more particularly to an optical deflection element and an image display device using a ferroelectric liquid crystal.

  In an optical deflection element using a ferroelectric liquid crystal (for example, Patent Documents 1 and 2), since the orientation of the ferroelectric liquid crystal is very sensitive to an external field, static electricity generated during handling, Due to the bias of the spontaneous polarization caused by directing the spontaneous polarization of the ferroelectric liquid crystal in the same direction over the entire effective area, there is a problem that the orientation defect easily occurs in the effective portion and the optical performance is deteriorated. It was. However, the above prior art makes no mention of these measures.

  As a countermeasure against alignment disturbance caused by static electricity of a liquid crystal element, in Patent Document 3, a transparent dummy electrode is provided in a portion where a liquid crystal driving electrode is not provided, and the dummy electrode is connected to a driving circuit. Has been taken. In this element, since a relatively large voltage is used as the drive voltage, when the dummy electrode and the drive circuit are connected, a portion where a large electric field is generated between the dummy electrode and the drive electrode is formed. Since the liquid crystal in the part tends to go in a different direction from the other parts, a defect occurs in that part, which affects the optical performance.

In Patent Document 4, a method of arranging floating electrodes in a frame shape or an island shape around the display screen is taken. In this element, if a dummy electrode is provided in a frame shape, the dummy electrode has the same potential, and a relatively large voltage is used for driving as described above. Since a portion where an electric field is generated is formed, the liquid crystal in that portion tends to be directed in a different direction from other portions, so that a defect occurs and affects the optical performance. Further, in the island-shaped electrode, a gap is opened between the island-shaped electrodes, so that an oblique electric field is applied between the parallel electrode and the island-shaped electrode group extending in the vertical direction and the drive electrode end. , That part causes a deterioration in alignment and causes a deterioration in optical performance.
JP 2002-328402 A JP 2003-0985502 A JP 07-294948 A Japanese Patent Application Laid-Open No. 08-171082

  The present invention has been made in view of the above-described problems, and in a ferroelectric liquid crystal element, prevents deterioration in liquid crystal orientation in an effective portion due to static electricity or bias of spontaneous polarization, and provides optical performance. An object of the present invention is to provide a ferroelectric liquid crystal element that does not deteriorate the characteristics.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a pair of transparent substrates and a chiral smectic C phase having a homeotropic orientation filled between the substrates are bonded to each other using a sealing material. A liquid crystal layer to be formed, and a first line electrode that generates a parallel electric field that is an electric field in a direction parallel to at least the liquid crystal layer, and other than the first line electrode on at least one of the pair of substrates This is an optical deflecting element having an independent electrically floating dummy electrode.

  The invention according to claim 2 is characterized in that the dummy electrode is a second line electrode extending in a direction perpendicular to the parallel electric field with a predetermined distance on both sides of the drive electrode. The optical deflection element according to Item 1.

  The invention according to claim 3 is the optical deflection element according to claim 2, wherein the dummy electrode has a length equal to or longer than the first line electrode.

  According to a fourth aspect of the present invention, the light according to any one of the first to third aspects is characterized in that an insulating film is formed on the substrate so as to cover the drive electrode and the dummy electrode. It is a deflection element.

  The invention according to claim 5 is the optical deflection element according to any one of claims 1 to 4, wherein the dummy electrode has the same material and the same film thickness as the drive electrode.

  The invention according to claim 6 is the light deflection element according to any one of claims 1 to 5, characterized in that the dummy electrode is disposed from below the sealing material to the liquid crystal layer. .

  According to a seventh aspect of the present invention, there is provided the light deflection element according to any one of the first to sixth aspects of the present invention and the illumination light for each of a plurality of image subfields obtained by further subdividing the image field in terms of image information. An image display element that performs spatial light modulation and emits image light based on the image display element, wherein the light deflection element is synchronized with the image display element and driven for each image subfield. The image display device is characterized in that the optical path of image light incident from each pixel is deflected to increase the apparent number of pixels of the image display element for display.

  According to the present invention, in a ferroelectric liquid crystal element, a ferroelectric liquid crystal element that prevents the alignment of the liquid crystal in the effective portion from deteriorating due to bias of static electricity or spontaneous polarization and does not deteriorate the optical performance is provided. Is possible.

Hereinafter, preferred embodiments of the present invention will be described.
The light deflection element of the present embodiment includes a pair of transparent substrates, a liquid crystal layer that forms a chiral smectic C phase having a homeotropic alignment filled between the substrates, the substrates being bonded together using a sealing material, In a liquid crystal element having a first line electrode that generates an electric field in a direction parallel to at least the liquid crystal layer (hereinafter referred to as a parallel electric field), at least one of the pair of substrates is electrically connected independently of the electrodes. It has a floating electrode (hereinafter referred to as a dummy electrode).

The purpose of the configuration having such characteristics is to prevent alignment deterioration due to static electricity or the like. According to the configuration, charges generated by electrostatic induction are released by an electrode other than an electrode that generates an electrostatic field. Therefore, disorder of orientation can be prevented, and the bias of spontaneous polarization can be reduced.
Hereinafter, examples will be described with reference to the drawings.

Example 1
FIG. 1 shows the structure of an optical deflection element according to this embodiment. A pair of glass substrate substrates having a thickness of 1.1 mm were provided with transparent line electrodes having a width of 10 μm, a pitch of 100 μm and a number of 400 so as to alternate with each other, thereby forming a drive electrode (drive electrode 1 in FIG. 1). The length of the electrode was 40 mm. That is, the effective area was 40 mm square. In this element, ITO (Indium Tin Oxide) is used as the electrode material, but other transparent electrode materials may be used.

  The outermost electrode of the line electrode group is used as an extraction electrode (extraction electrode 2 in FIG. 1), and a driving voltage device is connected to the liquid crystal to drive the liquid crystal. In this element, a take-out electrode is provided in order to drive by applying a voltage to the electrodes at both ends, but this is not restrictive depending on the voltage application method.

  A line-shaped dummy electrode (dummy electrode 3 in FIG. 1) that is electrically floating with respect to the drive electrode is formed outside the drive electrode at a predetermined interval. At this time, the dummy electrode had the same length as the longitudinal direction of the driving line electrode. The electrode material of the dummy electrode may be anything as long as it is a conductor, but is preferably a transparent electrode, and particularly preferably the same material and the same thickness as the line electrode for driving. In FIG. 1, a dummy electrode is formed on the lower substrate for convenience, but it may be formed on the upper substrate or on both substrates.

  The dummy electrode 3 is a line electrode extending at a predetermined distance on both sides of the drive electrode 1 and extending in a direction perpendicular to the parallel electric field. In this case, in particular, it is possible to prevent alignment deterioration in the drive region. That is, by providing dummy electrodes on both sides of the drive electrode, charges generated by electrostatic induction can be released, so that it is possible to prevent the occurrence of alignment deterioration at the end of the drive region, resulting in improved optical performance. . Further, if the dummy electrode has the same length as the longitudinal direction of the driving line electrode, or more than the same length, the parallel electric field is not disturbed and orientation deterioration can be prevented. Further, if the electrode material of the dummy electrode is the same material and the same film thickness as the driving line electrode, the gap in the cell is made uniform, and optical performance deterioration can be prevented.

  A uniform resistor (resistor 4 in FIG. 1) is formed so as to straddle the driving line electrode, so that stepwise voltage is applied to each line electrode, and the direction perpendicular to the line electrode is applied. The horizontal electric field is generated. Although a resistor is formed on the line electrode here, an external device that can apply a voltage stepwise may be connected to each line electrode to generate a lateral electric field.

  A vertical (homeotropic) alignment film (alignment film 5 in FIG. 1) of a polyimide compound having a thickness of 0.06 μm was formed on the surface of the pair of substrates. 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. Here, a polyimide compound is used as the vertical alignment film. However, an inorganic hybrid vertical alignment film, an alignment film such as SiOx, or the like may be used, and if the liquid crystal is aligned vertically, no alignment film may be formed. Good.

  A 50 μm gap material was mixed with a UV thermosetting sealant (sealant 6 in FIG. 1) and applied to the substrate. At this time, the application position is preferably applied so as to partially overlap the upper portion of the dummy electrode. Further, it is particularly preferable to apply the seal material so that the seal material application position overlaps the drive region in the longitudinal direction of the drive line electrode. The presence of the dummy electrode under the sealing material makes it possible to produce a cell without gap unevenness.

A prescribed amount of liquid crystal that forms a chiral smectic C phase is applied in the area where the sealant is applied, and the upper and lower substrates are bonded together in a vacuum. Then, the pressure is returned to atmospheric pressure, and the UV light is 3000 mJ / The sealing material was pre-cured by irradiation with cm ² or more, and baked in an oven at 120 ° C. Here, with respect to the liquid crystal injection method, a portion where no sealant is applied may be provided, and injection may be performed using a capillary method or a vacuum injection method.

  The device manufactured by the above-described method has almost no alignment deterioration due to static electricity or the like, compared to a device without a dummy electrode.

(Example 2)
FIG. 2 shows the structure of the optical deflection element according to the second embodiment. Basically, the structure is the same as that of Example 1, except that an insulating film is sandwiched between the alignment film and the electrode. Therefore, other parts are omitted here, and only the insulating film layer will be described. In this example, the insulating film layer was formed before forming the alignment film in Example 1. Here, the insulating layer preferably has a surface resistivity of about 1 × 10 ¹⁰ to 1 × 10 ¹³ Ω / □. The solution was applied onto a substrate by flexographic printing, dried in an oven at 100 ° C., and then irradiated with UV light so that the accumulated light amount was 7100 mJ / cm ² or more. Thereafter, it was baked in an oven at 300 ° C. to form an insulating film. Thereafter, an alignment film was applied, and cell formation was performed in the same manner as in Example 1.

  The optical deflecting element thus fabricated showed good characteristics with no alignment deterioration due to static electricity or the like as compared with the optical deflecting element of Example 1.

(Example 3)
An example of application to an image display device will be described. FIG. 3 shows the configuration of the image display apparatus according to this embodiment. In FIG. 3, a light source 21 is 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, a transmissive liquid crystal panel 24 as an image display element, and a projection lens as an optical member for observing an image pattern 25 are arranged in order. The light source 21 is driven by the light source drive unit 27. Similarly, the liquid crystal drive unit 28 drives the transmissive liquid crystal panel 24.

  Here, an optical path deflecting element 29 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 29, a liquid crystal element as in the first and second embodiments is used.

  The illumination light that is controlled by the light source drive unit 27 and emitted from the light source 81 becomes illumination light that is made uniform by the diffusion plate 22, and is controlled by the condenser lens 23 in synchronism with the illumination light source by the liquid crystal drive unit 28 to be a transmission type The liquid crystal panel 24 is illuminated. The illumination light spatially modulated by the transmissive liquid crystal panel 24 enters the optical path deflection element 29 as image light, and the optical path deflection element 29 shifts the image light by an arbitrary distance in the pixel arrangement direction. The light transmitted through the optical path deflecting element 29 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 amount of shift by the light deflecting means 29 is set to ½ of the pixel pitch because 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.

  Specifically, a 0.9 inch diagonal XGA (1024 × 768 dots) polysilicon TFT liquid crystal light valve was used as the image display element. The pixel pitch is about 18 μm both vertically and horizontally. The aperture ratio of the pixel is about 50%. Further, a microlens array is provided on the light source side of the image display element 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 irradiated to the one liquid crystal panel at a high speed. In the present embodiment, the frame frequency of image display is 60 Hz, and the subfield frequency for pixel multiplication by 4 times by pixel shift is 240 Hz, which is 4 times. In order to further divide one subframe into three colors, an image corresponding to each color is switched at 720 Hz. A full color image can be seen by an observer 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.

  In this example, the liquid crystal element of Example 2 was used as the optical path deflecting element. Two sets of these elements were used, the incident side being the first optical path deflection element and the exit side being the second optical path deflection element. The line electrodes are arranged so that the directions of the line electrodes are orthogonal to each other and coincide with the arrangement direction of the pixels of the image display element. In this embodiment, the light emitted from the liquid crystal light valve is already linearly polarized light and the direction of polarization is arranged so as to coincide with the light path deflection direction of the first light path deflecting element. In order to ensure the degree of polarization, a linearly polarizing plate was provided as a polarization direction control means on the incident surface side of the optical path deflecting element. Therefore, the generation of noise light that goes straight without being deflected by the first light deflection 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 formed by spin-coating a polyimide alignment material on a thin glass substrate (3 cm × 4 cm, thickness 0.15 mm) to form an alignment film of about 0.1 μm. A rubbing treatment was performed after the annealing treatment of the glass substrate. An empty cell was fabricated by sandwiching an 8 μm thick spacer between the two glass substrates and pasting the upper and lower substrates so that the rubbing directions were orthogonal. Into this cell, a nematic liquid crystal having a positive dielectric anisotropy and an appropriate amount of a chiral material mixed was injected under normal pressure to produce a TN liquid crystal cell in which the orientation of liquid crystal molecules was twisted by 90 degrees. Since this cell is not provided with an electrode, it functions as a simple polarization rotation element.

  The polarizing plate of light emitted from the first optical path deflecting element and the incident surface of the polarization rotating element are arranged so as to be sandwiched between two optical path deflecting means so that the rubbing directions of the incident surface of the polarizing rotating element coincide with each other. The polarization plane of the light emitted from the first optical path deflection element is rotated by 90 degrees by the polarization plane rotation element, and coincides with the deflection direction of the second optical path deflection element. A pixel shift element comprising a first optical path deflecting element, a polarization plane rotating element, and a second optical path deflecting element was installed immediately after the liquid crystal light valve.

  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. The shift amount of the light deflection element under these conditions was 9 μm. By rewriting the subfield image to be displayed on the image display device at 240 Hz, a high-definition image in which the apparent number of pixels in the vertical and horizontal directions was multiplied by 4 could be displayed. In addition, light scattering due to orientation degradation was suppressed, and a clear image could be displayed.

  The preferred embodiment of the present invention has been described above, but the present invention is not limited to this, and various modifications can be made without departing from the scope of the invention.

It is a figure which shows the structure of the optical deflection | deviation element which concerns on Example 1 of this invention. It is a figure which shows the structure of the optical deflection | deviation element which concerns on Example 2 of this invention. It is a figure which shows the structure of the image display apparatus which concerns on Example 3 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 8 Drive electrode 2, 9 Extraction electrode 3, 10 Dummy electrode 4, 11 Resistor 5, 12 Alignment film 6, 13 Sealing material 7, 14 Liquid crystal layer 15 Insulating film 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 Liquid crystal drive unit 29 Optical path deflecting element 30 Drive unit

Claims (7)

A pair of transparent substrates, and a liquid crystal layer that forms a chiral smectic C phase in which the substrates are bonded together using a sealing material and have a homeotropic alignment filled between the substrates;
A first line electrode that generates a parallel electric field that is an electric field in a direction parallel to at least the liquid crystal layer, and
An optical deflecting element having an independent electrically floating dummy electrode other than the first line electrode on at least one of the pair of substrates.   2. The optical deflection element according to claim 1, wherein the dummy electrode is a second line electrode that is spaced a predetermined distance from both sides of the drive electrode and extends in a direction perpendicular to the parallel electric field.   The optical deflection element according to claim 2, wherein the dummy electrode is longer than the first line electrode.   4. The optical deflection element according to claim 1, wherein an insulating film is formed on the substrate so as to cover the drive electrode and the dummy electrode. 5.   5. The optical deflection element according to claim 1, wherein the dummy electrode has the same material and the same film thickness as the drive electrode.   6. The optical deflection element according to claim 1, wherein the dummy electrode is disposed from under a sealing material to the liquid crystal layer. An optical deflection element according to any one of claims 1 to 6,
An image display element that spatially modulates illumination light based on image information and emits it as image light for each of a plurality of image subfields obtained by further subdividing the image field in time,
The light deflection element is
Synchronizing with the image display element, the optical path of image light incident from each pixel of the image display element driven for each image subfield is deflected to multiply the apparent number of pixels of the image display element An image display device characterized by being displayed.

Images