JPS6151129A - Liquid crystal optical switch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application] The present invention is characterized in that the time between successive color fields is divided into a plurality of electrically isolated and independently electrically driven cell segments. The present invention relates to a liquid crystal optical switch suitable for application to a field sequential color display system equipped with a liquid crystal element that is shortened and has improved color characteristics of images.

[Prior Art and Problems to be Solved by the Invention] A high performance field sequential liquid crystal color display system can display high resolution multicolor images with good contrast and good color purity. However, a well-known problem with the liquid crystal switching devices used here is that the quality of the color images displayed by display systems incorporating these devices is relatively poor. In particular, the response speed of the liquid crystal (on field orientation)
It is known to be relatively slow when switching from the state to the released (off) state. As a result, during the transition of the liquid crystal element from the on state to the off state, information in a certain color field is displayed in the color of the immediately previous color field.

A solution to this problem is shown in Midleton US Pat. No. 4,295,093 for a spectrum analyzer with liquid crystal switching elements. The liquid crystal switching element is separated into first and second adjacent regions of liquid crystal material, and each of these regions is independently controlled by voltages generated from different outputs of the drive circuit. These regions share a common electrode that is maintained at a fixed reference potential.

In column 4, lines 21-38 of Midleton's US patent specification, the structure of the liquid crystal element is explained as follows with reference to FIG. 2 thereof. "This device consists of a film of twisted nematic liquid crystal material...on one side of this film (a) a single transparent electrode (211) maintained at a fixed potential is provided, Two transparent electrodes (c) and (c) covering each half of the film are provided on the other side.These two transparent electrodes are connected to a color selection circuit (15) via conductors c!4 and (c). The above-mentioned liquid crystal element is arranged in front of a shadow tube screen that performs cylindrical scanning with an electron beam.

The separation line that separates the adjacent first and second regions of the liquid crystal element is substantially parallel to the line scanning direction of the rask scanning pattern. To explain the operation, in the first color state, the first
scanning the area while switching a second area of liquid crystal material from a first color state to a second color state.

By alternating the color states of the first and second regions of the liquid crystal element, the previously scanned region is set to another color state before the electron beam returns to the previously scanned region.

U.S. Pat. No. 4,328,493 to Shanks et al., like the aforementioned Midleton U.S. patent, discloses a color display with liquid crystal elements configured as first and second adjacent regions of liquid crystal material. . The Shanks et al. patent describes the timing sequence of signals generated at the output of the drive circuit. This signal is an alternating current pulse of two frequencies, one of which is connected to the first
and the second region alternately. In a manner similar to that described in the above-mentioned Midleton patent, the alternating two-color beams at the output form a multicolor image.

The liquid crystal devices disclosed in the Midleton and Shanks et al. patents have the disadvantage of optical cross talk between adjacent regions of the liquid crystal device. This cross talk means that an electric field supplied to a region scanned by an electron beam is transmitted to a non-scan region, and streaky transmission of light occurs from there. Therefore, two adjacent liquid crystal materials
The two regions are electrically isolated from each other and are not optically independent. This results in a reduction in image quality for color display systems.

Therefore, one of the objects of the present invention is to provide a liquid crystal optical switch suitable for application to a high-performance field sequential liquid crystal color display system that displays high-resolution multicolor images with strong contrast and good color purity.

Another object of the present invention is to provide a liquid crystal optical switch suitable for application in a multi-segmented display system with a minimum amount of optical cross talk.

Still another object of the present invention is to provide a liquid crystal optical switch suitable for use in a display system that reduces the time between successive color fields and improves the image color characteristics of the display system.

Another object of the invention is to provide a liquid crystal switching element that is divided into a plurality of segments, each of which has an independent reference voltage [pole] to minimize optical cross-talk between cell segments. The present invention provides a liquid crystal optical switch suitable for use in display systems.

SUMMARY OF THE INVENTION The present invention relates to a liquid-crystal device that operates as a high-speed optical switch in a color display system.

A liquid crystal display element receives light from a light source in a predetermined polarization state. The liquid crystal display device is comprised of first and second adjacent cell segments, the first cell segment having first and second separated electrode structures with a liquid crystal material sandwiched therebetween, and the second cell segment having first and second separated electrode structures with a liquid crystal material sandwiched therebetween. - The segment has third and fourth separate pole structures with liquid crystal material sandwiched between them. 1st
and electrically connecting the third electrode body to an electrical reference of the switching means or circuit.

A first output of the switching circuit is connected to the second electrode structure. The first output supplies a first voltage across the electrodes of the first cell segment to create a first voltage in the cell φ segment.
Generates an electric field. A second output end of the switching circuit is connected to a fourth electrode. This second output terminal is the second cell
A second g voltage is applied between the electrodes of the segment to generate a 42tlE field within this cell segment. The switching circuit operates to independently vary the polarization state characteristics of the light beam passing through each of the first and second cell segments.

The first and third electrode structures of the liquid crystal device are electrically isolated to isolate the first and second electric fields within the cell segment. Thus, a change in the polarization state characteristic of a light ray passing through one cell segment results in a minimal change in the polarization state characteristic of a light ray passing through the other cell segment.

In a preferred field sequential color display system,
The liquid crystal element of the present invention is placed in front of the screen of a scanning cathode ray tube and receives light from this screen.

The liquid crystal element acts as a variable optical retarder and is disposed between the color selective polarizing filter and the achromatic light polarizing filter. A polarizing filter that receives light from the cathode ray tube determines the polarization state of the light that enters the variable optical retarder. A variable optical retarder changes the characteristics of the polarization state of a light beam passing through it in response to a voltage applied by a switching means or circuit. The variable optical retarder has a first amount of optical retardation that causes the display system to produce light output of a color, and a second amount of optical retardation that causes the display system to produce light output of a second color. The first quantity provides essentially zero turbulence for all wavelengths of light, and the second quantity provides a fraction of the color produced by the display system.
Approximately half-wavelength tarpsion is performed on light beams of two wavelengths.

A liquid crystal variable optical retarder is separated into upper and lower cell segments. Each cell segment is independently controlled by a different output of the switching circuit in a predetermined timing order.
In each color field, half of the optical image information generated by the register-scanning cathode ray tube is displayed.

The liquid crystal device disclosed in the Midleton and Shanks et al. patents mentioned above uses a common electrode structure connected to an electrical reference for both cell segments. However, the liquid crystal element of the present invention has a separate or "electrically isolated" electrode structure connected to the electrical reference of the switching circuit. Separate electrode structures are used to isolate the effects of noise voltages induced in the reference electrode of one cell segment from the other cell Φ segment,
Minimize electrical cross talk between segments. By minimizing electrical cross talk, we also minimize optical cross talk between two cell segments. As a result, the display system changes the color field very quickly and produces high quality color images with minimal spurious transmission of colored light.

Other objects and advantages of the invention will be understood from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.

〔Example〕

(Schematic structure and operation of color display system) FIG. 1 shows a preferred example of a field sequential color display system α designed using a liquid crystal optical switch according to the present invention.
, this system 00) is a liquid crystal variable optical retarder [121
Contains. This retarder (121 is optically related to the color selection polarizing filter side and the achromatic polarizing filter αe,
It is placed between these filters. The input surface (181) of the variable optical retarder uz is connected to two grounded separated electrode structures (2z and (
24). Output surface of variable optical retarder α2 +2
6) is divided into two separated electrode structures c3 and Gz along a horizontal non-25-electrode separation line (to) K. As shown, an electrode structure (22 and (by 301 the first or upper cell segment) C34) is formed, and the electrode structure 2
41 and (32) constitute the second, ie, downlink 1a cell segment (to).

The color selection polarizing filter I has orthogonal polarization states,
One polarization state allows only the first color of light to pass, and the other polarization state allows only the second color of light to pass. Colorless polarizing filter (lt9 has two orthogonal polarization states,
One polarization state allows all colors of light to pass through, and the other polarization state absorbs all colors of light. In a preferred embodiment of this color display system, a polarizing filter (14
) and (l(9) have linear polarization axes arranged at right angles to each other.

The optical assembly consisting of a variable optical retarder az and polarizing filters U, aS constitutes a fast color switch,
Placed in front of the light source, ie the image source.

This image source generates light from a phosphor screen screen to produce light images of two basic colors, eg red and green.

In a preferred embodiment of this display system, the signal generated by the rask generator (42) in response to the output of the image source (effectively a television-type rask-scanned cathode ray tube, frame synchronization circuit G14) 7V-frames of information are sequentially represented. Each frame contains two fields of image color information, alternating between first and second color field periods.

During a first color field period, fluoresces information relating to both the shape of any image that appears in a first color, e.g. red, and the shape of any image that appears in a combination of red and a second color, e.g. green. body screen (write to 40. 2nd
During the color field, the phosphor screen (
Write to 4G. The color selection polarizing filter I is a phosphor filter I.
J+n (4G) and polarizes the light orthogonally and linearly for red and green. The polarized light is then transmitted to the input fixture of the variable optical retarder α2.

Switching means or circuit +46) H receives at its input a signal from the output of the frame synchronization circuit 04) and drives the variable optical retarder uz in synchronization with the sequential frame rate of the image information generated by the image source. do. Thus, during the first color field, switching circuit f45 sequentially places cell segments of variable optical retarder α2 in a partially released state, ie, in an off state, as described below. In the optical axis direction of this off-state cell segment, the green light that has passed through the polarizing filter I undergoes approximately half-wavelength tarpsion. During this period, the green color does not pass through the linear polarization axis (161) and the unwanted image components of the green color appearing on the phosphor screen (40) during this first period are removed.

During the 8g two-color field, as described below, the switching circuit (46) sequentially changes the variable optical retarder (12+ cell self-segments (to) and (to) to field orientation states,
That is, it is turned on. In the optical axis direction of this on-state cell segment, there is a substantial zero turbulence for both the red and green light passing through the polarizing filter α4. Furthermore, as will be described later, the absorption axis of the colorless polarizing filter le absorbs only red light.

FIG. 5 is a timing diagram showing the timing relationship between the switching signals provided to cell segment c341 and cell segment C341 to generate the two color fields of an image frame. The first color field period extends from time T1 to time 15, and the first color field period extends from time T5 to time T9. Line A in FIG. 5 represents the switching circuit G1 supplied to the electrode structure 0Q of the cell segment.
Line B shows the voltage signal at the output 5 (I) of the switching circuit (46), which is supplied to the electrode structure 03 of the cell segment country.

Cell segment (to) and national electrode sliding body and (2
The voltage signal applied to turn on each cell segment is preferably peak-to-peak. 1 to 4 when the value is 54V or the effective value is 20V
This is a kHz AC pulse, which is shown in FIG. 5 as a shaded rectangle. The voltage signal applied to turn each cell segment off is preferably zero volts.

8g1 to reduce the time between consecutive color fields
and the second color field period into first and second sub-periods. As shown in FIG. 5, the first sub-period of the first color field extends from time Tl to T3K, and the second sub-period of the first color field extends from time T3 to T5.

From time Tl to T3, cell segment G341
is in the off state and receives the light beam generated by the scanning electron beam, causing red light to be the output of the portion of the display system covered by cell segment C34). Between time points T3 and T5, the cell segment remains off and receives the beam generated by the scanning electron beam, causing red light to be the output of the portion of the display system covered by the cell segment. From time T to T2, the cell segment (to) remains in the on state, and the light emitted from the phosphor of screen (4) is Delay the change to the off state of the first color field of the illustrated image 7 ram until it disappears.
Ensure color continuity of composite images in each color field1
6. As shown by line AK in FIG. At time T4, cell segment Cl1l is switched to allow sufficient time for the liquid crystal molecules to stabilize in the on state K, before time 'r5, at the beginning of the first sub-period of the second color field period. .5th
As shown in line B of the figure, cell segment) C36
At time T6, before the electron beam starts scanning the area of the screen f41 covered by 1, the cell segment is turned on.

8 by switching the cell segment forces at time T6.
g Time point T at which the second sub-period of the two-color field period starts
Before 7K, allow sufficient time for the liquid crystal molecules to stabilize in the on state.

As shown in FIG. 5, the first sub-period of the second color field extends from time T5 to T7, and the second sub-period of the second color field extends from time T7 to T9. Between time points T5 and T7, the cell segment C34) is on, receives the light rays generated by the scanning of the electron beam, and produces green light as the output of the display system covered by the cell segment (b). Between time points T7 and T9, the cell segment (a) is in the on state and receives the light rays generated by the scanning of the electron beam, producing green light as the output of the display system covered by the cell segment (a). do. cellu segment) G4) and (to) K from time T7 to T8 and from time T9 to T'i, respectively.

and the change to the off state in the first color field of the next successive image frame is delayed for the same reasons as described above for time Tl to T2.

As shown in line A in FIG.
Turn on. cell segment (goods) at time T8
This allows sufficient time for the liquid crystal molecules to stabilize in the off state before the start time T9 of the first color field of the next consecutive image frame. Repeat the above process for successive image frames.

Alternating image information fields in the first and second color field periods are transmitted through a color selective polarizing filter (14) and synchronously to a variable optical retarder az and an achromatic polarizing filter αe. During two periods corresponding to alternating fields of the television rask signal, the information appearing at the output of the polarizing filter (161) due to afterimages in the retina of the observer's eye is accumulated and the effect of a single polychromatic image is Intensity modulation of the optical image source produces all colors within the spectral range between red and green.

(Direction of light components) In FIG. 1, the polarizing filter α4 has a color selection vertical polarization axis 15 that passes light of color C1 such as red, and a color selection horizontal polarization axis that passes light of color C2 such as green. There is a shaft 64. The polarizing filter (161) has a light absorption vertical polarization axis 15G that does not allow light to pass through, and a light transmission horizontal polarization axis 6 that allows light of all wavelengths to pass.

The variable optical retarder +17J includes nematic liquid crystal cell segments, each of which constitutes a zero to approximately half wavelength optical retarder. This retarder selectively provides essentially zero retardation for normally incident light of all colors in the on state and approximately half-wave retardation for normally incident green light in the off state. Cell segment 3
The light transmission surface (projection of the optical axis on 67J ([io)] and the light transmission surface of the cell segment (36) (projection of the optical axis on 6) f64) are The polarization axes are shown in dotted lines on the plane (62 and t66) of the variable optical retarder 121.

Each of the cell segments and fields of the variable optical retardation z independently switches between two optical retardation states. The two optical retardation states are applied to the display system (1) as two selectable optical transmission states, each state producing a display system output of red or green light.

A voltage signal applied to the output conductor of the switching circuit (46) causes the horizontal polarization axis 5a of the polarizing filter I to be brought into an off optical retardation state by placing one of the cell segments of the OT variable optical reader U in an off-optical retardation state. The polarization direction of the passing green normally incident ray is rotated by 90 degrees.

The green light beam is projected onto a polarizing filter (iGK) and absorbed by the vertical polarization axis 60 of the polarizing filter a0. The polarization direction of the red normal incident light beam that has passed through the vertical polarization axis a of the polarizing filter a0 is Variable optical retarder Cl2 in off state
#1) Rotate to an angle slightly different from 90 degrees. The red light beam is thus separated into components along the vertical and horizontal polarization axes of the polarization filter. The red light beam includes a large component of light that is projected onto the polarizing filter (16) and transmitted with the horizontal polarization axis 6s, and a small component of light that is projected onto the polarizing filter (161) and absorbed by the vertical polarizing cap 6e. There is.

Thus, in the first optical transmission state, pure red light is generated from the display system [alpha]. As a result of the vertical polarization axis c′iω of the polarization filter αG absorbing a small amount of red light,
In the first optical transmission state, the brightness of the red light is actually reduced very slightly.

The voltage signal supplied to the output conductor of the switching circuit (4G) causes the vertical polarization axis 521 of the polarization filter (14) to change when either one of the cell segments of the variable optical retarder (IZ) is in the on-optical retardation state. The polarization directions of the red ray passing through and the green ray passing through the horizontal polarization axis 1!54) do not change, and these rays pass through the variable optical retarder qz and hit the polarization filter (161).The vertical polarization axis of the polarization filter αθ 60 absorbs the red orthogonally incident rays and outputs the green orthogonally incident rays from the display system αω via a polarizing filter (formerly a horizontal polarization axis).

Thus, in the second optical transmission state, pure characteristic green light is output from the display system.

Table 1 summarizes the color of light output from the display system (I) in each of the two optical transmission conditions mentioned above.

Table I (Structure of Liquid Crystal Element) A preferred embodiment of the display system includes a liquid crystal element with the structure described below.

2 and 3 are a plan view and a side sectional view of the liquid crystal element. The liquid crystal element (100) includes first and second electrode structures (102) and (104) that are spaced apart and substantially parallel;
Third and fourth electrode structures (106
) and (ios). Electrode structure (102
) and (106) and electric @ structure (104) and (108
) is provided with a continuous region of nematic liquid crystal material (110). [Polar structures (102) and (106)
has a generally planar common glass dielectric substrate (112) with two adjacent layers of conductive, transparent material such as indium tin oxide on its inner surface, namely regions (114) and (
116). The conductive region (114) becomes part of the first electrode structure (102) and the conductive region (116) becomes part of the third electrode structure (102).
It becomes part of the electrode structure (106). A straight non-conducting gap or separation line (118) separates the 28-conducting regions (114) and (116). Separation line (
The width of the substrate (118) is approximately 0.0250, and a laser beam is preferably used to form this separation line and the width of the substrate (118) is approximately 0.0250.
2) Dividing the single layer of conductive material on top into approximately equally sized regions (114) and (116).

The director alignment film layer (120) is attached to the electrocardiographic area (11
4) and (116) to form a boundary between the liquid crystal material (110) and the electrode structures (102) and (106). The constituent materials of the director alignment film (120) and the corresponding adjustment method will be described in detail later.

The construction of electrode structures (104) and (ios) is similar to electrode structures (102) and (106), and the components of these electrode structures (102) and (106) are designated with a prime sign in their reference numbers. Shown.

Great? (122) C. Construct from a suitable material such as polyester film or fused glass frit to maintain the desired spacing between the glass substrates (112) and (112). In a plane approximately perpendicular to the surface, the separation line (118) and (
These glass substrates are appropriately arranged so that the 118-fold direction matches. The electrode groove bodies (102) and (104) become the first cell segment (124), and the electrode structure (
106) and (108) are the second cell segment (12
6). Cell segments (124) and (126) are shown within the dotted lines in FIGS. 2 and 3.

When incorporating the liquid crystal element (100) into a display system (such as 101), the switching circuit (46) (first
The individual voltage signals generated independently at the output end of the cell
Terminals (128) of segments (124) and (126)
and (130), respectively. cell segment) (
A common reference potential for (124) and (126) is provided to the respective terminals (132) and (134). These terminals (1
32) and (134) are preferably switching circuits (
46) Connect to the ground potential (Figure 1).

During Ji# operation of the display system, as the cell e segment switches between optical retardation states, a noise voltage is generated on the grounded electrode structure of the cell segment. A non-471L isolation line (118) separates the conductive layers (114) and (1161) so that noise voltages on one ground electrode have minimal effect on the electric field characteristics in the adjacent cell segment. Such isolation of the electric fields minimizes optical cross-bone talk between cell segments, thus eliminating spurious transmission of colored light from the display system caused by optical cross-talk.

Those skilled in the art will appreciate that a liquid crystal device can be divided into two or more cell segments and each cell segment provided with an independent reference electrode structure to achieve the effects described above. Furthermore, designing as a separate reference electrode structure can also reduce optical cross-talk in color display systems incorporating other liquid crystal elements, such as lysted nematic elements.

(Liquid Crystal Variable Optical Retarder) In a preferred example of the display system α■ to which the present invention is applied,
It incorporates a variable optical retarder α2 consisting of a liquid crystal element, which is divided into two cell segments,
Each operates as a zero to approximately half-wave optical retarder. Cell segment of liquid crystal element (100) (124)
The operation of a cell segment as a variable optical retarder will be explained by way of example with respect to the molecular orientation form of the liquid crystal material packed therein.

For clarity of explanation, the switching circuit (4
Switching between optical retardation states will be described with occasional reference to operation 6).

FIGS. 4A and 4B are diagrams showing the director orientation configuration of one cell segment of a liquid crystal device according to the present invention. Liquid crystal cell segment) (124) layer (120)
The nematic director orientation configuration of (120') is described in U.S. Pat. No. 4,333,708 to Boyd et al., column 7, lines 48-55. but,
The liquid crystal cell described in the Dade et al. patent differs from the present invention in that it has an alternating tilted geometry, with only a partial director orientation of the liquid crystal element. The cell of the Dade et al. patent undergoes disclination movement within the cell to become a bistable switching element.

The electrode structure (102) is arranged so that the directors (140) welded to the surface of the electrode structure are arranged parallel to each other at an angle of →θ in a counterclockwise rotation direction with respect to the surface of the film layer (120). Adjust the film layer (120). Further, the electrode groove body (104) is arranged so that the directors (142) in contact with the surface of the electrode structure are arranged parallel to each other at an inclination of 10 in the clockwise direction with respect to the surface of the film layer (120 mm). The film layer (120') is adjusted so that on the opposite surfaces of the director alignment layers (120) and (120') of the electrode groove bodies (102) and (104), the directors (140) and (142') are in contact with these surfaces. )
The cell segments (124) are configured such that the cell segments (124) are tilted in opposite directions.

A first preferred method of achieving the desired orientation of the surface-contact director utilizes polyimide as the material constituting the orientation films M (120) and (120') on the electrode structures (102) and (104). Each oriented film layer is rubbed to adjust the tilt angle 1θ1 to an appropriate range of 2 to 5 degrees. A second preferred method of achieving the desired orientation of the surface contact director is to provide the oriented film layer (1) of the electrode groove bodies (102) and (104).
Silicon monoxide is used as a material constituting 20) and (120'). This -silicon oxide layer is vaporized,
10 to 30 degrees, preferably 15 to 2 degrees to the electrode structure surface
Sufficient amount of vaporized material is deposited, preferably at an angle of 5 degrees, to provide an inclination angle 1θ1 in the range of 5 degrees.

Methods of depositing silicon monoxide or other alignment materials to orient liquid crystal molecules in desired directions are conventional and known to those skilled in the art. One such method is disclosed, for example, in U.S. Pat. No. 4,165,923 to Janning.

Figure 4A shows an AC signal ■1 with an effective value of 20 V at approximately 2 kHz.
shows the direction of the surface non-contact director (144) when added to the conductive layers (114) and (114') of the electrode structures (102) and (104), respectively. The signal vl of the conductive layer (114) to the grounded conductive layer (114) allows the first switching state produced at the output end (48) of the switching circuit (4e) to be realized and the cell segment to be connected to the conductive layer (114).
An alternating electric field E is generated between electrode structures (102) and (104) in (124) to bring this cell segment into an on-optical retardation state. A large number of plane non-contacting directors (144) of liquid crystal material (110) of positive anisotropy value are oriented end-to-end along the direction of the electric field lines (146) within the cell segment. let This direction is perpendicular to the tuned plane of the electrode structure. Thus, when the cell segment (124) is placed in an on-optical retardation state, the surface non-contact director (144)
are oriented perpendicular to the plane of the cell segment.

FIG. 4B shows that the signal vl is removed and the electrode structure (104)
surface non-contact director (144) after maintaining it at ground potential.
) indicates the direction. Orientation of surface non-contact director, cell
It is not affected by the electric field generated between the electrode structures (102) and (104) in the segment, but due to the intermolecular elasticity υ which releases the plane non-contacting director from the edge-to-edge orientation of the on-optical retardation state. Overshadowed. By grounding the electrode structure (104), the switching circuit (46)
A second switching state is realized by the output terminal +48. The director orientation shown in FIG. 4B corresponds to the director orientation of the off-optical retardation state of the cell φ segment.

It also removes the signal l and momentarily grounds the IrL pole structure 4), immediately releasing the liquid crystal material in the cell segment to an off state, lower than the signal l, typically about 1 ．． The switching circuit (461
(Even if the 4S AC/DC signal v2 is added to the cell segment layer (114') K, the cell segment) (124
) can be switched to an off-optical retardation state. This value of signal v2 maintains this orientation of the liquid crystal molecules of the cell segment and keeps it in the off state. The frequency of the signal v2 is approximately equal to the frequency of the signal ■1.

While the cell [phase] segment transitions from an on-optical retardation state to an off-optical retardation state, the surface non-contacting director moves from the end-to-end orientation normal to the electrode (
J￥The structure changes towards the surface, and can be regarded as almost parallel to the nearby director.

Therefore, the surface non-contact directors (144a) and (144
b) rotates in the clockwise direction as shown by the arrow (148a), and the directors (140) and (144a) are in a substantially parallel relationship. In addition, a surface non-contact director (1
44c) and (144d) are rotated clockwise as shown by arrow (148), and the directors (142) and (144c) are approximately parallel to each other. Therefore,
When the cell segment (124) is dissolved to an off-optical retardation state, each of the numerous surface non-contacting directors is oriented to direct the director component toward the cell segment surface. However, a portion of the surface non-contacting director remains in the plane perpendicular to the cell segment surface.

Due to the manner in which the liquid crystal cell segment (124) operates as a zero to approximately half-wave optical retarder, the free surface non-contact director of the disclinations produces an oriented electric field, i.e., an on-optical retarder as shown in FIG. 4A. from the retardation state to the planar configuration, ie, the off-optical retardation state shown in FIG. 4B.

In the present invention, the liquid crystal cell segment (124) acts as an approximately half-wavelength optical retarder, the optical axis of which corresponds to the orientation direction of the non-contacting surface director (144).

When the liquid crystal cell segment is in the on-optical retardation state, linearly polarized light propagating in the direction (150) perpendicular to the surfaces of the electrode structures (102) and (104) is directed to the surface non-contacting director (144). ) direction. The on-optical retarder 7
The projection of the optical axis on the plane of the electrode structure of the cell segment can be ignored. These circumstances cause the liquid crystal cell segment (124) to be in the direction (150).
greatly reduces the optical retardation of incident light transmitted to the

When the liquid crystal cell segment is in the off-optical retardation state, linearly polarized light transmitted in the direction (150) perpendicular to the surfaces of the electrode structures (102) and (104) is directed toward the surface of the non-contacting director. The orientation direction does not match. Since the directors (144) are in an off-optical retardation state, each of the numerous directors projects an image element onto the electrode structure surface of the cell segment. Due to these circumstances, liquid crystal cell segment) (124)
Provides effective birefringence for nearly perpendicular incident light. Depending on the direction of the surface non-contact director (144), approximately half-wave optical retardation is given to light having a wavelength that satisfies the following equation.

Δnd/λ=1/2 where d represents the thickness 152) and Δn represents the actual birefringence of the cell segment.

〔Effect of the invention〕

As described above, according to the present invention, the liquid crystal device is composed of a plurality of cell segments, and the reference potential electrodes of each cell segment are independent from each other, so that optical crosstalk can be minimized.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a field sequential color display system incorporating a preferred embodiment of the present invention, FIG. 2 is a top view of a liquid crystal device used in a preferred embodiment of the present invention, and FIG.
4A and 4B are diagrams for explaining the director alignment state of the liquid crystal element, and FIG. 5 is a timing chart of voltage signals for switching cell segments of the liquid crystal element. In the figure, (46) is a switching circuit, (100)
are liquid crystal elements, 341, (361, (124) and (
126) is a cell segment, (2z, (2(a), (
7), G3a, (114), (116),
(114') and (116') are electrodes.

Claims (1)

[Claims] a liquid crystal element; and a switching means for controlling the liquid crystal element;
and a second electrode, the first cell segment having a reference potential supplied to the first electrode, and third and fourth electrodes facing each other with a liquid crystal material interposed therebetween, the third electrode having the reference potential supplied to the third electrode. a second cell segment adjacent to said first cell segment, said switching means selectively applying a voltage signal to said second electrode to cause a second cell segment to enter said first cell segment; 1 electric field and selectively applying a voltage signal to the fourth electrode to generate a second electric field in the second cell segment and passing through each of the first and second cell segments. A liquid crystal optical switch that is characterized by independently changing the polarization state of light.