Source: http://www.google.com/patents/US5654784?dq=7565338
Timestamp: 2014-03-09 12:08:11
Document Index: 159321609

Matched Legal Cases: ['in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'in fine', 'art 6', 'art 6', 'art 6', 'Application No. 3']

Patent US5654784 - Liquid crystal devices comprising a multitude of domains having different ... - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA liquid crystal device comprises a pair of substrates and a liquid crystal provided between the paired substrates wherein domains whose threshold voltages are different from one another are finely distributed throughout the liquid crystal. In particular, the respective substrates each has a transparent...http://www.google.com/patents/US5654784?utm_source=gb-gplus-sharePatent US5654784 - Liquid crystal devices comprising a multitude of domains having different threshold voltages for switching liquid crystalsAdvanced Patent SearchPublication numberUS5654784 APublication typeGrantApplication numberUS 08/139,908Publication dateAug 5, 1997Filing dateOct 22, 1993Priority dateOct 24, 1992Fee statusPaidAlso published asDE69327700D1, DE69327700T2, DE69333354D1, DE69333354T2, DE69333414D1, DE69333414T2, EP0595219A2, EP0595219A3, EP0595219B1, EP0831358A2, EP0831358A3, EP0831358B1, EP0831359A2, EP0831359A3, EP0831359B1, US6040884Publication number08139908, 139908, US 5654784 A, US 5654784A, US-A-5654784, US5654784 A, US5654784AInventorsYang Ying Bao, Eriko Matsui, Keiichi Nito, Hidehiko Takanashi, Akio YasudaOriginal AssigneeSony CorporationExport CitationBiBTeX, EndNote, RefManPatent Citations (20), Non-Patent Citations (12), Referenced by (22), Classifications (18), Legal Events (6) External Links: USPTO, USPTO Assignment, EspacenetLiquid crystal devices comprising a multitude of domains having different threshold voltages for switching liquid crystalsUS 5654784 AAbstract A liquid crystal device comprises a pair of substrates and a liquid crystal provided between the paired substrates wherein domains whose threshold voltages are different from one another are finely distributed throughout the liquid crystal. In particular, the respective substrates each has a transparent electrode and an alignment film formed thereon in this order and the substrates are assembled to establish a given space therebetween, and a ferroelectric liquid crystal being injected into the given space wherein domains are finely distributed as set out above, thereby providing a a liquid crystal display device. The fine distribution is such that when a transmittance through inverted domains is 25%, the number of domains (microdomains) having a size of larger than 2 μmφ in a field of 1 mm.sup.2 is not smaller than 300, preferably not smaller than 600, and the width of the threshold voltage within the domains is not smaller than 2 volts within a transmittance range of from 10 to 90%. The liquid crystal device, particularly the display device, keeps a high contrast and can easily, reliably realize an analog gray-scale display at low costs.
What is claimed is: 1. A liquid crystal device of the type which comprises a pair of substrates, each having a planar conductor, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed in said liquid crystal, wherein a temperature dependence of a cone angle of liquid crystal molecules constituting a plurality of domains whose threshold voltages are different from one another is smaller than that of a monodomain.
2. A liquid crystal device of the type which comprises a pair of substrates, each having a planar conductor, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed in said liquid crystal wherein fine particles are added to said liquid crystal, so that fine domains whose threshold voltages are different from one another are formed, and wherein said fine particles are surface treated to improve dispersability thereof.
3. A liquid crystal device of the type which comprises a pair of substrates, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed in said liquid crystal, wherein an alignment film formed on at least one of the substrates is an obliquely evaporated film consisting of a multitude of rhombic columns wherein at least a part of a conductive material is intervened in between adjacent rohmbic columns.
4. A liquid crystal device according to claim 3, wherein said conductive material has an electric conductivity which is higher than an electric conductivity of the evaporated film and/or said liquid crystal.
5. A liquid crystal device according to claim 3, wherein said conductive material has an electric conductivity not smaller than 1 S/cm.
6. A liquid crystal device of the type which comprises a pair of substrates, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed, in said liquid crystal, wherein said liquid crystal has angles of layer inclination which are different from each other at regions in the vicinity of an alignment film formed on at least one of said substrates and at bulk regions other than the first-mentioned regions.
7. A liquid crystal device according to claim 6, wherein peaks of the X-ray diffraction intensity have a half width of not smaller than 8
8. A liquid crystal device of the type which comprises a pair of substrates, each having a planar conductor, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed in said liquid crystal wherein said device comprises a pair of substrates each having a transparent electrode and an alignment film formed thereon in this order, the paired substrates being arranged to have a given space therebetween so that the respective alignment films are facing each other, and a ferroelectric liquid crystal being injected into the given space, wherein the number of domains having a size larger than 2 μmφ in a field of 1 mm.sup.2 is not smaller than 300, and a transmittance through inverted domains is 25%, and the width of the threshold voltage within the domains is not smaller than 2 volts within a transmittance range of from 10 to 90%.
9. A liquid crystal device of the type which comprises a pair of substrates, each having a planar conductor, and a liquid crystal provided between the paired substrates, fine domains whose threshold voltages for switching the liquid crystal are different from one another being finely distributed in said liquid crystal wherein said device comprises a pair of substrates each having a transparent electrode and an alignment film formed thereon in this order, the paired substrates being arranged to have a given space therebetween so that the respective alignment films are facing each other, and a ferroelectric liquid crystal being injected into the given space, wherein the number of domains having a size larger than 2 μmφ in a field of 1 mm.sup.2 is not smaller than 300, and a transmittance through inverted domains is 25%, and the width of the threshold voltage within the domains is not smaller than 2 volts within a transmittance range of from 10 to 90%, wherein when said liquid crystal is subjected to measurement of x-ray diffraction, two or more highest peaks of an x-ray diffraction intensity which exhibit angles of the layer inclination exist at an incident angle of x-ray not higher than 90 or not lower than 90
10. A liquid crystal device according to claim 8, wherein fine particles added to said liquid crystal have a specific gravity which is 0.1 to 10 times that of said liquid crystal.
11. A liquid crystal device according to claim 8, further comprising a film formed on each of said alignment films and made of a material selected from the group consisting of charge transfer complexes, organic pigments, metals, oxides and fluorides.
12. A liquid crystal device according to claim 11, wherein said material is a conductive material.
13. A liquid crystal device according to any of claim 3 and 5 to 21, wherein said alignment film is annealed after vacuum deposition.
14. A liquid crystal device according to claim 8, wherein said respective alignment films is a vacuum deposition film of silicon oxide.
15. A liquid crystal device according to claim 8 or 9, wherein a distribution width of an apparent pretilt angle of liquid crystal molecules constituting a plurality of domains whose threshold voltages are different from one another is not less than 6
16. A liquid crystal device according to claim 8 or 9, wherein said device is applied with two or more levels of voltages whereby two or more gray-scale levels are obtained.
17. A liquid crystal device according to claim 8 or 9, wherein fine particles added to said liquid crystal have surfaces whose pH is not smaller than 2.
18. A liquid crystal device according to claim 8 or 9, wherein fine particles are added to said liquid crystal in an amount of not larger than 50 wt %.
19. A liquid crystal device according to claims 8 or 9, wherein fine particles added to said liquid crystal are comprised of carbon black obtained by a furnace process.
20. A liquid crystal device according to claims 8 or 9, wherein fine particles added to said liquid crystal are comprised of amorphous titanium oxide.
21. A liquid crystal device according to claim 8 or 9, wherein fine particles added to said liquid crystal have has a controlled size distribution whereby a gray-scale display characteristic is controlled.
22. A liquid crystal device according to claim 21, wherein said size distribution of said fine particles has a standard deviation of not smaller than 9 nm.
23. A liquid crystal device according to claim 8 or 9, wherein an apparent tilt angle of liquid crystal molecules constituting a plurality of domains whose threshold voltages are different from one another is varied within a range not less than +1
PREFERRED EMBODIMENTS OF THE INVENTION The liquid crystal device of the invention may be so arranged that the device comprises a pair of substrates, each substrate having a transparent electrode and an alignment film formed thereon in this order, the substrates being arranged at a given space therebetween so that the alignment films of the respective substrates are facing each other, and a ferroelectric liquid crystal injected into the given space. The term "fine domains whose threshold voltages for switching the liquid crystal are different from one another are finely distributed" means that when the transmittance through inverted domains (e.g. black domains in white and vice versa) is 25%, the number of domains having a size of larger than 2 μmφ (microdomains) in a field of 1 mm.sup.2 is not smaller than 300 preferably not smaller than 600 and that the width of the threshold voltage within the domains is not smaller than 2 volts within a transmittance range of from 10 to 90%.
As is particularly shown in FIG. 1, the liquid crystal device of the invention undergoes a relatively gentle change of transmittance in relation to the variation of an applied voltage. This is contrary to the prior art device where the transmittance is abruptly changed as shown in FIG. 38. As stated hereinabove, this is because fine domains or microdomains whose threshold voltages (V.sub.th) are different from one another appear within one pixel and thus, the transmittance of the microdomains are changed depending on the applied voltage. When the liquid crystal molecules are bistable in one domain, a memory function is imparted, so that flicker-free still images can be realized. Since one pixel consists of domains in the order of μm whose threshold voltages differ from one another, a continuous gray-scale display becomes possible.
In FIG. 1, among the threshold voltages at which the transmittance is varied, the threshold voltage is taken as V.sub.th1 at a transmittance of 10% and as V.sub.th2 at a transmittance of 90%, the width of the variation of the threshold voltage, i.e. ΔV.sub.th =V.sub.th2 -V.sub.th1, is not smaller than 2 volts. The microdomains should be present at a rate of 300 microdomains, with a size of larger than 2 μmφ, per mm.sup.2 when the transmittance is 25%. This is schematically shown in FIG. 2A wherein microdomains are indicated by MD. By the presence of the microdomains which are fine light-transmitting portions; a half-tone picture (transmittance) can be realized. Such a microdomain structure assumes a so-called starry sky and will be hereinafter referred to as "starlight texture".
In the practice of the invention, the microdomains can be formed by dispersing ultrafine particles in a liquid crystal. FIG. 3 shows an FLC display having a fundamental structure as shown in FIG. 38 and is not particularly described except that ultrafine particles 10 are dispersed in the liquid crystal 5.
The variation of the threshold voltage caused by the ultrafine particles 10 is principally set forth. When the size of the ultrafine particles 10 is taken as d.sub.2, the dielectric constant of the particles 10 as ε.sub.2, the thickness of the liquid crystal 5 except for the ultrafine particles 10 as d.sub.1, and the dielectric constant of the liquid crystal 5 as ε.sub.1, the electric field, Eeff, exerted on the ultrafine particles can be expressed as follows.
Eeff=(&#949;.sub.2 /(&#949;.sub.2 d.sub.2 +&#949;.sub.2 d.sub.1))
Accordingly, when ultrafine particles whose dielectric constant is smaller than that of the liquid crystal is added (ε.sub.2 &lt;ε.sub.1), this leads to the incorporation of fine particles (d.sub.2) whose size is smaller than the total thickness dgap (=d.sub.1 +d.sub.2) of the liquid crystal. Thus,
Eeff&amp;lt;Egap
When ε.sub.1 &gt;ε.sub.2, Eeff&lt;(Vgap/(d.sub.1 +d.sub.2)=Vgap/dgap=Egap.
When ε.sub.1 =ε.sub.2, Eeff=Egap.
When ε.sub.1 &lt;ε.sub.2, Eeff&gt;Egap.
From the above, it will be seen that the starlight texture is suitable for realizing a continuous gray-scale, under which different transmittances (two or more gray-scale levels) can be obtained by controlling an applied voltage (magnitude and pulse width) under the addition of ultrafine particles. In contrast, mere presence of fine particles as in prior art results in the structure as shown in FIG. 2B. Especially, when fine particles with a size of 0.3 to 2 μm are placed in a fine gap of about 2 μm, an intended display performance cannot be attained. If the gap is not narrow, color shading will be produced owing to the presence of the fine particles. This will be described in bore detail in comparative examples appearing hereinafter. In the practice of the invention, such defects can be overcome and intended characteristic properties can be obtained.
The ultrafine particles which are added to the liquid crystal are not critical provided that such fine particles serve to distribute the intensity of an effective electric field which is applied to the liquid crystal 5 existing between the facing transparent electrode layers 2a, 2b of FIG. 3. For instance, a mixture of fine particles consisting of a plurality of materials having different dielectric constants may be used. By the presence of fine particles having different dielectric constants, the distribution of the dielectric constant is formed in the respective pixels. As a consequence, when an external electric field is applied uniformly to the transparent electrode layers 2a, 2b of the pixel, the effective electric field intensity applied to the liquid crystal in the pixel can be distributed. Thus, the width of the threshold voltage for switching the liquid crystal (especially, a ferroelectric liquid crystal) between the bistable states can be widened, enabling one to make an analog gray-scale display in one pixel.
Where the fine particles having the same dielectric constant are used, a size distribution is appropriately controlled to obtain similar results. In this case, the presence of fine particles having the same dielectric constant but having different sizes leads to the distribution in thickness of the liquid crystal layer. As a result, when an external electric field is uniformly applied between the transparent electrode layers 2a, 2b in one pixel, the intensity of the effective electric field applied to the liquid crystal in the pixel is distributed, with the possibility of making an analog gray-scale display in the pixel. The particle size distribution should preferably be wider because a better analog gray-scale display is obtained.
The fine particles added to the liquid crystal should preferably have a pH on the surface of not less than 2 This is because if the pH is less than 2.0, acidity is too strong, the liquid crystal is liable to degrade by the attack of protons.
In the liquid crystal device of the invention, the angle of inclination of the liquid crystal layer at regions in the vicinity of the alignment film should differ from that in bulk regions other than the first-mentioned regions. Moreover, it is preferred that there are at least two X-ray diffraction intensity peaks, which exhibit the angles of inclination of the liquid crystal layer, at an incident angle of X-ray of not larger than 90 that the half width of the peaks of the X-ray diffraction intensity is not smaller than 38 gradation display.
In the practice of the invention, an apparent tilt angle (cone angle) of liquid crystal molecules which constitute a plurality of domains having different threshold voltages should preferably be varied by .+-.1.degree. or over from the monodomain state. The temperature dependence of the cone angle of liquid crystal molecules should preferably be smaller than that in the monodomain state
The distribution width of the apparent pretilt angle of the liquid crystal molecules should preferably be not smaller than 6 not smaller than 8 liquid crystal molecules is distributed within a range where the alignment of the liquid crystal is not disturbed, there can be effectively formed a number of microdomains whose threshold values for switching between the bistable states of the liquid crystal within one pixel are different from one another. This may be realized, for example, by forming a specific type of thin film on a SiO oblique vacuum deposition layer.
A substance selected from the group consisting of charge transfer complexes, organic pigments, metals, oxides and fluorides is formed on the alignment film. This is more particularly described with reference to FIGS. 5 to 7.
FIG. 5 shows a liquid crystal display device similar to that of FIG. 3 except that a charge transfer complex thin film 6 is formed on each of the SiO oblique vacuum deposition layers 3a, 3b. More specifically, a builtup structure A is provided as having a substrate 1a, a transparent electrode 2a, a liquid crystal alignment film 3a, such as a SiO oblique vacuum deposition layer, for realizing high contrast and good domains and a charge transfer complex thin film 6 built up in this order. Likewise, a builtup structure B has a substrate 1b, a transparent electrode 2b, a liquid crystal alignment film 3b, such as a SiO oblique vacuum deposition layer, and a charge transfer complex thin film 6 built up in this order. The structures 3A and 3B are so arranged that the liquid crystal alignment layers 3a, 3b are in face-to-face relation.
In this device, the charge transfer complex thin films 6 are, respectively, vacuum deposited on the SiO oblique vacuum deposition layers 3a, 3b. The vacuum deposition is preferably effected in the following manner. The substrates 1a, 1b are, respectively, formed with the electrode 2a, 2b and the SiO oblique vacuum deposition layers 3a, 3b to provide substrate bases 20 as shown in FIGS. 6A and 6B. Then, a substance whose surface energy is different from that of SiO of the SiO oblique vacuum deposition layer is vacuum deposited as islands A of FIGS. 6A and 6B. Subsequently, the charge transfer complex thin film is formed on the islands-bearing SiO layer 3a or 3b. By this, it becomes possible that the pretilt angle of the liquid crystal molecules is distributed in a favorable fashion.
The potential for the electric field treatment should preferably be in the range of .+-.3 V to .+-.50 V (i.e. V.sub.p-p =6 V to 100V). The frequency and treating time may be Arbitrarily selected. In general, the electric field treatment is carried out by application of a rectangular wave of 100 Hz .+-.30V for about one minute.
TABLE 1______________________________________Abbreviation Name of Compound______________________________________TTF          tetrathiafulvaleneDHTTF        dicyclotetrathiafulvaleneDMTTF        dimethyltetrathiafulvaleneTMTTF        tetramethyltetrathiafulvaleneHMTTF        hexamethylenetetrathiafulvaleneDSDTF        diselenadithiafulvaleneDMDSDTF      dimethyldiselenadithiafulvaleneHMDSDTF      hexamethylenediselenadithiafulvaleneTSF          tetraselenafulvaleneTMTSF        tetramethyltetraselenafulvaleneHMTSF        hexamethylenetetraselenafulvaleneTTT          tetrathiotetraceneTST          tetraselenatetraceneQ            quinolineNMQ          N-methylquinolinium iodide______________________________________
TABLE 2-A______________________________________Abbreviation   Name of Compound______________________________________Ad      acridineNPM     N-methylphenazium methylsulfateDEPE    1,2-di(N-ethyl-4-pyridinium)ethyleneMTCNQ   2-methyl-7,7.8.8-tetracyanoquinodimethaneDMTCNQ  2.5-dimethyl-7,7,8,8-tetracyanoquinodimethaneDETCNQ  2,5-diethyl-7,7,8,8-tetracyanoquinodimethaneMOTCNQ  2-methoxy-7,7,8,8-tetracyanoquinodimethaneCTNQ    2-chloro-7,7,8,8-tetracyanoquinodimethaneBTCNQ   2-bromo-7,7,8,8-tetracyanoquinodimethaneDBTCNQ  2,5-dibromo-7,7,8,8-tetracyanoquinodimethaneCMTCNQ  2-chloro-5-methyl-7,7,8.8-tetracyanoquinodimethaneBMTCNQ  2-bromo-5-methyl-7,7,8,8-tetracyanoquinodimethaneIMTCNQ  2-iodo-5-methyl-7,7,8,8-tetracyanoquinodimethaneTNAP    11,11,12,12-tetracyano-2,6-tetracyanoquino-dimethaneHCB     1,1,2,3-hexacyanobutadieneTCNQ    tetracyanoquinodimethane______________________________________
TABLE 3______________________________________Examples of Charge Transfer Complexes______________________________________tetrathiafulvalene-2-methyl-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2,5-dimethyl-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2,5-diethyl-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2-methoxy-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2-chloro-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2-bromo-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2,5-dibromo-7,7,8,8,-tetracyanoquinodi-methanetetrathiafulvalene-2-chloro-5-methyl-7,7,8,8,-tetracyanoquinodimethanetetrathiafulvalene-2-bromo-5-methyl-7,7,8,8,-tetracyanoquinodimethanetetrathiafulvalene-2-iodo-5-methyl-7,7,8,8,-tetracyanoquinodimethaneditetrathiafulvalene-2-chloro-5-methyl-7,7,8,8,-tetracyanoquinodimethanetetrathiafulvalene-11,11,12,12-tetracyano-2,6-naphthoquinodimethaneditetrathiafulvalene-1,1,2,3-hexacyanobutadienetetrathiafulvalene-chloride.sub.0.71tetrathiafulvalene-bromide.sub.0.70-0.76tetrathiafulvalene-iodide.sub.0.70-0.76______________________________________
TABLE 4-A______________________________________Examples of Charge Transfer Complexes______________________________________tetrathiafulvalene-thiocyanate.sub.0.55-0.73tetrathiafulvalene-seleninic cyanate.sub.0.55-0.62dihydroxytetrathiafulvalene-tetracyanoquinodimethanedihydroxytetrathiafulvalene-2-bromo-5-methyl-tetracyanoquino-dimethanedihydroxytetrathiafulvalene-2,5-diethyl-7,7,8,8-tetracyanoquinodimethanedimethyltetrathiafulvalene-7,7,8,8-tetracyanoquinodimethanen-methylquinolium iodide-11,11,12,12-tetracyano-2,6-naphtho-quinodimethane1,2-di(n-ethyl-4-pyridinium)ethylene-7,7,8,8-tetracyano-quinodimethanetetramethyltetrathiafulvalene-2-methyl-7,7,8,8-tetracyano-quinodimethane______________________________________
TABLE 4-B______________________________________Examples of Charge Transfer Complexes______________________________________hexamethylenetetrathiafulvalene-7.7.8.8-tetracyanoquino-dimethanehexamethylenediselenadithiafulvalene-7.7.8.8-tetracyanoquinodimethanedimethyldiselenadithiafulvalene-7.7.8.8-tetracyanoquinodimethanetetraselenafulvalene-7,7,8,8-tetracyanoquinodimethanetetraselenafulvalene-bromide.sub.0.8tetraselenafulvalene-methyl-7,7,8,8-tetracyanoquino-dimethane.sub.x -7,7,8,8-tetracyanoquinodimethane.sub.1-xtetramethyltetraselenafulvalene-7,7,8,8-tetracyano-quinodimethanetetramethylselenafulvalene-2,5-dimethyl-7,7,8,8-tetracyanoquinodimethane______________________________________
TABLE 5-A______________________________________Examples of Charge Transfer Complexes______________________________________hexamethylenetetraselenafulvalene-7.7.8.8-tetracyanoquino-dimethanehexamethylenetetraselenafulvalene-11,11,12,12-tetracyano-2,6-naphthoquinodimethanetetrathiotetracene-7,7,8,8-tetracyanoquinodimethane 2tetrathiotetracene-2,5-dimethyl-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-2,5-diethyl-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-5-methoxy-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-2,5-dimethoxy-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-2-methoxy-S-ethoxy--7,7,8,8-tetracyanoquinodimethanetetrathiotetracene-2,5-diethoxy-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-2-bromo-5-methyl-7,7,8,8-tetracyanoquino-dimethane______________________________________
TABLE 5-B______________________________________Examples of Charge Transfer Complexes______________________________________tetrathiotetracene-2-iodo-5-methyl-7,7,8,8-tetracyanoquino-dimethanetetrathiotetracene-iodide.sub.1-1.5tetrathiotetracene-11,11,12,12-tetracyanonaphtho-quinodimethane(tetrathiotetracene.sub.0.5 -tetraselenacene.sub.0.5 -7,7,8,8-tetracyanoquinodimethane 2)tetraselenacene-tetracyanoquinodimethanequinoline-7,7,8,8-tetracyanoquinodimethanen-methylquinolium iodide-7,7,8,8-tetracyanoquinodimethane______________________________________
FIG. 7A is a schematic sectional view of a liquid crystal display device which includes an uppermost thin film layer 7 on each of the liquid crystal alignment layers or SiO oblique vacuum deposition layers 3a, 3b. The uppermost layer 7 consists of an organic conductive compound, oxide, fluoride or metal. By the formation of the thin film 7, fine multidomains whose threshold values for switching the liquid crystal between the bistable states are formed.
The organic conductive compounds used to form the thin film 7 include a variety of organic conductive compounds. For instance, a ytterbium diphthalocyanine (YbPc.sub.2) thin film may be used. When organic conductive compounds having a conductivity of not less than 1 thin film of the organic conductive compound is preferably in the range of not larger than 300 angstroms, more preferably from 40 to 80 angstroms.
The oxide films may be those films of oxide compounds such as, for example, SiO, SiO.sub.2, MgO, TiO, TiO.sub.2, Al.sub.2 O.sub.3 and the like. The thickness of the oxide thin film is preferably in the range of not larger than 100 angstroms.
The fluoride thin films are those films of various fluorides such as MgF.sub.2, CaF.sub.2, AlF.sub.3 and the like. The thickness of the fluoride thin film is preferably not larger than 100 angstroms.
Subsequently, a charge transfer complex, oxide, fluoride or metal is subjected to vacuum deposition, preferably from the direction vertical to the substrate, thereby forming a thin film thereof on the SiO oblique vacuum deposition layer of the builtup structure. Two builtup structures are assembled to obtain a liquid crystal cell. A liquid crystal in which fine particles are uniformly dispersed is injected into the cell gap to obtain a liquid crystal display device. The liquid crystal alignment film may be rubbed polyimide film, or SiO oblique vacuum deposition film, SiO.sub.2 oblique vacuum deposition film, magnesium fluoride oblique vacuum deposition film, calcium fluoride oblique vacuum deposition film or the like.
It has been confirmed through SEM and electrochemical analyses that the SiO oblique vacuum deposition layer used as the alignment film is constituted of a multitude of SiO rhombic columns X as shown in FIG. 7(b) and that interstices d are present in the SiO oblique vacuum deposition layer along the SiO rhombic columns. When the charge transfer complex thin film 6 or 7 formed on the SiO oblique vacuum deposition layer is thermally treated, at least a part 6' or 7' of the constituent material of the thin film 6 or 7 may be present between or incorporated in the interstices d of the rhombic columns X of the SiO layer. This has also been confirmed through RAS measurement of FT-IR (Fourier transformation infrared spectroscopy). For instance, the angle of inclination of the rhombic columns X is about 45 total surface area.
This eventually leads to a smaller thickness of the thin film 6 or 7, and part of the SiO oblique vacuum deposition layer is caused to be in direct contact with the liquid crystal molecules, thereby keeping the alignment of the liquid crystal molecules. More particularly, as shown in FIG. 7B, the liquid crystal display device wherein at least a part 6' or 7' of the charge transfer complex thin film 6 or 7 is incorporated into the interstices d of the SiO rhombic columns X of the SiO oblique vacuum deposition layers 3a, 3b can keep the alignment of the ferroelectric liquid crystal and can reduce the accumulated surface charge by the spontaneous polarization of FLC molecules or impurities of FLC mixtures. This is considered for the following reason: when, for example, the thin film is made of tetrathiafulvalene-tetracyanoquinodimethane complex (TTF-TCNQ), the CN groups are tilted from the substrate parallel and the highest conductive direction of TTF-TCNQ complex alignes along the rhombic columns of SiO.
More particularly, it is assumed that the conductive material such as the above complex (TTF-TCNQ) serves to connect between the liquid crystal 5 and the electrodes 2a, 2b, which results in good response at the time of application of a voltage without adversely influencing the alignment of the liquid crystal, thereby ensuring a high speed response.
The electric conductivity of the conductive material should preferably be higher than that of the vacuum deposition thin film and/or the liquid crystal and should preferably be not lower than 1 S/cm.sup.2, more preferably not lower than 1 most preferably not lower than 1 with the above TTF-TCNQ complex, it has a conductivity of 1 S/cm.sup.2.
In order to permit at least a part 6' or 7' of FIG. 7B of the conductive material to intervene between adjacent rhombic columns of the oblique vacuum deposition film, the conductive material is formed as a thin film with a thickness of from 3 to 40 nm by a vacuum deposition method and thermally treated or fired at a temperature of 50 C. thereby causing the part to be charged inbetween the rhombic columns. Alternatively, the conductive material may be charged in the form of a liquid.
EXAMPLES 1, 2 and Comparative Examples 1, 2 To 100 mg of a ferroelectric liquid crystal composition CS-1014 (Example 1) or CS-1028 (Example 2) commercially available from Chisso Petrochemical Co., Ltd. was added 1 mg of carbon black Mogul L of Cabot Corp., which was ultrafine carbon black particles, followed by heating to 100 (i.e. heating to an isotropic temperature) and uniform dispersion by use of a ultrasonic homogenizer. The above procedure was repeated using no carbon black for comparison (Comparative Examples 1 and 2 corresponding to Examples 1 and 2, respectively).
Each composition was heated to an isotropic temperature in vacuum and poured into a test cell. The alignment film of the test cell was a SiO oblique vacuum deposition film. The angle of the deposition was 85 with respect to the normal line of the substrate, and the substrate temperature was 170 completion of the vacuum deposition, the vacuum deposition film was annealed in air at 300
In the fabrication of the liquid crystal cell, a glass substrate on which a 400 angstroms thick transparent ITO film having a surface resistance of 100Ω/cm.sup.2 was formed by sputtering was provided, on which a 500 angstroms thick SiO oblique vacuum deposition film was formed as a liquid crystal alignment film by heating (resistance heating) a tantalum boat having therein SiO powder with a purity of 99.99% (commercially available from Furuuchi Chem. Co., Ltd.).
The resultant two glass substrates were assembled using spacers having a diameter of 1.6 μm (true spheres: commercially available from Catalyst Chemical Co., Ltd.) and a UV-curing adhesive (Photorec: commercially available from Sekisui Fine Chemicals Co., Ltd.) in such a way that the SiO oblique vacuum deposition films were facing each other but the directions of the vacuum deposition were opposite to each other, thereby obtaining a liquid crystal cell. The ferroelectric liquid crystal was injected into the cell gap to obtain a liquid crystal cell. The cell was applied with an AC electric field of a frequency of 100 Hz and .+-.35V to obtain a liquid crystal display device.
TABLE 6______________________________________(Comparison of Starlight Textures With Known Systems)    Example 1             Comp. Ex. 1                        Example 2                                Comp. Ex. 2    starlight             prior art  starlight                                prior artStructure    texture (I)             structure (I)                        texture (II)                                structure (II)______________________________________Liquid   CS-1014  CS-1014    CS-1028 CS-1028CrystalCone Angle    25             45                                42(electricfield: on)Cone Angle    16             43                                38(electricfield: off)Width of 7        2          6       2ThresholdVoltage (V)Contrast 70       70         70      70Pulse Width    350      500        20      20______________________________________
In these examples and comparative examples, the alignment films are arranged in non-parallel to each other. In the case, the prior art cells are known to have a bookshelf structure. With the starlight texture structure based on the present invention, the layer structure is considered to have an increasing number of domains on the surface of the alignment film wherein liquid crystal molecules are in an immobilized state relative to an electric field. Thus, it is considered that in the vicinity of the surface of the alignment film, the angle of inclination of the layer is changed. This is why when using CS-1014, the cone angle is likely to change at the time of the applied voltage being on and off. With the starlight textures, the cone angles are changed by .+-.1.degree. or over on comparison with those of the monodomain structures (prior art systems).
The liquid crystal display devices obtained above were subjected to measurement of the relation between the applied voltage and the contrast ratio in the following manner. A drive waveform as shown in FIG. 8 was applied to each display device under crossed Nicols. Initially, a reset pulse (V.sub.reset pulse) with a pulse width of 1 msec., was applied, followed by application of a grey pulse (V.sub.gray pulse) with a pulse width of 1 msec., which was less than the reset pulse. The degree of light transmission after the application of the reset pulse (dark level) and the degree of light transmission after the application of (grey level) were compared to determine a contrast ratio.
EXAMPLE 3 The general procedure of Example 1 was repeated except that CS-1014 was used as the liquid crystal, titanium oxide was used as ultrafine particles, i.e. 1 wt % of high dispersion-type IT-UD was added as selected from titania products of Idemitsu, thereby obtaining a liquid crystal cell. The titanium oxide used was characterized by its amorphousness and had an average size of 17 nm.
The device of Example 3 using titanium oxide ultrafine particles and the device of Comparative Example 1 using CS-1014 alone without use of any ultrafine particles were subjected to measurement of the temperature dependence on the angle of cone. The results are shown in FIG. 10 wherein the cone angle at 30
EXAMPLE 4 In the same manner as in Example 1, CS-1014 was used as the liquid crystal and the alignment film used was a SiO alignment film. Ultrafine particles used were three types of titania particles of Idemitsu IT-S, IT-PA and IT-PB, which had all hydrophilic surfaces and different size distributions, respectively. The average sizes of these particles IT-S, IT-PA and IT-PB were, respectively, 17 nm, 24 nm and 40 nm with size distributions being shown in FIG. 11 for the respective titania particles. Liquid crystal cells were fabricated in the same manner as in Examples 1 using the above ingredients.
The relation between the transmittance and the applied voltage is shown in FIG. 12 for the cells using 1 wt % of the respective titania ultrafine particles. From the figure, it will be seen that the gradient is decreased in the order of IT-S&gt;IT-PA&gt;IT-PB. Accordingly, the width of the threshold value and the variation in the applied voltage can be appropriately controlled by controlling the size distribution of the ultrafine particles. When the size distribution of the titanium oxide is widened, the width of the threshold value tends to be widened. The liquid crystal display devices obtained in this example have different contrast ratios depending on the voltage. The width of the threshold voltage for switching the ferroelectric liquid crystal between the bistable states is great, giving evidence what an analog gray-scale can be displayed. This ensures image display in a simple matrix without providing any active element such as TFT for every pixel.
The relation between the standard deviation of the size distribution and the inclination of variation of the transmittance was determined, revealing, that they are almost in a linear relation as shown in FIG. 13. More particularly, the control of the threshold voltage characteristic for tone display is possible by controlling the size distribution of the particles to be added. If the standard deviation is not less than 9.0 nm, a good inclination of variation of the transmittance (i.e. a good width of variation of the threshold voltage) is attained, making it easy to obtain a starlight texture structure.
EXAMPLE 5 The general procedure of Example 1 was repeated except that CS-1028 of Chisso Petrochemical Co., Ltd., was used as the liquid crystal instead of CS-1014 and 24 wt % of Mogul L was added to the liquid crystal thereby obtaining a liquid crystal cell.
The cells of Examples 1 and 5 were subjected to measurement of the number of domains with a size of larger than 2 μmφ per mm.sup.2 while controlling the voltage so that the transmittance was 25% provided that the transmittance was taken as 100% when the cell was in the brightest. The results are shown in Table 7 below.
TABLE 7______________________________________Liquid Crystal + Fine Particles                 Number of Domains______________________________________Example 1   CS-1014 (anti-parallel) +                     100,000   Mogul L 1 wt %Example 5   CS-1028 (anti-parallel) +                     450 to 1075   Mogul L 24 wt %______________________________________
With the CS-1014 system, the domains were observed through a microscope of 500 magnifications to count the number of the domains in a region of 20 μm square. 40 domains were found. For calculation of the number of the domains per mm.sup.2, 40 multiplied by 2500 made 100,000. With the CS-1028 system, the liquid crystal was observed at 72 magnifications to count the number of the domains in an area of 200 μm square thereby finding out 18 to 43 domains. The calculation of the number of the domains per mm.sup.2 revealed 450 to 1075 domains per mm.sup.2.
EXAMPLE 6 1) Formation of a SiO Oblique Vacuum Deposition Alignment Film and Method for Fabricating Cells for Evaluation
A 2.5 mm thick glass substrate having a sputtered ITO film with a surface resistance of 100 Ω/cm.sup.2 was provided so that the normal line of the glass substrate made an angle of 85 vertical line. While keeping the glass substrate at 170 conditions of a degree of vacuum of 8 monoxide (SiO) placed in a Ta boat with opened pinholes (Japan Backs Metal Co., Ltd.) and subjected to resistance heating at a deposition rate of 1 angstrom/second to form an oblique vacuum deposition film with a thickness of 500 angstroms. The film thickness and the deposition rate were feedback controlled by use of a quartz oscillator thickness meter.
The glass substrate was thermally treated at 300 a clean oven (DT62 of Yamato Science Co., Ltd.) in order to improve the alignment of the liquid crystal. Thus, two glass substrates were fabricated. A UV curing resin (Photorec of Sekisui Fine Chemical Co., Ltd.) dispersing spacers with a diameter of 1.4 μm (true spheres: Catalyst Chemical Ind. Co., Ltd.) was provided between the two glass substrates so that the oblique vacuum deposition films were facing each other to make the directions of the oblique vacuum deposition anti-parallel. The resin was cured by irradiation with UV light to form an intended cell gap.
In order to induce the development of fine domains capable of half tone, fine particles were dispersed in a ferroelectric liquid crystal as set out in Example 1. 100 mg of a ferroelectric liquid crystal, CS-1014, of Chisso Petrochemical Co., Ltd., which was heated to an isotropic phase temperature of 100 L, followed by agitation by means of a ultrasonic homogenizer. The ratio by weight of the fine particles was approximately 1%. The ferroelectric liquid crystal, CS-1014, of the isotropic phase in which the fine particles were dispersed was injected into the cell and was allowed to cool to room temperature.
The ferroelectric liquid crystal display device fabricated above was placed between crossed polarizing plates so that one of the memory states was coincident with the transmission axis of the polarizing plates to determine a transmitted light intensity, T.sub.dark, after application of a rectangular wave (reset pulse with a pulse width of 1 msecond and a voltage of .+-.25 V and a transmitted light intensity, T.sub.bright, after application of a rectangular wave (select pulse) with a pulse width of 1 msecond and a voltage of .+-.30 V or below. The contrast ratio, CR, was determined as follows:
CR=T.sub.bright /T.sub.dark
By changing the voltage of the select pulse, the threshold value characteristic of the contrast ratio (i.e. a width of voltage of from the lowest contrast ratio (=1) to the highest contrast ratio) was measured. The results of the measurement are similar to those of FIG. 9 wherein the abscissa axis indicated a voltage of the select pulse and the ordinate axis indicates the contrast ratio in a memory state). With the ferroelectric liquid crystal display device using no fine particles, the width of the threshold value is so sharp as about 1 volt, whereas the width of the ferroelectric liquid display device using fine particles is increased to 10 V, enabling a half-tone display.
Using the X-ray diffraction method, the layer structure in the SmC* phase having the ferroelectric characteristic of the device fabricated above was analyzed. Taking the quantity of transmission of X-ray into consideration, 100 μm thick glass substrates were used to make a ferroelectric liquid crystal display device used for the analyses. The rotating target X-ray source RU-300 of Rigaku Electric Co., Ltd., (target: Cu, Kα ray 1.542 angstroms, 50 kV and 240 mA) were used.
As shown in FIG. 14, the incident X-ray which was converged to a beam diameter of 2.5 mm by means of a pinhole collimator was diffracted with a sample which was attached to a wide angle goniometer, CN2155D5, of Rigaku Electric Co., Ltd., used in combination with a fiber sample mount FS-3 of Rigaku Electric Co., Ltd., in such a way that the direction of the aligning treatment was held horizontal. After selecting a wavelength (i.e. CuKα ray of 1.542 angstroms in this case) by means of a monochromator fixed at a double angle (2θ.sub.B =3.08.degree. for CS-1014) of the Bragg angle θ.sub.B inherent to the sample with respect to the incident X-ray wherein there was provided a slit between the sample and the monochromator of 1 mm square, counts per second were made by use of NaI Scintillation Counter SC-30 of Rigaku Electric Co., Ltd. A 2-inch slit was provided between the monochromator and the scintillation counter.
The angle of incidence, α, of the incident X-ray and the angle, β, of rotation within the plane of the sample could be, respectively, changed by means of the wide angle goniometer and the fiber sample mount. The angle, α, was determined as an origin when the face of the sample substrate was in parallel to the incident X-ray and was 90 when the incident X-ray was vertical to the face of the sample substrate. As viewed from the above, the angle was positive as turned in a clockwise manner. The angle, β, was taken as an origin when the direction of aligning treatment of the sample was horizontal and was positive in a clockwise fashion.
&#948;=
wherein where the angle, α, is scanned at β=0 β=180 diffraction intensity is taken as α.sub.1 and α.sub.2, respectively. This is particularly shown in FIGS. 15A and 15B. If the diffraction intensity peaks are plural in number, a similar calculation can be made on peaks which are in symmetrical position relative to α=90 β=180 since it was difficult to arrange the face of the sample substrate exactly vertical to the incident X-ray.
The results of the measurement of the diffraction X-ray intensity are shown in FIG. 16A for a ferroelectric liquid crystal display device whose threshold characteristic (threshold width) is 1 V and also in FIG. 16B for a threshold width of 10 V. In FIG. 16A, the diffraction intensity peak is only one (angle of layer inclination of 32 with a peak half width of 2 broad peaks with angles of layer inclination of 8 45 range of α of 90
From the above measurements, the possible layer structures for threshold widths of 1 and 10 are considered as shown in FIGS. 17A and 17B, respectively. In the figures, the angle, δ, is the angle of the layer inclination with respect to the normal of the substrate determined from the X-ray diffraction method. The half of the half width (i.e. an extent of the layer inclination angle) of the X-ray diffraction peak is indicated as .+-.values after the value of δ.
Based on the difference in the layer structure, consideration is taken on the difference in the threshold width. With the case wherein the threshold width is 1 V, the X-ray diffraction peak is very sharp and the liquid crystal molecules, i.e. spontaneous polarization which is a switching source, are uniformly aligned. When an electric field of a certain magnitude is applied, most of the liquid crystal molecules are simultaneously switched. In contrast, with the case where the threshold width is 10 V, the layer structure has various angles of the layer inclination and the liquid crystal molecules, i.e. spontaneous polarization, are aligned to have a wide distribution. Accordingly, when an electric field is applied, some molecules are switched and some are not switched, thereby displaying a half-tone as a whole of the pixel. The half=tone display in one pixel is considered owing to the layer structure whose angle of the layer inclination is in a wide distribution. In the case, the angle of the layer inclination is changed in the vicinity of the alignment film and the angle of the layer inclination in other bulk portions is not changed.
EXAMPLE 7 In this example, how to drive the FLC display devices of the foregoing examples and comparative examples is described.
The cell was fabricated in the following manner. Two glass substrates each having an ITO transparent electrode and a size of 40 were used to make a liquid crystal cell. The glass substrate was made of a standard or ordinary soda glass and the transparent electrode was coated by sputtering in a thickness of 500 angstroms. The resistance of ITO was 100Ω/cm.sup.2.
An alignment film for aligning liquid crystal molecules was formed on each substrate by oblique vacuum deposition of SiO. The angle of the vacuum deposition was 85 angstroms. Two types of liquid crystal cells were fabricated including one wherein the directions of the vacuum deposition of the alignment films were parallel to each other and the other wherein the directions of the vacuum deposition were anti-parallel to each other. The gap of the liquid crystal cell was controlled by mixing fine silica particles with a sealing material for bonding two glass substrates therewith. The size of silica particles was in the range of 1.4 to 2.0 μm.
CS-1014 of Chisso Petrochemical Co., Ltd., was used as a ferroelectric liquid crystal. The liquid crystal was degassed in an isotropic phase (110 substrates by utilizing the capillary action in the isotropic phase. After complete injection of the liquid crystal, the cell was gradually cooled down to room temperature. It took 2 to 3 hours before the cooling.
For gray-scale display, the ferroelectric liquid crystal cell was fabricating using transparent electrode-attached glass substrates 1a and 1b as shown in FIG. 18. The transparent electrodes were such that a group of N electrodes 2b which were parallel to the direction of X were formed on the substrate 1b and a group of M electrodes 2a which were parallel to the direction of Y were formed on the substrate 1a. In the figure, the alignment films were not shown. As shown in FIG. 19, electric signals for selecting display of a pixel was applied to the transparent electrodes in the direction of Y, and an electric signal for displaying the content of display information, or white or black or a half tone was applied to the transparent electrodes in the direction of X.
1. A select pulse consists of two pulses which are positively and negatively symmetric with each other. The voltage intensity and height of the pulse are determined according to the threshold value of the liquid crystal display device shown in FIG. 1. The pulse width is determined by the response time of the liquid crystal. The height of the pulse is a voltage at which the starlight texture appears in the monodomain of the liquid crystal displaying a black color, i.e. a threshold voltage V.sub.thlow of the T.sub.r -V curve showing the relation between the variation in transmittance (T.sub.r) of the liquid crystal cell established between the crossed polarizing plates and the applied voltage (V).
2. A symmetric reset pulse is set prior to the select pulse. The width of the reset pulse doubles the select pulse. The height is a voltage at Which the liquid crystal is completely switched, i.e. V.sub.thhigh of the T.sub.r -V curve+ΔV. ΔV is a maximum signal voltage which is applied to the electrodes in the direction of X of the substrate 1b as will be described hereinafter.
1. The signal electric signal consists of two pulses which are positively and negatively symmetric with each other. The pulse width is equal to the width of select signal. The height, Vs, of the signal voltage is changed between 0 and V.sub.yhhigh -V.sub.thlow according to the grey level of the liquid crystal to be displayed.
2. The polarity of the signal voltage pulse is so set that it is opposite to that of the select pulse. By this, the voltage which is applied to a pixel at (n, m) on the display is the sum of V.sub.o +V.sub.thlow and is changed between V.sub.thhigh and V.sub.thlow.
The width of a signal pulse was set at 850 μs and a reset pulse width was set at 700 μs which was double the width of the signal pulse. The threshold voltage was 34 V for the cell, so that the reset voltage was determined at 35 V. The voltage for signals was changed between 18 and 30 V, thereby measuring a variation in transmittance of the cell. As will be apparent from FIG. 20, the transmittance of the cell is continuously changed within a rage of the applied voltage of from 18 V to 28 V. This reveals that the voltage control can control the transmittance of the cell.
EXAMPLE 8 FIG. 21 shows the relation between the transmittance and the applied voltage of a cell which was fabricated in the same manner as the cell set out with reference to FIG. 20 wherein the cell gap was 1.8 μm and the SiO alignment films were so arranged that the directions of the vacuum deposition were in anti-parallel to each other. The direction of the cell was set so that the transmittance of the cell became maximal when no electric field was applied.
EXAMPLE 9 Based on the data of Examples 7 and 8, a cell using a ferroelectric liquid crystal mixed with carbon fine particles was subjected to matrix drive in a tone display.
The cell was fabricated in the following manner. Glass substrates used were 7059 glass plates of Corning Glass Works having a size of 52 sputtering. The electrode pattern is shown in FIG. 22. The resistance of ITO was 100 Ω/cm.sup.2. The cell was fabricated using two glass substrates in such a way that the electrodes were crossed as shown in FIG. 23. The liquid crystal alignment film used as a SiO oblique vacuum deposition film formed on each substrate. The two substrates were so assembled that the directions of the vacuum deposition were in anti-parallel to each other. The cell gap was set at 1.5 μm. A liquid crystal was CS-1014 of Tisso Petrochemical Co., Ltd., to which 2 wt % of carbon fine particles, Mogul L, was added.
Voltage waveforms which are applied to the direction of X of the substrate 1b and to the direction of Y of the substrate 1a are shown in FIGS. 24 and 25, respectively.
EXAMPLE 10 The general procedure of Example 1 was repeated except that a 300 angstroms thick tetrathiafulvalene-tetracyanoquinodimethane charge transfer complex film was formed on the SiO oblique vacuum deposition film of each substrate, followed by annealing at 100 fine particles added to the liquid crystal were those of MT Carbon (Colombia Carbon Co., Ltd.), thereby obtaining a liquid crystal display device.
In this example, it was confirmed that when the tetrathiafulvalentetracyanoquinodimethane complex (TTF-TCNQ) was formed on the oblique vacuum deposition film and then annealed at 100 1 hour, at least a part of the TTF-TCNQ might be, in some case, incorporated among rhombic columns as shown in FIG. 7B.
EXAMPLE 11 The general procedure of Example 10 was repeated except that a 100 angstroms thick ytterbium diphthalocyanine thin film was formed on the SiO oblique vacuum deposition film and annealed at 150 thereby obtaining a liquid crystal display device.
EXAMPLE 12 ITO-attached glass substrates fabricated in the same manner as in Example 1 were obliquely vacuum deposited with SiO, after which each glass substrate was held horizontal and formed with a vacuum deposition film of a tetrathiafulvalene-tetracyanoquinodimethane complex on the SiO film. The vacuum deposition was effected in the following manner. Tatrathiafulvalene (TTF) and tetracyanoquinodimethane (TCNQ) were placed in separate boats. Initially, in order to form a number of domains, TTF alone was formed on the SiO film in a thickness of about 10 angstroms at a substrate temperature of from room temperature to 120 1 TTF at a deposition rate of 1 to 3 angstroms/second and TCNQ at a deposition rate of 0.1 to 1 angstrom/second. Thereafter, TTF was further built up singly in a thickness of about 50 angstroms or over. After the formation of the film, the film was annealed at a temperature of 50 the aligning properties of liquid crystal molecules.
The device was subjected to measurement of a pretilt angle of the liquid crystal molecules according to a magnetic field capacitance method using a magnetic field intensity of 7.5 to 8.0 KGausses. In the case, one pixel with a size of 1.2.times.1.2 cm was divided into 25 domains with an area of about 2 mm.sup.2 as shown in FIG. 28. The divided domains (Nos. 1 to 25) were, respectively, subjected to measurement of a pretilt angle. The results are shown in Table 8 and in FIG. 29A.
Comparative Example 3 The general procedure of Example 10 was repeated except that the tetrathiafulvalene-tetracyanoquinodimethane complex film was not formed and the electric field treatment was not performed, thereby obtaining a liquid crystal display device. The device was subjected to measurement of a pretilt angle of the liquid crystal molecules in the same manner as in Example 12. The results are shown in Table 8 and in FIG. 29B.
Comparative Example 4 The general procedure of Example 10 was repeated except that for the formation of deposition film of the tetrathiafulvalene-tetracyanoquinodimethane complex, the complex which had been preliminarily prepared was placed in a boat and subjected to vacuum deposition at room temperature as a substrate temperature, a deposition rate of 5 angstroms/second and in a thickness of 100 angstroms and that any treatment in an electric field was not effected, thereby obtaining a liquid crystal display device. The device was subjected to measurement of a pretilt angle of liquid crystal molecules in the same manner as in Example 12. The results are shown in Table 8 and in FIG. 29B.
TABLE 8______________________________________Pixel     Pretilt Angle (degree)Domain No.     Example 12   Comp. Ex. 3                            Comp. Ex. 4______________________________________1         23           33        242         20           34        263         27           32        274         27           33        245         22           35        256         24           33        247         24           33        248         25           33        279         25           33        2510        24           34        2411        26           34        2512        23           33        2713        24           33        2514        23           35        2515        28           33        2616        24           33        2517        21           34        2518        23           34        2419        25           33        2720        24           35        2621        23           32        2522        24           34        2723        22           33        2424        26           33        2525        25           32        26______________________________________
As will be apparent from Table 8 and FIG. 29A, the liquid crystal display device of Example 12 has a distribution width of the pretilt angle of the liquid crystal molecules of 9 gently increased or decreased depending on the applied electric field intensity within a certain range, thereby enabling the analog tone display.
In contrast, as will be apparent from Table 8 and FIG. 29B, the liquid crystal display devices of Comparative Examples 3 and 4 have, respectively, a distribution width of the pretilt angle as small as 4 12.
EXAMPLE 13 The general procedure of Example 12 was repeated except that spacers with a diameter of 1.4 μm (true spheres of Catalyst Chemical Co., Ltd.) were used, thereby obtaining a liquid crystal cell. A ferroelectric liquid crystal (CS-1014 of Chisso Petrochemical Co., Ltd.) was injected into the cell. The cell was subjected to an electric field treatment by application of a frequency of 100 Hz and a rectangular wave of .+-.30 V for one minute to obtain a liquid crystal display device.
The device was subjected to measurement of the relation between the applied electric field intensity and the contrast ratio in the following manner. The device was applied with a bias voltage of .+-.6 V twenty times and then applied with a V.sub.reset pulse of .+-.30 V with a pulse width of 500 μseconds, as shown in FIG. 8, under crossed Nicols. Thereafter, a V.sub.gray pulse not larger than .+-.30 V (with a pulse width of 500 μseconds) was applied. The contrast ratio was calculated from the the light transmission intensity after the application of the V.sub.reset pulse and the light transmission intensity after the application of the V.sub.gray pulse. The results are shown in Table 9 and in FIG. 30A.
Comparative Example 5 The general procedure of Example 13 was repeated except that the tetrathiafulvalene-tetracyanoquinodimethane complex film was not formed and the electric field treatment was not effected, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied electric field intensity and the contrast ratio in the same manner as in Example 13. The results are shown in Table 9 and in FIG. 30B.
TABLE 9______________________________________Electric FieldIntensity (V/&#956;m)       Example 13 Comp. Ex. 5                            Comp. Ex. 6______________________________________7.7         1.5        1.0       1.08.2         4.1        1.0       1.08.8         7.1        1.1       1.09.4         14.0       1.0       0.910.0        28.4       1.0       1.010.6        40.4       45.0      12.311.2        49.3       50.2      12.511.8        47.8       50.2      12.612.4        56.7       50.4      12.512.9        62.0       50.4      12.313.5        54.0       51.0      12.514.1        52.1       50.1      12.616.5        50.9       50.3      12.6______________________________________
EXAMPLE 14 The general procedure of Example 13 was repeated except that a ytterbium diphthalocyanine thin film was used instead of the tetrathiafulvalene-tetracyanoquinodimethane complex film and the film was not subjected to the electric field treatment, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied electric field intensity and the contrast ratio. The results are shown in Table 10 and in FIG. 31A.
Comparative Example 7 The general procedure of Example 14 was repeated except that no ytterbium diphthalocyanine thin film was formed and no electric field treatment was carried out, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied electric field intensity and the contrast ratio. The results are shown in Table 10 and in FIG. 31B.
TABLE 10______________________________________Electric FieldIntensity (V/&#956;m)          Example 14                    Comp. Ex. 7______________________________________2.5            1.0       1.03.8            1.1       1.15.0            1.8       1.15.6            3.0       1.06.3            4.7       1.16.9            7.4       1.17.5            13.2      1.08.1            18.8      1.08.8            20.2      1.19.4            21.7      1.010.0           22.1      1.010.6           23.6      45.011.3           23.8      50.211.9           25.4      50.212.5           23.1      50.415.0           25.3      50.017.5           25.9      51.020.0           27.6      50.3______________________________________
EXAMPLE 15 After oblique vacuum deposition of SiO on ITO-attached glass substrates fabricated in the same manner as in Example 1, each glass substrate was kept horizontal, on which a 20 angstroms thick SiO vertical vacuum deposition film was formed on the oblique deposition SiO film under the same conditions as for the oblique vacuum deposition film. After the film formation, the film was annealed in air at 300
Two glass substrates obtained above were assembled by use of spacers with a diameter of 1.4 μm (true spheres of Catalyst Chemical Co., Ltd.) and a UV curing adhesive (Photorec of Sekisui Fine Chemical Co., Ltd.) in such a way that the SiO vertical vacuum deposition films of the substrates were facing each other and the directions of the vacuum deposition of the SiO oblique vacuum deposition films were in anti-parallel to each other. A ferroelectric liquid crystal (CS-1014 of Chisso Co., Ltd.) was injected into the resultant cell gap to obtain a liquid crystal display device. The liquid crystal of the device was formed with microdomains with a diameter of about 10 μm.
The device was applied with a rectangular wave of .+-.30 V at a frequency of 20 Hz and then subjected to measurement of the relation between the applied electric field intensity and the contrast ratio in the same manner as in Example 13. The results are shown in FIG. 32.
EXAMPLE 16 The general procedure of Example 15 was repeated except that a MgF.sub.2 deposition film was used instead of the SiO vertical deposition film, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied electric field intensity and the contrast ratio in the same manner as in Example 15. The results are also shown in FIG. 32.
Comparative Example 8 The general procedure of Example 15 was repeated except that the SiO vertical vacuum deposition film was not formed, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied voltage and the contrast ratio. The results are shown in FIG. 32.
EXAMPLE 17 After formation of the SiO oblique vacuum deposition film on the ITO-attached glass substrate fabricated in the same manner as in Example 1, a 40 angstroms thick Ag vertical deposition film was formed on the SiO oblique deposition film by an electron beam method. The method was carried out under conditions of a substrate temperature of room temperature, a degree of vacuum of 9 angstrom/second.
The two glass substrates were obtained in this manner and assembled by use of spacers with a diameter of 1.4 μm (true spheres of Catalyst Chemical Co., Ltd.) and a UV curing adhesive (Photorec of Sekisui Fine Chemical Co., Ltd.) in such a way that the Ag vertical films were facing each other and the directions of the vacuum deposition of the SiO oblique deposition films were in anti-parallel to each other, thereby obtaining a liquid crystal cell. A ferroelectric liquid crystal (CS-1014 of Chisso Co., Ltd.) was injected into the cell gap to obtain a liquid crystal display device.
The device was applied with a rectangular wave of .+-.30 V at a frequency of 20 Hz for one minute, after which it was subjected to determination of the relation between the applied electric field intensity and the contrast ratio in the same manner as in Example 15. The results are shown in FIG. 33.
Comparative Example 9 The general procedure of Example 17 was repeated except that the Ag vertical deposition film was not formed, thereby obtaining a liquid crystal display device. The relation between the applied electric field intensity and the contrast ratio was determined. The results are shown in FIG. 33.
As will be apparent from FIG. 33, the device of Example 17 has a threshold value width as great as approximately 3 V/μm and the contrast ratio is gently increased or decreased depending on the electric field intensity within a certain range. Thus, the device has an analog tone property. In contrast, as will be apparent from FIG. 33, the device of Comparative Example 9 has a threshold voltage width as small as approximately 1 V/μm. Thus, the device does not have any analog gray-scale display.
EXAMPLE 18 The general procedure of Example 17 was repeated except that an Au film was formed by sputtering instead of the Ag vertical deposition film, thereby obtaining a liquid crystal display device. The device was subjected to determination of the relation between the applied electric field intensity and the contrast ratio in the same manner as in Example 15, in which the bias voltage was .+-.2.5 V and the V.sub.reset pulse was .+-.25V. The results are shown in FIG. 34.
Comparative Example 10 The general procedure of Example 18 was repeated except that the Au vertical deposition film was not formed, thereby obtaining a liquid crystal display device. The relation between the applied electric field intensity and the contrast ratio was determined. The results are shown in FIG. 34.
Comparative Example 11 An FLC display device was fabricated according to information disclosed in the afore-indicated Japanese Laid-open Patent Application No. 3-276126.
A Polyimide JALS-246 of Japan Synthetic Rubber Co., Ltd. was spin coated in a thickness of 500 angstroms on an ITO transparent electrode-attached glass substrate with a length of 40 mm, a width of 25 mm and a thickness of 3 mm. The ITO had a surface resistance of 100 Ω/cm.sup.2 and was formed in a thickness of 500 angstroms. The spin coating was effected under conditions of 300 r.p.m. for three seconds and 3000 r.p.m. for 30 seconds. The polyimide-coated glass substrate was rubbed three times with a rubbing device having a rayon cloth fixedly wound about a roller under conditions of a hair-forced depth op 0.15 mm, a frequency of the roller of 94 r.p.m. and a stage feed speed of 5 cm/minutes.
Alumina particles with a size of 0.5 μm were sprayed over the substrate by use of a spacer spraying machine of Sonokom Co., Ltd., at a rate of 300 particles per mm.sup.2. This is because the spraying of a greater number of the particles results in coagulation of the alumina particles. Spacers with a size of 2 μm were further sprayed using the same machine. In this case, the spraying density was 25 particles/mm.sup.2.
Another glass substrate was provided and applied with a sealing agent of Structobond of Mitsui-Toatsu around a peripheral margin thereof. Both substrates were registered, after which a uniform pressure or force was applied to the substrates until a uniform gap of 1.7 μm was established. Two cells were made so that the directions of alignment were in parallel to and in anti-parallel to each, respectively. The pressure was 1 kg/cm.sup.2. While bonding, the respective cells were placed in a hot air heater and allowed to stand at 180 the sealing agent. Thereafter, the cell gap of the respective cells was measured using a cell gap measuring instrument of Ohtsuka Electronic Co., Ltd., revealing that the gap was controlled at 1.7 μm .+-1 μm throughout the cell.
A ferroelectric liquid crystal composition of ZLI-3775 of Merck Co., Ltd., was degassed at 80 within an isotropic temperature range, followed by injection into the respective cells in vacuum. For the injection, it took 1.5 hours. The cells were each allowed to cool down to room temperature. After cooling down to room temperature, the cell was sandwiched between crossed polarizing plates and subjected to observation of of the alignment of liquid crystal molecules through a microscope and also to measurement of electrooptic characteristics.
1) Alignment of Liquid Crystal Molecules
The spraying density of the spacers were then changed to check its influence. As a result, it was experimentally confirmed that with a cell wherein the spraying density was in the range of 0 to 500 particles/mm.sup.2, the switching characteristic of the cell as a whole was just like the above case using a spraying density of 300 particles/mm.sup.2.
The change in cell gap was also checked using a center value of 1.8 μm and 1.5 μm for the parallel alignment (in either case, the cell gap was controlled within .+-1 μm). Similar device characteristics as set out above were obtained. With the anti-parallel alignment, the cells using cell gaps having center values of 1.5 μm and 1.8 μm, respectively, were checked with similar results being obtained.
Once again, the liquid crystal device of the invention comprises a pair of substrates and a liquid crystal provided therebetween, characterized in that domains whose threshold voltages for switching the liquid crystal are finely distributed throughout the liquid crystal. Especially, microdomains whose threshold voltages (V.sub.th) differ from one another exist in one pixel, so that the transmittance of the microdomains can be relatively gently changed depending on an applied voltage. Within one domain, if the liquid crystal molecules are bistable, a memory function is imparted. Thus, flicker-free still images can be formed. In addition, since one pixel consists of domains whose threshold voltages differ from one another and have a size in the order of μm, an analog continuous tone display is possible at high contrast. The gradation can be realized without resorting to a specific type of pixel and a specific manner of driving and such a liquid crystal device can be fabricated at low costs in a easy and reliable manner.
DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing the relation between the transmittance and the applied voltage, which shows a threshold voltage characteristic, of a liquid crystal display device according to the invention;
FIG. 13 is a graph showing the relation between the standard deviation of a size distribution and the gradient of the variation of a transmittance of a liquid crystal display device;
FIGS. 15A and FIG. 15B are, respectively, a schematic view illustrating a diffraction phenomenon for different incident angles of X-ray at the time of the measurement of X-ray diffraction;
FIGS. 17A and 17B are, respectively, schematic views showing angles of inclination of the liquid crystal layer for different widths of threshold voltage;
As a display technique of such ferroelectric liquid crystals, there has been proposed by Clark et al (U.S. Pat. No. 4,387,924) a surface stabilized ferroelectric liquid crystal display device wherein the cell gap between the display panels is so controlled as to be not larger than 2 μm and liquid crystal molecules are aligned by use of a molecule alignment regulating force established at the interface between the panels, thereby attaining bistable energy states. Based on the high speed response in the order of microseconds and the memorizing effect of images, this device has been intensively studied and developed.
Such a ferroelectric liquid crystal display device has a structure as, for example, schematically shown in FIG. 36. More particularly, a transparent substrate la such as glass is provided, on which a transparent electrode layer 2a such as ITO (indium tin oxide) and a liquid crystal alignment film 3a such as, for example, a SiO oblique vacuum deposition layer are formed to provide a builtup structure A. Likewise, a substrate 1b is provided on which a transparent electrode layer 2b and, for example, a SiO oblique vacuum deposition layer 3b are formed to provide a builtup structure B. These structures are so arranged that the SiO oblique vacuum deposition layers 3a, 3b, which are, respectively, used as a liquid crystal alignment film, are facing each other. Spacers 4 are intervened between the structures to provide a liquid crystal cell. A ferroelectric liquid crystal 5 is injected into a given cell gap to complete a liquid crystal display device.
With conventional ferroelectric liquid crystal devices (e.g. surface stabilized ferroelectric liquid crystal devices), the alignment direction of the molecule M is switched between state 1 and state 2, as shown in FIG. 37 relative to an externally applied electric field E. This change in the alignment of the molecule is developed as a change in transmittance when the liquid crystal device is placed between the polarization plates which are intersected at right angles. As shown in FIG. 38, the transmittance relative to the applied electric field is abruptly changed from 0% to 100% at a threshold voltage V.sub.th. The range or width of the threshold voltage within which the transmittance undergoes the abrupt change is generally not larger than 1 V. Accordingly, with known liquid crystal devices, it becomes difficult to have a stable threshold voltage width in the transmittance/applied voltage curve. Thus, the analog gray-scale display based on the control of the voltage will be difficult or impossible.
To cope with the difficulty, there has been proposed a a gray-scale method wherein sub-pixels are provided to appropriately control an area of pixels (pixel area gradation method), or a method wherein using high speed switching of a ferroelectric liquid crystal, the switching is repeated during one field (time integration gradation method). However, these methods have not been satisfactory with respect to the analog gray-scale display yet.
More specifically, with the area gradation method, an increasing number of gradations results in the increase in number of necessary sub-pixels. From the aspect of fabricating and driving display devices, it will be apparent that cost performance is not good. On the other hand, the time integration gradation method is disadvantageous in its practical utility when used alone or in combination with the area gradation method.
In order to carry out an analog gray-scale display for every pixel, there has been proposed a method wherein the electric field intensity is locally graded by changing the distance between the facing electrodes within one pixel or by changing the thickness of a dielectric layer formed between the facing electrodes. Alternatively, a method has been proposed in which the voltage is graded by changing materials for the facing electrodes.
SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a ferroelectric liquid crystal device which overcomes the drawbacks of the prior art devices.
Patent CitationsCited PatentFiling datePublication dateApplicantTitleUS3620889 *Jun 11, 1968Nov 16, 1971Vari Light CorpLiquid crystal systemsUS3734597 *Apr 9, 1971May 22, 1973Ncr CoProcess for producing a color state in a display deviceUS4796979 *Apr 3, 1987Jan 10, 1989Canon Kabushiki KaishaFerroelectric liquid crystal device having dual laminated alignment filmsUS4861143 *Dec 2, 1987Aug 29, 1989Semiconductor Energy Laboratory Co., Ltd.Liquid crystal display capable of displaying grey toneUS4906074 *Sep 28, 1988Mar 6, 1990Semiconductor Energy Laboratory Co., Ltd.FLC liquid crystal electro-optical device having microdomains within pixelsUS4986638 *Sep 19, 1988Jan 22, 1991Semiconductor Energy Laboratory Co., Ltd.Liquid crystal electro-optical deviceUS5078477 *Nov 8, 1989Jan 7, 1992Mitsubishi Gas Chemical Company, Inc.Ferroelectric liquid crystal cellUS5138472 *Feb 11, 1991Aug 11, 1992Raychem CorporationDisplay having light scattering centersUS5155611 *Jan 21, 1992Oct 13, 1992Semiconductor Energy Laboratory Co., Ltd.Liquid crystal electro-optical device having a plurality of micro-domains formed in the chiral smectic liquid crystal layerUS5196954 *Sep 12, 1988Mar 23, 1993Semiconductor Energy Laboratory Co., Ltd.Liquid crystal displayUS5223963 *Feb 12, 1992Jun 29, 1993Canon Kabushiki KaishaChiral smectic liquid crystal device with different pretilt angles in pixel and non-pixel areasUS5321538 *Sep 1, 1993Jun 14, 1994Canon Kabushiki KaishaMethod for gradation display using a liquid crystal optical element with minute insulation portions on the electrodesUS5347379 *Nov 10, 1993Sep 13, 1994Canon Kabushiki KaishaLiquid crystal device with MIM insulator formed as a continuous monomolecular filmUS5353140 *Nov 30, 1992Oct 4, 1994Semiconductor Energy Laboratory Co., Ltd.Liquid crystal displayUS5381256 *Dec 10, 1992Jan 10, 1995Canon Kabushiki KaishaFerroelectric liquid crystal device with fine particles on insulator, having diameter less than substrate gapEP0240010A1 *Apr 1, 1987Oct 7, 1987Canon Kabushiki KaishaOptical modulation deviceEP0402984A1 *Jun 6, 1990Dec 19, 1990Philips Electronics N.V.Passive ferro-electric liquid crystal display device and method of manufacturing such a deviceEP0508227A2 *Mar 26, 1992Oct 14, 1992Canon Kabushiki KaishaOptical modulation elementJPH036526A * Title not availableJPH03276126A * Title not available* Cited by examinerNon-Patent CitationsReference1 *Martinot Lagarde P et al., Molecular Crystals and Liquid Crystals, vol. 75, No. 1 4, 1981, pp. 249 286.2Martinot-Lagarde P et al., Molecular Crystals and Liquid Crystals, vol. 75, No. 1-4, 1981, pp. 249-286.3 *Ouchi Y et al., Japanese Journal of Applied Physics, Letters, vol. 27, No. 11, Nov. 1988, pp. 1993 1995.4Ouchi Y et al., Japanese Journal of Applied Physics, Letters, vol. 27, No. 11, Nov. 1988, pp. 1993-1995.5Patent Abstracts of Japan, No. JP3276126, vol. 016, No. 096, 10 Mar. 1992, Kazuo, I., "Ferroelectric Liquid Crystal Panel".6 *Patent Abstracts of Japan, No. JP3276126, vol. 016, No. 096, 10 Mar. 1992, Kazuo, I., Ferroelectric Liquid Crystal Panel .7 *Patent Abstracts of Japan, vol. 015, No. 116, 20 Mar. 1991 & JP A 03 006 526, Matsushita Electric Ind. Co. Ltd., 14 Jan. 1991.8Patent Abstracts of Japan, vol. 015, No. 116, 20 Mar. 1991 & JP-A-03 006 526, Matsushita Electric Ind. Co. Ltd., 14 Jan. 1991.9 *Verhulst A G H et al., Proceedings of the SID, vol. 32, No. 4, 1991, pp. 379 386.10Verhulst A G H et al., Proceedings of the SID, vol. 32, No. 4, 1991, pp. 379-386.11Yasuda et al., "Molecular Alignment Engineering for Ferroelectric Liquid Crystals by SiO Obliquely Evaporated Films", Proceedings of the 12th Int. Display Research Conf, Japan Display '92, Paper P2-21, 12 Oct. 1992, pp. 511-514.12 *Yasuda et al., Molecular Alignment Engineering for Ferroelectric Liquid Crystals by SiO Obliquely Evaporated Films , Proceedings of the 12th Int. Display Research Conf, Japan Display 92, Paper P2 21, 12 Oct. 1992, pp. 511 514.* Cited by examinerReferenced byCiting PatentFiling datePublication dateApplicantTitleUS5764328 *Jul 2, 1996Jun 9, 1998Citizen Watch Co., Ltd.Liquid crystal device with plural ferroelectric or antiferroelectric layer tilt angles per pixelUS5952676 *Jun 6, 1997Sep 14, 1999Semiconductor Energy Laboratory Co., Ltd.Liquid crystal device and method for manufacturing same with spacers formed by photolithographyUS5963288 *Jun 6, 1995Oct 5, 1999Semiconductor Energy Laboratory Co., Ltd.Liquid crystal device having sealant and spacers made from the same materialUS6084652 *Jul 22, 1998Jul 4, 2000Sharp Kabushiki KaishaLiquid crystal display with the pre-tilt angle set within a range that gray scale inversion is preventedUS6091471 *Dec 30, 1996Jul 18, 2000Lg Electronics Inc.Liquid crystal cell and a method for fabricating thatUS6118512 *Apr 24, 1998Sep 12, 2000Sharp Kabushiki KaishaManufacturing method of a liquid crystal display elementUS6169531 *Feb 7, 1997Jan 2, 2001U.S. Philips CorporationLiquid-crystal control circuit display device with selection signalUS6268897May 15, 1998Jul 31, 2001Lg Electronics Inc.Liquid crystal display deviceUS6295111Nov 12, 1999Sep 25, 2001Lg Electronics Inc.Liquid crystal cell and a method for fabricating thatUS6297865 *Mar 10, 1998Oct 2, 2001Sony CorporationLiquid crystal element having polarization moderating propertiesUS6317111 *Dec 2, 1999Nov 13, 2001Sony CorporationPassive matrix addressed LCD pulse modulated drive method with pixel area and/or time integration method to produce covay scaleUS6320635 *Feb 5, 1999Nov 20, 2001Sony CorporationLiquid crystal element and manufacture thereofUS6469763Dec 15, 2000Oct 22, 2002Lg Electronics Inc.Liquid crystal cell and method of manufactureUS6493057Jul 2, 1999Dec 10, 2002Semiconductor Energy Laboratory Co., Ltd.Liquid crystal device and method for manufacturing same with spacers formed by photolithographyUS6559919May 25, 1999May 6, 2003Sharp Kabushiki KaishaLiquid crystal device manufacturing methods of controlling a partial switchingUS6853431Nov 27, 2002Feb 8, 2005Semiconductor Energy Laboratory Co., Ltd.Liquid crystal device and method for manufacturing same with spacers formed by photolithographyUS6862057Feb 14, 2002Mar 1, 2005Nec CorporationActive-matrix addressed reflective LCD and method of fabricating the sameUS6870583 *Apr 5, 2001Mar 22, 2005Canon Kabushiki KaishaConductive liquid crystal device and organic electroluminescence deviceUS7075607Jun 26, 2001Jul 11, 2006Lg Philips Lcd Co LtdLiquid crystal cell and method of manufactureUS7123330 *May 31, 2002Oct 17, 2006Citizen Watch Co., Ltd.Liquid crystal panel substrate having alignment film and method for forming alignment film by varied evaporation angleUS7440065 *Sep 29, 2006Oct 21, 2008Lg Display Co., Ltd.Liquid crystal display with wide viewing angle and method for making itUS7623213 *May 30, 2006Nov 24, 2009Fuji Electric Holdings Co., Ltd.Switching device* Cited by examinerClassifications U.S. Classification349/172, 349/129, 349/133International ClassificationG02F1/137, G02F1/133, G02F1/1333, G02F1/141, G02F1/1337, G09G3/18Cooperative ClassificationG02F1/133711, G02F2001/133796, G02F1/141, G02F2203/30, G02F1/133734, G02F1/133707European ClassificationG02F1/141, G02F1/1337F, G02F1/1337CLegal EventsDateCodeEventDescriptionSep 30, 2008FPAYFee paymentYear of fee payment: 12Feb 7, 2005FPAYFee paymentYear of fee payment: 8Jan 7, 2003CCCertificate of correctionDec 3, 2002CCCertificate of correctionJan 29, 2001FPAYFee paymentYear of fee payment: 4Oct 22, 1993ASAssignmentOwner name: SONY CORPORATION, JAPANFree format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:YASUDA, AKIO;NITO, KEIICHI;MATSUI, ERIKO;AND OTHERS;REEL/FRAME:006771/0456;SIGNING DATES FROM 19931012 TO 19931015RotateOriginal ImageGoogle Home - Sitemap - USPTO Bulk Downloads - Privacy Policy - Terms of Service - About Google Patents - Send FeedbackData provided by IFI CLAIMS Patent Services©2012 Google